RIVET FOR BLIND FASTENERS, ASSOCIATED SETTING TOOL AND
METHOD FOR SETTING SUCH A RIVET
The present invention concerns blind fasteners, i.e. fasteners installed
5 through structures to be assembled from only one side of the assembly,
normally known as the "accessible" side. These fasteners are used for
example for assembling the structures of an aircraft.
In particular, the present invention concerns a rivet for a blind fastener,
of the type comprising a screw with a handling element, a breaking groove
10 designed to hold under a tensile stress and break under a torsional stress, a
head separated from the handling element by the breaking groove, a smooth
shank and a threaded part, and a sleeve comprising a collar able to receive
the screw head, and a tubular shank comprising an internal thread intended
to come into engagement with the threaded part of the screw. This type of
15 rivet is known for example from documents EP 1 635 994 and US 3,236,143.
The invention also concerns a setting nose for installation of such rivets.
To increase the production rate of aircraft and reduce the assembly
costs, manufacturers seek to automate the assembly process with robots
equipped with a nose assembly. In contrast to a human operator who can
20 grip a rivet of complex shape and introduce it without difficulty into a bore, a
robot can only install a fastener correctly if, before introduction of the rivet
into the structure, the axes of the setting nose and the rivet are strictly
coaxial. Known rivets for blind fasteners and known setting noses do not
allow such a coaxiality to be achieved. When the rivets are inserted in the
25 setting nose, the ends of the rivets have a significant angular deviation from
the axis of the setting nose. Therefore when the robot attempts to introduce
the rivet into a borehole opposite which it is positioned, the end of the rivet
hits against the structure and cannot be introduced into the borehole.
The aim of the invention is to resolve the drawbacks of the rivets of the
30 prior art, and in particular to provide a blind rivet and an setting tool which
allows a robust automation of installation.
For this, the rivet according to the invention is of the abovementioned
type, such that the handling element of the screw comprises a first handling
portion able to guide the introduction of the rivet in an setting tool, and a
second handling portion able to transmit a torque, the two handling portions
5 being separated by a blocking portion able to limit an axial movement of the
rivet in an setting tool.
Such a rivet may be gripped and held firmly by a setting nose such
that its axis is virtually coaxial with the axis of the setting nose.
The device according to the invention also preferably has at least one
10 of the following characteristics:
- the blocking portion is cylindrical and is linked to each handling portion by
a radiused portion,
- the sleeve comprises two welded elements,
- the sleeve comprises a zone for bulb formation with an elastic resistance
15 less than the elastic resistance of the rest of the sleeve,
- the sleeve comprises at least one compression groove made on an outer
portion of the tubular shank of the sleeve between the collar and the zone
for formation of the bulb,
- the torque is transmitted by means of splines, polygonal faces or a
20 cylindrical face,
- the first handling portion comprises a chamfer,
- the sleeve comprises an end portion opposite the collar, with outer
diameter smaller than the outer diameter of the shank.
The invention also concerns a setting nose for installation of a blind
25 rivet. The setting nose comprises a cylindrical body with a pierced front face,
a tubular sheath arranged inside the body, a mouth piece arranged inside the
sheath and defining an inner passage. The mouth piece comprises two
receiver portions for the handling element of the rivet, with a form
complementary to said handling portions, at least one of the receiver portions
30 being able to transmit a torque. Said receiver portions are axially separated
by a median portion comprising at least one element movable radially in the
inner passage and able to limit an axial movement of the rivet. Such a setting
nose allows the rivet to be held firmly, coaxial with the axis of the setting
nose. It also allows application of a high traction force to the rivet and
application of a rotational torque to the same rivet.
The setting nose according to the invention also preferably has at least
5 one of the following characteristics:
- the torque is transmitted by means of grooves, polygonal faces or a roller
cage,
- the median portion comprises at least one housing in which the radially
movable element is housed,
10 - an elastic means radially compresses the movable element towards the
inside of the mouth piece,
- the mouth piece is movable axially and in rotation inside the sheath.
The invention also concerns a method for installation of a blind rivet
according to the invention using a setting nose according to the invention,
15 comprising a first step of engagement of the setting nose with the handling
element of the screw, a second step of axial traction on the handling element
and formation of a bulb on the sleeve, a third step of screwing of the screw
into the sleeve and breakage of the handling element of the screw at the
level of the breaking groove. During the step of engagement of the setting
20 nose with the handling element of the screw, a radially movable element
limits an axial movement of the rivet in the setting nose.
