Patent Description:
It may be necessary to shim or fill the gap between components joined together. One technique for doing so involves using a peelable polyimide solid shim. Producing and applying such solid shims is a laborious task because it may involve manual gap measurement followed by manual sculpting of a peelable sheet material to varying shapes and thicknesses. These peelable shim materials may also be relatively expensive.

Another technique includes applying a paste or "butter" into the gap. This type of shim may be difficult to apply in a large joint, and further down the line, may be difficult to clean due to its highly viscous nature. Since it is difficult to apply, there is a risk of uneven application and of non-structural voids which must be detected and repaired.

An example of a document which describes means for compensating uneven surfaces to allow joining of a structure and an anchor, by using a settable material, can be found in <CIT>.

Aspects of the invention provide a liquid shim and a method as claimed in the appended claims.

According to an embodiment of the disclosure, a liquid shim comprises a bag defining a closed inner volume and having sealed openings spaced inwardly from a periphery of the bag. The sealed openings may be sealed from the closed inner volume and delimit holes extending through the bag. The liquid shim material may be flowable through the closed inner volume around the sealed openings and may be curable to form a solid. The liquid shim material may have a liquid shim material volume being less than the closed inner volume of the bag.

In an embodiment, the periphery of the bag includes a peripheral portion defining a peripheral edge of the bag. The peripheral portion may be temporarily closeable to decrease the closed inner volume. The peripheral portion may be expandable.

In an embodiment the peripheral portion is folded about a fold line spaced inwardly from the peripheral edge. The peripheral portion may be unfoldable about the fold line to close and expand the peripheral portion.

In an embodiment, a pressure within the bag is approximately zero.

The method may comprise permanently fastening the components together over the solid shim after removing the sealed bag from the solid shim.

The method may comprise removing the sealed bag from a cold-storage unit before positioning the sealed bag in the gap.

In an embodiment, displacing the components towards one another includes compressing portions of the sealed bag to further compress the liquid shim material and fill the gap.

In an embodiment, curing the compressed liquid shim material includes one or more of exposing the compressed liquid shim material to ambient temperature, and applying localized heat to the compressed liquid shim material.

In an embodiment, curing the compressed liquid shim material includes exposing the compressed liquid shim material to ambient temperature, and subsequently, applying localized heat to the compressed liquid shim material.

In an embodiment, curing the compressed liquid shim material includes applying localized heat to the compressed liquid shim material using one or more of convection heating, infra-red heating, and electrical-resistance heating.

According to a further aspect of the disclosure, a method of creating a liquid shim, comprises providing a liquid shim material into a sealed bag, the liquid shim material being flowable through an inner volume of the sealed bag and being curable to form a solid, the liquid shim material having a liquid shim material volume being less than the inner volume of the sealed bag.

In an embodiment, providing the liquid shim material into the sealed bag includes providing the liquid shim material into the sealed bag while reducing a pressure of the inner volume of the sealed bag.

In an embodiment, providing the liquid shim material into the sealed bag includes injecting the liquid shim material into the sealed bag.

In an embodiment, providing the liquid shim material into the sealed bag includes providing the liquid shim material into the sealed bag while reducing a pressure of a volume of air surrounding the sealed bag.

The method may comprise closing a portion of the sealed bag to decrease the inner volume of the sealed bag.

In an embodiment, closing the portion of the sealed bag includes closing the portion of the sealed bag before providing the liquid shim material into the sealed bag.

The method may comprise opening the portion of the sealed bag after providing the liquid shim material into the sealed bag.

In an embodiment, providing the liquid shim material into the sealed bag includes spreading the liquid shim material through the inner volume of the sealed bag.

The method may comprise forming holes sealed from the inner volume and extending through the sealed bag before providing the liquid shim material into the sealed bag.

In an embodiment, forming the holes includes heat sealing the holes.

The method may comprise storing the liquid shim material in a cold-storage unit.

According to a still further aspect of the disclosure there is provided a joint between components defining a gap therebetween, the joint comprising a cured shim disposed within the gap and having a shape substantially similar to a shape of the gap, the cured shim having holes extending therethough, the joint having fasteners connecting the components and extending through the holes in the cured shim.

One or more embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying figures in which:.

Referring to the drawings and more particularly to <FIG>, an aircraft is shown at <NUM>, and is generally described to illustrate some components in the present disclosure. The aircraft <NUM> has a fuselage <NUM> having a fore end at which a cockpit is located, and an aft end supporting a tail assembly. The tail assembly comprises a vertical stabilizer <NUM> with a rudder, and horizontal stabilizers <NUM> with elevators. The tail assembly has a fuselage-mounted tail, but other configurations may also be used for the aircraft <NUM>, such as cruciform, T-tail, etc. Wings <NUM> project laterally from the fuselage <NUM>. The aircraft <NUM> has engines <NUM> supported by the wings <NUM>, although the engines <NUM> could also be mounted to the fuselage <NUM>. The aircraft <NUM> is shown as a jet-engine aircraft, but may also be a propeller aircraft. The fuselage <NUM> defines a cabin <NUM> generally located between the cockpit and the tail assembly. The aircraft <NUM> has doors <NUM> configured to allow ingress to, and egress from, the cabin <NUM>.

