Process and tool for producing a barrel for a telescopic universal transmission joint

A barrel to be formed has internal tracks of circular profile which abut ridges (4). The process starts with a sheet-metal blank which is arranged around an inner shaping mandrel equipped with protuberances integral or rotatably attached and defining shaping surfaces for the tracks. Three dies are displaced radially and have a projection which initiates a fold and which than forces this fold between the protuberances in order to produce the ridge as a result of a flow of material towards this region, which will undergo a very high load during operation.

BACKGROUND OF THE INVENTION 
(1) Field of the Invention 
The present invention relates to a process for producing a barrel of a 
telescopic universal transmission joint, especially for motor vehicles. 
The present invention also relates to a tool for producing such a barrel. 
The present invention likewise relates to a telescopic universal 
transmission joint comprising such a barrel, especially for motor 
vehicles. 
(2) State of the Prior Art 
FR-A-2,607,883 makes known a homokinetic transmission joint comprising an 
internal member, also called a "tripod", equipped with three arms arranged 
substantially radially in relation to its axis and each partially 
surrounded by two roller segments. Radially outer faces of curved 
transverse profile of the roller segments are in longitudinal rolling and 
lateral oscillation contact with longitudinal tracks formed on the inner 
face of a barrel, which surrounds the internal member and which is 
connected to one of two shafts between which transmission is to be 
obtained. 
The interposed members, each consisting, according to this document, of 
roller segments, transmit forces oriented tangentially between the arms of 
the internal member and the corresponding tracks of the barrel at a point 
on the tracks which is a function of the state of telescopic compression 
of the joint, of the angle between the axes of the internal member and the 
barrel, and of the position of the particular arm in relation to the plane 
in which these two axes are located. Instead of being roller segments, the 
interposed members can be blocks which slide along the tracks or composite 
members capable of rolling and sliding, as provided according to 
FR-A-2,622,653, or members of variable configuration, as described, for 
example, in FR-A-2,525,306. Conventionally, the internal member has three 
radial arms, which is why it is usually called a tripod, but this number 
is not mandatory, and internal members having, for example, two or four 
arms are possible. 
The barrel is often closed on one side by a bottom, so as to form with this 
bottom what is called a "bowl" of a generally cylindrical shape. 
The barrel is produced from a steel blank having a cylindrical outer 
surface and an inner surface in which the longitudinal tracks are 
machined. The barrel is generally the part of the joint involving the 
highest outlay because of its volume of material and the difficulty of 
machining the tracks with the accuracy and the surface state required on 
the inside of this part closed by the bottom. 
Attempts have been made to carry out cold or semi-hot extrusion processes, 
but the surface quality, profile accuracy and correctness necessary for 
the tracks are insufficient to ensure that, in the production of large 
series, these joints have the expected high degree of comfort during 
operation under economically competitive conditions. 
Moreover, each track has a length which is large in relation to its 
diameter, and therefore the grinding of the tracks involves too high an 
outlay. 
SUMMARY OF THE INVENTION 
The object of the present invention is to provide a process and a tool for 
producing a barrel under especially economical conditions and a 
transmission joint equipped with such a barrel. The production process and 
tool must allow the joints equipped with the barrels so obtained to 
benefit in full from their inherent high comfort performance. 
According to a first aspect of the invention, the process for shaping a 
barrel for a sliding universal transmission joint, this barrel comprising 
an annular wall, an inner face of which defines tracks of substantially 
circular profile which extend parallel to an axis of the barrel, is 
characterized in that a substantially cylindrical lateral wall of a blank 
is placed between an inner shaping mandrel located radially within the 
lateral wall and having shaping surfaces substantially complementary with 
the tracks to be formed and dies located radially outside the lateral 
wall, succeeding one another circumferentially with a circumferential play 
between them and having pressure surfaces towards the lateral wall of the 
blank, and in that a simultaneous displacement towards the axis of the 
mandrel, is imparted to the dies so that their pressure surface compresses 
the lateral wall of the blank radially against the shaping surfaces of the 
mandrel. 
All the tracks to be formed on the inner face of the annular wall of the 
barrel are thus produced very simply and in a single quick and accurate 
operation. 
The blank used at the outset of this process can be a deep-drawn 
sheet-metal blank, the wall of which has a substantially constant 
thickness. 
