US3771901A

US3771901A - Rotary pump

Info

Publication number: US3771901A
Application number: US00233692A
Authority: US
Inventors: S Svensson
Original assignee: Alfa Laval AB
Current assignee: Alfa Laval AB
Priority date: 1971-03-16
Filing date: 1972-03-10
Publication date: 1973-11-13
Anticipated expiration: 1990-11-13
Also published as: DD98142A5; DE2211819A1; FR2129654A5; GB1330082A; IT950005B; AU3965872A; SE351011B

Abstract

The peripheral wall of the pump chamber includes a surface of revolution having its axis coinciding with that of the pump rotor, the latter being provided with radial vanes cooperating with said peripheral wall to divide the chamber into a suction side and a pressure side. A diaphragm having an inner surface forming part of said peripheral wall is urged against the pump rotor by an air cushion enclosed in a space defined by the diaphragm and a bowl seated against the diaphragm''s outer surface.

Description

United States Patent 1191 Svensson Nov. 13, 1973 ROTARY PUMP [75] Stig Ake GostaSvensson, Sodertalje,

Sweden [73] Assignee: Alia-Laval AB, Tumba, Sweden [22] Filed: Mar. 10, 1972 [21] Appl. No.: 233,692

Inventor:

[30] Foreign Application Priority Data Primary Examiner-C. J. Husar Attorney-Cyrus S. I-Iapgood et a1.

[57] ABSTRACT The peripheral wall of the pump chamber includes a Mar. 16, 1971 Sweden 3347/71 surface of revolution having its axis coinciding with 52 US. c1. 418/156 that of the P rotor the latter being Provided with 51 1m. (:1. ..F01 5 04 radial vanes cooperating with Said Peripheral Wall to 158 Field of Search 418/152, 153, 156; divide the chamber into a Suction Side and a Pressure 73/262 side. A diaphragm having an inner surface forming part of said peripheral wall is urged against the pump 5 References Cited rotor by an air cushion enclosed in a space defined by UNITED STATES PATENTS the diaphragm and a bowl seated against the diaphragm s outer surface. 2,409,688 10/1946 Momeau 418/153 2,738,775 3/1956 Smyser 418/156 4 Claims, 2 Drawing Figures ROTARY PUMP The present invention relates to pumps of the type comprising a pump rotor which is journalled concentrically in a pump chamber defined by a surface of revolution and which is provided with radially directed vanes cooperating with the pump chamber wall to divide the pump chamber into a suction side and a pressure side, the outer edges of the vanes forming generatrices of the surface of revolution.

Pumps having a pump rotor journalled eccentrically in the pump chamber and provided with vanes of rubber have been used for pumping liquids, such as milk. Due to the eccentric journalling of the pump rotor, the vanes are folded and unfolded with a high frequency at their attachments adjacent to the pump rotor, while dragging against the pump chamber wall due to the centrifugal force. This rapid and severe flexing of the pump rotor vanes causes the vane material to become fatigued so that the vanes are torn off. As soon as the vane has been torn off, the entire pump rotor must be exchanged, which means expensive pump repairs.

An object of the present invention is to provide a durable pump which is also easy to clean, which latter circumstance is of importance when the pump is used for liquids of the character of food, such as milk.

The pump according to the invention is characterized in that a part of the pump chambers peripheral wall is formed by a diaphragm and that a bowl engaging the outside of the diaphragm encloses, in cooperation with the diaphragm, an air cushion which maintains the diaphragm against the pump rotor.

By means of this arrangement, it is no longer necessary to use foldable vanes. According to the invention, the vanes can be quite rigid and consequently are not worn out through a high frequency folding. The dividing of the pump chamber into a suction side and a pressure side is effected by the cooperation of the vanes with the resilient diaphragm, which is urged against the pump rotor and consequently against passing vanes. The diaphragm is subjected only to bulging movements and thus has a lifetime many times greater than that of the rubber vanes of the prior pumps. In addition, the rubber diaphragm is very cheap to exchange, compared with a pump rotor having rubber vanes.

If the diaphragm has an oval shape and is inserted in a circular space, it lies effectively against the pump rotor, especially under the influence of said air cushion.

According to a preferred embodiment of the invention, three pump vanes are used, since this number is sufficient for giving the pump a good volumetric efficiency.

The vane leaving the pressure side of the pump chamber, and consequently lying against the diaphragm, may entrain into the rotation a liquid quantity which is confined between the vane and the diaphragm. To avoid this effect, the pump rotor vanes are placed obliquely in relation to the axial direction. This oblique position of the vanes makes it possible for the aforementioned liquid quantity to flow back in the direction toward the pump outlet, whereby the volumetric efficiency of ,the pump is increased. j

If the outer edges of the pump rotor vanes are parallel to the rotor shaft, the diaphragm is subjected to .a certain wear. This wear can be reduced appreciably by shaping the edges of the vanes substantially as an. arc of a circle, the surface of the pump chamber being shaped correspondingly (preferably about spherical).

In this way, bending away of the diaphragm, effected by the vanes, will be greatest at the center of the diaphragm.