Referring to <FIG>, the aircraft <NUM> has joints <NUM> formed between adjacent components of the aircraft <NUM>. The joints <NUM> may be formed between two or more components of the aircraft <NUM>, whether the components are made from the same materials or different materials (e.g. composites and metal). One example of a possible joint <NUM> is shown in <FIG> shows the joint <NUM> formed between a front wing spar 5A of one of the wings <NUM>, a rib 5B of the same wing <NUM>, and part of the wing skin 5C.

<FIG> shows a magnified view of a portion of <FIG> in the region of the joint <NUM> between the front wing spar 5A and the wing skin 5C. As a result of the manufacture and assembly process, a gap 9A may form between the front wing spar 5A and the wing skin 5C. This gap 9A is filled by a shim <NUM>. Shimming may be required between structures (such as the wing skin 5C and the front wing spar 5A). For some aircraft components, shimming is required to fill gaps between the components that occur when assembling them together, and/or when assembling components such as actuators, hinges, and brackets to a structure.

The shim <NUM> is a solid body that has a three-dimensional shape that is substantially similar to the three-dimensional shape of the gap 9A. By "substantially similar", it is understood that the shim <NUM> conforms to the shape of the gap 9A within acceptable limits or tolerances, such as those of the Gapman™ measuring system. The solid shim <NUM> occupies substantially all of the volume of the gap 9A and may abut against some or all of the surfaces of the components of the joint <NUM>. The formation of the solid shim <NUM>, and its placement in the gap 9A, are described in greater detail.

<FIG> show a liquid shim <NUM>. The liquid shim <NUM> includes a liquid shim material <NUM> which is flowable to assume the shape of the gap 9A to be filled. The liquid shim material <NUM> has a viscosity that allows for it to flow under pressure to fill the gap 9A. The liquid shim material <NUM> is considered "liquid" because of its ability to flow or be displaced in conditions where it is positioned in the gap 9A. The viscosity of the liquid shim material <NUM> is high enough so that after it has been deformed under pressure, it remains deformed. The liquid shim material <NUM> is also curable to form a solid object, such as the solid shim <NUM> described above. Once cured, the liquid shim material <NUM> is no longer "liquid" or flowable, and remains in the shape it forms when it cured. The liquid shim material <NUM> may cure under any suitable conditions depending on the liquid shim material <NUM> being used. For example, the liquid shim material <NUM> may cure upon being exposed to room/ambient temperatures for a duration of time, or by being heated. For example, the liquid shim material <NUM> may have liquid-like properties (i.e. is flowable) at cold temperatures, and may cure at room temperature to solidify into the solid shim <NUM>. The liquid shim material <NUM> may provide electrical or thermal insulation properties when cured into the solid shim <NUM>. Examples of the liquid shim material <NUM> include, but are not limited to, Henkel EA9377, EA <NUM>, and <NUM> EC7272 Magabond <NUM>.

The liquid shim <NUM> has a bag <NUM> which contains the liquid shim material <NUM>. The bag <NUM> is a body which is impermeable to the liquid shim material <NUM> in order to contain the liquid shim material <NUM>, and to isolate it from the environment surrounding the bag <NUM>. The bag <NUM> is non-porous. The bag <NUM> is transparent to see the liquid shim material <NUM> therein. The bag <NUM> may be made from any suitable material to accomplish such functionality. For example, the bag <NUM> may be made from suitable polymeric materials.

The bag <NUM> defines an inner volume <NUM>. The liquid shim material <NUM> is disposed in the inner volume <NUM> of the bag <NUM>. As described in more detail below, the liquid shim material <NUM> is added to the inner volume <NUM> of the bag <NUM>. The liquid shim material <NUM>, before being cured, is free to flow through the inner volume <NUM> to assume the shape of the gap 9A to be filled. After receiving the liquid shim material <NUM>, the bag <NUM> forms a closed body that is sealed. The inner volume <NUM> then becomes a closed volume. The liquid shim material <NUM> is thus sealed from the environment outside the bag <NUM> by the closed body of the bag <NUM>. Air, fluids, and solids from outside of the bag <NUM> are thus prevented from entering the inner volume <NUM> and contaminating the liquid shim material <NUM>. In <FIG>, the pressure within the bag <NUM>, and thus of the inner volume <NUM>, is approximately zero. A substantial vacuum is present within the bag <NUM>, which may allow the liquid shim material <NUM> to be displaced unhindered within the inner volume <NUM>.

The liquid shim material <NUM> has a volume that is less than the closed inner volume <NUM> of the bag <NUM>. The liquid shim material <NUM> occupies less than an entirety of the closed inner volume <NUM> of the bag <NUM>. The smaller volume of the liquid shim material <NUM> allows the liquid shim material <NUM> to flow through the bag <NUM>, and to change shape to fill the gap 9A when the bag <NUM> is compressed, as explained in greater detail below. In some embodiments, the volume of the liquid shim material <NUM> is only slightly less than the inner volume <NUM>.

