MACHINE TOOL

Abstract

A machine tool comprising tool spindle (12) having a chuck (26) and a spindle motor, in which the chuck (26) can be actuated for the purpose of receiving and releasing a tool, a sealing air channel (40) is provided which extends at least partially radially outside the chuck (26). The sealing air channel (40) terminates in or at a protective cap (34).

Claims

1. A machine tool comprising a tool spindle (12) having a chuck (26) and a spindle motor, a sealing air channel (40) which extends at least partially radially outside the chuck (26), wherein the chuck (26) can be actuated for receiving and releasing a tool, and wherein the sealing air channel (40) terminates in or at a protective cap (34).

2. The machine tool as claimed in claim 1, wherein an annular gap (46) is provided between the protective cap (34) and the tool (14) or the chuck (26) or a rotating part of a machine tool (10), of which one gap side is formed by the tool (14) or the chuck (26) or another rotating part of the machine tool (10) and the other gap side is formed by the protective cap (34).

3. The machine tool as claimed in claim 1, wherein the protective cap (34) is bell-shaped or trapezoidal or has an S-shape or trapezoidal contour when viewed in cross-sectional view.

4. The machine tool as claimed in claim 2, wherein the protective cap (34) terminates at the annular gap (46) and is fitted, screwed or otherwise fastened onto a housing (16) of the spindle (12) or the machine tool (10) or another fixed part.

5. The machine tool as claimed in claim 1, wherein a rear end (58) of the protective cap (34) is fixedly connected to a part of the machine tool (10) by forming a press fit, form-fit, friction fit or rotation and is circumferentially sealing and/or is detachable.

6. The machine tool as claimed in claim 1, wherein the protective cap (34) comprises a radial extension or diameter in a front region adjacent to the annular gap (46) and extending over at least 20% of an axial total length, with respect to the rotating parts of the machine tool (10), the radial extension (64) which exceeds that of the rotating parts by less than 30%.

7. The machine tool as claimed in claim 1, wherein a positive pressure space (44) is formed in the protective cap (34) and the flow resistance of the air through the positive pressure space (44) and the protective cap (34) at this point is less than in the region of the annular gap (46) which closes off the positive pressure space (44).

8. The machine tool as claimed in claim 1, wherein the tool (14) has at least one tool ring (28) which protrudes radially outwards, and wherein the sealing air channel (40) terminates on the tool ring (28) or terminates at maximum of 1 cm below the tool ring (30).

9. The machine tool as claimed in claim 1, wherein a bearings air channel (42) is formed on bearings (36, 38) of the spindle (12) and is supplied with positive pressure between 0.5 bar and 6 bar and has a flow volume between 5 l/min and 80 l/min.

10. The machine tool as claimed in claim 1, wherein a bearing air channel (42) is formed on bearings (36, 38) of the spindle (12) and supplies the sealing air channel (40) between the spindle (12) and spindle housing (16).

11. The machine tool as claimed in claim 1, wherein an annular gap (46) on the protective cap (34) has a gap dimension between 0.05 mm and 1.5 mm.

12. A machine tool comprising a spindle which is intended for clamping a tool (14), and a spindle housing (16), on which the spindle is mounted, which spindle protrudes from the spindle housing (16) at a front end of the spindle housing (16), wherein the spindle housing (16) forms, at its front end, a protective cap (34) towards the spindle, which protective cap (34) has, at the protective cap's front end (58), a diameter, which is smaller than a diameter at the protective cap's other, rearward end (54), and forms, at the front end (58), an annular gap (46) with a rotating part of the machine tool or the tool (14), at which annular gap (46), a positive pressure space supplied with air, terminates.

13. A protective cap for a machine tool comprising a spindle, a spindle housing (16) and a tool (14), wherein the protective cap (34), which is mounted or fastened on a fixed part of the machine tool (10) has, at a front end (58), a diameter smaller than a diameter at an other, rearward end (54) and has, at the front end (58), a slender shape in comparison to the other rearward end (54), said slender shape approximating the end-side inner diameter (60) at the front end (58).

14. The protective cap as claimed in claim 13, wherein said protective cap is fitted onto the spindle housing (16), when in the state of being fitted onto the spindle housing (16), has an annular nozzle flank (62) which, together with a rotating part of the machine tool, as a second annular nozzle flank, forms a nozzle in the form of an annular gap (46).

15. The protective cap as claimed in claim 13, wherein the protective cap (34) covers a sealing air channel (40) and displaces the end of the sealing air channel (40) towards the tool or another rotating part.

16. The protective cap as claimed in claim 13, wherein the seat of the protective cap (34) is formed as a threaded fit, a plug fit and/or as a press fit, by which the protective cap (34) can be mounted on a fixed part of the machine tool (10) by press fit and in a centered manner and/or wherein the protective cap (34) is formed on a seat in such a manner that it functions as a replacement part or as an accessory part for existing machine tools (10) and fits onto fixed parts thereof.

