Gas-supported rolling diaphragm seal for piston and cylinder assembly

Claim 2

Compression apparatus comprising a cylinder, a piston axially movable in the cylinder, the piston having an outer body part with opposite compression and remote end parts, the piston and cylinder having a first set of adjacent walls corresponding to said body part remote end of the piston and defining a first annular space between said walls, and a second set of adjacent walls corresponding to said compression end part of the piston and defining a second annular space therebetween, the compression end of the piston defining with the cylinder a variable volume compression space for working medium containable therein, a rolling diaphragm seal secured between said first set of walls and defining and separating said first annular space into axially spaced first and second portions thereof for containing compressible medium at relatively different average pressures, a second seal disposed in said second annular space, axially between said first portion of the first annular space and the compression space, the second seal having an operative diameter unequal to the effective diameter of said first rolling seal and operative as a one-way valve for providing a constant pressure differential across said first seal.

Claim 3

Apparatus according to claim 1 wherein said rolling seal has a concave side facing said second seal, and said second seal permits gas flow only toward the rolling seal from the compression space.

Claim 4

Apparatus according to claim 1, wherein at least one of the walls of said First set has a stepped diameter such that the volume of said first outer annular space remains constant during axial movement of the piston.

Claim 5

Apparatus according to claim 1 wherein said second portion of the first outer annular space is in open communication with the remote space, the second seal (having an operative diameter different from the effective diameter of the rolling diaphragm) produces volume variations of the first portion of the first outer annular space and resultant pressure variations in said first portion space which are at least substantially equal to and in phase with the pressure variations occurring in the remote space and in the second portion of the first outer annular space communicating therewith, the average pressure in said first portion differing from that in the remote space and in the second portion.

Claim 6

Apparatus according to claim 1 wherein said piston''s remote end and the cylinder define a third set of adjacent walls defining a third annular space, the apparatus further comprising a third seal disposed in said third annular space, this third seal being operative on the same diameter as the effective diameter of the rolling diaphragm.

Claim 7

Apparatus according to claim 1 wherein said second seals comprise piston rings, and said apparatus includes for each ring a groove in one of the adjacent walls of said piston and cylinder, and displacer-connecting rod and piston, and communication means is provided between said groove and one of said two spaces on the opposite sides of said seal.

Claim 8

Apparatus according to claim 1 wherein said second seals are formed by narrow gaps.

Claim 9

Apparatus according to claim 1 further comprising duct means communicating said working space with said remote space, a by-pass valve within said duct means opening toward said working space which is facing the concave side of said rolling diaphragm seal.

Claim 10

Apparatus comprising a cylinder, a piston axially movable in the cylinder, the piston having a body part and a compression end part, the latter part cooperating with the cylinder to define a variable volume working space containing a working medium, the cylinder and piston having first and second pairs of adjacent wall surfaces corresponding respectively to said body and end parts of the piston, a first rolling diaphragm seal secured between said first adjacent surfaces and separating a first annular space from a second annular space, these spaces containing working medium of different average pressures, a first ring seal secured between said second adjacent surfaces and separating said first annular space from said working space, at least one of said piston and cylinder wall surfaces extending between said first rolling seal and said first ring seal defining a stepped construction, and said first ring seal having an effective diameter substantially equal to that of the first rolling seal, such that the pressure differential between the first and second annular spaces across said first rolling seal is substantially constant.

Claim 11

Apparatus comprising a cylinder, a piston axially movable in the cylinder, the piston having a body part and a compression end part, the latter part cooperating with the cylinder to define a variable volume working space containing a working medium, the cylinder and piston having first and second pairs of adjacent wall surfaces corresponding respectively to said body and end parts of the piston, a first rolling diaphragm seal secured between said first adjacent surfaces and separating a first annular space from a second annular space, these spaces containing working medium of different average pressures, a first ring seal secured between said second adjacent surfaces and separating said first annular space from said working space, at least one of said piston and cylinder wall surfaces extending between said first rolling seal and said first ring seal defining a stepped construction, and said first ring seal having an effective diameter substantially equal to that of the first rolling seal, such that the pressure differential between the first and second annular spaces across said first rolling seal is substantially constant.

Claim 12

Apparatus according to claim 9 wherein the piston has the remote end opposite the compression end and the piston remote end and the corresponding cylinder part have third adjacent wall surfaces, the apparatus further comprising a second ring seal secured between said third adjacent surfaces with the second annular space between said first rolling seal and said second ring seal, this second ring seal having An effective diameter equal to that of the first ring seal.

Claim 13

In a hot-gas engine including a cylinder, a compression piston reciprocally movable in the cylinder, a displacer to which is connected a displacer rod that extends through the bore in said piston with a variable volume compression space defined between said piston and displacer, said piston having a body part and a compression end part, the cylinder and piston having first and second adjacent wall surfaces corresponding respectively to the body and compression end parts of said piston, a first rolliNg diaphragm secured between said first adjacent surfaces and separating a first annular space from a second annular space, these spaces containing working medium at different average pressures, a first ring seal secured between said second adjacent surfaces and separating said first annular space from said compression space, at least one of said piston and cylinder wall surfaces extending between said first rolling seal and said first ring seal defining a stepped construction, said first ring seal having an effective diameter substantially equal to that of the rolling seal, such that the pressure differential between said first and second annular spaces across said rolling seal is substantially constant, said apparatus further comprising third and fourth adjacent wall surfaces between said rod and piston bore and similar to said first and second adjacent wall surfaces and rolling and ring seals therebetween.

Claim 14

In a hot-gas engine including a cylinder, a compression piston reciprocally movable in the cylinder, a displacer to which is connected a displacer rod that extends through the bore in said piston with a variable volume compression space defined between said piston and displacer, said piston having a body part and a compression end part, the cylinder and piston having first and second adjacent wall surfaces corresponding respectively to the body and compression end parts of said piston, a first rolliNg diaphragm secured between said first adjacent surfaces and separating a first annular space from a second annular space, these spaces containing working medium at different average pressures, a first ring seal secured between said second adjacent surfaces and separating said first annular space from said compression space, at least one of said piston and cylinder wall surfaces extending between said first rolling seal and said first ring seal defining a stepped construction, said first ring seal having an effective diameter substantially equal to that of the rolling seal, such that the pressure differential between said first and second annular spaces across said rolling seal is substantially constant, said apparatus further comprising third and fourth adjacent wall surfaces between said rod and piston bore and similar to said first and second adjacent wall surfaces and rolling and ring seals therebetween.

Claim 15

An engine according to claim 11 wherein said piston has a remote end opposite the compression end, and the piston remote end and corresponding cylinder part have fifth adjacent wall surfaces, and said piston remote end and displacer rod therethrough also have sixth adjacent wall surfaces, the apparatus further comprising third and fourth ring seals secured respectively between the fifth and sixth adjacent wall surfaces, said third and fourth ring seals each having an effective diameter equal to that of the first and second ring seals respectively, such that the pressure differential across the rolling diaphragm seals is substantially constant.