RU2266454C1 - Face seal for shaft - Google Patents

Abstract

FIELD: sealing engineering.

SUBSTANCE: face seal comprises shaft, housing, and movable and unmovable members that are in a contact with each other. The unmovable member is mounted on the housing. The movable member is mounted on the shaft for permitting movement along the axis of the shaft and is loaded in the direction to the unmovable member with the use of the spring that bears on the shaft. The shaft is provided with the bushing which can move along the shaft axis. The spring bears on one side of the bushing. At least one lever whose axle is mounted on the shaft abuts against the other side of the bushing. The lever can be unequal-arm, with the short arm facing the bushing. The longer arm can be provided with weight.

EFFECT: enhanced reliability.

3 cl, 2 dwg

Description

The invention relates to the field of sealing technology and can be used mainly when creating seals of rotating shafts of various power units (internal combustion engines, gearboxes and transfer cases, gearboxes, etc.), which are subject to high demands on the service life and retention.

A mechanical shaft seal is known, comprising a shaft, a housing, a fixed and movable contacting elements, the fixed element being mounted on the housing, and the movable element mounted on the shaft [1].

A mechanical shaft seal is also known, comprising a shaft, a housing, a fixed and movable contacting elements, the stationary element being mounted on the housing, and the movable element mounted on the shaft with the possibility of movement along the axis of the shaft and loaded in the direction of the stationary element using a spring that rests on the shaft [2].

A disadvantage of the known structures is their relatively low service life associated with the inevitable wear of both contacting elements at the place of their conjugation and, in the first place, a softer element made on the basis of an elastomer (e.g. rubber) or from a composite based on, for example, fluoroplastic (polytetrafluoroethylene) ) This is especially important when working in harsh conditions (large pressure drop between the sealing and the external environment, a large temperature difference between them, a high shaft speed, etc.). This is most important for periodically operating facilities, including those for long-term storage, which require high performance at the time of removal from storage (agricultural seasonal equipment, military equipment, equipment used in emergency situations, etc.).

During long-term storage (season, year or several years), the softer contacting element loses its elasticity and, consequently, its sealing ability. In addition, when stored or parked with prolonged contact and relatively high contact stresses typical for such structures, the softer seal material diffuses into the counterbody material, and at the initial moment of operation, less durable material breaks out in the contact zone, which can immediately lead to compaction in complete unsuitability.

The objective of the invention is to increase the service life and persistence of the mechanical seal.

This problem is solved in that a sleeve is mounted on the shaft with the possibility of movement along its axis, on one side of which a spring rests, and at least one lever abuts on the other side of the sleeve, the axis of which is mounted on the shaft.

The invention is illustrated by drawings. Figure 1 shows the mechanical seal at zero shaft speed (ω = 0), Fig. 2 shows the same seal when the shaft rotates (ω ≠ 0).

The seal (FIGS. 1, 2) separates the two cavities (A and B) and consists of a fixed element (housing 1) with an insert 2 made of hard material (for example, steel) and a movable element 4, which rotates with the shaft 3, having an elastic insert 5 (for example, made of filled polymer) and an elastic sealing ring 6. The movable element 4 is pressed by one end of the coil spring 7 in the direction of contact between the inserts 2 and 5. The other end of the spring 7 rests on the sleeve 8, which, in turn, abuts against the short end of the lever 9, the axis 10 of which is stationary o is fixed on the protrusion 12 of the shaft 3. The long end of the lever 9 can have a load of 11, the lever 9 can freely rotate around the axis 10. The pin 13 serves to fix the element 4 relative to the shaft 3 in the circumferential direction.

One of the cavities, for example A, can be partially filled with liquid lubricant necessary for lubricating the mechanisms and parts installed in this cavity and kinematically connected with the shaft 3. In this case, the cavity B, for example, is the atmosphere. The number of levers 9 (respectively, and protrusions 12 with axes 10) may be more than one.

