US3612733A

US3612733A - Porting for variable displacement vane pump with rotating end plates

Info

Publication number: US3612733A
Application number: US41148A
Authority: US
Inventors: John P Wilcox
Original assignee: JI Case Co
Current assignee: Case LLC
Priority date: 1970-05-25
Filing date: 1970-05-25
Publication date: 1971-10-12
Anticipated expiration: 1988-10-12

Abstract

A single-lobe sliding-vane rotary fluid pump in which end plates are affixed to the rotor. The cam ring is moved to adjust the displacement rate. This also varies the timing between port spaces, in the cam ring, and the vanes. To overcome the variations, auxiliary ports in the sealing spaces of the cam ring cooperate with grooves in the rotor end plates to provide additional fluid paths that control the timing.

Description

United States Patent John P. Wilcox Inventor Columbus, Ohio Appl. No. 41,148 Filed May 25, 1970 Patented Oct. 12, 1971 Assignee J. I. Case Company Racine, Wis.

PORTING FOR VARIABLE DISPLACEMENT VANE PUMP WITH ROTATING END PLATES 18 Claims, 5 Drawing Figs.

US. Cl 418/16, 418/31, 418/79, 418/189 Int. Cl F0lc 21/16, F04c 15/04, F04c 29/10 Field of Search 418/16, 24,

[56] References Cited UNITED STATES PATENTS 2,433,484 12/1947 Roth 418/26 2,985,109 5/1961 Ernst 418/26 FOREIGN PATENTS 462,620 1/1950 Canada 418/26 24,923 9/ 1934 Australia 418/26 Primary Examiner-Carlton R. Croyle Assistant ExaminerJohn J. Vrablik Att0meysGray, Mase and Dunson, John L. Gray, William J.

Mase, Philip M. Dunson, Robert B. Watkins, Kenneth R. Warburton and Kenneth E. Shaweker v PATENTEDUBT 1 2 197i SHEET 20F 2 llll III VIE! I2 L9 23 l'igwrnn I Fig. 2

JOHN P. COX

IN TOR ATTORNEYS PORTING FOR VARIABLE DISPLACEMENT VANE PUMP WITH ROTATING END PLATES BACKGROUND OF THE INVENTION This invention relates to variable-displacement vane pumps and meansof porting thereof. More specifically, it concerns the provision of auxiliary ports to provide a controlled variation of timing with cam ring displacement settings.

A vane pump having a continuously variable displacement rate over its range is one of the more desirable types for use in a hydrostatic transmission. A single-lobe sliding-vane pump with rotating end plates can be used. Such a pump may comprise a rotor containing radially disposed slidable vanes which rotate inside a substantially round cam ring whose inside diameter is slightly greater than the diameter of the rotor plus an amount equal to the full forward to full reverse stroke. The circumference of the cam ring consists of four sections which consecutively are an inlet or suction port, a pumping-lap space, an outlet or discharge port, and a sealing-lap space. The pumping action is brought about by displacing the cam ring relative to the rotor to adjust the clearance between the rotor and the pumping and sealing lap spaces.

When the cam ring of a variable displacement vane pump is moved to change the displacement, the length of the cam surface subtended by adjacent vanes varies with its distance from the center of the rotor. If ports in the cam ring are timed by the vanes in the usual manner, there can be only one displacement setting where the arc length of the cam ring between the inlet and outlet ports (the pumping lap space) is equal to the arc length between the tips of the vanes. Should the displacement be made greater, the arc length between successive vanes becomes greater than the pumping-lap space, thereby causing leakage. If the displacement is made smaller, the arc length between adjoining vanes becomes smaller than the pumping-lap space thereby causing slugging (compression of a trapped volume of fluid).

In this invention auxiliary ports are provided in a rotary vane pump to avoid leakage and slugging at any displacement setting of the cam ring. Each sealing space is made long enough to be at least equal to the arc length between successive vanes at the maximum displacement setting. Auxiliary ports are provided in the ends of the cam ring at the sealing spaces. Each auxiliary port consists of a passageway connecting the end of the cam ring with either the inlet or the outlet passage of the pump. Further, grooves are provided in the rotating end plates between adjacent vanes. These grooves communicate with the pumping chambers contained within adjacent vanes, the rotor, and the sealing spaces, and each groove is so positioned in its end plate that it registers with the auxiliary port at the proper time.

