GB1576284A - Collet chucks - Google Patents

Abstract

Provided in the clamping surface of a chuck (1) actuated by a taper element (2) are annular grooves (4) in which toroidal sealing rings (5) of elastomeric material are arranged, the diameter of which is greater than the depth of the grooves (4). Thus workpieces can be reliably clamped while avoiding undesirable deformations or damage; rotationally symmetrical clamping can also be obtained in the case of workpieces whose profile does not completely coincide with a circular profile. <IMAGE>

Description

(54) COLLET CHUCKS (71) We, CARL FREUDENBERG, a German company (a Kommanditgesellschaft, the present personally responsible partners of which are Helmut Fabricius, Hans Erich Freudenberg, Otto Schildhauer, Hermann Freudenberg, Dieter Freudenberg, and Reinhart Freudenbert) of 6940 Weinheim Bergstrass, Höhnerweg 2, West Germany, do hereby declare the invention, for which we pray that a patent may be granted to us and the method by which it is to be performed, to be particularly described in and by the following statement:- This invention relates to collet chucks with cone operation for clamping pressuresensitive workpieces.

For the manufacture of cylindrical massproduced parts, automatic lathes or millers are for various reasons frequently equipped with special chucks which are adapted in their configuration to the individual workpiece. Collet chucks, driven hydraulically, pneumatically or electrically, which are closed or opened by axial displacement of a taper sleeve or mandrel, have found wide acceptance. In the use of such collet chucks it is of particular note that their clamping surface, by reason of the design, forms a circular profile during the closing movement only at a quite specific diameter.

From this fact difficulties can arise, in as much as workpieces with difierent diamete-rs- - are no longer clamped uniformly over the whole periphery, but what occurs is pres sing of the workpiece concentrated at a few clamping points. In order to diminish this disadvantage, in departure from the ordinary three-part collet chuck, collet chucks having a six-part or nine-part chuck member are also used. The fundamentally existing difficulty stated above could not however be overcome by this.

A further disadvantage of such collet chucks has now become apparent in the mechanical working of deep-drawn sheet metal parts. The roundness of the parts achieved by the deep-drawing operation did not satisfy the set requirements. For this reason mechanical subsequent working was necessary, for which the parts were clamped in a collet chuck. However, an elastic change of their profile then occurred to match the cylindrical clamping surface of the collet chuck, which had the consequence that the parts, irrespective of the mechanical working, displayed considerable departures from an ideal round profile after removal from the machine.

The present invention is based upon the problem of developing a collet chuck which overcomes the above-mentioned disadvan tages and imparts a reliable and central seating to the clamped-in parts, with con stantly simple operation.

According to the invention this problem is solved by a chuck for clamping pressure sensitive workpieces, comprising a collet having a clamping surface, and a tapered member for opening and closing the collet by axial displacement relatively to the collet, the collet including one or more annular grooves in the clamping surface, with 0 rings of an elastomer material arranged therein, the depth of the grooves being smaller than the cross-sectional diameter of the O-rings.

- Two examples of collet chucks embody ing the invention are illustrated in the accompanying drawing, and will be ex plained in greater detail bellow. In the drawing: Figure 1 shows an externally-clamping collet chuck having a collet divided in six; and Figure 2 shows an internally clamping collet chuck.

The collet chuck according to Figure 1 in its general layout is the same as known chucks. It consists essentially of a collet 1, a taper ring 2 and an adjusting ring 3.

The formation of the collet is of course not limited to a form divided in six, but it is equally possible to select a form divided into three, nine or more parts. The collet has two annular grooves 4 in its clamping surface, and in each groove there is an Oring 5. The depth of each groove is less than the cross-sectional diameter of the utilised O-rings. Preferably, as shown, the bottom of each groove has a rectangular profile. In general for the achievement of a satisfactory seating of the clamped-in parts, a protrusion of the O-rings above the clamping surface of 0.5 mm in the unloaded condition suffices. However this dimension is to be regarded only as a guide, and in dependence upon particular properties of the parts to be clamped and upon the clamping diameter it can be modified in the positive and negative directions. In every case the ideal protrusion can be ascertained for the individual case by simple experiments, and its determination thus involves no difficulty of any kind for the person acquainted with the art.

