US2876832A - Burner safety pilot apparatus - Google Patents

Description

Nial'thrlo,v A lw PETERS t y BURNER SAFETY PILOT APPARATUS c0\ INVENTQR.

BY AlA/Peers' dir ,I

A. W. PETERS BURNER SAFETY PILOT APPARATUS March-1o, 1959 vs sheets-sheet 2 mea- Jari. l11. i955 III OJ Mw Wd P m W. A M

March 10, 1959 A. wi PETERS BURNER SAFETY PILOT APPARATUS Filed Jan. l1. 1955 3 Sheets-Sheet v3 j w, .W1 -wf\ /wm .w QN uw wv QN Ammw. Nrw ABM- WW m uw uw H 4Arthur' W. Peters, Toledo,

:for the front end 2,876,832 BURNER SAFETY PrLoT APPARATUS Ohio, assignor to Surface Comhustion Corporation, Toledo, Ohio, a corporation of "Ohi Application January 11, 1955, Serial No.481,127 4 Claims. (Cl. 15S- 115) The present invention relates to va safety pilot for a heatingpunit comprising va burner which formsa closure of a cylindrical combustion chamber wherein a whirling stream of air is utilized for supporting combustion of the fuel issuing from the burner. The primary object of the invention is to provide a safety pilot which shall embody improvements in means for producing a pilot flame which may not vbe readily extinguished and which shall embody an improved thermal Velement for shutting ofi the main fuel valve of the heat ing unit in case the pilot ame becomes extinguished. Other related objects will more fully appear hereinafter. Fora consideration of what l believe to benovel and my invention, attention is directed to the following portion of the specification 'and the drawings and claims appended thereto. i

`In the accompanying drawings forming part of this specication,

Fig. l shows apparatus embodying the present inven tion. v

'Fig 2-is a fragmentary end elevation with a portion in section of the left 'hand portion of the apparatus shown in Fig. l.

Fig. 3 is a section al view shown in Fig. 1.

Fig. 4 is a section on line 4 4 of Fig. v3.

Fig. 5 is a partial section on line 5*5 of Fig. 3.

Fig. 6 is a sectional view of a portion of the apparatus as shown in Fig. 3 with modified piping for fuel supply.

Figure 7 is a wiring diagram for the apparatus.

In Fig. l, the front portion of a cylinder lwhchrequires to be internally heated is indicated at 10, this cylinder defining the combustion chamber of va heater wherein fiuid medium required to be heated is confined about the outer side of said cylinderby a surrounding jacket 11.

.A burner for internally heating the cylinder l is generally indicated at 12, the burner having a peripheral flange 13 by which it is detachably secured to a complemental fiange 14 on the heater. The burner cornprises a front wall l which forms a closure for the front end of the combustion cylinder except for a central circular opening 16 which constitutes an inlet for combustion supporting air froma circular chamber 17 whose back wall is indicated at 20 and whose circumferential side wall is indicated at 21. The chamber 17 has a `tangential air inlet 22 so that a stream of air entering with :relatively high velocity will .whirl in said chamber and thus issue from the central opening 16 of said chamber with a whirling motion. Air under pressure is con` ducted to the tangential inlet 22 by a supply pipe litt leading from a motor driven blower not shown. The burner also comprises a central fuel discharge nozzle 23 which extends through the airchamber 17 coaxial with the central opening lo thereof. The fuel discharge noz- 21e 23 extends from a hollow head 24 .to which vgas .is delivered by a supplypipe 25 having a normally closed motor operated shut-off valve 2'6. lThelfuel.issuesfrom of a portion of the apparatus v axial with the combustion chamber 36 at 'the nozzle 23 with `relatively low velocity and because the air from the opening 16 enters the combustion cylinder with a whirling motion the fuel rapidly intermixes with the air, hence the flame of combustion will also tend to whirl in 'said cylinder as will now be readily The fuel thus delivered to the combustion 'cylinder 10 understood. l

