ROCKER SWITCH ASSEMBLY

Abstract: A rocker switch assembly includes a rocker (l6) mounted for pivotal movement about a central axis (20), an actuator (28) that is responsive to movement of the rocker and is arranged to pivot about either end, and conductive rubber push-button switches (24) that are selectively operable by the actuator with minimum lateral deformation. The actuator is translucent, to serve as a light conductor to carry light from an adjacent lamp (26) to the rocker, which bears translucent legends. The actuators of adjacent pairs of switch mechanisms are lit by means of a single lamp disposed between them.

Description: This invention relates to manually operable rocker switch assemblies as specified in the preamble of claim l, for example as disclosed in US-A-4 40l 864. Push-button switches of the elastomeric-dome variety are convenient to use in many applications in which manual switching is required, since they provide tactile feedback to the user and they can be manufactured in arrays which are easy to assemble to multiple switching panels. Furthermore, such push-button switches can readily be secured to printed circuit boards. These push-button switches have a potentially long life when properly used, but they have the disadvantage that lateral deformation during operation tends to shorten switch life and cause poor switch contact. Although some lateral travel during switch operation is acceptable, it is nevertheless desirable to minimise such lateral travel. Rocker switch actuators are a preferred type of switch for a switching function involving a choice between two mutually exclusive operations. The rocker of the switch should be pivoted at a central axis so that upon actuation it has a definite motion in one or the other direction and does not experience a net inward movement, that is, when one end of the rocker is pushed in the other end should move out by an equal amount. This provides the best tactile feel to the user, and it also ensures that only one switch can be operated at a time. It is known to use a rocker to actuate push-button switches, and the elastomeric-dome switches may be used in combination with such a rocker. However, the angular movement of the rocker inherently results in a component of lateral travel, which results in lateral deformation of the associated elastomeric-dome switch. It is accordingly desirable to minimise the effects of lateral travel of the rocker, to ensure that the acceptable limits of the elastomeric-dome switch are not exceeded. It is also often desirable to illuminate a switch actuator, to display a legend. It is known to provide a small lamp within a switch assembly and a translucent region on the actuator to effect such illumination. Although this can be done in the case of a rocker switch, the resulting assembly tends to be complicated and expensive. The present invention is concerned with the provision of a rocker switch assembly in which push-button switches can be actuated with a minimum of lateral travel. To this end a rocker switch assembly in accordance with the present invention is characterised by the features specified in the characterising portion of claim l. A preferred form of rocker switch in accordance with the present invention is arranged to be illuminated from a light source disposed externally of the rocker switch mechanism. It is further within the scope of the invention to utilise a common element to effect the illumination and travel-limiting functions in a rocker switch as aforesaid. In a preferred form of rocker switch assembly in accordance with the present invention, the rocker has a face bearing a translucent indicium (or an opaque indicium on a translucent background), a light source is mounted on the circuit board laterally adjacent the actuator, and the actuator comprises a transparent light-conducting material for the passage of light from the light source to the rocker to illuminate the indicium (or, respectively, its background). In the drawings: Figure l is a fragmentary sectional end view, with parts in elevation, of a preferred embodiment of a manually operated rocker switch assembly in accordance with the present invention; Figure 2 is a fragmentary sectional side view, with parts in elevation, of the switch assembly of Figure l, on the line 2--2, in the direction of the arrows; Figure 3 is a top view of a portion of the switch assembly of Figure l; Figure 4 is a top view of an actuator of the switch assembly of Figure l; Figures 5, 6 and 7 are fragmentary sectional views of a push-button switch forming part of the switch assembly of Figure l, shown in various conditions of operation; and Figures 8 and 9 are comparative illustrations of switch assembly operation, contrasting the operation of a manually operated rocker switch assembly in accordance with the present invention with that of a rocker switch assembly forming part of the prior art. With reference now to the drawings, there is shown in Figures l, 2, 3 and 4 a manually operated rocker switch assembly in accordance with the present invention in the form of a linear array of switch mechanisms l0 that are supported by a housing l2 having a plurality of apertures l4 each containing a rectangular rocker l6 pivotally mounted to housing walls l8 by pins 20 extending from the walls. One side of the housing l2 is closed by a printed circuit board 22 secured to the housing by means not shown. The circuit board 22 carries a plurality of push-button switches 24, as well as lamps 26 which are disposed between adjacent pairs of the switch mechanisms l0. The push-button switches 24 are arranged in pairs, each pair being operated by one rocker l6. An actuator 28 moulded from a transparent plastics material has the same general rectangular shape as the respective rocker l6, and is disposed between the rocker l6 and its corresponding push-button switches 24. Housing walls 30 which extend along each end of the rockers l6 and associated actuators 28 define shoulders 32 facing the circuit board 22. The shoulders 32 engage the ends of the actuators 28 so that the shoulders as well as the rockers l6 hold the actuators against the push-button switches 24. Since the push-button switches 24 are resilient, the actuators can be biased lightly against them to hold the parts firmly and prevent rattling. A switch compression of about 0.l mm is sufficient for this purpose. The actuators 28 each have a lower flange 34 protruding from each end for engagement with respective ones of the shoulders 32. The contact line between the flange and the corresponding shoulder provides