Method for resin delivery including metering introduction of external air to maintain desired vacuum level.

(54) Title: METHOD FOR SUPPLYING RESIN THAT INCLUDES THE MEASUREMENT OF INTRODUCTION OF EXTERNAL AIR TO MAINTAIN A DESIRED VACUUM LEVEL.

(54) Title: METHOD FOR RESIN DELIVERY INCLUDING METERING INTRODUCTION OF EXTERNAL AIR ΤΟ MAINTAIN DESIRED VACUUM LEVEL.

(57) Summary

Method and apparatus for pneumatically conveying granular plastic resin material from a resin supply to a process machine includes a vacuum pump, a conduit connecting the resin supply to a suction inlet of the vacuum pump, a sensor for detect the level of vacuum drawn by the pump at the suction inlet and a valve to supply air to the duct.

(57) Abstract

Method and apparatus for pneumatically conveying granular plastic resin material out of a resin supply to a process machine includes a vacuum pump, a conduit connecting the resin supply to a suction intake of the vacuum pump, a sensor for sensing vacuum level drawn by the pump at the suction inlet and a valve for supplying air to the conduit.

METHOD FOR SUPPLYING RESIN INCLUDING OUTDOOR AIR INTRODUCTION MEASUREMENT TO MAINTAIN A VACUUM LEVEL

WANTED

Background of the Invention

The plastics industry is very diversified; there are thousands of different products, hundreds of materials, dozens of processes, and they are all very different from each other. The only thing that all these differences have in common is that the source material is some kind of plastic.

The equipment sold to this industry is, therefore, highly diversified in its design. Plastics factories have multiple process machines, sometimes several hundred in one location. Virtually all plastics manufacturing operations require that each process machine, i.e. a molding press or extruder, be automatically supplied with the necessary resin raw material on a continuous basis. This resin can be supplied in large boxes, called Gaylords Corrugated Containers, in fiber drums, in 50 pound (22.68 kg) bags, or more typically it can be supplied by bulk truck or railroad car, with the material of resin that is later transferred in bulk in storage silos. In all cases the resin material must be additionally distributed by

Ref. 280155 the entire plant to each and every one of the process machines. For this reason, a large amount of capital and design expense is devoted to the automatic distribution of the resin raw material throughout the plant.

These resin distribution systems, more commonly known as Charging Systems, must deal with many variables. A set of variables includes the type, shape, size, and consistency of the granular material.

Resin pellets, nominally about 1/8 inch in size, come in a variety of shapes, the most common being round, square, and cylindrical.

Flowing resin powder is also an option, and very fine but free-flowing resin pellets and other granular materials can be transported as well.

Design variables to consider for each client include:

one. Type of resin that is transported.

2. Size and consistency of the resin pellets.

3. Distances in which the resin pellets are to be transported.

Four. Variability of these distances from the shortest to the longest.

5.

Acceptable range for the speed of travel of resin material through the lines.

6. Resin yield rate required for each machine.

7. Total resin yield rate for the entire plant.

8. Overcapacity performance margin so a molding or extrusion process is not interrupted by short-term loading problems.

9. Loss of resin material from, or in the supply, so that only air is drawn, thereby reducing system vacuum levels and reducing overall design performance.

10. Sequence loading, or priority, when multiple receiving stations demand material.

eleven. Detection of problems and alarm conditions.

12. The proper air-to-material ratio for resin transport.

13. Detection of clogged lines due to poor resin flow or resin material overfeed.

14. Dust condition and filter requirements.

fifteen. Reliability.

16. Functional ability.

17. Easy to use.

18. Cost.

19. Type of vacuum pump, that is, positive displacement, regenerative, and others.

twenty. Vacuum pump power and nominal CFM capacity, as well as vacuum levels.

In all of these areas, system designers seek to find better methods and solutions whenever possible.

