US2289982A - Switching means - Google Patents

Description

operation takes place.

and 2. 'allel branch circuits, each of which is connected Patented July 14, 1942 James F. Mc'Kenney, Pittsfield, Mass assignor'to General Electric Company, a corporation of New York Application April 19 1941, Serial No.389l382 6 Claims.

This invention relates to switching means and more particularly to improvements in operating mechanisms for contactors included in load ratio control equipment.

'By load ratio control equipment is meant the equipment with which some electric transformers are provided whereby the transformer ratio irzay be changed under load by changing tap connections on at least one of its windings. In certain equipments of this kind arcing contactorsare employed for alternately opening parallel circuits so that the actual tap changing takes place in branch circuits which are not carrying current at the time that the tap changing Normally the transformer current divides substantially equally between the arcing contactors but when one is opened all of the transformer current passes through the other one. It is, therefore, important that both of them should never be open at the same time as this would cause an interruption of the transformer load current. It is also important that the contactors or arcing switches open quickly so as to minimize destructive arcing.

In accordance with this invention there is provided a novel and compact mechanism or linkage for operating the arcing contactors of transformer load ratio control equipment, which is characterized by the use of a single spring for producing snap action of the switches in the opening direction combined with a compound cam arrangement for controlling the entire mechanism.

Although this mechanism has been developed primarily for loadratio control applications, it should be understood it is not necessarily limited thereto and that it may also be used to operate switches in other kinds of circuits.

An object of the invention is to provide a novel and compact automatic operating mechanism for a pair of alternately operated switches.

Another object of the invention is to provide an improved spring drive mechanism for load ratio control arcing contactors.

The invention will be better understood from the following description taken in connection with the accompanying drawing and its scope will be pointed out in the appended claims.

Referring now to the drawing, in which there is shown a perspective view of the essential elements of a preferred embodiment of the invention, the two arcing contactors are shown at I They are connected respectively in parat oneend to' different ratio adjusting or tap changing switches 3 and at the other end to the terminals of a mid-tapped reactor 4 whose electrical midpoint is connected to an external circuit 5 for a transformer winding 6 provided with a plurality of taps 'l'with which the tap changing switches 3 cooperate. The operating mechanism consists of a main link 8 to which force is applied at its center by a compression spring 9 acting through a yoke I0. A pin H passing through the yoke and link serves to connect these elements, and a roller [2 is pivoted on the pin and serves to cooperate with the lobes of a cam l3 for purposes which will be described later. The right hand end of the "spring is restrained by a hollow stop member M through which a rod 55 passes. This rod terminates in an enlargement such as a nut or washer l6 between which and the'stop 14 there is a buffer spring H.

The main link 8 is prevented from moving in the direction of the spring force by means of latches i8 and I9 pivoted respectively on shafts 226 and 2!, In order to reduce friction, rollers 22 and 23 are mounted in the ends of the main link 8 for cooperation respectively with the latches i8 and I9. The contactors I and 2, which are normally closed, are opened by means of secondary links 24 and 25 connected therebetween and the respective ends of the main link 8.

The cam 13 is driven by any suitable operating means, such as an electric motor 26 and it is provided with two lobes 21 and 2B displaced degrees from each other so that the spring 9 will be compressed twice for every revolution of the cam, the roller l2 serving to reduce the friction whenever the compressing action takes place.

For tripping the latches i8 and I9 there is provided an auxiliary cam or cam surface [3 which may be mounted on or otherwise associated with the cam l3. This cam has a single lobe and actuates linkages 29 and 38 connected respectively to the latches l8 and I9.

For locking each latch in its latched-in position when the other latch is tripped, there is provided an additional cam surface or groove 3| terminating at its ends in a pair of surfaces 32 for restoring or resetting each of the latches.

