Tools – Wrench – screwdriver – or driver therefor – Responsive to torque on work
Patent
1996-09-30
1998-04-14
Meislin, D. S.
Tools
Wrench, screwdriver, or driver therefor
Responsive to torque on work
81477, B25B 23159, B25B 23144
Patent
active
057379831
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a dynamometric wrench comprising a manually grippable, handle-forming part and an elongated torsion body, which in the region of a first end is co-rotatively connected with the handle part and in the region of an opposed, second end has means for directly or indirectly joining the torsion body to a screwable element, for instance a screw, a nut or similar, the torsion body in the region of said second end being co-rotatively connected to a socket- or ring-like part that is rotatable relative to the handle part when said body is submitted to torsion due to it being loaded with a torque.
BACKGROUND OF THE INVENTION AND PRIOR ART
In order to obtain reliable screw joints, it is important that the screw or nut in question is tightened with an optimal torque, i.e., a torque that is neither too large, nor too small. In practice, dynamometric wrenches of simple, as well as sophisticated, costly designs are used for this purpose. To the latter group belong such dynamometric wrenches that are adjusted to a preset torque value and give off a signal to the operator when this value has been attained, e.g. a sound or light signal. Not seldom, two tools are used for applying the screw element, more specifically on one hand a screw wrench or a straight socket wrench in order to first slightly tighten the screw element, and on the other hand a dynamometric wrench for the final tightening of the screw element. For the latter purpose also combination tools exist. In this case, a release mechanism is included in the tool shaft, which mechanism mostly consists of a spring-activated locking sphere that is located in a groove in a wrench rod mounted in bearings in the tool shaft. The disadvantage of the latter tool is that high precision is required for the involved parts and that these are well greased and protected against intruding impurities. An alternative design is to detect the actual torque by a sensor, for instance in the form of a strain gauge or a piezo-electric sensor. However, all of these alternative problem solutions make the tools expensive and in need of frequent calibrations.
Beside the sophisticated and costly tools, also a number of simpler and cheaper dynamometric wrenches exist. Thus, in U.S. Pat. No. 4,838,134 a dynamometric wrench is disclosed of the type as defined in the preamble of claim 1, according to which the torque may be read by means of a scale. More specifically, in FIGS. 7 and 8 of said document a dynamometric wrench is shown comprising a torsion body in the shape of an elongated hexagonal bar one end of which is inserted into and is co-rotatively connected with a handle portion and which in the region of its opposite end is cc-rotatively connected with a socket having a ring-shaped flange at its end turned towards the handle portion, on which flange a scale is applied which cooperates with a point-shaped indicating hand on the handle portion. When the bar is submitted to torsion, the applied torque may be read on the scale. However, a disadvantage of this known tool is that the operator is left to visually read the torque in question on the scale. This implies that if the operator is inattentive or forced to work under difficult external conditions, for instance in narrow spaces, then he may easily happen to tighten the screw element with an erroneous, i.e. not optimal torque, either it being too small or too large. In the latter case, the tightening may even be accomplished to such an extent that the screw element is destroyed and/or the hexagon bar is sheared into the region of plastic deformation, i.e., the bar is submitted to such a large torque that it is distorted and permanently deformed. In such cases, the tool looses any ability to precisely indicate moments and in practice becomes unusable.
OBJECTS AND FEATURES OF THE INVENTION
The present invention aims at removing the above-mentioned shortcomings of the dynamometric wrench according to U.S. Pat. No. 4,838,134 and provide a simple and low-priced dynamometric w
REFERENCES:
patent: 3611796 (1971-10-01), Hayward
patent: 3678744 (1972-07-01), Blattner
patent: 3701295 (1972-10-01), Mende
patent: 4238978 (1980-12-01), Leone
patent: 4838134 (1989-06-01), Ruland
Meislin D. S.
Torque System Sweden AB
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