Patent Publication Number: US-3878344-A

Title: Cam operated switch assembly having split housing, double action wiping resilient contacts and detent structure

Description:
United States Patent [191 Lockard CAM OPERATED SWITCH ASSEMBLY HAVING SPLIT HOUSING, DOUBLE ACTION WIPING RESILIENT CONTACTS AND DETENT STRUCTURE [75] Inventor: Joseph Larue Lockard, Harrisburg,  
 [73] Assignee: AMP Incorporated, Harrisburg, Pa.  
 [22] Filed: Feb. 1, 1974 [21] Appl. No.: 438,881  
  Related US. Application Data [63] Continuation-in-part of Ser. No. 374,841, June 29,  
 1973, abandoned, Continuation-impart of Ser. No. 243,678, April 13, 1972, abandoned.  
 [52] US. Cl. 200/6 B; 200/6 BB; 200/153 L; 200/153 LB; 200/164 R; 200/241; 200/294;  
 ZOO/303; 200/318 [51] Int. Cl. H01h 21/80; HOlh 1/50; I-lOlh 9/02 [58] Field of Search 200/6 R, 6 B, 6 BA, 6 BB, ZOO/6 C, 11 DA, 17 R, 153 L, 153 LA, 153  
 [ Apr. 15, 1975 Primary ExaminerJames R. Scott Attorney, Agent, or Firm-Gerald K. Kita; AMP Incorporated [57] ABSTRACT A miniature switch having a manually actuated cam in a first position resiliently biasing a pair of resilient spring contacts to positions disengaged from each other thereby interrupting electrical contact therebetween. The contacts are maintained in their resilient biased condition to prevent chattering of the contacts. The cam is manually pivoted to a second position in order to resiliently deflect at least one of said contacts into ,wiping engagement with the other contact and thereby provide electrical contact therebetween. With the cam in its second position, the contacts are maintained in resiliently biased conditions to prevent chatter when the contacts are in electrical engagement. integral stops are provided on the cam to limit rotation thereof. The cam geometry provides positive detent action with at least one of the contacts to provide positive positioning and retention of said cam at either of 242 said first and second positions.  
 [56] References Cited 20 Claims, 12 Drawing Figures UNITED STATES PATENTS 3,729,600 4/1973 Solomon et a1. ZOO/l6 D 7e &#39;60 I z f 5m! 28 r 50 L M 5e IO l2 4 6 Z I i I e es 18 l8 24 W 39 44 i-&#34;ITENTEEZAPR I SE75 SHEET u 95 Z F XTENTED 3,878 344 SHEET 5 [if CAM OPERATED SWITCH ASSEMBLY HAVING SPLIT HOUSING. DOUBLE ACTION WIPING RESILIENT CONTACTS AND DETIENT STRUCTURE CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation-in-part application of application Ser. No. 374.84l filed June 29. I973. and now abandoned. which is a continuation-in-part of application Ser. No. 243.678 filed Apr. l3. I972. and is now abandoned.  
  This invention relates to a miniature switch having a manually actuated cam in a first position resiliently bi asing a pair of resilient spring contacts to positions disengaged from each other thereby interrupting electrical contact therebetween. The contacts are maintained in their resilient biased condition to prevent chattering of the contacts. The cam is manually rotatable or pivoted to a second position in order to resiliently deflect at least one of said contacts into wiping engagement with the other contact and thereby provide electrical contact therebetween. With the cam in its second position. the contacts are maintained in resiliently biased conditions to prevent chatter when the contacts are in electrical engagement. Integral stops are provided on the cam to limit rotation thereof. The cam geometry provides positive detent action with at least one of the contacts to provide positive positioning and retention of said cam at either of said first and second positions. As the cam is rotated about its axis of rotation or pivoted from its first position to its second position a projection on the periphery of the cam is displaced along an arcuate path of displacement. The projection engages one of the contacts at an intermediate point along the path of displacement and resiliently biases the contact into positive engagement with the other contact to complete the electrical circuit therebetween. The projection remains in engagement with the contact until the projection is further displaced to an end point of the arcuate displacement path where the projection is received in a recess of the contact to provide a positive detent action. Also as the contacts are in engagement. displacement of the projection along the arcuate displacement path purposely creates first a maximum deflection of the engaged contacts followed by a partial return deflection. thereby producing a wiping action between the engaged contacts which improves electrical conduction therebetween. The entire switch assembly has a low profile and is readily adapted for miniaturization. enabling a plurality of rotary switch assemblies to be located in a standard duaI-in-line package (DIP) microelectronic component. The resilient spring contacts are advantageously formed into DIP leads for plugging into a printed circuit board or a DIP header.  
  Accordingly it is an object of the present invention to provide a miniature switch having a manually actuated cam resiliently biasing a pair of spring contact either into or out of electrical engagement with each other.  
  Another object ofthe present invention is to provide a miniature switch with a cam for selectively biasing a pair of resilient spring contacts into electrical engagement with each other. the cam purposely providing a wiping action between the contacts.  
  Another object of the present invention is to provide a manually actuable miniature switch of low profile to enable a plurality of similar switches to be incorporated into a DIP microelectronic component. with the contacts of each switch advantageously forming the electrical leads for the DIP package.  
