EXPANSION DLEEVE FOR A HYDRAULIC EXPANSION CHUCK

Abstract

An expansion sleeve for the sealed insertion into an axial receiving opening of a base body of a hydraulic expansion chuck. The expansion sleeve has a sleeve body extending along a longitudinal central axis, which has a central clamping bore for receiving and clamping a cylindrical shank of a machining tool. On the outer circumference in the region of the clamping bore, the sleeve body has a jacket surface, which forms a radially elastically deformable material web, which revolves in a ring-shaped manner and which delimits a pressure chamber with the inner circumferential surface of the receiving opening. To clamp tools in the large spectrum of shank diameters, in several recesses are formed in the sleeve body radially within the jacket surface, which recesses extend along the longitudinal central axis and are distributed around the clamping bore, preferably spaced apart equiangularly, and are closed with respect to the jacket surface and the clamping bore.

Claims

1. An expansion sleeve for the sealed insertion into an axial receiving opening of a base body of a hydraulic expansion chuck, with a sleeve body extending along a longitudinal central axis, which has a central clamping bore for receiving and clamping a cylindrical shank of a machining tool, wherein on an outer circumference in a length region of the clamping bore, the sleeve body has a jacket surface, which forms a radially elastically deformable material web, which revolves in a ring-shaped manner and which delimits a pressure chamber with an inner circumferential surface of the receiving opening, wherein: several recesses are formed in the sleeve body radially within the jacket surface, which recesses extend along the longitudinal central axis and are distributed around the clamping bore, and are closed with respect to the jacket surface and the clamping bore.

2. The expansion sleeve according to claim 1, wherein the material web has, radially on an outer side, two annular grooves, which stand at an axial distance from one another.

3. The expansion sleeve according to claim 1, wherein the recesses are connected to one another by means of a circumferential annular gap (52).

4. The expansion sleeve according to claim 1, wherein on the inner circumference, the sleeve body has several coolant/lubricant slots, which are open towards the clamping bore and which are distributed around the clamping bore and extend over the entire length of the clamping bore.

5. The expansion sleeve according to claim 4, wherein the coolant/lubricant slots and the recesses are present in equal numbers.

6. The expansion sleeve according to claim 5, wherein the recesses extend so far radially inwards in a radial direction that they overlap radially with the coolant/lubricant slots.

7. The expansion sleeve according to claim 1, wherein the recesses are filled with a damping material.

8. The expansion sleeve according to claim 1, wherein the recesses are formed by closed chambers and/or are formed by radial webs of several sub-chambers lying axially one behind the other.

9. The expansion sleeve claim 1, wherein the sleeve body has, on one axial end, a collar, which extends radially beyond the jacket surface for abutting against the base body of the hydraulic expansion chuck.

10. The expansion sleeve according to claim 9, wherein the collar delimits an annular groove in the jacket surface.

11. The expansion sleeve according to claim 1, wherein a length of at least one of the recesses measured in a direction of the longitudinal central axis lies in the range of 0.8 to 0.9 times a length of the clamping bore.

12. The expansion sleeve according to claim 11, wherein the clamping bore has an axially internal end section with expanded inner diameter, whereby an effective clamping length results, which is shortened with respect to the length of the clamping bore and which is smaller, the smaller the diameter of the clamping bore.

13. The expansion sleeve according to claim 1, wherein the recesses extend essentially over an entire axial length of the jacket surface in axial direction.

14. The expansion sleeve according to claim 1, wherein a radial extension of the recesses corresponds to half a wall thickness of the material web.

15. A hydraulic expansion chuck with a base body extending along a longitudinal central axis and an expansion sleeve according to claim 1, which is inserted into an axial receiving opening in the base body with a defined joining clearance.

16. The expansion sleeve according to claim 1, wherein the recesses are distributed around the clamping bore, spaced apart equiangularly.

17. The expansion sleeve according to claim 2, wherein the two annular grooves lie close to axial end sections of the clamping bore.

18. The expansion sleeve according to claim 3, wherein annular gap connects radially outer end regions of the recesses.

19. The expansion sleeve according to claim 4, wherein the coolant/lubricant slots are spaced apart equiangularly.

20. The expansion sleeve according to claim 5, wherein the coolant/lubricant slots and the recesses are arranged centrally offset angularly from the recesses.

