GB2097588A

GB2097588A - Flexible switch member

Info

Publication number: GB2097588A
Application number: GB8131659A
Authority: GB
Original assignee: Brady Corp
Current assignee: Brady Corp
Priority date: 1978-01-25
Filing date: 1979-01-09
Publication date: 1982-11-03
Also published as: GB2097588B; JPS54103584A; GB2013401B; BE873717A; DE2900633A1; AU4327479A; NL7812296A; FR2415870A1; GB2013401A; GB2072428A

Abstract

A flexible switch member comprises a flexible plastics layers 16 carrying on one surface a first contact 48 and a first conductive lead 50, and a flexible tail 22 secured at its upper end to the flexible layer 16, bent downward from the layer inward from the edge of the layer, and carrying a second conductive lead 50 electrically connected to the first conductive lead, wherein the first contact 48 can be electrically connected to external circuitry. The flexible layer 16 is spaced by a spacer 18 from a facing surface 20 carrying a second contact 74 aligned with the first contact 50. <IMAGE>

Description

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GB 2 097 588 A

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SPECIFICATION Flexible switch

5 This invention relates to a flexible switch. Such a switch is described in Application No. 2013401, from which the present application is divided.

According to the present invention there is provided a flexible switch for mounting on an under-10 lying frame, comprising: a flexible plastic layer carrying on one surface a first contact portion and a first conductive lead, means for spacing said flexible layer from a facing surface carrying a second contact portion aligned with said first contact portion so that 15 said first and second contact portions are electrically isolated in the absence of an external compressive force tending to bring said layer into contact with said facing surface, and a flexible tail secured at its upper end to said flexible layer, bent downward 20 from said layer inward from the edge of said layer, and carrying on one surface a second conductive lead electrically connected to said first conductive lead, the tail being connectable to external circuitry, whereby said first contact portion can be electrically 25 connected to external circuitry by means of the electrical path formed by said first and second leads.

The flexible tail can be integral with the said flexible layer and defined at its inner end by two inward cuts made from one edge of the layer. The 30 first and second leads can be one continuous lead following a path leading from said first contact portion onto that portion of said flexible layer which is cut to form the tail. An insert can occupy the void formed where the tail is bent downward. 35 In preferred embodiments two flexible layers carry aligned contacts on facing surfaces to provide an X-Y matrix, and a spacer layer with apertures aligned with holes in the contact separates the two contact-carrying layers: and a further layer with apertures 40 aligned with and equal in size to the holes in the contact overlies the upper contact-carrying layer, and a continuous over-lay underprinted with translucent ink portions at individual touch switches covers the further apertured layer, light being transmitted 45 continuously from an incandescent light source beneath the switch through the two apertures and through the two holes in the facing contacts.

The structure and operation of a preferred embodiment of the invention will now be described, by 50 way of example, with reference to the drawings, in which :-

Figure 1 is an exploded isometric view, partially broken away, of said embodiment;

Figure 2 is a partial sectional view through Figure 55 1 at the centreline of the flexible tail (thicknesses are exaggerated for clarity); and

Figure 3 is a partial sectional view through Figure 1 at the location of one pair of transfer pads joined by a conductive epoxy insert.

60 Turning to Figure 1, there is shown a flexible switch panel 10 for telephone Touch-Tone (Americal Telephone and Telegraph Company trademark) switching. The panel 10 consists principally of five adhesively-joined transparent flexible layers; an 65 overlay 12, a spreader layer 14, an upper contact-

carrying layer 16. a spacer layer 18, and a lower contact-carrying layer 20. A flexible tail 22 integral with the upper layer 16 is bent downward through slots 24,26 in the spacer layer 18 and the lower layer 20. An insert 28 occupies the void left in the upper layer 16 by bending the tail 22 downward. Below the panel 10 an incandescent light source (Figure 2) provides backlighting. A frame (not shown) supports the panel 10.

