Clamping device for tool holder

Abstract

A clamping device for releasably holding a tool holder handle (71), the clamping device comprising: a spindle (2) rotatably mounted inside a housing (3); a drawbar (8) axially movable in a hole (5) in the housing; an engagement member (20) movable into locking engagement with the tool holder handle under the action of the drawbar; an actuating member (13) slidably mounted on the spindle; a motion transmission mechanism (30) for converting axial movement of the actuating member into movement of the drawbar; and a hydraulic actuator (50) having a piston unit (52) for moving the actuating member. A valve assembly (83) having two parallel and oppositely directed check valves (85a, 85b) provides a residual hydraulic pressure in a hydraulic chamber (83b) of the hydraulic actuator, which will effect an automatic return movement of the piston unit after the drawbar is moved to a retracted locking position.

Description

Technical Field

[0001] The invention relates to a clamping device according to the invention which is intended for connecting a tool holder to a machine tool. Background Art

[0002] In the field of machine tools for metal cutting, a cutting tool for machining a workpiece of metal material, for example in the form of a drill or a milling tool, is usually fixed to a tool holder and rotates together with the tool holder, which in turn can be detachably clamped to a rotatable spindle of the machine tool so as to rotate together with the spindle. It is previously known to clamp the shank of such a tool holder to the rotatable spindle by 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 another cutting tool is clamped to the spindle.

[0003] A clamping device is previously known from EP 1 468 767 B1, which comprises a spindle with a clamping mechanism suitable for an automatic tool changing operation. In the clamping device according to EP 1 468 767 B1, an actuating member in the form of a first drawbar is slidably mounted inside the spindle and is configured to achieve an axial displacement of a second drawbar by a force amplification mechanism, which comprises a plurality of cooperating wedges arranged between the drawbars. A gas spring inside the spindle is configured to push the two drawbars into a retracted locking position in which the 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 in order to achieve a displacement of the two drawbars into an advanced release position in which the tool holder can be released from the spindle. Summary of the invention

[0004] The object of the present invention is to achieve a further development of a clamping device of the type mentioned above, in order to provide a clamping device suitable for automatic tool changing operations which is improved in at least one respect.

[0005] According to the invention, this object is achieved by a clamping device having the features defined in the invention.

[0006] The clamping device according to the present invention comprises:

[0007] -case;

[0008] - a spindle rotatably mounted inside the housing and having a front end, a rear end and a hole intersecting the front end and extending rearwardly from the front end, wherein a mounting portion for receiving a tool holder handle is disposed at the front end of the hole;

[0009] - a drawbar slidably mounted inside the bore so as to be reciprocally movable along its longitudinal axis within the bore between an advanced release position and a retracted locking position;

[0010] an engagement member disposed about the drawbar at a forward end thereof, wherein the engagement member is movable from a first position, in which the engagement member allows the tool holder handle to be moved into and out of the mounting portion of the bore, to a second position, in which the engagement member is in locking engagement with the tool holder handle and retains the tool holder handle fixed to the spindle, upon movement of the drawbar from an advanced release position to a retracted lock position;

[0011] - an actuating member arranged inside the housing, wherein the actuating member is slidably mounted to the spindle so as to be movable relative to the spindle in its axial direction;

[0012] - a motion transmission mechanism arranged inside the housing, wherein the motion transmission mechanism is mounted to the spindle and is configured to convert an axial movement of the actuation member relative to the spindle in a first axial direction into a movement of the pull rod from an advanced release position to a retracted locking position;

[0013] a hydraulic actuator arranged in or mounted on the housing and configured to axially move the actuating member relative to the spindle, wherein the hydraulic actuator comprises a piston unit slidably received in a space of the hydraulic actuator and configured to divide the space into a first hydraulic chamber and a second hydraulic chamber;

[0014] a first hydraulic line connected to the first hydraulic chamber, wherein hydraulic fluid can be fed into and discharged from the first hydraulic chamber via the first hydraulic line; and

[0015] A second hydraulic line which is connected to the second hydraulic chamber, wherein hydraulic fluid can be fed into and discharged from the second hydraulic chamber via the second hydraulic line.

[0016] By feeding hydraulic fluid into the first hydraulic chamber via the first hydraulic pipeline, the piston unit is able to move in a first direction so as to allow the piston unit to apply a pulling force or a pushing force on the actuating member in the first axial direction directly or via a connecting element, thereby achieving movement of the pull rod from the forward release position to the retracted locking position, and by feeding hydraulic fluid into the second hydraulic chamber via the second hydraulic pipeline, the piston unit is able to move in the opposite second direction.

[0017] The clamping device further comprises a valve assembly, hereinafter referred to as the first valve assembly, which is arranged in the second hydraulic line and comprises:

[0018] - a first flow channel and a second flow channel arranged parallel to each other;

[0019] a first check valve, preferably in the form of a spring-loaded check valve, arranged in the first flow channel and configured to allow a flow of hydraulic fluid through the first flow channel towards the second hydraulic chamber and to prevent a flow of hydraulic fluid through the first flow channel away from the second hydraulic chamber; and

[0020] a second non-return valve, preferably in the form of a spring-loaded non-return valve, which is arranged in the second flow channel and is designed to open when the hydraulic pressure in the second hydraulic chamber exceeds the opening pressure p of the second non-return valve. C2 When the hydraulic fluid is allowed to flow away from the second hydraulic chamber through the second flow channel, the hydraulic fluid is prevented from flowing toward the second hydraulic chamber through the second flow channel.

[0021] According to the invention, the actuating member is rotatable together with the spindle relative to the piston unit, which means that the piston unit and all other parts of the hydraulic actuator can remain stationary during the machining operation while the tool holder rotates together with the spindle. By avoiding rotating parts in the hydraulic actuator for moving the actuating member in connection with the automatic tool changing operation, the construction of the hydraulic actuator and the associated hydraulic system is facilitated and no rotating seals are required at the interface between the housing and the spindle which would limit the possible rotation speed of the spindle. The use of a hydraulically operated piston unit to move the actuating member and thereby achieve movement of the drawbar means that the clamping device according to the invention is suitable for use in automatic tool changing operations.

[0022] The purpose of the first valve assembly is to ensure that when the hydraulically influenced movement of the piston unit in the first direction stops, a small amount of residual pressure remains in the second hydraulic chamber at this moment, and after the tie rod moves to the retracted locking position, the hydraulic pressure in the first hydraulic chamber is released. The magnitude of this residual pressure depends on the opening pressure p of the second non-return valve. C2 , and this residual pressure will effect a shorter return movement of the piston unit in the above-mentioned second direction in order to release possible residual frictional contact between the piston unit and the actuating member or possible connecting element. This contact may be maintained due to the friction between the piston unit and the associated sliding surface in the hydraulic actuator. By selecting a check valve with a suitable opening pressure, it can be ensured that after the tool change operation is completed, the piston unit automatically moves out of contact with the actuating member or the connecting element (as the case may be), so that after the tool change operation is completed, when the actuating member rotates at high speed relative to the piston unit together with the spindle, no frictional heat is generated at the interface between the piston unit and the actuating member or the connecting element (as the case may be). In the absence of a valve assembly of the above-mentioned type, there is a risk of high frictional heat being generated at the interface, which may cause damage to the clamping device. The opening pressure p of the second check valve C2 must be high so that the opening pressure p C2The product of the effective pressure area on the side of the piston unit facing the second hydraulic chamber is higher than the maximum value of the friction between the piston unit and the associated sliding surfaces in the hydraulic actuator, and preferably, it is about 0.2-2 MPa.

[0023] The clamping device according to the invention can be mounted to a tool turret of a machine tool, wherein the rotatable spindle of the clamping device is connected 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 be connected to such a main spindle without any intermediate tool turret.

[0024] According to an embodiment of the invention, the actuating member is configured to assume a self-locking axial position on the spindle when the drawbar is forced into the retracted locking position under the action of the actuating member and the motion transmission mechanism, so as to thereby hold the drawbar in the retracted locking position. Thus, during the rotation of the spindle, the actuating member is able to hold the drawbar in the retracted locking position without requiring any external force from the piston unit, which means that when the spindle and the actuating member are in a stationary position, the piston unit only needs to exert a pulling or pushing force on the actuating member in relation to the tool changing operation.

