JPH0587715B2 - - Google Patents

Description

Detailed Description of the Invention Technical Field The present invention relates to a seal structure used in a part where a piston or piston rod operating under the action of fluid pressure penetrates the wall of a cylinder, and a seal member incorporated in the seal structure. Pertains to. The present invention is particularly useful in seal structures that are alternately exposed to high and low fluid pressures.

BACKGROUND OF THE INVENTION Good fluid seals are difficult to obtain when the seal is exposed to alternating high and low pressures. In order to solve this problem, US Pat. No. 3,909,016 proposes a seal structure that combines a pressurizing force generating member such as an O-ring and a seal member as a seal structure used for two mechanical parts that move relative to each other. has been done. In this seal structure, when exposed to low fluid pressure, the seal member comes into line contact with a moving mechanical part such as a piston at an annular corner formed on its inner periphery, thereby causing frictional force. When the seal structure is exposed to high fluid pressure, the position where the compressive force is applied by the O-ring moves in the axial direction, thereby preventing fluid leakage in the low-pressure system. The member deforms torsionally about the annular center of the ring and contacts the mechanical component at an annular surface adjacent to the corner.

U.S. Pat. No. 3,942,806 discloses that an annular seal member has a cylindrical recess extending axially inward from one end and a conical recess extending axially inward from the other end on the inner circumference of the annular seal member. A seal structure is described in which an annular corner is formed at the intersection of the annular seal member and an O-ring-shaped pressure generating member is fitted around the annular seal member. In this case, too, when low fluid pressure is applied, the sharp corners of the sealing member are in contact with the moving mechanical parts, but when high fluid pressure is applied, the annular sealing member along with the pressure generating member is aligned with the axis. As it is compressed in the direction, it expands in the radial direction, and the corner portion in contact with the moving machine part collapses, so that the annular surface is pressed against the machine part.

U.S. Patent No. 4,449,718 includes U.S. Patent No. 3,942,806
As an example of a modification of the seal structure described in the above publication, a seal structure is described in which chamfers are provided at the corners to facilitate mounting of packing rings on moving parts such as pistons.

U.S. Pat. No. 3,663,024 discloses that an annular surface facing a moving mechanical component contacts the surface of the mechanical component at a narrow annular surface when exposed to a low fluid pressure; In some cases, a seal structure is described in which a seal ring is deformed by a pressing force generating member such as an O-ring and has a sled-like cross section that contacts the surface of the mechanical component with a wider annular surface in combination with the pressing force generating member. has been done.

DISCLOSURE OF THE INVENTION One object of the present invention is to provide improved fluid seal structures and fluid seal members for use in mechanical components having moving parts.

Another object of the present invention is that the sealing member has a line contact portion when a low fluid pressure is applied, and in addition to the line contact portion when a high fluid pressure is applied. It is an object of the present invention to provide a fluid seal structure and a fluid seal member configured to have another contact area at a position displaced from this.

Yet another object of the invention is to provide a shallow recess between the two contact parts which retains fluid when the seal member is pressed against a moving mechanical component under conditions of high fluid pressure. It is an object of the present invention to provide a fluid seal structure and a fluid seal member that are configured to reduce friction between the seal member and a moving component and thereby reduce wear of the seal member.

Yet another object of the present invention is to provide a seal member constructed such that the squares of conventional seal members are reduced, thereby reducing stress and damage due to stress concentrations. It is.

Yet another object of the present invention is to provide a sealing member with an inclined surface in contact with the pressure member so as to increase the degree of compression of the high-pressure contact area under conditions of high fluid pressure. It is to establish.

In order to explain the present invention, a seal structure and a seal member in a structure in which a housing is disposed around a piston rod will be described below. The seal structure is built into an annular groove provided in the housing and includes a seal member and a pressure member. The sealing member has four circumferentially extending sides and two areas for contacting the piston rod.

The seal member is an annular toroid member,
In the following description, for convenience, the annular sealing member will be described as having a shape seen in a cross section along a plane including the central axis of the annular ring. In that case, therefore, a point contact is actually a line contact along the circumferential direction, and a line contact is actually a surface contact along the circumferential direction.

