Polygonal driving means with inbuilt collar
This invention relates to a polygonal driving means with an inbuilt
collar and fitted with socket faces.
The technical field of the invention relates, in a general manner, to that
of driving means. More particularly, the invention relates to nuts and screws
with inbuilt frustoconical-type collars.
In the prior art, the teaching particularly of model USD206402 is
known and describes a reinforced nut with a frustoconical collar, represented
in a schematic manner in figures 1A and 1B.
Figure 1A represents a front view of such a nut 1 and figure 1B
represents a side view with a partial cross-section of the same nut 1. The
cross-section is defined by planes A-A. The nut 1 comprises a shank 2 and a
frustoconical collar 3. A cylindrical inner wall 4 of the nut 1 is threaded and
may have a recess. Six buttresses 5 connect the collar 3 to the shank 2.
In the prior art, non-reinforced nuts with frustoconical collars are also
known, such as those represented in figures 2A and 2B. The same types of
geometries are found with regard to the screw heads.
Figure 2A represents in a schematic manner an oblique perspective
view of an example of a forged nut 5 with a frustoconical collar 6. A junction
between a hexagonal shank 7 and the frustoconical collar 6 of the forged nut
5 comprises a fillet present in the form of an elliptical rim 8. A circular base 9
of the cone of the collar 6 extends into a cylinder 10. When a wrench socket,
not represented, is threaded around the shank 7, one end of the socket abuts
against the elliptical rim 8. A height 11, separating a crest 12 of the elliptical
rim from an upper surface 13 of the forged nut 5, is effectively in contact with
the wrench socket during a tightening or loosening operation of the forged
screw 5; this is the wrenching height or useful height 11. The cylindrical inner
wall 4 of the forged nut 5 is threaded and may have a recess.
Figure 2B represents in a schematic manner an oblique perspective
view of an example of a machined nut 14 with a frustoconical collar 15. A
junction 16 between a hexagonal shank 17 and the frustoconical collar 15 of
the machined nut 14 is machined so as to form a fin and so that the shank 17
has perfectly rectangular sides. A circular base 18 of the cone of the collar 15
extends into a cylinder 19. When a wrench socket, not represented, is
threaded around the shank 17, one end of the socket abuts against the
junctions 16. A useful height 20, separating a junction 16 from an upper
surface 21 of the machined nut 14, is effectively in contact with the wrench
socket during a tightening or loosening operation of the machined screw 14.
The cylindrical inner wall 4 of the machined nut 14 is threaded and may have
a recess.
For nuts with identical dimensions, the useful height 11 of the forged
nut 5 is therefore shallower than the useful height 20 of the machined nut 14.
Due to the elliptical rims 8, the support surface with the appropriate wrench
socket is less significant, which reduces the transmissible torque.
Figure 2C schematically represents a side view of half of a forged nut
5 with a frustoconical collar 6 and half of a machined nut 14 with a
frustoconical collar 15 from the prior art. This figure shows, for the same
overall height 22, collars 15 and 6 to be different and the wrenching height 20
to be identical. In particular, the cylindrical part 10 is shallower than the
cylindrical part 19.
Figure 2D schematically represents a side view of half of a forged nut
5 with a frustoconical collar 6 and half of a machined nut 14 with a
frustoconical collar 15 from the prior art. This figure shows collars 15 and 6 to
be identical and the wrenching height 11 of the forged nut 5 to be shallower
than that 20 of the machined nut 14.
It has become apparent that the dimensions of the collar nuts of the
same nominal size, i.e. of the same inner threading, may vary according to
the method of manufacture. This also applies for all driving means such as
screw heads. This is why, in the following text, it must be remembered that
the invention relates to all driving means with an inbuilt collar.
It is initially advised that, if the useful wrenching height is to be kept
the same for both a forged driving means and a machined driving means, the
height of the shank must be increased by a length equal to the height of a
rim, the total height of the driving means therefore being increased to the
same extent.
This heterogeneity of shank heights for driving means intended for the
same use is a source of numerous technical problems.
Indeed, as the shank height of a forged driving means is greater than
that of a shank of a machined driving means, the forged driving means have
a greater volume, therefore a greater mass and more material, which is
problematic and costly with regard to their storage, transport and use, in
particular in aircraft.
If, on the other hand, the height of the collar is reduced, this reduction
is detrimental to the mechanical aspect, i.e. the strength of the collar.
