WO1998015376A1

WO1998015376A1 - Chuck

Info

Publication number: WO1998015376A1
Application number: PCT/CZ1997/000035
Authority: WO
Inventors: Josef Javorsky
Original assignee: R^¿ÍHA, Milan; KOVÁR^¿, Jaroslav
Priority date: 1996-10-10
Filing date: 1997-10-09
Publication date: 1998-04-16
Also published as: AU4374897A; DE29703719U1

Abstract

A chuck is disclosed comprising a chuck body (1), a casing (9), a nut (6), and a carrier ring (10), with the chuck being provided with at least three and preferably five clamping jaws (3) seated in skew openings in the chuck body having T-shaped upper ends (4) suspended in radial grooves (11) on the carrier ring (10) suspended and seated on the nut (6) with active surfaces (12) of the radial grooves on the carrier ring and active surfaces (4) of the upper ends of the clamping jaws forming with a radial plane of the chuck an angle (x) which is the same as the angle (x) that is formed by the clamping jaws and a longitudinal axis of the chuck.

Description

C H U C K

BACKGROUND AND SUMMARY OF THE PRESENT INVENTION

The present invention concerns a chuck with smooth jaws to chuck tools, especially to chuck drills and other machine-tools having cylindrical shanks.

Chucks for. drills and other machine tools which have been known by now have a ring with grooves to suspend clamping jaws. The ring is typically provided with an external or an internal thread which reaches a nut thread of a casing or a bolt. In the former case, there is considerable friction during handling and a large tangential force is required in the thread to move the jaws, e.g., through a gear drive, performed by a wrench with a rack and pinion. In the latter arrangement, the bolt is located on the bottom of the body with a clamping surface for the machine. The bolt is seated on a bush, on which it can revolve, which has skew openings to guide the jaws. This concept requires a precise fitting of the body and the bush to achieve the minimum necessary clearance and it also makes the chuck relatively longer which results in an undesirable distance between the tool and the end of the machine spindle.

There is also known a three-jaw chuck under the Czechoslovak Patent No. 128,438. The body of the three-jaw chuck is provided with a clamping surface for the machine and skew openings to guide the jaws, and on its mounted part, the chuck has a thread which is reached by the nut. A ring with radial grooves for clamping jaws is suspended on the nut so that it can revolve, preferably using an anti-friction bearing on rolling bodies. The nut is provided with lobes which fit into recesses in the casing inner wall which leans against the non-mounted part of the body and a safety pin is located on the upper part of the chuck body. The disadvantage of this known design consists in the fact that the clamping force resulting from the constant thread lead is not sufficient and the resulting weight of such a chuck is very high.

The aforesaid shortcomings can be, to a major extent, eliminated with the chuck according to the present invention which is made in a usual way with a chuck body, a casing, a nut, and a carrier ring. The chuck has at least three clamping jaws mounted in skew openings in the chuck body, with the clamping jaws seated with T-shaped upper ends provided in radial grooves of the carrier ring. The carrier ring is suspended, so that it can revolve, and seated on the nut which is screwed on the mounted part of the chuck body provided with a thread. The outside circumference of the nut has lobes which fit into recesses in the casing inner wall. The nature of the technical design hereunder consists in the fact that active surfaces of the carrier ring radial grooves and those of the upper ends of the clamping jaws form with the radial plane of the chuck the angle α which is the same as that formed by the clamping jaws and the longitudinal axis of the chuck. The chuck according to the present invention enables the thread lead to be reduced by tg α (i.e., by the tangent of the angle α) when the clamping jaws move downwards, i.e., when the tool is clamped. Adversely, when the clamping jaws move upwards, i.e., when the tool is released, the thread lead is increased by tg α (i.e., by the tangent of the angle α).

In order to achieve a large clamping force and to improve centering of the clamped tool, it is advantageous for the chuck to have five smooth cylindrical clamping jaws whose lower ends create a clamping surface with a V-shaped cross- section with the vertex angle β = 72 °. The casing, nut, carrier ring and shaped ring shall be preferably made of plastic in order to reduce the weight of the chuck.

Another preferable feature of the chuck according to the present invention consists in the feet that the casing is mounted on a shaped ring which is provided with an inside radial collar. This collar fits into a recess in the chuck non- mounted part while the shaped ring is configured as an axially segmented one, from two semi-circles. It is preferably to provide the shaped ring with a toothed rim. The chuck lower part shall have openings to insert a shaped toothed pinion which enables the generation of a larger force to revolve the casing which results in better tightening of a tool to be chucked. The advantages of the chuck according to the present invention include, in particular, the fact that a larger force can be generated for tool chucking due to the adjustment of the thread level by tg α (i.e. , by the tangent of the angle α) and due to better contact between the clamping surface and a tool to be chucked, The chuck according to the present inveπtion has a simple configuration and can be easily handled without any wrench and improves centering of a tool to be chucked. The configuration of the chuck also permits modern plastic materials to be used for its manufacture which results in its lower weight and reduces quantity of labor necessary for its manufacture, The plastic components of the chuck can be produced with pressure or injection molding. These technologies enable high precision of entire manufacture batches which results in high precision of the resulting chucks hereunder. This precision is higher compared to that of classical machining of metallic parts.

The use of plastic components to manufacture a chuck according to the present invention facilitates its use for drift drilling without any additional modifications due to a low weight of the casing which reduces inertial forces. Also, the anti- friction seating of the carrier ring on the nut is more flexible with plastic components which increases the effect of drift drilling.

