US2913581A

US2913581A - Method and apparatus for controlling production machines

Info

Publication number: US2913581A
Application number: US382374A
Authority: US
Inventors: Marvin E Simonton; John O Yeiser
Original assignee: Individual
Current assignee: Individual
Priority date: 1953-09-25
Filing date: 1953-09-25
Publication date: 1959-11-17
Anticipated expiration: 1976-11-17

Description

Nov. 17, 1959 M; E. SIMONTON ETAL 2,913,581

METHOD AND APPARATUS FOR CONTROLLING PRODUCTION MACHINES 2 Sheets-Sheet -1 Filed Sept. 25. 1953 v INVENTORS Marv/)7 E limo 7 for; y John 0. yelser ATTORNEYS Nov. 17, 1959 M. E. SlMONTON ETAL 2,913,581

METHOD AND APPARATUS FOR CONTROLLING PRODUCTION MACHINES Filed Sept. 25. 1955 2 Sheets-Sheet 2 "5 I INVI ZNTOR5 Marv/n f. .Y/mqnfon BY John 0 Ye/ser ATTORNE Y5 YZMJW METHOD AND APPARATUS FOR CONTROLLING-.-

- PRODUCTION MACHINES Marvin E. Simonton and John O. Yeiser, Berkeley, Calif.,

assignors, by mesne assignments, to Bernard R. Katshen, Redwood City, Calif.

Application September 25, 1953, Serial No. 382,374

6 Claims. (Cl. 250-836) This invention relates generally to methods and apparatus for controlling the operation of various machines.

It is well known that in the operation of production machines suchas metal working presses, lathes, milling machines and the like, various types of safety controls are desirable for the protection of workmen. For exa1nple,,in the operation of a reciprocating punch press, control means of a photoelectric type has been employed whereby when the operators handis in a danger .zone, the light beam to the photoelectric tube is interrupted to preventnormal operation. Another type of control which has been used employs cords which are attached to the hands of the operator, and which serve to operate control switches whereby the machine cannot be operated until the hands are withdrawn to a safe position.

Safety controls of the type described above are subject tojcertain inherent objectionable features. A control of the photoelectric type is subject to false operation, because any interruption of the light beam, which may occur accidentally or otherwise, serves to operate the control. Safety controls ofthe type which attach cords to the hands of the operator serve to unduly restrain the free movement'of the operaton In general, it is the object of the present invention to' provide an improved safety control for production machines which avoids the disadvantages of previous arrangements.

Another object of the invention is to provide a safety control of the above character which is responsive only to one signal and which is not subject tofalse operation.

Another object of the invention is to provide a'safety control of the above characterwhich is operated by a penetrating radiation from an emitter, such asgamma and beta rays.

Another object of the invention is to provide a method of the above character in which the emitter is attached to one or both hands of the operator, and in which a movement of the emitter into a danger zone will effect the desired control of the. machine, as for example,to make it inoperative.

Additional objects and features of the invention will appearfrom the following description in which the preferred embodiment has been set forth in detail in conjunction with the accompanying drawing.

Referring to the drawing:

Figure 1 is a circuit diagram illustrating one embodiment of the invention. f f

Figure 2 is another circuit diagram illustrating another embodiment of the invention. l

1 Fig. 3 is a schematic view illustrating how our invention can be applied. to a production press.

Figure 4 is a perspective view partly in section, showinga radiation emitter for attachment to the wrist of an operator;

Q In general, the present invention makes use of a sensitive indicator of radiations, such as a tube of the Geiger-Muller type. This is to be positioned in such a manner with respect to the production machine that it is responsiveto emanations from an emitter placed Within a specified danger zone, The Geiger tube is connected to means which produce ajresponsive current of sufl'icient magnitude for controlling the machine. By way of'example, the control may be such that the machine cannot proceed with its normal operating cycle when the emitter is within the danger zone.

apparatus includes time delay means whereby after a predetermined time interval following actuation of the radiation detector, the control is conditioned to prevent normal operation of the machine until such operation is initiated by again placing the emitter in the danger zone. Thus the machine cannot be used except by an operator wearing an emitter.

