The invention relates to a hydraulic expansion chuck (1) with a hydraulic expansion mechanism (23) that is integrated into a chuck body (10, 20) and exhibits an expansion bushing (23a) with a continuous cylindrical interior wall, and to a reducing bushing (24) arranged in the expansion bushing (23a) for accommodating a shank tool (W), in particular a tap drill. According to the invention, the outer circumference of the reducing bushing (24) is positively connected with the chuck body (10, 20) in a torque-proof manner, and its inner circumference is designed to be positively connected with the shank tool (W) in a torque-proof manner.

The invention relates to a hydraulic expansion chuck with a hydraulic expansion mechanism that is integrated into a chuck body and exhibits an expansion bushing with a continuous cylindrical interior wall, and to a reducing bushing arranged in the expansion bushing for accommodating a shank tool, in particular a tap drill.

Such hydraulic expansion chucks are known from WO 2012/013629 A1 or the 2009 product catalogue of the applicant, for example. In order to be able to reliably transfer high torques of up to 50 Nm to the shank tool with such a hydraulic expansion chuck, a continuously round shank without lateral flatted areas having a diameter tolerance in the h6 range is usually recommended. By contrast, a lower diameter tolerance can significantly reduce the torque transmission capacity. It was discovered that a torque of up to 15 Nm can now be transmitted at a diameter tolerance in the h9 range with a conventional hydraulic expansion chuck.

In addition, it is recommended that a reducing bushing be used in particular for shanks with a lateral flattened area, e.g., according to DIN 6535 Form HB or HE, and for bridging a diameter difference between the (larger) inner diameter of the expansion bushing and the (smaller) outer diameter of the shank of a shank tool to be clamped into the hydraulic expansion chuck. An axially central length section of a conventional reducing bushing exhibits a plurality of longitudinal slots equidistantly distributed around the circumference of the reducing bushing, which make it possible to uniformly distribute the expansion force in a circumferential direction from the expansion bushing of the hydraulic expansion mechanism to the shank tool accommodated in the expansion bushing. The longitudinal slots are concentrated on an axially central length section. Such a reducing bushing can increase the permissibly transferable torque by comparison to direct clamping, provided a shank tolerance of h6 is maintained.

However, a diameter tolerance in the h6 range is not common for tap drill shanks. The shanks of tap drills are usually fabricated with a diameter tolerance in the h9 range. Therefore, a clearly diminished torque transmission capacity results for these kinds of tap drills during use with a conventional hydraulic expansion chuck. For example, the torque transmission capacity could basically be increased by having the shank of the tap drill exhibit a lateral entraining surface, e.g., according to the aforementioned DIN 6535 Form HB or HE, and by modifying the hydraulic expansion chuck, e.g., guided by the instruction described in the aforementioned WO 2012/013629 A1. This publication proposes a torque-proof arrangement for a shank tool clamped in a hydraulic expansion chuck, in which an entrainer screw that is held in the base body of a hydraulic expansion chuck in a radially adjustable manner and guided through a radial opening in the expansion bushing is positively engaged with a lateral entraining surface on the shank of the shank tool. However, such a modification is associated with a considerable structural and financial outlay, and entails both a weakening of the base body due to the threaded hole in the base body, and a non-uniform clamping of the shank tool due to the radial opening in the expansion bushing.

Therefore, the object of the invention is to further develop a conventional hydraulic expansion chuck with a hydraulic expansion mechanism that is integrated in a chuck body and exhibits an expansion bushing with a continuous cylindrical interior wall without a radial opening in a cost effective and structurally simple manner, so as to produce a reliable clamping between a shank tool, in particular a tap drill, and a shank fabricated with a larger diameter tolerance, i.e., h9, for example, which has a quality corresponding to a significantly tighter diameter tolerance, e.g., h6, and enables the transmission of a higher torque. This object is achieved by a hydraulic expansion chuck according to claim1. Advantageous further developments are the subject of dependent claims.

