Gate valve body with improved seal groove

Abstract

A valve body portion (12 figure 2) of a knife gate valve (10 figure 2) comprises an outer peripheral portion (44 figure 2) surrounding a central opening (30 figure 2) with a lower seal groove (60 figu

Description

TECHNICAL FIELD

[0001] This disclosure relates to industrial valves of the knife gate type, and particularly relates to a knife gate valve body having an improved seal groove for extending the service life of the seal. BACKGROUND

[0002] Industrial knife gate valves are commonly used is a variety of industries to regulate the flow of a fluid media through a pipe system, which is typically comprised of a multitude of pipes connected together to provide a pathway for transportation of fluid media from one point to another. The placement of a gate valve between adjacent pipes in the pipe string allows for selective interference of the flow of media from one pipe to the next by obstructing or isolating the pathway between adjacent pipes.

[0003] Knife gate valves generally comprise a valve body formed with a central opening and a peripheral frame or sides that surround the central opening. A gate, generally comprising a flat plate-like structure, is positioned to pass through the valve body to obstruct the central opening. An elastomeric seal is located about the inner circumference of the central opening and registers against the sides of the gate as it moves between open and closed positions relative to the central opening. The seal is compressed against the valve body by the lateral sides of the gate as the gate moves through the valve body, thereby sealing against in-line leakage.

[0004] Problems associated with prior art knife gate valves are illustrated in more detail with reference to FIG. 1, which is a partial sectional view in elevation depicting part of a knife gate valve 1 having an in-situ O-ring seal 2 in a conventional groove 3 defined by a rear body portion 4 and a front body portion 5 coupled thereto. A conventional knife gate 6 defines opposing planar front and rear sides 6a,b. The rear side 6b is shorter than the front side 6a. The knife gate 6 defines a profiled lower surface comprising a beveled edge 7 extending from a lower part of the rear side 6b towards the front side 6a, and a flat surface 8 extending from the front side 6a to the beveled edge 7. The rear body portion 4 defines a sloping portion 9 complementary to the slope of the beveled edge 7 of the knife gate 6 and extending to the groove 3. The groove 3 is substantially arcuate in cross section. CO

[0005] As shown in FIG. 1, the bottom portion of the knife gate 1 is formed with a beveled edge 7 which aids in stopping the flow and compressing the O-ring seal 2 along its perimeter during closing, and the beveled edge 7 acts as a secondary metal seat after complete closure of the gate. The flat surface 8 of the knife gate 6 registers against the O-ring seal 2 and causes compression thereof within the groove 3 housing the O-ring seal 2 to complete the seal and to prevent in-line leakage.

[0006] As the profiled lower surface of the knife gate valve 1 approaches the rear body portion 4, the flat surface 8 contacts the O-ring seal 2 retained within the seal groove 3. The flat surface 8 compresses the O-ring seal 2 causing the O-ring seal 2 to be extruded outwardly along the sloping portion 9, and potentially being nipped between the beveled edge 7 and the sloping portion 9. After repeated openings and closings of the knife gate 6 in normal operation, the compression of the flat surface 8 against the O-ring seal 2 causes wear and tear of the O-ring seal 2. The wear on the O-ring seal 2 reduces the serviceable life of the O-ring seal 2 and necessitates replacement thereof.

[0007] It is among the objects of an embodiment of the present invention to obviate or mitigate the above disadvantages or other disadvantages of the prior art, or to provide a useful alternative. SUMMARY

[0008] Features of one aspect described below may be applied to other aspects.

[0009] According to the invention, there is provided a knife gate valve comprising (i) a valve body having a first body side and a second body side, each having a continuous outer peripheral portion for mutually coupling together, and each having an inner circumferential surface defining a central opening having a longitudinal axis extending therethrough; (ii) a knife gate positioned for slidable movement within the valve body transverse to the longitudinal axis to selectively move from an open position, where the knife gate is located away from the central opening, to a closed position, where the knife gate blocks the central opening, the knife gate having a lower angled edge; (iii) a lower seal groove formed in a lower sector portion of one or both of the first body side or the second body side, the lower seal groove defining (a) a seal mounting area and (b) an expansion cavity adjacent the seal mounting area; and (iv) an elastomeric seal having a circular cross section and being (a) located only LO CM within the seal mounting area when the knife gate is in the open position, (b) located in both the seal mounting area and the expansion cavity when the knife gate is in the closed position, (c) maintained in compression in the direction of the longitudinal axis when the knife gate is in both the open and closed positions, and (d) maintained in compression in both the direction of the longitudinal axis and the direction transverse to the longitudinal axis, when the knife gate is in the closed position.

