US3374655A

US3374655A - Cable-type drawbenches

Info

Publication number: US3374655A
Application number: US516488A
Authority: US
Inventors: Fred E Halstead
Original assignee: HALSTEAD METAL PRODUCTS Inc
Current assignee: HALSTEAD METAL PRODUCTS Inc
Priority date: 1965-12-27
Filing date: 1965-12-27
Publication date: 1968-03-26
Anticipated expiration: 1985-03-26

Description

March 26, 1968 s E 3,374,655

CABLE-TYPE DRAWBENCHES Filed Dec. 27, 1965 INVENTOR. FRED E. HALS'FEAD ATTORNEY United States Patent 3,374,655 CABLE-TYPE DRAWBENCHES Fred E. Halstead, Rochester, Pa., assignor to Halstead Metal Products, Inc., Zelienople, Pa., a corporation of Pennsylvania Filed Dec. 27, 1965, Ser. No. 516,488 5 Claims. (Cl. 72-287) This invention relates to drawbenches of the type employing cables for moving a draw carriage away from and toward a stationary drawing die, and more particularly to improvements in the take-up and adjustment of the cables of said drawbenches.

Cable-type drawbenches incorporate a cable system which consists of draw cables and return cables. The draw cables extend from the draw carriage, in the direction of draw, to a'prime mover which provides the power necessary to draw the workpieces through the drawing die. The return cables extend from the draw carriage, in the opposite direction, to a secondary mover which, at the completion of a drawing operation, returns the draw carriage to a position adjacent the drawing die. The secondary mover may be incorporated into the prime mover or may comprise a separate power component.

Cable-type drawbenches have several disadvantages which the present invention seeks to overcome. For example, long lengths of the cables in such drawbenches, have an inherent catenary sag due to their weight. This is particularly true in the return cables when the draw carriage is drawing workpieces through the drawing die. In the past, the catenary sag was eliminated, in part, by applying a very heavy preload to the cable system while the drawbench was idle. Some of the'preload remained on the return cables during the drawing operation. However, even with this heavy preload, a certain amount of sag and hence, slack, was always present in the return cables.

During a drawing operation, the draw cables are subjected to a large tensile force which tends to elongate them. The return cables, however, are under a very minor amount of tension, if any, inasmuch as the tensile forces in the draw cables are counterbalanced by the tensile forces in the workpieces being drawn. During the drawing operation, the return cables have a certain amount of sag or slack which does not atfect the drawing operation of the drawbench. However, at the completion of the drawing operation, the workpieces disengage from the drawing die and the tensile forces in the workpieces are suddenly transferred to the return cables. The draw carriage jumps forward, that is, in the direction of draw, until such time as the tension on the return cables and the draw cables equalizes. There results a violent reaction which tends to snap the return cables as the full drawing tension in the draw cables is released and the draw cables suddenly return to their normal shorter length. It should be evident that this violent reaction subjects the various drawbench components to severe shock loads which considerably shorten their operating life.

When the prime mover and secondary mover are combined and comprise a single main hydraulic cylinder and piston assembly, it is conventional to employ a cable reeving system comprising sheave devices arranged such that the short distance traveled by the piston is multiplied to move the draw carriage over the full length of the track structure. In this and other cable-type drawbenches, it is necessary at installation and periodically thereafter, to be able to adjust the position of the draw carriage relative to the drawing die when the piston is at the end of its stroke. This is necessary due to cable stretch. In the past, it has been necessary to provide two take-up mechanisms, one at each end of the cable reeving system, for example.

ice

When an adjustment in the position of the draw carriage was necessary, one take-up mechanism was loosened and the other take-up mechanism was tightened until the required position of the draw carriage relative to the drawing die was achieved. This manner of adjusting the position of the draw carriage is, of course, a time-consuming operation and requires many workmen for its completion.

Accordingly, as an overall object, the present invention seeks to provide an improved cable-type drawbench which does not have the aforementioned disadvantages.

Another object of the invention is to provide improved take-up means for cable-type drawbenches whereby the sag or slack in the cables is substantially entirely eliminated.

Still another object of the invention is to provide an improved cabletype drawbench having cable slack take-up means whereby jumping forward of the draw carriage and the subsequent whiplash action of the return cables are eliminated.

