US1941573A - Conveying system - Google Patents

Description

J. H, MoRRow 1594],573

v CONVEYING SYSTEM Filled Sept. 20, 1932 2 Sheets-Sheet l Jan. 2, 1934.

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INVENTOR BY ,/z MFM/4l M1. :Maga/k1:

TTORNEYJ- Jan. 2, 1934. J. H. MoRRow CONVEYING SYSTEM Filed Supt. 20. 1932 2 Sheets-Sheet 2 INVENTOR B `,df/$.07 f

Patented Jan. 2, 1934 UNITED STATES PATENT OFFICE CONVEYING SYSTEM ration of Delaware Application September 20, 1932 Serial No. 633,974

16 Claims.

This invention relates to vthe conveying of pulverized or nely divided materials, such as portland cement, pulverized limestone, powdered coal, etc., which have the characteristic of becoming fluid when mixed with air under proper conditions. kMore particularly, the invention is concerned witha novel method and apparatus for conveying such materials through closed conduits or pipe lines, the invention affording especial advantages when employed in the conveying of materials which are supplied at rates which are variable or less than the maximum capacity of the system.

The method and apparatus of the invention constitute an improvement on the conveying system of the Knyon Patent No. 1,553,539, dated September 15, 1925. and on the apparatus disclosed in my co-pending application, Serial No. 612,616, filed May 20, 1932, the improved system providing substantial economiesv in operation when used under the conditions above-mentioned. r

The conveying system of the Kinyony patent, which has now come into wide use, is characterized in that the material to be conveyed is supplied to a pump which contains an impeller screw, and the material is advanced into and through the transport line by the action of the screw. At the end of the screw, air is injected into the material to render it fluent. and the material is caused to ow through the line by the mechanical action of the screw which is assisted to some extent by the expansion of the air. In order to prevent the injected air from flowing back into the barrel of the pump and entering the material between the flights of the screw, a seal is provided by compacting the material between the end of the screw and the point of air injection. The Knyon patent discloses various methods of forming this seal, and in practice, it is common to use a screw of differential pitch, or to provide a substantial space betwen the end of the screw and the point of air injection, or to use a combination of these expedients. The effectiveness v of the seal required to prevent backward flow of the air varies considerably under different conditions of operation, and, in a specific system, care is taken to provide a seal which is of no greater effectiveness than is necessary, since the use of a denser seal than is needed results in power losses and makes the system uneconomical to operate.

lf the supply of material to the pump of a given system is to be constant throughout operation, it is a simple matter to calculate in advance the effectiveness of the seal required to prevent-the rearward escape of air, even though the distance of conveyance varies during the normal operad tion of the system as, for example, byreason of the material being supplied selectively toA a number of receiving bins at different point's'along the pipe line In such a system, a seal-is provided which will resist the maximum back-pressure developed during conveying to the farthest point, and the power consumption in the'motor driving the pump is not excessive since a drop in back-pressure co-incident with delivery to an intermediate point decreases the reaction against the impeller screw and correspondingly reduces the power input to the motor.

But when such a conveying system is used to transport material from storage silos, bins, hopper-bottom railroad cars, etc., thev supply of the material to the conveyor is often erratic, since most 'pulverized materials tend to arch or bridge across the discharge openings of the container vor in the spouts leading to thel hopper of the pump, and, when this occurs, the rate of supply of the material to the pump is likely to vary over wide ranges, usually less than full capacity. Also, this condition obtains when the pump is used to convey the output of a number of grinding mills, the normal operation of which in#- volves less than' the full number being run continuously.

Under these conditions of variable supply at less than the full capacity of the system, it has been found necessary in practice with the equipment heretofore used, to increase the seal density considerably beyond that required for the full capacity of the conveyor. This is commonly achieved by employing a pump with a long barrel, using a screw having flights decreasing substantially in pitch toward the terminal flight, providing a dead space of extraordinary length between the point of air admission and the terminal flight of the screw, and rotating the screw at a relatively high speed so that centrifugal force will supplement the veffect of the other means to form a plug of material which prevents 100 the backward escape of air. The formation of the seal is also affected by the back-pressure of the remainder of the transport system and each of the elements mentioned involves substantial friction losses and adversely affects the power 105 input of the screw motor. In a system constructed and arranged in the manner described, the power losses become excessive and continuous when operation approaches normal and when an extremely dense seal is provided, the air in- 11o jccted must be at relatively high pressure in order to break down the heavily compacted material and render it fluent. Also, air at high pressure is necessary to assist in reacting against the advancing material to formthe seal and to permit the necessary volume of air to flow into the system.

