PUMP WITH IMPROVED SUPPORT ARRANGEMENT FOR THE CONTROL OF THE AXIAL POSITION BACKGROUND OF THE INVENTION This invention relates in general to a support arrangement in a pump and more particularly relates to a pump shaft mounting assembly, which limits the unwanted axial movement caused by loads in the drive line. Rotary vane pumps can be used in many fluid transfer applications and are especially applicable in the transfer of fluids that must be stored and transferred in closed tanks and piping systems to their vapor pressure or above their respective pressures. steam, to be contained in liquid state, such as. propane, carbon dioxide and ammonia. By nature of their internal geometry, rotary vane pumps require main bearings or bearings designed for the radial shaft loads produced by the hydraulic pumping forces and the torque produced by an appropriately installed drive and primary motor. In applications where conventional drive systems can not be used effectively, such as a tank truck, provision must be made in the pump drive shaft to protect the pump mechanism from the unpredictable axial forces of line couplings. Common rigid drives of U-joint drives and axial forces produced by some flexible coupling devices. Accordingly, there is a need for an improved support or bearing arrangement in a rotary fluid transfer vane pump which handles axial thrust loads from the drive lines of the prime mover or instigator. BRIEF DESCRIPTION OF THE INVENTION In order to improve the capacity of the known pump to accept all the possible radial and axial forces produced by the primary motors (ie, power start actuators), the present invention provides a pump with a Improved support or bearing arrangement to locate and protect the pumping components. The pump has a housing within which a shaft is rotationally arranged. The shaft has opposite ends, and the present invention provides embodiments wherein the shaft is configured to have either one or two drive or drive ends. In either modality, the tree is held rotationally at each opposite end; the pumping components, such as the rotor and the vanes, are secured between the ends of the shaft. The improved bearing or support arrangement includes first and second support mounts at each of the opposite ends and which rotationally and axially support the pumping components. Each bearing or bearing assembly has a main radial bearing with an internal race ring secured to the shaft. A mounting ring slides on the shaft and adjacently comes into contact with the inner race of the main radial bearing. A thrust bearing assembly has an internal and external thrust washer that contains the axial bearing which is brought into contact against the mounting ring and the bearing caps. The thrust bearing receives the axial thrust loads and limits the axial movement of the pumping components. The first and second bearing caps are secured to the housing and hold respective bearing arrangements. The bearing caps are secured at opposite ends of the housing heads to the first and second thrust bearings respectively. Each bearing cap retains the respective thrust bearing against its mounting ring. According to one aspect of the invention, first and second baffles or wedges can be provided, each baffle or wedge is disposed between the respective bearing caps and pump heads. Each baffle or wedge has a selected thickness to generally center the pumping components within the housing. A related advantage of the pump is that the axial position of the internal pumping components can be tightly adjusted to prevent undesired wear. In a modality, first and second external tree seals are provided. The first and second external shaft seals are disposed in the first and second bearing caps, respectively. Each seal of the outer tree is seated around the tree. In one embodiment, the first and second seal assemblies are sealingly arranged around the shaft, between the internal pumping components and the respective bearing assemblies. In one embodiment, a lubrication cavity extends between the thrust bearing assembly and the main radial bearing. During the use of the pump, axial thrusts can be introduced to the pump via flexible couplings or by rigid mounting of the PTO coupling to the pump shaft. The axial thrust bearing assembly of the present invention is designed to transfer the axial thrust force through the shaft and the inner race of the opposite main radial bearing and the bearing ring of the axial bearing via contact with the outer circumference of the bearing ring of the inner bearing. The thrust bearing assembly is mounted transversely to the longitudinal shaft to allow continuous rotation of the shaft. The thrust bearing assembly allows the internal thrust washer to rotate with the pump shaft and the thrust bearing mounting ring while the external thrust washer remains static with the bearing cover. The thrust bearings roll at half the speed of the pump shaft. The thrust bearing assembly limits the internal axial movement generated by the axial thrusts, while maintaining the necessary separations of the internal pumping component. Unwanted contact wear of the internal pumping component is avoided. Accordingly, an advantage of the present invention is to provide an improved bearing arrangement. More specifically, an advantage of the present invention is to provide an improved bearing arrangement for a rotary vane pump, which limits the axial movement of the internal components, generated by the thrust forces. A relative advantage is to reduce the friction between the wear surfaces inside the pump. Another advantage of the present invention is to provide an improved bearing arrangement which absorbs axial thrust forces from each axial direction along the shaft of a pump, the bearing assembly is applicable to a pump having either a configuration of Single-ended or double-ended drive shaft. A further advantage of the present invention is to provide axial adjustability of the bearing or bearing arrangements in order to center the components of the pump to reduce wear. Additional features and advantages of the present invention are described in, and will become apparent from, the detailed description of the presently preferred embodiments and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a sectional view of one embodiment of a rotary vane pump according to the present invention, wherein the pump has a shaft with two driving ends, the section is generally taken along line II of Figure 2. Figure 2 is a sectional view of the pump of Figure 1, the section is taken generally along line II-II of Figure 1. Figure 3 is a sectional view fragmentary also generally taken along line II of Figure 2, which shows enlarged illustrations of the bearing arrangements of the pump of Figure 1.
