TRUING DEVICE FOR CIRCULAR TOOLS AND METHOD FOR MOUNTING/REMOVING CIRCULAR TOOLS

Abstract

A truing device includes a housing and a truing mandrel (1) with a shaft (10) used to mount a circular tool having a concentric opening, in particular a grinding disc (3), and with a first bearing (11) fixed on the housing (4) and located in a first end region of the truing mandrel (1) The shaft (10) includes a hydraulic clamping device (20) having a chamber (21) containing hydraulic medium, to which a pre-clamping pressure can be applied with a preclamping element (23) The hydraulic clamping device is formed from a clamping section (22) lying above the chamber (21) in the radial direction and held in the shaft on both sides. The outer surface of the clamping section forms the clamping surface and which, when the hydraulic pressure in the chamber (21) increases, can be reversibly moved or bent outwards in the radial direction such that a radial clamping force can be exerted on the inner surface of the concentric opening of the circular tool penetrated by the clamping section (22). A method provides for mounting and removing a circular tool on the truing mandrel of a truing device of this kind.

Claims

1. Dressing device, comprising: a housing (4), and a dressing mandrel (1) having a shaft (10), which serves for the mounting of a circular tool with a through-passing concentric opening, in particular a grinding disk (3), and a first bearing (11), which is fixed on the housing (4) and is located in a first end region of the dressing mandrel (1), and a dressing tool for dressing the circular tool which is mounted on the dressing mandrel (1), the shaft (10) having a hydraulic clamping device (2), which extends through the opening in the circular tool and comprises a chamber (21) with a hydraulic medium, which can be subjected to a preclamping pressure by means of a preclamping element (23), the hydraulic clamping device being formed from a clamping section (22), which is held in the shaft at both sides and, in a radial direction, is located above the chamber (21) and of which the outer surface forms the clamping face and which bulges outwardly in a radial direction on an increase of the hydraulic pressure in the chamber (21), such that a radial clamping force is exerted on the inner surface of the concentric opening of the circular tool, through which the clamping section (22) passes.

2. Dressing device according to claim 1, wherein the dressing tool is a diamond roll.

3. Dressing device according to claim 1, wherein the clamping section (22) is at least partly designed as a sufficiently thin, hollow-cylindrical material cover that is integral with the shaft (10).

4. Dressing device according to claim 1, wherein the chamber (21) is circumferentially subdivided into a plurality of congruent subchambers (21.1-4), which are disposed rotationally symmetrically about a longitudinal axis (L) of the shaft (10).

5. Dressing device according to claim 1, wherein a plurality of chambers (21a, 21b) are present along the shaft (10).

6. Dressing device according to claim 1, further comprising a second bearing (12) of the dressing mandrel (1), which is disposed in particular on that side of the clamping device (20) that is opposite the first bearing (11).

7. Dressing device according to claim 1, wherein the clamping section (22) comprises two or more clamping bodies (29), which are held such that they are displaceable in the radial direction as far as a stop.

8. Dressing device according to claim 7, wherein the clamping bodies (29) are disposed in the radial direction below the chamber (21), the stop being formed by the underside of the base (211), which separates the underside of the chamber (21) from the movement space of the clamping body/bodies or by those sides, lying opposite the clamping bodies, of the space that contains the clamping bodies and the outer surface (292) of the clamping bodies projects into the hydraulic chamber (21) such that the outer surfaces are in direct contact with the hydraulic medium.

9. Dressing device according to claim 7, wherein the clamping bodies (29′) are disposed in a radial direction above the chamber (21) and are entirely disposed below the clamping section (22) or the clamping section (22) is penetrated such that at least a portion of the clamping face is formed by the outer surface of the clamping bodies (29), the stop being formed by at least two opposing end sides of the clamping bodies (29) and, on reaching the stop, the outer surface (292) of the clamping bodies (29) projects beyond the surrounding surface of the shaft (10).

10. Dressing device according to claim 1, wherein the preclamping element (23) is a clamping screw, which is screwed into a threaded bore (24) of the shaft, which is in fluid communication with the chamber (21).