a pivot axis for movement of the actuator 28 when the rocker depresses one end of the actuator to close one of the push-button switches. The resilient push-button switches 24, when depressed, provide a return force to maintain the actuators and rockers in a neutral position in the absence of an operator force. A pair of buttons 35, integral with each actuator, are positioned to contact the respective switches 24. A semi-circular recess 36 in each side of each actuator allows the actuator to partially surround an adjacent lamp 26 for efficient light gathering. Although only one side requires such a recess 36, the symmetrical design facilitates assembly of the actuator. One lamp is sufficient to illuminate an adjacent pair of switch mechanisms. Light entering the transparent actuator is directed towards the rocker l6, which has a translucent legend 37 on its outer, "top" surface. The top 38 of the rocker is formed of a translucent plastics material having a covering of paint 40 or other masking material or applique in a pattern to define a desired legend 37, so that light is emitted from the unmasked portions. A laterally extending flange surrounds the top 38 to extend beyond the apertures and prevent light leakage around the rockers. The remainder of the rocker l6 comprises a thin-walled rectangular skirt portion 42 secured to the rocker top 38. An aperture 44 in the centre of each side of the skirt portion 42 is pivotally mounted to the pins 20 of the housing. Slots 45 on either side of the apertures 44 lend enough flexibility to the aperture regions of the skirt portion to facilitate assembly. The switches 24, which are best seen in Figures 5, 6 and 7, are commercially available key-pad switches or conductive rubber-dome switches. They comprise a sheet 46 of an elastomer, preferably silicone rubber, formed with a plurality of domes 48 in an array according to the desired switch layout. The sheet 46 is clamped to the circuit board 22 by means of a rigid plastic plate 49 that is secured to the circuit board 22. The circuit board carries conductor paths 50 that are to be interconnected upon switch closure. A conductive pad 52 in the centre of each dome is arranged to bridge the conductor paths 50 upon depression of the dome 48. A vent 53 in the dome 48 prevents an increase in air pressure upon depression. As is shown in Figure 6, proper actuation of the dome switch results in complete switch closure. This requires that the dome be pushed in a direction substantially perpendicular to the circuit board. Only a small amount of lateral movement of the dome is permissible. Figure 7 reveals the results of too much lateral movement during switch depression: the conductive pad 52 is tilted, and so makes poor contact or no contact with circuit runners corresponding to the conductor paths. The improper deformation of the dome walls also causes wall fatigue and deterioration of the switch function. The combination of the rocker l6 and the actuator 28 provides superior switch performance as well as simple illumination. It is required that the rocker be able to close only one switch at a time, to avoid ambiguous signals arising from both push-button switches being closed. This requirement is met by the central pivot of the rocker l6, which can rotate either clockwise or counter-clockwise to close either switch but not both. The actuator 28 pivots about one end flange 34 and a shoulder 32 in response to the rocker movement to depress the switch at its moving end. The switch could have been depressed by the rocker directly if the actuator 28 had been omitted from the design. In that case, however, the rocker would experience a substantial lateral movement at its point of contact with the push-button switch 24, and transfer that movement to the switch to cause the type of deformation which is sought to be avoided. The actuator, on the other hand, experiences much less lateral travel for the same amount of travel normal to the circuit board. The diagrams of Figures 8 and 9 illustrate the geometrical basis for the improved switch operation. The prior-art arrangement represented by Figure 8 shows the movement of a switch rocker l6′ as it would be designed in the absence of an actuator 28, the spacing between the rocker surface and the circuit board remaining the same as in Figure l. In Figure 8, A′ is the pivot point, B is the contact point with the switch 24 in a switch-open position, and B′ is the contact point with the switch 24 in a switch-closed position. With the plane of the circuit board defining the horizontal, the vertical distance T is the switch travel required for switch closure, and the horizontal distance between B and B′ is the amount of lateral movement D of the contact point. The distance between A′ and B is identified as r. The line A′-B lies at an angle a below the horizontal, and the rocker moves through an angle b to achieve the travel T. The distance D is equal to r[cos a - cos(a + b)]. The lateral movement D thus increases with an increase in either the angle a or the angle b. The actuator movement in conformity with the present invention, represented by Figure 9, requires smaller angles corresponding to a and b, and results in a smaller lateral movement D′ even though the lever arm is longer. In Figure 9, E is the actuator pivot point, F and F′ are the switch contact points for the switch-open and switch-closed positions respectively, and the distance E-F is identified as r′. The amount of angular movement of the actuator is d. The angle c of the line E-F below the horizontal is very small, due to the position of the pivot axis on the shoulder 32, which is very close in the vertical direction to the plane of the switch contact points. The distance D′ is equal to r′[cos c - cos(c + d)]. With the prior-art construction, the use of values of r = l4 mm, T = l.3 mm and a = 37.6° results in values of b = 8.4° and D = l.37 mm. With the present construction, on the other hand, values of r′ = 25 mm, c = 4.6°, d = 3.5° and D′ = 0.l6 mm are obtainable. On the basis of these comparative figures, the use of the actuator reduces the lateral movement at the contact point by a factor of eight. This improvement is sufficient to ensure switch operation with good electrical contact and good tactile feedback. The switch assembly described herein is particularly useful for effecting actuation of pairs of key-pad switches with mutually exclusive operation, while minimising lateral deformation of the push-button switches and, where required, simultaneously providing convenient illumination of legends on the switch rocker.