Another difficulty encountered under conditions of variable supply of material in the use of the Kinyon system as heretofore constructed is that when the seal breaks, the material in the screw becomes aerated and cannot be effectively removed by the screw. If the seal is broken when the supply of material is at a minimum,

the air in the pump barrel may under certain conditions oler enough resistance to prevent the material in the hopper from descending so that the seal can be reformed. As it is not customary to have an attendant presentA at the pumpA during thc normal operation of the sysum, considerable volumes of air may be' lost upon breaking of the seal andthe conditionof the pump may not be detected until a dust nuisance has been created or damage has been caused by the failure of delivery of material to equip-- ment `supplied by the conveying system.

.It is obvious that under conditions of variablev material supply, a Kinyon system as heretofore constructed is likely to be uneconomical in power consumption and breakage of the seal is liable to put the system out of operation. The poor economy in power consumption affects both the pump motor and the compressor equipment, the latter particularly, since the use ofv high air pressures greatly increases the cost of compressing the air. as the compressor power input increases rapidly, and the compressor efficiency decreases rapidly due to air slippage, as the pressure is raised.

The present invention is accordingly directed to the provision of a system operating on the Kinyon principle, which performs economically under the conditions mentioned, the newsystem using relatively low 'transport line andinlet pressures with a minimum differential between them under all conditions of Variable material supply. The new system thus elects economies in power represented by compressor pressure and, to a lesser degree, in volume of compressed air, in input to the pump motor, because of the decreases in the'force represented by back-pressure which the pump must overcome, and iny the friction of the material advanced by the screw. Also, in the the new system, an economy is effect- .ed by decreasing the air consumption of the system, the admission of air being controlled, if desired, in accordance both with the advance of material into the system and with the backpressure of the system, the latter being indicative not only of the distance to which the material is conveyed in a system having intermediate delivery points but also of the actual volume or the material handled. Moreover, the new equipment has the decided advantage that interruption of the conveying operation due to breaking of the seal is avoided and the pump may have a relatively short barrel, which reduces friction losses.

The new system includes a pump of the characteristic Kinyon type and more particularly of the kind illustrated in Figs. 6 to 8 of the patent, the new pump also including a number of features disclosed in my co-pending application aboveidentified. This pump includes the usual barrel and impeller screw and atthe end of the barrel /iiap valve tends to close, retarding the advance of the materials and causing them to accumulate in the seal space. In such a position, the valve supplements the effect of the other means employed for forming the seal andialso decreases the effective opening of the valve through which the back-pressure of t-he system reacts. Since the effectivebarrel opening decreases with a decrease in thequantity of material advanced, the formation and maintenance of the seal is accomplished with a minimum friction loss under all conditions ofsupply of the material to the pump, thus affording a maximum power saving in normal full load operation. l

`Another advantage of the new system is that the pressure of the advancing material may be employed to control the admission of air used to create-the initial fluent condition of the material in the system. Accordingly, the screw may be started :before air is admitted rather than afterward andl this simplifies starting and avoids losses in time .and air y Thev control of the air by the material is provided by `a mechanical connection between the flap valve and an air valve through which 'airows into the material in an amount suicient to provide the desired initial iluidity, the additional air necessary to render the variable quantity of material uent to the degree required for conveyance being introduced into the material through a second valve as the material enters the transport line. The degree of opening of the second valve is controlled by the reaction of the back-pressure or' the system and, since the backpressure depends both on the volume of the material moving through the system as well as the distance to which the material is being conveyed, it is evident that by means of the valve responsive to back-pressure, it is possible to keep the air injected into the material to render 'it iiuent at a minimum at all times.

