US2054139A - Snap switch - Google Patents

Description

Sept. l5, 1936. N.c. SCHELLNGER 2,054,139v

SNAP SWITCH Filed Oct. 22, 1934 2 Sheets-Sheet 1 JNVENTOR.

NEA/70N .JCHMLENGEB Sept. l5, 1936. N. c. SCHELLENGER 2,054,139

SNAP swITcH Filed Ot. 22, 1954 2 Sheets-Sheet 2 INVEN TOR 5CH LL E1s/GER'.

Patented Sept. 15, 1936A UNITED srxrlazs^ SNAP SWITCH,

Newton C. Schellenger, Elkhart, Ind., assignor to Chicago Telephone Supply Co., Elkhart, Ind., a corporation of Indiana Application October 22, 1934, Serial No. 749,322

s claims. (ci. zoo-6 7) Myinvention relates to electric power switches, 'and more particularly to electric power switches of the fast-break or snap action type which are adapted for use in radio receiving sets. AAt the present time there is a great demand for exceedingly high capacity switches, which are very small in physical dimensions. It is desir- It is obviously an exceedingly difficult task to i 15 construct a switch embodying the necessary ruggedness and durability of construction to withstand the extreme requirements mentioned above, without exceedingV the given physical dimensions imposed. Conversely, it' has been practically im- 20 possible to build a small switch of the desired size, without sacrificing physical. strength and current carrying capacity of the component parts thereof. 1

Heretofore, devices of the prior art have been 25 built to conform, as nearly as possible, to the small sizes desired by the trade, whereby relatively light materials' have been utilized in the construction of their component parts, in order that theiroverall dimensions might be corre- 30 spondingly' small. The contact pieces in such switches have been formed from very' light stock, and have been of substantial length to provide the degree of resiliency necessary to insure a certain amount of contact pressure.

35 'Ihe contact pressure thus obtained has not been sufficient to provide a very low contact resistance between contacts. Furthermore, the lightness of the stock from which such contacts have been made, combined with the excessive '40 length necessary for their resiliency, has resulted in these contact pieces having'a relatively high internal resistance, which has often resulted in 'their overheating, melting or burning-out, upon being subjected to heavy currents.

l4:5 These conditions have been considerably aggravated, and the periods of usefulness of the contacts further shortened, by the constant hammering to which the present day snap switch mechanisms subject them. In these devices, the

50 movable contact, motivated by the customary snap switch mechanism, is driven, by the unre' strained force of the drive spring and inertia of the moving parts, into violent engagement with some suitable abutmentor stop, which acts to 55 define the limits of movement of the movable contact. This collision of the moving 'parts upon the stationary parts often results in` rebounding or- Vbouncing of the movable contact upon the stationary contact, whereby excessive arcing ensues therebetween, accompanied by a consequent burn- 5 ing thereof, resulting in further increasing the resistance of the switch.

It is one object of my invention to provide a high capacity power switch suitable for radio work-which is of relatively small dimensions.

It is another object of my invention to provide a power switch of rugged construction having a minimum number of current carrying parts.

It is still another object of my invention to provide .a power snap switch wherein the actuating'spring also supplies the contact pressure between the contacting members.

It is still another object of my vinvention to provide a power snap switch wherein the spring supplying the pressure between contacting members 'is insulated from the power circuit thereby insuring the spring against damage from overheating. A

It is still another object of my invention to provide a power switch of the snap action type, wherein the resistance of the actuating spring is utilized to provide a cushioning, or breaking effect on the moving parts.

It is a further object of my invention to provide a snap switch in which the contacts are in forceful wiping engagement to maintain a polished contact surface.

It is still a'further object of my invention to provide a switch wherein overheating of the parts in circuit and a portion of the arcing between contacts, is eliminated.

It is still a further object of my invention to provide a switch unit wherein molded mountings or special preformed bases are dispensed with.

