US2417909A - Cyclic safety control for burners and the like - Google Patents

Description

3 Sheets-Sheet 1 G. D. BOWER Filed Nov. 22, 1940 CYCLIC SAFETY CONTROL FOR BURNERS AND THE LIKE Q /1/ P/EKNUSTAT March 25, 1947.

March 25, 1947. QW 2,417,909

cYcLIc SAFETY CONTROL FOR BURNERS AND THE LIKE Filed'Nov. 22, 1940 3 Sheets-Sheet 2 lM/E/W'an: I 660176: 0. learn,

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Patented Mar. 25, 1947 CYCLIC SAFETY CONTROL FOB BUBNERS ANDTHE George D. Bower, Universityflity, Mm, assignato Automatic Control Corporation, St. Louis, Mo., a corporation of Delaware Application November 22, 1940, Serial No. 366,512

28 Claims. (01. 158-28)- This invention relates to a control for a heatchange device, particularly a burner such as an oil or a gas furnace, but capable in whole or in part of more general application.

The mechanism includes generally. a device subject to movement upon change of heat, a space or room thermostat, a relay, here operated with a transformer in connection with the space thermostat, a timing or control motonand a series of cam-operated switches controlled by'the timing motor. The mechanism is used with an ignition device and a fuel supply device or air supply device, or both, generally designated a burner motoror burner operating device.

The mechanism provides a starting period, a running period and a scavenging period. In normal operation, upon demand by the space thermostat a starting period is instituted, by an instituting circuit closed for a limited interval. After it is established it becomes independent of the room thermostat. It includes a first phase at the end of which, absent ignition; lock-out occurs, and a second phase. at the end of which, with ignition, a running period is established, dependent upon the room thermostat, if starting was effective. Upon satisfaction of the room thermostat, the running period yields to a scavenging period, at the end of which the mechanism stops prepared for a new operation.

If ignition is not efiective at the beginning and during the second phase of the starting period, the mechanism assumes a lock-out position, as noted, requiring manual reset. Such manual reset establishes the scavenging period at the end of which the mechanism tries once again to start.

If ignition failsduring the running period, the scavenging period is established, at the end of which the mechanism may attempt to restart, and if it fails, locks out. At the lock-out position, the entire mechanism is deenergized. It may be manually reset by a shifting of the cams.

If power falls during the interval of closure of the instituting circuit,- upon restoration, the starting period continues. If power fails during the established starting period, upon restoration the mechanism operates through the remainder of the starting period, the scavenging period, and starts anew.

If power fails duringthe running period, upon restoration, the mechanism proceeds through the scavenging period, and restarts.

It will be observed that at the end of any operation, normal or abnormal, there is a scaveng ing period prior to restart. This is true even after lock-out.

The objects of the invention are to accomplish each and all of the above operations, and to do so with a simple and economical novel construction.

A further object of the invention is to provide a control device readily adapted to secure either continuous or intermittent ignition,

A further object is to provide a cycle of this kind, with or without all of its details, operated with periods of fixed duration.

A further object is to provide in a mechanism of this kind, an ignition-responsive device directly controlling the burner motor; and to provide means to prevent continued operation of the mechanism" and motor if the-said devicefails in either its hot or its cold position.

Further objects include the provision of a cycle means of this kind, insuring a scavenging period after each operation; and to provide a cycle having its lock-out occurring prior to the running period.

In the drawings:

Fig. 11s a front elevation of the device mounted on a pipe;

Fig. 2 is a side elevation with the pipe in section;

Fig. 3 is a front elevation with the cover removed;

Fig. 4' is a horizontalsection taken on the line 4-4 at the top of Fig. 3;

Fig. 5 is a Vertical section taken on the line 5-5 at the right of Fig.3;

Fig. 6 is a vertical section taken on the line 6-6 of Fig.5; a a

Fig. 7' is a front elevation ,of the casing with all the mechanism removed except the switch operated by the heat-change responsive device, mounted on the casing;

Fig. 8 is a rear elevation of the partition wall with the mechanism mounted thereon;

Fig. 9 is a section on the line 9-9 of Fig. 4 showing only the front cam and its switches;

Fig. 10 is a section on the line lll-l0 of Fig. 4 showing the middle cam and its switches;

Fig. 11 is a section on the line I l-H of Fig. 4

' showing the rear cam and its switches;

Fig. 12 is a diagram of the program of the mechanism; and,

Fig. 13 is a general wiring diagram of the mechanism. I V

The mechanism includes an encased unit 40 having a heat-responsive device I projecting from the back thereof and supported in a pipe 42 so as to be influenced by heat changes therein. The mechanism 4| is almost instantly responsive to all changes in heattaking place at or above a given rate and reversing the heat condition from hot to cold or cold to hot; and it is of the typeshown in co-pending application No. 328,177, filed April 6,1940, PatentNo. 2,323,370, issued July 6, 1943. v

Recapitulating briefly from said applications, the stack unit includes an outer tube and an inner member preferably also a tube. The two may have the same coemcient of expansion. The

outer tube is located so as to receive immediately the relatively unlimited supply of heat if the burner ignites and produces flame, such as in the furnace stack, and desirably is of thin material so as to respond almost instantly to rapid changes in temperature such as may occur in normal starting or stopping of the flame; and it may also respond to fluctuations in heat of the flame.

