GB2052866A

GB2052866A - Electric switch

Info

Publication number: GB2052866A
Application number: GB7915481A
Authority: GB
Original assignee: Hoover Ltd
Current assignee: Hoover Ltd
Priority date: 1979-05-03
Filing date: 1979-05-03
Publication date: 1981-01-28
Also published as: IT1127455B; FR2455788B1; FR2455788A1; AU542837B2; DE3016995A1; AU5784880A; IT8048570A0; GB2052866B

Abstract

A pair of contact plates 26, 28 support a bridging piece 60 which is moved by a rocker 44 via a spring 56 so as to slide as well as pivot on contact plate 26. The contact plate 28 has a turned over upper end with a very shallow- curved surface 33 with which the bridging piece makes tangential contact. The bridging piece 60 is of shallow V-form and is arranged to make (Fig. 6) and break (Fig. 5) contact at different regions (82, 84 and 79, 80) of the bridging piece and the plate 28, both regions being displaced from the contact region 74 of the stable position shown in Fig. 1. <IMAGE>

Description

SPECIFICATION Switches This invention relates to electric switches and is concerned with the design of an extremely simple and inexpensive construction which nevertheless has excellent characteristics, particularly from the points of view of compactness, current capacity and maintaining corrosion-free contacts.

The present applicant's British patent application 46667/77 has a number of embodiments of switch wherein a bridging piece is moved by means of a rocker with the interposition of a coil spring. The bridging piece in an on/off switch bridges a pair of contact elements in the on position, but by a combination of sliding and rotary movements, is caused to move to an off position. Specifically, the bridging piece is of shallow V-form.

Switches of this type have considerable advantages over prior switches but the present invention develops the embodiments of that prior application further with further advantageous results.

According to one aspect of the present invention, an electric switch includes at least two contact elements, a bridging piece operative regions of one side of which contact operative regions of two of the contact elements in a stable operative position of the bridging piece, and an actuator to move the bridging piece between its operative position and another stable position, making and/or breaking of contact between the bridging piece and one of the contact elements occurring at a surface region or regions of the one contact element and a surface region or regions of the bridging piece which are different from the operative regions.

According to another aspect of the present invention, a switch includes at least two contact elements, a bridging piece of shallow Vform, the limbs of which on one side subtend an angle of less than 180 facging away from the contact elements, whilst operative regions of the opposite surface of the bridging piece contact operative regions of two of the contact elements in a stable operative position of the bridging piece, and an actuator to move the bridging piece between its operative position and another stable position, the actuator including a rocker member which is interconnected with the bridging piece by means of a coil spring, one end of which is carried by the rocker member, making and breaking of contact between the bridging piece and one of the contact elements occurring at a surface region or regions of the one contact element and a surface region or regions of the bridging piece which are different from the operative regions.

After making contact with the contact element, the bridging piece preferably moves relatively to the one contact element such that it comes to rest in the operative position with further surface regions of the bridging piece and contact element then in contact, these regions being different from the making and breaking surface regions. Specifically, the one contact element may comprise a plate having a portion extending substantially parallel to the other contact element, and the one contact element having said surface regions disposed on an end of the plate which is turned over towards the other contact, and in this case the surface regions of the one contact element are conveniently formed by a shallow curved surface with which the bridging piece is in tangential contact.

According to another aspect of the present invention, an electric switch includes at least two contact elements, a bridging piece of shallow V-form, the limbs of which on one side subtend an angle of less than 180 facing away from the contact elements, whilst operative regions of the opposite surface of the bridging piece contact two of the contact elements in an operative position of the bridging piece, and an actuator to move the bridging piece to and from its operative position, the actuator including a rocker member which is interconnected with the bridging piece by means of a coil spring, one end of which is carried by the rocker member, and breaking of contact between the bridging piece and one of the contact elements occurring at surface regions of the bridging piece and the one contact element which are different from the operative regions.

According to yet another aspect of the present invention, an electric switch includes at least two contact elements, a bridging piece of shallow V-form the limbs of which on one side subtend an angle of less than 180 facing away from the contact elements whilst operative regions of the opposite surface of the bridging piece contact operative regions of two of the contact elements in an operative position of the bridging piece, and an actuator to move the bridging piece to and from its operative position, the actuator including a rocker member which is interconnected with the bridging piece by means of a coil spring, one end of which is carried by the rocker member, making of contact between the bridging piece and one of the contact elements occurring at surface regions of the bridging piece and the one contact element which are different from the operative regions.

Preferably the operative region of the other contact element wipes the operative region of the bridging piece when the bridging piece moves from its operative position to the other stable position.

