Knife valve

Abstract

Disclosed is a valve comprising a body having an aperture for material to pass through. The valve has a slot located in the body, the slot providing passage for a blade to pass into the body and seal the aperture when inserted into the slot. A rib is located on the body to provide rigidity for the slot and extends across the slot and down towards the aperture in the body. The rib has flanges extending towards the aperture at a side wall of the slot, the flanges extending further than a central portion of the rib extends towards the aperture.

Description

Knife Valve Technical Field

[001] The present invention generally relates to the field of knife valves. More particularly, the present invention relates to a reinforcing rib for a knife valve. Background

[002] Flow control a pipe may be carried out by a valve located either in the pipe or at the end of the pipe. Different type of valves can be used for different applications, such as some valves being used for on / off flow control while other valves are used to regulate flow of material in the pipe. As such, there are many different types of valves, such as butterfly valves, ball valves, gate valves, knife valves and choke valves. The type of valve selected for use will depend on factors such as the material moving through the pipe, pipe size, pressure and the type of control required.

[003] Typically a valve will have at least one inlet port and one outlet port. Flow of material through the valve from the inlet to the outlet port may be controlled by blocking the flow of material using a device such as a gate of a gate valve or a disc of a globe valve. In addition to the inlet and outlet ports, the valve may also have an aperture through which a stem or rod may pass to move a disc. For valves such as a gate or knife valve the aperture or slot may be larger to allow a gate or blade to move into the path of the material in the pipe. Such an aperture may be a source of structural weakness for the valve.

[004] Referring to Fig. 1 (prior art) by way of example, there is illustrated a known conventional knife valve 100. The knife valve 100 shows two parts, a sustaining structure 110, only partially shown, and a main body 120 attached to the sustaining structure 110. Part of the sustaining structure 110 includes a blade 130 attached by a blade bracket 140 to a telescopic rod 145. The telescopic rod 145 pushes the blade 130 to block an aperture 170 in the main body 120 to close the knife valve 100. The telescopic rod 145 may also retract the blade 130 into the sustaining structure 110 to open the aperture 170 and allow material to pass through the valve. The main body 120 is formed from two parts with a back part of the main body 120, not shown, being attached to a front part of the main body 120 by body bolts 150. When the knife valve 100 is inserted into a pipe, flanges on the pipe may be used to attach the knife valve 100 using bolts that screw into threads in bolt holes 160.

[005] Located on the main body 120 and above the aperture 170, is a rib 180. The rib 180 provides rigidity to the main body 120 where the blade 130 passes through a slot, not visible, as the blade 130 is slid into the aperture 170. When the knife valve 100 is closed, pressure from the material in the pipe is applied to the blade 130 as well as applied, via the material carried by the pipe, to the slot of the main body 120. The rib 180 provides reinforcement to the main body 120 near the slot to prevent deformation and leaking of material from the knife valve 100.

[006] There is a need for a new or improved knife valve, which address or at least ameliorate one or more problems in the prior art.

[007] The reference in this specification to any prior publication (or information derived from the prior publication), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that the prior publication (or information derived from the prior publication) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. Summary |008| This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[009] In one embodiment, there is provided by way of example only a valve comprising: a body having an aperture for material to pass through; a slot located in the body, the slot providing passage for a blade to pass into the body and seal the aperture when inserted into the slot; a rib located on the body to provide rigidity for the slot, the rib extending across the slot and down towards the aperture in the body, the rib having flanges extending towards the aperture at a side wall of the slot, the flanges extending further than a central portion of the rib extends towards the aperture.

[010] In one embodiment of the valve the rib is attached to the body using fasteners.

[011] In one embodiment, the valve is a knife valve.

[012] In one embodiment of the valve the rib and the body are made of different materials.

[013] In one embodiment, the body of the valve is made of a material that has resistance to material that passes through the aperture of the valve and the rib is made of a material that is more rigid than the resistant material of the body.

[014] In one embodiment of the valve the rib curves from the central portion of the rib to the flanges as the flanges extend toward the aperture.

[015] In one embodiment of the valve the flanges of the rib are thinner than the central portion of the rib.

[016] In one embodiment of the valve a thickness of the flanges is determined by a thickness of a flange attaching a pipe to the valve.

[017] In one embodiment of the valve the rib is attached by a plurality of bolts to the body of the valve.

