US2471815A - Electric switch - Google Patents

Description

J. A. FAVRE ELECTRIC swr'rcn May 31, 1949.

2 Sheets-Sheet 1 Original Fild Sept. 25, 1944 Inventor:

John A. F'avT-e,

His Attorneg.

May 31, 1949. J, A. FAVRE 2,471,815

ELECTRIC SWITCH Original Fild Sept. 25, 1944 2 Sheets-Sheet 2 Fig.2.

Inventor; John A. Pavre,

His Attorney.

F med May 31, 1949 ELECTRIC SWITCH John A. Favre, Drexel Hill, Pa... asslgnor to General Electric Company, a corporation of New York 7 Original application September 25, 1944, Serial No.

555,630. Divided and this application January 3, 1946. Serial No. 638

Claims. (Cl. 200-153) My invention relates to improvementsin electric switches and more particularly to improvements in automatic circuit breakers which are opened in response to abnormal circuit conditions, and an object of my invention is to reduce the time of the opening operation.

This application is a division of my application Serial No. 555,630,.filed September 25, 1944, and assigned to the same assignee as this invention. My invention will be better understood from the following description when considered in connection with the accompanying two sheets of drawings, and its scope will be pointed out in the appended claims. Q i

In the accompanying two sheets of drawings, Fig. 1 is a partially exploded view in perspective of a polyphase circuit breaker embodying my invention; Figs. 2 through 6 are fragmentary views showing the circuitbreaker operating mechanism in different positions, Figs. 5 and 6 being diagrammatic; and Fig. 7 is a detail illustrating an embodiment of my invention.

For the purpose of illustrating my invention, I have shown an embodiment thereof as applied to an automatic trip-free circuit breaker for three-phase circuits. As shown in Fig. 1, the circut breaker comprises three pivoted switch arms I, 2 and 3, arranged to be connected in the separate legs of a three-phase circuit, and an operating mechanism by means of which the contact arms'are moved between their open and closed circuit positions by a handle 4 (Fig. 4) mounted on a pivoted arm 5. This operating mechanism is associated with the middle contact arm 2, the two outer contact arms being operated through a common rotatably mounted cross bar 6.

The operating mechanism may be more clearly understood by firstreferring to the diagrammatic Figures 5 and 6, showing the contact arm 2 respectively in its closed and open circuit positions. The contact arm 2 is mounted on a stationary pivot 'l and is operated by means of a multiple link toggle consisting of links 8 and 9 having a floating pivot ill. The link 8 is relatively long and has its outer end mounted on the bar li which is in 'eifect a stationary pivot, while the relatively short link 9 has its outer end pivotally connected at I2 to the contact arm 2. Thus, by moving the toggle between its made position (shown in Fig. 5) and its collapsed or broken position (shown in Fig. 6), the contact arm is moved between its two positions.

A second multiple link toggle is provided for operating the first toggle 8, 9. This toggle consists of links I 3 and I4 having a floating pivot IS. The relatively short link l3 has its outer end connected to the pivot l0 while the relatively long link M has its outer end pivotally connected at Hi to anoperating arm ll whose other or left hand end is pivotally mounted at l8 on a pivoted trip member I9, the pivot 18 being intermediate the length of the trip member l9. The upper end of the trip member I9 is mounted on a stationary pivot 20 while its lower end is normally held by a current responsive latch projection 2!.

By means of a helical tension spring 22 having its left hand end connected to the pivot l5 and its upper end connected to a stationary support 23, the various linkages are caused to assume the positions shown in Figs. 5 and 6 and are caused to move between these positions when the handle 4 is moved between the positions shown in Figs. 5 and 6. The handle 4 is mounted on the right hand end of the operating lever or arm 5 which is mounted on a stationary pivot 26 and connected by a link 21 to the operating arm I1, the ends of the link 21 being pivotally connected to the lever 5 and the arm l1.

In the operation of the mechanism, it will be observed that with the switch closed, as shown in Fig. 5, the spring 22 which pulls the pivot l5 toward the point of support 23 applies a force tending to straighten the toggle I 3, l4 whereby an upward force is applied to the floating pivot l0 of the first toggle 8, 9 thereby to secure this toggle in its straightened position with the switch closed. This final position of the toggle 8, 9 is preferably not quite a fully made or straightened position whereby the rapid movement of the contact arm to its open circuit position on overload is facilitated. This underset position of the toggle 8, 9 is defined by the left hand end of the stop 28, as seen in Fig. 5, secured to the link 8 with which engages a projection 29 on the link l3. With the two outside contact arms I and 3 (Fig. 1) the links 9 are extended and engage the stops 28. The substantially made position of the toggle I3, I4 is a further assurance against breaking of the toggle 8, 9 in response to a severe shock. In this position it will be noted that the handle 4 and the operating lever 5 are in their extreme upper or counterclockwise positions whereby the operating arm I! is moved to an extreme clockwise position about the pivot I8 and is held in that position through the link 21 by the lever 5, whereby the pivot I6 is fixed in the position shown.

