Heating apparatus for composite structure repair

• US 6,031,212 A
• Filed: 06/05/1995
• Issued: 02/29/2000
• Est. Priority Date: 04/09/1991
• Status: Expired due to Term

• Current Assignee: The Boeing Co.
• Original Assignee: The Boeing Co.
• Inventors: Westerman, Everett A., Roll, Phillip E.
• Primary Examiner(s): Jeffery, John A.
• Application Number:
  US08/464,489
• Time in Patent Office: 1,730 Days
• Field of Search: 219/528-529, 219/535, 219/544, 219/548-549, 219/530, 219/540, 392/339, 392/443, 156/285, 156/583.1
• US Class Current: 219/535
• CPC Class Codes: B29C 2035/0211 resistance heating B29C2035/0811 takes precedence
• CPC Class Codes: B29C 35/02 Heating or curing, e.g. crosslinking or vulcanizing during moulding, e.g. in a mouldcold vulcanisation B29C35/18 ; vulcanising tyres, presses therefor B29D30/0601
• CPC Class Codes: B29C 65/02 by heating, with or without pressure
• CPC Class Codes: B29C 65/18 using heated tools
• CPC Class Codes: B29C 65/30 Electrical means B29C65/38 takes precedence
• CPC Class Codes: B29C 66/00145 Vacuum, e.g. partial vacuum
• CPC Class Codes: B29C 66/002 Removing toxic gases
• CPC Class Codes: B29C 66/1122 Single lap to lap joints, i.e. overlap joints B29C66/45, B29C66/472, B29C66/52272 take precedence
• CPC Class Codes: B29C 66/133 Fin-type joints, the parts to be joined being flexible the parts to be joined being rigid B29C66/1312
• CPC Class Codes: B29C 66/433 Casing-in, i.e. enclosing an element between two sheets by an outlined seam for bookbinding B42C11/06; for packaging B65B; by laminating B32B37/00; enclosing tubular articles between substantially flat elements B29C66/53261
• CPC Class Codes: B29C 66/4332 by folding a sheet over
• CPC Class Codes: B29C 66/45 Joining of substantially the whole surface of the articles methods or apparatus for laminating B32B37/00
• CPC Class Codes: B29C 66/71 characterised by the composition of the plastics material of the parts to be joined welding bar compositions B29C65/125
• CPC Class Codes: B29C 66/712 the composition of one of the parts to be joined being different from the composition of the other part
• CPC Class Codes: B29C 66/81241 being porous or sintered
• CPC Class Codes: B29C 66/81261 Thermal properties, e.g. thermal conductivity, thermal expansion coefficient
• CPC Class Codes: B29C 66/81455 being a fluid inflatable bag or bladder, a diaphragm or a vacuum bag for applying isostatic pressure inflatable element positioned between the joining tool and a backing-up part B29C66/82421
• CPC Class Codes: B29C 66/81459 being a filled deformable bladder, e.g. bladder filled with oil, with granules or with a meltable solid material B29C66/81455 takes precedence
• CPC Class Codes: B29C 66/82661 by means of vacuum
• CPC Class Codes: B29C 66/91221 of the parts to be joined
• CPC Class Codes: B29C 66/91411 : of the parts to be joined, e.g. the joining process taking the temperature of the parts to be joined into account
• CPC Class Codes: B29C 66/91443 : following a temperature-time profile B29C65/38 takes precedence
• CPC Class Codes: B29C 66/91445 : by steps
• CPC Class Codes: B29C 66/91651 : by controlling or regulating the heat generated by Joule heating or induction heating
• CPC Class Codes: B29C 66/919 : characterised by specific temperature, heat or thermal flux values or ranges specific electrical resistance values B29C66/81262
• CPC Class Codes: B29C 66/91921 : in explicit relation to another temperature, e.g. to the softening temperature or softening point, to the thermal degradation temperature or to the ambient temperature
• CPC Class Codes: B29C 66/91951 : in explicit relation to time, e.g. temperature-time diagrams
• CPC Class Codes: B29C 66/92443 : following a pressure-time profile
• CPC Class Codes: B29C 66/92921 : in specific relation to time, e.g. pressure-time diagrams
• CPC Class Codes: B29C 66/961 : involving a feedback loop mechanism, e.g. comparison with a desired value
• CPC Class Codes: B29C 73/12 : Apparatus therefor, e.g. for applying B29C73/30 takes precedence
• CPC Class Codes: B29C 73/32 : using an elastic element, e.g. inflatable bag
• CPC Class Codes: B29C 73/34 : for local heating
• CPC Class Codes: B29K 2077/00 : Use of PA, i.e. polyamides, e.g. polyesteramides or derivatives thereof, as moulding material
• CPC Class Codes: B29K 2083/00 : Use of polymers having silicon, with or without sulfur, nitrogen, oxygen, or carbon only, in the main chain, as moulding material
• CPC Class Codes: H05B 3/00 : Ohmic-resistance heating
• CPC Class Codes: H05B 3/28 : heating conductor embedded in insulating material

