Clamping device for a tool holder

Abstract

A clamping device for releasably holding a tool holder shank (81) comprises: - a spindle (2) rotatably mounted inside a housing (3); - a drawbar (8) axially movable in an internal bore (5) in the housing between an advanced, release position and a retracted, locking position; - an engagement member (20) movable into locking engagement with the tool holder shank under the action of the drawbar; - an actuation member (13) slidably mounted to the spindle; - a motion transmission mechanism (30) for converting axial movement of the actuation member into movement of the drawbar; and - a cylinder housing (60) and associated piston member (70) for moving the actuation member relative to the spindle. The cylinder housing (60) is arranged in axial floating manner in the housing (3). The actuation member (13) is rotatable with the spindle (2) relative to the cylinder housing (60) and the piston member (70).

Description

Technical Field

[0001] The present invention relates to a clamping device according to the preamble of claim 1, which is intended for connecting a tool holder to a machine tool. Background Technology

[0002] In the field of machine tools used for metal cutting, cutting tools (e.g., in the form of drills or milling cutters) for machining workpieces of metallic materials are typically fixed to and rotate with a tool holder, which can be detachably clamped to the rotatable spindle of the machine tool so as to rotate with the spindle. It is previously known to clamp the shank of such a tool holder to the rotatable spindle by means of a clamping mechanism arranged in the spindle. When it is necessary to change the cutting tool, the tool holder is released from the spindle, and a new tool holder with the other cutting tool is clamped to the spindle.

[0003] A clamping device is previously known from EP 1 468 767B1, which includes a spindle having a clamping mechanism suitable for automated tool changing operations. In the clamping device according to EP 1 468 767B1, an actuating member in the form of a first pull rod is slidably mounted inside the spindle and is configured to achieve axial displacement of a second pull rod via a force amplification mechanism, the force amplification mechanism including a plurality of engaging wedges arranged between the pull rods. A gas spring inside the spindle is configured to push the two pull rods to a retracted locked position, in which a tool holder is clamped to the spindle, and a hydraulic piston can be configured to act on a piston at the rear end of the gas spring to achieve displacement of the two pull rods to an advanced release position, in which the tool holder can be released from the spindle. However, this previously known clamping device has a relatively long axial travel, and is therefore unsuitable for use when the tool holder is to be detachably secured to the outer periphery of the tool turret, where the available axial space for the clamping device is limited at the outer periphery of the tool turret.

[0004] The clamping device of the preamble of claim 1 is previously known from EP 3 825 047A1. Summary of the Invention

[0005] Purpose of the invention

[0006] The object of the present invention is to provide a clamping device of the above type, which has a new and advantageous design and is suitable for use with the tool turret of a machine tool. Invention Overview

[0008] According to the present invention, the objective is achieved by means of a clamping device having the features defined in claim 1.

[0009] The clamping device according to the present invention includes:

[0010] -case;

[0011] - A spindle, which is rotatably mounted inside the housing, and has a front end, a rear end, and an inner bore that intersects the front end and extends rearward from the front end, wherein a mounting portion for receiving a tool holder shank is provided at the front end of the inner bore.

[0012] - A pull rod, which is slidably mounted inside the inner bore so as to be able to move back and forth between the forward release position and the return lock position along its longitudinal axis within the inner bore;

[0013] - An engaging member arranged around the front end of the pull rod, wherein, under the action of the pull rod moving from the forward release position to the retracted locking position, the engaging member is capable of moving from a first position to a second position. In the first position, the engaging member allows the tool holder shank to move into and out of the mounting portion of the inner bore. In the second position, the engaging member is locked into the tool holder shank and holds it fixed to the spindle.

[0014] - An actuating member, which is arranged inside the housing, wherein the actuating member is slidably mounted to the spindle so as to be able to move relative to the spindle in its axial direction;

[0015] - A motion transmission mechanism, disposed inside the housing, wherein the motion transmission mechanism is mounted to the main shaft and configured to convert axial movement of the actuating member relative to the main shaft in a first axial direction into movement of the lever from a forward release position to a retracted locking position; and

[0016] - A hydraulic actuator for axially moving an actuating member relative to a main shaft, the hydraulic actuator being arranged in a housing and including a cylinder housing and a piston member, wherein the piston member extends about the main shaft and is slidably mounted to the cylinder housing so as to be axially moved hydraulically relative to the main shaft to allow the piston member to apply a pulling or pushing force on the actuating member in a first axial direction, thereby realizing the movement of the lever from a forward release position to a retracted locking position.

[0017] The actuating member can rotate with the spindle relative to the cylinder housing and piston assembly, meaning that the hydraulic actuator can remain stationary during machining operations while the tool holder rotates with the spindle. By avoiding rotating parts in the hydraulic actuator, the construction of the hydraulic actuator and associated hydraulic system is simplified, and a rotary seal at the interface between the housing and the spindle, which would limit the possible rotational speed of the spindle, is unnecessary. Using a hydraulic actuator to move the actuating member and thereby move the pull rod means that the clamping device according to the invention is suitable for use in automated tool change operations.

[0018] The cylinder housing extends about a main shaft and is slidably mounted inside the housing of the clamping device to allow axial movement relative to the main shaft between a first end position and a second end position. In the first end position, the cylinder housing abuts against a first shoulder on the main shaft, which restricts movement of the cylinder housing relative to the main shaft in the first axial direction. In the second end position, the cylinder housing abuts against a second shoulder on the main shaft, which restricts movement of the cylinder housing relative to the main shaft in the opposite second axial direction. The piston assembly includes an annular piston head slidably received in a space within the cylinder housing, wherein a first hydraulic chamber is formed in the space, located on a first side of the piston head. By feeding hydraulic fluid into the first hydraulic chamber, the cylinder housing can be moved to the second end position, and the piston assembly can be moved in the first axial direction.

[0019] Therefore, the cylinder housing is mounted axially floating inside the clamping device housing, allowing it to move a short distance axially relative to the housing and spindle. When the lever is about to be moved to the retracted locked position, hydraulic fluid is fed into the first hydraulic chamber, causing the cylinder housing to move to its second end position and abut against the second shoulder on the spindle. The second shoulder on the spindle acts as a stop for the cylinder housing, and as hydraulic fluid is further fed into the first hydraulic chamber, the piston member is pushed in the first axial direction, thereby causing the actuating member to move the lever to the retracted locked position. During this axial movement of the piston member and lever, the piston member applies a force to the actuating member in the first axial direction, while the cylinder housing applies a corresponding reaction force to the spindle via the second shoulder on the spindle. Therefore, during the lever's movement to the retracted locked position, no force is transmitted to the clamping device housing, and thus, during this actuation of the hydraulic actuator, the rotary bearing between the clamping device spindle and housing is not subjected to any axial force, which in turn means reduced stress on the rotary bearing. In existing solutions, the rotary bearing between the spindle and housing of the clamping device is subjected to axial stress during the movement of the pull rod. Compared with existing solutions, the solution according to the invention allows for the use of a smaller rotary bearing without reducing its expected service life, or allows for a longer expected service life of the rotary bearing when using a rotary bearing of the same size.

[0020] The clamping device according to the invention can be mounted to the tool turret of a machine tool, wherein the rotatable spindle of the clamping device is connected to or can be connected to a drive mechanism in the tool turret. However, the clamping device is not limited to use in a tool turret. Instead, the rotatable spindle of the clamping device can constitute the main spindle of the machine tool, or can be connected to such a main spindle without any intermediate tool turret.

