Abstract:
A high-pressure gate valve for control of bulk materials includes a main body with an opening for passing bulk material, an upper body, a slideable blade, and lifting structure configured to raise the blade in a planar motion, perpendicular to the primary direction of travel and seal it against the upper body when the blade is extended. An actuating cylinder coupled with a rear edge of the blade extends and retracts the blade. A rear portion of the valve is enclosed to protect the rear edge of the blade, the actuating cylinder, and the coupling between the two.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not applicable.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable.  
       BACKGROUND OF THE INVENTION  
       [0003]     1. Field of the Invention  
         [0004]     The present invention relates to valves, and more particularly to gate valves used in the control of flow of materials. The invention is particularly applicable to gate valves which are utilized in handling bulk solids in installations where the pressure exceeds atmospheric.  
         [0005]     2. Description of Related Art  
         [0006]     Various valves are used in manufacturing and production facilities to control the flow of materials within the facility, or within systems in the facility. Slide-gate or knife-gate valves are commonly used to control a variety of material types, including bulk solids, liquids, gases, and slurries. These gate valves commonly have a structural frame with an opening for passing material with a sliding blade to block and unblock the opening. The blade is typically driven by a linear actuator using pneumatic or hydraulic power to extend and retract the actuator and blade.  
         [0007]     Various blade nose configurations are used depending on the type of material being used and the sealing properties desired. For example, in liquid, gas and slurry applications, the nose of the blade typically seats against a resilient seal, such as an o-ring. In dry material applications, the nose edge of the blade is typically thrust upward against an elastomeric seal as an actuating cylinder pushes the blade horizontally. This combination of horizontal and vertical thrust motion can, however cause uneven seal wear as the leading edge of the blade has a higher seal seat contact pressure than the rear of the blade. It also stresses the cylinder shaft and places uneven loads on the cylinder seals. The perpendicular thrusting motion (relative to the direction of movement) places a torsional force on the actuator shaft causing premature wear of the actuator seals and potentially damaging the actuating cylinder. Any time a valve is operated in a pressurized environment the issues surrounding proper sealing are greatly enhanced.  
         [0008]     Gate valves according to the prior art have most often been designed to be used with liquids and gases. These materials displace themselves when subject to the action of the gate and accordingly proper sealing of the valve is relatively easy to accomplish. “Bull nose” knife or gate valves have long been successfully used to control the flow of liquids and gases. Using gate valves with dry material presents problems with material “packing” into the valve seat area and getting trapped, preventing the valve from fully closing and seating. Particularly vulnerable is the void area formed between the valve housing and the radius of the typical rounded “bull nose” end of the blade. Material is easily trapped and wedged into the void formed between the blade and the housing. This trapped material may preclude proper sealing of the valve by preventing it from fully closing and will increase power consumption by the actuator as it works to overcome the obstruction. The “packed” material being handled may also be damaged by the wedging action. Trapped material also contributes to cross-contamination when different materials are routed thru the same valve.  
         [0009]     At the rear edge of the blade, a sealed bonnet may be used to separate the actuating cylinder from the material path. This bonnet protects the working mechanism and also precludes materials passing through the valve from escaping into the environment. A bonnet seal assembly may be utilized to seal the bonnet area from the material flow opening. This bonnet seal is also subject to uneven wear and premature failure. The uneven perpendicular thrusting motion of the blade, referred to above, causes uneven compression on the bonnet seal, which in-turn leads to wear and premature seal failure. Since the bonnet seal provides the only isolation between the valve blade and the atmosphere, failure of the seal allows material to escape into the atmosphere. Material leaking into the bonnet may also interfere with proper valve operation.  
         [0010]     Thus, there remains a need in the art for a positively sealing gate valve capable of handling dry bulk solid materials without the problems of seal failure and material packing inherent in the prior art valve designs.  
       BRIEF SUMMARY OF THE INVENTION  
       [0011]     The present invention is directed to a high-pressure gate valve having a housing defining an opening through which dry, liquid, or gaseous material passes, a slideable blade which moves on blade support guides attached to the housing, an actuating cylinder to extend and retract the blade, and lifting structure to raise the blade in a generally planar motion as the blade is extended into its closed position. “High pressure” is used herein to refer to any valve operating above atmospheric pressure but especially installations where the pressure is in the range of 50-90 p.s.i.g. The perpendicular lifting of the blade (relative to the primary closing movement) positively seals the upper surface of the blade to an annular elastomeric seal in upper portion of the housing.  
