US3238885A - Positive displacement fluid pump - Google Patents

Description

March 8, 1966 F. M. PASKl 3,238,885

POSITIVE DISPLACEMENT FLUID PUMP Filed Feb. 10, 1964 2 Sheets-Sheet 1 Z [/6 247 f 4I2||| HI I I l I I I [I b 00 Hi I q! 7 i! II I I I March 8, 1966 F. M. PASKl 3,238,385

POSITIVE DISPLACEMENT FLUID PUMP Filed Feb. 10, 1964 2 Sheets-Sheet 2 Q7? f/M' M/ 5660/1/05 A a, MA

W M /l from/5Y5 United States Patent "ice 3 238,885 PUSITIVE DISPLACEMENT FLUID PUMP Fred M. lPaski, Farmington, Mich, assignor to Ford M0- tor Company, Dearhorn, Miclm, a corporation of Delaware Filed Feb. 10, 1964, Ser. No. 343,536 4 Claims. (Cl. 103-136) My invention relates generally to positive displacement pumps and more particularly to a vane pump capable of being driven by a powered member of an automotive vehicle driveline to provide a fluid pressure source for engine driven accessories.

I am aware of various pumps commonly referred to as vane pumps. They include a rotor that is eccentrically mounted for rotation within a pump chamber formed by the pump body. Radially disposed vanes carried by the rotor are adapted to reciprocate within slotted rotor openings. Sealing contact is provided between the radially outward margins of the vanes and the inner surface of the pump chamber.

It is common practice to provide high pressure porting and low pressure porting in the pump structure at a location adjacent the fluid pressure cavity defined by the rotor and the associated pump chamber formed in the pump body. As the vanes traverse the region of the intake port the segmental fluid pumping volume between two adjacent vanes receives low pressure fluid from the intake port and transfers it tangentially with respect to the axis of rotation of the rotor until it is brought into the region of the high pressure outlet port. The volume of fluid is caused to traverse the pumping arc in this fashion.

There exists a tendency for the fluid to become pressurized before each moving segmental volume of fluid reaches the so-called leading edge of the high pressure port. This is due to the change in volume of the arcuate segment between two adjacent vanes as the rotor rotates relative to the stationary body. The resulting localized sharp pressure increase is several times higher than the magnitude of the pressure that is maintained in the pressure outlet port at normal operating speeds. This tends to produce an undesirable audible vibration and sharp pressure fluctuations.

It is an object of my invention to provide a vane pump mechanism wherein provision is made for eliminating these localized pressure surges thereby reducing the operating noise.

It is a future object of my invention to provide a vane pump with radially movable vanes wherein the vanes are formed with recessed portions that define flow re stricting orifices of variable capacity. I contemplate that the segment of oil that is received from the intake port between two adjacent vanes will be subjected to a controlled degree of backfiow as the segment traverses the pumping arc. As the segment approaches the high pressure outlet port, the degree of restriction provided by the variable vane orifices is at a maximum. Thus, the localized pressure that is created in the segment during its movement through the pumping arc develops gradually and reaches a maximum substantially at the instant that the leading edge of that segment passes over the leading edge of the high pressure outlet port. By appropriately tailoring the geometry of the orifices defined by the vanes, the degree of the localized pressure build-up can be made consistent with the magnitude of the pressure that exists on the high pressure side of the pump so that shock loading can be avoided. Undesirable pumping noise is avoided also for this reason.

As the individual vanes continue to traverse the arcuate extent of the high pressure outlet port, the vanes move radially inwardly and the orifices defined by the vanes 3,238,885 Patented Mar. 8, I966 thus become sealed off. By appropriately tailoring the point at which the orifices become completely sealed, a proper pumping function can be achieved.

The provision of a vane pump having these characteristics is a further object of my invention.

