US2444529A - Electrical switch - Google Patents

Description

July 6, 1948. M. PUSTER ELECTRICAL SWITCH Filed April 4, 1947 G i' i'onzegs Patented July 6, 1948 Louis M. Pastor,

Knoxville, Tenn., assignor to Robertshaw-Fulton Controls Companma corporation of Delaware Application Aprll 4, 1947, Seriai No. 789,428 '7 Claims. (Cl. 200-67) This invention relates to electrical switches, and more particularly to electrical switches of the snap action type.

It is an object of the present invention to provide an improved electrical switch of the snap action type which is so constructed as to minimize sparking.

Another object of this invention is to provide an improved snap action electrical switch wherein the actuating member may be moved through a predetermined distance without initiating the snap action.

Another object of this invention is to provide an improved snap action electrical switch of the type last characterized wherein the snap action is independent of the speed with which the actuating means is moved.

Another object of an improved snap action electrical switch wherein the initial movement of the actuating means tends to urge the electrical contacts together with increased pressure up to the instant the snap action becomesefiective to separate the contacts abruptly.

Another object of this invention is to provide an improved snap action electrical switch which is composed of a minimum number of easily fabricated parts so that it is inexpensive to produce.

Another object of this invention is to provide an improved snap action electrical switch which may be readily adjusted to predetermine the characteristics of the snap action.

Other objects will appear as the description of the invention proceeds.

The invention is capable of receiving a variety of mechanical expressions, only one of which has been illustrated on the accompanying drawings, and it is therefore to be expressly understood that the drawings are for purposes of illustration only, and are not intended to be a definition of the limits of the invention, reference being had to the appended claims for that purpose.v

Referring in detail to said drawings, wherein the same reference characters are used to designate corresponding parts in the several figures,

Fig. 1 is a perspective elevation of an embodiment of the present invention;

Fig. 2 is an enlarged cross section on the line 22 of Fig. 1;

Figs. 3 and 4 are views corresponding to Fig. 2 but illustrating the position of the parts at different times during the movement of the actuating means; and a Fig. 5 is a cross section on the line 65 of Fig. 2.

this invention is toprovide- I her I it and cover it 20 and thereby Referring in detail to the drawings, the parts of the switch are shown as enclosed within a housing of any suitable size, configuration and material, illustrated as comprising a. body memof insulating material providing therein a switch chamber l2. Cover i I may be permanently secured to the body member it] after the parts are assembled, although if preferred provision may be made for rendering the cover detachable from the body member to gain access to the parts of the switch.

Mounted on the body member it approximately midwayof its length is an upstanding wedgeshaped fulcrum projection it, and extending downwardly from the cover it is a like projection it so disposed that the apices of the two projections are in alignment when the cover i l is in position on the body member it. Mounted be-. tween said fulcrum projections it and i5 is an elongated leaf spring it of any suitable width, the apicesof said projections engaging the opposite faces of said spring at approximately the midpoint of its length. At its extremities said spring is received in the approximately v-shaped or U- shaped recesses ill and it of a pair of depending brackets is and 20 secured in any suitable way to the cover i l as by rivets 2|. Leaf spring it has a length such as to be somewhat longer than the length between the bottoms of the recesses l1 and it so that when said spring is supported at its ends in said recesses it must assume a bowed configuration and then, when the cover is installed on the body member so that the aligned apices of the projections It and i5 engages said spring midway of its length as shown in Fig. 2,

said spring is forced to assume a somewhat sinusoidal form, that is, with one half of the spring bowed upwardly, as shown at '22 in Fig. 2, and the other half bowed downwardly, as shown at 23 in Fig. 2.

Provision is preferably made for adjusting the extent to which the sring it may be bowed, and to this end at least the bracket is is made sumciently resilient so that it may be bent to varying extents, and suitably mounted in the end wall of the cover It is a short threaded stud or screw 26, rotatable in a nut 25 embedded in the material of the cover, with the inner end of the screw it engaging the socketed end of the bracket is so that by adjustment of the screw inwardly or outwardly with respect to the cover the socketed end of the bracket is may be varied in position to vary its effective distance from the bracket vary the extent to which the Sprin 48 is hnmnll block is, although has a stop,

