US1695748A - Time-element electroresponsive device - Google Patents

Description

Dec. 18, 1928. 1,695,748

G. R. TOWNSEND TIME ELEMENT ELECTRORESFONSIVE DEVICE Original F l 1925 iv Inventor: George R. Towrfisend,

Patented Dec. 18, 1928.

UNITED STATES 1,695,748 PATENT OFFICE.

GEORGE E. TOWNSEND, OF SCHENECTADY, NEW YORK, ASSIGNOR- TO GENERAL ELEC- TRIC COMPANY, A CORPORATION OF NEW YORK.

TIME-ELEMENT ELECTRORESPONSIVE DEVICE.

Application filed August 5, 1925, Serial-N0. 48,422. Renewed July 20, 1928.

above character that is controlled positively and automatically with a time delay action by an electroresponsive mechanism of relatively small size and power. 1

The invention is particularly advantageous when applied to an undervoltage protective switch. In a preferred form of the invention, the circuit controlling switch is biased to the eircuit opening position and is arranged to be latched in the closed position and released a time interval after a predetermined reduction in the energization of electroresponsive mechanism responsive to the voltage of the controlled circuit. The electroresponsive releasing mechanism is entirely automatic and operates to an inactive position upon energizat ion of the voltage responsive means above the n-edetermincd value so that manual or other resetting operation is unnecessary. To enable the circuit controllii'ig switch to be controlled by an electrm-esponsive releasing mechanism of relatively small power, an improved torm of latching mechanism is provided for holding the switch closed. This mechanism is very easily released and still is not subject to accidental release by extraneous jars or vibrations.

Although of quite general application to undervoltage or power failure protective switching apparattls, the present invention is of particular advantage when applied to an alternating current motor starting switch which is biased to an off position between a starting and a running position. Ordinarily, such a motor starting switch is provided witha latch for holding the switch in the running position and also for preventing operation of the. switch to the running position until after operation to the starting position. By means of my present invention such a motor starting switch easily may be adapted to afford time element under-voltage protection to the motor,

the switch being maintained in the runningposition during temporary voltage fluctualions and released only when the undervoltage condition persists for an appreciable time interval.

The accompanying drawing illustrates the invention embodied in a motor starting switch not the above specified type. Fig. l diagramii-iatically shows the motor starting switch provided with a preferred form of voltage responsive latch mechanism for holding the switch in the running position; Fig. 2 shows the relative positions of the operating parts of the switch and the voltage responsive latching mechanism with the switch in the off posi tion; and Fig. 3 is a circuit diagram showing the electrical connections of the motor starting switch and the voltage responsive latching mechanism therefor.

Referring toFig. 1, it will be seen that the motor starting switch is shown very diagrammatically since the particular construction of the switch itself is not of the essence of my present invention. The switch comprises a movable circuit controlling member which is mounted upon the pivoted switch shaft 11 and is operable to a running position in which it engages with a set of stationary contacts 12 and to a starting position in which it engages with a set: of stationary contacts 13. An arm 14 is secured to the switch shaft 11 to move synchronously with the "switch member 10 and suitable mechanism is provided for biasing the movable switch member 10 to the off position which is between the starting and the running positions. In the form shown, the biasing mechanism comprises the pivoted ' levers 15 and 16 which are interconnected by t the biasing spring 17 so that when one of the levers 15' or 16 is engaged by the lower end of the arm 14 upon movement of switch member 10 from the off position, the other. arm will engage with the stop 18, thereby setting up a strain in the spring 17 which tends to return the switch member 10 to the off position from either the starting or the running position.

In order to hold the switch member 10 in the running position, the latch 19 is pivotally mounted upon the pin 20 and is operable into the path of the arm 14 and arranged to be held in sliding engagement with the upper end of the arm 14, as shown in Fig. 1, when the switch is in the running position. The toggle mechanism 21 is pivotally connected between the latch 19 and the stationary pin 22 and adapted when extended to hold the latch 19 against movement; out.- of the path of the arm 14, by the strain of biasing spring 17, thereby effectively locking the swltch in the running position. Preferably the toggle mechanism 21 is biased to the extended position by its own weight, although an additional biasing spring 23 may be provided in order to render the toggle mechanism more secure against accidental tripping by extraneousjars or shocks, if desired.