When, as so often happens, the barrel to be produced comprises concave 
tracks, each extending on one flank of a ridge separating it from an 
adjacent track extending on the other flank of this ridge, the pressure 
surfaces of the dies used have projections, by means of which the material 
of the blank is made to flow radially inwards into clearances, each 
defined between protuberances of the mandrel which carry the surfaces for 
shaping two adjacent tracks to be produced. 
This flow of material generates a kind of reinforced bead in one of the 
regions of the barrel which undergoes an especially high stress when the 
transmission joint is in operation. 
According to a second aspect of the invention, the press tool for forming a 
barrel for a sliding universal transmission joint is characterized in that 
it comprises a mandrel intended to be connected to a press piston for 
movement parallel to a central axis of the mandrel. This mandrel has on 
its periphery cylindrical shaping surfaces on an axis parallel to the 
central axis, the tool furthermore comprising dies succeeding one another 
circumferentially with, at least in a position of rest, a circumferential 
play between them. The dies are mounted on slideways having orientations 
converging towards the axis of the mandrel. A pusher is intended to be 
connected to the press piston in order to simultaneously to compel the 
dies to slide along the slideways in the direction converging towards the 
axis of the mandrel. 
Because the dies are mounted on oblique slideways, the straight movement of 
a press can be converted into a simultaneous movement of the dies towards 
the axis of the mandrel, and this movement, although being oblique in 
relation to the slideways, can be strictly radial relative to the blank 
and to the mandrel, since the mandrel, being connected to the press 
piston, can have, together with the blank, a movement corresponding to the 
axial component of the movement of the dies. 
According to a third aspect of the invention, the telescopic universal 
transmission joint, especially for vehicles, comprising an internal member 
equipped with arms arranged substantially radially in relation to its axis 
and each partially surrounded by two interposed elements, of which the 
radially outer faces of curved transverse profile bear on longitudinal 
tracks of substantially complementary profile belonging to the inner face 
of an annular wall of a barrel, in relation to which each arm of the 
internal member is movable over a predetermined telescopic stroke, is 
characterized in that the annular wall is produced from sheet metal and 
has an outer profile which approximately follows the inner profile of this 
wall. 
According to a preferred embodiment, in which the tracks are concave and 
are distributed in pairs separated by ridges, the radial thickness of 
material of the annular wall is increased in line with the ridges. 
Other particular features and advantages of the invention will also emerge 
from the following description.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
In the example illustrated in FIGS. 15 and 16, the homokinetic transmission 
joint comprises a first member or tripod comprising a ring 201 having an 
axis T, from which three radial arms 202, equally angularly spaced about 
the T axis, extend radially outwards. The lateral wall of each arm 202 
consists of a convex spherical zone 203, the center S of which is located 
at a distance from the axis T. This tripod is fitted onto and fastened to 
a shaft 204, the rotational movement about the axis T of which is to be 
transmitted universally and telescopically to a rotary element 77 of axis 
Z which can be an axle stub for driving a vehicle drive wheel. 
Each arm 202 of the tripod is partially surrounded by two roller segments 
206, a radially inner concave spherical surface of which (relative to the 
axis of the arm) is in ball-and-socket contact with the spherical zone 203 
of the arm. 
The roller segments 206 possess, furthermore, a radially outer toroidal 
face 208 (relative to the axis of the arm), by means of which the roller 
segments are each in rolling contact, respectively, with six tracks 1 
formed longitudinally on the radially inner face of an annular wall 211 of 
a barrel 3 having an of axis Z and fixed to the axle stub 77. In the 
example illustrated, the barrel 3 is produced in the form of a "bowl", in 
that the annular wall 211 is connected at one of its ends to a bottom 8 to 
which the axle stub 77 is fastened, for example welded. 
In this example of a joint, the roller segments 206 roll along the tracks 1 
of the barrel 3 during telescopic movements of the shaft 204 in relation 
to the axle stub 77 or when each arm 202 moves in relation to the two 
corresponding tracks 1 during each revolution of the joint as a result of 
the presence of an angle between the axes T of the shaft 204 and Z of the 
axle stub 77 (mode of operation at an angle is according to a situation 
not shown). 
The top of FIG. 16 shows the rollers 206 in the end position around the 
associated tripod arm 202. 
FIG. 1 and the left-hand part of FIG. 2 show a barrel 3 which can be used 
to produce the joint described by way of example with reference to FIGS. 
15 and 16 and to produce other joints described, for example, in 
FR-A-2,607,883, 2,622,653 and 2,525,306. 
