RU2363873C1 - Ovander's floating seal - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: invention relates to sealing appliances and can be used for water proofing of shafts, rods and cylinders in hydro pneumatic lubrication systems, steam machines and internal combustion engines. Proposed seal comprises sealing element made from elastic or rigid-elastic material and arranged, with a clearance with respect to seat bottom in one of the sealed joint part (piston, rod box or shaft cover) and with interference fit with respect to other part of sealed joint (cylinder, rod or shaft). Proposed seal represents a plate spring made up of plates with their height exceeding the width of seat groove.

EFFECT: improved tightness at low pressure difference and its reversal as well as at sliding direction reversal.

Description

The invention relates to a sealing technique and can be used to seal moving joints of shafts, rods and cylinders in hydropneumatic lubrication systems, steam engines and internal combustion engines.

The well-known "Sealing devices for radial joints with reciprocating motion" GOST 23823-79, containing an elastic seal made of highly elastic material - rubber, installed in the landing groove of one of the parts of the hermetic joint (piston or stem axle box) with interference on the bottom of this groove and on the sliding on it the surface of another part of the hermetic joint (cylinder or rod). Their disadvantages are low permissible pressure drops of the pressurized media (in the absence of additional protective rings made of more rigid materials), high friction forces, low permissible sliding speeds, often insufficient working life and high sensitivity to radial displacements of the sealed parts, which weaken the tightness of the seals. These disadvantages are associated with the need to use in this design a large compression of the sealant over its cross section, which is allowed only by highly elastic materials having low strength and wear resistance, as well as a high coefficient of friction.

Known for the prototype are floating seals containing a gasket of elastic material, placed with gaps along the bottom of the landing groove and its ends in one of the parts of the hermetic joint (piston, rod end or shaft cover) and an interference fit on the other part of the hermetic joint (cylinder, rod or shaft). Due to the gap along the bottom of the groove, the sealant can radially shift (float) inside the groove following the radial displacements of the sliding part. The sealant is made of rubber (see the book “SEALS” Edited by V.K.Zhitomirsky, M., Mechanical Engineering 1964, p. 180, Fig. 9) or metal (see the book “Theory of a Piston Ring” B.Ya. Gunzburg M., Mechanical Engineering 1979, p. 246, fig. 140). In this design, due to the transition from compression of the annular seal in its radial cross-section to compression or extension in diameter, it became possible to use more rigid materials for it - plastics and metals with increased strength, wear resistance and antifriction. Therefore, such seals are operational at high sliding speeds and pressure drops, have an increased service life and minimal friction forces and heating from these forces. The presence of a gap between the seal and the bottom of the groove makes the seal insensitive to radial displacements of the parts being sealed. Avoiding compression of the seal over the cross section to its compression along the diameter reduces the friction forces even when making the seal from rubber (see the above book “SEALS” p. 180).

The disadvantages of the prototype are increased leaks that occur at low pressure drops of the pressurized medium, with reversal of the direction of sliding of the sealant and with reverse pressure drop. These shortcomings are caused by the lack in the seal of its own pressing forces to the ends of the landing groove. The forces of pressing the seal to the ends of the grooves occur only under the influence of the friction forces or forces from the pressure drop on the seal. If these forces are small or reverse, the seal loses tight contact with the end of the groove and the seal gives increased leakage.

The purpose of the invention is the elimination of leaks in the seal at small pressure drops, their reverses and reverses the direction of sliding of the seal.

This goal is achieved by the fact that in a floating seal containing a seal made of elastic material, placed with a gap along the bottom of the landing groove in one of the parts of the hermetic joint (piston, rod end or shaft cover) and an interference fit on the other part of the hermetic joint (cylinder, rod or shaft) according to the invention, the seal is made in the form of a disk spring, the height of which in the free state is greater than the width of the landing groove.

The claimed design through the use of a seal in the form of a Belleville spring having normalized interference on the surface of the sliding part of the hermetic joint (cylinder, rod or shaft) and along the ends of the landing groove in another part (piston, rod end or shaft cover), ensures their tight connection at all operating conditions, including low pressure drops and their reverses, as well as reversals of the sliding direction, as keeps the seal tight contact with at least one of the ends of the landing groove.

The drawing shows the design of a floating seal with a seal in the form of a Belleville spring 1, consisting of two plates. The number of plates can be assigned depending on the dimensions, friction forces and reliability of the seal from one to ten. The spring is installed in the landing groove 2 of the piston 3, the stem axle box or the shaft cover with a gap 4 along the bottom 5 of this groove and an interference fit 6 along the cylinder 6 sliding along it, the rod or shaft. The height S of the spring in the free state, indicated by the dotted line in the drawing, is greater than the width L of the landing groove, therefore, in the landing groove it is in a compressed state. The elastic material of the Belleville spring can be both highly elastic rubber and hard plastics and metals. In the case of using rigid materials that do not withstand mounting deformations when installing springs in one-piece grooves, the landing groove can be detachable with a removable part 7 forming the end of the groove.

Sealing works as follows. Due to the elastic forces, the belleville spring compressed in the axial direction is hermetically adjacent to the ends of the landing groove, and its tightness along the cylinder, rod or shaft ensures tight contact with these parts as well. Due to this, both the sealed parts are tightly interconnected. Under the influence of high pressure drops, one of the ends of the spring can be squeezed from the end of the groove, however, its second end will maintain a tight connection between the spring and the part where the groove is located, and the pressure of the medium to be sealed into the gap at the bottom of the groove will additionally compress the spring in its contact areas, ensuring self-sealing effect. When materials with low friction coefficients are used for the spring, the small effect of the friction forces at its ends on the contact pressures along the sliding part is ensured; therefore, the radial displacements of the parts to be sealed, leading to the spring ends slipping along the groove ends, do not reduce the seal tightness. In the case of a seal operating on a rotating shaft, its mechanism of action differs only in the ability to rotate the seal in the groove when it rotates together with the shaft. However, such a rotation does not reduce the tightness and resource of the seal, if the ends of the grooves have the required processing quality.

The technical result of the proposed seal compared to the base seal, for which the prototype is adopted, is to maintain high tightness in all operating modes, including low pressure drops and their reverses, as well as sliding direction reversals.

Claims (1)

A floating seal containing a seal made of elastic material placed with a gap along the bottom of the landing groove and an interference fit on one of its parts (a piston, rod end or shaft cover) and an interference fit on the other hydraulic joint part sliding along it (cylinder, rod or shaft ), characterized in that the seal is made in the form of a disk spring of plates.

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