itwill be observed that latch 19 is provided wit-h a suitable notch 241 with which the up per end of arm ll engages when the switch is in the oil position as shown in Fig. 2. In this way initial operation of the switch to the running position is prevented. However, when the switch is operated to the start ing position, the arm H is moved to the right and rides along the lower cam shaped por tion of the latch 19, thereby raising the notch 2% out of latching relation with the upper end of the arm 1%. Thus, upon a quick operation of the switch from the starting to the running position the arm l-l will clear the notch 2-l and the latch 19 will fall into engagement with the upper end of the arm as shown in Fig. 1.

in order to release the switch from the running position a time interval after the occurrence of under-voltage or power failure in the circuit controlled by the switch, the movable releasing member 25 is suitably biased as by means of the weight 26 to op rate the tripping pin 2? into engagement with the toggle mechanism 21. The releasing member 25 is under the control of an electromagnet 28 which, as shown in Fig. 3, is connected to be energized in accordance with the voltage of the circuit controlled by the switch 10. In the ar angement shown the magnetic movable member, or plunger, 29 ot' the electromagnet 28 is pivotally connected to the releasing member :25 through the link 30, thereby permitting the member to be operated to and maintained in an inactive position when the energizing voltage of electromagnet 28 exceeds a predetermined value. However, upon a predetermined reduction in the energization of the electromagnet 28 the attractive force of the electromagnet is no longer able to maintain the member in the inactive position and, consequently. the member is released to return into tripping engagement with the toggle mechanism.

The return movement ot' the member 25, however, is delayed by suitable time element means such as the flywheel gear train mechanism 31 shown in the drawing, although other forms of time delay devices may be employed if desired. As shown, the releasing member 25 is provided with a pawl which is biased by the spring 33 to engage the teeth of the gear wheel 3-l to which the flywheel 35 is connected through suitable speed multiplying gearing 36. The pawl 32 only engages with the teeth of the gear wheel when the member 25 is released by the voltage responsive electromagnet 28. Thus, the return movement of the member 25 is delayed for the time interval required to accelerate the flywheel 35.

The operation of the motor starting switch mechanism and the time element undcrvoltng'c protective arrangement is as follows: lVith the movable switch member 10 in the oil position in which it is shown in Fig. 2 the voltage responsive clectromagnet 28 is decnergized when connected as indicated in Fig; 3f Hence, the movable member 25 is in its biased position in which it rests upon the stop 3i and the toggle mechanism it is buckled to permit raising of the latch 19 by the arm 2'1; when the switch is thrown into the starting position. l'ith the connectimis shown in Fig. 3 the three phase alternating current induction motor 38 connected to receive power from suitable supply lines 239 through the voltage reducing transformers or compensators it) when the movable switch member ll) engages with the stationary contacts 13 in the starting position. Since the electromagnet 28 is energized atthe reduced voltage applied to mot-or 2-38, the plunger 29 may not be sutliciently attracted to rai e the releasing member from the stop 37. However. undervoltagc protection is unessential during the starting of the motor at reduced potential since the switch 10 ordinarily is held in the starting position against its bias to the open position only while the. motor accplerating. Upon operation of the switch 'lrom the starting to the running position in which the movable switch member ll) engages with the stationary contacts 12. both the motor 3s and the electromagnet 28 are energized at the full voltage :t the supply lines :39. The plunger 29 is immediately attracted by the electi'oinagnet 2b and quickly moves the releasing member .25 to the inactive position in which it is shown in Fig. 1', thus permitting the toggle 21 to straighten out and lock the switcli in the running position. When the member is raised the pawl 32 rides over the teeth oi the gear wheel Ill, and thus no restrain is imposed upon the movement of the. member to the inactive position. it will be observed that the latch 19 is held in the path of movement of the arm ll and. consequently, the force exerted upon the arm by the biasing spring 17 tends to move the latch 19 out of the path of the end of the arm ll. Hence. when the toggle 21 is moved slightly out of the extended position the force exerted by the arm 1% upon the latch 19 tends to continue buckling the toggle and thereby permits the switch 10 to be easily released from the running position. Due to the advantageous leverage thrtmgh which the biasing weight 26 acts to force the tripping pin 24 against the toggle 21, only a relatively small biasing weight is required to buckle the toggle. llcncc, the electromagnet :28 required to exert a correspondingly small attractive force in order to maintain the member in the inactive position and consequently, the power illl lilt) consumption of the electromagnet is relatively small. This is of Considerable practical advantage since the 'electromagnet 28 is energized during the entire running operation of the motor 38.

