2. Description of Related Art In a conventional process that uses virgin plastic material in granular form, a gravity hopper feeds the plastic material into one or more unvented extruders, through a filter, and through at least one blown film die that forms plastic film. It is a common to recycle or reuse plastic since for most purposes the recycled plastic is entirely satisfactory. Recycling also saves energy and reduces the cost of the article being manufactured and eliminates the need to dispose of used or scrap plastic.

In a conventional process that uses scrap plastic material, the material is first ground and fed through a hopper and then fed directly through usually two extruders.

The result is sent through a filter and then directly through at least one die and granule former. The plastic granules are

usually sold to a broker or directly to a blown film producer who makes plastic film essentially the same way that blown film is made from virgin plastic material.

U. S. Patent No. 5,407,624 issued to Engh, III et al.

("Engh") discloses a method and apparatus for processing raw plastics, wherein raw plastics are fed through a shredder to form pelletized plastic pieces for use in a normal plastic extrusion machine. The system processes raw plastic without requiring the removal of foreign matter prior to the shredding of the raw plastic into chunks. A plurality of magnet plates and metal detectors allow a second hopper to receive the plastic chunks in a substantially pure form. An extruder allow the chunks to pass through a normal heating and melting process to transform the chunks into a liquefied state. A screen changer removes any remaining impurities from the plastic. However, Engh incorporates an extra step in the process by utilizing a pelletizer to form small pellets of plastic which are ultimately used in a plastic material extrusion process.

The present invention overcomes the problems of the prior art by providing a streamlined process of converting scrap plastic to blown plastic film without pelletizing the plastic after extrusion and utilizing only one extruder and one blown film die thereby reducing the cost, the time, and the maintenance involved in standard systems.

BRIEF SUMMARY OF THE INVENTION An apparatus for producing blown plastic film from scrap plastic comprising a grinder or shredder which receives the scrap plastic and feeds it to a crammer density increaser which removes air between the voids in the compressed plastic therefore making the plastic mass more dense. A vented extruder operatively connected to the crammer density increaser pressurizes the plastic resulting in a molten and pressurized mass. The mass is then extruded to a filter, a melt pump, a mixer, and a film die to provide a blown film of 8 mils or less thick.

A method for manufacturing plastic film from scrap plastic material including the steps of feeding particles of scrap plastic material into a crammer to increase to mass density of the scrap plastic particles, feeding the dense plastic particles to the extruder and melting and pressurizing the particles of scrap plastic material received from the crammer, pressurizing, stabilizing and controlling the pressure of the molten scrap plastic received from the extruder with a melt pump, and using a blown film die to create blown plastic film from the molten plastic mixture received from the melt pump.

The present invention requires only one extruder whereas prior manufacturing methods require two or more extruders.

This results in a 30% savings in equipment cost. Extruders

are generally the most expensive pieces of equipment in blown film making.

The equipment comprising this invention also uses at least 20% less energy to operate since there is only one extruder to run. Extruders are the largest energy users of all of the equipment used in blown film making and their energy consumption exceeds that of the next largest consumer of energy by at least seventy percent (70%). The reason there isn't even a larger energy savings with this invention is that the invention uses a crammer and a melt pump. These two pieces of equipment may use up to thirty percent (30%) of the energy used by one extruder. It should be noted that all comparisons are for making the same quality and quantity of end product from scrap plastic.

This invention also provides a stronger product than current systems. The plastic film end product resulting from this invention has higher tensile strength and is more elastic since the plastic scrap is put through one less extruder and die. Therefore, the more a plastic material is passed through an extruder and die the less tensile strength and elasticity the end product will have.

There is significantly less maintenance involved in this invention than in the prior art systems. This is true since there is one less extruder and die to maintain with this invention and an extruder is the piece of equipment in a blown film line that requires the most maintenance from a man-hour

and cost standpoint. The process or method of this invention is also simpler and easier to operate than previous processes since it has only a one-step process that basically takes plastic scrap and produces blown film, without the need for an extra step if pelletizing the scrap plastic. This is much easier and less costly than the old processes that use this extra step.