The inner member is exposed at most only at its outer end to the flame, and contains an inner portion connected to a cold reservoir, as the switch casing and the control casing. The two members are secured together toward their outer ends, and preferably the heat from the flame reaches the inner member in its major portion from the outer member. Heat applied to the outer tube causes it to expand. A portion of this heat is transmitted to the inner tube, but that tube does not expand as much, owing to its dissipation of heat into the cold reservoir. Hence their will be a relative movement of the inner ends of the members causing the snap switch to operate to its closed position. In the starting position of the tubes, the snap switch is held in an intermediate position, so that it may move in either direction, and stay there under the influence of the snapaction means;

Continued application of heat to the tubes will never bring them to the same length, owing to the constant dissipation of the limited amolmt of heat supplied to the inner. Even if the inner tube should heat to a point of providing approximately the same length differential as at the start, the switch will not shift, as the starting condition has the switch floating at a mid-point of the snap-action means. Not until a positive reversal of the length differential occurs can the switch be moved, by overcoming the force of the snap-action.

If the flame stops, the outer tube will rapidly cool, but the inner tube cannot cool so rapidly. This reverses the length differential, and the outer tube, therefore, displaces the inner, returning the switch to its first position. Continued cooling does not change this, because even in the initial position the length differential would only put the switch into neutral position, and the force of the snap-action is ordinarily adequate to prevent even this.

It will be seen that the device will thus function upon any sudden heat change reversing the length differential, regardless of the temperature. Normal fluctuations or modulations occur at too slow a rate to cause the function. For instance, in a relatively slow decline of heat, the rate of heat dissipation from the outer member is less than the rate of heat dissipation from the inner, or at least is not so much greater a rate as to cause displacement of the end of the inner tube suflicient to move the switch to a point wherefrom it will snap over.

The uni? itself has a main casing having a rear wah 43, side walls I and jptep wall. and bottom wall ll. The sid walls do not extend forwardly a far as do the top and bottom walls and have inwardly extending flanges upon which is mounted a partition wall ll that provides an inner chamber 48. A U-shaped cover flts over the top and bottom walls and back to the sidewalls to enclose a switch chamber.

The mechanism itself includes generally the heat change responsive unit 41, a switch 53 operated thereby, the switch being of the type disclosed in copending application, No. 328,177, filed April 6, 1940, having four terminals. The mechanism also generally includes a control motor or timing device I, a transformer 55 and a relay N, the last three being mounted on the back of the partition wall.

The switch 53, as noted, has four terminals. The pair of terminals 81 are closed by the switch upon increase of heat applied to the unit II, and the pair of terminals I. are closed upon decrease of heat.

The control motor 54 operates three banks oi control switches that are supported on the front side of the partition wall II. The motor itself is mounted on a bracket ll secured to the partition wall. The motor has a driving gear ll (Fig. 6) that, in turn, drives a gear I! fltted within an opening in the partition wall. The ratio of these gears determines the spread of the cycle, which, therefore, may readily'be changed. A ratchet dog II on the gear 82 is spring-pressed into engagement with a ratchet M integral with a hollow cam shaft it that projects through the partition wall toward the front of the mechanism.

It will be seen that rotation of the gear II in a counterclockwise direction, in Fig. 6 looking from the back, will cause the gear I to rotate in a clockwise direction which, through the medium of the ratchet. causes corresponding rotation of the cam shaft 8!. Looking from the front, as in Figs. 4 and 9-11, the cams rotate counterclockwise.

The cam shaft supports three cams, a front cam 01, a middle cam II and a rear cam 89. The cams are maintained in spaced relation and have a noncircular opening fltting over the noncircular cam shaft 85. A shield II shields of! the opening through the partition wall 48 in which the ear I flts.

Within the hollow cam shaft is a shaft Ii on which is mounted a knob II. This knob is like the one in copending application, No. 328,177, flied April 8, 1940, and is designed to permit only a limited movement of the knob. The knob also has a projecting leaf spring 13 at the back thereof that is adapted to engage at certain times with a button II on the front cam "I. By this means in a manner the same as described in the mentioned copending application, the knob 12 may rotate the cams in a counterclockwise direction a distance limited to the permitted movement of the knob II. Release of the knob thereafter allows' it to spring back into starting position.

The front cam II, as shown in Pig. 9, has a lobe II, a deep notch 84 and an edge ll between the notch M and the lobe II. This cam operates two switches II and II. There is a cam follower arm ll having a contact ll adapted to close with the contact II on a blade II to constitute switch I. The blade II is limited in its movement by a stop blade I.

A spacer member ll on the arm 0! holds an additional blade 04 spaced from the arm I. This blade has a contact II adapted to engage with the contact 98 on a spring blade 81 which also has a stop blade OI to form switch :1.

When the follower is on the lobe II, the switch 86 is open, and switch 81 is closed. when the cam drops the follower to the edge ll, both switches are open, and when it further drops the follower into the notch ll, the switch ll closes.

Referring to Fig. 3, it may be seen that all of these several blades are supported on the partition wall between two brackets "II and Ill. Each switch blade carrying a contact is insulated from the others by a series of insulating blocks I02, and each blade also extends back of the brackets and insulating blocks to provide terminal portions to receive connections. The several banks of, switches are spaced in accordance with the spacing of the several cams and all are insulated and connected, as will be obvious, to obtain the objectives of the wiring diagram.

The middle cam and its switches are shown in Fig. 10. The cam 68 has a lobe I04 from which there extends a somewhat lower lobe I05 followed by a low edge I06, and then a notch I01.

This bank of the switches includes three switches I00, I09 and H0. There is a follower arm III'that has a contact I I2 adapted to close with a contact II3 to form the switch I08. The contact II3 is mounted on a switch blade II4 having a stop blade H5 to limit its movement.

