US2313340A - Combustion control - Google Patents

Description

J. L. HARRIS 2,313,340 COMBUSTION. CONTROL Filed Dec. 23, 1959 s Sheets-Sheet 1 Fig. 2

Y finngnfor John I Harris March 9, 1943. J. LHARRIS I comsuswxom CONTROL Fil'ed Dec. 23, 1939 I S She'etS-Shee't 2 ,{Snvontor John I.\. Harris IIIIIIIIIIIIIIIIIIIIIIII 'ro ruma IIIIIIIIIIIII III m H NY 8 Hmmmfinmf. w W m W m J m m Patented Mar. 9, 1943 John L. Harris, Minnea polls, Minn, assignor to Minneapolis-Honeywell Regulator Company,

a corporation of Delaware 1 7 application December 23, 1939, Serial No. 310,687

Minneapolis, Minn,

11 claims. This invention relates to automatic, burner controls and more particularly to automatic controls for gas or oil fired steam boilers.

It ls an object of this invention to provide a simple burner control system which modulates the flow of fuel to a burner in accordance with the actual demand, which prevents the flow of fuel to the burner from being reduced below that necessary to provide proper burner operation,

which intermittently places the burner into and.

out of operation when the minimum operating rate of the burner is greater than the actual demand, and which places the burner out of 1 operation regardless of the demand for burner operation whenever unsafe operating conditions occur.

\ More specifically, it is an object of this invention to provide a pressure actuated burner control system of the type employing a pressure motor for regulating fuel flow with a simple and positive arrangement for regulating the flow of fuel to the burner and discontinuing operation of the burner upon the occurrence of improper oprating conditions.

Other objects of the invention will appear from th following description and the appended claims.

I and a flue ll having an uptake damper l2 therein. This damper is operated by a chain l3 running over pulle l4 and connecting to a lever l 5 attached to the main fuel valve 5. The boiler l is also provided with a low water cut-off l6 and with a safety pilot control I l. The low water cut-01f l6 includes a float operated switch (not shown) which is opened whenever the water level in the boiler falls too low. The safety pilot con trol 'Il consists of a switch which is opened by a thermostat responding to the pilot flame temperature, this switch opening whenever the pilot becomes extinguished.

Referring to Figure 2, themain fuel valve 5 consists of a valve body 20 having aninlet chamber 2| and an outlet chamber 22 separated by a partition 23 having a valve port 24 located therein. 'Thls valve is provided with the usual valve bonnet 25 having mounted thereon the packing gland 26 for the valve stem 21, this valve stem 21 carrying a valve member 28 located below the i For a full disclosure of this invention reference accompanying drawings. in which Figure 1 illustrates diagrammatically a boiler control system embodying the features of this invention,

Figure 2 is an elevationpartly insection of the fuel valve employed in Figure 1,

Figure 3 is a sectional elevation of the fuel valve controller,

Figure is a sectional view-taken on line 4-4 of Figure 3,

Figure 5 is an elevation partly in section of a modified valve controller,

Figure 6 is a diagrammatic illustration of a? modified boiler control system, and

employed in the system of Figure 6.

Referring to Figure 1, reference character I in'- l made to the following description and to the dicates a boiler having a combustion chamber 2 1 l in which is located a gas burner 3 which is supplied with gas through a pipe 4 leading from a main fuel valve generally indicated as 5, this valve being connected with a gas main 6; The burner 3 is provided with a pilot burner 'l which is connected to the gas main 6 by pipe 8 having a control valve 9 interposed therein. The boiler l is provided with the usual steam off-take pipe valve port 24. The bonnet 25 is also formed to support a diaphragm cage 29 in which is mounted the diaphragm 30. This diaphragm 30 preferably consists of a number of superposed and communicating metallic cells 3|, the topmost cell 3| engaging thebover plate 32 for the diaphragm cage. Abutting the lower surface of the lower diaphragm 3| is a pressure plate 33 which engages the head 34 of the valve stem 21. -'A spring 35 rests on the packing gland nut and engages a cup member 36 which in turn abuts the valve stem head 34. It will b apparent that by this arrangement the spring 35 serves to force the valve stem 21 upwardly thereby normally collapsing the diaphragm 3B and forcing the valve member 28 against its seat. It will also be apparent j'that'when'pressure is applied to the di-- aphragm 30, it will expand against the action of spring'35i'for moving the valve stem 21 downwardly for thereby forcing the valve member 28 vg from its seata The lever l5 for operating the V .uptakedamper' Figure 7 is a detail view of the valve controller I2 is pivoted to :a shaft 40 which may. e'xtendfrom side to side of the diaphragm cage. This lever is formed with a curved portion surrounding thecup member 36 and is provided with a pin 42 engaging a slot 4| formed in the cup member. By this arrangement downward motion of the cup member 36 will cause downward rocking of the lever l5 about its pivot 40. This in turn will cause opening of the uptake damper 2. diaphragm 3| the main gas valve to the burner is opened and the uptake damper I2 is simultaneously therewith.