In <FIG>, the bag <NUM> has a rectangular shape. The bag has a first wall 28A, a second wall 28B spaced apart from the first wall 28A across the inner volume <NUM>, and side edges 28C that join the first and second walls 28A, 28B. The side edges 28C are peripheral edges of the bag <NUM> in <FIG>. The side edges 28C define a periphery P of the bag <NUM> in <FIG>. In an alternate embodiment, the side edges 28C are part of side walls of the bag <NUM> which extending between the first and second walls 28A, 28B. The joined first wall 28A, the second wall 28B, and the side edges 28C delimit the closed inner volume <NUM> of the bag <NUM>. Other shapes for the bag <NUM> are possible. For example, in an alternate embodiment, the bag <NUM> is cylindrical. For example, in another alternate embodiment, the bag <NUM> is spherical.

Referring to <FIG>, the bag <NUM> includes one or more peripheral portions <NUM> that define a peripheral edge PE of the bag <NUM>. Each peripheral portion <NUM> is a segment of the bag <NUM> that is hollow to receive therein the liquid shim material <NUM>, and which is closed off to the surrounding environment. The peripheral portion <NUM> is closeable to temporarily reduce the inner volume <NUM> of the bag <NUM> through which the liquid shim material <NUM> may flow, and is expandable to increase a volume of the peripheral portion <NUM> and thereby increase, or restore, the inner volume <NUM> of the bag <NUM>. Temporary closing off portions of the inner volume <NUM>, as shown in <FIG>, allows for reducing the inner volume <NUM> when there is less need for the liquid shim material <NUM> to flow through the bag <NUM>, while expanding the peripheral portions <NUM>, as shown in <FIG>, allows for restoring the full inner volume <NUM> of the bag <NUM> at a later time to provide more space into which the liquid shim material <NUM> may displace when the liquid shim <NUM> is placed into the gap 9A.

The expansion of the peripheral portions <NUM> may take different forms. For example, and as shown in <FIG>, the peripheral portions <NUM> are folded about a fold line FL that is spaced inwardly from the peripheral edge PE. The fold line FL may be pre-formed with the bag <NUM> or created when the peripheral portion <NUM> is folded. When the peripheral portions <NUM> are folded about the fold line FL, the fold line FL forms a temporary peripheral edge of the bag <NUM>, as shown in <FIG>. As shown in <FIG>, each peripheral portion <NUM> extends inwardly into the bag <NUM> from one of the side edges 28C of the bag <NUM>. The side edges 28C define some of the peripheral edges PE of the bag <NUM>. Each peripheral portion <NUM> extends between one of the side edges 28C and its fold line FL. The fold line FL is parallel to the side edge 28C.

When the peripheral portions <NUM> are folded about the fold line FL, as shown in <FIG>, the inner volume <NUM> is reduced. The peripheral portion <NUM> in its folded position is temporarily attached to one of the first and second walls 28A, 28B such as with tape, and unattached therefrom when it is desirable to expand the peripheral portion <NUM> and restore the inner volume <NUM>. The inner volume <NUM> in <FIG> is thus reduced to a first value when the peripheral portions <NUM> are closed or folded about the fold line FL, and the inner volume <NUM> has second value in <FIG> greater than the first value when one or more the peripheral portions <NUM> is expanded or unfolded about the fold line FL. In an embodiment, the liquid shim <NUM> is initially provided for use in filling the gap 9A with the peripheral portions <NUM> folded or "pinched". Once placed in the gap 9A, the peripheral portions <NUM> are then unfolded about the fold line FL to restore the inner volume <NUM> and permit the liquid shim material <NUM> to flow through the entire inner volume <NUM> if needed.

Other techniques for expanding the peripheral portions <NUM> are also possible. In an alternate embodiment, the peripheral portion <NUM> is defined by portions of the first and second walls 28A, 28B that are temporarily stuck together, and which are separable from each other to restore the inner volume <NUM>. In another alternate embodiment, the bag <NUM> has a temporary seal, in place of the fold line FL, which separates the liquid shim material <NUM> from the peripheral portions <NUM>. In such an embodiment, the seal may be broken to allow for expansion of the peripheral portions <NUM> and for the liquid shim material <NUM> to flow therein.

Referring to <FIG>, the bag <NUM> has one or more sealed openings <NUM>. The sealed openings <NUM> are voids that extend through the bag <NUM>, and thus define holes <NUM> or channels extending through the bag <NUM>. The holes <NUM> receive locating fasteners that are used to mount the bag <NUM> to the components that need to be shimmed, as described in greater detail below. The sealed openings <NUM> are all spaced inwardly from the periphery P or peripheral edge PE of the bag <NUM>. The sealed openings <NUM> are disposed along the body of the bag <NUM> and not along its periphery P. They are "sealed" because the sealed openings <NUM> are closed off from a remainder of the interior of bag <NUM>. The sealed openings <NUM> are not in fluid communication with the inner volume <NUM> or with the liquid shim material <NUM> therein. Each of the sealed openings <NUM> defines a closed seal separating the corresponding hole <NUM> from the inner volume <NUM> of the bag <NUM>. Each of the sealed openings <NUM> is defined by an edge with a closed periphery or boundary that is spaced inwardly from the periphery P of the bag <NUM>. The holes <NUM> cannot communicate with the interior of the bag <NUM> and vice versa. Therefore, when the liquid shim material <NUM> flows through the inner volume <NUM>, it will flow around the sealed openings <NUM> and their holes <NUM>. Any suitable technique may be used to form the sealed openings <NUM>. In an embodiment, and referring to <FIG>, the sealed openings <NUM> are formed using a heat sealing tool <NUM> applied against the first and second walls 28A, 28B of the bag <NUM>. This causes the first and second walls 28A, 28B to fuse together and form a seal or edge delimiting the hole <NUM>. The holes <NUM> are thus defined through, and by, the interconnected first and second walls 28A, 28B. The one or more of the sealed openings <NUM> may thus have a heat seal 23A. Another possible technique includes forming channels with the sealed openings <NUM> which extend along their own axes and have impermeable channel walls extending between the first and second walls 28A, 28B.

