Multiple Circuit Selector Switch Assembly Having Movable Contact Means Adapted To Retain Itself In Closed Circuit Position

Abstract

A switch assembly has an apertured grate superimposed upon a contact board on which a plurality of independent electrical contacts are located. The apertures in the grate are respectively associated with the contacts to expose the contacts through the grate. A cross-curved elongated contact strip is operatively connected to the grate on the side thereof opposite the contacts in a predetermined position and configuration such that the strip is flexed between its points of connection to the grate in order to form a single projection which extends into one of the apertures and engages the contact associated therewith. The cross-curved contact strip flattens at the projection within the aperture because of the flexing of the strip, and thus holds the strip in that aperture until the strip is urged through another aperture in the grate, either manually or by a pushbutton or the like, thereby causing the projection in the strip to occur at the other aperture and relieving the projection at the aperture in which it was previously formed.

Description

The present invention relates to electrical switches, and more particularly to a selector switch which permits one circuit to be selected from a group of circuits.

Selector switches of various types have been previously proposed which will enable an operator to select one circuit from a group of circuits in order to perform a desired operation. Typically, such selector switches are provided with a plurality of pushbutton control members that are movable between two operative positions and interconnected with each other such that as any one of the control members is moved to one of its operative positions a control member previously in that operative position is returned to its other operative position. The problem with such pushbutton selector switches is that they require relatively complex arrangements of springs, plates or levers for interconnecting the respective control members in order that they operate in the desired manner. Moreover, the number of control members or pushbuttons which can be operatively associated with each other in the control device is usually limited because of the complexity of the interconnections required to control the positions of the pushbuttons. Also, because of the complexity of such previously proposed pushbutton selector switches, it is relatively difficult to assemble the components in their housings and thus a relatively large amount of hand labor is required in order to complete the assembly. As a result, it is not possible to obtain a rapid production rate in the manufacture of such selector switches.

Accordingly, it is an object of the present invention to provide a selector switch which has a minimum of movable components.

Yet another object of the present invention is to provide a selector switch by which one circuit can be conveniently selected from a series of circuits.

Another object of the present invention is to provide a selector switch which is relatively inexpensive to produce and is durable in use.

Another object of the present invention is to provide a pushbutton device which requires a minimum of force in order to make the selected contact, and yet has sufficient strength to maintain the contact at all times until another circuit is selected.

In accordance with an aspect of the present invention a selector switch assembly is provided by which individual circuits can be selected by the engagement of a contact strip with contact elements positioned on a printed circuit board. The switch includes a contact or printed circuit board having electrical contacts located thereon and an apertured grate which is operatively connected to the contact board on the side thereof containing the electrical contacts. The grate has a plurality of apertures formed therein which are respectively associated with each of the individual electrical contacts on the contact board, thereby to expose the contacts through the grate. A resilient electrically conductive common contact strip is operatively connected to the grate at the opposite end portions thereof. The contact strip is cross-curved about its longitudinal axis and its length between the points of connection thereof to the grate is greater than the distance between the points of connection so that the strip is thus flexed into a projection which extends towards and enters one of the apertures in the grate. As a result, the projection engages the contact member associated with the aperture in which it has entered.

Because of the cross-curved construction of the common contact strip, the strip has an unstable column strength and thus flattens across its width at the projection in an aperture; the flattening of the strip in this manner holds the strip in that aperture until the strip is urged through another aperture in the grate, either manually or by a pushbutton, thus causing the projection to occur at the other aperture and relieving the projection of the strip at the first aperture. As a result, the first contact is broken and a new contact is made.

In one embodiment, means are provided for automatically relieving the projection when manual pressure is removed, whereby the switch can be used to make intermittent contacts.

