US 2588032 A
Description (OCR text may contain errors)
March 4, 1952 O'BRIEN 2,588,032
ROTARY PUMP Filed Nov. 10, 1947 Patented Mar. 4, 1952 Packard Motor Car Company, Detroit, Mich., a corporation of Michigan Application November 10, 1947, Serial No. 785,164 3 Claims. (Cl. 103- 120.
The present invention relates to rotary pumps and has for its object the provision of an improved rotary pump of the type primarily designed and intended to deliver liquid at'a substantially constant pressure despite wide variations in required pump output and wide variations in the speed at which the pump is driven.
In my co-pending application, Serial No. 785,163, filed November 10, 1947, there is disclosed and claimed an improved rotary fluid pumpin which the vane carrying rotor is mounted upon a drive shaft and the cylinder which encircles the vanes of the rotor is housed within a cham ber of slightly larger diameter so that the cylinder may be bodily moved into a position in which it is concentric with the axis of the shaft or into any one of a number of positions of eccentricity, the position of the cylinder with respect to the axis'o'f the drive shaft determining the volumetric output of the pump. The arrangement is such that the cylinder is normally urged toward the position of maximum eccentricity, and when the cylinder is in this position the volume of liquid delivered by the pump is greatest. A novel form of resilient means is provided for thus urging the cylinder toward eccentric position and opposing its movement toward a position in which it is concentric with the drive shaft, one purpose being to provide a pump Which lends itself particularly to quantity production at low cost.
The present invention is likewise concerned with the provision of a 'novel means for normally urging the bodily movable cylinder of the pump toward the position of maximum eccentricity to the drive shaft, and for yieldingly opposing movement of the cylinder away from that position. Essentially this yielding means comprises an elongated resilient element which encircles the cylinder and is attached at one point to the casing within which the cylinder is housed. Most advantageously this elongated cylinder encircling resilient element may comprise a helical spring of low rate type since a spring of this character can not only apply the necessary force to the cylinder but can likewise function as a damper which prevents rapid oscillation of the cylinder with sudden variations in liquid pressure. Thus the spring, which is always under some tension, closely engages the outer surface 60 of the cylinder throughout nearly the entire periphery of the cylinder and, by reason of the close engagement of the individual turns or convolutions of the spring with the surface of the tionally opposed by the spring so that sharp or rapid oscillations are prevented or damped out by friction. Hence the operation of the pump is quite smooth and a change in output will occur gradually and without periods of sudden increase followed by periods of sudden decrease.
In the form of the invention selected for disclosure by way of example the helical tension springis seated in a groove formed in the outer surface of the cylinder and a complementary groove is formed in the cylindrical wall of the casing so that, despite the fact that the tension spring'is between the cylinder and casing wall it in no wise tends to prevent free movement of the cylinder to its position of greatest eccentricity, i. e. when it is in contact with the wall of the casing in which it is housed.
In the drawings:
Figure 1' is a side elevation of the pump as seen from the outside, the drive shaft being shown in section;
Figure 2 is a similar view upon a somewhat larger scale, the cover plate of the pump casing having been removed in order to more clearly disclose the working parts of the pump, and portion of the casing having been broken away; Figure 3 is a section on line 33 of Figure 2; and
Figure 4 is a section on line 44 of Figure 2.
Many features of the rotary pump illustrated are conventional and need not be described in great detail. The driveshaft ID is supported for rotation about a fixed axis and may be driven by any suitable source of power, as for instance by power taken from the power plant of a motor vehicle, in which case the speed of revolution will obviously vary within wide limits. Encircling the drive shaft is a casing comprising the main casing member H and cover plate l2, the casing defining a chamber which has a generally cylindrical inwardly facing wall surface l3 concentrio with the axis of shaft l0, and mutually facing parallel side walls disposed normally to this axis. Within the chamber thus formed by the casing is disposed a cylinder I5 and within the cylinder is a rotor l6 fixed upon shaft In, this rotor carrying vanes l1, radially movable, and the outer ends of which slidably engage the cylindrical inner surface of the cylinder 15.
