US3024333A - Electrical switch - Google Patents

Description

March 6, 1962 K. A. BRANDENBERG 3,024,333

ELECTRICAL SWITCH Filed Nov. 16, 1959 2 Sheets-Sheet 1 16 7 70 7/ 12 K I ll 3- --r 6 I PWHI I l 3 I 40 I I 44 4 02 v,1 -34 6 M k 525 I I- .54

KARL A. 5EANPENBERG ATTORNEY March 6, 1962 K. A. BRANDENBERG 3,024,333

ELECTRICAL SWITCH Filed Nov. 16, 1959 2 Sheets-Sheet 2 1 N VEN TOR. KARL 4. fieA/v m/ame 3,024,333 ELECTRICAL SWITCH Karl A. Brandenberg, Milwaukee, Wis., assignor t Square D Company, Detroit, Mich., a corporation of Michigan Filed Nov. 16, 1959, Ser. No. 853,288 6 flaims. (Cl. 200-159) This invention relates to electrical switches, and more particularly to an electrical switch adapted for use in conjunction with push-button pilot light devices used on electrical instrument and control panels.

Pilot lights are often used to monitor electrical circuits and, when so used, are mounted on switch and control panels remote from the devices to be monitored, with the indicating lamps in such pilot lights being connected into the electrical circuits of the monitored device. With this arrangement, either one of two types of failures will cause the lamp to become extinguished. The first of these failures is the interruption of the load current to the device to be monitored, this being the normal operation of the indicating lamp. In the second type of failure, the filament of the indicating lamp may become burned out and, in such event, the pilot light would not perform its required function of indicating a power failure to the monitored device.

To alleviate this condition, conventional push-button pilot lights were developed. These pilot lights are constructed such that when pressure is applied to the lens cap of the pilot light, a plunger arm is depressed which actuates an electrical switch which, in turn, establishes a test circuit, which is independent of the load circuit being monitored, for testing the filament circuit of the lamp in the pilot light. With this arrangement, defects such as a burned out pilot light lamp or a defective connection between the pilot light lamp and its source of electrical power .are thus detected.

One of the common sources of trouble in the use of push-button pilot lights is the inadvertent failure of the electrical switch used in conjunction with the pilot light mechanism. Because of the limited space requirements and long intervals of non-use, prior switches of this nature could not be depended upon for effective and trouble-free operation throughout the life of the switch.

A specific problem with such pilot light switchesis the inadvertent fouling and pitting of the electrical contact points therein. Such fouling may be caused by oxides or foreign material. Pitting is caused by electrical arcs occurring between the points of contact immediately upon making and breaking contact, such arcing eating away the contact points of the switch and causing premature failure of the same.

It has been found that such arcing and the resultant pitting of the contact points can be substantially reduced if the contact points can be made to rub or wipe one over the other upon making and breaking of contact. Such wiping action not only reduces arcing and pitting, thereby substantially increasing the life of the switch, but also establishes a more firm contact of the contact points to effect a more positive electrical connection therebetween. However, because of the space limitations, it has been impractical and unduly expensive hereto-fore to incorporate such wiping action into a pilot light push-button switch.

It is an object of the present invention to provide a push-button pilot light switch that is positive in action and dependable in use.

A further object of the invention is to provide a pushbutton pilot light switch in which the pitting and fouling of the contact points therein is substantially reduced.

A further object of the invention is to provide a pushice button pilot light switch having mating contact points which make and break contact with a wiping action.

A further object of the invention is to produce a pushbutton pilot light switch in which the useful life thereof is substatially increased over that of like prior devices.

A further object of the invention is to provide a push button pilot light switch that is simple and durable in construction, eflicient and reliable in operation, and that is economical to produce.

