Inductive clamping device for clamping and unclamping tools

Abstract

Device for inductively clamping and unclamping a shank (9) of a tool, in particular a rotary tool, in a tool holder (1) which has a clamping sleeve (3) made of electrically conductive material, open at its free end, for frictionally locking the shank (9), wherein the clamping sleeve (3) forms an axis of rotation (7) with the tool holder (1), with an induction coil assembly (13) surrounding the clamping sleeve (3) comprising two coil units (14a, 14b) arranged coaxially and axially adjustable relative to each other, a concentrator assembly made of magnetically conductive and electrically non-conductive material surrounding the induction coil assembly (13), and a further concentrator assembly made of magnetically conductive and electrically non-conductive material, which is formed from several ring-shaped concentrator elements (46a, 46b).which are adjustable relative to the axis of rotation (7) into their operating position for inductive heating of the collet (3), in which the concentrator elements (46a, 46b) at least partially cover the free end face (50) of the collet (3), characterized in that the concentrator elements (46a, 46b) are displaceable relative to the axis of rotation (7) with a radial and axial component into the operating position with at least partial coverage of the free end face (50) of the collet (3).

Description

[0001] The invention relates to an inductive clamping device according to the preamble of claim 1, i.e. a device with which tools can be fixed in a tool holder by shrink fitting through inductive heating.

[0002] For rapid tool changes of rotary tools, such as milling cutters, drills, and the like, quick-change tool systems are known that operate on the induction principle (see DE 39 25 641 A1). These systems use tool holders for clamping the tools, which have a collet whose mounting bore is smaller than the outer diameter of the tool shank. An induction coil, mounted concentrically on the collet and powered by an alternating current or pulsed direct current generator at a frequency of, for example, 10 to 50 kHz, generates eddy currents within the collet due to the introduced magnetic flux field of the induction coil. These eddy currents cause the collet to heat up, leading to a corresponding expansion of the collet's mounting bore.The tool, with its shank inserted into the collet's receiving bore, is held in place by friction through a shrink fit after the collet has cooled sufficiently. To remove the tool, the collet is inductively heated, causing the receiving bore to expand and allowing the tool to be easily removed. To facilitate targeted heating of the collet, magnetic flux concentrators are known (see "Steel Heat Treatment Handbook," Marcel Dekker, IR, INC 1997, Chapter 11A, Induction Heat Treatment). These concentrators are typically located on both end faces, but also on the outer circumference of the induction coil. They focus the magnetic flux lines generated by the coil and direct them precisely into the area of ​​the collet to be heated. Such magnetic flux concentrators can be constructed from so-called...They may be formed from transformer laminations arranged in a ring shape on the end faces of the induction coil, or consist of oxide ceramic material, in particular ferrite. These materials are characterized by being magnetically conductive but electrically non-conductive.

[0003] Known inductive clamping and unclamping devices with magnetic flux concentrators arranged on the end face of the induction coil often use ring-shaped concentrator elements (see JP S49 - 10 034 A or DE 199 15 412 A1). In these known devices, the ring-shaped concentrator elements extend not only over the end face of the induction coil but also, at least partially, over the free end face of the component to be heated for clamping purposes. The disadvantage of these devices, however, is that they are designed to accommodate components, such as tools, with only a specific diameter. This is particularly disadvantageous for tool changing devices, since tools with different diameters typically need to be clamped alternately, requiring different collet sizes.

[0004] This not only makes a quick-change system more expensive but also more difficult to use.

[0005] To overcome this disadvantage, it is known (DE 10 2005 014 984 A1) to use a multi-part induction coil assembly, which in particular consists of two coil units that are mounted concentrically on a collet and are axially adjustable relative to each other with respect to the axis of rotation clamped by the collet. This allows the length of the induction coil assembly to be adapted to the respective size of the collet used. It is known that larger collets are used for tools with larger shank diameters, which have a longer clamping length for the tool shank than collets for tools with smaller diameters. By appropriately adjusting the coil units of the induction coil assembly axially relative to each other to match the size of the collet, such an inductive clamping device can be used for different collets and thus tool diameters.To ensure effective transmission of the magnetic flux lines generated by the induction coil assembly into the collet, even with tools of varying diameters, the known device, in addition to axial adjustment of the induction coil assembly, also provides for adjustment of the diameter of the magnetic field concentrator. In this known device, the concentrator is formed by ring-shaped, overlapping, aperture-like concentrator elements that can be pivoted radially inwards along a radial plane perpendicular to the axis of rotation defined by the collet. This allows the aperture-like concentrator elements to be pivoted into a suitable overlap with the free end face of a collet of varying sizes.The axial adjustment of the induction coil assembly and the radial adjustment of the concentrator elements are coupled and achieved via a rotatable adjusting ring. The rotation of this ring determines both the relative axial position of the movable coil units and the radial pivoting position of the aperture-like concentrator elements. This device has proven effective in practice, but can be further improved, particularly with regard to automated processes and the desired targeted and optimized introduction of the magnetic flux lines concentrated by the concentrator elements into the clamping sleeve to be heated for holding the tool.

