Compressor with rolling diaphragm seal

Claim 3

A device as claimed in claim 1, in which the section of the piston situated between the connection of the rolling diaphragm and the working space is formed by two or more piston parts the diameter of which decreases in the direction of the working space, the annular surfaces formed by the transitions of said piston parts each being capable of varying the volume of a further working space, characterized in that at least one piston ring is present between the first space and the nearest further working space, and at least two piston rings are present between the further working spaces mutually and between the working space and the nearest further working space, which rings separate the said spaces paIrwise from each other, the piston rings being each incorporated in a groove situated in the part of the piston wall or cylinder wall which is situated between each pair of the said spaces, the annular spaces situated between the piston rings separating each pair of further working spaces respectively the working space and the nearest further working space from one another each communicating with at least one buffer space, an open communication being furthermore always present with each piston ring between the space in the associated groove behind the piston ring and the space situated on the side of the piston ring facing the working space.

Claim 4

A device as claimed in claim 1 in which the rolling diaphragm faces the first space with its concave side, characterized in that a control member is present which is incorporated in a communication between on the one hand the first space and on the other hand the working space or one of the further working spaces, said member releasing the communication when the suction pressure of the device falls below a particular minimum valve.

Claim 5

A device as claimed in claim 3, characterized in that a chamber is present in the piston the boundary of which on the side remote from the working space is formed by a further piston which reciprocates therein in the axial direction of the piston and is connected, via a valve stem, to a valve body which can cooperate with a valve seating incorporated in the end face or in one of the annular surfaces of the piston and which opens in the direction of the working space or one of the further working spaces for releasing communication between said space and the chamber, an open communication being present between the first space and the chamber and resilient means being present which exert a force on the assembly of further piston, valve stem and valve body in the direction of the working space in such manner that the valve body releases the communication between the first space and the working space, or one of the further working spaces, when the suction pressure of the device falls below a particular minimum value, an abutment member being furthermore present which limits the movement of the assembly in the direction of the working space.

Claim 6

Apparatus for supplying a compressed gaseous medium and operable with means for driving the apparatus, comprising: a cylinder with a bore, a piston reciprocally movable within said bore by said drive means, the piston having first and second axially spaced parts, the first part defining with the bore a variable-volume working space, inlet and outlet valves to said working space, a rolling diaphragm seal secured between said bore and the second part of the piston, a space for gas being defined above the seal and a space for liquid defined below the seal, inlet and outlet means to both said gas and liquid spaces, and control means communicating with said gas and liquid spaces for maintaining a substantially constant pressure differential across said seal, a portion of the piston intermediate the first and second parts of the piston formed as an annular groove, said inlet valve to the working space comprising a piston ring disposed in said groove and extending outward and engaging the bore and forming a one-way valve permitting a flow only into the working space from the gas space.

Claim 7

Apparatus for supplying a compressed gaseous medium and operable with means for driving the apparatus, comprising: a cylinder with a bore, a piston reciprocally movable within said bore by said drive means, the piston having first and second axially spaced parts, the first part defining with the bore a variable-volume working space, inlet and outlet valves to said working space, a rolling diaphragm seal secured between said bore and the second part of the piston, a space for gas being defined above the seal and a space for liquid defined below the seal, inlet and outlet means to both said gas and liquid spaces, and control means communicating with said gas and liquid spaces for maintaining a substantially constant pressure differential across said seal, a portion of the piston intermediate the first and second parts of the piston formed as an annular groove, said inlet valve to the working space comprising a piston ring disposed in said groove and extending outward and engaging the bore and forming a one-way valve permitting a flow only into the working space from the gas space.

Claim 8

Apparatus according to claim 5 operable with a source of compressible gaseous medium, said inlet to the gas space communicating with said source for receiving said medium which is flowable from the gas space to the working space through said one-way inlet valve to working space.

Claim 9

Apparatus according to claim 6 operable with a source of liquid for supporting the seal, said inlet to the liquid space being in communication with said liquid source, the apparatus further comprising pump means for pumping liquid from said source of liquid to said liquid space.

Claim 10

Apparatus according to claim 5 wherein the piston has a projection having a near end extending from said first part oF the piston and having smaller diameter than said first part, and a remote end forming with the bore a second working space, the cylinder bore having a reduced diameter adjacent said projection and conforming thereto, said projection having a pair of spaced annular grooves intermediate its near and remote ends, a piston ring in each groove forming with the bore a one-way valve communicating into the second working space, the projection further defining internally a buffer space with duct means communicating said buffer space through the one-way valve to the second working space.

Claim 11

Apparatus according to claim 5 wherein said seal has a convex surface facing said liquid space and a concave side facing the gas space, said control member comprising a second part which selectively permits and blocks communication between the working space and said gas space.

Claim 12

Apparatus according to claim 9 wherein said piston has an axial bore for communicating said working space and the gas space, and said control means second part comprises a valve cooperating with said bore in the piston with means urging the valve to open when pressure in the gas space is less than pressure in the liquid space.