GB2373456A

GB2373456A - Control of dilution ratio of cleaning chemicals

Info

Publication number: GB2373456A
Application number: GB0102494A
Authority: GB
Inventors: Simon Walker
Original assignee: Washtec UK Ltd
Current assignee: Washtec UK Ltd
Priority date: 2001-02-01
Filing date: 2001-02-01
Publication date: 2002-09-25
Anticipated expiration: 2021-02-01
Also published as: GB2373456B; GB0102494D0

Abstract

A dilution unit 20 for diluting a concentrated cleaning chemical, which can be used in a vehicle washing plant, has a body in which is provided an inlet passage 26 leading to a mixing chamber 28. A first inlet 22 for concentrated cleaning chemical or detergent communicates through a first restricting duct 24 with the inlet passage 26 and the second inlet 23 for dilution water communicates through a second restricting duct 25, with the inlet passage 26 disposed further from the mixing chamber 28, than the first restricting duct 24. A screw-threaded flow restrictor 38 is arranged in the inlet passage 26 between the first and second inlet ducts 22,23 so that the dilution ratio may be controlled by suitable adjustment of the restrictor 38. A flow outlet 29 for diluted chemical leads away from the mixing chamber 28. The cleaning chemical can then be pumped by dosing pump 18 to spray bar 11 where it is mixed with water from inlet 15.

Description

DILUTION OF CHEMICALS This invention relates to a dilution unit for use in a washing plant dilution system, where a concentrated cleaning chemical or washing agent is diluted in a controlled manner before use. The invention further relates to a dilution system using such a unit and also to a washing plant including the dilution system.

The washing plant with which the present invention is concerned is primarily intended for the washing of motor vehicles. The plant could however be used for the washing of other articles and so the dilution unit, the dilution system and the washing plant itself are not to be regarded as expressly limited to this use. Nevertheless, the invention will be described primarily with reference to a vehicle washing plant.

A known form of a vehicle washing plant has a spray arch which traverses over the vehicle to be washed, with a diluted washing agent issuing from spray nozzles in the arch to impact on the vehicle. The conventional practice is to supply the washing agent in a concentrated form but sufficiently dilute such that the agent may be mixed with water in the spray arch to issue from the nozzles at an appropriate final concentration. However, practical tests have shown that only a certain degree of dilution in the spray arch can be achieved, if the concentrated chemical is simply mixed with water separately supplied to the arch. The consequence is that washing agents must be supplied to a vehicle washing plant operator in a relatively dilute form.

The chemical manufacturers would prefer to supply washing agents in a more concentrated form, to obviate the need to transport large quantities of water and also to minimise the packaging and transport demands of a relatively

dilute agent. As a result, there have already been proposals for pre-dilution units, able to accept highly concentrated washing agents and to perform a first dilution step so as to yield a washing solution comparable to that currently supplied by chemical manufacturers ready for use by many washing plants.

Such solution is directed to a spray arch for further dilution with water supplied separately to the arch. For example, such a pre-dilution unit is described in US-5655173.

The system of US-5655173 has the disadvantage that in the pre-dilution unit, inadequate mixing of the chemical washing agent can take place with water supplied separately to that pre-dilution unit and this can result in inconsistent results. It is important that the pre-dilution is performed at a closely controlled ratio, so that adequate washing agent issues from the spray arch to fulfil the cleaning function, but without wastage of the relatively expensive highly concentrated agent. The present invention results from attempts to improve the design of pre-dilution units for use in vehicle washing plants, to ensure consistent, reliable and efficient mixing of highly concentrated washing agent with water, prior to the supply of the diluted agent to a vehicle washing plant where that agent is further diluted prior to being sprayed on to a vehicle.

The present invention provides a dilution unit for use in a washing plant dilution system where a concentrated cleaning chemical is diluted in a controlled manner prior to the mixing of the diluted chemical with water, which unit has an inlet passage leading to one end of an elongate mixing chamber, a first inlet for concentrated cleaning chemical which first inlet communicates through a first restricting duct with the inlet passage adjacent the mixing

chamber, a second inlet for dilution water which second inlet communicates through a second restricting duct with the inlet passage further from the mixing chamber than the first inlet duct, the other end of the mixing chamber leading to the outlet, and a screw-threaded flow-restrictor arranged in the passage between the second and first inlet ducts whereby the mixing chemical dilution ratio may be controlled by adjusting the restrictor.

Experiments have shown that the dilution unit of the present invention, when used with a relatively viscous highly concentrated cleaning chemical such as an agent for vehicle washing, is able to achieve a consistent dilution ratio of pre-determined proportions. This results in a working solution of the required concentration suitable for direct supply to a spray arch where that working solution is further diluted by water supplied separately to the arch.

