Device and method for fixing objects using magnetic forces

Abstract

The invention relates to a device and a method for fixing objects by means of magnetic forces generated by an arrangement of magnets (2). At least one linear arrangement of magnets (2) is provided, wherein the poles of magnets (2) of this linear arrangement are switchable.

Description

[0001] The invention relates to a device and a method for fixing an object by means of magnetic forces.

[0002] Such devices can, for example, be designed as magnetic clamping systems.

[0003] Magnetic clamping systems are used in workpiece machining to clamp workpieces. By clamping the workpieces using the magnetic clamping system, they are fixed in predetermined positions within the area of ​​the machining center, allowing the machining center to process the workpiece with suitable tools.

[0004] Clamping a workpiece is achieved by magnetizing it through the magnetic field of the magnets.

[0005] Such magnetic clamping systems can, in particular, feature a linear arrangement of magnets. The magnets form a fixed, predetermined arrangement of alternating north and south poles, thereby obtaining a fixed pole pitch for the linear arrangement.

[0006] The polar division is defined by the distance between the center of a north pole and the nearest south pole, or vice versa.

[0007] These clamping systems are particularly well-suited for clamping workpieces of considerable length, sometimes in the meter range. The dimensions of the linear arrangement are adjusted accordingly.

[0008] In particular, with such clamping systems, a key requirement is to clamp two preferably identical workpieces one above the other in order to then be able to machine the two workpieces simultaneously with a machine tool, resulting in a significant rationalization effect.

[0009] In order to securely clamp a workpiece, magnetic fields with appropriate field heights must be generated using magnets, so that the magnetic fields extend as completely as possible over the height of the workpiece.

[0010] This requirement applies particularly when two workpieces are to be clamped one above the other. In such cases, the magnets must generate magnetic fields with field heights such that the magnetic fields extend not only through the lower workpiece but also through the upper one.

[0011] With the aforementioned magnetic clamping systems, the field heights of the magnetic fields are often insufficient to clamp both workpieces uniformly over their entire length.

[0012] Even when sufficiently high magnetic field heights are achieved to clamp two workpieces on top of each other, a problem often arises: the magnetic fields protrude locally beyond the upper workpiece. This portion of the magnetic fields protruding beyond the upper workpiece contributes nothing to the holding force, i.e., the magnetic clamping force generated by the magnets. This means that the holding forces are locally reduced, so uniform clamping of the workpieces along their lengths is not guaranteed.

[0013] This leads to unsatisfactory results when machining the workpieces using a machine tool. Because the workpieces are clamped with lower adhesive forces in certain areas, their holding power is reduced locally, allowing for local movement. This results in unevenness in the machining process, meaning the workpieces are not machined uniformly along their length.

[0014] The invention is based on the objective of providing a device and a method by which a reliable, reproducible fixing of different objects is made possible by means of magnetic forces.

[0015] To achieve this object, the features of the independent claims are provided. Advantageous embodiments and expedient developments of the invention are described in the dependent claims.

[0016] The invention relates to a device for fixing objects by means of magnetic forces generated by an arrangement of magnets. At least one linear arrangement of magnets is provided, wherein the poles of magnets in this linear arrangement are switchable.

[0017] The invention also relates to a corresponding method.

[0018] In its simplest form, the device according to the invention comprises only a linear arrangement of magnets that form specific poles.

[0019] According to the invention, at least for some of the magnets a pole reversal can be provided, i.e. the poles of these magnets can be switched by switching operations.

[0020] This pole switching allows the pole pitch of the magnets in the linear arrangement to be selectively changed. The pole pitch is defined by the distance from the center of one north pole to the center of the next. If the linear arrangement has an alternating arrangement of north and south poles, the pole pitch corresponds to the distance between two consecutive magnets. If, for example, the linear arrangement has an alternating arrangement such that two consecutive north poles are followed by two consecutive south poles, and so on, the pole pitch is twice as large.

[0021] The invention is based on the understanding that the field strength of the magnetic fields generated by the magnets can be changed by varying the pole pitch. Generally, the field strength increases with the greater the pole pitch.

