EP0614204B1 - Switch dome for push-button switch - Google Patents

Description

The invention relates to a switch cap according to the preamble of Claim 1.

Switch caps made of a plastic injection molding compound or the like are in Pushbutton switches as actuators and reset elements for the pushbutton inserted.

One such is known from DE-OS 41 12 754 and EP-A-0 509 368 Switch cap for one with a push button Pushbutton switches known that have a base, one opposite the base base with a narrower cover and one the base base and the Has lid connecting flexible thin-walled membrane. A The contact surface for bridging fixed contacts is on the cover of its surface facing the base base or on the base base attached to its surface facing the lid. When pressing the Push button switch, the push button acts on the lid or the Base base of the switch cap, so that the lifting movement to Actuation of the switch cap through the cover towards Base base or through the base base towards the lid.

Due to tolerances in the installation position of the push button and the Switch cap in the housing of the pushbutton switch has an effect the push button on the switch cap already in the unactuated State of the push button switch possible, so that the cover or The base base has already covered part of the lifting movement. This shortens the stroke length that is still available between the unactuated state and the actuated state of the Pushbutton switch corresponds to the route. It can happen that the stroke after installation of the push button switch is not more like the specifications. Since switch caps also for small strokes are made, there is even a risk that that the push button switch is no longer functional overall.

In JP-A-04 137 414 (closest prior art) and GB-A-2 039 417 there is further one out Rubber material or silicone rubber existing switch cap shown, where the lifting movement through the cover towards the base base he follows. With this switch cap there is an attachment on the cover arranged. The approach according to JP-A-04 137 414 consists of several tapered protrusions during the approach after the GB-A-2 039 417 from a hollow body with elastic wall parts consists. When the switch cap is actuated, the attachment flips over, with what a stroke extension to improve the feeling of actuation given by the user.

In JP-A-04 137 414 and GB-A-2 039 417 means for Extension of the stroke for a switch cap described, if this is not sufficient. However, there is no indication for that automatic compensation of tolerances during assembly in one Push button switch, in particular for a switch cap, in which the Actuated by the base base towards the cover, given.

The invention has for its object a switch cap type mentioned in such a way that a independent compensation of installation-related tolerances on the Switch cap is possible.

This task is performed by a switch cap of the generic type characterizing features of claim 1 solved.

Further refinements of the invention are the subject of Subclaims.

The advantages achieved with the invention are in particular that a equipped with the switch cap according to the invention Pushbutton switches can be made functionally reliable without rejects can, because of the installation position of the switch cap or push button Tolerances occurring do not affect the actual stroke of the Impact switch cap. Another advantage is that any Large additional overstroke by extending the advance path is achievable. With conventional switch caps, the height of the Membrane and the base or cover determined Have proportions so that the one you want Specifications corresponding snap operation when the Switch cap occurs as well as a certain tactile feeling for the User is present during the switching process. Therefore Any stroke lengths are not always with conventional switch caps constructively. The resilient approach to the Switch cap according to the invention can be of any size design so that each desired lead and thus stroke can be achieved.

Fig. 1

einen Schnitt durch eine Schalterkappe,

Fig. 2

ein Kraft-Weg-Diagramm für die Schalterkappe,

Fig. 3

einen Schnitt durch eine Schalterkappe in modifizierter Form,

Fig. 4

eine Draufsicht auf die Schalterkappe gemäß Fig. 3,

Fig. 5

einen Schnitt durch eine Schalterkappe in einem weiteren Ausführungsbeispiel,

Fig. 6

einen Schnitt durch einen schematisch dargestellten Drucktastenschalter mit Schalterkappe in nochmals weiterer Ausführungsform und

Fig. 7

ein Transportband bei der Herstellung einer Schalterkappe gemäß Fig. 6.

An embodiment of the invention is shown in the drawings and will be described in more detail below. Show it

Fig. 1

a section through a switch cap,

Fig. 2

a force-displacement diagram for the switch cap,

Fig. 3

a section through a switch cap in a modified form,

Fig. 4

3 shows a plan view of the switch cap according to FIG. 3,

Fig. 5

3 shows a section through a switch cap in a further exemplary embodiment,

Fig. 6

a section through a schematically illustrated push button switch with switch cap in yet another embodiment and

Fig. 7

a conveyor belt in the manufacture of a switch cap according to FIG. 6.

