US2503260A - Burner control system - Google Patents

Description

April 11, 1950 w. D. HALL 2,503,260

BURNER CONTROL SYSTEM Filed Dec. 4, 1945 2 Sheets-Sheet 2 Patented Apr. ll, 1950 UNITED STATES PATENT OFFICE animan. ooN'raoL srs'rm wmum n. mu, wuninmn, n. o.

museum December 4, 194s, sein se. sans s claim. (ci. s-zal l 'I'his invention relates to control systems and more particularly to means for controlling a burner. The primary object 'of this invention is to provide a simple and inexpensive control system that is safe in operation. Other objects of the invention include the provision of means whereby the control operations are performed rapidly when rapid operation is desired for safety reasons.

Briefly speaking the detailed character of the invention is that a massive slidable member is moved by a bimetallic strip, which strip is responsive to the heat from the burner, and the position of this member with respect to fixed reference controls the energization of the igniter. The fuel flow to the burner is controlled in accord with the lost-motion" action of the slidable member and the bimetallic strip. `The circuit 'to the fuel controller of the burner is closed for a limited time period by mechanical means such as a relay or by mechanically bringing together contacts which may be respectively located on the bimetallic strip and the slidable member. Further details ofthe invention will hereinafter appear as will further objects and advantages.

In the drawings:

Figure 1 is a schematic diagram of one form of the invention and employs a relay for closing the circuit to the fuel controller.

Figure 2 illustrates by schematic diagram another form of the invention in which electromagnetic means are employed to attract a leader attached to the bimetallic strip to close the circuit to the fuel controller.

Figure 3 is a top view of a burner having a control system embodying the invention thereon.

Figure 4 is a sectional view of another form of my invention, except that Bourdon tube |03 is shown in perspective, and the parts encircled by line |50 are in a plane at right angles to that shown.

Referring specifically to the form, of invention shown ln Figure 1, a burner Il is schematically illustrated. In actual practice the burner may be any conventional gas, gasoline. or oil, burner, or any other form of burner. An igniter shown as an igniter of the hot-wire type, is located in igniting relationship with the burner. A valve I2 is controlled by a solenoid II. A bimetallic strip I4 is fixed at its lower end and has a free end extending into a slot in the metallic massive slidable member I5. The rear arm of the member I5 is an insulating member II which is rigidly attached to the member I5, The slid- 2 able member Il slides on the square bar Il, the member I! having .a rectangular hole therethrough. No substantial forces other than friction and the bimetallic strip I4 functionally have any effect on the bimetallic strip I4, or on the slidable member Il. A` switch designated generally at Il may be of the ,commercial type known as the Microswitch" nianufactured by Microswitch Corporation, Freeport, Illinois. Bo far as is necessary for an understanding here. the switch Il consists of a stationary contact 22. a snap-member 2l, and a trigger member 2|. When thel bimetallic strip Il cools to a sufllcient degree it will move its free end to the right thus moving the slidable member Il to the right thus moving the trigger member 2| to the rightrand causing the snap member 2l to snap its lower end to the right and close a circuit with contact 22. 'I'he normal off position of the apparatus is that bimetallic strip Il is completely cool, its

upper end forcing members Il and Il to the right, and with the circuit closed at contact point 22. An electrical relay 2l has an amature 2l which is normally in open-circuit relation with '25 contact point 21. The parts 25, 2l, 21 and 2U form the usual latch-out safety switch which is well known in the art. Briefly these parts are the biased spring elemen 2l which will move down and away from sta ionary contact point 28 if and when the bimetallic strip 21 is sumciently heated by electrical heater 2l.

