GB2406333A

GB2406333A - Anti-siphon tank inlet

Info

Publication number: GB2406333A
Application number: GB0322594A
Authority: GB
Inventors: Brian Wholey
Original assignee: TISS Ltd
Current assignee: TISS Ltd
Priority date: 2003-09-26
Filing date: 2003-09-26
Publication date: 2005-03-30
Anticipated expiration: 2023-09-26
Also published as: GB2406333B; GB0322594D0

Abstract

Anti-siphon fluid tank inlet assembly for fitting to an inlet aperture of a fluid tank (1) comprises a substantially straight inlet pipe (2) depending from a radially extending mounting flange (3). The inlet pipe (2) supports a float valve (4) at its lower end. The float valve (4) comprises a float (5) trapped in an apertured float chamber (6) and cooperates with a valve seat (8) defined adjacent the end of the inlet pipe (2) to allow fluid flow from the inlet pipe (2) into the tank (1) but to prevent return flow. An obstruction (a) is located within the inlet pipe (2) to permit the flow of fluid but block passage of a siphon tube. At least one vent aperture (11) is provided in the mounting flange which communicates with the interior of the tank (1).

Description

ANTI-SIPHON TANK INLET

The present invention relates to an anti-siphon inlet for a fluid tank such as a vehicle fuel tank.

The theft of fuel by siphoning from the fuel tanks of vehicles, and in particular commercial road vehicles, is a recognised problem. It is conventional to fit vehicles with a lockable fuel tank filler cap to prevent unauthorised access to the tank inlet.

However, since the fuel filler cap is accessible it is vulnerable to tampering and can often be forced open by the determined thief. In addition, it is not always practical to fit a vehicle with a lockable fuel filler cap.

This probleru has been addressed in the prior art by provision of a fluid tank inlet incorporating a non-return valve to prevent fuel being drawn off by siphoning from the tank inlet.

For example, French patent FR 2 534 888 discloses a fuel tank inlet pipe provided with a float valve at its inner end. The float valve comprises a ball float retained in an apertured float chamber and which sits against a valve seat defined at the end of the inlet pipe when the fuel level in the tank is above the end of the inlet pipe to thereby prevent fuel flow back through the pipe. A grill is fitted in the inlet pipe a short distance above the valve seat to prevent a siphon tube being used to force the ball valve away from its seat. The grill itself is protected by a gentle S bend in the inlet pipe which prevents insertion of a rigid tool to penetrate the grill. A would be thief would only be able to remove any fuel present in the inlet pipe above the level of the grill.

However, this prior art device presents a number of problems when it comes to filling the fuel tank. If the tank is empty (or at least the fuel level is below the level of the valve seat) fuel from a conventional fuel dispensing nozzle inserted into the inlet pipe should simply flow into the tank through the float chamber. As the fluid level within the tank rises above the level of the valve seat the pressure generated at the dispensing nozzle should nevertheless force the ball float clear of the valve seat to allow continued filling of the tank. Gas vent holes are provided around the circumference of the inlet pipe at a location just below the top of the tank. These are ë *e. -.

.. - ' . . . . intended to allow the gas to escape as the fuel level rises yet further to enable the tank to be filled to its very top.

In fact, tests conducted by the present inventor have shown that the fuel dispensed from the nozzle tends to well up within the inlet pipe, rather than flow through the float valve and into the tank, either spilling out of the inlet or causing the dispensing nozzle to shut off (most fuel dispensers are designed to shut off when the fluid level reaches the end of the dispensing nozzle). In addition, the gas vent holes are at least partially blocked by insertion of the dispensing nozzle into the inlet pipe so that they do not allow sufficient gas to escape to equalise pressure quickly enough to allow the tank to be filled to the top.

It is an object of the present invention to obviate or mitigate the above disadvantages.

According to the present invention there is provided a fluid tank inlet assembly for fitting to an inlet aperture of a fluid tank, the inlet assembly comprising; a substantially straight inlet pipe having a longitundal axis depending from a radially extending mounting flange located at its proximal end and supporting a float valve at its distal end, the float valve comprising a float trapped in an apertured float chamber and which cooperates with a valve scat defined adjacent the distal end of the inlet pipe to allow fluid flow from the distal end of the inlet pipe but to prevent return flow through the inlet pipe; an obstruction located within the inlet pipe to permit the flow of fluid but block passage of a siphon tube; at least one vent aperture provided in said mounting flange which in use communicates with the interior of a tank within which the inlet assembly is installed.

A specific embodiment of the present invention will now be described, with reference to the accompanying drawings, in which: Figure l is a schematic cross-section through a fuel tank inlet assembly according to the present invention; and Figure 2 is a plan view of the fuel tank inlet assembly of Figure 1.

Referring to Figures 1 and 2, the fuel tank inlet assembly of the present invention is shown fitted to a fuel tank 1. For simplicity, details of the fuel tank cap and cap mounting features are omitted (and may be entirely conventional). The inlet .e ace a e -e e . e - - ' assembly comprises a straight inlet pipe 2 provided with a mounting flange 3 at one end and supporting a float valve 4 at its other end. The float valve 4 comprises a ball float S retained within a float chamber 6 which is provided with axial slots 7 for the passage of fluid. The upper portion of the chamber 6 defines an annular valve seat 8 against which the ball float 5 sits when the fluid level within the tank rises above the level of the seat 8. The valve is protected by a grill 9 which extends across the diameter of the inlet pipe 2 immediately above the valve seat 8.