A further object of the invention is to provide a cabletype drawbench wherein the position of the draw carriage relative to the drawing die may be adjusted in a rapid manner with a minimum amount of labor.

The present invention is particularly useful in all of those drawbenches wherein cables connected between the draw carriage and a cable retracting mechanism, are used to return the draw carriage to its starting point adjacent the drawing die and wherein cables or other suitable means are employed to forcibly move the draw carriage during the drawing operation.

The drawbench may employ a double-acting hydraulic cylinder, such as illustrated in the drawing, for forcibly moving the draw carriage or other types of drive means, such as electric motors.

In accordance with the present invention, means is provided for applying a preselected tensile force on the return cables, of an amount suflicient to eliminate substantially entirely all sage in the return cables. The tensile force applying means is operated at all times during operation of the drawbench, that is, during the draw stroke, during the return stroke and during the idle time required to introduce new workpieces through the drawing die and into the gripper jaws of the draw carriage.

The tensile force applying means preferably comprises a single-acting hydraulic operated piston and cylinder means wherein the piston is connected to the return cables. Conduit means connected to the cylinder, introduces pressurized operating fluid therein which, acting on the piston and cylinder, creates the aforesaid preselected tensile force in the return cables. Control elements are provided in the conduit means for (a) maintaining the working fluid at a preselected pressure level sufiicient to produce the aforesaid preselected tensile force, and (b) for relieving, at a moderate rate, those excessive pressures created in the piston and cylinder means when the large tensile forces in the workpieces being drawn are suddenly transferred to the return cables as the workpieces disengage from the drawing die.

Further, in accordance with the invention, a single cable adjustment means is provided for adjusting the position of the draw carriage relative to the drawing die. The tensile force applying means is arranged such that the position of the draw carriage may be adjusted while the tensile force applying means is operating.

The above and other objects and advantages of the present invention will become apparent from the following detailed description by reference to the accompanying drawing, in which there is illustrated a cable-type drawbench incorporating the improved cable take-up and adjustment means of the invention.

General description or guideways 26; a hydraulic actuating cylinder 28 secured to a stationary support member 30; a pair of distance multiplying cable and

sheave assemblies

32, 34 disposed at the draw and return ends, respectively, of the drawbench a reversible, variable volume, high pressure pump 36 connected to the hydraulically actuated cylinder 28 by means of

conduits

38, 40; and a constant speed, electric motor 42 for driving the pump 36. In accordance with the invention, the drawbench 10 further includes a tensile force applying means 44 acting on the return cable of the distance multiplying cable and sheave assembly 34, and a single cable adjustment means 46 acting on the draw cable of the distance multiplying cable and sheave assembly 32.

As is known, the draw carriage 16 is guided by the track structure 22 in its movement away from the die 12 during the draw stroke and toward the die 12 during the return stroke. During the draw stroke, workpieces represented herein by the dash-dot centerlines 48, are

clamped by the gripper jaws 18 of the draw carriage 16' and are pulled through the die openings 14 of the drawing die 12.

The hydraulic actuating cylinder 28 comprises a cylinder 50 having a piston 52 which is slideable longitudinally through the cylinder 50. A first piston rod 54 is secured to the piston 52 and extends away from the drawing die 12 toward the distance multiplying cable and sheave assembly 32. A second piston rod 56 is secured to the piston 52 and extends toward the drawing die 12 and the dis tance multiplying cable and sheave assembly 34. The piston 52 has a first piston face 58 adjacent the first piston rod 52 and a second piston face 60 adjacent the second piston rod 56. The diameter of the first piston rod 54 is less than the diameter of the second piston rod 56. Consequently, the area of the first piston face 58 is greater than the area of the second piston face 60. The overall arrangement is such that the force created when working fluid acts on the first piston face 58 will be considerably greater than the force created when working fluid acts on the second piston face 60. During the drawing stroke, working fluid is communicated into the cylinder 50, by means of the conduit 38 to act on the first piston face 58 and thereby provide the large force required to draw the workpieces 48 through the drawing die 12. Conversely, during the return stroke working fluid is introduced into the cylinder 50, by way of the conduit 40, to act on the second piston face 60 and thereby provide the lesser force required to return the draw carriage 16 to its starting position adjacent the drawing die 12.

