US3422318A - Multiswitch lock - Google Patents

Description

Jan. 14, 1969 O R. E. MOODY MULTISWITCH LOCK Filed March 5, '1967 Sheet fOE INVENTOR RICHARD E. MOODY ATTORNEY Jan. 14, 1969 R. E. MOODY MULTISWITCH LOCK Sheet Filed March 3, 1967 FIG.5

FIG .3

INVENTOR RICHARD E. MOODY FIGZ ATTORNEY Filed March 5, 1967 Sheet .3...

MULTISWITCH LOCK INVENT OR RICHARD E. MOODY ATTORNEY United States Patent 3,422,318 MULTISWITCH LUCK Richard E. Moody, Newark, DeL, assignor to E. I. du

Pont de Nemours and Company, Wilmington, Del., a

corporation of Delaware Filed Mar. 3, 1967, Ser. No. 620,496

US. Cl. 317-136 Int. Cl. H01h 47/00 4 Claims ABSTRACT OF THE DISCLOSURE Brief summary of the invention Generally, this invention comprises an electromechanical interlock for a plurality of momentary operating multicontact pair design pushbutton switches wherein each switch is provided with an individual electromagnetic actuator fitted with a mechanical locking member for the associated switch, which actuator is connected to one side of a control voltage source directly via a first terminal and to the other side of the source via a second terminal and a reserved pair of contacts in the associated pushbutton switch, with parallel cross connection to the second terminals of the actuators of all other switches, so that closure of a given pushbutton switch locks all of the remaining switches out of operation until the given switch again opens.

Drawings The construction of a preferred embodiment is detailed in the drawings appended, as to which:

FIG. 1 is a schematic circuit diagram of a multiple switch installation according to this invention incorporating (a) a time delay auxiliary for disengagement of locking members after a preselected time interval, and (b) provision for direct operator choice of lock-out time duration,

FIGS. 2 (partially cut away) and 3 are, respectively, side elevation and plan views of a preferred embodiment of a solenoid (moving core) type actuator according to this invention, shown with pushbutton depressed and solenoid de-energized,

FIGS. 4 (partially cut away), and 5 are, respectively, side elevation and plan views of the same apparatus as shown in FIGS. 2 and 3, but with pushbutton not de pressed and solenoid energized,

FIG. 6A is a perspective view of a fixed core electromagnet embodiment of lockout actuator according to this invention, and

FIG. 6B is a side elevation view of the actuator of FIG. 6A.

Referring to FIG. 1 there is shown a design of multiple switch interlock for the starting and stopping of a multiplicity of electrical drive motors, only one of which is detailed, each of which motors has its own start and stop switching stations denoted, individually A, B etc. It will be understood that, while only two such stations are detailed, others can be added as indicated by the right-hand continuing circuit interconnections drawn in broken line representation.

The interlock of this invention is intended for use with 3,422,318 Patented Jan. 14, 1969 the conventional design of momentary operating multicontact pair design pushbutton switches which are widely employed for remote service control of industrial drive motors and the like. As shown in FIGS. 2-5, one popular type of this switch incorporates modules 33, each having two switching contact pairs (the connection terminals of which are denoted 34), one pair of which is normally open while the other pair is normally closed. This type has provision for adding other modules on in parallel switch contact disposition by screw attachment end-toend, so that additional switching units can be readily attached in sequence to build up a switch for the simultaneous switching of a multiplicity of circuits in a wide variety of dilferent interrelated patterns. Such a pushbutton switch, having two normally open contact pairs, closed in unison as indicated by the broken line connection drawn therebetween, is generally shown at 10, FIG. 1, for starting service of a three phase electric drive motor 11 shown schematically below station A, whereas another pushbutton switch incorporating a normally closed contact pair together with two open contact pairs for braking service of the same motor is denoted generally at 14.

Because the motor start and stop switching operations must be interrelated so that only one is carried out at any given instant, the upper pair of contacts of start switch 10, denoted 10a, are connected in series circuit with the normally closed contact pair 14a of the motor stop switch 14. Control voltage mains 12, typically a low voltage AC. or DC. source, are connected via the contact pairs 14a and 10a, when the latter are closed, to the opposite terminals of motor starting relay 15. Relay 15 is self-locking through its normally open contacts 15a, shunt-connected with respect to switch contact pair 14a, and, when energized, closes the three motor driving current supply contacts 11a, 11b and supplying motor driving current from a conventional three phase AC. power supply.

Each pushbutton switch is provided with an electromagnetic actuator such as 16 for pushbutton switch 10 provided with a locking device 16a adapted to move leftwards as seen in FIG. 1 whenever actuator 16 is energized, thereby locking the switch against closure, it this particular pushbutton is not already depressed. The actuators for each individual switch are energized from the control voltage mains 12 by connection through a reserved switch contact pair 1% connected to one terminal of actuator 16 the other terminal of which is connected directly to the remaining main 12 via lead 17. A lead 18 is connected to all of the actuator terminals adjacent contact pairs 10b for all of the stations A, B, etc., as a parallel electrical circuit connection interlocking actuator operation for all of the multiplicity of stations.

