Browse Prior Art Database

Floating Base Plate Touch Sensor for a CRT

IP.com Disclosure Number: IPCOM000060466D
Original Publication Date: 1986-Apr-01
Included in the Prior Art Database: 2005-Mar-08
Document File: 3 page(s) / 44K

Publishing Venue

IBM

Related People

Williams, JA: AUTHOR

Abstract

Several touch-sensitive CRT panel devices exist in the marketplace. This disclosure describes another design for meeting the requirements of a touch-sensitive panel on the CRT display which does not involve placing anything over the face of the display at all. This design is a floating base plate mounted on spherical balls or friction-free pads that remove all but normal forces from application to an array of static sensors. The sensors are preferably strain gauge devices capable of sustaining a steady output under load. Fig. 1 illustrates a side view of a CRT 1 mounted on a base plate 2 that is supported within a tray 5 on support balls 3 that apply forces to the sensors 7. Fig. 2 illustrates a plan view of the balls 3 identified as 3A, 3B and 3C. Fixed stop members 6 are attached to the floating base plate 2.

This text was extracted from a PDF file.
At least one non-text object (such as an image or picture) has been suppressed.
This is the abbreviated version, containing approximately 52% of the total text.

Page 1 of 3

Floating Base Plate Touch Sensor for a CRT

Several touch-sensitive CRT panel devices exist in the marketplace. This disclosure describes another design for meeting the requirements of a touch- sensitive panel on the CRT display which does not involve placing anything over the face of the display at all. This design is a floating base plate mounted on spherical balls or friction-free pads that remove all but normal forces from application to an array of static sensors. The sensors are preferably strain gauge devices capable of sustaining a steady output under load. Fig. 1 illustrates a side view of a CRT 1 mounted on a base plate 2 that is supported within a tray 5 on support balls 3 that apply forces to the sensors 7. Fig. 2 illustrates a plan view of the balls 3 identified as 3A, 3B and 3C. Fixed stop members 6 are attached to the floating base plate 2. When a finger touch force F is applied to the face of display 1 in Fig. 1, stop members 6 apply the force to balls 3B and 3C which will transmit only normal forces to the sensors 7, as seen in Fig. 2. A rotational moment about the base of display 1 will also increase or decrease the normal force W applied to ball 3A with its sensor 7A oriented to sense changes in vertical loads. The three different forces can be measured by the sensor 7, and from a simple calculation, the position of application of force to the face of display 1 can be determined. The bottom support tray 5 contains guides that keep the floating plate 2 constrained within its general confines but permits slight motion of the base plate 2 to occur in the normal direction in response to pressure on the face of the display screen. A spring 4 holds the floating tray 2 against horizontal sensors 7B and 7C that interface balls 3B and 3C. These sensors 7 sense the absolute force in the horizontal direction on the face of the screen. The differential force between them is also available. The absolute force can be used to detect when the face is actually being touched and when the output from the combined sensors 7B and 7C is above a fixed threshold. The differential between the forces sensed by sensors 7B and 7C can be utilized to determine the lateral position of the horizontal force application. Also with the absolute horizontal force known, a calculation of the vertical touch position can be made based on the force information from sensor 7A. The balls 3 minimize all forces other than normal forces acting upon the sensors 7. In...