Vishnu M Sishtla

US Patent:

6506011, Jan 14, 2003

Filed:

Sep 21, 2001

Appl. No.:

09/957778

Inventors:

Vishnu M. Sishtla - Cicero NY

Assignee:

Carrier Corporation - Farmington CT

International Classification:

F04D 2946

US Classification:

415 1, 415150

Abstract:

A diffuser for a centrifugal compressor includes an inner ring and an outer ring. An actuator drives a pinion gear which interfaces with a rack gear which is mounted to the inner ring. The actuator is operable to position the inner ring between a fully open position and a partially closed position with respect to the outer ring. In the fully open position, the rack gear is offset from an outer ring stop a distance equivalent to five degrees of actuator movement. The control logic of the actuator is modified so that the open position of the actuator moves the pinion gear so that the rack gear stops at or near the offset distance, leaving five degrees as the margin for error. Any overtravel by the actuator does not cause the rack gear to impact the outer ring stop, thus avoiding possible stall of the actuator.

US Patent:

6506031, Jan 14, 2003

Filed:

Apr 4, 2001

Appl. No.:

09/826485

Inventors:

Vishnu M. Sishtla - Cicero NY

Assignee:

Carrier Corporation - Syracuse NY

International Classification:

F04B 1700

US Classification:

417366, 417365, 4174104, 4182011, 418203

Abstract:

A screw compressor having balanced axial thrust includes a housing having a fluid inlet and a fluid outlet; a rotor disposed in the housing for receiving low pressure fluid from the inlet and discharging increased pressure fluid from the outlet, the rotor having a discharge end and a motor end; a balance piston arranged to exert a balancing force on the motor end of the rotor; and a conduit for conveying a high pressure fluid to the balance piston so as to exert the balancing force.

US Patent:

6547520, Apr 15, 2003

Filed:

May 24, 2001

Appl. No.:

09/863228

Inventors:

Thomas M. Zinsmeyer - Pennellville NY
James R. Barrett - Sheds NY
Vishnu M. Sishtla - Cicero NY

Assignee:

Carrier Corporation - Syracuse NY

International Classification:

F04W 2946

US Classification:

415150, 415160, 415164

Abstract:

A vaned diffuser for a centrifugal compressor has provision for selectively adjusting the pitch of the vanes in order to accommodate variable load conditions. Each of the vanes is rotatable about a pivot pin near its leading edge and is engaged with an actuation member near its trailing edge. The actuation members are attached to a common ring which can be selectively rotated to move to the vanes in unison. The ring is supported by rollers at its outer periphery and is positioned at the outer periphery of a diffuser wall such that there is no forward facing step projecting into the flow stream.

US Patent:

6554567, Apr 29, 2003

Filed:

Sep 21, 2001

Appl. No.:

09/957728

Inventors:

Vishnu M. Sishtla - Cicero NY

Assignee:

Carrier Corporation - Farmington CT

International Classification:

F04D 2946

US Classification:

415150

Abstract:

An annular radially disposed split ring diffuser for a centrifugal compressor includes an inner ring and an outer ring. A drive positioning mechanism includes a pinion gear on a pinion axle driven by an actuator. A rack gear is mounted to the inner ring and adapted to engage in meshing arrangement with the pinion gear. The actuator is operable to position the inner ring between a fully open position and a partially closed position with respect to the outer ring. A travel limiter is provided to positively limit the travel of the inner ring at the fully open and the partially closed positions. A compliant mechanical stop on a side of the rack gear touches an outer ring stop on the outer ring when the inner ring is in the fully open position to prevent the gear teeth from being stripped by the actuator torque output.

US Patent:

6619430, Sep 16, 2003

Filed:

Oct 12, 2001

Appl. No.:

09/975333

Inventors:

Jianping Zhong - Michigan City IN
Vishnu Sishtla - Cicero NY

Assignee:

Carrier Corporation - Farmington CT

International Classification:

F01M 100

US Classification:

184 616, 384479, 277457

Abstract:

Refrigerant gas at a few psi higher than suction is supplied via labyrinth or annular groove type seals located between the suction side bearings and suction and between the suction side motor bearing and the motor. The buffer gas flow divides with part going to suction and part to a drain along the oil flowing from the bearings.

US Patent:

6632077, Oct 14, 2003

Filed:

Jan 11, 2002

Appl. No.:

10/044533

Inventors:

Vishnu M. Sishtla - Manlius NY

Assignee:

Carrier Corporation - Farmington CT

International Classification:

F04B 1700

US Classification:

4174236, 41742312, 417 63, 417228

Abstract:

A centrifugal compressor that includes a low speed shaft connected to a drive motor and a high speed shaft containing an impeller. The high speed shaft is coupled to the low speed shaft by a gear train. The low speed shaft is supported by hydrodynamic, oil lubricated, bearings while the high speed shaft is supported by roller and ball bearings. Any vibrational stresses developed in the high speed shaft are dampened by the low shaft system through the gear train coupling.

US Patent:

6739147, May 25, 2004

Filed:

Nov 27, 2002

Appl. No.:

10/306326

Inventors:

Vishnu Mohan Sishtla - Manlius NY

Assignee:

Carrier Corporation - Syracuse NY

International Classification:

F25B 4302

US Classification:

62192, 62 84

Abstract:

A system for reclaiming oil from a combined refrigerant/oil liquid mixture at an evaporator takes a tap of discharge pressure refrigerant from a screw compressor. This hot refrigerant is utilized to boil off refrigerant in the combined liquid refrigerant/oil mixture in a vaporizer. The separated oil is returned to an oil sump and utilized to lubricate the compressor. The tapped discharge pressure refrigerant can be tapped from two distinct locations, and each of these taps receives a valve. The two valves are controlled based upon system conditions. The two valves are selectively opened and closed to provide the hottest temperature refrigerant to the vaporizer to achieve the maximum separation efficiency.

US Patent:

6814540, Nov 9, 2004

Filed:

Oct 22, 2002

Appl. No.:

10/277861

Inventors:

Vishnu M. Sishtla - Manlius NY
Thomas M. Zinsmeyer - Pennellville NY

Assignee:

Carrier Corporation - Farmington CT

International Classification:

F04D 2946

US Classification:

415150, 415148

Abstract:

A vaned diffuser for a centrifugal compressor has provision for selectively adjusting the pitch of the vanes in order to accommodate variable load conditions. Each of the vanes is rotatable about a pivot pin near its leading edge and is engaged with an actuation member near its trailing edge. The actuation members are attached to a common ring which can be selectively rotated to move to the vanes in unison. The ring is supported by rollers at its outer periphery and is positioned at the outer periphery of a diffuser wall such that there is no forward facing step projecting into the flow stream. A throat is defined between adjacent vanes, and the pivot pin for each vane is located downstream of the throat on the pressure side of the vane to reduce turbulence in the flow at the throat.