Piston unit

Claim 2

A piston unit comprising: cylinder means having a pair of opposed axial ends and substantially filled with liquid medium; piston means slidably mounted in said cylinder means; spring means for urging said piston means toward one axial end of said cylinder means; an operation rod having one end portion coupled to said piston means so as to be movable therewith and a shank portion extending to the outside of said cylinder means; sealing means for sealing said liquid medium in said cylinder means, said sealing means including a flexible membrane having a central portion fixedly interposed between said one end portion of said operation rod and said piston means and a corrugated portion integrally extending from said central portion, said corrugated portion having a peripheral edge region liquid sealingly engaged with said cylinder means such that said membrane seals said liquid medium in said cylinder means and defines a space within the cylinder means which is devoid of the liquid medium, said operation rod being situated in said space fluidly isolated from and not in contact with said liquid medium; and control means for providing that fluid resistance presented by said liquid medium to movement of said piston means toward one of said ends of said cylinder means is different from the fluid resistance presented by said liquid medium to movement of said piston means toward the other one of said ends of said cylinder means, said control means including a through bore formed in said piston means and a valve member coupled to said piston means adapted to open and close said through bore, said valve member being plate-shaped and having a small bore therein situated in substantially opposed relationship to said through bore.

Claim 3

A piston unit as claimed in claim 1, wherein said liquid medium is silicon oil.

Claim 4

A piston unit as claimed in claim 1, wherein said liquid medium is a mixture of ethylene glycol and water.

Claim 5

A piston unit as claimed in claim 1, wherein said membrane is made of synthetic rubber.

Claim 6

A piston unit as claimed in claim 1, wherein said spring means includes a coiled spring disposed between the inner end of said cylinder means and said piston means.

Claim 7

A piston unit as claimed in claim 1, wherein said spring means includes a coiled spring disposed between the outer end of said cylinder means and said operation rod.

Claim 8

A piston unit as claimed in claim 1, wherein said spring means comprises a membrane having a regularly corrugated portion.

Claim 9

A piston unit as claimed in claim 1, wherein said central portion of said membrane comprises a hardened portion which is fitted firmly to said piston means, and wherein said corrugated portion extends continuously from said hardened central portion.

Claim 10

A piston unit as claimed in claim 1, wherein said central portion of said membrane includes a thick-walled portion at which said membrane is fitted firmly to said piston means, said corrugated portion being integrally connected to said thick-walled portion and wherein said peripheral edge region of said corrugated portion has a bead formed thereon, said bead being fixed liquid-tightly to said cylinder means.

Claim 11

A piston unit comprising: cylinder means having a pair of opposed axial ends and including a switch member and a switch actuating member for actuating said switch member, said cylinder means being substantially filled with liquid medium; piston means slidably mounted in said cylinder means, said switch actuating member being operatively connected to said piston means; spring means for urging said piston means toward one axial end of said cylinder means; an operation rod having one end portion coupled to said piston means so as to be movable therewith and a shank portion extending to the outside of said cylinder means; sealing means for sealing said liquid medium in said cylinder means, said sealing means including a flexible membrane having a central portion fixedly interposed between said one end portion of said operation rod and said piston means and a corrugated portion integrally extending from said central portion, said corrugated portion having a peripheral edge region liquid sealingly engaged with said cylinder means such that said membrane seals said liquid medium in said cylinder means and defines a space within the cylinder means which is devoid of the liquid medium, said operation rod being situated in said space fluidly isolated from and not in contact with said liquid medium; and control means for providing that fluid resistance presented by said liquid medium to movement of said piston means toward one of said ends of said cylinder means is different from the fluid resistance presented by said liquid medium to movement of said piston means toward the other one of said ends of said cylinder means, said control means including a through bore formed in said piston means and a valve member coupled to said piston means adapted to open and close said through bore.

