US3800112A

US3800112A - Push-pull switch having self-biasing elastomeric material contacts with discrete conductive particles dispersed therein

Info

Publication number: US3800112A
Application number: US00237297A
Authority: US
Inventors: Rocher G Du
Original assignee: Essex International Inc
Current assignee: Lear Corp EEDS and Interiors
Priority date: 1972-03-23
Filing date: 1972-03-23
Publication date: 1974-03-26
Anticipated expiration: 1991-03-26

Abstract

A push-pull switch having a pair of axially aligned, extensible and retractable links and a pair of resilient, normally nonconductive switching members one of which may be compressed and rendered conductive in response to extension of the links and the other of which may be compressed and rendered conductive in response to retraction of the links. The resilience of the compressible switching members normally maintains the links in such positions that neither of the switching members is conductive.

Description

United States Patent [191 Du Rocher Mar. 26, 1974 [5 PUSH-PULL SWITCH HAVING 3,629,774 12/1971 Crites 338/114 SELFJHASING ELASTOMERIC MATERIAL 2,441,888 5/1948 Lansing..... ZOO/l6 B 3,386,067 5/1968 Costanzo 338/100 CONTACTS WITH DISCRETE 2,793,260 5/1957 Ciosek 200/153 w ux CONDUCTIVE PARTICLES DISPERSED 3,258,549 6/1966 SIOl 200/153 v ux THEREIN Inventor: Gideon A. Du Rocher, Mt. Clemens,

Mich.

Essex International Inc., Fort Wayne, Mich.

Filed: Mar. 23, 1972 Appl. No.: 237,297

Related U.S. Application Data Division of Ser. No. 851,343, Aug. 19, 1969, Pat. No. 3,653,237.

Assignee:

References Cited UNITED STATES PATENTS 4/1970 Harshman et al 200/159 X Primary Examiner-Herman J. Hohauser Assistant Examiner-Robert A. Vanderhye Attorney, Agent, or Firm-Learman & McCulloch [5 7] ABSTRACT A push-pull switch having a pair of axially aligned, extensible and retractable links and a pair of resilient, normally non-conductive switching members one of which may be compressed and rendered conductive in response to extension of the links and the other of which may be compressed and rendered conductive in response to retraction of the links. The resilience of the compressible switching members normally maintains the links in such positions that neither of the switching members is conductive.

8 Claims, 3 Drawing Figures VIII/III] PUSH-PULL SWITCH HAVING SELF-BIASING ELASTOMERIC MATERIAL CONTACTS WITH DISCRETE CONDUCTIVE PARTICLES DISPERSED THEREIN RELATED APPLICATION This application is a division of application Ser. No. 851,343, filed Aug. 19, 1969, now US. Pat. No. 3,653,237.

The invention disclosed herewith relates to a switch construction of the pull-push type for operating electrical devices such as reversible DC. motors and includes a pair of compressible, resilient, normally nonconductive switching members. The switching members are so arranged with relation to the remaining switch structure that one of them is compressed and rendered conductive when the switch structure is subjected to a pulling force and the other of the switching members is compressed and rendered conductive when the switch structure is subjected to a pushing force. The arrangement is such that it is not possible to render both switching members conductive simultaneously.

A switch of the kind disclosed herein is particularly well adapted for controlling power apparatus for locking and unlocking the door latching means of vehicles, but has many other uses.

An object of this invention is to provide an improved switch construction for controlling the operation of power apparatus such as reversible electric motors.

Another object of the invention is to provide a switch construction of the kind referred to which precludes energization of a reversible motor or the like in more than one direction at any one time.

Other objects and advantages of the invention will be pointed out specifically or will become apparent from the following description when it is considered in conjunction with the appended claims and the accompanying drawings, wherein:

F l6. 1 is an elevational view of a switch constructed in accordance with the invention;

FlG. 2 is a vertical sectional view on a greatly enlarged scale of the switch; and

FIG. 3 is a schematic wiring diagram of a typical circuit with which the switch may be used.