The invention may be carried into practice in a number of ways but one specific embodiment will now be described, by way of example, with reference to the accompanying draw ings, in which: Figure 1 is a sectional side elevation through a rocker-type switch according to the invention, Figure 2 is a side elevation of the bridging piece of the switch of Fig. 1, Figure 3 is an under plan view of the bridging piece shown in Fig. 2, Figure 4 is a sectional end elevation on the line A-A of Fig. 2, Figure 5 is a scrap sectional side elevation of the switch of Fig. 1 with the bridging piece in a break position, i.e., just before it moves to an open position, Figure 6 is a view similar to Fig. 5 with the bridging piece in a make position, i.e., just before it moves to a closed position, Figure 7 is an end elevation of one contact element, and Figure 8 is a side elevation of the element of Fig. 7.

Referring to Fig. 1, this shows an on-off switch which includes a moulded plastics housing 10 having a side wall 11 terminating at its upper end in an outward flange 1 2. The moulding includes a base 14 and a pair of flaps 1 6 which, in their relaxes position shown in the drawing, project laterally beyond the flange 1 2 but which can be pressed towards the side wall 11 when the switch, as a whole, is inserted into a socket in a machine. At this time, the flaps 1 6 bend around their lower ends to lie closely along the side walls 11.

The base 14, which is also capable of providing for a changeover switch, as distinct from the on-off switch shown in Fig. 1, has extending through it a pair of metallic plates 26 and 28. The plate 28 is shown in detail in Figs. 7 and 8. These plates pass through vertical apertures 32 formed in the base 14 of the moulding, these apertures each having an enlarged lower end 34 to receive a sprag 36 struck out from the associated plate 26 or 28.

The plate 26 has a rounded upper end 30, which, as will be described, forms a fulcrum for a bridging piece generally shown at 60 which will be described in detail later. In contrast to the rounded end 30 of the plate 26, the upper end of the plate 28 is curved in the manner shown in Fig. 8 so that it extends towards the first plate 26. The upper surface of the curved portion of the plate 28 includes a relatively sharply curved corner 31 (radius = 0.9 mm) whilst the remainder of the surface 33 has a shallow curvature (radius = 15.0 mm).

Located in the upper part of the space formed within the moulding 10 is a rocker 44 having on its underside a central downwardly projecting stem 50. The lower end of the stem 50 has a counterbore 52, the upper end of which has located within it a stud 54, for retaining the upper end of a coil spring 56 during assembly. It is to be observed that the spring has minimum working clearance in the bore 52 and the last two to three coils of the spring 56 normally project below the lower end 58 of the stem 50. The underside of the lowermost coil of the spring is ground substantially flat.

Figs. 2-4 illustrate the particular form of the bridging piece 60 which is made, in this embodiment, of hard cadmium copper. The bridging piece 60 is of generally shallow Vform, having two limbs 61 and 62, the upper faces of which, in this embodiment, subtend an angle between them of approximately 152". This angle can vary according to requirements, but is preferably between 140 and 175 . Referring to Fig. 3, the main sides 63 of the bridging piece are substantially parallel and end portions 64 are stepped inwardly at 65 in order to clear vertically extending pillars 66 of the housing 10.

Struck out from the central portion of the bridging piece 60 is a vertically upstanding inverted tab 68, the sides of which taper upwards and inwards to a curved upper edge, as shown in Fig. 4. On each side of the tab 68 there is stuck out inverted V-form abutment 70 on the apices of which the lower end of the spring 56 acts as shown in Fig. 1.

The bridging piece 60 has two stationary positions, one of which is shown in Fig. 1, in which it bridges the plates 26 and 28 to place the switch in an on condition. In the other of the positions, the bridging piece extends between the plate 26 and a sloping surface 72 of the housing. The ends of the undersides of the bridging piece are chamfered at 73 in order not to dig into the plastics material in the region 72. Where the switch is a changeover switch, the plate 28 will be duplicated on the left hand side and the bridging piece will then have two operative positions in which it bridges the central plate 26 and one or other of the outer plates 28.

As illustrated in Fig. 1, between two and three coils of the lower end of the spring 56 extend beyond the counterbore 52 and these coils are therefore capable of deflecting out of the general axial line of the spring within the remainder of the counterbore 52. In the stable position of Fig. 1, the spring 56 is exerting a downward force on the bridging piece via the apices of the V-form abutment 70. The line of action of the spring is quite close to the end of the turned over upper end of the plate 28 and thus relatively close to the region of contact 74 between the bridging piece and the plate 28. This ensures a good pressure between the bridging piece and the plate to maintain contact.

The rocker 44 has a skirt 82 which engages one or other of two shoulders 84 formed within the housing 10 to limit the movement of the rocker from one position to the other.

