US 3167021 A
Abstract available in
Claims available in
Description (OCR text may contain errors)
Jan. 26, 1965 L. H. SENCE NONCLOGGING CENTRIFUGAL. PUMP 2 Sheets-Sheet 1 Filed April 15, 1963 1965 H. SENCE 3,167,021
NONCLOGGING CENTRIFUGAL PUMP United States Patent 3,167,021 NONCLOGGING CENTRIFUGAL PUMP Leonard H. Sauce, Milford, Ohio, assignor to Allis- Chalmers Manufacturing Company, Milwaukee, Wis. Filed Apr. 15, 1263, Ser. No. 273,164 2 Ciaims. ((11. 103-4103) This invention relates generally to centrifugal pumps. More specifically this invention relates to nonclogging, solids handling centrifugal pumps.
There has long been a problem in the hydraulic industry in connection with pumping solid material or fibrous material. These materials tend to clog the impeller of a centrifugal pump. However, there is a trend toward pumping more and larger solid material suspended in liquids. One Way of solving this problem is to take a conventional centrifugal pump impeller and position it in a recessed area alongside a swirl or pumping chamber. The impeller is spaced from the opposing wall of the pump oasing a distance equal to the diameter of the inlet of the pump so that any material entering the pumping chamber can be pumped outward through the discharge without engaging the impeller vanes. Although pumps of this type have been successful to a certain degree, they can only develop a very limited head and their efficiency is extremely low. As a result, such a pump is used only where it is absolutely necessary to pump solids of such a size that they frequently clog the impeller of a conventional centrifugal pump.
Applicant overcomes the problemsmentioned above by providing a unique impeller which permits the use of the vanes in the pumping chamber and is still capable of pumping any solid which enters the inlet of the pump. The impeller vanes are formed so that they are very narrow near the center of the impeller and gradually widened to a distance substantially equal to the distance across the impeller chamber near the periphery of the impeller. The vanes are arranged so that when the impeller is in the pumping chamber with the edges of the vanes almost touching the opposing wall surface, the vanes combine with the backplate of the impeller and the casing to define a passageway extending from the eye of the impeller to its periphery which has a minimum size equal to a sphere of the same diameter as the inlet of the pump. Such a pump which is fully described in applicants copending US. patent application Serial No. 243,112, now Patent No. 3,130,679, is nonclogging in that there is a continuous path through the pumping chamber which is the equivalent size of a sphere equal to the diameter of the inlet.
Experience in operating the above described pump has shown that an interesting and unusual phenomenon occurs when the impeller is moved away from the opposing wall surface of the impeller chamber. The head, rather than dropping sharply as expected on the basis of experience with conventional centrifugal pumps, remains substantially the same until the impeller is withdrawn completely out of the impeller chamber. Furthermore, the pumps efiiciency remains high during the same period. These unusual and highly desirable results are due at least in part to the unique formation of the impeller blades which actually exert a force on the swirling Water in the impeller chamber as the water is forced radially out of the chamber. In comparable prior art, solids handling pumps such as shown in US. Patents 2,958,293, R. F. Pray, Ir., and 2,635,548, C. H. Brawley, a swirl of liquid is formed in the pumping chamber by the blades positioned just outside of the pumping chamber and the swirling liquid imparts the force on the incoming liquid and solids being pumped. Hence, there is a significant loss of both efilciency and head. On the other hand, in the pump of this invention, substantially all the liquid being pumped enters the eye of the impeller and is thrown radially outward. As the liquid flows radially outward, it also flows away from the backplate or shroud of the impeller. However, in this area the vanes also extend further away from the shroud and hence still engage the water being pumped and continue to exert a direct force on it. It is believed that this type of action which occurs even when the impeller is retracted almost entirely out of the impeller chamber accounts for the unusually high efl'iciencies and head of this pump in all positions of the impeller. A pump with a retractable impeller is especially useful in pumping long stringy material which tends to ball up or get stuck between the impeller vanes and the pump casing.
Therefore, it is the object of this invention to provide a new and improved centrifugal pump.
Another object of this invention is to provide a nonclogging solids handling pump with improved head and efliciency.
Another object of this invention is to provide a new and improved nonclogging solids handling pump having an impeller that is movable axially within the pumping chamber.