One of the most important considerations is maintaining the correct speed for the resin material being conveyed. The type of resin material dictates the target conveying speed. To maximize the resin material transfer rate, a high conveying speed is preferred, and the air speed in any case should be sufficient to keep the resin pellets suspended and moving in the air stream. However, the speed must be limited in order not to damage the pellets. The hard, brittle pellets can fracture and break when transported, resulting in excess dust.

Softer pellets can slide along the conduit walls, causing so-called angel hair as a result of the plastic resin melt at the high speed point making contact with the conduit wall; this leaves a thin film on the wall. Very thin angel hair strings build up, thereby effectively reducing the diameter of the conduit and thereby causing problems in the system.

Air speed and resin conveying speed are directly related to pump capacity (nominal CFM) and power, as well as conveying line diameter. There is always a correct speed range for each type of resin material. It is a design challenge to ensure that the resin material is conveyed within the correct speed range.

Transport distances affect system design. Transportation over short distances requires a less powerful vacuum source than over longer distances. Systems are generally sized to produce the best balance for material velocity between the shortest and longest conveying distance. The required conveying rate typically dictates the line size (pipe diameter), and this in turn determines the CFM required to maintain the correct speed in a given diameter conduit. This means that different tube sizes in the same system can be a problem if a vacuum pump is to draw air and resin through several different diameter conveying lines. The pumps have known CFM ratings. Removing air through a small tube will result in a higher velocity flow than removing the same CFM through a larger tube.

Excessive speed can damage the pellets.

The type of vacuum pump to be selected is important. Regenerative blowers deliver a wide CFM range that is dependent on the vacuum level. Positive displacement type pumps provide high levels of vacuum, and have a flatter CFM curve over their vacuum range. Regenerative blowers are quieter and generally cheaper. Positive displacement blowers may require sound enclosures and tend to cost more, but are generally more reliable and more tolerant of airborne dust.

The simplest systems employ a fixed speed motor to drive the vacuum pump, and a single size conveyor line to service all receivers regardless of distance, rate requirement, or material.

The inventive technology offers controls and devices that can maximize performance for the variety of conditions that actually exist in a plant.

VFD (Variable Frequency Drive) motors allow vacuum pumps to be operated at different speeds, and therefore at different CFM rates, with the vacuum pump drawing different levels of vacuum depending on the preset information on each receiver serviced, and / or make adjustments based on real-time feedback from vacuum sensors located at various locations in the system.

The addition of a SCFM limiter (standard cubic feet per minute (m³ standards per minute)) in the air flow line allows large vacuum pumps to be used without risk of excessive speed transport. SCFM limiters restrict airflow to a preset SCFM. This maintains the desired airflow SCFM at the inlet, which is critical for proper conveying for a given size conveying line. This concept is the subject of US patent application 14 / 185,016.

Vacuum levels read at various points indicate to the control processor if the line is open, which means that only air and no material is present and that the air is flowing freely. This is a sign of a loss of material at the source. A high vacuum reading indicates a plugged or nearly plugged line. Normal conditions are present when the material is flowing correctly at the sensed half vacuum levels.

One line size for all receivers ensures that the resin transport rate is more likely to be in the acceptable range. However, most processes require the base resin material to be supplied at 50 times the rate of additives, such as color concentrate. Virgin (or natural) pellets may have to be loaded at a rate of 453.39 kg (1000 pounds) per hour, which requires a line size of 6.35 or 7.62 cm (2.5 or 3 inches), while color is required that is only delivered at a rate of 9.07 to 18.14 kg (20 to 40 pounds) per hour. A smaller receiver is used for color, that is, a receiver that carries maybe 2.27 kg (5 pounds) at a time, while the receiver for virgin resin material will be larger, perhaps that loads 22.68 kg (50 pounds). pounds) in each charge cycle. A 6.3 5 cm (2.5 in) line on a 2.2 7 kg (5 pound) receiver would be too large. A 1.5 inch (3.81 cm) line would be standard, and a 1.5 inch (3.81 cm) resin conveying line would be best. However, there is a risk of excessive speeds. This results in solutions that compromise the design.

