GB1599207A

GB1599207A - Cold forming process and apparatus

Info

Publication number: GB1599207A
Application number: GB18066/78A
Authority: GB
Original assignee: Supervis
Current assignee: Supervis
Priority date: 1977-05-06
Filing date: 1978-05-05
Publication date: 1981-09-30
Also published as: FR2389431A1; ATA315278A; JPS53138959A; FR2389431B1; BE866735A; AT357395B; IT7823084A0; JPS6247614B2; CH617368A5; ES469545A1; IT1095876B; DE2819167A1; NL7804854A

Abstract

In order to be able to achieve a high degree of cold deformation in one working stage, the material of a cylindrical blank is forced radially outwards into the cavity of a die (14, 15) with symmetrical flow of the material in relation to its end faces by two rams (12, 13) which move towards one another. The symmetric flow of material is achieved by the fact that the rams are connected to the two die halves by elastic means (16, 17). The method is particularly suitable for the production of journal crosses (22). <IMAGE>

Description

(54) COLD FORMING PROCESS AND APPARATUS (71) We, ETABLISSEMENT SUPERVIS, a Liechtenstein body corporate, of P.O. Box 34 749 Vaduz, Liechtenstein, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to a process for the manufacture of a workpiece by cold forming from a cylindrical blank, and to apparatus for use in this process.

Various processes for the manufacture of universal-joint crosses for cardan joints are known; all these require a great labour effort and are thus expensive.

According to a first aspect of the present invention, there is provided a process for producing a workpiece from a blank by cold forming, the process comprising the steps of: placing the blank in a die cavity comprising two symmetrical die halves, a fixed ram closing one end of the cavity in the first die half and a movable ram closing the opposite end of the cavity in the second die half, the respective die halves being elastically connected to their punches; moving said movable ram toward said fixed ram by a predetermined distance and simultaneously together moving said die halves toward said fixed punch by a distance substantially equal to half said predetermined distance; whereby the pressure on said blank is symmetrical, the two die halves move symmetrically with respect to the rams and the material of the workpiece blanks flows within the die cavity symmetrically with respect to the central line of the die coincident with the plane between the die halves.

This process is suitable for the manufacture of the most diverse workpieces. The process can be used for the manufacture of a universal-joint cross member, in which case four spider arms, uniformly distributed on its periphery, are pressed from the centre of the cylindrical blank.

According to a second aspect of the invention, there is provided apparatus for producing a workpiece from a blank by cold forming, said apparatus comprising: a first fixed carrier plate; a second carrier plate movable with respect to said first carrier plate; a first ram mounted to said first carrier plate; a second ram mounted to said second carrier plate; a first die half, first means for elastically coupling said first die half to said first ram; a second die half; second means for elastically coupling said second die half to said second ram, said die halves together forming a die cavity adapted to receive the blank and the rams; means adapted for moving the second carrier plate and the second ram toward the first carrier plate and the first ram by a predetermined distance; and means for moving said die halves as a unit toward said first carrier plate and said first ram by substantially half of said predetermined distance; whereby, in use, said first and second rams move toward each other into the die cavity, extruding said blank into the die cavity, by equal distances with respect to the center plane of the cavity, the center plane being perpendicular to the axes of the rams, thereby forcing the material to the blank symmetrically into the die cavity with respect to said center plane.

Preferably, a hydraulic piston is fitted to each die half, each piston being displaceably mounted in a cylinder, and each cylinder being, in use, filled with pressure fluid.

The invention will be further described with reference to the accompanying drawings, in which: Figure 1 is a diagrammatic representation, partially in section, of an embodiment of the present invention, adapted for the manufacture of a universal-joint cross by the cold extrusion process before the extrusion step; Figure 2 corresponds to Figure 1 after the extrusion step; Figure 3 is plan view of a universal-joint cross member; Figure 4 is a side view of the universaljoint cross; Figure 5 is a sectional view through a second embodiment of the present invention in section, the right-hand half of the Figure showing the apparatus before the cold forming step and the left-hand half showing the apparatus after the cold forming step; and Figure 6 is a sectional view through a further embodiment, the right-hand half of the Figure showing the apparatus before the cold forming step and the left-hand half showing the apparatus after the cold forming step.

