US2848087A

US2848087A - Electric controllers for machines

Info

Publication number: US2848087A
Application number: US512156A
Authority: US
Inventors: Verne H Simson; Kenneth L Smith
Original assignee: Cutler Hammer Inc
Current assignee: Cutler Hammer Inc
Priority date: 1955-05-31
Filing date: 1955-05-31
Publication date: 1958-08-19
Anticipated expiration: 1975-08-19

Description

Aug. 19, 1958 v. H. SIMSON ETAL ,8 8,

ELECTRIC CONTROLLERS FOR MACHINES Filed May 51, 1955.

L1 L2 L5 /////,l v l//// ELECTRIC CONTROLLERS FOR MACHINES Verne H. Simson, Milwaukee, Wis, and Kenneth L. Smith,

Detroit, Mich, assignors to Cutler-Hammer, Inc., Milwaukee, Wis, a corporation of Delaware Application May 31, 1955, Serial No. 512,156

4'Claims; (Cl. 192-144) This'invention relates to improvements inelectric controllers for effecting single-cycle operation-ofmachines.

An object of the invention is to provide an electric controller of the character described in which is incorporated improved safety means.

In their efiorts to provide machine controllers which will protect machine operators against their owncarelessness andwillingness totake dangerous-risks, control engineers'have tried to anticipate all of the dangerous ac-tionspossible to be taken by the operator and to design control equipment which will prevent personal-injury caused by the taking of such actions. For example, it is common, in controllers for formingipresses and-certain other machine tools, to provide twospaced Run buttons for each operator. The buttons must be held-,- one with eachhand, untilthe punch and-die haveclosed so that a'hand may not be inserted-between theme To'insure thatthe operator cannot defeatthe-purpose of'the Run buttons by fastening themdown, the controller'is arranged so that all of the Run buttons'must be released and then reclosed before another cycle-ofpress-operation can be initiated.

Suchsingle-cycle machine operation can be" accornplished with a source of supply power; an operators switch having normally open andnormally closed contacts, first and second machine operatedswitche's,-a-non repeat electromagnetic contactor having two=norrnally opencontac-ts and electro-responsivemeans tostart-and lstop machine operation. The first machineoperated Switch is connected across the'supply source in series withthe coil of the contactor and a parallel circuit the branches of which contain, respectively, acontact of the contactor and the normally closedcontact of the operators switch. The electro-responsivemeans i is connected across: the source'in series with a parallel circuit-having the second machine" operated switch-in-one branch and the other contact of the contactor and the normally open contact of the operators switch-insc-ries in-the other 'branch. Of course, many variations of this singlecycle circuit are possible.

A specific object of this invention is to provide" in a single-cycle circuit, means" to=insuresa-feoperation of the'controlled machine if thenon-repeat e-lein'ent-s should fail.

The safety and control functions of the c'on-troller are so closely related that a change in components or circuitry to provide one function mayeffect-the performance ofthe controller inrespect of other functions;- The-problemis to provideall' of the desired functions *insucha way as to preclude dangerous malfunctioning: of thecontroller andv the machine in the event that one component er -circuit should fail.

Accordingly, a broader object ofthe inventionisto provide a control scheme which -willprovidethe safety and machine control features-which-are commonlyprovidcd and which in addition will fail-safel so that upon failure of any component the press-ormachine willcome to rest immediately or at the end of its stroke.

rates Pfltdit' Another object of the invention is to provide a controller in which the foregoing safety features are extended to include control of the drive motor for the machine as well as for the machine itself.

Other objects and advantages of the invention will hereinafter appear. v p

The accompanying drawings illustrate one embodiment of the invention, it being understood that various modifi cations maybe made in the embodiment illustrated and that-other embodiments are possible to be made without departing from the spirit of the invention and the scope of the appended claims.

In the drawing,

Figure 1 is a diagrammatic illustration of an electric controller embodying; the inventiomand Fig. 2 is a chart illustrating the operation ofthe controller of Fig 1.

