WO2001015189A1

WO2001015189A1 - A switch for a touch pad

Info

Publication number: WO2001015189A1
Application number: PCT/AU2000/001000
Authority: WO
Inventors: Mark Fisher
Original assignee: Kajlich Anton; Mark Fisher
Priority date: 1999-08-24
Filing date: 2000-08-24
Publication date: 2001-03-01
Also published as: WO2001015189A9; AUPQ241699A0

Abstract

A switch for a touch pad (1), the switch comprising a first conductor (3) and a second conductor (4) located on a surface of a first supporting medium (2), a non-conducting separation means (5) and a conducting means (7) separated from the first and second conductors by the separation means, wherein the separation means is deformable, when pressure is applied to the switch to enable the conducting means to contact part of the first and second conductors to create a conductive connection between the first and second conductors.

Description

A SWITCH FOR A TOUCH PAD FIELD OF THE INVENTION

The invention relates to an improved switch applicable to a waterproof touch. In particular, it relates to a touch pad in the form of a low pressure membrane switch. BACKGROUND TO THE INVENTION

Touch pads are important in swimming competition to determine the exact time a swimmer leaves the block and the exact time the swimmer touches the wall at the end of the race or at the end of each lap.

One type of touch pad construction is described in United States patent number 4117283, assigned to Societe Suisse pour V ndustrie Horlogere Management Services. The touch pad is constructed from a plurality of hollow extruded plastic panels each with a hook portion on one edge and a hook receiving portion on the other edge whereby the panels may be readily assembled to form a striker plate. The construction is quite complex and difficult to manufacture. This contributes to the cost and the failure rate.

Membrane switches from other applications have found application in the swimming pool situation. One type of membrane switch comprises a top conductive layer, an insulating middle layer and a bottom conductive layer.

A plurality of holes are formed in the insulating layer. Pressure applied to one of the conductive layers will force a contact through the holes. One embodiment of this type of membrane switch is disclosed in United States patent number 4360716 assigned to Texas Instruments

Incorporated, and titled Area Actuated Switch Array. The Texas Instruments switch array is designed for keyboard applications but is sealed at the periphery making it possibly suitable for swimming pool applications. Reference may also be had to United States patent number 4818827, assigned to AMP Incorporated. The AMP patent describes a low force membrane switch in which two arrays of conductors are separated by a dielectric and insulating coating formed by printing an array of spaced apart dots on top of at least one of the arrays of conductors. One of the arrays of conductors is printed on an inflexible surface and the other array is printed on a flexible insulting material. Pressure on the flexible layer causes deformation to effect a switch closure. The AMP membrane switch is unnecessarily complicated and therefore sub- optimal for swimming pool applications. Another type of membrane switch is disclosed in

United States patent number 5401922, assigned to Illinois Tool Works Inc. The Illinois membrane switch addresses the specific problem of localised vacuum being generated by the closing of a membrane switch. The localised vacuum can inhibit the opening of the switch after release of the closing pressure. Illinois describes a geometric pattern of dielectric cells that form the spacing between two conducting layers. The walls of the cells have breaks in the perimeter that allow passage of air to avoid formation of a localised vacuum. Although interesting, the arrangement is complex and expensive.

Despite considerable attention having been paid to the design of membrane switches there is yet to be devised a membrane switch that is both inexpensive to produce yet reliable in operation.

OBJECT OF THE INVENTION

It is an object of the present invention to provide an improved touch pad suitable for swimming pool applications . DISCLOSURE OF THE INVENTION

According to the present invention there is provided a switch for a touch pad, the switch comprising a first conductor and a second conductor located on a surface of a first supporting medium, a non-conducting separation means and a conducting means separated from the first and second conductors by the separation means, wherein the conducting means is moveable, when pressure is applied to the switch to enable the conducting means to contact part of the first and second conductors to create a conductive connection between the first and second conductors . It is preferred that the conducting means is deformable to move into contact with both the first and second conductors when pressure is applied to the switch.

According to another embodiment the conducting means is flexible and is able to be pressed into contact with the first and second conductors.

Preferably the conducting means is located on a surface of a second supporting medium.

It is preferred that the first and/or second support medium are flexible to allow movement of the conducting means and/or the first and second conductors in to contact with each other when the switch is pressed.

