US2377365A

US2377365A - Electrical control system

Info

Publication number: US2377365A
Application number: US482333A
Authority: US
Inventors: George H Pardey; Cornelius L Johnson
Original assignee: MOTOR REPAIR AND Manufacturing Co
Current assignee: MOTOR REPAIR AND MANUFACTURING Co
Priority date: 1943-04-08
Filing date: 1943-04-08
Publication date: 1945-06-05
Anticipated expiration: 1962-06-05

Description

June 5, 1945. s. H. PARDEY ET 2,377,365

ELECTRICAL common SYSTEM Filed A ril 8, 1945 INVENTORS Patented June 5, 1945 ELECTRICAL CONTROL SYSTEM George H. Pardey and Cornelius L. Johnson. Cleveland, Ohio, assignors to The Motor Repair and Manufacturing Company, a corporation of Ohio Application April 8, 1943, Serial No. 482,333

10 Claims.

Our invention relates in general to electrical control systems and more particularly to an electrical control system for controlling an intermittent drive. i

In this application we are illustrating the use of our invention as being applied to control the traverse of a tool device Withreference to a re clprocal work table upon which the work piece is mounted that is to be cut by the tool. Although we are showing theme of our invention as being applied to the machine tool as described, it is to be understood that our invention may be applied to other machinery having intermittent driving operations.

An object of our inventionis to provide for intermittently energizing a magnetic clutch which interconnects a driving shaft and a driven'shaft, whereby the driven shaft is operated through substantially a predetermined number of revolutions.

Another object of our invention is the provision of an electrical timing circuit which governs the duration during which the magnetic clutch is energized to transmit power from one shaft to another.

Another object of our invention is the provision of energizing the magnetic clutch for a predetermined length of time which governs the amount that the driven shaft is turned.

Another object of our invention is the provision of intermittently operating a driven shaft, wherein the intermittent operation is governed by an electrical timing circuit which may be adjubted to vary the duration of each intermittent operation. v

Another object of our invention is to provide for intermittently operating a tool device with reference to a reciprocal work table, in which the movement. of the tool device is governed by an electrical timing circuit which is set into operation in'accor'danc'e with the reciprocal movements of the work table.

Another object of our invention is the provision of operating or moving the tool device with reference' to the reciprocal work table during the interval or substantially at thesame time that the reciprocal work, table is being reversed.

Another object of our invention is to provide for electrically energizing the intermittent drive for the movement of the tool device substantially simultaneously at the same time that the electrical circuits are established for reversing the drive of the reciprocal work table. I O

Another object of our invention is to provide for using the tripping arrangement which reverses the direction of the drive for the reciprocal work table for also controlling the initiation of the electrical timing circuit which governs the amount of energization supplied to the electrical intermittent drive which moves the tool device with reference to the reciprocal work table.

Another object of our invention is to provide for arresting the movement of the tool device with reference to the reciprocal work table in the event that the electrical timing circuit fails to operate.

Other objects and a fuller understanding of our invention may be had by referring to the following description and claims, taken in conjunction with the accompanying drawing, in which the figure represents a diagrammatic illustration of a control system embodying the features of our invention.

As hereinbefore mentioned, our invention is shown as being applied to a reciprocal work table identified by the reference character H! which may be suitably driven by a drive and control unit indicated by the reference character ll. As diagrammatically illustrated, the drive and control unit may be operated in one direction by manually depressing the push button 2| and may be manually operated in the reverse direction by depressing the push button 22. Any suitable means may be employed to reciprocally operate the work table In and as illustrated we employ rack and pinion arrangement I2 and I3. The movement of the reciprocal work table to the right is designated as the forward direction and the movement of the reciprocal work table to the left isdesignated asthe reverse direction. When the reciprocal work table II] reaches the end of its forward movement, a projection 69 engages a toggle arrangement 6! which functions to close the contacts H and I2. The closure of the contacts ll establishes a circuit through conductor 18 for reversing the drive and control unit H to re ciprocate the work table It) in the reverse direction. The work table moves in the reverse direction until the projection 10 engages the toggle arrangement 68 which operates to close the contacts l3 and 14. The closure of the contacts 13 establishes a circuit through conductor 19 for reversing the operation of the drive and control unit II to reciprocate the Work table In in the forward direction. As the projections 69 and 10 pass back underneath their respective toggle arrangements, the operation is such that the con-' tacts controlled thereby are restored to their open" I position as illustrated in the drawing. The toggle respect to each other so that the projections 89 and I only engage their respective toggles. The showing and the operation of the reciprocal movements of the work table by the drive and control unit I I is abbreviated and condensed for the reason that this constitutes no portion of our invention, except only that our invention is associated with the particular diagrammatic arrangement as illustrated.

