GB2042271A

GB2042271A - A push button switch

Info

Publication number: GB2042271A
Application number: GB8002781A
Authority: GB
Original assignee: Kautt and Bux KG
Current assignee: Kautt and Bux KG
Priority date: 1979-02-07
Filing date: 1980-01-28
Publication date: 1980-09-17
Also published as: GB2042271B; DE2904646C2; FR2448780B1; FR2448780A1; IT8019737A0; DE7903379U1; DE2904646B1; IT1141357B

Abstract

A push button switch which occupies less space for a given current rating has a housing (1, 3), a push button (22), a return spring (not seen in Fig. 2), a pair of fixed contacts (4, 4), and a contact bridge (21) movable into and out of contact with the contacts (4, 4) and with a sliding engagement action therewith. A bridge holder (18) mounting the bridge (21) is movable in the direction of movement of the push button (22) and is pivotable about an axis (10) and also has a deflectable tongue (20) having a tapered, rounded upper end which engages specially shaped control surfaces (33, 34, 35) on the underside of an insert (24) in the push button (22). These control surfaces (33, 34, 35) are so inclined that when the push button is depressed, there is produced a component of force acting on the tongue (20) which causes it (and thereby the bridge holder (18)) to pivot about the axis (10) from one end position to another, and also to be deflected out of its plane of pivoting motion. <IMAGE>

Description

SPECIFICATION An improved push button switch The invention relates to a push button switch comprising:a housing; push button means biassed by a return device and longitudinally at least one pair of contacts in the housing; a contact bridge associated with the contacts and extending transversely of the direction of movement of the push button means and conductively connecting the contacts when the switch is closed; a bridge holder carrying the bridge and movable in the direction of movement of the push button means; and a deflectable push member which extends substantially in the direction of movement of the push button means and transmits its movement to the bridge.

As a result of the disposition of the component parts and the construction of the means of transferring the movement of the push button to the contacts, such known push button switches occupy considerable space in comparison with their rating. If such a switch is to be used in an appliance, this can lead to difficulties and make it necessary to use a rocker switch instead.

The invention is thus based on the need to provide a push button switch which has an improved ratio of switching capacity to space requirement but which is nevertheless simple in construction.

According to this invention there is provided a push button switch comprising: A housing; push button means biased by a return device and longitudinally movably guided in the housing; at least one pair of contacts in the housing; a contact bridge associated with the contacts and extending transversely of the direction of movement of the push button means and conductively connecting the contacts when the switch is closed; a bridge holder carrying the bridge and movable in the direction of movement of the push button means; and a deflectable push member which extends substantially in the direction of movement of the push button means and transmits its movement to the bridge, wherein: a) the bridge holder is mounted in the housing and is pivotable about an axis at right-angles to the direction of movement of the push button means and which is, in that direction, at a distance from the contact bridge; b) the push member moves with the bridge holder and extends from the latter towards the push button means; c) the push button means has on the side towards the push means two control faces which, in one and respectively the other end position of the pivoting range of the free end of the push means are aligned at least approximately at the said free end;; d) the two control faces are connected to each other by a saddle-like intermediate face, the ridge of which is at an acute angle to the pivoting plane of the push means; and e) the control faces and the intermediate face are so inclined that when the push button means is depressed, there is produced a component of force acting on the push means to cause a pivoting movement thereof into the other extreme position and a deflection out of the pivoting plane.

The reduction in the space requirement which can be achieved with the push button switch of the invention is such that just as favourable a ratio of switching capacity to space requirement is achieved as with a rocker switch. The latter can therefore be replaced by the push button switch of the invention.

A factor which contributes to the favourable ratio of switching capacity to space requirement is not only the reduction in the amount of space required but the increase in electrical loading capacity which is achieved, mainly because the contact bridge or bridges can approach the fixed contacts not only in the direction of movement of the push button but additionally with a sliding movement on the fixed contacts, so that frictional contact is made. Further advantages are that the switch of the invention can optionally be equipped with one ortwo sets of contacts for single pole or doulbe pole switching, that it can be a single pole or two-pole switch, and that it is possible to dispose a lamp in the push button without having to increase the size of the switch.

The push means may be a push rod in the form of a tongue of rectangular cross-section which is disposed between and at a distance from two side members of the bridge holder, and wherein the or each contact bridge is mounted astride one of the side members which, like the push rod, extend from a middle part of the bridge holder which is provided with bearing stud and towards the push button means. This arrangement makes it possible to achieve a minimum space requirement and also a simple construction of the switch. In the interests of a space saving but nevertheless functionally reliable mounting of the contact bridge or bridges, the free end portion of each side member may be a rodshaped bearing member on which the contact bridge is mounted via its middle portion which is in the form of a slot open towards the side member.

