EP1485929B1 - Control element based on a membrane switch - Google Patents

Abstract

The aim of the invention is to improve a control element which is used to operate an electronically controlled electrical appliance, said control element being suitable for combining with digital circuits and operating on the basis of a membrane switch. To this end, a movable knob (14, 15, 16, 17) comprising elastic contact springs (19) on its lower side is arranged in an opening of a front plate (11), and a membrane switching element (13) comprising a base layer, an upper layer consisting of a deformable material, and an elastic spacer layer is provided. The base layer and the upper layer are provided with strip conductors on their opposing surfaces, said strip conductors comprising contact points at defined points of intersection. The inventive control element is provided with an integrated circuit which continuously scans the electrical connections of all contact points in quick succession and is always operative, even in standby mode, in addition to an electronic, non-volatile memory which is used to store information about the respective switching position of the knob.

Description

The invention relates to a provided with an actuating element electrical switch for operating an electronically controlled electrical device which operates on the basis of a film switch, wherein the actuating element is suitable to be combined with a plurality of control elements in a control panel to form a functional unit and a method for evaluating the triggered by the actuator switching pulses.

Electrical devices with user-accessible functions have controls in the form of switches and regulators that convert actuation into electrical signals. For such control panels, a number of technologies are known.

Circuit boards can be equipped with rotary or sliding potentiometers that convert an operator into a specific electrical resistance, as well as switches that permanently open or close certain circuits depending on the position (changeover switch).

Circuit boards can also be equipped with a number of buttons that close contact briefly when pressed, and with rotary encoders that convert a rotary motion into a repeated key press, the number of which corresponds to the rotational movement.

Instead of a board assembly bare printed conductors of a board can also be covered with a flexible keypad, the key caps have a mechanical pressure point and bring in contact with an electrically conductive surface with the bare conductor tracks in contact.

Two foils, which are provided on the inside with electrical conductors, can be glued so flat over an additional film for spacing (English Spacer) that arise at defined recesses of the spacer foil buttons that close an electrical contact when pressed.

For better operation, membrane keys can also be equipped with mechanical key caps, which transmit pressure to the membrane keys. This construction is also common with typewriter keyboards for computers.

In addition to switches in the sense of buttons, foil panels can also be equipped with force-sensitive resistors (FSR), which convert the force of the contact pressure and possibly also the position (so-called linear potentiometer) into a defined electrical resistance.

From the standpoint of ergonomics boards with potentiometers and switches are the cheapest, because their operation is not only associated with a tactile movement of the elements, but the switching states are also visible by the position of the elements.

The second best in terms of ergonomics cutting boards with push buttons and rotary encoders. Again, the operation corresponds with a noticeable mechanical movement of the elements, but these then jump in a rest position, so that no switching states are recognizable at the position of the elements.

Keypads on printed circuit boards still offer a noticeable pressure point, but because of the softer material it feels much more spongy and inaccurate. A rotation can not be performed by keymats. Membrane keyboards deliver even weaker, barely noticeable feedback when they are actuated, because the triggering path is on the order of only one millimeter. In order for the actuation to be recognizable at all, membrane keys are often equipped with an acoustic signal generator, which acknowledges each key press with a soft "beep". But this is just a stopgap that is actually inferior to mechanically moving controls.

Foil-type force sensors so far offer no tangible feedback, are therefore only very rough and have not yet acquired any significant importance.

All of these control panel techniques can also be combined, but this rarely happens. The technical and economic qualities unfortunately behave inversely to the ergonomic qualities: potentiometers and switches are complex, expensive and prone to drive modern digital electronics. Mechanical buttons and rotary encoders are still ergonomically cheap, but relatively heavy, big and expensive.

Keypads are flatter, lighter and cheaper, but offer only second-rate mechanical feedback. Membrane keys are extremely flat, light and inexpensive, and are well-suited to combining with digital circuitry, but with minimal comfort.

Boards with potentiometers and switches are increasingly being replaced by boards with buttons and rotary encoders.

Membrane keyboards have become established for applications where a particularly flat design is required or where very few data inputs are required by a person (photocopiers, ATMs).

document US-A-6031190 discloses an actuator according to the preamble of claim 1.