A push button switch 1 can be seen in Fig. 6 and consists of a push button 2 shown only schematically, which in generally still provided with a mounting mimic, not shown and a switch cap 3. The switch cap 3 has one Base base 4 and has one compared to base base 4 narrower lid 7. The switch cap 3, shown in more detail in Fig. 1 compared to a conventional switch cap Upside down. Accordingly, the lid 7 with its lower one End face arranged on a circuit board 6, while the opposite the base base 4 wider 4 by means of a in Fig. 1 not push button shown with an actuating force is applied. Furthermore, the switch cap 3 has a Base base 4 and the cover 7 connecting flexible thin-walled Membrane 10 on. The base base 4 has the cover 7 on it facing surface a contact surface 9 for bridging on the Printed circuit board 6 fixed contacts 11 ', 11 ". The lifting movement the base cap then actuates the switch cap 3 4 in the direction 24 to the cover 7. The contact surface 9 can be made from a conductive layer of coal varnish, silver varnish, gold varnish or the like. consist.

1 and 4, the switch cap 3 frustoconical, the base base 4 a can have a circular basic cross section. The lid 7 is in the essentially cylindrical and the membrane 10 as Truncated cone surface formed.

The base cap 4 and the cover 7 are in the case of the switch cap 3 due to the massive shape, relatively rigid and rigid. The flexible membrane 10, however, is due to its thin walls very elastic. By pressing pushbutton 2 (see Fig. 6) a force acts on the acting as an actuator Switch cap 3 on. When the base base 4 is pressed down, the Contact surface 9 with those located on the circuit board 6 Fixed contacts 11 ', 11 "together, the contact surface 9 the bridges two fixed contacts 11 ', 11 ", so that the electrical Contact is closed. If pushbutton 2 is released, it has an effect the switch cap 3 due to the spring force of the elastic membrane 10 as a reset element and the base base 4 returns to his original position back.

The switch cap 3 consists of a plastic injection molding compound or the like. preferably a thermoplastic elastomer, and is in Injection molding process made. A has proven to be particularly suitable So-called block copolymer, which consists of a hard crystalline segment made of polybutylene terephthalate and a soft one amorphous segment based on long-chain polyether glycols. Such a plastic injection molding compound is called "HYTREL" distributed by the Du Pont company.

The stroke h specified in the design by the switch cap 3 is as can be seen from FIG. 1, by the distance of the contact surface 9 determined by the fixed contacts 11 ', 11 "in the unactuated state. By tolerances in the installation position of the push button 2 and Switch cap 3 in the push button switch, however, it can happen that the push button 2 already in the unactuated state on the base base 4 acts, so that this part of his stroke movement has traveled. However, this undesirably shortens the total available stroke h. To compensate for Tolerances between the installation position of the switch cap 3 and the Base base 4 actuating push button 2 has base base 4 the surface facing away from the cover 7 an extension 12 which resiliently in Direction 24 of the lifting movement is configured.

In the unactuated state, the push button 2 is not directly on Base socket 4 but 12 on this approach. Tolerances now occur between the installation position of the push button 2 and the switch cap 3 on, so in the unactuated state of the push button 2, only the Approach 12 deformed so that the base base 4 is in its original position maintains. In particular, deformation of the membrane 10 in effectively prevented from unactuated state.

In Fig. 5 in a schematic diagram three push button switches la, 1b, 1c with different and thus tolerant installation position seen in the unactuated state. As you can see, the Push buttons 2a, 2b, 2c differently the approaches 12a, 12b, 12c greatly deformed in the direction of the lifting movement while the position the contact surfaces 9a, 9b, 9c of the switch caps 3a, 3b, 3c and thus nor the size of the stroke h of the switch caps 3a, 3b, 3c changed.

When the push button 2 is actuated in the direction 24, the deforms Approach 12, if necessary, continue until the push button 2 touches Base base 4 (see FIG. 6) and only then the base base 4 its lifting motion. It can be seen that of the Dimensioning of the switch cap 3 predetermined stroke h (man see also Fig. 1) not shortened. If necessary, the total stroke through the additional deformation movement of the approach 12 extended. However, this is an added benefit because it does an increase in the advance path up to the actual switching point, where the contact surface 9 bridges the fixed contacts 11 ', 11 ", is achieved, which is due to design restrictions in the Dimensioning of the switch cap 3 otherwise not in all cases is achievable.

In Fig. 2 is the force-displacement diagram for the Switch cap 3 shown. If an operating force F on the Push button 2 exerted, so the approach 12 is first deformed, due to its spring action, the required force F in Dependence on the actuation path s approximately linear according to the curve branch 25 increases. For a certain actuation path s1, the approach is 12 fully compressed and the base 4 is now under Deformation of the membrane 10 moves, the actuating force F very strongly corresponding to the curve branch 26 up to the actuation path s2 increases. In the actuation path s2, the membrane snaps 10, so that the force F up to the actuation path s3 according to the curve branch 27 drops. There, the contact surface 9 bridges the fixed contacts 11 ', 11 ", the contact surface 9 resting on the printed circuit board 6, so that with further actuation the actuating force F is very steep increases, as shown with the curve branch 28.

To ensure in any case that a balance of tolerances by the deformation of the approach 12 and not the stroke 12 is undesirably shortened, the approach 12 can be designed so that it has a lower spring force than that which is caused by the elasticity of the membrane 10 has.

