GB2071213A

GB2071213A - Hydraulic gear pumps and motors

Info

Publication number: GB2071213A
Application number: GB8106933A
Authority: GB
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 1980-03-06
Filing date: 1981-03-05
Publication date: 1981-09-16
Also published as: GB2071213B

Abstract

In a gear pump, or motor, of the externally-meshing type the gear- wheels 13, 14 are mounted in bearings 16..19 that are given slight freedom to move radially, the driving or output shaft 15 being centred by an encircling plate e.g. a washer 26, lodged in or on a housing end-cover 11, which may be furnished with an annular spigot D. Alternative forms of the plate are described with reference to Figs. 2-5 (not shown). The plate may be situated wholly or mainly against the inner face of the end cover, rather than within the end cover, Figs. 6-8 (not shown). <IMAGE>

Description

SPECIFICATION An hydraulic gear pump or motor This invention relates to a gear pump or motor comprising externally meshing gear wheels arranged in a housing on shafts mounted in bearing members inside the housing.

With such machines, the driving shaft passes through a cover which closes one end of the housing in a fluid-tight manner. When in use, the driving shaft needs to be centered with respect to a centering spigot on the machine itself or some other auxiliary part, such as a flange on an electric motor. Thus, the driving shaft is not rigidly mounted in the housing but passes through the cover with slight radial play. This play is provided by making the bearing members slightly movable in a radial direction.

In the past it has been necessary to undertake the centering of the driving shaft with special apparatus during the mounting of the machine on the auxiliary part. This is laborious and the need for special apparatus makes the mounting operation very expensive.

In an hydraulic gear pump or motor in accordance with the invention, comprising externally meshing gear wheels arranged in a housing on shafts mounted in bearing members which are slightly movable in a radial direction, the housing being closed fluid-tight at one end by a cover through which the driving shaft passes with radial play, the cover is provided with a plate having an aperture surrounding the driving shaft for centering the driving shaft by adjusting the position of the cover with respect to the housing.

In one form of pump or motor in accordance with the invention, the plate is a centering washer arranged in a stepped bore in the cover and has slight play with respect to the driving shaft and with respect to the outer diameter of the stepped bore.

In another form of pump or nlotor in accordance with the invention, a passage is formed in the cover through which the driving shaft passes with play and the plate is fixed ,o the inside of the cover facing the bearing members and substantially follows the inner contour of the housing.

With either of these arrangements, centering of the driving shaft is effected automatically when mounting the cover on the housing.

In order that the invention may be clearly understood and readily carried into effect, several embodiments of gear pump in accordance with the invention will now be described with reference to the accompanying drawings in which* Figure 1 is a longitudinal section through a gear pump provided with a washer as a centering device for the driving shaft, Figures 2 to 5 show various forrns of centering washer, Figure 6 is a longitudinal section through a gear pump provided with a centering plate arranged on Lhe inside of the cover, Figure 7 shows one form of centering plate tor use in the pump of Figure 6, and Figure 8 is a partial longitudinai section through a gear pump showing a modified form of centering plate.

The gear pump shown in Figure 1 comprises a housing 10 which is closed fluid-tight by a cover 1 A cavity 12 is formed in the housing 10 in which are located two gear wheels 13 and 14 meshing in external engagement with one another. The driving shaft 1 5 for the gear wheel 13 is mounted in two bush-like bearing members 16 and 17 and the shaft 18 for the gear wheei 14 is likewise mounted in two such bearing members 1 9 and 20. At least in a radial direction, the bearing members are movable to a slight extent.

This is necessary for the running in of the gear wheels and can also be utilised for centering the driving shaft 1 5.

A stepped bore 21, through which the driving shaft passes, is formed in the cover 11. A sealing ring 22 -- preferably an oil seal ring -- which is secured against falling out with the aid of a snap ring 23, is arranged in the part 21 of f the stepped bore 21 with the larger diameter. The widened portion 21' of the stepped bore is directed towards the outside. Between the sealing ring 22 and the shoulder 24 formed by the stepped bore, a narrow gap 25 is formed in which is arranged a centering plate in the form of a washer 26, the aperture in which is very closely dimensioned to the shaft and at the outer diameter of which is very closely dimensioned to the inner diameter of the bore portion 21'.With the aid of this centering washer 26, the driving shaft 1 5 is very accurately centred with respect to a spigot D on the cover 11, concentric to the driving shaft 15, or with respect to a third part such as a flange on an electric driving motor. Thus, it is no longer necessary to undertake the centering with the aid of special apparatus during mounting.

During operation of the pump, a slight wear can take place between the centering washer 26 and the driving shaft 1 5 due to displacement of the latter and which, with an appropriate selection of materials, is uncritical.

For reducing the wear, it can be preferable to form substantially semicircular recesses 28 (Figure 2) extending radially outwards at the aperture in the centering washer which, however, do not lie so close that they interfere with the inner diameter of the washer.

