US 1967316 A
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Description (OCR text may contain errors)
y 1934- D. A. MEEKER 1,967,316
Original Filed Nov. 3, 1930 ATTORNEY S Patented July 24, 1934 UNITED STATES PUIHP David A. Meeker, Troy, Ohio, asaignor to The Hobart Manufacturing Company, Troy, Ohio,
a corporation of Ohio Original application No tube! 20, 1931 3 Claims.
This invention relates to a pump, and more particularly to a centrifugal pump.
One of the principal objects of the invention is the provision of a compact pumping unit of few parts constructed to effectively prevent leakage adjacent the pump shaft.
Another object of the invention is to provide a centrifugal pump in which packing glands for the pump shaft are avoided, and wear on the 1 relatively movable parts is minimized while at the same time leakage along the pump shaft is avoided.
Another object of the invention is to provide a pump of the character in which the construction of the impeller is such that during pumping operation an axial thrust is produced tending to move the impeller out of sealing engagement with the pump housing parts through which the pump shaft extends, while tight sealing engagement is maintained when the impeller has slowed down or is stationary.
Another object of the invention is to provide a pump having an impeller producing the above mentioned axial thrust, and in which the pump shaft extends loosely through an opening in the pump housing, together with means for producing a reduced or subatmospheric pressure within the pump housing adjacent the opening for the pump shaft to restrain leakage.
Still another object of the invention is to provide a combined pump and power or motor drive unit which is of simple and compact construction, is efficient in operation, and has long life.
Other objects and advantages of the invention will be apparent from the following description, the accompanying drawing and appended claims.
This is a divisional application of the copending application of David A. Meeker, Serial No.
492,915, filed November 3, 1930.
In the drawing, in which like characters of reference designate like parts throughout the several views thereof- Fig. 1 is a central vertical sectional view through the pump and motor unit of the present invention;
Fig. 2 is a fragmentary sectional view of a portion of Fig. 1, showing the parts in a different operating position;
Fig. 3 is a vertical sectional view taken on the plane of the line 33 of Fig.1; and
Fig. 4 is a fragmentary view in elevation of the rear face of the pump impeller.
Referring to the drawing, which discloses a preferred embodiment of the invention, the wall In Germany Goof a suitable tank or reservoir containing water or other liquid is indicated at 11. A centrifugal pump 17 is attached to the tank 11 at the side wall thereof. The pump is driven by an electric motor 18 which is supported from the housing of the pump. The pump and tank are provided with aligned openings; the central intake openings 20 of the pump communicating with the interior of the reservoir 11 through an opening 11'. The pump 17 discharges through a tangentially arranged discharge outlet 22.
The pump 17 and motor 18 form a unit in which a common shaft 28 is provided. The shaft 28 carries the motor armature 29 at one end and has mounted upon its opposite end, within the pump housing, an impeller 30. The impeller, which comprises a disc-like member having suitable water circulating vanes provided thereon, is arranged so that it may move axially with respect to the pump housing; this movement being provided to aid in maintaining a water-tight joint at the point of entrance of the shaft 28 within the pump housing without the use of a stumng box. The impeller is preferably fixed to the shaft 28 and is shown held to the shaft 28 by means of a key 31, and by a nut 32 which engages the threaded end of the shaft. The housing 33 of the pump is preferably a casting of volute form having an open side, defined by the circular wall 34, which is closed by an extending portion 35 of the frame 36 of the motor. In assembling the motor and pump the impeller 30 may be attached to the end of the shaft 28 protruding from the motor, and the motor and assembled impeller may then be attached to the pump housing 33, as by means of bolts 38, to provide a compact pumping unit.
The pump housing 33 is attached to the side wall of the reservoir 11 by means of the two screws 40 which are shown diametrically spaced one above the other, and is positioned so that the central intake opening 20 of the pump will coincide with the opening 11' of similar shape in the wall of the reservoir 11. A suction fitting 43 is attached to the inner side of the reservoir wall and is secured thereto in alignment with the opening 11' by means of the two screws 44 which are also diametrically spaced, and stand at right angles to the pump housing screws 40. Such an arrangement of attaching screws permits the parts to be readily assembled. The suction fitting is preferably a hollow casting of elbow shape having a passage opening downwardly and terminating a relatively short distance from thebottom wall 46 of the reservoir 11. Upon operation of the pump, water or other liquid, which is maintained at a suitable level in the reservoir 11. is drawn through the suction fitting 43 and communicating openings 11' and 20 6 to the interior of the pump for discharge from the pump outlet 22.