It should be noted that according to the preferred embodiment of the invention the conducting means is able to be flexed, but that the alternative is also possible, whereby the first and second conductors are flexible and the conducting means is also flexible or completely rigid.

Preferably the switch includes the second supporting medium. Preferably the switch includes first and second contacts connected to the first and second conductors respectively and for connection is an electrical circuit.

The first supporting medium preferably comprises a first member. The second supporting medium preferably comprises a second member.

The first member preferably forms a first layer and the second member preferably forms a second layer.

The first member includes a sheet of material and the second member preferably includes a sheet of material.

Either of the sheets may be flexible.

The first and second conductors are preferably located on an upper or lower surface of the first supporting medium and the conducting means is preferably located on an opposing upper or lower surface of the second supporting medium or vice versa. According to an alternative embodiment of the present invention the conducting means is supported by the separation means above the first and second conductors.

The first and second conductors may be located on both upper and lower surfaces of the first supporting medium.

The conducting means may be located opposite both upper and lower surfaces of the first supporting medium.

The conducting means may be a conductive sheet which is separated from the first and second conductors by the separation means.

According to another embodiment of the present invention, the first conductor comprises a plurality of tracks or a conductive surface with non-conductive regions which are adapted to receive the second conductor, or a single conductor arranged to cover the majority of the surface of the supporting medium.

The first conductor may comprise a serpentine path.

Preferably the first conductor comprises a plurality of branches.

The plurality of branches preferably are arranged in parallel.

The second conductor may be similar to any one of the embodiments of the first conductor. Preferably the second conductor is separated from the first conductor by non-conductive regions.

The first conductor preferably comprises a plurality of branches with each branch being located adjacent a corresponding branch of the second conductor. According to another embodiment the second conductor is provided in non-conductive regions of a conductive layer forming the first conductor. It is preferred that the conducting means covers arrangements of conductors which are able to form an electrical connection between the first and second conductors, regardless of where one surface of the switch is touched.

The conductive means may comprise at least on conductor .

The conducting means may comprise a plurality of conductors . The conducting means may form an array of conductors all electrically connected together.

The conducting means preferably comprises a plurality of parallel conductive lines electrically connected at each end by perpendicular lines to form a rectangular pattern.

It is preferred that the conducting means comprises a series of parallel conductors which are arranged perpendicular to the direction of parallel conductors of the first and second conductors. The conducting means may comprise a grid like pattern of connected conductors.

It is preferred that the separation means comprises a plurality of non-conductive spacers for separating the first and second conductors from the conducting means.

The separation means may comprise a plurality of substantially rigid dielectric dots arranged in an array on an upper and/or lower surface of the first supporting medium. Alternatively the separation means may be located on a surface of the second supporting medium which surface is opposite the surface of the first supporting medium on which the first and second conductors are located.

It is preferred that the first supporting medium and the second supporting medium are connected together to form a housing.

It is preferred that the housing is water tight. According to one embodiment of the present invention the switch includes an electrical circuit which is connected to contacts of the first and second conductors . According to another embodiment the switch is able to be connected through external wiring to other electrical devices.

It is preferred that the switch is connected to timing circuitry which is able to be activated by pressure applied to the switch.

It is preferred that the switch includes electronic components within the housing.

According to another embodiment the switch includes a display which is visible from outside the housing.

It is preferred that the display shows a time indicative of the period between touches of the switch.

In one form, the invention resides in a waterproof touch pad comprising: a first sheet; a plurality of first conducting tracks formed on the first sheet; a plurality of second conducting tracks formed on the first sheet and spaced from but adjacent to the first conducting tracks; means connecting said first conducting tracks and said second conducting tracks to respective voltage sources; a second sheet bonded at a periphery to said first sheet such that said tracks are disposed between said first sheet and said second sheet; conducting means on a face of the second sheet facing the first sheet; and spacer means formed on the first sheet, said spacer means holding apart said conducting means on said second sheet from said conducting tracks on said first sheet until pressure applied to said first sheet or said second sheet causes a deformation sufficient to bring the conducting means in contact with the conducting tracks. Suitably the spacer means are dielectric dots printed between the conducting tracks.

The pressure required to bring the conductive means into contact with the conducting tracks is suitably a function of the spacing of the dielectric dots.

