PETROL PUMP NOZZLE
This invention relates to a nozzle for dispensing a volatile liquid. In particular, but not exclusively, this invention concerns a forecourt petrol pump nozzle, for dispensing petrol into the tank of a motor vehicle. Though not limited to this particular use, the invention will be described hereinafter solely with reference to that use.
The ullage space within a motor vehicle tank contains a high concentration of petrol vapour which is displaced when more fuel is added to the tank. Historically, that vapour was allowed to escape to atmosphere but that no longer is environmentally acceptable and petrol pumps now incorporate vapour recovery techniques to reduce the amount of vapour lost to atmosphere.
Typically, the petrol pump includes a vacuum pump which draws the displaced vapour from the end of the dispensing nozzle back into the pump where the vapour is condensed and supplied back to the forecourt tank. The volume of recovered petrol can be quite considerable and apart from the environmental need to prevent the escape of the vapour, there is an economic advantage in doing so, as well.
The required mechanism to recover the vapour as described above is complex and requires maintenance. This adds to the cost of the petrol pumps, as well as the cost of installing the pumps in a forecourt and then running the forecourt. Moreover, to the customer, there is a loss of petrol which the customer has paid for but which is returned to the forecourt tank for dispensing to another customer.
It is a principal aim of the present invention to provide a dispensing nozzle particularly for a forecourt petrol pump which minimises the escape to atmosphere of vapour displaced from a vehicle tank, in the course of the filling of that tank, and which returns to the vehicle tank recovered vapour.
According to this invention, there is provided a nozzle for dispensing a volatile liquid, comprising: -a tube through which the liquid is passed to an exit orifice from the tube; -a venturi restrictor disposed in the tube at a location remote from the exit orifice to generate a reduced pressure downstream of the restrictor when liquid flows through the tube; and -a recovery sleeve fitted into the tube to extend between the restrictor and the exit orifice so that liquid flowing through the restrictor flows into the sleeve and out of the exit orifice end thereof, there being an opening between the restrictor and the sleeve, and the recovery sleeve defining at least one vapour recovery passage extending along the length of the sleeve between the inner wall of the tube and the inner wall of the sleeve, from a location at or adjacent the tube exit orifice and said opening between the restrictor and the sleeve.
When in use, liquid flowing through the nozzle is accelerated as it passes through the venturi restrictor. This reduces the static pressure in the liquid immediately downstream of the venturi restrictor. Vapour present in the vicinity of the exit orifice of the nozzle (which normally will be within the vehicle tank or within a hose leading to the vehicle tank) will be drawn into and along the vapour recovery passage by that reduced pressure and will then flow through the opening to become entrained in the main liquid flow through the tube. The vapour condenses in that flow and is returned to the vehicle tank as liquid.
Advantageously, the sleeve defines a plurality of substantially parallel vapour recovery passages, each extending along the length of the sleeve between the inner wall of the tube and the inner wall of the sleeve. Each passage may thus be in the form of a groove or channel let into the outer cylindrical surface of the sleeve, to extend along a generator thereof.
In one embodiment, each passage is open at the exit orifice end of the nozzle tube. Vapour may then enter the passages axially, from the end face of the sleeve fitted into the tube. In another embodiment, each passage is closed at the exit orifice end of the nozzle tube but there is a plurality of holes through the wall of the tube communicating with the passages. Vapour will then be drawn from around the nozzle tube through the holes and into the passages.
Preferably, there is one such hole for each passage, in alignment therewith.
In order to allow vapour drawn into the passages to become entrained in the fluid flow through the nozzle, the ends of the passages remote from the exit orifice of the nozzle (i.e. at the upstream end of the sleeve) must communicate with the reduced pressure region immediately downstream of the venturi restrictor. This may be done by profiling the sleeve such that each passage defines an opening leading to the reduced pressure region, for example by increasing the depth of each groove or channel at said upstream end. In the alternative, a gap may be left between the downstream end of the venturi restrictor and the upstream end of the sleeve whereby the upstream ends of the passages simply lead into that annular gap so that vapour then gets drawn into and is entrained with the fluid flow. A spacer may be provided between the downstream end of the venturi restrictor and the upstream end of the sleeve, to ensure that the gap has the required value. Conveniently, such a spacer consists of one or more pins or projections extending from the upstream end of the sleeve, to engage the downstream end of the venturi restrictor, or one or more pins or projections extending from the downstream end of the restrictor, to engage the upstream end of the sleeve.
