US2470969A

US2470969A - Hydraulic stoker control

Info

Publication number: US2470969A
Application number: US497897A
Authority: US
Inventors: Albert E Baak
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1943-08-09
Filing date: 1943-08-09
Publication date: 1949-05-24
Anticipated expiration: 1966-05-24

Description

May 24, 1949. A. E. BAAK 2,470,969

HYDRAULIC STOKER CONTROL Filed Aug. 9, 1943 ATTORNE Ys Patented May 24, 1949 HYDRAULIC STOKER CONTROL Albert E.Baak, Los Angeles, Calif., minier to Minneapolis-Honeywell Regulator Company,

Minneapolis,

Minn., a corporation of Delaware Application August 9, 1943, Serial No. 497,897

19 Claims.

This invention relates to system and apparatus for the control of stokers and similar combustion apparatus in which ignition is maintained by periodic operation of the stoker for short intervals during the periods when the Stoker operation in response to heat calls does not occur. The invention has particular usefulness in the control of stokers of the household type wherein it is desired to maintain ignition by periodically operating the stoker during intervals when there is no call for heat indicated in the space to which heat is furnished by the stoker apparatus.

It is an object of the invention to provide such a system and apparatus for the control of stokers and similar mechanism and particularly to provide controls for maintaining combustion in stokers of the household type. It is another ooject of the invention to provide a stoker control system and apparatus wherein periodic operation of the stoker for maintaining combustion is provided at uniform intervals but such combustion maintaining operations are not initiated until after a time delay period following a normal operation of the Stoker apparatus in response to a call for heat.

It is a further object of the invention to provide a system and apparatus for the control of stokers which is capable of being manually adjusted for operation under widely v arying cyclic conditions and which is capable of operation over long periods of time without servicing.

It is a further object of the invention to provide a stoker control system and apparatus which is economical to manufacture, rugged in construction and simple to operate.

Other and further objects of the invention are those inherent and implied by the apparatus illustrated, described and claimed.

The invention is illustrated with reference to the drawings in which:

Figure 1 is a wiring diagram in which certain of the control elements are shown in sectional elevation.

Figure 2 is a plan view, partly in section, of a. modified form of one of the control elements utilizable in the system illustrated in Figure 1.

Figure 3 is another view of the apparatus of Figure 2 and is a sectional elevational view partly broken away and taken along the lines A, B, C,

D of Figure 2.

Figure 4 corresponds to Figure 3 and is an elevational sectional view taken along the lines A, B, E, F of Figure 2.

Referring to Figure 1, there is illustrated a motor, generally designated l0, of the stoker, the

2 motor I 0 being provided for the feeding of fuel and for the blowing yof combustion air in the stoker apparatus. It will be appreciated that in some stokers separate motors are provided for 'feeding the fuel and blowing the combustion air through the stoker apparatus, and as to such systems, the motor Il may be regarded as schematically illustrating both motors.'

In the system, there are provided alternating current supply feeders il and I2, which are connected through lines |3 and i4 to the primary winding I5 of a transformer, generally designated I6. In the space to which heat is provided by the stoker mechanism i0, there is positioned a thermostat, generally designated 20, having a bimetallic element 2|, which is anchored at the post 22 and is provided with a pair of

contacts

24 and 25 which move to the right as illustrated in Figure 1 as the temperature of the space drops, and to the left as the temperature of the space increases.

Adjacent the stoker apparatus, there is provided a relay mechanism, generally designated 30, having an operating coil 3| and pairs of contacts 32-33 and 34-35 operated by the coil 3|. The post 22 of the thermostat 2Iis electrically connected by means of line 2l to contact 33 of relay 30, contact f32 beingA connected through line 3l to Junction 33. Line 33 connects junction 38 to the contact 23 of the thermostat 2|). The coil 3| of the relay is connected by line 40 to the junction 38 and is connected by line 4i to one terminal of the secondary i'l of the transformer i6, the opposite terminal of the secondary Il being connected by line 42 to the contact 29 of the thermostat 20. It will thus be observed that as the temperature of the space in which the thermostat 20 is positioned, decreases beyond a predetermined amount, contact 25 will first engage contact 29 and upon further temperature fall, contact 24 will engage contact 28. Thereupon a circuit is established through coil 3| beginning at winding l1 of the transformer the circuit extends through line 42, contacts 29-25, contacts 24-28,'line 39, junction 38 and line 40 to coil 3|, and through line 4| to the opposite terminal of the secondary I1 of the transformer.

