Spindle unit for a machining device with a spindle lock

Abstract

Spindle unit (2a) for a machining device, in particular a turning spindle unit or milling spindle unit, comprising: a spindle shaft (4a) rotatably mounted in a housing (3a), a clamping device (6a) arranged on the spindle shaft (4a) for clamping a workpiece or a tool, a motor drive (8a) connected to the spindle shaft (4a) for driving the spindle shaft (4a) about a drive axis (A), a clamping device (9a) for clamping the spindle shaft (4a) in a freely selectable angular position about the drive axis (A), wherein the clamping device (9a) is arranged between the spindle shaft (4a) and a fixed part of the spindle unit, and an actuating device (16) for actuating and / or releasing the clamping device (9a), wherein the clamping device (9a) is arranged between or substantially between an axial end of the spindle housing and the clamping device (6a) or in the region of the transition between the axial end of the spindle housing and the clamping device, characterized in that the clamping device (9a, 9b) has a clamping element (10), wherein the clamping element (10) has at least three elongate recesses (12a-f) in a plane perpendicular or substantially perpendicular to the drive axis (A), so that the clamping element (10) is elastically deformable in the axial direction and the axial extent of the clamping element (10) can be increased and / or decreased by actuating the clamping device.

Description

The invention relates to a spindle unit for a machining device, in particular a rotary spindle unit or milling spindle unit, and to a workpiece machining device having at least one such spindle unit.A workpiece clamped in a rotary spindle unit is driven to rotate for machining. In addition, when the spindle unit is at a standstill, the clamped workpiece can be machined, for example, with a drill or a milling cutter. In order to ensure precise workpiece processing, the workpiece must be held securely in a specific angular position by the spindle unit. For example, a brake can be used for locking or locking the spindle shaft, e.g. an expansion bushing arranged on the spindle shaft. When the expansion sleeve expands or deforms radially outward, the spindle shaft is locked in position.DE 1 112 873 B shows a clamping device with axially movable clamping jaws for a workpiece spindle. For this purpose, an extensible ring engages in a groove of the spindle. The ring consists of two ring parts fastened to the headstock housing 11 and each has a resilient side wall. For actuation, the interior of the ring is pressurized by fluid via a channel so that the walls of the ring press against the flanks of the groove.DE 39 13 139 C2 shows a machine tool with a spur toothing ring which can be axially displaced by means of pressure pistons and compression springs for locking the spindle.It is an object of the invention to provide a spindle unit for a machining device and a workpiece machining device with such a spindle unit that provides reliable machining of workpieces.This object is achieved with the features of claims 1, 5, 13 and 14, respectively. Advantageous embodiments are the subject matter of the dependent claims.According to claim 1 or 5, a spindle unit is provided, for example a milling spindle unit or a rotating spindle unit. The spindle unit can preferably be used both for clamping and rotating driving a workpiece and a tool (e.g. drill / milling cutter). For example, the spindle unit or a plurality of spindle units can be used in a vertically or horizontally oriented machining device. Vertical or horizontal refers to the alignment of the drive or working axis of the spindle unit(s). For clamping a workpiece or a tool, a clamping device is fastened or attached to the spindle shaft. A motor drive is connected to the spindle shaft, so that the spindle shaft can be driven about its drive axis or working axis. For example, the spindle unit is designed as a motor spindle, i.e. the spindle shaft is driven directly, wherein the motor shaft preferably simultaneously forms the spindle shaft. In claim 5, the spindle unit can alternatively be designed as a central rotary spindle or central drive unit, so that e.g. a rod-shaped workpiece can be clamped in the centre and machined (simultaneously) at both ends.The spindle unit has a clamping device which is arranged between the spindle shaft and a fixed part of the spindle unit. A fixed part of the spindle unit is a part of the spindle unit that is stationary when the spindle shaft is driven in rotation, for example a spindle flange of the housing via which the housing is connected to the spindle shaft. The clamping device is designed to hold or clamp the spindle shaft in any freely selectable angular position about the drive axis.For actuating and / or releasing the clamping device, an actuating device is provided. For example, the clamping device can be actuated by a pneumatically or hydraulically driven actuating device. Unless otherwise indicated, the spindle shaft is locked or clamped when the clamping device is "actuated", and the spindle shaft is freely movable about its drive axis when the clamping device is "released".According to claim 1 or embodiment according to claim 6, the clamping device is arranged between the motor drive and the clamping device. In particular, the clamping device is arranged adjacent or substantially adjacent to the clamping device, so that a rotationally secure fixing takes place