A spring may press on the or each contact bridge in the region of its middle portion and extend transversely to the direction of motion of the push button means, the spring having its ends braced against the push button means. This arrangement is space saving and structurally simple by virtue of the relatively considerable deflection which the spring undergoes every time the push button means is operated. A compression coil spring is preferred.

In a preferred embodiment, for best use of the space available, a return spring device does not bear on the push button means but on the bridge holder, on its side remote from the push button means.

If it is intended to use the switch of the invention not as a push button but as a circuit closure means, each contact bridge must be capable of being held in the closed position against the force of the return spring. In a preferred embodiment, the bridge holder has at least one locking lug at a distance from the pivoting axis, the switch housing having, for the or each locking lug, a notch with which the relevant locking lug is engageable during switch closure motion of the bridge holder. With this arrangement the bridge holder is locked in the closed position, because such a system of locking is structurally simple as a result of the pivoting movement performed by the bridge holder during both closing and opening of the switch, so that the space required for the locking means is small.This is particularly applicable if the side members of the bridge holder are extended rearwardly beyond the central portion, with each of the two extensions carrying one of the locking lugs on the outer face of its free end.

If it is not necessary to illuminate the push button means, it can be made in one piece and of translucent material, to enclose a lamp. The series resistor which is usually required in addition to the lamp is advantageously so inserted into an insert in the push button means that the parts of the insert which press against its connecting contacts are separated by a slot. In order to connect one connecting contact to the connecting wire of the lamp, it is necessary for this wire merely to be inserted between this connecting contact and the part of the insert which presses against it. The clamping pressure then provides for adequate contact.So that this clamping pressure does not have to be applied by the insert itself, the insert preferably has, on its side which is towards the interior of the button body, sloping faces which bear on sloping faces on the button body, the first sloping faces being at such an angle of inclination that a force tending to introduce the insert more deeply into the button body generates a force component which tends to close the slot. The spring or springs loading the contact bridge or bridges will maintain the insert pressed constantly against the sloping faces of the button body so that also the parts of the material of the insert which press against the connecting contacts of the series resistor are also loaded in the direction of closure of the slot.

A simple and space saving connection of the second connecting contact of the series resistor to a contact bridge is obtained by the provision of a spring loading the contact bridge, the spring having one end portion in contact with the resistor.

The invention will now be described by way of example with reference to the drawings, in which: Fig. 1 is a longitudinal section through an embodiment; Fig. 2 is a section on plane ll-ll of Fig. 1; Fig. 3 is a section on plane Ill-Ill of Fig. 1 but in the closed position of the switch, with parts in elevation; Fig. 4 is an underneath plan view of the lower side of the push button; and Fig. 5 is another longitudinal section.

Referring to the drawings, the push button switch is suitabie for fitment in applicances in protection category 11, since its surface leakage and air paths to the contactable surface of the switch amount to at least 8mm, the contact gap is at least 3 mm and the contact is made by friction. For a voltage of 220 V, the power handling capacity is 6 (4) amps.

The switch has a two-part switch housing, of which a rectangular upper part 1 (of injection moulded plastics material) has at its open end an encircling and outwardly projecting flange by which it can rest on a panel having a rectangular aperture to receive the switch. Integrally moulded on the outside of the upper part 1 are spring tongues 2 (Fig. 2) which maintain the flange in bearing contact with the panel. The size of the upper part 1 in a horizontal plane is 13 x 19 mm and it is 14.5 mm high.

Inserted into the lower end of the upper part lisa bottom part 3 of the housing which is likewise of injection moulded plastics material. It is locked to the upper part 1 by outwardly projecting lugs which engage in recesses in the upper part 1. The bottom part 3, which closes the upper part 1, serves as a carrier for fixed contacts 4 of the switch. The lower part 3 has for this purpose, and on opposite sides and located in a common plane, two slots through which are inserted the fixed contacts 4 each integral with its contact lug 5 which is adjacent and at rightangles to it, each contact lug 5 in the present embodiment being a plug-in type contact, although it could also be for example a soldering lug.Since these slots are masked by the upper part 1, afterthe upper and lower parts of the housing have been assembled, the fixed contacts 4 are held in the position shown in Figs. 2 and 3 in which their contact face which is towards the upper open end of the housing is free.