Thus upon application of pressure to the opened Mounted upon the diaphragm cage 29 is the valve controller generally indicated as 45. Also mountediiponthe diaphragm cage is a filter 46 (Figure 1) the inlet of which is connected with a pipe 41 leading from the steam off-take pipe ID. The outlet of this filter is connected by a pipe 48 to the inlet of the controller 45. The outlet of the controller 45 is connected by a pipe 49 (Figure 2) which is formed partly coil shaped and which is connected to. the diaphragm 3D. The filter 46 is also provided with the usual blow down connection 50 having a blow down valve located therein.

Referring now to Figure 3 the construction of the valve controller will be described. This valve controller consists of a casing 53 housing a pilot valve mechanism generally indicated as 54. This pilot valve mechanism includes a valve casing 55 which is secured to a restrictor member 56. This restrictor member is shown in detail in Figure 4 and is provided with an inlet passage 51 to which is connected the steam line 48 of Figure 1 which leads from the filter Q6. The restrictor member 51 is provided with a restriction 58 which cooperates with a needle valve member 59 in controlling the flow of steam from the inlet passage 5'! into an outlet passage 60. This outlet passage 60 is connected to the pipe 49 which leads to the diaphragm 30 of the main valve 5. It will be apparent that by adjusting the needle valve 59, the rate of flow of filtered steam from the boiler into the outlet passage 50 may be varied as desired. The outlet passage 60 is provided with a downwardly extending passage 6| which coincides with a passage iormed in the valve casing 55 and communicates with a bleed port member 62 which extends downwardly into thechamb'er G3 in the valve casing 55. The valve casing'55 is provided with a'threaded opening in its bottom wall for receiving a pilot valve guide member or plug {54 which is bored out to provide a guide for the pilot valve plunger 65, this plunger being secured to a sleeve member 66 carrying a crater shaped valve disc 61 cooperating with the bleed port member 62 in controlling the bleed of steam from the outlet passage 60 of the restrictor member. It will be apparent that movement of the valve plunger 65 will vary the pressure maintained in the outlet passage 50 and in the diaphragm 30 of main valve 5. Thus upon upward movement of the valve stem 65 the valve disc 61 will be shifted closer to the bleed port 62 thereby decreasing the flow of steam from the'outlet passage G0 which will cause the pressure in this passage and in the diaphragm 30 to-increase which will cause expansion of this diaphragm against the action of the spring 35 from opening the fuel valve and'uptake damper. The valve casing 55 is connected to a drain pipe '10 which conveys steam and condensate issuing from the bleed port 62 to a suitable drain. In order to prevent steam or condensate from escaping from the valve casing 55, the guide member 64 is provided with a stuffing box 1| which prevents escape of sterm or condensate around the valve plunger 65.

The valve plunger 65 is raised and lowered by means of a fioating lever I2. The right hand end of this lever 12 is carried by a knife edge I3 foirned on a link 74 which in turn is pivoted at to the clapper or armature '16 of an electromagnetic actuating device 11 such as employed in the well known clapper type electric relay. The electromagnetic device includes a stationary electromagnetic coil which attracts the clapper or armature 16 which is pivoted at the rear as appears in Figure 3, When the coil or electromagnet is energized the clapper IE is pulled upwardly which thereby causes the link 14 to be likewise pulled upwardly to a fixed position. However, when the electromagnet is deenergized, the clapper 16 will drop thereby causing the link 14 to be lowered. The left hand end of the floating lever 12 is carried normally by an adjusting screw mounted on lever 8|, this lever being pivoted at 82 and being actuated by a plunger 83 which is actuated by a bellows 84. This bellows 84 is surrounded by a cup 85 which is connected by a pipe 86 to the blow down pipe 5|! leading from the filter 46. Bellows B4 is therefore subjected to the steam pressure in the boiler. This bellows is biased by means of a spring 81 which urges the lever 8| in the clockwise direction about pivot 82. The spring 8| may be varied in tension by means of an adjusting nut 88 carried by a stationary screw 89. This adjusting nut may also carry an indicator 90 which extends through a slot 9| in casing 53 thereby indicating the pressure for which the instrument is adjusted.

Reference character indicates a follow-up lever which is pivoted to a shaft 96 carried by ears 9'! formed in the back of the casing 53, this follow-up lever extending through a slot 98 in the back of the casing and rearwardly to a point beneath the diaphragm 0 (Figure 2). This lever 95 is provided with a slot 99 for receiving a threaded actuating member or screw I00 which abuts the pressure plate 33. The end of the follow-up lever 95 which extends within the casing 53 is attached to a follow-up spring 12 which in turn is attached to the lever 8| immediately above the plunger 83. This follow up spring I02 thus serves to ur'ge the lever 35 in a clockwise direcdon as viewed in Figure 2 thereby maintaining the screw 10b in engagement with the pressure plate 33. It will be apparent that upon downward movement of the pressure plate 33 the lever 95 will be rotated counter-clockwise thereby increasing the tension or: spring H12 and that upon upward movement of the pressure plate 33 the lever 95 will be iotated in the opposite direction ior decreasing the tension on spring I02.

