US2833465A

US2833465A - Multi-vane positive displacement pump

Info

Publication number: US2833465A
Application number: US525846A
Authority: US
Inventors: Walter L Cable
Original assignee: Bendix Aviation Corp
Current assignee: Bendix Aviation Corp
Priority date: 1955-08-02
Filing date: 1955-08-02
Publication date: 1958-05-06
Anticipated expiration: 1975-05-06

Description

May 6, 1958 w. L. CABLE 2,333,455

MULTI-VANE POSITIVE DISPLACEMENT PUMP Filed Aug. 2, 1955 3 Sheets-Sheet 1 FIG. 1

as a

I6 IS IN VEN TOR.

WALTER L. CABLE BY a ATrOQ VEY' May 6, 1958 w. 1.. CABLE 2,833,455

MULTI-YANE POSITIVE DISPLACEMENT PUMP Filed Aug. 2, 1955 3 Sheets-Sheet 2 FIG. 3

IN V EN TOR.

WALTER L. CABLE BY i 197T Ole/V5 Y May 6, 1958 w. CABLE 2,833,465l

MULTI-VANE POSITIVE DISPLACEMENT PUMP Filed Aug. 2, 1955. 3 Sheets-Sheet 3 FIG. 4

' INVENTOR. WALTER L. CABLE MULTI-VANLZ rosirrvn DISPLACEMENT PUMP Walter L. Cahle, New Milford, N. J.., assignor to Bendix Aviation Corporation, Teterhoro, N. 1., a corporation of Delaware Application August 2., 1955, Serial No. 525,346

2 Claims. (Cl. 230-152) This invention relates to an improved rotary multivane positive displacement pump of a type disclosed and claimed in a copending application Serial No. 526,032, filed August 2, 1955', by Edward C. Breinig and Edward V. Manning, and more particularly to the structure of the vanes of such pump.

In multi-vane pumps of the aforenoted type, pumping vanes of the conventional solid type slidably fitted with close tolerance within corresponding rotor slots have certain disadvantages in that as each vane slides from its innermost to its extreme outward position, a suction force is created in its rotor slot at the inner end of the solid type vane which tends to retard the vane from mov* ing outwardly under centrifugal force to contact the pump housing surface at its vane tip. This lack of proper contact between the tips of the solid type vanes and the inner pump housing surface would result in a loss in pumping or volumetric etficiency in allowing the pumped air or gaseous medium to leak between the vane tips and the pump housing instead of the respective pump vanes containing the pumped air or gaseous medium as a slug and moving it towards the pump discharge port after the trailing pump vane has passed the inlet port.

An object of the invention is to avoid these disadvantages incident to such solid type vanes by providing a relieved section or volume in each vane in the vane surface facing the bottom of the rotor slot in which the vane is slidably mounted so as to minimize this suction effect and avoid the leakage paths aforenoted.

Another object of the invention is to provide in the inner end surface of each of the aforenoted vanes a series of holes having openings facing the bottom of the rotor slot in which the vane is slidably mounted so as to provide a relief volume, which volume built into the vane causes the air or gaseous medium entrapped therein and between the vane and inner end of the rotor slot to act as a variable rate spring which can adjust itself to particular inlet and outlet conditions of operation so as to provide the following improvements over the conventional solid type vane: (l) a much higher outlet flow of the pumped gaseous medium at a particular operating condition, (2) a higher pump suction under no flow conditions, and {3) less vane wear at the tips of the vanes due to the decrease in weight of each vane obtained by including the relief volume in the vane itself.

A further object of the invention is to provide a cornpact air pump of great efficiency in comparison to its size and of such simplicity in construction as to adapt it for manufacture and installation at low cost.