The inner profile of the annular wall 211 of the barrel 3 comprises six 
tracks 1 of axes Y parallel to the axis Z of the barrel and therefore 
extending longitudinally on the inner face of the annular wall 211. These 
tracks 1, which are rolling tracks in the example shown in FIGS. 15 and 
16, but which could be sliding tracks for joints in which the interposed 
members are blocks instead of being roller segments, are obtained in 
geometrical terms by the movement parallel to the axis Y of generatrices 
in the form of sectors of a circle or substantially in the form of sectors 
of a circle extending in a plane perpendicular to the axis Y. Each track 1 
is inscribed within an angle A, the value of which can be 90.degree. to 
120.degree., and they are arranged two by two and mutually opposed. Each 
mutually opposed pair is arranged symmetrically on either side of a 
half-plane 2 originating from the axis Z of the barrel 3. The half-planes 
2 are offset at 120.degree. relative to one another. The six tracks have 
the same radius, and their axes Y are located at the same distance from 
the axis Z and at the same distance from the respective half-plane 2. 
Each track 1 extends, in particular, on one flank of an inner ridge 4 
formed by an internal fold of the wall 211 of the barrel. The ridges 4 are 
directed axially and are arranged at 120.degree. relative to one another 
about the axis Z. Each ridge 4 separates two tracks 1 which belong to two 
different pairs and which each extend on one of the flanks of the ridge. 
The barrel 4 has a longitudinal groove or valley 5 on its outer surface in 
line with each of the ridges 4. The center angle B between the axes Y of 
two tracks 1 located on either side of a ridge 4 varies between 30.degree. 
and 60.degree., depending on the type of joint for which the barrel is 
intended, on the shaping tool used and on the malleability of the 
component steel. 
In line with each ridge 4, the radial thickness of the annular wall 211 is 
increased as a result of an incipient radial flow of the metal during 
shaping. This particular feature represents an effective reinforcement of 
this zone subjected to the torque transfer load from the interposed 
members, such as the blocks 206, and ensures the value of the aperture 
angle A and the correct orientation of the tracks 1. 
The barrel 3 is obtained from a blank 11 (FIG. 12) having the form of a 
bowl with a flat bottom 8 and with a cylindrical lateral wall 9. This 
blank is obtained according to known industrial processes by deep drawing 
from annealed sheet steel. The thickness of the material of this blank is, 
for example, on the order of 4 to 5 mm for a motor vehicle of medium size. 
As shown in FIG. 13, the bowl blank 11 can also have a rim 10 widened 
outwards substantially radially, making it possible to produce a barrel 
with a rim 6 oriented radially outwards, as shown in FIG. 5. This rim 
reinforces the barrel 3 near its orifice and may be desirable for the 
convenience of fastening a bellows (not shown) for protecting the 
homokinetic joint. 
On the contrary, FIG. 6 shows the barrel as obtained from the blank of FIG. 
12 without a rim. 
As also shown in FIG. 5 (although this is true of the embodiment of FIG. 
6), at the end of the annular wall 211 adjacent to the bottom 74 of the 
bowl the initial circular profile of the annular wall 211 has been left 
substantially unchanged. Moreover, starting from this end, the annular 
wall 211 has a transitional region 7 comprising successive transitional 
profiles corresponding to movements of material, the extent of which 
increases from the end to the region of constant profile occupying most of 
the axial length of the lateral wall 211. 
Thus, as shown in the lower right-hand part of FIG. 2 corresponding to a 
section through the transitional region 7, the angle A' within which the 
tracks 1 are inscribed in the transitional region 7 decreases 
progressively towards the bottom 74 of the barrel. 
For barrels having a rim 6 (FIG. 5), there is a second transitional zone 
108 for connection to the rim 6. In a way not shown, the angle within 
which the tracks 1 are inscribed is progressively cancelled along the 
transitional zone 108 in the direction of the rim 6. 
These transitional zones 7 and 108 involved in the shaping are relatively 
short and do not reduce the effective stroke of the relevant sliding 
joints. The barrels according to the invention are therefore highly 
suitable as main components for sliding universal joints. 
In the example of FIGS. 5 and 7, the barrel is welded at its bottom 74 to a 
flange 75 equipped with fastening holes 76, for example making it possible 
to fasten the barrel to a motor-vehicle gearbox output. The holes 76 are 
in the extension of the valleys 5. 
