EP0841674B1 - Electrical push button - Google Patents

Description

The present invention relates to a push button element electric that can be used, for example, with electric keyboards to establish contact electric and produce a control signal or special control.

Document US4 304 973 A shows an element according to the preamble of claim 1.

We know an element forming an electric push button of the type comprising a button which can be inserted into a fixed body to deform a metal cup of contact from a specific stroke of the button and establish electrical contact.

However, this known push button element is designed in such a way that the driving force of the key depends only on the effort required to deform the electrical contact cup.

It may be advantageous in certain applications of make an element forming an electrical push button to adjust the force of pressing the key regardless of electrical contact and / or mechanism contact control.

To this end, the invention provides an element forming electric push button according to claim 1.

Advantageously, the underside of the rim button device is pressing on the workpiece deformable by means of a circular bead attached to this face.

According to one embodiment, the key comprises a pad central bearing on the top of the contact cup and of a height substantially equal to the thickness of the deformable part.

This deformable part is preferably in the form of washer whose central hole contains the cup of contact.

According to another embodiment, the deformable part includes a base part on the upper side of which is in support the circular bead of the touch and touch the top of the cup contact ; a first annular projecting part secured to the underside of the base part and resting on a part forming the bottom of the fixed body of so as to form with the base part a housing of maintaining the contact cup; and a second annular projecting part integral with the face upper part of the base part and resting on the part bottom of the button.

The base part of the deformable part includes a central recess in the form of a concave spherical cap in which is housed the vertex of conjugate form of the contact cup.

Preferably, the first and second annular parts protruding have the same height and the second part annular is of a diameter smaller than that of the first annular part located approximately in plumb with the circular bead.

Advantageously, the deformable part is made of material foam or elastomer.

The invention also provides a device forming keyboard with at least one push button element such as as defined above and which is characterized in that the body of the push button element is fixed on a flexible keyboard membrane through a rigid fixing plate located on the other side of the flexible membrane and the contact cup includes several legs connected to contact points membrane electrics connected to at least one circuit electric control or special command.

Preferably, the keyboard device is used to control the audible warning circuit of a motor vehicle and is mounted in the steering wheel of direction of this vehicle.

In such an application, the flexible membrane of the keyboard device is arranged behind a air bag integrated into the vehicle's steering wheel.

Preferably, the flexible membrane comprises four push button elements attached respectively substantially at the four corners of it.

The invention will be better understood and other aims, features, details and benefits of it will appear more clearly during the description explanatory which will follow made with reference to the drawings attached given only as an example illustrating two embodiments of the invention and in which :

Figure 1 is a sectional view of a member forming electric push button according to a first mode of realization of the invention.

Figure 2 is a schematic view of a device forming a keyboard with several elements forming a push button according to a second embodiment of the invention and mounted behind the airbag integrated into the steering wheel of a motor vehicle.

Figure 3 is an enlarged view of the part circled in III of a push button element of the second mode for carrying out the invention.

Figure 4 is a top view of a flexible membrane to at least one element forming an electrical push button the invention can be used in the device forming keyboard of figure 2.

The electric push button element such as shown in Figure 1 is of the type comprising a body 1 generally cylindrical in shape fixed to a support 2, such a printed circuit board, a flexible membrane, or similar, may be part of a device forming keyboard; a button 3 retained in the fixed body 1 and able to sink axially therein to deform a metal contact cup 4 from a determined stroke of key 3 and establish contact electric. Contact cup 4, housed in the body 1, includes, as is known per se, a certain number of legs (not shown), for example number of four, electrically connected respectively to metallic points of electrical contact of support 2 connected to one or more electrical circuits individuals via conductive tracks of support 2 (not shown). The deformation by button 3 of the cup 4 causes it to come in contact with a central electrical contact point for circulate current between the different points of electrical contact associated respectively with the legs of the cup.

In the case where the support 2 is constituted by a flexible plastic membrane in which are engraved electrical contact points and tracks above mentioned conductive bodies 1 is attached to membrane 2 via a rigid plate or fixing base 5 located on the side of the membrane 2 opposite to where the body 1 rests so that this membrane be sandwiched between body 1 and the fixing plate 5, which can be circular. The fixing the body 1 to the plate 5 can be done by small cylindrical metallic axes (not shown) press fit into plate 5 and body 1 in crossing the membrane 2 transversely thereto as symbolized by the dashed lines in Figure 1.

