CA1169350A - Pulse combustion apparatus - Google Patents

Abstract

ROGERS, BERESKIN & PARR C A N A D A

Title: PULSE COMBUSTION APPARATUS

Inventor: JOHN A. KITCHEN

ABSTRACT OF THE DISCLOSURE
The disclosure relates to pulse combustion appara-tus generally and to air furnaces of the pulse combustion type. The invention provides a control system for the pulse combustion apparatus in which the air velocity in a combus-tion air intake is sensed and used for controlling the apparatus. The system responds to a first air intake velocity as indicating satisfactory operation of a starting blower and activates the gas supply and ignition means, and to a second air intake velocity as indicating establishment of combustion; the circuit will then de-activate the ignition means and blower. The system also includes a timer which will shut off the gas supply if the second velocity is not achieved after a predetermined time interval from initiation of a starting attempt.

Description

-~ 1 1 6935~) This invention relates to pulse combustion apparatus generally, and to air heaters of the pulse co~bustion type; for convenience, such heaters will hereinafter be referred to as pulse combustion air fur-naces.
United States patent literature contains n~mer-ous examples of prior art pulse combustion apparatus.
Typically, such an apparatus includes a combustion cha~ber and an exhaust pipe which forms a resonant system with t:~e combustion chamber. The apparatus operates on a cycle in which a fuel charge is a~mitted to the combustion cham~er and ignited. The charge then expands into the e~:haust pipe causing a partial vacuum transient in the co~bustio~
c:.al~ber, which both assists in dra~ing in a ~res:~ ~uel c:^a~-ae and causes hlgh temperature gas to be drawn b~ck into tine comDustion cham,ber irom the exhaust pipe. The fresh Lue~
cha~ge is ignl.ed spontaneously from flame fronts in t~e -etarning high temperature gas, thereby establishing the next cycle. Accordin~ly, the apparatus is sel~-sustaining after initial ignition. In a pulse combustion heater, a .:
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fluid to be heated is brought into heat exc:lance relation-ship with the exhaust pipe.
By way of e~ample, pulse combus,ion heaters are disclosed in my United States Patents Nos. 3,267,985, 4,241,720 and 4,421,723. The various for~s of apparatus disclosed are intended primaril~ ~but not ex-clusively) for use as boilers, i.e. for heating water.
Ho~ever, it has been proposed to use this t!~e of a?para-tus s~eci'ically for heating air. E~amples of this ,~pe of appara.us are shown in my United States ratent No.

2,916,032 and in ~nited States Patents Nos. 2r70S,926 (~uber et âl.) and 4,164,210 (Hollowell). I~ ~ollo~;e~l, ; hot sases from a tubular comb~stion chamber are deli~ered through a tail pipe into an e~haust ~ecoupli~g or e~_ansion chamber which absorbs the pulsating pressure ~aves prQduced by the repeated explosions in the combustiQn chamber. The exhaust gases then flow under steady conditions thrQush a ;~ s~c~n~ary heat exchanger. l,ir to be hea~ed is c~used to ~` 20 flow over the exteriQr surfaces of the ]-~a. exchanger and combustiQn chamber.
A general object of the present invention is to ; provide improvements in pulse combustion apparatus; a more ; specific object is to provide a pulse combustion apparatus havin~ a control system.
According to the invention thc apparatus include~
a combustion chamber having a fuel chargc inlet and an cxhaust gas outlet. An exhaust system communicat~s with the ou~lot and forms a resonant system with the combustion chamber.

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The apparatus also includes means associated with the combustion chamber inlet for admitting successive fuel .
charges to said chamber, including inlet means for combus-tion air communicating with said combustion chamber inlet .
and including an air intake, blower means downstream of said intake and operable to deliver combustion air under pressure to said combustion chamber for starting, ignition means coupled to said combustion chamber and operable to initiate combustion in the chamber~ gas supply means coupled to said combustion chamber inlet, and valve means adapted to control delivery of air/gas charges to said combustion chamber in accordance with the combustion cycle of the apparatus. The apparatus also includes a control system including startcr means operable to activate said blower means when the appara- .
tus is to be started. First switch means is provided and is responsive to a first predetermined air velocity in said air intake representing satisfactory operation of said blower .
means, said first switch means being coupled to and adapted to activate said gas supply means and said ignition means when said first predetermined velocity is achieved. Second switch means is also provided and is rcsponsive to a second :
predetermined air intake velocity represel-ting establishment of combustion in said combustion chamber and is adapted t.o de-activate the ignition means and blower means while main- :~:
taining the gas supply when the second predetermined air intake velocity is achieved. The contro~ system also i.nc~.udes : timer means coupled to the starter means, gas supply means and second switch means and adapted to sl~ut off the qas sup~ :
means if the second switch m~ans has not becn operated a~tcl^ ¦
a predetermined time interval from intial. opcration of ~.he . :: .

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~ ~9350 starter means.
In order that the invention ma~r be more cl~arly understood, reference will now be made to the accom~anying dra~7ings which illustrate a preferred cmbodiment of th~
invention by way of exa~ple, and in ~7hich:
Fig. 1 is a vertical sectior.al view through an air furnace ~ccording to the invention;
Fig. 2 is a plan view corres;~onding to Fi~. l;
Fig. 3 is a perspective viet~, partly broken a-~;ay and partly exploded, ofa chest ~hic's~ Lorms part of tne apparatus of Fig. l;
Fig. 4 is a detail sectional ~;ie~i on line I~7-IV of Fig. l;
Fig. 5 is a ver,ical sectional view on line V-V
of Fig. 3, showing the chest as installed;
Flg. 6 is a detail view of part of Fig. l;
Fig. 7 is an exploded perspective vie~ of part o- Fig. 6;
Fig. 8 is a detail vie~ of a fur,her feat~re OL
t:~e apparatus;
Fig. 9 is a schematic circ~t dia~3ram of a control s.em for the lurnace;
Fig. 10 is a circuit diagram of an alternate :
form of control system; and, Figs. 11 and 12 are detail sectiollal views illustrating further aspects of the invention.
Referring first to Flg. 1, the furnac~e 2S
t~hole is generally designated 20~and i.cludes a pulce oom-bustion apparatus indicated at 2~. A com~ustion chathcr ol the apparatus is indicated at 24 and is sho~n supportcd ~ ~ .

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by a chest 26 in the ~orm of a concrete c2sting. A sheet metal c2sins 28 t~hich is ~~ recta..~-.lar s`nGpe in cross-section ~nd which has open up?er and lc-.~er en~s surrounds combustion c~.amber 24 and àefines a ~e-tical ~assacetiay 30 through which air to be heate~ can flo~; a-ound chamber 24 generally in the direction of the arrows. Also ais~osed within air passaget~a~ 30 is an exhâust sys e~ 32 of the apparatus. The system includes a prir,ary exha~st pipe or jet pipe 34, a manilold 36 and a pl~rality of heat exchange pipes 33. The pi?es 38 are coupled to the ~aniSold 36 at their inner ends and to chest 26 at 'h2ir outer ends as will be more specifically described lâ,~r.
In this particular e~'oodi~ent, the furnac~ also includes a conventional squirrel-cage ty~e blo~er i~d-cated at 40 driven from an electric ~otor ~2 by a ~elt a4. The blower includes a casing 46 having an inlet 48 whicr s at the front as seen in Fig. l, the vanes O,c the blower rave not been shown since the blower itself forms no part CI
the present invention. For present purposes, it is a~'L~

ficient to note that the blower drat~7s in air in the axial direction through openirg 48 and deliv~rs it ,~.-~entially in the upward direc io~ indica.ec by the ar-o~s in Fig. 1. Casing 46 has a Qi-~7ergent outlet s_ctior. _3 w:rlich matches with the lower end of ',he cas~ng 28 r_^e-red to abo~7e. Thus, the air passa,e;.ay 30 defin-d by C_a'' n5 ,~ 28 in effect forms a plenum ch_mber recei-vinc, forcec air from blot~er 40.
An angle-iron framewo~k 52 is p~-ovic.ea arounc, blower 46 and forms a support ~o~ the puls2 co~busti3n appara-tus and casing 28. Thus, the -ramework cefi!:es a re_t_ncu-lar recess 54 t;hich opens up~a~-dly and -~7`aic:r. receive_ s;^est ~ 1 6~3~