[0010] The expansion cavity may comprise a recess defined by an angular wall, an arcuate wall, or a wall having a first radius.

[0011] The lower seal groove may further comprise an overhang extending from a side of the seal mounting area to above and partially overlapping the seal mounting area. The overhang is configured to prevent the elastomeric seal from being deformed upwards.

[0012] The overhang may extend to an area above the seal mounting area adjacent to an area onto which a flat area of a gate comes into contact.

[0013] The overhang may extend over the seal mounting area by between 5% and 50% of the width of the elastomeric seal, or between 10% and 35% of the width of the elastomeric seal, or between 15% and 30% of the width of the elastomeric seal.

[0014] The overhang may comprise an angled wall, an arcuate wall, or a wall having a second radius.

[0015] In an unclaimed aspect, a valve body portion comprises an outer peripheral portion surrounding a central opening having a longitudinal axis extending therethrough, the outer peripheral portion has an inner face oriented for positioning against another valve body portion, in use, and an outer face oriented to connect to a pipe flange in use, and the outer peripheral portion has an inner circumferential surface that defines the central opening; and a lower seal groove being formed along a lower sector of the central opening and positioned adjacent to and contiguous with the inner face of the outer peripheral portion, the lower seal groove having a wall surface comprising an angled floor surface and two radii. The valve body portion having the lower seal groove as structured provides a particular advantage in providing for extended service life of the seal.

[0016] In certain embodiments, the valve body portion further comprises an angled shoulder formed along the inner circumferential surface adjacent the lower seal groove, the angled shoulder extending from the inner circumferential surface to LO CM a terminal point of the wall surface of the lower seal groove and being angled in a direction toward the angled floor of the lower seal groove or toward the inner face of the outer peripheral portion.

[0017] In some embodiments, the angled shoulder extends along a lower one-third sector of the central opening.

[0018] In other embodiments, the angled floor of the lower seal groove extends along the wall surface in a direction away from an inner edge of the lower seal groove that is contiguous with the inner face of the outer peripheral portion and slopes in a direction away from the longitudinal axis of the central opening.

[0019] In certain embodiments, a first radius of the lower seal groove is formed adjacent to the angled floor of the wall surface and is spaced from the inner edge of the lower seal groove.

[0020] In still other embodiments, a second radius of the lower seal groove is formed adjacent to a terminal point of the wall surface, the terminal point of the wall surface being contiguous with the sloped shoulder. [0021 ] In some embodiments, an intermediate section of the wall surface extends between the first radius and the second radius.

[0022] In other embodiments, the intermediate section of the wall surface lies in a vertical plane that is oriented perpendicular to the longitudinal axis of the central opening.

[0023] In yet other embodiments, the valve body portion further includes an upper portion extending from the outer peripheral portion and in a direction away from the central opening, the upper portion being structured with opposing lateral sides that extend, in part, along the central opening, and wherein a lateral groove is formed along each of said lateral opposing sides for receiving an elastomeric seal therein.

[0024] In certain embodiments, the lateral groove formed in each of said opposing lateral sides is contiguous with the lower seal groove. In an unclaimed aspect, a knife gate valve comprises a valve body having a first body side and a second body side, each of the first body side and the second body side being structured with a continuous outer peripheral side, the outer peripheral side of the first body side being connected to the outer peripheral side of the second body side and each having an inner circumferential surface; a central opening located within the outer peripheral side of the first body side and the outer peripheral side of the second body side, the central opening being defined by the inner circumferential surfaces of the first body side and the second body side and having a longitudinal axis extending through the central opening; a knife gate positioned for slidable movement within the valve body to selectively move from a first position, where the knife gate is located away from the central opening, to a second position, where the knife gate is located to obstruct the central opening, the knife gate having a lower beveled edge; and a lower seal groove formed in a lower sector portion of one of the first body side or the second body side, thereby defining a grooved body side, the lower seal groove being structured to receive an elastomeric seal therein and being positioned to locate the lower beveled edge of the knife gate thereagainst, and wherein the lower seal groove has a wall surface that is formed with an angled floor and two radii. CO CM LO CM

[0032] In some embodiments, the knife gate valve further includes an angled shoulder formed in the inner circumferential surface of the grooved body side adjacent the lower seal groove, the angled shoulder extending from the inner circumferential surface of the grooved body side to a terminal point of the wall surface of the lower seal groove and being angled in a direction toward the angled floor of the lower seal groove.

