Shrinking device and shrinking system for preferably mobile use

Abstract

Shrink-fit device for clamping and unclamping tools (4) having a tool shank (H) with a tool holder having a sleeve section (HP) made of electrically conductive material open at its free end for frictionally engaging the tool shank (H), and with an induction coil (1) comprising the sleeve section (HP) of the tool holder, which can be supplied with a preferably high-frequency alternating current and is designed as a ring or cylindrical coil for heating the sleeve section (HP), wherein the induction coil (1) has a first sheath (3) made of magnetically conductive and electrically non-conductive material on its outer circumference, and the device comprises power semiconductor components (10) for generating an alternating current supplying the induction coil (1), as well as an induction coil housing preferably made of insulating material, characterized in thatthat the induction coil (1) and its first sheath (3) are surrounded on the outer circumference by a second sheath (9) which consists of magnetically non-conductive and electrically conductive material and is designed such that a stray field occurring in its vicinity generates eddy currents in the second sheath (9) and thereby weakens the stray field, and that at least the power semiconductor components (10) are housed together with the induction coil (1) in an induction coil housing which encloses the induction coil (1), its first and second sheaths (3, 9), and the power semiconductor components (10) at least along the circumference of the induction coil (1).

Description

Basic subject matter of the invention

[0001] The invention relates to a shrinking device according to the preamble of claim 1 and a shrinking system according to the preamble of claim 24. State of the art

[0002] Shrink-fitting devices for shrinking tool shanks into and out of tool holders have been around for some time. Originally, such devices were powered by a gas torch or hot air, which heated the sleeve section of the tool holder to expand it sufficiently to accommodate or release a press-fit tool shank. More recently, shrink-fitting devices have become widespread, heating the tool holder using an induction coil. This has made the shrink-fitting process significantly faster, more efficient, and easier to handle, thus contributing to its widespread adoption.

[0003] The first shrinking device suitable for practical use is described in the patent literature by the German patent application DE 199 15 412 B4.

[0004] All known shrink-fitting devices have the disadvantage of being relatively large. This is because they utilize a control cabinet of varying size, housing the power electronics and usually the associated control system, which is housed next to the induction coil on or in a table frame. The known shrink-fitting devices therefore form a de facto immobile station to which the tool holders whose tools are to be changed must be transported, and then returned to the respective machine tool after the tool change. This has been accepted until now. The problem underlying the invention

[0005] In view of this, it is the object of the invention to provide a shrinking device and shrinking system which is significantly more compact than the previously known shrinking devices or shrinking systems and which therefore forms a suitable starting point for designing a shrinking device or shrinking system for mobile use - ideally in such a way that the shrinking device or shrinking system is a device which can be transported in the manner of a small suitcase and which can be used in a new way by the operator by quickly bringing it to the machine tool which is to be subjected to a tool change and using it there in order to carry out a tool change on site at the machine.

[0006] This does not, of course, exclude the possibility that the shrinking device or shrinking system can also be used in a conventional manner in a stationary manner on a corresponding holding device, but mobile use is preferred. The inventive solution according to claim 1 and claim 24

[0007] This problem is solved by a shrinking device for clamping and unclamping tools having a tool shank according to claim 1 and by a shrinking system according to claim 24.

[0008] The shrinking device comprises a tool holder having a sleeve section made of electrically conductive material that is open at its free end for frictionally receiving the tool shank. Furthermore, the shrinking device includes an induction coil enclosing the sleeve section of the tool holder, which is designed as a toroidal or cylindrical coil and is supplied with a preferably high-frequency alternating current (ideally with a frequency of usually more than 1 kHz), for heating the sleeve section. The induction coil has a first sheath made of magnetically conductive and electrically non-conductive material, such as ferrite or a metal powder material, on its outer circumference. Electrically non-conductive material within the meaning of the invention does not necessarily have to be an insulator. A material is considered non-conductive if the eddy currents induced by magnetic fields cause only slight or no heating in the material.Furthermore, the shrink device according to the invention includes power semiconductor components for generating an alternating current that feeds the induction coil. Typically, so-called IGBTs are used here. However, thyristors or MOSFETs can also be used. The shrink device according to the invention also includes an induction coil housing, usually made of plastic. Such an induction coil housing typically exhibits no magnetic shielding effect, or at least no noticeable one. Its sole purpose is to protect the components contained therein from external influences and, at the same time, to prevent the operator from possibly coming into contact with live parts. The shrink device according to the invention is characterized in that the induction coil and its first casing are surrounded by a second casing on the outer circumference.This second jacket is made of a magnetically non-conductive and electrically conductive material. It is designed so that any stray field induces electrical currents within it, thus drawing energy from the stray field and weakening it. This means that it completely eliminates the stray field in its surroundings or at least reduces it to such an extent that the remaining stray field in its immediate vicinity—preferably without further measures or instead in conjunction with other accompanying measures—is so small that it has no negative impact on the power semiconductor components located there.

[0009] Furthermore, this inventive solution is characterized in that at least the power semiconductor components are housed together with the induction coil in an induction coil housing. The induction coil housing is preferably made of insulating material or is coated with such material on the outside. It comprises the following components on its circumference or houses them within its interior: the induction coil, its first and second casings, as well as at least the power semiconductor components, preferably also the capacitors located directly in the power circuit and / or the controller.

