WO1999015816A1

WO1999015816A1 - A fluid control valve

Info

Publication number: WO1999015816A1
Application number: PCT/DK1997/000403
Authority: WO
Inventors: Holger Tychsen
Original assignee: York International AS
Current assignee: York International AS
Priority date: 1997-09-24
Filing date: 1997-09-24
Publication date: 1999-04-01
Anticipated expiration: 2000-03-24
Also published as: AU4295897A

Abstract

A fluid control valve (1) comprises a conical valve seat (6), a closure element (4) and means (5) for displacing the closure element axially relative to the valve seat. The closure element comprises a valve cone (7) with a circumferential groove and an annular seal comprising a flat seal ring (15) of a resilient material, received in the groove. According to the invention the annular seal and the peripheral groove are matched for mutual engagement in order that annular seal will, in the absence of external influences, rest in the groove bottom, whereas the seal may yield resiliently to expand radially, depending on fluid pressure.

Description

A Fluid Control Valve

The present invention relates to a fluid control valve, and more particularly to a fluid control valve wherein a closure element may be displaced axially between an open and a closed position and vice versa m order to selectively open or close the valve.

The invention still more particularly relates to a fluid control valve for use m refrigerant loops designed for high fluid pressures, high differential pressures in either direction and a wide range of temperatures.

Swedish patent publication 337 148 discloses a fluid control valve adapted for controlling fuel oil fed to an oil burner and employing a valve seat m the form of an annular surface perpendicular to the valve axis together with a displacable closure element fitted with a seal ring adapted for sealing engagement with the valve seat. The seal ring is inserted m an annular, axially open groove, of which the opening section is reduced in order to secure the ring. The closure element comprises a core portion and a sleeve, the sleeve providing the outer wall of tne groove. The parts are assembled by fitting first the seal ring and subsequently the sleeve onto the core portion.

The inventor has tested a design of a fluid control valve which comprises a conical valve seat and a closure element, the closure element comprising a valve cone with a peripheral groove fitted with a ring type seal made of teflon. The groove may be split, being defined by two parts. A first part, defining that shoulder wall of the groove which is situated proximal to the valve seat, is provided by a washer, while a second part, defining the opposite wall of the groove, is integral with a cone stem portion. The components are assembled by putting initially the seal ring and subsequently the washer in position on the second part. The washer is then secured by a nut or a bolt which is tightened in order to compress the inner portion of the ring axially.

The function of a valve according to this design is satisfactory, however, there is an interest in finding a design which is more readily manufacured and which avoids all parts that might accidentally come loose inside the fluid conduit.

This is provided by the fluid control valve as defined in claim 1.

In this valve, the valve cone may effectively be manufactured by appropriate molding and shaping of one integral piece, avoiding all separate parts. The seal ring may subsequently be slipped over the cone to snap into the groove. Once installed, the seal is essentially free to expand radially as it might be liable to do if subjected to fluid pressure on the inner margin. A fluid pressure on the inner margin may arise in case the fluid pressure on that side of the seal which is situated proximal to the valve seat exceeds the pressure on the opposite side of the seal. In this situation the seal ring will, as long as the valve is closed, be restrained peripherally by its contact with the conical valve seat, and thus the ring is bound to stay in position. Should the closure element, however, be subsequently displaced axially in the attempt to open the valve, the valve cone effectively retreats from the seal outer margin, thus permitting the seal ring to expand radially. —

A design where the seal is free to expand radially has been held totally unacceptable for for applications where the valve cone could be subjected to any substantial proximal overpressure for fear that the seal ring could be blown radially outwardly and permanently dislocated from the annular groove.

However, the inventor has discovered that by selecting for the seal a flat seal ring of a resilient material and by proper designing and adaptation of the peripheral groove and the seal ring, radial expansion of the seal ring can be controlled to stay within the limits where it is still guided by the groove.