Mounted on and approximately midway of the section 23 of spring I6 is a movable contact member of any suitable construction, here shown as in the form of an inverted U-shaped block 26 of any suitable insulating material (see Fig. attached to the spring IS in any suitable way, as by one or more rivets 21, and having its downwardly extending extremities 28 and 29 bridged by a metal piece 30 with further insulation 3| interposed between the bridge member 30 and the the latter may be omitted if desired. In the form here shown, contact member 26 is provided with one or more suitable contact elements, shown as a pair of studs 32 and 33 retained in the member 25 in any suitable way and having below the bridge piece 30 contact heads 34 provided with contact surfaces 35. Mounted in any suitable way in the body member ID are one or more suitable opposed stationary contact elements, shown as contacts 36 and 31 provided with contact faces 38 in alignment with contact faces 35. Each of said stationary contacts 36 and 31 is shown as mounted on a metallic plate 33 suitable way, as by a screw 40 engaging threads on a tubular conducting element 4| which extends to the outer face of the body member In where a contact screw 42 similarly engaged with said tubular conducting element 41 may be used to secure any suitable electrical conductor 43 in conductive relationship with the tubular member 4|. Any other suitable provision for connecting the contact elements with any suitable conduc'torsmay be used if preferred.

Any suitable means may be used for actuating the spring l8. As shown, a thrust member 44, which may be opera-ted manually or by any suitable automatic mechanism, is reciprocatingly mounted in an aperture 45 of the cover and has its inner extremity 46 normally engaged with the section 22 of .the spring l6 approximately midway of its length. As here shown, thrust member 44 carries a depending inverted U -shaped bracket 41, and the downwardly extending legs of said bracket 41 carry a cup-shaped spring retainer 48 that is reciprocatingly mounted in a recess 49 in the body member Ill. Mounted in said recess 49 between the bottom of said recess and said cupshaped spring retainer 48 is a coil spring 50. Cupshaped spring retainer 48 also has-secured thereto an upwardly extending post 5| in alignment with but somewhat spaced from the thrust member 44 so that, as shown in Fig. 2, said post 5! is always out of contact with the section 22 of spring IE to provide some freedom of relative movement until said spring snaps into engagement with said post as shown in Fig. 4. The bottom of recess 49 shown as a circular shoulder 52, to limit the downward movement of retainer 48 to that position at which the spring l6, now engaged with the end of post 5!, retains the desired sinusoidal shape.

The parts of the switch are normally in the relative position shown in Fig. 2 with the downwardly bowed section 23 of spring l6 holding the movable contact member 26 in such position that contacts 34, 34 are firmly engaged with the stationary contacts 36 and 31. The upwardly bowed section 22 of spring I6 is in engagement with the inner end of the thrust member 44 but slightly spaced from the upper ehd of the post 54 Assuming that the thrust member 44 is to be manually actuated, thrust member 44 is pushed inwardly when it is desired to open the switch. The first inward movement of thrust member 44 merely secured to the body member I0 in any 4 flattens the section 22 of spring It as shown in Fig. 3, after which further inward movement of the thrust member 44 presses the cup-shaped spring retainer 48 downwardly as viewed in the drawings, moving the retainer inwardly into the recess 49 against the tension of the spring 5!] until it is stopped by shoulder 52. The flattening of the section 22 imposes increased compression on the section 23 of said spring 18 so as to press the movable contacts into engagement with the stationary contacts withincreased pressure. When the spring section 22 by inward movement of the thrust member 44 passes the position shown in Fig. 3 in which section 22 is unbowed, the spring l6 instantaneously snaps to the condition of opposite curvature shown in Fig. 4 wherein the section 23 of the spring is bowed upwardly and the section 22 of the spring is bowed downwardly. Thereby the movable contacts are abruptly separated from the stationary contacts. The contacts are then retained in their separated relationship, with the circuit open, as long as thrust member 44 is held in its inward position shown in Fig. 4, in which position the coil spring 50 is under compression. Therefore, when pressure isreleased on the thrust member 44 thesection 22 of the spring I6 is moved upwardly as viewed in the drawings by the action of the spring 53 until having passed the flattened relationship shown in Fig. 3 the spring I6 again abruptly reverses its direction of curvature, resuming the relationship shown in Fig. 2 and instantaneously moving the movable contacts into contact with the stationary contacts.

