US2278740A - Rotary pump - Google Patents

Description

April 7, 1942. A. c. ROESSLER 2,278,740

ROTARY PUMP Filed May 16, 1939 A; flmamlaw 6.

INVENTOR a ATTORNE Patented Apr. 7, 1942 ROTARY PUMP Amandus C. Roessler, Berea, Ohio, assignor to Bosec Company, Limited, Cuyahoga' County, Ohio, a limited partnership Application May 16, 1939, Serial No. 273,953

2 Claims.

This invention relates. to improvements in pumps, and more particularly, to the type of pump having a rotor provided with a sliding blade. r

An object of this invention' is to provide a rotary pump, which will be smooth in action and free from objectionable pulsation and vibration.

Another object is to provide a p mp in which the head pressure is prevented from surging against the incoming fluid in the suction line,

t thereby providing smooth and efficient action.

Another object is to provide a pump bore, having a curvature which is constructed and arranged in such manner, that deviation from a true circle is practically imperceptible, thereby insuring smooth travel of the rotating blade.

Another object of this invention is to provide provided with seats III and II respectively. Centrally, seat I is provided with a blind bearing l2, closed at its outer end as indicated at 13, this construction eliminating the necessity of packing the bearing l2, whileseat H is provided with an open bearing l4.

The pump chamber, indicated by the numeral II, is positioned and arranged, as hereinafter described, while a cylindrical rotor 16, extending from one side to the other of the pump chamber l has its ends fitted snugly into the seats I0 and H of the casing 5. One end of the rotor I6 is provided with a stud shaft l'l extending into the a rotary pump with the parts positioned and arranged in such manner that the discharge port may be opened after the suction port has been closed, the same being accomplished without danger of liquid from the discharge port causing hammering in the partially evacuated space.

Another object is to provide means for preventing foreign matter such as grit or sand, carried into the fluid being pumped, fromcatching in the wedged portion between the forward end of the blade and the point of rotor and bore contact.

Other objects are to provide a pump adapted to be produced at a relatively low cost, the same being durable and efllcient in operation.

Another object is to provide a rotary pump, of more than fractional size, capable of being operated at motor speed, which is approximately 1750 R. P. M.

Other and further objects of the invention will become apparent during the course of the following description.

In the drawing forming a part of this application, Figure 1 is a central vertical sectional view of a pump embodying my invention,

Figure 2 is a sectional view taken on the line 22 of Figure 1,

Figure 3 is a diagrammatic view illustrating the generation of the curvature of the casing, while Figure 4 is an enlarged fragmentary end view of rotor shown in Figure l.

g In the drawing the numeral ing of the pump which is mounted on an integrally formed base 6. Endplates or cylinder heads 'i and 8 are secured to the casing i by means of bolts 9 which are screw-threadedly received in the casing 5.

The inner faces of the end plates 1 and l are 5 refers to the easclosed bearing l2, while the other end of the rotor I6 is provided with a driving shaft I8, extending through the bearing l4,- and adapted to be driven by any suitable means, not shown herein, for actuating the herein disclosed pump in 'an obvious manner.

A slidably mounted blade assembly I9 is mounted in a slot 20, passing through the axis of the rotor" and corresponding in axial length to the axial length of the pump chamber IS. The blade I9 is preferably made of steel and in each end thereof a concave seat 2| is provided,

while a smaller groove is provided on each side i of the seat 2|, forming a depression in advance of the blade into which any small foreign matter will fall, and be carried over the point .of rotor and pump chamber contact, to be discharged into the fluid cavity and pass out at the discharge port. s

' Rockers 23, 23a are arranged in each seat 2|.

The rockers 23, 23a.may be formed of rods of packing material, circular in cross-section, having approximately the same radius as the arc of the seat It at the blade end. .Apor'tio'n of the material at one side of the rod curvature is then formed on the face thereof, corresponding to the average curvature of the wall of the pump chamber I5.

