Method and apparatus for manufacturing plastic structures

A system and a method for manufacturing plastic structures using ultra-violet curable plastic materials is provided. Specifically, the present invention applies a resin layer to a conveyor belt. The resin layer is then warmed and various types of reinforcing elements are added. The conveyor belt with the resin layer is then passed through a forming apparatus where a predetermined shape is imparted to the layer. The predetermined shape become permanent as the resin layer is exposed to ultra-violet radiation which cures and hardens the resin layer. The completed structure is then extracted from the process.

FIELD OF THE INVENTION 
The present invention relates generally to the fabrication of plastic 
structures. More specifically, the present invention relates to methods 
for forming curable plastic material into predetermined structures 
including boards and sheets. The present invention is particularly, but 
not exclusively, useful as an in-line, continuous, method for 
manufacturing ultra-violet cured plastic structures with reinforcing 
elements. 
BACKGROUND 
Historically, a large number of differing materials have been employed as 
building materials. For instance, the use of both wood and steel in the 
construction of commercial and residential buildings is well known. In 
general, selection between particular building materials, such as steel or 
wood, has been guided by a number of criteria. The criteria include cost 
and structural suitability and continuing efforts to balance these 
criteria have resulted in development of numerous alternative materials. 
Recently, various types of plastic and composites have been developed as 
alternative building materials. These materials have been found to be both 
strong and durable. Additionally, many molding and forming techniques for 
plastics are well known. These molding and forming techniques allow 
plastic materials to be easily shaped into numerous structures including 
flat sheets and boards. Plastic materials may also be used in combination 
with numerous other materials to form composites, allowing the cost and 
other characteristics of the resulting products to be easily tailored to 
meet varying demands. 
A prime consideration in the fabrication of plastic building materials is 
cost. In fact, market success of alternative building materials, such as 
plastics, is dependent on the cost effectiveness of these materials in 
relation to the more traditional materials that they are intended to 
replace. Cost effectiveness, is, in turn, dependent on the availability of 
low-cost fabrication methodologies and the use of low-cost raw materials. 
In the past, fabrication of plastic structures, including those intended as 
building materials, has generally involved the use of a step-by-step 
process involving a number of distinct subsystems. In these processes, the 
output from each individual subsystem becomes the input for the next 
subsystem. As a result, each subsystem is repeatedly started and stopped 
and may experience idle periods as it waits for input from the preceding 
subsystem. 
The non-continuous process typically employed to produce plastic structures 
includes a number of inherent disadvantages. One such disadvantage is high 
labor costs. Specifically, many of the individual subsystems may require 
supervision or operator intervention. Each subsystem that requires 
intervention or assistance generally increases the cost and unreliability 
of the fabrication process. 
Another disadvantage associated with traditional methodologies is 
inefficiency caused by wasted material or energy. In greater detail, it 
may be appreciated that many of the subsystems employed in the production 
of plastic structures may have a start-up time during which the subsystem 
is brought up to its operating parameters. For example, a curing oven may 
have to reach a specific temperature before it can be effectively used. 
Subsystems of this type may waste energy or raw materials during the 
start-up period or have other undesirable side-effects such as increased 
air emissions. In general, inefficiencies of these types may result in 
higher operating costs and an associated increase in the cost of the final 
product. 
Still another disadvantage typically associated with traditional 
manufacturing techniques for plastic structures is lack of output 
uniformity. Generally, it is highly advantageous if an industrial process 
may be conditioned to produce consistent results both within and between 
output batches. Consistency of this type allows the manufacturing process 
to be characterized and tuned to produce uniformly acceptable products. 
Unfortunately, manufacturing methodologies which operate in a step-by-step 
mode are often associated with inconsistent or varying output qualities. 
These inconsistencies are caused by the limited ability of the 
step-by-step process to continuously adapt to changing external conditions 
such as heat and humidity. Lack of consistency within batches and between 
batches may result in rejection of certain products and higher costs for 
the remaining products. 
