US2309524A - Heating system - Google Patents

Description

Patented Jan. 26, 1943 HEATER SYSTEM Wiiliam F. Miller, Evansville, Ind, assignor to Industrial Engineering Corporation, Evansville, Ind., a corporation of Indiana Application March 31, 1937, Serial No. 134,138

3 Claims.

The present invention relates to heating systems and more particularly to thermostatically controlled heating systems of the type wherein theoperation of the furnace or heater is controlled in Whole or in part by means of a thermostat located in a room to be heated.

In many heating systems periodic operation of the heater as a result of room temperature requirements, builds up a large supply of heat in the furnace or boiler to continue the supply or discharge of heat even after the room temperature requirements have been satisfied. This is particularly true in the case of coal stoker operation, wherein a room thermostat is provided to operate a stoker to feed coal to the the fire box. Such operation, of course, continues until the heat requirements of the room have been satisfied and the thermostats acts to stop the fuel feeding. At such time, however, there is a quantity of freshly fed unburned coal in the fire box, which continues to burn, thus continuing the supply of heat to the room and resulting in uncomfortable overheating conditions.

Furthermore, automatic coal stokers are usuallv provided with a kindling device or mechanism designed to automatically feed fuel to the fire box periodically, as for example once each hour, to periodically supply suflicient fuel to prevent the fire from' being extinguished in mild Weather, when the room temperature requirements for heat are few and infrequent. Such kindling devices operated to periodically feed fuel for a definite time, usually three to five minutes, irrespective of room temperature requirements. Hence in more severe weather when the heater is frequently operated in response to room temperature requirements as described above, the kindling mechanism may become operative immediately following the stopping of the burner when the room thermostat is satisfied, feeding additional fuel to the fire box and increasing materially the uncomfortable overheated condition described.

One of the primary aims and objects of my invention is to provide improved means for preventing the overheating conditions above described, and to this end the invention provides an improved, simple inexpensive and positive control for heating systems.

More especially the invention improves existing controls for automatic coal stokers by providing means for periodically feeding fuel to the burner or fire pot for a definite time, irrespective of room temperature conditions as Well as limiting the action of the room thermostat controlling the stokers so that overheating of the rooms will be substantially avoided.

In order that the invention may be fully understood reference is made to the accompanying drawing, which is illustrative of several preferred embodiments of the invention.

In the drawing Fig. 1 is a diagrammatic view of one form of control system embodying my invention;

Fig. 2 is a diagram illustrating one desirable time cycle arrangement for stoker operation.

In the drawing I have illustrated the several embodiments of the invention as applied to a coal stoker installation, wherein the fuel is mechanically fed to the fire pot of the stoker by any of the well known mechanisms operated by a stcker motor Hi. It will be understood that certain features of the invention are not limited to coal stoker installations, but are highly desirable in other installations which may or may not require a motor to feed fuel to the heater, as for example, gas and oil installations.

Referring more specifically to'the illustrated embodiments, such installations may includea suitable electrically operated fuel regulating device Iii herein illustrated and referred to as a motor, and a limit control switch II which may be thermostatically or pressure operated as desired, associated with the furnace or heater and adapted normally to be closed, but to open and break the circuit to the motor when the temperature or press'ure'of the furnace or heater, as the case may be, exceeds a predetermined degree. Most installations also include a room thermostat i2, located-in the room to be heated and connected to the motor 10 in series with the limit control H to operate the motor I!) in response to room temperature requirements.

' One rather simple circuit for controlling the motor H1 is illustrated in Fig. 1. When the room temperature drops to a pointat which the thermostat is set, the blade moves to engage a terminal iZ completing a 'circuit from one .of the line voltage wires L through line ll to limit control H, thence through line li ll to closed thermostat i2, thence through line l2 to motor and to voltage line L.

Various circuits for connecting the thermostat limit control and motor in series are old and well known both in high voltage and low voltage circuits (i. e. employing relays and transformers) and the circuit above described is intended only as illustrative of one manner of using the invention. v i As previously stated, operation of the heater in response to room temperature requirements, particularly in the case of coal stoker installations, often produces an excess amount of fuel or heat in the furnace or heater, which will continue to supply heat to the room after the room temperature requirements have been satisfled, resulting in an uncomfortable overheated room.

According to the present invention, this objectionable condition is substantially eliminated by making the operation of the furnace or heater subject to relatively frequent time cycles, as for example fifteen (15) minute cycles, and in rendering said thermostat ineffective for a substantial portion of each cycle, for example from two (2) to seven (7) minutes.

One simple and efiicient mannerof accomplishing the above stated advantage is to interpose in one of the thermostat lines, as herein illustrated line H a time controlled switch 20 driven by a synchronous motor 2| connected to power lines L and L and adapted to rotate shouldered timing cams 22 and 22, one revolution in any desired time scale, for example once in fifteen (15) minutes. A pair of switch arms 23, 23 may be mounted adjacent the cams and each have followers 24 adapted to engage the cams 22, 22 The switch arms each are provided with contacts 25 adapted normally to be closed as the followers engage the coinciding surfaces of the cams 22 and 22 and thus keep the circuit to the thermostat l2 closed. One of the cams, as for example, the cam 22, preferably is relatively adjustable with respect to the other cam, by means of the pin and slot construction 26 so as to adjustably space the shoulders of the two cams desired distance, from zero to substantially one-half of the cam periphery, the equivalent of from zero to seven (7) minutes of the timing cam cycle. Thus, as the follower 24 of the switch arm 23 drops from the shoulder to the low surface of cam 22, the switch contacts will be separated and the circuit broken. One suitable construction of time controlled switch for this purpose is that disclosed in my copending application Serial No. 30,674, filed July 10, 1935, Patent No. 2,190,603, Feb. 13, 1940, excepting that the switch contacts shown therein are designed to be closed as the followers engage non-coinciding cam surfaces instead of separated as above described.