The distance multiplying cable and

sheave assemblies

32, 34 provide a distance multiplication of 4:1. That is to say, the draw carriage 16 will be moved four feet for each foot of travel of the piston 52. The distance multiplying cable and

sheave assemblies

32, 34 are substantially identical and comprise, in general, first stationary 7 or fixed

sheave carriages

62, 64, the carriage 62 being positioned at that end of the track structure 22 remote from the die 12 and the carriage 64 being positioned adjacent to the die 12; second stationary or fixed

sheave carriages

66, 68 being positioned adjacent to the

first sheave carriages

62, 64, respectively; movable sheave carriages 70, 72, the movable carriage 70 being secured to the end of the first piston rod 54 and the movable carriage 72 being secured to the end of the second piston rod 56;

intermediate sheave devices

74, 76 adjacent the

stationary sheave carriages

62, 64, respectively; a draw cable 78; and a return cable 80.

devices 82 of the stationary carriage 62, toward and around sheave devices 84 carried on the movable carriage 70, toward and around sheave devices 86 carried on the second stationary sheave carriage 66, toward and around sheave devices 88 on the movable sheave carriage 70, and finally toward and around the intermediate sheave device 74. With this arrangement, a single predetermined length of cable is employed.

In a similar fashion, the return cable is connected to the draw carriage 16 and extends therefrom in a direction opposite to the direction of draw about sheave devices 90 of the first stationary sheave carriage 64, toward and around sheave devices 92 carried by the movable sheave device 72, toward and around sheave devices 94' carried by the second stationary sheave carriage 68, toward and around sheave devices 96 carried by the movable sheave carriage 72, and finally, toward and around the intermediate sheave device 76.

It should be evident, that as the piston 52 is moved toward the drawing die 12, the upper reach of the draw cable 78, that is, that portion extending from the draw carriage 16, will be retracted so that thedraw carriage 16 is moved away from the drawing die 12. Conversely,

when the piston 52 moves away from the drawing die 12, the upper reach of the return cable 80 will be retracted so that the draw carriage 16 is moved toward the drawing die 12.

The above-mentioned distance multiplication is, of

course, obtained by the arrangement of the various sheave" 6 devices. Inasmuch as four strands of the draw cable 78, for example, extend between the

stationary sheave carriages

62, 66 and the movable sheave carriage 70, the mechanical advantage has a value of four. Consequently, the carriage 16 will be moved four feet for each foot traveled by the piston 5'2.

Tensile force applying means 44 The tensile force applying means 44, of the invention, preferably comprises a single-acting hydraulic. cylinder 98 having a piston 100'which is slideable longitudinally therein. A piston rod 102 has one of its ends connected to the piston 100 and the other of its ends connected to a;

may comprise a part of a main sump 112 from which the pump 36 draws working fluid.

In the conduit 106 there is provided a check valve 114 and a pressure reducing valve 116 which is positioned downstream of the check valve 114. The pressure reducing valve 116 is of the self-bleeding type having a bleed conduit 118 extending to the main sump 112. As will be described in greater detail, working fluid will be returned to the main sump 112 by way of the bleed conduit 118 when the pressure in the hydraulic cylinder 98 exceeds a predetermined pressure level.

Cable adjustment means 46 In accordance with the present invention and as stated above, a single cable adjustment means 46 is provided which acts on the draw cable 78. The cable adjustment means 46 may comprise, for example, a rod 120 having one of its ends connected to a clevis member 122 which supports the intermediate sheave device 74 and having its opposite end threaded and extending through a support block 124 and a nut 126. Rotation of the nut 126 in one direction will cause the rod 120 and hence the intermediate sheave device 74 to be moved toward the die block 12 while rotation of the nut '126 in the opposite direction will cause the rod 120 and hence the intermediate sheave device 74 to be moved away from the drawing die 12. It should be noted at this time that any other suitable cable adjustment means may be employed.

Operation of tensile force applying means 44 The function of the tensile force applying means 44 is to place the return cable 80 under suflicient tension such that substantially entirely all sag or slack is eliminated from the return cable 80. As will now be explained, certain advantages result from tensioning the return cable 80.