In the example of FIGS. 6 and 8, a wheel axle stub 77 is welded to the 
bottom of the barrel which is cut out to allow centering means 78 of the 
stub 77 to pass through. 
FIG. 3 illustrates various steps in the process of shaping the tracks 1 on 
the inner face of the lateral wall 9 of the blank 11. 
This process employs a tool comprising three dies 12 distributed about a 
mandrel 17 having an axis which is called Z, because it coincides with the 
axis Z of the bowl during the shaping. 
After appropriate annealing, the bowl blank 11 is introduced around the 
mandrel 17 and between the three dies 12, which are sufficiently radially 
apart to leave sufficient annular space for the lateral wall 9 of the 
blank; see step a) at the top right of FIG. 3. 
The dies 12 each possess, facing the mandrel 17, that is to say facing the 
lateral wall 9 of the blank 11 when this is in place, a pressure surface, 
designated as a whole by 112, which is substantially complementary with 
the outer profile of the lateral wall 211 of the barrel to be formed. In 
particular, the pressure surface 112 of each die 12 has a projection 13 
the peak 14 of which extends parallel to the axis Z and is rounded. The 
projection 13 is contained between two arcs of a circle 15 having a 
profile corresponding substantially, with the exception of the wall 
thickness of the blank, to that of the tracks 1 to be produced. However, 
the circular regions 15 are inscribed within an angle C which is slightly 
smaller than the angle A within which the tracks 1 will be inscribed, as 
shown at the top left of FIG. 3. Furthermore, it is preferable that the 
axis Y' of the regions 15 be further away from the ridge 4 to be produced 
than the axis Y of the track 1 to be produced (as shown exaggerated in 
FIG. 3), so that the material of the blank is strongly compressed between 
the surface 15 and the mandrel in the vicinity of the ridge 4 where the 
metal experiences the greatest deformation. 
At its end opposite the projection 13, each region 15 is connected to a 
concave circular profile 16 which will be centered on the axis Z of the 
mandrel and of the barrel at the end of the shaping of the barrel. Each 
circular profile 16 is followed, on the side opposite the arc of a circle 
15, by an end region 27 of convex curvature, or rounded. 
The inner shaping mandrel 17 has an outer profile which, in general terms, 
is substantially complementary with that of the inner face of the annular 
wall 211 of the barrel to be produced. In particular, the mandrel has six 
convex longitudinal protuberances 21 or 21a, the outer surface 18 of which 
is a shaping surface of substantially circular cross-section. Each of the 
shaping surfaces 18 is intended for forming one of the tracks of the 
barrel, and its axis coincides with the axis Y of the track 1 to be 
formed. In line with each ridge 4 to be formed, the circular protuberances 
21 or 21a are separated by a longitudinal clearance 19 allowing full 
freedom for the shaping of the ridge. 
The adjacent protuberances 21 or 21a not separated by a clearance 19 are 
joined in pairs by circumferential arcs 20 centered on the axis Z and 
having a radius slightly smaller than that which the corresponding region 
of the inner face of the barrel will possess, so as to have a slight play 
28 relative to this region at the end of shaping. Thus, the shaping force 
is concentrated on the surfaces of the tracks 1 which require the highest 
accuracy and the best surface state. 
In the embodiment illustrated in the lower half of FIG. 3, the mandrel 17 
is integral and incorporates the protuberances 21a in one piece. 
In the embodiment illustrated in the upper part of FIG. 3, the mandrel is 
of a composite type, in that the protuberances 21 consist of six 
cylindrical rollers resting on concave cylindrical bearing surfaces 23 of 
complementary curvature belonging to a core 22 carrying the connecting 
surfaces 20. 
This composite mandrel technique allows an easier maintenance of the polish 
of the shaping surfaces 18 during intensive production and, if 
appropriate, a reconditioning involving only little outlay by the 
replacement of the rollers 21. Moreover, the freedom of rotation of these 
rollers on their bearing surface 23 makes it easier for the metal to flow 
during the formation of the ridges 4 under the thrust of the projections 
13 of the dies 12, especially when the thickness of the ridges 4 (measured 
in the circumferential direction) is small in relation to the thickness of 
the sheet metal of the blank. After each shaping of a barrel, a lubricant 
can be injected between the rollers 21 and the bearing surfaces 23 via 
suitable ducts (not shown) provided in the core 22, so as to assist the 
rotation of the rollers during the shaping of the next barrel. 
