US3457870A - Pump - Google Patents

Description

July 29, 1969 E. B. SLEETER 3,457,870

PUMP

Filed April 11, 1967 United States Patent 3,457,870 PUMP Edward B. Sleeter, Wausau, Wis., assignor to Marathon Electric Manufacturing Corporation, Wausau, Wis., a corporation of Wisconsin Filed Apr. 11, 1967, Ser. No. 629,974 Int. Cl. F04d 29/12 U.S. Cl. 103-111 2 Claims ABSTRACT OF THE DISCLOSURE A sleeve of heat shrinkable plastic tubing tightly encasing a portion of a drive shaft adjacent to its driving connection with the impeller of a pump prevents fluid being pumped from corrosive contact with the shaft.

This invention relates to pumps, and has more particular reference to electric motor driven pumps of the type known as jet pumps.

Such pumps comprise a housing, an impeller of the centrifugal type within the housing and an electric motor having a shaft to which the impeller is affixed to be driven by the motor, the motor in turn being rigidly fastened to the pump housing. Rotation of the impeller causes fluid to be drawn into an axial inlet in the impeller and then forcefully discharged through radial passages in the impeller into the interior of the housing, from whence the fluid under pressure issues through a delivery line communicating with an outlet in the housing.

Because the pump drive shaft must extend through an opening in a wall of the pump housing for connection to the impeller, a seal mechanism is ordinarily employed with jet pumps such as described to prevent escape of pressurized fluid from the interior of the pump housing along the exterior of the shaft and through the opening in said wall of the housing. One well-known seal mechanism used for this purpose is mounted at the exterior of the pump housing and comprises a stationary sealing ring loosely encircling the pump drive shaft and held in a synthetic rubber cup pressed into a recess in the pump housing, and a rotating assembly cooperating with the stationary sealing ring and driven by a synthetic rubber annulus tightly seated on the shaft at a location axially outwardly from the stationary ring.

From this it can be appreciated that liquid in the pump housing inevitably came into contact with the adjacent portion of the pump drive shaft, specifically that portion of the shaft extending between the synthetic rubber annulus of the seal mechanism and the impeller, which is ordinarily threaded onto the extremity of the shaft. This has long presented an annoying shaft corrosion problem which was particularly acute Whenever the liquid pumped contained active chemicals in solution.

Various attempts have been made to solve this corrosion problem, as by the expedient of plating the pump drive shaft, or by the use of a shaft made entirely of stainless steel or other corrosion resistant material, or by fitting a stainless steel sleeve around the end portion of a plain carbon steel shaft. In some cases, the entire end portion of the shaft was provided by a stainless steel stub shaft coaxially aflixed to a carbon steel main shaft portion. Of these expedients, the use of plating is the least expensive, but is generally inferior to shafts made from stainless steel. These, however, were not only quite costly, but more diflicult to machine than plain carbon steel.

The present invention provides an inexpensive but thoroughly satisfactory solution to the above described corrosion problem, by the expedient of tightly encasing a substantial portion of a plain carbon steel pump drive shaft in a sleeve of heat shrinkable plastic tubing, which ice sleeve not only extends toward the motor and beyond the synthetic rubber annulus of the seal mechanism, but also has an end portion which is clamped between the end of the impeller hub and a shoulder on the adjacent end portion of the drive shaft to act as a gasket in preventing liquid from contacting that part of the drive shaft having the impeller affixed thereto. This effectively prevents corrosion of the threaded shaft end and solves the attendant problem of difliculty in removing the impeller therefrom whenever necessary.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawing illustrates one complete example of the physical embodiment of the invention, constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

The single figure is a fragmentary sectional view of adjacent portions of a jet pump and drive motor close coupled to the pump, and illustrating how this invention protects the motor shaft against corrosion.

Referring now to the drawing, the numeral 5 generally designates a jet pump having an impeller 6 which rotates within the housing 7 of the pump. The inlet of the pump is coaxial with the throat 8 or inlet of the impeller, and passages 9 in the impeller radiating outwardly from its inlet force the liquid being pumped into the interior 10 of the housing during rotation of the impeller.

