GB2429064A

GB2429064A - Touch screen apparatus with tensioning mechanism

Info

Publication number: GB2429064A
Application number: GB0515370A
Authority: GB
Inventors: Nicholas Collins
Original assignee: Interactive Technologies Inc
Current assignee: Carrier Fire and Security Americas Corp
Priority date: 2005-07-26
Filing date: 2005-07-26
Publication date: 2007-02-14
Also published as: GB0515370D0

Abstract

A touch screen apparatus comprises a frame 1, a substrate 2 and a flexible membrane 4 overlying and spaced from the substrate 2. The membrane 4 is secured along its edges under a tension which maintains the membrane 4 at a desired spacing from the substrate 2. The membrane 4 may extend over an elongate insulating spacer (6) that extends along the edge of the substrate 2, where the insulating spacer (6) may have two conductive strips (7, 8) proximate to the membrane 4 and substrate 2 respectively. Along at least one edge of the substrate 2 there is a tensioning arrangement in which the membrane 4 is connected to an elongate first tensioning component 10 being capable, during assembly, of pivoting about an axis generally parallel to an edge of the substrate 2 so as to tension the membrane 4. A second tensioning component 12 is provided in the form of an elongate element having a first portion 13 which is secured to the frame 1 and a second portion 15 which engages the first tensioning component 10 so as to hold the first tensioning component 10 in a pivoted condition with the membrane 4 under tension.

Description

Touch Screen Apparatus The present invention relates to touch screen

apparatus and in particular, but not exclusively, to a resistive touch screen apparatus used for large display devices.

Resistive touch screens have conventionally been used for many years in small screen application such as person computer display monitors and more recently in Personal Digital Assistants (PDA's) and computers. However, resistive touch screens are now increasingly being used for large screen applications where large groups of users need to view a screen, such as in a school class, a lecture theatre and so forth. A touch screen may be used over a large display such as a plasma screen or large LCD screen, or a back projection screen, or over a screen onto which an image is projected. By moving a finger or stylus over the screen, signals are transmitted to a computer which then displays the pattern drawn out - such as alphanumeric characters, diagrams and so forth. Such screens can take the place of conventional black or white boards.

Touch screen devices, and in particular resistive touch screen devices, generally comprise a substrate having a conductive coating and a flexible membrane, also having a conductive coating, disposed above the substrate. A space is provided between the substrate and membrane such that when a user touches the screen the membrane the substrate and membrane are brought into electrical contact.

A suitable control unit (as are well known in the art) can then determine the exact coordinates of the point of electrical contact between the membrane and substrate which can be used as an input to a computer, display controller or the like. For use over a display monitor, the substrate and the membrane will be transparent. For use in a projection environment, the membrane or substrate can be white or they can again be transparent and placed over a white panel.

The operation of a resistive touch screen as discussed above is entirely dependent on the space which is provided between the membrane and substrate. If the space is not maintained then contact may occur between the two conductive members giving a false or inaccurate indication of coordinates. It is therefore essential for the operation of this type of touch screen that a sufficient space is maintained between the membrane and substrate over the expected life of the device.

In one conventional system the space between the substrate and membrane is provided by a plurality of insulated spacer rods positioned evenly across the membrane. In this arrangement the rods are formed as part of the membrane and contact the substrate. This type of spacer system is complex to manufacture because each of the spacer rods has to be precisely dimensioned and spaced apart on a thin membrane material.

In an alternative prior art system the membrane is suspended over the top of the substrate thereby removing the need for spacer elements. However, in this arrangement it is essential that the membrane remains tightly suspended over the substrate to prevent accidental contact between the two elements. Flexing or sagging of the membrane as a result of low tension in the membrane can result in inadvertent contact between the membrane and substrate thus resulting in erroneous contact signals.

In order to overcome the problem associates with a suspended membrane touch screen, the membranes are conventionally tensioned against the touch screen frame or housing. For larger screens, particularly of the type used in large presentations such as wall mounted units, a considerable tensile force must be applied to the membrane to prevent and flexing or sagging of the screen and to provide an accurate and uniform space between the membrane and substrate.