Preferably the spacing and location of the dielectric dots is adjustable to define the required pressure.

The first sheet may suitably be an inflexible sheet, in which case the second sheet is suitably a flexible sheet. Pressure is applied to the flexible sheet to bring the conducting means into contact with the conducting tracks.

The conducting means is preferably an array of tracks linked to form a single conducting element.

Alternatively, the first sheet may be a flexible sheet, in which case the second sheet is suitably an inflexible sheet. The inflexible sheet may suitably be a conducting sheet, such as a stainless steel plate.

Preferably the waterproof touch pad further includes electronics embedded in said touch pad. The electronics suitably include timing electronics and transceiver electronics.

It should be noted that words such as "comprising, including and having" should be interpreted in an inclusive sense and should not be considered as limiting the inclusion of additional options. BRIEF DETAILS OF THE DRAWINGS

To assist in understanding the invention preferred embodiments will now be described with reference to the following figures in which:

FIG 1 is an exploded perspective view of a touch pad;

FIG 2 is a cross-sectional side view of the touch pad of FIG 1;

FIG 3 is a plan view of the inflexible sheet of FIG 11; FIG 4 is a plan view of the flexible sheet of FIG

11;

FIG 5 is a cross-sectional side view of a second embodiment of a touch pad;

FIG 6 is plan view of the flexible sheet of FIG 5;

FIG 7 is an exploded perspective view of a third embodiment of a touch pad; and

FIG 8 is a schematic block diagram of electronics of the touch pad of FIG 7. DETAILED DESCRIPTION OF THE DRAWINGS

In the drawings, like reference numerals refer to like parts. There is shown in FIG 1 an exploded view of a touch pad 1 suitable for use in a swimming pool . The touch pad 1 comprises an inflexible sheet 2 which can be affixed to a swimming block or the wall at the end of a swimming lane, depending on the application. A first conducting track 3 is printed on the inflexible sheet 2 such that the track is well distributed across the surface of the inflexible sheet 2. In the preferred embodiment the conducting track 3 comprises a side rail 3a and a number of spurs, such as 3b. A second conducting track 4 is printed on the inflexible sheet 2 such that the track is well distributed across the surface and adjacent the first conducting track 3. The importance of the track distributions to the operation of the touch pad is explained below. Disposed adjacent the first conducting tracks 3 and the second conducting tracks 4 are a plurality of dielectric dots 5. The dielectric dots 5 serve to keep a space between the inflexible sheet 2 and a flexible sheet 6 that has a conducting means 7 on a face of the flexible sheet 6 abutting the dots 5. For ease of explanation, the flexible sheet 6 is shown transparent with the conducting means 7 visible through the sheet.

As can be seen in FIG 1 and FIG 4, the conducting means 7 is suitably a series of conducting lines, although it could equally be a plate or grid.

The arrangement of first conducting tracks 3, second conducting tracks 4 and dielectric dots 5 on the inflexible sheet 2 are seen most clearly in FIG 3. Each track terminates in a tail 3c, 4c to facilitate connection of the tracks to timing and transmission circuitry. The conducting means 7 on the flexible sheet 6 is shown most clearly in FIG 4.

As shown in Figure 3 the arrangement of first conducting tracks consists of a track which extends parallel to one side of the flexible sheet 2 and a plurality of parallel branches which extend at right angles from this track.

The second conducting track 4 also consist of a main conductive line running parallel to the opposite side of the sheet 2 and having a series of parallel branches extending at right angles and respectively adjacent branches of the main conductive line.

Thus a series of conductive lines are provided in parallel and evenly spaced across a major part of the sheet 2.

It should be noted that in practice there would be many more lines of conductors and these would be spread across the entire sheet 2 with minute spacing between adjacent conductors of the respective first and second conductors .

The conducting means shown in Figure 4 is formed as a rectangular conductive line with a series of parallel conductive lines arranged across the thus formed rectangle. Such an arrangement ensures that the conductive lines 7 are able to form a conductive cohnection between adjacent parallel branches of the first and second conductors.

