GB2111172A

GB2111172A - Frictional releasable shaft-hub connexion

Info

Publication number: GB2111172A
Application number: GB08235105A
Authority: GB
Inventors: Heinrich Fischer
Original assignee: Hurth Verwaltungs GmbH
Current assignee: Hurth Verwaltungs GmbH
Priority date: 1981-12-09
Filing date: 1982-12-09
Publication date: 1983-06-29
Also published as: DE3148676A1; GB2111172B; DE3148676C2; JPS58109721A; IT8249197A0; IT1149379B; JPH0221447B2

Abstract

A clamping bush for making a releasable frictional shaft-hub connexion, which is disposed between the shaft 1 and the hub 3 and is resiliently deformable under the pressure of a fluid. The clamping bush 2 is provided with a plurality of closed chambers 4 uniformly distributed in the circumferential direction close to its inner surface 8 and with a plurality- preferably the same number-of closed chambers 5 uniformly distributed in the circumferential direction close to its outer surface 9. The chambers may be pressurised independently of one another, or one inner chamber and the outer chamber radially adjacent thereto may be acted upon jointly. <IMAGE>

Description

SPECIFICATION Frictional releasable shaft-hub connexion The invention relates to a releasable frictional shaft-hub connexion.

There are known clamping bushes which have two annular chambers for holding a fluid, one of which is disposed in the vicinity of the inner surface and the other of which is disposed in the vicinity of the outer surface of the bush. If the fluid in the first chamber is pressurised, the clamping bush will be resiliently deformed in the vicinity of its bore, i.e. the diameter of the bore will be diminished and thus the clamping bush may be clamped on to a shaft or the like. If the fluid in the other chamber is pressurised the clamping bush will be resiliently enlarged in the vicinity of its outer surface, i.e. a hub of a machine part mounted on the bush will be firmly clamped.

However, even with the most precise manufacture of the shaft, clamping bush and machine part, concentricity tolerances cannot be eliminated. In the most unfavourable case the tolerances of the three parts are additive and lead to an unnacceptably large concentricity error or radial deviation in the machine part, e.g. a grinding wheel, a flywheel or the like.

The object of the invention is therefore to provide a shaft-hub connexion which, in addition to providing clamping or gripping between the shaft and the clamping bush on the one hand and between the clamping bush and the machine part on the other, allows the machine part to be aligned so as to obtain a small concentricity error as possible.

The object is attained with the features of Claim 1. The division of the hydraulic clamping system into a plurality of separate clamping systems makes it possible to compensate concentricity errors on the clamped or gripped machine part to a substantial extent by a local increase and/or reduction in pressure. In order to increase the rigidity of the clamping bush, the latter may be formed according to Claim 2. The chambers are advantageously arranged according to Claim 3 or 4. In this case each chamber may be acted upon individually which allows a delicate adjustment of the position of the clamped or gripped machine part. The cost of the pressure reguiating devices may be reduced if two radially adjacent chambers are acted upon jointly in each case (Claim 5), which is sufficient for many cases of use.

The arrangement of a plurality of spaces uniformly distributed in the peripheral direction for holding the fluid is known from the German Offenlegungsschrift (Laid-Open Specification) 30 00 637. The solution disclosed there, however, with annular segments inserted in corresponding recesses in the shaft or in the hub and sealed, is expensive to manufacture and awkward to assemble.

The invention is described in greater detail below wifh reference to one example which is illustrated in the accompanying drawings.

Fig. 1 is a longutidinal section through a shafthub connexion according to the invention, Fig. 2 is a cross-section along the line Il-Il, and Figs. 3 and 4 are two possible embodiments for assembling the clamping bush from a plurality of parts.

A machine part 3 is secured to a shaft 1 (Figs.

1 and 2) by means of a clamping bush 2. For this purpose the clamping bush 2 is provided with first closed chambers 4 uniformly distributed in the peripheral direction and with second closed chambers 5 likewise uniformly distributed. (The term "ciosed", is to be taken to mean that the chambers 4, 5 are confined on all sides by the clamping bush 2 and it does not exclude the existence of bores, to which reference will be made below). The chambers 4 are at a small radial distance 6 from the inner surface 8 of the clamping bush 2, and the chambers 5 are at a small radial distance 7 from the outer surface 9.