[0006] Further inductive clamping devices are known from DE 10 2006 047 796 A1, DE 10 2006 016 103 A1 and DE 20 2007 009 403 U1.

[0007] The object of the invention is to provide an inductive clamping device for clamping and unclamping tools, featuring axial position adjustment of an induction coil assembly consisting of at least two coil units and diameter adjustment of the concentrator elements. This device is designed to allow for optimal alignment of the coil units and the concentrator elements relative to the clamping sleeve, even when considering axial position changes in the induction coil assembly to accommodate different-sized clamping sleeves. Furthermore, the device should have a compact design and be easily convertible to semi-automatic or fully automatic operation.

[0008] This problem is solved according to the invention by the features contained in claim 1, wherein advantageous further developments of the invention are characterized by the features contained in the dependent claims.

[0009] The induction clamping device according to the invention comprises, firstly, an induction coil assembly concentrically surrounding the clamping sleeve, preferably consisting of two coil units arranged coaxially and adjustable axially relative to each other, and secondly, a concentrator arrangement made up of individual concentrator elements which, in the operating position of the induction coil mounted on the clamping sleeve, can be moved into a position in which they at least partially cover the clamping sleeve to be heated at its free end face. In this process, the concentrator elements are moved linearly, i.e., translationally, in the direction of the axis of rotation defined by the clamping sleeve, with both a radial and an axial component.This allows the concentrator elements, for example when adapting to a smaller collet for a small-diameter tool, to be moved not only radially inwards towards the axis of rotation defined by the collet, but also axially towards the free end face of the collet. Depending on the collet used, this enables optimal alignment of both the axially adjustable coil units and the concentrator elements covering the free end face of the collet to be heated.

[0010] For the positioning of the coil units, it is advantageous that they can be optimally adjusted or aligned to the respective fitting length of the collet, whereby, in particular, the coil unit assigned to the free end of the collet should be aligned as closely as possible with the front end of the collet. Furthermore, for the focused introduction of the magnetic flux lines and thus for optimized heating of the collet, it is advantageous if the concentrator elements are positioned as close as possible to the free end face of the collet to be heated. This can now be achieved very advantageously with the radially and axially superimposed positioning of the concentrator elements, and with an exceptionally compact design of the clamping device.

[0011] Furthermore, the clamping device according to the invention ensures that the axial adjustment of the coil units of the induction coil assembly relative to each other and the adjustment of the concentrator elements can be carried out independently of one another. This is important for optimal alignment of the components responsible for introducing the magnetic flux into the clamping sleeve, i.e., the coil units and concentrator elements. At the same time, this enables fully automatic as well as semi-automatic operation of such a device, in which the adjustment mechanism for the induction coil assembly and the adjustment mechanism for the diameter adjustment of the concentrator elements are driven by separate drives.

[0012] Advantageously, the concentrator elements are movable linearly in the direction of the axis of rotation defined by the clamping sleeve via slides, for which purpose the concentrator elements are received on the inwardly facing end faces of the slides. A practical embodiment has proven advantageous in that a total of six slides are arranged around the circumference, each of which is adjustable relative to the axis of rotation via linear guides arranged in a star-like pattern. The direction of movement of the slides with the axis of rotation preferably includes an angle of approximately 60 to 80°, and particularly preferably 65 to 75°. The slides are made of a non-magnetically conductive material, preferably ceramic or plastic, and are received in grooves of a guide ring, which is also made of a non-magnetically conductive material, in particular plastic.This is expediently accommodated within a further ring-shaped concentrator body, which essentially extends axially the magnetic flux concentrators arranged on the outer surface of the coil units.

[0013] Particularly with regard to the compact design of the clamping device, it is advantageous if the concentrator elements arranged at the inner end of the slides are alternately axially offset from each other and overlapping, which also has the advantage that in every radial position of the concentrator elements with respect to the axis of rotation clamped by the clamping sleeve a quasi closed magnetic field concentrator is formed, which is built up from the individual concentrator elements that are grouped around the axis of rotation in a ring-like fashion.

[0014] The feed movement of the slides is effected via a suitable cam / control cam mechanism, whereby the control cams are designed to adapt to the different sizes of the clamping sleeves to be used.

[0015] Advantageously, the concentrator elements are made of ferrite. In this context, it is advantageous if at least some of the slides, preferably every second slide, have a stop bar made of non-magnetically conductive material, preferably aluminum, which extends axially beyond the concentrator elements to a certain extent and thus acts as a stop against the free end face of the clamping sleeve. The projection of the stop bars beyond the concentrator elements is in the range of 0.2 to 0.6 mm, preferably 0.3 to 0.4 mm. This ensures gentle handling of the concentrator elements made of brittle material.

