JPS5830564A - Valve seal and valve - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The valve seal of a butterfly valve includes a U-shaped annular valve seat member disposed within an annular slot in the valve body and a retaining ring for holding the valve seat member in place. It is equipped with The cross section of the valve seat member includes two legs and a curved portion connecting the legs. The first leg is captured between the retaining ring and the valve body to retain the valve seat member in the slot and to allow limited rotational movement of the valve seat member. A radially inwardly projecting extension of the curved portion terminates in an annular sealing surface that cooperates with the valve disc. The valve seat member has a slotted hole between the valve chamber and the fluid pressure crab.
Contact t, b 1st degree axis direction. Side. . Divided into axial sides. The valve seal also includes an annular open helical buffer horn disposed within an annular recess formed in the slot by the two legs and the curved portion of the valve seat member. The annular portion is in fluid pressure communication with the second axial side of the slot. The loose members resist cross-sectional compression and create a reaction force that extends in a direction perpendicular to the cross-sectional compression force. This device can effectively seal system pressure from both sides of the seal.

The retaining ring is secured to the valve body by a mounting device having a plurality of threaded holes extending radially through the valve body and a plurality of conical blind holes formed in the retaining ring, each aligned with the threaded hole. be done. A screw with a conical end is received within each thread size and cooperates with the blind bore to urge the retaining ring axially toward the valve body. The valve and inner members are adapted to provide resistance to deformation for optimum sealing.

U.S. Patent No. 5.563,5 to Mr. Pr1eae
No. 10 shows a type of seal in which a "0" ring of rubber or elastomer or a spring consisting of a helically wound wire of round cross section compresses the inner member. A variant uses a spring made of flat wire as an elastic inner member held between two legs of an outer member clamped in the valve body. The two legs of the outer member have spacing members therebetween that provide a support surface that resists radially outward movement of the inner member when the disc is closed. This type of seal is manufactured by I) UR Engineering ROI CIOMPA1 in Cookeville, Tennessee.
It is incorporated into valves sold under the name ``@BIGM&!'' by iY Engineering Jio.

A third type of seal uses a sealing member that "floats" within a recess in the valve body and backs into said recess to force the floating member radially inwardly against the valve disc. It has a member.

+3 U.S. patent for Mr. Vain! 1,282,55
No. 8, same No. 5,497,178 against Mr. Pri 80
No. 5.642, 248 against Mr. Benware.
No. 3.98 against Mr. Wuaik, Jr. and others.
No. 6,699, No. 4,088,299 against Mr. Maiulaitis et al., No. 4,113,268 against Mr. Sinnoms et al., Whit ta
No. 4,130,285 against Mr. lce r, Ma.
No. 4,165, against Mr. Ciulaitig et al.
No. 859 as well as No. 4,194,749 to Bonaf Ouli disclose seals using that method. These U.S. patents disclose various devices as components. For example, in one embodiment of Mr. Benware's seal:
When system pressure is applied into the recess, the "0" ring deforms and forces the seal member radially inwardly against the valve disk. Be
It is generally known that the seal shown in the Nware patent uses a flat wire spring backing member. This flat wire spring resists radially outward pressing of the floating member' by reaction against the bottom of the recess, thereby holding the floating member against the valve disk. The seal shown in the BOnafoua US patent serves a similar function but uses a round cross-section wire instead of a flat wire spring. Mr. Benware's US patent and Whitt
Other US patents, such as the Aker US patent, also use garter springs as backing members. The garter spring produces a 7-7'EE compression force in the sealing member;
The sealing member is pressed against the valve plate, thereby producing a sealing effect different from that achieved by a backing member which is generally elastic in cross-section.

The last type of seal uses a sealing member having one leg that is retained within the valve body. The sealing member and valve body define a recess. A backing member is typically, but not necessarily permanently, disposed within the recess. U.S. Patent No. 2.988,520 to Mr. Kent
No. 3,260,4 against Mr. Borcherdt.
No. 96, No. 5,754.457 against Mr. RooB, No. 4.005 against Mr. llggleston,
No. 848 and No. 4.04 against Mr. Priege.
4,994 and @Royal Engineering n+1ulitri@15 of Suntaana City, California”
The ``Series 206 valve'' manufactured by ``Series 206 Valve'' is an embodiment employing this method. Kent, U.S. Pat. A garter spring made of round wire is shown. (RO'O
The U.S. patent of sff uses a flat metal 7-7° for the same purpose, and the U.S. patent of 01gg1eston uses a round wire as a fulcrum for leverage to bend the sealing member under the action of system pressure. A garter spring is used in the recess. In this way, the sealing member is pressed against the valve disc.