[0021] According to an embodiment of the invention, the actuating member is configured such that, when the pull rod has been forced into the retracted locked position by the actuating member and the motion transmission mechanism, the actuating member presents a self-locking axial position on the spindle, thereby holding the pull rod in the retracted locked position. Therefore, the actuating member is able to hold the pull rod in the retracted locked position during spindle rotation without requiring any external force from the piston member. This means that when the spindle and the actuating member are stationary, the piston member only needs to apply a pulling or pushing force to the actuating member related to the tool change operation. Therefore, during spindle rotation, friction between the actuating member and the piston member, and between the cylinder housing and the spindle, can be avoided, or at least reduced to a very low level.

[0022] According to another embodiment of the invention, a second hydraulic chamber is formed in the space within the cylinder housing, located on a second side opposite to the piston head. By feeding hydraulic fluid into this second hydraulic chamber, the cylinder housing can be moved to a first end position, and the piston member can be moved in a second axial direction to allow the piston member to apply a pulling or pushing force on the actuating member in the second axial direction. Thus, a dual-acting piston member is achieved, and therefore the same piston member can be used to move the actuating member in the first axial direction when the lever is about to move from the forward release position to the return lock position, and to move the actuating member in the opposite direction when the lever is about to move from the return lock position to the forward release position. This, in turn, means that the clamping device can be manufactured very compactly. When the lever is about to be moved to the forward release position, hydraulic fluid is fed into the second hydraulic chamber, which causes the cylinder housing to move to its first end position and bring the cylinder housing abutting against a first shoulder on the spindle. The first shoulder on the spindle acts as a stop member for the cylinder housing, and as hydraulic fluid is further fed into the second hydraulic chamber, the piston member is pushed in the second axial direction, thereby causing the actuating member to move the lever to the forward release position. During this axial movement of the piston member and the lever, the piston member applies a force to the actuating member in the second axial direction, while the cylinder housing applies a corresponding reaction force to the spindle via the first shoulder on the spindle. Therefore, during the movement of the lever to the forward release position, no force is transmitted to the housing of the clamping device, and thus, during this actuation of the hydraulic actuator, the rotary bearing between the spindle and the housing of the clamping device is not subjected to any axial force, which in turn means reduced stress on the rotary bearing.

[0023] According to another embodiment of the invention, the cylinder housing includes a first cylindrical wall and an opposing second cylindrical wall, the first cylindrical wall radially outwardly constraining the space in the cylinder housing, and the second cylindrical wall radially inwardly constraining the space in the cylinder housing. Therefore, the piston head of the piston assembly is slidably received between these cylindrical walls.

[0024] According to another embodiment of the invention, an internal bulge is provided on the inner side of the cylinder housing, wherein the cylinder housing is configured to abut against a first shoulder on the spindle via the internal bulge at the first end position and against a second shoulder on the spindle via the internal bulge at the second end position, and wherein the internal bulge on the cylinder housing is received in the gap between the first and second shoulders formed on the spindle, provided there is clearance. Therefore, during tool change operations, the connection between the cylinder housing and the spindle can be achieved in a simple and reliable manner.

[0025] According to another embodiment of the invention, the cylinder housing is configured to disengage from the spindle when positioned in an intermediate axial position between the first and second end positions. The cylinder housing is intended to be in this intermediate axial position between the moment of tool change, i.e., during machining operations when the tool holder rotates with the spindle. Therefore, frictional forces between the cylinder housing and the spindle can be avoided during spindle rotation.

[0026] According to another embodiment of the invention, the clamping device includes a spring-loaded return mechanism configured to act on the cylinder housing, wherein:

[0027] - The cylinder housing can overcome the spring force of the return mechanism and move from the intermediate axial position to the first end position, and can also move from the first end position to the intermediate axial position under the action of the spring force; and

[0028] - The cylinder housing can overcome the spring force of the return mechanism and move from the intermediate axial position to the second end position, and can also move from the second end position to the intermediate axial position under the action of the spring force.

[0029] Therefore, the cylinder housing is pushed toward the central axial position by the spring force of the return mechanism. This spring-loaded return mechanism ensures that after the tool change operation is completed, the cylinder housing automatically moves out of contact with the spindle, so that no frictional heat is generated at the interface between the cylinder housing and the spindle when the spindle rotates at high speed relative to the cylinder housing after the tool change operation.

[0030] According to another embodiment of the invention, the piston member includes a sleeve-shaped piston rod fixed to a piston head, wherein the piston member is configured to apply the pulling or thrusting force to the actuating member via the piston rod. Advantageously, the piston rod is configured to define a first hydraulic chamber radially inward.

[0031] According to another embodiment of the invention, the actuating member has the form of a sleeve, wherein the actuating member is arranged around the outer peripheral wall of the main shaft and is slidably mounted to the outer peripheral wall so as to be axially movable relative to the main shaft.

[0032] Another embodiment of the present invention is characterized in that:

[0033] - The motion transmission mechanism includes a first wedge portion slidably received in a first orifice, the first orifice extending radially through the outer peripheral wall of the main shaft, wherein the first wedge portion is configured to press the pull rod toward a retracted locking position when the first wedge portion is pressed radially inward in the first orifice.

[0034] -The first wedge-shaped portion includes a first pressure receiving surface extending outward from the main shaft;

[0035] - The actuating member has a first pressure-applying surface on its inner side, the first pressure-applying surface facing inward to contact a first pressure-receiving surface, and having a radial distance relative to the longitudinal axis, which increases when viewed in a first axial direction; and

[0036] - The first pressure applying surface is configured such that when the actuating member moves in the first axial direction, the first pressure applying surface presses the first wedge portion radially inward in the first orifice by pressing against the first pressure receiving surface.

[0037] By moving the actuating member in the first axial direction, the pull rod can move from the forward release position to the retracted locking position under the action of the actuating member and the first wedge. Because the first pressure applying surface has an increased radial distance from the longitudinal axis in the first axial direction, the movement of the actuating member in the first axial direction will cause pressure to be applied from the first pressure applying surface to the first pressure receiving surface on the first wedge. This pressure will have a radial component, causing the first wedge to be pressed radially inward toward the longitudinal axis.

