Valve for large scale irrigation

Abstract

A valve assembly (10) for large scale irrigation including a valve body (20) and a valve head (40). The valve head is adapted to reciprocally travel along a longitudinal axis, supported by a longitudinally aligned shaft (60) inside the valve body. The valve head includes a wall (41) terminating in a peripheral sealing contact surface (42), the wall extending inwardly from the peripheral contacting surface.

Claims

1. A valve assembly including a valve body and a non-planar valve head adapted to be fitted to a water supply line, wherein: the valve head is adapted to reciprocally travel along a longitudinal axis, supported by a shaft longitudinally aligned parallel to a general direction of water flow from the supply line; and the valve head includes a wall terminating in a peripheral sealing contact surface for sealing engagement with a valve seat in the valve body, the valve seat defining a valve opening that is adapted to be releasably sealed by the valve head and continuous with the supply line when the valve assembly is in an open position, the wall extending inwardly from the peripheral sealing contacting surface toward the shaft, wherein: the wall is in the form of a skirt and the peripheral sealing contact surface is in the form of a terminal edge that is formed from a downwardly depending edge of the wall; the width of the terminal edge corresponds to or is narrower than the wall thickness; the valve body has a wide base at its upstream end and a narrower neck at its downstream end; the shaft is secured radially relative to the valve body using at least two axially spaced bearing surfaces; interposed between the axially spaced bearing surfaces is a spring bias against the open position; and the valve head is adapted to axially shift toward downstream to an extent that its displacement distance is of a magnitude at least one quarter of the diameter of a valve opening to provide sufficient clearance by the valve head.

2. The valve assembly of claim 1, wherein the valve body is in the form of a truncated cone.

3. The valve assembly of claim 1, wherein the valve seat has a resiliently deformable surface.

4. The valve assembly of claim 1, wherein the wall is in the form of a dome.

5. The valve assembly of claim 1, wherein the wall terminates in and forms the peripheral sealing contact surface.

6. The valve assembly of claim 1, wherein the valve head is co-axially mounted to the shaft that is secured using an upper bearing surface located at or near the neck of the valve body.

7. The valve assembly of claim 6, wherein the at least two axially spaced bearing surfaces include a lower bearing surface located at or near the base of the valve body.

8. The valve assembly of claim 1, wherein the at least two axially spaced bearing surfaces include a first bearing surface that is located in an aperture at the apex of a dome of the valve head.

9. The valve assembly of claim 8, wherein the at least two axially spaced bearing surfaces include a second bearing surface that is located in a co-axially aligned plate bearing that is formed in a central aperture located in an internal plate through which the shaft passes.

10. The valve assembly of claim 1, wherein the valve body has a wider diameter end positioned lower than an upper narrower neck.

11. The valve assembly of claim 1, wherein the shaft is adapted for reciprocal linear travel in a dampener cylinder.

12. The valve assembly of claim 11, wherein a portion of the shaft extends into the dampener cylinder and the cylinder includes one or more apertures extending through the cylinder's wall that are adapted to progressively allow displacement of fluid in a bore of the cylinder as a terminal end of the shaft travels towards an end of the cylinder.

13. The valve assembly of claim 1, wherein in a sealed and closed position, the valve head maintains the integrity of its shape and structure.

14. The valve assembly of claim 6, wherein the upper bearing surface is laterally secured using an upper bracket attached to the valve body.

15. The valve assembly of claim 14, wherein the lower bearing surface is laterally secured using a star shaped bracket having one or more lateral spokes.

16. The valve assembly of claim 1, wherein the valve head is adapted to axially travel a maximum distance which is a displacement distance of a magnitude at least one quarter of a diameter of the aperture to provide sufficient clearance by the valve head such that water flow in a downstream direction is unimpeded as it flows into a space between the valve seat and the valve head and around the sides of the valve head as it travels in the downstream direction.

17. The valve assembly of claim 9, wherein, together with the valve head, the internal plate defines a cavity in the valve head.

18. The valve assembly of claim 9, wherein the skirt extends beyond the junction of an internal surface of the valve head and a peripheral edge of the internal plate.

