US3547562A - Variable displacement vane pump - Google Patents

Description

Dec. 15, 1910 E, @YNOR f 3,547,562

VARIABLE DISPLACEMENT VANE PUMP Filed Feb. 4, 1969 2 Sheets-Sheet 1 INVENTOR J.E, CYGNOR BYMMM/QW ATTORNEYS Dec, 15, 1970 J. E. CYNOR 3,547,562

VARIABLE DISPLACEMENT VANE PUMP Filed Feb. 4, 1969 2 Sheets-Sheet 2 United States Patent 3,547,562 VARIABLE DISPLACEMENT VANE PUMP John E. Cygnor, Middletown, Conn., assignor to Chandler Evans Inc., West Hartford, Conn., a corporation of Delaware Filed Feb. 4, 1969, Ser. No. 796,422 Int. Cl. F04c 15/04, 1/00 US. Cl. 418-31 7 Claims ABSTRACT OF THE DISCLOSURE BACKGROUND OF THE INVENTION Field of the invention This invention relates to the field of vane pumps. More particularly, this invention relates to the field of variable displacement vane pumps.

Description of the prior art Present vane pumps, either of the fixed displacement type or of the variable displacement type are known in the art. The most current 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) are con trolled by varying the eccentricity of the sealing block with respect to the rotor center line. This traditional variable displacement vane pump is a single acting pump in that it has one inlet and one discharge. Although mechanically simple, this 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 inlet 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 feature 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 require a design of increased load capability, thus leading to an undesirably heavy pump configuration. The vane dynamics problem severely limits the vane stroke and rotationel speed. Abrupt changes in the direction of radial motion of the vanes results in high dynamic stresses which lead to sealing problems between the vane and the eccentric seal block. Furthermore, 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 Patented Dec. 15, 1970 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 systern, such as requiring tungsten carbine vanes, seal blocks and end plates.

The traditional approaches in the art to solving these 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 are known in the art having a double acting design, i.e. two pairs of opposed inlets and discharges, and having contoured sealing blocks to control vane movement. 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 block. However, this alternative is actually an abandonment of the objective rather than a solution because it completely eliminates the variable displacement capability of the pump.

SUMMARY OF THE INVENTION The present invention is a variable displacement vane pump having minimal rotor bearing loads and having controlled radial vane movement to minimize instability and dynamic loading of the vanes. The present invention incorporates for the first time in a variable displacement vane pump a double acting inlet and discharge feature and a contoured seal block feature, both of these features cooperating and contributing to the minimizing of rotor bearing load and vane dynamic loading. The incorporation of these features for the first time in a variable displacement vane pump is realized through a seal block which is split into two segments having tongue and groove interlocks. The two seal block segments are movable with respect to each other and with respect to the axis of the pump rotor, the position of the seal block segments setting the net vane radial displacement as desired between the limits of full stroke and zero stroke for the pump vanes which cooperate with contoured surfaces on the seal blocks. The tongue and groove interlocks serve as bridges to guide the vanes from one sealing block element to the other sealing block element when the sealing block elements are separated, i.e. moved away from each other, to reduced flow positions. In order to eliminate any interference between the tips of the vanes and the ends of the sealing block segments, the bridge between the segments is tangential to the ends of the segments at all times. The double acting inlet and discharge port arrangement requires four seal areas which are positioned so that the bridges are in areas of zero pressure differential.

Stepped vanes are used to achieve optimum vane tip to seal block pressure loading while the vanes are transversing the various inlet, seal and discharge arcs. Inlet pressure, discharge pressure, or a combination of both may be introduced into the vane step areas to control the pressure loading between the vanes and the seal blocks to assure mechanical efliciency and reduce Wear.

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 variable seal blocks.

Still another object of the present invention is to provide a novel and improved vane pump having a variable displacement capability and incorporating features heretofore available only in fixed displacement vane 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 the vane pump of the present invention with the end plate removed.

FIG. 2 is a view similar to FIG. 1 showing the vane pump in an unloaded position.

FIGS. 3A and 3C are views of the rear and front end plates, respectively, removed from the pump.

