US2544011A - Control for pneumatic packing systems - Google Patents

Description

March 6, 1951 T. c. DUvALL 2,544,011

CONTROL FOR PNEUMATIC PACKING SYSTEMS Filed Deo. 2, 1946 faz/ Patented Mar. 6, 1951 NITED STATES OFFICE CONTRL FOR BNUMATIC PACKING SYSTEMS Thure C. Duvall, Cloquet, Minn., assigner to Wood Gonversion Company, St. Paul, Minn., a corporation of Delaware The present invention relates to pneumatically conveying and depositing solid materials, and in general to means and controls for automatically cutting oi operation at a predetermined cut-oli point. In particular, the .invention relates to pneumatic packing systems used vfor depositing insulating material pneumaticaliy into spaces to be insulated, and to equipment and controls for automatically stopping the operation of the system when the space is adequately lled- Recently, systems have been developed for pneumatically packing insulating material, such as ber, into insulating spaces exemplied by reirigeratcr cabinets'. The systems referred to have been developed for use in assembly-line manufacturing operations wherein cabinets, or doors therefor, to be filled, move in succession past a illiing station. In such operations the cabinet or other article to receive particles, such as in sulatingber, is arrested at the filling station for and during the filling operation. Certain mechanical operations may or may not be manually required, but where this is not so the operation may be completely automatic after initiation.

The present invention provides an automatic cut-off control for such systems, to be operated by dierential air pressure and adjustable to efrect the stoppage at a proper point in the completion of a filling job.V

In experimenting with pneumatic conveying and depositing systems of the kind herein de'- scribed, it has been determined that upon completion of a lling operation the discharge conduit of the system becomes effectively blocked to the extent that a quick change in dinerential pressure at the intake end is produced. Advantage is taken of this quick change of pressure to operate a responsive device which in turn operates suitabie controls, preferably electric.

The kind of apparatus to which the present invention applies is one having a fan-type blower and a conduit system receiving air from the atmosphere and ultimately discharging air to the atmosphere, while leaving the insulating material behind. A receptacle to be filled is suitably located with respect to the conduit system. and is adequately vented by iiltering means so that air passes on while the suspended particles are retained inthe desired space. The arrangement is such that whenl the space is lled, the said nltering means is wholly covered and the conveying system becomes rather suddenly blocked, not perfectly, but sufliciently to reflect a quick change in pressure at the suction end.

Means is provided for feeding solid material into the system to form a suspension for delivery, and then separation at the space being filled. Also, adequate valve `or gate means is provided in the conduit system to accommodate the system to continuous rotation of the blower therein. Such a system requires that the Valve means in the conduit system be closed when the receiving station is open and not ready for delivery. Consequently, means must be provided for stopping the feed of solid material into the system when the valve means is closed and also when there is no delivering flow of air, and to start such feed .vhen there is a delivering flow of air.

it is' an object of .the present invention to provide a suction-operated damper at the intake end of a fan blower system and to use the responsive movements of the damper to operate certain controls. f

Itis a particular object of the invention to provide a damper responsive to differential pressure with an adjustment regulating its response to certain predetermined differentials of pressure in order to adjust the operation to the particular conditions elsewhere prevailing in the system.

it is a particular object of the invention to provide a suction-operated cut-off device which so regulates the feed of material that feeding is limited to an operative ow oi air through the system.

Another object is to provide for automatic closure of the conduit valve means upon return movement in operation of the cut-off damper, and to provide if desired, a predetermined time delay before initiation yof valve closure after the stoppage of feed in order to purge the system of residual solid material. Y Numerous other objects and advantages of the invention will become apparent from the following description and explanation of the invention as it is shown inconnection with the accompanying drawing showing a preferred application of the invention.

d In the drawing, ,there is shown more or less diagrammatically, certain units of the system as they are combined and controlled by the included electric circuits and devices. i

