US3604879A

US3604879A - Lever-operated microswitches

Info

Publication number: US3604879A
Application number: US827733A
Authority: US
Inventors: Donald Courtney Beer
Original assignee: Otehall Ltd
Current assignee: Otehall Ltd
Priority date: 1968-05-29
Filing date: 1969-05-26
Publication date: 1971-09-14
Anticipated expiration: 1988-09-14
Also published as: CH513506A; DE1927202A1; FR2061836A5; GB1272066A

Abstract

An electric switch, particularly a microswitch, comprises an insulating casing housing the switch movement or mechanism. A rockable actuating member for the mechanism is mounted in an opening in the casing and, inside the latter, operates on a member of the mechanism. Rocking movement of the actuating member actuates the switch mechanism and causes a contact-carrying arm of the mechanism to snap over from one contact position to another. The actuating member is rockably mounted in the opening in the switch casing by means of a cylindrical boss portion of the actuating member engaged in generally part-cylindrical bearing recesses formed respectively in opposite sides of the opening.

Description

United States Patent [72] Inventor Donald Courtney Beer Newick, England [2]] Appl. No. 827,733 [22] Filed May 26, 1969 [45] Patented Sept. 14, 1971 [73] Assignee Otehall Limited Sussex, England [32] Priority May 29, 1968 [33] Great Britain [31 25819/68 [54] LEVER-OPERATED MICROSWITCHES 8 Claims, 5 Drawing Figs.

[52] US. Cl 200/172 B, 200/67 D [51] Int. Cl 110111 3/02 [50] Field of Search 200/67,

67.7, 68, 67 D, 67 B, 172 A, 172 B, 164,154

[56] References Cited UNITED STATES PATENTS 2,518,219 8/1950 Brasty 200/164 X Primary Examiner-David Smith, .1 r.

Attorney-Holcombe, Wetherill & Brisebois ABSTRACT: An electric switch, particularly a microswitch, comprises an insulating casing housing the switch movement or mechanism. A rockable actuating member for the mechanism is mounted in an opening in the casing and, inside the latter, operates on a member of the mechanism. Rocking movement of the actuating member actuates the switch mechanism and causes a contact-carrying arm of the mechanism to snap over from one contact position to another. The actuating member is rockably mounted in the opening in the switch casing by means of a cylindrical boss portion of the actuating member engaged in generally part-cylindrical bearing recesses formed respectively in opposite sides of the openmg.

LEVER-OPERATED MICROSWITCHES The present invention relates to electric switches, more particularly microswitches, of the type which have hitherto been operated via a plunger or button. The plunger or button is mounted in an opening in the switch casing which houses the switch movement or mechanism and inside this casing operates on a member of the movement. Depression of the plunger actuates the switch movement and thereby moves a contact-carrying member of the movement from one position to another.

The present invention has for an object to provide an arrangement of switch of the above type in which the plunger may be replaced by a rockable actuating member, such as a lever member or dolly, which may operate on the member or portion of the movement which is normally operated by the depression of the plunger. To this end, the said opening in the switch casing has two bearing recesses formed respectively in opposite sides of the opening for pivotally mounting a boss portion of a rockable actuating member. This enables the same opening in the switch casing, and thus the same casing, to be used for either a plunger or rockable actuating member. In the latter case, the boss portion of the actuating member is pivotally mounted in the beating recesses in the opening and the actuating member includes a cam portion projecting into the switch casing and bearing on said member or portion of the switch movement, whereby pivoting of the actuating member in one direction actuates the movement in order to move the contact carrying member from its one position to the other, and an externally projecting portion or part by which the actuating member may be rocked. Conveniently, the boss portion of the actuating member is generally cylindrical and the bearing recesses formed in opposite sides of the opening are of substantially part-cylindrical shape.

The externally projecting part of the actuating member may comprise a lever. The latter may be a separate part secured to the boss portion or may, alternatively, be integral therewith. Conveniently, the lever is formed from a metal strip whilst the boss and cam portions of the member are moulded from synthetic plastics material, such as nylon, and are moulded onto the metal strip. The lever may be directed to the right or left with respect to the pivoting axis of the boss portion. Alternatively the lever may be moulded of plastics material and may be moulded integrally with the boss and cam portions.

The invention is used with particular advantage in lever operated switches. Hitherto, when it was required to produce a lever-operated switch of the type above referred to, a lever was arranged to bear on the plunger and it was necessary to provide additional means on the switch, remote from the plunger, for forming a fulcrum for one end of the lever and about which the lever could be pivoted so as to depress the plunger and actuate the switch movement. With the present invention, it is unnecessary to provide a separate fulcrum for the lever. The fulcrum is the rocking axis of the actuating member of which the lever forms a part and which is substituted for the plunger.