19. The valve assembly of claim 1, wherein the valve head is formed from a hemi-spherical component.

20. A valve assembly including a valve body and a valve head fitted to a supply line, wherein: the valve head is adapted to reciprocally travel along a longitudinal axis, supported by a shaft longitudinally aligned parallel to a general direction of water flow from the supply line; and the valve head includes a wall terminating in a peripheral sealing contact surface for sealing engagement with a valve seat in the valve body, the valve seat defining an aperture that is continuous with the supply line when the valve assembly is in an open position, the wall extending inwardly from the peripheral sealing contacting surface toward the shaft, wherein: the wall is in the form of a skirt and the peripheral sealing contact surface is in the form of a terminal edge which corresponds to or is narrower than the wall thickness, and the valve body and the valve head are formed from a single dome piece.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention may be better understood from the following non-limiting description of preferred embodiments, in which:

(2) FIG. 1 is a sectional side elevation of a valve assembly according to a preferred embodiment;

(3) FIG. 1b is a sectional side elevation of the valve assembly shown in FIG. 1a, but with a valve head in an open position;

(4) FIG. 2 is a sectional isometric view of a valve head and shaft combination according to the embodiment shown in FIG. 1a;

(5) FIG. 3a is a isometric sectional view of a dampener component of the valve assembly shown in FIG. 1a in a closed position;

(6) FIG. 3b is an exploded isometric sectional view of the dampener component shown in FIG. 3a;

(7) FIG. 4a is a sectional side elevation of the dampener shown in FIG. 3a;

(8) FIG. 4b is a sectional side elevation of the dampener shown in FIG. 4a in an open position;

(9) FIGS. 5a-5b are exploded isometric views of the valve assembly shown in FIG. 1a;

(10) FIG. 6a is an upper exploded isometric view of the valve assembly shown in FIG. 1a;

(11) FIG. 6b is a lower exploded isometric view of the valve assembly shown in FIG. 1a;

(12) FIG. 7a is a lower isometric view of the valve assembly shown in FIG. 1b;

(13) FIG. 7b is a lower isometric view of the valve assembly shown in FIG. 1a;

(14) FIG. 8 is a side sectional view of a valve assembly according to a second embodiment shown in a closed position, with an open position of the valve head shown in ghosted outline;

(15) FIG. 9a is a top plan view of the valve assembly shown in FIG. 8;

(16) FIG. 9b is a side sectional view of the valve assembly according to the second embodiment, with the valve head shown in open and closed positions;

(17) FIG. 10 is a side plan view of components of a support structure used in the valve assembly of the second embodiment;

(18) FIG. 11a is a top plan view of a valve assembly according to a third embodiment shown;

(19) FIG. 11b is a side sectional view of the valve assembly according to the third embodiment, with the valve head shown in open and closed positions;

(20) FIG. 12 is a side sectional view of a valve assembly according to a fourth embodiment, with the valve head shown in open and closed positions;

(21) FIG. 13 is a side sectional view of a valve assembly according to a fifth embodiment, with the valve head shown in open and closed positions;

(22) FIG. 14 is a schematic side sectional view of a valve assembly according to a sixth embodiment; and

(23) FIG. 15 is a schematic side sectional view of a valve assembly according to a seventh embodiment

DETAILED DESCRIPTION OF THE DRAWINGS

(24) Preferred features of the present invention will now be described with particular reference to the accompanying drawings. However, it is to be understood that the features illustrated in and described with reference to the drawings are not to be construed as limiting on the scope of the invention.

(25) Referring to the drawings and particularly FIGS. 1a and 1b, there is shown a valve assembly for large scale irrigation. The valve assembly 10 includes a valve body 20, a valve head 40 and a central shaft 60.

(26) The valve body 20 comprises a truncated cone wall 21 having a wide base 22 and an upper narrower neck 23 with an upper terminal collar, flange or circular plate 24 defining an upper valve body opening 32.

(27) The base 22 has mounted by welding to its lower edge a rigid circular plate member 25 that may be formed by welding a pair of 6 mm thick circular plates 26 in super imposed relationship together. The upper surface of the base is formed from a third layer of hard rubberised material 27, such as nitrile (acrylonitrile butadiene) rubber, that forms a valve seat. The lower most plate 26b of the base includes a triplet of circumferentially spaced radial spokes 28. The spokes 28 may meet at a central position in a lower central bearing surface or ring 29 into which there may be inserted a lower bearing surface 30 having a low-friction (e.g. PTFE) internal surface to facilitate the axial reciprocal travel of the shaft 60 therein. Rather than three, there may be two or four or more spokes 28 and they may be spiral or otherwise outwardly extending from the ring 29, but a triplet of radial spokes is preferred for strength, symmetry and minimal interference with water flow.

