Device for Fixing a Thrust Bearing

1. Field of the Invention

The present invention relates to a device for fixing a rotatable shaft in its axial direction within a bearing housing. The shaft is journalled in its axial direction, in a roller or ball bearing (hereafter, for convenience, referred to as a "roller bearing"), which is fixed to the shaft and bears against a fixed supporting surface in the housing with a force determined by a resilient element within the housing, the roller bearing thus having a measure of radial movability within the housing.

2. Description of the Prior Art

A device of the above-described kind is disclosed in U.S. Pat. No. 4,227,755 and is primarily intended for fixing the rotor shafts in a rotary compressor. It was previously known to maintain the roller bearing pressed against the supporting surface by means of an annular element which was screwed to the outer ring of the roller bearing. However, such an element must be tightened to just the right amount within the outer ring, and in practice this has proved difficult to achieve. Thus, if the contact between the annular element and the roller bearing was made to be too tight, the radial movability of the bearing was reduced (or even prevented), whereby the roller bearing was forced to take up radial forces as well as axial forces, which had an adverse effect on the life of the bearing. On the other hand, if the annular element was not screwed up tightly enough against the outer ring, the outer ring of the bearing could rotate relative to the supporting surface and the annular element, which may result in wear occurring further loosening the engagement and risking further damage. By arranging a resilient element, for example in the form of a spacing sleeve and a spring, which maintains the roller bearing pressed against the supporting surface with a specified force, as was proposed in the abovementioned patent, the problem of proper fixing of the roller bearing within its housing appeared to be solved. However, it has proved to be difficult to adjust the compressive force of the resilient element, so that, on the one hand, the roller bearing has the desired radial movability, while, on the other hand, the roller bearing, in operation of the machine, is able to absorb a sufficient axial force.

According to the invention, the above-mentioned problem is solved by means of a screw-threaded fixing member, which is movable in the direction of the axis of the shaft by being screwed into a threaded opening in an element which is fixed relative to the housing, the fixing member in its screwed-in position thereby serving to restrict the axial movement of the roller bearing within the housing.

It is convenient to arrange a spacing sleeve between the screw-threaded fixing member and the roller bearing, and optionally also a gasketed plug between the fixing member and the spacing sleeve.

In a preferred embodiment of device, the end of the screw-threaded fixing member which is most remote from the roller bearing is formed as a pin, the cross-section of which does not conform to that of any readily available tightening tool so that it is likely to be tightened only to the degree possible with finger force.

The invention will now be further described in greater detail, by way of example, with reference to the accompanying drawing, wherein

FIG. 1 is a longitudinal section through part of a rotary machine which is provided with a short fixing device according to the invention, and

FIG. 2 shows an end view of the fixing device of FIG. 1.

In FIG. 1, 1 designates a rotatable shaft which is journalled in a radial bearing 2 mounted in a bearing housing 3. The shaft 1 is axially journalled in two roller thrust bearings 4, 5 which are mounted on the shaft 1 by means of a locking nut 6. The thrust bearings 4, 5 are separated by annular spacers 7. A cover plate 8 presses a generally cup-shaped spacing sleeve 10 against the thrust bearing 5 by means of a cup spring 9, so that the thrust bearing 4 engages an annular supporting surface 11 formed inside the housing 3.

In a screw-threaded opening 12 in the cover plate 8 there is screwed a fixing member in the form of a threaded pin 13. The free end 14 of the pin 13 has a semicircular cross-section (shown in FIG. 2) that is not adapted to engage with any of the conventional range of tightening tools. The free end 14 projects beyond the cover plate 8, and is non-rotatably attached to a locking disc 15, which is provided with an arcuate slot 16 whereby it is lockable by means of a conventional socket-headed screw 17. Between the pin 13 and the spacing sleeve 10, a spacing plug 18 is located. As shown, the plug 18 is provided with a gasket 19, but this is not essential.

The device operates as follows:

The cover plate 8 is fixed in place to close the housing 3 after the locking nut 6 has been lightly applied to the shaft 1 to hold the roller bearings 4, 5 in place. The cup spring 9 then takes over from the nut 6 and generates the required axially directed operating force needed to urge the bearing 4 against the annular supporting surface 11. This operating force is relatively small and is generated by a pressing the open end of the spacing sleeve 10 against the thrust bearing 5. The operating force is large enough to eliminate axial play between the bearing parts but not so large as to prevent movement of the roller bearings 4, 5 within the housing 3 in the radial direction of the shaft 1. The free end 14 of the fixing member 13 is now turned slightly through part of a full turn (e.g., using the fingers on the perimeter of the disc 15) to lightly bring the member 13 into contact with the plug 18, and the plug 18 into contact with the spacing sleeve 10. Thus, axial forces which are greater than those which can be absorbed by the cup spring 9 can now be absorbed by the fixing member, i.e. the pin 13. The locking disc 15 is secured in its finger-tightened position by the screw 17.

It will be appreciated that many modifications are possible to the device illustrated within the ambit of the following claims and all such modifications should be understood to be within the spirit and scope of the invention.