Patent Application
20140216806
The present disclosure generally relates to electromagnetic interference (EMI) gaskets.
This section provides background information related to the present disclosure which is not necessarily prior art.
During normal operation, electronic equipment can generate undesirable electromagnetic energy that can interfere with the operation of proximately located electronic equipment due to electromagnetic interference (EMI) transmission by radiation and conduction. The electromagnetic energy can be of a wide range of wavelengths and frequencies. To reduce the problems associated with EMI, sources of undesirable electromagnetic energy may be shielded and electrically grounded. Shielding can be designed to prevent both ingress and egress of electromagnetic energy relative to a housing or other enclosure in which the electronic equipment is disposed. Since such enclosures often include gaps or seams between adjacent access panels and around doors and connectors, effective shielding can be difficult to attain because the gaps in the enclosure permit transference of EMI therethrough. Further, in the case of electrically conductive metal enclosures, these gaps can inhibit the beneficial Faraday Cage Effect by forming discontinuities in the conductivity of the enclosure which compromise the efficiency of the ground conduction path through the enclosure. Moreover, by presenting an electrical conductivity level at the gaps that is significantly different from that of the enclosure generally, the gaps can act as slot antennae, resulting in the enclosure itself becoming a secondary source of EMI.
EMI gaskets have been developed for use in gaps and around doors to provide a degree of EMI shielding while permitting operation of enclosure doors and access panels and fitting of connectors. To shield EMI effectively, the gasket should be capable of absorbing or reflecting EMI as well as establishing a continuous electrically conductive path across the gap in which the gasket is disposed. These gaskets can also be used for maintaining electrical continuity across a structure and for excluding from the interior of the device such contaminates as moisture and dust. Once installed, the gaskets essentially close or seal any interface gaps and establish a continuous electrically-conductive path thereacross by conforming under an applied pressure to irregularities between the surfaces. Accordingly, gaskets intended for EMI shielding applications are specified to be of a construction that not only provides electrical surface conductivity even while under compression, but which also has a resiliency allowing the gaskets to conform to the size of the gap.
As used herein, the term “EMI” should be considered to generally include and refer to EMI emissions and RFI emissions, and the term “electromagnetic” should be considered to generally include and refer to electromagnetic and radio frequency from external sources and internal sources. Accordingly, the term shielding (as used herein) generally includes and refers to EMI shielding and RFI shielding, for example, to prevent (or at least reduce) ingress and egress of EMI and RFI relative to a housing or other enclosure in which electronic equipment is disposed.
This section provides a general summary of the disclosure, and is not a comprehensive disclosure of its full scope or all of its features.
According to various aspects, exemplary embodiments are disclosed of EMI shields, such as EMI gaskets. In an exemplary embodiment, the gasket includes a body of indefinite length. The gasket also includes a base with a generally flat outer surface, an upright portion extending generally upwardly away from the base, and a tail portion extending laterally away from the base. The base and the upright portion may intersect the tail portion at a fold line. One or more perforations and/or a crease may be along the fold line.
Further areas of applicability will become apparent from the description provided herein. The description and specific examples in this summary are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure.
The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.
Example embodiments will now be described more fully with reference to the accompanying drawings.
According to various aspects, exemplary embodiments are disclosed of EMI shields, such as EMI gaskets. The gasket includes a body of indefinite length. The gasket may include a portion (e.g., tail portion, etc.) foldable or bendable around or about the edge of a first substrate having first and second surfaces. The gasket also includes means for relieving residual stresses that may be caused by the bending or folding of the gasket portion about the edge of the substrate. As disclosed herein, the gasket may include a crease and/or one or more perforations along a bend or fold line of the gasket.
In an exemplary embodiment, a gasket includes a base, an upright portion extending generally upwardly away from the base, and a tail portion extending laterally away from the base. The body has a generally P-shaped profile or other profile collectively defined by the tail portion, the base, and the upright portion. One or more perforations (e.g., holes, openings, cutouts, slits, notches, etc.) may be at or adjacent to the intersection of the tail portion with the upright portion and base. For example, the base and the upright portion may intersect the tail portion at a fold line, and the one or more perforations may be at or along the fold line. The one or more perforations are configured to relieve residual stresses that may be caused by the bending or folding of the tail portion about an edge of the substrate, which thus reduces the chances of the gasket lifting off of or separating from the substrate after installation. Alternatively, the gasket may include additional or different means for relieving the stresses at the fold line or bend, such as a crease along the fold line or bend. The crease may be in addition to or an alternative to the one or more perforations.
In some exemplary embodiments, the gasket includes a generally P-shaped profile (e.g.,
In various exemplary embodiments, a gasket is provided that is deflectable into a collapsed orientation between first and second substrates. The gasket includes a body of indefinite length, a base (e.g., a generally flat leg or portion, etc.) having a generally flat outer surface, and an upright portion (e.g., generally vertical shape or member, etc.). The gasket further includes a tail portion that extends laterally away and generally parallel to the base in a free-standing state. Thus, the gasket may have a generally P-shaped profile (or other profile) collectively defined by the base, the tail, and the upright portion when the gasket is free-standing and uncompressed. One or more perforations (e.g., holes, openings, cutouts, slits, notches, etc.) may be adjacent, at, or about at the intersection or fold line of the upright portion and the tail portion. Alternative embodiments may have perforations at alternative or additional locations, and/or a crease along the fold line or intersection of the tail portion and the upright portion.