By use of a stop shoulder 52 as illustrated the spring retainer 48 is stopped at such a predetermined point as is necessary to bring the part 22 of spring ii to rest upon the end surface of the post 5|, but eliminating the possibility of a further inward actuation of the thrust member 44, which if moved further inward would develop a more inward bowing of the section 22 of spring 16 that would in turn introduce a somewhat non-sinusoidal curve of the spring l6, whereby the section 23 of said spring would have a tendency, under the above condition, to become somewhat straight, permitting the contact 34 to move inwardly toward the stationary contact 36 with the possible danger of causing an undesired arcing effect. Also, as is sometimes the case, if it is desired to have another contact engaged by a contact on member 26 in this outward position of the section 23 of spring it, said additional contact being suitably located above contact 34, excessive inward movement of member 44 would cause varying contact pressure on such contact with possibly a false break" of the contact but not enough to eliminate arcing. Furthermore, the use of this shoulder 52 as illustrated is a means of stopping the spring retainer 48 at that predetermined point which is necessary to bring the part 22 of spring 15 to rest upon the end of the post 5i so as to render the return force mechanism, including spring 50, retainer 48 and post 5!, capable of instantaneous action the moment pressure is released from thrust member 44.

It will therefore be perceived that whether the thrust member 44 is actuated manually or by any suitable automatic mechanism the speed at which said member 44 is moved is entirely independent of the abruptness with which the relatively movable contacts are moved into and out of engagement with the stationary contacts by the snap action oi the reverseiy bowed spring l6. When.

thrust member 64 is being moved inwardly to the.

flattened relationship of section 22 compression imposed on spring i6 is such as to press the movable contacts into firmer and firmer contact with the stationary contacts up to that instant at which the snap action takes place, and this in itself has a tendency to minimize sparking. The spring It may be nicely adjusted by actuation of the screw 24 so as to effect the desired bowing of the spring It. The switch is composed of a relatively few number of parts all of which Y are easy to fabricate and assemble and therefore a switch in conformity with the present invention can be manufactured at minimum expense.

While it is'preferred to embody the invention I in a switch which is actuated automatically when the thrust member M is released, it will be apparent to those skilled in the art that as respects certain features of the invention they may be embodied in constructions wherein the spring I6 is moved from one to the other of its extreme positions in both directions by suitable means extending to the exterior of the housing and controlled either manually or automatically. Furthermore. while the illustrated embodiment is one wherein the contacts are normally held,

in closed position and the thrust member 44 is actuated to hold the contact elements in open position, this relationship can be readily reversed so that the contact elements are normally retained in open position and engaged only when thrust elementM is actuated as above explained.-

While the embodiment of the invention illustrated on the drawings has been described with considerable particularity, it is to be expressly understood that the invention is not limited thereto as the same is capable of receiving a variety of mechanical expressions as will now be apparent to those skilled in the art, while changes may be made in details of construction, arrange-- ment, proportion of parts, etc., other provisions may be made-for mounting and connecting the relatively movable contacts with outside conductors, other means may be used for returning the spring it to its normal relationship when pressure is released on the thrust member M, etc., without departing from the spirit of the present invention. Reference is therefore to be had to the appended claims for a definition of the invention.

What is claimed is:

1. In a snap action electrical switch, in combination with a housing providing a switch chamber, a leaf spring in said chamber, means mountsaid bowed spring sections, at least one stationary contact element carried by said housing for cooperation with said movable contact element, and means cooperating with the other of said bowed spring sections approximately midway of its length for reversing the direction of curvature of said last'named section and thereby the direction of curvature of said first named section to .move said contact elements with respect to each other.

2. In a snap action electrical switch, in combination with a housing providing a switch chamber, a leaf spring in said chamber, means mounting said leaf spring at its ends, opposed fulcrum member engaging said leaf spring approximately midway of its ,length, the length of said spring being greater than the distance between said mounting means whereby with the cooperation of said fulcrum members said spring 'is' bowed in opposite directions on opposite sides of said fulcrummembers, at least one movable contact element mounted approximately midway of one of said bowed spring sections, at least one stationary contact element carried by said housing for cooperation with said movable contact element, means cooperating with the other of said bowed spring sections approximately midway of its length for reversing the direction of curvature of said last named section and thereby the direction oi. curvature of said first named section to move said contact elements with respect to each other, and means for adjusting the extent of curvature of said leaf spring.