The coil 3| of the relay is accordingly energized and causes contact 32 to engage contact 33, and also causes contact 34 to engage contact 35. The closure of contact 32 upon contact 33 establishes a holding circuit for the coil 3| of the relay as follows: From the left terminal of the secondary l1 of the transformer il through line 42 to stationary contact 23, thence through movable conaardgas 3 tact 25 and the thermostat bimetallic element 2 i post 22, line 21,

contacts

38 and 32, through line 31, junction 88, line 40, coil 3| and line 4| to the right terminal of the secondary I1. The coil 8| accordingly remains energized until movable contact 25 of the thermostat ls separated from the stationary contact 28, upon temperature rise.,

The closure of contact 84 upon contact 35 serves to establish a circuit from feeder through line 45, contacts 35 and 34, which are then closed, line 45 to junction 41, thence through line 48 to terminal 48 of the motor |0, thence from terminal 50 of the motor through line 5| to feeder |2. The motor or motors l of the stoker are accordingly energized and operate to supply fuel and combustion air to the stoker mechanism. Accordingly, the stoker operates and furnishes heat to the space in which thermostat 20 is located and after a time movable contact 24 separates from contact 28. 'Ihis breaks the initial energizing circuit but the holding circuit remains made. On further temperature rise, the movable contact 25 separates from the stationary contact 29 breaking the holding circuit of the relay 30 which accordingly de-energizes and opens the holding circuit at contacts 82-83 and the stoker control circuit. The stoker is therefore under the independent control of the thermostat 20 and operation will ensue at irregular intervals depending upon the needs for heat in the space in which thermostat 20 is positioned. r

Since the calls for heat as indicated by the thermostat 20 may occur at widely varying intervals, the degree of combustion in the stoker likewise varies considerably and occasionally the stoker firepot will be cooled to such a degree that combustion is discontinued between calls for heat.

Accordingly, upon a subsequent call for heat by thermostat 20, fuel will be fed and air supplied but combustion will not ensue. In order to obviate this diioulty, the Stoker is also placed under the independent control of a fire maintaining control apparatus illustrated in thev lower part of Figure 1.

The re maintaining control apparatus comprises a switch mechanism, generally designated 55, and a thermally operated timing apparatus, generally designated 60. The apparatus 60 of Figure 1 may be replaced by that shown in Figures 23 and 4, if desired.

Theswitch mechanism may be of any desired construction in which the circuit closing elements are capable of being operated by a relatively small movement of an actuating element. For this purpose, I prefer to use a switch such as that illustrated in my Patent No. 2,318,734 issued May 11, 1943. Details of the switch 55 are completely described in said patent and it is suiiicient for the purposes of description here to say that the switch 55 is capable of closing a circuit from terminal 56 to terminal 51 upon a very slight movement of the actuating plunger 58 and that the energy required to close and open the switch is of negligible proportion. It is obvious, of course, that any switch mechanism capable of being operated by a relatively slight low energy movement is suitable for use in the present invention and I do not therefore desire to be limited, in the present invention, to the use of the particular switch 55 herein illustrated or referred to.

The thermally .operated timing apparatus 60 includes an upper enclosed housing 6| to which there .is attached a bellows, generally designated 00. The upper enclosed vhousing 8| has an upper wall 82 provided with bosses 63 and 64, which are la drilled and threaded to receive

gland nuts

50 and 58 respectively, the gland nuts being arrangw so as to bear upon the compresslble packings a?! and 68. The upper housing wail 62 is threaded at 59 and 10 respectively to receive needle valve screws 1| and 12, the latter being provided with knurled or slotted heads 13.ar i d 14 respectively. The upper enclosed housing 5| is preferably of generally cylindrical shape having a cylindrical sidewall 15 upon which there is wound an insulated layer 18 of mica or other similar material. Around the mica, there is wound a heating coll o f any suitable number of turns. The lower wall 8| of the housing 6| is made in two levels Vso as to provide a depressed part 82 within the interior space 83. The bottom wall 8| is drilled through at 84 to provide a seat for the lower conical end of the needle valve screw 1|. The

