Rotary Machine With Rotor Axial Positioning Means

Abstract

A rotary motor of the sliding vane type is shown. The rotor has two stub shafts rotatably supported in the housing by means of ball bearings. A pile of Belleville springs are braced between a shoulder on one of the stub shafts and its associated bearing so as to bias the rotor into an axial position defined by a counterbalancing ring that is adjustably attached to the other stub shaft by means of a set screw.

Description

This invention relates to a rotary machine -- particularly but not exclusively of the type provided with vanes, for instance a vane motor, a vane pump or a vane compressor -- with a housing and a rotor which has two opposite stub shafts journalled by roller or ball bearings in the housing, the outer races of the roller or ball bearings being axially supported in the housing and the rotor being axially sealed to the housing by narrow clearances.

In such machines the rotor can either be axially fixed in a position between its axial end positions or be axially freely movable between the end positions. In an air pressure driven vane motor the distance between the end positions, i.e., the total axial clearance, is for instance 0.06 mm. An axially fixed rotor is preferable considering the wear. Furthermore, if the rotor can be fixed in a position which gives about the same clearance on both sides, a considerably reduced leakage is obtained.

The object of the invention is therefore to provide for the fixation of the rotor in an axial middle position in a way that is technically and economically favourable and does not require extreme tolerances of the dimensions of the fixation details. According to the present invention there is provided a rotary machine comprising a housing, a rotor with two opposite stub shafts each being journalled in the housing by means of a bearing with an outer race and an inner race and rolling elements, the outer races of the bearings being axially supported in the housing and the rotor having narrow axial clearances to the housing, a spring braced between a shoulder on one of the stub shafts and the inner race of one of the bearings so as to apply an axial load to the rotor and an element axially adjustably attached to the other of the stub shafts and abutting against the inner race of the other bearing so as to take up and transmit to this inner race the axial load applied to the rotor by the spring whereby to hold the rotor in an axially fixed position.

The invention will be further described with reference to the accompanying drawings in which: FIG. 1 is a longitudinal section along line 1--1 in FIG. 2 through an air pressure driven vane motor in accordance with the invention, FIG. 2 is a cross section along line 2--2 in FIG. 1, FIG. 3 is a longitudinal section through a detail shown in view in FIG. 1, and FIG. 4 is a longitudinal section similar to FIG. 1 through a modified embodiment.

The vane motor shown in the FIGS. 1-3 has a housing with a cylindrical part 11 and two end plates 12,13 screwed together in order to define a cylinder chamber. Instead of being directly screwed together the parts 11,12,13 can be clamped together by means of an outer housing not illustrated. A rotor 16 has two stub shafts 17,18 and a number of grooves 19 for vanes 20. A ball bearing, comprising an outer race 22, an inner race 23 and balls 21, is moved onto the shaft 17 so that the outer race is radially as well as axially supported in the end plate 12. In the same way, a ball bearing for the stub shaft 18 is mounted in the end plate 13. This bearing comprises an outer race 25, an inner race 26 and balls 24. The shaft 17 is provided with a groove in which a split snap ring 27 is mounted. Two Belleville springs 28,29 are braced between the snap ring 27 and the inner race 23 of the bearing 21,22,23. Thus, the balls 21 of the bearing will transmit the force of the springs from the inner race 23 to the outer race 22. The latter is axially supported in the end plate 12 and thus, the springs bias the rotor 16 towards the end plate 12, i.e., to the left in FIG. 1. A ring or washer 30 is axially supported by the inner race 26 of the other bearing 24,25,26 and by means of a set screw 31, the rotor 16 can be pulled against the end plate 13, i.e. to the right in FIG. 1, against the action of the springs 28,29. In FIG. 3, the stub shaft 18 and the washer 30 are shown in section.

