TO PREVENT RUNNING BACKWARDS ON HILLS.
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A New Type of Scotch Which. Once it is Placed Upon the Ground, Operates Automatically When and as it is Required.
AN INTERESTING and novel type of scotch has just been patented by Messrs. W. and W. P. Thomas, both of Primrose Cottage. Ynisderw, Pontardawe, Glamorgan, South Wales. R embodies two types of sprag, one being of the pointed type, designed to dig into the surface of the road, and the other of the shoe type, in which a shoe is pushed under the wheel so that the weight of the wheel comes to rest upon it, and any further motion must take place against the frictional resistance to motion of the shoe as it rubs upon the road.
. The shoe is carried by a link, which is suspended from the underside of the frame, the arrangement. of the respective parts being such that, as the link is lowered towards the ground by the release of a cable—one end of which is in the driver's cab—the shoe finds its own place beneath the wheel as has been described. A projecting portion of the shoe is pin-jointed to the dependent arm of a bell 'crank lever, the other, shorter, and horizontal arm of which carries a sprag. The lower and business end of the sprag is divided to form a jaw which embraces and supports a roller. The roller embodies a ratchet gear, which provides that the roller shall be free to rotate in one direction only, that in which it must rotate when it is on the ground and following the vehicle while it is travelling forwards. The spindle of the roller is mounted in slots in the jaw end of the sprag, so that, in circumstances which we are about to describe, it is free to ride up the slot and lift itself clear of the ground. When the roller is down, it covers and protects the point, of the sprag.
When the gear is not required at all —that is to say, when the vehicle to which it is fitted is travelling along a level road or along a decline—it is hitched up close to the underside of the frame, where it is entirely out of the way. It is held in that position by a second cable—not that one to which we have already referred as being attached to. the shoe—and the free end of this cable, too1 is located -within easy reach
of the driver. Release of the cable (which should take place when the vehicle is about to ascend a hill, in the course of which there may arise the possibility of use for the scotch) lets down the whole of the mechanism, which is supported on the roller at the bottom of the sprag, and it, trails comfprtably behind so long as tile vehicle continues B•30
to travel forwards or remains stationary. In the event, however, of the vehicle beginning to travel backwards, the roller, which cannot rotate in the re
verse direction, stops and climbs up the slot in the sprag, exposing its pointed end, which it has hitherto covered and kept. from contact with the ground. So soon as the sprag bites the ground. which, ,presumably, it does immediately it. is allowed, by the lifting of the roller, to come into contact. with the surface, it stops, and, as the vehicle continues to run backwards, the two, sprag and vehicle, approach one another. When this happens, the mechanism and linkage of the device operates to bring the shoe downward and forward,, thrusting it under the wheel of the vehicle and -making, it effective just at the time when the pointed sprag is also doing its work, thus affording, simultaneously, the combined effects of the two kinds of scotch.
It should be pointed out that the design permits of the shoe being lowered at any time by the release of its cable, so that by its use the driver can guard against backward running of the vehicle which he has brought to a standstill on a hill. Moreover, although reference has only been made in the above description to the existence of one sprag and one shoe, it is permissible, without departing from the principle covered by the patent, to use two, one for each rear wheel, or even more than two, as, for example, one for each wheel on the vehicle.
The specification is No. 217,366.