WO2007020471A1

WO2007020471A1 - Switches and control panels

Info

Publication number: WO2007020471A1
Application number: PCT/GB2006/003125
Authority: WO
Inventors: William Frank Tyldesley
Original assignee: Pelikon Limited
Priority date: 2005-08-19
Filing date: 2006-08-18
Publication date: 2007-02-22
Also published as: GB0517039D0

Abstract

A switch, comprising: a substrate having a set of switch contacts formed on a surface thereof, the switch contacts defining a gap between themselves; a resiliently-deformable contact layer, having a bottom face mounted on the substrate to face the surface carrying the switch contacts and a top face on the opposite side from the bottom face, the bottom face carrying a conductive portion thereon aligned with the gap, the contact layer being mounted on the substrate so that the conductive portion can be brought into contact with the switch contacts by exertion of a force on the switch by a user; in which there is further provided a protrusion on the top surface of the contact layer over the conductive portion.

Description

SWITCHES AND CONTROL PANELS

This invention relates to switches and control panels, such as are typically but non-exclusively used in remote control devices, domestic appliances (such as fridges and microwaves) and the like.

Remote control devices generally comprise a hand-held device with a number of buttons. Pressing the buttons causes activation of a switch, which in turn causes an electronic circuit to transmit a signal - typically an infra red signal - to a domestic electronic apparatus such as a television, hi-fi, video recorder, DVD player or so on in order to affect its behaviour.

In such a "man machine interface" situation, pressing a button is an important method of transferring information from the operator ("man") to the machine. There are many electrical and mechanical arrangements by which the pushing or pressing of a button may cause, or be converted into, a secondary action, and buttons are extensively used as input devices for electronic equipment. The present invention is particularly but not exclusively concerned with electrical and/or electronic buttons used to create an electrical/electronic event that can be measured by a microprocessor-controlled electrical circuit, and thus can be used to trigger another event under that microprocessor control, such as the emission of a remote control signal.

In such electronics, the buttons employed are usually of the non latching, or momentary, type, where the momentary (or otherwise) closing of two electrical contacts causes a circuit to be temporarily made, resulting in an electrical event that a microprocessor linked to that circuit can be programmed to use as a trigger to perform some calculation (e.g. to activate a further part of its program) . Typical non latching buttons employed in microprocessor-controlled electrical circuits are the metal dome variety; their construction is in the form of a pressed metal dome, with legs at the periphery, that is arranged on top of a printed circuit board (PCB) so that it is in constant electrical contact with an electrode that is one side of a "broken" electrical circuit (that is, a circuit in which there is a gap across two conductors, which gap is to be bridged by the dome when the switch is actuated) . In the traditional (a springy metal or metal-coated plastic) dome construction, when the dome is depressed the centre portion is deflected down and brought into contact with the other side of the broken electrical circuit, completing the circuit for as long as the dome is held deflected. And because the dome is made of a springy material, when the deflection force is removed it springs back to its original domed shape, so breaking electrical contact between the two parts of the electrical circuit.

Some buttons of this type utilise a force concentration layer - a moulded or thermoformed layer - laid over the dome to reduce the force needed to deflect the dome.

The metal dome button switch is quite an expensive form of construction, and cheaper but as effective structures are always being sought.

Another common type of button is that frequently employed in laminated film keyboard construction. In this type of construction of momentary switch, thin plastic sheets bearing on their facing surfaces the relevant conductive parts of the switch held apart by spacers are laminated together with adhesive so that they are held apart. The facing surface of one of the sheets is printed with electrical conductive paste that when cured forms a electrical circuit with a gap - broken - at a specific point, while the facing surface of the other of the sheets is printed with electrical paste which when cured forms a bridge for the gap, such that when the two sheets are pressed together the electrical circuit on the first sheet is made. Elasticity in the plastic ensures that when a closing force is absent the contacts are not touching, and so the circuit is not made.

In some cases an additional layer - a layer of a display-generating material (such as an electroluminescent display layer) - is placed over these button areas, allowing the function of the button to be highlighted (or even changed) , increasing the usability of the device of which the keypad forms a part. However, these display layers are commonly relatively thick and stiff by comparison with the underlying dome layer, and as a result their addition tends to deaden the feel of the dome deflection, so as to make it difficult for the User to press, and so removing any feedback that a button -pressing event has occurred.

