Electric Switch

This invention relates to an electrical switching device and more specifically switches of the type having nonconductive outer housings, resiliently supported contacts, and having momentary contact. In the past it has been difficult to provide a low cost reliable pendent type switch which was effectively insulated and sealed against intrusion of dust, water and oil. Such pendent type switches are used in many industrial applications such as for example to provide raise and lower electrical switching functions to a hoist or crane mechanism. Pendent type switches are normally suspended from an overhead structure by the electrical cable which may include an integral support rope or cable. It is highly desirable that the switch have an outer insulating cover. Because such a pendent switch is suspended and at times held in the operator's hand, certain size weight and impact resistant requirements compatible with such service must be obtained. Prior attempts to provide a rugged reliable pendent switch meeting these requirements have resulted in expensive complex mechanisms.

I provide the switching apparatus in which the contacts and a conductor bar are operably supported by integral portions of the housing members. The housing members provide for maintaining the switch in an off position, compensating for contact wear, and effective environmental sealing.

In momentary switches the electrical conductive path between two circuits usually require the forcible movement of a movable contact into physical contact with a stationary contact. A spring or other tensioning means is usually required to return the movable contact to its normal or off position after the switching force is removed. I provide for integral portions of the insulating housing members to rotatably support the movable contact, effect the return of the movable contact, and seal the contact portion of the switch from the external environment.

Accordingly, one object of this invention is to provide a novel switch housing which is inexpensive to manufacture, electrically insulated from the internal electrical conducting portions, and effectively sealed against intrusion of dust, water and oil.

Another object of this invention is to provide a highly reliable switching apparatus which is free of complex component parts and includes only a minimum number of interchangable component parts.

Another object of this invention is to provide an electrical switch which is easy to install, repair, and replace.

Another object of this invention is to provide a reliable switching mechanism which provides for a positive off position even following an operation which causes the movable contact to be partially welded to one or both of the stationary contacts by permitting at least one of the welded contacts to be freed.

Another object is to provide a switch housing which will effectively seal the internal switch mechanism from water, dust and oil even when various size electrical cables are attached to the switch.

Another object of this invention is to provide a switching apparatus in which some contacts are repositionable so as to provide additional electrical contact surface as the contact member wears. My invention further provides for rotatably mounting the movable contact so as to distribute the contact wear over a large surface area.

Another object of this invention is to provide a switching mechanism allowing over travel of the movable contact and allowing some under travel of the movable contact caused by the operators involuntary finger movement.

Other objects and features of the invention will become apparent to those skilled in the art as the disclosure is made in the following detailed description of present preferred embodiments.

FIG. 1 is a front view of the pendent switch with the interior outline of the outer housing member shown in dashed line.

FIG. 2 is a cross-sectional view of the right side of the switch taken along line 2--2 in FIG. 1.

FIG. 3 is a front view of the inner housing member showing the central cavity portion with all component parts removed.

FIG. 4a is a cross sectional view of the switch taken along line 4a--4a in FIG. 1 and shows the upper contact portion.

FIG. 4b is a cross sectional view of the switch taken along line 4b--4b in FIG. 1 and shows the center contact portion.

FIG. 4c is a cross sectional view of the switch taken along line 4c--4c in FIG. 1 and shows the lower contact portion.

FIG. 5 is a side view of the center contact post.

FIG. 6a-c show a diagrammatic representation of the switch operations as would generally be seen along line 2--2 of FIG. 1.