SUMMARY OF THE INVENTION A typical variable-displacement sliding-vane rotary fluid pump according to the present invention comprises a cylindrical rotor having vanes slidable in substantially radial directions therein, the tip of each vane maintaining substantial contact with the inner cylindrical surface of a cam surrounding the rotor as it traverses sealing spaces and port spaces in the cam alternately during rotation;

means for adjusting the relative positions of the rotor and a sealing space in the cam to vary the fluid displacement;

the arc length of each sealing space being at least substantially equal to the maximum arc length between successive vanes over the range of fluid displacement positions;

an end plate fixedly mounted at each end of the rotor to rotate therewith, extending over a portion of the cam at all fluid displacement positions and slidably fitting against the adjacent end of the cam to enclose the space within the cam;

at least one passage ineach sealing space of the cam communicating between a region on the portion of an end surface thereof over which the end plate extends and one port space in the cam; and A at least one groove in the end plate adjacent the passage, positioned between each pair of successive vanes, to communicate from the space otherwise enclosed by the outer surface of the rotor, the successive vanes, the inner surface of the cam, and the end plates, to the end of one passage at the end surface of the cam, and thus to communicate between the otherwise enclosed space and the port space at the other end of the passage, at predetermined positions during rotation where the successive vanes otherwise complete the enclosure of the space.

v In one preferred embodiment, a single elongated substantially radial groove is provided between each pair of successive vanes; and a pair of passages are provided in each sealing space, the ends of the passages at the end surface of the sealing space preferably being so positioned and spaced that the radial groove ends its communication with one passage at substantially the same position where it begins its communication with the other passage. The other end of each passage communicates with a different port space. The relative positions of the rotor and the sealing space are adjustable along the substantially radial direction of the groove at the position where the groove ends its communication with the one passage and begins its communication with the other.

Alternatively, a pair of elongate grooves may be provided between each pair of successive vanes and positioned substantially parallel to a radial locus between them; a pair of passages being provided in each sealing space, the ends of the passages at the end surface of the sealing space preferably being so positioned and spaced that one groove ends its communication with one passage at substantially the same position of the rotor where the other groove begins its communication with the other passage; and the other end of each said passage communicating with a different port space. The relative positions of the rotor and the sealing space are adjustable along the direction of the radial locus at the position of the rotor where one groove ends its communication with one passage and the other groove begins its communication with the other passage.

In another embodiment, a single elongate groove is provided between each pair of successive vanes and a single passage is provided in each sealing space; andthe end of the passage at the end surface of the sealing space is so positioned that the groove begins (ends) its communication with the passage at substantially the same position of the rotor where the trailing (leading) vane begins (ends) its contact with the sealing space. The other end of the passage communicates with the port space adjacent the exit (entrance) edge of the sealing space. Where the relative positions of the rotor and the sealing space are adjustable along the direction of the trailing (leading) vane at the position of the rotor where the groove begins (ends) its communication with the passage and the trailing (leading) vane begins (ends) its contact with the sealing space, the groove should be substantially parallel to the trailing (leading) vane. Where the relative positions of the rotor and the sealing space are adjustable along the direction of a radius to the central region of the sealing space, the leading (trailing) edge of the groove should be positioned and shaped to begin (end) its communication with the passage at substantially the same position of the rotor where the trailing (leading) vane begins (ends) its contact with the sealing space.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a transverse sectional view of a single-lobe variable-displacement vane pump incorporating an embodiment of this invention.

FIG. 2 is a sectional view in a plane through the axis of the pump of FIG. 1.

FIG. 3 is a sectional view as in FIG. 1 of a portion of a sealing space, the rotor, and the auxiliary porting arrangement, with the rotor in a different angular position.

FIGS. 4 and 5 are sectional views similar to FIG. 3 showing alternative porting arrangements.

DESCRIPTION OF PREFERRED EMBODIMENTS Referring to FIGS. 1 and 2, a pump includes a housing 11 with top and bottom plate 12 connected thereto by bolts 13 or the like. A rotor 14 is journaled into bearings 15 seated in the housing 11. THe rotor 14 is stepped down in diameter at the left end and protrudes out as a drive shaft 16. A shoulder 17 on the shaft is fitted with a pressure seal 18 to prevent leakage. The rotor 14 contains radially disposed slots 19 into which vanes 20 are slidably fitted. The vanes 20 are radially contained by the inside surface of a cam ring 21, and are laterally restrained by rotor end plates 22, which are attached to the large main portion of the rotor 14 by bolts 23 and extend radially outward to substantially cover the ends 24 of the cam ring 21.

The cam ring 21 is laterally and longitudinally restrained within the housing 11, but may be raised and lowered by means of an actuator 25 in order to vary the displacement. The interior surface of the cam ring 21 is subdivided into four regions consisting consecutively in a clockwise direction of an inlet port space 26, a pumping lap space 27, an outlet port space 28, and a sealing-lap space 29.

