Variable Displacement Vane Pump

Abstract

A variable displacement vane pump is presented in which the seal blocks are pivoted to control pump operation. The pump is double acting in that it has two pairs of opposed fluid inlet and discharges to minimize bearing loads. The seal blocks are appropriately contoured to provide desired vane displacement for pumping and also to provide the necessary sealing to accomplish the double acting operation. The seal blocks are force balanced to minimize actuating load requirements, and the vane elements are physically retained within their slots by stopping shoulders.

Parent Case Text

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 825,497 filed May 19, 1969 now abandoned.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to the field of vane pumps. More particularly, this invention is directed to the field of variable displacement vane pumps.

2. Description of the Prior Art

Vane pumps, either of the fixed displacement type or the variable displacement type are known in the art. The most prevalent form of variable displacement vane pump is one in which the vanes are constrained by an eccentrically mounted cylindrical vane track or sealing block. The sealing block is mounted eccentrically with respect to the center line of the pump rotor, and vane stroke (and hence pump displacement) is controlled by varying the eccentricity of the sealing block with respect to the rotor center line.

The traditional variable displacement vane pump is a single acting pump and it has one inlet and one discharge. Although mechanically simple, the traditional single acting variable displacement vane pump is characterized by high bearing loads on the rotor bearings and severe vane dynamics. The high bearing loads are caused by pressure unbalances arising out of the single acting input and discharge flow design, and the severe vane dynamics are caused by abrupt changes in direction of radial movement of the vanes resulting from the eccentric path which constrains the outer ends of the vanes. The single acting characteristic which results in the high bearing loads is dictated by the fact that the eccentric ring cannot be contoured to provide more than one inlet and one discharge while retaining a range of variable settings. The high bearing loads, in turn, require a design of increased load capability thus leading to an undesirably heavy pump configuration.

The vane dynamics problem also severely limits vane stroke and rotational speed. Furthermore, at least partly because of the severe vane dynamics, the vanes are traditionally left free in their slots and are constrained against outward movement only by the sealing blocks thus dictating a design in which the sealing blocks completely envelop the rotor structure. Abrupt changes in the direction of radial motion of the vanes result in high dynamic stresses which lead to sealing problems between the vanes and the eccentric seal block. Also, the shape of the eccentric track causes radial movement of the vanes with respect to the rotor axis when the vanes are passing through the pumping arc and are subjected to pressure differentials. This radial movement of the vanes produces a high friction force between the vanes and the rotor slots in which the vanes are housed, thus either further restricting vane stroke and rotational speed or imposing severe materials requirements on the system, such as requiring tungsten carbide vanes, seal blocks and end plates.

In addition, the high loads on the seal block structure in traditional prior art pumps has required an actuating mechanism of significant force capability for varying the position of the seal block structure.

The traditional approaches in the prior art to solving the previously discussed problems have been very unsatisfactory. Either a compromise is made with rotational speed and vane stroke parameters, or the variable displacement feature is completely abandoned in favor of a fixed displacement pump. Fixed displacement pumps having a double acting design, i.e., two pairs of opposed inlets and discharges, and each having contoured sealing blocks to control vane movement are known in the art. These fixed displacement pumps have very low bearing loads because of the double acting feature, and greater vane radial displacements can be accommodated without undue dynamic stresses because of the control of vane movement which can be accomplished by the contoured sealing blocks. However, this alternative completely eliminates the variable displacement capability of the pump.

One approach to solving the problems of the prior art has been presented in U. S. Application Ser. No. 796,422 filed Feb. 4, 1969 in the name of one of the coinventors named herein and assigned to the assignee of the present application. The present invention presents an alternative approach to solving these problems of the prior art.

SUMMARY OF THE INVENTION

The present invention, in both embodiments presented herein, is a variable displacement vane pump having minimal bearing loads and having controlled radial vane movement to minimize instability and dynamic loading of the vanes. The present incorporates, in a variable displacement vane pump, a double acting inlet and discharge feature and a pair of separated contoured seal blocks. The separated contoured seal blocks allow a radial as well as an axial fuel inlet. The vane structure is provided with stopping shoulders to limit the radial outward movement of the vanes and thus retain the vanes within their slots at the maximum stroke. The two separated seal block segments are movable with respect to each other and with respect to the axis of the rotor pump, preferably by a coordinated actuating system, and the position of the seal block segments sets the net vane radial displacement as desired between the limits of full effective stroke and zero effective stroke for pump vanes which cooperate with the contoured surfaces on the seal blocks. The vane retention mechanism limits the outward movement of the vanes, and the seal blocks are appropriately contoured so that there is a smooth pickup of the vane tips on the seal block surfaces without any stubbing interference therebetween. The inlet ports may be of equal size and diametrically opposed to each other. Similarly, the discharge ports may be of equal size and diametrically opposed to each other. Therefore, the pump structure may be essentially completely balanced with only minimal bearing loads on the rotor bearing.

The seal block segments are pivotally mounted for movement with respect to the rotor structure to vary the displacement of the vanes and hence the output of the pump. Actuation forces required for the movable seal block segments are minimized in one version of the pump by locating the pivot points on the resultant of forces acting on the seal blocks and in another version of the pump by exposing the backside of the movable seal block to the same pressure acting on the contoured surface.

Accordingly, one object of the present invention is to provide a novel and improved variable displacement vane pump.

