US3252314A - Shock absorber for drawbenches - Google Patents

Description

May 24, 1966 Filed Aug. 9, 1963 P. F. WINNAIL SHOCK ABSORBER FOR DRAWBENCHES :ISQI I I I"! 7 Sheets-Sheet l INVENTOR.

ATTORNEYS.

' May 24, 1966 P. F. WINNAIL 3,252,314

SHOCK ABSORBER FOR DRAWBENCHES V Filed Aug. 9, 1963 '7 Sheets-Sheet 2 INVENTOR. /DAUL E M/V/VA/L BY 5M4, M, A MM +/(m o'w-6 ATTORNEYS.

May 24, 1966 P. F. WINNAIL SHOCK ABSORBER FOR DRAWBENCHES 7 Sheets-Sheet 4 Filed Aug. 9, 1963 INVENTOR. 841/4 A" W/N/VA/L ATTORNEYS.

May 24, 1966 P. F. WlNNAlL SHOCK ABSORBER FOR DRAWBENCHES 7 Sheets-Sheet 5 Filed Aug. 9, 1963 INVENTOR.

/DAUL A W/N/V/i/L BY flmmaz, JW HMVM 1PM Arrow/5Y5.

May 24, 1966 P. F. WINNAIL SHOCK ABSORBER FOR DRAWBENCHES 7 Sheets-Sheet 6 Filed Aug. 9, 1963 INVENTOR PA UL F W/N/VA/L ,4 TTOR/VEYS.

May 24, 1966 P. F. WINNAIL SHOCK ABSORBER FOR DRAWBENCHES '7 Sheets-Sheet 7 Filed Aug. 9. 1965 m 5 RM mm CM WW m r WW4 L 0 5 w W M Q film NM 9 p w) w a 5 l ||U i l 0 w W E? Tu L I ww Nu m-w United States Patent 3,252,314 suocrr ansonnun FOR DRAWBENCHES Paul F. Winnail, Pittsburgh, Pa, assignor to Blaw-Knox Company, Pittsburgh, Pa, a corporation of Delaware Filed Aug. 9, 1963, Ser. No. 301,132 15 Claims. (Cl. 72-290) This invention relates to drawbenches and more particularly to shock absorbers for the gripper jaws of drawbenches to prevent damage to the material being drawn at the time that the trailing end of the material leaves the die. The invention is described herein as it is applied to the drawing of metallic tubes; however, it will be understood that the invention is also useful in connection with the drawing of other elongated workpieces such as wire, rod, bar and the like.

In conventional drawbench practice the pointed end of a tube to be drawn is inserted through a die that is mounted in a die stand at one end of a drawbench. The pointed end of the tube is grasped by gripper jaws or tongs mounted on a carriage that is then moved along-the drawbench away from the die stand, as by a chain, to draw the tube through the die. The workpiece is subjected to substantial tension during the drawing operation and this tension is suddenly released when the trailing end of the tube leaves the die. The elasticity of the tube then causes it to snap forwardly toward the carriage. This forward motion is utilized to release the tube from the gripper jaws but the energy released when the trailing end of the tube leaves the die stand is so great that the tube is very likely to be damaged by kinking or bending as it is released. This difiiculty is particularly severe with light gauge, small diameter tubes of considerable length.

Accordingly, a general object of the present invention is to provide an improved shock absorber mechanism for drawbenches whereby damage from kinking and bending of tubes as they are released from the drawing die of the drawbench is substantially prevented. Further objects and advantages of the invention will become apparent from the following description of a preferred form thereof, reference being made to the accompanying drawings. The essential characteristics of the invention are set forth in the claims. Briefly, a preferred form of the invention contemplates a gripper jaw mechanism for drawbench carriages in which the gripper jaws are first accelerated in a direction away from the die stand so that they move rapidly in the same direction as the leading end of the tube at the time that the trailing end of the tube is released from the die, thereby preventing imposition of substantial inertial forces on the tube, and then the forward motion of the jaws and tube is gradually slowed down by a shock absorber mechanism such as an air cylinder.

In the drawings:

FIGURE 1 is a side elevation of a drawbench embodying the present invention.

FIGURE 2 is a transverse section on an enlarged scale through the drawbench and drawbench carriage shown in FIGURE 1, the section being taken along the line 2-2 of FIGURE 1.

FIGURE 3 is a longitudinal sectional view taken along the line 33 of'FIGURE 2.

' FIGURE 4 is a plan view of the drawbench carriage, on an enlarged scale.

FIGURES 5A and 5B are sectional views on an enlarged scale taken along lines 5A5A and SB-SB of FIGURE 4, the views together constituting a longitudinal section through the shock absorber mechanism.

FIGURES 6, 7 and 8 are transverse sectional views taken along the lines 66, 7-7 and 88 of FIGURE 4.

FIGURE 9 is a plan view to an enlarged scale, partially in section, illustrating the jaw mechanism, the view being taken as indicated by line 9--9 of FIGURE 10.

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FIGURE 10 is a longitudinal sectional view taken along line 1010 of FIGURE 9.

