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(11) | EP 0 087 682 A1 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Metering and/or feeding unit for fluid materials |
| (57) A metering and/or feeding unit for fluid materials, particularly dry particulate
materials and semifluid materials, is disclosed. An elastic-walled tube (17) having
an open feed end and an open discharge end is vertically oriented. A power-driven
assembly, including tube rollers (28), are adapted to constrict the elastic tube (17),
beginning at its upper end and progressively moving down the length of the tube. The
material being metered or fed is introduced into the elastic tube at its upper end
and is progressively moved down the length of the tube as the tube roller (28) of
the power-driven assembly moves down the length of the tube. Valve means (39) are
provided to prevent entry of material into the feed end of the tube (17) at periodic
intervals and in coordination with constriction of the tube (17) so that when a tube
roller (28) initially engages the tube (17) near the feed end of the tube, that portion
of the tube (17) is substantially free of material. The material being fed may be
discharged into a plenum (47) through which a stream of pressurized gas is discharged
to convey the material to a work location. |
Technical Field
[0001] This invention relates to a method and apparatus for metering and/or feeding fluid materials, particularly dry particulate materials and semiliquid materials, into a pressurized or non-pressurized atmosphere.
Background Art
[0002] Finely divided particulate materials, such as Gunite, a sand-cement mixture, are difficult to feed. Several methods are known for feeding dry sand-cement mixtures to a nozzle with compressed air where it is wet with a proper amount of water and applied to a work surface. In general, the prior art machines utilize a pressure vessel, pressurized multiple chambers or a tapered rotary valve.
[0003] The Allentown Pneumatic Gun Company manufactures a feeder having single or dual chambers. With dual chambers, the material is discharged by compressed air from a lower chamber while the upper chamber is being filled with material. An operator is required to cycle feeding of the material from the upper chamber to the lower. The upper chamber must be vented to the atmosphere before refilling.
[0004] Nucretor pneumatic spraying equipment manufactured by The Nucrete Group of Companies, Melbourne, Australia, consists of a paddle mixer which discharges the granular material being fed into a feed chamber. In the feed chamber, a chain drive with fixed circular discs pulls a continuous stream of material through a rubber tube. Partway down the length of the tube, a series of air jets blows the material from between the fixed discs through a hose. No pressure vessel is required; however, wear and maintenance are problems.
[0005] A further type of equipment, manufactured by Schurenberg Beton-Spritzmaschinen (SBS) GmbH of Essen, West Germany, utilizes a rotary-type, tapered valve having multiple chambers for feeding materials intermittently to a pressurized chamber. Wear and sealing of the tapered valve is a problem. Also, the chambers in the rotary valve, after discharge of the material, must be vented to the atmosphere before being refilled.
[0006] NSF Industries of Troy, Michigan, manufactures a unit which employs a multi-chambered rotor mounted within a housing. Compressed air enters through a fixed rotor liner having an opening therein communicating with the chambers of the rotor and forces material from the respective chambers. Intradym AG of Switzerland manufactures a unit operating on a similar principle.
[0007] Because of the necessity of venting in certain of the machines in use today, production capacity is limited. Venting also creates dusting problems and results in a waste of pressurized gas.
[0008] Peristaltic pumps are known for pumping fluid and semifluid materials. U.S. Patent No. 2,015,123 discloses a device for transferring blood to a recipient from a donor by pressing an elastic-walled tube filled with blood with a worm arranged parallel to the tube, the worm being rotated to impart a peristaltic movement to the tube. U.S. Patent No. 2,629,333 discloses a liquid pump having an elastic-walled tube and a rotatable helical member engaging and progressively constricting the tube as the helical member is rotated. U.S. Patent No. 3,669,574 discloses a peristaltic pump for underwater pumping of fluids.
[0009] U.S. Patent No. 3,754,683 discloses a device for feeding dry particulate accelerator material for concrete into an airstream for entrainment which works in combination with a peristaltic pump.