[0010] "Enclosing" is understood, at a minimum, as an external enclosure at least along the circumference of the induction coil. Typically, the induction coil housing will also extend into the area of ​​the upper and lower end faces, covering them completely or partially. It then has a pot-like shape. The induction coil housing, at least along its circumference, generally has no wall openings – except for a local opening necessary for its function, such as for the supply line or similar. Further design options

[0011] The shrink-fitting device is preferably designed such that its power semiconductor components are arranged directly on the outer circumference of the second casing. Directly on the outer circumference can mean a maximum radial distance of up to 60 mm, or better still, only up to 15 mm, from the outer circumferential surface of the second casing of the induction coil. If this distance is missing, the outer circumferential surface of the first casing is decisive. Ideally, however, the power semiconductor components are in direct heat-conducting contact with the second casing with at least one of their surfaces, possibly mediated by an adhesive layer. The second casing is preferably designed to form a heat sink for the power semiconductor components. The second casing then absorbs the heat loss generated in the power semiconductor components and dissipates it away from them.

[0012] It has proven particularly advantageous if the second casing has one or preferably several recesses, each of which accommodates a power semiconductor component, preferably such that the semiconductor component is enclosed by the second casing on at least three or, better, four sides. Such a recess in the second casing forms an area that is particularly protected from any residual stray magnetic field that may still be present. This is because the stray field lines are unable to penetrate into this deeper recess, in which the power semiconductor component is located. Instead, they are captured by the surrounding, higher or further radially outward regions of the second casing.

[0013] It has proven particularly advantageous if the shrink-fitting device, which comprises at least one rectifier and at least one smoothing capacitor as well as resonant circuit capacitors involved in the device-internal production of a high-frequency alternating voltage for feeding the induction coil, has an induction coil around whose outer circumference the capacitors are grouped - usually in such a way that the capacitors, if one imagines them rotating around the center of the coil, form a cylindrical ring that encloses the induction coil. Here, too, the capacitors should be arranged directly on the outer circumference of the second casing of the induction coil. In this context, the term "directly on the outer circumference" can be understood to mean a maximum radial distance of up to 125 mm, preferably up to 40 mm, measured from the outer circumference of the second casing of the induction coil.If this is missing, the outer circumferential surface of the first shell is decisive.

[0014] A particularly advantageous embodiment of the shrinking device, for which not only dependent but also independent protection not dependent on preceding claims is claimed, consists of at least one induction coil for shrinking tool shanks in and out of tool holders, which induction coil is surrounded by a first casing made of magnetically conductive and electrically non-conductive material, wherein the induction coil and its first casing are surrounded by a second casing made of magnetically non-conductive and electrically conductive material. The above-mentioned applies to the second casing. Ideally, this second casing is also designed such that, under the influence of a stray field of the induction coil penetrating it, eddy currents are generated therein, which lead to the elimination of the stray field influence on the outer surface of the second casing.Here, the principle of so-called mutual induction can be utilized. Eddy currents are generated in the second cladding by the stray field penetrating it, which in turn create a counter-field that eliminates the disruptive stray field, at least to the extent that power semiconductor components can be installed in the vicinity of the second cladding without sustaining permanent damage.

[0015] Another particularly advantageous embodiment of the shrinking device, for which not only dependent but also independent protection not dependent on the preceding claims is claimed, consists of an induction coil for shrinking tools in and out of tool holders, which is housed in the induction coil housing together with the power semiconductor components assigned to it, which are required to produce the alternating voltage that feeds the induction coil and is converted from the mains voltage. Preferably, further components, such as capacitors in the power circuit and / or a rectifier and / or a transformer and / or the electronic control system, are also housed within the induction coil housing. A second casing is not present in this embodiment. It can be used, if necessary.This can be replaced by having the power semiconductor components and / or the control electronics and / or the rectifiers each have shielded housings or are housed in shielded compartments. Preferably, at least the power semiconductor components are actively cooled, for example, using the machine tool's coolant supply. This approach is possible with greater effort and is therefore included in the protection request.

[0016] This results in a particularly compact shrinking device that no longer requires a separate, somewhat large control cabinet located next to the shrinking device, in which these components are housed separately. This brings us a significant step closer to the goal of a mobile shrinking device.

[0017] Preferably, all variants of the shrink-fitting device according to the invention are designed such that the end face of the induction coil facing away from the tool holder is provided with a cover made of magnetically conductive and electrically non-conductive material. Ideally, this cover is designed as a pole piece that completely covers the entire end face of the induction coil. This is particularly important here to keep the exterior free from harmful stray fields. In exceptional cases, the cover may completely cover the entire end face of the induction coil, if not physically, then magnetically.

[0018] It has proven particularly advantageous if the cover has a shielding collar located locally in the center near the sleeve section, which preferably protrudes above the free end face of the sleeve section of the tool holder by at least twice the tool diameter in the direction of the longitudinal axis L. Such a shielding collar prevents the tool shank near the sleeve section from being exposed to a harmful stray field or from being the starting point for such a stray field, which extends from there into the environment and exerts the harmful influence to be avoided on the power semiconductor components arranged in the immediate vicinity of the induction coil.

[0019] It is advantageous if the end face of the induction coil facing the tool holder is also covered by a magnetically conductive and electrically non-conductive material and is preferably completely covered except for the receiving opening for the tool holder.

[0020] In a particularly preferred embodiment, the shrinking device has at least one electrical circuit board that is arranged directly on the outer circumference of the induction coil or surrounds the outer circumference of the induction coil, preferably in the manner of a ring that is predominantly or completely closed in the circumferential direction, and electrically contacts the capacitors and / or the power semiconductor components in the power circuit. A circuit board is preferably understood here to be a plate that is at least 0.75 mm thick and has conductor tracks made of metallic material applied thereto; alternatively, however, a foil provided with metallic conductor tracks can also be used. It is particularly advantageous if the circuit board is a circuit board ring disk whose axis of rotational symmetry is preferably coaxial, otherwise parallel, to the longitudinal axis of the induction coil.