FIGURE 11 is an end view of the jaw mechanism shown in FIGURES 9 and 10.

FIGURE 12 is a transverse sectional view taken along line 1212 of FIGURE 9.

FIGURE 13 diagrammatically illustrates the operation of the gripper jaws and the shock absorber mechanism and includes a diagram of the air circuits.

As shown particularly in FIGURES 1, 2 and 3, the invention is illustrated herein as applied to a drawbench of known construction comprising a bed '10, a die stand 11 at one end of the bed, and mandrel mechanism indicated in general at'12 for supporting the mandrel over which the tubes'are drawn and for loading the tubes over the mandrel disposed beyond the die stand 11. The mandrel mechanism, per se, forms no part of the present invention and any convenient mechanism may be employed. Tubes are reduced in diameter and elongated by drawing them through a die 14, mounted in die stand 11, by means of a carriage 15 that is movable back and forth on the bed 10 and provided with gripper jaws 16 that g are adapted to grip the pointed end of a tube and pull it through the die. The carriage 15 is supported by wheels 17 that ride on spaced tracks 18 carried, by the longitudinal members 19 making up the bed 10. These members are supported by generally C-shaped frame members 20 which may be spaced along the bed as required to provide the requisite support. The members 20 are shaped so that the space between the tracks 18 is left open and therefore tubes drawn on the bench can be discharged simply by permitting them to fall from the gripper jaws 16 onto sloping guide members 21 and into a box 22.

The carriage is moved back and forth along the tracks 18 by means of a pair of chains 23. The pull of the chains in the working direction is transmitted to the carriage 15 by means of an equalizer bar 25 pivoted to the forward end of the carriage at 26 as shown in FIGURE 4. The other ends of the chains are connected directly to the rear end of the carriage. The chains are driven by a main drive motor 27 through reduction gearing 28 and drive sprockets 29 (FIGURE 1). The chains also pass around pairs of adjustable idler sprockets 30 and fixed idler sprockets 31 at the drive end of the bench and pairs of idler sprockets 32 and 33 that are disposed at the die stand end of the bench. The motor is operated in one direction to move the carriage from the die stand toward the right in the arrangement shown in FIGURE 1 to draw a tube, and in the opposite direction to return the carriage to the die stand tograsp the end of another tube. The drive mechanism, like the bench itself, may be of conventional or known construction and hence will not be described further herein. While the particular type of bench illustrated lends itself to the present invention, it is to be understood that the invention may readily be adapted to benches of other types and designs.

The improvements constituting the present invention are associated primarily with the carriage 15 and the gripper jaws 16. -As shown particularly in FIGURE 4, the car riage 15 is an elongated rectangular structure comprising side members 35 that carry the wheels or rollers 17 for supporting the carriage on the tracks 18. The side members 35 are connected by transverse end members 37 and 38 and intermediate transverse member 39, 40, 41 and 42. Preferably, the side members and transverse members are welded together to provide a strong and rigid structure. The chains 23 are secured to the side members 35 at the rear end of the carriage, i.c., the end that is nearest the die stand and where the gripper jaws are supported. The pin 26 that supports the equalizer bar 25 is carried by a bench without damage.

3 bracket 43 that is secured to the transverse member 38 at the front end of the carriage.

In order to provide for the desired action in releasing a drawn tube from the gripper jaws 116, the gripper jaws are mounted in a slideway 44 extending from the rear end of the carriage for a substantial distance toward the front end to permit the tube and the gripper jaws to travel along together when the trailing end of the tube is released from the die until the energy of the tube has been dissipated sufficiently so that the tube can be disengaged from the gripper jaws and discharged from the draw- The slideway is disposed beneath the transverse members of the carriage. The rear end of the slideway is formed in a massive head member 45 that is detachably secured to the rear transverse members 3'7, being supported by wings 46 that rest on and are bolted to the members 37. As shown particularly in FIGURES 9 and 10, the walls :48 of slideway 44 converge as at 49 in order to provide camming surfaces for moving the gripper jaws 16 into engagement with the tube to be drawn, as explained more fully below. The gripper jaws 16 are disposed within the slideway 44 and supported therein by gibs 50 that are secured to the head member 45 as by cap screws. The gibs d are spaced to provide an opening through which a tube drawn on themachine can drop.

In the embodiment shown, the head member 45 extends toward the forward end of the carriage to the transverse member 39. Beyond the transverse member 39 the slideway for the gripper jaw mechanism is formed by a top plate 51 that is bolted to side members 52; the inner surfaces of the side members 52 are spaced to correspond to the spacing of the Walls 48 in the head member 45 and thus provide the remainder of the slideway 44. The side members 52 are welded at their ends to the transverse members 39 and '40. Gibs 53 that are spaced to correspond to the spacing of gibs 50 are bolted to the lower edges of the side members 52 to provide support for the jaw mechanism throughout the length of slideway 44 and to provide an opening through which the tube may drop. Thus, with this arrangement, the gripper jaw mechanism can travel from a drawing position adjacent the tapered portions 49 of the head member 45 to the opposite end of the slideway adjacent the cross member 46 and, as explained below, the travel of the gripper jaws throughout this distance is controlled so as to make it possible to discharge tubes from the machine without substantial damage to the tubes from kinking or bending.