A second factor that contributes to the cost effectiveness of plastic 
structures used for building materials is the cost of input materials. It 
may be appreciated that in the case of plastic structures, the cost of the 
underlying plastic material may be quite high, especially for large 
structures that require high volumes of plastic. Cost of input materials 
has been especially important where traditional manufacturing techniques 
have been employed and the entire output product is fabricated from solid 
plastic. 
One approach that has been successfully employed in an attempt to reduce 
the amount of raw input material used in the fabrication of plastic 
structures is the use of honeycomb or other hollow internal structure. 
This approach has yielded structures that are both strong and conserving 
of input materials. In practice, however, these structures are both 
complex and expensive to produce and require expensive adaptation and 
retooling for each different structure produced. 
In light of the above, it is an object of the present invention to provide 
a system and a method for manufacturing plastic structures which operates 
as a continuous and on-going process. It is another object of the present 
invention to provide a system and a method for manufacturing plastic 
structures which features high operating efficiency both in terms of 
energy and materials consumed. Yet another object of the present invention 
is to provide a system and a method for manufacturing plastic structures 
which is adaptable to the production of numerous input material types and 
output shapes. Another object of the present invention is to provide a 
system and a method for manufacturing plastic structures which provides a 
high degree of output uniformity. Still another object of the present 
invention is to provide a system and a method for producing plastic 
structures that is not labor intensive. Still another object of the 
present invention is to provide a system and a method for manufacturing 
plastic structures which is relatively simple to use, is relatively easy 
to implement and is comparatively cost effective. 
SUMMARY OF THE PREFERRED EMBODIMENT 
The present invention provides a system and a method for manufacturing 
plastic structures. Specifically, the present invention starts with a 
liquid plastic such as an acrylic resin. Numerous types of reinforcing 
elements may be added to the resin and the resulting material may then be 
formed into various shaped structures including flat and corrugated 
sheets. Once formed, the resin material is cured by exposure to 
ultra-violet radiation and the completed structure is removed from the 
process. Alternatively, different resin types may be used and differing 
curing methodologies may be employed. 
The apparatus for manufacturing plastic structures in accordance with the 
present invention includes a first conveyor belt which is preferably 
manufactured from a Teflon coated nylon fabric. The first conveyor belt is 
mounted on rollers to establish a substantially flat, continually moving, 
working surface upon which the plastic material may be manipulated. For 
purposes of description, it may be assumed that the first conveyor belt 
has an upstream, input end, and a downstream, output end. Additionally, it 
may be assumed that the motion of the belt is such that objects placed at 
the input end are transported in a downstream direction over the length of 
the working surface to the output end. 
In a more descriptive statement of the present invention, it may be noted 
that a resin dispenser is located over the input end of the first conveyor 
belt. The resin dispenser allows a continuous supply of the ultra-violet 
curable resin to be applied to the first conveyor belt. A doctor blade is 
also mounted over the first conveyor belt and positioned slightly 
downstream from the resin supply. The doctor blade spreads the resin 
applied by the dispenser into a film or layer on the working surface of 
the first conveyor belt. 
The combination of the resin supply and doctor blade form a resin 
application subsystem and may be replaced with a sprayer or other 
applicator which spreads a uniform film of resin on the working surface. 
Regardless of the particular application technology employed, a partial 
curing oven is positioned immediately downstream from the resin 
application subsystem and used to partially cure the newly applied resin. 
Immediately downstream from the partial curing oven, the working surface 
passes over a heating table which allows the working surface, and the 
resin on the working surface, to be heated for greater ease in 
manipulation. Next in line, a dispensing system for the reinforcing 
elements is located over the heating table and adds a continuous supply of 
reinforcing elements to the resin on the working surface. In general, the 
type and quantity of reinforcing elements may be varied widely to suit the 
desired qualities of the structures to be produced. 
