US2661181A - Air lock coal scale - Google Patents

Description

Dec. 1, 1953 A. J. sTocK AIR LOCK COAL SCALE 6 Sheets-Sheet l Filed Oct. 51, 1951 INVENTOR Dec. 1, 1953 Filed Oct. 31, 1951 A. J. sTocK AIR Locx COAL SCALE,

6 sheets-sheet 2 4 INVENTOR ATTORNEYS Dec. 1, 1953 Filed Oct. 51 J 1951 A. J. s'rocK 2,661,181

AIR LOCK COAL SCALE 6 Sheets-Sheet 3 4,18 on ,m 1,20

INVENTOR ATTORNEYS Dec. l, 1953 A. J. sTocK 2,661,181

AIR LOCK COAL SCALE Filed Oct. 3l, 195] 6 Sheets-Sheet 4 INVENTOR ATTORNEYS 4M/wlw@ BY @M Dec. l, 1953 A. J. s'rocK 2,651,181

AIR LOCK COAL SCALE Filed 0G12. 3l, 1951 5 Sheets-Sheet 5 1J J W um ATTORN E YS BY www QW l www Dec. 1, 1953 A. J. sTocK 2,661,181

AIR Loox COAL SCALE Filed 0G12. 51, 1951 S Sheets-Sheet 6 u 2D @f3/3 OOOQG@ OOGOOOO.

INVENTOR ATTORNEYS atented Dec. l, 1953 UNITED STATES PATENT OFFICE AIR LOCK lCOAL SCALE Arthur J. Stock, Cleveland, Ohio Application October 31, 1951, Serial No. 254,130

9 Claims.

This invention relates to a bulk material scale apparatus for operation with a system under pressure and more particularly vto a coal scale for use with either pressure or vacuum furnaces or burners.

In the handling of bulk material wherein it is transported from a starting point at atmospheric pressure through a weighing operation to a remote point under pressure, a stoppage of the bulk material will generally result in gases or vapors being blown back through the system from the remote point under pressure. These gases generally contain dust or other obnoxious impurities and usually gain access to the atmosphere at the starting point thereby polluting the surrounding area and resulting in the discomfiture of persons in the immediate vicinity. Similar difficulties are encountered when the lremote point is under vacuum where it is desirable to prevent the entry of air at the starting point.

While this problem is present in all types of bulk material systems of this nature, nevertheless, it has particular reference to coal handling installations feeding pressure or vacuum furnaces or burners where there is an added danger of fire. A normal coal installation of this type stores the coal in a bunker for transportation through a feeding system including conveyors, a scale apparatus, chutes, downspouts and a feeder, to a pressure or vacuum furnace.

In order to burn coal in very large boiler furnaces, it has been the custom in many installations to first pulverize the coal and then blow the powdered coal into the furnace where it burns as a gas. Equipment necessary to carry out the foregoing operation consists of a pulverzer, a feeder for that pulverizer, and a fan which picks up air and pulverized coal and forces that combustible mixture into the boiler furnace.

One arrangement of equipment places the fan between the pulverizer and the boiler furnace. If the pressure within the boiler furnace is slightly negative, as it usually is, then the interior of the pulverizer is under a small vacuum. Consequently, if the coal feed pipe between the coal feeder and the pulverizer were left open to the atmosphere, most of the combustion air would rush through this pipe. Therefore the feed pipe is made airtight by constantly having a solid head of crushed coal of several feet located therein to act as a reasonably good air seal between the atmosphere and the interior of the pulverizer, and thus only a small quantity of cold air leaks into the pulverizer.

With the arrangement as suggested above there is some wear on the blades of the fan due to the erosion caused by the coal dust from the pulverizer moving over the fan blades. In order to reduce fan maintenance, some installations place the fan ahead of the pulverizer. This puts the pulverizer under positive pressure and also the pulveriaer feeder. Here again, a column of coal several feet high ahead of the pulverizer feeder has been used as a seal to prevent loss of air into the atmosphere through the coal.