During the draw stroke, the pump 36 pressurizes the working fluid and conveys the same through the conduit 38 to the main hydraulic cylinder 28. Pressurized working fluid is also conveyed to the cylinder 98 by way of the conduit 106. However, the pressure of the working fluid is reduced by the pressure reducing valve 116, to a preselected pressure level which is suflicient to produce the aforesaid preselected tensile force in the return cable 80.

At the start of the draw stroke, the piston 52 moves toward the drawing die 12. The draw cable 78 will undergo a certain amount of elongation until the force required to draw the workpieces 48 through the die 12 has been attained. Consequently, as the draw cable 78 is elongated, the tension in the return cable 80 tends to be reduced and, in the absence of the hydraulic cylinder 98, would result in sag or slack in the return cable 80'. However, the hydraulic cylinder 98 maintains the return cable 80 under sufiicient tension whereby substantially entirely all sag or slack is eliminated. The return cable 80 will also be elongated slightly by the applied tensile force.

At the completion of the draw stroke, the workpieces 48 disengage themselves from the drawing die 12 and the tensile forces which were in the workpieces 48 are suddenly transferred to the return cable 80. At this time, the draw cable 78 attempts to return to its shorter length by tending to pull the draw carriage 16 and the return cable 80 in the direction of draw. The tensile forces in the draw cable 78 will be reduced until they are equal to and opposed by the tensile forces in the return cable 80. Since the return cable 80 is itself under tension and has substantially no sag or slack, the draw carriage 16 and the return cable 80 will move only a very slight distance in the direction of draw. Consequently, the drawbench components are not subjected to the shock loads which would result if there was sag or slack in the return cable 80.

As the draw cable 78 contracts and tightens, the pressure in the hydraulic cylinder 98 is intensified, that is, increased above the preselected pressure level. The pressure reducing valve 116 will gradually bleed excess working fluid to the bleed conduit 118 until such time as the excessive pressure within the cylinder 98 are relieved and the pressure within the cylinder 98 returns to the aforesaid preselected pressure level. Hence, the excessive backpressures created in the hydraulic cylinder when the workpieces are disengaged from the drawing die, are relieved at a rate which prevents damage to the various drawbench components.

As is known, differences in the metallurgy and the physical properties of the workpieces 48 may cause one or more of the workpieces 48 to be disengaged from the drawing die 12 before the remaining workpieces 48 are disengaged, that is, the workpieces 48 are not simultaneously disengaged from the drawing die 12. In this instance, the tensile forces in the workpieces 48 will be transferred to the return cable 80 in a stepwise manner. In turn, the hydraulic cylinder 98 and the pressure reducing valve 116 will cooperate and operate as described above, to reduce the resulting excessive backpressures in a stepwise manner.

6. Operation 0] cable adjustment means 46 The function of the cable adjustment means 46 is to reposition the draw carriage 16 relative to the drawing die 12. More specifically, when the piston 52 of the main hydraulic cylinder 28 is at the end of its stroke, that is, adjacent the conduit 38, the draw carriage 16 is at its starting position adjacent to the drawing die 12. Because of:variations in cable stretch, the draw carriage 16 will not, at all times, return to the exact starting position, as required. Consequently, at installation and periodically thereafter, the position of the draw carriage 16 must be adjustedto correspond to the desired starting position.

In the drawbench 10, only a single cable adjustment means 46 is included and required to reposition the draw carriage 16 relative to the die 12. In prior art drawbenches, two cable adjustment means were required, one acting on the draw cable. and the other acting on the return cable.

When it becomes necessary to reposition the draw carriage 16, the nut 126 is rotated in the direction which will move the draw carriage 16 either away from the die 12 or toward the die 12 so. that the draw carriage 16 is moved to the desired starting location. In the case where the draw carriage 16 must be moved toward the drawing die 12, the nut 126 must be rotated in a clockwise direction, assuming right-hand threads, such that the draw cable 78 is loosened. At this time, the working fluid acting on the piston will draw the return cable 80 to take up the slack in the draw cable 78. This process is continued until the draw carriage 16 is positioned at the exact desired starting position.

In the case where the draw carriage must be moved away from the drawing die 12, the nut 126 is rotated in a counterclockwise direction so that the tension in the draw cable 78 and the return cable 80 is increased. The increased cable tension will, of course, intensify the pressure within the hydraulic cylinder 98. The excessive pressure is, as described above, relieved by the pressure reducing valve 116 by bleeding working fluid to the bleed conduit 118. This process is continued until such time as the draw carriage 16 is moved to the exact required starting position.