         [0012]     Upper and lower plates cooperate to form a bonnet which encloses the rear portion of the valve with a continuous resilient bonnet load seal surrounding the blade at one end and isolating the actuating portion of the valve from the material handling portion. As the blade is raised by the lifting structure, the bonnet load seal at the rear portion of the blade compresses against an upper bonnet cover, thus maintaining a seal between the front material handling portion of the valve and the rear actuating portion. The bonnet load seal includes one or more continuous air cavities which when compressed on one side increase the pressure on the other sides. Additionally, the bonnet seal is designed to scrape material from the blade surface as the blade retracts.  
         [0013]     In one exemplary embodiment, the valve includes a housing having scalloped blade guides along opposing inner sides. A blade having a semi-circular shaped nose with flat portions on opposite sides of the semi-circle, slides on the guides to block and unblock an opening through the housing as the blade is extended and retracted. An actuating cylinder coupled to a clevis at the rear edge of the blade extends and retracts to operate the blade.  
         [0014]     Lifting structure, comprising multiple lifting lugs at the front of the housing and a ramp extending across the center portion of the housing, raises the entire blade in a generally planar motion as the blade extends to positively seal the upper surface of the blade against the elastomeric seal mentioned above. The lifting lugs engage replaceable nylon wear surfaces on the bottom of the blade to raise the front portion of the blade, while a tapered surface on the clevis at the rear of the blade engages the ramp to raise the rear edge of the blade. Thus, as the blade is extended the front edge engages the lifting lugs and the clevis at the rear edge engages the ramp to raise the blade in a planar motion. The blade will continue to seal as a result of the “ramping action” even as the elastomeric seal wears.  
         [0015]     A unique blade shape includes a rounded end which mergers into flat sections on either side which move over the blade guides. This configuration eliminates the void area between the blade and the housing where material can accumulate and become wedged upon blade closure.  
         [0016]     Additional aspects of the invention, together with the advantages and novel features appurtenant thereto, will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following, or may be learned from the practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]      FIG. 1  is a top plan view of an exemplary embodiment of a gate valve in accordance with the present invention.  
         [0018]      FIG. 2  is a cross-sectional side view of the gate valve of  FIG. 1 .  
         [0019]      FIG. 3  is an exploded, perspective view of the gate valve of  FIG. 1 .  
         [0020]      FIG. 3   a  is a vertical cross sectional view taken along line  3   a - 3   a  of  FIG. 3 .  
         [0021]      FIG. 4  is a partial, perspective view of the front portion of the valve of  FIG. 1  with the upper housing removed.  
         [0022]      FIG. 5  is an enlarged, partial view of the front portion of the valve of  FIG. 2  with the blade in a nearly extended position.  
         [0023]      FIG. 6  is an enlarged, partial view of the front portion of the valve of  FIG. 2  with the blade in its fully extended, closed position.  
         [0024]      FIG. 7  is an enlarged, partial cross-sectional view of the rear lifting ramp, floating clevis and bonnet load seal which encases one end of the blade.  
         [0025]      FIG. 7   a  is an enlarged vertical cross-sectional view illustrating the substantially vertical movement of the blade relative to the actuating cylinder coupler.  
         [0026]      FIG. 8  is an exploded view of the bonnet seal assembly of  FIG. 7 .  
         [0027]      FIG. 9  is a greatly enlarged cross-sectional view of the bonnet seal assembly showing the details of construction. 
     
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS  
       [0028]     A high pressure gate valve according to an exemplary embodiment of the present invention is depicted in  FIGS. 1 through 8 . While the invention will be described in detail hereinbelow with reference to this embodiment, it should be understood that the invention is not limited to the specific constructions or configurations shown in the exemplary embodiment. Rather, one skilled in the art will appreciate that a variety of configurations may be implemented in accordance with the present invention.  
         [0029]     Looking first to  FIGS. 1-3 , a gate valve in accordance with an exemplary embodiment of the present invention is designated generally by the numeral  10 . Gate valve  10  includes a main housing  12  having a front material-handling portion  14  and a rear actuating portion  16 . A circular opening  18  through front portion  14  allows material to flow through the valve.  