  Other objects and many attendant advantages of the present invention will become apparent upon perusal of the following detailed description taken in conjunction with the drawings. wherein:  
  FIG. I is an enlarged perspective ofa DIP incorporating a plurality of miniature rotary switch assemblies according to the present invention. together with a fragmentary perspective of an apertured printed circuit board receiving the electrical leads of the DIP;  
  FIG. 2 is an enlarged. fragmentary exploded perspective of the perferred embodiment shown in FIG. I and further illustrating the component parts of an exemplary miniature rotary switch assembly of the DIP;  
 FIG. 3 is an enlarged section taken along the line &#39;33 of FIG. I illustrating an exemplary rotary switch assembly with the resilient spring contacts thereof biased resiliently to interrupt electrical contact therebetween;  
  FIG. 4 is an enlarged section taken along the line 44 of FIG. I further illustrating the embodiment of FIG. 3 with the rotary cam in an intermediate position causing a maximum deflection of the contacts;  
  FIG. 5 is a section taken along the line S5 of FIG. 1 illustrating a positive detent action between the rotary cam and one of the spring contacts:  
  FIG. 6 is an enlarged perspective of another preferred embodiment according to the present invention:  
  FIGS. 79 are each enlarged fragmentary crosssections taken along the line 7-7 of FIG. 6 illustrating the modes of operation ofthe preferred embodiment of FIG. 6: and  
  FIG. 10 is an enlarged fragmentary section taken along the lines l0l0 of FIG. 6:  
  FIG. 11 is a perspective view of a portion of the embodiment illustrated in FIGS. 6-101 FIG. 12 is a fragmentary perspective of the embodiment shown in FIG. 11 mounted on a printed circuit board.  
  With more particular reference to FIG. I ofthe drawings. there is shown in FIG. I generally at l a DIP incorporating a plurality of rotary switch assemblies according to the present invention. As shown in FIG. I taken in conjunction with FIG. 2. the DIP includes a base 2 of electrical insulation material provided thereon with parallel spaced partitions. two of which are shown at 4. Each of the partitions has associated therewith corresponding wedge-shaped latches 6 located along each lateral margin 8 and also 8 ofthe base 2. Between each adjacent pair of partitions 4 are assembled a pair of resilient spring contacts 10 and 12. The spring contacts are generally of L-shaped configuration and may be stamped and formed from metal strip. The first contact 10 includes at one end thereof a recessed arcuate detent portion 14. The other end portion of the contact is formed into an electrical lead 16. Adjacent the lead. the contact is provided with a pair of opposed arcuate recesses 18. When assembled between the pair of partitions 4. the recesses 18 receive respective arcuate projections 20 on the edge margin 8 of the base 2. The projections 20 thereby positively locate the contact 10 in desired position on the base 2, with the lead 16 depending from the base. and with the detent portion I4 located between the partitions 4. The second contact 12 is similarly formed with an electrical lead portion 22 and recessed portions 24 adjacent the lead portion 22.  
 Such recessed portions 24 also receive projecting portions (not shown) on the base margin 8&#39; which are similar to the projections 20. The second contact 12 is thereby positively located in position on the base with one end disposed between the partitions 4 and the lead portion 22 depending from the base.-  
  With further reference to FIG. 2. the partitions 4 are provided with aligned notches 26 adapted to receive and support a shaft 28. A rotary cam of insulation material generally shown at 30 includes a central bore 32 which freely receives the shaft 28. thereby allowing the cam 30 to be freely rotatably mounted on the shaft 28. In assembly. the rotary cam 30 is disposed between the pair of partitions 4 in overlying relationship with respect to the contacts and 12. To complete the assembly. a recessed cover of insulation material generally shown at 34 is received over the pair of partitions 4. Each of the sidewalls 36 are provided with a pair of wedge-shaped recesses 38. With the cover received over the partitions 4. the latching portions 6 will be latchably received in corresponding recesses 38 to latchably secure the cover 34 to the base 8 in order to cover the assembly of the contacts 10 and 12. the rotary cam and the shaft 28. In addition. the sidewalls 36 of the cover will retain the depending lead portions 16 and 22 of the contacts against the edge margins 8 and 8&#39; of the base 2. Thus each contact will be constrained from motion by the base edge margins 8 or 8&#39;. the projections 20 which are received in the recesses 18 and 24 of the contacts and the cover plate sidewalls 36. Additionally. the depending leads l6 and 22 will be positively located in depending relationship from the base 8. This is an important feature as shown in FIG. I. wherein the leads l6 and 22 must be maintained in desired alignment for ease in pluggability into corresponding apertures 40 and 42 provided in a printed circuit board 44.  