In order to obtain the fullest economy resulting from the use or ow air pressures as abovementioned, it yif*refer-:hie to operate the system with a minimum differential between the backpressure and the supply pressure. Heretofore, the orifices through which air is supplied in a Kinyon pump have been carefully determined as to number and size or" opening so that the line or back-pressure will not exceed approximately 40% of the inlet pressure, thus providing a factor of safety to avoid loss in air delivery even though loss of flow is negligible if the back-pressure does not exceed about 50%. My experiments indicate, however, that by using over-size inlet orifices, such that the total effective area of the orifices compensates for the loss of airat the given differential, it is possible to operate at a much lower pressure differential than has heretofore been used. For example, in a specific system in which the back-pressure is l0 pounds, it is possible by the use of such inlet orices to maintain the necessary flow of air into the system by employing an inlet pressure of l2 pounds, and, similarly in a system which can be operated at a minimum Referring now to the drawings, the pump illus-d trated comprises a hopper section 1, having a barrel section 2 of relatively short length opening into its front wall, and a screw shaft 3 passing longitudinally through the hopper and extending into the barrel section in concentric alignment with it. The screw shaft passes through the rear wall of the hopper and-is supported for rotation in a unitary bearing support 4, beycndwhich it extends as at 5 for coupling to the usual prime mover (not shown). The hopper l and bearing assembly 4 are aligned on a common bed plate 6.

The barrel section is provlded with a longitudinally movable barrel liner 7, having an external flange 8 complementary to the flange 9 of the barrel section. Secured to the flange 8 is the flange 10 of the valve body 11, the flanges 8, 9, and l0 being secured by throughbolts 12. The flights of the screw shaft, beginning with the flight 13, increase progressively in diameter to the opening into the barrel liner 7, for the purpose of withdrawing the material to be conveyed uniformly throughout the length of the hop'per, as described more particularly in my application above-referred to. Within the barrel liner 7, the flights are of uniform diameter, clearing the inner wall of the liner by the usual @12" to U64.

The pitch of the nights lying within the barrel hner 7 may decrease toward the terminal flight 14. but the decrease in pitch is preferably the minimum permissible to assist in form'ng the seal in accordance with the anticipated back-pressure condition. For average conveying distances, the pitch may approach actual uniformity, it being my preference to rely particularly upon the seal space beyond the terminal flight 14, as in the mcdications shown 'in Figs. 6 to 8 of the Kinyon patent. To this end, the screw shaft 3, with its terminal flight 14, is arranged to extend into a cylindrical opening 1,5 in the valve, body 11, this opening serving as an extension to the conduit,

formed in part by the barrel liner '7. k

Air for increasing the mobility of the material advanced by the screw is admitted through a plurality of nozzles 16, arranged in an arc below the opening l5 into the valve body 11. In order to vary the relative distance between the air noz zles and the terminal flight of the screw to modify the seal density, substantially in the same manner. as the plurality of series of air ports inthe Kinyon patent referred to and particularly the modification above-described, the through-bolts 12 are provided with lock-nuts 17, whereby the relative spacing between the flanges 8 and 9 can be changed. In the position shown in Fig. l, the minimum seal distance is indicated and it will be apparent that the forward adjustment of the flange and the parts connected to it will increase the effective seal distance.

A flap valve 18 closes the discharge end of the opening 15 into the valve body 11this valve having a liner 19, of wear-resisting material, such as rubber or the alloy commonly known as Stellite. The valve is secured to the arm 20. which is keyed or.' otherwise fastened to the shaft 2l, thc latter extending through the side walls of the valve body 1i, and arranged for partial rotation in it. This valve lies inthe path of thev material issuingfrom the pump barrel and when there is a full supply of material fed to the pump, the valve is forced to full open position. If the supply of material drops below the capacity of the pump, or is erratic, the valve tends'to close and this causes the material to accumulate in the seal space between the valve seat-and the terminal flights of the screw, thus causing the seal to be maintained under all conditions of supply. If desired, the valve may be weighted and for this purpose, one end of the shaft 21 i's provided with a crank 22'. upon which is mounted an adjustable counterweight 23', to modify the degree of reaction of the flap valve against the advancing material. At its discharge opening the valve body 1l terminates in a flange 22, to which is secured a flange of the remainder of the condut or pipe line 23, which leads to the various delivery points.

The back-pressure of the system is indicated by an air pressure gauge 24, secured to a standpipe 25, which may conveniently be arranged as a part of the assembly of valve body 11, by connection to an opening 26 rinto the interior of the latter.

