US1918378A - Electric switch and closing and opening means therefor - Google Patents

Description

July 18, 1933- G. A. BURNHAM 1,918,378

ELECTRIC SWITCH AND CLOSING AND OPENING MEANS THEREFOR 11111/111111zllflrlllzllll/zlllll.

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Filed May 5l, 1929 Patented July is, 1933 UNITED STATES PATENT OFFICE GEORGE A. BURNHAM, OF SAUGUS, MASSACHUSETTS, ASSIGNOR TO CONDIT ELECTRICAL MANUFACTURING CORPORATION, A CORPORATION OF MASSACHUSETTS ELECTRIC SWITCH AND CLOSING AND OPENING MEANS THEREFOR Application led May 31,

This invention relates to electric switches and to controlling apparatus and systems therefor.

A switch is designed to carry its rated load and to open and close the loaded circuit successfully if the time intervals between successive opening operations is not too short. If the switch is opened repeatedly under a heavy load, with but a small interval between successive openings, the contacts become hot an-d burn, and destructive arcing can take place. For many purposes, and especially for the control of motors, it is not essential that the switch be opened repeatedly at a rapid rate, and such operation can in fact be harmful to the switch, the motor and to the circuit. Consequently, an object of this invention is to provide a switch and operating devices therefor so arranged that a suitably long period of time must intervene between successive openings of the switch upon heavy load.

A further object of the invention is the provision of a switch and control devices therefor so arranged that after the switch has opened, it cannot be reclosed before the expiration of a predetermined time interval.

The usual type of motor starting switches with which this invention is more particularly concerned are closed electrically and are held closed by an electro-magnet, the circuit of which is controlled -by push button circuit controllers.

A further object of the present invention is the provision of an lelectrically-closed motor starting switch and controlling switches or circuit controllers therefor and means so arranged that the circuit controllers are ineffective to effect successive openings of the motor starting switch within a predetermined time interval.

A further object of the invention is the provision of an electrically-operated motor starting switch and circuit controllers therefor with means so arranged that the circuit controllers are ineffective to effect the reclosing of the switch except after a predetermined time interval after it is opened under load.

A further object of the invention is gen- 1929. Serial No. 367,340.

erally to improve the construction and operation of electric switches and control systems and apparatus therefor.

Fig. 1 is a more or less diagrammatic representation of an electrically-operated motor starting switch and its connections with the push button circuit controllers therefor, the construction of the push button controllers being shown in section and arranged in accordance with the present invention.

Fig. 2 is a section along line 2-2 of Fig. l.

Fig. 3 is a view similar to Fig. l, but i1- lnstrating a modified mechanism for obtaining `delayed reclosing of the switch.

Fig. 4 is a more or less diagrammatic representation of a switch wherein the means to delay the reclosing of the switch for a predetermined time interval after the reclosing ofttihe switch is incorporated directly therewi The switch with which the present invention is associated is more or less diagrammatically shown and includes a movable bridging member 10 which is adapted to move upwardly and engage and bridge the stationary contact members 12 of one of the circuit conductors 14 of the herein shown single phase circuit that includes the other conductor 16. The switch may control the supply of power to any power consuming device as the motor 18.

While the switch here shown is illustrated as being in but one conductor of the circuit,

it is to be understood that the switch can be in all conductors of the circuit, as is common practice.

The bridging member 10 is here shown as mounted on an insulating bar 20 carried by the switch arm 22 which latter is pivoted loosely at its free end to one leg of an electromagnet 24 which has an actuating winding 26. The arrangement is such that when said winding is energized the electro-magnet attracts the lever 22' and moves the bridging member into engagement with the fixed contact members 12. thereby closing the switch. The switch is held closed by maintaining the electro-magnet energized. The circuit of the electro-magnet is controlled by a pair of push button controlled circuit controllers,

there being a push button 28 which is arranged to insure the initial energization of the magnet and thereby the closing of the switch and a second push button 30 which serves to effect the de-energization of the magnet and the opening of the switch. The switch closing push button 28 controls .a normally-open circuit controller and to th1s end, has a spring 32 that supports the movable contact member 34 of the controller normally above and out of contact with the fixed contact members 36 and 38 of the controller., The push button 28 can be depressed manually to bridge said fixed contact members but when the pressure is removed, the spring 32 carries the push button upwardly and interrupts the circuit. The switch o ening push button 30 controls a normally-c osed circuit controller and has a spring 40 which maintains the movable contact member 42 of the controller normally in bridging contact with the fixed contact member 38 and a second fixed contact member 44 of the controller. When the push button 30 is depressed the bridging member 42 is moved away from said contact members 38 and 44, thereby interrupting the closing circuit of the switch. When the pressure on the push button is removed, the spring 40 returns the push button to its aforesaid circuit closing position.