[0016] According to a further aspect of the invention, an induction attachment made of magnetically non-conductive but electrically conductive material, particularly copper, can be provided, especially on the free end face of the clamping device. The induction attachment actively shields the tool projecting outwards beyond the clamping device from stray fields remaining in the induction coil in this area. In the case of stray fields, the induction attachment generates eddy currents within the attachment, which in turn lead to the formation of a magnetic field that superimposes on and thus weakens the stray fields of the induction coil assembly.The induction attachment, in conjunction with or as an alternative to a shielding collar made of magnetically conductive material arranged in the transition area between the coil assembly and the clamping sleeve, leads to a corresponding targeted steering of the magnetic fields generated by the coil assembly towards the clamping sleeve and also to an active shielding of the tool section protruding above the clamping device, which overall leads to an optimization of the clamping and unclamping process.

[0017] For the axial adjustment of the coil units of the induction coil assembly, guide rings are advantageously provided. These are arranged concentrically and overlapping each other, with the inner guide ring being fixed to the device, while the outer guide ring is rotatable. Rotating the outer guide ring causes an axial displacement of the two coil units of the induction coil assembly. This displacement is also achieved via a cam / control cam mechanism, which is designed to accommodate the different clamping sleeves used with the clamping device.

[0018] By adjusting the outer guide ring accordingly, the axial position of the two coil units relative to each other can be set as desired.

[0019] Advantageously, the positioning movement of the concentrator elements, which are arranged on slides made of magnetic non-conductive material, is effected by a control ring mounted on the outer circumference of the outer guide ring. A control ring is mounted on the front of this control ring, featuring control cams distributed around its circumference for the respective slides. Corresponding cam pins are arranged on the slides, communicating with these control cams. The control ring is mounted on the outer guide ring via a roller bearing, allowing it to rotate independently of the outer guide ring. This makes the positioning of the slides completely independent of the adjustment of the coil units of the induction coil assembly, which is advantageous for fully automated operation.The bearing of the steering ring on the outer guide ring is expediently achieved via a pre-tensioned ball bearing band, resulting in a smooth and backlash-free adjustment of the steering ring for the purpose of adjusting the slides carrying the concentrator elements.

[0020] For the purpose of fully automatic or, if necessary, semi-automatic operation of the clamping device, it is advantageous if both the control ring for the feed movement of the slides and the outer guide ring for adjusting the coil units relative to each other are each provided with teeth, in particular with a toothed ring that rotates at least partially, so that both the control ring and the outer guide ring can be driven by a motor, advantageously via a suitable gearbox. Worm shafts that communicate with the teeth on the control ring and the outer guide ring are particularly suitable as gearboxes. Each of the two worm shafts is advantageously connected to a motor shaft via an intermediate gearbox consisting of a gear and a pinion.Both motors are expediently mounted on a slide which is guided linearly on a fixed table via a guide rail, so that the two motors arranged on the slide, including the intermediate gears, can be moved relatively in adaptation to the axial adjustability of the coil units.

[0021] Advantageously, this design allows both the diameter enclosed by the ring-shaped concentrator elements around the axis of rotation defined by the clamping sleeve and the relative position of the coil units of the induction coil assembly to be adjusted separately, thus offering controllable adjustment options, particularly for special applications. Furthermore, adjustments to the diameter and length of the induction coil assembly do not affect each other, which is crucial for control in automated operation.

[0022] In automated operation, the relevant geometry data of a chuck or a collet of a toolholder are automatically determined for a fully automated shrink-fitting process. For this purpose, the chuck or toolholder can be equipped with a corresponding data carrier. Alternatively, the data can be retrieved from an external database. The chuck geometry data can be automatically determined using digital image processing, laser scanners, distance sensors, etc., and the shrink-fitting parameters are automatically assigned by a computer, thus automatically adjusting the coil. A further advantage of using a worm gear is that it creates a self-locking mechanism, eliminating the need for separate detent positions in the control cams. Additional locking mechanisms are also unnecessary.Motors with absolute encoders are advantageously used, eliminating the need to approach reference points. The drive unit's power supply is conveniently switched on and off via a control signal along with the shrink-wrap electronics. Furthermore, the overall design allows for easy retrofitting of the clamping devices with automatic drive; this requires only the installation of the appropriate table with the mounting slide for the motors and the gearbox.

[0023] An embodiment of the invention is described below with reference to the drawing. The drawing shows Fig. 1 a sectional view through an embodiment of the inductive clamping device according to the invention in a first operating position, Fig. 2 a sectional view of the in Fig. 1 inductive clamping device shown in a second operating position, Fig. 3 a front view of the in Fig. 1. Device shown from the left side to illustrate details of linearly movable slides with concentrator elements of the device arranged on them, Fig. 4 a side view of the device according to the preceding figures, as well as Fig. 5 another side view of the device Fig. 4, but offset by 90° in one view.