The operation ofthe pumping system as above specifically described, assuming that the automatic valve mechanisms to be described hereafter are not employed, is as follows:

The distance between the terminal flight 14 of the screw and the air nozzles 16 is adjusted so that the seal to be formed will be substantially in excess of that estimated for normal service in conveying at the maxmum capacity of the pump to the longest conveying distance required. A full head or load of material is provided so that the ap valve 18 will be forced to its full open or inoperative position after the screw shaft 3 is started. Before the screw is started, compressed air is admitted through the nozzles in an excessive quantity and at the maximum pressure obtainable, or .at least beyond the estimated operating pressure. The volume of air, as well as the pressure, is then decreased by the operator until the power input io the motor (not shown) driving the screw shaft begins to rise, which indicates that the proper degree of aerat'on is not taking place. The operator then raises the pressure and volume of air until the power required for the pump screw motor falls to a minimum stable condition. The seal density is then decreased by moving the flange 8 of the barrel liner 7 rearwardly, unt-il a blow-back of air is noticed. The seal fs then increased and maintained at the minimum position permissible by the back-prcssure resulting from the resistance to the longest conveying distance at maximum capacity of the screw.

If the operator is unskilled, or electrical measuring instruments are not avalable, approximately the same results can be obtained by alternately and repeatedly adjusting the seal to GLS then decreased step by step and the operator adjusts the counterweight 23 on the crank .22Ll so that the resistance of the flap valve under all conditions of material delivery will be suflicient to retard the advance of material and cause it to accumulate and maintain the seal at a minimum density in combination with the remaining seal forming'expedients. It will be understood that no change in the air pressure or volume condition will be made. Since the ap valve 18 not only resists the advance of material, but also restricts the effective opening into the valve body ll, the effect of back-pressure against the advance of material is such that a minimum seal will be maintained from full to minimum load conditions.

It will thus be seen that a minimum power in compressed air and motor input is provided by the effect of the flap valve in supplementing the other sealing devices, and this saving obtains throughout the entire capacity range of the system. If the ilow of material stops entirely, the flap valve closes and functions as a simple check, but it has an additional function in conveying, since air under pressure is prevented from passing backwardly and holding up the flow of material, or at least causing aeration in the-barrel section, so that the seal cannot be reformed without the attention of an operator.

In order to eifect further economies in operation. the supply of air to the nozzles is controlled by devices responsive to the position of the flap valve and to the back-pressure in the system, these devices including valves through which air may be supplied to the nozzles and mechanism for operating them automatically.

The air from any suitable source is supplied to the system through a main air line 27 which contains a cut-olf valve 28 used to prevent air leakage when the system is shut down. A plug cock 29 in the line is employed to control the nal pressure ofthe air and, when the cock is adjusted, it serves as an orifice plate. Beyond the cock, a connection is made through a nipple 30 to a regulating valve 31 through which air ls admitted to the nozzles in quantities proportional to the amount of material advanced by the screw, but in less amounts than are necessary for rendering the material sufficiently fluent so that it can be transported to the nearest delivery point on the system. Air admitted to the nozzles through the valve 3l prevents initial discharge of unaerated material into the system, which would result in excessive back-pressure and overload on the pump motor.

The valve 3l includes an inner cylindrical chamber 32, which communicates through a helical series of orifices 33 leading to a concentric outer chamber 34 which communicates through the short nipple 35 with the air channel 36 through which the nozzles 16 are supplied. These nozzles have effective openings large enough to admit a volume of air considerably in excess of that required for aeration. The rate of air ow through the valve is controlled by a vertically movable piston 37, provided with an orice 38 to equalize pressures at its opposite ends. The piston is secured to a rod 39, which passes through a stufng box 40 and is threaded for purposes of adjustment and pivotally secured to links 41, pivoted at their upper ends to the crank 22', whereby movement of the ap valve 18 will control the position of the piston 37 and thereby control the ow of air through the valve.

Valve 3l is provided with a needle valve 42,

which serves to permit a very small quantity 0f air to flow into the system, when heavy materials, having the characteristic of quickly losing their fluidity, are handled and the flow to the pump hopper stops completely for long intervals. This valve may be adjusted so that this small quantity of air seeping through the material, particularly at elevations in the system or around bends, maintains the fluency, so that the motor will not be overloaded when material is again displaced into the system. A branch line 43 leads from the main line 27 between the valve 28 and the cock 29, this branch line containing a valve 44 and leading to the channel 36. When the system is to be shut down for' an indefinite period, the branch line is employed for introducing air at full receiver pressure and volume to clear the transport line of material while the latter is in its aerated uent condition. During this operation, the flap valve prevents the short-circuiting of air through the pump and the usual transport cut-off valve is not required.