  With reference to FIG. 2. taken in conjunction with FIGS. 3. 4 and 5. the cover 34 is shown to be provided with a generally rectangular slot 46 which is partially received over the rotary cam 30. The slot 46 not only properly aligns the cam 30 for free rotation between the partitions 4. but also allows operator access to the cam 30 for manual rotary actuation thereof. Adjacent the slot 46. the cover is provided with a pair of sidewalls 48 which are adapted to overlie the corresponding partitions 4. More particularly. each of the sidewalls 48 is defined by a pair of inverted inclined sidewalls 50 which intersect directly over the notch portion 26 of a corresponding partition 4. Also. each of the notch portions 26 is defined by inclined sidewalls. Thus. the shaft 28 is positively centered in the notch portions 26 by virtue of the inclined sidewalls shape of the notch portion and by the intersecting inclined surface configurations 50 of the cover plate partitions 48 which overlie the partitions 4. Thus what has been described is a miniature rotary switch assembly. The low profile of the switch assembly permits the partitions 4 to be spaced closely together enabling a plurality of similar switch assemblies to be located in adjacent spaced relationship and incorporated into a DlP as shown at l in FIG. 1. The leads l6 and 22 of each assembly are maintained on center spacings corresponding to the center spacings normally associated with other microelectronic circuit components. thus readily illustrating the miniaturization obtainable in the rotary switch according to the present invention. Each of the rotary switch assemblies of the DlP is independently operated. Accordingly. either a plurality of rotary switch assemblies may be incorporated into a DlP on a common rotary shaft 28. or a single rotary switch assembly may be fabricated and used by itself alone as desired.  
  For further details of the rotary cam 30 as well as details of operation of the switch. reference will be made to FIGS. 3. 4 and 5. The rotary cam 30 is generally circular in shape as shown in elevation in the figures. The cam being received in the slot 46 partially protrudes from the cover 34. The cam is provided with a pair of intersecting recessed planar surfaces 52 and 54 on the portion of the cam which partially protrudes from the cover 34. The cam is further provided with a radially outwardly projecting integral stop portion 58. The outer circumferential surface of the stop is generally arcuate and terminates in a shoulder 60 at one end thereof and a generally reduced diameter arcuate knob or projection 62 at the other end thereof. Immediately adjacent to the knob 62 the cam circular periphery is provided with an inverted notched or undercut relieved portion 64. Immediately adjacent to the undercut portion 64 is provided another projecting arcuate knob 66 provide on the circular periphery &#39;of the cam 30. The arcuate surface of the knob 66 is purposely continuous with the surface of the undercut portion 64 to form a smooth surface transition therebetween. ln circumferential spaced relationship from the knob or projection 66. the outer circular periphery of the cam 30 is provided with another projecting stop 68 provided at one end thereof with a shoulder 70. In operation. typically the assembly is mounted on the printed circuit board 44 with the leads 16 and 22 plugged into corresponding printed circuit board apertures 40 and 42. Typically the leads are soldered in place such that they make electrical contact with printed circuit paths illustrated at 72 and 74. The contacts 10 and 12 have portions overlapping each other. When the contacts 10 and 12 are in mechanical engagement. a circuit path is completed between the circuit path 72. through the contact 10. into the contact 12. and through the printed circuit path 74. As shown in FIG. 3. when it is desired to interrupt the circuit. an operator manually rotates the cam 30 clockwise by applying pressure to the planar surface 52 causing the cam to rotate clockwise until the surface 52 is generally coplanar with the top surface 56 of the housing 34. With the cam in such a desired position. the projection 62 will engage and resiliently bias or deflect the contact 12 generally counter-clockwise in cantilever fashion. In addition. the surface 70 0f the projecting shoulder stop 68 will stop against the undersurface of the top wall 56 of the cover 34 to prevent excessive clockwise rotation of the cam 34 by the operator. Also. the contact 10 will be at least partially received in and engaged on the surface of the undercut portion 64. The surface of the undercut portion will partially resiliently deflect the contact in cantilever fashion. Accordingly. with the cam in the position as shown in FIG. 3. the contacts 10 and 12 will be resiliently biased out of contact with each other to interrupt the described circuit path. In addition. the cam engages both contacts and resiliently biases them in cantilever fashion. thereby storing spring energy in the contacts in opposition to the biasing cam. The stored spring energy thus insures positive retention of the contacts in desired position by the cam to prevent chattering of the contacts and possible contact therebetween when the assembly in subjected to vibration or magnetic force fields. ln addition. the stored spring energy of the contact forcibly urges the cam in a clockwise direction. forcing the shoulder 70 to positively stop or seat against the top wall 56 of the housing 34 thus restraining the cam from inadvertent rotary movement. As the shoulder 70 is positively urged into seating relationship by the resilient stored spring energy of the spring contact [0. a positive detent action is experienced. indicating to an operator that the cam has been sufficiently rotated to a position whereby the circuit is interrupted by virtue of disengaging the contacts 10 and i2 from each other. In FIG. 5. the cam is shown rotated counterclockwise from its position in FIG. 3 to a second desired position whereby the circuit path is re-established by virtue of contact between the resilient spring contacts 10 and 12. In operation. an operator manually applies pressure to the surface 54 rotating the cam until the surface 54 is generally coplanar with the top