US3025802A - Rotary pump - Google Patents

Description

ROTARY PUMP Filed Apri1 8,- 1957 4 Sheets-Sheet 1 INVENTOR. ROBERT J. BROWNE BY f ATTOR EY March 20, 1962 R. J. BROWNE 3,025,802

ROTARY PUMP Filed April 8, 1957 4 Sheets-Sheet 2 Fig. 4

lNVENTOfi.

ROBERT J. BROWNE Fig. 5 BY March 20, 1962 Filed April 8, 1957 R. J. BROWNE ROTARY PUMP 4 Sheets-Sheet 5 INVENTOR. ROBERT J. BROWN E BY 4/ $52M; Y

March 20, 1962 R. J. BROWNE 3,025,802

ROTARY PUMP Filed April 8, 1957 4 Sheets-Sheet 4 IN V EN TOR. ROBERT J. BROWNE ATTORNEY 3,025,302 ROTARY PUMP Robert J. Browne, St. Clair Shores, Mich, assignor to Eaton Manufacturing Company, Cleveland, Ohio, a corporation of Ohio Filed Apr. 8, 1957, Ser. No. 651,545 27 Claims. (Cl. 103-135) This invention relates to a rotary pump of the type wherein a plurality of pumping elements are drivingly disposed in a rotor member contained within a housing provided with a cam means encompassing the rotor, and which provides a sealing surface and a working surface for the pumping elements. Rotary pumps of this type heretofore known have not operated satisfactorily at pres sures in excess of 200 or 300 psi. In automotive applications of pumps of this type, it is necessary to provide a pumping means which possesses satisfactory flow characteristics over a much higher pressure range and a wide speed operating range.

The structure described herein is illustrated as a roller pump having a plurality of rollers disposed in notches or slots in the rotor in a manner such that the rollers are free to move circumferentially an appreciable amount with respect to the rotor when the rollers are in a radially outward position and are substantially confined when the rollers are disposed radially inward. It is to be noted, however, that some of the novel features of the structure disclosed herein can be utilized with a pumping structure having other type pumping elements, such as substantially rectangular shaped slippers, vanes, etc., the only requirement being that the pumping elements be moved with respect to the rotor. A cam means is disposed in encompassing relation to the rotor and pumping elements and is provided with a constant radius portion which extends across the arcuate surface between the end of the discharge port and the beginning of the intake port to provide a sealing surface or arc, and a further constant radius portion of a greater radius which extends substantially across the arcuate portion between the end of the intake port and the beginning portion of the discharge port to provide a pumping surface or arc. The developed cam surface extending from the beginning of the intake port substantially to the end of the intake port has an intermediate portion of greater radius than the radius of the constant arc portion substantially between the end of the intake port and the beginning of the discharge port so that when the charge of oil trapped between adjacent pumping elements is traversed through the intake arc, there is an ove-rfilling before that volume is communicated to the pumping arc. This feature is to insure that the pump will fill completely, thus eliminating cavitation and noise. Also, this arrangement results in a slight precompression of the entrapped fluid which collapses any air bubbles present in the fluid.

Another novel aspect of this pump is the arrangement of the discharge port with respect to the pumping arc. The arcuate length of the pumping arc is equal to the arcuate distance measured on the cam are between adjacent pumping elements. When the leading pumping element commences to move inwardly on the cam surface, the entrapped volume between the leading and trailing pumping elements is decreased, resulting in a further increase in pressure of the oil which is entrapped between the adjacent pumping elements. The ports are arranged for optimum conditions for the most frequently used operating condition. However, there will be a tendency to overcompress this entrapped volume at other speeds and viscosities. At this time, the leading pumping element will be moved away from the trailing portion of the rotor slot as soon as pressure in excess of that in the discharge port is created, thereby providing additional communi- 3,025,802 Patented Mar. 20, 1962 cation between the entrapped volume and the discharge means. This check-valve action limits the pressure buildup in the entrapped volume to a pressure slightly in excess of the pressure existing in the discharge means.

An object of this invention is to provide a fluid pumping means which has optimum operational features at both low and high speed and high and low fluid pressure throughout the viscosity range of the fluid.

Another object is to provide means to insure complete filling of the pump.

A further object is to provide pumping elements that move outwardly on the inlet stroke Without the use of springs or exposure of the pumping element to discharge pressure.

A still further object is to provide a pump structure wherein a rotor type seal or a pumping element type seal can be utilized without any structure modifications in the pump.

Another object is to provide means to eliminate mechanical and fluid noises in the pump.

These and other objects and advantages will become more apparent from the following detailed description of the device and from the accompanying drawings wherein:

FIGURE 1 illustrates the external pump housing viewed from the cover side of the pump.

FIGURE 2 is a section taken on 2-2 of FIGURE 1.

FIGURE 3 is an internal end view of the pump body taken on 33 of FIGURE 2 but with the pump rotor removed.

FIGURE 4 is a section of the pump body.

FIGURE 5 illustrates the internal side of the pump cover.

FIGURE 6 is a section of the pump cover.

FIGURE 7 is a schematic showing of superimposed portions of the pump with a portion of the rotor rotated to two different positions.

FIGURE 8 is a view of the rotor and body with the cover removed, and

FIGURE 9 is a partial view of a modification of FIG- URE 8.

Referring to the drawing for a more detailed description of the device, a pump 10 is provided with a body portion 12 and a cover portion 14 disposed adjacent thereto. The body and cover are adapted to be held in assembled relation by a plurality of bolts or studs 15 and locating pins 16. A rotor shaft having end portions 18 and 20 is supported in the body and cover portions by' means of sleeve hearings or bushings 22 and 24, respectively. An intermediate portion of the rotor shaft has keyed thereto a rotor 26 so that rotation of the rotor shaft results in rotation of the pump rotor. A cam ring 27 having a cam surface or peripheral wall 27 is receivable within the working chamber provided in the body 12 and is fixed from rotation with respect to the body portion by a suitable pin means. It is to be understood that the cam surface can be formed as an integral part of the pump body and is illustrated as a separate ring meansfor ease of manufacture.

The body portion 12 is provided with a fluid inlet conduit 28 which is communicable through a passage 48 with the intake ports 30 and 32 arranged in an end wall of the working chamber. Discharge ports 34 and 36 are also provided in the working chamber end wall and are comprised of arcuate recesses in the end wall of the pump body pumping chamber and are disposed opposite to discharge ports formed in the cover member, to be hereinafter described. Cam ring 27 is provided with an arcuately extending cutout portion 37 which extends circumferentially a short distance past the end of discharge port 54;. An opening 38 is provided in the sealing face of body portion 12 and communicates with an opening 49 formed in the sealing face of cover 14. A bore 41 is also provided in the cover 14 which is adapted to receive a flow control valve mechanism. The details of the flow control valve mechanism form no part of the present invention and it is of a structure similar to that disclosed in US. Patent a t-2,752,853, patented July 3, 1956. A passage 42 is in communication with opening 40, bore 41 and a smaller passage 43 which communicates with intake port 32'.