Referring to the drawing, there is shown a mechanical I ress, or other machine having a cyclically driven element 1'0'which is-driven by a three phase electric motor 12 through the medium ofa Clutch-Brake combination 14 when a solenoid 16 is energized. Powerfor the motor 12 is supplied-from a-suitable three phase alternating power s'ourcesuch aslines L1, L2 andL3.

The function of the remainder of the system-is to control energization of motor 12"and-solenoid16. Only so much of the control system is illustrated as is necessary to single-cycle or non-repeat operation of the machine or press It). In this-mode of operation it is intended that the motor 12 be run continuously. Each cycle of press operation -is-to require operation of a pushbutton; and, thepush-button must-be released before another cycle of machine operation can be initiated.

The control circuit comprises: amain electromagnetic contactor 18 having normally open contacts 18*,

18 18", 18 and 18 and an energizing. coil 18 a control contactor 20 having normally open contacts 20 Ztl and-20, normally closed contacts 20 and lfl and an operatingcoil 20 a-first non-repeat contactor 2'2 having'norr'nally

open contacts

22 and 22 normally closed contact 22 and an: energizing coil 22 a second nonrepeat contactor 24 'having normallyv opencontact24, normally closed contact 24* and an energizing coil 24;

limit switches

28 and 30 which are operative at-selected positions of the movable element of the machineya normally, closed Stop switch 32; a normally open Start switch 34; Run buttons 36 and 37 having normally closed contacts 36 and 37 and normally open contacts3 =6 and 37 a Reset button 54; and a timing relay 52 havinglan energizing-coil 52 and normally opencontacts 52 'and 52 which close rapidly but are opened at a selected time following de-cnergi ZatiOn of coil- 52 7 Power for the control circuits is supplied by lines L4 and L5 fromlines Ll and L3- through anisolati-ng transformer 38; When more than one operator is required to operate the press additional pushbuttonsare provided. The limit switches 28 and'30 may be mechanically connected to the machine directly or indirectly and may be mechanically or electrically operated.

Fig. 2 illustrates the operation of limit switches 28and 30, the darkened areas indicate a closedlimit switch contact and the undarkened-areas indicate anopen limit switch contact. The leftand'right-hand side of Fig. 2, marked 0 degrees and 360 degrees respectively,.indicatc the upper extreme position of the ram of press 10. The degree position in'Figt 2 indicates the lower extreme position of-the ram of press 10.

T hebrake portionof the Clutch-Brake combination l4 is'arranged to'stop the press 10 with its ram'at itsuppermost or zero position. When the ram is in this position,

limit switches

28 and 30 are closed andopen, respectively.

Energiz'atioh of the motor 12' and the control circuit 3 is initiated by pressing Reset button to complete a circuit from line L4 through coil 52 of relay 52, the Reset button, and through normally closed contact 20, and through normally closed contact 22 to line L5. Contact 52 closes to establish a maintaining circuit for coil 52 around the Reset button 54. Contact 52 of relay 52 closes to complete a circuit from line L5 to a conductor 40 and through Stop switch 32 to the Start switch 34.

Upon closure of Start switch 34, the latter circuit is continued through coil 18 of relay 18 to line L4. Upon energization of coil 13, contacts 18 18 and 18 are closed to energize and effect operation of motor 12. Contact 18 closes to complete a maintaining circuit for coil 18 Contact 18 is closed to complete a circuit from conductor 40 to conductors 42 and 44.

The energizing coil 24 of contactor 24- is then energized through a circuit which may be traced from conductor 44 through normally closed contacts 36 and 37 of Run buttons 36 and 37 and coil 24 to line L4. Contactor 24 picks up to open its contact 24 and to close its contact 24. Closure of the latter contact completes a circuit from conductor 42 through contact 24, normally closed contact 20 energizing coil 22 of contactor 22 and limit switch 28 to line L4. Energization of coil 22 results in the opening of contact 22 and closure of

contacts

22 and 22 Closure of contact 22 completes a maintaining circuit for coil 22 around

contacts

24 and 20 Closure of contact 22 completes a circuit from conductor 44 through contact 22 to one terminal of normally open contacts 36 of Run button 36.

