Push button disposition on a circuit board

p0001The invention relates to a push button arrangement on a circuit board. In such applications, as they are for example used in panel construction, the switch contact is produced via a snap-action disc, which is embedded in a spacer, and is protected by a cover against external attack.

p0002Several of these pushbuttons arrangements are summarized generally to keypads on circuit boards.

p0003A device according to the preamble of claim 1 is known from the patent publication US 4,365,120. This patent shows pushbuttons on a circuit board having a circular snap disk with a recess in the center for performing a light source. The light source protrudes up to a temperature above the snap dome cap, which is supported by an annular surface on the snap disc. A disadvantage of this arrangement is that all operating forces thus be transferred to the contact surfaces including those that are much too large. Furthermore there is a risk that the cap tilted on one side, if an eccentric attack power as in the bad habit of actuation occurs at the periphery with sharp writing utensils. In addition, a trace of the back of the circuit board is performed under the snap disc on the front, which inevitably a Handlötstelle on the front or at a lower contact plate (17), presupposes with durchsteckbaren to the rear solder tails, head to the back of the PCB.

p0004In the patent US 4,056,701 are shown with LEDs fitted pushbuttons, which are designed in a sophisticated and intended for large series construction. With this arrangement, a single keypad is achieved in flat, the keys are lit when operating or Anspeisen outside. A disadvantage of this construction is that it comprises four support body (58, 46, 22, 12), which requires an accurate processing and covering of the processed fields. Small series with individual keypads are no longer economical to produce in this technique. The keys, which light is not necessary, although need not be driven on their associated LEDs, but still run in this complex design.

p0005The patent FR 2280291 shows pushbuttons on a circuit board with torsion springs which are pushed over the key tops to a contact. Every still so big key press is transmitted to the contact. The spiral springs are in their longitudinal direction substantially across the width of the buttons in front, which limits the distance between the keys, and they are required when operating with a central bore for guiding the key body. Eccentric actuating forces can generate on the bending spring in the longitudinal direction displacement forces.

p0006The object of the invention is to apply outwardly protected pushbuttons with little individual elements in a flat on a circuit board.

p0007This problem is solved with the characteristics of claim. 1

p0008The advantage of the invention is that the user-induced fiscal burden sealers and the domes are so kept within limits that no translations degradation and destruction occur.

p0009The dependent claims 2 to 4 represent advantageous developments of the invention.

p0010In the following the invention will be described based on an embodiment.<dl id="dl0001"><dt>Fig. 1</dt><dd>schematically a section in perspective view through an inventive push button arrangement on a circuit board and</dd><dt>FIG. 2</dt><dd>is a reduced scale a plan view without cover and without cover.</dd></dl>

p0011In the figures, a push button arrangement is on a Leite shown rplatte which consists in its basic structure of a circuit board 1 with conductor tracks 6 and a snap disc 5 which rests one hand on the conductor tracks 6 and on the circuit board 1 and the other hand in their movement from one covering the protective cap 4 is limited, which is held by a cover 3 in an opening 12 of the spacer second

p0012The apertured 12 electrically insulating spacer 2 is connected via a tie tight to the circuit board 1 and on the opposite side with the cover. 3 The deformation of the cover 3 and the snap disc 5 is limited by the range of motion of needs in the opening 12 of the spacer 2 cap. 4 The cap 4 has an on board 1 above the outer edge 13, so that the snap disc is 5 included in operating the printing task arrangement between cap 4 and the circuit board 1 and a path limitation arises. The protective cap 4 engages only at a single, cup-shaped engagement surface in the center of the snap disc. 5

p0013The position of the snap-action disc 5 is secured by two protruding tabs 11, each of which engages in a recess 10 of the printed circuit board first Under the circuit board 1, a light source 9 can be attached, which illuminates the latter through an opening 7 of the circuit board 1 and through an opening 8 of the snap disk 5 when cap 4 and cover 3 transparent executed.

p0014Despite calls for a flat construction as possible, the thickness of the spacer 2 mm is performed greater than. 1