[0038] Preferably, the first pressure-applying surface and the first pressure-receiving surface are inclined at an angle α relative to the longitudinal axis, such that when the pull rod has been forced into the retracted locking position by the actuating member and the first wedge, the first wedge holds the actuating member in a self-locking axial position on the outer peripheral wall. In this case, when viewed in a longitudinal section through the spindle, the first pressure-applying surface and the first pressure-receiving surface extend in the same direction. Angle α is chosen to be below the self-locking threshold angle, such that when the pull rod has moved inside the bore to the retracted locking position, the actuating member reaches the self-locking axial position relative to the first wedge. To obtain the self-locking axial position, angle α should be sufficiently small, i.e., below the self-locking threshold angle. The self-locking axial position refers to the axial position where the static friction between the first pressure-receiving surface on the first wedge and the first pressure-applying surface on the actuating member is greater than the opposing force in the friction plane, caused by a force applied to the first wedge in a radial direction perpendicular to the longitudinal axis. Therefore, the self-locking axial position is obtained within an angular range depending on the coefficient of friction between the first pressure receiving surface on the first wedge and the first pressure applying surface on the actuating member. This coefficient of friction depends on various parameters, such as the materials used, the coatings on the surfaces, the use of lubricants, etc. Therefore, the self-locking threshold angle depends on such parameters. Those skilled in the art will be able to identify, or at least predict or assess whether an angle is below such a self-locking threshold angle, by using common sense and / or routine experiments. Generally, it is preferred to choose an angle α much lower than the self-locking threshold angle, thereby ensuring a self-locking configuration. Another advantage of using a small angle α is that a force amplification effect is achieved because a small angle α means that a relatively long axial displacement of the actuating member will result in a relatively short axial displacement of the tie rod. However, an angle α that is too small may be inefficient and does not work well in practice. For example, a very small angle α may make it difficult for the actuating member to release from the self-locking axial position. Advantageously, the angle α is between 2° and 10°. With the angle α in this range, both the self-locking effect and a suitable force amplification effect can be achieved.

[0039] According to another embodiment of the invention, the first wedge portion includes a wedge surface facing the rear end of the spindle and in contact with a first sliding surface on the pull rod facing the front end of the spindle.

[0040] Another embodiment of the present invention is characterized in that:

[0041] - The motion transmission mechanism includes a second wedge portion slidably received in a second orifice extending radially through the outer peripheral wall of the main shaft, wherein the second wedge portion includes: a wedge surface facing the front end of the main shaft and contacting a second sliding surface on the pull rod facing the rear end of the main shaft; and a second pressure receiving surface facing outward from the main shaft. The second wedge portion is configured to press the pull rod toward a forward release position when the second wedge portion is pressed radially inward in the second orifice.

[0042] - The actuating member has a second pressure-applying surface on its inner side, the second pressure-applying surface facing inward to contact the second pressure-receiving surface, and having a radial distance from the longitudinal axis, which increases when viewed in the second axial direction; and

[0043] - The second pressure applying surface is configured such that when the actuating member moves in the second axial direction, the second pressure applying surface presses the second wedge portion radially inward into the second orifice by pressing against the second pressure receiving surface.

[0044] By moving the actuating member in the second axial direction, the pull rod can move from the retracted locked position to the forward released position under the action of the actuating member and the second wedge. Because the second pressure applying surface has an increased radial distance from the longitudinal axis in the second axial direction, the movement of the actuating member in the second axial direction will cause pressure to be applied from the second pressure applying surface to the second pressure receiving surface on the second wedge. This pressure will have a radial component, causing the second wedge to be pressed radially inward toward the longitudinal axis.

[0045] According to another embodiment of the invention, the clamping device includes two or more such first wedges spaced apart in the circumferential direction of the outer peripheral wall, wherein each first wedge is received in a corresponding first orifice extending radially through the outer peripheral wall. The clamping device may also include two or more such second wedges spaced apart in the circumferential direction of the outer peripheral wall, wherein each second wedge is received in a corresponding second orifice extending radially through the outer peripheral wall. Preferably, the first orifices and associated first wedges, as well as the second orifices and associated second wedges, are uniformly distributed in the circumferential direction of the outer peripheral wall. Thus, a well-balanced clamping device with a good force distribution is obtained. However, a very large number of wedges and associated orifices may be disadvantageous because each orifice reduces the strength of the housing. Three first wedges and three second wedges, along with associated orifices, will provide a well-balanced clamping device with an appropriate level of force distribution while still maintaining sufficient strength of the housing. Advantageously, the first wedge and the second wedge are arranged alternately as seen in the circumferential direction of the outer peripheral wall, wherein each of the first wedges is followed by a second wedge in the second wedge as seen in the circumferential direction of the outer peripheral wall, and each of the second wedges is followed by a first wedge in the first wedge as seen in the circumferential direction of the outer peripheral wall.

[0046] Further advantageous features of the clamping device according to the invention will become apparent from the following description. Attached Figure Description

[0047] Referring to the accompanying drawings, the following is a detailed description of embodiments of the present invention, cited by way of example. In the drawings:

[0048] Figure 1 This is a plan view of the clamping device and tool holder according to an embodiment of the present invention.

[0049] Figure 2 yes Figure 1 A partially sectional perspective view of the clamping device and tool holder, with the tool holder detached from the clamping device.

[0050] Figure 3a It runs through Figure 1 A longitudinal cross-sectional view of the clamping device and tool holder, wherein the lever of the clamping device is shown in the forward release position, and the cylinder housing is shown in the first end position.

[0051] Figure 3b It corresponds to Figure 3a The longitudinal cross-sectional view shows the tie rod in the retracted locked position and the cylinder housing in the second end position.

[0052] Figure 3c It corresponds to Figure 3a The longitudinal cross-sectional view shows the tie rod in the retracted locked position and the cylinder housing in the intermediate axial position.

[0053] Figure 4 Is included Figure 1 A partially cut-away perspective view of a part in a clamping device.

[0054] Figure 5 It runs through Figure 4 The diagram shows a longitudinal cross-sectional view of the tool holder and clamping device components, with the tool holder in a clamping state.

[0055] Figure 6 It corresponds to Figure 5 The longitudinal cross-sectional view shows the tool holder in an unclamped state.

[0056] Figure 7 yes Figure 4 Exploded view of the parts of the tool holder and clamping device shown, and

[0057] Figure 8 From Figure 4 An exploded view of the tool holder and clamping device parts from another direction. Detailed Implementation

[0058] exist Figures 1 to 8 The figure shows a clamping device 1 according to an embodiment of the present invention. The clamping device 1 is configured to releasably clamp a tool holder 80 (illustrated very schematically in the figure) to a rotatable spindle 2 in the clamping device, and to enable the workpiece to be machined by means of a cutting tool (not shown) fixed to the tool holder 80.

[0059] The spindle 2 is rotatably mounted to the housing 3 of the clamping device 1 by means of a rolling bearing 4, which is, for example, a tapered roller bearing or any other suitable type of roller bearing. The spindle 2 has a front end 2a, a rear end 2b, and an inner bore 5 intersecting with and extending rearward from the front end 2a. Thus, the inner bore 5 has an inlet opening at the front end 2a of the spindle. The spindle 2 can be connected to the drive mechanism of the machine tool, such as the drive mechanism in the tool turret of the machine tool, via a connecting pin 6 at the rear end 2b of the spindle, so as to allow the spindle to be driven to rotate by the drive mechanism.

[0060] Installation section 7 (see installation section 7) Figure 2 and Figure 4 A mounting shank 81 is provided at the front end of the inner hole 5 to receive the tool holder 80. This mounting shank 81 is referred to herein as the tool holder shank.

[0061] The pull rod 8 is slidably mounted inside the inner bore 5 so that it can be in the forward release position along its longitudinal axis L within the inner bore 5 (see...). Figure 3a and Figure 6 ) and return to the locked position (see Figure 3b , Figure 3c and Figure 5 The lever 8 moves back and forth between the inner bore 5 and the neck 10. The lever 8 has a front end facing the inlet opening of the inner bore 5 and a rear end facing the opposite direction. A head portion 9 and a neck portion 10 are provided at the front end of the lever 8. The head portion 9 is located in front of the neck portion 10, as seen in the longitudinal direction of the lever, wherein the head portion 9 is connected to the neck portion 10 via a rearwardly facing chamfered surface 11 on the head portion 9. A sealing ring 12 is arranged between the inner surface of the lever 8 and the inner bore 5. In the illustrated example, the sealing ring 12 is received in a groove on the outer side of the lever 8.

