US3040670A - Pumps - Google Patents

Description

June 26, 1962 FIG-1 R. c. SCHENCK ETAL 3,040,670

PUMPS Filed Oct. 16. 1959 INVENTORS ROBERT C. SCHENCK Y a JACOB B. FREED ATTORNEYS United States Patent t) 3,040,670 PUMPS Robert C. Schenck and Jacob "B. Freed, Dayton, Ohio, assignors to The Duriron Company, Inc., Dayton, Ohio, 'a corporation of New York Filed Oct. 16, 1959, Ser. No. 846,833 6 Claims. (Cl. 103-103) This invention relates to centrifugal pumps.

The invention is especially'related to centrifugal pumps of the type wherein the impeller is mounted on a shaft which projects into the pumping chamber from outside the pump housing and which therefore requires a running seal such as a stufllng box type of seal where it enters the pumping chamber. It is a primary object of the present invention to provide a centrifugal pump of this type which is of such construction and operating characteristics that it is capable of developing a high discharge pressure while maintaining a low pressure effective on the seal between the shaft and the pump housing, and in particular while minimizing the effect of high discharge pressure on the seal.

Stated from another aspect, it is a primary object of the present invention to provide a centrifugal pump'of the above type which is of such construction and operating characteristics that it is capable of "maintaining zero or negative pressure effective on the seal between the impeller shaft and the pump housing while developing and maintaining a high discharge pressure.

It is-also anobject of the invention to provide a centrifugal pump as outlined above which is readily designed in accordance with the principles of the invention to develop and deliver a desired discharge pressure while maintaining the pressure eifectiveon the seal between the impeller shaft and the pump housing at a low positive or negative value minimizing the possibility of leakage therethrough in either direction.

Additional objects-and advantages of the invention will be apparent from the following description, the accompanyirig drawing and the appended claims.

In the drawing FIG. 1 is a fragmentary sectional view-through a centrifugalpump constructed'in accordance with the invention, the 'view being taken in section through the impeller as indicated by the line 1-1 of FIG. 2;

FIG. .2 is a front elevational view of the impeller in '-the pump of FIG. =1;

'FIG. 3 is an elevational 'view of the back of theim- 'peller of FIG. 2, partly broken away in section;

'FIG. 4 is a fragmentary perspective view .taken in section 'as indicated by the line 4-4-of FIG. 3; .and

FIG. =5 is a fragmentary view similar to-FIG. 2 showing a modified construction of the impeller.

Referring to the drawing, which illustrates preferred embodiments of the invention, the pump in FIG. 1.00mprises a'housing forr'ned'by a pump casing and cooperating cover plate 11 which are secured together in cooperation with-the bracket or adapter shown fragmentarily 'at12 and define apumping' chamber 13 in which the im peller 15 operates on the end'of the impeller shaft'16. Theinlet'to the pumping-chamber 13 is shown at 17, and the-outlet is shown at 18. The impeller shaft 16 projects into the pumping chamber 13 from the side oppo- V 'site the inlet 17, and the'junction between-the. shaft and thecover plate 11- is'shown as'provided with a running seal indicated fragmentarily at 20 as a conventional "stuffingbox'seal. Alternatively, this running seal may incorporate a multiple lip-seal'arrangement as shown in the copnding application of Jacob-B. Freed andRobert P. Sharpe Serial No. 780,467, filed December 15, 1958, -no'w-Pate'ntNo. 2,945,7l0,'-and assigned to the same assignee as' this application.

3,040,070 Patented June 26, 1962 'ice The impeller 15 is of special construction shown in detail in FIGS. 2-4. It is of the semi-open type comprising a single disk or shroud 30 which is attached to the end of the shaft 16, the particular "attachment means being shown as a threaded boss 31 projecting centrally from the back of the shroud 30, but any other suitable form of attachment means may be employed within the scope of the invention. Main pumping vanes 33 are formed on the front of the shroud 30, and the outer periphery of the shroud 30 is scalloped at 35 between the outer ends of the vanes 33 to provide shroud portions of substantially reduced radius with respect to the uniformly arcuately curved portions 36 adjacent the ends of the vanes 33.