To overcome this problem it is usual to insert a third "actuator" layer between the display layer and dome layer. The actuator is conveniently a thin layer of plastic that has been thermoformed with small pimples aligned with and facing the centres of the domes; the pimples localise the depression force caused by a pressing finger on the surface of the display layer, so that it is concentrated at the centre of the relevant dome, thus causing a more precise and controlled deflection of the dome with less input force.

According to a first aspect of the invention, there is provided a switch, comprising: a substrate having a set of switch contacts formed on a surface thereof, the switch contacts defining a gap between themselves; a resiliently-deformable contact layer, having a bottom face mounted on the substrate to face the surface carrying the switch contacts and a top face on the opposite side from the bottom face, the bottom face carrying a conductive portion thereon aligned with the gap, the contact layer being mounted on the substrate so that the conductive portion can be brought into contact with the switch contacts by exertion of a force on the switch by a user; in which there is further provided a protrusion on the top surface of the contact layer over the conductive portion.

Accordingly, when a user presses on the switch, the protrusion acts to localise the force exerted by the user, resulting in a more reliable switching action. This invention can therefore do away with the need for a separate actuator layer.

Preferably, the protrusion is formed by printing onto the top surface of the contact layer. This is advantageous, as it is much simpler and hence cheaper than thermoforming such a feature. The protrusion is preferably in register with the conductive portion.

The switch may comprise at least one spacer, which acts to keep the conductive portion away from the switch contacts when no force is being applied to the switch. Preferably, the or each spacer is integrally formed with the contact layer, typically on the bottom surface. The or each spacer is preferably printed onto the bottom surface of the contact layer; again this is particularly simple to perform.

The switch may also have any of the optional features of the second aspect of the invention described below.

According to a second aspect of the invention, there is provided a switch, comprising: a substrate having a set of switch contacts formed on a surface thereof, the switch contacts defining a gap between themselves; a resiliently-deformable contact layer, having a bottom face mounted on the substrate to face the surface carrying the switch contacts, the bottom face carrying a conductive portion thereon aligned with the gap, the contact layer being mounted on the substrate so that the conductive portion can be brought into contact with the switch contacts by exertion of a force on the switch by a user; in which the bottom face of the contact layer is provided with a plurality of integral spacer portions, the spacer portions surrounding the conductive portion.

Having the spacer portions surrounding the conductive portion is particularly advantageous, as this means that less spacing is required of the contact sheet from the substrate. Typically, the spacer portions comprise areas of increased thickness of the contact layer which are, in the preferred embodiment, formed by printing onto the bottom face of the contact layer. In a preferred embodiment, the spacer portions are thicker than the conductive portions.

By surround, we typically mean in proximity to the conductive portion; where the conductive portion has a diameter, the spacing portions may be within two, or roughly two diameters, or preferably one or roughly one diameter, from the conductive portion. Furthermore, the spacing portions may also be centred on the conductive portion. There may be four or approximately four spacers surrounding each conductive portion.

This provides a particularly convenient switch, in which the spacer is integral with the contact layer. Unlike normal membrane switches, the contact layer need not be comprehensively bonded to the substrate. The contact layer may be substantially unattached to the PCB, except at the edges of the substrate; it may be held down only over a small part of the substrate. This free attachment of the array contributes to easy flexing, and further reduces the force required to actuate the switch. The switch may have any of the features of the first aspect of the invention.

The switch may also conveniently be a switch according to the first aspect of the invention. The effects of the protrusion and the spacing portions work together to reduce the force required to activate the switch; the contact layer can be seen to act as a lever, with the load being applied at the protrusion and pivoting about a fulcrum where the spacing portions contact the substrate.

The switch of either aspect of the invention may further comprise an electroluminescent display positioned over the top face of the contact layer. Electroluminescent displays are typically flexible enough such that a user may press on them in order to actuate the switch of the present invention.

According to a third aspect of the invention, there is provided an array of switches according to the first or second aspects of the invention, in which the switches share a common contact layer and a common substrate.

Such arrays are convenient for use in devices that require a plurality of switches, such as remote controls, household appliances and the like.