With the above objects in view, and others an- 40 cillary thereto, I prefer to accomplish one embodiment of? my invention Aas follows:

I provide'a substantially planar disc of insulation as the base or mounting for the component parts of my switch. The disc is of such size as to permit all of various parts, when assembled thereon, to lie a reasonable distance within its borders. 'I'he disc may be of any desired size and shape consistent with the size and shapeof switch to be mounted thereon, but since I contemplate a switch for use in a radio set, which can be associated with Ia. rheostat or volume control unit, I prefer to make it of circular configuration about one and one-half inches in diameter.

15 a switch actuating crank or cam. which has a y Pivoted adjacent one edge of the disc or base is an arm, also of insulating material, whi'ch is adapted to oscillate back and forth across the base in'v a plane spaced slightly from the base and substantially parallel thereto. The arm has .an Aelongated aperture adjacent one of its ends through which a stationary pivot pin carried by the base extends to constitute the pivotal bearing. The elongated pivot aperture permits the arm to have reciprocatory movement in substantially a radial direction, in addition to its oscillatory movement about thepivot.

The stationary pivot pin carried by the base extends sufciently far beyond the surface of the arm to aiord a pivotal bearing or trunnion for pitman arm pivoted eccentrically at its extremity. The pitman passes through an opening in a thrust plate, which is carried by the arm, andv stantially normal to the plane of thesurface of the arm as well as to the longitudinal axis (or central radius) thereof.

Disposed about the pitman is a helical spring, bearing at one of its ends against a portion of the pitman adjacent the cam or crank, and bearing at its other end against the thrust plate. The spring is of the compression type, and acts to drive the arm to the extremes of its movement upon actuation of the crank. Since this structure is substantially the same as disclosed in my application bearing Serial No. 576,232, filed November 20, 1931, I do not consider it necessary to go more fully into the operation of the cam, pitman, spring and arm. Let it suffice to say that the various elements, above described, combine to impart, through the usual lost motion drive, an oscillatory snap-action movement to the arm when the cam is actuated by external means.

The arm at the end opposite its pivotal mounting is less wide than at its intermediate portion. Each side edge is off-set toward the central axis of the arm to form a reduced end p ortion thereon. The end edge of the reduced end portion of the arm is of general arcuate shape. Located adjacent the center of this reduced end portion is a small aperture or window.

A metallic contacter of a thickness 4to loosely lie between the arm and base, is positioned beneath the reduced end portion thereof so that one of its edges passes beneath the small window. Thiscontactor is essentially flat at the side which is disposed against the base to permit it to be slid thereover with a minimum amount of friction. However, its end portions adjacent the edges of the reduced portion of the arm are turned upl is provided with an upturned ear which lies within the window to constitute a pivot for the contactor upon the arm. The edges of the reduced portion of the arm and the upturned ends of the metallic member which lie substantially about them, are suitably spaced to afford free rocking movement of the contacter about its pivoton the arm through a range ofapproximately 4 or 5 degrees of inclination.

Secured to l the base are two relatively heavy metal terminalcontacts of substantial width, which have upturned end portions adjacent the arm disposed substantially perpendicularly to the faces, and are so spaced and positioned as to be engaged simultaneously by the respective outwardly extending ends of the contactar carried bythe arm.

The arcuate paths traversed by the arcuate edge portion of the arm, and the extreme end portions of the contactonassociated therewith, may be said to be, for facility of explanation, segments' of concentric circles, since both of them have a common center. The circle in which. the arcuate edge of the arm lies, is the circle of less magnitude, which happens to be, in the present structure, the appropriate magnitude. The contact faces of the terminal contacts are. disposed alonglines which are tangent to the lesser circle, above described,` and which are chords to the greater circle. The terminal contacts are both positioned so that a corresponding portion of the contact surface of each extends within the greater circle, with their remaining portions, respectively, positioned without. Thus, the contact faces of the terminal contacts are disposed to arrest the movement of the armby intercepting the ends of the contactor carried thereby. This would effect quite an abrupt stop of the moving parts, tending to cause a rebound with consequent arcing and scoring o1' the contacts, followed by an ultimate wedging action which would cause the parts to stick and jamb, were it not for the elongated pivot slot by which the arm is mounted. L

The helical drive spring, always being under compression, tends to force the arm away from the pivot pin, whereby said pin occupies a position at the end of the elongated slot which ls nearenthe end edge ofthe arm. However, when the arm is actuated to drive the contactor into engagement with the terminal contacts, the contact faces of said contacts, being disposed as has hereinbefore been described, function as cam surfaces to force the arm to recede in substantially a radial direction, against the expansive force of the spring until the kinetic energy of the moving parts has been dissipated.

