GB2120014A - Electrical switch - Google Patents

Abstract

A switch comprises a housing 11 in which is disposed fixed contact means and a slider 10 which carries movable contact means 27, 28 and which is mounted for slidable movement within the housing 11. The slider 10 (or the housing 11) is formed as a synthetic resin moulding which has integrally moulded therewith at least one projecting resilient finger 17, 18 which is/are engageable, during movement of the slider relative to the housing, with abutment means 25, 26 formed in the housing 11 (or on the slider 10). The inter-engagement of the or each resilient finger and the associated abutment serves to flex and stress the finger so that after the finger and the abutment are disengaged the finger will recover its original unflexed position and in so doing will release energy stored during the flexing and thereby cause relatively rapid movement of the slider 10 relative to the housing 11 between positions represented by an "on" position of the switch and an "off" position thereof. <IMAGE>

Description

SPECIFICATION Switch This invention relates to a switch of the kind which is commonly referred to as a slider switch. Such a switch may be used to control the operation of electrically actuated tools such as drills, saws, hedge trimmers and other tools. In one known form of such a switch two springs are employed, one spring being used to bias the switch towards its inoperative position and the other to act on a ball or roller bearing which can drop into a groove or notch as the switch is operated in order to store energy so that a fast contact is made, thereby reducing arcing and wear. In this kind of construction, the ball or roller bearing tends to wear away the edge of the groove or notch and the efficient operation of the switch is thereby impaired.Furthermore, particles of electrically conductive material may become trapped in grease used to lubricate the aforesaid ball or roller, thus causing a tracking path to become established. The object of the present invention therefore is to provide an improved switch which does not have the above-mentioned disadvantages.

In accordance with the invention there is provided a switch comprising a housing in which is disposed fixed contact means and a slider which carries movable contact means and which is mounted for slidable movement within the housing, one of the two components represented by the housing and the slider being formed as a synthetic resin moulding which has integrally moulded therewith at least one projecting resilient portion and the other component having abutment means which, during movement of the slider relative to the housing, is arranged to engage said projecting resilient portion to flex and stress it so that on disengagement of said abutment means and said portion the latter will deflect towards its unstressed position and thereby release the energy stored by the aforesaid flexing to cause the slider to move rapidly between the positions of electrical contact represented by an "on" position and an "off" position of the switch.

Conveniently, the slider is provided with the projecting resilient portion or portions which may comprise one or more resilient fingers.

The switch may also be provided with a slider locking member which is mounted on the housing so that its inner end can, by means of externally applied pressure, be displaced inwardly into the interior of the housing and into a slide-way in which the slider is mounted so as to be adapted to engage a part of the slider and prevent movement thereof relative to the housing, said inner end of the slider locking member being shaped so that it can be compressed whilst being pushed through an aperture formed in the wall of the housing whereafter said inner end expands outwardly behind the inner periphery of said aperture so as thereby to prevent separation of the slider locking member from the housing.

The invention will now be more particularly described with reference to the accompanying drawings wherein Figure 1 is an elevational view of part of one example of a switch constructed in accordance with the invention, the figure showing the slider of the switch and a part of the housing thereof, Figure 2 is a view of the aforesaid slider showing the opposite side to that shown in Fig. 1, Figure 3 is an end view of the slider, and Figure 4 is a part-sectional view of the slider locking member when assembled to that part of the switch housing seen in Fig. 1.

Referring now to the drawings the switch shown therein includes a slider which is formed as a moulding in a suitable synthetic resin material and which is generally indicated by reference numeral 10. There is also pro- vided a housing which is formed in two parts, each part also being formed as a synthetic resin moulding and one of such parts being generally indicated in the drawings by reference numeral 11. The slider 10 is arranged so that its inner end is located in a slide-way 1 2 formed in the housing part 11, the opposite or outer end of said slider having an enlarged head 1 3 which can be engaged by the user of a tool or other equipment which the switch is intended to control.

There is also provided a coiled return spring 1 4 which at one end enters into a bore 1 5 formed in the inner end of said slider and which at its other end bears against the adjacent end of said slide-way 1 2 so that said slider will be urged by the spring 1 4 into the position shown in Fig. 1 in which the face 1 6 of said slider is spaced from said adjacent end of the slide-way 1 2.

The slider 10 is also formed, as an integral part of the moulding, with at least one and, as shown, two projecting portions 1 7 and 1 8 which each form a finger which, by the nature of the synthetic resin material used for the moulding of the slider, is resilient. Furthermore, as shown, each of said projecting resilient fingers is shaped at its free end to a rounded configuration.

On each side of said slide-way 1 2 formed in the housing part 11 there is provided an abutment 1 9 or 20 formed by a shoulder projecting into the slide-way. Proceeding along the slide-way in a direction away from the aforesaid end on which said coil spring 1 4 bears the width of the slide-way increases along portions indicated by reference numerals 21 and 22 and then decreases along portions indicated by reference numerals 23 and 24. Furthermore said portions 23 and 24 terminate in further abutments indicated by reference numerals 25 and 26.