[018] In one embodiment of the valve the rib is integrally formed as part of the body of the valve.

[019] In one embodiment of the valve the rib has a profile that partially conforms to a shape of an aperture in the valve.

[020] In one embodiment of the valve the rib is located near a blade slot of the valve.

[021] In one embodiment of the valve the rib is protrudes from the body.

[022] In one embodiment, there is provided a detachable rib for a valve, the detachable rib having a longitudinal axis and a flange extending from the detachable rib in a transverse direction to the longitudinal axis, the flange being located proximate to an end of the detachable rib and extending further than a central portion of the detachable rib extends in the transverse direction.

[023] In one embodiment the detachable rib has a second flange extending from the detachable rib in the transverse direction of the flange, the second flange being located proximate to a second end of the detachable rib and extending further than the central portion of the detachable rib extends in the transverse direction.

[024] In one embodiment of the detachable rib the flange and the second flange are symmetrically positioned, on the detachable rib, about a centrally located axis in the transverse direction.

[025] In one embodiment of the detachable rib, the detachable rib has a plurality of holes for attaching the detachable rib to a valve.

[026] In one embodiment of the detachable rib the flange and the second flange are thinner than the central portion of the detachable rib.

[027] In one embodiment of the detachable rib, the detachable rib is for attaching to a valve.

[028] In one embodiment of the detachable rib a thickness of the flange and the second flange is determined by a thickness of a flange attaching a pipe to the valve. Brief Description of Figures

[029] Example embodiments are provided in the following description, which is given by way of example only, of at least one preferred but non-limiting embodiment, described in connection with the accompanying figures.

[030] Fig. 1 (prior art) illustrates a conventional knife valve;

[031] Fig. 2 illustrates an isometric view of an example of a knife valve with a detachable rib;

[032] Fig. 3 illustrates a front view of the knife valve with detachable rib;

[033] Fig. 4 illustrates a main body of the knife valve with detachable rib;

[034] Fig. 5 illustrates cross section of the knife valve with detachable rib;

[035] Figs. 6A and 6B illustrate a bolt on reinforcement rib for use on a main body of a knife valve;

[036] Figs. 7A and 7B illustrate an example of a main body of a knife valve;

[037] Fig. 8 illustrates an isometric view of an example of a knife valve incorporating a rib as part of a main body; and

[038] Fig. 9 illustrates an example of a profile view of a rib for a main body of a knife valve. Detailed Description

[039] The following modes, given by way of example only, are described in order to provide a more precise understanding of the subject matter of a preferred embodiment or embodiments. Example Reinforcement Rib for a Valve

[040] Described is a valve having a body with an aperture through which material can pass. The valve has a slot located in the body and the slot provides passage for a blade to pass into the body and seal the aperture when inserted into the slot. A rib located on the body to provide rigidity for the slot. The rib extends across the slot and down towards the aperture in the body. The rib has flanges extending towards the aperture at a side wall of the slot and the flanges extend further than a central portion of the rib extends towards the aperture.

[041] Also described in a detachable rib for a valve, the detachable rib has a longitudinal axis and a flange extending from the detachable rib in a transverse direction to the longitudinal axis. The flange is located proximate to an end of the rib and extends further than a central portion of the rib extends in the transverse direction.

[042] The valve operates to stop the flow of material through a pipe. The material may be fluid or a fluid with high solid content, such as a slurry. A knife valve may be used for material with a high solid content. The blade of the knife valve, having a cutting edge, slices through the material, even with a high solid content. A slot, through which the blade passed into the aperture, may cause a region of reduced rigidity for the region of the knife valve around the slot.

[043] To improve rigidity of the knife valve around the slot, the knife valve has a dog bone, bow tie, or dumbbell shaped reinforcement rib providing additional strength for a main body of the knife valve. A longitudinal direction of the dog bone shaped rib extends in a direction across the blade of the knife valve with ears, or flared ends, of the rib extending perpendicular to the longitudinal axis, that is, away from the longitudinal direction of the rib, or in a transverse direction to the longitudinal axis. Typically the flared ends will extend towards an aperture of the knife valve and in some embodiments the dog bone shape may conform, or partly conform, to the shape of the aperture in the knife valve. The flared end may extend further towards the aperture than a central portion of the rib. The rib may have one flared end or two.

