GB1568584A - Snap action switches - Google Patents

Description

(54) SNAP-ACTION SWITCHES (71) We, BURGESS MICRO SWITCH ANY LED, a British Company, of Dukes Way, Team Valley, Gateshead, Tyne dt Wear, NEll OUB, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to snap-action switches and more particularly to such switches of the over-centring type.

Heretofore it has been common practice to provide a combination of a light-emitting diode and a photo-sensitive transistor to control the state of an associated solid state circuit, a vane or like member being movable into and out of a position between the diode and the transistor to interrupt the beam of light from the said diode which is normally directed onto said transistor.

However the speed of movement of vanes in known arrangements is relatively slow, with the result that the change in state of the transistor is gradual rather than instantaneous. Such a problem has been overcome to a certain extent by applying a reference voltage to the transistor such that the switch-over is effected at a pre-determined intensity, but this requires the provision of additional electronic equipment.

According to the present invention there is provided a snap-action switch comprising a housing containing a snapaction mechanism having a movable member displaceable from a rest position to a fully displaced position, the housing further containing a light-emitting semi-conductor device positioned to direct a beam of light onto a photosensitive semiconductor device within the housing, the arangement being such that, on snapaction of said movable member from its rest position to its fully displaced position, a portion of said member is brought into a position between said devices to interrupt said beam of light whereby the electrical state of the photosensitive device is changed.

Thus it will be appreciated that the snapaction mechanism of such a switch provides a purely mechanical trigger for effecting the desired change in electrical state of a circuit associated with the photosensitive device, said trigger being movable at a substantially greater speed than in known arrangements.

By way of example only, an embodiment of the invention will now be described in greater detail with reference to the drawing accompanying the provisional specification which shows the internal mechanism of a snap-action switch according to the invention.

Referring to the drawing, the basic snapaction mechanism of the illustrated switch is of well-established construction, comprising an anchor member indicated generally at 2 fixed within a housing 4, and a movable member 6 one end of which seats in notches 8 formed in front legs 10 of the anchor member 2, said member 2 thereby constituting support means for the member 6. A coil spring 12 has one end connected to the upwardly extending rear end 14 of the anchor member 2 and its other end hooked into an aperture in the movable member 6, said spring thereby urging the one end of the member 6 into bearing engagement with the notches 8 in the anchor member 2. Such an arrangement provides a pivotal connection between the members 2 and 6.

Slideably mounted in the housing 4 to engage with the spring 12 at a region inter mediate the legs 10 and the rear end 14 of the anchor member 2 is an operating button 16, said button projecting from the housing whereby depression thereof by external means deflects the spring 12 so that the centre-line of the forward portion of the spring is moved downwardly below the line joining its point of engagement with the member 6 and the point of engagement of the member 6 with the notches 8. This over-centring movement causes a downward snap-action of the member 6 about its pivotal connection at 8 whereby said member 6 moves from its rest position shown in dotted lines in the drawing to a displaced position shown in full lines in the drawing.

On release of the button 16, the spring 12 returns to its original position and the member 6 returns to its rest position.

More particularly the movable member 6 includes a main portion 18 the one end of which seats in the notches 8 and from the other end of which depends, at rightangles thereto, a vane portion 20 integral with but bent over from said main portion 18. The rest position of the member 6 is determined by abutment of the angle between the portion 18 and the portion 20 with a first stop 22 within the housing 4, while the displaced position of the member 6 is determined by abutment of the free end of the portion 20 with a further stop 24 within said housing.

Two pairs of terminal arms 26, 28 project from the housing 4 which is opaque.

Within said opaque housing, a light-emitting diode 30 is mounted on said arms 26.

The diode 30, in the form of a semiconductive chip, is housed within a transparent plastics sheath 32 secured on the arms 26 with the chip electrically conneo ted between said arms 26. A photosensitive transistor 34 housed within a further transparent plastics sheath 36 is mounted on to be in electrically-conducting relationship with, the terminal arms 28. The diode 30 and transistor 34 are positioned such that a beam of light emitted from the energised diode 30 is normally incident on the photosensitive transistor 34.

In the above-mentioned rest position of the movable member 6, the vane portion 20 thereof is located above and out of the path of the light beam from the diode 30 to the transistor 34. On operation of the mechanism, however, the movable member 6 snaps into its displaced position in which the vane portion 20 is interposed between the diode 30 and the transistor 34 to interrupt the beam of light in its passage to said transistor. Thus the state of the photosensitive transistor is changed, the changeover taking place rapidly and in accordance with the speed of movement of the member 6 to its displaced position. Clearly the change in state of the transistor 34 will be transmitted to associated solid state equipment.

Switches according to the invention provide interfaces between mechanical movements and solid state control systems, the snap-action mechanisms, having no electrical loads thereon, not being subject to electrical wear, and therefore being very accurate over a large number of operations.

It will be appreciated that the invention extends to switches incorporating snap-action mechanisms diferent from that shown in the drawing, although the preferred application of the invention is in subminiature switches of the illustrated type.

