1. Field of the Invention
The invention relates to consumer products, and more particularly, methods and apparatus for controlling the fit of cosmetic parts attached to a consumer electronic product.
2. Description of the Related Art
Consumer products occasionally require the attachment of parts that while not essential to the operation of the consumer electronic product, still must conform to the overall aesthetic look and feel of the product as a whole. It would be of little benefit for a manufacturer to expend a large amount of resources in both time and money in developing an aesthetically pleasing consumer product that with the addition of a minor cosmetic part degrades the overall look and feel of the product. Most consumers would tend to focus on any small imperfection that could result in an overall degradation in their appreciation of the product.
For example, the overall fit and finish of the product can be as almost an important factor to a consumer's appreciation of a product as the functionality of the product itself. Therefore, it is essential that any cosmetic part attached to a consumer product, especially to that portion of the consumer product that is readily visible, be attached in such a way as to appear that the cosmetic part is part of the whole and not added on.
Therefore, an improved manner of attaching a cosmetic part to a consumer product is desired that is strong, easily practiced, and results in a fit and finish that enhances the overall look and feel of the product.
Broadly speaking, the embodiments disclosed herein describe a composite formed of an open cell foam material impregnated with an adhesive.
A composite material includes at least a foam substrate interspersed with a plurality of foam cells having an average foam cell size related to a porosity of the foam substrate and a liquid adhesive having a viscosity value. In the described embodiment, the viscosity value of the liquid adhesive and the foam substrate porosity are interrelated in such a way that an amount of the liquid adhesive migrates into the foam substrate such that most of the plurality of foam cells within at least a first portion of the foam substrate are substantially and uniformly filled with the liquid adhesive.
A small form factor consumer product is described that includes at least a housing arranged to enclose a plurality of operational components, the housing having a form factor small enough to be easily carried about by a user with one hand, a feature attached to the housing at a reveal, and an adhesive composite arranged to adhesively attach together the feature such that the reveal is not visible to the user and is not tangible to the user. In the described embodiment, the adhesive composite is formed of at least a foam substrate having a number of foam cells, and substantially uniform distribution of liquid adhesive amongst the number of foam cells.
A method can be carried out by performing at least the following operations: providing a foam substrate having a range of porosity values, determining a viscosity of a first liquid adhesive, the viscosity of the liquid adhesive in accordance with a substantially uniform distribution of the liquid adhesive in at least a portion of the foam substrate, and forming a foam/adhesive composite material by causing the liquid adhesive to impregnate at least the portion of the foam substrate.
Other aspects and advantages will become apparent from the following detailed description taken in conjunction with the accompanying drawings which illustrate, by way of example, the principles of the invention.
The described embodiments will be readily understood by the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals designate like structural elements, and in which:
In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the concepts underlying the described embodiments. It will be apparent, however, to one skilled in the art that the described embodiments can be practiced without some or all of these specific details. In other instances, well known process steps have not been described in detail in order to avoid unnecessarily obscuring the underlying concepts.
Broadly speaking, the embodiments herein describe a composite that includes at least a foam substrate formed of a plurality of foam cells. In one embodiment at least one liquid adhesive can be uniformly distributed throughout the plurality of foam cells. In order to maximize the likelihood that the liquid adhesive is uniformly distributed in the foam substrate, the viscosity (μ) of the liquid adhesive and the average foam cell size (referred to as porosity measured in pores per inch, or PPI) are considered. As well known in the art, viscosity is a measure of liquid's resistance to flow, i.e., the lower/higher the viscosity the lesser/greater the resistance to flow. For example, water has a lower resistance to flow than molasses and as a consequence, water has a lower value of viscosity (μ≈1.0 cP) than molasses (μ≈5000 cP). The known viscosity of the liquid adhesive to be used to form the composite can determine in part the choice of a foam substrate based upon a range of porosity likely to result in a substantially uniform distribution of the liquid adhesive. Alternatively, if the porosity of the foam substrate is known, then a liquid adhesive of the proper viscosity can be selected. For example, in order to assure that a foam substrate having a porosity in the range of between 100 and 200 PPI is fully impregnated with liquid adhesive, the viscosity of the liquid adhesive can be on the order of that approximating water, namely about 1 cP. However as the porosity decreases (i.e., the average foam cell size increases) to about 15 ppi, the viscosity of the liquid adhesive will commensurably increase.
That having been said, once the foam substrate and liquid adhesive have been selected, the liquid adhesive can be introduced to the foam substrate in any number of ways. For example, in one particularly simple approach, the foam substrate can be immersed into a bath of liquid adhesive thereby allowing the liquid adhesive to migrate through the foam substrate by filling the voids represented by the plurality of foam cells. In some cases, it may be advantageous to modify the external conditions in order to facilitate the migration of the liquid adhesive through the foam substrate. For example, the liquid adhesive can be put under pressure providing an additional impetus for the liquid adhesive to migrate through the foam substrate. Other approaches can include exposing the foam substrate to a vacuum or other negative pressure and then introducing the liquid adhesive to be forcibly drawn into the foam substrate by way of the pressure differential.