[044] The ears, or flared ends, of the dog bone shape may be asymmetrical along the longitudinal axis but are generally symmetrical about an axis in the transverse direction with the ears being mirrored at each end of the reinforcement rib. The reinforcement rib typically only has the ears extending in one direction, making the rib asymmetric about the longitudinal axis.

[045] An example of a detachable reinforcement rib may be seen on knife valve 200 of Figs. 2, 3, 4 and 5. The knife valve 200 operates by sliding a blade into an aperture to prevent flow of material from an inlet port to an outlet port, through the aperture. The knife valve 200 is generally either in an open position, that leaves the aperture unobstructed by the blade, or in a closed position where the blade blocks flow of material through the aperture. The knife valve 200 has three main components, a sustaining structure 210, a main body 220 and an actuator 248. The sustaining structure 210 is located between the main body 220 and the actuator 248 and connects the main components together. The sustaining structure 210 is connected to the main body 220 using structure bolts 212 that screw into the structure bolt holes 214 located at a top of the main body 220.

[046] When mounted in a pipe, the main body 220 forms part of the pipe with material flowing through the pipe and passing through an aperture 270 in the main body 220. The knife valve 200 of Fig. 2 is shown in the closed state with a blade 230 blocking flow of material in the pipe when the knife valve 200 is attached to the pipe. When the knife valve 200 is opened the blade 230 moves out of the main body 220 and into the sustaining structure 210, allowing material to pass through the aperture 270, from the inlet port to the outlet port.

[047] The main body 220 has two main parts and is formed of a front body 222 and a rear body 224. A two part main body 220 allows a blade slot 232, as shown in Fig. 4, to be formed with machining of the cast parts. The blade slot 232 is formed in the rear body 224 while an internal face of the front body 222 that mates with the rear body 224 may be flat. The blade slot 232 has slot sidewalls 234, being the shorter of the sides of the blade slot 232. The blade slot 232 also has slot endwalls 236 which are the longer sides of the blade slot 232, i.e. the slot endwalls 236 are longer than the slot sidewalls 234. One slot endwall is formed as part of the rear body 224 while the other slot endwall is part of a mating surface of the front body 222. As will be discussed later, machining the blade slot 232 into the rear body 224 removes metal from the main body 220 and reduces the strength of the main body 220 around the blade slot 232.

[048] While the main body 220 is shown formed from the front body 222 and the rear body 224, an alternative may be to use a single cast piece. However, a single component main body may increase manufacturing complexity due to additional machining required for the blade slot.

[049] When forming a two piece main body 220 the front body 222 and the rear body 224 may be bolted together using bolts, as seen in Figs. 3, 4 and 5. Main body bolts, such as main body bolt 262 are only visible on the front body 222. As seen in Fig. 5, the main body bolts pass through the front body 222 and screw into threaded holes located on a mating surface of the rear body 224. The main body bolts are used to hold the front body 222 and the rear body 224 together. Due to the blade slot 232, the bolts do not encircle the aperture 270. Instead the bolts extend along the slot sidewalls 234 at the top of the main body 220 so as to not interfere with the operation of the blade 230. A gasket may be used to seal between the mating surfaces of the front body 222 and the rear body 224.

[050] When in operation, the knife valve 200 attaches to flanges on the pipe using bolts that are screwed into the main body 220. The main body 220 has bolt holes, located around the aperture 270, on the front body 222 and the rear body 224. The bolt holes, such as flange bolt holes 260, are threaded to allow the bolts to screw into the main body 220.

[051] The blade 230 is connected to the actuator 248 by a telescopic rod 245. The actuator 248 may move the blade 230 from the closed position, blocking the aperture 270, to the open position where the blade 230 is withdrawn from the aperture 270. When moving between the open and closed position the blade 230 passes through the blade slot 232. When the blade 230 is in the open position the blade 230 may be partially inserted in the blade slot 232 to block flow of material through the slot. Alternatively, the blade 230 may be completely removed from the blade slot 232 and be located in the sustaining structure 210. The sustaining structure 210 may have transparent panels, or gaps, that allows visual confirmation of the position of the blade 230 by plant operators. The actuator 248 may be operated by hydraulic, pneumatic, electrical, manual or any other driving means to move the blade 230.

