Programable deformation of elastomeric parts using internal lattice structures

A compressible part having a solid portion and a compressible portion. The solid portion includes a first polymer material. The compressible portion has a lattice structure adjacent to the solid portion. The compressible portion includes a second polymer material that is an elastomeric polymer. The lattice structure is configured to provide for increased elastic deformation of the compressible part under compressive stress compared to the same compressible part made completely of the elastomeric polymer in solid form.

DETAILED DESCRIPTION

Field of the Disclosure

The present disclosure is directed to a programmable deformation of elastomeric parts using internal lattice structures.

BACKGROUND

Compressible parts can be employed in a variety of applications. For instance, blown foam rubber is used in inlet plugs, which are known for covering secondary heat exchanger inlets of aerospace vehicles when the vehicles are not in use. One such inlet plug is shown inFIGS.7A and7B. The inlet plug is inserted into secondary heat exchanger inlets118(FIG.6) and thereby protects the inlets118from moisture, insects and other debris. In the past, such inlet plugs have been held in place in the secondary heat exchanger inlets118by a friction fit. The term “friction fit” is defined herein as a fastening between two parts which is achieved by friction after the parts are pushed together, rather than by any other means of fastening. In particular, a blown foam rubber pad10is attached at one end of an outer cover of the inlet plug, as shown inFIG.7A. The outer cover is made of metal, plastic and rubber impregnated cloth. When the inlet plug is pushed into the secondary heat exchanger inlet118, the blown foam rubber pad10is compressed and provides a compressive force against the side of the secondary heat exchanger inlet, thereby holding the inlet plug in place by increased friction caused by the compressive force. However, it has been found that over time the blown foam rubber pads deform to the shape of the secondary heat exchanger inlets, as shown inFIG.7B, and no longer provides sufficient compressive force to hold the inlet plugs in place.

Thus, there is a need in the art for materials and processes that can provide both compressibility and long term compressive force.

SUMMARY

The present disclosure is directed to a compressible part. The compressible part comprises a solid portion comprising a first polymer material; and a compressible portion comprising a lattice structure adjacent to the solid portion. The compressible portion comprises a second polymer material that is an elastomeric polymer. The lattice structure is configured to provide for increased elastic deformation of the compressible part under compressive stress compared to the same compressible part made completely of the elastomeric polymer in solid form.

The present disclosure is directed to an inlet plug. The inlet plug comprises an outer cover and a compressible part attached to the outer cover. The compressible part comprises a solid portion comprising a first polymer material and a compressible portion comprising a lattice structure adjacent to the solid portion. The compressible portion comprises a second polymer material that is an elastomeric polymer. The lattice structure is configured to provide for increased elastic deformation of the compressible part under compressive stress compared to the same compressible part made completely of the elastomeric polymer in solid form.

The present disclosure is also directed to a compression fit system. The system comprises a compressible part and a receptacle for receiving the compressible part. The receptacle is sized so that the compressible part is insertable in the receptacle and maintainable therein by a friction fit. The compressible part comprises a solid portion comprising a first polymer material and a compressible portion comprising a lattice structure adjacent to the solid portion. The compressible portion comprises a second polymer material that is an elastomeric polymer. The lattice structure is configured to provide for increased elastic deformation of the compressible part under compressive stress compared to the same compressible part made completely of the elastomeric polymer in solid form.

The present disclosure is further directed to a method of making a compressible part. The method comprises forming a compressible part by three-dimensional printing. The compressible part comprises: (i) a solid portion comprising a first polymer material and (ii) a compressible portion comprising a lattice structure adjacent to the solid portion. The compressible portion comprises a second polymer material that is an elastomeric polymer. The lattice structure increases elastic deformation of the compressible part under compressive stress compared to the same compressible part made completely of the elastomeric polymer in solid form.

It should be noted that some details of the figures have been simplified and are drawn to facilitate understanding rather than to maintain strict structural accuracy, detail, and scale.

