DE8714573U1 - Short-stroke pushbutton - Google Patents

Description

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i Alfons Motsch
5276 Wiehl

Description 1 b u .n g

The present invention relates to a short-stroke pushbutton in which a disk-shaped pushbutton element acts on an elastic contact element which, over a short stroke, indirectly or directly contacts a counter-contact element.

can be pressed in with a spring, thereby connecting the poles of a separate circuit.

Such short-stroke pushbuttons are known in principle and have been brought onto the market under various names, particularly in this decade. The basic principle is described in DE-GMS 79 02 331 "Flat membrane switch" and DE-OS 31 33 779 "Membrane key switch": contact fields and connecting conductors are pressed onto an elastic membrane and an inelastic counterplate; the membrane and counterplate are spatially separated from one another by a spacer ring and are each connected to one pole of an electric circuit. If the elastic membrane is pressed against the counterplate, a switch is made; if the pressure is removed, the elastic membrane returns to its original position.

This seemingly simple technology causes a number of problems in practice, especially for those short-stroke pressure switches that are exposed to wind and weather outdoors

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15

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25

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The air space between the touch foil and the counter-switching element must be hermetically sealed so that moisture and dust cannot penetrate; the air pressure in this space is accordingly temperature-dependent. Since outdoor switching devices are generally required to function in the temperature range - 30 ⁰ C to + 80 ⁰ C, the user is required to apply very different key pressures at different temperatures in order to reliably switch the device. However, it is of considerable importance that the required switching pressure is as constant as possible, because with such switches in particular the user only knows whether the switch has been switched when he sees the result. The finger strength of children and old people is also naturally weaker, so that only a low switching pressure is sufficient when switching public objects such as train and bus doors, traffic lights, elevators, etc. For example, if a child has tried several times in vain to switch on a pedestrian traffic light, he will cross the street without the light turning green - with all the usual consequences.

The inventor of OS 29 038 98 wants to eliminate this disadvantage by giving his key switch a switching stroke that is greater than the thickness of the insulating intermediate ring between the key foil and the counter plate. For this purpose, he provides the counter plate with

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a central recess, but this significantly limits the area on which the user can effectively exert a switching pressure* This shortcoming is very significant, because it is particularly important for public objects to be switched that the user does not have to look and think for long before switching, quite apart from the fact that children and old people do not always reach for the &Oacgr; 10 switch accurately. In addition, a larger switching stroke inevitably means a larger air space with larger switching pressure differences due to temperature.

The surface membrane switches described in principle at the beginning are not always reliable, e.g. if contaminants such as dust particles etc. get between the switching surfaces. In order to achieve reliable switching, DE-OS 29 29 574 "push button switch arrangement" provides metal disks as switching poles , which are separated by a spacer foil with recesses. The upper (outer) metal foil is covered with an elastic insulating touch foil. If you press on this touch foil, the upper metal foil, which has a surface structure, is pressed against the lower metal foil in the area of the recesses and

This circuit is also only safe if the user ’s finger pressure is in or at least close to a recess.

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The invention does not change the fact that the required finger pressure strength is temperature-dependent, because the air space between the foils must be hermetically sealed for the reasons already mentioned at the beginning.

A similar idea underlies the DE-GMS 81 32 "flat switch keyboard", with the same disadvantages, but also with the alleged advantage that the folding of the concave dome on the upper key ^foil is accompanied by a cracking noise, which is intended to inform the user that the switch has been switched. However, the ^dome can very well crack without switching at all. The inventor also believes that the arrangement of a number of small switch compartments provides security against the ingress of small foreign bodies such as dust, grains, etc. This view may be very bold.

DE-PS 29 02 769 describes a pressure

. button switch, which consists of a bent insulating foil, on whose opposite

the poles for switching the circuit are arranged on the inner surfaces, which are turned and separated by intermediate layers. The side of the entire foil facing upwards (outwards) is designed with a flat dome, under which the upper pole is attached. In order to operate the switch, the dome must be pressed in, i.e. moved from a convex position to a concave one. This requires relatively

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a lot of finger pressure has a tiring effect on the foil material and does not change the fact that in the relatively large air space between the foil wings, temperature differences cause considerable pressure differences.