Other objects and advantages will be apparent from the following description when read in connection with the accompanying drawings in which:
FIG. 1 is a cross sectional view of a centrifugal pump embodying the impeller of this invention;
FIG. 2 is an end view of the impeller of this invention taken along the lines lIII of FIG. 1;
FIG. 3 is a graph comparing the capacity, head and efficiency of a pump of this invention run at 1150 r.p.m. with the impeller in a fully retracted, 50 percent retracted and a nonretracted position; and
FIG. 4 is a graph plotting the percent head and efficiency against percent opening of the impeller with the pump capacity held constant.
The pump assembly 9 illustrated in FIG. 1 comprises generally a pump casing 10 having an inlet 11 and a discharge 12. The casing 10 defines an impeller or pumping chamber 13 in which an impeller 14 of this invention is normally positioned. The chamber 13 has a peripheral volute 15 to gather the discharge from the impeller and direct it into the discharge nozzle or opening 12.
The impeller 14 is connected to a shaft 17 which extends rearwardly from the pump casing 11) to a source of power. The shaft 17 is surrounded by a conventional shaft sleeve 16 and a suitable seal illustrated as a stufling box 18 having the usual packing 19 and a gland 20. The shaft 17 is also surrounded by a bearing and bearing cartridge 23 which is in turn mounted in a bearing bracket 24. The bearing bracket is in turn connected to the pump casing 10 and a base member 25.
The pump 9 is also equipped with a rear cover plate 28 which in this particular embodiment surrounds the stufiing box 18 and is positioned in a cylindrical neck portion 30 of the pump casing 10 a distance equal to the width of the impeller so that the impeller can be with drawn entirely out of the chamber 13 into the neck portion 30.
The impeller has a rear shroud 29 having a hub portion 39 with an axial bore 40 formed therein. The bore 40 is threaded for connection to the end of the shaft 17. As shown in FIG. 2, vanes 35 are arcuately spaced around the shroud 29 and extend from near the hub 39 to the periphery. The thickness 42 of the vanes as shown in FIG. 2 is substantially the same throughout their length although it could be varied if desired. However, the
width 43 of the vanes 35 shown in FIG. .1 varies from a very narrow width near the hub 39 of the impeller to a maximum width near the periphery of the impeller at which point the width of the vanes is substantially equal to the width of the impeller chamber 13.
The vanes 35 are so formed that when the impeller 14 is in the nonretracted position with the edges of the vanes almost touching the opposing wall 36 of the impeller chamber 13, the vanes, the shroud plate 29 and the wall 36 combine to define a plurality of fluid impelling passages 45 that extend from the inlet end of the pump to the discharge. The minimum size of these passageways 45 with the impeller in the nonretracted position is equivalent to a sphere of the same diameter as the inlet 11 of the pump. Hence, any solid material entering the inlet of the pump can pass through one of these passages through the impeller chamber into the discharge regardless of the position of the impeller. The minimum size of these passages is made possible by forming the leading edge 46 of the vanes so that it curves away from the wall 36 of the impeller chamber 13 near the hub of the impeller where the arcuate space between adjacent vanes is very small. In this area the distance between the edge 46 of the vane and the wall 36 of the casing is substan tially equal to the diameter of the inlet.
As the vane extends radially outward, the edge 46 of the vane curves toward the opposing wall surface 36 of the impeller chamber. In areas radially outward from the hub, the sphere can move between adjacent vanes 35 and a portion of the sphere extends inwardly from the edge of the vanes toward the shroud plate 2 of the impeller. In this position it does not require as much space between the edge 46 of the impeller vane and the casing wall 36 to pass a sphere the size of the inlet. For this reason the edge of the vane. can extend closer to the opposing wall surface as the vane extends radially outward. The curve on the edge of the vanes continues until a point is reached where the distance between adjacent vanes is equal to the diameter of the inlet or the diameter of the theoretical sphere which is to be passed through the pump. At this point, depth of the blades or vanes 35 is substantially equal to the width of the chamber 13.
In some applications, the material being pumped consists of long stringy material such as rags and intestines of animals. Such material tends to wind itself around the impeller vanes and wedge into narrow spaces between the vanes and the opposing wall surfaces. This problem can be overcome by moving the impeller away from the opposing wall surface 36 a sufiicient distance to prevent any clogging between the impeller and the casing wall.