As the fluid to be pumped is drawn in from an opening to the inlet port space 26, it is captured between pairs of adjacent vanes 20 as the rotor 14 rotates. As the rotor 14 is further rotated, a quantity of fluid is captured in the pumping chamber 45 consisting of the volume bounded by the pumping-lap space 27, the rotor surface 33, the front exposed surface 34 of the trailing vane 20, the back exposed side 35 of the leading vane 20, and the end plates 22 at each end (FIG. 3). In a perfectly timed pump, the time when the tip 38 of the leading vane 20 clears the exit edge 37 of the pumping-lap space 27 and the time when the tip 36 of the trailing vane 20 seals the entrance edge 32 of the pumping-lap space 27 are nearly the same and have a desired relationship to one another. Some of the fluid is driven out through a discharge opening 39 by the rotational forces of the rotor 14. The remainder is carried back to the inlet opening 30 as the vanes cross the sealing-lap space 29.

At a given rotational speed, the volume of fluid pumped is proportional to the difference in volume of the pumping chambers at the pumping-lap space 27 and the sealing-lap space 29. Their respective volumes are determined by the displacement between the axes of the rotor 14 and the cam ring 21, which is slidably adjusted by means of the actuator 25, connected at 31 to the cam ring 21.

"The inlet and

outlet port spaces

26, 28 are herein sometimes called merely port spaces, while the pumping-lap space 27 and the sealing-lap space 29 are herein sometimes referred to generically as sealing spaces. This is done partly for convenience, as in the claims, and partly because the cam ring 21 could be moved down to a region where its axis would be lower than the axis of the rotor 14, causing the sealing space 29 to act as a pumping-lap space, the sealing space 27 to act as merely a return flow sealing-lap space, the port space 28 to act as an inlet, and the port space 26 to act as an outlet; the fluid being pumped from right to left; with the rotor 14 still rotating clockwise.

When the cam ring 21 is moved to change the displacement, the length of the cam surface subtended by the

tips

36 and 38 of adjacent vanes 20 varies with the distance from the center of the rotor 14. If communication with the

ports

30, 39 in the cam ring 21 is determined by the vanes 20 in the usual manner, the desired relationship between the time at which the tip 36 of the trailing vane 20 seals the entrance edge 32 of the pumping-lap space 27 and the time at which the tip 38 of the leading vane 20 clears the exit edge 37 of the pumping-lap space 27 is obtained at only one displacement setting. A smaller or larger displacement setting will cause the arc length between

vane tips

36 and 38 to be shorter or longer than at the design condition, and these conditions will cause slugging and leakage, respectively, of the fluid in the pumping chamber. The same problems are encountered on the sealing-lap space 29.

To prevent such slugging. or leaking, the end of the cam ring 21 is provided with a porthole 41 connected to the inlet port space 28 by a passageway 42, and a porthole 41' connected to the outlet port space 28 by a passageway 42. The spacing between the two

portholes

41 and 41 is substantially equal to the width of a radially elongate groove 43 provided in the end plate 22.

The inner end of the groove 43 extends at least to the periphery ofv the rotor 14, and the outer end extends to the

portholes

41, 41 when the cam ring is positioned for its maximum pumping volume displacement, as in FIG. 1. The longitudinal axis of the groove 43 is substantially radial and approximately midway between the vanes 20 and thus, in FIG. 3, I

lies in approximately the same direction as the travel of the cam ring 21 (designated by the arrow 44) when changes are made in the displacement setting, so that the timing of register by the groove 43 over the ports 41, 41' is controlled for all displacement settings. The relative timing of the ports 41, 41' depends upon the distance between them and the width of the groove 43, and is independent of displacement setting. The rotor position at which the groove 43 ceases to communicate with the port 41 and begins to communicate with the port 41' depends upon the exact location and direction of the groove 43, and can be made to vary with displacement setting if the designer so desires.

As the rotor 14 is rotatably driven, the groove 43 registers over, and is in communication with, the porthole 41 connected to the inlet port 30 before, during, and after the time when the trailing vane tip 36 passes the entrance edge 32 of the pumping-lap space 27. The groove 43 then passes from the input porthole 41 to the output porthole 41 thereby connecting the pumping chamber 45 with the outlet port 39. The groove 43 remains in communication with the outlet porthole 41' before, during, and after the time when the tip 38 of the leading vane 20 passes the exit edge 37 of the pumping-lap space 27. The action at the sealing-lap space 29 is similar.

