# US 5,341,725 A · Twin piston power cylinder > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,341,725 A - Document ID: US5341725A - Status: Granted - Kind: A - Application number: 08/076,445 - Filed: 1993-06-14 - Granted: 1994-08-30 - Earliest claimed: 1993-06-14 - Inventors: James B. Dick - Web page: https://patentgrep.com/patent/US5341725A ## CPC - F01B 7/00: Machines or engines with two or more pistons reciprocating within same cylinder or within essentially coaxial cylinders (in opposite arrangement relative to main shaft F01B1/08) - F01B: MACHINES OR ENGINES, IN GENERAL OR OF POSITIVE-DISPLACEMENT TYPE, e.g. STEAM ENGINES (of rotary-piston or oscillating-piston type F01C; of non-positive-displacement type F01D; internal-combustion engines F02B; combustion-product engine plants F02G; machines or engines, other than of positive-displacement type, for liquids F03B; positive-displacement engines driven by liquids F03C; wind motors F03D; positive-displacement machines for liquids F04B; rotary-piston, or oscillating-piston, positive-displacement machines for liquids F04C) ## Abstract A power cylinder (10) has two pistons (12, 20) slidably mounted within separate cylinders (14, 22) to define inner and outer chambers (16, 18; 24, 26) within each cylinder. One or more rods (28) are coupled between the pistons. The outer chambers (18, 26) are coupled together to allow pressurized hydraulic or pneumatic fluid to flow therebetween. The inner chambers (16, 24) are coupled together to allow pressurized hydraulic or pneumatic fluid to flow therebetween. The fluid flow aforesaid may be achieved by using two hollow rods (128, 130) and allowing the fluid to flow through the rods between the respective chambers. A guard (44) may surround first and second cylinders (14, 22). Bearings (46, 48) may be fixed around the opposed inner ends of cylinders (14, 22) to allow slidable displacement of the cylinders relative to guard (44). Seals (146, 148) may be fixed around the opposed inner ends of cylinders (114, 122) to provide a hydraulic chamber (158) enclosed by the guard (144) between the cylinders (114, 122). Where two rods interconnect the dual cylinders, the first piston (212) may be connected to the second cylinder (222) and the first cylinder (214) may be connected to the second piston (220). ## Claims ### Claim 1 A power cylinder (10) having a first piston (12) slidably mounted within a first cylinder (14) to define inner and outer chambers (16, 18) within said first cylinder, a second piston (20) slidably mounted within a second cylinder (22) to define inner and outer chambers (24, 26) within said second cylinder and at least one rod (28) coupled between said first and second pistons, characterized by: (a) first fluid flow means (40) coupled to said first and second cylinder inner chambers; (b) second fluid flow means (42) coupled to said first and second cylinder outer chambers. (c) a cylindrical guard (44) surrounding said first and second cylinders; and, (d) bearing means for allowing slidable displacement of said first and second cylinders relative to said guard. ### Claim 2 (depends on 1) A power cylinder as defined in claim 1, further comprising: (a) sealing means (46, 48; 146, 148) between said guard and said first and second cylinders for hydraulically isolating a chamber (58; 158) between said guard and said first and second cylinders; and, (b) a fluid flow port (162) in said guard for fluid flow to and from said isolated chamber. ### Claim 3 (depends on 3) A power cylinder as defined in claim 3, further comprising filtration means (151, 153) for preventing foreign matter penetration between said guard and said first or second cylinders. ### Claim 4 A power cylinder (100) having a first piston (112) slidably mounted within a first cylinder (114) to define inner and outer chambers (116, 118) within said first cylinder, a second piston (120) slidably mounted within a second cylinder (122) to define inner and outer chambers (124, 126) within said second cylinder, characterized by: (a) a first hollow rod (130) coupled between said first and second pistons for fluid flow through said first rod between said first and second outer chambers; (b) a second hollow rod (128) coupled between said first and second pistons for fluid flow through said second rod between said first and second inner chambers; (c) a first fluid flow port (134) in one of said outer chambers; (d) a second fluid flow port (132) in one of said inner chambers; and, (e) a cylindrical guard (144) surrounding said first and second cylinders. ### Claim 5 (depends on 4) A power cylinder as defined in claim 4, further comprising: (a) sealing means (46, 48; 146, 148) between said guard and said first and second cylinders for hydraulically isolating a chamber (58; 158) between said guard and said first and second cylinders; and, (b) a third fluid flow port (162) in said guard for fluid flow to and from said isolated chamber. ### Claim 6 (depends on 5) A power cylinder as defined in claim 5, further comprising filtration means (151, 153) for preventing foreign matter penetration between said guard and said first or second cylinders. ### Claim 7 A power cylinder (200) having a first piston (212) slidably mounted within a first cylinder (214) to define inner and outer chambers (216, 218) within said first cylinder, and a second piston (220) slidably mounted within a second cylinder (222) to define inner and outer chambers (224, 226) within said second cylinder, characterized by: (a) a first rod (228) coupled between said first piston and said second cylinder; (b) a second rod (230) coupled between said second piston and said first cylinder; (c) first fluid flow means (240) coupled to said first and second cylinder inner chambers; and, (d) second fluid flow means (242) coupled to said first and second cylinder outer chambers. ### Claim 8 A power cylinder (300) having a first piston (312) slidably mounted within a first cylinder (314) to define inner and outer chambers (316, 318) within said first cylinder, and a second piston (320) slidably mounted within a second cylinder (322) to define inner and outer chambers (324, 326) within said second cylinder, characterized by: (a) a first-rod (328) coupled between said first piston and said second cylinder; and, (b) a second rod (330) coupled through said first rod between said second piston and said first cylinder. ### Claim 9 (depends on 8) A power cylinder as defined in claim 8, further comprising: (a) a cylindrical guard (344) surrounding said first and second cylinders; and, (b) bearing means (350, 352) for allowing slidable displacement of said first and second cylinders relative to said guard. ### Claim 10 (depends on 9) A power cylinder as defined in claim 9, further comprising: (a) sealing means (346, 348) between said guard and said first and second cylinders for hydraulically isolating a chamber (358) between said guard and said first and second cylinders; and, (b) a fluid flow port (360) in said guard for fluid flow to and from said isolated chamber. ### Claim 11 (depends on 10) A power cylinder as defined in claim 10, further comprising filtration means (151, 153) for preventing foreign matter penetration between said guard and said first or second cylinders. ### Claim 12 A power cylinder (400) having a first piston (412) slidably mounted within a first cylinder (414) to define inner and outer chambers (416, 418) within said first cylinder, a second piston (420) slidably mounted within a second cylinder (422) to define inner and outer chambers (424, 426) within said second cylinder, characterized by: (a) a first hollow rod (430) coupled between said first and second pistons for fluid flow through said first and second pistons for fluid flow through said first rod between said first and second outer chambers; (b) a second hollow rod (428) coupled between said first and second pistons for fluid flow through said second rod between said first and second inner chambers; (c) a first fluid flow port (434) in one of said outer chambers; (d) a second fluid flow port (432) in one of said inner chambers; (e) an upper cylindrical guard (402a) having one end fixed around a lower end of said first cylinder; and, (f) a lower cylindrical guard (402b) having one end fixed around an upper end of said second cylinder; wherein opposed ends of said upper and lower guards slide over one another during extension or retraction of said power cylinder, enclosing said rods.