According to another characteristic of the installation method
according to the invention, during the steps of bulb formation, screwing of the
screw and breakage of the handling element, the handling portions of the
25 screw are contained in the receiver portions of the mouth piece, the blocking
portion of the screw rests against the movable element, and the mouth piece
is contained inside the sheath so as to prevent any radial movement of the
movable element.
Further aims, characteristics and advantages of the invention will
30 appear from the description of exemplary embodiments of the invention,
which is given in conjunction with the drawings in which:
figure 1 is an isometric view of a rivet according to a first embodiment
of the invention, in an uninstalled state,
figure 2 is a cross-section view of a rivet according to a first
embodiment of the invention, in an uninstalled state,
5 figure 3 is a cross-section view of a rivet according to a first
embodiment of the invention, in an installed state,
figure 4 is a view of a rivet according to a second embodiment of the
invention, in an uninstalled state, comprising a sleeve formed from two
welded sleeve elements,
10 a figure 5 is a view of a rivet according to a third embodiment of the
invention, in an uninstalled state, comprising grooves made in an outer
portion of the sleeve,
figure 6 is a view of a rivet according to a fourth embodiment of the
invention, in an uninstalled state, comprising handling portions of
different forms,
figure 7A is a cross-section view of a setting nose for a rivet according
to a first embodiment of the invention,
figure 7B is a cross-section view of a setting nose according to a
second embodiment,
20 figure 7C is an isometric view of a perimetric spring used in the setting
nose of figure 7B,
figure 7D is a section along axis 7D-7D of figure 78,
figures 8 to 15 are cross-section views of a rivet in figures 1 to 3, and
of the setting tool in figure 7A, illustrating the different steps of setting
the rivet.
To facilitate understanding of the drawings, only the elements
necessary for comprehension of the invention has been shown. The same
elements carry the same references from one drawing to another.
With reference to figures 1 to 3, a rivet 10 according to one
30 embodiment of the invention comprises a screw 12 and a sleeve 14. The
screw 12 comprises a handling element 16 intended to break on installation
of the rivet, a breaking groove 18, a countersink head 20, a smooth
cylindrical shank 22, a transition portion 24 and a threaded portion 26. The
transition portion 24 allows the cylindrical shank 22 to be connected to the
threaded portion 26, and has a maximum diameter smaller than the diameter
5 of the cylindrical shank 22. The transition portion 24 is here depicted in
curved form but may assume a conical form.
The handling element 16 comprises a first handling portion 28, a
blocking portion 30 and a second handling portion 32. At its free end, the first
handling portion 28 has a chamfer 34 which facilitates centring and
10 introduction of the handling element 16 in a setting nose. In this example,
each handling portion 28, 32 comprises torque transmission means in the
form of twenty-four splines 36. These splines are arranged axially over a
cylindrical part of the outer periphery of each handling portion 28, 32,
distributed regularly and aligned axially to each other. The two handling
15 portions 28, 32 have a function of centring the fastener in a setting nose and
transmitting the torque between the setting nose and the fastener. The use of
a large number of splines on the first portion 28 associated with the chamfer
34 helps automatic engagement.
The centring achieved by the double spline system allows adjustment
20 of the axis of the rivet 10 with the axis of the setting nose, which is itself
adjusted by the robot to the axis of the drilling in the structure to be
assembled. Thus such a handling element 16 allows a robot to introduce the
rivet 10 into a drilling without interference or damage on the structure.
Without such an axial alignment, introduction of the rivet by a robot into a
25 drilling of the structure to be assembled would be impossible.
The breaking groove 18 is dimensioned so that it has the smallest
diameter of the screw 12 able to support a given traction stress on installation
and break under a given torsional stress.
The blocking portion 30 comprises a smooth cylindrical median part
30 and two concave radiused portions 30A and 308, linked respectively to the
handling portions 28, 32. The diameter of the smooth cylindrical part of the
blocking portion 30 is smaller than the diameter of the handling portions 28,
32 but greater than the smallest diameter of the breaking groove 18. The
blocking portion cross-section is therefore greater than the cross-section of
the breaking groove. The radiused portions 30A, 30B ensure the stop of the
handling element in a setting tool in the axial direction, blocking any axial
5 movement of said rivet during installation.