The invention aims an actuator provided with an electric switch for operating an electronically controlled electrical device which operates on the basis of a membrane switch, wherein the actuator is suitable to be combined with a plurality of control elements in a control panel to a functional unit with different housing shapes to create , which is flat, light, unbreakable, robust against environmental influences, such as moisture, is wear-free use and can be produced as far as possible in a controlled fully automated manufacturing process on appropriate machines.

The invention is based on the object, a space-saving and cost manufacturable actuator for operating an electronically controlled electrical device that operates on the basis of a membrane switch and that is suitable for direct combination with digital circuits and a variety of different controls provides that a mechanically palpable Provide feedback and their position on the panel can signal different switching states, and to develop a method for evaluating the triggered by the actuator switching pulses. The object is achieved by the features mentioned in the characterizing part of the independent claims.

A front panel fixes controls on a foil with membrane switches so that they remain movable for operation. The underside of the controls is equipped with mechanical activators, which briefly trigger switches in the film switching element when the controls are moved. A matrix circuit, such as keyboards, assigns the activation of switches to the respective function of a control element.

Thus, a control panel appears from the outside as conventional controls and switches, while the electrical properties are identical to those of keyboards. The film circuit offers a particularly robust, inexpensive and flat construction.

All other disclosed in the claims features of the invention serve the solution and the embodiment of the invention.

Fig. 1

Stellelemente als Bestandteile eines Bedienpanels

Fig. 2

einen Folienschalter im Ruhezustand und im aktivierten Zustand,

Fig. 3

eine Ansicht des erfindungsgemäßen Bedienpanels einer Waschmaschine,

Fig. 4

eine Frontplatte des Bedienpanels ohne Stell- elemente,

Fig. 5

Schaltzustände der Stellelemente,

Fig. 6

Leiterbahn-Layout eines Waschmaschinen-Bedien- panels, obere Ebene,

Fig. 7

Leiterbahn-Layout des Waschmaschinen-Bedienpanels, untere Ebene,

Fig. 8

Raststufe eines Stellelements an der Frontplatte im Ruhezustand,

Fig. 9

Raststufe eines Stellelementes an der Frontplatte im Schaltzustand

Fig. 10

Zulässige Bereiche für Folienschalter, abhängig von Raststufen

Fig. 11

Variante des Bedienpanels in Flachausführung

Fig. 12

Flachausführung eines Stellelements im Querschnitt im Ruhezustand,

Fig. 13

Flachausführung eines Stellelements im Querschnitt im aktiven Zustand,

Fig. 14

Zustandsabfolge bei Betätigung eines Stell- elementes in Flachausführung,

The invention will be explained in more detail below using an exemplary embodiment. In the accompanying drawing show:

Fig. 1

Control elements as components of a control panel

Fig. 2

a membrane switch in the idle state and in the activated state,

Fig. 3

a view of the control panel according to the invention a washing machine,

Fig. 4

a front panel of the control panel without actuators,

Fig. 5

Switching states of the control elements,

Fig. 6

Ladder layout of a washing machine control panel, upper level,

Fig. 7

Ladder layout of the washing machine control panel, lower level,

Fig. 8

Latching step of a control element on the front panel at rest,

Fig. 9

Locking step of a control element on the front panel in the switching state

Fig. 10

Permissible ranges for membrane switches, depending on latching levels

Fig. 11

Variant of the operating panel in flat design

Fig. 12

Flat design of an actuator in cross-section at rest,

Fig. 13

Flat design of an actuating element in cross-section in the active state,

Fig. 14

Sequence of states when actuating a control element in flat design,

In Fig. 1 are formed according to the invention control elements as components of a control panel. A front panel 11 is mounted on the chassis 12 of an electronically controlled electrical device and secured with a conventional snap lock or screw.

Between chassis 12 and front panel 11 is a switching film 13, on which rest the control elements. The example is a dial 14, a rotary switch 15, a slide switch 16 and a button 17. The handles 14; 15; 16; 17 of these control elements protrude from the appropriate openings of the front panel 11, so that they are easily accessible for operation and movable according to the intended switching positions.

