GB2043181A - Shaft bearing system - Google Patents

Abstract

During operation of a machine, a shaft (2) rotatable in a housing (1) is subjected to a load having an axial component. For rotatably mounting the shaft and for supporting the axial load component, thrust rolling bearings (9, 10) are arranged in parallel between the shaft (2) and housing (1). One part of the axial load component is transmitted from the inner race (11) of bearing (9) to the housing by way of the outer race (13) of the same bearing (9) and by way of a ring (28), whereas another part of the axial load component is transmitted from the said inner race (11) of bearing (9) to the housing by way of a spacer sleeve (12), the inner race (11) of bearing (10), the outer race (13) of bearing (10) and fluid pressure means. The fluid pressure means may comprise one or several pistons (15), or an annular fluid duct. <IMAGE>

Description

SPECIFICATION Shaft bearing system This invention relates to a bearing arrangement for the shaft of a machine, the shaft being rotatably mounted on a housing and being subjected to a load having an axial component.

The invention has particular application in a machine in which the shaft is drivingly interconnected with a drum rotatable about an axis inclined to the axis of-rotation of the shaft, a piston rod being connected to the shaft at a region spaced from its axis of rotatation, the piston rod carrying a piston arranged to reciprocate in an axial bore in the drum, the bore being spaced from the axis of rotation of the drum. Rotation of the drum and shaft will always be accompanied by reciprocation of the piston in its bore in the drum because the axes of rotation of the drum and shaft are inclined relative to one another.

The above machine can be used as a pump, in which case the shaft drives the drum and the forced reciprocation of the piston is used to pump liquid under pressure. Alternatively, the machine can be used as a motor, in which case liquid under pressure is fed to the bore in the drum to force the piston to reciprocate to drive both the drum and shaft.

In either case, the piston rod exerts on the shaft a load having both a radial and an axial component. Various bearing arrangements have been proposed for the shaft, but bearing arrangements which have been efficient and hard wearing have also been complicated, expensive; and difficult to service. For example, the arrangement described in German DOS 2112822 uses two radial bearings, two thrust bearings disposed between the radial bearings, and a liquid pressure biased annular piston disposed between the two thrust bearings to exert a "back-up" force on an outer ring of one of the thrust bearings. Obviously the seals of the "back-up" piston are not readily accessible because the piston is sandwiched between the various bearings.Also the shaft has to be stepped at various places where it transmits load to the housing, and the housing is also stepped so that the construction is expensive to manufacture.

An aim of the invention is to provide an improved bearing arrangement for the shaft of a machine, which shaft is subjected to a load having an axial component, and with this aim in view the invention is directed to a machined comprising a housing, a shaft rotatably mounted in the housing, means drivingly interconnected with the shaft and imposing on the shaft during operation of the machine a load having an axial component, and bearing means serving for rotatably mounting the shaft and for supporting the said axial load component, said bearing means comprising first and second thrust bearings disposed in line on the shaft, each such bearing comprising an inner race, an outer race, and rollers or balls disposed between the inner and outer races, the bearing means further comprising fluid pressure means acting to exert pressure on an end face of the outer face of the second bearing which is remote from the first bearing, and force transmitting means to transmit an axial force between the inner races of the bearings, the arrangement being such that one part of the axial load component is transmitted from the inner race of the first bearing to the housing via the outer race of the first bearing, whereas another part of said axial load component is transmitted from the inner race of the first bearing to the housing via the force transmitting means, the inner race of the second bearing, the outer race of the second bearing, and the fluid pressure means.

When the invention is applied to a said machine mentioned above usuable as a pump or motor, then the said shaft is mounted to rotate about a first axis, the said means drivingly interconnected with the shaft comprising a drum mounted to rotate about a second axis, a piston rod extending between the shaft and the drum, the piston rod being connected to the shaft at a region spaced from its axis of rotation and being connected to a piston reciprocable in an axial bore in the drum, said bore being spaced from the axis of rotation of the drum, the axes of rotation of the shaft and drum being disposed at an angle to each other whereby rotation of the shaft and drum is accompanied by reciprocation of the piston, said piston serving to pump liquid under pressure if the machine is a pump, or being reciprocated by liquid under pressure if the machine is a motor, the said liquid which is either pumped by the piston, or is used to reciprocate the piston, serving to provide the pressure for said fluid pressure means acting to exert pressure on the second bearing, the piston rod exerting a force on the shaft having both an axial and a radial component, the first bearing being on a part of the shaft adjacent the drum and the second bearing being remote from the drum.