wall 56 ofthe housing 34. This rotates the knob 62 out of engagement with the spring contact 12. With the cam in this position. the surface 60 of the stop 58 becomes positively seated against the undersurface of the top wall 56 of the cover 34. In addition. the knob 66 is displaced in an arcuate displacement path about the axis of the shaft 28. The knob engages the spring contact 10 and forcibly biases or deflects it resiliently clockwise in cantilever fashion and in opposition to the stored spring energy therein. The knob 66 also deflects the spring contact 10 into engagement with the contact 12 to establish the electrical circuit therebetween. Once contact between the springs l0 and I2 is accomplished. arcuate displacement of the knob is continued in order to forcibly deflect both spring contacts 10 and 12 in resilient cantilever fashion. At the end point of its displacement path. the knob 66 registers in the recess portion 14 of the contact 10. Since the contact 10 is resiliently deflected by the knob 66. a positive detent action will be experienced when the knob registers within the recess portion 14. This indicates to an operator that sufficient counterclockwise rotation of the cam has been accomplished to complete the electrical circuit by virtue of electrical contact between the spring contacts 10 and 12. With the knob 66 in registration within the recess portion 14. both contacts 10 and 12 will be resiliently biased by the cam in cantilever fashion. Resilient spring energy will thus be stored in the contacts l0 and 12 to assure the application of pressure therebetween which improves electrical conduction at the point of engagement between the contacts. In addition. the spring energy retains both contacts positively in resilient opposition against the cum to prevent chattering of the contacts when the assembly is subjected to vibration or magnetic force fields. As a further feature. the resilient stored energy of the spring contact 10 is transmitted in a direction offset radially with respect to the shaft 28 tending to urge the cam counterclockwise to positively seat the shoulder 60 against the top wall 56 of the housing 34. and prevent inadvertent movement of the cam from its desired position as shown in FIG. 5. The smooth surface transition from the undercut portion 64 to the knob 66 assures relatively friction free travel of the cam over the contact 10 which allows smooth rotation of the cam and smooth operation of the switch.  
  As a further feature of the invention reference will be made to FIG. 4. As shown in the figure. the cam is in an intermediate position during counterclockwise rotation from its position shown in FIG. 3 to its position shown in FIG. 5. The knob 66 engages the contact in an intermediate point along its arcuate displacement path about the axis of the shaft 28. As shown the knob engages and forcibly deflects the contact 10 into engagement with the contact 12. In addition. both contacts 10 and 12 are deflected to a relative maximum deflection with the knob 66 in its intermediate point as shown in FlG. 4. Thus. the knob engages the contact 10 at an intermediate point along the path of displacement resiliently biasing the contact into positive engagement with the other contact to complete the electrical circuit therebetween. The projection remains in engagement with the contact until the projection is further displaced along the arcuate displacement path to an end point where the projection is received in a recess of the contact to provide a positive detent action. In addition. with the two contacts in engagement. displacement of the projection along its arcuate path from its intermediate point to its end point purposely creates a relative maximum cantilever deflection of each contact in op position to their spring energy. followed by a partial return cantilever deflection of each contact when the knob is received in the recess portion 14, thereby producing a wiping action between the engaged contacts which improves electrical conduction therebetween.  
  Advantageously. the recess portion 14 forms a protruding line contact between the contacts 10 and 12. As a further feature. aperture 76 may be provided in the cam adjacent to each of the surfaces 52 and 54. such that when a plurality of cams are located in a DlP. the corresponding apertures 76 of similarly positioned cams will be in alignment to allow passage there-- through of a wire which locks the cams from rotation. Of course. when it is desired to reposition the cams. the wire may be removed from the apertures to allow individual rotation of the cams over the common shaft 28. As a modification each recess 38 of the cover may include a flared relieved portion 39 to permit entry of a prying tool for separating the cover from the assembly.  
  FIGS. 6 through 10 illustrate another preferred embodiment according to the present invention wherein there is shown generally at 78 a switch having a base portion 80 molded of a dielectric material into a generally U-shaped channel configuration. The base portion includes spaced rows of resilient spring contacts 82 which are stamped and formed from metal strip and are similar to the contacts 12. More particularly. each contact 82 is generally of L-shaped configuration and is provided at one end thereof with an arcuate portion 84. with the other end portion of the contact formed into an electrical load 86 which projects outwardly through the sidewall of the base 80 in depending relationship for connection within apertures of a printed circuit board illustrated generally at 88. As shown the contacts 82 of one row have their arcuate portions formed upwardly. whereas the contacts 82 of the other row have the end portions 84 downwardly and initially in spaced relationship with the upwardly bent arcuate portions 84 of the contacts in the one row. The base has a pair of sidewalls 81 into which the contacts 82 are molded. Two sidewalls 83 bridge across the sidewalls 81. although the sidewalls 83 are of shorter elevation than the sidewalls 81. Each of the sidewalls have a pair of integral projecting arcuate feet 85 positioned at each corner of the base 80.  
  A cover portion for the base is illustrated generally at 88 and comprises a singular molded member of dielectric material.  
