US3536872A - Electrical switch having actuating means maintained in uniform engagement with pivotable contact rocker - Google Patents

Description

Oct. 27, 1970 B. GILARDYENGHI 3,536,872

ELECTRICAL SWITCH HAVING ACTUATING MEANS MAINTAINED IN UNIFORM ENGAGEMENT WITH PIVOTABLE CONTACT ROCKER Filed March 18, 1968 3 Sheets-Sheet 1 -27,1970 B.GILARDENGHI I [3,536, 7

ELECTRICAL SWITCH HAVING ACTUATING MEANS MAINTAINED IN UNIFORM ENGAGEMENT WITH PIVOTABLE CONTACT ROCKER I Filed March 18, 1968 3 Sheets-Sheet 2 Oct. 27, 1970 B. GIYLARDENGHHI I I 3,536,872

ELECTRICAL SWITCH HAVING ACTUATING MEANS MAINTAINED IN UNIFORM ENGAGEMENT WITH PIVOTABLE CONTACT ROCKER Filed March 18, 1968 3 Sheets-Sheet 5 United States Patent Int. Cl. Hinh 13/28 US. Cl. 200-67 2 Claims ABSTRACT OF THE DISCLOSURE An electrical switch has a molded plastics base and cover which are snap-engaged with each other. Pivotable rockers carrying movable contacts are movable by a plastics key which is pivoted to and snap-engaged with the cover. The assembled switch can be snap-fitted to a support.

The invention relates to electrical switches and concerns more particularly but not exclusively switches for use in the electrical circuits of motor vehicles.

Electrical switches of this type generally comprise a base provided with fixed contacts relative to which at least one movable contact is displaceable by rocking movement of a key pivotally mounted in a cover attached to the base.

Known switches of this type usually comprise a large number of components, some of metal and some of insulating material, the components being interconnected by rivets or similar fastening means.

An object of this invention is to provide a switch of the abovementioned type which is simple, tough and inexpensive in construction, and which is easily and quickly assembled without requiring special fastening means for interconnecting its components.

A further object of the invention is to provide a switch of the abovementioned type which is made up of a small number of components, all of simple and inexpensive construction and adapted to be interconnected without employing metal fastening means such as rivets, nails or the like.

The main characteristic feature of the switch according to the invention is that the base and the cover are both molded from plastics and are interengageable by snap action, the key is engageable by snap action on the cover for rocking movement about a transverse axis, and means are provided for snap-fastening the switch to a support.

Further characteristic features and advantages of the invention will be understood from the following description, given by way of example only, with reference to the accompanying drawings, wherein:

FIG. 1 is a diagrammatical longitudinal sectional view of a switch according to one embodiment of the invention, shown in its closed, or operative, position;

FIG. 2 is a cross sectional view on line IIII of FIG. 1;

FIG. 3 is a plan view of the switch with its key and cover removed;

FIG. 4 is a perspective view of the base of the switch casing;

FIG. 5 is a longitudinal sectional view on line VV of FIG. 4;

FIG. 6 is a side elevational view of the cover of the casing;

FIG. 7 is a plan view of said cover;

FIG. 8 is a cross sectional view on line VHIVIII of FIG. 6;

FIG. 9 is a perspective of the switch key;

3,536,872 Patented Oct. 27, 1970 FIG. 10 is a partly exploded cross-sectional view on line XX of FIG. 9;

FIG. 11 is a perspective view of the lower side of one switch rocker element;

FIG. 12 is a perspective view of a central one of the fixed contacts, and

FIG. 13 is a perspective view of an end one of the fixed contacts.

The switch according to the invention comprises a casing having a base 1 and a cover 14, both of which are mtglded from plastics, and adapted to snap-engage each 0 er.

The base 1, which is shown in detail in FIGS. 4 and 5, is of open box shape and comprises a rectangular floor of bottom portion 2 surrounded by upstanding walls 3. Two external teeth 4, 5 are provided centrally on the shorter walls 3 for snap-engagement with the cover 14 as described hereafter. The longer Walls 3 are each provided with a large and a small external projection 6, 7 respectively at opposite ends. The projections 6, 7 assist in positioning the switch in a supporting structure such as an instrument panel in a motor vehicle, as described hereinafter.

