ROTARY PUMP WITH DISCHARGE CONTROL

Abstract

A positive displacement rotary fluid pump assembly includes a pump housing and a rotor supported within the housing for rotation about an axis offset with respect to a housing axis and including a plurality of chambers of increasing volume on an low pressure side of the pump and of decreasing volume on a high pressure side of the pump. A fluid inlet communicates with the plurality of the chambers of increasing volume for admitting fluid into the pump under a first low pressure, and a fluid outlet communicates with a plurality of the chambers of decreasing volume for selectively expelling fluid from the pump under a second higher pressure. At least one fluid control valve is operative to selectively close one or more of the chambers of decreasing volume from communication with the fluid outlet when the fluid pressure in such chambers is below the predetermined value and to open one or more other chambers of decreasing volume when the fluid pressure in such chambers is at or above the predetermined value.

Claims

1. A positive displacement rotary fluid pump assembly, comprising: a pump housing having an inner wall encircling a space disposed about a first housing axis; a rotor supported within the space of the housing for rotation about a second rotor axis offset with respect to the first housing axis and having radially spaced peripheral portions engaging the inner wall to define a plurality of chambers of increasing volume on a low pressure side of the pump and of decreasing volume on a high pressure side of the pump; a fluid inlet in communication with a plurality of the chambers of increasing volume for admitting fluid into the pump under a first low pressure; a fluid outlet in communication with a plurality of the chambers of decreasing volume for expelling fluid from the pump under a second higher pressure, the plurality of chambers of decreasing volume chambers including leading-most chambers and trailing-most chambers in relation to the direction of rotation of the rotor; and a least one fluid control valve operative to close when exposed to fluid pressure below a predetermined value and to open when exposed to a fluid pressure at or above the predetermined value; the fluid control valve communicating between the fluid outlet and at least some of the plurality of chambers of decreasing volume and operative to selectively close one or more of the chambers of decreasing volume from communication with the fluid outlet when the fluid pressure in such chambers is below the predetermined value and to open one or more other chambers of decreasing volume when the fluid pressure in such chambers is at or above the predetermined value.

2. The assembly of claim 1, wherein the fluid control valve operates to seal trailing ones of the chambers of decreasing volume from relatively higher fluid pressure in leading ones of the chambers of decreasing volume.

3. The assembly of claim 1, wherein the pump is a vane pump and includes a plurality of moveable vanes supported by the rotor and wherein the housing includes end plates covering opposite ends of the housing space in which the rotor is contained.

4. The assembly of claim 3, including a port plate adjacent at least one of the end plates having a plurality of circumferentially spaced outlet ports in an inner face thereof and a reed valve overlying the ports on a backside thereof and operative in response to exposure to fluid under pressure to open one or more of the ports when the fluid pressure in such ports is at or exceeds the predetermined fluid pressure and to close one or more of the ports when the fluid pressure in such ports is below the predetermined fluid pressure.

5. The assembly of claim 4, wherein the port plate further includes a slot-shaped inlet port radially opposite the plurality of outlet ports, and wherein the end plates includes an fluid inlet fitting in flow communication with the inlet port of the reed plate and an outlet fitting in flow communication with the outlet ports.

6. The assembly of claim 3, wherein the fluid control valve includes a plurality of exhaust valves carried by the rotor, wherein there is an exhaust valve in each of the plurality of chambers.

7. The assembly of claim 6 wherein each exhaust valve includes a valve slot in the rotor that is open to the respective chamber at a peripheral surface of the rotor and is further open to at least one end of the rotor and including a float valve captured within the valve slot that is moveable between closed position in which the float valve is seated edges of the valve slot to close the valve slot from flow communication with the chamber and an open position in which the float valve is unseated from the slot edges of the valve slot to expel fluid from the respective chamber into the valve slot.

8. The assembly of claim 7, wherein the housing includes an inner sleeve freely rotatable relative to the housing and defining the inner surface of the housing engagable with the vanes.

9. The assembly of claim 8, wherein the vanes comprise swing vanes.

10. The assembly of claim 9, wherein the swing vanes overly the exhaust valve when swung against the rotor.

11. The assembly of claim 10 wherein the swing vanes are received in vane slots of the rotor on opposite sides of each valve slot.

Description

THE DRAWINGS

[0011] These and other features and advantages of embodiments of the invention will become better understood when considered in connection with the following representative drawings and detailed description of preferred embodiments, in which:

[0012] FIG. 1 is an exploded fragmentary perspective view of a positive displacement vane pump according to an embodiment of the invention;

[0013] FIG. 2 is a fragmentary cross-sectional view of the vane pump of FIG. 1;

[0014] FIG. 3 is an exploded fragmentary perspective view of a positive displacement Gerotor pump according to another embodiment of the invention;

[0015] FIG. 4 is an exploded fragmentary cross-sectional view an a positive displacement vane pump according to another embodiment of the invention; and

[0016] FIGS. 4a-4c are enlarged fragmentary perspective views of the pump of FIG. 4.

