JPH0416029Y2 - - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The present invention is used in food transport pumps, stirrers, etc., in which a stationary sealing ring and a rotating sealing ring slide on their sealing end faces, and the rotating sealing ring is This invention relates to an outside mechanical seal that is biased toward the sealed end surface.

[Conventional technology]

As shown in FIG. 4, the outside mechanical seal has a stationary sealing ring 103 fixed to the passage through the rotating shaft 102 of the device 101, and is mounted on the rotating shaft 102 outside the device 101 so as to be movable only in the axial direction. The rotary sealing ring 104 is connected to the annular sealing end surface 1
At 04a, the fluid side X is sealed from the atmosphere side Y by slidingly contacting the sealing end surface 103a of the stationary sealing ring 103. Said rotary sealing ring 104
is urged toward the stationary sealing ring 103 by a compression spring 106 so that the sealing end surface 104a comes into sliding contact with the sealing end surface 103a of the stationary sealing ring 103 with a predetermined pressing force. And the rotating shaft 10
2. In order to prevent sealing fluid from leaking along the outer peripheral surface, an O-ring 107 is interposed between the rotary seal ring 104 and the rotary shaft 102. Conventionally, this O-ring 107 is It was supported by a member such as an O-ring support ring 108 fixed to the shaft 102 to prevent it from being dislodged from the installed position due to the pressure of the sealing fluid.

[Problem that the invention attempts to solve]

However, the pressure of the sealed fluid sometimes becomes abnormally high due to various factors, and in this case, the degree of sealing between the sealed side X and the atmospheric side Y is kept high, as in the conventional example shown in Figure 4. If this is done, the thrust force applied to the sealed end surfaces 103a and 104a will increase, causing a problem that the rotational load will increase. Furthermore, while the stationary sealing ring 103 is generally made of a hard material such as ceramic, the rotating sealing ring 103 is made of a material with high hardness such as ceramic.
4 is made of a relatively brittle material such as carbon, and when the above-mentioned increased thrust is applied, the rotary sealing ring 104 may be damaged or the sealing end face may be seized. Further, when the device itself to which the mechanical seal is attached is a presswork product, the pressure resistance is poor, and the device itself may be damaged due to an increase in the pressure inside the device. When such troubles occur, the sealed end surface becomes unusable due to erosion caused by sudden fluid leakage or encroachment of dirt, etc.
There were problems in that the mechanical seals were damaged and the equipment to which the mechanical seals were installed became unusable.

The present invention was developed in view of the above-mentioned problems, and is designed to prevent mechanical seals from being damaged or the device itself becoming unusable even when the pressure of the sealing fluid becomes abnormally high. Another object of the present invention is to provide an outside mechanical seal that can safely protect the device itself equipped with the outside mechanical seal.

[Means for solving problems]

In order to achieve the above object, the present invention forms a shaft packing groove on the inner peripheral surface of the rotary sealing ring extending from the back of the sealing end surface to the other end side, and in this shaft packing groove, the rotary sealing ring and the rotating shaft are connected. A shaft gasket is installed to create an airtight seal between the rotary sealing ring and the rotary shaft, and when the shaft gasket receives abnormal pressure from the sealing fluid, the shaft gasket is pressed, and the shaft gasket moves by the amount that moves to the position where it releases the airtightness between the rotating sealing ring and the rotating shaft. It is characterized in that a shaft packing spring that can be bent in the axial direction is provided via an annular support member.

[Effect]

With the above arrangement, when the sealing fluid reaches an abnormal pressure, the O-ring is pressed by this pressure and moves in the axial direction while bending the spring, and the airtightness between the rotary sealing ring and the rotary shaft is lost. Therefore, the abnormal pressure escapes to the atmosphere along the outer circumferential surface of the rotary shaft, and does not place an excessive burden on the outside mechanical seal itself or the device in which it is installed.

〔Example〕

Hereinafter, the present invention will be explained based on illustrated embodiments.

In FIGS. 1 and 2, 1 is a housing of the device, 2 is a rotating shaft inserted into the housing 1, and the inside of the housing 1 is the fluid side X, and the outside is the atmosphere side Y.

A recess 1a is formed in the housing 1 at the opening end through which the rotary shaft 2 is inserted, and a stationary sealing ring 3 through which the rotary shaft 2 passes is fitted into the recess 1a. This stationary sealing ring 3 is made of ceramics, for example, and its outer circumferential surface is in close contact with the inner circumferential surface of the recess 1a. A cover 4 is attached to the surface of the housing 1 and covers the outer peripheral edge of the end face of the stationary sealing ring 3.