as close as possible to the clamping device or to the clamped workpiece / tool, and thus the highly precise machining of a workpiece is possible. If, in contrast to this embodiment, a locking takes place at a greater distance from the clamping device, e.g. on or behind the motor drive, there is the risk that the spindle shaft cannot hold a clamped workpiece exactly in a locked position (e.g. due to the lever and torsion forces occurring during machining), whereby the precision of the machining is reduced. In one embodiment, the clamping device is arranged between or substantially between an axial end of the spindle housing and the clamping device or in the region of the transition from the axial end of the spindle housing and the clamping device.According to claim 5 or in the embodiment according to claim 4, the clamping device can be actuated in the axial direction or the actuating device causes a movement of the clamping device or of a clamping element of the clamping device in the direction of the drive axis. When the clamping device is actuated, an axial or substantially axial clamping action / force acts in the direction of the drive axis. Unless stated otherwise, the term "axial" refers hereinafter to the drive axis of the spindle shaft or spindle unit. Preferably, when the clamping device is actuated, the clamping force acts between two axially opposite or substantially opposite ends of the clamping device.In the case of the above-described conventional expansion bushing, which expands radially in order to lock a spindle shaft, there is the risk, at high rotational speeds of the spindle shaft and the centrifugal forces occurring in the process, that the (released) expansion bushing deforms radially and unintentionally brakes the spindle or heats it by friction. In contrast, the clamping device according to claim 5 or 4 is axially actuated or moves in the axial direction to generate an axially acting clamping force. That is to say, the centrifugal forces occurring during operation of the spindle unit cannot actuate the clamping device unintentionally. This allows reliable machining of a workpiece at any time.The clamping device preferably has a first clamping surface connected in a rotationally fixed manner to the housing of the spindle unit and a second clamping surface connected in a rotationally fixed manner to the spindle shaft, which is arranged opposite and preferably parallel to the first clamping surface. The first and / or the second clamping surface can be displaced in the axial direction by means of an actuating device, so that a gap can be selectively adjusted between the clamping surfaces by means of the actuating device ("clamping device released") or the clamping surfaces come to rest against one another ("clamping device actuated"). Since the housing of the spindle unit is fixed (also during operation of the spindle unit), the first clamping surface connected to the housing is also fixed. That is to say that when the first and second clamping surfaces bear against one another or are pressed against one another, the (rotatable) spindle shaft is connected to the (fixed) housing in a rotationally fixed or rotationally fixed manner, with the result that the spindle shaft is locked as described above.Particularly preferably, the clamping device has an actuating device and a clamping element with a second clamping surface. For example, the clamping element is designed as a clamping disk. By means of the actuating device, the clamping element or the part of the clamping element on which the clamping surface is arranged can be actuated in the axial direction, so that a clamping is effected in that the second clamping surface bears against a first clamping surface. Additionally or alternatively, the clamping element is actuatable in (an opposite) axial direction in order to release the clamping by removing the second clamping surface from the first clamping surface.For example, when the clamping device is actuated, two metallic clamping surfaces act on one another or at least two metallic surfaces are clamped against one another. Alternatively, for example, one clamping surface or both clamping surfaces can be covered with a (brake) lining or be roughened, so that the static friction between the clamping surfaces is increased, in order in turn to improve the holding effect with constant clamping force or contact pressure.The clamping surfaces of the clamping device are preferably paired with one another with respect to their surface shape. When the surfaces are in mutual contact, no gap or gap region is present. The clamping surfaces can, however, also be (slightly) curved and, for example, come to bear completely against one another only by the clamping and deformation or completely over a region. The basic shape of the surfaces is preferably perpendicular to the spindle axis, but can also be formed inclined (e.g. cone-surface-shaped).Preferably, the first and / or the second clamping surface are configured to be smooth or substantially smooth or do not have a structured surface. In particular, the clamping surfaces have no toothing and no angular division. As a result, the spindle shaft can be arrested or clamped continuously at arbitrarily adjustable angles. Preferably, the clamping device, in particular a clamping element of the clamping device, is connected to the spindle shaft or alternatively connected to the fixed part of the spindle unit. For example, a clamping element is