The tool device is illustrated by the reference character I4 and is arranged to be moved laterally with respect to the work table as each cut is made upon the work piece. As diagrammatically illustrated, the tool device may be moved in a transverse arrangement with respect to the work table by means of a screw traverse assembly I5 which may be driven by an electric motor I1 through means of an electric magnetic clutch I8 and reducing speed gears I 6. An electric brake I9 is associated with the magnetic clutch so that when the magnetic clutch is energized to transmit power the electric brake I9 is released through the energization of the brake windings 20.

The electric motor I! may be energized from a suitable alternating current supply indicated by the reference character 25. The starting and stopping of the electric motor Il may be accomplished by a relay 29 having contacts 30 and the direction of rotation of the electric motor II may be controlled by the reversing control unit 26 which when the push button 21 is depressed operates the motor in one direction and when the push button 28 is depressed the motor operates in the reverse direction. The motor I! is continuously driven and the magnetic clutch I8 is operated intermittently to intermittently move the tool device I 4 with reference to the reciprocal work table upon actuation of the toggle arrangement 81 or 68 depending upon the direction of travel of the reciprocal work table and upon whether the transfer switch I5 is engaging contact 84 or 85. The duration through which the magnetic clutch is energized is governed by an electrical timing circuit indicated generally by the reference character 3B which comprises a grid controlled rectifying tube 31, a condenser 48, an adjustable resistor 49, a fixed resistor 5|, and the

secondary windings

33, 34 and 35 of a transformer 32 which in turn is energized by a transformer 31 connected to the alternating current supply 25. The grid controlled rectifying tube comprises a heated cathode 38, a plate 39 and a control grid 40. The cathode 38 is heated by the secondary winding 35 of the transformer 32. The plate circuit of the rectifying tube is energized by the secondary winding 34 and may be traced from the left-hand terminal of the secondary winding 34 through conductor 45 to the cathode 38, the plate 39, a conductor 45 to the winding of a relay 44 and through a conductor 4'! to the opposite terminal of the secondary winding 34. When the tube 81 is conducting current the relay 44 is energized and closes the

contacts

52, 54 and 55 and opens the contacts 58 and 53. The closure of the con.- tact 52 connects the secondary winding 33 in electrical circuit connection with the condenser 48 which electrically charges the condenser 48 preparatory to discharging same through the adjust able resistor 49 upon the reclosure of the contact 58 which connects the adjustable resistor 49 in closed circuit relation with the condenser 48. During the discharging of the condenser 48 through the adjustable resistor 49, the tube 3! becomes non-conducting until the condenser has been discharged to a predetermined condition,

after which it again becomes conducting to resume the cycle of operation.

The operation of the complete circuit arrange-- ment may be described as follows: assuming that the work table III is moving to the right as shown in the drawing, and that the rectifying tube 31 is conducting, in which event the relays 44 and 58 are energized, the motor I! may then be started by depressing the start push button 42 which establishes a circuit for energizing the re" lay 29 for closing the contacts 30 which connect the motor l1 to the alternating current supply conductor 25. The relay 29 when once energized by depressing the push button 42 is continuoush energized through the contacts 4| which are closed when the relay is once energized. Consequently, the motor II continues to run even though the contacts 55 of the relay 44 are open and even though the start push button 42 is open. The rectifying tube 31 continues to be conducting and the relay 44 continues to be energized until the projection 69 engages the toggle arrangement SIat which time the contacts II and 12 are closed. Th closure of the contacts II provides for reversing the direction of the drive and control unit for reversing the movement of the reciprocal work table III to the left. The closure of the contacts I2 establishes a circuit for energizing therelay 65 which circuit extends from the direct current supply conductor 80, the winding of the relay 85, a conductor IS, the contacts I2. a conductor I1 and a transfer switch I5 to the pposite side 54 of the supply source. The energization of the relay 65 opens the contact 678 for disconnecting the condenser 48 from circuit relation with the secondary transformer winding 33 Interruption of the circuit by the opening of the contact 86 causes the condenser 48 to affect the control grid 48 such that the tube 31 becomes non-conducting at which point the relay 44 is deenergized. The de-energization of the relay 44 closes the contact 53 which establishes a circuit for energizing the magnetic clutch I8 and the windings 20 of the brake I9. The circuit for energizing the magnetic clutch I8 and the brake winding 20 may be traced as follows: beginning with the direct current supply conductor 50. current flows through conductor 88, the contacts 53, conductor 8|, the magnetic clutch I8 and the brake winding 20, and conductor 82 to the op posite side of the direct current supply source 64. The relay 44 remains de-energized for supplying current to the magnetic clutch for a short interval of time as determined by the rate at which the condenser 48 is discharged through the adjustable resistor 49 which is connected in closed circuit relation with the condenser 48 through the closed contacts 50. As previously explained. when the condenser 48 is discharged to a predetermined condition the tube 31 again becomes conducting at which point the relay 44 is again;