The first side is a substantially S-curved side (in cross section) facing a high pressure port in the base of the housing. The S-shaped curve extends in a direction along the axis of the piston rod and in a radial direction perpendicular to this, with an upper part (outer part of the ring) convex radially inward and a lower part (outer part of the ring) concave radially inward. (inner part of the ring).

The second side faces the piston rod and has a shallow recess extending over substantially its entire length. The intersection of the first and second sides defines a point of contact for the piston rod.

The second side terminates in an arcuate portion that forms a second contact area with the piston rod under conditions of high fluid pressure, the arcuate portion extending upwardly and toward the low pressure side. There is. When the seal structure is exposed to high fluid pressure, the pressurizing member moves toward the low pressure side, thereby increasing the pressurizing force, causing the sealing member to rotate around the point contact,
A portion of the arcuate portion is pressed against the piston rod. A shallow cavity extending over substantially the entire length of the second side surface is formed between the sealing member and the piston rod between the point contact portion and the contact area formed by the circular arc portion caused by the above-mentioned rotation. The liquid trapped in the air acts as a lubricant, extending the life of the seal structure. The contact area of the arcuate portion should be increased in area as necessary to achieve a complete seal when the sealing structure is exposed to high fluid pressures, but should not be increased unnecessarily. If the area of the contact area is increased more than necessary, the frictional resistance of the seal structure will become too high.

The third side surface is substantially straight and extends radially from the arcuate portion of the second side surface toward the pressure member. Under conditions of low fluid pressure, the third side forms a V-shaped cavity with the low-pressure radial wall of the annular groove, and the arcuate portion of the third side forms a V-shaped cavity. Adjacent portions are in contact with said radial wall. The V-shaped cavity facilitates pivoting of the seal member in response to increases and decreases in fluid pressure. When the sealing structure is exposed to high fluid pressure, the sealing member pivots about the point contact and the entire third side is pressed against the radial wall of the annular groove.

A fourth side of the seal member extends between the radially outer ends of the first side and the third side for positioning the pressure member under conditions of low fluid pressure. It has an inclined portion that is inclined slightly away from the center axis of the piston rod as it goes from the high pressure side to the low pressure side. The slope may be a flat surface or a shallow recessed surface. When the fluid pressure increases, the pressure member is pushed and moved toward the low pressure side, thereby riding on the above-mentioned inclined surface and pushing down the low pressure side end of the sealing member downward (radially inward), The arcuate portion is pressed against the piston to exert a high pressure force on the contact area to achieve a good fluid seal at the contact area. This pressing by the inclined portion is particularly effective when the pressing member is an O-ring.

The sloping portion begins approximately 1/3 to 1/2 along the fourth side from the end that intersects the first side. Preferably, the ramp is at an angle of about 5 DEG to 10 DEG with respect to the central axis of the piston rod under conditions of low fluid pressure.

It is important that the sealing member is able to pivot about said point contact. This allows the arcuate portion to contact the piston rod under high fluid pressure conditions, and the third side of the seal member to contact the radial wall of the annular groove to form a seal. can do. Conversely, under conditions of low fluid pressure, the seal member pivots upwardly and away from the piston rod around the point contact, and the third side surface pivots upwardly away from the piston rod. and moves in a direction away from the radial wall surface of the annular groove. The pivot angle of this pivot is approximately 5° to
Preferably it is 10°, more preferably about 7° to 9°. When the contact between the second sealing part, i.e. the arcuate part and the piston rod is released,
The frictional resistance of the seal structure is reduced, and the frictional wear of each component is greatly reduced.

The sealing member and pressure member may be formed from fluoroplastic materials such as polytetrafluoroethylene, composites thereof, or other high modulus plastic materials used in high pressure systems. The pressure member typically may be an elastomeric ring, such as an O-ring.