Briefly, the foregoing objects are accomplished by the provision of the push-button pilot light switch having a switch lever assembly pivotable to preselected contact positions by the actuating plunger arm of the push-button pilot light. The switch includes a housing having an interior switch chamber therein. The switch lever assembly is pivotally mounted intermediate its ends in the chamber for rocking movement therein, with one end of the assembly being connected to the plunger such that reciprocation of the plunger will pivot the switch lever assembly to predetermined switch contact positions. The switch lever assembly includes a pair of elongated flexible spring members which are disposed in superimposed face to face relation and retained together in such position at a point intermediate the ends thereof by a suitable connecting means. With this construction, the respective ends of the flexible spring members are free. At each end of the lever assembly movable contact members are resiliently clamped between the free ends of the spring mem has for limited pivotal movement therebetween. The construction is such that when the plunger pivots the lever assembly to a contact position, the respective movable contact member which is clamped between the free ends of the spring members contacts an associated stationary contact in the switch chamber with a rocking, pivotal action such that contact between such movable contact member and the stationary contact member is made with a wiping action.

In one form of the invention, the spring members are formed of a resilient material such as spring steel. However, at least one of such spring members may be formed of a rigid material.

Other objects and advantages of the invention will be apparent from the following description taken in conjunction with the drawings, in which:

FIG. 1 is a front elevational view of a push-button pilot light assembly having a pilot light switch constructed in accordance with the invention;

FIG. 2 is an enlarged bottom light switch with part thereof being shown in section, and taken along the line 22 of FIG. 1;

FIG. 3 is an enlarged upright vertical sectional view of the switch shown in FIG. 1, and showing the interior switch lever assembly in one contact position, and is taken on line 3-3 of FIG. 2, part thereof being shown in elevation;

FIG. 4 is a view similar to FIG. 3 but showing the switch assembly in another contact position;

FIG. 5 is a bottom plan View of the switch lever assembly shown in FIGS. 2, 3, and 4;

FIG. 6 is a side elevational view of the switch lever assembly shown in FIG. 5;

FIG. 7 is a bottom plan view of the modified form of the switch assembly shown in FIG. 5 and FIG. 8 is a side elevational view of the switch lever assembly shown in FIG. 7.

Although the invention is shown and described herein with reference to a switch adapted for use with a push-button pilot light assembly, it will be understood that the invention may be employed with any type of device requiring an electrical switch actuated by a re ciprocable plunger, such as a lever arm, push button, or the like.

plan view of the pilot Referring to FIG. I, there is shown a pilot light mechanism, generally designated at P, and having at its lower end a pilot light switch S constructed in accordance with the invention. A transformer T is interposed between the pilot light and the switch S and functions to supply suitable electric current to the lamp in the pilot light. The pilot light P is of conventional construction and includes a base having a lens or color cap 12 reciprocably mounted on the base by means of the ring nut 14, there being an interior, axially-shiftable, upwardlybiased sleeve (not shown) which normally retains the color cap in an upwardly biased position, as shown. To establish the filament test circuit heretofore mentioned, the color cap 12 is depressed and causes the sleeve to move downwardly which, in turn, efliects downward movement of the arm or plunger 16, such plunger thereby actuating the switch S to preselected switch contact positions in a manner to be described. Specific structural details of the pilot light are set forth in the copending US. patent application of Earl F. Mekelburg, Serial No. 702,940, filed December 16, 1957, and are not described herein since such structure forms no part of the present invention.

Selective switching from the monitored circuit to the filament test circuit and back again is effected by the switch S, now to be described, and which is substituted for the switch in the above copending application. The switch S includes a housing formed of two coacting mating halves and 22 (FIG. 3) which, when joined together, form an interior switch chamber 24. The halves 20 and 22 may be retained together by any suitable means such as the screws 26 (FIG. 2), such screws extending upwardly and being threadedly secured in the pilot light base 10. The mated halves 20 and 22 form also a bore 28 in which the pilot light arm or plunger 16 is received for reciprocable translating motion therein. The housing half 20 contains a recess 27 in its upper surface for receiving a portion of the transformer T.

