US2479315A - Fluid actuated circuit breaker operating mechanism - Google Patents

Description

Aug. 16,1949.

2,479,315 KER SM T. R- COGGESHALL FLUID ACTUATED CIRCUIT BREA OPERATING MECHANI Filed June 12, 1945 Inventor Thellwell R. Coggeshali, by

His Attorney.

Patented Aug. 16, 1949 FLUID ACTUATED CIRCUIT BREAKER OPERATING MECHANISM Thellwell R. Coggeshal l, Bala Cynwyd, Pm, al-

signor to General Electric Company, a corporatlon of New York Application June 12, 1945, Serial No. 599,000 9 Claims. (Cl. 175-294) 1 My invention relates to a fluid actuated operating mechanism for an electric circuit breaker, and more particularly is an improvement on my copending application Serial No. 512,179, filed November 29, 1943, now Patent No. 2,381,336, is-

sued August 7, 1945, and assigned to the same assignee as the present application. I

Fluid actuated operating mechanisms have become quite popular in recent years particularly since the extensive use of the gas blast circuit breaker. As a matter of fact, such fluid actuated operating mechanisms are now being generally used, whether the circuit breakers are of the gas blast type or not, due to numerous advantages thereof. It is essential that such fluid actuated operating mechanisms be trip free so that the means to be actuated, such as the circuit breaker, can be released with respect to the actuating means during the course of the closing stroke and prior to completion thereof. The trend in operating circuit breakers is continually toward higher operating speeds and today a three-cycle breaker is a common thing. Accordingly, it is desirable that an operating mechanism capable of very high speed operation be available for high speed circuit breakers.

It is an object of my. invention, therefore, to provide 'a new and improved high speed fluid actuated operating mechanism for an electric circuit breaker.

It is another object of my invention to provide a new and improved trip-latch arrangement for an operating mechanism of an electric circuit breaker.

Further objects and advantages of my invention will become apparent as the following description proceeds and the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming a part of this specification.

For a better understanding of my invention reference may be had to the accompanying drawing in which the single flgure thereof diagrammatically illustrates an electric switch or circuit breaker embodying the fluid actuated operating mechanism of my invention.

Referring now to the drawing, I have illustrated my invention in connection with an electric switch such as a circuit breaker having a contact structure I, whose operating mechanism generally indicated at 2 is fluid pressure actuated to close the circuit breaker. This circuit breaker is schematically illustrated as a three-pole switch biased to the open position by suitable means, such for example as suitable opening springs not shown. The contact structure I of the circuit breaker is arranged to control an electric circuit comprising conductors I, l and 5. As shown in elevation, the operating mechanism 2 is of the roller toggle type and comprises an operating or output crank i and a pivotally mounted cam lever l. The crank 0 is mounted on a stationary pivot I and is pivotally connected at I to a circuit breaker operating rod ll indicated schematically in part by the dash-dot line II. For actuating the crank i in a clockwise direction to close the circuit breaker comprising the contact structure I, the cam lever I is pivotally mounted on a stationary pivot II and provided at its free end with a cam II. The cam I2 is adapted to engage with a roller I! mounted on the free end of crank t. The cam i2 is so designed that the closing force curve substantially approximates the curve representing the opposing breakerforces that successively increase in magnitude as means such as opening springs (not shown) are compressed, as short circuit stresses are encountered, and as the abutting spring-biased breaker contacts are closed. A predetermined cam contour can be selected that produces quite rapid and exact changes in mechanical advantage which cannot be obtained as satisfactorily by prior art arrangements. Cam lever l is provided with one or more kick-off springs it which serve to urge cam lever 1 initially out from under output crank 6, thereby to minimize opposition to the breaker opening movement and consequently to permit very high speed operation.

The contact structure I of the switch or circuit breaker is restrained in the closed position by one or more prop-type trip latches, such as 15, which engage with suitable rollers such as it, pivotally mounted at H to cam lever 'l. Preferably two rollers Ii are provided, one on either side of cam lever I and consequently two proptypetrip latches I I for engaging these rollers are also provided. In order to further increase the opening speed of the circuit breaker the surface II of the trip latch is adjacent roller i8 is not concentric relative to pivot it about which trip latch I rotates but is made with an offcenter or downhill radius so that the downward force of the roller I5 associated with cam lever I tends to push trip latch I5 to its unlatched position. Consequently, ,as soon as latch I5 is tripped instantaneousv opening movement of the contact structure I of the circuit breaker may occur without the slight'delay that would otherwise attend the brief dwell of the roller I6 if it engaged a concentric latching surface.

