Patent Description:
Sandwich panels are composite panel structures that have at least three layers including a pair of exterior, relatively thin and rigid layers (typically referred to as face sheets or skins) separated and coupled by an internal, relatively lightweight and thick core layer (referred to herein simply as a core). Relative to conventional panels comprising a single layer or multiple parallel layers, sandwich panels may provide a combination of high structural rigidity and low weight. Sandwich panels are used in various applications and therefore the skins and cores may be formed of various materials and have various structures. The cores may include a solid filling such as a low-density, open- or closed-cell foam or a structure having plurality of connected walls that are out-of-plane with the skins (e.g., honeycomb structure).

Sandwich panels have been widely adopted, especially in industries such as the automotive, aerospace, marine, shipping, and sports equipment industries where reductions in weight may provide substantial benefits. As a specific example, sandwich honeycomb paneling is commonly used in aircraft manufacturing as a lightweight, rigid solution for bulkheads, cabin dividers, and other structures. The sandwich honeycomb paneling generally have a core between the face sheets that includes an array of hollow cells that are hexagonal in shape and defined by a plurality of connected walls that are oriented perpendicular to the face sheets.

While the sandwich panels can provide several significant benefits, mounting objects to the sandwich panels may be challenging due to the low density and/or partially hollow core. A common approach to addressing this issue involves the use of low-profile potted-in inserts (also referred to as wall panel inserts or floating inserts). Potted-in inserts generally include a tubular shaft having a pair of flanges on ends thereof and an inner bore therethrough. Typical installation of potted-in inserts includes drilling a hole in the sandwich panel, locating the potted-in insert within the hole (typically such that a face of one of the flanges is flush with adjacent exterior surfaces of the corresponding face sheet), and then injecting a potting compound (e.g., an epoxy) into the sandwich panel to fill a cavity surrounding the potted-in insert. Once the potting compound cures, the inner bore of the potted-in insert can receive a fastener and thereby provide an attachment point within the sandwich panels for securing objects thereto.

Currently available potted-in inserts may suffer from various drawbacks. For example, the weight rating of the installed potted-in inserts may be too low for securing relatively heavy objects (e.g., large wall-mounted televisions) to the sandwich panels. This may result from poor bonding between the potted-in insert and the sandwich panel. For example, the potted-in inserts often comprise relatively smooth tubular shafts that may not promote a robust bond with the potting compound. Further, air pockets can occur during installation if the potting compound does not entirely fill the cavity surrounding the tubular shaft.

Hence, there is a need for potted-in inserts that are capable of promoting a robust bond with sandwich panels and are therefore capable of securing relatively heavy objects thereto.

<CIT> discloses an adhesive anchor for insertion into a lightweight building panel having a honeycomb structure.

A potted-in insert according to claim <NUM> is provided for use as an attachment point for securing an object to a sandwich panel. The potted-in insert comprises a shaft having a first outer diameter, a first end having a second outer diameter, wherein the second outer diameter is greater than the first outer diameter, a second end having a third outer diameter, and an inner bore extending through the first end, the shaft, and the second end. The inner bore defined by interior surfaces thereof, and having an inner diameter. A lattice structure is between the first end and the second end and in an area adjacent the shaft between the first outer diameter and the second outer diameter. The lattice structure is fixed to the first end, the second end, and/or the shaft. The lattice structure has a plurality of interconnected unit cells each comprising struts connected at nodes to define voids between the struts. The voids are sufficiently large to receive therethrough a potting compound.

A method according to claim <NUM> is provided for securing an object to a sandwich panel. The method comprises providing a potted-in insert comprising a shaft having a first outer diameter, a first end having a second outer diameter, wherein the second outer diameter is greater than the first outer diameter, a second end having a third outer diameter, and an inner bore extending through the first end, the shaft, and the second end, defined by interior surfaces thereof, and having an inner diameter. A lattice structure is between the first end and the second end and in an area adjacent the shaft between the first outer diameter and the second outer diameter. The lattice structure is fixed to the first end, the second end, and/or the shaft. The lattice structure has a plurality of interconnected unit cells each comprising struts connected at nodes to define voids between the struts. The voids are sufficiently large to receive therethrough a potting compound. The method further comprises boring a hole in the sandwich panel, inserting the potted-in insert into the hole, injecting the potting compound into the hole such that the potting compound is received through the voids in the lattice structure, curing the potting compound, and securing the object to the sandwich panel using the inner bore of the potted-in insert as an attachment point.