Figure 4 is a sectional view of another pump according to the present invention, wherein the pump has a shaft with a single driving end. DETAILED DESCRIPTION OF CURRENTLY PREFERRED MODALITIES The present invention provides an improved bearing arrangement, which is suitable for a pump shaft configured with either two drive ends, as shown in FIGS. 2 and 3, or only one drive end as defined in FIGS. is shown in Figure 4. Referring to Figures 1 and 2, a vane pump 10 is provided, which generally has a housing including a head 12, 12 'at each end. The pump 10 also includes a shaft 14 and pump components, such as a rotor 16, cam 20, impellers 28 and paddles 26. In the embodiment of FIGS. 1-3, the pump 10 is generally symmetric, has opposite sides. which are images in the mirror with each other. In addition, in this embodiment, the shaft 14 has double drive ends. The numbers of parts indicated with a bonus (') herein refer to parts of the right side of Figures 1 and 3 that have a symmetric counterpart to the left of these figures. The shaft 14 and the rotor 16 are rotatable within the cam 20. The head 12 is preferably manufactured from multiple components including the first and second sides 13, 13 'and bolted to a central housing 15. These components are bolted together. In the double end driving mode of Figures 2 and 3, the shaft 14 has a first shaft end 18 and a second shaft end 18 ', each extending from the head 12 for connection to a drive system (not shown), such as a power take-off system of a motor vehicle engine. The rotor 16 is secured to the shaft 14 for rotation therewith. As illustrated in Figure 2, a generally annular cam 20 surrounds the rotor 16. The cam 20 has a variable wall thickness, which defines a pumping cavity 22 of increasing shape between the cam 20 and the rotor 16. cam 20 is secured in relation to the housing 15 of the pump by a cam key 23. The pumping cavity 22 is further defined by a pair of side plates 24 either on one side or the other of the rotor 16 (Figure 1). A plurality of sliding vanes or blades 26 are disposed radially in the rotor 16 at regularly spaced angles. The opposing pairs of vanes 26 are joined by a solid rod-like vane driver 28. Each vane driver 28 is diametrically slidably disposed through the rotor 16 and the shaft 14. Each vane driver 28 holds the associated vanes 26 such that an outer edge of each vane 26 is held against the cam 20 in all directions. one revolution of the rotor 16. Thus, as the rotor 16 rotates, the fluid is transported between the blades 26 from an inlet hole (not shown) at one end of the pump cavity 22 to an outlet orifice (not shown). ) at the opposite end of the cavity, to result in a pumping of the fluid from an inlet 30 in the housing to an outlet 32. Various mechanisms can be used to move the vanes 26, such as by hydraulic fluid means or by mechanical means, such as an internal cam ring (not shown). Optionally, the pump 10 may include a relief valve 34 to prevent damage within the pump 10 due to an excessive pressure differential. Such