Finally, as the forged driving means are generally produced in large
quantities compared to the machined driving means, the aforementioned
problems are all the more incapacitating.
On the machined version, numerous fins can be observed in a
transition zone between the hexagonal socket faces and the collar. These
fins originating from the machining process are not suited to forging. Indeed,
identical angular shapes cannot be forged as this creates material filling
problems. Furthermore, for the forged version, elliptical fillets replace the
machining fins to ease the filling of a die with the chosen material such as a
titanium alloy, stainless steel, nickel alloy or even an aluminium alloy.
It therefore follows that, for the same wrenching height and the same
height of the driving means, the machined driving means and the forged
driving means do not have the same collar height. The collar strength is
therefore weaker on a forged driving means.
In order to produce equal levels of strength between the machined
collar and the forged collar, either the height of the forged driving means
must be increased, which has the disadvantage of making it heavier than the
machined driving means, or the wrenching height reduced, which reduces
the transmissible torque for tightening and loosening operations.
The inbuilt-collar solution proposed by the invention is suited to all
modes of manufacture such as machining, forging, sintering, casting and
plastic injection moulding, and can be manufactured without adversely
affecting the dimensions of the driving means, its strength or its mode of
installation.
The main modification was provided to the collar, where a recess at
the bottom of each socket face avoids the need for elliptical rims produced by
the forging method.
Fillets are fitted between the socket faces and the sides of the
hexagonal shank of the driving means, preferably rays or ellipses or any
other form providing for a good flow of material during forging.
In the prior art, during a screwing or unscrewing operation of a driving
means using a power tool, the rotation speed of the driving means leads to a
significant increase in the temperature of the driving means, via friction.
This raised temperature is the source of various technical problems:
- the operator may burn himself/herself while manually holding the
screw or nut,
- the material on which the screwing operation is performed may
become damaged and deformed, above all if this is made out of composite
material such as that used in aeronautics,
- the coating, for example anticorrosion and/or lubricating coating,
covering the screw or nut, may become deteriorated, which is detrimental to
its efficiency,
- the braking system, applied to some nuts to prevent them from
loosening once fitted, may become degraded.
The invention has numerous advantages.
A recess made at the bottom of each socket face leads to a reduction
in the mass of the driving means. This recess does not affect the mechanical
strength of the driving means, as the hollowed out area is subject to very little
mechanical stress. Ideally, a driving means such as that represented in figure
10 corresponds to a maximal recess in terms of mass.
The design is universal, thus making all modes of manufacture
possible without requiring major dimensional changes. The wrenching height
no longer poses a problem and the mass remains identical.
A single-shaped driving means of the same nominal size, for whatever
method of manufacture, enables the driving means and its height to be more
easily recognised visually.
The star-shaped recesses produced on the collar can take several
different shapes, as represented in figures 3 to 10. Moreover, this type of
solution can be applied to a bi-hexagonal driving means.
The inbuilt collar according to the invention, due to its reduced mass
via recesses in the material, has increased thermal diffusion properties,
which reduces the amplitude and duration of the temperature rise of the
driving means during screwing and/or unscrewing operations, and resolves at
least in part the aforementioned problems.
Thus, the idea underlying the invention involves deleting the elliptical
rims 8 in order to create a useful height identical to the height of the shank. In
order to achieve this, the frustoconical collar is pushed in towards its centre
along the extension of the sides of the shank.
Via this invention, the same dimensions are obtained for driving
means in machined mode and forged mode, leading to an identical mass and
the same wrenching heights and therefore to identical transmissible torques.
The star-shaped collar solution proposed overcomes the restrictions
related to the method of manufacture with regard to the dimensions of the
driving means, and produces a reduction in mass with identical strength and
wrenching heights. The star shape enables a more significant tightening and
loosening torque to be transmitted by using a tool adapted to suit this shape.
The socket faces generated by the invention allow for the simple
production of different colourings or markings such as the part reference
number, a diameter marker or the material used, which up to now have been
difficult to produce on a driving means with a classic collar.
The invention therefore relates to a polygonal driving means with an
inbuilt collar, obtained by forging via a die or by machining, characterised in
that
- the collar comprises socket faces, hollowed out with regard to a
collar surface and aligned with the lateral sides of the driving means.