The length of the smooth shank 22 is selected as a function of a
thickness range of the structures to be assembled, varying between a
minimum thickness and a maximum thickness.
The screw 12 is inserted with clearance in a sleeve 14 which
10 comprises a widened collar 40 able to receive the countersink head 20 of the
screw, and a tubular shank 42. Before installation of the rivet 10 in a
structure, the outer surface of the tubular portion 42 is cylindrical and at its
end opposite the collar 40 has a cylindrical portion 44 of reduced outer
diameter, facilitating insertion of the rivet 10 in a bore. This thinner portion 44
15 is optional and the sleeve may have a constant outer diameter over the entire
length of the tubular portion 42.
The tubular shank 42 has a smooth cylindrical inner surface 46 and a
threaded inner surface 48 arranged at the end of the sleeve 14 opposite the
collar 40. The threading of the screw 12 and the internal threading of the
20 sleeve 14 are complementary. These are for example threads to standard
AS8879, commonly used for aeronautical fasteners.
The total length the sleeve 14 is divided into three successive,
adjacent zones performing separate functions. A first zone G, called the
clamping zone, comprises the collar 40 and a portion of the tubular shank 42
25 with a smooth inner surface 46, corresponding to a minimum thickness of the
structure to be assembled.
A second deformation zone U extends over the rest of the tubular
shank 42 with a smooth inner surface 46. This zone U, when the rivet 10 is
not installed, covers the remaining portion of the smooth shank 22 of the
30 screw, the transition zone 24 and a threaded portion 26. The zone U of the
sleeve is intended to be deformed, to form a bulb which will rest on the blind
side of the structures to be assembled. To facilitate formation of the bulb, the
zone U may be annealed in annular fashion, for example by means of an
induction machine, or comprise a shoulder (not shown) over a portion of the
smooth inner surface 46 of the sleeve, reducing the thickness of the sleeve
over the length of this zone.
5 The third zone L of the sleeve extends over the entire threaded portion
of the tubular shank 42. Its function is to prevent any translation movement
between the sleeve and the end of the screw, and allow the screw to be
screwed into the sleeve. When the rivet is not installed, this zone L is in
contact with an end portion of the thread 26 of the screw 12.
10 Figure 3 shows the rivet 10 of figures 1 and 2 in the installed state in
two structures 50, 52 to be assembled. The handling element 16 has been
broken at the level of the breaking groove 18, so that only the head 20 of the
screw and the collar 40 of the sleeve remain, together forming the head of
the rivet and embedded in a countersinking previously made in an accessible
15 face 54 of the structure 50. The first zone G of the sleeve 14 is fully
embedded in the structures 50, 52. The second zone U of the sleeve is
deformed and comprises a bulb 58, one face of which is in contact with the
blind side 56 of the structure 52 opposite the accessible side 54. The tension
set between the rivet head 20, 40 and the bulb 58 keeps the structures 50,
20 52 assembled. The third zone L of the sleeve, in the installed position, covers
a portion of the thread 26 of the screw adjacent to the transition portion 24.
The screw is for example made of a titanium alloy Ti6A14V coated with
a layer of lubricant, and the sleeve is for example made of passivated steel
A286. In the second annealed zone U, the strength is around 600 MPa,
25 whereas the strength of the first and third zones G and L is around 1200
MPa.
Figure 4 is a view of a rivet 10A according to a second embodiment of
the invention. In figure 4, elements identical to those of figures 1 to 3 retain
the same references, different elements comprise the same reference to
30 which the letter A has been added. The only difference between the rivet of
figure 4 and the rivet of figures 1 to 3 lies in the sleeve 14A, which in the
second embodiment is formed from two elements 14A' and 14A" welded
together.
The first sleeve element 14A' comprises an enlarged collar 40A' and a
tubular portion 42A' of smooth inner surface, able to cover a smooth shank
5 portion 22 of the screw, corresponding to the minimum thickness of the
structure to be clamped. The total length of this first sleeve element 14A' has
substantially the same length G as the first zone of the sleeve 14 of the rivet
described in connection with figures 1 to 3. The sleeve element 14A' is for
example made of work-hardened and age-hardened steel A286, with a
10 strength of 1200 MPa.