[0062] The tool holder shank 81 can be inserted into the mounting portion 7 of the inner bore 5 via an inlet opening at the front end 2a of the spindle 2. The head portion 9 of the pull rod is received in the engaging inner bore 82 of the tool holder shank 81, and the tubular wall 83 of the tool holder shank is received in the space between the head portion 9 and the inner surface of the inner bore 5. In the illustrated embodiment, the mounting portion 7 of the inner bore 5 is tapered and has a slightly “triangular” or polygonal non-circular cross-sectional shape, suitable for receiving a tool holder shank 81 of a similar shape. This tapered shape ensures a play-free connection between the tool holder shank 81 and the spindle 2 in both the radial and axial directions, while the non-circular cross-section ensures that the tool holder shank 81 is non-rotatably fixed to the spindle 2. However, the mounting portion 7 of the inner bore 5 can also have any other suitable shape for receiving other types of tool holder shanks.

[0063] A multi-segmented engaging member 20 is arranged around the front end of the pull rod 8. When the pull rod 8 moves from the forward release position to the return locking position, the engaging member 20 can move from the first position (see...) Figure 3a and Figure 6 Move to the second position (see) Figure 3b , Figure 3c and Figure 5 In the first position, the engaging member 20 allows the tool holder shank 81 to move into and out of the mounting portion of the inner bore 5. In the second position, the engaging member 20 engages with the engaging groove 84 in the engaging inner bore 82 of the tool holder shank 81, thereby holding the tool holder shank 81 fixed to the spindle 2.

[0064] In the illustrated embodiment, the engaging member 20 is arranged around the neck portion 10 of the pull rod 8, and is secured by a retainer ring 21 arranged in the inner hole 5 and surrounding the neck portion 10 (see [reference]). Figure 6The retainer ring 21 and the elastic O-ring 22 are held in place around the neck portion. Each engaging member 20 has an outwardly facing flange portion 23 that engages in an inner groove in the retainer ring 21. The O-ring 22 is received in an outwardly facing groove at the rear end of each engaging member 20. A compression spring 24, a thrust ring 25, and a stop ring 26 are also arranged in the bore 5 and configured to surround the pull rod 8. The compression spring 24 is mounted between the shoulder of the pull rod 8 and the thrust ring 25 and is configured to push the thrust ring 25, the retainer ring 21, and the engaging member 20 forward. Forward movement of the retainer ring 21 toward the inlet opening of the bore 5 is restricted by the stop ring 26, which is mounted in a groove in the inner surface of the bore 5.

[0065] At the front end of each engaging member 20, each engaging member 20 is provided with an outwardly pointing engaging flange 27, which is configured to engage with the engaging groove 84 in the tool holder shank 81 when the engaging member 20 is in the second position described above. When the pull rod 8 is in the forward release position, the front end of the engaging member 20 is located behind the head portion 9 of the pull rod 8, and the engaging flange 27 disengages from the engaging groove 84 in the tool holder shank 81, as... Figure 3a and Figure 6 As illustrated in the figure, when the pull rod 8 moves axially backward along its longitudinal axis L in the inner bore 5, the chamfered surface 11 on the head portion 9 of the pull rod will contact the front end of the engagement member 20, wherein the front end of the engagement member 20 will slide on the chamfered surface 11 and be pressed outward, such that the engagement flange 27 on the engagement member engages with the engagement groove 84 in the tool holder shank 81, thereby pulling the tool holder shank 81 into firm contact with the inner surface of the spindle 2 in the mounting portion of the inner bore 5.

[0066] The clamping device 1 also includes an actuating member 13, which is concentric with and slidably mounted to the spindle 2 so as to be axially movable relative to the spindle 2 along the longitudinal axis L. The actuating member 13 is non-rotatably mounted to the spindle 2, i.e., preventing rotation relative to the spindle 2, and is therefore configured to rotate with the spindle 2. A motion transmission mechanism 30 is mounted to the spindle 2 and is configured to convert the axial movement of the actuating member 13 relative to the spindle 2 in a first axial direction D1 into movement of the pull rod 8 from a forward release position to a return locking position. In the illustrated embodiment, this first axial direction D1 is toward the front end 2a of the spindle 2. Therefore, in this case, the movement of the pull rod 8 from the forward release position to the return locking position is achieved by the forward axial movement of the actuating member 13 along the spindle 2. However, as an alternative, the actuating member 13 and the motion transmission mechanism 30 can be arranged to cooperate such that the movement of the pull rod 8 from the forward release position to the return locking position is achieved by the rearward axial movement of the actuating member 13 along the spindle 2.

[0067] Furthermore, the clamping device 1 includes a hydraulic actuator 17 for axially moving the actuating member 13 relative to the spindle 2. The hydraulic actuator 17 is disposed within the housing 3 and includes a cylinder housing 60 and a piston member 70. The cylinder housing 60 is configured to surround a portion of the spindle 2. The cylinder housing 60 is slidably mounted within a space inside the housing 3 so that it can be positioned at a first end (see [reference]). Figure 3a ) and second end position (see Figure 3b The cylinder housing 60 moves axially relative to the housing 3 and the main shaft 2. In a first end position, the cylinder housing 60 abuts against a first shoulder 61a on the main shaft 2, which restricts the movement of the cylinder housing 60 relative to the main shaft 2 in a first axial direction D1. In a second end position, the cylinder housing 60 abuts against a second shoulder 61b on the main shaft 2, which restricts the movement of the cylinder housing 60 relative to the main shaft 2 in the opposite second axial direction D2. Preferably, the cylinder housing 60 is configured to disengage from the main shaft 2 when it is in an intermediate axial position between the first end position and the second end position, such as... Figure 3c As shown in the diagram.

[0068] In the illustrated embodiment, an internal bulge 62 is disposed on the inner side of the cylinder housing 60, wherein the cylinder housing 60 is configured to abut against a first shoulder 61a on the spindle 2 via the internal bulge 62 in a first end position, and against a second shoulder 61b on the spindle 2 via the internal bulge 62 in a second end position. Therefore, in this case, the internal bulge 62 is configured to act as an abutment member by which the cylinder housing 60 abuts against the corresponding shoulders 61a, 61b on the spindle in the said end positions. The internal bulge 62 is received in the gap formed between the first shoulder 61a and the second shoulder 61b on the spindle 2 with clearance, thereby allowing the cylinder housing to disengage from the spindle 2 when in an intermediate axial position between the first and second end positions. In the illustrated example, the internal bulge 62 has the form of a locking ring, which is mounted in an annular groove provided in the cylinder housing 60; however, alternatively, it can be formed as an integral part of the cylinder housing. In the illustrated embodiment, the first shoulder 61a and the second shoulder 61b on the spindle are formed by opposing surfaces in an annular groove provided on the outer side of the spindle 2. However, the first shoulder 61a and the second shoulder 61b on the spindle, as well as the associated abutment member 62 on the cylinder housing, can also be designed in any other suitable manner.