In order to move the switch from the closed position of Fig. 5 to the open position of Fig. 6, the operating handle 4 is moved through a rela- 3 tively small angle in a clockwise direction about the pivot 26 whereby the operating arm I1 is moved about its pivot IS in a counterclockwise direction to bring its end to the upper side of the direction of the force applied by the spring 22. When the end of the arm moves to the upper side of the spring 22, the direction of the force applied by the spring to the link I4 is reversed, the spring then tending to move-the link l4 in a counterclockwise direction about the pivot H; on the end of the arm This counterclockwise movement of the link |4 immediately breaks or collapses the toggle l3, l4, which in turn breaks the toggle 8, 9 whereby the contact arm 2 is movedclockwise by the spring and finally comes to rest against the end of the stop arm 28 secured to the arm 8. It will be understood that this movement of the operating linkages and the switch arm takes place very quickly with a snap action. It begins as soon as the pivot l6 of the floating link l4 moves to the upper side of the direction of force of the spring 22.

The positions of the parts when the switch is opened in response to an overload or overcurrent will be understood from Figs. 2 and 3. It will be:

observed that the spring 22, when the switch is in. its closed circuit position of Fig. 5, applies a force to the operating lever II, which force is transmitted to the trip arm l9, tending to move the lower end of the trip arm toward the right hand. When the latch 2| is moved in response to overload or short circuit to release the trip arm, this lower end moves counterclockwise about the pivot 20 in response to the force applied by the spring. At the time the projection 29 on the link l3 is in engagement with the link 8 and as a result the two links 8 and I3 swing together about the pivotal axis of the bar 6 whereby the switch arm is moved to its open circuit position, the other parts including the arm I! and the link 21 moving to the positions shown in Fig. 3.

For purposes of illustration, Fig. 2 shows the manual operating lever 5 as held in its fully closed circuit position during overcurrent opening, although the handle will move from that position to the position of Fig. 3 if it is not held. In this position the handle lever 5 holds the arm l1 in such position that the projection 29 has disengaged the left hand end of the stop 28 (Fig. 2). In the movement from Fig. 2 to Fig. 3, when the handle is released, the link I3 turns through a slight additional angle counterclockwise about its pivot I until the projection 23 (Fig.3) on the link |3 comes to rest against the lower end of the stop 28. In this final movement, the arm I1 is moved through a small angle counterclockwise about its pivot I8 (Fig. 2) and through the link 21 moves the lever through a small angle in a clockwise direction to an intermediate position (shown in Fig. 3) betweenthe closed and open positions. This intermediate position gives an indication to the operator, upon inspection of the position of the handle 4, that the circuit breaker has opened in response to an overload or short circuit. The trip arm I9 is brought to rest by the engagement of a laterally extending projection 30 on its upper end with an edge of the supporting frame 3| for the mechanism.

The mechanism is reset from Fig. 3 by moving the handle 4 downward from the position shown in Fig. 3 to the fully open position shown in Fig. 4.

. During this movement a roller or projection 32 jection 33 on the trip ar l3 whereby the trip arm is moved clockwise bout its pivot back 4 by the latch 2|. It is assumed that the current .responsive means has cooled sufllciently to return the latch 2| to a holding position. The parts are then in the normal open circuit 'position shown in Figs. 4 and 6. The circuit breaker may thereafter be closed by moving the handle upward to the closed circuit position.

The arrangement of the'operating linkages and other parts is shown in further detail in Fig. 1. The operating mechanism, as previously stated, is associated with the middle contact arm 2. The supporting frame 3| is a substantially U-shaped member having its base secured to an insulating support, not shown, for the circuit breaker and with two parallel arms extending outward from the support and terminating in two parallel projections 35 and 35 (Fig. 1). These projections are offset toward each other at the points 31 and 33 to provide space for the links l4 and I1. It should be noted that actually the link l4, for purposes of additional strength, consists of two duplicate parallel links Ma and MD (Figs. 2 and 4) which are connected rigidly together by means of a cross member 39. Also, certain other links are provided in duplicate, as will now be pointed out. The operating lever 5 is constructed with duplicate parallel arms 5a and 5b joined together by a cross member at their right-hand ends, to which the handle 4 is secured.