The contact layer may comprise a plurality of further spacing portions which are not immediately surrounding the conductive portions - say at least one or two diameters of the conductive portion away from each conductive portion. These aid the positioning of the contact layer over the substrate, and hence may reduce the need for the contact layer to be bonded to the substrate. These further spacing portions are preferably formed on the bottom surface of the contact layer, typically by printing.

According to a fourth aspect of the invention, there is provided a control panel, comprising a flexible display layer and a switch, the switch comprising: a substrate having a set of switch contacts formed on a surface thereof, the switch contacts defining a gap between themselves; a resiliently-deformable contact layer, having a bottom face mounted on the substrate to face the surface carrying the switch contacts and a top face on the opposite side from the bottom face, the bottom face carrying a conductive portion thereon aligned with the gap, the contact layer being mounted on the substrate and the display layer being mounted over the top surface of the contact layer with a bottom surface of the display panel adjacent to the top surface of the contact layer, such that the conductive portion can be brought into contact with the switch contacts by exertion of a force on the display panel by a user; in which there is further provided, in register with the conductive portion, a protrusion on one of the top surface of the contact layer or the bottom surface of the display panel.

Such a display panel has the same advantages described above in that the protrusion may act to localise the force exerted on the display panel by a user. Accordingly, a user may successfully operate the switch by pressing the display panel over a wider area than would be the case without the presence of the protrusion.

The control panel may be provided with a plurality of switches spaced apart under the display panel. This allows multiple functions to be selectable by a user. The switches may share a common substrate and a common contact layer, and there may be a protrusion for each switch. The display panel may further comprise an icon in register with the or each switch. By pressing on the icon, the user may be able to activate the switch. The protrusion may be so sized and shaped to allow a user pressing anywhere within the area of the icon to activate the switch. By having the protrusion is formed on the display panel, it can be ensured that the protrusion is aligned with the icon thereby ensuring that the area of the display panel which the user can press is correctly aligned with the icon.

Typically, the display panel will be an Electroluminescent (EL) display. The protrusion may be formed by printing onto either of the relevant surfaces.

According to a fifth aspect of the invention, there is provided an electrical appliance comprising at least one of: an array of switches according to the third aspect of the invention and an electroluminescent display over the top of the switches; or a display panel according to the fourth aspect of the invention. The appliance may be an appliance such as a dishwasher, washing machine, tumble dryer, fridge, microwave or a remote control.

According to a sixth aspect of the invention, there is provided a method of making a contact layer for a switch, comprising: printing a conductive portion onto a. first face of a flexible sheet; and at least one of: printing a protrusion on the second face of the flexible sheet, in register with the conductive portion; and printing a plurality of spacer portions on the first face of the flexible sheet, surrounding the conductive portion. These steps may be executed in any order, and provide a convenient method for providing the contact layer of any of the previous aspects of the invention. Indeed, the contact layer and features printed thereon may have any of the optional features described with reference to the preceding aspects of the invention.

There now follows, by way of example only, an embodiment of the present invention, described with reference to the accompanying drawings, in which:

Figure 1 shows the substrate of a switch according to an embodiment of the present invention;

Figure 2 shows the underside of the contact layer of the switch of Figure 1 ;

Figure 3 shows the top side of the contact layer of the switch of Figure 1 ;

Figure 4 shows a plan view through a plurality of switches of

Figure 1, also showing how such switches can be arranged in a matrix;

Figure 5 shows a cross section through the switch of Figure 1; and Figure 6 shows a cross section through a switch according to a further embodiment of the invention.

According to an embodiment of the invention shown in the accompanying Figures, a switch comprises a substrate 1 on top of which two spaced- apart switch contacts 2 have been formed. Conveniently, the switch contacts 2 are copper tracks on a Printed Circuit Board (PCB) substrate 1. Bridging the gap between the switch contacts 2 reduces the resistance between the tracks, which can be used to signal other electronic circuitry (not shown) . The substrate and the switch contacts can best be seen in Figure 1.