In the drawing, numeral i!) represents an opened previously-wired bale of fiber resting on an `endless belt conveyerll operating over the pulleys l2 and i3, one of which is suitably driven, as by the electric motive means 1M. The belt il' travels slowly in order gradually to feed the bale to a baleebr'eaking device, such as a roto-r iSv/ithin a housing i6, The rotor le is operated by powered means il. The bale-I breaking means l5 is effective to disintegrate the compacted fiber of bale HJ into a loose and luy form which is discharged from the housing I3 through outlet I8 opening into an intake conduit i9 of a fan blower 28. The arrangement of the foregoing parts is such that both the blower 20 and the rotor I5 may operate continuously so that by arresting the travel of the conveyer and the bale l into the housing i6, the feeding of fluied ber to the blower 2li is also arrested. Since the invention involves means to stop the feeding of the ber or like material, it is preferred to have such means operate upon the electric motive means I4 to arrest the feeding mechanism. This control will be later described.

The fan blower 28 discharges centrifugally and, as shown, discharges preferably downwardly from the blower through conduit 2| to a discharge or depositing or filling station at the lower end of conduit 2|. It is desirable to have means to control the ow in the blower conduit system. Such flow control involves a valve or gate which functions to stop the delivery through conduit 2E of air during operation of fan blower 23. Suc-h a valve or gate may be placed either in the intake conduit i9 or in the discharge conduit 2|, or in both places. For the purpose of simplifying the description, such valve means is illustrated in both places and described with reference to that one which is in the intake conduit I9 wherein such valve is designated 25. Where two are used they are preferably operated together and by the same means. A second valve is shown at 25'.

Valve 25 is preferably operated by uid control, for example, by compressed air. There is a movable gate 21 in the valve casing and a gateholding chamber 28 outside the valve proper, in which -chamber the gate 21 is housed when the gate is in open position. The gate carries an operating stem 29 projecting from the housing 28 and movable into and out of the housing 28 to close and open the gate. The operating stem 29 is connected to a piston rod 38 having a piston head 3| operating in cylinder 32. The two ends of the cylinder 32 each have a connection to a compressed air supply so that by introducing air into the one connection and exhausting it from the other, the piston is moved to operate the gate. Numeral 34 represents the connection for supplying air to close the gate and numeral 35 represents the connection supplying air to open the gate. It is also to be observed that there is a connection 36 between the connection 35 and the gate housing 28 so that when the gate is being opened and is open, an air stream passes through connection 36 into the gate housing and along into the blower system. This is for the purpose of keeping the gateways and seat free from fiber and to avoid the accumulation of ber in the air spaces of the gate valve where it would eventually impede its proper operation.

Further means for controlling the operation of the gate 21 involve control of the air supply to the cylinder 32. The numeral 38 represents a pipe line supply of air under pressure (greater than in conduit I9 or 2|) as a connection to a control valve housing 39 which housing has discharge outlet 45. The illustrated control valve 39 is merely a conventional representation of any suitable valve for the purpose, and in such representation the diagrammatic rotary valve member 4| is moved to shift the air supply from one to the other of the connections 34 and 35 to the cylinder 32. Diagrammatically represented, the aforesaid connections of the valve housing 39 are arranged 90 apart in the following order, 34, 38, 35, and 43. When the valve element 4| is in the full-line position shown, air pressure passes through connection 34 to hold piston 3| down and hence hold the gate 21 closed. By turning the valve element 4| through to dotted-line position 4m, the Supply of air and the exhaust connection are shifted and the piston 3| is moved to open the gate 21 and to hold the gate open. The present invention involves electrically controlled means to move the valve member 4| from one of its two positions to the other. Such control means is designated by the numeral 42 and has the electrical wires 43 leading to it to energize the device 42 to open gate 21. The device 42 may be a solenoid-operated device controlling the position of valve member 4|.

The discharge station may be such as to receive a receptacle to be filled, such as a refrigerator cabinet, and such as to establish operating connection to it. This is preferably accomplished by moving the receptacle onto a platform section which moves into a connecting position, preferably as a lift. Control means is provided for raising and lowering such a lift to effect connection of the receptacle to suitable xture means on the end of discharge conduit 2|. The lift is preferably operated by fluid pressure such as pneumatic pressure in suitable means, and such means may be of the type used to raise and lower the gate valve 21. However, such means forms no part of the present invention.

