THERMOSTATIC ELEMENT

The present invention relates to a thermostatic element, i.e., an element which, by
using a thermally expanding material, converts heat energy into mechanical energy.
Such elements are commonly used in the field of fluid regulation, since they make it
possible to divide a fluid supply path into one or more distribution paths, depending on the
5 heat of the fluid to be regulated andlor other heat sources. These elements are for example
arranged within cooling circuits in which a cooling fluid circulates, in particular cooling circuits
for motor vehicle heat engines or similar. Of course, other application examples can be
considered, such as motor oil and gearbox circuits, as well as domestic supply water circuits.
Typically, a thermostatic element includes a metal cup with a generally tubular shape
10 and containing a thermally expanding material such as a wax. The element also includes a
piston coaxial to the cup and translatable relative to said cup under the effect of the
expansion of the thermally expanding material contained in the cup, when that material is
heated. In expanding, thermally expanding material partially drives the piston, such that the .)
latter is deployed outside the cup whereas, during cooling of the thermally expanding
15. material, the piston can be retracted inside the cup, generally under the action of a return
spring associated with the thermostatic element. To guide the translational movements of the
piston, the thermostatic element includes a bored metal guide, inside which the piston slides,
that guide thus constituting a guide part that is firmly secured to the cup. Furthermore, to
prevent the .thermally expanding material from escaping outside the cup during movements
20 of the piston and; at the same time, a liquid outside the thermostatic element, typically in
which that thermostatic element is bathed, from being able to infiltrate along the piston up to
the end of the piston submerged in the cup, it is known to seal the thermally expanding
material relative to the outside using a flexible part whereof a tubular part is arranged
coaxially around the piston. Traditionally, two main families of thermostatic elements are
25 distinguished based on the extent of the covering of the piston by the flexible part. More
precisely, when the flexible part forms a blind thimble, i.e., a sack delimiting a non-emerging
cavity, the piston is received therein without establishing direct contact with the thermally
expanding material: during an expansion of that material, it applies pressure forces on the
sack, which then becomes pinched such that the piston is ejected therefrom, producing the
30 translational movement. Conversely, when the flexible part is axially passed all the way
through by the piston and is thus similar to a globally annular seal, centered on the axis of
translation of the piston, the piston plunges directly into the thermally expanding material and
is subject, without any intermediary, to the pressure applied by the material when it is heated.
The invention specifically relates to thermostatic elements that incorporate such an
35 annular seal and in which opposite axial parts of that annular seal are subject to pressing
bearing, which is substantially antagonistic, by the guide and the cup, respectively, so as to
E C D*% ~2 ~
-- - - - - A _ _ ----- --_ - - - - - -
2
. compress the seal around the piston and thereby seal the cylindrical interface between the
seal, which remains stationary relative to the guide and the cup compressing it, and the
sliding piston.
During use, this sealing gasket is subject to high pressures coming from the thermally
5 expanding material, which tend to extrude the flexible material making up the seal outside
the thermostatic element, by forcing the flexible material to pass between the piston and the
central bore of the guide. It is therefore known.to interpose, axially between the seal and the
guide, an anti-extrusion washer that is mounted coaxially around the piston. ,
Over the course of the usage cycles of the thermostatic element, it is observed that
10 the flexible material making up the sealing gasket tends to wear and have permanent
deformations, which gradually decreases the contact pressure between the seal and the
piston, until the pressure becomes insufficient to guarantee sufficient sealing with respect to
the outside of the thermostatic element. Independently of the aforementioned wear
phenomenon, a critical situation may also occur when the thermostatic element is subject to
15 a rapid and/or significant decrease in temperature, while bathing in a liquid under high
pressure: under these severe usage conditions, the aforementioned liquid quite often
succeeds in infiltrating along the piston, due to the accumulation of an abrupt retraction of the
piston and the cup and the high pressure of the liquid. To avoid these drawbacks, it is known
to attach a flexible packing, forming a sealing bellows, that is fastened to the piston and the
20 guide, while covering the outlet thereof to the outside. That being the case, the placement of
such a packing remains complex operation that is therefore expensive to implement.
Furthermore, other solutions to prevent an outside liquid from being able to infiltrate the
thermostatic element along the piston have been proposed in the past, but like the solution
consisting of the aforementioned packing, they systematically cause an excess product cost
25 and a non-negligible excess process cost.
The aim of the present invention is to propose an improved thermostatic element, the
sealing of which with respect to the outside is reinforced simply, reliably and cost-effectively.
To that end, the invention relates to a thermostatic element including:
- a rigid cup, which contains a thermally expandable material,
30 - a rigid piston, which is translatable, along its axis, relative to the cup, under the
action of the thermally expandable material during an expansion of that material,
- a rigid guide for guiding th- e.- .t .r anslation of the piston, said guide being rigidly secured -
to the cup,
- a flexible seal for sealing the thermally expandable material with respect to the
35 outside of the thermostatic element, said flexible seal having a globally annular shape that is
centered on the axis and that is axially crossed all the way through by the piston, said flexible
zIIxxcn
3
seal including first and second opposite axial parts, against which the guide and the cup are
respectively pressed substantially antagonistically so as to compress the seal around the
piston, and
- an anti-extrusion washer, which is mounted coaxially around the' piston and is axially
interposed between the guide and the first part of the seal,
characterized in that the thermostatic element includes means for over-compression of the
first part of the seal around the piston, which are suitable for making the compression rate of
the first part of the seal equal to a' value strictly greater than its value associated with an
operational thermostatic element formed by the cup, the piston, the guide, the seal and the
anti-extrusion washer assembled to each other without the over-compression means.
One of the ideas at the base of the invention is to seek further tightening around the
piston, specifically the part of the seal turned toward the guide, while only marginally
modifying the overall pre-existing structure of the thermostatic element and thus not causing
a significant excess cost regarding the parts making up the thermostatic element and the
assembly of those parts. Thus, the thermostatic element according to the invention copies all
of the preexisting parts in a thermostatic element of the prior art and additionally incorporates
mechanical means that are specific to the invention: the aforementioned parts can be
assembled to each other, without incorporating the aforementioned specific means, so as to
form a thermostatic element of the prior art that is operational, i.e., that can be used in a
satisfactory manner, but with limited sealing performance levels of its seal with respect to the
outside, as explained above. The aforementioned specific means are, in a way, added to the
pre-existing and self-sufficient parts, so as to increase the crushing of the first part of the
seal, i.e., the part turned toward the guide, within the thermostatic element according to the
invention in the assembled state: moie specifically, the means specific to the invention are
designed to increase the compression rate of the flexible material making up the first part of
the seal, which amounts to saying that in the presence of the aforementioned specific
means, the material making up the first part of the seal is forced to occupy a smaller volume
than that occupied by the material of fhe first part in the absence of said specific means
andlor that, in the presence of the aforementioned specific means, the first part of the seal is
forced to occupy the same volume, but includes more material than that first part in the
absence of those specific means. The contact pressure between the first .part of the seal and
the piston is increased as a result, which locally reinforces andlor extends the sealing over - . . .- . . . ..
time with respect to a liquid outside the thermostatic element, without significantly altering the
cooperation between the rest of the seal and the piston. In particular, the reinforced sealing
at this first part of the seal is such that the latter performs a real anti-absorption function of
liquid under severe usage conditions, in particular in case of abrupt retraction of the piston
- 0253 U-X ~ t ~ ~ - ~ ~ B _ . - I
4
into the cup, related to a rapid andlor significant decrease in temperature, whereak the
thermostatic element is in a high-pressure liquid medium. As explained in more detail below,
the invention provides that the implementation'of the aforementioned specific means may
relate to the guide and/or the anti-extrusion washer and/or the first part of the sealing gasket.