The handles 14; 15; 16; 17 of the adjusting elements held by protruding edges 18 under the front panel 11. The handles 14; 15; 16; In the simplest case, 17 of the adjusting elements can rest loosely on a switching foil 13 which has no openings, as shown. If necessary, the seat of the handles 14; 15; 16; 17 of the control elements are supported by special formations of the chassis 12, conceivable would be, for example, rotatable axes for the handles 14; 15. Such supporting parts of the chassis 12 may be accessible through openings in the switching film 13. An activator spring 19 moves with the actuation of the respective handle 14; 15; 16; 17 of the adjusting elements and can close certain switches in the switching film 13.

In Fig. 2 the film switch 13 is shown enlarged. The structure of the layers of the film switch corresponds to that of the circuit films 13, which are installed eg in PC keyboards: A base layer 21 is connected to a spacer layer 22, on which the top layer 23 is mounted. The spacer layer 22 is provided at certain contact points with recesses which each form a cavity 24 there.

At this cavity 24, a conductor 25 on the lower base layer 23 can form an electrical contact with a further conductor track 26 on the upper layer 21, if they by an activator 27 and activator spring 19 in Fig. 1 be compressed slightly mechanically. This is a technique similar to the known membrane keyboards, with the difference that the topsheet 23 is not touched directly with the finger, but is triggered by the activator 27.

From the outside see the handles 14; 15; 16; 17 of the controls and feel the same as conventional rotary knobs and switches. As an example, in Fig. 3 a control panel of a washing machine shown, which is constructed according to the invention. As controls, a rotary control 31, a rotary switch with four positions 32, a slide switch with two positions 33 and a button 34 are present, the elements 14, 15, 16 and 17 of Fig. 1 correspond.

The handles 14; 15; 16; 17 of the controls are movably inserted in recesses of the front panel 11. Fig. 4 shows the front panel 11 after Fig. 1 without controls with the four recesses. For example, the round hole 41 serves to receive the button 34 after Fig. 3 and 17 after Fig. 1 , By a protruding edge 18 after Fig. 1 are the handles 14; 15; 16; 17 of the controls each secured against falling out. Slide switch 33 after Fig. 3 and sliders require rectangular, elongated recesses in the front panel; 11 rotary control 14 and rotary selector switch 15 are in round openings.

The switch positions 51; 52 of the handles 14; 15; 16; 17 of the controls, as they are visible on the front panel 11 correspond to certain contact points on the tracks 25, 26 of the film switch 21; 22; 23; 24, 25; 26 after Fig. 2 , However, these contact points on the interconnects 25, 26 are not, as usual with boards, the switch positions assigned directly. That would be the obvious solution, which is not feasible with membrane switches. When the activators 27 after Fig. 2 and 19 after Fig. 1 permanently press a membrane switch, the elastic top layer 23 would after Fig. 2 namely deform the switching film 13.

On the one hand, the activator 27 on the film switch would not conclude a reliable permanent contact, because the spring force of the activator 27 is too weak, nor the contact would be reliably opened, if another switch position would be selected. The upper layer 23 of the switch mechanically activated over a relatively long period of time would, as mentioned, deform, remain practically sticky and have an undefined electrical conductivity. That's why So far, no permanent switch of this type realized on the basis of film switches.

Instead, the invention utilizes the mechanical locking positions of the operating elements in order to produce a short-term mechanical and electrical contact in the intermediate states during the operating procedure. Accordingly, as in the switching position 52 after Fig. 5 recognizable, only three contact points necessary to four switching positions of the rotary switch 32 after Fig. 3 evaluate. Only during the movement of the control element individual contact points are briefly touched and closed the corresponding electrical contacts.

The actuated contacts act electrically like a conventional keyboard with push buttons, while the operation corresponds to the old electromechanical switches. The control element and the control panel according to the invention provided with control elements can be constructed so that it can not be distinguished from a control panel with electromechanical switches during operation.

However, the invention offers new possibilities. Thus, a plurality of switching positions 51 may be arranged in a circle or in a line, which approximately results in the operation of a rotary or sliding potentiometer. This is possible because these multiple switch positions or membrane switches are provided with a minimal mechanical detent, which is not perceived as a function of a switch. With mechanical switches this would be very difficult to achieve because they must be provided with stronger spring forces to ensure a permanent contact even with shocks.

