US2831434A - Self-priming centrifugal pump - Google Patents

Description

April 22, 1958 R. F. PAASHAUS.

SELF-PRIMING CENTRIFUGAL PUMP I 2 Sheets-Sheet 1 Filed April 5. 1956 7 Z 4 a a a a IIIIIIIIIIIIIIM ROBERT F. PAASHAUS FIGS April 22, 1958 R. Fl PAASHAUS 2,831,434

SELF-PRIMING CENTRIFUGAL PUMP Filed April 5, 1956 2 Sheets-Sheet 2 ROBERT F. PAASHAUS v INVENTOR. FIG. 6. B

United States Patent SELF-PRllVHN G CENT RIFUGAL PUlWP Robert F. Paashaus, Madison, N. 1., assignor to Worthington Corporation, Harrison, N. J., a corporation of Delaware Application April 5, 1956, Serial No. 576,442

4 Claims. (Cl. 103-113) This invention relates generally to centrifugal pumps and more particularly to self-priming centrifugal pumps adapted to be operated at different capacities or heads by substintution of impellers of varying diameter for one another depending on the variation in capacity or head desired.

In self-priming centrifugal pumps, it is the present practice to obtain varying heads and capacities by varying the speed of the impeller through the use of a cumbersome belt drive or a slow speed motor which is also undesirable because of large frame sizes.

Where constant speed motors are utilized to drive self-priming centrifugal pumps of the recirculation passage type, in order to vary the head or capacity of the pump, it is necessary to vary the size of the impeller diameter. It has been found, however, that relatively small variations in the diameter of an impeller for a fixed volute chamber will unduly affect the priming time required for the pump. This is especially the case where the diameter of the impeller is reduced.

The present invention overcomes this problem by providing a self-priming centrifugal pump having means thereon for varying the head or capacity of the pump which includes a casing having a volute adapted to accommodate an impeller or impellers having diameters sized between the predetermined minimum and predetermined maximum limits for the particular volute, and means forming a plurality of spaced tongues in said casing defining a recirculation port therebetween which may be sized or varied to fit the particular impeller so that the operative relation between the recirculation port, the tongues and the impeller periphery will provide rapid self-priming characteristics for the centrifugal pump.

Said another way, it is an object of the present invention to provide in a self-priming centrifugal pump means to coact with replaceable impellers of varying diameters which functions to maintain the necessary pressure differential between the separation chamber for the pump and the point of return in the volute chamber in which the impeller operates to provide rapid self-priming characteristics for the pump.

Further objects and advantages of the invention will become evident from the following description with reference to the accompanying drawings in which:

Figure l is a side view, partly in section, of the selfpriming centrifugal pump embodying the invention.

Figure 2 is a section taken on line 22 of Figure 1.

Figure 3 is a plan view taken on line 33 of Figure 1.

Figure 4 is a fragmentary side view of a self-priming centrifugal pump of the same type shown in Figure 1 showing a modified form of the present invention.

Figure is a perspective view of the recirculation port and the confining tongue elements for the modified form of the invention in Fig. 4.

Figure 6 is a fragmentary side view partlyin section of a self-priming centrifugal pump of the type shown in Figure 1 showing a further modified form of the present invention.

2,831,434 Patented Apr. 22, 1958 Figure 7 is a plan view taken on line 7--7 of Figure 6.

Figure 8 is a side view of the further modified form of recirculation tube element and the confining tongue shown in Figure 6.

Figure 9 is a top view of the recirculation tube and confining tongue elements shown in Figure 8 Referring to the drawings, Figures 1 and 2 show a selfpriming centrifugal pump generally designated 1 which includes a casing 2 having a volute or working chamber 3 into which a shaft 4 will extend through the packing gland 5 provided on one side of the casing 2. An impeller 6 disposed in the volute is mounted on the end of the shaft 4 by any suitable means such as threaded member 7 so that the impeller is fixed to and rotatable with the shaft 4. The shaft 4 and impeller 6 will be rotated by any suitable type of prime mover, not shown, such as an electric motor which is preferably directly coupled to the shaft 4 in the manner well known in the art and hence not more fully shown or described herein, it being understood that a belt drive or a slow speed motor could be utilized as the driving means in the present invention without departing from the spirit thereof.

