US2468551A

US2468551A - Snap action electric switch

Info

Publication number: US2468551A
Application number: US705358A
Authority: US
Inventors: Robert W Goff
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1946-10-24
Filing date: 1946-10-24
Publication date: 1949-04-26
Anticipated expiration: 1966-04-26

Description

April 26, 1949. R. w. GoFF 2,468,551

SNAP ACTION ELECTRIC SWITCH Filed Oct. 24, 1946 2 Sheets-sheet 1 Inventor Robert Vf. Golpfl,

His Attorney.

` April 26, 1949. R. w. GoFF 2,468,551

SNAP ACTION ELECTRIC SWITCH Filed Oct. 24, 1946 2 Sheets-Sheet 2 Inventor-z Robert W. Gof`f`,

H i5 Attovh'eg.

iatentcd Apr. 2,6, 1949 2,468,551 f SNAP Ac'rIoN ELECTRIC swrrcn Robert W. Goff, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application October 24, 1946, Serial No. 705,358

(Cl. 'Z4-100) 7 Claims.

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

The invention has particular application to 'double throw limit switches of the snap action facture, 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 specication taken in conjunction with the acoompanying drawings, in which Fig. 1 is a front elevational view of a snap acting limit switch embodying my invention; Fig. 2 is a cross-sectional view taken along the line 2 2 of Fig. l looking in the direction of the arrows; Fig. 3 is a fragmentary view of the switch actuating mechanism shown at Fig. 1, certainparts being shown in section in the manner indicated by the line 3-3 of Fig. 2; Fig. 4 is a fragmentary cross-sectional view taken along the line 4--4 of Fig. 2; Fig. 5 is a rear elevational view of the switch shown at Fig. 1; Fig. 6 is a cross-sectional view taken along the line 6-6 of Fig. 5, looking in the direction of the arrows; and Fig. 7 is a detailed view of the switch arm shown at Figs. and 6. The distinctively new and novel features which characterize the invention, together with the scope of the invention, will be pointed out with particularity in the claims appended tovthis application.

Referring now to the drawings, and particularly to Fig. 1, I have shown an electric limit switch mounted within a casing I having an internal dividing wall 2 and provided upon opposite sides thereof with covers 3 and-4 to provide separate compartments 5 and 6' for the switch operating mechanism and lthe switch contact mechanism, respectively. The switch compartment 6 is provided with a tapped conduit connection 8 for the entrance of suitable conducting lead wires. The casing 'cover 3 for the operating mechanism compartment 5 is shown formed of metal, while the casing A4'for the switch compartment B is formed-cfa suitable 'insulating material,

such as a molded insulating compound or the like.

By way of illustration of the invention, I have shown a pair of double-pole double-throw limit switches actuated by a common switch arm 9. The switch arm 9, shown best at Figs. 2, 5, 6, and 7, is mounted upon one end of a rocker Shaft I0 journaled in the dividing wall 2 and carrying at its other end a rocker arm II. The rocker arm II and the switch arm 9, together with the connecting rocker shaft Il), form a unitary switch member actuable by the switch operating mechamsm.

As shown particularly at Figs. 5 and 6, each double-pole double-throw limit switch in the compartment 6 comprises two spaced pairs of switch contacts I2 and I3, and movable bridging contact members I4. The bridging contacts I4 are slidably mounted upon a rectangular supporting bar I5 and are resiliently biased to a central position within a slidable yoke IB by a pair of helical compression springs Il positioned between the Contact members I4 and the parallel sides of the yoke. As clearly shown at Fig. 6, the yoke I8 is slidably mounted upon the contact supporting bar I5. For the purpose of sliding the yoke I6 longitudinally of the bar I5, thereby to move the bridging contacts I4, I have provided on each yoke a pin I8 extending rearwardly from the bight of the yoke I6 into one of a pair of slots I9 formed at opposite ends of the pivotally mounted switch arm 9 (see particularly Fig. 7).

The switch operating mechanism will be best understood by referring now particularly to Figs. 1, 2, 3 and 4. As hereinbefore described, the rocker arm II mounted upon one end of the rocker shaft I0 extends into the compartment 5 housing the operating mechanism. From Figs. 1 and 3 it will be observed that a pair of latch levers 20 and 2l are pivotally mounted in the base at points 22 and 23, respectively, and are biased into engagement with opposite ends of the rocker arm I I by means of associated

helical compression springs

24 and 25, respectively. The

springs

24 and 25 are seated in recesses in the latch levers 2c and 2|, respectively, and bear against abutments 26 and 2l, respectively. The abutments are formed on opposite sides of the casing I adja-4 cent the latch levers and serve as limiting stops in the latch disengaging movement of the associated latch members.