The impeller is driven by an electric motor 11 which, in the embodiment illustrated, is mounted on the top wall 12 of the pump housing with its shaft 13 vertical. The lower end portion 14 of the shaft projects downwardly from the bottom end bell 15 of the motor through a seal mechanism 16 and through an opening 17 in the top wall 12 of the pump housing, to have the impeller 6 drivingly connected to its extremity 18. The extremity 18 of the shaft is reduced in diameter to provide a downwardly facing shoulder 19 at the end of the lower portion 14 of the shaft, which shoulder closely opposes the end 20 of an upwardly extending hub 21 on the impeller. The extremity 18 of the shaft is threaded and screwed into a tapped hole in the hub 21 to provide the driving connection between the shaft and the impeller.

The lower portion 14 of the drive shaft is also reduced in diameter to define a downwardly facing shoulder 22 at its upper end; and a circumferential groove 23 is cut in the shaft directly under the shoulder 22.

According to this invention the entire outer or lower portion 14 of the drive shaft is protected by a tight fitting liquid proof sheath or sleeve 25 of plastic material, which loosely fits the opening 17 in the top wall of the pump housing. The purpose of the sleeve is to prevent corrosion of the shaft by contact therewith of the liquid being pumped.

The sleeve 25 is preferably provided by a length of heat shrinkable plastic tubing encircling the lower portion 14 of the shaft, and having its upper end portion 26 contracted into tight engagement with the bottom of the groove 23 under the upper shaft shoulder 22 to anchor the upper end of the sleeve axially to the shaft. The lower end portion 27 of the sleeve is contracted inwardly and under the bottom shoulder 19 and tightly clamped between the latter and the adjacent end 20 of the impeller hub to anchor the lower end of the sleeve to the shaft.

As shown, the lower end of the sleeve terminates in a short downwardly extending axial neck 28 which more or less snugly embraces the undercut portion 29 joining the threaded extemity 18 of the shaft to the shaft portion 14 thereabove.

The lower end portion 27 of the sleeve, being clamped between the shoulder 19 and the end of the impeller hub, acts as a gasket to prevent liquid in the interior of the pump housing from contacting the threaded extremity 18 of the shaft. The remainder of the sleeve 25 cooperates with the seal mechanism 16 in preventing liquid from contacting the shaft portion 14 above the impeller.

The seal mechanism 16 is of a conventional type, having a stationary annular seal face 30 loosely encircling the shaft portion 14 and clearing the sleeve 25 thereon. The seal face 30 is mounted in a rubber holder 31 of angle shaped cross section, pressed into an upwardly opening recess 32 in the top wall of the pump housing, concentric with the opening 17 therein. The rotating seal face 33 bears upon the stationary face 30 and provides a seat for one end of a bellows 34. The other end of the bellows is seated upon an annulus 35 of synthetic rubber, which encircles the upper portion of the sleeve 25 in fluid tight relation thereto, just below the anchored end 26 of the sleeve. The annulus 35 thus rotates with the shaft and drives the rotating seal face 33. A coiled compression spring 36 encircling the bellows yieldingly urges the seal faces 30-33 into fluid tight engagement with one another, and a washer 37 is interposed between the upper shoulder 22 on the shaft and the seal mechanism to hold the latter effective.

Liquid from the interior of the pump housing is free to flow upwardly through the opening 17 in the top wall of the pump housing and along the exterior of the plastic sleeve 25 to the interior of the seal mechanism 16. The rubber annulus 35, however, prevents leakage of liquid upwardly out of the seal mechanism, while the remainder of the seal mechanism prevents leakage of liquid radially outwardly from the space enclosed thereby.

The seal mechanism thus cooperates with the plastic sleeve 25 to prevent liquid from contacting any surface of the shaft 13, while that portion of the shaft extending between the rubber annulus 35 and the impeller hub 21 is covered and protected by the plastic sleeve 25 alone. One of the features of this invention resides in the fact that the plastic sleeve 25 does not come into rubbing contact with any stationary part of the seal 16, the pump, or the drive motor therefor.