[0069] Additionally, the piston member 70 is configured to surround a portion of the main shaft 2. The piston member 70 is slidably mounted to the cylinder housing 60 to allow for hydraulic axial movement relative to the main shaft 2, enabling the piston member 70 to apply a pulling or pushing force on the actuating member 13 along a first axial direction D1, thereby achieving movement of the lever 8 from an advance release position to a return lock position. In the illustrated embodiment, the piston member 70 is configured to move the actuating member 13 in the first axial direction D1 by applying an axially directed pulling force on the actuating member 13. Alternatively, the piston member 70 may be configured to move the actuating member 13 in the first axial direction D1 by applying an axially directed pushing force on the actuating member 13. The piston member 70 includes an annular piston head 71 slidably received in a space within the cylinder housing 60, wherein a first hydraulic chamber 63a is formed in the space, located on a first side of the piston head 71. By feeding hydraulic fluid into the first hydraulic chamber 63a, the cylinder housing 60 can be moved to the second end position, and the piston component 70 can be moved in the first axial direction D1.

[0070] In the illustrated embodiment, the cylinder housing 60 includes a first cylindrical wall 64 and an opposing second cylindrical wall 65. The first cylindrical wall 64 radially outwards restricts the space within the cylinder housing, and the second cylindrical wall 65 radially inwards restricts the space within the cylinder housing. In the illustrated example, the cylinder housing 60 consists of a first cylinder housing portion 60a and a second cylinder housing portion 60b (see...). Figure 6 The first cylinder housing portion 60a and the second cylinder housing portion 60b are formed such that they can be secured to each other by means of a threaded joint 66 or any other suitable method, wherein a first cylindrical wall 64 forms part of the first cylinder housing portion 60a and a second cylindrical wall 65 forms part of the second cylinder housing portion 60b. Sealing rings 72a and 72b are arranged on opposite sides of the piston head 71, wherein the first sealing ring 72a is mounted in a groove in the outward-facing surface of the piston head for sealing contact with the first cylindrical wall 64, and the second sealing ring 72b is mounted in a groove in the inward-facing surface of the piston head for sealing contact with the second cylindrical wall 65. Of course, the cylinder housing 60 can also be designed in any other suitable manner.

[0071] In the illustrated embodiment, a second hydraulic chamber 63b is formed in the aforementioned space within the cylinder housing 60, located on the opposite second side of the piston head 71. By feeding hydraulic fluid into this second hydraulic chamber 63b, the cylinder housing 60 can be moved to a first end position, and the piston member 70 can be moved in a second axial direction D2, allowing the piston member 70 to apply a pulling or pushing force to the actuating member 13 along the second axial direction D2. In the illustrated embodiment, the piston member 70 is configured to move the actuating member 13 in the second axial direction D2 by applying an axially directed pushing force to the actuating member 13. Alternatively, the piston member 70 can be configured to move the actuating member 13 in the second axial direction D2 by applying an axially directed pulling force to the actuating member 13.

[0072] In the illustrated embodiment, the piston member 70 includes a sleeve-shaped piston rod 73 fixed to the piston head 71, wherein the piston member 70 is configured to apply the aforementioned pulling or pushing force to the actuating member 13 via the piston rod 73. Preferably, the piston rod 73 is concentric with the actuating member 13 and extends about the main shaft 2. The piston rod 73 defines a first hydraulic chamber 63a radially inward, while a second hydraulic chamber 63b is defined radially inward by the aforementioned second cylindrical wall 65. In the illustrated example, the second cylindrical wall 65 extends into the gap between the inner surface of the piston rod 73 and the outer surface of the actuating member 13.

[0073] The piston rod 73 can be configured to apply the aforementioned force to the actuating member 13 by acting on an annular outer bulge 15 and a locking ring 16 disposed on the outer side of the actuating member 13, wherein the outer bulge 15 and the locking ring 16 are spaced apart in the axial direction of the actuating member 13. In the illustrated embodiment, an annular inner bulge 74 is disposed on the inner side of the piston rod 73. The inner bulge 74 on the piston rod 73 is received in the gap formed between the outer bulge 15 and the locking ring 16 when there is clearance. In this case, when the piston member 70 moves the actuating member in the first axial direction D1, the axial force is transmitted to the actuating member 13 via the inner bulge 74 and the outer bulge 15, and when the piston member 70 moves the actuating member in the second axial direction D2, the axial force is transmitted from the piston member 70 to the actuating member 13 via the outer bulge 74 and the locking ring 16. Of course, the piston member 70 and the interface between the piston member and the actuating member 13 can also be designed in any other suitable manner.

[0074] The actuating member 13 is rotatable together with the main shaft 2 relative to the cylinder housing 60 and the piston member 70, which are configured to remain stationary in the housing 3 when the main shaft 2 rotates relative to the housing 3.

[0075] Preferably, the cylinder housing 60 and piston member 70 are concentric with the actuating member 13 and the main shaft 2. However, it is also possible to use a cylinder housing 60 and piston member 70 whose respective central axes are arranged parallel to the central axis of the main shaft 2, but slightly off-center relative to the central axis of the main shaft 2. To save space in the longitudinal direction of the clamping device 1, it is advantageous to arrange the cylinder housing 60 and piston member 70 to at least partially overlap with the actuating member 13.

[0076] The actuating member 13 is preferably configured such that, when the pull rod 8 has been forced into the return-locked position by the actuating member 13 and the motion transmission mechanism 30, the actuating member 13 presents a self-locking axial position on the spindle 2, thereby allowing the actuating member 13 to hold the pull rod 8 in the return-locked position. Therefore, when the spindle 2 is stationary and the pull rod 8 is about to move from the return-locked position to the forward release position and then back to the return-locked position, the piston member 70 only needs to apply force to the actuating member 13 for tool change operations. In the self-locking axial position, friction between the actuating member 13 and the portion of the motion transmission mechanism 30 and / or the spindle 2 in contact with the actuating member 13 prevents axial displacement of the actuating member in the second axial direction D2.

[0077] Importantly, frictional forces must be avoided, or at least kept as low as possible, between the actuating member 13 and the piston member 70, and between the spindle 2 and the cylinder housing 60, during machining operations. This is because, during machining operations, the actuating member 13 rotates at high speed together with the spindle 2, while the piston member 70 and the cylinder housing 60 remain stationary. In the illustrated embodiment, frictional forces at the interface between the piston member 70 and the actuating member 13 are avoided by having a small clearance in the radial and axial directions between the connection formed by the aforementioned mating portions 15, 16, 74 of the actuating member and the piston member. Correspondingly, frictional forces at the interface between the cylinder housing 60 and the spindle 2 are avoided by having a small clearance in the radial and axial directions between the connection formed by the aforementioned mating portions 62, 61a, 61b of the cylinder housing and the spindle.

[0078] Advantageously, the clamping device 1 is provided with a spring-loaded return mechanism 90 acting on the cylinder housing 60, wherein:

[0079] - The cylinder housing 60 can overcome the spring force of the return mechanism 90 and move from the intermediate axial position to the first end position, and can also move from the first end position to the intermediate axial position under the action of the spring force; and

[0080] - The cylinder housing 60 can overcome the spring force of the return mechanism 90 and move from the intermediate axial position to the second end position, and can also move from the second end position to the intermediate axial position under the action of the spring force.

