Centrifugal pump

May 28, 1935. f. b. allen 2,003,168

CENTRIFUGAL PUMP

Filed Aug. 21, 1930

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Patented May 28, 1935

2,003,168

UNITED STATES PATENT OFFICE

2,003,168

CENTRIFUGAL PUMP

Frank B. Allen, Lower Merion Township, Montgomery County, Pa., assignor to The AllenSherman-Hoff Company, a corporation of Pennsylvania

Application August 21, 1930, Serial No. 476,734

Claims. (Cl. 103—111)

This invention relates to the art of pumps and pumping and more particularly to centrifugal pumps for pumping liquids containing abrasive materials.

The common types of pumps in use today are not well adapted to pump liquids containing abrasive materials, such as the ashes from coal-burning furnaces, because of the wear caused on the pump parts by the passage of the abrasive-carrying water through the pump. In centrifugal pumps particularly, the clearance spaces between the rotating parts and the stationary parts must be kept small to secure efficient operation of the pump. In the ordinary form of centrifugal pump these spaces become worn and enlarged when abrasive carrying liquid is pumped, thus allowing excessive leakage and resulting in a serious decrease in pump efficiency.

Various ways have been suggested for preventing wear in centrifugal pumps which are intended for use with abrasive carrying liquids, among which may be noted my co-pending U. S. patent application, Serial No. 368,289, filed June 4, 1929. This application discloses a centrifugal pump in which the harmful abrasive materials are positively prevented from entering the small clearance spaces. In this type of pump, clear water is forced through the clearance spaces into the pump casing under higher pressure than the pressure within the main pumping chamber. However, in the apparatus disclosed in my application, Serial No. 368,289, a considerable quantity of the high pressure clear flushing water passes into-the main pump casing through the clearance space between the inner edge of the impeller and the end of the pump intake pipe. At this point the pressure of the abrasive carrying liquid is comparatively low and, as the pressure of the clear liquid is comparatively high, there is a relatively large pressure differential between the clear and abrasive liquids. This causes a considerable flow of clear liquid through the clearance space into the main pump chamber and, although this in itself is not harmful, it does result in a somewhat wasteful use of the clear water and decreases the amount of abrasive liquid which can be pumped.

It is among the objects of my present invention to provide a centrifugal pump in which the clearance spaces or communicating passages between the rotating and stationary parts will be continuously flushed and kept clear of abrasive material and in which the pressure of the clear water at the clearance space adjacent the pump intake will be only slightly greater than the pressure of the abrasive-carrying liquid within the pump intake.

Another object is the provision of a centrifugal pump having means for forcing clear water through the passages into the main pump cham- 5 ber under pressure greater than that which exists in the main chamber at the respective passages.

A further object is to provide a centrifugal pump in which the kinetic energy of pumped 10 clear water in the auxiliary chambers is converted into static energy which is effective to force the clear water steadily into the main impeller chamber against the existing pressure therein at the respective communicating passages j 5 between the main and auxiliary chambers.

The above and other objects of my invention will appear from the following description of a preferred form thereof, reference being had to the accompanying drawing, in which: 20

The figure is a vertical section through a vertical type centrifugal pump embodying my invention.

In the vertical centrifugal pump illustrated in the figure the impeller 50 is mounted on a verti- 25 cal shaft 5t and is enclosed in the main pump casing 52. The shaft 51 may be driven by any suitable source of power such as an electric motor and extends upwardly through the top cover plate 53 of the sump. The pump casing 52 is 30 provided with an inlet pipe 54 and a discharge pipe 55. The liquid to be pumped is drawn up through the pipe 54 by the main impeller blades 56 and is thrown out into the annular chamber 57 by the centrifugal action of the rotating impeller 35 In well known manner. The top and bottom cover plates 58 and 59 together with the impeller 50 and the main casing casting 52 divide the interior of the pump into the main pumping chamber 57 and the auxiliary chambers 60 and 61. 40

The impeller 50 in addition to the main blades 56 carries auxiliary impeller blades 62 and 63, which are secured to the main impeller by the tie bolts 64. These tie bolts 64 extend through holes in the webs 65 of the main impeller and hold 45 the auxiliary impeller blades securely in position. The auxiliary blades 62 rotate in the auxiliary chamber 60 and the auxiliary blades 63 rotate in the auxiliary chamber 61.

