EP0134422B1 - Method of making a switching device for an electric key switch - Google Patents

Description

The invention relates to the manufacture of a switching device with at least one fixed contact part and at least one contact arm part and an interposed insulating part, the fixed contact part and the contact arm part being punched out of electrically conductive strip material and provided with fastening breakthroughs and separated from the strip material after mutual alignment and connection to the insulating part are, the tapes are also moved to each other in cycles. Such a method has become known from DE-AS 12 91 833. Here, it is considered disadvantageous that the relatively small insulating part is individually assigned to a metallic carrier part and connected to it in a complex operation. These procedural steps are not only very difficult, but also contribute to the increase in price and, moreover, the connection or fastening method in particular gives rise to rejects. It is difficult to simultaneously insert the four tabs of each connection point formed by a mandrel into their associated opening of the insulating part, although it should also be noted that four such connection points are created at the same time. The subsequent attachment of the contact springs is carried out in the same complex, difficult and incorrect connection-prone manner. The latter arise when only three of the four wedge-shaped tabs reach through the hole and one is clamped between the parts.

From GB-PS 13 53 090 a connection method has become known which avoids the previous flaring and forming of rags, but instead plastic parts are used which are complex to manufacture. They have a plate-like shape with three molded collars. The latter have to be inserted into three corresponding punched-outs of a contact spring at the same time, and this requires correspondingly large tolerances. This in turn has the consequence that a permanent connection is only possible if the collar end projecting outwards is permanently deformed. Both this operation and the plastic part itself lead to comparatively high production costs. This publication, however, shows the processing of insulating parts connected in strips in a machine punching out the contacts.

The arrangement of two contact springs on opposite sides of an insulating part is known for example from DE-PS 6 19 902. The connection is made there with the help of rivets. It is a complex and expensive operation that no longer meets the current requirement for inexpensive production, especially in the context of the production of mass articles. In addition, the use of rivets is more likely with larger switching devices. Like. Common, but hardly applicable to miniaturized versions, as you can find in particular in small computers and. Like. needed.

DE-AS 1081 954 also shows the arrangement of two electrically conductive contact springs on both sides of an insulating layer. For the connection, the use of swelling pimples is proposed on the one hand, and the encapsulation with a thermoplastic layer on the other hand. In particular, the insertion of the pipules into the punch holes and the subsequent swelling are expensive operations.

DE-AS 10 67 504 describes the connection of a metallic support with a metallic housing part, from which a rivet shaft is pressed out. The latter is dimensioned in such a way that it can easily be inserted through an opening in the metallic carrier with a molded-on contact piece, the cross-sectional shapes not necessarily having to be the same. In order on the one hand to allow the rivet shaft to be easily pushed through the opening of the contact carrier and on the other hand because the protruding end is subsequently flattened by means of a stamp, it is recommended to provide a certain play between the rivet shaft and the hole. In this connection method, the connection element - here the rivet shank - must be manufactured in a work step upstream of the plugging together. In addition, as in the method according to DE-AS 12 91 833, caulking is necessary.

Thus, this prior art is also an expensive, complex connection method that is not very suitable for modern mass production.

The object of the invention is therefore to develop the method of the type mentioned in such a way that the switching devices can be produced in a simple, cost-saving manner.

To achieve this object, it is proposed according to the invention that the method according to the preamble of claim 1 is designed in accordance with the characterizing part of this claim.

By using a flat strip material, from which the insulating parts are punched out and still attached to it before being connected to at least one of the metal parts, the insulating part can be handled much more easily, but nevertheless more precisely and faster than in the known prior art, for example according to DE -AS 12 91 833. On the other hand, preforming fasteners on one of the parts of the switching device is unnecessary. There is also the fact that simply by pushing material parts of the insulating part into openings in the respectively assigned contact arm part or fixed contact part, a problem-free and fast and permanent connection is achieved will create. The breakthroughs in the metal parts of the switching device are therefore used in two ways. On the one hand, they represent a form for the precise production of the protuberances serving as connecting elements, whereby they act in the manner of punching dies and, on the other hand, this automatically leads to a «zero fit», which is due to the resilience present in the protuberance after the plastic deformation holds the two parts together securely.

This results in a simple, quick to carry out manufacturing process for a switching device of the type in question, which is also inexpensive and, because of the small number of manufacturing steps required, is also inexpensive and runs safely and thus largely eliminates rejects.