There is disclosed a method of shimming the gap 9A between components. Referring to <FIG>, the gap 9A is defined as part of the joint <NUM> between the front wing spar 5A and the wing skin 5C. The method thus relates to using the liquid shim <NUM> to fill gaps 9A between adjacent parts within the aircraft <NUM>. The method may also be used to shim the gap formed between other components, and between components of other types of vehicles.

The method includes positioning the sealed bag <NUM> containing the liquid shim material <NUM> in the gap 9A, as shown in <FIG>. In <FIG>, this includes placing the holes <NUM> sealed from the inner volume <NUM> of the bag <NUM> over fasteners 9E attached to one more of the components. The liquid shim <NUM> is placed into the gap 9A by mounting the bag <NUM> by its holes <NUM> onto the fasteners 9E of the wing skin 5C, for example. Once the liquid shim <NUM> has been positioned in the gap 9A and its holes <NUM> aligned with the temporary fasteners 9E, the bag <NUM> may be taped to adjacent structure to prevent it from displacing. The fasteners 9E may be temporary and used only to position the liquid shim <NUM>. The function of the temporary fasteners 9E is to "tack" the mating components together to enable a first fit of the components. The location and positioning of the holes <NUM> in the bag <NUM> are predetermined and correspond to predrilled areas on the components. The holes <NUM> are located in line with predrilled and temporary assembly holes in the components. The holes <NUM> are also used to ensure that the solid shim <NUM> is correctly located in position during final drilling and fastening. Alternatively, the fasteners 9E may be the same fasteners used to permanently attached the front wing spar 5A to the wing skin 5C.

In an alternate embodiment, the sealed bag <NUM> is positioned in the gap 9A without using the fasteners 9E. In such an embodiment, the liquid shim <NUM> is positioned into the gap 9A by placing it on a component and using gravity to hold it in place, or temporarily taping it in place. For example, the sealed bag <NUM> containing the liquid shim material <NUM> may be placed between two mating surfaces with no hole in the liquid shim <NUM>, and tape may be used to stop the bag <NUM> from slipping out of the joint <NUM> if, for example, the joint <NUM> is vertical. The liquid shim <NUM> will become solid and the joint <NUM> may, or may not, be drilled. In the case of a drilled joint, the solid shim <NUM> may be relocated after trimming using the drilled holes. For a non-drilled joint, the solid shim <NUM> may be relocated using the footprint of the liquid shim <NUM>.

Before positioning the sealed bag <NUM>, it may be desirable or necessary to remove the liquid shim <NUM> from a storage unit. In an embodiment, the liquid shim <NUM> is removed from a cold-storage unit, such as a freezer, before being positioned in the gap 9A.

Referring to <FIG>, the method includes displacing the components towards one another. The components may all displace toward each other to close the gap 9A, or only one of the components may displace toward the other component(s) (i.e. a relative displacement) to close the gap 9A. In <FIG>, only the wing skin 5C is displaced in direction D toward the front wing spar 5A. The components displace and contact the bag <NUM> to squeeze the bag <NUM>. This applies pressure to the bag <NUM>. The pressure applied to the closed bag <NUM> compresses the bag <NUM> and its contents (i.e. the liquid shim material <NUM>), to thereby cause the liquid shim material <NUM> to displace and substantially fill the gap 9A, as shown in <FIG>. The components may then be temporarily assembled using the fasteners 9E so that the pressure is maintained and the liquid shim material <NUM> is squeezed to fill out the inner volume <NUM>, and thereby assume the shape of the gap 9A to have the same thickness as the gap 9A throughout the extent of the gap 9A. In the depicted embodiment, the components are moved towards each other along the fasteners 9E. In an alternate embodiment, another device, such as an expandable bladder, is used to close the gap 9A and compress the bag <NUM>, which may be secured in place using any suitable technique.