It should be noted that the first and second conductors may be arranged in different patterns and likewise the conducting means 7 may also have a different arrangement of conductors so as to ensure an electrical connection can be made between first and second conductors regardless of where pressure is applied to either of the sheets 2 or 6. The periphery of the flexible sheet 6 is sealed to the inflexible sheet 2 in any suitable manner to provide a barrier to entry of water. The inventers have found that glue is acceptable. In use, size, height and spacing of the dielectric dots 5 are selected to set a desired pressure required to deform the flexible sheet 6 sufficiently to bring the conducting means 7 into contact with the tracks 3, 4. For example if there is significant spacing between adjacent dots then it is effectively easier to depress the conducting means 7 into contact with the tracks 3, 4. Alternatively if the dielectric dots are placed very close together it is almost impossible to depress the conducting means 7 without using a pointed tool. The conducting means 7 closes a circuit between the tracks thereby allowing a current to flow which can be used for starting or stopping timing equipment. The spacing between the conducting tracks is also suitably set to suit the application. By way of example, the inventor has found that a spacing between tracks of around 3mm is most suitable.

The touch pad 1 may be used on the blocks of a swimming pool to detect when a swimmer leaves the block. In this case, the conducting tracks are connected to a timing circuit that starts when the switch circuit goes open. The touch pad 1 may also be used on the wall of a swimming pool to detect when a swimmer touches the wall. In this case the conducting tracks are connected to a timing circuit that stops the timer when the circuit is closed.

The appropriate switch pressure will be different for each of these applications. The switch pressure is easily set at manufacture by selecting an appropriate size and spacing for the dielectric dots. The selection is a matter of engineering design for the specific situation.

A second embodiment of a touch pad 10 is shown in FIG 5. An inflexible sheet 8 of a conducting material such - li ¬

as stainless steel is affixed to the wall of the swimming pool. First conductive track 11, second conductive track 12, and dielectric dots 13 are printed on a face of flexible sheet 9. When pressure is applied to the flexible sheet 9, the first conductive track 11 and the second conductive track 12 are brought into contact with the surface of the conductive material 8. A circuit is closed between the tracks thereby allowing a current to flow which can be used to start or stop a timing circuit, as described above .

The flexible sheet 9 is bonded to the inflexible sheet 8 around the periphery in any suitable manner. A heat bonding arrangement in which the periphery of the flexible sheet is turned around the edges of the inflexible sheet would be suitable. As mentioned above, glueing is also acceptable.

The inventor has found that timing and transmission circuitry can conveniently be located in the touch pad. A suitable arrangement is shown in FIG 7. There is shown a second sheet 14 that, in use, is fixed to a swimming block or wall. A conductive means 15 is attached to the second sheet 14. A hole 16 is cut in the first sheet 14 and conductive means 15 for housing timing and transceiver circuitry 17. A first sheet 18 has first conducting tracks 19 and second conducting tracks 20 connected to the circuitry 17.

The timing and transceiver circuitry is shown in moire detail in the block diagram of FIG 8. The circuitry 17 comprises a timing circuit 21 and a transceiver 22 that connects to an antenna 23. The conducting tracks on the first sheet form a switch matrix that provides a signal to the timing circuit 21. The timing circuit can operate in different modes, as described below. Depending on the mode, a signal is sent by transceiver 22 to a master timing device remote from the touch pad.

A power supply 24 is also included to power the circuitry 17. The circuitry is normally in a quiescent mode until awoken by an event, such as a trigger signal from the first sheet or a signal to the transceiver. Alternatively, additional switches can be built into the touch pad for control purposes. The inventors have calculated that a lithium power cell could provide up to ten years of normal operation . It is therefore possible to seal the power supply within the touch pad.

The touch pad may be configured to operate by synchronisation from an external master controller. In this mode, a number of touch pads, for example in lanes of a pool, are started synchronously with the initiation of a race. A touch on the pad stops the local timing circuit and the result, an absolute time, is transmitted to the master controller.

In another configuration, the touch pad timing circuit starts when there is a local signal and stops when a signal is received from a master controller. The elapsed time is sent to the master controller which than calculates the start time.

In a third configuration a number of touch pad timing circuits are started together and synchronised from an external source, for example a satellite signal. Absolute times are then recorded when a local signal stops the timing circuit.

