Wireworking – Implements – Stretchers
Patent
1999-04-08
2000-09-19
Larson, Lowell A.
Wireworking
Implements
Stretchers
254216, B21F 900
Patent
active
061197343
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a tool for binding a belt around an object, in particular around a cable harness, which tool contains a tightening device for the tough elastic belt which is resistant to bending. The tightening device comprises a toothed tightening roller and a roller abutment which supports the belt on the side opposite to the tightening roller. The tightening roller is continuously driven during the tightening operation and also continues to rotate when, on reaching a predetermined belt tension, the belt is at a standstill and is cut through.
In a known tool of this type (EP-A 432477) the tightening roller and the roller abutment, which is formed by a single support roller, are connected to one another at a constant axial distance. The sharp teeth of the tightening roller engage in the surface of the belt which consists of tough elastic plastic. When it reaches its predetermined belt tension, the tensile force exerted on the belt by the teeth of the tightening roller is no longer sufficient to move it further; it comes to a halt and the teeth of the tightening roller cut into the surface of the belt. Although this does lead to belt tension values which can be reproduced extremely well, since this tension is independent of any frictional influences on the surface of the belt, the wear to the belt is a detrimental factor. Also, while the belt is at a standstill, with increasing wear thereto, the force exerted on the belt by the tightening roller falls, so that the belt may move backwards slightly but, in some cases, to a sufficient extent to make it difficult for the protruding end of the belt to be cut through cleanly and tightly.
Also known are belt tightening tools (EP-A-371,290, U.S. Pat. No. 4,610,067) in which the limit tension to be reached is set by means of a slipping clutch on the tightening roller. In the case of this type of tool, it is necessary to ensure that the belt does not slip through with respect to the tightening roller, since otherwise there is no guarantee of reaching the desired belt tension. Secure attachment of the belt to the tightening roller is ensured by the fact that a plurality of support rollers are provided which press the belt against the circumference of the tightening roller. Since providing a special slipping clutch is costly, the present invention is based on the prior art explained above in which it is provided for the slipping through on reaching the desired belt tension to take place between the belt and the tightening roller.
The invention is based on the object, in the case of a cable binding tool, of improving the reproducibility of the belt tension and to prevent it from decreasing during the tightening operation.
The abutment is formed by at least two support rollers which are arranged one behind the other on the circumference of the tightening roller and are pressed towards the tightening roller by spring force. They have the effect of pressing the belt onto the tightening roller not only at the contact points of the support rollers but also, owing to its resistance to bending, in the entire section between these points. Thus the tightening roller interacts with the belt not merely, as it were, in a punctiform manner, but rather over an extended distance which is delimited by the support rollers. The consequence of this is that the pressure, i.e. the force with which the belt is pressed onto the circumference of the tightening roller per unit length, can be reduced, and consequently the teeth of the tightening roller do not, or scarcely, cut into the material of the belt in an abrasive manner when the belt is at a standstill. Generally there are only plastic deformations. This result is surprising because experience has shown that the influence of changing surface conditions (moisture, contamination, grease coating) has less effect on the friction force as the force per unit area increases, because there is then a higher probability of any impurities being penetrated by the teeth of the tightening roller, so that only the properties of the belt mater
REFERENCES:
patent: 3205916 (1965-09-01), Willis
patent: 4610067 (1986-09-01), Hara
patent: 4934416 (1990-06-01), Tonkiss
Larson Lowell A.
Paul Hellermann GmbH
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