The axial association of the O-rings with the clamping chuck also requires no further explanation. It readily appears from the form of workpiece to be clamped in.

Figure 2 shows a collet chuck which is intended for the internal clamping of corresponding workpieces. Its function corresponds to the manner of operation as described above, the clamping surface however being formed by the exterior of a collet 1. The actuation of the chuck 1 is effected by axial displacement of a taper mandrel 2.1, which is directly in sliding connection with a tapered internal surface of the collet 1. As in Figure 1; here again the collet can be divided into three, six, nine or more parts.

The arrangement and formation of the groove 4 for the reception of an O-ring corresponds to that in Figure 1. Here however it must be taken into consideration that the protrusion of the O-rings in the unloaded condition beyond the clamping surface must be made comparatively larger than in the case of an externally-clamping chuck, because during the clamping operation, in contrast with the compression in that case, a stretching of the ring and thus a reduction of its cross-sectional diameter occur.

The essential advantage of a collet chuck according to the invention consists especially in that the clamped-in workpieces are extraordinarily reliably held, avoiding undesired deformation or damage, and it is of particular importance that a rotationally symmetrical clamping is guaranteed even in the case of those parts whose profile does not conform completely with a circular profile.

WHAT WE CLAIM IS: 1. A chuck for clamping pressure-sensitive workpieces, comprising a collet having a clamping surface, and a tapered member for opening and closing the collet by axial displacement relatively to the collet, the collet including one or more annular grooves in the clamping surface, with 0rings of an elastomer material arranged therein, the depth of the grooves being smaller than the cross-sectional diameter of the O-rings.

2. A chuck according to claim 1, wherein the groove bottoms have a rectangular profile.

3. A chuck according to claim 1, substantially as described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. The formation of the collet is of course not limited to a form divided in six, but it is equally possible to select a form divided into three, nine or more parts. The collet has two annular grooves 4 in its clamping surface, and in each groove there is an Oring 5. The depth of each groove is less than the cross-sectional diameter of the utilised O-rings. Preferably, as shown, the bottom of each groove has a rectangular profile. In general for the achievement of a satisfactory seating of the clamped-in parts, a protrusion of the O-rings above the clamping surface of 0.5 mm in the unloaded condition suffices. However this dimension is to be regarded only as a guide, and in dependence upon particular properties of the parts to be clamped and upon the clamping diameter it can be modified in the positive and negative directions. In every case the ideal protrusion can be ascertained for the individual case by simple experiments, and its determination thus involves no difficulty of any kind for the person acquainted with the art. The axial association of the O-rings with the clamping chuck also requires no further explanation. It readily appears from the form of workpiece to be clamped in. Figure 2 shows a collet chuck which is intended for the internal clamping of corresponding workpieces. Its function corresponds to the manner of operation as described above, the clamping surface however being formed by the exterior of a collet 1. The actuation of the chuck 1 is effected by axial displacement of a taper mandrel 2.1, which is directly in sliding connection with a tapered internal surface of the collet 1. As in Figure 1; here again the collet can be divided into three, six, nine or more parts. The arrangement and formation of the groove 4 for the reception of an O-ring corresponds to that in Figure 1. Here however it must be taken into consideration that the protrusion of the O-rings in the unloaded condition beyond the clamping surface must be made comparatively larger than in the case of an externally-clamping chuck, because during the clamping operation, in contrast with the compression in that case, a stretching of the ring and thus a reduction of its cross-sectional diameter occur. The essential advantage of a collet chuck according to the invention consists especially in that the clamped-in workpieces are extraordinarily reliably held, avoiding undesired deformation or damage, and it is of particular importance that a rotationally symmetrical clamping is guaranteed even in the case of those parts whose profile does not conform completely with a circular profile. WHAT WE CLAIM IS:

1. A chuck for clamping pressure-sensitive workpieces, comprising a collet having a clamping surface, and a tapered member for opening and closing the collet by axial displacement relatively to the collet, the collet including one or more annular grooves in the clamping surface, with 0rings of an elastomer material arranged therein, the depth of the grooves being smaller than the cross-sectional diameter of the O-rings.

2. A chuck according to claim 1, wherein the groove bottoms have a rectangular profile.

3. A chuck according to claim 1, substantially as described with reference to the accompanying drawings.