11. Dressing device according to claim 1, wherein an abutment shoulder (14) of the shaft (10), which serves for axial positioning of the circular tool.

12. Dressing device according to according to claim 11, further comprising a fixing disk (16), which, in connection with said abutment shoulder (14), serves for axial fixing of the circular tool, and can be screwed onto a screw thread (15) of the shaft (10).

13. Dressing device according to claim 12, wherein the preclamping element (23) is formed by the fact that at least that section of the shaft (10) that bears the screw thread (15) deviates at least partially along its axial extension from a circular cross-section, in particular having an oval or elliptical form, the difference between a maximum and a minimum radius being several per mille to percent, and an average radius corresponding to approximately the radius of a passable opening (150) of the fixing disk (15) having an internal thread, and the chamber (21) extending to below that section of the shaft (10) that bears the thread (15).

14. Dressing device according to claim 11, wherein the preclamping element (23) is formed by the fact that in an end face of the abutment shoulder (14) which faces the circular tool, there is at least one force transmission element, the chamber (21) extends into the abutment shoulder (14) and as far as below the force transmission element, and the force transmission element being a pin (231), which is inserted into a bore (230) extending into the chamber (21) or a projection (232) integrally formed on the surface of the abutment shoulder (14).

15. Method for mounting a circular tool having a concentric opening on a dressing mandrel of a dressing device according to claim 1, comprising: a) in a first step, if appropriate, the fixation of the dressing mandrel in the housing of the dressing device is released at at least one side, b) in a subsequent second step, if appropriate, an axial fixation and positioning means, which is independent of the preclamping element, such as a fixing disk (16) is released from the shaft and removed, c) then in a third step, by means of the preclamping element the pressure of the hydraulic medium and thus the external diameter of the clamping section is reduced to such an extent that it is at least slightly smaller than the clear width of the opening of the circular tool, d) in a subsequent fourth step, this is pushed onto the shaft, e) in a subsequent fifth step by means of the preclamping element, the hydraulic medium in the chamber (21) is subjected to a desired preclamping pressure, f) then, if appropriate, in a sixth step, an axial fixing means which is independent of the preclamping element, for example a fixing disk (16) is mounted and fastened, and g) if appropriate, in a subsequent seventh step, the free end of the dressing mandrel is again fixed in the housing (4) of the dressing device.

16. Method for removing a circular tool fastened on a dressing mandrel of a dressing device according to claim 1, comprising: a) in a first step, if appropriate, the fixation of the dressing mandrel in the housing of the dressing device is released at at least one side, b) in a subsequent second step, if appropriate, a fixation means, which is independent of the preclamping element (23), such as a fixing disk (16) is released and removed, c) then in a third step the preclamping element is brought into a relaxation position and the hydraulic pressure in the chamber (21) and thereby the preclamping force acting on the circular tool is reduced until it can be pulled off the shaft, and d) in a subsequent third step, the tool is pulled off the shaft and removed.

Description

[0054] Further properties and features of the present invention result from the figures of exemplary embodiments that are described in detail below. These are only intended to illustrate the invention, and in no way to limit it, wherein:

[0055] FIG. 1 shows a perspective view of an embodiment of a dressing machine according to the invention with an inserted dressing mandrel

[0056] FIG. 2 shows a dressing mandrel of a dressing machine according to a first preferred embodiment in longitudinal and cross section

[0057] FIG. 3 shows a dressing mandrel of a dressing machine according to a second preferred embodiment in longitudinal as well as two cross sections.

[0058] FIG. 4 shows a dressing mandrel of a dressing machine according to a third preferred embodiment in longitudinal as well as two cross sections

[0059] FIG. 1 shows a possible embodiment of a dressing device according to the invention. This housing 4, which consists of two foldable halves, into which the dressing mandrel 1 is inserted and, after folding closed and securing of the housing halves, is held and fixed on bearings 11 and 12 disposed on both sides of the shaft 10. A circular tool in the form of a profiled grinding disk 3 is shown clamped on the dressing mandrel 1. For rapid exchange of the tool, the half shells are articulated at their lower edge and are connected at their upper edge by means of an interlocking mechanism that can be actuated without tools.

