FR2562319A1 - MEMBRANE SWITCH - Google Patents

Abstract

THE INVENTION RELATES TO A DIAPHRAGM SWITCH. THIS SWITCH INCLUDES A LAYER OF A SWITCHING CIRCUIT FORMING PASSIVE MEMBRANE, THAT IS FIXED 16, AN INSULATING SEPARATION OR SPACING LAYER 28 APPLIED TO THIS LAYER 16 AND INCLUDING AT LEAST ONE OPENING 30, AS WELL AS AN LOWER SWITCHING CIRCUIT LAYER FORMING ACTIVE MEMBRANE, THAT IS MOBILE, APPLIED ON THE OTHER SIDE OF THE SPACING LAYER AND INCLUDING AT LEAST ONE TOUCH ELEMENT WITH THE EFFECT OF CLICK 22 EXTENDING UPWARDS. THE LAYER FORMING FIXED MEMBRANE INCLUDES ELECTRIC CONDUCTORS 26 ARRANGED IN A GEOMETRIC DESIGN AND COOPERATING WITH THE COVERS 30 TO DEFINE LOCATIONS OF CIRCUITS AND SWITCHES. THE INVENTION IS USED TO INCREASE RELIABILITY AND EXTEND THE LIFETIME OF KEYPADS.

Description

1 P-DSF-36 / EN

  The present invention relates to keyboards

  with tactile membrane. In particular, the preface

  This invention relates to tactical membrane keypads

  tile exerting a powerful tactile click and

  having an extremely long functional life

  ford. Touch-screen keypads are in addition

  additionally used and accepted in many

  industrial and domestic cations. Thus,

  for example only, this type of keyboard has -

  found utility in outlet outlets -

  at the retail level, airline terminals,

  fast-food restaurant terminals, the terminals

  data, calculators, and any other

  apparatus in which a digital input is required

re.

  A classic keyboard includes a game of

  which can be operated individually to close a pair of contacts of an electrical circuit associated with each of the keys. It is often considered desirable to provide a tactile feedback system, so that when

  keys are pressed by the finger of a person

  By touching the keypad, the keys produce a "click", while a force discontinuity is transmitted to the user's finger, thus indicating that the key has been actuated and that an electrical signal has therefore been transmitted.

  was generated in the circuit associated with this key.

  A membrane type keyboard with tactility as described above consists of a membrane switch assembly which includes a

  reinforcement layer, a layer of

  baked fixed membrane switching applied on this

  reinforcement layer, an insulating separation or spacer layer on the fixed membrane layer, and a switch circuit layer of

  active membrane applied to the other side of the cou-

  spacer. This membrane layer activates

  It is often made up of several tactile click-action elements such as domes that extend upward from the fixed membrane bottom layer. On the two layers forming membranes

  fixed and active, are trained electrical

  (adopting road training techniques)

  cooked, for example, by means of ink

  ductrice) arranged in a desired and cooperating design

  with openings or holes in the

  separation plan to define a group of

  circuits and switches. The ap-

  an appropriate force at a switch location (in this case, a touch dome) on the

  upper surface of the active layer brings this

  active controller and its particular switching component to establish electrical and mechanical contact, via the

  hole of the spacer layer, with the

  sin of circuit formed on the fixed or passive layer of

the membrane.

  Conventional tactile membrane keypads of the prior art pose a problem with respect to the lack of reliability and uniformity in

  functional or operational life (ie

  ie the number of actuations before failure) of the tactile domes. To a large extent, this problem appears to result from degradation or breakage of the conductive ink applied to the active membrane layer. It can be assumed that the constraints and fatigue resulting from

  action or continuous flexing of the tactile dome

  Finally, the degradation of the conductive

  trice (for example, an ink) located on the surface-

  inside the dome. Therefore, after such a break, the touch dome that acts as a contact center

  for classical keyboards, will no longer be able to

  blink an adequate electrical contact. A break in

  conductive materials applied to the surface of

  tact of the active layer has the effect of either

  prevent the keyboard from being

  unnecessary increase in maintenance costs, replacement

  placement and labor for repairs.

