FR2576373A2 - Device for transmitting a rotation movement - Google Patents

Abstract

Device for transmitting a rotation movement between a motor block and a working tool comprising a core on which a coil of polyamide fibres according to the main patent is wound. According to the present addition, the external sheath surrounding the Kevlar coil cannot be compressed and keeps a length which is identical to that of the internal cable during operation. Application: flexible link in particular for rotating hand tool.

Description

DEVICE FOR TRANSMITTING A ROTATION MOTION
We have described in main patent No. 84 18251 of 30/11/84 a mechanical connection device comprising a flexible core on which is wound a spiral of Kevlar coated in a layer of Teflon, the direction of winding of the Kevlar fibers being opposite the direction of rotation of the movement to be transmitted. It is thus possible to use the tensile strength characteristics of Kevlar.

The present addition relates more particularly to the use of such a connection for the transmission of a rotational movement between an engine block and a tool.

Hoses already exist consisting of a steel cable rotating inside bearings inside a sheath.

Unfortunately, during the transmission of forces, the core generally constituted by a steel cable stores by elasticity a certain amount of energy so that it has been found, in certain cases, that these hoses break, this breakage due to the release of energy stored by elasticity inside the steel cable. Since Kevlar has an elongation at break in% which varies appreciably between 2 and 4, this material does not have the possibility of storing. energy and remains constantly inert. As a result, the drawback indicated above for steel cable hoses no longer exists in the case where a Kevlar spiral is used to transmit the movement.

The main patent has provided an outer sheath of the shower hose type made up of rings which can interpenetrate over a greater or lesser depth depending on the movement which is given to the hose. This solution is satisfactory when the torques to be transmitted are of low importance. On the other hand, when high torques are to be transmitted between the motor unit and the operating tool, compression may occur on the sheath which prevents proper transmission of the rotational movement.

According to the present addition, the device according to claim of the main patent comprising a core on which is wound a Kevlar spiral is characterized in that the outer sheath is incompressible.

Of course the sheath must remain flexible and the incompressibility can result from various means and for example from the incorporation of metal wires in a plastic sheath, the metal wires extending parallel to the longitudinal direction of the hose. It is indeed necessary that there is no variation in length of the sheath during work, the latter remaining identical to the length in the longitudinal direction of the cable or of the rotation core.

 In practice, the end of the Kevlar cable is poured into a compound base which ensures its immobilization relative to the core on which the spiral is wound. The compound bases rest, for example, on bearings provided on the ends of the hose.

It goes without saying that many variants can be introduced in particular by substitution of technically equivalent means without leaving the scope of this addition.

Claims (1)

CLAIM Device for the transmission of a rotational movement according to claim 2 of the main patent, characterized in that the flexible outer sheath is incompressible.