In order to. cause the trip latch I5 to reset it is provided with a resetting spring 20 which is effective to reset the latch under-the latch roller I6, but is ineffective to oppose the opening forces of the circuit breaker. The additional force required for holding prop-type latch I5 in its looking position under trip roller I6 is provided by a high speed release magnetic device generally indicated at 2| and described in greater detail hereinafter. Magnetic device 2| includes an,armature 22 supported on a crank 23 rotatable with a shaft 24 upon which prop-type trip latch I5 is also fixedly mounted. When the armature 22 is released, as will be brought out in greater detail hereinafter in connection with the description of the magnetic or'electromagnetic device 2!, the breaker opening forces quickly brush aside the prop-type latch I5 which, together with crank 23, rotates in a counterclockwise direction as viewed in the drawing. The unlatching rotational movement of the trip shaft assembly including shaft 24 and crank 23 is limited and brought to rest by a suitable spring buffer 25 which is engaged by the armature crank arm 23.

If the trip latch I5, with the circuit breaker mechanism in the open position, were permitted to rotate back to its latching position under the pull of its resetting spring 20 the attractive force of the electromagnetic device 2| would again become effective to hold trip latch I5 in its latched position so that the roller I6 in its upward sweep during an ensuing closing operation, wouldhave to rotate the latch I5 forcibly from its magnetically held position. To avoid this difficulty it is desirable to block the trip latch IS in its unlatched position whenever the circuit breaker is in other than its closed position. To this end the cam lever I is provided with a projecting lug or latch guide 26, which together with the periphery of the roller IB, prevents the latch I5 from assuming its latching position except in the extreme upper'position of cam lever I when the operating mechanism assumes its breakerclosed position.

In accordance with my invention the mass of the rotatable latch assembly including trip latch I5 involves appreciable inertia forces so that the resetting spring 29 moves trip latch I5 relatively slowly from its blocked to its'latched position. This resetting delay is an advantage for during a trip-free operation trip latch I5 is not speedy enough to move under the closing roller I6 where it would momentarily impede the otherwise free reversal of the mechanism including cam lever I and output crank 6, under the urge of the breaker forces, such as the opening springs, for example. Consequently, this slow resetting time of trip latch I5 represents a contributing factor by which fast tripping time on trip-free operations is obtained.

For actuating the operating mechanism 2 to close the circuit breaker having contact structure I, I provide fluid pressure actuated means such as a fluid motor 21 comprising a cylinder 28 witht in which is slidably mounted a piston 29 carry- 4 ing a piston rod 30. Piston rod 30 on its upstroke upon the admission of fluid under pressure beneath the piston 29 engages a roller on cam lever I; preferably between rollers I6, thereby to move the lever I clockwise until the parts of the operating mechanism 2 are positioned as shown in the drawing with the circuit breaker in the closed position. After the latch I5 has moved into latching engagement with roller I6 the piston 29 may return to the lower position shown in the drawing.

While any suitable fluid under pressure may be utilized to actuate piston 29 to close the circuit breaker or switch, it is usual to employ air under pressure in a receiver or tank 3| from which the air is supplied to the cylinder 28 through control valve means 32. On the upstroke of the piston 29 suitableenergy storage means, such as the spring 33, is compressed to effect a down, or return stroke, of the piston 29 to the lower position shown. This downstroke operation follows the cutting off of the air supply of the valve 32 through the medium of a dump valve generally indicated at 34.

The control valve 32, fluid motor 21 and dump valve 34 are ver similar to the corresponding parts disclosed in my copending applications, Serial No. 512,179, referred to above, and Serial No. 512,180, filed November 29, 1943 and assigned to the same assignee as the present application. The control valve 32 is illustrated as a pilot differential type employing a pilot valve, which in turn controls the operation of a main valve. For opening the pilot valve there is provided electromagnetic means, generally indicated at 35, comprising an armature 36, a magnetic housing 31, a pole piece comprising the magnetic elements 38, 39 and 40, and a valve opening winding 9i. As illustrated, the electromagnetic'means is of the plunger and solenoid type with the armature 36 directly connected to the pilot valve (not shown). In order to hold the armature 36 in the attracted position the pole piece -magnetic element 39 is of permanent magnetic material, examples of which are well known to the art. The pilot valve is normally maintained in its closed position by means of a spring 42. The electromagnetic means 35 for operating control valve 32, in addition to winding 4| for causing the valve to open, is also provided with windings 4 3 and 45, the energization of either one of which induces a counterflux to neutralize the eifect of winding 4| thereby closing the closing valve 32. The arrangement of the three windings 4|, 44 and 45 is identical with their arrangement in the second of the prior copending applications referred to above.

