US3028813A - Water pump shaft seal - Google Patents

Description

April 10, 1962 R. s. NEELY WATER PUMP SHAFT SEAL Filed March 30, 1960 Z O? SilNVEN TOR. BY kl FIGS United States Patentflfiice 3,028,813 Patented Apr. 10, 1962 vanra Filed Mar. 30, 1960, Ser. No. 18,636 3 Claims. (Cl. 103-117) This invention is intended to prevent loss of prime in outboard motor cooling pumps where the drive shaft enters the pump housing above the water level and there is a tendency for air to be drawn into the pump cavity around the shaft. In a preferred form, the pump housing has a cup surrounding the shaft connected to the high pressure side of the pump by a slot which keeps the cup full of water and not only prevents sucking of air into the pump cavity, but also permits the escape of air from the pump cavity into the seal cup. The slot is virtually unblockable by sand and other foreign material, thereby providing reliable sealing action under all conditions.

In the accompanying drawing, FIG. 1 is a sectional elevation of an outboard motor cooling water pump, FIG. 2 is a section at right angles to FIG. 1, FIG. 3 is a section of the pump impeller, FIG. 4 is a plan view of the pump impeller, FIG. 5 is a bottom plan view of the upper pump housing, and FIG. 6 is a section on line 6-6 of FIG. 5.

The pump is driven by a vertical drive shaft 1 extending through top and bottom pump housings 2 and 3. The pump inlet 4 is in the bottom housing 3 and the pump outlet 5 is in the top housing 2. Within the pump hous ing is a flexible blade impeller having a hub 6 fixed to the shaft and bonded to radially extending spokes 7 of rubber or similar elastomeric material, on the top and bottom surfaces of which are trapezoidal blades described in greater detail in application Serial No. 832,686. Within the upper and lower housing parts are inner and outer conical walls or surfaces 9 and 10 with which sloping edges 11 and 12 of the blades 8 make wiping or sliding contact. Between the conical surfaces 9 and 10 are outwardly sloping surfaces 13 parallel to the upper and lower surfaces 14 of the spokes 7 with which edges 15 of the blades 8 make wiping or sliding contact. The surfaces 13 vary from a maximum axial separation at the left of FIG. 2 to a minimum axial separation at the right of FIG. 2 so that as the impeller rotates, the blades are alternately compressed and expanded to vary the volume between adjacent blades. The inlet 4 is located in a suction region in which the volume between adjacent blades is increasing, thereby producing a suction drawing water into the pumping chamber and the outlet 5 is located in a pressure region in which the volume between adjacent blades is diminishing, thereby producing the pressure required to force the water out the outlet. The pump so far described may be used for circulating cooling water in outboard motors, in which case the shaft 1 is the propeller drive shaft and the shaft may enter the pump housing above the water level so that the joint or seal between the shaft and the pump housing is exposed to atmospheric pressure resulting in the sucking of air into the pump cavity and the possible loss of prime if enough air accumulates in the pump cavity. This problem is present in flexible blade pumps in which the shape of the blades and of the pumping cavity is substantially different from the specific construction illustrated. In pumps for outboard motor cooling water, the problem is aggravated by the presence of sand and other foreign matter in the water which tend to cause failure of conventional seals which might be ar ranged between the shaft and the pump housing.

To overcome the problem, the upper pump housing 2 has a seal cup 16 surrounding the shaft which is kept full of water by a slot or channel 17 in an annular surface 18 on the upper housing 2. The inner end of the slot communicates with the space 19 between the shaft 1 and the bottom of the seal cup while the outer end of the slot communicates with the pressure side of the pump cavity, thereby connecting the bottom of the cup 16 with the pressure side of the pump cavity. The adjacent annular surface 20 on the impeller spans the slot and the blades 8 sweep past the inner ends of the slot. The sweeping of the impeller past the slot tends to keep it clear of foreign matter. Although the slot 17 can have a relatively large area, there is no excessive flow of water into the cup because the axis of the slot is transverse or substantially perpendicular to the axis of the cup and enters the base of the cup generally tangentially to the side walls on the cup through a relatively long passage providing a substantial back pressure. The slot is arranged at a slight angle to the radial so that the entrance to the slot provides a scooping action directing water toward the cup. This insures flow of water into the cup at all times because it takes advantage both of the pressure and velocity of water within the pump cavity. Although the slot is shown in a plane perpendicular to the shaft, it could be located in an inclined plane so as to improve the self-cleaning properties. The slot provides a slight excess of Water which overflows the seal cup and drains over the outside of the pump housing. The bleeding of water into the seal cup is directly from the pump cavity and carries air with it so that trapping of air in the pump cavity is eliminated. Swirling of water in the cup 16 is prevented by ribs 21 on the inner surface of the cup.

In many outboard motors, the upper pump housing is within the exhaust leg of the outboard motor and is exposed to the exhaust gases at greater than atmospheric pressure. Under these conditions, the seal is maintained and sucking of air into the pump cavity is prevented. The lower pump housing is always submerged. The upper pump housing may on occasion be submerged but it is frequently exposed to air or exhaust gases so that the seal is necessary.

What is claimed as new is:

1. A rotary pump comprising a vertical shaft, a housing having an upper portion and a lower portion with walls surrounding the shaft and defining a pump cavity, an impeller having a plurality of angularly spaced flexible blades having wiping engagement with said walls, the radial cross sectional area of the pump cavity varying from a minimum to a maximum around the shaft whereby the volume between adjacent blades alternately increases and decreases as the impeller rotates, an inlet to the pump in the suction region in which the volume between adjacent blades is increasing, an outlet from the pump cavity in the pressure region in which the volume between adjacent blades is decreasing, a cup on the upper portion of the housing surrounding the shaft, said cup opening upward and having a bottom with an opening therein providing a space between it and the shaft, said upper portion of the housing and said impeller having adjacent annular surfaces around the shaft and the annular surface of said upper housing having a slot therein leading from said pressure region of the pump cavity to said space between the shaft and the bottom of the cup for bleeding water to the cup to maintain a water seal for the shaft.

2. The pump of claim 1 in which the slot is inclined to the radial so that the end of the slot in the pump cavity has a scooping action directing water into the slot.

3. A rotary pump comprising a vertical shaft, a housing having an upper portion and a lower portion with walls surrounding the shaft and defining a pump cavity, an impeller having a plurality of angularly spaced flexible blades having wiping engagement with said Walls, the radial cross sectional area of the pump cavity varying from a minimum to a maximum around the shaft whereby the volume between adjacent blades alternately increases and decreases as the impeller rotates, an inlet to the pump in the suction region in which the volume between adjacent blades is increasing, an outlet from the pump cavity in the pressure region in which the volume between adjacent blades is decreasing, a cup on the upper portion of the housing surrounding the shaft, said cup opening upward and having a bottom with an opening therein providing a space between it and the shaft, said upper portion of the housing having a channel leading from said pressure region of the pump cavity to said space between the shaft and the bottom of the cup for bleeding water to the cup to maintain a water seal for the shaft.

References Cited in the file of this patent UNITED STATES PATENTS Fernstrum Feb. 20, 1951 Weyer Aug. 18, 1953 Neely Aug. 9, 1960 FOREIGN PATENTS Great Britain Mar. 1, 1917 Great Britain May 13, 1949 Germany Apr. 3, 1952 France Mar. 30, 1942

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