WO2007104104A1

WO2007104104A1 - Anti-siphon system

Info

Publication number: WO2007104104A1
Application number: PCT/AU2007/000316
Authority: WO
Inventors: Damien J. Zaf; Andrew Zaf
Original assignee: Fuel Protection Systems Pty Ltd
Priority date: 2006-03-15
Filing date: 2007-03-15
Publication date: 2007-09-20
Also published as: AU2007225018A1

Abstract

An anti-siphon device including two means of positioning, the first being a throat fitting such as provided by the twisting of the resilient head into the throat of the opening and the second being a spacer means engaging the internal base of the fuel tank to provide substantial adjacent positioning of the restricting head to the opening of the fuel tank, wherein the anti-siphon device allows safe selective retrofitting to fuel tanks as required.

Description

ANTI-SIPHON SYSTEM

FIELD OF THE INVENTION

The present invention relates to an anti-siphon system for use in preventing or limiting the effects of unauthorised siphoning of fuel from fuel tanks such as those on large machinery.

BACKGROUND

Many large pieces of .machinery are left unattended for long periods. This can include large earth moving equipment or vehicles that are left at the new roadwork site, mining equipment at mine sites, or semi-trailers and trucks left at truck depots or at roadsides. The length of the unattended period can be hours while the user has a sleep or overnight to the next day shift, or for longer periods such as over a weekend or holiday period.

The construction of such equipment and vehicles is to have a separate attached fuel tank. Therefore there is ready access to the fuel. Unlike on modem passenger vehicles the use of locks is considered cumbersome, as it will require separate keys for the different locks. Otherwise to have single keys is not cost effective, as therefore the fuel tank lock must be of the same standard as the ignition key lock.

The loss of fuel by illegal siphoning can be a great expense both in the amount of fuel lost, as wefl as the inconvenience of being left with a vehicle or equipment with little or no fuel. The maintaining and coordinating of fuel supply is thrown into turmoil. A large organisation with many vehicles or equipment cannot run a cost effective fuel strategy when at any time any one or more of its vehicles or equipment is not available for use. Any downtime is lost production and wasted man-hours and can also affect others work schedules.

It is known but not commonly known to use anti-siphon systems. This can be a system for preventing access of a siphon pipe into the feeding hose into the tank. For example in the United States of America patent no. US 3,991,792 there is shown a circular disk recoiled spring lodged in the feeding hose and spaced from the entrance to the hose. The problem with such a system is that the circular spring disc must be fitted in a single plane and if misaligned or knocked out of alignment is easily rendered ineffective. Therefore there are difficult installation procedures and ready de-installation procedures. However a primary problem with such a system is that it is remote from the tank and requires a tank pipe inlet that could be readily removed, detached or punctured. Most heavy vehicles or equipment do not have inlet pipes and therefore such system is not applicable.

Tn another category of anti-siphon systems that have been suggested but not shown to be in wide use is the use of restricting means attached to the opening of the tank.

Such systems such as the one shown in Canadian patent application no. CA 948,573 can include a spiral-coiled spring that is attached to the flange of the tank. This is achieved by a rotation of the spring. However such a system requires either a locking flange cover to prevent ready removal by simply reversing insertion. Alternatively a free hanging system can be further inserted and dropped into the tank to render it ineffective.

Generally any system currently in use requires a welding to the opening flange. Welding around fuel tanks is dangerous as the fuel or fumes are readily ignitable. Therefore for safety such systems must be installed at initial manufacture. This does not allow the retrofit of systems and requires all tanks whether they need them or not to be fitted at manufacture. Faced with this increase in cost without known need the systems are often not included at all.

OBJECT OF THE INVENTION

It is an object of the present invention to overcome or at least ameliorate the problems of the prior art.

It is therefore an aim of the invention to provide a system to minimise or at least limit the cost and inconvenience of unauthorised siphoning of fuel and to allow selective filling when required.

It is another object to provide an improved anti-siphon system that can be used to form a deterrent or prevention system that will not accidentally disassemble.

It is a further object of the invention to provide a method of retrofitting an anti- siphonϊng system.

SUMMARY OF THE INVENTION

According to the present invention, there is provided an anti-siphon device for use in a fuel lank and comprising: a restricting head having a size and shape substantially corresponding to the opening of a tank and shaped to substantially prevent a hose or pipe being inserted while including openings to allow flow of fuel into the tank; and further including a spacer means attached to the restricting head and having a size and shape to be inserted within the opening of the tank and to extend to the base of the tank and retain the restricting head adjacent the opening of the tank.