The above, and other objects, features and advantages of this invention, will be apparent in the following detailed description of illustrative embodiments thereof which are to be read in connection with the accompanying drawings, wherein:

FIG. 1 is a perspective view of a selector switch constructed in accordance with one embodiment of the present invention;

FIG. 2 is an enlarged exploded perspective view of the selector switch illustrated in FIG. 1;

FIG. 3a is a sectional view taken alone line 3--3 of FIG. 1;

FIG. 3b is a partial sectional view similar to FIG. 3a of another embodiment of the invention;

FIGS. 4 and 5 are sectional views of the contact strip used in the present invention taken along lines 4--4 and 5--5 respectively in FIG. 3a;

FIG. 6 is a sectional view, similar to FIG. 3, of another embodiment of the present invention;

FIG. 7 is a sectional view similar to FIG. 6, of yet another embodiment of the present invention;

FIG. 8 is a sectional view of still another embodiment of the present invention; and

FIGS. 9 and 10 are partial exploded perspective views of two additional embodiments of the invention.

Referring now to the drawing in detail, and initially to FIGS. 1 and 2 thereof, it is seen that a selector switch 10, constructed in accordance with the present invention, includes a plurality of pushbuttons 12 slidably mounted therein (as described more fully hereinafter) with which an operator may select any one of a series of electrical circuits connected to the switch assembly along its contact edge 14. The switch is constructed so that only one of the circuit connections 15 along edge 14 is selected at any given time by the depression of one of the pushbuttons 12 in the assembly.

As seen most clearly in FIG. 2, switch assembly 10 includes a printed circuit board element 16, also referred to hereinafter as a contact element or contact board, on which a plurality of contacts 18 are formed or otherwise positioned in any conventional manner in electrical contact with circuit connections 15. A grate plate 20, preferably formed of an electrical insulation material, is superimposed on the side 22 of contact board 16 on which contacts 18 are printed. The grate is provided with a plurality of independent apertures 24 which are located in the plate to be directly above and associated with individual contact members 18, so that those contacts are exposed through the grate.

A common contact element 26 in the form of an elongated electrically conductive strip is provided in the switch assembly 10 in order to allow an operator to make selective contact with the contacts 18, thereby to select the desired electrical circuit. As would be apparent to those skilled in the art, the common connector strip may be connected in any convenient manner through external circuits to a source of current so as to form a complete electrical circuit with the circuits to which connectors 15 are connected when the contact between the connector strip 26 and the respective contacts 18 is made, in the manner described hereinafter. However, in the embodiment of the invention illustrated in the drawing, connector strip 26 is provided with a permanent bend or corrugation 26' adjacent one end 30 thereof, which corrugation extends through an opening 24' in grate 20 into permanent contact with a contact 18' which is connected through a connector 15' on the printed circuit board to a source of current. Alternatively, corrugation 30 can be eliminated and strip 26 connected to the current source by a wire lead or the like in any convenient manner.

Contact strip 26 is connected to grate plate 20 and to contact board 16, in any convenient manner, and preferably by rivets 28, as illustrated in FIGS. 1 and 2, at the opposite ends thereof. The contact strip is provided as a cross-curved metallic element (preferably of thin spring steel), i.e. an element which is curved about its longitudinal axis, transversely of its width. This is most clearly illustrated in the sectional view of FIG. 4, wherein it is seen that in the normal relaxed configuration of the strip 26, the strip maintains a curved configuration in cross-section.

In accordance with the present invention, the length of the strip 26 between the points of connection 27 thereof to grate 20 is selected to be somewhat longer than the distance between rivets 28. As a result of this differential in length, the strip 26 will be flexed between its ends 30, i.e. between the rivets 28, so as to form a projection 32, as seen in FIG. 3. The difference in length between the length of the strip 26 and the distance between the rivets 28 determines the size of projections 32 and that difference is selected so that projection 32 will contact one of the contacts 18 through its associated aperture 24 in grate plate 20. The selection of which contact 18 is engaged by projection 32 is made by depressing one of the buttons 12, as described hereinafter. It is noted that formation or movement of projection 32 does not effect corrugation 26' since the latter is located on the other side of rivet 28'; thus the contact between corrugation 26' and contact 18' is always "made." In addition, strip 26 may have gold strips or the like plated or otherwise secured thereto at the locations on its lower surface with which it engages contacts 18. Such strips will allow the switch to accommodate heavy current flows therethrough.