In Fig. 5 , the contact points 51 of the rotary control 31 are after Fig. 3 and 14 to Fig. 1 displayed. For these contact points, eleven contact points suffice to characterize twelve switch positions, wherein these switch positions have soft latching levels such that they can be moved approximately like a conventional potentiometer. In the example of a washing machine temperature setting, twelve distinctions are completely sufficient for the function. In other applications, such as a volume or brightness control, there are about fifteen to sixty levels of switching to create the illusion of stepless adjustment.

The rotary selector switch 15 after Fig. 1 and 32 after Fig. 3 with the contact points 52 works in an analogous manner to the rotary switch 32 with the contact points 51, but has only four positions with a more tactile detent.

For the slide switch 16 after Fig. 1 and 33 after Fig. 3 Only a single contact is needed to signal the transition between the two positions. Since only the transitions are signaled and not the position itself, the position of all elements must be reflected in a non-volatile memory. In addition, this results in the requirement for the control panel according to the invention that, firstly, an initialization with known positions take place once and, second, that the switches must be permanently monitored by the associated electronics. This corresponds to the often existing in today's electronic devices standby mode with running clock and key verification even in the seemingly "off" state.

At the button 17 after Fig. 1 and 34 after Fig. 3 As with all conventional buttons a contact point 54 is necessary to fulfill the function. The button 17 in the control panel has in contrast to the other three controls no special properties that distinguish him from known membrane keys with mechanical activator. The pressure point of such buttons can be formed according to the prior art via a dome (small convex shape) in or on the film or via a spring mechanism on the key edge.

A possible trace layout, the switching positions 51; 52 accordingly, is in Fig. 6 (upper side, view from above) and Fig. 7 (lower side, view from above) shown. At each contact point, a thickening of the conductor track is formed by recesses of the spacer cavity 24 in Fig. 2 forms a foil switch exactly at these contact points. Outside the contact points, the conductor tracks 25; 26 is isolated from the upper layer 23 and the base layer 21 by the spacer layer 22 from each other. The Methods for the Construction of Such Double-Sided Flexible Circuits 25; 26 are basically known, only the layout and the application for moving activators on circuit boards are new.

From the example of 6 and 7 It is clear that only 4 + 4 tracks are needed to control the relatively powerful washing machine panel to realize both a rotary knob, a 4-way selector switch, a slide switch and a button.

The 4 plus 4 tracks are routed out of plug contacts 61 and can be connected to a board equipped with electronic components to interpret the data. These plug contacts 61 form a flexible band, since the switching film 13 after Fig. 1 is thin and flexible and can thus save cables that would otherwise be needed to connect the control panel and motherboard of the device.

This surprisingly small number is achieved in that these 4 + 4 lanes can be scanned in rows and columns, as the known keyboards electronic devices. With conventional switches, this would be impossible because the permanent contact of an element would hinder the combined scanning of all elements in a matrix.

From these statements, it will be seen that the invention of the operation feels like a traditional, mechanically complex actuator or of several combined in a control panel actuator with potentiometers and selector switches, but is electrically identical to a keyboard. Accordingly, existing key matrix scan modules can also be used directly for connection to the article of the invention.

When knob 14 and also in the rotary selector switches 15 and slide switch 16, the handles 14; 15; 16; 17 the actuator does not permanently activate the contacts, as this - as mentioned - could damage (deform) the upper foil layer. When button 17; This is already ensured by the mechanical construction according to the prior art. This is new for controls with several latching positions.

The perceptible during operation detent positions of the handles 14; 15; 16; 17 of the actuator are generated in the invention as in the prior art, characterized in that a rounded spring 84 after Fig. 8 to a wave-shaped counterpart 81 suppressed. The spring 84 and the counterpart 81 are now with each movement of the handles 14; 15; 16; 17 the actuator moves past each other. The spring drives the elevations 82; 85 and recesses of the wavy counterpart 81 from. The projections force the spring to compress slightly against its spring tension. Thus, the actuator comes in rest position always in the wells to stand, as in Fig. 8 shown, because the spring on each survey is not stable.