[0024] Fig. Figure 1 shows a typical standard tool holder in the form of an adapter, used for clamping tools, such as turning tools, drills, and the like, in a high-speed machine tool, such as a lathe. The tool holder 1 is made of a material that is at least electrically conductive, such as steel, and has a clamping sleeve 3 at its front end (shown on the left) for clamping a tool. The tool is clamped in the clamping sleeve 3 by its shank. The clamping sleeve 3 is conical in shape and has a central bore 5, which defines an axis of rotation (designated 7) and is open towards the free end of the clamping sleeve 3. The shank 9 of the tool to be clamped, shown only schematically here, is inserted through this opening so that the shank 9 then rests in the bore 5.The outer diameter of the shaft 9 is slightly larger than the free nominal diameter of the bore 5, so that the shaft 9, when inserted into the bore 5, is held in the clamping sleeve 3 in a frictional press fit for the transmission of the working torque.

[0025] To insert and remove the shaft 9 from the tool holder 1, the clamping sleeve 3 is expanded by heating. For this purpose, the inductive clamping and unclamping device, generally designated 11, is used, which has an induction coil assembly designated 13 consisting of two coil units 14a and 14b, the windings in the two coil bodies 15 being represented only schematically by circles.

[0026] To heat the clamping sleeve 3, the clamping device is placed onto the clamping sleeve 3 from the left, whereby the induction coil assembly 13, or the two coil units 14a and 14b, concentrically enclose the clamping sleeve 3. The induction coil is powered by an alternating current or pulsed direct current with a frequency of, for example, 10 to 50 kHz via a current generator (not shown). The magnetic flux generated by the approximately cylindrical winding of the coil former 15 induces eddy currents in the clamping sleeve 3, which heat the clamping sleeve 3 in a relatively short time and thus expand the bore 5 accordingly, so that the oversized shaft 9 can be inserted into the bore 5 of the clamping sleeve 3.

[0027] After cooling, the collet 3 shrinks around the inserted shaft 9, so that the shaft is held in the tool holder 1 by friction fit through the shrink fit of the collet 3.

[0028] To remove the tool, the clamping sleeve 3 must again be heated via the induction coil in an analogous manner, so that the receiving bore 5 is widened accordingly and then the tool can be pulled out of the receiving bore 5.

[0029] Each winding of a coil unit 14a, 14b and thus each coil former 15 is arranged according to the representation in Fig. 1 surrounded by a coil housing 17a and 17b made of temperature-resistant plastic or ceramic, wherein the coil housing 17b has a sleeve section engaging under the coil housing 17a, so that, as is shown in more detail below, a relative axial adjustment of the two coil units 14a and 14b along the axis of rotation 7 is possible.

[0030] The coil former 15 of both coil unit 14b and coil unit 14a is surrounded by a sleeve-like concentrator 19b or 19a, respectively, on the outer surface of the coil formers. The concentrator sleeve 19b overlaps the cylindrical section of the concentrator sleeve 19a; that is, the two sleeves are concentric with each other and with respect to the axis of rotation 7 and are inserted into one another, again for the purpose of the axial displacement of the two coil units relative to each other, as described later. The concentrator sleeve 19a also covers the end face of coil unit 14a on the right side. Fig. 1. However, such an end-face overlap of the coil unit 14b does not exist for the concentrator sleeve 19b, which merely concentrically encloses the coil unit 14b. However, a concentrator ring designated 21 adjoins the left end face of the concentrator sleeve 19b. This ring, like the concentrator sleeves 19a and 19b, is made of magnetically conductive but electrically non-conductive material, such as an oxide ceramic material, in particular ferrite. The concentrator ring 21 thus continues the concentrator sleeve 19b axially at its free end face, but does not overlap it, as can be seen from the diagram. Fig. As can be seen from Figure 1, the free end face of the coil unit 14b. In the illustrated embodiment, the free end face of the coil unit 14b is therefore not closed off by a concentrator.

[0031] In the opening of the concentrator ring 21, a guide ring 22 made of a magnetically non-conductive and preferably also electrically non-conductive material, such as plastic, is arranged, which has guide grooves 24 distributed around its circumference. These grooves serve to receive adjustable slides, which will be described below. In the illustrated embodiment, a total of six circumferential guide grooves 24 are provided, as can be seen in particular from Fig. 3 results.

[0032] Concentrically positioned above the induction coil assembly 13 is an outer guide ring, designated 26, which is designed for the relative axial adjustment of the two coil units 14a and 14b. Within the guide ring 26 is a further inner guide ring 28, which is fixed to the inductive clamping device. In contrast, the outer guide ring 26 is rotatable relative to the guide ring 28. Suitable control cams are provided on the outer circumference 30 of the inner guide ring, distributed around its circumference, into which cam pins of the outer guide ring 26 (not shown) engage. Furthermore, the concentrator sleeve 19b is connected to the inner guide ring 28 in a rotationally fixed but longitudinally displaceable manner.