The overlay 12, a 0.25 mm thick flexible non-conductive layer of General Electric Lexan (trade mark) polycarbontefilm of grade 8B05 (which includes a velvet texture top surface) and colour 112 carries on its undersurface translucent zones of graphic ink 36,38 and opaque black and gray zones of graphic ink 35 and 40. These are acrylic-based System II inks obtained from KC Coatings, Incorporated, Kasas City, Missouri and applied by screening. The layers of ink form a black background 35, gray button areas 40, and white translucent indicia 36,38 including button outlines and centrally-located lettering, numbers, and symbols. Back-lighting from an incandescent translucent white light source (not shown) is transmitted through indicia 36,38.

Spacing the overlay 12 from the upper layer 16 and adhering to each of these two layers is a spreader layer 14, a 0.075 mm thick transparent Mylar (Dupont trademark) polyethylene terephtha-late layer 41 having on both its surfaces thermoset (after it is in plate) acrylic transparent pressure-sensitive adhesive layers 42,44. Each adhesive layer is 0.0375 mm thick. A suitable adhesive is the 3M Company's 467 Firm Acrylic Pressure Sensitive Adhesive. The spreader layer 14 is diecut to provide openings 46 (approximately 6mm by 7.5mm) underneath each button area. All indicia 36,38 are aligned inside openings 46.

The upper contact-carrying layer 16 (0.125 mm thick transparent Mylar) has printed on its undersurface three columns of four 0.0175 mm thick conductive paint contacts 48. The conductive paint is sold by Acheson Colloids of Port Huron, Michigan, under the designaton Electrodag 415SS. The contacts 48 are connected by leads 50, which continue onto the tail 22. Each contact 48 has the form of a rectangle with a centre rectangle removed, thus allowing light transmission through an open and therefore transparent centre 52. The contacts are approximately 14 mm by 16 mm and the transparent centres are 6mm by 7.5mm, equal to the size of the spreader openings 46.

Extending from one edge of the upper layer 16 is the tail 22. Two cuts 54 each about 6mm long are made in the upper layer 16, and the tail 22 is bent downward inside the edge of the panel 10. The tail carries leads 50 from the contact 48 on the upper layer 16 and leads 56 from transfer pads 58 located adjacent the bend in the tail. The transfer pads 58 are connected to transfer pads 59 and leads 60 on the lower layer 20 through unhardened conductive epoxy inserts 62 in the spacer layer 18. The conductive epoxy comprises an epoxy resin unmixed with hardener and having dispersed therein silver particles. The epoxy is supplied by Amicon, Lexington, Massachusetts, under the trademark Uniset, type

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C-14. All leads and transfer pads are printed using the same conductive paint as used forthe contacts 48. In all, the tail 22 carries seven leads, one for each column on the upper layer 16 and one for each row 5 on the lower layer 20. By bending the tail 22 down inside the edge of the panel 10, leads 50,56 can be connected to circuitry (not shown) beneath the supporting frame (not shown) and the panel can be sealed to the frame around the panel's entire 10 periphery. The insert 28, made of the same 0.125 mm transparent Mylar as the upper layer 16, fits into the void between the cuts 52.

Spacing the upper layer 16 from and adhering it to the lower layer 20 is the spacer layer 18. Identical in 15 composition to the spreader layer 14, the spacer layer 18 consists of a 0.075 mm Mylar layer 64 sandwiched between two 0.0375 mm adhesive layers 66,68. Rectangular spacer holes 70 are diecut underneath the contacts 48. The spacer holes 70 are 20 largerthan the openings 46 in the spreader layer 14, and just slightly smaller than the contact 48 (Figure 2). The slot 24 receives the tail 22. On either side of the slot 24 are four round holes 72, which receive unhardened conductive epoxy 62 during assembly 25 for electrically connecting transfer pads 58 and 59. The holes 72 are all 6mm in diameter.