In some cases, the foam substrate can be impregnated with more than one species of adhesive uniformly distributed throughout the foam substrate. In this way the different species of adhesive can cooperate to provide the composite with compound properties that can work in synergy with each other. For example, a first thermal cure adhesive having a first cure temperature can be combined with a second thermal cure adhesive having a second cure temperature that is higher than the first cure temperature. In this way, the first adhesive can cure without substantially any cure of the second adhesive providing, for example, a technique for self fixturing of an assembly cured at or above the second cure temperature.
In any case, once the composite is properly constituted, the liquid adhesive is for the most part uniformly distributed throughout the foam substrate and can be used to control a fit between cosmetic parts attached to a housing of, for example, a small form factor consumer electronic product. In one approach, when the composite is in an uncured state (i.e., the liquid adhesive has not “set”), the composite can be placed in contact with at least one surface of at least one of the parts slated to be joined together to form what is referred to as an assembly. Even in the uncured state, the composite can possess sufficient inherent “stickiness” that no additional effort is required for the composite to remain attached to the surface thereby allowing an easy assembly process.
The assembly can then be subjected to an external “fixturing” force that compels the assembly to conform to the desired specifications of the finished product. Due to the natural tendency of the foam substrate to return to its original dimensions, the composite responds to the compressive fixturing force by generating a uniform preload force in an opposite direction (and normal to composite surface) to that of the fixturing force having a magnitude in line with a spring force of the foam substrate alone. In this way, the uniform pre-load force can be used to better control the alignment and placement of the constituent parts of the assembly thereby assuring close fit between the constituent parts of the assembly. It should be noted that in order to optimize the advantages presented by the uniform pre-load force, consideration is taken of the natural spring force of the substrate and post cure properties of the liquid adhesive, such as, for example, post cure expansion or contraction and so on. While still fixtured within the fixturing device, the adhesive portion of the composite is cured. For thermal cure type adhesives, fixture heating to at least a cure temperature for at least a cure time. For example, the fixturing device can be heated by using an external heat source that can raise the temperature of at least the assembly to at least the curing temperature and held there for at least the cure time. In this way, the cured adhesive is incorporated into the lattice of foam cells.
In some cases, the adhesive can take the form of a binary type adhesive, such as a two part epoxy formed of a base agent and a linking agent. At least a portion of the composite can be impregnated with the base agent by incorporating the base agent into that part of the foam substrate nearest a surface of the composite to be placed against the part(s) to be attached. The linking agent can be placed on those surfaces of the parts to be attached that are to be placed in direct contact with corresponding surfaces of the composite having the base agent. In this way, a binary reaction (i.e., cross linking) can occur between the base agent and the linking agent when the composite is brought in contact with the parts to be attached and compressed by the fixturing device. In another embodiment, the adhesive can be a UV cure type adhesive allowing the composite to be formed into any shape deemed appropriate. For example, the composite can take on a curvilinear shape and compressed in such a way that the counterforce generated by the foam in the compressed state is in a direction normal to a surface of the compressed curvilinear shaped composite.
In additional embodiments, a composite having regions of differing properties can be formed by providing a predetermined and well defined non-uniform distribution of a liquid adhesive in the foam substrate. This non-uniform distribution of liquid adhesive can take many forms not the least of which is the non-uniform distribution of a single species of liquid adhesive, the non-uniform distribution of two different specifies of liquid adhesive (such as one species having a lower cure temperature than a second species, one species having a different curing process vis a vis the other species, and so on). The pre-determined non-uniform distribution of the liquid adhesive can result in the composite having overall composite properties not possible with the composite having the uniform distribution. For example, a composite can have regions of differing mechanical properties based upon the characteristics of the liquid adhesives used to impregnate those regions. For example, a first region of the substrate can be impregnated with a first species of liquid adhesive characterized as having a first cure temperature that is lower than of a second species of liquid adhesive used to impregnate a second region. In this configuration, when the composite is exposed to a temperature greater than the first cure temperature and less than the second cure temperature, the first region will have substantially different properties than that of the uncured second region.
One of the many advantages to the composite is that there is essentially no post cure shrinkage of the composite as compared to the post cure shrinkage evident when adhesive alone is used. Therefore, the composite can provide a well controlled and easy to use approach to bonding parts together in a cosmetically appealing manner. The composite is also well suited for attaching features to small form factor electronic devices. The features can include for example, an antenna window attached to a housing of the small form factor electronic device.