Pivotally mounted within the chamber 24 is a switch operating lever assembly, generally designated as A, with which the present invention is particularly concerned. The assembly A includes a pair of elongated leaf members 32 and 34 joined in fiatwise face to face relation and retained in such relation by suitable connecting means, such as the rivet 36, with the respective opposed ends of the spring members being free and unattached. One or both of the members are resilient, flexible leaf springs. In the form illustrated in FIGS. 1 through 6, the member 34 is made of a suitable resilient material such as, for example, spring steel having suitable flexure characteristics, with the member 32 being formed of a relatively stiff and non-flexible material. Resiliently clamped at each end of the assembly A between the respective free ends of the spring members 32 and 34, for rocking movement fiatwise, are the U-shaped bridging or movable contacts and 42 of electrical conducting material. With this construction, the contacts 40 and 42 are free to rock flatwise substantially universally in their clamped position between the free ends of the spring members. To prevent the contacts 40 and 42 from slipping out of such clamped position and from rocking appreciably edgewise, the member 32 is provided with constraining means in the form of retaining tabs 44 and 45 for the member 40 and tabs 46 and 47 for the member 42. The tabs are loosely received in aligned apertures in the respective movable contacts, thereby allowing flatwise rocking action of the contact member, yet preventing edgewise movement in any direction from such clamped position. The outer portion of the arms of the U-shaped contact 40 are silver-tipped, to form good electrical contacts, as indicated at 4011 and 40b, while the outer portion of the arms of the U- shaped contact 42 are silver-tipped to form good contacts, as indicated at 42:: and 42b.

In the present instance, the switch lever assembly A is pivotally mounted within the chamber 24 by means of pivot engaging means in the form of the spaced ears 52 and 54 on the spring member 34, such ears being loosely received at their ends in notches 52a and 54a in the housing and rockably mounted between the ridges 56 and 57 in the respective housing halves. Such rocking pivotal movement of the switch assembly is flatwisc or in a direction generally normal to the faces of the assembly.

Pivotal movement of the assembly A is effected by movable means which, in the form illustrated, is the plunger 16. The plunger 16 has a semi-circular notch 60 for connectably receiving the right end portion of the switch assembly A. In the preferred form, the member 32 has an outer extending portion 62 which is received in the notch 60 to form the connection between the plunger and the switch assembly. If the switch S is to be used independently of the pilot light P, the plunger 16 may be replaced by any like actuating rod or plunger, such as a conventional reciprocable push button having a notch similar to the notch 60 for receiving therein the end of the assembly A.

Interposed in the path of the respective movable contacts on the assembly A for contact therewith are the stationary contacts 70, 71, 72, and '73, which may be secured in the respective housing halves by any suitable attaching means such as the threaded stud shown in FIG. 3.

In operation, as the plunger 16 is displaced to its lower position, contact between the movable contact 42 and the stationary contact 73 is broken and contact between the movable contact 40 and the stationary contact 71 is established, as shown in FIG. 4. When the plunger returns to its upper position, the movable contact 4-3 and the stationary contact 71 break contact, while contact is established between the stationary contact 73 and the movable contact 42.

It will be noted that, as a result of the manner of mounting the movable contacts 40 and 42 between the leaf members, the movable contacts make and break contact with the respective stationary contacts with a wiping action by rocking fiatwise from their normal clamped position between the respective free ends of the spring members 32 and 34. Such rocking action results in sufiicient rubbing or wiping action of the movable contaots over the stationary contacts when contact therebetween is established or interrupted to alleviate the fouling and pitting of the contact points.

A modification of the switch lever assembly A is shown in FIGS. 7 and 8, wherein each of the members and 82 are formed of a resilient flexible material, such as spring steel, the members being joined intermediate their ends by the rivet 84. U-shaped movable contacts 86 and 88 are clamped between the respective free ends of the spring members 80 and 82 in the same manner heretofore described with respect to the contacts 40 and 42 of the assembly A. By forming both of the spring members 80 and 82 of a resilient material, effective flexibility in the wiping action at the time of contact between the mov able and stationary contacts is obtained.