         [0030]     A disc-shaped upper flange  20  attaches to the upper surface of main housing  12  with fasteners. Flange  20  includes apertures  22  for connecting valve  10  to various inlet lines, tubes or couplers. An elastomeric annular seal  24  extends around the lower surface of housing  20  and protrudes into the opening  18  area of main housing  12 , presenting a circular sealing surface.  
         [0031]     A lower housing  26  extends the length of housing  12 , and attaches to the lower surface of this housing with fasteners. An approximate perimeter o-ring seal  27  ( FIG. 4 ) between housing  12  and housing  26  at the interface between the two assures an air tight seal. Lower housing  26  covers rear portion  16  of main housing  12  and provides a funnel-shaped exit passage  28  for opening  18 . Thus housing  26  forms the lower half of a bonnet which encloses the rear portion of the valve. A flange  30  extending outwardly from exit passage  28  includes numerous apertures  32  for connecting the lower cover  26  to other components of the system. An upper cover plate  34  and a seal retainer plate  36  attach to the upper surface of housing  12  to form the upper half of the valve bonnet. Main housing  12 , flange  20 , lower housing  26 , upper cover  34 , and seal retainer plate  36  are preferably made of strong, rigid material. Most preferably they are made of aluminum or stainless steel.  
         [0032]     As best seen in  FIGS. 2-4 , front and rear blade support guides  38 ,  40  are attached to opposing inner walls of main housing  12 . Front guides  38  attach within front portion  14  of housing  12  and rear guides  40  attach within rear portion  16  of the housing. The guide tracks present an “L”-shaped ledge upon which blade  42  rides. As shown in  FIG. 2 , front guides  38  form scalloped portions  44  along the length of the ledge. Front and rear guides  38 ,  40  are preferably made from a rigid polymeric material or high temperature metal alloy.  
         [0033]     Referring to  FIGS. 3, 8  and  9  a bonnet load seal assembly is designated generally by the numeral  46  and includes an elastomeric perimeter load seal  148 , forward scraper housing  150 , scraper seals  152 , elastomeric packing gland  154  and housing support  156 . Details of construction of load seal  148  are shown in  FIG. 8 . Load seal  148  is made of an elastomeric material and includes a tung portion  148   a  which is received in a correspondingly shaped groove formed in the assembly by scraper  150  and housing  156 . Two air passages  148   b  are formed in the load seal body and extend the length of the seal. Overlying these passages are raised portions  148   c.  Bonnet seal assembly  46  extends across main housing  12 , separating front portion  14  from rear portion  16 . Assembly  46  presents a slot  48  through which blade  42  passes. The compressible load seal  148  extends around the outer perimeter of scraper  150  and housing  156 , engaging seal retainer plate  36  on the top and a frame cross member support  47  at the bottom. Seal  148  also engages the sides of housing  12  at the opposite ends of the assembly. Preferably seal  148  is made of a resilient material, most preferably it is made of silicone rubber.  
         [0034]     An actuating cylinder  52  is attached to the rear edge of main housing  12  and includes a shaft  54  which extends into rear housing portion  16  and is enclosed within the bonnet. Various o-rings and seals provide a leak-proof junction where shaft  54  passes through the rear of main housing  12 . A cylinder clevis coupler  56  is attached to the end of shaft  54  and is received by a floating clevis yoke  58 , which is in-turn attached to the rear edge of blade  42 . A ramp  60  extends between and is attached to the frame cross member  47  of main housing  12  just to the rear of bonnet seal assembly  46 , presenting an inclined upper surface  62 . As best seen in  FIG. 7 , the leading edge of clevis yoke  58  includes a tapered lower surface  64  corresponding to the taper of the upper surface  62  of ramp  60 .  
         [0035]     Referring now to  FIGS. 3 and 4 , a forward support liner  68  having protruding lifting lugs  70  is attached along the inner surface of the front-most portion of housing  12 . Lifting lugs  70  protrude from liner  68  into opening  18  and present angled surfaces for engagement with the lower surface of blade  42 . A number of replaceable lug lifting guides  72  are attached within cutouts  74  in the lower surface of blade  42  at positions corresponding to the locations of lifting lugs  70 . Blade  42  is preferably made of a strong, rigid material. Most preferably it is made of stainless steel. Guides  72  are preferably made from a strong polymeric material. Most preferably they are nylon.  