The arm I I I is provided with a spacer member 6 by means of which it is held in spaced relation to a spring blade II1 having a contact IIO that is adapted to close with a contact II 9 to form the switch I09. The contact H9 is secured to'a spring blade I20 that has a stop blade RI.

The contact H8 has an opposed'contact I22 on the blade lill-thatis adapte to'"clos"with"a2- contact I23 to form the switch II 0. The contact I23 is secured to a spring blade I24 which has a stop blade I25. The several blades are mounted between the brackets I and I M and are duly insulated from each'other, as shown.

They are also provided with suitable terminal ends to receive connections.

When the cam I04 is in the position shown, the switch I08 is closed and the switches I09 and H0 are open. When a short time later the cam' lifts the follower out of the notch I01 onto the edge I06, it opens the switch I08 without closing I09 or IIO. Sometime'thereafter, the edge I lifts the follower to close the switch I00, and, upon reaching the edge I 06, also closes the switch H0.

The rear cam 69 (Fig. 11) has a lobe I30 followed by an edge I3I that is quit low, and between the edge I3I and the lobe I30 there is a medium-high edge I32. This cam operates switches I33, I34 and I35. It has a follower arm I36 with a contact I31 adapted to engage'with a contact I36 to form the switch I33. Thecontact I38 is secured to a switch blade I30 and there I is a stop blade I40 to limit the movement thereof.

The follower arm I36 also has a second contact I4I adapted to be engaged with the contact I42 on a blade I43 to form the switch I34. A spacer member I45 holds the blade I43 spaced from another blade I46 that has a stop blade I41 to limit its movement. The blade I46 has a contact I40 adapted to close with the contact I49 on a blade I50 to form the switch I35. The blade I50 also has a stop blade I5I to limit its movement.

When the position shown in Fig. 11 is attained, the switches I34 and I 35 are closed. When the cam rotates so that the follower I36 drops-to the edge I3I, switches I34 and I 35 will snap open and the switch I33 will close. Thereafter, when the cam presents the middle edge I32 to the fol- -lower arm, it opens the switch I33, but does not close the switches I34 and I35. These two switches are reclosed by the cam lobe I30.

The transformer 55 includes aprimary I60 and a secondary I6I, as shown in the wiring diagram.

The relay 56 includes a coil I62 that, when deenergized, releases an armature I63 that is biased to close with the contact I64, and to open the switch I66. When the relay is energized, the.

armature is closed with the contact I65, and the switch166 is closed also.

The relay coil I62 is in series with the secondary of the transformer and also with the room thermostat I61.

The unit itself on the front of the partition wall has six terminals. The terminals I and "I are adapted to be connected to the leads from the room or space thermostat. The terminals I12 and I13 are the power lines. From theterminal I14 goes one line to the burner motor, the other line of which is brought back to the ground power line I13, and from the terminal I goes one lead to the igniter mechanism, the other from which also goes to the ground power line I13. The twoground lead lines from the igniter and burner motor may, if desired, be connected to the terminal I13. The remaining connections will be clear from the accompanying wiring diagram.

It will be seen that one terminal 51 of the stack unit is connected to the switches 81 and I08, and to the terminal I14. The other terminal of the switch I03 leads to a bracket I11 (Fig. 5) attached to the partition 48, and overlying in spaced relation anextension of'the terminal I 15. A screw I18 passes through the extension and is adapted to contact the bracket I11 when tightened, or to be spaced therefrom whenloosened. This screw forms a selective switch I13, and determines whether or not the igniter operates continuously through the running period, or stops at the end of the first phase of the starting period.

The operation of this cycleis shown in Fig. 12. At the start, the cams present the several points S to their followers. Reference'to the program and to the other figures will show that switches 01, I08, IIO, I33, I34 and I are open, and switches 86 and I03 are closed by their cams,

establishing an instituting circuit through the primary winding I60. The heat switch 58 is closed because the unit H is cold, and the switch I63 isreleased against the contact I64. When the room thermostat switch I61 closes, demanding heat, the secondary coil I6I causes the flow of current through the thermostat switch to the relay coil I62. This closes the switch I63 against the terminal I 65, and also closes the switch I66. Thereupon, a circuit to the control motor is established from the terminal I12, switch I63, switch I03, through the control motor to the terminal I13. The control motor then begins to operate and to rotate the cams. After about two and a half seconds of operation of the control motor, the switches IIO, I34 and I36 close; Closing of the switch I34 shunts the switch I63 and holds its circuits independently of the coil- I62 and, hence, of the room thermostat, thus insuring that, for the interval of closur of the switches I34 and I00,'the control motor will con- 0 tinue to operate. Also, there is an additional holding circuit for the primary I of the transformer which is independent of the switches 86 and 50, and which includes either the switch I34 or the switch I63, the switch I09, the switch I35, the switch I66 and the primary I60.

Closing of the switch IIO puts the ignition device in circuit directly in parallel with the control motor. The igniter thereupon begins to operate. After the lapse of about twelve and 70 one-half seconds the switch 06 opens and the I switch 01 closes. Opening of the switch 86 has no eiiect at this time. because of the previously established'holding circuitto the coil I60 through the switch I 35. It does prevent reclosing of the primary circuit upon lock-out or after the runhing period, and thereby insures that the switch I63 will remain against contact I to insure the scavenging period, as will be seen. Closing of the switch 81 establishes the circuit to the bumer motor which includes either the switch I or the switch I63, the switch I", the switch I, the switch 81 and the burner motor. When the burner motor starts, fuel is supplied and in due course will be ignited by the igniter. It is to be observed that the lgnlter is operated prior to the burner motor, a desirable safety feature.