[0081] In the illustrated embodiment, the return mechanism 90 includes two or more balls 91 distributed circumferentially on the cylinder housing 60, wherein these balls are received in an annular groove 92 on the outer side of the cylinder housing. The groove 92 has a cross-sectional shape adapted to the shape of the balls 91, such that opposing sidewalls in the groove 92 guide the balls toward a central position in the groove. Each ball 91 extends through a corresponding orifice 93 in the housing 3 of the clamping device 1 (see...). Figure 3a The orifice 93 leads to an associated cavity 94 in the housing. A spring unit 95 is housed in the cavity 94, and a ball 91 rests against the spring unit 95, which is configured to act on the ball 91 to push the ball radially inward into an annular groove 92. In the illustrated example, each spring unit 95 comprises a compression spring element formed by stacking Bainckia washers. The spring-loaded return mechanism 90 can also be designed in any other suitable manner.

[0082] In the illustrated embodiment, the actuating member 13 has the form of a sleeve. In this case, the actuating member 13 is arranged around the outer peripheral wall 14 of the main shaft 2 and is slidably mounted to the outer peripheral wall so as to be able to move axially relative to the main shaft.

[0083] The motion transmission mechanism 30 can be designed in many different ways. For example, it can include: one or more first wedges 40 for converting axial movement of the actuating member 13 relative to the main shaft 2 in a first axial direction D1 into movement of the pull rod 8 from a forward release position to a return lock position; and one or more second wedges 50 for converting axial movement of the actuating member 13 relative to the main shaft 2 in a second axial direction D2 into movement of the pull rod 8 from a return lock position to a forward release position.

[0084] In the illustrated embodiment, the motion transmission mechanism 30 includes three first wedges 40 spaced apart in the circumferential direction of the outer peripheral wall 14. Each first wedge 40 is slidably received in a corresponding first aperture 45 that extends radially through the outer peripheral wall 14. The first wedges 40 are configured to collectively press the pull rod 8 toward a retracted locking position when they are pressed radially inward in the associated first aperture 45.

[0085] Each first wedge 40 includes a first pressure receiving surface 41 facing outward from the outer peripheral wall 14 of the main shaft 2, and the actuating member 13 has a first pressure applying surface 31 on its inner side, the first pressure applying surface 31 facing inward for contacting the first pressure receiving surface 41 on the first wedge. Each first pressure applying surface 31 has a radial distance from the longitudinal axis L, which increases when viewed in the first axial direction D1. The first pressure applying surface 31 is configured such that when the actuating member 13 moves in the first axial direction D1, the first pressure applying surface 31 presses the first wedge 40 radially inward in the first orifice 45 by pressing against the first pressure receiving surface 41 on the first wedge. Preferably, the first pressure applying surface 31 and the first pressure receiving surface 41 are inclined at an angle α relative to the longitudinal axis L such that (see Figure 5 This angle allows the first wedge 40 to hold the actuating member 13 in a self-locking axial position on the outer peripheral wall 14 when the lever 8 has been forced into the retracted locking position by the actuating member 13 and the first wedge 40.

[0086] Each first wedge 40 also includes a wedge surface 48 facing the rear end 2b of the main shaft 2 and contacting a first sliding surface 18 on the pull rod facing the front end 2a of the housing. When the actuating member 13 presses the first wedge 40 radially inward in the first orifice 45, the wedge surface 48 of each first wedge 40 slides against and presses against the corresponding first sliding surface 18 on the pull rod, thereby forcing the pull rod 8 to move toward the retracted locked position.

[0087] In the illustrated embodiment, the clamping device 1 includes three second wedges 50 spaced apart in the circumferential direction of the outer peripheral wall 14. Each second wedge 50 is slidably received in a corresponding second aperture 55, which extends radially through the outer peripheral wall 14. The second wedges 50 are configured to collectively press the pull rod 8 toward the forward release position when they are pressed radially inward in the associated second aperture 55.

[0088] Each second wedge 50 includes a second pressure receiving surface 52 facing outward from the outer peripheral wall 14 of the main shaft 2, and the actuating member 13 has a second pressure applying surface 32 on its inner side, the second pressure applying surface 32 facing inward for contacting the second pressure receiving surface 52 on the second wedge. Each second pressure applying surface 32 has a radial distance from the longitudinal axis L, which increases when viewed in the second axial direction D2. The second pressure applying surface 32 is configured such that when the actuating member 13 moves in the second axial direction D2, the second pressure applying surface 32 presses the second wedge 50 radially inward in the second orifice 55 by pressing against the second pressure receiving surface 52 on the second wedge.

[0089] Each second wedge portion 50 also includes a wedge surface 59 facing the front end 2a of the main shaft 2 and contacting a second sliding surface 19 on the pull rod facing the rear end 2b of the housing. When the actuating member 13 presses the second wedge portion 50 radially inward in the second orifice 55, the wedge surface 59 of each second wedge portion 50 slides against and presses against the corresponding second sliding surface 19 on the pull rod, thereby forcing the pull rod 8 to move toward the forward locking position.

[0090] Each first wedge 40 may also include a third pressure receiving surface 43 facing outward from the outer peripheral wall 14 of the main shaft 2 (see...). Figure 6 The actuating member 13 has a third pressure applying surface 33 on its inner side, which faces inward to contact the third pressure receiving surface 43 on each of the first wedge portions. Each third pressure applying surface 33 has a radial distance from the longitudinal axis L, which increases when viewed in the first axial direction D1. The third pressure applying surface 33 and the third pressure receiving surface 43 are inclined relative to the longitudinal axis L at an angle β greater than the aforementioned angle α (see...). Figure 6The first pressure applying surface 31 and the third pressure applying surface 33, as well as the first pressure receiving surface 41 and the third pressure receiving surface 43, are respectively arranged sequentially on the actuating member 13 and each of the first wedge portions 40, such that when the actuating member 13 moves in the first axial direction D1, the third pressure applying surface 33 is configured to slide against and press against the associated third pressure receiving surface 43 during the initial first stage of movement, and subsequently the first pressure applying surface 31 is configured to slide against and press against the associated first pressure receiving surface 41 during the subsequent second stage of movement. Therefore, in the initial stage of clamping, the pull rod 8 can move rapidly in the first axial direction D1 under the action of a large angle β. This initial clamping stage does not require a large force. However, during the final stage of clamping, a large force is required to displace the pull rod 8 a short distance. When actual clamping occurs, i.e., when the engaging member 20 is in the first position described above, the pull rod 8 moves in the first axial direction D1 under the action of a small angle α, such that the axial movement of the pull rod 8 is smaller compared to the axial movement of the actuating member 13, resulting in a force amplification effect, also known as "assistance". The angle β is suitably between 10° and 75°, preferably between 35° and 65°, which provides efficient initial axial movement of the pull rod 8. By using a steep angle β for the initial axial movement of the pull rod 8 and a small angle α for actual clamping, the actuating member 13 (and thus the entire clamping device 1) can be manufactured to be relatively short in the axial direction while still providing a self-locking clamping mechanism with a significant force amplification effect.

[0091] The first wedge portion 40 and the second wedge portion 50 are non-rotatably received in associated first orifices 45 and second orifices 55 in the outer peripheral wall 14 of the main shaft 2, that is, to prevent each wedge portion from rotating in the associated orifice.