. .
5 . According to advantageous features of the thermostatic element according to the
invention, considered alone or according to any technically possible combination(s):
- the over-compression means are partially, or even exclusively, supported by the
. .
guide, while being integral with the guide;
- the over-compression means comprise, or even consist of, a raised portion
10 protruding from a surface of thg guide that is pressed against the first part of the seal for
compression of the seal around the piston;
- the surface of the guide is substantially spherical and of revolution around the axis,
and the raised portion forms a string centered on the axis;
- the over-compression means comprise, or even consist of, at least one washer in
15 addition to the anti-extrusion washer, which is mounted coaxially around the piston and
which is axially interposed either between the guide ,and the anti-extrusion washer, or
. ,
.between the anti-extrusion washer and the first part of the seal;
- the or each additional washer.is individually identical to the anti-extrusion washer;
- the over-compression means are partially, or even exclusively, supported by the first
20 . part of the seal, while being integral with that first part of the seal;
- the over-compression means comprise, or even consist of, a bead, which is
provided radially protruding inward from the wall of the through hole, centered on the axis
and delimited by the seal to 'receive the piston, and which is canceled out by radial crushing
when the piston is received in the through hole in the assembled state of the thermostatic
25 element;
- the anti-extrusion washer has a rigidity greater than that of the seal, but less than
that of the cup, the piston and the guide;
- the cup, the piston and the guide are made from metal materials, the seal is made
from rubber, and the anti-extrusion washer is made from PTFE.
The invention will be better understood upon reading the following description,
provided solely as an example and done in reference to the drawings, in which:
- figure 1 is a longitudinal cross-section of a thermostatic element of the .- . . . . .p. rior art;
- figure 2 is an exploded view of part of the thermostatic element of figure 1;
- figures 3 and 4 are views similar to figures 1 and 2, respectively, illustrating a first
35 embodiment of a thermostatic element according to the invention;
5
- figures 5 and 6 are views similar to figures 1 and 2, respectively, illustrating a
I second embodiment of a thermostatic element according to the invention; and .
- figures ,7 and 8 are views similar to figures 1 and 2, respectively, illustrating a third
embodiment of a thermostatic element according to the invention.
1 Figures 1 and 2 show a thermostatic element 1 including a rigid cup 10 typically made
I from a metal alloy that conducts heat well, for example brass. This cup 10 has a globally
tubular shape, centered on an axis X-X. In the example embodiment considered in the
figures, the cup 10 includes a main barrel 11 with a cylindrical shape, with a circular base
centered on the axis X-X. This barrel 11 is closed at one of its axial ends by a bottom wall 12.
1 10 In this way. the cup 10 contains a thermally expandable material 20 stored inside the barrel,
that thermally expandable material for example being made up of a wax, optionally filled with
a powder having good heat conductivity, for example a copper powder.
For convenience, the rest of the description is oriented considering that the terms
"lower" and "bottom" designate a direction extending along the axis X-X and oriented toward
15 the bottom wall 12, in other words toward the bottom part of the figures, while the terms
"upper" and "top" designate an opposite direction.
. The thermostatic element 1 includes a piston 30 arranged coaxially to the cup 10. The
lower end part of that piston 30 is housed inside the barrel 11 to undergo the action therein of
the thermally expandable material when that material expands after heating. Through the
20 developments described below, the variation of the volume of the heated thermally
expandable material causes an upward translational movement of the piston 30 along the
axis X-X relative to the cup 10.
The translational movement of the piston 30 is guided by a rigid part forming a guide
40 belonging to the thermostatic element 1. This guide is in particular made from metal, like
25 the piston 30. The guide 40 includes a bored upper plate 41, which extends globally in a
plane perpendicular to the axis X-X and whereof the central bore 42 is centered on that axis.
In cross-section transverse to the axis X-X, the bore 42 has a profile substantially adjusted
on the outer profile of the piston 30, such that the piston is axially received and guided in the
bore 42. The guide 40 also includes a globally tubular lower collar 43, which is centered on
30 the axis X-X and extends axially protruding downward from the plate 41. Outwardly, this
collar 43 is adapted to be rigidly secured, in particular by crimping, to a collar 13 of the cup
10, provided at the upper end of the barrel 11, figure 2 illustrating the assembled state of the - .. . -. .
thermostatic element 1 with the cup and the guide assembled to one another by crimping of
the collar 13 on'the collar 43.
35 In order to seal the thermally expandable material 20 with respect to the outside of
the cup 10, in particular in order to limit, or even ~reventa liauid. tv~icallvi n which th
6
thermostatic element 1 is bathed during use, from being able to infiltrate downwardly along
the piston 30, the thermostatic element 1 includes a sealing gasket 50 that is made from a
flexible material, in particular either natural or synthetic rubber, i.e., elastomer. This seal 50
has an annular overall shape, centered on the axis X-X. Thus, the seal 50 delimits a through
5 hole 51, which crosses axially all the way through the seal, connecting its upper end surface
50A, which is turned toward the guide 40, and its lower end surface 50A, which is turned
toward the thermally expandable material 20 contained in the cup 10, to each other.
In the assembled state of the thermostatic element 1, the piston 30 is received
coaxially in the through hole 51, while extending axially both on either side of the seal 50,
10 protruding axially upward from the surface 50A and protruding axially downward from the
surface 50B, and the inside of the seal 50, between the surfaces 50A and 506 thereof. The
seal 50 is mounted gripped around the piston 30, i.e., mounted compressed around the
longitudinal part of the piston, extending between the surfaces 50A and 506. To that end, in
the assembled state of the thermostatic element 1, in particular under the effect of the rigid
15 securing between the cup 10 and the guide 40, at least part of the upper end face 50A of the
seal 50 is pressed downward by a bearing face 43A, which is delimited by the guide 40
inside the collar 43 and on which the bore 42 emerges downward, whereas, substantially
antagonistically, at least part of the lower end surface 50B of the seal 50 is pressed upward
by a bearing surface 13A, which is delimited by the cup 10 inside the collar 13 and on which
20 the barrel 11 emerges upward, thus, by downward bearing of the bearing surface 43A
against an upper terminal part 52 of the seal 50 and by antagonistic upward bearing of the
bearing surface 13A against a bottom terminal part 53 of the seal 50, the seal is compressed,
with the result that its through hole 51 tends to contract radially inward, which results in
radially gripping the seal 50 all around the piston 30 in light of the presence of a longitudinal
25 part of the latter between the opposite surfaces 50A and 50B of the seal. It will be noted that
this compression of the seal 50, making it possible to compress the latter around the piston
30, relates to both the upper 52 and lower 53 parts, as well as an intermediate part 54 of the
seal 50, which, in the embodiment considered in figures 1 and 2. as an example, axially
connects the upper 52 and lower 53 parts to each other: thus, in this example embodiment,
30 the seal 50 is made up of the parts 52, 53 and 54, with the result that on the one hand, the
through hole 51 extends successively, along the axis X-X, through the parts 52, 54 and 53
and, on the other hand, the upper 50A and lower 508 end surfaces are respectively delimited
by the top 52 and bottom 53 parts, while the intermediate part 54 outwardly delimits a
peripheral side surface 50C of the seal 50, which is cylindrical and centered on the axis X-X,
35 and which, in the assembled state of the thermostatic element 1, is received in an adjusted
manner in the downward opening of the collar 43.