FIG. 3B is a perspective view showing the casing and wear blocks of the pump of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIG. 1, the vane pump of the present invention is shown in a front elevation view with the front end plate removed. It will be understood to those skilled in the art that the pump 10 as shown in FIG. 1 must be contained in a suitable housing, such as a tubular bore, during operation. It will also be understood that the axial length of pump 10, i.e. its dimension perpendicular to the plane of the paper as shown in FIG. 1 will depend on the design requirements of the particular installation in which the pump is to be employed.

Pump 10 has an outer casing 12 within which the active elements of the pump are contained. It also has a pair of seal blocks 14 and 16 each of which has fiat upper and lower surfaces 18 and 20, respectively, which mate with the ride on fiat surfaces 22 and 24 on the interior of casing 12. Seal blocks 14 and 16 are movable within casing 12 along these mating fiat surfaces, and spaces 26 and 28 between the outer surfaces of seal blocks 14 and 16, respectively, and casing 12 is provided to accommodate this outward movement of the seal blocks.

A rotatable shaft 30 is centrally positioned with respect to casing 12, rotatable shaft 30 being supported for rotation by bearing surfaces in the pump end plates which will be described in connection with FIGS. 3A and 3C. A rotor element 32 is fixed to shaft 30 for rotation therewith, rotor 30 extending the full axial length of the pump between the end plates of FIGS. 3A and 3C. Rotor 32 has a plurality of radial slots 34, and a vane 36 is positioned in each of the slots 34. Although only four slots and vanes are shown in FIG. 1, it will be understood that the four slots and vanes are shown only for purposes of illustration; the slot and vane structure extends entirely around rotor 32 with the slots and vanes being spaced equidistantly around the entire 360 of the rotor. It will also be understood that the slots and vanes extend the full axial length of rotor 32. The slots and vanes are stepped as shown to provide upper and lower pockets 38 and 40 between the slots and the vanes, and each vane is movable in its slot radially with respect to shaft 30 so that the size of pockets 38 and 40 may vary as the vanes rotate with rotor 32.

The inner surfaces 42 and 44 of seal blocks 14 and 16 are contoured so that parts thereof are circular arcs while other parts thereof form cam surfaces which interact with the vanes to cause the vanes to move in and out with respect to the slots.

A specifically defined relationship exists between the circular and cam arcs on the inner surfaces of the sealing blocks and the inlet and discharge ports on the end plates. The areas outlined by the arcuately shaped dotted lines in FIG. 1 indicate the inlet and discharge passages on the rear end plate: passage 46 is the major inlet passage; passage 48 is the major discharge passage; passage 50 is the minor inlet passage; and passage 52 is the minor discharge passage. The space between any two adjacent passages constitutes a transfer are as indicated by the double ended arrows 54, 56, 58 and 60. These transfer arcs are the areas between the inlet and discharge passages wherein the fluid between any two vanes must be sealed to prevent communication between adjacent end plate inlet and discharge passages. Accordingly, the contour of the inner surface of the sealing blocks in the areas coextensive with the designated transfer arcs are circular arcs so that there is 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 a point at the tip of one vane to a corresponding point at the tip of an adjacent vane. The circular contour of the sealing block in the area of each transfer are and the stated minimum arc length of each transfer are 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 42 and 44 of the sealing blocks in the area of the inlet and discharge passages 46, 48, 50 and 52 are all cam surfaces in that the distance between these surfaces and the outer periphery of rotor 32 changes along the arcs of these passageways. Therefore, there is a net vane displacement as these inlet and discharge passages are traversed by the vanes resulting in a fluid discharge as each of the discharges is traversed and a fluid intake as each of the inlet passages is traversed.

At this point, an example of the operation of the pump as the vanes traverse the vane track or guide defined by the inner surfaces of the sealing blocks will be described. Assuming that shaft 30 and rotor 32 are rotating clockwise, the analysis will begin at the edge of major passage 46 at its juncture with transfer are 58. Bearing in mind that the contour of surface 44 over the length of transfer are 58 is a circular arc, the contour changes to a cam contour wherein the surface 44 is receding from rotor 32 as inlet passage 46 is traversed in a clockwise direction so that the separation between surface 44 and rotor 32 increases at successive clockwise stations along the arc of inlet passage 46. Assuming that the outer ends of vanes 36 are caused to remain in contact with the inner surfaces of the sealing blocks, either by centrifugal or other forces, each vane 36 is caused to move within its slot radially outward from the axis of rotor 30 as the vane traverses the arc of inlet passage 46, 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. There is thus a net increase in the volume defined between the end plates and any two vanes as the vanes move in a clockwise direction along the arc of inlet passage 46, and thus fluid (such as fuel) made available to the inlet passages 46 at each of the end plates is drawn into that expanding volume as the vanes traverse the arc of the inlet passages 46.