The operation of the device of Figure 1 is as follows. When the thermostat T closes current flow via the following path: 30-26-25-3 |-20- 32-33-20-22-49-4 I-u--Il Hence the igniter warms up and the relay 23 clem its armature. The latter operation clom another circuit as follows: lil--Z--sI-Il-N-M- 31-4 |-|338-35. 'Ihis operation causes the valve |2 to open thus enabling fuel to flow to the burner III where it is ignited by the igniter Heat from the flame causes bimetallic strip i4 to move to the left whereby its free end soon touches slidable member Il closing another circuit as follows: 30-28-25-3I-28-32-3l- |l|5|4404||33838. As the heat of the burner increases bimetallic strip Il continues to move to the left thus causing slidable member I5 to move to the left whereby the latter disengages trigger member 2| causing the circuit` at contact 22 to be` broken thus deenergizing the igniter and the solenoid 28. Hence, the only circuit through the solenoid valve Il at this time is the onethrough bimetallic strip Il. As the temperature of bimetallic strip! 'accesso I4 rises the strip will move slidable member l5 to the left. When the temperature of the burner reaches some high temperature assume the flame at the burner is accidentally extinguished. The strip I4 will quickly reverse its direction thus dlsengaging slidable member l5 thereby closing the valve |2-3, stopping fuel iiow to the burner i0. Due to extinguishment of the name the burner will cool and strip i5 will move to the right until the slidable member i5 engages trigger 2| to reclose the ignitei` circuit at 22. Both the igniter il and the relay 23 are now energized and a circuit through the armature 2 and solenoid i3 will cause fuel to again ow to the hot igniter H. Hence the fuel will probably be relighted and the heat from the ame will cause strip i6 to move to the left to close the valve circuit at member i5 and to cause the igniter circuit to be 'broken at 22.

Assume that an initial attempt to ignite fails,

the fbimetallic strip |4 will remain bent to the right and the circuit through the ignlter il will remain closed until the heater 28 heats bimetaliic strip 2l sumciently to cause the latter to move to the right and release the biased member 25 to break the circuit at 26 to all parts of the system, thus deenergizing the igniter and the solenoid I3, and in turn closing the valve l2. Whenever, however, the initial attempt at ignition is effective to ignite the flame, the circuit z to igniter is broken and this reduces the current through heater 28 sufficient to prevent tripping of switch 25 Referring to the top view of a burner employing the control system of Figure l, namely Figure 3, we see an elongated burner l0 having the igniter and the bimetallic strip I4 at opposite extreme ends. This makes sure that the burner must ignite for its full length otherwise the safety switch `25-26---27--28 will operate. It is not necessary that all of the parts of the control system be located in the combustion chamber, since the bimetallic strip i4 is the only part that must respond to the burner heat. Therefore in Figure 3, strip i4 is located in the combustion chamber, the parts |5, Il, etc., are located just outside the combustion chamber, and the box is located at any suitable distance therefrom. y

I will now describe lthe control system of Figure 2. The two wires k"52 and.63 Iconnect to a suitable source of electricity. The burner 50, has a motor-driven pump STL-5I for feeding fuel to the burner. A spark-gap igniter 52 is fed `by wires 64-55. A spark-gap step-up transformer l0 raises the voltage to a high value for use by gap 52. A bimetallic strip 53 is fixed at its lower end and has a leader 54 of resilient magnetic material which is attached to strip 53 by rivet 55. A metallic' massive slidable member 57 has as its rear portion an insulation member 58. At the left of member 5l is a contact arm '59 adapted to engage contact t0. A large electromagnetic solenoid 6| is rigidly supported with respect to fixed reference slightly to the right of the center of slidable member 51 so that when the solenoid 5| is energized it exerts a small force tending to move member 5l to the right. The leader 54 also is of such composition as to be attracted by the field of solenoid 6|.

'I'he operation of Figure 2 is as follows. When the room thermostat T closes the circuit, current flows as follows: 62-'ll--l2--6l-60-59-51- SS-SS-T-GB. 'dlhe ow of current through this circuit causes the spark gap 52 to be energized and also causes the solenoid 6| to set upa magnetic field. The magnetic iield of coil ti does two things (1) it draws member 51 to the right thus insuring excellent contact between 59 and 00, and (2) the flux of coil 6| draws leader 54 into contact with metallic member 57. The latter operation establishes a circuit as follows: t2t`i 58--53-54-57-56-SS-T-B8. The closure of this circuit starts motor M thereby effecting iiow of fuel by pump 5|. Hence at this stage, both the Vigniter 52 and the fuel motor M are jointly operating. Assuming that the fuel ignites, the bimetallic strip '53 will move to the left pushing slidable member 57 to the left thus breaking the circuit to the transformer li and the solenoid tl. As a result the igniter 52 is deenergized but the motor M continues to run since the heat from the burner will cause continued movement of slidable member to the left with maintenance of contact between leader 50 and member 5l. Should at a later time the name become extinguished the direction of motion of bimetallic strip 53 will reverse thus withdrawing the leader from contact at 5l breaking the circuit to the motor. The burner will cool further until bimetallic strip 53 moves into contact with insulation member 58 and for such time after that as is required for strip 53 to cool enough to move member 57 suiciently far to close contacts 59 and 60. When the latter contacts close, the igniter 52 and the solenoid 5l will be reenergized and the burner will be relighted as in the case of the original attempt. If an attempt at ignition fails, safety switch SS lwill latch out after a predetermined time. It is understood of course that leader 54 is a flexible resilient member and can move rather easily under the iniiuence ofthe magnetic eld without moving the bimetallic strip 53. After leader 54 touches member 5l, the