Referring to the circuit diagram in Fig. 1, we have shown a tube 10, preferably of the thyratron type, havtype, they are provided cylindrical and

axial elements

13 and 14. Although" two tubes 11 and 12 are shown in Figure 1, it will be evident that in many instances a single tube will suflice. Two or more tubes canbe used where it is desired to obtain a radiation response when an emitter is placed in either one of two sensitive or danger zones.

' Suitable means is provided for applying operating voltage across the terminals of the tubes 11 and 12. Byway of example, we have shown a power supply transformer 16, having its primary connected to a suitable source of alternating current, such as the ordinary 17 has the heater of its cathode connected to the terminals of the secondary 18. 'The secondary winding 19' is shown with its one terminal grounded, and its other" terminal connected to the cathode of tube 17. Lead 21 connects the anode of rectifier tube 17 to one side of the tubes 11 and 12. The other terminals of tubes 11 and12 are connected to ground through the series connected

resistors

22 and 23. Resistor 23 is shown shunted by a condenser 24 for a purpose to be presently de scribed. Transformer 16 is provided with another sec ondary 25 for supplying cathode heater current to various vacuum tubes. 1

Suitable filter means is provided for reducing the alternating current ripple of the direct voltage applied ".to the tubes 11 and 12, and may consist of resistors 26- and 27, together with the

grounded condensers

28 and 29. The mid point between

resistors

26 and 27 is connected to ground through the voltage regulating tube 31, which may be of the type known by manufacturers specifications as No. 5950.

Resistors

32 and 33 are connected in a series between the terminals of the cathode heater of tube 10, and the adjustable tap 34 on resistor 33 is'connected to the cathode.

7 can be of the thyratron type, however, it is to be under stoodthat ordinary vacuum tubes in an analogous circuit can be used to accomplish a similar result, The. heater terminals of tube 37 can be connected to the transformer secondary winding 25, and one terminal lead is; connected to the cathode through the peel current limit Patented Nov. 17, 1959 L Preferably the A rectifier tube This provides an adjustable bias which can be i used to adjust sensitivity. The control grid of tube 10' V 3 a ing resistor 38. The suppressor grid is directly connected to the cathode. The control grid of tube 37 is connected by lead 39 to thecontact 41 of A.C. relay 42.; Lead-39 -is-also connected to ground through the resistorv 43, whichis shunted by condenser 44.:

.The winding 46 of-the-relay 42 is connected in series With-the-plate'lead-of the tube '10. Thus one terminal.

of this -winding-connects directlyrto the plate,-and -the other terminal-is-connected byway of-voltagedropping resistor-47 and lead 48-With tl1e-tap.-36 on the trans former winding. 19." A .fil ter condenser 49 is shown shunted across the windingAfi-and the resistor-47 to elimi:

nate, chattering. of'thetcontacts on relay 42 Theplate oftube 37 likewise has a conductive connection: with.

lead48. Thus ansecond AC. relay-51 has awinding 52, which has one terminal connected 'to the plate of tube 37, and its other terminal-connected -to voltage dropping,-resistor"53- through the-lead -48 Filter condenser 54 isshuntedracrossathe resistor 53 and relay winding, 46*to eliminate 1 chattering :ofthe contacts-on relay 51.

Therelays :42 and '51-serve -to control a circuit-56' which'can beexten'ded totany point desired, and which in turnserves to eflect control of the production machine in-the desired manner. The-circuit can include a response device 57 such, as-a machine clutch disabling means; or the like, and a-sourceof current represented by the "battery 58. The back contact 59 and movablecontact 61 of relay 51 are connected in series with one side of circuit 56. Likewise,- the-circuitis' seriallyconnectedwith the-frontcontact 62 and movable contact 63 oftherelay 42; both relays 51:and42-must--be-closed-to close circuit 56: The-back contact 41 of relay 42 is open withrespectto the contact 64, when the

contacts

62 and 63 are closed Contacts 41 and 64serve-to apply voltage to thecontrol' grid of tube 37. and for charging the condenser 44,

winding 46 is de-energized. Relay 51 islikewise biasedtoward 'its back "contact, whereby contacts 59 and 6 1 are closed when the winding 52is de-energized.