At a point in the casing substantially tangential to the volute or working chamber 3 a discharge outlet 8 is provided and a discharge flange 9 is formed on the portion of the casing about or including the discharge outlet. Formed integrally with the casing at a point adjacent the discharge outlet is an inwardly projecting portion 10 which in assembled position segregates or acts to separate the discharge portion or outlet 8 from the volute from the portion of the volute remote from the discharge outlet. The side of the casing remote from the side having the packing gland 5 is closed by a combined cover plate and trap mechanism 11 which has a flange 12 to provide means for connecting the member 11 to the casing as by circumferentially spaced threaded members 13 which extend therethrough into the casing. The member 11 is further provided with an opening as at 14 to form the suction opening for the casing 2 all of which is clearly shown in Figure 2 of the drawings.

Figure 2 further shows that in the assembled relationship the inner face of the cover plate and trap mechanism 11 engages as at 15 the side face of the inwardly projecting portion 10 so that the inwardly projecting portion can operate to provide the desired segregation between the discharge outlet and the remote portions of the volute relative thereto.

The inwardly projecting portion 10 has a bore therein extending substantially parallel-to the discharge outlet which forms a recirculation port 16, the leading tongue or front edge 17 and the trailing tongue or rear edge 18 of the inwardly projecting portion 10 acting as the confining boundaries for the recirculation port. The radial position of the respective innermost edges or ends of the leading tongue 17 and the trailing tongue 18 will always be in close clearance relation with the outer periphery of the particular impeller 6 mounted in the volute as is clearly shown in Figures 1 and 2 of the drawings.

Since the inwardly projecting portion 10 is formed integrally with the casing this form of the invention shown in Figure 1 is referred to as the fixed length recirculation port type to distinguish it from the variable length recirculation port type illustrated in the form of the invention shown in Figures 4 and 6 of the drawings and hereinafter described.

In this fixed length recirculation port type of construction the diameter of the impellers can only be varied by cutting the leading and trailing tongues 17 and 18 of the inwardly projecting portion 10 to provide the desired radial position of these elements relative to the periphery of the particular impeller disposed in the volute. Thus,

theimpeller diameters can only be varied in this-type or form of the invention from a predetermined minimum to a predetermined maximum diameter, and once out only impellers of larger diameter up to the physical limits of the construction can be mounted in the volute but never impellers of a lesser diameter. In the modified form of the invention hereinafter described, impellers of greater or lesser diameters can be inserted in the volute tosecure any desired variation in head andcapacity within the predetermined-minimum and maximum diameter limits for the impellers that can be fitted to the particular casing.

Figures 1 and 2 further show a; housing 19 forminga separation chamber 20 as connected by its flange 2 to the discharge flange 9 of the casing 2. The separation chamber is generally of cylindrical form and has a partition 22 extending inwardly into the chamber a short dis tance parallel to the line of fluid flow which is in alignment with the outer end of the leading tongue 17 so that an inlet port 23 and a return port 24 formed by the partition in the separation chamber will be in alignmentwith the respective discharge outlet 9 and recirculation port 16 in the casing. A gasket 25 and threaded members 25 provide the necessary means of connecting the respective flanges in fiuid tight engagement.

The important factor in the success of priming a pump is the flow rate with which the fluid, free of air, returns from the separation chamber through the recirculation port to the volute chamber during the priming cycle. This rate is a function of the differential pressure in the separation chamber and at the point A at the outlet of the recirculation port 16. In the present invention, by reason of the spaced relation of the leading tongue 17 and the trailing tongue 18 and the angle therebetween so that the respective tongues are maintained in close clearance relation to the periphery of the impeller 6 regardless of the size, the desired differential pressure is obtained to produce the rapid self-priming characteristics desired in this type of centrifugal pump.

Operation During initial operation or at any time when the pump has been drained the pump may be filled through the filling opening shown at 27 or through the Vent that is customarily provided in the casing of this type pump. Generally, however, where the pump has been in operation, suflicient water will be retained in the volute or working chamber 3 and the cover and suction trap ele ment 11 for priming the pump. With this priming fluid present, the prime mover, not shown, may be placed in operation to rotate the shaft 4 and impeller 6.

