RU2534194C1 - Magnetic fluid seal of nonmagnetic shaft with adjustable holding capacity ps39 - Google Patents

Abstract

FIELD: machine building.

SUBSTANCE: magnetic fluid seal of a nonmagnetic shaft with adjustable holding capacity includes an annular magnetic system in a nonmagnetic housing, the system consists of magnetic fluid in gaps and annular permanent magnets with similar poles turned to each other, and envelopes the shaft, the annular permanent magnets form gaps between each other and a gap with the housing. The seal is equipped by a mechanism to adjust the gaps between the annular permanent magnets. The mechanism to adjust the gaps between the annular permanent magnets is made as a nut set on the seal housing with the possibility of axial movement by a threaded connection and a bush installed between the nut and the extreme annular permanent magnet of the magnetic system.

EFFECT: provision of magnetic fluid seal of a nonmagnetic shaft with adjustable maximally held pressure difference.

2 cl, 1 dwg

Description

The present invention relates to a sealing technique and can be used to seal non-magnetic shafts operating under differential pressure.

A magnetically liquid seal is known (USSR Author's Certificate No. 1283476, IPC F16J 15/40, 1987) containing an annular permanent magnet, pole attachments with conical protrusions, stacked washers with non-magnetic gaskets between them, while the protrusions of adjacent washers adjoin the conical protrusions of the pole prefixes of opposite polarity.

The disadvantage of this seal is the inability to control the maximum held differential pressure.

A magnetically liquid seal is known (USSR Author's Certificate No. 1308803, IPC F16J 15/43, 1987), adopted as a prototype in which the magnetic system consists of permanent magnets facing each other with the same poles and separated by pole attachments, the surface of the latter facing the shaft is flush with the surfaces of the magnets, while ring grooves are made on the surfaces of the pole attachments and the shaft, opposite the magnets.

The disadvantage of this magneto-liquid seal is the inability to control the maximum held differential pressure.

The technical result achieved by the invention is to create a magneto-liquid seal of a non-magnetic shaft with an adjustable maximum held differential pressure.

The technical result is achieved by the fact that in a magnetically liquid seal of a non-magnetic shaft with adjustable holding capacity, containing a magnetic system in a non-magnetic housing, consisting of ring permanent magnets facing each other by the same poles, covering the shaft, magnetic fluid in the gaps, ring permanent magnets form each other the gaps and the gap with the housing, and the seal is equipped with a mechanism for regulating the size of the gaps between the ring permanent magnets. The mechanism for controlling the magnitude of the gaps between the ring magnets is made in the form of a nut placed on the seal housing with the possibility of axial movement by means of a threaded connection and a sleeve located between the nut and the extreme ring permanent magnet of the magnetic system.

The drawing shows the proposed seal.

Magneto-fluid seal of a non-magnetic shaft with adjustable holding capacity consists of a magnetic system located in a non-magnetic housing 1, consisting of annular permanent magnets 2 facing each other with the same poles. Permanent magnets 2 are separated by air interpolar gaps 3 and installed in the housing 1 on a sliding fit, the outer cylindrical surfaces of the permanent magnets 2 form an annular gap with the housing 4. The magnetic system covers the non-magnetic shaft 5 and forms a working gap 6. With it, the working gap 6 and magnetic fluid 7 is introduced into the annular gap 4. A thread 8 is made on the housing 1, on which a nut 9 is placed. A sleeve 10 made of non-magnetic material is located between the nut 9 and the extreme magnet.