A plurality of projections 9 arranged in two longitudinally extending rows extend from the outer face of the bottom portion 2 of the base 1. Each projection 9 is formed with an internal bore 8 of rectangular cross section extending through the bottom portion 2 and provided with a flared mouth 8a opening into the interior of the base 1. The outer end of each projection 9 is stepped at 8b (FIG. 5).

Conductive elements 39 carrying fixed central contacts 41 of the switch are fitted by snap action into respective said bores 8. In the illustrated embodiment there are two conductive elements 39 (FIG. 12), each fitted into one of the four bores 8 in the central region of the base 1, on opposite sides of the longitudinal centre-line of the base 1. Each element 39 has an integral blade portion 39a acting as a connector tab and passing through the bore 8 in the bottom portion 2. An integral tongue 40 is stamped from the portion 39a and is adapted to snap on the stepped portion 8b of the bore 8 to secure the element 39 to the base 1. Each conductive element 39 also has a contact portion 39b bent over at right angles to the portion 39a and adapted to rest on the bottom portion 2 of the base 1. The portion 39b is formed with an upraised end portion 39c carrying one of the fixed contacts 41, said contact 41 having a plane face.

A further conductive element 42 (FIG. 13), similar to the elements 39 described above is fitted into one of the bores 8 at a longitudinal end of the bottom portion 2. The element 42 has a blade portion 42a extending outwardly through the bottom portion 2 to act as a connector tab. The blade portion 42a is provided with a retaining tongue 43 similar to the tongue 40. The element 42 also has a contact portion 4212 which rests on the bottom portion 2 and which carries a fixed end contact 44.

More than one conductive element 42 may be provided. In the illustrated embodiment there are two conductive elements 42 at opposite respective ends of the base 1, each carrying a respective end contact 44.

Two parallel rockers 35, 35' are longitudinally arranged on the bottom portion 2 of the base 1. The rockers 35, 35' are identical, the rocker 35 being illustrated in FIG. 11 and being in the form of a conductive plate centrally provided with symmetrical lateral projections 36 adapted to be located in pairs of facing grooves 10, 11 formed respectively in the inwardly facing surface of the wall 3 and in a central integral pillar 12 extending from the bottom portion 2 (FIGS. 3 and 4).

Each rocker 35, 35' is provided on its face which on assembly is turned towards the bottom portion 2 with a central contact 37 having an outwardly convex surface adapted to bear on one of the fixed central contacts 41 provided on the conductive elements 39. The contacts 37 act as fulcra for the two rockers 35, 35' which are therefore capable of rocking movement about a common axis extending transversely of the bottom portion 2. In addition to the central contact 37, each rocker 35, 35' carries at one end a further outwardly convex end contact 38 adapted to cooperate with one of the fixed end contacts 44 carried by the conductive elements 42.

Oscillation of the two rockers 35, 35' about their respective fulcra will close or open selectively, respective circuits including the respective central fixed contacts 41 and one of the fixed end contacts 44.

In the embodiment shown the base 1 is provided with six bores 8 which can accommodate any number of fixed contacts between two and six, depending upon the intended function of the switch, for example, a shunting or changeover switch or the like.

The cover 14, which is fitted by snap action on the base 1 is shown in detail in FIGS. 6, 7 and 8. The cover 14 comprises a hollow shell molded from plastics, having a tapered top portion 141: defined by two parallel side walls and two converging end walls. The end walls merge with a substantially rectangular body of the cover 14 at respective end portions 14!), each of which is provided centrally with a resilient depending tab 15, 15' formed with a respective rectangular slot 16, 16'. The slots 16, 16' are adapted to snap-engage over the teeth 4, of the base 1 when the cover is fitted over said base.

Two resilient depending wings 17 are formed integrally with the cover 14 as respective extensions of the two parallel side walls of the top portion 14a. Each wing 17 is provided with a pair of laterally outwardly extending converging tongues 18 for snap-fitting the assembled switch t'o a support, such as a recess formed in an instrument panel of a motor vehicle, as indicated in broken outline at P in FIG. 8.