The combination of the dispensing system for the reinforcing elements and 
the heating table forms a reinforcing subsystem and it may be appreciated 
that the combination of the resin application subsystem and the 
reinforcing subsystem produces a two layer resin film on the working 
surface. In detail, it may be appreciated that downstream from the 
reinforcing subsystem, the working surface carries a layer of resin and a 
layer of reinforcing elements positioned over and partially mixed into the 
resin layer. For the purposes of the present invention, additional resin 
application subsystems and reinforcing subsystems may be added to produce 
final products with additional layers of resin or reinforcing elements. 
The ability to add additional layers by adding additional subsystems 
allows the present invention to be easily tailored to produce varying 
products. 
A second conveyor belt, preferably fabricated from the same Teflon coated 
nylon material used in the first conveyor belt, is positioned over the 
working surface downstream from the reinforcing subsystem. The working 
surface and the second conveyor belts are positioned and oriented to 
establish a moving zone where the working surface and the second conveyor 
belt surround and sandwich the resin layer and reinforcing elements. It 
may be appreciated that the two outer surfaces provided by the working 
surface and the second conveyor belt allow the resin and reinforcing 
elements to be easily manipulated and shaped. 
Once the working surface and the second conveyor belt have been joined, the 
working surface is passed through a forming apparatus which manipulates 
the working surface and the second conveyor belt to impart a predetermined 
shape to the resin layer which is sandwiched therebetween. The actual 
shape imparted may be varied by employing alternate forming apparatuses 
but generally includes shapes such as corrugation. The predetermined shape 
created by the forming apparatus is made permanent by passing the working 
surface and resin layer through an ultra-violet curing oven. The curing 
oven includes an ultra-violet radiation source which works in conjunction 
with the ultra-violet sensitizer in the resin layer to permanently harden 
the resin layer into the predetermined shape. Once curing is complete, the 
now-finished plastic structure is extracted as the second conveyor belt 
separates from the working surface at the output end of the working 
surface. 
In certain cases, it may be desirable to form a second resin layer on the 
second conveyor belt before the second conveyor belt joins with the 
working surface. Application of the second resin layer allows the second 
conveyor belt to add an additional resin layer to the final product and 
can easily be accomplished by positioning a resin application subsystem 
over the second conveyor belt to apply the second resin layer. 
The process of the present invention is initiated as a layer of plastic 
material is applied to the working surface by the resin application 
subsystem. Although many differing types of plastic may be used, it has 
been found that a mixture of acrylic resin and an ultra-violet sensitizer 
is particularly practical. A layer of reinforcing elements are then added 
by the reinforcing subsystem and partially mixed with the resin layer. 
Additional resin application subsystems and reinforcing subsystems may be 
added to create additional layers of resin and reinforcing elements. Next, 
the resin layer and reinforcing elements are covered by the second 
conveyor belt and passed through the forming apparatus where shaping such 
as corrugation may be added. After shaping, the curing oven exposes the 
layer to ultra-violet radiation which hardens the layer into a completed 
structure which may be extracted as the second conveyor belt separates 
from the working surface downstream from the curing oven.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
The present invention provides an in-line system and method for 
manufacturing plastic structures. The apparatus used to implement the 
present invention is shown in FIG. 1 and designated 10. In general, the 
apparatus 10 may be used to produce a wide variety of plastic structures 
such as the sheet shown in FIG. 2 and designated 12. Alternatively, the 
corrugated panel 14 shown in FIG. 3 may be produced as well as the 
laminated board 16 shown in FIG. 4. Importantly, and as shown in FIGS. 2, 
3, and 4, the sheet 12, corrugated panel 14 and board 16 are all formed to 
include reinforcing elements 18 as part of their basic structures. 
Additionally, as shown in FIG. 4, the apparatus 10 may be used to form 
laminated structures which include layers of resin 20a, 20b and 
alternating layers 22a, 22b which include reinforcing elements 18. 