The second sleeve element 14A" comprises a tubular portion 42A" of
sufficient length to cover the remaining smooth shank portion 22, the
transition portion 24 and the majority of the thread 26 of the screw. This
second element has a length equal to the sum of the lengths of the second
15 and third zones U and L of the sleeve 14 of the rivet 10 described in
connection with figures 1 to 3. In the same way as described above, the
second sleeve element 14A" is locally annealed or thinned over the second
zone L, so as to have a lower strength allowing the formation of the bulb. The
sleeve element 14A" is for example made of annealed stainless steel, with a
20 strength of 600 MPa maximum. Other materials or treatments may be used.
The two sleeve elements 14A' and 14A" are welded, for example by
means of welding by laser, electron beam or friction.
The advantage of using two sleeve elements is to facilitate production
of the sleeve 14A, for example by reducing the inner lengths to be machined
25 and the associated difficulties for obtaining tight tolerances, without
significantly increasing the cost. A second advantage is to allow production
on an industrial scale, and hence at low cost, of a large number of second
elements 14A" of identical lengths, and to weld them to first elements 14A' of
different lengths but the same diameter, thus adapting to different
30 thicknesses of structures to be clamped.
Figure 5 is a view of the rivet 10B according to a third embodiment of
the invention. In figure 5, elements identical to those of figures 1 to 3 retain
the same references, while different elements comprise the same reference
to which the letter B has been added. The only difference between the rivet
of figure 5 and the rivet of the previous figures is that the sleeve 14B
comprises two annular grooves 146 and 148 made on the outer surface of
5 the smooth tubular portion 428 of the sleeve 14B, arranged on the first zone
G, between the widened collar 40B and the second zone U for bulb
formation.
Because of their arrangement over a zone of the sleeve in contact with
the inner wall of a bore of structure, the annular grooves 146 and 148
10 compress between the sleeve 14B and the structure when a traction force is
applied to the screw to form a bulb. On compression, the grooves thus allow
compensation for variations in form and dimension of the bulb due to the
different thicknesses which may be clamped by a rivet 10B of a given length.
In particular, the grooves allow syskmak formation of a single bulb of
15 satisfactory diameter systematically on contact with the blind face of the
structures to be assembled, irrespective of the thickness to be clamped, over
the entire clamping range of the fastener. The number of grooves, their
shape and depth may vary over the length of the first zone G as a function of
the length of the zone G, the thickness of the sleeve and its outer diameter.
20 Figure 6 is a view of a rivet 10C according to a fourth embodiment of
the invention. In this embodiment, the first portion 28C of handling element
16C is a cylinder and comprises a chamfer 34C with the same function as the
chamfer 34 of rivet 10. The second handling portion 32C comprises
polygonal faces 36C distributed over its periphery. In this example, the first
25 handling portion 28C has a function of centring and guiding the handling
element in a setting tool, while the second handling portion 32C has a
function of transmitting torque between the setting tool and the rivet 10C. The
diameter of the first handling portion 28C is here less than or equal to the
maximum diameter of the second handling portion 32C. The length of the first
30 handling portion 28C in the axial direction is greater than the length of the
second handling portion 32C, in particular to reduce the angular deflection at
the end of the rivet because of an increase in the contact surface between
the setting tool and the second portion. This configuration shown in figure 12
allows alignment of the axes of the rivet and the setting nose with excellent
precision of the order of one degree. The blocking portion 30C is identical to
the blocking portion of the rivet 10 and performs the same function as a stop
5 in translation of the rivet 10C in a setting tool. The sleeve 14C comprises, at
the opposite end to the collar, a chamfer 44C which facilitates insertion of the
rivet in a borehole and absorbs a slight angular clearance between the axis A
of the rivet 10C and the axis of the setting nose.
Figure 7A is a cross-section view of the setting nose 60 which may be
10 used on a setting tool and is suitable for installing a rivet 10, 10A or 10B
described above. The setting nose 60 comprises a hollow cylindrical body 62
with a front face 64 intended to come into contact with the accessible side of
a structure. The front face 64 is pierced in its centre with an opening 66 of
sufficient diameter to allow passage of the handling element 16 and the head
15 20 of the screw 12. The cylindrical body 62 receives in its interior a hollow,
cylindrical, fixed sheath 68. The sheath 68 is arranged in the body 62 so as
to provide an inner annular space E at the front end of the body 62 close to
the front face 64.