The gripper jaws '16 are of generally conventional construction and operation. The jaws are moved into gripping engagement with the pointed end of a tube by an air cylinder. During the drawing operation the tension exerted by the tube causes the jaws firmly to grip the tube and upon displacement of the tube in the forward direction with respect to the jaws, the jaws are automatically released. To accomplish this mode of operation, the jaw mechanism, as shown in FIGURES 9 to 12, preferably comprises a pair of jaw members 55 having tapered outer surfaces 56 corresponding to the tapered surfaces 49 on the head member The forward ends of the jaws 55 are square and slidably engage the rear end of a jaw supporting block 57 as at 58. The jaws are also guided and supported by the link 59 that are pivoted as at 60 at their forward ends to the jaw supporting block 57 and at their rear ends are pivoted as at 61 to the forward ends of the jaw members 55. The links 59 operate in slots 62 in the jaw supporting block 57 and are urged apart by a spring 63, as shown in FIGURE 12.

It will be evident that when the block 57 is pushed to the rear of the guideway 48, the tapered surfaces 49 will cause the jaws S5 to approach each other and grip a tube disposed between them. The teeth 64 on the jaws firmly engage the tube and when the carriage is moved in the drawing direction away from the die stand, the force exerted by the tube on the jaws 55 will tend to cause them to grip the tube more firmly because of the tapered walls 49 that engage the tapered surfaces 56 of the jaws. However, when the tension on the tube is released, the gripping force is immediately reduced and as the jaws move forward in the slideway they are separated from the tube and moved farther away from each other by the action of the spring 63.

In conventional gripper jaw mechanisms, when the trailing end of the tube leaves the die, the jaws are moved in the forward direction solely by the forward snap of the tube and the permitted movement does not greatly exceed the movement required to release the jaws from the tube. According to the present invention, the jaws are first accelerated in the forward direction so that the forward end of the tube is not required to push the jaws against the resistance that otherwise would be offered by the inertia and friction of the jaw mechanism and then the movement of the jaw mechanism is gradually slowed down as the mechanism travels through a substantial distance.

In .order to control the movement of the gripper head and the jaws in the desired manner, a tubular connecting rod 66 is secured to the jaw supporting block 57 by a connection member 67 that is pressed into the tube and is provided with a portion 68 of reduced diameter that slidably fits into a recess 69 in the block 57 in which it is removably retained by a pin 70 (FIGURES 9 and 10). As shown particularly in FIGURES 4, 5A and 5B, the connecting rod 66 extends toward the front end of the carriage throughout the entire length of the slideway 44 and is slidably supported by a bushing and spring seat member 72 carried by the transverse member 40. Connecting rod 66 also slides in an elongated cylinder head, spring seat and bushing member 73 that in turn is slidable within the end portion of an elongated air cylinder 74. At the forward end of the connecting rod there is a piston 75 that operates within the cylinder 74. Cylinder 74 is supported by transverse members 411 and 42 and is provided with fluid connections 76 and 77 at its front and rear ends, respectively. A spring 78 acting between the spring seat 72 and the spring seat portion of member 73 retains the member 73 in the position shownin FIG- URE 5B except when the air pressure within the cylinder '74 is sufficient to move the piston and the member 73 to the left or rear against the action of the spring 78.

It will be evident that by controlling the fluid pressure in the cylinder 74 the position of the gripper jaws can be controlled and the rate of movement of the gripper jaws when the tube is released from the die may also be controlled. The preferred mode of operation will be evident from a consideration of the somewhat diagrammatic showing of FIGURE 13, in conjunction with EIG- URES 4, 5A and 5B. In FIGURES 4, 5A and 5B the piston 75 abuts the cylinder head, spring seat and bushing member 73 and the spring 78 holds the member 76 in the cylinder as far as it will go. When the piston is in this position the jaw supporting block 67 is in the position shown in FIGURE 9, with the jaw members 55 moved forwardly away from the rear end of the head member 45 and spaced apart by the action of spring 63 to receive the pointed end of a tube. This is the position the parts take as the carriage approaches the die stand to grasp a tube to draw it through the die.

When the carriage is in position adjacent the die stand, wtih the pointed end of a tube T positioned between the jaw members 55 as shown in 'FIGURE 5A, air is admitted through the connection 76 under a pressure great enough to overcome the force exerted by the spring 7 8, and to clamp the jaws 55 onto the end of the tube. The air pressure within the cylinder 74 moves the piston and the member 73 to the position shown in full lines in FIGURE 13, compresses the spring 78 and moves the jaw supporting block 57 rearwardly, thus causing the jaws 55 to be cammed inwardly by the surfaces 49 to grip the pointed end of the tube T. In practice, air pressure of 90 to 100 pounds per square inch is employed for this purpose with a cylinder about 2% inches in diameter, and the motion required for this final push up may be of the order of 3 or 4 inches. The motor 27 is then operated to move the carriage in the forward or drawing direction away from the die stand. The force required to draw the tube through the die is exerted through the jaws and tends to cam them inwardly, thus increasing the grip of the jaws on the tube.