Furthermore, other desirable features and characteristics of the [system/method] will become apparent from the subsequent detailed description and the appended claims, taken in conjunction with the accompanying drawings and the preceding background.

<FIG> represent various aspects of a nonlimiting embodiment of a potted-in insert <NUM> (also referred to as the insert <NUM>) that may be installed in a sandwich panel (also referred to as the panel) to provide an attachment point for securing an object to the panel. The insert <NUM> includes a body having a shaft <NUM> extending between a first end <NUM> and a second end <NUM>. In the embodiment represented in the figures, the body is generally tubular such that the shaft <NUM>, the first end <NUM>, and the second end <NUM> have circular outer perimeters or cross-sections. Alternatively, in some embodiments, the body and/or the individual components thereof, including the shaft <NUM>, the first end <NUM>, and the second end <NUM>, may have outer perimeters that define various shapes other than circular. An inner bore <NUM> is provided through and defined by interior surfaces of the body, including the shaft <NUM>, the first end <NUM>, and the second end <NUM>. The inner bore <NUM> extends along and is co-axially aligned with a central, longitudinal axis <NUM> of the body. The inner bore <NUM> has openings at exterior faces of the first end <NUM> and the second end <NUM> of the body and includes an inner diameter.

The shaft <NUM> has a first outer diameter that is less than second and/or third outer diameters of the first end <NUM> and the second end <NUM>, respectively. The second and third outer diameters may be the same or different. An open area is defined between the first end <NUM> and the second end <NUM> along and surrounding the shaft <NUM>. Optionally, the body may include a first intermediate portion <NUM> between the first end <NUM> and the shaft <NUM> and a second intermediate portion <NUM> between the second end <NUM> and the shaft <NUM>. The first intermediate portion <NUM> and the second intermediate portion <NUM> may have tapered outer perimeters with diameters (e.g., fourth and fifth outer diameters, respectively). Specifically, the fourth outer diameter of the first intermediate portion <NUM> may transition between the first outer diameter of the shaft <NUM> and the second outer diameter of the first end <NUM>, and the fifth outer diameter of the first intermediate portion <NUM> may transition between the first outer diameter of the shaft <NUM> and the second outer diameter of the second end <NUM>. In the embodiment of the figures, both the first intermediate portion <NUM> and the second intermediate portion <NUM> have outer diameters with a constant rate of change to define linear outer profiles. In some embodiments, the first intermediate portion <NUM> and the second intermediate portion <NUM> may have outer diameters with a nonconstant rate of change to define nonlinear outer profiles (e.g., concave).

A slot <NUM> is provided through the first end <NUM> of the body that fluidically couples the exterior face of the first end <NUM> with the open area adjacent the shaft <NUM>. In the embodiment represented in the figures, the slot <NUM> is defined by recessed surfaces of the first end <NUM> and the first intermediate portion <NUM>.

The body includes a lattice structure <NUM> within the area surrounding the shaft <NUM> that at least partially encircles the shaft <NUM>. As shown most clearly in <FIG>, the lattice structure <NUM> comprises a plurality of unit cells each including struts <NUM> or portions thereof connected at nodes <NUM> to define a void. The lattice structure <NUM> may include one or more separate two-dimensional structures, or, preferably, one or more three-dimensional structures. As used herein, the lattice structure <NUM> is considered to be a three-dimensional structure if the lattice structure <NUM> includes more than one layer of unit cells in a direction extending radially from the longitudinal axis <NUM> of the shaft <NUM>. In the embodiment represented in the figures, the lattice structure <NUM> is a three-dimensional structure with the struts <NUM> being linear and longitudinally oriented at <NUM> or <NUM> degrees relative to the longitudinal axis <NUM> of the shaft <NUM>, and each unit cell includes twelve of the struts <NUM> or portions thereof that are connected such that in combination the struts <NUM> define a rectangular cuboid void. In some embodiments, the lattice structure <NUM> may have other structures that include, for example, the struts <NUM> being linear and longitudinally oriented at other angles relative to the longitudinal axis <NUM> of the shaft <NUM>, the struts <NUM> being nonlinear, or combinations thereof. The voids defined by the struts <NUM> may have various shapes and sizes.