The apparatus of Figure 1 comprises two backing plates 10 and 11. The lower backing plate 10 is fixed to a stationary part of a mechanical or hydraulic press which is not shown and the upper backing plate 11 is fixed to a movable part of this press. A first upwardly pointing ram 12 is fixed to the lower backing plate 10 and a second downwardly pointing ram 13 is fixed to the upper backing plate 11. The two rams 12 and 13 are of the same design and the same length. Two die halves 14 and 15 are located between the two backing plates 10 and 11. A compression spring 16 is located between the lower backing plate 11 and the lower die half 14, and a second compression spring 17 is located between the upper backing plate 11 and the upper die half 15. These two compression springs 16 and 17 tend to press the two die halves 14 and 15 against one another.It can also be seen from Figure 1 that the lower die half 14 has a central through-bore 18 into which the ram 12 protrudes, and that the upper die half 15 likewise has a central through-bore 19 into which the ram 13 protrudes. The two die halves 14 and 15 are displaceably guided on the rams 12 and 13 by these bores 18 and 19.

Between the two rams 12 and 13, there is a cylindrical blank 20, from which a universaljoint cross member 22 according to Figures 3 and 4 is to be manufactured. The shape of this universal-joint cross member 22 is determined by the recesses in the two die halves 14 and 15.

As can be seen from Figure 2, the universal-joint cross 22 according to Figures 3 and 4 is formed from the blank 20 as a result of pressing the two backing plates 10 and 11 together by the distance h. As a result of this displacement of the upper backing plate 11 by the distance h, the blank 20 is also compressed by the amount of h, and matter is pressed out of the centre of the blank 20 into the recesses in the die halves 14 and 15.

Since the two compression springs 16 and 17 are designed to have the same force, they are both compressed by the same amount, that is to say each is compressed by the amount of h/2. The surfaces, by which the two die halves 14, 15 bear against one another, are thus displaced downwards likewise by the amount of h/2--due to the symmetrical design of the equipment shown in Figures 1 and 2.

The dies arranged thus in a movable arrangement are called "floating dies".

The magnitude of the distance h is related to the quantity of material which is to be pressed radially outwards, that is to say the larger the two spider arms 21 of the universal-joint cross member 22 in Figures 3 and 4, the larger is the quantity of material to be pressed radially outwards and the larger is the required distance h.

Instead of the compression springs 16 and 17, the embodiment of Figure 5 contains hydropneumatic springs for the dies in a floating arrangement, as is described in more detail further below.

Exactly as in the first illustrated embodiment, two backing plates 10 and 11 are present, of which the lower backing plate 10 is fixed to a stationary part of a mechanical or hydraulic press which is not shown. The upper backing plate 11 is fixed to a movable part of this press. A ram carrier 12a, pointing upwards, is fixed to the lower backing plate 10, and a ram carrier 13a, pointing downwards, is fixed to the upper backing plate 11.

In this case also, the two ram carriers 12a and 13a are of the same design and the same length. The actual ram 12 is located on the lower ram carrier 12a and the actual ram 13 is located on the upper ram carrier 13a; the cylindrical blank 20 is between the two rams 12 and 13.

A first hydraulic piston 24 is displaceably mounted on the lower ram carrier 12a and a second hydraulic piston 25 is displaceably mounted on the upper ram carrier 13a. These two hydraulic pistons 24 and 25 are displaceably located in two hydraulic cylinders 26 and 27, the lower hydraulic cylinder 26 being fixed to the lower backing plate 10 and the upper hydraulic cylinder 27 being fixed to the upper backing plate 11. In the interior of the two hydraulic cylinders 26 and 27, a chamber 28 and 29 respectively is formed between the backing plates 10, 11 and the hydraulic pistons 24 and 25.

These two chambers 28 and 29 are connected via lines 30, 31 to sources of pressure oil, which are not shown. These sources of pressure oil are formed, for example, by diaphragm accumulators in which the oil is subjected to the required pressure by a compressed gas, for example N2. These diaphragm accumulators generate in the chambers 28 and 29 a precisely identical pressure, by means of which the dies 32 and 33, which are described further below, are pressed against one another. These two dies 32 and 33 are fixed to two die carriers 36 and 37 with the aid of one fixing ring 34, 35 in each case. The die carriers 36 and 37 are in turn fixed in each case to one of the two hydraulic pistons 24 and 25 by fixing means, for example screws, which are not shown.

On the surfaces in mutual contact, the two dies 32 and 33 have recesses corresponding to the shape of the workpiece to be manufactured, for example in the shape of the universal-joint cross member shown in Fig ures 3 and 4.

The two ram carriers 12a and 13a each have a longitudinal bore in which an ejection rod 38 and 39 is displaceably mounted.