These and other embodiments are discussed below with reference to
When housing 200 is formed of metal and is used to enclose at least some operational components that the portable communication device (such as an RF antenna) that support RF based functionality, it is advantageous to remove a portion of housing 200 to form recess 202. Recess 202 can include part of bottom surface 204 of housing 200. Recess 202 can be sized to accommodate a feature formed of RF transparent materials such as ceramic, or plastic. Accordingly, recess 202 can be formed in close proximity to an RF antenna enclosed within housing 200 used to send and receive RF energy. Therefore, in order to minimize RF signal degradation caused by the presence of metal housing 200, recess 202 can be replaced with feature 206, formed of radio transparent material, commonly referred to as antenna window 206. However, in order to assure both the integrity of housing 200 as well as the aesthetic look and feel of housing 200, the reveal formed at the junctions of antenna window 206 with bottom surface 204 and exposed surfaces 208 and 210 of housing 200 must be structurally strong and resilient but also present a sense of both visual and tangible continuity between housing 200 and antenna window 206.
According,
Assembly 400 can then be placed within a fixturing device (not shown) that can generate fixturing force Ffix applied to assembly 400. It should be noted, however, that unlike using adhesive alone, due to the natural tendency of the foam substrate 104 to return to its original shape and contour, composition portion 302 responds to the application of Ffix by generating counterforce Fcount that can have a magnitude related to a spring force constant of foam substrate 104 and a direction in opposition to Ffix. In some cases, Fcount can be normal to a surface contour of composite portion 302. In this way, Fcount can be used to accurately and securely control the placement of antenna window 206 on exposed surface 208 in relation to housing 200 and exposed surface 210 within the fixturing device. Once properly secured within the fixturing device, assembly 400 can be exposed to an external environment suitable for curing the liquid adhesive used with foam substrate 104 to form composite portion 302. For example, if the species of liquid adhesive used is thermal cure adhesive, then assembly 400 is exposed to an external temperature of at least the cure temperature for a duration of time suitably long for an appropriate amount of curing to occur. However, again unlike adhesive used alone, any natural contraction of the adhesive due to the curing process within the foam cells can be at least partially offset by the structural integrity of the foam substrate itself. In this way, the dimensional integrity of composite portion 302 can be substantially intact over that possible using adhesive alone. Moreover, in the cured state, composite portion 302 of can become rigid and essentially unyielding resulting in highly stable bond between antenna window 206 and housing 200.
It should be noted that any appropriate adhesive and foam substrate can be used. For example, the adhesive can be a binary adhesive such as two part epoxy, having a base and linker agent. In this embodiment a surface portion of foam substrate can be impregnated with base agent. In another embodiment, however, substantially all of the foam substrate can be impregnated with base agent. Linker agent (material that when combined with base agent results in a cross linking reaction to occur providing a strong bond). In either of the embodiments, the linker agent can be placed on the surfaces to be attached together. In this way, when the coated surfaces are brought in contact with the foam substrate impregnated with the base agent, the cross linking reaction will occur at the surface/foam boundary.
For example,
Regions 602 and 604 can be secured to anchoring structure 608 that can, for example, take the form of a housing. Since region 606 does not effectively have any adhesive, the physical properties of region 606 remain substantially unchanged from that of the pre-cure even after actuator mechanism 600 undergoes a cure process. In contrast, however, regions 602 and 604 undergo substantial change from pre to post cure by the curing of adhesive A1. For example, regions 602 and 604 can have properties that change from being flexible and pliant at pre-cure to rigid and firmly attached to anchoring structure 608 at post cure. In this way, by remaining pliant and flexible, region 606 can respond to a applied force F by deflecting distance δ in contrast to regions 602 and 604 that remain rigid and exhibit little or no mechanical deflection caused by force F. In this way, actuator mechanism 600 can respond to force F as would a switch such as a dome button, as an example.
One of the advantages of either form of the composite (with either uniform or non-uniform distributions of adhesive) is the ability to provide well controlled and directional pre-load forces. For example,
The many features and advantages of the present invention are apparent from the written description and, thus, it is intended by the appended claims to cover all such features and advantages of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, the invention should not be limited to the exact construction and operation as illustrated and described. Hence, all suitable modifications and equivalents may be resorted to as falling within the scope of the invention.
This patent application takes priority under 35 U.S.C. 119(e) of U.S. Provisional Patent Application having Ser. No. 61/309,410 entitled “FOAM/ADHESIVE COMPOSITE AND METHODS OF USE THEREOF” by McClure et al. filed Mar. 1, 2010 which is incorporated by reference in its entirety for all purposes.
Number | Date | Country | |
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61309410 | Mar 2010 | US |