(28) The base 25 defines a central valve opening 31. Similarly, the upper plate 24 defines the upper central open end 32 and has a triplet of radial spokes 33 that laterally secure an upper central ring 34 into which an upper bearing 35 is mounted to locate the upper section 61 of the shaft 60 against radial movement, whilst permitting the shaft 60 to reciprocally travel along a longitudinal axis 36 of the valve body 20.

(29) The valve head 40 comprises a semi-spherical dome 41 having a dome wall 41a terminating in a lower peripheral edge 42 and having a central aperture 43 at its apex 43b through which an intermediate portion 62 of the shaft 60 extends. The intermediate portion 62 is fixed to an intermediate bearing surface 63, the lower most end 64 of which is welded to the apex 43b of the dome 41 surrounding the aperture. Therefore, the shaft 60 and valve body 40 are fixed and move together.

(30) Inserted within the dome 41 and lying in a plane 44 normal to the longitudinal axis 36 is an internal plate 45 that is solid, impervious and preferably disc-shaped, but for a central aperture 46 through which the lower portion 65 of the shaft 60 extends. Of course, the internal plate 45 could be replaced by two or more circumferentially spaced radial braces, but a solid plate is preferred to exclude fluid from the inner space of the dome 41, which may effect turbulence. The lower portion 65 is welded in fixed relationship to the internal plate 45, so that the valve head 40 is laterally and torsionally stabilised relative to the shaft 60 by virtue of the fixed attachment points at the apertures 43, 46.

(31) Interposed between the intermediate bearing 63 and the upper bearing 35 is an axial compression spring 66 that provides bias against the open position shown in FIG. 1b and urges the valve body 40 towards the closed position shown in FIG. 1a.

(32) The internal plate 45 is inserted into the dome 41 to an extent between about 3%-50% of the height 47 of the dome. The height of the dome may be measured from a point taken from the lower edge 42 up to a position laterally equivalent to the apex 43b. The lower portion of the dome wall 41 may provide a skirt 48. The lower edge may be beaded, folded, flattened for a broad surface, or bevelled or sharpened, for example by laser cutting. The skirt 48 advantageously terminates in the sharp lower edge 42. Accordingly, the lower edge may be in width advantageously the equivalent of the thickness of the dome wall 41. Or the edge 42 may be bevelled to provide a sharper edge. For a broader edge, the dome may be cut through a plane parallel to plane 44 or the lower edge 42 may be rolled into a bead or bent into a shoulder or flange.

(33) In use, upon the valve head 40 being urged downwardly into abutment with the base 25 and, more particularly, the valve seat 27, the lower edge 42 deforms the corresponding contacting surface of the valve seat 27, or causes an indentation therein without breaking the integrity of the surface thereof, to ensure a good seal. The seal is improved by the spring 66 bias and the head of water on the upper (downstream) side of the base 25.

(34) To open the valve assembly 10, an upstream 2 pump may be activated to provide positive pressure on the lower (upstream) side 2 of the base 25 thereby forcing the valve body 20 upwardly as water enters a recess 49 defined by the skirt 48 and the lower surface of the internal plate 45. Where the internal plate 45 is a solid plate and not substituted with radial braces, for example, water does not enter the cavity 50 defined by the upper section of the dome wall 41 and the upper surface of the internal plate 45. The valve head 40 is adapted to axially shift upwardly (towards downstream) to an extent whereby water entering the valve opening 31 is substantially unimpeded by the valve head 40. The applicant has found that a displacement distance 51 of a magnitude at least one quarter of the diameter of the valve opening 31 provides sufficient clearance by the valve head 40 such that water flow in the direction 4 is unimpeded as it flows into the intervening space 52 between the base 25 and the valve head 40 and around the sides of the valve head 40 as it travels in the downstream 4 direction.