FIG. 1 is a front view of a pendent switch showing the outer insulating housing member 1 with the interior surface of the outer housing member indicated in dash line. The outer housing 1 is made of an electrically insulating and resilient material, such as for example neoprene, rubber, plastic, or other elastomeric material. In normal operation outer housing 1 is suspended from an overhead structure either by a cable which enters the cable entrance 10 or by a separate susepension cable which can be attached to the outer housing 1 by means of an inverted U-shaped hanger bracket which attaches to 16a and 16b respectively by known fastening means such as for example a metal rod extending through the switch housing members on by a screw on each side of the U-shaped bracket engaging the stiffener member 2. The elongated cable entrance 10 projecting from the uppermost portion of the outer housing 1 permits access for the electrical cable which feeds electrical signals to the switch and provides support for the pendent switch. In referring to FIGS. 1 and 2 it can be seen that the cable entrance 10 has exterior surfaces having discrete incrementally stepped diameters while the interior surface of the cable entrance 10 is generally conically shaped with the taper diverging inwardly. Such configuration allows the pendent switch to be used with a number of different size electrical cables. As the outer housing 1 and the cable entrance 10 are made of a resilient material a pressure or interference fit between the cable and the housing can be made between the adjacent portions. During installation the cable entrance 10 may be cut back or severed perpendicular to the axis of the tapered bore to a stepped diameter such that the diameter of the tapered surface forcibly accepts the sized cable being used and maintains a resilient seal against the intrusion of water and dust between the cable and the outer housing 1. Such clamping means provides a pressure fit between the outer surface of the electrical cable and the inner tapered surface of the cable entrance 10.

The outer housing 1 has two resilient diaphragms 11 and 12 and corresponding push buttons 13 and 14 associated with such diaphragms. In one application of the pendent switch, such as for example when the switch is used to direct the operation of an overhead hoist push button 13 would be used to initiate a raising of the hoist and push button 14 would be used to initiate the lowering of the hoist. In such an application the pendent switch functions as a single pole double throw momentary switch, with an off or a non-conducting position leaving all circuits in an open state when neither button is depressed.

The interior sides of the outer housing 1 contains integral knobs 15a through 15h which project inward and are used to engage corresponding apertures on the internal members of the switch such as for example in the embodiment shown in FIG. 2 the stiffening member 2. When for example the knobs 15 are of circular cross section as in the present preferred embodiment the diameter of such cross section may vary from knob to knob so as to provide a unique interlock between the stiffening member 2 and the outer housing 1. The maximum dimension of the knobs engagingly interlock with corresponding dimensions on the apertures on the stiffening member 2. In the embodiments of FIG. 1 the projections are of circular cross-section and the outer circumferential surface is the engaging interlocking surface. In some embodiments the height or projection extent is the interlocking variable. As can be seen in FIG. 1 of the present preferred embodiment an opening 18 bottom of the outer housing 1 provides for insertion and withdrawal of the internal parts 2 through 9, and for access to the terminal ends of wires coming into the switch through cable entrance 10. Knobs 15a and 15e are of smaller diameter than knobs 15b and 15f which respectively are of smaller diameter than knobs 15c and 15g which respectively are smaller than the diameter of knobs 15d and 15h. Decreasing in the diameter of the knobs 15 as the distance of such knobs from the opening 18 increases allows corresponding apertures in the stiffening member 2 to engage only those knobs having a corresponding diameter. This allows for easy insertion and withdrawal of the stiffening member 2 into the outer housing member 1 by means of the bottom opening 18; because small diameter apertures in the stiffening member 2 will override the larger diameter knobs in the outer during the insertion process until all such knobs and apertures are in alignment with corresponding knobs. Such alignment and resulting engagement between knob 15a and aperture 61 can be seen in FIG. 4a.

As can be seen in FIG. 1 an annular sealing channel 17 extends circumferentially around the lower inner surface of the outer housing 1. This channel 17 and the corresponding annular rib or ring 47 extends continuously around the corresponding adjacent surfaces of the outer housing 1 and the inner member 3. Referring to FIG. 2 shows the cable entrance 10 of the outer housing 1 which, as previously had been explained, is sealed upon the insertion of the wiring cable. The lower opening in the outer housing 1 is sealed by engagement of an annular ring 47 of the inner housing 3 with the outer housing sealing channel 17. As both housing members 1 and 3 are made of a resilient material, the ring 47 adjacent channel 17 is made slightly larger than the dimension of the channel 17 such that when the switch is assembled the channel 17 is forceably engaging the ring 47 on the adjacent portion of inner housing member 3. Such resilient forceable engagement results in an effective water, dust, and oil seal on the lower portion of the housing members 1 and 3. As has been shown when an electric cable of proper size is fitted within the cable entrance 10 and the inner member 3 is inserted within the opening 18 the internal mechanism of the switch is effectively sealed from contaminates.

