Plastic article or earthenware shaping or treating: apparatus – Means feeding fluent stock from plural sources to common...
Reexamination Certificate
1997-09-26
2001-07-17
Heitbrink, Tim (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Means feeding fluent stock from plural sources to common...
C264S075000, C366S076100, C366S077000, C425S573000
Reexamination Certificate
active
06261074
ABSTRACT:
The present invention relates to the manufacture of injection-molded products. More particularly, the present invention relates to a method and apparatus for manufacturing multi-colored, injection-molded products.
Various devices are known for the making of multi-colored injection-molded parts. For example, one such device is taught in U.S. Pat. No. 4,183,673 issued to Easley et al. Easley et al. teaches the use of a reciprocating extruding screw with a plurality of injectors for adding colors to the main stream of material. Easley et al. teaches the use of injecting pressures of at least three times (preferably 3600 psi) the maximum internal pressure within the feed screw housing, which is nominally 1000 psi. Another specific teaching is that color dye must be injected where the feed screw is operative. Finally, it would seem both a desired feature and a necessary result of the Easley et al. configuration that the two colors injected would be intermixed, an undesirable result for the products of the present invention.
U.S. Pat. No. 4,315,724 to Toaka et al. discloses a device for producing multi-colored injection-molded products that utilizes a combining cone that receives colorized molten material from three or more identical feed screws. This means added expense since each feed device must be capable of moving molten resin. In addition, to produce a fully marbleized product of the type depicted in
FIG. 14
, timed release from a series of valves is necessary. The use of such valves and timing mechanism increases the cost significantly.
U.S. Pat. No. 5,387,381 Saloom teaches the use of apparatus for producing multi-colored extruded product by adding color pellets into one of two feed streams of material. Saloom's two feeders are, otherwise, identical. The accent color beads soften at a higher temperature than the base material during the extrusion process and produce a color streak in the base material (e.g., simulated wood grain). This duplication of feeders increases the expense of the apparatus and process.
The method and apparatus of the present invention produces a multi-colored, injection-molded product much more simply and inexpensively than previous attempts. An injection nozzle having multiple passageways that each substantially receive equal portions of the molten feed stock is positioned downstream of the primary feed tube. Each of the multiple passageways has a laterally extending opening that has connected thereto a fluid piston that introduces a colorant into the primary feed stream. Each portion of colorant is carried along with the primary feed stream with a minimum of blending so that the end product has a splash of each of the added colors in addition to the color of the primary feed stream. High pressure injection and expensive injection systems, valves, timers, etc., are unnecessary.
The method of making a multi-colored, injection-molded part which is used in the present invention comprises the steps of feeding a primary molten resin stream through a nozzle which has at least two parallel passageways each said passageway receiving substantially equal amounts of said primary molten stream; injecting a mass of a first color pigment into a first of said at least two passageways so that said mass of a first color pigment is conveyed along by said primary molten stream; injecting a mass of a second color pigment which is a different color from said first color pigment into a second of said at least two passageways so that said mass of said second color pigment is carried along by said primary molten stream substantially independently of said first mass of said color pigment; injecting said primary molten stream carrying along said first mass of color pigment and said second mass of a different color pigment into an injection mold in such a manner that there is little or no blending of said two masses of color pigment with said primary molten stream or with each other. In addition, the first and second masses of color pigment are selected from a group consisting of i) liquid colorant, ii) powdered colorant, and iii) a concentrated pelletized colorant.
The method and apparatus of the present invention permit the manufacture of multi-colored, injection-molded parts much more inexpensively and easily than previous devices. Colors can be added to a primary resin stream without duplication of expensive primary feed systems, without the need for controllable valves or complicated timing mechanisms. Further, color can be added with a minimum of blending to produce a more attractive multi-colored product.
Various other features, advantages and characteristics of the present invention will become apparent after a reading of the following specification.
REFERENCES:
patent: 4183673 (1980-01-01), Easley et al.
patent: 4249875 (1981-02-01), Hart et al.
patent: 4315724 (1982-02-01), Taoka et al.
patent: 5387381 (1995-02-01), Saloom
EMSCO Inc.
Heitbrink Tim
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