7
Advantageously, in particular for reasons related to distribution of the bearing
stresses pressing the guide 40 on the seal 50, the bearing surface 43A is at least partially, or
even completely, as in the example embodiment considered in figures 1 and 2, made in the
form of a sphere portion, allowing the axis X-X as the geometric axis of revolution. For its
part, the bearing surface 13A delimited by the cup 10 advantageously includes, as in the
example embodiment considered in the figures, both a planar surface, which fits into a
geometric plane substantially perpendicular to the axis X-X, in particular for axial positioning
purposes of the seal 50 during the assembly of the thermostatic element 1, and a flared
element, .which connects, while becoming gradually narrower toward the bottom, the
aforementioned planar surface to the inner wall of the barrel 11, in particular for centering
purposes on the axis X-X of the seal 50 during the assembly of the thermostatic element.
In order to prevent the extrusion of the flexible material making up the seal 50 outside
the thermostatic element 1 via the bore 42 of the guide 40, the thermostatic element 1 further
includes an anti-extrusion washer 60, which is mounted coaxially around the piston 30 and
which is axially interposed between the guide 40 and the upper part 52 of the seal 50. In the
assembled state of the thermostatic element, this washer 60 is upwardly curved, while
hugging the perimeter of the downward opening of the bore 42.
In practice, this washer 60 has a rigidity greater than that of the seal 50, but lower
than that of the guide 40 and the piston 30. Thus, in the event the piston 30 and the guide 40
are made from metal and the seal 50 is made from rubber, the anti-extrusion washer 60 is
advantageously made from PTFE.(polytetrafluoroethylene).
Figures 3 and 4 show a thermostatic element 101 that includes a cup 110, a thermally
expandable material 120, a piston 130, a seal 150 and an anti-extrusion washer 160, which
are respectively identical, both functionally and structurally, to the cup 10, the thermally
expandable material 20, the piston 30, the seal 50 and the washer 60 of the thermostatic
element I . In particular, the cup 110 comprises a barrel 11 1, a bottom wall 112 and a collar
113, which are centered on an axis X-X and which are respectively identical to the barrel 11,
the bottom wall 12, and the collar 13 of the cup 10. Likewise, the seal 150 is made from'an
upper part 152, a lower part 153 and an intermediate part 154, which are respectively
identical to the upper 52, lower 53 and intermediate 54 parts of the seal 50.
The thermostatic element 101 also includes a guide 140, which includes both an
upper plate 141, identical to the plate 41 of the guide 40, in particular while being inwardly
provided with a bore 142 identical to the bore 42, and a collar 143, which is identical to the
collar 43, with the sole difference that its bearing surface 143A, which is functionally similar
to the bearing surface 43A of the guide 40, bears an additional string 144 that protrudes
downward from the surface 143A. Thus, in the example embodiment considered in figures 3
8 _ _ -
--- --
-
- - -.
-EEaxELB-srrr-2*Es A - - k b - k +
8
and 4, the bearing surface 143A, as described above in light of figures 1 and 2, assumes a
spherical shape of revolution around the axis X-X, while the string ,144 runs over that
spherical bearing surface 143A while being centered on the axis X-X and while being integral
with that bearing surface.
5 The shape of the string 144 described just above is not limiting on the embodiment of'
the invention illustrated by figures 3 and 4, inasmuch as that string 144 can, as an alternative
that is not illustrated, be replaced by any form of raised portion protruding from the surface
143A: in the assembled state of the thermostatic element 101, this string 144 or, more
generally, the aforementioned protruding raised portion locally crushes the flexible material
10 making up the upper part 152 of the seal 150, while locally increasing the compression of the
material by the guide 140, compared to the compression of the rest of that material by the
bearing surface 143A. When the upper part 152 of the seal 150 is considered globally, it is
understood that its volume compression rate, i.e., the ratio' between its volume in a
compressed state of the material making up that upper part 152 when the thermostatic
15 element 101 is assembled and the .volume of the same material in the free state of the seal
150, .in particular before assembly with the rest of the thermostatic element 101, has a value
strictly greater than the value of the compression rate of the upper part 52 of the seal 50 of .
the thermostatic element 1 in the assembled state thereof. In other words, in light of the
identity between the thermostatic element 1 and the thermostatic element 101 except
20 regarding the additional presence of the string 144 or, more generally, the aforementioned
protruding raised part, the upper part 152 of the seal 150 is compressed more, under the'
action of that'seal or that protruding raised portion, than the upper part 52 of the seal 50,
which amounts to saying that that string or, more generally, that protruding raised portion
makes it possible to over-compress the top part 152 around the piston 130. The sealing of
25 that .piston with respect to the outside of the'thermostatic element 101 is strengthened as a
result.
Figures 5 and 6 show a thermostatic element 201 that includes a cup 210, a thermally
expandable material 220, a piston 230, a guide 240, a seal 250 and an anti-extrusion washer
260, which are respectively identical, both functionally and structurally, to the cup 10, the
30 thermally expandable material 20, the piston 30, the guide 40, the seal 50 and the washer 60
of the thermostatic element 1. In particular, the cup 210 comprises a barrel 21 1, a bottom
wall 212 and a collar 213, which are centered on axis X-X and which are respectively
identical to the barrel 11, the wall 12, and the collar 13 of the cup 10. Likewise, the guide 240
includes an upper plate 241, a central bore 242 and a lower collar 243, which are
35 respectively identical to the plate 41, the bore 42 and the collar 43 of the guide 40.
Additionally, the seal 250 includes an upper part 252, a lower part 253 and an intermediate
9
part 254, which are respectively identical to the upper 52, lower. 53 and intermediate 54 parts
of the seal 50.
The thermostatic element 201. differs from the thermostatic element 1 through the
additional presence of a washer 270, which is separate from the anti-extrusion washer 260
5 and which, advantageously, as in the example embodiment considered in figures 5 and 6, is
individually identical to that anti-extrusion washer 260. In the assembled state of the
thermostatic element 201, the additional washer 270 is mounted coaxially around the piston
and is axially interposed between the anti-extrusion washer 260 and the upper part 252 of
the seal 250. As an alternative that is not shown, the position of the additional washer 270
10 may be provided on the other axial side of the anti-extrusion washer 260, which amounts to
saying that, in that case, the additional washer is axially interposed between the guide 240
and the anti-extrusion washer 260.