Another object of the present invention is to provide a novel and improved variable displacement vane pump having low bearing loads.

Still another object of the present invention is to provide a novel and improved variable displacement vane pump wherein problems of vane dynamics are eliminated or minimized.

Still another object of the present invention is to provide a novel and improved variable displacement vane pump wherein pump displacement may be varied by altering the position of movable seal blocks.

Still another object of the present invention is to provide a novel and improved vane pump having a high flow capability and wherein the fluid to be pumped can be introduced both axially and radially thereby minimizing inlet pressure requirements to suppress cavitation.

Still another object of the present invention is to provide a novel and improved variable displacement vane pump having pivotable seal block segments wherein low actuating forces are sufficient to position the seal block segments.

Still another object of the present invention is to provide a novel and improved variable displacement vane pump incorporating features heretofore usually found only in fixed displacement pumps.

Other objects and advantages will be apparent and understood from the following detailed description and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, wherein like elements are numbered alike in the several figures:

FIG. 1 is an elevation view of one embodiment of the vane pump of the present invention with the end plates removed, the pump being shown in a fully loaded position.

FIG. 2 is a view of the pump of FIG. 1 in an unloaded position.

FIG. 3 is a view of another embodiment of the present invention with end plates removed and in a loaded position.

FIG. 4 is an elevation view of the pump of FIG. 3 in an unloaded position.

DESCRIPTION OF THE PREFERRED EMBODIMENT

To facilitate the description of the pumps of the present invention, the pumps are shown in all of the drawings with the front and rear end (bearing/seal) plates removed. However, it will be understood to those skilled in the art that appropriate end plates must be provided for the pump, such plates being standard elements known in the art such as may be seen, for example, in U. S. Pat. No. 2,669,189, U. S. Pat. No. 2,612,114, or in the above-identified application. These end plates provide axial inlet and/or discharge passages for the fluid to be pumped, which passages are indicated in the drawings in dotted lines as will be more fully discussed hereinafter, these end plates completely covering the pump rotor element and at least partly overlapping the seal block segments. It will also be understood to those skilled in the art that the pumps of the present invention must be contained in a suitable housing or casing during operation, and it will also be understood that the axial length of the pump, i.e., its dimension perpendicular to the plane of the paper as shown in the drawings, will depend on the design requirements for the particular installation in which the pump is to be employed.

Referring now to FIG. 1, a vane pump 10 is shown in front elevation. Pump 10 has a main rotor 12 which is fixed to a rotor shaft 14. Rotor 12 is a right circular cylindrical element having its axis perpendicular to the plane of the paper, and shaft 14 is positioned with its center on the axis of rotor 12. Shaft 14 extends beyond the front and rear surfaces of rotor 12 and is supported for rotation by bearing surfaces in the pump end plates which abut the front and rear surfaces of the rotor. Pump 10 also has a pair of seal blocks 16 and 18 which are fixed to pivot shafts 20 and 22, respectively. The ends of pivot shafts 20 and 22 extend beyond the front and rear surfaces of seal blocks 16 and 18 and are mounted for rotation in bearing surfaces in the end plates or in other casing structure. Alternately, the pivot shafts 20 and 22 could be fixed and seal blocks 16 and 18 could be rotatably mounted on the pivot shafts. Referring once again to the construction of rotor 12, the rotor has a plurality of radial slots 24, each of which has an enlarged root section 26. A vane 28 having an enlarged base portion 30 is positioned in each of the slots 24 with the base portion 30 being housed in the root section 26, the outer ends of the vanes extending beyond the outer peripheral surface of rotor 12. It will be understood that the slot and vane structure described immediately above extends entirely around rotor 12 with the slots and vanes being spaced equidistantly around the entire 360.degree. of the rotor. It will also be understood that the slots and vanes extend the full axial length of rotor 12, and it can be seen that the junction of each slot 24 in root section 26 provides a shoulder or limit stop for base 30 to prevent the vanes from being thrown out of the rotor structure as the rotor is rotating. As will be more fully described hereinafter, the inner surfaces 32 and 34 of seal blocks 16 and 18 are contoured to provide desired arcs and cam surfaces which interact with the ends of the vanes to cause the vanes to move in and out with respect to the slots, it being understood that the slots and vanes are radial with respect to the axis of rotor 12.

A specific defined relationship exists between the contours on the inner surfaces on the sealing blocks and the inlet and discharge ports on the pump end plates. The areas outlined by the arcuately shaped dotted lines in FIG. 1 indicate the inlet and discharge passages on either one or both of the front and rear end plates: passages 36 and 38 are inlet passages, preferably of equal size, arc length and shape; passages 40 and 42 are discharge passages of equal size, arc length and shape. The space between any two adjacent inlet and discharge passages constitutes a transfer arc as indicated by the double ended arrows 44, 46, 48 and 50. These transfer arcs are the areas between the inlet and discharge passages wherein the fluid and the space between any two vanes (sometimes referred to herein as the intervane space) must be sealed to prevent communication between adjacent inlet and discharge passages. Accordingly, the contour of the inner surface of the sealing blocks in the areas coextensive with the designated transfer arcs is contoured to have very little slope with respect to the periphery of rotor 12 so that there is little or no vane displacement while the vanes are traversing these transfer arcs. In addition, the arc length of each of the transfer arcs is at least equal to or greater than one vane spacing, i.e., equal to or greater than the arc distance from the point at the tip of one vane to a corresponding point at the tip of an adjacent vane. This contour of the sealing blocks in the area of each transfer arc and the stated minimum arc length of each transfer arc combine to assure that the inlet and discharge passages will be isolated from each other so that leakage therebetween is prevented.