Place an annular seal like those used in butterfly valves in place.
A typical structure for retaining the valve body includes a retaining ring held opposite the valve body. The seal is disposed within an annular slot formed by the valve body and the retaining ring. The valve body is provided with seven flange for connecting the valve to the seven flange of the fluid line.

In the prior art, the retaining ring is held to the valve body by a bolt disposed axially through the valve body and the retaining ring. An example of such a structure is Br0dv
In such a structure, as shown in the U.S. patent specification of AY, the 7 flanges of the fluid piping system directly support the axial surface of the retaining ring, so the head of the bolt is aligned with the axial direction of the retaining ring. 1
Must be placed within the plane.

The present invention includes an annular valve body defining a valve chamber, a valve closing member movable within the valve chamber between an open position and a closed position, and an annular valve body fixed to the valve body and together with the valve body. and an annular retaining ring defining a slot.

The valve seal of the present invention includes a position having a generally U-shaped cross section, the catch device being adapted to rotate the valve seat member to a limited extent about the catch device relative to the cross section of the slot. Hold in slot. The U-shaped profiled legs cooperate with the sides of the slot to limit rotation of the valve seat member. The valve seat member is divided into a first axis side and a second axis side that are sealed to each other by a slotted fastening device, wherein each of the first and second axis sides is closed to the valve chamber by fluid pressure. is in contact with.

The curvature of the U-shaped cross section is provided with an annular sealing surface for cooperating with the valve closing member. The annular sealing member defines an annular recess in the slot substantially radially aligned with the sealing surface and coupled by fluid pressure to the second axis side of the slot. The annular valve seat member is arranged such that when the valve seat member rotates toward the second axis and the pressure on the first axis
When the pressure on the axis side of tr3 is higher by a predetermined amount, the annular quadrant tr3 contracts. The valve seal also includes an annular pack member capable of compressing a cross section disposed within the recess.

Another aspect of the invention includes a mounting device for retaining the retaining ring to the valve body. The attachment device includes a threaded hole extending radially through the body and a conical blind hole in the retaining ring aligned with the radially extending threaded hole.

A screw with a conical end is inserted into a radially extending thread of the body and cooperates with the blind hole to force the retaining ring axially towards the valve body. Figure 2 shows a butterfly valve 10.

The butterfly valve 10 includes a valve body 12 defining a valve chamber 14 . Valve body 12 has a shaft 16 rotatably mounted therein. A disc 18 is attached to the shaft 16 by bolts 1B or other suitable assemblies. As illustrated in FIG. 2, the disc 1B serves as a valve closing member that is opened and closed by the rotation of the shaft 16. FIG. 2 shows two positions used in such a valve. First, the plane of the disc 18 is axially offset from the centerline of the valve shaft 16. Second, the valve shaft 16 is very slightly displaced (either upwardly or downwardly as shown in FIG. 2) from the centerline of the valve chamber 14. ``The initial deflection moves the valve disk 1B away from its seal and into the fully open position.

Without initial deflection, the portion of the seal that attaches the valve disc 18 to the body 12 will rub and become abnormally worn.

The second deflection causes the final movement of the valve disk 1B, approaching the axially closed position of the valve chamber 14. This two-kill geometry is well known to those skilled in the art and is particularly advantageous in conjunction with the seal of the present invention. Stopper 2o is valve disc 1
B's rotation is restricted and its closed position is defined. The stopper 20 is cast together with the valve chamber 12 and is attached to the valve disk 1.
8 is machined to accurately position it in the closed position.

As shown in FIG. 1, the shaft 16 is mounted within the post 21 and seals and packings 22 prevent leakage of fluid from the valve chamber 14 around the shaft 16. ? The stopper 1 is integrally formed with the valve body 12. The valve body 12 also has a circumferentially extending mounting surface 24. The mounting surface '24 includes a through hole (not shown) for mounting the valve body 12 on the seven flanges of the pipe fP forming the fluid piping system.

