GB2112677A

GB2112677A - Expansion device for axial and radial clamping of annular member on a mandrel

Info

Publication number: GB2112677A
Application number: GB08235104A
Authority: GB
Inventors: Heinrich Fischer
Original assignee: Hurth Verwaltungs GmbH
Current assignee: Hurth Verwaltungs GmbH
Priority date: 1981-12-09
Filing date: 1982-12-09
Publication date: 1983-07-27
Also published as: IT8249198A0; GB2112677B; JPS58109206A; IT1149380B; JPH0134721B2; DE3148677A1; DE3148677C2

Abstract

For releasable radial and axial clamping of a tool or workpiece 30 provided with a central bore on a mandrel 10, a clamping sleeve 20 has a nut 21 integral therewith which is screwed onto a mandrel, the sleeve being resiliently deformable radially under the pressure of an internal fluid to grip the workpiece or tool, and the nut 21 laterally abutting against the workpiece tool and being reliently deformable to press it against a collar 13 on the mandrel under the pressure of internal fluid. The clamping sleeve may be provided with respective annular fluid chambers 41 close to its inner surface and 42 close to its outer surface, and the nut 21 has a chamber 46 close to its abutment surface. Instead of the annular chambers, a plurality of part-annular chambers may be arranged uniformly distributed in the circumferential direction. The chambers may be acted upon independently of one another, in groups, or all together. <IMAGE>

Description

SPECIFICATION A device for the releasable radial and axial clamping of a tool or workpiece provided with a central bore on a mandrel or the like This invention relates to a device for the releasable radial and axial clamping of a tool or workpiece provided with a central bore on a mandrel or the like.

An apparatus is known from the German Patent 743 530 in which a tool or workpiece is secured to a mandrel or the like by a clamping sleeve which is resiliently deformable under the variable pressure of a fluid, the clamping sleeve filling the annular space between the mandrel or the like and the tool or workpiece. Clamping is performed only in the radial direction, clamping in the axial direction not being possible with this apparatus.

It is also known to hold tools, e.g. shaving wheels for the precision machining of gearwheels, directly on a mandrel, the centering necessarily being subject to play. Clamping is effected in the axial direction by means of a mechanical or hydraulic nut against a collar or other fixed stop on the mandrel (German Gebrauchsmuster (Utility Model) 76 16 406).

A disadvantage of these solutions is that despite very precise manufacture and the observation of the smallest possible manufacturing tolerances the tool, e.g. a shaving wheel, clamped on to the mandrel, can have a concentricity error which is no longer acceptable, for example by combination of the individual tolerances of the mandrel, the clamping sleeve and the workpiece.

The object of the invention is therefore to provide an apparatus for clamping as precisely as possible and in a manner centering without play, a tool operating very precisely or a workpiece to be machined very precisely on a mandrel or the like, in which the radial and the axial clamping are effected by a single element so as not to produce additional inaccuracies through the inter-action of two elements.

In order to attain the object, an apparatus is proposed which has the features of Claim 1.

The clamping sleeve formed in this way is screwed on to the mandrel or the like until the abutment face of the nut portion comes to bear against the tool or workpiece. The sleeve portion issituated in the annular space between the mandrel or the like and the tool or workpiece. By altering the pressure of the fluid the tool or workpiece is then clamped radially and axially. One annular chamber for holding the fluid is provided in the nut portion for clamping axially and two annular chambers for holding the fluid are provided in the sleeve portion for clamping radially. For this purpose advantageous designs are set out in Claims 2 and 3. Instead of the annular chambers, a plurality of chambers uniformly distributed in the peripheral direction may also be provided in each case, for which purpose various expedient designs are set out in Claims 5 to 8.In the case of all the designs each chamber may be acted upon individually, which permits delicate adjustment of the position of the clamped tool or workpiece. The expense required for the pressure regulating devices may be reduced if the annular chambers or the corresponding chambers are acted upon jointly, which is sufficient for many cases of applications.

The invention is described below by way of example with reference to the accompanying drawings in which: Figures 1 and 2 are a longitudinal section and a transverse section along the line Il-Il through an apparatus according to the invention, Figures 3 and 4 are a longitudinal section and a transverse section along the line IV-IV through another embodiment of an apparatus according to the invention, and Figure 5 is a possible embodiment for the assembly of the clamping sleeve from a plurality of parts.

A tool 30, e.g. a shaving wheel, or a workpiece is secured by means of a clamping sleeve 20 to a mandrel 10 shown only in a cut away manner (Figs. 1 and 3). The clamping sleeve 20 comprises a nut portion 21 screwed on to a thread 11 on the mandrel 10 and a sleeve portion 22 joined to the said nut portion 21. The inner surface 23 of the sleeve portion 22 surrounds a cylindrical portion 12 of the mandrel 10 and its outer surface 24 is surrounded by the wall 31 of the bore of the tool 30. A plane side 32 of the tool 30 rests, where appropriate by way of an interposed washer 55, on a collar 13 of the mandrel 10.