[0021] Ideally, there are two circuit board discs between which the capacitors in the power circuit are arranged along the circumference of the induction coil.

[0022] In a particularly preferred embodiment, the second shell forms one or more cooling channels, which preferably run within its interior when viewed as a whole. For this purpose, the second shell can be constructed in two or more parts. The individual parts of the shell are then sealed from one another. This significantly simplifies the production of internal cooling channels:

[0023] Another particularly advantageous embodiment of the shrinking device, for which not only dependent but also independent protection not dependent on preceding claims is claimed, is a shrinking device characterized in that the shrinking device has a coupling for attaching the shrinking device to the holder of a machine tool spindle. This embodiment also comes significantly closer to the goal of creating a practically usable mobile shrinking device. It is dangerous to work with a mobile shrinking device that is merely exposed near the machine tool without being secured in some way that ensures operational reliability. This problem is eliminated with the coupling according to the invention. The coupling makes it possible to attach the shrinking device to the machine spindle in place of the shrink chuck that is to be subjected to a tool change after it has been removed.Here the shrinking device is held securely for the duration of its operation and can then be quickly uncoupled and removed.

[0024] In one variant, the coupling can also be used to store the shrink fit device in the machine tool's tool magazine. From the magazine, it can be automatically inserted into the machine spindle via the tool changer.

[0025] In another variant, the tool changer can retrieve the shrink fit device from the tool magazine, not to insert it into the machine spindle, but to move it directly to a shrink fit holder clamped in the machine spindle and shrink the tool in or out. The shrink fit device's own coupling is particularly advantageous for this purpose.

[0026] Ideally, the shrink fit device is also designed in such a way that, if it has internal cooling, it can be supplied with coolant via the cooling system of the machine tool.

[0027] It is particularly expedient to design the shrink-fitting device such that the induction coil, with its first and, if present, its second casing, and at least with the power semiconductor components and / or the capacitors and / or ideally also the electronics for controlling the power semiconductor components, is housed inside a coil housing or coil housing ring that at least encloses the circumference of the induction coil and preferably also at least partially overlaps one, or better still, both, end faces of the induction coil. This results in a compact unit that accommodates all components required for operation, if necessary. These components are protected from external influences by the common housing and reliably shielded from contact with live parts by the operator.

[0028] Ideally, the coil housing is equipped with a plug, typically a Schuko plug (preferably in the form of a plug attached to the end of a flexible supply cable), for the direct feeding of single-phase AC mains voltage from the public grid (preferably 110 V or 230 V). This allows the shrink device to be operated almost anywhere. It only requires one of the sockets customary for electrical devices and, if necessary, a standard extension cable. It goes without saying that the invention is not necessarily limited to this particularly preferred type of power supply. The power supply can also be 3-phase and with other voltages, depending on the power required in the individual case and the power supply available at the respective location. Other voltages are of course also possible, particularly in countries that use a different mains voltage in the public grid.

[0029] Alternatively, equipping the shrinking device with a battery to power it has proven particularly advantageous. Such a device can also be highly mobile. It would then be advisable to provide a chassis, similar to a highly maneuverable hand truck, with the battery (e.g., a vehicle starter battery) in the lower section and the shrinking device in the upper section.

[0030] Furthermore, protection is also claimed for an entire shrink-fitting system consisting of a shrink-fitting device of the type according to the invention, which is characterized in that the shrink-fitting system additionally includes various couplings that can be attached to the shrink-fitting device and by means of which the shrink-fitting device can be secured to the spindle of a machine tool. This allows the shrink-fitting device to be attached to differently equipped machine tool spindles, so that it no longer matters whether the machine tool spindle is equipped for inserting, for example, an HSK coupling or a steep taper coupling.

[0031] Further design options, modes of operation and advantages can be found in the description of the embodiments provided below with the aid of the figures.

[0032] An intermediate jacket is preferably located between the first and second jacket. This preferably serves as a coolant-carrying element to protect the second jacket or the semiconductor elements mounted thereon from overheating. In contrast to the second jacket, it is preferably not split to ensure simple coolant guidance. Therefore, the intermediate jacket is either at least electrically (not thermally) insulated from the second jacket or it is made of electrically non-conductive material from the outset. It goes without saying that the coolant guide is sealed from the other components of the shrink device. Alternative concepts for cooling the second jacket without a specially designed intermediate ring are conceivable. Of course, this intermediate jacket can also be designed to additionally serve as (additional) shielding. Character list The Fig. 1 shows a first embodiment in the central longitudinal section. The Fig. 2 shows the first embodiment in a central longitudinal section, which in comparison to the Fig. 1 is rotated by 90° around the longitudinal axis L. The Fig. 3 shows the first embodiment in a perspective view obliquely from above, with the shielding collar removed. The Fig. 4 shows the first embodiment from above, with the shielding collar attached. The Fig. 5 shows the second shell of the first embodiment, equipped with power semiconductor components. The Fig. 6 shows a second embodiment which differs from the first embodiment only in the type of attachment to the machine tool or to the stand and is therefore identical to the first embodiment with regard to the arrangement of the capacitors and the circuit boards or printed circuit boards shown here. The Fig. 7 shows the circuit diagram of a circuit for feeding the induction coil which can be used according to the invention for the embodiments. Examples of implementation

[0033] The Fig. 1 gives a first basic overview of the device according to the invention. The basic principle of inductive shrinking and unshrinking

[0034] Clearly visible here is the induction coil 1 with its individual windings 2, into whose center a tool holder 4 is inserted to shrink the holding shaft H of a tool W into or out of the sleeve section HP. The functional principle underlying the shrinking and outward shrinking is described in more detail in German patent application DE 199 15 412A1. The content of this application is hereby incorporated into the present application. The shielding of the induction coil with magnetically conductive and electrically non-conductive means

[0035] The present invention places high demands on the shielding of the induction coil, even on the conventional shielding of which the type is already known.

