US3243980A - Material handling arm mechanism - Google Patents

Description

April 5, 1966 F. J. SEHN ETAL 3,

MATERIAL HANDLING ARM MECHANISM Filed June '7, 1961 6 Sheets-Sheet 1 M140 lti CIA Ma Br a .r

A TI'OR/VA-fS A ril 5, 1966 F. J. SEHN ETAL 3,243,980

MATERIAL HANDLING ARM MECHANISM 7 Filed June 7, 1961 6 Sheets-Sheet 2 F J. SEHN ETAL MATERIAL HANDLING ARM MECHANISM April 5, 1966 6 Sheets-Sheet 5 Filed June 7, 1961 April 5, 1966 F. J. SEHN ETAL 3,243,930

MATERIAL HANDLING ARM MECHANISM Filed June 7, 1961 6 Sheets-Sheet 5 IN VEN TORS 5094 0: J. saw/v B 45/66 M. 6267910 6 A/Wz n47 A ril 5, 1966 F. J. SEHN ETAL MATERIAL HANDLING ARM MECHANISM 6 Sheets-Sheet 6 Filed June 7, 1961 soz-c INVENTORS news/c1: J. crew/v nna K2 twigs United States Patent 3 243 980 MATERIAL ARM MECHANISM Francis J. Sehn, 3515 Brookside Drive, Bloomfield Hills, Mich, and Maurice M. Clemons, 32664 Inkster Road,

Franklin, Mich.

Filed June 7, 1961, Ser. No. 116,658 13 Claims. (Cl. 72-24) The present application is a continuation-in-part of our copendin-g application, Serial No. 35,784, filed June 13, 1960, expressly abandoned by the filing of the present application.

This invention relates to a material handling arm mechanism and more particularly to a swinging arm mechanism which may be mounted on the face of a stamping press or the like for the purpose of unloading workpiece stampings after they are formed.

The arm is suspended from a stationary framework and is provided at its lower end with an extensible jaw mechanism operable when the press is open to move horizontally in and grip the flange of a workpiece. The arm is thereupon actuated producing a path for the jaws which is briefly vertical to lift the workpiece from the lower die with rapid transition to a substantially horizontal gradually ascending path at the end of which the workpiece is entirely removed from the press and released by the jaw mechanism onto a moving or gravity conveyor leading away from the press.

In a material handling mechanism of this type, the path of jaw travel is critical and preferably changes rapidly from an initial vertical lifting path to a substantially horizontal gradually ascending path that is free of any momentary downward dip after the transition to horizontal movement. Such dip in the jaw path has been a persistent problem in prior swinging arm constructions and it is one of the principal objects of the present construction to completely eliminate any dip from all positions of adjustment for the arm mechanism. This is accomplished basically by forming the main arm at its upper end as a bell crank member with a center pivot movable along a vertical path while an end pivot of the bell crank is constrained to move along a circular arcuate path by control arms having a fixed pivotal axis in initial horizontal alignment with the end pivot of the bell crank arm. Thus, at the beginning of actuation, both the center and end pivots of the bell crank arm move in a substantially vertical path providing the initial vertical lift for the jaw mechanism whereafter the progressively increasing pivotal actuation of the bell crank arm as the control arm departs from a horizontal position provides the desired transformation of path.

The actuation of the swinging arm to a raised position is effected by pressurizing an air cylinder while its return to a lowered position is effected by gravity upon the exhausting of air pressure from such cylinder. While it is desirable from the standpoint of speed of operation that free fall of the arm should not be unduly inhibited by restriction of the exhaust, a tendency for the arm to bounce against the air cushion near the end of the air piston stroke upon the downward gravity return of the swinging arm has made it difficult to obtain a smooth deceleration of the arm to its lowermost home position. This problem has been solved by providing an adjustable pressure relief valve in parallel with an adjustable orifice for regulating the exhaust flow from the air cylinder during the descent of the swinging arm.

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These principal and other objects will be more readily understood from the following detailed description of a preferred embodiment of the invention with reference to the drawings, wherein:

FIGURE 1 is a side elevation of a preferred embodiment of the invention;

FIGURE 2 is an enlarged end elevation taken along the line 22 of FIGURE 1;

FIGURE 3 is a further enlarged sectional elevation taken along the line 33 of FIGURE 2;

FIGURE 4 is a schematic side elevation similar to that of FIGURE 1 showing certain of the control elements;

FIGURE 4a is a modification of the pneumatic control circuit shown in FIGURE 4 adapted to eliminate bounce from the downstroke; and

FIGURE 5 is a schematic electrical control diagram for a typical automatic and manual control circuit.