As each vane reaches the end of the arc of inlet passage 46, it enters into the area defined as transfer are 60. Bearing in mind that the inner surface of the sealing block encompassed by transfer are 60 is a circular arc and that the arc length of transfer are 60 is at least equal 5 to or greater than one vane spacing, the volume between any two vanes (sometimes referred to as intervane volume) remains constant in traversing are 60, and the volume is at least momentarily sealed from inlet passage 46 and discharge passage 48. The fact that the contour of the inner surface of the sealing block is a circular arc along transfer are 60 produces the result that there is no attempt to compress the incompressible fluid contained in the volume between two successive vanes when traversing transfer are 60, thus avoiding a serious overload on the pump. Also, there is no inward or outward movement of the vanes as they traverse transfer are 60, and thus sliding friction loads between the vanes and their slots are avoided as the vanes traverse are 60.

As each vane passes through transfer arc 60 it passes through a bridge area between seal block 16 and seal block 14 (the design characteristics and features of this bridge area being described more fully hereinafter), and the vanes then enter into the are determined by major discharge passage 48. The inner surface 42 of seal block 14 is a cam contour throughout the arc length of discharge passage 42, the contour being such that surface 42 advances toward rotor 32 as discharge passage 48 is traversed in a clockwise direction. Thus, the separation between surface 42 and rotor 32 diminishes as the discharge passage is traversed in a clockwise direction, and each vane is cammed inwardly in its slot as the vane traverses discharge passage 48.

Presuming that discharge passage 48 is exposed to a load of some sort (such as, for example, a fuel nozzle or a pressurizing valve) the fluid in an intervane volume will become pressurized as the fluid in the intervane volume traverses transfer arc 60 and becomes exposed to discharge passage 48. The pressurized fluid then coming within the arc of discharge passage 48 will then be forced out through the discharge passage as a result of the vanes being displaced inwardly on their slots by the camming action of the cam contour of surface 42 along the arc of discharge passage 48. 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 48, 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 48 and are cammed inwardly.

After traversing discharge passage 48, each vane then enters into transfer are 54. The inner surface of sealing block 14 within transfer arc 54 is, like transfer are 60, a circular are so that there is no inward or outward displacement of the vanes as they traverse are 54. The are width of are '54 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 are 48 toward the beginning of inlet are 50. Thus, leakage between discharge passages 48 and inlet passages 50 is avoided.

As each vane continues its clockwise movement, it then enters into the are of minor inlet passage 50. As with major inlet passage 46, the contour of the inner surface of seal block 14 within the arc of inlet passage 50 recedes from rotor 32 as inlet passage 50 is traversed in a clockwise direction. Thus, the inner surface of seal block 14 within the arc of inlet passage 50 is a cam surface which results in an increasing intervane volume and a drawing of fluid into the increasing intervane volume as the vanes traverse inlet are 50 in a clockwise direction.

Immediately after leaving inlet are 50, each vane passes through another area bridging seal blocks 14 and 16 and enters into another transfer are 56. Transfer are 56, like transfer arcs 54 and 60 previously described, is of circular contour and is at least equal to or greater than one vane spacing so that there is no vane displacement while traversing the transfer are and so that the intervane spacing between any two vanes is at least momentarily sealed from both inlet passages 50 and discharge passages 52 to prevent leakage therebetween.

After traversing transfer are 56, each vane then enters into the arc defined by minor discharge passage 52. The contour of the inner surface of seal block 16 when in the arc of discharge passage 52 is a cam surface which advances toward rotor 32 as the are is traversed in a clockwise direction. Thus, the separation between the inner surface of seal block 16 and rotor 32 diminishes as discharge passage 52 is traversed in a clockwise direction thereby resulting in an inward displacement of each vane in its slot as the vane traverses discharge passage 52. In a manner similar to the previous description with respect to discharge passage 48, the fluid in an intervane volume traversing transfer are 56 becomes pressurized as the intervane volume comes under the influence of discharge passages 52, and that pressurized fluid is then forced out of the discharge passages 52 in each end plate as the vanes are displaced inwardly in their slots and the intervane volume decreases during the traversal of the arc of discharge passage 52.