[0022] If, in the linear arrangement according to the invention, the properties of the magnets, such as the strengths of the generated magnetic fields, are fixed and unchanged, the pole pitch can be changed simply by switching the poles of the magnets in this linear arrangement, thus achieving a variation in the field heights of the magnetic fields.

[0023] According to the invention, this effect is used to enable the device to securely fix different objects.

[0024] In particular, the device according to the invention can be used to fix objects with different heights, especially objects stacked on top of each other. The device according to the invention is advantageously designed as a magnetic clamping device for clamping workpieces, wherein the workpieces clamped by the clamping device are machined using machine tools.

[0025] A streamlined machining of workpieces is achieved in particular by clamping two, preferably identical, workpieces one above the other with the clamping device, so that they can be machined simultaneously with the machine tool.

[0026] In particular, elongated, rod- or rail-shaped workpieces can also be clamped using the clamping device according to the invention. The longitudinal axis of the workpiece(s) on the clamping device runs in the direction of, preferably parallel to, the longitudinal direction of the linear arrangement of the magnets.

[0027] The pole pitch of the magnets is predetermined depending on the training and the number of clamped workpieces.

[0028] Generally, the pole pitch is determined based on workpiece characteristics such as geometry, alloy composition, heat treatment, and the like. Furthermore, the pole pitch is selected depending on whether only one workpiece or two workpieces stacked on top of each other are to be clamped.

[0029] These specifications are stored in the form of characteristic curves, for example in a computer such as a PC, and can be retrieved by a user so that he can specify the pole pitch of the magnets in a suitable manner.

[0030] According to the invention, the variation of the pole pitch of the linear arrangement of magnets is achieved by a pole switching of magnets of this linear arrangement.

[0031] According to an advantageous embodiment, the magnets have coils by means of which the polarities of the magnets are predetermined.

[0032] Then, by controlling a coil, the polarity of the respective magnet can be switched.

[0033] The magnets are best designed in the form of electromagnets or electro-permanent magnets.

[0034] For varying the pole pitch of the linear arrangement of the magnets, a switching unit is advantageously provided, by means of which the poles of the pole-changing magnets can be switched.

[0035] The switching unit can include a computing unit, such as a microprocessor, which controls the switching elements associated with the pole-changing magnets. These switching elements can, for example, control the direction of the current supplied to the coils of the pole-changing magnets.

[0036] In principle, all magnets in the linear arrangement can be pole-changing, so that almost any pole pitch can be achieved in the linear arrangement.

[0037] In particular, only every second magnet in the linear arrangement, or half of the magnets, is pole-changing. This significantly simplifies the control logic for pole switching, as only every second magnet, rather than every single one, needs to be controlled by the switching unit. While this allows for a limited number of pole pitch configurations, these are sufficient for a large number of different applications, especially for situations where only one workpiece or two stacked workpieces need to be clamped with the clamping device.

[0038] If only one workpiece is clamped with the clamping device, a smaller pole pitch is advantageously chosen than in the case where two workpieces are clamped one above the other with the clamping device.

[0039] This pole reversal generates magnetic field heights for both applications such that they are entirely contained within the workpiece(s), specifically preventing any areas of the magnetic field from protruding beyond the workpiece(s). This avoids local reductions in clamping forces when clamping the workpiece(s), meaning the magnetic flux densities are essentially homogeneous and constant along the length of the workpiece(s). As a result, the workpiece(s) can be machined reproducibly and uniformly along their entire length using a single machining center, eliminating any waviness in the machining result.

[0040] The ability to switch poles generally reduces uneven magnetic flux density distributions and the resulting secondary effects. An example of this is the geometric changes in workpieces due to magnetostriction in the range of 0.2 µm to 0.8 µm.

[0041] The device according to the invention, in particular the clamping device, can be further developed to include a matrix arrangement of magnets. Thus, the device has multiple linear arrangements of magnets in both the column and row directions.

[0042] Then, magnets of linear arrangements in row and / or column direction can be switched in their polarity, so that the pole direction of linear arrangements of magnets can be changed in both the row and column direction of the matrix.