When the ignition takes place, the stack switch operates almost instantly so that the switch 51 is closed and the switch 58 is opened. This then establishes a circuit to the burner motor by way of either the switch III or the switch I", and the switch 51. It also establishes an additional circuit to the coil I from the switch I1 and through the switch 01 and the switch I. It likewise establishes an additional circuit to the control motor from the switch 1, the switch 8'! and the switch I, and additionally establishes a circuit to the igniter through the switch IIO.

After the lapse oi a period of sixty seconds, the first phase of the starting period, the switches I and H0 open and the switch I" closes. Opening of the switch Ill breaks its circuit to the control motor, but that motor continues because oi. the alternative circuit through the switch 51. This circuit holds the coil I60 through the switches 81 and I, the control motor through the switches 81 and I35, ignition device through switch IIII, and the burner motor. Thereupon, the continued holding of the circuits depends upon the continued flame to hold the stack switch 51 closed.

Thus, continued operation of the normal cycle depends upon the condition at the end of sixty seconds. If normal ignition takes place. the mechanism will continue for an additional ten seconds interval. until the lapse of seventy seconds, at which time the switches I and III will open and the switch I" will close. This interval is th second phase of the starting period. It is a lock-out period. Closing oi! the switch in has no effect as long as the switch IE3 is closed against the contact I". Opening of the switch I34 leaves the circuit dependent upon the position of the switch I" and. therefore, upon the condition of the room thermostat. Opening of the switch I" has no effect on the coil I" as long as flame continues, because of the alternate circuit to the coil through the switches 51, I1 and I". It does, however, have an eflect on the condition of the control motor which was previously in circuit only through the switch I35. This m'otor, therefore, stops. The ignition device remains in circuit through the switches 51, I" and I1! if the latter is closed. For some burners this is a desirable safety feature. For others, it is not necessary, and so, upon loosening the screw I'll to open the switch I19, the efiect of the switch I" in holding the igniter in circuit is nullified, and it ceases operation upon opening of the switch III at the end of sixty seconds. The switch I" is held closed for a short time beyond the seventy-second point to insure operation of the igniter even when the control motor floats or coasts for an interval after deenergization. V

when the control motor stops, the mechanism is in the operating or running stage, and is wholly dependent for continuance of this stage upon continusdclosureoitheroomthermostaathestsck switch II, and the relay switch III. of course, the'timing motor switch Tl must remain closed.

As soon as the room thermostat is satisfied and opens, the coil I" is deenergized, the switch I" shifts to the contact I, and the switch I" opens. The fact that the instituting circuit is broken at the switch It prevents energization of the primary at this point, so that th switch I can shift. This cuts the primary I" out oi circuit. It cuts the burner motor out oi circuit because it breaks the line to the switch '1. It cuts the ignition device out oi circuit for the same reason. However, closing the switch Ill with the contact I, with the closure of the switch III, establishes a circuit through those two switches to the control motor which again begins to operate.

Very promptly (preferably and normally a matter of seconds) alter the burner motor stops, the heat will dropai; the stack unit II at a great rate so that the switch a closes and the switch 51 opens. Thishas no eflect on the established circuits.

After the lapse of flve more seconds or, disregarding the running period, seventy-live seconds from the start, the switch I opens. This has no immediate eiiect. Continuing the switch Ill beyond the seventy-second point assuresoperation of the igniter, despite the floating or coasting interval of the control motor. This, of course, assumes that the switch I'll is closed. Alter the lapse of eighty seconds, the switch 01 opens with no immediate eflect. The switch II likewise accommodates the coasting period.

The control motor alone will continue to operate until almost the end or the entire cycle, which cycle is here shown at 240 seconds. This insures along scavenging period to take care oi! allunburned fuel.

Alter the lapse of 230 seconds. the switch Ill again closes. This has no eiiect. because the switch I is closed against the contact Ill and because even any circuit established through the switches III and I is broken at the switch II, and any circuit to the switch I] is broken at switch I34.

Thereafter, at 235 seconds, the swtich ll closes again to reestablish a circuit to the primary I. The primary, however, is inactive because the room thermostat is open. No other circuits are established by this act.

At the end of 240 seconds, the switch I opens again and thereby all circuits other than the instituting circuit to the coil I open. The control motor stops and the mechanism awaits a new call by the room thermostat.

It has previously been noted that, alter a sixty-second interval, the circuit is dependent upon ignition, because it is dependent upon the condition of the switch 51, which closes only upon the existence of ignition at the sixty-second point. If it be assumed that ignition does not exist at this time and that the switch I is open, the mechanism will stop after this lapse of sixty seconds. Thisis the look-out position.

At this lock-out position, the button ll on the front cam 01 has lust passed under and is in front of the leai spring 13 on the knob I2. The mechanism can be reoperated only by manual rotation 0! this knob counterclockwise as far as it will go, here about 45 It then may be released, and will automatically return to its first position after having displaced the cams.

At the time the mechanism stops, prior to turning the knob, the switches II, I, I", III and 81 are closed and switches 51, 88, I33, I86 and I III are open. The switches occupy these positions in Figs. 9, and 11. All circuits, including those to the primary I68, are open.

Rotation of the knob shifts the cam 61 until 5 the lobe 83 is removed from the follower 88, which rests upon the edge 85. In this position, switches 86 and 81 are both open. Rotation shifts the cam 68 beyond the notch I01 until the follower III rides on the edge I66, in which position all of its switches I08, I68 and III! are open. Rotation also shifts the cam 63 until its follower I36 falls onto the edge I3I, in which switch I33 is closed, switches I34 and I35 open.

