US2390365A - Electric switch - Google Patents

Description

R. W. GOF F ELECTRIC SWITCH E n n ill Filed Jan. 2, 1943 Inventor: Robert, Gcaff"s J/ H ls Attorn.

Patented Dec. 4, `l 945 ELECTRIC SWITCH Robert W. Goff, Schenectady, N. Y., assigner to General Electric Company, a corporation of New York Application January 2, 1943. Serial No. 471,137

(Cl. 20G-70) 1() Claims.

My invention relates to electric switches and more particularly to snap action switches of the latched-in type.

The invention has particular application to double-throw limit switches of the snap action type having a switch actuating rocker lever alternatively latched in one of two predetermined spaced circuit controlling positions and slidable overcenter spring means for disengaging the latches and moving the rocker lever.

The invention has for its principal object the provision of a new and improved limit switch of the above character which shall be simple in construction, inexpensive and economical to manufacture, reliable in operation, and characterized by a greatly improved operating life.

My invention itself together with further objects and advantages thereof may be fully appreciated by referring now to the following detailed specification taken in conjunction with the accompanying drawing in which Fig. l is a front elevational view of a limit switch embodying my invention in one form; Fig. 2 is a crosssectlonal view taken along the line 2-2 of Fig. l looking in the direction of the arrows; Fig. 3 is a rear elevational view of the limit switch of Fig. 1; Fig. 4 is a cross-sectional view taken along the line 4--4 of Fig. 3 looking in the direction ci the arrows; and Fig. 5 is an exploded perspective view oi' the principal operating parts of the switch shown at Figs. i to 4. The distinctively new and novel features which characterize the invention together with the scope of the invention will be pointed out with particuiarity in the claims appended to this specification.

Referring now to the drawing and particularly to Fig. 1, I have shown an electric limit switch mounted within -a casing IU having an internal dividing wall I I and provided upon opposite sides thereof with covers I2 and I3 to provide separate compartments I4 and I5 for the switch contacts and operating mechanism, respectively. The switch compartment Il is provided with a gas outlet vent I6 and a tapped conduit connection l1 for the entrance of suitable conducting lead wires.

By way of illustration of the invention I have shown a double-pole, double-throw limit switch comprising two spaced pairs of stationary contacts I8 and I9 and a movable bridging contact member 2li. The bridging contact 20 is slidably mounted upon a rectangular contact supporting bar 2i and is reslliently held in a. central position within a slidable yoke 22 by af pair `of `helical compression springs 23 positioned between the contact member 2li and the parallel sides of the yoke. As clearly shown in Fig. 5, the yoke 22 is slidably mounted upon the contact supporting bar 2I. For the purpose of sliding the yoke 22 longitudinally of the bar 2i to move the bridging contact 20, I have provided a pin 24 extending rearwardly from the bight of the yoke 22 into a slot 25 of a pivotally mounted switch arm 2G. The arm 25 forms part of a switch member comprising a rocker shaft 21 iixedly connected at one end to the arm 2E and at the other end to the center of a rocker lever 28. The rocker shaft 21 is rotatably journaled intermediate its ends in the casing partition or dividing wall lI. The rocker lever 28 forms part of the switch operating mechanism and lies in the compartment I5.

The switch operating mechanism will be best understood by referring now particularly to Figs. 3 and 5. From Fig. 3 it will be observed that a pair of latch levers 29 and 38 are pivotally mounted in the base at points 3| and 32, respectively, and are biased into engagement with opposite ends of the rocker lever 28 by means of associated helical compression springs 33 and 3i, respectively. The springs 33 and 34 are seated in abutments 35 and 36, respectively, which limit the latch disengaging movement of the associated latch members.

Each latch lever 23 and 38 is provided with a latching shoulder 31 with which the opposite ends of the rocker lever 28 are alternatively engageable. Each latch lever 29 and 30 is also provided with a limit stop shoulder 38 with which the opposite ends of the rocker lever 28 are also alternatively engageable in inverse relation with respect to the latch shoulders 31. That is, when the latch shoulder 31 of the lever 30 is in engagement with one end of the rocker lever 28, the stop shoulder 38 of the other lever 29 is in engagement with the opposite end of the rocker lever 28, as shown at Fig. 3. Conversely, the latch shoulder 31 of the lever 29 and the stop shoulder 38 of the lever 3II will be simultaneously eiective when the rocker lever 28 is in its other circuit controlling position. The operation of the rocker lever 28 and the function of the latch and stop shoulders 31 and 38 will be more clearly understood after the remainder of the operating mechansm has been more fully described.