At the start of the process, the projections 13 of the dies are radially 
opposite the clearances 19 of the mandrel 17, and the dies 12 have between 
them a circumferential play designated by J in FIG. 3. According to the 
present invention, the annular wall 211 of the barrel is shaped by 
displacing the dies 12 simultaneously towards the axis Z. 
In the plane of FIG. 3, this movement corresponds to a displacement of the 
projection 13 at a speed V without any tangential component. In contrast, 
the other shaping surfaces 15, 16, 17 extending at an equal 
circumferential distance on either side of the peak 14 have the same speed 
V as the peak 14, but, since their angular position about the axis Z is 
different, this speed V, for example as regards the chamfer 27 at the top 
right of FIG. 3, breaks down into a radial component VR and a tangential 
component VT. The tangential component VT brings about a progressive 
reduction of the circumferential play J between the dies. 
The dashes in the upper right-hand part of FIG. 3 represent the position of 
the dies 12 at the start of shaping. At this stage, the ends 27 of the 
dies come into contact with the wall 9 of the bowl 11, whilst the three 
peaks 14 have already given the bowl an intermediate shape between a 
circle and a triangle. At the intermediate shaping stage shown at the 
bottom of FIG. 3, the dies 12 have come even closer to the axis Z in 
comparison with the situation represented by the dashes at the top right 
of the Figure. The profile of the lateral wall 9 of the blank is 
compressed circumferentially on itself, and a fold 24, the peak 25 of 
which has been initiated as a result of the radial thrust of the 
projection 13 of the dies 12, becomes more pronounced and comes 
spontaneously up against the cylindrical shaping surfaces 18 of the 
mandrel 17, while the oppositely directed folds 26 located on either side 
of each projection 13 roll towards the adjacent projection 13. 
Because of the progressive reabsorption of the circumferential play J 
between the dies 12, the ends 27 of the dies 12 slide on the outer surface 
of the lateral wall 9 of the blank. Since the ends 27 are chamfered, this 
does not result in any damage to the wall of the blank. 
The upper left-hand part of FIG. 3 shows the situation at the end of travel 
of the dies 12 towards the axis Z. The circumferential play J between the 
dies 12 has disappeared completely. The projections 13 have forced the 
material of the blank to flow between the adjacent shaping surfaces 18 
with a very high pressure thereagainst. There remains a slight spacing 28 
between the connecting arcs 20 of the mandrel and the corresponding inner 
face of the lateral wall 211 of the barrel, and because of this the 
pressing force imparted by the dies 12 is concentrated over the entire 
angle A within which the tracks 1 are inscribed. The peak 29 of the ridge 
4 obtained as a result of the folding 25 and then of the flow between the 
surfaces 18 has not reached the bottom 19a of the clearance 19. 
FIG. 4 illustrates another embodiment of the process according to the 
invention. 
The dies 12 are similar to those of FIG. 3 and therefore will not be 
described in detail. In contrast, the mandrel 17 is modified to make it 
easier to shape the ridges 4, the radial height of which governs the 
amount by which the tracks envelop the interposed members (roller segments 
206 of FIGS. 15 and 16) or, in other words, the value of the angle A. 
For this purpose, the inner shaping mandrel comprises three shaping 
elements 31 contractible radially, that is to say movable towards the axis 
Z, during the shaping. To this effect, the shaping elements 31 each 
comprise a plane oblique rear face 34 bearing slidably against the lateral 
faces 32 of a core 33 in the form of a pyramid with an equilateral 
triangular base. The movement of the shaping elements 31 towards the axis 
Z during shaping occurs as a result of a relative axial movement between 
the core 33 and the shaping elements 31. 
Each shaping element 31 carries two protuberances 21 defining the 
substantially cylindrical shaping surfaces 18 for two mutually opposite 
tracks 1. The two shaping surfaces 18 are joined by a connecting surface 
20. The projections 13 of the dies 12 are located opposite the clearances 
19 which are formed between the successive shaping elements 31, and the 
ridges 4 of the barrel will be shaped in these clearances 19. 
Dashes at the bottom of FIG. 4 represent the situation before the start of 
movement of the dies 12. The shaping elements 31 are then in the position 
represented by unbroken lines at the bottom of FIG. 4, in which the 
clearances 19 have a relatively large circumferential dimension. 