It will be apparent that the position assumed by the lever 8| is dependent upon three forces, namely, a counterclockwise force produced by the pressure on bellows 84, a clockwise force produced by the biasing spring 81 and a counterclockwise forccproduced by the tension followup spring I32. Under no mal operating conditions as will be presently described more in detail, the electromagnetic device will be energized which causes the right hand. end of the floating lever 12 to be stationarily pivoted in normal position as shown in Figure 3. Upon a decrease in boiler pressure, the force produced by bellows 84 will decrease thereby .causing ,the lever- 8| to be rocked clockwise by the biasing spring 31. This will cause the left hand end of the floating lever 12 to be raised which will in turn raise the valve plunger 65. This will cause the valve disc 61 to approach the bleed port 52 for reducing the rate of bleed of steam from this port thereby increasing the pressure applied to the diaphragm 30. This increase in pressure will cause diaphragm 30 to expand thereby drivingthe valve stem 21 downwardly against the action of spring 35 for opening the gas valve wider and simultaneously rocking le er l5 for opening the lfl gun of the lever 95 about its pivot thereo; .s'ng tension on the follow-up spring .02. This increase in tension on the spring 592 will serve to cause the left hand. end of lever 8| to be lowered as the main valve opens thereby lowering the pilot valve plunger 65 and increasing the rate oi bleed from the passage M which loware the pscssure apd to the diaphragm 30. In other wor as #11. diaphragm 30 expands due LO the increase in pressure applied to it. the pilot valve is repositioned by tr e follow-up spring for lowering the pressure applied tothe diaphragm. By this arrangement a point is reached wherein the pressure applied to the diaphragm is just sufficient to maintain it stationary against the action of biasing spring 35. Stated another way, upon a decrease in boiler pressure, the valve plunger 65 will be initially shifted considerably farther than necessary in order to cause the main valve to assume the desired position. Then as the main valve approaches the desired positicri the pilot valve is forced back by the increase in tension on the follow-up spring so that when the main valve reaches the desired position,

the pilot valve is positioned for just maintaining the main valve stationary. This arrangement in which the pilot valve is initially positioned. farther than necessary and returned to 16 proper position, provides a positive driving force for causing the valve to assume the proper position in spite of friction either inthe valve packing gland or in the uptake damper operating mechanism. Upon an increase in pressure in the boiler the opposite action will occur, namely, the lever M will be rotated counter-clockwise for low ering the end of lever l2 and thus lowering the valve plunger 65 which increase the rate of bleed through port 62. This decreases the'pressure applied to the diaphragm which permits the spring 35 to-cause upward movement of the valve stem for closing the valve and uptake damper. This upward movement permits clockwise rotation of th( follow-up lever 95 which decreases the tension on the follow-up spring H12, thi in turn causing clockwise movement of lever 85 for raising the valve pluhger 55. Thus when the main valve reaches the proper position for the existing boiler pressure, the valve plunger 65 is positioned for maintaining the main valve in this correct. position. With this positive follow-up arrangement it will be apparent that the valve plunger 65 will be positioned for applying as necessary either maximum pressure or zero pressure to the diaphragm 30 for causing it to move to the position demanded by the bellows 84. It should be noted that in the event of failure of the follow-up spring [02 the system will still continue to function and the only resultof such breakage will be a hunting action of the valve due to the fact that the valve plunger 55 is moved more than necessary by the bellows B l.

In the control of a gas burner it is essential that. the flo of gas to the burner must not be reduced below an amount necessary to maintain the burner in proper operation. In order to prevent the control system just described from reducing the flow of gas to the burner below the minimum allowed amount, provision is made for taking control of the valve plunger 65 away from the bellows 3% whenever this bellow attempts to close the valve beyond a predetermined minimum position. This minimum positlon'arrangement includes a lever Hll carrying an adjustment screw HI and being pivoted to a. knife edge member H2. The lever H0 is also attached to a minimum position follow-up spring H3 which is in turn attached to a horizontal extension Ht of the follow-up lever 95. The lever HE is also attached to a minimum position adjusting spring I it which is attached to an adjusting screw Hh mounted upon a bracket H1. It will be apparent that as the diaphragm 30 expands for opening the gas valve, the follow-up lever will be rotated for increasing the tension of spring H3. The tension on spring H3 is therefore dependent upon the valve position. The adjusting spring H5 due to its being connected to the lever Hil on the opposite side of the knife edge member H2 from the spring H3 acts as a balancer for spring H3. When the main valve is opened beyond the desired minimum position as determined by the tension of spring H5 the tension of spring H3 will overcome spring H5 for rocking the lever H0 countor-clockwise thus causing the screw HI to be entirely disengaged from the floating lever 12. However, as the main valve closes, the tension on spring H3 will be reduced which will permit the spring H5 to rotate lever Hi3 clockwise for causing the adjusting screw HI to engage lever '12 at the time that the main valve assumes its minimum position. Now the valve plmger 65 will be held up by the lever HD independently of the lever 8!. Consequently the lever 8| is incapaole of causing the main valve to be closed beyond the predetermined minimum position. By adjusting the tension of spring l Hi the minimum position may be readily adjusted as desired. Thus by increasing the tension on spring H5 the main valve must be open a greater extent before the spring H3 overcomes the tension of spring H5 and thus the valve is opened wider at its minimum position. Conversely as the tension on spring H5 is decreased the valve is permitted to close'a greater extent.