This is preferably done by making a recess 13 in the Approach 12 reached, as shown in Fig. 1. Does he have Base base 4 has a cylindrical shape, so it lends itself to the Approach 12 circular and the recess 13 also to be continuous in a circular shape. Approach 12 in one piece on the base base 4 when producing the switch cap 3 be injected. The cross section of the recess 13 can triangular, as shown in Fig. 3, or trapezoidal be. Such an approach 12 also has approximately the shape of a disc spring.

Alternatively, it is also possible to start from the base 4 to form individual, non-continuous segments 14 ', 14 ", like 3 and 4 is shown in more detail. Each of these segments 14 ', 14 " is in turn resilient in the direction 24 of the lifting movement. It is also possible to use an individual approach instead Segments 14, 14 ', 14 "' (see FIGS. 3 and 4) the approach 12, as in 1 and 5 shown to design continuously.

To fix the switch cap 3 on the circuit board 6 can, as in Fig. 6 is shown, on the cover 7 on the base base 4 facing away Surface a fastening part 30 may be arranged, the such is designed so that it is in a recess 31 as the carrier part serving circuit board 6 can be used latching. Preferably for this purpose the fastening part 30 centrally and positively into the Recess 31 arranged appropriately.

The fastening part 30 is a separate part in FIG Shape of a pin that has a shaft 32 with a round cross section and a head arranged on the side opposite the cover 7 33 owns. The recess 31 in the circuit board 6 continues from a through hole is formed. The shaft 32 is adapted in cross section to the recess 31, while the head 33 is somewhat larger in cross section than the recess 31. The Fastening part 30 is now inserted into the recess 31 that the head 33 rests on the underside 34 of the circuit board 6.

The fastening part 30 has on the head 33 facing away from it End of a fastening button 35. The fastening part 30 is such from the base base 4 facing side into an opening 36 of the Cover 7 (see Fig. 1) used that the fastening part 30th is held on the cover 7 by the fastening button 35. It lends itself to the fastening part 30 made of a hard plastic produce, for example a polycarbonate, polyamide, Polyacetal, polyester, polybutylene terephthalate or the like. It is also possible for the fastening part 30 to be made of metal to manufacture.

To simplify the assembly of the switch cap 3 can, as well 6, the fastening part 30 is elastically resilient be trained. This is achieved in that the shaft 32 with a slot 37, which also passes through the head 33, is provided. At the Introducing the shaft 32 into the recess 31 can Reduce the cross section of the head 33 due to the slot 37, see above that this can be easily passed through the recess 31 can. Once the head 33 the bottom 34 of the circuit board 6th has reached, the head 33 springs back to its original size apart and the fastening part 30 is latching into the recess 31 used.

In the manufacture of a switch cap 3 according to the embodiment 6 is expediently the fastening part 30 at the same time manufactured with a conveyor belt 38 in the injection molding process, as in Fig. 7 can be seen in more detail. Two each on the conveyor belt 38 located fasteners 30 have the same distance d from each other. Preferably in the manufacture of the Fastening part 30 a holding part 39 between the fastening button 35 and the conveyor belt 38 injection molded, being at the transition a predetermined breaking point between the fastening button 35 and the holding part 39 40 is located.

In the manufacture of the conveyor belt 38 are in this Transport holes 41 are introduced at regular intervals. With help this transport holes 41 will be the conveyor belt 38 with the located fastening parts 30 in another Machined station where the switch caps 3 on the Fastening parts 30 are attached, as in Fig. 7 based on the fastening part 30 on the right is shown. Alternative is it is also possible in this processing station, the fastening part 30 with the switch cap 3.

After the switch caps 3 have been fitted onto the fastening part 30 then the switch caps 3 with inserted fastening part 30 broken off at the predetermined breaking point 40 from the holding part 39 and can then later used in the circuit board 6 (see Fig. 6). On the other hand, it is of course also possible that Switch caps 3 with the fastener 30 inserted Feed conveyor 38 to another processing station, where they are inserted into the circuit board 6 and then where subsequently the holding part 39 is broken off.

The invention is not limited to that described and illustrated Embodiments limited. Rather, it includes everyone professional training within the scope of the inventive concept. So can in particular the switch cap 3 provided with an extension 12 also used in keyboard arrangements with several single keys Find.