Thus, rotation of the knob advances the mechanism to a short distance beyond the start of the scavenging period, skipping the intermediate period and running period. The control motor is in circuit, and completes its cycle. Here, again, the fact that the switch 81 is open prevents operation of the relay, and enables the scavenging is to occur. If the room thermostat demands at the end of the cycle, the mechanism will start over again.

In case of flame failure during the running period, occasioned by break of fuel supply or any familiar cause, the igniter being in circuit will normally restart the flame before the failure is eff ctive on the stack switch. If the stack switch cools to open the switch and close the switch during the runningperiod, as switch 86 is, open, the primary will be deenergized, the switch I 63 will close with contact I64, the scavenging period will occur and the mechanism will return starting position where it will be under control oi the room thermostat. If the thermostat continuesto demand heat, a new cycle will begin. If flame. failure was due to some cause that prevents ignition in the new cycle, the mechanism will pass to the lock-out position.

In case of power failure and restoration dur ing the first twelve and one-half seconds during which the switch 86 and the instituting circuit are closed, the mechanism will take up where it left off. Upon power failure between twelve and one-half and sixty seconds, the coils I60 and I6I i will be deenergized, opening the switch I66, and

shifting the switch I63 to the contact I 64.

Restoration of power will produce circuits around the switch I63, through switch I34, but the coils will not be reenergized because the switch I66 is open. The control motor will run, through switches I34 and I89, the ignition device through switch III), and the burner motor through switches I35 and 81., when the sixty point is reached, the switch I69 opens, but if ignition has occurred, the switch 51 has closed, and the burner motor continues through switches I34 and 51, with the control motor continuing through switches I34, 51, 81 and I35, and the nition device through switches I34, 51 and new- 1y closed switch I88. The cycle will continue to theseventmsecond interval, the normal start of the running period. At this point, switches I34 and I35 open. This breaks the circuit to the burner motor, because the switch I63 is closed with contact I84. However, at this time, the switch I33 has ciosed, so that the normal scavenging period is established, and the mechanism will complete it and restart, if the thermostat demands. It thus may be said that the power condition at twelve and one-half seconds predetermines what will happen at seventy seconds, viz., whether the running period will occur or not.

If power fails and is restored during the inposite positions.

termediate interval between sixty and seventy seconds, the coils I and I6I will be deenerize'd, switch I63 shifts to contact I64, and switch I66 opens. As the switch I33 is open at this time, lock-out will result, unless the power failure occurred so near the end of the intermediate period that the control motor coasted to a point closing the switch I33, and thereupon setting the mechanism for a scavenging operation upon power restoration.

If power fails and is restored during the running period, the coils will be deenergized, the switch I63 shifted to the contact I 64, and the scavenging eriod started at once, returning the mechanism to starting position.

If power fails and is restored during the scavenging period, the mechanism will take u where it left off, By considering the wiring diagram, it may be seen that the switch 86; when closed, permits the instituting circuit to be closed. The switch opens prior to lock-out to render the look-out effective, since otherwise the circuit to the primary would not be broken by opening of the switchfIIliI, and the control motor, ignition and burner motor could continue by circuits through switches 86, 58, I66, either I35 or 81, with I08 and III). The switch 86 opens also to render th mechanism subject to power failure.

The switch 58 has the function of preventing recycling if the switch 51 fails in hot position, because the switch 58, under such circumstances, will be. open, prohibiting closing of the in'stitutin circuit, the two switches being mechanically disposed to be operated by'the switch blade in cp- If the switch fails cold, the instituting circuit will be broken, as noted, by the switch 86, and lock-out will occur.

The switch- I34, as noted, insures a starting cycle up to lock-out once the control motor has operated to close it, regardless of the condition of the room thermostat. If ignition does not take place-prior to opening of the switch I08. lockout will occur. If ignition does occur, then the opening of the room thermostat will release the switch I63 to contact I65, and will open the switch I66, but the burner motor will remain in circuit through the switch 51, the control motor through 51, 81 and I35, until the switch I34 opens, and the switch I33 simultaneously closes, establishing the scavenging period. -Hence, operation of the room thermostat during any phase of the starting period does not disrupt the normal cycle. s,

The switch I 63 is a selector switch, determining whether the scavenging or operating circuits of the control motor shall function. It, of course, interlocks its circuits with the room thermostat. and the selection it makes is dependent upon the room thermostat. Likewise, it selects in response to heme failure, when it is dependent upon the switch 51 for its position, and it selects in response to power failure, when it is dependent upon the switch I86. Its holding circuit, being at times dependent upon flame switch 51, power failure switch I66, and the room thermostat I61, its selection depends upon the conditions of these switches.

The switch I66 is the power failure switch. As it controls the holding circuit for the room thermostat and the selector switch, it controls the entire mechanism for power failure. It is ineffective only when the instituting circuit is closed.

The switch I33 controls the scavenging opera,-

tion. Upon failure of ignition, with lock-out,

the selector switch droos over to scavenging position. If the switch I38 were not present, lock-- out could not occur. as the scavenging cycle would' start forthwith. Thus, the switch I" spaces the start of scavenging from the point of lock-out.

The switch I is the look-out switch. When mentioned manner of rendering the lock-out circuit efiective.

The switches liil and Ill, thelatter with the switclfllfi, control operation of the igniter.

The switch 81 has two primary functions. If it were not present, the initial burner motor circuit would be closed upon closure of the switch I, prior to energizing the igniter, an obvious disadvantage. Also, if it were not present, there would be a burner motor circuit immediately upon closing of the room thermostat and the switch i", through 8', 58, I", the circuit across I1 and the burner motor. The switch l'l must be open during the effective period of the instituting circuit and until it is desired to energize the burner motor; it must be closed to operate the energizing circuit; and it must be closed durin the second phase of the starting period and during the running period to close the holding circuit for the selector switch, the power failure switch and the room thermostat circuit.

