US3432632A

US3432632A - Electrical snap action switch

Info

Publication number: US3432632A
Application number: US581306A
Authority: US
Inventors: Werner Schenke
Original assignee: J&J Marquardt KG
Current assignee: J&J Marquardt KG
Priority date: 1965-09-23
Filing date: 1966-09-22
Publication date: 1969-03-11
Anticipated expiration: 1986-03-11
Also published as: GB1154003A; DE1291399B

Description

March 11, 1969 w, SCHENKE 3,432,632

ELECTRICAL SNAP ACTION SWITCH Filed Sent. 22, 1966 INVENTOR. WERNER SCHENKE A r ramvxs United States Patent Sch 37,766 us. Cl. 200-67 4 Claims Int. Cl. H01h 21/24, 21/40 1 ABSTRACT OF THE DISCLOSURE An electrical switch includes a housing with an interior cavity having a pair of spaced fixed contacts therein. The switch mechanism includes an actuating angle lever which is povotally mounted at its one end and, includes two portions at right angles to each other one of which extends across the housing cavity. A movable contact arm extends through the cavity and through a slot in a support angle, and between two stop elements formed by the housing, and it includes a contact button formation on each side disposed between the fixed contacts. A tipping member is articulated to the lower end of the portion of the angle lever, which extends across the cavity, and to the movable contact arm. A spring is secured at one end to the supporting angle, which extends across the cavity, and at its opposite end to the contact arm. The single spring element both aids in the snap actuation of the contact by the depression of a ram member against the angle lever and it also permits the return of the contact to a neutral position after the actuating ram member is released. In addition, the movable contact is moved through an arcuate path so that there is a wiping action between the movable contact and the associated one of the fixed contacts during the actutation of the switch, so that the contacts are cleaned by this action.

This invention relates, in general, to switch constructions and, in particular, to a new and useful electrical switch which includes a movable contact arm supported on an angle support member and biased 'by a spring so that it forms an angle with the axis of the spring in the neutral position and urges the actuating lever for the switch to a rest position against the actuating button.

The invention deals, in particular, with an electric switch which includes a contact arm switch lever which is snappable between two fixed contacts and which carries at its free end a contact which is movable selectively into association with the two fixed contacts. The switch of this type includes an actuating lever and a tipping member held between the lever and the movable contact carrier. Switches of this nature are known under the general designation of snap or micro switches. These special characteristic is the snap action switching of the contacts.

In order to avoid the disadvantage of the various known snap and jump systems,'wh0se contact'iorce decreases to zero as the switchingprocess is approached, various designs have been proposed in which a contact force sutficient for the switching energy is maintained until the switching process takes place, that is, the breaking of the contacts. Thus, for example, there are switches with snap systems having a precession lever and a contact lever which act one upon the other. Such complicated arrangements require costly adjustment. Another construction provides a minimum contact force only in one direction and it is therefore unsuitable as a reversing switch. There are other known switch constructions which include rocker links or control members or counterpoises and these have a plurality of complicated parts which result in considerable manufacturing cost. Switches without suitable resili- 3,432,632 Patented Mar. 11, 1969 once or storing capacity require an additional spring element. While it is possible to design a switch element as a spring element by adapting the proper form, the high grade material required causes an undesirable increase in cost of the switch.

Other switches are known in which only the spring elemerit is current conducting. They are not suitable for permanent operation because the heating due to current flow causes fatigue of the spring material which may lead to failure of the switch. When the fixed contacts are made with lagging elasticity in relation to the switching contact, in order to prevent the gradual decrease in the contact force before switching, such a structural arrangement does not sutficiently fulfill its purpose, and, because of the small cross section of the elastic contact carriers, there is an increase of electrical resistance or a reduced switch energy. In addition, insufficient riveting of the contacts constitutes an additional source of electrical disturbance. In accordance with the present invention, there is provided a simple switch construction in which two fixed contact carriers are arranged to present fixed contacts within the interior of a housing on each side of a movable contact which is carried on an arm member which may be moved between two stops of a simply constructed support angle. The support angle also provides a means for mounting a spring which is advantageously arranged so that its axis will be disposed between the two fixed contacts and it will bias the movable contact carrier in a position against one stop formed on the angle member. The switch is characterized by a simple construction which includes an actuating lever which is pivoted in the housing and which is connected through a tipping member to the movable contact arm. The tipping member is advantageously supported between the actuating lever and the movable arm on knife edges. In the neutral position at which one of the fixed contacts is engaged by the movable contact, the actuating lever will be biased upwardly against the actuating button or ram.