It is desired in many installations to preheat the combustion air. Hence it is necessary to reduce to a minimum the leakage through the feed pipe.

The above and foregoing remarks have been made in reference to a boiler furnace operating under a slight negative pressure by reason of the utilization therewith of an induced draft fan. However, the more recent tendency is to utilize a forced draft fan. This means that the boiler furnace operates under a positive pressure, and as a result the'pressure existing at the pulverizer feeder is several times as great as it was with installations employing an induced draft fan. Therefore, in order to prevent leakage of air back through the coal as it is fed to the pulverizer feeder, it is necessary to provide a higher column of coal in the feed pipe to form a satisfactory seal.

Also during the recent years there has been developed another method of firing coal under very large boilers which is known as the cyclone burner. This burner consists of a large watercooled cylinder into which the coal is brought along with air under a fairly high pressure. Because of the high pressure on the forced draft air, there is a very high air velocity developed as the air enters the cyclone burner. These conditions cause combustion to take place almost instantly with a very minimum of excess air, and therefore the eiiiciency of this method of combustion is excellent. However, the high pressure of the system necessitates the use of a still higher head of coal in the feed pipe to form a satisfactory seal.

If a standing column of coal is used as a seal, there also is a problem with the coal scales which are very often employed to weigh the coal as it A need be employed in order to make the coal scales accurate.

It has been found in many plants that it is impossible to provide a suicicnt column of coal ahead of the feeders in order to give satisfactory sealing on a space or headroom basis. It has also been found that feeding the coal against the pressure of the air is not as reliable as it should be because wet, line, sticky coal tends to make a more perfect seal but the air pressure has a tendency to cause such coal to stop flowing entirely. Therefore, in order to insure more reliable coal flow and also in order to reduce the overall height of the boiler plant some other method of sealing against the air pressure is necessary.

One other such method is to use a. star-type seal or feeder between the coal feeder and the cyclone burner. Such seals result in the coal being fed in a succession of small batches. Therefore combustion is not as satisfactory as it would be if the feed were more uniform. Furthermore the loss of air back through such a seal is greater than it should be and the maintenance of this type of equipment is quite high because of the rubbing of the star-shaped core against the housing.

Another type of seal that has been employed is the screw feeder which is run full of coal at all times and which has a short pitch at its discharge end. It has been found dimcult to force the coal into the screw at the feed end partly due to the air pressure differential that exists across the screw and partly due to the relatively small size of the screw in relation to the other equipment.

In the operation of boiler plants with pressure furnaces, there also exists a danger, that the coal may hang up in the bunker and not flow out through the outlet provided therefor. Under these conditions, if the operator stops the flow of feed air to the burner, the hot furnace gases will vent back through the system to the bunker. Inasmuch as the temperature within the furnace is several thousand degrees, it is obvious that damage will result to the various pieces of equipment between the bunker and the furnace, and also the coal that does remain in the bunker will catch on fire. This can happen almost instantly. Such a condition is very dangerous to operators and also it may result in the complete stoppage of steam generation and in the case of a public utility may shut down the entire plant. For safety of operation of pressure furnaces, it is necessary that the system at some point ahead of the furnace be completely shut off at all times.

Accordingly, this invention provides apparatus in the nature of a bulk material scale for alleviating the undesirable features in pressure of vacuurn systems as above described. More particularly, this invention provides a coal scale apparatus for eliminating the danger of fires and overcoming other disadvantages of coal feeding systems operated with pressure furnaces or burners. This is accomplished by this invention with reference to coal handling by providing a coal scale apparatus wherein a pair of gas valves are arranged to effect a gas lock to prevent gases under pressure from traveling back through or into the system. At all times, at least one of the gas valves is maintained closed to stop any gases under pressure from moving beyond the apparatus. Further, a vent to any desired location can be provided in the apparatus to reduce the pressure of the gases trapped in the lock to substantially atmospheric pressure. In order to permit the gas valves to operate quickly and efficiently nature indicated which will prevent gases under pressure from escaping at undesired points, or, in the event of a vacuum system, lwill prevent air entering the system at the point from which the bulk material is fed.

