Abstract:
A rotary switch is disclosed. The switch has a rotatable barrel which has an axis of rotation. The switch also has an encoder pattern for sensing rotation of the barrel. The encoder pattern extends in a longitudinal direction with respect to he axis of rotation of the barrel.

Description:
BACKGROUND ON THE INVENTION  
         [0001]    This invention relates to a roller switch. It particularly relates to a roller switch suitable for use in handheld electronic equipment such as portable radio telephones.  
           [0002]    Portable radio telephones require a number of keys to enable the user to operate the phone. As well as the regular alphanumeric keys (0-9, *, #), additional function keys are necessary in order to access menus, adjust volume, or scroll up or down for instance. Scrolling up or down through a long list of possible options can be time consuming and awkward when individual key presses have to be used.  
           [0003]    Possible alternative means of scrolling that have been suggested or implemented are the trackball, as used in a computer ‘mouse’, or the roller switch  10 , as used in the Nokia® 7110 mobile phone  1 , as shown in FIG. 1. Trackballs tend to be difficult to implement in hand-held equipment, and are prone to malfunction due to ingress of dust and dirt, and so are not the preferred option at present. Whilst offering only one-dimensional control and not two-dimensional control like the trackball, roller switches are found to offer satisfactory performance in portable telecommunication equipment. Indeed, they are found to offer several advantages over using individual up/down or left/right keys. For instance, entering text into a mobile phone using only the numeric keypad can be time-consuming and prone to error due to the grouping of several letters on each key (2=abc, 3=def, 4=ghi etc.) and the multiple key presses that are required to access any given letter. For instance, to enter the word ‘switch’, the following key presses are required: 7-7-7-7-9-4-4-4-8-2-2-2-4-4 i.e. fourteen individual key presses are needed to enter this six-letter word.  
           [0004]    The use of a roller switch  10  can enable easier entry of characters. When the phone is in a text entering mode, an alphabetical list  11  is presented on the phone display, and the user can scroll up or down the list by rolling the roller switch  10  in an upward or downward direction respectively. This enables the user to scroll through all letters of the alphabet with one continuous action. To increase functionality further, the roller switch is additionally adapted to be depressed, with the depression triggering a further switch that can be used to indicate selection of a highlighted option on the display. In the example shown in FIG. 1, the letter ‘j’ is highlighted, and depressing the roller switch  10  will select that letter and enter it into the text at the entry point defined by a cursor.  
           [0005]    Such a roller switch is disclosed in co-assigned patent application EP0901262A. FIG. 2 a  shows a view of the roller switch assembly of this patent application, and FIG. 2 b  shows a view of the roller barrel and associated encoder parts in isolation.  
           [0006]    [0006]FIG. 2 a  shows the roller barrel mounted for rotation in its support structure. It shows the hinge  28  which connects the assembly to the telephone. It is the structure of this point that allows the switch to be depressed, effectively rotating about the hinge  28 , thus actuating a further micro switch positioned underneath the roller barrel assembly. Also shown is a terminal part  62  which carries the electrical contacts from the switch.  
           [0007]    [0007]FIG. 2 b  shows an end view of barrel  60 , and the encoder pattern  70  disposed thereon. The encoder pattern comprises conducting and non-conducting portions. The conducting portions are shown as the white areas. The non-conducting portions are the shaded areas. Also shown are the positions of the three sensors X, Y and Z which co-operate with the encoder to sense the rotation of the barrel  60 .  
           [0008]    The sensors themselves are arranged to be parallel with the end face of the barrel. The signals received by a microprocessor from each of the sensors will depend on whether it is currently contacting a conducting or non-conducting portion of the encoder pattern. From changes in these signals it is possible to determine whether the roller barrel is being rotated, and also in which direction rotation is occurring. A full description of this process can be found in EP0901262A.  
           [0009]    However, a problem with such a switch arrangement occurs when the overall thickness of the telephone is reduced. Telephones are now feasible which have an overall thickness approximating, or even smaller than, the diameter of the roller switch shown in FIGS. 1 and 2. In order to provide suitable encoding structures, a certain barrel diameter is required. This can result in a roller switch which is disproportionately large compared to the rest of the telephone and, consequently, difficult to accommodate within the housing.  