26 and casing 28 so that the pulse combusticn a?paratus i'self "sits" on fram-work 52. Although the appara~us will be quite stable if it is not pysically connected to frarle-work 52, suitable retaining means such as scr~ws (not shown) may be provided between the framework and casing 28 and/or c;~est 26. An outer casing or shell is indicated in outline 56 but has not been shown in detail since it is not sig-nificant to the invention, With shell 56 in place, the - furnace as a whole will have an overall a?pearance resembling that of a conventional burner-type air furnace and will form a self-contained unit which san be coupled to ductwork as in a conventional forced air heating system.
Rererring now to Fig. l in so~e~,at more de-tail, the combustion chamber 24 of the pulse combustion a??aratus defines an internal conbustion cavity 58 t~hich is generally of flattened spherical shape (see the ~otted line indicated at 58 in Fig. 2). Cavity 58 extends about a median plane which is indicated as P in Fig. 2 and in w'-lich ~he section of Fig. l is taken. T:~e ca~-ity is circular in plane P and curves inwardly from both sides -~ o" the plane around its entire periphery tow_rds sor.e-~-a. flattened ends 60 and 62 (see Fig. 2). ~ s?ar};
?lug 64 is received in a screw-t.lrea~ed open-'ng dis-pcsed at end 60 of cavity 58. .'~ hig`n-ter.sion electrical 2~ lead (not shown) is connec,ed to the spark p ug and ~he -~
?lug is used to initia.e co~bustion in cha~er 2~ as will be described later.

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~ ~ ~9350 Once initiated, combustion is self-sustainins and sFark pluy 64 is not used.
Combustion chamber 24 h~s an inlet 66 (Fic.
1) through successive fuel charges enter cavity 58, and an exhaust gas outlet 68. Inlet 66 and outlet 68 are ~th disposed in median plane P. Inlet 66 e~;tends raaially of cavity 58 and aenerally horizontally, while outle_ 68 is tangential with respect to the cavity and extends dcwr.-wardly. The outlet is in fact inclined slightly to .he vertical so that the primary exhaust pipe 34 can be dis-posed in an inclined position as shown in which it ia well clear of chest 26 for good cooling by the air lo-~ing through passageway 30 but at the same ti~e is positi~rec to allow a relatively compact overall eY.ha~st ss~ste~
arrangement.
The shape of combustion cham~er cavity 58 ~rd ;~ its disposition in what might be termed "edge on" rela~
; tionsh'ip to chest 26 are selected so t-nat t',~e combus'ion chamber is also well exposed to the air flowing in passageway 30 for good heat transfer to ',he air and cooling or its associated valves (see la,er).
In this particular embodimen'_, ,he com~ust-'on c:~amber is made of two iron castings d-~noted respect-vel~
~`~ 70 and 72 in Fig. l. Casting 70, whic:n misht be re'^rre~
to as the main casting,is formed internally with cav'ty 58 and externally with a plurality of heat-radiatins firs 74 which encircle the casting and whic'n are disposed generally parallel to the direction of air flow in p_s,2 e-. ~ . :

I 1~9~5~) , g way 30. Casting 72 defines an internal passage~-ay 76 through which fuel charges flow to the combustion c:-a~ber inlet 66. The two castings are secured together by four equi-angularly spaced soc~e'-headed bolts, two of which are visible at 78 in Fig. 1. The bolts extend outw~rdl~- through plain openings in a flange 80 of casting 72 (which n effect forms another heat radiating Lin on the combustion cha~ber~
and each bolt is received in a screw-~hreaded opening in casting 70. A thln alumirum Dlate 82 is trapped between the two castings with the interposition of asbestos gaskets (not shown) and forms a heat sink to inhibit heat t-ansrer from casting 70 to casting 72. Tne co~bustion cham~er is se-cured to chest 26 by four further bolts (not shot~n) which are disposed between the bolts 78 and which extend inwardly through 1~ tne outer wall of chest 26 and which receives nu_s -nside the chest. Casing 28 is traped between the co.~bustion cham~er and chest 26.
Associated with the co~bustion chamber inlet 66 are ~eans generally indica~ed at 84 for admitting s~cces-sive luel charges to the chamber. Tnese means includepressure-res~onsive valves ~.hich open to admit air ~nd gas to the combustion chamber during each vacuum transie~t in cavity 58, and which close in response to increasin pres-sure in the chamber curing each explosion therein. De-2~ tails OL the valve construction will be provided later withparticular reference to ~ig. 6 and 7 of the drat~-irss. In the meantime, the exhaust svstem 32 will now be described in more detail primarily witn reference to Figs. 1, 2 and 4.
The primary eihaust pipe 34 cor,prises a le~gth 1 1 6~ 3 , ~ -- 10 --of straign~ cast iron ?ipe 86 having integrally formed on its external surface, a plurality OI ~ adially projecting i~s 88 which are spaced equi-angularly about pi?e 86 In this par-ticular embodiment, twelve such fins are employed and again serve to assist heat transfer to the air flowing through passageway 30 The upper end portion of pipe 86 is internally screw-threaded and receives an externally screw-threaded nipple 90 which is also engaged with cor-responding internal screw threads in the exhaust outlet 68 from casting 70 At its lower end, two lugs or ears project radially from pipe 86 for the purpose of connecting the pipe to manifold 36 as best illustra.ed in Fig 4 In that view, the two lugs on pipe 86 are indicated at 92 ; and 94 With continued reference to that view, it will !' 15 be seen that manifold 36 is of eloncate form and has a central inlet 96 to which the primary exhaust pipe 32 is coupled, and a plurality of outlets 98 which are spaced along the manifold and which communicate with inlet 96 by way o~ an internal passageway 100 Inlet 96 is cefined - 20 by an annular formation on the manifold, which has a ~air of laterally projecting ears or luss 102 and 104 at its u?per end which match .he lugs 92 and 94 on Lhe prirary exhaust pipe The exhaust pipe and manifold are secured together by bolts passing through openings in lugs 92 and 94 and received in screw-.hreaded openincs in lugs 102 and 104 ~ anifold 36 is an iron casting As r,anu-factured, internal passageway 100 is open at both ends and the end portions of .he passageway are internally screw-threaded for receiving .:

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~ 3 6935~) sealing plugs 101; alternatively, the ~lugs ~zy be welded in place. P2ssaseway 100 is of slightly smaller d-'ame.er ad-jacent the plugs than i~ the vicinity of inlet 6 and ~apers outwardly from the inlet. This is done in orcer to provice a more constant velocity along the ~anifold and less tur-bulence than would otherwise occur. The seal~ng plugs at the ends of the manifold are disposed as close as possible to the endmost outlets so as to minimize the possibilit~ o~
pressure waves being reflected Lrom the plugs. This fec~ure combined with the tapering of p2ssaaeway 100 r.akes for a smoother and more constant gas flow through the manifold than would otherwise be achieved. Finally, it will be noted .h~t the manifold is formed with a plurality of lntecrally cast heat-radiating fins 106, the elevational shape of which is best seen in Fig. 1.
Each oi the manifold outlets 98 receives one Of the heat exchange pipes 38 (Fig. 1). As can best be seen from that view, each pipe 38 extends from the ~znifold acr~ss the air passageway 30 and then curves downwarclty and back across passageway 30 to chest 26. In other wor~s, each ?i~e delines an upper run 381 and a lo~er run 382 through which exhaust gases flow successivelv. 3O'h ?ipe runs are expossd to the air to be heated, so that the air will ?ass upwardl-.
through what are in eLIect two "~anks" of heat exchancers 'de-2~ fined by the lower and upper runs -espectively o~ all o t'^e ~ipes 38~ in counter flow to the exh~ust gases. In fact, '_he ~urnace is designed so .hat the air to be heat~d flows cou ter to the direction of exhaust gas -low over the ~.hole lenc'h o~
~he air passage~7ay. This counter -low design ~nsures that '.

