Capacity control valve for screw compressor

Claim 2

In a screw compressor: a rotor housing having two parallel intersecting bores forming a working chamber; an inlet port and a discharge port opening into said working chamber; a high pressure end wall at one end of said working chamber and a low pressure end wall at the opposite end of said working chamber; interengaged male and female screw rotors located in said bores and operable to entrap and compress gas admitted to said working chamber through said inlet port; a capacity control valve including a valve member comprising a wall portion of said working chamber axially movable to open a bleed port formed by said valve member and said rotor housing for venting gas from said working chamber, said valve member including a pressure surface thereon; and, housing means including an interior area in communication with said discharge port and forming a flow path for pressure gas discharged from said working chamber, and said pressure surface is in communication with said interior area and is responsive to pressure gas discharged from said discharge port acting on said pressure surface to bias said valve member to open said bleed port.

Claim 3

The invention set forth in claim 1 wherein: said housing means includes a transverse face forming said high pressure end wall of said working chamber and said discharge port opens through said high pressure end wall into said interior area of said housing means.

Claim 4

The invention set forth in claim 1 wherein: said capacity control valve includes valve actuating means comprising a piston disposed in a pressure fluid chamber and connected to said valve member, said piston being responsive to pressure fluid admitted to said chamber to move said valve member to close said bleed port.

Claim 5

The invention set forth in claim 3 wherein: said compressor includes means for locking said valve member in a predetermined axial position.

Claim 6

The invention set forth in claim 4 wherein: said means for locking said valve member includes an elongated screw rotatably mounted on said compressor and engaged with means connected to said valve member forming a nut threadedly engaged with said screw, and said screw is rotatable in response to a force applied to said valve member which is sufficient to axially move said valve member and said nut.

Claim 7

The invention set forth in claim 5 wherein: said means for locking said valve member includes means for nonrotatably clamping said elongated screw comprising a member mounted on said screw nonrotatably with respect to said screw and engageable by a clamping member mounted on said compressor for nonrotatably clamping said member and said screw to lock said valve member in a predetermined axial position.

Claim 8

The invention set forth in claim 3 wherein: said pressure surface is formed on said piston.

Claim 9

The invention set forth in claim 7 wherein: said piston is formed integral with said valve member.

Claim 10

In a screw compressor: a rotor housing having two parallel intersecting bores forming a working chamber; an inlet port and a discharge port opening into said working chamber; a high pressure end wall at one end of said working chamber and a low pressure end wall at the opposite end of said working chamber; interengaged male and female screw rotors located in said intersecting bores and operable to entrap and compress gas admitted to said working chamber through said inlet port; said rotor housing including a portion forming a bore spaced from said intersecting bores forming said working chamber; a capacity control valve including a valve member located in said bore and comprising a wall portion of said working chamber, said valve member being axially movable in said bore to open a bleed port formed by said valve member and said rotor housing; passage means in said rotor housing for conducting injection liquid to said working chamber; and, guide means comprising a member removably interfitted between said rotor housing and said valve member for guiding said valve member to provide for substantial alignment of a crest edge on said valve member with a corresponding crest edge formed by said intersecting bores in said rotor housing, said guide means defining, in part, said passage means.

Claim 11

In a screw compressor: a rotor housing having two parallel intersecting bores forming a working chamber; an inlet port and a discharge port opening into said working chamber; a high pressure end wall at one end of said working chamber and a low pressure end wall at the opposite end of said working chamber; interengaged male and female screw rotors located in said intersecting bores and operable to entrap and compress gas admitted to said working chamber through said inlet port; said rotor housing including a portion forming a bore spaced from said intersecting bores forming said working chamber; a capacity control valve including a valve member located in said bore and comprising a wall portion of said working chamber, said valve member being axially movable in said bore to open a bleed port formed by said valve member and said rotor housing; passage means in said rotor housing for conducting injection liquid to said working chamber; and, guide means comprising a member removably interfitted between said rotor housing and said valve member for guiding said valve member to provide for substantial alignment of a crest edge on said valve member with a corresponding crest edge formed by said intersecting bores in said rotor housing, said guide means defining, in part, said passage means.

Claim 12

In a screw compressor: a rotor housing having two parallel intersecting bores forming a working chamber; an inlet port and a discharge port opening into said working chamber; a high pressure end wall at one end of said working chamber and a low pressure end wall at the opposite end of said working chamber; interengaged male and female screw rotors located in said intersecting bores and operable to entrap and compress gas admitted to said working chamber through said inlet port; said rotor housing including a portion forming a bore spaced from said intersecting bores forming said working chamber; a capacity control valve including a valve member located in said bore and comprising a wall portion of said working chamber, said valve member being axially movable in said bore to open a bleed port formed by said valve mEmber and said rotor housing; passage means in said rotor housing for conducting injection liquid to said working chamber; and, guide means disposed in said rotor housing for guiding said valve member to provide for substantial alignment of a crest edge on said valve member with a corresponding crest edge formed by said intersecting bores in said rotor housing, said guide means defining in part said passage means, and said guide means comprising a cylindrical guide pin removably interfitted in cooperating grooves formed in said valve member and said rotor housing.

Claim 13

In a screw compressor: a rotor housing having two parallel intersecting bores forming a working chamber; an inlet port and a discharge port opening into said working chamber; a high pressure end wall at one end of said working chamber and a low pressure end wall at the opposite end of said working chamber; interengaged male and female screw rotors located in said intersecting bores and operable to entrap and compress gas admitted to said working chamber through said inlet port; said rotor housing including a portion forming a bore spaced from said intersecting bores forming said working chamber; a capacity control valve including a valve member located in said bore and comprising a wall portion of said working chamber, said valve member being axially movable in said bore to open a bleed port formed by said valve mEmber and said rotor housing; passage means in said rotor housing for conducting injection liquid to said working chamber; and, guide means disposed in said rotor housing for guiding said valve member to provide for substantial alignment of a crest edge on said valve member with a corresponding crest edge formed by said intersecting bores in said rotor housing, said guide means defining in part said passage means, and said guide means comprising a cylindrical guide pin removably interfitted in cooperating grooves formed in said valve member and said rotor housing.

Claim 14

The invention set forth in claim 10 wherein: said passage means for injecting liquid into said working chamber include grooves formed in said bore and in communication with said working chamber and said passage means defined by said guide pin.

Claim 15

The invention set forth in claim 11 wherein: said grooves formed in said bore include a first pair of circumferential grooves and a second pair of circumferential grooves spaced axially in said bore from said first pair of circumferential grooves and said guide pin is characterized in that one of said pairs of circumferential grooves is blocked from receiving injection liquid through said passage means by said guide pin while the other of said pairs of circumferential grooves is in communication with said passage means defined by said guide pin.

Claim 16

The invention set forth in claim 11 wherein: said bore and said pairs of circumferential grooves formed in said bore together with injection liquid supplied to said circumferential grooves form a hydrostatic bearing for supporting said valve member.