Interlock Pushbutton Assembly

This application relates to, but is in no way dependent upon, co-pending application of common ownership, Ser. No. 06/292,776, filed Aug. 14, 1981.

This invention relates, in general, to electric pushbutton switches and, in particular, to an interlock mechanism for a pair of pushbutton switches. The interlock mechanism prevents the depression of both pushbuttons simultaneously. That is, once one of the pushbuttons has been depressed, the other pushbutton is locked into its normal non-depressed position.

Numerous mechanisms for interlocking pushbuttons can be found in the prior art. The use of rocker arms is only one type of many different mechanical linkages which have been utilized. In comparison to the present invention, these prior art mechanical linkages are more complex in construction, and movement of the linkage occurs when either pushbutton switch is depressed.

This invention has general applicability but is most advantageously applied to a pair of electric pushbutton switches. The present invention has special applicability to the multiple position pushbutton switches disclosed in the referent co-pending application.

It is a general object of the present invention to provide for a pair of electric pushbutton switches an improved interlock mechanism.

It is another object of the present invention to provide an interlock mechanism which requires a minimum number of parts and is easy to manufacture.

It is a further object of the present invention to provide an interlock mechanism which allows only one pushbutton of the pair of pushbuttons to be depressed at any one time.

It is another object of the present invention to provide an interlock mechanism which requires movement when only one of the two pushbutton switches is depressed.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claims. The invention, together with further objects and advantages, may best be understood by reference to the following description taken in conjunction with the accompanying drawings, in the several figures of which like reference numerals identify like elements, and in which:

FIG. 1 is a perspective view of the pushbutton electric switch mechanism embodying the present invention;

FIG. 2 is a perspective view of a housing for the pushbutton switches;

FIG. 3 is a perspective view of an interlock plunger utilized as part of the present invention;

FIG. 4 is a perspective view of a cover which is used with the housing;

FIG. 5 is a partially cut-away view of the electric pushbutton switch mechanism illustrating the present invention; and,

FIGS. 6A, 6B and 6C illustrate how the present invention operates.

This invention relates to a novel pushbutton switch mechanism for use with a pair of pushbutton switches. In particular, the mechanism provides for an interlock between the two pushbutton switches such that only one pushbutton switch may be depressed at a time. The present invention will now be described. In general terms, the novel pushbutton switch mechanism is for use with a pair of pushbutton switches with electrical contacts. More specifically, an interlock mechanism is provided between the switches which comprises a shoulder on each of the pushbutton switches and an interlocking plunger for contacting the shoulders of the pushbutton switches. Furthermore, a return spring is provided in contact with the interlock plunger for retaining the plunger in a predetermined position. A plunger support and a plunger guide in the pushbutton switch mechanism is provided for defining an area in which the interlock plunger is contained. When one of the pushbutton switches is depressed, the interlock plunger contacts the shoulder of the other pushbutton switch thereby preventing the other pushbutton switch from being depressed simultaneously.

FIG. 1 is a perspective view of a pair of pushbutton switches embodying the present invention. FIG. 5 is a partially cut-away view of the FIG. 1 embodiment showing the novel interlock mechanism. The novel pushbutton switch mechanism comprises first and second pushbuttons 10 and 12. Each of the pushbuttons 10 and 12 has a cam 14 with a cap 16 attached to a first end 18 of the cam 14. A cam return spring 20 is attached to a second end 22 of the cam 14. At least two sets, 24 and 26, of electrical contacts are provided and are activated by the cam 14. The cam 14 also has a shoulder 28.

A housing 30 is provided for containing each of the cams 14 of the first and second pushbuttons 10 and 12. The housing 30 has an open bottom 32. (See FIG. 2.) A cover 34 is attached to the open end 32 of the housing 30. The cover 34 has a support post 36 for each of the cam return springs 20 of the first and second pushbuttons 10 and 12. (See FIG. 4.)

As shown in FIGS. 3 and 5, a cylindrical interlock plunger 40 is provided for contacting the shoulders 28 of the cams 14. An interlock plunger return spring 42 is attached to the interlock plunger 40 for retaining the plunger 40 in a predetermined position.

A plunger support section 44 on the housing 30 and a plunger guide 46 on the cover 34 are provided for positioning the interlock plunger 40 and the interlock plunger return spring 42 when the cover 34 and the housing 30 are assembled.

The interlock plunger 40 has a first end 51 which is substantially larger than a second end 52. The first end 51 has an outward extending conical section 54 and the second end 52 is flat. The plunger return spring 42 contacts a rear portion 56 of the larger first end 51 and also contacts a portion of the plunger support section 44 and a portion of the plunger guide 46 when the unit is assembled, thereby retaining the plunger return spring 42 in position as shown in FIG. 5.

Referring to FIG. 2, the plunger support section comprises a pair of walls 58 with a groove 60 located substantially in the center of the walls 58. The bottom 62 of the grooves 60 is rounded to fit the configuration of the interlock plunger 40. Referring now to FIG. 4, the plunger guide 46 comprises a block 64 having a predetermined length, the ends of which fit in the grooves 60 of the plunger support section 44. The plunger guide 46 further comprises a pair of side walls 66 which fit between the walls 58 of the plunger support section 44. The top 68 of the block 64 is rounded to fit the configuration of the interlock plunger 40. When the cover 34 is assembled with the housing 30 the plunger support section 44 and the plunger guide 46 define an area in which the interlock plunger 40 and the interlock plunger return spring 42 are positioned as shown in FIG. 5. The interlock plunger 40 is held in a first predetermined position when neither of the first or second pushbuttons 10 and 12 are depressed as shown in FIG. 5.

FIGS. 6A, 6B and 6C illustrate the operation of the interlock plunger 40. In FIG. 6A neither the first nor second pushbutton 10 or 12 is depressed. In this position the interlock plunger 40 occupies a first predetermined position in which the conical section 54 of the interlock plunger 40 contacts the shoulder 28 of the second pushbutton 12. FIG. 6B illustrates that when the second pushbutton 12 is depressed, the shoulder 28 of the second pushbutton 12 causes the interlock plunger 40 to move to a second predetermined position in which the second end 52 of the interlock plunger 40 contacts the shoulder 28 of the first pushbutton 10 thereby preventing the first pushbutton 10 from being depressed. In the second predetermined position the plunger return spring 42 has been compressed and when the second pushbutton 12 is released the plunger return spring 42 will cause the interlock plunger 40 to return to the first predetermined position as shown in FIG. 6A. The conical section 54 of the interlock plunger 40 allows the second pushbutton 12 to move the interlock plunger 40 when the pushbutton 12 is depressed. In FIG. 6C the first pushbutton 10 has been depressed which causes no movement of the interlock plunger 40; however, when the second pushbutton 12 is attempted to be depressed after the first pushbutton 10 has been depressed, the interlock plunger 40 is restrained from moving by a surface on the cam 14 of the first pushbutton 10 and the flat end 52. Thus, the present invention provides a novel interlock mechanism requiring few moving parts which prevents the two pushbuttons from being depressed simultaneously.

The invention is not limited to the particular details of the apparatus depicted and other modifications and applications are contemplated. Certain other changes may be made in the above-described apparatus without departing from the true spirit and scope of the invention herein involved. It is intended therefore that the subject matter in the above depiction shall be interpreted as illustrative and not in a limiting sense.