Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Patent
1990-02-13
1991-02-19
Thrulow, Jeffery
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
1563031, 156293, 264249, 264268, 264274, 264275, 264310, 425185, 425186, 425125, 425429, 425435, 425517, 249 97, B29C 3314, B29C 4104, B29C 4130
Patent
active
049941321
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION AND PRIOR ART
The present invention relates to a method for attaching an insert at least partly composed of thermoplastic material in an opening into a hollow body having at least a portion thereof formed of a thermoplastic material for attachment of the insert. More specifically, the invention is related to a method and apparatus for mounting an insert having a thermoplastic mounting portion in the opening into a molded thermoplastic hollow body.
In accordance with prior art techniques for producing hollow bodies, such as drums or tanks, the body is usually completely fabricated and the insert is then attached using screws and, optionally, a sealing ring. Alternatively, the insert may be welded or glued to the outside of the body over an opening provided in the wall of the body for this purpose.
The foregoing methods are expensive due to the manual labor and expertise required to attach the insert to the hollow body. Also, an insert attached with such methods does not provide a sufficiently tight seal between the body and the insert, especially if the body is to be subjected to internal pressure during its use.
In rotational molding or casting techniques, the complex mold movements, high molding temperatures and long molding cycles are believed sufficiently severe to have heretofore substantially precluded automatic insert assembly techniques. For example, polyethylene drums having about a 2' diameter and a 4' height require about a 15 minute molding cycle at 500.degree. F.
In contrast with the foregoing relatively severe conditions of rotational molding, blow molding of similarly sized drums is done in a stationary mold apparatus using about a 5 minute cycle and a parison temperature of about 300.degree. F. Thus, it has been possible in blow molding techniques to mount an insert for the hollow body opening on the blow pin and, after blowing, to retract the blow pin to cause the insert to contact and fuse with the body wall.
SUMMARY OF THE INVENTION
A method and apparatus are provided for attaching or mounting an insert in an opening in a molded body with fusion of adjacent thermoplastic materials to provide a substantially integral insert and body assembly. The insert is judiciously positioned within the mold cavity to allow wall formation and to avoid deformation or damage of the insert due to the heat emitted by the molten thermoplastic material as the wall is being formed. Following a predetermined cooling and hardening of the molten thermoplastic material, the insert is brought into contact with the thermoplastic wall at the body opening to provide a fused joint therewith.
As indicated above, the insert is brought into contact with the molten thermoplastic material while it is cooling and at a time when it is still somewhat above its processing temperature. In this manner, the thermoplastic material forming the mounting portion of the insert comes into contact with the still hot thermoplastic material and is briefly heated above its processing temperature and surface melting occurs. The mounting portion of the insert thereby fuses with the thermoplastic material of the hollow body, resulting in a very secure bonding without using any separate adhesive material or mechanical form of fixing, such as screws. The phrase "processing temperature" is used herein to refer to the melt temperature of a thermoplastic material, the thermoplastic material being sufficiently soft or molten at such temperature to shape by molding and to fuse with a similar or different thermoplastic material to form a homogeneous or integral joint therewith.
In the present method, the thermoplastic material is spread in a conventional manner over the inner walls of the mold with heating in a layer of almost uniform thickness. The insert is then brought into contact with the still molten or hot thermoplastic material in the mold. After further cooling, the hollow body with the attached insert may be removed from the mold as soon as it is sufficiently hard.
In accordance with the invention, it is neces
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Kepler Arthur M.
LeBreton Edward T.
Liekens Michel
Essef Corporation
Thrulow Jeffery
Vargot Mathieu
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