One terminal of the winding 26 of the electro-magnet is connected by a conductor 46 to the conductor 16 of the power circuit. The other terminal of the winding 26 is connected by a conductor 48 with the fixed contact member 44 and thus through the normally closed opening controller with the fixed contact member 38 of the closing controller. The other fixed contact member 36 of the closing controller is connected by the conductor 50 with the other conductor 14 of the power circuit. Thus, when the closing controller is depressed, the electro-magnet winding is placed across the power circuit and is thus energized and the switch is closed. The closing of the switch serves to establish a shunt circuit for the electro-magnet around the closing circuit controller so that the push button can be released and its circuit broken without causing the switch to open. This shunt circuit includes a conductor 52 which is connected with the fixed contact member 38 of the closing controller and with the bridging member 10 of the switch. Thus, when the switch is closed, and the circuit through the closing controller is interrupted, the circuit through the electro-magnet winding is maintained complete through the conductor 52. The closing circuit controller and the shunt circuit 52 are in seriesvwith the opening controller so that when the push button thereof is depressed, the electro-magnet circuit is opened and the switch thus falls open. When the switch is opened, the shunt circuit is opened, so that the switch stays open .until rccloscd by the second depression of the closing push button.

The two circuit controllers are usually contained in a suitable casing 54 which may be disposed in any suitable position regardless ly under load either to satisfy his curiosity as to the operative condition of the switch or in an attempt to keep the switch closed on such heavy overload or other abnormal conditions that the protective devices instantly open the switch after its reclosure. Such rapidly repeated openings of the switch on heavy load are detrimental to the switch since insuflicient time is thus given to permit the contact members of the switch to cool 0H and the arc gases to be dissipated. Consequently, with rapidly repeated openings under load, the contact members become hot and destructive' arcing can take place. Moreover, the rapidly repeated closings and openings of the switch under heavy load or short circuit obviously can be detrimental to the power circuit and to the apparatus associated therewith. Consequently, means are herein provided to prevent the rapidly repeated opening of the switch under heavy overload exce t after the expiration of predetermined time intervals following each opening operation, and specifically to prevent the reclosing of the switch after it is opened until the expiration of such time interval.

Figs. 1 and 2 illustrate an arrangementv 58 operab e therein and maintained normally in elevated position by suitable means as the spring 60. The cylinder is fixedly supported beneath the push button 28 and the piston 58 has a piston rod or stem 62 which extends upwardly between the contact members 36 and 38 and is terminated immediately under but free from fixed engagement with said push button. The arrangement is such that as said push button and its bridging member` is depressed, it will also depress said stem and the piston 58 and thereby compress the spring 60. The dashpot is so arranged, as by having a check valve 64 which controls the flow of Huid between opposite sides of the piston through thel passage 66, that the piston can descend freely in the cylinder but has its upward movements under the action of the spring 60 retarded. The time that it takes the piston to move upwardly into its normal elevated position is the period that the push button 28 and its circuit controller is locked in elevated and unoperative position; and this time can be varied in any suitable manner not necessary to illustrate herein, since it is generally known in the art.

The dashpot controls a latch 68, see especially Fig. 2, which is vertically extended upwardly beside the movable contact member 34 of the controller button and is adapted, immediately after the push button has been restored to its elevated position to move under said contact member and to be held in such position until the dashpot operates to move it away from such position. To this end, the latch, which can be made of insulating material, or otherwise suitably insulated from the control circuits, is pivoted at its lower end on a support and has a spring 72 or other biasing means which normally tends to hold it yieldingly under and in the path of downward movement of the push button. The latch has a forwardly extended arm 74 that overlies the stem 62 of the dashpot and a shoulder or abutment 76 of said stem. The arrangement is such that when the stem 62 is in its normal elevated position, the shoulder 76 thereof engages the arm 74 and thus holds the latch 68 in an unoperated position, the spring 60 of the dashpot being stronger than the spring 72 of the latch.

When, however, the push button is depressed to close the switch, the stem 62 is also depressed, thereby freeing the latch. While the push button instantly returns to its elevated position, the piston of the dashpot is delayed in its upward movement. Thus, the latch 68 can snap into position under the push button and hold it in elevated position against a second downward movement until the piston is moved upwardly sufiiciently for the abutment 76 to move the latch out of locking relation with the push button. The time period during which the push button is locked out of operation can be anything desired by a suitable design or adjustment of the dashpot. The time may be five seconds, or ten seconds, or more or less, but is adapted to be such at least as to give the switch contacts time enough' to cool oil prior to successive openings under load so that the rated load of the switch can be interrupted successively an indefinite number of times without damage to the switch, and also without damage to the apparatus controlled by the switch.