[0036] On its outer circumference, the induction coil is provided with a first sheath 3 made of electrically non-conductive and magnetically conductive material. Typically, the first sheath 3 consists of either a ferrite or a metal powder or sintered metal material, the individual particles of which are electrically insulated from one another and thus, viewed as a whole, are magnetically conductive and electrically non-conductive. To rule out attempts to circumvent patent law, it should be noted that, in exceptional cases, a laminated sheath made of layered transformer laminations separated from one another by insulating layers is also conceivable. In the vast majority of cases, however, such a laminated sheath will not fulfill the desired purpose.

[0037] Particularly preferably, the first casing 3 is designed in such a way that it is completely closed in the circumferential direction, i.e. it completely covers the circumferential surface of the coil, so that even in theory no “magnetic gaps” remain, apart from irrelevant local breakthroughs, such as individual and / or small local holes or the like.

[0038] In exceptional cases, it is conceivable to design the casing 3 in such a way that it consists of individual segments covering the circumference, which have certain free spaces between them (not shown in the figure). This may work poorly in individual cases if the radial thickness of the individual segments is chosen to be so large in relation to the dimensions of the free spaces that the field entering the respective free space from the inside is attracted by the segments while still in the area of ​​the free space, thus preventing any significant stray field from passing through the free spaces.

[0039] Preferably, the shielding made of magnetically conductive and electrically non-conductive material does not end with the first sheath.

[0040] Instead, a magnetic cover 3a, 3b made of the said material is attached to at least one, preferably both, end faces of the first jacket 3, which cover usually contacts the first jacket 3.

[0041] On the end face of the induction coil facing away from the tool holder, the magnetic cover 3a is preferably designed as a pole piece that can be replaced completely or preferably in sections, i.e. as an annular structure with a central opening that forms a passage for the tool to be clamped or unclamped. The term "replaceable" preferably describes tool-free interchangeability, ideally achieved with the aid of a connection that can be operated with the bare hand, such as a bayonet connection. In this way, tool holders that accommodate different tool shank diameters can be machined. Nevertheless, it is ensured that the end face of the respective sleeve section HP on the inside of the coil comes to rest against the pole piece.

[0042] On the end face of the induction coil facing the tool holder, the magnetic cover 3b is preferably designed as a flat annular disc, which ideally completely covers the windings of the induction coil and has a central passage for the sleeve section.

[0043] Although not mandatory for the invention, it is highly advantageous if the magnetic covers 3a, 3b provided on the end face project (at least locally, preferably by at least 75%, ideally completely all the way around) in the radial direction beyond the first casing 3, preferably by a radial dimension that exceeds the radial thickness of the first casing 3 by a multiple, in many cases by at least four times. The radial projection should preferably run at an angle of 75° to ideally 90° to the longitudinal axis L. In this way, a reinforced "shielded trench" running circumferentially around the coil is created, the function of which according to the invention will be explained in more detail later.

[0044] Fig. Figure 1 shows a particularly preferred embodiment in which the pole shoe consists of a permanently in-place pole ring disc 3aa, which is coated on the outside with an insulating material, for example, plastic. A replaceable shielding collar 3bb is attached to the pole ring disc 3aa. As can be seen, the pole ring disc 3aa and the shielding collar 3bb are preferably connected to each other without any magnetic interruption. This is achieved by the shielding collar contacting the pole ring disc, preferably by resting on it from above.

[0045] As the Fig. 1 also shows, it can be particularly advantageous if the shielding collar has a stop section AS for engagement with the sleeve section, which extends into the interior of the induction coil.

[0046] As can also be seen from the Fig. 1, it is particularly advantageous in many cases if the shielding collar is divided into individual segments which can be moved obliquely with a movement component in the radial direction and a movement component in the direction parallel to the longitudinal axis L - so that both the free inner diameter of the shielding collar, which is available as a tool passage, and the depth to which the end of the shielding collar facing the sleeve section penetrates into the interior of the induction coil can be adjusted.

[0047] Ideally, the shielding collar has a conical shape or a shape that widens in the direction of the coil's longitudinal axis towards the tool tip.

[0048] In order to ensure the particularly high-quality shielding desirable for the purpose according to the invention, the shielding collar projects in the direction of the longitudinal axis L by at least twice, better by at least 2.75 times, the amount of the tool diameter over the free end face of the sleeve section of the tool holder. The additional shielding with an electrically conductive and magnetically non-conductive agent

[0049] Even careful shielding using the first casing 3 and the magnetic covers 3a, 3b cannot prevent a certain stray field, which is harmful to semiconductor components, from remaining on the outer circumference of the induction coil or on or in the area of ​​the circumferential surface of the first casing 3. For this reason, it is actually prohibited to place electronic components in this area that are sensitive to interference voltages induced by the stray field. This is particularly the case with semiconductor components, which form a significant part of the resonant circuit operating near resonance and used to power the induction coil.

[0050] In order to further improve the shielding, the invention provides for the induction coil and its first casing 3 to be surrounded on its outer circumference by a second casing 9 - at least if cooling of the second casing is omitted, preferably in such a way that the first and the second casing touch each other, ideally on the predominant or entire part of their mutually facing circumferential surfaces.