Claim 12

A piston unit comprising: cylinder means having a pair of opposed axial ends and including a switch member and a switch actuating member for actuating said switch member, said cylinder means being substantially filled with liquid medium; piston means slidably mounted in said cylinder means, said switch actuating member being operatively connected to said piston means; spring means for urging said piston means toward one axial end of said cylinder means; an operation rod having one end portion coupled to said piston means so as to be movable therewith and a shank portion extending to the outside of said cylinder means; sealing means for sealing said liquid medium in said cylinder means, said sealing means including a flexible membrane having a central portion fixedly interposed between said one end portion of said operation rod and said piston means and a corrugated portion integrally extending from said central portion, said corrugated portion having a peripheral edge region liquid sealingly engaged with said cylinder means such that said membrane seals said liquid medium in said cylinder means and defines a space within the cylinder means which is devoid of the liquid medium, said operation rod being situated in said space fluidly isolated from and not in contact with said liquid medium; and control means for providing that fluid resistance presented by said liquid medium to movement of said piston means toward one of said ends of said cylinder means is different from the fluid resistance presented by said liquid medium to movement of said piston means toward the other one of said ends of said cylinder means, said control means including a through bore formed in said piston means and a valve member coupled to said piston means adapted to open and close said through bore.

Claim 13

A piston unit as claimed in claim 10, wherein said piston means include a coiled spring adapted for urging said switch actuating member toward said switch member.

Claim 14

A piston unit as claimed in claim 10, wherein said spring means is interposed between said piston means and said switch actuating member and wherein said switch actuating member is constituted by a piston adapted to be displaced slideably in said cylinder means and operatively connected to said piston means by means of said spring means.

Claim 15

A piston unit comprising: cylinder means having a pair of opposed axial ends and including a cylinder cap attached thereto, a switch member disposed on said cylinder cap and a switch actuating member adapted to actuate said switch member, said cylinder means being substantially filled with liquid medium; piston means slidably mounted in said cylinder means; spring means for urging said piston means toward one axial end of said cylinder means; an operation rod having one end portion coupled to said piston means so as to be movable therewith and a shank portion extending to the outside of said cylinder means, said switch actuating member of said cylinder means being operatively connected to said operation rod; sealing means for sealing said liquid medium in said cylinder means, said sealing means including a flexible membrane having a central portion fixedly interposed between said one end portion of said operation rod and said piston means and a corrugated portion integrally extending from said central portion, said corrugated portion having a peripheral edge region liquid sealingly engaged with said cylinder means such that said membrane seals said liquid medium in said cylinder means and defines a space within the cylinder means which is devoid of the liquid medium, said operation rod being situated in said space fluidly isolated from and not in contact with said liquid medium; and control means for providing that fluid resistance presented by said liquid medium to movement of said piston means toward one of said ends of said cylinder means is different from the fluid resistance presented by said liquid medium to movement of said piston means toward the other one of said ends of said cylinder means, said control means including a through bore formed in said piston means and a valve member coupled to said piston means adapted to open and close said through bore.

Claim 16

A piston unit comprising: cylinder means having a pair of opposed axial ends and including a cylinder cap attached thereto, a switch member disposed on said cylinder cap and a switch actuating member adapted to actuate said switch member, said cylinder means being substantially filled with liquid medium; piston means slidably mounted in said cylinder means; spring means for urging said piston means toward one axial end of said cylinder means; an operation rod having one end portion coupled to said piston means so as to be movable therewith and a shank portion extending to the outside of said cylinder means, said switch actuating member of said cylinder means being operatively connected to said operation rod; sealing means for sealing said liquid medium in said cylinder means, said sealing means including a flexible membrane having a central portion fixedly interposed between said one end portion of said operation rod and said piston means and a corrugated portion integrally extending from said central portion, said corrugated portion having a peripheral edge region liquid sealingly engaged with said cylinder means such that said membrane seals said liquid medium in said cylinder means and defines a space within the cylinder means which is devoid of the liquid medium, said operation rod being situated in said space fluidly isolated from and not in contact with said liquid medium; and control means for providing that fluid resistance presented by said liquid medium to movement of said piston means toward one of said ends of said cylinder means is different from the fluid resistance presented by said liquid medium to movement of said piston means toward the other one of said ends of said cylinder means, said control means including a through bore formed in said piston means and a valve member coupled to said piston means adapted to open and close said through bore.