         [0036]     Still referring to  FIGS. 3 and 4 , blade  42  includes a rear edge  76  to which clevis yoke  58  is joined and a semi-circular shaped front nose portion  78 . Two flat portions  80   a,    80   b  join front nose portion  78  to the side edges  80   c  of the blade. Flat portions  80   a,    80   b  effectively position nose portion  78  back from the sides of blade  42 . Flat portions  80   a  and  80   b  extend perpendicular to a tangent to the arcuate nose portion  72  at the two terminal ends of the arc and are also perpendicular to guides  38  and  40 . Preferably the side edges  80   c  of blade  42  are convex to maximize seal integrity while the blade passes through bonnet seal assembly  46 . See  FIG. 3   a.    
         [0037]     With the valve fully assembled, blade  42  extends from rear portion  16  of housing  12  to front portion  14  of housing  12 , passing through seal assembly  46 . Clevis yoke  58 , attached to the rear edge of blade  42 , is coupled via clevis coupler  56  to shaft  54  of actuating cylinder  52 , which is attached to the rear of housing  12 . Each side edge of blade  42  rests on the ledge portion of the corresponding front and rear blade guides  38 ,  40 , which are attached on opposing sides of main housing  12 .  
         [0038]     Seal assembly  46 , cover plate  34 , seal retainer  36 , and lower housing  26  form the bonnet which encloses rear portion  16  of housing  12 , protecting actuator shaft  54 , coupler  56 , and yoke  58 . With the covers in place, seal  148  engages retainer  36 , support member  47 , and opposite sides of main housing  12 . Any air leakage or minute material ingress across seal assembly  46  is retained within the bonnet allowing equalization of pressure between rear portion  16  and front portion  14  of housing  12 .  
         [0039]     In normal operation, with power applied to actuating cylinder  52  and shaft  54  retracted, blade  42  is fully retracted and opening  18  is unblocked to allow material to pass through the valve. As actuator  52  is extended, blade  42  moves to begin blocking opening  18 . As best seen in  FIG. 5 , as the actuator extends and the nose of blade  42  approaches the front edge of main housing  12 , blade  42  passes under annular seal  24 , eventually blocking opening  18 .  
         [0040]     Referring to  FIGS. 6 and 7 , as the cylinder is extended further, guides  72  on the lower surface of blade  42  engage lifting lugs  70  at the front of main housing  12 . The angle of the lifting lugs raises the front edge of blade  42  to force the upper surface of blade  42  against annular seal  24 . Simultaneously, at the rear of blade  42  tapered lower surface  64  of clevis yoke  58  engages the tapered upper surface  62  of ramp  60 . The angle of the engaged tapered surfaces raises the rear portion of blade  42  against annular seal  24 . With reference to  FIG. 3 , clevis yoke  58  presents an oblong slot  82  which receives clevis coupler  56  such the yoke  58  is free to move vertically relative to coupler  56  while the two components remain coupled. This simultaneous lifting of both ends of blade  42  in a substantially planar motion and perpendicular to the direction of travel of shaft  54  positively seals the upper surface of blade  42  against annular seal  24 . See  FIG. 7   a  where the raised positions of blade  42  and clevis  58  are shown in broken lines.  
         [0041]     This perpendicular planar movement of blade  42  allowing it to float relative to shaft  54  also eliminates torisional loads that uneven, nonplanar vertical movement would place on the shaft using a conventional fixed clevis coupling. The force of the blade against seal  24  will limit the cylinder stroke once a material tight seal is obtained. Seal wear is reduced by the perpendicular planar motion of the blade and the absence of substantial sliding movement between seal  24  and the blade  42 . It is also to be noted that the inclined ramp surfaces presented by lifting lugs  70  and ramp  60  are of a length such that when the shaft  54  of cylinder  52  is extended a gap G 1  ( FIG. 2 ) is present between the front edge of the blade and the housing  12  and a similar gap, G 2  is present between the leading edge of ramp  60  and the leading edge of clevis yoke  58 . These gaps accommodate further vertical and horizontal movement of blade  42  as seal  24  wears over time. Another advantage of the aforedescribed construction is that as a result of the perpendicular planar motion of blade  42  the power requirements for cylinder  52  are reduced over conventional knife gate valves which rely to some extent upon an uneven wedging action to accomplish the desired seal. When cylinder  52  is to be retracted, blade  42  can slide down the inclined ramp surfaces away from the elastomeric seal with virtually no sliding contact between the two components.  