[0025] Smaller pressure peaks may occasionally occur in the hydraulic system connected to the hydraulic actuator. These pressure peaks can be transmitted to the second hydraulic chamber via the second hydraulic line and the above-mentioned first non-return valve and can lead to an undesired movement of the piston unit, which in turn can lead to an unintentional movement of the tie rod towards the forward release position. By selecting a non-return valve with an opening pressure of at least 0.1 MPa, preferably 0.2 MPa or more, such pressure peaks can be prevented from being transmitted to the second hydraulic chamber.

[0026] According to another embodiment of the invention, the first valve assembly is arranged in or mounted on the housing. Thus, all components of the clamping device can be arranged in or mounted on the housing, which makes it possible to provide the clamping device in the form of a compact unit suitable for detachably mounting to a conventional tool turret of a machine tool. However, as an alternative, the first valve assembly can be arranged at a distance from the housing of the clamping device, for example in a tool turret of a machine tool configured to carry the housing.

[0027] According to another embodiment of the invention, the clamping device comprises a hydraulic accumulator, preferably in the form of a spring-loaded accumulator, which is arranged in fluid communication with the second hydraulic chamber. When the hydraulic actuator is operated to move the drawbar into the retracted locking position, the hydraulic accumulator will be preloaded to a pressure corresponding to the above-mentioned residual pressure in the second hydraulic chamber defined by the opening pressure of the second non-return valve. During the above-mentioned shorter return movement of the piston unit under the effect of the residual pressure of the piston unit in the second hydraulic chamber, the pressurized hydraulic fluid in the hydraulic accumulator will contribute to the movement of the piston unit and make it possible to increase the stroke of the piston unit during the return movement for a given value of the maximum residual pressure in the second hydraulic chamber. Thus, by using a hydraulic accumulator, the required opening pressure p of the second non-return valve is reduced. C2 The hydraulic accumulator is dimensioned for a maximum accumulation pressure that is lower than the opening pressure p of the second non-return valve. C2 , preferably corresponds to the opening pressure p of the second non-return valve C2 80-90% of.

[0028] According to another embodiment of the invention, the clamping device comprises a second valve assembly, which is arranged in the first hydraulic line and comprises:

[0029] - a third flow channel and a fourth flow channel arranged parallel to each other;

[0030] a third check valve, preferably in the form of a spring-loaded check valve, arranged in the third flow channel and configured to allow a flow of hydraulic fluid through the third flow channel towards the first hydraulic chamber and to prevent a flow of hydraulic fluid through the third flow channel away from the first hydraulic chamber; and

[0031] a fourth check valve, preferably in the form of a spring-loaded check valve, which is arranged in the fourth flow channel and is configured to allow a flow of hydraulic fluid away from the first hydraulic chamber through the fourth flow channel and to prevent a flow of hydraulic fluid toward the first hydraulic chamber through the fourth flow channel when the hydraulic pressure in the first hydraulic chamber exceeds an opening pressure of the fourth check valve,

[0032] The opening pressure of the fourth check valve is p C4 has a value that satisfies the following conditions: p C4 <p C2 A2 / A1,

[0033] where p C2 is the opening pressure of the second check valve, p C4 is the opening pressure of the fourth check valve, A1 is the effective pressure area on the side of the piston unit facing the first hydraulic chamber, and A2 is the effective pressure area on the side of the piston unit facing the second hydraulic chamber.

[0034] The second valve assembly is constructed to limit the length of the above-mentioned return stroke of the piston unit so as to prevent the return stroke from causing frictional contact between the piston unit and the actuating member or the connecting element (as the case may be) at the following interface, and the piston unit is constructed to exert a force on the actuating member through this interface when the pull rod moves from the retracted locking position toward the advanced release position.

[0035] As mentioned above, small pressure peaks may occasionally occur in the hydraulic system connected to the hydraulic actuator. These pressure peaks may be transmitted to the first hydraulic chamber via the first hydraulic line and the above-mentioned third non-return valve and may lead to undesired movements of the piston unit. By selecting a non-return valve with an opening pressure of at least 0.1 MPa, preferably 0.2 MPa or more, such pressure peaks can be prevented from being transmitted to the first hydraulic chamber.

[0036] According to another embodiment of the invention, the actuating member has the form of a sleeve, wherein the actuating member is arranged around a peripheral wall of the spindle and is slidably mounted to the peripheral wall so as to be axially movable relative to the spindle. Thus, the actuating member can be incorporated into the clamping device in a simple and space-saving manner.

[0037] Another embodiment of the present invention is characterized in that:

[0038] - the motion transmission mechanism comprises two or more wedges spaced apart in the circumferential direction of the spindle, each wedge being received in a respective aperture extending radially through said peripheral wall of the spindle, wherein the wedges are configured to press the drawbar towards a retracted locking position when they are pressed radially inwardly in the associated aperture;

[0039] - Each wedge comprises a first pressure receiving surface facing outwardly from the main axis;

[0040] the actuating member being provided with a first pressure applying surface on its inner side, facing inwards for contacting a first pressure receiving surface on each wedge, the radial distance of the first pressure applying surface to the longitudinal axis increasing when seen in said first axial direction; and

[0041] The first pressure-exerting surface is configured to press each wedge radially inwards in the associated orifice by pressing against the first pressure-receiving surface on each wedge when the actuation member is moved in said first axial direction.

[0042] Since the radial distance of the first pressure applying surface to the longitudinal axis increases in the first axial direction, movement of the actuating member in the first axial direction will cause pressure to be applied by the first pressure applying surface on the first pressure receiving surface of each wedge. The pressure will have a component in the radial direction, so that each wedge is pressed radially inwardly toward the longitudinal axis.

[0043] According to another embodiment of the invention, the first pressure-applying surface and the first pressure-receiving surface are inclined at an angle α relative to the longitudinal axis, so that when the pull rod is forced into the retracted locking position under the action of the actuating member and the wedge, the wedge will keep the actuating member in a self-locking axial position on the main shaft. In this case, when viewed in a longitudinal section through the main shaft, both the first pressure-applying surface and the first pressure-receiving surface extend in the same direction. The angle α is selected to be lower than the self-locking threshold angle so that when the pull rod has been displaced to the retracted locking position inside the hole, the actuating member obtains a self-locking axial position relative to the wedge. In order to obtain the self-locking axial position, the angle α should be small enough, i.e., lower than the self-locking threshold angle. The self-locking axial position refers to an axial position in which the static friction between the first pressure-receiving surface of each wedge and the first pressure-applying surface of the actuating member is greater than the opposing force in the friction plane, which is caused by the force applied to the wedge in a radial direction perpendicular to the longitudinal axis. Therefore, the self-locking axial position is obtained within the following angle range, which depends on the friction coefficient between the first pressure receiving surface of each wedge and the first pressure applying surface of the actuating member. The friction coefficient depends on various parameters, such as the material used, the coating on the surface, the use of lubricants, etc. Therefore, the self-locking threshold angle depends on these parameters. Those skilled in the art will be able to identify the self-locking threshold angle applied in each specific case by using common knowledge and / or routine experiments, or at least predict or evaluate whether a certain angle is lower than this self-locking threshold angle. Generally, it is preferred to select an angle α that is much lower than the self-locking threshold angle, thereby ensuring a self-locking configuration. Another benefit 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 pull rod. However, too small an angle α may be inefficient and may not work well in practice. For example, a very small angle α may make it difficult to release the actuating member from the self-locking axial position. The angle α is advantageously between 2° and 10°. When the angle α is within this range, a self-locking effect and an appropriate force amplification effect can be achieved.

[0044] Another embodiment of the present invention is characterized in that:

[0045] - each wedge comprises a second pressure receiving surface facing outwardly from the main axis;

[0046] - the actuating member is provided with a second pressure applying surface on its inner side, which second pressure applying surface faces inwards for contacting a second pressure receiving surface on each wedge and which has an increasing radial distance from the longitudinal axis when seen in said first axial direction;

[0047] the second pressure-exerting surface and the second pressure-receiving surface are inclined relative to the longitudinal axis by an angle β which is greater than the angle α; and

[0048] -The first pressure applying surface and the second pressure applying surface and the first pressure receiving surface and the second pressure receiving surface are respectively arranged successively on the actuating member and on each wedge member, so that when the actuating member moves 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 member during a first stage of movement, and the first pressure applying surface is configured to slide and press against the first pressure receiving surface on each wedge member during a subsequent second stage of movement.