Radial expansion of the ring by the fluid pressure will only take place, if the fluid pressure should find its way into the bottom of the groove, where it would exert a radial pressure on the ring inner margin. Radial expansion will be driven by the differential fluid pressure and will be balanced by the contracting force by the inherent ring resilience and by friction, mainly between the ring distal face and the second shoulder. A fluid pressure on the valve cone proximal side exceeding that on the valve cone distal side may or may not find its way to the inner margin of the ring.

It is envisaged that upon closing the valve, the ring is quite likely to be seated so hard against the bottom surface of the groove due to the force applied by the engagement with the conical valve seat that any fluid pressure will in fact rarely find its way into the bottom of the groove, where it could exert a radial force on the ring inner margin. In case no substantial fluid pressure should find its way into the bottom of the groove, the seal ring will simply stay in place during opening of -the valve. Although this sequence of events is likely to prevail on most occasions, the features provided by the invention are considered to be necessary precautions against the mere chance of any fatal events, if the fluid pressure should occasionally finds its way into the groove bottom.

According to a preferred embodiment the seal ring and the groove are adapted for mutual cooperation in order that the seal ring may expand radially to the position where an outer peripheral portion of the seal ring projects beyond the second shoulder, whereby the seal ring distorts by the fluid pressure applying onto the ring proximal side, to increase the friction between the seal ring sides and the shoulders and thereby to check further expansion. In essence the fluid pressure acting on the outer peripheral portion of the ring tends to tilt the ring which is, however, being guided by both shoulders in the groove. The tilting increases the friction, in particular between the inner edge of the ring promixal side and the first shoulder, thus providing an added check against further expansion.

According to a preferred embodiment the first shoulder and the seal ring are sized for cooperating engagement in order that the first shoulder engages the inner portion of the ring proximal side through a radial expansion of the ring of at least 6% but no more than 9%, as measured on the ring outer diameter. This permits at least 6% radial expansion of the ring without the ring becoming dislocated. On the other hand, no more than 9% radial expansion is required in order to free the ring of its engagement in the groove. Thus fitting of the ring may take place by expanding the ring by at least 9% and slipping it over the first shoulder. The ring may be expanded by any procedure known in the art, e.g.- -by pushing it over an applicator cone. According to a further preferred embodiments the seal ring sides are substantially mutually parallel and the shoulders are also substantially mutually parallel and spaced to receive the seal ring with an axial play, preferably in the range from 2-20% of the ring axial dimension. The parallel surfaces and the play ensure that the ring may expand and contract inside the groove. Limiting the axial play to the range mentioned provides a limit to axial expansion of the ring, as may take place when the ring is being forced against the groove bottom by the closure element being forced into the conical valve seat.

Axial expansion of the seal ring inside the groove is likely to make the ring stick in the groove, leaving no space by which fluid pressure could enter the groove bottom and therefore more likely to ensure that the ring will stay in its innermost position during opening of the valve. This behaviour is furthered by selecting for the ring a resilient material with slow recovery.

According to a preferred embodiment the second shoulder provides an annular planar surface perpendicularly to the valve axis.

This design is readily manufactured to a very accurate result. The planar surface permits the ring to be forcibly driven against the bottom of the groove by the action of the conical valve seat, and the surface provides friction, checking ring expansion while the closure element is being displaced away from the seat.

According to a preferred embodiment the seal -ring comprises a material with properties in respect of resilience, hardness and recovery similar to those of polytetrafluorethylene modified with carbon or graphite. The material properties are linked to the environmental conditions to which the seal ring is subjected, in case of refrigerant loops, pressures up to 40 bars, and temperatures within the range from -60 to +150 °C .

Polytetrafluorethylene modified with carbon or graphite has been found to exhibit the proper qualities under these circumstances. A particularly favored composition comprises from 10-151 of carbon or graphite. Other environmental conditions may dictate other materials in order to obtain similar material properties in terms of resilience, hardness and recovery.