[0033] If the outer guide ring 26 is rotated manually, for example, then as a result of the cam control mechanism described above, this guide ring 26 will, for example, be in Fig. 1 is axially adjusted to the left, thereby taking the coil unit 14b with the concentrator sleeve 19b, the concentrator ring 21 and the guide ring 22 arranged therein translationally to the left. Thus, the induction coil assembly 13 is axially extended by extending the coil unit 14b translationally or linearly in a telescopic manner along the axis of rotation 7, whereby a correspondingly extended position is formed by Fig. 2 results.

[0034] This type of longitudinal adjustment of the coil unit 14b relative to the coil unit 14a can of course be carried out in completely different ways and is known in itself, for which reference is made, for example, to DE 10 2005 014 984 A1, which is included here and has already been described at the beginning as the prior art of the generic type.

[0035] In the illustrated embodiment, the rotation of the outer guide ring 26 does result in an axial adjustment of the coil unit 14b, including the surrounding concentrator sleeve 19b and the concentrator ring 21, which projects the concentrator sleeve 19b axially outwards, including the guide ring 22 contained therein. However, these elements are only longitudinally displaceable and are not rotationally fixed to the outer guide ring 26, so that these components do not rotate with the outer guide ring 26.

[0036] On the outer guide ring 26, another housing ring, namely an adjusting ring 32, is rotatably arranged. This arrangement is facilitated by a ball-bearing band, shown only schematically, which is mounted on the outer guide ring 26 and is advantageously pre-tensioned to prevent play and ensure smooth adjustment. The ball-bearing band is designated 34 and comprises a multitude of bearing balls distributed around its circumference within a single band. Such components are known and therefore do not need to be described in detail.

[0037] This roller bearing allows the adjusting ring 32 to rotate very easily and without play relative to the outer guide ring 26. An adjusting ring 38 is firmly connected to the adjusting ring 32 by the screw connections indicated by 36, so that it rotates along with the adjusting ring 32. The adjusting ring 38 has several, preferably a total of six, control cams 40 distributed around its circumference on its surface facing the clamping sleeve 3. Cam pins 42, which are arranged on slides 44, interact with these control cams 40. These slides are fixed against rotation but linearly displaceable within the guide grooves 24 of the guide ring 22.

[0038] In the illustrated embodiment, a total of six slides 44 are provided, distributed at uniform angular intervals around the circumference, as can be clearly seen from Fig. 3. These sliders are made of magnetically non-conductive and preferably electrically non-conductive material, in particular plastic or ceramic, and are mounted to be displaceable linearly or translationally in the guide grooves 24 in the direction of the axis of rotation 7. Accordingly Fig. 3 the guide grooves 24 and the slides 44 which can be moved therein are grouped radially in a star shape around the axis of rotation 7.

[0039] Concentrator elements 46 are provided at the front inner ends of each slide 44, with two different concentrator elements 46a and 46b being provided in the illustrated embodiment for a total of six slides 44. This is best illustrated by Fig. 3. The in Fig. Three slides designated 44a have concentrator elements 46a at their inner ends, whereas the other concentrator elements designated 46b have concentrator elements designated 46b, one of which is in Fig. For clarity, the part of slide 44b that lies behind the two laterally adjacent slides 44a is shown with dashed lines. This means that the concentrator elements 46a and 46b are slightly axially offset from each other relative to the axis of rotation 7.

[0040] To ensure this, the slides 44b, which are essentially flush with those of the slides 44a with their two main surfaces, are stepped at 48, so that the in Fig. The 3 dashed section of the slide valve at 30 engages the front sections of the slide valve 44a. This design was chosen so that the in Fig. The three concentrator elements 46a shown in Figure 3, which are arranged at the front inner ends of the slides 44a, together form a quasi-ring-like concentrator that acts like a closed concentrator ring but is composed of individual concentrator elements. In the operating position of the Fig. 1. The free end face 50 of the collet 3 is radially covered, preferably substantially completely. This formation of a quasi-annular concentrator from the concentrator elements 46 with radial coverage of the free end face 50 of the collet 3 should also be fulfilled in the case of a collet 3 with a larger diameter for clamping a tool shank with a larger diameter, and thus also in a position according to Fig. 2, in which the slides 44 have been displaced outwards away from the axis of rotation in the manner described below. This is achieved by the arrangement and design of the concentrator elements 46a and 46b described above, since in the position of the slides and thus the concentrator elements further away from the axis of rotation 7, the concentrator elements 46a and 46b, which then alternately overlap, again form a quasi-ring-shaped concentrator that radially covers the free end face 50 of the larger clamping sleeve 3 in the same way as Fig. 2 shows quite clearly.