The switch I is clearly a fiarne safety switch. Its being in series with the power failure relay holding switch causes it to control the entire mechanism, and when opened to effect deenergization of the entire mechanism, unless a proper recyclingoccurs. If it fails cold, lock-out results; if it fails hot, no starting can occur, as above noted in connection with its companion switch ll.

It will be seen that no separate power failure relay is here required, owing to the connections making the main relay into a power failure relay. The resistor shown controls the amount of current in the transformer and thermostat circuit.

In the foregoing, the object has not been to explain every function of each switch and each circuit, but rather to elucidate some of the purposes of the several parts. It may be noted, for instance, that the use of a choke coil and separate thermostat circuit to short circuit it as well as to receive a utilitarian current could be replaced by a direct connection of the thermostat and the relay coil. Other like substitutiom could be made within the scope of the appended claims.

What is claimed is:

1. Inamechanismofthekinddescribed,afuel supply device, a thermostat, a circuit for the thermostat, a first switch in said circuit, a circuit for the supply device, including means connecting the supply device circuit into the thermostat circuit after the first switch, and dependent upon continued power to hold the thermostat circuit through said connection independently of the first switch, timing means to open the first switch and to close the fuel supply device circuit at the same time, and means to start operation of the timing means upon closure of the thermostat circuit.

2. In a mechanism of the kind described, a fuel supply device, a timing device having a plurality of cam switches for producing a complete cycling operation of the fuel supply device, means including a cam operated switch adapted to be opened to stop operation of the timing device short of the end of the cycle, and means to displace the camswitchestocauserestartingofthetiming device.

3.Inamechanismofthekinddescribed,a burner, a fuel supply device, a control means for the fuel supply device to provide a first period during which ignition may ordinarily occur and a running period for the burner, a power failure relay including a relay switch, means to cause energization of the relay to effect closure of the relay switch, a circuit through the relay switch for starting the control means, a shunt circuit closed by the control device after its operation has begun, to maintain the control device in operation for the first period independent of the relay, and means to prevent reenergiaation of the relay upon failure of power during the said first period, independent of the existence or lack of combustion.

4.'Ina mechanism ofthe kind described, a burner, a fuel supply device, a first control for the fuel supply device adapted for movement to open and closed positions, a second control means for the fuel s pply device adapted to provide a first period during which ignition may normally occur, and a running period thereafter, a circuit for the second control means adapted to be closed upon closure of the first control means, means operated by the second control means to maintainthesecond controimeansinoperationfor said first period regardless of opening of said first control during said first period, and means to prevent the existence of the running period if the first control is opened during said first period during operation of said maintaining means.

5. In a mechanism of the kind described. a fuel supply means. a first control therefor, a second control adapted to provide a first period of operation' of the fuel supply means during which ignition may occur. and a running period thereafter, said first control being operable to two positions, a first circuit for the second control through the first control in its first position. and a second circuit for the second control through the first control in second position, means to operate the first control to second position to cause operation of the second control through said second circuit, means operated by the second control means to maintain said second control in operation for the first period regardless of the position of the first control, and means maintaining said second control in operation after said first period through said first circuit, whai saidfirstcontrolisinitsfirstpositionattheend of said first period.

6. Inamechanismof the kind described, afnel supply means, a first control therefor a relay and a relay switch. the switch being actuated from a first position when the relay is deenergized to a second position when it is energized. thermostatic means operable to cause energization of the relay only when a predetermined temperature condition is reached, a second control adapted to provide sequentially a first period of operation of the fuel supply means duringwhichignitionmayoccuhandarunning a second circuit for the second control through the first control in first position, and said maintaining means being adapted to render the second control subject to continued operation through the relay swith in first position at the end of said first period when said relay switch has returned to its first position.

7. In a mechanism of the kind described, a burner, a fuel supply device therefor, a control means to provide a first period during which ignition may occur, and a running period for the burner, a power failure relay including a relay switch, means to cause energization of the relay to effect closure of the relay switch, a circuit through the relay switch for starting the control device, a circuit for starting the fuel supply device, means to maintain the control device and the fuel supplv device in operation for the said first period independent of the relay, and means to prevent continued operation of the fuel supply device after'said period upon failure of power and release of the relay during said period. j

8. In a mechanism of the kind described, a burner, a fuel supply device therefor, a. control means to provide a first period during which ignition may occur, and a running period for the burner, a power failure relay including a relay switch, means to cause energizatlon of the relay to effect closure of the relay switch, a circuit through the relay switch for starting the control device, a circuit for starting the fuel supply device, means to maintain the control device and the fuel'supply device in operation for the said first period independent of the relay, an additional circuit for the fuel supply means dependent upon the energization of the relay, the opening of said maintaining means'rendering the fuel supply means dependent upon said additional circuit, and means to prevent reenergizatlon of the relay once it has'been released. I

9. In a mechanism of the kind described, a burner, a fuel supply device'therefor, a control means toprovide a first period during which ignition may occur, and a running periodfor the burner, a power failure relay including a relay switch, means to'cause energization of the relay to effect closure of the relay switch, a circuit through the relay switch for starting the control device, a circuit for starting the fuel supply device, means to maintain the control device and the fuel supply device in operation for the said first period independent of the relay, an addi- 10. In a mechansim of the kind described, a

burner, a fuel supply means therefor, a power failure means, a control "mechanism adapted to provide a first period for the burner during which I ignition may occur, an intermediatepe'riod, and a running period, means to cause starting of the fuel supply means during the first period, means dependent upon existence of conibustion to maintainthe fuel supplymeans in operation for the intermediate period, and means dependent upon combustion for maintaining the fuel supply means in operation for the running period, means to maintain the control mechanism in operation for the first period independently of the power failure moans, means to maintain the control mechanism in operation for the intermediate period independently of the power failure, means but dependent upon combustion, and means to stop the fuel supply means but to maintain the control mechanism in operation after the intermediate period upon failure of power during the first period. I

