Switch Mounted On Printed Circuit Board

Abstract

A switch for use with a printed circuit board has a square cover body with flexible clamps for engaging the edges of a square aperture to hold the switch casing on the board. One push button version has a spring biased button moving a guiding rod alongside a contact operating peg for depressing a contact spring mounted on the board. A pivot mounted version has a spring biased detent mechanism operating over a V-shaped ridge for holding the contact operating peg in either a closed or open switch position. The switch elements are mounted on the printed circuit board, and the casing is positioned to operate the contacts.

Description

This invention has reference to electrical switches for inclusion in a circuit formed on or in a substrate material in sheet or block form. By the term `substrate material` is meant the material which mainly determines the physical properties -- principally rigidity -- of the combination of the material and the circuits formed on or in the material, examples of such `substrate materials` are the sheet of insulating material of a printed circuit board and the substrate material of an integrated circuit.

It has been known that hitherto to provide electrical switches for forming part of a circuit formed on or in substrate materials has had the disadvantage that the switches have required specially -- made mountings in order to connect the switch of the circuits on the circuit board. Such special mountings have resulted in the use of switches which were more complex in construction and more expensive to construct than the switches used in other applications.

The object of the present invention is to provide an electrical switch for forming part of a circuit formed on or in substrate material.

According to the present invention there is provided an electrical switch for forming part of a circuit formed on or in a substrate material, the switch including a contact assembly, the contact assembly being directly connected to the conducting material formed in or on the substrate material with one contact of the contact assembly being connected to one part of the conducting material and another contact of the contact assembly being connected to another part of the conducting material to form part of a circuit thereon or therein; means for mounting on the substrate material in close juxtaposition with the contact assembly, the mounting means directly attachable to the substrate material; and means to operate the contact assembly, the operating means being mounted on the mounting means.

Constructional embodiments will now be described, by way of example only, with reference to the accompanying drawings wherein:

FIG. 1 shows a front elevation of a first embodiment of an electrical switch made in accordance with the present invention;

FIG. 2 shows a plan view of the switch shown in FIG. 1;

FIG. 3 shows the underneath view of the switch shown in FIG. 2;

FIG. 4 shows a sectional front elevation of the switch shown in FIG. 1 with a section taken along the line A--A shown in FIG. 2;

FIG. 5 shows a sectioned front elevation of the switch shown in FIG. 1 with a section taken along the line B--B shown in FIG. 2;

FIG. 6 shows a partial view of the switch shown in FIG. 1 to show the attachment of the switch to the circuit board;

FIG. 7 shows a front elevation of a second embodiment of an electrical switch made in accordance with the present invention;

FIG. 8 shows a plan view of the switch shown in FIG. 7 with the pivotable switch top removed;

FIG. 9 shows a sectioned front elevation of the switch shown in FIG. 7 with a section taken along the line C--C shown in FIG. 8; and

FIG. 10 shows a sectioned front elevation of the switch shown in FIG. 7 with a section taken along the line D--D shown in FIG. 8.

The FIGS. 1 to 6 show a first embodiment of an electrical switch 1 which forms part of a circuit formed on a substrate material in the form of a printed circuit board 3. As shown in FIGS. 2 and 3, the switch 1 has a square cross-section in the plan view. The top of the switch projects through a square aperture 2 in a cover plate 4 which is positioned above and parallel to the circuit board 3. The switch 1 includes, as shown in FIGS. 2, 3 and 5, a contact assembly comprising one contact in the form of a contact 5 and another contact in the form of a contact spring 7. The contact 5, which is shaped in the form of a rivet and is made of silver graphite, is secured to the circuit board 3 by inserting the stem of the contact 5 through a hole 8, shown in FIG. 5 in the board 3. The projecting end of the stem is peened over and may be soldered to electrically connect the contact 5 to a one part 9 of a printed circuit carried on the circuit board 3. The contact spring 7 is made of phosphor bronze and is shaped in the form of hook with a short arm at one end and a double set at the other end of the long arm. The contact spring 7 also has two tags 11 which are diagonally opposite on the short arm and project normally from the short arm. The tags 11 are inserted through holes 12 in the board 3 are crimped to the board 3 and are then soldered to another part 13 of the printed circuit carried on the circuit board 3.

The switch 1 also includes a mounting maens in the form of a casing 15 and an operating means for the contact assembly in the form of a key assembly 17 which is described later.