The contours of the inner surfaces 32 and 34 of the sealing blocks in the area of the discharge passages 40 and 42 slope inwardly with respect to the periphery of rotor 12 (when viewed in a clockwise direction) to provide a diminishing distance from the inner surfaces of the seal blocks to the periphery of rotor 12 when the seal blocks are positioned as shown in FIG. 1; conversely, the contours of the inner surfaces of the seal blocks in the areas of the inlet passages 36 and 28 slope outwardly with respect to the periphery of rotor 12 (as viewed in a clockwise direction) to provide an increasing distance from rotor 12 when the seal blocks are positioned as shown in FIG. 1. The contours of the seal blocks thus serve to form cam surfaces which stroke the vanes in and out in their slots as the various parts of the inner surfaces of the seal blocks are traversed by the vanes in contact therewith.

As this point, an example of the operation of the pump as the vanes traverse the vane track defined by the inner surfaces of the seal blocks will be described with respect to FIG. 1 wherein the seal blocks are shown in the position wherein the pump is fully loaded. Assuming that shaft 14 and rotor 12 are rotating clockwise, the analysis will begin with a vane at the edge of inlet passage 36 at its juncture with transfer arc 50. Bearing in mind that the contour of inner surface 34 in the area of inlet passage 36 is such that there is an increasing distance from the periphery of rotor 12 to that part of surface 34, it can be said that surface 34 is receding from rotor 12 at each successive clockwise station along the arc of inlet passage 36 as inlet passage 36 is traversed in a clockwise direction. Assuming that the outer ends of vanes 28 are in contact with inner surface 34 of sealing block 18 at the entrance to inlet passage 36, either by centrifugal or other forces, and that the vane at this point has been cammed inwardly with respect to slot 24 and root section 26 (as shown by the position of the vane immediately upstream of inlet passage 36), each vane is caused to move in its slot radially outward from the axis of rotor 12 as the vane traverses the arc of inlet passage 36, and each successive vane in a clockwise direction will be in a more extended position than the vane immediately trailing it in the direction of rotation so long as the separation between inner surface 34 and rotor 12 does not exceed the fully extended length of the vane.

As the vane approaches the end of seal block 18, it comes under the influence of an exit section 52 in the form of a gently sloping ramp which allows the vane to reach its fully extended position whereby the base 30 contacts the shoulder between root section 26 and slot 24 to prevent any further radially outward movement of the vane. The gently sloping nature of the exit 52 results in a termination of the outward movement of the vane with a minimum of loading or undesirable vane dynamics on the vanes.

Fluid to be pumped is drawn into the intervane volume as the vanes traverse inlet passage 36 and the intervane volume increases with movement in the clockwise direction. Each vane then enters an open spacing between seal block 18 and seal block 16 and this open spacing, which may extend the entire axial length of the pump, can serve as a radial inlet passage for introduction of more of the fluid to be pumped along with the fluid being introduced axially through the inlet passages 36 in the end plates.

As each vane continues to move in a clockwise direction in its fully extended position, it moves into an entrance section 56 of seal block 16. The first part of entrance 56 is contoured so that its separation from the outer surface of rotor 12 is greater than the maximum extension of the vane to insure that there will be no interference between the vane and the edge of the entrance section. As each vane continues to move in the clockwise direction it then contacts the inner surface 32 of seal block 16 in the vicinity of entrance 56 which constitutes a gentle ramp to reestablish contact between surface 32 and the vane tip with a minimum of dynamic loading. The vane then enters the area covered by transfer arc 44 wherein the inner contour of surface 32 is either constantly spaced from or gently sloping toward the periphery of rotor 12 (it being the intention that there be no substantial radial movement of the vanes as they traverse transfer arc 44). Bearing in mind that the arc length of transfer arc 44 is at least equal to or greater than one vane spacing, the volume between any two vanes, i.e., the intervane volume, remains essentially constant in traversing arc 44 and the volume is at least momentarily sealed from inlet passage 36 and discharge passage 48. The fact that the intervane volume remains essentially constant while traversing transfer arc 44 produces the result that there is no attempt to compress an incompressible fluid (such as engine fuel) contained in the volume between two successive vanes when traversing transfer arc 44, thus avoiding a serious overload on the pump. Also, inward and outward movement of the vanes is eliminated or minimized as the vanes traverse transfer arc 44, and thus sliding friction loads between the vanes and their slots are avoided as the vanes traverse arc 44. After passing through transfer arc 44, each vane then enters into the arc determined by discharge passage 40. The inner surface 32 of seal block 16 is contoured so that its spacing from the periphery of rotor 12 diminishes sharply in the clockwise direction so that the vanes are cammed radially inwardly in their slot as the vanes traverse discharge passage 40.