Disclosure of Invention
[0010] A metering and feeding unit for fluid materials is disclosed employing at least one elastic-walled tube which is vertically oriented to hold the material to be fed. A power-driven assembly is positioned adjacent to and along the length of the tube having tube means for engaging a portion of the tube to collapse the tube against itself, starting at the feed end of the tube and working progressively toward the discharge end where the tube is allowed to rein- flate and the material in the tube is discharged from the discharge end of the tube. Valve means are provided to allow entry of the fluid material into the feed end of the tube at periodic intervals, the valve means working in coordination with the power-driven assembly so that when one of the tube means of the power-driven assembly initially engages the tube to collapse it, that portion of the tube is substantially free of material. The material may be discharged from the discharge end of the tube into a plenum through which a pressurized stream of gas is directed, the gas conveying the material to a work location. To provide a continuous flow of material, multiple units or other means, as described hereafter, may be used. Two types of units which function in much the same manner are described.
Brief Description of the Drawings
[0011]
Fig. 1 is a perspective schematic view of the preferred unit of this invention;
Fig. 2 is a vertical cross-section of the unit along section lines 2-2 of Fig. 1;
Fig. 3 is a horizontal cross-section of the unit along section lines 3-3 of Fig. 2;
Fig. 4 is a horizontal section of the unit along section lines 4-4 of Fig. 2;
Fig. 5 is a series of schematic drawings illustrating the unit of Fig. 1 in operation;
Fig. 6 is a perspective view of three units of the type shown in Fig. 1 mounted in side-by-side relationship for continuous feeding of material;
Fig. 7 is a partial cross-sectional view illustrating an alternative means for providing continuous flow of material from a unit such as shown in Fig. 1 into an air-pressurized plenum;
Fig. 8 is a partial view of still another alternative way of continuously feeding material from a unit of the type illustrated in Fig. 1;
Fig. 9 is a schematic diagram of a vaccuum- pressure system employing a unit of the type illustrated in Fig. 1.
Fig. 10 is a perspective view of another type of metering and/or feeding unit of this..invention;
Fig. 11 is a perspective schematic view-of the unit of Fig. 10;
Fig. 12 is a horizontal cross-section of the unit of Fig. 10;
Fig. 13 is a perspective of a single modular unit including an elastic-walled tube and its mounting;
Fig. 14 is a partial horizontal cross-sectional view of a single elastic-walled tube and its corresponding hold-down means;
Fig. 15 is a schematic of the unit of Fig. 10, together with means for filling and emptying a coolant, such as oil, through the container for the unit;
Fig. 16 is a vertical cross-sectional view along section line 16-16 of Fig. 12; and
Fig. 17 is a schematic illustrating the manner in which the particulate material is fed from the respective elastic-walled tubes into the plenum as the helical member rotates to engage the tubes in sequential order.
Best Mode for Carrying Out the Invention
[0012] Fig. 1 illustrates a metering and/or feeding unit for fluid materials. The unit includes a housing 10 for the metering and feeding unit having an upper plate 11 and a lower plate 12 separated by intermediate support plate 13 and side plates 14. Openings are included in the upper and lower plates directly opposite each other, as illustrated in Fig. 2, the openings positioned adjacent to the support plate 13. The support plate 13 may be made adjustable relative to its distance from the respective openings in plates 11 and 12, if desired. The opening in the upper plate 11 includes a flange 15 around the opening. The flange 15 extends above and below the surface of the upper plate 11.
[0013] An open-ended, elastic-walled tube 17 is tightly secured at its upper or feed end around the lower portion of flange 15 and at its lower or discharge end. The tube 17 is secured at its upper end by a band or clamp 18. A similar clamp 16 may be used for securing the lower or discharge end of the tube around the flange of the sleeve which extends into the opening in lower plate 12. The elastic tube 17 is preferably a woven, reinforced rubber material having a smooth surfaced interior wall. Its thickness may range from about 0.635 cm to 1.905 cm, preferably 1.27 cm. Between the tube 17 and the support plate 13, a resilient pad 19 (suitably about 1.27 cm in thickness) is provided which extends the length of the tube to provide a resilient backstop between the elastic tube and the support wall 13.