(35) As shown in FIGS. 3a-4b, a dampener 80 may be mounted to the lower bearing 30 and star bracket 28. The dampener 80 comprises a cylinder 81 with a central bore 82 sized to receive the lower shaft portion 65 in a substantially tight, but low friction relationship in which the lower shaft portion 65 (refer to FIG. 2) is adapted to travel axially within the bore 82. When the valve head 40 is in the open position, the lower portion 65 of the shaft 60 travels axially upwardly out of the bore 82 and is retained in the corresponding and coaxial bore of the lower bearing 30.

(36) If inflow into the valve assembly 10 ceases, for example because an upstream 2 pump is turned off, the head of water downstream 4 and filling the valve body 20 cavity 50 provides a head of pressure that may vary between 1 and 20, more typically 3-18, and most typically 3-6 metres head of pressure, depending on the local application and conditions. This head of pressure bears down on the upper surface of the dome wall 41a and water in the cavity 54 begins rushing through a gap 53 between the lower edge 42 and the valve seat 27, and through the aperture 31. The effect of gravity and the spring 66 bias urges the valve head 40 downwardly towards the valve seat 27. As the lower edge 42 approaches the valve seat 27, water passes through the gap 53 at an ever accelerating rate.

(37) However, the shaft 60 is fixed to and moves with the valve head 40, so that the lower shaft portion 65 enters the central cylinder bore 82 and approaches an end 83 of the bore 82. At the lower end 86 of the cylinder 81, there are provided a series of escape ports 84-85 that provide graduated egress of water trapped in the bore end 83. The lower section 65 of the shaft 60 serves to block the side apertures 84 as it passes thereby to reduce the potential surface area available for egress for water from the bore end 83, so that the downward travel of the shaft 60 is substantially arrested after passing the side apertures 84. A small aperture port 85 is provided at the very end of the bore end 83 to enable the shaft 60 to complete its downward travel to its fullest extent to the bore end 83, thereby permitting downward travel of the shaft, but at a restricted velocity as it approaches the downward end of its travel.

(38) With reference to FIGS. 8-10 a terminal inlet valve 110 is shown according to a second embodiment.

(39) The inlet valve 110 includes a support structure 120. The support structure 120 comprises an arm 120a. The arm 120a is shaped like an arch. The arm 120a is asymmetrical. The arm 120a includes a first leg 121a with a steeply inclined side wall edge 122a, a second spaced leg 121c, and a bridge 121b spanning therebetween. The first leg 121a is contiguous with an upper corner portion 122b at a hinge end of the bridge 121b.

(40) The support structure 120 includes the first arm 120a, and a second arm 120b. The pair of arms 120a,b are the mirror image of each other. The arms 120a,b each include two legs 121a, including the steeply inclined leg 121a and the second leg 121c contiguous with the bridge 121b. The second leg 121c curves up from a base 123, transitioning into the bridge 121b.

(41) The arms 120a,b are positioned to stand in parallel planes P.sub.1,2 spaced from each other.

(42) Apertures for the hinge 125 lie in registration in each corner 122b to receive and support a hinge shaft or a pair of hinge pins extending therethrough. Preferably, a journalled hinge shaft or a spacer sleeve is provided to support the correct spacing of the arms 120a,b in their respective parallel planes P.sub.1,2. The correct spacing is determined by the spacing needed to allow the lever 130 to pivot without being encumbered by the arms 120a,b.

(43) In the corner portion 122b, a hinge 125 is provided. The hinge 125 rotatably supports the lever 130. The spaced support arms 120a,b define a channel 128 in which the lever 130 travels reciprocally in a central plane P.sub.3 as it pivots about the hinge 125. Spacing of the pair of arms 120a,b at their lower portions is achieved by mounting the arms 120a,b at their bases 123 to an upper surface of a circular plate 126a forming part of a valve seat 127 structure. The pair of arms 120a,b are also spaced by a pair of spacer bolts 129b set in the upper region 129a of the arms 120a,b.

(44) The arms 121a,b are formed from thick plate steel or aluminium or any other suitable substantially rigid material. The arms 120a,b may be cut out of the same type of steel sheeting used to form an internal plate 145 formed in a valve head 140. The valve head 140 formed in a similar manner to the valve head 40.

