Air conditioning systems

Claim 1

An air conditioning system for controlling the air supply to an enclosure comprising: temperature-responsive means responsive to the air temperature in the enclosure and delivering a first variable pulse train signal wherein the number of pulses occurring in unit time represents the actual temperature in said enclosure; reference signal-generating means delivering a second pulse train signal wherein the number of pulses occurring in unit time represents a desired temperature for said enclosure; a digital comparator receiving said first and second pulse train signals and having first and second output channels, the comparator being operative to deliver output pulses the number of which occurring in unit time represents the difference between actual temperature and desired temperature, said output pulses appearing on said first output channel if the frequency of pulses in said actual temperature signal pulse train exceeds the frequency of pulses in said reference signal pulse train, said output pulses appearing on said second signal channel if the frequency of pulses in said reference signal pulse train exceeds the frequency of pulses in said actual temperature signal pulse train; a digital logic network receiving and processing the output pulses on said first and second output channels from said digital comparator, said logic network having at least three phase channels operative in response to said output pulses to deliver processed pulses sequentially in said channels at a rate proportional to the pulse frequency of said output pulses received from the comparator, said processed pulses being delivered by said phase channels in one sequence if the comparator output pulses appear on its first comparator output channel and in the reverse sequence if the comparator pulses appear on its second output channel; a fluid flow control valve controlling flow of air in a duct leading to said enclosure; a digital valve actuator operative to change the position of said valve by moving it through a discrete increment in response to each processed pulse delivered thereto on said at least three phase channels by said digital logic network, said actuator operating at a speed determined by the rate of delivery of said processed pulses on said phase channels and in one direction or the reverse direction according to whether the pulses applied to said phase channels are in said one sequence or said reverse sequence.