Abstract:
The present invention provides an actuated gate valve including a gate valve housing and an actuating device attached to one end of the gate valve housing. The gate valve housing includes a displaceable valve plate, and the actuating device includes an actuator rod connected to the valve plate so that a force applied to the valve plate by the actuator rod is coincident with a displacement of the valve plate.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/673,381, filed Apr. 21, 2005, which is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to valves. More particularly, the present invention relates to actuated gate valves. 
     2. Description of Related Art 
     Gate valves are used to stop the flow of fluid in a tube or pipe. Typically, gate valves can handle material similar to the viscosity of water, or higher, as well as material that is in a vacuum or under small levels of pressure. 
     An exemplary prior art gate valve  100  is depicted in  FIG. 1 . An activation device  105 , such as a pneumatic valve, is attached to the back side of a valve assembly frame  110  and transmits opening and closing forces to a valve plate  115 , located on the front side of the valve assembly frame  110 , using an actuator rod  125  coupled to a link  120  connected to an intermediate stem  155 . A sealed housing  135  encloses the valve plate  115 , and includes a coupling  130  through which the intermediate stem  155  passes. A piping interface plate  140 , located on the front side of the housing  135 , connects to a piping system (not shown), while another piping interface plate  142 , located on the back side of the housing  135 , attaches the housing  135  to the valve assembly frame  110 . The piping interface plate  141  is coupled to the piping system (not shown) through an opening in the valve assembly frame  110 . An additional piping interface plate (not shown) may also be attached to the back side of the valve assembly frame  110 . 
     If the link  120  is connected directly to the intermediate stem  155  (not shown), an undesirable torque is applied to the intermediate stem  155  due to the misalignment of the line of action of the force applied by the activation device  105  and the centerline of the intermediate stern  155 . This torque produces undesirable stresses in the intermediate stern  155  and the valve plate  115 , as well as misalignments among the various components. 
     In order to reduce the effects of these undesirable stresses and misalignments, a spring assembly  150  can be incorporated into the gate valve  100  (shown), The spring assembly  150  includes upper and lower nuts  152 ,  154 , attached to the intermediate stem  155 , and upper and lower springs  156 ,  158 , acting between the upper and lower surfaces of the link  120  and the upper and lower nuts  152 ,  154 , respectively. Forces applied by the link  120  to the spring assembly  150  are transmitted to the intermediate stem  155  through the upper and lower nuts  152 ,  154 , while misalignment of the Intermediate stern  155  is reduced due to the transverse flexibility of the spring assembly  150  and the freedom of movement afforded by the simple, contact interfaces between the upper and lower surfaces of the link  120  and the upper and lower springs  156 ,  158 , respectively, as well as between the upper and lower springs  156 ,  158 , the upper and lower nuts  152 ,  154 , respectively. 
     However, the prior art gate valve  100  is mechanically complex, the undesirable stresses and misalignments have not been entirely eliminated and the upper and lower springs  156 ,  158  can limit the force that can be applied by the activation device  105  to the valve plate  115 , resulting in unsatisfactory performance in many situations. Therefore, there is a need for an actuated gate valve that does not suffer from these infirmities. 
     BRIEF SUMMARY OF THE INVENTION 
     Embodiments of the present invention provide an actuated gate valve including a gate valve housing and an actuating device attached to one end of the gate valve housing, The gate valve housing includes a displaceable valve plate, and the actuating device includes an actuator rod connected to the valve plate so that a force applied to the valve plate by the actuator rod is coincident with a displacement of the valve plate. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)  
       The above and other advantages of this invention will become more apparent by the following description of invention and the accompanying drawings. 
         FIG. 1  shows a prior art gate valve design. 
         FIG. 2  depicts a gate valve in accordance with an embodiment of the present invention. 
         FIG. 3  is an exploded view of a gate valve in accordance with an embodiment of the present invention. 
         FIG. 4  illustrates an application of the present invention in accordance with an embodiment thereof. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIGS. 2 and 3  depict a gate valve  200  in accordance with an embodiment of the present invention. 