The cover member 14 also has provided therein intake ports 30 and 32' and discharge ports 34 and 36. When the body portion and cover portion are assembled, ports 30, 32, 34, and 36 are disposed oppositely to ports 30, 32', 34', and 36, respectively. Also disposed in the cover portion as shown in FIGURE 5, is a communicating portion 44 which provides for flow of fluid from the discharge ports 34' and 36 to the flow control valve disposed in bore 41, and thence to a discharge conduit 46 which is also formed in the cover member.

The communicating passage 48 is provided in the body member to provide for flow of fluid from intake conduit 23 and opening 38 to intake ports 39 and 32. When the flow requirements are such that only a portion of the discharge is required, the flow control valve (not shown) functions to bypass the remainder of the discharge through passage 42 to passage 43 and inlet port 32 and through opening 40 in the cover and opening 38 in the body, back to communicating means 48 which is in communication with the inlet ports Stl and 32. It is to be noted however, that the novel aspects of this pumping mechanism, to be hereinafter described, can be utilized without a flow control or pressure relief valve means, and such flow control valve means is shown merely to illustrate the novel pump device in an exemplary structure.

FIGURE 7 is a composite view showing rotor 26, cam surface 27, and the intake and discharge ports which are formed in the body member. This view is merely a schematic representation of the novel structure and is not intended to be an actual representation along any given section. For descriptive purposes, a portion of rotor 26 is shown at one position spanning arc DE and in another position spanning arc AB. FIGURE 8 shows the complete rotor and for purposes of description, reference Will be had to FIGURES 7 and 8 in the following explanation of the pump. Referring to FIGURE 7, cam surface 27' is provided with an inner-peripheral surface 66 which is comprised of a constant arc portion AB having a radius R which is referred to as a seal arc.

Arcuate portion B-C is a developed cam surface having a radius R at the point B with the radius becoming progressively larger as the cam surface approaches point C until it reaches the maximum radius R at point C. Arcuate portion CD is also a developed cam surface with the maximum radius R at the point C progressing to a minimum radius R, at point D. The arcuate portion BD is designated as the intake arc. A pumping are portion DE has a constant radius R and a discharge are portion EA has a maximum radius R at point E, diminishing progressively to a minimum radius R at point A. A plurality of equally spaced slotted portions 68 are provided in rotor 26. Each of the slots is comprised of a trailing wall portion 72 and a leading wall portion 74 which are disposed in a manner such that when pumping element 70 is in the radially inner position, the pumping element is substantially confined, but when element 70 is in a radially outer position, it is free to move circumferentially with respect to the rotor along the walls of the cam surface. By using a rotor element with divergent slot walls, it is possible to design a slot that can be machined by hobbing or similar generated cutting means which is more economical than machining parallel sided slots. Although the divergent slot design is preferable for this and other reasons to be hereinafter discussed, many of the novel features disclosed hereinafter would also apply to devices using parallel sided slots.

For a pump having a 2.00" diameter rotor, the total clearance betweent he pumping element and the slot walls when the pumping element is in contact with the cam surface at the radius R is on the order of This clearance would vary for an increased or decreased rotor diameter.

Also, by disposing the slot walls at an outwardly divergent angle, the wail clearance between the slot and the pumping element is gradually increased as the pumping element progresses along the cam rise on the intake arcuate portion which allows the fluid to be moved outwardly by centrifugal force to the radially outer portion of the volume to be filled, thus aiding in the filling of that volume. This filling action occurring from the root of the slot also provides a force to augment centrifugal force to move the pumping element outwardly on the intake stroke. The bottom portion 76 of the slot is shaped in a manner to insure adequate filling of the bottom portions when the rotor slots are communicated with the intake port 32 at the beginning of the intake cycle. On the example cited here using /2 diameter rolls, it is necessary to have approximately clearance at the root in a slot having a substantially flat wall bottom portion or an equivalent clearance volume when other bottom shapes are used.

Pushing elements 70 are shown as being circular in cross-section and having a hollow interior portion. Hollow pumping elements are utilized to reduce the mass of the elements so that the elements respond more readily to the forces acting on them as will be hereinafter disclosed.

A seal groove 78 is formed in cam ring 27 so that the base portion 80 of the groove communicates with an arcuately extending cutout portion 79 formed in the cam ring and tapers to an apex 82 spaced from cutout portion 79.

A tapering opening is formed at the end of port 32 in body member 12 and is designated as an intake groove 84 which has a base portion 86 in communication with the end of intake port 32 and an apex portion 88 spaced therefrom.

A discharge groove 90 is also formed in body member 12 and has a base portion 92 in communication with the beginning of discharge port 36 and an apex portion 94 spaced therefrom. The apex portions 88 and 94 of the intake groove and the discharge groove, respectively, are circumferentially spaced in a manner such that a rotor slot 68 is positionable so that when the trailing edge 72 of the slot 68 is coincident with apex 88 of intake groove 84, the leading edge 74 of slot 68 is coincident with apex 94 of discharge groove 99. This relationship can be varied, depending on the operating pressure range of the pump; for example, at extremely high pressure, the apex 94 of discharge groove 90 should be slightly advanced in the direction of rotation and due to the amount of bleed-back of high pressure fluid, the effective positioning of the beginning of the discharge groove would then be at a position similar to that shown in FIGURE 7 when the pump is operating in a lower pressure range. It is to be noted that the intake and discharge grooves are radially positioned at a point to communicate with the bottom of the rotor slots because this portion of the slots is most difficult to fill.

A discharge extension portion 96 is also formed in the body member and has an end portion 97 in communication with the end of discharge port 36 and the closing end portion 98 spaced therefrom. This groove is not restricted to the shape shown in the drawing. It is to be noted that grooves 84 and 90, and discharge extension portion 96 could be provided in the pump cover instead of the body, or both, with a necessary decrease in size if provided in both locations, and are shown in the body merely for manufacturing convenience. Also, seal groove 73 could be formed in the body or cover, or both, insteadof cam. ring 27.

Before setting forth the specific operating details and cooperative relationship of the cam surface, rotor slot shape, and positioning of the ports with respect to the various portions of the cam surface, a brief operating cycle Will be set forth. Fluid flows from a reservoir (not shown) and/ or the discharge side of a fluid operated circuit (not shown) through fluid inlet conduit 28, passage 48 and into intake ports 30, 32, 30-,and 32'. Pump rotor 26 is driven from a suitable source and propels the fluid through the pumping cycle and into discharge ports 34, 36, 34- and 36' under pressure. The pressurized fluid flows from the discharge ports through communicating portion 44 into a flow control valve (not shown) which is adapted to be positioned in bore 41. A characteristic of the flow control valve is that only a predetermined maximum quantity of fluid per unit of time is allowed to pass through the valve and into discharge conduit 46. The remaining quantity of fluid is bypassed by the valve so that the remaining quantity flows through opening 40 and back to the inlet side through a first path 42, 43 and a second path 38, 48. As heretofore noted, the flow control valve structure is disclosed in detail in US. Patent No. 2,752,853.