Claim 17

A piston unit comprising: cylinder means having a pair of opposed axial ends and substantially filled with liquid medium; piston means slidably mounted in said cylinder means; spring means for urging said piston means toward one axial end of said cylinder means; an operation rod having one end portion coupled to said piston means so as to be movable therewith and a shank portion extending to the outside of said cylinder means; sealing means for sealing said liquid medium in said cylinder means, said sealing means including a flexible membrane having a central portion fixedly interposed between said one end portion of aid operation rod and said piston means and a corrugated portion integrally extending from said central portion, said corrugated portion having a peripheral edge region liquid sealingly engaged with said cylinder means such that said membrane seals said liquid medium in said cylinder means and defines a space within the cylinder means which is devoid of the liquid medium, said operation rod being situated in said space fluidly isolated from and not in contact with said liquid medium; and control means for providing that fluid resistance presented by said liquid medium to movement of said piston means toward one of said ends of said cylinder means is different from the fluid resistance presented by said liquid medium to movement of said piston means toward the other one of said ends of said cylinder means, said control means including a through bore formed in said piston means and a valve member coupled to said piston means adapted to open and close said through bore, said valve member including a plate located in opposed relationship to said through-bore, said plate being formed of a mesh or network-like material.

Claim 18

A piston unit comprising: cylinder means having a pair of opposed axial ends and substantially filled with liquid medium; piston means slidably mounted in said cylinder means; spring means for urging said piston means toward one axial end of said cylinder means; an operation rod having one end portion coupled to said piston means so as to be movable therewith and a shank portion extending to the outside of said cylinder means; sealing means for sealing said liquid medium in said cylinder means, said sealing means including a flexible membrane having a central portion fixedly interposed between said one end portion of aid operation rod and said piston means and a corrugated portion integrally extending from said central portion, said corrugated portion having a peripheral edge region liquid sealingly engaged with said cylinder means such that said membrane seals said liquid medium in said cylinder means and defines a space within the cylinder means which is devoid of the liquid medium, said operation rod being situated in said space fluidly isolated from and not in contact with said liquid medium; and control means for providing that fluid resistance presented by said liquid medium to movement of said piston means toward one of said ends of said cylinder means is different from the fluid resistance presented by said liquid medium to movement of said piston means toward the other one of said ends of said cylinder means, said control means including a through bore formed in said piston means and a valve member coupled to said piston means adapted to open and close said through bore, said valve member including a plate located in opposed relationship to said through-bore, said plate being formed of a mesh or network-like material.

Claim 19

A piston unit comprising: cylinder means having a pair of opposed axial ends and substantially filled with liquid medium; piston means slidably mounted in said cylinder means; spring means for urging said piston means toward one axial end of cylinder means; an operation rod having one end portion coupled to said piston means so as to be movable therewith and a shank portion extending to the outside of said cylinder means; sealing means for sealing said liquid medium in said cylinder means, said sealing means including a flexible membrane having a central portion fixedly interposed between said one end portion of said operation rod and said piston means and a corrugated portion integrally extending from said central portion, said corrugated portion having a peripheral edge region liquid sealingly engaged with said cylinder means such that said membrane seals said liquid medium in said cylinder means and defines a space within the cylinder means which is devoid of the liquid medium, said operation rod being situated in said space fluidly isolated from and not in contact with said liquid medium; and control means for providing that fluid resistance presented by said liquid medium to movement of said piston means toward one of said ends of said cylinder means is different from the fluid resistance presented by said liquid medium to movement of said piston means toward the other one of said ends of said cylinder means, said control means including a through bore formed in said piston means and a valve member coupled to said piston means adapted to open and close said through bore, said valve member including a plate having slits formed therein, said slits being located in opposed relationship to said through bore formed on said piston means.

Claim 20

A piston unit comprising: cylinder means having a pair of opposed axial ends and substantially filled with liquid medium; piston means slidably mounted in said cylinder means; spring means for urging said piston means toward one axial end of cylinder means; an operation rod having one end portion coupled to said piston means so as to be movable therewith and a shank portion extending to the outside of said cylinder means; sealing means for sealing said liquid medium in said cylinder means, said sealing means including a flexible membrane having a central portion fixedly interposed between said one end portion of said operation rod and said piston means and a corrugated portion integrally extending from said central portion, said corrugated portion having a peripheral edge region liquid sealingly engaged with said cylinder means such that said membrane seals said liquid medium in said cylinder means and defines a space within the cylinder means which is devoid of the liquid medium, said operation rod being situated in said space fluidly isolated from and not in contact with said liquid medium; and control means for providing that fluid resistance presented by said liquid medium to movement of said piston means toward one of said ends of said cylinder means is different from the fluid resistance presented by said liquid medium to movement of said piston means toward the other one of said ends of said cylinder means, said control means including a through bore formed in said piston means and a valve member coupled to said piston means adapted to open and close said through bore, said valve member including a plate having slits formed therein, said slits being located in opposed relationship to said through bore formed on said piston means.