The extending portion 35. which comprises an integral part of the motor frame, is provided with spaced disc-like walls 57 and 58. The wall 57 of the motor frame carries a bearing 59 for the support of one end of the motor armature shaft 28; the other end of the shaft being supported by a bearing carried by the motor frame in the usual manner. The wall 58 is provided with a sealing member 60 to restrain leakage along the passage through which the shaft 28 passes for attachment of the impeller 30. The sealing member 60, which is of bronze or other suitable material, provides a free or loose passage for the shaft 28 and is formed on the side of the wall 58 within the pump housing with an extending annular flange or face. Sealing means are provided within the pump housing to cooperate with the sealing member 60 and prevent the e of leakage water from the housing along the shaft while the pump mechanism is at rest, and means are provided which are operable during pumping to maintain a subatmospheric pressure within the pump housing adjacent the shaft passage so that leakage is restrained during operation of the pump. The hub portion of the impeller may function as a sealing means or, as shown, a washer 68 may be provided of some suitable hard material such as stainless steel, which is held on the shaft between a shoulder 69 and the hub portion 70 of the impeller and during periods of rest bears against the sealing member 60 to close the shaft passage against leakage.
Resilient means such as the spring 72, shown positioned on the shaft 28 between the motor armature 29 and suitable washers 78 which bear against the wall 57, provides a thrust on the shaft which tends to move the shaft 28 to the right so that the washer 68 will be held in sealing contact with the face of the bearing 60. Means are incorporated in the construction of the impeller to create a force upon rotation that will move the impeller and its associated parts to the left (as viewed in Fig. 1), so that during normal operation of the pump the washer 68 will be maintained out of contacting engagement with the member 60. During operation of the pump the impeller thrust overcomes the tension exerted by the spring 72 and the washer 68 is drawn away from the sealing member 60. When the motor circuit is opened after use, and at some point during the time that the impeller and its shaft are slowing down, the tension of the spring 72 overcomes the thrust imparted by the impeller so that the washer 68 is moved into contact with the face 75 of the sealing member and is thereby ground into a sealing fit each time the motor circuit is opened after operation of the pump. As the washer 68 is maintained out of contact with the face of the sealing member during normal operation wear on these parts from frictional contact is reduced so that long life of the operating parts is assured, while reducing the power consumption by minimizing friction of operation of the motor and impeller shaft. While the axial shifting of the shaft 28 to move the washer 68 away from the sealing member 60 increases somewhat the compression of the spring 72 against the washers 73, ample provision for lubrication of the washers 73 is provided by the lubricant feed channel 73' so that these washers act as a lubricated thrust bearing without substantial increase in friction and wear of the thrust parts.
Within the space between the walls 57 and 58 is provided a well 62 for the collection of any leakage water which may happen to pass from the pump along the shaft 28. The well 62 is provided with a drain outlet passage 63 having a lower threaded end 64 to which a drain pipe may be attached or, as shown. a sealing plug 65 may be provided. Suitable means are provided upon the shaft 28 within the area of the well 62 to prevent any possible leakage through the member 60 from continuing on along the shaft 28 and into the lubricated motor bearing 59. As shown, a ring 77 is fixed to the shaft 28 and is provided with an outwardly extending flange 78 which is adapted to throw off by centrifugal force any water that may pass through the member 60. The extending portion 35 of the motor frame which comprises the disc-like walls 57 and 58, and the well 82, is open in its upper portion, to provide accessibility to the shaft 28 and permit the screws 38 which fasten the motor housing to the pump to be inserted and tightened. Strengthening and supporting webs 80 connect the walls 57 and 58 at this upper open portion of the motor frame. The space between walls 57 and 58 is thus freely open to atmosphere so that the outer end of the loose shaft opening through member 60 communicates with the atmosphere. A ring-like groove 81 is provided within the wall 58 and is positioned in line with the plane of the flange 78 so that any water thrown from the flange will be collected within the groove 81 and will be carried into the well 62. Small quantities of water collecting here may be evaporated by the normal circulation of air through this space or, as mentioned, the well may be connected to a drain pipe.