In the above, the present invention has been described in the case where the seal structure is incorporated into the stationary part of the machine.
It should be understood that the seal structure according to the invention may be incorporated in a similar manner on the side of moving or rotating parts of a machine. Further, the present invention may be applied to butterfly valves, ball valves, gate valves, etc.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The same reference numerals indicate the same members in the accompanying drawings. FIG. 1 shows the seal structure under conditions of low fluid pressure. The structure includes an annular groove 3 and a rod 7 provided in a stationary member 5 (only partially shown). The annular groove 3 is formed by an axially extending wall surface 13 and radially extending wall surfaces 9 and 11 connected to both ends thereof.

A pressure member shown as an O-ring 15 in the figure is disposed within the groove 3, and this pressure member is in the state shown in FIG. 1 when low fluid pressure is applied from the left side in the figure. It is in contact with the wall surface 13 and is arranged around an annular sealing member 17. In the illustrated embodiment, seal member 17 is a ring formed of polytetrafluoroethylene or polytetrafluoroethylene composite material. An annular passage 19 is formed between the stationary member 5 and the rod 7. As indicated by the symbols P+ and P-, the high pressure side is on the left side of the stationary member 5 in the view, and the low pressure side is on the right side of the stationary member 5 in the view. The state in which high fluid pressure is applied or the state in which low fluid pressure is applied refers to a state in which the fluid pressure acting on the high pressure side is high or low, respectively.

The sealing member 17 of the present invention has a first side surface 21 that faces the wall surface 9 and is a toroidal surface over most of the part, and this surface has an S shape when viewed in cross section.
It is a surface with a curved shape. The upper part of the side surface 21 is a radially inwardly convex part 21a, and the lower part thereof is a radially inwardly concave part 21b. The lower end of the concave portion 21b forms a steep angle, approximately 90°, with respect to the plane of the piston rod, and makes point contact (actually line contact) with the piston rod 7 at a point 23. The second side 25 facing the piston rod 7 begins at the point contact 23 and extends axially over substantially the entire length of the side 25 and has a shallow recess 27. The end of shallow recess 27 closest to wall 11 is rounded starting from point 29 to form an arcuate portion 31 curved through about 90 degrees or more. The side surface 25 (including the arcuate portion 31) also actually forms a toroidal surface.

The third side 33 of the sealing member 17 is substantially straight in cross section and faces the wall surface 11 .

The fourth side 35 is the side furthest from the piston rod 7. This side surface has an inclined portion that extends slightly in diameter toward the low pressure side depending on the axial position relative to the point contact portion 23 . This slope may be a linear slope.

FIG. 1 shows the seal structure of the present invention under conditions of low fluid pressure. The only contact between seal member 17 and rod 7 is point contact 23. The joint between the side surface 33 and the arcuate portion 31 is the wall surface 1
I am in contact with 1. The pressure member 15 is in contact with the sealing member in a substantially central portion of the side surface 35, i.e. in an axial position corresponding to the point contact portion 23, which is in contact with the axial wall surface 13. This provides a certain degree of compressive force to the seal member 17.

FIG. 2 shows the seal structure of the present invention under conditions of high fluid pressure. In this state, the pressure member 15 and the seal member 17 are pressed to the right in the figure and are pressed against the wall surface 11. The sealing member 17 is pressed radially inward by the pressure member 15, so that the point 29 of the arcuate portion 31
is in sealing contact with the piston rod 7 and a certain amount of fluid is trapped within the recess 27. When the high fluid pressure is released, the pressure member 15 moves to the left in the figure and the seal member 17 is point contact part 2
3, thereby releasing the seal at point 29, and the side surface 33 pivots around the lower end arcuate portion 3.
It contacts the wall surface 11 only at the joint with the wall surface 11. This returns the entire seal structure to the relationship shown in FIG. 1 again.

FIG. 3 shows a seal member 50 that is a modification of the seal member 17 in the embodiment shown in FIGS. 1 and 2. In FIG. Seal member 50 has a generally arcuate surface 52 that is curved at a position corresponding to the axial position of point contact point 56 along dashed line 54 under conditions of low fluid pressure. It is shaped so that it comes into contact with the pressure member. In all other respects, seal member 50 is similar to seal member 17 described above.