When such a time controlled switch is interposed in the thermostat circuit line, as for example the line |l, the opposite sections of that line may be connected to the respective switch arms 23, 23 which have suitable electrical conduction to the contacts. Thus the thermostat control of the motor I is subject to a desirable time cycle, for example of 15 minute duration, and that control is broken for a definite period of that cycle, which period may be adjustable, for example from 1 to seven (7) minutes.

As stated above, many stoker installations include a kindler to periodically feed fuel to the fire pot to prevent the fire from being extinguished in mild weather when the thermostat operates only at long intervals. Such a kindler mechanism may include a time controlled switch 30, such as disclosed in my prior application Serial No. 30,674 above referred to. This switch may be powered by a synchronous motor 3i connected to line voltage wires L and L by wires L and L The cams 32. 32" of the switch 30 are similar to the cams 22, 22 and are preferably geared to the synchronous motor 3| so as to make one revolution in every fifteen minutes as in the case of the thermostat limit timer 20. The cams may be relatively adjustable as in the case of the cams 22, 22 in order to adjustably vary the duration of the kindling period, but in the case of fifteen minute cam cycles a fixed period of feeding, say of two minute duration, will be sufficient to prevent the fire from being extinguished. The switch arms 33, 33 of the timer 30 have contacts 35 and followers 34 and are arranged so that the contacts are normally spaced, as the followers ride on coinciding surfaces of the cams 32, 32*. As the follower for spring arm 33 drops on the low part of cam 32 and the follower on arm 33 remains upon the high part of cam 33**, the switch contacts are closed.

The contacts and conductor spring arms are connected to the circuit by wires ll and ll. so as to be in parallel with the room thermostat. Thus the kindling timer may operate the stoker for a definite period of time to feed fuel to the fire pot, independently of the room temperature conditions.

Advantageously the two timers 20 and 30 are synchronized so that the circuit closing periods will not overlap as is illustrated in Fig. 2. For example, for any given time cycle, that illustrated being of fifteen minute duration, the kindling timer may first operate the stoker for a definite duration, for example two minutes, to keep the fire alive. At the termination of the two minutes kindling period, the further control of the stoker is subject to the room thermostat, except for such variably adjustable time illustrated in black, as the switch contacts may be open and the thermostat circuit to the motor is broken. In this way long thermostat controlled operation immediately in advance of the kindling operation is prevented.

Advantages of my invention reside in the simple, novel control for heating systems employing the usual thermostat control. Particularly in the case of coal stoker installations an improved relation between the kindling fuel feeding and the thermostatically controlled fuel feeding is provided.

The particular control means illustrated and described herein are simple of construction, positive of operation and economical in manufacture, and provide an inexpensive, highly efiicient control which may be easily incorporated in existing installations, whether of the high voltage or low voltage types.

It will be apparent to those skilled in the art that the invention is susceptible of wide variation from the construction and specific installations shown and described, and obviously it is not to be so limited to such details.

The present application is a continuation in part of my prior application Serial No. 30,675, filed July 10, 1935, now Patent No. 2,077,250, of April 13, 1937.

I claim:

1. In a mechanism of the kind described, a main circuit, normally independent means controlling the circuit, said means including two additional circuits adapted to control the main circuit, a time-controlled means in one additional circuit adapted to close the same at predetermined intervals of time, and to open again thereafter, a temperature-responsive mechanism in the other additional circuit adapted to close and to remain closed during such time as the temperature condition remains beyond a predetermined value, said temperature-responsive control circuit being normally continuously closed when the temperature-responsive mechanism is closed, and means for opening the temperature-responsive circuit independently of the heat conditions for a predetermined interval before the time-controlled circuit is closed, whereby to prevent overloading of the furnace by action of both circuits in such rapid succession.

2. In a heating system of the character described, in combination with a furnace, an electrically controlled fuel feeding device therefor, of time controlled means for intermittently operating said fuel feeding device at predetermined intervals of time and for predetermined durations, a temperature responsive circuit including the fuel feeding device and a room thermostat having contacts adapted to close and remain closed during such time as the temperature condition remains beyond a predetermined value, means for periodically opening said temperature responsive circuit for a predetermined interval of time before the time controlled circuit is closed, regardless of room temperature, whereby to prevent overloading of the furnace by action of both the thermostat and time controlled means in rapid succession, said temperature responsive circuit being closed at all other times when the thermostat contacts are closed.

3. In a heating system of the character described in combination with a furnace, an electrically controlled fuel feeding device therefor, of time controlled means for intermittently operating said fuel feeding device at predetermined intervals of time and for predetermined durations, a temperature responsive circuit including the fuel feeding device and a room thermostat having contacts adapted to close and remain closed during such time as the temperature condition remains beyond a predetermined value, means for periodically opening said temperature responsive circuit for a predetermined interval of time greater than the period the time controlled circuit is closed, regardless of room temperature, Whereby to prevent overloading of the furnace by action of both the thermostat and time controlled means in rapid succession, said temperature responsive circuit being closed at other times when the thermostat contacts are closed.

WILLIAM F. MILLER.

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