A further feature of the construction is that when the movable arm is in a neutral position, it forms .a certain angle in respect to the axis of the spring which corresponds substantially to the angle which is formed by the movable contact arm and the spring when it is in .an actuated position engaged with the other contact. Because the switch requires only thesimple parts including the actuating lever, the tipping member, the movable contact carrier arm and the spring, it is a simple matter to construct such a spring and to assemble the parts within a switch housing. The construction is such that, until the snap contact jumps over, the contact pressure is maintained at a finite value. In addition, with the arrangement. of the switch moving parts, the contacts are moved to slide on each other during the switching process resulting in a known very useful self-cleaning effect.

A further advantage of the construction is that the ram or actuating button may be slowly displaced in or- ;der to etfect. a good utilization of the current loadability of the contacts because the contact force always exhibits a finite value. The above advantages make is possible to use a switch of the invention for application where snap switches of conventional design could not be used because of their tendency to faulty operation. This is especially so in respect to use in a system'which is subject to high vibration and there is a requirement for shock stability. The switch parts are arranged so that when the actuating force is removed, the displaced movable contact arm is automatically returned to its starting or neutral position without any additional returning spring or other parts. Thus, the switch can be used as a reversing switch.

Accordingly, it is an object of the invention to provide angle in respect to the axis of its associated spring at each end position.

A further object of the invention is to provide a micro switch which includes a housing in which is located a supporting angle which provides a mounting for a spring for a movable contact arm which may be moved to cause a contact at one end to engage selectively one or the other of two fixed contacts and which has an opposite end which will be urged against a stop member of the angle member in each position.

A further object of the invention is to provide an electric switch which is simple in design, rugged in construction and economical to manufacture.

The various features of novelty which characterize the invention are pointed out with particularly in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention.

In the drawings:

FIG. 1 is a perspective view of a microswitch constructed in accordance with the invention;

FIG. 2 is an enlarged partial elevational and partial axial sectional view of the switch of FIG. 1;

FIGS. 3 and 4 are diagrammatic representations of parts of the switch indicated in a neutral position and a reversing or actuated position, respectively and FIGS. .5 through 8 are diagrammatic representations of the switch illustrating the forces acting in different positions of the switch.

Referring to the drawings, in particular, the invention embodied therein comprises a :microswitch having a substantially box-shaped switch housing a which includes a cover portion b permanently enclosing an interior snap mechanism chamber. The cover b is fastened to a complementary housing part a such as by rivets or other suitable fastening means 6.

In accordance with the invention, the housing defines an interior space permitting assembly of the necessary switch parts in a simple manner. The switch includes fixed contact members d and e which include portions projecting outwardly to the exterior of the housing and defining spaced terminals to permit the switch to be plugged into an electrical circuit. The contact members d and e carry fixed contacts 7'' and g, respectively, which are arranged in fixed spaced relationship within the interior of the housing. The snap actuating mechanism for the switch includes a supporting angle member generally designated h which includes a fiat portion 71' which rests against one wall of the interior of the housing, a transverse portion h which extends across the housing and through the opposite wall, and angled portions h' and h" which are arranged on the exterior of the housing for mechanically mounting the switch, for example. The supporting angle h includes an opening in the flat part h which forms a pivot support v for an actuating angle lever member k. The actuating lever member k is pivotally connected through a tipping member r to a movable contact arm or switch lever n. The movable contact arm n extends through a slot x defined in the transverse portion h" of the supporting angle h. The walls of the part h" on each end of the slot x define fixed stops t and u, respectively.