Superimposed above grate 20 and contact strip 26 is a cover plate 33 connected to the switch assembly by rivets 28. Cover plate 33 has a plurality of apertures 34 formed therein which slidably receive pushbuttons 12. The latter have a complementary configuration in plan to the configuration of apertures 24 and are provided with laterally extending flanges 36 which prevent the buttons from being inadvertently withdrawn from the assembly. The buttons are freely slidably mounted in the apertures 34, except as limited by the flanges 36, and have projection portions 38 which are located to engage the upper surface 40 of contact strip 26, as seen most clearly in FIG. 3. In addition, an insulating pad 42 is positioned between the projections 38 of pushbuttons 12 and the upper surface 40 of contact strip 26. The insulator pad 42 is preferably formed of a waterproof material such as nylon or silicon rubber and it serves to protect against inadvertent contacts with the strip 26 through plate 33 which may cause shorting in the circuits connected to connectors 15. However, in certain applications this strip may be eliminated.

In the illustrative switch of the present invention, as shown in FIGS. 1-3, the switch is adapted to be operated intermittently, that is contact of the strip 26 with a contact 18 is maintained only as long as a button 12 is held depressed. When the button is relieved, the strip will automatically return to a position out of engagement with the contact board. This is accomplished by the provision of a pair of spacers 44 located at the opposite ends of the switch assembly. These spacers hold cover plate 33 sufficiently above grate plate 20 to accommodate the curved cross-sectional configuration of contact strip 26 and have downwardly bent ends 45 which engage strip 26. The bent ends 45 of spacers 44 bend strip 26 downwardly slightly into opening 47 in board 20 and hold the strip bent at these locations thereby normally taking up the extra length of the strip between rivets 28 so that the strip normally remains straight above grate 20. Thus, when one of the buttons, e.g. 12b, is depressed, it forms the projection 32 and causes it to engage its associated contact 18b, as seen in FIG. 3, thereby urging strip 26 at its ends upwardly against bent ends 45 of the spacers. However, as soon as the pressure on button 12b is relieved, the spring force of the bent ends of the spacers will overcome the tendency of strip 26 to maintain projection 32 and thus will bend the strip into opening 47, relieve projection 32, and return the strip to its straight configuration over opening 24. On the other hand, where it is desired that the strip 26 maintain its contact with a contact 18 for extended periods, i.e. not be intermittently operated, then the bent ends 45 of spacers 44 are eliminated. In that case, as described hereinafter, the strip 26, because of its configuration, will hold projection 32 in contact with the selected contact until another button 12 is pushed.

This latter form of the invention is shown in FIG. 3b wherein it is seen that in the assembled configuration of switch 10, without the bent spacer ends 45, strip 26 is flexed, due to the differential in length between its ends and the points of connection 28 on grate 20 so that a projection 32 is automatically formed which will enter one of the apertures 24 in the grate and contact one of the contacts 18 on contact board 16. Thus, for example, as shown in FIG. 3b, one of the contacts 18b is engaged by the projection 32. In that position the button 12b is, in effect, depressed and slides into its lowermost position under the influence of gravity. On the other hand, the remaining buttons 12 remain in their uppermost position resting on the upper surface 40 of strip 26. In this position the buttons also prevent the projection 32 from forming in a direction away from grate 20.

