Patent Application
20150145384
Manufacturers of mobile devices are constantly working to make them thinner. One method used for making mobile devices thinner involves using a thinner material, for example, sheet metal for a housing/enclosure instead of or in addition to a typical thicker material, for example, plastic that is typically used for the enclosure. It is important, however, that thinner enclosures have the same strength as thicker enclosures. One avenue for maintaining the strength of an enclosure that includes thinner material is to over-mold a prefabricated thinner material, for example, the sheet metal to a thicker material, for example, a plastic enclosure. Consider an example where in a front housing keypad compartment of a mobile device the backing thickness for a plastic keypad bezel attached to a keypad Mylar stack up is reduced by over-molding the bezel and Mylar stack to a sheet metal instead of to a thicker plastic. In some instances, the thickness of the sheet metal may be 0.5 millimeters (mm) and the thickness of the plastic may be 1.2 mm, reducing the thickness of the enclosure by up to 58%. The process of over-molding two different materials with different thickness and properties (i.e., over-molding the prefabricated sheet metal to the plastic) is referred to herein as bi-material processing.
When a mobile device enclosure includes a thinner material over-molded to a thicker material, the enclosure must provide certain levels of protection as set forth in standards that cover enclosures for electrical equipment. For example, the IP Code, Ingress Protection Rating, as published by the International Electrotechnical Commission (IEC), classifies and rates the degree of protection mechanical casings with electrical components must provide against intrusions, dust, accidental contact and water. In particular, the IPX7 and IPX8 standards set forth the level of protection required of mechanical enclosures including electrical equipment against the ingress of water (referred to herein as the ingress protection requirement). For example, devices manufactured according to the IPX7 standard must be able to be immersed in up to 1 meter of water for thirty minutes without water entering through the enclosure, and devices manufactured according to the IPX8 standard must be able to be immersed in more than 1 meter of water for a period, as set by the manufacturer, which is greater than thirty minutes without water entering through the enclosure. Although enclosures created using bi-material process must satisfy the ingress protection requirement, after the materials are molded together, at the perimeter joints of the two materials, a leak path (i.e., a path through which water may travel to enter enclosure and reach internal electrical components) may exist. While the bi-material processing is used widely in the mobile device designs, current bi-material processes fail to provide a robust seal feature that integrates the two different materials and thereby provide adequate ingress protection.
Accordingly, there is a need for an apparatus and method of providing a seal around a perimeter of a bi-material enclosure.
The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views, together with the detailed description below, are incorporated in and form part of the specification, and serve to further illustrate embodiments of concepts that include the claimed invention, and explain various principles and advantages of those embodiments.
Skilled artisans will appreciate that elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. For example, the dimensions of some of the elements in the figures may be exaggerated relative to other elements to help to improve understanding of embodiments of the present invention.
The apparatus and method components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.
Some embodiments are directed to methods and apparatuses for created in enclosure from a bi-material process. The enclosure includes a seal is co-molded to first material to form a sub-assembly in which the first material is securely adhered to the seal. The seal is designed to collapse in a specific direction during an injection molding process. The enclosure also includes a second material over-molded on the sub-assembly during the injection molding process. The seal is compressed in the specific direction during the injection molding process to produce a consistent wetting at least at one desired perimeter joint between the seal and the over-molded second material, forming the bi-material enclosure. The first material and the second material are dissimilar materials with different thermal expansion qualities.
Subsequent to thicker material 104 being over-molded to thinner material 102, when materials 102 and 104 are subjected to temperature cycles and shock, thermal expansion of thinner material 102 and thicker material 104 may occur. Over multiple temperature cycles, because of the inherent dissimilar coefficient of thermal expansion (CTE) of the materials 102 and 104, flaws in the joints between materials 102 and 104 may become obvious. In other words, over multiple temperature cycles, the joints of over-molded materials 102 and 104 may weaken due to thermal expansion of two dissimilar materials with dissimilar CTE. As the joint integrity between materials 102 and 104 is weakened by materials 102 and 104 being subjected to multiple temperature cycles and shock, there is a potential for water to leak into enclosure 100 through a leak path, as shown by arrows 106 or for a vacuum to form between materials 102 and 104.
