Title:
ELECTRICAL SWITCHES
United States Patent 3794790


Abstract:
An electrical switch including a first flexible elongated conductor and a second flexible elongated conductor coaxial with the first conductor. An insulating element which is both resilient and deformable spaces the first conductor from the second conductor along the whole length of the first conductor, and the insulating element is loaded with conductive particles. The nature of the insulating element containing the conductive particles is such that compression of the element in a direction to decrease the spacing between the first and second conductors establishes a conductive path within the element between the first and second conductors.



Inventors:
LEYLAND K
Application Number:
05/326339
Publication Date:
02/26/1974
Filing Date:
01/24/1973
Assignee:
RISTS WIRES CABLES LTD,GB
Primary Class:
Other Classes:
200/85A, 200/86A, 338/114
International Classes:
H01H35/00; G08G1/01; H01B7/10; H01H1/029; H01H1/06; H01H13/52; (IPC1-7): H01H13/16
Field of Search:
338/99,100,114 200
View Patent Images:
US Patent References:
3710050ELECTRONIC PRESSURE SENSITIVE SWITCH1973-01-09Richards
3509296RESILIENT VARIABLE-CONDUCTIVITY CIRCUIT CONTROLLING MEANS1970-04-28Harshman et al.
3321592Safety closure edge1967-05-23Miller
2445660Electric treadle1948-07-20Bruestle
2305717Circuit controlling means1942-12-22La Bell



Primary Examiner:
Smith Jr., David
Attorney, Agent or Firm:
Holman & Stern
Claims:
I claim

1. An electrical switch including a first flexible elongated conductor in the form of a conductive wire, a second flexible elongate conductor in the form of a conductive braid, and a resilient, deformable insulating sheath spacing said first conductor, throughout its length, from said second conductor said sheath encircling said first conductor, the material of said sheath being loaded with conductive particles, whereby compression of said sheath in a direction to decrease the spacing of said first and second conductors establishes a conductive path within said sheath between said first and second conductors.

2. A switch as claimed in claim 1 wherein the switch also includes an outer flexible protective sleeve.

Description:
This invention relates to electrical switches.

A switch according to the invention includes a first flexible elongated conductor, a second flexible elongated conductor, and a resilient, deformable insulating element spacing the first conductor, throughout its length, from the second conductor, the insulating element being loaded with conductive particles whereby compression of the element in a direction to decrease the spacing of the first and second conductors establishes a conductive path within the element between the first and second conductors.

Desirably the first conductor is in the form of a conductive wire or lead, the insulating element is in the form of a sheath within which the first conductor extends, and the second conductor is in the form of a conductive braid encircling said element.

Conveniently the switch also includes an outer flexible protective sleeve.

The accompanying drawing is a diagrammatic representation of an electrical warning system utilizing a switch in accordance with one example of the invention.

Referring to the drawing the switch 11 includes a first electrical conductor in the form of a copper wire 12. Encircling the wire 12 is an insulating element 13 in the form of a sheath of a resilient deformable insulating material which is loaded with spaced electrically conductive particles, whereby compression of a part of the element 13 urges the adjacent particles into contact to render that part of the element 13 conductive. The first conductor 12 extends within the element 13, the element 13 constituting a sheath encircling the conductor 12. Encircling the element 13, is a woven copper braid 14, and in the rest condition of the element 13, the element 13 serves to electrically insulate the copper braid 14 from the copper wire 12. Both the wire 12 and the braid 14 are of course flexible. Deformation of the element 13 at any point along its length, in a manner to move a portion of the braid 14 towards the wire 12 renders the compressed region of the element 13 conductive, so that an electrically conductive path is established between said region of the braid 14 and the wire 12.

The switch constituted by the wire 12 the element 13 and the braid 14 can be of virtually any desired length, and can for example be suplied in lengths wound on drums. In particular, the switch is suitable for use in traffic monitoring, or warning systems where a length of the switch will be laid across the path of the vehicle. As the vehicle passes over the switch an electrical circuit will be completed momentarily between the braid 14 and the wire 12, and the switch can thus be used to control a device 15 for example a bell or a buzzer in the case of a warning system, and a counter, in the case of a monitoring system.

If desired the braid layer 14 can be protected by an outer, flexible sleeve of insulating material, for example polyvinylchloride. Moreover, it is to be appreciated that the wire conductor 12 could be replaced with a braided copper lead.