Each latch lever 20 and 2| is provided with a latching shoulder 28 with which the opposite ends of the rocker arm Il are alternately engageable. Each latch lever is also provided with a limit stop shoulder 29 with which the opposite ends of the rocker arm Il are also alternately engageable in inverse relation with respect to the latch shoulders 28. That is. when the latch shoulder 28 on the latch lever 28 is in engagement with one kend of the rocker arm Il, the stop shoulder 29 of the other latch lever 2| is in engagement with the opposite end of the rocker arm ll, as shown at Figs. 1 and 3. Conversely, the latch shoulder 28 of the lever 2| and the stop shoulder 29 of the lever 20 will be simultaneously effective when the rocker arm is in its other circuit controlling position. This latching mechanism including the limit stop shoulder 29 is more vparticularly described and claimed in my Patent 2,390,365, issued December 4, 1945.

The rocker arm 28 is actuated with a snap ac-` tion between two angularly spaced limiting' circuit controlling positions by means of a pair of oppositely reciprocable arms 3D and 3| movable substantially transversely of the rocker arm and in opposite directions, alternately to disengage the engaged latching shoulder 28 on the

operative latch lever

20 or 2| and simultaneously to lstore energy in an actuatingspring for moving the rocker arm when the latch shoulder is released. As shown more particularly at Fig, 2, each of the reciprocable arms 38 and 3l is formed of a pair of

plates

32 and 33 connected together in parallel spaced relation by a pair of

transverse blocks

34 and 35. The arms 3l|y and 3| for the greater part of their length are disposed in substantially parallel spaced relation, but at their upper ends the

arms

30 and 3| are bent outwardly away from the center line of the switch. The

reciprocable arms

30 and 3| are pivotally mounted at their upper ends upon

pivot pins

36 and 31, respectively, which are carried at opposite ends of a centrally pivoted operating arm 39. The operating member 38 is pivotally mounted at its center upon the base for limited rocking movement.

The

spacing blocks

34 and 35 forming part of the

reciprocable arms

30 and 3| are spaced apart longitudinally of the arms and are apertured to support loosely between the plates 32 and 33 a pair of actuating pins 39 and 40, the pin 39 being slidably mounted in the arm 30 and the pin 40 being slidably mounted in the arm 3|. The spacing blocks 35 receive the pins 39 and 48 in laterally elongated slots 35a so that the pins 39 and 40 are loosely mounted within the arms 3|) and 3| for limited lateral lost motion with respect to the arms. Moreover, the actuating pins 39 and 40 are reciprocable within the arms 38 and 3l and are arranged for alternate spring press engagement with opposite ends of the rocker arm upon downward actuating movement of the associated

arms

30 or 3|. For this purpose, each actuating pin 39 and v40 is provided with a collar 4|. The collars 4| serve as seats for a pair of actuating springs 42 and 43 interposed between the collars 4| and the spacing blocks 34 in the reciprocable arms 30and 3|, respectively. As illustrated particularly at Figs.\1 and 3, the surface of the rocker arm in the regions of engagement with the actuating pins 39 and 40 is cylindrically dished, as at Ila and IIb, for a purpose which will be more fully described hereinafter.

The outer plates 32 of the

reciprocable arms

30 and 3| are longer than the inner plates 33 and extend below the rocker arm into camming engagement with a cam roller 44 rotatably mounted upon the base For this purpose the depending ends ofthe reciprocable arms 30 vand 3| are provided with sloped camming surfaces 45 and 46, respectively.

The centrally pivoted operating arm 38 is biased to one of two angularly spaced terminal positions by a compression spring 41 interposed between one end of the operating member 38 and the adjacent abutment y26 on the casing I. Obviously, the operating member 38 may be biased to either position simply by locating the biasing spring 4l either upon the abutment 26 or upon the abutment 2. The operating member 38 is moved about its pivot against the bias of the spring 41 by a reciprocable push rod 48 extending through the upper portion of the switch casing i into engagement with an upwardly extending arm 48 on the operating member. Connection between the arm 49 and the push rod 48 is made by a pin 58 which extends from the upper end of the arm 49 into an elongated slot 5| in the push rod 48. The pin 50 is normally held centered in the slot 5| by a pair of opposing compression springs 52 within the push rod 48, the compression springs and the slot 5| providing a limited amount of overtravel of the push rod 48 with respect to the pin 50 and the operating member 38.