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_~ - 12 -maximum temperature differentials and he~ce maximum heat trans-fer rates are achieved bet-~een the air a~d gas over the whole length of the pulse combustion apparatus.
Heat radiating fins 108 are provi~ed on bGtr.
runs 381 and 382 of the heat exchange ?ipes 38. Each fin takes the form of a thln and narrow elon~ate plate ~-hich extends over all of the pipes in the rel-vant run ara -~hich is formed with openings through which the pipes ext~nd. Each fin is in fact simply friction fitted to the associ2ted pipe.
Between its two runs 381 and 3~2~ each pi~e ?~sses through a wall of casing 28 for support as shown in Fig. 1.
The pipe then returns along run 382 and ~asses thro~gr the o?posite ~-all of casing 28 and into chest 26.
The primary exhaust pipe 32, t:~e manifold 36, and the heat exchange pipes 38 ~orm a reso~ant system with the combustion chamber so that ignition of s~ccessive fuel charges in the char~er causes pressure waves to oscillate throughout the whole exhaust system including the heat exchan.ge pipes. It has been found that the presence of ,hese oscillatin~ ~~ressure ~aves in the heat exchange pipes causes a much higher rate of heat transfer to the air flowing through passagew,2y 30 than would occur under steady flow conditions such as in -r appara--; tus in ~hich the heat exchanger is decoll?led from ^- conbus-tion cha~nber, for e~ample in the manner ~isclosed ir ratent :~o. 4,164,210 discussed above. This is 2chieved bv iesigning the manifoId 36 so that its internal passage~7ay (lOC) presents a ~inimum cross-sectional area to gases ~lowing the-e.hrough, wi.h the result that the mani old oflers su~stantiallv no cushioning effect to the cas pressure ~;à-Jes. In o_`-ar words, . :

~ . . -I 1 6~35 ~) the pressure waves are transmitted to the heat exch_n~e pipes rather than being absorbed as in the case in which a ie-oupling chamber is provided. In fact, practical tests have s~own that the rate of heat transfer achieved with the invention c~n be such that the temperature OL the exhaust gases leav-ng .he heat exchange pipes 38 can be as low as 100F c~mpared w t:~ ~em-peratures of the order of 3000F at the combustion chcmber outlet Counter flow of the exhaust gases with res~e~t to the air to be heated (as discussed above) is believed to 3e a sig-nificant fac~or contributing to this hiah efficiency In a particular elmbodiment of the invention, .hetotal length of the gas flow path from the combusticn c;~amber exhaust outlet to the outer ends of .he outermost hea. exchange pipes 38 ~-as an average of approximately 6~ inches an~ .he apparatus was found to resonate at a frequency of a~oLt 70 cycles per second (operating on the ~asic '-requency) ~hich confirms the fact that the entire apparatus ~7as in re-orance.
From the viewpoint of minimizing carbon dio~:ic~
emissions in the exhaust from the furnace~ it is desira~le to design the exhaust s~stem so that combustion is subs~Gn.ially complete before the exhaust gases enter the heat exc:~ance pipes 38 The high velocity of the gcses en.ering the exr~Lst s~stem and the r~esulting rate of heat .rans~er o the air in pa~ssage-way 3~ together with the tempela.ure dro? ~hich occurr- Gue to 2~ e~pansion, lnevitably results in some car~on monoxice in the exhaust gases. By providing an exhaust system in whic~ sub-stantially all of the co~bustion takes place upstreæm OL the heat exchan~e pipes 38, the exhaust sases remain suf~iciently hot lor the carbon monoxide in the gases to re-associz e with . , . . : -, ' . ~ ~ , ' . ' ' ' -" ' ' ' 1 3 ~935 - available oxygen (and form CO2) before rapid cooling t~.kes ~ce in .he pipes 38. In practical tes~s it has been found ~I.at Lhe particular design of the pr.imary exhaust pipe 34 and - the manifold 36 as shown in the dra~ings will re~uce the co~ustion gas temperature to about 900F (from a terper-a.ure of the order of 3000~F at the exhaust outlet of the cor~ustion cha~ber), allowing the carbon monoxide to re-associate with the available oxygen. In this connection, lt has been found that the ratio OL length to internal d ameter of the primary exhaust pipe 32 ~referably should not be less than of the order of 8:1.
The heat exchange pipes t~emselves are copper t-ibes internally coated with lead for coxrosion res-stance.
The ends of the ~ubes which are to be cou~pled to che mar.ifold 36 are fitted with convention.al inverted flare fittings, one of which is indicated at 110 in Fig. 1. The openings 98 in the manifold (Fig. 4) are internally screw-threaded and the flare fittings are screwed into those openings.
A. .heir opposite ends, each pipe 38 p~sses through a ?lain opening in the outer wall of chest 26 and is e~-t~rnally screw-threaded. Nuts 112 2nd 114 are provided on he screw-t.-eaded portion o' .he pipe and clam ed or.o o~posite sides of the chest uall ~lth the lnter-oosition of sui.able gaskets.
The chest itself is sho-.n in some detail ln Fig.
` ~ 3; in that view, the chest is seen rom .he side opposite .h2 outer ~all referred to a~ove. The chest is r.ade up of a nu~.~er of castings in high density concrete. These castings ~.
include a main c2stlng 116 which has the general form of a ~; ' - . . , , . - ,~ : :, . .
' 1 1 f~'~35~3 ` - 15 -rectangular tray or box having a plurality of interr.al cham-bers. The chanbers are open at their rear ends(conci~ering .he chest in its position O,c use), ~nd the open ends are closed by cast rectangular panels, the principal one of which is indicated at 118 in Fig. 3. The main casting 11~ has a base which defines the outer wall of the casting, a~d wnich is denoLed 120 in Fig, 3. A n~mber of other walls extend oUL-~-ardly from the outer wall 120 and deiine the clar~ers re-ferred to above.

