US2449538A

US2449538A - Control apparatus

Info

Publication number: US2449538A
Application number: US496359A
Authority: US
Inventors: Harold S Ackerman
Original assignee: Hubbard and Co
Current assignee: Hubbard and Co
Priority date: 1940-11-19
Filing date: 1943-07-27
Publication date: 1948-09-21
Anticipated expiration: 1965-09-21

Description

P 1948- H. s. ACKERMAN 2,449,538

CQNTROL APPARATUS Original Filed Nov. 19, 1940 FIG. 1. 70

72 Fmnz.

INVENTOR Harold S. Ackcrmun ATTORNEY I Patented Sept. 21, 1948 CONTROL APPARATUS Harold S. Ackerman, Dayton, Ohio, assignor to Hubbard and Company, Pittsburgh, Pa., a corporation of Pennsylvania Original application November 19, 1940. Serial No. 366,281. Divided and this application July 27, 1943, Serial No. 495,359

Claims. (Cl. 122-504) The present invention relates to control apparatus and is particularly applicable to control ap- Daratus for fuel burners.

It is an object of the present invention to provide a control apparatus for a space heater including a boiler, with a combination liquid level and fluid pressure operated governing means for increasing the safety of operation, the governing means being ei'iective, upon an undue rise in pressure or lowering of the liquid level in the boiler, to interrupt the supply of fuel to the burner for the boiler.

It is an object of the invention to provide a device for determining the presence of a fluid. which device comprises an electrically operated mechanism having a circuit therefor that includes a cathode and plate of an electron tube, the circuit being controlled by a grid between the cathode and plate, and the potential on the grid being controlled by a circuit having electrodes arranged to be subjected to the fluid to be detected.

Another object of the invention is to provide a mechanism for determining a predetermined liquid level, which mechanism includes an electrically responsive device controlled by a circuit including the cathode and plate of an electron tube, the flow of current between the cathode and plate being controlled by a grid, and the voltage on the grid being controlled by a circuit including an electrode disposed in the liquid at the level to be determined and a second electrode disposed in the liquid below the level.

A further object of the invention resides in the provision of a control apparatus for a space heater having a boiler, with a pair of switches connected in series for governing the operation of a fuel valve control circuit, either switch being operative to affect the circuit in such a way as to discontinue fuel flow to the boiler burner, one of the switches being pressure operated and the other being fluid operated.

A still further object of the invention resides in the provision of an electrical control apparatus for boil'er burners in which a plurality of current interrupting devices are connected in series to govern the operation of a fuel valve section of the control circuit, any of the devices being capable of so affecting the circuit as to interrupt fuel flow to the boiler burner, one of the devices being responsive to pressures developed within the boiler, another being responsive to changes in the liquid level therein and a third being responsive to temperature changes adjacent the burner itself, all of the devices cooperating to invalve 32 is connected in the pipe 3|.

2 crease the efficiency, flexibility and safety of the control apparatus.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferred form of embodiment of the invention is clearly shown,

This application constitutes a true division of my co-pending application Serial Number 366,281, filed November 19, 1940, entitled Control apparatus, now Patent No. 2,327,690.

In the drawings:

Fig. 1 is a diagrammatic view of the improved control system for controlling the flow of gas to a gas burning boiler; and

Fig. 2 is a perspective view, but on a larger scale, of an element of the control system shown in Fig. 1.

Referring to the drawings, for the purpose of illustrating one form of the invention, I have shown a control system 20' for controlling the flow of fuel to a burner and for igniting the same. In the particular embodiment shown, a gas fuel burner is illustrated but it is to be understood thatothertypes of burners or fuels may be employed. The fuel burner is shown at 22 and it is adapted to heat water in a boiler 23, a part of the boiler being shown directly over the burner. The water heated in the boiler 23 may be utilized for heating rooms in a building. The burner is connected with a gas main by a pipe 24 and a valve 25 is connected in the pipe for controlling the flow of fuel to the burner. The valve ZLis opened by a solenoid 26 when the solenoid is energized and is arranged to be closed automatically er 22 and is arranged to direct a flame over the top of the burner 22 for igniting the fuel. The pilot burner 30 is connected to the fuel pipe 24 ahead of the valve 25 by a pipe 3i and a fuel The valve 32 is opened by a solenoid 33 when the solenoid it's-energized and is arranged-to close automatically when the solenoid is deenergized.