energized which interrupts the circuit for supplying the current to the magnetic clutch. Durin the interval that the magnetic clutch is energized,

the motor [1 drives the gears I6 and the screw traverse assembly l5 for moving the tool device I4 a small distance with reference to the reciprocal work table for taking another cut upon the Acccrddevice a small distance, upon the projection 69 pp the toggle arrangement 61. The movement of the tool I4 is substantially concurrent.

with the tripping of the toggle arrangement so that the projection 69 need not move much lieyond the toggle arrangement for effecting the proper movement of the tool H. The operation the toggle arrangement 61. Upon the transfer of the switch 15 to the opposite contact 85, the movement of the tool I4 is eifected when the projection 10 engages the toggle arrangement 68/ When the toggle arrangement 61 or 68 as the case may be are restored to their normal position upon the reversal of the work table, the relay 65 is again de-energized which closes the relay contacts 66 for re-establishing the timing circuit by connecting the secondary transformer winding 33 in circuit relation with the condenser 48 and the fixed resistor through the closed contacts 52 for again recharging the condenser 48 preparatory to another cyclic operation. The tube 31 remains conducting and the relay 44 remains cnergized until the relay 65 is again re-energized for interrupting the contact 66. Conse quently, the relay 44 remains energized throughout the period that the movable work table travels before the projection 59 or 10, as the case might be, engages the respective. toggle arrange ment, and momentarily remains deenergized during the time that the electrical timing circuit 36 causes the tube 31 to be non-conductive.

Accordingly, in our control system the magnetic clutch is energized momentarily through the closure of the contacts 53 during the period that the relay 44 is de-energizcd which is determined by the discharging of the condenser 48 through the adjustable resistor 49. The distance that the tool I4 is moved may be accordingly varied by adjusting the adjustable resistor 49 which varies the discharge rate of the condenser 48. In the event that the tube should fail forany other reason so that the relay 44 remains de-energized for too long a period, we provide for tie-energizing the motor l1 through means of a relay 58 which is energized through a circuit including the con tacts 54 of the relay 44. The circuit for energizing the relay 58 may be traced from the direct current supply conductor 60 through conductor iii, the adjustable resistor 62, the winding of the relay 58, and the contact 54 to the opposite side of the direct current supply source 64. The condensor 63 is connected in parallel with the adjustable resistor 52 and the winding 58 which tends to hold the relay 58 energized for a redetermined length of time after the contacts 54 are open upon the de-energization of the relay 44. Thus, the relay 58 is set for a longer period of time than the setting of the electrical timing circuit 36 so that in the ordinary operation of the electrical timing circuit 36 the relay 58 always remains closed. However, in the event that the relay 44 remains open for a longer period of time than that de tcrmined by the discharge of the condenser 48, such for example, as upon the failure of the tube 31, the relay 58 becomes de-energized and opens the contacts 59 for energizing the relay 29 which disconnects the motor [1 from the alternating current supply 25. The relay 58 may thus be characterised as a safety relay to prevent the motor" from driving the tool H in the event of failure of the electrical timing circuit 36. A push button is connected in parallel with the contacts 53 so that upon depressingthe push button 83 the magnetic clutch I8 may be energized separately from the electrical timin circuit for continuously moving the tool M. The push button 83 may be used for setting the tool 14 for the initial settingoperation.

We find fromactual experience that the arrangement provides forgiving very accurate control over the movements of the tool device I4 with reference to the reciprocal work table and that the movement of the tool with respect to the workpiece is substantially concurrent with the tipping of thetoggle arrangement for reversing the direction of the movement of the reciprocal work table. The entire system for operating the tool device maybe arrested by olepressing the stop button 43.

Although we have described our invention with. a certain degree of particularity, it is understood that the present disclosure has been made only by way of example and that numerous changes in the details of construction and the combination and arrangement of parts may be resorted to Without departing. from the spirit and the scope of the invention as hereinafter claimed.

We claim as our invention:

1. In a control system having a driving shaft, a driven shaft, amagnetic clutch between the two shafts, and a source of electrical current, the improvement of circuit means for. momentarily energizing the magnetic clutch for transmitting power from the driving shaft to'the driven shaft, said improvement comprising circuit connection means for connecting the magnetic clutch to the sourc of electric current, and an electrical timing circuit including a grid-controlled tube and a capacitor for governing the circuit connection means.

