US1920572A - Furnace grate stoker control - Google Patents

Description

ug 1, 1933. w. A. LACKE FURNACE GRATE STOKER CONTROL Filed Nov'. 2, 1928 s sheets-sheet 1 MUH|| w. A. L AcKE 1,920,572

FURNACE GRATE STOKER CONTROL 3 Sheets-Sheet 2 Filed Nov. 2, 1928 Aug l, 1933. w. A. LAcKE 92572 FURNCE @RATE STOKER CONTROL Filed Nov. 2, 1928 Patented Aug. l, 1933 UNITED STATES -PATENT OFFICE mesne assignments, to Pullman Car & Manufacturing Corporation, a Corporation of Delaware Application November 2, 1928 Serial No. 316,704

4 Claims.

The invention relates generally to devices for feeding coal to furnaces equipped with Achain grate stokers, and has particular reference to means for automatically regulating the length of the re on the stoker.

The invention further contemplates the use of audible or visual signal devicescontrolled by the means regulating the length of the re.

Another object of the invention is to provide a thermal unit adjacent the discharge end of the stoker and within the heat zone of hot coals or ashes passing from the stoker to the ash-pit and adapted to be affected by the radiant energy emanating therefrom.

A still further object is to so form and dispose thethermal unit and mounting therefor that the sensitivity of `the device to the radiant energy of the hot ashes and coals will'not be too greatly alected by the heat in the ash-pit.

The foregoing and other objects are attained by the mechanism illustrated in the accompanying drawings, in which Fig. 1 is a vertical section through a boiler of the water tube type equipped with a chain grate stoker and fitted with the control mechanism of the invention;

Figs. 2 and 3 are side and end elevational views, respectively, of the stoker operating mechanism;

Fig. 4 shows the electrical connection between a thermostat and the stoker operating 'mechanism; and

Figs. 5 and 6 are plan and side elevational views of a thermostat and its mounting supported from the furnace wall.

In stokers heretofore used a great loss of fuel resulted from the inability of the operator to properly regulate the speed of the stoker to maintain the fire at its highest eciency. This difficulty has been overcome by the present invention in which mechanism has been provided to automatically accelerate or decelerate the speed of the Stoker through the medium of an automatic control unit responsive to heat radiations 5 and electrically connected to a solenoid4 operable to engage or disengage a ratchet operating pawl for the purpose of shortening or lengthening the nre on the stoker. The stoker mechanism is operable at two speeds, one too fast, if maintained,.and causing the hot coals to be wasted into the ash-pan, and the other too slow to keep the fire against the waterback of the boiler. :v

'Ihe mechanism for effecting the change from one speed of the stoker to the other is indicated in the drawings, in which 10 represents a water tube boiler of any approved type having the usual waterback 11 arranged immediately above a re bed 12 carried upon a chain grate stoker 13 fed from coal hopper 7.

In the present embodiment, the stoker is operated by an electric motor 14 having a pinion 60 15 engaging a gear wheel 16 mounted upon driving shaft' 17 carrying a pair of eccentrics 18 havilng link connection with ratchet operating levers The eccentrics rotate in strap frames 20 hav- 65 ing link extensions 21 pivoted at their ends to ratchet operating Llevers 19 by pins 22 as best indicated in Figs. 2 and' 3. The eccentrics are relatively offset to cause alternate oscillating movement of ratchet levers 19. The leversl 19 70 carry pawls 23 adapted for engagement with respective ratchet wheels 24 fixed to transmission shaft 25 to which is secured a worm gear 26 designed to mesh with a gear wheel 27 on Stokeractuating shaft 28. For the purpose of eiecting a change in grate speed hereinbefore noted, and thereby control the length of the fire 12 on the grate 13, the pawl 23 on one of the operating levers 19 is adapted to be disengaged from its ratchet 24 by means of an electro magnet or solenoid 30 carried by the lever 19 and positioned above the pawl 23 which is to be lifted by it. As shown in Figs. 2 and 3, a magnet is secured to lever 19 by a yoke piece 31 straddling the pawl and riveted astride the lever to support the magnet 30 the proper distance above the pawl 23 to allow it to be lifted by the magnet when energized. The lifting of the pawl will result in its disengagement from the respective ratchet 24 on shaft 25 and consequent reduction in the number of impulses to be given said shaft, that is to say, the movement of the stoker will be reduced to its set minimum speed to prevent unconsumed fuel from being discharged into the ash-pit 32. In the embodiment shown, two levers 19 have been used, 95 operated by the respective eccentrics 18 through linkextensions 21, and equipped with pawls 23 for engaging the respective ratchets 24.