The dump valve 34 is substantially identical with the arrangement disclosed and claimed inmy copending application, Serial No- 512,180, referred to above. The dump valve difiers from this prior application in that thevalve member 46 for controlling the exhaust port 41 to atmosphere is biased by spring means 48 to the posicut-oil switch 58 is 82 for quick return of piston 28 during a trip-free operation following manualclosing.

The fluid motor 21 also controls two switches,

a cut-oi! switch 88 and a pressure transfer switch 84. The cut-ofl switch 58, which is adapted to bridge contacts 85, is normally biased to the open position and is provided with a pin 58 which extends into cylinder 28 and is engaged by piston 28 as it reaches its uppermost position whereby closed to perform a suitable controlling operation as the piston 28 reaches a position corresponding to the closed position of the associated circuit breaker or switch. The pressure transfer switch 54 is also a normall open switch for controlling contacts 51. Whenever fluid under pressure is supplied to cylinder 28 below piston 28 pressure transfer switch 54 is actuated to close contacts 81. Pressure transfer switch 54 includes a cylinder 58 connected to cylinder 28 and a piston 58 directly connected to switch 54 and biased to the position shown by a suitable spring 88.

For the very fast trip-free tripping time required by high speed circuit breakers spring 88 does not reverse the motion of piston 28 with sufllcient speed, and the mass of the piston might impede the otherwise free reversal of the breaker connected output crank 8 and cam lever 1. Accordingly, I provide another tripping time reducing arrangement comprising a piston return control valve generally indicated at 62. Piston return valve 82 is connected between tank 3| and cylinder 28 above piston 29 by conduits 88 and 84. Piston return valve 62 comprises a valve member 88 normally biased to the closed position shown in the drawing by spring means 88. The valve member 88 is connected to an armature 81 and opening of the valve is controlled by energization of a winding 88 arranged in concentric relationship with respect to armature 81. When piston return valve 82 is in the position indicated the volume above piston 28 of fluid motor 21 is connected to atmosphere through a suitable exhaust port 88. As will be described hereinafter, the control circuit for winding 88 of auxiliary piston return valve 82 is such that only when the associated circuit breaker is closed on a short circuit is winding 88 energized to aid in the high speed reversal of piston 28. As soon as piston return valve 82 is opened, a fully open passageway is provided through which air or gas may flow to the upper end of cylinder 28. On the other hand, the ports 48 of the non-return valve 58 throttle the how of air into cylinder 28 below piston 28. This throttling scheme whereby the closing valve supply is handicapped in favor of the auxiliary piston return valve permits the speed of the closing stroke to be regulated as required, while the slightly increased closing time is not objectionable in view of the faster trip-free opening time that is made possible thereby.

. As was mentioned above, my invention contemplates a delayed trip latch resetting characteristic to insure high speed opening in the event that the circuit breaker is closed on a short 'circult. This delayed resetting of the trip latch necessitates that the upward thrust of the piston plunger 88 must be continued during a switching closed operation at least until the trip latch I8 is safely in its restraining position under the roller I. This requirement is met in accordance with my invention by the provision of an additional cut-off switch III which controls contacts ll. Cut-ofl switch I8 is controlled by an arm I2 mounted to rotate with shaft 24. Latch cut-off switch 18 is moved to the position indicated in the drawing closing contacts 1| when trip latch |l moves to its latching position with respect to roller II. This latch cut-oi! switch 18 prevents closing control valve 82 from closing as will be described in connection with the description of the control circuits, thereby maintaining the piston 28 and plunger 88 in their uppermost position until resetting of trip latch I5 is assured.