The pre-publication points to a fact that has not been considered by any other inventor so far: even in a closed air space, metallic pole surfaces corrode over time and lose their conductivity. The inventor of DE-PS 29 02 769 believes that he has overcome this disadvantage by causing the pole surfaces to perform a lateral grinding movement against one another due to the bending movement of the dome. Whether this leads to self-cleaning, as the inventor believes, is irrelevant; in any case, an important fact has been pointed out.

' The newest and most advanced

The previous publication is DE-OS 33 38 810 "Key pressure initiator ¹¹ . It is also based on the teaching of the DE-GMS 79 02 331 (") cited at the beginning and has set itself the task of developing a

To create a pushbutton switch that has a short switching path, i.e. a high sensitivity of the switching element, and to design a correspondingly low-vibration embedding of the switch. This has been achieved by means of a special embedding of the switching elements, but has the disadvantage that the touch surface, which is located between a clamping ring attached to the housing and the housing

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itself is clamped, is exposed to lateral displacement impulses due to the elastic cushioning of the housing and corresponding leaks at the edges. In addition, the space between the printing film and the Gecren film is

hermetically sealed air space; the finger pressure required by the user for switching is therefore highly dependent on temperature. Finally, the touch pressure initiator has a light-emitting diode (^) 10 on the transparent touch surface

which signals that the switching device is ready for operation; however, this was already known at that time through DE-OS 31 33 779.

Despite the well thought-out design, particularly in terms of manufacturing technology, the push-button initiator does not represent a satisfactory version of a short-stroke push button. Like all other inventions cited here , it is only a fragmentary improvement of the DE-GWS 79 02 331, far from an optimal

Short-stroke pushbutton. To do this,

s~\ all claims listed below

be asked:

a) the switching pressure required for reliable switching must be low (children)

and be temperature independent,

b) the switching stroke must be short, but not bridgeable by fluttering, vibrations on the holding object, etc.

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c) the switching must also be reliable if the user presses the button eccentrically on the elastic touch disk (hereinafter referred to as "touch element"),

5 d) the switching stroke must be adjustable so that all relevant switching requirements can be met with a single design of the short-stroke pushbutton,

e) the air space between the pushbutton element and the counter-contact element should be hermetically sealed.

O be enclosed, but with a pressure

| be provided with a balancing device that

k Air pressure in the airspace. all in question

i temperatures (- 3o° to + 80 ⁰ C)

' 15 equals,

f) the button element must be attached to the button housing

ij must be arranged so that neither heavy vibrations

I nor violence (breaking tools of course

I loan excluded) the way into the counter

¹ 20 inner could open,

!· g) the key element shall be separated from the contact and

'k Counter contact elements must be galvanically separated,

h) next to behind the transparent key element

arranged LEDs to signal 25 that the device is ready for operation, a different colored LED should be arranged to signal that the device is not ready for operation,

i) and finally, the contact-closing parts must not be able to freeze even at very low temperatures 30 (a major problem with all switches known to date).

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The present invention has for its _object to provide a short-circuit proof pushbutton which , with a comparatively low technical outlay , eliminates the described deficiencies of the known pushbutton switches and fulfils all the basic requirements set out here.

This inventive task is solved with the technical means described in the claims:

According to claim 1, a central reinforcement is formed on the contact side of the elastic pushbutton element , to which a flexible elastic contact disk made of conductive material (e.g. metal) is attached coaxially, which maintains a distance from the plane of the pushbutton element radially outwards from the central reinforcement. This construction ensures the galvanic separation of the pushbutton element from the current-carrying parts.

The contact disk is located at a short distance above a plurality of pole pairs v of the circuit to be closed. The pole pairs

form a plane with their pole ends that runs parallel to the plane of the contact disk in the neutral position of the probe element.

When an eccentric button is pressed , at least one pair of poles is always touched by the contact disc and the circuit is closed.

