WO2014060935A1

WO2014060935A1 - Protective case of a portable electronic device

Info

Publication number: WO2014060935A1
Application number: PCT/IB2013/059347
Authority: WO
Inventors: Stuart Colam
Original assignee: Individual
Current assignee: Individual
Priority date: 2012-10-15
Filing date: 2013-10-14
Publication date: 2014-04-24
Anticipated expiration: 2015-04-15

Abstract

A protective case is described to be releasably secured to a mobile electronic device of the type having a front face incorporating a control panel, a rear face and a loudspeaker. The case is shaped to fit over the rear face of the device and incorporates, or defines in conjunction with the rear face of the device, a flat acoustic waveguide for amplifying sound emitted from the loudspeaker.

Description

PROTECTIVE CASE FOR A PORTABLE ELECTRONIC DEVICE

Field of the invention The present invention relates to a protective case for a portable electronic device that incorporates a

loudspeaker .

Background of the invention

It is known to provide portable electronic devices, such as cell phones and tablets, with a protective case that is releasably attached to the device but is intended to remain on the device at all times. Such a case is intended to protect the device against physical damage, for example from scratching, and it covers at least the rear part of the housing of the device.

There are many compact portable electronic devices that are currently in common use that produce sound and

incorporate a loudspeaker. Such devices include cell phones, tablets, music players and personal digital assistants, though this list is not intended to be exhaustive. The small size of the loudspeakers in such devices limits the quality and level (i.e. loudness) of the sound that they can

generate .

Summary of the invention According to the present invention, there is provided a protective case releasably securable to a portable

electronic device of the type having a front face

incorporating a control panel, a rear face and a

loudspeaker, the case being shaped to fit over the rear face of the device and having substantially the same area as the plan area of the device, the case being characterised by incorporating, or defining in conjunction with the rear face of the device, a flat acoustic waveguide for amplifying sound emitted from the loudspeaker of the device, wherein the waveguide has a throat for coupling acoustically to the loudspeaker and a mouth that opens laterally at the longest side of the case, the cross-sectional area of the waveguide increasing monotonically from the throat to the mouth, and the waveguide being shaped to occupy at least 70% of the plan area of the device. An acoustic waveguide has a throat acoustically coupled to a sound source, a mouth from which sound is emitted and a cross sectional area that varies with the distance from the throat. The cross sectional area at any point along the length of the waveguide is determined by its width and depth dimensions. The term "flat" is used herein to indicate that at the mouth of the waveguide, the width dimension exceeds the depth dimension by a factor of at least ten, more preferably thirty or forty. In some embodiments, the throat of the waveguide has a smaller cross-sectional area than the area of the

loudspeaker .

The width of the mouth of the waveguide may, in some embodiments, be equal to at least half of the length of the longest side of the protective case.

The depth of the waveguide, in some embodiments, may be substantially uniform over the length and width of the waveguide, though this need not necessarily be case.

The cross-sectional area of the waveguide may increase exponentially with the distance from the throat though it may alternatively vary hyperbolically . To avoid internal sound reflections back to the loudspeaker, it is essential for the increase in cross-sectional area with distance from the throat to be monotonic. It should be mentioned that there are currently

available docking stations for cell phones that

include an acoustic waveguide to increase the loudness of the sound emitted from the loudspeaker. The waveguides in these docking stations are not flat and, because of their resultant bulk, such docking stations cannot be permanently attached to the device or be considered suitably portable.

By using a flat waveguide, the invention allows acoustic amplification to be performed by a protective case that may be left attached to the device at all times without detracting from its portability. Despite the compactness of the acoustic waveguide, a suitably designed waveguide is capable of more than doubling the perceived loudness of the emitted sound.

It would be possible for all the walls of the waveguide to be part of the protective case but for increased

compactness the rear face of the device may, in some

embodiments, act as a wall of the waveguide.

In such embodiments of the invention, the protective case may comprise a base plate securable to the device in a position to overlie the rear face of the device, the base plate having projecting lands to contact the rear surface of the device, the lands being shaped to define between the plate and the rear face of the device an amplification horn acoustically coupled to the loudspeaker. A protective cover constructed in this manner need only add 3-4 mm to the depth of the device, while the plan area of the device need only be increased by a minimal amount on account of the wall thickness of the protective case and waveguide depth, in the case of a device that does not incorporate the loudspeaker on the rear face. The coupling between the loudspeaker of the device and the throat of the waveguide will depend on the position of the loudspeaker. In some cases, such as with some Apple® cell phones, the loudspeaker is on an edge of the device and a small extension of the waveguide is required to engage over the loudspeaker. In other cases, such as with some Samsung® cell phones, the loudspeaker opens onto the back of the device and no special adaptation of the waveguide is required .

The material of the protective case may be relatively rigid, such as a PES or polycarbonate plastics material, or it may be flexible or semi-rigid, such as an elastomer or a rubber .

In some embodiments, selected regions of the case are made of a rigid plastics material, while remaining regions are made of a conformable plastics material in order to achieve an effective seal between the case and the

electronic device. The rigid plastics material may be a polyurethane (TPU) while the conformable plastics material may be a polyethylene (TPE) .