The details of the manufacturing apparatus 10 may be, perhaps, best 
appreciated by reference to FIG. 1 where the manufacturing apparatus 10 is 
shown to include a first conveyor 24 mounted on a series of rollers 26a, 
26b, 26c, 26d. Preferably, the first conveyor 24 is fabricated from a 
flexible belt of Teflon coated nylon cloth. Functionally, the first 
conveyor 24 provides a flat, continuously moving working surface 28 
between the rollers 26a and 26d. The movement of the first conveyor is 
shown diagrammatically in FIG. 5 where the working surface 28 may be seen 
to travel in the direction indicated by the downstream arrow 30. For the 
purposes of illustration, the direction of travel indicated by the 
downstream arrow 30 will be referred to as the downstream direction. 
Returning to FIG. 1, it may be seen that a resin dispenser 32 is located 
over the working surface 28 to apply a continuous supply of resin 34 to 
the working surface 28 just downstream from roller 26a. The rate at which 
the supply of resin 34 is added to the working surface 28 is controlled by 
a metering means 36 included in the resin dispenser 32. A doctor blade 38 
positioned downstream from the resin dispenser 32 spreads the supply of 
resin 34 into a resin layer 40 on the working surface 28. Together, the 
resin dispenser 32, metering means 36 and doctor blade 38 comprise the 
resin application subsystem which functions to create the resin layer 40. 
To achieve the goals of the present invention, any number of differing 
resin types may be applied by the resin application subsystem to form the 
resin layer 40. For example, the use of a mixture of an acrylic or 
polyester or combination acrylic/polyester based resin of a type similar 
or the same as manufactured by Alpha or BASF, and an ultra-violet 
sensitizer of a type similar or the same as manufactured by Ciba-Geigy has 
been found to be highly beneficial. It should be appreciated, however, 
that these materials are intended to be exemplary and other materials 
types are equally practical. 
Downstream from the resin application subsystem, the working surface 28 and 
the resin layer 40 pass over a heating table 42 where the resin layer 40 
is warmed and increased in pliability. As shown in FIG. 1, a dispenser 44 
for dispensing reinforcing elements 18 is located over the working surface 
28 and positioned slightly downstream from the heating table 42. Like the 
resin dispenser 32, the dispenser 44 for reinforcing elements includes a 
metering means 46 allowing the dispenser 44 to apply a continuous layer of 
reinforcing elements 18 to the working surface 28, over the resin layer 
40. Together, the heating table 42, dispenser 44, and metering means 46 
form a reinforcing subsystem which functions to create the layer 48 of 
reinforcing elements 18. 
To achieve the goals of the present invention any number of differing types 
of reinforcing elements may be used to form the layer of reinforcing 
elements 48. For example, in cases where a high-strength structure is 
being produced, the layer of reinforcing elements 48 may include glass, 
Kevlar or other fibers. Alternatively, in cases where a low cost structure 
is required and strength is not of paramount importance, wood chips or 
even processed refuse products maybe used to form the layer of reinforcing 
elements 48. 
Downstream from the reinforcing subsystem, the working surface 28, carrying 
the resin layer 40 and the layer 48 of reinforcing elements 18, passes 
through a partial curing oven 50 where the resin layer 40 is partially 
hardened by exposure to ultraviolet radiation. Preferably, the partial 
curing oven 50 hardens the resin layer 40 to a point where it may be 
formed and shaped without causing the resin layer 40 to flow. 
As the working surface 28 leaves the partial curing oven 50, it is covered 
by a second conveyor 52. Like the first conveyor 24, the second conveyor 
52 is mounted on a series of rollers 54a, 54b, 54c. Preferably, the second 
conveyor 52 is fabricated from the same Teflon coated nylon material used 
to form the first conveyor 24. 
Functionally, the second conveyor 52 is intended to provide a cover for the 
working surface 28 and to effectively sandwich the resin layer 40 and the 
layer of reinforcing elements 48 between the working surface 28 and the 
second conveyor 52. Therefore, and as shown in FIG. 1 and FIG. 5, the 
second conveyor 52 is positioned and oriented to face the working surface 
28. In fact, the second conveyor 52 is positioned to contact and ride on 
top of the working surface 28 so that movement of the working surface 28 
causes an equivalent movement of the second conveyor 52. For clarity, the 
direction of movement for the second conveyor 52 is in FIG. 5 shown by the 
arrow designated 56. 