screwed and / or connected in a positive-locking manner to the spindle shaft. By means of the actuating device, an unfixed end of the clamping element can then be pressed against the fixed part of the spindle unit or a part of the clamping unit, in particular against a spindle flange. That is to say, in this embodiment, the clamping element rotates about the drive axis together with the spindle shaft (when the clamping device is released). Alternatively, when the clamping member is connected to the fixed part of the spindle unit, the clamping member is stationary during operation of the spindle unit.A clamping element of the clamping device is designed to be elastically deformable or elastic / flexible axially, i.e. in the direction of the drive axis. For example, when actuating the clamping element (fastened to one end or one side), it is possible to extend or expand the clamping element from a starting position in the axial direction, so that the elastically deformable clamping element contracts again in the axial direction or resumes its starting position when the clamping device is released. Alternatively, the clamping element is compressed or prestressed in the released starting position and, upon actuation, the clamping element expands in the axial direction, for example so that the first and second clamping surfaces are pressed against one another by means of the prestressing of the clamping element.When the clamping device is actuated (i.e. when clamping), the axial extent of the clamping element increases in the direction of the drive axis. For example, when the clamping device is released, a clamping gap is present between the two clamping surfaces of the clamping device. When the clamping device is actuated, the clamping element is axially stretched or tensioned by means of the actuating device, so that the first and second clamping surfaces of the clamping device abut against one another or are pressed against one another. When the clamping is released, the resilient / elastic clamping element again assumes its original shape. When the clamping device is released, the axial expansion of the clamping element automatically decreases. Since the clamping element is fastened on one side or an (axial) end, the restoring force of the elastic or resilient clamping element has the effect that the clamping gap is again present between the two clamping surfaces. This ensures that when the clamping device or actuating device is released, the clamping surfaces are reliably spaced apart from one another or that the clamping surfaces do not touch one another unintentionally.The clamping element of the clamping device has at least three elongate recesses or openings in a plane perpendicular or substantially perpendicular to the drive axis, so that the clamping element is elastically deformable in the axial direction. For example, at least three slot-shaped recesses which impart the resilient or elastic property to the clamping element in the axial direction. Preferably, the longitudinal axes of the (elongate) recesses run parallel to the direction of rotation of the spindle shaft. Alternatively, the elongated recesses may be arranged spirally around the circumference of the clamping element. Alternatively or additionally, the clamping element advantageously has an axial expansion device which prevents torsion about the axis during the axial expansion and compression of the clamping element.Preferably, the recesses of the clamping element are arranged axially offset from one another. For example, elongate recesses are arranged in at least two planes which are axially spaced apart from one another, such that the recesses or slots of the planes partially overlap one another or are azimuthally offset or are offset at an angle to one another. Due to the number and arrangement of the recesses, a desired elasticity of the clamping device can be easily adjusted.Particularly preferably, a one-piece clamping element is provided which is simple to produce and stable. For example, the above-described recesses are milled into a cylindrical base body (with clamping surface). Alternatively, the clamping element has, for example, a spring element, such as a helical spring, to which a clamping part is fastened with a continuous clamping surface or a plurality of clamping surfaces.The clamping device and / or a clamping element of the clamping device is preferably formed circumferentially around the spindle shaft, in particular annularly. Particularly preferably, the first and / or second clamping surface of the clamping device is formed so as to run circumferentially around the spindle shaft, so that the clamping force or clamping action acts uniformly around the spindle. For example, the clamping element has a continuous (uninterrupted) clamping surface around the spindle shaft.Preferably, the actuating device is hydraulically or pneumatically actuatable. In particular, the actuating device has a piston element which can be actuated by hydraulic or pneumatic actuation from a first side in a first axial direction and / or from a second side in an (opposite) second axial direction, wherein the first and second axial directions are the opposite directions of the spindle axis. For example, when operated in the first axial direction, the clamping device is operated, i.e. the spindle shaft is clamped, and when operated in the second axial direction, the clamping device is released or the spindle shaft is released. For