drill hole 84 is shaped at its lower side to receive a ball check valve 86, which is pressed upwardly by means of spring 81 held in the thimble 88, the thimble in turn being threaded into the bottomwall 8| as shown at'89. The thick portion of the bottomwall 8| at the left in Figure 1, is drilled out as illustrated at 80 to receive a threaded valve seat member 92 which has an aperture 93 in line with the lower conical end of the needle valve screw 12. The valve seat member 92 also serves slightly to compress a spring 95 which bears upon the ball check valve member 96, which in turn rests upon the conical seat of aperture 91.

The cylindrical sidewalls 15 of the upper housing 6| extend downwardly as illustrated at 98, and upon the outer surface there is sweated or otherwise secured the upper edge of a bellows |00. The lower closed end |0| of the bellows |00 is pro'- vided with a central pivot block |02 which rests in a, notch |03 of the operating arm |05. The arm |05 is pivoted upon block |08 and the arm is normally drawn upwardly by means of a tension spring |01. The arm |05 is arranged so as to bear against the operating plunger 58 of the switch mechanism 55 and as the bellows |00 moves from the full line position shown in Figure 1 to the position in which the pivot block |02 and the bottom surface |0| are shown in the dotted line position of Figure 1, the switch mechanism 55 is operated so as to establish a circuit between terminals 56 and 51.

The heating coil 80 is connected by means of line |09 to junction ||0 and thence through line I I to junction 41 of lines 45 and 48. From junction ||0 there also extends a line |i3 to terminal 51 of the switch 55, the cooperating terminal 55 of the switch being connected by line ||4 to a1- ternating current feeder The opposite terminal of the heating element 80 is connected by means of line ||5 to stationary contact H5 of a switch, and through the movable contact ||1 of the switch and line ||8 to alternating current feeder |2. The movable contact ||1 is positioned so as to be in the path of movement of the outer tip |08 of the operating arm |05 so lthat the movable contact 1 will be moved out of engagement with the stationary contact ||6 when the outer tip of the operating arm |05 assumes the dotted line position shown at |08 of Figure 1.

The entire volume of the interior space of the bellows |00 and a considerable portion of the volume of the interior space 83 of the upper housing 6| is lled with a volatile iiuid such as an alcohol or ether, the amount of fluid being such that when the entire apparatus 80 is at room temperature and the bellows is pressed upwardly under the influence of sprring |01, and the natural resiliency of the bellows |00, the liquid level will be at line II9.

It will be observed that whenever the switch 55 is operated so as to establish a circuit between terminals 55 and 51, a circuit is established from alternating current feeder I through line ||4 through the closed contacts 55 and 51 of switch 55, line II3, junction |I0, line |09, heater coil 80, line |I5 through normally closed contacts ||5 and I I1 and line I I 8 to alternating current feeder I2. The heater coil will accordingly be energized and will supply heat to the housing 5|. After a predetermined period, the volatile liquid in the housing 5| is heated to the vaporization temperature and sufficient vapor pressure is generated so as to overcome the resistance of ball check valve 86, which is spring pressed upwardly by spring 81 against the seat of drill hole 84. Therefore, the volatile liquid in the upper chamber 88 of the housing 6I will be driven through the drill hole 84 at a rate depending upon the adjustment needle valve screw 1I in respect to the seat 84. By varying the position of the screw 1 I, the effective size of the orifice 84 may be widely varied and accordingly the time interval required foi` driving a prescribed quantity of the volatile liquid downwardly into the bellows may be lvaried throughout a wide range. So long as the switch 55 remains closed, the heat provided by coil 80 causes the liquid in space 83 to be driven downwardly through the orifice 84 and after a time interval, depending upon the adjustment of screw 1|, the bellows |00 will be moved from the dotted line position to the full line position of Figure 1 and in so doing, will move the operating arm causing the plunger 58 to move downward with resultant operation of switch 55 to` open the circuit between terminals 58 and 51, When this occurs, the circuit to coil 80 is interrupted, and the body 5| of apparatus 50 begins to cool.

