DE3412414A1 - KEY SWITCH WITH CONE SPRING - Google Patents

Description

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Push button switch with conical spring

The invention relates to a key switch for keyboards according to the preamble of claim 1. In particular, it relates the invention relates to pushbutton switches with capacitive switching elements or contact switching elements and conical springs, with which the pushbuttons of the pushbutton switch an upward bias is impressed, and the allow actuation of the pushbutton switches beyond the point at which contact occurs. The invention relates to Furthermore, a capacitive push button switch for keyboard doors, in which springs are used, the capacity of which is im Rest is essentially zero, and which have a certain measurable capacitance when compressed are.

With capacitive keyboards, a change in capacitance between at least two capacitor plates is used, to indicate the actuation of a pushbutton switch. To do this, one of the capacitor plates is mounted in a manner that allows reciprocating movement with respect to an underlying fixed plate, in order to achieve an increased capacity after pressing the switch. It has already been proposed the movable one Design capacitor plate in the form of a conical spring, which the push button switch a right upwards. tete bias impresses and which is compressed to a greater capacity after pressing the pushbutton switch to represent.

Membrane switch

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Membrane push-button switches are made with a stationary contact and a movable contact element arranged above it manufactured, which is mounted on an elastic membrane. If a pushbutton is pressed during operation, it bends the membrane down until the contact element is pressed against the stationary contact. After the push button switch was released, the flexible membrane lifts the contact element from the contact again. There were too springs have already been used to push such pushbutton switches upwards in the rest position.

Has in the ergonomic design of pushbutton switches it has been found desirable to push the pushbutton switch a short distance past the point on which the switch is operated. This excess actuation distance allows the operator a natural actuation of the pushbutton switch with enough pressure to reliably trigger the switch function. aside from that it is advisable to change the tactile feel when pressing the switch after the actual switch function has been triggered, so as to indicate to the operator that the excess service route is beginning. It is also desirable that Clearly indicate the end of the excess operating distance to indicate that the switch has been released should be.

Capacitive keyboards generally have many individual pushbutton switches that are pressed and released to define active or inactive switch states. Every push button switch has a capacitive element, for example a capacitive spring that has a low capacitance when the pushbutton switch is not actuated is and a relatively larger capacity when the push button switch

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switch is printed. The change in capacitance of a push button switch therefore indicates the actuated state of the switch.

When the pushbutton of the pushbutton switch is in the rest position during operation, the spring is fully extended, a minimum capacitance value with respect to an underlying dielectric film and a to represent stationary capacitor plate. When the push button is pressed, the spring is compressed, see above that their windings spread on the dielectric film and the underlying capacitor plate. The compressed windings of the spring are adjacent to the underlying capacitor plate and thus define a larger capacity as long as the push button is pressed. The change in capacitance from the idle state to the pressed state is determined by a circuit that monitors the capacitance then turns on associated devices controlled by the switch.

Such a system, which detects the capacity of the switches, works more reliably and can be constructed more simply when the switch is in its idle state

2.5 has a capacitance that is essentially zero. The improved operation arises because it is simpler and is more reliable, a change from a capacity with the approximate value zero to a larger capacity determined as a change between two capacitance values which are essentially non-zero.

The present invention therefore has the object of specifying a pushbutton switch of the type mentioned above,

whose

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whose mode of operation is designed to be ergonomically favorable.

This object is achieved by the invention characterized in claim 1; Embodiments of the invention are characterized in the subclaims.

In one embodiment of the invention, the Pushbutton switch has a stationary contact and an adjacent movable contact element which is included Pressing a push button is bent to a conductive connection with the stationary contact. Of the Contact is arranged on a substrate, and the movable contact element on an elastic membrane mounted, which is held by a spacer above the stationary contact. The spacer points an opening through which the contact element can be bent to press against the underlying contact to become.

A spring provides an upward bias for the key. The spring has a conical (conical) Base on which exerts an exponentially increasing counterforce when the key is pressed to the underlying one To operate switch contacts. The upper part of the spring is designed and cylindrical delivers a linearly increasing counterforce when the key is pressed after the actual contact point has been reached is depressed a further distance. A stop element prevents the button from moving downwards at the end of this excess range of motion.

In one embodiment of the invention, the Bottom winding of the spring through slots in a switch housing

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tergehäuse held at a certain distance from the underlying elastic membrane. In another Embodiment of the invention, the lowermost turn of the coil is concentric by a spacer Arrangement attached to the opening of the spacer.

In a further embodiment, the push button switch according to the invention includes a conductive solid base plate. The base plate is covered by a dielectric film on which a conductive spring is placed over the base plate is arranged. The lower part of this spring is conical and provides an exponentially increasing one Counterforce when the button is pressed to compress the spring. If the spring is up to one is compressed in a certain position, it defines an actuation capacity and expands when released the key again in order to then define a capacity in the idle state which is smaller than the actuation capacity.

The upper part of the spring is designed in the shape of a cylinder, which is compressed when the button is over the point is pushed out, on which the actual switch function takes place. When squeezing the cylindrical Part of the spring a linearly increasing counterforce is generated when the button is pressed, so that the beginning of the additional movement distance after the actual switch actuation can be clearly felt. The push button Also includes a stop device to prevent the button from being depressed any further can be when the end of this additional movement path is reached.

In

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In another embodiment of the invention, an improved capacitive push button switch for a Keyboard a housing for holding the conductive conical spring described above over an underlying one capacitive plate with a dielectric coating. The bottom winding of the conical spring engages in the slots of this Housing, so that the spring is held in the housing and a certain distance above the one below capacitive plate retains.

A key can slide back and forth in the housing is pushed up by the conical spring. The spring defines a capacitance value with respect to the one below capacitive plate which is essentially zero when the key is in its rest position. When the button is pressed, the spring is compressed, so that a certain between the plate and the spring measurable capacity occurs. The capacity returns to its original value when the button is released from essentially zero.

The spring proposed here with a conical and a cylindrical part enables ergonomic desirable perceptible differentiation of the movement distance of the key up to the triggering of the actual one Switch function and the subsequent additional distance. The end of this extra stretch is also made clearly perceptible by a stop device. The very small capacitance value of the push button switch in its rest position enables a simple and reliable differentiation between the two switch states. The assembly of the pushbutton switch is easy, since the springs are inserted into slots in a housing

can

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can and has an end piece that can be easily soldered leave, for example with a circuit card. As the springs of the push button switch proposed here in a certain way Are arranged spaced above the base plate, the keyboard built therefrom can over a printed circuit board be arranged without serving as a resonance element for the sound of the actuated spring; the The keyboard therefore works very quietly during operation.

Embodiments of the invention will now be based on explained in more detail by drawings; show it:

Fig. 1 shows a cross section through a keyboard

Membrane push-button switches in which cone-shaped Actuating springs installed according to the invention

are;

Fig. 2 is an enlarged view of the membrane contacts

for the push button switch according to FIG. 1; 20th

3 shows a cross section of a keyboard with capacitive key switches in which the conical actuating spring according to the invention is installed;
25th

Fig. 4 shows a cross section through a keyboard

Membrane push buttons and conical actuating springs which are held in slots of a housing;
30th

5 shows a cross section through a keyboard with membrane pushbutton switches and conical actuating springs mounted on a diaphragm;

Fig. 6

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Fig. 6 is a side view of a capacitive key switch according to the invention;

FIG. 7 shows a view of the capacitive pushbutton switch according to FIG. 6 from below with the conical spring removed; FIG.

8 is a view of the capacitive key switch

6 from below with built-in conical spring;
IO

Figure 9 is a cross-section along line 9-9

the switch of Figure 6 when the push button is in the rest position; and

Fig. 10 is a cross-section along the line 9-9 of

Switch in Fig. 6 when the push button is pressed.

The further description contains preferred embodiments of the invention and refers to the appended ones Drawings in which like reference characters refer to like parts.

Fig. 1 shows a cross section through part of a keyboard with a membrane switch. According to this drawing, the keyboard contains a pushbutton switch 1, which is shown in its rest position, and an adjacent pushbutton switch 2, which is shown in the actuated position.
30th

The pushbutton switches 1 and 2 have push buttons 3 which are attached to stamps 5. These stamps are in one Housing 7 mounted so that they can slide back and forth.

Everyone

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Each of the pushbutton switches contains an elastic actuating spring 9, for example made of copper or stainless Steel can be made. The windings of the spring 9 are shaped so that a conical Lower part 11 and a cylindrical upper part 13 results.

Each of the springs is supported on a relatively thin elastic insulating membrane 15, for example consists of a suitable flexible dielectric material, for example a polycarbonate or a polyester such as polyethylene terephthalate. The elastic membrane 15 carries overhead conductive metal plates 17, which are attached to the membrane with conventional photo- lithographic processes can be produced. An insulating substrate carries lower conductive ones Plates 19 facing the plates 17. An insulating spacer 31 with openings 32 carries the membrane 15. The openings 32 are oriented so that each overhead plate 17 is over a corresponding one lower plate 19 lies.

Fig. 2 shows an enlarged cut-open perspective. tivische representation of part of the substrate 21, the conductive plates 17 and 19, the spacer 31 and of the elastic insulating membrane 15. According to FIG. 2, the lower conductive plates 19 each contain one conductive eyelet 23 which is conductively connected to the plate via a metallic interconnection 25. the

Upper plates 17 have corresponding conductive eyelets 27 and conductive connections 29. As already mentioned, the flexible insulating membrane is spaced apart by the insulating spacers 31 held by the underlying substrate 21. The spacer

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Stand holder has openings 32 which are aligned with respect to upper and lower plates 17 and 19.

According to FIG. 1, each of the punches 5 contains an extension 33, which engages in the upper cylindrical part 13 of the spring and holds it so that the upper part the spring is aligned with respect to the pushbutton switch 1,2. A lower coil 16 of the spring rests on the flexible insulating membrane 15 and is supported by the spacer 31. The spring coils over the bottom Windings are dimensioned to engage opening 32 when the button is pressed. The lowermost spring coil 16 is carried by the spacer so that it sits on the membrane 15 above the opening no downward force occurs when the pushbutton switch is in the rest position. One on the membrane The force exerted in the rest position of the switch is undesirable as this leads to a permanent displacement of the membrane material could lead into the opening.

According to Fig. 1, the actuating spring 9 of the push button switch 1 pushes this upwards, so that the underlying Contacts 17 and 19 are separated from each other, and thus represent an open conductor connection.

When the pushbutton switch is pressed, as the example of pushbutton switch 2 shows, the moves 5 punch down against an exponentially increasing counterforce from the conical part 11 of the Spring is caused when it is compressed. The exponentially increasing counterforce mediates that Operator of the push button switch a pleasant feeling of operation and shows him that the button is up to their position is pressed at which the keying process

he follows.

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he follows. When the button is depressed, the spring 9 bends the elastic insulating membrane 15 until the upper conductive one Plate 17 the opposite lower conductive plate 19 is based. The conductive contact of the two opposite Plates indicates that the pushbutton switch has been pressed.

After the plates 17 and 19 have touched, the pushbutton switch in Fig. 1 moves when you continue to press it further down. This movement beyond the actual contact point is ergonomic Desirable for reasons because it allows quick and convenient operation with a minimum of operating errors.

During the movement of the plunger 5 beyond the contact point, the plunger that is compressed in the process is generated upper part 13 of the spring has a linearly increasing counterforce. This linearly increasing counterforce is conveyed to the operator a clearly different feeling of operation, which shows the movement beyond the contact point. The operator therefore first feels an exponentially increasing counterforce in the operating sequence up to the actual one Contact point of the two plates 17 and 19. The subsequent linearly increasing counterforce provides a The feeling of use for movement beyond the contact point is clearly different from this. The shaping the spring 9 therefore produces the desirable feedback when the pushbutton switches in FIGS. 1 and 2 are operated about the feeling of using the buttons.

The extension 33 of each punch 5 can be dimensioned so that they at the end of the movement path that takes place after the actual contact point, on the membrane 15 and the underlying plates 17 and 19

bumps

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triggers in order to prevent a further downward movement of the punch 5 and thus to indicate to the operator that that the key should no longer be pressed. The extension therefore allows the operator to use a To avoid excessive actuation pressure, and thus secures the components of the push button switch a relative longer lifetime. The downward movement of the switch can also be stopped by the push button 3 abuts against the housing 7 or due to the compression and the resulting stiffening the cylindrical spring winding.

Fig. 3 shows a cross section of part of a capacitive keyboard according to the invention. Learns when operating a push button switch 37 by a conductive spring 9 an upward bias, in the manner as it is based of Fig. 1 was explained. The spring 9 lies over a stationary capacitive plate 39, which is covered with a dielectric Film 41 is covered. The spring 9 and the associated capacitive plate 39 therefore constitute a capacitor represent.

When the spring 9 is compressed during actuation, the windings of its conical part 11 are in the Close to the underlying stationary plate 39 and therefore form a larger capacity. The switch is triggered when the spring 9 has been compressed enough to have a capacity characteristic of the switch to surrender.

The conical part 11 of the spring 9 in FIG. 3 provides an exponentially increasing counterforce as well as an increasing one Capacity when the punch 5 is pressed down

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is pressed. After the characteristic for the switch tripping Capacity has been reached, the stamp 5 still moves downwards with further pressure, so that the upper part 13 of the spring provides a linearly increasing counterforce for the after the actual Movement that takes place in contact is characteristic. This counterforce is provided earlier with reference to FIG. 1 explained desirable operating characteristics.

When the downward pressure on the push button switch ceases, the spring 9 guides the switch with an elastic Return force upwards into the position which is shown for the pushbutton switch 37 in FIG. 3. In the In the rest position, the switch capacitance is reduced to a nominal value.

In the figures 1 to 3 for a better understanding of the features of the invention are two adjacent pushbutton switches shown. It goes without saying, however, that the invention does not apply to a specific number of pushbutton switches is limited. The term keyboard used so far includes a device in which one or several push button switches with the features of the invention are included.

Fig. 4 shows a keyboard with membrane switches and a preferred embodiment of a conical breathing spring. According to Fig. 4, a conical spring 45, the shape of a. Hourglass resembles, a cone-shaped lower part and a cylindrical upper part 49. The bottom winding 51 of the spring is in a slot 53 of the housing 7 held so that it maintains a distance from the elastic membrane 15 below. This distance

the

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the lowermost winding is provided to prevent the surface of the membrane 15 from entering the opening 32 of the insulating spacer 31 is pressed when the pushbutton switch is in its rest position, as it is for Switch 55 was shown. According to the earlier explanation, pressure on the diaphragm during the Idle state of the switch lead to the fact that the membrane sinks permanently into the opening 32 and thereby the proper Operation of the switch interferes.

In Fig. 4, a pushbutton switch 57 is pressed so far that it reaches the position for triggering the switch, in which the conductive plates 17 and 19 touch each other. The upper cylindrical windings are in this position 49 not completely compressed while the windings 47 of the lower part entered the opening 32 to bend the membrane downwards and thereby compress the plates.

In Fig. 4, the push button switch 59 is shown at the end of the movement path after the actual switch trigger he follows. After the position shown for the pushbutton switch 57, the switch actuation moves the push button switch further down until the upper cylindrical windings 49 are completely compressed. The end of the switch actuation for the pushbutton switch in FIG. 4 is precisely defined by the fact that a part 61 of the push button in the push button switch 59 abuts the upper surface of the housing 7.

Fig. 5 shows the rest position, the position for the actual switch triggering and the position at the end the movement distance after the switch has been triggered using the example of pushbutton switches 63 or 65 and 67. In the pushbutton switches

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switches according to Fig. 5, the lowermost winding 51 is on the upper surface of the membrane 15. The lowermost winding however, does not push the membrane into opening 32 because it is detached from the underlying insulating spacer 31 is worn. The windings in the conical part 47 of the spring above the lowermost winding 51 are so dimensioned / that engage in the opening 32 and thus cause the switch to trigger, as it is for the pushbutton switch 65 is shown. According to the above explanation, the pushbutton switch moves after the triggering of the actual switch function further down to an end position, which is illustrated using the example of pushbutton switch 67 is shown.

Fig. 6 shows a side view of a capacitive switch according to the invention. According to this figure will a housing 101 of the switch is supported on a printed circuit board 103 which is a conductive capacitive plate 105 and an overlying dielectric film 107. A conductive cone spring 109 shown in phantom is supported within the housing. The bottom coil 109A of the spring engages in slots 111, which are arranged on opposite sides of the housing. The base of the spring is therefore in held a certain distance above the isolated capacitive plate 105.

One end 113 of the coil spring 109 is bent downward and engages in an eyelet 115 lying below, the was formed in the printed circuit board 103 in a known manner. The eyelet is conductive with a (not shown) contact connected to a (also not shown) circuit for measuring the

capacity

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Capacity is connected. The end 113 of the spring is soldered in the loop so that a conductor path between the Circuit for monitoring the capacity and the spring is available. The eyelet 115 is at a distance from the capacitive plate 105 and is isolated from it, so that it is the capacitance relationship between the coil and the plate doesn't bother.

The end 113 of the spring 109 can be easily aligned with the underlying eyelet during the manufacturing process and thus be soldered, since the spring is firmly clamped in the housing 101 and the end 113 is a has a fixed position.

The housing 101 is fastened to the printed circuit board with a screw 117, which is inserted through the printed circuit board The printed circuit board extends and engages in a support 119 of the housing 101. A push button 121 is held by the conical spring 109 provided with an upward bias so that the spring is in the rest position of the push button is expanded. When the push button 121 is pressed, the conical spring 109 underneath is compressed, see above that their turns interlock and approach the capacitive plate, and so a circuit capacitance define between the coil and the plate.

FIG. 7 shows a view of the switch according to FIG. 6 from below, with the conical spring 109 removed. Corresponding As shown in FIG. 2, the guide rails 125 formed in the housing engage in associated slots

a stamp plate 123. The stamp plate 123 reciprocates along the rails 125 within the housing. According to Fig. 6, the stamp plate 123 is also in the housing

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housing through lugs 129 protruding from it, the slide in guide slots 131 of the housing. In operation, the slots 131 define the extent of the upward and downward movement of the stamp plate 123. 5

FIG. 8 shows a view of the switch according to FIG. 6 from below with built-in conical spring 109. According to FIG. 6, it engages the conical spring in slots 111 of the housing and is therefore in the housing at a certain distance above the Plate 105 supported.

Fig. 9 shows a cross section through the switch of Fig. 6 along a line 9-9. According to the representation in 9, the conical spring 109 is fully expanded in order to press the push button 121 into an upper, the rest position. The housing 101 of the capacitive switch is within the cover 133 of the keyboard by elastic wedges supported, which protrude from the housing 101 to the outside. For installation, the housing 101 is inserted into an opening 132 of the Cover 133 of the keyboard pressed, the elastic wedges 135 when passing the housing through the opening inward so that the housing between the circuit board 103 and the cover 133 comes. if the housing has reached its correct position over the printed circuit board 103, the wedges 135 spring up outside and thereby wedge the housing in the opening of the cover 133 of the keyboard.

The push button 121 is detachably connected to a cylindrical stamp part 137 of the stamp plate 123. After the In FIGS. 7 and 9, the cylindrical punch 137 has ribs 139 running in the longitudinal direction with paragraphs 141, in which the reinforced ridges of thorns 145 of the push button 121 engage with

one

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are provided with an inwardly directed bias. The ridges 143 and the associated paragraphs 141 grip into each other and thus form a snap lock between the push button 121 and the stamp 137. The push button 121 and a punch 137 thus move in the housing as a unit. The upper part of the coil spring is cylindrical and abuts the lower parts 147 of the longitudinal ribs 139, so that the push button is pushed up to its rest position. The lower part of the spring 109 is tapered designed and the turns lying at the lower end are isolated over an underlying one Plate 105 and thus create a quiescent capacitance which is essentially zero.

Fig. 10 shows the cross section shown in Fig. 9 when the push button 121 is pressed down and the Conical spring is compressed to produce a predetermined capacitance value. According to the representation in Figure 10 is the windings at the lower end of the tapered portion of the spring 109 against the insulated surface 107 of the capacitive plate below, in order to generate a capacitance that triggers the switch leads and that of a detector circuit (not shown) slightly from the quiescent capacitance can be distinguished, which is essentially zero.

After the windings in the conical part of the spring 109 are pressed against the insulated surface 107, the windings in the upper cylindrical part become the spring is compressed and thus create the feeling of operation that the movement after the actual Identifies the contact point. When the push button 121 is released, the tapered and the

cylindrical

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cylindrical part of the spring 109 until the entire spring as shown in FIG. 9 again in a certain distance above the capacitive plate. The distance between the spring and the plate is defined a capacitance, the value of which is essentially zero and which is easily seen as the idle state of the switch can be interpreted.

The capacitive spring 109 is supported so that its windings are the underlying isolated capacitive Do not touch the plate when the push button 121 is in its rest position. The pen is displayed in the Mounted in a floating manner to facilitate the assembly of the switch. In addition, when the spring is suspended the noise of the movement of the conical spring windings is not transmitted to the printed circuit board underneath and amplified there when the push button is pressed. The capacitive switch according to Figures 9 and is therefore easy to assemble and works more quietly than a switch with windings that hit the printed circuit board during the initial movement of the push button touch.

It should be noted that the invention does not apply to the use of capacitive elements such as springs or such elements as in Fig. 10 contact an isolated capacitive plate. For example A piece of foam with an electrically conductive one can therefore also be used as a movable capacitive element Film can be used. In addition, another spring could be used to follow the push button 121 to give upward bias.

Of the

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The foam, the spring or another movable capacitive element can in the idle state of the switch be held with a certain distance above an underlying capacitive plate and can be in the Near the plate are guided to indicate the actuation of the switch when the switch is actuated Generate capacitance without touching the plate.

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Claims (18)

PATENT CLAIMS Ij key switches for keyboards, characterized by ile the following features: a stamp (5, 137) which, when a pressure is exerted, moves downwards from a rest position into a release position moves, in which the switch function is triggered, and then to a stop position, and the when released, moved up to the rest position; Switching devices (17 j 19) with which the trip The switch function takes place when the ram is in the trigger position reached, and which release the switch when the punch moves to its rest position; a helical spring (9, 109) which, in the rest position of the ram, has an upward return force exercises and with which the switching devices are triggered according to the movement of the ram; wherein the helical spring has a conically configured first part (11), which upon compression a predetermined counterforce generated and actuated the switching devices to trigger the Switch function - 2 - CH 16 P - 2818 Switch function to indicate when the punch reaches the trigger position: and wherein the spring has a second part (13) which, upon movement of the ram from the release position the switch function generates a counterforce up to the stop position. 2. Push button switch according to claim 1, characterized in that the second part of the spring is cylindrical 1Ö and a linearly increasing counterforce during compression exerts, which indicates that a movement is taking place over the trigger position of the switch function. 3. Push button switch according to claim 1 or 2, characterized in that the conical first part (11) the spring is at a distance from the switching devices. 4. Push button switch according to one of claims 1 to 3, characterized in that between the first and the second Part of the spring (45) a connecting piece is provided, the diameter of which is smaller than the smallest diameter of the second part of the spring is. 5. Push button switch according to one of claims 1 to 4, characterized in that a at the lower end of the stamp (5) Mandrel (33) is provided which engages in the second part (13) of the spring and defines the holding position. 6. Push button switch according to one of claims 1 to 5, characterized in that the switch devices have a capacitance Define which corresponds to the degree of compression of the conically configured first part of the spring. 7. Push button switch - 3 - CH 16 P - 2818 7. Push button switch according to one of claims 1 to 5, characterized in that the switching devices have two conductive ones Have switch contacts (17, 19) which are brought into a conductive connection when the cone-shaped first part of the spring up to the trigger position the switch function is pressed, and that the contacts are separated when the conical first part of the spring expands to return the plunger to its rest position.
10 8. Push button switch according to claim 7, characterized in that one of the contacts (17) on an elastic membrane (15) is arranged that spacers (31) are provided which a certain distance between the switch contacts (17, 19) and which have at least one opening (32) that is aligned with the contacts, that the punch bends the elastic membrane during its movement and brings the contacts into contact, and that the elastic membrane is not bent in the rest position of the punch. 9. Push button switch according to claim 8, characterized in that the spring at its lower end from the spacer (31) is supported and is arranged concentrically to the opening (32) with the contacts. 10. Push button switch according to claim 8 or 9, characterized in that the spring at a distance from the elastic Membrane is arranged. 11. Push button switch according to claim 10, characterized in that the lowermost winding of the spring in slots (53) a housing (7) is supported. 12. Push button switch - 4 - CH 16 P - 2818 12. Push button switch according to one of claims 8 to 11, characterized in that the elastic membrane consists of a insulating plastic. 13. Push button switch according to one of claims 8 to 12, characterized in that the cone-shaped the first part of the spring is telescopically compressed during compression and the elastic membrane bends, to bring the switching contacts into contact with one another. 14. Push button switch according to claim 6, characterized in that the spring (109) made of electrically conductive material and is arranged over a stationary conductive plate (105), and that the spring is in the rest position the stamp and the trigger position for the switch function have two different capacitance values Are defined. 15. Push button switch according to claim 14, characterized in that the lowermost winding of the spring (109A) in at least two slots (111) of a housing (101) is supported so that a predetermined distance from the conductive plate (105) is observed so that in the rest position of the ram (137) a capacitance value arises which in the is essentially zero. 16. Push button switch according to claim 15, characterized in that a push button (121) is connected to a stamp (123) is, which has guide lugs (129), and that in the housing (101) guide slots (131) are provided ", in which engage the guide lugs (129). 17. Push button switch - 5 - CH 16 P - 2818 17. Push button switch according to claim 15 or 16, characterized in that that the push button (121) extends in the longitudinal direction spikes (145) with in the transverse direction extending ridges (143), and that a cylindrical Part (139) of the stamp (123) is provided, which has shoulders (141) into which the ridges (143) of the push button. 18. Push button switch according to one of claims 14 to 17, characterized in that the push button switch has a printed circuit (103) with a soldering lug (115) is attached, in which the bent end (113) of the bottom winding of the spring is soldered.