.subsequent motion of bimetallic strip 53 will cause that strip to move to the right side of leader 54 and then push the leader and thus in turn push the member '54. It is not essential, however, that leader 54 be resilient. It may equally well be rigid provided the solenoid 5| has sufficient ampere-turns to actually bend the bimetallic strip 53 itself.

Referring now to Figure 4, there is shown a bulb |00 of Bourdon tube |03. The tube 90| connecting the bulb |00 and the Bourdontube |03 is mounted to slldably rotate in supporting block |02. Mounted at the left end of bulb i is a member |04 which carries plate |05 that in turn supports hot-wire igniter |06 above the burner |01 which may be a round burner with jets emerging from all portions of its periphery. Therefore, when the bulb |00 rotates, as will hereinafter appear, the igniter |05 will be moved at right angles to the plane of the drawing and be removed from the ame. The bulb |00 connects by tube l0! to the Bourdon tube |03 which is arranged for rotation in a plane perpendicular to the plane of the drawing paper although this tube |03 is shown in perspective. The lower end ||5 of Bourdon tube |03, carries armature Hd. The end I l5 and the armature H4 are shown in the plane of the drawing paper movable to the right and left, but as heretofore stated all of the parts inside of line |50 are in a plane at right angles to the paper. The armature l I4 is adapted to move between stops ||2 and H3. The vertical arm |5011 is pivoted at pivot I i and carries mercury switch IIO. The mercury switch ||0 is biased for counterclockwise motion by weight W, hence the arm asoaaco |60 always follows the amature III. A solenoid is arranged to attract the armature III.

When the tube |00 is in its normal olf position, the igniter |06 is over the burner |01 and the mercury switch |09 is closed. vOn closure of starting switch |49, current then flows as follows: ||6|09|08||B|06||8|2||Il Hence lgniter |06 becomes hot and armature ||4 is attracted by solenoid |06. The motion of armature I I4 to the right rotates mercury switch I0 clockwise thus closing the circuit to motor M as follows: I|6-||0-|22-|20 |2||49. As the burner |01 heats the bulb |00. the Bourdon tube |03 will push armature III to the right, keeping the mercury switch ||0 rotated to its extreme clockwise position thus keeping the motor circuit closed. Since the armature ||4 is stopped in its motion when arm |50 strikes stop H2, further heating of the bulb |00 will result in a torque being exerted on the tube |0| which is in fact also a shaft. The rotation of shaft |0| will rotate the igniter |06 away from -contact with the flame and will also rotate mercury switch |09 to break the circuit through solenoid |08 and the igniter |06. Upon extinguishment of the flame, the bulb HBO will immediately cool slightly thus causing Bourdon tube |03 to move armature I4 away from stop ||2 and into stop H3. This will happen quickly in view of the lost-motion construction previously described. Hence the mercury switch ||0 willpromptly breakA the motor circuit. Further cooling of bulb |00 will result in rotation of the bulb |00, shaft |0|, and mercury switch |09. Upon sufficient rotation to bring the igniter over the burner ports, the mercury switch |09 will close thus reenergizing the igniter |06.

It is recognized that it is difllcult to show in a single illustrative view the exact relationship of the parts of Figure 4, but it is clear to those skilled in the art that the Bourdon tube |03 will tend to uncoil when heated and that it is in a plane at right angles to the shaft |0|. The uid from bulb 00 is conducted through the shaft in the usual manner -to the tube |03. When the bulb is heated, the free end of the Bourdon tube moves the arm |50 into contact with stop |2.

I claim to have invented:

l. In a burner control system, a burner, a thermal element responsive to combustion, a support, a lost-motion driven slidable element carried by said support and moved in first and second opposite directions relative thereto by said thermal element respectively in responsey to rising and falling temperatures of said element, said slidable element being mounted on said support for unbiased .movement relative thereto, means for maintaining one end of the thermal element in fixed position relative to said support, the other end of said thermal element having a driving engagement with said slidable element, fuel control means for the burner controlled by the direction of motion of said slidable member, and an igniter for the burner normallyin igniting position and moved by said slidable element away from the burner in response to rising temperature of the thermal element.