It is a further object of this invention to provide a coal scale apparatus for use in installation systems as previously described that will eliminate the danger of fires and that will overcome other disadvantages of present systems.

It is a still further object of this invention to provide a coal scale apparatus that will operate more efficiently and economically than any such apparatus presently available,

Other and further objects of the present invention will become readily apparent from a detailed consideration of the following description when taken in conjunction with the drawings in which:

Figure 1 is a View in side elevation partly broken away showing the coal scale apparatus of the present invention;

Figure 2 is a view in vertical section of Figure l taken along line 2 2;

Figure 3 is a view in vertical section of Figure l taken along line 3 3;

Figure 4 is a view in vertical section of Figure 2 taken along line 4 4;

Figure 5 is a view in horizontal section of Figure 4 taken along line 5 5;

Figure 6 is a view in vertical section of Figure 5 taken along line 6 6;

Figure is a View in vertical section of Figure 5 taken along line land Figure S is a view in side elevation partly broken away showing a modified form for operation of the gas valves.

Referring now to the drawings, Figures 1-7 inclusive illustrate the new and improved coal scale apparatus. A. main housing lil encloses an endless conveyor belt i2 carried on pulleys lll which are mounted on shafts i5 which are bearing supported in side plates 2S. A weigh hopper I8 is suspended from one end of a weigh lever mechanism to be described hereinafter. Auxiliary housings 2l and 22 are arranged on the main housing is to encase and protect portions of apparatus located outside the main housing l. Further, an electrical compartment 25a is mounted on the main housing iii for location of the necessary electrical equipment for operation of the apparatus. Each of the housings and the cornpartinent are provided with doors to permit access thereto.

Within the main housing it, the endless conveyor belt l2 is mounted on pulleys i4 as above described. Side plates 26 are mounted between shafts l5 to securely maintain the relative positions of the pulleys l. Small rollers 2c support the conveyor frame and allow the entire feeder assembly to be removed for aelt replacement. The upper part of the conveyor belt is supported by a fiat plate Directly above the belt l2 at this point is an opening 32 in the main housing l. Skirt plates 3 are vertically mounted on either side of belt l2 between the opening 32 and the conveyor. Also an end plate 33 is transversely positioned across the belt |2 at one end thereof.

The appara-tus is normally joined to a source `of coal such as a bunker by connecting opening 52 to the bunker outlet directly or through intermediate apparatus such as a coal valve, chute or dcwnspout or any combination thereof. Hence, coal is fed to the belt I2 through opening 32 and is transported to the right of the conveyor, as shown in Figure fl, to be dumped. A scraping bar 35 is mounted with the conveyor just beyond the dumping point to keep coal from sticking on the belt I2 during its return run. However, practical experience indicates that some coal, particularly ne, evades the operation of scraping bar 35 and consequently a compartment 35 is provided for the collection of this coal.

The coal being dumped from the conveyor belt l2 passes through an opening 38 in a plate 40 and is received in the weigh hopper I8. Two pins project from opposite sides of weigh hopper I8. The pins 42 are given rigidity by a conventional strut arrangement 44. A loop 46 attached to one end of a shaft 48 is secured to each pin 42. The other ends of the shafts 48 project through partitions 58 which constitute one wall of each of compartments 52 and are each joined to a scale bearing loop The shafts 48 at their points of projection through partitions 5E! are encased in molded rubber bellows 5| so that the compartments 52 are maintained pressure tight with respect to the space occupied by the weigh hopper i3. The compartments 52 communicate with the auxiliary housing 2 I. The scale bearing loops 54 cooperate with pivot pins 5G rigidly fastened to weigh levers 58 to provide a knife-edge attachment for the weigh hopper I8 with one end of the weigh levers 58. Each of the weigh levers 58 in compartments 52 is provided with a knife-edge pivot or fulcrum (not shown) by means of scalebearing loops and pins. The other ends of the weigh levers 58 are interconnected by a bar 68 so they will operate as a single unit. Scale-bearing loops 52 cooperate with pins 54 rigidly fastened to weigh levers 58 to form a knife-edge attachment for a counterweight 66 with the other ends of weigh levers 58. The counterweight 56 is suspended between the scale-bearing loops 62.