The fuel thus delivered to vthecombu'stion cylinder 10 is ignited by a ilame issuingfrom a pilot combustion tube `V27, the tube extending within the burner nozzle 23 to a point where the iiam'e issuing from the tube kwill serve to ignite the combustible mixture outside of said'no'zzle. Because the pilot flame issues from said tube 27 with =`substantial velocity, the discharge end of said tube 27 may, terminate in relatively close proximity to the discharge end of the burner nozzle 23. The pilot ame thus issuing from the outlet end of the pilot combustion tube 27 is produced by a pilot burner head 28 mounted on the front, or inlet end of, said tube, to the end that the said tube may be internally heated for a reason presently appearing. The pilot combustion tube 27 is supported by a tubular support 34 through-'which it extends coaxial with the burner nozzle 23 from beyond the end Wall 35 of the hollow head 2d from which said nozzle 23 extends, said tubular support 34 being mounted on and extending from said wall 3S, The tubular'support 34 and the pilot combustion tube 27 are rigidly interconnected at a point remote from said end wall by :a weld 33, the tube being otherwise freeto thermally expand and contract relative to said support for a reason presently appearing.

The pilot burner-apparatus comprises wall means ttl and 41 forming a cylindrical combustion chamber v36 in the pilot-burner head 2S. The end wall 41 is mounted on theinlet end of the pilot combustion tube 27. A stream of air under pressure is supplied tangentiall'y to the Walls d@ of the combustion chamber through 'anim let 42 to which air under pressure'is delivered by a tangential supply pipe 43 so that the air thus entering said chamber 36 tends to Whirl therein. ln the burner head 2S nozzle means `for deliveringl fuel gas to the cornbustion chamber 36 forms a passage vor chamber' 44 c'oa gas discharge port in wall 40 thereof through which port gas vis normally delivered into the axis of the combustion chamber 36. The passage or chamber 44 is amply large -to accommodate the electrodes of spark plug means 5d mounted on the pilot burner structure and adapted to produce an ignition spark in the gas chamber or passage 44. The outer end of the passage 44 is 'closed by a sight glass 45. A supply pipe d6 having its own shutoff valve 53, shown in Fig. l, forms gas conduit means kfor delivering fuel gas to the gas chamber it through a fitting having a gas metering orifice 47. The gas thus admitted to the gas inlet passage 44 requires to be admixed with air to be ignita'ble by the spark plug 5t). Airis delivered by air conduit means comprising. air supply pipe 51 through an air metering oriice 52 in said fitting, this is preferably a relatively small modicum or stream of air compared to the stream of gas fed through orifice 47 to the chamber "i4 and is normally insufficient to form an ignitable mixture therein when the valve 53 is vfully opened. To obtain such an ignitable mixture, the gas valve 53 is turned closed or shut of and air is allowed to pass through the fitting and the chamber d4 to purge gas therefrom,l Thus lthe lair required to be admixed with the gas in the gas inlet passage or chamber 44 before the gas can be ignited by the spark plug 5t) is air already present in the passage and in the connecting combustion chamber 36 at the time the shut-ott vaive 53 in the gas pipe t6-is opened,l the air being present 'because the firstv step in starting the heating apparatus lis ,to lstart the combustion lair blower which delivers air to the plug may thereafter main air supply duct 18 and therefore also to the branchair pipes 43 and 51, at which time the gas valve 53 in the gas conduit 46 upstream of the fitting where the air conduit 5l joins said gas conduit is closed wherebyv the air may flush gas lfrom the chamber 44 as before described. The first surge of gas into the gas inlet passage or chamber 44 upon opening the gas valve 53 provides an air-gas mixture in the gas chamber 44 for initially igniting the pilot burner, said mixture being readily ignited by the spark plug 50. Once ignited, the gas remains ignited in the pilot combustion chamber 36 and therefore the spark be de-energized. By thus locating the electrodes of the spark plug in an ignition chamber 44 separate from the combustion chamber 36 proper and in a passage which during normal operation of the pilot burner is purged with an unignitable gas, the electrodes do not become overheated and they do not tend to retard the whirling of the air in the pilot combusion chamber 36.

In an alternate arrangement, the pilot burner, shown separately in Fig. 6, is supplied vwith combustion air through the inlet 42 and with fuel gas through supply pipe 46 and the chamber 44. This differs from the arrangement in Fig. 3 only in that air is not supplied to the fuel gas inlet to the chamber 44. In this case, air from the tangential inlet 42 is relied on to purge the chamber 44 before the fuel gas is turned on, and in other respects the operation is as described for Fig. 3.

