Plastic and nonmetallic article shaping or treating: processes – With printing or coating of workpiece – Coating or impregnating workpiece before molding or shaping...
Reexamination Certificate
1998-11-05
2001-01-30
Silbaugh, Jan H. (Department: 1732)
Plastic and nonmetallic article shaping or treating: processes
With printing or coating of workpiece
Coating or impregnating workpiece before molding or shaping...
C264S261000, C264S263000, C264S265000, C264S277000
Reexamination Certificate
active
06180038
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method of bonding tubes to devices, especially channelled devices, in which the tubes and devices are formed from thermoplastic polymers, so as to provide fluid flow communication through the devices, through the tubes and channels, especially through tubes extending through the devices. In particular, the method relates to the bonding of tubes into devices that are articles forming all or part of headers or manifolds in the manufacture of plastic heat exchangers.
BACKGROUND TO THE INVENTION
Panel heat exchangers formed from thermoplastic polymers and methods for the manufacture of such heat exchangers are known. For instance, a number of heat exchangers formed from thermoplastic polymers and methods for the manufacture thereof are disclosed in PCT Patent Application WO91/02209 of A. J. Cesaroni, published Feb. 21, 1991, and in the published patent applications referred to therein. Thermoplastic polymer heat exchangers of a tubular construction are described in U.S. Pat. Nos. 4,923,004, and 5,078,946, issued May 8, 1990 and Jan. 7, 1992, respectively, both of E. L. Fletcher and T. H. Kho, in which tubes are integrally formed with a manifold section in a moulding or similar process. A preferred material of construction for the heat exchangers is polyamide, especially aliphatic polyamide.
While heat exchangers formed from thermoplastic polymers have been fabricated by the techniques described in the above patents and published patent applications, improvement in the construction and methods of fabrication would be beneficial to add further flexibility and economy to the fabrication and use of heat exchangers formed from thermoplastic polymers. In particular, assembly of tubes into headers or manifolds or other structures in the manufacture of tube heat exchangers is usually a tedious and time-consuming process, often involving use of adhesives to bond the tubes into position.
British Patent 1,379,511—Gibbons et al, published 1975, discloses a method of making a heat exchanger in which a low-melting metal is first poured into a cavity surrounding tubes, preferably incorporating plug portions protruding into the tubes to keep the tubes open; then polypropylene (PP) is cast on the ends to form headers encapsulating the tubes. Finally the low-melting metal is melted out, leaving the PP exposed to the inside of the heat exchanger.
U.S. Pat. No. 2,225,856—Buck (1940) discloses a heat exchanger with aluminum tubes sealed through an apertured sheet or plate of resilient rubber between pairs of spaced header plates. There is no suggestion to cast a polymer instead of using a preformed apertured sheet of rubber.
U.S. Pat. No. 4,323,115—Stafford et al (1982) discloses a tube heat exchanger with tube sheets comprising first a layer of insulation such as fiberglass reinforced polymethyl methacrylate, then with preferably a liquid resin poured in around the tubes on top of the insulation. Preferably catalysed epoxy resin are used which set at ambient temperatures. A key goal is to use a resin that can be burned out without damaging the tubes which can be made of plastic. Instead of the insulation material, a temporary wooden form can be used to hold in place the liquid resin until it solidifies. As an option, the epoxy can be in two layers with fibers in one for insulation and particles in the other for reinforced strength. In any event, there is no suggestion of injecting a thermo plastic filler between two solid plates to form a header, with tubes threaded through holes in the two solid plates.
SUMMARY OF THE INVENTION
A method for the bonding of thermoplastic polymer tubes into thermoplastic polymer devices in a fluid tight manner has now been found.
Accordingly, an aspect of the present invention provides a method for bonding a tube into a device each of which is formed from a thermoplastic polymer, said device having a first solid member and a second solid member in spaced apart relationship to form a hollow cavity therebetween, said device having at least one channel extending through each of said solid members in an aligned relationship, the channel through at least one of said solid members being linear and being of a shape and size to accommodate a tube in sliding engagement such that the tube may be passed through said member, through the hollow cavity and into the channel of the other solid member to provide fluid flow communication through the device; comprising the steps of:
inserting said tube into the linear channel, such that it extends through the hollow cavity and into the channel of the other solid member;
injecting molten polymeric composition into the hollow cavity, said molten composition having a temperature lower than the melting point of said thermoplastic polymer, said composition being selected and being used in an amount so as to bond to the thermoplastic polymer and to the tube to form fluid-tight bonds therewith.
In a preferred embodiment of the method of the present invention, there are a plurality of channels through each solid member in an aligned relationship.
In another embodiment, the polymeric composition is injected in an amount so as to fill said hollow cavity.
In a further embodiment, the tube and device are formed from a polyamide, and preferably said composition is also a polyamide.
In yet another embodiment, the channels through both solid members are linear, and the tube extends through both solid members.
In a still further embodiment, the tube is coated with an adhesive to promote adhesion to said polymeric composition and/or said tube is a co-extruded tube with the outer layer to promote bonding of said tube to said polymeric composition.
In a further embodiment, the device is formed in two parts that mate together to provide said hollow cavity, especially where the composition also bonds the two parts of the device together.
In another embodiment, the cavity of the device comprises 10-50% by volume of the device.
In a further embodiment the device is part of a header or manifold for a plastic heat exchanger.
REFERENCES:
patent: 2225856 (1940-12-01), Buck
patent: 2969956 (1961-01-01), Forgo
patent: 4328862 (1982-05-01), Gossalter
patent: 4369157 (1983-01-01), Conner
patent: 4643249 (1987-02-01), Grawey
patent: 5036912 (1991-08-01), Woosnam
patent: 022234 (1981-01-01), None
patent: 1379511 (1975-01-01), None
Burgess Richard H.
Joseph Anthony Cesaroni
Lee Edmund H.
Silbaugh Jan H.
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