US2277425A

US2277425A - Switch

Info

Publication number: US2277425A
Application number: US380492A
Authority: US
Inventors: Horace G Wiest
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1941-02-25
Filing date: 1941-02-25
Publication date: 1942-03-24
Anticipated expiration: 1959-03-24
Also published as: GB554086A; FR938649A

Description

/ H. G. WIEST SWITCH March 24, 1942.

Filed Feb. 25, 1941 Flgl.

Inventor: Horace G.

ih's Attornes.

Wiest,

Patented Mar. 24, 1942 SWITCH.

Horace G. Wiest, Nahant, Mass, assignor to General Electric Company, a corporation of New York Application February 25, 1941, Serial No. 380,492

6 Claims. (Cl. 200-164) My invention relates to switches, and although not limited thereto, it has application in dynamo electric machines for controlling the circuits of starting windings in single phase induction motors, repulsion induction motors, or other electrical devices in which it is desired to control the circuits thereof, in accordance with the speed of rotation of the machine or device.

An object of my invention is to provide an improved switch structure which is simple in design, reliable in operation, and easy to manufacture.

Another object of my invention is to provide an improved switch construction in which the desired movement between the contacts may be obtained with minimum movement of the operating mechanism. I

A further object of my invention is to provide an improved switch structure in which a sufficient contact pressure will be obtained with a minimum pressure being exerted by the operating mechanism.

. Further objects and advantages of my invention will become apparent from the following description. referring to the accompanying drawing, 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.

In the drawing, Fig. l is a partial sectional side elevation of a dynamo-electric machine which is provided with a switch construction embodying my invention; Figs. 2, 3 and 4 illustrate the switch construction employed in Fig. 1 during three stages of operation, Fig. 4 in addition illustrating a modification of the structure shown in Fig. 1; Fig. 5 is an exploded perspective view of the parts of the switch structure illustrated in Fig. 1, and Fig. 6 illustrates another modification of the switch shown in Fig. 1.

In the drawing, I have illustrated my improved switch structure in its applicationwith a centrifugal switch mechanism for disconnecting the starting winding of a capacitor motor. However, it is to be understood that my switch construction may be employed wherever it is desired to open or close the circuit in response to movement of a suitable operating mechanism. The illustrated structure includes a base member, an actuating arm adapted to be pivotally mounted on the base member, and a contact finger adapted to overlie the actuating arm and be pivotally mounted thereon. The contact finger carries a movable contact and the base or support carries a contact in alignment therewith, so that upon movement of the actuating arm, relative -movement will be efiected between the contacts. As in the conventional centrifugal switch structure whichis employed in the starting winding of a dynamo-electric machine, the switch contacts are closed when the motor is stationary and will open when the motor attains any suitable critical speed. Thus, the contacts are held in a closed position through the pressure exerted on the actuating arm by the push collar of a centrifugal mechanism which is mounted on the rotatable part of the dynamo-electric machine, and when the machine attains the critical speed, the push collar will be movedaway from the actuating arm and allow the contacts to break the circuit of the starting winding circuit.'

Referring more particularly to Fig. l of the drawing, I have illustrated a dynamo-electric machine the stationary structure of which includes a frame member l0 and end shields H and I2. The frame member supports laminations it having suitable slots to receive running windings l4 and starting windings l5. Adapted to rotate in suitable bearing structures carried by the end shields ll and i2, is a rotatable member indicated generally by the numeral 16 which cooperates electrodynamically with the-stationary exciting'structure. Upon the end shield ll there is mounted my improved stationary switch structure indicated generally by the numeral 11, by bolts I 8. Operating mechanism [9 for the switch structure I! is mounted on a shaft 20 of the rotatable member l6, and may be of any suitable type. The centrifugal mechanism I9 which is illustrated in Fig. 1 forms no part of my invention and is described and claimed in a copending application, Serial No. 359,728, to B. M. Cain, filed October 4, 1940, and which is assigned to the same assignee as this present invention. The centrifugal mechanism includes a push collar 2| which is adapted to be moved upon movement of outwardly movable weights 2'2. Springs 23 are connected between the weights and o. supporting structure 24 which is stationarily mounted on the shaft 20. When the critical speed is attained, above which the starting windings I 5 are not needed, the weights 22 move outwardly against the bias of the springs 23 and cause movement of the push collar 2| through connecting links 25. Therefore, upon the dynamoelectric machine having reached this critical speed the push collar 2| will move to the right and allow the contacts of the switch structure- I! to be open circuited.