The lattice structure <NUM> may contact and be fixed to surfaces of the first end <NUM>, the second end <NUM>, the shaft <NUM>, the first intermediate portion <NUM>, and/or the second intermediate portion <NUM>. In the embodiment of the figures, at least some of the struts <NUM> of the lattice structure <NUM> adjacent to and along surfaces of the shaft <NUM>, and the first intermediate portion <NUM>, and the second intermediate portion <NUM> are in contact with and fixed thereto (e.g., integral therewith). According to the invention, one or more channels are provided in the lattice structure <NUM> along all or a portion of the longitudinal length of the shaft <NUM>. For example, <FIG> represents the body as including a linear channel through the lattice structure <NUM> that is aligned with the slot <NUM> in the first end <NUM> of the body.

<FIG> represents an exploded view of the insert <NUM> and a sandwich honeycomb panel <NUM> that illustrates the relative orientation of the insert <NUM> upon installation thereof into the sandwich honeycomb panel <NUM>. In this example, the sandwich honeycomb panel <NUM> includes a first face sheet <NUM> and a second face sheet <NUM> with a core <NUM> therebetween having an array of hollow cells that are hexagonal in cross-sectional shape and defined by a plurality of connected walls that are oriented perpendicular to the first face sheet <NUM> and the second face sheet <NUM>. A hole <NUM> is formed in the first face sheet <NUM> and extends into or through at least the core <NUM> to receive the insert <NUM>.

<FIG> represents nonlimiting steps in a method for installing the insert <NUM> in a sandwich panel and subsequently securing an object to the sandwich panel using the insert <NUM> as an attachment point. In this example, the sandwich panel includes first and second face sheets coupled by a core therebetween. In step <NUM>, a hole is formed in the sandwich panel through the first face sheet and into the core, for example, by drilling. The hole may extend through an entirety of the core and out through the second face sheet, or the hole may extend only through a portion of the core such that the second face sheet remains intact.

In step <NUM>, the second end <NUM> of the insert <NUM> is located in the hole and the remainder of the body is inserted therein at least to an extent such that the opening of the hole in the first face sheet is sealed with the first end <NUM> of the body. If the hole extends through the second face sheet, the opening thereof in the second face sheet is preferably sealed with the second end <NUM> of the body. Optionally, the insert <NUM> may be inserted into the hole to an extent sufficient such that the exterior face of the first end <NUM> of the body is flush with adjacent exterior surfaces of the first face sheet. In some embodiments, the core may be reamed to expand the size of the cavity therein.

In step <NUM>, a potting compound may be injected into the hole through the slot <NUM> in the first end <NUM> of the body. Preferably, a sufficient volume of the potting compound is injected at a sufficient pressure to substantially or entirely fill the hole, any cavities within the core fluidically connected to the hole, and the area adjacent the shaft <NUM> of the insert <NUM>. The channel, if present, may promote flow of the potting compound and thereby increase the likelihood that an entirety of the hole, the cavities connected thereto, and/or the area adjacent the shaft <NUM> are filled.

In step <NUM>, the potting compound is allowed to cure. This may be accomplished by passively allowing sufficient time for the potting compound to cure, or curing may be actively promoted, for example, by application of heat. After the potting compound has cured, an object my be secured to the panel using the insert <NUM> as an attachment point in step <NUM>. In some embodiments, this may include inserting a fastener into the inner bore <NUM> of the insert <NUM>.