DETAILED DESCRIPTION

[0017] FIG. 1 illustrates a positive displacement rotary pump 10 constructed according to a first exemplary embodiment. The pump 10 of this embodiment is a sliding vane pump and includes a rotor 12 having a plurality of radial slots 14 in which a corresponding plurality of vanes 16 are supported. The pump 10 includes a housing 18 having an inner wall 20 that has an associated inner wall axis. The housing 18 is closed at its opposite axial ends. As illustrated, the housing 18 may be closed at back end by a first end plate 22. The opposite front end of the housing 18 may be closed by a second end plate 24 and an intervening valve plate 26.

[0018] The rotor 12 is mounted on a shaft 28 that extends through an opening 30 in the valve plate 26 and which is supported for driven rotation about a rotor axis by external means, such as a motor or engine. The shaft 28 is suitably supported by at least one and preferably both end plates with bearing(s) 32. The rotor 12 may extend through one of the end plates 24 for engagement by the driving mechanism. The rotor 12 and vanes 16 are disposed within the space defined by the inner wall 20 and end plates 22, 24 and intervening valve plate 26. The axis of the rotor is offset eccentrically relative to the inner wall axis. Both the outer surface of the rotor 12 and the inner wall 20 of the housing 18 are preferably cylindrical and with that of the rotor 12 being smaller in diameter and axially offset but with their respective surfaces arranged very close together at a close point 34 of the pump 10. The geometries and offset placement define a crescent-shaped space 36 between the rotor 12 and inner wall 20 that is near zero in clearance at the close point 34 and widest opposite the close point, as illustrated also in FIG. 2.

[0019] The pump 10 includes a fluid inlet 38 that communicates with a part-crescent-shaped inlet port 40 of the valve plate 26. The pump further includes a fluid outlet 42 that communicates with a fluid outlet port 44 of the valve plate 26. The direction of rotation of the shaft 28 in the illustrated pump 10 of FIG. 1 is counterclockwise. With rotation of the rotor 12, the vanes 16 are caused to slide outward in their slots 14 and engage and keep contact with the inner wall 20 during operation of the pump 10. As the vanes sweep by the elongated inlet port 40, a suction is created which draws fluid (such as air) into the pump 10. As the vanes move past the inlet port 40, a fixed amount of air is trapped between the adjacent pair of vanes 16 that have just swept by, the plates 22,24, 26, the rotor 12 and inner wall 20. As the rotor 12 continues to rotate, the entrapped fluid is transported by the moving chamber from the inlet or suction side of the pump 10 to the outlet or discharge side of the pump. One the discharge side, the crescent-shaped portion of the space 36 is progressively diminishing in size as rotation moves toward the close point. The trapped fluid is pressurized as the chamber 46 progressively decreases in volume as it moves toward the close point 34. Successive one of the vanes passing by the inlet port 40 entrap subsequent volumes of air in trailing chambers 48. It will be appreciated that the leading-most chamber 46 at or near the close point 34 is smallest in volume and its fluid is under the highest pressure, whereas the one or more trailing chambers 48 have trapped fluid that is under progressively less fluid pressure.

[0020] The chambers 46, 48 on the discharge side of the pump 10 are in communication with the discharge port 44, 42. The discharge port 42 is fitted with a control valve 50 that allows pressured fluid to escape from the chambers 46, 48 into the outlet 42, but not to return. The discharge port 44 is preferably segmented such that a plurality discrete openings 52 are a provided that are open to the discharge side of the space 36, but which are walled off from one another by intervening wall segments 54. The valve 50 includes a reed 54 that is secured to an outer surface of the valve plate 26 and which overlies the plurality of openings 52. The reed may comprise a thin piece of metal. The reed is anchored at one end, preferably adjacent the leading end of the series of openings 52 of the discharge port 44. The inlet port 40 is not fitted with a valve.

[0021] In operation, high pressure fluid from the leading chamber 46 is expelled into the outlet 42 through corresponding ones of the openings 52 that align with the rotational position of leading chamber 46. The reed valve operates as a one-way or unidirectional valve and allows the high pressure fluid to push the distal portion of the reed 54 away from sealing contact with the valve plate 26 in the region covering the corresponding openings 52 associated with the leading chamber 46. Once expelled, the high pressure fluid from the leading chamber 46 cannot enter the one or more trailing chambers due to the presence of the one-way valve 50. Specifically, the pressure on the back side of the reed valve caused by the high pressure fluid expelled from the leading chamber keeps the reed tight and sealed against the valve plate 26 in the region of the openings 52 associated with the position of the trailing chambers 48. Only when the fluid pressure in a trailing chamber(s) 48 exceeds the pressure exerted on the backside of the reed 54 in that area does the reed 54 deflect and allow the fluid to pass, and even then it is one-way so there is no opportunity for higher pressure fluid from the outlet side to enter the chambers during operation. In this way, the trailing chambers 48 are not subject to counterforces exerted by backflow of higher pressurized fluid expelled from the leading chamber 46 that would otherwise occur if the control valve 50 were not present. Recognized benefits include reduced torque in driving the rotor 12 and improved efficiency and performance of the pump 10.

