Abstract:
A key assembly for a keypad is disclosed. The key assembly is arranged to operate each of three switches. The key assembly has a key and pivot members which provide respective pivot axes about which the key is pivotable for operation of respective ones of the switches.

Description:
BACKGROUND OF THE INVENTION  
         [0001]    This invention relates to a key for a keypad. It finds particular, but not exclusive use in portable telecommunications devices such as portable telephones and wireless computers or digital assistants.  
           [0002]    Most portable telephones and personal digital assistants (PDAs) require a keypad in order to allow a user to enter operational instructions. Portable telephones, in particular, normally require an alphanumeric keypad consisting of at least 10 keys corresponding to the digits 0 to 9. Two further keys carrying the legends # and * are normally provided also. In addition to these keys, however, it is normal practice to provide further keys corresponding to particular functions of the telephone. These may include on-hook and off-hook keys, and, additionally, menu, cursor (up/down and/or left/right), volume and select keys.  
           [0003]    Portable telephones pose a particular problem in the area of user interface design. There is a customer demand to reduce the overall size of the telephone for ease of portability and storage, as well as a need for larger displays to facilitate the display of large amounts of data e.g. Internet browsing. These two factors combined have the effect of reducing the area available on the telephone to accommodate the keypad.  
           [0004]    As a consequence of the growth in data access via WWW and WAP on telephones, it is desirable to provide an input device which can operate in a manner similar to the mouse commonly used with personal computers. This input device is required to provide 2-dimensional control of a cursor on the display. One possible input device is a miniature joystick, but this tends to be too deep to be accommodated in a slim telephone. It is also difficult to provide a weather-proof seal around the joystick. The provision of back-lighting to the joystick is a further problem.  
           [0005]    Other devices which may be used to provide input control signals are roller balls or rotary switches. Like the joystick, these devices can be comparatively bulky, difficult to accommodate, difficult to back-light and hard to seal against ingress of dust and water.  
         SUMMARY OF THE INVENTION  
         [0006]    According to a first aspect of the present invention there is provided a key assembly for a keypad, arranged to operate each of three switches, the key assembly comprising a key and pivot members disposed to provide respective pivot axes about which the key is pivotable for operation of respective ones of the switches.  
           [0007]    Advantageously, a key assembly according to embodiments of the invention allow greater functionality to be incorporated into a smaller space than would be the case if individual keys were supplied for each function.  
           [0008]    Preferably, the key assembly is used to provide navigational functionality for a portable telephone. The key may replace separate keys for any combination of up, down, left, right and select functions.  
           [0009]    A key assembly according to embodiments of the invention allows a user to operate equipment comprising the key assembly such that mis-keyings are less likely to occur. This is due to the increased mechanical isolation between adjacent switches.  
           [0010]    In a preferred embodiment, the user is able to pivot a key about a first axis to operate a first switch. He is also able to pivot the key about a second, different axis to operate a second switch. Additionally, he is able to operate a third switch by depressing the key such that it does not pivot. The different tactile experiences of each operation can preferably be enhanced through the use of different tactile materials on the surface of the key, or by providing raised/recessed portions.  
           [0011]    In a preferred embodiment, a pivoting action of the key operates a first and second switch. A third switch is operated by depression of the key such that pivoting does not occur.  
           [0012]    Preferably, the operation of the key to operate the third switch requires depression of the key in such a way that such depression can be considered as being a position between the two pivoted orientations required to operate the other switches.  
           [0013]    In a preferred embodiment, pivoting is achieved through the provision of projections between individual switch actuators.  
           [0014]    One of the switch actuators may be arranged to be larger than the other actuators, thus further decreasing the chance of inadvertently operating a neighbouring switch.  
           [0015]    In a preferred embodiment, the two pivot axes are parallel.  
           [0016]    There are many possible relative positions for the switches, but they may be arranged to be collinear.  
           [0017]    Preferably, the key assembly forms part of a keypad for use in an electronic apparatus. The electronic apparatus may be a portable communication device such as mobile telephone, a wireless computer or organiser.  
