US3421445A - Glandless electrically driven pumps - Google Patents

Description

1969 v. IVANOFF GLANDLESS ELECTRICALLY DRIVEN PUMPS Filed June 21, 1966 R F NF E0 u mw I m T m V ATTORNEY United States Patent 3,421,445 GLANDLESS ELECTRICALLY DRIVEN PUMPS Victor Ivanolf, Harpenden, England, assignor to Hayward Tyler & Company Limited Filed June 21, 1966, Ser. No. 559,261 Claims priority, application Great Britain, June 24, 1965,

26,799/ 65 US. Cl. 10387 2 Claims Int. Cl. F0411 13/06; F04d 29/10; F04d 29/02 ABSTRACT OF THE DISCLOSURE The invention relates to glandless electrical motor/ pump combinations in which the motor housing and pump housing are in communication with each other through a narrow annular clearance between the shaft and a neck portion surrounding the shaft. In such combinations, the-re is a tendency, when the pump is at rest, for convection currents to be established which convey hot liquid up one side of the narrow annular clearance and cooler liquids down the other side. This results in distortion of the pump shaft which is removed in accordance with the invention by providing the shaft, in the neck region, with a sleeve of thermal insulating material. This can take the form of a layer of asbestos or heat resistant plastics material, or may be constituted by a layer of liquid within an outer retaining sleeve.

The invention relates to vertical glandless electrically driven pumps, particularly for pumping hot liquids. In such units the motor is normally of the squirrel cage induction type constructed for operating filled with the pumped liquid cooled to a lower temperature. The motor housing forms a common liquid enclosure with the pump housing, the two housings being connected by a neck portion and the communicating space between the two being the narrow annulus round the driving shaft, where it extends through the neck portion.

In the particular case where the driving motor is positioned above the pump there is a tendency for thermal convection currents to be set up between the cold relatively heavy liquid in the motor and the hot relatively light liquid in the pump. When the unit is running these convection currents are broken up by the peripheral drag of the rotating shaft, but when the unit is stopped convection currents are quickly established.

The hot liquid tends to rise in the annulus on one side of the shaft into the motor and the cold current tends to descend into the pump on the other side of the shaft. This produces unequal heating of the opposite sides of the shaft within the annulus and distorts it by asymmetrical thermal expansion. This distortion of the shaft may cause a closing up of the fine working clearances between the rotating and the stationary components within the pump and may result in seizure on starting up the pump again.

The purpose of the invention is to minimise this distortion of the shaft to a very small acceptable value.

In accordance with the invention (whose precise scope is defined in the appended claims) the shaft, where it passes through the neck portion, is provided with a thin sleeve of thermal insulating material. The fitting of this sleeve does not directly affect the temperatures of the ascending and descending currents, but causes the main temperature drop between the two sides of the shaft to Patented Jan. 14, 1969 take place in the insulation itself, thus reducing substantially the temperature differences in any transverse plane within the shaft and thereby greatly reducing the shaft distortion.

Some constructional forms of insulating means in accordance with the invention will now be described, by way of example, with reference to the accompanying drawings in which:

FIGURE 1 is a diagrammatic part sectional elevation of a glandless, electrically driven pump,

FIGURE 2 is a sectional elevation, on a larger scale, through the neck portion of the pump shown in FIGURE 1; and

FIGURE 3 is a view, similar to FIGURE 2 of a second embodiment of the invention.

The electrically driven pump shown in FIGURE 1 comprises, in known manner, an upper, motor housing 11 connected by a narrower neck portion 12 to a pump housing 13, and a driving shaft 14 which extends through the neck portion with annular clearance and carries the motor rotor at its upper end and the pump impeller 16 at its lower end. The narrow annular clearance between the neck portion 12 and the shaft 14 affords liquid communication between the pump housing 13 and the motor housing 11 which both normally contain some of the liquid to be pumped.

In accordance with the invention, and as best seen in FIGURE 2, the shaft 14, where it passes through the neck portion 12, is provided with a thin sleeve 21 of asbestos or other thermal insulating material retained in a cylindrical recess in the bore of a thin outer sleeve 22 of a rigid material, preferably metal which is secured to the shaft 14 by being shrunk onto it or fixed by one or more screws 23.

In a modification of this embodiment, the solid insulating material is omitted and the rigid outer sleeve 22 has a hole or gap so that the cylindrical recess fills with liquid. The liquid in the recess then forms the insulating sleeve 21, as most liquids are poor conductors of heat unless agitated.

In the embodiment shown in FIGURE 3, the outer sleeve 22 is omitted, and the insulating sleeve 21 is constituted by a layer of insulating material applied direct and adhering to the shaft 14. This sleeve may, for example, be constituted by a layer of ceramic material formed by spraying onto the shaft a hot ceramic powder, or by a coating of heat resistant synthetic plastics material.

I claim:

1. In a vertical, glandless electrically driven pump of the type comprising a pump housing, a motor housing, a neck portion connecting said housings, and a drive shaft extending from the motor housing with annular clearance through said neck portion into the pump housing so that said annular clearance permits the flow of liquid between said housings, the improvement comprising the provision of a thin sleeve of thermal insulating material encompassing that portion of the shaft which extends through said neck portion, and an outer rigid sleeve secured to said shaft for retaining said insulating sleeve in position on said shaft portion within the neck portion.

2. The improvement claimed in claim 1, wherein said sleeve of insulating material is constituted by a layer of liquid within said outer sleeve.

(References on following page) 3 References Cited 1,925,898 9/1933 Fritz 103114 3,255,702 6/1966 Gehrm 103--114 UNITED STATES PATENTS FOREIGN PATENTS 2 19 Miller 3 114 5 1,239,467 7/1960 France. 12/1939 1 b 10387 6/1947 gg f i HENRY F. RADUAZO, Primary Examiner. 2/1954 Guyer 10387 11/1959 White 103 s7 12/1963 Moser 103-87 10 103111, 114; 308237

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