In a rotary pump having pumping elements in contact with an encompassing cam surface, a major problem is that of sealing between the end of the discharge port and the beginning of the intake port. If a structure is utilized wherein the seal is obtained by maintaining a very close fit between the rotor and cam surface in the arcuate portion between the end of the discharge port and the beginning of the intake port, desirable pump operation can be obtained, but the problem of maintaining the necessary tolerances between the rotor and cam means are very objectionable.

If a structure is utilized wherein the seal between the end of the discharge port and the beginning of the intake port is obtained by maintaining a seal between the pumping element and cam surface, and between the pumping element and rotor slot, the clearance problem between the rotor and cam surface is eliminated but other objectionable problems are encountered. These problems are created by the fact that the pumping element must seal against the leading wall of the slot instead of the trailing wall where it normally rides. This movement of the pumping element in the slot can create objectionable mechanical noise.

The instant pump is of novel design such that regardless of whether a rotor type seal is utilized, that is, close clearance between the periphery of the rotor and the inner-periphery of the cam means across the arcuate surface between the end of the discharge port and the begining of the intake port, or a pumping element type seal is utilized, the pump will operate with maximum efficiency at either low or high speed operating conditions and possesses the same flow characteristics independent of the type of seal which is utilized Without any objectionable mechanical noise.

The structure and operation of the pump will now be discussed wherein a pumping element type seal is utilized as illustrated in FIGURE 9. The inner-peripheral arcuate portion of cam 27 is a constant radius portion with a clearance on the order of .005.025" between the periphery of rotor 26 and the cam surface AB as shown at 29 in FIGURE 9. Cam portion B-C has a radius R at point B and increases in radius progressively to a radius R at point C. Assuming that a given pumping element is at the point B, the rotor 26 carries the pumping element counterclockwise through the arc B-C with the pumping element moving progressively outward in contact with the increasing radius of the cam surface. Obviously, as this pumping element is being swept through the arc B-C, all of the other pumping elements are being moved in a counterclockwise direction along with the rotor member, and a volume of fluid is disposed between adjacent pumping elements as they pass through the intake cycle.

6 It is important to note that while centrifugal-force is perhaps the principal force that starts the pumping element IIlOVll'lg outwardly as it leaves the radius R there are also other forces involved in keeping the pumping element firmly against the cam surface. First, it is desirable to open the inner inlet port 32 before the outer inlet port 30. The resulting flow creates a slight pressure differential across the pumping element that augments centrifugal force. Secondly, the root of the slot must be formed as previously mentioned to admit oil between the pumping element and the inner diameter of the slot. Thirdly, the ports are proportioned so a stubstantial amount of oil must flow from the inner inlet port past the pumping element to help fill the increasing volume disposed between adjacent elements. This flow of oil also creates a pressure differential to aid in maintaining the pumping element in position. The rotor design using divergent sided slots is valuable herein assisting the pumping element to move outwardly by giving substantial freedom to the pumping element and also in permitting substantial amount of oil flow around the element.

The volume of fluid entrapped between adjacent elements is progressively increased as the rollers move from the point B to the point C. The arcuate cam surface CD has a radius R at the point C which is greater than the radius R at the point D. Therefore, the leading roller is moved inwardly from the point C to the point D, a distance equal to the difference between R and R It is to be noted that when the contact point .between the leading pumping element and thecam surface is coincident with a radius line drawn through point D, the trailing wall portion 72' of the rotor slot'is coincident with the apex 88 of intake groove 84, and therefore, at this point, the rotor slot which carries the leading pumping element, passes out of communication with the intake groove.

Obviously then, while the trailing pumping element is being swept from the point C to point D, the rotor slot which carries the pumping element is still in communication with the intake port and also, it is to be noted that the trailing pumping element is moved radially inward due to the difference in radius R and R There is therefore, an over-filling effect becausethe radius of the cam surface at an intermediate point (point C) is greater than at the end of the intake cycle (point D). This structure insures that there will be an adequate filling of the volume between the leading and trailing pumping elements. Total filling of course, is of utmost importance because if the entrapped volume to be swept into the pumping are is not completely filled, back-filling can take place when this volume of oil is communicated with the discharge port and also, the physical capacity of the pump is not completely utilized, which results in a decreased output of the pump and irregular and intermittent flow characteristics. When the trailing pumping element is being swept from point C to point D, the excess amount of entrapped fluid is pumped through intake groove 84 and into the successive trailing volume of oil wherein the aforementioned trailing pumping element is the leading element. At this point, therefore, due to the overfilling function which is brought about the maximum radius of the cam surface being intermediate the beginning and the end of the intake ports in cooperation with the intake groove which allows excess fluid to be pumped into the next trailingvolume through intake groove 84, the volume defined by the leading pumping element and the trailing pumping element is completely filled with oil and the trailing pumping element is now at a point ready to enter the pumping arc which is defined by the arcuate portion of the cam surface between points D and E. While the trailing pumping element is being traversed through the arc C-.D, communication 'between the entrapped volume and intake port 32 is gradually reduced due to the configuration of intake groove 84 and the trailing pumping element continues to move radially inward due to the shape of the cam surface, thus increasing the fluid pressure in the entrapped volume before communication with discharge groove 90 is commenced. This arrangement insures a precompression of the entrapped volume sufliciently to collapse any air bubbles which might be present in the fluid. If air bubbles are present in the entrapped volume when communication with the discharge means is commenced, a condition similar to cavitation is caused by the shock and noise which occurs when the air bubbles are collapsed in the discharge means.

It is to be noted also that the pumping elements are in an abutting relation with the trailing wall portion 72 of each slot at all times while the pumping elements are swept through the arcuate portion defined between points B and D due to the tendency of the pumping elements to lag relative to the rotor and also because the frontal or leading portion of each of the pumping elements is always under a fluid pressure equal to or greater than the fluid pressure imposed on the trailing or rear surface of the pumping element after the pumping element is in a counterclockwise position slightly past point B.

