US2028768A - Die press safety system - Google Patents

Description

Jan. 28, 1936. c. EKSERGIAN DIE PRESS SAFETY SYSTEM Filed July 22, 1930 I N VEN TOR.

CARoLus L EKSERGAN A TTORNE Y.

. Patenteoi ian. 28,,1936

ED s'rArrss PATENT OFFICE;

2,028,768 .mr: mass SAFETY SYSTEM Carolus L. Eksergian, Detroit, Mich., assignor to Edward Budd Manufacturing Company, Philadelphia, Pa., a corporation of Pennsylvania Application July 22, 1930, Serial No. 469,784

7 Claims.

erating presses hand started, and particularly those in connection with which there are em-' ployed a number of operatives, the press is'sometimes startedby oneof the operators before an.-

other has completed the attention he is giving the work on the machine. But while it is the special aim of this invention to relieve these conditions and assure safety to the operatives of such presses, my invention has a" wider scope still in its possible applicability to any machines having working cycles and parts which analogously endanger the limbs of their operatives.

Numerous systems and methods have heretofore been proposed to remedy these conditions. None of them, so far as I am aware, have been completely effective. Some-have been mechanical and some electrical. The most common in intermittently operating presses has been the location of the control lever or, control button of the electrical control circuit at a distance so remote from the dies as to require the operator to remove his hands or himself from each of the dies in order to reach the control.

Another device has been that of duplex control in which two control elements have been provided, one for operation by. each hand of an operative, whereby neither hand is available during control of the press for engagement with the machine or the work.

Yet with these and other safeguards, accidents have continued due, among others, to situations like the following. Power control devices or the presses-at times stopped in the on position, thereby continuing operation of the press expected by the operative to terminate at the end of the stroke. Operatives, sometimes-carelessly and sometimes in an endeavor to save time, oper-' ated dual control devices, both by one hand, and at the other, times blocked off one of the controls to avoid the necessity of using both. The two operatives, once the press was started, if the control system was such as to permit it to continue, 'removedtheir hands from the control devices and gave attention to work on the machine before the completion of the down stroke, while there was still danger that the hands projected between the dies or other parts of the machine the same might result in As a general rule, control once instituted has been automatic for the completion of at least one full stroke of the machine, and with control handles or push buttons, as the case may be, the same might readily be released after initial actuation. Thisoperation has been favored because it permitted, more leisurely, picking up and presenting of the work for the succeedingoperation. The objects of my invention have especially to do with the meeting of these situations. More general objects of my invention are the attainment of a perfect safety system in which not 'only the special situation is met, but each and every other situation of danger to the operative is eliminated, the efficient combination of manual control by the operative and automatic control 15 by the press, and the achievement of an efficient, simple and inexpensive safety system for large power presses embodying servomotor control of the power cut on and cut oif devices.

The single figure of'the drawing is a diagram- 20 matic showing of the system, some parts being represented schematically, and others in elevation consequently the dimensions of the various parts in the drawing are disproportionate to their true dimensions. 1

In this showing the press and the dies are subordinated to the enlargement and clarification of the general diagram of the system. For--the most part, the press is indicated in dotted lines. I0 is its bed located on foundation II, l2 and I3 30 are the lower and upper dies, respectively, I4 the connecting rods, I5 the crank shaft, and IS the axis of the crank shaft. A power cut on andcut off device is diagrammatically represented by the showing of the pivoted lever I! of the form usually employed toactuate the'power cut on and cut off device. The'lever is usually pivoted to the frame of the press or its foundation I I and provided at its upper end with pull handle I8, by means of which it may be oscillated from the dotted line off position to the full line on position. I

According to my system I provide a servomotor I9 to actuate this lever. This is a fluidpressure servomotor comprising a cylinder 20 containing piston 2i having an enlarged piston rod 22 projecting forwardly and provided with a reduced end 23 pivotally connected with the lever H. The opposite end of the cylinder 20 is pivotally connected at 23', to a bracket 24 on the base block 25 mounted on the foundation I I or some part of sure and the piston biased therefore rearwardly, 6Q

end of cylinder 2| to atmosphere.

thereby biasing control lever E1 of the power cut on and Mt ofi device to its rearward dotted line off position. The rear port 21 is indirectly connected to the source 23 through a fluid pressure relay valve 29 by way of a conduit 30 including the valve. The details of this valve are not shown. Suffice it to say that it comprises a valve per se 3| which when opened, admits fluid pressure to the rear of piston 2|, and which, when closed, cuts fluid pressure therefrom and exhausts the rear It is of a well known type. The valve 3! is actuated by diaphragm motor 32.