The lower contact-carrying layer 20 (0.125 mm thick transparent Mylar) has printed on its top surface conductive paint contacts 74, leads 60, and 30 transfer pads 59, and carries an adhesive layer 73 (3M adhesive described above) on its undersurface. The contacts 74 are connected by an extension of a lead 60 to a transfer pad 59. The contacts 74 are registered with the contacts 48 on the upper layer 16, 35 and have the same rectangular shape with rectangular transparent centres 76. The slot 26 receives the tail 22. An ashesive layer 73 adheres the entrire panel 10 to the supporting frame (not shown).

In use of the switch, a person selects the desired 40 button and presses it with his finger generally in the centre of the button outline. The force applied by the finger is radially spread in the spreader layer 14to the periphery of the corresponding opening 46 (Figure 2). The spread out force pattern thus bears 45 directly on the rectangular contact ring 48, and assures engagement between contacts 48 and 74. Without the spreader layer, a centrally applied force might not exert enough force at the contact periphery to engage the periphery. When the con-50 tacts 48 and 74 touch, a circuit is completed between one row lead 60 on the lower layer 20 and one column lead 50 on the upper layer 16. The layers 16 and 20 thus form an X-Y matrix. The circuit is completed through the unhardened conductive 55 epoxy 62 connecting one pair of corresponding transfer pads 58,59. The incandescent light source (not shown) illuminates the button outlines 36 and the other centrally-located indicia 38 to identify buttons in low light or night conditions. Light is 60 transmitted through the transparent centre 76 in the lower layer 20, the spacer hole 70, the transparent centre 52 in the upper layer 16, the opening 46 in the spreader layer 14, and the translucent indicia 36,38 in the overlay 12.

65 The contacts 48 and 74 need not be connected in an X-Y matrix. One contact could be a pattern of two spaced-apart circuit paths and the other an electrical bridging element to complete the circuit beween the circuit paths. The appropriate conductive pattern 70 could be provided on a surface of the substrate or frame to which the flexible switch is attached. The spacer layer 18 need not be included in the flexible switch panel, but could be built into the surface of the substrate or frame, as could any adhesive that is 75 used for mounting the switch panel. Air channels could connect the adjacent apertures 46,70, to soften the tactile feel of the switch.

Claims

CLAIMS 80

1. A flexible switch for mounting on an underlying frame, comprising: a flexible plastic layer carrying on one surface a first contact portion and a first conductive lead, means for spacing said flexible

85 layerfrom a facing surface carrying a second contact portion alignd with said first contact portion so that said first and second contact portions are electrically isolated in the absence of an external compressive force tending to bring said layer into contact with 90 said facing surface, and a flexible tail secured at its upper end to said flexible layer, bent downward from said layer inward from the edge of said layer, and carrying on one surface a second conductive lead electrically connected to said first conductive 95 lead, the tail being connectable to external circuitry, whereby said first contact portion can be electrically connected to external circuitry by means of the electrical path formed by said first and second leads.

2. A flexible switch as claimed in claim 1 wherein 100 said flexible tail is integral with said flexible layer and is defined at its inner end by two inward cuts made from one edge of said layer, and said first and second leads are one continuous lead following a path leading from said first contact portion onto that 105 portion of said flexible layer which is cut to form said tail.

3. Aflexible switch as claimed in claim 2 further comprising an insert occupying the void formed where said tail is bent downward, said void being

110 the planar zone bordered by th edge of said flexible layer, said two inward cuts, and the junction of said tail and said layer.

4. A flexible switch as claimed in claim 1 wherein said facing surface and second contact portion are

115 part of said underlying frame.

5. A flexible switch as claimed in claim 1 further comprising a second, lower flexible layer beneath said first-mentiond flexible layer, and wherein said facing surface and second contact portion are on

120 said second layer, and wherein said flexible tail emanates from above and lower layer, and is bent downward from said flexible switch inside the edge of said switch and through a slot in said lower layer.