By the accurate placement of the portholes 41, 41' in the cam ring 21, and of the groove 43 in the end plates 22, the timing function is made independent of the vanes 20. The

port spaces

26,28 may therefore be made shorter than normal, and need not be as accurately placed as when the timing function is controlled by the vanes. This greatly simplifies the casting and finishing operations of the cam ring 21, thereby reducing the production costs.

In a manually controlled hydrostatic transmission, it is desirable from the standpoint of safety thatforces generated within the pump should tend to return the cam ring to the zero displacement condition. This result may be insured by angling the grooves 43 such that their radially outward ends lead their radially inward ends. Pumped pressure will then act, on the average, over a greater portion of the sealing-lap space 29 than of the pumping-lap space 27.

The groove 43 can be made wider than it appears in FIG. 3, so that the portholes 41, 41' can be spaced farther apart, and the passageways 42, 42' need not be as long. THe middle portion of a wide groove is unnecessary and can be omitted; so the wide groove can be replaced by two narrow grooves 43, 43', comprising what would be the left and right extremities of a wide groove, as in FIG. 4. The arrangement and operation are the same as in FIG. 3; the trailing groove 43 communicating at the proper time with the input porthole 41 and the leading groove 43' communicating at the proper time with the output porthole 41.

Another variation, shown in FIG. 5, is similar to the embodiment in FIG. 3, but with the input porthole 41 and its passageway 42 omitted and with the groove 43 tipped to the left. The groove 43 is substantially parallel to the trailing vane 20 so that the time when it begins to communicate with the porthole 41' and the time when the tip 36 of the trailing vane 20 reaches the entrance edge 32 of the pumping-lap space 27 are nearly the same and have a desired relationship to one another. Thus the relative timing is correct for any displacement setting. However, the rotor position at which the pumping chamber 45 ceases to communicate with the inlet port 30 and begins to communicate with the outlet port 39 varies with the displacement setting, so that the undesirable forces may be transmitted to the displacement control. These forces may be modified by varying the direction-of cam ring motion when the displacement is varied. For instance, the cam ring may be moved in the direction shown by the arrow 44, instead of that shown by the arrow 44, without substantially affecting the correct action of the ports as shown. The action of the sealing-lap space is similar.

The arrangement of FIG. 5 would also provide correct timing in a similar way if the rotor 14 were rotated counterclockwise. Then communication between the porthole 41' and the groove 43 would end substantially as the tip 36 of the leading vane reached the exit edge 32 of the pumping-lap space 20. (The operation would be similar with the rotor 14 rotating clockwise and with the positions of the groove 43, the porthole 41', and the passageway 42 turned over left-to-right to the mirror image of the positions shown in FIG. 5.)

While the forms of the invention herein disclosed constitute presently preferred embodiments, many others are possible. And of course the invention can be used in two-lobe and multiple-lobe pumps as well as in single-lobe pumps. It is not intended herein to mention all of the possible equivalent forms or ramifications of the invention. It is to be understood that the terms used herein are merely descriptive rather than limiting, and that the various changes may be made without departing from the spirit or scope of the invention.

l claim: 1. A variable-displacement sliding-vane rotary fluid pump comprising a cylindrical rotor having vanes slidable in substantially radial directions therein, the tip of each vane maintaining substantial contact with the inner cylindrical surface of a cam surrounding the rotor as it traverses sealing spaces and port spaces in the cam alternately during rotation; means for adjusting the relative positions of the rotor and a sealing space in the cam to vary the fluid displacement;

at least one passage in each sealing space of the cam communicating between a region on the portion of an end surface thereof over which said end plate extends and one said port space in the cam; and at least one groove in the end plate adjacent said passage, positioned between each pair of successive vanes, to communicate from the space otherwise enclosed by the outer surface of the rotor, said successive vanes, the inner surface of the cam, and the end plates, to the end of one said passage at the end surface of the cam, and thus to communicate between said otherwise enclosed space and the port space at the other end of said passage, at predetermined positions during rotation where said successive vanes otherwise complete the enclosure of said space.

2. A pump as in claim 1, wherein a single elongate substantially radial groove is provided between each pair of successive vanes.

3. A pump as in claim 2, wherein a pair of passages are provided in each sealing space, the ends of said passages at the end surface of the sealing space being so positioned and spaced that the radial groove ends its communication with one said passage at substantially the same position where it begins its communication with the other said passage.

4. A pump as in claim 3, wherein the other end of each said passage communicates with a different port space.

5. A pump as in claim 3, wherein the relative positions of the rotor and thesealing space are adjustable along the substantrally radial direction 0 the groove at said position where the groove ends its communication with one said passage and begins its communication with the other.

6. A pump as in claim I, wherein a pair of elongate grooves are provided between each pair of successive vanes and positioned substantially parallel to a radial locus between them.