           [0018]    Embodiments of the invention provide a number of advantages over prior art solutions. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0019]    For a better understanding of the present invention, and to understand how the same may be brought into effect, the invention will now be described, by way of example only, with reference to the appended drawings in which:  
         [0020]    [0020]FIG. 1 shows a front perspective view of a keymat according to an embodiment of the invention;  
         [0021]    [0021]FIG. 2 shows a rear perspective view of a keymat according to an embodiment of the invention;  
         [0022]    [0022]FIG. 3 shows a partial detailed view of the front of the keymat of FIGS. 1 and 2;  
         [0023]    [0023]FIG. 4 shows a sectional view of the keymat of FIG. 3 along the line A-A, in position above a switch assembly of a portable telephone;  
         [0024]    [0024]FIG. 5 shows the keypad assembly of FIG. 4 when used to actuate the ‘up’ keydome;  
         [0025]    [0025]FIG. 6 shows the keypad assembly of FIG. 4 when used to actuate the ‘select’ keydome; and  
         [0026]    [0026]FIG. 7 shows an alternative embodiment of the invention having a key with 5 keydome actuators.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]    Referring to FIG. 1, there is shown a perspective view of the front of a keymat  100  according to an embodiment of the invention. The keymat  100  comprises a flexible planar element  200 , further comprising several keys. A suitable material for the keymat is a silicone rubber material. Integrally formed with the planar element  200  are several alphanumeric keys  110 . The alphanumeric keys  110  comprise a single key for each number, 0 to 9, as well as a key each for * and #, as is customary. Also provided is an off-hook (or SEND) key  120 , an on-hook (or END) key  130 .  
         [0028]    The keys at the upper end of the keymat are also integrally formed with the keymat and comprise various navigational, and special function keys. Keys  170   a  and  170   b  are soft-keys, whose function is dictated by the current status of the telephone. Labels are provided in the display of the telephone indicating the current function of the keys. They are physically accommodated in a single key, but each end of the soft-key is arranged to actuate a different switch mounted on the underlying circuit board. Key  160  is a dedicated key allowing one touch access to data services. For example, in the Japanese PDC system, this key may be used to select the so-called ‘i-mode’. In other systems, this key could allow easy access to the Internet or World Wide Web (WWW).  
         [0029]    Keys  140  and  150  are respectively ‘left’ and ‘right’ navigational keys, and are used to steer a cursor about the display. Alternatively, keys  140  and  150  may be used to scroll through a list of possible menu or other options on the display.  
         [0030]    Key  180  is a navigation key comprising three separate functions. Regions  180   a  and  180   b  are used to select ‘up’ and ‘down’ functionality respectively.  180   c  corresponds to a ‘select’ region, and is used to select a menu item shown on the display, or to follow a link in a displayed WWW page of information. Key  180  may be considered to combine the functionality of three separate keys—‘up’, ‘down’ and ‘select’—in one physical key.  
         [0031]    It is common practice to combine the functionality of two keys into a single physical key. For instance, this is often done for scroll keys offering up and down regions. A particular problem arises when the functionality of three or more keys is incorporated into a single key as the key region positioned between other regions is likely to be inadvertently actuated by a user, particularly as the key dimensions become ever smaller.  
         [0032]    Referring to FIG. 2, it can be seen that for each key  110 , there is a projection  210 , which acts as a keydome actuator, positioned on the reverse side of the keymat in direct correspondence to a respective key on the upper surface of the keymat  100 . Each keydome actuator is arranged to correspond with a keydome positioned above a circuit board arranged beneath the keymat  100 . Each keydome is a hollow conductive partially hemispherical structure positioned above two non-connected conductive traces on the circuit board. A sheet of material comprising several keydomes is situated between the keymat and the PCB carrying the traces. When pressure is applied to key  110 , keydome actuator  210  moves to contact the keydome. With increased pressure, the keydome is temporarily distorted. The conductive keydome thus provides a conductive path connecting the two previously non-connected traces. This change in connection status may be registered by a processor to detect a key press. When the pressure is released, the keydome springs back to its original state, and the connection is terminated. Thus, each key press triggers only a temporary actuation of its respective switch. The period of actuation corresponds to the period for which pressure is applied to the key.  