[052] A bolt on or detachable rib 280 is located at the top of the main body 220, near the blade slot 232. There are two detachable ribs 280 with one rib located on the front and one rib located on the back of the main body 220, mounted on the front body 222 and the rear body 224 respectively. As described above, the purpose of the detachable rib 280 is to provide additional rigidity to the main body 220 around the blade slot 232. When the knife valve 200 is in the open position the material will flow through the pipe and only a small amount of the material may try to move through the blade slot 232. However, when the knife valve 200 is in the closed position, the blade 230 will prevent material from flowing through the knife valve 200. The pressure pushing the material through the pipe will press against the blade 230 in the aperture 270. The pressure in the pipe may be sufficient to force material past seals in the knife valve 200. The material in the pipe, blocked by the blade 230, may exert a force on the blade slot 232 at a blade slot aperture opening 238. If the pressure is sufficient the material may enter the blade slot 232 and work past aperture slot seals 274 and even upper slot seals 276 to pass out the blade slot 232 at a blade slot top opening 239.

[053] Movement of the slurry through the blade slot 232, via the blade slot aperture opening 238, may be reduced or even prevented by ensuring that the aperture slot seals 274 and the upper slot seals 276 remain in contact with the blade 230 with sufficient pressure. In some situations the blade slot 232 may deform, reducing the pressure on the seals and allowing the material to travel in the blade slot 232. Deformation of the blade slot 232 may be prevented by making the main body 220 sufficiently rigid around the blade slot 232. The detachable rib 280 provides additional rigidity for the blade slot 232, particularly at the blade slot top opening 239 and for the area near the upper slot seals 276.

[054] The detachable rib 280 is attached to the main body 220 using bolts such as rib attachment bolt 282. The detachable rib 280 may be attached with bolts or other types of mechanical fasteners. When using bolts, the bolts attaching the detachable rib 280 do not pass through the front body 222 or the rear body 224 so that the bolts do not interfere with the blade slot 232. Instead, holes on the front body 222 and the rear body 224 are threaded to allow the detachable rib 280 to be attached. The detachable rib 280 has rib attachment bolt holes distributed evenly over the rib. The number of rib attachment bolt holes will depend on factors such as the expected forces exerted by the material in the pipe on the blade slot 232, in particular near the blade slot top opening 239, the size of the bolts used, how far the bolts are threaded into the main body 220, and the materials used to construct the bolts, the detachable rib 280 and the main body 220. The number of bolts may be selected to ensure that the detachable rib 280 and the main body 220 move as a unified body.

[055] The detachable rib 280 may also have main body bolts, such as rib main body bolt 264 that pass through the detachable rib 280 and are used to attach detachable rib 280 and the front body 222 to the rear body 224. The rib main body bolts may attach to threaded holes located on the mating surface of the rear body 224. Alternatively, the main body bolts on the detachable rib 280 may screw into threaded holes located on a mating surface of the detachable rib 280 on the rear body 224, or a combination of both the rear body 224 and the detachable rib 280 on the rear body 224. An advantage of the rib main body bolts attaching to the opposite detachable rib is that the ribs may be made of a stronger material than the main body 220. This may make the detachable rib 280 stronger than the rear body 224 for attaching the rib main body bolts. The main body bolts on the detachable rib 280 also attach the detachable rib 280 to the main body 220 and are located at each end of the rib to ensure that that the bolts do not interfere with the blade slot 232.

[056] While the rib attachment bolts, such as rib attachment bolt 282, are shown evenly distributed on the knife valve 200, alternative designs may have an uneven distribution of the bolts. Such an arrangement may occur when the force required to securely attach the detachable rib 280 vary significantly across the rib. More bolts may be used in areas where the forces on the detachable rib 280 are high, while fewer bolts may be used in areas where the forces are low. For example, more bolts may be used at the centre of the detachable rib 280 than at the edge. Alternatively, the density of bolts may be higher new the edge of the detachable rib 280 than at the centre.

[057] As described above, the detachable rib 280 attaches to the front body 222 and the rear body 224. In one embodiment, as shown in Fig. 2, the detachable rib 280 has a single attachment to components of the knife valve, being the attachment to the main body using bolts or other mechanical fasteners. Other components of the knife valve, such as the sustaining structure 210, are not attached to the detachable rib 280.

