Electricity: conductors and insulators – Conduits – cables or conductors – Insulated
Patent
1995-05-08
1998-05-12
Ledynh, Bot L.
Electricity: conductors and insulators
Conduits, cables or conductors
Insulated
174117F, H01B 700
Patent
active
057509328
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a multi-core cable intended for communicating electric power and electrical signals to and from a hand held power nutrunner.
In particular, the invention concerns a multi-core cable of the type having two or more sections each with a geometric centers and extending in parallel with each other such that in any cross section of the cable the geometric center are disposed on-a straight line.
2. Description of the Prior Art
In the prior art, electric communication with hand held power nutrunners is accomplished via cables with the electrical conductors arranged in concentrically disposed cores, i.e. cables with a substantially circular cross section.
One drawback inherent in cables of this known type is that, although they are universally flexible, they tend to be rather stiff, because the high number of conductive cores causes a large outer diameter of the cable and, accordingly, a large radius from the center of the cable to the outermost located cores.
This causes not only a stiffer cable and a more awkward handling of the power nutrunner, but results in high tension forces and large relative displacement of the outermost cores at bending of the cable. This results in turn in a shorter service life of the cable since frictional wear and the risk for breakage of the outer cores are high.
Another problem concerning prior art concentric cables refers to the electrical distortion on the signals communicated from the nutrunner. This is caused by the electromagnetic field existing around the power supplying cores connecting the nutrunner motor to a power source, and since the signal and power supplying cores are located very closely to each other the electromagnetic influence on the signals is inevitable.
A solution to the above mentioned problems is obtained by using a flat type of cable wherein a better separation of the power and signal communicating cores may be obtained as well as a shorter distance to the cable centre in one direction for the outermost cores. The latter feature is advantageous since it causes less tension and displacement of the outermost cores at bending of the cable in the direction of the small dimension of the cable. The bending force in that direction is substantially lower as well compared to a prior art concentric type of cable.
However, using such a flat type of cable with two or more core sections located in parallel brings another problem to which this invention is a solution, namely how to reduce the bending forces as well as the core tensions caused in the direction of the large dimension of the cable. The large dimension of such a flat type of cable is much larger that the outer diameter of a concentric type of cable which means that the flat type of cable is almost completely stiff in that direction. This means that such a cable would make the handling of the nutrunner very awkward.
A further problem inherent in prior art cables of circular outer shape refers to the difficulty to discover whether the cable has been unintentionally twisted during use of the nutrunner. Such twisting the cable easily leads to tangling of the cable which in turn might cause damage to the cable itself as well as impairment of the nutrunner handling. This problem is solved by using a flat type of cable, twisting of which is easy to observe.
SUMMARY OF THE INVENTION
An object of the invention is to solve the above problems. The multi-core flat type cable of the present invention for communicating electric power and electrical signals between a hand held power nutrunner (10) and a power supply and control unit (14) comprises at least three longitudinal sections (16-18) extending in parallel with each other. The at least three longitudinal sections (16-18) each have a geometric center (20-22) such that in any cross section of the cable (15) the geometric centers (20-22) are disposed on a straight line (24). The flat multi-core flat type cable (15) includes a first portion (A) extending from the nutrunner (10) and a seco
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Atlas Copco Tools AB
Ledynh Bot L.
Nguyen Chau N.
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