Referring to FIGURE 1, the present preferred material handling arm is mounted on the face of a press, not shown, by a pair of hooks 11 and a mounting plate 12 having an adjustment screw 13. A rigid framework suspended from the hooks 11 includes a pair of side plates 14 (one of which is omitted from FIGURE 1 to more clearly show the internal mechanism), an upper end plate 15 on which a mounting plate 16 is adapted to hold actuating cylinder 17, a lower end plate 18, a pair of channel tie bars 19 welded to attaching pads 20, and three guide rails 21a, 21b, and 21c secured to the inside of each of the side plates 14. The material handling arm per se 22 includes a bell crank weldment formed by a pair of side members 23 joined by a formed spacer plate 24 and a tie bar 25. A lower arm 26 formed as a tapered channel member is provided with a pair of hooks 27 for engaging the tie bar and is adjustably secured in any of several positions 28 by suitable bolts passing through the lower ends 29 of the side plates 23. A tubular extension 30 of the lower arm 26 is adjustably secured by a pair of clamps 31 on the inside of the lower arm 26 and serves to mount a workpiece gripping mechanism 32 by a pivotally mounted clamp 33 positioned by adjustment screw 34. Workpiece gripping jaws 35 are adapted to be advanced to the right, as shown in FIGURE 1, and closed by an actuating cylinder 36 and piston rod 37 to engage the edge flange of a workpiece (not shown) after it is formed and the dies are opened in a manner known to the art whereupon the jaws and workpiece are moved along a path 38 by actuation of the arm 22 to the phantom position 39 by actuating mechanism now to be described.

The basic linkage mechanism by which the material handling arm is actuated and controlled may be clearly understood by reference to the simplified schematic view in FIGURE 4 wherein it will be seen that rollers 40 control the vertical movement of the bell crank arm 23 between fixed straight guide rails 21a and 21b, while the outer end 41 moves along a circular are established by control arms 42 pivoted on a fixed axis 43. Actuating links 44 pivotally connected to the bell crank arm 23 and control arm 42 at the end 41 are also connected at 45 to an actuating piston rod 46.

Referring to the corresponding mechanism illustrated in FIGURES 1, 2 and 3, it will be seen that the rollers 40 running between guide rails 21a and 2111 are secured to the sidewalls 23 of the bell crank weldment by suitable mounting pads 47 and stub axles 48 while rollers 49 running between guide rails 21b and 21c are connected by a cross block 50 to the piston rod 46 and to the actuating links 44 which are in turn pivotally connected by a cross 3 shaft 51 to the end 41 of the bell crank arm 23 as well as the corresponding ends 52 of the control arms 42.

When the piston rod 46 is initially actuated in upward direction, the initial direction of movement of the pickup jaws 35 will be substantially vertical due to the substantially horizontal position of the control arm 42 and vertical direction of guide tracks 41a and 41b. This initially lifts the workpiece in a vertical direction from the dies of the press which is desirable particularly in the case of deep draws. The path of the jaws is thereafter rapidly transformed to a substantially horizontal path due to the horizontal component of movement imparted to the end 41 of the bell crank arm multiplied by the relative distance of the jaws from the pivot center 40 of the bell crank arm. It will be noted that as the rollers 40 move upwardly and the bell crank is actuated in a clockwise direction, as seen in FIGURES 1 and 4, such upward movement is to some extent olfset by the downward component of the jaws initial movement in pivoting around the center 40. Such downward component becomes progressively less as the arcuate rate of actuation of the bell cr-ank arm for given increment of vertical travel becomes progressively greater resulting in a highly desirable substantially flat gradually sloping retraction curve for the jaws 35 as shown at 38. One particularly desirable feature of such path is the complete absence of an initial dip (as illustrated at 38a) which has been characteristic of the jaw path of prior swinging arm unloading mechanisms. It is to be further noted that as the arm is progressively raised, the mechanical advantage of the linkage progressively increases compensating for the increasing moment arm on which the effective center of load arm weight operates thereby permitting a relatively low and substantially constant actuating pressure to be employed in the cylinder 17.