The weigh hopper I8 is provided with a closure member 68 pivoted as indicated at 'I0 and has mounted .therewith a counterweight assembly 'I2 which tends to keep closure member 68 shut. A solenoid housed in compartment I4 mounted on the weigh hopper I8 operates responsive to an electrical circuit to hold the closure member 68 against opening during the weighing cycle. After the desired weight is in hopper I8, the electrical circuit controlling the solenoid opens, thus allowing the closure member 68 to swing open and discharge the coal from the hopper I3. Coal being dumped from the hopper |8 passes out of the apparatus through outlet 'I5 to a downspout, chute, or pulverizer feeder or the like.

An electric motor 'I6 supplied from a suitable source is mounted on top of auxiliary housing 28. The motor output shaft F3 passes into auxiliary housing 2| where it is connected to a gear reducer 8). The output shaft 82 of the gear reducer 88 passes into main housing I8 and has a gear 84 mounted on its end. A gear 8&5 mounted on shaft I6 of the forward pulley I4 of the conveyor meshes with gear 84. Accordingly, the motor 'I6 is mechanically connected to the forward pulley I4 of the conveyor and thereby power is supplied to drive the conveyor belt I2.

The space occupied by the weigh hopper I8 is completely enclosed by the plate 48 xed to Ithe main housing l@ above hopper I8 as indicated at 88, a plate 82 fixed to the main housing Il below hopper I8 as indicated at Sii, a series of partitions extending between the plates lll) and 92 generally indicated as 36 and part of the main housing lil. As noted previously, plate It is provided with an opening 38. Joined by bolts 88 to plate Il@ bounding opening 38 are steel bars Idil each provided with a Stellite edge |Il2 mounted thereon. Similarly plate 82 has an opening Ilfl. Jointed by bolts to plate 52 bounding opening Idil are steel bars ID3 each provided with a Stellite edge II mounted thereon. Series of rollers |I2 and I I3 each biased by a spring I ill or I I5 respectively are mounted on opposite sides of each of the openings 38 and |88 respectively. Each of the rollers I I2 and I |3 is mounted on a diagonal element I I8 and I II respectively, pivotally supported on an elongated member I i8 and lill respectively so that they are individually urged toward their respective opening by the spring bias. 'lliis preoise structure will be considered in greater detail with specific reference to Figures 5-'7 inclusive. Plates |28 and |2| preferably of stainless steel are carried on each series of rollers |52 and IIB respectively.

A motor |28 mounted in auxiliary housing 2li is supplied from a suitable source of energy. The output shaft |28 of motor 28 drives a gear reduoer |38 preferably of the worm gear type. The output or low speed shaft Il-Z of reducer |38 has mounted thereon a crank |34. A link itt` has one end pivotally attached to the crank i3d and the other end pivotally attached to crank |3'I, the other end of which is rigidly fixed to a shaft |38 which projects into main housing It. This shaft |38 is mounted in bearings |48 and within main housing I8 has mounted thereon a pair of levers |42. The other ends of levers |62 are pivotally connected to one end of operating shafts Ille. The other ends of operating shafts lliil are pivotally joined to one side of plate IM. Hence operation of motor IES will cause levers |42 to oscillate and thereby effect movement of the plate |2| on rollers ||3. Mounted in conjunction with link |36 and crank |32i are limit switches |45 and |41 to control the operation of motor |25.