         [0033]    The keymat is secured in place by a front cover of the telephone, as is well known in the art. This cover has an aperture corresponding to each key position, and ensures that the keymat is held securely against the circuit board and the sheet of keydomes.  
         [0034]    The 3-way key  180  combines up and down scrolling, together with the functionality of a ‘select’ or ‘enter’ key. The single key  180  comprises three regions,  180   a ,  180   b  and  180   c , respectively associated with ‘up’, ‘down’ and ‘select’ functionality. Given the requirements already described, of the desire to miniaturise the keypads of portable telephones, it can clearly be seen that grouping the functionality of more than one key into a physical area tending towards that occupied by a single key, offers advantages to designers of portable telephones. Such a grouping also enhances the operability of the user-interface of the telephone, as the user is able to easily use the phone with a single hand, and reduces the need to look away from the display of the telephone. This is particularly desirable in the case where the user is accessing information via the WWW, and will not want to constantly look away from the screen to ensure that the correct key is being pressed.  
         [0035]    In order to describe the operation and structure of the multi-function key  180 , reference will be made to FIGS. 3 and 4. FIG. 3 shows a detailed plan view of the top part of the keypad previously mentioned, including key  180 . FIG. 4 shows a cross section through the keypad along line A-A of FIG. 3.  
         [0036]    In order to understand the operation of the multi-function key, it is instructive to describe how the key may be used by a user of the telephone. Most portable telephones have a hierarchical menu structure, via which the user may access a particular function of the telephone. The user may move through the telephone&#39;s menu structure using the ‘up’ and ‘down’ regions  180   a ,  180   b  of key  180  until he arrives at the menu page of interest. To select this page, he must use the ‘select’ function, operated by region  180   c  of the multi-function key  180 . This will normally lead to a further set of options which may need further navigation before he comes across the feature of interest.  
         [0037]    It can be seen from FIG. 4 that each region of the key  180  corresponding to up  180   a , down  180   b  and select  180   c  has a corresponding keydome actuator,  280   a ,  280   b  and  280   c  respectively, on the underside of the keymat. FIG. 4 shows the keymat in position above keydome switches  580   a ,  580   b  and  580   c . It can be seen that keydome actuator  280   c  extends further from the plane of the planar surface  200  than keydome actuators  280   a  and  280   b , which are of equal size. That is, the keydome actuator  280   c  is closer to keydome switch  580   c  in its stable position than actuators  280   a  and  280   b  are to their respective keydome switches  580   a  and  580   b.    
         [0038]    [0038]FIG. 2 shows structures  310   a ,  310   b ,  320   a  and  320   b  which are located in the region of the keydome actuators  280   a ,  280   b  and  280   c .  310   a  and  310   b  are provided a short distance either side of an imaginary line joining  280   b  and  280   c . Likewise,  320   a  and  320   b  are located a short distance either side of an imaginary line joining  280   c  and  280   a . Structures  310   a ,  310   b ,  320   a  and  320   b  are protrusions from the plane of the keymat, and their function can be understood by reference to FIG. 4.  
         [0039]    In FIGS. 4, 5 and  6  the protrusions  310   a ,  310   b ,  320   a  and  320   b  can be seen as non-shaded elements as they do not actually lie on the line A-A.  
         [0040]    [0040]FIG. 5 shows the situation when the user selects the ‘up’ function by depressing region  180   a  of key  180 . When finger or thumb pressure is applied to region  180   a , the entire key  180  is caused to pivot about protrusions  320   a  and  320   b . The applied pressure causes the top part  180   a  of the key  180  to travel downwards towards the PCB  400 , and the lower part  180   b  of the key  180  to move relatively upwards.  
         [0041]    As the key pivots about protrusions  320   a  and  320   b , the protrusions serve to mechanically isolate keydome switch  580   a  from neighbouring keydome switch  580   c , which actuates the ‘select’ function. When the pressure is sufficient to distort keydome switch  580   a , the protrusions  320   a  and  320   b  act to ensure that keydome switch  580   c  is not actuated.  