In operation ofthe pilot burner l.ithas lbeen observed that initial ignition takes place'without fail when the fuel gas initially mixes with residual air'in the cham- Y safety pilot ber 44,'then the ame front movesv away from'the spark plug, through the combustion chamber 36, and by proper adjustment of fuel gas and combustion air streams, the llame ignition front may be made to move .into the pilot combustion tube 27. Thus the electrodes of the spark plug are surrounded by a cold fuel gas atmosphere, and when the flame from the pilot burner has caused sufficient expansion in the tube 27 to actuate the switch 30, the spark plug will be de-energized. The satisfactory operating life for these spark plugs has been found to be 'beyond reasonable measure, and this is a distinct improvement in an art where fouling and electrode deterioration are commonplace. Switch 30 is a Vcommercially available limit switch having a set of normally open contacts SP1 and a set of normally closed contacts .SP-2. When tube 27 is cold, the switch 30 is depressed by adjustable actuator 32 carried on projection 19 of the burner generally indicated at 12, andv contacts SPfl are closed while the contacts SP-2 are open. Upon expansion of tube 27 due to heat from the pilot burner, the switch 30 moves away from the actuator 32, and contacts SP-1 and SP-2 revert to their normal positions.

The control system for the burner safety pilot apparatus is shown in detail in Figure 7, as applied to a liquid heater wherein liquid to be heated is circulated to the space between walls 10 and 11 of Figure l by a liquid pump not shown.

A liquid pressure switch with a normally open contact PS is placed atA the pump outlet.- A temperature limit switch having a contact TLS and a temperature control switch TS are placed in the liquid circuit to avoid overheating the liquid, and to normally control the heater. Control switch 30 contains two safety pilot switch contacts SP-l and SP-2 in a single pole, double throw fast operating switch so that they cannot both be closed at the same time.

When the liquid pump is started, pressure on the pres sure switch closes contact PS. Then the burner starting switch SW is closed. If the liquid is cold, i. e., 'below the high limit control temperature for TLS and also 4 is below operating temperature, switch contact'SPl of switch 30 will be closed and Vswitch contact SP-Z will be open. A spark relay coil SR will thus be energized and its contacts SR-l and SR-2 will close.

Closing of SR-l energizes a control relay coil CR, thus closing its contacts CR-l and CR-2.

The closing of CR-l locks the control relay CR closed, and the closing of CR-2 starts the air fan motor FM for supplying combustion air to the pipe 18. When the fan motor FM is nearlyup to speed, an air pressure switch AS closes, energizing the coil SVP of the pilot gas valve 53, and energizing the spark plug 50 through a spark transformer ST.

As the gas is ignited and burned in the pilot burner, the tube 27 expands and actuates the switch 30 to its hot position, opening contact SP-l to de-energize the spark relay coil SR and energize the main burner valve coil SVB. This opens the main gas burner valve 26 and the main burner starts to burn at full rate. Y

When the liquid is suciently heated to satisfy the temperature control switch, TLS opens, which in turn opens CR to close both gas valves 53 and 26. No short interruption of electric service will allow valves 53 and 26 to re-open because the holding circuit CR-l is broken and SP-l is held open until the pilot tube 27 contracts by cooling suicient to actuate switch 30.

As will beappreciated by persons versed in the art, this control system can be altered slightly to provide a constant burning pilot by lmoving the temperature control switch TS from its position as shown in Figure 7 to-the circuit conduit connecting the main burner valve solenoid SVB, so that upon satisfaction of the ternperature control system, the circuit to the relays SR and CR would not be broken; similarly, if a throttling control system is desired, then a suitable throttling control valve is placed in the main gas line 25 of Figure l, and contact TS is eliminated from Figure 7. A bulb controlled valve, with the temperature responsive bulb placed in the heated liquid circuit, is commonly used for this type of control system.

From the foregoing description it is believed to be apparent that the present invention provides a safety pilot which is well adapted for its intended purpose.

This application is a continuation-in-part of my ap plication Serial No. 78,025, filed Feb. 17, 1949, now abandoned.