The arcuate portion of the cam surface between points D and E is a constant radius portion having a radius R The included angle between points D and E is substantially equal to the angular distance between corresponding portions of adjacent rotor slots. Assuming that the trailing roller is still at the point D and there is a full volume of oil entrapped between the leading and trailing pumping elements, the pumping elements are moved counterclockwise by the rotor 26 and since arcuate cam surface DE is a constant radius portion, the trailing pumping element does not move radially as it passes from point D to point B, but the leading pumping element moves radially inward along arcuate portion EA. The movement of the trailing pumping element from the point D to point E represents the pumping arc of the pump. During this movement of the trailing pumping element from the point D to the point E, there is a peculiar cooperation between the discharge groove and the ability of the leading pumping element to advance circumferentially with respect to the rotor. As soon as the trailing pumping element progresses an increment past point D, the apex portion 94 of discharge groove 90 is communicable with the volume of fluid entrapped between the leading and trailing pumping elements. Due to the configuration of the discharge groove, this opening becomes progressively larger as the rotor moves ahead. At the same time, due to the decrease in radius of the arcuate portion EA, the leading pumping element moves radially inward, thereby decreasing the entrapped volume and tending to increase the pressure of the fluid confined therein. Since the flow of fluid through the discharge groove 90 into the discharge port 36 and discharge conduit is less than the amount of fluid actually pumped due to the advance of the rotor and there is, therefore, an increase in pressure in the entrapped volume to a value above the pressure in the discharge port. The frontal or leading portion of the leading pumping element and the bottom or radially inward portion of the leading pumping element is exposed to discharge pressure and the trailing radially outer quadrant of the leading pumping element is exposed to the pressure of fluid in the entrapped volume. When the pressure differential reaches a given magnitude, the increased pressure exerted on the trailing radially outer quadrant of the leading pumping element becomes sufficiently high to cause the leading pumping element to advance with respect to rotor 26, thereby breaking the seal between the leading pumping element and the trailing wall portion 72 of the leading pumping element slot. Obviously, the pressure in the entrapped volume will only momentarily be higher than the pressure in the discharge means and only reaches a magnitude suflicient to advance the leading pumping element with respect to the rotor enough to allow communication between the entrapped volume and discharge ports through the opening between the leading pumping element and the trailing wall portion of the leading pumping element slot. This pressure differential is minimized because the portion of the discharge groove in communication with the entrapped volume is gradually increased which provides an increased flow rate through the discharge groove. As the rotor continues to advance in a counterclockwise direction, the pumping action across the arcuate portion D--E continues and the leading pumping element will maintain an advanced position with respect to the rotor since the opening through the discharge groove is not suflicient to accommodate all of the pumped fluid.

This phenomena will be hereinafter referred to as the check-valve principle. When the increased cross-sectional area of the discharge groove is sufiicient to carry all of the pumped fluid, the aforementioned unbalanced pressure condition on the leading pumping element is overcome, but the leading pumping element remains in a position adjacent the leading wall of the pumping element slot due to a novel conditon which will be hereinafter discussed in conjunction with discharge extension 96. This unbalanced pressure condition must, of necessity, be overcome after the portion of the leading pumping element in contact with cam surface 27' communicates with discharge port 34 and the trailing pumping element slot communicates with discharge port 36. This structure eliminates the difficulty which has heretofore been present in rotary pumps wherein the entrapped volume of fluid was communicated to the discharge port before the fluid was raised to discharge pressure, which resulted in a back-flow of fluid from the discharge conduit into the pumping volume causing fluid shock and very objectionable fluid noise along with a very erratic pump output and also the condition wherein the entrapped volume of fluid was not communicated with the discharge port until the pressure of the entrapped volume of oil was raised to a pressure considerably higher than the discharge conduit pressure.

When the trailing pumping element reaches the point B, the pumping function of the leading and trailing pumping elements has been completed and the cycle is repeated with the trailing pumping element then becoming the leading pumping element for the next consecutive entrapped volume of fluid.

When the pumping element which has heretofore been referred to as the leading pumping element reaches the point A, it is moved radially inward to a position in which the pumping element is substantially confined in the rotor. This clearance between the pumping element and the leading and trailing wall portions is not critical; in a pump having a 2" diameter rotor, the clearance is on the order of .010" which permits easy manufacturing. However, this circumferential clearance condition could cause mechanical noise problems on the transfer from discharge to intake except that the novel discharge extension groove and transition groove prevents such noise and will be hereinafter discussed.

When a pumping element is progressing along arcuate portion EA, it advances circumferentially with respect to the rotor to a position adjacent the leading wall of the pumping element slot due to the operation of the check-valve principle and is maintained in an advanced position in the following manner. The beginning of discharge port 37 is advanced in the direction of rotation with respect to point A in a manner such that the leading pumping element has traversed an appreciable portion of the discharge are before communicating with the outer discharge port, and as the leading pumping element continues to be swept through the discharge arc, flow into the discharge port 37 is restricted due to the size of the opening with respect to the amount of fluid to be pumped. Such restriction results in an increase in pressure on the trailing portion of the pumping element which maintains the pumping element in a position adjacent the leading wall of the pumping element slot. This pressure condition continues throughout most of the discharge cycle which insures that the pumping element will maintain an advanced position with respect to the pumping element slot until the pumping element approaches the point A.

When the pumping element advances toward the leading wall of the rotor slot, immediate contact is prevented due to a retarding effect caused by the fluid buildup in front of the pumping element, the fluid buildup on the leading wall of the slot caused by the rotation of the pumping element in the slot, and the fluid buildup or stagnant layer on the cam surface. The force acting to advance the pumping element with respect to the rotor (due to the advanced position of discharge port 37) is not suflicient to overcome the aforementioned fluid conditions. The partial advance of the pumping element up to this point does not result in any objectionable mechanical or fluid noise because the aforementioned fluid conditions act to prevent impact of the pumping element against the leading wall of the pumping element slot.

The discharge extension 96 is in communication at end 97 with discharge port 36 and has a closing end portion 98 remote from discharge port 36. This discharge extension is not restricted to the shape shownin the drawing, but can be of any shape as long as it is, in effect, an extension of the inner discharge port.

Seal groove 78 which is in communication with the beginning of intake port 30, is formed at the end of constant arc portion AB and increases in cross-sectional area in a counterclockwise direction. When the pumping element immediately ahead of the leading pumping element is at the point B, a continued movement of the rotor brings that pumping element into communication with seal groove 76, thereby providing communication between intake port 30 through seal groove 78 and the radially outer leading quadrant of the leading pumping element. At this point, the radially inner quadrants and trailing radially outer quadrant of the leading pumping element are still in communication with discharge extension 96. Due to the shape of seal groove 78, communication of the pumping element immediately ahead of the leading pumping element'with intake port 30 is very gradual and consequently, the pressure exerted on the radially outward leading portion of the leading pumping element is dropped from discharge pressure to intake pressure very gradually. Since the trailing portion of the leading pumping elementis still in communication with discharge extension 96, the differential pressure condition causes the leading pumping element to gradually penetrate the aforementioned stagnant layers of fluid and move from a position adjacent to the leading'wall of the rotor slot to a position in contact with the leading wall. When the leading pumping element comes into contact with the leading wall of the rotor slot, the sealing function is transferred from the pumping element immediately ahead of the leading pumping element to the leading pumping element.