Theenergization of the electromagnetic device i1 is controlled by the low water cut-oil IS, the

safety pilot control ll, and also by a mercury switch l20 which is located within the casing 53. This mercury switch is mounted upon a pivoted switch carrier l2! having a slot I22 therein which receives a'pin I23, this pin being carried by a lever 12d attached to the lever 81. The mercury switch I20 is therefore actuated by the bellows 8% which responds to boiler pressure. Upon an increase in boiler pressure/the lever'ill and its extension lid are rotated counter-clockwlse which causes rotation of the mercury switch clockwise to open position. The parts are so proportioned and adjusted that the mercury switch !20 remains closed as shown) when the boiler pressure is within the normal operating range of the pilot valve. However, when the boiler pressure rises slightly above this normal operating range, the mercury switch I26 is opened.

Referring again to Figure 1, reference character 28 indicates a step-down transformer one terminal of which is connected by wire Hi to the low water cut-oil it. This low water cut-off is in turn connected b wire 92% to the safety pilot control I! which is in turn connected by wire !29 leading to the electromagnetic device ll of the valve controller. This device is in turn connected by wire itl'l (Figure 3) to the mercury switch 320, the other terminal being connected by a wire 13% to a pressure responsive device I32, this ergize the electromagnetic device I1.

ln turn being connected by wire I 33 to the transformer I26. The pressure controller I32 is connected by pipe I34 to the pipe 43 which leads from the outlet passage 60 of the restrictor device 56 to the diaphragm 30 of the main valve. This controller I32 therefore responds directly to the steam pressure in the diaphragm 30. Its function is to open its switch whenever the pressure in diaphragm 30 rises to the maximum pressure which the diaphragm 30 may safely be subjected to.

Due to the series circuit arrangement between the low water cut-off, the safety pilot control; the controller I32, and the mercury switch I20, all of the switches must be closed in order to en- In the event that either the boiler water level falls to an unsafe value, the burner pilot becomes extlnguished, or the boiler pressure rises too high, the energizing circuit for the electromagnetic device 11 will be broken which will cause the clapper or armature I6 to drop about its pivot for lowering the position of knife edge I3. This will lower the valve plunger 65 for increasng the rate of'bleed through port 62" to a max mum which causes the main valve to close entirely. At

this time; a stop screw I35 which is carried by a bracket I36 prevents either the lever Ill or the lever IIO from raising the left hand endof lover I2 sufliciently to causesufficient upward movement of valve 54 as would cause the main valve to open. This stop screw I35 has the additional function of preventing upward movement of the valve plunger 65-to an extent which would cause the pressure applied to the diaphragm to be excessive. stop screw I when properly adjusted deterimines the maximum pressure which can be-applied to the diaphragm 30 and in addition prevents the levers BI and IIfl-from causing opening of the main'valve when the electromagnetic device 11 is deenergized.

" In the event that the'pressureapplied to the diaphragm 30 becomes excessive dues to either improper adjustment of the'stop screw I35 of improper adjustment of the needle valve member 59, the pressure responsive device I32 will deenergize the device 11 [for causing the valve plunger 65 to drop to its lowermost position for reducing the pressure applied to d a hragm 30.

In some cases it may be desirable to provide for positively closing the main valve in the event that the pilot valve 62--61 fails to function properly. To obtain this result, the outlet passage of the restrictor member may be provided pivoted at I50 and which is engaged by a knife edge member I5I carried by the plunger 03.

Under normal conditions the lever I49 will not engage the plunger I41 and therefore the valve member I4I will normally remain against its seat. However if boiler pressure rises above the setting of the control, the lever I49 will engage plunger I41 forcing it upwardly. This will cause the plunger I46 to engage plunger I43 for forcing the valve member I4I away from its seat against the 35 In other words, this pressure of the steam in the chamber 50. The spring I46 will then serve to snap the valve I40 wide open for thereby reducing the pressure in outlet passage and the diaphragm 30 to zero which will permit the main valve to close entirely. It will be noted that the safety pilot valve I has the same function as the mercury switch I20,

namely, causing complete closing of the main valve when boiler pressure rises above the setting of the control. Unless the added safety afforded by utilizing both arrangements is desired, either the mercury switch or the safety pilot valve may be omitted.