Fig. 3 illustrates essentially the same arrangement of switch and push button circuit controllers as shown in Fig. 1 except that the push buttons and especially the closing push button 28 is located in a well 78 of the casing 54 so that it is in best position to be depressed only when it is at the top of the well. Instead of positively locking the starting push button in an elevated and inoperative position for a predetermined period of time as in Fig. 1, means are illustrated in Fig 3 to delay the return of the push button into position for a second operation.

Said delaying means includes a ratchet wheel 80 which is connected through a oneway clutch 82 with a spur gear 84 that is driven by a rack 86 of said push button. The ratchet wheel is engaged by a pivoted pawl 88 having the timing weights 90 the position of which from the pivotal center of the pawl determines the rate of vibration of the pawl. The one way clutch 82 is so arranged that the push button 28 can be depressed freely to effect the closing of the switchl without operating the ratchet wheel and pawl. l

The upward movement of the push button under action of its spring 32, however, causes the engagement of the clutch and thus the driving of the ratchet wheel and pawl. The rate of upward movement of the push button is thus governed by the rate of vibration of the pawl so that the push button is returned to its elevated position only after a predetermined period of time.

In Fig. 4 means are associated directly with the switch to prevent the closing thereof until after the expiration of a suitable time after it has opened. To this end. the arm or lever 22 of the switch is adapted to be locked in switch open position by a latch 108 for a suitable period of time so that the switch can not be reclosed during such time. The latch is held normally in lockingr relation with the switch arm by a spring 110 but is held normally out of locking position by being engaged by the stem 112 of a piston 114 working within a dashpot cylinder 116 and being urged for upward movement by a spring 118, the latter spring overpowering the spring 110. The switch arm 22 has a horizontally slidable latch finger 120 that engages a projection 124 which removes the latch from engagement with the dashpot stem thus permitting it to move slowly upwardly under the urge of the spring 118. iVhen the stem 112 is moving downwardly, the latch 108 is free to move into a position above the switch arm 22 so as to hold it in switch open position until the stem 112 moves upwardly to move the latch out of holding position whereupon the switch is then free to be reclosed. The time that it takes the piston of the dashpot to move the latch 108 away from holding position is thus the time that the switch is prevented from reclosing. This time can be varied by suitable design or adjustments to the dashpot in the usual manner.

I claim:

1. 'lhe combination of an electric switch having electromagnetic closing means for it including a winding that is adapted to be maintained energized to hold the switch closed, a manually-operated circuit controller to open the circuit of said winding and thereby to open the switch, a second manually-operated circuit controller to close the circuit of said winding and thereby to close the switch immediately, and time-governed locking mechanism operated by one operation of said second controller having means to prevent a second operation thereof until after the expiration ot' a. predetermined time period.

2. An electro-magnetically operated electric switch having closing means for it including a winding that is adapted to be maintained energized to hold the switch closed, a circuit controller arranged to close the circuit of said winding to close the switch, and time-governed means operated by one operation of said controller to delay the completion of a second ope-ration thereof including a latch arranged to hold the controller in an inoperative osition, and means operated by said contro ler arranged to move said latch away from holding position after a predetermined time period.

3. An electro-magnetically-operated electric switch including a Winding that is adapted to be maintained energized to hold the switch closed, a circuit controller arranged to close the circuit of said winding to close the switch, and time-governed means operated by one operation of said controller to delay the completion of a second operation thereof including a latch arranged to hold the controller in an inoperative position, a dashpot having a plunger which is depressed by the switch-closing movement of said controller, and means to move said piston slowly in the opposite direction and into engagement with said latch, whereby to remove said latch from controller-holding position.

4. An electro-.magnetically-operated electric switch including a winding that is adapted to be maintained energized to hold the switch closed, a circuit controller adapted to close the circuit of said winding to close the switch, means normally biased into a position to lock the controller in an unoperated position thereof, and timc-governed means etective after an interval following an operation of said controller to remove said locking means from locking position.

5. An electro-magnetically-operated electric switch including a winding that is adapt-ed to be maintained energized to hold the switch closed, a circuit controller adapted to close the circuit of said winding to close the switch, means normally biased into a position to lock the controller in an unoperatxal position thereof, and time-governed means actuated by a switch-closing operation of said controller and eli'ective after a predetermined time following such operation1 thereof to remove said locking means from locking position.

G. A circuit controller having electro-inagnetic closing means for it including a winding adapted to be maintained energized to hold the switch closed, a manually-operative circuit controller to close the circuit of said winding and close the switch, said controller including a member movable between circuit-open and circuit-closed positions, a latch biased for movement into position to hold said member from movement in one direction, a timing member normally holding said latch away from holding position disposed in position to be engaged and moved away from said latch by a movement ot said member, whereby to permit said latch to move into a position to hold said member from movement, and means to return said timing member slowly to its original position free from said member to reengage said latch and remove it from holding position.

GEORGE A. BURNHAM.

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