     The gate valve  200  includes an activation device  205  which is attached to one end of a sealed housing  235 . In a preferred embodiment, the activation device  205  may be a double-acting hydraulic or pneumatic cylinder  205  that includes activation fluid couplings  206 ,  207 , while in other embodiments, the activation device  205  may be an electric actuator, an electric motor, etc. The cylinder  205  includes an interface plate  208 , which is attached to an actuator interface plate  236  of housing  235  using, for example, bolts  209  and nuts  239 , welds or weldments, etc. A gasket may be interposed between interface plates  208  and  236 , if necessary. The source of the activation fluid may be, for example, a hydraulic system on the vehicle on which the gate valve  200  is mounted, etc. In a preferred embodiment, cylinder  205  operates under a pressure range of about 1,500 to 3,000 psi. 
     In the preferred embodiment, the double-acting cylinder  205  advantageously provides a direct closing force of up to 4000 pounds in order to clear any small obstructions in the gate valve  200 , such as, for example, sand, straw, sediment, etc. Furthermore, a closing force of this magnitude ensures complete closure of the valve plate  215 , which is depicted in an open position in  FIG. 2 , and in a closed position in  FIG. 3 . The gate valve  200  may also regulate the fluid flow by positioning valve plate  215  in a partially open (or partially dosed) position. 
     The cylinder  205  hosts an actuator rod  225  attached to the valve plate  215  using, for example, a pin  226  passing through holes  227 ,  228  in the actuator rod  225  and valve plate  215 , respectively. The direct, in-line connection of the actuator rod  225  to the valve plate  215  provides several advantages over the prior art. For example, the link  120 , the intermediate stem  155  and the spring assembly  150  (shown in  FIG. 1 ) are not required, thereby completely eliminating the undesirable stresses and misalignments attendant to prior art devices. Commensurately, the coupling  130  is also eliminated, thereby eliminating the need for stem packing or some other form of seal at the top of the housing  135 . 
     In one embodiment, the gate valve  200  is made of stainless steel, and housing  235  may be cast or machined as two identical parts, such as a front housing  235   f  with a front actuator interface plate  236   F , and a back housing  235   b  with a back actuator interface plate  236   b . Front and back housings  235   f ,  235   b  may be attached together using, for example, bolts  238  and nuts  239 , welds or weldments, etc. A gasket may be interposed between front and back housings  235   f ,  235   b , if necessary. A cylindrical cavity  246   f ,  246   b  is formed In each housing  235   f ,  235   b  to permit the actuator rod  225  to move the valve plate  215  in a vertical direction (labeled “displacement”) within the main cavity  244   f ,  244   b . An additional cutout region,  245   f ,  245   b  may also be formed within each housing  235   f ,  235   b  to hold grease or other material to help seal and lubricate the valve, as well as to provide a cavity in which undesirable foreign material may be captured so as to prevent the valve plate  215  from pinching at the top of the main cavity  244   f ,  244   b . 
     A front piping interface plate  240   f , located on the front housing  235   f , is connected to the piping system (not shown), while a back piping interface plate  240   b  (not visible), located on the back housing  235   b , is similarly connected. Piping interface plates  240   f ,  240   b  include openings  242   f ,  242   b  for fluid inlet and outlet. 
     Accordingly, the gate valve  200  presents several advantages over the prior art devices, such as eliminating the necessity of assembling two halves of the gate valve and then drilling and tapping the assembly to provide a cavity for the seal packing and nut. These advantages simplify the manufacturing processes, improve performance and promote better reliability in the field. 
       FIG. 4  presents an application of the present invention in accordance with an embodiment thereof. For example, one application of the gate valve  200  would be on a liquid waste-handling tank  300  to stop the flow to a discharge pipe. Other applications may include liquid waste pumps, generally, as well as pumping systems in which an in-line, shut-off valve is needed but in which small debris pose a challenge for standard gate valves. 
     While this invention has been described in conjunction with specific embodiments thereof, many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth herein, are intended to be illustrative, not limiting. Various changes may be made without departing from the true spirit and full scope of the invention as set forth herein.