2. In a burner control system, a slidable member, means for slidably mounting the slidable member for sliding movement, a thermal force producing element connected at one end with said slidable member and having a relatively free end, said force producing element including means tending to move said relatively free end in first and second directions with reference to the slidable member in response to heating and cooling respectively of the element and for causing motion of the slidable member when the tendency of said free end to move is restrained, means limiting the motion of the relatively free end in each of said ilrst and second directions, an armature fastened to said free end, means actuated by motion of said free end in a first direction for permitting fuel flow and for stopping fuel flow in response to motion of said free end in the reverse direction, electromagnetic means for attracting said armature in said first direction, an ignlter for the burner, a circuit for the igniter, and a switch controlled by the position of said slidable member to close the circuit to said ignlter and electromagnet when the slidable member is in a position corresponding to a low temperature of the thermal element and to break the circuit to said igniter and electromagnet in response to motion of the slidable member corresponding to a rise in temperature of said thermal element.

3. In a heating system, a burner, a Bourdon tube, a bulb for said Bourdon tube in good heat transfer relation with the burner, a fixed support, a shaft mounted for rotary motion on said support and carrying said bulb, said Bourdon tube comprising a coiled tube having its inner end connected to and adapted to rotate the shaft, stops to limit motion of the outer end of the Bourdon tube, an igniter for the burner, an igniter switch operated by rotation of said shaft to deenergize said igniter when the Bourdon tube expands, a circuit including means to control fuel now to the burner, and a fuel switch operated by the position of the outer end of the Bourdon tube to control said circuit to maintain fuel now when the Bourdon tube is expanding and to stop fuel flow when the Bourdon tube is contracting, and starting means operable to eil'ect operation of the last-named switch to thereby start the system.

4. The system defined by claim 3 in which the starting means comprises electrical means for initially moving the outer end of the Bourdon tube to thereby actuate the switch.

5. The system defined by claim 4 in which the heating system includes circuit means to deenergize the electrical means when the shaft roates in response to expansion of the Bourdon 6. The system of claim 5 in which the outer end of the Bourdon tube carries an armature, in which said electrical means is an electromagnet, in which said igniter switch is directly in series with said igniter and in series with said electromagnet, and in which said fuel switch is directly in series with the fuel control circuit and is closed to cause fuel flow when the Bourdon tube is expanding.

7. In a heating system, a fixed burner, an igniter for the burner, fuel control means for the burner, means for controlling the fuel control means comprising a thermal element responsive to heat from the burner and means responsive to the direction of motion of said element for controlling said fuel control means to admit fuel when the element is expanding and to stop fuel flow when the element changes from an expanding to a contracting motion, said second-named means including an armature which when attracted in a given direction operates the fuel control means to admit fuel flow, an electromagnet which when energized attracts said armature in said given direction, and means responsive to the relative position of the thermal element with respect to a fixed reference point for controlling the energizations of said igniter and said electromagnet to energize them when the tempe'rature of the thermal element is below a predetermined value and to, deenergize them'when the temperature of the thermal element is above a predetermined value.

8. The heating system of claim 7 in which said fuel control means includes an electrically operated element for controlling the flow of fuel to admit fuel when the element is energized and to stop fuel flow when the element is deenergized, said second-named means including a pair of contact points connected in series with said electrically operated element, said second-named means also including means for closing said contact points when said armature is attracted in said given direction, said second-named means also including an additional pair of contact points,

respective contact points o1 said pairs of points being respectively connected together.

9. The heating system dened in claim 7 in which said thermal element is supported at one end and is free to move at ay second end for a limited distance, said armature being attached to the second end of said element, said secondnamed means including electrical contacter means position? adjacent said amature and ment being disposed to tend to move said arma-- ture in said given direction when the temperature of the thermal element is rising.

WILLIAM D. HALL.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PAT\ENTS Number Name Date 1,320,936 Scott .\Nov. 4, 1919 1,674,051 McCabe June 19, 1928 1,675,897 McCabe July 3, 1928 1,693,070 Crane Nov. 27, 1928 1,720,900 Ileman July 16, 1929 1,908,495 Bogie May 9, 1933 1,969,968 Dever Aug. 14, 1934 2,149,853 McCabe Mar. 7, 1939 2,261,586 McGrath Nov. 4, 1941 2,269,443 Deubel Jan. 13, 1942 2,399,673 Hall May 7, 1946

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