In one form the restricting head is a spiral spring with a diminishing radius to provide a spiral closure with interspaced openings for allowing inlet fuel to pass outwardly therethrough.

Preferably the restricting head includes a top open channel section having a central cylindrical channel before incurring a shaped closure means preventing further progress of a pipe or hose. In this way a fuel pump nozzle can be inserted to allow filling of the tank but prevents further access by a siphoning hose.

The restricting head can include an expansion means for providing expanding fitting when placed into the throat of a fuel tank opening.

The restricting head can include a resilient means to allow compressible fitting within the throat of the opening.

Preferably the restricting head includes a top spiral spring with a substantially constant radius attached to a spiral spring with a diminishing radius to provide a spiral closure with interspaced openings for allowing inlet fuel to pass outwardly therethrough. The top spiral can be dimensioned slightly larger than the throat of the opening and by rotation of the spring be frictioπaJly held within the throat and maintained in position by the spacer means. The restricting head can include a cross member extending across the radius of a portion of the restricting head and engageaple by a mechanical or automatic rotating to effect the rotational twisting force onto the restricting head and insertion into the fuel tank opening having a slightly smaller radius.

The spacer means can include one or more legs attached to a lower portion of the restricting head and extending substantially in a linear direction to a spacer base for engaging the fuel tank base opposite the fuel tank opening.

Preferably the spacer means includes a plurality of linearly extending legs mounted to a spacer base. This improves the rigidity of the structure.

However the spacer means can include a plurality of legs crossing over each other and being attached at the top to the restricting head, at the crossover, and at the spacer base. Such a structure provides a structure able to withstand longitudinal stresses as well as torsional strains caused by rotational insertion.

The spacer means can Include a length altering means to allow for selection of a length suitable to a particular fuel tank. This length altering means can include a telescopic means with locking means such as saw tooth fittings to lock to a selected length and prevent collapsing. In another form the spacer means can include add on lengths that are selectively attached to form the length of spacer means required. Such system could be screw on sections. Clearly such structures remain substantially longitudinally aligned and with a radius less than the opening of the fuel tank to allow insertion therein.

The anti-siphon device is constructed of a material that will not affect the fuel quality or affect or increase the safety of the fuel in the fuel tank.

It can be seen that an important aspect of the anti-siphon device is the two means of positioning. This includes the throat fitting such as provided by the twisting of the resilient head into the throat of the opening. The second is the Spacer means engaging the internal base of the fuel tank lo provide substantial adjacent positioning of the restricting head to the opening of the fuel tank. Therefore the anti-siphon device allows safe selective retrofitting to fuel tanks as required.

The anti-siphon system can be achieved by means of a combination of a fuel tank having a circular tubular opening in a top section and an anti-siphon device, wherein the anti-siphon device has a restricting head shaped to substantially prevent a hose or pipe being inserted while including openings to allow flow of fuel into the tank, and a spacer with a spacer base for engaging the fuel tank at a position opposite the top opening.

The restricting head can Include a top spiral spring with a substantially constant radius attached to a spiral spring with a diminishing radius to provide a spiral closure with interspaced openings for allowing inlet fuel to pass outwardly therethrough. The top spiral can be dimensioned slightly larger than the throat of the opening and by rotation of the spring be frictioπally held within the throat and maintained in position by the spacer means. The restricting head can include a cross member extending across the radius of a portion of the restricting head and engageable by a mechanical or automatic rotating to effect the rotational twisting force onto the restricting head and insertion into the fuel tank opening having a slightly smaller radius.

It can be seen that an important aspect of the combination of the fuel tank and anti- siphon device is the related sizing of the restricting head to the fuel tank opening and the length of the spacer means to the depth of the fuel tank.

Another importance of the combination is the lack of need for any welding or other dangerous method of fitting into the fuel tank.