Advantages of a machine according to the invention are explained below in the following description of preferred embodiments of machine according to the invention and illustrated in the accompanying drawings, in which Figure 1 is a cross-section on the line I-I in Fig. 2 through a shaft and housing of a machine according to the invention; Figure 2 is a longitudinal sectional view of the machine of Fig. 1; Figure 3 is a view corresponding to Fig. 2, but showing a second embodiment of the invention; Figure 4 is a view on an enlarged scale of a detail of Fig. 3; Figure 5 is a view corresponding to Fig. 1, but showing a third embodiment of the invention; and Figure 6 is a view corresponding to Figs. 2 and 3 of the embodiment of Fig. 5.

The machine which is shown in Figs. 1 and 2 may operate as a pump or as a motor, but in the following description it is assumed that the machine is operating as a pump. The pump comprises a housing 1 in which a drive shaft 2 (driven by any suitable means not shown) is rotatably mounted.

A drum 5 is also mounted in the housing 1 and is rotatable on and with a central pin 4.

One end of the pin 4 has a part-spherical head 4a mounted in a mounting plate 3 formed, for example, integrally at the base of shaft 2. The centre of the part-spherical head 4a is disposed at the point where the axis of rotation of the shaft 2 meets the axis of rotation of the drum 5, these two axes being inclined relative to each other. The head 4a may be formed with a splined type universal joint whereby rotation of shaft 2 can be transmitted to the pin 4 and thus to the drum 5 which may be keyed to the pin 4. The lower end of the pin 4 is mounted to rotate in a central opening 23 in a stationary plate 24.

The stationary plate 24 has a curved surface 25 which serves as a bearing for the lower end of the drums. Formed in the drum 5 are cylindrical bores 8 in which pistons 7 reciprocate, the bores 8 being spaced from the axis of rotation of the drum 5. The pistons are driven by piston rods 6 which are connected to the mounting plate 3 of shaft 2 at regions spaced from the axis of rotation of the shaft 2. it will be appreciated that as the shaft 2 and drum 5 rotate the distance between each bore 8 and the mounting plate 3 will increase and decrease between a minimum when the bore is adjacent the left-hand side of Fig. 2 and a maximum when the bore 8 is at the position illustrated in Fig. 2 at the righthand side of drum 5. Thus each piston 7 will reciprocate up and down once during each revolution of the shaft and drum.

As the pistons 7 reciprocate they serve to pump liquid through bores 26 in the stationary bearing plate 24, the fluid being conveyed to means not shown. It will be seen that the shaft 2 will be subjected to loads having both axial and radial components, such loads being applied to the mounting plate 3 by the piston rods 6. The present invention is concerned with the bearing arrangement for supporting the shaft 2 against these loads, such bearing arrangement including a pair of thrust bearings 9 and 10 disposed in line axially of shaft 2.

Each thrust bearing 9, 10 comprises a stationary outer race 1 3 adjacent the housing 1, an inner race 11 which rotates with the shaft 2, and tapered rollers disposed between the inner and outer races, The bearings have cone angles ss, the apices of which are in line, lying on the axis of rotation of shaft 2.

The angle between the axes of rotation of the shaft and the drum is shown at a. Part of the load acting on the shaft 2 via its mounting plate 3 is supported by the outer race 1 3 of the bearing 9 adjacent the drum, the load acting on such outer race via its inner race 11 and its tapered rollers. This outer race in turn transfers the load to the housing 1 to which it is secured by rings 27, 28.

Another part of the axial component of the load acting on the shaft 2 is transferred to a cover plate 14 which is secured to the housing by a ring 29. This load transfer is achieved as follows. The inner race 11 of bearing 9 abuts one end of a spacer sleeve 12, the other end of which abuts the inner race 11 of bearing 1 0. The outer race of bearing 10 is supported by three pistons 1 5 slidably mounted in bores in the cover plate 14 and equally spaced apart around the periphery of the plate. The pistons 1 5 are biased towards engagement with the outer race of bearing 10 partly by springs 30, but mainly by fluid pressure acting behind the pistons.

High pressure fluid is bled off from the fluid pumped by the pistons and is conveyed to a space behind the pistons 1 5 by way of a duct 16 in the housing wall.

It will be seen that, in contrast to the arrangement described in German DOS 2112822, the shaft 2 is not stepped except where it joins the mounting plate 3. Similarly, the housing wall 1 is not stepped, but is merely provided with recesses for rings 27, 28, 29. The machine is thus cheap to build.