As Figs. 2 and 3 show, the contact lugs 5 of one and the same pole are separated by a projection 6 of the lower housing part 3 and form a crosssectionally rectangular guide passage 7 (Fig. 1), the longitudinal axis of which is oriented at the centre of and is perpendicular on the free cross-sectional area of the upper part 1. The guide passage 7, which also passes through the part of the lower part 3 which is inside the upper part 1, to some extent accommodates a plastics injection moulded bridge holder 8 of generally H shape. The ends of the rod-shaped middle part 9 of the bridge holder 8 project outwardly beyong the two arms of the H to form two bearing studs 10, each guided and rotatable in a slot 11 open towards the interior of the switch housing and parallel with the longitudinal axis of the guide passage 7, and for displacement in the longitudinal direction of the slot.

The at least substantially parallel arms 12, which project from the middle part 9 of the H into the guide passage 7, each carry at their respective free lower ends an outwardly projecting locking lug 13 (Fig. 1), the lugs 13 engaging into respective step-like notches formed in that wall of the guide passage which is towards the locking lug. As Fig. 2 shows, the notch forms two faces 14 and 15, the first at a greater distance from the lower, free end of the projection 6 than the latter. In the off position of the switch, each locking lug 13 engages behind the notch face 14 so preventing the bearing studs 10 emerging from the slots 11 underthe action of a return spring 16 (a coil compression spring) which rests at one end on a web 17 across the guide passage 7 and at the other end on the middle part 9 of the H. If the bridge holder 8 is moved towards the free end of the guide passage 7 (as is the case during a switch-on movement of the switch), then after some motion in the longitudinal direction of the guide passage 7, the bridge holder8 is pivoted about the axis of the studs 10 in a clockwise direction (as seen in Fig. 2) because the notch widens out at the level of the second notch face 15. At the end of this pivoting movement, each locking lug 13 engages behind the second notch face 15 so that the bridge holder 8, which is subject to the force ofthe compressed return spring 16, is locked in the switching-on position.

If the switch is constructed as a non-locking push-on switch, then instead of the second notch face 15, a sloping abutment face 15', indicated by a broken line, may be provided and prevents locking.

The two parallel arms of the H which extend upwardly form side members 18 and each at its free end forms an outwardly projecting bearing member 18'. The generatrices of these members 18' (of identical, mirror-image shape) are parallel with the pivoting axis of the studs 10. Adjacent the outer end of each bearing member 18' is a connecting stud 19 of smaller diameter.

In the centre between the two side members 18 and integral with the bridge holder 8, is a tongue 20 which extends upwardly, although it is longer than the side members 18, and is of rectangular crosssection, its dimension in the direction of the axis of the studs 10 being considerably less than its dimension in the pivoting plane. The tongue 20 is therefore not deformable in the pivoting plane but can only be deflected out of that plane to one side or the other.

Its upper end part is tapered in wedge fashion (Fig. 2) but its end is not pointed but rounded, as shown.

In the present embodiment, a contact bridge 21 straddles only one of the two bearing members 18'.

In the case of a 2-pole switch, the other bearing member 18' would also carry an identical contact bridge. The middle portion of the contact bridge 21, made from a piece of strip, forms (Figs. 2 and 3) a slot which is open towards the lower part3 of the housing, the width of the slot being greater than the width of the bearing members 18' measured in this direction, so that the contact bridge 21 can to a limited extent pivot in relation to the bearing member 18'.The clearance between the bearing member 18' and the sides of the slot may however only be sufficiently great for the pivoting movement of the side members 18 to bring about a movement of the bridge 21 in its longitudinal direction, so that a frictional contact is made, i.e. the contacts of the bridge 21 slide in the longitudinal direction of the bridge on the contact face of the associated fixed contact 4. The length of the two outwardly extending arms of the bridge 21, and which on their side which is towards the associated fixed contact 4 in each case one of the contact pieces, is adapted to the distance of the fixed contacts 4 from each other.

Longitudinally displaceably and non-rotatably guided in the upper part 1 of the housing is a push button 22, which has a button body 23, open towards the interior of the switch and made of translucent plastics, and an insert 24, which is of injection moulded plastics and which is inserted from the open end into the button body 23. As Fig. 1 shows, the button body 23 on opposite sides has in each case an outer shoulder and a rounded inner shoulder 25. The outer shoulder has over it an inwardly projecting part of the flange on the housing upper part 1, so that the maximum projection of the button body 23 from the housing is positively established.