A hydraulic expansion chuck according to the invention exhibits a hydraulic expansion mechanism, which is integrated in a chuck body, and has an expansion bushing along with a reducing bushing arranged in the expansion bushing for accommodating a shank tool, in particular a tap drill.

The primary area of application for the hydraulic expansion chuck according to the invention involves thread generation, in particular via tapping or thread molding. In particular, a hydraulic expansion chuck according to the invention is thus designed in such a way as to enable an axial compressive/tensile force length compensation, and advantageously also a torque compensation, in order to compensate for synchronization errors between the spindle feed and pitch of the thread to be fabricated, as is usually the case for screwing chucks. In a preferred embodiment, the chuck body can be divided into a base body and a receptacle joined with the base body at least in an axially elastic, preferably in a torsionally and axially elastic, manner, wherein the hydraulic expansion mechanism with the reducing bushing accommodated in the expansion bushing is integrated into the receptacle. However, the hydraulic expansion chuck according to the invention is not limited to use for thread generation, but rather is universally suitable for various shank tools, e.g., drills, milling cutters, etc.

According to the invention, the outer circumference of the reducing bushing is positively connected with the chuck body in a torque-proof manner, either directly or indirectly by means of the expansion bushing immovably fixed in the chuck body, while its inner circumference is designed to be positively connected with the shank tool in a torque-proof manner. The resultant twofold positive fit achieved for the reducing bushing—with the chuck body of the hydraulic expansion chuck on the one hand and with the shank of a shank tool to be clamped in the hydraulic expansion chuck on the other-yields a reliable, torque-proof accommodation of the shank tool in the hydraulic expansion chuck that basically does not depend on the tolerance for the shank diameter of the shank tool. By comparison to conventional hydraulic expansion chucks, the solution according to the invention hence enables the transmission of higher torques without any additional torque entrainers for a larger tolerance field, e.g., h9, with respect to the shank diameter of the shank tool to be clamped, which could previously only be accomplished with significantly tighter tolerances, e.g., h6. In addition, the solution according to the invention makes it possible to clamp various shank diameters into one and the same hydraulic expansion chuck due to the reducing bushing.

Conventional hydraulic expansion chucks can be modified relatively easily by replacing or reconfiguring the expansion bushing in such a way as to obtain the twofold positive fit mentioned above between the expansion bushing and reducing bushing, or between the reducing bushing and shank tool.

Because of the positive fit between the reducing bushing and chuck body on the outer circumference, the hydraulic expansion chuck according to the invention also offers the option to centrally supply coolant/lubricant along the rotational axis of a feed site on the machine tool spindle side, through the hydraulic expansion chuck and to a clamped shank tool. For example, a known MQL (minimum quantity lubrication) transfer system can be used for this purpose.

Therefore, the invention makes it possible to modify, in a structurally easily manageable, and hence cost effective manner, a conventional hydraulic expansion chuck in such a way that a shank tool having a shank fabricated with a larger diameter tolerance, e.g., h9, can be clamped with a level of quality that corresponds to a significantly tighter diameter tolerance, e.g., h6, and permits the transmission of higher torques. In addition, the hydraulic expansion chuck enables a central supply of coolant/lubricant to a clamped shank tool.

As already mentioned, the reducing bushing can positively connected with the chuck body either directly or indirectly via the expansion bushing of the hydraulic expansion mechanism rigidly accommodated in the chuck body. The indirect positive fit by way of the expansion bushing is to be preferred from a manufacturing standpoint, since the expansion bushing is easy to access for machining before it is integrated into the chuck body.