An abutment surface 25 of the nut portion 21 rests on the other plane side 33 of the tool 3, where appropriate by way of an interposed washer 56.

The sleeve portion 22 of the clamping sleeve 20 is provided with a first closed annular chamber 41 (Figs. 1 and 2) and a second closed annular chamber 42 surrounding the latter. (In this context and below, the term "closed" should be taken to mean that the chambers are confined on all sides by the clamping sleeve 20, and does not exclude the existence of connected ducts, to which reference will be made below). The chamber 41 is at a small radial distance 43 from the inner surface 23, and the chamber 42 is at a small radial distance 44 from the outer surface 24, of the sleeve portion. In order to provide the sleeve portion 22 with the necessary inherent stability the radial distance 45 between the first chamber 41 and the second chamber 42 is greater than the radial distances 43 and 44 respectively from the adjacent surfaces.

The nut portion 21 of the clamping sleeve 20 is provided with a third closed annular chamber 46 which is at a small axial distance 47 from the abutment surface 25.

The chambers 41, 42 and 46 are filled with a fluid. By means of a thrust screw 60 it is possible to vary the pressure in the chambers, which for this purpose are connected to the thrust screw 60 by way of ducts 64. The thrust screw 60 has adjacent to a threaded portion 61, a cylindrical shaft 62 with a sealing ring 63. After the clamping sleeve 20 has been screwed so far on to the thread 11 that the surface 25 and the plane side 32 come to bear loosely against the plane side 33 and and the collar 13 respectively, the clamping of the tool is performed with the thrust screw 60. The further this is screwed in, the more the pressure increases in the chambers and the more securely the adjacent surfaces 23, 12; 24, 31; 32, 13; 33, 25 are clamped together as a result of the resilient deformation of the thin walls of the clamping sleeve.In order to give the assembling mechanic an indication of the pressure which exists, a pressure gauge 70 is provided which is connected to the ducts 64a by way of a duct 71: a sealed piston 73, fastened to a pin 74 with division markings 75 projecting from the clamping sleeve 20, is pressed against the force of a spring 72. The number (or the colour) of the markings indicates the pressure.

It has been found in practice that in many cases it is sufficient to provide a common thrust screw 60 for all the chambers 41, 42, 46. It is sometimes advantageous, however, for an individual thrust screw 60, 60' and an individual pressure gauge 70, 70' to be provided at least for the third chamber 46 for clamping in the axial direction, and also where appropriate for each of the three chambers, as indicated in Fig. 2. This embodiment is applied in particular in the case of tools which are wide axially and have only narrow radial abutment surfaces, e.g. in the case of hob cutters.

Generally, however, it is desirable to be able to orientate the workpiece in the radial direction in order to eliminate any possible concentricity error in the clamped tool. The sleeve portion 22 of the clamping sleeve 20 is then provided with first closed chambers 48 uniformly distributed in the peripheral direction (Figs. 3 and 4) and with second chambers 49 likewise uniformly distributed in the peripheral direction and which extend predominantly in the axial and in the peripheral direction. The chambers 48 are at a small radial distance 43 from the inner surface 23 and the second chambers 49 are at a small radial distance 44 from the outer surface 24.

The radial distance 45 between the first chambers 48 and the second chambers 49 is again greater than the radial distance 43 and 44 respectively. The nut portion 21 of the clamping sleeve 20 is provided with third closed chambers 50 which are uniformly distributed in the peripheral direction, are at a small axial distance 47 from the bearing surface 25 and extend predominantly in the radial and in the peripheral direction.

The chambers 48, 49 and 50 are filled with a fluid, the pressure of which may be varied by means of thrust screws 60 described above. If an individual thrust screw 60, 60' etc. is available for each individual chamber 48, 49 and 50, the concentricity error of the tool 30 may be compensated very delicately.

The clamping sleeve 20 is secured to the mandrel 10 by the pressure in the first chambers 48, the pressure in the second chambers 49 is used to secure the tool 30 to the clamping sleeve 20 and the clamping in the axial direction is effected by the pressure in the third chambers 50. If, for example, it is found while testing the concentricity that the tool 30 must be "raised"-with respect to Fig. 4--relative to the mandrel 10, then the pressure will be increased in the chamber designated 48' and also where appropriate in that designated 49', and at the same time the pressure will be slightly reduced in the chamber designated 48" and also where appropriate in that designated 49". In certain circumstances the pressure must be temporarily reduced in the third chambers 50 in order to allow the tool 30 to be radially displaced.

In order to be able to identify clearly the chambers 48, 49, 50 to be acted upon to compensate a concentricity error with a higher or a lower pressure, as many first chambers 48 are provided as second chambers 49 and third chambers 50. In this way one first chamber 48 and one second chamber 49 are radially adjacent in each case and one third chamber 50 is axially adjacent to them.