[0051] This second sheath 9 is made of a magnetically non-conductive and electrically conductive material. "Electrically conductive" here means not just a material that is electrically conductive locally, so to speak, "grain by grain," but rather a material that allows the formation of eddy currents to the extent relevant to the invention. More on this later.

[0052] The special thing about the second jacket is that it is preferably designed in such a way, and preferably made so thick in the radial direction, that eddy currents are generated in it under the influence of the stray field of the induction coil penetrating it, which weaken the unwanted stray field. The principle of active shielding by means of an opposing field is therefore used here. This can reduce the stray field on the outer surface of the second jacket by more than 50%, ideally by at least 75%. It is crucial that the stray field on the surface of the second jacket is reduced to such an extent that semiconductor components can be arranged there safely. It is crucial that this second jacket is thick in the radial direction oris magnetically separated from the induction coil by the first sheath, as otherwise it would heat up too much - which is not the case here, as it is not in the main field but only in the stray field.

[0053] The term “jacket” used here in connection with the second jacket is defined accordingly as that used above in connection with the first jacket. However, the term “jacket” in connection with the second jacket does not mean that a circumferentially endless tube section must be used. Instead, the jacket is preferably divided into individual segments that are electrically insulated from one another, for example by gaps filled with adhesive or plastic. This type of design serves to prevent a series short circuit, which would result in an endless tube section if a voltage breakdown into the second jacket occurs at a power semiconductor component and all power semiconductor components along the second jacket are at the same potential.It is important, however, that the individual segments are designed to be large enough so that the stray field can induce field-weakening eddy currents in them. In individual cases, a full jacket is not required, but a conductive grid structure of sufficient thickness (taking into account the specific individual conditions) may be sufficient.

[0054] It should be emphasized at this point that a radially thin-walled housing intended solely for mechanical protection purposes is insufficient, even if it were made of electrically conductive material. To achieve the desired effect according to the invention, a targeted design of the radial wall thickness of the second shell is required.

[0055] The preferred material for producing the second jacket 9 is aluminum.

[0056] The second casing 9 can have in its interior cooling channels which preferably run in the circumferential direction and may be helical, which in the latter case ideally form a thread.

[0057] In this case, it is particularly advantageous to construct the second casing 9 in two or more parts. The first part then has cooling channels machined into its periphery, which the second part seals.

[0058] At this point, the left part of the Fig. 2. Here you can see the coolant feed lines 17, which feed fresh coolant at the beginning of the cooling channel(s) 16 and remove used coolant. The special arrangement of the power semiconductor components, the capacitors and, if applicable, the electronic control

[0059] How to use the Fig. 2 and the Fig. 5, the second jacket is surrounded on its circumference by the power semiconductor components 10, which will be explained in more detail below and which are arranged directly on the outer circumference of the second jacket.

[0060] In the present case, the power semiconductor components have two large main surfaces and four small side surfaces. The large main surfaces are preferably more than four times larger than each of the individual side surfaces. The power semiconductor components 10 are arranged such that one of their large main surfaces is in thermally conductive contact with the second casing 9, usually at its outer circumference. Ideally, the respective large main surface of the power semiconductor component 10 is bonded to the circumferential surface of the second casing 9 using a thermally conductive adhesive. The second casing 9 therefore has a dual function here. It not only improves shielding and thus enables the arrangement of the power semiconductor components in its radial vicinity (less than 10 cm from its circumferential surface), but also optionally functions as a heat sink for the power semiconductor components.

[0061] Particularly preferably, the second casing 9 is provided with recesses 11, each of which accommodates a power semiconductor component, cf. Fig. 5. It is clearly visible that the recesses 11 are ideally designed to completely surround the power semiconductor component 10 they house on four sides. In this way, the power semiconductor component 10 sits in a depression, so to speak, and is therefore particularly well shielded.

[0062] As can also be clearly seen, each of the power semiconductor components 10 has three terminals 12 for the voltage supply. The terminals 12 of each power semiconductor component 10 extend into a region of the second casing 9 forming a recess 13, see FIG. Fig. 5. This optional recess 13 may facilitate the wiring of the terminals 12 of the respective power semiconductor component 10.

[0063] In the exemplary embodiment discussed, however, the novel arrangement of the power semiconductor components 10 does not end there. Instead, a particularly preferred solution is implemented here in which the capacitors 14a, 14b are grouped around the outer circumference of the induction coil. The capacitors 14a are preferably smoothing capacitors that are a direct component of the power circuit, while the capacitors 14b are preferably resonant circuit capacitors that are also a direct component of the power circuit. If one imagines them rotating around the center of the coil, the capacitors 14a, 14b form a cylindrical ring.

[0064] This cylindrical ring surrounds the induction coil and preferably also the power semiconductor components grouped around its circumference. To electrically connect the capacitors 14a, 14b, several electrical circuit boards 15a, 15b are provided, each enclosing the outer circumference of the induction coil. Each of these circuit boards 15a, 15b preferably forms an annular disk. Each of the circuit boards is preferably made of FR4 or similar materials commonly used for circuit boards. As can be seen, the rotational symmetry axis of each of the two circuit boards, designed here as circuit board annular disks, is coaxial with the longitudinal axis of the coil. Optionally, each of the circuit boards is attached to the inside of the trench of the magnetic covers 3a, 3b, where the magnetic covers 3a, 3b protrude radially beyond the second casing.

[0065] The upper of the two electrical boards 15a carries the capacitors—such as the smoothing capacitors 14a or the resonant circuit capacitors 14b—whose terminal lugs extend through the board or are connected to it using SMD technology, so that the smoothing capacitors hang from the board. The lower of the two boards is constructed similarly, with the capacitors—such as the resonant circuit capacitors 14b or the smoothing capacitors 14b—projecting upwards from it. Overall, the two electrical boards 15a, b accommodate all the capacitors 14a, 14b of the power circuit feeding the induction coil between them, viewed along the longitudinal axis of the induction coil.