Irrespective of the axial side of the anti-extrusion washer 260 where the additional
washer 270 is provided, it will be understood that the presence of the latter reduces the
15 space available for the upper part 252 of the seal 250 during the compressed mounting of
that seal within the thermostatic element 201: in other words, the presence of the additional
washer 270 increases the value of the volume compression rate of the material making up
the top part 252 of the seal 250, compared to the value of the compression rate associated
with the top part 52 of the seal 50 of the thermostatic element 1 in the assembled state
, 20 thereof. This results in over-compression of the upper part 252 of the seal 250 around the
piston 230, thereby reinforcing the sealing of the thermostatic element 201 with respect to a
liquid outside the thermostatic element.
As an alternative that is not shown, two, or even more additional washers 270 are
provided.
25 Figures 7 and 8 show a thermostatic element 301 that includes a cup 310, a thermally
expandable material 320, a piston 330, a guide 340 and an anti-extrusion washer 360, which
are respectively identical, both functionally and structurally, to the cup 10, the thermally
expandable material 20, the piston 30, the guide 40 and the washer 60 of the thermostatic
element 1. In particular, the cup 310 comprises a barrel 31 1, a bottom wall 312 and a collar
30 31 3, which are centered on andaxis.x-x and which are respectively identical to the barrel 11,
the bottom wall 12 and the collar 13 of the cup 10. Likewise, the guide 340 includes an upper
plate 341, a central bore 342 and a lower collar 343, which are respectively identical to the
plate 41, the bore 42 and the collar 43 of the guide 40.
The thermostatic element 301 also includes an annular sealing gasket 350 that is
35 formed by an upper part 352, a lower part 353 and an intermediate part 354. the lower 353
and intermediate 354 parts respectively being identical to the lower 53 and intermediate 54
_ _ _ _ _ ------ - =---- -
--a e ; E O E E k M B 3A 9 - E-EXEG-Z 5
10
parts of the seal 50, while the upper part 352 is identical to the upper part 52 of the seal 50
with the sole difference that that upperpart 352of the seal 350 bears an additional bead 355.
As clearly shown in figure 8, this bciad 355 is arranged in the upward opening of the through
hole 351 of the seal 350, which is functionally similar to the through hole 51 .of the seal 50,
5 i.e., the'bead 355 protrudes radially.inward from the wall of the through hole 351, delimited
by the upper part 352 of the seal 350.
During the assembly of the thermostatic element 301, the bead 355 interferes radially
with the piston 330 received in the hole 351, until it is canceled out by the radial crushing
under the action of the piston 330, as shown in figure 7. It will be understood that. this
10 cancellation of the bead 355 results in increasing the quantity of the flexible material making
up the seal 350 in the available free.space, within the thermostatic element 301, for the
upper part 352 of the seal 350, whereas the aforementioned free space is unchanged
compared to the case of the thermostatic element 1. In other words, the volume compression
rate of the upper part 352 of the seal 350 is, under the effect of the cancellation of the
15 additional bead 355 by the piston 330 in place in the through hole 351, increased relative to
the compression rate of the upper part 52 of the seal 50 in the assembled state of the
thermostatic element 1. This upper part 352 of the seal 350 is thus over-compressed as a
result around the piston 330, then reinforcing the sealing of the thermostatic element 301
with respect to the outside. .
20 Various arrangements and alternatives to the thermostatic elements 101, 201 and
301 described thus far can also be considered. For example:
- the three embodiments, respectively associated with the thermostatic elements 101,
201 and 301, can be combined two by two, or combined all three, further accentuating the
over-compression of the upper part of the seal of the thermostatic element thus obtained by
25 combination, around the piston of that thermostatic element; and/or
- optionally, the piston 130, 230 or 330 may be inwardly provided with an electric
heating resistance, designed to heat the thermally expandable material 120, 220 or 320
through the inside, electricity supply conductors of that heating resistance extending from the
end of the piston opposite that submerged in the cup 1 10, 21 0 or 31 0.
30
11
CLAIMS '
1 .- A thermostatic element (1 01 ; 201 ; 301), including:
- a rigid cup (1 10; 210; 310), which contains a thermally expandable material (120;
5 220; 320),
- a rigid piston (130; 230; 330), which is translatable, .along its axis (X-X), relative to
the cup, under the action of the thermally expandable material during an expansion of that
material,
- a rigid guide (140; 240; 340) for guiding the translation of the piston, said guide
10 being rigidly secured to the cu'p,
- a flexible seal (150; 250; 350) for sealing the thermally expandable material With
respect to the outside of the thermostatic element, said flexible seal having a globally annular
shape that is centered on the axis and that is axially crossed all the way through by the
piston, said flexible seal including first (1 52; 252; 352) and second (1 53; 253; 353) opposite
15 axial parts, against which the guide and the cup are respectively pressed substantially
antagonistically so as to compress the seal around the piston, and
- an anti-extrusion washer (160; 260; 360), which is mounted coaxially around the
piston and is axially interposed between the guide and the first part of the seal,
characterized in that the thermostatic element (101; 201; 301) includes means (144; 270;
.20 355) for over-compression of the first part (152; 252; 352) of the seal (150; 250; 350) around
the piston (130;'230; 330), which are suitable for making the compression rate of the first part
of the seal equal to a value strictly greater than its value associated with an operational
thermostatic element (I)for med by the cup, the piston, the guide, the seal and the antiextrusion
washer assembled to each other without the over-compression means.
25 2.- The thermostatic element according to claim 1, characterized in that the overcompression
means (144) are partially, or even exclusively, supported by the guide (140),
while being integral with the guide.
3.- The thermostatic element according to claim 2, characterized in that the overcompression
means comprise, or even consist of, a raised portion (144) protruding from a
30 surface (143A) of the guide (140) that is pressed against the first part (1 52) of the seal (1 50)
for compression of the seal around the piston (1 30).
4.- The thermostatic element according to claim 3, characterized in that said surface
(143) of the guide (140) is substantially spherical and of revolution around the axis (X-X), and
in that said raised portion forms a string (1 44) centered on the axis (X-X).
35 5.- The thermostatic element according to any one of the preceding claims,
characterized in that the over-compression means comprise, or even consist of, at least one
12
washer (270).in addition to the anti-extrusion washer (260); which is 'mounted coaxially
around the piston (230) and which is axially interposed either between the guide (240) and
the anti-extrusion washer, or between the anti-extrusion washer and the first part (252) of the
seal (250).
5 6.- he thermostatic element according to claim' 5, characterized in that the or each
additional washer (270) is individually identical to the anti-extrusion washer (260).
. . 7.- The thermostatic element according to any one of the preceding claims,
characterized in that the over-compression means (355) are exclusively supported by the
first part (352) of the seal (350), while being integral with that first part of the seal.