As the carriage moves away from the die stand, the pressure within the cylinder 74 is reduced to a low value, for example, three or four pounds, which is much less than is required to overcome the force exerted by the spring 78. However, because of the force exerted on the jaws by the tube being drawn, the drawing operation continues with the parts inthe position shown in full lines in FIGURE 13. The parts remain in their position throughout the draw, but at the instant the trailing end of the tube leaves the die, the tension on the tube is suddenly released and the tube tends to shoot forward. This releases the rearward pull on the gripper jaws and the .spring 7 8 then rapidly moves the parts back to the original position shown in FIGURES '4, 5A and S-B. The spring thus accelerates the entire jaw mechanism, the connecting rod 66 and the piston 75 in the forward direction. Because of the rapid acceleration of these parts by the spring, the drawn tube is not required to overcome the inertia and friction of the parts and, therefore, is not subjected to buckling or bending at the time that it moves forwardly after being released from the die. Instead, the pointed end of the tube engages the bottom 80 of a recess in the rear of the block 57, but this engagement is not violent enough to result in damage to the tube because the spring has accelerated the block to a substantial velocity by the time the end of the tube strikes it. The forward movement of the carriage is stopped by conventional means, such as a limit switch controlling the motor 27, shortly after the trailing end of the tube leaves the die. The member 73 stops when its flange 79 engages the resilient washer '81, but the gripper jaw assembly, connecting rod and piston continue to move to the right with the connecting rod 66 sliding in the bushing portion of the member 73. The motion of these parts and of the tube is slowed gradually by the damping effect of the piston. Preferably, the air pressure in the cylinder is not permitted to build up substantially but is held at about the initial value as the piston moves forward in the cylinder, this value being sufiicient to stop the piston before it reaches the forward end of the cylinder, as shown in broken lines in FIGURE 13. Since the cylinder may be as much as 60 inches long, or longer if desired, the drawn tube is decelerated gradually as it travels through a substantial distance and finally simply drops out of engagement with the gripper head and falls down between the tracks 18 onto the guides 21 and then into the box 22, the forward motion of the tube having been substantially arrested at this time. Thus, unduly sudden deceleration and kinking, bending or like damage to the tube are prevented.

After the tube has dropped out of the jaws and while the carriage is being returned to the die stand to pick up another tube, air under pressure in the cylinder 74 returns the piston, connecting rod and gripper jaws to the position shown in FIGUR E-S 4 and 5A. The air pressure utilized for this purpose is insuflicent to overcome the spring 78 so that the parts remain in the position shown in these figures until high air pressure is admitted to cause the gripper to grip a tube.

If it is desired to move the gripper jaws 16 and piston 75 from the full line positions shown in FIGURES 5A and SE to the broken line positions shown in FIGURES 5A and 5B, then air is admitted to the cylinder 74 in back of the piston 75 through the connection 77 to move the parts to the broken line positions. The gripper head is then disposed beneath a hinged cover 82 (see FIGURES 4 and 5A) of the slideway. When the gripper head is in this posit-ion, the pin 70 may be removed and the gripper head disconnected from the connecting rod so that it can readily be removed and repaired or a different gripper head substituted for it.

The piping and valves for controlling the air for operating the gripper jaws are shown in FIGURES 4 and 5A and diagrammatically in FIGURE 13. When the carriage is in position adjacent the die stand, an air needle 84 makes engagement with an air supply stand 85, as shown 1n FIGURES 5A and 13, and air under pressure is admitted through the needle to the .air pressure system on the carriage. A solenoid valve 86 in a conduit 87 leading to an air supply (not shown) is opened when the needle .18 properly engaged in the stand and closed when the needle is being withdrawn and before it is completely disengaged from the stand. Valve 86 is controlled by a limit switch operated by the carriage in a conventional manner. The needle and stand are also of well known construction and per se form no part of the present invention.

. The arrangement of valves and conduits on the carriage is such that the previously described sequence of operatrons is carried out automatically without requiring any additional controls, limit switches or the like. This is accomplished reliably and simply by the conduits and valves shown diagrammatically in FIGURE 13. From the air needle 8 a conduit 90 leads to a T connection 91, from one side of which .a conduit 92 leads to reservoir 94. A check valve 95 is provided in conduit 92 to permit air under pressure to flow from the supply through the air needle into the reservoir while preventing discharge of air through the conduit 92 from the reservoir when the air needle is disconnected from the stand 85. From the other side of the T connection 91, a conduit 97 leads to the exhaust connection of a quick exhaust valve 98. A preferred form of quick exhaust valve is typified by the Schrader quick exhaust valve No. 3340, manufacture by A. Schraders Son division of Scoville Mfg. Co. Inc., Brooklyn, New York. Valves of this type are provided with an inlet connection, an outlet connection and an exhaust connection. These valves provide open communication at all times between the inlet and the outlet. When the back pressure on the outlet exceeds the inlet pressure, open communication is provided between the outlet and exhaust. Similarly, when the back pressure on the exhaust exceeds the inlet pressure, open communication is provided between the inlet and the exhaust ports.

