Electric heating – Inductive heating – With heat exchange
Reexamination Certificate
1999-10-21
2001-09-11
Leung, Philip H. (Department: 3742)
Electric heating
Inductive heating
With heat exchange
C219S635000, C219S672000, C219S675000, C156S272400, C156S380200
Reexamination Certificate
active
06288375
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to a conformable loop heating apparatus and method for reducing the cure time of a geometrically shaped bondline defined by a thermally responsive bonding material positioned between two members, the apparatus including a manually reshapeable cable assembly positionable adjacent the shaped bondline.
BACKGROUND OF THE INVENTION
In the automotive industry, exterior metal panels (i.e., closure panels) on vehicles are attached to the vehicle structure during manufacturing using resistance spot welds. Non-metal panels are attached to the metal structure with adhesives or by mechanical fasteners. Subsequent replacement of a metal panel (e.g., due to damage from a collision) is typically accomplished by welding or by a combination of welding and bonding the panel to the metal structure. Thermally responsive bonding materials (e.g., thermally curable adhesives) are utilized for bonding a replacement panel to the metal structure. The cure times of a thermally responsive bonding material can be reduced by applying heat to the bonding material. The bonding materials utilized are typically one-part or two-part adhesives. Such adhesives may be epoxy, urethane, acrylic, or acrylic-epoxy based adhesives.
In the collision repair process, the bonding material is either applied to the replacement panel or to the vehicle structure, or both. The panel is fixed in proper alignment with the vehicle structure. The panels must remain stationary in a heated shop to cure the bonding material until the bonding material has at least developed handling strength. During the time that a collision repair shop waits for the bonding material to cure, the vehicle occupies valuable shop space which could be utilized for other purposes. Different two-part adhesives require varying times to cure adequately to achieve handling strength, and even longer cure times are required for the adhesive to reach its full structural strength. One-part adhesives are not used as frequently in collision repair since one-part adhesives usually require moisture or heat to cure the adhesive. Moisture is known to be slow to penetrate into a thin adhesive bondline sandwiched between a replacement panel and the vehicle structure.
A collision repair shop is required to replace many different sizes and shapes of vehicle closure panels. Known heating apparatuses and methods for accelerating bonding material cure times include infra-red heat lamps, silicon-coated resistant heat tapes, hot-air heat guns, and paint bake booths. Each of the above methods have known disadvantages. Infra-red heaters can provide high-heat to broad areas. However, the high temperature necessary for rapidly curing some bonding materials may also cause damage to unprotected adjacent heat sensitive materials in/on the vehicle. Silicon-coated resistance heat tapes can be taped or clamped along a bondline. As the tape heats, it expands and portions “lift up” from the heated surface. The areas of the bondlines under the raised portions of the heat tape may not receive adequate heat. Paint bake booths can be used for accelerating the cure time of a bonding material, but the whole vehicle occupies a very expensive piece of equipment necessary for curing paints. Some paint bake booths can not be heated to an adequate temperature to cure known structural bonding tapes (SBT) or one-part paste adhesives. If such high temperatures were obtained, the heat could also damage heat sensitive components of the vehicle. Hot air heat guns are able to obtain the temperatures necessary to accelerate the cure of thermal bonding materials. However, curing of a bondline with a point source heater like a heat gun is a very time consuming operation. Only small sections or “spots” of the bondline are heated at a time. In use of a heat gun, it may not be very easy to uniformly control the ultimate bonding material temperature. This may result in overheating of the bonding material to a point of decomposition. Alternatively, inadequate heat could result in an incomplete cure.
Induction heating has been known to be used in the manufacture and assembly of automotive vehicles involving high production rates of similar parts. Electric induction coils are employed to provide heat to accelerate the curing of thermally responsive bonding materials positioned between juxtaposed metal sheets. Such induction coils carry high frequency electrical current which generates a magnetic field and causes heating of the metal sheets. Heat is conducted from the metal sheets to the bonding material disposed between the metal sheets. Known methods of induction heating include the use of spot induction heaters or rigid copper induction applicators. Spot induction heaters concentrate a large amount of heat at a small, localized area or “spot”. It is common to employ spot induction heaters at selected locations along the length of a bondline so as to spot cure the bonding material at the locations of the induction coils to achieve handling strength. The remainder of the bonding material is cured at a later time during the assembly process, such as when the automotive vehicle passes through a paint bake booth. One known spot induction heater is disclosed in U.S. Pat. No. 5,442,159 to Shank issued Aug. 15, 1995.
The use of rigid copper induction applicators requires a different shaped applicator for each different shaped bondline or panel geometry. Such rigid induction applicators would not be desirable for use at a collision repair shop, which often requires bondlines of a different panel geometry for each use. Further, due to the high current in the inductor, rigid copper induction applicators often require additional cooling (e.g., a water cooling system) to avoid overheating of the rigid copper induction applicator. One known rigid copper induction applicator is disclosed in U.S. Pat. No. 4,602,139 to Hutton et al. issued on Jul. 22, 1986.
SUMMARY OF THE INVENTION
The present invention provides an induction heating apparatus and method for heating a substantially continuous bondline defined by a length of thermally responsive bonding material positioned between a first member and a second member. The first member or second member is made of an electrically conductive material or positioned adjacent an electrically conductive material. The inductive heating apparatus includes a flexible, reshapeable cable assembly positionable adjacent the first member along the first bondline. The flexible, reshapeable cable assembly is capable of being manually shaped to a first shape of the first bondline, and is capable of being manually re-shaped to a second shape of a second bondline different than the first shape of the first bondline. An alternating current power supply is electrically coupled to the flexible, reshapeable cable assembly. When the alternating current power supply is activated the reshapeable cable assembly operates to inductively heat the electrically conductive material for conductive heating of the thermally responsive bonding material substantially uniformly along the first bondline.
The flexible, reshapeable cable assembly is positionable in a non-dipole or dipole configuration adjacent the first bondline. In one aspect, the flexible, reshapeable cable assembly is positionable adjacent the second member along the first bondline.
In one aspect, the flexible, reshapeable cable assembly includes a plurality of wires stranded together. The cable assembly may further comprise a first insulating layer covering each wire forming an insulated wire, and a jacket layer covering all of the insulated wires. In one aspect, the first insulating layer is made of a polymeric material. In one aspect, the jacket layer is made of a polymeric material. In one preferred aspect, the flexible, reshapeable cable assembly is a litz wire.
The alternating current power supply is a high frequency power supply having an output frequency greater than 1 kilohertz. In one aspect, the output frequency is between 10 kilohertz and 400 kilohertz.
The inductive heating apparatus may fur
Boettcher Robert J.
Lappi Larry R.
Miller David G.
Miller Richard F.
3M Innovative Properties Company
Leung Philip H.
Pribnow Scott R.
LandOfFree
Conformable loop induction heating apparatus and method for... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Conformable loop induction heating apparatus and method for..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Conformable loop induction heating apparatus and method for... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2521194