Starting from the position represented by dashes, the dies 12 are displaced 
as described with reference to FIG. 3, that is to say at a speed which 
does not have any tangential component for the projections 13. At this 
stage, the shaping elements 31 are kept stationary (with the exception of 
a purely axial movement which will be described later). The dies 12 push 
back the wall of the blank which comes to bear strongly with its inner 
surface on the connecting surface 20 of each shaping element 31. 
In the tool illustrated in FIG. 4, the ends 27 of the dies do not have the 
reversed curvature described with reference to FIG. 3, but alternatively 
the radius of curvature R1 of the connecting surfaces 20 of the shaping 
elements 31 is larger than the final inner radius of the corresponding 
regions of the barrel (radius R2 at the top of FIG. 4), in order to reduce 
the pressure on the ends 27 of the dies 12 and thus prevent the end edges 
35 of the dies from damaging the outer surface of the barrel as a result 
of the relative circumferential movement between these edges 35 and the 
wall of the barrel. However, the radius R1 is smaller than or 
substantially equal to the inner radius R3 of the lateral wall of the 
blank, in order, during the intermediate shaping phase (at the bottom of 
FIG. 4), to allow the above-described mutual bearing between the blank and 
the connecting surfaces 20 of the elements 31. 
In the intermediate shaping phase (bottom of FIG. 4) when the shaping 
elements 31 have not yet begun to move towards the axis Z, the fold 25 of 
the lateral wall 9 of the blank 11 has formed in the clearance 19 more 
easily than in the embodiment according to FIG. 3 because the clearance 19 
has a larger circumferential dimension. 
In the rest of the process, the dies 12 continue their movement towards the 
axis Z, but this movement is accompanied by a movement of the shaping 
elements 31 likewise towards the axis Z as a result of a relative axial 
movement of the core 33 in the appropriate direction. The movement of the 
shaping elements 31, as seen in a plane perpendicular to the axis Z (the 
plane of FIG. 4), has a speed W which has no tangential component in the 
axial mid-plane P of each element 31. The speed of the other points of 
each shaping element 31 is the same speed W as in the plane P. However, at 
a distance from the plane P, especially along the shaping surfaces 18, as 
shown at the top left of FIG. 4, the speed W breaks down into a radial 
speed WR and a tangential speed WT. The presence of this tangential 
component causes the circumferential dimension of the clearances 19 to 
decrease. In other words, the shaping surfaces 18, after allowing the fold 
25 to form between them, subsequently grip the fold 25 between them, 
whilst the projections 13 of the dies 12 prevent the material from 
escaping radially outwards, so as more effectively to form ridges 4 which 
can have a particularly small circumferential thickness. 
Between the regions carrying the tracks 1, which are therefore in contact 
with the shaping surfaces 18, during the final shaping phase the wall of 
the blank has undergone a circumferential or tangential compression which 
has laid it against the pressure surface 16 of the dies 12 as a result of 
an arching effect. A play 36 therefore occurs between the inner wall of 
the barrel and the connecting surfaces 20 of the shaping elements 31. 
As in FIG. 3, at the simultaneous end of the movement of the dies 12 and 
the movement of the shaping elements 31, the top 29 of each ridge 4 is set 
apart from the bottom of the corresponding clearance 19. 
FIGS. 9 to 11 illustrate diagrammatically the press tool according to the 
invention allowing the economical industrial shaping of barrels from the 
deep-drawn blanks of FIGS. 12 and 13 by means of the inner mandrel 17 of 
invariable configuration of FIG. 3. 
Each die 12 has a rear face directed radially outwards which is oblique 
relative to the axis Z and which bears on one of three stationary 
complementary inclined slideways 37 which for the dies 12 define sliding 
directions converging downwards towards the axis Z. A tubular pusher 38 
fastened to the piston (not shown) of a press bears on the upper side of 
the three dies 12. The effect of the descent of the press piston is to 
move the three dies 12 jointly downwards on the slideways 37, thereby 
bringing the dies radially closer to the axis Z from their initial 
position (left-hand part of FIGS. 9 and 10 corresponding to the upper 
right-hand part of FIG. 3) to the end-of-shaping position (right-hand part 
of FIGS. 9 and 10 corresponding to the upper left-hand part of FIG. 3). 
The slideways 37 are machined on segments 39 which are retained externally 
by a binding ring 40 and which are fastened to a platen 41 of the press by 
means of screws 42. The function of the binding ring 40 is particularly to 
withstand the reaction forces directed radially outwards which occur as a 
result of the force exerted radially inwards on the blank by the dies 12. 