A mouth piece 70 is arranged inside the sheath 68 and is able to move
20 axially and in rotation inside the sheath 68. The mouth piece 70 comprises an
inner wall 70A delimiting a passage 72 which extends axially over the entire
length of the mouth piece. The mouth piece 70 comprises a front end 74, the
outer frustoconical surface of which is housed in the opening 66 of the body.
The inner surface of the front end 74, forming a front end of the passage 72,
25 comprises a first receiver portion 76 with drive surfaces 80 complementary to
the splines 36 of the handling portions 28, 32 of the screw. The mouth piece
70 comprises a second receiver portion 78 in the passage 72, arranged
axially at a distance from the first portion 76. The second receiver portion 78
also comprises drive surfaces 80 complementary to the splines 36 of the first
30 handling portion 28 of the screw. In this example, the drive surfaces 80
consist of twenty-four axial splines made on the inner surface of the wall 70A
of the mouth piece. The splines are continuous from the front end of the
mouth piece 70 to the opposite rear end. They are distributed regularly over
the inner surface of the wall 70A and correspond to the arrangement and
number of splines 36 of the handling element of the screw. The radial
dimensions of the splines of the setting nose correspond to the radial
5 dimensions of the splines of the screw, within a slight clearance allowing
translation movements in the axial direction between the screw and the
mouth piece.
The two receiver portions 76, 78 are separated by a median portion 82
in which four housings 84 are produced radially through the full width of the
lo wall of the mouth piece 70, opening into the passage 72. An element 86,
movable in the radial direction, is arranged in each housing 84. The movable
elements 86 are typically made of high hardness steel. They comprise an
inner surface 88 of toric form complementary to the blocking portion 30 of the
handling element 16 of the screw, and an outer cylindrical face 90 able to
15 slide in the sheath 68. An elastic means (not shown) is arranged in annular
fashion in a groove 92 made on the outer face of the movable elements and
the outer face of the mouth piece. The elastic element tends to compress the
movable elements radially towards inside of the mouth piece 70 in the inner
passage 72. The movable elements allow variation of the inner diameter of
20 the median portion 82 depending on the radial position they adopt. In the
rest, or zero spacing, po s,it-ion the movable elements 86
open into the passage 72. The inner diameter of the median portion 82 is
then less than the smallest diameter of the receiver portions 76, 78. This
inner diameter corresponds to the outer diameter of the cylindrical part of the
25 blocking portion 30 of the screw 16. In the maximum spacing position, the
movable elements are pressed inside the housings 84 towards the outside of
the mouth piece 70, such that the inner diameter of the medium portion is at
least equal to the largest diameter of the receiver portions 76, 78.
The inner wall 70A between the second receiver portion 78 and its
30 rear end 96 is smooth and has a diameter at least equal to the largest
diameter of the receiver portions 76, 78 so as to allow removal of the
handling element 16 once broken.
In general, over the first receiver portion 76, the setting nose
comprises a surface with a form suitable for receiving the handling portions
28, 32 of the screw 12, since these two portions slide inside the first portion
76 of the setting tool. Over the second receiver portion 78, the setting nose
5 60 comprises a surface with a form complementary to the first portion 28 of
the handling element 16 of the screw which is housed fully in this receiver
portion.
Figure 7B shows a setting nose 60C suitable for installing a rivet IOC,
comprising a body 62C, a frustoconical sheath 68C and a cylindrical mouth
10 piece 70C. The nose 60C comprises a first receiver portion 76C with twelve
splines equivalent to the twelve splines of the second handling portion 34C of
the rivet 10C. The nose also comprises a second receiver portion 78C with a
smooth cylindrical inner surface, with inner diameter identical -within a given
clearance - to the outer diameter of the first handling portion 28C of the rivet
15 10C. In this example, the movable elements 86C have a cylindrical outer
surface 90C without groove, and are held in place by an elastic means 98
extending between the outer surface of the sheath 68C and the inner surface
of the body 62C.