So long as the circuit through switch 55 is maintained, and yduring the time that coil 80 is energized and is supplying heat to the casing 5I, a circuit is also established tothe stoker motor or motors I0 as follows: From alternating current feeder |I, line I|4 through closed contacts 55 and 51 of switch 55, line IIS, junction IIO, lines |I| and 48 to terminal 49 of the motor I0, thence from terminal 50 of the motor through line 5| to the alternating current feeder I2. Therefore, while the coil 80 is energized and heating body 5| (and hence during the time interval that the bellows is being expanded), the stoker motor or motors likewise operate supplying fuel and combustion air to the stoker so as to maintain combustion in that mechanism.

When switch 55 has been moved to the open circuit condition due to the expansion of bellows |00, the circuits to heating coil 80 and Stoker motor or motors 4I0 are interrupted and since the coil 80 is therefore no longer heated, the resiliency of spring |01 and/or the natural resiliency `of the bellows |00 apply pressure to the liquid contained in the bellows and cause the fluid to be driven upwardly through the orifice 91 and past the check valve 95, through the orifice 93, which is controlled screw 12 to the space 83 in the upper housing 5I. During this interval, it will be noted, check valve 85 prevents the passage of liquid inwardly through the orifice 84, and therefore the time interval for the passage of a given quantity of liquid from the bellows chamber to the upper housing 5| is determined by the adjustment of screw 12.

by needle valveA Aits natural resiliency until contact This time interval is preferably much longer than the time interval required for driving the liquid downwardly into the bellows so as to allow a reasonable waiting period between each fire maintaining operation of the stoker. It will, however, be appreciated that the time intervals of the fire maintaining operation (which is under the control of the adjustment screw 1|), and the time interval vbetween fire maintaining operations, (which is under the control of the adjustl ment screw 12), may be varied at the will of the operator, as desired.

During the time period that the stoker motor or motors I0 are operated under the influence of the thermostat 20 and relay 30, a circuit is also established to the heating coil as follows: From alternating current feeder through line 45, through closed switch contacts 34-35, line 45, junction 41, line I||, junction |I0, line |09, coil 80, line II5, normally closed switch contacts II5-II1 and line ||8 to alternating current feeder I2. Therefore, as the Stoker motor I0 operates under control of thermostat 20 and relay 30, the upper housing 5| of the apparatus 50 is also heated and fluid from the upper enclosure 83 is driven downwardly into the bellows space |00. Inasmuch as the heat providing operations of the Stoker under the command of the room thermostat are normally of greater duration than the fire maintaining operations, the heat provided through coil 8 0 is likewise greater and causes the bellows to expand downwardly beyond the full line position shown in Figure 1 until the operating arm |05 reaches the position such that its outer end |08 is in the dotted line position |08'. When tip |08 is in this dotted line position, the bellows |00 is expanded considerably beyond the position at which opening of switch 55 occurs. Hence, the position of opening of switch |I5--II1 is not reached during the fire maintaining operations previously described. When bar |05 is so moved, the adjustment screw II2 through the end of bar |05 bears against the movable contact I I1 and moves it away from the stationary contact I I5, which accordingly breaks the circuit previously described, through the heating coil 80, without however interrupting the circuit tothe stoker motor or motors I0. The interruption of circuit to heating coil 80 accordingly permits theV upper housing 5| to cool and the bellows is moved upwardly by spring |01 and I I1 is again permitted to engage upon stationary contact |I5 wnereupon heating of coil 80 is resumed so long as the stoker motor or motors I0 are energized under the control of the thermostat 20.