A typical automatic and manual control circuit for the preferred arm mechanism is illustrated in FIGURES 4 and 5. Assuming that the arm is to be employed in an unloading operation with switch SW1, shown off, depressed to on position, connecting line voltage to the control circuit, switch SW2 in automatic position, as shown, and switch SW3 in the arm down position, as shown, limit switch LS1 is actuated by retraction of the press head (not shown) after the forming operation. A timer T1 and relay CR1 the energizing coils for which are respectively designated by encircled T1 and CR1 are energized and held by a CR1 contact in series with the energizing coils closed by the energizing of relay CR1. Another CR1 contact closed by the energizing of relay CR1 energized the coil of solenoid valve SOL-A in series with such contact which actuates corresponding valve shown in FIG. 4 which moves the jaws forward and closes same to engage the flange of a formed workpiece (not shown). Upon the passing of a predetermined time after the timer T1 is first energized the closing of a timer T1 contact in series with the coil of solenoid SOL-B will energize the solenoid moving the piston rod 46 and arm to up position. On the way up, limit switch LS3 and timer T2 are energized and upon the opening of a timer T2 contact, the timer T1 and relay CR1 coils in series therewith are de-energized which in turn de-energize solenoid SOL-A causing retraction and opening of the jaws to release the workpiece. As the arm reaches its uppermost position, limit switch LS4 is closed energizing timer T3 and solenoid SOL-C causing the arm to return to its normal down position. The press closes only if LS5, the jaw limit switch, is actuated by retracted position while limit switch LS6 returns the press to the top.

If switch SW3 is depressed closing circuits associated with limit switch LS2, timer T3 and limit switch LS a similar automatic cycle results with the exception that the arm is normally up in its starting position. After the press forms the workpiece and limit switch LS1 is closed, this time energizing solenoid SOL-C, the arm will go down actuating limit switch LS2, energizing the 4 timer T1 and relay CR1 moving the jaws forward and closing same. When the timer T1 contact closes and the solenoid SOL-B is energized, the arm goes up and on the way up limit switch LS3 is depressed, timer T2 is energized which in turn de-energizes the jaw and arm up solenoids and the arm stays up. The press closes only if limit switch LS5 is actuated and if the timer T3 is energized signifying that limit switch LS4 is depressed or that the arm is up.

For manual operation, the selector switch SW2 is depressed whereupon manual operation of switch SW4 will move the jaw forward and close while the manual operation of switch SW5 will move the arm up or down.

With reference to FIGURE 4a, solenoid SOLA controlling the horizontal jaw cylinder is also adapted to control the admission and release of air pressure from the line 50 for raising and lowering piston rod 46 adapted to actuate the swinging arm assembly as in the case of FIGURE 4. The pneumatic circuit includes a pilot valve 51, a quick exhaust valve 52 through which pressure can also pass from line 59 to line 50, an adjustable pressure relief valve 53 and adjustable orifice one-way speed control valves 54a, 54b, 54c and 54d. It will be understood that where the disc seal element in valve 52 is shifted to the left by pressure in line 59, air can pass around the outer perimeter into line 50 while being sealed from line 60 and that release of pressure from line 59 permits pressure in line 50 to shift the disc to the right connecting line 50 to line 60. When air pressure is admitted through line 55 to the retract side of the horizontal jaw cylinder, air is simultaneously exhausted through an exhaust port in valve controlled by solenoid SOL-A from line 56, branch line 57 and, at a rate regulated by speed control valve 540, from the top end of pilot valve 51 causing the valve to be spring returned to the exhaust position shown where pressure line 58 is blocked and pressure is exhausted from line 59 and the communicating chamber of quick release valve 52 through the exhaust port in the valve 51 thereby exhausting pressure from line 50 into exhaust passage 60 leading to the respective pressure relief valve 53 and speed control valve 54a. During the initial portion of the down stroke, the air pressure will be entirely exhausted through the orifice of speed control valve 54a and little resistance will be offered to the free fall of the swinging arm. However, as the arm is accelerated by gravity, pressure progressively builds up on the orifice of valve 54a and finally near the end of the downstroke becomes high enough to open pressure relief valve 53 providing an auxiliary exhaust path for the air. In the absence of the pressure relief valve 53, the pressure build up on the exhaust orifice of valve 54a would be suflicient to cause an air cushion bounce in the downward travel of the swinging arm to its home position and the use of an adjustable orifice on itself has been found inadequate to eliminate such bounce without undue delay of the downward movement. However, by properly adjusting pressure relief valve 53, any rapid build up of high bounce pressure is effectively prevented with the result that the arm can be smoothly decelerated to its final home position with no bounce whatsoever and no delay in its rate of downward travel.