Numeral 45 represents a lift having a platform for a receptacle 46 thereon to be connected to a xture 41 placed directly above the lift at the end of conduit 2|. Numeral 48 represents a conduit through which air is discharged after having been freed from the ber or the like deposited in the receptacle, suitable screening or filtering means 49 being operatively associated with the fixture 41 and the receptacle 46. Numeral 45a represents the position of the lift when it is out of operating position, as for example, when it is being loaded with a receptacle to be lled. It is important at this time when the lift 45 is out of indicated full-line position, that the conduit system |9-232| be free from fiber and that it not discharge air, nor air and fiber, into the atmosphere when conduit 2| is open to the atmosphere by reason of there being no receptacle 46 in place to receive the fiber. Consequently, it is important under these conditions that there be no feed of ber i3. It is also important that the feed of ber be prevented except when the conduit system is open to carry it away and the lift 45 is in raised or receiving position, of course with a receptacle 46 in place,

In the intake conduit I9 there is a lateral duct |9a opening from the atmosphere to the interior of conduit I9. At the end of the lateral duct I3@ there is a swinging damper 1| rotating on axis 12, urged into normal and static position (as shown) by means such as counterweight 13. rZhe arrangement is such that a predetermined degree of suction in duct lila resulting from movement of air by the blower when the gate 21 is open, draws in the damper against the counterweight 13, thereby operating a control mechanism 18.

The control mechanism 1U is represented as a simple switch box containing a single point switch 16 for the two wires 11 and 18 leading to it.

Said switch is directly operated' to' close it bythe projecting' arm 8E when it moves from fullline position Si! to dotted-line position Bu. Said arm 80 is connected by a link 8T pivotly secured at its respective extremities to the arm 8e and to a stern 82 on the' damper 'II which stern carries the counterweight T13'. The stem 82 is threaded' over a long region designated 84 and the counterweght 'I3 is threaded thereon in order' to adjust 'the effect of cour'lterweight4 'I3 and predetermine the degree of suction to which it responds.

The numerals IUI and' ft2 represent electric power lines for operating the lift 45 by means not shown, for operating the valve control means 42, for operating the bale-breaker motor' II, and for operating the motive means I4 to feed ber` III. Means is provided for placing under manual operation a control to open the gate 21. The cut'- off control 'IU is arranged automatically to enect closure of the gate 27 by de-energizing the valve opening means e2. To simplify the representation of controls, the valveop`ening operation is illustrated as initiated by holding down push button switch IGS thereby completing a circuit from power line IUI, through connection I``4, through one or more controls diagrammaticall'y represented at IUE and for the present purposes to be considered as constituting a closure of the circuit from connection IOR to the valve opening means 12, thence to the junction IUS, thence through the push button operated switch |03 to junction I''I, and then by a connection IBB to the power line H321 By-passing the said push button switch IUS, is a solenoid-operated switch I I between the junctions I6 and IGI. Switch II is normally open and is closed only when solenoid I I I is energized. Thus, when solenoid II'I is energized the open gate Zf'I is held open by closure of switch I Iii, and during this status the push button switch I VE13 may be opened by the operator. Numeral I I2 represents conventional timing means capable of being set to vary the time interval from() to any predetermined time, after de-energizing solenoid III to its action to open switch III), this action being suitably indicated in the drawing.

The energization of solenoid I I I is not intended to open the gate 21 but only to hold it open after it has been opened yby manual push button E63. Hence, the eil-ect of having opened the gate 2'I is relied upon to energize solenoid III, and this is accomplished by the suction in duct I9@ on opening the gate.

The suction in duct VIlla draws in damper 'II, and closes switch 76. This energizes solenoid I I5 by completing the circuit: power line I, connection TI, switch I6, connection i8, solenoid IIE, and thence to power line itl. Solenoid IIE is employed as a convenient device to cause the suction to perform more than one function. Therefore, by operating the one switch I6, the solenoid SI5 extends the eiiect by operating more switches, such as relay switches I It and II'I which are closed by energizing the solenoid IE5, and opened by cle-energizing it. y Switch H6 is in the circuit from lines It! and I02 to the feeding motive means Ill, so that fiber I0 is fed only when the damper ll is in its suction-operated position. Switch III isk in series with solenoid III across the lines IDI and H12', so that solenoid III is energized only when the damper II is in suction-operated position.