A retaining ring 26 fits into an annular groove on one side of the valve body 12. Retaining ring 26 holds in place valve seal 100, which forms an aspect of the invention.

Valve seal 10G cooperates with valve disc 18 to prevent fluid flow through the fluid line system when valve disc 18 is closed.

FIG. 3 shows the rotation of the valve body 12, retaining ring 2-6, and various attachment devices. FIG. 6 is a radial cross-sectional view taken at a circumferential position remote from the post 21.

Valve seal 100 includes an annular valve seat member 102 constructed from a relatively hard yet flexible material such as Teflon synthetic resin polymer. The valve seat member 102 has two legs 1
04.106 and the curved part 108 connecting these legs
The curved portion 108, which is a U-shaped member, includes a radially inwardly projecting extension 110. Extension part 1
10 marks an annular sealing surface 112 that cooperates with the outer surface of the valve disk 1B. As shown by the dotted lines in FIG.
The ten-valve seal 100 which is a force fit also includes an annular back-up member 114 that is compressible in cross section. The valve body 12 and retaining ring 26 have a valve seal 100 therein.
An annular slot 116 is formed into which the groove is fitted.

One leg 104 of the valve seat member 102 forms a fastening device 11B. A catch device 118 is captured between the valve body 12 and the catch ring 26 to retain the valve seat member 102 within the slot 116. The valve body 12 has a serrated cutout portion on its axial surface. In this serrated cutout, the leg 104 is captured between the valve body 12 and the retaining ring 26. The axial distance between the valve body 12 and the retaining ring 26 over which the leg 104 is captured is a comb less than the axial thickness of the leg 104. The retaining ring 26 is
It is equipped with 120. The length f120 further reduces the axial distance ym* between the valve body 12 and the retaining ring 26. When the retaining ring 26 is pushed axially against the valve body 12, the lip f120 causes a cold flow of the leg 104 radially outwardly of the lip and into the serrated cutout. Assists in cold flow of legs 104. Valve seat member 1
02 is thus held firmly within the slot 116 and the leg 104 serves as a secondary seal to ensure that no fluid flows across the seal 100.

The primary force that axially clamps the retaining ring 26 against the valve body 12 is caused by the axial compressive force created when the valve body is clamped between pi fP. However, it is necessary to place the seal 100 in the proper position and to maintain the valve body 12 and retaining ring 26 in the proper relative positions before inserting the valve into the fluid line. This attachment is done using a device for attaching the retaining ring.

Positioning before assembly is performed using a set screw 200. The axis of the set screw 200 is arranged in the radial direction. A plurality of radially extending threaded holes 202 equidistantly spaced around the circumference of the valve body 12 receive set screws 200 . Retaining ring 26 has a plurality of identical blind conical holes 204 aligned with radial threaded holes 202 . Set screw 200 has a conical end 20B. The conical end 206 extends from the slope of the blind bore 204 so as to force the retaining ring 26 axially to the right as viewed in FIG. 5 when the set screw 200 is threaded radially into the bore 204. Work with the sides. This retaining ring attachment, which replaces the axial hole through the retaining ring 26 used in the prior art, allows the apparatus to facilitate preliminary assembly of the valve body 12 and retaining ring 26. Also, by not forming an axial hole through the retaining ring 26, a potential source of fluid leakage can be eliminated. Although any number of attachments may be used as a device, it has been found that four provide acceptable results.

Figures 6 and 4 show the seal 10 when the valve is open.
It shows the position occupied by 0. The cross-sectional shape of the annular slot 116 formed by the valve body 12 and the retaining ring 26 is substantially similar to the shape of the annular valve seat member 102. The annular slot 116 narrows axially to define a circumferentially extending opening. , a radial extension 110 of the curved portion 108 projects into the valve chamber 14 through its opening. Valve seat member 102 divides slot 116 into a first axial side 122 and a second axial side. Both first side 122 and second side 124 are in fluid communication with valve chamber 14 .

Slot 116 includes a radially inwardly facing shoulder 126. Shoulder 126 defines an annular recess 128 with legs 104, 106 and curved portion 10B. The annular recess 128 is generally radially aligned with the annular sealing surface 112. Four parts 1 formed by the valve seat member 102
The radially inwardly facing walls of 28 have a circular cross section and are shaped to match the outer surface of backup member 114. The recess 12B is formed by the groove 11 due to fluid pressure.
6 and a second axial side 124 thereof. The annular sealing surface 112 has a surface 130 on one axial side of the sealing surface 112 .