[0060] FIG. 2 shows the dressing mandrel of a dressing machine according to the invention in a preferred embodiment.

[0061] Partial figure A shows a longitudinal section in a plane containing the axis of rotation L, while partial figure B shows a cross-section along the line BB.

[0062] The dressing mandrel 1 comprises shaft 10 with the abutment shoulder 14, which serves for axial positioning, as well as two bearings, which are disposed on both sides of the shaft 10, a first bearing 11 and a second bearing 12, which serve for fixing the shaft in a housing of the dressing machine according to the invention, for example according to that shown in FIG. 1. The bearings 11, 12 are presented here as roller bearings, however other bearing types, for example (pneumatic) plain or magnetic bearings can also be used within the scope of the present invention. On the end face of the outer bearing sleeve of the second bearing 12, sensor 13 is positioned, which may be in particular an acoustic sensor and, in a manner familiar in the prior art, serves for monitoring and determining the (operating) state and the correct function of the machine. The shaft 10 of dressing mandrel 1 in turn comprises the clamping device 2, consisting of the elastic clamping section 22, (hydraulic medium) chamber 21, which lies radially below said clamping section and is filled with a pressurized hydraulic medium and the preclamping element 23 for setting the hydraulic chamber pressure. The outer and clamping face of clamping section 22 has the form of a cylindrical surface, while the inner surface has the supporting structures 221, which can be seen in the longitudinal section (partial figure A). These supporting structures serve to increase the stability of the clamping section 22 with respect to the effect of radially directed forces, which exceed the hydraulic chamber pressure locally or else over a larger range, as a result of which damage of the clamping device 2 may be threatened. The clamping section 22 is offset inwardly at both ends, the cylindrical springs 222a and 222b being inserted into complementary grooves or notches 101a and 101b of the shaft 10. As a result the clamping section 22 is securely and firmly held in the shaft. Furthermore, the leak-tightness of the shaft-clamping section connection against leaking out of the pressurized hydraulic medium is thereby ensured.

[0063] The preclamping element 23 for setting the static hydraulic chamber pressure consists of a screw 233 which is inserted as displacer into a radial bore in the side of the shaft 10. This bore leads into the the hydraulic chamber, which, at least at this place, extends beyond the clamping section, or into an offshoot of the chamber. Further screwing in or screwing out again of screw 233 changes the effective volume of the hydraulic chamber and therefore also the pressure of the medium therein. Thus, the desired (static) preclamping can be set as desired: if a circular tool is mounted or removed, the screw 233 is rotated out to such an extent that the outer diameter of the clamping section 22 is smaller than the opening of the tool or no significant clamping is exerted on the tool. The tool can now be mounted or taken off. In contrast to the thermal shrinking or expansion used in the prior art, which takes many hours and is associated with a high risk of damaging both the tool and the dressing mandrel, the process with the mandrel according to the invention only takes several to several tens of seconds at most. This is a time gain that can hardly be overestimated in practice. The disadvantage at which it is bought is the design-dependent higher elasticity of the dressing mandrel: the thin-walled and correspondingly elastic clamping section and the hydraulic medium generally have higher elasticity than a solid shaft. This is expressed as increased vibration and a reduced true-running and axial run-out under non-uniformly acting forces. The supporting structures 221 present in the embodiment according to FIG. 2 on the inside of the clamping section can only compensate for this to the extent that the amplitude of the vibrations is larger than the distance of the structures from the base of the hydraulic chamber 21. An operational possibility for reducing these vibrations is to note, during dressing of the circular tool, that as far as possible, only uniform, that is to say mutually compensating forces are exerted on the tool and therefore on the dressing mandrel. However, if increased stability by design, that is to say reduced elasticity, is required, a circumferential and/or axial subdivision is proposed by the present invention, as are shown in the embodiments according to FIG. 3 or 4.

[0064] FIG. 3 shows a dressing mandrel with clamping bodies of a dressing machine according to the invention according to another preferred embodiment.

[0065] Partial figure A shows a longitudinal section, while partial figures B and C show a cross-section along the lines BB and CC in each case from partial figure A.