Before positioning the liquid shim <NUM> in the gap 9A, while it is in the gap 9A, while the components are being displaced, or after the components have been displaced, the inner volume <NUM> may be increased (or restored, depending on the configuration of the bag <NUM> in the gap 9A). As described above, increasing or restoring the inner volume <NUM> may be done by expanding one or more of the peripheral portions <NUM> of the bag <NUM>. Before or during the removal of the liquid shim <NUM> from the cold-storage unit, the peripheral portions <NUM> may be expanded. When the liquid shim <NUM> is in the gap 9A and being compressed by the components, portions of the bag <NUM> may be further compressed to additionally compress the liquid shim material <NUM> and fill the gap 9A. It may occur that the liquid shim material <NUM> has not filled up all of the gap 9A, or has not filled up all of the gap 9A to the desired thickness. In such a situation, a portion of the bag <NUM> nearest the unfilled part of the gap 9A, such as one of the peripheral portions <NUM>, may be squeezed to cause more liquid shim material <NUM> to flow into the unfilled part of the gap 9A. The portion of the bag <NUM> may be squeezed by hand, with a clamp, clip, or using any other suitable technique or tool. The bag <NUM> may therefore be used to apply pressure back inside the bag <NUM> after the liquid shim <NUM> has already been assembled in the joint <NUM>, to help ensure that any sagging/wrinkles in the bag <NUM> are removed. The bag <NUM> and/or its peripheral portions <NUM> allow for re-pressurizing parts of the bag <NUM>.

Referring to <FIG>, the method includes curing the squeezed or compressed liquid shim material <NUM> while it is still within the sealed bag <NUM> in order to become the solid shim <NUM>, which fills the gap 9A. The solid shim <NUM> is thus formed within the bag <NUM>. The liquid shim material <NUM> may be cured or solidified using any suitable techniques. For example, in the depicted embodiment, the liquid shim material <NUM> cures when exposed, for a given period of time, to the room or ambient temperature of the environment around the joint <NUM>. Another possible technique for curing the liquid shim material <NUM> in the gap 9A includes preheating the liquid shim material <NUM> before placing it in the gap 9A to accelerate the curing process. This involves heating the liquid shim material <NUM> while it is still in the bag <NUM>. Yet another possible technique for curing the liquid shim material <NUM> includes applying localized heat to the compressed liquid shim material <NUM> while it is in the gap 9A and being compressed. This involves heating the liquid shim material <NUM> while it is still in the bag <NUM>. Heating the liquid shim material <NUM> may accelerate the time it takes for it to cure and form the solid shim <NUM>. For example, every 10ºC increase in the cure temperature may decrease the time needed for curing by half.

It will be appreciated that one or more of these techniques may be performed at the same time. For example, in an embodiment, the liquid shim material <NUM> is left to cure by being exposed, for a short setting time, to the room or ambient temperature of the environment around the joint 9A. After the short setting time ends, heat is applied to accelerate and achieve full cure. Full cure in this instance is a state where the shim <NUM> is solid enough such that fastener compression forces may be applied.

<FIG> show possible techniques for heating the liquid shim material <NUM> while it is in the gap 9A. <FIG> shows the bag <NUM> containing the liquid shim material <NUM> in the gap 9A between the front wing spar 5A and the wing skin 5C. An electric wire 13A runs through the inner volume <NUM> of the bag <NUM> and through the liquid shim material <NUM>. The electric wire 13A is thus embedded in the bag <NUM> and the liquid shim material <NUM>. Seals 13B are applied as needed where the electric wire 13A pierces the bag <NUM>. Referring to <FIG>, the liquid shim material <NUM> may generate resistance when exposed to an electrical current, such that current passing through the electric wire 13A causes the liquid shim material <NUM> to heat up. Referring to <FIG>, the liquid shim material <NUM> may include conductive materials, such as conductive nano-materials, carbon nanotubes, and conductive microplates, such that current passing through the electric wire 13A causes the liquid shim material <NUM> to heat up. Referring to <FIG>, a metal 13C in liquid or powder form may be sprayed or otherwise applied to the surface of the bag <NUM> to provide electrical conductivity. A thin film may be coated over the metal 13C to provide insulation. A current passing through the electric wire 13A may excite the metal 13C and cause the liquid shim material <NUM> to heat up. It will be appreciated that one or more of these techniques may be used at the same time. Other techniques may also be used to heat the liquid shim material <NUM> while it is in the gap 9A. For example, a hot air blower may apply convection heating to the bag <NUM>. In another example, an infra-red lamp may be used to apply infra-red heating to the bag <NUM>.

In the embodiment where the liquid shim <NUM> is mounted on the locating fasteners 9E, as shown in <FIG>, the liquid shim <NUM> may be cured while positioned on the fasteners 9E. The bag <NUM> containing the cured, solid shim <NUM> may then be removed off the fasteners 9E. This allows for further processing to be done to the solid shim <NUM> away from the joint <NUM>. For example, the bag <NUM> may be removed from the solid shim <NUM>, and the solid shim <NUM> may be trimmed as needed. The solid shim <NUM>, now without the bag <NUM>, may then be placed back into the gap 9A and located in the desired position using the same locating fasteners 9E. The solid shim <NUM> has holes extending through the solid shim <NUM> which correspond to the location of the holes <NUM> in the bag <NUM>. The holes in the solid shim <NUM> are formed while curing the liquid shim material <NUM>, which was disposed around the fasteners 9E. The components (e.g. the wing skin 5C and the front wing spar 5A) may then be permanently assembled around the solid shim <NUM>. The thickness and/or density of the solid shim <NUM> may then be measured or tested.