The inlet of valve 98 is connected to a conduit 99 which lead-s to reservoir 94. A pressure regulating valve of conventional construction 100 is interposed in conduit 99 to reduce the pressure in the reservoir to a desired low value, for example 3 or 4 pounds per square inch, at the inlet of valve 98. The outlet of valve 98 is connected to a conduit 101 which leads to the inlet of another quick exhaust valve 102. The outlet of valve 102 is connected to conduit 76 leading to the forward end 'of cylinder 74 and the exhaust of valve 102 is open to the atmosphere.

With this arrangement, when high pressure air from the conduit 87 is admitted to the air needle under high pressure, the reservoir is charged with air .at substantially the same pressure. At the same time, high pressure air flows through the conduit 97, the quick exhaust valve 98, conduit 101, quick exhaust valve 102 and conduit 76 into the cylinder 74. This high pressure air moves the piston 75 from the position shown in FIGURE 5B to the position shown in FIGURE 13, compressing the spring 78 and causing the jaws 55 to grip the pointed end of the tube T. This action, of course, takes place when the carriage is adjacent the die stand, the air needle is engaged with the air supply stand 85 and the solenoid valve 86 is open.

Preferably a flow control valve 193 is interposed in the conduit 101 to reduce the rate of travel movements of the piston 75 to a desired value.

When the carriage starts on its working movement in a forward direction away from the die stand, the valve 86 is closed by an appropriate limit switch and the air needle is withdrawn from the stand 85. The pressure in the conduits 90, 92 and 97 is then reduced to atmospheric. The reservoir supplies pressure substantially equal to the original high pressure to the pressure regulator 100 which reduces this pressure to a low value, say 3 or 4 pounds, in the conduit 99 leading to the inlet side of the quick exhaust valve 98. As described above, the outlet valve 98 is connected to the inlet of quick exhaust valve 102. Because of the action of the pressure regulator the inlet pressure on valve 102 drops to the desired low value; thereupon the high pressure within the cylinder 74 is exhausted through the conduit 76 and the valve 102 to atmosphere until the pressure within the cylinder reaches a value substantially equal to the value determined by or the setting of the pressure regulator 100. This value is maintained during the drawing movement of the carriage, the gripper jaws being held in engagement with the tube .by pull of the tube on them. When the trailing end of the tube leaves the die 14, the spring 78 moves the cylinder head, spring seat and bushing member 73, the piston 75, connecting rod 76 and the jaw mechanism rapidly in the forward direction. This motion continues, as described above, under the forward thrust of the suddenly released tube. As the piston moves forwardly through cylinder 74, the pressure in the cylinder tends to increase to a value above the inlet pressure in conduit 101 and air from the cylinder is therefore exhausted through the exhaust port of valve 102, thus preventing any substantial increase in pressure on the forward side of piston '75. The resistance offered to the forward movement of the piston by the air within the cylinder can be controlled by adjusting pressure regulating valve 100.

When the forward motion of the tube has been slowed sufficiently, the tube drops out of engagement with the gripper head and falls between the tracks of the drawbench into the box 22. The forward motion of the piston and associated parts then stops. The reservoir at this time still contains air under substantial pressure. Then air under the reduced pressure determined by the pressure regulator 100 flows through the conduit 99, the quick exhaust valve 98 and the quick exhaust valve 162 into the conduit 76 leading to the cylinder 74 and'moves the piston and the gripper jaw mechanism back to the position shown in FIGURES 4, 5A and 5B, ready for the beginning of another cycle of operations.

From the foregoing description of a preferred form of the invention, it will be seen that the invention pro-- vides a simple and effective shock absorber mechanism for draw benches whereby the tube is not subjected to undue decelerating forces upon its release from the die inasmuch as the gripper jaws and associated mechanism are accelerated by the spring 78 at the instant the tube is released from the die and then gradually slowed down by the action of the air cylinder. This is accomplished by a simple pneumatic system made up of well known and reliable components, without requiring any remote control of the parts of the system that are mounted on a moving carriage.

Those skilled in the art will appreciate that variou changes and modifications can be made in the invention without departing from the spirit and scope thereof. For example, the invention may be readily adapted to multiple draw units and to drawbenches and carriages of other types. Other changes will be evident to those skilled in the art and it is evident that the invention can :be adapted to drawbenches and carriages of varying types. It is therefore to be under-stood that the foregoing description of a preferred form of the invention is given by way of example and that the scope of the invention is defined in the appended claims.