When the thermostat 20 interrupts the circuit between

contacts

25 and 29 and hence interrupts the circuit to the stoker motor or motors I0, this likewise interrupts the circuit to heating coil 80 of the nre maintaining timer apparatus 50, but since the bellows |00 has been expanded to a marked degree to open the circuit between contacts |I5 and I|1, the time period which Aelapses before the bellows |00 has contracted sufficiently again to close switch 55 is greater than the time period between normal fire maintaining operations. This time period may-be adjusted, as desired by varying the position of the adjusting screw II2 on the outer end |08 of the operating lever |05. Thus by turning the adjusting screw II2 downwardly. the time period for beginning the me maintaining operation after a call for heat has ended. may be shortened whereas by screwing itvupwardly with respect to the outer end |08 oi lever |05, this time period is lengthcned. After a normal operation of the stoker i in response to a call for heat from thermostat 20, the nre in the stoker will normally be quite hot and will therefore be capable of maintaining combustion for a considerable period. Therefore, by suitably adjusting the screw ||2 with respect to the outer end |06 of the operating lever |05, it is possible to provide a desirably long period after a call for heat stoker operation before the rst fire maintaining operation of the stoker occurs, under the influence of the mechanism 60. The time interval between the rst, second and subsequent fire maintaining operation is, however, under the control of the adjustment screw vv12 and therefore may be as long or as short as desired.

Referring to Figures 2, 3 and 4, there is illustrated a modied form of iire maintaining control apparatus in which the upper housing, generally designated |20, is provided with a cap |2|, held in place by a plurality of screws |22, afiuidtight joint between the cap and the housing being maintained by a suitable gasket |23. The housing is provided with an annular chamber |24 into which bosses |25 and |25A extend. From the sidewall |21 of the housing |20, there is a tubular extension |26 upon which is sweated a relatively thin metallic shell |28, the shell being provided with a heater element, generally designated |30, which is insulated from the shell by mica or other suitable insulation |3|. The bosses and |25A are respectively provided with drilled holes and |60 shown respectively in Figures 3 and 4.

Referring to Figure 4, it will be observed that the cover |2| is provided with a second bellows |41 which is sweated to the inner surface of the cover |2I, and is provided with another adjustment screw |48. The boss |25A is likewise drilled at a second place at |60 to receive another valve member |6| which is spring pressed upwardly by means of the interior spring |62. The valve member |60 is provided with a stem |63, the lower conical end of which is aligned with drilled passageway |64 communicating with the ball check valve chamber |65 containing the ball check valve |66, the latter being spring pressed against the passageway |61 by means of the spring |68. The passageway |61 is connected by means of the drill hole |69 to the chamber |50 of the bellows |5|. The ball check valve chamber |65 is sealed by means of a suitable screw plug |10. The boss |25 is preferably side drilled, as shown at |29, so as to allow passage of uid from the annular chamber |24 to the space below the valve member |55 and the boss |25A is similarly drilled at |58 to allow the {flow of iluid from beneath the valve member |60 into the annular chamber |24.

The operation of the apparatus illustrated in Figures 2, 3 and 4 is similar to that shown at 60 in Figure 1. When the mechanism is cooled, the uid stands at the lever illustrated by the dotted line |1|. When heat is supplied by heater element |30, the volatile liquid which entirely iills the bellows chamber |50 and fills the upper chamber |24 to the level |1|, causes the volatile liquid to be vaporized and the liquid is driven downwardly from the upper chamber |24 through holes |29, through the oriiice determined by the position of valve stem |51 in respect to the drill passageway |38, thence past the ball check valve |4| and through chamber |40 and passage |45 to the bellows |50. The ilow continues until the circuit to heater |30 is broken, as previously described, and thereupon the resiliency of the bellows |5| and any force applied to it causes the liquid in the bellows chamber |50 to be returned through passages |69 and |61, past the ball check valve |66 through the orifice, the position of which is determined by the valve stem |63 in respect to the passage |64, and thence through hole |58 to the upper housing chamber |24. The timing of the ow downwardly may be adjusted at will by means oi screw |33 and the return ow may likewise be adjusted at will by means of the screw Many obvious variations will be apparent to those skilled in the art and such are intended tol be within purview of the invention illustrated, described and claimed.

I claim as my invention:

1. A stoker control system comprising a Stoker motor, a rst switch connected in circuit with the stoker motor for controlling the operation of said motor in response to calls for heat, a second switch connected in circuit with said motor i'or operating it to maintain combustion in the stoker, thermal means for operating said second switch including an expansible bulb, a reservoir chamber above said bulb, a iuid in said bulb and reservoir, uid connection means between said reservoir and bulb, iiow regulating means in said I iiuid connection means for restricting the now to a predetermined rate in each direction between said` bulb and reservoir, an electrical heater element for said reservoir connected to said rst switch, said second switch means also in circuit with said heater element, said switch means being closed so as to energize the heater and motor when the expansible bulb is in a contracted condition and open when said bulb is expanded to a predetermined amount, and means for controlling said first and said second named circuits to cause a selectively greater expansion of said bulb by said first circuit than by said second circuit.