To effect energization of solenoid 16 to release the brake and connect the clutch of Clutch-Brake 14 for operation of the press by motor 12, the press operator must depress the Run buttons 36 and 37 to open contacts 36 and 37 and close contacts 36* and 37 By this action coil 24 is de-energized and contact 24 is opened. Coil 22 remains energized by virtue of the maintaining con nection through its contact 22.

Contact 22 remains closed and current flows from conductor 4-4 through contact 22*, through the now closed contacts 36 and 37 of Run buttons 36 and 37 and the now closed contact 24* of contactor 24, and through energizing windings of contactor 24) to line L4. Contactor 20 is actuated to close

contact

20 and 20 to complete a circuit from line L5 through solenoid 16 to line L4. The Clutch-Brake combination 14- interconnects press 10 and motor 12 and the press begins to move. At the same time, contact 26 closes and contacts 2% and 20 open.

Upon opening of contact 20, the energizing circuit for coil 52 is interrupted to begin a timing operation after which

contacts

52 and 52 will open unless contact 22 is reclosed first.

Energization of coil 22 is maintained through its contact 22. Although contact 24 is closed, coil 22 is not energized from conductor 42 because contact 26 is open.

After the press parts have moved to a position in which the operator cannot get hurt, limit switch 30 closes to complete a maintaining circuit for coil 20 from conductor 44, through limit switch 30, through the now closed contact 20 and through coil 24V to line L4. The operator may, and normally does, release the Run button 36 at this time. Upon release of the Run button, contacts 36 and 37 are closed and coil 24 is re-energized to close its contact 24 preparatory to re-establishment of the main energizing circuit for coil 22 Coil 24 having been reenergized, contact 24 opens. A short time later in the cycle of press operation, limit switch 28 opens to deenergize coil 22 Contact 22 is opened to open the maintaining circuit for coil 22 Contact 22 is opened to open the main energizing circuit for coil 20 Contact 22 closes to re-establish the maintaining circuit for coil 52 before contacts 52 can open.

Somewhat later in the cycle of press operation limit switch 28 re-closes. Coil 22 is not energized because its maintaining contact 22 is open and its main energizing circuit is open at contact 20 Near the end of the cycle of press operation, limit switch 30 opens to interrupt the maintaining circuit for coil 2%. Coil 20 is deenergized to open

contacts

26, 20 and 20 and to deenergize solenoid 16 and operate the Clutch-Brake combination 14 to stop the press 10 when the ram reaches the top of its stroke. The control circuit has now been returned to its original condition following closure of Start switch 34. A new cycle of press operation may be initiated by operation of Run buttons 36 and 37.

Contact 20 is connected in parallel with contact 22 so that the motor 12 can continue to run during periods when the press is stopped. The press stops with its ram in the uppermost position. Contact 22 is open so that the main energizing circuit for the coil 52 of the timing relay is interrupted. But contact 29 is closed, when the press is stopped, to establish an auxiliary energizing circuit for coil 52.

The operator cannot cause the press to run continuously by keeping the Run buttons depressed throughout the entire operating cycle of the press. If he attempts to do so, contact 24 will remain open. After relay 22 is deenergized by the opening of limit switch 28 and after contact 22 opens, an energizing circuit cannot be established for 'coil 20 even tho-ugh contacts 36 37 and 24 are all closed. The control circuit checks itself on each stroke of the press. If a failure should occur, the circuit will fail safe and prevent commencement of the next press stroke.

Upon failure of supply power, contactor 18 drops out and the motor and press both stop. The Reset and Start buttons must be operated to restart the motor.

If relay 22 fails to pick up, coil 20 cannot be energized. If contactor 22 fails to drop out, contacts 52 of relay 52 will open to interrupt the energizing circuit for coil 52 and contacts 52 will open to de-energize coil 18 and conductor 40. The motor and the control circuit will be de-energized and the motor and press will stop. These results are obtained even if the operator fails to release the Run button during a press stroke.