[058] The dog bone shape of the detachable rib 280 is formed from a narrow central portion 286 that extend to ears, or flanges 284. The narrow central portion 286 extends towards the aperture 270 at each end of the detachable rib 280 at the ears 284. The detachable rib 280 curves from the narrow central portion 286 to the ears 284. Typically, the ears 284 extend further towards the aperture 270 than the narrow central portion 286. The dog bone shape may provide a number of advantages over a rectangular rib. One advantage is that the ears 284 provide additional width to each end of the detachable rib 280. The increased width, compared to a rectangular rib, provides additional rigidity for the detachable rib 280 in a lateral direction. Additionally, the ears 284 increase rigidity of the detachable rib 280 in the axial direction due to an increase in the amount of metal in the rib. This may be of assistance in reducing the bowing of the slot endwalls 236 by limiting the deformation of the blade slot 232 near the slot sidewalls 234. The increased width of the detachable rib 280 at the ears 284 allows the thickness of the rib to be reduced overall. As such, the thickness of the detachable rib 280 at the narrow central portion 286 may be smaller than an equivalent rectangular rib. Additionally, the ears 284 may allow the detachable rib 280 to be positioned closer to the aperture 270 as the rib conforms to a shape of the flange bolt holes 260 positioned around the aperture 270. The ears 284 also allow more bolts to attach the detachable rib 280 at each end as there is a larger surface area for placement of bolts.

[059] The slot endwalls 236 may bend due to pressure of the material blocked by the blade 230 when the knife valve 200 is closed. The slot endwalls 236 bend in a manner that the slot sidewalls 234 act as a "pivot" point with the slot endwalls 236. As the front body 222 and the rear body 224 are bolted together at, or near, the slot sidewall 234, the slot endwalls 236 may bow outwards, away from the blade slot 232, due to pressure from the material. The detachable rib 280 may reduce or even prevent the bowing of the slot endwalls 236 due to the extra rigidity provided.

[060] Another advantage of the detachable rib 280 is that the reduced thickness, compared to a rectangular rib, allows better access to bolts attaching the pipe to the flange bolt holes 260 located under the rib. As the detachable rib 280 may be thinner than a rectangular rib, access to the bolts located under the rib may not be impeded by the rib. Another advantage of the detachable rib 280, provided by the bolt on aspect, is that the rib may be installed after the knife valve 200 has been installed in the pipe. The knife valve 200 may be attached to the pipe before the detachable rib 280 is installed on the front body 222 and the rear body 224. However, the reduced thickness of the detachable rib 280 may make such a process unnecessary.

[061] While the detachable rib 280, front body 222 and the rear body 224 may all be cast, it may be desirable to manufacture the detachable rib 280 and the front body 222 and the rear body 224 from different metals. Such a situation may occur when the metal for the main body 220 is selected for good wear resistance or chemical resistant properties. The wear resistance or chemical resistance may be chosen to improve resistance to the material that passes through the valve. In such a situation, the metal may have lower mechanical properties, such as being more flexible or susceptible to breaking. Having a detachable rib allows the rib to be cast using a rigid metal, such as carbon steel. A carbon steel rib would be more rigid than a main body made from a metal such as Ni-resist cast iron. The result is a knife valve 200 with chemical and / or corrosion resistant properties for the main body 220, yet still suitably rigid around the blade slot 232 due to the rigidity of the detachable rib 280. The use of stronger metals for the rib allows stiffness to be added to the valve and reduce bowing under pressure and leaking of the main body 220. Although the main body and the rib are typically made of metal, other materials may also be used, such as plastic.

[062] Another advantage of the detachable rib is that different sized ribs may be used for the same main body. An example of such a situation occurs when a knife valve is repurposed and the pressure of the material in the pipe is higher than for the previous use of the knife valve. In such a situation the rib may be replaced with a thicker rib to provide extra rigidity.

[063] An example of a dog bone shaped cast rib 600 will be described in relation to Figs. 6A and 6B. The cast rib 600 is shown after casting and before machining. The cast rib 600 has the ears 284 as well as the narrow central portion 286. After machining, the cast rib 600 is shown as the detachable rib 280 of Fig. 6B where the rib attachment bolt holes, such as rib attachment bolt hole 682 have been machined into the detachable rib 280, along with the rib main body bolt holes, such as rib main body bolt hole 664. The detachable rib 280 of Fig. 6B has been machine for attachment to the front body 222 as the rib on the front body 222 has rib main body bolt holes, such as rib main body bolt hole 664.