The top portion 14a of the cover 14 is surmounted by a flat wall 14c (FIG. 7) in which a substantially rectangular laterally elongated opening 19 having rounded edges is formed. Two projections 20 extend upwardly from the wall 140 and are disposed centrally of the longer sides of the opening 19. Two part-cylindrical projections 21 are arranged centrally of the shorter lateral sides of the opening 19, the projections 21 extending laterally outwardly from the side walls of the portion 14a. The outer faces of the projections 21 are formed with respective bevelled shoulders 21a.

The projections 21 serve to define a laterally extending pivot axis for rocking movement of an oscillatory key 22, shown in FIGS. 9 and 10. The key 22 comprises a body portion molded from plastics and having a shaped casing 22a defined by two parallel lateral flanks 22b and having V-shaped surface 23, one face 24 of which carries laterally extending ribs for easier grip by the fingers, and the opposite face 24a of which carries a symbol or character engraved thereon to identify the function of the switch, for example, windscreen wiper control.

The two lateral flanks 22b of the key 22 are each formed with a circular hole 25. An outwardly sloping ramp portion 26 (FIG. is formed on the internal surface of each flank 22b beneath each respective hole 25. The ramp portions 26, together with the bevelled shoulders 21a, facilitate fitting of the key 22 by snap action on the top portion 14a of the cover 14. Upon such fitting the projections 21 on the cover 14 are engaged in the holes 25 in the key 22, the latter being thereby retained on the cover while being capable of rocking about a transverse axis coinciding with the common axis of the projections 21.

The key 22 is formed internally with two tubular sleeves 27 arranged side by side, each having a cylindrical bore 28 with a respective piston 30 slidably mounted therein. Each piston 30 is formed with a blind cylindrical bore in which a respective helical biasing spring 31 is disposed, the ends of each spring 31 abutting the bottom of the respective bore 28 and the bottom of the respective piston bore respectively.

Each sleeve 27 has a longitudinal slot 29 (FIG. 10) in which a laterally projecting tooth 33 carried by the respective piston 30 is engaged to prevent ejection of the piston from the sleeve by effect of the spring 31 and to prevent rotation of the piston 30 in the sleeve 27. Each piston 30 comprises a tubular body of plastics formed with at least one longitudinal slit 32 to permit resilient deformation of the piston wall for snap-engaging the tooth 33 in the slot 29.

The pistons 30 bear upon the respective rockers 35, 35' when the switch is assembled; the outer free end of each piston 30 is defined by bevelled surfaces 34 which form a rounded contact edge extending parallel to the pivotal axes of the rockers 35, 35', so that said edges may slide along the upper surfaces of the respective rockers 35, 35'.

Under normal conditions the two springs 31 acting on the pistons 30 cause the key 22 to take up an inclined position corresponding to one of two operative positions of the switch. Moreover, the two pistons 30 maintain both rockers 35, 35 oppositely inclined to the key 22, so that one or each of said rockers 35, 35' can act as a conductive bridge for the selective establishing or breaking electrical continuity between one of the central fixed contacts 41 and one of the fixed end contacts 44 in accordance with the position of the key 22.

In order to effect change-over of the condition of the switch it is sufficient to press with one finger whichever face of the V-shaped surface 23 of the key is projecting outwardly to cause the key 22 to rock about the fulcra formed by the projections 21 on the cover 14. During this rocking movement the pistons 30 slide along the rockers 35, 35' and are withdrawn into their sleeves 28 as the ends of the pistons approach an unstable overcentre position in which the ends of the pistons coincide with the common axis of rotation of the rockers 35, 35'. Beyond this position the pistons 30 are forced out of the sleeves 28 causing the rockers 35, 35' to rock rapidly about the respective axes defined by the abutting central contacts 37, 41 into their other operative positions, the key 22 being at the same time forced into its other position. A positive switching action is therefore obtained.