Apparatus constructed in accordance with the invention comprises a' hollow, cylindrical casing 1 formed of insulating material such as nylon or the like and within which is a concentric, electrically conductive sleeve 2 constituting a contact of a circuit yet to be described. The sleeve has an axially elongated, diametral, lost motion slot 3 between its ends. The upper end of a link 4 extends into the sleeve 2 and is fixed to the latter by means of a pin 5. The lower end of a link 6 also extends into the sleeve 2 and is connected to the latter by means of a force transmitting pin 7 which passes through the slot 3 so as to permit limited lost motion between the link 6 and the sleeve 2 and between the links 4 and 6. The links 4 and 6, together with the pin 7, constitute switch operating means as will be pointed out hereinafter.

Encircling the sleeve 2 and arranged on opposite sides of the pin 7 is a pair of electrically conductive washers 8 and 9. in face to face engagement with the washer 8 is an annular, pressure sensitive switching member 10 and in axially spaced, confronting relation with the member 10 is an annular conductor 11 having a pair of axially extending contact legs 12 which parallel the inner wall of the housing 1. Fitted within the legs 12 is a rigid, annular plug 13 formed of insulating material such as nylon and which is fixed with respect to the casing 1 by the pin 5 and by an electrically conductive screw 14 which extends through the casing l and through one leg 12 of the conductor 11 so as to connect to the latter an electrically conductive wire 15.

in face to face engagement with the conductive washer 9 is a pressure sensitive switching member 16 similar in all respects to the member 10. In axially spaced relation to the switch 16 is an annular conductor 17 corresponding to the conductor 11 and from which extends a pair of contact legs 18 which parallel the wall of the casing 1. An insulating plug 19 similar to the plug 13 is accommodated between the legs 18 and is fixed with respect to the casing 1 by a pair of screws 20 corresponding to the screw 14. One of the screws 20 connects a wire 21 to one of the legs 18 of the conductor 17. A wire 22 is coupled by means of a conductive clamp 23 to the link 6.

The central opening in each of the annular conductors 11 and 17 is larger than the outside diameter of the sleeve 2, thereby providing an annular space between each of the annular conductors and the sleeve. The

plugs

13 and 19, however, include axially extending, annular projections 24 and 25, respectively, which occupy the annular spaces and bear against the associated switches 10 and 11. The projections 24 and 25 thus perform the function of providing axial spacing between the switches and their respective conductors 11 and 17, and the projections also provide concentrated force applying means in a manner and for a purpose presently to be described.

Each of the

switches

10 and 16 may correspond to one of those disclosed in application Ser. No. 857,941, filed Sept. I5, 1969, and to which reference may be had for a more detailed disclosure of the manner of constructing the switches. Briefly, however, each

switch

10 and 16 comprises an annular pad of resilient, deformable, non-conductive, synthetic rubber material such as that produced by combining Dow Corning silicone 3120 with Dow Corning catalyst S or F and throughout which is dispersed a large number of electrically conductive particles such as commercially available, silver coated, copper particles. The body of each switch is completely moisture impervious and may be formed by mixing the silicone resin and catalyst and stirring the conductive particles therein, following which the mixture may be cast in a mold and cured. The dispersion, the size and the quantity of particles are such that when the body is in its normal, unstressed condition the electrical resistance of the body is infinite and the body is non-conductive. When the body is subjected to compressive force of sufficient magnitude, however, the particles are forced to move relatively to one another into particle-to-particle engagement. The resistance of the body changes to that of the metal particles and the body becomes electrically conductive. Upon release of the compressive force, the inherent resilience of the body restores it to its normal, unstressed condition whereupon the particles again move relatively to one another, but in this instance in such manner as to disengage one another and render the body non-conductive. The two pads constituting the switches yieldably maintain the links 4 and 6 in their normal positions in which neither of the switches is conductive.

Only one of the switchesl and 16 may be rendered conductive at one time. If the switch is to be rendered conductive, a compressive force of sufficient magnitude must be applied to it to establish a conductive path via the conductive particles between the conductors 8 and 11. This may be accomplished by applying a downward force on the link 6 of sufficient magnitude to take up the lost motion between the pin 7 in the slot 3 in the sleeve 2 and to cause the pin 7 to bear against the conductor 11 so as to compress the pad 10 between the conductor 11 and the conductor 8. The projection 24 will provide a concentration of force adjacent the conductor 11 so as to assure establishing a conductive path through the switch 10.