This technique of click stops is known in numerous variations. Whether the spring 84 is located on the front panel 11 and the counterpart 81 on the front panel 11 or vice versa, plays no role for the locking function. Nor does it matter whether the elevations and depressions move horizontally or vertically between actuators and front panel Fig. 1 are arranged. The important thing is that There are tactile rest steps and the intermediate stages are pushed away, so that they are taken only for a short time.

The invention uses precisely this effect to prevent permanent actuation of the film switches and concomitant damage to the top film layer. As in Fig. 10 shown, where the spring 84 moves straight from the survey into the recess, correspond to the surveys 102 of the counterpart 81 after Fig. 8 with the contact points 51, 52, 53, 54 after Fig. 5 and with the contact points on the tracks 25, 26 after Fig. 2 and the recesses 101 with the areas of the switching film, with the spacer film 22 after Fig. 2 are provided.

Thus, the mechanics of the actuators with their detent steps causes the membrane keys always close the contact only briefly and the entire switching foil works like a keyboard, although the handles 14; 15; 16; 17 of the actuators occupy fixed positions. That is new.

Apart from the protection of the membrane keys against overuse the push button function of the invention causes the contacts of the control elements can be summarized electrically in the form of a matrix, which drastically reduces the number of required control lines.

Exactly calculated, conventional switches with y positions x times y plus require control lines, while the invention requires only twice the square of (x times (y-1)) on control lines. For five switches with eight switch positions each, these are 5 * 8 = 40 or 2 * square root (5 times 7) = approx. 12. This is less than a third of the control cables. At the same time, the bill makes it clear why conventional switches are less practical in digital electronics.

The small number of control lines could be further reduced if at each contact point ( Fig. 5 ) not only a membrane switch, but two or more membrane switches are located. Based on the sequence and size of these contacts and the resulting pulse sequences and amplitude lengths, each contact point and thus each actuation of a control element could be safely identified. This would be the 4x4 matrix of Fig. 6 and Fig. 7 reduce from eight control lines to a mere three. These three control lines would provide "Morse codes" for each position on two channels for each actuation of an element.

However, such a combination of membrane switches would be associated with either less reliability or significantly greater demands on the precision of the film and controls at contact points. Therefore, such a combination solution would only be economically justified if the smallest possible number of control lines are an essential criterion. This could be the case with special applications, such as an extremely large number of switches on a control panel.

As hardware, the control element according to the invention or a control panel consisting of control elements for controlling only one of the known systems for keyboard scanning required. This hardware must be permanently active (even in standby mode) and initialized at initial startup by bringing all controls into a defined state.

This initialization can be semi-automatic by software, provided that all multiple switches with more than two positions are once operated so that at least two adjacent contact points are activated and the double sliding switches are brought into a predetermined position (about each to the right and bottom).

The firmware (operating software of the control panel) constantly manages an electronic image of the switch positions. This is necessary because only when changes are generated impulses. Each time an activated contact point similar to a key code is reported as a position on the query matrix, the corresponding transition is retrieved from a table and the image of the switch position is updated accordingly. In this case, the method can use a uniform program code for any control panels according to the invention, ie store the specific contact point occupancy in a table.

Instead of latching steps, there is another way to prevent permanent stress on the upper part of the film. In Fig. 11 is a variant of the invention to see with actuators in flat design. This variant is suitable for very small devices such as portable audio players, cameras. Here, the small size and low weight plays a special role, and also the control elements of the device during transport should not be accidentally adjusted.

The rotary selector switch in flat design 111 protrudes only minimally (at most 2 to 3 mm) out of the housing front panel and can therefore only be operated with a finger or the thumb. Turning the selector by touching the edge is impossible, because this deliberately flat selected.

Likewise, the flat slide switch 112 is not actuated by lateral displacement of a protruding handle, but by a firm pressure on the top of the handle. The same applies to the slider 113, which, in contrast to the first-mentioned variant of the invention has no latching steps.