  More particularly. the cover portion includes an encircling frame having integral sidewalls 90. 92. 94 and 96. Each of the sidewalls 94 and 96 straddles across the sidewalls 81 and includes an integral depending rectangular portion 98 which is inserted between the sidewalls 81 in the base portion 80. The rectangular sidewall portions 98 thereby provide partitions at each end of the U-shaped channel base portion 80. with the contacts 82 contained within the housing interior formed by the cooperating cover 88 and base portion 80. The cover 88 is provided with a plurality of adja cent and spaced cams some of which are shown at 100. Each cam 100 has a relatively thin web or hinge 102 adjoining the cam integrally with the sidewall 90. Each cam 100. as shown in FIGS. 7-10, is generally of inverted elbow-shaped configuration. with one arm portion of the elbow illustrated at 104 and provided with a first shoulder portion 106 at the terminal end of the outwardly projecting arm portion 104. An inverted shoulder 108 is provided at an opposite end of the arm portion 104 adjacent to the bend in the elbow shaped portion of the cam 100. Each cam 100 adjacent to the hinge portion 102 thereof has a relatively thickened portion 110 which terminates in an arcuate cam surface 112 which projects internally into the interior of the housing formed by the cooperating cover portion and baseportion. As shown in FIG. 7. each cam portion 100 has its relatively narrow resiliently deformable hinge 102 outwardly flaring into an inverted shoulder 114 which registers in overlying relationship against a corresponding partition 81 and which is integrally joined to the sidewall 90.  
  Also shown in FIGS. 7 through 10. the sidewall 92 is provided with an elevated projecting portion 116. As shown in FIG. 10. the sidewall 92 is generally L-shaped with the projecting portion 116 forming an upright leg of the L-shaped portion. A generally horizontal extending leg 118 of the L-shaped sidewall 92 is provided thereon with a plurality of projecting latching portions 120 which are adjacent to in spaced relationship from the projecting wall portion 116. Each latching portion 120 has a projecting tip defined by a tapered inclined sidewall portion 122 which terminates in an inverted shoulder 124 to define a generally inverted hookshaped latching portion. Each latching portion 120 terminates in a relatively reduced thickness resiliently deformable hinge portion 126 integral with the leg 118 of the sidewall 92.  
  With reference to FIG. 10. the sidewall 90 and the leg portion 118 are each provided with a plurality of integral depending latching arms 128 which terminate in inverted wedge-shaped latches or hook portions 130. Each of the depending portions 128 register within corresponding grooves 132 provided in the outer surfaces ofthe sidewalls 81. The grooves 132 communicate with notch portions 134 provided in the outer surfaces of the sidewalls 81. When the cover portion 78 is received over the sidewalls 81, the latch portions 130 will register withinthe notch portions 134. The sidewalls 81 will thereby be compressibly received between the partitions 98 and the latch portions 128.  
  In operation reference will be made to FIGS. 7. 8 and 9..lnitially. the cam 100 is illustrated in its relaxed position as shown in FIG. 7 with the arcuate projection 112 thereof in adjacent spaced relationship with respect to one of the arcuate contact portions 84. The contact portions 84 are in spaced relationship with respect to each other. When the cam is pivoted about its resiliently deformable hinge 102. in a clockwise direction as shown in FIGS. 7 and 8. the arcuate projection 112 thereof will initially engage the contact portion 84 of one of the contacts 82. deflecting the portion of the contact 82 which projects into the housing interior in cantilever resilient deflection until it initially engages the other contact portion 84 of the other contact 82. Such pivotal displacement of the cam 100 causes the projection 104 thereof to engage against the latching member adjacent its inverted hook portion 124. This will cause the latching member 120 to pivot resiliently about its resiliently deformable hinge 126 in a clockwise direction as shown in FIG. 8. Although contact between the projection 104 of the cam 100 and the latch member 120 is not illustrated. the latching member 120 is illustrated in a greatly exaggerated deflected position for the purpose of illustrating that the latching member 120 is capable of pivotal deflection until engagement against the projecting leg 116 of the sidewall 92 to prevent excessive deflection and breakage along the resiliently deformable hinge portion 126. Thus the projecting leg portion 116 provides an antioverstress stop limiting the pivotal motion of the latching member 120.-Accordingly. merely upon manually pivoting the cam member 100 in a clockwise direction. it will engage the latching member 120 and cause it also to pivot clockwise. thereby eliminating the need for purposely pivoting the latching portion 120 by separate operation.  
  Clockwise pivotal motion of the cam 100 continues until the arcuate projection or cam surface 112 engages and deflects one of the contact portions 84 into forceful engagement against the other contact portion 84. Clockwise pivotal motion ofcam 100 is continued with both of the contact portions 84 in mutual engagement. thereby causing both contacts 82 to resiliently deflect in cantilever fashion while their contact portions 84 thereof are in mutual engagement. Since the contacts 82 are fixedly secured in their respective sidewalls 81, and since the contact portions 82 undergo cantilever deflection with their contact portions 84 in engagement. a substantial sliding action occurs between the surface of the contact portions 84 to provide a wiping action. Such wiping action provides a scrubbing or cleaning of the surfaces of contact between the contact portions 84 to improve the electrical engagement therebetween. The pivotal displacement of the cam 100 continues until the arcuate projecting cam surface 112 registers within the concave configuration of the contact portion 84 to provide a positive detent action of the cam geometry with at least one of the contact portions 84 and to provide positive positioning and retention of said cam in its position shown in FIG. 9. In addition. the inverted shoulder 108 of the cam 100 will engage against the top surface of the sidewall 81 of the base portion of the housing. Accordingly. the housing provides a positive stop against which the cam is seated to position and retain the cam in its position as shown in FIG. 9. The shoulder portion 106 of the cam 100 will be received under the inverted shoulder or hook portion 124 of the latching member 120. Since the latching vmember 120 originally was resiliently deflected in counterclockwise pivotal-motion. the hinge 126 will cause resilient counterclockwise pivotal motion of insure that the hook portion 124 is received over the shoulder portion I06 of the cam 100. again positively positioning and retaining the cam in its position as shown in FIG. 9. ln addition as shown in FlG. 9 the shoulder 106 is retained in partial compression against the latching member 120 retaining it in a slightly clockwise displaced position in order to retain some residual spring energy in the hinge portion 126 and thereby insuring that the latch portion [24 is resilient biased by the hinge portion 126 into a latching engagement over the shoulder portion 106 of the cant 100. The cam 100 in its position shown in FIG. 9 retains the contacts 82 in partially deflected conditions with their contact portions 84 is mutual engagement to complete a circuit path therebctween. The contacts are maintained in their resilient biased condition to prevent chattering of the contacts due to vibration.  
