Patent Application
20050202237
The invention relates to heat shields for protecting items subjected to radiant heat sources.
Automotive, aeronautical and marine components positioned in engine compartments or near heat sources such as exhaust manifolds may be subjected to harsh thermal environments involving high temperature radiant heat transfer. Further, undesired heat transfer may also occur between heat sources such as engines, exhaust systems and/or transmissions and the passenger compartment of an automobile, aircraft or boat.
It is found advantageous to use insulating panels comprised of a number of overlying layers to reduce heat transfer from a heat source to other adjacent components. The insulating layers comprising the panel may include, for example, a reflective surface such as aluminum foil, an insulating scrim layer of temperature resistant material such as woven fiberglass, and a backing layer comprising a pressure sensitive adhesive for attachment of the insulating panel to a component or structure.
While such insulating panels are effective at reducing radiant heat transfer, they are often inappropriate for use where they will be subjected to contaminating fluids such as oil, gasoline, engine coolants such as ethylene glycol, hydraulic fluids as well as water which is encountered in almost any environment. The fluids tend to penetrate between the various layers through exposed edges of the panels and accumulate within the panels. This diminishes the insulative effectiveness of the panels and often leads to their accelerated corrosion and deterioration. If the fluids are flammable, the panels can become a fire hazard as well. It would be advantageous to provide insulating panels forming a heat shield that could be used in the presence of fluids without the aforementioned disadvantages.
The invention concerns a heat shield effective at reducing radiant heat transfer. The heat shield comprises a first layer having a reflective surface and a first edge and a second layer comprising a fusible material positioned overlying the first layer. The second layer has a second edge aligned with the first edge. The heat shield also includes a third layer positioned overlying the second layer. The third layer has a third edge aligned with the first and second edges of the first and second layers. A portion of the second layer is fused to the first and third layers along the first, second and third edges thereby forming a seal along these edges that prevents fluid from penetrating between the various layers.
Preferably, the first layer comprises an aluminum foil, and the second layer comprises a non-woven polymer such as polyester. The third layer may comprise another layer of aluminum or could also be a pressure sensitive adhesive substrate to allow the heat shield to be conveniently attached to a surface or structure.
An insulating layer may be positioned between the first and the third layers. Such a layer may comprise a woven glass fiber substrate, glass fiber being advantageous for high temperature applications.
First layer 12 is in overlying relation with a second layer 16 formed of a heat fusible material. Second layer 16 is preferably a non-woven material made of a polymer such as polyester. The non-woven layer may range in thickness between 0.05 inches and 0.25 inches and is preferably fusible over a temperature range between about 245° C. and about 265° C. A third layer 18 overlies the second layer on a side opposite the first layer 12, the second layer 16 being sandwiched between the first and third layers. The third layer 18 may also comprise a reflective surface like the first layer or it may be a layer of pressure sensitive adhesive substrate that provides a means for attaching the heat shield 10 to a component or other structure as described below.
Each of the layers 12, 16 and 18 have at least one edge 12a, 16a and 18a, respectively, that substantially align with one another and form a portion 20 of a perimeter 22 of the heat shield 10. The layers 12, 16 and 18 are joined to one another by applying heat and pressure along at least edges 12a, 16a and 18a but preferably substantially continuously along all of the edges defining the perimeter 22. Various methods may be employed to apply the heat and pressure, such as by means of ultrasonic rotary dies, ultrasonic die stamping, a heated rotary die, and hot die stamping. Crimping of the edge may also be used to apply pressure, and flame cutting or flame applied directly to the perimeter applies heat.
The heat and pressure melt a portion of the second layer 16 near and at the various edges to which the heat and pressure are applied. This causes the second layer 16 to bond with the first and third layers 12 and 18, joining the layers together to form the heat shield 10 when the second layer cools and fuses. Because it melts and fuses, the second layer 16 forms a seal 24 along the edges that prevents fluid from diffusing between the layers 12, 16 and 18 as would otherwise happen if a seal were not present. Preferably, the seal 24 extends completely around the entire perimeter 22 of the heat shield. It is also possible to melt either or both of the first and third layers in the region of the edges to have increased interpenetration between the first and third layers 12 and 18 and the second layer 16. Joining the layers along edges such as 12a, 16a and 18a also helps to prevent delamination of the heat shield 10, especially when the edges are joined around the entire periphery 22.
Manufacture of heat shields according to the invention is preferably effected using ultrasonic welding equipment such as the Sonobond Ultrasonic Welder or the Branson Ultrasonic Welder to apply heat and pressure to the edges along the perimeter of the heat shield. Other techniques, such as clamping the edges between hot surfaces or dies would also be effective at creating the seal 24 around perimeter 22.
Heat shields according to the invention may be applied to automobile chassis between a heat source and the passenger compartment to inhibit radiant heat transfer. Examples of heat sources include exhaust pipes, the engine compartment, as well as the transmission. Because they have sealed edges, heat shields according to the invention are especially useful where fluids are found. For example, the heat shield may be positioned around a master cylinder of a brake system, a power steering pump or hydraulic fluid reservoir, fluid windshield washer reservoir or near the engine radiator without fear that the heat shield will become contaminated by the fluids with which it will come into contact.
| Number | Date | Country | |
|---|---|---|---|
| 60551682 | Mar 2004 | US |