DESCRIPTION

Reference will now be made in detail to the present teachings, examples of which are illustrated in the accompanying drawings. In the drawings, like reference numerals have been used throughout to designate identical elements. In the following description, reference is made to the accompanying drawings that form a part thereof, and in which is shown by way of illustration specific examples of practicing the present teachings. The following description is, therefore, merely exemplary.

The present disclosure is directed to a compressible part that includes a lattice structure. The amount of material employed in the lattice structure and the lattice structure design can be chosen to achieve the desired compressibility of the part. The compressible part can be employed in various applications, such as, for example, to provide sufficient compressibility and durability to maintain a friction fit when inserted into a receptacle.

FIG.1illustrates an example of a compressible part100comprising a solid portion102comprising a first polymer material and a compressible portion104. Compressible portion104includes a lattice structure106that is adjacent to, and physically attached to, and/or at least partially and in some embodiments fully encompassed within, the solid portion102. Compressible portion104comprises a second polymer material that is an elastomeric polymer. The lattice structure106is configured to provide for increased elastic deformation of the compressible part100under compressive stress compared to the same compressible part made completely of the elastomeric polymer in solid form (e.g., the part is made from solid elastomer without the lattice structure). The solid portion102can optionally include one or more holes103to allow for easy attachment to another part or structure, as will be illustrated below.

The particular configuration of the lattice structure106can be chosen to provide the desired compressibility and durability. For example, increasing the percentage of polymer material per unit volume of the lattice, thereby decreasing the volume of air gaps in the lattice, will decrease the compressibility; while decreasing the percentage of polymer material per unit volume will increase the compressibility. The percentage of polymer material per unit volume can be as low as 5% or as high as 95% depending on the stiffness desired. The lattice can have lattice patterns that include any geometrical shape. For example, a lattice pattern comprised of rectangular, diamond, triangle or other polygon patterns having from about 3 to about 10 sides, or about 4 to about 8 sides, circular or oval shape patterns, spiral patterns or any other suitable lattice pattern. Diamonds shapes are easiest to design. With 3D printing technology, the ability to create a variety of other shapes, such as spiral, spring like structures, is possible, as the structure can be strong enough to self-support during fabrication. The lattice can have a single pattern or multiple different patterns as part of the same lattice structure. For example,FIG.3B, discussed in greater detail below, illustrates a first lattice pattern111A of repeating diamond shapes and a second lattice pattern111B within the first lattice pattern111A. The second lattice pattern111B can be the same as, or different than, the first lattice pattern111A, and can be rotated at an angle, such as 90 degrees, relative to the first lattice pattern111A so as to support the first lattice pattern. For example, where both the first lattice pattern111A and the second lattice pattern111B comprise repeating diamond shape patterns, the lattice patterns111A and111B can be physically attached with one another at the intersecting diamond shapes. The lattice pattern chosen can provide an asthetic appearance, while being strong and stable. Employing one or more second lattice patterns at a 90 degree off set allows the first and second lattice patterns to support each other at adjacent intersections, thereby increasing the stability of the structure while still allowing compressibility. Such lattice structures designs can also allow for an outer “skin” to be formed on the sides thereof, (e.g., on the top, front and back of the lattice structure), thereby allowing fabrication of a plug that can effectively act as a barrier for moisture, dirt, bugs, and debris when installed.

A solid layer108of polymer can surround one or more side and/or top portions of the lattice structure106, as illustrated, for example, inFIG.1, and shown in more detail inFIGS.3A and3B. The solid layer108can increase the strength and improve structural integrity of the lattice region106. In certain applications the solid layer108can provide a barrier that reduces or prevents moisture, insects, dust and so forth from penetrating the lattice structure106. Optionally, side portions109of the lattice structure106can remain open in order to increase compressibility and also to allow air out during compression. In an alternative example, the lattice structure106can be entirely surrounded by a solid layer108, thereby sealing the lattice structure.

The first polymer material can be the same as, or different than, the second polymer material. In an example, the first polymer material is an elastic material that is different than the second polymer material. In another example, the first polymer material is an elastic material that is the same as the second polymer material. Employing the same elastic polymer for both the solid portion and the compressible portion allows both portions to be integrally formed together (e.g., by 3D printing or any other suitable method) as a single part with no additional assembly required.

