US1768385A - Electric switch - Google Patents

Description

June 24, 1930. L. s. WALLE 1,768,385

ELECTRIC SWITCH Filed June 13, 1928 Fig.1.

I I 2i 22 /5 a Inventor Ludwig S. WQLLe, 22 b5 His Attorneyr Patented June 24, 1930' UNITED STATES PATENT OFFICE LUDWIG S. WALLE, OF SCOTIA, NEW YORK, .A SSIGNOB TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK ELECTRIC SWITCH Application filed June 13,

My invention relates to electric switches and particularly to switches adapted for use in controlling power circuits which carry heavy currents.

It has been found that switches heretofore employed in such circuits and which had copper contacts sometimes developed an objectionable amount of heat at the contacts. This was found to be due to an oxide film which forms on the copper contacts,

thus materially raising the resistance at the points of contact. An occasional openin and closing of the switch is usually su ficient to rub off this film and restore a low resistance connection between the cooperating contacts, but in certain industries using electrical power it is ver undesirable to have any interruption o the supply of 'power occur over long intervals of time. As a substitute for copper I have tried contacts ofsilver since the oxide of this metal, unlike that of copper, has a conductivity but little lower than the metal itself. While a switch having such contacts will operate continuously closed over lon periods of time 'without heating, I have ound that in certain switch constructions wherein the closing operation the main contacts are brought together with considerable force, the silver of the contacts, being somewhat softer than the copper formerly employed, became deformed after repeated operations. of .the switch. It is an object of my invention therefore to provide an improved switch construction of this character whereby deformation of the contacts incident to the closing of the switch is greatly reduced if not entirely avoided.

My 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 to the drawing, Figs. 1v and 2 15 are perspective views of a portion of a liquid break switch illustrating my invention respectively in'open and closed positions; and 'Fig. 3 is a cross sectional view of the movable bridging member. I have 50 illustrated my invention as applied to a 1928." serial No. 285,162.

liquid break .switch of the t pe in which two fixed contacts are suspen ed in a vessel of insulating liquid and are bridged by a movable contact member. Since this type of switch is common and well known I have omitted any showing of the vessel containing the insulating liquid and have confined the illustration to those parts of the switch which relate to the invention. The two similar main fixed contacts 1 are supported from the cover of the containing vessel, not shown, in the usual manner b means of insulator bushings 2 through -w ich extend the conducting studs 3. The contacts 1 have wedge-shaped contact portions to which are secured in any suitable manner as, for example, by welding the contact plates 4 of silver. Main contacts 1 also have arcing or auxiliary contacts 5 which are shown as comprising separate members set into the contacts 1 and secured thereto by means of bolts 6.

Between the fixed contacts extends the operating rod 8 which by suitable operatin mechanism, not shown, is raised and lowere respectively to close and open the switch. The movable contact portion of the switch which bridges the space between the two fixed contacts comprises essentially a pair of rod-like members 10 arranged side b side and resiliently pressed toward eac other. I have shown these two members as tubular in form and as having in the central portion of each a rod insert 11 into which are threaded the two suspending I bolts 12. These bolts are pivoted to the cross head 13 secured to the lower end of the operat-- ing rod 8, the construction being such that members 10 may swing laterally relatively to each other but are maintained parallel or substantially so and are restrained against relative longitudinal movement. For resiliently pressing the" two members 10 toward each other I have shown two pairs of springs 14 arranged on the rods 15 located at opposite sides of the rod inserts 11. This part of the construction is shown more clearly i-n Fig. 3 where it will be seen that each of the two rods 15 passes through the members 10 and is provided at its middle portion I spaced apart an appreciable distance.

with the loose sleeve 16 which serves to space the members. At their outer portions the springs 14 pass freely through members 10 but at their inner ends engage the members and press them against the sleeve 16, the tension of the springs being adjusted by the nuts 17. Conforming to the curved face of each member 10 are the silver contact plates 18 which may be secured thereto in any suitable manner as, for example, by welding. It will be understood that plates 18 are so arranged on the members 10 that when the switch is closed they will contact with plates at and that the extent of the closing movement is such that the points of contact between plates 4 and 18 will not be carried byond the limits of plates 4:. After the plates 18 are secured to the members 10 I face them off as for example by turning in a lathe and in this operation I leave the plates thicker in their central ortions, the contact face of each plate thereby comprising preferably two conical surfaces. By so sha ing the plates I avoid the necessity of care ully aligning the parts to insure proper contact. 'Point contact to be sure is obtained by this construction but this has been found to be sufficient even for large capacity switches. The point of contact, however, has a limited location on each contact plate 18 which point is central of the contacts irrespective of small manufacturing inaccuracies that may occur and without the switches requiring individual adjustment after assembly. Mounted in and projecting from the two ends of each member 10 are the plugs 20 which engage the arcing contacts 5. In shape these contacts resemble the head of an arrow and are so constructed and arranged that in the closing operation of the switch they first engage the plugs 20 forcing apart the members 10 until the cooperating plates 4: and 18 are in the proper position to engage each other. At this point the plugs 20 ride off the shoulders 22 of contacts 5, leaving plates 4 and 18 in contact with each other. The blow of the closing movement of the'switch is thereby taken by the contacts 5 and plugs 20 which constitute the cooperatnig arcing contacts and the transfer of pressure from these contacts to the main silver contacts is gradual whereby the latter contacts are relieved of the more or less severe battering which they would otherwise receive. In the final closed circuit position of the switch, as shown by Fig. 2, the main or silver contacts only are in engagement, the arcing contacts being then In this position also the springs 14 are under compression thus insuring good contact between the cooperating main contacts. As the switch moves to open circuit position the point of contact with members 10 is transferred back from the plates 4 to the contacts 5 so that the final break occurs between the arcing contacts 5 and 20.