Presuming that discharge passage 40 is exposed to a load of some sort (such as, for example, a fuel nozzle or pressuring valve), the fluid in an intervane volume will become pressurized as the fluid in the intervane volume traverses transfer arc 44 and becomes exposed to discharge passage 40. The pressurized fluid then coming within the arc of discharge passage 40 will then be forced out through the discharge passage as a result of the vanes being displaced inwardly by the camming action of the contour of surface 32 along the arc of discharge passage 40. This inward displacement of the vane results, of course, in a reduced volume between any two vanes as the vanes move clockwise along the arc of discharge passage 40, and the fluid is thus forced to move from this reducing volume out of the discharge passages 48 at the end plates at each end of the pump. The pump capacity will, of course, be a direct function of the displacement of the vanes as the vanes traverse discharge passage 40 and are cammed inwardly.

After traversing discharge passage 40, each vane then enters into transfer arc 46. The inner surface of sealing block 16 within the arc of transfer arc 46 is, like transfer arc 50, essentially constantly spaced from the periphery of rotor 12 so that there is little or no outward displacement of the vanes as they traverse arc 46. The arc length of arc 46 is also at least equal to or greater than one vane spacing so that the intervane space between any two successive vanes is at least momentarily sealed as the vanes advance from the end of discharge arc 40 toward the beginning of inlet arc 38. Thus, leakage between discharge passage 40 and inlet passage 38 is avoided.

As each vane continues its clockwise movement, it then enters into the arc of inlet passage 38. Both the size and shape of inlet passage 38 are essentially identical to inlet passage 36, and the relationship between the rotor structure and the sealing block elements 16 and 18 is essentially identical to the relationship between the rotor and vane structure and sealing blocks 18 and 16. Thus, as the vanes enter the area of inlet passage 38, the spacing between inner surface 32 and the periphery of rotor 12 increases as the vanes move in a clockwise direction so that the vanes are caused to move radially outward to take in fluid to be pumped within the intervane volume. The vanes eventually reach an exit 58 at the end of sealing block 16 which is contoured to form a gently sloping ramp to allow the vanes to reach their full extended position with a minimum of vane dynamics, and the vanes then enter into the area of the open space 60 between seal blocks 16 and 18 where additional fluid can be introduced in a radial direction.

After the vanes pass through open space 60 each vane moves into an entrance section 62 of seal block 18, which entrance section is essentially identical to entrance section 56 of seal block 16. Thus, the entrance section presents a gentle ramp contour to gently diminish the space between inner surface 34 and rotor 12 at the entrance area so that the fully extended vanes are again brought into contact with inner surface 34 with a minimum of vane dynamics loading.

The tip of each vane is in full contact with inner surface 34 as the vane leaves the arc of inlet passage 60 and enters into transfer arc 48. Transfer arc 48, like transfer arcs 50, 44 and 46 previously described, is contoured to provide either a constant spacing or an essentially constant spacing between inner surface 34 and the periphery of rotor 12 and is at least equal to or greater than one vane spacing so that there is no vane displacement while traversing the transfer arc and so that the intervane spacing between any two vanes is at least momentarily sealed from both inlet arc 38 and discharge arc 42 to prevent leakage therebetween. After traversing transfer arc 48, each vane then enters into the arc defined by discharge passage 42. The contour of the inner surface of seal block 18 when in the area of discharge passage 42 provides a decreasing spacing between surface 34 and the periphery of rotor 12 as movement progresses in a clockwise direction. Thus, the separation between the inner surface of seal block 18 and rotor 12 diminishes as discharge passage 42 is traversed in a clockwise direction thereby resulting in an inward displacement of each vane in its slot as the vane traverses the discharge passage. In a manner similar to the previous description with respect to discharge passage 40, the fluid in an intervane volume traversing transfer arc 48 becomes pressurized as the intervane volume comes under the influence of discharge passage 42, and that pressurized fluid is then forced out of the discharge passage 42 in each end plate as the vanes are displaced inwardly in their slots and the intervane volume decreases along the traversal of the arc of discharge passage 42.

After passing through the arc of discharge passage 42, each vane then enters into transfer arc 50 to repeat the above-described process.

The foregoing illustrative description of the operation of the pump as rotor 12 moves in a clockwise direction has been directed to an analysis as a vane or pair of vanes traverses the guide or track defined by inner surfaces 32 and 34 of seal blocks 16 and 18. It will, of course, be understood that the actions previously described in connection with the inlet and outlet passages and the transfer arcs are all operating simultaneously with respect to vanes or sets of vanes around the circumference of the rotor so that the several described inlet, discharge and sealed transfer actions are all occurring simultaneously. It will also be understood that the inlet and discharge passages shown in dotted lines in FIG. 1 may be located at either or both of the front and rear end plates of the pump, which plates have been removed for the purpose of ease of illustration but which would be secured to the pump structure and butted against the opposed end surfaces of the rotor, vane and seal block structure.

The seal blocks are positioned in FIG. 1 to provide maximum pump output and maximum loading. As can be seen from FIG. 1, the discharge passages 40 and 42 are diametrically opposed from each other and are the same size and shape, and inlet passages 36 and 38 are also diametrically opposed to each other and are the same size and shape. The incorporation of two sets of inlet and discharge passages constitutes the pump as a double-acting pump, and the direct diametrically opposed positioning of the discharge and inlet passages result in a force balance to minimize loads on the bearings which support rotor 12. Also, the smooth contoured transitions along the inner surfaces of seal blocks 16 and 18, coupled with the vane retaining structure defined by the shoulder between slot 24 and root section 26 and its interaction with base 30 result in minimum vane dynamics problems regardless of the position of the seal blocks in any position between maximum pump flow and minimum pump flow.