The invention is explained more in detail below, reference being made to the accompanying drawing in which FIG. 1 is a sectional view of an example of the new pump, taken at right angles to the axis of rotation of its rotor, and

FIG. 2 is a longitudinal sectional view of the same example, showing the rotor in side elevation.

In FIG. 1, a pump housing 1 has a generally spherical pump chamber 2 provided with an inlet 3 and an outlet 4. A pump rotor 5 with three vanes 6 is journalled concen'trically in the pump chamber 2. The direction of rotation of the pump rotor is indicated by an arrow, shown in the pump chamber. In the position of the rotor 5 as shown in FIG. 1, an oval rubber diaphragm 7 lies in a circular space 8 against the pump rotor body 5 proper and the two upper vanes 6. The rubber diaphragm is clamped in the pump housing 1 by means of an inverted bowl 9, which is secured to the housing 1 by suitable clamping means (not shown) of conventional form. The bowl 9 encloses above the diaphragm an air cushion, which keeps the diaphragm pressed against the rotor 5.

As shown in FIG. 2, the edge of each vane 6 forms an arc of a circle so that it conforms to the arcuate shape of the chamber wall 2a. Also, as shown in FIG. 2, the vanes As shown in FIG. 2, the edge of each vane 6 forms an arc of a circle so that it conforms to the arcuate shape of the chamber wall 2a. Also, as shown in FIG. 2, the vans are disposed obliquely in relation to the axial direction. The pump rotor 5 has two gudgeons l0 journalled in corresponding recesses in the pump housing, and the right-hand gudgeon is connected to a shaft 11 of a driving motor (not shown). The lead-through of the shaft 11 in the pump housing is sealed by means of a gasket 12. The right-hand gudgeon 10 has a diametrical groove (not shown) which receives a corresponding driving projection (not shown) on'the shaft 11. When the rotor 5 is turned so that said groove extends vertically, the rotor can easily be lifted from the pump housing so as to'be inspected and cleaned.

When the pump rotor rotates in the direction of the arrow, there is formed in the left-hand part of the pump chamber 2 (FIG. 1) a suction side which, by means of the lower vane 6, is separated from a pressure side formed in the right-hand part of the pump chamber. The right-hand upper vane 6 will come into contact with the diaphragm 7 and slide past it while lifting it against the action of the air pressure in the bowl 8. Thus, the sealing (necessary for the pumping function) between this vane and the diaphragm is obtained. Due to the arcuate shape and the oblique position of the vane, the diaphragm is lifted successively and mostly at its center, whereby it is subjected to minimum wear. lf

' the edges of the vanes 6 were parallel to the axis of rotation, the vanes would, when passing the diaphragm, entrain a liquid quantity confined between the diaphragm and the vanes. Through said oblique positioning of the vanes, however, such liquid quantity will slide along the entraining vane in the direction toward the pump outlet 4, whereby the volumetric efficiency of the pump is increased.

l. A pump comprising means defining a pump chamber, said chamber having a peripheral wall including a surface of revolution and also having an inlet and an outlet, a rotor journalled in the housing for rotation in said chamber about an axis concentric to said surface of revolution, the rotor having vanes extending radially outward and cooperating with said peripheral wall to divide the chamber into a suction side and a pressure side communicating with said inlet and said outlet, respectively, the outer edges of said vanes forming generatrices of said surface of revolution, said means including a flexible diaphragm having an inner surface forming part of said peripheral wall and engageable with each said vane along the entire outer edge thereof, a

ing a shapecorresponding to said arc.

4. A pump according to claim 3, in which said vanes extend obliquely relative to said rotation axis.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 1 I Dated November 13 1973 l lg Ake Gosta Svensson It is certified that error appears in the above-identified patent Y and ,that said Letters Patent are hereby corrected as shown below:

7 Col. 2', lines 27, 2s, 29, and 30 should be deleted.

Col 2, line 34, "vans" should be --vanes Claim 2,,line2, "s'i'ad" should be --said--.

7 Signed anc l 'sealed this 6th day of Augustl974.

(SEAL) Attest: MCCOY M.- GIBSON; JR; C. MARSHALL DANN Attesting Officer Commissioner of Patents

Claims

1. A pump comprising means defining a pump chamber, said chamber having a peripheral wall including a surface of revolution and also having an inlet and an outlet, a rotor journalled in the housing for rotation in said chamber about an axis conceNtric to said surface of revolution, the rotor having vanes extending radially outward and cooperating with said peripheral wall to divide the chamber into a suction side and a pressure side communicating with said inlet and said outlet, respectively, the outer edges of said vanes forming generatrices of said surface of revolution, said means including a flexible diaphragm having an inner surface forming part of said peripheral wall and engageable with each said vane along the entire outer edge thereof, a bowl seated against the outer surface of said diaphragm and cooperating therewith to form an enclosed space, and an air cushion in said space urging the diaphragm against said rotor.

2. A pump according to claim 1, in which said space is circular, siad diaphragm having an oval shape.

3. A pump according to claim 1, in which each of said vane edges extends lengthwise of said axis in substantially an arc of a circle, said surface of revolution having a shape corresponding to said arc.