Figure 7C is an isometric view of the perimetric spring 98 visible on
20 figure 7B. The spring 98 comprises a circular end 100, the inner diameter of
which sits without clearance on the outer surface of the sheath 68C. Six
flexible arms 102, regularly distributed, extend from the end 100. Each
flexible arm, at an end opposite the circular end, terminates in an end portion
104 in an arc covering an angular surface of 60". In the rest position, the
25 assembly of six end portions 104 forms a circular end of inner diameter
smaller than the outer diameter of the median portion 82C. In this example,
the spring 98 is mounted on the sheath 68C such that each arcuate portion
104 has a part resting on the median part 82C and on a moveable element
86C (figure 7D). Thus when a movable element 86C moves radially towards
30 the outside, only a part of each end portion 104 is subjected to a radial force.
Such a spring 98 is made of heat treated and hardened steel, is significantly
stronger than an elastic part of rubber and will perform a large number of
installation cycles without requiring maintenance. This spring does not
become oval, in contrast to a spring with one or more windings, and can
exert a compressive force on the movable elements 86 in a very restricted
annular space.
5 The method of installing a rivet 10 described in relation to figures 1 to
3 in a structure S is illustrated in figures 8 to 15. For reasons of simplification,
only a single structure S is depicted but it is understood that this structure is
composed of several structural sub-elements to be assembled.
Also the installation method described below is precisely the same for
10 installing a rivet IOA, 10B or 10C described above.
In uninstalled state, the rivet 10 is for example arranged in a container
P and is gripped by a robot provided with a setting nose 60 described above.
As illustrated on figure 8, the setting nose 60 is advanced in the direction of
the handling element 16 of the screw (arrow FI) until it comes into contact
15 therewith. Guided by the chamfer 34 of the handling element, the splines 36
of the first handling portion 28 penetrate axially into the splines 80 of the first
receiver portion 76 of the setting nose 60. The chamfer 34 pushes the
movable elements 86 radially towards the outside as the setting nose
approaches the container and the handling element 16 of the rivet advances
20 in the mouth piece 70.
The spacing between the movable elements is at a maximum when
the first handling portion 28 is arranged between the two receiver portions 76,
78 of the setting nose as illustrated on figure 9.
When the first handling portion 28 enters into the second receiver
25 portion 78 of the tool (figure lo), the movable elements return radially
towards the inside to come into contact with the blocking portion 30 of the
rivet 10 under the effect of the elastic ring housed in the groove 92. The
handling element 16 of the screw is then fully contained in the setting nose
60. In this position, the first handling portion 28 is inserted in the second
30 receiver portion 78 of the setting nose, the blocking portion 30 is held by the
inner surfaces 88 of the movable elements, and the second handling portion
32 is inserted in the first receiver portion 76 of the setting nose. The mouth
piece 70 is then pushed back such that the movable elements come to rest
against the radiused portion 30A. Since the sheath 68 is immobile inside the
body 62, the cylindrical outer surface 90 of the movable elements gradually
slides into the sheath 68. The movable elements 86 can then no longer move
5 in the radial direction (figures 10 and 11). Under traction, the stroke of the
movable elements is limited by the radiused portion 30A of the blocking
portion.
The handling element 16 of the screw is blocked in rotation in the
mouth piece because of the engagement of the complementary surfaces of
10 the handling element of the screw and the receiver portions able to transmit a
torque, and also blocked in translation because of the engagement of the
movable elements and the blocking portion of the screw.
The centring associated with the blocking of the rivet motion in the
setting tool ensures support with a minimum angular clearance at the end 44
15 of the rivet, such that the rivet axis is substantially coaxial with the axis of the
setting nose. As shown on figure 11, the axis of rivet 10 and the axis of the
mouth piece 70 coincide or substantially coincide, with an angular clearance
of less than a few degrees. The robot can then move to face a bore made in
the structure S and align itself, for example by optical recognition. Thus the
20 rivet 10 is substantially aligned with the axis of the bore.
The rivet 10 is then placed by the robot through the bore from the
accessible side, the reduced diameter 44 at the fastener end (or the chamfer
44C for the rivet 10C) helping to centre and guide the rivet in the bore. The
bore here comprises a countersinking able to receive the head of the rivet,
25 comprising the collar of the sleeve 40 and the head 20 of the screw. When
the rivet head is in contact with the countersinking, the threaded end 26
protrudes from the structure on the blind side. In the position shown in figure
12, the handling element 16 of the screw is fully contained within the handling
nose 60, and the front face 64 rests against the collar 40 of the sleeve and
30 the accessible face of the structure S.
