WO2008054295A1

WO2008054295A1 - Hydromechanical clamping device

Info

Publication number: WO2008054295A1
Application number: PCT/SE2007/000973
Authority: WO
Inventors: Niclas Rosberg
Original assignee: ETP Transmission AB
Current assignee: ETP Transmission AB
Priority date: 2006-11-02
Filing date: 2007-11-01
Publication date: 2008-05-08
Anticipated expiration: 2009-05-02
Also published as: SE530537C2; SE0602320L

Abstract

A hydromechanical clamping device comprises a fastening part (P1) adapted to be mounted in a machining device, and a holder part (P2) adapted to releasably hold a tool shaft (V), the holder part (P2) comprising an inner sleeve (2) with an axial recess, intended to receive the tool shaft (V), the inner sleeve (2) and an outer sleeve (3) defining a chamber in which an annular piston (12) is axially movable, the annular piston and one of the inner sleeve and the outer sleeve having cooperating conical surfaces (13, 14), which in axial movement of the piston in a first direction are arranged to produce a radial compression of the inner sleeve and in axial movement of the piston in a second direction, opposite to the first direction, to allow a radial expansion of the inner sleeve. The clamping device (1) further comprises an actuating means (5) arranged to produce a movement of the annular piston (12) in said first direction, and a deactuating means (4) arranged to produce a movement of the annular piston (12) in said second direction. The actuating means (5) and the deactuating means (4) are located, seen in the axial direction, on the same side of the annular piston (12).

Description

HYDROMECHANICAL CLAMPING DEVICE

Technical Field

The present invention relates to a hydromechanical clamping device according to the preamble of claim 1.

Technical Background

WO 2004/007129A1 discloses a hydromechanical clamping device according to the preamble of claim 1 , which has the form of a chuck or a mandrel. The clamping device is adapted to be with one end thereof mounted in a possibly rotary machining device, such as a drilling machine, a milling machine, a lathe machine etc. and with the other end to releasably hold a shaft tool, a work piece, a transition element or a similar object, such as a drill, a milling tool etc.

A drawback of the above-mentioned clamping device is that to be able to arrange connecting means for feeding of compressed fluid to the actuating pressure chamber and the deactuating pressure chamber on the same side of the clamping device, seen in the axial direction, a duct has to be provided through the inner sleeve or the outer sleeve, which makes it difficult to reduce the radial extension of the clamping device, thus making the clamping device radially unwieldy, and also increasing its weight. Another drawback is that the presence of the duct causes problems of strength, which have to be compensated for by an increase of the material thickness of the clamping device or by load limits on the clamping device.

Summary One object is to provide an improved or alternative clamping device. A specific object is to provide a clamping device which is less unwieldy in the radial direction. A further object is to provide a clamping device having a lower weight.

The above objects are wholly or partly achieved by a clamping device according to the independent claim. Embodiments will be evident from the dependent claims, from the following description and the accompanying drawings.

Thus, a hydromechanical clamping means is provided, comprising a fastening part adapted to be mounted in a machining device, a holder part adapted to releasably hold a tool shaft. The holder part comprises an inner sleeve with an axial recess, intended to receive the tool shaft. The inner sleeve and an outer sleeve define a chamber in which an annular piston is axially movable, the annular piston and one of the inner sleeve and the outer sleeve having cooperating conical surfaces, which in axial movement of the piston in a first direction are arranged to produce a radial compression of the inner sleeve and in axial movement of the piston in a second direction, opposite to the first direction, to allow a radial expansion of the inner sleeve.

The clamping device further comprises an actuating means arranged to produce a movement of the annular piston in said first direction, and a deactuating means arranged to produce a movement of the annular piston in said second direction. The actuating means and the deactuating means are located, seen in the axial direction, on the same side of the annular piston. By arranging the actuating and deactuating means on the same side, or at the same end, of the piston, it is no longer necessary to provide a connection through the inner sleeve or the outer sleeve for controlling an actuating or deactuating means provided at the other side of the piston, whereby a thinner, lighter and/or stronger clamping device can be obtained. By arranging the actuating and deactuating means on the same side of the piston, their dimensions are not limited by the size of the piston, which makes it possible to adjust the surfaces absorbing the forces which are to be transferred to the piston.

