Note: Descriptions are shown in the official language in which they were submitted.
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TITLE OF THE INVENTION
KEYPAD INPUT INTERFACE FOR PERSONAL ELECTRONIC DEVICES
TECHNICAL FIELD OF THE INVENTION
This invention relates to a keypad for a personal digital assistant
("PDA"). More particularly, this invention relates to an ergonomically
l0 optimized keypad for data entry using single or dual thumb input operation
and a method for inputting and displaying data on the screen of a personal
digital assistant using such keypad.
BACKGROUND OF THE INVENTION
The problem of designing a user input interface for PDAs is that
screen size and available keypad area are limited. PDAs are usually
equipped with a few control buttons on the front surface and a stylus. The
2o complexity and inefficiency of the touch screen input has determined the
need for a small, intuitive to use keypad allowing the same number of
characters, punctuation, and functions as the normal size PC keyboard,
and being small enough to avoid the crowding of the display screen.
The PDA disclosed in US Patent No. 5,515,305 uses a chord
keyboard allowing entry of a number of characters substantially greater
than the number of keys in the chord keyboard. In order to display a
character on the screen the user must depress several keys
simultaneously according to a pre-established combination for that
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particular character. As a result the entry of 256 unique characters can be
accommodated with only 8 keys.
US Patent No. 5,487,616 discloses an ergonomic one-finger
keyboard used for small hand held computers with the keys corresponding
to the most commonly used characters positioned in a central area. The
rest of the keys are further arranged such that keys most frequently used
in conjunction with each other are located in adjacent locations.
1o A miniaturized keyboard that allows an easy operation of the keys is
described in US Patent No. 6,103,979. In this case each key has an
elongated shape and is supported by a fulcrum which allows it to tilt when
the operator presses either end of the key establishing two different
switches provided for each key of the keyboard. As a result the overall
dimension of the keyboard is reduced and the number of possible input
characters is the same as on a traditional keyboard.
Such prior art keyboard arrangements have certain limitations and
disadvantages. Chord keyboards like the one described in US Patent No.
5,515,305 involve depressing multiple keys simultaneously for obtaining a
single keystroke. The other two US Patents Nos. 5,487,616 and 6,103,979
do not offer the best possible solution for reducing the overall dimensions
of a keyboard for PDAs.
The present invention proposes to solve these problems by
providing for an easy to use electro-mechanical key interface offering 128
symbols and a graphical interface which will make input items easier to
identify.
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SUMMARY OF THE INVENTION
The present invention proposes a keypad of a circular shape
because the circle contains the greatest possible working area in the
smallest possible linear dimensions. The input keys are wedge-shaped
radiating out from the center. The input characters are arranged on the
keys in two concentric rings. One shift key is used for providing two inputs
from each key by selecting one of the two characters that are positioned
on either the inner or the outer concentric ring on the keys. An inner/outer
selector key is used for selecting one pair of characters positioned on the
inner or outer concentric ring.
Because the human thumb has great agility and because one tends
to hold PDAs in the palm and fingers, the present invention proposes
single or dual thumb operation input although preferences will vary.
In addition, because confirmation of digital input may be different
from the ultimate digital input into a line entry in an application, the
present
invention proposes a preliminary display of the desired input symbol in a
format far larger than its actual input form. In this way the user will be
able
to preview the character that was entered before the entry is actual send to
the computer.
Other aspects of the invention are defined in the claims and will be
appreciated by reference to the detailed description of the preferred
embodiment and to the drawings that follow.
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BRIEF DESCRIPTION OF THE DRAWINGS
The preferred embodiment of the invention will be described by
reference to the drawings thereof in which:
Fig. 1 is a plan view of a keypad according to the preferred
embodiment of the invention;
1o Fig. 2 is a cross sectional view of a wedge-shaped key, Fib. 2A
showing a side view and Fig. 2B showing an end view of the key;
Fig. 3 is a side view of the wedge-shaped key;
Fig. 4 is an illustration of the device screen illustrating the
confirmation phase of character input; and,
Fig. 5 is an illustration of the whole device showing all of the
operating buttons.
DETAILED DESCRIPTION OF THE
PREFERRED EMBODIMENT
The preferred embodiment of the present invention comprises a
circular keypad 10 for a personal digital assistant (PDA). Thirty-two wedge-
shaped keys 14 radiate out from the center of the keypad. The input
characters and symbols are distributed in pairs arranged in two concentric
rings on the outer perimeter of the keypad. The keypad also comprises a
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tilting circular enter/cursor key positioned in the center that serves to
position the cursor and that incorporates an enter/select functionality
similar to a mouse click.
A shift key 16 and an inner/outer selector key 18 are positioned on
the left hand side of the device at a certain distance from the keypad. The
combination of these two keys allows the input of four characters per key
simultaneously (an inner/outer arrangement of two pairs of shiftable
characters on each wedge-shaped key).
to
The keypad is can be any of a multiplicity of diameters according to
the dimensions of the device for which it is intended, but a 3 inch diameter
keypad will serve for the purposes of describing the preferred embodiment.
Each wedge-shaped key is 0.285 inch wide at the outer edge and 1.5 inch
long covering an angle of 11.25 degrees on the 3 inch diameter circle of
the keypad.
As shown in Figs. 2 and 3, each key 12 has a sloping shoulder 20
and a flat top 22 on which the characters are printed. This shape allows for
2o sufficient separation between keys to enable depression of individual keys
to be effected without interference with adjacent keys by the operating
digit. The depression of the key also provides for a graduated process by
which the character corresponding to the key which is depressed is
displayed on the screen in a larger format upon initial touch as shown in
Fig. 4 for facilitating the visual confirmation that the appropriate character
has been selected. Upon increased pressure the selected character is
entered into the appropriate input space on the screen in its normal screen
format size. This provides for an easy user confirmation of selected
characters.
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The present invention provides for a total of 128 characters (32 on
the outer ring with a shift option creating 64 characters and 32 characters
on the inner ring with a shift option creating another 64 characters). Each
wedge-shaped key has two pairs of two possible input characters on it
which can be displayed when the wedge-shaped keys are used in
combination with the shift key and inner/outer key.
The mechanism for establishing electrical contact upon depression
to of the keys utilizes prior art circuit technology. Similarly display of
initial
oversize characters on the screen upon first phase digital key depression
followed by regular sized character display upon completion of digital key
depression also utilizes prior art which those familiar with the field will
appreciate.
The specific arrangement of characters on the keys can follow any of
a multiplicity of designs although in the preferred embodiment the letters
will be arranged alphabetically on the outer circumference with 'A' in the
twelve o'clock position moving clock wise and with numerals 1 to 0 on the
2o inner circumference with 1 at the corresponding twelve o'clock position,
the
others following clockwise. Punctuation and other symbols and functions
fill the remaining spaces as shown in Fig. 1.
It will be appreciated that although the preferred embodiment of the
invention has been described in some detail, modifications may be made
and variations may be practised without departing from the broader
principles of the invention.