[0066] One can therefore say that the power semiconductors form a first imaginary cylinder surrounding the induction coil, and the capacitors 14a, 14b form a second imaginary cylinder surrounding the first imaginary cylinder. Preferably, the capacitors, which are less sensitive to the stray field, form the imaginary outer cylinder, while the power semiconductor components, which require an installation space with as little stray field as possible, form the imaginary inner cylinder. The special design of the control board or other boards

[0067] It may be necessary to shield the circuit board on which the control unit is located and / or the circuit boards that contact the capacitors located directly in the power circuit.

[0068] For this purpose, multilayer circuit boards, or the so-called multilayer technology, are preferably used. Two or more circuit boards are stacked on top of each other. The conductor tracks run predominantly or essentially inside the resulting circuit board package. At least one outer main surface of the circuit board package is essentially fully metallized and therefore serves as shielding. The special supply of the induction coil

[0069] First of all, as a general remark, it should be noted that the Fig. The coil shown in Figure 1 is preferably not "fully wound" over its entire length. Instead, it preferably consists of two, generally essentially cylindrical, winding packages. These each form one end face of the induction coil. Preferably, one (here the lower one) of the two coils is movable in a direction parallel to the longitudinal axis L and can thus be adjusted during operation so that only the area of ​​the respective sleeve section that requires heating is heated. This prevents unnecessary heating and also the generation of an unnecessarily strong field, which naturally has a corresponding effect on the stray field encountered.Such a coil also contributes to reducing reactive power, as it lacks the windings in the central area, which are not absolutely necessary from the point of view of the most effective heating of the sleeve section of the tool holder, but which - if present - have the tendency to produce additional reactive power without making a really important contribution to heating.

[0070] In order to supply the induction coil in such a way that it has the desired effect and heats up the sleeve section of a tool holder sufficiently quickly, it is usually not sufficient to simply connect the induction coil directly to the 50 Hz AC mains voltage.

[0071] Instead, the frequency of the voltage supplying the coil must be increased. This is usually done electronically using a frequency converter. However, if the coil is simply supplied with a frequency converter without taking any special measures, as has often been the case in practice, high reactive power losses will occur.

[0072] These reactive power losses are not relevant from the point of view of energy efficiency, since the duty cycles of a shrinking device are short - after just a few seconds of duty cycle, the induction coil has heated the sleeve section of a tool holder to such an extent that the tool shank can be installed or removed, which is why the reactive power losses have not been perceived as disturbing so far.

[0073] The inventors have now recognized that avoiding reactive power losses is nevertheless important, as they lead, among other things, to heating of the induction coil itself. To avoid these reactive power losses, the invention provides for supplying the induction coil via a resonant circuit. In the resonant circuit according to the invention, the majority of the required energy oscillates periodically (at high frequency) back and forth between the induction coil and a capacitor unit. As a result, in each period or periodically, only the energy withdrawn from the resonant circuit through its heating power and other power losses needs to be replenished. This eliminates the previously very high reactive power losses. This means that, for the first time, the components of power electronics can be miniaturized to such an extent that - usually with an additional solution to the special shielding problem inherent in this installation - they can be integrated into the coil housing.This puts a portable induction shrinking device within reach, which, due to its total weight of less than 10 kg, can be carried by the user to the machine tool for on-site use.

[0074] The power electronics feeding the induction coil is preferably designed in such a way that the Fig. 7 and is characterized by the following features: On the input side, the power electronics are preferably supplied with the generally available mains current NST, which in Europe is 230 V / 50 Hz / 16A max(equivalent values ​​in other countries, e.g., 110 V in the USA). This is possible for the first time by eliminating the reactive power required previously, whereas a 380 V three-phase connection was previously required. This does not preclude the possibility that a three-phase connection may still be necessary under special conditions, e.g., high power requirements. Of course, three-phase current can also be used for low power requirements.

[0075] The mains current is then preferably stepped up to a higher voltage (transformer T) to reduce the currents flowing at a given power level. The current drawn from the mains is converted by the rectifier G into direct current, which in turn is smoothed by the smoothing capacitor(s) 14a.

[0076] This direct current feeds the actual resonant circuit SKS. The backbone of the resonant circuit consists of the power semiconductor components 10, the resonant circuit capacitors 14b, and the induction coil 1 used for shrinking and unshrinking. The resonant circuit is controlled and regulated by the control electronics SEK, which is essentially an integrated circuit (IC) and is fed with a low-voltage direct current via its own input GNS. This voltage is tapped, if necessary, after the rectifier G and the smoothing capacitor(s) 14a via a corresponding voltage divider resistor.

[0077] The power semiconductor components 10 are preferably implemented by transistors of the type “Insulated-Gate Bipolar Transistor” (IGBT for short).

[0078] The control electronics SEK preferentially switches the IGBT at a frequency that specifies the operating frequency set at the resonant circuit SKS.

[0079] It is important that the oscillating circuit SKS never operates exactly at resonance, which occurs when there is a phase shift between voltage U and current I of cos φ = 1. This would lead to the rapid destruction of the power semiconductor components 10 due to the voltage peaks. Instead, the control electronics SEK are designed to operate the power electronics or their oscillating circuit SKS in an operating range that is only close to the resonance or natural frequency of the system. Preferably, the oscillating circuit is controlled or regulated such that 0.9 ≤ cos φ ≤ 0.99 applies. Values ​​in the range 0.95 ≤ cos φ ≤ 0.98 are particularly favorable. This again prevents voltage peaks and therefore further promotes miniaturization.