It will be noted that steam pressure in the boiler is required in order to render automaticcontrol of the valve possible. In order to start up a cold, boiler it is necessary to manually open the valve. This is done simply by pressing down on the lever I5 which both opens the gas valve and the uptake damper. The lever I5 is then held in depressed position by means of a stop I54 which is pivoted to the diaphragm cage 29 by screw I55, this screw being located above and to one side of the lever I 5. This stop I54 is preferably arranged so that it will hold the lever I5 depressed s'ufilciently to maintain the valve in approximately half open position. This will prevent maximum firing of the boiler when it is cold and thus avoid any damage to the boiler and brick work due to sudden heatlngn When the boiler begins to steam, steam will flow through the pipe 41, filter 46, and pipe 48 to the inlet of the restrictor member 56 past the restriction' and through tube49 into the diaphragm 30. At this time the boiler pressure will be below the setting of the control which will cause the lever 12 to be forced upwardly against the stop screw I35 by lever 8| which will position valve plunger to reducethe bleed to a minimum. Thus as the boiler pressure rises initially, the steam pressure will cause th ediaphragm 30 to expand thereby opening the gas valve and uptake damper wide. The stop I54, due'to its being pivoted to one side of the lever I5 will now fall system to complete automatic controlK'Thevalve and uptake damper will remain wide open until the boiler pressure rises to within the control range of the controller at which time the pressure on bellows 84 will be sufiicient to overcome the biasing spring 81 for lowering the valve plunger 65 which causes the main valve and damper to i'ecede from their wide open positions an amount sufficient to maintain the boiler pres; sure constant. The control will now function in the manner described in detail above for main- 1 Thus thetaining the desired boiler pressure.

control will serveto positively position the valve 1 and uptake damper between their minimum and wide open positions in accordance with the,load on the boiler. However, at no time will the lever 8I close the valve and damper beyond their minimum positions due to the action of the minimum position arrangement described. In the event that the load on the boiler is so low that operatiOn of the burner at its minimum rate produces more steam than necessary, the boiler pressure will rise to a point wherein the mercury switch I20 opens for deenergizing the electromagnetic device 11 which will cause complete closure of the valve and uptake damper. At such times the valve and damper will be galternately closed and opened to their minimum positions for maintaining the proper boiler pressure. a

Referring to Figure 5, this figure shows a Y independently of the pilot valve.

modified form of controller for controlling the.

main valve. In this modification the electromagnetic device instead of positioning the valve plunger as in Figure 3, positions a vent valve which is capable of venting the motor diaphragm In this figure the restrictor and pilot valve mechanism are contained in a single housing I60. This housing I60 is provided with a connection for the pipe 48 leading from the filter and opening into a passage I6I in which the needle valve screw I62 is located. The steam after flowing past the restriction enters an outlet passage i63 communicating with the motor diaphragm through pipe 49. The passage I63 also communicates through a valve port member I64 with a valve chamber I65 containing pilot valve mechanism which is substantiallythe same as shown in Figure 3. If desired a spring I66 maybe employed for forcing the pilot valve and plunger 65' downwardly. This plunger 65' is operated by a pivoted lever I61, the pivot for this lever being fixed instead of being movable as the corresponding lever of Figure 3; This lever I61 is actuated by the levers 8I' and corresponding to the levers 8| and H0 of Figure 3. The operating mechanism for these levers is the same as in Figure 3 and accordingly this mechanism is not redescribed at this point.

The chamber I63 also communicates with a relief valve passage I69 which communicates with a valve port covered by a valve member I10. =This valve member is urged upwardly by means of a spring HI and is provided with a valve stem I12 extending upwardly through a plug I13. The valve stem I12 is attached to a member I14 having a slot I15 for receiving the lever I16 which is attached to the clapper or armature I11 of the electromagnetic device I18. When this electromagnetic device I18 is energized, the clapper I11 is pulled upwardly as shown which causes the I lever I16 to force the valve stem .I12 downwardly thereby forcing the valve member I against its seat. At this time the control will function in the same manner as the device of Figure 3, that is, the pilot valve will control the pressure applied to the valve diaphragm for positioning the valve and damper in accordance with boiler pressure, and providing also for preventing the valve from being closed'beyond the minimum ,position. The electromagnetic device I18 is controlled by exactly the same controls as shown in Figure l including the mercury switch I20. Whenever the electromagnetic device I18 is deenergized the weighted clapper or armature I11 will drop downwardly thus causing the lever I16 to engage the top of slot I with a hammer action'for disengaging valve member I10 from its seat. This action wlll'also be supplemented by the spring Ill and also by the pressure under valve I10 to thereby insure'that the valve I10 will disengage its seat even though it may tend to stick. This will exhaust'all pressure from the motor diaphragm for thereby causing the gas valve and damper to close completely. It will be noted that by the arrangeregulating valve ahead of the throttling valve, as