WHAT WE CLAIM IS:- 1. A snap-action switch comprising a housing containing a snap-action mechanism having a movable member displaceable from a rest position to a fully displaced position, the housing further containing a light-emitting semi-conductor device position to direct a beam of light onto a photosensitive semi-conductor device within the housing, the arrangement being such that, in use and on snap-action of said movable member from its rest position to its fully displaced position, a portion of said member is brought into a position between said devices to interrupt said beam of light whereby the electrical state of the photosensitive device is changed.

2. A snap-action switch as claimed in claim 1 in which the light-emitting device comprises a light-emitting diode housed within a transparent plastics sheath.

3. A snap-action switch as claimed in claim 1 or claim 2 in which the photosensitive device comprises a photosensitive transistor housed within a transparent plastics sheath.

4. A snap-action switch as claimed in any one of claims 1 to 3 in which the movable member includes a main portion a free end of which is resiliently urged against, for pivotal movement on, support means of the snap-action mechanism, and a vane portion depending from the other end of said main portion, the rest position of the movable member being determined by abutent of the angle between the main portion and the vane portion with a first stop member in the housing and the fully displaced position of the movable member being determined by abutment of the free end of

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (5)

**WARNING** start of CLMS field may overlap end of DESC **. mediate the legs 10 and the rear end 14 of the anchor member 2 is an operating button 16, said button projecting from the housing whereby depression thereof by external means deflects the spring 12 so that the centre-line of the forward portion of the spring is moved downwardly below the line joining its point of engagement with the member 6 and the point of engagement of the member 6 with the notches 8. This over-centring movement causes a downward snap-action of the member 6 about its pivotal connection at 8 whereby said member 6 moves from its rest position shown in dotted lines in the drawing to a displaced position shown in full lines in the drawing. On release of the button 16, the spring 12 returns to its original position and the member 6 returns to its rest position. More particularly the movable member 6 includes a main portion 18 the one end of which seats in the notches 8 and from the other end of which depends, at rightangles thereto, a vane portion 20 integral with but bent over from said main portion 18. The rest position of the member 6 is determined by abutment of the angle between the portion 18 and the portion 20 with a first stop 22 within the housing 4, while the displaced position of the member 6 is determined by abutment of the free end of the portion 20 with a further stop 24 within said housing. Two pairs of terminal arms 26, 28 project from the housing 4 which is opaque. Within said opaque housing, a light-emitting diode 30 is mounted on said arms 26. The diode 30, in the form of a semiconductive chip, is housed within a transparent plastics sheath 32 secured on the arms 26 with the chip electrically conneo ted between said arms 26. A photosensitive transistor 34 housed within a further transparent plastics sheath 36 is mounted on to be in electrically-conducting relationship with, the terminal arms 28. The diode 30 and transistor 34 are positioned such that a beam of light emitted from the energised diode 30 is normally incident on the photosensitive transistor 34. In the above-mentioned rest position of the movable member 6, the vane portion 20 thereof is located above and out of the path of the light beam from the diode 30 to the transistor 34. On operation of the mechanism, however, the movable member 6 snaps into its displaced position in which the vane portion 20 is interposed between the diode 30 and the transistor 34 to interrupt the beam of light in its passage to said transistor. Thus the state of the photosensitive transistor is changed, the changeover taking place rapidly and in accordance with the speed of movement of the member 6 to its displaced position. Clearly the change in state of the transistor 34 will be transmitted to associated solid state equipment. Switches according to the invention provide interfaces between mechanical movements and solid state control systems, the snap-action mechanisms, having no electrical loads thereon, not being subject to electrical wear, and therefore being very accurate over a large number of operations. It will be appreciated that the invention extends to switches incorporating snap-action mechanisms diferent from that shown in the drawing, although the preferred application of the invention is in subminiature switches of the illustrated type. WHAT WE CLAIM IS:-

1. A snap-action switch comprising a housing containing a snap-action mechanism having a movable member displaceable from a rest position to a fully displaced position, the housing further containing a light-emitting semi-conductor device position to direct a beam of light onto a photosensitive semi-conductor device within the housing, the arrangement being such that, in use and on snap-action of said movable member from its rest position to its fully displaced position, a portion of said member is brought into a position between said devices to interrupt said beam of light whereby the electrical state of the photosensitive device is changed.

2. A snap-action switch as claimed in claim 1 in which the light-emitting device comprises a light-emitting diode housed within a transparent plastics sheath.

3. A snap-action switch as claimed in claim 1 or claim 2 in which the photosensitive device comprises a photosensitive transistor housed within a transparent plastics sheath.

4. A snap-action switch as claimed in any one of claims 1 to 3 in which the movable member includes a main portion a free end of which is resiliently urged against, for pivotal movement on, support means of the snap-action mechanism, and a vane portion depending from the other end of said main portion, the rest position of the movable member being determined by abutent of the angle between the main portion and the vane portion with a first stop member in the housing and the fully displaced position of the movable member being determined by abutment of the free end of

the vane portion with a further stop member within the housing, said vane portion, in said fully displaced position of the movable member, being located between said devices.

5. A snap-action switch substantially as described with reference to and as illustrated by the drawing accompanying the provisional specification.