In a currently preferred further development of the hydraulic expansion chuck according to the invention, the positive connection between the reducing bushing and chuck body is provided on a longitudinal end section of the reducing bushing, in particular the axially interior one. In this further development, the outer circumferential positive fit can be realized without any problem, for example on a reduced-diameter inner longitudinal end section of the reducing bushing. To this end, the inner longitudinal end section can thus have a smaller outer diameter by comparison to the axially outer longitudinal end section and a central longitudinal section lying between the inner and outer longitudinal end section. The smaller diameter of the inner longitudinal end section shortens the length of the central longitudinal section of the reducing bushing that is to be machined to fit and used for transmitting the radial clamping force from the expansion bushing to a shank tool. The positive fit can be achieved by means of an outer polygonal profile, preferably an outer two-edge profile (also referred to as width across flats or outer dihedral), on the reduced-diameter longitudinal end section, which is positively accommodated in a corresponding inner polygonal profile, preferably an inner two-edge profile (also referred to as inner dihedral), of the chuck body. Because the positive fit between the reducing bushing and chuck body is shifted to a longitudinal end section, the axially central longitudinal section of the reducing bushing can continue to be used without limitation to transfer the force from the expansion bushing of the hydraulic expansion mechanism to the shank tool, thereby ensuring a uniform distribution of the clamping force via the reducing bushing to the shank tool.

Similarly to the positive fit between the reducing bushing and chuck body, the positive connection between the reducing bushing and shank tool is preferably provided on a longitudinal end section of the reducing bushing, in particular the axially interior one. To this end, the reducing bushing can exhibit an inner polygonal profile, preferably an inner four-edge profile, for the positive accommodation of an outer polygonal profile, preferably an outer four-edge profile, at the shank end of the shank tool.

The torsion of the reducing bushing can be minimized or prevented by axially restricting the position of the positive connection between the reducing bushing and chuck body, and of the positive connection between the reducing bushing and shank tool, to a shared longitudinal section of the reducing bushing, in particular the axially interior one.

The axially outer longitudinal section of the reducing bushing can further exhibit a supporting flange that axially abuts against a tool-side face of the chuck body. This makes it possible to axially restrict the axial position of the reducing bushing inside the expansion bushing of the hydraulic expansion mechanism, and hence the axial position of a clamped shank tool relative to the chuck body.

The attached drawings will be used below to describe an embodiment of a hydraulic expansion chuck according to the invention.

FIGS. 1 to 4show an embodiment of a hydraulic expansion chuck1according to the invention.FIGS. 5ato 5eand6show a detailed view of a reducing bushing24arranged in the hydraulic expansion chuck1according to the invention.

The hydraulic expansion chuck has an essentially two-part chuck body, which consists of a base body10and receptacle20, and is shown in detail onFIG. 2andFIG. 4. The base body10and receptacle20are joined together in a torsionally elastic manner for torque transmission by way of a torque entrainment device, and in an axially elastic manner for axial length compensation by way of a spring arrangement40. The hydraulic expansion chuck1further exhibits a centrally arranged coolant transfer unit50that extends along the rotational axis2.

The base body10is functionally divided into a shank section11and a bushing section12, which extend along the rotational axis2of the hydraulic expansion chuck1. The shank section11is used for coupling the hydraulic expansion chuck1to a shank tool machine spindle (not shown) or a shank tool module (also not shown) of a modularly designed shank tool system. To this end, the shank section11has a hollow shank taper13with an axial interior recess14and a central recess in the form of a stepped bore15that can be accessed via the interior recess14and is open on the machine tool side. In the direction of the receptacle20(from right to left onFIG. 2andFIG. 4), the stepped bore15exhibits a threaded hole section15athat empties into the interior recess14of the hollow shank taper13, as well as a cylindrical hole section15bwith a smaller diameter that adjoins the threaded hole section15a. The cylindrical hole section15bincorporates one (42) of two spring elements41,42of the spring arrangement40. The bushing section12that axially lengthens the shank section11in the direction of the receptacle20-exhibits a central guide borehole16that is open on the tool side. The guide borehole16is separated from the axial recess15of the shank section11by a radial dividing wall17. The guide borehole16incorporates the other (41) of the two spring elements41,42of the spring arrangement40. An axial opening in the form of a central through borehole18is provided in the dividing wall17. The guide borehole16of the bushing section12, the through borehole18in the radial dividing wall17, along with the central recess15and interior recess14of the shank section11all extend along the rotational axis2of the hydraulic expansion chuck1.