example, at least three pistons are provided which, when actuated in the first axial direction, press the clamping element (or the first clamping surface) against the opposite second clamping surface. Alternatively, a continuous ring piston is provided, by means of which the first and second clamping surfaces of the clamping device can be pressed against one another and / or can be released from one another again.Preferably, a flange-shaped projection or a flange blade is formed on the clamping device or on the clamping element. The first clamping surface of the clamping device is formed on the flange-shaped projection. The clamping surface in the radial direction is increased by the projection, so that the holding effect is improved. In one embodiment, the clamping device has a flange-shaped projection on its outer periphery and a first clamping surface of the clamping device is formed on the projection.Preferably, when the clamping device is released, a clamping gap is present between the opposite clamping surfaces of the clamping device. For example, the (parallel) clamping gap has an extension of at least 0.2 mm in the direction of the working axis, preferably of at least 0.4 mm, in particular between 0.2 and 0.5 mm.Preferably, the clamping gap or the clamping device is arranged such that an overpressure prevailing in the interior of the spindle unit (sealing air or sealing gas / medium) prevents foreign substances from entering the clamping gap. For example, the clamping device can be connected cost-effectively to an existing sealing air seal for the spindle shaft.In one embodiment of the spindle unit, the clamping device has an actuating device and a clamping element with a second clamping surface, wherein the clamping element or the part of the clamping element on which the clamping surface is arranged can be actuated in the axial direction by means of the actuating device in order to effect the clamping by the second clamping surface bearing against a first clamping surface. Alternatively or additionally, the clamping element or the part of the clamping element on which the clamping surface is arranged can be actuated in the axial direction by means of the actuating device in order to release the clamping by removing the second clamping surface from the first clamping surface.According to claim 13, a machining device with at least one spindle unit as described above is provided. For example, the processing device is designed as a vertical turning machine, a horizontal turning machine or a milling machine. Preferably, a control of the spindle unit or the machining device is designed to actuate the clamping device only when the spindle shaft is at a standstill, in order to secure the spindle shaft in a predefined angular position. For example, the angular position is monitored by means of a rotary encoder. That is, the clamping device is not used for braking the spindle unit, but only for locking or securing the position of the spindle shaft that is already stationary.In the method for locking a spindle unit, the spindle unit has a clamping device with a clamping element which is at least partially displaceable in the axial direction of the spindle shaft, and the clamping element has a second clamping surface which is displaceable against a first clamping surface in order to bring about the clamping in the axial direction. The spindle unit and / or the clamping device are advantageously configured according to the above and / or the following description. According to the method, the following steps are provided: positioning the spindle shaft in a predetermined or freely predeterminable angular position, preferably by actuating the motor drive until the spindle shaft assumes the predetermined angular position; and locking the spindle shaft in the predetermined angular position by displacing the clamping element or a part of the clamping element in the axial direction until the first and second clamping surfaces come to bear against one another.The motor drive is advantageously deactivated, so that at least the angular positioning is deactivated during motor control or the motor is preferably switched to a force-free state. Particularly preferably, the control of the spindle unit or machining device is designed to deactivate a position control of the motor drive when the clamping device is actuated. The clamping device can lock the spindle shaft in any desired angular position. In this case, it can occur that the freely selectable angular position of the spindle shaft lies between two (adjustable) positions of a (more inaccurate) position control of the (NC) motor drive. In order to prevent intervention of the motor drive control, the position control of the motor drive is therefore deactivated when the clamping device is actuated. In the event of an angular deviation in the clamped position detected by the motor controller, this prevents the motor from "running up" as a result of repositioning pulses which would work against the clamping.The various embodiments and individual features of the spindle unit and the machining device described above can be combined with one another in any desired manner.Embodiments of the invention are explained in more detail with reference to the figures. The following are shown: FIGS. 1 a- b are perspective views of a motor spindle unit with clamping device, once with a chuck (FIG. 1 a) and once without a chuck (FIG. 1 b), FIG. 2 is an exploded perspective view