An annular skirt 40 of generally cylindrical section is formed on the back of the shroud 30, and the rearward end portion of the skirt 40 extends in telescoping relation within a portion of the cover plate 11 to form a horizontal seal ring. The telescoping portions of these parts are in closely fitting running relation forming an auxiliary running seal as indicated at 41, and if desired, a separate clearance ring may be inserted in the cover plate 11 rather than the integral construction shown in FIG. 1. The skirt 40 thus cooperates with the impeller shaft '16 to define an annular chamber 42 which surrounds the inner end of the seal 20. r

In the operation of a conventional pump of this general type, the main "seal 20 is subjected to a pressure which is made up of the suction pressure, which may be positive or negative depending upon the static head condition effective on the inlet 17, plus a proportion of the total discharge pressure of the pump. The invention is directed particularly to the provision of means for reducing the pressure on the seal 20as closely .as possible -to zero without sacrificing the pumping ability of the pump. Referring particularly to FIGS. .3 and 4, the impeller 15 includes a plurality of ribs '44 on the back-surface of-the shroud 30 which extend generally tangentially outward'from the skirt 40 and thus form a setof auxiliary pumping vanes. These ribs 44 are generally rectangular in section, and also they are hollow throughout the entire length thereof to provide a corresponding plurality of passages 45 which extend through the skirt 40. and lead outwardly from the chamber 42 to the outer periphery of the impeller.

In the operation of this vpump with .the impeller 15 constructed as described, the main pumping vanes 33 function to develop a discharge pressurein the usual'way,

but with the shroud 30 scalloped to provide in effect bypass passages 35 around the impeller, some of the liquid makes its -way to the space 46 behind the shroud 30.

.The ribs 44 act as pumping vanes in this space 46, de-

veloping a pumping force in the liquid which reaches this space and thereby augmenting the action of the main vanes 33 in developing the total discharge pressure of the .pump. At the sametime, centrifugal force created by rotation of the impeller develops an outward velocity in the passages 45, thereby causing liquid in the chamber .142 .tobe pumped out and added to the output of the pump as a whole.

Under these operating conditions, it will be seen that not only are there a plurality of forces tending to minimize access of pressure liquid to the seal;20, but also that whatever liquid does penetrate to this seal area tends .to be promptly removed. Thus the discharge pressure developed in the pumping chamber 13 must'first penetrate through the auxiliary running seal 41, and itis also opposed by, the pumping forces developed in the space '46 by the auxiliary vanes 44 and the resulting suction effective [on the seal 41. Then ifany of' this liquid does pass through the seal'41 to the chamber 42., it will be at comparatively reduced pressure due to the pressure drop aca em througl thet sfeal 41i1 and it will in turn be picked up and pumpe ou rom t e cha" b A the vanes or ribs 44. m er 42 by the passaggs 45 m b. The scalloped portions 35 in the shroud 3d are of major imp rtance in achieving the purposes and advantages of the invention, for several reasons. In particular, they assure that sufficient liquid will reach the space 46 to maintam effective pumping action by the vanes 44, both as an augmentation of the pumping action of the main vanes 33 and to maintain suction on the seals 41 and 20. In addition, the provision of the scalloped portions 35 reduces the area of the shroud on which the pressure differential on the opposite sides of the impeller acts, thus minimizing the thrust load on the supporting bearings for the impeller shaft 16.