  Accordingly, it would be highly desirable and

  to have a tactile membrane keyboard that

  not only retains an information return function

  adequate tactile feedback (click effect), but also

  a longer or more satisfactory operating life. According to the present invention, there is provided a membrane switch comprising a first circuit sheet having at least a first sheet of insulating material on which is formed a first electrically conductive contact element; a second circuit sheet having a second

  sheet of insulating material; at least one tacit

  tile formed in and extending from this second

  sheet, this second sheet of insulating material defining a flat surface at the base of this touch element; a second electrically conductive contact element formed on this flat surface around

  the periphery of the touch element; an element of space

  planned between the first and second sheets of

  circuits, this spacing element comprising several

  openings, so that the touch element can be actuated by applying a

  force, to move the second contact element con-

  conductor of electricity through one of these

  res and in electrical contact with the first element

contact contact.

  As in prior art keyboards, the fixed membrane bottom layer has an electrically conductive contact area (eg, traces of copper or ink

  conductor) who are placed there in a drawing and cooperating

  with holes in the layer of sepa-

  ration to define a unique group of circuit and switch locations. Unlike the systems of the prior art, this

  invention provides for a further improvement which resides

  of in the location and structure of the surface

  contact of the active layer. This new surface

  this contact which can be made of an ink con-

  ductor or other conductive material, is

  to the active layer, around the periphery of the base of a dome defined on the flat surface of the layer

  active, preferably in the form of an annular crown.

  lar. Therefore, since no part of the upper annular contact surface adheres to the flexible surface of the dome as is the case in the

  prior art, the conductive material constitutes

  killing the contact surface will not be subject to

  or the constraints discussed above and will not suffer the resulting breakage when the dome is repeatedly operated for a long time. As a result, the touch membrane keyboard of the present invention has a significantly improved and prolonged operating life, which in turn provides better performance and reliability, while allowing manufacturers and keyboard buyers to realize more

  big savings. It should be noted that the present

  The invention requires less conductive ink than in the prior art and therefore

reduced manufacturing.

  In order to achieve this modified annular contact structure along the periphery of the domes, the diameter of the openings in the separating or spacing layer is increased compared to conventional keyboards. In the same way, the contact area of the fixed lower layer is enlarged correspondingly to be equal to that of the

  openings. In this way, there is sufficient space

  for the achievement of the annual contact crowns

  on the active layer so that, when the dome is actuated, the annular ring will define an open path to make contact with the

  electrical conductors formed on the fixed layer.

  The particular structural arrangement of the present invention

  vention makes it possible to establish an electrical contact before the dome has arrived at the end of the race, this end of

  dome stroke and click or return

  tactile training informing the operator that the implementation

switch action took place.

  Various modifications and forms of

  of the tactile membrane keypad of this

  The invention includes segmenting one or both of the switching contact surfaces to allow multiple contacts in parallel on the

  upper and lower circuits. Similarly, the

  invention is also applicable to a multitu-

  of configurations of domes, in particular, but without

  a limitation, oval domes and domes

  I'm crawling. Finally, the absence of conductive material along the inner surface of the dome effect of

  trigger allows the incorporation of an indi-

  rect, that is to say a lighting from below the keys.

  The aforementioned advantages of the present invention

  as well as others will appear in and will be

  taken from the person skilled in the art on reading the description

  detailed description given below with reference to the

  annexed. Referring now to these drawings in which like elements are designated by the

  same reference figures in the different

res:

  FIG. 1 is a partial view in elevation

  and in cross section of the upper portion of an individual touch membrane element according to the present invention;

  FIG. 2 is a plan view of the tactical dome

  tile according to the present invention illustrated in Figure 1;

  FIG. 2A is a view similar to FIG.

  re 2, but illustrating a modified structure; and Fig. 3 is an elevational and cross-sectional view illustrating a keyboard assembly.

  with a tactile membrane according to the present invention.

  Referring to these drawings, we represent

  part of a keyboard according to the present invention.

  In these drawings, we represent one or two key locations, but it will be understood that a full keyboard

  comprises a monolithic diaphragm circuit structure

  consisting of any number of individual tactile keys or domes, the specific number being determined by the conditions to which

  answer the particular application and keyboard

Sages.

  Figure 3 illustrates a two-part

  of a circuit assembly or keyboard to

  Monolithic brane 10. The switching structure

  or the monolithic membrane keyboard comprises a

  stiffening sheet or reinforcing sheet

  12 which may be a sheet of metal or plastic having a rigidity and flatness

  equivalent to those of a sheet of aluminum alloy

  6061 with a thickness of about 0.5 mm. The sheet

  the reinforcement 12 serves to support and maintain, in a plane state, a layer circuit sheet

  fixed or passive switching assembly to all

  which consists of a leaf or cou-

  lower insulating layer 14, preferably in one pel-

  Polyester "Mylar", as well as a drawing

  lower circuit 16 formed on the latter.