  To release the cam I00 and to interrupt the circuit between the contact portions 84. the latching member 120 is manually grasped and forcefully pivoted in clockwise deflection. to its position as shown in FIG. 8. This removes the hook portion 124 from engagement on the shoulder portion 106 of the cam 100. permitting the cam 100 to pivot in counterclockwise fashion due to the resilient action of its resiliently deformable hinge I02. The cam 100 therefore will be allowed to resiliently pivot and return to its original position as shown in HO. 7. thereby allowing the contact portions 84 to separate and assume their initial positions shown in FIG. 7 and interrupt the circuit therebetween.  
  With more particular reference to FIGS. ll and 12. additional features of the preferred embodiment illustrated in FIGS. 6-10 will be explained in detail. FIG. 11  
 more particularly illustrates the base portion as having an enlarged interior compartment 136 defined by the encircling side walls 128 and the end walls 83. As shown the compartment 136 is completely uncovered and thus fully exposes the contacts 82 which are mounted in protruding relationship through the side walls 128 as described. Also as shown in FlG. H. a plurality of optional interior partitions 138 may be fabricated integral with the side walls 128 to divide the interior compartments 136 into a plurality of smaller compartments 13611. 136/). 136v. and 136d. Each compartment accordingly holds or separates one corresponding pair of contacts 82 from the other pairs of contacts. It is however to be understood that the partitions 138 are optional and that the contacts 82 may be located in spaced pairs by the sidewalls 128 along without a need for the partitions 138. The base portion 80 is fabricated as shown in FIG. ll purposefuily to prevent enclosure of the contacts until the cover portion 88 is assembled to the base portion. The advantage of such a construction will become apparent by reference to FlGS. 8 and 12. As shown in the figures. the base portion 80 is first mountable on the printed circuit board 88 with the depending end portions 86 of the contacts 82 being received in corresponding apertures of the printed circuit board 88 and being soldered in place to secure the base portion on a surface of the printed circuit board at a desired location. The feet portion 85 engage the surface of the printed circuit board 88 and therefore slightly space the base portion 80 away from the surface of the printed circuit board. The end walls 83, the side walls 128, the partitions 138. if provided. and the contacts 82 therefore are spaced from the surface of the printed circuit board 88. The printed circuit board 88 may then the subjected to a cleaning operation while the base portion 80 is mounted thereon. Since the base portion is spaced from the surface of the printed circuit board 88 cleaning and rinsing chemicals and solutions are allowed to pass freely under the base portion 80 to thoroughly clean the surface of the printed circuit board 88 which lies beneaththe base portion. Since the cover portion 88 has not yet been assembled to the base portion 80. there is no danger that the cleaning and rinsing operation would result in trapping chemicals or other contaminants within the enclosure [36 ofthe base portion. In fact. the exposed contacts 82 also may be cleaned and rinsed during the same operations together with the surfaces of the printed circuit board 88. Also the exposed nature of the base portion 80 permits a thorough inspection after the cleaning and rinsing operations to ensure that no contaminants are in fact contained within the enclosure I36. Subsequent to the cleaning and rinsing operations. the cover portion 88 may be removably assembled to the base portion 80 as previously described. The resultant structure of the switch embodiment described thus fulfills a long existing need in the prior art for a switch which avoids internal contamination. Previously such a switch was in the form of a completely sealed capsule. It was difficult to fabricate and seal such a switch because the mating parts were of miniature size and had to be fabricated with close tolerances. To add to the difficulty. sealant material in the form of an epoxy. adhesive or other fluid or semi-fluid substance was utilized to seal all the seams between mating parts. Due to the miniature size of the parts. however. the sealant material was difficult to control a would often migrate to cover the contacts and other operative moving parts of the switch which were utilized to make and break the contacts during the required switching operations. The present invention resulted from a need to eliminate such disadvantages of a sealed switch. Instead it was discovered advantageous to provide a completely exposed base portion of the switch which allowed free passage therethrough of cleaning and rinsing solutions. Thus instead of attempting to provide a completely sealed switch in order to avoid entrapment of contaminants. the switch according to the present invention avoids entrapment of contaminants by providing a switch interior which is fully exposed for cleaning. and more particularly for preventing accumulation of contaminants therein. Thus the switch according to the present invention fulfills a long existing need for a switch which can be mounted on a printed circuit board and yet avoid entrapment of contaminants on the printed circuit board when subjected to cleaning and rinsing operations. The provision of such a switch allows such cleaning and rinsing operations to be delayed until all of the contaminant impervious circuit components are mounted on the printed circuit board and soldered in place. Since all the components are mounted to the board before a final cleaning operation. there is no danger that the board surfaces will be recontaminated by repeated handling. and yet the components when mounted to the printed circuit board will be either impervious to the cleaning solutions. or. in the case of the switch accordingly to the present invention. will avoid internal contamination by being purposely exposed during such cleaning and rinsing operations.  