For larger cross-sectional area seals, portion 58 of seal member 50 may be flat rather than curved as shown in FIG.

The embodiments of the invention described above are merely exemplary. It will be apparent to those skilled in the art that various changes, modifications, and substitutions may be made within the scope of the invention.

[Brief explanation of drawings]

FIG. 1 is a partial cross-sectional view showing a sealing structure of the present invention including a sealing member and a pressure member disposed in an annular groove provided on the side of a stationary part of a machine under conditions of low fluid pressure; The relationship of the sealing member and the pressure member to the piston rod is shown. FIG. 2 is a partial sectional view showing the seal structure shown in FIG. 1 under conditions of high fluid pressure. FIG. 3 is a sectional view showing another embodiment of the invention regarding a seal member.

Claims (1)

[Claims] 1. An annular seal member used in a seal structure of a fluid pressure system, having first to fourth side surfaces extending in the circumferential direction, and having a cross section taken by a plane including the center axis of the ring. As seen, the first side surface has an S-shaped curve including a radially inwardly convex radially outer portion and a radially inwardly concave radially inner portion; and the second side surface has an S-shaped curve. a recess extending substantially in the axial direction from one end connected to the inner end of the concave portion of the first side surface and extending over substantially the entire length; a convex arcuate portion formed at the other end, the third side surface extending substantially linearly and radially from the arcuate portion, and the fourth side surface extending radially from the arcuate portion; extending axially between the radially outer ends of the first and third side surfaces and slanting radially outward from at least a midpoint thereof toward the third side surface; When mounted around the machine part, the intersection of the first side surface and the second side surface is in point contact with the mechanical component, and the fourth side surface is connected to the third side surface. An annular sealing member, characterized in that when the end portion is pressed radially inward, a portion of the arcuate portion of the second side surface forms a contact area that contacts the mechanical component. . 2. In the annular seal member according to claim 1,
An annular seal structure, wherein the fourth side surface has a substantially arc shape. 3 A fluid seal structure that fluidly seals between outer and inner mechanical parts that fit into each other and move relative to each other in the axial direction, the structure being disposed in an annular groove provided in the outer mechanical part. The annular seal member includes an annular seal member and an annular pressure member, the annular seal member has first to fourth side surfaces extending in the circumferential direction, and when viewed in cross section along a plane including the central axis of the ring, the first the side surface has an S-shaped curve including a radially outer portion that is radially inwardly convex and a radially inner portion that is radially inwardly concave; A recess extending substantially in the axial direction from one end connected to the inner end of the concave portion and extending substantially over the entire length thereof, and a recess formed at the other end on the opposite side from the one end. a convex arcuate portion, the third side surface extending substantially linearly radially from the arcuate portion, and the fourth side surface extending from the first and third side surfaces. extending axially between the radially outer ends of and sloping radially outwardly from at least a midpoint thereof toward the side of said third side surface, when mounted around an inner mechanical component; The intersection of the first side surface and the second side surface is in point contact with the inner mechanical component, and under a situation where low fluid pressure is applied from the side of the first side surface. The arcuate portion of the second side surface is spaced apart from the inner mechanical component, and the third side surface forms a V-shaped cavity between adjacent radial wall surfaces of the annular groove. In a situation where high fluid pressure is applied from the first side surface, the pressure member moves to ride on the inclined part of the fourth side surface, and An end of the side surface connected to the third side surface is pressed axially and radially inward, and a part of the arcuate portion of the second side surface forms a contact area that contacts the mechanical part. , a fluid seal structure characterized in that the V-shaped cavity is configured to disappear. 4 In the fluid seal structure set forth in claim 3,
A fluid seal structure characterized in that the fourth side surface has a substantially arcuate shape. 5. The fluid seal structure according to claim 3 or 4, wherein the seal member and the pressure member are made of a fluoroplastic material having strong elasticity. . 6. The fluid seal structure according to claim 3 or 4, wherein the pressure member is made of elastomer. 7 In the fluid seal structure of claim 6,
A fluid seal structure characterized in that the pressure member is an O-ring.