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According to claim 2, a fastening pin can be formed on the central reinforcement, parallel to the axis, onto which the ring-shaped, flexible contact disk is placed and secured by means of a subsequently placed,

The fastening sleeve is clamped onto the probe element using a pin.

Claims 3, 4 and 5 describe a preferred embodiment of the invention in which

w 10 the pole ends of the pole pairs designed as contact conductors facing the flexible contact disk are arranged in a circle around the vertical axis of the contact disk in such a way that positive poles follow negative poles in a clockwise direction, one after the other, whereby the contact conductors tapered at the pole ends are arranged in longitudinal grooves aligned with the cylinder surface lines of a cylindrical contact carrier that can be inserted into the cylindrical recess of the key housing or into a molded ring inserted into it. The

/ pressing the elastic button element and thus

The associated pressing down of the contact disk leads to a number of point contacts, which close reliably even in the presence of foreign bodies and also cause self-cleaning of the contact elements when the contact disk is inclined relative to the pole end plane. The adjustment of the switching distance, i.e. the switching stroke, is carried out by

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a longitudinal axial displacement of the contact carrier in the mold ring, whereby both the contact carrier and the mold ring can be provided with a thread (claims 5 and 6).

In a further preferred embodiment, the elastic sensing element is in one piece with clwiti ¹ P^s^av-nahäuaa ^rt sfsz'ti ^rr t ^ claim "7 ^ and between the elastic sensing element s on the one hand and the counter-contact member serving as

the contact carrier on the other hand, the otherwise hermetically sealed air space is connected to a highly elastic pressure compensation hose which projects into a cavity in the button housing and whose end facing away from the air space is closed (claim 8).

This measure means that access to the tactile area and air space can only be achieved by breaking the force; vibrations of any kind are not capable of doing this. On the other hand, the air pressure between the tactile element and the contact

. slow at all possible temperatures O (- 30° C to + 80° C) constant.

Finally, claim 9 describes the arrangement of operational readiness signals in that behind .25 the transparent button element, in addition to light-emitting diodes as signals of operational readiness, a differently colored light-emitting diode as a signal of non-operational readiness can also be arranged.

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In summary, it is clear that an application of the technical teachings described in claims 1 to 9 takes into account all requirements a) to h) to be met for the creation of an optimally effective short-stroke button. The multi-point circuit,

which is caused by the common contact disk touching a number of pole end tips, is of particular importance for the precision of the circuit and for the switching reliability.

The design of the contact-closing parts (contact disk-contact conductor) and of the contact carrier (counter-contacting element) described in claims 1, 4 and 5, in conjunction with the pressure equalization in the hermetically sealed air space described in claim 8, ensures that the contact-closing parts cannot freeze solid.

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Example

An example of implementation is shown and explained below using drawings. They show:

Figure 1 shows a short-stroke pushbutton according to the invention in a cross section (pages

opinion) ,

Figure 2 shows a contact carrier with contact conductors ^ and current strands, schematically and from

viewed from below (towards the touch-IQ element),

Figure 3 shows section A- A of Figure 1

Figure 4 is a schematic representation of the switching element of the short-stroke pushbutton according to the invention in its neutral _position (i.e. without the influence of a key pressure), on an enlarged scale compared to Figure 1,

Figure 5 the switching element Figure 4 during the ^> exercise of a centrally acting key

pressure; all pole ends are paired

connected with each other

and

Figure 6 the switching element Figure 4 under the influence of an eccentrically applied ! key pressure; here at least two j pole ends located next to each other are connected to each other. _m

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The pushbutton element 1 of the short-stroke pushbutton is cast in one piece with the pushbutton housing, which is made of a suitable insulating synthetic resin, e.g. polycarbonate. This ensures that the control room is completely sealed against air and moisture, as well as a previously unknown level of stability for the pushbutton element 1. The pushbutton element 1 can only be separated or an opening leading into the interior of the pushbutton can only be made using breaking or drilling tools, but not by even the most severe shocks.

The button housing 2 is attached to the wall 4 of the push button carrier via a rubber sealing ring 3.