  This circuit sheet or this switching layer

  fixed or passive key is bonded by means of an adhesive to the reinforcing sheet

  insulation 14 may have any desired thickness

  preferably a thickness of between 0.05 mm and 0.18 mm, while the conductive pattern

  can be trained by any technique

  naked embodiment of printed circuits, for example,

  by printing with a conductive ink, -im-

  pressure or bite of a conductive metallic foil

  this, etc. Preferably, the conductive pattern 16 should be fairly thin (ie a thickness of the order of 0.01 to 0.05 mm, preferably a thickness of about

0.025 mm).

  A circuit board or a circuit

  mobile or active switching

  above the lower circuit design 16. This

  mobile or active switching

  insulating upper 20, for example, "Mylar".

  The upper insulating layer 20 comprises a set of ele-

  tactile or snap-action projections 22 having the shape of a curved dome 24 of configuration

  frustoconical with a flat top surface. AIN-

  if it was mentioned previously, the present invention

  It is also applicable to touch domes with other shapes, including but not

  limitation, hemispherical domes, oval domes

  the, ramp-shaped domes, etc. Isolation layer

  lante 20 of the active switching layer comprises

  a contact surface or a circuit conductor im-

  awarded 26 having the configuration of an annular crown

  and formed by any known technique for producing printed circuits (for example, using a conductive ink). This surface of

  annular contact ring 26 extends beyond

  around the outer periphery of the base of the dome 24 and is bonded by means of an adhesive or otherwise

  on the flat surface of the active switching layer.

  An insulating layer of separation or space

  28 having a plurality of openings 30 may be secured in place by means of an adhesive or otherwise on the one hand to the fixed layer on which the lower circuit pattern 16 is located and on the other hand at the upper insulating layer 20. The total thickness of the spacer layer 28 may be used to adjust the distance between the conductor

  upper 26 and the lower circuit design 16.

  The opening 30 in the spacer layer 28 should be larger than the overall diameter or dimensions of the conductive pattern 26, so that the dome 24 can jump across it in a click-and-divide manner. drawing 26 in contact with circuit pattern 16 to make contact

  between the switching components.

  The curved domes with flat top 24 and the con

  ring-shaped ring-shaped conductors

  correspondingly related links 26 are arranged

  lower circuit design 16, so that the domes 24 spring upward away from

  this last. This provision defines a group of employees

  switch placements or single circuits.

  When a force of sufficient amplitude is applied

  At a dome 24, the projection 22 is moved downwardly as a click through the opening 30.

  formed in the spacer layer 28, thereby displacing

  if the annular contact surface 26 in electrical contact

  mechanical and mechanical with lower circuit design

  16. This electrical contact acts to close a switch

  and transmit an electrical signal. We understand

  that with the new design of the present invention, electrical contact is established between the respective contact surfaces 16 and 26 before the

  dome has arrived at the end of the race. The return of information

  However, the necessary tactile feedback is ensured as the dome will continue to travel with a click effect, thus indicating to the operator

  keyboard, that a contact has been established.

  As previously mentioned, a major problem encountered in conventional membrane keyboards of the prior art has been the

  lack of reliability of keyboards and the impossibility

  to predict its functional life. This pro-

  bleme is solved by the membrane keyboard of the pre-

  this invention. Whereas in the prior art

  upper surface of the conductive contact

  was applied by means of an adhesive to the surface

  of a dome according to the present invention, the

  upper conductive surface 26 is formed, preferably

  in the form of an annular ring, on the flattened surfaces of the insulating layer 20 (and not

  the flexible zone located inside the dome).

  The advantage of the ring-shaped conductive surface 26

  side in a clear reduction of constraints and the

  fatigue, as well as in a lower flexion of the over-

  In other words, since no part of the annular contact surface 26 will adhere to any surface of the dome 24, the surface 26 will not experience bending and repeated stresses of the interior surface of the dome. 24 during the activation of the keys. Reduced fatigue associated with

  The present invention therefore confers a longer

  life with the active contact element.

