Source: http://www.freepatentsonline.com/8795455.html
Timestamp: 2018-09-25 20:54:36
Document Index: 200894221

Matched Legal Cases: ['art 304', 'art 306', 'art 304', 'art 306', 'art 304', 'art 306', 'art 304', 'art 305', 'art 306', 'art 310', 'art 305', 'art 310', 'art 304', 'art 306', 'art 305', 'art 310', 'art 305', 'art 310', 'art 310', 'art 305', 'art 305', 'art 310', 'art 310', 'art 310', 'art 400', 'art 502', 'art 502', 'art 400', 'art 1000', 'arts 332']

United States Patent 8795455
A patch may be used to rework a composite structure in the field. The patch is bonded to the structure by a layer of adhesive and includes perforations that allow the escape of air from the adhesive as the patch is compressed against the structure. A spacer may be introduced between the patch and the structure to control the thickness of the adhesive layer.
12/554554
B29C73/10; B29C65/78
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USPTO Office Action, dated Jan. 13, 2011, regarding U.S. Appl. No. 12/613,810, 17 pages.
Response to Office Action, dated Apr. 19, 2011, regarding U.S. Appl. No. 12/613,810, 27 pages.
USPTO Final Office Action, dated Jun. 22, 2011, regarding U.S. Appl. No. 12/613,810, 16 pages.
Response to Final Office Action, dated Oct. 21, 2011, regarding U.S. Appl. No. 12/613,810, 31 pages.
This application is a continuation-in-part of U.S. patent application Ser. No. 12/328,903 filed Dec. 5, 2008, the entire disclosure of which is incorporated by reference herein.
1. A method of reworking an area of a structure, comprising: placing a layer of viscous bonding adhesive of a substantially uniform thickness, with at least one spacer, over and around the area, the at least one spacer having a size that is about equal to said substantially uniform thickness; placing a patch on the layer of viscous bonding adhesive and over and around the area; placing an anti-caul plate around a periphery of the patch, the anti-caul plate surrounding an entirety of the patch; and pressing the patch against said viscous bonding adhesive using a caul plate, the caul plate covering the entirety of the patch and also covering at least a portion of the anti-caul plate.
2. The method of claim 1, wherein placing a spacer between the patch and the structure includes introducing at least one of a plurality of beads and a screen into the adhesive.
3. The method of claim 1, wherein placing the spacer includes introducing the spacer into the adhesive before the adhesive is placed between the structure and the patch.
4. The method of claim 1, further comprising: preparing a surface of the structure; preparing the viscous bonding adhesive by mixing at least two reactive components; placing a template over the surface of the structure defining the area on the structure to be reworked, and wherein placing the bonding adhesive includes using the template to apply the adhesive to the defined area of the structure; and applying a heat producing device over the patch to cure the layer of adhesive.
5. The method of claim 1, wherein the patch includes perforations, the method further comprising: using the perforations in the patch to allow at least one of air and adhesive to be squeezed out from the patch through the perforations in the patch as the patch is pressed against the said viscous bonding adhesive; and confirming that any air beneath the patch has been substantially eliminated by observing flow of excess adhesive through the perforations in the patch.
6. The method of claim 1, wherein the spacer comprises a substantially non-compressible screen through which the viscous bonding adhesive may pass.
7. The method of claim 1, wherein the spacer comprises a plurality of substantially non-compressible beads dispersed in the viscous bonding adhesive.
8. The method of claim 1, wherein the patch includes perforations, the method further comprising: using the perforations in the patch to allow at least one of air and adhesive to be squeezed out from the patch through the perforations in the patch as the patch is pressed against the said viscous bonding adhesive.
9. The method of claim 1, wherein an interior edge of the anti-caul plate is radially spaced outside the periphery of the patch, creating a space between the periphery of the patch and the anti-caul plate.
10. The method of claim 9 further comprising: allowing some of the viscous bonding adhesive to squeeze out from the periphery of the patch and into the space.
11. The method of claim 1, wherein a shape of a bottom surface of the anti-caul plate is selected to match a shape or contour of a surface of the structure.
12. The method of claim 1 further comprising: reducing or preventing substantial tipping, slanting, or bending of the caul plate using the anti-caul plate while the caul plate applies pressure to the patch and to the anti-caul plate.
13. The method of claim 1 further comprising: reducing or preventing tapering of a bond line of the viscous bonding adhesive at or near the periphery using the anti-caul plate while the caul plate applies pressure to the entirety of the patch and to the anti-caul plate, thereby promoting a substantially constant thickness of the bond line over the entirety of the patch.