Reference symbol list:

1:

Push button switch

1a, 1b, 1c:

Pushbutton switch (when installed, subject to tolerances)

2, 2a, 2b, 2c:

Push button

3, 3a, 3b, 3c:

Switch cap

4:

Base base

6:

Circuit board

7:

cover

9, 9a, 9b, 9c:

Contact area

10:

membrane

11 ', 11 ":

Fixed contact (on the circuit board)

12.12a, 12b, 12c:

Approach (at the base base)

13:

Recess

14.14 ', 14 '':

Segment (at the base)

24:

Direction (of the lifting movement)

25, 26, 27, 28:

Curve branch (with force-displacement diagram)

30:

Fastener

31:

Recess

32:

shaft

33:

head

34:

Underside (of the PCB)

35:

Fastening button

36:

Opening (in the lid)

37:

slot

38:

Conveyor belt

39:

Holding part

40:

Predetermined breaking point

41:

Transport hole

Claims (17)

1. Switch cap (3) consisting of an injected synthetic material or the like as the actuating member and restoring element for a push button switch (1), which comprises a base socket (4), a cover (7) which is narrower in comparison with the base socket (4) and a flexible, thin-walled membrane (10) connecting the base socket (4) and the cover (7), the cover (7) being located by its end face on a support part, such as a printed circuit board (6), on its surface facing the cover (7) the base socket (4) comprising a contact surface (9) for bridging fixed contacts (11', 11'') located on the support part and the stroke movement for actuating the switch cap (3) taking place due to the base socket (4) able to be acted upon by an actuating force and which is wider in comparison with the cover (7), in the direction of the cover (7),

   in which case on the surface remote from the cover (7), the base socket (4) comprises a projection (12),

   which is designed to be resilient in the direction (24) of the stroke movement,

   the projection (12) having a lower spring force than that which is caused by the elasticity of the membrane (10),

   and in which case in the unactuated state of the push button switch (1), only a deformation of the projection (12) takes place.
2. Switch cap according to Claim 1, characterised in that a recess (13) is located in the projection (12).
3. Switch cap according to Claim 2, characterised in that the cross-section of the recess (13) is triangular.
4. Switch cap according to Claim 2, characterised in that the cross-section of the recess (13) is trapezoidal.
5. Switch cap according to one of Claims 1 to 4, characterised in that the projection (12) is injected in one piece on the base socket (4).
6. Switch cap according to one of Claims 1 to 5, characterised in that the projection (12) is constructed in the form of a circular ring.
7. Switch cap according to Claim 6, characterised in that the recess (13) is constructed continuously in the form of a circular ring.
8. Switch cap according to Claims 6 and 7, characterised in that the projection (12) has approximately the shape of a cup spring.
9. Switch cap according to one of Claims 1 to 5, characterised in that the projection consists of individual, noncontinuous segments (14, 14', 14").
10. Switch cap according to one of Claims 1 to 9, characterised in that the switch cap (3) consists of a thermoplastic elastomer.
11. Switch cap according to Claim 10, characterised in that the thermoplastic elastomer is a block copolymer of a hard crystalline segment of polybutylene terephthalate and a soft amorphous segment based on long-chain polyether glycols.
12. Switch cap according to one of Claims 1 to 11 for location on a support part, such as a printed circuit board (6), characterised in that located on the cover (7) on the surface remote from the base socket (4) is a fastening part (30), which is constructed so that it can be inserted in a locking manner in a recess (31) in the support part, preferably constructed as a continuous bore in the support part, the fastening part (30) preferably fitting in a form-locking manner in the recess (31) and being located centrally on the cover (7).
13. Switch cap according to Claim 12, characterised in that the fastening part (30) is constructed as a pin, which has a shaft (32) with a preferably round cross-section and a head (33) located on the side opposite the cover (7), in which case the shaft (32) is adapted as regards its cross-section to the recess (31), whereas the head (33) has a larger cross-section than the recess (31) and that the pin in particular is constructed as a separate part with a fastening stud (35), in that the pin is inserted in an opening (36) in the cover (7) from the side facing the base socket (4) so that the pin is held fast on the cover (7) by the fastening stud (35).
14. Switch cap according to Claim 12 or 13, characterised in that the fastening part (30) has a resilient construction, in that the shaft (32) is provided with a slot (37).
15. Switch cap according to Claims 12, 13 or 14, characterised in that the fastening part (30) consists of hard synthetic material, such as polycarbonate, polyamide, polyacetal, polyester, polybutylene terephthalate or the like or of metal.
16. Method for the manufacture of a switch cap according to Claims 12, 13, 14 or 15, characterised in that the fastening part (30) is produced by the injection moulding method with a conveyor belt (38) preferably comprising conveying holes (41) at regular intervals, the same spacing (d) existing between respectively two fastening parts (30) located on the conveyor belt (38), and at a further processing station the switch caps (3) being mounted on the fastening parts (30) or the fastening parts (30) being injection moulded with a switch cap (3).
17. Method according to Claim 16, characterised in that at the time of manufacture of the fastening part (30), a retaining part (39) is injected between the fastening stud (35) and the conveyor belt (38), a predetermined breaking point (40) being located at the transition point between the fastening stud (35) and the retaining part (39).

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