After passing through the arc of discharge passage 52, each vane then enters into transfer are 58 wherein the contour of the inner surface of sealing block 16 is a circular arc of an arc width at least equal to or greater than one vane spacing. Thus, as previously described with respect to transfer arcs 60, 54 and 56, transfer are 58 is an area of zero vane displacement and comprises at least a momentary seal for each intervane space between discharge passage 52 and inlet passage 46 to prevent leakage therebetween.

The foregoing illustrative description of the operation of the pump as rotor 32 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 42 and 44 of seal blocks 14 and 16. 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 occurring 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 are located at the rear end plate of the pump, the read end plate being shown in FIG. 3A. The front end plate, which has inlet and discharge passages identical to the rear plate and which is shown in FIG. 30, has been removed to show the elements depicted in FIG. 1, but it will be understood that both the front and rear end plates would both be fixed to opposite ends of casing 12 and would butt against the opposed end surfaces of rotor 32 and vanes 36.

As can be seen from FIG. 1, major discharge passage 48 and minor discharge passages 52 are approximately diametrically opposed, and major inlet passages 44 and minor inlet passages 50 are also approximately diametrically opposed. The incorporation of two sets of inlet and discharge passages constitutes the pump as a double acting pump, and the approximate diametrically opposed positioning of the discharge and inlet passages results in a substantial force balance to minimize loads on the bearings which support rotor 30. The designation of the inlet and discharge passages as major and minor corresponds to the relative volumes of fluid taken in and discharged to each set of inlet and discharge passages. The spacing requirements for the four transfer arcs to accomplish the desired sealing operation and the preferred location of the bridge areas between seal blocks 14 and 16 in areas of zero pressure differential result in unequal flow volume capacities between the discharge passages 48 and 52 if the pump is to have a maximum flow capacity, and thus there must be some unbalanced load transmitted to shaft 30. However, this load is minimal compared to the unbalanced loads heretofore present in single acting variable displacement pumps. Also, the smooth contour transitions along the inner surface of seal blocks 14 and 16 result in minimum vane dynamics problems. As will also be discussed hereinafter in connection with the bridge structure between the seal block segments, is that smooth transition and minimal vane dynamics is also preserved regardless of the relative position of the seal blocks in any position between maximum pump fiow and minimum pump flow.

Referring now to FIG. 2, the pump of the present invention is shown with the seal blocks 14 and 16 moved apart to a position where spaces 26 and 28 are fully taken up and the pump is fully unloaded. If desired, movement of just one of the seal blocks could be used to unload the pump. Of course, it will be understood that the seal blocks could be caused to assume any position between the loaded position of FIG. 1 and the unloaded position of FIG. 2 for partial loading, and any appropriate actuating and control mechanism may be employed to accomplish the desired movement of the seal blocks. As can be seen from a comparison of FIGS. 1 and 2, each seal block has a projection 62 located in a recess 64 in casing 12 to serve as a physical stop to limit movement of the seal blocks toward each other when the blocks are moving from the FIG. 2 position to the FIG. 1 position. The seal blocks must either be designed to stop on themselves or incorporate physical stops such as projections 62 in order to prevent destruction interference between the seal blocks and the vanes as the seal blocks are moved to the fully loaded position of FIG. 1.

Referring now to both FIGS. 2 and 3B, the spacing between seal block segments 14 and 16 is spanned by a bridge comprised of a tongue 66 projecting from one of the seal block segments and engaging a groove 68 in the other of the seal block segments. The perspective view of FIG. 3B shows the pump elements including casing 12, and the seal block segments 14 and 16, and it can best be seen in FIG. 3B that the tongue and groove interlocking bridge structure is located at a midpoint along the axial length of the seal blocks. Although only one of the tongue and groove elements can be seen in FIG. 3B, it will be understood that there are two such bridges located 180 apart and spanning both gaps between the seal block segments, as indicated in FIG. 2.

