US2570862A - Fluid pump with direction responsive impeller blades - Google Patents

Description

.1951 F. A. ROSENKRANS ETAL 2,570,862

FLUID PUMP WITH D IRECTION RESPONSIVE IMPELLER BLADES Filed Oct. 29. 1949 Inventors: Frank A. Ro'senkrans,

Ernest AW agner; I by A 40 Then Attorney.

Patented Oct. 9, 1351 s PATENT OFFlCE FLUID PUMP WITH DIRECTION RESPONSIV IMPELLER BLADES Frank A. Rosenkrans, Bridgeport, and Ernest A. Wagner, Stratford, Conn., assignors to General Electric Company, a corporation of New York Applicatlon october 29, 1949, Serial No. 124,338

1 Claim. (01. 103-91) This invention relates to a pump impeller embcdying an improved blade construction pursuant to which the impeller will pump a substantial head of liquid when rotating in one direction but a negligible head, with minimum resistance to operation, when rotating in the opposite direction.

Our invention makes it practicable to use drive means common to two pumps, or two groups of pumps, to operate the pumps selectively merely by reversing the direction of drive. A typical usage is in automatic washing machines of the type disclosed in United States Patent No. 2,432,271 granted to Herbert F. Barifli December 9, 1947. In such machines, the clothes are washed and spin dried in a basket supported within an outer tub. During the washing operation water is pumped continuously in a circuit from the tub to the basket and return; during draining and rinsing operations water is pumped from the tub to the waste disposal connection. It has been the practice to use individual pump and motor units for these services for the reasons, among others, that suitable dual function pumps have not been available and with'conventional impeller pumps the use of a common motor would require relatively expensive auto- "matically controllable clutch or gear shifting devices.

We accomplish our general objective of providing an improved pump impeller having blades automatically adjustable to the direction of impeller rotation to effect the desired liquid discharge only when operated in one direction, and our more specific objective of providing a single motor dual pump unit for effectively handling the above noted pumping requirements for automatic washing machines, by equipping the impeller with flexible blades having a pre-established pitch which will distort to create an effective pumping surface for one direction of rota,- tion and will feather for minimum flow resistance during the opposite direction of rotation.

' by which term we mean to include suitable rubber compounds and synthetic rubber-like materials-integral with a mounting hub, although thin, flexible, blades of metal may be used, and we have satisfactorily demonstrated constructions in which the hubs and blades were separate,

the blades being affixed to the hubs by shaft means suitably locked to establish a normal blade pitch. The accompanying drawing and the following detailed description thus relates to what we now feel is a preferred embodiment of our invention. In said drawing, Fig. 1 is a fragmentary side elevation of a pump embodying our invention as affixed to a projecting shaft of a drive motor, the pump casing and the central portion of the impeller hub being in section; Fig. 2 is an end elevational view taken in section on lines 22 of Fig. 1; Fig. 3 is a section of the impeller blade at rest, taken on lines 3-3 of Fig. 2 but on an enlarged scale; and Figs. 4 and 5 are views similar to Fig. 3 but showing respectively the shape assumed by the blades during impeller rotation in a pumping direction and in a nonpumping direction.

In. Fig. 1 the pump impeller 1 embodying our invention is shown aflixed to a. shaft 2 of a motor 3. It is to be understood that the. motor is of any conventional reversing type and that at the opposite end of the motor a similarly projecting shaft end may mount a second, similar, impeller. Preferably integral with each end bell 4 of the motor is a pump casing 5 of conventional involute shape having a tangential discharge outlet 6 communicating with which is a suitable tube 1 for connection with a conduit, not shown. A cap 8 having an inlet fitting I0 is arranged to be secured to the pump body by any suitable means. Pursuant to conventional practice the inlet fitting I0 is concentric with the impeller I. It is intended that the casing be arranged for permanent flooding or that'priming means (not shown) be employed to fill the casing before operation.

As previously stated, we prefer to make the hub and blades of the impeller integral with each other, and utilize suitable rubber compositions or synthetic substitutes which are readily moldable. The hub II is advantageously provided with a metallic core I2 suitably treaded to -receive the threaded end of the motor shaft 2. Stuffing box means have been conventionalized at ll.