As shown inFIGS.1and2, the compressible part can be in the form of a pad. As an example, the compressible part has a length dimension, L, a height dimension, H, and a width dimension, W, as shown inFIG.2. The compressible portion104may extend, for example, for about 10 to about 95% of the height dimension, H. In another example, the compressible portion104may extend, for example, for about 25% to about 70%, or about 30% to about 50%, of the height dimension. The compressible portion extends for about 70% to about 100%, such as about 80% to about 100%, such as about 90% to about 100%, of the length dimension, L; and about 70% to about 100%, such as about 80% to about 99%, such as about 90% to about 95%, of the width dimension, W. The relative size of the compressible portion can range from about 10% to about 95%, such as 20% to about 60%, such as about 30 to about 50%, by volume of the compressible part.

The dimensions of the compressible part100can be chosen as desired to form a pad of the desired shape and size. In an example, the height dimension, H, ranges from about 0.5 inch to about 8 inches, such as about 1 inch to about 6 inches, or about 1.25 inches to about 2 inches; the length dimension, L, ranges from about 0.5 inches to about 10 inches, such as about 1 inch to about 4 inches, or about 2 inches to about 3 inches; and the width dimension, W, ranges from about 0.3 inches to about 3 inches, or about 0.5 inches to about 2 inches, or about 0.5 inches to about 1.5 inches.

The compressible portion104has a first width edge110and a second width edge112opposing the first width edge110. In an example, the first width edge110and the second width edge112are curved, as shown inFIG.2. The curve of the first width edge110and second width edge112can allow for easy insertion of the compressible portion104into a receptacle, as shown, for example, inFIG.3C.

The elastomeric material is chosen to provide properties that can aid in achieving both the desired durability and compressibility of the compressible part, including a desired hardness, tensile strength and elongation at break. As examples, the elastomeric material of compressible part100has a Shore A Hardness of from about 40 to about 100, such as about 50 to about 90, such as about 60 to about 80, or about 65 to about 75, or about 68 to about 73, or from about 70 to about 72, or about 70. The elastomeric material has a tensile strength of, for example, from about 5 MPa to about 15 MPa, such as about 8 MPa to about 12 MPa, or about 10 MPa to about 11 MPa. The elastomeric material has an elongation at break of, for example, about 210% to about 410%, such as about 230% to about 390%, or about 240% to about 480%. Employing materials with hardness, tensile strength and elongation at break within these ranges can provide for compressible parts that last for long periods of time without fatiguing out. The tensile strength and elongation at break can be determined using ASTM D412.

Any elastomer that provides the desired properties (e.g., is flexible and can be formed to the desired shape by 3D printing, molding or another method) can be employed. For example, elastomers having one or more of a Shore A hardness within the ranges described herein, tensile strength within the ranges described herein and elongation at break within the ranges described herein, can potentially be employed. As examples, the elastomeric material can be polyurethane, polyethylene plastic, rubber or mixtures thereof. In an example, the elastomeric polymer is photocurable. Commercial examples of suitable elastomeric polymers include TPU 92A, available from Stratasys LTD, of Rehovot, Israel; and CARBON EPU 40, available from Carbon3D, Inc., of Redwood City, Calif.

The compressible part100can be made using any suitable known or later developed methods. An example of a suitable method of making a compressible part will now be described. The method comprises forming a compressible part by three-dimensional printing. The compressible part can be any of the compressible parts described herein. For example, the compressible part comprises: (i) a solid portion comprising a first polymer material and (ii) a compressible portion comprising a lattice structure adjacent to the solid portion. The compressible portion comprises a second polymer material that is an elastomeric polymer. The lattice structure increases elastic deformation of the compressible part under compressive stress compared to the same compressible part made completely of the elastomeric polymer in solid form. In an example, the three-dimensional printing process employed is fused deposition modelling. Suitable fused deposition modelling techniques are well known in the art. In an example, the first polymer material and the second polymer material are the same elastomeric polymer. The elastomeric polymer can be any of those described herein. The entire compressible part can be formed during a single print process using any of the printing processes described herein. For instance, the entire compressible part can be formed and then cured together in a single print. Fused deposition modeling has the advantage of allowing the entire part to be printed using an elastomer material.