3. In a. snap action electrical switch, in combination with a housing providing a switch chamber, a leaf spring in said chamber, means mounting said leaf spring at its ends, opposed fulcrum members engaging said leaf spring approximately midway of its length, the length of said spring being greater than the distance between said mounting means whereby with the cooperation of said fulcrum members said spring is bowed in opposite directions on opposite sides of said fulcrum members, at least one movable contact element mounted approximately midway of one of said bowed spring sections, at least one stationary contact element carried by said housing for cooperation with said movable contact element, means cooperating with the other of said bowed spring sections approximately midway of its length for reversing the direction of curvature of said last named section and thereby the direction of curvature of said first named section to move said contact elements with respect to each other, and spring means tensioned by the reversal of curvature of said leaf spring for returning said spring to its original curvature when pressure is released on said second named spring section.

ing said leaf spring at its ends, opposed fulcrum members engaging said leaf spring approximately midway of its length, the length of said spring being greater than the distance between said mounting means whereby with the cooperation of said fulcrum members said spring is bowed in opposite directions on opposite sides of said fulcrum members, at least one movable contact element mounted approximately midway of one of 4. In a snap action electrical switch, in combination with a housing providing a switch chamber, a leaf spring in said chamber, brackets provided with recesses in which the ends of said spring are mounted, opposed fulcrum members engaging the opposite faces of said spring approximately midway of its length, said spring being of greater length than the distance between and thrust means cooperating with other of said spring sections approximately midway of its length and adapted to reverse the direction of therewith.

5.'In a snap action electrical switch, incombination with a housing providing a switch chamber, a leaf spring in said chamber, brackets provided with recesses in which the ends of said spring are mounted, opposed fulcrum members engaging the opposite facesof said spring approximately midway of its length, said sprin being of greater length than the distance between. the bottoms of the recesses in said brackets whereby with the cooperation of said fulcrum members the sections of said spring at opposite sides of said fulcrum members are bowed in opposite directions, a movable contact member mounted on said spring approximately midway of the length of one of said bowed sections, stationary contact means carried by said housing for cooperation with said movable contact member, thrust means cooperating with other of said spring sections approximately midway of its length and adapted to reverse the direction of curvature thereof to thereby reverse the direction of curvature of the first spring section and move the movable contact member abruptly with respect to the stationary contact means when said thrust member has moved a predetermined distance to flatten the spring section associated therewith, and means cooperating with one of said brackets for flexing the same to vary the distance between the bottoms of the recesses in said brackets.

6. In a snap action electrical switch, in combination with a housing providing a switch chamber, a leaf spring in said chamber, brackets provided with recesses in which the ends of said spring are mounted, opposed fulcrum members engaging the opposite faces of said spring approximately midway of its length, said spring being or greater length'than the distance between the bottoms of the recesses in said brackets whereby with the cooperation of said fulcrum members the sections of said spring at opposite sides of said fulcrum members are bowed in opposite directions, a movable contact member mounted on said spring approximately midway of the length of one of said bowed sections, stationary contact means carried by said housing for cooperation with said movable contact member, thrust means cooperating with other of said spring sections approximately midway of its length and adapted to reverse the direction of curvature thereof to thereby reverse the direction of curvature of the first spring section and move the movable, contact member abruptly with respect to the stationary contact means when said thrust member has moved a predetermined distance to flatten the spring section associated therewith, and a spring tensioned by the reversal of fiexure of said second section to restore said second section to its "original direction of flexure when pressure is released on said thrust member.

7. In a snap action electrical switch, in combination with a housing providing a switch chamber, a leaf spring in said chamber, means providing recesses in which the ends of said spring are mounted, the distance between the bottoms of said recesses being less than the length of said spring, opposed fulcrum members carried by the opposite walls of said chamber and engaging said spring approximately midway of its length at opposite faces thereof whereby the sections of said spring at opposite sides of said fulcrum membars are bowed in opposite directions, a movable contact member carried by one of said sections approximately midway of its length, stationary contact means carried by the wall of said chamber in position for cooperation with said movable contact member, a. thrust member extending to the exterior of said housing and extending interiorly of said chamber intoposition for cooperation with the other of said spring sections approximately midway of its length, a member aligned with said thrust member and adapted to be engaged by said last named spring section when said thrust member is actuated to flatten said section, and a spring cooperating with said last named member and tensioned when the curvature of said second spring section is reversed by operation of said thrust member, reversal of curvature of said second spring section effecting reversal of curvature of said first spring section to move said movable contact member abruptly relatively to said stationary contact means and said second named spring automatically restoring the curvature of said spring sections when pressure is released on said thrust member.

LOUIS M. PUSTER.

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