Operation of the circuit shown in Figurel is as follows: Assuming that the circuit is inthe condition shown in Figure 1, that is, that tube 'is conductingand tube 37 is not conducting, the relay 42 will be'energized because of plate current flowing from tube 10 and relay 51wil1 be de-energized. Thus, contacts 41 and 464*are open, 62 and 63 are closed and.59 and 61 are closed as illustrated. Let it alsobe assumed that the device 57 of the control circuit 56 is associated with a production machine in such a manner that when this circuit is energized, the machine will proceed with a-normal predetermined cycle of operation.-

Assuming that a radiation emitter 72 such as one emitting gamma and beta rays, is placed within effective range of'either one or-both" of the tubes 11 and 12, the resulting voltage response charges the condenser 24 negatively through current limiting resistor 22 to thereby bias the control grid of the .tube 10negatively, which stops the tube-10from conducting the next time the AiC; voltage onthe plate of the-tube 10 passes through zero: Thecessationof plate current from tube 10 deenergizes--the winding'46--ofrelay*42 with'the result that- Itwill be evident thatthecontacts of' 4,

contacts

62 and 63 are opened to open the control circuit 56. Assuming that the emitter 72 is attached to the hands of the operator, and that it has been put into a sensitive or danger zone such as may be necessary for placing work in a machine or removing work, then under such conditions and becauseof the opening of the circuit 56, the production machine is temporarily rendered inoperative-to proceed'with its normal cycle of operation.

The resistor 23 and the condenser 24 act as an integrating circuit whereby the tube-10 is not affected by,

random voltage responses because the resistor- 23 -at all" times tends to discharge any charge on the condenser 24. Thus, in order to bias the tube 10 to stop it from conducting, it is necessary that a series of voltage responses be received in rather rapid succession in order that a change on condenser 24 can be built up before it is dissipated through resistor 23. Thus, as long as a continuous succession of voltage responses are received from the tubes 11 and 12 the tube 10 will remain biased. negatively. However, when the emitter 72 is removed from the danger or sensitive zone, the-tubes 11 and 12 will stop giving voltage responses whereby the condenser 24 will be discharged across resistor 23 and the grid of tube 10 will swing toward positive allowingv thettube'to become conducting again. As a result the winding of-relay 42 is again energized whereby

contacts

62 and 63 are again closed to energize the circuit 56. Now the con-- trol circuit has been reconditioned whereby the production machine may proceed with its normal operation;

In some instances a considerable loss of time may occur following positioning the-emitter in the dangerv zone. Under such circumstances the timing means is.

utilized to interrupt the control circuit 56. In other words, the arrangement is such that if not operated atregular intervals bythe emitter being'positioned in. op-

erative position with the Geiger tubes, the control circuit 56 will be automatically-opened and cannot be closed until an operator places an emitter in the danger zone.

This feature prevents unauthorized use of the machineby- 41 and 64. This chargingtakes place almost instanta' neously and thus a negative bias is maintained on the grid until the charge from the condenser 44 drains ofi across resistor 43 before the condenser 44 is recharged. In such a case the control grid will swingtoward' positive and the tube 37 will start conducting-to energize the winding of relay 51 to open the contacts 59"and '61. The discharging of thecondenser 44 across the resistor: 43 takes a predetermined" amount'of time, for example 15 seconds, which can be variedby'changing the circuit constants involved. It will be evident that if the contacts 41 and remain open for a period beyond this predetermined interval, the tube 37 'will start conducting. When subsequently an emitter is again placed in the danger zone to operate the tubes 11 and 12, the closing of

contacts

41 and 64 serves to recharge the condenser negatively whereby the grid'of tube 37 will regain control the next time the A.C. voltage of the plate of tube 37 goes through zero thereby rendering tube 37' nonconducting.