A motor |59 supplied from a suitable source of energy is mounted in auxiliary housing 22. The output shaft |52 of the motor |59 is coupled to the input shaft of a gear reducer |5ll preferably of the worm gear type. The low-speed shaft |55 of reducer |55 has xed thereon a crank I5?. To the end of crank |52' is pivotally connected a link |58. A crank |58 has one end pivotally attached to link |58 and the other end rigidly fixed to a shaft I 62 which projects into main housing Ill. This shaft |52 is mounted in bearings |84 and within main housing i8 has mounted thereon a pair of levers |556 and I8?. The other ends of levers I 56 and IS'I are pivotally connected to one end of operating shafts |58 and |68 respectively. The other ends of operating shafts |68 and |88 are pivotally joined to one side of plate |25. Therefore operation of motor I5@ will cause levers |56 and ll to oscillate and thereby effect movement of plate iilil on rollers H2. Mounted in conjunction with crank itil are limit switches IIll and I'II to control the operation of motor |50.

The structure immediately surrounding opening 38 is shown in detail in Figures 5-7 inclusive. The elongated members H8 are plates which are aesinet fastened to the main housing I and plate 40, as by Welding, on opposite sides of opening 38 as indicated in Figure 2. To eachvof these members IIB is joined an elongated block |80, as by welding, as indicated in Figure "1. At spaced intervals pivot ins |82 are located extending through member IIB and block |80. Each 'pin |32 is provided with bearings |84 and |86 adjacent either end. The member H8 is recessed to receive the head |88 of each pin |82 to prevent axial movement of the pin into and through the membe H3 and block |39. Each pin |82 projects beyond block iilii and has iixedly mounted on the end thereof the diagonal element H5. To one end ci each diagonal element is connected a roller i i2 by means of a short shaft |90 and suit able bearings (not shown) to permit the roller i I2 to rotate freely. The other end oi each diagonal element ii is biased by a spring ||4 positioned between this end of element i I6 and plate ilo. To assist the performance of spring M, the plate fili recessed as indicated at |92, see Figure '7, to secure the relative position of spring |4. As noted pre usly, bas lili) are connected to plate @lil bounding opening 38 and each bar Hill previa with a Stellite edge I|i2 mounted thereon. -Plate iil rides on rollers H2 and has guide strips itil joined to its under surface to maintain the relative position of the plate on the roll-ers iiil. Hence it can be seen that bars and i222 constitute a valve seat and that plate iil cons tutes a gate valve head. `The springs lill tend to pivot their respective diagonal elements i it about the airis of their respective pins Hill and move the rollers ||2 upivarclly t'iereby maintaining a gas-tight contact between the plate ll and bar lili) and edges |02. 'in order to prevent injury or damage to this valve structure, the roller assembly is laterally oset from opening 38.

Each roller i |22 is independently lubricated. A grease fitting it is connected to the shaft |99 mounted in diagonal element HG. The shaft iii@ hollow and communicates with the s i'or the roller iii. A ilexible tube lili! 'ltil are in communication with a manifold igure 4i) which supplied through a tericr of main housing il) by means of fittings tot.

The members iii have joined to one end thereoi' blocirs ist provided with threaded bores 2| il to permit the roller i E2 and plate 2li assembly to be connected to the main housing il? by means of bolts 2li.

While this assembly has been described as constituting the valve immediately above the Weigh hopper it, it is to be understood that this structure is substantially similar in all respects to the rollers liti and plate |2I assembly immediately below the hopper i8, and surrounding opening it.

