US2883213A - Pump - Google Patents

Description

April 1959 R. H. w. KROEKEL ET AL, 2,883,213

PUMP

Filed May 15, 1956 INVENTORS ROLF H. w. KROEKEL WILLIAM LUBACH BY jaw ATTORN W Rolf H. W. "Kroekel, Coventry, R1, and William F. Luhach, Arcadia, "Calif assignors to :the United States of America as represented by the Secretary of the Navy Application May 15, 1956, sei'lal No. 585,130

-1 Claim. erase-11.14 (Granted under Title 35, usxcoae 1952 see. 266) The invention described herein may be manufactured and used by or for the Gove'rnment of the "United States of America forgovernmental purposes without the payment of any royalties thereon or therefor.

This invention relates to iliquid :pumps and more particularly to improvements in'pumpshaft seals for pumps which deliver hydrogen peroxide "to combustion chambers such as those employed in underwater automobile torpedoes or other high performance ordnance "vehicles.

In certain torpedoes it has become "desirable to employ hydrogenperoxide as an oxidant for the fuel, the oxidant and fuel 'being metered to'a combustion chamberwherein they react and form gas 'und'erpiessur'e for operating a turbine or other prime mover. The pumpingof hydrogen peroxide has presented serious diificulties since it is un' stable in the presence of certain materials employed in pumps and may violently decompose causing an explo sion which may destroy the pump, rendering the ordnance device useless for its intended purpose.

Prior to this invention centrifugal and reciprocating plunger pumps, for the purpose previously referred to, were known to have been developed, at least to the point of establishing feasibility. Of these types the positive displacement pump, such as the plunger pump referred to, has certain advantages over the centrifugal type where weight and high pressures at reasonable efliciencies are important. Plunger pumps, however, are complex, costly and become unduly large when required to deliver fluid at rates approaching optimum application area of centrifugal pumps. Pumps of the rotary type which would fill a gap between the plunger and centrifugal pumps were not known to exist and it is to improvements in this field that this invention more particularly relates.

In the development of the pump which forms the subject of this invention it was found that pumping hydrogen peroxide is vastly different from pumping most other liquids since, in addition to properties of density, viscosity and corrosiveness which must be considered, this fluid may decompose under certain conditions liberating heat and gas which may be suiiicient to not only adversely affect pump operation but to cause destruction of it. Not only was it necessary to prevent rapid decomposition but also to prevent contamination of the liquid from particles rubbed off the pump parts which tend to cause decomposition of the liquid. It was found that the materials selected for the pump must not only be compatible with the liquid but must not suffer any corrosive action on wearing surfaces throughout the intended life of the pump. Lubrication of bearings and pump parts imposed other problems. With the exception of fluorinated hydrocarbons there is no known oil or grease compatible with hydrogen peroxide. Dry lubricants such as Molycote were not satisfactory, scoring of wearing parts indicating that these lubricants were washed away by the pumped liquid. It became apparent that the selection of the pump housing material and its surface finish, the specific material and hardness of the pumping elements, the shaft seal, and the bearings and lubrication were all related and re- 2,883,213 Patented Apr. 21, 1959 quired careful selection to produce a satisfactory pump. Of the various parts just referred to the development of a satisfactory shaft seal presented the greatest problem because of limitations imposed upon it that it be leak free, generate as little friction as possible and be of a minimum physical size. It was found that the stuifing box type seal could be modified to overcome its large physical size and high frictional-losses by use of V rings made of Teflon and pure tin, alternately disposed and compressed. The axial type seal, however, appeared to have greater promise and it is to modifications of a-known type of axial seal that this invention still more particularly relates.

One oftheobjects of this invention is to provide improvements in rotary positive displacement hydrogen peroxide pumps.

Another object is to provide an improved axial type shaft seal for use with hydrogen peroxide pumps.

Another object is to provide improvements in commercially available axial type seals which will render same suitable for use in hydrogen peroxide pumps.

'Still further objects, advantages, and salient features will become more apparent from the description to follow, the appended claim and the accompanying drawing, in which:

Fig. 1 is a fragmentary central section through a pump forming the subject of the invention, and

Fig. 2 is anenlarged detail of a portion of Fig. 1.