[0033] In certain embodiments, the angled shoulder extends along a lower one-third sector of the central opening.

[0034] In yet other embodiments, the angled floor of the wall surface extends from an inner edge of the lower seal groove, the inner edge being contiguous with an inner face of the grooved body side, and where the angled floor slopes in a-direction away from the longitudinal axis of the central opening.

[0035] In some embodiments, a first radius of the lower seal groove is formed adjacent to the angled floor of the wall surface and is spaced from the inner edge of the lower seal groove.

[0036] In certain other embodiments, a second radius of the lower seal groove is formed adjacent to the terminal point of the wall surface.

[0037] In other embodiments, an intermediate section of the wall surface extends between the first radius and the second radius.

[0038] In yet other embodiments, the intermediate section of the wall surface lies in a vertical plane that is oriented perpendicular to the longitudinal axis of the central opening.

[0039] In still other embodiments, the knife gate valve includes an upper portion extending from the outer peripheral portion and away from the central opening, the upper portion being structured with opposing lateral sides that extend, in part, along the central opening, and wherein a lateral groove is formed along each of the lateral opposing sides for receiving an elastomeric seal therein.

[0040] In some embodiments, the lateral groove formed in each of the opposing lateral sides is contiguous with the lower seal groove.

[0041] These and other features of the disclosure are further clarified in the following description and illustrated elements of the disclosure. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0042] FIG. 1 is a partial sectional view in elevation depicting part of a prior art knife gate valve;

[0043] FIG. 2 is a perspective view of a knife gate valve body and gate in vertical cross section according to one embodiment of the present invention;

[0044] FIG. 3 is an enlarged view of the lower portion of the valve body shown in FIG. 2 surrounded by the dash-dot line;

[0045] FIG. 3B is an enlarged view of a lower portion of the valve body shown in FIG. 3, at an area at which the gate comes into contact with the valve body, with a part (the elastomer ring) removed for clarity;

[0046] FIG. 4 is a perspective view of a valve portion or side of a valve body;

[0047] FIG. 5 is an enlarged view of the lower sector of the valve body portion shown in FIG. 4;

[0048] FIG. 6 is a partial view in elevation of a valve body portion in accordance with another embodiment of the present invention;

[0049] FIG. 7A is an enlarged view of the lower seal groove shown in FIG. 6 showing certain features;

[0050] FIG. 7B is an enlarged view of the lower seal groove shown in FIG. 6 showing other features; and

[0051] FIG. 8 is an enlarged view in elevation of a lower seal groove in accordance with the disclosure, having the lower edge of a knife gate positioned against the lower seal groove. DETAILED DESCRIPTION OF THE INVENTION

[0052] FIGS. 2 and 3 illustrate a type of knife gate valve 10 relevant to the present disclosure. Specifically, the knife gate valve 10, in relevant part, comprises a valve body 12 which includes a first body side (typically a downstream side) 14 and a second body side (typically an upstream side) 16. In use, the first body side 14 and second body side 16 are joined together around their periphery and, in certain configurations, may be secured together by such means as bolts (not shown) being positioned through openings 22 located about the outer periphery face 20 of each of the first body side 14 and second body side 16. In this embodiment, the second body side 16 defines threaded apertures aligning with the apertures 22 defined by the first body side 14.

[0053] Additionally, threaded apertures 18 are provided through the outer periphery face 20 of each of the upstream body side 14 and second body side 16 for receiving bolts (not shown) or the like for attaching the knife gate valve 10 to pipe flanges of pipes in a pipe system, as is known.

[0054] Each of the first body (downstream) side 14 and the second body (upstream) side 16 has an inner circumferential surface 26a, b which, together, define a central opening 30 through the valve body 12 and through which media can flow (from upstream to downstream). The central opening 30 has a longitudinal axis 32 extending therethrough. The upstream side inner circumferential surface (upstream inner surface) 26b is different to the first body side inner circumferential surface (downstream inner surface) 26a in that the upstream inner surface 26b includes an angled portion 33a nearest the gate 28 and a flat portion 33b, as described in more detail below (best seen in FIG. 3B).

[0055] The downstream body side 14 and upstream body side 16, when positioned adjacent to each other, provide a space 34 (best seen in FIG. 4) therebetween in which the gate 28 of the knife gate valve 10 is partially accommodated and can slidably move to protrude therefrom. The gate 28 can be slidably moved from a first position in which the gate 28 is in an open position, located away from the central opening 30 to thereby allow media to flow through the central opening 30, and a second position in which the gate 28, as shown in FIGS. 2 and 3, is in a closed position located to obstruct the central opening 30. The side of the gate 28 nearest the first body side 14 is first side (or downstream side) 28a and the side of the gate 28 nearest the second body side 16 is second side (or upstream side) 28b.

