Abstract: A high efficiency, low maintenance single stage or multi-stage centrifugal compressor assembly for large cooling installations. A cooling system provides direct, two-phase cooling of the rotor by combining gas refrigerant from the evaporator section with liquid refrigerant from the condenser section to affect a liquid/vapor refrigerant mixture. Cooling of the stator with liquid refrigerant may be provided by a similar technique. A noise suppression system is provided by injecting liquid refrigerant spray at points between the impeller and the condenser section. The liquid refrigerant may be sourced from high pressure liquid refrigerant from the condenser section.

Abstract: A high efficiency, low maintenance single stage or multi-stage centrifugal compressor assembly for large cooling installations. A cooling system provides direct, two-phase cooling of the rotor by combining gas refrigerant from the evaporator section with liquid refrigerant from the condenser section to affect a liquid/vapor refrigerant mixture. Cooling of the stator with liquid refrigerant may be provided by a similar technique. A noise suppression system is provided by injecting liquid refrigerant spray at points between the impeller and the condenser section. The liquid refrigerant may be sourced from high pressure liquid refrigerant from the condenser section.

Abstract: A high efficiency, low maintenance single stage or multi-stage centrifugal compressor assembly for large cooling installations. The assembly is highly efficient by virtue of a variable frequency drive (VFD) that drives a permanent magnet motor and matches compressor speed with compressor load, a direct drive impeller that eliminates gearing losses, and magnetic bearings that reduce frictional losses. The back-emf produced by the motor provides an intermediate power source for the magnetic bearings in the event of a loss of electrical power. A cooling system provides direct cooling of the rotor with gas refrigerant, and cooling of the stator with liquid refrigerant. Modular construction allows the compressor to be retrofit with upgrades. An inlet guide vane system operates without need for oil lubrication. The use of light metal castings and elimination of gearing reduces the weight to one-third or less of comparably powered conventional units.

Abstract: A high efficiency, low maintenance single stage or multi-stage centrifugal compressor assembly for large cooling installations. A cooling system provides direct, two-phase cooling of the rotor by combining gas refrigerant from the evaporator section with liquid refrigerant from the condenser section to affect a liquid/vapor refrigerant mixture. Cooling of the stator with liquid refrigerant may be provided by a similar technique. A noise suppression system is provided by injecting liquid refrigerant spray at points between the impeller and the condenser section. The liquid refrigerant may be sourced from high pressure liquid refrigerant from the condenser section.

Abstract: A high efficiency, low maintenance single stage or multi-stage centrifugal compressor assembly for large cooling installations. The assembly is highly efficient by virtue of a variable frequency drive (VFD) that drives a permanent magnet motor and matches compressor speed with compressor load, a direct drive impeller that eliminates gearing losses, and magnetic bearings that reduce frictional losses. The back-emf produced by the motor provides an intermediate power source for the magnetic bearings in the event of a loss of electrical power. A cooling system provides direct cooling of the rotor with gas refrigerant, and cooling of the stator with liquid refrigerant. Modular construction allows the compressor to be retrofit with upgrades. An inlet guide vane system operates without need for oil lubrication. The use of light metal castings and elimination of gearing reduces the weight to one-third or less of comparably powered conventional units.

Abstract: A ligating band dispenser has a plurality of elastic ligating bands at least one of which is supported on each of a series of partially nested cylinders. Inner and intermediate cylinders comprise axially sliding cylinders for dispensing the ligating bands. An outer cylinder,which may be attached to the distal end of an elongated introducer, surrounds at least the proximal portion of the intermediate cylinder and is adapted to receive the sliding cylinders slide into its distal end. A trip wire is connected to the inner cylinder and extends proximally therefrom through the elongated introducer. The trip wire is adapted to cause an axially sliding motion of the sliding cylinders during an application of force to the trip wire. A restraining means is associated with each sliding cylinder to restrain sliding motion thereof during the application of force to the trip wire.

Abstract: A ligating band dispenser for dispensing a plurality of ligating bands having located at the distal end of an elongated introducer responds to manipulation of an operating structure at the proximal end of the introducer. It has a spring loaded reciprocating inner cylinder movable within a spring loaded, radially expandable cone having inner teeth for engaging a plurality of ligating bands. When the dispenser is actuated, the inner cylinder us drawn proximally with respect to the cone, and the distal end surface of the cone forces the distal-most ring off the reciprocating cylinder and onto the internal tissue has been drawn or place by the inside cylinder.

Abstract: A centrifugal gas compressor having a shrouded rotatable impeller 14 in an impeller chamber 40, and provided with capacity control vanes 30 and a diffuser passage 18 throttle plate 38, is provided with surge control means including a thermistor 50 which senses a temperature rise beyond a predetermined value in the impeller chamber and exterior of the gas flow path through the impeller, and through relay means such as 52, 58 electrically connected to the thermistor 50 operates to change the compressor operation to a nonsurging condition.

Abstract: A centrifugal gas compressor having a shrouded rotatable impeller 14 in an impeller chamber 40, and provided with capacity control vanes 30 and a diffuser passage 18 throttle plate 38, is provided with surge control means including a thermistor 50 which senses a temperature rise beyond a predetermined value in the impeller chamber and exterior of the gas flow path through the impeller, and through relay means such as 52, 58 electrically connected to the thermistor 50 operates to change the compressor operation to a nonsurging condition.

Abstract: An impeller and shaft assembly includes an outwardly tapered socket 38 in the rear face of the impeller 12 and into which a frusto-conically shaped extremity 20 seats, the extremity circumferential wall having a plurality of axially extending grooves 42 alternating with intervening lands 44, the socket and extremity being dimensioned and configured so that in the finally seated relation of the parts the land plastically deforms the socket material which has a lower compressive yield strength than the extremity.

Abstract: An improved load balancing control circuit for at least three electric motor-driven centrifugal refrigerant compressors comprises a current transformer secondary 90', 91', 92' and a respective load resistor 93', 95', 97' in series to form the legs of a circuit in which the legs are connected in a delta, each leg having a shorting switch 110', 111', 112' connected across it, and a balancing resistance network including balancing resistors 94', 96', 98' are connected in a wye circuit with the delta circuit.

Abstract: A refrigerant system with a high speed centrifugal compressor has an arrangement for promoting the continuous return of oil to gear and bearing housing 12 including a coalescing type filter 62 from which separated oil is passed to a jet pump 74, a thermostatically controlled expansion valve 50 operating at a low superheat value, and inwardly pumping shaft seals 26.