The receptacle20is functionally divided into a receiving section21and a guide section22, which extend along the rotational axis2of the hydraulic expansion chuck1. The receiving section21is used to accommodate and clamp a tool W shown only onFIG. 1, and to this end exhibits a known hydraulic expansion mechanism23.

In a manner known in the art, the hydraulic expansion mechanism23encompasses a sleeve-like expansion bushing23athat is permanently soldered into the receptacle20or immovably arranged therein in some other way, and has a continuously smooth cylindrical inner wall, which tightly seals a hydraulic expansion chamber23bformed in the receptacle20. As a result, the expansion bushing23aforms a one-piece constituent of the receptacle20or chuck body. When the hydraulic expansion chamber is pressurized, the expansion bushing23aexpands from the inside out due to a flexible bushing wall23cin its axially central longitudinal section, which positively clamps a reducing bushing24precisely fitted in the expansion bushing. For this purpose, the axially central longitudinal section24gof the reducing bushing24(seeFIG. 5a, 5c) has a plurality of longitudinal slots24bequidistantly distributed around the circumference of the rotational axis2of the hydraulic expansion chuck1, which enables a circumferentially uniform distribution and transmission of the expansion force exerted by the expansion bushing23aof the hydraulic expansion mechanism23to a shank tool shank W accommodated in the expansion bushing23a(seeFIG. 1).

In contrast, the front or outer longitudinal end section24cin the tool feed direction (from right to left onFIG. 1, 2, 4) as well as the rear and/or inner longitudinal end section24dof the reducing bushing24in the tool feed direction are continuous in the circumferential direction, i.e., have no slots. As evident onFIGS. 5ato 5e, the inner ends of the longitudinal slots24beach terminate in a radial borehole24e, which is formed through the sleeve wall of the reducing bushing24, while the outer ends each terminate in a concave depression or recess24faxially worked into the reducing bushing24from the front face. Aside from the longitudinal slots24band radial boreholes24e, the axially central longitudinal section24gof the reducing bushing24is continuously cylindrical, i.e. it in particular exhibits no lateral flattened areas, entrainer surfaces, etc. By comparison to the central longitudinal section24g, the diameter of the frontal or outer longitudinal end section24cis enlarged by a radial supporting flange24h, while the diameter of the rear or inner longitudinal end section24dis slightly diminished.

The reducing bridge24bridges the difference in diameter between the inner diameter of the expansion bushing23aand the outer diameter of the shank of a shank tool W to be clamped (seeFIG. 1), and provides for a positive torque entrainment of the shank tool in the hydraulic expansion chuck1. According to the invention, the outer circumference of the reducing bushing24is for this purpose positively connected in a torque-proof manner with the chuck body, in particular the receptacle20of the chuck body. In the embodiment, the positive connection between the reducing bushing24and the receptacle20is provided at the axially rear or inner reduced-diameter longitudinal end section24dof the reducing bushing24. The outer circumferential positive fit can be realized on the reduced-diameter inner longitudinal end section24dof the reducing bushing24without any problem. To this end, the reducing bushing24in particular has an outer polygonal profile in the form of an outer two-edge [profile]24i, which is positively accommodated in a corresponding inner polygonal profile in the form of an inner two-edge [profile]23din the expansion bushing23arigidly incorporated in the receptacle20(seeFIG. 3,FIG. 5e).

According to the invention, a shank tool W to be clamped is further clamped in the hydraulic expansion mechanism23by means of the reducing bushing24with a positive torque entrainment between its shank and the reducing bushing24. To this end, the inner circumference of the reducing bushing24has an inner four-edge contour24afor the positive accommodation of an outer four-edge section visible onFIG. 3at the shank end of the shank of the shank tool W. In the embodiment, the positive connection between the reducing bushing24and the shank tool W is provided on the inner or rear longitudinal end section24dof the reducing bushing24.