This portion of the cycle is repeated when the radially outer trailing quadrant of the leading pumping element communicates with seal groove 78 and the trailing pumping element is gradually advanced into contact with the leading wall of its rotor slot, and the scaling function is at that time assumed by the trailing pumping element.

It is to be noted that discharge extension 96 also functions to maintain the pumping elements in contact with the cam surface while the pumping elements are being swept from the discharge to the intake because by having the bottom portion of the pumping elements in communication with the discharge means until the outer portion of the pumping element is communicated with the intake means, the bottom portion of the pumping element can never be at a lower pressure than the outer portion.

It is very important to note that the check valve principle, advanced position of the beginning of outer discharge port '37, the provision of the discharge extension 96, and seal groove 78, all cooperate to gradually move each of the pumping elements from the trailing Wall to the leading wall of the rotor slots as the pumping elements are swept through the arcuate portion D-B. This transfer of the pumping elements from the trailing Wall to the leading wall of the rotor slots is necessary if a pumping element type seal is relied on and with the aforementioned novel means, the advancement of the pumping elements with respect to the rotor is accomplished without any objectionable noise in a manner heretofore not known or used.

When the leading pumping element reaches a point slightly counterclockwise past the point B, the filling cycle is again commenced, At this point, therefore, the relationship between the leading pumping element and the rotor is restored to a position whereby a seal is maintained between the pumping element and the trailing wall portion because this pumping element has been restored to a state of pressure equilibrium. The pumping element will assume a contact position with the trailing wall portion of the slot due to the fact that the pumping element tends to lag relative to the rotor member and will be maintained in this position throughoutthe intake cycle due to the fluid forces which were considered in a previous discussion of the intake cycle.

Depending upon speed and pressure conditions, when the clearance between the rotor member and the cam ring across the arcuate portion A--B is maintained at less than approximately .005" for a rotor of approximately a 2" diameter, a rotor seal is effected across arcuate portion AB. When such a clearance is maintained between the rotor and cam ring, the intake and pumping cycles are identical with the aforementioned pumping element seal type pump Where the clerance is more than .005" between the rotor member and the cam surface across the arcuate portion AB. With the rotor seal, however, there is a pressure gradient across the arcuate portion AB which ranges from discharge pressure at the end of the discharge port to intake pressure at the beginning of the intake port. Such an arrangement inherently provides for a gradual forward movement of the pumping element with respect to the rotor when the pumping element is passing across arcuate portion AB. Therefore, the seal groove 78 is not actually needed in a rotor seal type pump, but this seal groove does not adversely affect the operation of a rotor seal pump in any manner whatsoever. If the clearance is greater than approximately .005", the pump will function as a pumping element seal type pump. There is no structure change whatsoever required in the rotor, body, cam means, or cover to effect this operation. It is noted therefore, that this novel structure eliminates the difficulty of maintaining a very accurate clearance between the pump rotor member and the cam means.

In summary, a pump structure is set forth in which positive means is provided to insure complete filling before the pumping cycle is begun. Such means is comprised of the overfilling structure; that is, providing a greater radius at the point C than at the point D, and also providing the intake and discharge grooves such that if there is too much fluid presented, the excess fluid is returned to the next preceding volume and thereby provides an additional amount of fluid to fill that volume. Positive means is set forth to insure that the volume pumped across the pumping arc is communicated with the discharge port at the proper time so that back-filling is eliminated and also, to insure that the pressure of the entrapped volume will not greatly exceed the discharge pressure and thereby cause a fluid shock when the fluid is communicated with discharge port. In addition, positive means is set forth in the form of the discharge extension to prevent leakage between a pumping element and the arcuate cam surface A-B when the pumping element is passing across this surface. An improved rotor slot design is set forth permitting economical manufacture as Well as improved operation. The porting conditions are arranged throughout the operating cycle so as to control the movement of the pumping elements to obtain optimum performance with respect to noise and delivery.

While the present invention has been described in conneotion with certain specific embodiments, it is to be understood that the foregoing description is merely exemplary and that the concept of this invention is susceptible of numerous other modifications, variations, and applications which will be apparent to persons skilled in the art. The invention is to be limited, therefore, only by the broad scope of the appended claims.

What I claim is:

1. A fluid pumping mechanism comprising a pump housing having a pumping chamber provided therein, rotor means disposed within said pumping chamber and rotatable about a fixed center in said housing, intake means and discharge means communicating with said pumping chamber, said pumping chamber including a continuous arcuate wall surface, pumping elements carried by said rotor means for engagement with said arcu ate wall surface, a portion of said wall surface having a constant radius disposed arcuately between the end of said discharge means and the beginning of said intake means, another arcuate portion of said wall surface having a larger constant radius than said radius of said first mentioned portion and extending substantially between the end of said intake means and the initial portion of said discharge means, a further arcuate portion disposed substantially peripherally coextensive with said intake means and having an intermediate arc portion of a radius greater than said radius of said second mentioned arcuate portion measured from said fixed center, a remaining arcuate portion extending substantially peripherally co extensive with said discharge means having a radius at an intermediate portion less than the radius of said second mentioned arcuate portion, and all of said radii being measured from the same center.

2. A fluid pumping mechanism comprising a housing means having a pumping chamber therein, intake means and discharge means communicating with said pumping chamber, a continuous peripheral Wall means in said pumping chamber, a rotor rotatably mounted in said chamber, pumping elements carried by said rotor and constructed and arranged for engaging said peripheral Wall means, said peripheral Wall means having a first,

arcuate portion of a constant radius and extending between said intake port and said discharge port, a second arcuate portion having a constant radius greater than the radius of said first mentioned arcuate portion and being disposed substantially diametrically opposed to said first mentioned arcuate portion, a third arcuate portion disposed in a circumferentially connecting relationship to said first and said second arcuate portions, an intermediate portion of said third arcuate portion having a radius greater than the radius of said second arcuate portion measured from the arc center of said second arcuate portion, and a forth arcuate portion disposed substantially opposite to said third arcuate portion and in a circumferentially connecting relationship to said first and second arcuate portions, an intermediate arc portion of said fourth arcuate portion having a radius less than the radius of said second arcuate portion, and all of said radii being measured from the same center.

