GB2207554A

GB2207554A - A push-button switch having cleaning means

Info

Publication number: GB2207554A
Application number: GB08810978A
Authority: GB
Inventors: Georg Seibel
Original assignee: Schoeller and Co Elektrotecnische Fabrik GmbH and Co
Current assignee: Schoeller and Co Elektrotecnische Fabrik GmbH and Co
Priority date: 1987-05-12
Filing date: 1988-05-10
Publication date: 1989-02-01
Anticipated expiration: 2008-05-10
Also published as: IT8821200V0; ES2008480A6; GB2207554B; DE3715765C2; GB8810978D0; FR2615320A1; FR2615320B1; IT213971Z2; DE3715765A1

Description

j 2 2 0 7 5) '-'] 4 A PUSH-BUTTON SWITCH The present invention relates to

a push-button switch having a dame-shaped metallic contact spring which is disposed above a printed circuit board, provided with the associated fixed contact, and on which spring an operating rod provided with the push-button acts.

A push-button switch having a push-button is already known (German Patent Specification No. 2 614 119), the cupola or dome-shaped, metallic contact spring disc of which is provided with recesses which are defined by radially extending segments and into which resilient contact tongues protrude.

These contact tongues effect wiping movements m the contact surface of the associated fixed contact when the spring disc is depressed. The wiping movement permits the contact surfaces to be cleaned automatically, with the result that the transitional resistance at the contacts is kept low.

The known switch is difficult to produce and necessitates complicated punching and forming tools, and thus relatively high manufacturing costs are incurred.

The invention seeks. therefore. to further improve the known switch and to provide a push-button switch which can be economically produced without being labour- and material intensive and which also ensures that its contact surfaces are satisfactorily cleaned.

According to the present invention, this object is advantageously achieved in that small, conical or other protuberances are provided in the cupola or dame of the contact spring and are disposed about the circumference of an imaginary circle, the diameter of which is slightly larger than the diameter of the portion of the operating rod acting with the contact spring, and the protuberances slide along the fixed contact when the contact spring is depressed.

The small, conical protuberances according to the invention are disposed slightly outwardly of the rod diameter and can be easily provided m the cupola of the contact spring by simple tools, so that the manufacturing costs are low. In addition, the conical protuberances ensure, with their tips, that there is provided a punctiform contact with ahigh, partial contact pressure. By arching the cupola of the contact spring and because of the subsequent pressure in the region of the points of contact, a resilient effect is produced and, in this way, the contacts are automatically cleaned by a displacement of the contact tips. This displacement of the points of contact, in conjunction with the high, partial contact pressure, causes the destruction of foreign layers and foreign particles and, in consequence, ensures that a positive contact is provided and that the contacts have a long service-life.

Additional features and advantages of the invention can be found in the sub-claims, in the drawing and in the associated description of the drawing.

The invention will be described further., by way of example, with reference to the embodiment of the accompanying drawings, in which:- Fig. 1 is a sectional view through a contact spring and a printed circuit board carrying it, the contact spring being in its initial position and the associated circuit being open; Fig. 2 is a sectional view in accordance with Fig. 1, but wherein the operating rod is depressed to such an extent 1 that conical protuberances touch the fixed contact for the first time with their tips; Fig. 3 is a sectim'al view in accordance with Fig. 2, wherein the operating rod is depressed as far as its end position; Fig. 4 is a plan view of the contact spring and the printed circuit board; and Fig. 5 is a sectional view through the central portion of the contact spring showing the conical protuberances.

A push-button switch is illustrated and comprises an operating rod 1, whith is guided in a housing (not shown) and is provided with a pushbutton and rests on the dish or dome 2 of a contact spring 3. A printed circuit board 4 accomodates a f ixed contact 14. The contact spring 3 is placed upon the printed circuit board 4 and secured to the printed circuit board 4 at its edge by means of soldering lugs 5 and 6 which form connection contacts. The soldering lugs 5 and 6 extend through openings 7 and 8 in the printed circuit board 4 and are securely soldered to conductor paths 10 and 11.