A rotary sealing ring 5 is attached to the rotary shaft 2 on the atmospheric side Y. This rotary sealing ring 5 is connected to the rotary shaft 2
It is movable in the axial direction and integrally mounted in the rotational direction. Further, this rotary sealing ring 5 is formed with an annular sealed end face 5a having an inner diameter d ₁ and an outer diameter d ₂ , and this sealed end face 5 a is connected to the sealed end face 3 a of the stationary sealing ring 3 exposed to the atmosphere side. Sliding contact.
Furthermore, an O-ring groove 5c is formed in the inner circumferential surface of the rotary sealing ring 5 from further behind the rotary shaft holding portion 5b behind the sealing end surface 5a toward the other end side. This O-ring groove 5c is formed on the sealing end surface 5.
a balance inner diameter part 5ca with an inner diameter d ₀ larger than the inner diameter d ₁ of a, and an enlarged diameter part 5 that is formed continuously with this balance inner diameter part 5ca and opens at the other end side of the rotary sealing ring 5.
Consists of cb.

A spring holder 6 is fixed to the rotating shaft 2 in front of the rotary sealing ring 5 .

Annular retainers 7 and 8 are attached to the rotating sealing ring 5 and the spring holder 6 at opposing portions, and a compression spring 9 surrounding the rotating shaft 2 is stretched between the retainers 7 and 8. has been done. Since this compression spring 9 rotates together with the rotating shaft 2, both ends thereof are engaged with the retainers 7 and 8, respectively, so that it does not come off from the retainers 7 and 8 during this rotation. Compression spring 9 provided in this way
As a result, the rotary sealing ring 5 is urged toward the stationary sealing ring 3, and a predetermined pressing force is applied between the sealing end surface 5a and the sealing end surface 3a of the stationary sealing ring 3 that slides thereon.

In the balance inner diameter portion 5ca of the O-ring groove 5c, an O-ring ₁ is provided at a predetermined position having a balance inner diameter d1 to make the space between the rotary sealing ring 5 and the rotary shaft 2 airtight.
0 is fitted so as to be movable in the axial direction.

Reference numeral 11 denotes an annular support member that supports the O-ring 10 from the atmospheric side Y direction, and an O-ring compression spring 12 is provided between the end face of this support member 11 and the spring holder 6. As is clear from the figure, this O-ring compression spring 12 surrounds the rotating shaft 2 inside the compression spring 9. Further, this O-ring compression spring 12 is provided in a state in which the O-ring 10 is not urged toward the stationary sealing ring 3 side in a normal state in which the O-ring 10 is in a predetermined position, and therefore, the O-ring compression spring 12 is provided in a state in which the O-ring 10 is not biased toward the stationary sealing ring 3 side. A pressing machine is not applied to the sliding surface of the sealed end surface 3a. Furthermore, this O-ring compression spring 12 is provided between the stationary sealing ring 3 and the rotating shaft 2, and between the rotating sealing ring 5.
When the sealing fluid that has reached the O-ring groove 5c via the rotating shaft holding portion 5b and the rotating shaft 2 reaches an abnormal pressure pfm, it is designed to be compressed by a set deflection amount _δ1 . That is, when the sealing fluid reaches an abnormal pressure pfm, the O-ring 10 is pressed by this abnormal pressure pf ₁ and moves by a stroke δ ₁ toward the other end of the rotating sealing ring 5, expanding its diameter as shown in FIG. It reaches the portion 5cb and forms a gap C between it and the inner circumferential surface of the enlarged diameter portion 5cb.

As is clear from this, the balance inner diameter portion 5ca and the enlarged diameter portion 5 forming the O-ring groove 5c are
The dimension of cb is that the O-ring 10 is the balance inner diameter part 5.
It is designed so that if it slides for a stroke δ ₁ from the predetermined position of ca, it will reach the enlarged diameter part 5cb, and a gap will be created between the inner peripheral surface of this enlarged diameter part 5cb and the O-ring 10.

Next, the operation of the outside mechanical seal configured as described above will be explained.

In FIG. 1, a thrust force F ₁ is applied to the sealed end surface 5a and the sealed end surface 3a that is in sliding contact with the sealed end surface 5a.
is expressed as F ₁ =π/4(d ₂ ² −d ₁ ² )·k·Pf·Ps ₁ , where pf is the pressure of the sealing fluid and Ps ₁ is the thrust force by the compression spring 9. Here, k is ^the balance ratio, k= _d02 ^{- d12} / _{d22 -} ^d12 , so the thrust _{F1 is F1} ⁼ π/4( _d02 ^- _d12 )・Pf＋Ps ₁ . Therefore, in a state where the O-ring 10 is airtight between the rotary sealing ring 5 and the rotary shaft 2, that is, in a state in which the O-ring 10 is in the balance inner diameter portion 5ca, when the pressure of the sealing fluid increases, the thrust force F ₁ also increases in proportion to it. increase

On the other hand, the thrust force F ₂ applied to the O-ring 10 by the sealing fluid is F ₂ =π/4(d ₀ ² −d ² )·Pf, where d is the diameter of the rotating shaft 2, and therefore The thrust force F _2n when the pressure reaches a predetermined abnormal pressure Pfm is F _2n =π/4(d ₀ ² −d ² )Pfm.

