MULTI-CHANNEL GRAVIMETRIC BATCH BLENDER

Abstract

A weighing apparatus for the preparation of a mixture of granular components that comprise batches of material required by a plurality of processing machines in a plant for the manufacture of plastic products is described. The apparatus comprises a Multi-Channel Gravimetric Batch Blender (MCGBB) configured to weigh predetermined weights of the raw materials and to combine the weighed portions of raw materials into batches according to a predetermined recipe for each processing machine and a computer that controls the operation of all components of the MCGBB. The MCGBB comprises several weighing units arranged in a way that allows material weighed in each of the weighing units to fall through individual chutes via a common funnel into a manifold that distributes the weighed batches to several processing machines via a system of delivery pipes.

Claims

1. A weighing apparatus for the preparation of a mixture of granular components that comprise batches of material required by a plurality of processing machines in a plant for the manufacture of plastic products, the apparatus comprising: a. a Multi-Channel Gravimetric Batch Blender (MCGBB) configured to weigh predetermined weights of the raw materials and to combine the weighed portions of raw materials into batches according to a predetermined recipe for each processing machine, said MCGBB comprising several weighing units arranged in a way that allows material weighed in each of the weighing units to fall through individual chutes via a common funnel into a manifold that distributes the weighed batches to several processing machines via a system of delivery pipes; and b. a computer that controls the operation of all components of the MCGBB.

2. The apparatus of claim 1, wherein each weighing unit comprises: a. a material hopper; b. a hopper loader feeder configured to draw one type of raw material from a raw material silo into the material hopper; c. a weighing station comprising a load cell; d. an opening with a feeding system at the bottom of the material hopper, the feeding system configured to be opened and closed or activated on command of the apparatus's computer to allow a controlled amount of material to fall by gravity from the material hopper into the weighing station; and e. an opening with a flap at the bottom of the weighing station, the flap configured to be opened and closed on command of the apparatus's computer to allow the weighed amount of material to fall by gravity from the weighing station via the funnel into the hopper

3. The apparatus of claim 1, wherein the weighing stations work in parallel, each weighing a required amount of material for one component of the batches of material to be delivered to the processing machines according to instructions received from the computer.

4. The apparatus of claim 2 wherein, when the computer determines that the correct weight of each of the materials required for a batch to be sent to a specific processing machine has been weighed by one or more of the weighing stations, then the computer opens the flaps at the bottoms of the one or more weighing stations allowing the weighed components of the batch to fall by gravity into the funnel.

5. The apparatus of claim 4 wherein, before the weighed amounts of material required for a batch to be supplied to a specific processing machine are allowed to fall into the funnel, the computer activates a motor that rotates a distributer pipe in the manifold, thereby connecting the bottom of the funnel to the delivery pipe that leads to the specific processing machine.

6. The apparatus of claim 5 wherein the funnel and distributer pipe in the manifold are automatically cleaned by high pressure air after the preparation of each batch.

7. The apparatus of claim 1, wherein the MCGBB comprises twelve weighing units and supplies batches of material to one hundred injection machines.

8. A weighing and mixing system for the preparation of a mixture of granular components required by a plurality of processing machines in a plant for the manufacture of a plastic product, the system comprising: a. a plurality of raw material silos; b. at least one Multi-Channel Gravimetric Batch Blender (MCGBB) according to claim 1; c. one mixer unit located at each of the processing machines; d. a system of delivery pipes configured to deliver predetermined batches of material from the MCGBB to the mixers at the processing machines.

9. The system of claim 8, wherein each silo is connected by piping to at least one weighing unit and each weighing unit is connected to only one silo.

10. The system of claim 8, wherein one computer controls the operation of more than one MCGBB.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0046] FIG. 1 schematically shows a typical prior art RCGB;

[0047] FIG. 2A and FIG. 2B are photographs showing a portion of the gravimetric blenders in an actual RCGB at a large manufacturing plant for producing plastic products;

[0048] FIG. 3 is a schematic perspective view of a system previously described by the inventor;

[0049] FIG. 4 schematically shows a perspective view of an embodiment of the Multi-Channel Gravimetric Batch Blender (MCGBB) of the invention;

[0050] FIG. 5 schematically shows a cross-sectional view of one of the weighing stations of the MCGBB and the manifold of the MCGBB; and

[0051] FIG. 6 schematically shows a typical arrangement of a plastic products manufacturing plant that incorporates a MCGBB of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0052] The present invention is designed to overcome all of the shortcomings of the Remote Central Gravimetric Blender (RCGB) that is presently used in the plastics industry as is described herein above. The invention accomplishes that goal by providing a Multi-Channel Gravimetric Batch Blender (MCGBB), a single one of which can replace a RCGB comprised of several gravimetric blenders, with the attendant savings in cost, space requirement, and complexity of the piping system. In addition the MCGBB of the invention is comprised of a single weighing unit for each of the components of the batches of material required by the processing machines in the plant allowing the components of each batch to be weighed in parallel, thereby saving time. Other advantages of the MCGBB over the prior art will be described herein below.

[0053] The MCGBB is part of a system that comprises at least one MCGBB that weighs material for batches to be supplied to a plurality of processing machines and a mixer that is located at each of the processing machines to enable maximum homogeneity.

[0054] An embodiment of the MCGBB of the invention will be described with reference to FIG. 4, which schematically shows a perspective view of the MCGBB, and FIG. 5, which schematically shows a cross-sectional view of one of the weighing stations of the MCGBB and the manifold of the MCGBB.

