Tactile electromechanical data input mechanism

Details Tactile electromechanical data input mechanism Tactile electromechanical data input mechanism

2001-06-20

2004-02-03

Wu, Xiao (Department: 2674)

Computer graphics processing and selective visual display system

Display peripheral interface input device

Including keyboard

C345S173000, C200S0050EA

Reexamination Certificate

active

06686906

ABSTRACT:

TECHNOLOGICAL FIELD
The invention relates in general to data input mechanism related to an electrical device. In particular the invention relates to an input mechanism especially suitable for small portable communication devices.
BACKGROUND OF THE INVENTION
A push button or a press key consists of a certain mechanical structure and of an accompanying electrical circuitry. When a user presses a push button or a key of an electrical device, the pressing of a button is converted to an electrical input signal for the device. Typically the mechanical part of a push button requires more space than the accompanying electrical circuitry.
A typical user interface of a portable electrical device comprises at least few push buttons or keys. In a mobile phone, for example, there typically is a display, push buttons for the digits and some push buttons for choosing proper action. As portable electrical devices become smaller and smaller, there is less space for the push buttons. Consider, for example, a communication device that has the shape of a watch, a pen or a pendant.
One solution is to reduce the size of push buttons, but this may result in devices that are difficult to use. Calculator watch having very small push buttons is one example of a device, whose usability is not very good. Another straightforward solution is to reduce the number of the push buttons. The problem here is that although the size of portable communication devices becomes smaller, the functionality such devices is usually similar as that of devices having larger size. Therefore it usually is not feasible to reduce the number of push buttons. Further reasons for reducing the number of push buttons are, for example, the aim to design classy devices and the aim to obtain a simple and robust structure.
A prior art push button or keyboard, where the pressing of a button is converted into an electrical signal, works usually in the following way. When a button is pressed down, an electrical contact is formed between two conductor strips, and when a button is in the rest position, there is no electrical contact between the conductor strips. Typically the mechanical structure of a push button is such that it automatically returns to the rest position (up position), when a user stops pressing the button.
FIG. 1
shows a cross section of a typical push button structure according to prior art. A button
104
typically has an upper part having a smaller diameter and a base, which has a larger diameter and is hollow. The button refers here to the plain button
104
, and term push button refers to the whole mechanical construction including the button
104
. The surface of a button
104
, which faces the circuit board
101
, is typically a circular rim. In the bottom of a button
104
there is a hole, which allows the housing of a dome
102
. When the button is in the up position, there is room for the dome
102
to be in its normal position. The button
104
has an actuator
105
, which presses the dome
102
down when the button
104
is pressed down. The dome
102
acts as a spring, and as a user stops pressing the button
104
down, the dome returns to its normal position and simultaneously pushes the button back to the up position. The actuator
105
is necessary, because if the whole surface of the button
104
would be pressed against the dome
102
, the spring effect of the dome
102
might be lost and the force needed to press the lower surface of the dome in contact with the circuit board
101
would be larger than when an actuator
105
is used. Typically the upper part of the button
104
is rigid, and the movement of the button
104
in the vertical direction is due to the thin rim connecting the upper part and the base of the button
104
. The material of the button
104
has to be elastic enough for allowing the rim to flex. A button
104
can be made, for example, of rubber.
The circuit board
101
comprises the necessary circuitry for detecting the pressing of a button
104
. A conductive area in the lower surface of the dome
102
is pressed against, for example, two conductor strips
107
, and an electrical contact between the conductor strips indicates the pressing of a button. If the whole dome is made of conductive material, there may be a separate isolating layer
103
to isolate the rim of the dome from the conductive strips. Another way to isolate the rim of the dome from the circuitry is to use multilayer circuit board. A further option is to make the dome of an isolating material and to deposit a conducting layer in a suitable area of the concave surface of the dome
102
.
FIG. 1
shows also a cover
106
, which has holes for the buttons. Typically the profile of a cover is not uniform to minimize the material needed for the cover and the mass of the cover. The height of a button
104
is usually few millimeters. The buttons of a keyboard are typically connected to each other at their base parts and they form a key mat. Typically it is quite difficult to obtain a waterproof push key mechanism, because it is difficult to fix a cover, which may have a non-uniform profile, and a key or a key mat to each other tightly.
In a mobile communication device there is typically a keyboard for inputting digits, some separate push buttons and a display in the front surface of the device. The smaller the device, the smaller usually the front surface and the less space for the display and the various push buttons. It typically is necessary to reserve enough room, for example, for the display. If the push buttons are made too small, it is difficult to press a correct button. Therefore reducing the size of the buttons is not a good solution. Furthermore, having many small buttons in a small device usually does not give the impression of a classy, well-designed device. The mechanical structure of small push buttons may also cause some problems. These problems arise also if small push buttons are placed in the side surface of a device. Another solution is to reduce the number of the push buttons, but unfortunately the functionality of communication devices is typically so versatile that to use conveniently a communication device, the device typically has to have at least few push buttons.
For design purposes and for achieving waterproof device, it may be advisable to eliminate the need for push buttons. One way to do this is to use a touch sensitive display. The advantages of a touch sensitive screen include at least the freedom to design a device without push buttons and to use the same area both as a display and as an input means. The disadvantages of such a display are that it is relatively expensive and that is lacks the tactile feel of a push button. The user cannot feel when he is pressing a key, or actually pointing a certain position on the display. The sense of pressing a button typically makes the use of a device more comfortable.
Patent application WO 98/29886 presents a way to integrate push button functionality and a display. A first plate of the display structure is arranged, using hinges, to tilt when the display is pressed. The first plate has conductive actuators extending from one surface and there are corresponding conductive coupling areas on the surface of a second plate. The display can be mounted so that the first plate can be tilted around an axis. This way it is possible to place two conductive actuators to the first plate. If the first plate is supported in one point in the middle of the plate, more conductive actuators, for example four, can be placed to the first plate. A contact between a conductive actuator and a conductive coupling area is made by tilting the first plate. The construction of the virtual touch screen presented in WO 98/29886 is complex and requires many separate parts. It is therefore most probably quite a difficult and expensive solution. Furthermore, it is not easy to make a waterproof device using this virtual touch screen.
SUMMARY OF THE INVENTION
An object of the invention is to present a data input mechanism, which acts as a set of push buttons or as a keyboard and a

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