FIG. 5 shows a portion of the preferred axially compressible backup member 114 in greater detail.

The backup member 114 is a spirally wound metal “
It consists of a flat wire spring element.

As the material for the backup member 114, stainless steel or Hastelloy is preferably used to provide resistance to deterioration by various media. The pitch of the springs is greater than the width of the wire to provide space between adjacent portions of the flat wire. Such an "open spiral" configuration allows fluid to flow freely through and around the backup member 114, thus allowing fluid pressure to be transmitted through the backup member 114. When the cross-section of backup member 114 is compressed in one direction, the member develops a reaction force that extends in a direction perpendicular to the compressive force. "Flat wire springs", i.e. springs formed from strips of spring material with a rectangular cross-section, convert an applied compressive force into a reaction force extending perpendicularly thereto more easily than springs with other cross-sectional shapes. can do.

The operation of the valve seal of the present invention will be most clearly understood with reference to FIGS. 6 and 7. FIG. 6 shows in solid lines the position of the valve seal when the valve disk 18 is closed and no system pressure is applied. Comparing FIG. 6 or FIG. 4 with FIG. 6, it can be seen that in FIG. I understand. The outer circumferential surface of disk 18 contacts sealing contact surface 112 and seat member 102 rotates toward second axial side 124 of slot 116 . The cross-sections of the annular recess 12B and the backup member 114 are slightly compressed approximately radially relative to the valve body 12. Backup member 114 resists compression and exerts a generally radial reaction force on the inside of shoulder 126 and curvature 108 to force valve seat member 102 against valve disk 18 .

In addition to the generally radial reaction force exerted by backup member 114 as a reaction to the compressive force, the interference fit between annular sealing surface 112 and the surface of disk 18 causes disk 18 to
forming a static component of the sealing force that holds the annular sealing surface 112 against the annular sealing surface 112 .

As illustrated in FIG. 2, when looking at FIG.
Approaching 02. The aforementioned two-stage displacement, the radius R formed on the valve disk 18, the flat seal 'rM1P, and the surface 132 of the annular sealing surface 112 result in the annular sealing surface 112 (sixth Valve disc 1 at an advantageous angle to facilitate seating of face F of valve disc 18 against face 130 of the valve disc 18 (see figure).
8 is brought into contact with the valve seat member 102. Ideally, when the valve disc 18 is fully closed, the annular valve seat member 102 is attached to the leg 1.
06 and the second axial side 124 of the annular slot 116 is rotated just enough to allow fluid pressure communication between the valve chamber 14 and the annular recess 128.

Fluid pressure adds a dynamic component to the sealing force regardless of which side of disc 18 is pressurized when the valve is closed. FIG. 6 shows in dotted lines the positions occupied by the annular valve seat member 102 and valve disk 18 when the valve is pressurized from the right side as shown. When the pressure on the right side of the disc 1B increases, the valve shaft 16, bearing and packing 22
(See FIG. 1) Due to manufacturing tolerances and wear that unavoidably create gaps between the disk 18 and the deflection of the disk 18 due to the applied pressure, the disk 18 is forced to move axially to the left.

The annular valve seat member 1-02 rotates to the left with the axial movement of the valve disk 18 until the leg 106 contacts the second axial side wall of the annular slot 116. Backup member 114 resists rotation and presses against annular sealing surface 112 and sealing surface A of valve disk 18.

If the fluid pressure is high enough, the fluid pressure will increase the pressure on the leg 104 facing the first axial side 122 of the slot 116.
The backup member 114 is compressed in the axial direction by pressing the surface of the back-up member 114. The dotted line of leg 104 shown in the sixth cross-section is exaggerated to illustrate this mode of operation of the valve seal. Anyway, Yoshi.

As portion 104 continues to move generally axially under the action of fluid pressure within valve chamber 14 and first axial side 122, the axial dimension of annular recess 128 is caused to decrease. Backup member 114 acts between annular shoulder 126 and annular valve seat member 102 to create a generally radial reaction force that urges annular sealing surface 112 radially inwardly against valve disk 18.