Also according to the invention there is provided an anti-siphon system installation including: providing a spacer means having a longitudinal length sized according to the depth of the tank and having a radius smaller than the radius of the fuel tank opening; providing a restricting head having a size and shape substantially corresponding to the opening of a fuel tank and shaped to substantially prevent a hose or pipe being inserted while including openings to allow flow of fuel into the tank; mounting the spacer means within the fuel tank and engaging the inside base of the tank opposite the fuel tank opening; and simultaneously or subsequently positioning the restricting head within the throat of the fuel tank opening and simultaneously or subsequently engaging the internal throat of the fuel tank opening with restricting head or fitting means for resilient frjctional fitting therein.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention is more readily understood, the invention will be further described by way of illustration with reference to the accompanying drawings, in which: FIGURE 1 is a side view of an anti-siphon device of a first embodiment of a the anti-siphon system in accordance wjth the invention;

FIGURE 2 is a photographic top view of the anti-siphon device of FIGURE 1 ; FIGURE 3 is a photographic close-up perspective side view of the anti-siphon device of FIGURE 1 showing the connection of the legs of the spacer means to the underside of the restricting head;

FIGURE 4 is a photographic partial side view of the bottom of the anti-siphon device of FIGURE 1 up to the crossover of the legs of the spacer means;

FIGURE 5 is a diagrammatic view of an anti-siphon system in accordance with the invention using a motorised mounting means; and FIGURE 6 is a diagrammatic view of an anti-siphon system in accordance with the invention using a mechanical mounting means;

FIGURE 7 is two side views of an anti-siphon device of a second embodiment of a the anti-siphon system in accordance with the invention;

FIGURE 8 is two perspective side views of the anti-siphon device of FIGURE 7 showing the legs of the spacer means to the underside of the restricting head;

FIGURES 9 and 10 are each two side views and an end view of embodiments of the leg of the anti-siphon device of FIGURE 7;

FIGURES I I , 12 and 13 are each views of components of the second embodiment of the leg of the anti-siphon device of FIGURE 7.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to the First embodiment of the invention as shown in Figures 1 to 4, there is shown in figure 1 an anti-siphon device 11 for use in a fuel tank 41 and comprising a restricting head 15 and a spacer means 17 attached to the restricting head.

The restricting head 15 as shown in detail in Figure 2 includes a top Spiral spring 23 with a substantially constant radius, attached to a spiral spring 21 with a diminishing radius to provide a bottom spiral closure. The benefit of the spirals is to provide structure while having interspaced openings for allowing inlet fuel to pass outwardly therethrough.

It can be seen that the combination of the substantially constant radius spiral spring 23 and the diminishing radius spiral spring 21 provides an opening for receiving a fuel pump nozzle which can be inserted to allow filling of the tank but prevents further access by a siphoning hose.

A cross member 25 can be positioned at the top of the restricting head 15 but preferably is located at the bottom of the restricting head. This is used to assist in mounting of the anti-siphon device Il in the fuel tank 41 as will be further described later.

As shown in Figures 3 and 4 there is a spacer means 17 comprising three linear legs 31 extending from a join 33 on an underside of the restricting head 17 to a spacer base

37 in the form of a ring. The 3 linear legs are aligned to crossover each other and intersect at a position substantially halfway between the join 33 and the spacer base

37, At the crossover 35 the legs are welded together. The resulting structure provides a structure able to withstand longitudinal stresses as well as torsional strains caused by rotational insertion.

Referring to Figures 5 and 6 there is shown the mounting of the anti-siphon device 11 in a fuel tank 41. The spacer means 17 attached to the restricting head 25 must have a size and shape to be inserted within the opening 42 of the tank 41 and to extend to the base 45 of the tank and retain the restricting head 15 adjacent the opening of the tank. This is generally achieved by the top spiral being dimensioned slightly larger than the throat 44 of the opening 42. The diminishing radius spiral 21 and the attached spacer means 17 including the legs 3Ϊ and the spacer base 37 extend substantially linearly and with a smaller radius than the top spiral 23. In this way the elongated structure of the anti- siphon device 11 can be inserted into the fuel tank 41 through the fuel tank opening 42.

Referring to the second embodiment shown in Figures 8, and 11 to 13 there is shown an anti-siphon device 71 for use in a fuel tank and comprising restricting head 75 having a size and shape substantially corresponding to the opening of a tank and shaped to substantially prevent a hose or pipe being inserted while including openings to allow flow of fuel into the tank; and further including a spacer means 77 attached to the restricting head and having a size and shape to be inserted within the opening of the tank and to extend to the base of the tank and retain the restricting head adjacent the opening of the tank.

The restricting head 75 is a spring which to fulfil most industrial uses can range in size from 50mm to 200mm. A tapered section of the spring prevents the insertion of a hose/tube for the purposes of siphoning. The round surface of the spring reduces splash back, foaming of diesel and improves flow of fuel.