of the clamping device of the spindle unit of FIGS. 1 a- b, FIG. 3 is a partial sectional view of the front portion of the chucked spindle unit of FIG. 1a, FIG. 4 shows a sectional view of the spindle head of the spindle unit of FIG. 1 b, FIGS. 5 a- b show details of the clamping device of the spindle unit of FIGS. 1 a- b, FIGS. 6 a- e show different views of a clamping disc of the clamping device of FIGS. 5 a- b, FIGS. 7 a- c show perspective views and top view of a center drive unit with a clamping device according to a further embodiment, and FIG. 8 shows a detail of the clamping device of the central drive assembly of FIGS. 7 a- c.FIGS. 1 aand 1 b show perspective views of a directly driven spindle unit 2 aand a motor spindle unit, respectively. FIG. 1 ashows the spindle unit with (indicated) chuck 6 aand FIG. 1 bshows the spindle unit 2 awith no chuck 6 a. The spindle unit 2a has a clamping device 9a for locking or clamping a spindle shaft 4a of the spindle unit 2a in a predetermined angular position. In this embodiment, the spindle shaft 4 ais directly driven, i.e. without a gear mechanism between the motor drive 8 aand the shaft 4 a, so that the spindle shaft 4 acan be rotationally driven about its drive axis A. The motor shaft of the motor 8a forms the spindle shaft 4a. A workpiece or a tool can be clamped in the clamping device or the chuck 6 a. That is, the spindle unit can preferably be used as a rotating spindle as well as as a milling spindle. For example, the spindle unit 2 aor a plurality of (adjacently arranged) spindle units 2 acan be used in a machining device having a vertical or horizontal machining axis.FIG. 2 shows an exploded view of the clamping device 9 aof the spindle unit 2 aof FIG. 1 b. The spindle shaft 4a is rotatably mounted about the drive axis A in a (fixed) housing 3a. The housing has a fixed spindle flange 5 to which a receiving flange 20 aof the clamping device 9 ais fastened by means of screws 36 a. A clamping disk 10 of the clamping device 9a is received in the receiving flange 20a. The clamping disk 10 is screwed at its inner region to the spindle shaft 4a by means of screws 36b. When the clamping device 9a is released, a clamping gap 24 is present between the clamping disc 10 and the receiving flange 20a (or its clamping surface 22) (FIG. 5b). When the clamping device 9a is released, the clamping disk 10 rotates together with the spindle shaft 4a.An annular piston 16 is arranged on the clamping disk 10 or in the clamping device 9 ain such a way that the annular piston 16 can be pressed against a flange 11 of the clamping disk 10. The annular piston 16 is guided in a cylinder flange 18 and corresponding supply and discharge lines for hydraulic or pneumatic actuation of the annular piston 16 are accommodated in the cylinder flange 18 (FIG. 5 a ). Furthermore, a labyrinth seal or a labyrinth ring 34 ais arranged on the cylinder flange 18. The labyrinth ring 34a provides a seal between the rotatable spindle shaft 4a and the fixed cylinder flange 18. In addition, the interior of the spindle unit 2 acan be pressurized (sealing air or sealing medium / gas) in order to prevent contaminants from entering the spindle unit 2 athrough the labyrinth ring 34 a.FIGS. 3 and 4 each show a (partial) sectional view of the spindle head of the spindle unit 2 aof FIGS. 1 aand 1 bin the region of the clamping device 9 a. Figures 5a-b show details of the sectional view of Figure 4 to illustrate the function of the clamping device 9a.In the figures, the clamping device 9 acan be seen in the released position or position (FIG. 5 b ). That is, a clamping gap 24 is present between receiving flange 20 a(or clamping surface 22) and clamping disk 10 in the released position, so that spindle shaft 4 ais free running or not clamped. By means of the clamping disk 10 and the annular piston 16, the clamping surface 22 of the clamping disk 10 can be brought to bear against the clamping surface 14 of the stationary or rotationally rigid receiving flange 20 a, so that the spindle shaft 4 ais locked in a rotationally fixed manner by means of the stationary spindle flange 5, the receiving flange 20 aand the clamping disk 10 when the position is locked. With this arrangement, the spindle shaft 4a can be locked or clamped at any desired angular position upon actuation of the clamping device 9a.The locking or clamping of the spindle shaft 4 ain a desired angular position is controlled by means of a controller (not shown) of the spindle unit (or a machining device). For example, the angular position of the spindle shaft 4 acan be controlled by means of a rotary encoder 40 (FIG. 9 ). In order to actuate the clamping device 9 a(i.e. in order to clamp the spindle shaft 4 a), the annular piston 16 presses against the clamping disc 10 and presses the clamping disc 10 (or the flange 11) against the receiving flange 20 a(or its clamping surface 22). For this purpose, a fluid (e.g. compressed air or hydraulic fluid) is introduced via a first pressure connection 26 into a cavity between the annular piston 16 and the cylinder flange 18. Thus, the annular piston 16 is pressed upward (FIG. 5 a) against the clamping disk 10 until the clamping disk 10 (or its clamping surface 14) bears against the receiving flange 20 (or its clamping surface 22). The hydraulically or pneumatically generated contact pressure of the annular piston 16 ensures the set angular position of the spindle shaft 4a. In FIG. 5 a, the course