US2720916A

US2720916A - Burner safety control apparatus for air heaters

Info

Publication number: US2720916A
Application number: US240747A
Authority: US
Inventors: Spackman Thomas Fred
Original assignee: American Air Filter Co Inc
Current assignee: American Air Filter Co Inc
Priority date: 1951-08-07
Filing date: 1951-08-07
Publication date: 1955-10-18
Anticipated expiration: 1972-10-18

Description

Oct. 18, 1955 SPACKMAN 2,720,916

BURNER SAFETY CONTROL APPARATUS FOR AIR HEATERS Filed Aug. 7, 1951 INVENTOR.

THOMAS F. SPACKMAN ATTORNEY United States Patent 2,720,916 BURNERSAFET'Y coN'TiroL APPARATUS FOR AIR HEATERS Thomas Fred Spackman, Cincinnati, ()hio, assignor to American Air FiIticampaiiy, In'c., Louisville, K a

corporatioho'f Delaware Application August 7, 1951, Serial No. 240,747 1 Claiin. c1. 158-28) The present invention relates to a portable combustion type air heater employing kerosene or similar liquid fuel, and relates in particular to the control mechanism for operating the heater unit.

It is an object of the present invention to provide a scavenging control in an air heater employing an air supply, and ignition and combustion control circuits, whereby the ignition and combustion control circuits may be placed in operation only after a period of operation of the air supply, and on shutting down the heater, the ignition and combustion control circuits may be shut off before the air supply stops.

The invention will be explained in detail in the following description taken in connection with the accompanying drawing illustrating a preferred embodiment of the invention by way of example, and wherein:

Figure l is a perspective view of a portion of the heater;

Figure 2 is a perspective view on an enlarged scale of the motor, blower and fan assembly; and

Figure 3 is a diagrammatic view of the invention.

Referring to the drawing, the heater is carried on a chassis supported by a pair of wheels 1 at one end and provided with a foot at the other end. By raising the foot end by means of suitable handles, the heater may be wheeled to any desired location. The wheeled end of the chassis has a platform 2 upon which is mounted the electric motor 3. A blower housing 4 for combustion air is suitably mounted on the platform, and the motor shaft 5 extending through the housing carries a blower in the housing and a fan 6 for supplying air to be heated by a suitable heat exchanger (not shown). The heater casing has an opening 7 shrouding fan 6 so that the fan forces air through the opening to the heat exchanger in the casing and the heated air discharged at the front end of the casing is conducted by suitable detachable ducts to any desired location. The fuel pump 8 is driven by the motor through a drive pulley 9 and belt (Figure 3) to supply fuel to the burner through a pressure opened valve 16 (Figure 3), and the blower housing 4 has a discharge duct 11 to supply air to the burner to support combustion.

The starting switch 12 has two contacts A and B, and a movable sweep contactor 13. When this contactor is turned to position A the motor 3 is energized through lead 14 and return lead 15, and motor 3 drives pump 8. The pump incorporates a bypass with a relief valve 16 controlled by a solenoid 17 and when valve 16 is open (as when solenoid 17 is deenergized) the pump outlet pressure is not sufficient to open relief valve and fuel does not flow to the burner 18. However, when bypass valve 16 is closed upon energization of the solenoid 17, pressure is built up at the pump outlet sufficient to open relief valve 16 to allow flow of fuel to the burner. At the same time if igniter 19 is energized by transformer 21 the fuel will be ignited. It should be observed that the solenoid 17 and transformer 21 are not directly connected to switch contact A so that upon turning the switch to "ice 2 pisi't'ion Allie-flow of fuel to the burner is not started, but the motoiwill drive the fan, which scavenge enmer chamber. hen the contactor 13 is 'fiivel'l 'to position B, it retains contact at A so that meter 3 "cant-iniies energized.

A limit control switch 22 is connected between contact B and the pfirnaryeoil er transformer 23, circuit being completed by lead 2410 wire 15. The seeoifilafy er the nansfonner includes lead 25 to switch -26, lead 27 to the frela'y coil 28, load 29, resistaneehea'ter 31 and-"switch 32. When switch 12 is turned to position B, relay 28 is energized to close SW-itch centa'cts '33, thus energizing the ignition transformer 21 ii-rough lean 34. A-t the seine time energizatien or may 28 closes switch contacts 35.