(45) The valve head 140 includes a lower peripheral circular edge 142 that forms a seal on a valve seat 127. The valve seat 127 is a ring of resilient and hard rubber axially trapped between a pair of circular steel plates 125,126 clamped together by bolts 126b circumferentially spaced around the upper and lower plates 126a,c. The upper plate 126a defines a wider aperture that exposes the upper surface of the seat 127. The seat 127 is well supported by the upper surface of the lower plate 126c. The rubber seal 127 and the lower plate 126c are preferably radially coextensive. The seat 127 and/or the lower plate 126c define a valve opening 131.

(46) The valve head 140 comprises a hemi-spherical dome 141 through which a shaft 160 is adapted to extend. The shaft 160 is coaxially located in the valve head 140 and extends through an aperture 143a near the apex 143b. The shaft 160 is located in place by one or more nuts 163 axially threadably mounted on the shaft 160 to axially fix the dome 141 relative to the shaft 160. Therefore the valve head 140 is fixed to and moves with the shaft 160. A lower portion 165 of the shaft extends through a centrally located ring 128b. The ring 128b is radially held in the central position by a set of, preferably comprising three, spokes 128a extending inwardly from the lower plate 126c. The shaft 160 is further fixed radially so that its travel is linear and coaxially in line with the shaft 160 axis 136 and with the valve head 140. The shaft 160 reciprocates through by a central aperture 146 formed in the internal plate 145.

(47) As best seen in FIGS. 8 and 9b, an upper portion 161 of the shaft 160 is terminally located in a ferrule 133. The upper portion 161 may be threadably inserted in a female recess of the ferrule 133. The upper end of the ferrule 133 includes a lateral pin 134 adapted to be received in a slot 135 formed in the terminal end 138 of the lever 130. The slot 135 is aligned parallel to the longitudinal axis (in line with plane P3) of the lever 130. The length of the slot 135 is sufficient to allow the rotational motion of the lever 130 to be transferred to linear motion of the shaft 160 whilst retaining the pin 134 in, and sliding relative to, the slot 133. The pin 134 reciprocally travels in the slot whilst the pin 134 travels up and down the longitudinal axis 136 of the shaft 160.

(48) It can be seen in FIG. 9b that the shaft 160 is adapted to move up and down along a linear pathway along the axis 136. The shaft's 160 movement is determined by the lever 130 being pushed up or down through the plane P.sub.3. As a consequence, the valve head 140 moves up and down with the shaft 160 to either expose the valve opening 131 or seal it shut by the placement of the lower peripheral edge 142 on the valve seat 127.

(49) The lever 130 may include a long lever arm 139 on an outer side of the hinge 125. The length of the lever arm 139 is determined according to the minimum amount of leverage force required to shift the valve head 140 from the open 140o to the closed position 140c and vice versa. Ideally, the length of the lever arm 139 is about 2-5 times, and preferably 3-4 times the length of a lifting arm 137. The lifting arm 137 being the section of the lever 130 between the hinge aperture at 125 and the slot 135.

(50) The lever arm 139 is preferably weighted to provide a counter-weight to the weight of the valve head 120 and the shaft 160, so that the amount of force required to move the valve head between the closed and open positions is relatively balanced. Ideally, the lever 130 includes an over-centre mechanism to favour the closed position 140.sub.c and the open position 140.sub.o, but not an intermediate position between positions 140.sub.c,o. Movement of the lever 130 may be powered by a solenoid or ram mechanism, and may be operated by a switch device. The lever 130 may be operated remotely.

(51) The terminal NRV 110 has application in forming a valve at the terminal end of a pipe and, as such, may be suitable for the control of the flow from a terminal feeder pipe into a channel or dam.

(52) FIGS. 11a-b show a third embodiment in the form of a non return valve (NRV) 210 that is similar in structure and function to the second embodiment. However, The valve head 240 is in the form of a shallow dome 241 that may comprise the upper portion of a part-spherical dome cut out of a semi-spherical dome piece such as the dome 141 shown in FIG. 8. A circular internal plate 245 extends laterally within the dome 241 The internal plate 245 is attached to the inside surface of the dome wall 241a by welds. The internal plate 245 lies in a plane normal to a shaft axis 236. The internal plate 245 has a central aperture through which the shaft 260 extends. in fixed relationship with the valve head 240 compared to the shaft 260. The valve head 240 is movable relative to a valve seat 227. In FIG. 11b, the valve head 240 is shown in a closed position 240c in which a lower peripheral edge 242 in solid lines, and in an open position 240o in which the valve head 240 is shown in broken lines.