The rotation of the impeller will pass fluid into the separation chamber 20' through the discharge outlet 8 and inlet port 23. In the separation chamber the air in the fluid is separated therefrom and the fluid, free of air, is returned through return port 24 and recirculation port 16 to the volute 3 by reason of the differential pressure effected as above described. This process keeps repeating itself until all the air is exhausted from the suction leg, not shown, to which the inlet 28 of the combined cover and trap element will be connected.

After the air is exhausted the pump continues to pump the fluid present through the discharge outlet 8 and inlet port 11 into the separation chamber 20where it is in turn passed through the pump outlet 29 to use or other desired disposal. If the pump is stopped and sufficient water is retained in the volute chamber cover and suction trap elements 11 as above described the pump will be self-priming thereafter whenever necessary.

If a different head or capacity is desired the pump is disassembled and the inwardly projecting portion 18 cut down to the point desired for a greater diameter impeller as is indicated by the phantomized lines in Figure l of the drawing. The new impeller may now be connected to the shaft 4 andthe pump reassembled- Since-the cutting down of the leading tongue 17 and trailing tongue 18 will be done to provide the same close clearance with the periphery of the new impeller, the self-priming characteristics of the pump with the new impeller will be retained as the recirculation port will operate to return fluid, free of air, to the volute 3 by reason of the fact that the differential pressure between the separation chamber and the point A will be retained by this construction.

Om modified form of the invention.

Figure 4 shows one modified form of the'invention in which the impellers of varying diameters either larger or smaller within the physical limits of the casing may be inserted to produce varying heads and capacities.

Except for the modified portion of the construction shown in Figure 4, the pump is otherwise identical in construction and operation to that shown in Figure l of the drawings and described above. Hence, only a fragmentary portion of the pump is illustrated.

Thus, Figure 4 shows that the casing 42 includes a V0- lute chamber 43 having an impeller 44 rotatedlymounted therein. The casing has a discharge outlet 45 about which is formed a discharge flange 46. A housing 47 forming the separation chamber 48 has a flange 49 to provide means for connecting the housing 47 to the easing 42.

In assembled position there is disposed between the flanges 46 and 49 the connecting plate 50 of a recirculation tube generally designated 51. The recirculation tube is held in adjusted position by the flanges 46 and 49 and gasket elements 52 and 53 disposed between each of the respective flanges as is clearly shown in Figure 4 of the drawings.

In adjusted position the recirculation tube 51 extends through the discharge outlet 45 into the volute or working chamber 43 where the innermost end thereof isdisposed in substantially close clearance with the periphery of the impeller 44 also clearly shown in Figure 4 of the drawings.

Figure 5 shows that the recirculation tube member generally designated 51 is relatively simple in construction. The connecting plate 50 is a flat plate-like member having openings 54 and 55 spaced on opposite sides of the center line thereof. Connected to one side of the connecting plate 50 about the opening 55 is an elongated tubular member or element 56 which extends outwardly or away from the side of the connecting plate to which it is connected. The tubular element 56 and the opening 55 provide or form the recirculation port 57 in the recirculation port member. The side of the recirculation tube 56 adjacent the discharge outlet or the front side thereof forms the leading tongue or edge 58 and the side remote or rear side forms the trailing tongue or edge 59 which confine the recirculation port 57 therebetween. It is particularly pointed out that the leading tongue 58 and trailing tongue 59 are disposed at an angle with respect to each other so that the proper clearance between the end of the recirculation tube 56 and the periphery of the impeller 44 may be obtained.

The recirculation tube member 56 for each particular recirculation tube element 51 is constructed in varying lengths which varying lengths correspond to the diameters of the particular impellers which may be inserted into the pump casing 42 varying between the predetermined minimum and predetermined maximum diameter limits of these impellers which of course is a function of the physical limits of the individual casings for these pumps as is indicated by the solid and dotted lines in Figure 4 of the drawings. When it is desired to vary the size of the impeller a specific recirculation tube member 51 of suitable length is selected for the particular impeller to be installed such that by setting in the. gaskets 52 and 53 between the recirculation port member 51 and the respective flanges 46 and 49 the desired close clearance relation between the end of the recirculation tube 56 and the periphery of the impeller will be obtained.