The first step of installation of the rivet 10 consists of forming a bulb.
For this, the mouth piece 70 performs an axial movement in the direction
opposite the structure - in the direction of arrow F2 - inside the body 62.
During this movement, the outer surface 90 of the movable elements 86
slides in the sheath 68 until the movable elements are fully captive in the
mouth piece 70. Thus the blocking groove 30 of the screw is firmly held by
5 the movable elements 86 which limit the axial motion of the rivet. On figure
12, the mouth piece 70 pulls on the handling element 16 of screw 12, the
collar 40 of the sleeve 14 being immovably held in structure by the front face
64.
The mouth piece 70 continues to move axially, driving the threaded
10 portion 26 of the screw and the internal thread 48 of the sleeve towards the
blind side of the structure S until a bulb 58 is formed, one face of which
comes to rest against the blind face (figure 13). The head 20 of the screw 12
is then contained in the annular space E of the setting nose.
The second step consists of screwing the screw 12 into the sleeve 14
15 to bring the head 20 of the screw into the collar 40 of the sleeve. The traction
applied to the mouth piece 70 is stopped, and a rotational movement is
applied to the mouth piece which is now free to move in translation in the
direction of the structure (arrow F3 on figure 14). Figure 14 illustrates the end
of this movement: the mouth piece 70 has returned to its initial place in the
20 sheath 68 such that the movable elements 86 are again free to move radially
within the stress limits of the elastic means. The movable elements have
stopped against the second radiused portion 30B of the blocking zone. The
head 20 of the screw rests in the collar 40 of the sleeve. The threaded
portion 26 of the screw largely protrudes from the thinner portion 44 of the
25 sleeve 14.
The third step consists of finalising -the installation of the rivet by
breaking the handling element 16 of the screw. Once the head 20 of the
screw rests in the collar 40 of the sleeve, the mouth piece 70 continues to
turn. The torque is transmitted to the screw through the two handling portions
30 30, 32 of the screw. The breaking groove 18 is designed to break above a
certain torque level. It breaks once this threshold is reached, leaving the
head 20 flush with the accessible surface of the structure S.
The handling element 16, once broken, is evacuated via the back or
the front of the setting nose. Figure 15 shows in exploded view the setting
nose 60, the broken handling element 16 and the rivet 10 installed in the
structure S.
5 The setting nose 60 is then withdrawn to move to the next rivet to be
gripped. The installation sequence may start again.
The rivet and the setting nose according to the invention are not
structurally limited solely to the examples described above. For example, the
rivet head may protrude instead of being countersunk. The handling portion
10 or portions 30, 32 able to transmit torque may comprise twelve splines,
polygonal faces or any other means allowing transfer of a torque. It may also
be of circular section. In this case the setting nose comprises, in the
complementary receiver portion, a circular means for torque transmission
such as a roller cage.
15 The rivet may combine several embodiments described above. For
example, the sleeve 14 may comprise two welded sleeve elements 14A',
14A", and compression grooves 146, 148 on the outer surface of the first
element 14A'. As a variant, the sleeve 14 may comprise a single sleeve
element and an annular groove on its outer surface.
20 The blocking portion 30 may take different forms as long as they allow
blocking of the rivet movement in the setting tool. For example the blocking
portion may be cylindrical, of the same outer diameter as the adjacent
handling portions, and comprise a continuous circular or oblong opening able
to receive a movable element of the setting tool sliding radially.
25 The housings 84 and the movable elements 86 may vary in number
and in form, complementary to the form of the blocking portion 30 of the rivet.
The housings must allow the radial motion of the movable elements 86
around the handling element 16 of the screw on its insertion in the setting
nose 60. There may be only a single housing in which a single movable
30 element is housed, for example in the form of a fork with two branches able
to support a blocking portion of reduced outer diameter of rivets 10, IOA, 10B
or 10C described, or in the form of a pin sliding radially through an opening.
The movable elements 86 may also be replaced by balls or elements of
conical form.
The inner sheath 68 may be replaced by an annular shoulder made on
the inner surface of the body 62, arranged over a sufficient length to block
5 the movable elements 86 in the radial direction on traction of the screw to
form the bulb.
