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Browse Prior Art Database

Flexible Screen CRT Touch Panel With Preloaded Piezoelectric Sensors

IP.com Disclosure Number: IPCOM000062657D
Original Publication Date: 1986-Dec-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 2 page(s) / 44K

Publishing Venue

IBM

Related People

Callaway, MB: AUTHOR [+3]

Abstract

In a CRT Touch Panel, a flexible touch screen, together with preloaded piezoelectric sensors, provides more consistent sensor output, improving touch panel resolution. Design details of this embodiment provide additional improvements over current technology. It is known that the output of a piezoelectric crystal (PZT) is more consistent and predictable when it is preloaded by a controlled constant force. It is also known that a PZT responds to the rate of change of the applied input force (i.e., the output signal is the differential of the input force). Therefore, an abrupt reduction, or cut- off of the input force at a predicted point, limits the peak of the PZT output signal to a defined range.

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Flexible Screen CRT Touch Panel With Preloaded Piezoelectric Sensors

In a CRT Touch Panel, a flexible touch screen, together with preloaded piezoelectric sensors, provides more consistent sensor output, improving touch panel resolution. Design details of this embodiment provide additional improvements over current technology. It is known that the output of a piezoelectric crystal (PZT) is more consistent and predictable when it is preloaded by a controlled constant force. It is also known that a PZT responds to the rate of change of the applied input force (i.e., the output signal is the differential of the input force). Therefore, an abrupt reduction, or cut- off of the input force at a predicted point, limits the peak of the PZT output signal to a defined range. The figure, which shows a horizontal cross-section for one PZT corner structure of a CRT Touch Panel, demonstrates the application of these two principles in the present embodiment. It is seen that flexible touch screen 1, preformed to the CRT curvature, snaps into rigid touch screen frame 2 and is held in place by its own prestressed tension. Frame 2 is enclosed by rigid bezel 3 and semirigid base 4, which are rigidly attached together. Frame 2 is held against cone-shaped PZT retainer 5 by PZT preload spring 6. Spring 6 is a spring-finger washer. The ID of spring 6 fits over a stud in bezel 3, and the OD fits in a counterbored recess in frame 2, thus accurately positioning frame 2 with respect to bezel 3 and base 4. The base of retainer 5 rests within a machined recess in base 4, and is recessed to capture and accurately position PZT 7 without the need for commonly used bonding agents. This permits the PZT to "float" and self...