[0056] As best seen in FIG. 3B, the gate 28, which is of a generally plate-like and planar construction, has a profiled lower edge 38 that includes: a bevel (or angled) portion 39a extending from the second side 28b towards the first side 28a, and a flat portion 39b, which is generally horizontal in this embodiment, extending from the first side 28a to the bevel portion 39a. The angled portion 39a is sloped at a similar, but slightly different, angle as the upstream inner surface angled portion 33a. In this embodiment, angled portion 39a extends at approximately 31 degrees to the horizontal; and inner surface angled portion 33a at approximately 30 (or 29.5) degrees to the horizontal. This slight difference in angle slope provides improved sealing.

[0057] When coupled together, the downstream and upstream body sides 14, 16 define a seal groove 40 therebetween, as best seen in FIGS. 3B and 6 to 8, in which an elastomeric seal 42 is located.

[0058] As best seen in FIGS. 4 and 5, which illustrate just the upstream body side 16 (which is a valve body portion) in accordance with an embodiment of the invention, the upstream body side 16 is generally formed in a frame-like configuration having an outer peripheral portion 44 at a lower part thereof, which surrounds the central opening 30.

[0059] The outer peripheral portion 44 has an inner face 46 and the outer periphery face 20. The inner face 46 is oriented for location adjacent an opposing inner face 47 (FIG. 3) of the first (downstream) body side 14 (not shown in FIGS. 4 and 5), when assembled. The outer peripheral portion 44 also defines the inner circumferential surface 26b.

[0060] The upstream body side 16 also has an upper portion 58 which extends from the outer peripheral portion 44 and in a direction away from the central opening 30. The upper portion 58 defines the space 34 between in the gate 28 is partially accommodated and through which it is movable. The upper portion 58 and outer peripheral portion 44 are contiguous.

[0061] As seen in FIGS. 4 and 5, a groove 60 is formed in opposing lateral sides 62 of the upper portion 58 of the upstream body side 16. The lateral grooves 60, at either lateral side 62 of the upper portion 58, extend to a lower portion 64 of the upstream body side 16, and extend in part on either side of the central opening 30. The lateral grooves 60 join with the seal groove 40 at the lower portion 64.

[0062] The seal groove 40 generally extends along the lower one-third sector of the central opening 30. In other embodiments, the seal groove 44 may extend by a greater or lesser amount than a lower one-third sector of the central opening 30.

[0063] The lateral grooves 60 and the seal groove 40 are positioned to retain the elastomeric seal 42 therein. The elastomeric seal 42 is only shown in FIGS. 3 and 8, and in outline in FIG. 7B.

[0064] The seal groove 40 will now be described in more detail, with particular reference to FIGS. 3B, 7A and 7B.

[0065] As best seen in FIG. 7A, the groove 40 comprises three main features: a seal mounting area 66, an expansion cavity 67, and an overhang 68.

[0066] The seal mounting area 66 accommodates the elastomeric seal 42 when the gate 28 is in the open or partly closed position.

[0067] The expansion cavity 67 is a recess adjacent a lower part of the seal mounting area 66 and on an opposite side thereof to the downstream body side 14. In this embodiment, the expansion cavity 67 comprises an arc shape in the form of a radius, but other arcuate or angular shapes may be used. In this embodiment, the expansion cavity 67 can accommodate up to 15% of the volume of the elastomeric seal 42, but in other embodiments, the expansion cavity 67 may be larger or smaller.

[0068] The overhang 68 extends from a side of the seal mounting area 66 furthest from the downstream body side 14 to above and partially overlapping the seal mounting area 66. The overhang 68 is configured to prevent the elastomeric seal 42 from being deformed upwards. In this embodiment, the overhang 68 extends over the seal mounting area 66 by between 10% and 30% of the diameter (or width) of the elastomeric seal 42. In other embodiments, a greater or smaller overlap may be used.

[0069] The groove 40 is primarily defined by a wall surface 70 that extends from an inner edge 72 to a terminal point 74. The inner edge 72 is contiguous with the inner face 46 of the outer peripheral portion 44 of the second body side 16. The terminal point 74 defines the lower edge of the angled portion 33a of the upstream inner surface 26b and an upper part of the groove 40. The angled portion 33a is angled downwards from the flat surface 33b.