What is claimed is:

1. In a draw bench having a bed, a die stand, a die carried by the die stand and a carriage movable on the bed in a forward direction away from the die stand and in a return direction toward the die stand, the combination of a gripper jaw assembly having jaws for gripping a workpiece to be drawn through said die and means for positively stopping forward movement of the workpiece with respect to the assembly, means for mounting said gripper jaw assembly on said carriage for substantial movement with respect to the carriage in directions parallel to said bed, means for causing the gripper jaws to engage a workpiece to be drawn, means acting between the gripper jaw assembly and the carriage for accelerating the gripper jaw assembly in the forward direction with respect to the carriage when the trailing end of the workpiece is released from the die, and means for thereafter gradually decelerating said gripper jaw assembly.

2. In a draw bench having a bed, a die stand, a die carried by the die stand and a carriage movable on the bed in a forward direction away from the die stand on the bed and in a return direction toward the die stand, the combination of a gripper jaw assembly mounted on the carrige for substantial movement with respect to the carriage in directions parallel to the movement of said carriage on said bed, said assembly having gripper jaws, means for causing the gripper jaws to engage a workpiece to be drawn, the force exerted by the workpiece on the gripper jaws maintaining the gripper jaws in engagement with the workpiece during the drawing operation and the workpiece being disengageable from the jaws upon forward movement of the gripped end of the workpiece with respect to the jaws, said assembly having means for positively stopping such forward movement of the workpiece with respect to the assembly, means acting between the carriage and the gripper jaw assembly for accelerating the gripper jaw assembly in the forward direction with respect tothe carriage when the trailing end of the workpiece is released from the die and means for thereafter gradually decelerating said gripper jaw assembly and thereby decelerating the workpiece.

3. In a draw bench having a bed, a die stand, a die carried by the die stand and a carriage mounted for movement on said bed in a forward direction away from the die stand and in a return direction toward the die stand, a gripper jaw assembly embodying gripper jaws for gripping a workpiece to be drawn through said die, means for mounting said gripper jaw assembly on said carriage whereby said assembly is permitted substantial movement with respect to said carriage in directions parallel to said bed, the gripping engagement of .said jaws on the workpiece being maintained by the force exerted by the workpiece on the gripper jaws during the drawing operation and released when said force is released, said gripper jaw assembly being moved in a forward direction on said carriage by the forward snap of said workpiece when the trailing end thereof leaves the die and said force is released, said assembly having means for positively stopping forward movement of the workpiece with respect to the assembly, said assembly traveling in a forward direction on said carriage along with the forward end of the workpiece, and means for gradually decelerating the forward movement of said assembly and of said workpiece as said assembly travels along said carriage.

.4. In a draw bench having a bed, a die stand, a die carried by the die stand and a carriage mounted for movement on said bed in a forward direction away from the die stand and in a return direction toward the die stand, a gripper jaw assembly embodying gripper jaws for gripping a workpiece to be drawn through said die, means for mounting said assembly on said carriage whereby said assembly is permitted substantial movement with respect to said carriage in directions parallel to said bed, the grip- I ping engagement of said jaws on the workpiece being maintained by the force exerted by the workpiece on the grippr jaws during the drawing operation and released when said force is released, said gripper jaw assembly being moved in a forward direction on said carriage by the forward snap of said workpiece when the trailing end thereof leaves the die and said force is released, resilient means for accelerating the gripper jaw assembly in the forward direction with respect to the carriage when said force is released, said gripper jaws traveling in a forward direction on said carriage along with the forward end of the workpiece, and fluid cylinder means for gradually dcel-erating the forward movement of said gripper jaw assembly and of said workpiece.

5. In a draw bench, a die stand, a die mounted in the diestand, a bed, a carriage mounted for movement on said bed in a forward direction away from the die stand and in a return direction toward the die stand, a gripper jaw assembly having jaw members and a jaw supporting block, said gripper jaw assembly being disposed in a slideway whereby said assembly is permitted substantial movement with respect to the carriage in directions parallel to the movement of said carriage, means at the end of said slideway toward said die stand for camming said gripper jaws into engagement with a workpiece when said assembly is moved rearwardly with respect to said camming means, said gripper jaws being released upon forward movement of said gripper jaws with respect to said camming means, the gripping engagement of said jaws on the workpiece being maintained by the force exerted by the workpiece on the jaws during the drawing operation and released when said force is released, resilient means for accelerating said assembly in the forward direction with respect to the carriage when the trailing end of the workpiece is released from the die and the tension in the workpiece is released, said jaw supporting block having a portion engageable by the forward end of the workpiece upon release of the workpiece from the die for positively stopping forward movement of the workpiece with respect to the assembly, the assembly traveling in the forward direction in said slideway along with and substantially the same speed as the forward end of the workpiece in response to the forward snap of the workpiece when the trailing end thereof is released from said die, and means for gradually decelerating the forward movement of said assembly and of said workpiece as said assembly travels along said slideway.