A reinforcement 5 with a pin 6 is formed on the central part of the probe element 1. A flexible contact disk 7 made of beryllium bronze (highly conductive and spring-elastic) is placed on this pin 6 and clamped to the reinforcement 5 by means of a truncated cone-shaped fastening sleeve 8 made of synthetic resin; the fastening sleeve 8 is anchored to the pin 6 with an adhesive 9. The contact disk 7 is at a distance 10 radially outward from the reinforcement 5 to the inside of the probe element 1.

A molded ring 11 made of synthetic resin is inserted into the button housing 2, coaxial with the button element 1, in which a round groove 12 is machined. In the cylindrical ring opening

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A cylindrical contact carrier 13, also made of synthetic resin, is inserted centrally into the molded ring 11 with a tight fit, which carries contact conductors 14, 15 made of beryllium bronze like the contact disk 7 in eight grooves arranged on its circumference, aligned with the cylinder surface lines, see Figure 3. At the end of the contact carrier 13 on the touch element side, a step is formed, from which the contact conductors 14, 15 protrude. Each contact conductor 14, 15 points with one contact point to the underside of the flexible contact disk 7 and, in the neutral position of the touch element 1, maintains a slightly shorter distance from the contact disk 7 than the surface of the contact carrier 13.

Centrally around the vertical axis of the pin 6, the contact carrier 13 has a truncated cone-shaped recess 16, the circumference of which is slightly larger than that of the

Fastening sleeve 8. In the neutral position of the \ button element 1, the smaller Ke

blunt surface of the fastening sleeve 8 at a slightly greater distance from the bottom of the recess 16 than the flexible contact disk 7 to the tips of the contact conductors 14,15.

The eight contact conductors 14,15 represent four positive and four negative pole ends. In ,Q clockwise direction there is always a positive

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Pole 14 to a negative pole 15, see Figure 2. All contact conductors 14,15 are anchored with their parts facing away from the tips in a circuit board 17 in which the current strands 18 _and 19 are attached, see Figures 1 and 2.

The electronic distribution device (not shown) is located between the molded ring 11 and the circuit board 17. The power supply is via connecting lines 20 from a

Plug 21.

In the molded ring 11 there is a bore 22 which opens via a seal 23 into a highly elastic pressure compensation hose 24, the other end 25 of which is closed. The pressure compensation hose 24 serves to compensate for pressure differences which arise in the air space 26 between the pushbutton element 1 and the contact disk 7 and in the adjoining air space 27 between the contact carrier element T3 and the molded ring 11 as a result of temperature differences, so that within the temperature limits of -30°C to +80°C provided for such pushbuttons, the air pressure in the air spaces 26, 27 always remains constant, so that the finger pressure required to release a circuit is also always the same.

At the bottom of the round groove 12 in the form ring 11, three holes are machined at an angular distance of 120° each, which, however, do not affect the material of the

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The holes do not penetrate the molded ring 11, but leave a thin (transparent) cover behind. Three LEDs 28 are arranged in these holes, which are supplied with power from the circuit board 17 and constantly light up, e.g. yellow or green, as a signal that the device is ready for operation. A red LED 29 is installed in a fourth hole of the same type, located between two of the LED holes, which is connected in such a way that it only lights up when the switching element is not working. This means that the supervisor does not have to search for long if a push button has failed somewhere in a control system.

This arrangement can be seen in Figure 3, a section through the short-stroke push button Figure 1 in the surface plane of the mold ring • 11.

The switching element according to the invention works as follows:

■ - In the neutral position of the switching element ^ ( Figure 4 ) the flexible

Contact disk 7 by a short switching stroke over the tips of the eight contact conductors 14,15. The switching stroke can be kept as short as possible because the air pressure in the air spaces 26,27 always remains the same due to the pressure compensation hose 24. Vibrations between the touch element 1 and the other

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Housing parts (form ring 11 and contact carrier 13) that could trigger circuits do not come into play because the pushbutton element 1 is an integrated component of the switch housing 2 and vibrates with it. Natural vibrations of the contact disk 7 are slowed down by the fact that only a relatively narrow edge area of the contact disk extends freely between the pushbutton element 1 and the contact conductors 14, 15.