The invention also provides a product that costs less than present products, therefore leading to lower raw material costs. For instance the raw material costs 50% less than virgin material and 40% less than granules made from scrap plastic, which are used like virgin granules.

Accordingly it is an object of the present invention to provide an apparatus and method for manufacturing blown plastic film from scrap plastic that is less costly then current apparatuses and manufacturing methods.

It is yet another object of the present invention to provide an apparatus and method for manufacturing blown plastic film from scrap plastic in which the method is streamlined and utilizes fewer steps.

It is another object of the present invention to provide an apparatus and method for manufacturing blown plastic film from scrap plastic where the equipment requires less maintenance than in prior art equipment.

It is also an object of the present invention to provide an apparatus and method for manufacturing blown plastic film

from scrap plastic where the blown plastic film product has a higher tensile strength than the prior art product.

It is also an object of the present invention to provide an apparatus and method for manufacturing blown plastic film product from scrap plastic that uses less energy in its manufacture than the prior art.

It is also an object of the present invention to provide an apparatus and method for manufacturing blown plastic film from scrap plastic that uses only one extruder whereas two extruders are generally required in the prior art.

It is another object of the present invention to provide an apparatus and method for manufacturing blown plastic film that can use readily available components.

In accordance with these and other objects which will become apparent hereinafter, the instant invention will now be described with particular reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS FIG. 1 is a block diagram of the present invention.

FIG. 2 is a flow diagram showing the method of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring first to FIG. 1, the apparatus and method for manufacturing blown plastic film from scrap plastic is

illustrated and is designated generally by the number 10 and comprises a grinder or shredder 12 that receives plastic scrap material designated as PS. The output from the grinder or shredder 12 is fed to temporary storage and/or to a crammer density increaser 14 via a conveyor 13. The crammer density increaser 13 is connected to a vented extruder 16 which extrudes the plastic, producing plastic film, which passes through a filter or screen 18. Screen 18 is connected to a melt pump 20 that is connected to a mixer 22 that is in turn connected to a blown film die 24 which extrudes the plastic film designated by the letters PF.

All of the components of the manufacturing apparatus of the invention are connected directly or indirectly to vented extruder 16. The individual components including grinder or shredder 12, crammer density increaser 14, filter or screen 18, melt pump 20, mixer 22, and blown die 24 are easily removable from the vented extruder 15. Consequently, any individual component can be removed for replacement, testing or repair without the need to disassemble the other numerous components of the invention. This greatly reduces the time that apparatus 10 will be non-operational.

Since the components of apparatus 10 are easily removable from each other, this means that the invention may be easily broken down to reduce its size and weight. This makes apparatus 10 easier to prepare for travel or storage.

All of the individual components of apparatus 10,

including grinder or shredder 12, crammer or density increaser 14, vented extruder 16, filter or screen 18, melt pump 20, mixer 22, and film die 24 are in themselves in use. However, they are used differently in apparatus 10 and it is the combination and sequence of the various mechanical machinery components in the invention that makes apparatus 10 unique for producing blown film from plastic scrap.

With respect to the past use for the components of the invention, various mechanical components that make up apparatus 10 have had the previous uses set forth as follows.

The crammer or density increaser 14 has been used in a solid material making process rather than in making blown film that uses scrap plastic as in the present invention. Vented extruder 15 has been used to make blown film, and filter or screen 18 is sometimes used in making blown plastic film, but not in the manner of the present invention. Pump 20 also has been used in making plastic sheet and film, but not blown film.

Present blown plastic film makers have produced film only as thin as 0.9 mils (0.0009 inch). Thus far, this invention has produced blown plastic film from scrap plastic as thin as 0.75 mils (0.00075 inch) in thickness. The invention's ability to make blown film thinner than other systems extruding scrap plastic is in part due to the use of only one extruder 15 and one die 24.