In order to provide the clamping bush 2 with sufficient inherent stability the radial distance 10 between the first and second chambers 4 and 5 is greater than the radial distances 6 and 7.

The chambers 4 and 5 are filled with a fluid.

The pressure in the chambers may be varied by means of thrust screws 11. Adjacent to a threaded portion 1 2 the thrust screws 11 have a cylindrical shaft 13 with a packing ring 14. The further the thrust screws 11 are screwed in, the more the pressure in the respective chamber 4 or 5 increases and the more firmly the respective surface 8 or 9 is pressed against the shaft 1 or the machine part 3. In order to provide the assembling mechanic with an indication of the pressure which exists, a pressure gauge 1 5 may be connected to each chamber 4, 5: a sealed piston 1 7, to which a pin 1 8 projecting out of the clamping bush 2 with division markings 1 9 is secured, is pushed against the force of a spring 1 6. The number (or the colour) of the divisions indicates the pressure.

If an individual thrust screw 11 and an individual pressure gauge 1 5 are provided for each first and each second chamber 4, 5, the concentricity error of the machine part 3 may be compensated very delicately. The pressure in the first chambers 4 is used to secure the clamping bush 2 to the shaft 1 and the pressure in the second chambers 5 is used to secure the machine part 3 to the clamping bush. If, for example, it is found during the concentricity testing that the machine part should be "raised"-with respect to Fig. 2-relative to the shaft, then the pressure will be increased in the chamber designated 5' and where appropriate also in that designated 4' and at the same time the pressure will be reduced somewhat in the chamber designated 5" and where appropraite also in that designated 4".In order to be able to identify clearly the chambers 4, 5 to compensate a concentricity error with a higher or lower pressure, the same number of first chambers 4 and second chambers 5 is provided, one first chamber 4 and one second chamber 5 being radially adjacent in each case.

In many cases it is sufficient for one common thrust screw 11 and one common pressure gauge 1 5 to be provided for the radially adjacent chambers 4 and 5. The radially adjacent chambers may then be connected to one another by bores 20, as illustrated in Fig. 2 with broken lines. A reduction in pressure occurring in chamber 4" when compensating a concentricity error in a manner similar to the method described above is compensated by the reduction in pressure in chamber 4'.

in Figs. 1 and 2 the clamping bush 2 is shown as a homogeneous part. There are various possibilities of manufacturing it. As a rule it will be assembled from a plurality of parts, in which the respective chambers have been milled, and welded tight. Fig. 3 may be taken as an example, where the clamping bush is assembled from three individual bushes 21, 22, 23. In the example according to Fig. 4 the clamping bush is made up from two parts 24, 25 assembled axially.

The invention is not, of course restricted to the examples of embodiment illustrated. The clamping bush 2 may also be made in a different way, the thrust screws 11 and/or the pressure gauges 1 5 may also be arranged axially instead of radially, the number of chambers is not restricted to four in each case, etc.

Claims

1. A clamping bush for making a releasable frictional shaft-hub connexion, the clamping bush being disposed in use between the shaft and the hub and being resiliently deformable under the controllable pressure of a fluid, which clamping bush has a plurality of first closed chambers uniformly distributed in the circumferential direction at a small radial distance from the inner surface of the bush and a plurality of second closed chambers uniformly distributed in the circumferential direction at a small radial distance from the outer surface of the bush.

2. A clamping bush according to claim 1. in which the radial distance between the first chambers and the second chambers is greater than the radial distances of the said chambers from the inner and outer surfaces respectively.

3. A clamping bush according to claim 1 or 2, in which the number of first chambers and second chambers is equal.

4. A clamping bush according to claim 3, in which each first chamber is radially in line with a respective second chamber.

5. A clamping bush according to claim 4, in which the first chamber and the second chamber radially in line with it communicate with one another inside the clamping bush.

6. A clamping bush substantially as herein described with reference to the accompanying drawings.