[0070] The angled portion 33a may extend along the lower one-third sector of the central opening 30 commensurate in length or distance to the extension of the seal groove 40 along the lower one-third sector of the central opening 30.

[0071] It is to be understood that the seal groove 40 may extend along the lower portion of the central opening 30 to a degree greater or lesser than an exact one-third of the lower sector of the central opening 30. Likewise, the angled portion 33a may extend to a degree greater or lesser extent than an exact one-third of the lower sector of the central opening 30.

[0072] The wall surface 70 comprises a sloping floor 80 that is angled away from the longitudinal axis 32 of the central opening 30 as it extends in a direction away from the inner edge 72.

[0073] The wall surface 70 further comprises two radii, both of which extend along the length of the seal groove 40 in the lower sector of the central opening 30. A first radius 82 is located adjacent to the sloping floor 80 of the wall surface 70 and is spaced from the inner edge 72. A second radius 84 is located adjacent to the terminal point 74 of the wall surface 70. The wall surface 70 may further comprise an intermediate section 86 that extends between the first radius 82 and the second radius 84. The intermediate section 86 may lie in a vertical plane X which is oriented perpendicularly to the longitudinal axis 32 of the central opening 30.

[0074] While the size and dimensions of the seal groove 40 will vary depending on the size of the knife gate valve 10, the angle of slope a of the sloping floor 80 may be between five degrees and twenty degrees, as measured between a plane A, which is parallel to the longitudinal axis 32 of the central opening 30 and in which the inner edge 72 lies, and a plane B in which the sloping floor 80 lies.

[0075] The angle of slope [3 of the angled portion 33a may be between twenty-five degrees and forty-five degrees as measured between a plane C, which is parallel to the longitudinal axis 32 of the central opening 30 and in which the terminal point 74 lies, and a plane D in which the angled portion 33a lies. The arc of radius of the first radius 82 and second radius 84 will also vary depending on the size of the knife gate valve 10.

[0076] As best seen in FIG. 7B, when the elastomeric seal 42 (in this embodiment, the elastomeric seal 42 is in the form of an elastomer tube) is located within the seal groove 40, the second radius 84 acts on an upper portion of the elastomeric seal 42 to urge it downwards in the event that it is compressed. This prevents the elastomeric seal 42 from extruding between the angled portions 33a and 39a and being damaged thereby.

[0077] The first radius 82 provides an expansion cavity 90 into which the compressed elastomeric seal 42 can move, in preference to being extruded between the angled portions 33a and 39a.

[0078] In other embodiments, the expansion cavity may be provided by a recess that is curved (but does not have a single radius) or angular. The function provided by the expansion cavity is to allow the elastomeric seal 42 to move without being trapped between a fixed and a moving part.

[0079] The operation of the valve 10 will now be described.

[0080] As the gate 28 is lowered to the closed position, the first side (or downstream side) 28a comes into close sliding contact with the opposing inner face 47 (FIG. 3) of the first (downstream) body side 14. This provides support for the gate 28 against the forces exerted by the medium flow as it is stopped by closing the valve 10. [0081 ] The flat portion 39b of the gate 28 then comes into contact with an upper part of the elastomeric seal 42 and compresses it, which urges it downwards. The terminal point 74 prevents the elastomeric seal 42 from rising upwards, and expansion cavity 90 provides an area in which the elastomeric seal 42 can deform into. As a result, no part of the elastomeric seal 42 protrudes between the angled portion 33a of the upstream inner surface 26b and the angled portion 39a of the gate 28 (specifically the profiled lower edge 38 of the gate 28).

[0082] The angled portion 39a of the gate 28 then comes into contact with the angled portion 33a of the upstream inner surface 26b thereby provided a seal therebetween to prevent fluid leakage.

[0083] The particular configuration of the seal groove 40 being provided with a sloping floor 80 and two radii 82, 84 provides for the deformation of the elastomeric seal 42 into the architecture of the wall surface 70 so that the elastomeric seal 42 is retained within the groove 40 and allows efficient compression against the gate 28, thereby enhancing the sealing function. As a result, the service life of the elastomeric seal 42 is extended.

[0084] In other embodiments, although less preferred, the orientation of the valve 10 may be reversed so that the first body side 14 is used as the upstream side and the second body side 16 is the downstream side.

[0085] In other embodiments, groove 40 may be formed in the first body side 14 instead of the second body side 16, or partly in each of the first and second body sides 14, 16 so that the assembled valve body provides the groove.