17. The machine tool as claimed in claim 1, wherein the protective cap (34) comprises a radial extension in a front region adjacent to the annular gap (46) and extending over at least 30% of an axial total length, with respect to the rotating parts of the machine tool (10), a radial extension which exceeds that of the rotating parts by less than 15%.

18. The machine tool as claimed in claim 1, wherein a bearings air channel (42) is formed on bearings (36, 38) of the spindle (12) and is supplied with positive pressure between 1 and 3 bar, and has a flow volume between 20 to 50 l/min.

19. The machine tool as claimed in claim 1, wherein an annular gap (46) on the protective cap (34) has a gap dimension in one of the following ranges: between 0.05 and 1.0 mm or between 0.15 and 0.8 mm or between 0.3 and 0.5 mm.

20. The machine tool as claimed in claim 2, wherein the other gap side is formed by the protective cap (34) at a nozzle flank 62.

21. The machine tool as claimed in claim 10, wherein a bearings air passes through the bearings (36, 38) of the spindle (12) and is fed with filtered air or an ultra high purity, to ensure the absence of particles in the bearings (36, 38) of the spindle (12).

22. The machine tool as claimed in claim 10, wherein at least one filter is provided upstream of the bearing air channel (42).

23. The machine tool as claimed in claim 11, wherein the gap of the annular gap (46) on the protective cap (34) is not deformable, especially while rotating.

24. The machine too as claimed in claim 11, wherein the gap width is constant, within a tolerance of 5 percent of the gap width, in all operating modes and operation states of said machine tool.

25. The machine tool as claimed in claim 11, wherein the protective cap and the spindle are made from a solid and undeformable material.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0095] Further advantages, details and features will be apparent from the following description of two exemplified embodiments of the invention with reference to the drawings in which

[0096] FIG. 1 shows a part of a machine tool in accordance with the invention, illustrating a part of the tool spindle and the tool;

[0097] FIG. 2 shows a sectional view through a part of a machine tool in accordance with the invention, illustrating the tool spindle in its upper part, including the tool, in a view enlarged compared to FIG. 1;

[0098] FIG. 3 shows a modified embodiment of a protective cap in accordance with the invention;

[0099] FIG. 4 shows an enlarged view of a portion of FIG. 2; and

[0100] FIG. 5 shows a marked flow path of the air channel.

DETAILED DESCRIPTION

[0101] FIG. 1 illustrates a part of a machine tool 10 in accordance with the invention. The machine tool 10 has a tool spindle 12 which carries a tool 14 and holds it in a clamped manner.

[0102] The tool spindle 12 has a spindle housing 16. In the machining region 22, the tool 14 has contact with a workpiece, not illustrated, and so chips are produced at this location.

[0103] The tool 14 has a shaft 24 which is held in a clamped manner in a chuck 26 illustrated in FIG. 2.

[0104] In the illustrated exemplified embodiment, the tool 14 has a tool ring 28 with three annular protrusions or flanges or webs, not illustrated, between which annular grooves extend. The annular grooves serve to hold the tool 14 in a gripping fork of a robot arm, not illustrated, and are thus used for tool replacement purposes.

[0105] The tool 14 has the annular tool ring 28 which delimits or borders the shaft 24 at the top. The tool ring 28 serves at the same time as a stop for introducing the tool 14 into the chuck 26.

[0106] Whereas here with reference to the drawing the reference sign 12 designates the spindle, it is understood that this can also be understood to be a rotating part of the spindle or the rotor. The chuck 26 is not illustrated in its actual form but instead is indicated only schematically.

[0107] During operation of the machine tool 10, accumulations are caused to swirl up by air nozzles which are additionally provided on the housing side. The accumulations are removed at least partially by means of bottom-side suction.

[0108] However, if the machine tool 10 is switched off, the supply to the air nozzles is also switched off and therefore the resulting milling dust and the associated chips can accumulate.

[0109] The accumulations occur inter aria also on the tool spindle 12 and up to now accumulations could also pass into the interior of the tool spindle 12.

[0110] Since the machine tool 10 operates at more than 30,000 rpm, it is not possible to provide a sealing ring because such a sealing ring would immediately wear out at rotational speeds above 5000 rpm.

[0111] The machine tool 10 has a centrifugal disk 30, as can be seen in FIG. 2. It is fixedly attached to the spindle 12.

[0112] On its outer periphery, the centrifugal disk 30 is the part of the spindle 12 with the largest radius. Furthermore, it has imbalance bores in its outer regions. They are provided in order to compensate for any imbalance of the spindle 12.

[0113] The centrifugal disk 30 covers a sealing air channel 40 which extends between the spindle housing 16 and the spindle 12.

[0114] The sealing air channel 40 forms the end of a bearings air channel 42, in which rolling bearings 36 and 38 are arranged which have bearing air flowing therethrough.

[0115] Since the sealing air channel 40 is substantially narrower than the bearing air channel 42, the flow rate at this location is higher. Nevertheless, accumulations could previously pass therein and possibly impair the bearings 36 and 38.