In accordance with the disclosed embodiments, a method is provided for bonding patches on structures in which the bond line or thickness of the bonding adhesive may be controlled over substantially the entire area of the patch. The method may not require a high level of installer skill and may provide consistent, repeatable results, even when performed in the field. Perforations in the patch may reduce or eliminate porosity in the bond by allowing air and/or excess adhesive to escape from the patch as it is forced against a structure during a patching operation. Patch installation may be carried out relatively quickly in the field using a set of prepackaged, preconfigured components.
According to one disclosed embodiment, a method is provided of reworking an area of a structure. The method includes preparing a patch, including forming a plurality of perforations in the patch, and placing a layer of bonding adhesive between the structure and the patch. The patch is pressed against the structure to achieve a desired bond line thickness. The perforations in the patch allow air and excess adhesive to escape from the patch as the patch is being pressed against the structure. The thickness of the adhesive layer may be controlled by placing a spacer between the patch and the structure. The spacer may comprise a screen and/or a plurality of beads that maintain a desired spacing between the patch and the structure. The method may further include placing a caul plate over the patch, applying pressure to the caul plate and limiting the pressure applied to the periphery of the patch through the caul plate by introducing an anti-caul plate between the caul plate and the structure.
According to another number of embodiments, a method is provided of bonding a patch on a structure, comprising placing the patch on the structure and placing a layer of bonding adhesive between the patch and the structure. A caul plate is placed over the patch and the patch is pressed against the structure by applying pressure to the caul plate. The method further includes limiting the pressure applied to the periphery of the patch by the caul plate. Limiting the pressure applied to the periphery of the patch may be performed by using an anti-caul plate to react the force applied to the caul plate around the perimeter of the caul plate.
According to another embodiment, a patch is provided for use in reworking an area of a structure. The patch comprises a generally planar member adapted to be pressed against the structure and bonded thereto by a layer of adhesive. The planar member includes a plurality of perforations therein allowing air between the patch and the structure to escape through the planar member as it is pressed against the structure. The perforations in the planar member may each have a width sufficient to allow excessive adhesive to flow there through and escape from the patch. The planar member may comprise a pre-cured composite material. The patch may further include a spacer adapted to be placed between the planar member and the structure for controlling the thickness of the adhesive layer.
FIG. 13 is an illustration of a flowchart showing a process for bonding parts in accordance with an advantageous embodiment; and
FIG. 14 is an illustration of a flowchart showing a process for bonding parts in accordance with an advantageous embodiment.
FIG. 15 is an illustration of a plan view of a section of a structure having an area requiring rework.
FIG. 16 is an illustration of a sectional view taken along the line 16-16 in FIG. 15.
FIG. 17 is an illustration of a plan view showing a template having been placed over the area being reworked.
FIG. 18 is an illustration of an isometric view of the patch, and showing perforations therein.
FIG. 19 is an illustration of a sectional view of the structure shown in FIG. 15 in which a patch and a layer of adhesive have been placed over the area requiring rework.
FIG. 20 is an illustration of a view similar to FIG. 19 but showing a caul plate and an anti-caul plate having been installed over the patch.
FIG. 21 is an illustration of a top view showing the caul plate wherein the position of the anti-caul plate and the patch is indicated in the phantom.
FIG. 22 is an illustration of an exploded view of apparatus for carrying out the patching method, including a heat pack and a compactor for applying force to the patch.
FIG. 23 is an illustration of a flow diagram showing the steps of a method for reworking a structure using a bonded patch.
FIG. 24 is an illustration of a block diagram showing components of a pre-packaged kit that may be used to rework a structure using a bonded patch.
Thus, the different advantageous embodiments provide a method and apparatus for bonding parts. An adhesive and a plurality of beads are applied onto a surface of a first part through a screen to form a layer of adhesive beads. The surface of the first part with the layer of adhesive beads is placed into contact with the surface of the second part to form an adhesive layer containing beads to form a structure. The structure may then be cured.
In these examples, the screen may have a thickness, and applying the adhesive and the plurality of beads onto a first surface of the first part through the screen may result in the layer of adhesive and beads having substantially the thickness of the screen.
The plurality of beads may have a size capable of causing a substantially uniform thickness for the layer of adhesive and beads when applied to the first surface of the part. The beads may be capable of maintaining the substantially uniform thickness for the layer of adhesive when joining parts together. Pressure applied to one or more parts being joined may not result in an uneven thickness. Further, the size of the beads may maintain the thickness under pressure.