  Although preferred embodiments of the present invention have been shown and described in detail. other embodiment and modifications of the present invention are intended to be covered by the spirit and scope of the appended claims wherein:  
 What isclaimed is:  
  l. A switch comprising. a housing. a rotary cam carried by said housing. and first and second resilient spring contacts. said cam in a first position engaging each of said contacts and resiliently deflecting each of said contacts to positions disengaged from each other. each of said resiliently deflected contacts with said cam in said first position storing spring energy which acts to provide engagement pressure against said cam and to prevent chattering engagement of said contacts. said cam being rotatable from said first position to a second position engaging said first contact and resiliently deflecting said first contact into electrical engagement with said second contact to complete an electrical circuit therebetween. said cam having a projection thereon displaceable along an arcuate displacement path as said cam is rotated from said first position to said second position. said projection being displaceable along said arcuate displacement path to an intermediate position between said first and said second positions and into engagement with said first contact and deflecting said first contact together with said second contact. with said contacts in engagement with each other. and thereby causing a first relative sliding engagement between said contacts to produce a first wiping action to improve the electrical engagement between said contacts. said projection being displaceable from said intermediate position to said second position along said arcuate displacement path allowing said first and said second contacts to deflect resiliently by resilient&#39;spring action and thereby cause a second relative sliding en gagement between said contacts to produce a second wiping action for improving the electrical engagement between said contacts. and an electrical terminal portion provided on each of said contacts for making an electrical connection externally of said housing.  
  2. The structure as recited in claim 1. and further including: a recess provided in said first contact receiving said projection therein with said projection in said second position along said arcuate displacement path. therebylatching said projecting in said recess and retaining said cam in its second position.  
  3. ln a switch. the combination comprising: a housing. first and second spring contacts in said housing. a rotary cam carried by said housing and rotatable in a first angular direction and deflecting said second spring contact in a direction away from said first spring contact. thereby interrupting electrical contact between said spring contacts. said cam including a first bearing surface. said first contact overlying and engaging said first bearing surface and retaining said rotary cam fixedly in a firstposition and preventing rotation of said cam. first stop means on said cam engageable on said housing with said cam in said first position. said cam being rotatable in a second angular direction to a second position. said cam in said second position being disengaged from said second spring contact and having said first stop means disengaged from said housing and further having said first bearing 7 surface disengaged from said first spring contact. said cam having a second stop means engageable on said housing with said cam in said second position. said cam including a second bearing surface engaging at least one of said spring contactsand deflecting said first and second spring contacts into engagement with each other to complete an electrical circuit therebetween.  
  4. The structure as recited in claim 3. wherein said second bearing surface is of arcuate projecting configuration and said first spring contact includes an arcuate detent means receiving said second bearing surface upon rotation of said cam to said second position.  
  5. The structure as recited in claim 4. and further ina cluding: said second bearing surface resiliently deflecting said first spring contact into engagement with said second spring contact and further resiliently deflecting said first spring contact and said second spring contact to cause relative sliding engagement between said first spring contact and said second spring contact to produce a wiping action and improve the electrical conduction therebetween. and said first and second spring contacts storing resilient spring energy in opposition to said deflection by said second bearing surface thereby resiliently retaining said first spring contact and said second spring contact into positive engagement in opposition to said cam to prevent chatter of said contacts when subjected to vibration or magnetic forces.  
  6. The structure as recited in claim 4. wherein said second bearing surface resiliently deflects both said first and second spring contacts while in mutual contact for storing resilient spring energy to provide pressure against each other and prevent chatter of said contacts.  
  7. The structure as recited in claim 3. wherein said housing includes a base and a cover. said contacts having portions protruding from said base. said cover including portions thereof overlying said contact protruding portionsand fixedly retaining said contact protruding portions on said base. and latching means connecting said base and said cover.  
  8. The structure as recited in claim 7. said housing further including-a tool receiving recess means adjacent said latching means for receiving a prying tool for releasing said latching means and unlatching said cover from said base.  
  9. The structure as recited in claim 3, wherein said first bearing surface engages and at least partially resiliently deflects said first spring. contact. said first contact storing resilient spring energy acting in opposition to deflection by said bearing surface whereby said first contact is maintained in pressure against said first bearing surface to prevent chattering of said first contact.  
