The invention relates to a device for clamping a workpiece holder to a collet chuck that can be fixed to a machine tool.
A device of this type is known from EP-A-1 068 918 wherein a hollow cylindrically designed workpiece holder is placed on the likewise hollow cylindrically designed collet chuck and is clamped to the collet chuck by means of a clamping device. The clamping device comprises a plurality of clamping elements distributed around the circumference of the collet chuck in the form of clamping balls which are functionally connected to a spring-loaded annular piston disposed in an annular space of the collet chuck. When the annular piston is acted upon hydraulically or pneumatically against the spring force the clamping balls are held in corresponding grooves of the collet chuck so that they do not project over its surface. If the pressure on the annular piston is reduced, the clamping balls are pressed by the annular piston due to the effect of the spring force into a circumferential annular groove of the workpiece holder, and in this way the workpiece holder is clamped to the collet chuck. The clamping forces are transferred over the puncitformly positioned clamping balls and are thus limited in size. If greater tensile forces occur, such devices fail due to exceedance of the Hertzian stress.
The object forming the basis of the present invention is to provide a device of the type specified at the start which also better withstands greater tensile forces.
This object is achieved according to the invention by a device having a plurality of clamping elements distributed around a circumference of the collet chuck that can be adjusted radially to an axis of the collet chuck from a release to a clamping position, and can be pressed against a circumferential surface of the workpiece holder positioned relative to the collet chuck in the clamping position in order to generate the clamping force securing the workpiece holder to the collet chuck. The clamping elements include rollers having axes aligned substantially tangentially to the collet chuck circumference such that in the clamping position, a determinable surface pressure is produced by mutual contact of these rollers with the workpiece holder, a clamping mandrel or an annular piston of the collet chuck and the collet chuck part.
Further preferred embodiments of the device according to the invention form the subject matter of the dependent claims.
With the device according to the invention wherein the clamping elements are designed as rollers having axes aligned tangentially to the collet chuck circumference which have a curved outer form at least over part of their length, the radius of the curve corresponding to the radius of the workpiece holder circumferential surface such that in the clamping position the rollers are advantageously in line contact with the workpiece holder circumferential surface, the surface pressure when the clamping forces securing the workpiece holder are generated can be considerably reduced, and the collet chuck can also be used in the range of greater tensile forces.
In the following the invention will be described in more detail using the drawings. These show as follows:
In
The collet chuck 2 comprises a piston/cylinder unit coaxial to the collet chuck axis 4 and which consists of a cylinder part 6 and a piston 7 disposed within the latter. A disc-shaped collet chuck part 8 is inserted into the cylinder part 6 from above. There is disposed between the disc-shaped collet chuck part 8 and the piston 7 a spring or a compound spring 9 optionally comprising two disc springs which strive to push the piston 7 downwards. The piston 7 can be acted upon pneumatically or hydraulically against the spring force, and so is held in its upper position according to
The piston 7 is connected, for example screwed, to a central clamping mandrel 10 which upon the axial piston adjustment is guided within a further, fixed collet chuck part 11. The collet chuck part 11 guiding the clamping mandrel 10 is securely connected to the aforementioned disc-shaped collet chuck part 8.
There are made in the fixed collet chuck part 11 a number of radial grooves 13 which are distributed over the circumference of the collet chuck 2 or the collet chuck part 11. It is advantageous, as regards production, if two grooves 13 respectively are arranged radially opposite one another. The grooves 13 are provided to each hold a further roller 20, described in more detail below, and are designed such that in a release position shown in
In order to clamp the workpiece holder 3 to the collet chuck 2 the pressure in the chamber 5 is reduced, and the piston 7 with the clamping mandrel 10 is pressed downwards by the compound spring 9. The rollers 20 are thereby pressed radially apart from one another over a conical outer surface 23 of the clamping mandrel 10 and pressed with their part projecting out of the respective groove 13 against a conical, downwardly tapering inner circumferential surface 25 of the workpiece holder 3.
In the clamping position shown in
The rollers 20 according to the invention, which can be adjusted radially from the release position into the clamping position and vice versa, are aligned with their axes 30 tangential to the collet chuck circumference, and according to
A particularly advantageous embodiment of a roller 20 is shown in
Another embodiment of a device 1′ for clamping a workpiece holder 43 to a collet chuck 42 is shown in
In turn, a number of rollers 60 are provided distributed over the circumference of the collet chuck 42 which are arranged in radial grooves 61 of the annular inner part 46. It is also an advantage with this embodiment, as regards production, if two grooves 61 are respectively arranged radially opposite one another although this does correspond to the illustration of
The clamping position is shown in
A particularly advantageous embodiment of a roller 60 is shown in
In
The size of the line lengths a, b, c (
With the device according to the invention in which the clamping elements are designed as rollers with axes aligned tangentially to the collet chuck circumference and which have a curved outer form, at least over part of their length, the radius of the curve corresponding to the radius of the workpiece holder circumferential surface such that in the clamping position the rollers are in line contact with the workpiece holder circumferential surface, the surface pressure can be considerably reduced by generating the clamping forces securing the workpiece holder, and the collet chuck can also be used in the range of greater tensile forces.
Within the framework of the invention this device can also be used when pressing, for example for pressing plastic or sintered metal parts with which a workpiece holder can also be understood to be a type of tool holder for dies or the like.
The rollers can also be cylindrical rollers or those with which, for example according to
Number | Date | Country | Kind |
---|---|---|---|
741/09 | May 2009 | CH | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/EP2010/002885 | 5/11/2010 | WO | 00 | 11/17/2011 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2010/130408 | 11/18/2010 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
1056076 | Wiard | Mar 1913 | A |
5870935 | Erickson et al. | Feb 1999 | A |
5909882 | Schill | Jun 1999 | A |
5918870 | Stark | Jul 1999 | A |
5997011 | Nordquist | Dec 1999 | A |
6160236 | Nordquist | Dec 2000 | A |
6161826 | Forrer | Dec 2000 | A |
6367814 | Luescher et al. | Apr 2002 | B1 |
6378877 | Luescher et al. | Apr 2002 | B1 |
6485214 | Schill | Nov 2002 | B2 |
6527266 | Yonezawa et al. | Mar 2003 | B1 |
6532861 | Etter | Mar 2003 | B2 |
6641127 | Haruna | Nov 2003 | B2 |
6641128 | Fries | Nov 2003 | B2 |
6905117 | Bernhard et al. | Jun 2005 | B2 |
7232121 | Haruna | Jun 2007 | B2 |
7520495 | Stark | Apr 2009 | B2 |
8152151 | Sandmeier | Apr 2012 | B2 |
8590878 | Haruna | Nov 2013 | B2 |
20040113346 | Kawakami et al. | Jun 2004 | A1 |
Number | Date | Country |
---|---|---|
3744092 | Jul 1989 | DE |
1068918 | Jan 2001 | EP |
593864 | Oct 1947 | GB |
Number | Date | Country | |
---|---|---|---|
20120056387 A1 | Mar 2012 | US |