[0041] Out of Fig. Figure 2 also clearly shows the shape of the concentrator elements 46a and 46b responsible for the overlap, specifically from the perspective view of the concentrator elements 46a, 46b near the end-face receiving opening of the clamping sleeve 3. Furthermore, the concentrator elements overlap in the Fig. 1 and Fig. 2 extremely well-depicted operating positions, namely in the position of the slides 44 shifted inwards towards the axis of rotation 7 in Fig. 1 and the outwardly shifted position of the sliders according to Fig. 2. The concentrator elements 46a and 46b cover the end face of the clamping sleeve 3 and essentially seal it radially. However, they do not extend into the area of ​​the free end face of the coil units of the induction coil assembly.

[0042] The control of the slides into the individual operating positions is effected by the cam-control cam mechanism 40, 42 already described, whereby when the adjusting ring 32 and thus the adjusting ring 38 is rotated, the cam pins 42 slide in the control cam and thereby move the slides 44, which are held in the guide grooves 24, linearly either towards or away from the axis of rotation 7. As described above, this widens or closes the ring-shaped ring of the concentrator elements 46a, 46b (see the operating positions in the Fig. 1 and Fig. 2) This is done depending on the size of the clamping sleeve 3 used. For this purpose, the control cams 40 distributed around the circumference are designed and, if necessary, indexed according to the clamping sleeve sizes usable for the clamping device, so that, depending on in which section of the control cams 40 the cam pins 42 are located, the slides coupled to them are positioned accordingly towards the axis of rotation 7. Such indexed control cams are known, for which reference is again made to the prior art according to DE 10 2005 014 984 A1.

[0043] A key feature of the clamping device according to the invention is that the adjustment of the slides, and thus of the concentrator elements 46, is carried out at an angle to the axis of rotation, so that the adjustment movement consists of a radial and an axial component. For this purpose, the bottoms of the guide grooves within the guide ring 22 are set at an angle, as shown in Fig. 2 and in Fig. 1 is clarified by the reference numeral 52. This oblique angle is in Fig. Figure 1 is indicated and labelled with the angle α. The angle α lies in the range between 60 and 80°, preferably between 65 and 75°.

[0044] Since the concentrator elements 46a, 46b are made of magnetically conductive material, usually ferrite or another suitable oxide ceramic material, which is comparatively brittle and fragile, stop strips 54 made of a more robust, non-magnetically conductive material are arranged on the slides 44b. Aluminum is preferably used for this purpose. These stop strips 54 are narrower than the concentrator elements 46a, 46b, as their only function is to act as a stop.

[0045] As is quite clear from Fig. As shown in Figure 2, each stop bar 54 has a rib-like projection on its radially inner section at 56, which protrudes slightly, namely by about 0.2 to 0.6 mm or 0.3 to 0.4 mm, beyond the free end face of the concentrator elements 46a and 46b adjacent to the clamping sleeve 3. This ensures that, during the linear movement of the slides towards the free end face 50 of the clamping sleeve 3, the aluminum stop bars 54 come into contact with the free end face 50 of the clamping sleeve 3 and not the brittle concentrator elements. At the same time, the concentrator elements are moved sufficiently close to the free end face of the clamping sleeve 3 so that the magnetic flux is very advantageously concentrated or focused into the clamping sleeve 3 via the concentrator elements to heat it.

[0046] As from the Fig. 1 and Fig. As shown in Figure 2, a further shielding collar 58 made of magnetically conductive, but electrically non-conductive material, in particular ferrite, is provided. This collar is ring-shaped and extends essentially axially to the axis of rotation 7, widening conically towards the outside. The collar is arranged in an opening of the adjusting ring 38. This provides further effective shielding of the part of the tool clamped in the clamping sleeve 3 that protrudes from the clamping sleeve 3, thus preventing it from heating up.

[0047] Alternatively or additionally, an induction attachment designated 60 can be provided, which is electrically conductive but magnetically non-conductive and preferably made of copper. The induction attachment 60 is formed here as a substantially flat annular disc made of copper, which is substantially flush with the front of the clamping device, but can also be designed as a conical induction attachment projecting outwards. However, the illustrated embodiment with the copper disc as the induction attachment 60 is very advantageous for space reasons, because it does not impair the compact design of the illustrated induction clamping device.

[0048] When the induction coil is in operation, any escaping magnetic stray fields generate eddy currents in the copper induction attachment 60, which in turn generate a counteracting magnetic field that weakens the magnetic stray field of the induction coil. This also provides additional, namely active, shielding in the outer area of ​​the clamping sleeve 3.