10 8.- The thermostatic element according to claim 7, characterized in that the overcompression
means comprise, or even consist of, a bead (355), which is provided radially
protruding inward from the wall of the through hole (351), centered on the axis (X-X) and
delimited by the seal (350) to receive the piston (330) and which is canceled out by radial
crushing when the piston is received in the through hole in the assembled state of the
I 5 thermostatic element (301).
9.- The thermostatic element according to any one of the preceding claims,
characterized in that the anti-extrusion washer (160; 260; 360) has a rigidity greater than that
of the seal (150; 250; 350), but less than that of the cup (110; 210; 310), the piston (130;
230; 330) and the guide (140; 240; 340).
20 10.- The thermostatic element according to claim 9, characterized in that the cup
(1 10; 21 0; 31 O), the piston (1 30; 230; 330) and the guide (140; 240; 340) are made from
metal materials, the seal (150; 250; 350) is .made from rubber, and the anti-extrusion washer
(160; 260; 360) is made from PTFE.

THERMOSTATIC ELEMENT

The present invention relates to a thermostatic element, i.e., an element which, by
using a thermally expanding material, converts heat energy into mechanical energy.
Such elements are commonly used in the field of fluid regulation, since they make it
possible to divide a fluid supply path into one or more distribution paths, depending on the
5 heat of the fluid to be regulated and/or other heat sources. These elements are for example
arranged within cooling circuits in which a cooling fluid circulates, in particular cooling circuits
for motor vehicle heat engines or similar. Of course, other application examples can be
considered, such as motor oi! and gearbox circuits, as well as domestic supply water circuits.
Typically, a thermostatic element includes a meta! cup with a generally tubular shape
10 and containing a thermally expanding materia! such as a wax. The element also includes a
piston coaxial to the cup and translatable relative to said cup under the effect of the
expansion of the thermally expanding material contained in the cup, when that material is
heated. In expanding, thermally expanding material partially drives the piston, such that the
latter is deployed outside the cup whereas, during cooling of the thermally expanding
15 material, the piston can be retracted inside the cup, generally under the action of a return
spring associated with the thermostatic element. To guide the translational movements of the
piston, the thermostatic element includes a bored metal guide, inside which the piston slides,
that guide thus constituting a guide part that is firmly secured to the cup. Furthermore, to
prevent the thermally expanding material from escaping outside the cup during movements
20 of the piston and, at the same time, a liquid outside the thermostatic element, typically in
which that thermostatic element is bathed, from being able to infiltrate along the piston up to
the end of the piston submerged in the cup, it is known to seal the thermally expanding
material relative to the outside using a flexible part whereof a tubular part is arranged
coaxially around the piston. Traditionally, two main families of thermostatic elements are
25 distinguished based on the extent of the covering of the piston by the flexible part. More
precisely, when the flexible part forms a blind thimble, i.e., a sack delimiting a non-emerging
cavity, the piston is received therein without establishing direct contact with the thermally
expanding materia!: during an expansion of that material, it applies pressure forces on the
sack, which then becomes pinched such that the piston is ejected therefrom, producing the
30 translational movement. Conversely, when the flexible part is axially passed all the way
through by the piston and is thus similar to a globally annular seal, centered on the axis of
translation of the piston, the piston plunges directly into the thermally expanding material and
is subject, without any intermediary, to the pressure applied by the material when it is heated,
as illustrated by EP-A-0,940,577.
35 The invention specifically relates to thermostatic elements that incorporate such an
annular seal and in which opposite axial parts of that annular seal are subject to pressing
2
bearing, which is substantially antagonistic, by the guide and the cup, respectively, so as to
compress the seal around the piston and thereby seal the cylindrical interface between the
seal, which remains stationary relative to the guide and the cup compressing it, and the
sliding piston.
5 During use, this sealing gasket is subject to high pressures coming from the thermally
expanding materia!, which tend to extrude the flexible material making up the seal outside
the thermostatic element, by forcing the flexible material to pass between the piston and the
central bore of the guide. It is therefore known to interpose, axially between the seal and the
guide, an anti-extrusion washer that is mounted coaxialty around the piston.
10 Over the course of the usage cycles of the thermostatic element, it is observed that
the flexible material making up the sealing gasket tends to wear and have permanent
deformations, which gradually decreases the contact pressure between the seal and the
piston, until the pressure becomes insufficient to guarantee sufficient sealing with respect to
the outside of the thermostatic element. Independently of the aforementioned wear
15 phenomenon, a critical situation may also occur when the thermostatic element is subject to
a rapid and/or significant decrease in temperature, while bathing in a liquid under high
pressure: under these severe usage conditions, the aforementioned liquid quite often
succeeds in infiltrating along the piston, due to the accumulation of an abrupt retraction of the
piston and the cup and the high pressure of the liquid. To avoid these drawbacks, it is known
20 to attach a flexible packing, forming a sealing bellows, that is fastened to the piston and the
guide, while covering the outlet thereof to the outside. That being the case, the placement of
such a packing remains complex operation that is therefore expensive to implement.
Furthermore, other solutions to prevent an outside liquid from being able to infiltrate the
thermostatic element along the piston have been proposed in the past, but like the solution
25 consisting of the aforementioned packing, they systematically cause an excess product cost
and a non-negligible excess process cost.
The aim of the present invention is to propose an improved thermostatic element, the
sealing of which with respect to the outside is reinforced simply, reliably and cost-effectively.
To that end, the invention relates to a thermostatic element as defined in claim 1.
30 One of the ideas at the base of the invention is to seek further tightening around the
piston, specifically the part of the seal turned toward the guide, while only marginally
modifying the overall pre-existing structure of the thermostatic element and thus not causing
a significant excess cost regarding the parts making up the thermostatic element and the
assembly of those parts. Thus, the thermostatic element according to the invention copies all
35 of the preexisting parts in a thermostatic element of the prior art and additionally incorporates
mechanical means that are specific to the invention: the aforementioned parts can be
3
assembled to each other, without incorporating the aforementioned specific means, so as to
form a thermostatic element of the prior art that is operational, i.e., that can be used in a
satisfactory manner, but with limited sealing performance levels of its seal with respect to the
outside, as explained above. The aforementioned specific means are, in a way, added to the
5 pre-existing and self-sufficient parts, so as to increase the crushing of the first part of the
seal, i.e., the part turned toward the guide, within the thermostatic element according to the
invention in the assembled state: more specifically, the means specific to the invention are
designed to increase the compression rate of the flexible materia! making up the first part of
the seal, which amounts to saying that in the presence of the aforementioned specific
10 means, the material making up the first part of the seal is forced to occupy a smaller volume
than that occupied by the material of the first part in the absence of said specific means
and/or that, in the presence of the aforementioned specific means, the first part of the seal is
forced to occupy the same volume, but includes more material than that first part in the
absence of those specific means. The contact pressure between the first part of the seal and
15 the piston is increased as a result, which locally reinforces and/or extends the sealing over
time with respect to a liquid outside the thermostatic element, without significantly altering the
cooperation between the rest of the seal and the piston, in particular, the reinforced sealing
at this first part of the seal is such that the latter performs a real anti-absorption function of
liquid under severe usage conditions, in particular in case of abrupt retraction of the piston
20 into the cup, related to a rapid and/or significant decrease in temperature, whereas the
thermostatic element is in a high-pressure liquid medium. As explained in more detail below,
the invention provides that the implementation of the aforementioned specific means may
relate to the guide and/or the anti-extrusion washer and/or the first part of the sealing gasket.