The deactuating means can comprise a deactuating pressure chamber, which when pressurised produces said movement of the annular piston for unlocking the clamping device. Furthermore, the actuating means can comprise an actuating pressure chamber, which when pressurised produces said movement of the annular piston for locking the clamping device. By "pressure chamber" is meant a space which when pressurised influences the activation of the clamping device.

The clamping device can further comprise a flange, which is joined to the annular piston and which separates said actuating pressure chamber from said deactuating pressure chamber. The extension of the flange in the radial direction from a centre axis can be selected so as to obtain assembling and disassembling surfaces of suitable dimensions. According to one embodiment, the flange can be integrated with the annular piston. The flange can, for instance, be formed integrally with the annular piston. The flange can have an assembling surface, which defines the actuating pressure chamber, and a disassembling surface, which defines the deactuating pressure chamber. The assembling surface and the disassembling surface both have a radial extension from the centre axis, and can coincide with the extension of the flange in the same direction. According to one embodiment, the disassembling surface is greater than the assembling surface, which results in a greater disassembling force than assembling force at the same pressure and which makes it possible to perform the disassembling operation at a lower pressure. Furthermore, a greater margin is obtained in this manner, since the pressure source does not have to be used to its maximum in connection with disassembly.

The assembling surface can have a greater area than a first cross- sectional area of the piston, which first cross-sectional area is located at a first end of a piston portion active against the inner sleeve and the outer sleeve, and is oriented in the same axial direction as the assembling surface. The disassembling surface can have a greater area than a second cross-sectional area of the piston, which second cross-sectional area is located at a second end of a piston portion active against the inner sleeve and the outer sleeve, and is oriented in the same axial direction as the disassembling surface. Alternatively, the actuating means can comprise an elastically compressible actuating means, which is arranged to produce said movement of the annular piston for locking the clamping device. Thus, a self-locking clamping device can be obtained. According to one embodiment, the inner sleeve can have at least one slot extending in said axial direction. By such slots, the force needed to produce the compression of the inner sleeve can be reduced.

A friction-modified surface can be provided on at least one of a surface of the annular piston cooperating with the inner sleeve, a surface of the annular piston cooperating with the outer sleeve, a surface of the outer sleeve cooperating with the piston and a surface of the inner sleeve cooperating with the piston.

A lubricating duct can be arranged on at least one of a surface of the annular piston cooperating with the inner sleeve, a surface of the annular piston cooperating with the outer sleeve, a surface of the outer sleeve cooperating with the piston and a surface of the inner sleeve cooperating with the piston.

The conical surface can consist of a contact surface between the inner sleeve and the annular piston.

Alternatively, or as a complement, the conical surface can consist of a contact surface between the outer sleeve and the annular piston.

Examples of embodiments will be described in more detail below with reference to the accompanying drawings.

Brief Description of the Drawings

Fig. 1 is a schematic sectional view of a first embodiment of a clamping device 1.

Fig. 2 is a schematic sectional view of a second embodiment of a clamping device 1 '.

Fig. 3 is a schematic sectional view of a third embodiment of a clamping device 1".

Fig. 4 is a schematic sectional view along the line A-A in Fig. 3 of the clamping device according to the third embodiment. Description of Embodiments

Fig. 1 is a schematic sectional view of an embodiment of a clamping device 1 , which is adapted to be mounted in a machine tool and to hold a shaft tool V. The clamping device 1 thus has a fastening part P1 and a holder part

P2 comprising an inner sleeve 2, which has a tool contact surface 22 and a piston contact surface 14; an outer sleeve 3, which has a piston contact surface 13. An axially movable annular piston 12 is arranged between the inner sleeve 2 and the outer sleeve 3. The fastening part P1 and the holder part P2 can be axially separate from one another, for example by being located at either end of the clamping device. For details concerning the design of the fastening part P1 , reference is made to WO2004/007129A1.

