US1929232A - Mechanism for controlling the operation of centrifugal pumps - Google Patents

Description

H.E. ADAMS 1,929,232

MECHANISM FOR CONTROLLING THE OPERATION OF CENTRIFUGAL PUMPS Oct. 3, 1933.

Filed Feb. 5, 1932 2 Sheets-Sheet l firold .E'. cfzdam's,

H. E. ADAMS 1,929,232 MECHANISM FOR CONTROLLING THE OPERATION OF CENTRIFUGAL PUIPa' Oct. 3, 1933.

2 Sheets-Sheet 2 Filed Feb. 5, 1932 Mrold E uZdams,

Patented Oct. 3, 1933 V MECHANISM FOR. CONTROLLING THE OPERATION or CENTRIFUGAL rUMrs Harold E. Adams, South Norwalk, Conn., as-,

signer to Nash Engineering Company, South Norwalk, Conn., a corporation of Connecticut Application February 5, 1932. Serial No. 591,199 4 Claims. (01. 103 -113) This invention has particular reference to improving the mechanism shown, described and claimed in my Letters Patent No. 1,803,885, dated May 5, 1931. a

When the inlet or supply to a centrifugal water pump is at a lower level than the eye of the impeller, an air pump is often employed to raise the incoming water to prime the centrifugal water pump. This air pump also is used to extract or remove any air which is entrained in the incoming water, so as to insure smooth action of the impeller.

As a centrifugal pump works most efficiently with a constant head on the supply, the above described apparatus is also designed to keep the level of the incoming water as constant as possible.

To this end a control chamber is arranged above the inlet, and the air pump is connected to the inlet through this control chamber. A vent valve controlled by a float is arranged in the control chamber so as to open and admit atmospheric air when the desired level is reached.

But owing to the snapping and opening action obtained by the float and to the eddies and whirls of the water in the control chamber, the head is not kept exactly constant and deleterious bounding or hunting action of the water column in the Figure 6 is an elevation on a still larger scale of the vent valve and its stem.

Figure '7 is asectionalelevation similar toFigure 1 of a modified form of apparatus, and,

Figures 8 and 9 are a plan view and a cross-sectional view, respectively, on an enlarged scale of the grid used in the apparatus shown in The improvement will be best understood from a detailed description of the mechanism.

Referring now to the first sheet of drawings,-

10 designates the impeller of a centrifugal water pump which is arranged in a casing 11. 12 designates the suction pipe which is connected through an elbow 13 to the intake 14 formed in the casing 11. The parts 12, 13 and 14 form the I water inlet to the eye 16 of the impeller 10. A control chamber 20 is formed immediately above the pump inlet 14, air being admitted and withdrawn from this chamber by a control valve 22 operated by a float 52 in a' manner hereinafter described. 30 designates the rotor of .the air pump, which rotor is secured on a shaft 31 extending from the motor M, the impeller 10 being secured on the endof this shaft, and the motor being carried by brackets or feet secured to the side of the pump casing 11.

A passage 32 formed in the casing 11 connects to a passage 33, formed in chamber 20. The top of the chamber is made up of a cover 34 which has a passage 35 registering with the passage 33.

The first improvement relates to a particular construction of the valve stem-.which connects the ball float 52 to the valve 22. The valve stem' is fitted to work in seat bushings 54 and 55 secured in the cover 34. The lowenportion 59 of the valve stem 51 is made of a reduced diameterand flutes or grooves 58 are cut in the stem, these flutes extending into the reduced portion 59 of the stem. The flutes or grooves are tapered or enlarged downwardly so as to provide larger passageways through seat bushing 54 as the valve 22 is raised.

During the initial priming action, the air pump draws air out of the water inlet to the centrifugal pump through passages 32, 33 and 35 and control chamber, 20, the air passing from the control chamber 20 to passage 35 through seat bushing 55 and the flutes 58. During this priming operation the valve 22 is closed, as shown in Fig. 2.

As this priming operation takes place, the water will rise in the inlet to the centrifugal pump, and will pass into the intake 14 thereof and will continue to rise in the control chamber 20. This will prime or start the centrifugal pump in operation and any air entrained in the incoming column will be carried up into the chamber 20.

As the air pump continues to operate, the water will rise in the chamber 20 .until it attains a level indicated approximately at A, A, when the same will engage the float. As soon asv the buoyancy of the float overcomes the weight of the same, the valve stem and the valve and the atmospheric pressure upon the top area of the valve, the valve 22 will open with rather asnap During this operation the column of As soon as the valve 22 moves upward from the closed position shown in Fig. 2, it will be noted that there is a progressive increase of the flow of atmospheric air into passage 35. This leakage is first illustrated by the relatively small clearance between the valve stem 51 and bushing 54, as shown in Fig. 3. Then it is increased as the stem rises to bring the gradually increasing openings of the flutes up through bushing 54 as shown in Fig. 4.

