METHOD AND A DEVICE FOR PREVENTING FLASHOVERS

Abstract: To prevent flashover between the body (S) of a vehicle, or the like conductive element, and a user (D) thereof, a pole (P) is arranged for electric connection to the car body through an electric resistor (R) having a suitable resistance value preferably between about 2 Mohm and about 5 Mohm, and an electric connection is established, at least temporarily, between the user (D) and the pole (P). In this way, the current peak transferred between the user and the car body can be brought down to such a value as to cause no inconvenience to the user.

Description: "Method and a device for preventing flashoverε" Technical Field This invention relates to a method and device for preventing electrostatic arcing between an object subjected to collect electric charges, specifically the car body of a vehicle, and a user thereof. Background Art As is well known, vehicles are liable, e.g. as a result of the motion to which they are subjected in use, to build up electric charges of the electrostatic type. This phenomenon is specially manifest with motor cars, in particular on dry weather days and in winter, in the form of a flashover between the user and the vehicle as the former contacts a conductive portion of the latter. Also known is that the extent of this phenomenon is tied to the presence of insulative materials that readily allow a potential difference to establish between two parts, as may be the user and the car body. The increased use of plastics materials, whose electrically insulating properties are well recognized, in the manufacture of modern motor vehicle parts and accessories has enhanced the phenomenon which, from an occasional occurrence tied to weather factors as above outlined, has growr. *-.o be frequent and widespread. To mitigate the inconvenience caused to the user by such occurrence of high-potential, albeit low-current, flashovers, expedients have been studied which are all based on the use of a sliding contact for ground connection of the vehicle. Typical in this respect is, for instance, the use of chains for electrically grounding vehicles involved in the transportation of explosives, or of a so-called "pigtail" or pendant made of a conductive plastics material and attached to the vehicle body at such a location as to be dragged over the ground while travelling. Such prior approaches, while providing at least a basic way of grounding a vehicle electrically, still have a serious drawback in that they cannot do the same for the user. Accordingly, and especially with vehicles incorporating a large number of plastics components, a potential difference may easily establish between the vehicle body, which in the best of cases would be restored to ground potential, and the user, whose potential may not be null with respect to ground. Disclosure of the Invention The technical problem addressed by this invention is to provide a method and a device which are conceived to overcome all of the drawbacks with which the above prior art is beset. This problem is solved according to the invention by a method for preventing flashover between an object liable to have built up electric charges, in particular the body of a vehicle, and a user thereof, which method consists of: providing a pole adapted to be connected electrically to said object through an electric resistor having a predetermined resistance value, and establishing, at least temporarily, an electric connection between said user and said pole. This method is preferably implemented by a device comprising a pole adapted for connection, at least temporarily, to said object and said user, and a resistor of predetermined value interconnecting said pole and said object. Brief Description of Drawings The invention will now be described in greater detail with reference to three preferred embodiments thereof, illustrated by way of example and not of limitation by the accompanying drawings, in which: Figure 1 is a diagram illustrating the method of this invention; Figure 2 is a top plan view of the inventive device as incorporated to a key for setting a vehicle to operate; Figure 3 is a sectional view taken along line III-III through the device in Figure 2; Figure 4 is a part-sectional top plan view of a variation of the device according to this invention; Figure 5 is a sectional view taken along line V-V in Figure 6 and showing a further variation of the invention; Figure 6 is a sectional view taken along line VI-VI in Figure 5 and showing the same variation; and Figure 7 is a perspective view of a detail of the embodiment of the invention shown in Figures 5 and 6. Best Mode of Carrying Out the Invention Shown schematically at S in Figure 1 is a ■ motor car body or body of another vehicle, known per se, which may or may not be provided with a conventional sliding ground contact T. Shown at D is a finger or another part of a user's body that, after a trip on the vehicle having the car body S, is now temporarily at a different electric potential from the potential of the body S. Under this condition, should the user touch a conductive portion of the car body, a current will flow which usually results, due to the high value of the potential difference, in a flashover in the form of an electric arc. Indicated at P is a conduction pole which is connected electrically to the car body S through a resistor R having a greater value than 0.2 Mohm, preferably a value in the 2 to 5 Mohm range. Upon an electric contact being established, at least temporarily, between the finger D or another part of the user's body and the pole P, the current peak resulting from the potential difference relative to the car body s will be brought by the. resistor R down to such a level as to eliminate any inconvenient effect to the user. In a preferred embodiment, the device of this invention is incorporated to a key 10 for setting the vehicle to operate, such as the ignition key therefor and/or a key for unlocking the access doors to the car body S. The key 10 includes a map portion 11 and an operation lug 12 of the same. The map portion is made of a metal material with electrically conductive properties, whereas the operation lug is generally molded from a plastics material or another insulating material. Note that the map portion of metal is embedded, with part of its length, in the operation lug, such that it will turn bodily with the latter. The operation lug is flattened and provided with two juxtaposed grip surfaces 12a,b. The pole P comprises in this embodiment a metal disc 13 or another conductive element which comes out through one or both grip surfaces and is connected electrically to the map portion 11 through the resistor 14. This arrangement for the inventive device is specially advantageous in that, each time that the user touches the pole 13 by grasping the operation lug in order to introduce and turn the key 10 into its keyhole for starting or stopping the vehicle engine, any potential difference between the user and the car body will be quietly discharged through the resistor 14. Likewise, after the user gets off the vehicle and introduces the key into a corresponding keyhole on the car body, e.g. to lock the vehicle doors, any residual potential difference between the user and the car body will be quietly discharged, again through the resistor 14. Shown in Figure 4 is a variation, generally designated 20, of the key in Figures 2 and 3. Similar parts are denoted by the same numerals as in the previous embodiment. In the key 20, a gas discharge lamp 11, such as a neon lamp, is connected serially to the resistor 14 between the map portion 11 and the operation lug 12. The lamp 21 will go on when a current of suitable strength flows between the car body S and the user. A further embodiment of this invention is shown in Figures 5 and 6. Shown in these Figures is a car key 30 of conventional construction having its operation lug 31 received in a plastics molded shell 32. The shell 32 is made up of two halves 32a, 32b which can be snap joined together through the provision of respective tooth-like lips 33 extending from one half-shell and engaging into corresponding sockets provided on the other half-shell. Each half-shell 32a,b includes a respective through-going opening 34, 35. The opening 34 is formed at a location, relative to the key 30, which is aligned to an optional pushbutton switch for operating an emergency light provided on the key alongside the map portion 36 thereof. Arranged in the shell 32 to accommodate this lamp is a hole 37. It is also envisaged that the pushbutton switch on the key may be used to control theft-prevention devices or the like. The opening 35 is closed by an electrically conductive disc-shaped element 35a, such as a disc of metal to which either of the leads 38a,b connecting the electric resistor 39 to the map portion 36 of the key 30 is taken. The other lead, namely the one designated 38b, is connected to the map portion 36 by a clip 40 shown best in Figure 7. It should be noted that this clip has two legs 41, 42, essentially parallel, of which leg 41 is arcuate to enhance its elastic deformability, whilst leg 42 is essentially flat and acts as a soldering terminal for the lead 38b. Said legs 41, 42 straddle the map portion of the key and clamp around it. Molded in the half-shell 32b are shallow projections 43a,b,c,d,e,f on the interior surface of the half-shell. The projections 43a and 43f act as protections and guides for the two leads 38a,b, whilst the projections 43b-e define a housing wherein the center body of the resistor 39 interfits. An optional cover (not shown) for this housing is formed at a corresponding location on the half-shell 32a so as to shut it when the half-shells are snapped together. Note, lastly, that a tubular opening, generally shown at 44, is formed halfway in each of the two half-shells 32a,b. The opening 44 is for engagement by an optional keyholder. The invention as described is open to • many modifications and variations within the scope of the inventive concept. As an example, the key may be replaced by another suitable object or accessory of the vehicle (e.g. a keyholder or the like) for electric connection, at least temporarily, to the car body through an electric resistor of appropriate value. Furthermore, the operation lug of the key may be formed from a plastics material made conductive with an appropriate electric resistance value, thereby the operation lug can constitute itself both the pole and the electric resistance for the purpose of the method and the device according to the invention.