In the pump of this invention, means are provided for moving the shaft 17 and the impeller 14 axially relative to the pump casing to vary the distance between the opposing wall surface 36 and the leading edge 46 of the impeller vanes. Any suitable means may be provided for moving the impeller relative to the wall but as specifically shown in FIG. 1, the bearing cartridge 23 is slidably mounted in the bearing bracket 24, and an adjusting mec, anism 49 is provided for moving the cartridge relative. to the bracket and locking it in place. The adjusting mechanism 49 has a flange th with a bore 51 formed therein attached to and extending outwardly from the bearing cartridge 23. The flange 50 and bore 51 are aligned with a suitable flange 52 and threaded bore 53 on the bearing bracket 24-. A suitable bolt 54 extends through the bore 51 in flange 5i) and threadedly engages the bore 53 in flange 52 for moving the bearing cartridge relative to the bearing bracket. A nut 55 threadedly engages the bolt 54 and is forced into abutting relation with the flange 50 to lock the adjusting mechanism 49 and hence the bearing cartridge in position.
With this adjusting mechanism 49, the impeller can be anywhere between a fully closed position shown in solid lines in FIG. 1 and the retracted position shown in the dot-dash lines in FIG. 1 and identified as 14'. An intermediate position with the impeller approximately half way between the retracted and nonretracted positions is also shown in dot-dash lines in FIG. 1 and is identified The results of the recent tests of the pump of this invention run at 1150 rpm. are summarized in the curve of FIG. 3. The three head capacity lines are labeled Non-Retracted, 50% Retracted and Retracted, respectively, to indicate the position of the impeller relative to the wall 36 and correspond to the impeller positions in FIG. 1. In the nonretracted position, the impeller is adjacent the side wall, in the retracted position the impeller is withdrawn into the neck portion 38, and in the 50 percent retracted position the impeller is positioned midway in the impeller chamber 13. The pump efficiency is shown in the form of constant efficiency lines A, B and C superimposed on the three head capacity lines. This shows that there is an eificiency loss from nonretracted to 100 percent retracted of about seven points. In percentage loss in eiiiciency, this is about twelve points.
The moderate loss in head as shown by the curves shown in F G. 3 is a distinct advantage, since the system head against which a pump of this type is normally working will be fairly constant. Assuming for instance the system head to be represented by line DE at 55 feet, then the pump could operate at points F, G or H, and still overcome the system head. Thus, various retracted positions might be taken'by the impeller up to fully retracted with the pumping head being maintained high enough to overcome the static head of the system, although at reduced capacity (g.p.m.). In a conventional open impeller pump designed to operate with the impeller vanes fitted closely to the casing front cover, a similar retraction would reduce the head values by almost fifty percent, so that the pump in many applications would be unable to overcome the system head. In a nonclogging pump, it is a distinct advantage to be able to retract the'impeller when desired and still maintain the total developed head near full value.
In the graph shown in FIG. 4, the characteristics of the pump of this invention are plotted in a slightly different manner. This curve shows that with constant capacity, the pump efficiency measured from point of maximum elficiency and developed head drop off only slightly as the percent of opening or retraction increases from 0 percent to 100 percent. strate two of the principal advantages of the present nonclog pump, namely, that of holding the developed head values to keep the liquid flowing against the system head and also the economy of power consumption represented by the efliciency line.
Below the curves of this pump is another curve showing the characteristics for another open impeller adjustable pump made by Allis-Chalmers. The characteristics of this pump are similar to those of other open impeller adjustable pumps presently on the market. In this pump, which we have identified as pump X, as the percent opening increases froni zero value the, head loss is very marked. For example, at 10 percent opening the head loss is 25 percent. Hence, the retractability of the impeller in this pump is a highly critical adjustment especially if the pump is part of a system pumping against a fixed system head. A very slight retraction of the impeller in such a pump may interrupt the continuity of flow unless other remedies are taken, such as speeding up the pump or reducing the system head.
In operation, as the impeller 14 begins to rotate, liquid with solids entrained therein are drawn in through the inlet 11. This liquid is then acted upon by the impeller and thrown radially outward. Any solids in the liquid move through the impelling passages 45 defined between the vanes 35, the internal wall surface 36 of the impeller chamber and the rear shroud 29. In this way, any solid which can enter the inlet of the pump can be impelled through the impeller into the discharge without clogging the pump.