After the working surface 28 is covered by the second conveyor 52, the 
working surface 28, resin layer 40 and layer of reinforcing elements 48 
are passed through a forming apparatus 58. The forming apparatus 58 may be 
used to apply any number of predetermined textures or shapes to the resin 
layer 40 to produce varying embodiments such as the corrugated panel 14 
shown in FIG. 3. To impart shapes and textures to the resin layer 40 and 
layer of reinforcing elements 48, the forming apparatus 58 applies 
pressure to the outer surfaces of the working surface 28 and the second 
conveyor 52 thereby manipulating the resin layer 40 and layer of 
reinforcing elements 48 sandwiched therebetween. 
Downstream from the forming apparatus 58, the working surface passes 
through a curing oven 60 where the resin layer 40 and layer of reinforcing 
elements 48 are exposed to ultraviolet radiation. The ultraviolet 
radiation interacts with the ultraviolet sensitizer in the resin layer 40 
causing the resin layer 40 to harden into the predetermined shape imparted 
by the forming apparatus 58. For the purposes of the present invention, 
the intensity of ultraviolet radiation used in the curing oven 60 is 
adjustable to account for varying input materials, structure shapes and 
environmental factors such as temperature and humidity. 
In addition to providing a means by which the resin layer 40 and layer of 
reinforcing elements 48 may be covered for the processing by the forming 
apparatus 58, the second conveyor 52 may itself be used to apply 
additional layers of resin or reinforcing elements to the working surface 
28. Application of an additional resin layer of this type is shown in FIG. 
1 where an additional resin dispenser 62 is shown located over the second 
conveyor 52. Like the resin application subsystem used to apply the resin 
layer 40 to the working surface 28, the additional resin dispenser 62 uses 
a metering means 64 to accurately deliver an additional resin supply 66 to 
the second conveyor 52. An additional doctor blade 68 spreads the 
additional resin supply 66 over the second conveyor 52 to form an 
additional resin layer 70. It may be appreciated that the additional resin 
layer 70 will form a covering layer for the layer of reinforcing elements 
48 as the second conveyor 52 covers the working surface 28. 
As the working surface 28 leaves the curing oven 60, the second conveyor 52 
separates from the working surface 28 exposing the resin layer 40 and 
allowing the resin layer 40 and layer of reinforcing elements 48, which 
have become the output structure 72, to be extracted from the 
manufacturing apparatus 10. 
It may be appreciated that the apparatus 10 is intended to be a modular 
system which allows the various subsystems to be combined in varying 
embodiments to produce varying output structures. For example, an 
alternative embodiment of the apparatus 10, shown in FIG. 6, includes the 
same resin dispenser 32, metering means 36 and doctor blade 38 shown in 
FIG. 1. As previously discussed, these elements form a resin application 
subsystem and function together to apply a resin layer 40 to the working 
surface 28. 
The apparatus 10 shown in FIG. 6 also includes the heating table 42, 
dispenser for reinforcing elements 44, and metering means 46 which form 
the reinforcing subsystem used in the apparatus 10 shown in FIG. 1. As a 
result, the resin layer 40 applied on the working surface 28 of the 
apparatus 10 shown in FIG. 6, is covered by a layer of reinforcing 
elements 48. 
Unlike the apparatus 10 of FIG. 1, however, the apparatus 10 of FIG. 6 
includes a second resin dispenser 74 positioned downstream from the 
partial curing oven 50 to apply a second resin supply 76 to the working 
surface 28. The second resin dispenser 74 is equipped with a metering 
means 78 to control the rate at which the second resin supply 76 is 
applied to the working surface 28. Once applied, the second resin supply 
76 is spread over the working surface 28 by a second doctor blade 80. 