Additional advantageous features of the thermostatic element according to the
25 invention are specified in the dependent claims.
The invention will be better understood upon reading the following description,
provided solely as an example and done in reference to the drawings, in which:
- figure 1 is a longitudinal cross-section of a thermostatic element of the prior art;
- figure 2 is an exploded view of part of the thermostatic element of figure 1;
30 - figures 3 and 4 are views similar to figures 1 and 2, respectively, illustrating a first
embodiment of a thermostatic element according to the invention;
- figures 5 and 6 are views similar to figures 1 and 2, respectively, illustrating a
second embodiment of a thermostatic element according to the invention; and
- figures 7 and 8 are views similar to figures 1 and 2, respectively, illustrating a third
35 embodiment of a thermostatic element according to the invention.
4
Figures 1 and 2 show a thermostatic element 1 including a rigid cup 10 typically made
from a metal alloy that conducts heat well, for example brass. This cup 10 has a globally
tubular shape, centered on an axis X-X. In the example embodiment considered in the
figures, the cup 10 includes a main barrel 11 with a cylindrical shape, with a circular base
5 centered on the axis X-X. This barrel 11 is closed at one of its axial ends by a bottom wall 12.
In this way, the cup 10 contains a thermally expandable material 20 stored inside the barrel,
that thermally expandable material for example being made up of a wax, optionally filled with
a powder having good heat conductivity, for example a copper powder.
For convenience, the rest of the description is oriented considering that the terms
10 "lower" and "bottom" designate a direction extending along the axis X-X and oriented toward
the bottom wall 12, in other words toward the bottom part of the figures, while the terms
"upper" and "top" designate an opposite direction.
The thermostatic element 1 includes a piston 30 arranged coaxially to the cup 10. The
lower end part of that piston 30 is housed inside the barrel 11 to undergo the action therein of
15 the thermally expandable material when that material expands after heating. Through the
developments described below, the variation of the volume of the heated thermally
expandable material causes an upward translational movement of the piston 30 along the
axis X-X relative to the cup 10.
The translational movement of the piston 30 is guided by a rigid part forming a guide
20 40 belonging to the thermostatic element 1. This guide is in particular made from metal, like
the piston 30. The guide 40 includes a bored upper plate 41, which extends globally in a
plane perpendicular to the axis X-X and whereof the centra! bore 42 is centered on that axis.
In cross-section transverse to the axis X-X, the bore 42 has a profile substantially adjusted
on the outer profile of the piston 30, such that the piston is axially received and guided in the
25 bore 42. The guide 40 also includes a globally tubular lower collar 43, which is centered on
the axis X-X and extends axially protruding downward from the plate 41. Outwardly, this
collar 43 is adapted to be rigidly secured, in particular by crimping, to a collar 13 of the cup
10, provided at the upper end of the barrel 11, figure 2 illustrating the assembled state of the
thermostatic element 1 with the cup and the guide assembled to one another by crimping of
30 the collar 13 on the collar 43.
In order to seal the thermally expandable material 20 with respect to the outside of
the cup 10, in particular in order to limit, or even prevent a liquid, typically in which the
thermostatic element 1 is bathed during use, from being able to infiltrate downwardly along
the piston 30, the thermostatic element 1 includes a sealing gasket 50 that is made from a
35 flexible material, in particular either natural or synthetic rubber, i.e., elastomer. This seal 50
has an annular overall shape, centered on the axis X-X. Thus, the seal 50 delimits a through
5
hole 51, which crosses axially all the way through the seal, connecting its upper end surface
50A, which is turned toward the guide 40, and its lower end surface 50A, which is turned
toward the thermally expandable material 20 contained in the cup 10, to each other.
In the assembled state of the thermostatic element 1, the piston 30 is received
5 coaxially in the through hole 51, while extending axially both on either side of the seal 50,.
protruding axially upward from the surface 50A and protruding axially downward from the
surface 50B, and the inside of the seal 50, between the surfaces 50A and 50B thereof. The
seal 50 is mounted gripped around the piston 30, i.e., mounted compressed around the
longitudinal part of the piston, extending between the surfaces 50A and 50B. To that end, in
10 the assembled state of the thermostatic element 1, in particular under the effect of the rigid
securing between the cup 10 and the guide 40, at least part of the upper end face 50A of the
seal 50 is pressed downward by a bearing face 43A, which is delimited by the guide 40
inside the collar 43 and on which the bore 42 emerges downward, whereas, substantially
antagonistically, at least part of the lower end surface 50B of the seal 50 is pressed upward
15 by a bearing surface 13A, which is delimited by the cup 10 inside the collar 13 and on which
the barrel 11 emerges upward, thus, by downward bearing of the bearing surface 43A
against an upper terminal part 52 of the seal 50 and by antagonistic upward bearing of the
bearing surface 13A against a bottom terminal part 53 of the seal 50, the seal is compressed,
with the result that its through hole 51 tends to contract radially inward, which results in
20 radially gripping the seal 50 al! around the piston 30 in light of the presence of a longitudinal
part of the latter between the opposite surfaces 50A and 50B of the seal. It will be noted that
this compression of the seal 50, making it possible to compress the latter around the piston
30, relates to both the upper 52 and lower 53 parts, as well as an intermediate part 54 of the
seal 50, which, in the embodiment considered in figures 1 and 2 as an example, axially
25 connects the upper 52 and lower 53 parts to each other: thus, in this example embodiment,
the seal 50 is made up of the parts 52, 53 and 54, with the result that on the one hand, the
through hole 51 extends successively, along the axis X-X, through the parts 52, 54 and 53
and, on the other hand, the upper 50A and lower 50B end surfaces are respectively delimited
by the top 52 and bottom 53 parts, while the intermediate part 54 outwardly delimits a
30 peripheral side surface 50C of the seal 50, which is cylindrical and centered on the axis X-X,
and which, in the assembled state of the thermostatic element 1, is received in an adjusted
manner in the downward opening of the collar 43.
Advantageously, in particular for reasons related to distribution of the bearing
stresses pressing the guide 40 on the seal 50, the bearing surface 43A is at least partially, or
35 even completely, as in the example embodiment considered in figures 1 and 2, made in the
form of a sphere portion, allowing the axis X-X as the geometric axis of revolution. For its
6
part, the bearing surface 13A delimited by the cup 10 advantageously includes, as in the
example embodiment considered in the figures, both a planar surface, which fits into a
geometric plane substantially perpendicular to the axis X-X, in particular for axial positioning
purposes of the seal 50 during the assembly of the thermostatic element 1, and a flared
element, which connects, while becoming gradually narrower toward the bottom, the.
aforementioned planar surface to the inner wall of the barrel 11, in particular for centering
purposes on the axis X-X of the seal 50 during the assembly of the thermostatic element.