Alternative arrangement As stated above, the present tensile force applying means 44 and the take-up adjustment means 46 are applicable to any drawbench having a return cable which, in the absence of these means, would sag during the drawing operation. In those drawbenches wherein prime movers other than the main hydraulic cylinder is employed, a small auxiliary power unit may be provided. Such an auxiliary pumping unit is illustrated in the drawing in dash-dot outline as comprising, for example, a small auxiliary pump 130 driven by an electric motor 132 and having a sump 134 associated therewith. The auxiliary pump 130 would pressure working fluid and convey the same to the conduit 106 to the hydraulic cylinder 98. The bleed line 118 would, of course, extend to the sump 134.

Although the invention has been shown in connection with certain specific embodiments, it will be readily apparent to those skilled in the art that various changes in form and arrangement of parts may be made to suit requirements without departing from the spirit and scope of the invention.

I claim as my invention:

1. In a drawbench having a drawing die, a track structure extending parallel to the central axis of said drawing die, a draw carriage movable along said track structure for pulling workpieces through said drawing die, return cable means connected to said draw carriage and extending therefrom in a direction opposite to the direction of draw, and means operable on said return cable means for returning said draw carriage adjacent said drawing die, the improvement comprising: means including a hydraulic cylinder for applying a preselected tensile force on said return cable means in a direction opposite to the direction of draw and of an amount sufi'icient to eliminate substantially entirely all sag in said return cable means.

2. The improvement as defined in claim 1 including valve means for maintaining the pressure of operating fluid in said hydraulic cylinder at a preselected pressure level sufficient to create said preselected tensile force, and means for relieving excessive backpressures created in said hydraulic cylinder when the workpieces disengage from said drawing die.

3. The improvement as defined in claim 1 including valve means for maintaining the pressure of operating fluid in said hydraulic cylinder at a preselected pressure level suflicient to create said preselected tensile force and bleed means incorporated into said valve means for bleeding a quantity of the working fluid from said hydraulic cylinder to relieve excessive backpressures created in said hydraulic cylinder when the workpieces disengage from said drawing die.

4. The improvement as defined in claim 1 including single means at the draw end of said track structure for moving said draw carriage toward and away from said 8 drawing die to adjust the position of said draw carriage relative to said drawing die.

5. The improvement as defined in claim 1 including single means at the draw end of said track structure for moving said draw carriage along said track structure to adjust its position relative to said drawing die, valve means for introducing operating fluid into said hydraulic cylinder to raise the pressure of operating fluid to said preselected pressure level when said draw carriage is moved toward said drawing die by said adjustment means, and means for relieving excessive backpressures in said hydraulic cylinder above said preselected pressure level when said draw carriage is moved away from said drawing die by said adjustment means.

References Cited UNITED STATES PATENTS 1,475,701 11/1923 John 72-291 Y CHARLES w. LANHAM, Primary Examiner.

H. D. HO'INKES, Assistant Examiner.

Claims

1. IN A DRAWBENCH HAVING A DRAWING DIE, A TRACK STRUCTURE EXTENDING PARALLEL TO THE CENTRAL AXIS OF SAID DRAWING DIE, A DRAW CARRIAGE MOVABLE ALONG AND SAID TRACK STRUCTURE FOR PULLING WORKPIECES THROUGH SAID DRAWING DIE, RETURN CABLE MEANS CONNECTED TO SAID DRAW CARRIAGE AND EXTENDING THEREFROM IN A DIRECTION OPPOSITE TO THE DIRECTION OF DRAW, AND MEANS OPERABLE ON SAID RETURN CABLE MEANS FOR RETURNING SAID DRAW CARRIAGE ADJACENT SAID DRAWING DIE, THE IMPROVEMENT COMPRISING: MEANS INCLUDING A HYDRAULIC CYLINDER FOR APPLYING A PRESELECTED TENSILE FORCE ON SAID RETURN CABLE MEANS IN A DIRECTION OPPOSITE TO THE DIRECTION OF DRAW AND OF AN AMOUNT SUFFICIEN TTO ELIMINATE SUBSTANTIALLY ENTIRELY ALL SAG IN SAID RETURN CABLE MEANS.