Sealing works as follows. Permanent magnets 2 in the seal serve as a source of magnetic field. Magnetic fluxes exit from the poles of neighboring magnets into the air-to-pole gap 3 separating them and are divided into two parts. One part goes to the working gap 6 between the magnets and the shaft, crosses it, is divided into two parts, again crosses the working gap 6 and, passing through the adjacent air-gap interpolar gaps 3, enters the opposite poles of the magnets. The second part of the magnetic flux along the interpolar gap 3 goes to the housing 1, crosses the annular gap 4, is divided into two parts, again intersects the annular gap 4, passes through the adjacent interpolar gaps 3 and enters the opposite poles of the magnets. In the annular gap 4 and the working gap 6 opposite the air interpolar gaps 3 creates a magnetic field of high tension, where the magnetic fluid 7 is drawn and forms a sealed annular tube with high internal pressure. Each magneto-liquid plug is capable of perceiving a certain pressure drop, depending on the maximum field strength in the working gap, and is found by the formula

$$\Delta p={\mu }_0{\displaystyle \underset{Nm\mathrm{and}n}{\overset{Nm\mathrm{but}x}{\int }}MdN\text{(one)}}$$

where µ ₀ is the magnetic constant, M is the magnetization of the magnetic fluid, H _max is the maximum magnetic field strength in the working gap, H _min is the minimum magnetic field in the working gap. The pressure differential held by the seal is determined by the sum of the drops of all the magneto-fluid plugs located in the working gap 6. The magneto-fluid plugs in the annular gap 4 prevent leakage of the medium being sealed between the magnets 2 and the seal housing 1. The magnetic flux coming from neighboring permanent magnets into the air-to-pole gap 3 , is divided in such a way that provides almost the same field strength in the working gap 6 and in the annular gap 4. Therefore, the total holding capacity of the magneto-liquid the robots in the working gap 6 is almost equal to the total holding capacity of the magneto-liquid plugs in the annular gap 4. The maximum magnetic field strength in the annular gap 4 and in the working gap 6 depends on the distance between adjacent magnets or on the size of the air interpolar gaps 3. The smaller the interpolar gaps 3, the higher the maximum magnetic field strength in the annular gap 4 and in the working gap 6, the higher the holding capacity of each magnetically liquid tube. The larger the interpolar clearances 3, the lower the maximum magnetic field strength in the annular gap 4 and in the working gap 6, the lower the holding capacity of each magnetically liquid tube. Those. when the distance between the permanent magnets changes, the holding capacity of the seal changes.

Permanent magnets facing each other with the same poles repel each other. In the seal housing, the magnets are locked from the divergence by a nut 9. The force from the magnets is absorbed by the nut 9 through the sleeve 10. When tightening the nut 9 on the housing 1, the values of the inter-pole gaps 3 decrease and the holding capacity of the seal increases, when the nut 9 is unscrewed by the repulsive forces, the magnets diverge, the polar the gaps 3 increase, the holding capacity of the seal is reduced. Thus, twisting or unscrewing the nut 9, change the maximum holding capacity of the seal, adjusting to a given maximum held pressure drop. This seal, in addition to the sealing function, is capable of performing the function of a safety valve in systems with increased internal pressure, preventing the housing of the device to be sealed from destruction under uncontrolled fluctuations in internal pressure. The magneto-liquid seal has the property of self-healing, i.e. under certain circumstances, restore its original holding ability, which allows it to be used for multiple safety breakthroughs.

Thus, the proposed magneto-liquid seal allows not only to ensure the tightness of the rotation input of the non-magnetic shaft, but also to use it as a safety valve of closed systems, expanding the functionality of the seals.

Claims (2)

1. Magneto-fluid seal of a non-magnetic shaft with adjustable holding capacity, containing a magnetic system in a non-magnetic housing, consisting of ring permanent magnets facing each other by the same poles, covering the shaft, magnetic fluid in the gaps, characterized in that the ring permanent magnets form gaps between them and a gap with the housing, and the seal is equipped with a mechanism for regulating the size of the gaps between the ring permanent magnets. 2. Magneto-fluid seal of a non-magnetic shaft with adjustable holding capacity according to claim 1, characterized in that the mechanism for adjusting the size of the gaps between the ring magnets is made in the form of a nut placed on the seal housing with the possibility of axial movement by means of a threaded connection and a sleeve located between the nut and the extreme ring permanent magnet of the magnetic system.