The opera-tion oi the apparatus is as follows: Coal is introduced onto conveyor belt i2 through or inlet from a bunker either directly or indirectly' and is carried to the end of belt i2 Where it is dumped through opening 38 into hopper i8 Where it is weighed. Subsequent thereto, it is dumped from the hopper |8 and passes through opening itil and outlet 75 to a downspout or the liifze and is eventually introduced into a zone of different gas pressure such as exists in a pressure furnace or a pressure burner such e tubing 213:1 communicating with the eX l as a cyclone-type burner. The operation is carried out in continuous batch fashion and consequently, the conveyor ceases to operate during the discharging cycle `from the Weigh hopper. The apparatus is generally divided into zones as regards pressure. The space occupied by the conveyor as well as all apparatus preceding in the system is maintained continually at atmospheric pressure. The apparatus succeeding outlet 'l5 is continually under pressure. rlhe space occupied by the weigh hopper i8 is a depressurizing zone and is alternately subjected to the pressure existing in the system and to atmospheric pressure.

The rollers ||2 and plate lili? assembly constitutes a gate valve to prevent ilow of 'gas through the system. Similarly the rollers li and plate |2| assembly constitutes a gate valve. For purposes of clarity hereinafter, the rollers I|2 and plate |20 assembly will be referred to as the top gas valve and the rollers H3 and plate I2| assembly will be referred to as the bottom gas valve. An important concept of the present invention is that both gas valves are never open at the same time during normal operation.

n order to protect the gas valves and maintain them pressure tight at all coal is never deposited or dumped directly cn either of plates |23 or IBI. A bulk material valve is provided ahead of each of the gas valves in the system to operate before valve in .e to the flow or coal before the gas valve is closed. also the gas valve is opened before the bulle material valve permits a resumption oi coal flow.

The conveyor belt i2 constitutes the top bulla material valve and its operation is correlated with the top gas valve. The closure til ol hopper it constitutes the bottoni bull' material valve and lil wise operation is eo ated with the bottom. gas valve.

Accordingly, the several valves cooperate in a cyo "c manner so that both gas valves are never open at the same time. This is accomplished by means of limit switches |113, iii?, i'i'ii and ill, the solenoid housed in compartment "ill, a suitable electrical circuit to control the operation of motors 75, 26 and lili, the solenoid in compartment 'i4 and a limit switch on the weigh hopper levers, and another limit switch in compartment '14. This last liinit switch is closed when gate Eil is closed. Operation of the Weighing electrical control is the saine as that described in my Patent No. 2,372,746 and as used in commercial coal scales of modern manufacture. he cycle of operation is follows:

Consider as a starting point 'that the top gas valve is open, the bottom valvel closed, the hopper IB is empty, and the conveyor is stopped. Since hopper gate EB is closed, the limit sii/'itch in housing i4 is also closed, hence the electrical control circuit energizes the motor iii and conveyor belt I2 begins its motion and dumps coal through opening 38 into the hopper i8. When hopper i3 receives a predetermined Weight of coal, the limit switch actuated by the weigh levers opens the motor i6 control circuit thus stopping motor le, thereby stopping the motion of the conveyor belt i2. The motor ili is energized to close the top gas valve. Thereafter, motor |26 is energized and causes the bottom gas valve to open. The solenoid is de-energized, permitting the Weight of the coal in hopper i8 to swing closure iis open against counterweight T2. The coal then passes out oi hopper i8 and through opening |04 and outlet l5. When all the coal has left the hopper i8, the counterweight 12 Will swing closure t8 shut. Thereafter, the solenoid is energized to hold closure 63 shut and motor |26 is energized to close the bottom gas valve. The motor E! opens the top gas valve. The cycle is then completed and the apparatus is in the condition as described in conjunction with the starting point.

The gas under pressure which is admitted to the depressurizing zone when the bottom gas valve is opened is quickly dissipated when the top gas valve is opened which incidentally occurs before the weighing operation. Hence, the weighing operation takes place at substantially atmospheric pressure thereby eliminating weighing errors which otherwise might be introduced should the weigh hopper I8 and the scale lever mechanism be subjected to substantially different pressures.