- When a pinger pressure is applied in the direction of the vertical axis of the pushbutton element 1 (vertical axis of the pin 5), the flexible contact disk 7 is pressed evenly onto all eight contact conductors 14, 15, see Figure 5. The base of the fastening sleeve 7, which in the neutral position is located at a distance slightly greater than the switching stroke s above the base of the recess 16, now rests on the base and thus prevents further displacement or deformation of the contact disk 7.

- When a finger pressure is applied to the edge zone of the touch element, the contact disk 7 will touch at least two contact conductors 14, 15, as shown in Figure 6 .

The mechanical limitation by placing the fastening sleeve 7 on the bottom of the recess 16 is carried out as described above.

The arrangement of eight contact conductors 14, 15 under a flexible contact disk 7 shown in the example has proven to be

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.ils proved to be very advantageous. The angular distance excludes any possibility that at least two contact conductor tips 14,15 are not brought from the contact disk 7 when a pinger is pressed at any point on the touch element 1. In most cases, even more pole pairs will be switched. This multi-point circuit provides a high level of safety for the triggering of a circuit even with low pinger pressures - e.g. by children. However, a sufficient level of safety for the triggering of a circuit can also be provided with six or even just four contact conductors 14,15. The decisive factor here is an appropriate ratio between the bending elasticity of the contact disk 7 and the switching stroke s (see Figure 4 ) _t The bending elasticity depends on the strength of the

Contact disk 7; if this is designed as

Tongue spring washer with six or four spring tongues (not shown), can be used with the same

Bending elasticity and the same switching stroke, a stronger spring plate must be used. However,

a tongue spring washer must be arranged in a rotationally fixed manner «

The safe switching by means of a light " and also eccentrically aligned finger pressure on the pushbutton element 1 does not in any way mean that there is a risk that, for example, the door of a railway carriage or a bus travelling through a forest could open under the influence of a

Branch opens suddenly, just as little as actuation

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opening of the doors of a vehicle during a washing process could be done by the pressure of a spray gun, because in such cases all door locks would be blocked together and separately, to prevent children, for example, from opening the doors while the vehicle is in motion. A short-stroke push button should be designed in such a way that it can be easily operated by anyone, including old people and children, and on the other hand it responds to the impact of a branch or

a hard jet of water is a technical impossibility.

It is used for different purposes

It is important to be able to provide the switching element with wear-resistant switching strokes s (see Figure 4 ). The switching stroke s suitable for the respective case is set by moving the contact carrier 13 in the molded ring 11.

The fit of the element 13 in the mold ring 11 is very tight, but in order to ensure air and

to ensure a moisture-tight seal,

§ , \ Sealed. This sealing, which simultaneously determines the switching stroke s, is carried out by applying an adhesive 30 in the open 25 !space between the longer mold ring 11 and the shorter contact carrier 13 (cf. g^gur 1 ) , whereby

f- the adhesive mass in the grooves of the contact lines

-; ter 14,15 penetrates. A particularly easy

_j controllable adjustment of the switching stroke s can

% 30 by that at the touch element 1

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a fine-pitch thread 31 is machined between the part of the contact carrier 13 facing away from the inner wall of the molding ring 11. Even when using a thread 31, a seal 30 must be applied to the underside of the molding ring 11 and contact carrier 13 after adjustment.

A further advantage of the molded ring 11-contact carrier 13 system is the design of a step on the contact carrier 13 that accommodates the air space 27. If the air humidity that is naturally always present in the already small air spaces 26, 27 condenses when the temperature changes, the corresponding very small amounts of water will collect in the air space 27 and freeze there at low temperatures. Ice cannot form on the contact tips 14, 15, just as it cannot form on the contact disk 7.