For the purpose of describing my improved structure more particularly, reference will be made to the accompanying drawings, wherein:

FIGURE 1 shows in transverse cross-sectional form a vane pump embodying the features of my invention;

FIGURE 1A is an isometric view of the structure of FIGURE 1;

FIGURE 2 is a longtit-udinal cross-sectional view of the structure of FIGURE 1 taken along section line 2-2 of FIGURE 1;

FIGURE 3 is a side elevation detail View of a vane used in the construction of FIGURE 1;

FIGURE 4 is an end view of the vane of FIGURE 3;

FIGURE 5 is a trace recording of the variation in the pressure at both the outlet port and in the pressure in the segmented volumes between pairs of vanes as a function of the degree of rotation of the rotor with respect to the housing. The recording of FIGURE 5 shows the pressure variation that would be experienced if the improvements of my invention were omitted from the vane pump structure of FIGURES 1 and 2; and

FIGURE 6 is a recording similar to FIGURE 5 although it shows the modification of the pressure variations for each degree of turn of the rotor that can be obtained by employing the teachings of my invention in a structure of the type shown in FIGURES 1 and 2.

Referring first to FIGURES 1 and 2, numeral 10 indicates generally a vane pump body or housing. It includes a cylindrical portion 12 and an axially extending portion 14. Portion 112 is formed with a pump chamber 16 which may be in the form of a cylindrical recess having a geometric center corresponding to the point 18 shown in FIGURE 1. Located within pump chamber 16 is a rotor 20 of cylindrical form. The geometric center of the rotor 20 corresponds to point 22 shown in FIG- URE 1. It is apparent from FIGURE 1 that the rotor is eccentrically positioned with respect to the chamber 16. This produces a crescent-shaped cavity 24 between the inner cylindrical Wall of the chamber 16 and the outer surface of the rotor 2d.

A cover plate 26 of circular form may be bolted or otherwise secured to the open face of the body 10 thereby defining a closed pumping chamber.

Rotor 20 is formed with a pair of driving dogs or keys 28 which are received within cooperating recesses 30 formed in a driving shaft 32. This shaft is journaled by means of a bush-ing 34 within a cylindrical bearing opening 36 formed in the extension 14 0f the pump body 10'. A suitable fluid seal 38 can be provided between the shaft 32 and the extension 14. As the shaft 32 is rotated the rotor 20 is driven.

A low pressure intake port or suction port may be formed in the cover 26 although I contemplate that in certain other embodiments the porting can be formed in the body 10. Since the porting is located out of the plane of the section of FIGURE 1, it has been indicated in FIGURE 1 by phantom lines as shown in part at 40.

Intake port 41 extends tangentially with respect to the axis of the chamber 16 and it communicates with the crescentshaped pumping chamber 24. In a similar fashion a high pressure outlet port 42 is located in the cover 26, and, like the port 40, it extends tangentially with respect to the axis of the chamber 16. Both ports 40 and 42 communicate with the pumping chamber 24.

Rotor 20 is formed with a series of circumferentially spaced radial slots 44. Each slot slidably receives a vane 46. The outermost extremities of the vanes 46 slidably engage the inner surface of the cavity 16. At the radially inward extremity of each slot 44 there is formed a transverse opening 48.

A pair of vane spacer rings 59 and 52 engage the inner ends of the vanes 46. These rings are located on either side of the rotor 20 within the cavity 16. They are adapted to position radially the vanes 46 and maintain them in sealing engagement with the inner surface of the cavity 16.

The pressure port is sealed from the intake port by a sealing are 54. It is formed by the engagement of the outer surface of the rotor 20 with the inner cylindrical surface of the cavity 16. In certain embodiments of my invention, however, it is not necessary to rely upon the sealing action between the rotor and the pump cavity since the vanes themselves may be caused to establish such a sealing action as they traverse the so-called sealing are between the trailing edge of the high pressure outlet port and the leading edge of the intake port.

