A TOOL WITH A DIVIDED DRIVING SHAFT

The present invention relates to a tool designed for high speeds and with a structure according to the preamble of Patent Claim 1.

The tool according to the invention is designed for speeds of up to 500,000 revolutions per minute and higher, for which reason the tool has a unique design. It is also possible for the tool to be made small, for example with a shaft diameter of as little as 2 mm or less.

By virtue of its high speeds but relatively low torques, the tool is especially suitable for use in nanotechnology, for example for grinding, drilling, milling, engraving, and so on.

The tool has a novel design, and the special features that distinguish it from the prior art in this field are set forth in the characterizing parts of the patent claims.

With regard to the tool, we refer also to patent applications No. 0600534-2 and No. 0600535-9 which were submitted by the Applicant at the same time as this one and which disclose and describe tools in which the drive part is connected directly to the tool shaft and follows the latter out of the tool housing during tool replacement. The concept of the present invention is to employ the same principle, in such a tool, in order to arrange the drive part permanently in the housing, as is set forth in the following description and the patent claims. The invention will be described below on the basis of examples and with reference to the drawing, in which Figures 1 and 2 show different embodiments of the invention.

The tool comprises a housing 1 designed with an axial bore 2 that receives radial fluid bearings 3, 4, 5 and 6. The fluid bearings 3-4 bear a rotatable shaft 7, one end of which supports a machining tool 8 that can be integrated in or releasably connected to the shaft 7. Moreover, a rotatably mounted axle 9 is arranged in the bearings 5 and 6. One end of the axle 9 engages, by way of a carrier 10, with that end of the shaft 7 remote from the tool 8. The end of the axle 9 directed away from the carrier 10 supports a rotor 11 of an electric motor, the stator of which is designated by reference number 12. The carrier 10 is designed such that, during rotation of the axle 9 driven by the motor 11, 12, it drives the shaft 7, but the latter can be released axially from the axle 9 in the direction out of the housing 1. The axle 9 can of course be made shorter than is shown. In the figures, reference number 13 designates a flywheel mass for increasing the rotation energy of the tool and thereby increasing the machining capacity of the tool. Instead of a separate flywheel mass 13, it is also possible for the rotor 11 of the electric motor itself to be designed to form a flywheel mass.

Fluid, liquid or gas (for example water or air), for the fluid bearing of the shaft 7 and of the axle 9 is introduced into an inlet 14, mainly supplying the shaft 7 with fluid, and an inlet 15, mainly supplying the axle 9 with fluid, as has been indicated by arrows. The fluid distributes itself in the radial bearings 3, 4 and 5, 6, respectively, and is conveyed away via outlet channels 16, 17 and 18. To secure the axial position of the shaft 7 and thus of the tool 8 in the housing 1 and thus prevent the shaft 7 from leaving the housing, a counter-force that seeks to maintain the shaft in the housing is generated by means of the bearing fluid being exposed to an underpressure, i.e. forced out with underpressure via the outlet channels 16, 17 and 18.

In Figure 1, the axle 9 with its drive part 11, 12 is mounted axially non- displaceably with axial bearings 19, 20. During the action of the aforementioned counter- force, an axial bearing 21 defines the inserted position of the shaft 7 in the housing 1 during engagement with the axle 9 via the carrier 10. This axial bearing 21 is supplied with the same bearing fluid as the radial bearing.

Figure 2 indicates that a carrier piece, for example in the form of a claw coupling 10, acts as an axial support for the shaft 7, in which case the axial bearing 20 is the active bearing.

Instead of operating with underpressure in the bearing fluid in order to use a force to maintain the shaft 7 and its tool 8 in the housing 1 , this force can, as is shown in Figure 2, instead be generated by a magnet 22 generating this force, which magnet 22 is connected to the flywheel mass 13 in the case illustrated. Alternatively, the magnet 22 can be supplemented with or replaced by a magnet connected to the carrier 10 and indicated here by 23. The use of magnets thus means that an underpressure in the outlet channels 16-18 is not necessary.

When the tool is to be removed from the housing, for example for tool replacement, an overpressure is applied in the outlet channels instead of an underpressure, which overpressure, in the case of magnets, overcomes the magnetic force and "pushes" the tool out of the housing 1, which action, as has been mentioned, is not prevented by the carrier 10.

With regard to the structure of the axial bearings, the shape of their bearing

surfaces and their lubrication with fluid, the features described in the Applicant's said patent applications No. 0600534-2 and No. 0600535-9 can be used. Similarly, the tool according to the invention can of course be combined to form a tool with several rotating shafts provided with machining tools and operating, if necessary, at different speeds.

Within the scope of the invention, it will be obvious to persons skilled in the art that the electric motor 11, 12 can be supplemented with or replaced by a liquid-driven or air-driven turbine (not shown here).