As a result of the cross-curved configuration of strip 26, the strip has an unstable column strength which makes it relatively easy to bend to form projection 32. However, when the projection is formed, the curved strip tends to flatten out, at the apex of the projection, as illustrated in FIG. 5. (This occurs in all embodiments of the present invention.) This flattening of the cross-curved band tends to hold the band in the flexed position, i.e. it serves to maintain the configuration of projection 32, until an outside force is placed on strip 26 at some other location. In effect, the cross-curved band acts as an "over the center member" when the band is flexed into the curved position. That is, at projection 32 the flexure of the strip causes the curved cross-section thereof to flatten out so that the center portion of the band moves downwardly, as seen in FIGS. 4 and 5, past a position at which the natural resiliency of the band will maintain its curved configuration. Once it has moved past that point, the band will maintain its flat configuration, or possibly even a reverse curved configuration until it is forced back in the opposite direction. This feature of the crosscurved strip enables the strip to maintain the projection 32 at a fixed location during the operation of the switch of FIG. 3b until another button 12 is depressed.

It is noted that although the strip 26 is shown in the drawing as being positioned to curve or open towards grate 20 and contact 18, the strip can be placed in the reverse position to curve or open towards cover plate 33 and will still operate in substantially the same manner, i.e. it will still flatten out at projection 32 to hold the projection in its associated grate aperture 24.

When it is desired to engage the common contact strip 26 with another contact element, for example contact 18a in FIG. 3b, pushbutton 12a is manually engaged and depressed against strip 26 and into the aperture 24a associated therewith. As a result of the manual force applied to the pushbutton 12a, band 26 is depressed and projection 32 is formed in the aperture 24a associated with contact 18a. Because the force on pushbutton 12a forms the projection 32 in this aperture, the projection 32 in aperture 24b is relieved, and the band returns to its curved and relatively straight configuration beneath pushbutton 12b, raising the latter to its uppermost position. Of course, in the embodiment of FIG. 3a this occurs automatically when pressure on pushbutton 12b is relieved due to the biasing effects of the spring bent ends 45 of spacers 44. In that case projection 32 is relieved and is not formed again until another pushbutton, e.g. 12a, is depressed and held down against the bias of spacers 44.

Because of the cross-curved configuration of strip 26, there is a positive snap action in the switch assembly so that the contacts between the strip 26 and the contacts 18 are made rapidly and positively. That is, projection 32 is rapidly snapped and unsnapped at the respective locations of the buttons 12 upon the actuation thereof. Thus, there is a clean, positive action contact in the switch.

In another embodiment of the present invention illustrated in FIG. 6, a toggle switch element 50 is utilized in lieu of the pushbuttons 12. As seen therein the toggle switch comprises an inverted Y-shaped member having a stem 52 and a pair of legs 54, 56 respectively. The toggle is pivotally mounted at 58 in the cover plate 33 of the switch assembly, with legs 54, 56 being positioned above respective apertures 24 formed in grate 20. It is noted for the purpose of simplifying the drawing, only two apertures 24 have been shown in FIG. 6, however, it is to be understood that the switch shown therein can have multiple toggle switches respectively associated with additional contacts 18 formed on board 16. In this embodiment of the invention the switch is constructed in a similar manner to the switch 10 in that a contact board 16 is provided with contacts 18 formed thereon. The apertured grate plate 20 is positioned in superimposed relation to the printed circuit board 16, with the apertures 24 thereof exposing contact elements 18, and a cross-curved common contact strip 26 is mounted above the grate plate 20 between that plate and the cover 33. As will be appreciated by a careful consideration of FIG. 6, by rotating toggle member 50 in opposite directions, as indicated by the arrow 60 in the drawing, legs 54 and 56 will alternately be urged into contact with common contact strip 26, causing the projection 32 to form in the aperture 24 in which the leg is inserted. The switch operates in substantially the same manner as the previously described switch of FIG. 3b in that the cross-curved contact member tends to flatten out in an over-the-center manner, to hold the projection 32 in the selected aperture 24 until the switch 50 is reversed.