With the foregoing detailed description of the various parts of my switch mechanism and their manner-of organization, it is believed that the mode of operation of the device will be evident from the following brief description.

Assuming that initially the mechanism is in the position shown in the drawings, and referring particularly to Figs. 1 and 3, movement of the bridging contacts |4 from the position shown at Fig. 5 into engagement with the contacts I3 is effected by movement of the push rod 48 from the position shown in solid lines at Fig. 1 to the dotted position shown at Fig. 1. More specifically, when the push rod 38 is moved to the left, as viewed at Fig; 1, the operating member 38 is rotated in a counterclockwise direction about its pivot point against the bias of the spring 41. Rotary movement of the centrally pivoted operating member 38 effects opposite longitudinal sliding movement of the reciprocable`

cam follower arms

30 and 3|, the arm 30 moving downwardly and the arm 3| moving upwardly as viewed in Figs. 1 and 3.

As the arm 30 moves downwardly, it is also forced laterally outward byl action of the cam surface 45 in moving over the cam roller 44. This outward movement of the arm 30 brings the spacing block 35 on this arm into engagement with the operative latch lever 20, thereby to effect disengagement of the latch shoulder 28 on the lever 20 with the end of the rocker arm 20. multaneously, the downward longitudinal movement of the reciprocable arm 30 brings the actuating pin 39 into engagement with the dished portion ||a of the rocker arm The rocker arm Il, however, cannot move until the latch shoulder 28 on the latch lever 28 is actually disengaged. Prior to such disengagement, the actuating spring 42 is compressed, thereby to store energy for moving the actuating pin 39 and the rocker arm l as soon as the latch lever 20 is disengaged.

During this downward and laterally outward movement of the arm 30, the actuating pin 39 remains in xed engagement with one point of the rocker arm by reason of the elongated slot 35a. which provides lateral lost motion between the actuating pin 39 and the arm 3|). In this connection, it should be noted that, were this lost motion not provided. the pin 39 would be forced to slide outwardly along the rocker arm amarsi 8 lll' as the reciprocable arm 20 is moved downward .and outward. Such forced sliding would cause binding ofthe pin 39 against one side of the 4slot in the spacing block 35 and the resultant iriction would result in lost power, if not un- 'certain operation, in the movement of the rocker arm ll. Thus, as the arm 3l is moved downfwardly and.outwardly, the spacing block 2B is also moved outwardly so that. at the moment of latch release, the pin 2l is on the inner side of the elongated slot 25a.

' As' soon as the latch shoulder 28 of the latch `lever 20 is released. the spring 42 presses the pin 29 downwardly, thereby to rotate the rocker Y,

'arm ll into engagement with the stop shoulder .'29 on the latch lever 20 and to bring the opposite end of the rocker arm into engagement with the latch shoulder 28 on the latch lever 2|. With this rocker arm in this position, the latch lever 2| becomes eiiective by reason of its biasing spring 25. The actuating pin 39, them-assumes the position of the actuating pin l0 as viewed at ,Fig 3, that is, the pin 39 then engages the low side of the rocker arm It will now be evident from Fig. 3 that the 'xactuating pinA which engages the low side of therocker arm moves to the outside of the elong'ated slot 35a by reason of the force of the .actuating spring and the slope of the dished rocker arm surface ll'a or IIb. In Fig. 3 the actuating pin 40 is shown in this position. Thus, to continue with the foregoing operation, it will be further evident that, after the actuating pin 39 is released to rotate the rocker arm il, the pin moves from the inside of the elongated slot 'to the outside. The pin remains in this position with respect to the slot upon reverse actuation, so that upon initiation of actuating movement of either pin, the pin begins its movement in the outside of the elongated slot 35a as illustrated by the pin 39 in Fig. 3. This will be evident from .following the action of the pin 40 in the arm 3| .as the pin 39 in the arm 3!) is moved downwardly. During such movement, the arm 3| is moved upwardly, and the pin 40 is withdrawn from engagement with the rocker arm Such Withdrawal leaves the pin 40 in the outside of the slot 35a, as shown at Fig. 3. During such withdrawing movement of the inactive actuating pin, the associated reciprocable arm 3| is held in following engagement with the cam roller 44 by the latch lever 2| andthe latch biasing spring 25.

It will now be evident from the foregoing description of the operation that a particular feature of my invention is the loose or lateral lost motion mounting oi the actuating pins 39 and 40 in the

reciprocable arms

30 and 3|, in combination with the cylindrically dished surfaces lla and Hb in the rocker arm These con- -structional features prevent binding of the 'actuating pins against the sides of the spacing block 35a during actuating movement of the mechanism.