FIG. 7 shows the position of the annular valve seat member 102 and valve disc 18 when the valve is pressurized from left to right.

The fluid pressure pushes the valve disk 1B to the right due to the presence of the gap and the deflection mentioned above.

The annular valve seat member 102 rotates to the right together with the disk 18. Since the valve seat member 102 was rotated to the left when the disk 1B was closed, the rotation in the opposite direction caused by the pressurization of the fluid from the left acts in the opposite direction to the initial rotation. The rotation of the annular sealing surface 102 in the opposite direction actually forces the annular sealing surface 112 against the sealing surface 7 of the valve disk 1B. This reverse rotation also causes the second axial side 124 of the slot 116 to
passage is opened and the annular recess 128 receives system pressure. The system pressure thus exerts a generally radially inwardly acting force in the annular recess 128 that further rotates the annular valve seat member 102 in the opposite direction and presses the sealing surface F of the valve disc 18 against the annular sealing surface 112. Generate on the inside.

Thus, the valve seal of the present invention exerts a static sealing force that preloads the seal when no system pressure is acting, and a dynamic sealing force regardless of the direction in which system pressure is acting on the valve disk. It is believed that the sealing effectiveness of known prior art valve seals under system pressure in one direction is less than when subjected to system pressure in the other direction. One reason for this is that known prior art seals do not allow for inevitable axial movement of the valve disc under pressure. However, the present invention can function very effectively regardless of the direction of system pressure.

As illustrated in FIG. 7, the second side 124 of the slot 116
The size of the passageway in is not a critical factor unless system pressure is present. Axial movement of the disc when system pressure is acting towards the right tends to open the passageway on the second side 124- as the annular valve seat member 102 rotates under that condition. arise. The open helical flat wire construction of backup member 114 has been found to be the most advantageous construction.

For example, a spring made of round cross-section wire would work, but each coil of the spring would provide insufficient support surface between the Teflon annular valve seat member and the spring, and the tearing force between the coils would cause It has been found that cold flow occurs between rO
A solid back-up member that deforms in cross-section, such as a J-ring, may also be used, but system pressure is introduced across the annular recess 128 when pressurized from left to right (see Figure 7). Since it is not possible to do so, it can be said that this is the least advantageous option.

Having thus described certain embodiments of this invention, as well as variations thereof, those skilled in the art will recognize other modifications that may be practiced within the scope of this invention.

For example, the invention may be used with other types of valves and is not limited to use with butterfly valves such as those shown in the parenthetical specification. Therefore, the above description merely indicates the preferred embodiments of the present invention, and the scope of the present invention is limited only by the claims.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a butterfly valve incorporating the present invention taken axially along the valve shaft, and FIG. 2 is a cross-sectional view of a butterfly valve incorporating the present invention.
6 is a detailed view of the valve seal of the present invention when the valve is open; 4.
Figure 5 illustrates an interference fit between the valve disc shown in dotted lines and the seal of the invention shown in the position it occupies when the valve is open; Figure 5 is used in a preferred embodiment of the invention; FIG. 6 is a detailed view of the back-up member consisting of an open helical flat wire spring; FIG. , the position of the seal is shown in solid lines when no system pressure is applied, and the position of the seal is shown in dotted lines when system pressure is applied from right to left in Figure 6, and Figure 7 shows the valve circle. Figure 8 is a detailed view showing the relative positions of the parts of the valve and the seal of the invention when the plate is closed and the system pressure is acting from left to right when looking at Figure 7; 10... Valve, 12... Valve body, 14... Valve chamber, 1
6... Shaft 7), 18... Valve disc, 21... Boss, P... Pinot, 26... Retaining ring, 100... Valve seal, 102... Valve seat member, 104,106...
Leg portion, 108... Curved portion, 110... Extension portion, 11
2... Sealing surface, 114... Backup member, 11
6... Slot, 118... Fastening device, 120... Ring, 122... First axis side, 124... Second
side of the axis, 126...shoulder, 128...recess, 2
00... Set screw, 202... Screw hole, 204...
・Blind hole. Agents: Asamura and Kogai Engraving of the drawings by 4 people (no changes to the content) Continued from page 1 0 Inventor: Lawrence Francis Stolshiic of Rhode Island, USA. Ekapaug-Winnapaug Avenue, Do State (No street address) Procedural amendment (method) September 22, 1930 Director-General of the Patent Office 1, Indication of the case Showa Tough Year Patent Application No. dρ〃gθ No. 2, Title of the invention F/-t and transfer 36 Relation to the case of the person making the amendment Patent issuer 4, agent 5, date of amendment order 81st day of August 1939 6, number of inventions increased by amendment 7 , subject to correction

