US2443556A - Intermittent combustion hot-air - Google Patents

Description

3 Sheets-Sheet 1 ni-zur f G. J. FAIRBANKS Jaw INTERNIT'XIEINTv COMBUSTIN-HOT :AIR HEATER "June 1.5, 1948K.y

- A:Filed Feb. 15, 1945 Q INTERMITTENT consumos HOT An HEATER Filed Feb. 15, 1945A l v s sheets-sheet 2 June15, 1948 lcs. J. r-AIRBAKS l 2,443,556

INTERMITTENT coMBUs'rIoN HOT AIREATER a heat exchanger.

Patented June 15, 1948 Gordon J. Fairbanks, Glenview, Ill., mignon' to Stewart-Warner Corporation, Chicago, lll., a corporation of Virginia Application February 15, 1945, Serial No. 577,955

Claims. 126-116) This'invention relates to internal combustion heaters and it is concerned with providing a simple, rugged, and compact structure adapted for use in various situations. l

One object of the invention is to provide a new and improved heater having an igniting device arranged for continuous operation whenever 'the heater is working and including means to render the ignition reliable at all times and especially at high altitudes when the heater is employed in aircraft.

Another object of the 'invention is to provide a new and improved heater of rela-tively simple construction and of the rapid cycling type in which a single thermostatcontrols the operation by controlling the fuel supply.

A further object of the invention is to provide a new and improved heater in which a.- single Imotor serves to operate a pump for supplying fuel Other objects and advantages of the invention i pared with Fig. 1, showing the fuel pump associated therewith;

Fig. 3 is an end elevation of the motor and pump taken as indicated at line 3 3 on Fig. 2;

Fig. 4 is a vertical sectional View taken as indicated at line 4 4 on Fig. 2;

Fig. 5 is a detail section of the pump mechanism taken substantially as indicatedl at line 5--5 of Figs. 3 and 4;

Fig. 6 is an elevation partly in section as indicated at line 6-6 on Fig. 4;

Fig. 7 is a detail section taken as indicated at line 1-1 on Fig. 5.

The drawing illustrates a type of internal combustion heater adapted to burn gasoline or similar liquid fuel mixed with air and to transfer its heat to a stream of Ventilating air by means of For simplicity of operation and also for reliability, this heater is provided with electrical igniting means whichremains in operation continuously whenever the heater is in service; and the fuel is supplied by means of al satisfactory maximum and will be placed in operation again as-soon as the temperature drops to a predetermined minimum. The lmaximum and minimum limits may be within a fairly close range, resulting in frequent operation or cycling of the heater. This result is secured by permitting the fuel pump to run-continuously but ar A ranging a thermostat to control a solenoid operated valve in the fuel line. so that when the maximum temperature is attained the fuel is held in the feed pipe and instantly available vwhen the temperature drops to the minimum limit. It is found that when a high tension spark is employed for igniting fuel under these condiltions it is not always effective instantly upon closing of the electric circuit; apparently the electrodes themselves must become heated by the spark to assist in igniting the fuel and this may require 10 or 15 seconds. Therefore, it is found y'preferable to operate the spark continuously even when the fuel valve is closed and the burner is not working; this insures instant ignition of the fuel when it is turned on again by the thermostat. It also has been found that the ordinary buzzer type of interrupter does not insure a reliable spark, especially at high altitudes, andthe present device therefore includes a cam driven make and break mechanism which will produce an effective reliable'spark under a wide range of conditions. Since the fuel pump Ais to be operated continuously and the spark mechanism is to be kept working even when the burner itself is idle, it is found convenient and desirable to operate the fuel pump and the make and break device by means of the same motor.

As shown in the drawings, the heater itself includes an outer cylindrical shell or housing i0, having an inlet i2 for Ventilating air and an outlet il through which the heated air is discharged either into a room or into suitable conduits by which it is carried to the space or spaces to be heated. Spaced within the shell ill there is mounted a smaller shell or plenum I6 having an inlet I8 for the portion of the air which is to be employed for combustion and within the plenum I8 there is secured a conical combustion chamber 20 having perforations 22 in its wall through which the combustion air is admitted. At the smaller end of the conical member 20 there is a threaded sleeve'24 in which the fuel nozzle 26 is secured. The mixture of fuel and air thus' 'provided in the combustion chamber 20 is ignited by vmeans of a. spark plug 28 having a single electrode 30 disposed within one of the holes 22 in the conical wall 20 so that the spark jumps from the electrode to the edge of the hole and is'carried into the combustion chamber in a U-shape because of the force of the air current flowing into the combustion chamber through the hole in which the electrode 30 is located. As a result,

rish, Ser. No. 490,162 led June 9, 1943, now

Patent No. 2,432,929, granted December 16, 1947, in which the products of combustion issuing from the conical chamber 20 ow into aA cylindrical space 32 which is closed by a wall ,34 at the end opposite the combustion chamber 20 but which connects laterally with a spirally formed chamber having' spaced convolutions seen at 3S and 38 in Fig. l. These convolutions are formed by the spaced spiral walls of an air space I extending longitudinally of the heater so that the Ventilating air entering at i2 iiows longitudinally through the spiral air space to the outlet l il and absorbs heat from the walls of the cylinder 32 and its connected spiral portions 36 and 38. The products of combustion leave the outermost portion of the spiral through an exhaust passage d2.

