GB2444092A

GB2444092A - Electronic device, keypad and switch mechanism

Info

Publication number: GB2444092A
Application number: GB0623162A
Authority: GB
Inventors: Avi Rozin; Eliezer Ribak; Michael Zevin
Original assignee: Motorola Inc
Current assignee: Motorola Solutions Inc
Priority date: 2006-11-21
Filing date: 2006-11-21
Publication date: 2008-05-28
Anticipated expiration: 2026-11-21
Also published as: GB2444092B; GB0623162D0

Abstract

An electronic device comprises a switch mechanism having a bridging element (210), the switch mechanism comprising a first contact (270) and a second contact (280). The bridging element (210) comprises a contact surface (260), which is arranged to be coupled to the first and second contacts (270, 280) of the switch mechanism. The bridging element (210) further comprises two or more bridging formations (220) located on the contact surface (260) such that, when the bridging element (210) is in the closed condition, at least one bridging formation (220) forms an electrical contact with one of the first or second contacts (270, 280). The bridging formations (220) are in the form of dimples or protrusions and the switch mechanism comprises a dome switch. The electronic device may be a mobile telephone handset, personal computer or a domestic, commercial or industrial appliance.

Description

1 2444092 Electronic device, keypad and Switch Mechanism

Field of the Invention

This invention relates to an electronic device, keypad and switch mechanism, and in particular to a bridging element for use in the electronic device.

Background of the Invention

In the field of this invention, it is known to use

electrical switches, such as dome switches in keypads, control panels, etc., in electrical and electronic devices. FIG. 1 shows a number of views of a known dome switch mechanism, such as an illustration of an overhead view 100. The switch mechanism comprises an outer contact and an inner contact 130, located on, for example, a printed circuit board (PCB) 110.

The dome switch mechanism further comprises a conductive dome as illustrated by the broken line 140. It is known in the art to provide a dimple 150, or similar protrusion, on the underside of the dome 140, to improve the making of an electrical contact between the dome 140 and the inner contact 130.

The purpose of the dimple 150 is generally to avoid a situation where foreign materials, which may accumulate on the inner contact 130, preventing the dome 140 making contact with the inner contact 130.

A dome without a dimple would simply crush the foreign material between the dome and the contact. The foreign material would subsequently become an obstacle in between the two. This may prevent an electrical contact being made.

Thus, the provision of a dimple provides a means of penetrating through the foreign matter, thereby maintaining the ability to create an electrical contact.

An enlarged cross-sectional view 105 of the dome switch mechanism, along the line A:A, is illustrated. As can be seen, in a resting' or open' position, the dimple 150 of the dome switch mechanism 100 is situated apart from the inner contact 130, due to the substantially convex shape of the dome 140. In the illustrated example, the edge of the dome 140 is in contact with the outer contact 120.

When a force is exerted on the upper surface of the dome 140, as represented by the arrow B', the dome 140 deforms such that its centre is displaced towards the PCB 110. Assuming sufficient force is supplied, the dimple comes into contact with the inner contact 130. In this manner, the dome 140, with the aid of the dimple 150, creates an electrical circuit between the inner contact 130 and the outer contact 120.

Referring now to a further enlarged cross-section view 170, there is illustrated a problem with this known dome switch mechanism. The problem arises due to non-conductive contaminants 160, such as dust particles, hairs, etc., which may become located between the dome and printed circuit board (PCB) inner contact 130.

1ff such contaminants become situated between the dimple and the inner contact 130, they can prevent contact being made between the dimple 150 and the inner contact 130.

Consequently, either no electrical contact is achieved, or a larger force is required such that the dome 140 is deformed sufficiently for another part of the dome 140 to come into contact with the inner contact 130. Even when electrical contact can he achieved by way of a larger force, the application of such a large force is likely to he unacceptable, and potentially uncomfortable, to a user as well as potentially deforming the dome 140. This is particularly the case for devices such as mobile telephone handsets comprising a keypad that makes use of such switch mechanisms. Users of such devices frequently make multiple depressions in rapid succession.

Consequently, if excessive force is required for any key, this will substantially inhibit the user's ability to make such inputs.

A need therefore exists for a switch mechanism, wherein one or more of the above-mentioned problems may be alleviated.

Summary of the Invention

In accordance with a first aspect of the present invention, there is provided an electronic device, as claimed in Claim 1.