The impeller blades I5 are characterized by a relatively heavy edge l6, Fig. 3, which fairs into the hub II as indicated in Fig. 2. The opposite edge of the blades, which during operation in the pumping direction is the leading edge, is relatively thin and flexible. Preferably the blades are molded to have a'gradually tapering cross section. In constructions wherethe blades and hub are integral, the mold shapes the blades with 3' a normal camber or angle of repose which slopes upwardly in the direction of rotation of the rotor for the pumping operation. In constructions in which the blades are separate from the impeller, the blade mounting means may fix the blade slope. Typically, the camber would be of the order of 5 from the horizontal. The illustrated embodiment is designed to eflfect pumping during a clockwise rotation of the impeller. During such.

rotation the resistance of the liquid content of the pump casing to rotation of the upwardly sloping blades will lift the flexible leading edge of the blades to the position schematically shown in Fig. 4 in which position the blade offers a very materially increased frontal projection A which increases the effective blade area, as considered with respect to the effective area of the blade at rest. The thus distorted impellers will function in accordance with the well known principles of impeller pumps. Upon reverse rotation, however, the resistance within the casing tends to flatten the blade as shown in Fig. 5, and the resulting streamline shape reduces the resistance to rotation of the blades in the liquid content of the pump casing to an almost negligible point.

For best operational eificiency we form the blades with suflicient stiffness or body to minimize the lifting of the trailing edge portion l8 relative to the floor of the housing and to prevent the radially outermost tip of the leading edge from folding back over the trailing portion. We also provide adequate casing clearance relative to the blade both in its Figs. 4 and 5 condition to eliminate frictional drag. The actual distortion of the blade in its operating condition of Fig. 4 is, of course, dependent on the viscosity of the liquid being pumped, as well as on the structural qualities of the blade material, speed and head. Fig. 4 is typical of blade shape when operating in water at a top speed of 1800 ft. per minute.

It will be obvious that with the impeller of a pump unit at one end of the motor shaft rotating clockwise as viewed in Fig. 2, the opposite end impeller unit will be rotating counterclockwise viewed from its own end. At the latter impeller unit, therefore, the flexible edge iii of each blade must be at the location of the rigid edge of Fig. 2 so that the blades of the counterclockwise-rotating impeller will feather. Said impeller may be operated as a pump merely by reversing the motor by any conventional means. Our test results have established that for one direction of drive shaft rotation one impeller will produce a 142-inch head while its companion impeller will generate only a 7-inch head. For all practical purposes, and particularly in automatic washing machines. this may be considered to be a pumping condition at one impeller and a nonpumping condition at the other.

While we have shown a particular embodiment of our invention, it will be understood, of course,

thatwe do not wish to be limited thereto since many modifications may be made; and we therefore contemplate by the appended claim to cover any such modifications as fall within the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

A direction responsive liquid pump comprising a casing having inflow and outflow passages, a rotatably driven shaft extending into said casing, an impeller having a hub portion attached to said shaft, said impeller having blades of a flexible material extending substantially radially from said hub portion and having a slight pitch, said blades being adapted to flex along lengthwise extending lines, one edge of each of said blades being thin and readily distortable and the other edge being relatively thick and stiff, whereby upon rotation in one direction the readily distortable edges bend to increase the pitch of the blades and develop a relatively large pumping head and upon opposite rotation feather to decrease the pitch and develop a negligible pumping head.

FRANK A. ROSENKRANS. ERNEST A. WAGNER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,518,916 Greenwell Dec. 9, 1924 2,149,267 Bouvy Mar. 7, 1939 2,370,600 Wightman Feb. 27, 1945 2,382,839 Wuensch Aug. 14, 1945 2,430,552 Bernal Nov. 11. 1947 2,432,271 Bariifi Dec. 9, 1947 2,442,783 Senn June 8, 1948 FOREIGN PATENTS Number Country Date 843,192 France -1 Mar. 20, 1938

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