GB2067254A - Anti-theft arrangement for vehicle identification plate - Google Patents

Abstract

The number plate 1 is fixed to the metal 2 of the vehicle by a screw 4, a locking washer 11 and a nut 10; the locking washer and nut have inter- engaging toothed tracks which, by ratchet action, prevent the nut being loosened. The nut is domed and provided with engagement surfaces for a tightening up tool only. A square hole in the washer 11 fits on a flatted part 6 of the screw shank. The identification plate can be removed by gripping the head of the screw and turning it together with the washer and the nut. Teeth 7 at the edge of the head then cut through the number plate which can be lifted over the screw heads, but is so damaged as to be unusable. <IMAGE>

Description

SPECIFICATION Anti-theft arrangement for vehicle identification plate This invention concerns an anti-theft arrangement for vehicle identification plates, such as number plates, which can be fixed to a vehicle using screws and nuts, each screw head having gripping surfaces for a tightening up tool, each nut having an essentially domed form and wherein a washer may be provided between the identification plate and the vehicle.

In a known anti-theft arrangement for vehicle identification plates of the above mentioned kind (German getrauchmuster 72 45 878), the vehicle identification plate is fixed in the usual manner by means of two screws and complementary nuts on to the bumper or another part of the vehicle. These screws and nuts, however, only perform the fixing function. In addition to these screws there is provided a further security screw. The security screw has a sunk head and in the vehicle identification plate there is pressed an outwardly projecting boss. This boss has a depression corresponding to the sunk head of the screw and in which the screw head of the security screw fits.

The security screw is engaged on the rear side of the bumper or a bracket by a nut with a conical or rounded head. After the security screw has been screwed into the nut, the official seal is stuck over it (referring to vehicle licensing practice in the Federal Republic of Germany for example). Apart from the fact that the use of this security screw requires especially formed vehicle identification plates, the known anti-theft arrangement possesses various disadvantages. Since the nut with a round or conical head cannot be gripped and turned with pliers or a wrench, it cannot be held fast when tightening up the security screw.

There is accordingly the danger that the nut will loosen and be lost, the security function of the security screw then being lost. Furthermore this anti-theft arrangement does not correspond to the current practice of vehicle licensing offices. When a vehicle is licensed, the officially prescribed seal is applied to the licensing plate in the offices of the licensing authority. In this case, the vehicle is still with the dealer or in the factory. Since it is not yet licensed it cannot be brought to the licensing offices. If the known antitheft device is to be employed, the vehicle must firstly be brought to the licensing offices with provisional licensing plates and there a mechanic has to fit the number plates to the vehicle and screw up the security screw. Only then can the prescribed seal be stuck over the security screw.This, however, can only be done by an official of the vehicle licensing authority since the seals themselves cannot be given out. The application of the known anti-theft arrangement would therefore involve serious additionai work and would make necessary a complete reorganisation of the existing licensing procedures. Moreover the known anti-theft arrangement is only suitable for the use of adhesive seals. There are now many vehicle licensing offices which do not use adhesive seal but strong plastic seals which are forced irremovably into fixing rings riveted to the identification plate. The known anti-theft arrangement cannot be used for such seal.

The object of the present invention is to provide an anti-theft arrangement for a vehicle identification plate which is of simple construction, easy to mount, offers the greatest possible security against unauthorised removal of the identification plate but which can be removed with partial destruction of the identification plate.

According to the present invention there is provided an anti-theft arrangement for a vehicle identification plate comprising a screw which is, in use, passed through the plate and part of the vehicle, a locking washer and a domed nut, the screw head having engagement surfaces for a tightening tool and having a plurality of teeth projecting from its underside so as, when installed, to bite into the identification plate, the screw having a flatted shank part between the head and a threaded shank part, the washer having a hole complementary to the flatted shank part, the mating surfaces of the nut and washer having toothed tracks which permit rotation of the nut only in the tightening up direction, and the nut having engagement surfaces allowing it to be tightened up, but not untightened, by a mounting tool.

The new anti-theft arrangement is simple to produce since it consists only of a few parts.

Mounting can be effected with the appropriate tools in a simple manner. When the nut is tightened up the teeth of its toothed track ride over the teeth of the track on the washer with ratchet action but the nut cannot be freed because the teeth block rotation of the nut in the opposite direction. To strengthen this effect, the nut only has engagement surfaces for a tightening up tool which operates to turn the nut in the tightening up direction. Since the nut otherwise has a domed form and advantageously consists of hardened steel, there are no kinds of engagement surfaces for a tool such as pliers which might otherwise be used to undo the nut. The precise shape of the domed nut is immaterial, so long as this effect is achieved. The nut may be part spherical or frusto-conical for example.