(53) The location of the internal plate 245 close to the peripheral edge 242 reduces the volume of internal space defined by the dome 242 that is outside a cavity 250 and below the internal plate 245 to a negligible volume. The lower surface of the internal plate 245 may be loosely aligned in a plane Pi that lies traverse with the axis 236, such that the uppermost edge 242a of the peripheral edge 242 lies in the plane Pi or close to the plane Pi. For example, with reference to expanded view A in FIG. 11b, the outer corner 242a seen in section of the peripheral edge 242 lies substantially in the plane Pi. As the peripheral edge 242, when viewed in section, is cut through a radial plane Pr relative to the curved or radiussed surface 241, the lowermost corner edge of the dome wall 242 presents a sharp edge 242b of small surface area to effect an effective seal with the valve seat 227.

(54) The minimisation of the dome wall 241 skirt depending below the internal plate assists to reduce the amount of water and suspended material that may be temporarily trapped underneath the internal plate 245 within the lateral footprint of the dome wall 241.

(55) The valve assembly 210 is supported by a pair of arms 221a,b having a truncated arch in which the lower edge 221d of the bridge 221b is a straight edged and the bridge 221b shape is broader to better obscure the upper portion 261 of the shaft 260.

(56) In FIG. 12 a non return valve 310 according to a fourth embodiment is shown that is similar in concept to the first embodiment and a dome 341 is provided that is similar in shape to the dome 241 of the third embodiment. However, the dome 341 and an associated valve body 320 are formed by cutting a single hemi-spherical piece through a plane Pt transverse to its axis A.

(57) FIG. 13 shows a NRV 410 that is similar in concept to the fourth embodiment shown in FIG. 12 with a larger valve body 420 formed by attaching two similarly semi-hemi-spherically shaped valve bodies in opposed orientation such that their wider openings are joined to opposite sides of a valve seat 427 structure. The narrow opening end 421a of the first valve body 420a component is connected to a pipe mating plate 422a of a downstream pipe. The narrow opening end 421b at the opposite end of valve assembly 410 of the second valve body 420b component is connected to a pipe mating plate 422b of an upstream pipe.

(58) FIG. 14 shows a valve assembly 510 according to a sixth embodiment having a similar function and operation to that of the first embodiment, and including an internal plate 545 intermediate the length of a valve head 540 that is in the form of a truncated cone.

(59) FIG. 15 shows a valve assembly 610 according to a seventh embodiment having a similar function and operation to that of the sixth embodiment, and including an internal plate 645 located at or near the lowermost region of the wall 641 of the valve head 640. The valve head wall 641 is concave shaped whereby the internal cavity 650 that the valve head wall 641 and the internal plate 645 define is small compare to the truncated conical or semi-spherical shaped dome walls. To provide an effective structure for the peripheral edge of the internal plate 645 to be attached to, a cylindrical skirt or flange 643 is attached to the peripheral edge of the concave valve head wall 641. The lower most edge 642 of the valve head wall 641 is formed from the lower most edge of the cylindrical skirt 643 and can be worked to suit the head pressure drop of the particular application. For example, a sharp edge may be desirable for lower head pressure drops, whereas a broad edge surface may be more appropriate for large head pressure drops.

(60) The features and components of each of the embodiments of the invention described in the detailed description and/or depicted in the accompanying drawings may be interchangeable as required, with regard to functional equivalency and compatibility. Just because a feature or component is only described with reference to one or not all embodiments, does not mean that it cannot be included with another embodiment of the invention in relation to which it has not been expressly described. Furthermore, just because a feature or component is described in relation a particular embodiment, it may yet be within the scope of the invention to omit the feature or component from the embodiment, unless the context and expressions used impute that the feature or component is essential to the invention as broadly described.

(61) Throughout the specification and claims the word “comprise” and its derivatives are intended to have an inclusive rather than exclusive meaning unless the contrary is expressly stated or the context requires otherwise. That is, the word “comprise” and its derivatives will be taken to indicate the inclusion of not only the listed components, steps or features that it directly references, but also other components, steps or features not specifically listed, unless the contrary is expressly stated or the context requires otherwise.