At the left hand side of casting 116 as seen in Fig. 3 is an inlet muffler cha~er 122 which is of narrow rectangular shape and which e~tends over a subsLant'al ?or-Lion of the height of the casting. A second, similcr c~ ber 124 is provided at the opposite side of the casLing and de-1~ fines an exhaust muffler chamber. The top wall of ,he casting includes an inlet opening 126 which co~r!unicates wi',h c:a~ber 124, Extending across the bottom of casting below cham~ers 122 and 124 and of similar shape there-Lo is an exha~st cushion cha~ber 130. The heat exch2nge pipes 3S commuicate with cham-ber 130 by way of openings in the outer wall of the chest asdiscussed above in connection with Fig. 1, Four of Lhese o?enings are indicated at 132 in Fig. 3 al_hough it wil' be understood that a series o~ such openincs will exte~d r ght across the outer wall of the chest, one '~or each he2i exc'nanse 2~ pipe 38. Cha~ber 130 commulicates with the muffler cha-ber 124 by way of an opening 13~ in the lower wall of c'-amber 124.
Disposed immediatsly above c:-.a~er 130 is a cenLral cavity in chest 26 which ,may be consicered to define an air cushion chamber 136 and a b'~ower chamb~r 138 se?arated by a .. . ~ ~ . .................. . .
', ~' ' ~ , partial horizontal wall 140- see Fig. 1. (On the o.her hand, ~hese chambers can be considered as a single chamber since wall 140 is not complete.) In any event, the outer casting ~-all 120 is formed with an opening 142 in air cushion cham-ber 136 through which part of the combustion chamber casting 72 extends in the assembled furnace (see Fig. 1). ~wo of the bolt holes used lor securing ihe combustion chamber to the chest are visible at 144. Combustion chamber 24 is a major source of noise in the furnace, but it has been found that by designing chest 26 as shown with muffler chamb2r 122 ~nd 124 on opposite sides of the combustion charber noise transmission to the environment can be minimized. The fact that c.est 26 is made of concrete also has a noise reducing elfec Blower chamber 138 is defined in part by an annu-1~ lar projection 1~6 from the outer wall 120 of casting 116. "' Projection 146 is arranged to provi~e a seating sur~ace for a blower indica.ed in ghost outline at 148 in Fig. 3 and s'nown in full lines in Fig. 1. As can best be seen fr-om Fig.
~- 1, a further chamber 150 is defined be.ween the outer wall 120 of casting 116 and the blower 148. Cham~er 150 communicates with the inlet chamber 122 by way of an opening 152 in the wall between the two chambers. Thus, air en.-ring 21r cham-ber 122 through inlet 126 can flow lnto cham~er 150 b-~- way of o~ening 152. 31Ower 148 will t'nen deliver the air ~rom the 2~ c~amber 150 into chamber 138 and the air will flow -rom that c`na~ber into the air cushion chamber 136 a~d will be 2rawn into the combustion chamber 24 as required.
Blower 148 includes a generally disc-shaped housing 1~4 for an impeller (not shown), and a electric motor 156 ' ~ :1 693~

.~hich is coupled to the impeller for rotating .he same about the longitudinal axis 158 of thQ blower. Housi~g 1;4 i~cludes a central inlet opening 160 which communica,es with c:~a~ber 150 and by which air is drawn into the housing and a ?eri-pherally arranged series of slots 162 thrcugh which air is discharged into chamber 138 as the impeller ro.ates. The blower is held in place on projection 1~6 (with the inter-position of a suitable rubber g~sket - not shown) by a com-pression spring 163 which extends between the blower housing 154 and the chest closure panel 118.
Blower 148 is used only during starting o~ _he pulse combustion apparatus. I~hen satisfactory conb~s_ion has been initiated, the po~er supply to the blower ~o_or 148 is switched off (as will be described) and the blowQr ~5 impeller will come to rest. The impeller is Gecigned to allow communication between the blower inlet 160 and .he outlets 162 even when the impeller is stationary so t~a.
air can continue to be drawn through the blower and into the air cushion chamber 136 as reauired by the pulse combustion apparatus.
Referring back to Fig. 3 r the closure panel 118 ~; - relerred to above is normally secured to cast-nc 116 ~y - bolts which pass through openinss in panel 118 such 2- -those indicated at 164 and which are received in SCrQ.- -. ~. . . .

1 3 8g3~) ~~ - 18 -threaded openings in the casting such zs those indica ~e2 at 166, Thus, panel 118 can be remove~ if necessar~ f-or servicing. The panel closes air cushion chamber 136 and chamber 138 except for a lower portion of the cha~ber which is permanently closed by a so.7r,ew:~at smaller ccncrete panel 168 permanently secured in ~lace by epoxy adhesive. This panel is formed with openings 170 a~.d 172 through power and gas supply lines are routed into c:~est .. 26. Opening 170 receives a power su~ply line for blot~7er - 10 1~8 while opening 1;72 receives a sas s~p?ly line for the pulse conbustion apparatus. Part of t:~e gas supply l~ne -. is indicated at 174 in Fig. 1 and a conduit sleeve ~or the power supply line is shown a 175 posi'_ioned in openlng 170.
The power line itself is not shown. Sllitable gaskets will . .~
of course be provided around the gas s~p~ly line and tne power line to prevent air leakage from chest 26.
Chambers 122, 124 and 130 are ?ermanently closed by panels similar to panel 168,which are permanently secured to casting 116 by e7~oxy adhesi-~e. These panels .: 20 are shaped to fit into recesses formed around the ou er ends of the respective chambers such, -or example, as the - recess indicated at 130a in the case o- chamber 130. :-c-.~- ~
; et.er, these panels have not been sho~in. The bo~,om .. all ~.
oS the exhaust cushion chamber 130 (wh ch is also the bot.om wall of casing 116) includes two o~enings 180 and 182 which are normally closed by blo~ ou~ plugs such as that indicated at 184 in Fig. 1. These 7~1ugs are pro-vided as a safely measure to ~revent ca-age to the ca~ins ' .

.: : --. . . . ~ ~ , ~ . , 1 3 ~9~5() 116 in the unlikely event of an unexpected explosio~. in the exhaust cushion cha~ber 120, for example due to faul.y or delayed ignition. ~he plugs normally close the op~r.ings 180 and 182 but are designed to blow out in respor.se to an abnormal increase in pressure in the chamber 130 ~nd thereby protect the casing from breakage.
Referring to plug 184 (Fig. 1) as represen_aiive of both plugs, the plug includes a cenLra1 spindle 136 which extends through opening 180. Three equally sp_ced arms 188 extend outwardIy Lrom the top of the spincl~ and have notche~ adjacent their outer ends which fit o-~e- ,he edge of opening 180 so that spindle 1~6 is in ef~e~t s~s-pended from the arms. Slidabl~ mounted on spind1e 136 below opening 180 is a clcsure disc 190 dimensioned _o fit 15 over and close opening 180. A gasket 192 is provide~ above disc 190. The disc and gasket are applied aaainst t~.e lower face of casting 116 by a compression spring 19' which extends between the disc and a washer supporte_ by a nut 196 on a lower, scre~-threaded end portion of 20 spindle 186. The spindle 186 is formed with a shoul_er (not shown) so that nut 196 can be tighLened acains. .-.e shoulder and will compress s~ring 194 to a prede,e-m ned extent, thereby biassing dlsc 190 into lts closed ~c~ ion under a predetermined biassing rorce. This force ~ l be selected to allow the closure disc to move dor.~n in r_sponse to a predetermined abnormal pressure in chamber 1~0. G~s~et lg~ is made of closed cell neopL-ene rub~er for ~:n ~I, zing noise trans]nission durlng normal lurnace operation.

~ ~.

I 1 ~935~

~o -In this parlicular embodiment,two '~lo-~-ou~ ?lugs have been provided and the holes 180 and 182 are of 2"
diameter and are spaced 9" apart. 7~hile this arrange7nent has been found suitable for a particular practical em~o~i-ment of the invention, it will of course be underst~od thatthe number, size and arrangement of the plugs may vary.

Referring back to Fig. 3, a condensa~e drain opening 198 is provided between the blow out plugs and is fitted with a barb-type sleeve or drain outlet 200.