[0049] The inclined guide of the slides, and thus the inclined positioning of the concentrator elements mounted inside the slides, offers the advantage that the concentrator elements are moved into the operating position not only radially towards the axis of rotation 7, but also with an additional axial component towards the collet 3. This ensures optimal alignment of the induction coil units 14a and 14b, even with tool holders of different sizes and collets of different sizes for different tool diameters. It is essential that, even when the coil units 14a and 14b are extended axially relative to each other, they are each favorably positioned with respect to the actual shrink-fit area within the collet 3. This means that, for the Fig. The coil unit 14b, shown on the left and extended, is positioned as close as possible to the free end of the collet 3 and completely overlaps it. At the same time, it should be ensured that the concentrator elements located on the slides are as close as possible to the free end face of the collet 3 and largely seal it, so that the magnetic flux generated by the induction coil can be concentrated and introduced into the collet area to be heated. This is achieved precisely by the angled positioning of the slides and the associated concentrator elements, which would not be possible with a purely radial adjustment movement of the concentrator elements to accommodate different collet diameters.

[0050] The illustrated embodiment is designed such that the adjustment of the slides with the concentrator elements covering the free surface of the clamping sleeve 3 can now be carried out separately and independently of the adjustment of the axial length of the two coil units 14a and 14b. This allows for individual adjustment, which is particularly advantageous for fully automated operation. This is achieved by decoupling the adjusting ring 32 from the outer guide ring 26 by means of an intermediate roller bearing, for which a ball roller belt is used.

[0051] For automated operation, it is advantageous to provide a toothed section on the outer circumference of the adjusting ring, which here is designed as a circumferential toothed ring 62. A further toothed ring is located on the outer circumference of the outer guide ring 26 and is designated 64. This enables motorized operation of both the adjusting ring 32 for adjusting the slides and the outer guide ring 26 for axially adjusting the coiling units 14a, 14b relative to each other. This is particularly advantageous in the Fig. 4 and Fig. 5 illustrates this.

[0052] In the illustrated embodiment, worm shafts 66 and 68 mesh with gear rings 62 and 64, which are arranged via a shaft on a mounting slide 70 that also accommodates two motors 72 and 74. Motor 72 drives a pinion 78, which is rotationally fixed to the worm shaft 66, via a gear 76. Thus, motor 72 actuates the gear ring 62 to advance and retract the slides with the concentrator elements 46a, 46b. Separately, motor 74 can actuate the worm shaft 68 via a gear / pinion pair 80, 82 to rotate the outer guide ring 26, allowing the coil units to be axially adjusted relative to each other.

[0053] The mounting slide 70, which also carries both motors 72 and 74 including their gearboxes, is arranged on a fixed mounting table 84 and is slidable along a linear guide 86. This allows the mounting slide 70 to follow the outer guide ring 26 during axial adjustment of the coil units, as the outer guide ring 26 is adjusted axially relative to the inner, fixed guide ring 28. This guidance also results from Fig. 5, from which the control curves 88 on the outer surface of the inner guide ring 28 of the cam control mechanism for the coil adjustment are also evident. A total of 4 guide grooves are provided here, with which the outer guide ring 26 interacts via corresponding cam pins (not shown).

[0054] This design allows for both diameter and length adjustment depending on different collet sizes and thus different tool diameters. Furthermore, the two adjustments can be motor-coupled or controlled independently, which is advantageous for special applications. The separate adjustment options for the diameter and length of the coil spacing between the coil units result in a simple control method for fully automatic operation.

[0055] In this process, the corresponding geometry and shrink parameters for different shrink chucks can either be read from an external data source or via a suitable scanner that reads a corresponding data carrier on the shrink chuck and, depending on suitable software, then enables the corresponding settings by controlling the two motors 72 and 74.

[0056] The geometry data of the chuck can be automatically determined in various ways, for example, via digital image processing, laser scanners, and distance sensors. This allows the shrink parameters to be automatically assigned according to the size of the shrink chuck, and the coil to be automatically adjusted with respect to its axial length. A single carriage can be used for both motors, which is advantageous for the desired space-saving and compact design.

[0057] The use of worm gears is advantageous because it allows for a self-locking drive, meaning that additional locking mechanisms for the set operating position are not required.

[0058] Provided that, where appropriate, a corresponding toothing is already provided on the adjusting ring 32 and the outer guide ring 26, the manually operated inductive clamping device can then easily be retrofitted to fully automatic or semi-automatic operation.

