FIELD OF THE INVENTION This invention relates to a fuel tank security device particularly, but not method shall exclusively, for use with motor vehicle fuel tanks. More particularly, the invention relates to an obstructive security device that is adapted to inhibit, and to all intents and purposes prevent, the introduction of a siphon tube into a fuel tank for the purpose of unauthorised removal of fuel or precious liquid by a would-be thief.

BACKGROUND TO THE INVENTION The theft of liquid fuel from a fuel tank, in particular a motor vehicle fuel tank, by siphoning fuel therefrom has long been a problem. Numerous different obstructive security devices have been proposed in the past and each of these has had the potential of being effective to greater or lesser extents.

Many of them, such as those described in United States patents 3,985, 259; 3,002, 649; 3,016, 162; 2, 496,992 and 2,281, 448 employ one or a multitude of fingers or a spring loop adapted to engage an internal step change in the diameter of the inlet pipe to a fuel tank generally at the inlet end of the pipe, or somewhere in the length of the pipe. Others such as those described in United States patents 4,344, 544; 3,892, 330 and 3, 888,381 provide a device that frictionally engages the walls of the inlet pipe There are numerous other configurations that have been proposed but will not be mentioned herein.

Suffice it to say that almost without exception the devices either need to be especially installed during fuel tank manufacture or, alternatively, as a separate modification of the fuel tank or, alternatively, they are not adequately anchored in position to effectively prevent them from being either forced into the fuel tank to thereby allow access to a siphon tube or to be pulled out of the filler pipe.

It should be noted that the actual configuration of the obstructive formations associated with the respective devices is largely immaterial so long as they effectively prevent a siphon tube from being manipulated past them so as to gain access to the interior of the fuel tank. The formations are generally coiled wire, a multitude of fingers, or perforated baffles.

OBJECT OF THE INVENTION It is an object of this invention to provide an obstructive security device for a fuel tank that is simple to install yet effective in combating its removal either by forcing it into the fuel tank or by forcing it out of the inlet filler pipe to the fuel tank.

SUMMARY OF THE INVENTION In accordance with this invention there is provided an obstructive security device for a fuel tank comprising obstructive formations for location within a fuel tank filler pipe between an inner and an outer end thereof and anchor means for inhibiting removal of the obstructive formations from their obstructive position within the fuel tank filler pipe, the device being characterised in that the anchor means includes both outer stop means for cooperating with a fuel filler pipe at or towards the outer inlet end thereof to prevent further movement of such stop means into the filler pipe and inner stop means for cooperating with an inner end of the fuel tank filler pipe to inhibit movement of the obstructive formations in a direction towards the

outer end of the filler pipe and wherein the inner stop means and outer stop means are interconnected by a connecting tie element.

Further features of the invention provide for the outer stop means to include a sleeve that is adapted to fit within the outer end region of a fuel tank filler pipe in which case the sleeve preferably has either a continuous or discontinuous peripheral flange at its outer end for engaging the outer end of the fuel tank filler pipe or, alternatively, a stop member on the outer surface of the sleeve for engaging a discontinuity in the fuel filler pipe such as, a breather hole ; for the sleeve to be fitted with a transverse baffle that defines, at least in part, the obstructive formations; for the inlet sleeve to optionally have a smaller diameter inlet pipe fixed thereto with the inlet pipe being adapted to receive the spout on a fuel supply pump; and for the inner stop means to comprise at least two diametrically opposite pivotally mounted stop arms movable between terminal positions in an inoperative one in which the arms are directed generally towards the connecting tie element and an operative terminal position in which they extend generally radially outwards on the inside of the inlet end of the fuel filler pipe and obstruct withdrawal of the device from the inlet pipe.

In order that the invention may be more fully understood various embodiments thereof will now be described with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:- Figure 1 is a schematic sectional view taken through a fuel tank that is typical of a transport vehicle and showing a device according to the invention in its operative position;

Figure 2 is a schematic detailed sectional elevation of one embodiment of the invention; Figure 3 is a similar view of a variation thereof; Figure 4 is a similar view of a device having an alternative outer stop means; Figure 5 illustrates, in the axial direction, one form of obstructive formation and outer stop means such as may be used in the embodiment of Figure 2; Figure 6 illustrates similarly an obstructive formation and outer stop means such as may be used in the embodiment illustrated in Figure 3; and, Figure 7 illustrates similarly the embodiment of the invention illustrated in Figure 4.

DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS Referring firstly to Figures 1 and 5 of the drawings, the obstructive security of this invention device, generally indicated by numeral (1), is adapted to be fitted into the inlet pipe (2) of a fuel tank (3) of the general type as is usually associated with a transport vehicle, being a rather short inlet pipe passing through the wall of the tank.

The security device has obstructive formations, generally indicated by numeral (4), outer stop means (5) that prevent the device from entering the fuel filler pipe further; and inner stop means (6) that prevent the device from being withdrawn from the fuel filler pipe. The outer stop means and inner stop means are interconnected by a connecting tie (7) permanently fixed to

both stop means. It will thus be appreciated that the obstructive security device according to this invention will generally be especially configured for a particular type of tank or range of tanks having similar size and configuration of fuel filler pipe.

Referring now more particularly to the embodiment of the invention illustrated in Figure 2, the outer stop means is formed as an outwardly directed flange (8) at the outer end of a tubular sleeve (9) that fits within the fuel filler pipe (10) of the fuel tank and that engages a shoulder (11) that is located inwards of the filler cap (12), The sleeve has secured to its inner end, by means of brackets (13), an obstructive member in the form of a perforated baffle plate (14).

The connecting tie element, in this case, is secured to the perforated plate and is in the form of a metal strip (15) that extends generally axially relative to the sleeve.

The remote end of the metal strip has secured thereto a transverse inner stop assembly consisting of a fixed transverse element (16) to which are pivotally attached a pair of oppositely directed arms (17) that form the inner stop means. The arms are pivotally movable between two terminal positions, an inoperative one illustrated in dotted lines in which they extend in the general direction of the axis of the sleeve so as to permit passage of the inner stop assembly through the fuel filler pipe, and one in which they extend outwards in diametrically opposite directions. In the latter position the arms form a substantially secure diametrically extending composite arm that has a length appreciably greater than the diameter of the fuel filler pipe and thus creates an interference with the inner end (18) thereof to prevent withdrawal of the device a the fuel filler pipe.

The arms can be instructed in any suitable way that is commensurate with adequate security and may either be made of metal plate or a suitable angle section, simply by way of example.

In this embodiment of the invention a loose circular"security"plate (19) is axially slidable on the metal strip (15) so that it shields the arms from interference by means of wires that may be passed down the fuel filler pipe in an attempt to move the arms to the inoperative positions and permit withdrawal of the device from the fuel filler pipe.

It will be understood that, in use, the device described above can be neither forced into the fuel tank or withdrawn from it with each of the outer and inner stops preventing such withdrawal in the appropriate direction. The perforated plate, of course, prevents a siphon tube from being introduced into the fuel filler pipe. The arrangement of the perforated plate and peripheral flange is shown clearly in Figure 5.

Referring now to Figures 3 and 6 of the drawings, there is illustrated a variation in which the obstructive member is an imperforate plate (20) that obscures a substantial part of the cross-section of the sleeve (21) that is to be located in the fuel filler pipe in the manner described above. In this case a smaller diameter inlet pipe (22) passes through the obstructive plate (20) with the inlet pipe being dimensioned to accommodate the spout of a fuel supply pump. The inlet pipe has a transverse stop (23) to prevent a siphon tube from being introduced into an associated fuel tank by way of the inlet pipe.

In this instance the peripheral flange is replaced by four equally angularly spaced outwardly directed stops (24). Also, in this instance, the filler pipe serves as the connecting tie element as well.

Turning now to the embodiment of the invention illustrated in Figures 4 and 7, there is illustrated a device in which a sleeve (25) has an outwardly inclined

stop (26) secured to its outer surface with the stop being arranged so that it will, when introduced into an appropriate fuel filler pipe, become engaged in an air breather hole (27) provided in the fuel filler pipe (28) and thereby act as a stop to prevent further movement of the sleeve into the fuel filler pipe.

It will be understood that numerous variations may be made to the embodiments of the invention described above without departing from the scope thereof. In particular, the invention also applies to somewhat longer fuel filler pipes and even filler pipes that are not entirely straight so long as the connecting tie element is adequately flexible to accommodate the bends.