Though the nozzle of this invention could be manufactured to include the venturi restrictor and recovery sleeve as defined hereinbefore, the invention may readily be implemented with an existing volatile liquid dispensing nozzle.
This may be done by providing the venturi restrictor and recovery sleeve within a tubular cartridge which is a close press-fit into the free end of the delivery tube of a dispensing nozzle such that the cartridge is pressed into the delivery tube until the end face thereof is in alignment with the exit orifice of the tube.
It is also possible to modify an existing nozzle so as to incorporate the venturi restrictor and recovery sleeve of this invention as defined above. This may be done by the steps of: * reaming the bore of the nozzle delivery tube to a prescribed depth so as to form a shoulder at said depth; * pressing the venturi restrictor into the reamed bore until the upstream end of the venturi restrictor engages said shoulder; and pressing the recovery sleeve into the reamed bore until the downstream end of the recovery sleeve is in alignment with the exit orifice of the delivery tube.
So long as the various dimensions for the restrictor and the sleeve are accurately controlled, along with the reaming of the bore, the size of the gap between the downstream end of the venturi restrictor and the upstream end of the recovery sleeve may be controlled to have a required dimension, such as around 5mm, though it is preferred for there to be a spacer to maintain that gap at the required value.
A conventional petrol delivery nozzle includes an automatic shut-off arrangement to prevent overtilling of a vehicle tank. This shut-off arrangement has a so-called vacuum pipe extending internally from a location adjacent the exit orifice back to the valve assembly for controlling the flow of petrol out of the nozzle. The vacuum pipe has a small entrance and is connected to a vacuum valve which allows the flow of petrol so long as gas can be drawn in through the small entrance into the pipe. As soon as liquid petrol comes into contact with the entrance, gas can no longer be drawn into the vacuum pipe and this causes the vacuum valve to close the main petrol delivery valve.
In implementing this invention, the vacuum pipe may be left extant, passing through slots formed in the external peripheries of both the venturi restrictor and the sleeve. In the alternative, when modifying an existing delivery nozzle, the original vacuum pipe may be cut short and connected to a pipe provided as a part of the sleeve such that the automatic shut-off function of the nozzle is not impaired.
This invention extends to a tubular cartridge having a venturi restrictor and a recovery sleeve disposed therein, for fitting to the delivery tube of a nozzle for dispensing a volatile liquid, as described above. The invention further extends to a method of modifying an existing dispensing nozzle so as to include a vapour recovery arrangement comprising a venturi restrictor and a recovery sleeve as herein before described.
By way of example only, one specific embodiment of petrol dispensing nozzle assembly of this invention and a method of installing the same will now be described in detail, reference being made to the accompanying drawings in which:-Figure 1 diagrammatically illustrates a conventional dispensing nozzle and the vapour recovery components to be installed therein; Figure 2 is an axial section through the nozzle tube, venturi restrictor and sleeve, with the restrictor and sleeve being fitted into the nozzle tube; Figure 3 is an axial section taken at 900 to the axial section of Figure 2 and showing the nozzle tube, with the venturi restrictor and sleeve fitted therein; Figure 4 is a perspective view of the sleeve used in this embodiment; Figure 5 is an end view on the sleeve when fitted in a nozzle tube; and Figure 6 is an end view on the restrictor, when fitted in a nozzle tube.
Figure 1 illustrates a conventional petrol dispensing nozzle provided at the end of a flexible hose of a petrol pump as installed in a forecourt petrol filling station. The nozzle 10 has a handle region 11 one end of which is connected to the flexible hose 12 and the other end of which leads to a dispensing tube 13, through a valve assembly 14. The valve assembly includes an automatic shut-off valve to prevent over-tilling of a vehicle fuel tank. The valve assembly is operated by a trigger 15 moving within a trigger guard 16. These components of the nozzle 10 form no part of this invention and will not be described in more detail here.