6. In a draw bench, a die stand, a die mounted in the die stand, a bed made up of a pair of spaced track members having an open space between through which a workpiece drawn on the draw bench can fall, a carriage mounted for movement on said tracks in a forward direction away from the die stand and in a return direction toward the die stand, a gripper jaw assembly having jaw members and a jaw supporting block, said gripper jaw assembly being disposed in a slideway whereby said assembly is permitted substantial movement with respect to the carriage in directions parallel to the movement of said carriage, means at the end of said slideway toward said die stand for camming said gripper jaws into engagement with a workpiece when said assembly is moved rearwardly with respect to said camming means, said gripper jaws being released upon forward movement of said gripper jaws with respect to said camming means, the gripping engagement of said jaws on the workpiece being maintained by the force exerted by the workpiece on the jaws during the drawing operation and released when said force is released, resilient means for accelerating said assembly in the forward direction with respect to the-carriage when the trailing end of the workpiece is released from the die and the tension in the workpiece is released, said jaw supporting block having a portion engageable by the forward end of the workpiece upon release of the workpiece from the die for positively stopping forward movement of the workpiece with respect to the jaw supporting block, the assembly traveling in the forward direction in said slideway along with the forward end of the workpiece and means for gradually decelerating the forward movement of said assembly as it travels along said slideway.

7. Apparatus according to claim 6 wherein said slideway has an open slot at the bottom thereof through which a drawn workpiece may fall.

8. On a draw bench, a die stand, a die mounted in the die stand, a bed, a carriage mounted for movement on said bed in a forward direction away from the die stand and in a rearward direction toward the die stand, a gripper jaw assembly having jaw members and a jaw supporting block, means for supporting said gripper jaw assembly for substantial movement with respect to the carriage in directions parallel to the movement of said carriage, means for camming said gripper jaws into engagement with a workpiece when said assembly is moved rearwardly with respect to said camming means, said gripper jaws being released upon forward movement of said gripper jaws with respect to said camming means, the gripping engagement of said jaws on the workpiece being maintained by the force exerted by the workpiece on the jaws during the drawing operation and released when said force is released, said jaw supporting block having a portion engageable by the forward end of the workpiece upon release of the workpiece from the die, means for controlling the movement of said gripper jaw assembly comprising a connecting rod extending forwardly from said jaw supporting block, a piston on the forward end of the connecting rod, a

, cylinder mounted on said carriage in which said piston operates, a pneumatic system comprising means for supplying air under pressure to said cylinder to force said piston, connecting rod and gripper jaw assembly in a rearward direction to cam said gripper jaws into engagement with a workpiece to be drawn preparatory to a drawing operation, means for substantially reducing the pressure in said cylinder when the drawing operation begins, resilient means acting between said gripper jaw assembly and the carriage for accelerating the gripper jaw assembly, connecting rod and piston in the forward direction with respect to the carriage when the trailing end of the workpiece is released from the die and the tension is released, said gripper jaw assembly traveling in a forward direction in said slideway under the impetus of said resilient means and the force applied to it by the forward snap of the released workpiece, and means for controlling the discharge of air from said cylinder in front of said piston to gradually slow down said gripper jaw assembly and said workpiece.

9. Apparatus according to claim 8 wherein the pneumatic system comprises an air needle mounted on the carriage, means for supplying air under substantial pressure to said air needle when said carriage is adjacent said die stand, connections on said carriage whereby air at the pressure supplied through said needle is supplied to the forward end of said cylinder to move said piston in a rearward direction and urge said gripper jaw assembly into engagement with said workpiece while said carriage is adjacent said die stand, a reservoir on said carriage, a connection between said reservoir and said air needle whereby said reservoir is charged with air when air is admitted to said air needle, said connection incorporating a check valve to prevent the discharge of air from said reservoir through said air needle when said needle is disconnected from said stand, conduit means leading from said reservoir to the forward end of said cylinder, a pressure reducing valve in said conduit, valve means for reducing the pressure in said cylinder to the low pressure setting of said pressure reducing valve when said air needle is detached from said air supplying means and valve means for permitting the exhaust of air in said cylinder to atmosphere when the pressure in 1 1 said cylinder exceeds the low pressure setting of said pressure reducing valve.

10. Apparatus according to claim 9 having a cylinder head slidably mounted in the rear end of said cylinder, said connecting rod being slidable in said cylinder head, stop means for limiting forward movement of said cylinder head with respect to said cylinder, a spring acting between the carriage and said cylinder head and urging said cylinder head forwardly, air at the pressure of air admitted to said air needle forcing said piston into engagement with said cylinder head and forcing said cylinder head outwardly in a rearward direction from said cylinder whereby said gripper jaw assembly is moved into gripping position and said jaws are cammed into engagement with a workpiece, said spring having sufficient strength to force the cylinder head and piston forwardly against the low pressure of air in said cylinder determined by said pressure reducing valve until the cylinder head engages said stop means but said spring having insuificient force to move the cylinder head, piston and gripper jaw assembly forwardly against the force exerted on the gripper jaw assembly by the workpiece during the drawing operation.

11. Apparatus according to claim 19 wherein air at the low pressure setting of said pressure reducing valve is supplied to the forward end of the cylinder from the reservoir after a drawing operation has been completed and the workpiece discharged from the gripper jaws, said reduced pressure being sufficient to move'the piston assembly rearwardly to a position in which the piston engages said cylinder head without moving said cylinder head substantially away from said stop and the gripper jaws are in position to be forced rearwardly by the application of high pressure to said cylinder to cause said gripper jaws to engage a workpiece.

