Electrical pushbutton snap switch

A switch for selectively establishing a first conductive way between a first conductive fixed contact and a second conductive fixed contact or a second conductive way between the first conductive fixed contact and a third conductive fixed contact. The switch includes a housing and a pushbutton extending out of the housing and comprising a driving portion formed by an extension extending into the housing, the pushbutton being arranged, when an external force is applied to the pushbutton, to be moved relative to the housing between a first pushbutton active position in which the first conductive way is established and a second pushbutton active position in which the second conductive way is established.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the priority benefit of European Patent Application No. 0816139.1 filed Aug. 4, 2008.

BACKGROUND

The present invention relates to an electrical switch, also known as a snap switch. Such an electrical snap switch is designed for selectively establishing either a first conductive way between a first conductive fixed contact and a second conductive fixed contact or a second conductive way between the first conductive fixed contact and a third conductive fixed contact. Typical electrical snap switches may include a housing and a pushbutton extending out of the housing and comprising a driving portion formed by an extension extending into the housing, the pushbutton being arranged, when an external force is applied to the pushbutton, to be moved relative to the housing between a first pushbutton active position in which the first conductive way is established and a second pushbutton active position in which the second conductive way is established. The electrical snap switch may further include a conductive unit which is fixed with respect to the housing and which includes first, second, and third conductive fixed contacts. The electrical snap switch may include a switching unit comprising a conductive swaying element, a first end of the conductive swaying element being pivotally engaged with the first conductive element, and the second end of the conductive swaying element being arranged to selectively electrically connect the first conductive fixed contact to either the second or the third conductive fixed contact, and a traction spring having a first end operatively connected to the housing and a second end secured to the swaying element such that when the pushbutton is in the first pushbutton position, the spring is in a first spring position and the spring causes the swaying element to electrically connect the first and second conductive fixed contacts, and when the pushbutton is moved to the second pushbutton position, the spring is moved to a second spring position and the spring causes the swaying element to also move to electrically connect the first and third conductive fixed contacts,

An example of such a switch is disclosed in U.S. Pat. No. 7,205,496, the contents of which are hereby incorporated by reference, in which the spring is a helicoidally wounded traction spring and in which the pushbutton driving portion acts on the middle section of the spring. Due to this arrangement, an abrupt changeover of the switching unit occurs but it is not possible to obtain a quick changeover and, furthermore, the elastic behaviour of the spring is affected by its cooperation with the driving portion and the changeover point, or instant, varies and the switch is therefore not reliable. The same drawbacks are also inherent to the design disclosed in U.S. Pat. No. 4,636,597.

An attempt to improve the working of such a snap switch is illustrated in U.S. Pat. No. 6,255,611 in which the switching unit is bistable between first and second positions of the swaying element, in which the switch comprises a return spring which is disposed between the housing and the pushbutton, in which, when an external force applied to the pushbutton is removed, the pushbutton is returned back to its original first active position by the return spring, and in which the traction spring has a first end connected to the driving portion of the pushbutton and a second end secured to the swaying element, so that when the pushbutton is in the first pushbutton position, the first end of the traction spring is in a first spring position, and when the pushbutton is moved to the second pushbutton position, the first end of the spring is moved to a second spring position.

According to such an arrangement, when an external force is applied to the pushbutton, the jointed end of the driving portion of the pushbutton and the elastic spring is forced to move downwards until it passes a critical line, at which point the swaying element is coupled with another conductive fixed contact to supply power or electrical signals.

However, the changeover speed remains insufficient and no solution is provided for a “double” or “twin” design for selectively establishing simultaneously two first conductive ways, each one between a first conductive fixed contact and a second conductive fixed contact. Similarly, there is no design that simultaneously provides two second conductive ways, each one between the first conductive fixed contact and a third conductive fixed contact.

SUMMARY

The invention described in this document is not limited to the particular systems, methodologies or protocols described, as these may vary. The terminology used herein is for the purpose of describing particular embodiments only, and is not intended to limit the scope of the present disclosure.

It should be noted that as used herein and in the appended claims, the singular forms “a,” “an,” and “the” include plural references unless the context clearly dictates otherwise. Unless defined otherwise, all technical terms used herein have the same meanings as commonly understood by one of ordinary skill in the art. As used herein, the term “comprising” means including, but not limited to.”