Claims: CLAIMS 1. A method for preventing flashover between an object (S) liable to have built up electric charges, in particular the body of a vehicle, and a user (D) thereof, which method consists of: providing a pole (P) adapted to be connected electrically to said body (S) through an electric resistor (R) having a predetermined resistance value, and establishing, at least temporarily, an electric connection between said user (D) and said pole (P) . 2. A method according to Claim 1, wherein the electric resistance value of said resistor (R) is greater than 0.2 Megaohms. 3. A method according to either Claim 1 or 2, wherein the electric resistance value of said resistor (R) is within the range of 2 to 5 Megaohms. 4. A method according to either Claim 1 or 2 or 3, wherein said electric connection between the user and the pole is established upon introduction and withdrawal of a key (10,20,30) for setting the vehicle to operate into/from a corresponding keyhole associated with the car body and electrically connected thereto. 5. A device for preventing flashover between an object liable to have built up electric charges, in particular the body (S) of a vehicle, and a user thereof, comprising a pole (P,13,35a) adapted for connection, at least temporarily, to said object and said user, and a resistor (R,14,39) of predetermined value interconnecting said pole and said object. 6. A device according to Claim 5, wherein said resistor has a greater value than 0.2 Megaohms. 7. A device according to Claim 1, wherein said resistor has a value within the range of 2 to 5 Megaohms. 8. A device according to one of Claims 5 to 7, wherein said pole (13,39) is connected electrically to the map portion (11,36) of a key for setting the. vehicle, to operate. 9. A device according to Claim 8, wherein said pole (13) is formed on an operation lug (12) of said key (10) which is insulated electrically from said map portion (11). 10. A device according to Claim 9, wherein said resistor (14) is embedded in said operation lug (12) and said pole (13) is mounted at the location of at least one of the grip surfaces (12a,b) defined thereon. 11. A device according to Claim 8, wherein a light source (21) is arranged in series with said resistor (14) between said map portion (11) and said pole (13). 12. A device according to Claim 11, wherein said light source (21) comprises a gas discharge lamp. 13. A device according to Claim 8, wherein said pole (35a) is mounted on a shell (32) fitting over an operation lug of said key (30). 14. A device according to Claim 13, wherein said shell (32) comprises two half-shells (32a,b) snap joined to each other, said resistor (39) being enclosed by said shell (32).

Inventors: FUJITA FUMIAKI, FUJITA, FUMIAKI
Applicants: CVG CENTRO VENETO GALVANICO, FUJITA FUMIAKI, C.V.G. - CENTRO VENETO GALVANICO - S.R.L., FUJITA, FUMIAKI
Application year: 1993
Main classification: B60R16
IPC codes: B60R16, H05F3