In accordance with a second aspect of the present invention, there is provided a switch mechanism, as claimed in Claim 14.

In accordance with a third aspect of the present invention, there is provided a keypad or control panel, as claimed in C1aim 17.

Further aspects and advantageous features of the present invention are as described in Lhe appended Claims.

In summary, the present invention relates to an

electronic device comprising a bridging element for use as part of a switch mechanism, the switch mechanism comprising a first contact area and a second contact area. The bridging element comprises a contact surface, which in use generally faces the first and second contacts of the switch mechanism. The bridging element further comprises two or more bridging formations located on a central region of the contact surface such that, when the bridging element is in a closed condition, at least one bridging formation forms an electrical contact with one of the first or second contact areas.

Brief Description of the Drawings

Exemplary embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: FIG. 1 illustrates of an overhead view and cross-sectional views of a known dome switch mechanism; FIG. 2 illustrates an overhead view and cross-sectional views of a bridging element; FIG. 3 illustrates a perspective view of the bridging element of FIG. 2; FIG. 4 illustrates a perspective view of a bridging element according to an alternative embodiment of the present invention; FIG. 5 illustrates an example of an electronic device in accordance with an embodiment of the present invention; arid FIG's 6 arid 7 illustrate cross-sectional views of the electronic device of FIG. 5.

Description of Embodiments of the Invention

Referring now to FIG. 2, there is illustrated an overhead view of a bridging element 210 according to an embodiment of the present invention. The bridging element 210 comprises a plurality of bridging formations 220.

There is illustrated a cross-sectional view 215 of the bridging element 210, along the line C:C. The bridging element 210 is illustrated as part of a switch mechanism, where the switch mechanism comprises a first, substantially concentric outer contact 270 and a second, inner contact 280. For the illustrated embodiment, the outer and inner contacts 270, 280 are located on a printed circuit board (PCB) 290.

For simplicity, the bridging element 210 will be described hereinafter as having an upper surface 250 and a lower surface 260, as illustrated in the cross-sectional view 215. The lower surface 260 acts as a contact surface, generally facing the contacts 270, 280 of the switch mechanism. However, it will be appreciated by a skilled artisan that, in use, a bridging element may be rotated along any axis as required, for example to correspond with the orientation of the PCB.

Consequently, depending upon the orientation of the bridging element, the use of the terms "upper" and "lower" to describe the surfaces of the bridging element may be understood as encompassing any two surfaces that distinguish respective areas of the bridging element.

For the illustrated embodiment, the bridging formations 220 each comprise a substantially semi-spherical, or dome shaped protrusion located on the lower surface 260 of the bridging element 210, in a substantially central region 230. However, the present invention is not limited to such dome shaped protrusions. The bridging formations 220 may comprise any other suitable shape arid/or configuration.

In the cross-sectional view 215, the bridging element 210 is in a resting, or "open" condition, whereby the substantially central region 230 of the bridging element 210, and in particular the bridging formations 220, are located substantially opposite, but distal from, the inner contact 280. An outer, or edge region 240 of the bridging element 210 is located substantially adjacent, and may as illustrated be in contact with, the outer contact 270.

When a force D is exerted on the upper surface 250 of the bridging element 210, for example as a result of a user pressing a button or key with which the switch mechanism is associated, the bridging element 210 deforms into, or otherwise takes on, a "closed" condition (not shown) In this closed condition, the substantially central region 230 of the bridging element 210 has been displaced towards the inner contact 280, such that the bridging formations 220 come into contact with the inner contact 280. Furthermore, the outer region 240 of the bridging element 210, ii not already in contact with the outer contact 270, comes into contact wit1 the outer contact 270.

When the force D is removed, for example when the user releases the button or key, the bridging element reverts back to its open condition, as illustrated. Consequently, the bridging formations 220 no longer make contact with the inner contact 280.

The bridging element 210 comprises an electrically conductive patch between the outer region 240 and the bridging formations 220. In this way, when in the closed condition, the bridging element creates a closed electrical circuit between the outer and inner contacts 270, 280 of the switch mechanism.

The electrically conductive path of the bridging element 210 may be achieved in any suitable manner. For example, the bridging element 210, including the bridging formations 220, may be made from a conductive material, such as stainless steel or the like, for example AISI 301 (American Iron and Steel Institute standardised numbered steel grade) Alternatively, the lower surface of the bridging element 210, including the surfaces of the bridging formations 220, may be coated in a conductive material, for example nickel, silver or gold plated.