[0055] The MCGBB 50 is a modular one that can be comprised of several weighing units 52 arranged in a way that allows the material weighed in each of the units to fall through individual chutes 54 via a common funnel 56 into a manifold 58 that distributes the weighed batches to the processing machines. The weighing units 52 each contain a single type of resin, masterbatch, or additive in granular form. A computer (not shown in the figures) controls the operation of each of the separate weighing units 52 in order to supply the exact weight of each of the individual components to the funnel 56.

[0056] Each weighing unit 52 comprises a hopper loader feeder 60 that draws one type of material, i.e. resin, masterbatch, or additive, from a raw material silo or container into material hopper 62. Hopper 62 has an opening with a feeding system 64 e.g. a flap, an auger, a screw, a vibratory mechanism, or paddles, at its bottom, which is opened and closed or activated when required by an element (not shown in the figure) that is controlled by a system computer (not shown in the figure) to allow a controlled amount of material to fall by gravity into weighing station 66 where it is weighed on a load cell 68.

[0057] The weighing stations 52 work in parallel, each weighing a required amount of material according to instructions received from the computer. When the computer determines that the correct weight of material introduced into weighing station 66 and weighed by the load cell 68 is equal to the required weight, then the system computer closes the feeding system 64 at the bottom of hopper 62. The computer activates motor 72, which rotates distributer pipe 74 in manifold 58, to complete a path from the bottom of funnel 56 to the delivery pipe 76 that leads to a specific processing machine in the plant. When the computer determines that the correct weights of each of the components of a batch to be sent to the specific processing machine have been weighed, the computer opens a flap 70 at the bottom of each of the relevant weighing stations 52 allowing the weighed amount of the components of the batch to flow by gravity through chutes 54 into funnel 56 through distribution pipe 74 and delivery pipe 76 through which a vacuum feeder draws the unmixed batch of material to the designated processing machine.

[0058] FIG. 6 schematically shows a typical arrangement of a plastic products manufacturing plant that incorporates a MCGBB of the invention. The plant comprises a plurality of silos 78 that contain the raw materials needed by the processing machines. Each of silos 78 is connected through a pipe to at least one of the weighing units of MCGBB 50. The weighed batches of material are distributed by manifold 58 through delivery pipes 76 to each of the respective processing machines 80. According to the present invention, a mixer unit 82 is located inside the free fall hopper that is connected to the inlet of each of the processing machines 80. With this arrangement, the weighed batches of material are delivered by a vacuum system directly to the mixing machine 82, where the batch is thoroughly mixed before entering the processing machine.

[0059] By replacing the remote mixers 20, 36 of the prior art with a plurality of local mixers at each of the processing machines and replacing the prior art automatic manifold 22 with the manifold 58, the present invention provides a direct route for the material for each batch directly to the processing machine, thereby minimizing the locations where material from previous batches could contaminate succeeding batches. In order to further prevent contamination, in the system of the invention the section of the funnel 56 and distributor pipe 74 of the manifold 58 that is common to all batches is automatically cleaned with high-pressure air after each time a batch is sucked through them by the vacuum system on the processing machines. In addition the problem of separation of the components of the weighed batches is solved by only mixing the batch at the processing machine. Finally, moving the mixer from the prior art RCGB 10 and Weighing and Mixing System 30 typically reduces the height of the MCGBB 50 by up to 1 meter.

[0060] The advantages of the system of the invention will be demonstrated by comparison with a typical prior art system. As an example we consider a manufacturing plant that makes use of ten different raw materials that are stored in silos. The blend of each batch is comprised of a combination of up to four different types of raw material. The plant has 100 injection machines and 60 remote gravimetric blenders that transport the batches to the injection machines via automatic manifolds.

[0061] In the prior art system, in order for each gravimetric blender to be able to prepare the blends required it must comprise four bins. In order to supply four types of material from the silos to each of the gravimetric blenders, 240 hopper loaders and pipes are needed.

[0062] In the system of the invention the raw material has to come from the silos to the hoppers of, for example, only twelve weighing units of the MCGBB. The savings in space and expense of 228 bins/hoppers, hopper loaders, and corresponding piping is very great.

[0063] The MCGBB produces batches of material for each processing machine according to its exact individual requirements. The control system of the system of the invention is programmed such that none of the processing machines ever has to wait for its exact batch. Because of the serial way in which the raw material is weighed in a RCGB, there sometimes arises delays in supplying batches to the processing machines. The prior art solution to this problem is to use buffer containers beside or underneath the gravimetric blenders that need space and contribute to separation of each batch. Furthermore in order to enable at least part of the gravimetric blenders of the RCGB to supply two or more processing machines the solution is to compromise with batches of “average”, and sometimes more expensive, composition. Because each weighing unit of the MCGBB can supply raw material to more than one processing machine there is no need to make such compromises as are sometimes necessary with a RCGB.

[0064] With a RCGB as described above, if it becomes necessary to change the type of raw material supplied to the bins in the gravimetric blenders, that gravimetric blender must be shut down and thoroughly emptied of the previous material and thoroughly cleaned. An advantage of the MCGBB is that, because each of the raw materials has at least one weighing unit dedicated to it, there is no necessity of changing material in a hopper, which leads to a large savings in time and expense and also prevents any possibility of contamination.

[0065] Since one MCGBB can serve in most of the cases at least 24 processing machines, therefore, due to its dimensions, five MCGBBs that require together 20-30 square meters of floor space instead of 200-300 square meters by a RCGB comprised of 60 gravimetric blenders.

[0066] Although embodiments of the invention have been described by way of illustration, it will be understood that the invention may be carried out with many variations, modifications, and adaptations, without exceeding the scope of the claims.