Preferably at the side of the pump opposite to that on which valve 3l is mounted, air under the control of the cock 29 is admitted to the back-pressure control valve 45, the additional air thus admitted being that necessary for completely fiuidizing the material under all conditions of capacity and conveying distance. The air enters an inner cylindrical chamber 45. which communicates with the outer concentric chamber 47 through a relatively larger number of ports 48, arranged in a helix of upwardly decreasing pitch and uncovered serially by the piston 49. The piston is provided with an orifice 50 for purposes of equalizing pressures, and is secured to a rod 5l which passes upwardly through stufiing boxes 52 and 53, where it is secured to a control piston 54 in cylinder 55. The control piston is subject to the reaction of back-pressure of the transport line system, the cylinder being in communication by a tube 56 with the stand-pipe 25 of the back-pressure gauge 24. The back-pressure acting against the under surface of the piston 54, causes the latter to rise against a coil spring 57 adjustable as to length by being threaded on the upper end of the piston, the tension of the spring being adjustable by set screw 58, secured to the spring retaining cap 59. As the piston 54 rises, it lifts piston 50, uncovering the ports successively and admitting an increasing amount of air to the channel 36 for injection into the material. The cylinder is suitably vented, as at 60, to relieve pressure in the event of air slippage beyond the piston 54.

In order to facilitate the starting of the system. a branch air line 6l lFig. 2) under the control of cut-off valve 62 leads from the main line 27 into the hopper 1 below the barrel liner 7 and near the screw shaft 3. When thesystem has been shut down for a long time, the materials which have lain dormant in the hopper become packed together and when the system is started, the starting torque is excessive and greatly out of proportion to the normal motor load. Under these conditions, the admission of air momentarily into the hopper renders the material in the hopper fluent and, when the material enters the screw barrel, the fluidity of the material causes the screw to operate at low etliciency for a short period. This enables the pump motor to function without heavy overloads and permits the use of small driving motors. such as internal combustion engines of relatively small size.

Also, it permits small electric motors to be employed to avoid unfavorable power factors.

In the operation of the complete system, conveying is started by opening the main air supply` valve 28 together with the plug cock 29. The back-pressure control valve is then adjusted so that it Will function to admit air in excess of that which may be required to fluidize the material, although no air flows into the system at this time, since the iap valve is closed and there is no back-pressure to open the air vvalve which is responsive thereto. The operator then starts the pump motor, and as the advancing material disu places the flap Valve from its seat, the piston 37 is lifted in proportion to the lifting of the flap valve and air is admitted at a sufficient rate to create the initial iiuent condition of the material.` Almost immediately, back-pressure reaction occurs, causing valve 45 to open to admit further quantities of air. The operator by reference to the line pressure gauge 24 now adjusts thel spring 57 so that the minimum quantity of air is admitted responsive to back-pressure to create the necessary uidity of the material for conveyance to the farthest discharge point of thesystem at the maximum capacity ofthe screw.

When the mechanism is adjusted in the manner described, it is set for all future operations since, as the back-pressure decreases because of a decrease in capacity or because of delivery of material to intermediate points, the air supplyy through the valve 45 is similarly decreased. The

ing been established, the plug cock 29 is adjusted for full load conditions.

It will be apparent that in the new system, the control of the air afforded by the valve 45 responsive to back-pressure in cooperation with the flap valve 18 per'mits conveying with the seal of minimum density under less than full load conditions. This result is achieved because as the back-pressure decreases and the air supply ,pressure and thus a seal of the least resistance for proper operation may be employed at all times with a consequent saving inpower. Similarly, by usingv over-size air nozzles, the air pressures employed are much llower than those heretofore thought necessary and this effects -a further economy of operation.

The new system functions on the Kinyon principle and in it the material is forced through the transport line by the mechanical action of the screw. The material is aerated as itleaves the screw and the action of the screwmay to some extent be supplemented and assisted by the expansion of air. As the material leaves the transport line, it flows sluggishly and tends to'seek a level. It retains this fluent condition until the air which has been injected into it has had an opportunity to escape. The system is, therefore, distinctly different in construction and operation from those systems in which the material is con-V veyed in suspension in air and a separator must be employed at the delivery point. Also, it operates on a distinctly different principle from that involved in those systems in which the material is forced through the line in the form of plugs.