Thus, when the furnace is in operation, water condenses from the combustion gases in the heat exchange tubes 38 and is spra~7ed in~o the exhaust cushion cha~jer 130. In condensing, the water gives up its latent heat of vapour-ization to the air flowing through ~assageway 30 which ~as some additional heating effect on the air. At the same time, the condensate which is sprayed into the exhaust cavity serves to muffle much of the noise which would nor-mally occur in this area. The relativel~7 larse volume o~
cha7.7l~er 130 further serves to at least partially absorb the pulsations inthe incoming exhaus. gas for a further reduction in noise.
Referring now more particuiarly to F~g. 5, .he exhaust gases entering cha~ber 130 flo~ upwardly throug~
o~ening 13~ and into the mufller cham~er 124. m~O S, aced layers of bonded glass fibre matting indicated a. 202 and 204 are disposea inside cha7.~er 124 ;iith the s ace there-between aligned with opening 134 (and ~iith exh~ust outle~
o?ening 128)jthus, the exhaust gases pass up-~ardly through :, I ~ ~i93S~) - the space between the two layers in travelling to outle~
128. It has been found that the glass ,'~re la~ers have a significant noise absorbing effect, further reducing the exhaust noise of the apparatus. The glass fibre layers are simply friction fitted into chamber 124. A single layer of bonded glass fibre is also provided in inlet chæ~ber 122 for the purpose of reducins inlet noise. This layer is disposed at the outer side of the chamDer (re-mote from wall 120) so as to avoid obstructing the cpening 1~2 (Fig. 3).
Referring back to Fig. 5, the exhaust outlet opening 128 is externally screw-threade~ and is fitted with a check valve 206 having an interr.al valve element 208 which norr.ally closes the exhaust outlet ;hen the furnace is not in use but which will be lifted by the exhaust gases to open the outlets when the furnace is oera-ting. Check valve 206 serves to reduce the convection e~fect which would otherwise tend to cause moist air to flow back through the apparatus and condense in chest 26 when the furnace is off. The provision of a check valve in the exhaust is particularly impor.ant for avoiding p~G~lems due to "icing" of the chest in cold climates, especially where two or more furnaces are coupled to a co.,-~on exhaust stack.

Reference will now be made to Figs. 6 and 7 in more particularly describing the means (denoted 84 in Fig. 1) for admitting successive fuel charges to the cor~usiion chæ~ber. Fig. 6 shows the co!~bustion cha~ber .,.. ~:'''' ' . . . ' ' : :
'`

3 5 ~) inlet casti~g 72 in section. The casting includes ~he inlet passageway 76 referred 'o above. The outer e..d por-tion of passageway 76 is of inwardly ~apering conical form - and receives a valve plate 210 which includes a con-cal S portion 210a shaped to fit closely inside the conical por-tion of the passageway, and an outwardly projecting flange 210b which overlies the outer end face of casting 72, Immediately upstream of the inner end o casing 72 (the end adjacent casting 70), passageway 76 deIines a cvlin-drical chamber 76a which receives a fla~e trap 212. Flame-trap 212 is ln the iorm of a spiral o~ corrusated s~ain-less steel strip; the corrugations de,~lre openings be~een the turns of the spiral through which fuel charges can flow while the strip itself prevents blcw-bac~ of burning gases through the combustion chamber inlet.
Associated with valve plate 210 is a sas cushion chamber 214 which is also visible in Fig. 1. As car. best be seen in that view, the cas cushion chamber compr~ses an o?en topped cylindrical body or "can" 216 fitted with a cap 218. The gas supply line 174 is cou?led to the can and delivers gas into the cus'nion chamber in use. A pin 220 ~ ha~ing a head at its outer end extends ,hrou~h the can and ; holds the can and cap in place. As can best been s~en -` lrom Fig. 6, pin 220 is screw-threaded at its inner end 2~ and is received in a complimen~arily screw-threaded bore in a support 222 secured to valve plate 210. The s~?port delines openings 223 between ,he valve plate and the cas . -.

1169.35V

cushion chamber through which air can flow into the com-bustion ch~mber lrom the air cuahion chamber 136. ~.t the same time, gas can flow from .he gas cushion chamber 214 into the combustion cha~er through four gas sup?ly t~bes, two of which are visible at 224 in ~ig. 6. These t~bes are open ended and extend out~-ardly from the gas cushior. cham-ber generally parallel to one another and into valve ?late 210.
Admission of air and sas to the combustior. cham-ber is controlled by four ~ressure responsive valvesassociated one with each of ,he tubes 224. ~o of t:~ese valves are indicated at 226 in Fig. 6 and are ~ore s?eci-fically illustrated in Fig. 7. Referring now to tha.
view, the conical portion 210a of valve plate 210 ter~.i-nates at a bottom wall 210c in which the valves 226 are dis~osed. One of the valves is shown exploded at 22O1 and another of the valves is shown in its fully assembled position at 2262; the other ~o vAlves ha~e been omi-ted.
The sas supply tubes ~ssociated with the two val~7es ~7hich are shown are visible in part in Fig. 7.
Referring particularly to valve 2261 r it w 11 be seen ,hat the valve includes inner and outer per^ora e~
discs 230 and 232 respectively which are essentially iden-tical and are provided ~?ith respective sets of ope-i-.ga 2~ 234 and 236. It will be notea that the openings inc:u~e a relatively large circular central opening surrou-.d-d by an annular series of rel2livel J small openings, -~.hic:- is i~self surrounded by a series of intermediate sized 3 5 ~) openings. While this particular configuration of openirgs ; has been found to be eminen~ly satis'ac.ory in practice, it is not considered to be essential. Also, it should be noted that the number of valves can be changed.
The inner disc 230 of each valve member is fo~ce-fitted into the associated opening 228 in valve plate 210.
It will be seen that the opening is in fact form~d with an - ~ annular rebate 236 which receives the disc so that the ~isc cannot move downwardly out of the opening. The associated gas inlet tube 224 is brazed or expanded into the centrâl opening in disc 230 and is provided with an annular rebate 238 at its outer end for this purpose. ~he outer disc 232 is supported parallel to and at a sp2cing from the inner disc 230 by support lugs indicated at 240. The lu~s are formed integrally with the bottom ~:all 210c of the v21ve plaie 210 and are arranged so that the outer disc of each valve can be supported by three lugs although some of ~ the lugs are used for more than one valve. Each lug is - shaped to define a step 240a posltioned to appropriatel~

~ 20 space the outer disc from the inner disc. When Lhe discs -~ are in place, the lugs~axe peened over aL their outer en s, ~cr example as indicated at 240b in ~i~. 7 to re~ain the outer valve disc.
Disposed between the ~wo per'orate dlscs 230 aad 232 o~ each valve is~an imperrorate disc 242 t~7hich acts 2s a val~7e ?~e~ber for controlling the llow of air and gas through t:~e openings in the lnner disc 230. Valve me~ber 242 lS lig:~t a~d freely movable and the t~o discs 230 and 232 are spa~ed - ~