All these elements move slightly towards the front panel during operation. In Fig. 12 is a flat control 121 to see, which is protected at the edges via a lock 122 on the front plate 123 against lateral displacement. A soft spring 124 presses against the switching foil 125 away from the contact points and prevents a rattling of the handle of the actuating element in the housing. The activator spring 126 does not touch the switching film 125 in the rest position, but has minimal distance to it.

When operating the flat element now moves the whole element 121 slightly downward, similar to a soft pushbutton. To move such an element laterally, namely, the operator must apply a certain force and ensure a firm grip. If the element were only slightly touched, then the latch 122 prevents lateral displacement in the form of intermeshing teeth.

So if the element is pressed down to move it sideways ( Fig. 13 ), then the activator spring 126 contacts the switching foil 125 at a contact point and thus closes a circuit. The latch 122 is released and allows lateral displacement. If the element is displaced laterally, the activator spring 126 can shoot different contacts according to the position of the element and thus act as a sliding or rotary switch.

The flat variant of the invention differs from the first described variant in that a permanent contact is not prevented by latching steps, but by the soft spring 124 in conjunction with the ability to push down each element slightly.

The sequence of these steps is in Fig. 14 demonstrated. At start 141 no contact is closed. If an actuator is now touched, then a contact 142 closes and remains closed as long as the actuator remains depressed. A lateral displacement or rotation to other contacts 143 and 144 is possible. After releasing 145, the contact is opened again.

The flat design of the invention is slightly more difficult to use than the large version, because the control elements can only be touched and moved on their upper side. This can be an advantage in mobile devices, since very small designs can be realized and because accidental adjustment by the lock is impossible.

In addition, the flat version allows stepless regulators to be used without detents (No. 113 in Fig. 11 ). Instead of a series of membrane switches, a foil-shaped linear potentiometer can be used, for example based on FSR technology (force sensing resistor, force-dependent resistor). Since the activator spring always rests only briefly, overstressing the film is excluded. The continuous measurement of the position by the linear potentiometer ensures a high-resolution control option.

Since the activator spring 126 in contrast to the finger movement has defined properties in terms of Andruckfläche, angle and force, can be used instead of a Linearpotentiometers also a low-cost, simple resistance strip on the slide. As with a conventional potentiometer, the electrical resistance in this variant depends on the position of the handle.

Linear potentiometers and resistor strips are otherwise a known technique. Since they were previously used only without mechanical activators, their ergonomic qualities were very limited. The visible and tactile position of such an actuator allows ease of use, which is comparable to conventional slide potentiometers; However, the invention is flatter, mechanically robust and protected by the film against contamination.

Compared to control panels with potentiometers and multiple switches, the invention provides an equally high ease of use in combination with much more favorable mechanical and electrical properties. The invention is much flatter, lighter and more robust and much cheaper and better adapted to the needs of digital electronics.

Compared to push buttons and rotary encoders, the invention provides a noticeably higher ease of use, because the position of the elements visibly and tangibly expresses the state of the electronic device. In particular, the invention allows to use controls without having to look at a display or pay attention to beeps. This is For example, in the auto industry a major factor in favor of safety. In addition, the invention is somewhat flatter, slightly lighter and significantly cheaper than boards with push buttons and rotary encoders.

Compared to membrane keypads, the operation of the invention is significantly more comfortable. After all, membrane keyboards are somewhat flatter, lighter and less expensive to manufacture than the invention. However, this should compensate for the disadvantage of their operation without noticeable feedback only in a few cases.

Price, weight, size and robustness are about the same compared to membrane keyboards with key caps, while the ease of use of the invention is much better due to the above-mentioned visible and tactile positions.

The switching foil according to the invention with activators can be produced predominantly automatically from a small number of components. It is unbreakable and protected by the assembly behind the front panel from damage. The plug contacts 61 in Fig. 6 ) can additionally save a cable. In addition, such a film is in principle foldable at certain points, whereby a plurality of housing sides of a device can be supplied with a film.

The invention provides the only control panel that communicates the states of the device to the user through the position of its elements and at the same time is suitable for combination with digital electronics. This not only saves Numerous display functions, but allows smaller devices that can be easier to use at the same time.