[0022] The reed is preferably one-piece and extends across all of the openings 52. The openings are not all of the same size or volume and narrow in accordance with the dimension of the diminishing crescent-shaped space 36 on the discharge side of the pump. The reed 54 is preferable curved and is widest it is base and progressively narrows toward its free distal end.

[0023] The inner wall 20 may take the form of a rotatable element. In particular, the inner wall 20 may be provided as an inner surface of an inner race 56 of a bearing 58 that is mounted in the housing 10. Rolling elements 60 support the inner race for rotation relative to both the housing 18 and the rotor 12. While the vanes 16 still slide along the surface of the inner wall 20, the inner wall 20 can also rotate to reduce friction and increase the efficiency of the pump 10.

[0024] FIG. 3 illustrates another embodiment of a positive displacement pump 110 in the form of a Gerotor pump. The same reference numerals are used to represent like parts, but are offset by 100. The pump 10 includes inner and outer Gerotor gears 62, 64 having n and n+1 teeth, respectively. The inner gear is fixed to a rotatable shaft 128 and the axes of the inner and outer gears are offset to define a variable increasing and decreasing volume of space on a suction side and discharge side of the pump 110, respectively. The pump 110 includes a housing 118 with an inner wall 120 that receives the outer surface of the outer gear 64. The inner wall 120 may comprise a bearing 158 that supports the outer gear 64 for rotation relative to the housing 118. The housing 118 has closed ends and includes at least one end plate 124 and an intervening valve plate 26 that may be the same as described above with respect to the pump 10 of the first embodiment, including the inlet and outlet ports 140, 144 and a control valve 50 at the outlet port 144. The outlet port may similarly be segmented as a plurality of successive and discrete openings 152 walled off from one another. The end plate 124 has a fluid inlet 138 communicating with the inlet port 140 on the suction side of the pump 110 and a fluid outlet 142 communicating with the outlet port 144 on the discharge side of the pump 110.

[0025] In operation, the rotation of the inner Gerotor gear 62 in the counterclockwise direction about the axis of the shaft 128 drives the outer gear 64 and as the teeth of the gears roll and slide past one another fluid such as air on the suction side of the pump 110 is drawn in to the pump 110 and becomes trapped in chambers that progressively decrease in volume as the chambers progress toward the close point between the gears on the discharge side of the pump 110. As with the vane pump of the first embodiment, the fluid trapped in the leading chamber 146 near the close point 134 is under the highest pressure and the fluid trapped in trailing chambers 148 is under relatively lower pressure. The high pressure fluid is expelled on the discharge side through the outlet port 44. As with the vane pump above, the openings 52 associated with the position of the leading chamber 146 direct the high pressure fluid out of the chamber, past the reed valve 54 and onto the outlet 42. Once expelled, the fluid is not able to return and specifically is not able to backflow to the trailing chambers 148. The same principles, features and benefits associate with the vane pump 10 are realized by the Gerotor pump 110 when outfitted with the control valve 150.

[0026] FIGS. 4 and 4a-c illustrate an alternative vane pump embodiment. The same numbers are used to represent like features but are offset by 200. The pump 200 includes a rotor 212, a housing 218, inner wall 220, closed ends including end plate 222 and valve plate 226. The vanes 216 in this case are wing vanes supported at their base ends by the rotor 212 for individual rotation relative to the rotor 212. Rather the sliding outward and inward to maintain engagement with the inner wall 220, the wings pivot outwardly and fold inwardly as necessary during movement through the suction and discharge sides of the pump 210.

[0027] The control valve 250 includes at least one opening 66 provided in the rotor 220 between each pair of vanes 216 (in other words, each chamber includes an opening 66) and a valve 68 is provided with each opening 66 to enable pressurized air to escape from the chamber into the outlet ports and outlet 42. The openings 66 may comprise slots and the valve 68 may comprise floating cylinders which seat against edge surfaces of the slots to keep the chambers closed until the fluid pressure in the chambers exceeds the holding force provided by the cylinders. The cylinders may span the full width of the rotor or may extend part way. In operation, high pressure fluid in the leading chamber forces the cylinder 68 of that chamber inward allowing the high pressure fluid to escape through the section of discrete openings 252 associated with the position of the leading chamber 246 and out of the pump 210. The valves 68 in the trailing chambers 248 remain closed so long as the backside pressure on the cylinders 68 exceeds the pressure in the trailing chambers 248. The slots 66 are larger than the cylinders 68 such that there is room below the cylinder for the cylinders 68 to move. The slots 66 are in communication with the discrete openings 252 and communicate fluid only so long as the associated cylinder 68 is open. The same feature, principles and advantages apply to this embodiment as they do the others.

[0028] Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that the invention may be practiced otherwise than as specifically described while still being within the scope of the invention.