In the modification'ofFigure 2,'timing means of the electric motor type has been used in place of'the electronic timing means of Figure 1. This motor type of timing device 76 has the winding of its motor connected to an energizing circuit 77, which includes the

relay contacts

78 and 79, and a-source of current provided by the A.C. supply lines. The motor drives'the'cam'81, which in turn operates the contacts 82"and' 83. Motor timing devicesof this kind generally use a motor of'th induction disc type, or a self-starting synchronous motor, which serves to rotate its shaft and cam 81 at a predetermined speed, when current is applied to the motor. The cam commences its movement from a stop position, and within a predetermined period of time serves to open the

contacts

82 and 83. Upon interrupting the current supply to the motor, the cam isreturned to its initial start position.

Instead of timing means of the electric motor type it may be desirable to use a dash pot relay to accomplish the same result. With the arrangement of Figure 2, it will be evident that when winding relay 42 is energized, the control circuit 84 to the control device 57 is closed. Likewise,

contacts

78 and 79 are closed to cause operation of the timing device 76. If a predetermined time interval passes before relay 42 is de-energized, by excitation of the Geiger tubes, then

contacts

82 and 83 are opened to open the circuit 84.

Figure 3 schematically illustrates a representative installation of our apparatus on a metal working press. The two die

parts

86 and 87 are carried respectively by the press head and bed, and it is assumed that the press is provided with a cycling clutch which is tripped as by means of a foot treadle. Assuming that one Geiger tube 11 is used, it is enclosed within the box or housing 88, which is mounted in a proper position whereby it is sensitive to radiation within the zone 89. This zone is arranged to correspond to a zone in which one or both hands of the operator must be placed in order to introduce or remove work from the machine. In other words it corresponds generally to what may be termed a danger zone, in that when the hands of the operator are within this zone, it is desirable to render the machine inoperative to perform its usual operations. The radiation emitter 2 is shown strapped to the wrist of the operators hand 91. A shaded zone 92 is shown in front of the zone 89, and may be referred to as an uncertain area through which .the emitter passes when the operator advances or withdraws his hands from the machine. In effect this is a transition zone between a safe region for the hands, and a danger zone. Cable 93 is shown connecting the Geiger tube to the assembly 94, which includes the thyratron tubes and associated parts. An.

electrical cable 96 extends from 94 to the unit 97, which may by means of the solenoid type for rendering the treadle operated trip means for the clutch, inoperative. Cable 98 is for power supply. It will be evident that with the installation of Figure 3, the machine is controlled in the desired manner by the radiations from the emitter. The radiations are effective through objects such as the work piece or the hands or other parts of the body, thus insuring proper operation.

Figure 4 shows a suitable emitter which can be strapped to the wrist. It includes the wrist strap 73 and the mounting 74 for the radiation emitting material 72. Suitable materials for this purpose are the radio-isotopes of cobalt 60, radium salts, and strontium 60. Such material may be contained in a capsule or incorporated in a suitable nonradioactive medium. The mounting can include a radiation shield 75 of suitable maten'alsuch as lead. a p

In the foregoing we have described our machine as applied to a production machine in which means such as a treadle is employed to trip the cycling clutch of the machine, for performing a cycle of operation. Many motor driven production machines employ start and stop push buttons which are associated with circuits for starting and stopping the machine. Device 57 may be a solenoid operated switch or relay which serves to control such a start circuit, whereby the machine cannot be cycled by pressing the start button, if the hands are in the danger zone. If the machine is arranged to carry out successive operations automatically, the stop circuit can be controlled whereby the machine is stopped if th hands are placed in the danger zone.

.Althoughparticular reference has been made to metal workingpresses, the inventionis applicable to a wide j machines, and the like. i

The present application is a continuation in part of our co-pending application Serial No. 282,048, filed April 12, 1952, now, abandoned.

We claim: r

1. In safety control apparatus for controlling a machine of the type having a predetermined work cycle, means including a detector tube sensitive to radiations from a radioactive emitter and serving to provide an electrical response, means for preventing a normal work cycle of the machine, said last means being conditioned by said electrical response to permit a normal work cycle, whereby the control'apparatus is conditioned to prevent the machine from carrying out a normal work cycle when an emitter is disposed in operative proximity with .the detector tube, additional means serving to condition the apparatus for'preventing a'normal work cycle of the machine, said additional means including time delay means and serving to prevent. a normal work cycle after a predetermined time lapse has occurred following a preceding actuation by an emitter, and means effectively reestablishing said time delay means at zero each time said emitter is disposed in operative proximity to the detector tube.