In order to achieve the required tension, in one known arrangement each of the four sides of a rectangular membrane is connected to a lever arrangement which is arranged to pivot against the edge of a frame of the touch screen. Each lever arrangement is provided by a length of angle iron which runs along the edge of the frame, with the intersection between the two legs of the angle iron bearing against the frame and acting as a pivot point. One leg is connected to the resistive membrane. The other leg is connected to the touch screen frame with tightening screw spaced along its length. Tightening the screws pivots the lever, thus providing the necessary mechanical advantage to tension the membrane. This arrangement effectively tensions the membrane but applies substantial loads to the screen frame where the lever are attached.. To accommodate these loads the lengths of angle iron and the frame edges have to be sufficiently strong, making the frame large, heavy and thus inconvenient to mount on display screens. It is also a labour intensive job to tighten the individual screws along the length of each angle iron.

There is therefore a need for a touch screen apparatus which provides a suspended resistive screen arrangement creating the necessary spacing between a membrane and a substrate which is both convenient to manufacture and which does not require heavy components.

Thus, viewed from a first aspect, there is provided touch screen apparatus comprising a frame, a substrate secured with respect to the frame, and a flexible membrane overlying and spaced from the substrate, the membrane being secured along its edges under a tension which maintains the membrane at a desired spacing from the substrate; wherein along at least one edge of the substrate there is a tensioning arrangement in which the membrane is connected to an elongate first tensioning component extending along that edge of the substrate on the other side of the substrate from the membrane, the first tensioning component being capable, during assembly, of pivoting about an axis generally parallel to that edge of the substrate so as to tension the membrane, and wherein a second tensioning component is in the form of an elongate element having a first portion which is secured to the frame along that edge of the substrate, and a second portion which engages the first tensioning component so as to hold the first tensioning component in a pivoted condition with the membrane under tension.

In general, the frame will be rectangular (having a short vertical side and a long horizontal side), and there is a tensioning arrangement along at least two perpendicular edges of the frame. In one possible arrangement the tensioning system may only be provided on two perpendicular edges of the substrate, in each case with the opposing edge of the membrane being fixed to the housing. However, in the preferred embodiments of the invention the tensioning arrangement, including the first and second tensioning components, is provided on each of the four edges of the touch screen frame in order to guarantee separation of the substrate and membrane. Thus, the membrane can be evenly and accurately tensioned in all four directions.

In assembly of the a touch screen apparatus, the membrane is tensioned according to this aspect of the present invention by attaching a second tensioning component along the edges of the frame, so that each cooperates with a corresponding first tensioning element, to pivot that tensioning element so that it moves from being at an angle ( e.g. perpendicular) to the substrate, towards being parallel to, and engaged against, the substrate. This applies tension to the membrane.

The tensioning apparatus according to this aspect of the present invention is compact and does not rely on a substantial housing arrangement to accommodate the tensioning forces.

In general, the first tensioning component will be of a thickness chosen so that the desired tension will be applied to the membrane. As the first tensioning element moves from an initial position in which it is perpendicular to the substrate, to lying over the substrate, the membrane will be tensioned by an amount corresponding to the thickness of the first tensioning element, which the membrane now has to pass over. The membrane will then be tensioned so as to extends in a plane parallel with the front surface of the substrate (i.e. the surface of the substrate which will faces a user) at a substantially constant spacing.

Adjacent each edge of the substrate, there is preferably provided an elongate spacer which defines the nominal spacing of the membrane from the substrate.

Despite the tension applied, this spacing may be reduced in a central region of the membrane, and this will be acceptable provided that there is no unwanted contact between the membrane and the substrate. In a preferred embodiment, the spacer is an electrically insulating. Preferably, the insulating spacer is aligned with the edge of the substrate and extends along the edge thereof. Thus, the spacing between the membrane and substrate is provided along the entire edge of the membrane. The spacer is selected so as to be sufficiently rigid to retain the separation of the membrane and substrate and to accommodate the forces applied by the tensioning components. The electrical insulation member may be formed of any suitable material such as a plastics material.

In a preferred embodiment, each edge region of the membrane passes around the corresponding edge of the substrate to connect with the first tensioning component. However, it would be possible for the edge of the membrane to be connected to a flexible connecting element which passes around the edge of the substrate and is connected to the first tensioning component Preferably, the second tensioning element forms a snap fit with the frame, urging the first tensioning element to pivot to lie over the substrate as it is snapped into place.