What I claim is:

1. Apparatus for conveying pulverized,A materials, comprising the combination of a conduit, a barrel section connected to the conduit, means ltion and into and through the conduit, means for injecting compressed air into the conduit to aerate the material to be' conveyed, the air being admitted beyond the advancing means to provide a space in the rear ofthe point of injection in which the materials will befcompacted and form a seal resisting the rearward flow of air, and mechanical means in the seal space between the advancing means and the point of air admission for resisting the advance of material and assisting in causing the material to accumulate at sumcient density to form the seal.

2. Apparatus for conveying pulverized materials, comprising the combination of `a conduit, a barrel section connected to the conduit, means for advancing material through the barrel section, means for admitting compressed air to the conduit for aerating the material to be conveyed,

`the said means being disposed beyond the advancing means to provide a space in which the material will be compacted as they are advanced to form a seal resisting the rearwardow of air, and valve means in the seal space between the advancing means and the point of air admission, said means resisting the advance of material and causing the latter to accumulate in said space at suicient density to form the seal.

3. Apparatus for conveying pulverized material, comprising the combination of a conduit, a receiving hopper, a barrel section connected to the conduit and to the hopper, a shaft supported for rotation within the hopper and barrel section and having screw. flights for advancing material from the hopper into the barrel section, means for admitting compressed air to the ,conduit for increasing the mobility of the ma- 'ing the rearward flow of air, and mechanical means between the `terminal flight of the screw and the point of air admission for resisting the advance of material and compacting the latter.

4. Apparatus for conveying pulverized materials, comprising the combinationA of a conduit, a barrel section connected thereto, means for advancing material through the barrel section and conduit, means for admitting compressed air to the conduit for aerating the material being conveyed,A said air'being admitted a distance beyond the advancing means to provide a space in which the material will be compacted as it advances and form a seal resisting the rearward flow of air, .anda flap valve in the seal space between the advancing means and the point of air admission for resisting the advance of material and causing the latter to accumulate in said space at sufficient density to form' the seal.

5. Apparatus for conveying ypulverized materials, comprising the combination of a conduit, a barrel section connected thereto, means for advancing material through the barrel section and conduit, means for admitting compressed air to the conduit for aerating the material to be conveyed, the said air being admitted a distancel beyond the advancing `means to provide a `space in which the material will be compacted as vit advances and form a seal resisting the rearward ow of air, and a flap valve biassed to close the barrel section against the advance of material, the valve being located in the seal space between the material advancing means and the point of air admission.

6. Apparatus for conveying pulverized ma terials, comprising, the combination of a conduit. a receiving hopper, a barrel section between the hopper and conduit and connected thereto, a screw shaft arranged for rotation in the hopper and barrel section and provided with screw flights for advancing the material to be conveyed into and through the conduit, means for admitting compressed air into the conduit for iluidizing the material therein, said means being located beyond the terminal flight of the screw to provide a seal space through which the material advances, said material being compacted in said space and resisting the rearward ilow of air, and a flap valve in the seal space between the terminal flight of the screw and the point of air admission, the valve being movable downwardly and biassed to a position in which it closes the barrel section.

'7. Apparatus for conveying pulverized material, comprising the combination of a conduit, a barrel section connected thereto, means for admitting material to be conveyed to the barrel section, means for injecting compressed air into the material in the conduit to increase the mobility of the material, and means responsive to the pressure of the material admitted for controlling the admission of air to the conduit.

8. Apparatus for conveying pulverized material, comprising the combination of a conduit, a barrel section connected to the conduit, means for admitting material to be conveyed to the barrel section and advancing it therethrough, means for injecting compressed air into the conduit beyond the material advancing means to increase the mobility of the material, a valve for controlling the supply of air to said means,l and means in the conduit between the advancing means and the point of air admission responsive to the pressure of advancing material, the said means being operatively connected to the Valve for controlling the opening of the latter.

9. Apparatus for conveying pulverized materials, comprising the combination of a conduit, a hopper, a barrel section between the hopper and conduit and connected thereto, a screw shaft supported for rotation in the hopper and barrel section for advancing materials therethrough, a nap valve tending to close the barrel section beyond the terminal ight of the screw shaft and movable by pressure of advancing material, means beyond the valve for admitting compressed air to the material to increase its mobility, a valve controlling the air supply, and means operatively connecting the rst valve with the air valve to control the opening of the latter in accordance with the opening of the flap valve.