Three counter-slideways 43 (FIGS. 9 and 11) are held on the press platen 41 
by means of screws 44 are each interposed circumferentially between two 
successive segments 39. Each counter-slideway 43 possesses, towards each 
of the segments 39 to which it is adjacent, a face 45 parallel to the 
axial plane of symmetry of this segment, in order to block the segments 
circumferentially by bearing on a corresponding face 39a of the segments. 
The raising of the dies 12 at the end of the shaping operation is carried 
out by means of a tubular plunger 47 subject to the action of a spring 48 
or any other equivalent means, such as a pneumatic or hydraulic jack. The 
plunger 47 acts simultaneously on the lower face of the dies 12 and on the 
bottom 8 of the barrel which has just been formed. The plunger contains an 
ejector 49, itself moved upwards in relation to the plunger 49 by a spring 
50 so as to lift the finished barrel out of the dies when these, having 
concluded their rising travel, come up against a stop ring 51 fastened to 
the upper face of the segments 39. The plunger 47 slides in a tubular 
guide 52 fastened to the press platen by means of a flange 53 and the 
screws 42 (FIG. 10) and 44 (FIG. 11). 
When the dies are up against the stop ring 51, they are set radially apart 
from the finished barrel as a result of the slope of the slideways 37. The 
press piston continues to rise, driving with it the pusher 38, which moves 
away from the dies 12, and the mandrel 17 to which it is likewise fixed. 
The ejector 49 raises, together with the mandrel 17, the finished barrel, 
which caps the free lower end of the mandrel 17. A stripping bush 54 which 
is interposed in an annular space between the inner mandrel 17 and the 
tubular pusher 38 comes to bear on the free annular edge of the finished 
barrel when, at the end of the return stroke of the piston, the finished 
barrel has come free of the dies 12. The stripping bush 54 then slides 
downwards in relation to the pusher 38 and the mandrel 17 in order to free 
the barrel from the mandrel 17. The stripping bush 54 can be actuated by 
coming up against a fixed point of the press cylinder at a particular 
stage of the rising stroke of the press piston or by a jack according to a 
known technique. 
The operation takes place as follows: the deep-drawn blank, suitably 
annealed and lubricated, is placed on the upper face of the ejector 49 
which at this stage is substantially flush with the upper face of the 
dies. 
The descent of the press piston (not shown), to which the mandrel 17 and 
the pusher 38 are fixed, is subsequently brought about. The mandrel 17 
projecting downwards relative to the pusher 38 pushes back the bottom 8 of 
the blank and the ejector 49 as far as the position shown in the left-hand 
half of FIG. 10, at the same time compressing the spring 50 
correspondingly. From this moment, the pusher 38 bears on the upper 
driving surfaces 57 of the dies 12 which descend along the inclined 
slideways 37, thereby coming radially closer to the axis Z and 
circumferentially closer to one another. The mandrel 17 and consequently 
the blank experience an axial movement together with the dies 12. 
The shaping proceeds until the end of the working stroke shown in the 
right-hand part of FIGS. 9 and 10. Subsequently, the press piston rises, 
driving the mandrel 17 and the pusher 38 upwards. When the barrel has been 
formed, the dies are pushed upwards by the plunger 47, and the barrel is 
then freed from the dies 12 by the ejector 49 and from the mandrel 17 by 
the stripper 54. 
The tool illustrated in FIG. 14, which will be described only in respect of 
its differences from that of FIG. 10, is designed for using a radially 
contractible mandrel according to FIG. 4, the initial shaping phase being 
shown on the left of FIG. 14 and the final shaping phase on the right of 
the Figure. 
The shaping elements 31 are held axially on the pusher 38 by a ring 57 
which forms an inner collar and which is itself fastened to the pusher 38 
by means of an elastic hoop 58. The shaping elements 31 receive this ring 
in an indentation in the form of a sector of a circle 59 and thus preserve 
their freedom of movement in the radial direction in relation to the 
pusher 38. Elastic clips 60 or 61 produced from a helical spring of 
annular axis and seated in indentations 71 and 72 of each of the three 
shaping elements 31 press the elements 31 against the oblique faces 32 of 
the pyramidal core 33. The indentation 72 is made in the lower face of the 
shaping elements 31 which is adjacent to the inner face of the bottom 8 of 
the blank during operation. The indentation 71 is formed axially beyond an 
end of the shaping surfaces of the elements 31, opposite the bottom 8 
during operation. 