The mechanical seal operates as follows (figures 1 and 2). In the event that there is no rotation of the shaft 3 (Fig. 1, parking or storage mode), the movable element 4 and the sleeve 8 also do not rotate, the relative movement of the inserts 2 and 5 does not occur. The sleeve 8 abuts against the short end of the lever 9, which, in turn, rests on the body of the shaft 3. Through a cylindrical coil spring 7, the sleeve 8 presses on the element 4 with the minimum necessary force, pressing the insert 5 fixed on it to the mating insert 2 of the housing 1, which creates the minimum sealing effect necessary for a stationary shaft 3. In this case, even with prolonged parking of the mechanism in which the seal is installed, there is no deformation of the sealing elements (inserts 2 and 5) and mutual diffusion of their surface layers. In addition, the minimum deformation of the turns of the spring 7 allows you to save a long time its elastic characteristics.

When you start the mechanism in which the seal is installed, and the beginning of rotation of the shaft 3 (figure 2) together with this shaft rotates the element 4, the protrusion 12 and, accordingly, the lever 9. Due to the friction forces between the element 4 and the spring 7, and also between the short end of the lever and the sleeve 8, the latter also rotates with the frequency of the shaft 3.

Due to the fact that during prolonged parking or during storage, contact pressures at the junction of inserts 2 and 5 are minimal and diffusion of their surface contacting layers does not occur, when straining from the place during the start of the mechanism, no softer material is pulled out of one of the inserts 2 and 5.

When the shaft 3 rotates, centrifugal forces act on the lever 9, and since its mass is distributed unevenly relative to the axis 10, the more massive long end of the lever rotates it so that the short end of this lever presses the sleeve 8 with its shoulder in the direction shown in FIG. 2 arrow. When this spring 7 is compressed, and there is an increase in the force acting on the element 4 with the insert 5 in the direction of contact of the latter with the insert 2 of the housing 1, which leads to an increase in contact pressure at the junction of the inserts 5 and 2 and increase the sealing ability of the seal. This circumstance makes it possible to compensate for the decrease in viscosity and the increase in the penetrating ability of the lubricant located in cavity A, the temperature of which increases during the operation of the mechanism in which the seal is installed.

Moreover, the higher the frequency of rotation of the shaft 3, i.e. the more loaded the mechanism, the higher the temperature of the lubricant, the higher the pressure of its vapor, the lower its viscosity and greater penetrating ability and the greater centrifugal forces act on the lever 9 and, accordingly, the higher the contact pressure in the sealing joint between inserts 2 and 5. This achieves a positive feedback between the sealing ability of the seal and the penetrating power of the lubricant. The relationship between the rotational speed of the shaft and the pressure in the contact surfaces of the inserts 2 and 5 can be adjusted by the ratio of the shoulders of the lever 9, weight and position of the load 11.

Thus, the proposed design of the mechanical seal allows, by reducing contact pressure between the sealing surfaces and eliminating their diffusion during long-term parking or storage, while ensuring high tightness during operation, to increase the performance of the seal and its persistence.

Sources of information:

1. Seals and sealing equipment: Reference book / L.A. Kondakov, A.I. Golubev, V. B. Ovander, and others; under the general. ed. A.I. Golubeva, L.A. Kondakova. - M.: Mechanical Engineering, 1986.- 464 p. - P. 16, Fig. 1.6.

2. Orlov P.I. Design Basics: Reference and methodological manual. In 2 kn. Prince I / Ed. P.N. Uchaeva. - M.: Mechanical Engineering, 1988 .-- 560 p. - S. 486-487, Fig. 644, 655.

Claims (3)

1. A mechanical shaft seal comprising a shaft, a housing, a fixed and movable contacting elements, the stationary element being mounted on the housing, and the movable element mounted on the shaft with the possibility of movement along the axis of the shaft and loading in the direction of the stationary element using a spring that rests on the shaft characterized in that a sleeve is mounted on the shaft with the possibility of movement along its axis, on which one spring rests, and at least one lever abuts on the other side of the sleeve, the axis of which is mounted rammed on the shaft. 2. The mechanical shaft seal according to claim 1, characterized in that the lever abutting against the sleeve is made unequal, with the short shoulder facing the sleeve. 3. The mechanical seal according to claim 2, characterized in that a load is mounted on the long arm of the lever.

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