The invention also relates to a cylindrical tightening and loosening
wrench socket for a polygonal driving means according to the invention, the
wrench socket comprising a cavity with a polygonal hollow shank and an end
fitted so as to be abutted against an inbuilt collar of the driving means, the
end of the wrench socket having sides with shapes complementing those of
the collar so as to be pressed against the latter during the abutment,
characterised in that
- the collar comprises socket faces hollowed out with regard to a collar
surface and aligned with the lateral sides of a shank of the driving means.
The invention and its different applications will be better understood
after reading the following description and after examining the accompanying
figures. These are intended for purposes of illustration only and are not
intended to limit the scope of the invention. The figures show:
- figure 1A, previously described: a schematic representation of a front
view of an example of a reinforced nut from the prior art,
- figure 1B, previously described: a schematic representation of a side
view with a partial cross-section of the same example of a nut,
- figure 2A, previously described: a schematic representation of an
oblique perspective view of an example of a forged nut with a frustoconical
collar from the prior art,
- figure 2B, previously described: a schematic representation of an
oblique perspective view of an example of a machined nut with a
frustoconical collar from the prior art,
- figure 2C, previously described: a schematic representation of a side
view of half of a forged nut with a frustoconical collar and half of a machined
nut with a frustoconical collar from the prior art,
- figure 2D, previously described: a schematic representation of a side
view of half of a forged nut with a frustoconical collar and half of a machined
nut with a frustoconical collar from the prior art,
- figure 3A: a schematic representation of an oblique perspective view
of a first example of a nut with a driving means with a frustoconical collar
according to the invention,
- figure 3B: a schematic representation of a side view of the first
example of a nut with a driving means with a frustoconical collar according to
the invention,
- figure 3C: a schematic representation of an oblique perspective view
of a second example of a nut with a driving means according to the invention,
- figure 5: a schematic representation of an oblique perspective view of
a third example of a nut with a driving means according to the invention,
- figure 6: a schematic representation of an oblique perspective view of
a fourth example of a nut with a driving means according to the invention,
- figure 7: a schematic representation of an oblique perspective view of
a fifth example of a nut with a driving means according to the invention,
- figure 8: a schematic representation of an oblique perspective view of
a sixth example of a nut with a driving means according to the invention,
- figure 9: a schematic representation of an oblique perspective view of
a seventh example of a nut with a driving means according to the invention,
- figure 10: a schematic representation of an oblique perspective view
of a minimised model of a nut with a driving means according to the
invention,
- figure 11: a schematic representation of an oblique perspective view
of a wrench socket with a partial cross-section for the first example of a
driving means according to the invention,
- figure 12: a schematic representation of an oblique perspective view
of an eighth example of a nut with a driving means according to the invention,
fitted with a washer enabling swivelling,
- figure 13: a schematic representation of an oblique perspective view
of an example of a screw with a driving means according to the invention.
Figure 3A represents, in a schematic manner, an oblique perspective
view of a first example of a nut with a driving means 23 with a frustoconical
collar 6 according to the invention. In one example, the driving means 23 and
its embodiments represented in the following figures are obtained by forging
via a die. Alternatively, said driving means may also be obtained via another
mode of manufacture such as, for example, machining, casting, plastic
injection moulding and sintering, so as to produce driving means with an
identical use from whatever mode of manufacture. The driving means 23
comprises a polygonal shank, in this example hexagonal in shape 7 and a
frustoconical collar 6. According to the invention, the collar 6 is fitted with
hollowed out socket faces 24. In the example given in figure 3, the socket
faces 24 are planar. According to the invention, hollowed out means that a
portion of the side is misaligned inwards with regard to the frustoconical
curved surface. A circular base 18 of the cone of the collar 6 extends into a
cylinder 19. The driving means 23 comprises fillets 25 fitted between the
socket faces 24 and the flat lateral sides 70 of the shank 7. In a preferred
example, the driving means 23 and its embodiments described hereinafter
are made out of a titanium alloy and covered with an organic resin-based
coating containing polytetrafluoroethylene, also known as PTFE.
Alternatively, this may be made out of stainless steel, a nickel alloy or an
aluminium alloy. The cylindrical inner wall 4 of the machined driving means
23 is threaded and may have a recess.