Description

[0027] Exemplary embodiments of the invention are explained in more detail below on the basis of schematic drawings, in which:

[0028] FIG. 1 shows a sectional view of a hydraulic expansion chuck with inserted expansion sleeve according to a first embodiment;

[0029] FIG. 2 shows the detail II in FIG. 1 in enlarged illustration;

[0030] FIG. 3 shows a longitudinal section according to III-III in FIG. 4 of the expansion sleeve used in the exemplary embodiment according to FIGS. 1 and 2;

[0031] FIG. 4 shows a front view of the expansion sleeve according to FIG. 3;

[0032] FIG. 5 shows the sectional view according to V-V in FIG. 4;

[0033] FIG. 6 shows the view of the section VI-VI in FIG. 5; and

[0034] FIG. 7 shows a sectional view, which is similar to FIG. 3, of a modified exemplary embodiment of the expansion sleeve.

[0035] A hydraulic expansion chuck, which has a base body 12, into which an expansion sleeve 30 with the central axis A30 is inserted, is identified with reference numeral 10 in FIG. 1. In the shown exemplary embodiment, the hydraulic expansion chuck with the central axis A10 is equipped with a hollow shank taper (HSK) 14 and is designed for an internal coolant/lubricant (KSM) supply. For this purpose, a KSM sleeve 18 is screwed into a central bore 16 of the base body 12, which protrudes into the expansion sleeve 30. It is important to note at this point that the hollow shank taper 14 is not crucial and the hydraulic expansion chuck can have a different clamping shank, for example a cylinder shank or steep shank taper, instead of the hollow shank taper 14. It is furthermore noted that an internal coolant/lubricant supply is not important for the invention.

[0036] The base body 12 of the hydraulic expansion chuck 10 has a receiving opening 31 with an inner surface 32 for the expansion sleeve 30, which is formed so that it delimits a closed pressure chamber 22, which is filled with pressurized fluid, of the length L22, in cooperation with the jacket surface 44 of the inserted expansion sleeve 30. This pressure chamber 22 is connected via a radial branch channel 24 to an axial pressurized fluid supply channel 26, via which pressurized fluid can be fed from a pressure generating chamber 28, which receives an actuating piston, into the pressure chamber 22.

[0037] The expansion sleeve 30 is inserted into the receiving opening 32 in a centered and sealed manner in such a way that not only the pressure chamber 22 but also the bore of the axial pressurized fluid supply channel 26 is closed. In the axially internal region, the expansion sleeve 30 has a first joining cylinder section 34, and, on the front side, a second joining cylinder section 36 in the design as radial collar, which is connected by means of a substance-to-substance bond, for example soldered, to the base body 12 of the hydraulic expansion chuck 10 for sealing the pressure chamber. A corresponding connection between expansion sleeve 30 and base body 12 can be selected in the region of the first joining cylinder section 34. The joining cylinder sections 34 and 36, via which the soldering to the base body 12 of the hydraulic expansion chuck takes place, are processed with high concentricity. The fits and tolerance specifications are selected so that the axes A10 and A30 in the assembled state of the expansion sleeve 30 are aligned as precisely as possible, so that the tool tension is ensured with the largest possible concentricity.

[0038] The structure of the expansion sleeve 30 will be described in more detail below with reference to FIGS. 2 to 5:

[0039] The expansion sleeve 30 has a sleeve body with three sections. An essentially circular cylindrical, radially elastically deformable material web 42, which revolves in a ring-shaped manner, lies between the joining cylinder sections 34 and 36, the radially external jacket surface 44 of which delimits the pressure chamber 22 when the expansion sleeve 30 is inserted in a fluid-tight manner into the base body 12 of the hydraulic expansion chuck 10. On the inner side, the material web 42 forms a circular cylindrical clamping bore or clamping cavity 40, respectively, for receiving and for clamping a tool shank. In the following, this centric clamping cavity will be identified throughout as clamping bore even if it is not manufactured as bore. The axial length of the clamping bore 40 is identified with L40 and it corresponds essentially to the length L22 of the pressure chamber 22. The diameter of the clamping bore is identified with D40 in FIG. 4.