         SUMMARY OF THE INVENTION  
         [0010]    According to the present invention, there is provided a rotary switch comprising: a rotatable barrel, having an axis of rotation; and an encoder pattern for sensing rotation of the barrel wherein the encoder pattern extends in a longitudinal direction with respect to the axis of rotation of the barrel.  
           [0011]    By positioning the encoder pattern such that it is longitudinal with respect to the axis of rotation of the roller barrel, it is possible to devote a greater surface area to the encoder pattern, thus allowing for greater reliability and accuracy in sensing the true position of the roller barrel, without needing to provide a large surface area at the end of the barrel. This allows the barrel diameter to be reduced.  
           [0012]    The encoder pattern consists of one or more discrete bands. The band, or bands, do not need to be arranged to be coaxial with the axis of rotation of the barrel, but the arrangement is simplified if this is the case.  
           [0013]    Adopting a roller switch structure as defined above allows the switch to have a smaller barrel diameter, which can be more easily incorporated into ever smaller portable telephones and other handheld equipment.  
           [0014]    The sensors, which contact the encoder pattern, are biased inwards, towards the encoder pattern to ensure reliable electrical contact.  
           [0015]    Advantageously, the encoder pattern is arranged to be cylindrical in shape.  
           [0016]    The encoder pattern can be implemented in a number of ways. Advantageous embodiments employ sensors relying on electrical contact with either conducting or non-conducting regions of the encoder pattern; or sensors responsive to magnetic and non-magnetic regions of the encoder pattern; or sensors responsive to light and dark regions of the encoder pattern.  
           [0017]    The rotary switch of the invention enjoys particularly advantageous use in handheld electronic apparatus, where size can be an important design factor.  
           [0018]    A particular use for the rotary switch may be found in portable radio telephones, including such wireless devices which offer data facilities, such as wireless access to the World Wide Web (WWW).  
       
    
    
       [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:  
       BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]    [0020]FIG. 1 shows a portable radio telephone comprising a roller switch according to the prior art;  
         [0021]    [0021]FIG. 2 a  shows a detailed perspective view of the roller switch assembly as used in the telephone of FIG. 1;  
         [0022]    [0022]FIG. 2 b  shows a detailed end view of the barrel and encoder section of the roller switch of FIG. 2 a;    
         [0023]    [0023]FIG. 3 shows detailed perspective view of a roller switch assembly according to a first embodiment of the invention;  
         [0024]    [0024]FIG. 4 a  shows a detailed view of a roller switch barrel and encoder section according to a second embodiment of the invention;  
         [0025]    [0025]FIG. 4 b  shows a schematic representation of the encoder section of the switch of FIG. 4 a;    
         [0026]    [0026]FIG. 5 a  shows a cross-sectional view of a roller switch barrel and encoder section;  
         [0027]    [0027]FIG. 5 b  shows a schematic representation of the encoder pattern used in the roller switch of FIG. 5 a;  and  
         [0028]    [0028]FIG. 5 c  shows an end view of an embodiment, in the direction of arrow X, of the roller switch barrel of FIG. 5 a.    
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]    Referring to FIG. 3, there is shown a roller switch  200  according to a first embodiment of the present invention. The roller switch has a roller barrel  230 , an encoder pattern  210  disposed on a cylinder  220 , a carriage  240  and a hinge member  250 .  
         [0030]    The roller barrel  230  is mounted for rotation, by a user, on carriage  240 . To assist the user, the surface of the barrel may be textured, or coated in a rubber like substance. The roller barrel  230  is mounted such that it rotates in a series of discrete steps, each one corresponding to a movement from one option to another. For instance, in the example presented earlier in relation to the prior art switch, each ‘click’ of the roller could correspond to a respective selection of the next letter available in the list so that a first step chooses ‘a’; a second step chooses ‘b’; and a third step chooses ‘c’, and so on. This tactile, and possibly audible feedback to the user may enable operation without needing to monitor the display continuously. The steps may be delimited through use of a suitably shaped cam member contacting a sprung element which provides a defined number of stable positions for each rotation of the barrel. Any number of steps may be provided, but a suitable number is 12 per revolution.  
