Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
2000-08-30
2001-08-14
Sells, James (Department: 1734)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S304600, C156S499000
Reexamination Certificate
active
06273988
ABSTRACT:
TECHNICAL FIELD
The present invention relates to apparatus and methods for butt welding plastic members. More particularly, the present invention relates to tools and methods that hold plastic members for welding together while reducing the waste flow of melted plastic on the exterior of welded joints of plastic members.
BACKGROUND OF THE INVENTION
Conventional doors and windows for buildings are typically manufactured with rectangular frames which hold the door or the glass. The frames assemble from elongate members joined at distal ends. The members are known in the art as profiles. Typically the members used for windows are made from thermo-plastic materials such as extruded polyvinyl chloride and the like. The members have distal ends which define mating 45 degree angles which when joined together form a perpendicular angle for squaring a corner of the window or door frame. Frame members made from non-thermo-plastic materials, such as aluminum, have mechanical linkages which join the pair of frame members together. However, members made with thermoplastic materials are generally joined to each other by butt welding the adjacent ends with heat.
There are existing two-head or four-head welding machines of various designs for the purpose of butt welding thermo-plastic members and forming the frame. In these devices, the members are securely clamped with special tools that attach to the machines. Each tool includes a lower support on which the lower surface of the member sits. An upper support in the tool moves vertically against the upper surface of the plastic member, thereby clamping the member in the tool. Adjacent pairs of tools then move towards each other to press distal ends of the aligned members against a heat plate for melting the distal ends of the aligned members. After a period of time, the heat plate is removed, and the tools brought together to engage the distal (now molten) ends of the members which weld or fuse together. During the welding process, melted plastic material flows around the joint.
More particularly explained, the melted plastic from the aligned ends of the members flows both outwardly and inwardly of the joint formed by the welding process. The waste material forms a plastic weld bead on the exterior and interior surfaces of the welded members. The waste bead on the interior of the welded members is not objectionable in that it strengthens the weld by providing additional thickness across the joint. However, the plastic weld bead on the exterior is unsightly for ornamental purposes as well as perhaps interfering with figment of the window or door. Machinery however is provided to trim the waste bead from the weld joints. The joined members are placed on the machine and are passed by a blade that trims the waste bead from the exterior surfaces of the joint.
While the welding machinery described above readily joins thermo-plastic members together to form frames for windows and doors, the resulting frame incurs the additional labor and costs to trim the waste bead. The separate machine must be purchased and placed in the manufacturing process for deburring the joint, that is, trimming the waste bead from the welded joint. An operator is required to handle the frames for deburring the corners of the frame.
Accordingly, there is a need in the art for an improved tool for welding plastic members which reduces the waste material on the exterior of joints formed during the welding process. It is to such that the present invention is directed.
SUMMARY OF THE INVENTION
The present invention meets the need in the art by providing a tool for welding plastic members which reduces the waste material on the exterior of the joint formed during the welding process. The tool holds a plastic member for welding to a second plastic member held by a second of said tools. The tool operates during the welding process to reduce the waste material on the exterior surface of the joint formed between the plastic members. The tool comprises opposing lower and upper dies that define opposing profile surfaces that conform to an exterior cross-sectional profile of a plastic member for being received and held therebetween. Opposing lower and upper plates are disposed in spaced-apart relation to the lower die and the upper die, respectively. The plates defines opposing surfaces that conform to the exterior cross-sectional profile of the plastic member for being received therebetween. Movable mount means connects the lower plate to the lower die and the upper plate to the upper die independently for lateral movement of the plates relative to the dies between a first distally spaced position to a second closely spaced position. During the welding process, the plates move laterally between the first position and the second position. The plates seal the weld material from flowing to the exterior of the joint being formed between the plastic members and forces the weld material to flow inwardly of the joint.
Two of the tools mount in an apparatus for butt welding two plastic members that from one corner in a frame. (Typically the apparatus has two or four heads, each with two tools, for simultaneous welding of two or four corners of the frame.) The present invention provides a method of welding a pair of plastic members while reducing the excess plastic on the exterior of the weld joint. The method places a pair of plastic members in respective tools which each have opposing lower and upper dies that define opposing member surfaces that conform to an exterior cross-sectional member of the plastic member received and held therebetween. The tools further include opposing lower and upper plates disposed in spaced-apart relation to the lower die and the upper die, respectively, which plates having opposing surfaces that conform to the exterior cross-sectional member of the plastic member for being received therebetween. Movable mount means connect the lower plate to the lower die and the upper plate to the upper die independently for lateral movement of the plates relative to the dies between a first distally spaced position to a second closely spaced position during the welding process. With the plastic members held between the dies and the plates, a heat blade moves between the tools. The tools move against the sides of the heat blade for melting the distal ends of the plastic members in contact therewith. As the distal ends melt, the plates seal the exterior of the plastic members from flow of molten plastic by moving the plates in contact with the heat blade laterally towards the dies as the distal ends of the aligned plastic members melt. After suitable melting, the tools move away from the heat blade. The plates move from the second position to the first position relative to the respective dies to maintain the seal against flow of molten plastic to the exterior of the plastic members. The heat blade retracts. The tools are then moved together forcibly to move the plates laterally to the second position while the melted distal ends of the plastic members compressingly fuse together.
Objects, advantages and features of the present invention will become apparent from a reading of the following detailed description of the invention and claims in view of the appended drawings.
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ATCO Automated Window Machinery (Innova
Rodney John T.
Zollinger Rolf A.
Baker, Donelson Bearman & Caldwell
Sells James
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