- : ~: ~ : :
' 1 3 6935~) by an amount sufficient to allow disc 2~2 to move betv:een extreme positions in which it closes the openings in t.e res~ective discs 230 and 232. Of course, the support lugs 240 for the outer discs 232 also serve to retain the discs 2~2 while allowing them rreedom of movement bet~een their extreme positions.
It will be readily appreciated that the v~lves 226 will operate automatically in response to pressure changes in the combustion cnamber. During a vacuum trans-ient in the chamber, the ne~ative pressure in the c~ ~erwill act on the valve members or discs 242 through t:~e o enings 236 in the outer discs 232 to cause the valve member 242 to move outwardl~ and allow gas and air to enter the combustion chamber through the openings 23~ in disc 230. Conversely, pressurized gas in ,he combu~_ion chamber will act on the valve ,members 242 through the openings 236 in discs 232 and cause the valve members to move inwardly and close the cas and air inlet op~nin~s in thQ inner discs 230.
In this particular embodiment, the discs 242 are made of Dacron (TM) fabric ccated ~.7ith pol~-chloro .rifluoroethylene solG under the ~-ade mark K_L-F
by M.W. Kellog Co. The discs 230 and 232 are brass ~t~m-pingS and the valve plate 210 is an aluminum cas~ing and is secured to the com~ustion chamber 72 by four ~olts (not sho~Yn) The gas cushion cha-~er support 222 is also an ; aluminum casting and is secured to the valve plate b!~ ~our rivets (not shown).
Reference will now be made to Figs. 8 and 9 in cescribing the control s;~stem for the pulse cor~us-ion aa~a-atus of t~e furnace. In this con~ection, i, ic to be understood that, while the control circ1lit is ~ei~
cescribed specifically in connection with an air ur-lace, its application is not limited in this regard and that the control sys.e~ may be used -~-ith other forms of pulse combustion appara~us incluQing, for example, those described in United States Patent ~o.
3,267,985 and inPatents Applications `.~cs. 960,975 an~
006,702 disc~-ssed above.
Referring now ~articularly to ,he embodime~t cescribed ab~ve, the control s~stem is ~^signed to provice for automatic starting of the pulse com~u,tion a~aratus in response to a call for heat from a ther-,ostat, 1~ and to automctically shut down the pulse combustion ap_a-ratus in the e~7ent that combustion is not esLablishe~ ~t the same time, the system will auto~,atica1ly contro the r,ain blo~er 40 of the furnace (Fig. 1). 3asically, he s~-stem o~erctes by detecting the reduction in veloci~y ~ ich occurs in the air intake o the appara.us ~hen com-blstion is established as compared ~iLh tne lntalr:e ~elocity ~-ring start-n (~hen only the starLing b-3;-.er l~S s in o~_ration). `e_suremont of the intake velocity is ac-;^ved by ~rovidiing a res riction in the air in-Lak2 and mea--uring 2~ t:~e pressure drop across that restrict on. In this -~r-ticular embo~iment, this is achieved by iroviding a ~er.turi irl the air inLG~e and measur-ng the pressure drop ac-oss t:~e venturi. The ~7enturi itself is shc~r in Fig. 8 anc .

-, I 1 ~93~V

~7ill be positioned in the air inlet opening 126 in the chest 26 or the pulse combustion apparatus; ,he venturi has not been shown in Fig. 3 but is indicated gener211y at 244 in Figs. 1 and 8.
Referring particularly to Fig. 8, the venturi 244 is sho~n mounted in the inlet opening 126 in casting 116. The direction ofair flow is indicated by the arrow in Fig. 8. The venturi 244 includes a throat 246 and is - fitted with 31ain tube 248 at its inlet side. Pressure ,a?~ings 250 and 252 are provided in tu~e 248 ups~ream of the venturi and in the region of throat 246. The two pressure tappings are coupled by pressure lines to a difIer-ential pressure responsive switch ~ssembly 254 which includes two switches Pl and P2 calibrated to respond to different pressure dirferentials across the venturi. The pressure lines or tappings each include a da7nping orific~ (not shown).
In this particular embodiment, swi-tch Pl is set to be opera-ted ~.7hen the pressure differential be.~een t~e two tap?ings 2~0 and 252 is 1.3" ~ater cauge. Switch P2 is set to op~r-- 20 ate 4" water gauge pressure. It has been found that, during starting o~ tne apparatus when blot-er 1~8 is in operation the ?ressure di ~erential across Lhe -~en,uri 2~4 will be approxir,atelv 1.4" ~-a,er gauge a~d that, when combus ion has been established in c`.am~er 24, that di~~erential will 2~ increase to ap~roximately 5.5" wa,er gauge. Accordl~cly, t7ne signals ge~erated by switches Pl and P2 can be taXen respectively as indicating that Dlower 148 is operating satisfactorily and that co.7L~ustion has been establis-ed.

These signals are then used in t.he electrical circui~ of ,: , . . ' ' - , the system, which is shown in Fig. 9.
Relerring to 'hat view the pressure s~;itches re-ferred to in connection with Fig. 8 are desiynated Pl and P2. The circuit is connected to a 115V 60Hz po;er supply at terminals 256 and 258. A main on/off switch is in-dicated at 260 and is of the type conventionally used for s.arting electric motors in which the switch incorporates a heater which will automatically open the switch after a predetermined time interval. The heater associated with switch 260 is indicated at 264 and the connection be'_ween these two elements is indicated by the dotted line 266.
The motor for blower 140 is indicated at 268 and has associated therewith a conventional fan and limit control 270 which is responsive to the air temperature in the 1~ furnace and which is designed to keep the fan motor running after the pulse combustion apparatus has switchea off and there is still heat in the heat exchansers.
A first transfor~er 280 provides a 24 volt ~ower supply to a conventional .hermostat 282 which, in ?ractice, would be installed in the living space to be heated by the furnace. The therrlostat is normally open and closes w:^,er. heat is called for. Trans~ormer 280 also has a centre a?ping which provides the power supply to .ne heater 264 for the on/off switch. The thermcstat 2~ circuit also includes a first relay indicated at lCR which has a pair of rormally open contacts lCR in the r,ain power supply line.
A second transformer 286 provides a 6,000 volt icnition power supply to spark plug 64. Pressure switch , . . . ..
. .
: ' , .

:, 1 :~ 6935~

Pl is connected in the supply line to ,ransformer 286 and h2s normally oDen contacts which interupt the power supply to the trans~ormer when the switch is inoperative. Switch Pl also controls the power supply to a solonoid 288 in the gas supply to the pulse combustion a?paratus.
Pressure switch P2 is connected in one of the power supply lines to the starting blower, the motor of ~hieh is indicate~ at 290. The contacts of P2 are normally closed and the switch also has normally open contacts in the supply to a lurther relay 3CR having relay contacts 3~R in series with the main blower motor 268. ~elay 3CR may be omitted if the fan and limit control has a fast te~perature response. Finally, a relay 2CR is con~ected in parallel ~-ith the starting blower motor 290 and has relay contacts 2CR in the supply to the ignition transformer 286. The c?eration of the circuit shown in Fig. 9 is as LOll0-~75:
The main power supply switch 260 to the circuit will be normally closed. I~hen thermostat 282 calls for heat, relay lC~ will be energized, closing its conlacts lCR and establishing a power supply to the starting blower motor 290. Blower 148 will then run to purge any residual ga es Lrom the co~bustion cha-ber. I~hen _he - pressure dif~erential at the air in~_ake ~enturi 2~ reaches 1.3" water gauge, switch Pl will be operated, energizing t`ne gas solonoid 288 and establishing the gas supply to the gas cushion cha~ber. Provided switch P2 has no L been e~ergized at this time, relay 2CR will be energized so that its contacts will be closed and the ignition trans- -~ - - . . . . . .
.: . ` , . :
.. :- ...... ~ . . . .~
,. : - ., :'., ', ~ ' ~ ':

