Abstract:
A chuck for non-circular ends of tool shanks having a bushing forming a chamber corresponding in cross-section to the tool shank and a ball which acts on the shank and is clamped by a spring biased sleeve which forms a wedge against the ball. The ball is mounted in a separate wing which is engaged by the sleeve and is displaceable relative to the bushing so that the ball engages a clamping surface formed by an end ring and the tool shank in a clamping position.

Description:
FIELD AND BACKGROUND OF THE INVENTION 
     The invention relates to a chuck for non-circular ends of tool shanks, particularly screwdriver bits. The inventions provides such a chuck which has a bushing whose chamber corresponds to the non-circular cross section of the tool shank end and a ball which acts on the shank and is associated with a sleeve which is displaceable against spring action, the association of the ball with the sleeve being such that a clamping surface, which narrows down in wedge-shape towards the shank-receiving end of the chuck presses against the ball, in which connection the sleeve is displaceable in the direction of insertion of the shank for passage into a release position, the ball being received in a protruding wing, and the clamping surface being on the inner wall of an end ring which surrounds the edge of the bushing and the wing. 
     The advantages of this reside essentially in the fact that, upon displacement of the sleeve, the chuck will not be moved out of the drilling machine even in case of an insufficiently firm seat of the chuck in the holder. In one embodiment, the wing in one piece with the sleeve. Since the wing corresponds to a segment forming the non-circular cross section of the bushing, the sleeve can be displaced only in the longitudinal direction of the chuck (DE OS No. 32 43 389). 
     The object of the present invention is to provide and improve a chuck of this type in the manner that, for the same size, a greater torque can be transmitted, with improved adjustment and handling. 
     SUMMARY OF THE INVENTION 
     The invention is achieved in the manner that a wing with a protruding ball therein and a sleeve are developed in two parts and, on the side of the wing away from the sleeve, a bushing is provided which has an annular region. This annular region is continuous in cross section and is surrounded by an end ring. 
     As a result of this development, a chuck is obtained which is characterized, on the one hand, by a stronger structural form and, on the other hand, by improved handling. The stronger structural form results from the fact that the bushing is closed on the other side of the recess in it which receives the wing, forming the continuous annular region which is surrounded by an end ring. The chuck can therefore transfer higher torques without danger. Furthermore, the surface of action and attachment for the end ring is increased at the annular region thereof, obtaining an improved seat of said ring on the bushing. Since the wing and the sleeve are now developed in two parts, the sleeve can turn relative to the bushing. This results in advantages upon the adjustment and therefore upon the placing of the screwdriver bit on a screw, since the sleeve can be held with one hand while the bushing, with the screwdriver bit seated in it, rotates. 
     One advantageous improvement resides in the fact that the inner wall of the annular region of the bushing is of polygonal shape in correct angular relationship to the polygonal surfaces of the chamber in the bushing. The polygonal surfaces of the bushing, which accordingly extend up into the annular region, lead to a stable seat of the screwdriver bit in the bushing itself. 
     Finally, it has also been found advantageous for the wing to have an outwardly directed tang or flange, which grips over an inwardly directed shoulder of the sleeve and forms a part of the support surface for a sleeve spring. Upon the displacement of the sleeve in order to release the inserted screwdriver bit, the shoulder carries the tang and thus the wing along with it, the ball entering into a position of release. After the sleeve is released, the sleeve spring brings the sleeve and the wing back into the basic holding position. Assembly can be effected in very simple fashion. The sleeve spring is, first of all, pushed onto the bushing. The wing is then inserted into the recess of the bushing in such a manner that a part of the sleeve spring rests against the outwardly directed tang of the wing. The sleeve is pushed thereon over the wing and part of the bushing, and the end ring is brought into a force fit on the bushing. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     One embodiment of the invention will be described below with reference to FIGS. 1 to 5 of the drawing, in which: 
     FIG. 1 is a view of a chuck containing a screwdriver bit, shown on a large scale; 
     FIG. 2 shows the individual part of the chuck in exploded view; 
     FIG. 3 is a longitudinal section through the chuck with a screwdriver bit inserted, shown on a greatly enlarged scale; 
     FIG. 4 is a section along the line IV--IV of FIG. 3, and 
     FIG. 5 corresponds to FIG. 3, but with the sleeve in the release position. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The chuck has a bushing 1 which is developed at its upper end as a chucking shaft 2. A chamber 3 of non-circular cross section is formed in the bushing 1 from its free end 1&#39;. In the present case, the chamber has a hexagonal cross section which corresponds to the cross section of the shank 4 of an exemplary screwdriver bit 5. The latter in this example is a screwdriver bit for Phillips screws. 
