Granular material delivery system with air flow limiter

Abstract

Apparatus and methods for conveying granular material from a supply to receivers that retain and dispense the material when needed by process machine include a vacuum pump, an air flow limiter connected to the vacuum pump, a first conduit connecting the receivers to the air flow limiter, and a second conduit connecting the material supply to the receivers.

Claims

1. A method for vacuum powered pneumatic conveying, without central control, granular resin plastic material from a supply to receivers, comprising: a) connecting self-contained, self-regulating air flow limiter for regulating flow rate between no flow and a preselected rate irrespective of pressure drop across the limiter, the limiter comprising a tube, a pair of open-ended tubular segments within the tube, a fixed outer tubular segment and a segment slideably axially movable along the fixed segment, a plate extending at least partially across the tube interior, positioned for contacting and limiting travel of the moveable tubular segment, the plate covering an outlet end of the movable tubular segment upon contact therewith, and a sail connected to the moveable segment, positioned in the tube upstream of the segments, the limiter maintaining flow to a preselected value, to a suction head of a vacuum pump, the flow limiter blocking flow when the preselected value is exceeded and blocking flow if vacuum draw ceases; c) connecting the receivers to the air flow limiter, each of the receivers being self contained without connection to or receipt of electrical signals; d) connecting a supply of granular plastic resin material to the receivers; and e) drawing vacuum from the supply via a conduit to the receivers and from the receivers via a second conduit to a vacuum pump suction intake, the vacuum drawing the granular plastic material from the supply to the receivers; and; f) blocking flow when either the preselected value is exceeded or vacuum draw ceases.

2. A method for vacuum pump powered pneumatic conveying granular plastic resin material without central control from a supply to receivers comprising: a) providing a vacuum drawing conduit connected to a suction head of a vacuum pump; b) providing self-contained, self regulating air flow limiter for regulating flow rate between no flow and a preselected rate irrespective of pressure drop across the limiter, the limiter comprising a tube, a pair of open-ended tubular segments within the tube, a fixed outer tubular segment and a segment slideably axially movable along the fixed segment, a plate extending at least partially across the tube interior, positioned for contacting and limiting travel of the moveable tubular segment, the plate covering an outlet end of the movable tubular segment upon contact therewith, and a sail connected to the moveable segment, positioned in the tube upstream of the segments, the limiter maintaining flow to a preselected value between each receiver and the vacuum drawing conduit; c) providing a conveying conduit between the supply and the receivers; d) drawing vacuum from the supply via a conduit to the receivers and from the receivers via a second conduit to a vacuum pump suction intake, the vacuum drawing the granular plastic material from the supply to the receivers; and; e) blocking flow from an individual receiver to the second conduit when either the preselected value is exceeded at the individual receiver or vacuum draw ceases.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic representation of a resin or other granular material delivery system with a single air flow regulator in accordance with aspects of the invention.

(2) FIG. 2 is a schematic representation of a resin or other granular material delivery system with a plurality of air flow regulators in accordance with aspects of this invention.

(3) FIG. 3 is an isometric view of the exterior of an air flow limiter portion of apparatus for pneumatically conveying granular plastic resin or other material granules in accordance with aspects of the invention.

(4) FIG. 4 is a front elevation of the air flow limiter illustrated in FIG. 3.

(5) FIG. 5 is an isometric sectional view of the air flow limiter illustrated in FIGS. 3 and 4, with the section taken at arrows 3-3 in FIG. 4.

(6) FIG. 6 is a sectional view in elevation of the air flow limiter illustrated in FIGS. 3 and 5, with the section taken at lines and arrows 3-3 in FIG. 4, with air flow through the air flow limiter being depicted in FIG. 6 by curved dark arrows.

(7) FIG. 7 is a sectional view in elevation similar to FIG. 6 but with the air flow limiter internal parts in position whereby there is no air entering the air flow limiter and hence there is no air flow upwardly through the air flow limiter, in contrast to such air flow being shown in FIG. 6.

(8) FIG. 8 is a sectional view in elevation similar to FIGS. 6 and 7 but with the air flow limiter internal parts in position where there is an excessive amount of air attempting to enter the air flow limiter but there is no air flow upwardly through the air flow limiter due to the air flow limiter valve having moved to block air flow upwardly through the air flow limiter, in contrast to upward air flow through the air flow limiter as shown in FIG. 4.

(9) FIG. 9 is an exploded isometric view of the air flow limiter illustrated in FIGS. 3 through 8.

(10) FIG. 10 is an isometric view of the movable portion of the air flow limiter illustrated in FIGS. 3 through 9.

(11) FIG. 11 is a sectional view of the air flow limiter similar to FIGS. 6, 7 and 8, illustrating an alternate construction of the baffle portion of the air flow limiter.

(12) FIG. 12 is sectional view of the air flow limiter similar to FIGS. 6, 7, and 11, illustrating a second alternate construction of the baffle portion of the air flow limiter.

DETAILED DESCRIPTION OF THE OF THE INVENTION

(13) In this application, unless otherwise apparent from the context it is to be understood that the use of the term vacuum means air at slightly below atmospheric pressure. The vacuum (meaning air slightly below atmospheric pressure) provides a suction effect that is used to draw granular plastic resin or other granular material out of a supply and to convey that resin or other granular material through various conduits to receivers where the resin or other granular material can be temporarily stored before being molded, extruded, or otherwise processed. Hence, in this application it is useful for the reader mentally to equate the term vacuum with the term suction.

(14) Referring to the drawings in general and to FIG. 1 in particular, apparatus for conveying granular plastic resin material or other granular material from the supply to receivers that retain and dispense the resin or other material granules when needed by a process machine is illustrated in FIG. 1. The apparatus, which is designated generally 88 in FIG. 1, preferably includes a vacuum pump designated generally 92 and shown schematically in FIG. 1. The vacuum pump preferably includes a vacuum pump suction head 93 also shown schematically in FIG. 1. Connected to the vacuum pump suction head 93 is an airflow limiter 30 shown only in schematic form in FIG. 1, but shown in detail in FIGS. 3 through 12. Airflow limiter 30 receives vacuum drawn by vacuum pump 92 through vacuum drawing conduit 100.

(15) Vacuum drawing conduit 100 is connected to a plurality of receivers 16, each of which receives, retains and dispenses, as needed, granular plastic resin material or other granular material to a process machine, such as a granulator, a blender, an extruder, or a molding press, as located preferably below a receiver 16. The process machines are not illustrated in FIG. 1 to enhance the clarity of the drawing.

(16) Further illustrated in FIG. 1 is a hopper 18 for storage of granular plastic resin material or other granular materials therein and a resin conveying conduit 98, which serves to draw resin from hopper 18 and to deliver the granular material through resin conveying conduit 98 to the respective receivers as vacuum is drawn by the vacuum pump, with vacuum propagating through air flow limiter 30, vacuum drawing conduit 100, the various receivers 16, and resin conveying conduit 98, back to hopper 18.

(17) FIG. 2 shows an alternate embodiment of the granular material conveying system where this alternate embodiment of the conveying system has been designated 88A. FIG. 2, as in FIG. 1, depicts a vacuum pump 92 shown in schematic form having a vacuum pump suction head 93 also depicted in schematic form. In the alternate embodiment illustrated in FIG. 2, vacuum drawing conduit 100 leads directly into and communicates with vacuum pump suction head 93. In the embodiment illustrated in FIG. 2, an air flow limiter 30 is provided for each receiver 16, with the air flow limiter 30 for a respective receiver 16 being located in a portion of a connection conduit 102 that connects a respective receiver to vacuum drawing conduit 100. In FIG. 2, each air flow limiter 30 is depicted in a vertical orientation, just as airflow limiter 30 is depicted in a vertical orientation in FIG. 1. Each receiver is connected by connection conduit 102 to vacuum drawing conduit 100 with air flow limiter 30 preferably forming a portion of connection conduit 102.

(18) In FIG. 2, as in FIG. 1, a first conduit 98 serves to convey granular plastic resin or other material granules from hopper 18 to the respective receivers in response to vacuum drawn by vacuum pump 92 as that vacuum propagates from vacuum pump 92 through second conduit 100, connection conduits 102, receivers 16, and granular material conveying conduit 98, to hopper 18.

(19) During operation of the granular material conveying systems shown schematically in FIGS. 1 and 2, upon actuation of vacuum pump 92, a vacuum preferably is drawn at vacuum pump suction head 93. This vacuum, as it propagates back to hopper 18, serves to draw granular material out of hopper 18 and into the respective receivers 16. In the embodiment illustrated in FIG. 2, individual air flow limiters 30 limit the suction or vacuum drawn by vacuum pump 92 through a given associated receiver 16. In the embodiment illustrated in FIG. 1, a single air flow limiter 30 limits the vacuum drawn through all of receivers 16 forming a portion of the granular resin or other granular material conveying system illustrated in FIG. 1.

(20) Referring to FIGS. 1 and 2, the air flow limiter 30 portion of the granular material delivery system is preferably in the general form of a substantially vertically oriented tube, preferably having inlet and outlet ends 54, 56 respectively. The preferably tubular character of air flow limiter 30 is apparent from FIGS. 3 through 8, where air flow limiter 30 preferably includes a vertically oriented exterior tube 32, with open-end caps 58, 60 defining and providing open inlet and outlet ends 54, 56 respectively. End caps 58, 60 are open, preferably of generally cylindrical configuration, and are configured to fit closely about vertically oriented tube 32 so as to provide a substantially air tight fit between end caps 54, 56 and tube 32.

(21) As illustrated in FIG. 5, air flow limiter 30 preferably includes, within vertically oriented exterior tube 32, a horizontally positioned plate 46, which is oriented perpendicularly to the axis of tube 32. Plate 46 is preferably configured as a circular disk of lesser diameter than the inner diameter of vertically oriented tube 32, with plate 46 further preferably including three legs extending outwardly from the circular interior disk portion of plate 46. Legs of plate 46 are designated 62 in FIG. 9, while the circular interior portion of plate 46 is designated 64 in FIG. 9. Plate 46 is secured to the interior of vertically oriented outer tube 32 by attachment of legs 62 to the interior surface of tube 32. Any suitable means of attachment, such as by welding, adhesive, mechanical screws, or end portions of legs 62 defining tabs fitting into slots within tube 32 as shown in FIG. 5, may be used.

(22) As best shown in FIGS. 5, 6, and 7, a baffle 52 is positioned within vertically oriented outer tube 32, below plate 46. Baffle 52 has a lower conical portion 66 and an upper cylindrical portion 44, with cylindrical portion 44 defining a fixed internal tubular segment of air flow limiter 30. Baffle 52 is preferably retained in position by a pair of screws designated 68, 70 respectively. Baffle 52 preferably rests on screw 68. Screw 70 preferably fits against the fixed internal tubular segment 44 portion of baffle 52 to secure baffle 52 in position within vertically oriented external tube 32. Lateral force applied by screw 70 in a direction perpendicular to the axis of vertically oriented external tube 32, with screw 70 in contact with fixed internal tubular segment 44, serves to effectively retain baffle 52 against movement within vertically oriented external tube 32.

(23) The upper portion of baffle 52, defining fixed internal tubular segment 44, is adapted for sliding, preferably telescopic engagement with and movement therealong by movable tubular segment 42. Fixed to movable tubular segment 42 is a first strut 48 preferably extending transversally across the upper portion of movable tubular segment 42 and preferably secured at either end to movable tubular segment 42, as illustrated in FIG. 10. Preferably extending downwardly from first strut 48 is a second strut 50, preferably secured to first strut 48 and preferably also to a sail 34, as illustrated in FIG. 10 and in FIGS. 5, 6, 7, 8 and 9.

(24) Movable sail 34 is preferably planar and positioned fixedly on second strut 50 to remain perpendicular with respect to the axis of vertically oriented outer tube 32. Movable sail 34 is preferably of generally triangular configuration, as best illustrated in FIGS. 9 and 10, with the sides of the triangle curving slightly inwardly. The curved edges 72 of movable sail 34 converge and terminate to form small rectangularly shaped extremities of sail 34, which are designated 76 in FIG. 9.

(25) Movable sail 34 is positioned within generally vertically oriented outer tube 32 so that rectangular extremities 76 are closely adjacent to but do not contact the inner surface of preferably vertically oriented outer tube 32, so long as sail 34 moves vertically up and down within preferably vertically oriented external tube 32. The rectangular shape of extremities 76 with their outwardly facing preferably planar surface assures minimal friction and consequent minimal resistance to movement of movable sail 34 in the event one of rectangular extremities 76 contacts the interior surface of vertically oriented tube 32, should sail 34 for some reason move laterally, or otherwise, and become skew to the vertical axis of tube 32.

(26) Movable internal tubular segment 42 is telescopically movable, unitarily with sail 34, relative to and along fixed internal tubular segment 44. A lower limit of movement of movable tubular segment 42 is illustrated in FIG. 7, where the first strut portion 48 of movable tubular segment 42 (shown in FIG. 10) rests on the upper circular edge of fixed internal tubular segment 44. This is the condition when no air is flowing or drawn through the air flow limiter 30 and gravity causes sail 34 together with movable internal tubular segment 42 to drop, with first strut 48 coming to rest on the upper circular edge of fixed tubular segment 44.

(27) When air is flowing through air flow limiter 30, as illustrated generally in FIG. 6, the moving air pushes against movable sail 34, moving it upwardly. Movable internal tubular segment 42 moves upwardly unitarily with sail 34 due to the fixed connection of movable tubular segment 42 and movable sail 34 made via first and second struts 48, 50, as illustrated in FIGS. 5, 6, 7, 9, and 10.

(28) If air flow upwardly through air flow limiter 30 reaches an extreme level, above an acceptable level of operation of the granular material delivery system of which air flow limiter 30 is a part, the excessive force (resulting from the high volume of air flow contacting sail 34) pushes sail 34 upwardly to the point that upper annular edge 78 of movable internal tubular segment 42 contacts plate 46. In this condition, which is illustrated in FIG. 8, no air can pass between the upper annular edge 78 of movable tubular segment 42 and flow limiting horizontal plate 46, and air flow stops.

(29) Once air flow stops through vertically oriented outer tube 32, gravity pulling downwardly on sail 34, connected movable internal tubular segment 42, and connected first and second struts 48, 50, causes these parts, which may preferably be fabricated together as a single integral assembly as shown in FIG. 8, to move downwardly, thereby again permitting air flow upwardly through air flow limiter 30 as depicted generally in FIG. 6. Consequently, air flow limiter 30 is self-regulating in that when air flow is too high, the force of air moving or impinging on sail 34 pushes movable internal tubular segment 42 upwardly until upper annular edge 78 of movable tubular segment 42 contacts plate 46 and no air can then escape upwardly between the upper annular edge 78 of movable tubular segment 42 and plate 46. This stops air flow through flow limiter 30 until downward movement of sail 34 together with movable internal tubular segment 42 moves upper annular edge 78 of movable tubular segment 42 away from plate 46, again permitting air to flow through the upper extremity of movable tubular segment 42, with air passing between upper annular edge 78 of movable internal tubular segment 42 and flow limiting horizontal plate 46, and then escaping through upper outlet end 56 of air flow limiter 30.

(30) With the self-regulating characteristic of air flow limiter 30, the assembly consisting of movable internal tubular segment 42, first and second struts 48, 50 and sail 34 may oscillate somewhat about the position at which air flow drawn by suction is at the desired level, as the speed of the vacuum pump drawing air through flow limiter 30 varies, and hence the flow varies in cubic feet per minute of air drawn.

(31) Desirably, ends of first strut 48, which is depicted as being horizontally disposed in the drawings, are mounted in movable tubular segment 42 in movable fashion such that first strut 48 can move slightly, rotationally, relative to movable internal segment 42. This is to provide a small amount of play in the event movable sail 34 and second strut 50, which is vertically oriented and connected to movable sail 34, become skew with respect to the vertical axis of vertically oriented exterior tube 32. Should this occur, the movable characteristic of first strut 48, being slightly rotatable relative to movable internal tubular segment 42, effectively precludes movable internal tubular segment 42 from binding with respect to fixed internal tubular segment 44 and thereby being restricted from what would otherwise be freely telescoping movement of movable internal tubular segment 42 relative to fixed internal tubular segment 44.

(32) Desirably first strut 48 is rotatable relative to movable internal tubular segment 42, to provide maximum freedom of vertical motion of movable internal tubular segment 42 in the event movable sail 34 becomes skew to the axis of vertically oriented exterior tube 32, with consequent frictional force restricting vertical movement of movable sail 34.

(33) Baffle 52 preferably includes two portions, the upper portion preferably being defined by fixed internal tubular segment 44 and a lower portion preferably being defined by conical portion 66 of baffle 52. A lower edge of baffle 52 is circular and is designated 84 in the drawings. Circular edge 84 fits closely against the annular interior wall of vertically oriented exterior tube 32 so that all air passing upwardly through air flow limiter 30, namely through preferably vertically oriented exterior tube 32, is constrained to flow through the interior of baffle 52. The tight fitting of the circular lower edge of baffle 52 against the interior wall of vertically oriented exterior tube 32 forces all air entering flow limiter 30 from the bottom to flow through the interior of baffle 52, flowing upwardly through lower conical portion 66 of baffle 52.

(34) The air then flows further upwardly through the interior of fixed internal tubular segment 44. Thereafter, if movable internal tubular segment 42 is spaced away from flow limiting horizontal plate 46, air flows along the surface of movable internal tubular segment 42, passing the upper annular edge 78 of movable internal tubular segment 42; air then flows around the space between edge 82 of flow limiting horizontal plate 46 and the interior annular wall of vertically oriented exterior tube 32. The air then flows out of air flow limiter 30 via open outlet end 56 formed in end cap 60.

(35) In an alternate embodiment of the air flow limiter, baffle 52 may be constructed from two pieces that fit closely together, with the two pieces being in facing contact in the area where they define fixed internal tubular segment 44, but diverging one from another in the area where they define conical portion 66 of baffle 52. As illustrated in FIG. 12, the two portions of baffle 52 are designated 66A and 66B where they diverge, with baffle portion 66A serving to channel air flow upwardly through vertically oriented exterior tube 32 into fixed internal tubular segment portion 44 of baffle 52. The space between the lower parts of baffle portions 66A and 66B is filled with a filler material 86 to provide additional assurance that all air entering vertically oriented exterior tube 32 from the bottom flows through fixed internal tubular segment 44 and on through movable internal tubular segment 42, and does not pass around the edge of baffle 52, namely between baffle 52 and the interior surface of vertically oriented exterior tube 32. Filler material 86 provides additional structural rigidity for flow limiter 30.

(36) In another alternative environment of the air flow limiter, baffle 52 is one single piece, preferably molded plastic, as illustrated in FIG. 11, where baffle 52 is designated 52B to distinguish it from the baffle construction illustrated in FIG. 12 and the baffle construction illustrated in the other drawing figures. In the baffle construction illustrated in FIG. 11, the one piece construction means there is no need or space for any filler material. The baffle construction illustrated in FIGS. 3 through 10 is preferred.

(37) The assembly illustrated in FIG. 10 comprising the moveable internal tubular segment 42, first strut 48, second strut 50 and moveable sail 34 may preferably be constructed as a single piece or several pieces as required. The assembly of moveable internal segment 42, first and second struts, 48, 50 and moveable sail 34 is referred to as a sail assembly. It is not required that first and second struts 48, 50 be separate pieces; they may preferably be fabricated as a single piece. Additionally, second strut 50, which has been illustrated as a machine screw in FIGS. 9 and 10, need not be a machine screw. Any suitable structure can be used for second strut 50 and it is particularly desirable to fabricate first and second struts 48 and 50 from a single piece of plastic or metal, by molding, by machining, or by welding, or by otherwise fastening two pieces together. Similarly with the hex nut, which is unnumbered in FIG. 10 and illustrated there, any other suitable means for attachment of the second strut or a vertical portion of a strut assembly to moveable sail 34 may be used.

(38) Air flow limiter 30 preferably contains no springs. Air flow limiter 30 preferably contains no sensors to provide feedback to a control device; no sensors are needed because flow limiter 30 is self-regulating. Air flow limiter 30 preferably includes a tubular valve, closing against a flat surface, where the tubular valve is defined by movable internal tubular segment 42 closing against flow limiting horizontal plate 46. Movable internal tubular segment 42 is in the form of an open-ended cylinder and is connected to a plate in the form of movable sail 34 to move movable tubular segment 42 against flow limiting horizontal plate 46. Air flow limiter 30 uses gravity alone to open the valve defined by the assembly of movable internal tubular segment 42, movable sail 34, and the connecting structure therebetween.

(39) In the air flow limiter illustrated in FIGS. 3 through 12, the movable internal tubular segment 42 is preferably made with a very thin wall, preferably from metal tubing, where the wall is preferably less than 1/32 inch in thickness.

(40) Air flow limiter 30 functions equally well with a vacuum pump drawing air through air flow limiter 30 from bottom to top by application of vacuum to outlet end 56 as depicted generally in FIGS. 1 and 2, or by air being supplied under positive pressure at inlet end 54 for passage upwardly through air flow limiter 30.

(41) While the invention and the modes of operation have been described clearly and in more than sufficient detail that one of skill in the art may practice the invention using the teachings of the instant application, and while the claims appended hereto are clear and concise and find full support in the foregoing specification, the invention is not limited to the embodiments described in the foregoing specification or to the literal language of the appended claims. The invention further embraces components, assemblies and methods not disclosed herein but which would perform substantially the same function in substantially the same way to achieve the same result as the apparatus and methods that are the subject of the appended claims, all in accordance with the spirit of the invention.

(42) In the claims appended hereto, the term comprising is to be understood as meaning including, but not limited to while the phrase consisting of is to be understood a meaning having only and no more. The phrase consisting essentially of is to be understood to mean the specified, recited elements, materials or steps, as well as those that do not materially affect the basic and novel characteristics of the claimed invention. See In re Herz, 537 F.2d 549; 190 USPQ 461 (CCPA 1976); 2111 Manual of Patent Examining Procedure, Ninth Edition, Revision 07 2015, Last Revised November 2015.