In assembled position the partition 60 for the separation chamber forming the inlet port 61 and return port 62 is disposed relative to the leading tongue 58 of the recirculation tube member 51 and the casing 42 whereby that portion of the discharge outlet 45 not included by the recirculation tube 56 will be in alignment with the opening 54 and the inlet port 61 while the return port will be in alignment with the recirculation port 57, all of which is clearly shown in Figure 4 of the drawings.

The operation of the type pump shown in Figure 4 is identical with that shown in Figure 1. This construction differs from the form of the invention shown in Figure 1 only in that the impeller can be varied between the predetermined minimum and predetermined maximum diameter limits for the particular pump, i. e., either a larger or smaller impeller can be put into this casing or the impeller can be changed from a larger diameter impeller to a smaller diameter impeller and vice versa, within the predetermined minimum and predetermined maximum limits. This is accomplished by the simple expedient of disassemblingthe pump, inserting the desired diameter impeller in the casing and thereafter fitting the proper length recirculation tube thereto as above described.

It is particularly pointed out that the lateral clearances between the sides or the recirculation tube and the respective sides of the casing must also be in relatively close clearance or else the desired low pressure differential between the separation chamber and the point B at the end of the recirculation tube in the volute 43 will not be obtained by reason of the bypassing of the fluid being pumped. In this respect it has been found that a maximum clearance of of an inch on either side is allowable without afiecting the operation of the pump.

Another modified form of the invention Figure 6 shows a second modification of the present invention in which once again impellers of varying diameters either larger to smaller or vice versa within the physical limits of the casing may be inserted to produce the varying heads and capacities desired.

Except for the modified portion of the construction as hereinafter described, the pump is once again otherwise identical in construction and operation to that form of the invention shown in Figure 1 of the drawings. Hence, only a fragmentary portion of the pump is illustrated.

Thus, Figure 6 shows that the casing 72 includes a volute chamber 73 having an impeller 74 rotatably mounted therein. The casing has a discharge outlet 75 about which is formed the discharge flange 76. A housing 77 forming the separation chamber 78 has a flange 79 to provide means for connecting the housing 77 to the easing 72.

In the casing adjacent the discharge outlet 75 is a threaded bore 76 in which is threadably mounted a recirculation tube generally designated 80 which is held in adjusted position by a key member 81.

Figures 8 and 9 show that the recirculation tube member 80 is a relatively simple construction consisting of a hollow cylindrical member threaded on the exterior portion as at 82 and at the end remote from the threaded end cut on the bias as at 83 so that in assembled position the front or leading tongue 84 and the rear or trailing tongue 85 form the confining boundaries for the recirculation port 36 formed by the hollow portion of the member 80 and the trailing tongue and leading tongue will be disposed in close clearance relationship with the impeller 74 so that the proper differential pressure between the separation chamber and the point C in the pump casing will be obtained.

The recirculation tube member 80 can be threaded into the adjusted position and then the key 81 inserted to hold it in the threaded position.

The recirculation tube member can of course be constructed in varying lengths as in the form of the invention shown in Figure 4 in which case for each change in impeller size a corresponding change will be made for the length of the recirculation tube member. However, it is believed clear that the recirculation tube member could be built of a single length and moved inwardly and outwardly by threading to provide the adjusted clearance relationship between the end of the recirculation port and the periphery of the impeller 74.

In assembled position, as shown in Figure 6, the partition 87 for the separation chamber 78 forming the inlet port 88 and the return port 89 is disposed relative to the recirculation tube 80 and the casing 72 such that the discharge outlet 75 and the inlet port 88 are in alignment with each other and the return port 89 and recirculation port 86 are in alignment with each other.

The operation'of this type pump shown in Figure 6 is identical with that shown in Figure 1. This construction, as in the case of the form of the invention shown in Figure 4, differs only in that the impeller can be varied as above described for the varying heads and capacities desired.

It is noted once again that the clearance between the sides of the recirculation tube member 80 and the sides of the casing are such that close clearance is provided in this respect. A clearance not greater than of an inch will provide the best conditions for producing the selfpriming characteristics of this pump at all the varying sizes of impeller diameters.