The material thicknesses shown in Fig. 1 are only schematic. The thickness of the inner sleeve 2, the outer sleeve 3 and the piston 12 can be dimensioned according to the application in which the clamping means is to be used.

According to the embodiment shown in Fig. 1 , the contact surface 14 between the inner sleeve 2 and the piston 12 is a conical surface, so that a movement of the piston 12 in the direction D2 (to the left in Fig. 1) causes an expansion of the outer sleeve 3 and a compression of the inner sleeve 2. To elucidate the description, the conical surface shown in Fig. 1 has a considerably greater conical angle than in a real application. Generally, the conical surfaces have a conical angle such that they become self-locking. For details concerning the selection of the conical shape of the conical surface, reference is made to the above-mentioned WO2004/007129A1.

The piston 12 has a flange 17, which projects radially from one end of the piston 12 and which has an assembling surface 7 and a disassembling surface 6 located on an opposite side of the flange 17. The assembling surface 7 is part of a boundary surface of an actuating pressure chamber 5. A radially projecting part 16 of the outer sleeve 3 forms yet another delimiting part of the actuating pressure chamber 5. Also a portion of the piston forms a boundary surface of the actuating pressure chamber 5. The disassembling surface 6 is part of a boundary surface of a deactuating pressure chamber 4. A radially projecting part 15 of the inner sleeve 2 forms yet another delimiting part of the deactuating pressure chamber 4. Also a portion of the outer sleeve located at the flange forms a boundary surface of the deactuating pressure chamber 4. Connecting means 10, 11 for compressed fluid communicate via ducts

8, 9 with the actuating pressure chamber 5 and the deactuating pressure chamber 4, respectively.

In Fig. 1 , reference numeral P indicates the piston portion active against both the inner sleeve 2 and the outer sleeve 3, i.e. the piston portion engaged in the transmission of force between the tool and the clamping device. Reference numerals E1 and E2 indicate the respective ends of the portion P. The portion Pv indicates the whole portion of the piston active against the inner sleeve 2 and, thus, also against the tool V.

The description will now be aimed at the function of the clamping device.

The fastening part is adapted to be mounted in a machining device in per se known manner.

In the clamping device 1 , the tool V is arranged so as to obtain some play (not shown) between the clamping device 1 and the tool V. By pressurising the actuating pressure chamber 5, a force is applied to the assembling surface 7, which causes the annular piston 12 to move in the direction D2 (to the left in Fig. 1), whereby cooperation at the contact surface 14 of the piston 12 and the inner sleeve 2 causes the compression of the inner sleeve 22 and thus produces a contact pressure in the contact surface 22 between the inner sleeve 2 and the tool V. The deactuating pressure chamber 4 can optionally be drained or unloaded in some other way when pressurising the actuating pressure chamber 5.

The contact pressure in the contact surface 22, together with the friction in the contact surfaces, secures the tool V in the clamping device 1 , so that any relative movement between them is counteracted or prevented.

By instead pressurising the deactuating pressure chamber 4, a force is applied to the disassembling surface 6, which causes the annular piston 12 to move in the direction D1 (to the right in Fig. 1), whereby the pressure in the contact surfaces 13, 14 between the piston 12 and the outer sleeve 3 and the inner sleeve 2, respectively, is unloaded, and thus also the pressure in the contact surface 22 between the inner sleeve 2 and the tool V, to allow removal of the tool V. One or both contact surfaces 13, 14 between the piston 12 and, respectively, the outer sleeve 3 and the inner sleeve 2 can have a modified friction coefficient. The purpose of such a modification may be to obtain a low and even friction coefficient and/or to obtain the smallest possible difference between the static and the dynamic friction coefficients of the contact surfaces 13, 14.

As a non-limiting example of a friction-reducing coating, mention can be made of surface coating of so-called chemical nickel.