[0092] When the tool holder 80 is about to be clamped onto the spindle 2, the tool holder shank 81 is inserted into the mounting portion 7 of the inner hole 5, wherein the spindle 2 is held in a stationary position and the pull rod 8 is positioned in the forward release position, as shown. Figure 6 As illustrated in the diagram. Therefore, the head portion 9 of the pull rod is received in the engaging bore 82 in the tool holder shank 81, and the engaging groove 84 in the tool holder shank 81 is positioned on the outside of the engaging flange 27 of the engaging member 20. Hydraulic oil is then fed into the first hydraulic chamber 63a to cause the cylinder housing 60 to move a short distance in the second axial direction D2 and engage with the second shoulder 61b on the spindle 2, as shown in the diagram. Figure 3bAs illustrated in the diagram, the piston member 70 moves in the first axial direction D1, thereby achieving a corresponding axial movement of the actuating member 13 in the first axial direction D1. During the first stage of this axial movement of the actuating member 13, the third pressure applying surface 33 on the actuating member 13 slides against and presses against the third pressure receiving surface 43 on the first wedge 40. Therefore, the first wedge 40 is pressed radially inward, and the pull rod 8 is axially displaced toward the retracted locked position. Due to the relatively steep angle β between the third pressure applying surface 33 and the third pressure receiving surface 43, the first wedge 40 initially moves inward quite quickly, resulting in a relatively rapid displacement of the pull rod 8. The relatively steep angle β is advantageous because the initial displacement of the pull rod 8 does not require a large force. The first pressure applying surface 31 and the third pressure applying surface 33, as well as the first pressure receiving surface 41 and the third pressure receiving surface 43, are arranged such that when the actuating member 13 has moved a certain distance, such that the third pressure applying surface 33 has passed the third pressure receiving surface 43 and the first pressure applying surface 31 has reached the first pressure receiving surface 41, i.e. at the transition between these respective surfaces, the pull rod 8 has almost reached its final retracted position in the inner hole 5. Therefore, the first pressure applying surface 31 and the first pressure receiving surface 41 are effective for the final clamping stage where a larger force is beneficial. In this stage, the relatively large movement of the actuating member 13 will result in a very small radial displacement of the first wedge 40 and even a smaller axial displacement of the pull rod 8, which will therefore provide a force amplification effect, which will allow the pull rod 8 to pull the tool holder shank 81 with a larger force to securely engage with the spindle 2. Furthermore, the small inclination angle α between the first pressure applying surface 31 and the first pressure receiving surface 41 provides a self-locking effect and ensures that the clamping device will remain in the clamped state without the need for any additional locking device. Therefore, when the pull rod 8 has reached the retracted locking position, the hydraulic pressure in the first hydraulic chamber 63a can be released. When the hydraulic pressure in the first hydraulic chamber 63a is released, the return mechanism 90 will automatically move the cylinder housing 60 a short distance in the first axial direction D1 and return it to its original position. Figure 3c The central axial position shown in the diagram means that the cylinder housing is moved to disengage from the spindle 2. During the movement of the lever 8 toward the retracted locked position, the second sliding surface 19 on the lever 8 presses against the wedge surface 59 on the second wedge 50, thereby pressing the second wedge 50 radially outward.

[0093] When a tool change operation is about to be performed and the tool holder 80 is about to be released from the spindle 2, the rotation of the spindle 2 stops and hydraulic oil is fed into the second hydraulic chamber 63b to move the cylinder housing 60 a short distance in the first axial direction D1, so that it engages with the first shoulder 61a on the spindle 2, as... Figure 3a As illustrated, the piston member 70 moves in the second axial direction D2, thereby achieving a corresponding axial movement of the actuating member 13 in the second axial direction D2. When the actuating member 13 is subjected to sufficient force in the second axial direction D2, the self-locking frictional engagement between the first pressure applying surface 31 on the actuating member 13 and the first pressure receiving surface 41 on the first wedge 40 is released, thereby enabling the actuating member 13 to move relative to the spindle 2 in the second axial direction D2. When the actuating member 13 moves in this direction, the second pressure applying surface 32 on the actuating member 13 slides against and presses against the second pressure receiving surface 52 on the second wedge 50. Therefore, the second wedge 50 is pressed radially inward, and the pull rod 8 is axially displaced toward the forward release position. When the pull rod 8 moves toward the forward release position, the outer end of the head portion 9 of the pull rod 8 impacts the surface 85 in the engaging inner hole 82 in the tool holder shank 81, thereby releasing the tool holder shank 81 from the spindle 2. During the movement of the lever 8 toward the forward release position, the first sliding surface 18 on the lever 8 presses against the wedge surface 48 on the first wedge portion 40, thereby pressing the first wedge portion 40 radially outward.

[0094] This invention is not, of course, limited in any way to the embodiments described above. Rather, it will be apparent to those skilled in the art that many possibilities exist for modifications to the invention without departing from the basic spirit of the invention as defined in the appended claims.

Claims

1. A clamping device for releasably retaining a tool holder shank, the clamping device (1) comprising: - Shell (3); - A spindle (2) is rotatably mounted inside the housing (3) and has a front end (2a), a rear end (2b) and an inner hole (5) that intersects with and extends rearward from the front end (2a), wherein a mounting portion (7) for receiving the tool holder shank (81) is provided at the front end of the inner hole (5); - A pull rod (8) is slidably mounted inside the inner hole (5) so as to be able to reciprocate between a forward release position and a return lock position along the longitudinal axis (L) of the inner hole; - A connecting member (20) arranged around the front end of the pull rod (8), wherein, under the action of the movement of the pull rod (8) from the forward release position to the retracted locking position, the connecting member (20) is capable of moving from a first position to a second position, in the first position, the connecting member (20) allows the tool holder shank (81) to move into and out of the mounting portion (7) of the inner hole (5), and in the second position, the connecting member (20) is locked into the tool holder shank (81) and holds the tool holder shank (81) fixed to the spindle (2); - An actuating member (13) disposed inside the housing (3), wherein the actuating member (13) is slidably mounted to the main shaft (2) so as to be movable relative to the main shaft (2) in the axial direction of the main shaft (2); and - A motion transmission mechanism (30) is disposed inside the housing (3), wherein the motion transmission mechanism (30) is mounted to the main shaft (2) and is configured to convert the axial movement of the actuating member (13) relative to the main shaft (2) in a first axial direction (D1) into the movement of the pull rod (8) from the forward release position to the retracted locking position. Its features are: - The clamping device (1) includes a hydraulic actuator (17) for axially moving the actuating member (13) relative to the spindle (2), wherein the hydraulic actuator (17) is arranged in the housing (3) and includes a cylinder housing (60) and a piston member (70); - The cylinder housing (60) extends about the main shaft (2) and is slidably mounted inside the housing (3) so as to be axially movable relative to the main shaft (2) between a first end position and a second end position, wherein in the first end position the cylinder housing (60) abuts against a first shoulder (61a) on the main shaft (2), the first shoulder (61a) restricting the movement of the cylinder housing (60) relative to the main shaft (2) in a first axial direction (D1), and in the second end position the cylinder housing (60) abuts against a second shoulder (61b) on the main shaft (2), the second shoulder (61b) restricting the movement of the cylinder housing (60) relative to the main shaft (2) in the opposite second axial direction (D2); - The piston member (70) extends about the main shaft (2) and is slidably mounted to the cylinder housing (60) so as to be axially movable relative to the main shaft (2) to allow the piston member (70) to apply a pulling or pushing force on the actuating member (13) in the first axial direction (D1), and thereby realize the movement of the pull rod (8) from the forward release position to the retracted locking position; - The piston assembly (70) includes an annular piston head (71) slidably received in a space within the cylinder housing (60), wherein a first hydraulic chamber (63a) is formed in the space, located on a first side of the piston head (71), and by feeding hydraulic fluid into the first hydraulic chamber (63a), the piston assembly (70) is movable in the first axial direction (D1), and the cylinder housing (60) is movable to the second end position; and - The actuating member (13) is rotatable together with the main shaft (2) relative to the cylinder housing (60) and the piston member (70).