2. A thermally operated time switch comprising a reservoir, a fiuid tight enclosure, the volume of which is capable of being changed under the influence of fluid pressure therein, a fluid capable of expansion upon heating in said reservoir and enclosure, fluid connection means between said reservoir and enclosure, independent flow regulating means in said fluid connection for selectively controlling the ow of said fluid in each direction, a heater element for the fluid in said reservoir, circuit means for energizing said heater, switch means in said circuit means, said switch means comprising a first switch operable under certain conditions to cause deenergization of said heater when said enclosure is expanded to a predetermined condition and a second switch operable under other conditions to cause energization and deenergization of' said heater when said enclosure is expanded beyond said predetermined condition.

3. A thermally operated time switch comprising a reservoir, a fluid vtight enclosure, the volume of which is capable of being changed under the influence of fluid pressure therein, a uid capable of expansion upon heating in said reservoir and enclosure, fluid connection means between said reservoir and enclosure, flow regulating means in said fluid connection-.for independently controlling the flow of said fluid in each direction, and hence the rate of contraction and expansion of said enclosure, a heater'element for the fluid in said reservoir, rst switch means in the circuit of said heater operable by said enclosure for intermittently energizing said heater, said first switch being movable to energize said heater when the enclosure is contracted to a predetermined condition and movable to deenergize said heater lwhen expanded to a predetermined amount, and

second normally` closed switch means in circuit with said heater and operable by said enclosure, said second switch means being normally closed and movable to deenergize said heater when the enclosure has expanded beyond said first switch opening condition.

4. A thermally operated time switch comprising a reservoir having one side enclosed by a cap, a bellows attached in fluid tight relationship to the reservoir wall opposite the cap, communicating passageways through the reservoir wall opposite the cap, spring retracted needle valves providing independent flow regulating means positioned in operative relation in respect to each of said passageways, bellows means on the cap, screw means threaded through the cap to expand said bellows means to form a stop for said spring retracted needle valves, each of said stops providing independent means for adjustably limiting the extent of movement of said needle valves, check valves in each passageway said valves being oriented so one checks flow from the reservoir to the bellows and the other checks flow from the bellows to the reservoir. a heat expansible fluid in the bellows and reservoir, electrical heater means for the fluid of the reservoir and a circuit closer in circuit with said heater, said circuit closer being movable to closed condition when the bellows is contracted and to open condition when the bellows is expanded to a predetermined degree, and a second circuit closer in circuit with said heater and movable to open and closed condition when said bellows is expanded to a predetermined degree beyond wail opposite the cap, spring retracted needle valves positioned in operative relation in respect to each of said passageways, bellows means on the cap, screw means threaded through the cap to expand said bellows means to form a stop for said spring retracted needle valves, check valves in each passageway said valves being oriented so one checks flow from the reservoir to the bellows and the other checks flow from the bellows to the reservoir, a heat expansible fluid in the bellows and reservoir, electrical heater means for the uid of the reservoir and a circuit closer in circuit with said electrical heater means, said circuit closer being movable to closed condition when the bellows is contracted and to open condition when the bellows is expanded to a predetermined degree, and second normally closed switch means operable by said bellows and in circuit with said electrical heater means and positioned to be opened when the bellows is expanded beyond said predetermined degree, said circuit closer and said second switch means being operableto intermittently deenergize said heater when said bellows is at said predetermined and said further expanded positions.

6. In a thermal timing mechanism, an electrically heated expansible and contractible thermal means, a normally closed switch moved to open position by said thermal means when heated and returned to closed position when cooled, a circuit for said thermal'means controlled by said switch, and means for independently adjusting the length of time required forA said thermal means to move from its switch closing position to its switch opening position and from its switch opening to its switch closing position, a second circuit for energizing said thermal means, and a second switch in said circuit opened by said thermal means after the same has moved a lesser extent than required for opening the first mentioned switch, said first and said second switches being operable to cause intermittent movement of said thermal means toward said first named switch closing position.