Either one or both sides of the vanes 46 may be formed with slots as shown at 56 and 58 in FIGURE 3. When the vanes are moved to their outermost radial position, the slots 56 or 58 extend outwardly from the outer surface of the rotor 20. When they assume an intermediate radial position, however, the slots 56 and 58 are received within the rotor.

The vanes 56 or 58 thus define orifices of variable size. Their fluid flow capacities are at a maximum when their associated vanes assume a maximum radial displacement in an outward direction. Their effective areas become reduced progressively as the vanes traverse the pumping arc until they reach a value of zero at some predetermined point during the pumping stroke.

It will be apparent from FIGURE 1 that each pair of adjacent vanes cooperates with the pumping chamber 24 to define a pumping sector. The volume of each sector is at a maximum when its associated trailing vane passes over the trailing edge of the intake port. As the vanes continue to traverse the pumping arc, the volume of the sector tends to decrease. The fluid is displaced upon a decrease in the volume of the sector through the variable orifice in the associated vanes. A continuous backflow to a lower pressure region associated with the intake port thus is accomplished.

As soon as the pumping stroke begins, the flow capacity of the orifice decreases progressively as the vanes traverse the pumping arc. This results in a gradual pressure increase in the sector and sharp pressure surges are eliminated.

Any shock loading of the vanes due to the pressure in the high pressure port becomes evenly distributed among the vanes by reason of the orificing characteristic. This also tends to contribute to quietness in pump operation.

In order to compare the pressure characteristics of a conventional vane pump with a vane pump embodying my improvements, I have provided in FIGURE a pressure diagram that illustrates the variation in the static pressure that exists in a pump sector as it traverses a pumping stroke. As each sector passes over the trailing edge of the intake port, a pressure surge indicated by curve A is developed. This pressure surge is characterized by a sharp peak and is followed by a gradual dampening as the pumping stroke continues. As the sector reaches the leading edge of the pressure port its value, of course, becomes equal to line pressure as represented by the line B. This line B thus serves as a reference line for measuring the pressure impulses in each sector.

An actual recording of the pressure in the discharge port would appear as shown in pressure line C in which line D is a so-called zero pressure reference line. The line C has been separated from the lines A and B in FIGURE 5 since it was measured in an actual installation with a separate recording instrument.

The corresponding curves for a pump embodying my improvements is illustrated in FIGURE 6. The pressure that exists in any given segment is represented by line A with line B functioning as a reference pressure line. A separate recording of the pressure in the discharge port is shown at C.

It will be apparent that the maximum peak value for the pressure represented by the line A is substantially less than the corresponding peak value for curve A in FIGURE 5. This is due to the orificing characteristic of the vanes of my improved construction.

Having thus described a preferred form of my invention, what I claim and desire to secure by United States Letters Patent is:

1. A positive displacement pump comprising a pump body, a pump cavity formed in said body, a rotor mounted rotatably within said cavity, radial openings formed in said rotor, a vane mounted within each radial opening and adapted for radial displacement, said rotor being eccentrically positioned with respect to said pump cavity, and a pressure intake port and a pressure outlet port communicating with said cavity at circumferentially spaced locations, at least one of the axial ends of said vanes being cut away to define orifices, said vanes cooperating with said openings to vary the area of said orifices in said cavity as the vanes in which said orifices are formed traverses the arcuate space between said ports, said vanes and said rotor defining within said body a series of pumping chambers, said orifices providing tangential fluid flow from one chamber to the other in a direction opposite to the direction of rotation of said rotor.

2. A positive displacement vane pump comprising a pump body, a pump cavity formed in said body a rotatable rotor eccentrically positioned with respect to said cavity within said body, said cavity and said rotor cooperating to define a crescent-shaped pumping chamber, an intake port and a discharge port communicating with said pumping chamber at circumferentially spaced locations, radial openings formed in said rotor, vanes mounted within said openings and adapted for radial movement with respect to said rotor as the latter is rotated with respect to said body, said vanes moving radially in said openings as they traverse said pumping chamber, and radial slots formed in said vanes and cooperating with said rotor to define orifices of variable area in said pumping chamber as the vanes traverse the pumping chamber whereby fluid may be displaced from the region of said pumping chamber between two adjacent vanes into a low pressure region of said pumping chamber as said vanes traverse the arcuate distance between said ports, the fluid flow through said orifices being in a direction opposite to the tangential delivery of fluid in said pumping chamber from said intake port to said discharge port.

3. A positive displacement pump comprising a pump body, a pump cavity formed in said body, a rotor mounted rotatably within said cavity and defining a crescent shaped pumping chamber, radial openings formed in said rotor, a vane mounted within each radial opening and adapted for radial displacement therein as they move through said pumping chamber, a pressure intake port and a pressure outlet port communicating with said pumping chamber at circumferentially spaced locations, said vanes being cut away to provide orifices, said vanes cooperating with said openings to vary the effective area of said orifices in said cavity as said vanes traverse the arcuate space between said ports, said orifices being in the form of radial slots formed in the axial ends of said vanes, said slots being received within the openings formed in said rotor as said vanes are moved towards the discharge port, said vanes and said rotor defining within said body a plurality of pumping chambers, said orifices providing tangential fluid flow from one chamber to the other in a dlrection opposite to the direction of rotation of said rotor.

4. A positive displacement vane pump comprising a,

pump body, a pump cavity formed in said body, a rotatable rotor eccentrically positioned with respect to said cavity within said body, said cavity and said rotor cooperating to define a crescent-shaped pumping chamber, an intake port and a discharge port communicating With said pumping chamber at circumferentially spaced locations, radial openings formed in said rotor, vanes mounted within said openings and adapted for radial movement with respect to said rotor as the latter is rotated with respect to said body, said vanes moving radially in said openings as they traverse said pumping chamber, and radial slots formed in said vanes, said vanes cooperating with said rotor to define orifices of variable area in said pumping chamber as said vanes traverse the pumping chamber whereby fluid may be displaced from the region of said pumping chamber between two adjacent vanes into a low pressure region of said pumping chamber as said vanes traverse the arcuate distance between References Cited by the Examiner UNITED STATES PATENTS 1,737,942 12/1929 Pagel 103-136 2,872,873 2/1959 Gardiner 103-136 2,967,489 1/1961 Harrington 103-136 3,098,451 7/1963 Scognamillo 103-136 DONLEY I. STOCKING, Primary Examiner.

JOSEPH H. BRANSON, ]R., Examiner.

Claims (1)

1. A POSITIVE DISPLACEMENT PUMP COMPRISING A PUMP BODY, A PUMP CAVITY FORMED IN SAID BODY, A ROTOR MOUNTED ROTATABLY WITHIN SAID CAVITY, RADIAL OPENINGS FORMED IN SAID ROTOR, A VANE MOUNTED WITHIN EACH RADIAL OPENING AND ADAPTED FOR RADIAL DISPLACEMENT, SAID ROTOR BEING ECCENTRICALLY POSITIONED WITH RESPECT TO SAID PUMP CAVITY, AND A PRESSURE INTAKE PORT AND A PRESSURE OUTLET PORT COMMUNICATING WITH SAID CAVITY AT CIRCUMFERENTIALLY SPACED LOCATIONS, AT LEAST ONE OF THE AXIAL ENDS OF SAID VANES BEING CUT AWAY TO DEFINE ORIFICES, SAID VANES COOPERATING WITH SAID OPENINGS TO VARY THE AREA OF SAID ORIFICES IN SAID CAVITY AS THE VANES IN WHICH SAID ORIFICES ARE FORMED TRAVERSE THE ARCUATE SPACE BETWEEN SAID PORTS, SAID VANES AND SAID ROTOR DEFINING WITHIN SAID BODY A SERIES OF PUMP-

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