In one general respect, the embodiments disclose a switch for selectively establishing a first conductive way between a first conductive fixed contact and a second conductive fixed contact or a second conductive way between the first conductive fixed contact and a third conductive fixed contact. The switch includes a housing and a pushbutton extending out of the housing and comprising a driving portion formed by an extension extending into the housing, the pushbutton being arranged, when an external force is applied to the pushbutton, to be moved relative to the housing between a first pushbutton active position in which the first conductive way is established and a second pushbutton active position in which the second conductive way is established. The switch also includes a conductive unit which is fixed with respect to the housing and which includes the first, second, and third conductive fixed contacts; and a switching unit. The switching unit includes a conductive swaying element, wherein a first end of the conductive swaying element is pivotally engaged with the first conductive fixed contact, and a second end of the conductive swaying element is arranged to selectively electrically connect the first conductive fixed contact to either the second or the third conductive fixed contact, and a traction spring having a first end operatively connected to a driving portion of the pushbutton and a second end secured to the swaying element. The switch is configured such that when the pushbutton is in the first pushbutton active position, the first end of the traction spring is in a first spring position and the traction spring causes the swaying element to electrically connect the first and second conductive fixed contacts, and when the pushbutton is moved to the second active pushbutton position, the first end of the traction spring is moved to a second spring position and the traction spring causes the swaying element to move to electrically connect the first and third conductive fixed contacts. The switch is further configured such that the switching unit is bistable between the first and second positions of the swaying element, the switch comprises a return spring which is disposed between the housing and the pushbutton, and when an external force applied to the pushbutton is removed, the pushbutton is returned back to its original first active position by the return spring.

In another general respect, the embodiments disclose a switch for selectively establishing simultaneously two first conductive ways, each one between a first conductive fixed contact and a second conductive fixed contact or simultaneously two second conductive ways, each one between the first conductive fixed contact and a third conductive fixed contact. The switch includes a housing and a pushbutton extending out of the housing and comprising a driving portion formed by an extension extending into the housing, the pushbutton being arranged, when an external force is applied to the pushbutton, to be moved relative to the housing between a first pushbutton active position in which the first conductive ways are established and a second pushbutton active position in which the second conductive ways are established. The switch also includes a conductive unit which is fixed with respect to the housing and which includes the first, second, and third conductive fixed contacts and a switching unit. The switching unit includes a pair of conductive swaying elements, a first end of each conductive swaying element being pivotally engaged with a first associated conductive fixed contact, and the second end of each conductive swaying element being positioned to selectively electrically connect the first associated conductive fixed contact to either a second associated conductive fixed contact or a third associated conductive fixed contact, and a traction spring having a first end operatively connected to the driving portion of the pushbutton and a second end secured to the swaying elements. The switch is configured such that when the pushbutton is in the first pushbutton position, the first end of the traction spring is in a first spring position and the traction spring causes the swaying elements to electrically connect the first and second associated conductive fixed contacts, and when the pushbutton is moved to the second pushbutton position, the first end of the traction spring is moved to a second spring position and the traction spring causes the swaying elements to also move to electrically connect the first and third associated conductive fixed contacts. The switch is further configured such that the switching unit is bistable between the first and second positions of the swaying element, the switch comprises a return spring which is disposed between the housing and the pushbutton, and when an external force applied to the pushbutton is removed, the pushbutton is returned back to its original first active position by the return spring.

DETAILED DESCRIPTION OF THE FIGURES

In the description that follows, identical, similar or analogous components are designated by the same reference numbers.

As a non-limiting example, to assist in understanding the description and the claims, the terms vertical, horizontal, bottom, top, up, down, transversal, longitudinal, and so on will be adopted with reference to the L, V, T trihedron indicated in the figures, and without any reference to the gravity. In the illustrated embodiment, the design of an electrical switch may be symmetrical with respect to the vertical median plane VMP corresponding to exemplary line5-5ofFIG. 4.

FIG. 1shows a snap switch10. The snap switch10may include a housing12, of rectangular parallelepipedic shape. The housing12may be made of a housing upper part or half16and a housing lower part or half14, each of which may be made of moulded plastics and ultrasonic welded to each other after mounting and assembly.

As shown inFIG. 2, the switch10may also comprise a vertically extending and displaceable pushbutton18having a free upper end20for receiving an actuation force. A main vertical upper stem22of the pushbutton18may extend through a hole24of the housing upper part14in combination with a sealing boot26. The pushbutton18may be a plastic moulded part comprising a lower driving portion28which is an extension of the main vertical stem22and which is arranged and extends inside the housing12. The lower driving portion28may comprises a pair of vertically and transversely extending lateral guiding wings30which are received in mating and complementary pairs of vertical grooves32and34which may be arranged in the two halves14and16of the housing10(as shown inFIGS. 8 and 9).