The casing 15 is in the shape of a square box which is open at the lower largest face and is made of a synthetic plastics material called Kamatel (Registered Trade Mark) other synthetic plastics material, for example, Nylon (Registered Trade Mark) could be used to make the casing 15. The casig 15 is attached to the circuit board 3 to enclose the contact assembly by means of three resilient tags 19 formed on opposite side faces of the casing 15 (one on one side face and two on the other side face as shown in plan view in FIGS. 2 and 3 and partly shown in front elevation in FIGS. 1,4,5 and 6. A side elevation of one the tags 19 is shown in FIG. 6 in which it is shown that the tag 19 has a tapered edge 21 which leads to a recess 23 whose width is equal to the thickness of the circuit board 3. As shown in FIGS. 2 and 3, the circuit board 3 has three rectangular slots 25 which are so positioned that the three tags 19 on the casing 15 are flexed inwards from their original, i.e., unflexed, position by the action of the tapered edges 21 of the tags 19 against the sides of the slots 25 until the tapered edges 21 are out of the slots 25 and the recesses 23 are aligned with sides of the slots 25 in the circuit board 3. When the recesses 23 and the sides of the slots 25 in the circuit board 3 are aligned, the tags 19 flex back back to their original positions so that the recesses 23 engage the circuit board 3 as shown in FIG. 6.

The casing 15 has a flanged bore 27 and an aperture 29 in an symmetric position on the upper largest face 24 opposite the open lower largest face. The outer flange of the flanged bore 27 has a pair of extension plates 31 situated with the aperture 29 between the extension plates 31. The largest face 24 also has a annular groove 33 to retain a helical spring as herein after described. The inner flange of the flanged bore 27 projects through a hole 34 in the circuit board 3, when the casing 15 is attached to the circuit board 3.

The key assembly 17 includes a key button 35 with a concave and chamfered top face of a well-known type. The key button 35 is made of a synthetic plastics material. The bottom face of the key button 35 has circular depression 36 whose diameter corresponds to the outer diameter of the groove 33 in the upper largest face 24 of the casing 15; an integral rod 39 in a position within the circular depression 36 corresponding to the flanged bore 27 in the upper face 24 of the casing 15; and a contact-operating-member in the form of an integral peg 41 in a position in the circular depression corresponding to the aperture 29 in the upper face 24 of the casing 15. The key assembly 17 also includes a helical spring 43 made of spring steel. The key button 35 is resiliently mounted on the casing 15 by engaging the spring 43 in the annular grooves 35 and the depression 36, by engaging the rod 39 and by slidably mounting the peg 41 of the key button 35 in the flanged bore 27 and in the aperture 29 respectively of the casing 15 to prevent rotation of the key button 35 with respect to the casing 15. The key button 35 is then depressed to compress the helical spring 43 and to cause the end of the integral rod 39 to project from the inner flange of the flanged bore 27. The projecting end of the integral rod 39 is then moulded into a flange 42. When the flange is removed from the mould (not shown) and the key button 35 is released, the helical spring 43 urges the key button 35 away from the casing 15 and the flange 42 of the integral rod 39 abuts the inner flange of flanged bore 27. When the casing 15 is attached to the circuit board 3, the integral peg 41 on the key button 35 is situated above the contact spring 7 of the contact assembly on the circuit board 3.

In operation the key button 35 is depressed to cause the integral peg 41 to pass through the aperture 29 in the casing 15 so as to push the contact spring 7 into contact with the contact 5. The contact spring 7 bows under the action of the peg 41 so that the end of the contact spring 7 is `wiped` across the contact 5. The movement of the key button 35 causes the helical spring 43 to be compressed and also causes the peg 41 to project through the bore 29 to keep the key button 35 in alignment with the casing 15. When the key button 35 is released, the helical spring 43, and to a certain extent the contact spring 7, return the key button 35 to the initial position where the flange 42 of the integral rod 39 abuts the inner flange of the flanged bore 27.

The FIGS. 7 to 10 shown an electrical switch 1' which is a second embodiment of an electrical switch 1 and which forms part of a circuit formed on a substrate material in the form of a printed circuit board 3. In this second embodiment the contact assembly comprising the contact 5 and the contact spring 7 are the same as those in the first embodiment. The contact assembly is covered by a casing 15' which is attached to the circuit board 3 in the same manner as the casing 15 of the first embodiment. The casing 15' is interchangable with the casing 15.