The subatmospheric pressure existing adjacent the sealing washer 68 during operation of the impeller is created by the provision of spaced openings 80 in the impeller disc adjacent the hub portion 70, thereby affording communication with the subatmospheric pressure existing within the suction inlet of the pump. Auxiliary vanes 83 which are positioned on the disc portion 84 of the impeller on the rear side, or that opposite to the water circulating vanes 85, assist in maintaining this subatmospheric pressure. As shown, the impeller vanes 83 are positioned within a close fitting ring-like groove 86 provided upon the adjacent face of the wall 58. The inner ends of the vanes 83 terminate in a ring 83' which is positionedconcentrically and in close fitting relationship to the inner wall of the groove 86 which is formed by the peripheral edge of the face 75 of the sealing member 60, thus giving a staggered passage between the impeller and the ad- Jacent side wall of the housing, the effective flow area of which in the various positions of the impeller is less than the combined areas of the openings 80. The openings 80 provide communication from the space adjacent the sealing washer 68 to the area adjacent the central opening 20 which is maintained under suction by the action of the impeller. A baiile, in the form of a ring 87, mounted on the impeller adiacent the openings 80 serves as a deflector to direct away from the openings the flow of water induced by the impeller blades and further increases the suctional pull through the openings 80 on the area adjacent the washer 68.
Axial movement of the impeller and associated parts, to relieve the sealing washer from sealing contact during operation, is induced by the pressure of the water adjacent the oflftake'22 .of the pump acting on the peripheral portion 88 of the rear face of the impeller. As shown, the impeller disc 84 is provided on the front face with circulating vanes which extend substantially to the periphery of the disc 84. The opposite or rear face of the impeller carries the auxiliary vanes 83 which are positioned some distance in from the periphery of the disc, thus providing an annular area 88 on the impeller disc. The impeller is shaped so that the area 88 lies closely adjacent the face of the web 58 with a small clearance space 89 therebetween which is open to the interior of the pump adjacent the peripheral edge 84 of the disc. Water pressure created by the impeller vanes 85 acts on the relatively narrow annular portion of the front face of the impeller extending between the vanes 85 and the periphery, and also acts on the oppositely positioned relatively larger area 88 on the rear face to produce an overbalancing pressure capable of moving the impeller to the left (as viewed in Fig. 1).
The auxiliary vanes 83, like the circulating vanes 85, tend to create a circulation outwardly, and this circulation coupled with the effect of the staggered passageway tends to restrain the passage of water from the clearance space 89 which is under pressure towards the area adjacent the washer 68, which is under suction. The closefltting relationship of the vanes 83 with the walls of groove 86 provides a clearance space which is considerably less than the area of the openings 80 and restrains the passage of water therethrough to an amount considerably less than the carrying capacity of the openings 80. Consequently the suction on the openings is effective to create the desired subatmospheric pressure. The vanes 83 therefore assist in maintaining the subatmospheric condition which restrains leakage along the shaft during operation, and aid in preserving the desired effective total pressure differential between the rear and front portions 88 and 90 respectively of the impeller. Even though the sealing washer 68 is removed from its seat under these conditions (as shown in Fig. 2), leakage past the sealing member 60 is prevented by the presence of subatmospheric pressure at this point. While the member 60 loosely receives the shaft 28 so as to avoid difliculties inherent in the provision of a third bearing for the motor shaft, nevertheless the spacing between the member 60 and the shaft is sufliciently small so as to prevent the ingress of objectionably large quantities of air from the open space between the walls 57 and 58 into the suction area adjacent the sealing washer 68.
For certain operating conditions, the pump and motor unit can be constructed so that the washer 68 remains in sealing contact with the sealing member 60 during operation of the impeller. This may be accomplished by so proportioning the parts of the impeller and the spring 72 that the axial thrust tending to remove the washer 68 from its seat during operation is insufficient to overcome the counterthrust of the spring 72 within the motor housing. By such suitable proportioning of the parts, the net resulting thrust tending to hold the washer 68 on its seat during operation can be regulated to any amount desired; for example, the first mentioned axial thrust can be such as to substantially balance the counter thrust of the spring, or a greater pressure of contact of the washer 68 with the sealing member 60 can be provided. In such case, the members 60 and 68 are preferably made of suitable wear-resisting materials which operate without objectionable friction, such as a hard stainless-steel washer 68 and a graphite-bronze or Durex sealing member 60. This construction provides an adequate sealing of the extended end of the motor shaft within the impeller housing, without the employment of the construction producing subatmospheric pressure adjacent the point of exit of the shaft from the pump housing and without the employment of stufling boxes.