According to further preferred embodiments the seal ring comprises a ring with a generally rectangular sectional outline, bevelled at the outer proximal corner, the radial width of the ring being at least 2 1/2 times and preferably at least 3 times the axial width of the ring and the ring radial width being at least 10% of the radius of the ring outer margin. The bevel provides an appropriate contact surface for interacting with the valve seat. The comparatively wide and flat design of the ring is important in order to provide the ring with sufficient structural strength to resist radial fluid pressures without excessive yield and in order to provide side surfaces for guiding the ring accurately over some range of expansion.

Further features and advantages of the invention will appear from the appended description of preferred embodiments given with reference to the drawings wherein

Fig. 1 shows the valve according to the invention in axial section, Fig. 2 shows a component of the valve in axial section,

Fig. 3 shows a detail from Fig. 2 in enlarged view,

Fig. 4 shows the seal ring in planar view,

Fig. 5 shows the seal ring in axial section,

Fig. 6 shows a detail of the valve in closed condition and in axial section, and

Fig. 7 is a view similar to Fig. 6 but in a situation where the closure member has been displaced partially away from the valve seat as during the early stages of opening the valve .

All figures are schematic and not necesarily to scale and illustrate only those parts which are essential in order to enable those skilled in the art to understand and practice the invention, whereas other parts are omitted from the drawings for the sake of clarity. Throughout the drawings identical references have been used to designate identical or similar features.

Reference is first made to Fig. 1 for a description of the valve according to the invention. The valve 1 according to the invention basically comprises a valve housing 3 which defines a fluid conduit 2 passing through the lumen bordered by a conical surface which constitutes a valve seat 6. A closure element 4 is displacable inside the valve housing along an axis 21 controlled by- a spindle 5. The closure element 4 may be moved from a position where the fluid conduit is blocked by the closure element engaging the seat 6, as illustrated in Fig. 1, and a position, wherein the closure element is spaced from the seat 6, where the fluid conduit is open to the passage of fluid.

The valve seat 6 is a generally rotational surface centered at the valve axis 21 and, in the preferred embodiment, angled to 45° from the valve axis. The closure element 4 is also a generally rotational body centered at the valve axis 21 along which it may be displaced.

The closure element 4 basically comprises a valve cone 7 and a seal ring 15 which has the function of providing an elastic surface capable of adapting to any irregularities of the harder surfaces of the cone 7 and the seat 6.

Reference is now made to Figs. 2 and 3 for a more detailed description of the valve cone 7. The valve cone 7 comprises a generally mushroom-shaped body with a stem portion adapted for mutual interaction with the spindle in a way which is generally known in the art, and a head portion, integral with the stem portion.

The head portion comprises a circumferential groove 22, open peripherally and delimited by a cone rim portion 11 and a cone lip portion 8.

Fig. 3 more clearly illustrates the groove 22 which is delimited upwardly in the figure by a rim-like surface of the cone lip portion 8. This surface is referred to as the proximal shoulder 9, this side of the groove being the one intended to be situated proximal to the valve seat. The groove 22 is delimited downwardly,—as illustrated in the figure, by a rim-like surface of the cone rim portion 11. This surface is referred to as the distal shoulder 12 since this part of the groove is intended to be situated distally from the valve seat. The inner, generally cylindrical surface in the groove 22 is referred to as the groove bottom 14.

The proximal shoulder 9 is bordered peripherally by a proximal shoulder bevel 10 and the distal shoulder 12 is bordered peripherally by a distal shoulder bevel 13. Both of the bevels are angled 45° from the axis, but in opposite directions so as to provide guiding surfaces directed towards the center of the groove.