The rocker lever 28 is actuated with a snap action between two angularly spaced limiting circuit controlling positions by means of an overcenter mechanism comprising a spring pressed ball or roller 39 mounted in the movable end of a pivoted actuating lever Ill for sliding movement longitudinally of the rocker lever 28 and overcenter with respect to therocker shaft 21. The ball 29 is biased outwardly toward the end of the lever l by a, helical compression spring 38a positioned within a counterbore in the lever 40. The actuating lever Ill itself is of rectangular cross se( tion and is bifurcated at the pivoted end, as at Il, and loosely mounted upon a switch operating shaft 42. The shaft l2 is journaled in the casing lll. In the embodiment of the invention shown by way of illustration the switch members 26, 21, 28 and the bridging contact 20 are normally held in one of their two circuit controlling positions by means of a helical compression spring 42 positioned between the actuating lever 40 and the casing III to bias the actuating lever to the position shown at Fig. 3. It will of course be understood by those skilled in the art that the particular biasing spring 48 shown is not a necessary part of the invention, but that the actuating lever It may be bi'ased in either direction, or may be left unbiased, as desired.

The operating shaft l2 has connected thereto an operating arm M carrying at the end thereof a roller 45. The shaft I2 is also resiliently connected to the actuating lever 40 through an overtravel mechanism comprising a spur gear 48 mounted upon the end of the shaft l2 and positioned within the bifurcated end ll of the actuating lever 40. The bight of the bifurcated end of the lever 40 is slightly enlarged and bored to receive a cylindrical gear rack Il in meshing engagement with the gear III. For the purpose of normally holding the rack l1 centrally positioned within the bight of the bifurcated end 4i of the actuating lever lli and thereby transmitting movements of the operating shaft I2 to the actuating lever Il), a C-shaped spring I8 is positioned to encircle the gear 4B and the bifurcated end of the lever lll so that the ends of the spring are in engagement with opposite sides of the rectangular actuating lever 4u and in the path of movement of the gear rack 41. Preferably, the rack Il is dlametrically slotted at lts ends to receive the turned over ends of the C-shaped spring, as clearly shown at Fig. 3. To prevent unnecessary play in the mechanism, the length of the gear rack 41 between the bases of the spring receiving slots is substantially the same as the parallel lateral dimension of the actuating lever 40 atthis point.

From the foregoing detailed description of the various parts of the switch mechanism and their manner of organization, it is believed that the operation of the device will be evident from the following brief description. Assuming that initially the mechanism is in the position shown in the drawing, and referring particularly to Figs. l to 3, movement of the bridging contact 2|) from the position shown at Fig. l and into engagement with the contacts Ill is effected by clockwise movement of the shaft 42, as viewed in Fig. 3, or counterclockwise movement of the operating arm 43, as viewed at Fig. 1. Referring specifically to Fig, 3, clockwise rotation of the shaft 42 will move the actuating lever 40 clockwise against the bias of the spring I3 until the free end of the lever l0 comes into engagement with the latch lever 3U. During this overcenter movement the spring I3 is compressed and the ball 29 is moved inwardly against the force of the spring 39a, since the C-shaped spring 48 is stronger than the springs alla and 43 combined. However, the rocker lever 28 is not moved because of its latching engagement with the shoulder 31 of the latch lever 30. Upon engagement of the actuating lever 40 With accuses the latch lever III, the latch lever lll is moved to its latch-disengaging position against the abutment le, whereupon the spring 28a becomes effective to rotate the rocker shaft 21 in a counterclockwise direction (Fig. 3) until the right-hand side of the rocker lever 2B engages the limitstop shoulder 2l of the lever lli. In this position it will be clear by analogy with Fig. 3 that the latch shoulder ll of the latch lever 2s has moved under the left-hand end of the rocker lever 2l to lock the rocker lever in the new position. It will be understood that rotation of the rocker shaft 21 and the attached switch arm 28 produces a sliding movement of the yoke 22 and bridging contact 20 along the contact supporting bar 2l.

In the event that after the contact actuating movement described above a further counterclockwise movement (Fig. 1) of the operating arm M is attempted, the Cshaped spring 4l will expand and permit overtravel of the arm u and shaft l2 with respect to the actuating lever Il. It will be evident from Figs. 3 and 5 that when the actuating lever 4U is in either of its circuit controlling positions, any further movement of this lever is prevented by the interposition of one of the latch levers 29 or 3|) and the associated abutment 25 or li between the lever lll and one wall of the casing l0. Thus, as the operating shaft 42 is further rotated, the gear IB drives the rack l1 out of one side or the other of the bifurcated end of the lever 40. Such movement of the rack 41 is possible, but is accomplished only against the bias of the C-shaped spring Il, causing this spring to expand toward the walls of the casing i0. It will be noted from Fig. 3 that the spring 48 is positioned in a separate small compartment having a shape similar to that of the spring and having walls positioned in closely spaced relation to the spring. The expansion of the spring 48 and thus overtravel of the operating arm M are limited by engagement of the spring 48 with the walls of the spring compartment.