An actuating ram or button I is slidably mounted in a wall of the housing and bears against the actuating lever k. In order to facilitate alignment of tthe button I with the actuating lever k, the button is provided with a longitudinally extending groove which receives the actuating lever. A helical spring m is hooked at its one end on the transverse portion h" of the supporting angle 11.

In the neutral position, indicated in FIG. 3, the spring in urges a movable contact member 0' against the fixed contact 1 and the contact carrier arm n is disposed at an angle a in respect to the axis of the spring. The spring in is connected to the movable arm at its end opposite its connection to the supporting angle h at the location C in FIGS. 3 and 4. In the position indicated in FIG. 3, the end of the carrying arm n is pressed against the knife edge p formed on the tipping member r which, in turn, includes a knife edge s which bears against the actuating lever k to maintain it in a position urging the button I upwardly.

The point of suspension for the helical spring m is located approximately midway between an upper stop t and a lower stop u formed by the transverse portion h" of the supporting angle h. The deflection angles a and a of the contact arm n are determined by the end positions of the arm against the respective stops t and u.

The switch is operated as follows: The lines designated A-B and C-D are imaginary median lines of the contact arm switch lever n and the helical extension spring m, respectively. Upon exerting pressure on angle actuating lever k through button, the lever is moved downwardly against the knife edge s of the tipping member 1' toward the line A-B of the contact arm switch lever it. After the equilibrium position of the actuating mechanism is passed, the end of the contact arm switch lever n which initially rests against the stop u jumps to the stop I and the movable contact 0 disengages from the fixed contact 1 and the movable contact 0 engages the fixed contact g. In this end position, as indicated in FIG. 4, the switch lever arm n has been moved through the line C-D of the spring m in a sudden movement. The switch position indicated in FIG. 4 persists as long as the force of the actuating button remains active.

Upon removal of the actuating force from the actuating button I, the movement of the composite snap mechanism automatically occurs in a reversed direction due to the resilience of the spring m acting on the actuating lever k. Thus, there will be a switching back to the neutral position or starting position without requiring any additional actuating parts. The knife bearing edge s describes an arc around the pivot bearing v so that a sliding movement is transmitting through the tipping member r to the contact arm switch lever 11 and hence to the reversing contacts 0 and o. In this manner, the contacts are wiped clean so that there will be no tendency for any pitting or similar arcing effects to remain on the contact. In addition, this action will ensure that there will be no likelihood that the contacts become welded in a closed position since they will be forced opened.

The forces acting on the parts of the switch during actuation thereof will be best understood by reference to FIGS. 5 through 8. When operating button I is depressed, a force is exerted on angle lever k and this force is transmitted, through tipping member r, to contact arm n. There acts, on contact arm n, the component H of the operating force exerted through button I and angle lever k. This component H of the operating force acts at the hinged junction of tipping member r and operating lever or contact arm n. The force F of spring m also acts on contact arm n. These forces result in a reaction or bearing force L2 on stop it and L1 on fixed contact f. If the forces H and F are divided into their horizontal and vertical components, the action of the forces on contact arm n is as indicated in FIG. 5.

With increasing swinging of angle lever k in a clockwise direction, in accordance with the increased distance with which button 1 is pressed into the switch housing, there is a corresponding decrease in the component Hy of the force H, and which component Hy extends perpendicularly to the longitudinal axis or length of contact arm n. On the other hand, the component Hx of force H, and which extends longitudinally of contact arm n, increases.