It is a common situation in industrial production lines that a multiplicity of driving motors 11 receive their operating current from a common power source which may, for example, be of solid state design, utilizing SCR components. Since electric motors all require an exceedingly large starting current when first switched in, it is essential that the common power source be protected against overload by switching in only one motor at a time, delaying switch-in of the next motor in sequence until the first has attained essentially full operating speed. Formerly, this was done manually by an operator, who was advised by a warning light or other appropriate signal device that a given motor was being brought into service, so that he would not switch in yet another one until the critical period was passed through.

This has not always been satisfactory, as heavy dependence is placed upon operator judgment and costly human errors are always possible.

This invention affords anautomatic safeguard against switch-in overloading by the incorporation of a common timing relay 20 in series circuit connection between one side of the control voltage mains 12 and the pushbutton switch-connected terminal of each of the actuators 16. This relay has its coil 21 connected through normally closed timed contact pair 20a on one side to lead 18 and on the other side to the other control voltage main 12 paired with the main to which is connected individual station contact pairs 10b. Relay 20 is also provided with a self-locking instantaneous contact pair 2% connected to the other control voltage main 12. Conventional automatic timing means (e.g., a slow advance extensible bellows type), not shown, is provided to open contact pair 2011 after the passage of a time interval preselected to be long enough so that an individual motor 11, started by momentary depression of pushbutton switch 10, will have passed through start-up and safely taken up its load before contact pair 20a opens, thereby de-energizing all of the actuators 16 and opening all of the locking devices 16a. It is then possible to choose the next motor 11 which it is desired to place in service, and the pushbutton switch 10 at the next chosen station is simply depressed, whereupon all other pushbutton switches of the circuit assembly are locked out until the second motor goes into service.

It is convenient to incorporate similarly protected individual motor braking facilities within stations A, B, etc., and this is readily accomplished by adding a double normally open contact pair 14b and 14 each connected in parallel with contact pair 14a and closed in unison by manual opening of the latter as indicated by the common broken line connection show in FIG. 1.

In this instance contact pair 14b is connected in series with braking relay coil 23 which has its Operating contacts 23a connected in series with DC. braking power leads 24 connected in circuit with two of the AC. driving leads for motor 11. When braking any given motor 11 the operator depresses the spring-biased Stop pushbutton and holds contacts 141) closed until the desired braking effect is obtained. The dynamic motor braking action results from magnetic saturation of the core and interaction with the motors rotating field.

Again, it is important to limit the effect of the power supply, in this instance the DC. supply, to that of a single motors braking and, accordingly, contacts 14c are reserved for energization of individual actuators 26 connected to one control voltage lead 12 through one terminal and, individually, via their other terminals and leads 17 to the other control voltage lead. Simultaneous energization of the actuators 26 at all stations A, B, etc., is effected by parallel connection of the common pushbutton switch side contacts of each together via lead 29. Since, in this instance, the braking action sought is at the operators discretion, control is achieved by duration of depression of the pushbutton of switch 14, making it unnecessary to employ a timing relay auxiliary as previously described with reference to relay 20.

A preferred design of actuator 16 (or 26) according to this invention employing a solenoid is shown in side elevation in FIG. 2 and in plan in relationship to the pushbutton switch with which it is associated in FIG. 3 for the condition where the solenoid is de-energized and the pushbutton has just been depressed by the operator. FIGS. 4 and are the corresponding views for the solenoid energized state.

The solenoid coil is denoted at 31, energizing DC. or A.C. current being conveniently supplied to it via plug-in sockets 31a.

The actuator is conveniently assembled to the pushbutton switch by a right angle mounting bracket 38 attached to the switch body proper by a tapped screw 38a, with the solenoid coil mounted on the upright arm by a pair of tapped screws 38b.

The solenoid plunger 32 is slotted at the outboard end 32a to receive the upper horizontal end 39a of the swiveling lockout member, indicated generally at 39, which is retained in the slot 32a by cotter pin 35. Lockout member 39 is biased into unlocked position by torsion spring 36 coiled around the vertical mid length thereof, with upper end bent to partially encircle horizontal end 39a on the inner side, to thereby press end 39:: firmly against cotter pin 35, whereas the lower end of spring 36 is anchored in a drilled hole, not detailed, in the actuator mounting bracket 38.

The lower end of lockout member 39 is formed into an offset crank portion 3912, which performs the lockout function of the device as hereinafter described.

