US3002060A - Switch assembly - Google Patents

Description

Sept. 6, 1961 D. w. LAVIANA 3,002,000

- SWITCH ASSEMBLY Filed May 24, 1960 34 I 2 5O 74 22 24 70 66 59 38 28 3o '8 l8 64 62 36 32 as so 6 l4 .2 l

Hg; ,3 INVENTOR.

Donald W Lav/emu.

His Aflomey United States Patent Patented Sept. 26, 1961 3,002,060 SWITCH ASSEMBLY Donald W. Laviana, Pittsford, N.Y., assignor to General Motors, Corporation, Detroit, Mich, a corporation of Delaware s Filed May 24, 1960, Ser. No. 31,372 11 Claims. (Cl. 200-'-38) 'Ihisinvention pertains to switches, and particularly to an improved switch assembly of the cam operated type. The present application is a continuation in part ofmy copending application Serial No. 786,953 filed January 15, 1959. I

Heretofore the. majority of cam' operated sequence switches .used in timers for controlling appliances, such as washing machines, have embodied integral leaf spring contact assemblies. In the design of cam operated sequence switches, several factors must be considered, among these being the following: to provide a switch element requiring a minimum torque at its operating cam; to provide a switch'element having a high initial contact pressure when it is disengaged from its operating cam and engages one fixed contact; and to require a minimum of additional force to move the switch element into engagement with another fixed contact and provide sufficient contact pressure with a minimum of additional deflection.

'The present invention relates to a switch assembly including leaf spring blades, or reeds, having a low forcedeflection gradient, the leaf spring blades being prestressed in one direction so as to have two spring rates. Accordingly, among my objects are the provision of an improved leaf spring switch assembly for timers; the further provision=of a leaf spring switch assembly having aseparate ca'm follower member attached thereto in such a manner so as to bend the intermediate portion of the leaf spring in the direction of its initialprestressing; the further provision of an improved leaf spring switch assembly of the aforesaid type having a low springrate inthe direction "of the prestressing and a high spring rate in'the opposite direction; and the further provision of a switch assembly including a leaf spring blade designed to accommodate substantial over-travel without exceeding the yield point of the material and, therefore, avoiding permanent deformation of the leaf spring blade.

' The aforementioned and other objects are accomplished in the present invention by prest'ressing the leaf spring blades adjacent their points of attachment to a base and attaching a saddle member thereto at the intermediate portion of each leaf spring to further prestress each leaf spring in the direction of its initial'prestr'essing. Specifically, the switch assembly includes a base, or terminal block, having a plurality of terminals attached thereto. One end of each leaf spring blade is staked, or otherwise rigidly attached, to a terminal, and the other end of each leaf spring blade carries a contact on each side thereof. One set of the spring blade contacts are engageable with a first set of fixed contacts attached to one set of terminals, and the other set of blade contacts are engageable with a second .set of fixed contacts attached to another set of terminals andspaced from the first set of fixed contacts. A saddle member, or harness, is attached to the intermediate portionof each leaf spring blade.

The saddle member is composed of insulating material tooth-type cam follower projecting from the upper side thereof. The saddle member is formed with a pair of openings on opposite sides of. the projecting cam follower tooth through which a leaf spring blade can be threaded. Each leaf spring blade is formed with a reinforcing bead adjacent the'contact end thereof and a circular hole in the medial portion, the circular hole being adapted to reand comprises a generally rectangular member having a ceive an integral nub, or stud, formed on the saddle member. The saddle member has transversely extending rails at each end thereof and the integral stud projects downwardly from the lower surface of the cam; follower projection. The surface on which the stud is formed is substantially parallel to and spaced above the upper surface of the'inner end rail, and the outer end rail is located in a plane spaced above the surface on which the stud is formed such that the leaf spring blade will be bent as it is threaded through the openings and attached totthe saddle member. More particularly, the leaf spring blade will-be bent in the same direction as its initial p'restressing by its attachment to the base.