- 3 ~ 6~35~1 former 286 will be energized to provide a spark at plug 54 l~hen combustion is established in chcm~er 24, .he pressure dif-erential across the inlet venturi will incr~ase and switch P2 will be operatea when that diffe~ential reaches 4" water gauge The ~lower motor 290 al-d hea.er 264 will then be de-energized as will relay 2CR, ~e-energizi~g the ignition transformer. At the same time, relay 3CR will be energized, energizing motor 268 and bringing the ~ain blower 40 into operation The power supply to the gzs solo-noid will be maintained through pressure switch Pl ~nen thermostat 282 opens the associated circuit, relay lCR will drop out, de-e~ergizing the gas solonoid 288 (to cut olf the gas supply) and relay 3CR Relay con~acts 3CR will open and the main bloter motor 268 will stop after a ~redetermined 1~ temperature decrease has occured, as determired by s~itch 270 In the unlikely event of a malfunction in the apparatus, the circuit will automatically "lock out" pre-venting further attempts to start until the main on/ofr switch 260 has been manually reset For e~ample, if thermostat 282 calls for heat but the starting blower ~o~s not operate, s~-itch Pl will not be operated so that ~he ~as solGnoid ard ignition transforrer will re~ain de-ener~ized ~:o;:ever, heater 264 will be eneraized and ~i'l operate to trir the ~ain on/off switch 260 alter a pre-2a determined _i~e If the starting blower 148 does op~ratebut combustion is not established, switch P2 will no.
opera.e and a~ain heater 264 will open switch 260 af.er a ' ' ~' ' ~ ' 1 1 693~) -- 31 ~
predetermined time. In this event, the main blower motor 268 will not operate because relay 3CR will remain de-energized.
While it has been found in practice that the circuit described above operates perfectly satisfactorily, in some cases, it may be desirable to incorporate means for intermittently interupting the power supply to the gas solonoid during the starting cycle to prevent a build up ~ of gas, and hence an overly "rich" mixture in the combus-tion chamber. The interupter would be switched out as soon as combustion had been established.
Another possible modification to the circuit of Fig. 9 would be to replace the heater-type switch 260 by some other form of timer designed to open the switch if combustion is not established after a predetermined time.
- Fig. 10 is a circuit diagram of a control system which incorporates a solid-state timer indicated by reference numeral 300. The circuit ~lso incorporates a second timer denoted by reference numeral 302 by which the circuit can be modulated as will be described later for the purpose of improving furnace efficiency. Timer 302 and an associated switch denoted 304 can simply be omitted if the circuit .is required to operate in a non-modulating mode.
Another dlfference as compared with the circuit ;~
of Fig. 9 is that the two individual pressure switches Pl and P2 have been replaced by a single dual pressure level switch denoted by reference numeral 306. This s~7itch is connected to the venturi 244 (Fig. 8) in the same manner as .

.~ ~
.. . , .
.. . ..

, ;
: .

I ~ 69~5~

the switches Pl and P2 and has two sets of contacts,denoted Pl' an~ P2' set to operate at respectively different pressure levels. As in the embodiment of Fig. 10, switch Pl' is designed to be operated when switch 306 detects a pressure differential of 1~3 inches water gauge between the two tappings 250 and 252 in venturi 244; switch P2' operates when this pressure reaches 4 inches water gauge~
Apart from the components indicated above, the circuit of Fig. 10 incorporates essentially the same components as Fig. 9. With the exception o~ the various relays, these components are designated in Fig. 10 by primed reference numerals corresponding to the reference numerals used in Fig. 9. ' Fig. 10 includes three relays denoted lCR, 2CR and 3CR having correspondinly denoted contacts. Neglecting timer 320, the circuit of Fig. 10 operates in essentially the same fashion as the circuit of Fig. 9. Thus, when thermostat 282' calls for heat, relay lCR is energized 50 that its contacts clo5e and apply power to blower 290' by way of switch 306. When the switch detects a pressure differential of 1.3 inches water guage, contacts Pl' deliver power to the gas supply '~ valve 288' and to the ignition transformer 286'. When combustion has been established, contacts P2' of switch 306 energize relay 2CR. By way of its contacts, rela,y 2CR
then de-energizes the lgnition transformer 64' and energizes ~; the main air circulation blower 268'.
Lock-out timer 300 is a~solid state timer having -' a 10 second run-down. The timer has normally-open contacts ' ... .

: ',, : .

1 ~ 6~35~) 308 which close at the end of the run-down period. Timer 300 is energized by way of normally closed contacts of relay 2CR when the gas valve 288' is energized. The timer then begins to run but will normally be de-energized by relay 2CR when combustion is established as detected by switch 306. If combustion is not established within 10 seconds, the timer contacts 308 will close, energizing relay 3CR.
That relay has one pair of normally open contacts and one pair of normally closed contacts. When the relay is energized from timer 300, the normally closed contacts 3CR will open and lock-out the circuit while the power supply to relay 3CR will be maintained through the normally open contacts of the relay. This arrangement of the contacts of relay 3CR has been found to be particularly convenient from the , 15 viewpoint of preventing any possible feed back through the timer contacts. Also, the fact that timer 300 has a 10 second run-down period is significant from the viewpoint of reducing the "gas-on" period of the furnace, which provides ` - a greater margin of safety than might otherwise be achieved.
~o Timer 302 is a "percentage" timer and is designe~ito modulate the control circuit so that the furnace will run intermittently in a modulated fashion according to the heat output required fxom the furnace. Modulation is important in terms of providing for efficient heat transfer between the exhaust gases in the heat exchange pipesof the furnace and the air to be heated. If the heat exchanger can operate at a lower temperature,efficiency is increased because a greater pro-portion of the vapour in the exhaust gases will then condense in the heat exchanger and give up their latent heat of ``:~ ` ` :

~. :

, 1 ~935~) vapourization to the air than would otherwise be the case.
In the particular en~odiment illustxated, timer 302 is designed to run on a one minute cycle although other cycle times could of course be used. Timer contacts 304 will close for a percentage of the cycLe time depending on the output required from the furnace. It is anticipated that the minimum operating time/cycle will be about 5 seconds for clean combustion; in other words, the ti~er contacts will be closed for approxi~ately 5 seconds in each one minute cycle. Expressed as a ratio, the operating time/cycle will be 11:1 (for every minute during which the main thermostat 282 is calling for heat, the timer contact 304 will be closed allowing the furnace to operate for 5 seconds and will be open for 55 seconds).
lS This ratio will be changed according to the heat output required from the furnace. For example, the ratio could be changed manually. However, in the preferred embodiment shown in the drawings, a secondary thermostat 310 is coupled to timer 302 and controls a rheostat 312 to automatically vary the~operating time/cycle of timer 302 in accordance with ambient temperature. It is believed that the percentage timer 302 will be particularly significant in optimizing the energy output of the furnace~(or of any other pulse combustion apparatus with which the control circuit ~s used) although it is to be understood that this is an o?tional feature of the invention.
Reference will now~ be made to FigsO 11 anc 12 in describing a further aspect of the invention.

. .

._ J 6~35~1 Fig. 11 is a detailed view corresponding to part of Fig. 1 and primed reference numerals have been used to denote corresponding parts. In Fig. ll part o~ the chest of the pulse combustion appara~us is indicated at 26' and the main rear panel which closes the rear of the chest is indicated at 118'. In accordance with this aspect of the invention, panel 118' is provided with a recess 314 at its nnerface and a diaphragm 316 is provided between the interior of chest 26' and recess 314. The purpose of this diaphragm is to reduce noise transmitted from the rear side of chest 26' when the pulse combustion apparatus is in operation. Thus, it has been found that diaphrag~ 316 will respond to and attenuate sound waves generated by the pulse combustion apparatus in operation and has a marked effect in reducing the noise transmitted from the apparatus. It is believed to be important that the diaphragm should have a significant mass but at the same time ahOUld be flexible so as to be capable of responding to pre~su^e changes within the chest 26'. In the illustrated embodiment, diaphragm 316 also acts as a gasket between panel 118' and chest 26' although this is not essential within the ~road scope of~this aspect of the invention.
In any event, with these ends in mind, dia?hragm 316 in the illustrated embodiment is of laminated construction and comprises a rubber gasket 318 sandwiched between two pieces 320 of sheet steel. Rivets ~not ,hown~
are used for securing the steel to the rubber. In a~
alternative embodiment, the diaphragm could be of dirferent `: :