Other objects and advantages of this invention are 2,833,465 Patented May 6, 1958 in the accompanying drawings which form a part of this specification, like characters of reference indicate like parts in the several views wherein:

Figure 1 is a fragmentary side view, partially in section, of a rotary multi-vanc positive displacement pump in which there may be embodied the novel features of the presen invention;

ilgnre If s a sectional end view of Figure 1 taken along the lines 2-2 and showing the relationship of the rotor and vane assembly in the pump cavity and by dotted lines in the pump vanes the relief section or excess volume built into the vanes;

Figure 3 is a diagrammatic view illustrating the mannor in which the gaseous medium or air entering through the pump inlet is entrapped between vanes of the pump at substantialy the same pressure as that entering the inlet port of the pump;

Figure 4 is a diagrammatic view illustrating the manher in which the air entrapped in the pump cavity may be compressed between the pump vanes and the decreasing contour of the pump chamber, and also showing by dotted lines that there is provided a minimum of at least one vane in contact with the cavity contour between the inlet and outlet ports at all times so as to prevent leakage of the relatively high pressure air from the discharge port back to the inlet port;

Figure 5 is an enlarged perspective view of a novel pump vane showing a series of holes therein having openings in the bottom surface of the vane.

Referring to the drawing of Figure 1, there is shown a rotary air pump of a type disclosed and claimed in the aforenoted copending application and including a power unit 10 and a pumping assembly ll constructed and arranged to be mounted and driven by the power unit 10. i

In the last-mentioned type of pump, the power unit it) comprises an electric motor 12 suitably mounted and enclosed within a hollow housing or casing 13, an end wall 14 closing one end of the housing 13, while the air pump unit 11 is suitably fastened to an opposite end wall 15 of housing 13 by bolts 1s.

The pump assembly 11 comprises a casing 17 and a head wall 1E. Head wall 18 is secured to the casing 17 and the end wall 15 of the casing 13 by the bolts 16 which pass through tubular openings in the head 18 and casing 17 and screw-threadedly engaged in the wall 15.

Motor 12 is provided with a shaft 21 rotatably mounted in bearings 23 and 25 carried by the end wall 15 and the head 18, respectively. Secured to the shaft 21 by keys 27 for rotation therewith is a rotor member 28. End plates 2&9 and 30 are provided in the end wall 15 and head 13, respectively to sealingly engage the side of the rotor member 23 and

rotor vanes

32, 33 and 34 slidably mounted therein, as best shown in. Figure 2.

The cylindrical rotor 28 has formed therein suitable

longitudinal slots

36, 37 and 38 each extending, as indicated in Figure 3, tangent to a circle Z having a common center to that of the rotor 28 and, as shown in Figure 2, in spaced relation to and in a plane at one side of the shaft 21 and center of rotation of the member 28. Slidably mounted in the

slots

36, 37 and 38 and extending from the rotor member 28 at an acute angle to the circumferential surface thereof and in a direction corresponding to the direction of rotation of member 28 are the

vanes

32, 33 and 34, respectively. The: outer edges of the vanes make contact with a profile of a pump cavity or chamber of oval cross-section formed within the casing l7 and act to seal at all times the pump inlet 40 from the pump outlet 42 so as to prevent hack rush of high pressure gaseous medium from the outlet to the inlet through the pump cavity, as shown diagrammatically by figures 3 and l. It is to be noted that about one-half of the rotor is uniformly closely-spaced to one end of the oval shaped cavity and that a compression chamber of extended crescent-like cross-section results.

Further, the profile of the cavity has a predetermined contour so designed as to progressively decrease the volume of a portion 39 of the cavity between the inlet 40 and the outlet 42 so that upon rotation of the element 28 gaseous medium drawn into the portion 39 may be entrapped between

successive vanes

32, 33 and 34 and precompressed prior to release of the gaseous medium through outlet 42.

The contact between the vanes and the profile of the cavity within the casing 17 is maintained by the radial component of the centrifugal force acting on the vanes during rotation of the rotor element 28 so as to maintain the outer edges of the vanes in contacting relation with the profile of the cavity without excessive friction and load at high speeds of rotation, as distinguished from vanes of the true radially extending type in which the centrifugal force applied at high speeds may cause an A excessive wear, friction and load to be applied to the outer edges of the vanes increasing with the speed of rotation.