According to an alternative embodiment of a clamping device 1 ', as shown in Fig. 2, the contact surface 14 between the outer sleeve 3 and the piston 12 is instead a conical surface.

Thus, in the embodiment shown in Fig. 2 the actuating pressure chamber 5 and the deactuating pressure chamber 4, on the one hand, and the assembling surface 7 and the disassembling surface 6, on the other hand, are reversed, the conical surface tapering instead in the direction D1 , so that actuation or assembling is achieved by the left pressure chamber (reference numeral 5 in Fig. 2) being pressurised, and the deactuation or disassembling is achieved by the right pressure chamber (reference numeral 4 in Fig. 2) being pressurised. This embodiment results in the assembling surface 7 being greater than the disassembling surface 6. According to another alternative embodiment (not shown), the contact surface 14 between the inner sleeve 2 and the piston 12, and the contact surface 13 between the outer sleeve and the piston 12 are both conical surfaces.

According to yet another embodiment, one or both of the contact surfaces 13, 14 are provided with lubricating ducts of the kind disclosed in US 4,616,948.

The pressurisation of the actuating and deactuating pressure chambers 5, 4, respectively, can be obtained by connecting a hydraulic pump. Alternatively, movable pistons (not shown) arranged in flanges in the inner sleeve 2 and/or the outer sleeve 3 may be used to obtain pressurisation of the respective pressure chambers 4, 5.

In the embodiment of a clamping device 1" shown in Figs 3 and 4, the actuating pressure chamber (reference numeral 5 in Fig. 1 and Fig. 2) is replaced with an elastically resilient actuating means 18, which is arranged to preload the piston in the direction D2, i.e. to provide the locking of the clamping device 1 " without the use of any external means, such as a hydraulic pump. The actuating means 18 can be a spring means, such as a cup spring, a helical spring, a gas spring, a compressible material or the like.

The deactuating pressure chamber 4 described with reference to Fig. 1 is still the same and works exactly as described in connection with Fig. 1 , i.e. when the deactuating chamber 4 is pressurised a movement of the piston is produced in the direction D1 , which unlocks the clamping device 1 ".

Fig. 3 also illustrates how the inner sleeve 2 may be provided with one or more longitudinal slots 25a, 25b, facilitating the contraction of the sleeve which arises when the piston 12 is moved and the clamping device 1 " is locked, thereby reducing the force required to lock/unlock the clamping device 1 ". The slots are arranged in the part of the inner sleeve 2 that cooperates with the piston 12 and extend in the radial direction through the entirety of the inner sleeve 2.

According to an alternative embodiment, also the piston, in conformity with the above-described slotted inner sleeve, is provided with one or more slots (not shown).

The slots (25a, 25b) described above are particularly suitable for use together with an elastically resilient actuating means 18, which is not capable of exerting a force as great as, for instance, that of the actuating pressure chamber 5 described with reference to Fig. 1. According to further alternative embodiments, also the inner sleeves 2 in the clamping devices 1 , 1 ' described with reference to Fig. 1 and Fig. 2 can be provided with one or more such slots. Furthermore, the gap between the inner sleeve 2 and the outer sleeve 3 where the piston 12 is positioned can be wholly or partly uncovered in the direction D1 , which makes it possible to limit the axial extension of the clamping device 1 , 1 ', 1", thus contributing to making the clamping device more compact in the axial direction.

In a corresponding manner, the embodiment shown in Fig. 2 can be modified (not shown) in accordance with that shown in Figs 3 and 4, the actuating pressure chamber 5 being replaceable with an elastically resilient actuating means. The person skilled in the art will realise that, in Fig. 1 or Fig. 2, it would instead be possible to replace the deactuating pressure chamber 4 with an elastically resilient deactuating means (corresponding to the elastically resilient actuating means 18), thus obtaining a self-unlocking clamping device (not shown). The flange 17 can be integrated with the piston 12. According to one embodiment, the flange and the piston are formed in one piece of material, and in another embodiment they are formed of separate pieces of material which are subsequently joined together, for instance, by a threaded coupling or by a weld joint. The inner sleeve and the outer sleeve can be joined together, for instance, by means of bolts or weld joints. A plurality of gaskets can be arranged in a manner known per se to prevent leakage.