[0049] Therefore, during the initial stage of clamping, the pull rod can move quickly in the axial direction under the action of the larger angle β. This initial clamping stage does not require a lot of force. However, during the final stage of clamping, a lot of force is required to displace the pull rod a shorter distance. When the actual clamping occurs, that is, when the engaging member presents the above-mentioned first position, the pull rod moves in the axial direction under the action of the smaller angle α, so that the axial movement of the pull rod will be smaller than the axial movement of the actuating member, which leads to a force amplification effect, also known as "power assist". The angle β is suitably between 10° and 75°, preferably between 35° and 65°, which provides an effective initial axial movement of the pull rod. By using a steeper angle β for the initial axial movement of the pull rod and a small angle α for the actual clamping, the actuating member (and therefore the entire clamping device) can be made relatively short in the axial direction, while still providing a self-locking clamping mechanism with a significant force amplification effect.

[0050] According to another embodiment of the invention, the piston unit is annular and extends around the spindle. Thus, the piston unit can be integrated into the housing of the clamping device in a space-saving manner.

[0051] Another embodiment of the present invention is characterized in that:

[0052] an annular outer protrusion is provided on the outer side of the actuating member, wherein the piston unit is configured to exert said tensile or thrust force on the actuating member by acting on the outer protrusion;

[0053] - an annular inner protrusion is provided on the inner side of the piston unit;

[0054] - a locking ring is fixed to the piston unit on the inner side of the piston unit, wherein the locking ring and the inner protrusion are spaced apart in the axial direction of the piston unit; and

[0055] The outer projection on the actuating member is received with play in the gap formed between the inner projection and the locking ring.

[0056] Thus, during a rotation of the spindle, the piston unit can be held in position in the axial direction relative to the actuating member in a simple manner, without any direct contact between the piston unit and the actuating member.

[0057] Further advantageous features of the clamping device according to the invention will emerge from the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0058] With reference to the accompanying drawings, the following is a detailed description of an embodiment of the present invention cited as an example. In the accompanying drawings:

[0059] Figure 1 is a schematic diagram of a clamping device and a tool holder according to an embodiment of the present invention,

[0060] Figure 2 is through including Figure 1 A longitudinal section of a component of a clamping device showing a drawbar of the clamping device in a retracted locked position,

[0061] Figure 3 is corresponding to Figure 2 A longitudinal section showing the lever in the forward release position,

[0062] Figure 4 is the tool holder and included in Figure 1 A partial perspective view of the components of the clamping device, wherein the tool holder is removed from the spindle,

[0063] Figure 5 yes Figure 4 A side view of the tool holder and parts of the clamping device shown, wherein the tool holder is in a released state,

[0064] Figure 6 It passes through Figure 4 A longitudinal section through the tool holder and parts of the clamping device shown, with the tool holder in a released state;

[0065] Figure 7 is based on Figure 5 The cross section of line VII-VII in

[0066] Figure 8 is a schematic, partially cut-away side view of components included in a clamping device according to an alternative embodiment of the present invention,

[0067] Fig. 9 is based on Figure 8 The cross section of line IX-IX in

[0068] Fig.10 is a schematic diagram of a clamping device according to another embodiment of the present invention,

[0069] Fig.11 is included in Fig.10 A perspective view of the components of the clamping device,

[0070] Fig.12 yes Fig.11 A side view of the components shown,

[0071] Fig.13 is based on Fig.12 A cross-sectional view along line XIII-XIII in FIG.

[0072] Fig.14 is based on Fig.12 The cross-sectional view along the line XIV-XIV in FIG.

[0073] Fig.15 is based on Fig.13 The cross-sectional view along the line XV-XV in FIG.

[0074] Fig.16 is included in Fig.10 A partially cut-away side view of the components of a clamping device, wherein the tool holder is clamped to the spindle of the clamping device,

[0075] Fig.17 yes Fig.16 A partially cut-away perspective view of components of the clamping device shown,

[0076] Figure 18 is a diagram of a knife holder and a Fig.16 A longitudinal section of some of the components of the clamping device shown, and

[0077] 19 is a top plan view of the tool holder and components of the clamping device shown in FIG. 18 , but with the actuating member removed from the spindle. DETAILED DESCRIPTION

[0078] The clamping device 1 according to the first embodiment of the present invention is Figure 1 Schematically shown in FIG. 1 , and according to another embodiment of the present invention, a clamping device is Fig.10 The clamping device 1 is configured to releasably clamp a tool holder 70 (shown very schematically in the drawing) to a rotatable spindle 2 in the clamping device and to enable machining of a workpiece by a cutting tool (not shown) fixed to the tool holder 70 .

[0079] The spindle 2 is rotatably mounted to the housing 3 of the clamping device 1 via rolling bearings 4. The spindle 2 has a front end 2a, a rear end 2b and a hole 5 that intersects the front end 2a and extends rearwardly from the front end 2a. Thus, the hole 5 has an inlet opening 5a at the front end 2a of the spindle (see Figure 4 ).

[0080] exist Figure 1-Figure 7 In the illustrated embodiment, the spindle 2 can be connected to a drive mechanism of a machine tool (eg, a drive mechanism in a tool turret of a machine tool) via a connecting pin 6 at the rear end 2b of the spindle to allow the spindle to be driven to rotate by the drive mechanism.

[0081] exist Figure 10-Figure 1 In the embodiment shown in Figure 9, the clamping device 1 includes a drive shaft 16, which is rotatably mounted to the housing 3 via rolling bearings 18a, 18b. The drive shaft 16 has a first end 16a facing the spindle 2 and an opposite second end 16b facing away from the spindle. The drive shaft 16 can be connected to a drive mechanism of the machine tool (for example, a drive mechanism in a tool turret of the machine tool) via a connecting pin 6' located at the second end 16b of the drive shaft to allow the drive shaft 16 to be driven and rotated by the drive mechanism. The drive shaft 16 is drivingly connected to the spindle 2 via a bevel gear arrangement 19, which is composed of a first bevel gear 19a and a second bevel gear 19b, the first bevel gear 19a being non-rotatably fixed to the drive shaft 16 at the first end 16a of the drive shaft 16, and the second bevel gear 19b meshing with the first bevel gear 19a and non-rotatably fixed to the spindle 2.

[0082] The mounting portion 7 for receiving the tool holder handle 71 on the tool holder 70 (see Figure 4 ) is arranged at the front end of the hole 5. The tool holder handle 71 is referred to as the tool holder handle here.

[0083] The pull rod 8 is slidably mounted in the hole 5 so as to be able to move in the hole 5 along its longitudinal axis L in an advanced release position (see Figure 3 and Figure 6 ) and retracted locked position (see Figure 2 , Fig.13 18). The pull rod 8 has a front end facing the inlet opening 5a of the hole 5 and an opposite rear end. A head portion 9 and a neck portion 10 are provided at the front end of the pull rod 8. As seen from the longitudinal direction of the pull rod, the head portion 9 is located in front of the neck portion 10, wherein the head portion 9 is connected to the neck portion 10 via a rearwardly facing inclined surface 11 on the head portion 9.

[0084] The tool holder handle 71 can be inserted into the mounting portion of the bore 5 via the inlet opening 5a at the front end 2a of the spindle 2. The head portion 9 of the drawbar is received in the engagement hole 72 in the tool holder handle 71, and the tubular wall 73 of the tool holder handle is received in the space between the head portion 9 and the inner surface of the bore 5. In the illustrated embodiment, the mounting portion 7 of the bore 5 is conical in shape and has a slightly "triangular" or polygonal non-circular cross-sectional shape, which is suitable for receiving a similarly shaped tool holder handle 71. However, the mounting portion of the bore 5 may also have any other suitable shape for receiving other types of tool holder handles.