Thus, as the shaft 21 is rotated, gaseous medium such as air may be drawn into the pump cavity and between the vanes, such as 32 and 33, through the pump inlet port, indicated in Figure 2 by the numeral 40, and thereby pre-compressed and finally delivered to the pump outlet port 42 under the compression force thereof.

Referring to the diagrammatic drawing of Figure 3, a charge of air or gaseous medium is entrapped in the portion 39 of the cavity between the

vanes

32 and 33 at substantially the same pressure as that entering the inlet port 40 so as to occupy a volume designated in the drawing of Figure 3 by the letter X.

Now referring to the drawing of Figure 4, it will be seen that the gaseous medium or air charge between

vanes

32 and 33, and indicated by the letter Y, has now been rotated to a location just prior to its discharge through outlet port 42 and, because of the predetermined non-symrnetrical profile of the portion 39 of the pump cavity of progressively decreasing volume, the charge of gaseous medium Y has now been compressed between the

vanes

32 and 33 with a consequent increase in pressure. Theoretically, the charge between the

vanes

32 and 33 has been precompressed adiabatically in accordance with a predetermined relationship.

Again referring to the schematic drawing of Figure 4, it can be seen that the relationship of the distance be tween the inlet port 40 and the outlet port 42 and the distance between any two vanes (indicated by dotted lines in Figure 4) is arranged to provide a minimum of at least one vane in contact with the contour of the pump cavity between the

ports

40 and 42 at all times. The importance of this feature is to prevent a direct leak of relatively high pressure air from the discharge port 42 back to the inlet port 40 Without the necessity of main taining any rubbing contact by the rotor 28 and the non symmetrical cavity surface and, further, without the necessity of maintaining even a critically close clearance between the surfaces of the rotor and housing cavity.

Thus, in multi-vane positive displacement pumps of the aforenoted type, the gaseous medium or air is squeezed or compressed between vanes of the rotor moving in the portion 39 of the pump cavity prior to the discharge of the air or gaseous medium through the exhaust conduit 42. This is shown by Figures 3 and 4 wherein the air or gaseous medium between the vanes 32. and 33 of the rotor 28 is shown in the process of being compressed. Since the volume of the portion 39 of the pump cavity progressively decreases in volume from the inlet 4% to the outlet 42, it will be seen that prior to release, the pressure of the gaseous medium or air compressed through the above means is increased to such a degree that upon released the same, as shown in Figure 4, by the dotted CPL Lit

such vane structure in minimizing the suction e" line vane 33, there is no backing up or back rush of air, instead the compressed gaseous medium carried in the cavity space 39 separating the

vanes

32 and 33 passes directly out the exhaust conduit 42 under the compres sion force thereof.

Through the use of built-in precornpression in a pump of the type described herein, there is provided a pump with relatively constant input torque or power require ments so as to make these pumps ideally suited for use with various driving means, particularly when used under a wide range of operating conditions.

The multi-vane pump so far described, as to Figures l4, is claimed in the copending application Serial No. 526,032, filed August 2, 1955, by Edward C. Breinig and Edward V. Manning, and assigned to Bendix Aviation Corporation, assignee of the present application. The present invention is directed to an arrangement in such a multi-vane pump of the vane structure described and claimed herein.

In the present invention, the vanes are formed of can bon or other suitable material and, as shown in Figure 5, have provided a series of longitudinal holes 56 having openings 52 in the bottom surface of the vane facing the inner end. of the rotor slot in which the vane is siidably fitted, as indicated in Figure 2, with a close tolerance between the surfaces of the slot and vane to maintain a minimum leakage path between the slot and vane surfaces.

Upon rotation of the rotor 28, each of the

vanes

32, 33 and 34 is forced outwardly into contacting relation with the inner surface of the pump housing causing an increase in the volume of the space at the bottom of the slot between the end of the vane and the inner end of the slot as the vane under centrifugal force moves to its outermost position, as indicated in Figure 4 for example by the vane 32.