The mode of action of the equipment shown in Figure 5 is as follows: The two halves of the equipment described are moved apart, with the aid of the press which is not shown, for such a distance that a blank 20 can be inserted between the two rams 12 and 13. During this insertion of the blank 20 between the two rams 12 and 13, the full hydraulic pressure prevails in the two chambers 28 and 29; nevertheless, the two dies 32 and 33 can be moved so far apart that sufficient space is provided between the dies for inserting the blank 20, since the stroke of the two pistons 24, 25 is limited by stops on the cylinders 26 and 27. In one half of the Figure, the pistons 24, 25 bear against these stops of the cylinders 26, 27, whilst in the other half, there is a distance h/2 between the pistons 24, 25 and the stops of the cylinders 26, 27.After the blank 20 has been inserted, the two rams 12 and 13 can be moved, without force, towards one another until the end faces ofthe rams 12 and 13 bear against the opposite end faces of the cylindrical blank. As can be seen from the left half of the drawing, the two dies 32 and 33 then also bear against one another. In this position of the two rams 12 and 13, however, where they both just make contact with the blank 20, a small gap between the two dies 32 and 33 may still be present, which gap must, however, close in good time during the compression of the blank 20 so that no matter from the blank 20 can pass into this gap.

Under the force of the press which is not shown, the two backing plates 10 and 11 with the two rams 12 and 13 are pressed towards one another by the amount of h and the blank 20 is compressed. During this step, matter is displaced radially outwards from the central part of the blank 20 and passes into the said recesses 23 in the dies 12 and 13.

During this process, pressure oil is displaced from the two chambers 28 and 29 via the lines 30 and 31 into the diaphragm accumulators which are not shown.

As a result, each of the two pistons 24 and 25 is displaced by the amount of h/2 in the corresponding cylinder 26 or 27, as can be seen from the left half of Figure 5.

As soon as the two rams have moved towards one another by the distance h, the blank 20 has already been formed by cold extrusion into a universal-joint cross according td Figures 3 and 4.

The floating mounting of the dies 12 and 13, which has been described, makes it possible to fix the lower ram 12 in a stationary arrangement on the machine and only to move the upper ram 13 downwards so that, during this displacement of the ram 13, the two dies 32 and 33 also move at half the speed but in the same direction as the ram 13. During this step, the material of the blank is pressed with precise symmetry from above and from below into the recesses 23 in the die.

In this manner, it is possible not only to manufacture the universal-joint cross shown in Figures 3 and 4, but also any desired centro-symmetrical bodies, for example gearwheels.

In Figure 6, the embodiment represented diagrammatically in Figures 1 and 2, is shown in somewhat more detail. A first stack 40 of disc springs is located between the lower die carrier 36 and the lower backing plate 10, and a second stack 41 of disc springs is located between the upper die carrier 37 and the upper backing plate 11. These two stacks 40 and 41 of springs are precisely matched in such a way that the closing pressure of the dies 32 and 33 is reached before the extrusion step, but the closing pressure always remains sufficiently large during the extrusion step and that the same forces are transmitted to the upper die 33 and the lower die 32.

A retraction device 42 is provided for the upper die carrier 37 with the upper die 33.

The spring deflection amounts to precisely h/2 for both stacks and 40 and 41 of springs.

The mode of operation corresponds to that of the embodiment of Figure 5.

WHAT WE CLAIM IS: 1. A process for producing a workpiece from a blank by cold forming, the process comprising the steps of: placing the blank in a die cavity comprising two symmetrical die halves, a fixed ram closing one end of the cavity in the first die half and a movable ram closing the opposite end of the cavity in the second die half, the respective die halves being elastically connected to their punches; moving said movable ram toward said fixed ram by a predetermined distance and simultaneously together moving said die halves toward said first punch by a distance substantially equal to half said predetermined distance; whereby the pressure on said blank is symmetrical, the two die halves move symmetrically with respect to the rams and the material of the workpiece blank flows within the die cavity symmetrically with respect to the central line of the die coincident with the plane between the die halves.

2. Apparatus for producing a workpiece from a blank by cold forming, said apparatus comprising: a first fixed carrier plate; a second carrier plate movable with respect to said carrier plate; a first ram mounted to said carrier plate; a second ram mounted to said second carrier plate; a first die half; first means for elastically coupling said first die half to said first ram; a second die half;