[0085] The segmented engagement member 20 is arranged around the pull rod 8 at the front end of the pull rod 8. Under the action of the pull rod 8 moving from the forward release position to the retracted locking position, the engagement member 20 can be moved from the first position (see Figure 3 and Figure 6 ) moves to the second position (see Figure 2 , Fig.13 18 ), in the first position, the engaging member 20 allows the tool holder handle 71 to move in and out of the mounting portion of the hole 5, and in the second position, the engaging member 20 is locked in engagement with the engaging groove 74 in the engaging hole 72 in the tool holder handle 71, thereby keeping the tool holder handle 71 fixed to the spindle 2.

[0086] In the illustrated embodiment, the engagement member 20 is arranged around the neck portion 10 of the pull rod 8 and is held in place around the neck portion by means of a retaining ring 21 (see FIG. 18 ) and an elastic O-ring 22, which are arranged in the hole 5 and around the neck portion 10. Each engagement member 20 has an outwardly facing flange portion 23, which engages in an inner groove of the retaining ring 21. The elastic O-ring 22 is accommodated in an outwardly facing groove located at the rear end of each engagement member 20. A compression spring 24, a thrust ring 25, and a stop ring 26 are also arranged in the hole 5 and are configured to surround the pull rod 8. The compression spring 24 is mounted between the shoulder on the pull rod 8 and the thrust ring 25, and the compression spring 24 is configured to push the thrust ring 25, the retaining ring 21, and the engagement member 20 forward. The forward movement of the retaining ring 21 towards the inlet opening of the bore 5 is limited by a stop ring 26 which is mounted in a groove in the inner surface of the bore 5 .

[0087] At the front end of each engagement member 20, each engagement member 20 is provided with an outwardly directed engagement flange 27, which is configured to engage with the engagement groove 74 in the tool holder handle 71 when the engagement member 20 is in the above-mentioned second position. Figure 6As shown, when the drawbar 8 is in the forward release position, the front end of the engagement member 20 is located behind the head portion 9 of the drawbar 8, and the engagement flange 27 is out of engagement with the engagement groove 74 in the tool holder handle 71. When the drawbar 8 moves axially rearward along its longitudinal axis L in the hole 5, the inclined surface 11 on the head portion 9 of the drawbar will contact the front end of the engagement member 20, wherein the front end of the engagement member 20 will slide on the inclined surface 11 and be pressed outward, so that the engagement flange 27 on the engagement member engages with the engagement groove 74 in the tool holder handle 71, and the tool holder handle 71 is then pulled by the drawbar 8 into firm contact with the inner surface of the spindle 2 located in the mounting portion of the hole 5.

[0088] The clamping device 1 further comprises an actuating member 13 which is concentric with the spindle 2 and slidably mounted thereto 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., is prevented from rotating relative to the spindle 2 and is therefore configured to rotate together with the spindle 2. A motion transmission mechanism 30 is mounted to the spindle 2 and is configured to convert an axial movement of the actuating member 13 relative to the spindle 2 in a first axial direction AD1 into a movement of the drawbar 8 from an advanced release position to a retracted locking position. In the illustrated embodiment, the first axial direction AD1 is a direction towards the rear end 2b of the spindle 2. Therefore, in this case, the movement of the drawbar 8 from the advanced release position to the retracted locking position is affected by the axial movement of the actuating member 13 backward along the spindle 2. However, as an alternative, the actuation member 13 and the motion transfer mechanism 30 may be arranged to cooperate in such a way that movement of the drawbar 8 from the advanced release position to the retracted locking position is effected by forward axial movement of the actuation member 13 along the spindle 2 .

[0089] At least one hydraulic actuator 50 is arranged in or mounted on the housing 3 and is configured to axially move the actuating member 13 relative to the main shaft 2. Each hydraulic actuator 50 includes a piston unit 52, which is slidably accommodated in a space 53 of the hydraulic actuator and is configured to divide the space into a first hydraulic chamber 53a and a second hydraulic chamber 53b. The hydraulic fluid can be fed into and discharged from the first hydraulic chamber 53a via a first hydraulic line 81, and can be fed into and discharged from the second hydraulic chamber 53b via a second hydraulic line 82. By feeding the hydraulic fluid into the first hydraulic chamber 53a, the piston unit 52 can move in the first direction D1 to allow the piston unit 52 to apply a pulling force or a pushing force on the actuating member 13 along the first axial direction AD1, thereby achieving the movement of the tie rod 8 from the advanced release position to the retracted locking position. By feeding the hydraulic fluid into the second hydraulic chamber 53b, the piston unit 52 can be moved in the opposite second direction D2.

[0090] exist Figure 1-Figure 9 In the embodiment shown, the clamping device 1 is provided with a single hydraulic actuator 50 arranged in the housing 3 .

[0091] exist Figure 10-Figure 1 In the embodiment shown in Figure 9, the clamping device 1 is provided with two hydraulic actuators 50, which are arranged on opposite sides of the main shaft 2 relative to each other. It is also possible to use more than two hydraulic actuators 50 distributed around the main shaft 2 in any suitable manner. Figure 10-Figure 1 In the embodiment shown in FIG. 9 , each hydraulic actuator 50 includes a separate actuator housing 51 that is fixed to the housing 3 on opposite sides of the housing 3. However, as an alternative, the hydraulic actuator 50 may be integrated into the housing 3. Figure 10-Figure 1 In the embodiment shown in FIG. 9 , the clamping device 1 further comprises a connecting element 60, which is configured to form a connection in a radial direction between the actuating member 13 and the piston unit 52 of the hydraulic actuator 50. The connecting element 60 is configured to convert an axial movement of the piston unit 52 relative to the housing 3 into a corresponding axial movement of the actuating member 13 relative to the spindle 2.

[0092] The actuating member 13 is configured to assume a self-locking axial position on the spindle 2 when the drawbar 8 is forced into the retracted locking position under the action of the actuating member 13 and the motion transmission mechanism 30, thereby allowing the actuating member 13 to hold the drawbar 8 in the retracted locking position. Therefore, when the spindle 2 is stationary, the piston unit 52 only needs to exert a force on the actuating member 13 in the tool change operation, and the drawbar 8 will move from the retracted locking position to the advanced release position and then back to the retracted locking position. In the self-locking axial position, the friction between the actuating member 13 and the components of the motion transmission mechanism 30 and / or the spindle 2 in contact with the actuating member 13 prevents the actuating member from being axially displaced in a direction opposite to the first axial direction AD1.

[0093] The clamping device is connected to a hydraulic system 90 which may have, for example, Figure 1 and Fig.10 The overall design shown in FIG. 1 is a hydraulic system including a hydraulic fluid reservoir 91, a pump 92 and a directional control valve 93, wherein the directional control valve is provided with a pressure port P and a return port R. The pump 92 is configured to pump the hydraulic fluid from the reservoir 91 to the pressure port P. The return port R is connected to the reservoir 91 so as to allow the hydraulic fluid to return from the directional control valve 93 to the reservoir via the return port. The first hydraulic chamber 53a of each hydraulic actuator 50 is connected to the directional control valve 93 through the first hydraulic line 81, and the second hydraulic chamber 53b of each hydraulic actuator is connected to the directional control valve 93 through the second hydraulic line 82.

[0094] The directional control valve 93 is provided with a valve core 94 which can move between the following positions:

[0095] a first working position in which the pressure port P is connected to the first hydraulic line 81 and the return port R is connected to the second hydraulic line 82,

[0096] a second working position in which the pressure port P is connected to the second hydraulic line 82 and the return port R is connected to the first hydraulic line 81 , and

[0097] A normal position in which the pressure port P is disconnected from the first hydraulic line 81 and the second hydraulic line 82 , and the return port R is connected to the first hydraulic line 81 .

[0098] exist Figure 1 and Fig.10 In FIG, the valve core 94 is shown in the normal position. Figure 1 and Fig.10 In the example shown, the valve core 94 will move from the normal position to the first working position by moving rightward under the action of an actuation force acting in a first direction on the valve core 94, and from the normal position to the second working position by moving leftward under the action of an actuation force in an opposite direction acting on the valve core 94. The valve core 94 is configured to automatically return to the normal position when the actuation force is removed.