The rockers thus formed are then set into the seats 1! respectively in such manner that the face portion of the rocker contacts thewall of the pump chamber l5 and the side portions project beyond the seat 2|. Due to this construction, the rockers are me te ock in the seats 2| as the blade I! revolves, order that the face of the rockers will at all t against the wall of the pump chamber IS.

The rockers 23 and 23a having a definite side area projecting beyond the end of the blade, it follows that when fluid is being forced through the pump, the pressure of the fluid will act against the sides of the rockers and cramp them conform and tightly press against the respective seats 2|, thereby greatly increasing the efficiency of the rockers.

A suction port 24 and a discharge port are provided, and are positioned and arranged as shown in Figure 1 and are related to the rotor as will hereinafter appear.

Referring to Figure 1, D represents the point of contact between the bore of the pump chamber and the rotor I6 while C indicates the center of rotation of the rotor l6, and O'indicates the center of the semi-circle A1, defining the lefthand half of the pump chamber i5 as viewed in Figure 1. The diameter chord of the semi-circle A1, is indicated by D, D1 and it will be noted that the center of rotation C is on that chord but is eccentric of the center 0. For reasons which will appear, the right-hand half of the pump chamber bore is not made semi-circular but is such that the volume of the right-hand half is greater than that of the left-hand half, as

. is equal to 21', where r is the radius of the semicircle A1, and the nature of the curve A2 defining the right-hand half of the pump bore is such that as the blade I!) rotates its effective chord length at all times defines the distance between the opposite surfaces of the pump bore contacted by the rockers 23, 23a.

Let it be assumed that the parts are in the position shown in Figure 1, so that the leading edge of the rocker 23 is at the point s, just closing the suction port 24. Then referring to Figure 3, the line s'-u represents a line from the leading edge of the rocker 23 to the trailing edge of the rocker 23a. As the leading edge of the rocker 23 moves from the point 8' to the point 8 the trailing edge of the rocker 23a moves from the point u to the point t and further movement W111, of course, begin to open the discharge port. The position of the point t relatively to the other parts is so selected that when the rocker 23a moves from u to t the volume in the arcuate fluid rushes upon opening of the discharge port, causing vibration and uneven flow.

My invention avoids all of these objectionable features, by so constructing and arranging the ports that the discharge port is opened after the suction port, thereby avoiding surge into the suction line, and .though the discharge port is opened after the suction port is closed, there will be neither undesired compression nor a partial vacuum, but, on the contrary, the volume of the pressure space of the pump will be the same when the discharge port opens as it was when the suction port closed. I

The character of the curve A: may be determined mathematically, as follows. Referring to Figure 3, Po represents a point on the desired curve. The line QPo has a length of 21' and it passes through the center of rotation C so that the line QPo represents the effective chord length of the blade 19. Assume first that the blade I9 is in the vertical position so that its effective chord length QPo coincides with the diameter D, D. circle A, while the line QPo always passes through the center of rotation C. the end of the chord opposite from Q will describe the desired curve A2.

For any position of the chord QPo we may aspump-space between it and t is equal to the sure side is the same as when the suction port was just closed. It will be apparentthat if the discharge port were opened at some intermediate point such as P the foregoing would not be true but, on the contrary, the volume in the pressure space would be larger than when the suction port 4 was closed, so thus there would be a partial volume or air space, into which liquid from the discharge pipe would rush and cause hammer as the discharge port was opened.