An alternative manner for operation of the gas valves is shown in Figure 8. Here, a link Se@ is connected between one end of the top gas valve 302 and a crank 354 mounted on shaft 30E. Also mounted on shaft 30.5 is a gear Stili which has gear teeth 308 over approximately one-fourth of its periphery. Also, the gear 3% is provided with a radial extending slot 3m. The gear 3d@ meshes with a similar gear 3l2 mounted on a shaft 3i3. A link 3M is connected between one end of the bottom gas valve 31S and a crank SIS mounted on shaft 3l9. Also mounted on shaft sie is a gear 32E similar to gear This gear also meshes with a gear 322 in like manner to gears 306 and 3|2. Gear 322 is mounted on shaft 323. Gear 395i does not mesh with gear dit nor does gear 3I2 mesh with gear @22 as pairs of gears 3DS-3H and 320-322 are laterally offset. A motor 324 supplied from a suitable source of power drives a gear reducer 325i. The low speed shaft 328 of reducer 32B has mounted at the end a Worm ESI. Meshing with the worm 335i is a worm gear 332 carried by a bearing mounted shaft 334. Fastened on shaft 334 is a crank 33t with a pin 33S projecting transversely at the end thereof. Accordingly, operation of the motor 32d will cause crank to rotate in a clockwise direction. As shown in Figure 8, the movement of crank 33S will result in pin tilt being received in radial slot Sit and moving gear in a counterclockwise direction for about 98 thereby moving crank to the position indicated as 34S and in opening the top gas valve 302. Movement of gear Std results in a clockwise movement of gear :H2 to the same angular degree. Hence, the radial slots will align and the pin will pass into the radial slot in gear 3ft and move this gear counterclockwise for about 90 returning it to its original position. lso the gear 30E will be moved clockwise the same degrec thereby closing the top gas valve Sti. As the radial slots in gears SI2 and 3222 now align, the pin S38 will pass into the radial slot in gear 322 and rotate this gear counterclockwise for about 99. This movement causes 'ear 3253 to rotate clockwise the same angular degree and results in opening the bottom gas valve lili and moving crank slt to the position indicated as 352. The radial slots in gears and now align and this permits the pin to be received in the radial slot in gear and rotate this gear about 90 in a counterclockwise direction thereby closing the bottom gas valve 31d and returning gear 322 to its original position. The crank 335 and pin 33S have now traveled through 360 and the gears and valves are again in their original positions. it therefore is apparent that the desired movements of both gas valves can emanate from the single motor 324. rlherefore, when subjected to the electrical controlling circuit, the operation of motor can be controlled in harmony with the cycle of operation, as previously described, to effectuate the desired result.

Since pin 33t enters the various slots travelling parallel to the sides of the slots, there is no hammer blow between the various parts. As a result, the mechanism can be run very fast Without undue wear of parts or noise.

While this invention has been described in conjunction with specific.- embodiments, nevertheless, various changes or modifications obvious to one skilled in the art are within the spirit, scope and contemplation of the present invention as claimed.

I claim:

l. A system for feeding material to a zone having a pressure different from atmospheric that comprises a gastight compartment having an inlet and an outlet, a weighing device in said compartment, said weighing device having a closure element to permit discharge of material, a normally opened rst valve positioned in. said inlet, a normally closed second valve positioned in said outlet spaced from the closure element of said weighing device, means responsive to the reception in said weighing device of a predetermined amount of material to successively close said first valve and open said second valve, and means responsive to the discharge of material from said weighing device to successively close said second valve and open said rst valve.

2. A system for feeding aggregate material to a zone having a pressure different from atmospheric that 'comprises a conveyor, an airtight compartment, a weighing device in said compartment, a normally open -rst valve establishing communication between said conveyor and said compartment, a normally closed second valve establishing communication between said compartment and said zone, means responsive to the reception in said weighing device of a predetermined amount of material to successively stop said feeding means, close said first valve and open said second valve, and means responsive to the discharge of material from said weighing device to successively close said second valve, open said first valve and start said feeding means.