[064] A cast rear body 700 is shown in Fig. 7A. The cast rear body 700 is shown after casting and before machining. The cast rear body 700 has the blade slot 232 with the slot sidewall 234 and the slot endwalls 236. The cast rear body 700 also has the aperture 270 and the blade recess 272. Cast into the cast rear body 700 is a rib mounting face 780 to which the detachable rib 280 is attached when the cast rear body 700 is assembled into a valve, such as knife valve 200. The rib mounting face 780 has a shape corresponding to the detachable rib 280 that includes rib mounting flanges 784 located at each end of the face as well as a narrow central portion 786.

[065] The cast rear body 700 is machined to produce the rear body 224 as seen in Fig. 7B. The rear body 224 of Fig. 7B has a number of threaded bolt holes machined into the surface, such as flange the bolt holes 260, the structure bolt holes 214 and rib main body bolt hole 764. The rear body 224 also has rib attachment threaded holes such as a rib attachment threaded hole 782 which may be used to bolt on the rib 280. Not visible in Fig. 7B are the threaded holes used to attach the front body 222 to the rear body 224. These holes are located on a rear face of the rear body 224.

[066] A knife valve 800 with a rib incorporated into a main body will now be described in relation to Fig. 8. The knife valve 800 is similar to the knife valve 200, however the rib of the knife valve 800 is formed into a main body. As with the knife valve 200, the knife valve 800 has three main parts, a sustaining structure 810, a main body 820 and an actuator 848, with the sustaining structure 810 being located between, and connected to the main body 820 and the actuator 848. The blade 830 is connected to a telescopic rod by a blade bracket 840. When in the open position, such as seen in Fig. 8, the telescopic rod in withdrawn into the actuator 848.

[067] The knife valve 800 of Fig. 8 is shown with a blade 830 in the open position so that material in a pipe would flow through an aperture 870 if the valve was installed in a pipe. When the knife valve 800 is open, the blade 830 is located in the sustaining structure 810 with a portion of the blade 830 in a blade slot to ensure that the blade slot is sealed.

[068] The main body 820 is formed from a front body 822 and a rear body 824 held together by bolts, such as main body bolts 862 or rib main body bolts 864 located on the rib 880. As with the main body bolts 262 of knife valve 200, the main body bolts 862 screw through the front body 822 and into threaded holes in the rear body 824 to bolt the two halves together. Upstream and downstream pipes are attached to the knife valve 800 using threaded bolt holes, such as flange bolt holes 860.

[069] A rib 880 is formed into each of the front body 822 and the rear body 824. The rib 880 is a dog bone or bow tie shape, similar to the detachable rib 280 of the knife valve 200. However, rib 880 is integrally formed into the front body 822 and the rear body 824 and is not detachable. The rib 880 has ears 884 located at each end of the rib. The ears 884 extend perpendicular, or in a transverse direction, to the axial direction of the rib 880, toward the aperture 870. As shown in Fig. 8, the ears 884 do not extend upwards, in a direction away from the aperture 870. The rib 880 also has a narrow central portion 886 located between the ears 884 at each end of the rib 880. The narrow central portion 886 curves to the ears 884. The rib 880 may have a single attachment to components of the knife valve, being the main body in the form of the front body 822 or the rear body 824. The ears 884 provide the same advantages as the ears 284 described above in relation to the knife valve 200 above. That is, the ears 884 provide additional rigidity to the rib 880 in a lateral direction as well as additional axial rigidity for the area of the main body 820 located near slot endwalls where the metal has been removed for the slot.

[070] In some situations, the rib 880 may be a rib mounting face, such as the rib mounting face 780 of the cast rear body 700. Such a situation may occur when the front body 822 and the rear body 824 have sufficient rigidity without the need to add additional reinforcement of a detachable rib, such as the detachable rib 280 of the knife valve 200. Typically this may occur when the metal used for the front body 822 and rear body 824 has suitable mechanical properties and / or the pressure in the pipe in which the knife valve 800 operates is sufficiently low. An advantage of such an approach is that the knife valve 800 and the knife valve 200 may use the same casting and machining set up when the valves are the same size. Additional machining may then take place to convert the front body 822 and the rear body 824 to accept a detachable rib, such as the detachable rib 280 used for the knife valve 200.