As illustrated inFIGS. 5A and 5B, the switch10may further comprise a return spring36disposed vertically between the lower part14of the housing12and the lower driving portion28of the pushbutton18. The return spring36may be a vertically and helicoidally wounded spring which is received in a pit40of the lower part14. The return spring may be positioned such that its upper end may act on a lower vertically extending finger42of the driving portion28.

The return spring36may be mounted so as to be vertically compressed in such a way that, when an external force applied downwardly to the free upper end20of the pushbutton is removed, the pushbutton is returned back to its upper rest position by the return spring36. This upper rest position may be defined by the position of upper edges31of the wings30with the upper bottoms35of the grooves34.

Starting from this upper position (and by compressing the return spring36), the pushbutton18may be pushed downwardly towards its extreme lower position as is defined by the position of lower edges of the wings30with the lower bottoms of the grooves34.

The lower driving portion28comprises an open V-shaped slit44. As shown inFIGS. 5A and 5B, the slit44may be delimited by a first upper driving inner wall46and a second lower opposite driving inner wall48. The pushbutton18may be longitudinally positioned at one end of the housing10and the V-shaped slit44may longitudinally converge towards the other opposite end of the housing10. Each wall46and48may plane and terminate in an inclined small plane face47,49, both of which may be positioned horizontal and parallel with respect to the other.

As shown inFIGS. 5A,5B and6, the snap switch10may include a conductive unit made of several conductive fixed contacts belonging to metallic fixed conductive pins made of a cut metal sheet. The conductive unit may include a pair of first conductive fixed contacts52. The two first contacts52may be a pair of vertical conductive pins, each one comprising a fixed contact zone53in the form of a V-shaped groove. The two first contacts52may align transversely in a vertical plane which is substantially a middle plane arranged longitudinally between the pushbutton switch18and the other associated fixed contacts.

The conductive unit may also include a pair of second conductive fixed upper contacts54. The two second contacts54may be a pair of vertical conductive pins, each pin having an upper horizontally bent portion56and a lower face thereof constituting a fixed contact zone57. The two second contacts54may align transversely in a vertical plane which is arranged longitudinally substantially at the longitudinal end of the housing10opposed to the pushbutton switch18.

The conductive unit may further include a pair of third conductive fixed lower contacts58. The two third contacts may be a pair of vertical conductive pins, each pin having an upper horizontally bent portion60and an upper face thereof constituting a fixed contact zone61. The two third contacts58may align transversely in a vertical plane which is arranged longitudinally substantially at the longitudinal end of the housing10opposed to the pushbutton switch18.

All four bent portions56and60may align in the same transversal plane such that they form two pairs of fixed facing contact zones57,61defining a vertical space there between. An imaginary horizontal plane passing through the centre of the grooves53may pass substantially in the middle of the vertical space between the pairs of fixed facing contact zones57,61as shown inFIGS. 5A and 5B.

As illustrated inFIG. 7, the snap switch10may further includes a switching unit62. The switching unit62may be made of a pair of twin mobile contact conductive blades64manufactured from a cut metal sheet. Each blade64may constitute a swaying element and may be configured to move between the second54and third58fixed contacts. Similarly, each mobile contact blade64may extend longitudinally between the first fixed contacts52at one end, and the other fixed contacts54and58at the other end.

As shown inFIG. 7, each mobile contact blade64may have a first end66slightly bent downwardly with respect to the general plane of the blade, and a transverse edge67thereof may be pivotally received in a corresponding groove of an associated first fixed contact. Each mobile contact blade64may also have a second end68in formed, for example, as a fork which is positioned between the facing opposite conductive zones57and61such that the contact blade may selectively electrically connect the first conductive fixed contacts52to either the second54or the third58conductive fixed contacts, depending on the position of the mobile contact blade64.

As shown inFIGS. 1,2and3, each of the conductive pins52,54,58may be inserted (e.g., by forced fitting) and positioned in the lower portion14of the housing. Similarly, each of the conductive pins52,54,58may extend outwardly through corresponding holes vertically beyond the lower face17in order to constitute connecting pins of the switch10for connection of the latter on a printed circuit board (not shown). These terminals may be sealed with some epoxy resin depending upon the application of the switch10.