In an alternate embodiment, the cured, solid shim <NUM> is processed while still within the gap 9A of the joint <NUM>. The bag <NUM> is therefore removed from the solid shim <NUM> while it is in the gap 9A, whether or not the solid shim <NUM> is mounted about the fasteners 9E. The solid shim <NUM> may also be trimmed or shaved while in the gap 9A. After the desired processing has been performed, the cured, solid and prepared shim <NUM> is all that is left in the gap 9A. The thickness and/or density of the solid shim <NUM> may then be measured or tested. The components (e.g. the wing skin 5C and the front wing spar 5A) may then be permanently assembled around the solid shim <NUM>.

Irrespective of whether the solid shim <NUM> is processed within the gap 9A or away from the gap 9A, an interfay sealant may be applied to the solid shim <NUM> to compensate for the thickness of the bag <NUM> that has been removed, so that the solid shim <NUM> alone has substantially the same thickness as the solid shim <NUM> and the bag <NUM> did when positioned in the gap 9A. <FIG> show one possible technique for trimming or fitting the solid shim <NUM>. Referring to <FIG>, clamps C are removed from the peripheral portions <NUM>, for example. Referring to <FIG>, the freshly-set solid shim <NUM> is removed from the gap 9A, and then the bag <NUM> is removed as shown in <FIG>. The solid shim <NUM> is then trimmed to its desired shape, as shown in <FIG>. If desired or necessary, the solid shim <NUM> may be baked in an oven to further cure, for example at 40ºC.

The components may be displaced away from each other to increase the size of the gap 9A, and facilitate either the removal of the solid shim <NUM> from the gap 9A or the processing of the solid shim <NUM> within the gap 9A. For example, after curing the liquid shim material <NUM> to form the solid shim <NUM>, the wing skin 5C may be removed. In another example, actuators may be used to displace the wing skin 5C in a direction opposite to the direction D a distance away from the front wing spar 5A. The components may all displace away from each other to increase the size of the gap 9A, or only one of the components may displace away from the other component(s) (i.e. a relative displacement) to increase the size of the gap 9A.

One possible sequence for mounting and curing the sealed bag <NUM> onto the fasteners 9E is shown in <FIG> shows the joint <NUM> between the wing skin 5C and the front wing spar 5A, and the gap 9A defined between these two components. The gap 9A in the depicted embodiment is tapered, such that its height varies along the gap 9A. Referring to <FIG>, the liquid shim <NUM> is placed into the gap 9A by mounting the bag <NUM> by its holes <NUM> onto the temporary fasteners 9E extending through holes 5F in both the wing skin 5C and the front wing spar 5A. Movement limiters <NUM> are mounted on either side of the bag <NUM> to constrain expansion of the liquid shim <NUM> and keep it confined to the gap 9A. The movement limiter <NUM> may be, for example, a solid shim <NUM> or another liquid shim <NUM>. The diameter of the temporary fasteners 9E is smaller than the diameter of the holes 5F in the wing skin 5C and the front wing spar 5A. The temporary fasteners 9E are thus "undersized", and used in this example only for positioning the liquid shim <NUM> in the gap 9A. Referring to <FIG>, the front wing spar 5A is brought closer to the wing skin 5C by rotating a nut <NUM> mounted about the fasteners 9E to drive the front wing spar 5A toward the wing skin 5C. During or prior to this movement, the peripheral portions <NUM> of the bag <NUM> may be expanded or opened to allow the liquid shim material <NUM> to flow therein. Referring to <FIG>, the temporary fasteners 9E are replaced with full-sized fasteners 9E' which have a larger diameter. The diameters of the full-sized fasteners 9E' is similar or equal to the diameter of the holes 5F in the wing skin 5C and the front wing spar 5A. Referring to <FIG>, the movement limiters <NUM> are removed from either side of the bag <NUM>, and liquid shim material <NUM> is allowed to fully expand in the bag <NUM> to fill the gap 9A. The liquid shim material <NUM> is then cured to form the solid shim <NUM>. If the full-sized fasteners 9E' are not the final fasteners used in the final assembly of the front wing spar 5A toward the wing skin 5C, the holes 5F may be enlarged to receive final fasteners. Such enlarged holes may have a diameter larger than that of the sealed openings <NUM>.

There is disclosed a method of creating the liquid shim <NUM>. Referring to <FIG>, the method includes providing the liquid shim material <NUM> into the sealed bag <NUM>. The liquid shim material <NUM> flows through the inner volume <NUM> and is curable to form the solid shim <NUM>. The liquid shim material <NUM> has a volume that is less than the inner volume <NUM>. Before providing the liquid shim material <NUM> to the bag <NUM>, the sealed openings <NUM> and the through-holes <NUM> defined thereby may be provided by heat sealing the holes <NUM>, such as by using the heat sealing tool <NUM> in <FIG>. The heat sealing tool <NUM> may be a heat press or punch that fuses the first and second walls 28A, 28B of the bag <NUM> together. The bag <NUM> may be formed using any suitable technique. For example, the first and second walls 28A, 28B may be fused together along their edges or along overlapping portions. In another example, the first and second walls 28A, 28B are taped together.

