Thermostat system

Claim 1

Heating apparatus for maintaining the air in a working space at a first predetermined temperature at one time and at a second predetermined temperature at another time comprising in combination: a heat source for generating heat into a heat reservoir; a voltage source for generating a control current; anticipator means including a thermistor responsive to the control current from the voltage source for dissipating heat at substantially the same steady-state rate at both the first and second predetermined air temperatures and over a predetermined range of voltages from the voltage source; control means for energizing the heat source in response to a control signal; electrical circuit means for interconnecting the voltage source, anticipator means and the control means, said electrical circuit means being switchable into a first state in which the control current is conducted to the anticipator means and the control signal is conducted to the control means so that the heat source generates heat, and switchable into a second state in which the control current is prevented from flowing through the anticipator means, and the control signal is terminated so that the heat source terminates the generation of heat; circulation means for commencing the circulation of heat from the heat reservoir to the working space after the heat reservoir has been heated to a fixed temperature and for continuing the circulation of heat from the heat reservoir to the working space while the electrical circuit means is switched to the first state and for a period of time after the electrical circuit means is switched to the second state; and thermostat means reponsive to the temperature of the air and in heat transfer relationship with the anticipator means, said thermostat means being settable to a first condition for switching the electrical circuit means to the first state at a first point in time when the air temperature decreases below the first predetermined temperature and for switching the electrical circuit means to the second state at a second point in time when the combined heat from the air and the anticipator means raises the temperature of the thermostat means to the first predetermined temperature, said thermostat means being settable to a second condition for switching the electrical circuit means to the first state at a third point in time when the air temperature decreases below the second predetermined temperature and for switching the electrical circuit means to the second state at a fourth point in time when the combined heat from the air and the anticipator means raises the temperature of the thermostat means to the second predetermined temperature, whereby the substantially constant steady-state rate of heat dissipation in the anticipator means at the first and second predetermined temperatures irrespective of voltage variations of the voltage source prevents a first time period between the first and second points in time and a second time period between the third and fourth points in time from decreasing below a predetermined minimum time duration.