Warning System for Tipping Vehicles
Page 70
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1-1 A WARNING system has been developed by Pilot Works, Ltd., Bolton, Lanes, to safeguard against the driver of a tipping lorry moving his vehicle away with the body fully or partially elevated. The system is particularly simple and is being fitted by Pilot on request.
There has been a number of accidents, in some cases fatal, when tipping lorries struck overhead wires, buildings and bridges, and these have been caused by drivers inadvertently driving with the body raised.
Before a tipping body can be elevated, the power take-ofl which drives the hydraulic pump must be engaged and the oil-release valve must be placed in the closed " (or " raised ") position. There is no particular merit in fitting a safety catch to the power take-off engagement lever to prevent accidental engagement, as in some cases the accident occurs immediately after a driver has completed a normal tipping operation. Similarly, any form of spring-loading for the power take-off lever or the oil-release valve to avoid accidental engagement is not a complete safeguard, as it is sometimes advisable for the driver to leave his cab while tipping.
The only method which appears to be reasonably effective is a warning-lamp system, which clearly indicates to the driver in his cab when the body has started to elevate.
The Pilot system consists of a weatherproof switch fitted to the outside of the chassis frame midway between the rear hinge bar and the back of the cab. This switch is operated by a " striker " in the form of a piece of angle iron bolted to one of the body longitudinal corners. The limit switch used is a Crabtree 14042/15 unit.
It is advisable that the warning lamp in the cab be fitted to the facia panel, or as near as possible to the normal line of vision. To minimize the danger arising from bulb failure, a rear-lamp assembly containing two bayonet sockets wired in parallel is used.
The entire system can be fitted in little more than an hour.