Referring now to FIG. 2, the pump of the present invention is shown with seal blocks 16 and 18 pivoted about their respective pivot shafts 20 and 22 to a position where the pump is unloaded and there is no flow. Of course, it will be understood that the seal blocks could be pivoted to assume any position between the fully loaded position of FIG. 1 and the fully loaded position of FIG. 2 for partial loading. The vanes and vane slots have been omitted from the showing in FIG. 2, merely for the purposes of ease of illustration, but it will be understood that all of the vanes are present as in the FIG. 1 showing. As can be seen from a comparison of the relative positions of the seal blocks with respect to the periphery of rotor 12 in FIGS. 1 and 2, the spacing between the inner surfaces of the seal blocks and the rotor periphery within the arcs of discharge passages 40 and 42 is essentially constant so that there is no effective radial vane displacement as the vanes traverse the arcs of discharge passages 40 and 42. Since there is no effective vane displacement during traversal of the discharge arcs, no fluid is pumped, and the pump structure is unloaded. Although the vanes are not shown in FIG. 2, it will be understood that the dimensioning of the spacing between the entrance and end sections of each of the seal blocks is such that the vanes are still guided to their full extended position by exit ramps 52 and 58 and are picked up by inlet ramps 56 and 62 without any interference between the edges of the seal block segments and the ends of the vanes so that there is still a smooth inward and outward vane movement with a minimum of vane dynamics.

The actuating structure for moving the seal block segments between the FIG. 1 configuration and the FIG. 2 configuration consists of a bifurcated bell crank 64 which is mounted for pivotal movement on a pivot shaft 66. One leg 68 of the bell crank engages a pin 70 which projects from seal block 16 and rides in a groove in leg 68, and the other leg 72 engages a pin 74 which extends from seal block 18 and rides in a groove in leg 72. Bifurcated bell crank 64 may be moved by any suitable actuating mechanism and is caused to pivot about pivot shaft 66 whereby each of the seal blocks is caused to rotate about its pivot shaft in either a clockwise or counterclockwise direction depending on the direction of movement of bell crank 64. As can be seen, both seal blocks will be caused to pivot in the same direction in response to movement of bell crank 64. If the right end of bell crank 64 is moved upwardly to pivot bell crank 64 counterclockwise, both of the seal block segments will be caused to move in a clockwise direction to move from the position shown in FIG. 2 toward the position shown in FIG. 1. Conversely, clockwise movement of bell crank 64 will cause counterclockwise movement of the seal block segments from the FIG. 1 position toward the FIG. 2 position.

The centers of pivot shafts 20 and 22 are positioned on a line passing through the axis of rotor 12 so that the axes of rotor 12 and pivot rods 20 and 22 are all in a common plane. This positioning of the pivot rods 20 and 22 places their axes on a line along the resultant of forces acting on each of the pivot blocks. The fact that the axes of the pivot rods are so positioned, coupled with the fact that the pump structure is essentially force balanced, makes it possible to actuate the seal block segments to move between the FIG. 1 and FIG. 2 positions with only a very light actuating force, notwithstanding the fact that extremely high pressures may be generated in the pump.

Turning now to FIGS. 3 and 4, another embodiment of the present invention is shown. The embodiment shown in FIGS. 3 and 4 is conceptually similar to that of FIGS. 1 and 2 in that it shows a variable displacement double-acting vane pump having contoured pivotable seal block elements. The principal structural difference is that only a part of each of the seal block segments are pivotable in the FIGS. 3 and 4 embodiment. Another major distinction is that the fuel inlet is mainly a radial inlet.

Referring now to the FIGS. 3 and 4 embodiment wherein several like elements are numbered as in FIGS. 1 and 2, the rotating structure including rotor 12, shaft 14, slots 24 with root sections 26 and vanes 28 with bases 30 is essentially identical to that shown in FIGS. 1 and 2. The pump also has a pair of seal blocks, each of which consists of a stationary part 76A and 78A and a pivotable part 76B and 78B. Although only several slots and vanes are shown in each of FIGS. 3 and 4 for purposes of illustration, it will be understood, as in the FIG. 1 and 2 embodiment, that the slot and vane structure extends entirely around rotor 12, the slots and vanes being spaced equidistantly around the entirety of the 360.degree. rotor; and it will also be understood that shaft 14 is supported by bearing surfaces in the pump and plates, as described with respect to FIGS. 1 and 2. Pivotable segments 76B and 78B are fixed, respectively, to pivot shafts 20 and 22. The inner surfaces of the seal blocks, indicated as 80A and 80B on seal block segments 76A and 76B and as 82A and 82B on seal block segments 78A and 78B, are contoured to provide desired arcs and cam surfaces which interact with the ends of the vanes to cause the vanes to move in and out with respect to the slots, it being understood that the slots and vanes are radial with respect to the axis of rotor 12.