BRIEF DESCRIPTION OF THE DRAWINGS Preferred embodiments of a chuck according to the present invention will be described in greater detail with reference to the accompanying drawings, wherein like members bear like reference numerals and wherein: Fig. 1 depicts a partial longitudinal cross-section of the chuck; Fig. 2 is an enlarged detail of the nut and carrier ring cross-section; Fig. 3 is an axial view of the chuck with clamping jaws wide open; and, Fig. 4 shows a clamping jaw with a T-shaped upper end. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A preferred embodiment of a chuck according to the present invention, with reference to Fig. 1, consists of a chuck body 1 with a chuck cavity 2 to clamp a spindle of a working machine. The chuck body 1 has five skew cylindrical openings which form with the longitudinal axis of chuck body 1 the angle α = 15°. The openings guide five smooth cylindrical clamping jaws 3 with T-shaped upper ends. The lower ends of the clamping jaws 3 serve as clampmg surfaces having a V-shaped cross-section with the vertex angle β= 72°.

Tips of the clamping surfaces of the clamping jaws are high-frequency hardened to the depth of 1 mm. After hardening, the cylindrical surface of the clamping jaw 3 remains non-deformed and is duly guided in the drilled openings. Active surfaces 4 of the upper ends of the clamping jaws 3 form with the radial plane of the chuck the angle α = 15°.

The chuck body 1 is in its upper pan 1 ' provided with a thread 5 to screw a nut 6. The nut 6 bears lobes 7 on its outer circumference which fit into recesses 8 in the internal wall of a casing 9, The shape of the lobes 7 and the recesses 8 can be selected depending on a particular technology to be employed for manufacture of the molds. A carrier ring 10 is suspended on the nut 6 so that it can revolve, with five radial grooves 11 on its bottom in which fit the upper ends of the clamping jaws 3. Active surfaces 12 of the radial grooves 11 on the carrier ring 10 form with the chuck radial plane the angle α = 15°.

In order to reduce friction between the nut 6 and the carrier ring 10, the chuck uses the advantage of anti-friction bearings, e.g., the balls 13, placed in the tracks made on mounted towards-turned surfaces of the nut and the carrier ring 10. The anti-friction bearing reduces axial pressure and reduces a resistance against revolving.

The casing 9 is seated on a shaped ring 14 with an inside radial collar 15 which fits into a recess in the non-mounted part of the chuck body 1. The shaped ring 14 is axially segmented and consists of two semi-circles. After inserting both of the semi-circles into the recess, the casing 9 is pressed onto the shaped ring 14. The outer surface of the casing 9 is provided with lobes, cuts or is roughened so that it does not slide in an operator's hand when it revolves. The shaped ring 14 uses the advantage of a toothed rim 16 while the lower part of the chuck body 1 has openings 17 to. insert a shaped toothed pinion. The casing 9, the nut 6, the carrier ring 10 and the shaped ring 14 for the chuck according to the preferred embodiment are manufactured from plastic.

When the casing 9 revolves, using either manual force or that of the shaped toothed pinion, the revolving is transferred via the recess 8 to the lobes 7 on the nut 6 and the latter moves accordingly in the direction of the chuck body 3 longitudinal axis. At the same time, this moves the carrier ring 10 which carries the clamping jaws 3. When the carrier ring 10 moves up towards the chuck cavity 2, the clamping jaws 3 are pulled upwards and their upper ends slide in the radial grooves of the carrier ring 10. Their clamping parts then open and it is possible to insert a shank of a tool, e.g.. a drill. Reverse revolving of the casing 9 moves the carrier ring 10 in the opposite direction and the clamping jaws 3 close to touch and chuck the tool. When the clamping jaws 3 and the carrier ring 10 move upwards, the size of the thread lead 5 increases by tg α, (i.e., by the tangent of the angle α), while their downwards movement causes the lead to decrease by tg α (i.e., by the tangent of the angle α). This enables fast and precise tool releasing and chucking with employing only relatively minor force to revolve the casing 9 while the clamping force holding the tool is higher,

The chuck according to the present invention can be used to chuck various cutting tools with cylindrical shanks on working machine spindles, in particular for drilling machines and machine-tools.

Claims

WHAT IS CLAIMED IS:

1. A chuck comprising: a chuck body, a casing, a nut, and, a carrier ring, said chuck being provided with at least three clamping jaws seated in skew openings in the chuck body, each of the clamping jaws having a T-shaped upper end with the T-shaped upper ends being suspended in radial grooves on the carrier ring, said carrier ring being suspended and seated on the nut, said nut being screwed on a mounted part of the chuck body with a thread, said nut having lobes on an external circumference of the nut which lobes fit into recesses in an inner wall of the chuck body with active surfaces of the radial grooves on the carrier ring and active surfaces of the upper ends of the clamping jaws form with a radial plane of the chuck an angle (α) which is the same as the angle (α) that is formed by the clamping jaws and a longitudinal axis of the chuck.

2. A chuck according to Claim 1, wherein said chuck is provided with five clamping jaws, each of the clamping jaws having a smooth cylindrical surface with lower ends of adjacent clamping jaws forming a V-shaped clamping surface having a vertex angle β = 72°.

3. A chuck according to Claim 1 wherein the casing, the nut, and the carrier ring are made of plastic,

4. A chuck according to Claim 1 wherein the casing is mounted on a shaped ring which is provided with an inner radial collar which fits into a recess provided in a non-mounted part of the chuck body, with the shaped ring being axially, segmented and comprising two semi-circles,

5. A chuck according to Claim 4 wherein the shaped ring is provided with a toothed rim and wherein a lower part of the chuck body is provided with openings to receive a shaped toothed pinion.

6. The chuck according to Claim 4 wherein the casing, the nut, the carrier ring, and the shaped ring are made of plastic.