When the vane motor is to be assembled, the washer 30 and the set screw 31 will be mounted as the last part. Suitably, the set screw 31 is first given a coat of a glue or of any other hardening fluid or substance, for instance an anaerob plastic, and the set screw is screwed to the position in which the rotor 16 easily can be rotated manually, i.e., until the axial force between the rotor 16 and the end plate 12 of the housing starts decreasing but the rotor still abuts the end plate. The angular position of the set screw 31 is now indicated and the screw is turned until it begins to be difficult to rotate the rotor manually again, i.e., until the rotor instead abuts the other end plate 13 of the housing. The angular position of the set screw 31 is again indicated. The screw is now adjusted into a position right between the indicated positions which results in the rotor 16 taking up its middle position in which the clearances between the rotor and the end plates 12,13 of the housing are equal. After some time, the anaerob plastic has hardened and the set screw 31, as well as the rotor, has been fixed in its positions. Of course, any other suitable locking method can instead be used for the screw 31.

The Belleville springs 28,29 are for instance selected to give a spring force of about 20 kp for a rotor diameter of 50 mm. Thereby, a very close sliding fit can be permitted between the stub shafts 17,18 and the inner races 23,26 of the bearings so that the wear between the stub shafts and the inner races will be almost eliminated. Still, the springs 28,29 will be strong enough to axially displace the rotor in the inner races of the bearings. The fact that the bearings constantly are axially loaded by such a great force as, for instance, 20 kp has no negative influence on their durability.

In the modified embodiment shown in FIG. 4 the rotor 16 is clamped between the inner sides of the inner races 23,26 of the two bearings instead of between the outer sides. The outer races 22,25 of the bearings have such a tight fit (i.e., press fit) that they will remain fixed in the end plates 12,13 of the housing in spite of the fact that they are loaded outwards by means of the spring 28,29. A shoulder 27 on the stub shaft 17 corresponds to the snap ring 27 and the other elments of FIG. 4 corresponding to elements in FIGS. 1-3 have also been given the same reference numerals as in FIGS. 1-3.

Claims

1. A rotary machine comprising:

a housing,

a rotor with two opposite stub shafts each of said stub shafts being journalled in the housing by means of a bearing with an outer race, an inner race and rolling elements, the outer races of the bearings being axially supported in the housing and the rotor having narrow axial clearances to the housing,

a shoulder on a stub shaft,

a spring braced between the shoulder on one of the stub shafts and the inner race of one of the bearings so as to apply an axial load to the rotor, and

an adjusting means axially adjustably attached to the other of the stub shafts and abutting against the inner race of the other bearing so as to take up and transmit to the inner race of said other bearing the axial load applied to the rotor by the spring whereby to hold the rotor in an axially fixed position which is defined by the position of said adjusting

2. A rotary machine as defined in claim 1 in which said shoulder is arranged on the outside of said one bearing and said spring is braced between said shoulder and the outer side of the inner race of the bearing associated therewith, said adjusting means abutting against the outer side

3. A rotary machine as defined in claim 1 in which said shoulder comprises

4. A rotary machine as defined in claim 1 in which said rotor is provided with a number of substantially radial grooves in which vanes are disposed to seal with their outer protruding edges against a cylindrical wall formed in the housing, said cylindrical wall and said vanes forming

5. A rotary machine as defined in claim 1 in which said adjusting means comprises a threaded member adjustably threaded into said other stub shaft

6. A rotary machine as defined in claim 1 in which said adjusting means includes an element fastened in the end of said other stub shaft by means

7. A rotary machine as defined in claim 6 in which said elment comprises a

8. A rotary machine as defined in claim 6 comprising a binding layer for

9. A rotary machine as defined in claim 1 in which said spring comprises at

10. A rotary machine as defined in claim 9 in which said spring comprises a

11. A rotary machine as defined in claim 1 in which said shoulder is arranged on the inside of said one bearing and said spring is braced between said shoulder and the inner side of the inner race of the bearing associated therewith, said adjusting means abutting against the inner side

12. A rotary machine as defined in claim 11 wherein said outer races of said bearings are press-fit in said housing so as to be retained therein.

13. A rotary machine as defined in claim 11 wherein said adjusting means comprises a first element axially slideably engaging said other stub shaft and abutting the inner side of the inner race of said other bearing, and a set screw adjusting the axial position of said first element relative to

14. A rotary machine as defined in claim 13 wherein said set screw threadably engages said first element and abuts the end of said other stub shaft.