: . ~

- : :
: : ~

~ 1 ~i9~5(~

construction; for example, rubber-coated steel could be used.
It is to be understood that the embodiment shown in Fig. 11 is only one example of a particular location in which a diaphragm can conveniently be used. It should also be noted that a similar diaphragm can also be used with advantage in other forms of pulse combustion apparatus and that there is no limitation to the particular furnace shown in the previous views. By way of example, Fig. 12 shows in ghost outline a pulse combustion boiler denoted 322 such as that described and claimed in my United States Patents Nos. 4,241,720 and 4,241,723. In Fig. 12, reference numeral 324 denotes the outer casing o such a boiler and a fan inside the casing is indicated at 326. The casing has a removable cover or lid 328 and a diaphragm 330 similar to diaphragm 316 is interposed between the lid and the sasing for the same purpose as diaphragm 316. The lid is recessed as indicated at 332 behind the diaphragm. As indicated above, the embodiments shown in F~gs. 11 and 12 are to be considered as examples only and not as limiting ~ potential applications of the diaphragm in other for~s of pulse combustion apparatus.
Many other possible modifications are possible within the broad scope of the invention; it will of course be understood that the preceding descxiption relates to pxeferred embodiments only. For example, referring to the ` circuit of Fig. 9 or 10, it would be possible to derive the . ..:

: ' -- ::

1 ~ 6935 signals provided by switches Pl and P2 in other ways. The venturi arrangement described is to be preferred in that the pressure loss which occurs in the venturi is sub-stantially recovered downstream. However, a simple re-striction in the intake pipe could be used to provide a similar effect. Other means responsive to the velocity changes which occur in the venturi during starting and after establishment of combustion could alternatively be used. In the embodiment of Fig. 8, pressure tapping 250 could of course be open to air.
It will also of course be understood that the particular materials and construction techniques referred to above are to be considered as representative .illustra-: tions only and do not limit the scope of the invention.
15 For example, although chest 26 has been described as being a concrete casting, it could be made in other materials such as steel or glass fibre; however, concrete is pre-- ferred because of its sound insulating properties.
This is a division of Canadian Patent Application Serial N~. 37-,153, rile- May 8, 1931.

'~ .

;~
-~ , .

~ ', ~' .. .

Claims (8)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A pulse combustion apparatus comprising:
a combustion chamber having a fuel charge inlet and an exhaust gas outlet;
an exhaust system communicating with said outlet and forming a resonant system with said combustion chamber;
means associated with said combination chamber inlet for admitting successive fuel charges to said cham-ber, said means including inlet means for combustion air communicating with said combustion chamber inlet and in-cluding an air intake, blower means downstream of said intake and operable to deliver combustion air under pres-sure to said combustion chamber for starting, ignition means coupled to said combustion chamber and operable to initiate combustion in the chamber, gas supply means coupled to said combustion chamber inlet, and valve means adapted to control delivery of air/gas charges to said combustion chamber in accordance with the combustion cycle of the apparatus; and, a control system comprising:
starter means operable to activate said blower means when the apparatus is to be started;
first switch means responsive to a first predetermined air velocity in said air in-take representing satisfactory operation of said blower means, said first switch means being coupled to and adapted to activate said gas supply means and said ignition means when said first predetermined velocity is achieved;
second switch means responsive to a second predetermined air intake velocity repre-senting establishment of combustion in said combustion chamber and adapted to de-activate said ignition means and blower means while maintaining said gas supply when said second predetermined air intake velocity is achieved;
and, timer means coupled to said starter means, gas supply means and second switch means and adapted to shut off the gas supply means if the second switch means has not been operated after a predetermined time interval from initial operation of said starter means.

2. An apparatus as claimed in claim 1, further comprising an air venturi disposed in said intake and in-cluding a throat, first and second pressure tappings disposed respectively upstream of said throat and in said throat, and wherein said first and second switch means comprise means responsive to the pressure differential between said first and second tappings, and first and second switches coupled to said pressure differential responsive means and arranged to be operated respectively when said venturi flow meter detects respective first and second combustion air inlet flow velocities in said venturi.

3. An apparatus as claimed in claim 1, adapted for use in heating a fluid, and including means for bringing said fluid into contact with said combustion chamber an exhaust system, and wherein said starter means comprises a thermostatic control circuit including a thermostat re-sponsive to the temperature of said fluid, and wherein said gas supply means includes an on/off solenoid valve, the apparatus further including power supply means for said thermostatic control circuit, solenoid and blower means, an on/off switch in said power supply means and which is normally closed when the system is operative, said timer means being coupled to said switch and adapted to open the same and thereby de-energize said solenoid valve if the second switch means has not been operated after said predetermined time interval.

4. In a pulse combustion apparatus including; a combustion chamber having a fuel charge inlet and an exhaust gas outlet; means associated with said combustion chamber inlet for admitting successive fuel charges to chamber, said means including inlet means for combustion air communicating with said combustion chamber inlet and including an air intake, blower means downstream of said intake and operable to deliver combustion air under pres-sure to said combustion chamber for starting, ignition means coupled to said combustion chamber and operable to initiate combustion in the chamber, gas supply means coupled to said combustion chamber inlet, and valve means adapted to control delivery of air/gas charges to said combustion chamber in accordance with the combustion cycle of the apparatus;
the improvement comprising:
a control system which includes:
starter means operable to activate said blower means when the apparatus is to be started;
first switch means responsive to a first predetermined air velocity in said air in-take representing satisfactory operation of said blower means, said first switch means being coupled to and adapted to activate said gas sup-ply means and said ignition means when said first predetermined velocity is achieved;
second switch means responsive to a second predetermined air intake velocity repre-senting establishment of combustion in said combustion chamber and adapted to de-activate said ignition means and blower means while maintaining said gas supply when said second predetermined air intake velocity is achieved;
and, timer means coupled to said starter means, gas supply means and second switch means and adapted to shut off the gas supply means if the second switch means has not been operated after a predetermined time interval from initial operation of said starter means.
5. An apparatus as claimed in claim 1, wherein said first and second switch means form part of a single switch.

6. An apparatus as claimed in claim 1, wherein said timer means comprises a solid state timer having a run-down period of approximately 10 seconds:

7. An apparatus as claimed in claim 1, wherein said contol system further comprises modulating timer means adapted to operate on a predetermined time cycle and coupled to said gas supply means, said modulating timer means being ply means and said ignition means when said first predetermined velocity is achieved;
second switch means responsive to a second predetermined air intake velocity repre-senting establishment of combustion in said combustion chamber and adapted to de-activate said ignition means and blower means while main-taining said gas supply when said second predetermined air intake velocity is achieved;
and, timer means coupled to said starter means, gas supply means and second switch means and adapted to shut off the gas supply means if the second switch means has not been operated after a predetermined time interval from initial operation of said starter means.

5. An apparatus as claimed in claim 1, wherein said first and second switch means form part of a single switch.

6. An apparatus as claimed in claim 1, wherein said timer means comprises a solid state timer having a run-down period of approximately 10 seconds.

7. An apparatus as claimed in claim 1, wherein said control system further comprises modulating timer means adapted to operate on a predetermined time cycle and coupled to said gas supply means, said modulating timer means being adapted to interupt said gas supply means for a predetermined portion of each said cycle so as to modulate operation of the pulse combustion apparatus.

8. Apparatus as claimed in claim 7, further com-prising thermostat means coupled to said modulating timer means and adapted to automatically vary the duration of the said portion of the cycle of the timer means in response to the temperature sensed by said thermostat means.