Also, because the pistons 1 5 are readily accessible by removal of ring 29 and removal of the housing cover plate 14, maintenance of the piston seals is simple. Another important advantage of the invention is that the pistons 1 5 act on a stationary part and not on a moving part as is the case in some known constructions. This avoids sealing problems which could occur, particularly when pumping low viscosity liquids such as water or HSA fluids (95-97% water and 5-3% lubricant).

In the embodiment of Figs. 3 and 4, "back up pistons such as pistons 1 5 are not used.

Instead, the feed duct 1 6 from the high pressure liquid opens into an annular duct 1 7 defined between the housing cover 14 and the face of the outer race of bearing 10 which is remote from bearing 9. Thus, fluid pressure acts directly on the outer race 1 3 of the bearing 10. The inner limit of annular duct 1 7 is defined by a ring seal 1 8 in cover 14, and seals 1 9 in the housing wall 1 prevent leakage from duct 1 7. This second embodiment is obviously cheap to produce and compact, and it may be possibie to modify an existing production run of machines to incorporate the invention in the form shown in Figs. 3 and 4 without great expense.

The embodiment of Figs. 5 and 6 differs from that of Figs. 1 and 2 in that the three pistons 1 5 are replaced by a single annular piston 20 mounted in the cover 14 directly over the outer race 1 3 of bearing 10. Piston 20 has a horizontal portion bearing on race 1 3 of bearing 10 and a vertical portion guided in an opening in the cover 14, i.e., between a recessed part of the cover 1 4 and the housing wall.

In each of the embodiments described above a radial bearing for the shaft may be provided as shown at 31 in Fig. 2. Each of the machines can be used as motors instead of pumps if the fluid is fed to the bores 8 under pressure whereby to force reciprocation of the pistons 7 to drive the shaft and drum to rotate.

Claims (6)

1. A machine comprising a housing, a shaft rotatably mounted in the housing, means drivingly interconnected with the shaft and imposing on the shaft during operation of the machine a load having an axial component, and bearing means serving for rotatably mounting the shaft and for supporting the said axial load component, said bearing means comprising first and second thrust bearings disposed in line on the shaft, each such bearing comprising an inner race, an outer race, and rollers or balls disposed between the inner and outer races, the bearing means further comprising fluid pressure means acting to exert pressure on an end face of the outer race of the second bearing which is remote from the first bearing, the force transmitting means to transmit an axial force between the inner races of the bearings, the arrangement being such that one part of the axial load component acting on the shaft is transmitted from the inner race of the first bearing to the housing via the outer race of the first bearing, whereas another part of said axial load component is transmitted from the inner race of the first bearing to the housing via the force transmitting means, the inner race of the second bearing, the outer race of the second bearing, and the fluid presure means.

2. A machine according to claim 1, in which said machine comprises a pump or motor, and the said shaft is mounted to rotate about a first axis, the said means drivingly interconnected with the shaft comprising a drum mounted to rotate about a second axis, a piston rod extending between the shaft and the drum, the piston rod being connected to the shaft at a region spaced from its axis of rotation and being connected to a piston reciprocable in an axial bore in the drum, said bore being spaced from the axis of rotation of the drum, the axes of rotation of the shaft and drum being disposed at an angle to each other whereby rotation of the shaft and drum is accompanied by reciprocation of the piston, said piston serving to pump liquid under pressure if the machine is a pump, or being reciprocated by liquid under pressure if the machine is a motor, the said liquid which is either pumped by the piston or is used to reciprocate the piston, serving to provide the pressure for said fluid pressure means acting to exert pressure on the second bearing, the piston rod exerting a force on the shaft having both an axial and a radial component, the first bearing being on a part of the shaft adjacent the drum and the second bearing being remote from the drum.

3. A machine according to claim 1 or claim 2, in which the fluid pressure means comprises a plurality of pistons slidable in bores in a housing cover which is secured to the housing and through which the shaft extends.

4. A machine according to claim 1 or claim 2, in which the fluid pressure means comprises an annular piston slidable in an opening defined at least partly in a housing cover which is secured to the housing and through which the shaft extends.

5. A machine according to claim 1 or claim 2, in which the fluid pressure means comprises an annular duct defined between the outer race of the second bearing and a housing cover which is secured to the housing and through which the shaft extends.

6. A machine having a bearing arrangement for a shaft substantially as described herein with reference to Figs. 1 and 2, or Figs. 3 and 4, or Figs. 5 and of the accompanying drawings.