IMPROVED HOUSING AND MANUFACTURE THEREOF

Field of Invention

The invention relates to electronic devices having display screens mounted within a housing. In particular, the types of electronic devices include hand held devices including PDAs, mobile phones, laptop computers and the like which are specifically adapted for portability and thus experiencing a varied environment as compared to desktop devices which are subjected to constant favourable conditions.

Background

Portable devices by their nature are subjected to environments which vary in temperature, humidity, exposure to sunlight etc, far greater than analogies devices used in an office or home environment.

More particularly, portable devices which are used in an industrial environment as compared to a commercial environment have an even greater variation in temperature, humidity etc. It follows that such devices will require a greater capacity to resist change and accommodate thermal and time dependent expansion and contraction so as to maintain high performance.

One component of said devices having a very high impact on performance is the display screen which in said devices is substantially comprised of a polymer film. Polymers, by

their nature, are both adversely affected by thermal and time dependent expansion and contraction when used in widely varying environmental conditions such as that experienced by the aforementioned devices. A particular problem experienced by such display screens may be collectively described as "puffiness" which includes swelling or deflation of the screen causing respectively convex or concave defamation of the polymer film. Alternatively or on a worse case together with this defamation, is corrugation of the polymer film which maybe caused by a number of different effects including a differential tension of the polymer film or frequent and or rapid changes in temperature leading to advanced time dependent effects.

For conventional display screens "puffiness" can be unsightly, detracting from the aesthetic appeal of the device. Further and particularly caused by deflation of the screen, diffraction patterns within the screen commonly referred to as "Newton's Rings" which cause discolouration of the screen and so obscuring the display.

Another drawback is that experienced by "touch screens" being a variation of the display screen used on such devices. In this case the touch screen provides an alternative data input mechanism whereby the operator depresses a portion of the polymer film so as to make an electrical contact between the polymer film and an underline film separated from the polymer film by a predetermined gap. It follows that in this application, should this predetermined gap vary outside acceptable limits, the performance of the device will suffer either through poor contact and, therefore, intermittent data input or in a worse case such as through deflation, decrease the gap

between the films and thus make it easier for accidental contact between the films and thus causing erroneous data input.

It would be advantageous if the long term effects of varying environmental conditions could be minimized so as to lengthen the effective life of such devices.

Statement of Invention

In general terms the invention provides for an arrangement of components so as to facilitate sliding as a means of time and/or temperature related stress relief.

In a first aspect the invention provides an electronic device comprising a first component in sealing engagement with a second component of said device, wherein said sealing engagement includes contact between a discontinuous portion of the first component and a continuous surface of the second component, said discontinuous portion being of a more rigid material than the surface of the second component.

Li a second aspect the invention provides An electronic device comprising; a housing; a display screen; a gasket located at an interface between said housing and display screen for sealing said interface; wherein the housing contacts the gasket at a continuous surface on said gasket, said surface arranged to facilitate sliding contact between the housing and the gasket.

In a third aspect, the invention provides an electronic device comprising; a housing; a display screen; a gasket located at an interface between said housing and display screen for sealing said interface; wherein the gasket contacts the display screen at a continuous surface on said screen, said surface arranged to facilitate sliding contact between the gasket and the display screen.

In a preferred embodiment the invention may include a sliding surface on the gasket so as to accommodate time and temperature dependent movement between the housing and the gasket.

In a further preferred embodiment the housing may include a discontinuity for contacting the sliding surface of the gasket.

Alternatively the screen may include a sliding surface with the gasket having a ^' discontinuity for contacting the sliding surface of said screen.

In a preferred embodiment the discontinuity may include a ridge projecting from the relevant component, said ridge having a distal contact point when viewed in cross section. Said contact point may provide a line contact along the longitudinal axis of the ridge as it contacts the corresponding sliding surface. Said point may include a sharp edge or a rounded edge having a radius of up to lmm. Preferably the radius of said edge will be less than 0.5mm and more preferably 0.25mm.

It will be appreciated that sliding will be as a consequence of overcoming friction between the corresponding elements. For instance, the gasket 2 housing interface may have a frictional constant in the range of 0.4 to 0.8.

In a further aspect the mechanism involves an arrangement of components having materials of differential stiffness used for the housing gasket and display screen. By comparison the types of material used for the housing may include ABS, polycarbonate or a homo-polymer polypropylene.

Conversely, the gasket may include materials such as polyurethane, polyethylene or

EPDM. By providing the sliding surface on the softer material with the discontinuity of a rigid material, the discontinuity will tend to maintain its shape and so minimize the contact area between the two components. Alternatively, by having the discontinuity of a softer material, the discontinuity will typically deform to an essentially continuous surface and thus provide a higher contact area between the components.

In a preferred embodiment, the components of construction of the electronic device may include a housing containing the electronics of the device, a display screen, which may be of a conventional type or a touch screen variety, and a gasket sealing the interface between the display screen and the housing.