7. In a stoker control system, a stoker, an electrically heated expansible and contractible thermal means, a normally closed switching means in control of said stoker which is moved to open position by said thermal means when heated and returned to closed position when cooled, a circuit for said thermal means controlled .by said switching means, means for independently adjusting the length of time required for said thermal means to move from its switching means closing position to its switching means opening position and from its switching means opening position to its switching means closing position, a second circuit for causing energization of said stoker and said thermal means, and a second switch in said second circuit for the thermalmeans opened by said thermal means after the same has moved to a greater extent than required for opening the first mentioned switching means.

8. In a hydraulic timing mechanism, in combination, a fluid operated member biased to a predetermined position, a fluid reservoir, electrical means energizable to force fluid from said reservoir into said member, a circuit for said means, a pair of switches in control of said circuit for intermittently energizing said electrical means, connections between said member and switches for opening one of said switches when the member has received a predetermined amount of fluid and for closing said switch upon reduction of the amount of fluid in said member and for opening the other of said pair of switches when said member has received ajpredetermined amount of fluid in excess of said 'first mentioned amount and for closing said voir, electrical means energizable to force fluid from said reservoir into said expansible member, a circuit for said means, a switchrin said circuit, connections between said expansible member and switch for opening said switch when the expansible member is expanded and for closing said switch upon contraction Aof said expansible member, means controlling the rate of fiuid delivery from said reservoir to said expansible member, means controlling the rate of return of fluid from said expansible member to said reservoir, means for selectively adjusting either of said rate controlling means, and a second switch in said circuit, said connections being disposed to operate said second switch to alternately energize and deenergize said electrical means when said expansible member is remote from its predetermined biased position and to operate said first switch to alternately energize and deenergize said electrical means when said expansible member isadjacent said predetermined biased position.

10. In a hydraulic timing mechanism, in combination, a fluid operated member biased to a predetermined position, a fluid reservoir, electrical means energizable to force fluid from said reservoir -into said member, a circuit for said means, a switch in control of said circuit, connections between said member and switch for opening said switch when the member has received a predetermined amount of fiuid and for closing said switch upon reduction of the amount of fluid in said member, means operable in conjunction with movement of said fluid operated member beyond said switch opening position for energizing and deenergizing said electrical means, a. first adjustable orifice regulating the flow of fluid from the reservoir to said member, a check valve preventing flow of fluid from said member to said reservoir through said first orifice, a second adjustable orifice regulating the flow of fluid from the member to the reservoir, and a second check valve preventing flow offiuid from said reservoir through said second orifice and to said member, said adjustable orifices providing means for selectively and independently controlling the rate of movement of said fluid operated mem- .ber in either direction.

11. In a hydraulic timing mechanism, in combination, a fluid operated member biased to a member and to remove -the fluid therefrom and hence control the rate of movement of said fluid operated member in each direction, and means operable to force fluid in addition to said predetermined amount into said member.

12. In a thermal timing. mechanism, a heated thermal actuated means, a, heater therefor, an

loperating member driven by said means, a first means operable by said member for controlling the energization of said heater to actuate said thermal means to drive said operating member in cyclic operations of greater and lesser extents. second means operable by said member for controlling the energzation of said heater which causes one of said cycles of operation to be confined to the operations of lesser extent.

13. In a control apparatus, a pressure actuated member, an electric heater therefor, first circuit means for energizing and deenergizing said heater for increasing and decreasing the pressure within said member to cause intermittent operation of said control apparatus, second circuit means operable to energize and deenergize said heater to increase and decrease the lpressure within said pressure actuated member, and said second circuit means being operable to maintain a greater pressure within said member when the apparatus is under the control of said second circuit means than when the apparatus is under the controlof said first circuit means.

14. In a control apparatus, a pressure actuated member, electric means for heating said pressure actuated member, a first circuit for said electric heater means, timing means for controlling said first circuit to intermittently raise the temperature and pressure within said pressure actuated member to a predetermined degree. a second circuit for controlling said electric means to raise the temperature and pressure within said pressure actuated member to a predetermined degree above said first mentioned degree, and means operable in conjunction with said second circuit for maintaining said temperature and pressure within a predetermined range above said first mentioned degree.