I have chosen the particular embodiment described above as illustrative of my invention and it will be apparent that various modifications ma be made without departing from the spirit and scope of my invention which modifications I aim to cover by the appended claims.

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

1. An electric switch comprising relatively movable cooperating contacts, one of the contacts being inclined relative to the direction of movement and having means operative when the contacts approach each other for directly engaging and movin the other contact laterally prior to actua engagement of the contacts.

2. An electric switch comprising relatively movable cooperating contacts, one of the contacts comprising laterally novable members, the other contact having oppositely inclined contact faces adapted to enter between the respective movable members and having a wedging portion arranged to engage and separate the movable members prior to the engagement thereof with the contact faces.

3. An electric switch comprising a wedgeshaped contact, a cooperating contact having laterally separable members arranged to receive the wedge-shaped contact, means for resiliently opposing the separation of said members and means comprising an auxiliary contact associated with the wedge-shaped contact for initiating the separating movement of said members during the closing of the switch.

4. An electric switch comprising relatively movable cooperating contacts one of said contacts having its contact face inclined relative to the direction of closing movement, the other of said contacts being movable both longitudinally and laterally of said direction of movement, and a member associated with said one contact constructed in the closing operation of the switch initially to engage and laterally move said other contact and finally to become disengaged therefrom.

5. An electric switch comprising a stationary contact having inclined contact faces, an auxiliary contact associated therewith, a cooperating movable contact havin portions arranged to engage said faces, an resilient means opposing the separation of said portions, said auxiliary contact arranged in the closing movement of the switch initially to engage and separate ,said portions and after engagement of the cooperating contacts to become detached therefrom.

6. An electric switch comprising a plurality of wedge-shaped contacts, auxiliary contacts associated therewith, a cooperating bridging member for both the wedge-shaped and the auxiliary contacts comprising similar rods, corresponding end portions of which engage opposite faces of the wedgeshaped contacts, and means for 'yieldingly opposing the separation of the rods.

7. An electric switch comprising fixed wedge-shaped contacts, auxiliary contacts mounted thereon, a movable bridging member therefor comprisin a pair of rods arranged to be separated by the auxiliary contacts and to receive therebetween the fixed contacts, an operating rod having a flexible connection with said rods and means resiliently opposing separation of the rods.

8. An electric switch comprising fixed wedge-shaped contacts, a pair of similar contact rods arranged to be moved into engagement with opposite faces of said contacts to bridge the same, and an arcing contact secured to each of said contacts and constructed initially to engage the rods and separate the same when the switch is bein closed and to make final engagement witn the rods when the switch is being opened.

9. An electric switch comprislng a fixed wedge-shaped contact having silver contact faces, an auxiliary contact mounted thereon, cooperating contacts for the fixed contact having silver contact faces, and means operated by the auxiliary contact during the closing movement of the switch for moving said cooperating contacts laterally, thereby reducing the blow received by thesilver contact faces incident to the closing operation of the switch. a

10. An electric switch comprising a main wedge-shaped contact having silver contact plates thereon, a plurality of cooperating separable contact members having silver contact plates thereon, springs opposing separation of the members, and arcing contacts on the wedge-shaped contact constructed to engage and separate said members prior to the engagement of said contact plates.

11. An electric switch comprising fixed wedge-shaped contacts, auxiliar arcing contacts mounted with respect t ereto, a bridging contact therefor comprising a pair of transversely movable parallel members having oppositely disposed contact faces each curved about the axis of the bridging contact and higher in its central portion than at either end whereby a int contact is made between the cooperating contacts, said auxiliary contacts adapted to engage and separate said parallel members during initial closing movement of the switch to hold said contact faceseout of engagement with the fixed contacts, thereby protecting said contacts from initial closing shock.

In witness whereof, I have hereunto set my hand this 12th da of June, 1928.

LU WIG S. WALLE.

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