Tandem cylinder apparatus and method of using same

Abstract

A tandem cylinder arrangement and a method of operating such a cylinder used particularly in valve actuators. Two load plates are provided with fluid acting on each load plate and the tending to move both load plates together. A cavity between the two load plates is isolated from the hydraulic fluid and a vent allows gasses to enter from and to ingress to the cavity.

I claim:  
     
         1 . Method of increasing the force applied to an piston rod and cylinder arrangement, said method comprising applying a pressure medium to a first cavity defined by a seal plate of a piston head and a first load plate of a movable cylinder, applying said pressure medium to a second cavity defined by a surface of a second load plate and the inside of said piston head, evacuating gasses from a third cavity defined by a surface of said second load plate and a surface of said seal plate and allowing said movable cylinder to move under said force applied by said pressure medium in said first and second cavities.  
     
     
         2 . Method as in  claim 1  wherein said piston rod and cylinder arrangement is an actuator.  
     
     
         3 . Method as in  claim 2  wherein said pressure medium is a fluid.  
     
     
         4 . Method as in  claim 3  wherein said pressure medium is hydraulic fluid.  
     
     
         5 . Method as in  claim 2  wherein said pressure medium is a gas.  
     
     
         6 . Method as in  claim 2  wherein said movable cylinder is connected to an indicator rod.  
     
     
         7 . Method as in  claim 1  wherein said piston rod and cylinder arrangement is single acting.  
     
     
         8 . Method as in  claim 1  wherein said piston rod and cylinder arrangement is double acting.  
     
     
         9 . Method of increasing the force applied to a piston rod and cylinder arrangement used in an actuator for opening and closing a valve, said method comprising applying a pressure medium to a first cavity defined by a seal plate of a piston head and a first load plate of a movable cylinder, applying said pressure medium to a second cavity defined by the upper surface of a second load plate and the inside of said piston head, evacuating gasses from a third cavity defined by the lower surface of said second load plate and the upper surface of said seal plate and allowing said movable cylinder to move under said force applied by said pressure medium in said first and second cavities.  
     
     
         10 . Method as in  claim 9  wherein said pressure medium is a fluid or a gas.  
     
     
         11 . Method as in  claim 10  wherein said fluid is hydraulic fluid.  
     
     
         12 . Method as in  claim 10  wherein said gas is air.  
     
     
         13 . Method as in  claim 9  wherein said piston and cylinder arrangement is pneumatic or hydraulic.  
     
     
         14 . Method of increasing the force applied to a piston rod and cylinder arrangement, said method comprising applying a pressure medium to a first cavity defined by a seal plate of a movable piston head and a first load plate of a cylinder, applying said pressure medium to a second cavity defined by the lower surface of a second load plate of said movable cylinder and the inside of said piston head, evacuating gasses from a third cavity defined by the upper surface of said second load plate and the lower surface of said seal plate and allowing said piston head to move under said force of said pressure medium in said first and second cavities.  
     
     
         15 . Method as in  claim 14  wherein said piston rod and cylinder arrangement is used with an actuator.  
     
     
         16 . Apparatus for enhancing the force applied to a hydraulic or pneumatic cylinder arrangement comprising a piston head, a seal plate associated with said piston head, a first load plate associated with a movable cylinder and being movable with said cylinder, a second load plate movable with said cylinder, a first cavity defined by a volume between said first load plate and said seal plate, a second cavity defined by a volume between said piston head and said second load plate, and a third cavity defined by a volume between said second load plate and said seal plate, said third cavity having a vent to allow the escape of gases from said third cavity during movement of said cylinder and said second load plate.  
     
     
         17 . Apparatus as in  claim 16  wherein said cylinder arrangement is an actuator used to open and close a valve.  
     
     
         18 . Apparatus as in  claim 17  wherein said first load plate is separate from and fixed to said movable cylinder.  
     
     
         19 . Apparatus as in  claim 17  wherein said seal plate is separate from and fixed to said piston head.  
     
     
         20 . Apparatus as in  claim 17  wherein said second load plate is movable within said piston head and fixed to an indicator rod.  
     
     
         21 . Apparatus as in  claim 20  wherein said indicator rod moves with said movable cylinder.  
     
     
         22 . Apparatus for enhancing the force applied to a hydraulic or pneumatic cylinder arrangement comprising a piston head, a first load plate means associated with a movable cylinder for movement with said cylinder, a second load plate means for movement with said cylinder, a seal plate means for sealing said piston head, a first cavity defining a volume between said first load plate means and said seal plate means, a second cavity defining a volume between said piston head and said second load plate means, and a third cavity defining a volume between said second load plate means and said seal plate means, said third cavity having a vent means for allowing the escape of gases from said third cavity during movement of said cylinder and second load plate means.  
     
     
         23 . Apparatus as in  claim 22  wherein said hydraulic or pneumatic cylinder arrangement is an actuator.