The flatted part of the screw shank and the corresponding hole in the locking washer fix the washer against rotation relative to the screw. By the use of this screw and nut fixing the identification plate can be quickly and simply fixed to the vehicle in a theft proof manner. When necessary, however, it can be removed from the vehicle. This is effected by the use of a suitable tool engaging the engagement surfaces of the screw head. By means of this tool the screw head is turned together with the locking washer and the nut. The teeth projecting from the underside of the head cut out an annular part of the identication plate. A washer utilized in conventional manner between the identification plate and the chassis of the vehicle will prevent damage of the vehicle.

Once the screw heads have cut through the identification plate, this can be removed. The cutting away of the metal also loosens the nut sufficiently for the toothed tracks no longer to engage, whereby the nut can be unscrewed. The screw and nut fixing is then usable for mounting another identification plate. The removed identification plate however has large cut-outs, the screw heads being made suitable large, so that it is no longer usable in unauthorised manner. The damage to the identification plate is clearly identifiable even from a long way off.

The invention will now be described in more detail, by way of example, with reference to the accompanying drawings in which: FIGURE 1 is a cross section through an antitheft arrangement embodying the invention; FIGURE 2 is a side view of the screw in the direction II of Figure 9; FIGURE 3 shows the underside of the nut; FIGURE 4 is a top view of the nut; FIGURE 5 is a side view of the nut in the direction V of Figure 4; FIGURE 6 is a cross section of the locking washer on the line Vil-VIl of Figure 7; FIGURE 7 is a plan view of the locking washer; FIGURE 8 is a partial section through the locking washer on the line VIll-Vill of Figure 7; and FIGURE 9 is a partial front view of the installed anti-theft arrangement.

In the drawings a vehicle number plate 1 is pressed in known manner out of aluminium sheet.

This number plate 1 is fixed to the chassis sheet metal 2 of the vehicle by means of the arrangement embodying the invention. To this end there is employed the screw and nut fixing now to be described.

The screw 3 has a screw head 4 and a threaded screw shank 5. Between the head 4 and the threaded part 5 of the shank there is a flatted, square portion 6. The screw shank has a diameter of 8 mm and the side of the square is also 8 mm.

At the outer periphery of the screw head 4 and on the underside of the head are cutting teeth 7. The teeth 7 project from the underside of the head by an amount a which is at least as large as the thickness D of the identification plate 1. Since a thickness for a number plate of 1.5 mm can be assumed, the projection a is made more than 1.5 mm.

The screw head 4 also has two flats 4a serving as gripping surfaces for a tool. In the illustrated embodiment these flats 4a extend in approximately the same plane as opposite surfaces 6a of the square shank part 6. Moreover the flats 4a continue into the cutting edges of the teeth 7. In order to achieve the cutting action of the teeth 7 efficiently, there is provided at each end of the head 4, as is seen in Figure 2, a V-shaped depression 9 running parallel to the flats 4a between two cutting teeth 7. The flanks of the V-shaped depression 9 provide the clearance surfaces of the teeth 7 whereas the surfaces which run into the flats 4a are the cutting surfaces.

In order that the cutting teeth 7 can have the necessary cutting action and particularly in order that the screw head 4 cannot readily be separated from the screw shank by any kind of tool for unauthorised removal of the number plate, the whole screw 3 consists of hardened steel. The screw head 4 should have a "diameter" d of at least 20 mm, diameter here meaning the longest dimension of the screw head. The significance of this dimension will be explained below.

The flatted part 6 of the shank is made sufficiently long to extend right through the chassis metal 2 of the vehicle. On the projecting part of the flatted part 6 is fitted a locking washer 11 which has a square hole 12 corresponding to the square shank part 6. The form of the locking washer is shown more clearly in Figures 6 to 8.

The locking washer 11 advantageously has a shallow, frusto-conical outer surface 13 and is provided on the surface facing the nut 10 with a saw tooth track 1 5. The toothing is recessed into the washer 11 and consists of essentially radially running teeth 1 6. Each tooth 16 has a ramp surface 6a rising at a shallow angle of about 100 in the tightening up direction A of the nut 10 and a blocking surface 1 6b facing in the other direction and extending approximately axially and radially.

The locking washer 11 also has on the side opposite to the track 1 5 a recess 1 7 which is so shaped that the locking washer 11 tapers off to a lip 1 3a at its outer periphery. This construction is apparent in particular from Figures 6. The locking washer 11 consists of spring steel.

The nut 10 has on its underside, i.e. the side facing the locking washer 11 and the chassis metal 2, a toothed track 18 with teeth complementary to those of the toothed track 1 5 on the washer. The nut 10 is domed with an approximately hemispherical outer surface 1 9.

The nut 10 has two diametrically opposite engagement surfaces 20 running approximately parallel to the nut axis and approximately radially, for engagement by a correspondingly formed tightening-up tool. The engagement surfaces 20 are at the ends of recesses 21 which extend approximately perpendicular to the engagement surfaces in the direction opposite to the tightening-up direction A, more or less up to the periphery 1 9a of the nut 10. Each recess 21 runs into the surface 1 9 against the tightening up direction A with inclined surfaces 22 and rounded surfaces 23. The nut 10 consists of hardened steel.