[071] The use of a cast dog bone shaped rib, such as the rib 880 may provide some of the same advantages that the detachable rib 280 provides for the knife valve 200. For example, the use of a dog bone shape rib allows for the rib to have a lower profile, that is thinner or not extending away from the main body 820, than a rectangular rib. The lower profile may be possible due to rigidity provided by the ears of the dog bone shape rib where extra metal located. The ears also provide additional rigidity in 2 dimensions, being axial rigidity as well a lateral rigidity. As with the detachable rib 280 of knife valve 200, the lower profile may provide better access to the flange bolt that are used to attach the pipe to the main body. The lower profile may also allow a clearer view of the flange bolts, making visual inspection of the flange bolts below the rib easier with a dog bone rib, compared to a rectangular rib.

[072] A side profile of the detachable rib 280 will be described in relation to Fig. 9. The detachable rib 280 can be seen with a thicker central portion, while the ears 284 are thinner than the central portion. While the side profile of the detachable rib 280 is shown as stepped, the profile may also be tapered from the top of the detachable rib 280 to the bottom of the rib, or may have a flat portion extending from the top to the bottom of the central portion, with a taper commencing at the top of the ears 284. The reduced thickness of the ears 284, compared to the central portion of the detachable rib 280 may allow better physical or visual access to the flange bolt holes 260 or main body bolts 862 located near the ears 284 while still providing sufficient rigidity. The detachable rib 280 protrudes, or is raised, from the main body of the knife valve 200 onto which the detachable rib 280 is attached. The detachable rib 280 may also attach to, and extend, a protrusion already on the main body, such as seen in Fig. 9.

[073] The profile of the detachable rib 280, as shown in Fig. 9, is stepped down near the ears 284. The step down is located near where the pipe flange is attached to the knife valve 200. This allows for sufficient room for to access the bolts that attach the pipe flange. In one embodiment, the thickness of the ears 284 is determined to match, or be close to, a thickness as the pipe flange. As a result, the thickness of the ears 284 can be determined by the thickness of the pipe flange. Such an arrangement places a plane that the bolt heads sit on with a surface of the ears 284 when the pipe is attached.

[074] While the detachable rib 280 of Fig. 9 is described as detachable, the rib profile may also be used for a rib formed as part of a body of a valve, such as the rib 880 of knife valve 800. Advantages of Reinforcement Rib

[075] One advantage of the dog-bone shape of the rib is that the rib uses more of the space available on the main body when compared to a rectangular valve. The ears allow the rib to cover more area than a rectangular rib so the dog bone shape of the rib provides more metal, therefore rigidity, than a comparable rectangular rib. As the rib is located near the seals, the design stiffens the valve in the area of the seals and helps to keep the seals in contact with the gate.

[076] Another advantage of the dog-bone shaped rib design is that the curved contours of the ears make the shape stiffer, when compared to sharp corners, and reduce stress raisers that may occur with shaper corners. The ears also provide additional metal for bolts to screw into when connecting two parts of the valve together.

[077] The surface of the main body, underneath the detachable rib may have a matching geometry to the rib. As a result, there is a matching rib profile platform, in the shape of the dog bone rib, cast into the main body. The matching rib-profile platform has enough thickness for the bolts of the rib to thread into.

[078] Another advantage of the dog bone shape rib is that the main body castings may have a more uniform thickness, compared to a rectangular rib casting. The dog bone shaped rib may reduce the overall thickness of the valve measured from rib to rib when compared to a main body with rectangular ribs.

[079] The reduced thickness of the valve may also have the benefit of simplifying machining of the main body. When rectangular ribs are used they may extend further from the main body than a dog bone shaped rib. Machining a main body with a large rib may require the use of tooling with a long reach to extend past the rib, especially in circumstances when the machinery has insufficient travel to move the main body into a position suitable for shorter tooling. Tooling with a long reach may be more expensive than shorter tooling, as well as more prone to breaking. The reduced thickness from the dog bone shaped rib may also reduce movement of the main body during machining as surfaces on the main body are easier to access. As a result, the cost of machining the main body may be lower compared to a rectangular rib.