With reference now to FIG. 3, a diagram of a bonding environment is depicted in accordance with an advantageous embodiment. In this illustrative example, bonding environment 300 may be used to create structural bond 302 between part 304 and part 306. Part 304 and part 306 may form structure 307. In these examples, part 304 and part 306 may be parts for platform 308. In these examples, platform 308 may be, for example, aircraft 200 in FIG. 2. Part 304 may take the form of composite part 305, and part 306 may take the form of composite part 310.
In these illustrative examples, composite part 305 may be skin panel 312, although other structures such as, and without limitation, floor panels, walls, frames, stringers, spars, doors, and other structures are contemplated. Composite part 310 may be patch 314. Part 304 and part 306 may be bonded to each other using bonding system 316. Bonding system 316 may include screen 318, template mask 320, applicator 322, caul plate 324, and heat source 326.
Openings 341 may have a size capable of allow beads 334 to pass through openings 341. Screen 318 also may have other parameters, such as, for example, without limitation, a screen weave, an opening between threads, a thread diameter, and/or other suitable parameters. These parameters may interact with bead size and adhesive properties, such as thickness, tackiness, surface tension, viscosity, and/or other adhesive properties.
Some small excess amount of adhesive 332 with thickness 338 prior to joining, greater than the diameter of beads 334 may be applied to reduce and/or eliminate potential air gaps that may occur during joining of composite part 305 and composite part 310. During joining of part 305 and part 310 parts may be under vacuum bag pressure or other pressure to squeeze out excess adhesive while maintaining a uniform bond line with thickness 332 very near a diameter of beads 334. This ensures adequate fill occurs above all surface area. Applying screen 318 and subsequent spreading process may avoid layer of adhesive and beads 336 from having thickness 338 that may result in a bond line that may be thicker than desired and weaker than desired.
After layer of adhesive and beads 336 has been formed, screen 318 and template mask 320 may be removed. Second surface 340 of composite part 310 may be placed in contact with first surface 328 of composite part 305. Beads 334 within layer of adhesive and beads 336 may maintain layer of adhesive and beads 336 with substantially thickness 338. Beads 334 may provide a structural element that may maintain thickness 338 at substantially the same level. Without beads 334 in layer of adhesive and beads 336, thickness 338 may become uneven in portions of area 330.
If composite part 305 and/or composite part 310 take the form of a metal or aluminum part, a different type of adhesive may be suitable. The particular adhesive selected may depend on the material of the parts being bonded to each other, the strength of the bond desired, and other suitable factors. Adhesives that may be used include, for example, without limitation, epoxy adhesives, urethane adhesives, acrylic adhesives, and other suitable adhesives.
For example, in some advantageous embodiments, the use of caul plate 324 may be unnecessary during the curing process. In yet other advantageous embodiments, vent holes may be formed in composite part 310 when composite part 310 takes the form of a patch. Vent holes may help squeeze out air trapped within layer of adhesive and beads 336. In yet other advantageous embodiments, structure 307 may be bagged for the curing process. Bagging may help to compress the bond line to the minimum thickness allowed by beads 334.
Turning next to FIG. 5, a diagram of a cross-sectional view of a structure with a layer of adhesive and beads is depicted in accordance with an advantageous embodiment. In this illustrative example, surface 404 of part 400 may be placed into contact with surface 500 of part 502. Part 502 may be, for example, a patch or other repair piece for part 400.
In some advantageous embodiments, thickness 422 may be greater than diameter 418. With this type of implementation, layer of adhesive and beads 420 may reduce in value to thickness 506 based on diameter 418 of beads 414.
Turning to FIG. 11, a diagram illustrating removal of a screen from a part with adhesive is depicted in accordance with an advantageous embodiment. In this illustrative example, screen 1002 has been removed from part 1000. Adhesive layer 1100 remains on surface 1004. In some advantageous embodiments, adhesive layer 1100 may take the form of an activator.
The process may begin by placing a mask onto the first surface of a first part (operation 1300). The process may then place a screen onto the mask to form an exposed area on the first surface of the first part (operation 1302). The process may then apply an adhesive and a plurality of beads onto the first surface of the first part through the screen to form a layer of adhesive and beads (operation 1304). The screen may be removed leaving the layer of adhesives and beads on the first surface of the first part (operation 1306).
