US2013455A - Pump - Google Patents

Description

' Sept. 3, 1935. Ax 2,013,455-

PUMP.

Filed Ma 5, 1952 2 Sheets-Sheet 1 I: verzfor? Bun/r5 M. BAXTER.

p 1935- B. M. BAXTER 2,013,455

PUMP

Filed May 5, 1932 2 Sheets-Sheet 2 Patented Sept. 3, 1935 .UNITED STATES.

PATENT OFFICE This invention relates to centrifugal pumps, and its principal object aims to provide a novel and improved pump of this general-type which is of very simple construction,-and which is capable of emcient operation at difierent capacities, and when handling solids in suspension as well as when handling fresh water.

Another object of my invention is toprovide an improved centrifugal pump wherein the impeller and easing are of such form that the flow of liquid through the fluid passages takes place with minimum shock and with minimum friction and eddy losses.

'Another object of this invention is to provide an improved centrifugal pump having a peripherally extending discharge chamber which is concentric with the axis of rotation of the impeller, and which is of "substantially uniform cross-sec- .tional area.

Still another object of my invention is to provide a centrifugal pump having a peripherally extending discharge chamber which is concentric with the .axis of rotation of the impeller, and wherein the impeller vanes are arranged to deliver fluid into said discharge chamber in a direction substantially tangentially of the chamber.

Afurther object of this invention is to provide a centrifugal pump of the type referred to, wherein the impeller is constructedwith spaced vanes so with fluid passages of relatively large cross-sectional area therebetween, and with curved surfaces of revolution of progressively decreasing radii of curvature for directing the fluid into 'said v Fig. '1 is a side elevational view showing a pump constructed, accordingto my invention, with a portion of the casing broken away.

Fig. 2 is a transverse sectional view taken substantially on line 2- -2 of Fig. 1.

Fig. 3 is a sectional view of.the impeller taken on line3-3 of Fig.2.

Fig. 4 is a side elevational view showing the impeller removed from the casing. 55 Fig. 5 is a diagrammatic view illustrating the manner of generating certain of the curved surfaces of the casing and impeller.

' Fig. 6 is an elevational view showing another pump embodying my invention, with the casin of the pump in section. 5

Fig. '7 is an elevational view of the impeller.

Fig. 8 is a transverse sectional view of the impeller taken on line 8-8 of Fig. 7, and

9 is another sectional view of the impeller taken on line 9-9 of Fig. 7. 10

Detailed reference will now be made to the accompanying drawings illustrating my improved centrifugal pump construction, but before proceeding with this detailed description, it should be understood that the principles of my inven- 15 tion may be embodied in various devices or pumps other than those herein illustrated.

' fluid passages with minimum shock and frictional losses, and with good operating efiiciencies for different capacities as well as for fluids of different characteristics.

The casing of my improved centrifugal pump is provided with an-impellerchamber I4 with which the passage I5 of the inlet nozzle ll communicates, and with a peripherally extending discharge chamber I6 which communicates with the impeller chamber and with the passage ll of the delivery nozzle l2. This casing is preferably,

' though not necessarily,- of sectional construction so as to facilitate assembly and inspection or 40 repair of the casing, as well as the insertion or removal of the impeller. As shown in this in-- stance, the casing is provided with stationary and removable side walls l8 and I9, and with an annular casing section 20 disposed therebetween.

In accordance with my invention, the peripherally extending discharge chamber is concentric with the axis of rotation of the impeller, and is of substantially uniform cross-sectional shape throughout its circumference. In this instance the discharge chamber is shown as being of circular cross-section, although various other crosssectional shapes can be used. In constructing the discharge chamber in the form of a hollow annulus which is concentric with the axis of rotanularly extending rim portions 23 and 25 are pro-.-

' fluid around the shaft may be prevented by protion of the impeller, the inner surface of this chamber can be readily machined or otherwise rendered smooth, so that frictional losses in this part of the device may be reduced to a minimum. Moreover, as will be explained hereinafter, the circular shape of the discharge chamber allows a mass of fluid to be rotated rapidly within the casing, and to be discharged through the passage of the delivery nozzle l2, which extends outwardly from the casing substantially in tangential relation-to the discharge chamber.

side wall or cover 19 of the casing is provided witha fiat portion 25, with which the nozzle H is integrally formed, and through which the inlet passage l extends. The side wall is is also formed with an annular rim 25 which forms a part of the discharge chamber 15. These :an-

vided with step-cut surfaces 25 which cooperate with similarly formed surfaces on the casing section 20. These step-cut portions permit fluidtight connections to be formed between the walls and the section of the casing without the use of troublesome gaskets or other packing material. The intermediate casing section 2i] may be formed of one or more parts, but is preferably formed of two sections, as shown in the drawings, which are connected together atdiametrically opposed points by means of bolts 27, and which are connected to the side walls of the casing by suitably located screws 28.

The impeller 53 is rotatably mounted inthe impeller chamber of the casing by being keyed or otherwise secured to an end of a drive shaft 29 which projects into the casing. This drive shaft may be actuated from any suitable source of power, and is supported in suitably arranged bearings including the bearing 30 which is mounted above the supporting base 32. Leakage of viding the stufling box 3| through which the shaft extends. Fluid may be supplied to the stuffchamber M with their opposite edges preferably connected by the circular rim 36.

According to my invention the vanes of the impeller. are spaced relatively far apart circumcross-sectional area than similar fluid passages heretofore provided in pumps of this type. These large fluid passages readily accommodate fluids having solids in suspension'thereln without clogging, even though the solids may be in the form of relatively large particles.

, than at their outer edges. v and arrangement for the vanes of the impeller vention the vanes 35 are so arranged that they will deliver fluid into the discharge chamber It in a direction substantially tangentially of this chamber,- instead elf-substantially radially of the chamber, as has. heretofore been customary'in pumps of this type. To obtain this tangential discharge of fluid from the impeller, I arrange the vanes 35 in the non-radial, angularly disposed position, as shown in Figs. 1 and 3 of the drawings, with the plane of each vane disposed with its outer end in a rearwardly inclined positlon 'with respect to the direction of rotation of the impeller. Additionally, I construct these vanes so. that each vane is of slightly curved form, as shown in Figs. 1 and 3, with the concave surface of the vanes on'the leading side thereof, and with the radius of curvature somewhat greater at the inner edges of the vanes I find that this hape is s'uch as to readly permit the fluid to enter and leave the passages 37 with a minimum amount of shock or disturbance. Moreover, I find that the large cross-sectional area of fluid passages, provided by this arrangement of vanes, allows a large volume 'offluid to be delivered into the discharge chamber in a direction substantially tangentially of this chamber and with a high' tangential velocity head, rather than with the high radial velocity for conversion into pressure head, that has heretofore been customary in pumps of the centrifugal type.

The delivery of fluid into the discharge chamber in a tangential direction by the impeller, causes a mass of fluid to be rotated within the discharge chamber at a speed which is dependent upon the pressure head against which the pump is operated. During the rotation of the mass of fluid within the discharge chamber ofthe casing, the

particles of fluid gradually move outwardly in the dicharge chamber and finally pass out through the tangential passage ll of the delivery nozzle l2. Since the delivery of fluid into the discharge chamber 46, by the impeller, takes place in a di-, rection substantially tangential of the discharge chamber, there is no tendency for the fluid to be directed across the chamber. and to be redirected back toward the impeller, as occurs in the operation of centrifugal pumps of the type having volute discharge chambers. In my improved pump the exit velocity created in the passages of the impeller is employed to maintain a velocity in the mass of fluid rotating within the discharge chamber, and since this exit velocity is not converted into pressure head, as in centrifugal pumps of the type having volute discharge chambers, there is little or no pressure in the discharge chamber tending to create a backflow between the plate and the side wall 22 of the casing, and between the annular rim 33 and the side wall 24 of the casing. Accordingly, I find that the use of sealing rings, between the impeller and the side walls of the casing, is unnecessary, thereby further simplifying my pump as to mechanical construction. It is desirable, however, to provide a clearance space 40 between the ring 36 and the side wall 24, and a clearance space 4| between the impeller plate 34 and the side wall 22. If desired; one or more openings 42 may be provided through the plate 34 to permit a,circulation of fluid through the clearthe fluid during the operation of my centrifugal pump, I provide for a gradual change in direction in the flow of fluid from its axial direction, on entering the pump casing through the passage l5, to a radial direction on entering the passages 31 of the impeller. To attain this gradual change in the direction of the flow of fluid, I provide the passage l and the plate 34 of the impeller with cooperating curved surfaces of peculiar shape.

' According to my invention, I construct these surfaces as surfaces of revolution having a progressively varying degree of curvature. shape of these curved surfaces may be varied somewhat, I find that excellent results are obtained when the curved surface of the inlet passage, and the curved surface of the impeller plate 34, are surfaces of revolution generated by rotation of involute curves about the axis of the impeller shaft 29. In Fig. 5 of the drawings I have illustrated diagrammatically the manner in which these curved surfaces may be generated. In this diagram I have shown an involute curve 43, such as would be produced by the locus of the end of a cord 46 being unwrapped from the circumference of a drum 45, being used to generate the curved surface of the impeller plate 34. The involute curve 43 is swung or rotated about the impeller axis 66 thereby providing the impeller with a curved surface 4'! which may be conveniently referred to as an involutoid of revolution.-

It will be noted, however, from the drawings that at the apex 48 of the impeller, the curved surface 41 departs slightly from the theoretical curvature of the involute 43. This departure is made for practical purposes to obtain an impeller apex which is of increased strength over the theoreti-' cal apex, and which will not be readily broken during the production of the impeller or use of the pump.

In a similar manner the curved inner surface 49 of the inlet passage l5 may be generated by revolution of an involute curve 50 about theimpeller axis 46. The involute 50 is here represented as the locus of the end of a cord 5| being unwrapped from the circumference of a drum 52.

' For convenience in referring to the curved surface of the inlet passage thus generated, I have also indicated this surface of revolution as an involutoid of revolution. During the operation of my improved centrifugal pump the curved surface of the inlet passage and of the impeller cooperate in forming a fluid passage of gradually changing curvature, whereby the direction of flow of fluid entering the impeller passages, is changed, with minimum shock, from an axial direction to a radial direction.

In Fig. 6 of the drawings I have shown my invention embodied in another centrifugal pump comprising a casing 55, and an impeller 56, and which diflers from the pump illustrated in Figs. 1 and 2 only as to the construction and arrangement of the vanes 51 of the impeller. In this instance I show the impeller vanes as being laterally inclined with respect to the plane of the impeller plate 58, which plane is perpendicular to the axis of the impeller shaft 59. These inclined vanes are integrally connected at one edge thereof to the impeller plate 58 and may be connected together at their opposite edge by the ring 60. As shown in Figs. '7, 8, and 9, these inclined vanes extend inwardly from the outer edge of the plate 58 toward the axis of the shaft 59, and merge with, or intersect, the curved surface 62 of the impeller plate, along irregularly curved lines 53 and 34, as indicated in Fig. '7.

Although the In this inclined position, the impeller vanes form fluid passages 64 in the impeller, which passages include the substantially V-shapedrecesses 65 extending between the inclined vanes and the impeller plate 58. I havejound that for pumping heavy materials, such as fluids having a large percentage of solid matter in suspension therein, this form of impeller is very efflclent and delivers the fluid into the circular discharge chamber 66 of the casing in a tangential direction to cause rotation of a mass of the fluid in the discharge chamber. In extending the inclined vanes inwardly to intersect the curved surface of the impeller plate, I find that the entry of the fluid into the impeller passages takes place with minimum shock or disturbance. Moreover, the intersection of the inner edges of the vanes with the curved surface of the propeller prevents these edges of the vanes from being chipped or broken by hard particles entrained in the fluid, and also prevents an accumulation of fibrous material or other substances along these edges of the vanes.

It should now be readily understood from th foregoing description and the accompanying drawings, that I have provided an improved form of centrifugal pump wherein the flow of fluid into the fluid passage of the impeller, as well as the discharge of fluid from these passages, takes place with minimum shock and disturbance. The elimination of shock at the entrance of the fluid passage of the impeller is due largely to the. action of the involutoid surface of the casing and impeller in changing the the fluid meets the vanes of the impeller. Moreover, it will be seen that with the arrangement of impeller blades which I have provided, the fluid passages between the blades are of relatively large cross-sectional area, so that velocity of the fluid through these passages may be low thereby obtaining minimum frictional lossand also'minimizing disturbance at the entry and exit of the impeller passages when the pump is operating at other capacities than its design ca-' pacity. It will be noted further that with the arrangement of impeller vanes and the concentric discharge chamber which I have provided, the fluid is delivered into the discharge chamber in a forward direction substantially tangential ofthis chamber or, in other words, in a direction to cause rotation of the body of fluid in the discharge chamber at a relatively high velocity. In delivering the fluid into a discharge chamber of this form from impeller passages of relatively large cross-section, it will be seen that relatively large streams of fluid will flow smoothly and without shock or disturbance into the discharge chamber in a tangential direction, and a high radial discharge velocity from the impeller for conversion into a high pressure head in the discharge chamber, which is characteristic of centrifugal pumps having volute discharge chambers and relatively'narrow impeller passages, ls not required in my improved pump. It is pointed out further that, since a high pressure head is'not built up in the discharge chamber of my pump, there is but slight tendency for a short-circuitlng flow of fluid along the outer edges of the impeller and back to the inlet side of the pump. Another advantage attained in my improved centrifugal pump is that the large fluid pasages in the impeller freely accommodate stray pieces of iron or other hard foreign bodies which may-be entrained in the 'direction of fluid flow to a radial direction before W ery of the impeller, as it does in volute-type pump cases, it will be impossiblefor such hard foreign particles to become wedged between the impeller and the casing wall.

Although, in disclosing my improved pump' construction, I have referred particularly to pumps having only -a single suction inlet, it should be understood, however, that my invention may also be applied to pumps having a double suction inlet.

While I have illustrated and described the device of my invention in a detailed manner, it should be understood, however, that I do not intend to limit myself to the precise details of construction and arrangement of parts illustrated and described, but regard my invention as including such changes and modifications as do not involve a departure from the spirit of the invention and the scope of the appended claims.

Having thus described my invention, I claim:

1. In a centrifugal pump, the combination of a,

casing, and an impeller rotatable in said casing, said impeller having a plurality of vanes spaced to provide fluid passages therebetween and also having a cone-like projection substantially coaxial with the axis of rotation of the impeller, said projection having a surface of progressively decreasing radius of curvature for directing the fluid into said passages.

2. In a centrifugal pump, the combination of a casing, and an impeller rotatable in said cascurved inner surface, and an impeller rotatable.

in said casing, said impeller having a plurality of vanes spaced to provide fluid passages therebetween and having a curved surface for cooperation with the curved surface of said inlet for directing fluid into said passages, each of said curved surfaces being substantially a surface of revolution generated by revolution of an involute curve about the axis of rotation of the impeller.

4. In a centrifugal pump, thecombination of a casing having a fluid inlet provided with a curved inner surface and also having a discharge chamber which is substantially concentric with the axis of the inlet and of substantially uniform cross-sectional area, and an impeller rotatable in said casing substantially on the axis of said inlet, said impeller having a plurality of vanes spaced to provide fluid passages therebetween and having a curved surface for cooperation with the curved surface of the inlet for directing fluid into said passages, each of said curved surfaces being substantially a surface of revolution generated by revolution of an involute curve about the axis of rotation of the impeller, said inlet and impeller passages being effective for causing fluid to flow relatively freely and substantially without shock and to be delivered into said concentric discharge chamber substantially tangentially in a forward direction and with relatively high velocity head. 7

5. In a centrifugal pump, the combination of a casing having a fluid inlet provided with a curved inner surface and also having a discharge chamber which is substantially concentric with the axis of the inlet and of substantially uniform cross-sectional area, and an impeller rotatable in ,said casing substantially on the axis of said inlet, said impeller having a plurality of rearwardly inclined vanes spaced relatively far apart circumferentially of the impeller and being relatively wide in the direction of the axis of the impeller to provide therebetween fluid passages of large cross-sectional area and said impeller also having a curved surface for cooperation with the curved surface of the inlet for directing fluid into said passages, each of said curved surfaces being substantially a surface of revolution generated by revolution of an involute curve about the axis of the impeller, said inlet and impeller passages being effective for causing fluid t'o flow relatively freely and substantially without shock and to be delivered into said concentric discharge chamber substantially tangentially in a forward direction and with relatively high velocity head.

BURKE M. BAXTER.

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