The invention provides the flattest control panels with mechanically movable control elements and the corresponding comfort.

List of reference signs

11

front panel

12

chassis

13

switching foil

14

knobs

15

Rotary switch

16

slide switches

17

button

18

edge

19

Aktivatorfeder

21

base layer

22

spacer layer

23

top layer

24

cavity

25

conductor path

26

conductor path

27

activator

31

knobs

32

switches rotary

33

slide switches

34

button

41

hole

51

switch position

52

switch position

53

54

switch position

61

plug contact

84

Spring loaded ball

81

counterpart

82

survey

83

84

feather

85

survey

111

Rotary switch

112

slide switches

113

slider

121

actuator

122

lock

123

front panel

124

feather

125

switching foil

126

Aktivatorfeder

141

begin

142

Contact

143

Contact

144

Contact

145

The End

Claims (19)

1. Control element based on a membrane switch for operating an electronically controlled electrical appliance, a knob (14; 15; 16; 17) being arranged to be movable in a front plate (11) in an opening (41) provided therein and to be mechanically actuatable with positions which may be varied visibly and perceptibly, resilient contact springs (19; 27; 126) being attached to the underside of the knob (14; 15; 16; 17), and below the knob (14; 15; 16; 17) a membrane switch element being provided, consisting of a base layer (21), made up of an upper layer (23) consisting of a deformable material and a resilient spacer layer (22), the base layer (21) and the upper layer (23) being covered on the surfaces facing one another with strip conductors (25; 26) in the form of a printed circuit, which are provided at defined points of intersection of the strip conductors (25; 26) with contact points (51; 52; 53; 54) and the spacer layer (22) comprising hollow spaces (24) at these contact points (51; 52; 53; 54), and an integrated circuit being provided which continuously scans the electrical connections of all contact points in quick succession, characterised in that the circuit is always operational, even in standby mode, and an electronic, non-volatile memory is provided, used for storing information about the respective mechanical switching position of the knob (14; 15; 16; 17).
2. Control element according to Claim 1, characterised in that the knob (14; 15; 16; 17) is provided below the edge of the opening (41) in the front plate (11) with a protruding edge (18), preventing the knob (14; 15; 16; 17) from falling out of the front plate (11).
3. Control element according to Claim 1 and 2, characterised in that the knob (14; 15; 16; 17) of the control element comprises a spring (84) with a mating piece (81) connected to the front plate (11) which, when the knob is moved into positions in which the spring engages in rounded indentations of the mating piece (81), produce one or more latching positions.
4. Control element according to Claim 1 to 3, characterised in that the knob (14) is rotatably configured as a control knob with a plurality of latching positions which are barely perceptible for almost stepless control.
5. Control element according to Claim 1 to 3, characterised in that the knob (16) is configured as a slide control with a plurality of barely perceptible latching positions for almost stepless control, for moving on an axis in a longer, rectangular front plate opening.
6. Control element according to Claim 1 to 3, characterised in that the knob (15) is rotatably configured as a rotary switch with a small number of clearly perceptible latching positions for switching between different positions.
7. Control element according to Claim 1 to 3, characterised in that the knob (17) is configured as a sliding switch with a small number of clearly perceptible latching positions for switching between different positions, for moving on an axis in a rectangular front plate opening.
8. Control element according to Claim 1 and 2, characterised in that the knob (14; 15; 16; 17; 121) is arranged to be able to move approximately 0.5 to 4 mm in the direction of a membrane switch (13; 125) located below the knob.
9. Control element according to Claim 1, 2 and 8, characterised in that the knob (16; 112; 113; 121) on the outer edge (18) and the underside of the edges of the openings (41) of the front plate (11; 123) are provided with teeth (122) and the displaceable knob (16; 112; 113; 121) is provided on its underside with a spring (124) pressing the knob (16; 112; 113; 121) in the direction of the front plate by a small force, in the resting state of the control element the teeth (122) of the knob (16; 112; 113; 121) being in an engaged position protecting the knob (16; 112; 113; 121) from inadvertent displacement whilst, when the control element is actuated, the knob (16; 112; 113; 121) is moved approximately 0.5 to 4 mm in the direction of the membrane switch (13; 125) located below the knob, so that the teeth (122) are released and thus, when actuated, the knob of the control element may be laterally displaced freely inside the opening (41).
10. Control element according to Claim 1, 2, 8 and 9, characterised in that the control element is rotatably configured as a planar control knob for almost stepless control.