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. ures 3 and 4. The two ram carriers 12a and 13a each have a longitudinal bore in which an ejection rod 38 and 39 is displaceably mounted. The mode of action of the equipment shown in Figure 5 is as follows: The two halves of the equipment described are moved apart, with the aid of the press which is not shown, for such a distance that a blank 20 can be inserted between the two rams 12 and 13. During this insertion of the blank 20 between the two rams 12 and 13, the full hydraulic pressure prevails in the two chambers 28 and 29; nevertheless, the two dies 32 and 33 can be moved so far apart that sufficient space is provided between the dies for inserting the blank 20, since the stroke of the two pistons 24, 25 is limited by stops on the cylinders 26 and 27. In one half of the Figure, the pistons 24, 25 bear against these stops of the cylinders 26, 27, whilst in the other half, there is a distance h/2 between the pistons 24, 25 and the stops of the cylinders 26, 27.After the blank 20 has been inserted, the two rams 12 and 13 can be moved, without force, towards one another until the end faces ofthe rams 12 and 13 bear against the opposite end faces of the cylindrical blank. As can be seen from the left half of the drawing, the two dies 32 and 33 then also bear against one another. In this position of the two rams 12 and 13, however, where they both just make contact with the blank 20, a small gap between the two dies 32 and 33 may still be present, which gap must, however, close in good time during the compression of the blank 20 so that no matter from the blank 20 can pass into this gap. Under the force of the press which is not shown, the two backing plates 10 and 11 with the two rams 12 and 13 are pressed towards one another by the amount of h and the blank 20 is compressed. During this step, matter is displaced radially outwards from the central part of the blank 20 and passes into the said recesses 23 in the dies 12 and 13. During this process, pressure oil is displaced from the two chambers 28 and 29 via the lines 30 and 31 into the diaphragm accumulators which are not shown. As a result, each of the two pistons 24 and 25 is displaced by the amount of h/2 in the corresponding cylinder 26 or 27, as can be seen from the left half of Figure 5. As soon as the two rams have moved towards one another by the distance h, the blank 20 has already been formed by cold extrusion into a universal-joint cross according td Figures 3 and 4. The floating mounting of the dies 12 and 13, which has been described, makes it possible to fix the lower ram 12 in a stationary arrangement on the machine and only to move the upper ram 13 downwards so that, during this displacement of the ram 13, the two dies 32 and 33 also move at half the speed but in the same direction as the ram 13. During this step, the material of the blank is pressed with precise symmetry from above and from below into the recesses 23 in the die. In this manner, it is possible not only to manufacture the universal-joint cross shown in Figures 3 and 4, but also any desired centro-symmetrical bodies, for example gearwheels. In Figure 6, the embodiment represented diagrammatically in Figures 1 and 2, is shown in somewhat more detail. A first stack 40 of disc springs is located between the lower die carrier 36 and the lower backing plate 10, and a second stack 41 of disc springs is located between the upper die carrier 37 and the upper backing plate 11. These two stacks 40 and 41 of springs are precisely matched in such a way that the closing pressure of the dies 32 and 33 is reached before the extrusion step, but the closing pressure always remains sufficiently large during the extrusion step and that the same forces are transmitted to the upper die 33 and the lower die 32. A retraction device 42 is provided for the upper die carrier 37 with the upper die 33. The spring deflection amounts to precisely h/2 for both stacks and 40 and 41 of springs. The mode of operation corresponds to that of the embodiment of Figure 5. WHAT WE CLAIM IS:

1. A process for producing a workpiece from a blank by cold forming, the process comprising the steps of: placing the blank in a die cavity comprising two symmetrical die halves, a fixed ram closing one end of the cavity in the first die half and a movable ram closing the opposite end of the cavity in the second die half, the respective die halves being elastically connected to their punches; moving said movable ram toward said fixed ram by a predetermined distance and simultaneously together moving said die halves toward said first punch by a distance substantially equal to half said predetermined distance; whereby the pressure on said blank is symmetrical, the two die halves move symmetrically with respect to the rams and the material of the workpiece blank flows within the die cavity symmetrically with respect to the central line of the die coincident with the plane between the die halves.

second means for elastically coupling said second die half to said second ram, said die halves together forming a die cavity adapted to receive the blank and the rams; means adapted for moving the second carrier plate and the second ram toward the first carrier plate and the first ram by a predetermined distance; and means for moving said die halves as a unit toward said first carrier plate and said first ram by substantially half of said predetermined distance; whereby, in use, said first and second rams move toward each other into the die cavity, extruding said blank into the die cavity, by equal distances with respect to the centre plane of the cavity, the centre plane being perpendicular to the axes of the rams, thereby forcing the material of the blank symmetrically into the die cavity with respect to said centre plane.

3. Apparatus according to claim 2 wherein said first and second elastic coupling means each comprise a hydraulic piston mounted to its respective die half, each hydrulic piston being movably mounted in a cylinder and each cylinder being filled with a hydraulic pressure fluid.

4. A cold forming process substantially as hereinbefore described with reference to and as illustrated in Figures 1, 2 and 6 or Figure 5 of the accompanying drawings.

5. A cold forming apparatus substantially as hereinbefore described with reference to and as illustrated in Figures 1, 2 and 6 or Figure 5 of the accompanying drawings.

6. A workpiece made by the process of Claim 1 or 4 or using the apparatus of any one of claims 2, 3 and 5.

7. A cross-member for a universal-joint made by the process of claim 1 or 4 or using the apparatus of any one of claims 2,3 and 5.