Yet another embodiment of the invention is illustrated in FIG. 7 of the drawing. The switch 70 shown therein is similar in construction to the switch illustrated in FIG. 3b of the drawing, however, in lieu of the pushbutton members 12 a slide element 72 is mounted for sliding movement in cover 33 between two extreme positions at the right and left side (not shown) of the switch along a straight path, indicated by the arrow 74, above openings 24 in grate 20. Slide element 72 has a resilient arm 76 secured thereto which is adapted to slidingly engage the upper surface 40 of the cross-curved common contact strip 26. As illustrated in FIG. 7, with leg 76 engaging the contact strip 26 in this manner, it depresses the strip and forms projection 32 therein which engages the contact element 18a associated with the aperture 24 in grate plate 20 thereabove. When the slide 72 is moved towards the right, the leg 76 thereof causes the projection 32 to be formed in the successive apertures 24 while relieving the projection 32 in a prior aperture by applying sufficient force to the strip to overcome its tendency to hold the projection in the prior aperture.

Another embodiment of the present invention is illustrated in FIG. 8 of the drawing. This embodiment is similar to that illustrated in FIG. 3, except that the pushbuttons 12 have been eliminated therefrom so that the switch can be directly operated manually. Thus, switch 80 includes a contact board 16 having electrical contacts 18 formed thereon at predetermined spaced locations along its upper surface 22. A grate 20 is mounted above contact board 16 in superimposed relation with the apertures 24 thereof respectively located above the contacts 18. In addition, a cross-curved metallic contact strip 26 is mounted above and adjacent grate 20, with its length being selected to be larger than the distance between the points of connection 28 of the contact element to the grate so contact to form the projection 32 therein. Cover 33 provides a series of apertures 34 through which a finger can be inserted to engage the contact strip 26. The apertures 34 serve to confine the finger pressure to the proper area over the desired contact element 18.

In this embodiment of the invention the contact strip 26 may be provided with an insulated coating on its exposed side, i.e. on its side facing the apertures 34. Alternatively, in certain applications, the contact element need not be insulated. For example, the selector switch 80 may be used in a vending machine wherein the selection is made prior to insertion in a coin in the machine; in that case there is no current through the switch until the coin is deposited. Thus, the purchaser simply makes a selection by inserting a finger in a selected aperture 34 in order to urge the contact strip 26 into engagement with the appropriate contact 18, thereby moving the projection 32 into the appropriate aperture 24 adjacent the selected contact, and then deposits his coin. At that point, his finger is removed from the switch and the coin activates an additional switch which supplies current to the circuit. Thus, no insulation of strip 26 will be required.

In this embodiment of the invention the cross-curved contact strip operates in substantially the same manner as the embodiments which were previously described in that the curved configuration thereof provides unstable column strength in the strip which permits the strip to be readily flexed in the desired direction and which holds the flexed strip with projection 32 in the appropriate aperture until an outside force is applied to the strip through a separate aperture 24.

FIGS. 9 and 10 of the drawings illustrate a portion of two additional embodiments of the present invention which are similar in construction to the embodiment of FIG. 3b. Each of these embodiments is provided with a contact strip compliance means 90, 100, respectively, formed therein. These compliance means serve to apply a compressive force in the longitudinal direction of their associated contact strip 26, which aids the strip in maintaining the projection 32 in a fixed position until an outside force is applied to the strip at another location. The compliance members are useful in the switches of the present invention because high tolerances between the respective lengths of the contact strip 26, between the apertures or points of connection 27 therein, and the distance between the rivets 28, such as is required to properly form the projections 32, are sometimes difficult to produce, particularly in mass production operations. More specifically, in the structure of the present invention, particularly in the embodiments described above, the projection 32 is formed by the compression effected upon the contact strip 26 because of the greater length between the apertures or connection points 27 in the contact strip and the distance between the rivets 28. Thus, the differential in these distances or lengths is highly important in effecting the formation of the projections 32 and small variations in the amount of this difference can seriously effect the operation of the switch. On the other hand, by the embodiments of the invention shown in FIGS. 9 and 10 of the drawings, the compliance members 90, 100, serve to apply a compression bias to the contact strip 26 so that any variation in the tolerance of the respective lengths of the strip and the distance between the points of connection, is overcome by the compression imposed on the strip from the compliance means.