2. In safety control apparatus for controlling operation of a machine of the type having a predetermined normal work cycle, means including an indicator sensitive to radiations from a radioactive emitter and serving to provide an electricalresponse, a control device serving to control operation of the machine to prevent a normal work cycle, means responsive to said electrical response and serving to effect operation of said control device, additional means for preventing a normal work cycle of the machine, and timing means for actuating said addi tional means, said timing means being re-set to zero each time the indicator is subjected to a radioactive emitter and serving to prevent operation of the machine after a predetermined time interval following operation of the indicator, said time lapse being substantially greater than the time required for a normal work cycle of the machine.

3. In safety control apparatus for controlling operation of a machine of thetype having a normal work cycle and adapted to be fed manually by a human operator between successive cycles, means sensitive to radiations from a. radioactive emitter and serving to provide an electrical response, said means including a detector sensitive to radiations from a predetermined danger zone located adjacent the working parts of the machine, a control device serving to prevent a normal work cycle of the machine or permitting such cycle, means including a tube responsive to said electrical response and having its output connected to operate said control device, additional means including a time delay device for interrupting the output of the tube after a predetermined time interval following an electrical response from said indicating means, said last means including a condenser, a source of voltage adapted to charge the condenser over a predetermined period of time, and tube means responsive to charging of the condenser for effecting operation of said control device, said time delay device providing a time period substantially greater than the normal time required for a Work cycle of the machine, the condenser of said time delay device being charged each time a radioactive emitter is placed within said zone.

4. In a method for the safety operation of a production machine of the type having a normal operating cycle, the machine having safe and danger zones for positioning the hands of the operator when the machine is performing its prescribed operation, attaching a radiation emitting source to at least one hand of the operatoridetecting the radiationremittedznfrom theisource in 65 Safe'ty control apparatus as in 'claimifi together with the' danger" zone, rendering thie machin'e inoperative: t0- additional means' serving to condition -the "apparatus for-- perform' -its prescribed-{functioni inmccordance wit lifith'e' preventing'a normal work' cycleof the machine, said adresponsethusobtained, rendering the machine inoper ditional means including-time delay-means and serving to ative in the event the time lapse followingiwithdrawal'of 5 prevent a normaLwork -cycle' after a predetermined time tliesource':from the dzinger zone; without reinsertiong iS lapse has occurred-' followinga-preceding actuation of beyond a-predetermined peri'odthatixis longer than the 4 said control means, said predetermined time lapse being period of a normal operating cycle ofithamachine;and greater than the normal Work cycle of'the-machine, and rendering the machine operative by reinsertionofthe means actuated-by said=emitter 'efle'ctivelyreestablishing sourceinithe'danger zone. 1 lo said time delay means at zero 'eachtimesaidemitter is .5: In a safety.control 'apparatus for controlling a ma disposed in operative proximity to said detecting means. chino I of-the type having a predetermined normal Workcycle,"a radioactive emitter, saidradioactive'emittenbeing References vcitedrin theme of this patent adaptedlto be carriedsbythe operator, detecting means responsive to the radiation from: said "emitter when saidr15 UNITED STATESPATENTS emitter is" within a predetermined czone;tsaidzrdetecting 2,082,210- McMaster' June 1, 1937 1 means serving,toprovide=anelectricalresponse,"and con-v 2,309,329 Powers June 26, 1943 troLmeans for preventing ;a normal WOIK? cyclecofihe 2,320,346 Broekhuysen June 1, 1943 machine, said controlvmeans beingzconditioned by said 2,331,023 Gayring Oct. 5, 1943 electricalresponseto prevent-a normal work cycle :until 20 2,499,889 Teichmann Mar. 7, 1950 i said emitter has been removed from said predetermined zoner