VANE PUMP INLET WINDOW SHAPE

Abstract

A vane pump has an inlet window and a discharge window formed within a cam surface. The vane pump includes a rotor carrying a plurality of radially extending vanes which are biased into contact with the cam surface. The rotor has a direction of rotation such that one end of the inlet window can be described as an upstream end, and an opposed end as a downstream end. The inlet window extends for a relatively long width along a rotational axis of the rotor at the upstream end. Angularly inwardly extending sides reduce an axial width of the inlet window in a direction moving in a downstream direction from the upstream end.

Description

BACKGROUND

This application relates to a vane pump, wherein a pump fluid inlet window has a unique shape.

Vane pumps are known, and typically include a rotor carrying a plurality of radially movable vanes. The vanes are urged outwardly into contact with a cam surface. The cam surface may be formed within a liner, which is mounted within an outer housing.

The rotor is mounted eccentrically within the cam surface, such that the size of pump chambers increase, and then decrease as the rotor moves from an inlet portion of a cycle toward a discharge portion. While the pump is moving through the inlet portion, fluid moves in through an inlet window, and the fluid is then discharged through an outlet window after the pump cycle is completed.

There are stresses and forces on the vanes and the cam surface from the interacting movement and pressure differentials across the pump. There are particular high contact stresses formed on the cam surface at areas associated with the inlet window, and in particular at downstream ends of the inlet window.

SUMMARY

A vane pump has an inlet window and a discharge window formed within a cam surface. The vane pump includes a rotor carrying a plurality of radially extending vanes which are biased into contact with the cam surface. The rotor has a direction of rotation such that one end of the inlet window can be described as an upstream end, and an opposed end as a downstream end. The inlet window extends for a relatively long width along a rotational axis of the rotor at the upstream end. Angularly extending sides reduce an axial width of the inlet window in a direction moving in a downstream direction from the upstream end.

These and other features of the present invention can be best understood from the following specification and drawings, the following of which is a brief description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a vane pump.

FIG. 1B shows a liner from the FIG. 1A vane pump.

FIG. 2A shows a cam surface for the FIGS. 1A and 2B vane pump.

FIG. 2B shows the shape of an inlet window associated with this embodiment.

FIG. 2C shows a detail of the shape of the FIG. 2B inlet window.

FIG. 3A shows a cam surface according to a second embodiment.

FIG. 3B shows the inlet window shape of the second embodiment.

FIG. 3C shows a detail of the shape of the FIG. 3B inlet window.

DETAILED DESCRIPTION

A pump 20 is illustrated in FIG. 1A having a rotor 22 carrying a plurality of vanes 23. The vanes 23 are forced outwardly against a cam surface 26, shown here as part of a liner 25. The liner 25 is typically mounted within a housing that has a supply of fluid to be pumped connected to an inlet window 28.

Pump chambers 24 are formed between the cam surface 26, and adjacent ones of the vanes 23. While not shown, the vanes 23 can move radially inwardly and outwardly of the rotor 22. The rotor 22 is mounted eccentrically within the liner 25, and driven to rotate such that the size of the pump chambers 24 increase as it moves through an inlet portion of a pump cycle, and over the inlet window 28, and then begin to decrease as it moves toward a discharge portion.

As shown in FIG. 1B, a discharge window 30 is formed circumferentially spaced from the inlet window 28.

FIG. 2A shows the shape of the cam surface 26 of the first embodiment as shown in FIGS. 1A and 1B. The inlet window 28 is formed on one side, with the outlet window 30 formed on an opposed side.

FIGS. 2B and 2C show the shape of the inlet window 28. As shown, an upstream end 32 is generally parallel to a rotational axis of the rotor. Curves 34 extend from ends of the upstream end 32. The curves 34 blend into portions 36 which extend parallel to each other, and which would be generally perpendicular to the upstream end 32. Angled portions 38 extend inwardly, or towards each other to reduce the width of the inlet window 28 shape, adjusting for the change in vane radial acceleration force as it moves toward a downstream end 39 and merging into curve 40. Width is defined as a dimension along the rotational axis. The curve 40 is a complex curve having a two part-circular section. A first part-circular section is formed at radius R₁, and a second part-circular section is formed at radius R₂.

In one embodiment, the angled portions 38 extend at an angle A of about 11.2°. The radius R₁ is 0.250″ (6.35 mm), and the radius R₂ is 0.125″ (3.17 mm). However, any number of other shapes and dimensions may come within the scope of this invention.

This window shape, by reducing the width of the inlet window 28 at locations moving in a downstream direction, reduces the contact stress concentration on the relatively thin sides of the liner 25 on opposed axial ends of the inlet window 28.

