The present invention relates to a retractor reel for a vehicle safety belt, and more particularly to a retractor reel for a vehicle safety belt adapted to be used in a motor car.
Many different retractor reels have been proposed previously for use with vehicle safety belts mounted in motor cars. In a typical prior proposed device the safety belt is automatically wound onto a shaft when the belt is not in use. The shaft is rotatably supported by appropriate bearings. Usually such a device incorporates a locking arrangement which prevents the belt withdrawn from the reel under certain circumstances, for example when the vehicle is subjected to a sudden deceleration, and/or when the belt is subjected to a force tending to withdraw the belt rapidly from the reel.
It has been proposed previously to utilize locking pins to effect the appropriate locking of the rotatable shaft in such a retractor reel. For example, U.S. Pat. No. 3,430,885 discloses an arrangement in which a plurality of locking pins are provided, which are arranged to extend radially of the rotatable shaft. The pins are kept in a retracted non-locking position by means of a permanent magnet located in the centre of the shaft. The locking pins are movable in a radial direction, and are thus adapted to be moved to an extended or locking position by the centrifugal force experienced by the pins when the belt is rapidly withdrawn from the reel. It will be appreciated that this locking mechanism is only actuated when the belt is rapidly withdrawn, and is, thus, only "belt sensitive". The mechanism is not "vehicle sensitive" in that locking is not effected as a direct consequence of the vehicle being subjected to rapid deceleration. This is clearly a disadvantage. Also, in the embodiment described in U.S. Pat. No. 3,430,885, the described shaft is difficult to manufacture.
U.S. Pat. No. 2,953,315 describes a retractor reel having two pins which are located in alignment, one on each side of the axis of a shaft, and which can move radially relative to the shaft. The pins are adapted to be moved as a consequence of relative movement between the rotatable shaft and an inertia body which is rotatably mounted on the shaft. This mechanism is only "belt sensitive" but can be adapted so as to provide a locking effect in response to deceleration of a vehicle, i.e. so that the locking mechanism is "vehicle sensitive" as well as "belt sensitive". However, this mechanism is very complicated to manufacture.
The locking mechanisms described in the above mentioned Patent Specifications all have a complicated shaft design because the force that may be exerted on a vehicle safety belt when the reel is locked under emergency conditions may be very high, and this force has to be transferred from the belt of the safety belt to the locking means through the shaft. Thus the shaft must be able to withstand the appropriate force without failing.
The problem of transferring the force from the belt to the locking means can be solved in a relatively easy way by providing a separate locking means capable of engaging one or two notched wheels attached to one or both ends of the shaft. However, if this solution is adopted other problems arise, for example the problem of providing a reliable control of separate locking means which engage two notched wheels.