A specific defined relationship exists between the contours of the inner surfaces of the sealing blocks and the inlet and discharge ports of the pump. The areas indicated by the arcuately shaped dotted lines 84 and 86 indicate axial discharge passages of equal size, arc length and shape in either one or both of the front and rear end plates. The large open generally radial spaces 88 and 90 indicate generally radial fluid inlets extending the entire length of the rotor structure and which may or may not communicate with axial inlet ports in the end plates. The space between any two adjacent inlet and discharge areas constitutes a transfer arc as indicated by the double-ended arrows 92, 94, 96 and 98. These transfer arcs are the areas between the inlet and discharge areas wherein the fluid in the intervane volume must be sealed to prevent communication between the adjacent inlet and discharge areas. Accordingly, the contour of the inner surface of the sealing blocks in the areas coextensive with each of the designated transfer arcs is constructed to have little or no slope with respect to the axis of rotor 12 i.e., to be essentially arcs of circles having axes coincident with the axis of rotor 12, so that there is little or no vane displacement while the vanes are traversing the transfer arcs. The entrances to the transfer arcs 94 and 98 at their junctions with inlets 88 and 90 are contoured to be tangent to the fully extended vanes or to provide a short gentle slope to pick up the vanes so that stubbing of the vane tips on the seal blocks is avoided. The arc length of each of the transfer arcs is at least equal to or greater than one vane spacing, i.e., equal to or greater than the arc distance from the point at the tip of one vane to a corresponding point at the tip of an adjacent vane. This contour of the sealing blocks in the areas of each transfer block and the stated minimum arc length of each transfer arc combine to assure that the inlet and discharge passages will be isolated from each other so that leakage therebetween is prevented.

The contours of the inner surfaces 80B and 82B of the sealing blocks in the area of discharge ports 84 and 86 slope inwardly (when viewed in a clockwise direction) to provide a diminishing distance from the inner surface of the seal blocks to the center of rotor 12 when the seal blocks are positioned as shown in FIG. 3 (which is the fully loaded position of the pump). The contours of the inner surfaces of the movable elements of the seal blocks, when positioned as in FIG. 3, thus serve to form cam surfaces which stroke the vanes inwardly in their slots as the various parts of the inner surfaces of the seal blocks are traversed by the vanes in contact therewith.

The operation of the pump as the vanes traverse the vane track is essentially as described in connection with the FIG. 1 embodiment. However, a brief description along the lines of that set forth above with respect to FIG. 1 will be set forth for purposes of illustration.

Assuming that shaft 14 and rotor 12 are rotating clockwise, the analysis will begin with a vane at the edge of discharge passage 86 at its juncture with transfer arc 92. Since the distance from inner surface 82B to the axis of shaft 12 is relatively constant along arc 92, there is little or no radial movement of this vane as it traverses arc 92. The vane then enters inlet area 88 wherein it is free to move radially outward at its maximum distance until base 30 contacts the shoulder stop defined by the junction of slot 24 and root section 26. In order to prevent undesirable vane dynamics, pressurized fluid may be selectively introduced into the space between base 30 and the shoulder stop to dampen the outward movement of the vane.

The intervane space is filled with fluid to be pumped (for example fuel) as it traverses inlet 88 and the vane then enters into transfer arc 94. As previously stated, inner surface 80A is essentially circular with respect to the axis of shaft 14 or slopes only very slightly with respect to the periphery of rotor 12 as the vanes advance in a clockwise direction, and the separation between inner surface 80A and the outer periphery of rotor 12 at the entrance to transfer arc 94 is either equal to or just slightly greater than the maximum distance a vane projects above the periphery of rotor 12 (depending on whether the separation of surface 80 from the periphery of rotor 12 is constant or slightly decreasing). Thus, the outer extremity of the vane contacts inner surface 80A as it enters into transfer arc 94 so that there is at least a momentarily intervane sealing of inlet 88 from discharge 84 as the vanes traverse transfer arc 94.

The vane then engages inner surface 80B of movable seal block segment 76B as the vane enters the arc defined by discharge passage 84, and the vane is cammed radially inwardly toward the axis of shaft 14 to discharge the pump fluid to a fluid consuming load. The vane then enters transfer arc 96 wherein there is little or no radial movement of the vane and at least a momentary seal of the intervane volume is established between discharge passage 84 and inlet 90.

The vane then enters the area of inlet 90 where more fluid to be pumped is introduced into the intervane spacings. The vane then advances to engage inner surface 82A of stationary seal block segment 78A which is contoured and positioned with respect to the rotor structure essentially identical to inner surface 80A. Thus, as the vane traverses the arc defined by transfer arc 98 at least a momentary intervane sealing is established to provide a seal between inlet 90 and exit 86. The vane then enters into and traverses inner surface 82B in the area of discharge passage 86 and it is cammed inwardly by the slope of surface 82B with respect to the periphery of rotor 12 whereby the intervane fluid is forced out of discharge passage 86 for delivery to a fluid consuming load. The vane then reenters the arc of transfer arc 92 to repeat the above-described process.

The foregoing illustrative description of the operation of the pump as rotor 12 moves in a clockwise direction has been directed to an analysis as a vane or pair of vanes traverses the guide or track defined by the inner surfaces of the inner seal blocks. It will, of course, be understood that the actions described in connection with the inlets and discharges and the transfer arcs are all operating simultaneously with respect to vanes or sets of vanes around the circumference of the rotor so that the several described inlet, discharge and sealed transfer actions are all occurring simultaneously.

