Browse Prior Art Database

Mid-Travel Guided Keypad Design

IP.com Disclosure Number: IPCOM000115213D
Original Publication Date: 1995-Mar-01
Included in the Prior Art Database: 2005-Mar-30
Document File: 4 page(s) / 91K

Publishing Venue

IBM

Related People

Basco, JP: AUTHOR [+5]

Abstract

Described is a hardware implementation to provide an improved keypad design for use on keyboards exposed to harsh environments. The keyboard incorporates a mid-travel guided keypad that is sealed from contamination and uses reliable dome switch technology with a desirable tactile feedback.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Mid-Travel Guided Keypad Design

      Described is a hardware implementation to provide an improved
keypad design for use on keyboards exposed to harsh environments.
The keyboard incorporates a mid-travel guided keypad that is sealed
from contamination and uses reliable dome switch technology with a
desirable tactile feedback.

      Fig. 1 shows a cross-section of the keypad.  The concept
consists of keytop 10 which when depressed presses down onto dome
actuator 11.  Sandwiched between plunger 12 and dome actuator 11 is
elastomer material 13 containing high resilience.  Elastomer material
13 is designed to support plunger 12 and to provide mid-travel
operation prior to the snapping of dome actuator 11 during the
pressure stroke.  Dome actuator 11 presses on membrane switch 14 so
as to activate the closing of the circuit.

      Plunger 12 is keyed so as not to rotate.  It is contained and
guided by frame 15 that surrounds plunger 12.  Fig. 1 shows a
cross-section of keytop 10 and plunger 12 with up- stop 16 and
down-stop 17 to prevent overloading dome 11 on impact when subjected
to a heavy pressure stroke.

      Frame 15 is permanently attached to printed circuit board 18
where dome 11 and membrane switch 14 are permanently mounted.  In
order to seal the entire assembly, thin molded elastomer membrane
seal 19 is positioned on top of plunger 12 and trapped with keytop
10.  Keytop 10 is keyed to plunger 12 for proper text orientation.

      Trapping membrane seal 19 between keytop 10 and plunger 12
provides the required seal.  The design allows for interchangeability
of keytop 10 if a different function/legend is required.  It also
allows the replacement of membrane seal 19 if it gets dirty or
damaged.  Graphic printing on a plastic keytop is considered to be
more reliable than on a flexible elastomeric membrane.

      Prior art utiliz...