In order to block leak path 106, a high temperature seal/gasket 108, for example, a high temperature silicon rubber is inserted in leak path 106, as shown in
In an embodiment, high temperature seal 108 may be adhered securely to thinner material 102 using a co-molding process. After high temperature seal 108 is securely attached to thinner material 102, a thinner material 102/high temperature seal 108 sub-assembly is over-molded on to a plastic over-molding tool for a subsequent injection of resin of thicker material 104. The co-molding process secures any leak paths in the sub-assembly. During a subsequent injection molding process where, for example, a plastic resin is over-molded to the sub-assembly, high temperature seal 108 is compressed in a specific direction according to the resin flow front (due to the effect of the plastic flow in the injection molding) and wetting will occur between high temperature seal 108 and the newly over-molded plastic resin (i.e., the thicker material) to produce a secure seal between thinner material 102 and thicker material 104 and block any leak paths or vacuum from forming between materials 102 and 104.
During the molding process when a resin of thicker material 104 is over-molded to the sub-assembly of the high temperature seal 108 and thinner material 102, as the resin flows on to high temperature seal 108, it will deform in the direction of the flow of the resin. Non-symmetrical rib 300 of high temperature seal 108 will therefore enable high temperature seal 108 to collapse at one side when high temperature seal 108 is compressed by the resin flow front in the injection molding process, as shown in 3B. Accordingly, after the molding process, rib 300 of high temperature seal 108 will be further off-centered, wherein the angle of the rib is denoted by B°. Thereafter, during temperature shock cycles when there is thermal expansion of at least one of the over-molded thinner material 102 and thicker material 104, materials 102 and 104 will expand at the different rates. Rib 300 of high temperature seal 108 may become relaxed or restored closer to its original shape when, for example, the plastic (i.e., the thicker material 104) expands. The shape of rib 300 before rib 300 is restored closer to its original shape is denoted by the area within the dashed lines in
Embodiments of methods and apparatuses disclosed herein provide a robust seal for an enclosure created from a bi-material process. The enclosure is created by over-molding a thicker material to a thinner material, thereby producing a significantly thinner enclosure. The seal blocks any leak paths or vacuum from forming between the thicker and thinner materials when the bi-material enclosure is exposed to temperature shock cycles. The seal therefore enables the bi-material enclosure to meet the ingress protection requirement as set forth, for example, in the IPX7 and IPX8 standards.
In the foregoing specification, specific embodiments have been described. However, one of ordinary skill in the art appreciates that various modifications and changes can be made without departing from the scope of the invention as set forth in the claims below. Accordingly, the specification and figures are to be regarded in an illustrative rather than a restrictive sense, and all such modifications are intended to be included within the scope of present teachings.
The benefits, advantages, solutions to problems, and any element(s) that may cause any benefit, advantage, or solution to occur or become more pronounced are not to be construed as a critical, required, or essential features or elements of any or all the claims. The invention is defined solely by the appended claims including any amendments made during the pendency of this application and all equivalents of those claims as issued.
Moreover in this document, relational terms such as first and second, top and bottom, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. The terms “comprises,” “comprising,” “has”, “having,” “includes”, “including,” “contains”, “containing” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises, has, includes, contains a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “comprises . . . a”, “has . . . a”, “includes . . . a”, “contains . . . a” does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that comprises, has, includes, contains the element. The terms “a” and “an” are defined as one or more unless explicitly stated otherwise herein. The terms “substantially”, “essentially”, “approximately”, “about” or any other version thereof, are defined as being close to as understood by one of ordinary skill in the art, and in one non-limiting embodiment the term is defined to be within 10%, in another embodiment within 5%, in another embodiment within 1% and in another embodiment within 0.5%. The term “coupled” as used herein is defined as connected, although not necessarily directly and not necessarily mechanically. A device or structure that is “configured” in a certain way is configured in at least that way, but may also be configured in ways that are not listed.
The Abstract of the Disclosure is provided to allow the reader to quickly ascertain the nature of the technical disclosure. It is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims. In addition, in the foregoing Detailed Description, it can be seen that various features are grouped together in various embodiments for the purpose of streamlining the disclosure. This method of disclosure is not to be interpreted as reflecting an intention that the claimed embodiments require more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive subject matter lies in less than all features of a single disclosed embodiment. Thus the following claims are hereby incorporated into the Detailed Description, with each claim standing on its own as a separately claimed subject matter.