The casing 15' has an open top to which is pivotably mounted a contact -- operating means in the form of a cranked switch top 45 having an integral contact arm 47 and an indexing means hereinafter described. The casing 15' has two projections 44 at opposite ends of the casing 15. The projections 44 have respective pips 46. The switch top 45 has two recesses (not shown) which are in corresponding positions to the projections 44 in the casing 15'. The projections engage in holes 48 (FIG. 7 -- only one shown) so that the switch top 45 is pivotably mounted on the casing 15'. The contact arm 47 has a contact-operating members in the form of a curved contact rib 49 in the shaped of a saw tooth which projects through an aperture 51 (FIGS. 8 and 9) in the upper largest face 24' in the casing 15' so as to be situated above the contact assembly, when the switch 1' is attached to the circuit board 3. As shown in FIG. 9, the contact arm 47 abuts the contact spring 7 in the `made` position of the switch top 45 to allow the contact to cause a `wiping` action between the end of the contact spring 7 and the contact 5. The position of the contact spring 7, when the switch is in the `rest` position with the contact arm of the switch top 45 abutting the casing 15', is shown in dotted outline in FIG. 9.

The indexing means for holding the switch top 45 in either the `made` or the `rest` position is in the form of a spring-loaded plunger which is integral with the switch top 45 and which co-operates with a ridged recess in the casing 15'. As shown in greater detail in FIG. 10, the switch top 45 has an integral boss 52 with a blind bore 53. In the blind bore 53 is situated a helical spring 55 one end of which is situated in a blind bore 57 in one end of a cylindrical plunger 60 having a rounded other end. The plunger 60 is made of a synthetic plastic material, for example Nylon (Registered Trade Mark). The rounded end of the plunger 60 projects into a recess 62 in the casing 15' (shown in plan view in FIG. 8) having a transverse V-shaped ridge 64, which divides the recess 62 into two parts. The rounded end of the plunger 60 abuts the side of the ridge remote from the side where the switch top 45 abuts the casing 15' so as to index or latch the switch top 45, in the position concerned and prevent movement out of that position. Depression of the raised part of the switch top 45 causes the plunger 60 to move into the bore 53 of the boss 52 under the pressure exerted by the ridge 64 when the rounded end of the plunger 60 passes over the crest of the ridge 64, the switch top 45 is held by the plunger 60 and the side of the ridge 64 in the other position.

The switch shown in the second embodiment can therefore act as an on -- off switch or as a switch that is latchable in either contact position.

The switches shown can be used on integrated circuit as well as printed circuit board.

The contact assembly can include multi-way and rotary switch applications.

The switch shown as the second embodiment in FIGS. 7 to 10 can be used as an on - off switch for mains voltage.

Claims

What we claim is:

1. An electrical switch for printed circuits comprising in combination, a circuit substrate having switch mounting aperture structure defined therein, a pair of electrically conductive circuits on said substrate, a switch contact assembly having a stationary contact affixed to one of said electrically conductive circuits and a movable contact element in the form of an elongated resilient member affixed at one end to the other one of said electrically conductive circuits in a position that the unconnected end is disposed adjacent to and spaced from said stationary contact to be moved into contact therewith by flexing of said resilient member, a switch casing assembly mounted on said substrate by mounting means engaging said mounting aperture structure and enclosing said switch contact assembly, manually movable contact operating means with a movable member disposed to bend said unconnected end of said movable switch contact element into said stationary contact to operate the switch contact assembly between open and closed switch positions between said pair of electrical circuits on said substrate, and mounting means holding said manually movable means on said casing assembly with said movable member in position to move said movable switch contact element in a wiping motion with said stationary contact.

2. A switch according to claim 1, wherein the substrate material is in the form of a sheet and said mounting means includes flexible tags for engaging the substrate at said aperture structure; and wherein the aperture structure in the substrate material comprises a plurality of slots; and wherein the tags of the mounting means are made of a resilient material and have a tapered edge which lead to a recess whose width is equal to the thickness of the substrate material at the side of the slots so that when the tags are inserted into respective apertures, the tapered edges of the tags being so positioned to act against the sides of the slots to flex the tags from their unflexed positions until the recesses are aligned with the sides of the slots, whereupon the tags flex back to their unflexed positions so that the recesses thereon engage the sides of the slots and the substrate material adjacent thereto.

3. A switch as defined in claim 1, wherein said movable contact operating member comprises a post and said substrate defines a guiding bore for defining a movement path therewith, and a separate peg member movable with said post that abuts the position of said movable contact element.

4. A switch as defined in claim 1 including an aperture in said substrate near the switch contact assembly and means movable with the contact operating means passing through said aperture.

5. A switch as defined in claim 1 wherein said movable contact operating means comprises a switch top member pivoted on said mounting means to move between two stable positions with structure flexing said movable contact element as said swtich top member is pivoted to close said switch in one of said two stable positions.

6. A switch as defined in claim 5, including indexing means for holding said switch top member in either of said two stable positions comprising a ridge member affixed to said mounting means, and a spring biased plunger assembly movable with said contact arm to engage said ridge member so that it passes over the crest of the ridge as the switch top member is pivoted from one position to the other.