In the case of a conventional solid type vane, this volume would normally be negligible if the vane be in its innermost position, as indicated for example by vane 34 of Figure 4, with no additional volume provided at the bottom of the vane or slot of the rotor so that in going from a zero volume to the maximum volume position, a suction would be created under the vane which would tend to retard a conventional solid type vane from moving out and properly contacting the inner pump housing surface. Such lack of proper contact of the solid type vane would result in a loss in pumping or volumetric eificiency due to leakage in the pumped air between the vane tip and the profile of the pump cavity in the pump housing.

However, by designing a relief section or volume into the vane by the provision of the holes 50, this suction effect can be minimized. Thus, in effect, the volume built into the vane acts as a variable rate spring which can adjust itself to particular inlet and outlet conditions of operation. This phenomena is particularly effective under low flow conditions in which high pump suction is desired, since it allows a greater efiiciency of operation under such conditions than that achieved in a pump of the aforenoted type having conventional type vanes lacking the relief section or excess volume provision.

The advantages of the arrangement with the vane structure illustrated at Figure 5 resides in the fact that t on the vanes gives to the pump (1) a much higher flo characteristic under particular operating conditions, (2) a higher pump suction under no flow conditions, and 3) less vane wear due to the decrease in weight obtained by including the relief section or excess volume in the vane itself.

Although only one embodiment of the invention has been illustrated and described, various changes in the form and relative arrangement of the parts, which will now appear to those skilled in the art, may be made without departing from the scope of the invention. Reference is, therefore, to be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

1. In a rotary multi-vane positive displacement pump of the type including a housing having a cavity, a rotor member rotatably mounted in said cavity, an inlet conduit for a gaseous medium opening into said cavity, an outlet conduit for said gaseous medium opening from said cavity, a plurality of slots in said rotor member; the improvement comprising a separate vane slidably fitted in each rotor slot with a continuous close tolerance, each vane having an inner end surface and an outer end edge surface, said housing cavity having a surface of predetermined contour cooperating with the outer end edge surfaces of said vanes so that upon rotation of said member the outer edge surfaces of said vanes continuously contact the surface of the cavity, each of said vanes having a plurality of closely-spaced holes opening at said inner end surface to the inner end portion of the slot in which the vane is slidably mounted and extending more than one-half the length of said vanes, said holes being substantially uniformly spaced from the sides of said vanes and from each other whereby the weight of the vane is reduced, said vanes being free of any passage between said holes and said outer end edge surface, means at both ends of said rotor arranged to prevent fluid communication with the space defined by said slots and the inner ends of said vanes, and the space defined by said slots and the inner end of said vanes being free of spring means. i

2. A rotary multi-vane positive displacement pump comprised of a housing having a central cavity of oval cross section; a cylindrical rotor member rotatably mounted in said cavity; said cylindrical rotor member and said oval-shaped cavity being constructed and arranged so that about one-half of the cylindrical surface of said rotor member is uniformly close1y-spaced to the surface of one end of said oval-shaped cavity and so that an extended crescent-like compression chamber is formed; an inlet opening into one end of said compression chamber; an outlet connected, adjacent the other end of said chamber,

to the space between said rotor member and said cavity where closely-spaced; three equi-spaced longitudinal slots in said rotor member; each of said slots extending tangentially to a circle having a center common to said rotor; three vanes slidably mounted in said slots with a continuous close tolerance and extending from the rotor member at an acute angle to the circumferential surface of the rotor member and in a direction corresponding to the direction of rotation of the member; each of said vanes having a plurality of closely-spaced holes opening into said slots and extending from the inner end of said vanes over one-half the length or" said vanes; said holes being substantially uniformly space-d from the sides of said vanes and from each other whereby the weight of the vane is reduced, said vanes being free of any passage from said holes to the outer end surfaces thereof; means at both ends of said rotor arranged to prevent fluid communication with the space defined by said slots and the inner ends of said vanes, and the space defined bythe surface of said slots and the inner ends of said vanes being free of any spring means.

References Cited in the file of this patent UNITED STATES PATENTS