[0066] The dressing mandrel 1 comprises a shaft 10, which in turn comprises, at one end, a region 15 having an external thread for screwing on an axial fixing disk 16 and at an opposite end an abutment shoulder 14, as well as, between them, a clamping region having a clamping device 2. Likewise, the dressing mandrel, which is not shown here, comprises at least one bearing, preferably two bearings disposed on both sides of the shaft 10, as well as a sensor as shown in FIG. 2. A circular tool in the form of a grinding disk 3 is mounted on shaft 10 or the clamping device 2.

[0067] Clamping device 2 comprises a hydraulic medium chamber, which is subdivided into an upper chamber 21a and a lower chamber 21b, which are located below the thin-walled clamping section 22, clamping section 22 being in turn integrally connected to the rest of the shaft 10 at both sides. Thereby, the force transmission into the shaft on one hand and the tightness against leaking out of the pressurized hydraulic medium on the other hand is improved compared to the embodiment in FIG. 2. In a cavity which is radially below the upper and lower hydraulic chambers 21a, 21b, which is [separated?] from them by a thin elastic material layer having a thickness comparable to that of the clamping section 22, radially displaceable clamping bodies 29 are present. They have a highest possible spatial density and radial extension in order to achieve a high areal density. Due to the centrifugal forces acting thereby on the clamping bodies during rotation of the dressing mandrel, the pressure of the hydraulic medium is dynamically increased and thereby the clamping force exerted statically on the tool 3 by virtue of the clamping device 2 is reinforced. The radial extension of the clamping bodies 29, however, is limited because of the necessary stability of the shaft 10.

[0068] In the embodiment according to FIG. 3, a two-part hydraulic chamber is used in which, as can be seen in partial figure B, an upper (sub)chamber 21a, which faces the abutment shoulder 14 and a lower chamber 21b are separated from one another by a solid partition wall, with the exception of certain passages for pressure equalization. The partition wall increases the stability of the shaft 10 and thereby the dressing mandrel against external acting forces. In addition to the axial subdivision, a circumferential subdivision into subchambers, as represented in FIG. 4, could also be provided in order to further increase the torsional and bending stiffness of the shaft.

[0069] Shaft 10 has an abutment shoulder 14, which interacts with the fixing disk 16, which is screwed onto the threaded section 15 of the shaft, in order to position and fix the tool 3 in an axial direction. The preclamping element 23 which serves for setting the hydraulic medium pressure is, in this embodiment, realised in that diametrically opposing force transmission elements, in the form of projections 233 in that end face of the abutment shoulder which faces the tool are present and the hydraulic chamber extends at least in offshoots as far as closely below these projections, so that that region of the abutment shoulder that bears the projections yields flexibly with the action of an axial force and thereby reduces the effective volume of the hydraulic chamber. If a circular tool is mounted and axially fixed by mean of screwing on the fixing disk, the axial force exerted by means of the fixing disk is transferred via the circular tool to the projections, which yield elastically and thus reduce the volume of the hydraulic chamber, thereby increasing the static pressure of the hydraulic medium. Additionally to or alternative to this type of preclamping generation, however, a further preclamping element, as used in the clamping screw shown in FIG. 2, could also be used.

[0070] FIG. 4 shows a dressing mandrel of a dressing machine according to the invention, according to a third preferred embodiment with clamping bodies radially above the hydraulic chamber.

[0071] Partial figure A again shows a longitudinal section while partial figures B and C in each case show a cross-section along the lines BB and CC from partial figure A.