In prior pump constructions the discharge port is so disposed that it is opened at the same time or slightly before the suction port closes in or'- der to avoid compression, for example the dis charge port would open at the point u, or at u, respectively. This disposition of the ports results in back pressure from the discharge line directly into the suction line, causing a backward surge and consequent vibration and noise. If, on the other hand, in order to overcome this objectionable feature the point of discharge opening is set back to say P, a backward surge of fluid takes place due to the fact that the position of the blade results in slightly increasing the cubical capacity of the fluid cavity thus forming tween the points C and Po. tween the points C and Q is equal to 2r-a: since the length of the chord QPo is equal to 21'. We may draw a radius r from the center 0 of the semi-circle A, to the point Q, and define the variable angle between the radius r and the diameter D, D1 as 0. The distance between the center of rotation C and the center 0 of the semi-circle A, is a constant K. 1

From the triangle OQCO We may obtain an expression form since one of the sides of this triange contains a: as a term. From plane trigonometry, in any triangle the square of any side is equal to the sums of the squares of the other two sides, minus twice their product into the cosine of their included angle. Hence the square of the side QC is equal to the square of the side Q0 plus the square of the side CO minus twice the product CO times Q0 into the cosine 0. Solving this equation for a: it can be shown that The values of 1' and k are of course known, so

a partial vacuum or'air pocket into which the number of different values to the angle 0 to determine any desired number of points P0 or the curve A2.

The efiect of back pressure upon the projecting portion of the blade is minimized by correct proportioning of the bore of the pump chamber and the rotor diameters with respect to each other. Such proportioning is also imperative for satisfactory high speed: operation. Satisfactory results are obtained when the pump chamber bore diameter does not exceed'that of the rotor diameter by more than approximately fifteen per cent. In other words, fifteen per cent of the rotor diameter added to this diameter results in a bore diameter of smooth and quiet operation at high speed of pumps of greater than fractional capacity.

It will be apparent to those skilled in the art that the invention herein disclosed, may be variously changed, used or modified, without departing from the s irit of the invention or sacrificing the adva tages hereof, and that the embodiments of the invention herein disclosed Now if we move the point Q along the semi- Then that part bea casing, a chamber positioned withinsaid'casing and comprising halves of difierent format opposite sides of a chamber diametrical chord,

the chamber on one side of the chord being cir- I cular and on the opposite side of the chord being enlarged beyond a true circle, a rotor positioned eccentrically within said chamber and in contact therewith at the upper intersection of the chord with said chamber, a single blade reciprocable diametrically within said rotor and adapted to make sealing contact with said chamber in all blade positions, a suction port in communication with the chamber through the circular half thereof at one side of the point of rotor contact, a discharge port in communication with the chamber through the enlarged half thereof at the other side of the point of rotor contact, and said ports being arranged so that when one end of the rotor blade. closes the suction port the blade travels a sufiicient distance before the other end of the blade opens the discharge port to restore-the volume confined between the ends of the blade to the same value attained when the suction port was closed whereby partial vacuum or compression in the pump space is prevented.

2'. A rotary fluid pressure machine comprising a casing, a chamber positioned within said casing and comprising halves of difierent form at opposite sides of a chamber diametrical chord, the chamber on one side of-the chord being circular and on t e Opposite side of'the chord structed and arranged in such manner that it is defined bythe end of a vector of variable length whose origin is disposed eccentrically on said diametrical chord th'e length of said 'vector is measured by the formula Y in which 1' is'the radius oi saidsemi-circle, and k is the eccentricity of said origin and 0 is the angle between said diametrical-chord and a radius of said semi-circle, the position of said radius being determine'd'by the intersection of the rearward projection of said vector with said semi.-

'circle,' a rotor positioned eccentricallywithin said.

chamber and in contact therewith at the upper intersection of the chord with said chamber, a single blade. reciprocable' diametrically within said rotor-and adapted to make sealing contact with said chamberin all blade positions, a suction port in communication with the chamber through the circular half thereof at one side of the point of rotor contact, a discharge port in communication with the chamber through the enlarged half thereof at the other side of the point of rotor contact, and said ports being arranged so that when one end of the rotor blade closes the suction port the blade travels a sumcient distance before the other end of the blade opens the discharge port to ,restore the volume confined between the ends of the blade to the same value attained when the suction port was closed whereby partial vacuum or compression in the pump space is prevented.

AMAND S C. ROESSLER.

being enlarged beyond atrue circle, said chamher on the opposite sideof the, chord being coni.

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