pressure differential could result from a flow path blocked inadvertently. If this happens, the relief valve 34 is opened, to recirculate the fluid from the outlet 32 to the inlet 30, to prevent excessive pressure or vacuum buildup. The valve 34 includes a plunger 33 which is predisposed by a spring 35 in a normally closed position. A cover 37 of the valve is secured to the housing, which can be removed for disassembly or maintenance of the valve 34. Referring to Figure 1, the shaft extends through the housing 12, 12 'in a preferably symmetrical manner, the first drive end 18 and the second opposite drive end 18' project outwards. The rotor 16 is secured to the shaft 14 between the double drive ends 18, 18 '. On the respective sides of the rotor 16, the pumping chamber is sealed by first and second rotational internal seal assemblies 36 and 36 ', respectively, positioned on the heads 12 and 12'. Also, outwardly of each internal seal, each first and second shaft end 18 and 18 'travel rotationally in a respective bearing arrangement 38, 38'. As shown in both Figures 1 and 3, the first and second bearing arrangements 38, 38 'each include a radial main bearing 40, 40' including an inner race 42, 42 'and an outer race 44 , 44 '. The rollers 43, 43 'of the bearing travel between the running rings 42, 42' and 44, 44 '. Each inner race 42, 42 'is mounted for its rotational movement with the respective end 18, 18' of the shaft. For example, the inner race 42, 42 'can be snapped or slid over the end 18, 18' of the shaft or, in one embodiment, the race 42, 42 'can be integral to the shaft 18, 18. ' Each outer rolling ring 44, 44 'closely fits each head 12, 12', and is retained therein by a respective retaining ring 46, 46 '. Each retaining ring 46, 46 'resides in an annular groove 48, 48' in each head 13 and 13 'and is pressed against one side of the outer race 44', 44 'with the face facing away from the rotor 16. Adjacent to each radial main bearing 40, 40 'and to one side thereof facing away from the rotor 16, a mounting ring 50, 50' of the annular thrust bearing slides on the respective end of the shaft 18, 18 ' in such a manner that it comes into contact against the inner raceways 42, 42 'of the main bearing 40, 40'. Each mounting ring 50, 50 'is formed to define a thrust face 52, 52' which is perpendicular to the shaft axis, facing away from the rotor 16. Still with reference to FIGS. 1 and 3, each arrangement 38 38 'of bearing includes an annular thrust bearing assembly 54, 54' which has an inner race or thrust washer 56, 56 'an outer race or thrust washer 58, 58' and a thrust bearing push 60, 60 'arranged between them. The internal washer 56, 56 'comes into contact against the thrust face 52, 52' of the mounting ring 50, 50 '. The external washer 58, 58 'with the face away from the rotor 16. A cover 62, 62' of the thrust bearing is bolted to each end of the head 12, 12 'which comes into contact against the washer 58, 58' which it absorbs the external thrust of the respective respective bearing assembly 54, 54 *.