Claim 21

A piston unit comprising: cylinder means having a pair of opposed axial ends and substantially filled with liquid medium; piston means slidably mounted in said cylinder means; spring means for urging said piston means toward one axial end of said cylinder means; an operation rod having one end portion coupled to said piston means so as to be movable therewith and a shank portion extending to the outside of said cylinder means; sealing means for sealing said liquid medium in said cylinder means, said sealing means including a flexible membrane having a central portion fixedly interposed between said one end portion of said operation rod and said piston means and a corrugated portion integrally extending from said central portion, said corrugated portion having a peripheral edge region liquid sealingly engaged with said cylinder means such that said membrane seals said liquid medium in said cylinder means and defines a space within the cylinder means which is devoid of the liquid medium, said operation rod being situated in said space fluidly isolated from and not in contact with said liquid medium; and control means for providing that fluid resistance presented by said liquid medium to movement of said piston means toward one of said ends of said cylinder means is different from the fluid resistance presented by said liquid medium to movement of said piston means toward the other one of said ends of said cylinder means, said control means including a through bore formed in said piston means and a valve member coupled to said piston means adapted to open and close said through bore, said valve member including a plate provided with a small bore located in opposed relationship to said through bore, and a bimetallic member having one end fixed to said plate and a closure member fixed to the other end of said bimetallic member adapted to selectively open and close said small bore.

Claim 22

A piston unit comprising: cylinder means having a pair of opposed axial ends and substantially filled with liquid medium; piston means slidably mounted in said cylinder means; spring means for urging said piston means toward one axial end of said cylinder means; an operation rod having one end portion coupled to said piston means so as to be movable therewith and a shank portion extending to the outside of said cylinder means; sealing means for sealing said liquid medium in said cylinder means, said sealing means including a flexible membrane having a central portion fixedly interposed between said one end portion of said operation rod and said piston means and a corrugated portion integrally extending from said central portion, said corrugated portion having a peripheral edge region liquid sealingly engaged with said cylinder means such that said membrane seals said liquid medium in said cylinder means and defines a space within the cylinder means which is devoid of the liquid medium, said operation rod being situated in said space fluidly isolated from and not in contact with said liquid medium; and control means for providing that fluid resistance presented by said liquid medium to movement of said piston means toward one of said ends of said cylinder means is different from the fluid resistance presented by said liquid medium to movement of said piston means toward the other one of said ends of said cylinder means, said control means including a through bore formed in said piston means and a valve member coupled to said piston means adapted to open and close said through bore, said valve member including a plate provided with a small bore located in opposed relationship to said through bore, and a bimetallic member having one end fixed to said plate and a closure member fixed to the other end of said bimetallic member adapted to selectively open and close said small bore.

Claim 23

A piston unit comprising: cylinder means having a pair of opposed axial ends and substantially filled with liquid medium; piston means slidably mounted in said cylinder means including a bimetallic member fixed at one of its ends thereto and a small plate attached to the free end of said bimetallic member; spring means for urging said piston means toward one axial end of said cylinder means; an operation rod having one end portion coupled to said piston means so as to be movable therewith and a shank portion extending to the outside of said cylinder means; sealing means for sealing said liquid medium in said cylinder means, said sealing means including a flexible membrane having a central portion fixedly interposed between said one end portion of said operation rod and said piston means and a corrugated portion integrally extending from said central portion, said corrugated portion having a peripheral edge region liquid sealingly engaged with said cylinder means such that said membrane seals said liquid medium in said cylinder means and defines a space within the cylinder means which is devoid of the liquid medium, said operation rod being situated in said space fluidly isolated from and not in contact with said liquid medium; and control means for providing that fluid resistance presented by said liquid medium to movement of said piston means toward one of said end of said cylinder means is different from the fluid resistance presented by said liquid medium to movement of said piston means toward the other one of said ends of said cylinder means, said control means including a through bore formed in said piston means and a valve member coupled to said piston means adapted to open and close said through bore and wherein the opening and closing of said through bore is controlled by said small plate which in turn is operated by said bimetallic member.

