Adhesive bonding and miscellaneous chemical manufacture – Methods – Surface bonding and/or assembly therefor
Reexamination Certificate
1999-04-14
2001-08-07
Ball, Michael W. (Department: 1733)
Adhesive bonding and miscellaneous chemical manufacture
Methods
Surface bonding and/or assembly therefor
C156S093000, C156S272200, C156S272800, C156S304300, C156S378000, C156S380900
Reexamination Certificate
active
06270599
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to method and means for welding such as plastics sheet or strip including as a seal over seaming of plastics or plastics coated material.
BACKGROUND OF THE INVENTION
The invention has arisen specifically relative to so-called Insituform (Registered Trade Mark) tube used to proprietary process or method of “no-dig” relining of typically underground services or utilities supply pipes. A flexible tube of coated woven or felt-type sheet material having a sewn seam is readily installed into an existing said pipe, say by inversion using a head of water; and usually before being impregnated with thermoset plastic material, such as polyester or epoxy resin. Water pressure within such tube of appropriate size can expand and force it into tight fit against interior of the host pipe; and subsequent heating of such water, typically as circulated from an above-ground boiler, can aid curing of the resin to form a solid durable lining or re-lining of existing host pipe, typically of diameters from about 100 millimetres or less to about 3 metres or more.
Typical such Insituform tube is made on a production line by sewing together long edges of folded-over plastics coated felt material strip of appropriate width to form a “lay-flat” tube of desired size. Coating on the felt material is usually applied by the felt manufacturer/supplier before shipping to the Insituform tube production plant, and is typically of thermoplastics material, specifically polyurethane (PU) or polyethylene (PE), in a thickness usually up to about 0.5 millimetre. It is important that Insituform tube affords a fully sealed pipe lining after installation; and any incidence of leaks or dripping of impregnating resin during installation are problematic, i.e. need to be avoided. Sealing of said seams of lay-flat tube as supplied to field sites for installation is thus required, and needs to be of a good and reliable nature. Two methods seam sealing are known or have been proposed.
One such method relies on solvent bonding a plastics tape over the seam, typically about 65 millimetre width of about 0.3 millimetre thick PU tape that is bonded using tetrahydrafuran (THF) solvent. Whilst equipment required is readily incorporated into production lines for lay-flat sewn-seam tube that is PU-coated, practical solvents that afford similar possibilities for PE-coated felt are not available. Moreover, even for PU-coated tube, use of THF can give rise to health and safety concerns.
The other such method relies on extruding a bead of molten plastics onto said sewn seams, then rolling still-soft extruded bead flat over and to cover/seal the seam, including fusing with the coating. Whilst this method is applicable in principle to either PU or PE coatings, there are practical problems. Thus bead extrusion is not readily started and stopped at will due to heating requirements and control relative to flow characteristics that must be achieved and maintained, which conflicts with norms for sewn-seam Insituform tube production lines where sewing machine and felt guidance operations tend to be subject to frequent interruptions, thus stops. Indeed, two separate production stages would appear to be required, with inevitable result of duplication of materials stacking and feed systems and extra staff requirement. Also, bead processing speed is limited by cooling rate of the plastics material concerned, which tends to be particularly slow for PE, thus further leads to requirement for substantial length of run-off space etc before further handling and/or use of cooling equipment which would be expensive to install. Extrusion thus looks an expensive option in terms of sophisticated capital equipment for extrusion possibly also cooling.
SUMMARY OF THE INVENTION
An object of this invention is to provide alternative method and/or means that can mitigate such problem(s), at least in application to producing Insituform tube.
According to first method and apparatus aspects of this invention, joining two members by heat-welding involves applying radiation through one of the members to layer(s) interposed between the two members and having inclusions through thickness thereof which inclusions are responsive to said radiation to raise temperature of said layer(s) through thickness thereof and promote bonds at interfaces with surfaces of said members.
Preferably, heat absorbed by said inclusions renders said layer(s) deformable, and pressure applied transversely of said layer(s) to bring said members together will deform said layer(s) to accommodate interface irregularity; and where said one member has low thermal conductivity and sufficient thickness to be cool enough at another surface thereof to allow freely rolling or sliding contact therewith, said pressure is applied by means making such rolling or sliding contact.
Said radiation can be applied only through said one member, and is preferably at least partially (typically less than 50%), reflected back into said layer(s) by the other of said members; said radiation can be applied to said one member through a or said means making rolling or sliding contact therewith; and said reflection by said other member can be after transmission from said layer through interface to radiation-transmissive coating on said other member.
First and second superposed component parts of said layer(s) may have inclusions that are, as sequentially encountered by said radiation, responsive as aforesaid to lesser and greater amounts, respectively.
Said radiation can be infra-red (preferably in near visible range) to which said one member is substantially transparent, with said layer(s) both transmissive and absorptive into said inclusions.
Said layer(s) and said one member may constitute sealing strip to be applied to said other member, usefully over a stitched seam of said other member; and such sealing strip constitutes a second aspect of invention including embodied as layers of thermoplastics material, which may be substantially the same or similar for all said layers save for said inclusions in inner or lower said layer(s), or at least compatible for welding together. Outer said layer as said one member is preferably substantially wholly transmissive to said infra-red radiation.
Suitable welding apparatus may comprise beam-producing means including source of infra-red radiation and aperture-defining means both within a rotatable hollow tube substantially transparent to said radiation to make rolling contact with means to or through which the produced beam of said infra-red radiation is applied; and such welding apparatus constitutes a third aspect of invention.
According to other method and apparatus aspects of invention, assessment is provided for weld(s) made by a radiation heated layer(s) below a radiation transmissive layer, the assessment involving using a thermal imaging camera to detect through said transmissive layer radiation from said heat layer(s) that is different from the radiation causing heating for welding purposes. Such other aspects may be additional step to above first aspects of invention.
According to system and apparatus aspects of invention production of members joined by welding involving heated layer(s) interposed between two said members, the layer(s) having inclusions through thickness and responsive to radiation to raise temperature of said layer(s) through thickness in promoting weld-bonds at interfaces with surfaces of said members, the production providing for interposing said layer(s) between said members, applying said radiation to said members with interposed said layer(s), and moving thus irradiated said members from said means for applying.
Said means for interposing may serve to supply one of said members along with said layer(s); and there may be further provision for assessing welding of said irradiated members, say as aforesaid using a thermal imaging camera.
REFERENCES:
patent: 3678276 (1972-07-01), Lampi et al.
patent: 4410381 (1983-10-01), Chapman, II
patent: 5512126 (1996-04-01), Kannabiran et al.
patent: 5840147 (1998-11-01), Grimm
Ball Michael W.
Chapman and Cutler
John Wood Enterprises Limited
Tolin Michael A.
LandOfFree
Heat-welding of plastics by radiation does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Heat-welding of plastics by radiation, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Heat-welding of plastics by radiation will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2484775