These two parallel levers 5a and 5b (Fig. 1) are located on opposite sides of the two arms of the support 3|, each being provided with its own pivot 26, only one of which is shown, on opposite sides of the support 3|, and the pivots being in alignment with each other. The two levers are spaced apart between the handle and the pivots 26 a somewhat greater distance than the width of the support 3| to provide space for the duplicate links H and I! on each side of the projections 35, 36. At its lower end each lever is bent toward the support 2| at the point 40 so that its lower end is in loose sliding relation with the adjacent sides of the support 3|.

Likewise, the trip arm I9 is formed in two parallel identical lengths positioned on opposite sides of the support 3| and connected together at their lower ends by a cross member to which is secured a latching projection 4| engaging the latch 2|. Each parallel length of the trip arm l9 has its own pivot 20 (Fig. 1) on the frame 3|, a washer 42 being provided between the trip arm and the support so as to space the two apart a distance providing for movement of theleft-hand end of the operating lever 5 between them.

The two parallel rigidly connected portions Ma and MD of the link l4 are connected at their right-hand ends to duplicate links H pivoted respectively on the two sides of the trip arm I9.

The left-hand ends of the duplicate links I40, and MD are joined together by a pin constituting the pivot l5, and this pin in turn is connected .through a single link l3 (Figs. 2 and 4) to the floating pivot in.

It will be noted that the togglelinks 8, 9 (Fig. 1) are each formed in two parallel portions which extend between the two sides of the support 3|, and likewise the contact arms are each formed in two parallel portions or arms mounted between the sides of the support 3| and provided with a separate movable contact 43 and 44. Also, the links 21 are provided in duplicate to connect the two portions of the operating lever 5 to the duplicate links H. Likewise, the spring 22 is provided in duplicate parallel lengths having their right-hand ends connected to the cross pin 23 (Fig. 1) secured to the outer ends of the these springs are connected to the floating pivot l5.

As shown in Fig. 1, a metal support 46 is provided for the current responsive tripping mechanism which controls the trip lever i9. An arm 41 mounted on this support on apivot 48 i provided with a projection 49 and also'with the projection 2| (Figs. 2-6) with both of which normally the projection 4| on the trip arm I9 engages so that the trip arm is held. The righthand end of the arm 41 has a downwardly pro jecting extension 58 which is adapted to move downward through a notch 5| in a rotatable latch member mounted on a trip shaft 52 when the cross shaft and latch memberare turned in response to an overcurrent to bring the notch 5| in registering relation with the projection 50. Normally, the shaft 52 is turned in a clockwise direction slightly beyond the registering position so that the left-hand edge of the projection 50 engages the bottom wall of the notch whereby the arm 41 is held in a latching position.

As shown, the trip shaft 52 extends across the three poles or switch arms I, 2 and 3. Thermal current responsive means 53 is provided in circuit with each switch arm for rotatin the shaft 52 through thesmall angle necessary to trip the circuit breaker when the current in any one or more of the poles exceeds a predetermined minimum value. sive trip mechanisms are identical in construction and interchangeable. Accordingly only the trip mechanism associated with the switch i will be described in'detail.

The thermal current responsive device 53 comprises two concentric electric resistance heater tubes made of a metal having suitabl electric resistance heating characteristics and heating a thermal expansion rod 54 (Fig. 1) extending through the inner tube and made of a suitable material having a high temperature coeflicient of expansion. The two concentric tubes have their right-hand ends mechanically and electrically connected together and their left-hand ends mechanically and electrically connected respectively to an electric terminal member 55 and a supporting conductor member 56, the outer tube being connected to the terminal member 55. Thus current flows between the two members 55 and 56 through the two tubes in series with each other whereby the rod 45 is heated in response to the current, and its right-hand end moves in accordance with'changes in its length. If desired the rod 54 can be heated by current passing directly through it.

The conductor member 56 also forms a support for two magnet pole members 51 and 58 (Fig. 1) made of magnet iron, the left-hand ends of which (not shown) extend laterally into two coil turns 59 electrically connected with the member 56. The magnet members 51 and 58 are additionally supported by a supporting plate 6| made of non-magnetic material such as copper or brass. The plate BI and the magnet members are secured to the conductor member 56 by means of screws 62 and 63, while screws 64 and additionally secure the plate 5| to the magnet members.