The liquid fuel is supplied to the nozzle 2c by means of a diaphragm pump M which is shown in some detail in Fig. 5. A supply pipe i6 leads to the inlet valve chamber 48 of the pump so that downward movement of the diaphragm 50 draws fuel into the pump chamber 52 above the diaphragm and upward movement of the diaphragm expels liquid through the outlet valve chamber 5d and feed pipe 56, the latter being connected to an elbow tting 58 mounted in the housing it of the heater and connected inside the housing with a pipe Sil leading to the nozzle 2c. The pump diaphragm 5d is actuated by rotary cam t2 which may be of eccentric form and which engages a rocker arm 64 pivoted at 66 in the lower half 58 of the pump casing. The diaphragm Ell is normally urged upwardly by a coil spring l@ seated on a shoulder l2 and within the casing Se, and the diaphragm is provided with a stem lf3 by which it is actuated downwardly. The stem l@ has a one Way drive connection to the rocker arm 6ft in the form of a member 16 carried on the pivot 66 and engaged by a lug 'i8 extending from the rocker arm 643. As one end of the arm 64 is moved upwardly by the cam G2 lthe opposite end carrying the lug ld swings the member 18 positively in downward direction, and the member '16, being engaged with the stem it, as shown in Fig. 7, pulls the stem 'it and diaphragm 50 downward in opposition to the spring lt. A light spring 8B tends to maintain the rocker arm 64 in contact with the cam 62, and return movement of the diaphragm in upward direction, which is its pumping stroke, is effected by the spring 10. The nozzle 2B is thus supplied with fuel at a pre-determined pressure which depends upon the strength of the spring lll. But if the feed pipe 56 is closed, preventing the discharge of fuel from the pump and blocking movement of the diaphragm 50, the rocker arm 64 will continue to be operated by the motor driven cam 62 while the arm 16 will remain stationary as long as the diaphragm is blocked at the lower limit of its range of movement. The pipe 19 is an atmosphere vent leading overboard.

The cam 62 is pinned to a shaft 82 as shown in Fig. 4 and this shaft carries a worm gear 84 meshing with a worm 86 on the shaft 88 of the electric motor 90. A source of electrical energy indicated as a battery at 92 on Fig. 1 has one d terminal grounded and has its opposite terminal connected through a switch 94 with a feed wire 96 extending to one contact member S8 of a thermostat indicated generally by the numeral ill. The thermostat is located in the air outlet i@ of the heater so as to be responsive to the temperature of the air delivered by the heater and its cooperating contact m2 is connected by a, wire |945 to a. solenoid-operated Valve M16. The feed wire 96 has a branch 96 connected to one terminal ofthe motor Q@ and the other terminal of the motor is grounded so that the motor Y circuit is completed whenever the switch 94 is closed and the motor runs continuously and independently of the thermostat. The solenoid valve GBE may be constructed so that it is normally held open as by means of a spring and closed when its solenoid is energized. Then when the burner is operating, the temperature of the air issuingfat Hl will rise to a point at which the contacts 98 and HD2 of the thermostat are engaged, energizing the solenoid to close the valve l'' and cutting o the fuel supply to the burner nozzle 26. Then when the air issuing at l has cooled sufficiently to separate the contacts et and ic, the circuit through solenoid m6 will be opened, permitting the valve to open and feed fuel to the burner nozzle 26. Since the motor continues to operate the cam 62 and the rocker arm dd, and the feed pipe 56 is kept filled with fuel even while the valve lll is closed, the opening of the valve causes the burner to. resume operation instantly.

As already mentioned, the reliable operation of the heater, particularly in high altitudes, requires a fat and long spark at the electrode 3d and to insure a spark of this quality it is preferable to employ a mechanically actuated make and break mechanism, As shown in Figs. 1 and 6, this consists of a lever l pivoted at il@ in a casing H2 which encloses also a cam llt carried on the end of the shaft 82. A follower tl on the lever H18 engages the cam iid and a contact element H8 at the opposite end of the lever cooperates with a xed Contact i2@ carried by a conductor arm l2? from which a lead wire ld extends to one terminal l26 of the primary winding of the spark coil denoted generally at E28; the other terminal E27 is connected by a Wire iig to the battery or other current source at 92. A spring 36 maintains engagement of the follower M6 with the cam iid so that as the shaft -82 rotates the contacts H3 and tic are alternately engaged and separated, producing, the desired surges of current in the secondary winding of the spark coil t28. One terminal |32 of the secondary winding is grounded and the other terminal is connected by a wire |35 to the electrode 30 of the spark plug 28. Whenever the switch 91! is closed it serves not only to energize the motor 90 and start the fuel pump 44 in operation, but it also closes the circuit through the primary winding of the spark coil 128 except as it may be opened by the make and break lever 108, and since the operation of the motor 90 causes continuous rotation of the cam Il! the lever |08 is actuated to close the primary circuit of the spark coil at frequent intervals, producing an effective and reliable spark at the electrode 3U. If the solenoid valve |06 is open the fuel will ow to the burner nozzle 26 and be ignited, raising the temperature of the Ventilating air owing through the heater until it is sufficient to actuate the thermostat 10B and close the fuel valve IUS. This may assauts occur at ten or fifteen second intervals under some conditions or at much longer intervals where only a moderate supply of heat is re-A quired. Preferably as shown in the drawings a condenser |49 is connected across the contacts Ill and to suppress arcing and increase the heat of the spark at the spark plug 28. But for all conditions this arrangement provides a relatively simple mechanism which is comparatively inexpensive to manufacture and which should require a minimum of servicing to keep it in operative condition.