In the position of the slider shown in Fig. 1 said resilient fingers 1 7 and 1 8 are in positions in which their rounded free ends are situated above (as seen in Fig. 1) the abutments 25 and 26 so that if said slider 10 is pushed downwardly in order to compress the coil spring 14 said two fingers 1 7 and 1 8 will be flexed inwardly in order that they can pass between the abutments 25 and 26 but having passed through said abutment the width of said slide-way 1 2 will of course increase between the portions 23 and 24 as the slider is moving downwardly so that the fingers 1 7 and 1 8 can move towards their unstressed positions so that the stored energy generated by the fingers 1 7 and 1 8 flexing inwardly over the abutments 25 and 26 is released suddenly, causing the slider to move rapidly through the points of electrical contact so that difficulty would be experienced in holding the switch just on the point of contact-i.e. the switch will be either "positively" on or "positively" off. The slider 10 will then be in a position in which its inner end engages the adjacent end of the slide-way 1 2 whilst the rounded ends of the fingers 1 7 and 1 8 will be engaged behind the abutment 1 9 and 20.

The aforesaid spring 1 4 has the effect of biasing the slider 10 towards an off position when said slider is released, i.e. when it is not held downwardly by the user.

The housing also includes another part (not shown) in which fixed contacts are mounted and the slider also carries moveable contacts in the form of rollers 27 and 28 but the construction and assembly of these contacts do not form any part of the present invention.

There is also provided a slider locking member which is generally indicated by reference numerai 29 in Fig. 4. Said member is also conveniently formed as a synthetic resin moulding and it is mounted on said housing part 11 so that it projects outwardly from the exterior thereof, the outer end of said member 29 being formed to provide a button which can be pushed inwardly by the user. As shown in Fig. 4 the housing part 11 has a guide in the form of a cylindrical rim 30 which enters at its outer end into an annular recess 31 formed in the outer end of said member 29, there being provided a spring 32 which is located between the exterior of the housing part 11 and a shoulder 33 formed on the member 29 so as to tend to urge said member 29 in a direction outwardly away from the housing.

The inner end of said member 29 is enlarged as will be seen in Fig. 4 so as to provide a shoulder 34, said shoulder 34 being connected to a short length of generally cylindrical configuration which is itself connected to a tapered portion 35 which is arranged so that its minimum diameter is at the end of said member 29. The member 29 is formed of a material which is sufficiently resilient to permit said member to be assembled to the housing part 11 by pushing said tapered portion 35 through an aperture 36 formed in the housing part 11, said inner end of the member 29 being somewhat compressed during this process until the shoulder 34 moves inwardly past the interior periphery of said aperture 36 whereupon it will expand to become located behind said interior periphery of the aperture as shown in Fig. 4.The member 29 will thus be securely mounted in position on the housing part 11 and, as stated above, the spring 32 will normally keep said shoulder 34 in the position shown in Fig. 4.

However if it is desired to lock the slider in position and prevent it from being moved relative to the housing when it is in a position which corresponds to an on position of the switch the outer or button end of the member 29 can be pushed inwardly until the inner end 35 of said member 39 engages in a recess 37 formed in the slider between a face 38 and one end of a projection 39 moulded in the slider. A suitable latch will then be applied to hold said locking member 29 in its inner position and the slider will be retained in the on position until the latch is removed by depressing the portion 1 3 of slider 10 when the locking member will move outwardly under the influence of spring 32 to permit the slider to be moved to its upper or off position as shown in Fig. 1.

In the above described construction the projecting resilient portions in the form of the fingers 1 7 and 1 8 are shown as provided on the slider, co-acting abutments and other surfaces being moulded in the housing part. It is however to be understood that if desired said resilient fingers can be moulded in the housing part with the co-acting abutments and other surfaces being provided on the slider.

Claims (5)

1. A switch comprising a housing in which is disposed fixed contact means and a slider which carries movable contact means and which is mounted for slidable movement within the housing, one of the two components represented by the housing and the slider being formed as a synthetic resin moulding which has integrally moulded therewith at least one projecting resilient portion and the other component having abutment means which, during movement of the slider relative to the housing, is arranged to engage said projecting resilient portion to flex and stress it so that on disengagement of said abutment means and said portion the latter will deflect towards its unstressed position and thereby release the energy stored by the aforesaid flexing to cause the slider to move rapidly between the positions of electrical contact represented by an "on" position and an "off" position of the switch.

2. A switch as claimed in Claim 1 wherein the slider is provided with the projecting resilient portion or portions, the or each portion being formed at its free end to a rounded configuration.

3. A switch as claimed in Claim 1 or Claim 2 wherein there is provided a slider locking member which is mounted on the housing so that it can be displaced relative to the housing between an operative position in which its inner end engages a part of the slider to prevent movement thereof and an inoperative position in which said inner end is not engaged with the slider, the inner end of the locking member being shaped so that it can be compressed whilst being pushed through an aperture formed in the wall of the housing whereafter said inner end will expand outwardly beyond the inner periphery of said aperture to prevent separation of the locking member from the housing.

4. A switch as claimed in Claim 2 wherein said abutment means comprises at least one projection which is formed in a slide-way provided in the housing in which said slider moves so as to project into said slide-way, a part of the surface of the slide-way adjacent to the projection being shaped to provide an increasing width of the slide-way in a direction away from the projection.

5. A switch substantially as hereinbefore described with reference to and as shown in the accompanying drawings.