In order to fix the number plate 1 the screw shank 5 is first pushed through a hole 1 a in the plate 1. Then a washer 14, advantageously of hardened steel, is fitted over the square shank part 6. This washer has a hole 1 4a which is larger than the diagonal of the square part 6. Furthermore the washer 14 has a diameter dl which is greater than the "diameter" d of the screw head 4.

The projecting shank 5 of the screw is then pushed through a hole in the chassis metal. The locking washer 11 is then fitted, being non rotatable with respect to the screw 3 because of its square hole 12 fitting over the square part 6.

Utilizing a suitable tool which engages the surfaces 20 of the nut, the nut is screwed in the tightening up direction A onto the screw shank 5, the lip-like border 1 a of the spring locking washer being pressed against the chassis metal 2.

As the nut is tightened up, the toothed tracks 1 5 and 1 8 engage with one another and are pressed firmly into contact because of the resilient characteristics of the locking washer 11. Since the blocking surfaces 1 6b extend radially and axially, the nut cannot be turned back in the direction opposite to the tightening up direction A.

Furthermore, because of the form of the nut, it has no kinds of engagement surfaces for a tool acting to undo the nut and cannot be gripped by any tool such as pliers. The identification plate 1 is accordingly fixed in a thief proof manner to the vehicle. Dismounting is only now possible if the flats 4a of the screw head 4 are gripped with a suitable tool and the screw head is turned. The cutting teeth 7 then press into the relatively soft aluminium of the number plate and cut out of the number plate 1 an annular piece R shown in Figure 9 in chain dotted lines. Since the outer diameter of this annular piece R is as large as the diameter d of the screw head 4, the number plate can be removed. Underneath the screw head remains an annular part S of the number plate.

Because of the cutting away of the annular track R and the annular part S, the number plate is so damaged that it can no longer be used. In order that the damage shall be visible from a greater distance, the screw head 4 has a "diameter" dof at least 20 mm.

After the annular track R has been cut through the identification plate, the annular part S of the number plate can drop into the recess 4b under the screw head between the teeth 7. The pressure on the nut 10 is released and the blocking surfaces 1 6b of the toothed tracks 1 5 and 1 8 are no longer held engaged. The hut can be removed again from the screw shank 5 and the screw and nut fixing can be used again.

Claims (16)

1. Anti-theft arrangement for a vehicle identification plate comprising a screw which is, in use, passed through the plate and part of the vehicle, a locking washer and a domed nut, the screw head having engagement surfaces for a tightening tool and having a plurality of teeth projecting from its underside so as, when installed, to bite into the identification plate, the screw having a flatted shank part between the head and a threaded shank part, the washer having a hole complementary to the flatted shank part, the mating surfaces of the nut and washer having toothed tracks which permit rotation of the not only in the tightening up direction, and the nut having engagement surfaces allowing it to be tightened up, but not untightened, by a mounting tool.

2. Arrangement according to claim 1 characterised in that the cutting teeth project a distance at least equal to the thickness of the identification plate.

3. Arrangement according to claim 2 wherein the projection of the cutting teeth is greater than 1.5 mm.

4. Arrangement according to claim 1, 2 or 3 wherein the engagement surfaces of the screw head are two flats.

5. Arrangement according to claim 4 wherein the flats on the screw head run into flats of the flatted shank part.

6. Arrangement according to claim 5, wherein the screw head flats also run into the cutting edges of the cutting teeth.

7. Arrangement according to claim 6 wherein, at each end of the screw head, two cutting teeth flank a V-shaped depression running parallel to the flats and providing relief surfaces for the teeth

8. Arrangement according to any of claims 1 to 7 wherein the maximum diameter of the screw head is at least 20 mm.

9. Arrangement according to any of claims 1 to 8 wherein the screw, including its head, is hardened.

10. Arrangement according to any of claims 1 to 9 comprising a further washer between the locking washer and the screw head and having a diameter greater than the largest diameter of the screw head.

11. Arrangement according to any of claims 1 to 10 wherein each tooth of the toothed tracks has a surface ramping up at a shallow angle of approximately 10 to a blocking surface extending approximately axially and radially.

12. Arrangement according to any of claims 1 to 11 wherein the locking washer has a frustoconical outer surface.

1 3. Arrangement according to claim 12 wherein the locking washer is so recessed on the side opposite the toothed track that its periphery tapers to a lip.

14. Arrangement according to any of claims 1 to 13 wherein the locking washer consists of spring steel.

1 5. Arrangement according to any of claims 1 to 14 wherein the nut consists of hardened steel.

16. Arrangement according to any of claims 1 to 1 5 wherein the nut has two diametrically opposite engagement surfaces extending approximate parallel to the nut axis and approximately radially for engagement by a tightening up tool, each engagement surface being at the end of a recess which so runs into the surface of the nut as to provide no engagement surfaces for an untightening tool.