More specifically, the compliance means 90 shown in the modification of the switch assembly in FIG. 9 of the drawings consists of a preformed and permanent corrugation in one end of the strip 26 on the same side of the opening 27 therein as the projections 32 to be formed. The corrugation 90 is located to enter an opening 92 formed in grate 20 to accommodate the corrugation. By this construction, when the strip 26 is secured in the assembled switch, i.e. secured to rivets 28, it is held in compression not only by the excess length of the strip between its openings 27, but also by the corrugation or crimp in the strip provided by the compliance means 90. Thus, a bias compression stress or force is placed on the strip 26 along its longitudinal axis by the compliance means 90. This force will hold the projections 32 formed in the switch in a stable configuration until another pushbutton is pushed to form the projection 32 at a different location, i.e. in a different aperture 24.

The embodiment of the invention illustrated in FIG. 10 of the drawing operates on the same principle as the compliance means discussed above with respect to FIG. 9. In this case, however, the cross-curved strip 26 is provided with an enlarged portion 102 having a central aperture 104 formed therein in order to define a pair of thin legs or connecting strips 106. By this construction, when the switch is assembled with strip 26 secured through its openings 27 to the rivets 28, the strip is compressed to form a projection 32 because of the difference between its length between openings 27 and the distance between the rivets 28. However, any difference in tolerance is accommodated by the compliance means 100, since the thin legs 106 thereof apply a longitudinal compressive force to the contact strip in the mounted assembly. Accordingly, the strip is maintained in compression and the projections 32 formed therein will be held in a fixed position even if the relative lengths between openings 27 and rivets 28 are not exactly correct. The legs 106, since they are formed of the same spring steel material as the strip 26, have a relatively high spring rate, i.e. they constitute a relatively stiff spring which maintains a substantial compression stress on the strip 26 to insure that the projections 32 when formed hold their position and contact with their associated contact member 18.

Accordingly, it is seen that a relatively simple and inexpensive switch assembly is provided wherein only a single moving part is utilized to provide a selection between a plurality of different electrical circuits. Moreover, this single moving element, i.e. the flexible cross-curved strip 26, is constructed so as to maintain the selected position as a result of its own configuration and strength rather than as a result of the application of outside forces by springs, latches or the like as are required in previously proposed devices. As a further result of the relatively simple construction of the invention, the switch assembly is inexpensive to produce and can be manufactured at relatively high production rates.

It will be apparent from the foregoing description that the cross-curved strip 26 should be of a suitable spring material for best results in the practice of the invention. Spring steel, preferably stainless spring steel, having the physical properties of the strip used to manufacture steel tape measures is a highly satisfactory material for the strip 26. Other alloys such as berillum copper, phosphor bronze, or a suitable spring brass can be used.

Although illustrative embodiments of the present invention have been described herein with reference to the accompanying drawings, it is to be understood that the invention is not limited to those precise embodiments, and that various changes and modifications may be effected therein by one skilled in the art without departing from the scope or spirit of this invention.

Claims

What is claimed is:

1. A switch assembly comprising a contact board having a plurality of electrical contacts positioned thereon, an apertured grate operatively connected to said contact board adjacent said electrical contacts and having a plurality of apertures formed therein respectively associated with each of said electrical contacts to expose said contacts through the grate, and a resilient electrically conductive contact strip having opposite end portions respectively operatively connected to opposite ends of said grate at predetermined points of connection on the side of said grate opposite said contact board, said contact strip being cross-curved about its longitudinal axis, transversely of its width; the distance between said predetermined points of connection on said grate being less than the length of said contact strip between said points of connection whereby a portion of said strip is flexed into a projection extending towards and entering one of the apertures in said grate to engage the contact member associated with said one aperture; said cross-curved contact strip being flattened across its width at said projection by the flexing of the strip thereby holding the strip in said one aperture until the strip is urged through another aperture in said grate, causing said projection to occur at said another aperture and relieving the projection and flattening of the strip at said one aperture; and means for maintaining one portion of said contact strip in electrical connection with an electrical conductor at all times, whereby said strip operates to provide an electrical connection between said conductor and a selected one of said contacts at substantially all times, in accordance with the selected location of said projection.