As has hereinbefore been mentioned, the contactor is pivoted adjacent the center line of the arm, whereby the force and pressure with which each of its yends Aengages its respective terminal contact, is evenly distributed between them and is equalized. Thus, in the mechanical movement explained in the last paragraph, the forces exerted by the terminal contacts in acting as cams, are transmitted equally through both legs of the contacter to the arm substantially along its 1onf is practicable. v

'I'he potential energy of the actuating spring is,

- in ther above described manner, converted not only to drive the arm in an oscillatory movement,

but, also, to exert a cushioning force upon the ment of the arm resulting therefrom is always against the springs resistance' to compression.

6 VThe force of the spring is, likewise, utilized to larity in the appended claims.

create a maximum contact pressure, such ashas never heretofore been possible without a prohibitive increase in operating torque, since the receding movement of the movableA contact is in a direction substantially along the -springs most effective leg of resistance to compression; i. e., substantially along its longitudinal axis.

The recession of the arm u'pon engaging the terminal contacts .permits the contactor to be wedged into more -intimate engagement with the contacts, due to the combined inertias of the arm, and its associated parts. Thus, the movable contacts are caused to forceably wipe over the contact faces of the stationary contacts to maintain them in highly polished condition. In this man- The novel features which I consider characteristic of my invention are set forth with particu- The invention itself, however, both as to organization and mode of operation, together with the various objects and advantages/thereof, may be understood with reference to the annexed specification when considered in the light of the accompanying drawings, in which:

Fig. l is aftop plan view of my invention with the switch illustrated in open-circuit position.

Fig. la'is a partial plan veiw of my invention as shown in Figfl', with parts removed to illustrate the relationship of the component parts of the switch when in off positi0n.

Fig. 211s a top plan view of my invention showing the parts of the switch positioned on dead center between the extreme oi and on positions.

Fig. 3 is a, top plan view of my invention with the switch illustrated in closed-circuit position.

Fig. 3a is a partial plan view of my invention as shown ln Fig. 3, with parts removed to illustrate the relationship of the component parts of the switch when in on position.

Fig. 4 is a mid-sectional view taken along line 4--4 of Fig`. 2. v

Fig. 5 is an enlarged fragmentary View offthe switch arm illustrating the movement of the short-circuiting contactor about its pivot in said arm.

Fig. 6 is a side elevational view of a combined switch and volume control unit, illustrated with parts broken away to show the relation of parts; the switch being made in accordance with my invention.

Fig. '7 is a'fragmen'tary top plan view of a modi- :lied form-of my invention, `'illustrated as being 'embodied'in'a double pole switch. i j Fig. 8 is a fragmentary top plan view of another iorm of double pole switch made in accordance with the present invention. l

Fig. 9 is a perspective view of -one form of a short-circuiting contactor which is pivoted'upon the arm.

Fig. 10 isA a sectional view taken iii-I0 ,in Fig. 7.

Fig. 11 is an enlarged sectional view taken `along line- Ill-II i'n Fig. 8. A

`:Referring more specically to the drawings, in which similar reference characters refer to like parts throughout: v f

In Figs. 1 to' 4 inclusive, I designates a switch -terial, an

along line duced end portionof the arm 5.

mounting or base which is comprised of a circular disc lof insulation.

Mounted eccentrically in the disc, adjacent the of the switch as will hereinafter appear.

Disposed upon the disc 'l is a metallic spider 3, which has projecting armsk arranged symmetrically on both sides of its center line. The spider is secured to the disc by the pivot pin 2 at one end, and by an integral downwardly depending nger 4 at the other, which extends through an opening adjacent the center of disc 2, and is clinched overtoengage'the disc. (See Fig. 4.)

