Clamping device for tool holder

Patent metadata

Field	Value
Publication number	US-12280437-B2
Application number	US-202017778330-A
Country	US
Kind code	B2
Filing date	Nov 16, 2020
Priority date	Nov 20, 2019
Publication date	Apr 22, 2025
Grant date	Apr 22, 2025

Abstract

A clamping device for releasably holding a tool holder shank includes a spindle rotatably mounted inside a housing. A drawbar is axially moveable in a bore in the housing between an advanced releasing position and a retracted locking position. A plurality of engagement members are moveable under the effect of the drawbar into locking engagement with the tool holder shank. An actuating sleeve is arranged around a peripheral wall of the spindle and axially moveable in relation to it. A motion transferring mechanism is arranged for transferring an axial movement of the actuating sleeve into a movement of the drawbar. A hydraulic cylinder arrangement is arranged for moving the actuating sleeve. The hydraulic cylinder arrangement includes a cylinder casing fixed to spindle and an annular piston head, which is fixed to or fixedly connected to the actuating sleeve and slidably received in an annular space inside the cylinder casing.

First claim

The invention claimed is:

1. A clamping device arranged for releasably holding a tool holder shank, the clamping device comprising:
a housing;
a spindle rotatably mounted inside the housing and having a front end, a rear end and a bore which intersects the front end and extends rearwardly therefrom, wherein a mounting portion for receiving the tool holder shank is provided at a front end of the bore;
a drawbar slidably mounted inside the bore so as to be reciprocally moveable in the bore along a longitudinal axis thereof between an advanced releasing position and a retracted locking position;
a plurality of engagement members arranged around the drawbar at a front end thereof, wherein the engagement members, under the effect of a movement of the drawbar from the advanced releasing position to the retracted locking position, are moveable from a first position, in which the engagement members allow the tool holder shank to move into and out of said mounting portion of the bore, to a second position, in which the engagement members are in locking engagement with the tool holder shank and keep it secured to the spindle; and
a hydraulically operated actuating sleeve arranged inside the housing, wherein the actuating sleeve is arranged around a peripheral wall of the spindle and slidably mounted to this peripheral wall so as to be axially moveable in relation to the spindle;
a motion transferring mechanism arranged inside the housing, wherein the motion transferring mechanism is mounted to the spindle and configured to transfer an axial movement of the actuating sleeve in a first axial direction in relation to the spindle into a movement of the drawbar from the advanced releasing position to the retracted locking position; and
a hydraulic cylinder arrangement arranged inside the housing and configured to move the actuating sleeve axially in relation to the spindle, wherein the hydraulic cylinder arrangement includes a cylinder casing, which is concentric with the actuating sleeve and which is fixed to spindle on the outside thereof so as to be rotatable in relation to the housing together with the spindle, and an annular piston head, which is fixed to or fixedly connected to the actuating sleeve, the piston head being slidably received in an annular space inside the cylinder casing and configured to divide this space into an annular first hydraulic chamber on a first side of the piston head and an annular second hydraulic chamber on an opposite second side of the piston head, wherein the actuating sleeve is moveable together with the piston head in said first axial direction by feeding of hydraulic fluid into the first hydraulic chamber and in an opposite second axial direction by feeding of hydraulic fluid into the second hydraulic chamber, wherein the motion transferring mechanism includes two or more wedges spaced apart in the circumferential direction of the spindle, each wedge being received in a respective aperture that extends radially through said peripheral wall of the spindle, wherein the wedges are configured to press the drawbar towards the retracted locking position when they are pressed radially inwards in the associated apertures wherein each wedge includes a first pressure receiving surface which faces outwards from the spindle, wherein the actuating sleeve on its inner side is provided with a first pressure applying surface which faces inwards for contacting the first pressure receiving surface on each wedge, the first pressure applying surface having a radial distance to the longitudinal axis that increases as seen in said first axial direction and wherein the first pressure applying surface is configured to press each wedge radially inwards in the associated aperture by pressing against the first pressure receiving surface on each wedge when the actuating sleeve is moved in said first axial direction.

2. The clamping device according to claim 1 , wherein the spindle and the cylinder casing form part of a rotatable unit that is rotatably received in an inner space of the housing, wherein the first hydraulic chamber is hydraulically connected to a first hydraulic channel in the housing via an annular first hydraulic connecting area at the interface between the housing and said rotatable unit, wherein the second hydraulic chamber is hydraulically connected to a second hydraulic channel in the housing via an annular second hydraulic connecting area at said interface, and wherein a plurality of rotary seals are arranged at said interface on either side of the first hydraulic connecting area and on either side of the second hydraulic connecting area.

3. A The clamping device according to claim 2 , wherein each rotary seal is arranged in a respective annular groove arranged in the housing at said interface.

4. The clamping device according to claim 2 , wherein each rotary seal includes an inner seal ring and an outer elastomeric O-ring, which surrounds the seal ring and which is arranged in a radially compressed state and configured to press the seal ring against an outer surface of said rotatable unit.

5. The clamping device according to claim 1 , wherein the actuating sleeve is configured to assume a self-locking axial position on the spindle when the drawbar has been forced into the retracted locking position under the effect of the actuating sleeve and the motion transferring mechanism, so as to thereby keep the drawbar in the retracted locking position.

6. The clamping device according to claim 1 , wherein the piston head forms part of an annular piston member, which is secured to the actuating sleeve.

7. The clamping device according to claim 1 , wherein the piston head and the actuating sleeve are formed in one piece.

8. The clamping device according to claim 1 , wherein the cylinder casing is fixed to the spindle through a threaded joint formed by an internal thread on the cylinder casing and a corresponding external thread on the spindle.

9. The clamping device according to claim 1 , wherein the first pressure applying surface and the first pressure receiving surfaces are inclined in relation to the longitudinal axis by such an angle α that the wedges will keep the actuating sleeve in a self-locking axial position on the spindle when the drawbar has been forced into the retracted locking position under the effect of the actuating sleeve and the wedges.

10. The clamping device according to claim 9 , wherein each wedge includes a second pressure receiving surface which faces outwards from the spindle, wherein the actuating sleeve on its inner side is provided with a second pressure applying surface which faces inwards for contacting the second pressure receiving surface on each wedge, the second pressure applying surface having a radial distance to the longitudinal axis that increases as seen in said first axial direction, wherein the second pressure applying surface and the second pressure receiving surfaces are inclined in relation to the longitudinal axis by an angle β which is larger than the angle α, and wherein the first and second pressure applying surfaces and the first and second pressure receiving surfaces are arranged consecutively on the actuating sleeve and on each wedge, respectively, such that, upon a movement of the actuating sleeve in the first axial direction, the second pressure applying surface is configured to slide and press against the second pressure receiving surface on each wedge during a first phase of the movement and the first pressure applying surface is configured to slide and press against the first pressure receiving surface on each wedge during a subsequent second phase of the movement.

11. The clamping device according to claim 1 , wherein the drawbar, under the effe

Assignees

• Sandvik Coromant Ab

Inventors

• Matlik Gunnar

Classifications

• Y10T409/309464

  and draw bar · CPC title

• B23B2270/025

  Hydraulics · CPC title

• B23B2260/034

  Drawbars · CPC title

• B23B2231/12

  Chucks having means to amplify the force produced by the actuating means to increase the clamping force · CPC title

• B23B31/265 Primary

  by means of collets · CPC title