From the foregoing detailed description of the structure and operation of my electric switch, the purpose and advantages of the limiting stops 38 on the latch levers 29 and Bn will become evident. It is to be observed from Figs. 1 and 3 that if the stop shoulders 3B were not provided, the spring 39a would rotate the rocker lever 28 and rocker shaft 21 until further movement was stopped4 either by complete compression of one of the wipe springs 23 associated with the bridging contact 2B, or until the latched end of the rocker lever 28 was raised olf the latch seat 21 and engaged some other part of the latch lever as a stop. By way of illustration let it be assumed that in Fig. 3 the right-hand end of the rocker lever 28 was raised away from the latch shoulder 31 of the lever 30. Then, upon movement of the actuating lever Ill toward the right-hand end of the lever 28, the lever 2l would be rotated into engagement with the latch shoulder and the contacts moved slightly as soon as the spring pressed ball 38 passed overcenter with respect to the rocker shaft 21 and before release of the latch lever 30. This slight play or backlash" has been found to ultimately destroy the wipe at the switch contacts and to cause destructive arcing between the contacts. Such operation considerably reduces the operating life of the switch, and it is primarily to overcome such operation that I provide the stop shoulders 28. These shoulders dennitely determine the circuit controlling positions of the rocker lever 28 and prevent disengagement of the rocker lever from the operative'latching shoulder. Accordingly, it is a feature of the invention that the stop shoulder 38 on each latch lever be so positioned with respect to the cooperating latch shoulder on the opposite latch lever that the rocker lever 28 will be held at all times in engagement with the operative latch shoulder.

While I have shown but one preferred embodiment of my invention by'way of illustration, many further modifications will occur to those skilled in the art. I therefore wish to have it understood that I intend in the appended claims to cover all such modifications as fall within the true spirit and scope of my invention.

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

1. AA snap-acting device comprising a rocker lever Ipivotally mounted intermediate its ends for movement between two spaced terminal positions, a pair of latch' members arranged alternatively to engage the ends of said rocker lever selectably to retain said lever in either of said positions, common actuating means for releasing said latch members and moving said rocker lever. and a limiting stop formed upon each of said latch members for alternative engagement with the ends of said rocker lever at the unlatched end thereof thereby to prevent overtravel of said rocker lever beyond its latched position.

2. A snap-acting device comprising a rocker lever pivotally mounted intermediate its ends for movement between spaced terminal positions, a pair of latch members arranged alternatively to engage the ends of said rocker lever selectably to retain said rocker lever in either of said positions, common actuating means for releasing said latch members and moving said rocker lever, a stop shoulder formed upon one of said latch members to determine one of said positions, and a latch shoulder formed upon the other of said latch members for releasably retaining said rocker lever in said one position.

3. An electric switch comprising a pair of relatively movable cooperating switch contacts, a movable switch member resiliently connected to one of said contacts for moving said contacts into and out of engagement, said switch member including a, rocker lever pivotally mounted intermediate its ends for movement between switch opening and switch closing positions, a pair of latch levers alternatively engageable with opposite ends of said rocker lever selectably and releasably to retain said rocker lever in said positions, a stop shoulder on one of said latch levers for engagement with one end of said rocker lever to determine said switch closing position and prevent movement of said rocker lever in one direction, a latching shoulder on the other of said latch levers for preventing movement of said rocker lever in the opposite direction thereby releasably to retain said rocker lever in said switch closing position, an actuating lever pivotally mounted at a. point spaced from the pivotal axis of said rocker lever and carrying at its free end a spring pressed roller in longitudinal sliding engagement with said rocker lever, said roller being arranged for movement overcenter with respect to said rocker lever first to engage the operative latch lever for movement to a latch releasing position and thereafter to rotate said rocker lever to its other circuit controlling position.

4. An electric switch operating mechanism comprising a base, an operating shaft rotatably journaled in said base, a. switch actuating lever having a bifurcated end rotatably mounted upon said shaft, a spur gear carried by said shaft and positioned within the bifurcated end oi said actuating lever, a gear rack slidably mounted within the blfurcated end of said actuating lever in meshing engagement with said gear, spring means for normally retaining said rack in a central position with respect to said actuating lever,

and operating means for turning said operating shaft thereby to move said actuating lever between predetermined angularly spaced limiting positions, said spring means permitting overtravel of said operating shaft with respect to said actuating lever.