Turning to the Figures,
To address the shearing issue shown in
As shown in
With continued reference to
In this particular embodiment, the perforations 220 are formed such that they extend completely through the fold line 224 from one side to the other. Accordingly, the perforations 220 thus also extend completely through the gasket material(s) (e.g., fabric, etc.) located at or along the fold line 224 from one side to the other. By way of example, the perforations 220 may be formed by a rotary die cutter. Alternative processes may be used to form one or more perforations extending completely through or only partially through a gasket.
Depending on the particular end-use or application, the gasket's base 216 may be affixed or adhered (e.g., adhesively bonded using a pressure sensitive adhesive, etc.) to a first surface 226 of the first substrate 102. And, the tail portion 210 may be affixed or adhered to a second surface 228 of the first substrate as can be seen in
Additionally, or alternatively, other exemplary embodiments may include different means for relieving the residual stresses at the bend than the perforations. For example, in another exemplary embodiment of a gasket, the means for relieving residual stresses at the bend comprises a crease along the fold line or bend, which crease may run the length of the gasket body. In this exemplary embodiment, heated rollers may be used to melt a hot melt adhesive on the fabric locally to help with the formation of the crease. In another exemplary embodiment of a gasket, the means for relieving residual stresses at the bend comprises the crease along the fold line and one or more perforations along the fold line.
The gasket 204 shown in
Referring to
As can be seen in Table 1, the presence of perforations reduced the stresses on the gasket fabric that result from bending the gasket around the edge of the first substrate at the fold line. Additionally, the longer the perforations represented as higher values of y, the greater the reduction in the stress forces. The gaskets of Table 1 were additionally subjected to 24 hours of 70° Celsius heating in an oven. In each instance, the unperforated gaskets suffered the defect shown in
Table 2 below provides exemplary test results for additional gaskets having dimensions of v=18 mm, w=7 mm, and x=4 mm that were installed on the edge of a substrate as shown in
As seen in Table 2, where a sample was marked FAIL, the defect seen in
The test results shown in Tables 1 and 2 are provided only for purposes of illustration and not for purposes of limitation. Other exemplary embodiments of gaskets may be configured differently (e.g., sized differently, etc.) and/or produce different test results than that shown in Tables 1 and 2.
In an exemplary embodiment and with reference to
Though the scale of a claimed gasket need not be so limited by the following dimensions, in certain embodiments and applications the gasket may have values of v that range from about 3.3 mm to about 13.5 mm, and values of w that range from about 6.6 mm to about 10.0 mm. By way of further example, in certain embodiments and applications, the tail portion of the gasket may have a thickness that is less than about 2.8 mm, and the upright portion may have a height, perpendicular to the width v that ranges from about 2.5 mm to about 10.5 mm.
In some preferred embodiments, such as that seen in
The fabric layer 206 may be adhered to the core 208 with any suitable adhesive known in the art. In an embodiment, the adhesive may be an acrylic non-conductive pressure sensitive adhesive having a high peel strength and temperature resistance. In another embodiment, the adhesive may be an acrylic conductive pressure sensitive adhesive having an electrical conductivity. In another embodiment, the adhesive may be a solvent based polyester adhesive that is substantially halogen free and includes at least one halogen-free flame retardant.
As shown in
The compression of the gasket 204 between the two substrates 102, 110 preferably helps the gasket establish electrical conductivity with the substrates sufficient for EMI shielding performance.
The gasket need not be limited to the P-Shaped gasket seen in
In a particular embodiment, the gasket is an electromagnetic interference gasket having a body of indefinite length. The gasket includes a base, an upright portion extending away from the base, and a tail portion extending laterally away from the base. In this example, the upright portion comprises a foam core surrounded by an outer fabric layer adhered to the core. Also in this example, the base has a generally flat outer surface, and the tail portion includes two fabric layers adhered together. The base and the upright portion intersect with the tail portion at a fold line that runs the length of the gasket body. The gasket further includes one or more perforations along the fold line. The one or more perforations may be a series of perforations that run the length of the fold line. And, a gap may be between each pair of adjacent perforations, where the gaps are unperforated fabric layers that link the tail portion to the upright portion and the base.
An exemplary embodiment includes a fabric-over-foam electromagnetic interference gasket having a body of indefinite length. The gasket may include a base with a generally flat outer surface, an upright portion extending generally upwardly away from the base, and a tail portion. The tail portion is foldable or bendable around an edge of a first substrate having first and second surfaces. The body has a generally P-shaped profile or other profile collectively defined by the tail portion, the base, and the upright portion. One or more perforations may be at or adjacent to the intersection of the upright portion and the tail portion. The gasket may be compressed between the first surface of the first substrate and a surface of a second substrate into the collapsed orientation characterized in that the upright portion compresses generally between the substrates.