         [0042]     Referring to  FIGS. 8 and 9 , scraper  152  removes material from blade  42  when the latter is retracted by cylinder  52 . Scraper  152  comprises upper and lower sections each of which has an outer layer  152   a  of elastomeric material and an inner blade contacting layer  152   b  of hard polymer material (see  FIG. 9 ). The elastomeric layer is live loaded when assembled so as to apply a compressive force on layer  152   b.  Packing gland  154  comprises a continuous oval shaped element formed from an outer layer  154   a  of elastomeric material and an inner blade contacting layer  154   b  of cord formed from a material such as Teflon. The elastomeric material is live loaded to place the Teflon cord under compression. Material removed by scraper  152  is precluded from entering the bonnet area. Scraper seals  152  are held in place by housing  150 , packing gland  154  and housing support  156 . The bonnet area is further sealed against the entry of material by load seal  148 . As blade  42  is extended into its flow blocking position and moves in a perpendicular direction as previously explained, the upper surface of the blade will apply pressure to bonnet seal assembly  46  causing compression of load seal  148 . The compressive force on the elastomeric material is further enhanced by raised portions  148   c  engaging retainer plate  36 . This compressive force causes air in passages  148   b  to be forced from the passage in the area where pressure is applied and the air is redistributed throughout the unobstructed length of the air passages. This increase in air pressure in the unobstructed portions of the passageways applies pressure to the elastomeric material and facilitates maintaining a material tight seal at the bottom and sides of the seal assembly  46 , notwithstanding the slight perpendicular movement of the entire assembly. When blade  42  moves to its retracted position seal assembly  46  returns to its neutral position and the air within the passageways of load seal  148  will equalize to provide equal compression on all sealing surfaces.  
         [0043]     Looking still to  FIG. 3 , slot  48  through seal assembly  46  allows blade  42  to extend and retract to block opening  18 . Slot  48  may not form an airtight seal with blade  42 , thus any air leakage will cause equalization of pressure between front portion  14  and rear portion  16  of main housing  12 . Once pressure is equalized, material is prevented from migrating via the air stream between front material handling portion  14  and rear bonnet portion  16  of the gate valve. Sealed bonnet area  16  prevents air and material leakage to environment.  
         [0044]     In operation of the valve bulk material lying on the surfaces of guides  38  is pushed out of the way by the flats  80   a  and  80   b.  The cutout areas of scalloped portions  44  allow material pushed off the upper surfaces of the guides to fall down and through the valve without wedging or jamming. Thus, as the blade is extended, material will be cleared from in front of the blade and will not be packed as the blade reaches the end of its path of travel where any material cleared from the guides is discharged into the material stream.  
         [0045]     From the foregoing it will be seen that this invention is one well adapted to attain all ends and objectives herein-above set forth, together with the other advantages which are obvious and which are inherent to the invention.  
         [0046]     Of course, other embodiments configuration will be apparent to those skilled in the art, and are contemplated by and within the scope of the present invention.  
         [0047]     Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matters herein set forth or shown in the accompanying drawings are to be interpreted as illustrative, and not in a limiting sense.  
         [0048]     The terms “substantially”, “generally”, “approximately”, and “relatively” as used herein may be applied to modify any quantitative representation which could permissibly vary without resulting in a change in the basic function to which it is related. For example, while the extending blade is described as “substantially” blocking the valve opening, variance from fully blocked is allowable if the variance does not materially alter the capability of the invention. Likewise, the variance from any quantitative representation, such as proximate or adjacent as used herein, is permissible if the variance does not materially alter the capability of the invention.  
         [0049]     While specific embodiments have been shown and discussed, various modifications may of course be made, and the invention is not limited to the specific forms or arrangement of parts and steps described herein, except insofar as such limitations are included in the following claims. Further, it will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.