The operation of the burners l0 and 22 is controlled by a thermostatic switch 35 that is responsive to the temperature in a room to be heated by the water heated in the boiler 23. The thermostatic switch 35 may be ofany suitable type in common use, and in the present embodiment it comprises a bimetal strip 26 anchored at one end and carrying a contact 3! at the opposite end. which contact is arranged to engage a relatively stationary contact 39. The contact 38 is mounted on a screw 40 that is threaded in a bracket 4|. A wire 42 connects the bimetal 38 with a secondary coil 43 of a transformer 44. The primary coil 45 of the transformer 44 is connected in a high voltage circuit, for example, 110 volts and is energized constantly. The voltage induced in the secondary winding is preferably 24 v. The bimetal 36 is adapted to close contacts 38 and 33 when the temperature of the room in which it is located falls to, for example, 70 F. and to open the contacts when the temperature increases slightly.

When the

contacts

38 and 39 of the thermostatic switch 35 close, a circuit is established from secondary coil 43 through wire 42, bimetal 36,

contacts

38 and 39, screw 40, bracket 4|, wires- 41, 43 and 48, solenoid 33 and wires 50 and 5|, and coil 43. The solenoid 33, being energized, opens the valve 32 for feeding gas to the pilot burner 30. A circuit is also established from wire 48 through wire 55, switch 58, including contacts 51, wire 58, solenoid 53, wires 80, 6i and 5|. The solenoid 58, when energized by completion of the above described circuit, closes a switch 42. The closure of switch 82 completes a circuit from the secondary coil 43 through wire 3, switch 52, wire 64, heating element 35,

wires

83, 81, 5| and iii to secondary coil 43. The wire 33 taps the secondary coil 43 intermediate the ends thereof for producing a voltage of 4 v. in the heating element circuit. The heating element 45 is formed by a col-l of Nichrome wire and it is arranged to ignite fuel issuing from the pilot burner 30.

The flames from the pilot burner are adapted to heat an element Hi positioned adjacent the burner. The element I0 is composed of material known commercially as INSULCON, manufactured by Stupekoif Laboratories, Inc., Pittsburgh, Pa. This material has a very high electrical resistance when at atmospheric temperatures, but when the temperature thereof is raised considerably, its electrical resistance decreases materially. I make use of this characteristic of the material for causing the fuel valve 25 to be opened after the gas at the pilot burner has become ignited and for causing the valve 25 to close in the event the pilot should be extinguished, for-any reason. The element 10 is formed by embedding two wires H and 12, preferably formed of platinum, in a small biscuit of Insulcon, these wires being spaced apart so that the resistance of the Insulcon controls the circuit between the wires. This element is then mounted adjacent the pilot burner 30 in a position where it will be subject to heating by the radiation from the path of a flame issuing from the burner. The wire H, for example, is connected to awhgf that is grounded to the boiler 23, and the wire 12 is connected to a wire Ii connected with the cathode 14 of an electron tube 13.

The electron tube 18 may be a number 46 or A6" and it includes 'the cathode 13, plate 1!, grid and heater ii for the cathode. The heater ll is connected in the circuit of the secondary coil 43 by

wires

43 and 44. Thus the heater II is energizedwhen the thermostatic switch closes the secondary circuit. The plate 19 is connected to a second secondary coil II of the transformer 44 by a wire 38. Preferably, the coil 45 is such that v. is induced in the circuit therefor. The cathode 18 is connected to the opposite side of the secondary coil 85 by a circuit including wire 81, solenoid 83 and wires 43 and II. The resistance of the solenoid is 2500 ohms.

A condenser is connected with wires 41 and I! in parallel with the solenoid 34. The condenser has a capacity of 25 mi. The grid 30 is connected to the wire 14 by a circuit that includes wires II and .1, switch 33, wire 39', plug I", water in the boiler, and boiler plate to wire 14. A resistance element I02 having a value of five hundred thousand ohms is connected in wire III between wires to and 38.

The plug I03 comprises a tubular, metallic member having an electrode 144 disposed on the inside thereof and insulated therefrom by waterproof material. The plug is threaded in an opening in the wall of the boiler at the minimum water level desired. One end of the electrode I44 extends inside the boiler, and the. wire 3| is connected to the opposite end of the electrode.

