SU811024A1 - Sealing ring - Google Patents

Description

The invention relates to a sealing technique, and more specifically to piston seals, mainly operating in the temperature range from normal (+ 25 ° C) to cryogenic (-196 ° C). 5

Various piston seals are known, such as stuffing boxes, labyrinths, cups and others.

The indicated seals during operation in the temperature range from +25 to –196 ° С have the following disadvantages: large shear forces; high degree of leakage; low reliability at high pressures.

These shortcomings were partially eliminated in the piston seals by U-shaped different cuffs with a mustache pre-tensioning in various ways [1].

Known lip seal made of plastic, including a sealing 20 mustache and interacting with the supporting elements of the base with a variable cross section [2].

The main disadvantage of the described seal is a decrease in the degree of tightness at low, for example, cryogenic, temperature due to the fact that a gap is formed between the outer mustache of the cuff and the cylinder diameter due to the higher linear expansion coefficient of 30 fluoroplastic compared to metal, and the force of the compression ring not enough to create a reliable seal.

The aim of the invention is to increase the tightness at cryogenic temperatures.

This goal is achieved _that the cuff base is made in the form of a trapezoid, the smaller base of which is facing the cuff axis, while the narrowing angle of the sides is selected according to the dependence a = arctg, where a is the maximum width of the base, R is the radius of the outer surface of the cuff.

In FIG. 1 and 2 show the design of the seal of the movable joint.

The proposed seal of the movable connection consists of a piston 1 inserted in the cylinder 2, a sleeve 3, the whisker A of which has an interference fit along the piston 1, and the base B is made in the form of a trapezoid, tapering to its axis, of a flange 4.

The work of the proposed seal rolling joint is as follows.

The control pressure is supplied into the cavity B of the cylinder 2 and acting on the area of the piston 1, limited by the mustache A of the cuff 3, which has an interference fit on the piston 1 at normal temperature, moves it to the required stroke. Being placed in an environment with cryogenic temperature, the cuff is compressed in height and to the axis and therefore the sealing of the piston 1 with a mustache A of the cuff 3 is monitored, and the cuff base is self-sealing along the trapezoid cone.

To ensure self-sealing of the cuff base along the trapezoid cone and to eliminate the failure (rupture) of the sealing ring, the narrowing angle is selected from the ratio of elongations:

a z = arctg, (1) where a is the angle of narrowing of the sides (degrees);

Aosn - the actual narrowing of the maximum width of the base of the cuff (mm);

AR is the actual decrease in the maximum radius of the cuff (mm).

Actual restrictions are determined by the well-known formula:

Δ = Α · Δ / · φ, (2) where Δ is the actual narrowing (mm);

A — long length (mm);

At is the difference between the assembly temperature of the compound and the temperature of its operation (degrees);

φ is the coefficient of linear expansion (narrowing).

We substitute values (2) in (1) taking into account FIG. 2:

where a is the maximum width of the base of the cuff [mm];

R is the radius of the outer surface of the cuff [mm].

Finally, a = s arctg y. (4)

Thus, at normal temperature, the tightness is carried out on the mustache A of the sleeve 3 and on the base B, tightened by the flange 4 when assembling the seal of the movable joint, and at a cryogenic temperature, the mustache A seals the piston 1 with a still tight fit; depressurization will not occur at the base of the cuff in connection with its execution in the form of a trapezoid, the smaller base of which is facing the braid of the cuff, while the narrowing angle of the sides is selected according to dependence (4).

To test the operability of the rolling joint seal, a piston-cylinder pair seal was made with a diameter of 70 mm, a fluoroplastic cuff — ZM, with a maximum base width of 4 mm and a radius of the outer surface of the base of 40 mm. The narrowing angle of the base was determined from relation (4);

tga = - = 0.1; a = arctan 0.1 = 5 ° 43 '.

Tightness at cryogenic temperature ensured the operability of the movable joint.

In addition, the proposed sealing of movable joints is simpler in design and cheaper to manufacture, since the cuff has a single mustache and does not require special additional clamping rings.

Claims (2)

A control pressure is applied to the cavity B of the cylinder 2 and, acting on the area of the solution 1, limited by the whisker A of the cuff 3, which has a tension g over the piston 1 at normal temperature, moves it to the required stroke. Being placed in an environment with a cryogenic temperature, the cuff is compressed in height and to the axis, and therefore the sealing of the piston 1 with the mustache A of the mansets 3 is tracked, and the base of the cuff along the trapezoid cone is self-sealing. To ensure the sealing of the base of the cuff to the trapezoid cone and to exclude the breakout of the sealing ring, the angle of narrowing is selected from the ratio of elongations: a arctan. (1) where a is the angle of narrowing of the sides (degrees); AOSN — actual narrowing of the maximum base width of the cuff (mm); AR is the actual reduction of the maximum cuff radius (mm). The actual constrictions are determined by the known formula:., (2) where A is the actual constriction (mm); And - the length size (mm); A / is the difference between the assembly temperature of the joint and the temperature of its operation (degrees); Ф - linear expansion (contraction) coefficient. We substitute in (1) the values (2) with regard to FIG. 2: a - arctg, Я-М-f where a is the maximum width of the base of the cuff R - the radius of the outer surface of the cuff mm. Finally a; arctg Thus, at normal temperature, the tightness is carried out on the USU A cuff 3 and on the base B, tightened by the flange 4 when assembling the seal of the movable joint, and at a cryogenic temperature, And even with a large tension, the piston 1 seals; the base of the cuff will not be depressurized due to its implementation in the form of a trapezoid, the smaller base of which reverses the cuff of the cuff, while the angle of narrowing of the lateral sides is chosen according to (4). To test the performance of the movable joint seal, a seal was made of a pair of piston-cylinder with a diameter of 70 mm, a fluoroplastic cuff of 3M, with a maximum base width of 4 mm and an outer surface radius of 40 mm. The base tapering angle was determined from the relation (4): tga - 0.1; a arctg 0.1 5 ° 43. The tightness at cryogenic temperature ensured the operability of the rolling joint. In addition, the proposed sealing of movable joints is simpler in design and more particularly in production, since the cuff has one bar and does not require special additional gland rings. Claims: A lip seal made of plastic, comprising a sealing mustache and a base interacting with supporting elements with variable cross-section, characterized in that, in order to increase tightness at cryogenic temperatures, the base is made in the form of a trapezium, the smaller base of which faces the cuff axis, at the same time, the angle of narrowing of the sides is chosen according to the dependence a arctg, where a is the maximum width of the base; - the radius of the outer surface of the cuff. Sources of information taken into account in the examination 1. USSR author's certificate number 180035, cl. F 16J 15/32, 1967. 2.Patent of Great Britain N ° 1442090, cl. F 2 V, publ. 1976 (prototype).