It will be understood that the invention is not to be limited to the specific construction or arrangement of parts shown but that they may be widely modified within the invention defined by the claims.

What is claimed is:

1. In a self priming centrifugal pump, a casing having a suction inlet and a discharge outlet, said casing having a volute formed therein, said volute to accommodate rotatable impellers of different diameters one at a time wherein the particular impeller diameter may vary from a predetermined minimum to a predetermined maximum diameter, a separating chamber connected to said casing to receive fluid discharged from the discharge outlet thereof, a detachable member comprising a tube extending into said casing and having a flange for fixedly connecting said member between said casing and said separating chamber, said flange including two flow passage means between said casing and separating chamber, said tube opening into one of said passage means and having leading and trailing edges at the end thereof extending into said casing whereby fluid is recirculated from said separating chamber to said casing through said tube, said detachable member selected for connection between said separating chamber and said casing including a tube of sufficient length whereby the leading and trailing edges of said tube are in close clearance with the outer periphcry of the impeller in said pump, and gasket means disposed between the separating chamber, the casing and the flange therebetween.

2. In aself-priming centrifugal pump, a casing having a suction inlet and a discharge outlet, said casing having. a volute formed therein, said volute to accommodate rc tatable impellers of different diameters one at a time wherein the particular impeller diameter may vary from a predetermined minimum to a predetermined maximum diameter, a separating chamber connected to said casing to receive fluid discharge from the discharge outlet thereof, a detachable member comprising a tube extending into said casing and having a flange for fixedly connecting said member between said casing and said separating chamber, said flange including two flow passage means between said casing and said separating chamber, said tube opening into one of said passage means and having leading and trailing edges at the end thereof extending into said casing whereby fluid is recirculated from said separating chamber to said casing through said tube, and said detachable member selected for connection between said separating chamber and said casing including a tube of suflicient length whereby the leading and trailing edges of said tube are in close clearance with the outer periphery of the impeller in said pump.

3. In a self priming centrifugal pump, a casing hav ing a suction inlet and a discharge outlet, said casing having a volute formed therein, said volute to accommodate rotatable impellers of different diameters one at a time wherein the particular impeller may vary from a predetermined minimum to a predetermined maximum diameter, a separating chamber connected to said casing to receive fluid discharged from the dischargeable outlet thereof, said casing and said separating chamber having attachment means, a detachable member comprising a tube extending into said casing and having a flange around said tube for fixedly and detachably connecting said member to and between said attachment means, said tube having leading and trailing edges at the end thereof extending into said casing whereby fluid is recirculated from said separating chamber to said casing through said tube, and said detachable member selected for connection to and between said attachment means including a tube of suficient length whereby the leading and trailing edges of said tube are in close clearancewith the outer periphery of the impeller in said pump;

4. In a self priming centrifugal pump, a casing having.

a suction inlet and a discharge outlet, said casing having a volute formed therein, said volute to accommodate rotatable impellers of different diameters one at a time wherein the particular impeller may vary from a predetermined minimum to a predetermined maximum diameter, a separating chamber connected to said casing to receive fluid discharge from the dischargeable outlet thereof, said casing and said separating chamber having attachment means, a detachable member comprising a tube extending into said casing and having a flange around said tube for fixedly and detachably connecting said member to and between said attachment means, said tube having leading and trailing edges at the end thereof extending said casing whereby fluid is recirculated from said separating chamber to said casing through said tube, said detachable member selected for connection to and between said attachment means including a tube of suflicient length whereby the leading and trailing edges of said tube are in close clearance with the outer periphery of the impeller in said pump, and gasket means between the attachment means on the separating chamber, the attachment means on the casing and the flange therebetween;

References Cited in the file of this patent UNITED STATES PATENTS 1,915,678 La Bour June 27, 1933 1,989,061 Longenecker Jan. 22, 1935 2,291,760 Rupp Aug. 4, 1942 2,405,836 La Bour Aug. 13, 1946 2,425,070 Nicolette Aug. 5, 1947 2,428,487 Fernstrum Oct. 7, 1947 FOREIGN PATENTS 679,246 Great Britain Sept. 17, 1952

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