Refrigerating and Air Conditioning Pressure and Temperature Controls – Commercial
An early automatic low side pressure control for commercial refrigeration\r\napplications, made in the form of the then familiar Bourdon tube actuated pressure gauge; equipped with line-voltage, tilting mercury bulb switch, with glass viewing window, Mercoid Switch, Federal Gauge Chicago, Ill., Circa 1928.
Features:
rear mounted manual adjustments, executed in brass see below; Beautifully etched name plate in sheet broass
Technical Significance:
An example of early pressure gauge design and construction based on the use of a relatively crude Bourdon tube-actuating device, found prior to the wide spread introduction of hydraulic bellows and extended capillary line actuators – See ID # 151-154
See also notes on significance, ID # 151
Mercoid Division , Dwyer Instruments Inc, Michican City Ind. Currently show in their catalogue listings a range of Bourdon tube pressure switches of very similar construction and operation, indicating something of the precision and reliability to be expected of this genre of commercial and industrial controller technology. See note 1
Industrial Significance:
The development of early automatic pressure controls started with the materials and understandings of the day. In the early 1920’s these included the Bourdon pressure tube and the mercury bulb switch.
The circular Bourdon tube is designed to responds to changes in internal pressure by changing its curvature, used here to move a mercury bulb switch through a simple and elegant brass linkage.
The control has a manual set knob on the back, as well as a means of repositioning the bulb, so as to re-set its control point.
The control is designed to operate over the commercial, So2 pressure/temperature range of 7-1/2 lbs. pressure to 5 inch of vacuum, requiring a large tube to respond to these low pressures.
A crude device, when compared with even mid-20th century practices, it provided the essential beginnings for the development of fully automated refrigeration equipment.