3. A fluid pumping mechanism comprising a pump housing having a pumping chamber therein, intake means and discharge means communicating with said pumping chamber, said pump housing being provided with a continuous peripheral wall, a rotor disposed in said chamber, pumping elements carried by said rotor and constructed and arranged for engaging said peripheral wall, said peripheral Wall comprising an intake arc portion, a pumping arc portion having a constant radius, a discharge are portion and a seal arc portion, said seal arc portion having a constant radius less than the constant radius of said pumping arc portion, and said intake arc portion having an intermediate portion of a radius greater than the radius of said pumping arc portion, all of said radii being measured from the same center.

4. A fluid pumping mechanism comprising a pump housing, a pumping chamber disposed in said pump housing, intake means communicating with said pumping chamber, rotor means disposed in said pumping chamber and having a plurality of circumferentially spaced slots therein, each of said slots having a radially inner portion and a radially outer portion, said radially outer portion being wider than said radially inward portion pumping elements of a width substantially less than the radially outer portion of said slots and being freely movable circumferentially in said radially outer portion of each of said slots, said pumping chamber having a continuous peripheral wall means including a fluid intake arc surface means in communication with said intake means, said pumping elements being engageable with said continuous peripheral wall means, said fluid intake are surface means having an intermediate arc portion of a greater radius than the radius of any remaining portion of said continuous peripheral wall means measured from the arc center of said intermediate arc portion, discharge means communicating with said pumping chamber, a fluid entrapping means comprising juxtaposed pumping elements and portions of said rotor and said continuous peripheral wall means lying substantially between said juxtaposed pumping elements, said continuous peripheral Wall means including a fluid discharge are surface means in communication with said discharge means, means including said fluid discharge are surface means for creating discharge fluid pressure in said discharge means and creating a differential fluid pressure in said fluid entrapping means with respect to the discharge fluid pressure when said fluid entrapping means is traversing said fluid discharge are surface and is isolated from said intake means and in restricted communication with said discharge means, to move one of said juxtaposed pumping elements to open said fluid entrapping means into communication with said discharge means whereby fluid in said fluid entrapping means is vented to the discharge means before the fluid entrapping means is in circumferential overlapping relationship with the discharge means allowing freely open communication therebetween.

5. A fluid pumping means comprising a pump housing, a pumping chamber provided in said housing, a pump rotor disposed in said pumping chamber and being rotatable relative to said housing, a plurality of circumferentially spaced slots in said rotor, a plurality of pumping elements disposed in said slots, said slots having a circumferential length along the periphery of said rotor substantially greater than the width of said pumping elements, intake means and discharge means communicable with said pumping chamber, said pumping chamber having a continuous peripheral wall means including a fluid intake arc surface means in communication with said intake means, said pumping elements being engageable with said continuous peripheral wall means, said fluid intake are surface means having an intermediate arc portion of a greater radius than the radius of any remaining portion of said continuous peripheral wall means measured from the center of rotation of said rotor, a fluid enclosure means comprising juxtaposed pumping elements and portions of said rotor and said continuous peripheral Wall means lying substantially between said juxtaposed pumping elements, said continuous peripheral wall means including a fluid discharge are surface means in communication with said discharge means, means including said fluid discharge are surface means for creating d ischarge fluid pressure in said discharge means and creating a fluid pressure sufliciently higher than discharge pressure in said fluid enclosure means when said fluid enclosure means is traversing said fluid discharge are surface means and is isolated from said intake means and in restricted communication with said discharge means, to move one of said juxtaposed pumping elements to open said fluid enclosure means into communication with said discharge means whereby fluid in said fluid enclosure means is vented to said discharge means before said discharge means is in freely open communication with said fluid enclosure means.

6. A fluid pumping mechanism comprising a pump housing having a pumping chamber provided therein, rotor means disposed within said pumping chamber, a plurality of circumferentially spaced slots provided in said rotor means and each of said slots having a leading wall portion and a trailing wall portion, intake means and discharge means communicating with said pumping chamber, said pumping chamber having a continuous peripheral wall, a pumping element positioned in each of said slots for engaging said peripheral wall, said peripheral wall comprising an intake arc portion, a pumping arm portion having a constant radius, a discharge arc portion, and a seal arc portion, said seal arc portion having a constant radius less than the constant radius of said pumping arc and said intake arc portion having an intermediate portion of a radius greater than the radius of said pumping arc portion, and all of said radii being measured from the same center.

7. A device according to claim 6, wherein the radius of said rotor means is substantially less than the radius of said seal arc portion to allow a relatively free flow of fluid between said rotor and seal arc portion.

8. A device according to claim 6, wherein the radius of said rotor means is substantially equal to the radius of said seal arc portion to form a relatively fluid tight seal between said rotor and said seal arc portion.

9. A device according to claim 6, wherein said intake means comprises an intake groove and an intake port, and said discharge means comprises a discharge groove and a discharge port.

10. A device according to claim 9, wherein said intake groove and said discharge groove are comprised of base portions communicable with said intake port and said discharge port, respectively, and each having apex portions spaced from said base portions.

11. In a fluid pumping mechanism, a pump housing, a pumping chamber having a continuous peripheral wall and being disposed in said pump housing, intake means and discharge means communicating with said pump housing, rotor means disposed in said pumping chamber having a plurality of circumferentially-spaced slots there.- in, each of said slots having wall portions diverging in a radially outward direction, a pumping element disposed in each of said slots for engaging said continuous peripheral wall and being of a width substantially less than the outer portion of said slots, said continuous peripheral wall having an intake arc portion, a pumping arc portion, a discharge are portion and a seal arc portion, said pumping arc portion having a constant radius, said seal arc portion having a constant radius less than the constant radius of said pumping arc portion, said in take arc portion having an intermediate arc portion of a radius greater than the radius of said pumping arc portion, and all of said radii being measured from the same center.

12. A device according to claim 11, wherein the radius of said rotor means is substantially less than the constant radius of said seal arc portion to allow a relatively free flow of fluid between said rotor and seal arc portion, and said intake means comprising a seal groove communicable with the end of said intake arc portion adjacent said seal arc portion.

13. A fluid-pumping mechanism comprising a pump housing having a pumping chamber provided therein, said pumping chamber being provided with a continuous peripheral wall, rotor means disposed within and rotatable about a fixed center in said pumping chamber, a plurality of circumferentially-spaced slots provided in said rotor means and having a radially inner portion and a radially outer portion, said radially outer portion being wider than said radially inner portion, hollow circular pumping ele ments of a diameter substantially less than the radially outer portion of said slots and being freely movable circumferentially in said radially outer portion of each of said slots for engaging said peripheral wall, intake means communicable with said pumping chamber comprising a seal groove, an inner intake port, an outer intake port, and an intake groove, discharge means communicable with said pumping chamber and comprising a discharge groove, an inner discharge port and an outer discharge port, said peripheral wall having an intake arc portion, a pumping arc portion having a constant radius, a discharge are portion and a seal arc portion, said seal arc portion having a constant radius less than the constant radius of said pumping arc and said intake arc portion having an intermediate portion of a radius greater than the radius of said pumping arc portion, and all of said radii being measured from the same center.