In position the anti-siphon device 71 sits one coil of the spring 75 on top of the fuel tank filler lip for extra rigidity and the spring compresses to variable size diameters to fit inside the fuel tank filler necks, enabling standard sizing (a significant advantage due to the large variations in neck size diameters across brands and models of industrial equipment).

The spring 75 absorbs the shock of impact by attack to the anti-siphon device. A cross bar 85 creates a leverage point to which an hydraulic drive unit can be attached to screw the anti-siphon device into position and prevent hose insertion.

The spacer 77 means is an elongated cylindrical pipe leg having a plurality of cut- outs. The tubular design of this embodiment allows ease of installation, able to be customized (cut to length) on site during installation. Slots in tube ensure no restriction to fuel flow and do not create a well of fuel in the tank.

Λ positive down stop, prevents the anti-siphon device from being pushed into tank. A synthetic bung attached to leg base is for prevention of abrasions.

The second embodiment of the anti-siphon device shown in Figures 8, and U to 13 also includes a baffle. This is angled to flow of fuel for greater fuel dispersion.

In structure, the baffle is formed by a plate inserted through slot on the side of tube (leg). The plate is the size it is so to allow smaller surface area than that of the hole in the bottom of the spring looking in to the leg. To allow fuel flow. The angle of the plate set up diverts hose into the side of the leg, stopping its insertion. This prevents penetration into the tank by 6mm hoseΛube and thereby prevents siphoning.

The spacer means of the anti-siphon device in the form of a cylindrical leg further includes a bung positioned at the foot of the leg. The bumg is made from poly- urethane, non corrosive to diesel, reduce damage to bottom of tank during impact attack. It is able to be assembled on site after leg is cut to length and held by single steel pin through the middle of the bung. A mushroom head reduces lateral movement.

In use the anti siphon device is positioned in the fuel tank 41 and located by rotation of the spring to be frictionally and resϊlϊently held within the throat 44 and maintained in position by the spacer means 17 engaging the internal base 45 of the fuel tank to provide substantial adjacent positioning of the restricting head 17 to the opening 42 of the fuel tank. To enable installation of the second embodiment 3 Screws are installed below fuel neck internal lip to create a secondary Hp for the anti siphon device to make contact with. Screw heads are reamed out so as to minimize likelihood of tampering by potential thief. For fuel tanks with no filler neck, 3 tags are installed below internal lip to act as secondary Hp. The secondary Up creates tension of spring coils in the space between original and secondary lips for retention within neck.

The and siphon device is installed at a greater diameter than the fuel necks inside diameter to create inward coil compression and thus spring retention within neck. the anti siphon device is sized at a greater length than the tank depth to create upward compression of the spring from its leg against the bottom of tank. The anti siphon device is driven intq tank through an incision in the internal lip, with screwing technique by a hydraulic drive motor] The drive bar extending from the hydraulic motor holds the bottom cross-bar of the tapered section of spring

As shown in Figures 5 and 6 the anti siphon device is screwed in by drive bar rotating the bottom cross-bar of tapered section of spring. A torque multiplier is attached between drive bar and hydraulic motor to allow for absorption of spring coil before screwing into tank. The torque multiplier allows for spring to coil as to minimize resistance against hydraulic motor when screwing in the anti siphon device

Once the and siphon device has been positioned correctly in tank, hydraulic motor is run in reverse until all tension is released from drive bar so it can be removed safely. The hydraulic motor is powered by hydraulic pump attached to power source

To complete installation a long screw (40mm) is installed into tank neck and rolled over spring to create extra safety as an S bolt

The restricting head 17 including the top spiral spring 23 with a substantially constant radius is dimensioned slightly larger than the throat 44 of the opening 42 and by rotation of the spring 23 is frictioπally held within the throat and maintained in position by the spacer means. The restricting head 17 includes a cross member extending across the radius of a portion of the restricting head and engageable by a mechanical 49 or automatic wrench 48 having a connecting rotating tooth 50 to engage the cross member 25 and effect the rotational twisting force onto the restricting head and insertion into the fuel tank opening throat 44 having a slightly smaller radius. A top inwardly extending flange 43 prevents removal.