As previously mentioned, the prior art suffers from the problem of non-conductive contaminant particles, such as dust, hair arid the like, becoming located between the bridging element, in particuiar the bridging formation, and the inner contact.

Consequently, either rio electrical contact is possible, or a Jarger force is required such that the bridging element is deformed sufficiently for a part other than the bridging formation to come into contact with the inner contact. Even when electrical contact can be achieved by way of a larger force, the application of such a large force is likely to be unacceptable, and potentially uncomfortable, to a user.

This is particularly the case for devices such as mobile telephone handsets comprising a keypad that makes use of such switch mechanisms. Users of such devices frequently make multiple inputs in rapid succession. Consequently, if excessive force is required for any key, this will substantially inhibit the user's ability to make such key depressions.

As will be appreciated by a skilled artisan, the present invention significantly alleviates this problem by providing a plurality of bridging elements. In this way, if a non-conductive contaminant particle should become located between the bridging element and the inner contact, even if the contaminant particle prevents contact between one bridging formation and the inner contact, an electrical contact can still be made between the inner contact and the or one or more additional bridging formation(s) In the illustrated embodiment, the bridging element 210 comprises three bridging formations 220 in a configuration substantially resemh]ing an equilateral triangle. This has been found to be the preferred number and configuration of bridging formations 220, since the apex regions of the formations create a general plane for creating a contact. Nevertheless, the present invention is not limited to this number or configuration of bridging formations. It is envisaged that any suitable arrangement of two or more bridging formations may alternatively be provided.

For example, the bridging formations 220 may be situated in a substantially square configuration (for example where four bridging formations are provided) or a generally polygonal configuration (for example where five or more formations are provided) Furthermore, the bridging formations 220 are illustrated substantially adjacent one another. If the bridging formations 220 are located too far apart, and/or located too far from the substantially central region 230 of the bridging element 210, when the bridging element 210 is in the closed condition, the under surface 260 of the bridging element 210 will come into contact with the inner contact 280 before the bridging formations 220.

As will be appreciated, this is undesirable since this would result in a situation akin to that where no bridging formation is present.

As previously mentioned, the purpose of the bridging formation 220 is to avoid the scenario of foreign materials, which may accumulate on the inner contact 280, from preventing the bridging element 210 from making contact with the inner contact 280.

A bridging element without a bridging formation would simply crush the foreign material between the bridging element and the contact. The foreign material would subsequently become an extended obstacle in between the two. This would further prevent an electrical contact being made.

However, a bridging formation provides a means of penetrating through the foreign matter, thus maintaining the ability to create an electrical contact.

Investigations have shown that this problem is substantially alleviated when the ratio between the diameter of the bridging formation distribution circle 205 and the height of the bridging formations 220 below the under surface 260 of the bridging element 210 is less than or equal to twenty three.

For clarity, the bridging formation distribution circle 205 is a circle whose circumference passes through the apex of each bridging formation 220.

Investigations have also shown that, if the bridging formations 220 are too close together, there is an increased likelihood that where a non-conductive contaminant particle is present, a number of the bridging formations 200 will be affected by it.

Consequently, in an exemplary embodiment of the present invention, the ratio between the diameter of the bridging formation distribution circle 205 and the height of the bridging formations 220 below the under surface 260 of the bridging element 210 may be between fifteen and twenty.

Referring now to a further cross-sectional view 225, there is illustrated a part of the substantially central region 230 of the bridging element 210. For the illustrated embodiment of the present invention, the bridging formations 220 are an integral part of the bridging element 210, produced by deforming the bridging element 210 itself such that convex protrusions are created on its the lower surface 260 to create the bridging formations 220, with concave formations being created on its upper surface 250. In this way, the bridging element 210 maintains a substantially uniform thickness.

In an alternative embodiment, each bridging formation 220 is provided by increasing the thickness of the bridging element 210, such that the upper surface 250 remains substantially smooth, whilst its lower surface 260 protrudes to create the bridging formation 220.

In a still further embodiment of the present invention, the bridging formations 220 are non-integral components, which are affixed to the lower surface 260 of the bridging element 210, for example by way of an adhesive, solder or weld, etc. Referring now to FIG. 3, there is illustrated a perspective view of the bridging element 210. For this illustrated embodiment of the present invention, the bridging element has a substantially circular configuration. However, the present invention is not limited to such a circular configuration, and may comprise any suitable configuration.