Reference is now made to Figs. 4 and 5 for an explanation of the seal. The seal comprises a seal ring 15 which is a flat, comparatively wide ring. As may be understood from Fig. 5 the ring section is generally rectangular, one of the outer edges being bevelled. The rim surfaces of the ring, oriented perpendicularly to the axis, are referred to as the seal ring promixal side 16 and the seal ring distal side 17, respectively, the seal ring being adapted to be oriented with the proximal side proximally to the valve seat. The edge surfaces, perpendicular to the seal ring sides, are referred to as the seal ring inner margin 18 and the seal ring outer margin 19, respectively. The seal ring bevel 20 is angled to match the valve seat, in the preferred embodiment by 45° from the axis.

The seal ring comprises a polytetrafluorethylene compound mixed with from 10-15% carbon or graphite. The addition of carbon or graphite serves to enhance resilience and structural strength.

Reference is now made to Figs. 6 and 7 for an explanation of the interaction of the components which seal -the valve. Figs. 6 and 7 are axial sections revealing just part of the closure element, part of the seal ring, and part of the valve housing with the valve seat. Fig. 6 illustrates the situation where the valve is closed, the closure element being forced axially against the valve seat 6. The Fig. 6 ilustrates these components in spaced relation for the sake of clarity only; during actual service these components will be tightly forced together. As may be understood from Fig. 6 the cone distal shoulder 12 is sized to provide a backing surface backing practically the entire distal side of the seal ring.

The proximal shoulder 9 provides a surface parallel to the surface of the distal shoulder but with a smaller radius so as to expose approximately the outer peripheral half of the seal ring proximal side 16.

When the closure element is forced against the valve seat, the angled seat 6 will engage the seal ring bevel 20 and force the seal ring distal side axially against the distal shoulder, thereby forcing the seal ring radially against the groove bottom 14. With sufficient pressure the seal ring may expand axially to wedge inside the groove between the shoulders.

Fig. 7 illustrates a view similar to Fig. 6 but in a situation where the closure element has been axially displaced a short distance away from the closed condition.

On most occasions the seal ring will simply stay in the groove in the position as illustrated in Fig. 6 while the closure element is being moved away from the seat. However, in case the fluid pressure on the proximal side of the cone 7, i.e. above the cone as illustrated in Figs. 6 and 7, substantially exceeds the fluid pressure at the distal side, i.e. below the cone, it might happen that this fluid pressure would find its way between the proximal shoulder 9 and the seal ring proximal side 16 into the groove bottom 14, where it would exert a radial pressure on the seal ring inner margin 18. Fig. 7 illustrates a situation where this has happened, and where the pressure has been sufficient to actually expand the ring radially to a position, where the ring inner margin is spaced from the groove bottom 14.

In the position shown in Fig. 7, the ring has expanded radially, but it is still guided by the proximal shoulder as well as by the distal shoulder. The fluid pressure will prevail all over the seal ring proximal side 16. As the outer peripheral portion of the seal ring is however no longer backed by the distal shoulder 12, the fluid pressure will tend to distort or tilt the seal ring, whereby the inner edge of the seal ring proximal side will be forced against the proximal shoulder 9. This engagement due to distortion of the ring will add to the frictional forces which will act on both sides of the ring and which will serve to check further expansion.

According to the invention the dimensions of the ring and of the groove and the choice of materials are adapted in view of the maximum rated pressure in order that the ring will never be expanded beyond the point, where it is still guided between both of the shoulders, i.e. roughly the situation depicted in Fig. 7. Thus, on further axial displacement of the closure element, the seal ring will move no further and the seal ring bevel 20 will lift off the valve seat 6 to relieve the differential fluid pressure. Once the fluid pressure is relieved, the ring will retract into the bottom of the groove by its inherent resilience.

The design has been tested in a valve wherein the diameter of the groove was 136 mm, the outer diameter of the cone lip portion 8 was 146 mm, and the outer diameter of the seal ring outer margin 19, when the seal ring was seated in the groove, was 156 mm. The outer diameter of the cone rim portion was 161 mm, however, due to the distal shoulder bevel, the outer diameter of the distal shoulder was only 155 mm. Thus, the distal shoulder provides support for practically the entire distal ring surface.