A flexible contact layer 3 is provided over the top of the substrate 1. The contact layer 3 is of flexible plastic materials such as Polyethylene terephthalate (PET) and is about 125 μm thick. On the bottom surface, shown in Figure 2 of the accompanying drawings, there is provided a conductive portion 6 of the form of a carbon dot. Surrounding the contact portion 6 are four spacing portions 5 where the contact layer 3 is thicker than elsewhere; conveniently these spacing portions 5 are formed by printing extra insulating material - typically of the same PET as the substrate - onto the contact layer.

The spacing portions 5 are of greater thickness than the carbon dot such that when the contact layer is placed adjacent to the switch contacts 2, the conductive portion is spaced away from the switch contacts 2. Flexing of the contact layer, due to pressure applied by a user, can cause the conductive portion 6 to bow to contact the switch contacts 2, thereby completing the circuit between the switch contacts 2. In this embodiment, the carbon dot forming the conductive portion is approximately 25 μm thick and the spacing portions 5 are approximately 50 μm thick.

On the top side of the contact layer 3 there is provided a protrusion 4. This is formed in register with the carbon dot conductive portion 6 on the bottom surface of the conductive portion. The protrusion acts to concentrate a force applied to the switch that may not be precisely aligned with the centre of the switch to operate the switch correctly.

As shown in Figure 5, a flexible electroluminescent (EL) display panel 8 is placed over the switch 10. This can be used to selectively display illuminated images to a user to form a control panel. These images can take the form of icons, which the user can press to request that some function be performed. If an icon is positioned in register with the switch, then a user pressing the icon will flex the EL display into contact with the contact layer 3 at or about the protrusion 4. This forces flexure of the contact layer 3 to bring the conductive portion 6 into contact with the switch contacts 2 as described above.

The protrusion 4 is of particular use in this case as it enables the user to correctly activate the switch 10 by pressing over a wider area of the EL display panel 8 than otherwise would be the case. The size and shape of the protrusion 4 can be changed to control over what area of the EL display panel the user can press to activate the switch 10. Whilst the protrusion is depicted herein as a rounded oblong, it could be circular, ovoid or elliptical.

The free flexing of the contact layer, in combination with the protrusion 6, allows low force actuation of the button to be achieved, even under the thick layers of the EL display.

Unlike normal membrane switches the contact layer 3 is not comprehensively bonded to the substrate 1. The contact layer 3 is left substantially unattached to the substrate, being held down only at the extreme edges by small patches of self adhesive tape (not shown) . This free attachment of the contact layer 3 contributes to easy flexing of the contact layer and reduces the force required to actuate the switch. Four such protrusions are shown in Figure 2.

Further spacing portions 7 spaced away from the conductive portion 6 are provided which aid in locating the contact layer relative to the substrate. A plurality of switches 10 of the present embodiment can be arranged in an array as depicted in Figure 4 of the accompanying drawings. These switches 10 share a common substrate 1 and contact layer 3, with the protrusions 4, spacing portions 5 and further spacing portions 7 formed on the common contact layer 3. The further spacing portions 7 are shared between adjacent switches 10.

A further embodiment of the invention is shown in Figure 6 of the accompanying drawings. Features common to the first embodiment are shown with the same reference numeral raised by 20.

In this embodiment, the control panel is formed of a switch 30 overlaid with an EL display 28. However, in this case the protrusion 24 is printed onto the bottom surface of the EL display 28 rather than the contact layer 23. The protrusion is printed in register with a selectively-illuminatable icon 29 in the EL display. This means that when a user presses on the icon 29 (typically when illuminated) the force is likely to be applied in the region of the protrusion 24. This enables the force to be transmitted to the remainder of the switch 30 to correctly operate the switch, by bringing the conductive portion 26 into contact with the switch contacts 22.

Claims

1. A switch, comprising: a substrate having a set of switch contacts formed on a surface thereof, the switch contacts defining a gap between themselves; a resiliently-deformable contact layer, having a bottom face mounted on the substrate to face the surface carrying the switch contacts and a top face on the opposite side from the bottom face, the bottom face carrying a conductive portion thereon aligned with the gap, the contact layer being mounted on the substrate so that the conductive portion can be brought into contact with the switch contacts by exertion of a force on the switch by a user; in which there is further provided a protrusion on the top surface of the contact layer over the conductive portion.