For example, FIG. 4 illustrates an alternative embodiment of the present invention, whereby a bridging element 410 comprises a substantial]y cross-shaped configuration. A bridging element comprising such a configuration is sometimes referred to as a square" dome, although it is envisaged that the dome may be of a substantially triangular, oval or indeed any other shape. In accordance with the present invention, the bridging element 410 of FIG. 4 comprises a plurality of bridging formations 420.

In addition to the bridging elements 420 located in a substantially central region of the bridging element 410, the bridging element 420 of FIG. 4 further comprises additional bridging elements 430 spaced around an outer region of the bridging element 420. These additional bridging formations 430 facilitate the creation of an electrical contact with an outer contact, such as the outer contact 270 of FIG. 2.

Referring now to FIG. 5, there is illustrated an example of an electronic device in which one or more bridging elements implementing the inventive concept may be provided. For the illustrated embodiment, the electronic device is a mobile telephone handset 500. However, it is envisaged that the inventive concept may be applied to any electronic device comprising a data entry mechanism, such as a mobile device installed in a vehicle, a portable or hand held communication, domestic item, etc. The mobile telephone handset 500 comprises various user interface components, such as a display 510, a keypad 520, a speaker 530 and a microphone 540.

The keypad 520 comprises a plurality of keys 550. The keys 550 may include, by way of example only, menu navigation keys, answer and end call keys, numeric 0-9 keys, a "k" key and a "#" key.

Referring now to FIG. 6 and FIG. 7, FIG. 6 illustrates an exploded cross-sectional view of the mobile telephone handset 500 along the line E:E of FIG. 5. FIG. 7 illustrates an un-exploded cross-sectional view of the mobile telephone handset 500 along the line E:E.

In the illustrated embodiment, the mobile telephone handset 500 comprises a front cover part 600, a central housing part 610 and a back cover part 620.

A printed circuit board (PCB) 630, comprising contacts 640, is located between the front cover part 600 and the central housing part 610, substantially adjacent the central housing part 610. A flexible membrane 650 comprising bridging elements 660, and a key mat 670 are also located between the front cover part 600 and the central housing part 610. Finally, a battery 680 is located between the central housing part 610 and the back cover part 620.

The key mat 670 comprises keys 675 extending therefrom, which in use extend through apertures 605 in the front cover part 600.

The bridging elements 660 are located on a surface of the flexible membrane 650 adjacent the PCB 630, and are affixed, for example by way of an adhesive, to the surface of the membrane 650.

The keys 675, bridging elements 660 and contacts 640 are located in substantially corresponding positions. In this mariner, when a key is pressed, the force exerted on the key displaces the key towards the central housing part 610. This, in turn, exerts a force on the corresponding bridging element 660, such that the bridging element 660 deforms into a closed condition, as described above. n the closed position, bridging formations (not shown) on a central region of the bridging element 660 come into contact w th an inner contact of the corresponding contacts 640, closing an electrical circuit and causing a signal to be sent to, for example, a processor (not shown), indicating that the key was pressed.

The inventive concept of the present invention has been illustrated in use within a mobile telephone handset 500.

however, it will be appreciated that the present invention may equally be used within any other electrical or electronic device comprising a keypad or control panel having one or more keys or buttons. Such devices may include, by way of example only: i) Handheld electronic devices, for example telephones, calculators, personal digital assistants, portable media players, etc. ii) Domestic appliances, for example washing machines, coffee machines, televisions, etc. iii) Commercial and/or industrial machinery and/or appliances.

Furthermore, in FIG. 6 and FIG. 7 the bridging elements 660 are illustrated as being affixed to a flexible membrane 650, with keys 675 provided by the key mat 670 in use, applying a force to deform the bridging elements into the closed condition. However, it will be appreciated by a skilled artisan that any other suitable arrangement may be provided for allowing a user to apply an appropriate force to the bridging elements.

For example, Lhe flexible membrane may comprise indicia representing keys/buttons on a reverse surface to that on which the bridging elements are located. In this way, a user applies a force directly to the flexible membrane 650.