7. A pump as in claim 6, wherein a pair of passages are provided in each sealing space, the ends of said passages at the end surface of the sealing space being so positioned and spaced that one said groove ends its communication with one said passage at substantially the same position of the rotor where the other said groove begins its communication with the other said passage.

8. A pump as in claim 7, wherein the other end of each said passage communicates with a different port space.

9. A pump as in claim 7, wherein the relative positions of the rotor and the sealing space are adjustable along the direction of said radial locus at said position of the rotor where one said groove ends its communication with one said passage and the other said groove begins its communication with the other said passage.

10. A pump as in claim 1, wherein a single elongate groove is provided between each pair of successive vanes and a single passage is provided in each sealing space.

11. A pump as in claim 10, wherein the end of said passage at the end surface of the sealing space is so positioned that said groove begins its communication with said passage at substantially the same position of the rotor where the trailing .vane begins its contact with the sealing space.

12. A pump as in claim 11, wherein the relative positions of the rotor and the sealing space are adjustable along the direction of said trailing vane at said position of the rotor where said groove begins its communication with said passage and said trailing vane begins its contact with the sealing space, and said groove is substantially parallel to said trailing vane.

13. A pump as in claim 10, wherein the relative positions of the rotor and the sealing space are adjustable along the direction of a radius to the central region of the sealing space, and the leading edge of the groove is positioned and shaped to begin its communication with said passage at substantially the same position of the rotor where the trailing vane begins its contact with the sealing space.

14. A pump as in claim 11, wherein the other end of said passage communicates with the port space adjacent the exit edge of the sealing space.

15. A pump as in claim 10, wherein the end of said passage at the end surface of the sealing space is so positioned that said groove ends its communication with said passage at substantially the same position of the rotor where the leading vane ends its contact with the sealing space.

16. A pump as in claim 15, wherein the relative positions of the rotor and the sealing space are adjustable along the direction of said leading vane at said position of the rotor where said groove ends its communication with said passage and said leading vane ends its contact with the sealing space, and said groove is substantially parallel to said leading vane.

17. A pump as in claim 10, wherein the relative positions of the rotor and the sealing space are adjustable along the direction of a radius to the central region of the sealing space, and the trailing edge of the groove is positioned and shaped to end its communication with said passage at substantially the same position of the rotor where the leading vane ends its con tact with the sealing space.

18. A pump as in claim 15, wherein the other end of said passage communicates with the port space adjacent the entrance edge of the sealing space.

Claims

1. A variable-displacement sliding-vane rotary fluid pump comprising a cylindrical rotor having vanes slidable in substantially radial directions therein, the tip of each vane maintaining substantial contact with the inner cylindrical surface of a cam surrounding the rotor as it traverses sealing spaces and port spaces in the cam alternately during rotation; means for adjusting the relative positions of the rotor and a sealing space in the cam to vary the fluid displacement; the arc length of each sealing space being at least substantially equal to the maximum arc length between successive vanes over the range of fluid displacement posiTions; an end plate fixedly mounted at each end of the rotor to rotate therewith, extending over a portion of the cam at all fluid displacement positions and slidably fitting against the adjacent end of the cam to enclose the space within the cam; at least one passage in each sealing space of the cam communicating between a region on the portion of an end surface thereof over which said end plate extends and one said port space in the cam; and at least one groove in the end plate adjacent said passage, positioned between each pair of successive vanes, to communicate from the space otherwise enclosed by the outer surface of the rotor, said successive vanes, the inner surface of the cam, and the end plates, to the end of one said passage at the end surface of the cam, and thus to communicate between said otherwise enclosed space and the port space at the other end of said passage, at predetermined positions during rotation where said successive vanes otherwise complete the enclosure of said space.

5. A pump as in claim 3, wherein the relative positions of the rotor and the sealing space are adjustable along the substantially radial direction of the groove at said position where the groove ends its communication with one said passage and begins its communication with the other.

6. A pump as in claim 1, wherein a pair of elongate grooves are provided between each pair of successive vanes and positioned substantially parallel to a radial locus between them.

11. A pump as in claim 10, wherein the end of said passage at the end surface of the sealing space is so positioned that said groove begins its communication with said passage at substantially the same position of the rotor where the trailing vane begins its contact with the sealing space.

17. A pump as in claim 10, wherein the relative positions of the rotor and the sealing space are adjustable along the direction of a radius to the central region of the sealing space, and the trailing edge of the groove is positioned and shaped to end its communication with said passage at substantially the same position of the rotor where the leading vane ends its contact with the sealing space.