While the form of apparatus herein described constitutes a preferred embodiment of the invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.
What is claimed is:
1. A centrifugal pump comprising a housing having a suction inlet passage and a pressure discharge passage, an axially movable and rotatable impeller mounted within said housing comprising a disk having pumping vanes on the front side thereof facing said inlet passage, a shaft for said impeller extending loosely through an opening in a shaft receiving portion of the pump housing to the exterior thereof on the rear side of said disk opposite to the said suction inlet passage, a sealing member axially movable with said impeller adapted to engage a cooperating part of the said shaft receiving portion of the housing to seal the said opening, resilient means for urging said impeller axially to maintain said sealing member in sealing engagement with said shaft receiving portion when the pump is at rest, said impeller and shaft receiving portion providing a fluid chamber on the rear side of said disk adjacent said shaft receiving portion of the housing, additional vanes on the rear side of said disk for resisting the back flow of fluid from the pressure discharge passage along the rear side of said disk to said fluid chamber, said additional vanes terminating farther from the periphery of the disk than said pumping vanes to provide an overbalancing axial fluid pressure on the rear side of said disk tending to move said impeller and sealing means axially away from sealing position against the action of said resilient means when the pump is operating.
2. A centrifugal pump comprising a housing having a suction inlet passage and a pressure discharge passage, a single disk impeller mounted within said housing having pumping vanes on the front face thereof facing said inlet passage, an axially movable and rotatable shaft carrying said impeller, said shaft extending loosely through an opening in a shaft receiving portion of the pump housing to the exterior thereof on the rear side of said disk opposite to the said suction inlet passage, a sealing member axially movable with said shaft and impeller adapted to engage a cooperating part of the said shaft receiving portion of the housing to seal the said opening, resilient means for urging said shaft and impeller axially to maintain said sealing member in sealing engagement with said shaft 145 receiving portion when the pump is at rest, said impeller and shaft receiving portion providing a fluid chamber on the rear side of said disk adjacent said shaft receiving portion of the housing, additional vanes on the rear side of said 1 disk positioned within a recess of the shaft receiving portion of the housing and providing a narrow staggered passage along the rear side of said disk from the periphery thereof to said fluid chamber and adapted to resist back flow of fluid from the pressure discharge passage to said fluid chamber, said additional vanes terminating farther from the periphery of the disk than said pumping vanes to provide an overbalancing axial fluid pressure on the rear side of said disk sufficient to overcome the force of said resilient means and move said shaft and sealing member axially away from sealing contact when the pump is operating, said disk having a port providing communication between said suction' inlet passage and said fluid chamber to produce a subatmospheric pressure in said chamber during operation of the pump.
3. A centrifugal pump comprising a housing having a suction inlet passage opening into the housing on one side thereof, and a pressure discharge passage adjacent the periphery thereof, said housing having an opening at the side thereof opposite said suction inlet passage. a driving motor having a motor frame attached to said pump over said opening and forming a portion of the enclosing housing of said pump, a motor shaft having an extension protruding loosely through a shaft receiving portion of said frame into the pump housing, an impeller carried by said shaft extension within the housing comprising a disk having pumping vanes on the front side thereof facing said suction inlet passage, and additional vanes on the rear side thereof adjacent said shaft receiving portion of the frame, motor bearings carried by said motor frame constituting the sole support for said shaft and impeller, said shaft being axially movable as well as rotatable in' said bearings, a sealing member axially movable with said shaft adapted to engage a cooperating part of the shaft receiving portion of said frame to seal the said opening loosely receiving said shaft, resilient means for urging said shaft axially to maintain said sealing member in sealing engagement with said shaft receiving portion when the pump is at rest, said additional vanes on the rear side of said disk terminating farther from the periphery of the disk than said pumping vanes to provide an overbalanclng axial fluid pressure on the rear side of said disk sumcient to overcome the force of said resilient means and move said shaft and sealing member axially away from sealing contact when the pump is operating, said disk having a port providing communication between said 7