The inner surface 70 of each of the tongues 66 is a fiat surface along the entire length and width of the tongue element, i.e. inner surface 70 of each tongue defines a flat plane. The flat plane of inner surface 70 is arranged to be tangent to surfaces 42 and 44 at the ends of the seal blocks at each of the bridge areas regardless of the degree of separation between seal block elements 14 and 16. The tangency of bridge surfaces 70 to the contours of the inner surfaces of both of the seal blocks insures that the vanes will be guided from one seal block to the other without any interference or stubbing of the vane ends on the end surfaces of the seal block segments. In other words, as a vane leaves one of the seal block surfaces it will come into contact with and be guided by tangent bridge surface 70 until the vane tip reaches the other seal block segment, at which time it will be traveling tangent to the inner surface of that other seal block and will be placed into contact with and be guided by the inner surface of that other seal block segment. Of course, if the seal block segments are abutting so that there is no spacing therebetween, then there will be a direct transfer from one seal block surface to the other. However, except in that one condition where the seal block segments are abutting, the transition of the vanes from the inner surface of one seal block to the inner surface of the other seal block is guided by surface 70 tangent to both the inner surfaces.

Referring now to FIGS. 3A and 3C, the front and rear end plates 72 and 74, respectively, are shown disconnected from the pump structure. The inner surfaces of each of the end plates is shown in FIGS. 3A and 3C, and it will be understood that these inner surfaces abut the ends of rotor 32 and the vanes when the end plates are in proper position. The inlet and discharge passages 46, 48, 50 and 52 in each of the end plates can be seen in FIGS. 3A and 3C, and each end plate has a bearing surface 76 to receive an end of shaft 30. It will be understood that the end plates are either fastened to outer casing 12 or retained by other suitable retention means. A plurality of transfer passages 73 are shown in each of the end plates, and these transfer passages serve to connect the inlet and discharge passages to the pockets 38 and 40 between the vanes and their slots. These transfer passages serve to provide fluid at either inlet or discharge pressure to the pockets to provide desired forces behind the vanes in accordance with the particular design requirements of the pump installation. The particular loading will vary as the vanes advance from station to station around the pump, but it will be understood that any net loading which may exist will always be in a radially outward direction behind each of the vanes to assist maintaining the vanes sealed against the inner surfaces of the sealing blocks.

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

What is claimed is:

1. A variable displacement vane pump including:

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

a vane positioned in each of the slots, the vanes being movable in the slots;

a pair of rigid seal block segments circumscribing the rotor and the vanes and being movable radially inwardly and outwardly with respect to the rotor and with respect to each other, each of the seal block segments having a contoured inner surface confronting the vanes and the rotor and cooperating with the rotor and vanes to define intervane inlet and discharge volumes for maximum pump displacement at the radially inward position of the block segments and minimum pump displacement at the radially outward position of the block segments, the confronting ends of the circumscribing block segments having cooperating tongue and groove portions, the inner surface of at least part of each of the tongue portions being flat and said tongue portions being enveloped at the projecting ends by at least the end of the cooperating groove portion at the radially outward position of the segments.

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

said inner contoured surface on each of said seal block segments includes at least one contoured inlet portion and one contoured discharge portion, the portions being separated by a circular arc portion.

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

the end of the inner surface of each of the groove portions is tangent to the flat inner surface of the cooperating tongue portion at each position of the radially movable seal block segments.

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

the inner surfaces of the tongue and groove portions extend continuously from the adjacent contoured surfaces of the seal block segments.

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

said inner contoured surface on each of said seal block segments includes at least one length of a circular arc and at least one length contoured to act as a cam surface for said vanes.

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

said contoured surface on one of said seal block segments includes one length of a circular arc and two lengths contoured to act as cam surfaces for said vanes; and wherein said contoured surface on the other of said seal block segments includes three lengths of circular arc and two lengths contoured to act as cam surfaces for said vanes.

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

two inlet passage means for introducing fluid to said pump; and two discharge passage means for discharging fiuid from said pump;

said inlet and discharge passage means being in flow communication with intervane spaces at selected areas of said contoured lengths, and said circular arcs cooperating with said vanes to seal the discharge passages from inlet passages.

References Cited UNITED STATES PATENTS Balsiger 103-120(PA) Calzoni 103-120(PA) Warman 103120(PA) Kendrick 103-120(PA) Pike 103-120(PA) Ferris 103120(PA) Ferris 103-120(PA) Stockett, Jr. 103-120(PA) Mitchell et a1. 103l20(PA) CARLTON R. CROYLE, Primary Examiner 15 W. J. GOODLIN, Assistant Examiner US. Cl. X.R.

Images