required with a valve position type control as in Figure 1. In Figure '6 the gas valve I is provided with a vertical frame IBI which supports a pressure motor I82. This pressure motor may consist of a casing I83 covered by a-flexible diaphragm I84 which is connected by a rod I85 to the junction of a pair of toggle memb :rs I86 and I81. The toggle member I 81 is pivotally connected to the valve stem I88 while the toggle member I86 is pivoted to the frame I8I. This toggle member I86 is formed as a bell crank carrying a weight I8.) for biasing the pressure motor This weight serves to collapse the toggle formed by the members which causes the valve Sl'llll I88 to be forced downwardly for forcing the valve member against its seat. Upon increase in pressure on the diaphragm I84 this diaphragm will move to the left which will cause upward movement of the valve stem I88 for opening the main valve. This valve stem I88 is also attached to a lever I90 which is pivoted so as to rotate in a counter-clockwise direction upon opening of the main valve. This lever I90 operates the uptake damper I2. The pressure motor I82 is connected by a pipe I9I to a float chamber I92 containing a float valve I93. This float chamber is in turn connected by a pipe I94 to the pilot valve I95 of the valve controller generally indicated as I96 (Fi ure '1) I The pilot valve mechanism per se I95 may be the same as shown in Figures 3 and 5 and includes a pilot valve plunger I91 which is actuated by a floating lever I98. The right hand end of this lever I98 is attached to a link I99 carried by. the clapper or armature 200 of the electromagnetic device 20I. The left hand end oi the floating lever I98 is carried by a second lever 202, this lever being supported at its left hand endby an aifiusting screw 203 which is carried by the lever 204, this lever being pivoted about a'knife edge 205 and actuated by a boiler pressure responsive device 206, against the action of a biasing spring 201 which is ,provided with an adjusting screw 208. The right hand end of the lever 202 is sup-' ported by a cam follower 209 which rides a cam 2I0, this cam being pivoted at 2 and actuated through a lever 212 by the plunger 2I3 which is mounted upon a diaphragm 2 I 4. This diaphragm H4 is housed by a housing or base member 2I5 which is supported by the pipe 2 I6 attached to the. delivery pipe 4. The diaphragm 2|4 is therefore subjected to the pressure of the gas being delivered to the burner. The gas pressure on the diaphragm 2 I4 is balanced by means of a biasing spring 2I1 which is attached to a lever 2I8 rotating the cam 2I0. This spring 2I1 is provided with an adjusting screw 2 I 9.

The pilot valve mechanism I95 is similar to the corresponding pilot valve mechanisms of Figures 3 and 5 and is provided with an inlet connection to its restrictor member which is connected by pipe 220to the outlet of the filter 22I which filter is connected by pipe 222 to the oiT-take pipe I0 01 the boiler I. This filter 22I is provided with a blow-down pipe 223 having a blow-down valve 224, this pipe being connected to the pressure responsive device 206.

The lever 204 in addition to actuating the lever 202 also actuates through an extension 225 the mercury switch carrier 226 which carries the mercury switch 221. This mercury switch 221, the low water cut-oil I 6, the safety pilot control I1, and the pressure responsive device I32 are wired in series with the electromagnetic device 20 I, the arrangement being the same as in Figure 1. Thus the electromagnetic device I is energized only when all of the operating conditions of the boiler are proper.

Assuming thrt all of the operating conditions are proper, the electromagnetic device 20I will be energized which causes the right hand pivot point of the floating lever I98 to be raised to.normal operating position. Assuming that the boiler pressure increases, the plunger 228 of the pressure responsive device 206 will rotate the lever 204 downwardly about its pivot 205 which will cause lowering of the left hand end of the floating lever 202. This in turn will lower the left hand end of lever I98 which will lower the .valve plunger I91 for reducing the pressure applied to the pressure motor. This will permit the weight I89 to operate toggle members I86 and I81 for moving the main valve towards closed position and for urging the diaphragm I 84 to the right. This will force condensate from the pressure motor into the float chamber I92. If the water level in the float chamber rises to a point wherein the condensate may be forced into pipe I94, the float valve I93 will open for permitting such excess condensate to escape. As the main valve closes due to the action just described, the discharge pressure of the gas will lower which will permit the'spring 2I1 to rotate the cam 2I0 counterclockwise against the action of diaphragm 2I4. This rotation of the cam 2I0 will raise the right hand end of the lever 202 for thereby shifting the pilot valve plunger I91 to a position for stopping further movement of the main valve. Upon a decrease in boiler pressure the opposite action will occur. Thus at such time the lever 204 will be rotated clockwise for raising the left hand end of lever 202 which in turn causes raising of the valve plunger I91. This will increase the pressure applied to thesurface of the condensate in float chamber I92 thus forcing condensate into the pressure motor which will cause the diaphragm I84 to move to the left for increasing the opening of the main valve and the uptake damper a greater extent. As the main valve opens, the discharge pressure will increase which will force the diaphragm 2M upwardly againstthe action of spring 2 I1, thereby rotating cam 2I0 clockwise for lowering the right hand end of floating lever 202 which will in turn cause lowering of the pilot valve plunger I91. Thus the main valve will be stopped when the discharge pressure falls suil'iciently to return the pilot valve plunger I91 to its neutral position. From the foregoing description it will be apparent that with the arrangement just described, the main valve is positioned to whatever position is necessary to maintain the required discharge pressure and that the discharge pressure is raised upon decrease in boiler pressure and is lowered upon increase in boiler pressure It should also be apparent that by this arrangement in which the valve position is controlled by gas discharge pressure, the valve will automatically assume whatever position is necessary to maintain this pressure and consequently a constant discharge pressure will be maintained irrespective of variations in gas supply pressure. For example, assuming that the discharge pressure should increase, the diaphragm 2 I 4 will raise for rotating cam 2I0 clockwise which will cause lowering of the valve plunger I91. This in turn will reduce the pressure applied to the pressure motor which will cause the main valve to close an amount sufficient to maintain the discharge pressure substantially constant.