         [0042]    In the absence of the protrusion  320   a  and  320   b , it can be seen that there is a likelihood that the pressure on region  180   a  may be transferred inadvertently to the central region  180   c  so as to actuate switch  580   c . Such actuation of the ‘select’ key as well as, or instead of, the desired actuation of the ‘up’ key may result in the user initiating an unwanted function in the telephone.  
         [0043]    The mode of operation of the ‘down’ function, initiated by depressing region  180   b  of key  180 , is similar to that described for the ‘up’ function as described and shown in FIG. 5, except that the key  180  now pivots about protrusions  310   a  and  310   b , which act to increase the mechanical isolation of keydome switch  580   b  from keydome switch  580   c.    
         [0044]    [0044]FIG. 6 shows the situation where the user applies pressure to region  180   c  to operate the ‘select’ function. As pressure is applied to region  180   c , the movement of the key  180  downwards also causes the protrusions  310   a ,  310   b ,  320   a  and  320   b  to move downwards. As they contact the planar part of the sheet of keydomes  500 , they act to increase the mechanical isolation of the central keydome  580   c  from the surrounding keydomes  580   a  and  580   b . In this way, it is less likely that inadvertent actuation of the ‘up’ or ‘down’ functions will occur.  
         [0045]    It can be seen that in the absence of protrusions  310   a ,  310   b ,  320   a  and  320   b , there would be a tendency for pressure on region  180   c  to actuate keydomes  180   a  and/or  180   b . The increased size of keydome actuator  280   c  in the direction perpendicular to the planar surface  200  also helps in ensuring that only keydome switch  580   c  is actuated when region  180   c  is depressed.  
         [0046]    It can be seen that the multi-function key  180  is able to replace three separate keys which would otherwise be required.  
         [0047]    The exterior surface of the keys, which protrude through the front cover of the telephone, are capped with a durable plastic enclosure bearing a suitable legend for each key. This provides for greater durability of the keypad over the life of the telephone, and permits customisation of colours and labels without altering the basic keymat.  
         [0048]    In the embodiment described, the up and down regions,  180   a  and  180   b , comprise portions which are raised slightly relative to the select region. This can be seen from FIGS. 4, 5 and  6 . This enables the user to sense a tactile difference between the select area  180   c  and the up or down areas  180   a ,  180   b  of key  180 .  
         [0049]    [0049]FIG. 7 shows an embodiment of the invention which demonstrates how a key can be constructed which is capable of combining the functionality of more than the three keys which have so far been described.  
         [0050]    [0050]FIG. 7 shows a view of the underside of a key  700  which can be used to operate five separate switches. An example of the use that could be made of such a key is in providing complete navigational control for a cursor. In this case, ‘up’, ‘down’, ‘left’, ‘right’ and ‘select’ functionality can be combined in a single key.  
         [0051]    The mode of operation of such a key is similar to that already described. The keydome actuators corresponding to the various navigation functions are: ‘up’  710 , ‘down’  720 , ‘right’  730 , ‘left’  740  and ‘select’  750 . The structure of the key  700  can be considered to be combine two of the three-way keys already described. One can imagine a first key being superimposed on a second which has been rotated by 90°.  
         [0052]    When the user wishes to move a cursor up the screen, he applies pressure to the part of the key above actuator  710 . In doing so, the key pivots about structures  760  and  770  in a manner already described. A summary of keydome actuator operation, together with pivot points used is shown in the table below:  
                                                               Points under           Function   Keydome actuator   pressure                           Up   710   760, 770           Down   720   780, 790           Right   730   760, 790           Left   740   770, 780           Select   750   760, 770, 780, 790                      
 
         [0053]    When the user presses the central part of key  700  to operate the ‘select’ function, the four surrounding pivot points serve to increase the mechanical isolation of the central actuator  750 . This helps to ensure that only the ‘select’ function is operated, and that no other function is inadvertently operated.  
         [0054]    In the light of the foregoing description, it will be clear to the skilled man that various modifications may be made within the scope of the invention.  
         [0055]    The present invention includes any novel feature or combination of features disclosed herein either explicitly or any generalisation thereof irrespective of whether or not it relates to the claimed invention or mitigates any or all of the problems addressed.