Simultaneously, the bearing forces L1 and L2 decrease. When force component Hy of force H has attained the value 0, the bearing force L2 has also dropped to 0. This is the case when contact arm n and tipping member 2' are exactly aligned as extensions of each other, as indicated in FIG. 6. At this time, only the component Fy of spring force F acts as a force perpendicular to contact arm n. This produces the reaction force L1 on fixed contact 1. This fixed contact now represents the fulcrum for contact arm n, which turns counterclockwise under the action of force component Fy. The action line A-B (FIGS. 3 and 4) of contact arm 12 now swing through and across the action line C-D (FIGS. 3 and 4) of spring m. After the parts pass through the labile or unsteady position, the movable contact on the end of contact arm n snaps from fixed contact 7 to the opposite fixed contact g. However, the end of contact arm n articulated to tipping member r has first snapped from stop it to stop t.

FIG. 7 illustrates the position of the parts after the reversal of the contact engagement and removal of the force on the operating button I. In the position of the part shown in FIG. 7, only the spring force F is effected, and this produces reaction forces L1 on fixed contact g and L2 on stop t. The component F"x of spring force component Fx, and Whose action line is spaced a distance a from the fulcrum v of angle lever k, produces, 0n angle lever k, a moment acting counterclockwise. Consequently, both tipping member r and angle lever k snap back to their starting position. After the parts reach the position shown in FIG. 8, the portion of contact arm n bearing on step t snaps from stop I to stop it under the action of the spring force component Fy. When contact arm n passes through the action line C-D of spring m, the movable double contact snaps from contact g to contact 1 so that the starting or initial position of the parts is reattained.

Thus, there is obtained a snap acting switch of small dimensions which requires very little technical expense and offers high safety of operation. A switch of this character is especially useful for systems in which the actuating button I must be moved slowly. The actuation is such that the contacts break away sharply so that burning off of the contacts and continuous sparking which would be likely when disconnecting inductive loads, for example, will not occur and thus the switch will not be subject to early deterioration of malfunctioning.

While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.

What is claimed is:

1. An electrical switch comprising a housing defining an interior switch cavity, a pair of spaced fixed contacts mounted in said cavty, an actuating angle lever pivotally mounted at its one end in said cavity and having a first portion and a second portion extending at an angle to said first portion in a direction across said housing cavity, a supporting angle pivotally supporting said actuatin g lever and having a portion extending across said cavity with an opening therethrough and walls defining a stop at each end of the opening, a movable contact arm extending through the opening of said support angle and having movable contact means adjacent one end disposed between and selectively contactable with a respective one of said spaced fixed contacts, a spring having one end secured to said angle member and an opposite end extending toward said fixed contacts and secured to said movable contact arm, a tipping member pivotally connected between said second portion of said actuating lever and the end of said contact arm which extends through said opening away from said spaced fixed contacts, an

actuating button engageable with said actuating lever and being movable against said actuating lever to displace said actuating lever from the neutral to an actuated position,

said spring basing said actuating lever against said actuating button in a neutral position and causing one end of said contact arm to rest against one of the steps of the opening of the supporting angle and to present said contact means in engagement with one of said fixed contacts, said actuating lever being movable to snap said contact arm to a position moved across the axis of said spring and to rest against the other of said stops defined at the other end of the opening in said supporting angle, the axis of said contact arm being movable through a plane beyond the axis of said spring when said spring is snapped to an actuated position and when it is returned from an actuated position to a neutral position.

2. An electrical switch, according to claim 1, wherein said spaced fixed contacts include portions extending through said housing defining at the exterior of the housing spaced plug terminals for plugging said switch into an electrical circuit.

3. An electrical switch, according to claim 1, wherein said actuating button is slidably mounted in said housing and said supporting angle includes a portion extending outwardly from said housing for connecting said switch.

4. Anelectrical switch, according to cliam 1, wherein said tipping member is pivotally connectedto said actuating lever and said contact arm by knife edge pivotal connections.

References Cited UNITED STATES PATENTS 2,728,826 12/1955 Lauder 200670 2,800,546 7/1957 Reitler 200670 ROBERT K. SCHAEFER, Primary Examiner. DAVID SMITH, JR., Assistant Examiner.