FR2685809A1 - Anti-theft switch for a motor vehicle - Google Patents

Abstract

The rotary anti-theft switch for a motor vehicle includes a support (100), comprising a base (1) closed by a hollow box (3), a rotor (4) which is manoeuvrable at will by the user and, housed within the box (3), at least one rotary cursor (5, 6) linked in rotation to the rotor (4), moving contacts (62 to 64 - 52 to 54, 58) integral with the cursor (5, 6) for interacting with point-type fixed contacts (7, 8) carried by the base (1) of the support (100). For interacting with the said moving contacts, the fixed contacts (7, 8) are coated with a layer (71, 81) of graphitic silver. Application to motor vehicles.

Description

 The present invention relates to a rotary anti-theft switch for a motor vehicle, of the type comprising an electrically insulating support, suitable for being fixed to a fixed part of the vehicle, comprising a base closed by a hollow housing, a rotor which can be operated as desired. user and, housed inside the housing, at least one rotary cursor linked in rotation to the rotor while being mounted movable relative thereto, movable contacts integral with the cursor for cooperation with fixed pontic contacts carried by the base of the support in order to establish electrical circuits in angular positions determined as a function of the position of the rotor.

Such a switch is described in the documents
FR-A-2 373 138 and FR 91 00907 not published to date.

 Such switches must have a very long service life. It follows that they must be maneuverable a very large number of times.

 Usually, the fixed contacts are based on copper and the said contacts are greased to in particular reduce friction.

 Such fixed contacts heat up and oxidize with the appearance of a layer of copper oxide increasing their resistance. In addition, lubrication causes pollution, in particular mobile contacts.

 The object of the present invention is to create, in a simple and economical manner, a new anti-theft switch with punctual fixed contacts which can be operated a very large number of times, while reducing the phenomena of pollution and limiting the increase in resistance. fixed contacts.

 According to the invention, a switch of the above-mentioned type is characterized in that, for cooperation with the movable contacts, the fixed contacts are coated with a layer of graphite silver.

 Thanks to this arrangement, the switch can be operated a very large number of times, without the need for lubrication and by limiting the increase in resistance of the fixed contacts.

 In fact, during operation of the device, the fixed contacts oxidize but this is not a problem since a conductive silver oxide layer is formed.

In addition, graphite makes it possible to reduce friction.

 The electrical contact resistance between each fixed contact and each movable contact increases in steps more slowly over time than when the fixed contacts are made of copper. In addition, when the movable contacts are made of copper, there is, over time, a silvering of said movable contacts favorable to a reduction in the electrical resistance. In addition, the friction is reduced.

 Advantageously, the layer of graphitized silver is added by brazing to the fixed contacts and has a thickness of 5 to 6 tenths of a millimeter.

 Advantageously, the fixed contacts are arranged in studs.

The following description illustrates the invention with reference to the accompanying drawings in which
FIG. 1 is a view in axial section of a switch according to the invention,
FIG. 2 is a front view of the first cursor of the switch,
FIG. 3 is a sectional view along line 3-3 of FIG. 2,
- Figure 4 is a front view of the second switch slider.

FIG. 5 is a sectional view along line 5-5 of FIG. 4,
FIG. 6 is a top view of the switch without its cover and its rotor,
- Figure 7 is a sectional view along line 6-6 of Figure 6.

 The device illustrated in the figures is a rotary electric motor vehicle anti-theft switch operating to connect the vehicle battery to the starter motor to turn the engine before it starts and to other electrical circuits of the vehicle.

 The other electrical circuits usually include an "accessory" circuit and at least one "ignition" circuit.

 Such switches must be safe and robust with contacts capable of withstanding fairly high currents and mechanical forces.

 More specifically, the rotary anti-theft switch of a motor vehicle is of the type comprising an electrically insulating support 100, suitable for being fixed on a fixed part of the vehicle, comprising a base 1 closed by a hollow housing 3, a maneuverable rotor 4 at the option of the user and, housed inside the housing 3, at least one rotary slider 5,6 linked in rotation to the rotor 4 while being mounted movable relative thereto, movable contacts 62 to 64 - 52 to 54.58 integral with the cursor 5.6 for cooperation with fixed pontic contacts 7.8 carried by the base 1 of the support 100 in order to establish electrical circuits in angular positions determined as a function of the position of the rotor 4.

 According to the invention a switch of the above-mentioned type is characterized in that, for cooperation with said movable contacts, the fixed contacts 7,8 are coated with a layer 71,81 in graphite silver.

 Here the support 100 is made essentially from an industrial plastic material intended to give strength and rigidity in addition to the electrical insulation. The support 100 has a base 1 on which is fixed on one of its faces, by any appropriate means, such as screwing clipping, the hollow housing 3. The other face of the base 1 is coated for fixing by a cap 2.

 Inside the housing 1, the rotor 4 and the sliders 5,6 are mounted. This rotor 4 has a free end passing through the bottom of the housing 3 and having a hole 41, here in the form of a keyhole, for its rotational drive by a finger operable at the discretion of the user. The other end of the rotor 4 has a finger received in a through passage 12 that has the base 1 for this purpose.

 The cap 2 has a centering nose 21 also penetrating into this passage 12 stepped for this purpose.

 The two rotary sliders 5,6 are linked in rotation to the rotor 4 by being mounted axially movable relative to the latter. These cursors are the image of each other. They are made of electrically conductive material, being axially staggered just like the rotor 4. Here these sliders 5,6 are copper-based.

