Gas compressor unloading means

Claim 1

In a rotary gas compressor having a compression chamber, chamber-confined rotary means for displacing and compressing gas in said chamber, and spaced-apart gas inlet and outlet ports in communication with said chamber; unloading means for the compressor, comprising: unloading port means, spaced apart from said inlet and outlet ports, opening both into said chamber and externally of said compressor; and valving means coupled to said unloading port means operative for opening and closing said unloading port means to a conduct of gas therethrough; wherein said compression chamber is defined by arcuate side walls and end walls joined to said side walls; said unloading port means is formed in at least one of said end walls; said outlet port is formed in at least one of said end walls; said rotary means comprises a plurality of cooperating and co-acting rotors; one of said rotors having a surface which cyclically exposes and occludes said outlet port; another of said rotors has a surface which cyclically exposes and occludes said unloading port means; said compression chamber is defined by a plurality of axially-extending, parallel and intersecting bores; said one rotor rotates in a first of said bores about the axis thereof; said another rotor rotates in a second of said bores about the axis thereof; said outlet port opens onto said first bore; said outlet port extends along an angular arc; drawn from said axis of said first bore, defining of said outlet port, relative to a rotary direction of said one rotor, leading and trailing portions, said trailing portion having a trailing edge; and said outlet port being located, relative to said unloading port means, such that a radial line drawn from said axis of said first bore and through the radially outermost portion of said trailing edge will substantially bisect said unloading port means.