The seal blocks are positioned in FIG. 3 to provide maximum pump output and maximum loading. As can be seen from FIG. 3, the discharge passages 84 and 86 are diametrically opposed from each other and are the same size and shape and the inlet areas 88 and 90 are also diametrically opposed to each other and are of the same size and shape. The incorporation of two sets of inlet and discharge passages constitutes this pump as a double-acting pump, and the direct diametrically opposed positioning of discharge and inlet passages result in a force balance to minimize loads on the bearings which support rotor 12. Also, the smooth contoured transitions along the inner surfaces of the seal blocks, the spacing of the fixed seal block segments 76A and 78A with respect to the rotor periphery, and the vane retaining structure defined by the shoulder between slot 24 and root section 26 result in minimum vane dynamics and retention problems regardless of the positioning of the seal blocks in any position between maximum pump flow and minimum pump flow. As has been previously pointed out, fluid under pressure can be selectively introduced into the spacing between base member 30 and the retaining shoulder to provide a dynamic damping when the vanes leave transfer arcs 92 and 96 and enter inlet areas 88 and 90, respectively. This selective introduction of fluid may be accomplished by grooves in the end plates, as described in U. S. Application Ser. No. 796,422.

Referring now to FIG. 4, the pump is shown with movable seal block segments 76B and 78B pivoted about their respective pivot shafts 20 and 22 to a position where the pump is unloaded and there is no flow. Of course, it will be understood that the seal blocks could be pivoted to assume any partially loaded position between the fully loaded position of FIG. 3 and the fully unloaded position of FIG. 4. As can be seen from the position of the vanes illustrated in FIG. 4, all of the vanes are at essentially the fully extended position when the pump is in the fully unloaded state so that there is essentially no effective radial vane displacement and no pumping action as the vanes traverse the arcs of the discharge passages.

Movement of the seal block segments between loaded and unloaded positions must be accomplished without stubbing the vane tips. To that end, the axis of shaft 20 lies in a plane which encompasses the axis of rotor 12 and also encompasses the end surface 100 of fixed seal block segment 76A; similarly, the axis of pivot shaft 22 lies in a plane which encompasses the axis of rotor 12 and also encompasses the end surface 102 of fixed seal block segment 78A. The contours of inner surfaces 80A and 80B in the areas where the fixed segment 76A and the movable segment 76B are adjacent to each other are contoured to be arcs of the same circle so that the point 104 on movable segment 76B always moves away from a periphery of rotor 12 when the seal block segment is being moved from the FIG. 3 to the FIG. 4 position. Thus, point 104 (which is actually a corner surface extending the length of the seal block segment perpendicular to the plane of the paper), is never closer to the periphery of rotor 12 than inner surface 80 and thus never presents any interference with the vane tips. Similarly, adjoining surfaces 82A and 82B also contoured to be arcs of the same circle so that pump 106, which is also a corner surface extending the length of the seal block segment, is never any closer to the periphery of rotor 12 than surface 82A when movable segment 78B is being moved from the FIG. 3 to the FIG. 4 position so that there is no interference between the vane tips and point 106.

As can best be seen in the FIG. 3 embodiment, a space 108 is present between the backside of each movable seal block segment and housing 110 when the movable seal block segments are in the position shown in FIG. 3, and that space exists to some degree at any loaded position of the seal block elements. Pressurized fluid is introduced into the spaces 108 by leaking past the opposed end surfaces of the fixed and movable seal block segments, and the pressurized fluid is then allowed to slowly leak back to the fuel inlets along a narrow flow path between end surfaces 112 on the housing and end surfaces 114 on the movable seal block segments. In order to patrol and limit the leakage along that flow path, end surfaces 112 and 114 are arcs of concentric circles, and the separation therebetween is extremely small. The presence of the pressurized fluid in spaces 108 provides a force balance across the movable seal block segments so that very little actuating force is required to change the position of the movable segments.

A boxed cam linkage mechanism, including a box 116 in which is located a cam 118 mounted on a rotatable actuating shaft 120, is employed to selectively position the seal block segments. Rods 122 extend from opposite sides of box 116, and arms 122 are pivotably connected to links 124, each of the links 124 being in turn fixed to pivot shafts 20 and 22. Assuming that the box cam linkage mechanism is in the position shown in FIG. 3, counterclockwise rotation of shaft 120 (as indicated by the arrow) will, through reaction of cams 118 with box 116 and then through arms 120 and links 124, result in movement of the movable seal block segments 76B and 78B from the fully loaded position of FIG. 3 toward the fully unloaded position of FIG. 4. Of course, it will be understood that the movable seal block segments can be caused to assume any position between the fully loaded position and a fully unloaded position and can be moved between two extremes as desired by selective clockwise or counterclockwise rotation of shaft 120 with a minimum of actuating force being required because of the pressure balance across the seal block segments resulting from the introduction of fluid to spaces 108.

While a preferred embodiment has been shown and described, various modifications and substitutions may be made without departing from the spirit and scope of this invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.

Claims

What is claimed is:

1. A variable displacement vane pump including:

a rotor;

a plurality of slots spaced around the periphery of said rotor;

a vane in each of said slots, said vanes extending beyond the periphery of said rotor and being movable in said slots to vary the extension of said vanes beyond said periphery;

vane retention means in each of said slots;

a pair of seal block elements spaced about said rotor, at least one of said seal block segments being pivotally mounted for pivotal movement with respect to said rotor, said seal block elements being physically spaced apart with spaces between said elements defining radial inlet passages for delivering fluid radially with respect to the rotor for pumping;

axial inlet passages for delivering fluid axially with respect to the rotor for pumping, said axial inlet passages spanning the space between said seal block segments and spanning said radial inlet passages;

discharge passages for discharging fluid from said pump;

a contoured inner surface on said one of said seal block elements, said contoured surface being spaced from the periphery of said rotor and cooperating with said vanes to determine the movement of said vanes in said slots during rotation of said rotor; and

means connected to at least said one seal block element to pivotally move said one seal block with respect to said rotor to vary the stroke of said vanes and vary the discharge volume of said pump.