The lattice structure <NUM> is configured to increase a bond strength of the insert <NUM> and the potting compound when installed within the panel relative to a potted-in insert without such lattice structure <NUM>, and thereby increase an installed weight rating of the insert <NUM> allowing for relatively heavy objects to be secured to the panel using the insert <NUM>. In addition to increasing a surface area of the insert <NUM> in contact with the potting compound, the voids of the lattice structure <NUM> are sufficiently large to receive therethrough the potting compound. During injection, the potting compound preferably flows throughout the lattice structure <NUM>, filling the voids thereof. Once the potting compound has been cured, the struts <NUM> are each individually and collectively embedded within and integrated into a matrix defined by the potting compound and thereby function to anchor the insert <NUM> in a fixed position relative to the potting compound. With such arrangement, the lattice structure <NUM> may reduce the likelihood of motion of the insert <NUM> in six degrees of freedom.

The lattice structure <NUM> likely precludes the ability and/or practicality to produce the insert <NUM> by certain conventional processing techniques, such as milling, casting, etc. However, the insert <NUM> may be produced using certain additive manufacturing techniques. Suitable techniques may include, but are not limited to, binder jetting, directed energy deposition, material extrusion, powder bed fusion, and vat polymerization. A particular benefit of the embodiment of the figures is that the first intermediate portion <NUM> and the second intermediate portion <NUM> may provide a substrate upon which the lattice structure <NUM> may be formed. In some embodiments, the insert <NUM> may be produced by additive manufacturing without use of supports. In such embodiments, the insert <NUM> may include an integral body wherein some or all of the components thereof are integral, that is, formed of particles or layers that are, for example, fused together rather than assembled components.

The insert <NUM> may be formed of various materials including certain polymeric, metallic, and ceramic materials, and combinations thereof. Further, the insert <NUM> and the components thereof may be produced to have various dimensions. In some embodiments, the insert <NUM> may be produced to have specific predetermined dimensions corresponding to, for example, a thickness of the panel and/or depth of the hole thereof in which the insert <NUM> is to be installed. Due to the nature of additive manufacturing, the predetermined dimensions may be modified for each individual application as necessary. Alternatively, the insert <NUM> may be produced to have predetermined dimensions, and then subsequently modified to reduce one or more of such dimensions (e.g., the longitudinal dimension). For example, the insert <NUM> may be configured in a manner such that at least one of the first end <NUM> and the second end <NUM> are configured to be selectively modified to have a reduced longitudinal dimension (e.g., by machining or sanding). As such, the dimensions of the insert <NUM> and its components may be adjustable during manufacturing thereof and/or by the end user.

Claim 1:
A potted-in insert (<NUM>) for providing an attachment point for securing an object to a sandwich panel, the potted-in insert comprising:
a shaft (<NUM>) having a first outer diameter;
a first end (<NUM>) having a second outer diameter, wherein the second outer diameter is greater than the first outer diameter;
a second end (<NUM>) having a third outer diameter;
an inner bore (<NUM>) extending through the first end (<NUM>), the shaft (<NUM>), and the second end (<NUM>), the inner bore defined by interior surfaces thereof, and having an inner diameter; and,
a lattice structure (<NUM>) between the first end and the second end and in an area adjacent the shaft between the first outer diameter and the second outer diameter, the lattice structure fixed to the first end, the second end, and/or the shaft, the lattice structure having a plurality of interconnected unit cells each comprising struts (<NUM>) connected at nodes (<NUM>) to define voids between the struts, the voids being sufficiently large to receive therethrough a potting compound,
characterised in that the lattice structure (<NUM>) includes more than one layer of the unit cells in a direction extending radially from a longitudinal axis of the shaft (<NUM>); and,
wherein the insert (<NUM>) further comprises a channel through, and defined by, the lattice structure (<NUM>) and extending along the shaft (<NUM>) to promote flow of the potting compound therethrough, said channel being aligned with a slot (<NUM>) that is through the first end (<NUM>) and is defined by recessed surfaces thereof, the slot fluidically coupling an exterior face of the first end (<NUM>) with the area adjacent the shaft (<NUM>).