11. In a mechanism of the kind described, a fuel supply means to supply fuel to be ignited, control means to provide sequentially a starting period during which combustion may occur, and

'a running period, automatic means to start the means responsive to existence of combustion to maintainsaid fuel supply means in operation,

power failure means adapted to render the fuel supply means inoperative, and means to continue operation of the fuelsupply means for additional time upon failure of power for an interval too short to cause the means responsive to combustion to'renderthe fuel supply means inoperative.

13. In a mechanism of the kind described, a fuel supply device, a control mechanism adapted to provide sequential operations for the fuel supply device, a combustion-responsive device closed upon existence of combustion, means to effect starting of the control mechanism, circuit means through the combustion responsive device including a branch for the control mechanism and a branch for the fuel supply device, means in the control mechanism to render the control mechanism and fuel supply device dependent upon said circuit means, means in the control mechanism branch operated by the control mechanism to render the control mechanism inoperative, a power-responsive means having a switch controlling said circuit'meanaand a coil, said circuit means having a third branch providing a coil energizing means, and means under control of the control mechanism to maintain said third branch closed when the control mechanism branch is opened, and an additional circuit to the control means adapted to be closed through the powerresponsive means switch when the coil is deenergized. I

14. In a mechanism of the kind described, a burner, a combustion-responsive means operable to hot or cold positions, means to cause the burner to operate for a running period dependent upon the combustion-responsive means, means providing a, scavenging period after the running period, said scavenging period means being adapted to operate after ,a running, period whether or not the combustion-responsive 'means operates to hot or cold position, means to prevent re-establishment of operation of the burner unless the combustion-responsive means is in cold position, and means to insure capacity to recycle if the combustion-responsive means is in cold position;

15. In a mechanism of the kind described, a burner, a relay switch, a combustion-responsive switch, a control mechanism, means to operate the control mechanism to provide sequential operation of the burner, a circuit for the burner including the relay switch and the combustionresponsive switch in series, whereby when either switch fails to function the burner may nevertheless be controlled by the other, and means to prevent restarting of the control mechanism upon failure of the relay switch and opening of the combustion-responsive switch.

16. In a mechanism of the kind described, a burner, a first control switch responsive to predetermined conditions, a combustion-responsive switch, a control mechanism including a plurality of sequentially operated switches, a first circuit including a control mechanism switch to maintain the control mechanism in operation for a predetermined interval, a second circuit means including the combustion-responsive switch to maintain the control mechanism and the burner in operation for an additional period, and a third circuit including the combustion-responsive switch and the first control switch in series to maintain the burner but not the control mechanism in operation after said additional period, whereby upon failure of either the combustionresponsive switch or the first control switch to open, the burner remains under control of the other switch.

17. In a mechanism of the kind described, a control device, a fuel supply device, a first switch, a second switch, said control device being adapted to maintain the first switch open when the second is closed, a first circuit including a branch to the control device and a branch to the fuel supply device, means to control said first circuit, to control both devices, said first switch being in the fuel supply device branch, and a second circuit for the control device including said second switch, whereby when the first switch is closed both devices may be energized through the first circuit, and when the first switch is open and the second closed, the control device may operate without operation of the fuel supply device.

18. In a mechanism of the kind described, a

control device, a fuel supply device, a first switch, a second switch, an ignition-responsive switch, said control device being adapted to maintain. the first switch open when the second is closed, a first circuit including a branch to the control device and a branch to the fuel supply device, means to control said first circuit to control both devices, said fuel supply device branch including said first switch whereby both devices may be operated through said first circuit when the first switch is closed, a second circuit to the fuel supply device including said combustion-responsive switch, whereby both devices may operate together through said second circuit when said ignition-responsive switch and first switch are closed, and whereby upon opening of the first switch said fuel supply device alone may be operated through the second circuit, and a third circuit for the control device including said second switch but not said first switch, whereby when the second switch is closed and the first open, the control device may be operated without the fuel supply device, and means to select the first or the third circuit.

19. In a mechanism of the kind described, a control device, a first circuit adapted to institute operation of the control device, a second circuit adapted to continue operation of the control device, a. connection between the circuits and dividing the first circuit into two parts, means operated through the second part of the first circuit to control the closure of the second circuit, a first 16 switch in the first part of the first circuit, and a second switch in the second circuit, said second switch being adapted to be opened to break the second circuit, and means opening the first switch as early as the second switch is opened.

20. In a'mechanism of the kind described. a control device, a first circuit adapted to institute operation of the control device, a second circuit adapted to continue operation of the control device, a connection between the circuits and dividing the first circuit into two parts, means operated through the second part of the first circuit to control closure of the second circuit, a first switch in the first part of the first circuit, and a second switch in the second circuit, said second switch being adapted to be opened to break the second circuit, and means opening the first switch as early as the second switch is opened, together with a fuel supply means, and a connection between the fuel supply means and the second circuit to cause operation of the fuel supply means when the second circuit is closed.