In many cases it is sufficient for a common thrust screw 60 and a common pressure gauge 70 to be provided for the chambers 48, 49 radially adjacent in each case. In this connexion it is also possible to provide one annular chamber 46 instead of the chambers 50 acting axially, as described in connexion with Figs. 1 and 2. The radially adjacent chambers 48, 49 may then be connected together by way of a duct which is indicated by broken lines in Fig. 3 and designated 65.

A reduction in pressure occurring in the chamber 48" while compensating a concentricity error in a manner similar to the procedure described above is compensated by the increase in pressure in the chamber 48'.

In Figs. 1 to 4 the clamping sleeve 20 is shown as a homogeneous part. There are various possibilities of manufacturing it. As a rule it will be assembled from many parts, in which the respective chambers are milled and/or cut, and welded tightly. By way of example, Fig. 5 shows how the clamping sleeve is made up of four parts 51 to 54.

Other embodiments are, of course, also possible.

The invention is not limited to the examples of embodiment illustrated and described.

Thus, for example, the thrust screws 60, 60' ... and/or the pressure gauges 70, 70' ...

may also be arranged axially instead of radially, the number of chambers is not limited to four in each case, etc.

Claims

1. A device for the releasable radial and axial clamping on a mandrel or the like of a tool or workpiece provided with a central bore comprising a clamping sleeve which is radially resiliently deformable under the controllable pressure of a fluid and is placed between the mandrel or the like and the tool or workpiece, and a nut which can be axially screwed, next to the tool or workpiece, on to the mandrel or the like to press the tool or workpiece against a collar or the like on the mandrel or the like, characterised in that the clamping sleeve is formed integrally with the nut to form a sleeve portion and a nut portion and the axial abutment surface of the nut portion is axially resiliently deformable under the controllable pressure of a fluid.

2. A device according to claim 1, characterised in that the nut portion has a closed annular chamber for holding the fluid, at a small axial distance from the abutment surface.

3. A device according to claim 1 or 2, characterised in that the sleeve portion has two annular chambers for holding the fluid, of which the first chamber is disposed at a small radial distance from the inner surface of the sleeve portion and the second chamber is disposed at a small radial distance from the outer surface of the sleeve portion, the second chamber surrounding the first chamber and the radial distance between the first and the second chamber being greater than the radial distances of the said first and second chambers from the inner and outer surfaces respectively.

4. A device according to claim 2 or 3, characterised in that the chambers are in fluid communication with one another.

5. A device according to claim 1, characterised in that the sleeve portion and/or the nut portion has a plurality of chambers for holding the fluid, which are uniformly distributed in the circumferential direction and can be acted upon independently of one another.

6. An apparatus according to claim 5, characterised by, first chambers uniformly distributed in the circumferential direction and at a small radial distance from the inner surface of the sleeve portion, second chambers uniformly distributed in the circumferential direction and at a small radial distance from the outer surface of the sleeve portion, the radial distance between the first and the second chambers being greater than the radial distances of the said chambers from the inner and outer surfaces respectively, and third chambers uniformly distributed in the circumferential direction and at a small axial distance from the abutment surface of the nut portion.

7. A device according to claim 6, characterised in that the number of the first, second and third chambers is equal.

8. A device according to claim 7, characterised in that in each case one first chamber and one second chamber are disposed radially in line with one another in the sleeve portion and one third chamber in the nut portion is arranged radially and axially offset with respect to the said aligned first chamber and second chamber.

9. A device according to claim 8, characterised in that the radially aligned first chamber and second chamber and optionally the corresponding third chamber arranged offset with respect thereto are in fluid communication with one another.

10. An apparatus according to claim 5 characterised by, first uniformly distributed in the circumferential direction and at a small radial distance from the inner surface of the sleeve portion, second chambers uniformly distributed in the circumferential direction and at a small radial distance from the outer surface of the sleeve portion, the radial distance between the first and the second chambers being greater than the radial distances of the said chambers from the inner and outer surfaces respectively, and a closed annular chamber in the nut portion, at a small axial distance from the abutment surface of the nut portion.

11. A device as claimed in claim 10 in which the radially aligned first chamber and second chamber are in fluid communication with each other.

12. A device as claimed in claim 10 or 11 in which fluid communication is provided between the first, second and third chambers.

13. A device for releasably fixing on a mandrel or the like a tool or workpiece provided with a bore, which device comprises a clamping sleeve and a clamping nut forming a unit whereof in use the nut is screwed on the mandrel or the like to hold the tool or workpiece against a stop with the sleeve encircling the mandrel or the like within the said bore, and wherein the sleeve has at least one internal chamber bounded by a thin radially deformable wall forming at least a portion of a circumferential surface of the sleeve, and the nut has at least one internal chamber bounded by a thin axially deformable wall forming at least a portion of the nut surface that retains the tool or workpiece, the said chambers being provided with ducting for application of a controllable fluid pressure to the chambers for axially and radially clamping the tool or workpiece by the deformation of the said walls.

14. A device for releasable radial and axial clamping of a tool or workpiece on a mandrel or the like, substantially as herein described with reference to Figs. 1 and 2 and 4, or 5 of the accompanying drawings.