Z. In a control system having a driving shat t. a driven shaft, a magnetic clutch between the two shafts, and a source of electrical current, the improvement of circuit means for momentarily energizing the magnetic clutch for transmitting power from the driving. shaft to the driven shaft, said improvement comprising circuit connection. means for connecting. the magnetic clutch to the source of electric current, and an electrical tim-,

ing circuit including a grid-controlled tube and a capacitor for governing the circuit connection means, said circuit connection means controlling the electrical timing circuit.

3. In a control system having a driving shaft, a driven shaft, a magnetic clutch between the two shafts, and a source of electrical current, the immovement of circuit means for momentarily energizing the magnetic clutch for transmitting power from the driving shaft to the driven shaft. said improvement comprising circuit connection means for connecting the magnetic clutch to the source of electric current, an electrical timing circuit including a grid-controlled tube and a capacitor for governing the circuit connection means, said circuit connection means controllin the electrical timing circuit, and means for arresting the rotation of the driving shaft upon failure of the electrical timing circuit.

4.. In a control system having a movable work table, a movable tool device, and a source of electrical current, the improvement of circuit means for moving the tool device with respect to the work table, said circuit means comprising, driving means for the tool device, magnetic clutch means for governing the driving means, circuit connection means for connecting the magnetic clutch to the source of electric current, an electrical timing circuit for governing the circuit connection means, said circuit connection means controlling the electric timing circuit, and means responsive to the movements of the work table for governing the electrical timing circuit.

5. In a control system having a movable work table, a movable tool device, and a source of electrical current, the improvement of circuit means for moving the tool device with respect to the work table, said circuit means comprising, driving means for the tool device, magnetic clutch means for governing the driving means, circuit connection means for connecting the magnetic clutch to the source of electric current, an electrical timing circuit including a grid-controlled tube and a capacitor for governing the circuit connection means, and means responsive to the movements of the work table for governing the electrical timing circuit.

6. In a control system having a movable work table, a movable tool device, and a source of electric current, the improvement of circuit means for moving the tool device with respect to the Work table, said circuit means comprising, electric means for controlling the movements of the movable tool device, circuit connection means for connecting the electric means to the source of electric current, an electrical timing circuit including a grid-controlled tube and a capacitor for governing the circuit connection means, and means responsive to the movements of the work table for governing the electrical timing circuit.

'7. In a control system having a movable wort; table, a movable tool device, and a source of electric current, the improvement of circuit means for moving the tool device with respect to the work table, said circuit means comprising, electric means for controlling the movements of the movw able tool device, circuit connection means for connecting the electric means to the source of electric current, an electrical timing circuit for governing the circuit connection means, means responsive to the movements of the work table for governing the electrical timing circuit, and means for arresting the movements of the tool device upon failure of the electrical timing circuit.

8. In a control system having a movable work table, a movable tool device, and a source of electric current, the improvement of circuit means for moving the tool device with respect to the work table, said circuit means comprising, an electric motor for driving the tool device, a magnetic clutch between the electric motor and the tool device, means for energizin the electric motor, circuit connection means for connecting the magnetic clutch to the source of electric current, an electrical timing circuit for governing the circuit connection means, and means responsive to the movements of the work table for governing the electrical timing circuit.

9. In a control system having a movable work table, a movable tool device, and a source of electric current, the improvement of circuit means for moving the tool device with respect to the work table, said circuit means comprising, an electric motor for driving the tool device, a magnetic clutch between the electric motor and the tool device, means for energizing the electric motor, circuit connection means for connecting the magnetic clutch to the source of electric current, an electrical timing circuit for governing the circuit connection means, means responsive to the movements of the work table for governing the electrical timing circuit, and means for tie-energizing the electric motor upon failure of the electrical timing circuit.

10. In a control system having a movable work table, a movable tool device, and a source of electric current, the improvement of circuit means for moving the tool device with respect to the work table, said circuit means comprising, an electric motor for driving the tool device, a magnetic clutch between the electric motor and the tool device, means for energizing the electric motor, circuit connection means for connecting the magnetic clutch to the source of electric current, an electrical timing circuit for governing the circuit connection means, said circuit connection means controlling the electrical timing circuit, means responsive to the movements of the work table for governing the electrical timing circuit, and means for de-energizing the electric motor upon failure of the electrical timing circuit.

GEORGE H. PARDEY. CORNELIUS L. JOHNSON.