         [0031]    Attached to one end of the roller barrel  230  is a cylinder  220  on which is disposed an encoder pattern  210 . When the switch is assembled into a telephone, only the roller barrel  230  is visible through the telephone housing; cylinder  220  is concealed from view inside the housing.  
         [0032]    The encoder pattern  210  consists of two discrete circumferential bands positioned adjacent each other at the outer end of the cylinder  220 . These co-operate with two sensors, not shown, to provide signals indicative of the rotation of the barrel. The operation of the encoder pattern is described in detail below.  
         [0033]    The entire switch  200  is pivotably attached to the telephone by hinge member  250 . This allows switch  200  to be depressed to actuate a further switch, positioned beneath carriage  240 , in the manner described previously in relation to the prior art. The roller frame  240  is biased away from the further switch by means of a spring arrangement. The force required to overcome the spring biasing and actuate the switch is arranged to be approximately 3 times the force required to move the roller from one step to the next. Example figures are 1N to move the roller one stop, and 3N to actuate the switch.  
         [0034]    [0034]FIG. 4 a  shows a second embodiment of the invention. Here is shown roller barrel  330 , from the end of which protrudes cylinder  320 , which carries the encoder pattern  310 . FIG. 4 a  also shows the sensors  300  which are associated with the encoder pattern. Although not shown, the apparatus of FIG. 4 a  is mounted in a carriage, and connected to the telephone as described in relation to the first embodiment of FIG. 3.  
         [0035]    Roller barrel  330  is in all key respects identical to roller barrel  230  of the first embodiment.  
         [0036]    Cylinder  320  protrudes from roller barrel  330  such that the barrel and the cylinder are arranged to share a common longitudinal axis. The encoder pattern  310  consists of three discrete circumferential bands disposed adjacent each other at the outer end of cylinder  320 . These three bands, A, B and C, are constructed in a fixed configuration. It can be seen that in this instance, each portion comprises relatively raised and recessed portions. The raised and recessed portions correspond to conducting and non-conducting portions respectively. All conducting portions are electrically connected together.  
         [0037]    [0037]FIG. 4 b  shows a schematic view of the three encoder portions, A, B and C. The conducting areas are shown as white, and the non-conducting areas as black. It can be seen that in this embodiment there are 12 distinct states forming one complete rotation of the barrel. With 3 sensors being used in the configuration shown here, the number of discrete steps is a multiple of three.  
         [0038]    As the roller barrel is rotated, the encoder pattern  310  moves relative to three fixed-position sensors  300 , each of which contact one of the three distinct encoder portions. The sensors  300  are formed from sprung connectors biased to contact the encoder pattern  310 . A suitable material for the sensors is steel.  
         [0039]    In the state shown in FIG. 4 a,  the sensors  300 A and  300 C are electrically connected via the conducting portions of the encoder  310 . As the barrel rotates anti-clockwise, as viewed from the outer end of the cylinder  320 , to the next state,  300 A will be connected to  300 B, and so on. By monitoring the changes in which two of the three sensors are mutually connected at any given instant, the relative motion and direction of rotation of the roller barrel can be deduced.  
         [0040]    The table below is derived from the schematic of the encoder portion shown at FIG. 4 b  and shows the connection states for the twelve steps corresponding to one rotation.  
                                                   Step   Connection Between                           1   B and C           2   A and C           3   A and B           4   B and C           5   A and C           6   A and B           7   B and C           8   A and C           9   A and B           10    B and C           11    A and C           12    A and B                      
 
         [0041]    For instance, if the starting state of the barrel is at step 7, then sensors  300 B and  300 C are electrically connected. If the microprocessor monitoring the connections detects that  300 A and  300 C are now connected, then the roller barrel has been moved one step in a first direction i.e. to step 8 in this instance. If, however, the microprocessor determines that  300 A and  300 B are now connected, then the roller barrel has moved one step in a second, opposite direction i.e. to step 6. The microprocessor is then able to adjust the display of the telephone in order to reflect this operation. For instance, the next or previous entry in the stored phone number directory can be displayed.  