[0080] It should also be noted that the minimized energy consumption allows battery operation for the first time. In the simplest case, a suitable high-current battery can be a car starter battery. Mobile unit

[0081] A special feature of the invention is that for the first time, a mobile shrink-wrapping unit is possible. It typically weighs less than 10 kg when ready for operation. This makes it easy to carry and maneuver, especially due to its design as a "spool housing with a connector plug." It is therefore "attached to the machine tool" for on-site use. This eliminates the previous concept of a stationary shrink-wrapping machine, to which the tool holders had to be delivered and removed again in order to perform a tool change and continue working.

[0082] First, it should be stated in general terms that at least the components "induction coil, the first shell and, if present, also the second shell, the power semiconductor components, and preferably also the capacitors" are housed in a common housing. Ideally, in addition to the induction coil, all components required for the operation of the induction coil, including the control electronics, are housed in the common housing.

[0083] Preferably, only a power cable exits the housing, which serves to supply power to the shrink device thus formed. Ideally, this cable has a plug at its end that allows tool-free connection to the power supply. Mains voltage is preferably used as the power supply, as mentioned above. The end of the power cable is then preferably equipped with a Schuko plug that complies with the respective national requirements.

[0084] If the shrinking device is to be held by hand, centering devices are advantageously attached to the coil housing to facilitate the central positioning of the coil relative to the tool axis. The centering devices can, for example, be designed as radially movable fingers Fi, as shown in Fig. 1 and Fig. 2 indicated.

[0085] It has proven particularly useful if the device is provided with at least one coupling KU, which allows it to be coupled to the machine tool.

[0086] This allows the device to be easily attached to the machine tool and then assumes a safe working position that is protected from contamination by coolant and chip particles.

[0087] This coupling KU preferably corresponds to the common coupling profiles used for the tool holders to be machined with the shrinking device according to the invention, e.g. an HSK profile, as Fig. 2. To move the shrink-fitting device according to the invention into a safe working position, all that is required is to uncouple the tool holder to be changed from the machine tool spindle and, instead, to couple the shrink-fitting device with its identical coupling profile to the machine tool spindle. It is particularly advantageous if the shrink-fitting device coupling can be removed from the shrink-fitting device during operation, preferably by hand without the need for tools (especially with a bayonet lock). This allows the shrink-fitting device coupling to be easily adapted to the coupling type used on the respective machine tool – steep taper coupling, HSK, etc.

[0088] Ideally, the respective couplings are connected to the shrinking device according to the invention in such a way that coolant / cooling lubricant discharged from the cooling system of the machine tool can flow through the at least one cooling channel that the shrinking device has, preferably in its second casing - as explained above.

[0089] In addition, a cooling device can be provided—preferably one integrated into the shrinking device (usually adjacent to the induction coil). The sleeve section of the tool holder is inserted into this cooling device after the shrinking process is completed in order to actively cool it to a safe contact temperature. This cooling device is also expediently fed by the cooling system of the machine tool, usually also via the aforementioned coupling. Therefore, protection is also claimed for the use of the cooling fluid discharged by a machine tool for cooling purposes (cooling the second sleeve and / or the tool holder) within a shrinking device.

[0090] Alternatively, the shrink fit device can also be stored in the machine tool's tool magazine. The tool changer can then either automatically insert the shrink fit device into the machine spindle or move it to a tool holder clamped in the spindle to shrink or shrink a tool. In the latter case, the power supply can be provided via a cable that is plugged directly into the shrink fit device. In both cases, the shrink fit device does not need to be held manually. List of reference symbols 1 induction coil 2 turns (electrical winding) of the induction coil 3 First coat 3a frontal magnetic cover, preferably in the form of a pole piece 3aa Pole ring disc 3bb shielding collar 3b frontal magnetic cover 4 tool holders 7 Passage of the pole piece 9 Second coat 10 power semiconductor components 11 Recess 12 Connection of a power semiconductor component 13 Rebound of the second coat 14a smoothing capacitor 14b Resonant circuit capacitor 15a Electrical board 15b Electrical circuit board 16 cooling channel 17 Cooling channel feed line AS stop section G Rectifier GNS DC low voltage to supply the control electronics H Tool holder shaft HP sleeve section of the tool holder IC integrated circuit as part of the control electronics KU coupling for coupling the shrinking device to a machine tool L Longitudinal axis of the induction coil and the tool holder NST mains power SEK control electronics SKS oscillating circuit T transformer W tool Fi radially movable finger for centering the sleeve section or the tool holder in the induction coil

Claims

[1] Shrink-fitting device for clamping and unclamping tools (4) having a tool shank (H), comprising a tool holder having a sleeve section (HP) open at its free end made of electrically conductive material for frictionally receiving the tool shank (H), and comprising an induction coil (1) enclosing the sleeve section (HP) of the tool holder, designed as a toroidal or cylindrical coil to be supplied with a preferably high-frequency alternating current, for heating the sleeve section (HP), wherein the induction coil (1) carries on its outer circumference a first casing (3) made of magnetically conductive and electrically non-conductive material, and the device comprises power semiconductor components (10) for producing an alternating current feeding the induction coil (1), as well as an induction coil housing preferably made of insulating material, characterized bythat the induction coil (1) and its first casing (3) are surrounded on the outer circumference by a second casing (9) which consists of magnetically non-conductive and electrically conductive material and is designed such that a stray field occurring in its environment generates eddy currents in the second casing (9) and thereby weakens the stray field and that at least the power semiconductor components (10) are accommodated together with the induction coil (1) in an induction coil housing which encloses the induction coil (1), its first and second casings (3, 9), and the power semiconductor components (10) at least along the circumference of the induction coil (1). [2] Shrinking device according to claim 1, characterized by that the power semiconductor components (10) are arranged directly on the outer circumference of the second casing (9). [3] Shrinking device according to claim 2, characterized bythat the second jacket (9) forms a heat sink for the power semiconductor components (10) [4] Shrinking device according to one of the preceding claims, characterized by that the second casing (9) has one or preferably several recesses (11), each of which accommodates a power semiconductor component (10), preferably in such a way that the power semiconductor component (10) is enclosed on four sides by the second casing (9). [5] Shrinking device according to one of the preceding claims, characterized by that the device comprises a rectifier (G) and smoothing capacitors (14a) and / or resonant circuit capacitors (14b) for producing a high-frequency alternating voltage within the device for feeding the power semiconductor components (10), wherein the smoothing capacitors (14a) and / or the resonant circuit capacitors (14b) are preferably grouped in a cylindrical ring shape on the outer circumference of the induction coil (1) around the latter. [6] Shrinking device according to claim 1 or claim 2, characterized by that the shrinking device has an induction coil (1) designed for shrinking and unshrunking tool shanks (H) from tool holders (4), that the induction coil (1) and its first casing (3) made of magnetically conductive and electrically non-conductive material are surrounded on the outer circumference by a second casing (9) which consists of magnetically non-conductive and electrically conductive material and is designed in such a way that it weakens a stray field occurring in its surroundings by forming eddy currents. [7] Shrinking device according to claim 1 or claim 6, characterized bythat the shrinking device has an induction coil (1) designed for shrinking and unshrinking tool shanks (H) from tool holders (4), and that the induction coil (1) and at least the power semiconductor components (10) required to produce the alternating voltage feeding the induction coil (1) and converted from the mains voltage (NST) are accommodated together with the induction coil (1) in the induction coil housing. [8] Shrinking device according to one of the preceding claims, characterized by that the end face of the induction coil (1) facing away from the tool holder is covered with a cover (3a, 3b) made of magnetically conductive and electrically non-conductive material, preferably in the form of a pole shoe (3a) covering the entire end face. [9] Shrinking device according to claim 8, characterized bythat the cover (3a, 3b) locally has a shielding collar (3bb) which projects in the direction of the longitudinal axis (L) by at least twice the amount of the tool diameter over the free end face of the sleeve section (HP) of the tool holder (4). [10] Shrinking device according to claim 9, characterized by that the shielding collar (3bb) can be replaced without tools. [11] Shrinking device according to one of the preceding claims, characterized by that the end face of the induction coil (1) facing the tool holder is covered by magnetically conductive and electrically non-conductive material. [12] Shrinking device according to one of the preceding claims, characterized in that the device has at least one electrical circuit board (15a, 15b) which surrounds the outer circumference of the induction coil (1) and electrically contacts the smoothing capacitors (14a) and / or the power semiconductor components (10), wherein it is preferred that the circuit board (15a, 15b) is covered on at least one of its outer sides with an electrically conductive layer which is earthed in order to reduce voltage potentials. [13] Shrinking device according to claim 12, characterized by that the circuit board (15a, 15b) is a circuit board ring disc, the rotational symmetry axis of which is preferably coaxial, otherwise parallel to the longitudinal axis (L) of the induction coil (1). [14] Shrinking device according to claim 13, characterized by that two circuit board ring discs are present, between which the smoothing capacitors (14a) are arranged along the circumference of the induction coil (1). [15] Shrinking device according to one of the preceding claims, characterized by that the second jacket (9) forms one or more cooling channels (16) which preferably run in its interior. [16] Shrinking device according to one of the preceding claims, characterized by that the device has a coupling (KU) for fastening the device in the holder of a machine tool spindle. [17] Shrinking device according to claim 16, characterized by that the shrinking device is designed in such a way that it can be supplied with coolant via the cooling system of the machine tool. [18] Shrinking device according to one of the preceding claims, characterized bythat the induction coil (1) with its first and second casing (3, 9) and at least the power semiconductor components (10) and / or the smoothing capacitors (14a) and ideally also the electronics for controlling the power semiconductor components (10) are accommodated in the interior of a coil housing or coil housing ring which at least encloses the circumference of the induction coil (1) and preferably also overlaps at least one, better both, end faces of the induction coil (1). [19] Shrinking device according to claim 18, characterized by that the coil housing has a plug for the direct feeding of mains alternating voltage (NST) from the public grid. [20] Shrinking device according to one of claims 1 to 18, characterized by that the shrink device is battery operated. [21] Shrinking device according to one of the preceding claims, characterized bythat a shielding collar (3bb) is provided which consists of individual segments which are movable in such a way that they can be moved with a movement component in the radial direction as well as with a movement component in the axial direction. [22] Shrinking device according to one of the preceding claims, characterized by that centering elements are provided on the end face of the induction coil (1) facing the tool holder (4) and / or in the air space inside the induction coil (1), which centering elements force the coaxial positioning of the sleeve section (HP) in the induction coil (1) when it is pushed into the induction coil (1) as far as it will go. [23] Shrinking device according to one of the preceding claims, characterized bythat the shrinking device has at least two coil winding sections which can be moved towards or away from each other in a direction parallel to the longitudinal axis (L) during operation for the purpose of adjusting to the geometry of a sleeve section (HP) to be heated. [24] Shrinking system consisting of a shrinking device according to one of the preceding claims 1 to 23, characterized by that the shrinking system also includes different couplings (KU) that can be attached to the shrinking device and by means of which the shrinking device can be fixed to the spindle of a machine tool.

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