Figure 3B schematically represents a side view of the first example of
a nut with a driving means 23 with a frustoconical collar 6 according to the
invention. Typically, the frustoconical surface of the collar 6 forms an angle of
at least forty-five degrees with the plane of the circular base 18 considered
as being horizontal.
Figure 3C schematically represents an oblique perspective view of a
second example of a nut with a driving means 26 according to the invention.
In this example, the driving means 26 comprises a hexagonal shank 7 and
has a hexagonal pyramidal collar 28. The planar socket faces 81 in this
example make up the collar 28. A hexagonal base 51 of the pyramid of the
collar 28 extends into a parallelepiped 27. The driving means 26 comprises
fillets 29 fitted between the socket faces 81 of the collar 28 and its flat lateral
sides 70. The cylindrical inner wall 4 of the machined driving means 26 is
threaded and may have a recess.
Figure 5 schematically represents an oblique perspective view of a
third example of a nut with a driving means 30 according to the invention. In
this example, the driving means 30 comprises a hexagonal shank 7 and a
semi-cylindrical 10, semi-frustoconical 50 collar and is fitted with socket faces
31 with regard to the frustum. In this example, the socket faces 31 are planar
with significant inclines. More precisely, the socket faces 31 intersect the
cylinder 10 at a periphery of a lower side 44 of the driving means 30. The
socket faces 31 have elliptical segments 45 and 46 at the junction with this
cylinder 10. Two adjacent socket faces 47 and 48, from all of the socket
faces 31, therefore join together at the junction 49 between the two elliptical
segments 45 and 46. Rather than comprising a fin corresponding to the
junction between these two socket faces 47 and 48, the collar 10 comprises,
at this junction, a portion of frustoconical connection surface 50, almost
triangular in shape, as its two longest sides 50.1 and 50.2 are elliptical with
very little curvature. The driving means 30 comprises fillets 32 fitted between
the socket faces 31 and the flat lateral sides 70. The cylindrical inner wall 4 of
the machined driving means 30 is threaded and may have a recess.
Figure 6 schematically represents an oblique perspective view of a
fourth example of a nut with a driving means 33 according to the invention.
The driving means 33 comprises a hexagonal shank 7 and a semi-
frustoconical 52, semi-rounded 53 collar fitted with socket faces 34 in the
form of lugs. A circular base 56 of the cone of the rounded part 53 extends
into a thin cylinder 57. The socket faces 34 are planar. The driving means 33
comprises fillets 35 fitted between the planar part 54 of the socket faces 34
and the flat lateral sides 70. An upper part 54 of the socket faces 34
intersects the frustoconical part 52 so as to leave one portion of frustoconical
connection surface 52.1 only, almost trapezium in shape as its two longest
sides 52.2 and 52.3 are elliptical with very little curvature. The lower part 55
of the socket faces 34 intersects the rounded part 53 and thus forms, at this
junction, an elliptical segment 58 with significant curvature, the crest 59 of
which almost touches the circular base 56. Alternatively, the socket face is
parallel to a cone's generator for the collar and thus forms, at the junction,
two rectilinear segments. The cylindrical inner wall 4 of the machined driving
means 33 is threaded and may have a recess.
Figure 7 schematically represents an oblique perspective view of a
fifth example of a nut with a driving means 36 according to the invention. The
driving means 36 comprises a hexagonal shank 7 and a frustoconical collar
60 fitted with concave socket faces 37. A circular base 56 of the cone of the
collar 60 extends into a thin cylinder 61. The socket faces 37 intersect the
frustoconical collar 60 and thus form, at these junctions, elliptical segments
62 and 67, the crests 63 and 68 of which almost touch the circular base 56.
Two adjacent socket faces 64 and 65, from all of the socket faces 37,
therefore join together at the junction 66 between the two elliptical segments
62 and 67 and form a concave fin 68 extending to a straight fin 69 separating
two flat sides 70 and 71 from the six sides of the hexagonal shank 7. The
cylindrical inner wall 4 of the machined driving means 36 is threaded and
may have a recess.
Figure 8 schematically represents an oblique perspective view of a
sixth example of a nut with a driving means 38 according to the invention.