[0043] The invention will be explained below with reference to the drawings. The drawings show: Fig. 1: Exemplary embodiment of the device according to the invention in the form of a clamping system with a clamped workpiece. Fig. 2: Block diagram of the device according to Fig. 1. Fig. 3a-d: Representations of pole switching of magnets of the device according to Fig. 1. Fig. 4: Device according to Fig. 1 with two clamped workpieces. Fig. 5: Exemplary embodiment of the device according to the invention with a matrix arrangement of magnets.

[0044] Fig. Figure 1 shows an embodiment of the device according to the invention in the form of a clamping device 1.

[0045] The clamping device 1 comprises a linear arrangement of magnets 2, which are mounted in a housing 3. The rod-shaped magnets 2 extend over the entire width of the housing 3, thus forming a series arrangement, wherein the arrangement according to Fig. 1. The magnets 2 with north poles N and south poles S are arranged alternately in the housing 3. The open top of the housing 3 is closed with a pole plate 4. The top of the pole plate 4 forms a support surface on which a workpiece 5 to be clamped is placed.

[0046] In the present case, the identically designed magnets 2 each have a core made of magnetizable material, which is surrounded by coils. The magnets 2 thus form electromagnets. If the core consists of permanent magnet material, the magnets 2 form electro-permanent magnets. In the representation according to Fig. The clamping device 1 has twelve magnets 2. Of course, a different number of magnets 2 can also be provided.

[0047] By energizing the coils of the magnetic fields, the magnets generate two magnetic fields, which magnetize the workpiece 5. The workpiece 5 is clamped in place by the magnetic forces thus generated, i.e., holding forces.

[0048] The workpiece 5 can be designed in a rod- or rail-shaped manner, such that its length is considerably greater than its extent perpendicular to the longitudinal direction. Accordingly, the magnets 2 of the clamping device 1 form a correspondingly dimensioned linear arrangement.

[0049] According to the invention, the poles of magnets 2 of this linear arrangement can be switched.

[0050] As in Fig. As shown in Figure 2, the clamping device 1 has a switching unit 6. This switching unit includes a computer unit, such as a microprocessor, which controls switching elements 7 that can switch the poles of the magnets 2 of the clamping device 1. For example, the switching is carried out by changing the current directions of the currents supplied to the coils of the respective magnets 2 using the switching elements 7.

[0051] Switching unit 6 is associated with an input / output unit 8, through which a user can enter commands to control switching unit 6. The input / output unit 8 can be integrated into a computer, such as a PC.

[0052] The switching unit 6 can, in principle, be used to switch the poles of all magnets 2.

[0053] Alternatively, the poles of a number of the magnets 2 of the clamping device 1 are fixed, whereby only the poles of the remaining magnets 2 are switched, which reduces the circuitry required to carry out the switching operations.

[0054] Such embodiments are shown in the Fig. 3a to 3d.

[0055] In Fig. 3a are the magnets 2 of the clamping device 1 according to Fig. 1 according to their order in the linear arrangement M1 ... M12.

[0056] Fig. Figure 3b shows a basic configuration of the magnets 2 with an alternating arrangement of north and south poles. This arrangement has a pole pitch (defined by the distance of one north pole to the nearest south pole) that corresponds to the distance between two adjacent magnets 2.

[0057] Fig. Figure 3c shows a configuration of magnets 2 in which two adjacent north poles are followed by two adjacent south poles, and so on. This arrangement has a pole pitch that is twice as large as the pole pitch of the arrangement according to Figure 3c. Fig. 3b is.

[0058] For switching between the configurations of Fig. 3b and Fig. For 3c, it is sufficient if magnets M2, M3, M6, M7, M10, and M11 are pole-changing. The remaining magnets do not need to be pole-changing.

[0059] Fig. Figure 3D shows a configuration of magnets 2 in which four adjacent north poles are followed by four adjacent south poles, and so on. This arrangement has a pole pitch that is four times larger than the pole pitch of the arrangement according to [reference missing]. Fig. 3b is.

[0060] For switching between the configurations of Fig. 3b and Fig. For 3d it is sufficient if the magnets M2, M4, M5, M7, M10, M12 are pole-changing.

[0061] Fig. Figure 1 shows an application in which a workpiece 5 is clamped with the clamping device 1, wherein the longitudinal axis of the workpiece 5 runs parallel to the longitudinal axis of the linear arrangement of the magnets 2.