In all embodiments, the conical surfaces can be arranged between the inner sleeve 2 and the piston 12, between the outer sleeve 3 and the piston 12 or both.

The chuck described above can be designed in the form of a mandrel, as illustrated in Fig. 6 of WO2004/007129A1. Furthermore, said chuck can be integrated with a fastening part P1 , i.e. a machine cone, as shown in Fig. 4 of WO2004/007129A1. For details concerning the design of the chuck or mandrel mentioned above, reference is made to WO2004/007129A1.

Claims

1. A hydromechanical clamping device, comprising: a fastening part (P1), adapted to be mounted in a machining device, and a holder part (P2), adapted to releasably hold a tool shaft (V), the holder part (P2) comprising an inner sleeve (2) with an axial recess, intended to receive the tool shaft (V), the inner sleeve (2) and an outer sleeve (3) defining a chamber in which an annular piston (12) is axially movable, the annular piston and at least one of the inner sleeve and the outer sleeve having cooperating conical surfaces (13, 14), which in axial movement of the piston in a first direction (D1 ; D2) are arranged to produce a radial compression of the inner sleeve 2 and in axial movement of the piston in a second direction (D2; D1), opposite to the first direction, to allow a radial expansion of the inner sleeve, the clamping device (1) further comprising: an actuating means (5, 18) arranged to produce a movement of the annular piston (12) in said first direction, and a deactuating means (4) arranged to produce a movement of the annular piston (12) in said second direction, characterised in that said actuating means (5, 18) and said deactuating means (4) are located, seen in the axial direction, on the same side of the annular piston (12).

2. A clamping device (1 , V, V) according to claim 1 , wherein said deactuating means comprises a deactuating pressure chamber (4), which when pressurised produces said movement of the annular piston (12) for unlocking the clamping device (1).

3. A clamping device (1 , 1') according to claim 1 or 2, wherein said actuating means comprises an actuating pressure chamber (5), which when pressurised produces said movement of the annular piston (12) for locking the clamping device (1).

4. A clamping device (1 , 1') according to claim 2 in combination with claim 3, further comprising a flange (17) which is joined to the annular piston (12), which separates said actuating pressure chamber (5) from said deactuating pressure chamber (4).

5. A clamping device (1 , 1') according to claim 4, wherein the flange (17) has an assembling surface (7), which defines the actuating pressure chamber (5) and a disassembling surface (6), which defines the deactuating pressure chamber (4), and wherein the disassembling surface (6) is greater than the assembling surface (7).

6. A clamping device (1 ") according to claim 1 or 2, wherein said actuating means comprises an elastically compressible actuating means (18), which is arranged to produce said movement of the annular piston (12) for locking the clamping device (1).

7. A clamping device (1 , 1 ', 1 ") according to any one of the preceding claims, wherein the inner sleeve (2) has at least one slot (25a, 25b) extending in said axial direction.

8. A clamping device (1 , 1', 1 ") according to any one of the preceding claims, wherein a friction-modified surface is provided on at least one of a surface of the annular piston cooperating with the inner sleeve, a surface of the annular piston cooperating with the outer sleeve, a surface of the outer sleeve (3) cooperating with the piston and a surface of the inner sleeve (2) cooperating with the piston.

9. A clamping device (1 , 1 ', 1 ") according to any one of the preceding claims, wherein a lubricating duct is arranged on at least one of a surface of the annular piston (12) cooperating with the inner sleeve, a surface of the annular piston (12) cooperating with the outer sleeve, a surface of the outer sleeve (3) cooperating with the piston and a surface of the inner sleeve (2) cooperating with the piston.

10. A clamping device (1 , 1 ") according to any one of the preceding claims, wherein said conical surface consists of a contact surface between the inner sleeve (2) and the annular piston (12), and/or a contact surface between the outer sleeve (3) and the annular piston (12).