To render the switch 16 conductive the pin 7 must be moved upwardly so as to compress the switch 16 between the conductors 9 and 17. Such movement of the pin 7 may be accomplished by upward movement of the link 6 a distance sufficient to take up the lost motion between the pin 7 and the sleeve 2 and effect compression of the switch 16 between the parts 9 and 17. The projection 25 will provide a high concentration of force adjacent the conductor 17 so as to assure the establishing of a conductive path through the switch 16.

Although the foregoing description refers to upward and downward movements of the link 6 to effect compression of the

respective switches

16 and 10, it will be understood that the application of a pulling force on the links 4 and 6 simultaneously, so as to extend the links, will effect compression of the switch 16, whereas the application of pushing forces on the links 4 and 6 simultaneously, so as to cause retraction of the links, will effect compression of the switch 10.

FIG. 3 discloses schematically one arrangement for operating electric motors by means of switches constructed according to the invention. As shown, there are four reversible DC. motors M, the armatures of all of which are connected in parallel circuit relation between power lines L-] and L-2. The switch 10 is shown connected between the wires and 22 and connected to a battery B by the line 22. The switch 16 is shown connected between the

wires

21 and 22 and connected to the battery by the line 22.

The apparatus includes a double pole, double throw relay 26 having two similarly wound

windings

27 and 28. One end of each winding is adapted to be connected to the battery B through the

switches

10 and 16, respectively. The opposite ends of the relay windings are joined and are connected to the emitter of a PNP transistor T having its collector grounded. A capacitor 29 is connected between ground and the base of the transistor T. The junction of the capacitor and the base of the transistor is connected through

resistors

30 and 31 to the

lines

15 and 21, respectively. The relay 26 has two switching

contacts

32 and 33 which are adapted to connect the four motors M to the battery B.

When the switch 10 is rendered conductive the relay 27 is energized and effects movement of the switching

contacts

32 and 33 to the left so as to connect the battery B to the armatures of all of the motors M via the lines L-] and L-2. The polarity of the battery should be such as to effect driving of the motors M in one direction.

When the switch 16 is rendered conductive, the winding 28 is energized to effect movement of the switching

contacts

32 and 33 to the right, thus connecting the armatures of the motor M to the battery B with a reverse polarity. The motors thus will be driven in the opposite direction.

Regardless of which switch is rendered conductive, the emitter of the transistor T will be connected to the positive side of the battery B through the appropriate winding 27 or 28 so as to bias the transistor forwardly into conduction. Simultaneously, the capacitor 29 will begin to charge and within a very short time, such as one second, the charge of the capacitor will be sufficient to decrease the forward bias on the base-emitter junction to render the transistor T non-conductive. When the transistor is rendered non-conductive, the current through the winding 27 or 28 ceases and the

switch contacts

32 and 33 return to their neutral positions as shown in FIG. 3, whereupon the motors M will be disconnected from the power source. In essence, therefore, each of the motors is energized by a current pulse of short duration.

Although the transistor T is rendered non-conductive shortly after energization of the motors M in either direction of operation, the capacitor 29 will maintain its reverse biasing charge through the

resistor

30 or 31 until such time as the actuated switch is rendered nonconductive and opens the circuit to the capacitor 29, at which time the capacitor will discharge through the transistor T. The discharge of the capacitor is at a slower rate than its charging rate, however, so as to require two or more seconds before the transistor can be rendered conductive. Thus, the apparatus has a time delay characteristic which prevents rapid motor reversing operations such as may be attempted by a child and which would be harmful to the apparatus.

The relative sensitivities of the

switches

10 and 16 may be varied in any one of several ways. For example, the switch 10 could have incorporated in it a larger number of conductive particles than are included in the switch 16. Alternatively, the switch 10 could be made much thinner than the switch 16, thereby requiring less travel of the links 4 and 6 toward one another to render the switch 10 conductive.

The disclosed embodiment is representative of the presently preferred form of the invention, but is intended to be illustrative rather than definitive thereof.