     That end 1&#39; of the bushing 1 which is remote from the chucking shaft 2 is developed in stepped-down shape. Hence there is produced a shoulder 6 against which one end of a coil compression spring 7 rests seated around the bushing end 1&#39;. A part of the other end of said spring rests against an inwardly directed shoulder 8 on a sleeve 9, which sleeve is arranged for both longitudinal displacement and rotation on the bushing 1. The remaining support surface for this other end of the coil compression spring 7 is formed by an outwardly directed tang 20 of a wing 10&#34;, which tang is interposed thereat between said pring and said shoulder 8 and thus comes against the shoulder 8 as a result of spring load. The shoulder connects two guide surfaces F and F 1 of different size of the sleeve 9. The one guide surface F 1 slides on the stepped-down end 1&#39; of the bushing while the other guide sleeve F surrounds the part of the bushing of larger cross section. 
     The wing 10&#34; which is coupled to the sleeve 9 at shoulder 8 is of segmental or partial hemispherical cross-sectional shape in such a manner that its inner flat surface 10&#39; is aligned as a side wall of the chamber 3 in bushing 1. In order to make this possible, the end 1&#39; of the bushing 1 is provided with a recess 11&#39; so that the wing 10&#34; together with the remaining cross section of the end 1&#39; located at the same height forms a circular shape; see FIG. 4. The height of the recess 11&#39; is greater than the height of the wing 10&#34;. The recess 11&#39;, however, terminates at a distance in front of the free edge of the end 1&#39; so that the bushing forms an annular region Z of continuous cross section on the other side of the wing 10&#34;. 
     Within the wing 10&#34; there is a mounting hole 12, arranged transverse to the longitudinal direction of the sleeve 9, in order to receive a ball 13. The diameter of the ball 13 is, in this connection, greater than the thickness of the wing 10&#34; in radial direction. The ball 13 is prevented from falling out of the mounting hole 12 by an inward-directed edge R. Assurance is had, however, that the ball 13 has sufficient play in radial direction. 
     The inner wall 3&#39; of the annular region Z is of polygonal shape, namely in correct angular position with respect to the polygonal surfaces of the chamber 3 so that in this way increased resting surface for the shank 4 of the screwdriver bit 5 is also assured. 
     Both the annular region Z of the bushing 1 and the wing 10&#34; are surrounded by an end ring 14. The latter is arranged in a force fit on the annular region Z and the adjacent region of the end 1&#39; in such a manner that the wing 10&#34; is not included in this force fit but retains its freedom of movement. 
     The end ring 14 forms an inner clamping surface 15 which narrows in wedge shape towards the free end and by virtue of which narrowing presses against the ball 13. The clamping surface 15 continues via a step 16 into a hollow 17 which is adapted to the outer circumference of a stepped free end 9&#39; of the sleeve 9, assuring the freedom of movement of the sleeve 9. 
     If a screwdriver bit 5 is present in the chamber 3 then it will be held in position in the manner that the coil compression spring 7 displaces the wing 10&#34;, together with sleeve, opposite the direction of insertion of the screwdriver bit. In this connection the ball 13 rests against the clamping surface 15 of the end ring 14 and is moved in radial inward direction, exerting a pressure on the shaft 4 of the screwdriver bit 5. If a tensile force occurs on the latter the clamping force is increased. 
     In order to remove the screwdriver bit 5 it is necessary to displace the peripherally knurled sleeve 9 in the direction of bit insertion against the spring force. Due to this, the shoulder 8 of the sleeve 9 strikes against the tang 20 of the wing 10&#34; and carries the latter along, including the ball 13 present in it, the ball then passing out of the clamping position between clamping surface 15 and shank 4; see FIG. 5. The screwdriver bit 5 can then easily be removed. When the screwdriver bit 5 has been removed, the compression spring 7 moves the sleeve, together with wing 10&#34;, back into the basic position, the step 18&#39; of the sleeve 9 coming against the upper end edge 14&#39; of the end ring 14. The tang 20 then strikes against the shoulder 8. 
     As the screwdriver bit 5 is inserted, the wing can be displaced by a certain amount within the recess 11&#39; in the direction of the annular region Z, obtaining a subsequent tightening action between the shank 4, the ball 13 and the clamping surface 15. With the screwdriver bit inserted, the tang 20 is accordingly located a slight distance above shoulder 8.