US3252423A

US3252423A - Variable volume vane type pump

Info

Publication number: US3252423A
Application number: US337043A
Authority: US
Inventors: Charles H Whitmore; Russell G Winquist; Sheldon E Thorson
Original assignee: Continental Machines Inc
Current assignee: Continental Machines Inc
Priority date: 1964-01-10
Filing date: 1964-01-10
Publication date: 1966-05-24
Anticipated expiration: 1983-05-24

Description

y 1966 c. H. WHITMORE ETAL 3,252,423

VARIABLE VOLUME VANE TYPE PUMP 3 Sheets-Sheet 1 Filed Jan. 10, 1964 22mm yum mm y 1966 c. H. WHITMORE ETAL 3,252,423

VARIABLE VOLUME VANE TYPE PUMP 3 Sheets-Sheet 2 Filed Jan. 10, 1964 y 1955 c. H. WHITMORE ETAL 3,252,423

VARIABLE VOLUME VANE TYPE PUMP Filed Jan. 10, 1964 3 Sheet s:Sheet 5 aonomsmi'amasok R United States Patent 3,252,423 VARIABLE VOLUME VANE TYPE PUMP Charles H. Whitmore, Savage, Russell G. Winquist, St.

Paul, and Sheldon E. Thorson, St. Louis Park, Minn,

assignors to Continental Machines, Inc., Savage, Minn,

a corporation of Minnesota Filed Jan. 10, 1964, Ser. No. 337,043 9 Claims. (Cl. 103120) This invention relates to pumps and refers more particularly to variable volume vane type pumps.

Pumps of this type have a rotor which revolves on a fixed axis, and a ring which encircles the rotor and shifts radially towards and from concentricity with. the rotor, to vary the volume of fluid delivered by the pump. The closer the ring is to being concentric with the rotor, the less fluid the pump delivers; but the pressure developed by the pump remains substantially constant throughout the full volume range.

As is conventional in pumps of this type, the rotor has circumferentially spaced slots extending inwardly from its periphery in which vanes are slidably received to be carried around circular orbits by the revolving rotor with their outer end portions projecting beyond the periphery of the rotor and spanning the distance between the rotor and the ring. The vanes thus cooperate with the rotor, the ring, and end walls in the pump body between which the rotor, ring and vanes are confined, to

define pumping chambers which increase and decrease in size as the rotor revolves, because of eccentricity between the ring and the rotor; and since these chambers are in communication with an inlet port as they are increasing in size and communicate with a discharge port as they decrease in size, the rotating vanes produce suction at the inlet port to draw fluid into the pump and pressure at the discharge port.

For more than half the circular orbit of the vanes which encompasses their travel through the pressure zone, the fluid pressure in the pump presses the vanes against the inside surface of the ring as they slide therealong; but the force with which the vanes are pressed against the ring is not uniform, being greatest as the vanes enter and as they leave the pressure zone. This difference in pressure exerted upon the ring by the vanes and the fact that the areas of the ring surface subjected to the greatest pressure were always the same, caused a very marked unevenness in wear on the ring in pumps of this type heretofore available. Long before any other portion of the pump began to show any signs of significant wear, the inside surface of the ring was hopelessly worn. While the ring could be replaced, to do so often was extremely expensive due to the need for shutting down the equipment with which the pump was used. In any event,'the need for frequent replacement of the ring was an irksome inconvenience.

In recognition of this objection to variable volume vane type pumps heretofore available, the present invention has as its purpose and object to provide a pump of the character described wherein the wear on the volume adjusting ring against which the vanes bear will be uniformly distributed around the entire circumference of the ring, which of course greatly increases its useful life.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate one complete ice example of the physical embodiment of the invention,

constructed according to the best mode so fardevised for the practical application of the principles thereof, and in which:

FIGURE 1 is a cross sectional view through a pump embodying this invention;

FIGURE '2 is a sectional view through FIGURE 1 on the plane of the line 22; and

FIGURE 3 is a greatly enlarged view of a portion of the pump rotor and the ring which encircles it, to illustrate how the forces that act upon the ring are utilized in this invention to solve the problem to which the invention is directed.