Claims: 1. A rocker switch assembly for selectively actuating a pair of switches, in which a rocker (l6) is pivotally mounted in an aperture (l4) in a housing (l2) for movement about an axis (20) at the centre of the aperture (l4), for effecting selective actuation of a pair of push-button switches (24) by pivotal movement of the rocker (l6), characterised in that the push-button switches (24) comprise resilient push-button switches mounted on a circuit board (22) opposite the aperture (l4) in the housing (l2), the axis (20) for pivotal movement of the rocker (l6) comprises an axis (20) which is fixed relative to the housing (l2), and an actuator (28 is disposed between the rocker (l6) and the push-button switches (24) and is movable by the pivotal movement of the rocker (16), the actuator (28) having a pivot axis (32,34) at each end thereof permitting pivoting of the actuator (28) in a first direction about one end thereof to actuate one of the push-button switches (24) when the rocker (l6) is pivoted about the fixed axis (20) in a first direction, and pivoting of the actuator (28) in a second direction about the other end thereof to actuate the other of the push-button switches (24) when the rocker (l6) is pivoted about the fixed axis (20) in a second direction. 2. A rocker switch assembly according to claim l, characterised in that the resilient push-button switches (24) comprise elastomeric dome-type switches having a low tolerance to lateral deformation, and the actuator (28) is arranged to depress a respective one of the push-button switches (24) at one end thereof while pivoting at the other end thereof so that lateral movement at the one end thereof is minimised. 3. A rocker switch assembly according to claim l or 2, characterised in that the push-button switches (24) have switch contact points disposed in a plane parallel to the said axes, and the pivot axes (32,34) at the ends of the actuator (28) are near the said plane such that lateral movement of the actuator (28) at the switch contact points is minimised. 4. A rocker switch assembly according to any one of claims l to 3, characterised in that the resilient push-button switches (24) are of an elastomeric-dome type having low tolerance to lateral deformation, and each of the pivot axes (32,34) at the ends of the actuator (28) is formed by co-operation between a configuration (34) on the actuator (28) and a shoulder (32) on the housing (l2) facing the circuit board (22), with the actuator (28) being trapped between the resilient push-button switches (24) and the shoulders (32) so that when one end of the actuator (28) is depressed by the rocker (l6) to actuate one of the push-button switches (24), the other end of the actuator (28) thereby pivots about the adjacent shoulder (32) such that lateral movement at the one end of the actuator (28) depressing the push-button switch (24) is minimised. 5. A rocker switch assembly according to any one of claims l to 4, characterised in that the rocker (l6) has a face bearing a translucent indicium (37), a light source (26) is mounted on the circuit board (22), and the actuator (28) comprises a transparent light-conducting material for the passage of light from the light source (26) to the rocker (l6) to illuminate the indicium (37). 6. A rocker switch assembly according to claim 5, characterised in that the housing (l2) defines a pair of apertures (l4) as aforesaid disposed adjacent one another and both disposed opposite the circuit board (22), two pairs of the resilient push-button switches (24) are mounted on the circuit board (22) opposite the respective apertures (l4), the light source (26) comprises a common light source (26) mounted on the circuit board (22) between the pairs of resilient push-button switches (24), a pair of rockers (l6) as aforesaid each have a face bearing a translucent indicium (37), the rockers (l6) are pivotally mounted in the respective apertures (l4) of the housing (l2) for movement about a fixed axis (20) at the centre of the respective apertures (l4), a pair of actuators (28) as aforesaid and made of transparent material are mounted between the respective rockers (l6) and the corresponding resilient push-button switches (24) and on opposite sides of the light source (26) and serve as light conductors to illuminate the indicia (37), and each actuator (28) has a pivot axis (32,34) at each end permitting pivoting of the respective actuator (28) in a first direction about one end thereof to actuate a respective one of the resilient push-button switches (24) when the rocker (l6) is pivoted about its axis (32,34) in the first direction, and pivoting about the other end thereof in the second direction to actuate the respective other of the resilient push-button switches (24) when the rocker (l6) is pivoted in the second direction, whereby the resilient push-button switches (24) are selectively actuated when the respective rockers (l6) are pivoted, and the indicia (37) on both rockers (l6) are illuminated by the common light source (26).

Inventors: BAITY, DONALD NORMAN, KIDWELL, CHARLES EDWARD, SCHWANDT, GREGORY JOHN
Applicants: GENERAL MOTORS CORPORATION
Application year: 1987
Main classification: H01H23
IPC codes: H01H13, H01H23