It will be appreciated that the touch pad has considerable manufacturing advantages over the prior art switches. Conducting tracks need only be printed within tolerances on one surface. The conducting surface on the flexible sheet can be manufactured by any available technique with minimal regard to tolerances. Furthermore, the dielectric dots are printed onto the same surface as the conducting tracks and can therefore be printed as part of the same process as is used for printing the tracks. This avoids the need for multiple processes and excessive handling of the sheets. In fact, the second embodiment only requires printing on one surface and can therefore be manufactured extremely cheaply compared to prior art touch pads .

Throughout the specification the aim has been to describe the preferred embodiments of the invention without limiting the invention to any one embodiment or specific collection of features.

Claims

1. A switch for a touch pad, the switch comprising a first conductor and a second conductor located on a surface of a first supporting medium, a non- conducting separation means and a conducting means separated from the first and second conductors by the separation means, wherein the conducting means is movable, when pressure is applied to the switch to enable the conducting means to contact part of the first and second conductors to create a conductive connection between the first and second conductors.

2. The switch as claimed in claim 1 wherein the conducting means is located on a surface of a second supporting medium.

3. The switch as claimed in claim 1 or claim 2 wherein the switch includes the second supporting medium.

4. The switch as claimed in claim 3 wherein the first and second conductors have first and second contacts respectively for connection in an electrical circuit.

5. The switch as claimed in claim 4 wherein the first supporting medium comprises a sheet of material and the second supporting medium comprises a sheet of material .

6. The switch as claimed in claim 5 wherein the first and second conductors are located on an upper or lower surface of the first supporting medium and the conducting means is located on an opposing surface of the second supporting medium.

7. The switch as claimed in claim 6 wherein the first conductor comprises a plurality of conductive tracks .

8. The switch as claimed in claim 7 wherein the second conductor comprises a plurality of conductive tracks.

9. The switch as claimed in claim 6 wherein the first conductor comprises a first plurality of branches and the second conductor comprises a plurality of branches, with each of the branches arranged adjacent a respective branch of the other conductor.

10. The switch as claimed in claim 1 wherein the conducting means comprises a plurality of conductive tracks .

11. The switch as claimed in claim 10 wherein the conducting means tracks are arranged in a pattern whereby pressure applied to the second supporting medium causes the conducting means to form an electrical connection between part of the first conductor and part of the second conductor.

12. The switch as claimed in claim 11 wherein the conducting means is a conductive sheet.

13. The switch as claimed in claim 1 wherein the separation means comprises a plurality of nonconducting spaces.

14. The switch as claimed in claim 13 wherein the spaces are located on the first supporting medium and are resiliently depressible.

15. A waterproof touch pad comprising: a first sheet; a plurality of first conducting tracks formed on the first sheet; a plurality of second conducting tracks formed on the first sheet and spaced from but adjacent to the first conducting tracks; means connecting said first conducting tracks and said second conducting tracks to respective voltage sources; a second sheet connected at a periphery to said first sheet such that said tracks are disposed between said first sheet and said second sheet; conducting means on a face of the second sheet facing the first sheet; and spacer means formed on the first sheet, said spacer means holding apart said conducting means on said second sheet from said conducting tracks on said first sheet until pressure applied to said first sheet or said second sheet causes a deformation sufficient to bring the conducting means in contact with the conducting tracks.

16. The touch pad of claim 1 wherein the spacer means are dielectric dots printed between the conducting tracks .

17. The touch pad of claim 15 wherein the pressure required to bring the conductive means into contact with the conducting tracks is a function of the spacing of the spacer means.

18. The touch pad of claim 15 wherein the spacing and location of the spacer means is adjustable to define the pressure required to bring the conductive means into contact with the conducting tracks.

19. The touch pad of claim 15 wherein the first sheet is an inflexible sheet and the second sheet is a flexible sheet.

20. The touch pad of claim 15 wherein the conducting means is an array of tracks linked to form a single conducting element.

21. The touch pad of claim 15 wherein the first sheet is a flexible sheet and the second sheet is an inflexible sheet.

22. The touch pad of claim 21 wherein the inflexible sheet is a conducting sheet.

23. The touch pad of claim 21 wherein the inflexible sheet is a stainless steel plate.

24. The touch pad of claim 15 further comprising electronics embedded in said touch pad. 25 The touch pad of claim 24 wherein the electronics include timing electronics and transceiver electronics .