of the force flow through the clamping disk 10 when the spindle shaft 4 ais clamped is indicated by a double arrow.After clamping, a workpiece clamped into the spindle unit 2 acan be machined, for example, with a grinding tool, a milling cutter or a drill. Even high torsional forces which act during machining are effectively transferred by the clamping device to the housing of the spindle unit 2 athat is mounted so as to be secure against rotation, so that highly precise machining is made possible. When the clamping device 9 ais released again, the same workpiece can be rotationally machined without the need for re-clamping the workpiece.In order to release the clamping device 9 a(i.e. the spindle shaft 4 ais freely movable), a fluid is conducted via a second pressure connection 28 into a further cavity between receiving flange 20 aand annular piston 16, so that the clamping surfaces 14, 22 are separated and are spaced apart from one another again, so that the spindle shaft 4 ais freely movable again. In order to ensure a (fluid) tight connection of the cavities adjoining the pressure connections 26, 28, a plurality of seals are provided. The annular piston has circumferentially on its sides located on the outside and on the inside in the radial direction a quad ring 32 a, 2 band on its outside an O-ring 30 b. The receiving flange 20a has a circumferential O-ring 30a on its outer periphery.FIGS. 6 a- e show different views of the clamping disc 10 of the clamping device 9 a. The clamping disk 10 is constructed in one piece, wherein the clamping surface 14 is formed on its circumferential flange 11. On its inner periphery, the clamping disk 10 has a plurality of screw holes 38 for screwing the clamping disk 10 to the spindle shaft 4a. The clamping surface 14 of the clamping disk 10 and the clamping surface 22 of the receiving flange 20 aare smooth metallic surfaces or they do not have mutually engaging structures such as, for example, a toothing. As a result, the spindle shaft 4 acan be clamped in any desired angular position, i.e. the clamping device 9 ado not specify a grid. Alternatively, one of the clamping surfaces 14, 22 or both clamping surfaces 14, 22 can have a coating or can be treated in such a way that an increased friction is produced between the (compressed) clamping surfaces 14, 22. As a result, the static friction and thus the holding force (with constant contact pressure) are increased.FIGS. 6 dand 6 e show sectional views of the clamping disk 10 along the axially offset planes A-A and B-B (FIG. 6 c ) perpendicular to the drive axis A. It can be clearly seen that the clamping disk 10 has six elongate recesses or slots 12 a- falong its circumference. On each plane perpendicular to the axis A, three slits 12a-c and 12d-f are provided, respectively. The slots 12a in each plane are offset from each other so that the clamping disc 10 is resilient in the axial direction.When the clamping device 9a is released, the clamping disc 10 is in the resting position, i.e. the clamping surfaces 14, 22 do not abut each other. When the clamping device 9a is actuated, the clamping disk 10 is extended in the axial direction or drawn axially into the length by means of the (hydraulically or pneumatically driven) pressure piston 16. If the clamping device 9a is subsequently to be released again, the pressure piston 16 is activated pneumatically or hydraulically as described above. In addition, the release of the clamping device 9 ais assisted by the restoring force of the elastic clamping disc 10. For example, if the hydraulic or pneumatic actuation fails, then the resilient clamping disc 10 ensures that the spindle shaft 4a is in any case free-wheeling or non-clamped.FIGS. 7 a- c show perspective views and a plan view of a further spindle unit 2 bin the form of a central drive unit and a central rotary spindle, respectively. Unless otherwise specified, the elements and functions of the spindle unit 2 bdescribed below correspond to the elements and functions of the spindle unit 2 adescribed above. Identical or identically acting elements are identified by the same reference numerals.In contrast to the above-described motor spindle unit 2 a, the central drive unit 2 bhas a continuous opening or clamping device 6 bfor receiving and holding an (elongate) workpiece. The center tension between the two ends of a workpiece offers the advantage that both ends of the workpiece can be machined in one tension (without re-clamping). The motor drive 8 bis arranged radially offset with respect to the drive axis A of the spindle shaft 4 b.The spindle shaft 4 bof the center drive unit is mounted rotatably about a drive axis A in a housing 3 b. At one end of the spindle shaft 4 band adjacent to one end of the spindle shaft 4 b, a clamping device 9 bis arranged in order to clamp the spindle shaft 4 bin a predetermined angular position in a rotationally secure manner. Unless otherwise stated, the elements of the clamping device 9 bdescribed below correspond to the clamping device 9 adescribed above. Identical elements are identified by the same reference numerals.FIG. 8 is a sectional view showing a detail of the clamp 9 bof the spindle unit 2 b(lower part of the section C-C in FIG. 7 c ). One end of a clamping disk 10 is fixed to the spindle shaft 4b by means of screws. The axially opposite (or substantially opposite) end of the clamping disc 10 has a clamping surface 14 which extends perpendicularly to the drive axis A. As described above, the clamping surface 14 of the clamping disc 10 is arranged to confront a corresponding clamping surface 22 of a fixed receiving flange 20b. A round bottom flask 16 as described above is configured to press the clamping disk 10 against the receiving flange 20b. For this purpose, as described above, a pressure connection 26 or 28 is provided on the spindle unit 2 bfor clamping or releasing the clamping device 9 bor the clamping disk 10. A labyrinth ring 34b is provided between the rotatable spindle shaft 4b and the fixed spindle flange 20b to provide a labyrinth seal therebetween.As described above, the clamping disk 10 is provided with a plurality of slits 12 a- farranged perpendicular to the drive axis A to ensure elastic or resilient deformability of the clamping disk 10. The clamping device 9 bis operated and released like the clamping device 9 adescribed above. The force flow through the clamping disk 10 when the clamping device 9 bis actuated is indicated by the double arrow.Both embodiments of the spindle unit 2 aand 2 bor clamping device 9 a, 9 bprovide an axial or substantially axially acting clamping force which acts close to the clamping device 6 a, 6 bor close to a clamped workpiece / tool. That is, torsion forces and lever forces cause no or an extremely low rotation in the clamped spindle shaft 4 a, 4 b. By means of the spindle units 2 a, 2 bdescribed above, the respective spindle shafts 4 a, 4 bcan be held securely in their (predetermined) angular position when the clamping device 9 a, 9 bis actuated.List of reference characters2 a, 2 bspindle unit / main spindle 3 a, 3 b housing 4 a, 4 bspindle shaft 5 spindle flange 6 a, 6 bspanting device / chuck 8 a, 8 bmotor 9 a, 9 bspanting device 10 clamping disk 11 clamping disk flange 12 a- fslot 14 clamping surface (clamping disk) 16 ring piston 18 cylinder flange 20 a, 20 btaken flange 22 clamping surface (take-up flange) 24 clamping gap 26 pressure connection (spindle clamping) 28 pressure connection (spindle releasing) 30 a, 30 bO-ring 32 a, 32 bquarters 34 a, 34 b maze ring 36 a- ccylinder screw 38 screw hole 40 rotary encoder A drive axis

Claims

Spindle unit (2a) for a machining device, in particular a rotary spindle unit or a milling spindle unit, which has: a spindle shaft (4a) rotatably mounted in a housing (3a); a clamping device (6a) arranged on the spindle shaft (4a) for clamping a workpiece or a tool; a motor drive (8a) connected to the spindle shaft (4a) for driving the spindle shaft (4a) about a drive axis (A); a clamping device (9a) for clamping the spindle shaft (4a) in an freely selectable angular position about the drive axis (A), wherein the clamping device (9a) is arranged between the spindle shaft (4a) and a fixed part of the spindle unit, and an actuating device (16) for actuating and / or releasing the clamping device (9a), wherein the clamping device (9a) is arranged between or substantially between an axial end of the spindle housing and the clamping device (6a) or in the region of the transition from the axial end of the spindle housing and the clamping device, characterized in that the clamping device (9a, 9b) has a clamping element (10), wherein the clamping element (10) has at least three elongate recesses (12a-f) in a plane perpendicular or substantially perpendicular to the drive axis (A), such that the clamping element (10) can be elastically deformed in the axial direction and the axial extent of the clamping element (10) can be increased and / or decreased by actuating the clamping device.Spindle unit according to claim 1, wherein the clamping device (9a) has a first clamping surface (22) connected in a rotationally fixed manner to the housing of the spindle unit and a second clamping surface (14) connected in a rotationally fixed manner to the spindle shaft (4a, 4b), which is arranged opposite and parallel to the first clamping surface, wherein the first clamping surface is arranged on that end side or in the region of that end side of the housing of the spindle unit which lies on the side of the clamping device (6a).Spindle unit according to claim 1 or 2, wherein the first and / or the second clamping surface (22, 14) are displaceable relative to one another by means of an actuating device (16), so that a gap (24) can be selectively adjusted between the clamping surfaces by means of the actuating device (16) or the clamping surfaces come to bear against one another, and / or wherein the spindle shaft protrudes axially from the housing of the spindle unit on the side of the clamping device (6a) and the second clamping surface (14) is connected to the spindle shaft (4a) in a rotationally fixed manner via an element (10), which extends radially outwards from the protruding end of the spindle shaft.Spindle unit according to claim 1, 2 or 3, wherein the clamping device (9a) can be actuated axially in the direction of the drive axis (A), so that when the clamping device (9a) is actuated an axial or substantially axial clamping force acts in the direction of the drive axis (A).Spindle unit (2a, 2b) for a machining device, in particular a rotary spindle unit or a milling spindle unit, which has: a spindle shaft (4a, 4b) rotatably mounted in a housing, a clamping device (6a, 6b) arranged on the spindle shaft (4a, 4b) for clamping a workpiece or a tool, a motor drive (8a, 8b) connected to the spindle shaft (4a, 4b) for driving the spindle shaft (4a, 4b) about a drive axis (A), a clamping