The insert 24 bears on the two inner shoulders 25 and (Fig. 5) does so via corresponding faces 26 in the region of one of its ends. As Fig. 3 shows, on the sides which carry the shoulder, each side wall of the button body 23 has a hook 27 which is integral with the wall. These hooks engage below the studs 19 of the bridge holder 8 but permit limited relative movement of the studs 19 in relation to the button body 23 in the direction of movement thereof.

For each contact bridge 21 provided, the two end portions of a compression coil spring 28 are placed in the insert 24 in such a way that the longitudinal axis of the spring 28 would lie more or less parallel with the associated contact bridge if the exposed middle spring portion were not in pretensioned contact with the yoke of the central raised portion of the bridge 21, Fig. 2. The relatively small amount of flexion of the spring 28 towards the insert 24, which is present even when the switch is in its off position, on the one hand maintains the middle portion of the bridge 21 bearing down against the bearing member 18' and on the other, presses the insert 24 against the inner shoulders 25 of the button body 23.

In the space defined by the actuating face of the button body 23 and also by the insert 24 there is a glow discharge lamp 29. Its associated series resistor 30 is placed into the insert 24 from the side directed away from the bridge holder 8 and in such a way that one end cap of the resistor 30 is in contact with an end portion of the coil spring 28 (Figs. 2 and 5) and the longitudinal axis of the resistor extends more or less at right angles to the axis of the spring 28. The two material parts of the insert 24 which accommodate the end caps of the resistor 30 are separated by a slot 31 parallel with the edges resting on the inner shoulders 25. As Fig. 5 shows, one connecting wire of the lamp 29 is in contact with that end cap of the resistor 30 which is not in contact with the spring 28.By virtue of the sloping faces 26 by which the insert 24 rests on the inner shoulders of the body 23, the force exerted by the spring 28 on the insert 24 generates a component which tends to close the slot 31. In consequence, there is at all times sufficient contact pressure between one wire of the lamp 29 and the relevant cap of the resistor 30. The other connecting wire of the lamp 29 is connected to one of the two fixed contacts 4 via a contact coil spring 32 (Fig. 5) having one end in a blind bore in the insert 24, on the bottom of which the connecting wire rests. In the case of a 2-pole switch on the other hand, this connecting wire of the lamp 29 is clamped between one end of the coil spring loading the other contact bridge and the supporting face which accommodates that end. It would also be possible to connect the supply leads of the lamp to separate contacts.

To convert the motion of the push button 22 into the combined translatory and rotary movement of the bridge holder 8, which is needed to open and close the switch, the insert 24 has on the side remote from the lamp 29 and in the area opposite the tongue 20, two control faces 33 and 34 which (Fig. 2) are inclined in the same direction as one or other of the sloping faces on the tapering end portion of the tongue 20, although they enclose a greater angle than those sloping faces. The two control faces 33 and 34 are staggered in a direction parallel to the pivoting axis of the bridge holder 8, in other words, in that direction in which the tongue 20 can be deflected.

However, they partially overlap and the overlapping portions are connected to each other by a saddle-like intermediate face 35 (Fig. 4). The back of this inter mediate face, formed by an edge in the present embodiment, extends obliquely to the direction of deflection of the tongue 20. The angle in the centre of the back is about 45" and is greater in the two end portions.

In the switched off position of the switch (Fig. 2) the rounded tip of the tongue 20 points towards X (Fig. 4) on the flank of the intermediate face 35 which is towards the control face 33. When the push button 22 is pressed into the housing, the tip of the tongue comes to bear on the point X, but is then deflected towards the exposed portion of the control face 33.

Therefore, actuation of the push button 22 not only produces longitudinal displacement of the bridge holder 8 but, by virtue of the fact that one sloping face of the tongue end portion 20 rests on the control face 33, also produces a pivoting movement during which the tip of the tongue passes the intermediate face 35 in the free space 36 which is adjacent the control face 33. The translatory movement of the bridge holder 8 causes the bridge 21 to bear on the associated fixed contacts 4 whereby, by virtue of the increasing restoring force of the return spring 16, the spring 28 undergoes increasing flexion.The rotary movement of the bridge holder 8 into the position shown in Fig. 3 leads on the one hand to a sliding movement of the contacts of the bridge 21 on the contacts4 and on the other results in the locking lugs 13 engaging the two notch faces, 15, so locking the switch in the switched on position.