CLAIMS
1. Rivet (10, IOA, IOB, 10C) comprising a screw (12) with a handling element
(16), a breaking groove (18) designed to hold under a tensile stress and break
under a torsional stress, a head (20) separated from the handling element by
the breaking groove, a smooth shank (22) and a threaded portion (26); a
sleeve (14, 14A) comprising a collar (40) able to receive the head (20), and a
tubular shank (42, 42A, 428) comprising an internal thread (48) intended to
come into engagement with the threaded portion (26) of the screw,
characterized in that the handling element (16) of the screw comprises a first
handling portion (28, 28C) able to guide the introduction of the rivet into a
setting tool, and a second handling portion (28C, 32C) able to transmit a
torque, the two handling portions being separated by a blocking portion (30)
able to limit an axial motion of the rivet in a setting tool.
15
2. Rivet (10, IOA, IOB, 10C) according to Claim 1, wherein the blocking portion
comprises a cylindrical median portion and is connected to each handling
portion by a radiused portion (30A, 308).
20 3. Rivet (10A) according to Claim 1, wherein the sleeve (14A) comprises two
welded elements (14A', 14A").
4. Rivet (10, IOA, IOB, 10C) according to Claim 1 or 3, wherein the sleeve
comprises a zone (U) for bulb formation with an elastic strength less than the
elastic strength of the rest of the sleeve.
5. Rivet (10B) according to any of the preceding claims, wherein the sleeve
comprises at least one compression groove (146, 148) made on an outer
portion of the tubular shank (42) of the sleeve between the collar (40) and the
zone (U) for formation of the bulb (58).
6. Rivet (10, IOA, IOB, 10C) according to Claim 1, wherein the torque is
transmitted by means of splines with polygonal faces or a cylindrical face.
7. Rivet (10, IOA, IOB, 10C) according to Claim 1, wherein the first handling
portion (28, 28C) comprises a chamfer (34, 34C).
5 8. Rivet (10, IOA, IOB, 10C) according to Claim 1, wherein the sleeve comprises
an end portion (44, 44C) opposite the collar (40), with outer diameter smaller
than the outer diameter of the shank (42).
9. Setting nose (60, 60C) for installing a rivet (10, IOA, IOB, 10C) according to
10 any of the preceding claims, the setting nose comprising a cylindrical body
(62) with a pierced front face (64), a tubular sheath (68) arranged inside the
body, a mouth piece (70) arranged inside the sheath and defining an inner
passage (72), characterized in that the mouth piece (70) comprises two
receiver portions (76, 78; 76C, 78C) for the handling element (16) of the rivet,
with a form complementary to said handling portions (30), at least one of the
receiver portions being able to transmit a torque, said receiver portions being
axially separated by a median portion (82) comprising at least one element
(86) movable radially in the inner passage and able to limit an axial motion of
the rivet.
20
10. Setting nose (60) according to Caim 9, wherein the torque is transmitted by
means of splines (go), by means of polygonal faces or by a roller cage.
11. Setting nose (60) according to Claim 9, wherein the median portion (82)
comprises at least one housing (84) in which the radially movable element (86)
is housed.
12. Setting nose (60) according to Claim 9, wherein an elastic means (98) radially
compresses the movable element (86) towards the inside of the mouth piece.
30
13. Setting nose (60) according to Claim 9, wherein the mouth piece (70) is
movable axially and in rotation inside the sheath (68).
14. Method for installation of a rivet (10, IOA, IOB, 10C) according to any of
Claims 1 to 8, using a setting nose (60, 6OC) according to any of Claims 9
to 13, characterized in that the method comprises the steps of:
- engagement of the setting nose with the handling element (16) of the
5 screw,
- axial traction on the handling element (16) and formation of a bulb (58) on
the sleeve (14, 14A, 14B),
- screwing of the screw (12) into the sleeve and breakage of the handling
element of the screw at the level of the break groove (18),
10 characterized in that during the step of engagement of the setting nose with
the handling element (16) of the screw, a radially movable element (86) limits
an axial motion of the rivet in the setting nose.
15. Installation method according to Claim 14, characterized in that during the
15 steps of bulb formation, screwing of the screw and breakage of the handling
element, the handling portions (28, 32; 28C, 32C) of the screw are contained
in the receiver portions of the mouth piece (70, 70C), the blocking portion (30)
of the screw rests against the movable element (86), and the mouth piece (70,
70C) is contained inside the sheath (68, 68C) so as to prevent any radial
20 movement of the movable element (86).