The touch screen membrane itself may be any membrane suitable for use in a touch screen device. The membrane material may for example be a transparent polyester film. The inner side of the membrane (that is the side facing the substrate in use) is provided with a uniform conductive coating.

The touch screen substrate may be any suitable substrate for use with a resistive touch screen device. Preferably, the substrate is a glass layer having a uniform conductive coating disposed on a surface which faces the membrane.

The first and second tensioning components preferably extend along a substantial portion of the edge of the frame. Most preferably, the first and second tensioning components extend along the entire edge of the touch screen housing.

Thus, a uniform tensile load can be applied along the entire length of the membrane S edge. However, in some circumstances it may be possible for the components - and particularly the second component - to be arranged in a number of spaced lengths.

The touch screen frame is preferably in the form of an extruded aluminium section, preferably having a box section to provide strength and rigidity. The section may have having a recess arranged to receive a portion of the second tensioning component and to act as a pivot point, there also being a portion to retain the second tensioning component in the pivoted condition. The first tensioning component is thus arranged to pivot about the recess in the frame section and to rotate generally inwards and towards the touch screen membrane and first tensioning component. Thus, the tensioning components do not extend beyond the edges of the touch screen frame once the membrane has been tensioned.

The second tensioning component is preferably provided with a protrusion which engages with a corresponding protrusion on the touch screen frame section such that once the first and second tensioning components have cooperated to rotate the first tensioning component (and thereby tension the membrane) the second tensioning component engages with the protrusion to secure the component in position.

The first tensioning component is preferably in the form of a rigid elongate element which is fixed to the edge of the membrane. The rigid elongate element is preferably bonded to the membrane. Most preferably, a portion of the membrane is wrapped around the element so as to firmly secure the membrane to the element.

The membrane may be bonded to the element with a suitable adhesive.

In an un-tensioned position, prior to assembly, the first tensioning component is preferably aligned and in contact with an edge of the substrate proximate the housing. The first tensioning component may be any suitable shape which is arranged to connect to the membrane and which acts to tension the membrane as the component rotates against the substrate surface. Preferably, the first tensioning component is generally rectangular in cross-section with a short side of the component in contact with the substrate and a long side of the component generally extending perpendicular to the substrate surface.

The first and second tensioning components are preferably arranged to cooperate such that the second component contacts a portion of the first component, causing the first component to pivot on the surface of the substrate. The membrane is preferably connected to the first component such that rotation of the first component applies a tensile force to the membrane as the component rotates on the substrate surface. The tension generated by the rotation of the first component is a function of the thickness of the component. The membrane dimensions are preferably selected, in combination with the dimensions of the component, to provide a pre-defined tension in the membrane.

Preferably, insulating spacers along the sides the frame are each provided with an elongate electrical connector (or sensor) on one side of the spacer.

Preferably, an electrical connector (or sensor) is provided on one side of a spacer on each of the four sides of the frame. The electrical connectors on the vertical portions of the frame are preferably electrically connected to the membrane and the electrical connectors on the horizontal portions of the frame are preferably electrically connected to the substrate. Most preferably there is provided a pair of vertical electrical connectors, one connected to each of the spacers on each vertical side of the frame and a pair of horizontal electrical connectors, one connected to each of the spacers on each horizontal side of the frame.

The electrical connectors are preferably in the form of thin conductive strips disposed along the length of the respective side of the insulation member.

In use, the electrical connectors are electrically connected to processing apparatus which can be used to determine the coordinates at which the screen has been touched. The vertical electrical connectors can be used to determine the y coordinate of contact on the screen and the horizontal electrical connectors can be used to determine thex coordinate of contact on the screen.

Techniques used to determine the coordinates in response to signals received from the electrical connectors are well known in the art and are not therefore described in detail.

Viewed from a second aspect, the invention provides a method of tensioning a touch screen membrane in the manufacture of touch screen apparatus, comprising the steps of providing a frame, positioning a substrate within the frame, and positioning a 1 5 flexible membrane so that it overlies and is spaced from the substrate, the membrane being secured along its edges under tension which maintains the membrane at a desired spacing from the substrate; wherein along at least two perpendicular edges of the substrate there is provided a spacer on the side facing the membrane, the membrane passing over the spacer and being connected to an elongate first tensioning component extending along that edge of the substrate on the other side of the substrate from the membrane, a second tensioning component in the form of an elongate element has a first portion which is secured to the frame along that edge of the substrate, and a second portion which engages the first tensioning component, and wherein the second tensioning component is pivoted about an axis generally parallel to that edge of the substrate so that the second portion causes the first tensioning component to pivot and to place the membrane under tension.