In order to prevent the extrusion of the flexible material making up the seal 50 outside
the thermostatic element 1 via the bore 42 of the guide 40, the thermostatic element 1 further
includes an anti-extrusion washer 60, which is mounted coaxially around the piston 30 and
which is axially interposed between the guide 40 and the upper part 52 of the sea! 50. In the
assembled state of the thermostatic element, this washer 60 is upwardly curved, while
hugging the perimeter of the downward opening of the bore 42.
In practice, this washer 60 has a rigidity greater than that of the seal 50, but lower
than that of the guide 40 and the piston 30. Thus, in the event the piston 30 and the guide 40
are made from metal and the seal 50 is made from rubber, the anti-extrusion washer 60 is
advantageously made from PTFE (polytetrafluoroethylene).
Figures 3 and 4 show a thermostatic element 101 that includes a cup 110, a thermally
expandable material 120, a piston 130, a seal 150 and an anti-extrusion washer 160, which
are respectively identical, both functionally and structurally, to the cup 10, the thermally
expandable material 20, the piston 30, the seal 50 and the washer 60 of the thermostatic
element 1. In particular, the cup 110 comprises a barrel 111, a bottom wall 112 and a collar
113, which are centered on an axis X-X and which are respectively identical to the barrel 11,
the bottom wall 12, and the collar t3 of the cup 10. Likewise, the seal 150 is made from an
upper part 152, a lower part 153 and an intermediate part 154, which are respectively
identical to the upper 52, lower 53 and intermediate 54 parts of the seal 50.
The thermostatic element 101 also includes a guide 140, which includes both an
upper plate 141, identical to the plate 41 of the guide 40, in particular while being inwardly
provided with a bore 142 identical to the bore 42, and a collar 143, which is identical to the
collar 43, with the sole difference that its bearing surface 143A, which is functionally similar
to the bearing surface 43A of the guide 40, bears an additional string 144 that protrudes
downward from the surface 143A. Thus, in the example embodiment considered in figures 3
and 4, the bearing surface 143A, as described above in light of figures 1 and 2, assumes a
spherical shape of revolution around the axis X-X, while the string 144 runs over that
spherical bearing surface 143A while being centered on the axis X-X and while being integral
with that bearing surface.
7
The shape of the string 144 described just above is not limiting on the embodiment of
the invention illustrated by figures 3 and 4, inasmuch as that string 144 can, as an alternative
that is not illustrated, be replaced by any form of raised portion protruding from the surface
143A: in the assembled state of the thermostatic element 101, this string 144 or, more
5 generally, the aforementioned protruding raised portion locally crushes the flexible material.
making up the upper part 152 of the seal 150, while locally increasing the compression of the
material by the guide 140, compared to the compression of the rest of that material by the
bearing surface 143A. When the upper part 152 of the seal 150 is considered globally, it is
understood that its volume compression rate, i.e., the ratio between its volume in a
10 compressed state of the material making up that upper part 152 when the thermostatic
element 101 is assembled and the volume of the same material in the free state of the seal
150, in particular before assembly with the rest of the thermostatic element 101, has a value
strictly greater than the value of the compression rate of the upper part 52 of the seal 50 of
the thermostatic element 1 in the assembled state thereof. In other words, in light of the
15 identity between the thermostatic element 1 and the thermostatic element 101 except
regarding the additional presence of the string 144 or, more generally, the aforementioned
protruding raised part, the upper part 152 of the seal 150 is compressed more, under the
action of that seal or that protruding raised portion, than the upper part 52 of the seal 50,
which amounts to saying that that string or, more generally, that protruding raised portion
20 makes it possible to over-compress the top part 152 around the piston 130. The sealing of
that piston with respect to the outside of the thermostatic element 101 is strengthened as a
result.
Figures 5 and 6 show a thermostatic element 201 that includes a cup 210, a thermally
expandable material 220, a piston 230, a guide 240, a seal 250 and an anti-extrusion washer
25 260, which are respectively identical, both functionally and structurally, to the cup 10, the
thermally expandable material 20, the piston 30, the guide 40, the seal 50 and the washer 60
of the thermostatic element 1. In particular, the cup 210 comprises a barrel 211, a bottom
wall 212 and a collar 213, which are centered on axis X-X and which are respectively
identical to the barrel 11, the wall 12, and the collar 13 of the cup 10. Likewise, the guide 240
30 includes an upper plate 241, a central bore 242 and a lower collar 243, which are
respectively identical to the plate 41, the bore 42 and the collar 43 of the guide 40.
Additionally, the seal 250 includes an upper part 252, a lower part 253 and an intermediate
part 254, which are respectively identical to the upper 52, lower 53 and intermediate 54 parts
of the seal 50.
35 The thermostatic element 201 differs from the thermostatic element 1 through the
additional presence of a washer 270, which is separate from the anti-extrusion washer 260
8
and which, advantageously, as in the example embodiment considered in figures 5 and 6, is
individually identical to that anti-extrusion washer 260. In the assembled state of the
thermostatic element 201, the additional washer 270 is mounted coaxially around the piston
and is axialiy interposed between the anti-extrusion washer 260 and the upper part 252 of
the seal 250. As an alternative that is not shown, the position of the additional washer 270
may be provided on the other axial side of the anti-extrusion washer 260, which amounts to
saying that, in that case, the additional washer is axialiy interposed between the guide 240
and the anti-extrusion washer 260.
Irrespective of the axial side of the anti-extrusion washer 260 where the additional
washer 270 is provided, it will be understood that the presence of the latter reduces the
space available for the upper part 252 of the seal 250 during the compressed mounting of
that sea! within the thermostatic element 201: in other words, the presence of the additional
washer 270 increases the value of the volume compression rate of the material making up
the top part 252 of the seal 250, compared to the value of the compression rate associated
with the top part 52 of the seal 50 of the thermostatic element 1 in the assembled state
thereof. This results in over-compression of the upper part 252 of the seal 250 around the
piston 230, thereby reinforcing the sealing of the thermostatic element 201 with respect to a
liquid outside the thermostatic element.
As an alternative that is not shown, two, or even more additional washers 270 are
provided.
Figures 7 and 8 show a thermostatic element 301 that includes a cup 310, a thermally
expandable material 320, a piston 330, a guide 340 and an anti-extrusion washer 360, which
are respectively identical, both functionally and structurally, to the cup 10, the thermally
expandable material 20, the piston 30, the guide 40 and the washer 60 of the thermostatic
element 1. In particular, the cup 310 comprises a barrel 311, a bottom wall 312 and a collar
313, which are centered on an axis X-X and which are respectively identical to the barrel 11,
the bottom wall 12 and the collar 13 of the cup 10. Likewise, the guide 340 includes an upper
plate 341, a central bore 342 and a lower collar 343, which are respectively identical to the
plate 41, the bore 42 and the collar 43 of the guide 40.
The thermostatic element 301 also includes an annular sealing gasket 350 that is
formed by an upper part 352, a lower part 353 and an intermediate part 354, the lower 353
and intermediate 354 parts respectively being identical to the lower 53 and intermediate 54
parts of the seal 50, while the upper part 352 is identical to the upper part 52 of the seal 50
with the sole difference that that upper part 352 of the seal 350 bears an additional bead 355.