The liquid shim material <NUM> may be provided into the sealed bag <NUM> while reducing or eliminating a pressure of the inner volume <NUM>. The liquid shim material <NUM> may thus be provided while the bag <NUM> is under vacuum. A vacuum chamber may be setup to infuse the liquid shim material <NUM> into the bag <NUM>. The bag <NUM> may be filled within the liquid shim material <NUM> while it is within a vacuum chamber and while vacuum is applied to the inner volume <NUM>. Filling the bag <NUM> with the liquid shim material <NUM> in this manner may reduce or eliminate the risk of air being present in the bag <NUM>, which might hinder the flow of the liquid shim material <NUM> through the inner volume <NUM>. With little or no pressure within the bag <NUM>, the liquid shim material <NUM> may flow easier through the inner volume <NUM>.

Irrespective of whether the bag <NUM> is under vacuum or not, the liquid shim material <NUM> may be provided by injecting the liquid shim material <NUM> into the sealed bag <NUM>, as shown in <FIG>. In <FIG>, the bag <NUM> has a rectangular shape, and the liquid shim material <NUM> is injected with an injector <NUM> at one end of the bag <NUM>. The bag <NUM> in <FIG> is sealed and has an exhaust to allow air to exit the bag <NUM> as the inner volume <NUM> is being filled with the liquid shim material <NUM>. Once the bag <NUM> is filled with the liquid shim material <NUM> to the desired thickness, the exhaust is closed or sealed, and the bag <NUM> remains closed.

An example of a technique for filling the bag <NUM> under vacuum is shown in <FIG>. The empty bag <NUM> is placed inside a vacuum chamber <NUM> which has an opening 38A through which air is drawn out of the vacuum chamber <NUM> to create a vacuum therein. The injector <NUM> is inserted through another opening in the vacuum chamber <NUM> and the opening is closed with a seal 38B. An exit nozzle 38C is mounted to an end of the bag <NUM> opposite to the injector <NUM>. Air is drawn out of the bag <NUM> via the exit nozzle 38C to create a vacuum in the bag <NUM>. Referring to <FIG>, during or after the vacuum is created in the bag <NUM> and the vacuum chamber <NUM>, the liquid shim material <NUM> is injected with the injector <NUM> into the inner volume <NUM> of the bag <NUM>. The liquid shim material <NUM> is thus provided to the bag <NUM> while or after reducing the pressure of the volume of air in the vacuum chamber <NUM> around the bag <NUM>. With little or no pressure within the bag <NUM> and around the bag <NUM> inside the vacuum chamber <NUM>, the liquid shim material <NUM> is able to flow through the inner volume <NUM> without restriction.

If it is desired to distribute the liquid shim material <NUM> within the inner volume <NUM> so that the liquid shim material <NUM> has a uniform thickness, the liquid shim material may be spread through the inner volume <NUM>. Referring to <FIG>, a spreader <NUM> is used to apply pressure to one of the first and second walls 28A, 28B of the bag <NUM> to spread the liquid shim material <NUM> through the bag <NUM>. The spreader <NUM> has rollers <NUM> at its ends and a pin <NUM> extending between the rollers <NUM>. The rollers <NUM> have a diameter greater than the diameter of the pin <NUM>. When the spreader <NUM> is used on a flat surface, the rollers <NUM> space the pin <NUM> a desired distance from the flat surface. The desired distance becomes the thickness of the liquid shim material <NUM> within the bag <NUM> when the pin <NUM> is applied to the bag <NUM>, as shown in <FIG>. As it is spread through the bag <NUM>, the liquid shim material <NUM> flows around the sealed openings <NUM> and the holes <NUM>, as shown in <FIG>. Other devices may be used to spread the liquid shim material <NUM>.

The spreader <NUM> is shown in <FIG>. The spreader <NUM> in <FIG> is used to spread the liquid shim material <NUM> so that it has a substantially constant or same height A within the bag <NUM>. The rollers <NUM> have a diameter greater than the diameter of the pin <NUM>. When the spreader <NUM> is used on a flat surface FS, the rollers <NUM> space the pin <NUM> a desired distance from the flat surface FS. The desired distance becomes the uniform thickness or height A of the liquid shim material <NUM> within the bag <NUM> when the pin <NUM> is applied to the bag <NUM>, as shown in <FIG>. The height A is equal to half the difference between the diameter of the rollers <NUM> and the diameter of the pin <NUM>. Referring to <FIG>, the peripheral portions <NUM> of the bag <NUM> are temporarily folded about the FL when the spreader <NUM> is applied against the first or second wall 28A, 28B of the bag <NUM>. The peripheral portions <NUM> in <FIG> are not filled with, or are free of, the liquid shim material <NUM> as it is being spread in the bag <NUM>.

