Keyboard with moveable base plate providing key travel

Details Keyboard with moveable base plate providing key travel Keyboard with moveable base plate providing key travel

1999-11-29

2002-05-21

Hilten, John S. (Department: 2854)

Typewriting machines

Key-board or key lever-actuating mechanism

C400S491000

Reexamination Certificate

active

06390699

ABSTRACT:

TECHNICAL FIELD
This invention particularly relates to the design of keyboards that are very thin but which provide sufficient key travel for touch-typing purposes. The keyboards are particularly suitable for use in or with compact portable apparatuses such as notebook computers and personal digital assistants. However, the characteristic features of the invention can be incorporated in thicker keyboards and the keyboards, whether thicker or thinner keyboards, can be used with non-portable apparatuses.
BACKGROUND ART
Compact portable apparatuses such as notebook computers and personal digital assistants have become and will continue to become smaller and lighter because of the advancement of computer technology. However, the keyboard has remained something of a problem while the electronic parts reduce in size and weight. To allow for comfortable typing, and touch-typing in particular, the width and depth of a keyboard cannot be made too small because too close a spacing between small sized keys prevents comfortable and efficient typing, and particularly touch-typing. A foldable keyboard is one way of providing a keyboard which is large enough to allow touch-typing while enabling the width of the keyboard to be reduced when it is folded, for example, for the purpose of storing the keyboard in a compact apparatus. However, the only way left to reduce the overall volume of a keyboard, whether of the folding type or not, is to reduce the thickness of the keyboard, and in particular, to reduce the thickness of the keys of the keyboard.
Touch-typists like the keys of a keyboard to have a good feel when they are pressed. They should move downwardly in a stable manner when pressed and offer resistance to the fingers while doing so. The difficulties in constructing a very thin key while maintaining good feel can be explained by reference to FIG.
1
. This figure shows a cross section illustrating the structure of a typical prior art key used in a thin keyboard. The key
10
comprises a key cap
11
and a silicon rubber support
12
to which the key cap is mounted and which spaces the key cap above a printed circuit board
13
. When a finger presses the key at point A, the resilient flexibility of the rubber support
12
allows its deformation whereby the key cap
11
is lowered vertically and evenly to enable a projection
14
of the support
12
to make contact with the printed circuit board
13
. The projection
14
functions as a switch means enabling the pressing of the key to be registered when it contacts the printed circuit board. However, if the key
10
is pressed off-center at point B, the key cap
11
may tilt. In this case, there will not be a good feel about the movement of the key and, furthermore, a proper contact between the projection
14
and the printed circuit board
13
might not be made.
Lever mechanisms are often used to make sure that the whole key cap can travel evenly and vertically when pressed. Such mechanisms are normally placed beneath the key cap and above a support plate, such as a printed circuit board. Each key has its own individual lever mechanism supporting it. In a typical key structure such as that shown in
FIG. 1
, it can be seen that the keyboard cannot be made very thin because there is firstly a need to have a silicon rubber support
12
or other spring-like mechanism beneath the key cap
11
and there is secondly a need to have a lever mechanism placed beneath the key cap for stabilization purposes. For the key to have reasonably good feel for touch-typing, the key travel needs to be at least 2-4 mm. Even with a key travel of 2 mm, the thinnest keyboard constructed with the type of key shown in
FIG. 1
is not likely to have a thickness of less than about 5.5 mm.
U.S. Pat. No. 5,424,516 (Emmons) and U.S. Pat. No. 5,519,569 (Sellers) show ways of constructing lever mechanisms to reduce the overall thickness of the keys, and hence of the keyboard. However, the presence of the lever mechanisms placed beneath the key caps still places a limit on the degree to which the thickness of the keys, and hence the keyboards, can be reduced.
In other keyboards, lever mechanisms are not used and other approaches are taken to try and obtain uniform vertical movement of the keys when pressed. Examples are given in European Patent Publications 88,365 and 556,426 and in U.S. Pat. No. 5,422,477 (Spence).
As to the overall width of the keyboard, U.S. Pat. No. 3,940,758 (Margolin) shows a folding keyboard. However, as already indicated, while a folding keyboard allows the width of a keyboard to be reduce for storage, the thickness of the folded keyboard is increased. In other words, the volume occupied by the keyboard is not reduced.
There is therefore a need to provide a keyboard having a small volume, that is, a thin keyboard, which keyboard has key caps which travel evenly and substantially vertically when pressed and which, preferably allow for a good touch-typing feel.
DISCLOSURE OF THE INVENTION
An object of the invention is to provide a thin keyboard having keys with key caps having a good degree of travel and stability. A preferred object is that these features, together with the spacing of the keys, is such as to allow for touch-typing. Another object of the invention is to provide a thin keyboard, which is particularly suitable for use with portable apparatuses, and which can be manufactured at relatively low cost. However, as has already been indicated, the essential characteristics of the present invention can be incorporated in thicker keyboards if that should be desired.
The present invention broadly consists of a keyboard including a substantially rigid base plate; supporting means for supporting the base plate so as to be movable between an extended position and a retracted position; biasing means biasing the base plate to the extended position; a plurality of keys arrayed over an outer surface of the base plate; and a switch means associated with each key; wherein, when any key is pressed sufficiently firmly, the supported base plate moves against the action of the biasing means substantially from the extended position to the retracted position thereby providing for at least some travel of the pressed key, and the switch means associated with the pressed key enables the registration of the pressed key, and wherein release of the pressed key allows the base plate to return to the extended position under the action of the biasing means.
From this, it will be realised that according to the present invention, the travel of the pressed key is provided, at least in part, by the movement of the base plate.
In a preferred embodiment of the invention, each key includes a key cap biased to a raised position spaced from the base plate and movable to a depressed position against the base plate when an outer face of the key cap is pressed sufficiently firmly. The pressing of any key sufficiently firmly to move the base plate from its extended position to its retracted position is also sufficient to move the key cap of that key from its raised position to its depressed position. In this embodiment, the full travel of the key cap is provided by two movements. There is firstly the small degree of movement of the key cap from its raised position to its depressed position against the base plate and then there is the movement of the base plate from its extended position to its retracted position. It is the movement of the base plate which preferably provides most of the overall movement of the key cap. The main purpose of the initial movement of the key cap from its raised position to its depressed position is to actuate the switch means associated with the pressed key enabling its registration.
The switch means associated with each key preferably includes an electrical circuit closing means on an inner face of the key cap and separated electrical contacts on the base plate corresponding to that key. The electrical circuit closing means makes contact with and closes the corresponding electrical contacts on the base plate when the key cap is pressed to its depress

Affiliated with

Also associated with

Rating

Keyboard with moveable base plate providing key travel does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Keyboard with moveable base plate providing key travel, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Keyboard with moveable base plate providing key travel will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2827526