As can be seen in FIG. 1 and in referring to FIGS. 4 the switch and more particular the outer housing has diverging sides to provide a tapered exterior and interior to said outer housing member 1. This taper provides for ease of insertion of the stiffening member 2, the inner member 3, and engagement of the projection 15 with apertures on the stiffening member 2.

Referring to FIG. 2 shows a cross section of the pendent switch assembled and unwired to an external circuit. The stiffening member 2 is made of a rigid material, such as for example steel, and is held intermediate between the inner and outer housings 1 and 3. The stiffening member 2 preferably extends around the inner surface of outer housing 1 on the three inside surfaces of the outer housing 1 without obscuring the operation of the diaphragms 11 and 12. It is desirable to attach the stiffening member 2 to the inner housing member 3 prior to insertion of the stiffening and inner members into opening 18. The stiffening member 2 may be attached to the inner housing member by, for example, an adhesive coating, a friction fit between the inner member 3 and the stiffening member 2 or by projections of the stiffening member 2 being received in corresponding pockets in the inner member 3.

The stiffening member 2 is preferably made of steel or other rigid electrically conductive material, and of generally channel shape with apertures in the channel sides corresponding to the knobs 15a through h. The back side of the channel 2 maybe solid as shown in FIG. 2 or have perforations such that the volumes behind diaphragms 32, 33 and 34 may be in vented communication. The operation of diaphragms 11, 12, 32, 33 and 34 results in a displacement of the air on one side of the diaphragm in the present preferred embodiment all diaphragms are interconnected and in fluid communication with each other by passageways. The displaced air behind the diaphragm may then flow into the other diaphragm spaces and into the cavities and channels of the switch, so that the switching pressure on button 13 and 14 do not depend upon such fluid flow rate.

It will be apparent to those skilled in the art that the electrical cable enters the outer housing through the cable entrance 10, then enters the inner housing member 3 by means of the cable opening 30. A cable chamber 31 is provided for termination of the cable shielding and necessary space is provided for separation of the individual conductors within the cable bundle. Cable chamber 31 may include provision for securing a support wire or rope within the electric cable bundle to either the stiffening member 2 or the nonconducting parts of the switch. Such connection means would include, for example, a machine screw attached to a ground wire within the electrical cable bundle threaded into the stiffening member 2. In addition a wiring tie or worm driven hose clamp may be used to clamp the cable within opening 30 to the inner member 3 and the stiffener 2. The electric wires for carrying switch signals are then directed through specific wiring channels within the inner housing member 3 to specific electric contacts. In the present preferred embodiment wiring channels 35 and 36 are used to provide passageway for three electric wires which are connected to contact members 6, 7 and 8 respectively. Channels 35 and 36 are shown in FIGS. 3, 4a, 4b and 4c. As shown in FIG. 2 the present preferred embodiment when used in a hoist circuit is to connect contact member 7 to a common electric wire, contact 6 to a "lower" signal wire, contact 8 to a "raise" signal wire the wiring of the switch to other external circuits will be apparent to those knowledgeable in the art. As shown in FIG. 2 the switch is in its normal non-conducting state or off position without any electrical connection between contacts 6, 7, or 8. A conducting rod 4 is resiliently supported in a position of nonconduction with contacts 6, 7 and 8. The buttons 13 and 14 are integral parts of the outer insulating housing member 1 and are attached thereto by means of integral deformable resilient diaphragm portions 11 and 12 respectively of the outer housing 1. On the interior side of the outer housing 1 immediately adjacent buttons 13 and 14 are integral support projection portions 23 and 24. The inner member 3 has integral resilient diaphragms 32 and 33 connected to integral support portions 40a and 40b respectively. Diaphragms 11, 12, 32 and 33, as shown in FIG. 2, are in a nondeformed state or condition, and provide resilient support to flat washers 5 which in turn rotatably support connecting rod 4. Diaphragms 11 and 32 act to support and center washer 5 between the contacts 6 and 7 associated with the upper end of rod 4. Diaphragms 12 and 33 likewise support washer 5 at the lowermost end of rod 4. As shown in FIG. 2 the connecting rod 4 has end portions of smaller diameter than the center portion such that a shoulder is formed between the center section and each end portion. The washers 5 respectively ride on these shoulders to rotatably retain the rod 4 in spaced relationship between diaphragm pair 32, 11, and pair 33, 12. The center contact 7 is supported by resiliently deformable diaphragm 34, which allows for a limited rearward movement of the contact 7 by deformation of the diaphragm 34.