The pyramidal core 33 carries an axial shaft 62 on its base facing upwards, 
possessing, at a distance above the elements 31, a widening 63 which 
receives a transverse axle 64 passing through axial slots 81 of the bush 
54, and elongate apertures 65 machined axially in the wall of the tubular 
pusher 38. The widening 63 also receives, above the transverse axle 64, 
the end 66 on the a rod of Z axis of a hydraulic or pneumatic jack (not 
shown) and, under the axle 64, the base of a compression spring 68 which 
opposes this jack and the other end of which bears on the top of the 
shaping elements 31. The spring 68 surrounds the shaft 62 and is 
surrounded by the pusher 38. 
Furthermore, here, the ring 51 limiting the upward return travel of the 
dies 12 serves as a stop for the transverse axle 64 and therefore for the 
pyramidal core 33, starting from the intermediate shaping phase 
represented by unbroken lines at the bottom of FIG. 4. 
The operating mode is as follows. At the outset, as in the preceding 
example, the upper surface of the ejector 49 is level with the upper 
surface of the dies 12, and the pusher 38 and the mandrel 17 are raised 
sufficiently to allow the blank 11 to be put in place. 
Subsequently, the pusher 38 is lowered and drives the shaping elements 31 
via the ring 57, and the jack for actuating the rod 66 is activated, 
thereby placing the axle 64 at the lower end of the aperture 65, 
compressing the spring 68 and putting the shaping elements 31 in the 
position radially set apart, the assembly as a whole being as shown in the 
left-hand part of FIG. 14 at the moment when the pusher 38 comes to bear 
on the top of the dies 12. From this position, the pusher 38 pushes the 
dies 12 downwards, the ejector 49 continues its downward travel and the 
plunger 47 begins its downward stroke. 
In a first part of the working stroke as far as the position represented by 
unbroken lines at the bottom of FIG. 4, the axle 64 remains laid against 
the lower ends of the apertures 65 by the actuating jack for the rod 66. 
During this time, the dies 12 begin to come radially closer to the axis Z. 
At a particular stage in the working stroke, the axle 64 encounters the 
stop ring 51, thus interrupting the downward travel of the pyramidal core 
33. The tubular pusher 38 continues its working stroke, driving the 
shaping elements 31 by means of the ring 57. The shaping elements 31 
therefore execute in relation to the pyramidal core 33 a sliding movement 
which is converted, relative to the blank and to the dies, into a movement 
directed towards the axis Z without any axial component. This movement 
towards the axis Z is greatly assisted by the radial thrust of the dies 12 
which is transmitted by the lateral wall of the blank, this taking place 
until the profile of the upper part of FIG. 4 is obtained. 
The final shaping phase is also illustrated in the right-hand part of FIG. 
14. The axial stroke of the pusher 38 after the axle 64 has encountered 
the stop ring 51 is such that, in the final shaping phase (right-hand part 
of FIG. 14), there remains a slight play between the axle 64 and the upper 
end 70 of the apertures 65. 
The ejection of the part and its stripping are carried out in the same way 
as in the arrangement illustrated in FIG. 10, except that the control of 
the rising of the press piston cancels the pressure to the auxiliary jack 
actuating the rod 66 and thus allows the opposing spring 68 to lift the 
pyramidal core 33 until the transverse axle 64 comes up against the upper 
end 70 of the apertures 65, thereby relieving the radial pressure of the 
contractible mandrel within the barrel formed and making the stripping 
easier. In fact, the previous retraction of the dies 12 and, in 
particular, of their projections 13, allowed a slight elastic relaxation 
of the ridges 4 radially outwards (by a few tenths of a millimeter) and 
consequently a relaxation of the grip exerted on the ridges 4 by the 
elements 31, despite the fact that the elements 31 come slightly closer to 
one another circumferentially when the axle 64 changes from the position 
shown on the right of FIG. 4 to the position up against the end 70 of the 
apertures 65. 
In the example of FIG. 10, as in that of FIG. 14, the working force 
necessary for shaping the barrels is at a maximum at the end of travel. 
Consequently, mechanical knuckle-joint or crank presses are especially 
advantageous, as well as hydraulic presses with two working speeds. 
The shaping of barrels with six tracks which are the most common has been 
described in detail, but it is clear that the shaping process and the 
simple high-performance press tool could easily be used for shaping a 
barrel having a different number of tracks.