10. Apparatus for conveying pulverized materials comprising the combination of a conduit, a hopper, a barrel section, between the hopper and conduit and connected thereto, a screw shaft supported for rotation in the hopper and barrel section for advancing material therethrough, a nap valve tending to close the barrel section beyond the terminal flight of the screw shaft, the said valve being arranged for partial rotation with a supporting shaft, one end of the latter extending outside of the conduit and terminating in a crank, means for admitting air to the conduit beyond the flap valve, a valve for controlling the air supply valve, and a connection between said air valve and crank for controlling the supply of air in accordance with the degree of opening of the flap valve.

11. Apparatus for conveying pulverized materials comprising means for admitting material to be conveyed to a conduit, means for admitting compressed air to the conduit to increase the mobility of the material and assist in its transportation through the remainder of the conduit, the said air admitting means including an air supply control valve, and means responsive to the back-pressure in the conduit for controlling the degree of opening of the valve.

A12. Apparatus for conveying' pulverized materials comprising means for admitting material to be conveyed to a conduit, means for admitting compressed air to the conduit to increase the mobility of the material and assist in its transportation through the remainder of the conduit, an air supply control valve, and means responsive to the back-pressure of the system for controlling the degree of opening of `said valve, said means increasing the supply of air in proportion to increases in the back-pressure of thesystem.

13. Apparatus for conveying pulverized materials, comprising the combination of a conduit, a hopper for receiving material to be conevyed, a barrel section connecting the hopper and conduit, a screw shaft arranged for rotation in the hopper and barrel section for advancing material into and through the conduit, means for supplying compressed air to the conduit at a point beyond the terminal night of the screw, a valve for controlling said air supply means, and

,means responsive to the back pressure in the remainder of the conduit operatively connected to the valve for controlling its degree of opening.

14. Apparatus for conveying pulverized materials, comprising the combination of a hopper, a barrel section opening into the hopper and forming a part of a conduit, a screw shaft arranged for rotation in the hopper and barrel section for advancing material therethrough, means for admitting compressed air to the conduit for increasing the mobility of the material, a valve for controlling the supply of air so admitted, means responsive to the back-pressure in the remainder of the conduit for controlling the degree of opening of the valve, and a nap valve between the terminal flight of the screw and the point of air admission to resist the advance of material and cause it to accumulate to form a seal and to restrict the eiective surface area of. the material exposed to the back-pressure of the system.

15. Apparatus for conveying pulverized materials, comprising the combination of a receiving hopper, a barrel section opening into the hopper and forming a part of a conduit, a screw shaft mounted for rotation in the hopper and barrel section to advance material therethrough, a nap valve in the conduit tending to close the barrel section and movable responsive to the pressure of advancing material, means for supplying compressed air to the conduit beyond the flap valve for increasing the mobility of the material, an air control valve for admitting a supply of air sufficient for the initial aeration of the material, said valve being operatively connected to the flap valve and controlling said air supply in proportion to the degree of opening of the ap valve, a second air supply control valve through which the air necessary to complete the aeration of the material is admitted, and means responsive to the back-pressure in the remainder of the conduit operatively connected to said second valve and controlling its degree of opening in proportion to the back-pressure.

16. Apparatus for conveying pulverized materials, comprising the combination of a receiving hopper, a barrel section opening into the hopper and forming a part of a conduit, a screw shaft mounted for rotation in the hopper and barrel section to advance material therethrough, a flap valve in the conduit tending to close the barrel section and movable responsive to the pressure of advancing material, means for supplying compressed air to the conduit beyond the ap Valve for increasing the mobility of the material, an nir control valve for admitting a supply of air sufficient for the initial aeration of the material, said valve being operatively connected to the flap valve and controlling said air supply in proportion to the degree of opening of the ap valve, a second air supply control valve through which the air necessary to complete the aeration of the material is admitted, means responsive to the back-pressure in the remainder of the conduit operatively connected to said second valve and controlling its degree of opening in proportion to the back-pressure, and a manually operated valve for controlling the maximum volume and pressure of air supplied.

JOSEPH H. MORROW.

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