Rocking movement of the key 21 in both directions is limited by the projections 20 on the cover 14, as illustrated in FIG. 1. Two stop projections 13 (FIG. 4) are arranged at opposite ends of the bottom portion 2 of the base 1 to ensure that both rockers 35, 35' assume the same inclination even should one of the conductive elements 42 accidentally fail.

Since the rockers 35, 35 are not rigidly fulcrumed to the switch base 1 and could, therefore, take up irregular positions, for example by rotating about axes perpendicular to the plane of FIG. 3, thereby adversely affecting proper operation of the switch, the free end of each piston 30 is made such as to exert an evenly distributed force over the surface of each respective rocker 35, 35' the resultant of which force is coplanar with the line interconnecting the contact point of the central contacts 37, 41 and the contact point of the end contacts 38, 44 of the respective rocker. It will be apparent that the switch as described is made up of a small number of parts molded from plastics, with the exception only of the rockers, the contacts and the springs. Moreover, the said parts are interconnectable simply by snap action, avoiding any metal interconnecting members such as rivets, screws or the like and thereby facilitating assembly of the switch.

The contact-bearing metal components of the switch (FIGS. 11-13) are of simple construction and can he formed from sheet metal by punching and bending operations.

Simplicity of operation gives the switch a long operational life. The pistons 30 are preferably made of plastics having self-lubricating properties, thereby minimising wear of the pistons and of the rockers 35, 35' on which they move.

It will be understood that constructional details of the embodiment as described may be widely varied with respect to the specific disclosure and drawing without departing from the scope of the invention as defined by the appended claims.

I claim:

1. An electrical switch assembled by snap engagement of its component parts, the switch comprising, in combination, a base of plastic material formed as an open box with a floor and upstanding walls surrounding the floor, at least two apertures being formed in said -floor and each having a stepped outer end; a fixed conductive element with a blade portion projecting through each of said apertures and having a laterally projecting tongue that is retained by snap engagement in said stepped end of its respective aperture, each conductive element also having a contact portion bent at an angle to said blade portion and located adjacent the floor of said base; said base further having connecting means on two opposite walls; a cover of plastic material fitted on said base and having connecting means in snap engagement with said connecting means on the base, thereby to retain the cover to the base; said cover having a central aperture opposite the floor of said base and two lateral sides on each of which is formed a projection extending laterally outwardly beyond the central aperture; a key of plastic material having two lateral flanks each formed with an aperture, said key being pivotally mounted on the cover by snap engagement of said cover projections within said key apertures; a conductive rocker of plate material contained in said base; guide means formed in said base to guide said rocker for rocking movement about a fulcrum formed by the contact portion of a first of said conductive elements, said rocker being guided for movement between a first position in which it contacts the contact portion of a second of said conductive elements and a second position in which it is spaced from said second conductive element; and means 'operatively connecting said rocker to said key to cause the rocker to move between said first and second positions in response to pivotal movement of said key on said cover, said connecting means comprising a tubular sleeve mounted on said key and extending through said central aperture in the cover towards said rocker, a spring disposed within said sleeve, and a piston of plastic material slidably disposed in said sleeve and urged by said spring into engagement with said rocker, said piston having a projecting tooth and said sleeve having a longitudinal slot in which said tooth is snap-engaged to retain said piston in said sleeve and to prevent rotation of said piston while allowing it limited longitudinal travel, the outer end of said piston having a bevelled surface which engages said rocker substantially uniformly across the width thereof; and outwardly projecting locating means adapted to locate theswitch by snaoengagement with a support. 2. A switch according to claim 1 wherein said locating means comprises a resilient depending wing on each side of said switch, each wing having an integral, flexible, outwardly extending tongue adapted for snap-engagement behind the support.

References Cited UNITED STATES PATENTS 2,927,983 3/1960 Brown. 3,329,785 7/-l967 Baer et al 200-68 3,403,237 9/1968 Wysong. 3,444,345 5/ 1969 Mackiewicz.

HERMAN O. JONES, Primary Examiner D. SMITH, JR., Assistant Examiner US. Cl. X.R. 200-l 68

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