[0099] The clamping device 1 comprises a first valve assembly 83 which is arranged in the second hydraulic line 82 and comprises:

[0100] A first flow channel 84a and a second flow channel 84b arranged in parallel with each other;

[0101] a first check valve 85a, preferably in the form of a spring-loaded check valve, disposed in the first flow passage 84a and configured to allow hydraulic fluid to flow through the first flow passage 84a toward the second hydraulic chamber 53b and to prevent hydraulic fluid from flowing through the first flow passage 84a away from the second hydraulic chamber 53b; and

[0102] A second check valve 85b, preferably in the form of a spring-loaded check valve, which is arranged in the second flow channel 84b and is configured to open when the hydraulic pressure in the second hydraulic chamber exceeds the opening pressure p of the second check valve 85b. C2 When the hydraulic fluid is allowed to flow away from the second hydraulic chamber 53b through the second flow channel 84b, the hydraulic fluid is prevented from flowing toward the second hydraulic chamber 53b through the second flow channel 84b.

[0103] Therefore, the first check valve 85a and the second check valve 85b are arranged parallel to each other and in opposite directions. The first valve assembly 83 ensures that the opening pressure p corresponding to the second check valve 85b is reached when the hydraulically influenced movement of the piston unit 52 in the first direction D1 stops. C2 The residual pressure will remain in the second hydraulic chamber 53b, and after the drawbar 8 moves to the retracted locking position, the first hydraulic chamber 53a is connected to the fluid reservoir 91. This residual pressure will cause the piston unit 52 to perform a short return movement in the second direction D2.

[0104] In order to achieve the above-mentioned return movement of the piston unit 52, the opening pressure p of the second check valve 85b is C2 Must have a value that satisfies the following conditions: C2 >F 摩擦 / A2, where F 摩擦 is the maximum value of the friction force between the piston unit 52 and the associated sliding surfaces in the hydraulic actuator 50, and A2 is the effective pressure area on the side of the piston unit 52 facing the second hydraulic chamber 53b. C2 The value of must also be adjusted according to the desired length of the return stroke of the piston unit 52. The opening pressure p of the second check valve 85b C2 The first check valve 85a advantageously has an opening pressure p of 0.1 MPa or higher, preferably 0.2 MPa or higher. C1 .

[0105] exist Figure 1 and Fig.10 In the illustrated embodiment, the clamping device 1 further comprises a second valve assembly 87, which is arranged in the first hydraulic line 81 and comprises:

[0106] - a third flow channel 84c and a fourth flow channel 84d arranged parallel to each other;

[0107] a third check valve 85c, preferably in the form of a spring-loaded check valve, which is arranged in the third flow channel 84c and is configured to allow the flow of hydraulic fluid through the third flow channel 84c towards the first hydraulic chamber 53a and to prevent the flow of hydraulic fluid through the third flow channel 84c away from the first hydraulic chamber 53a; and

[0108] a fourth check valve 85d, preferably in the form of a spring-loaded check valve, which is arranged in the fourth flow channel 84d and is designed to open when the hydraulic pressure in the first hydraulic chamber exceeds the opening pressure p of the fourth check valve 85d. C4 , the hydraulic fluid is allowed to flow away from the first hydraulic chamber 53a through the fourth flow passage 84d, and the hydraulic fluid is prevented from flowing toward the first hydraulic chamber 53a through the fourth flow passage 84d.

[0109] Therefore, the third check valve 85c and the fourth check valve 85d are arranged in parallel with each other and in opposite directions. The opening pressure p of the fourth check valve 85d is C4 has a value that satisfies the following conditions: p C4 <p C2 A2 / A1, where p C2 is the opening pressure of the second check valve 85b, A1 is the effective pressure area on the side of the piston unit 52 facing the first hydraulic chamber 53a, and A2 is the effective pressure area on the side of the piston unit 52 facing the second hydraulic chamber 53b. The third check valve 85c advantageously has an opening pressure p of 0.1 MPa or more, preferably 0.2 MPa or more. C3 .

[0110] A hydraulic accumulator 86, preferably in the form of a spring-loaded accumulator, may be arranged in fluid communication with the second hydraulic chamber 53b in order to add hydraulic power to the above-mentioned return movement of the piston unit 52. The hydraulic accumulator 86 is dimensioned for a maximum accumulation pressure that is lower than the opening pressure p of the second non-return valve 85b. C2 , preferably corresponds to the opening pressure p of the second check valve 85b C2 80-90% of Figure 1 In the illustrated embodiment, the hydraulic accumulator 86 is connected to the second hydraulic chamber 53 b via the second hydraulic line 82 .

[0111] The first valve assembly 83 and the second valve assembly 87 as well as the hydraulic accumulator 86 are preferably arranged in the housing 3 or mounted on the housing 3 .

[0112] exist Fig.10 In the illustrated embodiment, two hydraulic actuators 50 are connected to the hydraulic system 90 in parallel with each other and are configured to share the same first valve assembly 83, second valve assembly 87. Therefore, in this case, the first valve assembly 83 is connected to the second hydraulic chambers 53b of the two hydraulic actuators, and the second valve assembly 87 is connected to the first hydraulic chambers 53a of the two hydraulic actuators. If the hydraulic actuators 50 are connected to the hydraulic system 90 in other ways, each hydraulic actuator 50 may also be provided with its own first valve assembly 83, second valve assembly 87.

[0113] exist Figure 1-Figure 9 In the embodiment shown, the piston unit 52 is annular and is configured to surround a portion of the main shaft 2. In this case, the piston unit 52 is slidably mounted to the housing 3 so as to be hydraulically movable axially relative to the housing. Figure 1-Figure 7In the embodiment shown, the piston unit 52 is configured to move the actuation member 13 in the first axial direction AD1 by exerting an axially directed tensile force on the actuation member 13. Figure 8 and Fig. 9 In the embodiment shown, the piston unit 52 is configured to move the actuation member 13 in a first axial direction AD1 by exerting an axially directed thrust on the actuation member 13. The annular piston unit 52 is configured to remain stationary in the housing 3 when the spindle 2 rotates relative to the housing 3.

[0114] exist Figure 1-Figure 7 and Figure 10-Figure 1 In the embodiment shown in FIG. 9 , the actuating member 13 has the form of a sleeve. In this case, the actuating member 13 is arranged around a peripheral wall 14 of the spindle 2 and is slidably mounted to the peripheral wall so as to be axially movable relative to the spindle.

[0115] exist Figure 1-Figure 7 In the illustrated embodiment, the piston unit 52 comprises an annular piston head 56 and a sleeve-shaped piston rod 57 fixed to the piston head, wherein the piston unit 52 is configured to exert the above-mentioned pulling force or pushing force on the actuating member 13 through the piston rod 57. The piston head 56 and the piston rod 57 are preferably concentric with the actuating member 13 and extend around the main shaft 2. The piston rod 57 can be configured to exert the above-mentioned force on the actuating member 13 by acting on the annular external protrusion 15 provided on the outer side of the actuating member 13. Figure 1-Figure 7 In the illustrated embodiment, an annular inner protrusion 58 is provided on the inner side of the piston rod 57, and a locking ring 59 is fixed to the piston rod 57 on the inner side of the piston rod 57, wherein the locking ring 59 and the inner protrusion 58 are spaced apart in the axial direction of the piston rod 57. The outer protrusion 15 on the actuating member 13 is accommodated with play in a gap formed between the inner protrusion 58 and the locking ring 59. In this case, when the piston unit 52 moves the actuating member in the first axial direction AD1, the axial force is transmitted from the piston unit 52 to the actuating member 13 via the locking ring 59, and when the piston unit 52 moves the actuating member in the opposite direction, the axial force is transmitted to the actuating member 13 via the inner protrusion 58.

[0116] exist Figure 10-Figure 1 In the embodiment shown in FIG. 9 , the connecting element 60 comprises a central portion 61 and an arm portion 62, the connecting element being connected to the actuating member 13 via the central portion 61, and each hydraulic actuator 50 having an arm portion, the connecting element 60 being connected to the piston unit 52 of the hydraulic actuator via the arm portion 62. Each arm portion 62 is fixed to the central portion 61 and protrudes from the central portion in the radial direction. Depending on the specific design of the clamping device 1, the connecting element 60 can of course be designed in many different ways.