The buttons 13, 14 and respective diaphragms 11, 12 are recessed from the front surface of the switch housing 1 as shown along the right side of the view in FIG. 2. Such recessing of the buttons tends to prevent undesired operation of the switch by accidental pressure on the switch such as occurs for example when the switch is dropped or struck sharply.

FIG. 3 shows a front view of the inner member 3 with the cable opening 30 leading into the cable chamber 31. Contact 6 is supported in an upper contact channel 37, and the wire connecting to the upper contact 6 is routed from chamber 31 by means of wiring channel 35. The lower contact 8 is supported in the lower contact channel 38, and the wire to connect contact 8 is routed from the cable chamber 31 by means of wiring channel 35 and the wiring channel extension 36. The middle contact member 7 is supported within a middle contact channel 39 by means of two contact support posts 9 which respectively fit within post holes 41a and 41b in the inner insulating member 3. The top portion of the middle diaphragm 34 appears in FIG. 3 in a position so as to support contact 7 when it is placed within the channel 39. Extending down the center of the inner housing member 3 is a longitudinal channel 42 which allows for rotation and pivoting of the conducting rod 4. FIG. 3 shows diaphragms 32 and 33 which are integral parts of the inner housing and have integral portions 40a and 40b which provide rear support to the conducting rod 4.

As is apparent in FIG. 3 the channels 35, 36, 37, 38, 39, 42, holes 41a, 41b, and diaphragms 32, 33, 34 form a central cavity in the inner housing member 3 in which the switching components are mounted.

As shown in FIG. 3 is an annular ring 47 on the lowermost portion of the inner housing member 3 so as to effectively seal the outer housing 1 in the area of the annular sealing channel 17.

FIG. 4a shows a cross section of the switch taken along line 4a--4a of FIG. 1 and shows the upper portion of the switch in the vicinity of contact 6. The outer housing member 1 circumferentially encloses the switch as shown in this cross section. Knob 15a can be seen to interlock with the aperture hole 61 in the stiffening member 2. It is to be understood that similar apertures exist in the stiffening member 2 to interlock with knobs 15b through 15h as shown in FIG. 1, and such apertures vary in diameter so as to correspond with respective adjacent knobs. Wiring channel 35 which extends along one side of the switch provides a route for the wires to all of the contacts. As shown in FIG. 4a wiring channel 35 provides access for a wire to one end of contact 6. The rod 4 is generally centered within the rod channel 42 and is in spaced relationship from any surface on the contact 6. The stiffening member 2 surrounds the inner member 3 on three sides and is electrically insulated from contact 6 and conducting rod 4 shown at 4b is an interim position of the end of the conducting rod 4 prior to the conducting rod 4 making electrical contact with the contact member 6. During normal switch operation when button 14 is depressed and diaphragm 12 deformed the end of conducting rod 4 closest to contact 6 rises to the position of 4b, as shown in FIG. 4a, and continues upward until physical and electrical contact is established with contact members 6. As can be seen in FIG. 4a the contact 6 is positioned such that the rod 4 contacts the contact member 6 off center, that is as shown in FIG. 4a to the left of the midpoints between the wire bores 62a and b. During use contact wear is initially restricted to the portion of contact 6 directly above position 4b. After a normal amount of wear occurs in that section of the contact 6, the contact 6 may be flipped end for end so as to reverse the positions of slots 62a and 62b. This procedure allows for additional contact wear on member 6 on the end associated with slot 62b. The electrical signal wire is brought to contact 6 by means of channel 35, and secured to contact 6 by insertion of the wire to either bore 62a or 62b whichever of the respective bores is in position adjacent to channel 35. The signal wire may be secured in the bore 62a or alternatively 62b by known methods, such as for example crimping of the contact 6, soldering, or by means of a set screw. Contact 6 is preferably of circular transverse cross section. Contact 6 is resiliently supported and insulated from the other portions of the switch by the inner housing member 3 and the outer housing member 1. By constructing contact 6 with a circular cross section and resiliently mounting contact 6 in channel 37, allows limited rotation and movement of contact 6 to maximize the contact wear surface available and cushions the impact during switching operations. By positioning contact 6 so that electrical contact between rod 4 and contact 6 occurs other than at the longitudinal midpoint, allows contact 6 to be flipped end for end and produces a contact component which is easily renewed for double the normal life expectancy.

