Force sensitive touch panel

• US 5,241,308 A
• Filed: 07/23/1992
• Issued: 08/31/1993
• Est. Priority Date: 02/22/1990
• Status: Expired due to Fees

• Current Assignee: AVI Systems Incorporated
• Original Assignee: Paragon Systems Incorporated (Securitas AB)
• Inventors: Young, Thomas
• Primary Examiner(s): Yusko, Donald J.
• Assistant Examiner(s): GIUST, JOHN
• Application Number:
  US07/918,917
• Time in Patent Office: 404 Days
• Field of Search: 341/22, 341/34, 178/18, 340/706, 340/712, 340/718, 364/556, 364/558
• US Class Current: 341/34
• CPC Class Codes: G06F 3/0414 using force sensing means to determine a position

Abstract

A touch panel generates any of a plurality of different signals that are selected by touching different specific areas of a panel member. Spaced apart supports at the edges of the touch sensitive area hold a panel member in spaced apart relationship to the underlying surface. Force sensitive circuit elements, such as strain gauges or pressure sensitive resistors, sense the force which the panel member exerts on each support when finger pressure is applied to the member. Additional circuit components compare the forces exerted on each support to determine the location on the panel that is being touched and generate the particular signal that correlates with that location. The touch panel may be used to enter instructions and other data into a computer or the like or to transmit selected control signals to other types of equipment. The panel may be transparent and be attached to the screen of a visual data display enabling entry of menu selections or other data by simply touching the screen.

Claims

1. In a touch sensitive panel for generating selected ones of any of a plurality of different signals each of which is generated by touching a different location on the panel, the combination comprising:

a rectangular panel formed of material which exhibits a degree of elasticity,

a plurality of panel member supports which support said panel member at spaced apart regions thereof, the panel member supports being separate from the panel member,

force sensing means positioned upon said panel member for sensing the magnitudes of the forces that are applied to each of said spaced apart supports by said panel member when said panel member is touched at a selected location thereon, wherein said forces are sensed by detecting the deformation of said panel member in the vicinities of each of said supports that is caused by touching of said panel member, and

location analyzing means for determining the location on said panel member that is being touched by comparing the magnitudes of said forces that are applied to said spaced apart supports by said panel member and for generating the one of said signals that corresponds to the determined location.

2. The apparatus of claim 1 wherein said panel member has a touch sensitive area with said first and second opposite ends and wherein at least one of said panel member supports is situated at each of said ends and wherein said location analyzing means compares the force which said panel member exerts at said first end of said touch sensitive area with the sum of the forces exerted by said panel member at both ends of said area in order to sense the position of said touched location along said panel.

3. The apparatus of claim 1 wherein said panel member has a touch sensitive area bounded by first and second ends and first and second sides and wherein at least one of said panel member supports is situated at each of said ends and at each of said sides, and wherein said location analyzing means senses the position of said touched location along a first axis by comparing the force exerted by said panel member at said first end of said area with the total force exerted by said panel member and senses the position of said touched location along a second orthogonal axis by comparing the force exerted by said panel member at said first side of said area with the total force exerted by said panel member.

4. The apparatus of claim 1 wherein said location analyzing means produces signals which have a first signal component indicative of the location at which said panel member is touched and a second signal component indicative of the magnitude of the pressure which is exerted against said panel member at said location.

5. The apparatus of claim 1 wherein said force sensing means includes a plurality of electrical circuit components of the type which exhibit a change of electrical properties in response to forces exerted thereon.

6. The apparatus of claim 5 wherein said circuit components exhibit a change of electrical resistance in response to forces exerted thereon, further including a plurality of electrical resistors and a plurality of circuit junctions, each of said resistors being connected to a separate one of said circuit components at a separate one of said circuit junctions, a direct current power supply connected to each of said circuit components and resistors to transmit current through each of said components and the one of said resistors that is connected thereto, and wherein said location analyzing means generates said signals in response to voltage changes at said circuit junctions.

7. The apparatus of claim 5 wherein said circuit components are strain gauges secured to said panel member in the vicinity of said supports.

8. The apparatus of claim 7 wherein a pair of said strain gauges are secured to said panel member in the vicinity of each of said panel member supports, the strain gauges of each pair being secured to opposite surfaces of said panel member, each of said strain gauges having an output terminal which exhibits a voltage that varies in response to flexing of the strain gauge, further including a plurality of differential amplifiers each having inputs connected to said output terminals of a separate pair of said strain gauges and each having an output coupled to said location analyzing means to transmit a signal thereto that is indicative of the voltage difference at the output terminals of the pair of strain gauges to which the amplifier is connected.

9. The apparatus of claim 5 wherein said location analyzing means includes a digital computer, further including analog to digital signal conversion means for converting the electrical voltages at said circuit junctions into digital signals which represent said voltages.

10. The apparatus of claim 1 wherein said panel member is transparent.

11. The apparatus of claim 10 further including a visual data display device having a display screen and wherein said transparent panel member is disposed in front of said display screen in spaced apart relationship therewith.

12. The apparatus of claim 11 wherein said panel member supports extend from said panel member to said visual data display device and secure said panel member thereto.