In a further development of the invention, it is proposed that the protuberances be pushed beyond the opening and the protruding end of the protuberance is pressed broadly. This increases the security of the connection and leads to an even more robust switching device. In addition, this allows the use of particularly thin sheets, in the sheet level of which the anchoring alone would not be sufficiently guaranteed. The protuberances comparable to "rivet heads improve the anchoring there considerably.

Another variant of the method is that the wide pressing takes place with simultaneous thickening. A very uniform rivet head is hereby achieved.

A further embodiment of the method is characterized in that the insulating part is only removed after the wide pressing. Thus, the parts to be connected to one another are correctly assigned to one another during the spreading operation. This makes a separate holding device for one or the other or both parts superfluous during the spreading. Both parts are, at least up to the finished formation of the protuberances, still connected to their strip material, which can be safely aligned in a known manner by means of a perforation and transported in cycles. Therefore, the method according to the invention is also particularly suitable for mass production, in which, in a known manner, the saving of fractions of a penny is also important, because such penny fractions can also add up to a quite considerable amount.

The insulating part is first removed from its tape. As soon as it is connected to the contact arm part and the fixed contact part, the fixed contact part is also separated from its belt, so that the switching device is finally transported in a further cycle with the aid of the supporting belt of the contact arm part. In this respect, a further method step advantageously consists in that the completed switching device is separated from the supporting band of the contact arm part and is thus available for further use, in particular for installation in a keyboard or the like.

A preferred embodiment of the invention provides that the bands of the insulating part and the fixed contact part are shifted clockwise parallel to one another and perpendicular to the band of the contact arm part, the fixed contact part being fastened on one side and the contact arm part on the other flat side of the insulating part, as is the principle according to is known.

Another development of the invention is characterized in that the contact arm part and the fixed contact part are connected to the insulating part at the same time. Of course, this requires a corresponding arrangement of the tapes with the three parts and a design of the switching device parts adapted to this process step.

The invention is explained below with reference to the drawing. The drawing shows schematically both the switching device and the various steps in the manufacturing process of this switching device.

• Fig. 1 eine Draufsicht auf die eine Seite einer Schaltvorrichtung,
• Fig. 2 eine Seitenansicht,
• Fig. eine Draufsicht auf die andere Seite der Schaltvorrichtung,
• Fig. 4 mehrere an einem Reststreifen gehaltene Schaltvorrichtungen vor dem Abtrennen, in etwas verkleinerter Darstellung,
• Fig. schematisch das Herstellungsverfahren für diese Schaltvorrichtungen.

It represent

• 1 is a plan view of one side of a switching device,
• 2 is a side view,
• FIG. 1 shows a plan view of the other side of the switching device,
• 4 a plurality of switching devices held on a remaining strip before the separation, in a somewhat reduced representation,
• Fig. Schematically shows the manufacturing process for these switching devices.

The switching devices are expediently produced using three flat bands, band 1 and band 2 being made of electrically conductive material, while band 3 being made of electrically non-conductive material, in particular a thermoplastic material. Instead of a thermoplastic material, press board or a similar plastically deformable material can also be used. The bands 2 and 3 run parallel to one another in the same or slightly. about levels of material offset in height, while the band 1 runs transversely, preferably perpendicularly, to the two bands 2 and 3. In particular, it is provided that the belts 2 and 3 run over the belt 1. The directions of advance of the belts 1, 2 and 3 are symbolized by arrows 4, 5 and 6. The feed movement is gradual, as will be explained in more detail below.

The contact arm parts 7, the fixed contact parts 8 from the band 2 and the insulating parts 9 are punched out from the band 1. However, all parts initially remain connected to a remaining strip 10 or 11 or 12, in particular a side strip, of the strip via at least one bridge and are only separated therefrom at the predetermined point in time. One recognizes that the contact arm part 7 has a contact arm 13 with a movable contact 14 and one which extends in the opposite direction Connection element 15 has. The movable contact is formed by the feathered free end of the contact arm 13. Special contact rivets are not provided in the exemplary embodiment. In addition, two fastening openings 16 and 17 have been punched in one or in a second operation. The slightly larger opening 18 is used for transporting the belt 1. Corresponding openings 19 and 20 are provided on the belts 2 and 3.