The fixed contact 14 comprises a circular disc 15 which lies on the printed circuit board 4 and has a pin 17 mounted thereon which extends through opening 16 in the printed circuit board 4. The pin 17 is securely soldered to a conductor path 18 on the printed circuit board 4. The dome 2 of the contact spring 3 is stamped into a rectangular sheet metal strip 20, which is placed upon the printed circuit board 4, and such dome extends to the two edges of the sheet metal strip 20 to form, with the printed circuit board 4, lateral slots through which the current supply to the fixed contact 14 below the dame 2 passes. Instead of there being only one dome 2 provided as shown, a sheet metal strip 20 may alternatively be used having a plurality of dames 2 (not shown). Four conical protuberances 23 to 26 (tips) are disposed in a circ-le 19, i.e. evenly around the circumference of an imaginary circle 19 the centre of which lies on the axis 21 of the operating rod 1, and the protuberances are spaced from me another at an angle of 900; the tips of the protuberances pointing downwardly in the direction of the circular disc 15 of the fixed contact 14. The diameter of the circle 19 is slightly larger (a few tenths of a millimeter) than the diameter of the lower portion 28 of the operating rod 1, which touches the dome 2 of the contact spring 3, and smaller than the diameter of the circular disc 15 of the fixed contact 14. The fixed contact 14 can also be pressed onto the printed circuit board 4, so that it does not have to be inserted as.a separate component part into the printed circuit board 4. When the operating rod 1 is depressed, the dame 2 is pressed inwardly until the tips of the conical protuberances 23 to 26 sit for the first time on the circular disc 15 of the fixed contact 14 (Fig. 2) and an electrical current can flow via the contacts 2 and 14. The protuberances 23 to 26 are then pressed laterally and slide along the circular disc 15 until the central portion of the deme 2 reaches the circular disc 15 (Fig. 3). Because the tips of the protuberances 23 to 26 slide along the circular disc 15, the contact surfaces are automatically cleaned. Once the push-button is released, the dme'2 springs back into its initial position and resumes it dome-shaped form, with the result that the circuit is broken.

The invention has been explained more fully above with reference to me embodiment. However, it is in no way limited 1 A to this embodiment because a large number of modifications are possible for the configuration of the contact spring and for the arrangement of the conical protuberances of the invention, without thereby departing from the scope of the invention as claimed in the appended claims although may include the switch components not mounted on the printed circuit board.

Claims

1. A push-button switch including a cupola- or dome-shaped, metallic contact spring which is disposed above a printed circuit board, provided with an associated flat stationary contact. and on which spring there acts a portion of an operating rod provided with the push-button, wherein small conical or other protuberances are provided in the cupola or dame of the contact spring and are disposed on the circumference of an imaginary circle, the diameter of which is slightly larger than the diameter of the portion of the operating rod acting anthe contact spring, and the protuberances slide along the fixed contact when the contact spring is depressed.

2. A push-button switch as claimed in claim 1, wherein the stationary contact is a f ixed contact and is in the form of circular disc which is provided with a pin for extending through an opening in the printed circuit board and for secure soldering to a conductor path.

3. A push-button switch as claimed in claim 1 or 2, wherein the diameter of the circular disc forming the stationary contact is slightly larger than the diameter of the imaginary circle around which the conical or other protuberances of the contact spring are disposed.

4. A push-button switch as claimed in claims 1 to 3, wherein four conical protuberances are provided and are spaced from one another at an angle of 90 0 subtended at the centre of the imaginary circle.

5. A push-button switch as claimed in claims 1 to 4, wherein soldering projections or lugs are provided on the edge of the 1k dame-shaped contact spring, such lugs engaging in or extending into openings in the printed circuit board and forming connection contacts.

6. A push-button switch as claimed in claims 1 to 5, wherein the deme of the contact spring is formed in a rectangular sheet metal strip, which is located on the printed circuit board, and such dome extends to the two edges of the sheet metal strip to form, with the printed circuit board, lateral slots through which the current supply to the stationary contact below the cupola;-passes.

7. A push-button switch as claimed in claims 1 to 6, wherein a plurality of cupolas or danes are provided on the sheet metal strip.

8. A push-button or like switch substantially as herein described wiLh reference to the accompanying drawings.