  Another difference between the present invention

  tion and the prior art lies in the dimensions

  comparisons of the openings of the

  28 and the lower contact surface 16 formed on the passive layer 14. In order to achieve a membrane keyboard according to the present invention, the relative dimensions of the constituent parts must

  be calculated in such a way that the surface of

  upper annular tact 26 can freely establish a mechanical and electrical contact with the surface of

  lower contact 16, while at the same time

  24 domes, to retain the characteristic of ef-

  touch-sensitive click. As a result, the

  30 openings in the space layer

  28 is increased compared to the opening of

  predicted in the spacing layer of the technical

  than earlier. In the same way, the diameter of the lower contact surface 16 formed on the layer

  lower insulation 14 is increased correspondingly

  dante. Therefore, the flat annular zone defined on the inner surface of the insulating layer 20 capable

  to support the annular contact surface 26 is ex-

  placed on the lower contact surface 16, although

  that contact can be established between them.

  In another embodiment of the present invention,

  In this invention, the contact surfaces 16 and 26 can

  Segmented, so as to allow multiple contacts in parallel on the two upper and lower layers forming membranes. The segmented upper contact surface is illustrated in FIG. 2A, in which the dome or the touch element 22 is surrounded by curved contact segments 26a and 26b. The surface

  16 could be segmented in the same way.

  re. This segmented configuration is very difficult,

  impossible to achieve with conventional keyboards

  touch-screen membranes in which the upper contact surface is attached to the inner surface of the dome. The touch membrane keyboard of this

  invention is extremely economical both for the

  than for the manufacturer. Improved operating life and increased reliability translates into significantly higher maintenance and replacement costs

  reduced. In the same way, from the point of view of the manufacturer

  The annular ring of conductive ink, paint or other conductive surface requires less material than in the prior art. Similarly, if

  the conductive contact surface 16 formed on the cover

  passive lower arm is shaped into an

  of the same configuration as the annular crown

  layer 26 formed on the active layer (instead of an integral contact pad), it will then be necessary to

  still less conductive ink or similar material

  ble, thereby significantly reducing costs.

  Another advantage of the present invention is

  side in the possibility of illuminating the

  touching the keys from below them.

In the prior art, the presence of conductive ink or the like under the dome prevented

  a light source to pass through. Being given

  that in the present invention, the conductive ink

  it is applied only around the periphery of each key, it is not able to block the transmission of light through the key and, by

  therefore, indirect lighting can be easily

if desired.

Claims (9)

claims   A membrane switch comprising: a first circuit sheet, said first circuit sheet having at least a first sheet (14) of insulating material on which is formed a first electrically conductive contact element (16),   a second circuit sheet having a se-   conde sheet (20) of insulating material, at least one touch element (22) formed in and extending from this second sheet (20),   this second sheet (20) of insulating material de-   finishing a flat surface at the base of the tac-   tile (22), a second electrically conductive contact element (26) formed on this flat surface around the periphery of the touch element (22),   a spacing element (28) provided between the first and second   first and second circuit boards,   this spacer element (28) having a plurality of   openings (30), so that the element   (22) can be operated by means of   a force, for moving the second electrically conductive contact element (26) through an aperture (30) and in electrical contact with the first   conductive contact element (16).   2. Membrane switch according to the claim   1, characterized in that the tactile element   (22) is a click dome (24).   3. Membrane switch according to the claim   2, characterized in that the dome   snap (24) a.a curved shape with a flat top.   4. Membrane switch according to any one   one of claims 1 to 3, characterized in that   that the second conductive contact element (26) has an annular shape.   5. Membrane switch according to the claim   4, characterized in that the first element   conductive contact member (16) has an annular shape cor-   corresponding to that of the second contact driver (26).   6. Membrane switch according to any one   conque of claims 1 to 5, characterized in that   the first and second conductive contact elements   consist of a conductive ink.   7. Membrane switch according to any one   conque of claims 1 to 6, characterized in that   the first and second conductive contact elements   segmented to allow for multiple contacts   in parallel on the higher circuit higher and lower.   8. Membrane switch according to any one   Claim 1 to 7, comprising:   a reinforcing sheet (12) attached to the sheet   the lower circuit by supporting it.   9. Membrane switch according to any one   conque of claims 1 to 8, characterized in that   the touch element (22) is free of conductive material   electricity within its periphery, so that it is suitable for indirect.