According to the invention, the push button element also includes a part 6 made of a material elastically deformable housed in the body 1 between the button 3 and the support 2 forming the bottom of the body 1 of way to adjust, depending on the material used for the deformable part 6, the pressing force of the key 3 to deform the contact cup 4.

Preferably, the deformable part 6 is produced in a plastic foam material which ensures at the same time the tightness of the push button element.

The deformable part 6 is preferably in the form of washer, in the central hole 6a of which is housed and maintained the contact cup 4.

Key 3 is pressed on a peripheral part upper part deformable 6 by one side lower edge 3a of button 3 formed at the bottom of this key and, on the other part, by the reaction force of the deformable part 6, on a peripheral edge 1a of the body 1, which delimits a opening 1b for passage of the cylindrical external part 3b of the key, by the upper face of the edge device 3a of this key.

Preferably, the underside of the peripheral rim 3a of the key 3 is supported on the deformable part 6 by means of a circular bead 7 secured of this face.

Key 3 also includes a central pad cylindrical 8 resting on the top of the cup contact 4 and a height substantially equal to the thickness of the deformable part 6.

To deform the contact cup 4 and thus establish an electrical contact by the latter on the support 2, the operator must exert an effort on key 3 predetermined penetration depending on the material used to make the deformable part 6. So, by changing type of material used to make the part deformable 6, the force necessary to press the key 3 and deform the metal cup 4 is also changed. The material of part 6 is defined in the factory depending on the desired pressing force of the button.

Figure 2 shows, without limitation the particular application of a device forming soft membrane type keyboard like this shown in Figure 1 to control a circuit electric horn of a motor vehicle, the keyboard device then being mounted in the steering wheel thereof, preferably back of the air-bag system housed in a housing 9 integrated into the steering wheel.

The flexible membrane of this keyboard device can have a number of push button elements of the type shown in Figure 1, for example four push button elements attached respectively at four corners of the membrane as we will see with reference to Figure 4 so as to allow the driver of the motor vehicle to use the audible warning device by actuating, by pressing one of these four elements on the steering wheel.

However, Figure 2, in conjunction with Figure 3, shows another possible embodiment of each push button element of the invention capable of be mounted on the membrane 2 in place of the element Figure 1.

According to this element, whose components identical to those of the element of figure 1 or performing the same functions have the same references, the part deformable 6 includes a base part 6b on the face upper of which is supported the bead circular 7 of key 3, part 6b being contact on the top of the contact cup 4; a first annular projecting part 6c secured to the underside of the base part 6b of the part 6 and resting on the membrane 2 so as to form with the base part 6b a cup holding housing contact 4; ; and a second annular projecting part 6d secured to the upper face of the base part 6b and pressing the lower part of the button 3 comprising the annular rim 3a.

The first and second annular projecting parts 6c, 6d have the same height and the second annular part 6d is smaller in diameter than the first part annular 6c which is located approximately plumb circular bead 7.

By modifying the heights of the annular parts by projection 6c, 6d of the deformable part 6, for the same material of this one, we also modify the force necessary to press key 3 to deform the contact cup 4. Thus, it is possible, for each type of steering wheel, use one element forming a push button with an appropriate pressing force of his touch by adopting a deformable part 6 whose annular parts 6c, 6d thereof have a height factory preset according to the type of flywheel used.

The base part 6b of the deformable part 6 comprises a 6th central recess in the shape of a spherical cap concave in which the vertex of conjugate form is housed of the contact cup 4 so as to maintain positively the cup under the deformable part 6.

Each circular fixing plate 5 of an element forming a push button attached to the membrane 2 is embedded in a recess of conjugate shape 10 produced in the upper surface of a plate 11 for fixing the steering wheel assembly with the diaphragm 2 in support on this upper face.

FIG. 4 represents a flexible membrane 2 of a keyboard device mounted in the steering wheel steering of a motor vehicle to operate the audible warning device thereof.