Together, the second resin dispenser 74, metering means 78 and second 
doctor blade 80 form a second resin application subsystem which functions 
to apply a second resin layer 82 over the layer of reinforcing elements 
48. It may be appreciated, then, that the second resin application 
subsystem is, in effect, a replication of the first resin application. 
As shown in FIG. 6, the second resin application subsystem is followed by a 
second reinforcing subsystem which includes a second heating table 84, 
second dispenser for reinforcing elements 86 and a metering means 88. 
Functionally, the elements of the second reinforcing subsystem cooperate 
to apply a second layer of reinforcing elements 90 to the working surface 
28. Downstream from the second reinforcing subsystem, a second partial 
curing oven 92 partially cures the newly applied second resin layer 82 and 
second layer of reinforcing elements 90. 
It may be appreciated that the addition of the second resin application 
subsystem and second reinforcing subsystem to the apparatus 10 shown in 
FIG. 6 results in the application of additional layers of resin and 
reinforcing elements to produce a laminated structure such as the board 16 
shown in FIG. 4. For the purposes of the present invention, the number of 
additional resin application subsystems and reinforcing subsystems may be 
varied to suit the requirements of the intended output structure. 
Specifically, as many as eight to ten resin application subsystems and 
eight to ten reinforcing subsystems have been found to be practical. 
It should also be appreciated that the elements that comprise the resin 
application subsystems and reinforcing subsystems may be varied to suit 
the requirements of differing types of resin and differing types of 
reinforcing elements. For example, in FIG. 6 an alternative embodiment for 
the resin application subsystem consisting of a resin sprayer 94 is shown 
positioned downstream from the second partial curing oven 92. 
Functionally, the resin sprayer 94 performs the same basic task as the 
combination of resin dispenser 32 and doctor blade 38 previously 
discussed. The resin sprayer, however, is generally more suitable for 
certain resin types. 
OPERATION 
The manufacturing apparatus 10 of the present invention is intended to be 
used as part of a continuous, in-line, production process. The process 
starts as shown in FIG. 1, as the resin application subsystem applies a 
resin layer 40 to the working surface 28. After the resin layer 40 is 
applied to the working surface 28, a layer of reinforcing elements 22 is 
applied over the resin layer 40 by the reinforcing subsystem. The newly 
applied resin layer 40 and layer of reinforcing elements 48 are then 
partially cured by exposure to ultraviolet radiation. 
For the purposes of the present invention, the application of resin layer 
40 and layer of reinforcing elements 48 is intended to be a modular 
process and additional layers of resin or reinforcing elements may be 
added by providing additional resin application subsystems or reinforcing 
subsystems. In this manner, multi-layer laminated structures of varying 
complexity may be produced. 
In cases where shaping or texturing is required, the resin layer 40 and the 
layer of reinforcing elements 48 are covered by the second conveyor 52. 
The resin layer 40 and the layer of reinforcing elements 48 are then 
passed through the forming apparatus 58 where a predetermined shaping may 
be applied to produce a predetermined shape, such as the corrugated panel 
14 shown in FIG. 3. Generally, the type of predetermined shape added to 
the resin layer 40 and the layer of reinforcing elements 48 by the forming 
apparatus 58 is widely variable and entirely dependent on the intended use 
of the output structure 72. 
The resin layer 40 and the layer of reinforcing elements 48 are then 
hardened by exposure to ultraviolet radiation in the curing oven 60 which 
completes the output structure 72. The process of the present invention is 
completed as the output structure 72 is removed from the manufacturing 
apparatus 10. 
While the particular system and method for manufacturing plastic structures 
as herein shown and disclosed in detail is fully capable of obtaining the 
objects and providing the advantages herein before stated, it is to be 
understood that it is merely illustrative of the presently preferred 
embodiments of the invention and that no limitations are intended to the 
details of the construction or design herein shown other than as defined 
in the appended claims.