The twofold positive fit of the reducing bushing—with the receptacle20of the chuck body of the hydraulic expansion chuck1on the one hand and with the shank of a shank tool W to be clamped in the hydraulic expansion chuck1on the other—already yields a reliably torque-proof arrangement of the shank tool W in the hydraulic expansion chuck1that basically does not depend on the size of the tolerance field—e.g., whether it be h9 or h6—for the shank diameter of the shank tool W. As a consequence, torque transmission from the chuck body (base body10and receptacle20) to the shank tool W is first and foremost achieved by the twofold positive fit between the reducing bushing24and chuck body (base body10and receptacle20), and between the reducing bushing24and shank tool W. Therefore, the non-positive fit achieved by the hydraulic expansion mechanism1between the reducing bushing24and expansion bushing23amust essentially still only ensure the transfer of axial tensile/compressive forces from the chuck body to the shank tool W.

By comparison to conventional hydraulic expansion chucks, the solution according to the invention hence enables the transmission of higher torques for a larger tolerance field, e.g., h9, with respect to the shank diameter of a shank tool W to be clamped, which had previously basically only been possible with significantly tighter tolerances, e.g., h6. In addition, the solution according to the invention makes it possible to clamp various shank diameters into one and the same hydraulic expansion chuck1due to the reducing bushing. Therefore, the invention makes it possible to modify, in a structurally easily manageable, and hence cost effective manner, a conventional hydraulic expansion chuck in such a way that a shank tool W having a shank fabricated with a larger diameter tolerance, e.g., h9, can be clamped with a level of quality that corresponds to a significantly tighter diameter tolerance, e.g., h6, and permits the transmission of higher torques.

The torsion of the reducing bushing24can be minimized by axially restricting the position of the positive connection between the reducing bushing24and chuck body, and of the positive connection between the reducing bushing24and shank tool W, to a shared longitudinal section of the reducing bushing24, in particular the inner or rear longitudinal end section24dof the reducing bushing24.

The front or outer longitudinal end section24cof the reducing bushing24has the aforementioned radially projecting supporting flange24h, which axially abuts against a tool-side face of the receptacle20, as may be gleaned in particular fromFIG. 6, for example. The supporting flange24hestablishes the position of the reducing bushing24within the expansion bushing23aof the hydraulic expansion mechanism23, thereby also restricting the axial position of a clamped shank tool W relative to the chuck body. The outer circumference of the reducing bushing24exhibits an annular groove24k, which is situated axially within the supporting flange24hbetween the outer or front longitudinal end section24cand the central longitudinal section24g, and is incorporated in an O-ring gasket241that seals the joint play between the reducing bushing24and expansion bushing23a.

The cylindrical guide section22that lengthens the receiving section21in the direction of the base body10is accommodated in the guide borehole16of the base body in an axially movable manner with a defined lateral play. The annular gap between the outer circumference of the guide section22of the receptacle20and the inner circumference of the guide borehole16of the base body10is sealed by means of two O-ring gaskets25a,25b, which are each accommodated in an outer circumferential annular groove22a,22bof the guide section22. The guide section22has running through it a central stepped bore26, which in the direction of the base body10(from left to right onFIG. 2andFIG. 4) exhibits a cylindrical hole section26a,a threaded hole section26bwith a smaller diameter, and a threaded hole section26cwith a larger diameter.