The housing used to contain the electronics of the device may be in several discrete portions, which are assembled to perform the containment function. For the purposes of the invention, the housing relates to that portion proximate to, and in engagement with,

the display screen, whether this be in several portions joined together, or a single portion.

In a preferred embodiment, the first component may be the housing and the second component may be the gasket. In this case, the discontinuous portion may be a ridge projecting from said housing positioned to contact the continuous surface of said gasket.

Alternatively, the first component may be the gasket and the second component may be the display screen. In this case, the discontinuous portion may be a ridge projecting from said gasket positioned to contact the continuous surface of said display screen. Further, contact between the gasket and screen may be through corresponding contact surfaces.

hi a preferred, the continuous surface may include a low friction layer to facilitate said sliding. For instance, a Teflon layer may be added to said surface, hi a another embodiment, a lubricant may be added to the surface. Alternatively, the material of the respective component may be selected from a suitable low friction material.

The continuous surface may be a planar surface, or having a curvature of high radius, hi any event, the surface must avoid having portions upon which the sliding component may be prevented from sliding.

Brief Description of Drawings

It will be convenient to further describe the present invention with respect to the accompanying drawings that illustrate possible arrangements of the invention. Other arrangements of the invention are possible and consequently the particularity of the accompanying drawings is not to be understood as superseding the generality of preceding description of the invention.

Figure 1 is an isometric view of a PDA having a screen mounted within a housing; Figure 2 is a detailed sectional view of the present invention according to a first embodiment; Figure 3 A is a schematic view of the present invention according to a second embodiment and; Figure 3 B is a schematic view of the present invention according to a third embodiment.

Description of Preferred Embodiment

Figure 1 shows an electronic device 5, in this case a PDA having a housing 10 into which is mounted a screen 15. The device 5, as shown, is by external appearances of a conventional construction. Figure 2 shows a cross sectional view of the arrangement of the housing 10 and screen 15 having a gasket 20 intermediate the housing 10 and screen 15. The gasket provides a sealing function by preventing the ingress of moisture and detritus and is formed for use in industrial conditions.

A wide contact interface 40 between the housing 10 and the gasket 20 is provided as is an interface 25 between the gasket 20 and the screen 15. A further interface is provided

whereby the housing 10 having a discontinuous edge 35 presses into the gasket 20 at a contact surface 30. Thus, the positive resilient engagement between the housing 10 and gasket 20 is provided not at the wide interface 40 but instead by the interaction between the discontinuous edge 35 and the surface 30.

The interference shown in Figure 2 between the discontinuous edge 35 and a surface 30 suggests the force contact between the two components so as to provide positive engagement. However, with time and temperature effects, differential expansion and contraction between the various components requires there to be some permissible movement within the arrangement so as to not cause a deformity of the screen 15. Such deformity may lead to a "puffϊness" of the screen 15 such as may be caused by shrinkage of the housing applying an internal force to the screen 15 via the gasket 20. Conversely on expansion of the housing 10, the corresponding force applied to the screen will tend to stretch said screen, with time dependent relaxation of the screen leading to deformity, such as concavity or a ripple effect on said screen.

Any deformity of the screen may lead to the image being obscured through an effect such as Newton's rings or in the case of a touch screen display, may adversely affect the contact distance between the screen and the underlying contacts.

The present invention minimizes these detrimental effects by providing a sliding engagement between the discontinuity 35 of the housing 10 and the sliding surface 30 of the gasket 20. In this embodiment, the discontinuity 35 being of a more rigid material than the gasket 20 maintains its shape and thus minimizes the contact area between the

sliding surface 30 and the gasket 20. In this arrangement, sliding is promoted so as to limit the effects of temperature and time related influences.

Figure 3 A shows a second embodiment of the present invention whereby the housing 50 again has a discontinuity 65 in contact with the sliding surface 60 of the gasket 45. Here the gasket 45 has a large contact area with the screen 55 so as to avoid significant movement between the gasket 45 and the screen 55.

Figure 3B shows a further embodiment whereby the housing 75 also engages the gasket 70 which correspondingly engages the screen 80. In this embodiment, the contact area between the housing 75 and gasket 70 is provided by mutually engaging surfaces at interface 85. However, the gasket 70 further includes a discontinuity 95 which engages the sliding surface 100 of the screen 80. As previously discussed, a discontinuity aids in the sliding effect of corresponding components where the discontinuity is relatively stiff compared to the contact surface. In this case, as the screen must have a flat display surface 100, it will aid in the sliding effect by providing the discontinuity 95 on the gasket 70. As mentioned previously, the differential rigidity of materials aids in the sliding effect. In this case, there is again a differential in rigidity between the gasket 70 and the screen 100 in that the gasket and in particular, the discontinuity in this case a non-flexural projecting edge 95 bears on to the softer material of the surface 100 of the screen 80.