Claims

[1] Device for inductively clamping and unclamping a shank (9) of a tool, in particular a rotary tool, in a tool holder (1) which has a clamping sleeve (3) made of electrically conductive material, open at its free end, for frictionally engaging the shank (9), wherein the clamping sleeve (3) forms an axis of rotation (7) with the tool holder (1), with an induction coil assembly (13) surrounding the clamping sleeve (3) comprising two coil units (14a, 14b) arranged coaxially and axially adjustable relative to each other, a concentrator assembly made of magnetically conductive and electrically non-conductive material surrounding the induction coil assembly (13), and a further concentrator assembly made of magnetically conductive and electrically non-conductive material, which is formed from several ring-shaped concentrator elements (46a, 46b),which are adjustable relative to the axis of rotation (7) into their operating position for inductive heating of the collet (3), in which the concentrator elements (46a, 46b) at least partially cover the free end face (50) of the collet (3), , characterized by , that the concentrator elements (46a, 46b) are displaceable relative to the axis of rotation (7) with a radial and axial component into the operating position with at least partial overlap of the free end face (50) of the clamping sleeve (3). [2] Device according to claim 1 characterized by , that the displacement of the concentrator elements (46a, 46b) is translational. [3] Device according to claim 1 or 2 characterized by , that the concentrator elements (46a, 46b) are each received in slides (44) which are translationally (linearly) displaceable at an angle α of 60 to 80°, preferably of 65 to 75° relative to the axis of rotation. [4] Device according to claim 3, characterized by, that the slide-like slides (44) are made of magnetically non-conductive material, preferably ceramic material or plastic, and the concentrator elements (46a, 46b) are each accommodated at the free end of the slides (44) pointing in the direction of the axis of rotation. [5] Device according to claim 4, characterized by , that six ring-shaped grouped slides (44) are provided which are slidably guided in linearly directed grooves of a guide ring (22) made of magnetically non-conductive material. [6] Device according to any one of claims 3 to 5, characterized by, that at least a part of the slides, preferably in the ring-like grouping every second slide (44b), each carries a stop strip (54, 56) made of magnetically non-conductive material, preferably aluminium, which as a stop (56) protrudes slightly, namely 0.2 to 0.6 mm, preferably 0.3 to 0.4 mm, beyond the end face of a concentrator element (46b) pointing towards the clamping sleeve 3. [7] Device according to any one of claims 3 to 6, characterized by , that the control of the sliding movement of the slides (44) is carried out by cam pins (42) on the slides which engage in corresponding control cams (40) of an adjusting ring (38). [8] Device according to any one of the preceding claims, characterized by, that an additional ring-shaped concentrator (58) is provided, which is fixedly arranged in the radial space between the coil units (14a, 14b) and the concentrator elements (46a, 46b) received on the slides (44). [9] Device according to any one of the preceding claims, characterized by , that the device carries a ring-shaped induction attachment (60) made of magnetically non-conductive and electrically conductive material, preferably copper, which is designed and / or arranged in such a way that it acts as an active shielding element, generating a counter-magnetic field against magnetic stray fields generated by the induction coil. [10] Device according to claim 8 or 9, characterized by , that the additional concentrator (58) and / or induction attachment (60) are arranged on a cover ring arranged on the front face, which is fixed to the housing or on the adjusting ring (32). [11] Device according to claim 1 or any of the dependent claims 2 to 10, characterized by , that the two coil units (14a, 14b) including the associated concentrator sleeves (19a, 19b) are axially adjustable relative to each other via a longitudinal guide, wherein the guidance of the concentrator sleeve (19b) is provided along an inner guide ring (28) which is engaged by an outer guide ring (26) arranged concentrically above it, wherein the two guide rings (26, 28) communicate with each other via a cam mechanism for the purpose of axial adjustment of the coil unit (14a, 14b). [12] Device according to claim 11, characterized by , that the inner guide ring (28) has four control cams on its outer circumference, with which the outer guide ring (26) communicates by means of a cam each. [13] Device according to claim 11 or 12, characterized by, that a positioning ring (32) for the linear adjustment of the slides (44) and concentrator elements is rotatably mounted on the outer guide ring (26). [14] Device according to claim 13, characterized by , that the positioning ring is supported on the outer guide ring (26) by a rolling bearing, in particular a ball bearing strip (34). [15] Device according to claim 13 or 14, characterized by , that a toothed ring for the rotary drive of the adjusting ring (32, 38) and of the outer guide ring (28) is provided on the adjusting ring (32) and on the outer guide ring (26). [16] Device according to claim 15, characterized by , that the drive of the gear rings (62, 64) of the adjusting ring (32, 38) and outer guide ring (26) is each motor-driven and via a gearbox. [17] Device according to claim 16, characterized by, that the motor and gearbox (72, 76, 78, 66) for the adjusting ring (32, 38) and the motor and gearbox (74, 80, 82, 68) for the outer guide ring (26) are arranged on a common slide (70) which is arranged on a linear guide (86) on a fixture-fixed clamping table (84), such that both motors and gearboxes together are moved with the outer guide ring (26) during an axial adjustment of both coil units. [18] Device according to claim 16 or 17, characterized by , that a worm shaft (66, 68) is used for the drive of the adjusting ring (32, 38) and the outer guide ring (26), which engages with the respective gear ring (62, 64) and acts in a self-locking manner.

Images