It is desirable for the waveguide to be as long as possible while still fitting within an area of the same size as the rear face of the device. In order to achieve this, the flat waveguide may be convoluted, following a generally sinuous path between the throat and the mouth. The lands forming the side walls of the waveguide may be solid or hollow. If hollow, some of the side wall sections may act as resonant spring masses and this effect may be used to advantage to enhance the performance of the waveguide at some frequencies.

Many devices incorporate a photographic camera with a lens positioned on the rear face of the device. For such devices, it is desirable to ensure that a hollow land is positioned in alignment with the camera lens and dimensioned to avoid the field of the view of the lens being obstructed or obscured by the protective cover.

If solid, the lands may be made of the same material as the remainder of the plate and the two may be formed at the same time by injection moulding. On the other hand, it may be possible to form the lands separately and to secure them to the base plate.

For its attachment to the device, the case may have upstanding side walls with a retaining lip to the clipped over the sides of the device, the cover being retained in place by the resilience of the side walls. As an

alternative, the side walls may have lips on three sides to form an open channel into which the electronic device may be slid from the fourth side.

Brief description of the drawings

The invention will now be described further, by way of example, with reference to the accompanying drawings, in which :

Fig. 1 is a plan view of a protective case of the invention intended for use with a portable electronic device having a loudspeaker on its edge,

Fig. 2 is a perspective view from one side of the case shown in Fig. 1,

Fig. 3 is a perspective view from the other side of the case shown in Fig. 1, and

Fig. 4 is a perspective view to an enlarged scale of the throat end of the waveguide in Fig. 2. Detailed description of the preferred embodiment

The protective case 10 shown in the drawings comprises a base plate 12 with upstanding sides 14 around its entire perimeter. The sides wall 14, in use, surround the edge of a portable electronic device, such as a cell phone, and have various openings to allow access to control buttons and connectors . Two lands 20 and 22 project above the inner surface of the base plate 12. In use, a device sits within the case and is gripped by the sides 14 with it rear face is contact with the upper surfaces of the lands 20 and 22. In this way, there is defined within the case 10, that protects the rear surface and the housing of the device, a flat sinuous acoustic waveguide 16 of rectangular cross-section, of which the lower surface as viewed in Figs. 2 to 4 is formed by the base plate 12, the upper surface is formed by the rear face of the housing of the device and the two sides are formed by the lands 20 and 22, respectively.

The acoustic waveguide, which occupies at least 70% of the plan area of the case, has a throat 18 acoustically coupled to the loudspeaker of the device and a wide mouth 24 formed by a cut-out at the lower edge of one of the

upstanding sides 14. Between the throat 18 and the mouth 24, the waveguide cross-sectional area increases monotonically with the distance from the throat, following an exponential or parabolic relationship.

The illustrated case 10 is intended for a cell phone having a loudspeaker on its edge and to couple the throat 18 of the waveguide 16 to the loudspeaker a small extension is provided on one corner of the case that overlies a cut-out 26 in line with the throat of the waveguide. In use, sound emitted from the loudspeaker of the device travels by way of the extension into the throat 18 of the acoustic waveguide. The sound then travels along, and is amplified by, the waveguide 16, before exiting by way of the wide narrow mouth 24 which opens onto the longer side of the case 10 and extends over more than half its length.

The case 10, at the same time as protecting the housing of the device, offers the advantage of acting as an

amplifier of the sound emitted from the loudspeaker of the device. The case 10 may remain permanently attached to the device and only adds a few millimetres, typically three or four, to the depth of the device. If both the base plate 12 and the rear face of the device housing are flat, the depth of the waveguide 16 will be substantially uniform over its length and width. This however need not be so, as the upper surfaces of the lands 20 and 22 can be differently contoured to mate with the rear face of the device and upper surface of the base plate 12 need not itself be flat.

The coupling between the loudspeaker of the device and the throat of the waveguide will depend on the position of the loudspeaker. The illustrated embodiment is suitable for cell phones, such as some Apple® telephones, where the loudspeaker is on an edge of the device. With other devices, such as with some Samsung® cell phones, the loudspeaker opens onto the back of the device and this would avoid the need for a lateral extension.

The material of the protective case may be relatively rigid, such as a PES or polycarbonate plastics material, or it may be flexible or semi-rigid, such as an elastomer or a rubber. It is possible for the case to be made of two different materials. The first material may be relatively flexible and conformable to achieve a better seal where needed and the second material may be made of a more rigid material for better acoustic performance.

Thus, the case may be formed of a substantially rigid outer shell forming the back, the internal lands and at least part of the sides and a conformable inner layer may be applied to the regions of the case that come into contact with the sides and back of the device, i.e. the lands and inner surfaces of the side walls. Typical examples of these materials are polyurethane (TPU) for the outer shell and polyethylene (TPE) for the compressible lining, though any other appropriate material may be used. The compressible material is employed to provide an airtight seal between the case and the device and to avoid the need for exacting tolerances in the case. It is envisaged that a 'two shot' injection moulding process would be used to mass produce the case.