It is conceivable that within the scope of the appended claims, a single lever 19, tted with two 10o pawls acting alternately, one of which may be lifted out of engagement with the ratchet 24 by the solenoid 30, may be substituted for the two lever mechanism indicated.

The magnet 30 is energized by the closing of the 105 electric' circuit 8 controlled by a unit 33 located at the discharge end of the stoker 13 within the radiant energy zone of the hot coals or ashes passing to the ash-pit 32.

In the preferred embodiment shown. a thermostat is mounted upon the inner end of a tube 34 supported at its opposite end in the furnace wall 35 and of a length that will permit the thermostat 33 to be placr d at the medial plane of the stoker 13. The tube 34 is insulated from the heat 'of the ash-pit 32 underneath by a covering 36 of asbestos shielded by metal sheathing 37 to protect the asbestos from thc deleterious action of the furnace heat and fumes of combustion. The thermostat 33 rests upon a panel 38, supported upon a portion of the tube 34 cut away for a portion of its length as best shown in Figs. 5 and 6, leaving an extended portion 39 projecting from the base of the remainder of the tube, the panel beingheld upon the tube by screws 40 let into the tube segment 39. The panel 38 supports the thermostat ribbon 41 at the positive terminal 42 of the circuit with its pole piece 43 held normally away from the negative post 44 as indicated in Fig. 5. To preserve the integrity of the thermostat 33 thus positionedand exposed to the dust and `heat of the ash-pitbelow it and the radiant heat of the discharging hot coals or ashes from the stoker, the tube 34 is left open to the outer air as at 45 to allow the relatively cool air to enter the tube and sweep across the thermostat 33 and beneath the panel 38 to minimize the effect of the enveloping heat from the ash-pit and adjacent portion of the furnace whereby the thermostat ribbon 41 is cooled and rendered more sensitive to the relatively greater heat of the hot coals or ashes passing from the stoker 13. The air currents thus established tend also to carry away the stoker dust and ashes to prevent clogging and resultant failure of the ribbon 41 to respond to temperature variations.

In operation, assuming the fire bed 12 to be toc` short to be kept against the water back 11 of the boiler, the radiant heat from the dis charging ashes from the stoker 13 will be too low to cause thermostat 33 to respond to it. At this stage of operation the thremostat is out of contact with terminal post 44 as shown in Figs. 4 and 5, the electromagnet 30 de-energized, and both pawls 23 operatively engaging the ratchet wheels 24. The movement of the eccentrics 18, connected by links 21 to the ratchet operating levers 19, will actuate the levers to cause intermittent rotation of the worm shaft '25 through attached ratchet Wheels 24 both of which are engaged by their respective pawls 23. The operation of both ratchets will accelerate the speed of the Stoker 13 and continue todrive the stoker at the higher speed until the length of the re on the stoker has sufficiently increased to extend the fire to the water-back 11 and close to the thermostat 33 when the heat emanating from the hot coals and ashes passing from the stoker will cause the ribbon 41 of the thermostat to move against the terminal post 44 whereupon the circuit 8 energizing the magnet 30 and lighting the signal lamp 9 will be closed.

The magnet 30 thus energized by the closing of the circuit 8 becomes effective to lift adjacent pawl 23 from engagement with its ratchet wheel 24 to cause a reduction of the speed of the Stoker to the minimum set by the operation of but one pawl and ratchet mechanism since by the action of the magnet 30 the lever carrying it vibrates idly upon the shaft 25. As the stoker continues to be driven at the lower speed under the power of the single operating ratchet, the fire on the stoker begins to shorten and recede from water back 11 and thermostat 33l until the heat from nant as it sweeps through the tube 34 and across the hot ashes passing from the Stoker becomes too low to operatively affect the thermostat.

As the heat radiations from the stoker decline,

the cooling effect of the outer air becomes domi- 80 the thermostat ribbon 41 which then moves out of Contact with the other terminal post 44, thus breaking the circuit, de-energizing the magnet and dropping the pawl 23, and extinguishing the signal lamp 9, and the cycle of operations repeated. The intermittent flashing of the signal 9 serves to advise the attendant of the continuity in the cycle of operations. An audible signal may be substituted for the lamp 9 if desired, but the visual signal has been found satisfactory for the purpose.