Accordingly, as soon as the suction fails, the switch 'I6 is opened, andthe fiber feed Ill is'thereby cut-olf immediately by opening Switch' H6. Residual fiber the System maybe cla'ri't Out 6. by delaying closure of the gate 271, as by' the adjustment of the timing device H2 to control the time of opening switch- III) after the damper EII moves to its cut-off position.

The present invention is one feature of a more complex control system in which there are other means associated with the means of the present invention. For example, broken line I2@ running from the lift i5 in its raised position to the control means IIJE, represents a control of the oircuit to the gate-opening device l2 such that the gate 2l may be opened only when the lift is in the raised position shown. Numeral IZI represents operating means to raise and lower the lift lby the indicated connection I22. Broken line I23 running from the lift-operating means I2I to the gate stem 29 represents a control to prevent lowering the lift when the gate 2l is open. Numeral I2Lil represents a manual push button switch to Voperate device I2I initially to raise the lift. Numeral I25 represents means electrically by-passing switch |24 to permit its release only when the lift is in raised position and to hold it raised. Such control |25 may be additionally rendered inoperative for said purposes until the gate 21 is open, as for example by a control indicated by broken line I26 from the control |25 to the control I 23 under influence of the gate position.

The operation of the device in the preferred manner described can best be understood by explaining how such a blower system operates when the discharge end 2l is wholly blocked or only partially blocked. The deposition of bers in receptacle It involves the passage of` air through the filter means 49 as the receptacle is filled. rIhe velocity will'decrease as the escapement area for air is lessened'. When the blower 2U positively feeds into conduit 2i more air than can escape through outlet Q8, some of it channels back in conduit 2 I, through the'blower housing 2I and back into intake conduit IQ, this being a well-known result called "backpressure. Thus, conduit IS may exhibit rst a lessening of suction, and later a positive back pressure at the conduit walls, while the core of the conduit I9 still draws in air.

The damper 'II may be adjusted to move inwardly initially by' attaining a predetermined suc-- tion in duct ISa, and to move back when less than said predetermined suction exists, and this may includereversal of the dinerential by backpressure. The construction and adjustment may be such that back-pressure is no more eiiective on the damper than a static condition of no differential at allL The delay in closing the gate. after eut-off or feed results in the ber already in the system and not deposited, being carried to the i :stur-e d1 where it is deposited by its own inertia as vehicular air is either filtered through the already deposited liber orf turned back" in said channelling effect, or both. Experience has shown that at the end of an operation such as one filling the receptacle lle, continued supply of air and )Tiber enects a growing deposit in conduit 2l accom'- panied by back-pressure. Thus, ber may be 'deposited after the damper operates to open switch T6. The adjustment of counterweight i3; and of the timing device II2 of relay having solenoid III, are such with respect to the prevailing conditions of the apparatus, that the deposition may be halted automatically so as to'control the end point, leaving" the receptacle short' of lfull, just 7 full, or over full, as desired, and uniformly so in successive operations.

The damper-type of cut-off is to be distinguished from the manometer type moving in response to all differential pressure changes. rihe damper-type moves with snap action from one to the other of its two limiting positions in passing through critical changes in differential pressures. This motion is accompanied by appreciable mechanical movement and power available for mechanically operating one or more controls. The extent of movement and the inertia in the moving parts minimizes fluttering as the diiferential pressure may flutter above and below the -desired critical point, thus giving positive actions in the controlling operation.

The invention is capable of numerous departures from the illustrative use thereof, and these and other modifications are contemplated as falling within the scope of the appended claims.

I claim:

l. In an intake conduit to a fan-blower system arranged for drawing air from the atmosphere and having means to feed solid material into said system for suspension in air therein, a feed-control device comprising a suction duct leading from the atmosphere to the intake conduit and subject to suction to admit air into the system, a moving member associated with said duct and responsive to suction of a predetermined value to move from normal static position to abnormal operating; position and to admit air to said duct when air is moving through the system, and means arranged for operation by said moving member to effect operation of said feeding means in said abnormal position and non-operation of said feeding means in said normal position.