'Ihe largest portion 2b of the shank. of the pivot'pin 2 projects suiiiciently far above the top surface of the spider 3 to space the .arm 5-there from. The arm 5 is composedofinsulatory mahas an elongated pivot hole 6 adjacent one.of its ends. (See Figs. 1a and 3a.)

'Ihe arm 5 is positioned upon the pivotpin'2 in such a manner that the enlarged portion 2a of the'pivot pin shank extends through the slot 6, and the under face of the arm adjacent thereto bears against the shoulder portion formed by the largest portion 2b of the p in shankv 2.

An actuating crank or cam 1 is carried by the pivot pin 2 above the arm-5, and is spaced from the arm by the shoulder formed by the .enlarged portion 2a of the shank of the pin, and by a suitable washer. (See Fig. 4.)

The arm 5 is provided with a pair of openings 8, through which legs 9 of a thrust platev I0 extend to securely fasten it thereto. The thrust plate I0 is provided with a central aperture II,.-

cam shown herein is described and claimed in'- my copending application Serial No. 576,232, illed November 20, 1931. y

The metal spider 3 has the vextremities of its arm portions turned Aupwardly substantially 90 to the base I. The upwardly disposed ends I 5' of the spider serve as kick-offs for the switch' mechanism, and, as such, project through openings 8 in the arm to provide fulcrums for the spring and pitman -to operate upon.

The movement of the arm is limited by the upturned ends I6 of the spider 3, which act asv stops. Otherstops are provided at I1 tol limit the movement ofthe cam 1 at the extremes 'of its effective stroke. Y y

Disposed beneath the arm 5 at the end opposite its pivotal mounting is an integral, metallic, contact short-circuiting orbridging member I8, which has an upturned ear I9 disposed within an opening 20 in the arm. One side 20a of this opening iscut on a bias for reasons to appear hereinafter.

The end` portionsZI and 22 of vthe bridging member or contactor I8 are turned upwardly substantially to lie about the edges of the re- These end portions are spaced from and are substantially parallel to thev edges of the. arm, whereby the contactor is permitted 'freedom of movement about its pivotal bearing through 4 or 5 degrees of inclination relative to the arm 5. This movement is desirable, as will appear more fully hereinafter, since it permits the contactor to equalize the contact pressure between the stationary terminal contacts 23 and 24.

The stationary terminal contacts 23-24 are preformed piecesof metal, formed to provide perl,

pendicular contact faces adjacent one of their ends, and terminal portions 26 at their opposite extremities. They are fastened to the base I by means of rivets 21.

The contact'faces 25 of the terminal contacts Kare disposed partially within the path of movement of the ends 2I-22 of the contactor- I8, and are thereby positioned to arrest movement thereof, when the switch is being actuated to on position. If the arcuate path of travel of the ends 2I--22 of the contactor were generated beyond the terminal contact faces, it would be seen that said faces are disposed along lines which form'chordsto the arc so generated. Hence, when the contactor is actuated into engagement with the terminal contact faces, a wedging action ensues, which tends to ldisplace the contactor in a direction away from said 'contact faces. Since the contactor engages the v arm, this displacement thrust is imparted thereto.

When the switch is in off` position as shown in Figs. 1 and 1a, the toggle spring I3 keeps the a-rm 5 in a position that forces the outside end of its pivot slot 6 against the pivot pin. However, when the switch is in. -on position as is slown inv Figs. 3 and 3a, the wedging action between the contactor I 8 and the stationary terminal contacts 23- 24, being transmitted to the arm 5 as explained in the last paragraph, causes said arm to tend to recede from the contacts in an axial or radial direction byvirtue of the pivot slot 6.

` Since the /cam and pitman pivot is stationary, and by virtue of the cam stop I1, when th-e switch is in the position illustrated in Figs. 1-1a, the compression spring I3 is aiorded'a rigid bearing against'whichto exert itsjexpansive force. The

arm, therefore, upon its recessive movement,`

causes the thrust plate I0 to recede. along the pitman, whereby the spring is forced into ahigher degree of compression.' In this manner, the direct a contacts through the arm and contactor.

