GB2275886A

GB2275886A - Drill chuck.

Info

Publication number: GB2275886A
Application number: GB9323167A
Authority: GB
Inventors: Karl Wanner
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1993-03-12
Filing date: 1993-11-10
Publication date: 1994-09-14
Anticipated expiration: 2013-11-10
Also published as: GB9323167D0; GB2275886B; DE4307780A1

Description

Ath

Drill chuck Prior Art

The starting point of the invention is a drill chuck according to the preamble of Claim 1. Prom German

Offenlegungsschrift 36 17 106 a keyless drill chuck is already known in which the chuck jaws are movable in the radial direction relative to the axis of the drill chuck.

A differential screw thread is provided there in order to make it possible for clamping purposes to overcome the internal resistance in the chuck and to apply the necessary clamping force by hand. The entire construction of the chuck is relatively expensive and labour- intensive in respect of assembly.

Advantages of the Invention The drill chuck according to the invention, which has the characterizing features of Claim 1, has in comparison therewith a simplified construction in which frictional forces are considerably reduced, while it is easy to assemble or to dismantle for cleaning purposes. In addition, there is a saving in weight and material. The drill chuck has an extremely short overall length.

Through the measures described in the subclaims advantageous further development and improvement of the drill chuck indicated in the main claim are possible. Production of the main body in plastics material provides the advantage that the drilling tool is electrically insulated in relation to the driving machine, and the operator is thus effectively protected if he should drill into a voltage-carrying cable. A centring cone in the main body improves the true running of the drilling tools.

Drawing Three exemplary embodiments of the invention are illustrated in the drawing and explained more fully in R.25981 the following description. Figure 1 shows a first drill chuck in longitudinal section. Figures 2, 3 and 4 show a second, third and fourth exemplary embodiment, in longitudinal section in each case. All the f igures show in the top half the adjustment for a thick tool stem. and in the bottom half that for a thin stem.

Description of the Exemplary Embodiments

The keyless drill chuck has a substantially cylindrical main body 2, which on its rear f ace has a threaded bore 3 for screwing onto a spindle (not shown) of a drilling machine or the like. The main body 2 tapers towards its front end and in its front pi-art has a central bore 4 to receive a tool stem 5. A plurality of radial slots 6 (two in Figure 1), which are open at the front, are provided in the sleeve-like front part. A chuck jaw 7 is guided laterally in each of them. At their rear end the chuck jaws 7 are pivotally connected to the main body 2 by means of pivot pins 8 f orming axes,, and have a convex external contour 9. On the inner side, facing the tool stem 5. clamp surfaces 10 provided with transve rse and/or longitudinal grooves are formed on the end of the chuck jaws 7 remote from the axes 8, to enable the clamp jaws 7 to make better contact with the tool stem and to achieve better centring of the latter. The pivot pins 8 are arranged in a tangential direction in the main body 2, so that the chuck jaws 7 are pivotable radially inwards and outwards. Between the chuck jaws 7 and the main body 2 a spring 11 is arranged such that it urges the chuck jaws 7 in the outward direction.

The main body 2 and the chuck jaws 7 are surrounded by a sleeve 12 of steel. which is conically tapered in the forward direction. Its interior contour 13 is bell-shaped, that is to say it is increasingly reduced in diameter in the forward direction, so that an increasingly concave shape is formed. On the outside the sleeve 12 is surrounded by a jacket 14 of plastics material for electrical insulation and improvement of operating comfort by reducing the conduction of heat. The R.25981 sleeve 12 may however also be made entirely of a highstrength plastics material. At the front it has a central bore 15 for the insertion of the tool stem 5. At the rear the sleeve 12 is provided with an internalscrew thread 16 engaging with an external screw thread 17 on the periphery of the main body 2. The sleeve 12 can thus be moved axially relative to the main body 2, thereby effecting the opening or closing of the chuck jaws 7.