Viewed from another aspect, there is provided touch screen membrane tensioning apparatus comprising a first lever component arranged to cooperate with a touch screen frame and a second lever component fixed to a portion of a touch screen membrane; wherein the first lever component is arranged in use to cooperate with the second lever component and to pivot said second lever component on a portion of a touch screen substrate so as to apply a tensile force to the touch screen membrane Viewed from another aspect there is provided a method of tensioning a touch screen membrane, there being provided a first lever component arranged to cooperate with a touch screen frame and a second lever component fixed to a portion of a touch screen membrane; wherein the first lever component cooperates with the second lever component so as to pivot said second lever component on a portion of a touch screen substrate so as to apply a tensile force to the touch screen membrane.

It will be appreciated that although the invention disclosed herein particularly relates to a touch screen membrane tensioning arrangement, the invention can equally be applied to other membranes which require tensioning.

Thus, viewed from another aspect there is provided a method of tensioning a membrane over a substrate, comprising the steps of providing a frame, positioning a substrate within the frame, and positioning a flexible membrane so that it overlies and is spaced from the substrate, the membrane being secured along its edges under tension which maintains the membrane at a desired spacing from the substrate; wherein along at least on edge of the substrate there is provided a spacer on the side facing the membrane, the membrane passing over the spacer and being connected to an elongate first tensioning component extending along that edge of the substrate on the other side of the substrate from the membrane, a second tensioning component in the form of an elongate element has a first portion which is secured to the frame along that edge of the substrate, and a second portion which engages the first tensioning componeflt and wherein the second tensioning component is pivoted about an axis generally parallel to that edge of the substrate so that the second portion causes the first tensioning component to pivot and to place the membrane under tension. - 10-

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Figures I to 10 show the steps in tensioning and securing a membrane across a substrate in the construction of resistive touch screen apparatus in accordance with an embodiment of the present invention; and Figure II shows the touch screen apparatus in diagrammatic form.

Figures IA and lB show portions of the tensioning arrangement in profile before assembly. Figure 1A shows a vertical portion of the frame i.e. a short side of the rectangular frame in figure 11 and Figure lB shows a horizontal portion of the frame i.e. a long side of the rectangular frame shown in figure II.

The frame portions or housings I shown in figure 1 A and 1 B are formed of an extruded aluminium section onto which the substrate and membrane are mounted.

The frame has a box section from which project two flanges.

The glass substrate 2 has a conductive coating 3 on the surface opposing the flexible membrane 4 (the front surface). The flexible membrane 4 is formed of a transparent polyester layer having a conductive coating 5 on the side opposing the substrate 2.

The space between the substrate 2 and membrane 4 is provided by an elongate insulating member 6 positioned so as to be aligned with the end of the substrate 2 proximate the housing. A portion of membrane 4 extends beyond this end of the substrate in an unassembled position. The insulating member 6 extends along the entire length of each edge of the touch screen housing 1.

Figure IA illustrates an insulating member 6 with electrical conductive strip 7 on a first side. This arrangement is used to determine the vertical coordinates of the point at which the screen has been touched.

Figure lB illustrates an insulating member 6 with electrical conductive strip 8 on a second side. This arrangement is used to determine the horizontal coordinates of the point at which the screen has been touched.

The conductive strips extend along the entire length of each edge of the membrane/substrate respectively. The first conductive strip 7 is electrically connected to the conductive coating 5 on the inner surface of the membrane 4.

Similarly, the second conductive strip 8 is electrically connected to the conductive coating 3 on the substrate 2.

Figure 2 shows the next step in forming the tensioning apparatus. In figure 2 the substrate 2 and membrane 4 are located against a support portion 9 of the frame 1. The support portion 9 forms the front of the housing which faces the user when the apparatus is in use. As shown, the end of the membrane 4 has been folded around the end of the substrate 2 so as to be perpendicular to the front portion 9.

The insulating member 6 is disposed between the substrate and membrane against the frame front portion 9.