By comparing the relative positions of the contactor and stationary terminal contacts in Figs. 2

and 3a, it will be seen that the contact faces are forcefully wiped across substantially their entire extremity by the contactor. .This maintains the terminal contacts in highly polished condition, and entirely free from oxidation and foreign matter, `thus aiding in minimizing the contact resistance.

The contactor"'l8 is not positively fastened to the arm 5, but merely rests upon. the base I. The

ear I9 of the contactor registers with the opening 20 in the arm, and engages the edge thereof.

The arm is caused to-bear7down upon the contactor as will be seen in Fig. 4, since the pitman I2 and the compression spring I3 are mounted higher in relation to the base-at their ends adjacent the cam 1 than they are at the thrust plate I0. This causes the spring to exert a downward thrust upon the arm, which in turn bears upon the contactor, and prevents the accidental withdrawal of the ear I9 from the opening-20 therein.

The oblique edge 20a of the opening 20 in the arm is provided for the purpose of off-setting the thrust of the compression spring I3 toward the stationary terminal contact 24 when the switch is being actuated to on position, o r when it is at rest in that position. By referring to Fig. 3, it will be seen that the spring I3 is disposed to /exert its expansive force directly toward the contact 24. The equalizing movement of the contactor, about its pivotal bearing 20 in the arm, would not be sufficient lto overcome this unequal thrust. However, by forming the bearing edge 20a on a bias, an off-center bearing is provided for the ear I9, whereby this difficulty is overcome. By referring to Fig. 5, it will be seen that the end 22 of the contactor which engages the terminal contact 24 is permitted, by virtue of the bias of the edge 20a, to recede from the contact 24, whereas the other end 2l is supported, through the ear IQ, by the small end of the opening 20 in the arm to forcefully bear upon the contact 23. In this manner, the thrust of the spring is distributed equally to the two terminal contacts,

which results. in uniform contact pressure.

The same result may be accomplished by placingthe opening 20 to one side of the center line of the arm; i. e., nearer the side opposite to the one to which the springs thrust is directed, in which case, the bias on the bottom edge thereof may be omitted.

The switch described thus far has been of the single pole type, wherein .the contactor I8 closes the circuit by electrically connecting the contacts 23 and 24 together. However, the present invention may also be applied to switches of the double pole variety as illustrated in Figs. '7 and 8.

In Fig. 7, the arm 5 carries a pair of contact bridging members or contactors I8a and I8b. The

contactor I8b is disposed between the arm and the base, as has'herenbefore been described, and engages the arm Within the opening 20h with its pivot ear ISb.

The contactor Ia is disposed on the side of the arm opposite to that which contactor IBb occu' pies, and is secured thereto by means of rivet R. Both of these. ontactors are capable of performing the pivot equalizing movement to evenly distribute the contact pressure between their respective terminal contacts.

The contactor IBa engages4 the stationary contacts 23a-24, and acts to close the circuit therebetween. The contactor I8b closes the circuit with which stationary contacts 23h- 24h are directl'y associated by bridging the gap therebetween.

By reference to Fig. 10`it will be seen thatl where the two circuits cross, and are brought into proxiniity with each other, the arm 5 providesan adequate amount of insulation between them.

` To compensate for the one-sided thrust of the 'spring la, its thrust plate Io is mated oir-center on the arm, so as to direct more force to the side opposite to that which would ordinarily receive the springs thrust.

To insure an equal distribution of contact pressure between the many contacts, an over-size hole 6a is provided in the arm 5 in lieu of the slot illustrated in Figs. 1a and 3a. This hole, being considerably larger than the pivot pin2 which projects through it, permits the arm to undergo a substantially planar, universal movement. In this manner, it may not only recede against the springs resistance to compression to effect a maximum contact pressure, but it may move in any direction in response to any unequal pressure on certain contacts, until the moving parts come to rest in equilibrium upon the stationary parts.