  10. The structure as recited in claim 3, wherein said first bearing surface and said second bearing surface are adjacent each other along the periphery of said cam. said cam upon rotation from said first position to said second position displacing said second bearing surfacein an arcuate path about the axis of rotation of said cam with said second bearing surface forcing said contacts to resiliently deflectfirst to a relative maxi- I mumand then allowing partial return deflection of said contacts to create a wiping action between the engaged contacts.  
  ll. In a switch array comprising a plurality of switches in relatively closely spaced relationship and individually programmable for either completing or interrupting respective circuit paths through the switch spaced partitions. a space between each adjacent pair of partitions receiving a pair of resilient spring contacts of electrically conducting material having first portions projecting into the space between adjacent pair of spaced partitions and having second portions projecting outwardly of said base. a rotatable cam of insulation material rotatably mounted in the space between each adjacent pair of spaced partitions each said rotatable cam having first biasing means thereon and being capable of rotation on said single shaft to a first position engaging said biasing means against at least one of said first portions of corresponding spring contacts to deflect resiliently at least one of said corres mnding spring contacts into electrical engagement with the other and thereby establish an electrical circuit path therebetween. each said rotatable cam having second biasing means thereon and being capable of rotation to a second position disengaging said first biasing means from said first portion of at least one of said corresponding spring contacts and engaging said second biasing means against said first portions of said corresponding spring contacts to deflect resiliently said corresponding spring contacts out of engagement with each other. thereby interrupting the electrical circuit path therebetween. said cover overlying said second portions of said spring contacts and retaining said second portions of said spring contacts against said base and in depending relationship therefrom to provide depending electrical leads. each said rotatable cam having portions thereof protruding from said cover for receiving thereon externally applied forces required for rotating said cam. each said partition being relatively closely spaced with each said rotatable cam and corresponding spring contacts being of relatively low profile permitting miniaturization of said switch array.  
  12. The sturcture as recited in claim 11 and further including: a first shoulder on each said rotatable cam engageable with said housing upon rotation of said cam to said first position. at least one of said corresponding spring contacts resiliently biasing said cam to urge said shoulder against said housing to prevent inadvertent movement of said cam front said first position. and a second shoulder on each said rotatable cam engageable on said housing with said cam in said second position. at least one corresponding spring contact resiliently biasing said cam to urge said second shoulder against said housing to prevent inadvertent movement of said cam from said second position.  
  13. The structure as recited in claim 12. wherein said first biasing means of each cam purposely deflects at least one of said corresponding spring contacts into sliding engagement with the other to produce a wiping action between the corresponding electrical contacts and thereby improve the electrical continuity of the electrical circuit path established therebetween.  
  14. The structure as recited in claim 11. wherein. as each cam is individually rotatable to a corresponding first position. said first biasing means of each cam initially deflects at least one of said corresponding spring contacts into engagement with the other. and further resiliently deflects both of said corresponding spring contacts with said contacts retained in engagement with each other to produce relative sliding engagement therebetween and thereby provide a wiping action which improves the electrical continuity of the electrical circuit path established therebetween.  
 15. A switch. comprising:  
 a housing defined by sidewalls.  
 a pair of contacts molded into the sidewalls of said housing and projecting into the interior of said housing.  
 said housing having a cam thereon connected to said housing by a resiliently deformable hinge.  
 said housing having a latching portion thereon connected to said housing by a resiliently deformable hinge portion.  
 said contacts protruding into said housing and initially being in spaced relationship.  
 said cam being pivotable about its hinge to deflect one of said contacts into engagement with the other contact and complete an electrical circuit therebetween.  
 said cam being latchably engageable with said latching portion to retain said contacts in engagement with each other.  
 16. A switch having a base and a removable cover portion. comprising:  
 a plurality of electrical contacts mounted on said base portion and having depending electrical terminal portions providing electrical terminals esternally of said base portion.  
 said base portion defining an exposed enclosure receiving said electrical contacts.  
 feet means on said base portion for elevating said base portion.  
 said cover portion having thereon having a plurality of manually actuable cams for biasing selected electrical contacts into and out of mutual engagement. and  
 said cover portion being selectively removable from said base together with said cams to selectively expose said enclosure and said electrical contacts received in said enclosure.  
  17. The structure as recited in claim 16. wherein. said enclosure communicates with a space beneath said base portion. which space is defined by elevating said base portion with said feet means.  
 18. A switch. comprising:  
 a housing.  
 at least a pair of contacts mounted on said housing initially in spaced relationship and having portions projecting from said housing providing pluggable electrical terminals.  
 at least one actuator cam mounted in said housing and being displaceable into engagement with at least one of said contacts deflecting one of said contacts into engagement with the other of said contacts.  
 said actuator cam being further displaceable to an intermediate position deflecting both said contacts while engaged with each other to produce a first wiping action to improve the electrical engagement between said contacts. and  
 said actuator cam being further displaceable from said intermediate position to another position permitting return resilient deflection of said contacts while engaged with each other to produce a second wiping action to improve the electrical engagement between said contacts.  
  19. The structure as recited in claim 18. and further including: detent means on one of said contacts. said actuator cam being detented in said detent means when said actuator cam is in said another position.  
  20. The structure as recited in claim 18. wherein. said housing includes at least a pair of partitions. said actuator cam is rotatably supported between said partitions. and said contacts are received between said partitions.