13. The apparatus of claim 1 wherein said panel member supports are formed of resilient material.

14. A touch panel for generating selected ones of a plurality of different signals wherein each of said signals is correlated with a different location on said touch panel, comprising:

a rectangular panel member having a touch sensitive area bounded by first and second sides and first and second ends,

a plurality of panel member supports which support said panel member at spaced apart regions which are situated at said sides and ends of said touch sensitive area, the panel member supports being separate from the panel member,

a plurality of strain gauges of the type in which electrical resistances varies in response to strain, each of said strain gauges being secured to said panel member at a location thereon which is near an associated one of said panel member supports to sense the force which said panel member exerts on said associated one of said panel supports by detecting deformation of said panel member in the vicinity of said associated one of said supports,

means for producing a plurality of electrical voltages each of which varies in response to changes of said resistance of a separate one of said strain gauges and thereby indicates the force sensed by that strain gauge, and

data processing means for determining the location on said panel member where pressure is exerted thereagainst by comparing said forces which are sensed by said strain gauges and for producing the one of said signals that correlates with said location.

15. The apparatus of claim 14 wherein one of said panel member supports is situated at each corner of said touch sensitive area and wherein said strain gauges are secured to the corner regions of said panel member at locations adjacent to said support members.

16. The apparatus of claim 14 wherein said data processing means includes a digital computer, further including a visual data display device coupled to said computer and having a screen on which data generated by said computer may be displayed, and wherein said panel member is transparent and is positioned in front of said screen in spaced apart relationship therewith and wherein said panel member supports extend between said panel member and said data display device.

17. In a touch sensitive panel for generating selected ones of any of a plurality of different signals each of which is generated by touching a different location on the panel, the combination comprising:

a rectangular panel member

support means for holding said panel in spaced apart relationship with an underlying surface,

a plurality of pressure sensitive resistors disposed between said panel member and said support means in position to be compressed against said support means when force is exerted against said panel member, said resistors being strips of resistive material of a type which exhibit a change of electrical resistance when pressure is exerted against the resistor, said resistors being disposed to extend along spaced apart regions of the periphery of said panel member,

force sensing means for sensing the magnitudes of the forces that are applied to said support means through each of said resistors when said panel member is touched at a selected location thereon by detecting changes of the electrical resistance of each of said resistors that result from said touching of said panel member, and

location analyzing mans for sensing the location on said panel member that is being touched by comparing the magnitudes of said forces and for generating the one of said signals that corresponds to the sensed location.

18. The apparatus of claim 17 further including a plurality of strips of elastomeric material each being disposed between a separate one of said pressure sensitive resistors and said support means.

19. The apparatus of claim 17 wherein said pressure sensitive resistors extend along edge regions of said panel member and wherein said support means includes linear support members fitted onto said edge regions of said panel members, said support members having grooves extending therealong in which said edge regions of said panel members and said pressure sensitive resistors are disposed.

20. The apparatus of claim 17 wherein pairs of said pressure sensitive resistors extend along edge regions of said panel member, the resistors of each pair being disposed on opposite faces of said panel member edge regions and wherein said support means includes support members extending along said edge regions of said panel members and having grooves in which said edge regions of said panel members including said pairs of resistors are received, further including a plurality of strips of elastomeric material disposed in said grooves of said support members, said strips of elastomeric material being situated between said pressure sensitive resistors and said support means and wherein said grooves of said support members are proportioned to compress said strips of elastomeric material against said pressure sensitive resistors whereby touching a surface of said panel member increases the compression of one of each pair of pressure sensitive resistors and reduces compression of the others of each pair of pressure sensitive resistors.

21. The apparatus of claim 17 wherein said panel member is substantially rectangular and wherein at least one of said pressure sensitive resistors extends along each edge region of said panel member and wherein said support means includes four channel shaped support members each being fitted onto a separate one of said edge regions of said panel member.

22. The apparatus of claim 21 further including strips of elastomeric material disposed within said channel shaped support members between the pressure sensitive resistors and the inner walls of said support members.

23. In a touch sensitive panel for generating selected ones of any of a plurality of different signals each of which is generated by touching a different location on the panel, the combination comprising:

a rectangular panel member formed of material which exhibits a degree of elasticity,

a plurality of panel member supports which support said panel member at spaced apart regions thereof, the panel member supports being separate from the panel member,

force sensing means positioned on said panel member for sensing the magnitudes of the forces that are applied to each of said spaced apart supports by said panel member when said panel member is touched at a selected location thereon, wherein said forces are sensed by detecting the deformation of said panel member in the vicinities of each of said supports that is caused by touching of said panel member, and

location analyzing means for sensing the location on said panel member that is being touched by comparing the magnitudes of said forces that are applied to said spaced apart supports by said panel member and for generating the one of said signals that corresponds to the sensed location

wherein said force sensing means includes a plurality of strain gauges of the type which exhibit a change of electrical properties in response to forces exerted thereon,

and further wherein a pair of said strain gauges are secured to said panel member in the vicinity of each of said panel member supports, the strain gauges of each pair being secured to opposite surfaces of said panel member, each of said strain gauges having an output terminal which exhibits a voltage that varies in response to flexing of the strain gauge, further including a plurality of differential amplifiers each having inputs connected to said output terminals of a separate pair of said strain gauges and each having an output coupled to said location analyzing means to transmit a signal thereto that is indicative of the voltage difference at the output terminals of the pair of strain gauges to which the amplifier is connected.