US 3781149 A
Description (OCR text may contain errors)
United States Patent [1 1 Weaver et al.
[4 1 Dec. 25, 1973 ROTARY FLUID-PRESSURE MACHINES Dowty Hydraulic Units Limited, Cheltenham, England Filed: July 12, 1971 BRl.-ll9l ll6 r.
Foreign Application Priority Data Aug. 1, 1970 Great Britain 37250/70 Assignee:
US. Cl. 418/131, 418/206 Int. Cl. F01c 19/08 Field of Search 418/206, 131, 132,
References Cited UNITED STATES PATENTS 3,490,382 Joyner 3,632,240 l/l972 Dworak 418/131 FOREIGN PATENTS OR APPLICATIONS 1,067,552 5/1967 Great Britain 418/131 Primary Examiner-Carlton R. Croyle Assistant ExaminerMichael Koczo, Jr. Attorney-Irvin S. Thompson and Robert J. Patch [5 7 ABSTRACT H A rotary fluid-pressure machine includes a casing,
toothed intermeshing rotors supported for rotation in the casing, and wear plate means having a first sideface-portion and a second side-face-portion. The one portion is substantially co-planar with the other and both portions are engageable with a side-face of a rotor. The second side-face-portion is of arcuate form, has better wear-resisting properties than said first sideface-portion and has an outer periphery at a radial distance from the rotational axis of the rotor which is substantially the same as the radius of the trace of the roots of the teeth of the rotor. A part of the first sideface-portion crosses the gap between the two ends of the second side-face portion.
1 Claim, 2 Drawing Figures ROTARY FLUID-PRESSURE MACHINES This invention relates to rotary fluid-pressure machines.
According to this invention a rotary fluid-pressure machine includes a casing, toothed or lobed intermeshing rotors supported for rotation in the casing, and wear plate means bodily movable into thrust-bearing engagement with a side face of a rotor, said wear plate means comprising two rotor-engaging parts, one part having better wear-resisting properties than the other and'having an outer periphery at a radial distance from g the rotational axis of the rotor which is substantially the same as the radius of the trace of the roots of the teeth or lobes of the rotor.
The said one part may be of annular form, or alternatively may be of part-annular form.
The said one part may be separate from said other part and be bodily axially-movable with respect thereto.
It may be arranged that the said radial distance is slightly greater than the radius of said trace.
Where said one part is of part-annular form it may be mounted in a correspondingly-shaped recess in said other part, the two extremities of said one part each bearing against the corresponding extremity of the recess. Resilient means may be provided between said one part and the base of its said recess.
The said resilient means may comprise a flexible element which forms a seal between the base of the recess and that face of said one part remote from the respective rotor. This element may be of elastomeric material.
Where the rotary fluid-pressure machine is a gear pump or a gear motor, said one part of part-annular vform may be positioned adjacent the high fluidpressure side of the machine so that it effectively seals over a relatively large arc of the high pressure side of the rotor side face substantially to prevent leakage of high pressure fluid to the low pressure side of the pump from occurring either directly between the engaging faces of the wear plate means and the rotor and/or indirectly along the shaft of the rotor.
The wear plate means may include a bush in the form of an insert fitted in a bore therein, which bush forms a journal bearing for a shaft of the rotor.
The wear plate means may be pressure-balanced by subjecting a zone of the face thereof remote from the rotor to fluid under high pressure and by subjecting another zone on that face to fluid under low pressure.
The said one part having better wear-resisting properties may be so shaped in cross-section as to have the ability to tilt with respect to the said other part to ac-' commodate slight tilting in operation of the rotor and its shaft with respect to said casing.
In a two-rotor gear pump or motor, the wear plate means may include separate abutting members of D- shaped cross-section, one pair of abutting members being provided on each side of the intermeshing rotors, or alternatively one pair thereof on only one side of the intermeshing rotors. Alternatively, instead of providing a pair or pairs of separate abutting D-shaped members, the members of a pair may be formed integrally, thereby constituting a spectacle-type wear plate, one such plate being provided on only one side of the rotors, or alternatively on both sides of the rotors.
One embodiment of the invention will now be particularly described by way of example with reference to the accompanying drawings, of which,
FIG. 1 is a cross-sectional side elevation of a tworotor gear pump, and,
FIG. 2 is a cross-section taken along the line ll-[I on FIG. ll.
Referring to the drawings, a rotary fluid-pressure machine in the form of a gear pump comprises a casing 11 having a centre portion 12 and two closure or end plates 13 and I4. The centre portion 12 is provided with overlapping bores 15 and 16 in which a pair of intermeshing gears 17 and 18 are mounted for rotation. The centre portion 12 is provided with an inlet port 19 and an outlet port 20 as shown in dotted detail in FIG. 2.
The casing portions are held together by four through bolts which are shown in cross-section at 21 in FIG. 2.