In order to compensate for the difference in diameter between the shaft 1 5 and the outer diameter of the bore 21', it can be preferable to form resilient lugs 28', 29 on the outer and/or inner periphery of the centering washer 26' (Figure 3). Furthermore, it is possible to provide the centering washer, referenced 26" according to the embodiment of Figure 4, with a slot 30 which passes completely through on one side but only extends into a portion of the washer on the opposite side. As the embodiment according to Figure 5 shows, a preferably thin, coating 31 of uniform thickness, which preferably consists of an elastic material, can also be applied to the outer and inner peripheries of the washer for the purpose of reducing play.It is preferable to form the centering washer as a stamping.

The gear pump shown in Figure 6 also comprises a housing 10 which is closed fluid-tight by a cover 11. A cavity 12 is also formed in the housing 10 in which are located the two gear wheels 1 3 and 14 meshing in external engagement with one another. As in Figure 1, the driving shaft 1 5 for the gearwheel 13 is mounted in two bush-like bearing members 16 and 17 and the shaft 1 8 for the gear wheel 14 is likewise mounted in two such bearing members 19 and 20. At least in a radial direction, the bearing members are movable to the slight extent necessary for running in the gear wheels and for centering purposes.

A through passage 21" is formed in the cover 11 but in this case the driving shaft 1 5 passes outwardly through the passage 21" with play. A sealing arrangement 23' is arranged in a widened portion 22' of the passage 21".

A relatively thin metal plate 25' which is soldered to the flat inside of the cover 11 and which is provided with an aperture 26' for the driving shaft 15, is located within the housing between the cover 11 and the bearing members 16 6 and 19. The aperture 26 extends up to the driving shaft 15, that is to say the latter passes through the aperture 26' almost without clearance. This means that, as soon as the cover 11 is mounted, the driving shaft is centered by the plate 25' or its aperture 26'. Thus, it is no longer necessary to undertake the centering with the aid of a special device during mounting, as in the past.

During operation of the machine, a slight wear can take place between the aperture 26' and the driving shaft 1 5 due to displacement of the latter and which, with an appropriate selection of materials, is again not critical. To reduce wear, it can be preferable to form radially outwardly extending somewhat semi-circular recesses 27 (see Figure 7) at the inner periphery of the aperture 26' which do not however lie so close to one another that they upset the inner diameter of the washer.

In the embodiment according to Figure 8, the plate serving for centering is made slightly modified. It is referenced 30, is also located in the same position as the plate 25' in Figure 6 and has a flange 31 around the aperture 26' which projects into the gap between the driving shaft 1 5 and the passage 21. The plate 30 is likewise rigidly connected to the cover 11 for example by adhesion or soldering and is preferably produced as a stamping.

Claims

1. An hydraulic gear pump or motor comprising externally meshing gear wheels arranged in a housing on shafts mounted in bearing members which are slightly movable in a radial direction, the housing being closed fluid-tight at one end by a cover through which the driving shaft passes with radial play, the cover being provided with a plate having an aperture surrounding the driving shaft for centering the driving shaft by adjusting the position of the cover with respect to the housing.

2. A gear pump or motor according to claim 1, in which the plate is a centering washer arranged in a stepped bore in the cover and has slight play with respect to the driving shaft and with respect to the outer diameter of the stepped bore.

3. A gear pump or motor according to claim 2, in which a shaft sealing ring is arranged in that portion of the stepped bore having the larger diameter and that the centering washer is located in a gap between the sealing ring and a shoulder formed by the stepped bore.

4. A gear pump or motor according to claim 2 or claim 3, in which radial recesses are formed at the inner periphery oF the centering washer.

5. A gear pump or motor according to any one of claims 2 to 4, in which resilient lugs are formed at the outer and/or inner periphery of the centering washer.

6. A gear pump or motor according to any preceding claim, in which the centering washer is radially slotted.

/. A gear pump or motor according to any preceding claim, in which a surface coating of uniform thickness is arranged at the inner and outer periphery of the centering washer.

8. A gear pump or motor according to claim 7, in which the surface coating consists of elastic material.

9. A gear pump or motor according to any one of claims 2 to 8, in which the centering washer is a stamping.

10. A gear pump or motor according to claim 1 in which a passage is formed in the cover through which the driving shaft passes with play and the plate is fixed to the inside of the cover facing the bearing members and substantially follows The inner contour of the housing.

11. A gear pump or motor according to claim 10, in which the aperture in the plate has only very slight play with respect to the driving shaft.

12. A gear pump or motor according to claim 10 or claim 11, in which substantially semicircular recesses are formed at the periphery of the aperture.

13. A gear pump or motor according to claim 10, in which portions of the plate surrounding the aperture are flanged, with very slight play, into the gap between the driving shaft and the passage in the cover through which the driving shaft passes.

14. A gear pump or motor according to any one of claims 10 to 13, in which the plate is soldered to the inside of the cover.

1 5. A gear pump or motor according to claim 1 3, in which the plate is stuck to the inside of the cover.

1 6. An hydraulic gear pump or motor substantially as herein described with reference to Figure 1, Figure 1 in combination with any one of Figures 2 to 5, Figure 6, Figures 6 and 7 or Figure 8 of the accompanying drawings.