As described herein the contacts 6, 7, 8 and rod 4 have a circular cross-section, but other shapes are included within the invention, such as for example square, rectangular, oval, and triangular shaped cross-sections. While described herein the electric contact between conducting members of the switch is described as a surface area, such contact includes the limited surface or point contact occurring typically between two curvilinear surfaces such as the cylindrical shaped rod 4 and cylindrical shaped contacts 6, 7 and 8.

Referring to FIG. 4c shows a cross section of the pendent switch taken along line 4c--4c in FIG. 1. The lower end of the conducting rod 4 is shown centered in the rod channel 42 in the inner housing 3. The stiffening member 2 is interposed between the outer housing 1 and the inner member 3 so as to provide stiffened wall portions on three sides of the switch, and leaves open the front portion of the inner housing 3. In FIG. 4c is shown an interim position 4a of the end portion of the connecting rod 4 as it rises to contact contact member 8 as would occur when only button 13 is depressed. The signal wire is routed to contact 8 by means of wiring channel 36. Contact 8 is positioned in such a manner within channel 38 that normal contact wear occurs at either of two alternative portions on the contact which are positionable above the area of 4a. Wire bores 60a and 60b are provided so that the signal wire may be alternatively attached to either end of the contact 8. The contact 8 may be positioned within contact channel 38 such that either bore 60a or 60b is adjacent channel 36 and available for connection to the signal wire. The contact 8 is similarly constructed having circular cross-section and positioned off center with respect to rod 4 so as to provide maximum contact life as hereinbefore described with regard to the upper contact member 6.

Referring now to FIG. 4b which is a cross section along 4b--4b of FIG. 1 shows the outer housing member 1 and the inner housing member 3 with the stiffening member 2 intermediate thereto and partially surrounding the inner housing 3. Positioned within the midle contact channel 39 are two contact support posts 9 and the middle contact member 7. The signal wire is brought to contact 7 from chamber 31 by means of wiring channel 35, and the signal wire is then electrically connected to contact 7 by either alternatively bore 63a or 63b. Contact 7 is similarly positioned off center as has been described with respect to contacts 6 and 8 such that contact 7 may be flipped end for end, thereby exchanging bore 63a with 63b so as to provide an unused portion of contact 7 to be positioned directly beneath the conducting rod 4. The contacting point 64 on the outer surface of the conducting rod 4 will then be brought into electrical contact at a different area on contact 7 during switch operations.