One effective way to initially adjust these controls is to tighten the pressure relief valve 53 to a value rendering it ineffective and, starting with a small opening in the orifice of valve 54a, progressively increasing such opening until a rapid downward travel of the swinging arm occurs with a pressure build up sutficient to create an air cushion bounce at the end of its downward travel without striking the home stop. The spring load on the pressure relief valve 53 is then progressively decreased until the bounce is eliminated and the swinging arm decelerates smoothly to its final home position.

A manual valve MA'N. by passing the pilot valve 51 can be used with the automatic valve AUTO turned off to raise the arm regardless of the jaw position.

While a particular preferred embodiment of the invention and typical control circuit have been described above in detail, it will be understood that numerous further modifications might be resorted 'to without departing from the scope of the invention as defined in the following claims.

We claim:

1. A material handling arm mechanism for unloading a stamping press or the like characterized by a fixed frame, a fixed guide track mounted on said frame, a load arm having a first pivot movable along a linear path established by said guide track above the center of gravity of said load arm, a control arm, a fixed pivotal connection between said control arm and said frame, a pivotal connection between asid control arm and said load arm spaced from asid first load arm pivot and said fixed pivotal connection, means including an actuator with variable mechanical advantage linkage connected to said load arm for moving said load arm under the combined control of said control arm and fixed guide, said linkage providing a variable mechanical advantage increasing to a maximum when said center of gravity reaches a maximum lateral displacement from said first pivot and workpiece engaging means at an end of said load arm remote from said load arm pivotal connections.

2. A press unloader as set forth in claim 1 wherein said workpiece engaging means includes fluid pressure actuated extensible jaw means adapted to move horizontally into gripping engagement with the workpiece when the press is open, separate fluid pressure actuated means for moving said load arm, and automatic fluid pressure control means for producing an unloading cycle in response to the opening of the press.

3. A press unloader as set forth in claim 1 wherein said workpiece engaging means includes fluid pressure actuated extensible jaw means adapted to move horizontally into gripping engagement with the workpiece when the press is open, separate fluid pressure actuated means for moving said load arm, and automatic fluid pressure control means for producing an unloading cycle in response to the opening of the press, said fluid pressure control means including manually operable switch means for selectively establishing a control cycle terminating with the load arm in its lowermost position or in raised position.

4. A swinging arm press unloader as set forth in claim 1 for attachment to the frame of a press adapted to engage a workpiece and swing it outwardly and upwardly away from the press, air cylinder means adapted to impart unloading movement to said arm, gravity being at least partially employed in returning said arm to its lowermost position, control means for cushioning said return movement of said arm to its lowermost position including means for regulating the exhausting of air from said air cylinder, said last means including orifice means for regulating the rate of exhaust flow, and supplemental pressure relief valve means for limiting the maximum exhaust pressure to that required for decelerating the arm at the end of its return movement thereby avoiding an air-cushion bounce in the downward travel of the arm to its home position.

5. A material handling arm mechanism as set forth in claim 1 operable between fixed end positions, air cylinder means for actuating said arm mechanism, control means for restricting the exhaust flow from said air cylinder means to cushion the travel of said arm mechanism toward one of its end positions, said last means including adjustable, restrictive orifice means, and supplemental adjustable pressure relief means for limiting said exhaust pressure to a maximum value to that required for decelerating the arm at the end of its return movement thereby avoiding an air-cushion bounce in the downward travel of the arm to its home position.

6. A press unloader characterized by a fixed frame adapted for attachment to the frame of a press, a fixed guide track on said frame, a load arm having a pivot movable along a linear path established by said guide track above the center of gravity of said load arm, a control arm having a fixed pivot on said frame and a piv ot connected to said load arm spaced from said movable and fixed pivots, and means including an actuator with linkage connected to said load arm for actuating said load arm under the combined control of said guide track and said control arm, said linkage providing a variable mechanical advantage increasing to a maximum when said center of gravity reaches a maximum lateral displacement from said first pivot.