Claims (1)

[Scope of Claims] (1) an annular valve body defining a valve chamber; a valve closing member movable within the valve chamber between an open position and a closed position;
A valve seal for use in a valve having an annular retaining ring fixed to the valve body and defining with the valve body an annular slot having a shoulder, for cooperating with a fastening device and the valve closure member. an annular valve seat member having an annular sealing surface, the catch device having an annular groove configured to rotate the valve seat member to a limited extent about the catch device relative to a cross section of the annular slot; the valve body and the retaining ring for retaining the slot in the bore and dividing the slot into a first axial side and a second axial side, each of which is in fluid pressure communication with the valve chamber; said valve seat member, together with said shoulder, forming an annular recess substantially half-j aligned with said sealing surface and in fluid pressure communication with said second axial side; and the valve seat member rotates when the valve seat member rotates toward the second axis and the first
compressing the annular recess when the pressure on the side of the first axis is higher than the pressure on the second axis by a predetermined amount, and further contacting the wall of the annular recess and the shoulder. further comprising an annular back-arrangement member disposed within the annular recess, wherein the parafatge member resists compression of the cross-section and generates a force as it expands perpendicular to the force that causes the cross-section to “-”. Valve seal. (2) The valve seal of claim 1, wherein the buffer ladder member includes an open helically wound spring element having a rectangular cross section, the long sides of the rectangular cross section being A valve seal characterized in that the valve seat member cooperates with the wall portion of the recess and the shoulder portion. (8) The valve seal according to claim 1, wherein the valve seat member has two (1) leg portions and It is formed in a U-shaped cross section with a curved part connecting the legs.1.
a first of the legs includes the fastening device, the two legs and the curved portion cooperate with the shoulder to form the recess;
A valve seal wherein said curved portion includes a radially inwardly projecting extension terminating in said sealing surface. (4) In the valve seal according to claim 3, the U-shaped cross section is! one predetermined axial dimension, the extension has a second smaller predetermined axial dimension, and the slot is axially interposed to a circumferentially extending axial opening; A valve seal characterized in that the extension projects into the valve chamber through the opening. (5) The valve seal according to claim 4, wherein the radial inner surface of the annular recess is a part of a circular cross section, and the backup member has an open spiral shape with a rectangular cross section. Valve seal characterized in that it is a rolled spring element, said rectangular, long side cooperating with the wall of said annular recess and said shoulder. (6) an annular valve body defining a valve chamber; a valve closing member attached to the valve body for moving between an open position and a closed position within the valve chamber; an annular retaining ring defining an annular slot having an inwardly facing shoulder; and a valve seal for interacting with the valve closure member when in the closed position; A valve whose seal is made of a valve seal according to any one of claims 6, 4, and 5. (7) The valve according to claim 6, wherein the valve body includes a boss, and the valve closing member includes a disc fixed to a shaft mounted to rotate within the boss. , a valve characterized in that a peripheral portion of the valve closing member cooperates with the valve seat member to seal the valve closing member when in the closed position. (8) Claim 7 In the disclosed valve, the radially inwardly projecting extension of the curved portion is tightly fitted to the disk to position the valve seat member on the side of the second axis when the disk is closed. and forming a seal between the disc and the valve seat member such that the pressure on the first axis side of the slot is equal to the second axis. the first leg moves axially toward the second axis side of the slot and moves the annular recess and the backup member in a generally axial direction Claim 6, characterized in that the sealing surface is compressed to produce a substantially radially extending reaction force that presses the sealing surface toward the disc.
The valve according to paragraph 1, wherein the retaining ring and the valve body compress the first leg therebetween, one of the valve body and the retaining ring having a serrated surface, and the valve body and the retaining ring having a serrated surface. the other comprising a ring, the ring and the serrated surface cooperating to induce cold flow in the first leg.・-)