In one embodiment of the invention, the switch movement comprises a spring-loaded, overcenter mechanism arranged to cause the contact carrying member to snap over from its one or rest position to the other or actuated position in response to actuation of the mechanism by the actuating member. The mechanism automatically returns the contact-carrying member to said one position, under the action of its spring, upon release of the actuating member.

In prior lever-operated switches where a separate fulcrum is provided for the lever which bears on the plunger, the lever has a certain amount of side play, which is not ideal. With the present invention, the fact that the lever forms part of or is integral with the boss portion of the actuating member and the spring return action of the overcenter switch mechanism presses the boss portion into its bearing recesses tends to eliminate side play.

By a suitable arrangement of the cam of the actuating member, the spring-loaded, over center mechanism may be locked in the actuated position and prevent automatic restoring of the contact member to its rest position upon release of the actuating member. When using such a locking arrangement, the equipment to which the switch is fitted must incorporate its own on and off tripping mechanism for positively returning the actuating member to its initial position so as to effect release of the overcenter mechanism and return of the contact-carrying member to its rest position.

In order that the present invention may be more readily understood, reference will now be made to the accompanying drawings, in which;

FIG. 1 is a side view of a lever-operated microswitch constructed in accordance with the invention, the switch being illustrated with the facing sidewall of its casing removed so as to show the switch mechanism,

FIG. 2 is a fragmentary view of the switch of FIG. 1 illustrating the use ofa plunger in place of the lever,

FIGS. 3 and 4 are fragmentary views of a switch similar to that illustrated in FIG. 1 with the cam portion of the lever-type actuating member designed to effect locking of the overcenter mechanism of the switch in its actuated position, and

FIG. 5 is a fragmentary view of a switch similar to that shown in FIG. 1 and illustrating the use of a dolly as the actuating member.

Referring to FIG. 1 of the drawings, the snap action microswitch includes a moulded insulating casing 1 provided with two fixing apertures 2. It is a two-way switch in which a terminal 3 may be connected through a hinged contact-carrying arm or member 4 to one or other of the

terminals

5 and 6. The contact-carrying arm is hinged at one end to a support member 7 which is an integral extension of the terminal 3 and has its end remote from the terminal 3 supported in slot 8 formed in the top wall of the casing l. The contact-carrying arm is a bifurcated member and the free ends of the fork arms 14 form a hinge connection with an inclined part of the support member. The support member has a slot 15 extending along a major portion of its length and the free ends of the fork arms are formed with projecting portions 16 which rest against transverse shoulders (not shown) at opposite sides of the slot 15 whilst the transverse shoulders 17 adjacent the projecting portions 16 rest on the support member.

The end of the contact-carrying arm 4 remote from its hinge is provided with contacts 9 for engaging fixed contacts 10 and 11 associated respectively with the

terminals

5 and 6.

The contact-carrying arm is moved about its hinge selectively to engage the contacts 9 with the contacts 10 and 11 by the over center action of a rocker member 12 hingedly connected at one end to the arm 4 and, at its opposite end, to a leaf spring or strip spring 13 which is held under compression between the end of the rocker member and the support member 7.

Through the rocker member, the spring resiliently urges the moving contact-carrying arm against its hinge connection with the support member 7.

The rocker member 12 extends through the slot 15 and is hinged to the arm by a tongue portion 19 bearing against one end of a rectangular opening 20 in the arm 4 and transverse shoulders 22 at opposite sides of the tongue portion resting on the arm on opposite sides of the aperture therein. At its opposite end the rocker member is hinged to the leaf spring 13. At this end, the member 12 is bifurcated and each fork arm 23 has a laterally projecting portion 24 forming a transverse shoulder 25. The free ends of the arms 23 are bent downwardly and the shoulder 25 engage respectively behind a pair of spaced lugs 26 which project from the adjacent end of the spring 13. The arms 23 also rests on aligned transverse edges of the adjacent end of the spring between the lugs 26.

The other end of the spring 13 is hinged to the support member 7. A tongue 27 at this end of the spring projects into the slot 15 and engages against the transverse end wall 28 of the slot. Moreover, transverse shoulders on opposite .sides of the tongue portion rest respectively against the support member.