By bending the intermediate portion of each leaf spring blade, each leaf spring blade is additionally prestressed to obtain the requisite contact pressure between the leaf spring blade contacts and the fixed contacts closest to the cam. The leaf spring blades have low spring rates, or are very limp, when bent in the same direction as the direction of the prestressing, and have high spring rates, or'are very stiff, and thus resist bending in'the opposite direction. The stiffening bead adjacent the contact end of each leaf spring prevents bending of the leaf springs due to initial prestressing, or preloading, against the fixed contacts closest to the cam. Only a small additional force is required to move the reed into engagement with the fixed contacts spaced farthest from the cam, and after engagement of the leaf spring blades with the latter set of fixed contacts the requisite contact pressure is achieved by bending the spring blades in the direction of their prestress, which due to the low spring rate of theblades in this direction, requires a minimum force. This low spring rate enables the switch assembly to accommodate substantial overtravel without exceeding the yield point of the spring blade material and thus avoids premanent deformation.

While the embodiment of the inventionas herein disclosed constitutes a preferred form, itis to be understood that other forms might be adopted. 1

In the drawing: FIGURE 1 is a plan view of a switch assembly constructed according to the present invention.

FIGURE 2 is a sectional view taken along lines 22 'of' FIGURE 1 showing a segment of an actuating cam with the leaf spring blade engaging a fixed contact closest to'the cam.

FIGURE 3 is a view similar to FIGURE 2 showing thev leaf spring blade engaging the fixed contact farthest from the cam;

FIGURE 4 is a perspective view of the novel cam follower member, or saddle.

With particular reference to FIGURES 1 through 3, the switch assembly includes a base, or terminal block, 10 of insulating material having spaced sets of spadetype' terminals 12, 14 and 16 molded therein. The sets of terminals 12, 14 and 16 project from both sides of the base 10 and have staking lugs 18 located on the upper side of the base. As depicted in FIGURES 2 and 3, a set of substantially S-shaped Phosphor bronze strips 20'are staked to the set of terminals 14, and a second set of substantially S-shaped Phosphor bronze strips 22 are staked to the set of terminals 16. The strips 20 carry fixed contacts 24 which are located in a planeinclined to the base 10, and the strips 22 carry fixed contacts 26 which are locatedin a plane substantially parallel to and spaced from the plane of the contacts 24.

The switch assembly also includes a plurality of Phosphor bronze leaf spring blades, or reeds, 28. The inner end of each leaf spring blade is staked to one of the terminals 12 and is transversely bent along a line indicated generally by the numeral 30 so that the outer end of each leaf spring blade is prestressed, or preloaded,

thereof engageable 3 towards the fixed contact 26; The outer end of-each-leaf spring blade carries contacts 32 and 34 on opposite sides respectively with fixed contacts 24 and 26. V

' :The intermediate portion of each leaf spring blade '28 has-a circular hole 36 formed therein. Asaddle member, or harness,"38,-such as depicted in-FI GURE 4, is assembled with each leaf spring blade and is attached to the medial portion thereof. The saddle-members 38 are composed of insulating material, 'such as a phenolic condensation product, and comprise side rails 40- and- 42, end

rails.44. and 46, and anintermedia-te web 48 having an upstanding' toothed-type cam follower 50. A generally rectangular opening 52. is formed between the web 48 and --end. rail 44, and .a second generally rectangular opening 54 is formed between the cam follower tooth 50 and the end rail 46. I i

As seen particularly in FIGURES 2 and 3,. the upper surface 56. of the endrail 44 and a portion 58: of the :lowernsurface of web 48.1ie in substantially parallel planes. with the portion 58. spaced above. the surface 56. The. end rail .44 is formed with a charnfered inner edge .60,- ,andi'the portion-5.8 of the lower surfaceof the web =48 gis formed. .withlanintegral downwardly projecting nub,

I :orstud, 62. The lower surface 64 of the cam follower s-tQoth-JSO. is inclinedupwardly with respect to the lower :surfacesof the sidetrails 40 and 42. The upper surface =66, of,;end rail. 46,,is located in a plane substantially parallel .tobutfspaced above both the upper surface 56 of the. end rail 44 and the lower surface 50. of the web .48.

The inneredge ofend rail 46 is, fo'rmedwith a chamferedq-portion168, which extends in a direction opposite to, the chamfered, edge 60'.