Therefore the installation includes mounting the spacer means within the fuel tank and engaging the inside base of the tank opposite the fuel tank . opening and simultaneously positioning the restricting head within the throat of the fuel tank opening and simultaneously engaging the internal throat of the fuel tank opening with restricting head for resilient frictional fitting therein. The system allows ready fitting (o a range of fuel tanks by its novel design. This includes providing a restricting head having compression means to allow compression of the restricting head into a range of diameters of throats of fuel tanks and providing a spacer means having a continuous elongated structure that allows for ready alteration to a required length. Thereforer in the field the installer undertakes the determining and providing of the required length of the spacer means to engage the base of the fuel tank and allowing for correct positioning of the restricting head in the throat of the fuel tank. The anti- siphon system can therefore be modified on site and installed to fit a range of fuel tanks.

An important aspect of the design of the spring is not only the bottom restricting part that prevents access but the top consistent diameter that allows the restricting head to be rotated into the throat to allow compression and change diameter of the spring to fit into the selected tank. This can allow compression and change diameter of the spring of the order of up to 10% to fit into the selected tank. Further an important aspect is the substantial continuity of the spacer means in the form of a continuous cylinder with cut-outs to allow ready cutting to size while providing a spacing means and a torsional and compressioπal strength to the spacer means. A bung is inserted in the end of the cut to size spacer means to provide a stable non deteriorating foot to the anti-siphon installation system in the fuel tank.

It should be understood that the above description is of a preferred embodiment f the invention. Clearly person skilled in the art would understand variations without the need for inventive input and such variations are included within the scope of this invention as defined in the following claims.

Claims

J . An ami -siphon device for use in a fuel tank and comprising: a. a restricting head having a size substantially corresponding to the opening of the fuel tank and shaped to substantially prevent a hose or pipe being inserted while including openings to allow flow of fuel into the tank; and further including b. a spacer means attached to the restricting head and having a size and shape to be inserted within the opening of the tank and to extend to the base of the tank and retain the restricting head adjacent the opening of the tank.

2. An anti-siphon device according to claim 1 wherein the restricting head is a spiral spring with a diminishing radius to provide a spiral closure with - interspaced openings for allowing inlet fuel to pass outwardly therethrough,

3. An anti-siphon device according to claim 1 wherein the restricting head includes a top open channel section having a central cylindrical channel above a shaped closure means preventing further progress of a pipe or hose whereby a fuel pump nozzle can be inserted to allow filling of the tank but prevents further access by a siphoning hose.

4. An anti-siphon device according to claim 1 wherein the restricting head includes an expansion means for providing expanding fitting when placed into the throat of a fuel tank opening.

5. An anti-siphon device according to claim 1 wherein the restricting head includes a resilient means to allow compressible fitting within the throat of the opening.

6. An anti-siphon device according to claim 1 wherein the restricting head includes a top spiral spring witii a substantially constant radius attached to a spiral spring with a diminishing radius to provide a spiral closure with interspaced openings for allowing inlet fuel to pass outwardly therethrough with the top spiral dimensioned slightly larger than the throat of the opening and by rotation of the spring be frictionally held within the throat and maintained in position by the spacer means.

7. An antϊ-siphon device according to claim 1 wherein the restricting head includes a cross member extending substantially across the diameter of a portion of the restricting head and engageable by a mechanical or automatic rotating means to effect a rotational twisting force onto the restricting head and allow insertion into the fuel tank opening having a slightly smaller radius.

8. An anti-siphon device according to claim 1 wherein the spacer means includes one or more legs attached to a lower portion of the restricting head and extending substantially in a linear directiOE to a spacer base for engaging the fuel tank base opposite the fuel tank opening.

9. An anti-siphon device according to claim 1 wherein the spacer means includes a plurality of linearly extending legs mounted to a spacer base.

10. An anti-siphon device according to claim J wherein the spacer means includes a cylindrical extending legs mounted with the longitudinal axis substantially coplanar with the axis of thhe restricting head wherein the fuel entering the restricting head that does not dissipate into the fuel tanhk through the restricting head can dissipate through openings in the spacer means wherein the restricting means prevents access of a siphoning hose beyond the restricting head and the spacer means maintains the restricting head at an upper portion of the fuel tank,

1 1. An anti-siphon device according to claim 10 further including baffle means at an upper portion of the spacer means and below the restricting head to assist prevention of access to the fuel tank and ready dissipation of incoming fuel.