The external contour 9 of the chuck jaws 7 and the internal contour 13 of the sleeve 12 have configurations such that the necessary or ideal radial force for clamping drills of any diameter is produced to the correct extent, by the angle of inclination 0 then formed at the point of contact of the contours 9113 and the lever distance a between the axis 8 and the effective clamp surface 10, when the operator tightens the sleeve 12 with the torque that can usually be applied by hand. The clamp surfaces 10 of the chuck jaws 7 act in each case as far forward as possible on the tool stem, so that the latter can be clamped over the greatest possible length.

The sleeve 12 is secured against rotation by a spring-mounted toothed sleeve 19. The latter is mounted, as an extension of the sleeve 12, externally on the main body 2 in such a manner as to be axially movable but nonrotatable thereon. In order to open the drill chuck, the toothed sleeve 19 is pulled backwards by hand.

The second exemplary embodiment according to Figure 2 differs from the first in some details. For component parts having the sam effect use will be made of the same terminology and of reference numerals increased by 100 in relation to the first exemplary embodiment. The main body 102 is also cylindrical in its front slotted part and is provided centrally, in the direction of the central bore 104, with a centring,cone 120. The end of the tool stem 105 inserted will in every case come to lie against said cone, whatever the diameter of the stem.

The sleeve 112 is in the form of a hollow 4 - R.25981 cylinder. In it is received a ring 122 which has a concave internal contour 113 and is supported rotatably relative to the sleeve 112 by means of a rolling-contact bearing 123. The rolling-contact bearing 123 may be in the form of a thrust and/or radial bearing. The chuck jaws 107 are urged outwards by leaf springs 111 inserted into the main body 102; they lie with their external contour 109 against the ring 122. In the feed movement of the drill chuck the friction on the chuck jaws 107 caused by the rotation of the sleeve 112 is thereby completely eliminated. There remains only a very slight rolling friction between the sleeve 112 and the ring 122.

The drill chuck according to -Figure 2 can be largely made of plastics material. In particular, all parts which can be touched from the outside are of plastics material. This provides full electrical insulation, so that no vagabond voltage can pass from the drill bit to the drill spindle or other parts of the casing. only the ring 122. the rolling-contact bearing 123, the chuck jaws 107, the pivot pins 108 and the spring 111 are still made of steel. If -necessary, the centring cone 120 may also be made of steel, for example in the form of an integrally moulded insert in the main body 102.

The third exemplary embodiment shown in Figure 3 also dif f ers only slightly from the first. For components having the same effect use is made of the same terminology and of reference numerals increased by 200 in relation to the first exemplary embodiment. The main body 202 has a more compact construction, thus giving a shortened overall length of the drill chuck. The chuck jaws 207 are almost completely embedded in the slots 206. The bell-shaped internal contour 213 of the sleeve 212 and the convex external contour 209 of the chuck jaws 207 here have configurations such that the transmission of force necessary to clamp the drill bit 205 is effected as far forward as possible in relation to the sleeve 212 or the chuck jaws 207. The necessary axial movement of the sleeve 212 between maximum opening for a 13mm stem to R.25981 minimum opening for a lmm stem thus becomes as small as possible. The springs used may be the space-saving leaf springs from the second exemplary embodiment. The slots 206 also partly cut into the centring done 220. The threaded bore 203 is moved far forward, to a point near the outlet of the slots 206.

The fourth exemplary embodiment according to Figure 4 differs only slightly from the second or first. For components having the same effect use is made of the same terminology and of reference numerals increased by 300 in relation to the first exemplary embodiment. The chuck jaws 307 and the ring 322 are altered relative to the second exemplary embodiment. The.. chuck jaws 307 consist of two congruent cheeks 3071 lying one on each side of a guide extension 3061 of the main body 302. They are guided in two parallel slots provided, in the main body 302, one on each side of the guide extension 3061.

At the front the chuck jaws 307 have shoes 324 which are mounted between the cheeks 3071 for pivoting about pivot axes 325. The external contour 309 is disposed on the shoes 324 instead of directly on the rear side of the cheeks 3071. This enables the clamp surfaces 310 to lie against the tool stem 305 over their entire area, what ever the diameter to be clamped. The external contour 309 and also the internal contour 313 of the ring 322 are strictly conical. that is to say neither convex nor concave. A compression spring 311 urges each of the chuck jaws 307 against the ring 322 into their open position.