The mounting flange 3 is provided with diametrically opposed and radially extending tabs 10 adapted to receive a fitting (such as a screw/bolt etc) to secure the inlet pipe to the ball of the tank 1. The flange itself is provided with a circumferential array of gas vent holes 11. The inlet assembly is designed to be fitted to an aperture 12 provided in the fuel tank l sized to receive the mounting tabs 10 without obscuring the vent holes 11.

In essence, the illustrated embodiment ol the present invention has the same basic components as the prior art device disclosed in French patent number FR 2 534 888 discussed above. However, the present invention includes a number of features which avoid the filling problems associated with the prior art.

Firstly, the provision of a substantially straight fuel inlet pipe 2, rather than a curved pipe as provided in the prior art, greatly reduces the tendency of fuel to well up within the inlet pipe 2 as the tank is being filled. In addition, the inventors have found that the tendency of fuel to well up within the fuel pipe can be reduced yet further by ensuring that the flow chamber 6 has at length at least half that of the inlet pipe 2. For instance, in one particular embodiment of the present invention as illustrated in Figure 1, the inlet pipe has an axial length of 205mm extending from the flange 3 to the grill 9 and a float chamber length of approximately 1 lOmm, both the inlet pipe and float tank having a diameter of approximately 50mm.

A second advantage of the present invention is the provision of vent holes 11 in the mounting flange rather than in the inlet pipe 2. This prevents the vent holes 11 from being blocked by a dispenser nozzle inserted into the inlet pipe 2 and allows sufficient gas to escape as the tank is being filled to allow the fuel level to rise to the very top of the tank.

e see see e eea e e e e e e e e e e e e e e e e e ee e e e e e e e e Once the tank is full, the only fuel accessible to a would be thief would be the tiny amount of fuel present in the inlet pipe above the grill 9. The grill 9 will prevent insertion of a siphon tube into the flow chamber to force the ball float 5 away from the seat 8.

It will be appreciated that modifications and enhancements may be made to the basic design illustrated in Figures 1 and 2. For instance, the float chamber 6 may be manufactured as a separate component from the inlet pipe 2 and attached thereto by a screw thread or similar connection. The grill 9 could be fabricated integrally with either the How chamber or inlet pipe 2 or could be separate a component. Detail of the float chamber may also be varied from that shown. For instance, other forms of float and valve seat, and also apertures for allowing fluid flow, could be provided as will be readily appreciated by the skilled person.

The particular form of the features provided for securing the inlet to the tank 1 may be varied to suit a particular tank design. However, it is fundamental to the present invention that the inlet assembly has a flange provided with vent holes 11 which communicate with the interior of the tank. Otherwise, details of the flange and fixing to the tank may be varied. The flange and inlet pipe may for instance be fabricated as separate component.

It will be appreciated that the present invention is not limited to installation in vehicle fuel tanks but can be fitted to any fluid tank where there is a potential for theft by siphoning.

Other possible applications and modifications of the present invention will be readily apparent to the appropriately skilled person a L ..

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Claims

1. A fluid tank inlet assembly for fitting to an inlet aperture of a fluid tank, the inlet assembly comprising; a substantially straight inlet pipe having a longitundal axis depending from a radially extending mounting flange located at its proximal end and supporting a float valve at its distal end, the float valve comprising a float trapped in an apertured float chamber and which cooperates with a valve seat defined adjacent the distal end of the inlet pipe to allow fluid flow from the distal end ol the inlet pipe but to prevent return flow through the inlet pipe; an obstruction located within the inlet pipe to permit the flow of fluid but block passage of a siphon tube; at least one vent aperture provided in said mounting flange which in use communicates with the interior of a tank within which the inlet assembly is installed.

2. A fluid tank inlet assembly according to claim 1, comprising a plurality of said vent holes provided in said mounting flange.

3. A fluid tank inlet assembly according to claim 1 or claim 2, comprising two or more mounting tabs extending radially from said mounting flange for fixing to a fluid tank to support said inlet assembly therein.

4. A fluid tank inlet assembly according to any preceding claim, wherein said obstruction comprises a grill.

5. A fluid tank inlet assembly according to claim 4, wherein said grill is located adjacent said float valve seat.

6. A fluid tank inlet assembly according to any preceding claim, wherein said float valve chamber is generally cylindrical and comprises a plurality of fluid flow slots arranged axially relative to the inlet pipe.

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7. A fluid tank inlet assembly according to any preceding claim, wherein said float is a ball float.

8. A fluid tank inlet assembly according to any preceding claim, wherein the float valve is secured to the end of the inlet pipe by a screw thread connection.

9. A fluid tank inlet assembly according to any preceding claim, wherein the float chamber has an axial length no less than hall the axial length of the inlet pipe.

10. A fluid tank fitted with a fluid tank inlet assembly according to any preceding claim, wherein said vent holes allow gas to escape from the tank as the tank is filled from a fluid dispensing nozzle inserted within the inlet pipe.

11. A vehicle having a fuel tank fitted with a fluid tank inlet assembly according to any one of claims l to 10.

12. A fluid tank inlet assembly substantially as hereinbefore described, with reference to the accompanying drawings.

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