Claim 24

A piston unit comprising: cylinder means having a pair of opposed axial ends and substantially filled with liquid medium; piston means slidably mounted in said cylinder means including a bimetallic member fixed at one of its ends thereto and a small plate attached to the free end of said bimetallic member; spring means for urging said piston means toward one axial end of said cylinder means; an operation rod having one end portion coupled to said piston means so as to be movable therewith and a shank portion extending to the outside of said cylinder means; sealing means for sealing said liquid medium in said cylinder means, said sealing means including a flexible membrane having a central portion fixedly interposed between said one end portion of said operation rod and said piston means and a corrugated portion integrally extending from said central portion, said corrugated portion having a peripheral edge region liquid sealingly engaged with said cylinder means such that said membrane seals said liquid medium in said cylinder means and defines a space within the cylinder means which is devoid of the liquid medium, said operation rod being situated in said space fluidly isolated from and not in contact with said liquid medium; and control means for providing that fluid resistance presented by said liquid medium to movement of said piston means toward one of said end of said cylinder means is different from the fluid resistance presented by said liquid medium to movement of said piston means toward the other one of said ends of said cylinder means, said control means including a through bore formed in said piston means and a valve member coupled to said piston means adapted to open and close said through bore and wherein the opening and closing of said through bore is controlled by said small plate which in turn is operated by said bimetallic member.

Claim 25

A piston unit comprising: cylinder means having a pair of opposed axial ends and substantially filled with liquid medium; piston means slidably mounted in said cylinder means; spring means for urging said piston means toward one axial end of said cylinder means; an operation rod having one end portion coupled to said piston means so as to be movable therewith and a shank portion extending to the outside of said cylinder means; sealing means for sealing said liquid medium in said cylinder means, said sealing means including a flexible membrane having a central portion fixedly interposed between said one end portion of said operation rod and said piston means and a corrugated portion integrally extending from said central portion, said corrugated portion having a peripheral edge region liquid sealingly engaged with said cylinder means such that said membrane seals said liquid medium in said cylinder means and defines a space within the cylinder means which is devoid of the liquid medium, said operation rod being situated in said space fluidly isolated from and not in contact with said liquid medium; and control means for providing that fluid resistance presented by said liquid medium to movement of said piston means toward one of said ends of said cylinder means is different from the fluid resistance presented by said liquid medium to movement of said piston means toward the other one of said ends of said cylinder means, said control means including a through bore formed in said piston means and a valve member coupled to said piston means adapted to open and close said through bore, said valve member being plate shaped and fixed at one end to said piston means.

Claim 26

A piston unit comprising: cylinder means having a pair of opposed axial ends and substantially filled with liquid medium; piston means slidably mounted in said cylinder means; spring means for urging said piston means toward one axial end of said cylinder means; an operation rod having one end portion coupled to said piston means so as to be movable therewith and a shank portion extending to the outside of said cylinder means; sealing means for sealing said liquid medium in said cylinder means, said sealing means including a flexible membrane having a central portion fixedly interposed between said one end portion of said operation rod and said piston means and a corrugated portion integrally extending from said central portion, said corrugated portion having a peripheral edge region liquid sealingly engaged with said cylinder means such that said membrane seals said liquid medium in said cylinder means and defines a space within the cylinder means which is devoid of the liquid medium, said operation rod being situated in said space fluidly isolated from and not in contact with said liquid medium; and control means for providing that fluid resistance presented by said liquid medium to movement of said piston means toward one of said ends of said cylinder means is different from the fluid resistance presented by said liquid medium to movement of said piston means toward the other one of said ends of said cylinder means, said control means including a through bore formed in said piston means and a valve member coupled to said piston means adapted to open and close said through bore, said valve member being plate shaped and fixed at one end to said piston means.