2. The clamping device according to claim 1, characterized in that, The actuating member (13) is configured such that when the pull rod (8) has been forced into the return-lock position by the actuating member (13) and the motion transmission mechanism (30), the actuating member (13) presents a self-locking axial position on the main shaft (2) so as to hold the pull rod (8) in the return-lock position.

3. The clamping device according to claim 1 or 2, characterized in that, A second hydraulic chamber (63b) is formed in the space within the cylinder housing (60), located on the opposite second side of the piston head (71), and by feeding hydraulic fluid into the second hydraulic chamber (63b), the cylinder housing (60) is able to move to the first end position, and the piston member (70) is able to move in the second axial direction (D2) to allow the piston member (70) to apply a pulling or pushing force on the actuating member (13) in the second axial direction (D2).

4. The clamping device according to any one of claims 1 to 2, characterized in that, The cylinder housing (60) includes a first cylindrical wall (64) and an opposing second cylindrical wall (65), the first cylindrical wall (64) constraining the space in the cylinder housing outward in the radial direction, and the second cylindrical wall (65) constraining the space in the cylinder housing in the radial direction inward.

5. The clamping device according to any one of claims 1 to 2, characterized in that: - An internal bulge (62) is provided on the inner side of the cylinder housing (60), wherein the cylinder housing (60) is configured to abut against the first shoulder (61a) on the main shaft (2) via the internal bulge (62) in the first end position, and abut against the second shoulder (61b) on the main shaft (2) via the internal bulge (62) in the second end position; and - The internal bulge (62) on the cylinder housing (60) is received in the gap between the first shoulder (61a) and the second shoulder (61b) formed on the main shaft (2) with clearance.

6. The clamping device according to any one of claims 1 to 2, characterized in that, The cylinder housing (60) is configured to disengage from the main shaft (2) when it is in an intermediate axial position between the first end position and the second end position.

7. The clamping device according to claim 6, characterized in that, The clamping device (1) includes a spring-loaded return mechanism (90), which is configured to act on the cylinder housing (60), wherein: - The cylinder housing (60) is able to overcome the spring force of the return mechanism (90) and move from the intermediate axial position to the first end position, and is also able to move from the first end position to the intermediate axial position under the action of the spring force; and - The cylinder housing (60) can overcome the spring force of the return mechanism (90) and move from the intermediate axial position to the second end position, and can move from the second end position to the intermediate axial position under the action of the spring force.

8. The clamping device according to any one of claims 1 to 2, characterized in that, The piston assembly (70) includes a sleeve-shaped piston rod (73) fixed to the piston head (71), wherein the piston assembly (70) is configured to apply the pulling force or the thrust force to the actuating member (13) via the piston rod (73).

9. The clamping device according to claim 8, characterized in that, The piston rod (73) is configured to define the first hydraulic chamber (63a) radially inward.

10. The clamping device according to any one of claims 1 to 2, characterized in that, The actuating member (13) has the form of a sleeve, wherein the actuating member (13) is arranged around the outer peripheral wall (14) of the main shaft (2) and is slidably mounted to the outer peripheral wall so as to be able to move axially relative to the main shaft.

11. The clamping device according to claim 10, characterized in that: - The motion transmission mechanism (30) includes a first wedge (40) slidably received in a first orifice (45) extending radially through the outer peripheral wall (14) of the main shaft (2), wherein the first wedge (40) is configured to press the pull rod (8) toward the retracted locking position when the first wedge (40) is pressed radially inward in the first orifice (45); - The first wedge (40) includes a first pressure receiving surface (41) facing outward from the main shaft (2); - The actuating member (13) has a first pressure applying surface (31) on its inner side, the first pressure applying surface (31) facing inward to contact the first pressure receiving surface (41), and having a radial distance from the longitudinal axis (L), the radial distance increasing when viewed in the first axial direction (D1); and - The first pressure applying surface (31) is configured such that when the actuating member (13) moves in the first axial direction (D1), the first pressure applying surface (31) presses the first wedge (40) radially inward in the first orifice (45) by pressing against the first pressure receiving surface (41).

12. The clamping device according to claim 11, characterized in that, The first wedge (40) includes a wedge surface (48) facing the rear end (2b) of the main shaft (2) and in contact with a first sliding surface (18) on the pull rod facing the front end (2a) of the main shaft.

13. The clamping device according to claim 12, characterized in that: - The motion transmission mechanism (30) includes a second wedge (50) slidably received in a second orifice (55) extending radially through the outer peripheral wall (14) of the main shaft (2), wherein the second wedge (50) includes: a wedge surface (59) facing the front end (2a) of the main shaft (2) and contacting a second sliding surface (19) on the pull rod facing the rear end (2b) of the main shaft; and a second pressure receiving surface (52) facing outward from the main shaft (2), and the second wedge (50) is configured to press the pull rod (8) toward the forward release position when the second wedge (50) is pressed radially inward in the second orifice (55); - The actuating member (13) has a second pressure applying surface (32) on its inner side, the second pressure applying surface (32) facing inward to contact the second pressure receiving surface (52), and having a radial distance from the longitudinal axis (L), the radial distance increasing when viewed in the second axial direction (D2); and - The second pressure applying surface (32) is configured such that when the actuating member (13) moves in the second axial direction (D2), the second pressure applying surface (32) presses the second wedge (50) radially inward in the second orifice (55) by pressing against the second pressure receiving surface (52).

14. The clamping device according to claim 13, characterized in that, The clamping device (1) includes two or more such second wedges (50) spaced apart in the circumferential direction of the outer peripheral wall (14), each second wedge (50) being received in a corresponding second aperture (55) extending radially through the outer peripheral wall (14).

15. The clamping device according to claim 11, characterized in that, The clamping device (1) includes two or more such first wedges (40) spaced apart in the circumferential direction of the outer peripheral wall (14), each first wedge (40) being received in a corresponding first aperture (45) extending radially through the outer peripheral wall (14).

16. The clamping device according to claim 11, characterized in that, The first pressure applying surface (31) and the first pressure receiving surface (41) are inclined at an angle α relative to the longitudinal axis (L) such that when the pull rod (8) has been forced into the retracted locking position by the actuating member (13) and the first wedge (40), the first wedge (40) will keep the actuating member (13) in a self-locking axial position on the outer peripheral wall (14).

17. The clamping device according to claim 14, characterized in that, The clamping device (1) includes three second wedge-shaped portions (50).

18. The clamping device according to claim 15, characterized in that, The clamping device (1) includes three of the first wedge-shaped portions (40).

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