The pushbutton member 40 of the switch is of conventional form, normally spring-biased to outward open switch position as shown in FIG. 4 by compression spring 41, but adapted to be depressed manually to closed circuit condition as shown in FIG. 2. When solenoid 31 is de-energized, crank portion 3% lies closely adjacent the inside peripheral boundary of inner disk 40a 'of pushbutton 40, but clear of the line of advance thereof, so that, with the solenoid de-energized, pushbutton 40 can be freely depressed inwardly as detatiled in FIG. 2 with disk 40a clear of the end of crank 3912, thereby effecting the switchs contact closing function by members internal of modules 33, not herein shown. It will be understood that, while closure of the given switch also energizes its associated solenoid, disk 40a will have, by that time, ad-

: vanced inwardly past its lockout crank 39b, overriding the rotatory action of the relatively weak solenoid, which therefore has no lockout effect as to this switch.

However, when the solenoids 31 of any other switches are energized, the solenoid plungers 32 are retracted inwardly, rotating crank ends 3% counter-clockwise through a relatively small angle of about 15, whereupon the depending ends of 3% overlie the upper faces of disk 40a, as shown in FIGS. 4 and 5, barring pushbutton inward advance and locking the switches out of closed contact position until the operator releases the given switch selectively closed, or until such release is effected automatically b toll-out of timing relay 20, hereinbefore described.

Referring to FIGS. 6A and 68 a second embodiment of lockout device according to this invention is of the magnetically operated fixed core type, shown in relationship only with the inside top face of a pushbutton switch 43 identical in design with those hereinbefore detailed in FIGS. 2-5, inclusive, with inner pushbutton disk shown at 43a.

In this design, an electromagnet 44 is employed instead of solenoid 31, this being attached to the upstanding arm of an L-shaped bracket 48, which is itself secured to the upstanding arm of the larger L-shaped bracket 45 employed for mounting the lockout device on the switch body. I

As shown in FIG. 6B, the electromagnet clapper 46 is provided with a lug 46a on its lower inside face and this is drilled to receive loosely pin 47 attached to the outboard end of bracket 48, thereby permitting clapper 46 to rotate clockwise freely into contact with the electromagnet pole piece when the electromagnet is energized. Additional lugs 48a, on the underside of bracket 48, and 46b, on the lower end of clapper 46, are provided for attachment of the two ends of tension spring 49, which biases the clapper into its normal vertical position when electromagnet 44 is de-energized.

A clapper extension piece 46c is attached to the outside face of clapper 46 by machine screws 50 and this depends through a slot 51 machined in the base of bracket 45. The bottom end of extension piece 460 is formed into a pair of inclined feet 52 which normally occupy the position indicated in full line representation in FIG. 6B clear of the line of upward displacement of pushbutton switch disk 43a, but rotate clockwise into switch-locking position across the disk, as indicated in broken line showing, when electromagnet 44 is energized,

From the foregoing it will be understood that this invention can be modified in numerous ways within the skill of the art without departure from its essential spirit, and it is accordingly intended to be limited only within the scope of the appended claims.

What is claimed is:

1. An electromechanical interlock for a plurality of momentary operating multicontact pair design pushbutton switches operable to prevent closure of any of the remainder of said pushbutton switches during the period in which a given one of said pushbutton switches is held in closed contact position comprising, in combination, individual electric actuators associated with each of said pushbutton switches, said actuators having mechanical locking members preventing closure of all said remainder of said pushbutton switches whenever said electric actuators are energized, a control voltage source, circuit means connecting said actuators at one terminal through an interlock elfectuation reserved contact pair of the associated pushbutton switch with a first side of said control voltage source and at the other terminal directly to the other side I of said control voltage source, and a common circuit connector connecting in parallel electrical circuit said firstnamed terminals of each of said actuators.

2. An electromechanical interlock for a plurality of momentary operating multicontact pair design pushbutton switches according to claim 1 wherein said common circuit connector is connected to said first side of said control voltage source through a time delay relay maintaining said actuators energized for a predetermined period of time after the closure of said given one of said pushbutton switches.

3. An electromechanical interlock for a plurality of momentary operating multicontact pair design pushbutton switches according to claim 1 wherein said individual electric actuators are moving core solenoids having direct mechanical connection with lockout members shifted into locking ,position across the line of pushbutton advance whenever said solenoids are energized and biased clear of said line of pushbutton advance at all other times.

4. An electromechanical interlock for a plurality of momentary operating multicontact pair design pushbutton switches according to claim 1 wherein said individual electric actuators are fixed core electromagnets attracting, when energized, pivoted clapper members shifted into locking position across the line of pushbutton advance, and biased clear of said line of pushbutton advance at all other times.

References Cited UNITED STATES PATENTS 2,712,101 6/1955 Salati 317-136 2,792,012 5/1957 Howard 317-136 3,365,555 1/1968 Ponsy 200-5 GEORGE HARRIS, Primary Examiner. HAROLD BROOME, Assistant Examiner.

US. (:1. X.R.

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