For example, operation 1306 may be omitted to leave the screen and beads in place when placing the first surface in contact with the second surface. In yet other advantageous embodiments, the layer of adhesive may be placed through the screen without beads and the screen left in place. For example, in some advantageous embodiments, adhesive also may be applied to the second surface of the second part.
Thus, the different advantageous embodiments provide a method and apparatus for bonding parts to each other. The different advantageous embodiments may provide a capability to create a layer of adhesive that may have a thickness that is around a substantially desired value. Further, the use of beads in the adhesive may maintain the layer of adhesive with the value for the desired thickness. Further, when pressure is applied to the parts, the layer of adhesive and beads may maintain a substantially uniform thickness throughout.
Attention is now directed to FIGS. 15 and 16 which illustrate a composite skin panel 312 such as that which may be found on an airplane. In this example, the skin panel 312 has a localized area 312a that is to be reworked. As used herein, “rework”, “reworked” and “reworking” are used in their broadest sense and are intended to include, without limitation, rework, repair, restoration, improvements and modifications that may either return a structure to its original loading carrying ability and/or specifications, or improve or increase the performance of the structure in one or more respects. In the illustrated example, the area 312a is a depression 328a (FIG. 16) which extends down from the outer surface 328 into several plies 312b of the skin panel 312.
The rework may begin by reworking a section 1500 (FIG. 15) generally surrounding the area 312a requiring rework. Referring to FIG. 17, a template mask 320 includes a central opening 320a, which in the illustrated example, is substantially circular, however other shapes of openings are possible, depending on the application. The central opening 320a may serve as both a sanding template during the preparation of the surface 328 of the skin panel 312, and as a template for centering a patch 314 (FIG. 18) over the area 312a requiring rework. The template mask 320 further includes ring shaped, intermittent perforations 320b concentrically surrounding the central opening 320a. The ring shaped perforations 320b may be used to mark the outer boundary on the surface 320a where paint is to be removed from the skin panel 312 as part of the rework process. Further details of the process for preparing the surface 328 to receive the bonded patch 314 will be discussed below in more detail.
FIG. 18 illustrates a patch 314 suitable for reworking the area 312a on the skin panel 312 shown in FIGS. 15-17. In this example, the patch 314 is substantially circular and includes a plurality of through hole perforations 314a that are distributed across the patch 314. As will be discussed below, the perforations 314a may allow the escape of air 1800, as shown by arrows 1802 from beneath the patch 314 as it is being compacted against the surface 328 of the skin panel 312 during the patch installation process. Desirably, each of the perforations 314a may have a diameter or maximum width “w” that is sufficiently great to also allow the escape of excess adhesive 1804 from beneath the patch 314.
Referring now to FIG. 19, the patch 314 may comprise multiple plies 314b of pre-cured composite materials. The patch 314 is bonded to the skin panel 312 overlying the area 312a to be reworked by a layer of viscous adhesive 336 forming a bond line 337 having a controlled thickness 338. As used herein, “viscous” refers to the fact that the adhesive 336 is spreadable and may flow to some degree as force is applied to it. The layer of adhesive 336 may be a fast curing type of adhesive tailored to the particular application by selecting predetermined viscosity, tackiness and surface tension properties in its uncured state. The viscosity and tackiness of the adhesive 336 should be such that it will stick to the skin panel 312 and/or the patch 314, yet remain flowable during completion of the patch installation process.
The adhesive may include the previously discussed beads 334, and/or a screen 318 (see FIG. 3). The screen 318 and/or the beads 334 function as a spacer 339 having a thickness that substantially corresponds to the desired thickness 338 of the bond line 337. In other embodiments, the screen 318 may be used to apply adhesive 332 to the controlled thickness 338 of the desired bond line 337, following which the screen 318 may be removed prior to the application of the patch 314, in which case the remaining beads 334 assist in controlling the thickness 338 of the bond line 337. The layer 336 of adhesive 332 and beads 334 substantially fill the area 312a being reworked, including the depression 328a (FIG. 16) in the skin panel 312.