As clearly shown in figure 8, this bead 355 is arranged in the upward opening of the through
hole 351 of the seal 350, which is functionally similar to the through hole 51 of the seal 50,
9
i.e., the bead 355 protrudes radially inward from the wall of the through hole 351, delimited
by the upper part 352 of the seal 350.
During the assembly of the thermostatic element 301, the bead 355 interferes radially
with the piston 330 received in the hole 351, until it is canceled out by the radial crushing
under the action of the piston 330, as shown in figure 7. It will be understood that this
cancellation of the bead 355 results in increasing the quantity of the flexible material making
up the sea! 350 in the available free space, within the thermostatic element 301, for the
upper part 352 of the seal 350, whereas the aforementioned free space is unchanged
compared to the case of the thermostatic element 1. In other words, the volume compression
rate of the upper part 352 of the seal 350 is, under the effect of the cancellation of the
additional bead 355 by the piston 330 in place in the through hole 351, increased relative to
the compression rate of the upper part 52 of the seal 50 in the assembled state of the
thermostatic element 1. This upper part 352 of the seal 350 is thus over-compressed as a
result around the piston 330, then reinforcing the sealing of the thermostatic element 301
with respect to the outside.
Various arrangements and alternatives to the thermostatic elements 101, 201 and
301 described thus far can also be considered. For example:
- the three embodiments, respectively associated with the thermostatic elements 101,
201 and 301, can be combined two by two, or combined all three, further accentuating the
over-compression of the upper part of the seal of the thermostatic element thus obtained by
combination, around the piston of that thermostatic element; and/or
- optionally, the piston 130, 230 or 330 may be inwardly provided with an electric
heating resistance, designed to heat the thermally expandable materia! 120, 220 or 320
through the inside, electricity supply conductors of that heating resistance extending from the
end of the piston opposite that submerged in the cup 110, 210 or 310.

CLAIMS
1.-A thermostatic element (101; 201; 301), including:
- a rigid cup (110; 210; 310), which contains a thermally expandable material (120;
5 220; 320),
- a rigid piston (130; 230; 330), which is translatable, along its axis (X-X), relative to
the cup, under the action of the thermally expandable material during an expansion of that
material,
- a rigid guide (140; 240; 340) for guiding the translation of the piston, said guide
10 being rigidly secured to the cup,
- a flexible seal (150; 250; 350) for sealing the thermally expandable material with
respect to the outside of the thermostatic element, said flexible seal having a globally annular
shape that is centered on the axis and that is axially crossed all the way through by the
piston, said flexible seal including first (152; 252; 352) and second (153; 253; 353) opposite
15 axial parts, against which the guide and the cup are respectively pressed substantially
antagonistically so as to compress the seal around the piston, and
- an anti-extrusion washer (160; 260; 360), which is mounted coaxiaily around the
piston and is axially interposed between the guide and the first part of the seal,
characterized in that the thermostatic element (101; 201; 301) includes means (144; 270;
20 355) for over-compression of the first part (152; 252; 352) of the seal (150; 250; 350) around
the piston (130; 230; 330), which are suitable for making the compression rate of the first part
of the seal equal to a value strictly greater than its value associated with an operational
thermostatic element (1) formed by the cup, the piston, the guide, the seal and the antiextrusion
washer assembled to each other without the over-compression means.
25 2.- The thermostatic element according to claim 1, characterized in that the overcompression
means (144) are partially borne by the guide (140), while being integral with the
guide.
3.- The thermostatic element according to claim 2, characterized in that the overcompression
means comprise a raised portion (144) protruding from a surface (143A) of the
30 guide (140) that is pressed against the first part (152) of the seal (150) for compression of the
seal around the piston (130).
4.- The thermostatic element according to claim 1, characterized in that the overcompression
means (144) are exclusively borne by the guide (140), while being integral with
the guide.
35 5. The thermostatic element according to claim 4, characterized in that the overcompression
means consist of a raised portion (144) protruding from a surface (143A) of the
11
guide (140) that is pressed against the first part (152) of the seal (150) for compression of the
seal around the piston (130).
6.- The thermostatic element according to claim 3 or claim 5, characterized in that
said surface (143) of the guide (140) is substantially spherical and of revolution around the
5 axis (X-X), and in that said raised portion forms a string (144) centered on the axis (X-X).
1 - The thermostatic element according to any one of claims 1 to 3 and 6 inasmuch
as it depends on claim 3, characterized in that the over-compression means comprise at
least one washer (270) in addition to the anti-extrusion washer (260), which is mounted
coaxially around the piston (230) and which is axiaily interposed either between the guide
10 (240) and the anti-extrusion washer, or between the anti-extrusion washer and the first part
(252) of the seal (250).
8.- The thermostatic element according to claim 1, characterized in that the overcompression
means consist of at least one washer (270) in addition to the anti-extrusion
washer (260), which is mounted coaxially around the piston (230) and which is axially
15 interposed either between the guide (240) and the anti-extrusion washer, or between the
anti-extrusion washer and the first part (252) of the seal (250).
9.- The thermostatic element according to claim 7 or claim 8, characterized in that the
or each additional washer (270) is individually identical to the anti-extrusion washer (260).
10.- The thermostatic element according to any one of claims 1 to 3, 6 inasmuch as it
20 depends on claim 3, 7 and 9 inasmuch as it depends on claim 7, characterized in that the
over-compression means (355) are partially borne by the first part (352) of the seal (350),
while being integral with that part of the seal.
11.- The thermostatic element according to claim 10, characterized in that the overcompression
means comprise a bead (355), which is provided radially protruding inward from
25 the wall of the through hole (351), centered on the axis (X-X) and delimited by the seal (350)
to receive the piston (330), and which is canceled out by radial crushing when the piston is
received in the through hole in the assembled state of the thermostatic element (301).
12.- The thermostatic element according to claim 1, characterized in that the overcompression
means (355) are exclusively borne by the first part (352) of the seal (350), while
30 being integral with that first part of the seal.
13.- The thermostatic element according to claim 12, characterized in that the overcompression
means consist of a bead (355), which is provided radially protruding inward
from the wall of the through hole (351), centered on the axis (X-X) and delimited by the seal
(350) to receive the piston (330), and which is canceled out by radial crushing when the
35 piston is received in the through hole in the assembled state of the thermostatic element
(301).
12
14.- The thermostatic element according to any one of the preceding claims,
characterized in that the anti-extrusion washer (160; 260; 360) has a rigidity greater than that
of the seal (150; 250; 350), but less than that of the cup (110; 210; 310), the piston (130;
230; 330) and the guide (140; 240; 340).
5 15.- The thermostatic element according to ciaim 14, characterized in that the cup
(110; 210; 310), the piston (130; 230; 330) and the guide (140; 240; 340) are made from
metal materials, the seal (150; 250; 350) is made from rubber, and the anti-extrusion washer
(160; 260; 360) is made from PTFE.