5. An electric switch operating mechanism comprising a base. an operating shaft rotatably journaled in said base, a. switch actuating lever having a bifurcated end rotatably mounted upon said shaft. a spur gear carried by said shaft and positioned within 'the bifurcated end of said actuating lever, a gear rack slidabiy mounted in the bight of said bifurcated end in meshing engagement with said gear and for lateral movement with respect to said actuating lever. spring means between said actuating lever and said gear rack for normally retaining said gear rack centrally positioned Nithin said bight, and means for turning said operating shaft thereby to move said actuating lever between predetermined angularly spaced limiting positions, said spring means permitting overtravel of said operating shaft with respect to said actuating lever.

6. An electric switch operating mechanism comprising a base, an operating shaft rotatably journaled in said base. a switch actuating lever having a bifurcated end rotatably mounted upon said shaft, a spur gear carried by said shaft and positioned within the bifurcated end of said actuating lever, a gear rack slidably mounted within the bight of said bifurcated end of said lever for meshing engagement with said gear and for lateral movement with respect to said lever, a C-shaped spring encircling said gear and the end of said actuating lever and having its ends in engagement with opposite sides of said lever in the path of movement of said rack thereby normally to retain said rack centrally positioned within the bight of said bifurcated end, said actuating lever being movable between predetermined angularly spaced limiting positions and said gear rack and spring providing a resilient driving connection between said shaft and said lever thereby to permit overtravel of said shaft with respect to said lever, and operating means for turning said shaft to move said lever.

'l'. An electric switch operating mechanism comprising a base, an operating shaft rotatably journaled in said base, a switch actuating lever having a bifurcated end rotatably mounted upon said shaft, a spur gear carried by said shaft and positioned within the bifurcated end of said ac\ tuating lever, a gear rack slidably mounted in the bight of said bifurcated end of said actuating lever in meshing engagement with said gear, said rack being arranged for lateral movement with respect to said actuating lever, a G-shaped spring embracing said gear and the bifurcated end of said lever and having end portions of greater width than the width of said rack, the ends ci said C-shaped spring being positioned on opposite sides of said actuating lever in the path of movement of said rack and the length of said rack between the ends of said spring being substantially equal to the parallel lateral dimension of said actuating lever, whereby said spring normally engages opposite sides of said lever to retain said rack centrally positioned within the bight of said lever thereby to provide a resilient driving connection between said shaft and said lever, and an operating lever mounted upon said operating shaft to move said actuating lever between predetermined sngularly spaced limiting positions, said resilient connection providing for overtravel of said operating lever with respect to said actuating lever.

8. In an electric switch actuating mechanism, a movable switch member including a rocker lever pivotally mounted intermediate its ends for movement between two spaced circuit controlling positions, a pair of latch members biased into engagement with opposite ends of said rocker lever to prevent movement of said rocker lever in opposite directions, each said latch lever having a latch shoulder and a stop shoulder in spaced apart relation each' arranged to prevent movement of said rocker lever in the same direction, and movable actuating means in spring pressed sliding engagement with said rocker lever lor selectively disengaging said latch levers, said actuating means upon disengagement of one ot said latch levers moving said rocker lever against the stop shoulder on the disengaged latch lever and into position to be engaged by the latch shoulder on the other lever thereby to prevent reverse movement of said rocker lever.

-9. An electric switch comprising a pair of relatively movable cooperating switch contacts, a movable switch member resiliently connected to one of said contacts for moving said contacts into and out of engagement, said switch member including a. rocker lever pivotally mounted intermediate its ends for movement between two spaced circuit controlling positions, a pair of latch levers biased into engagement with opposite ends of said rocker lever to prevent movement of said rocker lever in opposite directions, each said latch lever having a stop shoulder and a latch shoulder in spaced apart onset relation `engageable with said rocker lever in said two positions respectively to prevent movement thereof in the same direction, an 'actuating lever pivotally mounted at a point spaced from the pivotal axis of said rocker lever and carrying at its ends a spring pressed roller in longitudinal sliding engagement with said rocker lever, said actuating lever being arranged for movement overcenter with respectto said rocker lever selectively to disengage said latch shoulders and thereby to permit said roller to move said rocker lever from one said position to the other said position in engagement with the stop shoulder on the same latch lever and the latch shoulder on the other latch lever.