The switch 33 is adapted to be snapped to the open and closed position by a bellows I" that is connected with the interior of the boiler 23 by a tube I08. When the pressure in the boiler exceeds a predetermined amount, the bellows expand' to move a snap mechanism for causing the switch to be opened, and when the pressure recedes, the snap mechanism is operated by the collapsing of the bellows to close the switch.

The solenoid 38 is adapted, when energized, to move the switch 56 to bridge contacts lit for establishing a circuit through the solenoid 24 from wire 48, contacts H0, wire H2, solenoid 24, wires H3, 81, ii, if, secondary coil 43, thermostatic switch 35 and wires 4'! and 43. When the switch 53 is moved by the solenoid 33 to bridge contacts I I0, contacts 51 are opened and the solenoid 58 is de-energized. The switch I! is arranged to open automatically when the solenoid 38 is de-energized for breaking the circuit for th heater element 8!.

The operation of the system is as follows: When the thermostatic switch is above 70' F., solenoids 28 and 33 of

fuel valves

25 and 32, respectively, are de-energized and the valves are closed. Solenoid 53 is also de-energized and switch 02 is therefore open. Solenoid 34 is also de-energized and the switch 54 is in the position to bridge contacts 31. When the thermostatic switch 33 closes, the solenoid 33 is energized and opens valve 32 and gas is fed to the pilot burner 33. Solenoid I3 is also energized and closes switch 32 for completing the circuit for .the heater element 45. The heater ll of the electron tube 14 is also energized to heat the cathode ll. After a second or so of such closure of switch 42, the element 35 will ordinarily ignite the gas flowing from the pilot burner 30 and the flame resulting from such ignition and the continued combustion of the gas being jetted from the burner constitutes a radiant heater, the radiation from which heats the element 14. As the resistance through the element decreases until an electrical circuit is established from the grid 44 through wires 34, I1, switch ll, wire 34, pluglll, water and boiler, wire I4, element 14 and wire 15 to the cathode 14. This circuit reduces the potential on the grid to permit a flow ofcurrent to the plate 13 from the cathode for establishing a circuit from secondary coil II through wires 30, 33, solenoid 44, wire 41, cathode 14, plate 13, and wire 44 to secondary coil II. The solenoid 44, being energized, moves the switch 54 to bridge contacts H4 for completing the circuit of the solenoid 24 and opens contacts II to (le energize the solenoid II. The solenoid 24 opens the gas valve 2| for feeding gas to the burner 22, which use is ignited by the flame from the pilot bin-nor 30. The de-cnergization of solenoid ll opens switch 02 for de-energizing the heatin element ll.

Incase the pilot flame fails to ignite for any reason, the element ll remains at room temperature and, having extremely high electrical resistance at such temperature, prevents a reduction in the normal negative charge built up on the grid 80 so that current suiiicient to energize the solenoid II is prevented from flowing to the plate I9. This condition of plate-current blocking exists on initial failure of pilot-burner lighting, and also in the event of, or on failure of combustion after ignition has once occurred. In the latter case, solenoid OI is de-energized and the circuit for solenoid 2| is de-energized by movement of the switch it from contacts ill. De-energization of the solenoid 28 causes the valve to terminate the flow of fuel to the burner 22.

When the water is above the electrode IN, the water forms a path for the current of the grid circuit from the electrode to the boiler (wall. If the water level should fall below the electrode I, the circuit from the grid 80 to the cathode 16 will be broken and the potential on the grid will cause a reduction in the flow of current from the cathode to the plate and the solenoid 88 will be de-energized to cause the switch 56 to open the contacts H0 in the circuit for solenoid 28. This causes de-energization of the solenoid 26 and the fuel valve 25 closes automatically. This arrangement for determining the level of the water will not produce any appreciable electrolysis in the boiler 22 because the current through the water is practically immeasurable. Thus, when water is absent from the end of the electrode IN, the circuit for the grid 80 is broken and causes the burner 22 to be shut off.