Motor 32 receives its fluid pressure under control of an electro-pneumatic valve 33 comprising a valve per se, 34 and an electro-magnet 35. When the electro-magnet 35-is energized, valve 34 is opened to admit fluid pressure by way of conduit 36 connecting it to the diaphragm motor 32 and when magnet 35 is de-energized, valve 34 closes ofi the motor 32 from the source 23 and opens motor 32 to atmosphere, thereby closing valve 3|.

Circuit of electro-magnet 35 is controlled from a source of. electric power 31 as applied through line switch 38 over conductors 39. Two control means are provided. One 4|! is manual. It comprises a plurality of pairs 4| of push buttons 42 arranged individually in series in a circuit 43 adapted to complete the connection of electromagnet 35 to source 31 by way of conductor 39. The contacts of each pair are spread so far apart that they cannot be spanned by one hand, but require to be reached one by each hand in order simultaneously to operate them. Moreover, they are placed at points requiring the removal of hands and limbs of the operator beyond all danger regions of the dies and other parts of the press to be avoided by the operator in the working stroke. Each pair 4| of contacts 42 is provided with a .by-pass 44 which is normally opened but is adapted to be closed on special occasions by switch 45, thus cutting out the pair and permitting the series circuit 43, 39 to be completed without the particular pair or pairs cut out. This is to provide for cases of variation of the number of operatives, since each pair of contacts 4| provides for control by one operative, and it is required that a pair be provided for each operative to secure safety for all as well as for each.

The other of the means for completing the connection of the control electro-magnet 35 to the source of power 31 is a circuit 46 in parallel to the circuit 43 of the pairs of contacts 4| in series. Circuit 46 is normally opened at spring contacts 41, but is adapted to be closed by the projection of pin 46 between the adjacent ends of contacts 41. Pin 48 is a pin of conducting material carried at the end of and insulated from the body of a bell crank lever 49. This lever is actuated by a cam mounted upon and angularly adjustable about the axis l6 of the main crank shaft I15 of the press. Follower 5| on the opposite end of lever 49 from the pin 48 rides on cam 50 and as the main crank shaft l5 of the press revolves,

rides onto and off of cam 50 to open and close the circuit 46. The angular adjustment of cam 50 asures that circuit 46 is open substantially at the extreme upper end of the upward stroke of the press, remains open as follower 5| rides on cam 50 during substantially the entire down stroke of the press, and as the press moves into the extreme of its down stroke, the follower 5| rides off of cam 50 and closes circuit 46 in parallel stroke.

with and independently of the push bottons 42 of the pairs 4|.

To operate the system one closes the switch 38 while the press is idle and the crank shaft substantially at the extreme "of its upward stroke, substantially 180 from the position shown. Each operative, as he finishes his attention to the work on the machine, removes both hands from the work and assumes a'body position enabling him to reach both buttons 42 of the pair 4| assigned to him. By reason of the electrical control, the buttons maybe arranged at any points on or near the machine most convenient for the emcient movement of the particular operative to whom assigned. Each operative presses down the buttons assigned to him. When the last of the operatives has so pressed the buttons 42 assigned to him, and not until the last has so pressed them, can the circuit 39, 43 of electromagnet 35 be completed. The instant it is completed, valve 34 is opened, throwing fluid pressure from source 23 by conduit 36 upon diaphragm motor 32 and opening valve 3|, thereby throwing fluid pressure by conduit 33 upon the rear of the piston 2| to servo-motor 20. Immediately the piston 2| .is operated to the full line position shown the press starts its downward stroke toward the dotted line position shown.

At no time until the press reaches substan circuit 46 continues open at contacts 41 until the dies or other parts l2, l3 are so close together as to preclude the entry of the hands or limbs of an operator between. When they have reached a position so close together, however, pin 48 electrically connects contacts 41 and the press control circuit 46 supplants the operatives control circuit 39, 43, whereupon the operatives may freely release their hold on push buttons 42 and the press will continue to the end of its downward stroke and to the end of its upward stroke without further attention from the operator. During this portion of the cycle, cam follower 5| has rolled ofi of the cam 50 and remains oif until the press reaches the extreme of its upward At this instant it rolls again onto the cam 50, contacts 41are electrically separated, magnet 35 is de-energized, and valve 3| is opened to exhaust fluid pressure from motor 20 and throw the lever l1 from the full line on position to the dotted line off position. Through the adjustment of cam 50 in angular position and inusing duplex cam members which can be angularly adjusted relatively, as is well known to change the length of operation of the cam, the closure and opening of contacts 41 may be adjusted with respect to the end of the downward and the end of the upward stroke with great nicety.

' Thus are the ends and aims of my invention achieved.