By means of layers of suitable fibrous electrically insulating material 88, 61 and 68, the magnet members 51 and 58' are electrically insulated from the members 5| and 6| and from the turns 59. Also, the lateral extensions (not shown) on the magnet members which extend into the turns 59 are suitably insulated from the These three temperature respon: v

arm'

turns by layers of electrically insulating material (not shown). The right-hand ends of the magnetic members 5! and 58 form pole pieces 01' a magnet whose magnetic strength depends upon the current in the turns 59. Associated with the pole pieces is a pivoted armature 89 balanced about its pivot support "I0 so as to be free from the effect of shocks. This armature carries an arm I I which extends to a position adjacent an operating arm 12 on the trip shaft 52. An adjustment screw 18 is provided on the end of the arm II which engages with the arm '12 when the armature is attracted and turned clockwise as seen in Fig. 1 by the magnet poles in response to a current greater than a predetermined value whereby the shaft 52 is turned in a counterclockwise direction and tract the armature 69, i. e., currents of overload magnitude, and the device 53 is heated by these currents to operate in inverse time relation with these currents.

The right-hand end of the rod 54 operates an arm 14 mounted on a pivot and the upper end of this arm carries an adjustment screw 16 cooperating with a second operating arm 11 secured breaker.

to the trip shaft 53. Thus, in response to excessive currents, the end of the rod 54 moves toward the right hand thereby turning the arm 14 in a counterclockwise direction and turning the trip shaft 52 counterclockwise to trip the circuit A relatively strong helical spring 18 is provided for the arm I4, this spring surrounding the pivot pin 15 and having one end fixed and its other end 19 engaging the arm 14 and applying a counterclockwise bias to the arm. The spring 18 thus takes up all looseness in the parts and, by biasing the arm 14 in a tripping direction, assures that the arm 14 cannot be moved in a tripping direction by severe shocks.

A helical tension spring is provided for biasing the armature G9 to its unattracted position, this armature being substantially free from shocks because of its balanced construction about its pivot. A helical tension biasing spring 8| is also provided for the shaft 52 whereby the shaft is biased in a clockwise direction to its latching position with the arm 11 against the arm 14. The operating arms 12 and i1 are made of electrically insulating material, preferably a molded electrically insulating material, firmly secured to the metal shaft 52 whereby the current responsive trip mechanism is electrically insulated. from the shaft.

The terminals 55 and 60 not only provide for the connection by suitable leads, not shown, of the current responsive mechanism in circuit with the switch arm I, but also provide means for securing the mechanism to a suitable insulating support, not shown.

plate and also to the ends of flexible electric 7 conductors-86. The opposite ends of the conductors 88 are suitably secured at 81 to the terminal member 84. These various connections may be made by welding or preferably by brazing. The terminal 84 is formed tofit the flexible members 86 up to the point 88 where it is bent away from the flexible members to form a fulcrum point about which the members 88 bend upon engagement of the movable contacts with the stationary contacts.

Pressure is applied to the stationary contacts by means of a helical compression spring 88 just below the flexible members 88 and positioned midway of the length and midway between the stationary contacts. This spring extends into a suitable cavity provided in the insulating support, not shown. Movement of the stationary contacts by the spring 89 is limited by a headed pin 90 extending through holes in the members 85 and 86 and secured to the end of the ter- 88 while at the same tim the two stationary contacts are free to twist a sufficient amount to equalize the contact pressures between the two pairs of contacts. The steel plate '85 is provided between the stationary contacts and the flexible conductors 88 for the purpose of magnetically shielding the conductors. Two thin sheets 9| of electrically insulating material, such as horn fibre, are provided over the iron member 85 to prevent the are from striking to the iron member when th switch is opened.

In accordance with my invention, I provide means for reducing the time of the opening operation of the circuit breaker. As shown, this means for speeding up the opening of the-circuit breaker in response to an excessive current, comprises special loose bearings for mounting the square operating shaft 6 in the supporting framework 3l, two'of such bearings 92 and 93 being shown in Fig. 1. As shown more clearly in Fig. '1, each bearing comprises a bushing or sleeve 9|! having an irregularly shaped aperture or bore through which the shaft 6 extends, these sleeves being in turn journaled in the framework 3| for the required amount of rotation. The aperture in the sleeve is provided with a raised portion or cuit controlling members I, 2' and 8 are in their closed circuit positions, while the adjacent sides. 96 and 91 of the aperture are slightly diverging" thereby to allow for a slight amount of rocking movement of the shaft on the hump 95 independently of the sleeve 94. This freedom of rolling movement of the shaft on the hump 95 :is preferably 10 or 15 degrees. This construction permits a limited initially free angular or rocking movement of the shaft 6 whereby to expedite the buckling or collapse of the toggle 8, 9 and also has the effect of eliminating. during this preliminary movement, the static friction of the bushings 94 in their bearings, whereby greater initial freedom of turning of the shaft is provided. Moreover, the shaft is moving when it engages the side of each of the bushings, and consequently more easily overcomes the static friction of the bushing.