The receptacle20is anchored in the base body10via the anchor30. The anchor30is functionally divided into an anchor shank31that extends through the through borehole18in the radial dividing wall17of the base body10and an anchor head32situated on the anchor shank31. In the embodiment, the anchor30is designed like a cap screw. The anchor shank31is screwed into the larger-diameter threaded hole section26cof the guide section22of the receptacle20by way of a male thread provided on its tool-side end section31a, and accommodated with a defined lateral play in the through borehole18of the radial dividing wall17in an axially and rotationally movable manner by means of a cylindrical middle section31b. As a result, the anchor30provides the receptacle20with an additional axial guide in the base body10. The anchor head32has a cylindrical outer circumference32a, and forms a stop for the spring element42. The anchor shank31and anchor head32are designed as a single piece in the embodiment. Therefore, the anchor30is bolted to the receptacle20so that it can be displaced axially relative thereto. An axial through borehole in the form of a stepped bore33runs through the anchor30. The stepped bore33exhibits a hole section33awith a larger diameter, a hexagon socket section33band a hole section33cwith a smaller diameter in the direction of the receptacle20(viewed from right to left onFIG. 2andFIG. 4). A matching shank tool wrench can be introduced into the hexagon socket section33bonFIG. 2andFIG. 4from the right via the interior recess14in the hollow shank taper13, the recess15in the shank section11of the base body10, and the larger-diameter hole section33aof the stepped bore33in the anchor30, so as to axially adjust the anchor30via bolting in the base body10.

As already mentioned, the spring arrangement40that generates the spring preload between the base body10and receptacle20is realized by the two spring elements41,42, wherein the spring element41is situated between the machine tool-side face of the guide section22of the receptacle20and the tool-side face of the radial dividing wall17of the base body10, and the spring element42is located between the machine tool-side face of the radial dividing wall17and the tool-side face of the anchor head32of the anchor30. The two spring elements41,42are each designed as a spring packet comprised of several plate springs made out of metal and/or polymer material, and have the same spring characteristics. In particular,FIG. 2andFIG. 4show that the spring packets are each composed of three plate springs, which are connected in series as a whole, but with two of the three plate springs being connected in parallel. The anchor shank31extends centrally through the two spring elements41,42. The two spring elements41,42provide for a small axial distance between the base body10and receptacle20that is required for axial length compensation, and enable length compensation in both the compressive and tensile directions along the rotational axis2of the hydraulic expansion chuck1. Bolting the anchor30relative to the receptacle20brings about a synchronous change in the spring preload or spring travel of the two spring elements41,42. As mentioned above, the anchor30is actuated by means of a suitable shank tool wrench via the interior recess14of the hollow shank taper13and the central recess15of the shank section11adjacent thereto in order to set the spring preload of the spring arrangement40.

The axially opposing faces10a,20aof the base body10and receptacle20are positively and non-positively joined together in the rotational direction for transmitting the torque between the base body10and receptacle20. The positive and non-positive connection between the opposing faces10a,20bof the base body10and receptacle20is realized by two diametrically arranged cylindrical entrainer pins61,62, which axially project from the face10aof the base body and engage into opposing engagement boreholes61a,62a(engagement openings) on the receptacle20in an axially movable manner. The two entrainer pins61,62are each arranged over a fitting sleeve61c,62cthat is made out of an elastic polymer material and rests in an axial receiving borehole61b,61c(receiving opening) on the base body10, and each engage in an axially movable manner into a fitting sleeve61d,62dthat is made out of an elastic polymer material and inserted into the allocated engagement borehole61a,62aon the receptacle20. Therefore, the base body10and receptacle20are not rigidly connected with each other in a rotational or torsional direction, but rather joined together in a torsion-attenuated and rotationally elastic manner due to the elastic fitting sleeves61c,62c,61d,62d. As shown onFIG. 2andFIG. 4, the positive and non-positive connection between the base body10and receptacle20realized by the entrainer pins61,62is established radially outside of the guide section22of the receptacle20when viewed axially, making it possible to transmit a high torque.

As further evident fromFIG. 2andFIG. 4, the face10aof the bushing section12of the base body10has an annular projection10bthat runs around the outer circumference and envelops a cylindrical projection20bof the face20aof the receptacle20with a defined lateral play. An O-ring gasket27rests on the outer circumference of the cylindrical projection20bof the receptacle20a. As a consequence, the O-ring gasket27is situated between the annular surface20cthat envelops the cylindrical projection20bof the receptacle20and faces the base body10and the face of the annular projection10bof the bushing section12of the base body10that faces the receptacle20. The O-ring gasket27produces a seal for the axial gap between the base body10and receptacle20, which is necessary for length compensation and ensured by the spring preload, and provides for an axial attenuation between the receptacle20and base body10. In addition to the axial guidance by the guide section22of the receptacle20accommodated in the guide borehole16of the bushing section12, the axial engagement by the cylindrical projection20bof the receptacle20into the annular projection10bof the bushing section12of the base body10yields a further, if only slight, axial guidance of the receptacle20relative to the base body10.