12. Apparatus according to claim 11 having mean for supplying air to the rear end of said cylinder to move said piston and said gripper jaw assembly to the forward limit of their travel, and means giving access to said assembly when said assembly is in such position.

7 13. In a draw bench having a bed, a die stand, a die carried by the die stand and a carriage mounted for movement on said bed in a forward direction away from the die stand and in a rearward direction toward the die stand, gripper jaws for gripping a workpiece to be drawn through said die, means for mounting said gripper jaws on said carriage whereby said gripper jaws are permitted substantial movement with respect to said carriage in directions parallel to said bed, means for causing said gripper jaws to grip a workpiece upon rearward movement of said jaws with respect to said carriage near the limit of such rearward movement, the gripping engagement of said jaws on the workpiece being maintained by the force exerted by the workpiece on the gripper jaws during the drawing operation and released when said force is released, said gripper jaws being moved in a forward direction on said carriage by the forward snap of said workpiece when the trailing end thereof .12 eling in a forward direction on said carriage along with the forward end of the workpiece, and pneumatic cylinder and piston means for urging said jaws rearwardly and into gripping engagement with a workpiece and simultaneously compressing said spring.

14. Ina draw bench having a bed, a die stand, a die carried by the die stand and a carriage mounted for movement on said bed in a forward direction away from the die stand and in a rearward direction toward the die stand, gripper jaws for gripping a workpiece to be drawn through said die, means for mounting said gripper jaws on said carriage whereby said gripper jaws are permitted substantial movement with respect to said carriage in directions parallel to said bed, means for causing said gripper jaws to grip a workpiece upon rearward movement of said jaws with respect to said carriage near the limit of such rearward movement, the gripping engagement of said jaws on the workpiece being maintained by the force exerted by the workpiece on the gripper jaws during the drawing operation and released when said force is released, said gri per jaws being moved in a forward direction on said carriage by the forward snap of said workpiece when the trailing end thereof leaves the die and said force is released, a spring acting between the carriage and said jaws for accelerating the gripper jaws in the forward direction with respect to the carriage when said force is released, said gripper jaws traveling in a forward direction on said carriage along with the forward end of the workpiece, and a single pneumatic cylinder and piston means for urging said jaws rearwardiy and into gripping engagement with a workpiece and simultaneously compressing said spring and for gradually decelerating the forward movement of said gripper jaws and of said workpiece.

15. The method of drawing an elongated workpiece through a die and preventing damage to the workpiece by the forward snap of the workpiece when it leaves the die through which it has been drawn, which includes the steps of grasping the forward end of the workpiece in a gripper jaw assembly, moving the gripper jaw assembly away from the die to draw the workpiece through the die, accelerating the gripper jaw assembly by a force independent of the workpiece in a direction away from the die at substantially the instant that the trailing end of the workpiece is released by the die, positively stopping forward movement of the workpiece with. respect to the gripper jaw assembly and thereafter gradually decelerating the gripper jaw assembly and thereby decelerating the workpiece by engagement between the gripper jaw assembly and the workpiece.

References Cited by the Examiner UNITED STATES PATENTS 2,776,695 1/1957 Wells 20524 FOREIGN PATENTS 701,367 1/1941 Germany. 1,005,921 4/1957 Germany.

=636,158 4/1950 Great Britain.

CHARLES W. LANHAM, Primary Examiner.

H. D. HOINKES, Assistant Examiner.

Claims (1)

1. IN A DRAW BENCH HAVING A BED, A DIE STAND, A DIE CARRIED BY THE DIE STAND AND A CARRIAGE MOVABLE ON THE BED IN A FORWARD DIRECTION AWAY FROM THE DIE STAND AND IN A RETURN DIRECTION TOWARD THE DIE STAND, THE COMBINATION OF A GRIPPER JAW ASSEMBLY HAVING JAWS FOR GRIPPING A WORKPIECE TO BE DRAWN THROUGH SAID DIE AND MEANS FOR POSITIVELY STOPPING FORWARD MOVEMENT OF THE WORKPIECE WITH RESPECT TO THE ASSEMBLY, MEANS FOR MOUNTING SAID GRIPPER JAW ASSEMBLY ON SAID CARRIAGE FOR SUBSTANTIAL MOVEMENT WITH RESPECT TO THE CARRIAGE IN DIRECTIONS PARALLEL TO SAID BED, MEANS FOR CAUSING THE GRIPPER JAWS TO ENGAGE A WORKPIECE TO BE DRAWN, MEANS ACTING BETWEEN THE GRIPPER JAW ASSEMBLY AND THE CARRIAGE FOR ACCELERATING THE GRIPPER JAW ASSEMBLY IN THE FORWARD DIRECTION WITH RESPECT TO THE CARRIAGE WHEN THE TRAILING END OF THE WORKPIECE IS RELEASED FROM THE DIE, AND MEANS FOR THEREAFTER GRADUALLY DECELERATING SAID GRIPPER JAW ASSEMBLY.

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