Referring now particularly to the accompanying drawings, the numeral 5 designates the body of the pump and which, as best seen in FIGURE 2, comprises a base section 6, a rotor housing 7 and a cover 8. These three parts are bolted together with the rotor 9 of the pump in position inside its housing 7 and mounted on the pump shaft 1b which is journalled in bearings 11 and 12, respectively located in the base section 6 and in the cover 8.

The rotor 9 has a plurality of substantially radially disposed slots 13 extending in from its periphery and opening to the opposite ends or faces of the rotor, which are flat. Slidably received in these slots are vanes 14, the vanes being freely movable radially with respect to the rotor, to permit their outer end portions to project beyond the periphery of the rotor to span the space between the rotor and the inside surface 15 of a pressure ring 16 which encircles the rotor. Thus the ring 16, the rotor, the vanes and end walls-provided by a port disc 17 and a thrust plate or disc 18 between which the assembled rotor, vanes and pressure ring are confinedcoact to define fluid pumping chambers 19 which travel in circular orbits as the rotor revolves.

The pressure ring 16 is normally eccentric to the axis of the rotor and, hence, the pumping chambers 19 increase in size. during one-half of their orbital rotation about the rotor axis, and decrease in size during the other of rotation. As the pumping chambers 19 increase in size or volume, they sweep past and communicate with an arcuate inlet port 20 in the port disc 17 to receive fluid therefrom, and as they decrease in size they sweep past and communicate with an arcuate discharge port 21 in the port disc and, in so doing, force the fluid into this port for delivery out of the pump. There is, therefore, a suction zone at one side of the rotor axis and a pressure zone at the opposite side thereof.

An inlet 22 in the base section 6 communicates with the inlet port 20, and an outlet 23, also in the base section 6, communicates with the discharge port 21.

A governor spring 25 which reacts between the pressure ring 16 and the pump body, yieldingly urges the ring to its position of maximum eccentricity with respect to the rotor, which position may be defined by an adjustable stop 26 located diametrically opposite the spring 25.

The governor spring 25 is preferably located in a pocket 27 that projects radially from the main cavity or bore 28 of the rotor housing, and applies its force upon the pressure ring through a shoe 29 which has an arcuate surface corresponding to and fitting the outer cylindrical surface of the ring. Attention is directed to the fact that the engagement of the shoe 29 with the ring is symmetrical with respect to the axis along which the spring exerts its thrust upon the ring and that this axis is radial to the rotor.

The magnitude of the bias exerted upon the pressure ring by the governor spring 25 is adjustable by means of a screw 30, and by its adjustment the pressure developed and delivered by the pump may be set.

As the work being performed by the hydraulic system supplied by the pump varies, the volume of fluid delivered must accordingly vary, and this result is accomplished by the translatory shifting of the pressure ring towards and from its position of maximum eccentricity with respect to the rotor. It should be noted that in shifting from one position to another, the pressure ring moves along a path which coincideswith the axis of thrust of the governor spring and that, in all positions of the ring, its axis lies in a plane which is common to the rotor axis, and in'FIGURE 3 is identified by the line 31. It should also be noted that the in let port and hence the suction side of the pump, lies at one side of the plane identified by the line 31 (below the plane in the drawings) and that the discharge port 21 and the pressure zone of the pump, when in operation, is at the other side of this plane (above the plane in the drawings).

Inside the ring the hydraulic force is nearly constant throughout the full range of volume of fluid delivered by the pump. However, the direction of this force changes as the volume of delivered fluid varies, to the end that the horizontal component of this hydraulic force, i.e. along the plane of line 31, opposing the governor spring 25, is at all times substantially equal to the force of the spring. To illustrate at full volume output, the spring force may be 450 lbs. balanced by a 450 lb. horizontal component of the hydraulic force, while at no volume the spring force might be 750 lbs. balanced by a 750 lb. horizontal component of the hydraulic force. Those skilled in the art will, of course, appreciate that during the no volume" condition of operation, inevitable slippage, i.e. fluid that passes from the pressure zone across the vanes to the suction zone, and leakage-ordinarily termed case drain-keeps the pressure ring from moving into exact concentricity with the rotor. In other words, even when the pump is not delivering fluid, the ring 16 is still not absolutely concentric with the rotor.