If it is desired to change the position of the impeller 14 in the chamber 13, the nut 55 is loosened and the bolt Si? is rotated in the proper direction to vary the relative These substantially fiat curves demonpositions of the bearing cartridge and the pump casing. For example, to move the impeller away from the wall 36, the bolt 50 is rotated in a counterclockwise direction and the nut 55 is tightened against flange 50 to move the cartridge, shaft and impeller away from the wall 36 until the nut engages flange 50 to lock the adjusting mechanism and the cartridge, shaft and impeller in place. To move the impeller closer to the wall 36, the nut is loosened and the bolt 54 is rotated in a clockwise direction to move the flange 50, cartridge 23, shaft 17 and impeller 14 toward the wall 36 When the desired position is achieved, the nut 55 is again tightened against the flange 50 to lock the part in place.
Although but one embodiment of this invention has been illustrated and described, it will be apparent to those skilled in the art that various modifications and changes can be made therein Without departing from the spirit of the invention or the scope of the appended claims.
Having now particularly described and ascertained the nature of my said invention and the manner in which it is to be performed, I declare that what I claim is:
1. A centrifugal pump comprising: a casing having walls defining an impeller chamber and a cylindrical neck portion extending therefrom, said chamber having an axial inlet and a radially spaced discharge opening, an impeller mounted for rotation in said chamber, said impeller having a rear shroud plate and a plurality of arcuately spaced vanes mounted thereon, said vanes extending from the periphery of said plate radially inward to near the center of said impeller, the depth of said vanes being smaller near the center of said impeller than near its outer periphery, the depth of the radially outer portion of said vanes being substantially equal to the width of said chamber, said vanes being arranged on said impeller so as to define with said shroud plate and the opposing wall of said impeller chamber a plurality of passages continuous from the inlet of said chamber to said outlet, adjusting means for moving said impeller axially be tween a position adjacent said oposing wall and a position substantially within said neck portion and outside of said chamber, the minimum size of said passages for any position of said impeller being at least equal to a sphere of the same diameter as the width of said inlet, whereby any solid body entering said chamber through said inlet can be passed through said impeller to said discharge for any position of said impeller.
2. A centrifugal pump comprising: a casing having walls defining an impeller chamber and a cylindrical neck portion extending therefrom, said chamber having an axial inlet and a radially spaced discharge opening, an impeller mounted for rotation in said chamber, a shaft connected to said impeller and extending through said neck portion and out of said casing, said impeller having a rear shroud plate and a plurality of arcuately spaced substantially radially extending vanes mounted thereon, said vanes extending inward to near the center of said impeller, the depth of said vanes being smaller near the center of said impeller than near its outer periphery, the depth of the radially outer portion of said vanes being substantially equal to the Width of said chamber, said vanes being arranged on said impeller so as to define with said shroud plate and the opposing Wall of said impeller chamber a plurality of passages continuous from the inlet of said chamber to said outlet, a bearing bracket connected to said pump casing, a bearing cartridge slidably mounted in said bracket and surrounding said shaft, means to prevent axial movement of said shaft relative to said cartridge, means adjustably engaging said cartridge and said bracket to vary the position of said cartridge relative to said bracket and thereby move said impeller axially between a position adjacent said oposing wall and a position substantially within said neck portion and outside said chamber, the minimum size of said passages for any position of said impeller being at least equal to a sphere of the same diameter as the Width of said inlet, whereby any solid particle entering said chamber can be passed through said impeller to said discharge for any position of said impeller.
References Cited in the file of this patent UNITED STATES PATENTS 952,993 Mathis Mar. 22, 1910 2,693,312 Lanter Nov. 2, 1954 2,874,642 Forrest Feb. 24, 1959 3,010,402 King Nov. 28, 1961 FOREIGN PATENTS 1,055,511 France Oct. 19, 1953 808,796 Germany July 19, 1951 413,573 Great Britain July 19, 1934 441,385 Great Britain Jan. 20, 1936 574,079 Great Britain Dec. 19, 1945 82,497 Switzerland Oct. 1, 1919