The safety control for the apparatus includes the limit control thermostat switch 22, and the thermal

responsive switches

26 and 32. Switch 22 is responsive to the temperature of the heated air discharged from the front of the heater casing. Switch 32 is located in the stack where, at the beginning of operation, there will be a predetermined minimum temperature rise, for example, 50", in one minute. This switch ordinarily is closed, that is, when the stack is cold, and once the minimum temperature rise is attained, it opens and thereafter will not close except upon a shutdown sufiiciently long to cause a temperature drop of about 50. However, this switch is arranged to be closed manually when required.

Switch 26 is closed When cold and is located to be exposed to the heat from element 31. The fiow of current through the operating circuit of relay 28 causes heater 31 to heat switch 26. If switch 32 remains closed a predetermined minimum time, as for example seconds, the switch 26 is opened by the heat of element 31, thus opening the operating circuit of the relay 28 to open contacts 33 and deenergize the igniter and solenoid 17, so that fuel flow to the burner stops. However, should switch 32 be opened by the predetermined stack temperature rise, the operating circuit of relay 28 is opened, but the relay is held in position by a holding circuit at reduced voltage comprising lead 36, contacts 35, leads 29, 27, switch 26 and lead 25. The opening of switch 32 deenergizes heater 31 and switch 26 of the holding circuit remains closed. This is the normal operating condition.

However, should the burner fail to ignite, switch 32 remains closed because of the failure of the temperature to rise, and heater 31 causes switch 26 to open, thus opening the circuit of the relay 28 to open contacts 33 and deenergize the igniter at the same time that the fuel is shut off to the burner.

The switch 12, it will be observed, provides a sequence of operation involving first energization of motor 3 to operate the blower in housing 4 and fan 6, then turning on the fuel supply to the burner and energizing the igniter. By having the motor 3 operate first, the air will scavenge the combustion chamber at the start. Thereafter the burner is ignited. A stop 38 limits turning of the switch contactor so that the switch must be reversely turned to shut off the burner. Upon reverse turning, the fuel supply is first shut oir and then the motor 3 and blowers driven thereby are stopped. Normally there is suflicient manual delay in turning from position A to position B, or in reverse operation from position B to position A, but if desired, the switch may incorporate a conventional automatic delay mechanism.

I claim as my invention:

In an air heater: a fuel burner; a motor; a pump driven by said motor for supplying fuel to said burner; electrically operated means controlling flow of fuel from the pump to the burner; an igniter adjacent the burner; means driven by said motor to supply air to said burner to support combustion; an actuating electric circuit for said igniter and 3 I a said electrically operated means; means controlling said circuit including a relay coil having a main operating circuit in which are connected in series an electric heater, a normally closed temperature responsive switch subject to be opened by the heat of saidelectric heater, and a normally closed combustion responsive switch controlling current flow through said electric heater, said combustion responsive switch being located to be opened by the heat of the burner and upon failure of the burner to ignite allowing a temperature rise of said heater to open said temperature responsive switch to deenergize said relay coil; a holding circuit for said relay coil including said temperature responsive switch, whereby opening of said combustion responsive switch to deenergize the main circuit leaves the holding circuit energized; a main switch having one contact for energizing said motor, and a sec ond contact for energizing said actuating circuit; a movable sweep contactor to successively and thereafter concurrently engage said contacts when operated in one direction to first energize the motor and then energize said actuating circuit; and a stop to limit turning of the contactor, the reverse movement of said main switch acting to serially deenergize said actuating circuit and the motor.

References Cited in the file of this patent UNITED STATES PATENTS I 2,020,710 Warner Nov. 12, 1935 2,034,311 Rubel Mar. 17, 1936 2,080,580 Shaw May 18, 1937 2,188,565 Bower Jan. 30, 1940 2,427,675 Holthouse Sept. 23, 1947 2,447,373 Smoot Aug. 17, 1948 2,469,271 Logan May 3, 1949 2,575,289 Nycum et al.' Nov. 13, 1951