MACHINE TOOL

Abstract

The invention relates to a machine tool, in particular a lathe grinding machine, comprising a tool spindle having a collet and a spindle motor, wherein the collet has at least two clamping jaws which are actuatable for receiving and releasing a tool, and comprising an air channel which runs radially on the outside of the collet, wherein the air channel is configured as a sealing air channel (42) and forms a positive pressure chamber (44) at least partially above the clamping jaws (26).

Claims

1. A machine tool comprising a tool spindle having a collet chuck and a spindle motor, an air channel which runs radially outside of the collet chuck, wherein the collet chuck has at least two clamping jaws which are configured for receiving and releasing a tool, and wherein the air channel is configured as a sealing air channel (42) and forms a positive pressure chamber (44) at least partially above the clamping jaws (46).

2. The machine tool as claimed in claim 1, wherein the positive pressure chamber (44) terminates in an annular gap (40) or wherein the annular gap (40) is arranged downstream of the positive pressure chamber having one gap side formed by the tool (14) or the tool spindle (12).

3. The machine tool as claimed in claim 1, wherein an annular gap (40) located downstream of the positive pressure chamber (44) has a gap size of between 0.03 mm and 0.5 mm.

4. The machine tool as claimed in claim 1, wherein an annular gap (40) located downstream of the positive pressure chamber (44) has an orientation coaxial to the tool axis or an orientation which deviates from the axis of the tool spindle (12) by +/−30°.

5. The machine tool as claimed in claim 1, wherein the tool (14) has at least one annular flange (28, 30, 32) which protrudes radially to the outside, and wherein the sealing air channel (42) terminates at the annular flange (30).

6. The machine tool as claimed in claim 1, wherein the sealing air channel (42) is configured as a bearings air channel (50) upstream of the positive pressure chamber (44).

7. The machine tool as claimed in claim 1, wherein the collet chuck is provided with compressed air which acts on the clamping jaws (26) from behind via a pressure plate (86) to open the clamping jaws (26).

8. The machine tool as claimed in claim 7, wherein the compressed air feeds the sealing air channel (42) via a pressure reduction valve (42).

9. The machine tool as claimed in claim 7, wherein the sealing air channel (42) is fed at a positive pressure of between 0.5 bar and 4 bar and has a flow volume of between 5 liters per minute and 50 liters per minute.

10. The machine tool as claimed in claim 1, wherein, when the collet chuck is open, the compressed air source may output an air impulse of more than 6 bar along the collet chuck and the tool (14) for cleaning chips from the collet chuck.

11. The machine tool as claimed in claim 2, wherein the annular gap (40) which is covered and/or limited by an annular flange (28, 30, 32) has a radial orientation or an orientation which deviates from the radial orientation by between −5 and 30° to the front, relative to the tool spindle (12).

12. The machine tool as claimed in claim 2, wherein the annular gap (40) has an axial orientation or an orientation which deviates from the axial orientation by a maximum of −5 and 30°, relative to the tool spindle (12).

13. The machine tool as claimed in claim 1, wherein a plurality of nozzles is arranged distributed around the tool (14) at the tool spindle (12), said nozzles being directed at least partially to a machining area (22) between the tool (14) and the workpiece and being provided in a nozzle plate which extends in a shape of a circular ring.

14. The machine tool as claimed in claim 13, wherein the nozzle plate is arranged radially on the outside of the annular gap (40) and surrounds the annular gap (40).

15. The machine tool as claimed in claim 14, wherein the nozzle plate is arranged with a deviation of less than 5 mm at the same axial height as the annular gap (40).

16. The machine tool as claimed in claim 1, wherein the machine tool is a lathe grinding machine.

17. The machine tool as claimed in claim 1, wherein an annular gap (40) located downstream of the positive pressure chamber (44) has a gap size of between 0.08 and 0.15 mm.

18. The machine tool as claimed in claim 7, wherein the sealing air channel (42) is fed at a positive pressure of between 0.5 bar and 4 bar and has a flow volume of between 10 to 20 liters per minute.

19. The machine tool as claimed in claim 14, wherein the nozzle plate is arranged with a deviation of less than 2 mm at the same axial height as the annular gap (40).