The saddle member .3 8 -is assembled with the leaf spring 7 blade 28 by threading the inner end thereof through the lope lillg .54 and through the opening 52. prior to attachment of-the inner end to the terminal 12. When the ,.stud .62. is aligned with-the circular hole 36 in the leaf spring, the diameter of the stud being substantially the ..'same as the diameter of the opening 36," the saddle mem- ':;ber 38 will be securely attached to the leafspringblade 28. In threading the leaf spring blade through the openings 54 and 52, the lower surface of the leaf spring blade .engages the upper surfaces 56 a d. of the end rails 44 and 46 respectively, and the lower surface portion 58 ,of. the web 48, whereby the medial portion of the leaf springblade will be bent intermediate its ends in the. same direction as the prestressing bend 30.

As 'seen particularly in FIGURES 1 through-3, each A leaf springblade is formed with a reinforcing bead 70 adjacent, its outerend. The reinforcing 'beads 70, stiffen the leaf spring blades in the direction of; the prestress and prevent deflection of each leaf spring blade 28- due to engagement with the fixed contact 34.

The. cam follower tooth 50 is adapted to be engaged by a; rotating cam 72,. a fragmentary portion of which :is depicted in FIGURES 2 and 3. The cam 72 may inl-cludea plurality of; rises '14, and dwells 76 suchthat when the-follower 50 engages a rise -74. the leaf spring blade .28 will be moved into engagement with fixed contact 24,

an'dwhen the-followenSt}lisaligned with. a dwellld the leaf spring blade .28..will engage. the fixed contact 26.

@When the. follower 5.0 engages-a portion of the cam/7 2 between'therise 74.and thedwell 76, the contacts carried by .the leaf spring blade will engage neither contact 24.nor

contactv 26. The leaf spring blades 28. are prestressed or preloaded in a direction to engage the fixedcontacts 26 which, clearly seenin thedrawing, are located. closest to the cam'72; The fixed contacts 24, on theotherhand,

7 prehea ed-farthest. from-the earn .2- r

"Th le -f pringfjblj de Zahara in effec wo spring rate by vi tu 'of th fp estres n y' he bend 30 and the intermediate bendby the. saddle memb'er. 3z3. In otherfword's, the-leaf spring blades, 28 .ha'vea low spring rate, or are easily flexed, in the direction of tl'ieprestress that is towards the fixed contacts 26which are closest to I d the cam 72. However, the leaf spring blades have a high spring rate, or are very stiff, and thus resist bending in the opposite direction. In this manner, the high contact reaction force when the switch blade contacts 34 engage 1 38, to the position of engagement with the fixed contacts 26. The contact pressure at the'fixed contacts 24 isthe force necessary to bend the spring blades to their final curvature supported at their attachments tothe-base, the contacts 24, and the surface 58 of the saddle member-38.

It is pointed out that the leaf spring blades are disengaged from the surface 66 of the saddle member only during overtravel when the contacts 32 engage fixed contacts 24-. The leaf spring blade engages thesurface 66 of the saddle member when the spring blade is suspended between the,

contacts 24 and 26 as well as when the contact 34 engages fixed contact 26.

During rotation'of the cam 72 in the direction of the arrow in FIGURE 2, the cam follower 50 will be engaged by the cam surface so as, to move the leaf spring blade28 towards the base 10 and disengage leaf spring contact 34 from fixed contact 26. At this time the leaf spring blade is suspended between the fixed contacts 26 and 24 while constrained within the saddle member 38.,- When the cam fol-lower 50 engages the rise 74. on the cam 72, the :contact 32 will engage the fixed'contact' 24. :Only a minimum force is required to move the switch blade from engagement with contact 26 to engagement with contact 24. After engagement of leaf spring contact'32 with fixed contact 24 the requisite contact pressure is obtained by bending the medial portion of the leaf spring spring blade 28 in the direction of its prestress as seen in FIGURE 3. Since the spring blade28 has, a'low spring, rate in this direction, it requires very little: additional force to obtain the requisite contact pressurebe tween the leaf spring blade contact-32and the fixed contact 24. By enablingthe leaf spring blade 28 to. bend 7 intermediate itsends and become disengaged from the upper surface, 66 of the end rail 46, overtravel can be accommodated without stressing the spring blade beyond its elastic limit thereby avoiding permanent deformation.