If contactor 24 fails to pick up, contactor 22 cannot be energized and the press will stop at the end of its stroke. If contactor 24 fails to drop out, contactor 20 cannot be energized and a new cycle of press operation cannot be initiated.

If dummy plugs are inserted in the Run button stations, contactor 24 will continue to be energized so that contactor 20 cannot be energized. Thus a new cycle of press operation cannot be initiated.

If contactor 20 fails to pick up, the solenoid 16 cannot be energized and the press cannot be started. If contactor 20 fails to drop out, its normally closed contact 20 will be open so that the energizing circuit to coil 22 will be open. Therefore, contact 22 will be opened and it will be impossible to re-energize coil 20 even though the Run button is operated properly.

We claim:

1. In an electric controller for a cyclically operable machine driven by an electric motor through a clutch, said controller being of a type having electro-responsive means sensitive to energization and deenergization to operate the clutch to engage and disengage the machine and motor, a main electromagnetic contactor to control energization of the motor and an energizing circuit for the main contactor and a control circuit for efiecting cyclic operation of the machine through the medium of the clutch, said control circuit comprising an operators switch having normally open and normally closed contacts, a limit switch operated by the machine to open its contacts during a portion of the operating cycle of the machine, a second electromagnetic contactor in series with the limit switch and being dependent for initial energization on closure of the normally closed contacts of the operators switch, and an energizing circuit for said electro-responsive means comprising in series the normally open contacts of the operators switch and a normally open contact which is closed in response to energization of said second contactor, the improvement which comprises, an electromagnetic timing relay having a safety contact in series with the energizing circuit of the main contactor and the second contactor and the electro-responsive means, and an energizing circuit for the timing relay comprising in series with the relay parallel branches one containing a normally closed contact operated in response to energization of the second contactor and the other containing a normally closed contact which is operated in response to energization of the electro-responsive means, the timing relay acting when energized to close its contact and to open said contact after a time interval longer than the duration of said portion of the cyclic operation of the machine following de-energization of said timing relay unless the latter is re-energized sooner.

2. In an electrical controller for an electric motor driven cyclically operable machine having means including electro-responsive means to complete and interrupt the driving connections to the machine, in combination, a first electromagnetic contactor energizable to complete an energizing circuit for the electro-responsive means, a second electromagnetic contactor, an electromagnetic relay having means affording it time delay drop out, means including means under the control of said second contactor for completing a first energizing circuit for said relay whenever said second contactor is deenergized and further including means under the control of said first contactor for completing a second energizing circuit for said relay whenever said first contactor is deenergized, a manual switch, a second switch operable to close circuit during a selected portion of the cycle of the machine,

means for completing an energizing circuit for said second contactor whenever said manual switch is in a first position and said second switch closes circuit, and means including means under the control of said relay for completing an energizing circuit for said first contactor Whenever said relay is energized and said manual switch is operated to a second position, said means affording time delay drop out of said relay providing maintenance of energizing connections for said first contactor for a predetermined period in which completion of the selected portion of the cycle of the machine drop out of said second contactor and recompletion of said first energizing circuit for said relay normally occurs.

3. The combination according to claim 2 wherein said relay has an operating winding and normally open contacts, wherein the means under the control of said first and second contactors respectively comprise normally closed contacts which when closed complete said second and first energizing circuits respectively for the operating winding of said relay and wherein the normally open contacts of said relay are in said energizing circuit for said first contactor to afford drop out of the latter in the event said second contactor fails to drop out upon expiration of said predetermined period.

4. The combination according to claim 2 together with a fourth electromagnetic contactor and means for completing an energizing circuit for said fourth contactor which is interruptible by drop out of said relay.

References Cited in the file of this patent UNITED STATES PATENTS 1,357,384 Date Nov. 2, 1920 2,133,161 Colbert Oct. 11, 1938 2,636,138 Few Apr. 21, 1953 2,675,507 Geiger Apr. 13, 1954