Tools – Wrench – screwdriver – or driver therefor – Responsive to torque on work
Reexamination Certificate
2000-05-16
2001-12-18
Eley, Timothy V. (Department: 3723)
Tools
Wrench, screwdriver, or driver therefor
Responsive to torque on work
C081S467000, C081S480000
Reexamination Certificate
active
06330846
ABSTRACT:
FIELD AND BACKGROUND OF THE INVENTION
The invention relates to a chuck having a shank which provides two shank sections, forms a clamping section at one end for clamping in place in a drive member and forms a tool mounting at the other end for mounting a tool, in particular a screwdriver bit, having an elastic element between the clamping-side shank section and the tool-mounting-side shank section for permitting a stop-limited twisting capability of the clamping section relative to the tool mounting.
Such a chuck, which in particular can be clamped in place with its clamping section in an electric screwdriver, has been previously disclosed by U.S. Pat. No. 3,744,350. This publication discloses a multiplicity of elastic elements of different formation, these elastic elements acting between the two shank sections.
DE-A 197 22 776.7 and DE-A 198 04 081.4, likewise describe chucks of the type in question. The solutions described there are distinguished by the fact that the elastic element is formed as a torsion element, having a cylindrical torsion section lying between its two ends, the ends being connected substantially free of play in each case to one of the two shank sections. The solution described there permits a narrow type of construction.
SUMMARY OF THE INVENTION
The object of the invention is to provide a chuck of the introductory-mentioned type which can be produced in a narrow type of construction.
This object is achieved first and foremost by the elastic element being formed as a bending spring which is bendable transversely to the axis of the chuck and connects the two shank sections to one another. In this case, the bending spring is seated in a cavity, which is defined by half-shell sections, running parallel to one another, of the shank sections. The half-shell sections are separated from one another by a gap extending in the axial direction. Gap edges of this gap define stop edges. The two stop edges defined by the gap come into contact if the spring is bent transversely to the axis of the chuck when applying a certain torque. Bendability is possible in both the anticlockwise and clockwise directions. In an advantageous manner, the two restraining edges, extending in the axial direction, of the substantially rectangular bending spring are each seated in a groove, which is associated with the hollow inner wall of one of the two half-shells.
Furthermore, the object underlying the invention is achieved by a screw-thread-guided axial spring biassing of the two shank sections. The elastic element can likewise be accommodated in a cavity of one of the shank sections. One of the two shank sections preferably has a captive section, which is spring-biassed in both axial directions relative to the other shank section. In this case, the captive section may be the widened end of a ram, which is fixedly connected to one of the two shank sections. The captive section may have an external thread. This external thread may be screwed into a tapped hole of the other shank section. Screw thread guidance is achieved with simple means as a result of this thread guidance. However, it is also possible for one of the two shank sections to provide a pin which projects radially outwards and engages in a screw thread slot of the other shank section in order to thus form screw thread guidance. The screw thread guidance lies within the range outside self-locking, so that return biassing/return rotation is ensured. The ram is preferably spring-biassed on either side. The springs may be formed by compression springs and in particular by disc springs. One spring may be supported on the base of the tapped hole. The other spring may be supported against a pressure portion screwed into the opening of the tapped hole. The two spring packages may be compressed by screwing in the pressure portion. Preloading can therefore be provided. The pressure portion may be secured against rotation, for example, by split pin or grub screw.
The stops may in principle be configured as desired. For example, it is conceivable, in the version with axial spring biassing, to provide the stops by abutment surfaces engaging one another in the axial direction. Preferred, however, is a configuration is such that the two separating grooves intermesh in a comb-like manner. In this case, the stops are defined by a comb-like section of the separating groove. At the same time, the intermeshing shank sections define a gap between them which extends in the axial direction. Furthermore, it is advantageous if the separating groove is covered by a sleeve.
The solution according to the invention permits stop-limited torsion of the clamping-side shank section relative to the shank section forming the tool mounting. An elastic yielding capability is possible in both the anticlockwise and clockwise directions. There is movement play on both sides. During the movement of the two shank sections relative to one another, either the bending spring is bent or one of the two compression springs is compressed. Up to an initial limit torque, the chuck behaves like a virtually rigid body. The initial limit torque is defined by the dimensioning of the bending spring or of the compression springs and their pretreatment. In addition, this limit torque is also defined by the preloading of the compression springs. If the initial limit torque is exceeded, the elastic element yields, in the course of which the two shank sections twist relative to one another until the two stops abut against one another. Between the two limit torques, the two shank sections can rotate relative to one another by the movement play. As soon as the stops abut against one another, the chuck again acts as a virtually rigid body. With regard to the mode of operation, for the reference is made to the entire disclosure content, which is hereby incorporated herein, of DE-A 197 22 776.7 and DE-A 198 04 081.4.
REFERENCES:
patent: 3744350 (1973-07-01), Raff
patent: 4063474 (1977-12-01), Klopping
patent: 4249435 (1981-02-01), Villeneuve et al.
patent: 5735183 (1998-04-01), Sasaki et al.
patent: 6076439 (2000-06-01), Dzieman
patent: 4143218 (1992-09-01), None
patent: 19722776 (1997-02-01), None
patent: 19804081 (1998-12-01), None
Berry Jr. Willie
Eley Timothy V.
Farber Martin A.
Wera Werk Hermann Werner GmbH & Co.
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