The addition of an auxiliary hydraulic system to heavy construction equipment increases the versatility of the vehicle by allowing it to perform additional functions with different attachments. Depending upon the vehicle, whether an excavator, a back-hoe or a front-end-loader, the auxiliary hydraulic system may vary. Vehicle interface fittings, length from pump to attachment and vehicle control systems require various configurations of hydraulic power unit pdf auxiliary hydraulic system.
Auxiliary hydraulic systems usually include external fluid fittings to facilitate connecting and disconnecting the hydraulic fluid supply lines of the attachments to the vehicles’ hydraulic pump. They also usually include valves configured to control the supply of hydraulic fluid through the fittings. This page was last edited on 19 May 2017, at 13:41. Such devices were first used in 1963 as a tool to free race car drivers from their vehicles after crashes.
These tools may be either single-acting, where hydraulic pressure will only move the cylinder in one direction, and the return to starting position is accomplished using a pressure-relief valve and spring setup, or dual-acting, in which hydraulic pressure is used to both open and close the hydraulic cylinder. Recently, manufacturers of these rescue tools have begun offering options for electrically-powered versions as well using simple electric rotation motors or screw pistons rather than the aforementioned setup, promising greater reliability, lower cost of ownership, lower weight and better handling, greater portability, quicker and more direct operation, and greater potential power. The Hurst Rescue Tool was invented by George Hurst, circa 1961, after he viewed a stock car race accident in which it took workers over an hour to remove an injured driver from his car. In comparison, hydraulic spreader-cutters are quieter, faster, stronger, and more versatile: they can cut, open, and even lift a vehicle. The hydraulic spreader was originally developed in 1972 by Tim Smith and Mike Brick, who later developed a cutter and a hydraulic ram. When an occupant is trapped the tool is used to pry or cut the car to remove the occupant. It takes about two minutes to take the roof off a car.
Mike Brick coined the phrase “Jaws of Life” after he observed people saying that their new device “snatched people from the jaws of death”, then used as a registered brand name for Hurst products. The cutter is a hydraulic tool that is designed to cut through metal—a pair of hydraulically powered shears. It is often called the jaws of life, owing to the shape and configuration of its blades. Sometimes specified as to its capacity to cut a solid circular steel bar, these are most commonly used to cut through a vehicle’s structure in an extraction operation.
Cutter blades are replaceable, and blade development progresses as vehicle technology progresses in order to be able to cope with the new car protection technology. A spreader is a hydraulic tool designed with two arms that come together in a narrow tip, and that uses hydraulic pressure to separate or spread the arms. Spreaders may also be used to “pop” vehicle doors from their hinges. While a cutter or spreader tool is designed for a particular application, a combination tool, or combi-tool as popularly referred to by the fire department, is also available, which combines the cutting and spreading functions of separate tools into a single tool. In operation, the tips of the spreader-cutter’s blades are wedged into a seam or gap—for example, around a vehicle door—and the device engaged. Once the seam has been spread, the now-open blades can be repositioned around the metal.