What is claimed is:

1. A switch construction comprising a pair of normally non-conductive switching members each of which is composed of a resilient, compressible body of non-conductive, elastomeric material having a plurality of electrically conductive, discrete particles dispersed therein, the quantity and size of said particles being such that each of said switching members is nonconductive until a sufficient compressive force is applied thereto to compress said body and effect movement of a sufficient number of said particles into engagement to establish through said body an electrically conductive path having a resistance corresponding substantially to the resistance of the engaged particles; electrically conductive force applying means interposed between said switching members in a position to bear against either of said switching members to apply a compressive force thereto; and operating means for moving said electrically conductive force applying 3. The construction set forth in claim 1 including means associated with said switching members and operable to concentrate the force applied by said force applying means to said selected one of said switching members.

4. The construction set forth in claim 1 including a casing in which said switching members are contained in spaced apart relation.

5. The construction set forth in claim 5 wherein said operating means comprises a pair of relatively movable links extending into said casing from opposite ends of the latter, and a force applying member carried by one of said links and interposed between said switching members.

6. A switch construction for connecting an input circuit line to either of a pair of coutput circuit lines comprising a pair of normally non-conductive switching members each of which is composed of a resilient, compressible body of non-conductive, elastomeric material having a plurality of electrically conductive, discrete particles being such that each of said switching members is nonconductive until a sufficient compressive force is applied thereto to compress said body and effect movement of a sufficient number of said particles into engagement to establish through said body an electrically conductive path having a resistance corresponding substantially to the resistance of the engaged particles, each one of said switching members being adapted to be connected to a different one of said output lines; electrically conductive force applying means interposed between said switching members in a position to bear against either of said switching members to apply a compressive force thereto; and electrically con ductive operating means, adapted to be connected to said input circuit line, for moving said force applying means into and out of force applying relation with a selected one of said switching members to connect said input line to one of said output lines via a path including said operating means and said one of said switching members.

7. The construction set forth in claim 6 wherein at least one of said switching members has an opening therein through which said operating means extends.

8. The construction set forth in claim 6 wherein each of said switching members has an opening therein through which said operating means extends, said operating means comprising a pair oflinks axially extensible and retractable relative to said casing.

Claims

1. A switch construction comprising a pair of normally nonconductive switching members each of which is composed of a resilient, compressible body of non-conductive, elastomeric material having a plurality of electrically conductive, discrete particles dispersed therein, the quantity and size of said particles being such that each of said switching members is nonconductive until a sufficient compressive force is applied thereto to compress said body and effect movement of a sufficient number of said particles into engagement to establish through said body an electrically conductive path having a resistance corresponding substantially to the resistance of the engaged particles; electrically conductive force applying means interposed between said switching members in a position to bear against either of said switching members to apply a compressive force thereto; and operating means for moving said electrically conductive force applying means into and out of force applying relation with a selected one of either of said switching members to apply a compressive force sufficient to render it electrically conductive, said operating means being capable of applying such force to one only of said switching members at any one time.

2. The construction set forth in claim 1 wherein said switching members are arranged in spaced relation and wherein said operating means includes a force applying member interposed between said switching members.

3. The construction set forth in claim 1 including means associated with said switching members and operable to concentrate the force applied by said force applying means to said selected one of said switching members.

6. A switch construction for connecting an input circuit line to either of a pair of coutput circuit lines comprisinG a pair of normally non-conductive switching members each of which is composed of a resilient, compressible body of non-conductive, elastomeric material having a plurality of electrically conductive, discrete particles being such that each of said switching members is nonconductive until a sufficient compressive force is applied thereto to compress said body and effect movement of a sufficient number of said particles into engagement to establish through said body an electrically conductive path having a resistance corresponding substantially to the resistance of the engaged particles, each one of said switching members being adapted to be connected to a different one of said output lines; electrically conductive force applying means interposed between said switching members in a position to bear against either of said switching members to apply a compressive force thereto; and electrically conductive operating means, adapted to be connected to said input circuit line, for moving said force applying means into and out of force applying relation with a selected one of said switching members to connect said input line to one of said output lines via a path including said operating means and said one of said switching members.

8. The construction set forth in claim 6 wherein each of said switching members has an opening therein through which said operating means extends, said operating means comprising a pair of links axially extensible and retractable relative to said casing.