The driving means 38 comprises a hexagonal shank 7 and a frustoconical
collar 72 fitted with concave socket faces 39. A circular base 73 of the cone
of the collar 72 extends into a thin cylinder 74. The socket faces 29 intersect
the frustoconical collar 72 and thus form, at these junctions, hemispherical
segments 75 and 76. Two adjacent socket faces 77 and 78, from all of the
socket faces 39, join together at a junction point 87 between the two elliptical
segments 75 and 76, said junction point 87 being on the same axis as a
straight fin 69 separating two flat sides 70 and 71 from the six sides of the
hexagonal shank 7. A lower crest 79 of the segment 75 almost touches the
circular base 73. An upper crest 87 of the segment 75 continuously joins the
side 70; i.e. without a fillet. The cylindrical inner wall 4 of the machined
driving means 38 is threaded and may have a recess.
Figure 9 schematically represents an oblique perspective view of a
seventh example of a nut with a driving means 42 according to the invention.
The driving means 42 comprises a bi-hexagonal shank 91 and a
frustoconical collar 92 fitted with twelve socket faces 95 in furrows 102. The
furrows 102 separate the socket faces 95 into two sides 103 and 104. The
sides of the shank 91 have a cylindrical part 93 and a concave part 94. The
socket faces 95 have a flat part 96 and a concave part 97. The socket faces
95 intersect the frustoconical collar 92 and thus form, at these junctions, saw-
toothed segments 98 and 99. Two adjacent socket faces 100 and 101 from
all of the socket faces 95 intersect the frustoconical collar 92 so as to leave a
small connection part 93 and 94 only of the twelve sides of the shank 91. The
cylindrical inner wall 4 of the machined driving means 42 is threaded and
may have a recess.
Figure 10 schematically represents an oblique perspective view of a
minimised model of a nut with a driving means 119 according to the
invention, corresponding to a maximal recess in the material, not adversely
affecting the mechanical strength, with buttresses 88 and 89 located on
either side of the alignment of a side 70 of the shank 120, large in height
compared to the previous embodiments of the driving means. Buttresses 88
and 89 are present in the form of two thin right-angled triangles. The
buttresses 88 and 89 are connected by their lower base via a thin, flat
hexagonal collar 90. The cylindrical inner wall 4 of the machined driving
means 119 is threaded and may have a recess.
Figure 11 schematically represents an oblique perspective view of a
wrench socket 131 with a partial cross-section according to the invention.
The wrench socket 131 has a semi-frustoconical 132, semi-cylindrical 133
outer shape. Such a wrench socket is intended for tightening and loosening
operations for one of the driving means 23, 26, 30, 33, 36, 38, 42, or 119
according to the invention, represented in the previous figures. In this
example, the wrench socket 131 comprises a cavity 134 with a polygonal
hollow shank 135, in this case hexagonal in shape, and an end 136 fitted so
as to be abutted against the frustoconical collar 6 of the driving means 23
represented in figure 3. The end 136 has two sides 137 and 138 with shapes
complementing those of the socket faces 24 and of the collar 6 of the driving
means 23 so as to be pressed against them during the abutment. Finally, the
wrench socket 131 comprises a square hollow shank 139 intended to
accommodate one end of a tightening and loosening wrench, not
represented.
Figure 12 schematically represents an oblique perspective view of an
eighth example of a nut with a driving means 140 according to the invention,
fitted with a washer 141 enabling swivelling, The driving means 140
comprises a hexagonal shank 7 and a frustoconical collar 142 fitted with
socket faces 147, in this case planar in shape. The socket faces 147
intersect the frustoconical collar 142. The cylindrical inner wall 4 of the
machined nut 140 is threaded and may have a recess. The collar 142 has a
spherical lower support surface 143, complemented and connected, in the
same way as a ball and socket joint, with the washer 141 enabling swivelling.
The washer 141 has a diameter greater than that of the collar 142. In one
example, the section of the washer 141 is rectangular or even square in
shape, from which an inner corner 144 in contact with the lower side 143 of
the collar 142 has been bevelled into an arc of a circle. The washer 141
therefore has a concave housing 145 in the shape of a portion of a sphere,
so as to accommodate the spherical support collar 142. Therefore, when the
driving means 140 is screwed around a screw to tighten an element, an inner
side 146, in this case flat in shape, of the inserted washer 141 is supported
by said element, even if the screw axis is not perpendicular to the surface of
the element being tightened in the tightening zone. The misalignment of a
central axis of the washer 141 with regard to the screwing axis can have a
value of more or less ten degrees.