Referring in detail to the drawing, the pump housing comprises a pair of end plates 10, 11, and a central plate 12, these being secured together'by a plurality of angularly disposed bolts (not shown). Central plate 10 is provided with a bore 13 which receives a Teflon sleeve 14, the inner surface of which receives a rotary internally toothed ring 15, the teeth of which engage the teeth of a rotor 16 aflixed to shaft 17. In the example illustrated the ring is provided with seven teeth and the rotor with six teeth. Kidney shaped chambers are provided in plates 10, 11 which communicate with opposite faces of the ring and rotor and to these chambers the inlet and discharge conduits are connected. These features are all somewheat conventional and have been omitted in the drawing to simplify same. Shaft 17 is journaled at one end in plate 11 and to plate It) by another bearing (not shown).

Plate 10 carries an axial type seal 18 in a bore 19, this seal being of the type disclosed in the US. Patent 2,249,188. It comprises an outer cup 20 into which is pressed an inner cup 21 having a rolled in flange 22 which retains the various parts contained therein in assembled relation. A sleeve 23 having a radial flange 24 thereon is disposed within cup 21 and may axially slide relative thereto. An 0 ring 25, or similar seal, is disposed within cup 21 and engages sleeve 23, preventing leakage in a direction to the left. A ring or washer 26 is disposed in cup 21 against a shoulder 27 and an annular crimped type spring 28 abuts same and flange 24 urging the latter to the right. A concentric flange or sleeve 29 projects to the right from flange 24, the normal function of which is to support and confine a seal ring of carbon material which is bendable by suitable cement to one end of sleeve 23 (forming the right face of flange 24) and the inner surface of sleeve or flange 29, these parts hereafter to be referred to as a seal ring carrier.

As previously referred to, the axial seal was provided with a seal ring of carbon material. This material was not found satisfactory in the presence of hydrogen peroxide. One explosion occurred and is believed attributable to carbon flakes which may have worn from the seal ring. Various materials were substituted such as various ceramics, glass and Teflon with varying success. In

34 of shoulder 35 of shaft 17 while with softer materials the end face of the seal ring unduly wore. Exhaustive experiments with various materials indicated that the ideal seal ring material should be softer than ceramic, harder than Teflon, tougher than glass and still be compatible with hydrogen peroxide.

The material found to possess the characteristics just referred to was found to be Kel-F No. 300. This material, like Teflon, cannot be bonded to a metal surface hence it became necessary to devise a suitable me chanical support for the seal ring. Referring again to Fig. 2, ring 30, of the material just referred to, is machined to the shape shown with an internal conical face 31. A sleeve 32 having an external conical face 33 is press fitted into the bore of sleeve 23 as shown which mechanically retains the seal ring in place. Kel-F is defined in Trademark Registration No. 516,531 of the Principal Register as a High temperature thermoplastic formed as a solid core and as granules of molding powder to be used in the fabrication of molded, coated or lined articles. It has been otherwise defined as a monochlorofluoroethylene polymer, a synthetic resin. Teflon previously referred to is a Du Pont product which has been defined as a tetrafiuoroethylene polymer, a plastic.

To simplify the drawing only one seal has been illustrated and the pump shaft is illustrated as being journaled on a plain bearing in plate 11. In the actual construction, a seal device 18 is provided in plate 11, identical to the one shown in plate 10, and the left end of the shaft is supported by a sealed double row ball hearing the same as provided in plate 10, the construction being such that axial pressures on the pump shaft, produced by pump pressure, are balanced.

Obviously many modifications and variations of the present-invention are possible in the light of the above teachings. It is thereforerto be understood that within the scope of the appended claim the invention may be practiced otherwise than as specifically described.

What is claimed is:

In a shaft seal of the type having a non-rotatable metallic seal ring carrier having a first bore therein adapted to surround a. pump drive shaftin spaced relation thereto and a second bore of larger and of uniform diameter than the first bore 'adjacent'one end thereof; said bores being joined by a radially disposed annular surface forming a shoulder; a seal ring of plastic material compatible with hydrogen peroxide and unbondable to metal having a uniform outer diameter to be slideably received within said second bore, an annular inner end, and an internal frus'to-conical surface adjacent said annular inner end; and a metallic sleeve press fitted within the first bore having an external frusto-conical surface engaging said internal frusto-conical-surface and retaining said annular innerend in engagement with said shoulder.

References Cited in the file of this patent FOREIGN PATENTS Great Britain of 1899 Sweden Oct. 26, 1937 OTHER REFERENCES Sealed, published by Stevenson Engineering Corp, of Providence, R.I. Bulletin No. 2; received in U.S. Patent Ofl'ice on Oct. 15, 1942. 1

New Products and Materials, published in Chemical Engineering, April 1950; page 164 relied upon.

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