Another example of the spreader <NUM> is shown in <FIG>. The spreader <NUM> in <FIG> is used to spread the liquid shim material <NUM> so that it has a varying or tapered height within the bag <NUM>. Referring to <FIG>, the height C of the bag <NUM> along one of its sides is less than the height D of the bag <NUM> along its other side. The rollers <NUM> include a first roller 134A having a first diameter, and a second roller 134B having a second diameter greater than the first diameter. The diameters of both the first and second rollers 134A, 134B are greater than the diameter of the pin <NUM>. When the spreader <NUM> is used on the flat surface FS, the first and second rollers 134A, 134B space the pin <NUM> a desired distance from the flat surface FS. The desired distance becomes the varying or tapered thickness or height of the liquid shim material <NUM> within the bag <NUM> when the pin <NUM> is applied to the bag <NUM>, as shown in <FIG>. The pin <NUM> has a longitudinal axis that is transverse to the flat surface FS. The height C is equal to half the difference between the first diameter of the first roller 134A and the diameter of the pin <NUM>, and the larger height D is equal to half the difference between the second diameter of the second roller 134B and the diameter of the pin <NUM>. Referring to <FIG>, the peripheral portions <NUM> of the bag <NUM> are temporarily folded about the FL when the spreader <NUM> is applied against the first or second wall 28A, 28B of the bag <NUM>. The peripheral portions <NUM> in <FIG> are not filled with, or are free of, the liquid shim material <NUM> as it is being spread in the bag <NUM>.

The spreading of the liquid shim material <NUM> with the spreader <NUM>,<NUM> may push air out of the inner volume <NUM>. To assist with the spreading of the liquid shim material <NUM> with the spreader <NUM>,<NUM>, the inner volume <NUM> may be under vacuum, and/or the bag <NUM> may be placed in the vacuum chamber <NUM>.

After providing the bag <NUM> with the liquid shim material <NUM>, the liquid shim <NUM> is prepared and ready to use. <FIG> shows an example of a prepared liquid shim <NUM>. The prepared liquid shim <NUM> may be stored in a cold-storage unit, such as a freezer or refrigerator. Depending on the type of liquid shim material <NUM> used, this may preserve or extend the lifespan of the liquid shim <NUM> by slowing or preventing curing of the liquid shim material <NUM> within the bag <NUM>. For some types of liquid shim material <NUM>, curing may begin the moment the liquid shim material <NUM> is mixed. Refrigerating or freezing these liquid shim materials <NUM> slows down curing and can extend the lifespan of the liquid shim <NUM>. Many prepared liquid shims <NUM> may be stored in the cold-storage unit in this manner and used when needed. It may therefore be possible to prepare multiple liquid shims <NUM> that can be used as and when required, which helps to minimise setup times. In one possible storage configuration of the cold-storage unit, a freezer kept at - <NUM> is used, and retards the curing process of the liquid shim material <NUM> such that the working life of the liquid shim <NUM> may be extended by an additional five days. It may be possible to further increase the working life of the liquid shim <NUM> by decreasing the temperature of the cold-storage unit to -<NUM>.

Before placing the liquid shim <NUM> in the gap 9A, a portion of the liquid shim <NUM>, such as one or more of the peripheral portions <NUM>, may be closed to temporarily decrease the inner volume <NUM> of the sealed bag <NUM>. The portions may be closed before the liquid shim material <NUM> is provided to the bag <NUM>, as shown in <FIG>, while spreading the liquid shim material <NUM> through the inner volume, as shown in <FIG>, or after the liquid shim material <NUM> has been provided to the bag <NUM>. In <FIG> and <FIG>, one or more of the peripheral portions <NUM> of the bag <NUM> are folded over to prevent the liquid shim material <NUM> from entering the peripheral portions <NUM> as the liquid shim material <NUM> fills the inner volume <NUM>. After the bag <NUM> has been filled with the liquid shim material <NUM>, and before placing the liquid shim <NUM> in the gap 9A, or while it is present in the gap 9A and before the components squeeze the bag <NUM>, the peripheral portions <NUM> may be expanded or opened. This restores the inner volume <NUM> to its original value. In <FIG>, opening the bag <NUM> is achieved by removing the tape which keeps the peripheral portions <NUM> attached to the bag <NUM>.

The methods and liquid shim <NUM> disclosed herein provide a relatively clean process because the liquid shim material <NUM> is contained in the bag <NUM>. The liquid shim <NUM> fills the gap 9A and helps to improve quality because the liquid shim material can assume the shape of the gap 9A almost perfectly. The liquid shim <NUM> is relatively easy to setup and layup, and easy to store, which helps efficiency by reducing the time taken to measure gaps across the joint <NUM>. The liquid shim <NUM> may also offer health and safety benefits because the operator handling the liquid shim is less likely to come into contact with the uncured liquid shim material <NUM>.

Claim 1:
A liquid shim (<NUM>), comprising:
a bag (<NUM>) defining a closed inner volume (<NUM>) and having sealed openings (<NUM>) spaced inwardly from a periphery of the bag (<NUM>), the sealed openings (<NUM>) being sealed from the closed inner volume (<NUM>) and delimiting holes (<NUM>) extending through the bag (<NUM>); and
a liquid shim material (<NUM>) being flowable through the closed inner volume (<NUM>) around the sealed openings (<NUM>) and being curable to form a solid, the liquid shim material (<NUM>) having a liquid shim material volume being less than the closed inner volume (<NUM>) of the bag (<NUM>).