[0040] It can be seen from FIG. 3 that the clamping bore 40 in the shown exemplary embodiment is slightly expanded in the inner diameter on its end region 41 facing the joining cylinder section 34, so that an effective clamping length L40* results, which is shortened with respect to the measure L40. The shortening to the measure L40* is selected to be larger, the smaller the shank diameter of the tools to be clamped. This expansion of the clamping bore 40, however, is not an absolutely necessary feature, so that the inner diameter of the clamping bore 40 could also be identical over the entire length L40 of the clamping bore 40, whereby the effective clamping length L40* would be identical to the length L40.

[0041] Adjoining the joining cylinder sections 34 and 35, an annular groove 46 or 48, respectively, is in each case formed in the jacket surface 44. The annular grooves 46, 48 lying axially at a distance from one another, thus lie close to the axial end sections of the clamping bore 40 and, in the inserted state of the expansion sleeve 30as can be seen in FIGS. 1 and 2they form radial widenings of the pressure chamber 22 and weaken the wall thickness W42 of the material web 42 on the axial end regions, whereby the resilience of the material web 42 in response to pressurization of the pressure chamber 22 is increased and the stiffness of the material web 44 is simultaneously raised in its central section. In the illustrated exemplary embodiment, the annular groove 48 extends into the region of the joining cylinder section 3, which is formed as collar, which radially protrudes beyond the jacket surface 44.

[0042] To control the radial constriction of the clamping bore 40 when applying pressurized fluid to the pressure chamber 22, several recesses 50 are formed in the material web 42 essentially centrally radially within the jacket surface 44, which recesses extend along the longitudinal central axis A30 and are distributed around the clamping bore 40, preferably spaced apart equiangularly, and are closed with respect to the jacket surface 44 and the clamping bore 40. In the shown exemplary embodiment, six such chambers 50 are provided, as can be seen from FIGS. 4 to 6, which are arranged at an angular distance of 60 from one another and which have a height H50, an axial length L50 and a width B50.

[0043] The recesses in the design of closed chambers 50 are connected to one another by means of a narrow, circumferential annular gap 52, wherein the annular gap 52 connects the radially outer end regions of the recesses 50. The radial width W52 of the annular gap 52 lies in the fraction range of one millimeter, for example between 0.1 and 0.3 mm.

[0044] In the central angular offset from the recesses 50, the sleeve body has, on the inner circumference, several regularly narrow coolant/lubricant slots 54, which are open towards the clamping bore 40 and which are distributed around the clamping bore and extend over the entire length of the sleeve body, so that coolant/lubricant (KSM) can flow along the clamped-in tool shank through the expansion sleeve 30 to the tool cutting edges. Due to the dimensioning and position of these coolant/lubricant slots 54, the radial resilience of the material web 42 can simultaneously be influenced or can be adapted to the deformation characteristic of the expansion sleeve 30, which is specified by means of the recesses 50.

[0045] The width B54 of the coolant/lubricant slots 54 routinely also lies within the millimeter range. In the case of an inner diameter of the clamping bore 40 of 3 mm, the measure B54 lies within ranges of 0.3 to 0.4 mm.

[0046] In the shown exemplary embodiment, the coolant/lubricant slots 54 and the recesses 50 are pulled so far radially outwards or inwards, respectively, that they slightly overlap one another in the radial direction.

[0047] In the shown exemplary embodiment, the recesses 50 are designed as hollow spaces. Tests have shown that the vibration tendency of a tool clamped into the hydraulic expansion chuck can be limited effectively when the recesses 50 are filled with a damping material. This filling can be formed most easily in that the sleeve body of the expansion sleeve 30 is formed in one piece by using a generative manufacturing method, such as, e.g., a 3D printing method. In that case, the recesses 50 have a closed design and are filled with non-solidified, molten or sintered, respectively, powdery material. The annular gap 52 also remains filled with powdery material thereby.

[0048] In tests, the following dimensions have turned out to be particularly advantageous:

[0049] The length L50 of the recesses 50 measured in the direction of the longitudinal central axis should lie in the range of 0.8 to 0.9 times the length L40 of the clamping bore 40.

[0050] The recesses 50 should preferably extend essentially over the entire axial length of the jacket surface 44 in the axial direction.

[0051] The radial extension H50 of the recesses 50 should essentially correspond to half the wall thickness W42 of the expansion sleeve 30, i.e., of the material web 42.