As has previously been described contact 4 is rotatably mounted within diaphragms 11, 32, 12, 33, and therefore different sections of the outer circumferential surface of conducting rod 4 as shown in FIG. 4b at 64 will be brought to bear upon contact 7 during switch operations. As shown in FIG. 4b contact 7 is restrained within the limits of the middle contact slot 51 and the upper diaphragm 34. Referring to FIG. 5 shows a middle contact support post 9 having an upper portion 54 which may act to secure such post 9 in the resilient inner or outer housings 3 and 1. The middle portion 55 of the post 9 is secured within respective post holes 41a or 41b as shown in FIG. 3. A bore 52 in post 9 and a bifurcated hook portion 53 provide for fixably engaging the stiffening member 2. FIG. 4b shows the hook portions 53 engaging such stiffening member 2. Post members 9 are preferably made of a nonconducting material, such as for example nylon. As shown in FIG. 5 the contact slot 51 is elongated to provide limited movement of the contact 7 in a plane perpendicular to the axis of rod 4. As shown in FIG. 4b the resilient diaphragm 34 urges the contact 7 to its uppermost position within slot 51. In operation as buttons 13 or 14 are depressed the portion of the contacting rod 4 as shown in FIG. 4b is caused to descend into electrical contact with the contact 7; and additional force on either of buttons 13 or 14 causes overtravel of the connecting rod 4 and which subsequently depresses resilient diaphragm 34 while maintaining electrical contact between the conducting rod and contact 7. As the rod 4 descends it tends to pivot about the axis of contact 7.

Referring now to FIGS. 6a through 6c wherein is shown a diagrammatical representation of switch operations as would generally be seen along the cross section line 2--2 of FIG. 1. In all three figures the conducting bar 4 is rotatably supported within washers 5; and washers 5 are supported intermediate the diaphragm pair 11 and 32, and diaphragm pair 12 and 33. Contacts 6 and 8 are resiliently supported within channels 37 and 38 respectively of the inner housing 3. Contacts 6 and 8 are resiliently supported but are permitted only relatively limited movement as supplied by the resilient material surrounding such contacts. Contact 7 is resiliently supported by diaphragm 34. In FIG. 6a the switch is shown in the off position with contacts 6, 7 and 8 electrically isolated and in a nonconducting relationship with the conducting rod 4. In FIG. 6a all four diaphragms 11, 12, 32, and 33 are in a relaxed, non-deformed state. FIG. 6a represents the switch function of a single pole double throw switch in a neutral or "off" position.

FIG. 6b shows the pendent switch in a position which brings contact members 7 and 8 into electrical contact. This is the state which occurs when only button 13 is depressed to deform diaphragm 11 downward and exert pressure on washer 5 which in like manner lowers and the conducting rod 4 pivots in a counterclockwise direction about contact 7. Whereby electrical contact is established between rod 4, contact 7 and contact 8. In FIG. 6b the downward force on the washer 5 held intermediate diaphragms 11 and 32 causes diaphragm 32 to collapse downward. In this state diaphragms 12 and 33 remain in a relatively nondeformed condition. It is to be noted that some minor deformation may occur in diaphragms 12 and 33 to allow alignment of the conducting bar 4 between contact 7 and contact 8. As shown in FIG. 6b diaphragm 34 is deformed downward under the pressure of the conducting bar 4 bearing against contact 7; such resilient deformation of diaphragm 34 insures forcible contact between contact 7 and the conducting rod 4, allows for limited over travel in the depression of button 13 and associated diaphragm 11, and allows for wear on contacts and support members. When button 13 is released the resilient actions of diaphragms 11 and 13 reposition the conducting rod to the position as shown in FIG. 6a and thereby terminate the conductive path between contacts 7 and 8.

The deformation of diaphragm 34 also allows for minor finger movement of the operator, which in a fixed movement switch would result in an interrupted circuit. The slot 51 in post 9 limit the over travel permitted by the diaphragm 34. Additional over travel may be gained by material choice and dimension in the integral resilient contact channels 37, 38, 39 of the inner housing member 3, which also permit limited over travel.

