Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
1999-11-29
2002-03-26
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S076000, C521S158000, C521S163000, C264S309000, C264S337000, C524S789000
Reexamination Certificate
active
06362302
ABSTRACT:
BACKGROUND
The use of artificial three dimensional shapes in artistic, architectural and landscaping applications has increased over the past decade. Museum displays, theme and entertainment park sets, motion picture and television sets, demonstration models, and consumer product prototypes and other similar three dimensional shapes are all examples of the use of the use of artificial three dimensional shapes in which the use of a genuine item is inappropriate, costly or both.
In the past, artificial three dimensional shapes have been made by a variety of processes utilizing a wide range of materials. However there remains an unmet need for a method of forming such three dimensional shapes under “field” conditions and at reasonable cost.
Polyester fiberglass has been employed in the past for producing three dimensional shapes but presents a problem in that of requiring a gel coat or barrier coat to be first sprayed in the mold. The polyester resin conventionally employed for structural strength requires fiberglass reinforcing due to the inherent brittleness of the polyester resin. Also low production is encountered due to the curing time of the resin thus limiting production to one or two parts per mold per day.
Plaster and concrete have also been employed but are of disadvantage in that they are often too heavy for producing large three dimensional shapes. Further, intricate shapes with high fidelity to the original surface is not always possible due to shrinkage and other factors. Durability, weathering and resistance to cracking and chipping represent further problems. Production is also generally limited to one or two parts per mold per day due to the drying time needed to solidify the cast shape.
Three dimensional shapes may be made in solid form of one type of plastic or another but have been limited in variety of design because of the high cost of molding as well as requiring time for production of both the mold and the molded product. For artistic, architectural or landscaping purposes different sizes and types of three dimensional shapes may be desirable and high mold costs and operation expenses may be limiting factors in the production shapes having slightly different size or appearance to simulate a natural setting.
A further problem is that in some cases, the three dimensional shape may be too large or heavy to move or install if the shape is not made on location (i.e. in the field). For example an artificial tree or rock wall often must be made in manageable sections and then assembled on site resulting in seams and other undesirable effects.
Larger structures, such as tree stumps, rocks, or rock walls also present the challenge in that they often lack the durability, strength and hardness to withstand the rigors of the environmental wear and tear that might be occasioned. Such shapes, if used in an outdoor setting, must be able to withstand a load, weathering over a period of time and substantial physical abuse by the public that may be encountered in the landscape or other type of setting in which the shapes are employed.
Conventional spraying of a polyurethane coating is carried out by employing expensive and difficult to control heated plural component equipment for delivering an isocyanate side and a polyol side to a spray gun where the polymerization reaction is initiated in a mixing chamber inside the gun. Because an exact ratio of the isocyanate and polyol components must be metered to the spray gun, difficulty or constant adjustment of the mixture may be needed as the two differing components change in characteristics (i.e. viscosity, temperature, lot composition) over time in order to achieve a consistent final product. Conventional plural equipment, such as that manufactured by Gusmer, Glascraft, Graco or Binks, is typical of the prior art method of spray dispensing polyurethane. The spray parameters of temperature and pressure employed in the process entail the use of a primary heater, a hose heater and a spraying pressure ranging from 500 PSI to 3000 PSI. Due to the potentially adverse impact of changing conditions of temperature, humidity, moisture content of the substrate or mold onto which the polyurethane is being sprayed and other environmental conditions, the use of this equipment requires skill and considerable experience. In addition a substantial capital expenditure is needed to obtain the necessary metering pumps and heater equipment. For this reason, spray coating of polyurethane remains a specialized skill that must be conducted under carefully controlled conditions in order to achieve a consistent high quality polyurethane coating.
An example of the above noted method which is representative of the state of the art for the production of artificial rocks is U.S. Pat. No. 4,940,558. As is specifically disclosed therein, a two component system is utilized to spray a polyurethane coating into a flexible mold. However, as noted above, the application of the techniques disclosed therein is not practicable for a significant number of persons due to the high capital cost and specialized skill and equipment necessary to achieve a consistent product. In addition, because the conditions of spraying must be carefully controlled, on-site coating of a preformed three dimensional shape, such as a wooden form or a expanded polystyrene foam core or a wall or other surface is not possible. In most cases, the presence of atmospheric moisture, a lack of temperature control, or the inability to control the metering pumps accurately under differing conditions results in a blistered or otherwise inferior coating.
Thus there exists an unmet need for a simple to use polyurethane coating method that can be used by the average person under conditions encountered in everyday life.
SUMMARY OF THE INVENTION
The present invention is generally directed to a method of producing three dimensional polyurethane shapes by spray molding a quasi-gel like polymer precursor composition that is first mixed and then sprayed by a hopper type spray gun. The spray coating of quasi-gel polymer precursor composition subsequently cures to form a molded polyurethane polymer shape. Such artificial three dimensional shapes may include rocks, rock walls or faces, tree stumps or limbs, animals, or art objects for use in creating displays, sets or other life-like settings. Further the three dimensional shape may be a prototype of a consumer product or other specialty product or part, or the three dimensional shape may be utilized in architectural settings in which a certain visual appearance is desired. An illustrative method of the present invention includes: creating a mold and supporting cradle having a mold cavity conforming to the exterior of shape desired, the mold having a substantial degree of flexibility; spraying a quasi-gel polymer precursor composition into the mold cavity, the quasi-gel polymer precursor composition comprising a mixture of an isocyanate portion and a curative portion and being mixed prior to introduction into a spray gun, carrying out the spraying to build up the molded three dimensional shape to a desired thickness and stripping the cradle and mold from the molded polyurethane three dimensional shape after the curing of the quasi-gel polymer precursor.
These and other features of the present invention are more fully set forth in the following description of illustrative embodiments of the invention.
DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
The production of a three dimensional shape, such as a simulated rock, tree limb or stump, animals such as fish, birds, reptiles, or mammals or the like, with high fidelity to the original three dimensional shape can be achieved by the use of a high density polyurethane elastomer in a flexible rubber mold. The rubber may be natural rubber or synthetic rubber. A three dimensional shape is produced in molded form, not limited in size. A flexible mold may be prepared by applying numerous coats of liquid uncured rubber forming materials, such as latex rubber, upon the exterior of the three dimensional model. The addition of a fab
Gorr Rachel
Howrey Simon Arnold & White
Nation Floyd
White Carter J.
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