When it is desired to move the bridging piece 60 to the off position, pressure is applied to the right hand side of the rocker 44 to move it downwards about its pivot 42. This in turn rotates the spring bodily about the pivot 42 and since the relative dimensions of the interior of the spring and the tab 68 provide for slight lost motion between these parts, the spring engages the right hand side of the tab 68 of the bridging piece and initially moves the bridging piece bodily to the left in Fig. 1 while still maintaining contact between it and the turned over end of the plate 28. The bridging piece always lies tangential to the plate 28 and there is a combined rolling and sliding movement.Eventually the position of Fig. 5 is reached, at which time the point of tangential contact 81 of the bridging piece on the fulcrum 30 has moved closer to the apex 63 of the bridging piece, whereafter the bridging piece rotates about the fulcrum 30, Fig. 5 indicating the instant at which this rotation takes place. At the moment of separation the bridging piece is lying tangential to the shallow curved surface at the point 77.

Thus separation of the bridging piece from the turned over end of the plate 28 occurs at the region 79 of the bridging piece and the region 80 of the plate 28.

Considering now the closing movement of the bridging piece, the bridging piece will move progressively to the right and rotate in a clockwise direction until the moment of contact is reached, which is shown in Fig. 6. It is to be noted when making contact occurs, the bridging piece 60 is lying tangential to the shallow curved surface of the plate 28 at the point 83 and contact is occurring between a region 82 of the bridging piece and a region 84 of the plate 28, these regions being different from those in which final contact occurs as shown in Fig. 1.

Consequently this construction has the very distinct advantage that the making and breaking regions of contact are different from the regions of contact which exist when the switch reaches its stable position of Fig. 1.

Accordingly any pitting or deposits which occur at the regions of breaking do not interfere with contact between the parts in the stable on position.

It is also to be noted that in moving from the just-make position of Fig. 6, to the static position of Fig. 1, the bridging piece 60 slides over the surface of the turned over end of the plate 28 in the region 80 at which separation takes place in Fig. 5. This wiping action assists considerably in keeping the bridging piece and upper end of the plate 28 clear of deposits in the break regions. Also, the rounded upper end 30 of the plate 26 wipes the region of contact 74 when the bridging piece passes to the left and the left hand end of the bridging piece comes to rest on the surface 72 of the housing 10.

Claims

1. An electric switch including at least two contact elements, a bridging piece operative regions of one side of which contact operative regions of two of the contact elements in a stable operative position of the bridging piece, and an actuator to move the bridging piece between its operative position and another stable position, making and/or breaking of contact between the bridging piece and one of the contact elements occurring at a surface region or regions of the one contact element and a surface region or regions of the bridging piece which are different from the operative regions.

2. An electric switch including at least two contact elements, a bridging piece of shallow V-form, the limbs of which on one side subtend an angle of less than 180 facing away from the contact elements, whilst operative regions of the opposite surface of the bridging piece contact operative regions of two of the contact elements in a stable operative position of the bridging piece, and an actuator to move the bridging piece between its operative position and another stable position, the actuator including a rocker member which is interconnected with the bridging piece by means of a coil spring, one end of which is carried by the rocker member, making and breaking of contact between the bridging piece and one of the contact elements occurring at a surface region or regions of the one contact element and a surface region or regions of the bridging piece which are different from the operative regions.

3. A switch as claimed in Claim 1 or Claim 2 in which the one contact element comprises a plate having a portion extending substantially parallel to the other contact element, and the one contact element having said surface regions disposed on an end of the plate which is turned over towards the other contact.

4. A switch as claimed in Claim 3 in which the surface regions of the one contact element are formed by a shallow curved surface with which the bridging piece is in tangential contact.

5. An electric switch including at least two contact elements, a bridging piece of shallow V-form the limbs of which on one side subtend an angle of less than 180 facing away from the contact elements whilst operative regions of the opposite surface of the bridging piece contact operative regions of two of the contact elements in an operative position of the bridging piece, and an actuator to move the bridging piece to and from its operative position, the actuator including a rocker member which is interconnected with the bridging piece by means of a coil spring, one end of which is carried by the rocker member, making of contact between the bridging piece and one of the contact elements occurring at surface regions of the bridging piece and the one contact element which are different from the operative regions.

6. An electric switch including at least two contact elements, a bridging piece of shallow V-form, the limbs of which on one side subtend an angle of less than 180 facing away from the contact elements, whilst operative regions of the opposite surface of the bridging piece contact two of the contact elements in an operative position of the bridging piece, and an actuator to move the bridging piece to and from its operative position, the actuator including a rocker member which is interconnected with the bridging piece by means of a coil spring, one end of which is carried by the rocker member, and breaking of contact between the bridging piece and one of the contact elements occurring at surface regions of the bridging piece and the one contact element which are different from the operative regions.

7. An electric switch as claimed in any one of the preceding claims in which the operative region of the other contact element wipes the operative region of the bridging piece when the bridging piece moves from its operative position to the other stable position.

8. An electric switch substantially as specifically described herein with reference to the accompanying drawings.