The compressible part100can be employed in applications where a polymer part is employed to provide a friction fit. For example, the compressible part100can be employed as part of a compression fit system114. As illustrated inFIG.3C, the compression fit system114may comprise the compressible part100and a receptacle116for receiving the compressible part100. Any of the compressible parts described herein can be employed as a plug120that is insertable into the receptacle116and retainable therein by friction fit. In other examples, as will be described in greater detail below, the compressible part100can be attached to other parts or structures to form a plug120for the receptacle116. For instance, a cover122can be attached to the compressible part100, as shown, for example, inFIG.4. The plug120can be sized to provide for a friction fit when the plug, including at least a portion of the compressible part100, is inserted into the receptacle116. In an example, the receptacle116is an inlet positioned on an aerospace vehicle. Thus, this disclosure includes the concept of a method comprising inserting a compressible part100, as described herein, into a receptacle and maintaining the compressible part in the receptacle by a friction fit.

The increased compressibility due to the lattice structure106of the compressible part100allows for an improved friction fit. Further, because the material of the lattice structure is chosen to provide good durability, resilience and/or elasticity, the compressible part100resists losing its shape over time compared to the foam plugs described herein above, and thereby can maintain the friction fit for a longer period of time.

FIGS.4and5illustrate an example of a plug120that can be employed, for example, as a secondary heat exchanger inlet plug for an aerospace vehicle. The secondary heat exchanger inlets118(shown as dashed lines inFIG.6) are intake vents positioned between the fuselage and the main engine intakes. The secondary heat exchanger inlet plug120is installed in the heat exchanger inlets118when the aircraft is not being operated. The plug120comprises an outer cover122and an optional handle124. The compressible part100is attached to the outer cover by any suitable attachment means126, such as one or more of screws, bolts, adhesive, and so forth. The compressible part100can be any of the compressible parts described herein. The outer cover122can comprise any material in any shape or size that is appropriate for insertion into the receptacle to provide for a friction fit. As an example, the outer cover122comprises at least one material selected from metal, fiberglass, cloth, wood, ceramic, and polymer, such as elastic and non-elastic polymers (e.g., rubber or plastic, such as vinyl).

Example 1. Preparation and Testing of Compressible Part

The compressible part shown inFIGS.1and2was printed by a fused deposition modelling process on a Stratasys 3D printer using a single print. The material employed was TPU 92A (a thermoplastic urethane). The compressible part was used to make an inlet cover, as shown inFIG.4. The covers were inserted into the secondary heat exchanger inlets of F15 fighter jets and maintained therein by friction fit for about two years. After two years, the compressible part continued to provide sufficient compressibility to maintain a friction fit for the inlet cover and showed little or no permanent deformation. Thus, the compressible parts of the present disclosure show increased durability (e.g., are able to maintain a friction fit for a longer period of time without incurring significant permanent deformation) compared to similar compressible parts made using blown foam rubber.

By comparison, when a blown foam rubber part10was used to make an inlet cover that was inserted into a secondary heat exchanger inlet, the part10may only last about 6 months before significant and permanent deformation of the part occurs, as shown inFIG.7B, thereby resulting in loss of the ability to maintain a friction fit.

While the present teachings have been illustrated with respect to one or more implementations, alterations and/or modifications can be made to the illustrated examples without departing from the spirit and scope of the appended claims. In addition, while a particular feature of the present teachings may have been disclosed with respect to only one of several implementations, such feature may be combined with one or more other features of the other implementations as may be desired and advantageous for any given or particular function. Furthermore, to the extent that the terms “including,” “includes,” “having,” “has,” “with,” or variants thereof are used in either the detailed description and the claims, such terms are intended to be inclusive in a manner similar to the term “comprising.” Further, in the discussion and claims herein, the term “about” indicates that the value listed may be somewhat altered, as long as the alteration does not result in nonconformance of the process or structure to the intended purpose described herein. Finally, “exemplary” indicates the description is used as an example, rather than implying that it is an ideal.