Mechanical seals

Details Mechanical seals Mechanical seals

1983-11-18

1985-09-03

Smith, Robert I.

Seal for a joint or juncture

Seal between relatively movable parts

Relatively rotatable radially extending sealing face member

277 93R, E16J 1534

Patent

active

045388210

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

This invention relates to mechanical seals of the type employed to seal a rotary shaft exiting a housing containing fluid, usually under pressure, to be retained within the housing.
The invention particularly relates to cartridge-type mechanical seals supplied as a preassembled unit and adapted to be positioned over the shaft. An end plate thereof is then simply bolted to the housing and a sleeve secured to the shaft.


BACKGROUND ART

Seals of these types are disclosed in a number of patent specifications of which U.S. Pat. No. 3,051,498 and British Pat. Nos. 1465069, 1471891 and 1471892 are examples. It is an object of this invention to improve existing designs.


DISCLOSURE OF INVENTION

In accordance with this invention there is provided a mechanical seal adapted to seal a rotary shaft exiting a housing containing a fluid product to be retained inside the housing, the seal comprising
(i) a sleeve adapted to be sealed and secured around the shaft and extending out of the housing;
(ii) an annular rotary seal element carried by said sleeve;
(iii) an end plate adapted to surround the sleeve and be sealed and secured to the housing;
(iv) an annular stationary seal element carried by said end plate; and
(v) means urging said seal elements into contact at opposed annular seal surfaces to form a running seal therebetween, characterised in that,
(vi) an annular bush is disposed in the end plate outside of said seal elements and which is a close fit on the sleeve to staunch any leak between said seal elements.
This bush forms the basis for a number of features which can simply be incorporated into the seal as desired without requiring greater complication of the design of the seal.
Thus it is preferable if the bush is so disposed in the end plate that in the event that the sleeve becomes unsecured from the shaft a flange on the sleeve abuts the bush and is prevented from contacting the end plate, the bush being constructed from a spark resistant material. Where the product is flammable it is essential that the possibility of sparking is reduced to a minimum. The bush being constructed from bronze or some such other spark resistant material reduces the possibility of sparking occurring either through its own continuous rubbing on the sleeve or more especially through the sleeve working loose in time and contacting the end plate under the influence of said urging means.
Preferably said means urging said seal elements into contact comprises a spring carried and positioned by said bush and acting on said stationary seal element. Thus the bush can also serve as a spring carrier to locate the spring relatively to the stationary seal elememt.
Moreover said bush is prevented from rotating with respect to the end plate and interlocks with the stationary seal element preventing said stationary seal element from rotating with respect to the bush.
Some form of antirotation device is always required for the stationary seal elememt and this provides a simple solution. Preferably a pin extends through the end plate and engages a slot in the bush whereby the bush is prevented from rotating.
Said bush may carry a lipseal adapted to seal the small gap between the bush and the sleeve and the bush is itself sealed to the end plate.
Moreover the space defined between the end plate and sleeve and between the seal elements and bush is adapted to be filled with a quenching medium supplied through a port formed in the end plate and drained through another port also formed in the end plate.
The quenching medium is circulated on the outside of the seal elements and serves to cool them and also wash away any fluid product leaking through the seal elements. Ports formed in the end plate may also be employed to circulate the fluid product around the inside of the seal elements so as to quench them and also to keep that area of the housing free from debris which could adversely affect the operation of the seal.
The bush may be sealed to the end plate by an O-ring disposed between substantially cylindrical surfaces of the end

REFERENCES:
patent: 2590759 (1952-03-01), Dale et al.
patent: 2797940 (1957-07-01), Michener, Jr. et al.
patent: 3099453 (1963-07-01), Dunn et al.
patent: 3578803 (1971-05-01), Huhn
patent: 3705728 (1972-12-01), Millar
patent: 3719226 (1973-03-01), Vallance
patent: 3953038 (1976-04-01), Ludwig
patent: 4175753 (1979-11-01), Wentworth, Jr.
patent: 4272084 (1981-06-01), Martinson et al.
patent: 4377290 (1983-03-01), Netzel
patent: 4410188 (1983-11-01), Copes
Hydrocarbon Processing, vol. 62, No. 1, Jan. 1983, (Houston, Texas), H. P. Bloch, "Selection Strategy for Mechanical Shaft Seals", pp. 75-81, see p. 79, left-hand column, paragraph 3-p. 80, left-hand column, paragraph 1; FIG. 6.

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