[0116] Furthermore, accumulations could previously reach the region of the centrifugal disk 30 and clog the imbalance bores. This impaired balancing of the spindle 12 could lead to bearing damage.

[0117] In accordance with the invention, a protective cap 34 is provided which is placed over the upper end of the spindle housing 16.

[0118] The protective cap 34 covers the upper end of the spindle housing 16 and thus in particular also the region of the centrifugal disk 30. The protective cap 34 extends along the front region of the spindle 12 and at that location hugs the outer contour thereof.

[0119] The protective cap 34 is mounted on the spindle housing 16 and does not rotate with respect thereto. Since the protective cap 34 covers the centrifugal disk 30, it is supplied and filled by the air from the sealing air channel 40. An excess or positive pressure space 44 is produced within the protective cap 34.

[0120] This excess or positive pressure space extends as far as an annular gap 46, at which the protective cap 34 terminates radially just outside the spindle 12. The annular gap 46 has a width of 0.4 mm, wherein the gap dimension can be adapted to requirements within wide ranges and e.g., can be between 0.05 mm and 1.5 mm.

[0121] The bearings air channel 42 has an excess or positive pressure between 2 and 3 bar, wherein the over or excess or positive pressure can also be in the range of 0.5 and 6 bar.

[0122] The air flowing through can amount to about 15 l/min, wherein the flow volume can also be in the range of 5 and 50 l/min.

[0123] The excess pressure space 44 has a slightly lower excess or positive pressure of e.g., 0.5 bar.

[0124] The annular gap 46 is formed on one gap side by the chuck 26 of the spindle 12 and is formed on its other gap side by the protective cap 34.

[0125] The protective cap 34 has a substantially S-shaped contour when viewed in cross-sectional view and at one side of the radius. It is fitted onto the spindle housing 16 by means of a press fit. Other shapes include trapezoidal and bell-shaped; bell-shaped defined as a ‘bell curve’ which is defined as a mathematical function having a characteristic “bell”-shaped curve. These functions are typically continuous or smooth, asymptotically approach zero for large negative/positive x, and have a single, unimodal maximum at small x. Hence, the integral of a bell-shaped function is typically a sigmoid function. Bell shaped functions are also commonly symmetric.

[0126] The spindle housing 16 has at that location a circumferential annular groove 48, into which a radially inwardly protruding web or flange or protrusion 56 of the protective cap 34 enters. As a result, the protective cap 34 is securely centered.

[0127] In a manner particularly preferred in accordance with the invention, the air supply in the bearings air channel 42 can be operated intermittently. A pulse of air can substantially improve the cleaning of the chuck 26.

[0128] A modified embodiment of the protective cap 34 can be seen in FIG. 3. Instead of the web 56 shown in FIG. 2, a support surface 52 is provided therein which is supported on the radially outer region of the spindle housing 16 and is likewise used for centring purposes.

[0129] It can be seen that the protective cap 34 can hug the outer contour of the spindle housing 16 and also of the tool spindle 12, which is assisted by the S-shape, as mentioned above.

[0130] The protective cap 34 is intended for a machine tool comprising a spindle, a spindle housing and a tool. At its rearward end 54, the protective cap has a shape which makes it suitable for mounting on a fixed part of the machine tool, such as the spindle housing 16. At its front end 58, i.e., close to the tool, it has a diameter smaller than the diameter at its other, rearward end, and has a slender shape approximating the end-side inner diameter 60.

[0131] The protective cap 34, when in the state of being fitted onto the spindle housing 16, has an annular nozzle flank 62 which, together with a rotating part of the machine tool, in particular the tool 14 or the spindle 12, as a second annular nozzle flank, forms a nozzle in the shape of the annular gap 46.

[0132] The protective cap 34, when in the state mounted on the machine tool 10, covers the sealing air channel 40 of the machine tool 10, in particular towards the tool 14, and in this respect displaces the end of the sealing air channel 40 forwards, i.e. towards the tool 14.

[0133] The seat of the protective cap 34 is formed as a press fit, by means of which the protective cap 34 can be mounted on a fixed part of the machine tool 10 by interference fit and in a centered manner. At this location, the protective cap 34 is formed on its seat in such a manner that it functions as a replacement part or as an accessory part for existing machine tools 10 and fits onto fixed parts thereof.

[0134] FIG. 4 shows an enlarged view of a portion of FIG. 2, showing the sealing air channel (40). FIG. 5 shows a marked flow path 65 of sealing air channel 40 a part of which is formed by the bearings air channel 42 and thus runs through the rolling bearings 36 and 38. Exemplarily, this flow path is only shown on one side of the spindle but it is to be understood that a corresponding flow path is on the other side as well.

[0135] Upstream of the rolling bearings 36 and 38, preferably at the inlet of the bearing air channel 42, at least one filter, preferably first at least one coarse filter upstream of at least one fine filter, is connected to ensure the purity of the bearing air. If more filters are used they are connected in series, while the air is filtered by ever finer filters to maximize air purity. This is essential because even slight impurities in the bearing air, like fine dust grains, could lead to a 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.