Keyboard

A keyboard includes a keyboard membrane where the membrane comprises a top layer, a spacer layer and a bottom layer. The spacer layer has interconnecting voids that are connected to the atmosphere by a common vent. A patch made of a hydrophobic material prevents water entering the keyboard membrane via the vent, but allows the air pressure inside the voids to remain balanced with the atmospheric air pressure.

BACKGROUND OF THE INVENTION 
The present invention relates to a keyboard such as that included in a 
self-service terminal, such as an automated teller machine (ATM). 
The keyboard of a self-service terminal may comprise a matrix of 
mechanically operable keys supported by a keyboard membrane below. The 
keyboard membrane contains a void that is connected to the air outside the 
membrane by a vent. The keyboard can be exposed to rain if the terminal is 
located outside. Water may thus seep between the keys and into the 
keyboard membrane below via the vent, damaging the membrane. 
What is needed therefore is a keyboard which is more resistant to damage by 
water. 
SUMMARY OF THE INVENTION 
In accordance with the present invention, there is provided a keyboard 
comprising an array of movable keys. Adjacent the keys is a flexible 
membrane layer comprising first and second outer layers separated by an 
inner layer having a multiplicity of interconnected voids. An array of 
switches corresponds to the moveable keys, where movement of a key causes 
the operation of a corresponding switch and causes expulsion of air from 
within the membrane layer. A venting aperture connects the inner layer of 
the membrane layer to the atmosphere, and a liquid resistant gas permeable 
layer is arranged to cover the venting aperture.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT 
While the invention is susceptible to various modifications and alternative 
forms, a specific embodiment thereof has been shown by way of example in 
the drawings and will herein be described in detail. It should be 
understood, however, that there is no intent to limit the invention to the 
particular form disclosed, but on the contrary, the intention is to cover 
all modifications, equivalents, and alternatives falling within the spirit 
and scope of the invention as defined by the appended claims. 
Referring to FIGS. 1 and 2, the ATM 10 shown therein includes a display 
screen 12 for displaying user information, a keyboard 14 for inputting 
data, a card reader 16 for receiving a user identity card 17 via a card 
slot 18, a cash dispenser 20 where currency notes stored in the dispenser 
20 are delivered to a user during a transaction via a slot 22, a receipt 
printer 24 for printing a receipt acknowledging a transaction made by a 
user and for issuing the receipt to the user via a slot 26, and data 
processing means 28 to which the screen 12, the keyboard 14, the card 
reader 16, the cash dispenser 20 and the receipt printer 24 are connected. 
Referring additionally to FIG. 3, the keyboard 14 comprises a 3.times.4 
matrix of mechanically operable keys 30 supported by a keyboard membrane 
32 below. When a key 30 is pressed, a switch (to be described later) 
inside the membrane 32 is activated, indicating to the data processing 
means 28 that that key 30 has been pressed. 
Referring to FIGS. 4, 5 and 6, the keyboard membrane 32 comprises a top 
layer 40, a spacer layer 42 and a bottom layer 44. The top layer 40 and 
bottom layer 44 are circuit layers that are insulated from each other by 
the spacer layer 42. Each circuit layer comprises a non-conductive sheet 
having a conductor pattern disposed on one surface. Below each key 30 
there is a normally open switch. The switch comprises a silver ink area 46 
that forms part of the conductor pattern on the underside of the top layer 
40 and a silver ink area 47 that forms part of the conductor pattern on 
the topside of the bottom layer 44 with a void 48 filled with air in 
between. When a key is pressed, the silver ink area 46 on the top layer 40 
connects with the silver ink area 47 on the bottom layer 44 closing the 
normally open switch. The silver ink areas 46,47 of the conductor patterns 
are part of a monitoring circuit (not shown) of known construction which 
identifies the pressed key and passes an appropriate signal to the data 
processing means 28 (see FIG. 2). All the voids 48 are interconnected by 
channels 50 in the spacer layer 42. Note that the top layer 40, the bottom 
layer 44 and the solid parts of the spacer layer 42 are shown hatched. A 
vent hole 52 through the bottom layer 44 provides venting of the voids 48 
with the atmosphere. The three layers 40,42,44 are glued together. 
A patch 54 covers the bottom of the vent hole 52. This patch 54 is made of 
a gas permeable hydrophobic material such as "Goretex" (.TM.) which 
prevents water penetration but allows air to pass through. "Goretex" 
(.TM.) is available from W. L. Gore and Associates UK Limited, Livingston, 
West Lothian, Scotland. 
Thus, the air pressure inside the voids 48 and outside the keyboard 
membrane 30 is kept balanced. If the membrane 30 was completely sealed to 
prevent water penetration, changes in atmospheric pressure could cause the 
switches to close due to an imbalance in pressure. 
Conventional keyboard membranes have been vented to the atmosphere from the 
side of the keyboard membrane and have thus been susceptible to water 
penetration via the gaps between the keys above. The invention overcomes 
this disadvantage since the patch prevents water entering the membrane.