In further alternative embodiments, a gasket includes a body that is a generally hollow extrusion of elastomer material or other suitable material. The gasket may be formed by extruding an electrically-conductive elastomer material, such as silicone or fluorosilicone rubber rendered electrically-conductive by its loading with a silver-based filler and/or a nickel-based filler. The extruded gasket may include a base with a generally flat outer surface, an upright portion extending generally upwardly away from the base, and a tail portion. The tail portion may be foldable or bendable around an edge of a first substrate having first and second surfaces. The body may have a generally P-shaped profile or other profile collectively defined by the tail portion, the base, and the upright portion. One or more perforations may be provided or formed (e.g., cut into, etc.) at or adjacent the intersection of the tail portion with the upright portion and/or base. Other manufacturing processes besides extrusion can also be employed to make such a gasket, such as molding, die-cutting, etc.
Example embodiments are provided so that this disclosure will be thorough, and will fully convey the scope to those who are skilled in the art. Numerous specific details are set forth such as examples of specific components, devices, and methods, to provide a thorough understanding of embodiments of the present disclosure. It will be apparent to those skilled in the art that specific details need not be employed, that example embodiments may be embodied in many different forms, and that neither should be construed to limit the scope of the disclosure. In some example embodiments, well-known processes, well-known device structures, and well-known technologies are not described in detail. In addition, advantages and improvements that may be achieved with one or more exemplary embodiments of the present disclosure are provided for purpose of illustration only and do not limit the scope of the present disclosure, as exemplary embodiments disclosed herein may provide all or none of the above mentioned advantages and improvements and still fall within the scope of the present disclosure.
Specific dimensions, specific materials, and/or specific shapes disclosed herein are example in nature and do not limit the scope of the present disclosure. The disclosure herein of particular values and particular ranges of values for given parameters are not exclusive of other values and ranges of values that may be useful in one or more of the examples disclosed herein. Moreover, it is envisioned that any two particular values for a specific parameter stated herein may define the endpoints of a range of values that may be suitable for the given parameter (i.e., the disclosure of a first value and a second value for a given parameter can be interpreted as disclosing that any value between the first and second values could also be employed for the given parameter). For example, if Parameter X is exemplified herein to have value A and also exemplified to have value Z, it is envisioned that parameter X may have a range of values from about A to about Z. Similarly, it is envisioned that disclosure of two or more ranges of values for a parameter (whether such ranges are nested, overlapping or distinct) subsume all possible combination of ranges for the value that might be claimed using endpoints of the disclosed ranges. For example, if parameter X is exemplified herein to have values in the range of 1-10, or 2-9, or 3-8, it is also envisioned that Parameter X may have other ranges of values including 1-9, 1-8, 1-3, 1-2, 2-10, 2-8, 2-3, 3-10, and 3-9.
The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an,” and “the” may be intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises,” “comprising,” “including,” and “having,” are inclusive and therefore specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. The method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed.
When an element or layer is referred to as being “on,” “engaged to,” “connected to,” or “coupled to” another element or layer, it may be directly on, engaged, connected or coupled to the other element or layer, or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly engaged to,” “directly connected to,” or “directly coupled to” another element or layer, there may be no intervening elements or layers present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between” versus “directly between,” “adjacent” versus “directly adjacent,” etc.). As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items.
The term “about” when applied to values indicates that the calculation or the measurement allows some slight imprecision in the value (with some approach to exactness in the value; approximately or reasonably close to the value; nearly). If, for some reason, the imprecision provided by “about” is not otherwise understood in the art with this ordinary meaning, then “about” as used herein indicates at least variations that may arise from ordinary methods of measuring or using such parameters. For example, the terms “generally,” “about,” and “substantially,” may be used herein to mean within manufacturing tolerances. Or for example, the term “about” as used herein when modifying a quantity of an ingredient or reactant of the invention or employed refers to variation in the numerical quantity that can happen through typical measuring and handling procedures used, for example, when making concentrates or solutions in the real world through inadvertent error in these procedures; through differences in the manufacture, source, or purity of the ingredients employed to make the compositions or carry out the methods; and the like. The term “about” also encompasses amounts that differ due to different equilibrium conditions for a composition resulting from a particular initial mixture. Whether or not modified by the term “about,” the claims include equivalents to the quantities.
Although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers and/or sections should not be limited by these terms. These terms may be only used to distinguish one element, component, region, layer or section from another region, layer or section. Terms such as “first,” “second,” and other numerical terms when used herein do not imply a sequence or order unless clearly indicated by the context. Thus, a first element, component, region, layer or section discussed below could be termed a second element, component, region, layer or section without departing from the teachings of the example embodiments.
Spatially relative terms, such as “inner,” “outer,” “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. Spatially relative terms may be intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the example term “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly.
The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements, intended or stated uses, or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.