[0117] The connecting element 60 may be fixed to the actuating member 13 so as to be movable together with the actuating member 13 relative to the spindle 2 in its axial direction, wherein the connecting element is configured to rotate together with the actuating member 13 and the spindle relative to the piston unit 52. Figure 10-Figure 1 In the embodiment shown in FIG. 9 , the actuating member 13 is rotatable together with the spindle 2 relative to the connecting element 60. In this case, the sleeve-shaped actuating member 13 can extend through a recess 63 having a circular cross-sectional shape in the central portion 61 of the connecting element 60. In the illustrated embodiment, an annular inner protrusion 66 is provided in the recess 63. In addition, an annular outer protrusion 15 is provided on the outer side of the actuating member 13, and a locking ring 28 is fixed to the actuating member 13 on the outer side of the actuating member 13, wherein the locking ring 28 and the outer protrusion 15 are spaced apart in the axial direction of the actuating member 13. The inner protrusion 66 on the connecting element 60 is accommodated with play in a gap formed between the outer protrusion 15 and the locking ring 28. In this case, when the piston unit 52 moves the actuation member 13 in the first axial direction AD1, the axial force is transmitted from the connecting element 60 to the actuation member 13 via the locking ring 28, and when the piston unit 52 moves the actuation sleeve in the opposite direction, the axial force is transmitted to the actuation member 13 via the external protrusion 15.

[0118] exist Figure 1-Figure 7 and Figure 10-Figure 1 In the embodiment shown in FIG. 9 , a release spring 17 preferably in the form of a helical compression spring is installed in a space located inside the spindle 2 and is configured to act on the rear end of the pull rod 8 so as to push the pull rod to the advanced release position. Under the action of the actuating member 13 and the motion transmission mechanism 30, the pull rod 8 overcomes the spring force from the release spring 17 and can move from the advanced release position to the retracted locking position.

[0119] The motion transmission mechanism 30 can be designed in many different ways. Figure 1-Figure 7 and Figure 10-Figure 1In the embodiment shown in FIG. 9 , the motion transmission mechanism comprises three wedges 31 spaced apart in the circumferential direction of the spindle 2. Each wedge 31 is accommodated in a corresponding aperture 32 extending radially through the aforementioned peripheral wall 14 of the spindle 2, wherein the wedges 31 are configured to press the drawbar 8 toward the retracted locking position when they are pressed radially inwardly in the associated aperture 32. Each wedge 31 comprises a first pressure receiving surface 33 facing outwardly from the spindle 2, and the actuating member 13 is provided with a first pressure applying surface 34 on its inner side, which faces inwardly for contacting the first pressure receiving surface 33 on each wedge. When viewed in the aforementioned first axial direction AD1, the radial distance of the first pressure applying surface 34 to the longitudinal axis L increases. The first pressure applying surface 34 is configured to press the wedges 31 radially inwardly in the apertures 32 by pressing against the first pressure receiving surface 33 on each wedge when the actuating member 13 moves in the first axial direction AD1. The motion transmission mechanism 30 shown also includes three wedge engagement members 35, which radially protrude from the pull rod 8 into a corresponding one of the apertures 32 and are fixed to the pull rod so as to be movable along the longitudinal axis L with the pull rod. Therefore, the movement of the wedge engagement members 35 along the longitudinal axis L will cause a corresponding movement of the pull rod 8. Each wedge engagement member 35 is in contact with one of the wedges 31. The motion transmission mechanism 30 may include any suitable number of wedges 31 and associated wedge engagement members 35, which are arranged to extend through a corresponding number of apertures 32 in the peripheral wall 14 of the main shaft 2.

[0120] Each wedge-shaped engagement member 35 has a sliding surface 36 (see FIG. 18 ) facing the front end 2a of the spindle 2, and each aperture 32 has a sliding surface 37 facing the rear end 2b of the spindle. In addition, each wedge 31 has a first wedge surface 38 facing the rear end 2b of the spindle and a second wedge surface 39 facing the front end 2a of the spindle, wherein these first wedge surfaces 38 and second wedge surfaces 39 approach each other in the radial direction toward the longitudinal axis L. The first wedge surface 38 of each wedge 31 is in contact with the sliding surface 36 of the associated wedge-shaped engagement member 35, and the second wedge surface 39 of each wedge is in contact with the sliding surface 37 of the associated aperture 32. When the wedge 31 is pressed radially inwardly in the aperture 32 by the actuating member 13, the first wedge surface 38 and the second wedge surface 39 of each wedge 31 will slide and press against the corresponding sliding surfaces 36, 37 of the associated wedge-shaped engagement member 35 and aperture 32, thereby forcing the pull rod 8 to move toward the retracted locking position. Preferably, the first pressure applying surface 34 and the first pressure receiving surface 33 are inclined at an angle α relative to the longitudinal axis L (see Figure 6), so that when the pull rod 8 is forced into the retracted locking position under the action of the actuating member 13 and the wedge 31, the wedge 31 will keep the actuating member 13 in a self-locking axial position on the main shaft 2.

[0121] Each wedge 31 may further comprise a second pressure receiving surface 43 facing outwardly from the spindle 2, wherein the actuating member 13 is provided on its inner side with a second pressure applying surface 44 facing inwardly for contacting the second pressure receiving surface 43 on each wedge. When viewed in the first axial direction AD1, the radial distance of the second pressure applying surface 44 from the longitudinal axis L increases. The second pressure applying surface 44 and the second pressure receiving surface 43 are inclined relative to the longitudinal axis L by an angle β (see Figure 6 ). The first pressure applying surface 34 and the second pressure applying surface 44 and the first pressure receiving surface 33 and the second pressure receiving surface 43 are respectively arranged successively on the actuating member 13 and on each wedge 31, so that when the actuating member 13 moves along the first axial direction AD1, the second pressure applying surface 44 is configured to slide and press against the second pressure receiving surface 43 on each wedge during the initial first stage of the movement, and then the first pressure applying surface 34 is configured to slide and press against the first pressure receiving surface 33 on each wedge during the subsequent second stage of the movement.

[0122] Each wedge-engaging member 35 further includes a release pressure receiving surface 40 (see FIG. 18 ) facing the rear end 2 b of the main shaft 2, and the actuating member 13 includes a release pressure applying surface 41 facing the front end 2 a of the main shaft. The release pressure applying surface 41 of the actuating member 13 is configured to contact the release pressure receiving surface 40 of the wedge-engaging member 35 when the actuating member 13 moves in the above-mentioned second axial direction, thereby allowing the actuating member to apply a forwardly directed axial force on the pull rod 8 via the wedge-engaging member 35 during the final stage of the pull rod moving from the retracted locking position to the advanced release position.

