High power hydraulic cylinder

Abstract

A hydraulic device that includes a case, and a substantially hollow rod slidably extending from the case. The rod has a ram on a first end thereof that caps the rod to form a first hydraulic piston. The rod has a second hydraulic piston on a second end thereof, inside the case. The first and second pistons are at least partially radially coextensive, and a pressure barrier inhibits high pressure on the first piston inside the hollow rod from reaching a side of the second piston that faces the first piston.

1 . A hydraulic device comprising;
 a case; and   a substantially hollow rod slidably extending from the case, the rod having a ram on a first end thereof that caps the rod to form a first hydraulic piston, and the rod having a second hydraulic piston on a second end thereof, inside the case;   wherein the first and second piston are at least partially radially coextensive, and a pressure barrier inhibits high pressure on the first piston inside the hollow rod from reaching a side of the second piston that faces the first piston.   
     
     
         2 . The hydraulic device of  claim 1 , further comprising a rod guide inside the case, and coaxial thereto, the second piston slidably interposing the case and the rod guide. 
     
     
         3 . The hydraulic device of  claim 2 , wherein the pressure barrier interposes the guide rod and the substantially hollow rod. 
     
     
         4 . The hydraulic device of  claim 3 , wherein a high-pressure, variable volume comprises a first volume inside the guide rod, a volume bound by the case and the second piston, and a volume between the first piston and the pressure barrier. 
     
     
         5 . The hydraulic device of  claim 4 , wherein a low-pressure, variable volume comprises an area bound by the case, the guide rod, the second piston, and the pressure barrier. 
     
     
         6 . The hydraulic device of  claim 5 , wherein the case and ram are urged apart by a relatively high pressure fluid inside the high pressure volume compared to the low pressure volume, and the case and ram are urged together by a relatively high pressure fluid inside the low pressure volume relative to the high pressure volume. 
     
     
         7 . The hydraulic device of  claim 5 , further comprising a high pressure port on the case entering the high pressure volume, and a low pressure port on the case entering the low pressure volume. 
     
     
         8 . The hydraulic device of  claim 5 , further comprising at least one pressure equalizing port defined in the rod guide. 
     
     
         9 . The hydraulic device of  claim 5 , further comprising at least one pressure equalizing port defined in the hollow rod. 
     
     
         10 . The hydraulic device of  claim 3 , wherein the case and rod guide have a substantially circular cross-section. 
     
     
         11 . The hydraulic device of  claim 3 , wherein the rod guide attaches inside the case on a first end thereof, and has a second tapered and threaded end that accepts the pressure barrier and retains the pressure barrier against the tapered end by an attached threaded cap. 
     
     
         12 . The hydraulic device of  claim 11 , further comprising a retainer on an open end of the case engaging the hollow rod and preventing the second cylinder from contacting the pressure barrier. 
     
     
         13 . A device comprising:
 a substantially cylindrical case having a first, open end and a substantially cylindrical guide member inside thereof attached to a second end, the case and guide member being substantially coaxial;   a fixed pressure barrier on and end of the guide member proximate the open end of the case;   a first piston defining a hollow center and located between the case and guide member, the piston being movable between the pressure barrier and the second end of the case;   a hollow rod attached on a first end to the first piston, encircling the pressure barrier, and attaching on a second end to a second piston.   
     
     
         14 . The device of  claim 13 , wherein the guide member defines a pressure equalizing port proximate the second end of the case such that a first single pressure volume of variable total size is defined by 1) the variable volume bound between the first piston, the case, and the guide member, 2) the volume inside the guide member, and 3) the volume between the pressure barrier, the second piston, and the hollow rod. 
     
     
         15 . The device of  claim 14 , further comprising a hydraulic port on the case accessing the first single pressure volume. 
     
     
         16 . The device of  claim 13 , wherein the guide member has a tapered portion and a threaded end, the guide member retaining the pressure barrier between the tapered portion and the threaded end by an attached threaded cap. 
     
     
         17 . The device of  claim 13 , further comprising a retainer attached to the open end of the case and abutting the hollow rod on a side opposite the pressure barrier such that the hollow rod slides into the retainer, the retainer sealing the second end of the case to prevent the first piston from leaving the case 
     
     
         18 . The device of  claim 13 , wherein the hollow rod defines a pressure equalizing port proximate the first piston such that a second single pressure volume of variable total size is defined by 1) the variable volume bound inside the hollow rod, outside the guide member, and between the first piston and pressure barrier, and 2) the variable volume bound outside the hollow rod, inside the case, and between the first piston and retainer. 
     
     
         19 . The device of  claim 18 , further comprising a hydraulic port on the case accessing the second single pressure volume. 
     
     
         20 . A method comprising:
 providing a substantially cylindrical case having a first, open end and a substantially cylindrical guide member inside thereof attached to a second end, the case and guide member being substantially coaxial;   inserting a piston that defines a hollow center between the case and guide member such that the guide member passes through the hollow center and the piston is movable along the guide member;   attaching a fixed pressure barrier on and end of the guide member proximate the open end of the case such that the piston does not leave the case;   attaching a first end of a hollow rod to the piston such that the hollow rod encircles the pressure barrier;   attaching a cap to a second end of the hollow rod, the cap being sized such that the cap and first piston are at least partially radially extensive.