Then, at least before the amount of deflection δ of the O-ring compression spring 12 reaches the set amount of deflection δ ₁ , the O-ring compression spring 12 is δ×G
(G is a spring constant) is designed so that the biasing force Ps ₂ is Ps ₂ <F ₂ m with respect to the above-mentioned thrust F ₂ m. Therefore, when the pressure of the sealing fluid becomes abnormal pressure Pfm, the O-ring 10 and can be deflected by at least δ ₁ .

Therefore, when abnormal pressure Pfm occurs in the sealing fluid, the O-ring 10 moves by a stroke δ ₁ toward the other end of the rotating sealing ring 5, and the expanded diameter portion 5 of the O-ring groove 5c moves.
Reach cb. As a result, as described above, a gap C as shown in FIG. 2 is created between the O-ring 10 and the inner peripheral surface of the O-ring groove 5c, and pressure escapes from this gap C.

By escaping the pressure in this manner, the thrust F1 at the sealed end faces 3a, 5a does not exceed a predetermined thrust.

When the pressure of the sealing fluid drops from abnormal pressure to normal pressure, the O-ring 10 is pushed back into the balance inner diameter portion 5ca of the O-ring groove 5c by the biasing force of the O-ring compression spring 12, and normal operation is performed again. .

As described above, according to the outside mechanical seal, when the pressure of the sealing fluid becomes abnormal, the O-ring 10 moves to release the pressure, thereby preventing the thrust force applied to the sealing end face from increasing.

FIG. 3 shows another embodiment of the present invention,
In this embodiment, a stepped portion 22a is provided on the rotating shaft 22,
The support member 31 of the O-ring 10 is engaged with the stepped portion 22a during normal operation when the O-ring 10 is in a predetermined position. If you do this,
It is possible to reliably prevent the thrust by the O-ring compression spring 12 from directly pressing the end face, and is therefore suitable when the normal operating pressure of the sealing fluid is high. However, in FIG. 3, the same parts as in FIGS. 1 and 2 are given the same reference numerals.

It should be noted that the present invention is of course not limited to the above-mentioned embodiments, and for example, in the embodiments, a case is explained in which an O-ring is used as the shaft packing.
A shaft packing having other cross-sectional shapes such as a square ring or an X-ring may also be used. In addition, both the elastic urging means for urging the rotary sealing ring toward the sealing end surface side and the spring for the shaft packing are large-diameter monocoil types that surround the rotating shaft, but one or both of them can be replaced with a small-diameter compression spring. It may also be a multi-spring type in which a plurality of springs are arranged on the circumference. Also,
The shape of the shaft packing groove is such that if the shaft packing moves by the amount of deflection of the shaft packing spring when the pressure of the sealing fluid reaches a predetermined abnormal pressure, the shaft packing will move between the rotating seal ring and the rotating shaft. Any shape is acceptable as long as it makes it impossible to maintain airtightness.

[Effect of idea]

As is clear from the above explanation, the outside mechanical seal according to the present invention prevents abnormal pressure from being applied to the sealing end face, which prevents damage to the rotating sealing ring, etc., and prevents sealing between the rotating sealing ring and the stationary sealing ring. The end face will not be damaged by seizure or erosion. Furthermore, there will be no damage to the main body of the device equipped with this outside mechanical seal.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing one embodiment of the outside mechanical seal according to the present invention, Fig. 2 is a partially enlarged sectional view showing the same state during operation, and Fig. 3 is a partially enlarged sectional view of another embodiment. FIG. 4 is a sectional view of a conventional example. 2... Rotating shaft, 3... Stationary sealing ring, 5... Rotating sealing ring, 9... Compression spring, 10... O-ring (shaft packing), 12... Compression spring for O-ring (spring for shaft packing) .

Claims (1)

[Claims for Utility Model Registration] An outside mechanical seal in which a stationary sealing ring through which a rotating shaft passes and a rotating sealing ring are in sliding contact with each other at an annular sealing end surface, and the rotating sealing ring is elastically biased toward the stationary sealing ring, A shaft packing groove is formed in the inner circumferential surface of the rotary sealing ring from the back of the sealing end surface to the other end side, and a shaft packing groove is installed in the shaft packing groove to make the space between the rotary sealing ring and the rotating shaft airtight, For a shaft packing that can be bent in the axial direction by an amount that presses the shaft packing when receiving abnormal pressure of the sealing fluid and moves the shaft packing to a position where the airtightness between the rotating seal ring and the rotating shaft is released. An outside mechanical seal characterized in that a spring is provided via an annular support member.