When the pressure in the boiler 23 exceeds a predetermined amount, the switch Bl is opened and the potential on the grid causes the current flow through the circuit of the solenoid 88 to be reduced so that the switch 56 moves from contacts ii to contacts 51 for breaking the circuit to thesolenoid 28 of the gas valve 25. This causes the valve 25 to close automatically. Thus the gas burner 22 will be rendered inoperative when the pressure in the boiler is excessive.

When the pressure is reduced to a predetermined degree. the switch 98 is reclosed by collapsing of the bellows I05 and normal operation of-the control system will be resumed.

When the temperature of the thermostatic switch 35 is raised to that desired, the thermostat breaks the circuits of the solenoids 28 and 32, causing

valves

25 and 32 to close, and de-energizes the heater ll of the tube 18. This causes de-energization of the solenoid 88 and the switch 56 is moved to the contacts 51, as is shown in Fig. l. The control system is then prepared for causing heating of the boiler 23 when the thermostatic for heating the cathode; means forming a second electrical circuit for controlling the voltage on guano ent invention as herein disclosed constitute preferred forms, it is to be understood that other forms might be adopted, all coming within the scope of the claims which follow.

Iclaim:

1. In combination, fuel burning means; a tank cuit for controlling the voltage on the grid, said second mentioned circuit including a terminal disposed at a selected minimum water level of the tank and adapted to contact the water when at said level, an electrical conductor connected through the tank with the water, and through the water with the terminal when the water contacts said terminal, and a switch; and means responsive to the pressure in the tank for operating the switch.

2. In combination, a main fuel burning means; a tank containing water heated by the main fuel burning means; electrically operated means for controlling the supply of fuel to the main fuel burning means, said electrically operated means including an electric circuit, an electron tube including a cathode, plate, and a grid, said cathode and plate being connected in said circuit, means for heating said cathode, a second circuit for controlling the voltage on said grid including a connection to the water in said tank, a terminal disposed at a selected minimum water level of the tank and adapted to contact the water and complete said second circuit through the water only at said level and above, and an electric circuit controlling device also interposed in said second circuit having a pilot fuel burning means for modifying the same.

3. In combination, a main fuel burning means; a tank containing water heated by the main fuel burning means; electrically operated means for controlling the supply of fuel to the main fuel burnin means, said electrically operated means including an electric circuit; an electron tube including a cathode, plate, and a grid, said cathode and plate being connected in said circuit, means for heating the cathode, and a second circuit for controlling the voltage on the grid including a terminal disposed at a selected minimum water level of the tank and adapted to contact the water at said level, an elec rical conductor connected through the tank with the water and through the water in the tank with the terminal when the water contacts said terminal.

4. In combination, a main fuel burning means; a tank containing water heated by the main fuel burning means; electrically operated means for controlling the supply of fuel to the main fuel burning means, said electrically operated means including an electric circuit; an electric tube including a cathode, plate and a grid, said cathode and plate being connected in said circuit; means the grid, said second mentioned circuit including a terminal disposed at a selected minimum water level of the tank and adapted to contact the water at said level, an electrical conductor connected through the tank with the water and through the water in the tank with the terminal when the water contacts said terminal, and a pair of addi tional electric circuit controlling devices also interposed in said second circuit. one of said electric circuit controlling devices comprising a switch and the other electric circuit controlling device comprising an element having a very high electrical resistance at atmosphere temperatures and decreasing the resistance when heated; means responsive to pressure in the tank for operating the switch; and means comprising a pilot fuel burning means for heating the other electric circuit controlling device.

5. In combination, a main fuel burning means; a tank containing water heated by. the main fuel burning means; a pilot fuel burning means; electrically operated means forcontrolling the supply of fuel to the main fuel burning means, said electrically operated means including an electric circuit; an electron tube including a cathode,

plate,- and a grid and having said cathode and plate connected in said circuit and compi'bing circuit controlling means interposed in said circuit and controlling the flow of electricity therethrough; means for heating the cathode; and means forming a circuit for controlling the voltage on the grid and having a plurality of current flow controlling means interposed therein, said current flow controlling means comprising a terminal disposed at a selected minimum water level 8 of the tank and adapted to contact the water at said level, a second electrical conductor connected with the water in the tank, and a controlling element responsive to heat from said pilot fuel burning means, said grip circuit being connected through the water in the tank with said terminal when the water contacts the terminal.

HAROLD 8. ACKERMAN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS