DE2337904A1 - ENTER KEY - Google Patents

Description

DATANETICS CORPORATION, incorporated under the laws of the State of California, 18065 Euclid Street, Fountain Valley , California 92708, V.St.A.

Enter key

Input keys are used for the manual input of information or commands in office machines and / or calculating machines used, for example, for typewriters, teleprinters, calculating machines, and data entry points for data processing machines · Several input keys are usually grouped together and form a control panel for entering alphanumeric information and function commands.

Older versions of control panels usually used reed switches or simple, open contacts, that were mechanically connected to a triggering switch. Membrane switches have recently been used in control panels or switchboards have been developed and this type of switch is notable for its low cost and at the same time high operational reliability.

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A membrane switch has two contacts, usually through a dielectric spacer be kept at a distance, the spacer element having an opening aligned with the contacts. At least one of the contacts is carried by an elastic or flexible diaphragm (membrane) that is used for Bringing the contacts together and closing an electrical current path correspondingly dented or deflected will. This type of switch is characterized by a normally very small switching path and can do a lot easy to protect the contacts from the ingress of dust particles, water vapor or corrosive gases be sealed so that these substances can interfere with the proper operation of the switch.

Although switchboard membrane switches directly through that Can be operated by an operator's fingertips, many users prefer a switch with relatively large switching path, whereby the operator can feel a signal when the switch is closed. Membrane switch are therefore combined with operating switches or buttons that are compatible with the short switching path of the switch and still offer the desired long-throw release that the user considers characteristic feels.

The input key according to the invention is a unitary structure with a housing in which a membrane switch is inside is housed, as well as with a movable slider that can accommodate an ordinary keycap. Two lines or connectors extend from the bottom of the housing. The unified formed is for direct mounting on a circuit board designed on which lines are available with which the

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Connections can be brought into electrical contact; Several uniform structures can very easily be combined into groups and in this way form a control panel of any size. Individual units can also Easily removed or replaced if the console format is to be changed, or if a special one Keypad becomes defective and needs to be replaced.

An important feature of the invention is the advantage of operational reliability and low cost that a membrane switch has offers, while at the same time there is an enter button that can be operated conveniently and effortlessly and which can be installed easily and without great effort in a larger control panel.

In short, the input key according to the invention has a housing which preferably consists of two identical housing halves which are connected to one another during assembly of the device. A long one The key slide is movably attached to the housing and can be moved by a linear stroke between a normally raised position and a depressed position. A membrane switch is fixed in the housing and has a flat button that is parallel to the stroke direction of the key slide is oriented.

An elastic switch spring is taken along by the key slide and contacts the button of the switch, when the key slide moves from the raised position to the depressed position after a downward stroke will. An elastic return device, for example in the form of a spiral spring, is between the key slide and the housing and pushes the slider to the normally raised position.

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Preferably, the key slide and the switching element, which, as mentioned, can be, for example, a switching spring can, interconnected by a lost motion connection, which enables the switching element in a limited Scope is movable with respect to the key slide parallel to the key slide stroke. The lost motion device is preferably a channel-shaped recess which is attached to the Side of the key slide is formed and in which the switching element slide Jcann. The lost motion connection results a kind of setting hysteresis that prevents the switch from wobbling or shaking when the user presses the Key slide stops randomly at a position that is close to the first contact.

The switching element is preferably a V-shaped spring, which has a point or a button at the point of its greatest curvature, the point being along a Switching element track rides, which is formed inside the housing. When the key slide makes a downstroke executes, the switching element tip leaves the track and snaps against the button of the switch. A further downward stroke of the key slide drives the switching element tip over the button, so that a rolling contact between the flexible electrodes of the switch is maintained. Connection terminals from the membrane switch are passed through the base of the housing to the outside, taking them can either be soldered to the cable paths below or connected to them without solder, the terminals then being wrapped around integrally molded leaf springs in the housing base.

The invention is described below with reference to the accompanying drawings. Show in detail:

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Fig. 1 shows a cross section through an input key, in which the key slide is raised Position is located;

Fig. 2 is a partial view of the button from Fig.l, wherein the key slide is still in an initial stage of its downward stroke;

3 shows a representation similar to FIG. 2, with the key slide in the fully depressed position Position can be recognized;

FIG. 4 shows a representation similar to FIG. 2, in which the key slide is in an intermediate position its stroke is explained;

Fig. 5 is a front view of a housing half; FIG. 6 shows a section along the line 6-6 from FIG. 5; 7 shows a plan view of a housing half;

8 shows a view from below of two assembled housing halves, the lower half the figure is sectioned along line 8-8 of FIG. 5;

9 is a longitudinal view of the key slide; Fig. 10 is a plan view of the key slide; 11 is a view from below of the key slide; 12 is a side view of the switching element; 13 is a front view of the switching element; 14 is a plan view of a membrane switch; 15 is a side view of the membrane switch;

16 is an exploded view of the membrane switch;

17 is a partial end view of another embodiment of a housing half;

18 shows a view from below of two assembled housing halves according to FIG. 17; and

FIG. 19 is a view taken along line 19-19 of FIG. 17.

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Fig. 1 shows an input key 10 which is equipped with the features of the invention. The single ones Components of the key are fastened to a housing 11, which consists of two identical housing halves 12 which are put together during the manufacture of the key.

As shown in FIGS. 5-8, each housing half 12 is a integrally injection-molded or molded component in the form of an upright body part 13 with a base 14. The body part 13 has outer side surfaces 15, a rear surface 16 and a flat, conplanar front surface 17, which against corresponding surfaces on the fit other half of the housing.

The body part 13 is stepped in the inner center in the height direction, so that a peripheral shoulder results, on which a bracket, not shown, or the like. to define the enter key on a circuit board or a control panel. The rear Surface 16 is also stepped inwards under the shoulder 18, so that a flange 19 (Fig. 6 and 8) results, which can fit into a Verexfungsbügel not shown and which is used in particular when several Input keys combined into groups in a control panel will.

A first guide slot 22 extends from the base 14 to the upper end of the body part 13 of the housing half in the vertical direction. A second partial guide slot 2 3 (dv- becomes a full guide slot when the two housing halves are put together) is formed by an inner wall IA , which extends in the vertical direction from the base 14 to the tip of the body part i3, and jumps from the Forehead-

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surfaces ι7 back. A lower central section of the Inner wall 24 above base 14 is recessed against rear surface 16 and forms the work space 2 5 for a return spring, an upper surface forming a stop 26 for the key slide and extends parallel to the base 14.

Two narrow and deep switch slots 29 extend on opposite sides of the first guide slot 22 in the vertical direction. In addition, enough they almost to the rear surface 16 from the inner edges of the end faces 17 and the outer edges of the Inner wall 24 from. An outwardly inclined bevel 30 extends rearwardly from each end face 17 against the inner wall 24 to below each switch slot 29 so that there is sufficient space for the electrical Connection pieces left when the membrane switch is installed is. A short post 31 extends from the inner wall 24 near the lower edge of each Switch slot 29 to the front.

The narrow end walls of the guide sub-slot 23 are stepped outward slightly below the upper end of the body part 13 and define a switching element track 33 in the vicinity of the upper portion of each switch slot 29. That is, each track 33 extends forward (on 5) from the inner wall 24 and the front edge of each track lies conplanar with the front surfaces 17. A switching element latching point 34 is formed in the vicinity of the lower edge of each switching element track.

A beveled pin 36 extends forward from one of the end faces 17 under the shoulder 18 and a correspondingly beveled socket 37 is formed at a corresponding point in the other end face 17.

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When the two housing halves 12 are joined together to form the housing 11 the pins 36 snap into the sockets 37 and are secured therein by, for example, ultrasonic welding permanently attached. To ensure a secure connection between the two halves, there is a pin at the end 36, an energy-conductive button 38 is formed.

An attachment opening 39 extends centrally in the body part 13 upward from the base 14. As can best be seen from FIGS. 7 and 8, a part of the vertical wall forming the working space 25 is slightly bent, to make space for the mounting hole.

Three feet 40 extend downwardly from the base 14 and their lower surfaces can against the one not shown Make contact with the circuit board or the panel of the control panel. One of the feet has a locking pin 41, which is made up of this extends downwards and with a corresponding opening in the shuttering panel or the mounting plate the console fits so that correct orientation of the enter key is ensured.

Two shallow slots 42 are cut through the base 14 from the front 17 rearward to the inner wall 24 under each switch slot 29. These slots represent openings through which the electrical connections from the membrane switch can extend downwards and can then be connected to the individual components on the circuit board or the mounting plate .

An integrally molded key slide 46 (Figs. 9-11) has a laterally extending upper flange 47. A cross-shaped post 48 extends upwardly from flange 47, the post being shaped to fit into a recess 51 of a common one Keycap 52

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(Fig.l) fits. The main body of the key slide under the flange 47 also has a cruciform cross-section and defines two vertical guide ribs 55 and 56.

An upwardly extending spring recess 57 is in the form of a V-shaped on the underside of the key slide Cutouts are formed on the underside of each guide rib. A laterally extending retention flange 58 for the key slide is integral between the guide ribs 55 and 56 at the lower end of the Key slide formed, namely just above the spring recess 57. As can be seen from Fig. 11, two corners of the retaining flange 58 are concave and mate with two convex surfaces of the inner wall 24 (Fig. 8) of the housing half 12.

Two switching element retention channels 61 (FIGS. 1 and 9) are formed in the opposite longitudinal edges of the guide rib 55. Each end of each retention channel is partially covered by a short longitudinally extending arm 62.

A V-shaped switch element spring 65 (Figures 12-13) is bent from a substantially rectangular strip of spring metal and has a central curvature 66 and two intermediate curves 67 on opposite sides of the central curve. The spring is on opposite Ends bent up at 68. In cross-section, the spring is essentially flat and planar except for of the central portion of the spring at the central bend 66 where it becomes an outwardly facing switch tip or Switch button 70 is bent up.

A membrane switch 75 suitable for use in the enter key 10 is illustrated in FIGS. 14-16. Of the

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Switch 75 is a thin, square laminate of two plastic outer fins 76, which are made by a dielectric spacer 77 are held apart. A metallic conductive strip 78 is attached to the inner surface of each lamella 76 and each strip extends substantially over it the edge of the associated lamella out into a connector 79. The dielectric spacer 77 of lamellar shape has a central opening 80 and a laterally extending insulating tongue 81, which is positioned between the connecting pieces 79.

The conductor strips 78 are provided with a heat-setting Adhesive attached to the outer lamellae 76. The dielectric spacer lamellas and the two outer lamellas are then also attached to each other with a heat-setting adhesive along the edge of the slats is applied, which is indicated by the dotted area 82 in FIG. The two conductor strips will be then in mutual alignment, but kept apart by the thickness of the dielectric spacer lamella 77, built-in. Depressing one of the outer slats 76 perpendicular to the slat surface closes the switch, by placing the associated conductor strip 78 in electrical contact with the other conductor strip through the central opening 80 is brought. The switch 75 and its lateral longitudinal extension can be kept very narrow can be less than half an inch (12.2 mm).

The outer plate 76 are preferably made of a sheet of polyimide plastic, such as of the type such as is available under the name "Kapton". A sheet about 0.002-0.003 inch (0.0508-0.0762 rtm) thick provides the appropriate flexibility to enable appropriate switching function. The dielectric spacer bar 77

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consists preferably of a sheet of polyester plastic (available under the name "Mylar *) from about 0.003 inch (0.0762 mm) thick. The conductor strips 78 are preferably about 0.002 inch copper tapes (0.0 508 mm) thickness, the surfaces of the conductor strips facing each other being nickel-plated and then are gold-plated to ensure good electrical contact.

The housing halves 12 are preferably made of injection-molded or molded polysulfone plastic and the key slide 46 is preferably made of an acetyl resin plastic, known as "Delrin". An ABS plastic is one for the key cap 52 suitable material, while the switching element spring 65 made of spring material such as heat-treated beryllium copper, can exist.

The enter key 10 is assembled with the parts described above in such a way that first the Membrane switch 75 is fully inserted into the final switch slot 29 in a housing half 12. The connection terminals 79 of the switch are bent away from each other below the support post 31, like that 1 and are then passed through the slots 42 in the base 14. The ends of the connectors, which extend under the base can be folded several times (Fig.l) to stiffen them and to To make it suitable for inserting and pushing through a circuit board on which the enter key is attached shall be.

After installing the membrane switch, the key slide 46 is inserted into the housing half 12 in such a way that the guide rib 55 in the guide slot 23 and a

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the guide ribs 56 slides in the guide slot 22. A key slide return spring 85 (preferably a usual spiral spring) is between the top of the base 14 and the bottom of the key slide 46 in the spring recess 57 (Fig.l) arranged.

Then the switching element spring 65 is pressed down slightly and inserted into the spring recess 57 of the key slide. A second housing half 12 is then carefully placed on the protruding parts of the membrane switch, the connecting pieces and the key slide guide ribs are pushed and the two housing halves are through Insertion of the alignment pins 36 into the sockets 37 assembled. The housing halves are then connected to one another, for example, by ultra-sonic welding. The assembly of the unit is completed by pressing the key cap i> ^ over the post 48 of the Key sniffer.

The Darn key can be used with success in numerous applications, among which its use on a circuit board equipped with openings that mate with the positioning pins 41 has particular advantages. Furthermore, the circuit board should have through holes for receiving the terminals 79, which can then be connected to the metal conductor paths on the board. The enter key can be fixed to the circuit board by a bracket resting on the shoulder 18 ; alternatively, it can be fixed by self-locking screws that are passed through the plate and screwed into the mounting holes 39.

In operation, the key slide 46 is normally held in a fully raised position, namely

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due to the restoring force of the retaining spring 85 (Fig.l). The upward movement of the key slide will limited by the retaining flange 58, which against the Abutment 26 rests on the housing halves. In the fully raised position, the button 17 of the switch element spring is located 65 against the switching element track 33 above the latching recess 34.

As can be seen in Figures 1-4, the switch element spring is built-in shorter than the retention channel 61, in which the spring sits. The retention channel is preferably about 0.060 inches (1.524mm) longer than the built-in one Spring, so that the retaining channel thus has a lost motion connection between the spring and the key slide forms. This means that when the spring is fully seated on one end of the channel, the key slide is 0.060 inches can move over what distance it slides next to the switch element spring before the opposite one The end of the spring rests against the other end of the channel and the spring is thereby taken along with the key slide will. The housing and the key slide are made of material whose coefficient of friction is chosen so that the switch element spring lighter on the key slide retention channel slides than on the switching element track or the membrane switch.

The locking recess in the track 33 is intended to ensure that the switch element spring is in the uppermost position located in the channel 61 before the button 70 of the spring falls off the track 33 and the membrane switch contacted. This effect is illustrated in FIG. 2, in which the parts are shown when the key slide has covered two thirds of its entire downward stroke. The button 70 sits in the locking recess 34 and the As a result, the switch element spring is temporarily

Direct downward movement prevented with the key slide until the upper end of the spring against the upper end of the Retention channel 61 (Fig. 2) is applied.

Further downward movement of the key slide leaves the switch element spring 65 down from the lower one Snap off the end of track 33 and the button 70 of the spring is slightly against the outer surface of the membrane switch 75 is pressed across the bottom of the track so that the conductor strips 78 are compressed and the switch closes. The key slide can be depressed further, approximately 0.060 to 0.070 in. (1.524-1.778 mm) until the lower end of the underside of the key slide rests against the surface of the base 14 (Fig. 3) With this continued rare movement of the key slide, the button 70 of the switch element spring 65 rides along the switch surface of the membrane switch 75 and keeps the conductor strips 78 in rolling contact, so that the switch remains closed.

When the user's finger pressure is released, the key slide 46 begins its upward or backward stroke under the action of the restoring force of the return spring 85. The switch remains closed for a substantial portion of the total return stroke, consisting of 0.060 to 0.070 inches (1.524-1.778 mm) Overtravel of the key slide plus about two thirds of the 0.060 inch degree of freedom that the switch element spring has in terms of freedom of movement in the retaining channel 61 . The switch button exits the button at a location about 0.020 inches (0.508 mm) below the bottom of the track, due to the spring shape, so that all backlash displacement is not interrupted until the switch opens on the upstroke.

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Even if the switch element spring tends to touch the key slide during the initial text of his To go along with the upstroke, the button 70 remains on the switch when a spring section over the button against the lower edge of the track 33 (Fig. 4) and the switching ice element spring will remain stationary with respect to the housing until the upstroke of the key slider dies Brought the spring almost to the bottom of her canal. At this point the inner edge of the lower arm 62 the lowermost of the intermediate kinks 67 in the switch element spring, and the spring is thereby slightly depressed against the base of the channel 61, so that that spring force from the return spring 85, which is required to push button 70 up over the lower edge of the track.

When the spring is depressed inward to raise the button above the bottom edge of the track, the button is located Spring against the bottom of the channel 61 and is forced to move the key slide along the track upwards to move with. The upward stroke of the key slide is terminated when the retaining flange 58 against the key slide stop 26 is applied, and the switch is then in the position shown in FIG.

The distance from the rest position of the button 70 (Fig.l) to the bottom of track 33 is about 0.060 inches (1.524 mm), As previously mentioned, the switch element spring also has a 0.060 inch degree of freedom within the Channel 61. A downstroke of 0.120 inches (3.05 mm) will therefore be required to place the switch element spring in the Slide channel 61 through its backlash, and then the spring from the lower end of track 33 against the membrane switch move away and close the switch.

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A gentle, resting surrender of the finger pressure on the button immediately after closing the switch becomes do not cause the switch element spring to move triggers from the membrane switch, because an upward movement of the key slide by about two thirds of the backlash of channel 61 or about 0.040 inches (1.016 mm) before the spring is positive up over the switch is taken along by the key slide. The switching action is therefore characterized by a position hysteresis, which prevents the key slide can be held in a position by the user in which no defined There is a switching contact, the switch rather "trembles" *. · That means that if the Once the switch is closed, a substantial upward movement of the key slide is required, to open the closed contacts · A travel of 0.060 to 0.070 inches is desirable so that the user can perform a full key downstroke that passes through the point of switch closure. One emotional sensation when closing the switch is conveyed by the switch element spring when it namely jumps over the lowest edge of the track and contacts the membrane switch · The size of this that Close indicating feeling can be changed that the restoring force of the switch element spring is set. Both channels can be used when a strong, emotionally pleasing signal is desired 61 switch element springs are used to control the Increase the snap action when the buttons 70 jump over the ends of the tracks.

The return spring 85 is selected so that there is a finger load of approximately 80 grams during the downstroke of the lever results before closing the switch is achieved. The switch element spring is chosen so

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that their closing force, which acts against the membrane switch, is about 20 to 30 g, with 10 g normally being sufficient to close the contacts of this type of switch.

Another factor that increases the reliability of the Enter key is that it extends over a long distance Line rolling contact between the conductor strips 78 as the switch element spring is along the button moved downwards. Even if the conductor strips should erode at their separation point immediately below the track 33 (due to, for example, too high a current or too long use), it will still be a reliable electrical Maintain connection below the separation point when the switch element spring is with the key slide moved downwards during the overrun section of the entire stroke.

The enter key has been described above as a single pole switch; however, a second membrane switch can be inserted into the unit in a second switch slot 29 on the right-hand side (Fig.l). The addition of a second switch element spring to operate the additional switch enables the button to perform two completely independent switching operations with a single enter button. The leads of the second switch are led out through slots 42 in the base of the housing under the switch. 17-19 show a modification of the input key described above. The modification involves the use of leaf spring contacts based on the input key housing, eliminating the need for a solder connection to a printed circuit board or board. Only the lowermost portion of the input key with its housing is illustrated in FIGS. 17-19, the remaining components of the arrangement described above, the

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correspond.

The modified arrangement has a housing 11a, which comprises two identical housing halves 12a, which during the assembly of the rest of the above described Enter key to be connected to each other. As FIG. 17 shows, each housing half 12a has a base 14a, End faces 17a, a first guide slot 22a, an inner wall 24a, a work space 25a and switch slots 29a on. Four deep recesses 90 are formed in the base 14a and define four beveled ones Leaf springs 91 which are arranged in pairs under each switch slot 29a. One down extending button 92 is formed on the free end of each leaf spring 91, and these buttons extend down under the flat underside of the housing half 12a.

The connecting tongues 79 from the membrane switch 75 are guided through the narrow slots on opposite sides of the leaf springs 91 (Fig.17 and 18). The connecting tongues run over buttons 92 and then bend back into the base, as best shown in Figure 17 can be seen.

This modified enter key is pressed against a printed circuit board (not shown) with a clamp so that the connecting tabs 79 are aligned with the conductor paths on the board. When the housing 11a is clamped against the circuit board, the leaf springs 91 bend upwards into the recesses 90 so that the underside of the housing rests snugly against the circuit board. However, the leaf springs exert a substantial force that the connecting tongues 79 in electrical contact with the

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Unfortunately paths on the board moved. Contact is automatically established in this way when the Enter key is installed on the board so that separate solder connections are no longer necessary.

The input key described can be used in a large number of data input processes with economic benefit · The button is reliable and durable and has self-contained membrane switches · Simultaneously has the enter key only has a low profile and is also equipped with overtravel and facilities that make a waning of the human operating force harmless and a sufficient switching feeling when driven over of the switching point. The closing point of the switch is always at the same point during the downward stroke of the key slide and is fixed due to the dimensions of the cast individual parts, so that it can be repeated almost indefinitely with absolute accuracy is. The use of the same housing halves and a modular membrane switch simplifies production and the assembly of the button and still enables the manufacture of a reliable inexpensive one Switch that can be used with benefit in a large number of switch panel applications.

Overall, there was an enter key with a key slide described, which is movably mounted in a housing. The housing also houses at least one flat membrane switch, the button of which is oriented parallel to the direction of movement of the key slide. the Switch element spring is connected to one side of the key slide via a lost motion connection, which causes a kind of hysteresis of the switching process, whereby the spring can be moved using the button and the switch closes when the key slide is depressed.

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Claims (1)

Expectations In particular for switching electrical circuits, characterized in that a key slide 14d,:.:. ; in a housing (11) between a normally raised position (Fig.l) and a depressed position (Fig. 3) attached to be linearly displaceable is; that at least one membrane switch (75) is fixed in the housing, the button parallel to the Direction of linear movement of the key slide is oriented; that a resilient switch element (65) of the key slide can be taken along and moves over the switch surface of the switch when the key slide extends the raised position to the depressed position is proceeded; and that an elastic restoring device (85) for restoring the key slide in its normally raised position is provided. 2. Button according to claim 1, characterized in that the membrane switch is fixed in a sealed manner in the housing is. 3. Button according to claim 1 or 2, characterized in that the switch element (75) from the current-carrying parts of the membrane switch is electrically isolated. 4. Button according to one of the preceding claims, characterized in that the switch element (65) and the Key slide (46,52) are coupled via a lost motion device (61), the switch element in limited The circumference of the key slide is movable parallel to the direction of the linear movement of the key slide, which- 3Q9888 / CU90 BATH ORIGINAL art that the membrane switch is closed at a first key slide position and opened at a second key slide division and the two positions are spaced apart and the first position is closer to the position of the depressed key slide than the second position. 5. Button according to claim 4, characterized in that the lost motion device has a channel (61) which is formed in a side surface of the key slide, wherein the switch element is shorter than the channel and retained in the channel between the housing and the key slide will. 6. Button according to one of the preceding claims, characterized in that the switch element with a spring a switch tip (66,70); that the housing has a switch element track (33) along which the tip rides during part of the key slide movement; that the switch surface of the switch is arranged near one end of the track, such that the switch element tip jumps away from the track towards the button when the key slide is depressed Position is shifted. 7. Button according to one of the preceding claims, characterized in that the track in the vicinity of its end locking depressions having the switch element tip temporarily can accommodate. 8. Key according to any one of the preceding claims, characterized in that the housing has a base (14) with openings of the substantially planar membrane switch are guided out through the connection tabs (79). 309886/0490 9. Button according to one of the preceding claims, characterized in that in the inner surface of the housing a narrow pocket (switch slot 29) is formed in which the essentially flat membrane switch can be used is such that its switch surface is oriented parallel to the stroke of the key slide. 10. Button according to one of the preceding claims, characterized in that the switch element track (33) in near its lower end has a latching recess (34) in which the switch element can be retained, until one end of the channel (61) against the end of the switch element when the key slide is moved downwards is present. 11. Key according to one of the preceding claims, characterized Characterized in that the switch element spring is bent in a V-shape and has a tip (66) at its greatest curvature; aag, the key glue has an arm f62} extending away from the base, which has the lower end there? Forms channel and against which the switch element spring rests on the return stroke of the key slide. Key according to one of the preceding claims, characterized in that the housing consists of two identical housing halves (12) that occurs when assembling the Button to be joined together; that the housing has a second pocket (second switch slot) for receiving a second Has membrane switch, the two membrane switches on opposite sides of the key slide bers are arranged and the key slide has a second channel for receiving a second switch element Operation of the second switch 309886/0490 13. Button according to one of the preceding claims, characterized in that the switch is a membrane switch, whose connecting tongues extend through the housing base, the housing base being spring elements (90,92) has, with which the connecting tongues can be pressed against outer contact pieces. 14. Key according to claim 13, characterized in that the spring elements are integrally formed on the base Leaf springs are. 309886/0490 Blank page