The auxiliary chamber 60 is divided into two 50 parts by the baffle disc 66 which is spaced from but carried by cover plate 58. In like manner the disc 67 divides the auxiliary chamber 61 into two portions. At their inner ends the auxiliary chambers 60 and 61 open into the large annular 55

2,003,168 chambers 68 and 69 respectively. These chambers 68 and 69 are connected to a supply of clean flushing water, by means of the pipes 70, 71 and 72. The pipe 72 may be connected to any suitδ able source of flushing water. The periphery of impeller 50 has a running fit with the casing 52, and the auxiliary impeller blade castings have running fits with the inner edges of the discs 66 and 67.

A spring-pressed sealing ring 75 has a sliding fit on the inner end of the intake pipe 54 and is adapted to have its end surface pressed into abutting contact wtih the inner edge of the impeller 50 by the spring 76. This sealing member 15 75 is cylindrical in form and is provided with slots 77 through which the screws 78 extend. These screws 78 are secured to the intake pipe 54 and prevent rotation of the sealing member 75 while permitting a limited longitudinal movement 20 thereof. The inner edge of the casting carrying the auxiliary blades 63 is sealed by the member 79, which has a sliding fit within the end casting 59 and is spring-pressed against the auxiliary impeller blade casting. A similar sealing member 25 80 is provided to seal the inner edge of the casting carrying the auxiliary impeller blade 62. This sealing member 80 is prevented from rotating while having a limited longitudinal movement by means of a slotted portion engaging the 30 screw 8i. The sealing member 79 may be similarly guided.

The drive shaft 51 has a bearing which may be generally designated as 82 and which is located immediately above the impeller 50. The lower 35 end of the bearing 82 lies within the chamber 68 and is provided with a floating sealing member 83. This sealing member 83 is generally similar to that described and claimed in the co-pending United States patent application of L. E. Mylting 40 Serial Number 491,140, filed Oct. 25, 1930, and comprises essentially a cup-shaped member having a close sliding fit on the outside of the bearing 82 and being spring-pressed into abutting contact with the end of the hub of the impeller 45 50 to prevent the inflow of water into the bearing. The shaft 51 is of reduced diameter immediately above the bearing 82 and is surrounded by a tubular sleeve 84 which extends upwardly and terminates in a cup 85. This cup 85 forms an 50 oil reservoir from which lubricating oil flows down around the shaft 51 to the bearing 82, where the spiral groove 86 coacts with the rotating shaft to form a pump drawing the oil down and thoroughly lubricating the bearing, then forc55 ing it back up through the pipe 87 and discharging it over the bearing 88 at the upper end of the shaft 51. The oil flows over the bearing 88, continuously lubricating it, and then to the reservoir c.up 85. It will be seen that by the 60 above described apparatus, a circulating lubricating oil system is provided by which both the upper and lower shaft bearings are thoroughly and positively lubricated.

The shaft 51 and the sleeve 84 are surrounded 65 by the tube 89 which is secured to the end plate 58 of the pump. This tube 89 extends upwardly and forms a stand pipe in which the clear flushing liquid which enters through the pipes 70 and 7 I may rise. An overflow opening 90 is provided 70 near the top of the stand pipe 89 and this overflow may be above the level of the sump overflow, so that the clear flushing liquid may be maintained at a greater head than that of the abrasive-carrying liquid which is being pumped. 75 This construction eliminates any possibility of the abrasive-carrying liquid backing up into the communicating passages between the auxiliary and main pumping chambers when the pump is stopped.

A float type of oil level gauge 91 may be con- δ nected to the oil reservoir cup 85 by a pipe 92 which passes through the overflow opening 90 in the stand pipe 89.