2. In an intake conduit to a fan-blower system arranged for drawing air from the atmosphere and having means to feed solid material into said system for suspension in air therein, a feed-control device comprising a suction duct leading from the atmosphere to the intake conduit and subject to suction to admit air into the system, an adjustable moving member associated with said duct and responsive to suction of a value predetermined by its adjustment to move from normal static position to abnormal operating position and to admit air to said duct when air is moving through the system, and means arranged for operation by said moving member to effect operation of said feeding means in said abnormal position and non-operation of said feeding means in said normal position.

3. In an intake conduit to a fan-blower system arranged for drawing air from the atmosphere and having means to feed solid material into said system for suspension in air therein, a feed control device comprising a suction duct leading from the atmosphere to the intake conduit and subject to suction to admit air into the system, a pivoted damper associated with said duct and responsive to suction of a predetermined value to move from normalstatic positionto abnormal operating position and to admit air to said duct when air is moving through the system, and means arranged for operation by said moving damper to effect operation of said feeding means in said abnormal position and non-operation of said feeding means in said normal position.

4. In an intake conduit to a fan-blower system arranged for drawing air from the atmosphere and having means to feed solid material into said system for suspension in air therein,

a feed-control device comprising a suction duct leading from the atmosphere to the intake conduit and subject to suction to admit air into the system, a pivoted damper associated with said duct and adjustably responsive to suction of a value predetermined by its adjustment to move from normal static position to abnormal operating position and to admit air to said duct when air is moving through the system, and means arranged for operation by said moving damper to effect operation of said feeding means in said abnormal position and non-operation of said feeding means in said normal position.

5. In an intake conduit to a fan-blower system arranged for drawing air from the atmosphere and having means to feed solid material into said system for suspension in air therein, a feed-control device comprising a suction duct leading from the atmosphere into the periphery of the intake conduit and subject to suction to admit air into the system, a moving member associated with said duct and responsive to suction of a predetermined value to move from normal static position to abnormal operating position and to admit air to said duct when air is moving through the system, and means arranged for operation by said moving member to effect operation of said feeding means in said abnormal position and non-operation of said feeding means in said normal position.

6. In an intake conduit to a fan-blower system arranged for drawing air from the atmosphere and having means to feed solid material into said system for suspension in air therein, a feed-control device comprising a suction duct leading from the atmosphere into the periphery of the intake conduit and subject to suction to admit air into the system, an adjustable moving member associated with said duct and responsive to suction of a value predetermined by its adjustment to move from normal static to abnormal operating position and to admit air to said duct when air is moving through the system, and means arranged for operation by said moving member to effect operation of said feeding means in said abnormal position and non-operation of said feeding means in said normal position.

7. Apparatus comprising in combination a centrifugal fan blower drawing air from the atmosphere and ultimately discharging air to the atmosphere, a conduit system for said blower including an intake conduit, valve means in said conduit system to open and close the system against the flow therethrough of air during 0peration of the blower, means to feed particles of solid material into said conduit system for forming and conveying an air-suspension of said particles, a lateral duct connected to and opening into said intake conduit and also opening to the atmosphere and subject to suction by operation of the blower to admit air into the system, a movable member associated with said duct and movable to enlarge the effective passageway through said duct and responsive to suction of a predetermined value to move the member from a normal position occupied in the absence of a predetermined value of suction to a suction-operated abnormal position, control means arranged for operation by said member to effect operation of said feeding means only during the suction-operated abnormal position of the member, and means arranged to be operated by the member in motion to the normal position to effect closure of the opened valve means, whereby an eective resistance to flow of suspended material in the .conduit .system eifectsmovement of `the member to .normal position `and vthereby e'ifects Acut-off of .the feed and closure of ,the valve means, the .arrangement .thus ybeing such that .material can .be fed into :the conduit system only during the flow of air therein to suspend Lit.

8. Apparatus comprising vin .combination -a centrifugal fan blower drawing .air from the-atmosphere and .ultimately discharging Lair to the atmosphere, a conduit As-ystem vfor said blower including an yintake conduit, valve means iin said conduit system to open and close the system against the flow therethrough of air during operation of the blower, means lto feed particles of ysolid vmaterial intosaid -conduit system for forming and conveying an air-suspension of'said vparticles, a lateral .duct connected to and opening :into said intake conduit and falso opening vto the atmosphere and subject tosuction by operation of the blower to adm-it air rinto the system, a movable member associated with said -duct and movable to enlarge the effective passageway through said duct and responsive to suction of la predetermined value to `move the member from la normal position occupied in the labsence of a resistance to new of suspended material in the conduit system effects movement lof the member to normal vposi-tion and lthereby effects lcut-off of the feed and thereafter closure of the valve means, the 'arrangement thus bei-ng such that material can be fed into-the conduit system only during the flow of air therein to Suspend it, and such that after stoppage of feed the lconduit system remains open for a time to clear it of residual particles 9, Apparatus comprising in combination a centrifugal fan blower drawing air from the .atmosphere and ultimately discharging air to the atmosphere, a conduit system `for ksaid blower including an intake conduit, valve means in said conduit system to open and close the system against the ow therethrough of air during operation of the blower, means to feed particles 'of solid material into said conduit system for 'forming and conveying an air-suspension of *said pa'rticles, a lateral duct connected to and 'opening into said intake conduit and also opening to the atmosphere and subject to suction by operation of the blower to admit air into the system, a movable damper associated Iwith said duct and movable in response to suction in the intake conduit into an abnormal position to enlarge the effective passageway through said duct during suction therein, means normally acting against suction to move the damper into a normal position in the absence of a predetermined value of suction, control means arranged for operation by said damper to effect operation of said feeding means only during the suction-operated abnormal position of the damper, and means arranged to be operated by the damper in motion to its normal position to effect closure of the opened valve means, whereby an effective resistance to flow of suspended material in the conduit system effects movement of the damper to normal position and thereby effects cut-off of the feed and closure of the valve means, the .arrangement thus being such that material can be fed into the conduit system only during the fiow of air therein to suspend it.

.10. Apparatus comprising in combination a centrifugal fan blower drawing air from the Aatmosphere and ultimately discharging air to the atmosphere, a conduit lsystem for 'said blower including an'intake conduit, valve means in said conduit system to 'open and close the system against the flow 'therethrough of air during operation of the blower, means to feed particles of solid material into said conduit system 'for forming and conveying an air-suspension ofsaid particles, a lateral duct connected to and opening into said intake conduit and also opening t'o the atmosphere and subject to suction by operation of 'the blower -to admit air into the system, a movable damper associated with -said duct and movable in response 'to suction in the intake conduit Vinto an abnormal position to enlarge the effective passageway through said duct during suction therein, means normally acting against suction to move the damper into a normal .position in the absence of a .predetermined value of suction, control means arranged for operation by said damper to effect operation of said vfeeding means only during the suction-operated `abnormal yposition of the damper, 1and timed Ymeans arranged to be operated -by the damper in motion to its normal position -thereafter ata controlled time to effect closure of the opened valve means, whereby an effective resistance to flow of suspended material in the conduit system `effects movement of 4the damper -to normal position and thereby effects cut-off of the feedand thereafter closure of the valve means, thearrangement being such that material can Abe fed Vinto the conduit system only-during therflow of -air therein tosuspend it, and such -that after stoppage of feed the conduit system remains open ,for -a time to clear it of residual particles.

l1. Apparatus comprising in combination a centrifugal fan blower arranged to 'draw air from and ultimately to discharge air to the atmosphere, a conduit system therefor including an intake conduit and a discharge conduit, valve means in said conduit system for cutting off flow through sa-id conduit system during the operation of said blower and closure -of the valve means, means providing a rcontrol opening into said intake con'- du-it, said opening being exposed to the 'atmose phere for the admission of air by suction from the blower, a Adamper member arranged to move with respect to said opening by suction therein resulting from operation of the blower, adjustable -means tc 'urge said 'damper member into normal position against suction of value less than a Value predetermined by the adjustment of said means, means to feed solid particles of material into said intake conduit for suspension in the air stream and for movement of an air-suspension of said material in said conduit system, valvecontrol means arranged when energized to open said valve means and when de-energized to close said valve means and thereby during operation of the blower `and with open valve means to establish a flowing stream of air and thereby to cause movement of the damper member with respect to said opening, said feeding means being arranged to operate to feed said material by movement of said damper member under the inuence of suction and not so to operate when the damper member is in normal position, receiving means associated with said discharge conduit to receive said solid material from the air stream up to a cut-off point such that the ilow of said air stream is resisted to an extent permitting movement of said damper member into its said normal position, and means associated with and operated by return of the damper member to normal position to cause de-energizing of said valve-control means, whereby at said cut-oil" point the damper member operates to effect stopping of said feed and closure of the conduit system.

12. Apparatus comprising in combination a centrifugal fan blower arranged to draw air from and ultimately to discharge air to the atmosphere, a conduit system therefor including an intake conduit and a discharge conduit, valve means in said conduit system for cutting oi flow through said conduit system during the operation of said blower and closure of the valve means, means providing a control opening into said intake conduit, said opening being exposed to the atmosphere for the admission of air by suction from the blower, a damper member arranged to move with respect to said opening by suction therein` resulting from operation of the blower, adjustable means to urge said damper member into normal position against suction of value less than a value predetermined by the adjustment of said means, means to feed solid particles of material into said intake conduit for suspension in the air stream and for movement of an airsuspension of said material in said conduit system, valve-control means arranged when energized to open said valve means and when de-energized to close said valve means and thereby during operation of the blower and with open valve means to establish a owing stream of air and thereby to cause movement of the damper member with respect to said opening, said feeding means being arranged to operate to feed said material by movement of said damper member under the influence of suction and not so to operate when the damper member is in normal position, receiving means associated with said discharge conduit system to receive said solid material from the air stream up to a cut-oil point such that the ilow of said air stream is resisted to an extent permitting movement of said damper member into its said normal position, and timedelay means associated with and operated by return of the damper member to normal position to cause subsequent de-energizing of said Valvecontrol means, whereby at said cut-off point the damper member operates to effect stopping of said feed and at a predetermined time thereafter closure of the conduit system.

13. A blower system having in combination a fan blower, an intake conduit therefor open to the atmosphere, an outlet conduit therefor for the discharge of air-suspension of solid material against a growing resistance to flow in said system, a duct tapped into the periphery of the intake conduit for admitting a portion of the air for the intake conduit, a movable damper associated with said duct and arranged to move from normal and closed static position to suctionoperated abnormal and open position upon attaining a predetermined suction in the intake conduit and to move back to normal and closed position at differential pressures less than that of said predetermined suction, and controllable means affecting operation of the blower system arranged to be controlled by the two movements of said damper, the location of the opening of said duct at the periphery of the intake conduit eiecting return of the damper to normal and closed position by both reduction of ow through the blower and back-pressure in the inlet conduit.

14. A blower system having in combination a fan blower, a conduit system therefor including an intake conduit opening to the atmosphere, said system being arranged for delivering an airsuspension of solid material against a growing resistance to flow in said system, a duct tapped into the periphery of the intake conduit for admitting a portion of the air for the intake conduit, a movable damper associated with said duct and arranged to move from normal and closed static position to suction-operated abnormal and open position upon attaining a predetermined suction in the intake conduit and to move back to normal and closed position at differential pressures less than that of said predetermined suction, and

controllable means aiecting operation of theY blower system arranged to be controlled by the two movements of said damper, the location of the opening of said duct at the periphery of the intake `conduit eiecting return of the damper to normal and closed position by both reduction of flow through the blower and back-pressure in the inlet conduit.

THURE C. DUVALL.

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

UNITED STATES PATENTS Number Name Date 1,203,703 Chevalier Nov, 7, 1916 1,206,112 Holbeck Nov. 28, 1916 1,778,393 Klugh Oct. 14, 1930 1,996,230 Bressler Apr. 2, 1935

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