14. A device according to claim 13 wherein said seal groove is communicable with said radially outer intake port, said intake groove is communicable with said radially inner intake port and said discharge groove and said discharge extension are communicable with said radially inner discharge port.

15. A device according to claim 14, wherein the radius of said rotor means is substantially less than the radius of said seal arc portion to allow a relatively free flow of fluid between said rotor and said seal arc portion.

16. A device according to claim 14 wherein the radius of said rotor means is substantially equal to the radius of said seal arc portion to form a relatively fluid-tight seal between said rotor and said seal arc portion.

17. A device according to claim 14 wherein the pumping arc portion is circumferentially arranged with respect to said discharge groove whereby when a leading pumping element of a pair of consecutive pumping elements is traversing the initial portion of said discharge arc, the trailing pumping element is traversing the initial portion of said pumping arc portion and said rotor slot carrying said trailing pumping element has restricted communication with said discharge groove so that further traverse of said pumping elements results in an increase in fluid pressure of the fluid entrapped between said pumping elements until said increased fluid pressure is suflicient to move said leading pumping element circumferentially with respect to said rotor to allow communication between said entrapped volume and said discharge ports.

18. A fluid pumping mechanism comprising a pump housing, a pumping chamber disposed in said pump housing, intake means communicating with said pumping chamber, rotor means disposed in said pumping chamber and having a plurality of radial, outwardly diverging, circurnferentially spaced slots therein, a pumping element disposed in each of said slots and being free to move circumferentially in the radially outer portion of each of said slots, said pumping chamber having a. circumferentially extending continuous arcuate surface means including a fluid intake are surface means in communication with said intake means, said pumping elements being engageable with said continuous arcuate surface means, said fluid intake arc surface means having an intermediate arc portion of a greater radius than the radius of any remaining portion of said continuous arcuate surface means measured from the arc center of said intermediate arc portion, discharge means communicating with said pumping chamber, a fluid enclosure means comprising a pair of consecutive pumping elements and portions of said rotor and said continuous peripheral wall means lying substantially between said consecutive pumping elements, said continuous arcuate surface means including a fluid pumping arc surface means and a fluid discharge arc surface means, means including said fluid discharge are surface means for creating discharge fluid pressure in said discharge means and creating a fluid pressure higher than discharge pressure in said fluid enclosure means when the leading pumping element of said pair of consecutive pumping elements is traversing the initial portion of said fluid discharge are surface means and the trailing pumping element of said pair of pumping elements is traversing the initial portion of said fluid pumping arc surface means and said fluid enclosure means has restricted communication with said discharge means whereby relative circumferential movement is effected between said leading pumping element and said rotor, thus providing additional communication between said entrapped fluid and said discharge means.

19. A fluid pumping means comprising a pump housing, a pumping chamber disposed in said pump housing, a rotor means disposed in said pumping chamber, a plurality of pumping elements carried by said rotor means and being circumferentially movable with respect to said rotor means, said pumping chamber having a continuous peripheral wall means having an intake arc portion, a pumping arc portion and a discharge arc portion, said pumping elements being engageable with said continuous peripheral wall means, said intake arc portion including an intermediate arc portion having a radius greater than the radius of any remaining portion of said continuous peripheral wall means measured from the arc center of said intermediate arc portion, discharge means communicating with said pumping chamber and advanced of the pumping arc in the direction of the discharge are so that a volume of fluid entrapped by a pair of consecutive pumping elements which are traversing the pumping arc and the discharge are respectively, has restricted communication with said discharge means when the trailing pumping element of said pair of pumping elements is traversing the initial portion of said pumping arc, resulting in an increase in fluid pressure of said entrapped volume and circumferential movement of the leading pumping element of said pair of pumping elements with respect to said rotor means to allow further communication between said entrapped volume and said discharge means.

20. A fluid pumping mechanism comprising a pump housing having a pumping chamber provided therein, rotor means disposed in said pumping chamber, a plurality of circumferentially spaced slots in said rotor and each slot having a leading wall portion and a trailing wall portion, pumping elements disposed in said slots and being freely circumferentially movable with respect to said rotor means, said pumping chamber being provided with a continuous peripheral wall means having an intake arc portion, a pumping arc portion, a discharge are portion and a seal are portion, said seal arc portion having a radius substantially greater than the maximum radial dimension of said rotor means to allow a relatively free flow of fluid between said rotor means and said seal arc portion, said pumping elements being disposed for engagement with said continuous peripheral wall means, intake means communicable with said pumping chamber and including a seal groove disposed substantially at the beginning of said intake arc portion in communication with said intake means, discharge means comprising a radially inner discharge port and a radially outer discharge port communicable with said pumping chamber,

'a fluid enclosure means comprising juxtaposed leading and trailing pumping elements and portions of said rotor means and said continuous peripheral wall means disposed substantially between said juxtaposed pumping elements, said trailing pumping element being exposed to fluid pressure in said discharge ports in a direction tending to advance said trailing pumping element with respect to said rotor means while said leading pumping element of said fluid enclosure means is communicable with said seal groove so that the fluid pressure in said fluid enclosure means is gradually diminished to intake pressure, resulting in a gradual forward circumferential movement of the trailing pumping element of said pair of pumping elements into contact with the leading wall portion of said rotor slot in which said trailing pumping element is positioned.

21. A fluid pumping mechanism comprising a pump housing having a pumping chamber therein, rotor means disposed within said pumping chamber, intake means comprising a radially inner intake port and a radially outer intake port communicating with said pumping chamber, discharge means comprising a radially inner discharge port and a radially outer discharge port communicating with said pumping chamber and wherein said pumping chamber is comprised of a continuous peripheral wall means, pumping elements carried by said rotor and being movable circumferentially with respect to said rotor, said pumping elements being engageable with said continuous peripheral wall means, an intake arcuate portion of said continuous peripheral Wall means having an intermediate arc portion of a radius greater than the radius of any remaining portion of said continuous peripheral wall means measured from the arc center of said intermediate arc portion, said continuous peripheral wall means also including a pumping arcuate portion, a discharge arcuate portion and the beginning of said radially outer discharge port being advanced substantially ahead of said pumping arcuate portion in the direction of said discharge arcuate portion so that fluid pumping commences before there is unrestricted communication between the fluid being pumped and said discharge ports.

22. A fluid pumping means comprising a pump housing having a pumping chamber therein, rotor means disposed within said pumping chamber, an intake port and discharge port communicating with said pumping chamber, said pumping chamber having a continuous peripheral wall means including an intake arc portion, a pumping arc portion, a discharge are portion, and a seal arc portion, pumping elements carried by said rotor for engagement with said continuous peripheral wall means, said intake arc portion including an intermediate arc portion having a radius greater than the radius of any remaining portion of said continuous peripheral wall means measured from the arc center of said intermediate arc portion, and the beginning of said discharge port being circumferentially spaced with respect to said discharge are portion so that fluid pumping commences before there is unrestricted communication between the fluid being pumped and said discharge port.