This figure shows the membrane 2 provided with an element forming a complete push button attached to the right corner and whose body 1, the key 3 as well as, by transparency, the fixing plate or base 5. The other push button elements located respectively in the other three corners of the membrane 2 were not fully represented, since only the metallic contact cup 4 of each of them is visible and includes all four legs 4a electrically connected to the corresponding electrical contact points 12 which can be seen in part in FIG. 4 and which are electrically connected to the conductive tracks 13 etched in the membrane 2. The conductive tracks 13 are connected to a sheet 14 with conductive connecting tracks 15 connected to the horn's electrical circuit motor vehicle so as to activate it when one of the keys 3 of a push button element is pressed.

By fixing the keyboard device provided with the membrane 2 and its elements forming a push button in rear of the vehicle steering wheel airbag, this entire device is preserved when the air-bag explodes during a frontal impact on the vehicle.

The above-described push button element the invention has a pressing force on its key correspondent independent of electrical contact and / or the control mechanism of this contact, unlike known push button elements. In addition, the deformable part of this element effectively removes vibrations of the corresponding cup likely to induce noise. The button element pusher of the invention can be applied to any type of keyboard to form so-called tactile keys.

Claims (12)

1. Element forming an electric push-button including a key (3) able to be driven into a fixed body (1) so as to warp a metallic contact cupel (4) from a specific travel of the key (3) and establish an electric contact including a part made of an elastically ductile material (6) housed in the fixed body (1), the key (3) being in support firstly on a peripheral portion of the ductile part (6), characterised in that the ductile element (6) is housed between the key (3) and the bottom of this body so as to adjust, depending on the material used for the ductile part (6), the force for driving in the key (3) so as to warp the contact cupel (4) and in that the key is in support on the peripheral portion of the ductile part via a lower face of a peripheral edge (3a) of the key (3) formed at the lower portion of the latter, and secondly via the reaction force of the ductile element (6) on a peripheral edge (1a) of the fixed body (1) which delimits a passage opening of the key (3) via the upper face of the peripheral edge (3a) of the key (3).
2. Element according to claim 1, characterised in that the lower face of the peripheral edge (3a) of the key (3) is in support on the ductile element by means of a circular flange (7) integral with this face.
3. Element according to claim 1 or 2, characterised in that the key (3) includes a central block (8) in support on the top of the contact cupel (4) and having a height approximately equal to the thickness of the ductile element (6).
4. Element according to one of claims 1 to 3, characterised in that the ductile element (6) has the shape of a washer whose central hole (6a) contains the contact cupel (4).
5. Element according to claim 1 or 2, characterised in that the ductile element (6) includes a base portion (6b) on the upper face of which the circular flange (7) of the key (3) is in support and in contact on the top of the cupel (4) ; a first annular projecting portion (6c) integral with the lower face of the base portion (6b) is in support on a portion forming a bottom for the fixed body (1) so as to form with the base portion (6b) a housing for supporting the contact cupel (4) ; and a second annular projecting portion (6d) integral with the upper face of the base portion (6b) and in support on the lower portion of the key (3).
6. Element according to claim 5, characterised in that the base portion (6b) of the ductile element (6) includes a central recess (6^e) with the shape of a concave spherical cap housing the conjugated top of the contact cupel (4).
7. Element according to claim 5 or 6, characterised in that the first and second annular projecting portions (6c, 6d) have the same height and the diameter of the second annular portion (6d) is smaller than that of the first annular portion (6c) situated approximately plumb with the circular flange (7).
8. Element according to one of claims 1 to 7, characterised in that the ductile element (6) is made of foam or an elastomer.
9. Element according to one of claims 1 to 8, characterised in that the ductile element (6) also ensures imperviousness of the element.
10. Device forming a keyboard with at least one element forming a push-button as defined in any one of claims 1 to 9, characterised in that the body (1) of the element is secured to a flexible membrane (2) by means of a rigid fixing plate (5) and situated on the other side of the membrane (2) and the contact cupel (4) includes several blocks (4a) welded to electric contact points (12) of the membrane (2) connected to at least one electric circuit.
11. Motor vehicle steering wheel including a device forming a keyboard according to claim 10, characterised in that the device is used to control the sound alarm circuit of the motor vehicle and is mounted in the steering wheel of this vehicle, the membrane (2) with at least one element forming a push-button being placed behind an airbag integrated with the steering wheel of the vehicle.
12. Steering wheel according to claim 11, characterised in that it includes four elements forming a push-button respectively fixed at the four corners of the flexible membrane (2).

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