The switch is is operated by an actuating member 29 pivotally mounted in the wall of the casing 1 so as to be rockable about an axis substantially parallel to the hinge axes of the various members of the overcenter mechanism. The actuating member is pivotally mounted in a rectangular opening 30 in the casing by having a cylindrical boss portion 31 engaged in a pair of opposed part-cylindrical bearing recesses 32 moulded in opposite sides of the opening. Projecting into the interior of the casing is a cam portion 33 of the actuating member which has a slightly curved cam surface 34 engaging a tongue portion 35 projecting from the adjacent end of the spring between the lugs 26. The tongue portion 35 is bent so that the cam surface 34 engages the upper surface of the tongue portion.

Projecting externally of the switch casing is a lever 36 which forms part of the actuating member, the lever being rigidly secured to the boss portion 31. The lever is formed from metal strip, for example, stainless steel strip, whilst the boss and cam portions of the actuating member are mounded from synthetic plastics material, such as nylon. The boss and cam portions are moulded onto' the downwardly projecting end portion 37 of the lever. This downwardly projecting end portion has notches 38 cut in opposite sides thereof and, where the end portion is embedded in the material of the boss portion, the material of the boss portion fills the notches during the moulding operation so that the lever is securedly fixed to the boss portion.

The contact-carrying arm 4 and the rocker member 12 are normally biassed by snaps over leaf spring 13 in the rest position shown in the drawing in which the contacts 9 and are in engagement. In this rest position, the end face 39 of the cam portion 33 of the actuating member abuts the inside of the casing 1, as shown, to limit movement of the overcenter mechanism. When the lever 36 is depressed, the actuating member 29 pivots in an anticlockwise direction about its rocking axis and the cam surface 34 acts on the tongue portion 35 to depress the left-hand ends of the spring and rocker member so that the line joining the hinge connections of the rocker member with the contact carrying arm 4 and the spring moves overcenter with respect to the hinge axis of the arm 4 on the support member 7, whereupon the arm 4 snaps over I from its upper or rest position shown in the drawing into its lower or actuated position in which the

contacts

9 and 11 are in engagement. Release of the lever arm permits the overcenter mechanism and actuating member to return to their initial positions under the action of the spring 13 and the contact-carrying arm snaps back into the rest position.

FIG. 2 illustrates the replacement of the rockable actuating member 29 comprising the boss, cam portion and lever by a conventional plunger 40. The plunger is slidably mounted in the rectangular opening 30 in the switch casing 1. The plunger is of rectangular cross section and projects externally of the switch casing. its lower inner end bears on the apex of the bend in the adjacent end of the rocker member and is formed with outwardly projecting flanges 41. Alternatively, the lower end of the plunger may bear on the spring 13. The flanges 41 serve as stops which engage the inside of the casing, as shown, to limit upward movement of the plunger under the spring return action of the overcenter mechanism. As will be apparent, depression of the plunger actuates the overcenter "mechanism to snap over the arm 4 into the position in which "it'sjcontacts "9 and 11 engage and, upon release of the plunger, the mechanism returns the arm to its position.

so that its cam surface 44 curves or nearly curves back on itself. In the rest position of the switch, the cam surface bears on the tongue portion 35 of the spring 13, as shown in FIG. 3, and

the overcenter mechanism in the same position as that illustrated in FIG. 1. Upon depression of the lever 45, the cam surface 44 moves in an anticlockwise direction and depresses the tongue portion of the spring so that the mechanism is actuated. In doing so, the actuating member moves to the position shown in FIG. 4. in this position, the action of the spring [3 on the cam surface tends to rotate the actuating member in an anticlockwise direction and not to return the actuating member in a clockwise direction to its initial position. Further anticlockwise movement of the actuating member is, however, prevented by the cam portion 42 abutting the inside of the switch casing and thus the cam portion and spring interengage to lock the overcenter mechanism in its actuated condition. In order to release the overcenter mechanism, it is necessary positively to raise the lever 45 and pivot the actuating member in a clockwise direction. When the elbow 46 of the cam surface moves over the apex of the tongue portion 35, the lock is released and the contact arm is snapped back into its rest position under the spring-return action of the overcenter mechanism.