6. A flexible switch as claimed in claim 5 wherein 125 said first layer carries a plurality of contacts on its undersurface.

7. A flexible switch as claimed in claim 6 wherein said first layer is spaced from said lower layer and said lower layer carries a plurality of contacts on its

130 upper surface aligned with said contacts on said first

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layer.

8. A flexible switch as claimed in claim 7 further comprising internal connection means for connecting said contacts on said lower layer to said first

5 layer, and wherein said conductive leads carried by said tail connect said contacts on both said first and lower layers to external circuitry.

9. A flexible switch as claimed in claim 8 wherein said means for spacing comprises a spacer layer and

10 said internal connected means comprises conductive material filling apertures in said spacer layer.

10. A flexible switch substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.

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New claims or amendments to claims filed on 29th April 1982

Superseded claims All New or amended claims:-

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1. A switch member for a flexible switch and for mounting on an underlying substrate or frame,

25 comprising: a flexible plastics layer carrying on one surface a first contact portion and a first conductive lead, said layer being adapted to be secured in spaced relation to a facing surface carrying a second contact portion aligned with said first contact portion

30 so that said first and second contact portions are electrically isolated in the absence of an external compressive force tending to bring aid layer into contact with said facing surface, and a flexible tail secured at its upper end to said flexible layer, bent

35 downward from said layer inward from the edge of said layer, and carrying on one surface a second conductive lead electrically connected to said first conductive lead, the tail being connectable to external circuitry, whereby said first contact portion can

40 be electrically connected to external circuitry by means of the electrical path formed by said first and second leads.

2. A switch member as claimed in claim 1 further comprising means for spacing said flexible layer

45 from said facing surface.

3. A switch member as claimed in claim 2 wherein said means for spacing comprises a spacer layer having an aperture aligned with said first contact portion on said flexible layer.

50 4. Aswitch member as claimed in claim 1,2 or3 wherein said flexible tail is integral with said flexible layer and is defined at its inner end by two inward cuts made from one edge of said layer, and said first and second leads are one continuous lead following

55 a path leading from said first contact portion onto that portion of said flexible layer which is cut to form said tail.

5. Aswitch member as claimed in claim 4further comprising an insert occupying the void formed

60 where said tail is bent downward, said void being the planar zone bordered by the edge of said flexible layer, said two inward cuts, and the junction of said tail and said layer.

6. A flexible switch comprising a switch member

65 as claimed in any one of the preceding claims and said underlying substrate or frame, said facing surface and second contact portion being part of said underlying substrate or frame.

7. A flexible switch comprising a switch member 70 as claimed in claim 2 or 3, or claim 4 or 5 when appendant to claim 2, and further comprising a second, lower flexible layer beneath said first-mentioned flexible layer, wherein said facing surface and second contact portion are on said second layer, 75 and wherein said flexible tail emanates from above said lower layer, and is bent downward from said flexible switch inside the edge of said switch and through a slot in said lower layer.

8. A flexible switch as claimed in claim 7 wherein 80 saidfrist layer carries a plurality of contacts on its undersurface.

9. A flexible switch as claimed in claim 8 wherein said lower layer carries a plurality of contact on its upper surface aligned with said contacts on said first

85 layer.

10. A flexible switch as claimed in claim 9 further comprising internal connection means for connecting said contacts on said lower layer to said first layer, and further comprising a plurality of conduc-

90 tive leads carried by said tail for connecting said contacts on both said first and lower layers to external circuitry.

11. A flexible switch as claimed in claim 10 as dependent upon claim 3 wherein said internal

95 connection means comprises conductive material filling apertures in said spacer layer.

12. A flexible switch substantially as hereinbefore described with reference to, and as shown in the accompanying drawings.

Printed for Her Majesty's Stationery Office, by Croydon Printing Company Limited, Croydon, Surrey, 1982.

Published by The Patent Office, 25 Southampton Buildings, London, WC2A1 AY, from which copies may be obtained.