It will be understood that an electronic device comprising the bridging element, as described above, tends to provide one or more of the following advantages: 1) a significant reduction of the adverse affects of non-conductive contaminant particles; ii) improved performance of switches arid/or keys utilising such a bridging element; iii) no alteration required to any other components, including, in particular, the size and or layout of a POB or the like on which the contacts are provided; iv) no adverse cost implications compared to the

prior art, since the cost of manufacture of

bridging elements embodying the inventive concept herein described is comparable to that of known bridging elements; or v) no variation in the user experience, for example the tactile fee1 of a switch.

Although the present invention has been described in connection with some embodiments, it is not intended to be limited to the specific form set forth herein.

Rather, the scope of the present invention is limited only by the accompanying claims. Additionally, although a feature may appear to be described in connection with particular embodiments, one skilled in the art would recognize that various features of the described embodiments may he combined in accordance with the invention. In the claims, the term comprising' does not exclude the presence of other elements or steps.

Furthermore, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. Also, the inclusion of a feature in one category of claims does not imply a limitation to this category, but rather indicates that the feature is equally applicable to other claim categories, as appropriate.

Furthermore, the order of features in the claims does not imply any specific order in which the features must be performed and in particular the order of individual steps in a method claim does not imply that the steps must be performed in this order. Rather, the steps may be performed in any suitable order. In addition, singular references do not exclude a plurality. Thus, references to "a", "an", "first", "second" etc. do not preclude a plurality.

Thus, an improved electronic device, keypad and switch mechanism, which incorporate an improved bridging element, have been described wherein the aforementioned disadvantages associated with prior art arrangements have been substantially alleviated.

Claims

Claims 1. An electronic device comprising a switch mechanism having a

bridging element and comprising a first contact and a second contact, wherein the bridging element comprises a contact surface that is arranged to be coupled to the first and second contacts of the switch mechanism wherein the bridging element is characterised in that it further comprises two or more bridging formations located on the contact surface such that, when the bridging element is in the closed condition, at least one bridging formation forms an electrical contact with one of the first or second contacts.
2. The electronic device of Claim 1 further characterised in that two or more of the bridging formations are located in a central region of the contact surface.
3. The electronic device of Claim 1 or Claim 2 further characterised in that the bridging element comprises three bridging formations in a triangular configuration.
4. The electronic device of any preceding Claim further characterised in that one or more bridging formation(s) is/are located on an underside of the contact surface.
5. The electronic device of Claim 4 further characterised in that a ratio between a diameter of a bridging formation distribution circle and a height of one or more bridging formation(s) is less than or equal to twenty three.
6. The electronic device of Claim 5 further characterised in that the ratio between the diameter of the bridging formation distribution circle and the height of one or more bridging formation is between fifteen and twenty.
7. The electronic device of any preceding claim further characterised in that the one or more bridging formations are an integral part of the bridging element.
8. The electronic device of Claim 7 further characterised in that the one or more bridging formations is an integral part of the contact surface of the bridging element.
9. The electronic device of any preceding claim further characterised in that the bridging element is made from a conductive material, such as stainless steel.
10. The electronic device of any preceding Claim further characterised in that the contact surface comprises a conductive material, such as nickel, silver or gold.
11. The electronic device of any preceding claim further characterised in that the bridging element assumes a closed position when a force is applied to a surface of the bridging element opposite the contact surface.
12. The electronic device of any preceding claim further characterised in that the bridging element further comprises one or more bridging formations located in an outer region of the contact surface.
13. The electronic device of any preceding Claim further characterised in that the electronic device is one of the following: a handheld electronic device, such as a Lelephone handset, calculator, personal digital assistant, portable media device; a domestic appliance; or a commercial and/or industrial machine/appliance.
14. A switch mechanism adapted to operate in the electronic device of any of the preceding claims.
15. The switch mechanism of Claim 14 further characterised in that the switch mechanism comprises an inner contact and an outer contact, and the one or more bridging formations of the bridging element form an electrical contact with the inner contact when the bridging element is in a closed condition.
16. A keypad adapted to operate in the electronic device of any of Claims 1 to 13.
17. An electronic device substantially as hereinbefore described with reference to, and/or as illustrated by, the accompanying drawings.
18. A keypad substantially as hereinbefore described with reference to, and/or as iiiustrated by, the accompanying drawings.
19. A switch mechanism substantially as hereinbefore described with reference to, and/or as illustrated by, the accompanying drawings.