GB2145191A - Pneumatic spring acting as electrical switch - Google Patents

Abstract

A pneumatic spring such as is used to assist the opening and closing of vehicle bonnets includes a metal bush 5 on the piston rod 2 and a conductive tongue 7 on the cylinder 1. In the contracted position of the piston 3 in the cylinder 1, the tongue 7 does not reach as far as the rod 2 and there is no electrical connection, but in the extended position, the tongue 7 makes contact with the bush 5, being of greater external diameter, to complete the circuit between terminals 8 and 9. The device can switch on, for example, the internal light of a car bonnet. <IMAGE>

Description

SPECIFICATION Pneumatic spring electrical connecting device This invention refers, as stated in the title of this specification, to an electric connecting device which has been specially designed for pneumatic springs.

(The term "spring" used herein also meaning "strut" or the like).

There are different types of pneumatic springs which are used to assist the opening and closing of vehicle bonnets, for lowering and raising the backs of car seats, for kitchen furniture and numerous other applications.

In certain cases, such as for example in the field of vehicles or of an entrance door to a completely dark enclosure, at the same time as opening the said element, it is wished to light the said enclosure and, consequently, this lighting has to be interrupted, also automatically, when it returns to the closed position.

The use is also known of pneumatic springs themselves as electric connecting and disconnecting elements, i.e. like switches as such, to feed the respective circuit. Electrical conduction is achieved thanks to the metal nature of the actual spring and the relative displacement between the cylinder and the shank is used for switch purposes.

The device which the invention proposes focuses its features specifically on a special arrangement to achieve the reliable connection and interruption of the electric circuit in the movements of the spring.

More precisely, the device preconized is specially designed for pneumatic springs in which the cylinder and the shank maintain perfect electrical insulation, in any position between them, thanks to the insulating nature of the actual piston of the shank and of a bushing fixed at the outlet of the cylinder, acting as a guide for this shank, centering its features on the means with which the connection can be made between these elements, specifically corresponding to the position when the spring is stretched to the maximum.

To do so, the packing of the plunger head of the shank, as mentioned above, is electroisolant, preferably plastic, and provided with a metal bushing which is prefectly adapted to the surface of the shank, in its end corresponding to the said plunger, while the inner side of the cylinde, near its outlet end for the shank, a metal bushing is fixed, provided with a strip or resilient tongue which in normal conditions approaches the shank, but does not make contact with the former.

In these conditions, when the spring is in a completely or partially retracted position, the said strip becomes independent of the shank, interrupting the continuous flow of electricity between these elements, whereas when this spring is stretched to the maximum, the metal bushing joined to the pack of the plunger and adapted perimetrically to the shank, touches the said strip, thereby establishing the electric continuity sought between these elements.

Obviously, in the free ends of the cylinder and of the relevant connection, terminals are arranged to place the spring in the supply circuit of the respective light point or electric element which is intended to be fed when the spring stretches.

As a complement of the structure disclosed, it has been foreseen that the cylinder be assisted by a plastic case which isolates it electrically from its surroundings.

To complete the description to be given below, and to assist a better understanding of the features of the invention, a sheet of drawings is attached to this specification, as an integral part thereof, in which with an illustrative and unlimiting nature, and in its single Figure, a side elevation view and diametrical cross-section has been shown of a pneumatic spring provided with the electric connector which comprises the object of this invention; said spring has been shown in two extreme positions, corresponding to the connected and disconnected situation.

In the light of this Figure, it can be seen how the electric connector which the invention proposes is applicable to a pneumatic spring made up of a cylinder 1 and a shank 2, with any conventional configuration and layout, but with the particularity that the packing 3 corresponding to the plunger of the shank 2 is electroisolant, and that the said shank 2 emerges through the inlet corresponding to the cylinder 1 through a guide bushing 4, also electroisolant.

The invention is centered on the fact that in the inner end of the shank 2, which is metal and has a conductor nature, a bushing 5 is fixed to the actual packing 3, said bushing being metal and a conductor, and perfectly adapted to the surface of shank 2.

On the other hand, in the end of the cylinder 1 corresponding to the outlet for the shank 2, said cylinder also being made of metal, a bushing 6 is fixed to it inside, said bushing having conductor features and being provided with an inner extension 7 forming a tongue which approaches the shank 2 without actually making contact with it.

As a complement to the structure disclosed, the said base element, i.e. the cylinder 1 and the shank 2 have two connecting terminals 8 and 9 at their free ends, through which the spring is inserted in the supply circuit of the pilot light or electric drive element concerned.

In accordance with the arrangement disclosed, when the spring is retracted to the maximum, as shown with a thin line in the Figure, or in any other intermediate extended position, the tongue 6 is physically independent of the shank 2 and, consequently, the electric circuit between terminals 8 and 9 remains open.

This inoperative situation, as mentioned above, is maintained during the progressive elongation of the spring, until the outstretched limit situation in which the strip or tongue 7 makes contact with the bushing 5 integrally joined to the shank, making the relevant electric communication and closing the circuit coupled to terminals 8 and 9.

From the foregoing, it can be deduced that the electric connecting device preconized has an extremely simple structure, with the consequent beneficial economic repercussion which this implies, apart from offering absolute functional reliability, due to its very simplicity.

It will of course be understood that the present invention has been described above purely by way of example and modifications of detail can be made within the scope of the invention.

Claims (3)

1. An electric connector for pneumatic springs, which, being specially designed for springs in which the cylinder and shank are made of metal and are electrically insulated thanks to the insulating nature of the packing corresponding to the plunger of the shank and of the guide bushing through which said shank of the cylinder emerges, springs through which it is sought to supply a light point or any other electric device, essentially characterised in that it consists of a bushing stiffly joined to the packing of the shank which is adapted to the side surface of the initial sector of the said shank, whereas in the inner surface of the cylinder, near the outlet for the shank, another metal bushing is adapted, which establishes electric continuity with it and which has a tongue or inner arched strip, with the particularity that the said tongue approaches the side surface of the shank, but without actually making contact with it; this contact is made when the spring is in the fully outstretched position, just when the bushing associated to the shank reaches the position corresponding to the tongue of the bushing associated to the cylinder, with the particularity that these elements, shank and cylinder, have terminals in their respective end areas, to be inserted in the relevant electric circuit to be controlled.

2. A pneumatic spring comprising a cylinder, a piston, the piston having a shank and head, the cylinder and shank being electrically conductive and the head being non-conductive, and an electrically insulating guide bush for guiding the shank within the cylinder, the spring further comprising electrical contact means extending around the shrank adjacent the head and a conductive tongue extending inwardly from and in electrical contact with the inside of the cylinder in the region of the guide bushing, the tongue extending towards but not contacting the piston shank, wherein when the piston is in an extended position relative to the cylinder the electrical contact means extending around the shank contacts the conductive tongue to provide an electrical connection between the shank and the cylinder.

3. A pneumatic spring or electrical connector substantially as hereinbefore described with reference to and as shown in the accompanying drawing.