[0072] In partial figure A as well as partial figure B, it can be seen that in this embodiment according to the invention, the clamping bodies 29, numbering 4 in total, are disposed above the hydraulic chamber. This serves to increase the distance of the clamping body from the axis of rotation of the dressing mandrel and thereby increase the above-described dynamic clamping effect. The clamping section 22, which is located above the clamping body and of which the outer surface represents the clamping face, is made as thin as possible in order to achieve a high elasticity. This is possible since bending forces acting on the shaft can be absorbed and dissipated by means of the separation sections located between the clamping bodies as well as by means of the clamping bodies. This is possible since the clamping bodies 29, in comparison to the chambers filled with hydraulic medium, which, in the other embodiments shown according to FIGS. 2 and 3, occupy the space that is held by the clamping bodies 29 here, have a significantly higher modulus of elasticity and are dimensionally stable as solid bodies. The clamping bodies 29 in this embodiment have a circular ring segment-shaped cross-section and have a certain radial movement tolerance such that they can effect a clear bulging of the clamping section 22. To achieve guidance of the clamping bodies that is as far as possible free of axial and tangential backlash, and still ensure freedom of the radial movement, a lubricant can be introduced into the cavities that are accommodated in the clamping bodies 29. Alternatively, a roller bearing can also be used.

[0073] The hydraulic chamber is subdivided into four circumferential, rotationally symmetrical subchambers 21.1 to 21.4, which for purposes of pressure equalization are in fluid communication via channels and of which each is assigned to one of the four clamping bodies, namely disposed directly below (see partial figure B). The chamber cross-section can, like that of clamping body 29, correspond to a circular ring segment or else be otherwise designed, with the only provision that the separating cover separating the chamber and the clamping body cavities is sufficiently thin and elastic in order to achieve a corresponding deformation and therefore radial displacement of the clamping body in the event of pressure change in the hydraulic medium chamber. In addition, to increase the resistance force, an axial subdivision of the chambers as in the embodiment according to FIG. 3 could be provided.

[0074] Partial figure C shows a cross-section through the shaft 10 in the region of the thread section 15, in which the fixing disk 16 is located, which, in interplay with the abutment shoulder, positions and fixes the tool 3 in the axial direction. As illustrated, the cross-section of the shaft here departs significantly from a circle: above each of the hydraulic (sub)chambers 21.1-21.4, there is a bulge 151. This is dimensioned such that the radius of the shaft, at the highest point of the bulge, is a little larger than the clear radius of the opening of the fixing disk 16. Since the chamber here, in a similar way to the clamping section, extends below the surface of the shaft, the shaft has a certain elasticity in these bulges 151. During screwing on of the disk, the curvatures are pressed inwardly and the volume of the hydraulic chamber is thus reduced and the pressure of the medium contained therein is correspondingly increased. To achieve a gradual increase of the pressure during screwing on of the disk, the threaded region 15 of the shaft 10 is designed such that its radius gradually increases from the end facing the abutment shoulder. This variation must be adapted to the compliance of the bulges; however will not exceed several percent in general.

[0075] Although this setting of the preclamping could basically be sufficient, force transmission elements are disposed in that end face of the abutment shoulder 14 that faces the tool 3, as additional elements for generating or increasing the static preclamping in a similar way to that shown in FIG. 3. Other than there, however, they consist of bores 231, which extend as far as into the hydraulic chambers 21.1 to 21.4, into which radially displaceable pins 232 are inserted.

[0076] Since the above-described geometry of the threaded section 15 effects a firm relationship between the number of screwed-on rotations of the fixing disk and the (radial) preclamping, it could be that for thin tools, a maximum preclamping is achieved before it is sufficiently axially fixed. It order to be able to compensate for this, a third element, which is not shown here, for setting the static hydraulic medium pressure and thus the preclamping could be provided, for example a clamping screw as in the embodiment in FIG. 2.

LIST OF REFERENCE CHARACTERS

[0077] 1 Dressing mandrel [0078] 10 Shaft [0079] 11 First bearing [0080] 12 Second bearing [0081] 14 Abutment shoulder [0082] 15 Thread section [0083] 151 Protrusion [0084] 16 Fixing disk [0085] 2 Clamping device [0086] 21 Hydraulic medium chamber [0087] 21.1-4 Circumferential subchambers [0088] 21a, 21b Lower, upper subchambers [0089] 22 Clamping section [0090] 23 Clamping element [0091] 231 Bore to receive 232 [0092] 232 Pin [0093] 233 Projection [0094] 29 Clamping body [0095] 292 Outer surface [0096] 3 Tool, grinding disk [0097] 4 Housing [0098] L Longitudinal and rotational axis of the dressing mandrel