Since the suction and pressure zones which obtain when the pump is in operation lie at opposite sides of the plane defined by the horizontal line 31 in FIGURE 3, with the pressure zone being thereabove, the fluid pressure inside the ring 16 also tends to push the ring to one side of this horizontal planeupwardly in the drawings-with a force that increases as the ring moves towards concentricity and decreases as the ring moves in the opposite direction.

Obviously, of course, this upward thrust upon the pressure ring tending to move it to one side of the plane 31, must be opposed, for otherwise the ring would not be confined to its desired translating movement along the plane 31. Heretofore, this was done by having the outer periphery of the ring bear against a shoe so mounted in the body of the pump that it did not in anywise interfere with free forth and back movement of the ring as the direction of the hydraulic force within the ring changed and the governor spring yielded or expanded to balance the fluid pressure opposing the spring. The Miller et al. Patent No. 2,764,941, illustrates this floating shoe support. It is significant that although this floating shoe support did not interfere with free forth and back movement of the ring, it did hold the ring against rotation.

As noted hereinbefore, for part of the orbit of the vanes, fluid pressure in the slots 13 under the inner ends of the vanes, forces them against the inside surface 15 of the ring 16. This occurs when the slots 13 are in communication with an arcuate outlet port 34 which opens to the pump outlet and through which the fluid in the slots is expelled; and arcuate inlet port 33 provides for the admission of fluid into the inner ends of the slots.

Since the arcuate outlet port 34 encompasses a greater angle of rotor rotation than the discharge port 21 and is substantially symmetrical with it, the inner ends of the slots are in Communication with the port 34 after the vanes leave the port 21. Accordingly, along that segment of the orbit of the vanes, identified in FIGURE 1 by the angle 35, the vanes have full pressure under them and little or no pressure on top of them. The same is true for that part of the segment of the orbit identified by the angle 35:: when the vanes are approaching the suction zone and after the pressure behind the vanes loses its effect upon the sloping outer edge of the vanes. The portions of the ring surface 15 traversed during these two portions of orbital vane travel, thus are subjected to the greatest vane pressure, and hence take far more wear than the rest of the ring surface 15.

It is this condition which was primarily responsible for the uneven wear on the inside surface of the pressure ring in pumps of this type heretofore available; but since the design requirements of pumps of this type preclude eliminating this increased outward pressure on the vanes as they approach the high and low pressure zones, and in any event press against the ring harder as they travel through the pressure zone than they do in the suction zone, the objectionable condition was reluctantly accepted as an inevitable consequence of a pump of this nature.

This invention does not eliminate the difference in pressure which the vanes exert upon the inside surface of the pressure ring as they travel around their orbit, but it does distribute the wear resulting therefrom substantially uniformly around the entire circumference of the ring by rotating the ring very slowly around the rotor.

Through the discovery of this invention, it is now known that if the freely shiftable thrust receiving shoe used in the past to hold the pressure ring against being shove-d out of a position at which its center is on the plane defined by the line 31, is replaced by a stationary abutment 40 having a fiat surface parallel to the plane of forth and back movement of the pressure ring, the ring will creep around the rotor and gradually present its entire inside surface to the zones of maximum pressure between the vanes and the ring.

The abutment means 40 is conveniently provided by the flat end of a screw 41 threaded into the rotor housing 7 with its axis normal to the plane 31. In this manner, the exact location of the flat surface which provides the abutment means, with respect to the center of the rotor and the ring, may be accurately adjusted. Since the pressure ring never occupies a position fully concentric with the rotor, it is preferable for the axis of the screw 41 to be slightly to that side of the rotor center opposite that at which the governor spring exerts its force.