The insulating part 7 has an essentially rectangular opening 35 to which the contact arm 13 and a fixed contact 21 on the fixed contact part 8 are assigned in the finished switching device. This fixed contact is a laterally projecting tab of the fixed contact part 8, which, like the contact arm part 7, has an electrical connection element 22. In addition, two fastening openings 23 and 24 are also present on the fixed contact part 8.

After the punching, but before the separation, a contact arm part 7 is assigned to an insulating part 9, the infeed being carried out in the direction of arrow 4 or 6. After completion of these steps, these two parts are superimposed as shown in FIG. 5. With a suitable tool, the material of the insulating part 9 is now pressed down at the points of the fastening openings 16 and 17 perpendicular to the image plane. The deformation is plastic, i. H. the pressed-out material parts of the insulating 9 remain in the form of bulges 26, 27 or protuberances in the two fastening openings 16 and 17. In particular, it is provided that they protrude downwards beyond these fastening openings, so that the projecting free ends are then moved in the opposite direction by means of a can press further tool, which at least creates an approach that is comparable to a rivet head.

Simultaneously with this riveting or in a subsequent step, the insulating part 9 is separated along the dash-dotted line 25 (FIG. 5).

In a further step, this unit, consisting of a fixed contact part and an insulating part, is transported further in the direction of arrow 4. At the same time or subsequently, a fixed contact part 8 is brought over this unit. Then, from below, material parts are pressed out of the insulating part through the fastening openings 23 and 24. The protruding ends of these expressions 28 and 29 are also flattened out, in particular with simultaneous thorning, which is symbolized by the circles 30 and 31. An immediate detachment from the remaining tire 10 or the retaining tab 32 is not provided, but is further transported, in the direction of arrow 4, with the next feed step of the tape 1. This is, however, a special feature of the exemplary embodiment, which is not absolutely necessary. Where and when to carry out the separation depends on the possibilities of the tool design and also the further use of the switching devices.

The retaining tab 32 of the band 1 corresponding retaining tab of the bands 2 and 3 are designated 33 and 34, respectively. While the retaining tabs 32 and 34 are relatively wide, the retaining tab 33 of the contact part 8 tapers towards it very sharply.

Claims (7)

1. Process for manufacturing a switching device with at least one fixed contact part (8) as well as at least one contact' arm part (7) and an insulating part (9) placed in the middle, whereby the fixed contact part and the contact arm part are punched out of electrically conductive strip material (1, 2, 3) and provided with fixing holes as also separated from the strip material after being aligned with each other and connected to the insulating part (9) and whereby in addition the strips advance whilst crossing each other in a cyclic movement, characterised in that the insulating part (9) is punched out of flat plastic strip material and is brought into contact with at least one of the electrically conductive parts and that after this the material of the insulating part (9) with the formation of a protuberance (26, 27 ; 28, 29) formed by the edge of each fixing hole (17, 18 ; 23, 24) is pressed into the corresponding fixing hole in each case whilst at the same time being subjected to plastic deformation, in that after this or simultaneously the second of the electrically conductive parts (7, 8) is connected in the same way to this unit after prior alignment and so that it is electrically separated and in that the insulating part (9) is only separated from its strip material after or during connection to the fixed contact part (8) and/or the contact arm part (7).

2. Process according to claim 1, characterised in that the protuberances (26, 27 ; 28, 29) are pushed out through the hole (17, 18 ; 23, 24) and the protuding end of the protuberances (30, 31) is in each case flattened outwards.

3. Process according to claim 2, characterised in that the diameter of the hole is opened out at the same time as the flattening operation.

4. Process according to claim 2 or 3, characterised in that the insulating part (9) is only separated after the flattening operation.

5. Process according to one of the preceding claims, characterised in that the switching device is separated from the carrier strip (1) of the contact arm part (7).

6. Process according to one of the preceding claims, characterised in that the strips of the insulating part (9) and the fixed contact part (8) are moved parallel to each other and perpendicular to the strip of the contact arm part (7), whereby the fixed contact part (8) is secured to one of the flat sides of the insulating part (9) whilst the contact arm part (7) is secured to the other flat side of the insulating part.

7. Process according to one of claims 1 to 5, characterised in that the contact arm part (7) and the fixed contact part (8) are connected simultaneously to the insulating part (9).

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