The construction of the high speed release electromagnetic device 2|, briefly mentioned above, embodies the same operating principle disclosed in Boehne Patent 2,188,803, granted January 30, 1940, and assigned to the same assignee as the present application. As in the above mentioned'Boehne patent, the holding power of the high speed electromagnetic device 2| is derived from a permanent magnet while its high speed release is eflected by means of a neutralizing flux path that is set up by the energization of a trip -coil. As is shown in the drawing, the electromagnetic device 2| comprises an Alnico magnet core 18 suitably supported by a magnetic frame 14 so as to define a magnetic structure of substantially E-shaped configuration with the Alnico core 13 constituting the center leg of the E. The annular space encircling the core 18 houses an exciting coil 15 which is energized for a short period of time during each breaker operation as will become apparent as the following description proceeds, for providing additional holding force in the magnets. A suitable laminated pole piece 18 is provided which acts as an extension of the center leg of the E-shaped magnetic structure and is spaced from the outer legs of the E-shaped frame by small air gaps 18. A trip coil rounds a portion of the laminated pole piece and the armature 22 is arranged to engage the pole piece 18 as well as the outer legs of the E-shaped magnetic structure. With the armature 22 attracted against the pole piece 18 as indicated in the drawing, the trip coil 11 unenergized, two complementary low reluctance twin magnetic circuits are set up, one through each half of the E-shaped frame as shown by the arrows in the drawing. Energization of the trip coil 11 establishes two counter-neutralizing flux circuits that short circuit the main twin flux paths from the armature by shunting them across the pole piece 16 through the narrow air gaps indicated at 18 in the drawing. The efiect of this is rapidly to neutralize the coercive force of the armature 22 so that the latter parts from the pole piece 18 at high speed due to the bias of the forces applied to trip latch IE to rotate the same in a counterclockwise direction.

The tripping winding the energization of which permits armature 22 to be released, is connected acrossa control source of power through a circuit breaker a switch 18 which normally bridges contacts when the contact structure i of the associated circuit breaker is closed and opens contact 80 when the contact structure of the associated circuit breaker is opened. Tripping winding 11 'of electromagnetic device 2| is energized in response to operation of a protective relay 8| or a tripping control switch 82. The protective relay 8| is illustrated simply as an over current relay connected to be energized from a current transformer 83 in the circuit conductor 3. It will be understood of course that any number of relays may be employed in accordance with the art of circuit protection. Whenever protective relay 8| or control switch 82 are actuated. winding 44 of the electromagnetic device 88 for consurtrolling closing valve 32 is energized and also winding 68 of piston return valve 62, providing that pressure transfer switch 54 has closed its contacts. windings 44 and 68 are connected in parallel with each other and this parallel circuit is connected in series with contacts 51 of pressure transfer switch 54, contacts 89 of a switch 19 and the contacts of either protective relay 8l or control switch 82.

For closing the circuit breaker comprising contact structure I there is provided a closing control circuit for the valve opening winding M of the electromagnetic device 35 associated with closing valve 32. As shown in the drawing, this circuit includes a closing control switch 84, contacts 85 of a minimum pressure switch 85 which opens when the pressure in tank 3| falls below a predetermined value, a conductor 86, contacts 81 of an auxiliary switch 88, open when the circuit breaker is in its latched closed position and actuated to the closed position by lever 12 when trip latch I5 moves to its unlatching position, conductor 89, the contacts 99 of a short time delay circuit opening reiay 9| whose winding 92 is energized upon the closure of the closing control switch 84, and conductor 93 connected through winding 4| to one side of a source of control potential (not shown). The opening of the circuit breaker closing control circuit by the slightly delayed contacts 99 of the relay 9| insures a positive opening of the closing control valve 32 in response to the energization of its winding 4| 8 latched position under the influence or relatively weak resetting spring 29, this action being opposed by the opening spring forces acting on conand also prevents reclosure of the associated circuit breaker as long as the control switch 84 is kept closed. In other words, witha single closure of the control switch 84 only one closure of the associated switch or circuit breaker comprising contact structure I can be effected.

The contacts 55 of the circuit breaker cutoff 53 control the energization of magnetizing winding 15 of high speed release electromagnetic device 2| and also through contacts II of latch cut-- oil switch I9 control the energization of winding 45 of the electromagnetic device associated with closing control valve 32. In other words, whenever piston 29 reaches the end of its closing stroke near the top of cylinder 28 to engage pin 56 and close switch 55, winding I5 of electromagnetic device 2I is energized to provide additional holding force, and as soon as latch cut-off switch 10 indicates that trip latch I5 is in the latched position winding 45 associated with the closing valve 32 is energized to cause valve 32 to close and permit piston 29 to return to the position indicated in the drawing.