20. The machine tool as claimed in claim 3, wherein the tool spindle comprises a spindle housing (16), wherein the positive pressure chamber (44) ends at the upper end of the spindle housing (16), at the annular gap (40), and wherein both the tool (14) or the tool spindle (12) and the spindle casing (16), also at the upper end, are made from a solid and undeformable material.

21. The machine tool as claimed in claim 3, wherein the gap width is constant within a tolerance of 5 percent of the gap width, in all operating modes and operation states of the machine tool.

22. The machine tool as claimed in claim 6, wherein the bearings air passes through the bearings (80, 82) of the spindle (12) and is fed with filtered air or air with an ultra high purity, to ensure the absence of particles in the bearings (80, 82) of the spindle (12).

23. The machine tool as claimed in claim 6, wherein at least one filter is provided upstream of the bearings air channel (50).

Description

BRIEF DESCRIPTION

[0080] Further advantages, details and features may be taken from the following description of several exemplary embodiments of the invention in conjunction with the drawings, in which:

[0081] FIG. 1 shows part of a machine tool, according to prior art, illustrating part of the tool spindle and the tool in a perspective illustration;

[0082] FIG. 2 shows a section through the corresponding part of an inventive machine tool, illustrating the upper part of the tool spindle, including the tool;

[0083] FIG. 3 shows a further view according to FIG. 2;

[0084] FIG. 4 shows a schematic sketch of a modified embodiment of the inventive machine tool, illustrating a differently arranged annular gap; and

[0085] FIG. 5 shows a section through the corresponding part of an inventive machine tool, illustrating the upper part of the tool spindle, including the tool.

DETAILED DESCRIPTION

[0086] In FIG. 1, a machine tool 10 according to prior art is illustrated in parts. The machine tool 10 comprises a tool spindle 12 which carries a tool 14 and holds it clamped.

[0087] The tool spindle 12 comprises a spindle housing 16 which is configured truncated cone-shaped and ends at a nozzle plate 18. The nozzle plate 18 comprises a plurality of nozzles 20 which are intended to clean a machining area 22.

[0088] In the machining area 22, the tool 14 is in contact with a workpiece which is not illustrated such that chips or milling dust is produced thereat which is to be removed by the nozzles 20.

[0089] The chips or the milling dust is deposited no later than when the compressed air from the nozzles 20 is turned off.

[0090] The tool 14 comprises a shaft 24 which is held clamped in a collet 26 which is not illustrated in FIG. 1, see FIGS. 2, 3 and 4.

[0091] In the exemplary embodiment illustrated, the tool 14 comprises three annular flanges 28, 30 and 32 between which annular grooves 34 and 36 extend. The annular grooves 34 and 36 serve to receive the tool 14 in a gripping fork of a robot arm which is not illustrated and thus serve the tool change.

[0092] In this solution according to prior art, as is illustrated in FIG. 1, deposits are to be whirled up during operation of the machine tool 10 by housing-sided air nozzles which are additionally provided. They are removed at least partially by a suction system at the bottom.

[0093] However, when the machine tool 10 is turned off, the supply to the air nozzles, among others, the nozzles 20, is also turned off and thus the resulting milling dust and the associated chips may be deposited.

[0094] Deposits occur, among others, also on and next to the nozzle plate 18. Up to now, it was impossible to prevent deposits from entering the interior of the tool spindle 12.

[0095] As the machine tool 10 works with a lathe grinding machine of more than 30,000 rev/min, it is not possible to realize a sealing ring as it would immediately wear out at speeds of rotation of more than 5,000 rev/min.

[0096] Now, the following is provided according to the invention:

[0097] The housing 16 of the spindle is extended further to the top and ends at an annular gap 40. The annular gap 40 is the outlet of a sealing air channel 42 and extends downstream and in particular at the same time above a positive pressure chamber 44.

[0098] The positive pressure chamber 44 itself is arranged at least partially above clamping jaws 46 of the collet 26.

[0099] Thus, sealing air may escape through the sealing air channel 42 in such a way that no deposits may enter the region of the clamping jaws 46.

[0100] The flow area of the annular gap 40 is considerably smaller than that of the positive pressure chamber 44 and also slightly smaller than the flow area of the bearing air channel 50 at which position the sealing air channel 42 receives the rolling bearings (not illustrated) for mounting the spindle 12 at the housing 16.

[0101] The inventive solution is illustrated in FIG. 2.