Several advantages result from protection of the pump drive shaft by heat shrinkable plastic tubing in the manner described. It allows the shaft to be made of plain carbon steel which is relatively inexpensive and easily machinable; it provides long lasting protection for the shaft at lower cost than any other expedient offering equivalent protection against corrosion; it provides a gasket effect at the driving connection between the shaft and the impeller hub to prevent liquid from coming into contact with the threads on the extremity of the shaft; and by choice of the proper heat shrinkable plastic tubing, it enables the drive shaft to be tailored for trouble free operation in various corrosive environments, such as when chemicals or petroleum products are to be pumped.

The application of the heat shrinkable plastic tubing to the pump drive shaft can be accomplished in an exceedingly simple and efficient manner which entails supporting a group of identical motor shafts in vertical positions in a tray or fixture, with their threaded extremities uppermost. Pieces of heat shrinkable plastic tubing of the proper length and of a diameter only slightly larger than the intermediate diameter portion 14 of the shafts are then slipped over the threaded extremities of the shafts to bottom on their large diameter shoulders 22. The tray containing the shafts can then be lowered into hot oil or other fluid at the temperature required to contract the heat shrinkable plastic tubing, and allowed to remain for the few minutes necessary to complete the shrinking step. This can be effected without immersing the plastic tubing in the hot oil or other liquid, as the required heat will flow upwardly into the shafts to initiate shrinkage of the tubes at their lower ends, where the tubing will anchor itself into the circumferential grooves 23 adjacent to the larger diameter shoulders 22.

The shrinkage of the tubing to form the sleeve 25 will take place progressively from the shaft shoulder 22 toward the threaded extremity 18 of the shaft. Since there will be axial as well as diametral shrinkage of the tubing, allowance should be made for lengthwise shrinkage to assure that the resulting sleeve will always extend inwardly over the smaller shoulder 19 adjacent to the threaded extremity 18 of the shaft.

From the foregoing description, together with the accompanying drawing, it will be apparent to those skilled in the art that this invention provides an exceptionally simple but eflicacious solution to the long standing problem of corrosion in the drive shafts of pumps.

What is claimed as my invention is:

1. In a motor driven pump of the type having a pump housing in which an impeller rotates to cause liquid to be drawn into and then expelled from the housing, and wherein the motor shaft has its extremity coaxially drivingly connected to a hub on the impeller and has a portion which projects from the end of the hub through an opening in one wall of the housing and through a seal mechanism at the exterior of the housing, said seal mechanism having a seal face fixed with respect to the housing and loosely encircling said portion of the shaft, and an annular elastic ring encircling the shaft at a location beyond the seal face and adapted to rotate with the shaft, the improvement which comprises:

(A) said portion of the motor shaft having a uniform diameter greater than that of said extremity thereof to define a shoulder from which the extremity projects, and which shouder is close to and opposes the adjacent end surface of the impeller hub;

(B) an elongated sleeve of plastic tubing tightly encircling said uniform diameter portion of the motor shaft to prevent liquid from contacting the same, said sleeve having one end portion directed inwardly over said shoulder and clamped between it and the adjacent end of the impeller hub to prevent liquid in the housing from contacting the extremity of the shaft at its connection to the hub, the sleeve extending loosely through said opening and the seal mechanism but having said elastic ring tightly seated on its end portion remote from the impeller;

(C) and means on the shaft engaged by said remote end portion of the sleeve at a location beyond said elastic ring, for anchoring said remote end portion of the sleeve to the shaft.

2. The motor driven pump of claim 1, wherein said last named means comprises a circumferential groove in the shaft, and an annular inwardly directed flange on the sleeve tightly engaged with the bottom of said groove.

References Cited UNITED STATES PATENTS 1,249,572 12/1917 Weitling 1031 l4 1,850,683 3/1932 Merrill l03l 14 1,925,898 9/1933 Fritz 1031 14 2,382,839 8/1945 Wuensch 1031 14 2,464,989 3/1949 Payne.

2,599,122 6/1952 Park 27786 HENRY F. RADUAZO, 'Primary Examiner U.S. Cl. X.R.

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