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List of reference symbols

1 button element

2 button housing

3 Rubber seal on switch housing 2

4 Wall of the push button carrier

5 Central reinforcement on the key element 1 ' 6 Pin on the reinforcement 5

7 flexible contact disc

8 Mounting sleeve for 7

9 Glue on the tenon 6

■&eeacgr; 10 Distance between touch element 1 and contact disc

yi Formting in switch housing 1

1 2 round stitches in the form ring 11

13 Contact carrier (counter-probe) 14,15 Contact conductor

; 1 6 truncated cone-shaped recess around 13

17 Circuit board

18 Current wire positive
1 9 Current strand negative
20 connection cables

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21 Plug for power connection

22 Hole for pressure equalization hose

23 Seal on the bore 22

24 Pressure equalization hose

25 closed end of 24

26 Air space at the touch element 1

27 Air space on contact carrier 1

28 LEDs, signal "switch ready for use"

29 red LED, signal "switch not working"

30 adhesive at 11,13

31 threads at 11 and 13

s Switching travel

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Claims (1)

- 1 - 616 Protection claims 1. Short-stroke pushbutton in which a disk-shaped pushbutton element made of insulating material acts on an elastic contact element which can be pressed against a counter-contact element over a short switching stroke and thereby connects the poles of a separate circuit with each other, characterized in that a central reinforcement (5) is formed on the contact side of the elastic ^pushbutton element (1), to which a flexible contact disk (7) made of conductive material is fixed axially, which maintains a distance from the plane of the pushbutton element (1) from the edge of the central reinforcement (5) radially outwards and is located at a short distance above a plurality of pole pairs (14, 15) of the circuit to be closed, the pole ends of the pole pairs (14, 15) forming a plane which in the neutral position vJ 20 ^{of the} probe element (1) parallel to the plane of the Contact disc (7). 2. Short-stroke pushbutton according to claim 1, characterized in that a pin (6) is formed on the central reinforcement (5) on the same axis, onto which the ring-shaped, flexible contact disk (7) is placed and - 2 - 616 is clamped to the probe element (1) by means of a fastening sleeve (8) which is then attached and can be fastened to the pin (5). 3. Short-stroke pushbutton according to claim 1, characterized in that the pole ends of the pole pairs (14, 15) facing the flexible contact disk (7) are arranged in a circle around the vertical axis of the flexible contact disk (7) in such a way that positive poles (14) follow negative poles (15) in a clockwise direction in rows. 4. Short-stroke pushbutton according to claim 1, characterized in that the pole pairs (14, 15) are designed as contact conductors (14, 15) tapered at the pole ends, which are arranged in cylindrical are arranged in longitudinal grooves aligned with the surface lines of a cylindrical contact carrier (13) that can be inserted into a cylindrical central recess in the button housing (2). 5. Short-stroke pushbutton according to claims 1 and 4, characterized in that a molded ring (11) is introduced into the cylindrical central recess of the button housing (2), which receives the adjustably insertable contact carrier (13). j—--,„&eegr;-,,.&Ggr; ■ ■■ ■■ ■'■■·' ·■-' - &igr; • t t t t t * * • 11 t · ■ •ti &iacgr; t t •t • it« * · • - 3 - ' * Short-stroke push button according to claims 1, 4 and 5, characterized in that there is an air space (27) between the contact carrier (13) and the upper parts of the contact conductors (14, 15). 7. Short-stroke push button according to claim 1, characterized in that the elastic push button element (1) is manufactured in one piece with the push button housing (2). 8. Short-stroke pushbutton according to claim 1, characterized in that the otherwise hermetically sealed air space (26, 27) located between the elastic pushbutton element (1) on the one hand and the contact carrier (13) serving as a counter-contact element on the other hand is connected to a highly elastic pressure compensation hose (24) which projects into a cavity in the pushbutton housing (2) and whose end (25) facing away from the air space (26, 27) is closed. 9. Short-stroke pushbutton according to claim 1 - characterized in that behind the transparent pushbutton element (1) there is arranged not only light-emitting diodes (28) as signals of readiness for operation but also a light-emitting diode (29) of a different color as a signal of non-operational readiness.