Having thus described my invention, I claim:

1. An electrical switch mechanism adapted for use with a push-button pilot light of the type having a reciprocable plunger arm for actuating the switch whereby the arm is reciprocable to switch contacting positions in response to pressure applied to the lens cap of the pilot light, said switch mechanism comprising a housing having an interor switch chamber therein, at least one stationary contact member disposed in said chamber, an elongated switch lever assembly pivotally mounted intermediate it ends in the chamber for rocking movement in a direction generally normal to the faces of the assembly about a first axis extending transversely of the lever, one end of the assembly being connected to the plunger so that reciprocation of the plunger pivots the switch lever assembly to predetermined switch contact positions about said axis, said switch lever assembly compriing a pair of elongated movable members disposed in flatwise face to face relation, at least one of said members being a leaf spring, and connecting means retaining the members together in such face to face position at a point intermediate their ends, and a movable contact disposed at at least one end of the assembly and positioned for contact with the stationary contact member when the assembly is pivoted to one of its contact positions, said movable contact being resiliently clamped between the free ends of the members for flatwise rocking movement therebetween against the clamping pressure of the free ends of the members about axes parallel to said first axis, respectively, whereby the movable contact member slides over the stationary contact with a wiping action when contact therebetween is established or interrupted.

2. A switch according to claim 1 wherein there are a plurality of stationary contacts disposed in the chamber and said movable contact member is a U-shaped member having its base portion clamped resiliently between the members and having contact portions on the outer portions of such U-shape adapted for contacting certain of said stationary contact members.

3. A switch mechanism comprising a body, two elongated members carried by the body, means engaging the members between their ends and supporting the members in face to face relation to each other for concurrent rocking flatwise substantially as a unit about a first axis extending transversely of the members, at least one of said members being resiliently flexible flatwise at at least one end portion for yieldable relative movement toward and away from the adjacent end portion of the other member in the rocking direction, a contact disposed between the members at said end portions of the members and resiliently clamped therebetween by the resilient one of the members for rocking relative to the members about a second axis parallel to and spaced from said first axis, means constraining the contact from displacement from between the members while permitting the contact to rock about said second axis in opposition to the clamping pressure of the members, movable means for rocking the members, said movable contact having contact portions spaced endwise of the members from said second axis, a complementary contact carried by the body and having contact portions disposed in the path defined by the movable contact portions as the movable contact rocks with said members about said first axis in one direction, whereby upon engagement of the complementary contact portions of the movable contact and complementary contact followed by continued rocking of the members about the first axis in said one direction, the movable contact is caused to rock about said second axis, and the contact portions of the movable contact are caused thereby to wipe the contact portions of the complementary contact.

4. The structure according to claim 3 wherein the other of the members is rigid, and the movable means engages the rigid one of the members for so rocking the members.

5. The structure according to claim 3 wherein both of said members are resilient.

6. An electrical switch mechanism comprising two elongated leaf members in flatwise facing relation to each other, at least one of said members being resiliently flexible flatwise toward and away from the other, means engaging the members intermediate their ends and supporting them for flatwise rocking substantially as a unit about a first axis extending transversely of the members, a contact disposed at one end of the members between their faces and resiliently clamped therebetween by the resilient one of the members, means constraining the contact from displacement edgewise of the members from between the members while permitting the contact to rock flatwise of the members about a second axis extending parallel to the first axis in opposition to clamping pressure of the members, said contact being a U-shaped memher having its base portion clamped resiliently between said first mentioned members and having contact portions spaced endwise of the members from said second axis, a stationary contact in the body having contact portions disposed in the path of movement of the contact portions, respectively, of the movable contact for engagement by the movable contact portions as the movable contact moves with said members in one direction, whereby upon engagement of the contact portions of the movable contact with those of the stationary contact followed by continued rocking of the members about the first axis in said one direction, the movable contact is caused to rock about said second axis and cause its contact portions to wipe across the contact portions of the stationary contact, and movable means engaging the other one of the members for rocking the members.

References Cited in the file of this patent UNITED STATES PATENTS Runner Nov. 19, 1935

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