Due to the diiiiculties encountered in ascertaining the position of the hole 6a relative to the pin 2, I have illustrated the double pole switch in Fig. 7 at the beginning of its make position, and have shown the pin and the hole in concentric relation, merely for facility of illustration.

'I'he double pole switch illustrated in Fig. 8, has the arm 5 provided with a pivot hole 6b, which snugly engages the pivot pin 2 so as to afford the arm no movement other than a. true arcuate one thereabout. The contact bridging members or contactors 28 and 29 close the circuit between contacts 23a-24a and 23h-24h, respectively. The contactors 28-29 are both positioned beneath the arm 5, and are held in position by the down;- ward thrust of the spring as is shown in Fig. 4.

The arm is provided with T-shaped openings 30, through which ears 3|-32 of the contactors project. The bottom edges of the openings 30 are provided with upstanding, integral guide pins 33, about which compression springs 34 are disposed. These springs force the contactors outwardly, and resist any forces which tend to displace the contactors inwardly of the arm.

The stationary contacts, being positioned in the same manner as has hereinbefore been described, function as cam surfaces. When the arm is actuated from off to on positions, these cam surfaces force the contactors inwardly against the expansive force of springs 34, whereby the contacts are forcefully wiped, and an exceedingly high contact pressure is effected.

The contact pressure is equalized between the individual contacts of each pair by the pivotal movement of the contactors about their ears 3| and 32, for which springs 34 act as fulcrums.

The present invention is readily adaptable t use in combination with a rheostat or volume control. This I have illustrated in Fig. 6 wherein I have illustrated a combined switch and volume control unit of the type shown and described in my copending application Serial No. 742,226, led August 31, 1934.

In the devices above described it will be seen that all of the current' carrying parts thereof, as the contactors and the stationary contacts, may be made of exceptionally heavy metal, since it is not necessary that any of these parts be resilient or flexible. This feature not only enhances the conductivity of the parts in circuit, and increases the capacity of the switch to handle heavy currents, but the heavy metal\parts form'excellent conductors of heat, whereby any tendency toward over-heating is precluded.

The present invention has eliminated all delicate springs from the current carrying circuit, and has reduced the number of current carrying parts to a minimum.

The heavy contactors make for low contact re-V sistance, and, also, due to their weight, increase the inertia of the moving parts, when the switch is actuated to on position, and are thereby driven into rm engagement with the stationary contacts, to eiect a good electrical connection therewith.

The structure of the present invention prevents rebounding or bouncing of the movable contacts upon the stationary contacts since the stationary contacts divert the moving contacts from their true arcuate path, which diversion isopposedby the drive spring, 'I'his creates a cushioning effect accompanied by a positive wedging action wherein the movable and stationary contacts come into iirm engagement without jarring and jolting. y In the device illustrated in Fig. 8, the individual springs 34 of the contactors, exert this cushioning iniiuence on the moving parts instead of the drive spring.

The contact pressures obtainable by the practice of the present invention are very great in comparison to any heretofore attained .in devices of the same general class. This is because no light, delicate springs are relied upon to provide the contact pressure, as in the case of resilient stationary contacts, nor is the contact pressure secured bythe pressure of the drive spring as applied at an ineffective angle. To the contrary, the switch of the present invention derives its contact pressure from the force of the drive spring applied in a direction in which its most effective power of expansion is utilized. This high contact pressure when coupled with the thoroughly by the switch arm, and a stop spider carried by the base member, said spider having stop members adapted to engage the switch arm at its limit of movement and having additional stop members adapted to engage the switch actuating cam at its limits of movement.

2. Switch mechanism comprising a base member, a fixed pivot secured thereto, a switch arm pivoted on the fixed pivot, a switch actuating camV carried by the pivot, a pitman connecting the cam and switch arm, xed contact means carried by the base, movable contact means carried by the switch arm, and a stop spider carried by the base member, said spider having stop members adapted to engage the switch arm at its limit of move- .ment and having additional stop members adapted to engage the switch actuating 'cam at its limits of movement, said stop spider being secured to the base member by the pivot member and by additional securing means spaced from the pivot member.

