Air conditioner servicing unit

TL;DR: In this article, the authors present an approach for servicing automobile air conditioning systems, as well as charging them with refrigerant and compressor lubricant, which is done to the suction side of the compressor while it is operating.

Abstract: Apparatus for servicing automobile air conditioning systems, as for charging them with refrigerant and compressor lubricant. Hoses connect to the high and low pressure charging fittings on the system and lead to pressure gauges for checking the system. The high pressure hose also leads to a dumping valve for emptying the system. The low pressure hose is connected through control valves (a) to a vacuum pump for purging the system, and also through a constant flow valve both (b) to a pressurized source of refrigerant liquid and (c) to a pressurized source of oil. Charging is done to the suction side of the compressor while it is operating. The flow valve passes liquid through a small orifice at a controlled pressure drop. This limits oil flow to a rate, such as one ounce in 45 seconds, slow enough to avoid damaging the compressor, and meters refrigerant in liquid state at a constant rate, e.g. one pound per 90 seconds. As refrigerant leaves the metering valve it is atomized and vaporized before entering the system. Preset timers control the periods of constant flow of oil and refrigerant and thereby meter the quantities charged to the system. A third hose and pressure gauge are provided for servicing those systems having a pressure ratio valve between the evaporator and the compressor.