[0123] like Figure 3 and Figure 6As shown, when the tool holder 70 is to be clamped to the spindle 2, the tool holder handle 71 is inserted into the mounting portion 7 of the hole 5, wherein the spindle 2 is held in a stationary position and the draw rod 8 is positioned in the forward release position. Therefore, the head portion 9 of the draw rod is accommodated in the engagement hole 72 of the tool holder handle 71, and the engagement groove 74 in the tool holder handle 71 is positioned outside the engagement flange 27 of the engagement member 20. Thereupon, hydraulic oil is fed into the first hydraulic chamber 53a of each hydraulic actuator 50 so as to move the piston unit 52 in the first direction D1, thereby achieving a corresponding axial movement of the actuating member 13. During the first stage of this axial movement of the actuating member 13, the second pressure applying surface 44 on the actuating member 13 will slide and press against the second pressure receiving surface 43 on the wedge 31. Therefore, the wedge 31 will be pressed radially inwardly, and the draw rod 8 will be axially displaced toward the retracted locking position. Due to the relatively steep inclination angle β of the second pressure applying surface 44 and the second pressure receiving surface 43, the wedge 31 will initially move inwards quite quickly, which results in a relatively fast displacement of the drawbar 8. The relatively steep angle β is advantageous because the initial displacement of the drawbar 8 does not require a large force. The first and second pressure applying surfaces 34, 44 and the first and second pressure receiving surfaces 33, 43 are arranged such that the drawbar 8 has almost reached its final destination at the rear end of the hole 5 when the actuating member 13 has moved such a distance that the second pressure applying surface 44 has passed the second pressure receiving surface 43 and the first pressure applying surface 34 has reached the first pressure receiving surface 33 (i.e. at the transition between these respective surfaces). Therefore, for the final clamping stage, in which a large force is beneficial, the first pressure applying surface 34 and the first pressure receiving surface 33 are active. At this stage, the relatively large movement of the actuating member 13 will result in a very small radial displacement of the wedge 31, and an even smaller axial displacement of the draw rod 8, which will therefore provide a force amplification effect that will enable the draw rod 8 to pull the tool holder handle 71 with a greater force so that it is firmly engaged with the spindle 2. In addition, the small inclination angle α of the first pressure applying surface 34 and the first pressure receiving surface 33 will provide a self-locking effect and ensure that the clamping device will remain in the clamped state without the need for any additional locking device. Therefore, when the draw rod 8 has reached the retracted locking position, the hydraulic pressure on the piston unit 52 can be released. When the hydraulic pressure on the piston unit 52 is released, the residual pressure retained in the second hydraulic chamber 53b due to the second check valve 85b will automatically cause the piston unit 52 to move a shorter distance in the second direction D2. Figure 1-Figure 7 In the embodiment shown, this return movement of the piston unit 52 means that the piston unit moves out of contact with the actuating member 13. Figure 10-Figure 1In the embodiment shown in FIG. 9 , a shorter return movement of the piston unit 52 causes the connecting element 60 to move out of contact with the actuating member 13 .

[0124] When a tool changing operation is to be performed and the tool holder 70 is to be released from the spindle 2, the rotation of the spindle 2 is stopped and hydraulic oil is fed into the second hydraulic chamber 53b so as to move the piston unit 52 in the second direction D2, thereby achieving a corresponding axial movement of the actuating member 13. When the actuating member 13 is subjected to sufficient force in the second axial direction D2 by the piston unit 52, the self-locking frictional engagement between the first pressure applying surface 34 on the actuating member 13 and the first pressure receiving surface 33 on the wedge 31 will be released, so that the actuating member 13 can move in the second axial direction relative to the spindle 2 under the action of the piston unit 52. When the actuating member 13 moves in this direction, the spring force applied by the release spring 17 on the rear end of the pull rod 8 will push the pull rod axially to the advanced release position. Therefore, the wedge engagement member 35 will exert a force on the wedge 31 and press the wedge 31 radially outward. When the actuating member 13 has moved a certain distance in the second axial direction, the release pressure applying surface 41 on the actuating member 13 will contact the release pressure receiving surface 40 on the wedge-shaped engaging member 35, which will allow the actuating member 13 to apply an axial force on the pull rod 8 through the wedge-shaped engaging member 35, and the axial force will push the outer end of the head portion 9 of the pull rod 8 against the surface 75 in the engaging hole 72 in the tool holder handle 71, thereby releasing the tool holder handle 71 from the spindle 2.

[0125] exist Figure 8 and Fig. 9In the embodiment shown, the actuating member 13 comprises a base portion 64 having a circular cross-sectional shape, which is slidably accommodated in the hole 5 inside the spindle 2 so as to be able to move in its axial direction relative to the spindle. In this case, the actuating member 13 also comprises two arms 65a, 65b, which are fixed to the base portion 64 so as to be able to move in its axial direction relative to the spindle 2 together with the base portion 64. The arms 65a, 65b protrude from the base portion 64 in the radial direction on opposite sides of the base portion 64. In the example shown, the arms 65a, 65b constitute opposite end sections of a transverse pin 65, which is fixed to the base portion 64 and extends through the base portion 64 perpendicularly to the central axis of the base portion. Orifices 67 for the arms 65a, 65b extend radially through the peripheral wall of the main shaft 2 on opposite sides of the main shaft, wherein each arm 65a, 65b extends through a corresponding one of the orifices 67. The orifices 67 are elongated and extend in the axial direction of the main shaft 2 so as to allow the arms 65a, 65b to move relative to the main shaft 2 in its axial direction. The outer end of each arm 65a, 65b is received with play in an annular groove 68 provided on the inner side of the annular piston unit 52, thereby allowing the piston unit 52 to exert a thrust on the actuating member 13 and also allowing the actuating member 13 to rotate relative to the piston unit 52 together with the main shaft 2. When hydraulic fluid is fed into the first hydraulic chamber 53a, the piston unit 52 will push the arms 65a, 65b backwards in the above-mentioned first axial direction AD1, thereby pushing the entire actuating member 13 backwards in the above-mentioned first axial direction AD1. When hydraulic fluid is fed into the second hydraulic chamber 53b, the piston unit 52 will push the arms 65a, 65b forward in the opposite direction, thereby pushing the entire actuating member 13 forward in the opposite direction. In this embodiment, the actuating member 13 is configured to act on the motion transmission mechanism 30 via a protrusion 69 that is fixed to the base portion 64 and protrudes from the front side of the base portion toward the front end 2a of the main shaft 2. Figure 8 and Fig. 9 The motion transmission mechanism 30 in the clamping device 1 is of the type described in US 6 370 995 B1. Therefore, the design and function of the motion transmission mechanism 30 are described in more detail in US 6 370 995 B1.

[0126] The invention is of course not limited in any way to the embodiments described above. On the contrary, many possibilities for modifications of the invention will be apparent to a person skilled in the art without departing from the basic idea of ​​the invention as defined in the appended claims.

Claims

1. A clamping device for releasably holding a tool holder handle, the clamping device (1) comprising: - a housing (3); - a spindle (2) rotatably mounted inside the housing (3) and having a front end, a rear end and a hole (5) intersecting the front end and extending rearwardly from the front end, wherein a mounting portion (7) for receiving the tool holder handle (71) is arranged at the front end of the hole (5); - a pull rod (8) slidably mounted in the hole (5) so as to be able to reciprocate in the hole along the longitudinal axis (L) of the hole between an advanced release position and a retracted locking position; - an engagement member (20) arranged around the drawbar (8) at a front end of the drawbar (8), wherein the engagement member (20) is movable from a first position to a second position under the action of the drawbar (8) moving from the advanced release position to the retracted locking position, in which the engagement member (20) allows the tool holder handle (71) to move into and out of the mounting portion (7) of the hole (5), and in which the engagement member (20) is in locking engagement with the tool holder handle (71) and holds the tool holder handle (71) fixed to the spindle (2); an actuating member (13) arranged inside the housing (3), wherein the actuating member (13) is slidably mounted to the spindle (2) so as to be movable relative to the spindle (2) in the axial direction of the spindle (2); as well as - a motion transmission mechanism (30) arranged inside the housing (3), wherein the motion transmission mechanism (30) is mounted to the spindle (2) and is configured to convert an axial movement of the actuating member (13) relative to the spindle (2) in a first axial direction (AD1) into a movement of the drawbar (8) from the advanced release position to the retracted locking position, Features: - The clamping device (1) comprises: a hydraulic actuator (50) arranged in or mounted on the housing (3) and configured to axially move the actuating member (13) relative to the spindle (2), wherein the hydraulic actuator (50) comprises a piston unit (52) slidably received in a space (53) of the hydraulic actuator (50) and configured to divide the space into a first hydraulic chamber (53a) and a second hydraulic chamber (53b), a first hydraulic line (81) connected to the first hydraulic chamber (53a), wherein hydraulic fluid can be fed into the first hydraulic chamber (53a) via the first hydraulic line (81) and can be discharged from the first hydraulic chamber (53a) via the first hydraulic line (81), and a second hydraulic line (82) connected to the second hydraulic chamber (53b), wherein hydraulic fluid can be fed into the second hydraulic chamber (53b) via the second hydraulic line (82) and can be discharged from the second hydraulic chamber (53b) via the second hydraulic line (82); - by feeding hydraulic fluid into the first hydraulic chamber (53a) via the first hydraulic line (81), the piston unit (52) is movable in a first direction (D1) so as to allow the piston unit (52) to exert a pulling force or a pushing force on the actuating member (13) in the first axial direction (AD1) directly or via a connecting element (60), thereby achieving movement of the pull rod (8) from the forward release position to the retracted locking position, and by feeding hydraulic fluid into the second hydraulic chamber (53b) via the second hydraulic line (82), the piston unit (52) is movable in an opposite second direction (D2); - the actuating member (13) is rotatable together with the spindle (2) relative to the piston unit (52); and The clamping device (1) comprises a first valve assembly (83), which is arranged in the second hydraulic line (82) and comprises: a first flow channel (84a) and a second flow channel (84b) arranged parallel to each other, a first check valve (85a) disposed in the first flow passage (84a) and configured to allow hydraulic fluid to flow through the first flow passage (84a) toward the second hydraulic chamber (53b) and to prevent hydraulic fluid from flowing out of the second hydraulic chamber (53b) through the first flow passage (84a), and a second check valve (85b), which is arranged in the second flow passage (84b) and is configured to open when the hydraulic pressure in the second hydraulic chamber (53b) exceeds the opening pressure p of the second check valve (85b); C2 When the hydraulic fluid is allowed to flow out of the second hydraulic chamber (53b) through the second flow channel (84b), the hydraulic fluid is prevented from flowing toward the second hydraulic chamber (53b) through the second flow channel (84b).