The hydraulic expansion chuck1shown onFIG. 1toFIG. 4also has an MQL (minimum quantity lubrication) lubricating coolant transfer unit50, which runs along the rotational axis2centrally through the tool mount1, and defines a central lubricating coolant channel51for feeding a lubricating coolant supplied on the machine tool side to a shank tool W accommodated in the receptacle20. The lubricating coolant transfer unit50exhibits a lubricating coolant transfer tube52that penetrates through the stepped bore33of the anchor30, an axial adjusting screw53screwed into the smaller-diameter threaded hole section26bof the guide section22accessible on the tool side, as well as a locking element54(threaded coupling) screwed into the threaded hole section15aof the recess15of the base body10accessible from the machine tool side. The tool-side end section52aof the lubricating coolant transfer tube52is accommodated in an axially movable manner in an axial through borehole53aof the axial adjusting screw53with a defined lateral play. The lateral play between the outer circumference of the lubricating coolant transfer tube52and the inner circumference of the axial adjusting screw53is sealed by an O-ring gasket55, which is arranged in an annular groove53bof the axial adjusting screw53located on the inner circumference side. The lubricating coolant transfer tube53further extends through the stepped borehole33penetrating through the anchor30, and its machine tool-side end section52bis pressed fluid-tight into through borehole54bof the locking element54overlapping the anchor30on the machine tool side, i.e., connected with the locking element54in a torque-proof and axially rigid manner. The outer circumference of the locking element54exhibits a male thread54a, which is screwed into the threaded hole section15aof the stepped bore15of the shank section11of the base body10. The locking element54prevents dirt particles from penetrating in the direction of the two spring elements41,42of the spring arrangement40via the lateral gap between the anchor30and base body10. In addition, the locking element54, whose axial position in the base body10does not depend on the location of the anchor30or axial adjusting screw53, forms an interface for connecting the lubricating coolant transfer unit50to a lubricating coolant feed site provided on the machine tool side (not shown).

As shown byFIG. 2, 4, the locking element54exhibits a tube projection54con the tool side that engages into the enlarged-diameter bore section33aof the stepped bore33of the anchor30, thereby additionally centering and securing the anchor30. Twisting the locking element54causes the lubricating coolant transfer tube52to be axially adjusted relative to the axial adjusting screw53or to the anchor30.

The hydraulic expansion chuck according to the invention is not limited to the embodiment shown onFIGS. 1 to 4, but can be modified within the scope defined by the claims.

Instead of indirectly, the reducing bushing24can be positively connected directly with the chuck body or receptacle20by way of the expansion bushing23aof the hydraulic expansion mechanism23that is permanently soldered into the chuck body, in particular the receptacle20of the chuck body, or in some other way fixedly integrated therein. The direct positive connection between the reducing bushing24and chuck body can be realized axially within, i.e., in back of the expansion bushing23aof the hydraulic expansion mechanism23as viewed in the feed direction of the hydraulic expansion chuck1, or axially outside, i.e., in front of the expansion bushing23aof the hydraulic expansion mechanism23, as viewed in the feed direction of the hydraulic expansion chuck1. For example, the reducing bushing24acan be fixed in a rotational direction by a positive fit between the radial supporting flange24hand the opposing face of the expansion bushing23aor opposing face of the receptacle20. For example, such a positive fit can be achieved with one or more axial extensions, noses, projections or the like on the chuck body-side annular surface of the supporting flange24h, which axially engage(s) in corresponding entrainer grooves, recesses, or the like when the reducing bushing24is axially introduced into the expansion bushing23a.

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