Referring to H6. 5, in this embodiment the actuating member is in the form of a dolly 48. As in the previous embodiments, it includes a cylindrical boss portion 49 pivotally mounted in the opposed part-cylindrical bearing recesses 32 in the switch casing l. Projecting inwardly from the boss portion is a spigot 50 which has a rounder inner end 51 engaging the tongue portion 35 of the spring 13. Projecting externally of the switch casing from the boss portion is a dolly operating portion 52. When the dolly is in the position illustrated, the contact arm is in its upper position shown in FIG. 1. Movement of the dolly in an anticlockwise direction causes. the spigot 50 to depress the tongue portion 35 of the spring and thereby snap the contact arm into its lower position. in this position, the spigot is in engagement with the spring at a position just over the apex of the bend 53 in the tongue portion 35 and the overcenter mechanism is locked with the contact arm in its lower position. The spring tends to pivot the dolly in an anticlockwise direction but this is prevented by the spigot engaging the inside of the casing. Movement of the dolly in the opposite direction releases the overcenter mechanism and permits the latter to snap the contact arm back into its upper position. The dolly may be a one-piece moulding of plastics material.

it will be apparent from the above description that the present invention readily permits a particular switching mechanism and its casing to be provided with any one of a variety of different types of actuating member which is selected according to requirements. One opening 30 in the switch casing is all that is necessary for suitably mounting any selected actuating member.

While particular embodiments have been described, it will be understood that modification can be made without departing from the scope of the invention as defined by the appended claims. For example, the lever arm 36 may be arranged to project in the opposite direction from that shown in the drawings, in which case, the cam surface 34 will also be inclined in the opposite direction from that shown in the drawings so that the cam surface bearson the spring 13 between the fork arms 23 of the rocket member 12. Moreover, the cam surface 34 may be alternatively arranged to act on the rocker member 12 or onadjacent portions of both the spring 13 and the rocker member. Any suitable construction of overcenter mechanism may be used, in place of that specifically illustrated, to control movement of the contact-carrying arm. I claim:

1. In a microswitch having a casing and a switch mechanism mounted within said casing, said casing having an opening therein for reciprocally receiving a plunger which is capable of projecting into said casing to engage said mechanism for actuating same upon depression of said plunger, the improvement comprising two concave bearing recesses formed respectively in opposite sidewalls of said opening, and a rockable actuating member mounted in said opening in place of said plunger, said actuating member having a boss portion pivotally mounted in said bearing recesses and a cam portion projecting into said casing to engage said mechanism and adapted to actuate said mechanism upon rocking of the actuating member in said recesses.

2. A microswitch as claimed in claim 1, wherein said switch casing is formed from insulating material, and said bearing recesses are formed in the insulating material defining said sidewalls of the opening as generally part-cylindrical bearing recesses, and wherein said rockable actuating member comprises a cylindrical boss portion pivotally mounted in said part-cylindrical bearing recesses, said cam portion projecting from said boss portion into said switch casing and bearing on a member of the switch mechanism, and an externally projecting part by which said actuating member is rocked to actuate the mechanism.

3. A microswitch as claimed in claim 2, wherein said boss and cam portions of said actuating member are integrally moulded from plastics material and said externally projecting part comprises a lever formed from metal strip and moulded into said boss portion.

4. A microswitch as claimed in claim 2, wherein said actuating member is in the form of a dolly and comprises a boss, cam and dolly operating portion integrally moulded from plastics material.

5. A microswitch as claimed in claim 2, wherein said switch mechanism comprises a spring-loaded, overcenter mechanism arranged to cause a movable contact carrying member to snap over from a rear position to an actuated position in response to actuation of said mechanism by said actuating member, said mechanism automatically returning said contact carrying member to its rest position, under the action of the spring, upon release of said actuating member.

6. A microswitch as claimed in claim 5, wherein said switch mechanism comprises a movable contact carrying arm arranged to snap over from a rest position to an actuated position about an axis substantially parallel to the axis of said boss portion upon actuation of the spring-loaded, overcenter mechanism, said mechanism comprising a rocker member connected to said contact arm and extending transversely to said arm axis to project on the opposite side thereof to that on which said rocker member is connected to said arm, and a compression spring connected to said rocker member at a position on said opposite side of said arm axis and arranged to act on said rocker member so as to urge the connection between said rocker member and said arm towards said arm axis, the connections of said rocker member to said arm and said spring being so disposed that a line joining said connections moves overcenter with respect to said arm axis upon actuation of said mechanism in order to cause said arm to snap over from said rest position to said actuated position, and wherein said opening mounting said rockable actuating member is disposed adjacent said connection between said spring and rocker member and said cam portion engages an adjacent part of one of these members.

7. A microswitch as claimed in claim 6, wherein said cam portion, in said rest position of said contact arm, engages said switch casing to serve as a stop limiting movement of said mechanism.

8. A microswitch as claimed in claim 6, wherein said cam portion is adapted to lock said spring-loaded mechanism in said actuated position of said contact arm and prevent automatic restoring of said contact arm to its rest position upon release of said actuating member.