While the embodiment of the invention as herein disclosed constitutes a preferred ,form, it; is to be understood that other forms might be adopted.

What is claimed is as follows:

1..A cam'operated switch including,'a base, a leaf spring having one end attached to said base; and prestressed adjacent its attachment in one direction, and a member attached to said leaf spring so asto bend the medial portion thereof in said one direction whereby said leaf spring has a low spring rate in said one direction and a high springv rate in the opposite direction.

contactsupported on said base in spaced relation thereto, -a leaf spring having one end attached to said baseand prestressed adjacent its attachment towards said fixed contact, and a member attached to said leaf spring so as to bend the medial portion thereof towards saidiixed contact whereby said leaf spring has a low spring rate: in the direction of said prestressing and a highspring.

rate inthe opposite direction.

3. A cam operated switch including; a base, a fixed contact attached to said base in spaced relation thereto, a leaf spring having one end attached to said' base and prestressed adjacent its attachment in a direction away from said fixed contact, and a member attached to said leaf spring so I as to bend the medial portion'thereofin .a direction away from said fixed contact wherebysaid leaf spring has a low spring rate in the direction away 2. A camoperated switch includingalbase; a fixed from said fixed contact and a high spring rate in a direction towards said fixed contact.

4. A cam operated switch including, a base, first and second fixed contacts attached to said base in spaced relation thereto and in spaced relation from each other, a leaf spring having one end attached to said base and prestressed adjacent its attachment towards one of said fixed contacts, the other end of said leaf spring being disposed between said fixed contacts, and a member attached to said leaf spring so as to bend the medial portion thereof in the direction towards said one fixed contact whereby said leaf spring has a low spring rate in the direction of said one fixed contact and a high spring rate in the pposite direction. I V

5. The cam operated switch set forth in claim 4 including a cam engageable with said member for moving said leaf spring in the opposite direction into engagement with said other fixed contact, the arrangement being such that when said leaf spring engages said other fixed contact said leaf spring is deflected in the direction towards said one fixed contact.

6. A cam operated switch including, a base, a leaf spring having one end attached to said base and prestressed adjacent its attachment in one direction, said leaf spring having a reinforcing bead adjacent its other end, and a member attached to said leaf spring so as to bend the medial portion thereof in said one direction whereby said leaf spring has a low spring rate in said one direction and a high spring rate in the opposite direction.

7. A cam operated switch including, a base, a fixed contact supported on said base in spaced relationship I thereto, a leaf spring having one end attached to said base and prestressed adjacent its attachment towards said fixed contact, and a saddle member having end rails, an intermediate web and spaced openings between said web and said end rails, said leaf spring being threaded through said openings so as to bend the medial portion thereof towards said fixed contact whereby said leaf spring has a low spring rate in the direction of said prestressing and a high spring rate in the opposite direction, said leaf spring having a reinforcing bead adjacent its outer end for preventing deflection of said leaf spring due to engagement with said fixed contact.

8. The switch assembly set forth in claim 7 wherein said leaf spring has a circular hole in the medial portion thereof.

9. The switch assembly set forth in claim 8 wherein said saddle member is formed with a projecting stud on said intermediate web, and wherein said stud extends through the circular hole in said leaf spring.

10. The switch assembly set forth in claim 7 wherein the lower surface of said leaf spring normally engages the upper surfaces of said end rails, wherein the upper surface of said leaf spring engages the lower surface of said intermediate web, and wherein the upper surfaces of said end rails and the lower surface of said web are located in spaced parallel planes.

11. The switch assembly set forth in claim 10 wherein the inner edges of said end rails are chamfered in opposite directions.

References Cited in the file of this patent UNITED STATES PATENTS 1,092,266 Howe Apr. 7, 1914 2,204,949 Richie June 18, 1940 2,559,568 Hooven July 3, 1951 2,856,473 Bell et al. Oct. 14, 1958

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