15. A Stoker control system comprising a stoker motor, a first switch for controlling the operation of said stoker motor, a second switch for controlling the operation of said motor, means for moving said second switch to closed and to open conditions including an expansible uidmotor, independent means for regulating the rate of expansion and contraction of said expansible fluid motor, a heater for said expansible fluid motor, and a third switch in series with said heater and adapted to be actuated by said motor, said heater being connected to the second switch so as to be energized when the second switch is' closed and also to be intermittently energized by action of said third switch when the first switch is closed, said expansible fluid motor operating over a different range when the first switch is closed than when it is open.

16. A stoker control system comprising a stoker motor, a first switch for controlling the operation o! said stokeimotor, a second switch for controlling the operation of said motor, meansfor moving said second switch to closed position and for moving said second switch to open position including an expansible chamber, an auxiliary chamber, an expansible fluid in said chambers, an electric heater for said expansible fluid connected so as to be constantly energized when the second switch is closed, and automatically operl ated switch means actuated by said expansible chamber for energizing and deenergizing said heater during the period said first switch is closed.

17. A stoker control system comprising a stoker motor, a iirst switch for controlling the operation ofl said stoker motor, a second switch for controlling the operation of said motor, means for moving said second switch to closed position and for moving said second switch to open position including an expansible chamber, an auxiliary chamber, an expansible iluid in said chambers, an electric heater for said expansible iluid connected so as to be constantly energized when the second switch is closed, and means responsive to the movement of said expansible chamber for intermittently energizing said heater while the rst switch is closed.

18. In a, stoker control system, a first switch and a second switch connected in parallel, a stoker motor and an electrically operated heat motor in parallel relationship with each other and in series with said switches, said heat motor being positioned to intermittently open and close the second switch when the ilrst switch is open, and a third switch in series with said two switches and said heat motor and positioned to be actuated by said heat motor intermittently to open and closed positions at a heat motor temperature different Irom that necessary to open said second 40 Number switch and when said first switch is closed.

14` 19. In a stoker control system, a rst switch and a second switch connected in parallel, a stoker motor and an electrically operated heat motor in parallel relationship with each other and in series with said switches, said heat motor being positioned to intermittently open and close the second switch when the rst switch is open,

means to vary the rates of the opel ing and closing movements of said heat motor, and athird switch in series with said two switches and said heat motor and positioned to be actuated by said heall motor intermittently to open and closed positions at a heat motor temperature diierent from that necessary to open said second switch and when said first switch is closed.

ALBERT E. BAAK.

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

UNITED STATES PATENTS Number Name Date Re. 17,820 Garrison Oct. 7, 1930 1,414,448 Windell May 2, 1922 1,660,959 Goodhue et al Feb. 28, 1928 1,856,586 Persons May 3, 1932 1,885,963 Teeple Nov. 1, 1932 1,983,314 Schultz Dec. 4, 1934 2,075,305 Sayre Mar. 30, 1937 2,226,293 Denison Dec. 24, 1940 2,228,515 Foulds Jan. 14, 1941 2,322,675 Vaughan et al June 22, 1943 2,331,737 Scoggin Oct. 12, 1943 2,348,206 Cunningham et al. May 9, 1944 2,373,103 Deubel Apr. 10, 1945 FOREIGN PATENTS Country Date 162,624 Switzerland Sept. 1, 1933 Certificate of Correction Patent No. 2,470,999 May 24, 1949 ALBERT E. BAAK It is hereby certed that error appears in the printed speccation of the above numbered patent requiring correction as follows:

Column 12, line 18, strike out the Word heated;

and that the said Letters Patent should be read With this correction therein that the same may conform to the record of the case in the Patent Ofce.

Signed and sealed this 14th day of February, A. D. 1950.

THOMAS F. MURPHY,

Assistant Uommz'ssz'oner of Patents.

Certificate of Correction Patent N o. 2,470,969 May 24, 1949 ALBERT E. `BAAK It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows:

Column 12, line 18, strike out the Word heated;

and that the said Letters Patent should be read With this correction therein that the same may conform to the record of the case in the Patent Olce.

Signed and sealed this 14th day of'February, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.