The operation of the drill chuck is very simple and is basically the same in all of the exemplary embodi- ments. The toothed sleeve 19/119/319 is pulled back by one hand and the other hand turns the sleeve 121112/212/ 312 in the anticlockwise direction until the clamp jaws 7/107/207/307 have been opened sufficiently to insert the tool stem 511051205/305. The chuck jaws 71107/207/307 are then pressed against the tool stem by clockwise rotation of the sleeve 12111212121312. The second hand on the toothed sleeve 19/119/319 serves as support while this is done. The jaw chuck is opened by turning the sleeve in 6 - R.25981 the "anticlockwise direction. In the third exemplary embodiment, in which there is no toothed sleeve, the spindle of the driving machine is held fast during the turning of the sleeve 212.

The invention is not restricted to the exemplary embodiments illustrated. In particular, combinations of individual features of the various exemplary embodiments are possible.

L L)

Claims

1. Keyless drill chuck for clamping tools, comprising a substantially cylindrical main body (2 r 102 F 202, 302) on which chuck jaws (7, 107, 207, 307) are mov ably arranged, and a sleeve (12, 112, 212, 312) which narrows towards the open end of the drill chuck and in relation to which the chuck jaws (7, 107, 207, 307) are movable in order to vary the opening width of the chuck, said sleeve being provided with an internal contour (13, 113, 213, 313) against which the chuck jaws (7, 107F 2071 307) are supported by their rear side, said main body (2, 102, 202, 302) and said sleev e (12, 112, 212, 312) being axially adjustable relative to each other, particularly by means of a screw thread (16117, 116/117, 216/217, 316/317), characterized in that the chuck jaws (7, 107, 207, 307) are pivotally connected to the main body (2, 102f 202o 302).

2. Drill chuck according to Claim 1, characterized in that the chuck jaws (7, 1071 2071 307) have bn their rear side a convex external contour (9, 109r 209, 309).

3. Drill chuck according to Claim 1 or 2, characterized in that the chuck jaws (7, 107, 207, 307) are guided laterally in slots (6, 106, 206) in the main body (2, 102r 202r 302).

4. Drill chuck according to one of the preceding claims, characterized in that the chuck jaws (7, 107,, 207, 307) are pivotable about axes (8, 108, 208, 308) which extend tangentially to the main body (2, 102, 202, 302).

5. Drill chuck according to one of the preceding claims, characterized in that the internal contour (13.

113,, 213,, 313) of the sleeve (12, 112, 212, 312) is at least slightly concave.

6. Drill chuck according to one of the preceding claims, characterized in that the internal contour (113. 313) is formed by a ring (122. 322) which is inserted into the sleeve (112, 312) and which is in particular R.25981 mounted in a rolling-contact bearing relative to the sleeve (112, 312).

7. Drill chuck according to one of the preceding claims, characterized in that the main body (2, 102, 202r 302) connectable to a spindle of a drilling machine is made of plastics material.

8. Drill chuck according to one of the preceding claims, characterized in that the main body (1021 2021 302) is provided centrally with a centring cone (120.

220, 320) widening in the direction of the open end of the chuck.

9. Drill chuck according to one of the preceding claims, characterized in that the chuck jaws (7,, 107r 307) are continuously held by springs (11,, lllf 311) against the internal contour (13, 113, 313) of the sleeve (12r 112f 312).

10. Drill chuck according to one of the preceding claims, characterized in that securing means.

particularly a toothed sleeve (19, 119, 319) prevent unintentional mutual displacement of the sleeve (12, 112, 312) and main body (2, 102, 302).

11. Drill chuck according to one of the preceding claims, characterized in that the sleeve (2, 102, 202r 302) is provided with a plastics jacket or is itself made of plastics material.

12. Drill chuck according to one of the preceding claims, characterized in that the chuck jaws (307) are provided in their front region with shoes (324) pivotally mounted thereon.

13. A drill chuck substantially as herein described with reference to Figure 1, or Figure 2, or Figure 3, or Figure 4 of the accompanying drawings.