Whilev I have shown a particular embodiment of my invention, it.will be understood, of course,

that I do not wish to be limited thereto since many modifications may be made, and I therefore contemplate by the appended claims to cover any such modifications as fall within the true spirit and scopeof my invention.

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

1. In combination with a switch operating mechanism having an extended toggle for holding the switch closed and means for collapsing the toggle to open the switch, a flat-sided pivot shaft fixedly secured to one end of the toggle to take the holding thrust thereof, and bearin means for said fiat-sided pivot shaft including a .rotatably mounted bushing provided with an irregularly shaped bore through which said shaft extends loosely and having an inward projection-on which said flat-sided shaft pivots during the initial part of the collapsing movement of said toggle to accelerate the opening of the switch.

2. In combination with a multipole switch operating mechanism having a plurality of extended toggles, each for holding a corresponding pole of the switch closed, and separate means for collapsing one of the toggles to open the switch, a flat-sided pivot shaft fixedly secured to one end of. each toggle to take the holding thrust thereof and effect simultaneous extension and collapse of the toggles, and bearing means for said flat-sided pivot shaft including a pair of spaced-apart rotatably mounted bushings, each provided with an irregularly shaped bore through which said shaft extends loosely and having an inward projection on which said flat-sided shaft pivots during the initial part of the collapsing movement of said toggles to accelerate the opening of the switch.

3. An automatic trip-free circuitbreaker comprising a movable circuit controlling member biased to an open circuit position, a shaft having a flat side, toggle means interconnecting said circuit controlling member and said shaft, means for operating said toggle means to move said circuit controlling member between open and closed circuit positions, releasable means for holding said toggle in a thrust transmitting condition whereby to maintain said circuit controlling member in the closed circuit position, a support for said shaft, a bearing for said shaft comprising a bushing rotatably mounted in said support and provided with an irregularly shaped bore through which said shaft extends loosely, and means operative for initially expediting the collapse of said toggle upon the release of said holding means comprising a pivotal projection on the wall of said bore opposing the flat side of said shaft, the thrust of said toggle being exerted against said projection when the switch is in the closed circuit position whereby the shaft first turns through a small angle independently of said bushing during the initial opening movement of said circuit controlling member.

4. An automatic trip-free circuit breaker comprising a movable circuit controlling member biased to the open circuit position, a shaft having a flat surface near each end, operating means comprising a toggleinterconnecting said circuit controlling member and said shaft for moving the circuit controlling member between open and closed circuit positions, releasable .means for holding said toggle in a thrust transmitting condition and a bearing for said shaft near each end thereof, each of said bearings comprising a rotatably mounted bushing provided with an opening through which the shaft extends loosely and a projection onfthe interior surface of said bushing against which the flat surface of the respective end of the shaft abuts to transmit the thrust of said toggle; while the circuit controlling member is in the closed circuit posi tion and on which the flat surface of the respective end of the shaft rocks through a relatively small angle during the initial portion of the circuit opening movement of the circuit controlling member whereby to expedite the collapse of said toggle upon the release of said holding means.

5. An automatic trip-free circuit breaker comprising a movable circuit controlling member biased to one circuit controlling position, a shaft having a flat surface near one end thereof, operating means comprising a toggle interconnecting said circuit controlling member and said shaft for moving the circuit controlling member between said one circuit controlling position and another circuit controlling position, releasable REFERENCES CITED The following references are of record in the file of this patent:

means for holding said circuit controlling memher in one of said circuit controlling positions, and a bearing forsaid shaft near said one end thereof comprising a rotatably mounted element provided with an opening through which said one end of the shaft extends loosely and a pro- UNITED STATES PATENTS Number Name Date 1,261,677 Atwood Apr. 2, 1918 1,626,528 Gregory Apr. 26, 1927 1,689,421 Burnham Oct. 30, 1928 1,770,953 Steinmayer July 22, 1930 1,831,187 Mohr Nov. 10, 1931 1,918,248 Cook July 18, 1933 2,224,848 Cole et al Dec. 17, 1940 2.338.725 Larson Jan. 11, 1944

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