In case the source supplying power to the supply lines 39 fails, or the voltage of the sup ply lines 39 decreases below the value required to maintain the member 25 in the inactive position, the latter is released and immediately starts to fall into tripping engagement with the toggle 21. Since the pawl 32 engages with the teeth of the gear wheel 34 upon the return movement of the member 25 the inertia of the flywheel 35 serves to opposc the movement of the member 25-. As the flywheel gradually accelerates, the movement of the member 25 continues and after a time interval the tripping pin 27 is carried into engagement with the toggle 21. This serves to throw-the toggle over center to permit the latch 19 to move out of the path of arm 14 and thereby release the switch for movement to the open position in accordance with its bias. As the switch opens the arm 14 slides along the latch 19 until the arm 14 drops into the notch 2t as shown in Fig. 2. The return of the switch 10 to the otfposition disconnects the motor 38 from the supply lines 39. Upon return ot normal voltage to the supply lines 2,9, motor 38. may be again started and connected for" running operation in the manner previously described. It will be evident, however, that in case the switch is thrown to the running position before the voltage of supply lines 239 has returned tonormal value the toggle 21 will be maintained buckled by the tripping pin 27 and. consequently, the switch will not be latched in the running position.

Although the voltage responsive electromagnet 28 is shown in Fig. 3 connected so as to be responsive to the voltage impressed upon the motor 38, it will be evident that the electromagnet may be permanently connected to the supply lines 39 so as to be responsiveto the voltage thereof at,..all times if desired. Under these conditions the operation of the rndcrvoltagc protective latch mechanism will be entirely automatic since the member 25 will be moved to the inactive position immediatcl y upon the return of normal voltage on the supply lines 39.

\Vhat I claim as new and desire to secure by Letters Patent of the United States is 1. A time element electroresponsive device comprising a movable element biased to a predetermined position, means for holding the element in another position comprising a relatively movable member operable into the path of the element and arranged to be operated therefrom by movement of the element in accordancewith'its bias, means for locking the said relatively movable member ilgilillShlllOVGlTlGl'lt by the element, and elec troresponsive'means biased to render said locking means ineffective a time interval after a predetermined variation in the energization thereof. I

2. A time element electroresponsive device comprising a movable element biased to a predetermined position, latch mechanism for holding the element in another position com prising a relatively movable member operable into the path of the element and a toggle arranged when extended to hold the member in the path of the element and thereby prevent movement of the element in accordance with its bias, and electroresponsive means biased to trip the said toggle to permit movement of the element in accordance with its bias a time interval after a predetermined variation in the energization of said means.

3. A time element electroresponsive device comprising a movable element biased to a predetermined position, a relatively movable member operable into the path of said element and arranged to be operated therefrom by movement of the element in accordance with its bias, a toggle connected to said member and arranged when extended to hold the member in the path of the element and thereby prevent movement of the element in accordance with its bias, an electromagnet having a movable magnetic member biased into engagement with the toggle to trip the same upon a predetermined reduction in the energiza'tion of the electromagnet, and time element means for delaying the movement of said magnetic member to trip said toggle. it. An automatic circuit protective device comprising a switch biased to circuit opening position, latch mechanism for holding the switch in the circuit closing position, a movable member biased to release said latch mechanism, an electromagnet connected to be energized rcsponsively to the voltage of the circuit for moving said member to an inactive position when the voltage of the circuit is above a predetermined value, and means for delaying the return movement of said member to release said latch mechanism for a time ipterval after a predetermined reduction in the voltage of said circuit.

5. An automatic circuit protective device comprising aswitch biased to circuit opening position,'latch mechanism for holding the switch in the circuit closing position, means for controlling said latch mechanism comprising an electromagnet connected to be energized responsively to the voltage of the circuit, and means cooperating therewith for biasing the said latch mechanism into latching relation with the switch when the voltage of the circuit is above a predetermined value and for biasing the said latch mechanism out of latching relation with the switch a time interval after a predetermined reduction in the voltage of the circuit.

6. An automatic circuit protective device comprising .a switch biased to circuit opening positiom latch mechanism for holding the switch in the circuit closing position, a 1novable member biased to release said latch mechanism. an electromagnet connected to be energized responsivelv to the voltage of the circuit and having a movable magnetic member connected to said rel as-in member for moving the same to an inactive position when the voltage of the circuit is above a predetermined value, and means engageable with said releasing member for delaviue' the return movement thereof to release said latch mechanism upon a prcdetermincd reduction in the voltage of said circuit.