Abstract

Apparatus for applying heat to a patch on a composite structure repair site includes a sealed bladder containing both a thermally conductive fluid and a heating element in thermal contact with the fluid. The heating element which comprises a flexible sheet having an electrical resistance wire uniformly placed thereon can be immersed in the fluid or otherwise in direct thermal contact therewith. Electrical power is applied to the heating element by conductors passing through the bladder surface. The heating element of disclosed structure can be attached to seal the bladder interior into two reservoirs, to permit fluid flow throughout the bladder or to form at least one outer surface of the bladder. Flexible supports can also be attached from the heating element to an interior bladder surface to maintain spacing between the heating element and the surface. To prevent diffusion of the thermally conductive fluid, a separate container of thermally conductive fluid impermeable material can be placed inside the bladder. The outer bladder may be sealed by mechanical frame apparatus which compresses the bladder surface material at a perimeter thereof.

Claims

1. A heating apparatus for applying substantially uniform heat to a repair site to heat the site to about 300°

F., comprising;

(a) a fluid impermeable material having a first surface for contact with a repair site and an outer surface, the material defining a reservoir for a heat transfer medium;

(b) a layer of insulating material attached to and cover the outer surface;

(c) a heat transfer medium in the reservoir, the medium being liquid at 300°

F.;

(d) a flexible heating element attached to the outer surface to trap heat within the reservoir; and

(e) means for applying heating power to said heating element.

2. The apparatus of claim 1 wherein said heating element comprises a predetermined length of electrical resistance wire substantially uniformly disposed on said first sheet.

3. The heating apparatus of claim 1 adapted for heating composite structure to a substantially uniform temperature of about 300±

15°

F. at a repair site, wherein the heat transfer medium is a phase change material that is solid at ambient temperature but liquid at 300°

F. in the fluid reservoir.

4. The apparatus of claim 3 wherein the reservoir is silicone rubber and the phase change material is beeswax.

5. The apparatus of claim 4 further comprising a polyamide bladder housing the phase change material in the fluid reservoir.

6. A heating apparatus for applying heat to a repair site comprising:

(a) a first sheet of fluid impermeable material having a flexible heating element attached thereto, said first sheet having a first and second surface;

(b) a layer of insulating material attached to and covering said first surface of said first sheet;

(c) a second sheet of pliable fluid impermeable material bonded at a perimeter of the first sheet to form a fluid reservoir;

(d) thermally conductive material that melts at about 140°

F. in the fluid reservoir in substantially direct thermal contact with said second surface of said first sheet; and

(e) means for applying heating power to said heating element, wherein the apparatus applies heat at a temperature of at least 300±

15°

F. to a repair site of a composite structure.

7. A heating apparatus for heating a repair site on a composite structure to a substantially uniform temperature of at least about 300°

F., comprising;

(a) a pliable, sealed bladder having a surface in contact with the repair site and an outer surface;

(b) a thermally-conductive fluid in the bladder;

(c) an electrical heater within the bladder for heating the fluid to heat the site to the substantially uniform temperature; and

(d) insulation on the outer surface for trapping heat within the fluid when the heater is energized.