By placing a flow limiter at the pump suction inlet, the maximum SCFM airflow can be limited to the design limit of the airflow limiting device; this is described and claimed in US Patent Application 14 / 185,016, noted above.

Summary of the Invention

In one of its aspects, this invention provides an apparatus for pneumatically conveying granular plastic resin material wherein the apparatus includes a vacuum pump having a suction inlet, a resin supply, a conduit connecting the resin supply to the suction inlet, a means of monitoring a vacuum level that is drawn by the vacuum pump at the suction inlet, and a valve for supplying air to the conduit at a location close to the resin supply location to maintain a desired level of suction.

The valve for supplying air to the conduit is preferably located in a position downstream of the first receiver; that is, the receiver furthest from the vacuum pump. Alternatively, the valve for supplying air to the conduit may be located upstream of at least one of the receivers. The vacuum pump can be a constant speed vacuum pump. The use of a variable speed vacuum pump is also within the scope of this invention.

In yet another of its aspects, this invention provides an apparatus for pneumatically conveying plastic resin material, wherein the apparatus includes a vacuum pump having a suction inlet, a conduit connecting a supply of resin to the suction inlet. , means for measuring the velocity of the air stream that is drawn by the vacuum pump at the suction inlet of the vacuum pump and a valve for supplying air to the duct at a location close to the resin supply to maintain a level desired suction. In this aspect of the invention, the valve for supplying air to the conduit is preferably located in a position downstream of the first receiver. Alternatively, the valve for supplying air to the conduit may be located upstream of at least one of the receivers. In this aspect of the invention, the vacuum pump can be a constant speed pump, or a variable speed vacuum pump. In this aspect of the invention, the apparatus may optionally further include one or more digital devices, preferably one or more microprocessors, to regulate the operation of the invention with respect to the delivery of granular plastic resin material to a given receiver or receivers when the given receiver (s) require additional plastic resin material. The connection between the digital device, preferably a microprocessor, and the receivers, and optionally furthermore, the valves that regulate the input and discharge by such receivers, may be wireless, through the Internet, or otherwise through a Ethernet connection.

In yet another of its aspects, this invention provides a method for conveying granular resin material from a supply thereof through a conduit to a receiver for supplying granular resin to a process machine wherein the method includes measurement of the velocity of air moving through the duct at a selected position, comparing the measured air velocity to a pre-selected acceptable range of air velocities, and introducing air into the duct when the measured air velocity is outside the pre-selected acceptable velocity range to maintain a desired level of suction. The method may further include introducing air into the duct in a measured amount as it is introduced. The metering of air in the duct can be done upstream of the first receiver, or at another location.

In still another of its aspects, this invention provides a method for transporting granular resin material from a supply thereof through a conduit to a receiver for supplying granular resin material to a process machine wherein the method includes measuring the vacuum level within a conduit that carries the granular resin material from the supply to a receiver, and / or measuring the vacuum level in a conduit drawing vacuum from the receiver to a vacuum pump, comparing the measured vacuum level to a pre-selected acceptable range of vacuum levels at the measurement position, and introducing air in the duct when the measured vacuum level is outside the preselected acceptable range to maintain desired effective transport within the duct.

The foregoing describes in general terms features of the present invention so that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention may be described hereinafter which may form the subject of some of the claims of the application. It should be appreciated by those skilled in the art that the specific concepts and modalities described herein can easily be used as a basis for modifying or designing other structures or methods to carry out the objectives and results achieved by this invention. It should also be noted by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims.

Brief Description of Figures

Figure 1 is a schematic representation of a resin delivery system embodying aspects of the invention.

Figure 2 is a schematic representation of an alternative resin delivery system embodying aspects of the invention.

With reference to the Figures where like reference numerals are identical to those used in this description to designate the same or similar elements throughout the various views, illustrative embodiments of the invention are shown and described. The figures are not to scale, and in some cases, the Figures have been partly exaggerated and / or simplified for illustrative purposes only. One of skill in the art will appreciate the many possible applications and variations of the invention that are possible based on the following illustrative embodiments of this invention.