While there is shown and described herein certain structure illustrating the invention, it is to be understood that the invention is not limited thereto or thereby but may assume numerous other forms and includes all modifications, variations and equivalents coming within the scope of the following claims.

I claim:

l. In combination with a liquid fuel burner, a pump connected to supply fuel thereto, spring means actuating the pump in its pumping stroke. a cam for actuating the pump in its return stroke; igniting means for the burner including a spark coil and a make and break device, a cam for actuating said make and break device, a shaft Journalled for rotation with both cams secured to said shaft, a continuously operating motor and speed reducing gearing connecting said motor to drive said shaft, means including a heat exchanger for directing a flow of ventilating air in heat exchange relation to hot gases from said burner, a fuel valve interposed between said pump and the burner, and 'temperature responsive means subject to the temperature of the air discharged from the heat exchanger and operative to control the opening and closing of said valve.

2. In combination.. with a liquid fuel burner, a pump connected to supply fuel thereto and in- .cluding a reciprocating member, spring means to actuate said member in its pumping stroke and a cam to actuate said member in its return stroke,

igniting means including a spark coil and a cam actuated make and break device therefor, a continuously operating v motor connected to drive the pump actuating cam and the cam of the make and break device, means including a heat exchanger for directing a flow of Ventilating air Y in heat exchange relation to hot gases from said burner, a solenoid valve interposed in the connection between the pump and the burner, a source oi' electrical energy and connections therefrom to the motor, the igniting means land the solenoid valve, and a thermostatic switch device actuating said valve independently of the motor and igniting means and responsive to changes in the temperature of the air discharged from the heat exchanger.

3. In combination with a liquid fuel burner, means including a pump connected to supply liquidfuel theretospring means arranged to actuate the pump in its pumping stroke, a cam arranged vto actuate the pump in its return stroke, a continuously operating motor connected to drive said cam, a fuel valve interposed in the connection between the pump and the burner,

" the heat exchanger and operative to close said fuel valve at afpredetermined temperature and to reopen said valve at a predetermined lower temperature, thereby causing the burner to operate intermittently.

4. In lcombination with a liquid fuel burner, means including a pump connected to supply liquid fuel thereto, driving means to actuate the pump including yielding means operative to cause the pumping stroke and a continuously actuated cam which effects the'return stroke, a fuel valve interposed in the connection between tlie pump and the-burner and adapted when closed to block the flow of liquid fuel from the pump to the burner while the cam continues to be actuated, continuously operative igniting means for the burner, means including a heat exchanger 4for directing a flow of Ventilating air in heat, exchange relation to hot gases from said burner, and means responsive to the temperature of the air discharged from the heat exchanger and operative to close said fuel valve at a predeterminedtemperature and to reopen said valve at a predetermined lower temperature. thereby causing the burner to operate intermittently.

5. In combination with a liquid fuel burner, means including a pump connected to supply liquid fuel thereto .and including a reciprocating member, driving means to actuate the pump comprising spring means operative to move said reciprocating member in pumping direction. a continuously-running motor with a one way drive device actuated thereby and operative to move said reciprocating member in the opposite direction and to stress said spring means, an igniter for the burner and means operated by said motor for energizing said igniter continuously, a fuel valve interposed in the connection between the pump and the burner and adapted when closed to block the flow of liquid fuel from the pump to the burner while said motor continues to actuate the one way drive de'vice, means including a heat exchanger for directing a flow ot ventilating air in heat exchange relation to hot gases from said burner, and means responsive to the temperature of the air discharged from said heat exchanger and operative to close said fuel valve at a predetermined temperature and to reopen said valve at a predetermined lower temperature, the continuous operation of said motor serving to condition the pump and igniter to insure prompt resumption of operation of the burner whenever said fuel valve is opened.

GORDON J FAIRBANKS.

narralunsciis crrsn The following references are of record in the ille of this patent:

Number Name l Date Re. 21,515 Karsei -l. July 23, 1940 1,283,654 Doble -s April 28, 1918 1,733,792 Good Oct, 29, 1929 1,931,083 Rodier Oct. 17. 1933 I1,957,689 Rockwell May 8, 1934 2,137,581 Mylar Nov. 22. 1938 2,148,397 Kommer Feb.l7, 1939 2,308,888 McCollum Jan. 19, 1943 2,330,298 McCollum Sept. 28, 1943 2,396,655 Heymann Mar. 19. 1946

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