Perhaps the most important contribution of the scalloped portions 35 to the advantages of the invention is best described in connection with FIG. 5. In the impeller of FIGS. l- -3, the main pumping vanes 33 extend to the periphery of the shroud and are therefore of the ii'iaiiiinumradial dimensions, which is the construction providing maximum discharge pressure and output for a pump of given dimensions operating under relatively low suction pressure. If, however, a particular installation calls for a somewhat lower output or higher suction pressures while still requiring a comparatively high discharge pressure, these-results are obtained in accordance with the invention by constructing the impeller with the main vanes 33 of reduced radial dimensions with respect to the shroud but with the same dimensions maintained for the shroud porhens 36 and the auxiliary vanes 44. This is illustrated in shbws a fragment of an impeller 15 wherein Y the math pumping vanes 33' are of reduced radial dimensions with respect to the shroud portions 36' and ribs 44. With the modified impeller construction of :FIG. 5, the

pumping ability of the van es 33 is less than that of the vanes 33 so that the contribution of the vanes 33' to the total discharge pressure is similarly less for an impeller which is otherwise of the same dimensions. However, the auxiliary vanes or ribs 44' are of the maximum dimensions for the impeller so that they are able both to augment the total discharge pressure of the pump and also to; maintain the desiredsuction in the associated chamber 42 and corjrespondingly' reduced pressure effective on the seal 20. i urtherhioiae, the difference in radial dimensionsbetween the yanes33' and 44' produces a difference in the output head developed by each of these sets of vanes, and with this difference in favor of the vanes 44', it can apply to offset a positive pressure which would otherwise be effective on the seal 20. a

It will therefore now be understood that the impeller of this invention is readily proportioned in accordance with the intended operating conditions of the pump to establish predetermined minimum pressures effective on the 'seal 20 while at the same time being capable of developing and maintaining a desired total discharge head. Thus tests pm a variety of impellers similar to the impellers 15 and 15 have established that the radial. dimensions of the main anes can be reduced by as much as one third without reducing the total discharge head by more than approximately 10% while at the same time increasing by as much as 300% the maximum allowable suction pressure for zero pressure effective at theseal 20. In contrast, tests on impellers of similar construction except that their shrouds were not provided with scalloped portions established that While corresponding reduction of the radial dimensions of the main pumping vanes increased the maximum allowable suction pressures for Zero pressure at the shaft seal, it greatly reduced the total discharge head of which the pump was capable.

While the forms of apparatus herein described constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention which 7 is defined in the appended claims.

What is claimed is:

l A centrifugal pump of the character described compnsing a housing defining a pumping chamber, an inlet for liquid in the front of said housing, a shaft projecting through said housing into said chamber from the side opposite said inlet, an outlet for liquid leading from said housing transversely of said shaft, means forming a running seal between said shaft and said housing, an impeller mounted on said shaft within said pumping chamber and including a shroud, main pumping vanes on the front surface of said shroud, an annular skirt projecting from the back surface of said shroud and defining with said shaft an annular chamber adjacent said sealing means, a plurality of ribs extending outwardly of said impeller along the back of said shroud from said skirt and forming a set of auxiliary pumping vanes, means within each said rib forming a passage leading outwardly from said annular chamber to apply suction thereto in response to rotation of said impeller, and said shroud being of generally scalloped configuration along the outer periphery thereof between said liquid in the front of said housing, a shaft projecting through said housing into said chamber from the side opposite said inlet, an outlet for liquid leading from said housing transversely of said shaft, means. forming a running seal between said shaft and said housing, an impeller mounted on said shaft within said pumping chamber and including a shroud, the outer periphery of said shroud consisting of alternate portions of uniformly arcuate curvature concentric with said shaft and portions of reduced main pumping vanes on the front surface of said shroud,

radius providing access for liquid from the front of said pumping chamber to the space therein behind said shroud,

an annular skirt projecting from the back surface of said shroud and defining with said shaft an annular chamber adjacent said sealing means, a plurality of ribs extending outwardly of said impeller along the back of said shroud portions of uniformly arcuate curvature from said skirt and forming a set of auxiliary pumping vanes for developing a pumping force e'lfective on the liquid reaching the space behind said shroud by way of said shroud portions of reduced radius, and means within each said rib forming :a passage leading outwardly from said annular chamber to'apply suction thereto in response to rotation of said impeller. p

'3. A centrifugal pump of the character, described comprising a housing defining a pumping chamber, an inlet for liquid in the front of said housing, a shaft projecting through said housing into said chamber from the side opposite said inlet, an outlet for liquid leading from said housingjtransversely of said shaft, means forming a running seal between said shaft and said housing, an impeller mounted on said shaft within said pumping chamber and including a shroud, main pumping vanes on the front surface of said shroud, an annular skirt projecting from the back surface of said shroud and defining with said shaft an annular chamber adjacent said sealing means, means forming an auxiliary running seal between said skirt and said housing, said shroud having portions of the outer periphery thereof of lesser radius than the remainder of said periphery to provide access for liquid from the front of said pumping chamber to the space therein surrounding said auxiliary seal, a plurality of ribs extending outwardly of'said impeller along the back of said shroud from said skirt and forming a set of auxiliary pumping vanes for developing a pumping force on said liquid in said space and thereby applying suction to said auxiliary seal, said shroud portions of lesser radius being spaced between said ribs, and means within each said rib forming a passage leading outwardly from said annular chamber to apply suction thereto in response to rotation'of said impeller.

4. A centrifugal pump of the character described comprising a housing defining a pumping chamber, an inlet for liquid in the front of said housing, a shaft projecting through said housing into said chamber from the side opposite said inlet, an outlet for liquid leading from said housing transversely of said shaft, means forming a main running seal between said shaft and said housing, an impeller mounted on said shaft within said pumping chamber and including a shroud, main pumping vanes on the front surface of said shroud, an annular skirt projecting from the back surface of said shroud and defining with said shaft an annular chamber adjacent said sealing means, means on said housing cooperating with said skirt to form an auxiliary running seal against access of liquid to said annular chamber from the space in said pumping chamber behind said shroud, a plurality of ribs extending outwardly of said impeller along the back of said shroud from said skirt and forming a set of auxiliary pumping vanes for applying suction to said auxiliary running seal in response to rotation of said impeller, means within each said rim forming a passage leading outwardly from said annular-chamber to apply suction thereto and to said main running seal in response to rotation of said impeller, and said shroud being of generally scalloped configuration along the outer periphery thereof 'between the outer ends of said ribs to provide access for liquid from the front of said pumping chamber to the space therein behind said shroud.

5. A centrifugal pump of the character described com prising a housing defining a pumping chamber, an inlet for liquid in the front of said housing, a shaft projecting through said housing into said chamber from the side opposite said inlet, an outlet for liquid leading from said housing transversely of said shaft, means forming a main running seal between said shaft and said housing, an impeller mounted on said shaft within said pumping chamber and including a shroud, the outer periphery of said shroud consisting of alternate portions of uniformly arcuate curvature concenttric with said shaft and portions of reduced radius providing access for liquid from the front of said pumping chamber to the space therein behind said shroud, main pumping vanes on the front surface of said shroud, anannular skirt projecting from the back surface of said shroud and defining with said shaft an annular chamber adjacent said sealing means, means on said housing cooperating with said skirt to form an auxiliary running seal against access of liquid to said annular chamber from the space in said pumping chamber behind said shroud, a plurality of ribs extending outwardly of said impeller along the back of said shroud portions of uniformly arcuate curvature from said skirt and forming a set of auxiliary pumping vanes for applying suction to said auxiliary running seal in response to rotation of said impeller, and means within each said rim forming a'passage leading outwardly from said annular chamber to apply suction thereto and to said main running seal in response to rotation of said impeller.

- 6. A centrifugal pump as defined in claim 1 characterized by the fact that said main pumping vanes terminate at the radially outer ends thereof in radially inwardly spaced relation with said ribs to provide said ribs With a maximum peripheral speed correspondingly greater than the maximum peripheral speed of said main vanes.

References Cited in the file of this patent UNITED STATES PATENTS 1,556,657 Wilfley Oct. 13, 1925 1,756,324 Wilfley Apr. 29, 1930 2,046,226 Weightman et al June 30, 1936 2,835,203 Cliborn May 20, 1958 2,835,320 McClure May 20, 1958 2,941,780 Von der Nuell et al. -June 21, 1960 FOREIGN PATENTS 348,466 Great Britain May 14, 1931 565,019 Germany Dec. 22, 1932

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