2. A variable displacement vane pump as in claim 1 wherein:

at least part of said contoured seal block element is spaced from the periphery of said rotor a distance greater than the maximum extension of any of said vanes beyond said periphery.

3. A variable displacement vane pump as in claim 1 wherein:

each of said seal block elements is pivotally mounted on an axis lying in a common plane including the axis of the rotor and in approximate alignment with the resultant of forces acting on the elements.

4. A variable displacement vane pump as in claim 1 wherein:

at least part of the contoured inner surface on each of said seal blocks is contoured to form a cam surface for said vanes.

5. A variable displacement vane pump as in claim 1 wherein:

said inlet passages are approximately diametrically opposed to each other and said discharge passages are approximately diametrically opposed to each other.

6. A variable displacement vane pump as in claim 1 wherein:

each of said seal block elements is pivotally mounted for movement with respect to said rotor; and wherein:

each of said seal block elements has a contoured inner surface spaced from the periphery of said rotor and cooperating with said vanes to determine the movement of said vanes in said slots during rotation of said rotor;

each of said contoured inner surfaces having, in order, an entrance portion, a seal arc at least equal to the spacing between two adjacent vanes, a discharge arc, a seal arc at least equal to the spacing between two adjacent vanes, and an exit portion; and including

means connected to each of said seal block elements to pivotally move each of said seal block elements with respect to said rotor to vary the stroke of said vanes and vary the discharge volume of said pump.

7. A variable displacement vane pump as in claim 6 wherein:

the exit portion of each of said seal block elements is physically disconnected and spaced from the entrance portion of the other of said elements; and wherein

the entrance section of each of said seal block elements is spaced from the periphery of said rotor a greater distance than the maximum extension of said vanes beyond the periphery of said rotor.

8. A variable displacement vane pump as in claim 7 wherein:

at least part of each of said entrance portions is contoured to provide a ramp sloping toward said rotor, each of said seal arcs is contoured to minimize vane displacement during vane traversal of said seal arcs, said discharge arc is contoured to slope toward said rotor to provide a cam surface for moving each vane inwardly in its slot during vane traversal of said discharge arc, and said exit portion is contoured to provide a ramp sloping away from said rotor.

9. A variable displacement vane pump including:

a rotor;

a plurality of slots spaced around the periphery of said rotor;

a vane in each of said slots, said vanes extending beyond the periphery of said rotor and being movable in said slots to vary the extension of said vanes beyond said periphery;

vane retention means in each of said slots;

a pair of seal block elements spaced about said rotor, each of said seal block segments having a fixed segment and a movable segment pivotal with respect to said fixed segment and said rotor about a predetermined axis, said seal block elements being physically spaced apart with spaces between said elements defining radial inlet passages for delivering fluid radially with respect to the rotor for pumping;

axial inlet passages for delivering fluid axially with respect to the rotor for pumping, said axial inlet passages spanning the space between said seal block segments and spanning said radial inlet passages;

discharge passages for discharging fluid from said pump; each of said fixed seal block segments and each of said movable seal block segments having contoured inner surfaces spaced from the periphery of said rotor and cooperating with said vanes to determine movement of said vanes in said slots; and

means connected to each of said movable segments to pivotally move each of said movable segments with respect to said rotor to vary the stroke of said vanes and vary the discharge volume of said pump.

10. A variable displacement vane pump as in claim 9 wherein:

said inlet passages are approximately diametrically opposed to each other and said discharge passages are approximately diametrically opposed to each other.

11. A variable displacement vane pump as in claim 9 wherein:

the inner surface of each of said fixed segments is contoured to define a seal arc at least equal to the spacing between two adjacent vanes; and wherein

the inner surface of each of said movable segments is contoured to define a discharge arc and a seal arc at least equal to the spacing between two adjacent vanes.

12. A variable displacement vane pump as in claim 11 wherein:

said movable segments are movable between a fully loaded position of the pump and an unloaded position of the pump.

13. A vane pump as in claim 12 wherein each of said movable segments in said fully loaded position abuts its associated fixed segment in a predetermined plane; and wherein

each of said movable segments is pivoted about an axis in said predetermined plane.

14. A vane pump as in claim 13 wherein:

the axis of said rotor is in each of said predetermined planes; and wherein

the contours of the adjacent inner surfaces of said fixed segment and said movable segment of each seal block are arcs of the same circle.

15. A vane pump as in claim 13 wherein:

said discharge arc of each movable segment in any loaded position of said pump slopes toward said rotor to cam said vanes inwardly with respect to said rotor during vane traversal of the discharge arc; and wherein

each of said seal arcs of each movable segment is contoured to minimize vane displacement during vane traversal of the seal arcs.

16. A vane pump as in claim 15 including:

means for introducing fluid from the discharge arc of a movable segment to a surface of said movable segment opposed to the contoured surface thereof.