Also shown in Figure 1 are a venturi restrictor 18 and a vapour recovery sleeve 19, which are positioned axially in alignment within the tube 13, with the downstream end 20 of the sleeve 19 in alignment with the exit orifice 21 of the tube 13. The restrictor 18 is positioned deeper within the tube 13 with the spacing between the restrictor 18 and sleeve 19 being maintained by means of a pair of pins 22 projecting from the upstream end 20 of the sleeve 19, to engage the downstream end 24 of the restrictor 18.
The configuration of the venturi restrictor 18 and vapour recovery sleeve 19 will now be described in more detail, with reference to Figures 2 to 6. The venturi restrictor 18 is a hollow body with a bore 25 having a taper of about 6°.
The external surface of the body has a first part 26 which is essentially cylindrical and a second part 27 which tapers but at a more acute angle than the bore of the body. The cylindrical first part 26 is a press-fit within the tube 13, which may have been reamed beforehand to a pre-deterrnined depth, in order to provide a shoulder 28 against which the upstream end of the venturi restrictor 18 engages, when pushed fully home as shown in Figure 3.
The sleeve 19 is essentially cylindrical but will be described in more detail below. The sleeve also is a close press-fit within the reamed part of the tube 13 and has a pair of rearwardly-projecting pins 22 which engage the downstream end 24 of the restrictor, when the sleeve has been pushed fully into the tube, again as shown in Figure 3. When in this position, the downstream end 20 of the sleeve is in alignment with the exit orifice 21 of the tube.
A vacuum pipe for the automatic shut-off valve extends internally within the nozzle to a location close to the exit orifice 21 of the tube. In order to allow the bore of the tube to be reamed so as to provide the shoulder 28, that vacuum pipe must be cut away beforehand. Following reaming, it is replaced by a further vacuum pipe 30 connected to the original pipe within the nozzle tube 13 by means of a tubular connector (not shown). That further vacuum pipe 30 is accommodated within a slot 31 extending in the external surface of the venturi restrictor, parallel to its axis, and an aligned further slot 32 extending in the external surface of the sleeve. The vacuum pipe 30 is shown in Figure 3 but not in Figure 2, as the section line of Figure 2 is at 900 to that of Figure 3.
Also as shown in Figure 3, the end of the vacuum pipe 30 adjacent the exit orifice 21 of the tube is located in a cut-away part 33 of the sleeve in order to allow correct operation of the shut-off valve. This prevents inadvertent operation of the shut-off valve by excess vapour or splashes, rather than when the vacuum pipe contacts rising fuel in the vehicle fuel tank or the filler hose thereof.
The sleeve 19 is shown in more detail in Figures 4 and 5. Though the external surface is essentially cylindrical, a plurality of channels 35 are cut into the external surface of the sleeve so as to extend linearly from one end of the sleeve to the other. Each channel extends partway through the thickness of the material of the sleeve and provides a vapour recovery passage when the assembly is in use. The bore of the sleeve is not strictly cylindrical and has a region 36 of greater wall thickness (except for at the cut-away part 33), defined by a flat 37 within the bore of the sleeve. The cut-away part 33 is formed on the underside of that flat and the vacuum pipe 30 is disposed therewith in.
Figure 6 is an end view on the venturi restrictor 18 located within the tube 13. As can be seen, the central opening 38 of the restrictor tapers from the upstream end towards the downstream end, in this example by approximately 6°.
The venturi restrictor 18 and sleeve 19 could be incorporated within the dispensing tube 13 of a nozzle, as original equipment. In the alternative, these components could be fitted into the tube after manufacture, in order to impart vapour recovery characteristics to an existing nozzle.
In use, when the petrol pump is operating and the valve assembly of the nozzle is opened, fuel flows along the tube 13 and out of the exit orifice 21. The speed of the fuel flowing through the venturi restrictor increases, so reducing the static pressure within that fuel. This generates a region of lower pressure immediately downstream of the venturi restrictor, and so in the vicinity of the upstream end 23 of the sleeve.
The channels 35 are open at the downstream end 20 of the sleeve and so this reduced pressure appears at the open ends of those channels. Any vapour present in the vicinity of those open ends will be drawn into the vapour recovery passages and back towards the restrictor. From there, the vapour will become entrained in the fuel flowing into the tank and will condense into that fuel. In this way, vapour displaced from the ullage space of a tank being filled may be recovered and deposited back in the tank as liquid fuel. -10-