2. A switch device as defined in claim 1 wherein said grate is formed of an electrical insulating material.

3. A switch as defined in claim 1 including a cover plate operatively connected to said grate, said cover plate being located on the side of said contact strip opposite said grate and having a plurality of apertures formed therein in position to be in alignment with the apertures in said grate.

4. A switch as defined in claim 3 including a strip of insulating material positioned over said contact strip on the side thereof adjacent said cover plate.

5. A switch as defined in claim 3 including a plurality of pushbuttons respectively slidably mounted in the apertures in said cover plate for movement towards and away from said contact board and having first end portions positioned adjacent said contact strip and adapted to be respectively urged into engagement with said strip and into their associated apertures in said grate to flex said strip and form said projection at their associated aperture in the grate to contact their associated contact member with said strip.

6. The switch as defined in claim 3 wherein said contact strip is positioned with one curved side thereof opening towards said grate.

7. The switch as defined in claim 3 including at least one toggle member pivotally mounted in said cover plate above and adjacent a pair of apertures therein; said toggle member including a pair of leg members positioned to respectively enter said pair of apertures in said cover upon pivotal movement of said toggle between first and second positions.

8. The switch as defined in claim 1 including a cover plate operatively connected to said grate, said cover plate being located on the side of said contact strip opposite said grate and having an elongated aperture formed therein in substantially vertical alignment with the apertures in said grate; and an insulative slide member slidably mounted in said cover plate above said contact strip for movement in the aperture of the cover between first and second positions with respect to the apertures in said grate, said slide member having a resilient leg adapted to slidably engage said contact strip, said leg member being adapted to urge said contact strip into the aperture in the grate therebelow to form said projection.

9. The switch as defined in claim 3 wherein said contact strip is formed of thin spring steel.

10. A switch assembly comprising, a contact board having a plurality of electrical contacts positioned thereon, a grate superimposed on and operatively connected to said contact board and having a plurality of apertures therein including apertures respectively located with respect to the contacts for exposing the contacts through the grate, and a cross-curved elongated contact strip operatively connected to said grate on the side thereof opposite said contacts in a predetermined position whereby the strip is flexed between its points of operative connection to the grate to form a projection extending into one of said apertures wherein the cross-curved strip is flattened across its width at said projection by the flexing of the strip thereby to hold the strip in said one aperture until the strip is urged through another aperture in said grate, causing said projection to occur at said another aperture and relieving the projection at said one aperture; and means for maintaining one portion of said contact strip in electrical connection with an electrical conductor at all times, hereby said strip operates to provide an electrical connection between said conductor and a selected one of said contacts in accordance with the selected location of said projection.

11. The switch assembly as defined in claim 10 wherein said contact strip has opposite end portions respectively connected to said grate at predetermined points of connection; the distance between said predetermined points of connection being less than the length of said contact strip between said points of connection whereby upon application of a force in a direction normal to said contact strip and towards said grate, said strip is flexed into a projection extending towards and entering one of the apertures in said grate to engage the contact member associated with said one aperture.

12. The switch assembly as defined in claim 11 including means in said assembly engaging said contact strip for urging the strip into a straight configuration above the apertures in said grate.

13. The switch assembly as defined in claim 11 wherein said distance and said lengths are selected in predetermined relation to each other such that flexing of said strip holds the strip in said one aperture until the strip is urged through another aperture in said grate, causing said projection to occur at said another aperture and relieving the projection at said one aperture.

14. The switch assembly as defined in claim 13 wherein said means comprises means for maintaining said one portion of said contact strip in engagement with one of said electrical contacts on said board at all times.