7. In cembination a switch biased to open. position. means for holding the switch in the closed position comprising a relatively movable membe operable into ens cement with the switch in the circuit closingposition and gred to be moved by the switch upon operation thereof from the circuit closing position, means for locking the said member against movement by the switch and thereby' preventing operation of the switch from the circuit closing position and voltage responsive means biased to render said locking; means ine iectiv a time interval t er a predetermined reduction in the one (T voltage thereof.

t In combination. switch biased to open position means tor holding th switch in the closed position comprisi a r latively movable member operable into sliding engagement with the switch in the circuit closing position and arranged to be moved by the svitch upon operation thereot from the circuit clesing posit means for locking the said member against movement by the switch and thercb preventing operation of the switch. from the circuit clo position and means respons to the voltage ot the circuit controlled a the switch arranged to ider said loc means ineiiective a time interval afte reduction in the voltage 'he circuit below a 1 t edeterniined value.

9. in electro-resnonsive time element circuit controlling- (lGvlCG comprising a switch based to open position, means tor holding the switch in the closed ition compris' c relatively movable ne nbe" ope ible into t 1 i r; the path of the switch and arranged to be operated therefrom by movement of the switch in accordance with its bias, a toggle connected to said movable member and arranged when extended to hold the member in the. path of the switch and thereby prevent movement ot the switch in accordance with its bias. and means responsiv'e to the. voltage of the circuit controlled by the switch including a movable member biased to trip said toggle a time inter 'al atter a predcter mined reduction in the voltage ot the con trolled circuit to permit said switch to operate in acctn-dance with its bias.

10. A c ectroaesponsive time clement cir end controlling; device comprising a switch biased to move from. the circuit closing position to the circuit opening position, a movable member disposed in the path of said switch and arranged to be ope 'atcd therefrom by movement of the switch in accordance with its bias, toggle-connected to said me nbe r and arranged when extended to hold the member in the path or the switch and thereby prevent movement of the. switch from the circuit closing positioin a movable membcr biased to maintain said toggle unexte nded. electro-res ionsive means connected to be energized rcsponsivelv to the voltage of the circuit controlled by the switch tor moving said biased member to an inactive position when the voltage above a predetermined value and time element means t'or delaying the return movement of said member to trip said toggle upon a reduction in the energizing voltage of the said electrorcsponsive means below said predetern'iined value:

combination., 1. switch biased to an ion between two circuit closin positions latch mecl anisn'i for holding the switch n one of sad circuit closing: positions and preventirc;

for operation of the switch to said one circuit closing position before operation thereot to the other circuit closing position and means responsive to the voltage ot the circuit controlled by the switch in said one crcuit: closingposition for corn trolling said latch mechanism to permit the switch to return to the oil position in accordance wi 1- its bias :1 time interval a her a reduction in the voltage oi the circuit below a predet *rnnned value.

12. combination, a switch biased to an oil position between two circuit closing positions. latch mechanism for holding the switch in one o't said circuit closing positions and for preventing operation of the switch to said one circuit closing position before operation of the switch to the other circuit closing poi on.v a movable member biased to render said latch mechanism inetl'ective to hold the said svitch in said one circuit closinp' position. means responsive to the voltage of the circuit controlled by the switch in said one circuit closing position for movinc said member to an inactive position when the voltage of the. circuit is above a. predetermined value and time. element means 't'or delaying the return movement ot said member to render said latch mechanisn'i incli'ective tor a time interval atter a substantial reduction in voltage of the circuit controlled by the switch in said one position.

18. In a potential starter the combination 0 a pivotall v mounted switch member havin an oil position between a starting and a and for preventing operation of the switch member to the running position before operation thereof to the starting position, a toggle connected to said latch and arranged when extended to hold the latch against movement when the said switch member is in the running position, a movable member normally biased to collapse said toggle, and an QlGCt-lO-HlftflllOt responsive to the voltage of the circuit controlled by the circuit in the running position for moving the said switch member to an inactive position'when the voltage of the circuit is above a predetermined value, and time element means for delaying the return movement of said member to collapse said toggle for a time interval after a substantial reduction in the voltage of the controlled circuit.

In Witness whereof I have hereunto set my hand this 4th day of August, 1925.

GEORGE R TOWNSEND.

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