Detailed description of the invention

In this application, unless otherwise apparent from the context it should be understood by the person skilled in the art that use of the term vacuum means air at slightly below atmospheric pressure. Vacuum (i.e. air at slightly below atmospheric pressure) provides a suction effect that is used to extract granular plastic resin material from a supply and to transport that granular plastic resin material through various conduits to receivers where the granular resin material can be temporarily stored before being molded or extruded. Therefore, when reading this application it is useful for the reader to mentally equate the term empty with the term suction.

Referring to Figures 1 and 2, there is illustrated apparatus for conveying granular plastic resin material from the supply to receivers which hold and dispense the resin material as needed by a process machine. The apparatus, which is generally designated 88 in Figure 1, preferably includes a vacuum pump generally designated 92 and is shown schematically in Figure 1.

Still referring to Figures 1 and 2, the vacuum extraction conduit 100 is connected to a plurality of receivers 16, each of which receives, holds, and dispenses, as needed, granular plastic resin material to a machine. process, such as a granulated mixer, or an extruder, or a molding press as it is preferably located below a receiver 16. Arrows A in the drawing figures are provided to schematically indicate the downward discharge of the granular resin material from a receiver 16. The downward discharge of the granular resin material is regulated by a controller, desirably a controller such as the microprocessor. 200. The discharge of granular plastic resin from a receiver 16 to an associated process machine in the downward direction indicated by arrow A occurs when the process machine and associated controls require resin material to be supplied . The process machines are not illustrated to improve the clarity of the Figures. The receptors 16 are most desirably of the type described in US Patent 8,753,432, incorporated herein by reference as noted above.

Also illustrated in Figures 1 and 2 is a hopper 18 for the storage of granular plastic resin material therein and a resin transport conduit 98, which serves to extract the resin from the hopper 18 and to supply the resin to through the resin transport conduit 98 to the respective receivers 16 while vacuum being drawn by the vacuum pump 92, with vacuum propagating through the vacuum extraction conduit 100, the various receivers 16, and resin transport conduit 98 back to hopper 18. In the Figures, resin transport conduit 98 has been shown to include a number of resin transport conduit valves designated 99 in the Figures. Valves 99 are desirably controlled by microprocessor 200 and are optional, but desirable as in connection with the apparatus and method of the invention. The resin transport conduit valves 99 are preferably of the open-closed type. The resin transport conduit valves 99 are not used, during normal operation of the invention, to measure the granular resin pneumatically transported in an associated receiver 16 through a segment of the resin transport conduit 98. The resin transport conduit valves 99 are provided primarily for shutdown purposes in the event that shutdown of the system is necessary due to a malfunction of the apparatus.

The vacuum extraction conduit 100 is optionally equipped with a vacuum extraction conduit valve 101. The valve 101 is preferably of the open-closed type and is mainly used for shutdown purposes in the event of a system malfunction. The vacuum extraction line valve 101 is optional with respect to the operation of any of the embodiments of the apparatus illustrated in Figures 1 and 2.

In the embodiment of the apparatus illustrated as 8 8A in Figure 2, a main resin transport conduit valve 109 is illustrated. The main resin transport conduit valve 109 is desirably of the open-closed type and is provided primarily for safety purposes. and protection of equipment in case of a malfunction of a system or device. The main resin transport line valve 109 is preferably controlled by the microprocessor 200. The main resin transport line valve 109 is optional with respect to the apparatus 88A illustrated in Figure 2.

During the operation of the resin transport systems shown schematically in Figures 1 and 2, during the actuation of the vacuum pump 92, a vacuum is drawn to the suction head of the vacuum pump 93. This vacuum, as it propagates back into hopper 18, it serves to draw resin out of hopper 18 and into respective receivers 16.