In order to prevent throttling of the gas to a point which would not provide proper burner operation, a stop screw 230 is provided for limiting the downward movement of the left hand end of floating lever 202. Thus when the boiler pressure rises to a point at which the lever 204 permits the lever 202 to engage stop screw 23!! a further increase in boiler pressure will have no effect upon the position of lever 202. At this time the screw 203 will merely disengage lever 202 and the diaphragm 2H acting through the cam 2I0 will position lever 202 for maintaining the minimum desired discharge pressure.

Whenever the mercury switch 221 opens, or

when any switch of controllers I6, I1, or I32 opens, the electromagnetic device 20I will be deenergized which will lower the right hand pivot of floating lever I98 an amount sufficient to in.- sure that plunger I91.is positioned for completely closing th main valve. At this time the lever 204 and cam -2I0 will be prevented from raising lever I98 an amount sufilcient to cause opening of the valve by means of the stop screw 23 I.. This stop screw also serves to limit the closing movement of the pilot valve for preventing execssive pressures from being applied to the pressure m0- tOr.

From the foregoing description it will be apparent that the present invention provides an automatic control system for a boiler or other device utilizing a burner and which controls theburner in a positive and safe manner. It will also be apparent that the present invention provides for graduatingly controlling the supply of fuel to the burner in accordance with the actual load; preventing the supply of fuel from being reduced below an amount sufficient to provide proper burner operation and completely discontinuing the supply of fuel to the burner whenever any operating condition in the system becomes unsafe. While the present invention has been shown and described as applied to control of a gas burner it is equally adaptable to control of other types of burners such for example as oil burners- While only a'few forms of th invention have been disclosed it will be apparent that many changes may be made without depart-.

ing from the scope or the invention. It is therefore desired to be limited only by the scope of the appended claims.

I claim as my invention:

1. In a burner control system, in combination, a fuel burner, a main valve for controlling the flow of fuel to the burner, a pressure motor comprising a chamber having a movable wall formoving said valve in opening direction, biasing means for biasing said main valve towards closed position, a source of actuating fluid for the motor, means including pilot valve meanscommunicating with said source and said pressure motor for varying the pressure applied to said motor, a first controller actuated in accordance with a condition indicative of the required output of the burner for actuating said pilot valve means, minimum flow stop means operating in response to the position of the main valve to limit control of said pilot valve means by said first controller for preventing said first controller from reducing the burner output beyond a predetermined minimum necessary for proper burner operation, and a second controller actuated in response to said condition for reducing the force applied to said pressure motor independently of said first controller for thereby causing complete closing of said main valve in the event that the value of said condition indicates that the minimum output of said burner is too great.

2. In a burner control system, in combination, a fuel burner, a main valve for controlling the fiow of fuel to the burner, apressure motor comprising a chamber having a movable wall for moving said valve in openihg direction, biasing meansfor biasing said main valve towards closed position, a source of actuating fluid for the mtor, means including pilot valve means communicating with said source and said pressure motor for varying the pressure applied to said motor, a first controller for actuating said valve for preventing said first controller from reduc ing the burner output beyond a predetermined minimum necessary for proper burner operation, and a second controller for actuating said pilot valve means independently of said first controller, said second controller having two positions, one in which the first controller is placed into control of said pilot valve means and another in which the pilot valve means is positioned independently of said first controller in a manner to completely close said main valve, said last position being assumcd whenever the value of said condition indicates that the minimum output of said burner is too great.

3. In a burner control system, in combination,

a fuel burner, a main valve for controlling the flow of fuel to the burner, a pressure motor comprising a chamber having a movable wall for moving said valve in opening direction, biasing means for biasing said main valve towards closed position, a source of actuating fluid [or the mo- .tor, means including pilot valve means communicating with said source and said pressure motor for varying the pressure applied to said motor, a first controller for actuating said valve means, condition responsive means responsive to a condition indicative of the required output of the burner for positioning said .first controller, minimum flow stop means for limiting control of said pilot valve means by said first controller for preventing said first controller from reducing the burner output beyond a predetermined minimum, said stop means including a movable member moved into control relationship with said valve means in response to reduction in fuel flow to the predetermined minimum, and a second controller for actuating said pilot valve means independently of said first controller, said second controller having two positions, one in which the first controller is placed into control of said pilot valve means and another in which the pilot valve means is positioned independently of said first controller in a manner'to completely close said for varying the pressure applied to said motor, a controller for actuating said pilot valve means, condition responsive means responsive to a condition indicative of the required output of the burner for positioning said controller, minimum flow stop means for limiting controlof'said pilot valve means by said controller for preventing said controller from reducing the burner output beyond a predetermined minimum, said stop means including a movable member moved into control relationship with said pilot valve means in response to reduction in fuel flow to the predetermined minimum.