As shown inFIGS. 5A,5B,6and7, the switch10may include a transmitting element70which may be a plastic component overmoulded on the metallic swaying contact blades64. The transmitting element70may function as a single and common spring force transmitting element.

In one example, the transmitting element70may be formed as a reversed U-shaped stirrup wherein each lower end72of a lateral transverse branch is overmoulded on a corresponding facing portion of the associated blade64which is positioned close to its first end66. The stirrup70may also include a central and substantially horizontal branch74which extends longitudinally towards the second free ends68of the blades64. The free end76of the central branch74may terminate in a hook78.

As shown inFIG. 7, as a result of the pivotal arrangement of the switching unit62, with respect to the fixed contacts52and around the horizontal and transverse axis A-A, between the two upper and lower positions of the switching unit, the snap switch10may permit selective and simultaneous establishing of two first conductive ways, each one between a first conductive fixed contact52and a second conductive fixed contact54when the mobile switching unit62is in the position illustrated inFIGS. 5A and 5B, i.e. when the pushbutton is in the first upper active position. The switching unit62may also permit selective and simultaneous establishment of two second conductive ways, each one between a first conductive fixed contact52and a third conductive fixed contact58when the pushbutton is in the second lower active position.

The switching unit may be bistable between the first upper position and second lower positions. In this example, the switch may comprise a traction spring80having a first end82operatively connected to the driving portion28of the pushbutton via, for example, a tilting lever, and a second end84secured to the mobile contacts by means of the force transmitting element70. The traction spring80may be a helicoidally wounded spring having its second end84hooked in a hook78of a branch74of the force transmitting element. The first end82of the traction spring80may be connected to the pushbutton18by means of a tilting lever86which is pivotally mounted with respect to the housing12.

The tilting lever86may be formed as a metal plate pivotally mounted around a transverse and horizontal axis B-B parallel to the plane of the plate86. The tilting lever86may generally be in the form of a T having two first parallel and lateral branches88, each one having a transverse free edge89. Each free edge89may be pivotally received in a corresponding groove of an associated fixed structural bracket element90.

The structural bracket90may be a metallic cut element inserted (e.g., via forced fitting) in the lower part16of housing12, but which has no conductive or electrical contact function. The tilting lever86may also comprise a second central longitudinally extending central branch94which constitutes the second end of the lever86which is received freely with play in the slit44. The tilting lever86may also comprises a central hole96in which the first end82of the traction spring80is hooked, the hole96being positioned at a point which is positioned between the first88-89and second94ends of the tilting lever86.

Due to the various geometrical parameters and dimensions, and under the action of the traction spring80and of the return spring36, the bistable switching unit62, the lever86and the pushbutton18may all normally be in their “upper” rest positions as illustrated inFIGS. 1to5B. When the users pushes downwardly on the stem22of the pushbutton, the driving portion28of the pushbutton18may act, by means of the upper inner wall46, on the second end94to pivot the lever86from its upper first lever position in which the first end82of the spring80is in its first stable “upper” spring position, to its second stable “lower” lever position in which the first end82of the spring80is in its lower second position.

This change of position may provoke the switching, i.e. the simultaneous interruption of the two first conductive ways between the fixed contacts52and54, and the subsequent simultaneous establishment of the two second conductive ways between the fixed contacts52and58. It may also provoke the compression of the return spring36. When the users releases any actuation effort on the stem22, the previously compressed return spring36may act upwardly on the pushbutton18to push it vertically and upwardly. The driving portion28of the pushbutton18may similarly act, by means of the lower inner wall48of the slit44, on the second end94to pivot the lever from its the second stable “lower” lever position in which the first end82of the spring80is in its lower second position, to its upper first lever position in which the first end82of the spring80is in its first stable “upper” spring position.

The described embodiment herein comprises a “double” or “twin” arrangement of two switches. However, the invention also applies to a “single” or “unique” switch for selectively establishing a first conductive way between a first conductive fixed contact and a second conductive fixed contact or a second conductive way between the first conductive fixed contact and a third conductive fixed contact. This switch is primarily used in the automotive industry for actuation of an electronic parking brake. However, this switch may be also used in many applications including automotive air-bag systems as a system shut off switch. This switch may also be used in any electronics application which, for instance, requires a double pole double throw circuit particularly if fast switching of both poles is desired.