7. A press unloader as set forth in claim 6 wherein said guide track establishes a substantially straight vertical path.

8. A press unloader as set forth in claim 6 wherein the pivots of said control arm are in a substantially horizontal plane when said first named pivot is at one end of its linear path.

9. A press unloader as set forth in claim 8 wherein said guide track extends in a substantially vertical direction.

10. A press unloader as set forth in claim 9 wherein said guide track extends in a substantially straight vertical direction, said load arm is provided with workpiece engaging means at an end remote from said pivotal connections, said workpiece engaging means is adapted to initially engage the workpiece at a point substantially spaced in a horizontal direction from the vertical line of said guide track, and wherein the pivot of said control arm connected to said load arm is horizontally spaced relative to said fixed pivot in a direction causing said engagement point to move toward the said vertical line as said control arm moves from its horizontal position.

11. A press unloader comprising a fixed frame adapted for attachment to the frame of a press, a fixed vertical guide track on said fixed frame, a vertically suspended load arm having an uppermost bell crank end, a pivot in said bell crank end movable along a linear path established by said guide track, a control arm having a pivot fixed on said frame and a pivot connected to said bell crank end of said load arm spaced from said other pivots, a fluid pressure cylinder mounted on said fixed frame having a piston and linkage connected to said bell crank end adapted to actuate said load arm, said linkage providing a variable mechanical advantage increasing to a maximum when said center of gravity reaches a maximum lateral displacement from said first pivot.

12. A material handling art mechanism for unloading a stamping press or the like comprising a fixed frame, a. load arm suspended from said frame having workpiece engaging means at its lower end, said means having a required path of travel initially substantially vertical rapidly converting to a substantially horizontal and then gradually ascending curve to a work released position in which the center of gravity of the loaded arm is substantially displaced laterally from the center of suspension as well as at its maximum height thereby imposing a maximum gravity moment force which must be overcome substantially in excess of the average force required to raise and swing the arm through its path of travel; said mechanism being characterized by arm actuating power cylinder means acting in a substantially vertical direction, a pair of spaced pivotal reaction points at and near the upper end of said arm for controlling the movement thereof, guide means on said frame adapted to confine one of said reaction points to a substantially vertical path, means on said frame adapted to confine the other of said reaction points to an arcuate path having an initial substantially vertical portion, variable mechanical advantage actuating linkage means between said power cylinder means and said load arm providing an increasing mechanical advantage as said load arm approaches its discharge position.

13. Material handling arm mechanism as set forth in claim 12 wherein said variable mechanical advantage actuating linkage means includes a radius arm pivotally connected to said frame for establishing said arcuate path and an auxiliary link interposed between said power cylinder means and said load arm providing a decreasing relative rate of actuation therebetween as said load arm approaches said discharge position.

References Cited by the Examiner UNITED STATES PATENTS Westin 2141.4

Sahlin 2141.4X Miller 214-147 X Haanes '2141.4

8 3,002,497 10/ 196 1 Gulick. 3,010,433 11/1961 Codling 121-38 3,040,685 6/1962 Ridley 2141.4 X

5 FOREIGN PATENTS 803,447 10/1958 Great Britain.

CHARLES W. LANHAM, Primary Examiner.

HUGO SCHULZ, NEDWIN BERGER, Examiners. 10 P. L. HENRY, R. J. HERBST, Assistant Examiners.

Claims (1)

1. A MATERIAL HANDLING ARM MECHANISM FOR UNLOADING A STAMPING PRESS OR THE LIKE CHARACTERIZED BY A FIXED FRAME, A FIXED GUIDE TRACK MOUNTED ON SAID FRAME, A LOAD ARM HAVING A FIRST PIVOT MOVABLE ALONG A LINEAR PATH ESTABLISHED BY SAID GUIDE TRACK ABOVE THE CENTER OF GRAVITY OF SAID LOAD ARM, A CONTROL ARM, A FIXED PIVOTAL CONNECTION BETWEEN SAID CONTROL ARM AND SAID FRAME, A PIVOTAL CONNECTION BETWEEN SAID CONTROL ARM AND SAID LOAD ARM SPACED FROM FIRST LOAD ARM PIVOT AND SAID FIXED PIVOTAL CONNECTION, MEANS INCLUDING AN ACTUATOR WITH VARIABLE MECHANICAL ADVANTAGE LINKAGE CONNECTED TO SAID LOAD ARM FOR MOVING SAID LOAD ARM UNDER THE COMBINED CON-

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