Attention is now directed to FIGS. 20 and 21 which illustrate a caul plate 324 placed over the patch 314 in preparation for compacting the patch 314 down onto the surface 328 of the skin panel 312. In accordance with the disclosed embodiments, a ring shaped anti-caul plate 2000 is placed between the caul plate 324 and the surface 328 of the skin panel 312, near the outer perimeter 2002 of the caul plate 324, so as to support the caul plate 324 at its outer perimeter 2002. The interior edge 2004 of the anti-caul plate 2002 is radially spaced slightly outside of the outer periphery 2006 of the patch 314. The anti-caul plate 2000 has a thickness “t” substantially equal to the combined thickness 314c of the patch 314 and the desired thickness 338 of the bond line 337. The bottom surface 2012 (FIG. 20) of the anti-caul plate 2000 engaging the surface 328 of the skin panel 312 is shown as being flat in the illustrated example, however the bottom surface 2012 may have other shapes or contours that may be selected to match the shape/contour of the surface 328 of the skin panel 312. In the illustrated example, the anti-caul plate 2000 has the shape of a continuous ring (see FIG. 21), however other shapes are possible. Also, in other embodiments the anti-caul plate 2000 may comprise two or more contiguous or spaced part sections (not shown) which support the outer perimeter 2002 of the caul plate 324 at multiple locations around the patch 314.
The anti-caul plate 2000 functions to react force applied by the caul plate 324 to the patch 314 near the outer periphery 2006 of the patch 314. By supporting the outer perimeter 2002 of the caul plate 324, the anti-caul plate 2000 may reduce or prevent substantial tipping, slanting and/or bending of the caul plate 324. As a result of controlling this force at the outer periphery 2006 of the patch 314, the force 2010 applied to the caul plate 324 is substantially constant over substantially the entire area of the patch 314. Consequently, the tendency of the caul plate 324 to apply higher forces near the outer periphery 2006 of the patch 314 (due to bending, tipping, slanting, etc.) may be avoided, which could otherwise result in tapering of the bond line 337 near the outer periphery 2006 of the patch 314. Therefore, the thickness 338 of the bond line 337 may remain substantially constant over the entire area of the patch 314 during the compaction process.
At step 2306, a screen 318 may be placed over the prepared surface, overlying the template mask 320, in preparation for the application of adhesive. At 2308, optionally, the previously discussed beads 334 may be mixed into at least one component of the adhesive 332 and at 2310, the component parts of the adhesive 332 may be mixed together to form a relatively quick drying bonding adhesive. In some embodiments, the adhesive 332 may comprise only one component, in which case the beads 334 may be mixed into the single component. Next, at 2312, a layer of the adhesive 332, optionally containing the beads 334, may be spread over the prepared skin surface 328 and/or to the patch 314 using an applicator 322 which may comprise, for example and without limitation, a toothed trowel (not shown) that may be used to achieve a predetermined thickness of the adhesive. In those applications where the optional screen 318 is employed, a slightly larger, excess amount of adhesive than is ultimately needed may be applied in order to reduce the possibility of air pockets, since the screen 318 may be used to control the final thickness of the adhesive layer 336. The trowel may be used to evenly spread the adhesive over the structure surface 328 and the patch 314. The template mask 320 may be used to control the shape and location of the adhesive layer 336 applied to the structure surface 328. It should be noted here that the template mask 320 and the screen 318 may be combined into as single component and manufactured using well known photolithographic techniques.
At 2314, the patch 314 is centered over the rework area 312a using the template mask 320 and the patch 314 is applied by hand to the structure surface 328, using the template mask 320 as a guide to locate and center the patch. Next, a peel ply (not shown) may be placed over the patch 314, following which, at 2318, the caul plate 324 and the anti-caul plate 2002 may be installed, as shown in FIG. 20.
As pressure is applied to the patch 314 by the caul plate 324, the anti-caul plate 2000 reacts the force applied near the periphery 2006 of the patch 314 so that the pressure applied over the entire area of the patch 314 may be substantially uniform. Further, as pressure is applied to the patch 314 during the compaction and curing process, the beads 334 and/or the screen 318 function as a spacer 339 to partially react the applied force which results in a desired thickness 338 of the bond line 337.
Attention is now directed to FIG. 24 which illustrates, in block diagram form, the components of a prepackaged rework kit 2400 that may be used by personnel to perform relatively rapid reworking of composite skin panels or similar structures in the field. The kit 24 may include a preconfigured doubler patch 314, a pre-measured amount of beads 334, a mesh-like screen 318, a template mask 320, an adhesive applicator such as a tooth trowel 322, a bonding adhesive 332 including pre-measured amounts of multiple reactive parts 332a, 332b, a heat pack 326a for use in curing the adhesive, a compaction device 2200 for applying pressure to the patch, a paint replacement film 240 that may be used to replace any paint on the skin surface that was previously removed, and any number of additional supplies 2402 such as cleaning supplies, solvents, gloves, release films, etc. that may be necessary to carry out the rework described above.
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