[0102] It is also apparent from FIG. 2 that a spindle motor 54 belongs to the spindle 12. It drives the collet 26 and thus the tool 14 and is suitable for the high number of revolutions.

[0103] Additionally, the spindle motor 54 is connected non-rotatably with a flywheel 52 which also serves to compensate for imbalances and may be adapted correspondingly.

[0104] A sealing 60 is provided laterally with respect to the spindle motor 54 towards the housing 16 of the spindle 12.

[0105] The sealing air channel 42 is supplied with compressed air from a compressed air source, in the magnitude of 2 bar, wherein the compressed air source and the supply are not illustrated in detail per se.

[0106] In the exemplary embodiment illustrated, the housing 16 of the spindle is additionally configured as two pieces. The housing 16 comprises a main housing 62 and a housing insert 64 which is inserted in the main housing 62 in the front region of the cone-shaped housing 16. Here, too, sealings 66 and 68 are provided.

[0107] Further, a nozzle line 70 is apparent from FIG. 2 which terminates in the nozzle 72. The nozzle 72 corresponds to the nozzle 20 according to FIG. 1 but is positioned on a considerably higher plane such that the nozzle channel 70 is also extended.

[0108] FIG. 3 shows an amended embodiment, compared to FIG. 2, in another view and enlarged. Here, the same reference signs indicate the same parts as in the further figures and the embodiment is slightly changed.

[0109] It is apparent that the tool 14 is held in a tool holder 76 in the collet 26. Especially this region in which the tool 14 is held radially in a clamped manner is protected inventively by the sealing air such that reliable and centered clamping of the tool 14 at its shaft 24 is possibly free of contamination.

[0110] A further modified configuration of the inventive machine tool 10 is apparent from FIG. 4. In this solution, the annular gap 40 is oriented radially. Even if the machine is at a standstill, a deposit which is deposited vertically may not enter the annular gap 40. Again, the annular gap 40 is between the annular flange 30 and the housing 16 of the tool spindle 12.

[0111] A nozzle plate 18 is configured radially on the outside of the annular gap 40 wherein a nozzle 72 with a nozzle channel 70 is illustrated.

[0112] It is also apparent from FIG. 4 that the positive pressure chamber 44 extends considerably above the collet 26. The collet 26 comprises clamping jaws 46 of which one clamping jaw 46 is illustrated in FIG. 4 in turn.

[0113] The sealing air channel 42 comprises also the bearing air channel 50 besides the positive pressure chamber 44. At this axial position rolling bearings are provided of which two rolling bearings 80 and 82 are apparent from FIG. 4. Bearings air streams through both rolling bearings 80 and 82 in a way known per se, said bearing air itself streaming through the positive pressure chamber 44 as sealing air and escaping at the annular gap 40.

[0114] It is also apparent from FIG. 4 that the clamping jaws 46 have a slightly conical external surface each. They interact with a corresponding surface at the collet 26.

[0115] FIG. 4 further shows an air flow path of the bearing air indicated by arrows through the bearing air channel 50 and thus through the rolling bearings 80 and 82.

[0116] Upstream of the rolling bearings 80 and 82, preferably at the inlet of the bearing air channel 50, at least one filter 77 (shown in FIG. 5), preferably first at least one coarse filter upstream of at least one fine filter, is connected to ensure the purity of the bearings air. If more filters are used they are connected in series, while the air is filtered by ever finer filters to maximize air purity.

[0117] This is essential because even slight impurities in the bearing air, like fine dust grains, could lead to substantial damage in the bearings or even destruction of the bearings at high rotational speeds like the ones used in the invention, especially at rotational speeds of more than 30,000 rpm, and even up to 60,000 rpm.

[0118] By means of a tension spring 84 the clamping jaw 46 is drawn to the rear in the axial direction such that it holds the tool 14 clamped at its shaft 24.

[0119] When the clamping jaw 46 is pushed to the front, i.e., in the illustration according to FIG. 4 to the top, by means of a pressure plate 86, the tool 14 is released and can be exchanged.

[0120] The clamping jaw 46 may be lifted by the pressure plate 86 activated by compressed air such that the sealing function thereat is cancelled and compressed air streams along the tool 14 and also enters the positive pressure chamber 44. This ensures that no deposits may enter the region of the tool holder.