The lands forming the side walls of the waveguide may be solid, as is the case for the land 22 or hollow as is the case of the land 20. The effect of the cavity 30 in the land 20 is to make the side wall section 32 act as a resonant spring mass and this effect is used to advantage to enhance the performance of the waveguide at some frequencies.

The cavity 30 is also positioned to overlie a camera lens located on the back of the device so as to avoid the protective case interfering with the field of view of the camera .

The lands 20 and 22 may be made of the same material as the remainder of the base 12 plate and the two may be formed at the same time by injection moulding. On the other hand, it would be possible to form the lands separately and to secure them to the base plate.

The illustrated embodiment additionally includes several small ribs 34 at the mouth 24 of the acoustic waveguide. These do not serve any purpose acoustically but provides mechanical support to the side section of the side wall 14 overlying the mouth 24. In the illustrated embodiment, the case has upstanding side walls 14 intended to the clipped over the sides of the device, the cover being retained in place by the resilience of the side walls 14. As an alternative, it would be

possible to form the side walls 14 with overhanging lips on three sides, so as to form an open channel into which the device may be slid from the fourth side.

The housing of the device is used in the illustrated embodiment of the invention to act as one wall of the acoustic waveguide, which makes for greater compactness. It would however alternatively be possible for all the walls of the waveguide to be part of the protective case, the

protective case forming a self-enclosed acoustic waveguide that is clipped on to the underside of the device.

While the illustrated protective case is intended for a mobile telephone, it will be clear that the invention is equally applicable to other electronic devices, such as tablets and music players, that have a built-in loudspeaker.

Claims

1. A protective case releasably securable to a portable electronic device of the type having a front face incorporating a control panel, a rear face and a

loudspeaker, the case being shaped to fit over the rear face of the device and having substantially the same area as the plan area of the device, the case being characterised by incorporating, or defining in conjunction with the rear face of the device, a flat acoustic waveguide for amplifying sound emitted from the loudspeaker of the device, wherein the waveguide has a throat for coupling acoustically to the loudspeaker and a mouth that opens laterally at the longest side of the case, the cross-sectional area of the waveguide increasing monotonically from the throat to the mouth, and the waveguide being shaped to occupy at least 70% of the plan area of the device.

2. A protective case as claimed in claim 1, wherein the throat of the waveguide has a smaller cross-sectional area than the area of the loudspeaker.

3. A protective case as claimed in claim 1 or 2, wherein the width of the mouth of the waveguide is at least half of the length of the longest side of the device.

4. A case as claimed in any preceding claim, wherein the depth of the waveguide is substantially uniform over the length and width of the waveguide.

5. A case as claimed in any preceding claim, wherein the cross-sectional area of the waveguide increases

exponentially with the distance from the throat.

6. A case as claimed in claim 1 or 4, wherein the cross-sectional area of the waveguide increases

hyperbolically with the distance from the throat.

7. A case as claimed in any preceding claim, wherein the rear face of the device acts, when the case is in use, as a wall of the waveguide.

8. A case as claimed in claim 7, comprising a base plate securable to the device in a position to overlie the rear face of the device, the base plate having projecting lands to contact the rear surface of the device, the lands being shaped to define the acoustic waveguide between the base plate and the rear face of the device.

9. A case as claimed in claim 8, wherein the lands forming the side walls of the waveguide are solid.

10. A case as claimed in claim 8, wherein at least one of the lands forming the side walls of the waveguide is hollow to avoid obstruction of a camera lens positioned on the rear face of the device.

11. A case as claimed in any one of claims 8 to 10, wherein the lands are made of the same material as the remainder of the base plate and are formed at the same time as the base plate.

12. A case as claimed in any one of claims 8 to 10, wherein the lands are formed separately and subsequently secured to the base plate.

13. A case as claimed in any preceding claim, for a device having a loudspeaker located on an edge of the device, wherein the case includes an extension to engage over the loudspeaker.

14. A case as claimed in any preceding claim, wherein the case is formed of a rigid material.

15. A case as claimed in claim 14, wherein the material of the case is a PES (PolyEtherSulphone) or a polycarbonate plastics material.

16. A case as claimed in any one of claims 1 to 13, wherein the case is formed from a flexible or semi-rigid material .

17. A case as claimed in claim 16, wherein the material of the case is an elastomer or a rubber.

18. A case as claimed in any one of claims 1 to 13, wherein selected regions of the case are made of a rigid plastics material and remaining regions are made of a conformable plastics material in order to achieve an effective seal between the case and the electronic device.

19. A case as claimed in claim 18, wherein the rigid plastics material is polyurethane (TPU) .

20. A case as claimed in claim 18 or 19, wherein the conformable plastics material is a polyethylene (TPE) .

21. A case as claimed in any preceding claim, wherein the flat waveguide is convoluted and follows a generally sinuous path between the throat and the mouth whereby to optimise the length of the waveguide.

22. A case as claimed in any preceding claim, having upstanding side walls with a retaining lip to be clipped over the sides of the device, the cover being retained in place on the device by the resilience of the side walls.

23. A case as claimed in any of claims 1 to 21, having upstanding side walls with lips on three sides to form an open channel into which the device may be slid from the fourth side.