In case spring 9 should break, or fail for any other reason, additional means is provided for insuring positive operation of the contactors at relatively slow speed. This additional means consists of a cam surface 33 provided on an extension on the under side of the yoke H! which is engaged and actuated selectively by a pair of lugs (I); projections 34 on the under side of the cam The operation of the illustrated embodiment of the invention is as follows. If the motor 26 turns the cam l3 in a clockwise direction, the lobe 21 will move from engagement with the roller H. After approximately ninety degrees of clockwise rotation the cam I3 will engage a projection on linkage 29, thereby tripping the latch l8 and causing the link 8 to pivot, under the influence of spring 9, about the pin through roller 23. This pin and the pin through roller 22 are restrained by stationary members 36 in all directions but the direction of the force of spring 9. The secondary link 24 impelled by the lefthand end of main link 3 is pushed rapidly forward and the contactor I is snapped open. The rotative motion of latch i8 is limited by the pin on which roller 22 is pivoted fitting into a slot in latch l8. During this time the corresponding projection on the linkage 33 has been trapped in a groove between the cam l 3 and the restraining cam surface 3! so that accidental tripping of the latch 53 is impossible. Further rotation will cause the lobe 28 to engage the roller I2 and compress the spring 3 and after about 180 degrees of rotation has taken place the right-hand (as viewed in the drawing) restoring cam surface 32, will have engaged the downward projection on the linkage 29 and will have forced it inwardly thereby resetting the latch E3. The parts are now in the positions shown in the drawing except that the cam elements have all been rotated 180 degrees.

Continued rotation of the cam in the same direction will cause the lobe 28 to move away from the roller 52 so that subsequent engagement of the downward projection of the linkage 30 by the cam 53 will trip the latch l9 thereby snapping the switch 2 open in a manner corresponding to the way that the switch I was snapped open. At the same time the linkage 29 is trapped between the cam 83 and the surface 3! so that during this time it is impossible to trip the latch l3. As the rotation of the cam nears a full turn the lobe 21 again compresses the spring 9 and the righthand restoring cam surface 32 resets the latch l9. Continued rotation of the cam in the same direction will repeat the above described cycle of operation. The switches are, of course, closed by the return motion of the links 24 and 25 when the spring 3 is compressed by the action of the lobes 2i and 28 of the cam 53.

Rotation of the motor 23 and the cam means in the opposite or counter-clockwise direction produces the same cycle of operation except that the order of operation of the switches is opposite, the switch 2 snapping open first and then this being followed by the snapping open of the switch l and this cycle will be repeated once every counter-clockwise revolution of the cam,

Strictly speaking, the latches consist of two cooperating pivoted elements, one latch being the member 53 and the roller 22 and the other latch being the member l9 and the roller 23. It will be observed that in each latch the two pivoted members have substantially different radii orv length from their centers of rotation and that they make contact with each other on a common center line. In the tripping of these latches the point of contact with these two members moves off their line of centers as the edge of the vertical portion of the latch l8 or the latch l9, as the case may be, moves sideways by reason of the rotation of their respective cooperating rollers. Contact between the parts ceases when this point of contact has moved ninety degrees from the position shown as measured about the center of rotation of the respective rollers 22 and 23.

If the spring 9 should fail to snap the switches open, they will nevertheless be positively opened by means of the projections 34 engaging the surface 33 which will be pulled forward due to its shape so that although the opening will take place slowly, nevertheless the switches l and. 2 will be positively opened in the proper order so as to prevent injury to the tap changing switches 3 by their attempting to interrupt current.

The tap changing switches 3 may be operated by any suitable drive which will preferably be interlocked by suitable well-known means to the cams so that the switches 3 move from tap to tap in the proper order whenever their serially connected contactors I and 2 are open.

Toward the end of the discharge stroke of the spring 9 the speed is checked by shock absorbers 35 and the motion is finally brought smoothly to rest by means of the bufier spring II. In this manner the initial opening motion of the switches is very rapid but at the same time destructive shocks to the mechanism are avoided.

While there has been shown and described a particular embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications can be made therein without departing from the invention and, therefore, it is aimed in the appended claims to cover all such changes and modifications as fall within the true spirit and scope of the invention.

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

1. In combination, a plurality of switches, a single spring, mechanical operating members for said switches connected to said spring, a separate latch for each switch for holding it closed against an opening force provided by said spring, a continuously rotatable member having a plurality of cam surfaces, means controlled by one of said surfaces for tripping each latch at least once for each revolution of said rotatable means so as to permit each switch to be snapped open by said spring, means controlled by another of said surfaces for placing said spring in a stressed condition before each latch is tripped, and means controlled by another of said cam surfaces for returning each latch to its latched-in position before the next latch is tripped and after said spring has been placed in a stressed condition, said rotatable means being reversible for reversing the order of operation of said switches.