[0014] Mounted within the frame is a drive assembly which includes tube rollers mounted so as to engage a portion of the tube, beginning at its feed end, to collapse that portion of the tube against itself and then work progressively downwardly toward the discharge end of the tube, where the tube roller disengages from the tube to allow reinflation of the tube. The tube rollers are mounted at spaced intervals on an endless belt, as illustrated in Fig. 2. Referring to Fig. 2, a pair of chains 22 extend about spaced sprockets 23, 24 and 25. Sprockets 23, 24 and 25 are secured to respective shafts 23a, 26 and 27, the respective shafts journaled in bearings 20 secured, respectively, to the upper ends of plates 31 and 32, which are secured to the sidewalls 14 of the housing (see Fig. 3). The sprockets 24 and 25 are mounted such as to provide a run along virtually the entire length of the elastic tube 17. Mounted to the spaced chains at spaced intervals are three tube rollers 28, each journaled in respective bearings on shafts 29 for rotation about the respective shafts (see Fig. 3). Guide rollers 30 are journaled on the ends of the respective shafts 29, the guide rollers traveling along the forward edge of guide plate 31 secured to the respective sidewalls 14 of the unit. The guide surface 31a (see Fig. 2) ensures that each tube roller 28, once it engages the tube 17 at its upper or feed end (as illustrated in Fig. 2) to collapse the tube against itself, will maintain the tube in collapsed condition as it progresses along the. entire length of the tube. Plates 32 are pivotally connected to the respective sidewalls 14 at 32a. A chain-tightening wedge 32b is provided for adjustment of sprocket 23 to tighten chains 22.
[0015] Pairs of side roller units 33 may be secured to the respective chains 22 between each of the tube rollers 28, as illustrated in Fig. 2. Each side roller unit 33 includes an elongated bracket 34 from which extend respective shafts 35. Rollers 36 are journaled for rotation on the respective shafts 35. Flanges 37, secured at one end to the shafts 35, are secured to the respective pairs of chains at their opposite ends. The distance between the pairs of rollers 36, as illustrated in Fig. 4, should be about the same as the diameter of the tube 17. The side roller units are designed to contact the walls of the tube after it has been collapsed by the tube rollers 28 and aid in reinflating the tube to the configuration illustrated in Fig. 4 from that illustrated in Fig. 3.
[0016] Referring to Fig. 2, a relatively short length of tubing 38 is secured around the feed opening in the upper plate 11 with a band or wire clamp 18a. The free end of the section of elastic tube 38 is closed and opened by valve means, such as an arcuate section of a wheel 39 secured above the feed opening for rotation to shaft 40. The shaft 40 is journaled for rotation to bearings secured to the. sidewalls of a bin 41 which receives and holds the fluid material to be fed into the metering unit. The wheel 39 includes an arcuate surface portion 42 which engages the free end of the section of elastic tube 38 to seal the feed opening against entry of material into the tube 17 at periodic intervals. Rather than the valve means shown, a cam-operated sliding valve may be used or other valve means which functions to open and close the feed opening at appropriate times.
[0017] The drive assembly for the tube rollers and the wheel 39 are driven by suitable means, such as a motor 43 (see Fig. 1) whose output shaft drives sprocket 25. The output shaft may have a sprocket 44 secured to it around which is trained chain 45 which is trained about sprocket 46 secured to shaft 40. The rotation rate of wheel 39 relative to that of the drive assembly is chosen to ensure that the feed end of .th-e tube is sealed against entry of material when the tube rollers 28 initially engages the tube 17 at its upper end so that the tube is substantially free of material, thus allowing the tube to be collapsed against itself by the tube roller.
Method of Operation of the Unit
[0018] Fig. 5 schematically illustrates operation of the unit. Referring first to Fig. 5D, the arcuate surface 42 of wheel 39 seals the feed end of the tube 17 against entry of material into the tube 17. Tube roller 28a, near the feed end of the tube, begins to compress the tube 17 to collapse it against itself. Particulate material previously fed into the tube during an earlier cycle moves down the tube as the tube roller 28a progressively moves down the tube. Referring to Fig. 5A, the upper tube roller 28a completely collapses the tube 17 against itself prior to the opening of the feed end of the tube by rotation of wheel 39. Referring to Fig. 5B, the lower tube roller 28b reaches the end of its run and disengages from the tube 17, allowing the material in the tube to discharge from the tube. At the same time, material from the bin 41 continues to feed into the tube 17 at the upper end. Referring to Fig. 5C, the surface 42 of the arcuate wheel 39 closes off the feed end of the tube 17 prior to the tube roller 28c contacting the tube near its upper or feed end. The cycle of operation continues until the material in the bin is exhausted.
[0019] Material discharged from the tube 17 may be discharged into a pressurized air plenum 47, as illustrated in Figs. 1, 2 and 5, or discharged in any other manner desired.
[0020] It may be desirable for certain operations to provide a continuous flow of material rather than the discontinuous flow which one such metering and feeding unit provides. Continuous flow may be obtained in a number of ways, three of which are illustrated by Figs. 6, 7 and 8. In Fig. 6, three side-by-side metering and feeding units are illustrated which are driven through a common drive shaft. The respective positions of -the- tube rollers 28 and arcuate circular members 39 of each unit are adjusted to provide a continuous flow of material into the air plenum 47 from the respective elastic-walled tubes in the three units. Referring to unit A of Fig. 6, the respective positions of the tube rollers 28 and the wheel 39 are such that the feed end of the tube has just been opened and a lower tube roller just disengaged from the tube to allow material in the tube to be fed into the plenum 47, as illustrated in Fig. 5B. The next adjacent unit (unit B of Fig. 6) has its tube rollers 28 and wheel 39 in a position similar to that of Fig. 5D, where the material has been loaded into the tube and is progressively moving down the length of the tube but has not been discharged. The next adjacent unit (unit C of Fig. 6) has its tube rollers 28 and wheel 39 in a position similar to that shown in Fig. 5C, where loading of the material into the tube has been completed and the feed end of the tube is sealed against further entry of material by the surface 42 of wheel 39. By staggering the cycles of the respective side-by-side units, a continuous flow of material can be provided to the air plenum 47.
[0021] Fig. 7 illustrates still another way of providing continuous flow of material to an air plenum. Referring to Fig. 7, an extension 48 of the tube 17 extends from the discharge end of the tube 17 to the air plenum 47. Mounted within that tubular extension is a rotatably mounted butterfly wheel 49 having spaced vanes extending from the central shaft of the wheel. The material discharged from tube 17 is prevented from entering the air plenum 47 all at once by the vanes of the butterfly wheel. The wheel is rotated at a rate sufficient to provide a continuous flow of material into the plenum as the material is discharged from the discharge end of the tube into the extension 48 above the butterfly wheel.
[0022] Fig. 8 illustrates still another method of providing continuous feed of material. In this instance, the discharge end of the unit is connected with a pneumatic feeder of the type manufactured by Schurenberg Beton-Spritzmaschinen (SBS) GmbH of Essen, West Germany. The material is discharged into a chamber 50 in which a rotating drum 51 is located. The chamber 50 includes a material outlet near its lower end. Pressurized air is fed through conduit 53, which discharges adjacent the discharge conduit 52 to entrain the material in the chamber and discharge it.
[0023] Fig. 9 illustrates a vacuum-pressure system making use of the metering and feeding unit of this invention. Referring to Fig. 9, the unit is encased in a housing 56 connected to a source of vacuum 54. The bin 58 above the unit holding the material to be fed is also connected to the source of vacuum 54 and to a material feed line 57. The vacuum created in the bin 58 aids in drawing in the material to be fed through line 59 where it feeds by gravity into the upper end of tube 17 of the metering and feeding unit as previously described. A filter 60 may be provided in the bin to prevent material in the upper part of the bin from being pulled into the vacuum pump 54. The vacuum drawn on the metering and feeding unit exteriorly of the tube 17 aids in reinflation of the tube to its original condition after being collapsed by the respective tube rollers 28.
[0024] With the preferred metering and feeding unit illustrated, it is possible to move relatively large volumes of fluid material economically and substantially maintenance free. For example, using an approximately 7.62-cm diameter elastic tube, approximately 3.823 m3 of material per hour can be moved. With a 10.16-cm diameter tube, approximately 6.10 m3 per hour can be moved. With a 30.48-cm diameter tube and feeding 3.0 m slugs of material between the respective tube rollers, with 30 slugs per minute being fed into an air plenum, about 400 m3 per hour of material can be moved. With 3 units, such as illustrated in Fig. 6, about 1200 m3 per hour can be moved.
[0025] An alternative unit is illustrated in Figs. 10-17. This unit utilizes a rotatable helical member which peripherally engages one or more vertically oriented tubes to constrict the tube as the helical member rotates, beginning at the infeed end of the tube and ending at the discharge end. Means are included to periodically cover and uncover the feed end of the tube at selected intervals to prevent entry of material to be conveyed into the tube so that when the helical member engages and constricts the tube, that portion of the tube is substantially free of material. The metering and feeding unit is housed in a container which may be filled with oil or other liquid to provide cooling and lubrication for the heat of friction generated during operation of the unit. The material is discharged from the discharge end of the tube or tubes into a plenum through which a pressurized stream of gas is directed, the gas conveying the material to a work location.
[0026] Fig. 10 illustrates a housing 70 for the metering and feeding unit having an upper plate 71, a lower plate 72, the upper and lower plates joined by sidewalls 73. The upper and lower plates include a plurality of annular openings 74 and 75 spaced equidistantly about the central axis of the housing. The housing may also includes vertical supports 76 (see Fig. 13) at spaced intervals. The sidewalls are bolted to the upper and lower plates, respectively. Suitable gas- keting is included near the top and bottom edges of the sidewalls and near the side edges to seal the unit. The gaskets near the side edges contact the vertical supports 76.
[0027] A shaft 77, coincident with and parallel to the axis of the housing, extends through respective openings in the top and bottom walls of the housing, as illustrated in Fig. 17. The shaft is journaled for rotation relative to the housing through bearings 78 which are nounted in the top and bottom openings of the shaft. Mounted to and surrounding the shaft is a rigid helical member 79, the function of which will be described.
[0028] Surrounding the shaft are a plurality of elastic-walled tubes 80a to 80h mounted in modular retainers 81 (see Fig. 13). Each of the retainers includes a back wall 82, a top wall 83 and bottom wall 84. The top and bottom walls include respective openings 85 and 86 which are coincident with openings 74 and 75 in respective top and bottom walls of the housing. The elastic-walled tube 80 of each of the . retaining units is tightly secured at its upper end around a serrated fitting 85a surrounding the opening 85. The tubes 80 are cut to provide a smooth interior surface between the inner wall of the serrated fitting 85a and the interior surface of the elastic tube. A four-part clamp 85b is used to clamp the tube about the fitting 85a. Similarly, the lower end of the elastic tubing is tightly secured around the opening 86 by similar means. A smooth interface is provided between the interior surface of the tube and the fitting 86a surrounding the opening 75. A clamp 86b clamps the tube about the fitting. A backstop 87, made of rubber or other resilient material (suitably about 1:27 cm in thickness), is mounted between the back wall 22 and tube 20 to contact the sidewall of the elastic tube adjacent the back wall of the retainer.
[0029] The respective modular retainers 81 are mounted in the housing as illustrated in Figs. 10 and 13. Each of the modular retainers is retained in the housing by a series of pins 88 extending upwardly from the bottom wall 72 against which shoulders 89 formed on the bottom wall 84 of the respective modular retainers 81 rest. Although not shown, there are corresponding pins extending downwardly from the top wall 71 against which shoulders 89 formed on the top walls 83 rest. Additionally, retaining screws 90, threaded into and extending from the upper and lower walls 70 and 72, are used to hold the bottom and top walls 84 and 83 of each of the modular units to prevent lateral shift of each of the units. This is best illustrated in Fig. 12.
[0030] Referring to Fig. 10, a cover 91 covers, at any given time, certain of the spaced openings 74 through which the particulate material drops into the respective elastic tubes 80. The cover is secured to the shaft 77 for rotation therewith by spaced supports 92 and 93 and sequentially covers and uncovers respective openings 74. A hopper 94 holding the particulate material to be fed into the metering unit has its discharge end fitted around the top 71 of the housing, as illustrated in Fig. 10. If necessary, vent openings to the atmosphere may be provided through the supports 93 in the cover 91 and shaft 77- to permit the tubes to reinflat-e after being compressed by the rod.
[0031] Secured to the bottom wall 72 and covering each of the bottom openings 75 through which the particulate material discharges is a plenum 95 into which pressurized air or other gas enters through port 96. The plenum includes a discharge end which conveys the material to a work location.
[0032] The housing is sealed and the interior of the housing filled with oil, lubricant, or other coolant. Referring to the schematic shown in Fig. 15, the housing is initially filled by opening valves 98 and 99 and closing valves 100, 101 and 102. An airtight filler cap 103 including an integral dipstick is opened and the housing filled with oil. The filler cap is then closed and the vacuum pump 104 started. A vacuum gauge 105 may be included to monitor the vacuum. The volume of oil held by the accumulator vessel 106 should approximately equal the volume of oil which is held in the housing.
[0033] If it is desired to drain the oil from the housing, the filler cap 103 is opened, valves 99, 100 and 102 opened, and valves 98 and 101 closed. The pump 104 is operated until the oil is moved to the vessel 106. To return oil to the housing, valves 99 and 100 are closed and valves 98, 101 and 102 opened. The pump 104, when operated, creates a vacuum in the housing and pressure in the accumulator 106. When all of the oil is transferred, valve 102 is closed.
[0034] To prevent lateral movement of the respective elastic-walled tubes 80 when engaged by the helical rod 79, each of the tubes is held within a flexible sling 107 (see Fig. 13) which is secured by rivets 108 (see Fig. 14) or other suitable means to the back stop along the side of the back stop where the rod 79 first engages the elastic tube. The sling is suitably manufactured from a reinforced elastomeric material, such as neoprene, having a thickness of about 0.318 cm.
[0035] The elastic tubes 80 preferably have a wall thickness of about 1.27 cm and are fabricated of a woven, reinforced-rubber material-having a smooth-surfaced interior wall.
Method of Operation of the Unit
[0036] Referring to Figs. 10 and 17, particulate material held in the hopper 94 falls by gravity into the respective elastic tubes 80e, 80f, 80g and 80h not covered by the cover 91. In Fig. 17, reference numeral 109 refers to the areas where the helical rod 79 initially engages an elastic tube to squeeze it against the opposite sidewall of the tube, as indicated in Fig. 16. Note in Fig. 17 that the cover 91 covers'tubes 80a, 80b, 80c and 80d. As the helical rod rotates, an air gap 110 is created beneath the cover 91. It is necessary to have this air gap so that when the helical rod 79 engages each of the elastic tubes 80 at their upper ends, the material in the tube will not prevent the tube from being flattened or constricted against the opposite wall of the tube, as illustrated in Fig. 16. The material in each of the tubes falls by gravity from the open discharge end of the tube into an airstream coursing through the plenum, where it is conveyed by the airstream for delivery to a desired work location. The tube constriction by the helical rod agitates the tube and prevents caking of the material in the tube.
[0037] The helical rod 79 and shaft 77 may be driven by a hydraulic motor 111, illustrated in Fig. 16. Hydraulic fluid is supplied to the hydraulic motor through line 112 from a reservoir 113 by a power source 114. The hydraulic fluid returns to the reservoir by way of line 115.
[0038] If desired, different materials may be fed to each of the elastic-walled tubes and discharged to different respective plenums or discharged into a common plenum for mixing. Also, rather than the cover 91 shown, any means of periodically opening and closing the infeed ends of the respective elastic tubes may be used. The device may be used to batch materials for a mixer or for other purposes. In such case, the plenum and air conveying means may be omitted.
1.- A metering and feeding unit for fluid materials, having an open-ended, elastic-walled
tube for receiving the material with an open feed end and an open discharge end, and
a power-driven assembly positioned adjacent the length of the tube including tube
means to engage the tube to collapse a portion of the tube against itself starting
at the feed end of the tube and working progressively toward the discharge end where
it disengages from the tube to allow reinflation of the tube and discharge of the
material from the tube, characterized in that valve means are provided at the feed
end by the tube to prevent entry of material into the feed end at selected intervals
in coordination with the power-driven assembly so that when the tube means of the
power-driven assembly initially engages the tube at the feed end, that portion of
the tube is substantially free of material.
2. The unit of claim 1 wherein the power-driven assembly includes spaced tube rollers
mounted on an endless, flexible, driven belt, the spaced tube rollers, in repeating
cycles, engaging the tube to collapse it against itself as the power-driven assembly
is driven.
3. The unit of claim 2 wherein the valve means includes an arcuate, rotatable member
having a surface which periodically covers and uncovers the feed end of the tube on
rotation.
4. The unit of claim 2 wherein the valve means is coordinated to open the feed end
of the tube after one of the spaced tube rollers has collapsed the tube near the feed
end of the tube.
5. The unit of claim 2, including at least one pair of side rollers mounted between
and essentially at right angles to the spaced tube rollers for engaging the sidewalls
of the tube, the side rollers engaging the sidewalls of the tube both before and after
the tube is collapsed against itself by the tube rollers to aid in reinflating the
tube.
6. The unit of claim 1, including a plenum communicating with the discharge end of
the tube and a source of pressurized gas flowing through the plenum to convey the
material discharged into the plenum.
7. The unit of claim 1 wherein the tube means for engaging the tube is a rotatable
helical member peripherally engaging the tube along its length to constrict the tube
against itself as the helical member rotates about its axis; and wherein the valve
means prevents entry of the material to be conveyed into the feed end of the tube
until after the helical member engages the upper portion of the tube so that that
portion of the tube is substantially free of material to be conveyed.
8. The unit of claim 7, including a plurality of elastic-walled tubes arranged equidistantly
about the axis of the helical member, the tubes being vertically oriented.
9. The unit of claim 8, including means to allow the interior of the tubes to be vented
periodically to the atmosphere to ensure their reinflation after constriction by the
helical member.
10. The unit of claim 8 wherein the tubes are housed within a container and the container
is filled with a coolant.
11. The unit of claim 7, including means for engaging and supporting the tube as the
helical member progressively constricts the tube along its length.
12. the unit of claim 7, including means preventing lateral movement of the tube when
the helical member initially engages the tube.
13. A method of feeding fluid materials, comprising the steps of:
(a) feeding material into the feed end of an open-ended, elastic-walled tube collapsed against itself partway down the length of the tube;
(b) progressively moving the point of collapse of the tube downwardly toward the discharge end to allow the material in the tube to flow by gravity down the length of the tube;
(c) closing the feed end of the tube to prevent flow of material thereinto;
(d) collapsing the tube against itself near the feed end thereof above the material already in the tube;
(e) reinflating the collapsed portion of the tube near the discharge end thereof to allow the material in the tube to be discharged;
(f) opening the feed end of the tube to allow additional material to flow into the feed end of the tube; and
(g) repeating steps (a) through (f).