Abstract: A keying system for assuring the proper sequence or arrangement of cable cards within a card grouper is provided. The grouper includes a plurality of slots to receive the cable cards. The cards include tab means at at least one side thereof which can be selectively trimmed to one of several specific extension distances from the card. The grouper includes a template which has grooves configured to receive cards having their tabs programmed to one and only one configuration. Thus any given card, when programmed, will fit in only one location. The cards and grouper also include coacting surfaces to allow the appropriate card to be inserted in only one orientation in any given slot.

Abstract: An oil return system for a multiple compressor refrigeration system in which said compressors have a common discharge and at least two of said compressors have their low pressure suction side connected to operate at substantially different suction pressures, said oil return system having oil and refrigerant separating means connected to receive the common discharge from said compressors and oil delivery means constructed and arranged to maintain compressor oil levels at the suction side of the respective compressors, and oil control valve means disposed between said separating means and oil delivery means for each of said two compressors, said oil control valve means for each such compressor having pressure means for maintaining the downstream oil pressure to the oil delivery means at a preselected value.

Abstract: An oil separator unit for use in an oil separation and return system for the compressor means of a refrigeration system, including a unitary oil separation and oil accumulator vessel having an upper vortex separation chamber, oil collecting and separating means, vapor deflector means, oil precipitation means, and a lower oil accumulator chamber for receiving and holding liquid oil.

Abstract: A pressure regulating valve for use in the oil separation and delivery system of a refrigeration system, including a valve body having an oil inlet chamber for connection with a separated liquid source on the high pressure side of refrigeration system compressor means, an oil outlet adapted for low pressure connection with oil level controls for the compressor means, internal valve means for controlling oil flow between the high side and low side chambers, and movable pressure means responsive to oil outlet pressure and compressor suction pressure acting in opposition for regulating said internal valve means.

Abstract: An oil separation system for a refrigeration system having compressor, condenser-receiver and evaporator means, including an oil separator having a vortex separation chamber disposed in the refrigerant gas discharge line between the compressor means and condenser-receiver means, an oil reservoir for receiving oil from the separation chamber, and oil control means for maintaining a predetermined oil level in the compressor means including a pressure differential valve for regulating the flow of oil from the reservoir to the compressor means.

Abstract: A laminar airflow biological safety cabinet apparatus is disclosed which is convertible by the user for changing the airflow pattern through the cabinet in order to meet different specialized conditions encountered in laboratory work with potentially hazardous biological specimens. Adjustable damper structure is provided adjacent the air outlet of the cabinet for simultaneously varying the amounts of air discharged and drawn into the cabinet, and the laminar flow of downwardly directed air through the work compartment thereof. An air filter is located immediately below the work surface of the cabinet and upstream of the air fan for removing contaminants from the air.