There are guite a few different solutions of the problem of guiding the energy transmission lines in such telescopic machine parts. A simple solution consists in providing flexible lines or hose pipes on the outside of the telescopic boom. The lines or hose pipes are long enough to permit maximum extension of the telescopic boom. When the telescopic boom is retracted, the lines or hose pipes form uncontrollable, depending bights, whereby the risk of damage of the lines or hose pipes is high.
In order to avoid such damages, German patent application 3,214,147 suggests a telescopic boom, wherein the flexible energy transmission line or hose pipe is arranged in a chain, which is flexible in one direction only, namely about transverse axes. By means of stops or cams, the chain is prevented from flection about the transverse axes opposite this direction. This chain extends between a point at the outer end of a base section of the boom and a point at a telescopic section. With retracted boom, the chain extends between the wall of the base section and the wall of the telescopic section and forms a c-shaped bight outside the boom. With extended boom, the chain extends along the telescopic section on the outside thereof. Because of the design of the chain, the chain cannot sag to a substantial extent, whereby the risk of damage of the energy transmission lines or hose pipes, for example due to being caught, is reduced.
Guiding the energy transmission lines or hose pipes on the outside of the boom is, however, disadvantageous, even if sagging of the lines or hose pipes is prevented. The guiding device and the lines or hose pipes are subjected to contaminations and influences due to weather, which can considerably affect their useful life.
German patent application 3,508,604 discloses a telescopic boom with a system for feeding a liquid under pressure through conduits from one end of the telescopic boom to the other end, wherein the conduit system extends inside the telescopic boom. The telescopic boom consists of three tubular elements of circular cross sections. The three tubular elements are movable relative to each other. An outer tube surrounds a median tube which, in turn, surrounds an inner tube. A hydraulically operated working unit is attached to the free end of the inner tube. One or more hydraulic conduits extend from a hydraulic source to a connecting socket, which is attached to the end of the outer tube. Hydraulic hose pipes extend from the connecting socket through the annulus between the outer tube and the median tube around a deflection roller and further to a hose coupling on the underside of the inner tube. From this hose coupling, a conduit extends to a hydraulically operated unit at the outer end of the inner tube. The deflection roller is attached to the inner end of the median tube. With respect to their relative movements, the telescopic tubes are forcedly controlled such that, when the median tube is moved into the outer tube or out of the outer tube, the deflection roller is axially moved and maintains the hydraulic hose pipes orderly straight, if the hose coupling moves inwards or outwards at twice the speed of the axial movement of the deflection roller. In order to obtain sufficient space for the conduits between the outer tube and the median tube, the median tube may be slightly eccentric with respect to the outer tube.
It has been found that the use of deflection rollers in the guiding device for such energy transmission lines not only generates undesirable strain but also causes wear of the conduits. Furthermore, the design is rather complex and expensive. In particular if hydraulic hose pipes are used as energy transmission lines, these disadvantages are considerable. As a rule, the hydraulic hose pipes are very long (10 meters and more). If they are exposed to pressure, there will be a considerable change of the length of the hose pipes, which may be 20 centimeters or more. Due to this change of length, the hose pipes may slacken and run off the deflecting rollers. High pre-tension of the hose pipes is required, if this is to be prevented.
German patent application 2,721,636 discloses a device in loading devices with extensible, telescopic booms. The boom has at least one telescopic arm, which is displaceable by a hydraulic jack and piston rod out of a box carrier. The hydraulic jack is attached to the displaceable arm. The piston rod extends to the rear from this arm and is attached to the rear end of the box carrier. Load carrying means are provided at the outer end of the telescopic arm. The load carrying means are operable by hydraulic actuators. Similar to the present invention, also German patent application 2,721,636 deals with the placement of hydraulic hose pipes from the boom to the hydraulic actuators of the load carrying means. In order to permit maximum extension of the arm relative to the boom, part of the hydraulic hose pipe forms a loop with a c-shaped bight. This c-shaped bight extends to the rear longitudinally of the boom and of the arm, and is accommodated in a space limited by the walls of the arm and of the boom. Thereby, the hydraulic hose pipes are located inside the boom and are protected from outside influences. The hydraulic jack and the piston rod are arranged centrally in the boom. Thereby little space is provided for the hydraulic hose pipes inside the boom, in particular for the c-shaped hose pipe bight. If a plurality of hydraulic hose pipes are provided, this has the consequence that some hose pipe bights have to be arranged on one side of the piston rod, while the other ones have to be arranged on the other side of the piston rod. In order to prevent wear of the hose pipes freely extending in the boom, the walls of the boom are provided with a smooth surface.
Also, this design and guiding of the energy transmitting lines presents problems. The hose pipes are subjected to friction inside the boom. Furthermore, the c-shaped hose pipe bights are uncontrolled and may, for example, get into contact with the piston rod. This is particularly problematic, if the lines are hose pipes which are is pressurized jerkingly. Then the hose pipes may be deflected in uncontrolled manner.
U.S. Pat. No. 4,129,277 describes a carrier track for protecting flexible electrical conductors or fluid conduits in a rolling support.
U.S. Pat. No. 4,809,472 discloses a carrier track assembly for extensible and retractable boom machines, wherein the carrier track is not only wholly contained within the telescopic boom sections but also supported by the fluid cylinder during the extension and retraction of the boom sections.