Each thrust bearing assembly 54, 54 'is thereby retained between its respective bearing cap 62, 62' and mounting ring 50, 50 '. A baffle or wedge 64, 64 'having a selected thickness is preferably installed between each bearing cover 62, 62' and the head 12, 12 'to retain the bearing arrangements 38, 38' at close separations of the internal pump . Thus, the rotor 16 and the vanes 26 can be axially centered at appropriate spacings in the pump 10 for optimum performance of the pump, even during operation under unwanted axial load. More particularly, the rotor 16 and the vanes 26 are prevented from moving axially within the cam 20, which could result in undesirable wear of the rotor 16 against one of the side plates 24. In one embodiment, they could provide multiple deflectors 64 or 64 'between the cover 62, 62' of the bearing and the housing 12. In this case, the combined thicknesses are selected to properly center the internal components. Each cap 62, 62 'of the bearing includes a seal 66,
66 'arranged around the shaft 14. In addition, each bearing cover 62, 62' is removable to allow access to the bearing arrangement 38, 38 '. Also, this configuration promotes easy assembly of the pump 10. The shaft 14 preferably includes sections of decreasing diameter outwardly from the rotor 16. Such a shape, the shaft allows the internal seal assembly 36, 36 ', main bearing 40 , 40 ', mounting ring 50, 50' and external seal 66, 66 'are consecutively removed or installed from each respective side. In addition, the decreasing diameter of the shaft in the portion over which the inner race 42, 42 'of the radial main bearing 40, 40' is secured. This forms a shoulder 68, 68 'on which the drive end 18, 18' transmits axial thrust forces from the shaft 14 outward to the inner race 42, 42 ', the axial thrust force is subsequently transmitted a and is restricted by the associated thrust bearing assembly 54, 54 '. As mentioned, due to the symmetric configuration, the pump 10 can be driven either from the drive end of the shaft 18, 18 'by supplying rotational energy to an operating end of the selected shaft 18, 18'. The radial loads are carried by the main bearings 40, 40 '. Any axial load transmitted by the main bearings 14 is carried by one of the thrust bearing assemblies 54, 54 '. Specifically, as illustrated in Figure 1, an external axial load A (transmitted from left to right) is transmitted through the shaft 14 to the shoulder 68 'of the second drive end 18' of the shaft, to the inner race 42 '. of the second radial main bearing 40 ', to the mounting ring 50 •, to the second thrust bearing assembly 54'. Conversely, an external axial load B (transmit from right to left) is transmitted through the shaft 14 to the shoulder 68 of the first drive end 18 of the shaft, to the inner race 42 of the first main bearing 40, to the mounting ring 50 , and to the first thrust bearing assembly 54. As shown in FIGS. 1 and 3, the first and second lubrication cavities 70, 70 'are provided, one respectively disposed adjacent to the first and second bearing assemblies 54, 54 '. Each lubrication cavity 70, 70 'has a nipple 72, 72' for grease, through which lubricant can be added to the cavity 70, 70 '. Each cavity 70, 70 'is exposed to the respective thrust bearing assembly 54, 54' and on the mounting ring 50, 50 'to the main bearing 40, 40' which provides lubricant to these components. Each lubrication cavity 70, 70 'also extends to the seal 66, 66' of the outer shaft for lubrication as well. The shaft seals 67 and 67 'are arranged around the shaft 18, 18' axially inward of the bearing arrangement 38, 38 '. Lubrication is contained by seals 66, 66 'and 67, 67' of the shaft.
The housing 15 of the pump also includes a flange 74 which serves as a mounting for installing the pump 10 for a particular application. Now returning to Figure 4, according to the present invention, a pump 110 having a single drive end can be provided. The pump 110 is substantially the same as the pump 10 described with reference to Figures 1-3, except that the pump 110 includes one end of the shorter shaft 118 'which is enclosed by a closed bearing cover 162'. The pump 110 is driven only at the opposite end 118 of the shaft, which extends through a bearing cover 162. In the pump of Figure 4, the ends of the shaft 118 and 118 'are held radially and axially rotationally by bearing arrangements 138, 138' and the internal components can be adjusted axially by deflectors 164, 164 'in the same manner as previously described. In another embodiment, not illustrated, each bearing cap has an annular threaded portion by which the bearing cap is threaded into the housing. This threaded coupling enters the bearing cover and the housing secures the housing cover and retains the bearing assembly in position. This mode provides a uniformly distributed force against the thrust bearing assembly, which eliminates any need to adjust torques of the bolts. Also, this mode allows easy adjustment of the internal spacings by rotating the respective end caps. An adjustment screw may be provided in the end cap rim of the bearing to maintain the desired position of the bearing cap. It should be understood that various changes and modifications to the currently preferred embodiments will be apparent to those skilled in the art. For example, the shaft could comprise either single-piece or multi-piece components, such as separate drive ends joined together or to the rotor. In addition, the bearing arrangement of the present invention could be used on a pump having a pump component other than a rotor, such as reciprocating piston pump, propeller pump, impeller, etc. Such changes and modifications can be made without deviating from the spirit and scope of the present invention and without diminishing its concomitant advantages. Accordingly, it is proposed that the appended claims cover such changes and modifications.