         [0042]    A detailed description of the ancillary apparatus related to the decoding process is not necessary to understand the operation of this invention, but if required, may be found in the previously referred to prior art document, EP0901262A.  
         [0043]    A third embodiment of the roller switch is shown in cross-section in FIG. 5 a.  This shows a roller barrel  400  having a cylindrical projection  420  at one end.  
         [0044]    The external appearance and properties of the roller barrel  400  are in all key respects identical to the previous embodiments. The mounting arrangement on a carriage, and its attachment to the telephone, is also identical in all key respects.  
         [0045]    In this embodiment, the encoder pattern may be made simpler. The sensors can be arranged to contact the encoder pattern such that they run substantially parallel with the roller barrel axis of rotation, rather than contacting the encoder pattern tangentially as in the previous embodiments. As the sensors may be positioned so as to be spatially distant from each other, the encoder pattern  500  may consist of a single band of conducting  510  and non-conducting  520  portions, rather than the three bands discussed previously. This is shown schematically at FIG. 5 b.  Again, the non-conducting portions are shown as black areas  520 , and the conducting portions are shown as white  510 . It can be seen that the conducting portion is arranged so that it forms an electrically contiguous block. The numbered arrows in FIG. 5 b  show the  12  possible equilibrium positions of the three sensors.  
         [0046]    The encoder pattern is disposed on the outer surface of a protruding cylinder  420 . This is positioned at a given end of the roller barrel  400 . With this arrangement, the three sensors are arranged as shown by the arrows in FIG. 5 c,  which is an end view of the roller barrel  400  in the direction of Arrow X. They take the form of sprung steel elements which contact the cylinder  420  in the positions shown by the arrows. The sensors are configured to exert an inward pressure on the cylinder  420 . Each of the three sensors is situated 120° from its neighbour. Other configurations comprising a greater or lesser number of sensors are envisaged, the use of three being exemplary only.  
         [0047]    In the case where three sensors are used, the principle of operation is as follows. Consider a starting position for the roller barrel  400  where the three 120° separated sensors are positioned at steps 3, 7 and 11 (Sensor A at position 3; sensor B at position 7; sensor C at position 11). In this roller position, sensors A and C are contacting the conducting portion  510  of the encoder, and so are electrically connected together. Sensor B is contacting a non-conducting portion  520 , and so is insulated from the other two sensors.  
         [0048]    Movement of the roller is possible in two directions. In the first direction, the sensors will be positioned at steps 2, 6, 10, and sensors A and B will be electrically connected. In the second direction, the sensors will be positioned at steps 4, 8, 12, and sensors B and C will be electrically connected. It can be seen that movement in the first direction produces a different set of connections to movement in the second direction, which is similar to the operation of the previously described embodiment.  
         [0049]    In view of the foregoing description it will be evident to a person skilled in the art that various modifications may be made within the scope of the invention. In particular, the encoding technique disclosed above relies on an electrical contact between sensors and respective conducting and non-conducting portions of the encoder pattern. Other techniques could equally be used to the same effect. For instance, optical encoding relying on detection of respective light and dark areas could be used. Also, magnetic encoding, relying on respective magnetic and non-magnetic areas of the encoder pattern could be used. These techniques are, in themselves, well known in the art, and the skilled man could easily determine appropriate modifications to the apparatus disclosed herein to achieve the desired result.  
         [0050]    The particular configuration of the encoder portion has been described in connection with three discrete bands in relation to the embodiment of FIG. 4 a,  and a single band in relation to the embodiment of FIG. 5 a.  The skilled man will immediately realise that these schemes may be interchanged, and indeed other schemes, requiring greater or fewer discrete bands may be implemented without departing from the scope of the invention.  
         [0051]    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.