Rings I8 engage the inner ends of vanes IT for the purpose of maintaining the outer edges of the vanes in contact with the cylinder, as described. The cylinder is provided with an outward projeotion IS with rounded end which is loosely recylinder, all movements of the cylinder are fricl5 ceived within a correspondingly shaped notch formed in the casing and diametrically opposite projection 19 is a shallow projection 20 with rounded outer surface as shown in Figure 2. The diameter of the cylinder is less than the diameter of the chamber in which it is housed and may be rocked about the end of projection l9 to a limited extent, as an axis or fulcrum, the projection 20 resting upon and sliding along the inner surface of the cylindrical wall of the casing member H.
The means provided for maintaining the cylinder in position of maximum eccentricity comprises a helical spring 22. This pring encircles the cylinder, closely engaging the cylinder at all times since it is always under some tension, and is connected to a bolt 23 which passes through both the main member II and cover plate l2 of the casing, the ends of spring 22 being hooked or wrapped around the bolt and the bolt having a reduced portion providing an annular recess within which these curved ends are received, as shown in Figure 4.
As may be observed from an inspection of Figures 2, 3 and 4, spring 22 is in part received within a recess l5a formed in the outer faceof the cylinder I 5 and the spring will remain seated in the groove thus provided for its reception at all times. In order to insure that the spring will not interfere with the movement of the cylinder bodily in a direction transverse to the axis of the shaft, the inner face of the cylindrical wall of the chamber is provided with a complementary groove of curved cross section, indicated at H a, the grooves Ha and [5a being of such depth, taken together, that the cylindrical surface of the cylinder may reach and contact with the cylindrical surface of the chamber despite the presence of the spring between cylinder and easing.
Each convolution of the elongated spring is in contact with the surface of the groove a of the cylinder l5 for a substantial distance and as a result bodily movement of cylinder 15 against the tension of spring 22 will be frictionally opposed at a great number of points, i. e. the points where the spring coils bear against the cylinder. This frictional resistance of the spring to movement of the cylinder is not sufliciently great to actually prevent movement of the cylinder as pressure within the pump builds up due to increased speed of rotation of the rotor but is. nevertheless, sufficiently great to dampen the cylinder movements and prevent the cylinder from, in effect, oscillating rapidly as the R. P. M. of the drive shaft varies. This damping effect 4 realized by the use of the elongated helical tension spring is oi material advantage in that it minimizes rapidity in the change of output of the pump and is helpful in maintaining a constant pressure regardless of variations in speed of rotation of the drive shaft and change in output requirements.
Having thus described the invention, what is claimed as new and desired to be secured by Letters Patent is:
1. In a rotary pump, in combination, a rotor, vanes carried by the rotor, a cylinder encircling the rotor and engaging the outer ends of the vanes, a casing defining a chamber having a cylindrical wall concentric with the rotor and of greater diameter than the cylinder so that the cylinder is shiftable bodily in said chamber, and an element completely encircling the cylinder and connected to the casing at one point, said element contacting the surface of the cylinder at closely spaced points throughout substantially the entire circumference of the cylinder, a portion of said element being resilient, whereby the cylinder is normally urged toward the chamber wall.
2. In a rotary pump, in combination, a rotor, vanes carried by said rotor, a cylinder encircling the rotor and engaging the outer ends of the vanes, a casing defining a chamber having a cylindrical wall concentric with the rotor and of greater diameter than the cylinder so that the cylinder is shiftable bodily in said chamber, a helical spring encircling the cylinder and closely engaging the outer surface thereof at a large number of closely spaced points, the points of contact defining a eries which substantially encircles the cylinder, said spring being under tension, and means attaching said spring to said casing whereby the cylinder is normally urged into contact with the cylinder wall.
3. The combination set forth in claim 2 in which the outer surface of the cylinder and the inner surface of the cylindrical wall of the chamber are provided with complementary grooves to receive the spring.
JAMES H. OBRIEN.-
REFERENCES CITED UNITED STATES PATENTS Name Date Streckert Oct. 28, 1930 Number