[0062] In this case, the configuration with alternating north and south poles is activated with the switching unit 6. With this configuration, the field heights of the magnetic fields are generated such that the magnetic fields run along the entire length of the linear arrangement within the workpiece 5, without the magnetic fields protruding upwards above the workpiece 5, which would lead to a local reduction in the holding force.

[0063] Fig. Figure 4 shows an application in which two workpieces 5 are clamped with the clamping device 1, wherein the longitudinal axes of the workpieces 5 run parallel to the longitudinal axis of the linear arrangement of the magnets 2.

[0064] In this case, the configuration with alternating north and south poles is according to Fig. 3c is activated with the switching unit 6. With this configuration, the field heights of the magnetic fields are generated such that the magnetic fields run within both workpieces 5 along the entire length of the linear arrangement, without the magnetic fields protruding upwards above the workpieces 5, which would lead to a local reduction in the holding force. Since the pole pitch of the linear arrangement of magnets 2 is twice as large as the pole pitch in the case of Fig. 1, correspondingly larger field heights of the magnetic fields are achieved, so that the magnetic fields are essentially uniform in both workpieces 5.

[0065] Thus, for both in the Fig. 1 and Fig. In the 4 applications shown, a uniform clamping of the workpieces 5 over their entire length is achieved.

[0066] The pole pitch, which can be set using the switching unit 6, is generally determined by the characteristics of the workpieces 5 (geometry, alloy composition, heat treatment, etc.) and by the number of workpieces 5 stacked on top of each other. Suitable pole pitches for these characteristics can be stored as characteristic curves in the switching unit 6. Using the input / output unit 8, a user can request the characteristic curve and select the appropriate pole pitch for the specific application.

[0067] Fig. Figure 5 shows a variant of the device according to the invention, in particular clamping device 1, with a matrix arrangement of magnets 2.

[0068] The magnets 2 in the individual rows and columns of the matrix form linear arrangements of magnets 2, for which, according to the embodiment of the Fig. 1 to 3 a pole reversal of magnets 2 is provided. List of reference symbols 1 clamping device 2 magnets 3 housings 4-pole plate 5 workpieces 6 switching unit 7 Switching element 8 Input / Output Unit North Pole S South Pole

Claims

[1] Device for fixing objects by means of magnetic forces generated by an arrangement of magnets (2), characterized by that at least one linear arrangement of magnets (2) is present, wherein poles of magnets (2) of this linear arrangement are switchable. [2] Device according to claim 1, characterized by that it has a matrix arrangement of magnets (2) in which poles of magnets (2) can be switched row by row or column by column. [3] Device according to one of claims 1 or 2, characterized by that in the or a linear arrangement of magnets (2) a predetermined number of magnets (2) are pole-switchable, and that the other magnets (2) of the linear arrangement are not pole-switchable. [4] Device according to one of claims 1 to 3, characterized by that the magnets (2) have coils by means of which the polarities of the magnets (2) are predetermined. [5] Device according to claim 4, characterized bythat the polarity of the respective magnet (2) can be switched by controlling a coil. [6] Device according to one of claims 1 to 5, characterized by that the magnets (2) are designed in the form of electromagnets or electro-permanent magnets. [7] Device according to one of claims 1 to 6, characterized by that a switching unit (6) is provided by means of which the poles of the pole-switchable magnets (2) can be switched. [8] Device according to one of claims 1 to 7, characterized by that a pole pitch for the or a linear arrangement of magnets (2) is specified by a pole switching of magnets (2). [9] Device according to claim 8, characterized by that the pole pitch is specified depending on the object to be fixed. [10] Device according to claim 9, characterized bythat the pole pitch determines the field heights of magnetic fields generated by the magnet or a linear arrangement of magnets (2). [11] Device according to one of claims 1 to 10, characterized by that two workpieces (5) lying on top of each other are fixed with it. [12] Method for fixing objects by means of magnetic forces generated by an arrangement of magnets (2), characterized by that at least one linear arrangement of magnets (2) is present, wherein poles of magnets (2) of this linear arrangement are switchable.

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