Figure 3 shows an elongate lever component 10 in the form of a strip which is bonded to the inner surface of the membrane 4. As shown, the lever component is located against the top surface of the substrate 2 proximate the housing. The lever component 10 is positioned so as to be in contact with the substrate and is bonded directly to the membrane using an adhesive.

Figure 4 shows the lever component 10 in position against the substrate 2 and bonded to the membrane 4.

Figures 5 and 6 shows the next stage of assembly in which the membrane 4 is rotated about the lever component 10 and bonded thereto. As shown in figure 6 the membrane is folded around the lever component so as to be firmly fixed to the - 12- component on both sides. An adhesive is used to bond the membrane to the lever component.

A further elongate insulating member 11, as shown in figure 7, is positioned against the lever component lOon top of the membrane 4 which has been wrapped around the component. As shown, the insulating member Ii is positioned against the substrate surface 2 and aligned with the edge of the lever component 10. The insulating member corresponds in length to the lever component 10.

Figure 7 shows the arrangement before the membrane is tensioned. As shown, before tensioning the membrane 4 is suspended above, and spaced from, the substrate 2 by the insulation member 6. The membrane 4 passes around the end of the substrate 2 and around the lever component 10. In this arrangement the membrane 4 is firmly coupled to the lever component 10. It will be appreciated that wrapping the membrane around the lever component provides a mechanical advantage when the lever is rotated as described below.

Figures 8, 9 and 10 illustrate the cooperation of the lever components to tension the membrane.

Figure 8 shows an elongate extrusion 12 which acts as a lever component and which is arranged to engage with the housing 1 and to cooperate with the lever component 10 so as to tension the membrane 4. The lever 12 is formed of an aluminium extrusion and corresponds in length to the housing I so as to engage with the housing along the entire length of the housing 1.

As shown in figure 8 the extrusion 12 is arranged to be pivotally mounted to the housing 1 by means of the protrusion 13 and recess 14.

Figure 9 illustrates the rotation of the extrusion 12 about the recess 14 and its engagement with the lever component 10. As shown, the flat portion 15 of the extrusion 12 engages with the upper portion of the lever component 10. As the - 13 - extrusion 12 rotates, the lever component 10 rotates about the opposing edge of the lever component (as shown by reference 16) against the substrate 2. As discussed above, the membrane 4 is fixed to the lever component 10 such that as the lever component 10 rotates a tensile load is applied to the membrane 4 which passes around the end of the substrate. The tension which is applied to the membrane is a function of the thickness of the lever component and insulation member 11.

Increasing the combined thickness of the lever component and insulation member (and also the pre-tension applied to the membrane 4 before the lever is operated) determines the how much the membrane is displaced and thus the tension which applied to the membrane.

Attaching of the component 10 to the extrusion 12 can be achieved by the use of suitable clamps, for example with one side of the frame being dealt with at a time.

Figure 10 shows the tensioning apparatus when the extrusion 12 is a locked position. As shown, the flat portion 15 of the extrusion 12 engages in a horizontal position with the lever component 10. The membrane 4 is tensioned as a result of the rotation of the lever component against the surface of the substrate as discussed above. The tension apparatus is fixed in a tensioned position by the engagement of the protrusions 16 and 17 disposed on the extrusion 12 and housing I respectively.

As shown in figure 9, the protrusions 16 and 17 are arranged such that when the flat portion 15 is engaged in horizontal contact with the lever component 10, the protrusions engage to prevent the tension being released from the membrane 4. The flat portion 15 may be provided with an adhesive layer to further prevent the release of the portion from a horizontal position.

Figure ii shows the constructed touch screen apparatus 18, with the frame 1 and membrane 4, disposed over the substrate 2. Leads 19 and 20 are connected to the conductive strips 7 and 8, and to a control unit 21, which determines the points on the screen where the membrane is pressed into contact with the substrate, and provides information to a personal computer 22. Various methods of determining - 14 - the x and y coordinates of contact using signals from the electrically conducting sensing strips 7 and 8 are known in the art and will not therefore be described.

The personal computer 22 in turn drives a projector 23 which projects output onto the touch screen apparatus, which in this case acts as an interactive whiteboard.

In other embodiments the touch screen apparatus can be mounted over a plasma screen display, for example.