Apparatus 10 is used in the following manner and the

method of the invention is also carried out in the following manner. First, particles of scrap plastic material, PS, are fed directly into grinder or shredder 12 where they are ground or shredded to reduce the size of the particles of scrap plastic material PS. From the shredder or grinder 12, the chopped or shredded reduced size scrap plastic particles (the particles may be stored before entering the crammer) are fed by conveyor 13 into crammer density increaser 14 where the density of the reduced size scrap plastic particles is increased and fed by crammer density increaser 14 to vented extruder 16 where the scrap plastic particles become molten and pressurized. The resulting molten and pressurized scrap plastic is then extruded into a filter or screen 18 where most solids in the molten and pressurized plastic are removed.

After the molten scrap plastic is fed through filter or screen 18, it is fed to melt pump 20 which stabilizes the pressure and feeds the stabilized molten plastic through mixer 22 which makes the stabilized molten plastic more homogeneous. The resulting molten plastic from mixer 22 is then fed to blown film die 24 where the plastic film PF is produced.

It should be noted that the step of increasing the density of the mass of the reduced size scrap plastic particles results in plastic particles from grinder 12 have varying size voids between them that are filled with air.

Crammer 14 receives this mass with the voids and reduces the size and number of these voids by compressing out the air and

hence making this plastic mass more dense. The mass of plastic particles, now containing a reduced amount of entrapped air, is fed into vented extruder 16.

To summarize, and as shown in Figure 2, the basic process comprises the following steps: providing grinder 12, conveyor 13, crammer 14, extruder 16, filter 18, melt pump 20, mixer 22, blown film die 24, and particles of scrap plastic material; using grinder 12 to reduce the size of the particles of scrap plastic material and feeding the reduced size particles of scrap plastic material from grinder 12 into the crammer; increasing the density of the mass of the reduced size scrap plastic particles with crammer 14 melting and pressurizing the dense reduced size particles of scrap plastic material received from crammer 14 with extruder 15; removing solid material from the molten scrap plastic material received from the extruder with filter 18 ; pressurizing, stabilizing and controlling pressure of the molten scrap plastic received from the filter utilizing melt pump 20 ; feeding the pressure stabilized and pressure controlled molten scrap plastic to mixer 22 with melt pump 20 ; preventing separation and creating a homogeneous molten scrap plastic mixture using mixer 22 ; and creating plastic film from the molten homogeneous plastic mixture from the mixer using blown film die 24.

In an alternate embodiment, no grinder, mixer or filter is used in the process described above.

Unless stated otherwise the scrap plastic is caused to

move from one component to another by pressure from a previous component. Conveyor 13, grinder 12, filter or screen 18 and mixer 22 do not exert pushing pressure.

In view of the foregoing, and Figure 1, it is readily apparent that vented extruder 16 is operationally or operatively connected to crammer density increaser 14 and that melt pump 20 is operatively connected to vented extruder 16, via filter 18. Blown film die 24 is operatively connected to melt pump 20 via mixer 22. Also, it is apparent that grinder or shredder 12 is operatively connected to crammer density increaser 14.

The various types of equipment and sources for this equipment that have been found to be the best so far in making blown plastic film from scrap plastic in accordance with this invention are set forth below: Cramer or density Increaser-Available from Battenfeld Gloucester Engineering Co., Gloucester, MA.

Vented Extruder-4 M Inch 30 to 1 available from Merritt Extruder/Davis Electric, 15 Marne Street, Hamden, Connecticut 06514 Filter or Screen-Available from L. C. I., Fluid Systems Division, P. O. Box 16348, Charlotte, North Carolina 28297 Melt Pump-Available from Moag Pump systems of America Inc., Matthews, North Carolina Grinder or shredder Available from Cumberland Engineer- ing, 100 Roddy Ave., South Attledor, Massachusetts 02703

Mixer-A Kenics available from Battenfeld Gloucester Engineering Co. of Gloucester, Massachusetts All equipment is available from many sources known in the art in addition to those set forth above.

Although the invention has been described in considerable detail with reference to certain preferred embodiments, it will be understood that variations or modifications may be made within the spirit and scope of the invention as defined in the appended claims.

The instant invention has been shown and described herein in what is considered to be the most practical and preferred embodiment. It is recognized, however, that departures may be made therefrom within the scope of the invention and that obvious modifications will occur to a person skilled in the art.