[0086] In other embodiments, the groove 40 may have a different shape, in particularly the expansion cavity may be located in a different part of the groove than described above.

[0087] In the foregoing description of certain embodiments, specific terminology has been resorted to for the sake of clarity. However, the disclosure is not intended to be limited to the specific terms so selected, and it is to be understood that each specific term includes other technical equivalents which operate in a similar manner to accomplish a similar technical purpose. Terms such as "upper" and "lower", "above" and "below" and the like are used as words of convenience to provide reference points and are not to be construed as limiting terms.

[0088] In this specification, the word “comprising” is to be understood in its “open” sense; that is, in the sense of “including”, and thus not limited to its “closed” sense, that is, the sense of “consisting only of”. A corresponding meaning is to be attributed to the corresponding words “comprise", "comprised" and "comprises" where they appear.

[0089] The preceding description is provided in relation to several embodiments which may share common characteristics and features. It is to be understood that one or more features of any one embodiment may be combinable with one or more features of the other embodiments. In addition, any single feature or combination of features in any of the embodiments may constitute additional embodiments. In addition, the foregoing describes only some embodiments of the disclosed structures, and alterations, modifications, additions and / or changes can be made thereto without departing from the scope and spirit of the disclosed embodiments, the embodiments being illustrative and not restrictive. Reference Numerals Knife gate valve 10 Valve body 12 First (downstream) body side 14 Second (upstream) body side 16 Threaded apertures 18 Outer periphery face 20 Openings 22 Downstream inner surface 26a Upstream inner surface 26b Gate 28 Downstream side of gate 28a Upstream side of gate 28b Central opening 30 Longitudinal axis 32 Upstream inner surface angled portion 33a Upstream inner surface flat portion 33b Space 34 Profiled lower edge 38 Angled (beveled) portion 39a Flat portion 39b Seal groove 40 Elastomeric seal 42 Outer peripheral portion 44 Inner face (of outer peripheral portion) 46 Opposing inner face (of downstream body side) 47 Upper portion (of upstream body side) 58 Lateral groove (in upper portion) 60 Lateral sides (of upper portion) 62 Lower portion (of upstream body side) 64 Seal mounting area 66 Expansion cavity 67 Overhang 68 Wall surface (of groove) 70 Inner edge (of groove) 72 Terminal point (of groove) 74 Sloping floor 80 First radius 82 Second radius 84 Intermediate section 86 Expansion cavity 90

Claims

1. A knife gate valve, comprising:(i) a valve body having a first body side and a second body side, each having a continuous outer peripheral portion for mutually coupling together, and each having an inner circumferential surface defining a central opening having a longitudinal axis extending therethrough;(ii) a knife gate positioned for slidable movement within the valve body transverse to the longitudinal axis to selectively move from an open position, where the knife gate is located away from the central opening, to a closed position, where the knife gate blocks the central opening, the knife gate having a lower angled edge;(iii) a lower seal groove formed in a lower sector portion of one or both of the first body side or the second body side, the lower seal groove defining:(a) a seal mounting area and(b) an expansion cavity adjacent the seal mounting area; and(iv) an elastomeric seal having a circular cross section and being:(a) located only within the seal mounting area when the knife gate is in the open position,(b) located in both the seal mounting area and the expansion cavity when the knife gate is in the closed position,(c) maintained in compression in the direction of the longitudinal axis when the knife gate is in both the open and closed positions, and(d) maintained in compression in both the direction of the longitudinal axis and the direction transverse to the longitudinal axis, when the knife gate is in the closed position.

2. The knife gate valve of claim 1, wherein the expansion cavity comprises a recess defined by an angular wall, an arcuate wall, or a wall having a first radius.

3. The knife gate valve of claim 1 or 2, wherein the lower seal groove further comprises an overhang extending from a side of the seal mounting area to above and partially overlapping the seal mounting area.

4. The knife gate valve of any of claims 1 to 3, wherein the overhang extends to an area above the seal mounting area adjacent to an area onto which a flat area of a gate comes into contact.

5. The knife gate valve of claim 4, wherein the overhang extends over the seal mounting area by between 10% and 30% of the width of the elastomeric seal.

6. The knife gate valve of any of claims 1 to 5, wherein the overhangcomprises an angled wall, an arcuate wall, or a wall having a second radius.7.The knife gate valve of any preceding claim, wherein the expansion cavity extends below a lowest point of the elastomeric seal.LO CM

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