The radial width of the seal ring was 10 mm, which is about 13% of the radius of the seal ring outer margin (78 mm) . The axial width of the seal ring was 3 mm. The material was polytetrafluorethylene with 13% carbon. It may be calculated that this design permits a radial expansion of 7.4% before the seal ring clears the proximal shoulder and the cone lip portion. It may be further calculated that the maximum radial expansion of the seal ring by a fluid pressure of 40 bars would be 5%, thus well within an acceptable limit. During testing, however, the ring stayed in contact with the bottom of the groove at all times.

Although various components have been explained in particular detail above, it should be remembered that this explanation has the sole purpose of exemplifying how the invention might be practised but is in no way intended to limit the scope of the invention which is defined exclusively by the appended patent claims.

Claims

PATENT CLAIMS

1. A fluid control valve comprising a substantially conical valve seat, a closure element and means for displacing the closure element axially relative to the valve seat between a position in sealing contact with the valve seat and a position spaced from the valve seat,

-wherein the closure element comprises a valve cone with a circumferential groove, defined by a first shoulder, proximal to the valve seat, a second shoulder, distal from the valve seat, and a bottom surface, and an annular seal comprising a flat seal ring of a resilient material, received in the groove,

-wherein the annular seal and the peripheral groove are matched for mutual engagement in order that annular seal will, in the absence of external influences, rest in the groove with the major portion of that side of the seal, which is situated distally from the valve seat, backed by the second shoulder, while the opposite side of the seal is guided by the first shoulder,

-whereas the seal is adapted to yield resiliently to expand radially, if not constrained peripherally and if subjected to fluid pressure on the inner margin and on that side of the seal, which is situated proximally to the valve seat, to reach a position, where the inner portion of the ring is spaced from the bottom surface, but still guided by the shoulders of the groove, from which position the seal will retract resiliently into the bottom of the groove, once the fluid pressure is relieved.

2. The fluid control valve according to claim 1, wherein the seal ring and the groove are adapted for mutual- cooperation in order that the seal ring may expand radially to a position, where an outer peripheral portion of the seal projects ' beyond the second shoulder, whereby the seal ring distorts by the fluid pressure to increase the friction between the seal ring sides and the shoulders, and thereby to check further expansion.

3. The fluid control valve acording to claim 1, wherein the first shoulder and the seal ring are sized for cooperating engagement, in order that the first shoulder engages the inner portion of the ring proximal side, through a radial expansion of the ring of at least 6% but no more than 9% of the ring outer diameter.

4. The fluid control valve according to claim 1, wherein the seal ring proximal side is substantially parallel to the seal ring distal side and the shoulders are substantially mutually parallel and spaced to receive the seal ring with axial play.

5. The fluid control valve according to claim 4, wherein the axial play is in the range from 2% to 20% of the ring axial dimension.

6. The fluid control valve according to claim 1, wherein the seal ring and the groove are matched for mutual cooperation in order that displacing the closure element into sealing contact with the valve seat, will cause the seal ring to be forced against the groove bottom and to be expanded axially, whereby it is wedged between the groove shoulders .

7. The fluid control valve according to claim 1, wherein the second shoulder provides an annular, planar surface, perpendicular to the valve axis.

8. The fluid control valve according to claim 1, wherein the seal ring comprises a material with properties in respect of resilience, hardness and recovery similar to those of polytetrafluorethylene modified with carbon or graphite.

9. The fluid control valve according to claim 1, wherein the seal ring comprises a ring with a generally rectangular section outline, bevelled at the outer, proximal corner, the radial width of the ring being at least two and a half times, and preferably at least three times the axial width of the ring.

10. The fluid control valve according to claim 9, wherein the ring radial width is at least 10% of the radius of the ring outer margin, when the ring is installed.