Tools – Wrench – screwdriver – or driver therefor – Responsive to torque on work
Patent
1995-06-22
1998-01-06
Meislin, D. S.
Tools
Wrench, screwdriver, or driver therefor
Responsive to torque on work
81477, 81900, 81436, B25B 2314
Patent
active
057042616
DESCRIPTION:
BRIEF SUMMARY
FIELD AND BACKGROUND OF THE INVENTION
The present invention relates to a tool, in particular a torque-transmitting tool, preferably a screwdriver or a screwdriver bit, having a shaft and a working region, and to a process for the manufacture of such tools.
A screwdriver bit of this type is known, for instance, from European Patent Application 0 336 136. In the screwdriver bit disclosed there, a twistable zone is provided in its shaft region. This twistable intermediate section represents an elastically yieldable element with corresponding return movement after overcoming the peak load. It endures large torques even upon repeated loading. The intermediate section acts as damper so that torque peaks do not act in directly proportional manner on the screwdriver tip section. In particular, if screws are to be driven by machine into metal thread with such screwdriver bits, considerable torque peaks occur when they are applied since the speed of rotation of the drive motor must drop to zero within a very short period of time. This period of time is lengthened by the elasticity of the torsion sections so that the torque load as a whole is reduced. With regard to the further advantages of such a torsion section, reference is had to Federal Republic of Germany 38 07 972. In the screwdriver bits disclosed there, the torsion zone in a tool the material of which has uniform properties is formed by a special geometrical development of this region of the shaft. This is essentially done by weakening the cross section in this region.
SUMMARY OF THE INVENTION
The object of the invention is to develop the damping region further in an advantageous manner in a tool of this type.
As a result of the invention, a tool is obtained in which the different twistability or hardness or strength of material of tip and shaft section is not necessarily obtained by the shaping of the tool but, rather, by different specific properties of the material of which the tool is made. In accordance with the invention, the damping region has a material which has a lower hardness or, what is the same thing, a lower strength of material. However, it is also provided that this damping region may have a lower torsion-bar constant than the working region. It is, finally, also provided that the damping region which is provided on the shaft has both a lower torsion-bar constant and a lower strength of material. While the working region, which in the case of a screwdriver bit consists of the tip of the screwdriver, is made of a material which has a torsion-bar constant or high hardness, the twistable shaft section is made of a material which has a lower torsion-bar constant or a low torsion spring constant. If the damping region consists of a material which is softer than the working region and therefore is of lesser strength, it can also be provided that the modulus of elasticity in the two sections of the shaft is identical or practically identical. The zone of softer material or lesser strength is then, to be sure, more plastically deformable than the working region. Upon a sudden stopping of the screwing tool, the energy of rotation of the screwing tool can thus flow into the plastic deformation of the section of the shaft. The hardness of this damping region is preferably reduced to such an extent that a plastic deformation of 30.degree. to 60.degree. is possible without the tool breaking. Particularly in the case of small angles of plastic deformation of 30.degree., it is provided that, after a positive elastic restoration by a few degrees, plastic deformations of larger amounts are again possible without the screwing tool breaking. If, in accordance with a preferred embodiment, the shaft regions have different moduli of elasticity, then an undesired twistability of the working region is avoided but the desired twistability (elasticity) of the shaft section of the damping region is obtained.
In accordance with the preferred further development, the shaft section has a material of lesser hardness than the working region. By this measure, different
REFERENCES:
patent: 3393722 (1968-07-01), Windham
patent: 3515602 (1970-06-01), Gross
patent: 4705124 (1987-11-01), Abrahamson
patent: 4838134 (1989-06-01), Ruland
patent: 5295831 (1994-03-01), Patterson et al.
Patent Abstracts of Japan, vol. 8, No. 178 (C-238)/Aug. 16, 1984 (1615) & JP,A,59 074 226 (Toyota Jidosha K.K.) Apr. 26, 1984.
Hoy Robert
Strauch Martin
Farber Martin A.
Meislin D. S.
Wera Werk Hermann Werner GmbH & Co.
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