 Each cursor 5,6 carries movable contacts for cooperation with fixed contacts 7,8 respectively carried by the base 1. The fixed contacts 7,8 are therefore staggered axially, the base 1 being shaped accordingly.

 It will be noted that this base 1 includes ears 11 for its attachment to a fixed part of the vehicle.

 Of course, the fixing of the support 1 to the vehicle can be done in another way, the box 3 being for example shaped to present the fixing lugs as in the document FR-A-2 373 138.

 Each slider 5,6 is subjected to the action of elastic means with axial action respectively 51,61, here in the form of coil springs, housed in the rotor 4 shaped for this purpose. Thus, this rotor 4 has in particular blind housings 58 for receiving springs 51.

 This rotor 4 is guided in rotation by the passage 12 as well as by the bottom of the housing 3 perforated for this purpose.

A return spring 9 is provided. Such a return spring is visible in particular in the document
FR 91 00907 and will not be described in more detail here.

 For the record, it will be noted that this return spring is in the form of a coil spring and that it has arms, one of which is armed by rotation of the rotor 4 in order to carry out a return.

 This spring 9 surrounds the rotor 4 while being surrounded for its mounting by a part 91 fixed to the rotor 4 by crimping.

 The cursor 5 is stamped locally to present stampings 54.58 distributed over a first circumference and stampings 53.54 distributed over a second circumference of diameter smaller than the first. These stampings form movable contacts in one piece with the cursor 5.

 For its rotational drive with axial mobility by the rotor 4, this slider 5 has a tongue 55 which engages in a corresponding groove in the rotor 4. There is further provided a finger 56 suitable for cooperating with a corresponding groove in the rotor 4 in order to mount the cursor 5 in a determined angular position.

 The cursor 5 is of annular shape. It is the same for the cursor 6, which also has two stampings 63,64 distributed over a first circumference and a stamping 62 formed on a second circumference of diameter smaller than the first. The cursor 6 also has an indexing finger 60 and an axial tab suitable for engaging in a corresponding hole made in the rotor 4.

 These sliders 5,6 are axially movable under the action of the springs 51,61. They are able to cooperate with fixed contacts 7,8 of electrically conductive material.

 As will be understood, by rotation of the rotor at the option of the user, the stampings (the movable contacts) are capable of coming into contact with the fixed contacts to establish the electrical circuits.

 Here, these fixed contacts consist of studs coated with the layer of graphite silver 71, 81 according to the invention. These studs constitute the rivet head respectively 7.8 here in copper. The foot of the rivets is used for fixing power supply terminals 72.82.

 The graphite silver layer here is 5 to 6 tenths of a millimeter thick. Of course it depends on the applications. This layer is added by brazing on the head of the rivets 7,8 which cross the base 1 provided with passages 73,83 respectively for this purpose.

 The cap 2 covers the feet of the rivets 7,8 in order to isolate them. The power supply terminals 72, 82 are connected to a power supply harness itself connected to the vehicle battery.

In FIG. 6, we see in dotted lines the contact pads with their coatings in graphite silver according to the invention with their different names. Thus the reference ST1 relates to the fixed contact inserted in the electrical supply circuit of the starter of the motor vehicle just like the fixed contact ST2. The fixed contact ACC belongs to the electrical circuit of an accessory such as the radio, while the contacts
IG1, IG2 belong to the vehicle's electrical ignition circuit.

 The contacts AM1, AM2 belong to the electrical circuit connected to the positive terminal of the vehicle.

 By operating the rotor, different electrical circuits are therefore established and thanks to the 71.81 coating in graphite silver it is possible to operate the switch a very large number of times, while having the possibility of passing high currents.

 The switch is therefore economical and robust.

 In addition, the sliders 5,6 being made of copper, silvering of the movable contacts of the latter occurs over time by contact with the graphite silver coatings 71,81 of the fixed contacts.

 This reduces the increase in electrical resistance between the contacts.

 In addition, the operation is carried out without pollution of the mobile contacts, with a minimum of friction and a minimum increase in the electrical resistance of the fixed and mobile contacts.

Claims (4)

 1) Motor vehicle anti-theft rotary switch, of the type comprising an electrically insulating support (100), suitable for being fixed on a fixed part of the vehicle, comprising a base (1) closed by a hollow housing (3), a rotor (4) maneuverable at the discretion of the user and, housed inside the housing (3), at least one rotary slider (5,6) linked in rotation to the rotor (4) while being mounted movable relative to the latter ci, movable contacts (62 to 64 - 52 to 54.58) integral with the cursor (5,6) for cooperation with pontic fixed contacts (7,8) carried by the base (1) of the support (100) in order to '' establishing electrical circuits in angular positions determined as a function of the position of the rotor (4), characterized in that, for cooperation with said movable contacts, the fixed contacts (7,8) are coated with a layer (71, 81) in graphite silver.  2) Switch according to claim 1, characterized in that the fixed contacts (7,8) consist of contact pads belonging to rivets (7,8), the head of which is coated with a layer of graphite silver.  3) Switch according to claim 2, characterized in that the graphite silver layer is added by brazing on the head of the rivets (7,8).  4) Switch according to any one of claims 1 to 3, characterized in that the rotary cursor (5,6) is based on copper.