The gear 17 is the driver gear of the pump and has a splined drive shaft 22 which extends outwardly of the pump as shown in FIG. ll. This gear also has a stub shaft (not shown) extending on the opposite side thereof from the shaft 22.
The idler gear 18 has stub shafts 23 and 24 as shown in FIG. 1, with annular grooves 25 and 26. The stub shafts are supported in bushes 27 and 28 and similar bushes are provided for the stub shaft and the shaft 22 of the gear 17. Also, similar annular grooves are provided in the shafting of the gear 17.
The bushes 27 and 28 form journal bearing means and each is carried in a respective primary wear plate 29 of D-shaped cross-section. As shown in FIG. 2, the primary wear plates 29 abut on their flat faces as at 30. The wear plates 29 together with their bushes 27, 28, four of which are thus provided in the pump, are movable bodily axially towards the respective side face 31 or 32 of the respective gear 17, 19.
The primary wear plates 29 together with their bushes are pressure-balanced in conventional manner by subjecting one zone 33 on the face of each wear plate remote from the respective gear and outwardly of continuous sealing means 34 to pump delivery pressure, while a zone 35 on that face and within the confines of the sealing means 34 is subjected to liquid under low pressure. A continuous sealing means 36 defines the outer boundary of the zone 33.
An arcuate recess 37 is provided around the periphery of each primary wear plate 29 on the high pressure side of the pump, extending back from the outlet port 20 to the point 38 shown in FIG. 2.
The pump is also provided with low pressure lubrication means for the gear shafts, of the kind described in the specification of US. Pat. No. 3,490,382, the passages 39, recesses 40, grooves 41, grooves 25, 26 and slots 42 forming parts of these means.
The face 43 of each primary wear plate 29 adjacent its respective gear 17 or 18 is provided with an arcuate recess 44, having radiussed end portions, which extends from a position 45 to a position 46, approximately 210 displaced from the position 45 and adjacent the outlet port 20. Carried in this recess 44 is an arcuate elastomeric member 47 of C-shape and a secondary wear plate 48 of cast iron, also of C-shape. The plate 48 has radiussed end portions which engage the end portions of the recess. In cross-section the secondary wear plate 48 is thicker in the radial sense than in the axial sense to give it rigidity when subjected to high pressure hydraulic loading on its exterior peripheral edge 49 which holds it in sealing engagement at its end portions with the radiussed end portions of the recess 44.
Each secondary wear plate 48 is formed with a small recess 50, extending for its full arcuate length, whereby the bearing area of the plate upon the respective gear side face has its outer periphery at a radial distance from the rotational axis of the gear which is substantially the same as the radius of the trace T of the roots of the gear teeth, although in this embodiment there is a very slight overlap by that periphery beyond the trace T in the radial outward sense. Such overlap is of the order of 0.060 inches.
The gears 17 and 18 and their shafts are of steel, the bushes 27, 28 are of lead bronze, the primary wear plates 29 are of die-cast aluminium and the casing components l2, l3 and 14 are also of die-cast aluminium.
In operation of the gear pump, drive thereto is provided from a rotary power source through the shaft 22, and liquid supplied from a reservoir to the inlet port 19 is pumped by the meshing driver gear 17 and idler gear 18, the resultant high pressure liquid passing from the pump through the outlet port 20 to a point of usage.
In conventional manner the zone 33 on the face of each primary wear plate 29 is subjected to pump delivery pressure while the zone 35 thereof is subjected to the pressure at the inlet port 19. The primary wear plates 29 are thus held bodily in pressure-balanced manner in desired running thrust-bearing and sealing contact with the respective faces of their gears 17 or 18, while each secondary wear plate 48 is also urged bodily through the intermediary of the elastomeric member 47 into engagement with the respective gear side face at a zone substantially radially-inwardly of the teeth roots. This zone is where in pumps, and also motors, hitherto, and under contaminated oil conditions, the major amount of local wear has taken place, but since the secondary wear plate 48, forming one part of the wear plate means, is of cast iron having better wearresisting properties than the die-cast aluminium material of each primary wear plate 29 which forms the other part of the wear plate means, provision is made to counteract such local wear and thus significantly to prolong the life of the combined primary and secondary wear plate means.
This therefore enables the majority of the wear plate means to be of a low grade material adequate to accommodate the wear to be expected at the interface between the primary wear plate and the end faces of the gear teeth themselves. The lead bronze inserts 27 and 28 in turn afford the necessary wear resistance at the journals of the gears.
Each cast iron secondary wear plate 48 affords good sealing where it is really necessary over the arc of approximately 210. It will be understood that the outer peripheral edge 49 of each secondary wear plate is subjected to delivery pressure, but since the end portions of the plate are thereby held in sealing engagement with the corresponding end portions of the recess 44, high pressure liquid, within the sector defined on the high pressure side of the pump between the lines X and Y, is unable to pass to the low pressure sector which is on the low pressure side of the lines, or to pass the elastomeric sealing member 47 and along the corresponding gear shafts. It will be understood that from the practical stand-point the lines X and Y correspond to the boundaries defined by the gear teeth flanks in cooperation with the recesses 37 and the recesses 51 adjacent the outlet port 20.