FIG. 6c shows a switch in a position in which contact member 6 and contact member 7 are in electrical contact. This state occurs when only button 14 is depressed deforming diaphragm 12 which in turn through forcible contact with washer 5 causes diaphragm 33 to be deformed downwardly, and the conducting rod 4 tends to pivot clockwise about contact 7. Contact 7 is forcibly brought to bear against conducting rod 4 such that diaphragm 34 is caused to deform downward slightly thereby insuring uniform pressure on the conducting rod 4 by the contact member 7. In the switch state shown in FIG. 6c diaphragms 11 and 32 are generally in a nondeformed state, but may be slightly deformed to allow alignment between the conducting rod 4 and contact member 6 and 7. Upon release of button 14, diaphragm 12 and 33 resiliently reposition rod 4 to the position shown in FIG. 6a, thereby interrupting the electrical path between contacts 7 and 8.

As has been described hereinabove when either button 13 or 14 is depressed the rod 4 moves until the rod touches contact 7, and then pivots about contact 7 until either contact 6 or 8 respectively is forcibly engaged by rod 4. It is to be understood that in some embodiments the rod 4 may engage either contact 6 or 8 first and then pivot about that contact until the rod touches contact 7. Other embodiments strive to have simultaneous physical contact between contact member 7 and either contact member 6 or 8. The distance between respective contacts and the geometry between the rod and the contacts along with the relative stiffness of the respective diaphragms determine the sequence of contact engagement during the switching operation.

As is apparent from FIGS. 6a, 6b and 6c the diaphragm pair 11 and 32 operate independently from the diaphragm 12 and 33. One of the advantages of such independent operation of these paired diaphragms, is that when both buttons 13 and 14 are depressed this causes all four diaphragms to deform downward such that the conducting rod 4 only contacts contact member 7, and therefore no conductive path is established between any pair of contact member 6, 7 and 8. A further advantage of this independent operation of paired diaphragms is apparent as in the case when the contacting rod is caused to weld to one of the contact members 6 or 8, whereby the conductive path is maintained even after the respective button has been released. This undesirable conductive path may be terminated by the simultaneous forcible depression of both buttons 13 and 14 which causes both ends of the conductive rod 4 to be forcibly removed downward from contact members 6 and 8. Depression of both buttons 13 and 14 causes all four diaphragms 11, 12 and 32 and 33 to deform downward such that the conducting rod is held in a position parallel to that position shown in FIG. 6a but at a level such that conducting rod 4 is spaced from contact elements 6 and 8.

As is apparent from the preceding consideration of FIGS. 6a, 6b and 6c the rod 4 pivots about the contact 7, and as such the outer circumferential surface of contact 7 provides a fulcrum for the pivoting of rod 4.

As shown in FIG. 6 the conducting rod 4 is loosely held within the center bore in washer 5 such that conducting rod 4 is freely rotatable within such washers. During normal operation of the switch which has outer housing member 1 and in housing member 3 composed of a resilient material such as for example rubber or plastic, some contact between the conducting rod 4 and the insulated surfaces of the rod channel 42 occur. As rod channel 42 in inner member 3 is a nonconducting material, such contact between the conducting rod 4 and the rod channel 42 or other insulated portion of the switch produces no harmful effects upon the switching characteristics of the device. Instead such physical contact provides an unbalanced frictional force on the outer surface conducting rod 4. Such frictional force upon conducting rod 4 causes rod 4 to partially rotate within support washers 5 during the depression or release of buttons 13 or 14. This rotation of conducting rod 4 results in a generally even distribution of wear along the outer circumferential surface of rod 4 in the areas where rod 4 contacts the contact members 6, 7 and 8. In this manner the rotation and resultant even distribution of wear on conducting rod 4 results in increased life to the conducting rod. Additional rotational forces on rod 4 result from frictional contact with 40a, 40b, 23, 24, and the actual contact members 6, 7 and 8.

As used herein words such as above, below, back, front, side, inward, outward, and words of similar import in the absence of an express indication to the contrary at a specific location are provided as a general indication and are not limiting.

Having described herein certain presently preferred embodiments of this invention it is to be distinctly understood that other variations, modifications and embodiments may be made without departing from the broad spirit and scope of the invention. It is to be understood that the invention is not limited to the present preferred embodiments described herein but may be otherwise variously embodied as provided within the scope of the appended claims.