While I have shown but one preferred embodiment of my invention by way of illustration, many modifications will occur to those skilled in the art and 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'. A snap. acting device comprising a rocker sign pivotailymeunted intermediate its ends for movement between angularly spaced terminal ."lmitions.v a pair o! laten means positions, a pair ot movable latch releasing menibers alternately operable to release said latch means, and a pair of actuating members resiliently mounted on said latch releasing members and arranged alternatively to engage opposite ends of said rocker arm to move said rocker arm between said positions with a snap action upon release of the engaged latch means.

2. A snap acting device comprising a rocker arm pivotally mounted intermediate its ends for movement between angularly spaced terminal positions, a pair of latch levers including means arranged alternately to engage opposite ends of said rocker arm selectably to retain said arm in either of said positions, a pair of movable latch releasing members alternately operable to release said latch means,v a pair of actuating pins slidably mounted on said latch releasing members, respectively, and arranged alternatively to engage opposite ends of said rocker arm, and spring means interposed between said latch releasing members and said actuating pins and alternately operable to press said pins into engagement with said rocker arm thereby to move said rocker arm .between said positions with ,a snap action upon release of the engaged latch means.

3. A snap acting device comprising a rocker arm pivotally mounted for movement between angularly spaced terminal positions, a pair ot latch members including means alternately engageable with opposite ends of said rocker arms selectably to retain said arm in either of said positions, a pair of reciprocable members oppositely movable substantially transversely of said rocker arm, a pair of spring pressed actuating members carried by said reciprocable members and alternately engageable with opposite ends oi said rocker arm to move said arm between said positions, and cam means operable upon actuating movement of said reciprocable members simultaneously to effectlatch releasing lateral movement of the operative reciprocal member.

4. A snap acting device comprising a rocker arm pivotally mounted for movement between angularly spaced terminal positions, a pair of latch members including means alternately engageable with opposite ends of said rocker arm selectably to. retain said arm in either of said positions, a pair of reciprocable members oppositely movable substantially transversely of said rocker arm, a pair of spring pressed actuating pins loosely mounted upon said reciprocable members and positioned alternately` to engage opposite ends of said rocker arm to move said rocker arm between said positions, the surface of said rocker arm at points of engagement with said actuating pins being of cylindrical dished formation, andcamming means operable upon actuating movement of said reciprocable members simultaneously to effect latch releasing lateral movement of the operative reciprocating member.

5. A snap acting device comprising a rocker arm pivotally mounted formovement between angularly spaced terminal positions. a pair of latch members including means alternately engageable with opposite ends of said rocker arm selectably to retain said arm in either of said positions, a pair.I of reciprocable camiollower arms oppositely movable. .substantially transversely of said rocker arm. a pair of spring pressed actuating pins slidably mounted upon said cam follower arms. lost motion means providing s angularly spaced terminal positions. a pair of latch members including means alternately engageable with opposite ends of said rocker arm.

selectably to retain said arm in either of said positions, a pair of reciprocable cam follower arms oppositely movable substantially" transversely of said rocker arm, a pair of spring pressed actuating pins slidably mounted upon said cam follower arms, lost motion means providing limited lateral movement of said pins with vrespect to said arms, and camming'- means engageable with said cam follower arms upon actuating movement of said arms simultaneously to effect latch releasing lateral movement of the operative follower arm.

7. A snap acting device comprising a rocker arm pivotally mounted intermediate its ends for movement between angularly spaced terminal positions, a pair of latch levers disposed substantially' perpendicularly to said rocker arm and pivotally mounted vfor movement toward and away from opposite ends of said rocker arm, said latch levers including latching .i shoulders arrangedraltemately to retain said rocker arm in either of saidterminal positions, a pair of reciprocable cam follower arms disposed in substantially parallel spaced relation intermediate,

said latch levers and substantially transversely of said rocker arm. an operating member connect'ed simultaneously to slide said cam follower arms transversely of said rocker arm in opposite directions.l a 4spring pressed actuating pin' mounted upon each of said cam follower arms for longitudinal sliding and limited, transverse movementvwith respect thereto, said actuating pins being positioned for engagement with opposite ends of said rocker arm, and camming means engageable with said cam follower arms upon actuating movement of said arms simultaneously to move said follower arms transversely inA the same direction, the operative follower arm by said transverse movement engaging and releasing the operative latch lever, thereby to permit the associated spring pressed actuating pin to movesaid rocker arm between said terminal positions with a snap action.

- ROBERT W.

REFERENCES I The following references are of record. ifi the me of this patent: f

Goi a Feb. 2.0, 19,45