10. An electric switch comprising a base. a pair of spaced stationary switch contacts, a movable switch contact slidably mounted intermediate said fixed contacts for alternative engagement therewith. a. pivoted switch arm resiliently connected to said slidable contact, said switch arm being mounted upon a rocker shaft Journalled in said base, a rocker lever mounted at its center upon said rocker shaft for moving said shaft between two predetermined angularly spaced circuit controlling positions, a pair oi' spring pressed latch levers pivotally mounted upon said base for engagement with opposite ends of said rocker lever to prevent movement of said rocker lever in opposite directions, each said latch lever having a stop shoulder and a latch shoulder in spaced apart offset relation engageable with said rocker lever in said two positions respectively to prevent movement thereof in the same direction, an actuating lever pivotally mounted upon said base for rotation about an axis substantially parallel to said rocker shaft, said actuating lever extending toward said rocker lever in substantially per- Certificate oi' Correction Patent No. 2,390,365.

December 4, 1945.

ROBERT W. GOFF It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 4, first column, line 27(i claim 8,

after the word other insert latch.; and that the said Letters Patent shoul be read with this correction therein that the same may conform to the record of the case in the Patent Oiiicel Signed and sealed this 21st day of May, A.. D. i946.

LESLIE FBAZEB,

First Assistant Commissioner of Patente.

bight of said lever thereby to provide a resilient driving connection between said shaft and said lever, and an operating lever mounted upon said operating shaft to move said actuating lever between predetermined sngularly spaced limiting positions, said resilient connection providing for overtravel of said operating lever with respect to said actuating lever.

8. In an electric switch actuating mechanism, a movable switch member including a rocker lever pivotally mounted intermediate its ends for movement between two spaced circuit controlling positions, a pair of latch members biased into engagement with opposite ends of said rocker lever to prevent movement of said rocker lever in opposite directions, each said latch lever having a latch shoulder and a stop shoulder in spaced apart relation each' arranged to prevent movement of said rocker lever in the same direction, and movable actuating means in spring pressed sliding engagement with said rocker lever lor selectively disengaging said latch levers, said actuating means upon disengagement of one ot said latch levers moving said rocker lever against the stop shoulder on the disengaged latch lever and into position to be engaged by the latch shoulder on the other lever thereby to prevent reverse movement of said rocker lever.

-9. An electric switch comprising a pair of relatively movable cooperating switch contacts, a movable switch member resiliently connected to one of said contacts for moving said contacts into and out of engagement, said switch member including a. rocker lever pivotally mounted intermediate its ends for movement between two spaced circuit controlling positions, a pair of latch levers biased into engagement with opposite ends of said rocker lever to prevent movement of said rocker lever in opposite directions, each said latch lever having a stop shoulder and a latch shoulder in spaced apart onset relation `engageable with said rocker lever in said two positions respectively to prevent movement thereof in the same direction, an 'actuating lever pivotally mounted at a point spaced from the pivotal axis of said rocker lever and carrying at its ends a spring pressed roller in longitudinal sliding engagement with said rocker lever, said actuating lever being arranged for movement overcenter with respectto said rocker lever selectively to disengage said latch shoulders and thereby to permit said roller to move said rocker lever from one said position to the other said position in engagement with the stop shoulder on the same latch lever and the latch shoulder on the other latch lever.

10. An electric switch comprising a base. a pair of spaced stationary switch contacts, a movable switch contact slidably mounted intermediate said fixed contacts for alternative engagement therewith. a. pivoted switch arm resiliently connected to said slidable contact, said switch arm being mounted upon a rocker shaft Journalled in said base, a rocker lever mounted at its center upon said rocker shaft for moving said shaft between two predetermined angularly spaced circuit controlling positions, a pair oi' spring pressed latch levers pivotally mounted upon said base for engagement with opposite ends of said rocker lever to prevent movement of said rocker lever in opposite directions, each said latch lever having a stop shoulder and a latch shoulder in spaced apart offset relation engageable with said rocker lever in said two positions respectively to prevent movement thereof in the same direction, an actuating lever pivotally mounted upon said base for rotation about an axis substantially parallel to said rocker shaft, said actuating lever extending toward said rocker lever in substantially per- Certificate oi' Correction Patent No. 2,390,365.

December 4, 1945.

ROBERT W. GOFF It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 4, first column, line 27(i claim 8,

after the word other insert latch.; and that the said Letters Patent shoul be read with this correction therein that the same may conform to the record of the case in the Patent Oiiicel Signed and sealed this 21st day of May, A.. D. i946.

LESLIE FBAZEB,

First Assistant Commissioner of Patente.

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