If the momentum of the water column carries the valve to such a height, that the vacuum in the passageway 35 is reduced to a value less than the vacuum in chamber 20, there will be a slow leakage of air from passage 35 through the restricted passage around the reduced portion 59 of the valve stem into chamber 20. This clearance relation is very critical and is an important one and has to be such that it does not allow excessive leakage to produce an abnormal acceleration of the water in a downward direction. This leakage is controlled so that the water column recedes or drops with the float and parts forming it at a slow rate.

As the parts drop. the amount. of flow from the atmosphere through bushing 54 is decreased to a point where the vacuum in the passage 35 builds up a value suflicient to overcome the leakage from passage 35 into the chamber 20 and to cause a slight flow from the chamber 20 into the passage 35. Because of this retarding action in bushing 55 the water column in the chamber will be brought to a complete stopin practically one operation. x

The relationship of the clearance. space between portion 59 of the valve stem and bushing 55 is tied up very closely with the timing of the flutes 58 and their size and rate of opening, while these are further closely related to the displacement or capacity of the air pump used to prime the water pump.

It will be further noted that the flutes give a quick closing action, compared with the initial upward movement of the parts and that the relatively long movement of the parts gives a relatively constant leakage area between the stem 59 and bushing 55, this travel of the stem with constant area of leakage being contrasted with the graduated opening through seat bushing 54 to atmosphere with the corresponding travel.

By properly proportioning the seat bushings and the various sections of the valve stem, the water column can be quickly brought to a constant height and kept at this height accurately I during the pumping operation, so that the censtruction is especially desirable when there is liable to be a positive head in the inlet. When the parts assume this position, which is illustrated in Fig. 5, it will be noted that the air pump is freely connected to the atmosphere through the flutes 58 and seat bushing 54. This arrangement protects the pump from damage by water flooding and also relieves the pump from duty when the chamber is filled.

It thus will ,be seen that in operation a twovalve'effect is obtainednamely valve 22, stem 51 and flutes 58 cooperating with seat bushing 54 control and regulate the supply of atmospheric air; and that stem 59, flutes 58 and nut or valve 53 cooperating with seat bushing 55 control and regulate the withdrawal of air by the air pump from chamber 20; and that the two effects are correlated and combined so as to maintain a flxed level in the control chamber after priming and so that the air pump is relieved to atmosphere to the proper degree without relieving the vacuum in the control chamber.

In the devices of the prior art, it has been found necesssary to provide a number of passages between the inlet and the control chamber. This leads to complication and muilled action. It will be noticed that there is one large passageway between the pump inlet and the control chamber, this passageway being directly over the eye or entrance to the impeller.

The second improvement relates to a means for providing for a smooth action of the float and connected valves. To this end, baiile plates 6061 are arranged to form the bottom of the chamber. It will be noted that these baflie plates are out of the path of the water flowing to the impeller.

Instead of using baiile plates a removable grid 62 may be employed between the inlet and the chamber, as illustrated in Fig. 7. This grid may be held in place by a screw 63. This grid can be easily removed by taking off the cover 34 of the chamber. Thus access is given to the inlet and impeller of the pump for cleaning or inspection purposes. The baflle plates. or grid arranged between the inlet and the chamber reduce and eliminate eddies and whirls in the rising column of water which might affect the operation of the float, but do not limit the flow of air or impede the flow of water to the eye 16 of of the impeller.

Thus by the improvements described, I have greatly improved the operation of the prior art devices. The details and arrangement herinafter shown and described may be greatly varied by a skilled mechanic without departing from the scope oi. my invention as expressed in the claims.

Having thus fully described my invention, what I desireto claim and secure by Letters Patent of the UnitedStates is:--

l. Mechanism for priming a centrifugal water pump, comprising an air pump, a control chamber communicating with the inlet of the centriiugal pump, a connection from the control chamber to the air'pump, a connection from atmosphere to said air pump, a vent valve unit for admitting atmospheric air to said last connection to the air pump and for regulating the withdrawal of air from the control chamber, a stem forming part of said unit, a float in said chamber and connected to said stem, and seat bushings in said connections, through which said stem slides and with which said valve unit cooperates, said stem having tapered flutes cooperating with said bushings.

2. Mechanism for priming a centrifugal pump, comprising an air pump, a control chamber communicating with the inlet of the centrifugal pump, a connection from the control chamber to the air chamber, a connection from atmosphere to said air pump, a vent valve for admitting atmospheric air to said last connection to the air pump, a second valve arranged to close and cut-off the admission of air to the control chamber, said valves being mounted on a stem, a float in said chamber connected to said stem and seat bushings in said connections through which said stem slides and with which said valves cooperate, said stem having tapered flutes between said valves, said floats cooperating with the bushings to maintain a constant head 01' water in the chamber and prevent bounding.

3. The combination specified in claim 2, in which the said flutes increase in area towards the second valve.

4. The combination specified in claim 1 including means for reducing water eddies in the control chamber, said means comprising baflle plates or a grid arranged between the inlet and control chamber and out .of the path of the inlet to the impeller.

HAROLD E. ADAMS.

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