When this pump is operating, the abrasivecarrying liquid is drawn up through the inlet io pipe 54 and discharged by the main impeller blades 56 through the annular chamber 57 and the discharge pipe 55. The auxiliary clear flushing water enters the auxiliary chambers through the pipes 70 and 71 and is thrown out by the aux- 15 iliary blades 62 and 63 into the auxiliary whirl chambers between the walls 58 and 59 and the discs 66 and 67. The clear water thrown out by the auxiliary impeller blades 62 and 63 is then directed back inwardly between the discs 66 and 20 67 of the walls 93 of the main pump casing 52. As the pressure within the main pump chamber 57 is less than that in the auxiliary chambers 60 and 61, there will be a positive flow of clear flushing water through the passages 73 and 74. 25 This flow prevents the wearing of the small clearance spaces between the stationary and rotating parts of the pump by the abrasive action of the pumped liquid. ,

At the joint 94 between the sealing member _3ϋ75 and the inner edge of the main impeller 50, the abrasive-carrying liquid to be pumped is at comparatively low pressure. This joint is also protected by a positive flow of clear flushing liquid from the chamber 69. To provide this posi- 35: tive flow it is only necessary to supply clear water through the pipe 71 at slightly greater pressure than that which exists at the point 94 within the pump. The reason for supplying the clear water to the chamber 69 at a pressure only slight- ₄₀ly greater than the pressure of the abrasive liquids within the pump intake is to create a positive flow of clear flushing water through the joint 94 and thus prevent abrasive wear of this joint. By limiting the pressure differential at ₄₅this point to a relatively small quantity the amount of flushing water which is used is materially reduced.

The sealing rings 79 and 80 serve to prevent the flushing water which is thrown out into the ₅₀auxiliary chambers 60 and 61 by the auxiliary impeller blades from flowing back into the chambers 68 and 69. Thus it will be seen that the pressure of the clear flushing water adjacent the joint 94 will be substantially that of the supply ₅₅line 72, while the pressure within the chamber 61 will be increased by the auxiliary impeller blades to a point sufficient to cause a positive flow of flushing water through the joint 74 into the main pumping chamber. The flow of clear wa- ₆₀ter will be from the auxiliary chamber into the main chamber even though the auxiliary impeller blades be of the same diameter as the main impeller blades, because the outlet from the auxiliary chambers is relatively restricted ₆₅and a greater pressure will be built up within the auxiliary chambers than will be built up by the main impeller blades in the main chamber, the outlet from which is relatively unrestricted.

From the above description, it will be seen that 70 the pump illustrated in the figure is adapted to pump abrasive carrying liquid without danger of wear due to the abrasive action of the gritty material in the spaces between the relatively moving parts. In my preferred pump construe- 75

2,003.168 3 tion there is created a relatively small pressure differential at each joint where abrasive material might do damage. This pressure differential causes a positive flow of clear flushing water 5 through the joint, preventing the inflow of abrasive material. By maintaining the pressure differential small, the consumption of clear water is maintained at the most economical point, and the efficiency of the pump is increased.

By making the auxiliary chambers 60 and 61 relatively large and dividing them into two parts by the baffles 66 and 67, the kinetic energy or velocity of the clear liquid, as it is thrown out by the auxiliary impeller blades, is converted 15 into static energy or pressure at the joints 73 and 74.. This construction gives a more even and positive flow of' clear water through the joints 73 and 74 than it is possible to obtain when the discs 66 and 67 are omitted or the 20 auxiliary chambers 60 and 61 are made too small.

Pumps of the type illustrated in the figure are frequently' installed in sumps and, as noted in the description, by locating the overflow opening in the tube 89 above the overflow level of the ²⁵ sump (indicated by dot and dash lines) the pressure of the clear flushing water will always be greater than that of the abrasive carrying liquid which enters the pump.

While I have described the illustrated embodiment of my invention in some detail, modifications and variations thereof may appear to those skilled in the art to which it appertains, and I do not therefore, limit myself to the precise de₃₅ tails shown and described, but claim as my invention, all embodiments thereof, coming within the scope of the appended claims.