2. The switch of claim 1 in which the protrusion is formed by printing onto the top surface of the contact layer.

3. The switch of claim 1 or claim 2 in which the protrusion is in register with the conductive portion.

4. The switch of any preceding claim in which the switch comprises at least one spacer, which acts to keep the conductive portion away from the switch contacts when no force is being applied to the switch.

5. The switch of claim 4 in which the or each spacer is integrally formed with the contact layer on the bottom surface.

6. The switch of claim 4 or claim 5 in which the or each spacer is printed onto the bottom surface of the contact layer

7. A switch, comprising: a substrate having a set of switch contacts formed on a surface thereof, the switch contacts defining a gap between themselves; a resiliently-deformable contact layer, having a bottom face mounted on the substrate to face the surface carrying the switch contacts, the bottom face carrying a conductive portion thereon aligned with the gap, the contact layer being mounted on the substrate so that the conductive portion can be brought into contact with the switch contacts by exertion of a force on the switch by a user; in which the bottom face of the contact layer is provided with a plurality of integral spacer portions, the spacer portions surrounding the conductive portion.

8. The switch of claim 8, in which the spacer portions comprise areas of increased thickness of the contact layer

9. The switch of claim 8 in which the spacer portions which are formed by printing onto the bottom face of the contact layer.

10. The switch of claim 9 in which the spacer portions are thicker than the conductive portion.

11. The switch of any of claims 7 to 10 in which the conductive portion has a diameter and the spacing portions are within two diameters from the conductive portion.

12. The switch of any of claims 7 to 11 in which the spacing portions are centred on the conductive portion.

13. The switch of any of claims 7 to 12, in which the contact layer is substantially unattached to the substrate, except at the edges of the substrate.

14. The switch of any of claims 7 to 12, which is also a switch according to any of claims 1 to 6.

15. The switch of any preceding claim, further comprising an electroluminescent display positioned over the top face of the contact layer.

16. An array of switches according to any preceding claim, in which the switches share a common contact layer and a common substrate.

17. The array of claim 16 in which the contact layer comprises a plurality of further spacing portions which are not immediately surrounding the conductive portions.

18. The array of claim 17 in which the further spacing portions are least two diameters of the conductive portion away from each conductive portion.

19. The array of claim 17 or claim 18 in which the further spacing portions are preferably on the bottom surface of the contact layer.

20. A control panel, comprising a flexible display panel and a switch, the switch comprising: a substrate having a set of switch contacts formed on a surface thereof, the switch contacts defining a gap between themselves; a resiliently-deformable contact layer, having a bottom face mounted on the substrate to face the surface carrying the switch contacts and a top face on the opposite side from the bottom face, the bottom face carrying a conductive portion thereon aligned with the gap, the contact layer being mounted on the substrate and the display layer being mounted over the top surface of the contact layer with a bottom surface of the display panel adjacent to the top surface of the contact layer, such that the conductive portion can be brought into contact with the switch contacts by exertion of a force on the display panel by a user; in which there is further provided, in register with the conductive portion, a protrusion on one of the top surface of the contact layer or the bottom surface of the display panel.

21. The control panel of claim 20 in which a plurality of such switches are provided spaced apart under the display panel.

22. The control panel of claim 21 in which the switches share a common substrate and a common contact layer there is a protrusion for each switch.

23. The control panel of any of claims 20 to 22 in which the display panel comprises an icon in register with the or each switch.

24. The control panel of any of claims 20 to 23 in which the display panel is an Electroluminescent (EL) display.

25. The control panel of any of claims 20 to 24 in which the protrusion may is formed by printing onto the relevant surface.

26. An electrical appliance comprising at least one of: an array of switches according to any of claims 16 to 19 and an electroluminescent display over the top of the switches; or a display panel according any of claims 20 to 25.

27. The appliance of claim 26 in which the appliance is a dishwasher, washing machine, tumble dryer, fridge, microwave or a remote control.

28. A method of making a contact layer for a switch, comprising: printing a conductive portion onto a first face of a flexible sheet; and at least one of: printing a protrusion on the second face of the flexible sheet, in register with the conductive portion; and printing a plurality of spacer portions on the first face of the flexible sheet, surrounding the conductive portion.

29. A switch substantially as described herein with reference to the accompanying drawings.