By virtue of the thrust of the pressure ring against the fiat abutment surface 40 and the fact that the engagement therebetween is as far to one side of the plane 31 as the diameter of the pressure ring will allow, it follows that with each translating motion of the pressure ring to adjust the volume of fluid delivered by the pump, the pressure ring will roll upon the abutment surface 40 despite any friction, represented by the arows 38, which may exist between the pressure shoe 29 and the ring; and to minimize this friction, the surface of the shoe 29 which bears against the pressure ring, has a covering or lining 29' of Teflon, or is otherwise rendered as frictionless as possible.

Although the pressure ring 16 rolls in one direction across the stationary surface 40 as the ring moves towards concentricity with the rotor, and in the opposite direction when the ring moves away from concentricity, it has been found that the angle through which the ring turns in one direction is always slightly greater than in the other. Why this is so is not entirely clear, but apparently it has something to do with the fact that the hydraulic pressure pressing the ring against the abutment 40 is increasing as the ring moves towards concentricity and decreasing as it moves in the oppoiste direction. Be-

cause of this, the diameter of the ring may be infinitesi- 1 5 mally greater while it is moving in one direction than it is when moving in the opposite direction; especially when the work being performed by the hydraulic system supplied by the pump requires a rapid change from a small volume to a larger volume and a slow change from greater volume to lesser volume.

Possibly also, there may be some very slight deformation of the surface of the ring or of the abutment 40, as the ring rolls back and forth, which conceivably could produce slippage between the contacting surfaces, greater in one direction than the other. But whatever the explanation may be, it is definitely known that with each cycle of forth and back motion of the pressure ring, the ring is given a tiny increment of rotation in one direction, so

' that the ring creeps very slowly around the rotor.

From measurements that have been made, it has been determined that several thousand movements of the ring are required to rotate the same one-eighth of an inch. Nevertheless, this very slow creeping of the ring around the rotor gradually and continually presents another portion or area of the inside surface of the ring to the most serious wear resulting from the friction between the vanes and the ring as they ride around the inside surface of the ring; so that instead ofhaving relatively short segments of the inside surface of the ring carry all of this most serious wear-producing force, the wear is distributed uniformly around the entire circumference of the ring. The net result is that the pressure ring will last practically as long as any other portion of the pump subject to wear.

From the foregoing description taken in connection with the accompanying drawings, it will be apparent that this invention constitutes a substantial improvement in vane-type variable volume pumps.

What is claimed as our invention is:

1. In a variable volume pump of the vane type, having a body, a rotor inside the body constrained to rotate about a fixed axis and having a plurality of slots opening to its' periphery and spaced around its circumference, a ring encircling the rotor and having an inside surface, vanes in said slots to be carried around orbits by the revolving rotor with their outer end portions projecting beyond the periphery of the rotor and spanning the distance between the rotor and the ring, and which are pressed against the inside surface of the ring by the fluid pressure developed .in the pump with a force that varies as the vanes travel decrease in size as the rotor revolves inside the ring as long as the ring is eccentric to the rotor, and biasing means acting upon the ring to yieldingly urge the same along said path toward a position of maximum eccentricity with respect to the rotor in opposition to fluid pressure developed in the pump so that the ring moves forth and back along said path as the volume of fluid delivered by the pump varies,

the improvement whereby wear on the inside surface of the ring caused by the sliding engagement under pressure between the vanes and said surface of the ring is distributed substantially uniformly around the entire circumference of the ring, and which improvement comprises:

means acting upon the ring and responsive to forth and back movement of the ring to effect rotation of the ring in one direction in tiny increments, so that the ring creeps aroundthe rotor as the pump operates to gradually and continually present a different portion of the inside surface of the ring to the most serious wear-producing pressure of the vanes upon the ring.