11. Control element according to Claim 1, 2, 8 and 9, characterised in that the control element is configured as a planar slide control for almost stepless control, for moving on an axis in a longer, rectangular front plate opening.
12. Control element according to Claim 1, 2, 8 and 9, characterised in that the control element is rotatably configured as a planar rotary switch for switching between different positions.
13. Control element according to Claim 1, 2, 8 and 9, characterised in that the control element comprising the knob is configured as a planar sliding switch for switching between different positions, for moving on an axis in a rectangular front plate opening.
14. Control element according to Claim 1, 2, 8 and 9, characterised in that a plurality of control elements are grouped together in a control panel.
15. Control element according to Claim 1 to 14, characterised in that the contact points (51; 52; 53; 54) of the control elements grouped together in a control panel are combined by means of the strip conductors (25; 26) in the form of a keyboard matrix which may be electronically scanned, the number of strip conductors (25; 26) required on the base layer (21) and the upper layer (23) being in each case at least the square root of the number of contact points (51; 52; 53; 54) used.
16. Method for producing switching pulses by the control elements arranged in a control panel according to Claim 1 to 7, 14 and 15, characterised in that the knob (14; 15; 16; 17) of the control elements, when actuated at the sides, performs a corresponding lateral movement and, when released, comes to rest at latching positions determined by indentations of the mating piece (81), when moved halfway between each latching position and as a result of the mechanical pressure of the contact spring (19), a variable electrical connection which is specific to the position being briefly produced in each case between the strip conductors by actuating the membrane switches at the contact points (51; 52; 53; 54), as in a keyboard matrix, whilst after release, all electrical contacts are opened and remain open.
17. Method for producing switching pulses by the control elements arranged in a control panel according to Claim 1, 2, 8 to 15, characterised in that the planar knob of the control element (121), when actuated on the upper face, is moved slightly counter to the force of a spring (124) approximately 0.5 to 4 mm in the direction of the membrane switch (125) and, as a result, when actuated, a contact spring (126), depending on the position of the control element, exerts mechanical pressure at specific contact points (51; 52; 53; 54) in the membrane switch and, as a result, variable electrical connections which are specific to the position are produced in each case between the strip conductors by actuating the membrane switches at these contact points (51; 52; 53; 54), as in a keyboard matrix, whilst after release, the knob is lifted again approximately 0.5 to 4 mm into its resting position and thus, after release, all electrical contacts are opened and remain open.
18. Method for producing analogue switching pulses by the control elements arranged in a control panel according to Claim 1, 2, 8, 15 to 17, characterised in that the planar knob of the control element (121), when actuated on the upper face, is moved slightly counter to the force of a spring (124), approximately 0.5 to 4 mm in the direction of the membrane switch (125) and, as a result, when actuated, a contact spring (126), depending on the position of the control element, exerts mechanical pressure at specific positions of the strip conductor in the upper layer of the membrane switch, which thereupon produces at this point an electrical contact with a strip-shaped electrical resistance on the surface of the lower layer of the membrane switch and said electrical connection consequently has an electrical resistance which is specific to the position of the control element, so that the control element, when actuated, has a variable resistance similar to a conventional potentiometer, depending on the position of the knob, whilst after release, the knob is lifted again approximately 0.5 to 4 mm into its resting position and, after release, all electrical contacts are opened.
19. Method for evaluating switching pulses by the control elements arranged in a control panel according to Claim 1 to 18, characterised in that an integrated switching circuit continuously monitors the electrical connections between the strip conductors for the closure of the contacts, even in the non-operating state of the electronic appliance, as in a keyboard matrix, successively in rapid sequence and approximately 20 to 1000 times per second, the new position of the knob being determined, when the knob is moved, using information about the previous position of the knob of the control element and the most recently closed contact and this current position of the knob being written in a non-volatile memory and kept available there for further processing.

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