FIG. 3A shows another embodiment 125, wherein there is an inlet window 128 and an outlet window 130. As can be seen, the cam surface 126 is distinct compared to the cam surface 26 of FIG. 2A. These two cam surfaces 126 and 26 have generated the two distinct inlet window profiles as shown. In general, the two cam profiles are “modified trapezoidal” cam surfaces. The two profiles shown differ in their respective sizes, and they utilize distinct major and minor radii. However, the broad teachings of this application extend to any number of other types of pumps and cam profiles.

FIGS. 3B and 3C show this embodiment. The shape of the inlet window 128 includes the first flat upstream end 132 and the curves 134 leading to relatively short parallel sides 136. A first angled end 138 extends inwardly at a relatively great angle B, and a second angularly inwardly extending portion 140 extends from the end of the first portion at a smaller angle C. The end 139 of the second angularly inwardly extending portions 140 runs into a curved downstream end 142. A radius R₃ of curved end 142 may be 0.130″ (3.30 mm). The angle B is selected to be more than twice the angle C. In one embodiment, the greater angle B is more than four times as large as the angle C. In one embodiment, the angle B was 27° while the angle C was 4.8°. Again, other angles can be utilized.

For purposes of complete description, the angles A, B, and C are measured to be the angle at which the sides extend axially inwardly to reduce the width of the inlet window 28, 128 in a direction moving downstream, and measured from a plane extending parallel to an axis of rotation of the rotor 22, and in particular the plane defining the straight sides 36, 136.

Although embodiments of this invention have been disclosed, a worker of ordinary skill in this art would recognize that certain modifications would come within the scope of this invention. For that reason, the following claims should be studied to determine the true scope and content of this invention.

Claims

1. A vane pump comprising:

an inlet window and a discharge window, said inlet window being formed within a cam surface;

a rotor carrying a plurality of radially extending vanes which are in contact with said cam surface, said rotor having a direction of rotation such that one end of said inlet window in an upstream end, and an opposed end is a downstream end; and

said upstream end of said inlet window extends generally for a width measured along a rotational axis of said rotor, and there being angularly extending sides which reduce the width of said inlet window in a direction moving towards said downstream end from said upstream end.

2. The vane pump as set forth in claim 1, wherein said upstream end of said inlet window extends parallel to said rotational axis of said rotor.

3. The vane pump as set forth in claim 1, wherein said angularly extending sides merge into a circular section at said downstream end.

4. The vane pump as set forth in claim 3, wherein parallel side portions are positioned between said upstream end and said angularly extending sides.

5. The vane pump as set forth in claim 3, wherein there are curved portions connecting said upstream end to said parallel side portions.

6. The vane pump as set forth in claim 3, wherein said circular section is a complex section having two circular sub-sections.

7. The vane pump as set forth in claim 1, wherein there are two sets of angularly extending sides.

8. The vane pump as set forth in claim 7, wherein a first set of angularly extending sides extend angularly inwardly at a first angle that is greater than a second angle of a second set of angularly extending sides which are positioned downstream of said first set of angularly extending sides.

9. The vane pump as set forth in claim 8, wherein said first and second angles extend axially toward an opposed side in each said set, and are measured from a plane extending parallel to said rotational axis, and wherein said first angle is at least twice as large as said second angle.

10. The vane pump as set forth in claim 9, wherein said first angle is at least four times as large as said second angle.

11. The vane pump as set forth in claim 1, wherein said inlet window is formed in a vane pump liner.

12. A vane pump comprising:

a liner body an inlet window and a discharge window, said inlet window being formed within a cam surface;

a rotor carrying a plurality of radially extending vanes which are in contact with said cam surface, said rotor having a direction of rotation such that one end of said inlet window in an upstream end, and an opposed end is a downstream end;

said upstream end of said inlet window extending for a width measured along a rotational axis of said rotor and parallel to said rotational axis, and there being angularly extending sides which reduce the axial width of said inlet window in a direction moving towards said downstream end from said upstream end;

said angularly extending sides merging into a circular section at said downstream end;

parallel side portions positioned between said upstream end and said angularly extending sides; and

curved portions connecting said upstream end to said parallel side portions.

13. The vane pump as set forth in claim 12, wherein said circular section is a complex section having two circular sub-sections.

14. The vane pump as set forth in claim 12, wherein there are two sets of angularly extending sides.

15. The vane pump as set forth in claim 14, wherein a first set of angularly extending sides extend angularly inwardly at a first angle that is greater than a second angle of a second set of angularly extending sides which are positioned downstream of said first set of angularly extending sides.

16. The vane pump as set forth in claim 15, wherein said first and second angles extend axially toward an opposed side in each said set, and measured from a plane extending parallel to said rotational axis, and wherein said first angle is at least twice as large as said second angle.

17. The vane pump as set forth in claim 16, wherein said first angle is at least four times as large as said second angle.