6 2. In a variable volume pump of the vane type, having a body, a rotor inside the body constrained to rotate about a fixed axis and having a plurality of slots opening to its periphery and spaced around its circumference, a ring encircling the rotor and having an inside surface, vanes in said slots to be carried around orbits by the revolving rotor with their outer end portions projecting beyond the periphery of the rotor and spanning the distance between the rotor and the ring, and which are pressed against the inside surface of the ring by the fluid pressure developed in the pump with a force that varies as the vanes travel around their orbits, end walls on the body between which the rotor, its vanes, and the ring are confined, means mounting the ring for translatory forth and back shifting in the body along a defined path in all portions of which the ring axis lies in a plane common to the rotor axis so that the rotor, the ring, the vanes and the end walls cooperate to form pumping chambers which increase and decrease in size as the rotor revolves inside the ring as long as the ring is eccentric to the rotor, and biasing means acting upon the ring to yieldingly urge the same along said pat-h toward a position of maximum eccentricity with respect to the rotor in opposition to fluid pressure developed in the pump so that the ring moves forth and back along said path as the volume of fluid delivered by the pump varies,

the improvement whereby wear on the inside surface of the ring caused by the sliding engagement under pressure between the vanes and said surface of the ring is distributed substantially uniformly around the entire circumference of the ring, and which improve- .ment comprises:

abutment means fixed with respect to the body and :bearing against a portion of the ring which is spaced to one side of said plane, the engagement of said aibutment means with the ring cooperating with the effect of the varying forces acting upon the ring during operation of the pump to cause the ring to turn slightly, first in one direction and then slightly farther in the other direction as the ring shifts forth and back, so that the ring creeps around the rotor as the pump operates and gradually and continually presents different portions of its inside surface to the most serious wear-producing pressure of the vanes upon it.

3. In a variable volume pump as set forth in claim 2, wherein the fluid pressure developed in the pump and reacting between the rotor and the ring also imparts an outward thrust upon the ring in the direction tending to move it to one side of said plane, and wherein said abutment means is at the same side of said plane and has a surface which bears against the outer periphery of the ring so that the ring rolls on said surface as the ring shifts forth and back.

4. In a variable volume pump, the structure set forth in claim 3, further characterized by: a shoe interposed between the biasing means and the periphery of the ring; and anti-friction means between the shoe and the ring.

5. In a variable volume pump, the structure set forth in claim 3, further characterized by the fact that said surface of the abutment means is flat and parallel with said plane.

6. In a variable volume pump, the structure set forth in claim 3, further characterized by the fact that said abutment means is a screw threaded into a portion of the body with the inner end of the screw facing the periphery of the ring and so positioned by adjustment of the screw as to have the periphery of the ring bear thereon when the center of the ring lies substantially on said plane.

7. The variable volume pump of claim 6, wherein the inner end of the screw is fiat and parallel with said plane. v

8. The variable volume pump of claim 7, wherein the axis of the screw is off-center with respect to the axis of the rotor and lies at the side of the rotor axis opposite that at which the biasing means is located.

9. In a variable volume pump of the vane type, having a body, a rotor inside the body constrained to rotate about a fixed axis and having a plurality of slots opening to its periphery and spaced around its circumference, a ring enclircling the rotor and having an inside surface, vanes in said slots to be carried around orbits by the revolving rotor with their outer end portions projecting beyond the periphery of the rotor and spanning the distance between the rotor and the ring, and which are pressed against the inside surface of the ring by the fluid pressure developed in the pump with a force that varies as the vanes travel around their orbits, end walls on the body between which the rotor, its vanes, and the ring are confined, means mounting the ring for translatory forth and back shifting in the body along a defined path in all portions of which the ring axis lies in a plane common to the rotor axis so that the rotor, the ring, the vanes and the end walls cooperate to form pumping chambers which increase and decrease in size as the rotor revolves inside the ring as long as the ring is eccentric to the rotor, and a spring reacting between the body and the ring to yieldingly urge the ring along said path toward a position of maximum eccentricity with respect to the rotor in opposition to fluid pressure developed in the pump so that the ring moves forth and back along said path as the volume of fluid delivered by the pump varies, the fluid pressure in the pump biasing the ring to one side of said plane,

the improvement whereby wear on the inside surface of the ring caused by the sliding engagement under pressure between the vanes and said surface of the ring is distributed substantially uniformly around the entire circumference of the ring, and which im provement comprises:

a screw threaded into the body at the side thereof towards which the fluid pressure in the pump biases the ring, with its axis perpendicular to said plane and its end bearing against the periphery of the ring, to support the same against the thrust imposed upon the ring by the fluid pressure in the pump, the end of the screw being flat and parrallel to said plane so that the ring rolls thereon as it shifts forth and back; a shoe interposed between said spring and the periphery of the ring; and

anti-friction means on the shoe and through which the thrust of the spring is applied to the ring, fiat and parallel to said plane so that the ring so that the force of the spring is applied to the ring without significantly resisting rotation of the ring as it rolls upon the end of the screw.

References Cited by the Examiner UNITED STATES PATENTS 2,035,465 3/1936 Erskine et al 103-120 2,592,247 4/1952 Coe 103-120 2,600,633 6/1952 French 103-120 2,764,941 10/1956 Miller et al. 103-120 2,955,542 10/1960 Gaubatz 103-120 3,052,189 9/1962 Head 103-120 3,091,185 5/1963 Eames 103-136 3,107,628 10/1963 Rynders et al 103-120 MARK NEWMAN, Primary Examiner.

W. I. GOODLIN, Assistant Examiner.

Claims

1. IN A VARIABLE VOLUME PUMP OF THE VANE TYPE, HAVING A BODY, A ROTOR INSIDE THE BODY CONSTRAINED TO ROTATE ABOUT A FIXED AXIS AND HAVING A PLURALITY OF SLOTS OPENING TO ITS PERIPHERY AND SPACED AROUND ITS CIRCUMFERENCE, A RING ENCIRCLING THE ROTOR AND HAVING AN INSIDE SURFACE, VANES IN SAID SLOTS TO BE CARRIED AROUND ORBITS BY THE REVOLVING ROTOR WITH THEIR OUTER END PORTIONS PROJECTING BEYOND THE PERIPHERY OF THE ROTOR AND SPANNING THE DISTANCE BETWEEN THE ROTOR AND THE RING, AND WHICH ARE PRESSED AGAINST THE INSIDE SURFACE OF THE RING BY THE FLUID PRESSURE DEVELOPED IN THE PUMP WITH A FORCE THAT VARIES AS THE VANES TRAVEL AROUND THEIR ORBITS, END WALLS ON THE BODY BETWEEN WHICH THE ROTOR, ITS VANES, AND THE RING ARE CONFINED, MEANS MOUNTING THE RING FOR TRANSLATORY FORTH AND BACK SHIFTING IN THE BODY ALONG A DEFINED PATH IN ALL PORTIONS OF WHICH THE RING AXIS LIES IN A PLANE COMMON TO THE ROTOR AXIS SO THAT THE ROTOR, THE RING VANES AND THE END WALLS COOPERATE TO FORM PUMPING CHAMBERS WHICH INCREASE AND DECREASE IN SIZE AS THE ROTOR REVOLVES INSIDE THE RING AS LONG AS THE RING IS ECCENTRIC TO THE ROTOR, AND BIASING MEANS ACTING UPON THE RING TO YEILDINGLY URGE THE SAME ALONG SAID PATH TOWARD A POSITION OF MAXIMUM ECCENTRICITY WITH RESPECT TO THE MOTOR IN OPPOSITION TO FLUID PRESSURE DEVELOPED IN THE PUMP SO THAT THE RING MOVES FORTH AND BACK ALONG SAID PATH AS THE VOLUME OF FLUID DELIVERED BY THE PUMP VARIES, THE IMPROVEMENT WHEREBY WEAR ON THE INSIDE SURFACE OF THE RING CAUSED BY THE SLIDING ENGAGEMENT UNDER PRESSURE BETWEEN THE VANES AND SAID SURFACE OF THE RING IS DISTRIBUTED SUBSTANTIALLY UNIFORMLY AROUND THE ENTIRE CIRCUMFERENCE OF THE RING, AND WHICH IMPROVEMENT COMPRISES: