Abstract
Method for pneumatically conveying granular material from a supply thereof through a conduit to a plurality of receivers for temporary storage of the material prior to molding or extrusion thereof by drawing vacuum in the conduit using a vacuum pump and varying the vacuum pump speed in response to sensed vacuum level in the conduit proximate the pump.
Claims
1. In a method for pneumatically conveying granular material from a supply thereof through a conduit to a plurality of receivers for temporary storage of the material prior to molding or extrusion thereof by drawing vacuum in the conduit using a vacuum pump, the improvement comprising varying the vacuum pump speed in response to sensed vacuum level in the conduit proximate the pump.
2. In a method for pneumatically conveying granular material from a supply thereof through a conduit to a plurality of receivers for temporary storage of the material prior to molding or extrusion thereof by drawing vacuum in the conduit using a vacuum pump, the improvement comprising: a) limiting air flow downstream of a receiver to a maximum value to be drawn by the vacuum pump; and b) varying vacuum pump speed in response to sensed vacuum level in the conduit at a position downstream of the location where air flow is limited.
3. In a method for pneumatically conveying granular material from a supply thereof through a conduit to a plurality of receivers for temporary storage of the material prior to molding or extrusion thereof by drawing vacuum in the conduit, the improvement comprising: a) sensing level of granular material in each receiver and replenishing granular material in that receiver in response to material level falling below a predetermined level; and b) sensing vacuum level in a conduit supplying granular material to the receiver from the supply and when vacuum level in the conduit is too low for effective conveyance of granular material to the receiver, overriding any signal indicative of sensed granular material level in the receiver being below the predetermined level.
4. In a method for pneumatically conveying granular resin material from a supply thereof through a conduit to a plurality of receivers for temporary storage of the resin material prior to molding or extrusion thereof by drawing vacuum in the conduit, the improvement comprising: a) sensing level of material in each receiver and replenishing material in that receiver upon material level falling below a predetermined level; and b) sensing vacuum level in a conduit supplying granular material to the receiver from the supply and blocking replenishment of granular material into the receiver whenever vacuum level in the conduit is too low for effective conveyance of material to the receiver.
5. A method for operating a vacuum driven pneumatic conveying system delivering granular material to receivers without central control of the system, comprising: a) pneumatically delivering granular material under vacuum to any receiver for which a signal indicates granular material level is below a predetermined threshold; b) sensing vacuum level in respective granular material delivery lines leading to the respective receivers; c) upon sensed vacuum level in a respective granular material delivery line falling below the level required for the respective receiver to load with granular material, overriding the level signal and blocking the delivery line for the respective receiver.
6. The method of claim 5 wherein there are a plurality of receivers, each receiver having a flow limiter connected to a vacuum discharge port of the receiver.
7. The method of claim 5 wherein there are a plurality of receivers and fewer than all of the receivers have a flow limiter connected to a vacuum discharge port of the receiver.
8. The method of claim 5 wherein the vacuum is drawn by a vacuum pump having a variable speed drive.
9. The method of claim 8 wherein there is a flow limiter immediately upstream of the vacuum pump.
10. The method of claim 9 wherein there are a plurality of receivers, each receiver having a flow limiter connected to a vacuum discharge port of the receiver.
11. The method of claim 9 wherein there are a plurality of receivers and fewer than all of the receivers have a flow limiter connected to a vacuum discharge port of the receiver.
12. The method of claim 6 wherein the receivers are of at least two different capacities.
13. The method of claim 12 wherein the flow limiters are of at least two different capacities.
14. The method of claim 7 wherein the receivers are of at least two different capacities.
15. The method of claim 14 wherein the flow limiters are of at least two different capacities.
16. The method of claim 9 wherein the receivers are of at least two different capacities.
17. The method of claim 16 wherein the flow limiters are of at least two different capacities.
18. A method for operating a vacuum driven pneumatic conveying system delivering granular material to receivers without central control of the system, consisting of: a) pneumatically delivering granular material under vacuum to any receiver for which a signal indicates granular material level is below a predetermined threshold; b) sensing vacuum level in respective granular material delivery lines leading to the respective receivers; c) upon sensed vacuum level in a respective granular material delivery line falling below the level required for the respective receiver to load with granular material, overriding the level signal and blocking the delivery line for the respective receiver.
19. A method for operating a vacuum driven pneumatic conveying system delivering granular material to receivers without central control of the system, consisting essentially of: a) pneumatically delivering granular material under vacuum to any receiver for which a signal indicates granular material level is below a predetermined threshold; b) sensing vacuum level in respective granular material delivery lines leading to the respective receivers; c) upon sensed vacuum level in a respective granular material delivery line falling below the level required for the respective receiver to load with granular material, overriding the level signal and blocking the delivery line for the respective receiver.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
[0069] FIG. 1 is a schematic view of first vacuum powered apparatus for delivery of granular plastic resin material in accordance with aspects of the invention.
[0070] FIG. 2 is a schematic view of a second vacuum powered apparatus for delivery of granular plastic resin material in accordance with aspects of the invention.
[0071] FIG. 3 is a schematic view of a third vacuum powered apparatus for delivery of granular plastic resin material in accordance with aspects of the invention.
[0072] FIG. 4 is a schematic view of a fourth vacuum powered apparatus for delivery of granular plastic resin material in accordance with aspects of the invention.
[0073] FIG. 5 is a schematic view of a fifth vacuum powered apparatus for delivery of granular plastic resin material in accordance with aspects of the invention.
[0074] FIG. 6 is a schematic view of a sixth vacuum powered system for delivery of granular plastic resin material in accordance with aspects of the invention.
[0075] FIG. 7 is a schematic view of a seventh vacuum powered system for delivery of granular plastic resin material in accordance with aspects of the invention.
[0076] FIG. 8 is a schematic view of an eighth vacuum powered system for delivery of granular plastic resin material in accordance with aspects of the invention.
[0077] FIG. 9 is a schematic isometric view of a receiver embodying aspects of the invention.
[0078] FIG. 10 is an isometric view of the exterior of a preferred air flow limiter.
[0079] FIG. 11 is a front elevation of the air flow limiter illustrated in FIG. 10.
[0080] FIG. 12 is an isometric sectional view of the air flow limiter illustrated in FIGS. 10 and 11, with the section taken at arrows XIII-XIII in FIG. 11.
[0081] FIG. 13 is a sectional view in elevation of the air flow limiter illustrated in FIGS. 10, 11, and 12, with the section taken at lines and arrows XIII-XIII in FIG. 11, with air flow through the air flow limiter being depicted in FIG. 13 by curved dark arrows.
[0082] FIG. 14 is a sectional view in elevation similar to FIG. 13 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. 13.
[0083] FIG. 15 is a sectional view in elevation similar to FIGS. 13 and 14 but with the air flow limiter internal parts in position where there is an excessive amount of air attempting to enter the air flow limited 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 air flow upwardly through the air flow limiter as shown in FIG. 13.
[0084] FIG. 16 is an exploded isometric view of the air flow limiter illustrated in detail in FIGS. 10 through 15.
[0085] FIG. 17 is an isometric view of the movable portion of the air flow limiter valve illustrated in FIGS. 10 through 16.
[0086] FIG. 18 is a sectional view of an air flow limiter similar to that shown in FIGS. 13, 14 and 15, illustrating an alternate construction of the baffle portion of the air flow limiter.
[0087] FIG. 19 is sectional view of an air flow limiter similar to that shown in FIGS. 13, 14, 15 and 18, illustrating a second alternate construction of the baffle portion of the air flow limiter.
DESCRIPTION OF THE PREFERRED EMBODIMENT AND BEST MODE KNOWN FOR PRACTICE OF THE INVENTION
[0088] Referring to the drawings in general and to FIG. 1 in particular, apparatus for delivery of granular plastic resin material in accordance with the invention is designated generally 100. Apparatus 100 conveys granular plastic resin material from a resin material supply 104 to a plurality of receivers, each of which is designated either 102A or 102B in FIG. 1. The resin is conveyed from resin material supply 104 to receivers 102A, 102B via resin conveyance conduits that are designated generally 106 where 106A denotes a first resin conveyance conduit and 106B denotes a second resin conveyance conduit. First resin conveyance conduit 106A conveys resin from supply 104 to receivers 102A that are shown generally aligned and in the upper portion of FIG. 1. Second resin conveyance conduit 106B conveys resin from supply 104 to receivers 102B that are shown generally aligned and in the lower portion of FIG. 1. First and second resin conveyance conduits 106A, 106B are preferably, but not necessarily, of the same diameter and convey resin to the respective receivers 102A, 102B as a result of vacuum drawn by vacuum pump 112.
[0089] Each receiver 102A, 102B is depicted as having a resin discharge conduit 108 at the bottom thereof for discharge of resin when needed from the associated receiver. Resin is discharged upon demand by a process machine requiring additional resin to continue manufacture of molded or extruded plastic parts. Receivers 102A and 102B are preferably all identical.
[0090] As depicted schematically in FIG. 1, resin is supplied to receivers 102A, 102B from above, with resin supply lines 107A connecting receivers 102A with a first resin conveyance conduit 106A and with resin supply lines 107B connecting receivers 102B with a second resin conveyance conduit 106B. The respective resin supply lines 107A, 107B lead downwardly into particular receivers 102A, 102B in order to deliver resin thereto. Resin is conveyed through resin conveyance conduits 106A, 106B due to vacuum drawn by vacuum pump 112.
[0091] Air drawn under vacuum by vacuum pump 112 leaves from each receiver 102 laterally via a side air vacuum discharge conduit designated 110A or 110B. Each receiver air discharge conduit 110A, 110B leads initially to an air flow limiter 30. Air as vacuum leaving a receiver 102A, 102B, after passing through an air flow limiter 30, travels on through the associated receiver discharge conduit 110A, 110B, with discharge conduits 110A and 110B joining as illustrated at the right side of FIG. 1. Air as vacuum coming from receiver air discharge conduits 110A and 110B combines and passes through another air flow limiter 30-1 before reaching vacuum pump 112.
[0092] Vacuum pump 112 is desirably equipped with a variable frequency drive unit 114, allowing precise control of vacuum pump 112.
[0093] Each receiver 102 is desirably of the type shown schematically in FIG. 5 and described in greater detail hereinbelow.
[0094] In the embodiment illustrated in FIG. 1, each receiver 102A, 102B has an air flow limiter 30 associated directly with the receiver. The receiver as air vacuum discharge conduit 110 for a given receiver leads directly into an air flow limiter 30 that is associated with that particular receiver. Each air flow limiter 30 is preferably of the type described hereinbelow in greater detail.
[0095] Air flow limiters 30 are all preferably identical. Air flow limiter 30-1 is desirably of larger size and hence of larger capacity than air flow limiters 30. However, air flow limiter 30-1 is preferably of the same design as air flow limiters 30, as disclosed above.
[0096] Still referring to the drawings and to FIG. 2 in particular, a second embodiment of apparatus for delivery of granular plastic resin material in accordance with the invention is designated generally 100A. Much like apparatus 100 illustrated in FIG. 1, apparatus 100A conveys granular plastic resin material from a resin material supply 104 to a plurality of receivers. In the apparatus illustrated in FIG. 2, receivers are two different sizes. The smaller receivers are designated 102B, while the larger receivers are designated 102X.
[0097] Similarly to the apparatus illustrated in FIG. 1, the resin is conveyed from raw material supply 104 to receivers 102B, 102X via resin conveyance conduits that are designated generally 106, where 106X denotes a first resin conveyance conduit and 106B denotes a second resin conveyance conduit. First resin conveyance conduit 106X conveys resin from supply 104 to resin delivery lines 107X for downward delivery to receivers 102X. Second resin conduit 106B conveys resin from supply 104 to resin delivery lines 107B for downward delivery to receivers 102B. Since receivers 102X are larger than receivers 102B, receivers 102X generally have larger capacity for storage of resin therein. Consequently, resin conveyance conduit 106X and resin delivery lines 107X may be of larger diameter than resin conveyance conduit 106B and resin delivery lines 107B, which convey resin to smaller receivers 102B. Despite their possible different diameters, both resin conveyance conduits 106X and 106B convey resin to respective receivers 102X and 102B as a result of vacuum, desirably drawn by a single vacuum pump 112.
[0098] Similarly to FIG. 1, each receiver 102B, 102X has a resin discharge conduit 108 at the bottom thereof for discharge of resin when needed from the associated receiver 102B or 102X. Resin is discharged upon demand by a process machine requiring additional resin to continue manufacture of molded or extruded parts.
[0099] As depicted schematically in FIG. 2, similarly to that shown in FIG. 1, resin is supplied to each receiver 102B, 102X from above, with resin supply lines 107B, 107X connecting to either first resin conveyance conduit 106X or second resin conveyance conduit 106B leading downwardly into a particular receiver 102X or 102B in order to deliver resin thereinto. All resin is conveyed through the resin conveyance conduit 106, specifically resin conveyance conduits 106B and 106X, due to vacuum drawn by vacuum pump 112.
[0100] Similarly to the arrangement shown in FIG. 1, air drawn under vacuum by a vacuum pump 112 leaves from each receiver 102A, 102 laterally via a side air as vacuum discharge conduit designated 110X or 110B, according to whether the discharge conduit is associated with a receiver 102X or a receiver 102. Each receiver air discharge conduit, whether it be discharge conduit 110X or discharge conduit 110B, leads initially to an air flow limiter that is associated with a particular receiver, with the air flow limiter being designated 30X if associated with a receiver 102X or with the air flow limiter being designated 30 if associated with a receiver 102B. Air leaving a receiver 102X or 102B, after passing through the associated air flow limiter 30X or 30, travels on through the associated receiver air discharge conduit 110X or 110B with discharge conduits 110X and 110B joining as illustrated at the right side of FIG. 2. Air coming from receiver air discharge conduits 110X and 110B combines and preferably passes through another flow limiter, this flow limiter being designed 30-2, before reaching vacuum pump 112. Desirably flow limiter 30-2 will be of larger capacity than either flow limiter 30 or flow limiter 30X due to the relevant portions of resin conveyance conduit 106X, receivers 102X, and air flow limiters 30X and air discharge conduits 110X being larger than the corresponding components and conduits illustrated in FIG. 1.
[0101] Vacuum pump 112, similarly to vacuum pump 112 illustrated in FIG. 1, is desirably equipped with a variable frequency drive unit 114, allowing precise control of vacuum pump 112.
[0102] Similarly to FIG. 1, each receiver 102X, 102B is desirably of a type shown schematically in FIG. 9 described in greater detail below.
[0103] Similarly to the apparatus illustrated in FIG. 1, each receiver 102X, 102B has an air flow limiter 30X, 30 associated directly with the receiver. Air flow limiters 30X being associated with larger size receivers 102X may be of larger size and hence larger capacity than air flow limiters 30. Similarly, air flow limiter 30-2 may be of still larger size and hence of still larger capacity than air flow limiters 30X. Desirably, air flow limiters 30X and 30-2 are of the same design as air flow limiter 30, as disclosed hereinbelow.
[0104] Referring to FIG. 3, apparatus for delivery of granular plastic resin material in accordance with the invention is designated generally 100B. Apparatus 100B conveys granular resin material from a resin material supply 104 to a plurality of receivers, each of which is designated either 102A or 102B in FIG. 3, in the same manner as in FIGS. 1 and 2. The resin is conveyed from resin material supply 104 to receivers 102A, 102B initially via resin conveyance conduits that are designated generally 106, where 106A denotes a first resin conveyance conduit and 106B denotes a second resin conveyance conduit, and then via resin supply lines 107A, 107B.
[0105] Similarly to FIG. 1, first resin conveyance conduit 106A conveys resin from supply 104 to receivers 102A that are shown generally aligned and in the upper portion of FIG. 3. Second resin conveyance conduit 106B conveys resin from supply 104 to receivers 102B that are shown generally aligned and in the lower portion of FIG. 3. First and second resin conveyance conduits 106A, 106B are preferably, but not necessarily, of the same diameter and convey resin to the respective receivers 102A, 102B as a result of vacuum drawn by vacuum pump 112. Each receiver 102A, 102B is depicted as having a resin discharge conduit 108 at the bottom thereof for discharge of resin when needed from the associated receiver 102A or 102B. Resin is discharged upon demand by a process machine requiring replenishment of resin in order to continue manufacture of molded or extruded plastic parts.
[0106] As depicted schematically in FIG. 3, much the same as in FIG. 1, resin is supplied to each receiver 102A or 102B from above, with first resin supply conduits 107A leading downwardly from portion of either first resin conveyance conduit 106A into receivers 102A and with second resin supply conduits leading from second resin conveyance conduit 106B downwardly into receivers 102B to deliver resin thereinto. Resin is conveyed through resin conveyance conduits 106A, 106B due to vacuum drawn by vacuum pump 112.
[0107] Air drawn under vacuum by vacuum pump 112 from each receiver departs that receiver, either 102A or 102B, laterally via a side air as vacuum discharge conduit designated 110A or 110B or 110X. Side air discharge conduits 110A and 110B discharge air as vacuum from an associated receiver 108 initially through an air limiter 30, if an air limiter 30 is present. Air as vacuum leaving a receiver 102A or 102B either through air discharge conduit 110A or 110B, after passing through an associated air flow limiter 30 if present, travels on through the receiver air discharge conduits 110A or 110B to a point of juncture therebetween, and from there through air flow limiter 30-3 to vacuum pump 112.
[0108] In the embodiment illustrated in FIG. 3, some receivers 102A, 102B do not have an air flow limiter 30 directly associated therewith. Air drawn under vacuum by vacuum pump 112 leaves those receivers laterally via a side air as vacuum discharge conduit designated 110A or 110B. Air leaving a receiver 102A or 102B via an air as vacuum discharge conduit 110A or 110B that lacks an air flow limiter 30 joins a main associated receiver air as vacuum discharge conduit 110A or 110B as illustrated and passes through flow limiter 30-3 before reaching vacuum pump 112.
[0109] Similarly to the apparatus depicted in FIGS. 1 and 2, vacuum pump 112 is desirably equipped with a variable frequency drive unit 114 allowing precise control of vacuum pump 112. Further similarly to FIGS. 1 and 2, each receiver, whether numbered 102A or 102B, is desirably of the type shown schematically in FIG. 9 and described in greater detail hereinbelow. Each air flow limiter 30, as well as flow limiter 30-3, is preferably of the type described hereinbelow in greater detail.
[0110] Referring to FIG. 4, apparatus for delivery of granular plastic resin material in accordance with the invention is designated generally 100D. Apparatus 100D is similar to apparatus 100A illustrated in FIG. 2 with the exception that there is no flow limiter 30-2 in the resin conveyance conduit leading immediately to vacuum pump 112 and vacuum pump variable frequency drive 114. Operation of the apparatus illustrated in FIG. 4 is similar to operation of the apparatus illustrated in FIG. 2, with the exception that the flow limiters 30, 30X in FIG. 4 may be internally configured differently and sized differently to account for the absence of any flow limiter 30-2 of the type illustrated in FIG. 2 in conduit 110 leading directly to vacuum pump 112. With each receiver 102B, 102X in FIG. 4 being an air flow limiter associated therein, presence of an air flow limiter such as illustrated in FIG. 2, in the position illustrated in FIG. 2, is not so critical to successful operation of the system without central control. Where some receivers do not have air flow limiters associated with them, as in the embodiment illustrated in FIG. 3, presence of an air flow limiter such as air flow limiter 30-3 in FIG. 3, is important for the successful operation of the system without central control.
[0111] Referring to FIG. 5, apparatus for delivery of granular plastic resin material in accordance with the invention is designated generally 100D. Apparatus 100D is similar to apparatus 100 illustrated in FIG. 1 but in FIG. 5, receivers 102A receive granular plastic resin material to be processed from resin material supply 104 while receivers 102B receive other material, which can be other granular plastic resin material, or additives, or solid colorant, from material supply 116. Since a given process, whether extrusion or molding, may require different amounts of granular plastic resin material from supply 104 and granular plastic resin material or additive or solid colorant from supply 116, material from supply 104 and material from supply 116 travel through separate conveyance conduits which have been numbered 106A and 118 in FIG. 5. Similarly, the receivers in FIG. 5 have been designated 102A and 102B to be consistent with the numbering of the smaller receivers throughout this disclosure. Receivers 102A, 102B are preferably of the type disclosed herein as set forth below and as illustrated in FIG. 9.
[0112] Similarly to the configuration illustrated in FIG. 1, a first resin conveyance line 106A conveys granular plastic resin material from supply 104 to receivers 102A via resin supply lines 107A. A material conveyance line 118 conveys material from supply 116 to receivers 102B. Conveyance lines 106A, 118 are of suitable size according to the volume of material being conveyed from supplies 104 and 116 to receivers 102A and 102B. As is the case with the configurations illustrated in FIGS. 1 through 4, all conveyance of materials in the apparatus illustrated schematically in FIG. 5 is pneumatic conveyance performed by a vacuum pump 112 desirably having a variable speed drive 114 associated therewith as illustrated schematically in FIG. 5.
[0113] Similarly to FIGS. 1 through 4, each receiver 102A, 102B is depicted as having a discharge conduit at the bottom thereof for discharge of material when the material is needed from the associated receiver 102A or 102B by a process machine. Material is discharged upon demand upon a process machine requiring additional material to continue manufacture of molded or extruded plastic parts. The discharge conduits of receivers 102A, 102B are designated 108 for consistency with the discharge conduits associated with the receivers in FIGS. 1 through 4.
[0114] Similarly to FIG. 1, the receivers illustrated in FIG. 5 all have associated therewith a flow limiter where the flow limiters have been designated 30. As with the flow limiters 30 illustrated in connection with FIG. 1 and as set forth elsewhere in this application, flow limiters 30 will be appropriately sized according to the size of the pneumatic conveyance conduit and the design goal flow rate with which a given flow limiter is associated. As illustrated in FIG. 5, each receiver 102A, 102B has a flow limiter 30 associated therewith to limit flow through the receiver as drawn by vacuum pump 112 and its controlling variable speed drive 114.
[0115] As further illustrated in FIG. 5, first and second pneumatic conveyance conduits 110A, 110B come together before reaching vacuum pump 112. After juncture of first and second pneumatic conveyance conduits 110A, 110B a flow limiter 30-4 is located downstream thereof. Provision of the flow limiters 30 and 30-4, together with the self-regulating character of the receivers 102A, 102B, as such self-limiting character is described with respect to the inventive receiver set forth elsewhere in this disclosure, allows the vacuum powered resin loading system illustrated in these drawing figures to operate without central control.
[0116] Further respecting the configuration illustrated in FIG. 5, similarly to that depicted schematically in FIG. 1, material is supplied to each receiver 122, 124 from above, with a portion of either first material conveyance line 107A or second material conveyance line 107B leading downwardly into a particular receiver 102A, 102B to deliver material thereto. Material is conveyed through first and second material conveyance lines due to vacuum drawn by vacuum pump 112.
[0117] Also similarly to FIG. 1, in the system configuration illustrated in FIG. 5 as apparatus 100D, air drawn under vacuum by vacuum pump 112 leaves each receiver 102A, 102B laterally via a side air as vacuum discharge conduit designated 110A or 110B according to whether the discharge conduit is associated with a receiver 102A or 102B. Both first and second pneumatic conveyance conduits 110A, 110B feed initially to an air flow limiter 30. Air leaving a receiver 102A or 102B, after passing through the associated air flow limiter 30, travels on through the associated receiver air as vacuum discharge conduit 110A or 110B, with those conduits joining as illustrated at the right side of FIG. 5. As with FIG. 1, each receiver 102A, 102B has an air flow limiter 30 associated directly with it. The receiver air as vacuum discharge conduit 110A, 110B for a given receiver leads directly to the associated air flow limiter 30 associated with it. Each air flow limiter 30 is preferably of the type described hereinbelow in greater detail.
[0118] FIG. 6 illustrates yet another embodiment of apparatus for delivery of granular plastic resin material and other associated materials such as regrind or virgin granular plastic resin material, solid colorant, etc., in accordance with the invention, with the apparatus being designated generally 100E. Much like apparatus 100A illustrated in FIG. 1, apparatus 100E conveys granular plastic resin material from a resin material supply 104 to a plurality of receivers 102X. In the apparatus illustrated in FIG. 6, the receivers 102X receiving granular plastic resin material from supply 104 are illustrated to be of a large size.
[0119] Also in FIG. 6, smaller receivers designated 102B receive other material, such as a different type of granular resin material, virgin granular resin material, or regrind resin material or colorant from a supply 116.
[0120] In FIG. 6, a first pneumatic conveyance conduit serving to pneumatically convey granular plastic resin material from supply 104 to receivers 102X is designated 106, while a second pneumatic conveyance conduit for conveying material from supply 116 to receivers 102B is designated 118.
[0121] Referring to FIG. 7, apparatus for delivery of granular plastic resin material in accordance with the invention is designated generally 100F. Apparatus 100F is similar to apparatus 100 illustrated in FIG. 1, but in FIG. 7 receivers 102A receive granular resin plastic material to be processed from a resin material supply 104 while receivers 102B receive other material, which can be other granular plastic resin material, or additives, or solid colorant, from material supply 116. This is similar to the arrangement illustrated in FIG. 6; however, in FIG. 7, all receivers are the same size.
[0122] Since a given process, whether extrusion or molding, may require different amounts of granular plastic resin material from supply 104 and granular plastic resin material, or additive materials, or solid colorants from supply 116, material from supply 104 and material from supply 116 travel through separate conveyance conduits which have been numbered 106A and 118 in FIG. 7. Similarly, receivers in FIG. 7 have been designated 102A and 102B to be consistent with the numbering of the similar, smaller receivers throughout this disclosure. Receivers 102A, 102B are preferably of the type disclosed herein as set forth below and as illustrated in FIG. 9.
[0123] Similarly to the configurations illustrated in FIG. 6 and in FIG. 5, a first resin conveyance line 106 conveys granular plastic resin material from supply 104 to receivers 102A via resin supply lines 107A. A material conveyance line 118 conveys material from supply 116 to receivers 102B. Conveyance lines 106A, 118 are of suitable size according to the volume and speed of material being conveyed from supplies 104 and 116 to receivers 102A and 102B. As is the case with the configurations illustrated in FIGS. 1 through 6, all conveyance of materials in the apparatus illustrated schematically in FIG. 7 is pneumatic conveyance performed by a vacuum pump 112 desirably having a variable speed drive 114 associated therewith, as illustrated schematically in FIG. 7.
[0124] Similarly to FIGS. 1 through 6, each receiver 102A, 102B is depicted as having a discharge conduit at the bottom thereof for discharge of material when the material is needed from the associated receiver 102A or 102B via a process machine. Material is discharged on demand upon a process machine requiring additional material to continue manufacture of molded or extruded plastic parts. Discharge conduits of receivers 102A, 102B are designated 108 for consistency with the discharge conduits associated with receivers illustrated in FIGS. 1 through 6.
[0125] Unlike the apparatus illustrated in FIG. 1 and unlike the apparatus illustrated in FIGS. 5 and 6, not all receivers 102A, 102B illustrated in FIG. 7 have an associated flow limiter. Flow limiters, where present and associated with a receiver 102A, 102B in FIG. 7 are designated 30, consistently with the practice of FIGS. 1 through 6. As with flow limiters 30 illustrated in other configurations of apparatus embodying the invention and as set forth elsewhere in this application, flow limiters 30 are appropriately sized according to the size of the pneumatic conveyance conduit and the design goal flow rate with which a given flow limiter is associated.
[0126] Since some receivers 102A, 102B illustrated in FIG. 7 do not have flow limiters 30 associated therewith, an overall system flow limiter 30-5 is immediately upstream of vacuum pump 112. Since certain of the receivers 102A, 102B lack flow limiters, presence of an overall system flow limiter such as flow limiter 30-5 in FIG. 7 is important for operation of the system without central control. Flow limiter 30-5 illustrated in FIG. 7 limits overall air flow throughout the entire system illustrated in FIG. 7 and thereby provides compensation for certain of the receivers 102A, 102B lacking a flow limiter 30 associated therewith. The position of flow limiter 30-5 is important, being between vacuum pump 112 and the position at which first and second pneumatic conveyance conduits 110A, 110B come together to form a single pneumatic conveyance conduit.
[0127] Further respecting the configuration of the apparatus shown schematically in FIG. 7, similarly to that depicted in the other drawing figures, material supplied to each receiver 102A, 102B from above with a portion of either first material conveyance line 107A or second material conveyance line 107B leading downward into a particular receiver 102A, 102B to deliver material thereinto. Material is conveyed through first and second material conveyance lines due to vacuum drawn by vacuum pump 112.
[0128] Also similarly to the other configurations of the apparatus embodying the invention, in FIG. 7, air drawn under vacuum by vacuum pump 112 leaves each receiver 102A, 102B laterally via a side air as vacuum discharge conduit designated 110A or 110B according to whether the discharge conduit associated with the receiver 102A or 102B. Some but not all of the first and second pneumatic discharge conduits 110A, 110B feed initially to an air flow limiter 30; FIG. 7 clearly illustrates the absence of air flow limiters 30 for some of the receivers 102A, 102B. Each air flow limiter 30 is preferably of the type described hereinbelow in greater detail. Air flow limiter 30-5 is preferably of the type described hereinbelow in greater detail but is preferably of a larger size, due to the larger capacity needed to limit air flow throughout the entire system illustrated in FIG. 7. All receivers 102A, 102B illustrated in FIG. 7 are preferably of the type shown in FIG. 9 and disclosed hereinbelow.
[0129] Referring to FIG. 8, apparatus for delivery of granular plastic resin material in accordance with the invention is designated generally 100G. Apparatus 100G is similar to apparatus 100E illustrated in FIG. 6 with the exception that in FIG. 8, an overall system flow limiter 30-6 has been provided immediately upstream of vacuum pump 112. This is to provide redundant capacity for flow limiting since each of receivers 102B, 102X in FIG. 8 has an air flow limiter 30, 30X associated with it. Other than the presence of system flow limiter 30-6 in FIG. 8, the apparatus of FIG. 8 and the operation thereof is essentially similar to the apparatus illustrated in FIG. 6.
[0130] Referring to FIG. 9 showing a receiver, in schematic form, in accordance with aspects of the invention, the receiver is designated generally 200 and includes a central body portion which in this case is illustrated schematically as being cylindrical. Other body shapes are, of course, possible; receivers in general are well-known in the art and have been constructed in a variety of shapes.
[0131] Receiver 200 preferably includes a material inlet conduit designated 204 and a material outlet conduit designated 206 in FIG. 9. Receiver 200 preferably further includes a pneumatic outlet conduit designated 208 in FIG. 9, a material outlet valve designated 210 in FIG. 9, and a material inlet valve designated 212 in FIG. 9.
[0132] Receiver 200 further preferably includes a receiver material level sensor 202 for sensing the level of material within receiver 200 and providing a suitable signal when the material reaches a low enough level that replenishment of material in receiver 200 is required.
[0133] Receiver 200 further preferably includes a vacuum level sensor 214 positioned in material inlet conduit 204, just upstream of material inlet valve 212. Vacuum level sensor 214 determines when the level of vacuum in the pneumatic conveying system, which is connected to material inlet conduit 204, is excessively low for receiver 200 to draw granular material through material inlet conduit 204 in response to the vacuum drawn by a vacuum pump acting through pneumatic outlet conduit 208.
[0134] Receiver 200 as illustrated in FIG. 9 is the preferred implementation of a receiver for use in the pneumatic conveying systems of the invention. Vacuum level sensor 214 operates to control opening and closing of material inlet valve 212, with vacuum level sensor 214 keeping material inlet valve 212 closed so long as vacuum level in material inlet conduit 204 is too low for receiver 200 to load successfully. The vacuum level in material inlet conduit 204 reflects what is going on elsewhere in the pneumatic conveying system, namely that a vacuum pump is pulling vacuum in order to draw granular plastic resin material or other granular material through the pneumatic conveyance lines of a pneumatic material conveying system. If that vacuum level is too low for successful loading of receiver 200, vacuum level sensor 214 maintains material inlet valve 212 closed. In such case, with receiver 200 essentially being out of the system, receiver 200 cannot contribute to a further drop in vacuum (actually an increase in air pressure) in the system.
[0135] With reference to FIGS. 1 through 9, as numerous ones of receivers operate independently one of another, the pneumatic material conveying system is self-correcting. Specifically, as the vacuum pump continues to pull vacuum, as a receiver such as receiver 200 senses that the level of vacuum is too low for the receiver to successfully load with material, the receiver (through operation of vacuum level sensor 214) keeps material inlet valve 212 closed, thereby preventing a further drop of vacuum level in the system. It is to be understood that a drop in vacuum or vacuum level actually means an increase in air pressure within the system. Similarly, an increase in vacuum or vacuum level actually means a reduction in air pressure within the system due to a vacuum pump pulling more vacuum in the system.
[0136] Referring to the drawings in general and to FIG. 10 in particular, a most preferred air flow limiter 30 is preferably in the general form of a vertically oriented tube, preferably having inlet and outlet ends 54, 56 respectively. The tubular character of air flow limiter 30 is apparent from FIGS. 10 through 15, 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, 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.
[0137] As illustrated in FIG. 12, 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. 16, while the circular interior portion of plate 46 is designated 64 in FIG. 16. 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 portion of legs 62 defining tabs fitting into slots within tube 32 as shown in FIG. 12, may be used.
[0138] As best shown in FIGS. 12, 13, and 14, 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.
[0139] The upper portion of baffle 52, defining fixed internal tubular segment 44, is adapted for sliding telescopic engagement with, and movement therealong by, movable tubular segment 42. Fixed to movable tubular segment 42 is a first strut 48 which preferably extends transversally across the upper portion of movable tubular segment 42 and is preferably secured on either end to movable tubular segment 42, as illustrated in FIG. 17. Preferably extending downwardly from first strut 48 is a second strut 50 which is preferably secured to first strut 48 and preferably also to a sail 34, as illustrated in FIG. 17 and in FIGS. 12, 13, 14, 15 and 16.
[0140] 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. 16 and 17, 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. 16.
[0141] 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 vertically oriented outer tube 32, so long as sail 34 moves vertically up and down within vertically oriented external tube 32. The rectangular shape of extremities 76 with their outwardly facing 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.
[0142] 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. 14, where the first strut portion 48 of movable tubular segment 42 (shown in FIG. 17) rests on the upper circular edge of fixed internal tubular segment 44. This is the condition when no air is flowing through the air flow limiter 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.
[0143] When air is flowing through air flow limiter 30, as illustrated generally in FIG. 13, 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. 12, 13, 14, 16, and 17.
[0144] If air flow upwardly through air flow limiter 30 reaches an extreme value, above an acceptable level of operation of the system of which air flow limiter 30 is a part, the excessive force (resulting from the high volume 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. 15, 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.
[0145] Once air flow stops through vertically oriented outer tube 32, gravity pulling downwardly on sail 34, connected movable internal tubular segment 42, and first and second struts 48, 50, causes these parts, which may be connected together and fabricated as a single integral assembly as shown in FIG. 17, to move downwardly, thereby again permitting air flow upwardly through air flow limiter 30 as depicted generally in FIG. 13. 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.
[0146] 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 the desired air flow is supplied, as the blower or vacuum pump driving or drawing air through flow limiter 30 varies in output of cubic feet per minute of air blown or drawn.
[0147] 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.
[0148] 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.
[0149] 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 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. 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.
[0150] In an alternate approach, 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. In such embodiment, illustrated in FIG. 19, 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.
[0151] In another alternate approach, baffle 52 is one piece, preferably molded plastic, as illustrated in FIG. 18, where baffle 52 is designated 52B to distinguish it from the baffle construction illustrated in FIG. 19 and the baffle construction illustrated in the other drawing figures. In the baffle construction illustrated in FIG. 18, the one piece construction means that there is no need or space for any filler material. The baffle construction illustrated in FIGS. 10 through 16 is preferred.
[0152] The assembly illustrated in FIG. 17 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. 16 and 17, 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, either by machining or by welding, or by otherwise fastening two pieces together. Similarly with the hex nut, which is unnumbered in FIG. 17 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.
[0153] Flow limiter 30 contains no springs. Flow limiter 30 preferably contains no sensors to provide feedback to a control device; no sensors are needed since because flow limiter 30 is self-regulating. 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. Flow limiter 30 uses gravity alone to open the valve defined by the assembly of movable internal tubular segment 42 and movable sail 34 and the connecting structure therebetween.
[0154] In the embodiment of the flow limiter illustrated in FIGS. 10 through 15, 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.
[0155] 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, or by air being supplied under positive pressure at inlet end 54 for passage upwardly through air flow limiter 30.
[0156] In the course of practice of the invention with any of the granular plastic resin material conveying systems illustrated, different line sizes may be used. While 2 inch and 1 inch line sizes respectively are suggested and ordinarily used for the primary resin conveying line and for the auxiliary or additive conveying line respectively, these line sizes may be varied. Also, the flow limiters may or may not each be of the same resistance or size, whether located in the primary resin conveyance line or in the secondary conveyance line, with the flow limiter selected for specific resistance to air flow for the particular line size in which it is located. Moreover, it is within the scope of the invention to use different size flow limiters on the same size primary and/or secondary lines, depending on the particular additive or other material being drawn therethrough (in the case of a secondary line) and depending on the nature and characteristic of the resin being drawn through the primary line.
[0157] Most plastic resin processes require the basic material be delivered at 50 times the rate of the additives, such as color concentrate. Virgin (or natural) pellets may have to be loaded at a rate of 1,000 pounds per hour, requiring a 2.5 or 3 inch line size, while color or another additive may only be required to be delivered at a rate of 20 to 40 pounds per hour. A smaller receiver is desirably used for the color or other additive, namely one that only loads perhaps 5 pounds at a time, while the receiver loading the virgin resin material will be large, loading as much as 50 pounds of resin material for each cycle of the process machine. A 2.5 inch line on a 5 pound receiver should not be used. 1 inch line would be the industry standard; use of a 1.5 inch convey line for the color or other additive would be better.
[0158] The variable frequency drive motor allows the vacuum pump to operate at different speeds, and therefore at different volume rates, and to pull different vacuum levels depending on preset information about each receiver served or making adjustment based on feedback of vacuum sensors associated with the receivers.
[0159] The flow limiter in the main air as vacuum flow line allows an oversized vacuum pump to be used without risk of conveying at excessive velocity. The flow limiters restrict air flow to a preset level. This maintains the desired rate of air flow at the upstream inlet to the system, which is critical for proper conveying for a given size convey line.
[0160] In the claims appended hereto, the term comprising is to be interpreted as meaning including, but not limited to while the phrase consisting of is to be interpreted to mean having only and no more and while the phrase consisting essentially of is to be interpreted to mean the recited elements and those others that do not materially affect the basic and novel characteristic of the claimed invention.
[0161] Although schematic implementations of present invention and at least some of its advantages are described in detail hereinabove, it should be understood that various changes, substitutions and alterations may be made to the apparatus and methods disclosed herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of this patent application is not intended to be limited to the particular implementations of apparatus and methods described in the specification, nor to any methods that may be described or inferentially understood by those skilled in the art to be present as described in this specification.
[0162] As one of skill in the art will readily appreciate from the disclosure of the invention as set forth hereinabove, apparatus, methods, and steps presently existing or later developed, which perform substantially the same function or achieve substantially the same result as the corresponding embodiments described and disclosed hereinabove, may be utilized according to the description of the invention and the claims appended hereto. Accordingly, the appended claims are intended to include within their scope such apparatus, methods, and processes that provide the same result or which are, as a matter of law, embraced by the doctrine of the equivalents respecting the claims of this application.
[0163] As respecting the claims appended hereto, the term comprising means including but not limited to, whereas the term consisting of means having only and no more, and the term consisting essentially of means having only and no more except for minor additions which would be known to one of skill in the art as possibly needed for operation of the invention.