The mere placing of a thermostat at the discharge end of the stoker would not of itself accomplish the desired result as the action of the thermostat would be too sluggish for practical purposes unless shielded and set as described to minimize the effect of the heat in the ash-pit.

In the use of thermal control units of the type indicated in the present embodiment it has been found necessary to adjust the distance between Contact 43 on thermostat ribbon 41 and the terminal post 44 to X the temperature required to move the contact 43 toward or away from the post 44 to effect a change in stoker speed at predetermined lengths of the fire.

For this purpose there has been provided an adjusting mechanism operable from the outside of the furnace, and of simple construction and application. The device consists of a wheel mounted for rotationon panel 38 and operatively secured by pin 49. The ribbon 41 is heldin thermostat post 48 secured to wheel 50 by machine screws 47 properly insulated from the post to avoid short circuiting. The post 48 has flexible electrical connection with terminal 42 through a brass washer 115 46 as best shown in Figs. 5 and 6. The Wheel 50 is preferably formed as a gear wheel, as indicated, and rotated by means of a worm gear 51 meshing therewith and itself actuated by a shaft 52 extending through tube 34 to the outside of the120 furnace wall 35 and there fitted with a knurled handle 53 for convenient manipulation of the worm. The worm is secured to a spindle 54 journaled in brackets 55 on panel 38, the spindle being connected to operating shaft 52 by a loose 125 coupling 56 to permit slight relative angularities in positions of said shaft and spindle and to facilitate the installation of the apparatus within the furnace.

It will be noted that by the operation of the mechanism described, the boiler is maintained at its highest efficiency and the fuel wastage held to a minimum and to an extent impossible of attainment by methods and machinery heretofore employed. The arrangement is simple in design and readily and economically applied without requiring any change in existing equipment.

What I claim is:-

l. vln grate stoker mechanism for feeding fuel through a furnace, the combination with a con- 140 trol unit comprising a tube anchored at one end in the wall of the furnace and having its inner end adjacent the discharge end of 'the Stoker and a thermostat supported thereon within the radiant heat zone of the hot coals and ashes passing from the stoker, of means associated with said unit for shieldingthe thermostat from the enveloping heat of the furnace and ashpit, and a solenoid in series with the thermostat and so placed with respect to said Stoker mechanism as 50 to cause reduction of speed thereof upon closure of said circuit, said tube at its Wall end being open to the atmosphere whereby the thermostat supported upon its inner end will be swept by air drawn therethrough and in the path of heated materials discharged from the stoker.

2. The combination in a furnace including an ashpit, of stoker control mechanism for feeding fuel thru the furnace and discharging into the ashpit, comprising a tube mounted n said ashpit and normally open to the atmosphere, and a thermostat controlling said mechanism supported on the inner end of said tube and exposed to the radiant heat energy of the hot coals and ashes passing from the stoker and in position to be swept by air therethrough and in the path of the heated materials discharged from the Stoker, and a solenoid in series with the thermostat, said solenoid being so placed with respect to the stoker mechanism as to cause reduction in the speed thereof upon closure of said circuit.

3. The combination in a furnace including an ashpit, of stoker control mechanism for feeding fuel thru the `furnace and discharging to the ashpit, comprising a tube mounted in said ashpit and normally open to the atmosphere, a thermostat controlling said mechanism supported on the inner end of said tube and exposed to the radiant heat energyvof the hot coals and ashes passing from the Stoker, thermostat adjusting means manually operable outside the furnace for establishing the temperature at which a change in stoker speed becomes effective, the thermostat being positioned in the path of air drawn thru said tube and of the heated materials discharged from the stoker, and a solenoid in series with the ther mostat, said solenoid being so disposed with respect to the stoker mechanism as to cause reduction in the speed thereof upon closure of said circuit.

4. The `combination with a furnace and grate stoker mechanism for feeding fuel therethrough, of means for controlling the rate of action of said mechanism, comprising a thermal unit including a tube mounted in a furnace wall and open at one end to the atmosphere and at its other end to a zone of the furnace adjacent the discharge end of the Stoker, a thermostat supported on the inner end of said tube in position to be swept by air drawn therethrough and in the path of heated materials discharged from the. Stoker, and a solenoid in series with the thermostat, said solenoid being so placed with respect to the stoker mechanism as to cause reduction in the speed thereof upon closure of said circuit.

WILLIAM A. LACKE.

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