5. In a burner control system, in combination, a burner, a main valve for controlling the flow of fuel to the burner, a pressure motor for positioning said main valve, pilot valve means for controlling the application of pressure to said motor, condition responsive means actuated in accordance with a condition indicative of the required burner output for actuating said pilot valve means, follow-up means influenced by the position ofv said main valve for cooperating with said condition responsive means in positioning said pilot valve means, minimum flow stop means for limiting control of said pilot valve means by said condition responsive means and follow-up means for preventing movement of said main valve under the control of said pilot valve means to a position reducing burner operation below a predetermined minimum, second pilot valve means associated with said first mentioned pilot valve means and said motor, said second pilot valve means having a first position in which said first pilot valve means is placed in control of said pressure motor and a second position which causes said pressure motor to close said main valve irrespective of said first pilot valve means, and electromagnetic means for moving said second pilot valve means between said first and second positions.

6. In a burner control system, in combination. a burner, a main valve forcontrolling the flow of fuel to the burner, a pressure motor for positioning said main valve, pilot valve means for controlling the application of pressure to said motor. condition responsive means actuated in accordance with a condition indicative of th required burner operation, a member positioned thereby ior actuating said pilot valve means, follow-up means including a device responsive to a condition which is indicative of the flow of fuel to the burner for cooperating with said member in positioning said pilot valve means, and stop means associated with said member for causing said member, operating under the control of said device, to position said pilot valve means for maintaining a predetermined minimum flow of fuel to the burner when the condition responsive means calls for a flow of fuel below said predetermined minimum.

7. In a burner control system, in combination, a burner, a main valve for controlling the-flow of fuel to the burner, a pressure motor for positioning said main valve, pilot valve means for controlling the application of pressure to said motor, condition responsive means actuated in accordance with a condition indicative of the required burner operation for actuating said pilot valve means, follow-up means including a device responsive to vflow of fuel to the burner for cooperating with said condition responsive means in positioning said pilot valve means, stop means associated with said condition responsive means for causing said flow responsive means to position said pilot valve 'means for maintaining a predetermined minimum flow of fuel to the burner when the condition responsive means calls for a flow of fuel below said predetermined minimum, electromagnetic means for positioning said pilot valve means in a manner to close said main valve irrespective of said stop means,/ and switching means actuated by said condition responsive means for energizing and deenergizing said electromagnetic means.

8. In a burner control system for a steam boiler,

in combination,,a burner for said boiler, a main valve for controlling the fiow of fuel to the burner, a. pressure motor for opening said main valve, biasing means for closing said main valve, connecting means between the boiler steam space and said pressure motor for utilizing steam pressure for actuating said pressure motor, said connecting means including pilot valve means for controlling the magnitude of the steam pressure applied to said pressure motor, a first controller for said pilot valve means, means responsive to the pressure in the boiler for graduatingly actu: ating said first controller, minimum flow stop means operated in response to the P sition of said main valve for preventing said first controller from actuating said pilot valve means in a manner to reduce the flow of fuel below a predetermined minimum necessary for proper burner operation, and a second controller actuated in accordance with boiler pressure for relieving pressure from the pressure motor independently of said first controller for thereby closing completely said main valve whenever the boiler pressure rises above a predetermined value indicating that the minimum fuel flow is too great.

9. In a burner control system for a steam boiler, in combination, a burner for said boiler, I

a main valve for controlling the flow of fuel to the burner, a pressure motor for opening said main valve, biasing means for closing said main .means, a device operated by a portion of said ing said first controller, minimum flow stop means for preventing said first controller from actuating said pilot valve mean in a manner to reduce and saiddevice.

the flow of fuel below a predetermined minimum necessary for proper burner operation, an electro-magnetic device having a first position for rendering said stop means .efiective to prevent closing of said main valve and a second position for closing said main valve independently of said first controller, and boiler pressure responsive switching means for deenergizing said electromagnetic device when said boiler pressure rises to a value indicating that the minimum flow of fuel is too reat.

10. A control device of the character described comprising in combination, pilot valve means for controlling the operating pressure of a pressure operated fuel valve, means adapted to respond to a condition indicative of thedemand for burner operation, a member positioned by said responsive means for operating said pilot valve means, follow up means adapted to be moved as a. result 1- 01 movement of said fuel valve for cooperating spond to a condition indicative of the need for complete termination of burner operation for operating said pilot valve means in a manner to cause closure of said fuel valve independently of said member.

controlling the operating pressure of a pressure operated fuel valve, means adapted to respond to ondition indicative'ofthe demand for burner operation, a member positioned by said responsive means for operating said pilot valve means, follow up means adapted to be moved as a result of movementof said fuel valve'for cooperating with said member in the operation of said pilot valve follow up means for taking the control of said pilot valve means away from said member when said fuel valve reaches a predetermined minimum open position to prevent said valve from closing further, and means adapted to respond to a condition indicative of the need for complete ter mination of burner operation for operating said pilot valve means in a manner to cause closure ofsaid fuel valve independently of said member JOHN L. HARRIS.

, 11. A control device of the character described comprising in combination, pilot valve means for

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