I claim:

l. Burner apparatus comprising, in combination, vwall means forming a cylindrical combustion chamber and an inlet thereto for supplying a stream of combustion supporting air to said chamber and causing said air to whirl in said chamber, a cylindrical gas nozzle extending into said chamber along the axis thereof, a relatively long pilot combustion tube having an inlet end and an outlet end, said outlet end being disposed within said gas nozzle and adapted to discharge a ame through said gas nozzle for ignition of fuel gas issuing therefrom, a pilot burner head mounted on the inlet end of said tube for supplying below the normal control temperature for TS, then the circuit is closed to the coil SR of a spark frelay. If the flame to the tube for heating the latter and causing thermal expansion thereof and for producing a flame at the outlet end of said tube, an elongate support for supporting said tube at a lpoint remote from said head, a fuel gas valve for controlling flow of fuel gas to said gas nozzle, and a control switch adapted to control said valve responsive to relative movement of said tube and said support.

2. In a safety control apparatus for a combustion unit having structure defining a combustion chamber, the

combination which comprises a fuel supply valve, a 'Y conduit for delivering fuel from the outlet of said valve to said chamber, a pilot combustion tube having an inlet end and an outlet end, a pilot burner head mounted on. the inlet end of said tube for supplying flame tothe tube for internally heating the latter and causing thermal expansion thereof and for producing a pilotV dame at the outlet end of said tube, said pilot burner head comprising a structure defining a cylindrical pilot combustion chamber having in its side a tangential inlet for air under pressure so that the entering air tends to whirl therein and having at one end an axial fuel gas inlet in gas receiving connection with a source of gas supply so that the whirling body of air initially tends to en velop the entering stream of fuel, a spark plug mounted on said pilot burner head for initially igniting the fuel gas entering said pilot combustion chamber from said fuel gas inlet, said spark plug having a spark gap disposed in said fuel gas inlet, a support for supporting said tube with the inlet end of the tube in sufiiciently close proximity to the point of entry of the fuel to said chamber to permit said pilot ame to ignite said fuel, said pilot combustion tube at a point remote from its inlet end being fixedly secured to said support so that between said point and its inlet end said tube may be free to thermally expand and contract relative to said support, and means responsive to said thermal expansion of said tube for closing said valve when said tube is relatively cold and for opening said valve when said tube is relatively hot.

3. In a safety control apparatus for a combustion unit having structure defining a combustion chamber, the combination which comprises: a fuel supply valve; a conduit for delivering fuel from the outlet of said valve to said chamber; a pilot combustion tube having an inlet end and an outlet end; a pilot burner head mounted on the inlet end of said tube for supplying flame to the tube for internally heating the latter and causing thermal expansion thereof and for producing a pilot iiame at the outlet end of said tube, said pilot burner head comprising a structure defining a cylindrical pilot combustion chamber having in its side a tangential inlet for air under pressure so that the entering air tends to whirl therein and having at one end an axial fuel gas inlet in gas receiving connection with a source of gas supply so that the whirling body of air initially tends to envelop the entering stream of fuel; a spark plug mounted on said pilot burner head for initially igniting the fuel gas entering said pilot combustion chamber from said fuel gas inlet, said spark plug having a spark gap disposed in said fuel gas inlet; a support for supporting said tube with the inlet end of the tube in sutiiciently close proximity to the point of entry of the fuel to said chamber to permit said pilot flame to ignite said fuel, said pilot combustion tube at a point remote from its inlet end being fixedly secured to said support so that between said point and its inlet, end said tube may be free to thermally expand and contract relative to said support; and means responsive to said thermal expansion of said tube for activating said spark plug when said tube is relatively cold and for de-activating said spark plug when said tube is relatively hot.

4. Burner apparatus comprising, in combination: wall means forming a cylindrical combustion chamber and an inlet thereto for supplying a stream of combustion supporting air to said chamber and causing said air to whirl in said chamber; a cylindrical gas nozzle extending into said chamber along the axis thereof; a relatively long pilot combustion tube having an inlet end and an outlet end, said outlet end being disposed within said gas nozzle and adapted to discharge a flame through said gas nozzle for iginition of fuel gas issuing therefrom; a pilot burner head mounted on the inlet end of said tube for supplying tiame to the tube for heating the latter and causing thermal expansion thereof and for producing flame at the outlet end of said tube; an elongate support for supporting said tube at a point remote from said head; a fuel gas valve for controlling flow of fuel gas to said gas nozzle; a spark plug in said pilot burner head; and a control switch adapted to activate said spari:-

plug responsive to relative said support.

movement of said tube and References Cited in the le of this patent UNITED STATES PATENTS

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