Referring to Figs. 2, 3, 4, and 5, my improved switch structure includes a base or supporting member 26 which is composed of any suitable material, such as a molded insulating material. The base member has two extending arms 21 and 26 through which the base may be stationarily mounted on any suitable support. Thus, when employing my improved switch structure in the starting winding circuit of a dynamo-electric machine the base may be supported on the end shield II through the bolts II which are adapted to extend through holes 28 in the extensions 21 and 26. The base member supports a relatively stationary contact 30 which may be connected in any suitable circuit, such as the starting winding l5, through a connecting strip 3|. Adapted to overlie one face of the base member, I provide a buffer or actuating arm 32 which may be composed of any suitable material, such as a molded insulating product. This buffer arm includes a body portion 33 of bifurcated construction, and a portion 34 extending therefrom at any suitable angle. The end or portion 34 is adapted to cooperate with any suitable operating mechanism for actuating my switch construction, and in the illustrated embodiment of my invention this includes the push collar 2] of the centrifugal operating mechanism. Bosses 35 extend from one face of the buffer arm and are adapted to fit into cooperating slots 36 on one face of the base or support member. The buffer arm 32 is adapted to be pivotally mounted on the base through the cooperating surfaces of the bosses 36 and slots 36, and the body portion 33 of the buffer arm will lie against the body of the base 26 when the switch construction assumes the position, as illustrated in Fig. 4, or when the dynamo-electric machine has attained its critical speed. A relatively movable contact 31 which is adapted to cooperate with the relatively stationary contact 33 is supported by a contact finger 36 which may be composed of any suitable material, such as metal. The relatively movable contact 31 is supported at one end of the contact finger 33 and near the opposite end I pro vide a pair of slots 39 which are adapted to receive a pair of bosses 4|! which extend from a face of the buffer arm opposite to that from which the bosses 35 extend. Centrally located of the contact ringer there is provided an aperture 4| and extending from the contact finger and over the aperture 4| there is provided an ear or tab 42 which is adapted to receive an end of a biasing spring 43.

My improved switch construction may be assembled by placing the actuating arm over one r face of the supporting member so that the bosses 35 extend into the cooperating slots 36. The contact finger 36 may then overlie the buffer arm so that the contact 31 is in alignment with the contact 36 and the slots 36 receive the bosses 40; and the contact finger, buffer arm, and base may be biased together by means of the spring 43 of another end 50 connected to a conducting strip 5| on the base member so that a .suitable lead in the winding circuit may be connected thereto.

Operation of my improved switch structure is as follows: Let us assume that the speed of the dynamo-electric machine is below the critical speed so that the relatively

movable contacts

31 and 30 contact each other and the starting winding is connectedin the circuit. The push collar 2| of the centrifugal mechanism will be pushing against the end 34 of the buffer arm and the movable contact '31 will be forced against the stationary contact 30 with the desired contact pressure. As the weights 22 of the centrifugal mechanism begin to move outwardly after the speed of rotation of the dynamo-electric machine has reached the critical speed, the push collar 2| begins to move to the right, thus causing pivotal movement between the actuating arm and the base plate at the fulcrum provided by the bosses and the indentations 36. Relative or pivotal movement will also be caused between an edge'52 of the contact finger and the cooperating portion of the actuating arm, thus providing a fulcrum between the edge 52 and the cooperating surface of the contact finger. At the same time there will also be relative movement between the

contacts

36 and 31, thus providing wiping movement therebetween. This relative movement between the contact finger and the actuat ing arm, and between the contact 31 and contact 33 will continue until the adjacent face of the contact finger completely overlies the buffer arm,

.as is illustrated in the position of the switch which one end 44 is attached to the ear 42 and r the other end 45 is attached to the base in any suitable manner. A hook is, therefore, provided at the end 44 to attach over the end of the ear 42 and the end 45 is enlarged so that it may be held by a countersunk portion 46 inihe base plate. With the switch parts thus biased together by the spring which extends through the aperture 4| in the contact finger. through a cutout portion 41 in the buffer arm, and through a hole 46 in the base plate, the parts are held se curely together. A pigtail is provided having one end 46 connected to the movable contact 31 and mechanism shown in Fig. 3. It will be apparent that the end 34 of the actuating arm will be caused to move to the right with the push collar 2i due to the force caused by the biasing means or spring 43. when the push collar 2! moves further to the right than that position which it assumes in Fig. 3, the relatively movable contact 3! will move away from the contact 30 and the contact finger and buffer arm will pivot as a unit around the fulcrum points 35 and 38. This movement of the buffer arm or actuating arm 32 will continue until its body portion 33 overlies the body portion of the base or support, this position being illustrated in Fig. 4. Further movement of the push collar 2| to the right will cause it to move away from the end 34 of the actuating arm.

As the dynamo-electric machine slows down and reaches a critical speed at which the force of the springs 23 overcomes the centrifugal force of the weights 22, the weights will fly inwardly and the push collar will be moved to the left so that it will push against the end 34 of the buffer arm, and the sequence of operation described above will occur in the reverse direction.

It is to be noted that with my improved construction the spring 43 extends between the con tact finger and the base relatively close to the fulcrum points 35 and 36. Since the fulcrum 52 of the contact arm is relatively further away from the spring 43 than are the fulcrum points 35 and 36 of the buifer arm, a longer moment arm will be provided for the force which produces the contact pressure, than for the force which presses the buffer arm against the push collar. In this manner with a very small force between the push collar and the actuating arm a relatively large contact pressure may be had. This very low pressure between the actuating mechanism and the contact arm may be made any suitable value by merely moving the spring 43 to a suitable position relative to'the fulcrum points 35 and 35. Thus, with a design as illustrated in the drawing and with the spring extended and the switch in a closed position as illustrated in Figs. 1 and 2, and with the tension of the spring about 7 or 8 ounces, the contact pressure will be about 3 ounces and the pressure between the push collar and the buffer arm only about 1 ounce. In this manner a high contact pressure may be combined with a low force on the push collar and, therefore, cause a minimum amount of wear between the rotating push collar and the non-ro-. tating buffer arm. It is also to be noted that when the contacts are moving'towards a closed position, that is, moving from the position illustrated in Fig. 4 to that illustrated in Fig. 3, and with the contacts just beginning to touch, as 11- lustrated in Fig. 3, the desired contact pressure may be immediately obtained, so that, although the overrun caused when the parts move from the position illustrated in Fig. 3 to that illustrated in Fig. 2 will cause the contact pressure to be increased, this increase in pressure need not sired to have the switch close another circuit.

when the actuating mechanism has moved away from the arm 32, another stationary contact 53 may be provided, as illustrated in Fig. 4, which is mounted on the base member 20 by a conducting bracket member 54. Another movable contact 55 may, therefore, be provided on the opposite side of the contact finger from that on which the movable contact 31 is placed in order to provide a cooperating movable contact for the stationary contact 53.

I may also provide a plurality of pairs of relatively movable contacts in order to.provide a double break in the circuit in which my switch construction is connected. In Fig. 6 the end of the contact finger 38 which is adapted to carry the contacts has been enlarged in order to accommodate two spaced contacts 55 and 51, which are electrically connected together through the connecting strip 58, which may be the end of the contact arm 38. Relatively stationary contacts 59 and 60 are provided on the -base member 25, these contacts 59 and 50 being supported by and electrically connected to conducting strips GI and 52 respectively. Conducting strips i and 52 may be connected in any suitable circuit, and when the switch construction is in the position as illustrated in Fig. 6 a double break will be provided in the circuit. However, when the operating mechanism abuts against the actuating arm 32, the contacts will cooperate in order to close the circuit. It will also be noted that in the modification as illustrated in Fig. 6 no pigtail need be provided.

In view of the foregoing considerations, it'will be seen that I have provided an improved switch construction which will have a reliable operation "xnd which is so designed as to facilitate the assembly of the parts thereof. Thus, the biasing means serves the threefold purpose of holding the contact finger, buffer arm, and base member together, providing the contact pressure, and

providing for the return motion of the operating arm. It will also be seen that full contact pressure is obtained the instant the contacts make and such pressure remains during any over-travel and up to the instant the contacts break again, and this is obtained with a minimum force exerted by the actuating mechanism.

Modifications of the particular arrangemen which I have disclosed embodying my invention will occur to those skilled in the art, so that I do not desire my invention to be limited to the particular arrangements set forth and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope of my invention.

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

1. A switch including a base member, a contact mounted on said base member, an actuating arm pivotally mounted on said base member, a finger pivotally mounted on said arm and having a contact adapted to cooperate with said first-mentioned contact upon movement of said arm, and biasing means for resisting relative movement of said switch parts, said biasing means being connected to said finger between the fulcrum of said finger and the fulcrum of said arm.

2. A switch including a base member, a contact mounted on said base member, an actuating arm pivotally mounted about a fulcrum on said base member, a finger pivotally mounted about a fulcrum on said arm and having a contact adapted to cooperate with said first-mentioned contact upon movement of said arm, said contacts being on one side of said arm fulcrum and said fulcrum of said finger being on the opposite side of said arm fulcrum, and spring. means for, resisting movement of said switch parts, said spring being connected to said finger between the fulcrums of said finger and said arm.

3. A switch including a base member, an actuating arm pivotally mounted about a fulcrum onaid base member, a contact finger overlying said arm and having a contact portion extending beyond the fulcrum of said arm, said contact finger being pivotally mounted about a fulcrum on said arm, means for substantially preventing longitudinal movement between said arm and finger but allowing pivotal movement therebetween, and

spring means connected to said finger and said base between the fulcrums of said finger and said arm.

4. A switch including a base member, an actuating arm having a portion adapted to overlie said base, said arm having an end pivotally mounted about a fulcrum on said base member and an opposite end adapted to be moved by an actuating mechanism, a contact finger adapted to overlie said 'arm and having a contact on one end extending beyond the fulcrum of said arm and an opposite end adapted to be pivotally mounted about a fulcrum on said arm, and biasing means connected to said finger and said support, said biasing means being adapted to exert a force on said arm relatively close to said arm pivot so as to minimize the force necessary to cause movement of said actuatin arm.

5. A switch including a base member having indentations, an actuating arm, bosses extending from a face of said arm and adapted to fit into said indentations on said base member so as to allow limited pivotal movement of said arm on said bosses in said indentations, a contact finger having slots, bosses on said arm extending from an opposite surface from said first-mentioned bosses, said last-mentioned bosses adapted to fit into said slots of said finger so as to substantially prevent movement thereof longitudinally but to allow limited pivotal movement of said finger on said arm, and biasing means extending between said finger and said base so as to uppose relative movement of said switch parts. 7

6. A switch including a base member having indentations, an actuating arm, bosses extending irom a face of said arm and adapted to fit into said indentations on said base member so as to allow limited pivotal movement 0i said arm on said bosses in said indentations, a contact finger having slots, bosses on said arm eatei'iding from an opposite surface from said first-mentioned bosses, said last-mentioned bosses adapted to fit into said slots of said finger so as to substantially prevent movement thereof longitudinally but to allow limited plvota1 movement of said finger on said arm; and biasing means extending between said finger and said base so as to oppose relative movement of said switch parts, said biasing means producing a forc acting 1elative1y closer to the line of contact between said indentations and said first-mentioned bosses than the line of contact between said contact finger and said actuatine arm.

HURAUE Ur. 'WIEST.