In view of the detailed description included above, the operation of the arrangement embodying my invention will be more or less obvious to those skilled in the art. With the circuit breaker or switch comprising contact structure I in the closed position shown an opening operation may be initiated, either by a fault on the system causing operation of overcurrent relay 8I or by the operation of manual opening switch 82. In either case the tripping winding 11 of electromagnetic device 2| is energized to cause armature 22 to be released whereupon the forces due to the breaker opening springs (not shown) cause output crank 6 and cam lever l to rotate unimpeded and push trip latch I5 out of the way. As the trip latch l5 moves out of its latching position, latch cutoff switch I9 is opened while contacts 81 are bridged by switch 88 to complete the closing control circuit. The projecting lug or latch guide 29 prevents trip latch I5 from returning to its tact structure I of the associated circuit breaker. When the circuit breaker is in the open position closing of contact structure I can be accomplished by actuating manual closing switch 84 whereupon opening winding 4| of closing valve 32 is energized through the contacts 98 of the anti-pump relay 9I which opens contacts 90 with a sufficient delay to insure full opening of control valve 32. The opening of closing control valve 32 causes piston 29 to move upwardly to actuate the operating mechanism 2 to close the associated circuit breaker or switch comprising contact structure I. When the piston 29 reaches the almost closed position of the associated circuit breaker piston 29 strikes the pin 56 of cutoff switch 53 to set up the energization circuit for valve closing winding 45 as soon as cutoff switch 19 has bridgedcontacts I I. When cutofi switch 18 closes contacts ll thus assuring that trip latch- I5 has latched the associated breaker in the closed position winding 45 is energized and closing valve 32 'is closed so that piston 29 may return to the lower position indicated in the drawing. The closing of cutofl switch 53 also completes the circuit through exciting winding 15 of high speed release electromagnetic device 2| thereby augmenting the coercive power of the permanent magnet 13 to hold armature 22 in its impact against pole piece 16. It also of course imparts a brief remagnetizafer switch 54 bridges contacts 51 whereupon' winding 44 of closing valve 32 is energized and also winding 68 of piston return valve 52 is energized. Under these conditions closing valve 32 is quickly moved to its closed position and by virtue of the fluid under pressure provided above piston 29 through opening of piston return valve 62, much higher speed of reversal of piston 29 occurs thereby permitting a higher speed of operation than was possible with prior art arrangements.

While I have described what I at present consider the preferred embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made without departing from my invention, and I therefore aim in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of my invention.

What I claim as new anddesire to secure by Letters Patent of the United States is:

1 In combination with an electric switch, an actuating device, an operating mechanism including a cam lever interrelating said switch and said actuating device, means for operating said actuating device to close said switch, latching means for holding said switch in the closed position, magnetic means for holding said latching means in latching position, a trip coil on said magnetic means, means for energizing said trip coil to render said magnetic means ineffective to hold said latching means in latching position -whereby high speed release of said latching means and opening of said electric switch can occur, and means including a latch guide mounted on said cam lever and movable therewith for engaging said latching means to hold said latching means out of latching position when said switch is open.

2. In combination with an electric switch, a

fluid motor including a piston and a cylinder,

an operating mechanism interrelating said switch and said piston, said piston being normally out of engagement with said mechanism, means'for supplying fluid under pressure to act on one side of said piston to move said piston from an initial position to close said switch, latching means for holding said switch in the closed position after said piston has moved it to the closed position, meansfor returning said piston to said initial position while said switch remains closed, and means for supplying fluid under pressure to the other side of said piston under predetermined conditions to supplement saidlast mentioned means and cause high speed return of said piston to its initial position.

3. In combination with an electric switch, a fluid motor including a piston and a cylinder, an operating mechanism interrelating said switch and said piston, said piston being normally out of engagement with said mechanism, means for supplying fluid under pressure to act on one side of said piston to move said piston from an initial position to close said switch, latching means for holding said switch in the closed position after said piston has moved it to the closed position,

spring means for returning said piston to said initial position while said switch remains closed,

and means for supplying fluid under pressure to 'the other side of said piston only when said switch is closed during a fault condition on the circuit controlled by said switch to supplement said spring means and cause high speed return of said piston to its initial position.