device (9a, 9b) for clamping the spindle shaft (4a, 4b) in an freely selectable angular position about the drive axis (A), wherein the clamping device (9a, 9b) between the spindle shaft (4a, 4b) is connected to the spindle shaft, 4b) and a fixed part of the spindle unit, and an actuating device (16) for actuating and / or releasing the clamping device (9a, 9b), wherein the clamping device (9a, 9b) can be actuated axially in the direction of the drive axis (A) so that when the clamping device (9a, 9b) is actuated an axial or substantially axial clamping force acts in the direction of the drive axis (A), characterized in that the clamping device (9a, 9b) has a clamping element (10), wherein the clamping element (10) has at least three elongate recesses (12a-f) in a plane perpendicular or substantially perpendicular to the drive axis (A), such that the clamping element (10) is elastically deformable in the axial direction and the axial extension of the clamping element (10) can be enlarged and / or reduced by actuating the clamping device.Spindle unit according to claim 5, wherein the clamping device (9a) is arranged between or substantially between an axial end of the spindle housing and the clamping device (6a, 6b) or in the region of the transition from the axial end of the spindle housing and the clamping device.Spindle unit according to one of the preceding claims, wherein the clamping device (9a, 9b) has a first clamping surface (22) connected in a rotationally fixed manner to the housing of the spindle unit and a second clamping surface (14) connected in a rotationally fixed manner to the spindle shaft (4a, 4b), which is arranged opposite and parallel to the first clamping surface, wherein the first and / or the second clamping surface (22, 14) can be displaced in the axial direction (A) by means of an actuating device (16), such that a gap (24) can be selectively adjusted between the clamping surfaces by means of the actuating device (16) or the clamping surfaces come to bear against one another.Spindle unit according to one of the preceding claims, wherein the axial extension of the clamping element (10), in particular of a clamping disc, of the clamping device increases upon actuation of the clamping device (9a, 9b), and / or wherein the axial extension of the clamping element (10) of the clamping device decreases upon release of the clamping device (9a, 9b).Spindle unit according to one of the preceding claims, wherein the clamping element (10) of the clamping device (9a, 9b) is designed to be resilient or elastic axially in the direction of the drive axis (A), and / or wherein the axial extent of the clamping element (10) automatically decreases when the clamping device (9a, 9b) is released.Spindle unit according to one of the preceding claims, wherein the clamping device (9a, 9b) and / or the clamping element (10) of the clamping device is formed so as to extend circumferentially around the spindle shaft (4a, 4b), in particular is annular.Spindle unit according to one of the preceding claims, wherein the clamping element (10) of the clamping device (9a, 9b) has at least three further elongate recesses (12a-f) in at least one second plane perpendicular or substantially perpendicular to the drive axis (A), and wherein the recesses (12a-f) of the first and second planes are arranged azimuthally offset or offset angularly with respect to one another.Spindle unit according to one of the preceding claims, wherein the clamping device (9a, 9b) has a first clamping surface (14) which is connected to the housing in a rotationally fixed manner and a second clamping surface (22) which is connected to the spindle shaft (4a, 4b) in a rotationally fixed manner and which come to bear for clamping and form a gap (24) between them in the released state of the clamping device, wherein in particular the first and / or second clamping surfaces (14, 22) are configured to be smooth or substantially smooth, in particular have no toothing and have no angular division.Machining device with at least one spindle unit according to one of the preceding claims, in particular a vertical turning machine, a horizontal turning machine or a milling machine.Method for locking a spindle unit, in particular a spindle unit according to one of Claims 1 to 13, wherein the spindle unit has a clamping device (9a, 9b) with a clamping element (10) and the clamping element (10) has a second clamping surface (22) which is displaceable against a first clamping surface (14) in order to effect the clamping, wherein the clamping element (10) has at least three elongate recesses (12a-f) in a plane perpendicular or substantially perpendicular to the drive axis (A), such that the clamping element (10) is elastically deformable in the axial direction, wherein the method comprises: positioning the spindle shaft (4a, 4b) in a predefined angular position, preferably by actuating the motor drive until the spindle shaft assumes the predefined angular position, locking the spindle shaft in the predefined angular position by elastic deformation of the clamping element (10), such that the axial extension of the clamping element (10) is increased until the first and second clamping surfaces come to rest against each other, and optionally deactivating the motor drive, such that at least the angular positioning is deactivated during the motor control or preferably the motor is switched free of force.

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