Claims

CLAiMS 1. Touch screen apparatus comprising: a frame, a substrate secured

with respect to the frame, and a flexible membrane overlying and spaced from the substrate, the membrane being secured along its edges under a tension which maintains the membrane at a desired spacing from the substrate; wherein along at least one edge of the substrate there is a tensioning arrangement in which the membrane is connected to an elongate first tensioning component extending along that edge of the substrate on the other side of the substrate from the membrane, the first tensioning component being capable, during assembly, of pivoting about an axis generally parallel to that edge of the substrate so as to tension the membrane, and wherein a second tensioning component is in the form of an elongate element having a first portion which is secured to the frame along that edge of the substrate, and a second portion which engages the first tensioning component so as to hold the first tensioning component in a pivoted condition with the membrane under tension.
2. Apparatus as claimed in claim I, wherein the membrane extends over an elongate insulating spacer extending along the edge of the substrate.
3. Apparatus as claimed in claim 2, wherein the insulating spacer is provided with a first conductive strip on a side proximate the membrane and a second conductive portion on a side proximate the substrate
4. Apparatus as claimed in claim 1, 2 or 3, wherein the membrane extends from a plane generally parallel to the front face of the touch screen substrate and around the edge of the substrate, to the first tensioning component. - 16-
5. Apparatus as claimed in any preceding claim, wherein the first tensioning component is an elongate member extending along the edge of the touch screen membrane.
6. Apparatus as claimed in claim 5, wherein the first tensioning component lies flat adjacent the substrate, with the membrane being tensioned over the thickness of the first tensioning component.
7. Apparatus as claimed in claim 6, wherein an insulating element is disposed between the first tensioning component and the substrate.
8. Apparatus as claimed in claim 6 or 7, wherein the second portion of the second tensioning component extends over and engages the first tensioning component.
9. Apparatus as claimed in claim 8, wherein the first portion of the second tensioning component is generally L shaped with one leg connected to the frame and extending generally parallel to the substrate, and the other leg extending perpendicularly to the first tensioning component.
10. Apparatus as claimed in any preceding claim, wherein the first portion of the second tensioning component forms a snap fit with the frame.
11. Apparatus as claimed in any preceding claim, wherein the frame comprises an elongate extrusion including a box section.
12. Apparatus as claimed in any preceding claim, wherein two elongate, parallel flanges extend from the box section, an inner flange being adjacent the substrate, and the first portion of the second tensioning component is attached to the flanges. - 17-
13. Apparatus as claimed in claim 12, wherein the outer flange engages the first portion of the second tensioning component in such a way as to permit pivoting during assembly.
14. Apparatus as claimed in any preceding claim, wherein the frame is rectangular and a tensioning arrangement having the features recited in the claims is provided along each edge.
15. Apparatus as claimed in any preceding claim, in combination with a screen on which data is viewed through the membrane and substrate.
16. Apparatus as claimed in any of claims Ito 14, incorporated in a board onto which data is projected.
17. A method of tensioning a touch screen membrane in the manufacture of touch screen apparatus, comprising the steps of: providing a frame, positioning a substrate within the frame, and positioning a flexible membrane so that it overlies and is spaced from the substrate, the membrane being secured along its edges under tension which maintains the membrane at a desired spacing from the substrate; wherein along at least one edge of the substrate the membrane is connected to an elongate first tensioning component extending along that edge of the substrate on the other side of the substrate from the membrane, a second tensioning component in the form of an elongate element has a first portion which is secured to the frame adjacent that edge of the substrate, and a second portion which engages the first tensioning component, and wherein the second tensioning component is pivoted about an axis generally parallel to that edge of the substrate so that the second portion causes the first tensioning component to pivot and to place the membrane under tension.
18. A method as claimed in claim 17, wherein the first portion of the second tensioning component is pivoted to a latched position in which the first portion is securely latched to the frame and the second portion holds the first tensioning component against the substrate.
19. A method as claimed in claim 17, wherein the first portion of the second tensioning component forms a snap fit with the frame in the latched position.
20. A method as claimed in claim 18 or 19, wherein during pivoting of the second tensioning component towards the latched position, the first tensioning component pivots from being perpendicular to the substrate to being parallel to the substrate.
21. A method as claimed in any of claims 17 to 20, carried out in the manufacture of apparatus as claimed in any of claims I to 16.
22. Touch screen apparatus, substantially as hereinbefore described with reference to the accompanying drawings.
23. A method, substantially as hereinbefore described with reference to the accompanying drawings.