(62) The prefix “semi” means “partial”, including “half” or a part thereof. The prefix “hemi” generally means “half” or “about half”.

(63) In the present specification, object terms such as “apparatus”, “means”, “device” and “member”, or similar terms, may refer to singular or plural items and are terms intended to refer to a set of properties, functions or characteristics performed by one or more items or components having one or more parts. It is envisaged that where the object term is described as being a unitary object, then a functionally equivalent object having multiple components is considered to fall within the scope of the object term, and similarly, where the object term is described as having multiple components, a functionally equivalent but unitary object is also considered to fall within the scope of the object term, unless the contrary is expressly stated or the context requires otherwise.

(64) Where the word “for” is used to qualify a use or application of an object term, the word “for” is only limiting in the sense that the device or component should be “suitable for” that use or application.

(65) Orientational terms used in the specification and claims such as vertical, horizontal, top, bottom, upper and lower are to be interpreted as relational and are based on the premise that the component, item, article, apparatus, device or instrument will usually be considered as if in a particular orientation, typically with the apex of the dome uppermost. However, the valve assembly or non-return valve may be oriented sideways or upside down, so that the apex, in some applications, may be oriented sideways or downward. It will be appreciated by those skilled in the art that many modifications and variations may be made to the methods of the invention described herein without departing from the spirit and scope of the invention.

(66) The following table provides a non-exhaustive list of indicative reference numerals for features and components included in the drawings.

(67) TABLE-US-00001 Ref Description Ref Description  2 Upstream  4 Downstream  10 Valve assembly 110 Non return valve (NRV)  20 Valve body  21 Truncated cone wall  22 Wide base defining a preferably central aperture  23 Upper narrower neck  24 Upper terminal collar, flange or circular plate  25 Rigid circular plate  26 Pair of superimposed circular plates forming aperture  26b Lower most plate  27 Upper surface of base forming the valve seat  28 Inner spokes extending from the lower plate to a central ring forming a star bracket  29 Ring supporting the spokes  30 Lower bearing surface  31 Lower valve opening  32 Upper valve opening  33 Upper inner spokes  34 Upper central ring  35 Upper bearing  36 Longitudinal axis  40 Valve head  41 Dome  41a Dome wall  42 Lower peripheral edge  43 Aperture near apex  43b Apex at central dome aperture  44 Transverse plane  45 Internal plate in dome  46 Central aperture in internal plate  47 Height of dome  48 Skirt of dome  49 Recess defined by the skirt and the lower side of the internal plate  50 Recess defined by the dome wall and the upper surface of the internal plate  51 Axial displacement distance of valve head  52 Intervening space immediately downstream of the valve opening  53 Gap between lower edge and the valve seat  54 Valve body cavity  60 Central shaft  61 Upper section of shaft  62 Intermediate portion of shaft  63 Intermediate bearing surface  64 Lowermost end of intermediate bearing surface  65 Lower portion of shaft  66 Axial compression spring  80 Dampener  81 Cylinder  82 Central bore  83 End of bore of cylinder  84 Side port  85 Small aperture at end of bore  86 Lower end of cylinder 110, Valve assembly P1 Plane of first arm 210 P2 Plane of second arm P3 Plane of lever Pi Plane of internal plate 120, Support structure 120a, 220a First arm 220 221d Lower edge of 121b, Bridge bridge 221b 121c, Second arm 221c 122a Steep side wall edge of first leg 122b Corner 123 Base 125 Hinge 126a Upper circular plate 126b Bolt fasteners 126c Lower circular plate 227 Valve seat 127 Valve seat structure 128a Spokes 128b Ring 129a Upper region 129b Spacer bolts 130 Lever 131 Valve opening 133 Ferrule 134 Pin 135 Slot 136, 236 Shaft axis 137 Lifting arm 139 Long lever arm 140, Valve head 140o, Open position 240 240o 140c Closed position 241 Shallow dome 141 Dome wall 241a Dome wall 142, 242 Lower peripheral edge 241b Radiussed surface 143 Aperture 242a Outer peripheral 143b Apex edge 242b Sharp lower 145, 245 Internal plate peripheral edge 160, Shaft 161, 261 Upper portion of shaft 260 165 Lower portion of shaft