4. In combination with an electric switch, a

fluid motor including a piston and a cylinder, an

operating mechanism interrelating said switch and said piston, means for supplying fluid under pressure to act on one side of said piston to move said piston from an initial position to close said switch, latching means for holding said switch in the closed position after said piston has moved it to the closed position, means for opening said switch, means for returnin said piston to said initial position, valve means for supplying fluid under pressure to the other side of said piston, and valve control means responsive to the presence of fluid under pressure acting on said one side of said piston during a closing operation of said fluid motor for opening said valve means to cause said piston to be returned to its initial position at high speed, said valve control means being operable only after actuation of said means for opening said switch.

5. In combination with an electric switch, a fluid motor including a piston and a cylinder, an operating mechanism interrelating said switch and said piston, means including a source of fluid under pressure for supplying fluid under pressure to act on one side of said piston to move said piston from an initial position to close said switch, latching means for holding said switch in the closed position after said piston has moved it to the closed position, means for opening said switch, spring means for returning said piston to said initial position, valve means for supplying fluid under pressure to the other side of said piston, and means responsive to the presence oi fluid under pressure acting on said one side of said piston during a closing operation and operable upon activation of said means for opening said switch, for opening said valve means to supply fluid under pressure to the other side of said piston and for simultaneously interrupting the flow of fluid from said source of fluid to said one side of said piston to cause said piston to return to its initial position at high speed.

6. In combination with an electric switch, a fluid motor, an operating mechanism including pivotally mounted cam means interrelating said switch and said fluid motor, means for operating said fluid motor to close said switch, latching means for holding said switch in the closed position, magnetic means for holding said latching means in latching position, a trip coil on said magnetic means, means for energizing said trip coil to render said magnetic means ineffective to hold said latching means in latching position, means for causing resetting of said latching means, and guide means mounted on said cam means and engaging said latching means for preventing resetting of said latching means while said switch is in other than its closed or substantially closed position.

7. In combination with an electric switch, a fluid motor including a piston and a cylinder an operating mechanism interrelating said switch and said piston, means for supplying fluid under pressure to act on one side of said piston to, move said piston from an initial position to close said switch, latching means for holding said switch in the closed position after said piston has moved it to the closed position, means for returning said piston to said initial position, and means responsive to an abnormal condition existing on the circuit controlled by said switch concurrently with the closing of said switch for supplying fluid under pressure to the other side of said piston to supplement said last mentioned means and cause high speed return of said piston to its initial position.

8. In combination with a biased .open electric switch, a fluid motor, an operating mechanism including a cam lever for interrelating said switch and said fluid motor, a roller on said cam lever engageable by said fluid motor, means for operating said fluid motor to close said switch, cam means on said cam lever for causing the closing force applied by said fluid motor tosaid switch during a switch closing operation to increase in magnitude substantially in accordance with the increase in the forces opposing the closing of said switch, latching means cooperating with said roller for holding said switch in the closed position, means for tripping said latching means to cause opening of said switch, and a latch guide on said cam lever for preventing said latching means from occupying its latching position when said switch is open.

9. In combination with a biased open electric switch, an actuating device, an operating mechanism for interrelating said switch and said actuating device comprising a pivotally mounted lever connected to said switch at one end of said lever, a roller mounted on the other end of said lever, an independent cam lever pivotally mounted at one end, roller means and a cam mounted on the other end of said cam lever, said roller on said first mentioned lever being engageable by said cam on said cam lever during closing of said switch to cause the closing force applied by said actuating device to said switch to increase in magnitude substantially in accordance with the increase in the forces opposing UNITED STATES PATENTS closing of said switch, and latching means fo Number Name Date engaging said roller means to hold said switch 7 64 Hall Jan. 24, 1905 in the closed position, said roller means being en- 5 2,1 3,982 Mercier June 27, 1939 gageable by said actuating device to impart 2, 03 Boehne Jan. 30, 1940 switch closing movement to said mechanism. ,2 ,023 Strang June 9, 1942 THEILWELL R. COGGESHALL. ,2 2, 95 Thumin Aug. 4 1942 2,378,270 Westervelt June 12, 1945 REFERENCES CITED 10 2,383,288 Boden et a1. Aug. 21, 1945 The following references are of record in the 2393982 I Hm July 1946 I me 01 this patent:

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