[080] The main body 220 and the main body 820 may use the same casts. This may be done using a pattern adder when a detachable rib is used, such as for the front body 222 or the rear body 224. The pattern adder will fill in space on the pattern, making the rib smaller for a main body with a detachable rib. The space taken by the pattern adder may then be used for the detachable rib, although the size of the detachable rib may have no relation to the size of the pattern adder.

[081] For a detachable rib or a rib cast into a main body, the dog bone shaped rib has the advantage of being thinner than a rectangular rib. As result, a valve with a dog bone shaped rib may be stiffer and cheaper to manufacture than a valve with a rectangular rib as machining the main body is easier, for reasons described above.

[082] While the above description is focused on a knife valve, the dog bone shaped rib may also be applied to other valve types where rigidity near an opening, or aperture, is required. Examples of such valve may include a gate valve or a ball valve.

[083] While the ears of the dog bone shaped rib are described as extending toward the aperture, the rib may also have one or more ears that extend away from the aperture. In such an arrangement the central portion of the rib may extend to a top of the main body. Alternatively, the rib may have only one ear extending toward the aperture. The ear may be located on a first end of the rib while a second end of the rib has a rectangular finish.

[084] Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Claims

1. A valve comprising: a body having an aperture for material to pass through; a slot located in the body, the slot providing passage for a blade to pass into the body and seal the aperture when inserted into the slot, the slot including side walls and end walls, the side walls being shorter than the end walls; a rib located on the body to provide rigidity for the slot, the rib extending across the slot and down towards the aperture in the body, the rib having flanges extending towards the aperture at each end of a central portion of the rib and at each side wall of the slot, the flanges extending further than the central portion of the rib extends towards the aperture, and wherein each end of the central portion of the rib extends across the slot and further than each of the side walls of the slot on the body, and wherein the flanges of the rib are thinner than the central portion of the rib.

2. The valve according to claim 1, wherein the rib is attached to the body using fasteners.

3. The valve according to either claim 1 or 2, wherein the valve is a knife valve.

4. The valve according to any one of claims 1 to 3, wherein the rib and the body are made of different materials.

5. The valve according to any one of claims 1 to 4, wherein the body of the valve is made of a material that has resistance to material that passes through the aperture of the valve and the rib is made of a material that is more rigid than the resistant material of the body.

6. The valve according to any one of claims 1 to 5, wherein the rib curves from the central portion of the rib to the flanges as the flanges extend toward the aperture.

7. The valve according to any one of claims 1 to 6, wherein a thickness of the flanges is determined by a thickness of a flange attaching a pipe to the valve.

8. The valve according to claim 2, wherein the rib is attached by a plurality of bolts to the body of the valve.

9. The valve according to claim 1, wherein the rib is integrally formed as part of the body of the valve.

10. The valve according to any one of claims 1 to 9, wherein the rib has a profile that partially conforms to a shape of the aperture in the valve.

11. The valve according to any one of claims 1 to 10, wherein the rib is located near the slot of the valve.

12. The valve according to any one of claims 1 to 11, wherein the rib protrudes from the body.

13. A detachable rib for a knife valve, the knife valve comprising: a body having an aperture for material to pass through; a slot located in the body, the slot providing passage for a blade to pass into the body and seal the aperture when inserted into the slot, the slot including side walls and end walls, the side walls being shorter than the end walls, wherein the detachable rib includes a central portion with a longitudinal axis and flanges extending from the central portion in a transverse direction to the longitudinal axis, the flanges being located proximate to each end of the central portion and extending further than the central portion of the detachable rib extends in the transverse direction, wherein the detachable rib is configured to attach to the body of the knife valve using fasteners, such that the rib extends across the slot and down towards the aperture in the body and wherein each end of the central portion of the rib extends across the slot and further than each of the side walls of the slot on the body, and whereby the flanges extends towards the aperture at a side wall of the slot and wherein the flanges are thinner than the central portion.

14. The detachable rib according to claim 13, wherein the flanges are symmetrically positioned, on the detachable rib, about a centrally located axis in the transverse direction.

15. The detachable rib according to claim 13 or claim 14, wherein the detachable rib has a plurality of holes for attaching the detachable rib to the valve.

16. The detachable rib according to any one of claims 13 to 15, wherein a thickness of the flanges is determined by a thickness of a flange attaching a pipe to the valve.