2. The clamping device according to claim 1, characterized in that The actuating member (13) is configured to assume a self-locking axial position on the spindle (2) when the pull rod (8) is forced into the retracted locking position under the action of the actuating member (13) and the motion transmission mechanism (30), thereby maintaining the pull rod (8) in the retracted locking position.

3. The clamping device according to claim 1 or 2, characterized in that: The opening pressure p of the second check valve (85b) C2 It is 0.2-2MPa.

4. The clamping device according to any one of claims 1 to 2, characterized in that: The opening pressure p of the first check valve (85a) is C1 0.1MPa or higher.

5. The clamping device according to any one of claims 1 to 2, characterized in that: The first valve assembly (83) is arranged in the housing (3) or mounted on the housing (3).

6. The clamping device according to any one of claims 1 to 2, characterized in that: The clamping device (1) comprises a hydraulic accumulator (86) which is arranged in fluid communication with the second hydraulic chamber (53b).

7. The clamping device according to claim 6, characterized in that The hydraulic accumulator (86) is dimensioned for a maximum accumulation pressure which is lower than the opening pressure p of the second check valve (85b). C2 .

8. The clamping device according to any one of claims 1 to 2, characterized in that: The clamping device (1) comprises a second valve assembly (87), which is arranged in the first hydraulic line (81) and comprises: - a third flow channel (84c) and a fourth flow channel (84d) arranged parallel to each other; a third check valve (85c) arranged in the third flow passage (84c) and configured to allow the hydraulic fluid to flow through the third flow passage (84c) toward the first hydraulic chamber (53a) and to prevent the hydraulic fluid from flowing out of the first hydraulic chamber (53a) through the third flow passage (84c); and a fourth check valve (85d) arranged in the fourth flow passage (84d) and configured to open when the hydraulic pressure in the first hydraulic chamber (53a) exceeds an opening pressure p of the fourth check valve (85d); C4 , allowing the hydraulic fluid to flow out of the first hydraulic chamber (53a) through the fourth flow passage (84d) and preventing the hydraulic fluid from flowing toward the first hydraulic chamber (53a) through the fourth flow passage (84d), The opening pressure p of the fourth check valve (85d) is C4 has a value that satisfies the following conditions: p C4 <p C2 A2 / A1, Among them, p C2 is the opening pressure of the second check valve (85b), p C4 is the opening pressure of the fourth check valve (85d), A1 is the effective pressure area on the side of the piston unit (52) facing the first hydraulic chamber (53a), and A2 is the effective pressure area on the side of the piston unit (52) facing the second hydraulic chamber (53b).

9. The clamping device according to claim 8, characterized in that The opening pressure p of the third check valve (85c) is C3 0.1MPa or higher.

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 a peripheral wall (14) of the spindle (2) and is slidably mounted to this peripheral wall so as to be axially movable relative to the spindle.

11. The clamping device according to claim 10, characterized in that: - the motion transmission mechanism (30) comprises two or more wedges (31) spaced apart in the circumferential direction of the spindle (2), each wedge (31) being received in a corresponding aperture (32) extending radially through the peripheral wall (14) of the spindle (2), wherein the wedges (31) are configured to press the drawbar (8) towards the retracted locking position when the wedges (31) are pressed radially inwards in the associated aperture (32); - Each wedge (31) comprises a first pressure-receiving surface (33) facing outwards from said main shaft (2); - the actuating member (13) is provided with a first pressure applying surface (34) on its inner side, the first pressure applying surface (34) facing inwards for contacting the first pressure receiving surface (33) on each wedge and having an increasing radial distance from the longitudinal axis (L) when seen in the first axial direction (AD1); and - the first pressure applying surface (34) is configured to press each wedge (31) radially inwardly in the associated orifice (32) by pressing against the first pressure receiving surface (33) on each wedge when the actuating member (13) moves in the first axial direction (AD1).

12. The clamping device according to claim 11, characterized in that The first pressure-applying surface (34) and the first pressure-receiving surface (33) are inclined at an angle α relative to the longitudinal axis (L) so that when the pull rod (8) is forced into the retracted locking position under the action of the actuating member (13) and the wedge (31), the wedge (31) will keep the actuating member (13) in a self-locking axial position on the main shaft (2).

13. The clamping device according to claim 12, characterized in that: - Each wedge (31) comprises a second pressure-receiving surface (43) facing outwards from said main shaft (2); - the actuating member (13) is provided with a second pressure applying surface (44) on its inner side, the second pressure applying surface (44) facing inwards for contacting the second pressure receiving surface (43) on each wedge (31) and having an increasing radial distance from the longitudinal axis (L) when seen in the first axial direction (AD1); - the second pressure applying surface (44) and the second pressure receiving surface (43) are inclined relative to the longitudinal axis (L) by an angle β which is greater than the angle α; and -The first pressure applying surface (34) and the second pressure applying surface (44) as well as the first pressure receiving surface (33) and the second pressure receiving surface (43) are respectively arranged successively on the actuating member (13) and on each wedge (31), so that when the actuating member (13) moves in the first axial direction (AD1), the second pressure applying surface (44) is configured to slide and press against the second pressure receiving surface (43) on each wedge during a first stage of movement, and the first pressure applying surface (34) is configured to slide and press against the first pressure receiving surface (33) on each wedge during a subsequent second stage of movement.

14. The clamping device according to any one of claims 1 to 2, characterized in that: The piston unit (52) is annular and extends around the main shaft (2).

15. The clamping device according to claim 14, characterized in that: an annular external protrusion (15) is provided on the outer side of the actuating member (13), wherein the piston unit (52) is configured to exert the tensile or thrust force on the actuating member (13) by acting on the external protrusion (15); - an annular inner protrusion (58) is arranged on the inner side of the piston unit (52); a locking ring (59) is fixed to the piston unit (52) on the inner side of the piston unit (52), wherein the locking ring (59) and the inner protrusion (58) are spaced apart in the axial direction of the piston unit (52); and - The external protrusion (15) on the actuating member (13) is received with play in the gap formed between the internal protrusion (58) and the locking ring (59).

16. The clamping device according to claim 1, characterized in that The first check valve (85a) is in the form of a spring-loaded check valve.

17. The clamping device according to claim 1, characterized in that The second check valve (85b) is in the form of a spring-loaded check valve.

18. The clamping device according to claim 4, characterized in that The opening pressure p of the first check valve (85a) is C1 0.2MPa or higher.

19. The clamping device according to claim 6, characterized in that The hydraulic accumulator (86) is in the form of a spring-loaded accumulator.

20. The clamping device according to claim 7, characterized in that The maximum accumulated pressure corresponds to the opening pressure p of the second check valve (85b). C2 80-90% of.

21. The clamping device according to claim 8, characterized in that The third check valve (85c) is in the form of a spring-loaded check valve.

22. The clamping device according to claim 8, characterized in that The fourth check valve (85d) is in the form of a spring-loaded check valve.

23. The clamping device according to claim 9, characterized in that The opening pressure p of the third check valve (85c) is C3 0.2MPa or higher.

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