It has been found that there is ample time during the upstroke for operatives to move new work toward the press and to feed it in without undue loss of time between press strokes. The rate of operation of presses with this system installed is quite as high as that of presses in which it has not been installed, and workmen are free angular extent, either by changing cams or by to move work toward the press after the danger 7,5

period of approach to the approaching parts of the machine has passed.

If at any time electric power goes oiT, by reason of the normal bias of piston 2| towards the off position by the connection of its front end.

to the source of fiuid pressure 28, the press is stopped immediately. It can only be started again by manual operation. Such connection to fiuid pressure also eliminates necessity for powerful springs and attendant wear and possible breakage, or the need for double action fluid pressure control.

The generic spirit of the invention should govern the scope of its claims independently of the circumstantial terminology used therein, in view of the substantial contribution over the prior art and the unavoidable evolution of modification and improvement.

What I claim is:

l. A safety system for power presses comprising a fluid actuated servo motor biased to inactive position, a differential pressure arrangement to actuate said motor, electrical means arranged to initiate said pressure means, a plurality of spaced switches in series circuit, arranged to energize said means, and a lock-in circuit arranged to maintain said electrical means energized during the extreme approach motion of the dies and during the retrograde motion of the dies only and independently of said manual means.

2. A safety system for power presses comprising a fluid actuated servo motor biased to inactive position, .a diiierential pressure arrangement to actuate said motoryelectrical means arranged to initiate said pressure means, a plurality of spaced switches in series circuit, arranged to energize said means, and a lock-in circuit arranged to maintain said electrical means energized during the extreme approach motion of the dies and during the retrograde motion of the dies only, said lock-in circuit only becoming operative due to the continued simultaneous actuation of said series switches throughout the approach die movement up to their extreme approach motion.

3. A safety system for presses comprising a pneumatically operated power control device, electrical means to control said device and parallel control circuits for said means, one of said circuits including a plurality of spaced switches in series circuit arranged to initiate said means upon simultaneous actuation thereof and to continue the energization thereof during the major approach motion of said press upon said continued actuation thereof, said other circuit comprising a master circuit to continue the press cycle of operation independently of said first named circuit during the extreme approach and retrograde motions only of said press.

4. In combination, a machine including ele- I ments for operation on an object, means controlling operation thereof, a fluid source, a fluid responsive motor connected to the control means and having large and small pressure faces operating the control means and, respectively, actuating and stopping the machine, a fluid responsive valve, the small pressure face being constantly connected to the fluid source and the large face being connected to the source through said valve, a conduit including an electro-responsive valve connecting the fluid source to means controlling the first valve, a source of electromotive force, a plurality of pairs of switches in series circuit relation between the electro-responsive valve and the electromotive source, each pair being inaccessible to an operator of another and the .switches of each pair requiring operation by the separate han$ of 5 its operator, a circuit including a switch shunting the pairs, and means controlled by the machine for closing the shunt switch to operate the machine during a final portion of the .approach, and during all of the separating, movement of the machine elements.

5. In combination, a machine including elements for operation on an object, means controlling operation thereof, energy source means, a motor connected to the control means and in- 15 eluding high and low energy receiving portions operating the control means and, respectively, actuating and stopping the machine, a valve or the like, the low energy portion being constantly connected to the energy source means and the high energy portion being connected to the source through said valve, means including a valve or the like connecting the energy source means to means controlling the first valve, a plurality of pairs of switches or the like in series relation between said second valve and the energy source means, each pair being inaccessible to an operator of another and the switches of each pair requiring operation by the separate hands of its operator, means including a switch or the like shunting the pairs, and means controlled by the machine for closing the shunt switch to operate the machine during a final portion of the approach, and during all of the separating, movement of the machine elements.

6. In combination, in a machine including members relatively reciprocable by a substantial distance for working on objects requiring placement, and removal from, between the members by a plurality of operators stationed at different positions, actuating means for the elements, control means for the actuating means biased toward inoperative position, and governing means for the biasing means including a plurality of pairs of interdependent handles corresponding to the number of operators and each spaced from the machine beyond the reach of an operator stationed to handle the object, each pair of handles being disposed at a position normally inaccessible to an operator at another and the handles of each pair being normally spaced to require manipulation by the respective hands of its operator, and means controlled by the machine for rendering the handles ineffective and controlling the actuating means to 65 operate the machine independently of the handles during a final portion of the approach, and during .a portion of the separating movement of the said machine members relative to the object.

7. A safety system for presses comprising a power cut on and cut off device of the press, and parallel control devices for said power cut on and cut off device, one manual and the other automatic, the latter being under control of the press in its upward stroke substantially .at the extreme upper end of said stroke only, and on the downward stroke of the press being under control thereof during substantially the entire downward stroke, said manual means requiring a plurality of pairs of hands for operation.

oARoLus L. EKSERGIAN.

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