12. An anti-siphon device according to claim 1 wherein the spacer means includes a plurality of legs crossing over each other and being attached at the top to the restricting head, at the crossover to each other leg, and at the bottom to the spacer base, thereby improving the rigidity of the structure, such that the structure is able to withstand longitudinal stresses as well as torsional strains caused by rotational insertion.

13- An anti-siphon device according to claim 1 wherein spacer means includes a length altering means to allow for selection of a length suitable to a particular fuel lank.

14. An anti-siphon device according to claim 1 wherein the length altering means includes a telescopic means with locking means such as saw tooth fittings to lock to a selected length and prevent collapsing.

15. An anti-siphon device according to claim I wherein the spacer means includes add on lengths that are selectively attached to form the length of spacer means required whereby such structures remain substantially longitudinally aligned and with a radius less than the opening of the fuel tank to allow insertion therein.

16, An anti-siphon device according to claim 1 wherein the anti-siphon device is constructed of a material that will not affect the fuel quality or affect or increase the safety of the fuel in the fuel tank,

17. An anti-siphon device including two means of positioning, the first being a throat fitting such as provided by the twisting of the resilient head into the throat of the opening and the second being a spacer means engaging the internal base of the fuel tank to provide substantial adjacent positioning of the restricting head to the opening of the fuel tank, wherein the anti-siphon device allows safe selective retrofitting to fuel tanks as required.

18, An anti-siphon device according to claim 17 wherein the anti-siphon system is achieved by means of a combination of a fuel tank having a circular tubular opening in a top section and an anti-siphon device, wherein the anti-siphon device has a restricting head shaped to substantially prevent a hose or pipe being inserted while including openings to allow flow of fuel into the tank, and a spacer with a spacer baser for engaging the fuel tank at a position 5 opposite the top opening.

19. An anti-siphon device according to claim 17 wherein the restricting head includes a top spiral spring with a substantially constant radius attached to a spiral spring with a diminishing radius to provide a spiral closure with

H⁾ interspaced openings for allowing inlet fuel to pass outwardly therethrough with the top spiral is dimensioned slightly larger than the throat of the opening and by rotation of the spring be frictionally held within the throat and maintained in position by the spacer means and with the restricting head includes a cross member extending across the radius of a portion of the

15 restricting head and engageable by a mechanical or automatic rotating to effect the rotational twisting force onto the restricting head and insertion into the fuel tank opening having a slightly smaller radius.

20. A method of anti-siphon system installation including: 0 a. providing a restricting head having compression means to allow compression of the restricting head into a range of diameters of throats of fuel tanks; b, providing a spacer means having a continuous elongated structure that allows for ready alteration to a required length; 5 c. determining and providing the required length of the spacer means to engage ihe base of the fuel tank and allowing for correct positioning of the restricting head in the throat of the fuel tank; wherein the anti-siphon system can be modified on site and installed to fit one of a range of fuel tanks, 0

21. The method of anti-siphon system installation of claim 20 wherein the restricting head is an open ended coil spring means that can be rotated to into the throat to allow compression and change diameter of the spring to fit into the selected tank.

22. The method of anti-siphon system installation of claim 21 wherein the restricting head is an open ended coil spring means that can be rotated to into the throat to allow compression and change diameter of the spring of the order of up to 10% to fit into the selected tank.

23. The method of anti-siphon system installation of claim 20 wherein the spacer means is a continuous cylinder with cut-outs to allow ready cutting to size while providing a spacing means and a torsional and compressional strength to the spacer means.

24. The method of anti -siphon system installation of claim 20 including a bung for insertion in the end of the cut to size spacer means to provide a stable non deteriorating foot to the anti-siphon installation system in the fuel tank,

25. A method of anti-siphon system installation including: a. providing a spacer means having a longitudinal length sized according to the depth of the tank and having a radius smaller than the radius of the fuel tank opening; b, providing a restricting head having a size and shape substantially corresponding to the opening of a fuel tank and shaped to substantially prevent a hose or pipe being inserted while including openings to allow flow of fuel into the tank; c. mounting the spacer means within the fuel tank and engaging the inside base of the tank opposite the fuel tank opening; d. simultaneously or subsequently positioning the restricting head within the throat of the fuel tank opening and e. simultaneously or subsequently engaging the internal throat of the fuel tank opening with restricting head or fitting means for resilient frictJonal fitting therein,

2(5, An anti-siphon device substantially as hereinbefore described with reference to the drawings.

27. A method of anti-siphon system installation substantially as hereinbefore described with reference to the drawings.