[0052] The above-described expansion sleeve 30 can be used to clamp tool shanks with a wide diameter spectrum. Special advantages compared to hydraulic expansion chucks, which operate with intermediate bushings, result when tools with very small shank diameters, for example of below 6 mm to below 2.5 mm are clamped. Exemplary dimensions are specified below for a hydraulic expansion chuck of this type.

[0053] The expansion sleeve 30 with an inner diameter D40 of the clamping bore 40 of 2.75 mm has an outer diameter of the material web 44 of 11 mm. The wall thickness W42 of the material web 42 thus lies in the range of 4 mm, in the region of the annular grooves at 3.55 mm. The total length of the expansion sleeve 30 is approximately 30 mm, the axial length of the radially elastically deformable material web and thus the axial extension L50 of the six recesses or chambers 50, respectively, which are evenly distributed over the circumference, lies at approximately 20 mm, the height H50 thereof at approximately 1.75 mm. The width B50 of the recesses 50 is approximately 1.5 mm. The length L40 of the clamping bore 40 then lies at approximately 24 mm, the effective clamping length L40* at approximately 17 mm. The cooling/lubricant slots 54, which are angularly offset from the recesses 50 by 30, have a width B54 of 0.75 mm and a radial extension of approximately 1 mm. The annular gap 52 was embodied with a width W52 of 0.18 mm.

[0054] It has become apparent during the generative manufacture of the expansion sleeve that advantageous results can be obtained with the use of steel powders, the particle size of which lies in the range of between 30 and 60 m, for example at 50 m. In order to keep the solder connection to the base body 12 of the hydraulic expansion chuck 10 permanent and highly resilient, it is advantageous to obtain the steel powder from the same material as that of the base body 12 of the hydraulic expansion chuck 10. Goods results with respect to elasticity and fatigue strength were attained with powders with particle sizes of 30 m and 50 m from the hot working steel X37CrMoV5-1 (material No. 1.2342). This material was machined at precision after suitable heat treatment by means of a stress relief heat treatment and was inserted into the base body of the hydraulic expansion chuck by means of a high-temperature soldering in the vacuum. Lastly, selected functional surfaces of the expansion sleeve were subjected to a curing and were annealed with low tension again.

[0055] Tests with a shank diameter of 4 mm were able to confirm that torques of 7.5 Nm at concentricity in the range of 0.002 to 0.004 mm can be realized by means of a hydraulic expansion chuck, which was fitted with an expansion sleeve of the above-described expansion sleeve structure.

[0056] It goes without saying that deviations from the described exemplary embodiment are possible without leaving the basic idea of the invention.

[0057] The recesses can thus have a cross section, which deviates from the shown rectangular cross section. They can also have at least one radial web, wherein the web can subdivide the chambers into sub-chambers lying axially one behind the other. In addition, the recesses 50 also do not have to be closed. FIG. 7 shows a variation, which is almost identical with respect to the structure to the embodiment according to FIG. 3, but in the case of which the recesses 150 are closed only on the side facing the joining cylinder section 134. The recesses can also be filled with a damping material.

[0058] Deviating from the above-described exemplary embodiment, the recesses can also run helically, at least in sections.

[0059] Deviating from the above-described exemplary embodiment, the recesses 50 and/or the annular gap 52 can be empty, i.e., not be filled with powdery material.

[0060] The invention thus creates an expansion sleeve for the sealed insertion into an axial receiving opening of a base body of a hydraulic expansion chuck. The expansion sleeve has a sleeve body, which extends along a longitudinal central axis and which has a central clamping bore for receiving and clamping a cylindrical shank of a machining tool. On the outer circumference in the region of the clamping bore, the sleeve body has a jacket surface, which forms a radially elastically deformable material web, which revolves in a ring-shaped manner, and which delimits a pressure chamber with an inner circumferential surface of the receiving opening. In order to be able to clamp tools in the large spectrum of shank diameters, in particular also with very small shank diameters with controllable pressures in the pressure chamber, several recesses are formed in the sleeve body radially within the jacket surface, which recesses extend along the longitudinal central axis and are distributed around the clamping bore, preferably spaced apart equiangularly, and are closed with respect to the jacket surface and the clamping bore.