This invention relates to devices for pulling a trip cable in order to trip a lever.
It is well known to employ trip levers for a variety of reasons and particularly on trucks to open doors or tail gates. Trip levers are used also on logging trucks to hold and release the ends of large cables that are wrapped around the outside of the bunk stakes to hold them up. The bunk stakes of course support the load of logs on the sides thereof and during use are arranged in a vertical position. However, when the load is to be dumped, the bunk stakes can be pivoted at their bottom ends and swung outwardly by simply releasing the cables that hold the stakes upright.
Problems have been encountered with the use of such trip levers on logging trucks both because of the great force often required to trip these levers and because of the danger involved for the workman who attempts to trip the levers. Another difficulty arises from the need to trip two of these levers at once in order that an unduly large strain is not placed on a single bunk stake assembly. It will be understood that normally each logging truck has two bunk stake assemblies, one at the front of the load and the other at the rear. Each of these assemblies has its own trip lever and if two men are not available to trip these levers at the same time, then one man, such as the driver of the truck, often attempts to trip both levers. Occasionally an inside stake supporting cable breaks under the tremendous strain of supporting the load on its own causing the logs to be dumped prematurely. Such accidents have sometimes resulted in people being killed, trucks being damaged, or the timber itself being damaged.
A variety of devices have been used in the past in an attempt to trip these levers safely but none have been completely satisfactory for one reason or another. One of these devices is known as a wheel trip which consists of a chain from the truck or tractor wheels to the trip lever. The levers are tripped by driving the loaded truck ahead a few feet. Such devices require considerable time to arrange, are awkward to set up, and are not dependable due to the badly misaligned pull that is exerted on the trip levers by the chains. Moreover sometimes one of the two levers is successfully tripped but the other is not. If it is the rear or trailer bunk stake assembly that is tripped and some of the logs shift so as to hang over the side of the truck, the truck with the operator in it can sometimes be turned over on its side by the weight of the logs. For these reasons wheel trips are seldom used in practice.
Small pneumatic cylinders and co-operating pistons have also been used to trip these levers. These devices are mounted on the inside of the stake bunk assemblies adjacent the trip levers. They have proven to be unreliable either because they cannot exert a sufficient force on the levers, which are sometimes heavily back centered, or they or their hoses freeze-up in winter. They can also be broken by logs hitting them or jammed or seized by mud and dirt in their mechanism.
An object of the invention is to provide a device for pulling a trip cable in order to trip a lever which overcomes many of the above-mentioned problems. The device enables a workman to trip one or more levers from a safe distance or in a location which protects the workman from failing logs. The device is more reliable in that it exerts a sufficient force on the lever to trip it each and every time without fail. The device can also be used quickly and easily and does not require the truck to be moved in order to trip the levers. When two of the devices are used simultaneously, a workman is able to trip both the truck and trailer levers simultaneously.
A further object of the invention is to provide a device for pulling a trip cable which is readily adaptable to present unloading methods. Often a large four wheel loader is employed to safely unload all of the logs from the truck. It will be appreciated that merely releasing the stakes of the two bunk assemblies will not normally cause all of the logs to fall off the truck. Some of the logs will remain on the truck, resting on the horizontal beam support of the tractor and trailer parts of the truck. A large loader is often used to push these remaining logs off the truck and its use helps to ensure that the logs fall off at the desired location. Preferably two of the devices of the invention are mounted on the loading mechanism, which may in the logging industry take the form of a large hydraulic grapple, of the loader and are operated by the loader operator. This operator is of course in a safe position as he is protected by the surrounding loader from any falling logs.
Another advantage of the cable pulling device of the invention is that the long trip cable is rewound quickly on a storage spool after the trip lever is tripped by the cable. Thus the trip cables do not interfere with the operation of the loader after the levers are tripped and are safely stored away for use in unloading the next load of logs. The tedious task of gathering up the trip cable after use is avoided and the trip cable can be located in a most convenient position for subsequent uses.