3. Switch mechanism comprising a base member, a fixed pivot secured thereto, a switch arm pivoted on the fixed pivot, a switch actuating cam carried by the pivot, a pitman connecting the cam and switch arm, xed contact means carried by the base, movable contact means carried by the switch arm, and a stop spider carried by the base member, said spider having stop members adapted to engage the switch arm at its limit of movement and having additional stop members adapted to engage the switch actuating cam at its limits of movement, said stop spider being secured to the base member by the pivot member and by additional securing means spaced from the pivot member, the base member having a perforation therein spaced from the pivot, said stop spider being secured to the base member by the pivot member and by an integral extension on the spider engaging in the perforationin the base.

4. Switch mechanism comprising a base member, a fixed pivot secured thereto, a switch arm pivoted on the fixed pivot, a switch actuating cam carried by the pivot, a pitman connecting the cam and switch arm, fixed contact means carried by the base, movable contact means carried by the switch arm, and a stop spider carried by the base member, said spider having stop members adapted to engage the switch arm at its limit of movement and having additional stop members adapted to engage the switch actuating cam at its limits of movement, the switch arm having openings therethrough, and extensions on the stopspider passing through said openings, said extensions serving as fulcrums for the pitman to assist in initiating movement of the switch in either direction.

5. Switch mechanism comprising a base member, a fixed pivot secured thereto, a switch arm pivoted on the fixed pivot, a switch actuating cam` carried by the pivot, resilient actuating means connecting the cam and switch arm and urging the arm toward the base, xed contact means carried by the base, the switch arm having a cut-away portion, a movable contact member carried between the switch arm and base, and a portion of the movable contact member engaging the cut-away portion of the switch arm whereby the movable contact member is moved by the switch arm into and out of engagement with the fixed contact means.

6. Switch mechanism comprising a base member, afixed pivot secured thereto, a switch arm pivoted on the xed pivot, a switch actuating cam carried by the pivot, resilient actuating means connecting the cam and switch arm and urging the arm toward the base, spaced xed contact'means carried by the base, the switch arm having a cut-away portion, a movable contact member carried between the switch arm and base, and a portion of the movable contact member engaging the cut-away portion of the switch arm whereby the movable contact member is moved by the switch arm into and out of bridging engagement with the iixed contact means.

'7. Switch mechanism comprising a base member, a fixed pivot secured thereto, a switch arm pivoted on the fixed pivot, a switch actuating cam carried by the pivot, resilient actuating means connecting the cam and switch arm and urging the arm toward the base, spaced xed contact means carried by the base, the switch arm having a perforation therein, a movable contact member carried between the base and the arm and having a portion loosely fitting in the perforation of the arm whereby the movement of the arm carries the movable contact member into and out of bridging engagement with the fixed contact members.

8. Switch mechanism comprising a base mem'- ber, a fixed pivot secured thereto, a switch arm pivoted on the xed pivot, a switch actuating cam carried by the pivot, resilient actuating means connecting the cam and switch arm and urging the arm toward the base, spaced xed contact means carried by the base, saidcontacts having lateral contact faces, the switch arm having a perforation therein, a movable contact member carried between. the base and the arm and having a portion loosely fitting in the perforation of the arm whereby the movement of the arm carries the movable contact member into and out of bridging engagement with the lateral contact faces of the xed contact members.

9. Switch mechanism comprising a base member, a xed pivot secured thereto, a switch arm pivoted on the iixed pivot, a switch actuating cam carried by the pivot, resilient actuating means connecting the cam and switch arm and urging the arm toward the base, spaced fixed contact means carried by the base, the switch arm having a perforation therein, a movable contact member carried between the base and the arm and having a portion loosely fitting in the perforation of the arm whereby the movement of the arm carries the movable contact member into and out of bridging engagement with the fixed contact members, the perforation in the arm having a face engaging the movable contact portion at an angle with the line of thrust of the resilient means connecting the cam and switch arm when in the closed position whereby the pressure of the movable contact member against the spaced fixed contact members is equalized.

NEWTON C. SCHELLENGER.

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