Temperature control device

Claim 3

A method according to claim 1 in which the second signal comprises a square wave signal of constant frequency whose on/off ratio is varied in proportion to the first signal.

Claim 4

A method according to claim 2 in which the square wave signal is filtered to produce, as the third signal, a rounded square wave signal.

Claim 5

A method according to claim 3 in which the first and third signals are combined to control the supply of heat.

Claim 6

A method according to claim 1 in which the first signal is averaged and the duration of the deviation of the second signal from the reference level is varied in proportion to the averaged first signal.

Claim 7

A method according to claim 5 in which the first signal is averaged by means of a low pass filter.

Claim 8

A method according to claim 6 in which the time constant of the filter is greater than the time constant of the temperature-controlled environment.

Claim 11

A method acccording to claim 8 in which the heat is supplied to the environment by means of an electrical heater to which the electrical supply is controlled in response to the combined averaged first signal and the rounded square wave signal.

Claim 12

A method according to claim 9 in which the electrical supply to the heater is controlled by means of a switch triggered by means of a trigger having a critical triggering level which is exceeded periodically by the combined averaged first signal and the rounded square wave signal.

Claim 13

Apparatus for controlling the temperature of a temperature-controlled environment, comprising: 1. temperature sensing means for sensing the temperature of the environment, 2. first signal generating means connected to the temperature sensing means for producing a first signal in proportion to the temperature, 3. second signal generating means operatively connected to the first signal generating means for producing a second signal having a periodic deviation from a reference level, the duration of the deviation from the reference level being in proportion to the first signal, 4. means for deriving from said second signal a third signal having a value which varies with time, 5. heat supply control means operatively connected to the first signal generating means and the third signal generating means for controlling the supply of heat to the environment in response to the first and third signals.

Claim 14

Apparatus for controlling the temperature of a temperature-controlled environment, comprising: 1. temperature sensing means for sensing the temperature of the environment, 2. first signal generating means connected to the temperature sensing means for producing a first signal in proportion to the temperature, 3. second signal generating means operatively connected to the first signal generating means for producing a second signal having a periodic deviation from a reference level, the duration of the deviation from the reference level being in proportion to the first signal, 4. means for deriving from said second signal a third signal having a value which varies with time, 5. heat supply control means operatively connected to the first signal generating means and the third signal generating means for controlling the supply of heat to the environment in response to the first and third signals.

Claim 15

Apparatus according to claim 11 in which the temperature sensing means comprises a thermistor.

Claim 16

Apparatus according to claim 11 which means for delaying the first signal is operatively interposed between the first signal generating means and the second signal generating means.

Claim 17

Apparatus according to claim 11 which the second signal generating means comprises square wave generator means for generating a square wave output signal of constant pulse repetition frequency the on/off ratio of which is proportional to the first signal.

Claim 18

Apparatus according to claim 14 in which the time constant of the square wave generator means is less than the time constant of the temperature-controlled environment.

Claim 19

Apparatus according to claim 15 in which the means for deriving the third signal from the second signal comprise low pass filtering means having a time constant similar to that of the square wave generator means.

Claim 20

Apparatus according to claim 11 in which the temperature-controlled environment is heated by means of electrical heaters, the heat supply control means comprising: 1. thyristor triggering means operatively connected to the square wave generator means, and 7. a thyristor connected in series with the electrical heater, with the gate thereof connected to the triggering means.

Claim 21

Apparatus according to claim 17 in which the thyristor triggering means includes means for generating thyristor triggering pulses when the combined first and third signals exceed a critical triggering level and when the instantaneous value of the volage of an alternating current supply connected to the thyristor and the thyristor triggering switch means is substantially zero.

Claim 22

Apparatus according to claim 17 and including detecting means for detecting when the heater is operating for a predetermined proportion of the total time and means for providing an alarm if the said heater operates for a proportion of the total time above a first preset limit or below a second preset limit.

Claim 23

Apparatus according to claim 19 including integrating means for averaging the proportion of the total time during which said heater operates.

Claim 24

In an apparatus for supplying heat to a temperature-controlled environment by means of an electrical heating means, including a.c. electrical current supply means, temperature sensing means, and means for regulating the supply of electrical current to the electrical heating means in response to the temperature of the environment as sensed by the temperature sensing means, the improvement in the means for regulating the supply of elctrical current, comprising in combination: 1. first signal generating means operatively connected to the temperature sensing means and adapted to produce a first signal proportional to a deviation of the sensed temperature from a predetermined reference temperature. 2. signal averaging means operatively connected to the first signal generating means, having a time constant greater than the time constant of the temperature-controlled environment and adapted to time average the first signal, 3. constant frequency square wave generator means operatively connected to the signal averaging means and having a time constant less than that of the temperature-controlled environment, the square wave generator means adapted to produce a square wave signal of constant pulse repetition frequency and of variable on/off ratio, the on/off ratio of the signal being proportional to the averaged first signal, 4. low pass filter means operatively connected to the square wave generator means and having a time constant similar to that of the square wave generator means, adapted to derive from the square wave signal produced by the square wave generator means a rounded square wave signal having sloping edges, 5. thyristor triggering means having a critical triggering level and adapted to produce thyristor triggering pulses at an output thereof when said critical triggering level is exceeded by an input signal, the thyristor triggering means being operatively connected at its input to the first signal generating means and the low pass filter means whereby said thyristor triggering means is actuated when the combined value of said first signal and rounded square wave signal exceeds the critical triggering level, 6. thyristor switch means in series with the electrical heater having its gate operatively connected to the output of the thyristor triggering means and adapted to conduct electrical current to the heater when triggered by said triggering pulses at the gate

Claim 25

In an apparatus for supplying heat to a temperature-controlled environment by means of an electrical heating means, including a.c. electrical current supply means, temperature sensing means, and means for regulating the supply of electrical current to the electrical heating means in response to the temperature of the environment as sensed by the temperature sensing means, the improvement in the means for regulating the supply of elctrical current, comprising in combination: 1. first signal generating means operatively connected to the temperature sensing means and adapted to produce a first signal proportional to a deviation of the sensed temperature from a predetermined reference temperature. 2. signal averaging means operatively connected to the first signal generating means, having a time constant greater than the time constant of the temperature-controlled environment and adapted to time average the first signal, 3. constant frequency square wave generator means operatively connected to the signal averaging means and having a time constant less than that of the temperature-controlled environment, the square wave generator means adapted to produce a square wave signal of constant pulse repetition frequency and of variable on/off ratio, the on/off ratio of the signal being proportional to the averaged first signal, 4. low pass filter means operatively connected to the square wave generator means and having a time constant similar to that of the square wave generator means, adapted to derive from the square wave signal produced by the square wave generator means a rounded square wave signal having sloping edges, 5. thyristor triggering means having a critical triggering level and adapted to produce thyristor triggering pulses at an output thereof when said critical triggering level is exceeded by an input signal, the thyristor triggering means being operatively connected at its input to the first signal generating means and the low pass filter means whereby said thyristor triggering means is actuated when the combined value of said first signal and rounded square wave signal exceeds the critical triggering level, 6. thyristor switch means in series with the electrical heater having its gate operatively connected to the output of the thyristor triggering means and adapted to conduct electrical current to the heater when triggered by said triggering pulses at the gate

Claim 26

In the apparatus of claim 21, thyristor triggering means adapted to produce triggering pulses when the instantaneous value of voltage of tha a.c. supply is substantially zero.