Referring specifically to Figure 1, an air supply conduit 106 connects to the transport conduit resin 98 in the position shown in Figure 1. A valve 102 admits air through the inlet air supply 104 to the conduit. supply air 106 and therefore in the resin transport conduit 98. Valve 102 is preferably a purge valve that can be adjusted, preferably automatically using a solenoid or other valve adjusting means, most desirably by microprocessor 200, to measure a desired variable amount of air in resin transport conduit 98 In Figure 1 the air supply conduit 106, air supply inlet 104, and valve 102 are all upstream of all receivers 16. In other words, all air metered in resin transport conduit 98 to maintain a desired vacuum level within resin transport conduit 98 will pass through at least one of the receivers 16. In Figure 1 the connections of cables between microprocessor 200 and receivers 16 and vacuum pump 92 have not been illustrated for clarity of the Figures. As noted above, the connection between microprocessor 200 and the other elements in the system, including valve 102 and potentially other optional valves, can be wireless, most preferably via the Internet.

In Figure 1 the point 3 0 located on the suction head of the vacuum pump 93, can be a vacuum indicator or a vacuum sensor to measure and monitor the level (in the case of a vacuum indicator) or presence (in the case of a vacuum sensor) vacuum is drawn by vacuum pump 92 to the suction head inlet of vacuum pump 93. In such a case, the vacuum gauge is preferably connected electronically or wirelessly, preferably via the Internet, to a control and feedback system including the microprocessor 200 to regulate the valve 102 and the amount of air supplied to the transport conduit. of resin 98 through air supply conduit 106, thereby maintaining a desired level of vacuum at the suction head of vacuum pump 93. Alternatively, point 30 in Figure 1 may be an anemometer or similar device to measure the velocity of the air stream being drawn by vacuum pump 92 at the suction head of vacuum pump 93. Similar to the vacuum gauge / vacuum sensor approach discussed immediately above, the anemometer approach preferably uses a digital anemometer connected with feedback loops or wirelessly, preferably via the Internet, to valve 102 in order to regulating the amount of air supplied to the resin transport duct 98 through the air supply duct 106, thereby to maintain a desired vacuum level at the suction head of the vacuum pump 93.

Referring to Figure 2, the apparatus is similar to that illustrated in Figure 1, except for the air supply inlet position 104, the air metering valve 102, and the air supply conduit 106. In Figure 2, air supply conduit 106 supplies air to resin transport conduit 98 at a position upstream of at least one of receivers 16. Other than the position of the air supply conduit 106, the air supply inlet 104, and the valve 102, as shown in Figure 2, the apparatus illustrated in Figure 2 is preferably identical to that shown in Figure 1 and previously described.

In the illustrated apparatus, the vacuum pump 92 may be a constant speed vacuum pump as schematically illustrated in Figure 1 and Figure 2, or the vacuum pump 92 may have a variable speed drive or speed component. variable of it.

Although the embodiments of the present invention and at least some of its advantages have been described in detail above, it should be understood that various changes, substitutions, and alterations may be made to the apparatus and methods described herein without departing from the spirit and scope of the invention. invention as defined by the appended claims. Furthermore, the scope of this patent application is not intended to be limited to the particular embodiments of the apparatus and methods described in the specification, nor to any of the manufacturing methods, compositions of matter, and the like, which may be described or inferentially described. understood by those of skill in the art to be present in the invention as described in this specification.

As a person skilled in the art will readily appreciate from the description of the invention as set forth hereinbefore, currently existing or later developed processes, manufacturers, apparatus, methods and steps, which perform substantially the same function or achieve substantially the same the same result as the corresponding modalities described earlier in this document, they can be used in accordance with the description of the invention and the claims appended thereto.

Therefore, the appended claims are intended to include within their scope such apparatus, methods and processes which provide the same result or which are, as a matter of law, encompassed by the doctrine of equivalents respecting the claims of this application.

In the appended claims, the term comprising is to be understood to mean including but not limited to, while 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 that would be known to a person skilled in the art as possibly necessary for the operation of the invention.

It is noted that in relation to this date, the best method known to the applicant for putting the aforementioned invention into practice is the one that is clear from the present description of the invention.