21. In a mechanism of the kind described, a control device, a first circuit adapted to institute operation of the control device, a second circuit adapted to continue operation of the control device, a connection between the circuits and dividing the first circuit into two parts, means operated through the second part of the first circuit to control closure of the second circuit, a first switch in the first part of the first circuit, and a second switch in the second circuit, said second switch being adapted to be opened to break the second circuit, and means opening the first switch as early as the second switch is opened, together with a fuel supply means, a connection between the fuel supply means and both the first and second circuits, switch means in said lastnamed connection, and means to maintain said last-named switch means open during closure of the first circuit.

22. In a mechanism of the kind described. a control device, a first circuit adapted to institute operation of the control device, a second circuit adapted to continue operation of the control device, a connection between the circuits and dividing the first circuit into two parts, means operated through the second part of the first circuit to control closure of the second circuit, a first switch in the first part of the first circuit, and a second switch in the second circuit, said second switch being adapted to be opened to break the second circuit, and means opening the first switch as early as the second switch is opened, together with a fuel supply means, a connection between the fuel supply means and the second circuit to render the fuel supply means dependent upon the second switch, a third circuit means dependent upon combustion to maintain the fuel supply means in operation upon opening of the second circuit, a switch means in the last-named connection between the third and second circuits, and means to maintain said last-named switch means open when the first circuit is closed.

23. In a mechanism of the kind described, a control device, a first circuit adapted to institute operation of the control device, a second circuit adapted to continue operation of the control device, a connection between the circuits and dividing the first circuit into two parts, means operated through the second part of the first circuit tocontrol closure of the second circuit, a first switch in the first part of the first circuit, and a second switch in the second circuit, said second r 17' switch being adapted to be opened to break the second circuit, and means opening the first switch as early as the second switch is opened, together with a fuel supply means, a connection between the fuel supply means and the second circuit to render the fuel supply means dependent upon the second switch, a third circuit means dependent upon ignition to maintain the fuel supply means in operation upon opening of the second circuit, a switch means in the last-named connection between the third and second circuits, and means to maintain said last-named switch means open when the first circuit is closed, said third circuit including a switch means dependent upon the existence of combustion to be closed.

the control means switch, the combustion-responsive switch, and the fuel supply device, a connection leading from the second circuit after the combustion-responsive switch to the timing means, said connection including the second timing means switch, said timing means being adapted to have its first switch to be closed at the start of a cycle and to open a, time interval thereafter, and being adapted to close its second switch before opening of its first switch, and to open itla time interval after opening of the first timing means switch, plus a third timing means switch and connections including the same to 24. In a mechanism of the kind described, an

operated device, a control mechanism including a plurality of switches, said control mechanism being adapted to operate the switche sequentially, circuit means including said switches, and adapted to provide sequentially a starting period, a lock-cut, an intermediate period, and a return period, for the operated device. said switches being bodily displaceable independently of operation of the control mechanism, and means to displace the switches from lock-out position to return position.

25. In a mechanism of the kind described, a control mechanism having a plurality of sequentially operated switches, and means for operating the same, a fuel supply device, means including at least one of said switches to provide a starting period for the fuel supply device, means including at least one of said switches to provide a look-out for said device, means including at least one of said switches to cause said control mechanism to restart after said lock-out, said switch operating means being displaceable independently of operation of the control mechanism, and means to displace said switch operating shunt the control means, said timing means being adapted to close said third switch after the timing means has started, and to open the same after a predetermined interval during which combustion may occur.

28. In a control mechanism, a control means operable in response to predetermined conditions, including a, switch, a fuel supply device, a timing means, a first timing means switch, a second timing means switch, a combustion-responsive switch, a first circuit to the timing means including the control means switch, the first timing means switch, and the timing means, a second circuit for the fuel supply device including the control means switch, the combustion-responsive switch, and the fuel supply device, a connection leading from the second circuit after the combustion-responsive switch to the timing means, said means independent of the control mechanism tion-responsive switch to the timing means, said connection including the second timing means switch. said timing means being adapted to have its first switch to be closed at the start of a cycle and to open a time interval thereafter, and being adapted to close its second switch before opening of its first switch, and to open it a time interval after opening of the first timing means switch.

2'1. In a control mechanism, a control means operable in res onse to predetermined conditions, including a switch. a fuel supply device, a timing means, a first timing means switch, a. second timing means switch, a combustion-responsive switch, a first circuit to the timing means including the control means switch, the first timin: means switch. and the timing'means. a. secand circuit for the fuel supply device including connection including the second timing means switch, said timing means being adapted to have its first switch to be closed at the start of a cycle and to open a time interval thereaftenand being adapted to close its second switch before opening of its first switch, and to open it a time interval after opening of the first timing means switch, plus a scavenging timing means switch, and connections including the same, said connections including the (control means switch in inoperative position, and the timing means, said timing means being adapted to close said scavenging switch after the timing means has started, and to maintain it closed for a predetermined time after the second timing means switch has opened, until the timing means returns to its starting condition.

GEORGE D. BOWER.

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

UNITED STATES PATENTS Number Name Date 1.877037 Parker Sept. 13, 1932 2.139504 King Dec. 6, 1938 2,085 577 Eaton June 29, 1937 1,888,602 Macrae et a1 Nov. 22, 1932 2,078,109 Townsend Apr. 20, 1937 I 1,732,174 Sweatt Oct. 15, 1929 1,883,242 Bogle Oct. 18, 1932 2021,647 DeLancey Nov. 19, 1935 1,991.185 Williams Feb. 12, 1935 1,774,137 Good at al Aug. 26, 1930 2,160,592 King May 30, 1939 FOREIGN PATENTS Number Country Date 173,006 Swiss Nov. 15, 1934

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