Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/17—Component parts, details or accessories; Auxiliary operations
  • B29C45/26—Moulds
  • B29C45/27—Sprue channels ; Runner channels or runner nozzles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/17—Component parts, details or accessories; Auxiliary operations
  • B29C45/26—Moulds
  • B29C45/27—Sprue channels ; Runner channels or runner nozzles
  • B29C2045/2766—Heat insulation between nozzle and mould

Definitions

• Apparatus for molding of plastics comprises dies mounted on die blocks which blocks in turn are mounted on the platens of a press. Molten or plasticized material is forced by pressure out of a nozzle through a sprue bushing which sprue bushing serves to transmit or conduct the plasticized material from the nozzle to the runners which feed the plasticized material to the various cavities.
• thermoplastics as outlined above, in that due to the temperature difference between the nozzle and the sprue bushing, it is necessary to heat the material at the nozzle to an excessively high temperature in order to be sure the plasticized material or compound will feed into the die.
• the high temperature required as indicated above can cause break down of the plasticized material, while without adequate heating, cold spots develop on passage from the nozzle through the sprue bushing into the runners, then to the cavities.
• injection molding of thermoset compounds it is important that the sprue bushing be insulated from the heated die to prevent premature curing or "setting" of the plasticized material or compound prior to filling of the molding cavities.
• an insulated sprue bushing is useful in thermoplastic and thermoset molding.
• Patent #3,698,849 to Czerski for "Injection Molding Assembly”. This patent covers a molding assembly which is suitable for use in the manufactu of cellular plastics particles, wherein the injection nozzle is insulated from the sprue bush by a thermally insulating element between the outlet end of the nozzle and the sprue bush.
• Patent #3,945,535 to Leiste et al . for "Injection Molding Apparatus”. This patent covers apparatus for injecting plasticized material containing a foaming agent into a mold from an extruder, and a heating element to maintain the nozzle needle at high temperature.
• Patent #4,069,003 to Cecchi for "Injection Molding Apparatus", which describes a sprue bushing provided with a plurality of grooves in its bore.
• Patent #4,273,525 to Reitan for "Injection Mold Bushing” which describes a sprue bushing having heating and cooling means.
• Patent #4,345,892 to Schulte et al . for "Injection Molding Die With Heavy-Duty Sprue Bush”. This patent covers a heated sprue bush along with air gaps, and injection molding gates are perpendicular to the longitudinal axis of the sprue bush.
• Patent #4,173,448 for Actuating Mechanism For Gate Valve of Injection Nozzle.
• This patent covers a "nozzle body" which is entirely different from a sprue bushing described in this Shaw invention.
• Patent 4,268,241 for Heated Injection Nozzle. This patent is for a heated nozzle and a sheath of resinous material around the nozzle — nozz
• O PI is highly heat conductive.
• This patent is not concerned with a "sprue «, bushing" as described in this Shaw invention. • * ⁇ It is an object of this invention to describe a sprue bushing insulated from the die so that the plasticized material maintains its 5 temperature for more efficient molding operation.
• Another object of this invention is to disclose means to insulate the sprue bushing from the die in molding of plastic materials.
• Another object of this invention is to reduce the temperature difference which exists between the nozzle and sprue bushing in injection 10 molding.
• This invention is to disclose means for insulating the sprue bushing from the die, so that the plasticized or melted material will maintain more closely its temperature coming out of the nozzle and through the sprue bushing.
• Another object of this invention is to prevent excessive temperature 15 variance of the plasticized compound or material on being fed into and through the sprue bushing.
• Another object of this invention is to disclose in a plastic molding apparatus comprising a die mounted in a press, the improvement consisting of an insulated sprue bushing mounted in said die, said sprue bushing 20 insulated from the die block at the shoulder and stem section of said sprue bushing.
• Another object of this invention is to prevent nozzle "freeze off" by means of an insulated sprue bushing.
• Another object of this invention is to disclose a sprue bushing with 25 an insulating collar molded thereon.
• Another object of this invention is to disclose an insulating collar for a sprue bushing mounting, said insulating collar to be removable from said sprue bushing.
• Another object of this invention is to reduce the temperature 30 difference between the nozzle and sprue bushing in plastic molding, by ⁇ means of an insulated sprue bushing, between said sprue bushing and the die.
• Fig. 2 End View of sprue bushing and insulating section wherein: 1. - Stem of sprue bushing 2. - Passage way through sprue bushing
• FIG. 3 Side View of insulating section ring wherein: 7. - Insulating section
• Fig. 1 shows the plastic insulating material molded onto the sprue bushing which had been machined "out” so that the plastic insulating material is molded onto the sprue bushing in the machined out section.
• Fig. 4 shows the plastic insulating material as a separate ring and shoulder section to be inserted into the machined out die block. The sprue bushing is then inserted in the die block holding the insulating section between said die block and the sprue bushing section.
• This invention discloses means to insulate a sprue bushing from the die in plastic molding.
• the sprue bushing is insulated at its shoulder and stem section from the die so that as plastic compound is forced from the press nozzle to and through the sprue bushing that the temperature of the compound is not adversely affected to cause problems in molding.
• the die temperature is below the congealing or freezing temperature of the plastic material.
• the sprue bushing is at or near the die temperature, thus when melted plastic compound is injected from the nozzle into and through the sprue bushing that the temperature of the melted plastic is reduced causing flow problems from the sprue bushing into the runners through the die gates and into the cavities of the dies.
• thermoset molding the die is at a high temperature for cure of the compound such as phenolic melamine or alkyd compound.
• thermoset molding The temperature of the die in thermoset molding is in the vicinity of 162.8 - 183°C, thus in conventional molding the sprue bushing is at or near this temperature.
• thermoplastic compounds can b reduced, and other advantages obtained as indicated in the fiv examples listed as follows: Case 1. Adaptor of 6/6 40% GF Nylon a. reduced nozzle temperature from 329.4 to 271.1° C b. eliminate small bent cores from cold flow resin. c. improved flatness & surface appearance. d. eliminated gas trapping. e. eliminated sprue sticking. f. eliminated nozzle freeze-off. Case 2. Fuse Holder of 30% Glass filled PBT a. reduced nozzle temperature from 260 to 232.2 C. b. eliminated nozzle freeze-off. c eliminated sprue sticking. d. eliminated voids in thick section. e.
• one method is to machine out a section of the sprue bushing and form the insulating section by injec molding phenolic compound to fill the machined out segment of the shoulder and section of the stem.
• the molded segment wil be of the same diameter as the sprue bushing stem.
• the thick of the molded section is of the order of 2.54 to 5.08 mm.
• Another method of insulating the shoulder and section of stem of the sprue bushing is to insert a molded cylindrical section called insulation section ring to be mounted between the shoulder and stem section of the sprue bushing and the die as shown in Fig. 4.
• This insulated section ring as shown in Fig. 3 can be molded of pheno'lic compound and have a wall thickness of 2.54 to 5.08 mm.
• Suitable materials for the sprue bushing insulating segment or ring are phenolic compounds or polyi ide thermoset compounds.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)

Applications Claiming Priority (2)

Publications (2)

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Family Applications (1)

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Citations (2)

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• 1983
  • 1983-04-29 JP JP1984600007U patent/JPS60500001U/ja active Pending
  • 1983-04-29 EP EP19830902007 patent/EP0130986A4/en not_active Ceased
  • 1983-04-29 WO PCT/US1983/000672 patent/WO1984002106A1/en not_active Application Discontinuation

Patent Citations (2)

Non-Patent Citations (1)

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