Since, by virtue of the elastomeric member 47, each respective secondary wear plate 48 is resiliently mounted with respect to its primary wear plate 29, the plate 48 is able to tilt to accommodate residual tilting under pressure balance between each gear and its pri mary wear plate, the arcuate secondary wear plate being disposed in the appropriate position to accommodate the likely maximum amount of tilt, and the degree of freedom of movement of the secondary wear plate affording maximum tilt compensation.
Thus by the invention, in providing a secondary wear plate difficulties with only a simple single wear plate are overcome where that wear plate would move up as far as it could, but due to local face wear radiallyinwardly of the gear teeth roots it could not move up bodily into intimate contact at that inward zone due to the more prominent and less worn areas in the vicinity of the end faces of the teeth themselves. Hence, a gap was hitherto formed inwardly of the tooth root region giving a leakage path between the high pressure and low pressure sides of the gear pump with consequent loss in volumetric efficiency.
Although in the embodiment above described with reference to the drawings the primary wear plate is of die-cast aluminium and the secondary wear plate is of cast iron, in other embodiments of the invention other suitable materials are provided, the material of the former being of less wear resistance than the latter. Such other materials may be again ofa metallic nature or alternatively of a non-metallic nature.
-Again, although in the embodiment described with reference to the drawings the primary wear plates are of D-shaped cross-section having abutting flat faces, in alternative embodiments the primary wear plates on each side of a pair of intermeshing gears are integrally formed, thereby comprising wear plates of the spectacle type, or are alternatively formed in a common end plate.
Further, although in the embodiment described with reference to FIGS. 1 and 2 of the drawings, primary and secondary wear plate means are provided on each side of the intermeshing gears, in alternative embodiments of the invention, primary and secondary wear plate means may only be provided on one side of the intermeshing gears.
The invention is not limited to gear pumps, as in alternative embodiments it is with advantage applied to gear motors, or again to machines having rotors of other intermeshing form. Further, the invention is not limited to the gear pumps or gear motors being of the two-gear type, as in other embodiments pumps or motors in accordance with the invention may have more than two intermeshing gears. For example, they may be of the kind having a sun gear with a plurality of planet gears in mesh therewith.
Again, the invention is not limited to the precise cross-sectional shape of the secondary wear plate described with reference to FIGS. 1 and 2 of the drawings, as in other embodiments of the invention the secondary wear plates may be of other cross-section and again have other resilient means for bodily urging them into contact with the respective rotor side face.
In alternative embodiments, instead of each secondary wear plate being of C-shape, it may be of complete annular shape, or may extend over an arc of other than 210.
Further, secondary wear plates may be of yet other shapes, and in certain cases those for a pair of separate primary wear plates, or those for a pair of spectacletype primary wear plates, may be formed integrally as a single member of suitable compound shape.
Although in the embodiment above described with reference to the drawings, the resilient means upon which each secondary wear plate is mounted comprises a member of elastomeric material, in other embodiments resilient means of a mechanical form, for example, a wave spring, may alternatively be provided.
Again, instead of the secondary wear plate means being carried by the primary wear plate means with provision for bodily axial movement with respect thereto, in alternative embodiments of the invention the secondary wear plate means may not have such provision but instead be held fast in suitable manner, (for example, by bonding or otherwise), with respect to said primary wear plate means, its operative thrust face being of greater wear resistance than that of the primary wear plate means.
1. A rotary fluid-pressure machine including a casing, toothed intermeshing rotors having shafts by which they are supported for rotation in the casing, wear plate means surrounding a said shaft, said wear plate means having a first side-face-portion and a second side-faceportion, both portions being substantially coplanar and both portions being engageable with a side-face of the rotor, said first side-face-portion being formed in a first part of said wear plate means and said second sideface-portion being formed in a second part of said wear plate means, said second portion being bodily axially movable with respect to said first portion and comprising an arcuate member disposed in an arcuate recess in said wear plate means, said member and recess terminating in ends that are spaced apart by a gap, the two ends of said member each bearing against a corresponding end of said recess, said second side-faceportion having better wear-resisting properties than said first side-face-portion and having an outer periphery at a radial distance from the rotational axis of the rotor which is substantially the same as the radius of the trace of the roots of the teeth of the rotor, a part of said first side-face-portion crossing said gap between the ends of said member and recess, said part including means defining a slot which extends from a region on one side of said trace to a region on the other side of said trace, said slot communicating with the shaft surrounded by the wear plate means, and means for inducing a flow of liquid along said slot for lubrication of said shaft.