Figure 13 schematically represents an oblique perspective view of an
example of a screw 148 with a driving means according to the invention. The
screw 148 comprises a shaft 149 of which at least one part 150 is threaded,
and a polygonal driving means 151 present in the form of a screw head. The
head 151 comprises a polygonal shank 7, in this case hexagonal in shape,
and an inbuilt frustoconical collar 152 obtained by forging using a die or by
machining. In order to optimise the wrenching height, according to the
invention, the collar 152 comprises socket faces 153, in this case planar in
shape, aligned with the lateral sides of the shank 7 of the head 151 of the
screw 148. The socket faces 153 intersect the frustoconical collar 152 and
thus form, at these junctions, elliptical segments 154 and 155. A circular
lower side 156 of the collar 152 is preferably flat so as to press against an
element being tightened. All of the profiles used for the driving means in
figures 3 to 11 can also be used for the head 151 of the screw 148, A classic
washer or a washer such as that seen in the previous figure in the case of a
spherical support collar, can be inserted between the lower side 156 and said
element being tightened.
WE CLAIM
1 - A polygonal driving means (23; 26; 30; 33; 36; 38; 42; 119; 140; 151)
with an inbuilt collar (6; 28; 50; 52; 60; 72; 92; 142; 152), characterised in that
- the collar comprises socket faces (24; 31; 34; 37; 39; 41; 43; 81; 97; 147;
153) hollowed out with regard to a collar surface (50; 52) and aligned with the
lateral sides (70; 71; 93; 96) of a shank (7; 91) of the driving means.
2 - A driving means according to claim 1, characterised in that
- the socket faces are planar or concave.
3 - A driving means according to one of claims 1 to 2, characterised in that
- it is obtained by forging via a die, machining, casting, sintering or plastic
injection moulding.
4 - A driving means according to one of claims 1 to 3, characterised in that
- the shank is hexagonal or bi-hexagonal and the collar is frustoconical.
5 - A driving means according to one of claims 1 to 4, characterised in that
- it comprises fillets fitted between the socket faces of the collar and the
lateral sides of the shank.
6 - A driving means according to one of claims 1 to 5, characterised in that
- it is made out of titanium alloy, stainless steel, nickel alloy or aluminium
alloy.
7 - A driving means according to one of claims 4 to 6, characterised in that
- the frustoconical surface of the collar forms an angle of at least forty-five
degrees with a circular base (18; 156) of the collar.
8 - A driving means according to one of claims 4 to 7, characterised in that
- the frustum has a polygonal base.
9 - A driving means according to one of claims 1 to 8, characterised in that
- the socket faces are marked and/or coloured.
10 - A driving means according to one of claims 1 to 9, characterised in
that
- the collar has a spherical lower support surface (143), complemented
and connected, in the same way as a ball and socket joint, with a washer
(141) enabling swivelling, greater in diameter to that of the collar, the washer
having a concave housing (145) to accommodate said collar.
11 - A cylindrical tightening and loosening wrench socket for a polygonal
driving means (23; 26; 30; 33; 36; 38; 42; 119; 140; 151) according to one of
claims 1 to 10, the wrench socket comprising a cavity (134) with a polygonal
hollow shank (135) and an end (136) fitted so as to be abutted against an
inbuilt collar (6; 28; 50; 52; 60; 72; 92; 142; 152) of the driving means, the
end of the wrench socket having sides (137; 138) with shapes
complementing those of the collar so as to be pressed against the latter
during the abutment, characterised in that
- the collar comprises socket faces (24; 31; 34; 37; 39; 41; 43; 81; 97; 147;
153) hollowed out with regard to a collar surface (50; 52) and aligned with the
lateral sides (70; 71; 93; 96) of a shank (7; 91) of the driving means.

It has become apparent that the dimensions of inbuilt-collar driving
means of the same nominal size may vary according to the method of
manufacture. The dimensions of the collar must therefore be adapted to suit
the mode of manufacture, at the expense of its strength or mass. Moreover,
the transmissible torque for tightening and loosening operations varies
according to a useful wrenching height. In order to have a useful height
identical to the height of the shank (7), the idea underlying the invention
involves pushing the frustoconical collar (152) of a driving means (151) in
towards its centre along the extension of the sides of the shank. The inbuilt-
collar driving means proposed by the invention is suited to all modes of
manufacture, and can be manufactured without adversely affecting the
dimensions of the driving means or its installation.