23. A fluid pumping mechanism comprising a pump housing having a pumping chamber therein, said pumping chamber having a continuous peripheral wall, intake means and discharge means communicating with said pumping chamber, said peripheral wall having an intake arc portion, a pumping arc portion having a constant radius, a discharge are portion, and a seal arc portion, said intake arc portion having an intermediate portion of a radius greater than the radius of any remaining portion of said peripheral wall measured from the arc center of said intermediate portion of said intake arc portion, rotor means disposed within said pumping chamber and having a plurality of circumferentially spaced slots therein, a pumping element disposed in each of said slots for engagement with said peripheral wall, an intake groove disposed at the end of said intake means communicable with said intake means in a manner such that when the leading pumping element of a pair of adjacent pumping elements is approaching the end of the pumping arc, the fluid entrapped therebetween gradually passes out of communication with said intake means so as to slightly precompress said entrapped fluid.

24. A fluid pumping mechanism comprising a pump housing having a pumping chamber provided therein, rotor means disposed within said pumping chamber and having a plurality of circumferentially spaced slots provided therein, a pumping element provided in each of said slots, said pump housing being provided with a continuous peripheral wall means having an intake arc portion, a pumping arc portion, a discharge are portion, and a seal arc portion, said seal arc portion having a radius substantially greater than the maximum radial dimension of said rotor means to allow relatively free flow of fluid between said rotor means and said seal arc portion, intake means including an intake port communicable with said pumping chamber, discharge means communicable with said pumping chamber and comprising a first discharge port circumferentially partially overlapping said seal arc portion, a second discharge port disposed radially outward of said first discharge port, a fluid entrapping means comprising successive leading and trailing pumping elements and portions of said rotor means and said continuous peripheral wall means disposed between said successive pumping elements, said trailing pumping element being urged by fluid pressure in said discharge ports in an advancing direction with respect to said rotor means while said leading pumping element of said fluid entrapping means is communicable With said intake port, means including said intake means to gradually diminish the fluid pressure in said fluid entrapping means from discharge pressure to intake pressure while said trailing pumping element is urged by fluid pressure in said discharge ports in an advancing direction with respect to said rotor means whereby said trailing pumping element is gradually moved forward in its rotor slot into sealing engagement with a leading wall of said slot to effect a seal so that the trailing pumping element will provide a seal between the discharge means and the intake means.

25. A fluid pumping mechanism comprising a pump housing, a pumping chamber disposed in said pump housing, intake means and discharge means communicating With said pumping chamber, rotor means disposed in said pumping chamber, circumferentially spaced openings provided in said rotor, a pumping element disposed in each of said spaced openings free to move to a non-sealing position, said pumping chamber being provided with a continuous peripheral wall surface having an intake arc portion, a pumping arc portion and a discharge are portion, said pumping elements being engageable with said continuous peripheral wall surface, said intake arc portion having an intermediate arc portion of a radius greater than the radius of any remaining portion of said continuous peripheral wall surface measured from the arc center of said intermediate arc portion, said discharge means being circumferentially advanced of the pumping arc portion in the direction of the discharge are portion so that when the leading pumping element of a pair of pumping elements is traversing said discharge are portion, the trailing pumping element of said pair of pumping elements is traversing the pumping arc portion and the pressure of fluid entrapped between said pair of pumping elements in increased above the pressure of fluid disposed ahead of the leading pumping element in the discharge means resulting in relative movement between the leading pumping element and the rotor, thus providing com- 18 munication between the entrapped fluid and the discharge means.

26. 'In a fluid pumping mechanism, a pump housing having a pumping chamber therein, intake means and discharge means communicating with said pumping chamber, a rotor in said chamber and being rotatable in said housing, said pumping chamber having a continuous wall surface means including a fluid intake are surface means in communication with said intake means, pumping elements carried by said rotor for engaging said continuous wall surface means, and said fluid intake are surface means having an intermediate arc portion of a radius greater than the radius of any remaining portion of said continuous wall surface means measured from the arc center of said intermediate arc portion.

27. Apparatus for controlling the inlet of a fluid pump mechanism having a pumping chamber and a rotor rotatably mounted therein, said pumping chamber including a circumferentially extending continuous arcuate surface, pumping elements carried by said rotor for engagement with said continuous arcuate surface, and said continuous arcuate surface having intake are means, said intake arc means including an intermediate arc portion having a radius greater than the radius of any remaining portion of said continuous arcuate surface measured from the arc center of said intermediate arc portion.

References Cited in the file of this patent UNITED STATES PATENTS 345,885 Colebrook July 20, 1886 1,051,360 Wisdom Jan. 21, 1913 1,265,070 Feyzes May 7, 1918 1,558,620 Kagi Oct. 27, 1925 1,749,121 Barlow Mar. 4, 1930 1,879,136 Dubrovin Sept. 27, 1932 1,922,951 Hawley Aug. 15, 1933 1,952,834 Beidler et a1. Mar. 27, 1934 1,984,365 English Dec. 18, 1934 1,996,875 McCann Apr. 9,1935 2,033,218 Yirava Mar. 10, 1936 2,045,014 Kenney et al June 23, 1936 2,278,131 Livermore Mar. 31, 9 2 2,294,352 White Aug. 25, 19 2 2,335,284 Kendrick Nov. 30, 1943 2,352,941 Curtis July 4, 1944 2,378,390 Bertea June 19, 19 5 2,424,466 Iessop July 22, 1947 2,460,047 Von Wangenheim I an. 25, 1949 2,538,193 Ferris Ian. 16, 1951 2,599,927 Livermore June 10, 1952 2,632,398 Ferris Mar. 24, 1953 2,711,136 Arnold June 21, 1955 2,725,013 Vlachos Nov. 29, 1955 2,737,121 Badalini Mar. 6, 1956 2,772,637 Doble Dec. 4, 1956 2,778,317 Cockburn Jan. 22, 1957 2,786,422 Rosaen et al Mar. 26, 1957 2,977,888 Livermore Apr. 4, 196

FOREIGN PATENTS 19,119 Great Britain 1911 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,025,802 March 20 1962 Robert J. Browne It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read. as

corrected below.

Column 4, line 26, for "Pushing" read Pumping column 9, llne 37, for "76" read 78 column 1O line 39, for "clerance" read clearance column 11, line 63, for "forth" read fourth (SEAL) Attest:

DAVID L. LADD Commissioner of Patents ERNEST W. SWIDER Attesting Officer

Images