3. A bulk material scale apparatus that comprises a housing divided into a feeding compartment with an inlet therefor and a gastight Weighing compartment with an outlet therefor, a weighing device in said gastight weighing device having a closure element to permit discharge of material, top valve means positioned between said compartments to cut off the flow oi gas therebetween, bottom valve means positioned below the closure element of said weighing device and in said outlet to cut oif the ow of gas therethrough and controlling means connected to said valve means and correlating their movements to maintain at least one of said valve means closed at all times.

4. A system for feeding material to a zone having a pressure different from atmospheric that comprises a housing defining therein an inlet and an outlet, material storing means at atmospheric pressure connected to said inlet, said outlet connected to said zone, said housing divided into an atmospheric zone and a depressurizing zone, feeding means positioned in said atmospheric zone to receive material Afrom said storing means, a hopper in said depressuriaing zone to receive material from said feeding means, scale means cooperating with said hopper to weigh the material therein, closure means on said hopper topermit the material to be discharged through said outlet into said zone, a top `valve establishing communication between said atmospheric zone and said depressurizing zone, :a bottom 4valve establishing communication .through Said outlet, and controlling ,means to operate the ,apparatus in continuous-batch 4fashion .so that `.one of said valves is maintained closed at all times.

f5. A system as defined in claim 4 wherein said feeding means and said .closure means constitute material valves and are `correlated by ,said .controlling means to prevent the deposition of .material .on said top and bottom valves,

6. A coal scale apparatus for use with a "furnace or the like having a pressure other than atmospheric vthat comprises va 'housing :divided into a feeding compartment with an "inlet `.therefor and a gastight Weighing compartment with an outlet therefor, said inlet `ibeing connected to a coal storing means, `a feeding means in said feeding compartment Ato receive coal lfrom said storing means and to discharge the -coal into said weighing compartment through an opening `:between said compartments, aweigh hopper in said weighing compartment 'to receive coal from said feeding means, closure ymeans .on said weigh hopper to permit the coal to be discharged vthrough said outlet to the furnace, a 'top `valve inthe opening between said compartments, .a bottom valve in the outlet, land controlling means 'to maintain one of `said `valves closedat all times.

7. A -coal sca'leapparatusas defined in .claim 6 wherein :said feeding means .and said closure constitute coal'valves `and are correlated by said conw l2 trolling means to prevent deposition of coal on saidtop and bottom valves.

.8. .A coal scale apparatus for use with a furnace or vthe like having a pressure other than atmospheric that vcomprises a housing defining therein an ,inlet and -an outlet, said inlet being connected to :a coal storing means, said outlet .being connected to coal receiving means communieating with the furnace, said housing Adivided into an .atmospheric pressure zone and a depressur izing .-zone, feeding means positioned in said atmospheric pressure ,zone to receive coal vfrom the coal storing means and to `discharge the coalintc the depressurizing zone, .a hopperin said depresf surizing ,zone to receive coal from said vfeeding means, scale means cooperating with said -hop per to weigh the coal therein, closure means on said hopper to permit the .coal to be discharged through said outlet, a top gas valve between said atmospheric pressure zone and depressurizing zone, a bottom gas valve in said outlet, and controlling means to maintain `one vof said gas valve meansclosed at all times` 9. A coal scale apparatus as dened in claim `8 Whereinsaid feeding means and said closure constitute =coal valves and are correlated by said controlling means to prevent deposition of coal on said gas valves.

ARTHUR J. STOCK.

veferences Cited in the ille of this patent UNITED STATES PATENTS Number Name Date 570,299 Richards Oct. 27, 1896 2,138,356 Ryan Nov. 29, 19.38 2,294,551 Guest Sept. l, 1942 `2,372,746 Stock Apr. 3 1945

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