2, In combination, a pair of switches, a control means for controlling said switches including a rotatable cam, a spring for providing the motive power for snapping said switches open, said cam having two 180-degree-displaced lobes for placing said spring under stress twice each revolution, a pair of latches for jointly holding said spring in a stressed condition, means including a tripping cam surface for successively tripping said latches in one order when said cam rotates in one direction and in the opposite order when said cam rotates in the opposite direction, said latches being tripped when said 180-degree-displaced lobes are in position to permit rapid disoperated by the discharge of said spring when one latch is tripped for producing snap operation of one of said switches, and means operated by the discharge of said spring when the other latch is tripped for producing snap operation of the other of said switches, said means acting to restore each switch when said spring is restressed by said cam.

3. In combination, a pair of switches, control means for controlling said switches including a rotatable cam, a spring for providing the motive power for snapping said switches open, said cam having two l80-degree-displaced lobes for placing said spring under stress twice each revolution, a pair of latches for jointly holding said spring in a stressed condition, means including a tripping cam surface for successively tripping said latches in one order when said cam rotates in one direction and in the opposite order when said cam rotates in the opposite direction, said latches being tripped when said lSO-degree-displaced lobes are in position to permit rapid discharge of said spring stress, means including a restoring cam surface for returning each latch to its latched-in position after said spring is stressed by said cam, means including a locking cam surface for preventing tripping of each latch when the other latch is tripped, means operated by the discharge of said spring when one latch is tripped for producing snap operation of one of said switches, means operated by the discharge of said spring when the other latch is tripped for producing snap operation of the other of said switches, said means acting to restore each switch when said spring is restressed by said cam, and means including a positive actuation cam surface for causing the two last-mentioned means to actuate said switches slowly upon failure of said spring.

4. In combination, a pair of switches, a main link, a spring arranged to apply force to the center of said link, separate latches for respectively preventing motion of the ends of said link under the influence of said spring whereby tripping of either latch will cause said link to pivot about the other latch, secondary links for connecting each switch with a different end of said main link so that the tripping of one latch will cause snap action of one switch and the tripping of the other latch will cause snap action of the other switch, and a cam for tripping each latch once each revolution thereof, said cam having a secondary surface for resetting said spring following each discharge thereof resulting from the tripping of a latch, and a tertiary surface associated with said cam for resetting each latch after said spring has been restored and before subsequent tripping of the other latch.

5. In combination, a pair of normally closed switches, a main link, a compression spring arranged to push against the center of said link,

separate latches for respectively normally preventing motion of the ends of said link under the influence of said spring whereby tripping of either latch will cause said link to pivot about the other latch, secondary links for connecting each switch with a different end of said main link so that the tripping of one latch will cause one switch to snap open and the tripping of the other latch will cause the other switch to snap open, and a cam for compressing said spring twice each revolution thereof, said cam being arranged to trip each latch once each revolution thereof, said cam being further arranged to prevent tripping of either latch while the other one is tripped and to reset each latch after it has been tripped and before the subsequent tripping of the other latch.

6. In combination, a pair of normally closed switches, a main link, a compression spring arranged to push against the center of said main link, separate latch means for respectively normally preventing motion of the ends of said main link under the influence of said spring, each of said latch means including two pivoted members of substantial difference in length which normally contact each other on a common center line, rotation of the longer pivoted member in one direction causing the point of contact to move off the line of centers until contact ceases when the point of contact has moved exactly ninety degrees from its original point as measured about the center of rotation of the shorter pivoted member whereby said spring puts in motion said main link in the shortest possible time with the least retarding action from friction, the disconnecting of either of said latch means causing said main link to pivot about the center of rotation of the shorter pivoted member of the other of said latch means, secondary links for connecting each switch with a different end of said main link so that the disconnecting of one latch means will cause one switch to snap open and the disconnecting of the other latch means will cause the other switch to snap open, a blocking cam means for preventing the disconnecting of more than one latch means at one time, a disconnecting cam means cooperative with said blocking cam means for selectively disconnecting each of said blocking means once each revolution thereof, a main cam means cooperative with said blocking cam means and said disconnecting cam means for compressing said spring and returning said main link to its normal position twice each revolution thereof, a resetting cam means cooperative with said blocking cam means for resetting each of said latch means once each revolution thereof, and a positive actuation cam means for causing said main link to move from its normal position twice for each revolution of said disconnecting cam means.

JAMES F. MCKENNEY.

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