If now the push button 22 is released, then the coil spring 28 pushes it back as far as allowed by the clearance of the locking lugs 19 in the hooks 27. The amount of travel is sufficiently great that the tongue tip 20 is released and can return to its neutral position, in which it is aligned at the pointY (Fig. 4) on that flank of the intermediate face 35 which is towards the control face 34. If the push button 22 is now again depressed to open the switch, then the tongue tip is deflected towards the exposed portion of the control face 34, and the tongue undergoes a translatory movement which leads to lifting of the locking lugs 13 off the two notch faces 15. Abutment of the sloping face which is towards the control face 34 on this control face, finally causes the bridge holder 8 to perform a rotary movement about its pivoting axis, during which, in the free space 37, the tip of the tongue passes by the intermediate face 35 until it is more or less at the height of the point X. If now the push button 22 is released, then it moves into its start position, and the tip of the tongue 20 is also released and returns to its neutral position in which it is aligned at the point X. The return spring 16 thus lifts the contact bridge 21 off the fixed contacts 4.

Claims

1. A push button switch comprising: a housing; push button means biased by a return device and longitudinally movably guided in the housing; at least one pair of contacts in the housing; a contact bridge associated with the contacts and extending transversely of the direction of movement of the push button means and conductively connect ing the contacts when the switch is closed; a bridge holder carrying the bridge and movable in the direction of movement of the push button means; and a deflectable push member which extends substantially in the direction of movement of the push button means and transmits its movement to the bridge, wherein: a) the bridge holder is mounted in the housing and is pivotable about an axis at right-angles to the direction of movement of the push button means and which is, in that direction, at a distance from the contact bridge; b) the push member moves with the bridge holder and extends from the latter towards the push button means; c) the push button means has on the side towards the push means two control faces which, in one and respectively the other end position of the pivoting range of the free end of the push means are aligned at least approximately at the said free end;; d) the two control faces are connected to each other by a saddle-like intermediate face, the ridge of which is at an acute angle to the pivoting plane of the push means; and e) the control faces and the intermediate face are so inclined that when the push button means is depressed, there is produced a component of force acting on the push means to cause a pivoting movement thereof into the other extreme position and a deflection out of the pivoting plane.

2. A switch according to claim 1, wherein the push means is a push rod in the form of a tongue of rectangular cross-section which is disposed between and at a distance from two side members of the bridge holder, and wherein the or each contact bridge is mounted astride one of the side members which, like the push rod, extend from a middle part of the bridge holder which is provided with bearing stud and towards the push button means.

3. A switch according to claim 2, wherein the free end portion of each side member is a rod-shaped bearing member on which the contact bridge is mounted via its middle portion which is in the form of a slot open towards the side member.

4. A switch according to claim 2 or claim 3, wherein, pressing on the or each contact bridge in the region of its middle portion and extending trans verselytothe direction of movement of the push button means, is a spring having its ends braced against the push button.

5. A switch according to claim 4 wherein the spring is a compression coil spring.

6. A switch according to any preceding claim wherein, on the side remote from the push button means, the bridge holder bears on one end of the return device, which is a spring, and has on its side members dogs which engage with clearance in the direction of movement of the push button means into recesses therein.

7. A switch according to any preceding claim, wherein at its end portion remote from the push button means, the bridge holder has at least one locking lug at a distance from the pivoting axis, and wherein the housing has forth or each locking lug, a notch with which the relevant locking lug is engageable during switch closure movement of the bridge holder.

8. A switch according to claim 7, wherein the side members are extended rearwardly beyond the central portion, each of the two extensions carrying one of the locking lugs on the outside face of its free end.

9. A switch according to any preceding claim, wherein the control faces and the intermediate face are provided on a insert of the push button means which at least partially closes the hollow button body which is open towards the bridge holder.

10. A switch according to claim 9 wherein the button body is of translucent material.

11. A switch according to claim 9 or claim 10 wherein, inserted into the insert is a series resistor for a lamp in the button body, the part of the insert, which accommodates one end of the series resistor and between which and the connecting contact of the series resistor one connecting wire of the lamp is inserted, being separated by a slot from the rest of the insert.

12. A switch according to claim 11, wherein the insert has, on its side which is towards the interior of the button body, sloping faces which bear on sloping faces on the button body, the first sloping faces being at such an angle of inclination that a force tending to introduce the insert more deeply into the button body generates a force component which tends to close the slot.

13. A switch according to claim 11 or claim 12 when dependent on claim 4 or claim 5, wherein the spring which bears on and contacts the contact bridge has one end portion in contact with the resistor.

14. A push button switch constructed and arranged substantially as herein described and shown in the drawings.