Preferably, the inlet passage is generally linear with each of the first and second inlet ducts extending substantially at right angles to the inlet passage.

In this case, the screw-threaded restrictor may comprise a screw threaded into a bore which extends transversely across the inlet passage whereby adjustment of the screw moves the inner end thereof to obstruct that inlet passage to a greater or lesser extent.

The diameters and lengths of the first and second restricting ducts should be selected having regard to the physical characteristics of the cleaning chemical before dilution and the (known) properties of the diluent water. Tests have shown that with typical highly concentrated and relatively viscous cleaning chemicals, good results can be obtained by having the first and second restricting ducts of essentially the same dimensions with the control on the flow of water being achieved solely by the use of the adjusting screw. A typical

dilution ratio achievable in this way is one part of concentrate to eight parts of water and for those concentrates with which the dilution unit has been tested, this provides a working solution with a suitable concentration of chemical for supply to a spray arch.

An important aspect of the dilution unit of the present invention is that a mixing chamber is provided to ensure proper, complete and consistent mixing of the concentrate with water. This may be enhanced by providing a mixing element in the mixing chamber which further promotes intermixing of the concentrate with water. Such a mixing element may comprise a static helicallyformed rod extending along the length of the mixing chamber and over which rod the chemical and water pass, the rod promoting turbulent flow in the mixing chamber. A preferred mixing element comprises a rod of double-helical form with two helixes of opposite hands, thereby promoting highly turbulent flow in the mixing chamber.

To assist the retro-installation of the dilution unit in a vehicle washing plant already in existence, so as to permit that plant then to use highly concentrated chemicals, the first and second inlets as well as the outlets may be screw-threaded to receive a respective connector for a flexible pipe.

Further, the first and second inlets may be fitted with respective non-return valves.

This invention extends to a dilution system for diluting a concentrated cleaning chemical prior to the mixing of the diluted chemical with water in a washing plant, in which system there is provided a dilution unit of this invention as described above, a first pipe connecting the unit first inlet to a reservoir for concentrated chemical, a second pipe connecting the unit second inlet to a

dilution water reservoir, and an outlet pipe connecting the unit outlet to a pump arranged to draw liquid from the mixing unit and to supply that liquid to a washing unit of the washing plant.

The invention further extends to a washing plant comprising a dilution system as described immediately above, in combination with a washing unit in the form of a spray bar, the spray bar having an inlet for diluted chemical to which the output from the pump is connected and further having an inlet for water, whereby additional dilution of the diluted chemical takes place within the spray bar prior to the issue of the cleaning chemical therefrom.

By way of example only, one specific embodiment of vehicle washing plant arranged in accordance with the invention and incorporating a dilution system having a dilution unit of this invention will now be described, reference being made to the accompanying drawings : Figure 1 diagrammatically illustrates the vehicle washing plant ; Figure 2 is an enlarged view on the dilution unit shown in Figure 1; and Figures 3 is an exploded view of the component parts of the dilution unit.

Referring initially to Figure 1, there is shown diagrammatically a vehicle washing plant having a spray arch 10 including a spray bar 11 having a plurality of spray nozzles 12 from which dilute cleaning chemical 13 issues. The spray arch is arranged to move along the length of a vehicle 14 stationary beneath the arch, whereby the dilute cleaning chemical is directed on to the vehicle to perform part of the cleaning process. The construction and operation of such a vehicle washing plant is well known in the art and will not be described further here.

The spray bar 11 is supplied with water at mains pressure, along pipe 15. Separately, the spray bar is provided with an injector 16 for pre-diluted cleaning working solution supplied along pipe 17 by a dosing pump 18.

Internally, the spray bar is appropriately configured to ensure adequate mixing of the working solution with the water delivered along pipe 15, as with conventional vehicle washing plants, where the working solution is derived direct from a container for that solution. However, in the embodiment of this invention, the working solution is obtained by a pre-dilution step performed on highly concentrated cleaning chemical stored in a container 19. That chemical is mixed in a dilution unit 20 with water drawn from a tank 21, at a pre-set mixing ratio whereby the working solution supplied to the spray bar 11 is at a pre-defined concentration.

Referring now to Figures 2 and 3, the dilution unit 20 is shown in greater detail. The unit is in the form of a main body having a concentrate inlet 22 and a water inlet 23, the two inlets being disposed with their axes parallel and leading to concentrate and water restricting ducts 24 and 25 respectively.

These two ducts 24 and 25 connect with an inlet passage 26 extending with its axis substantially at right angles to the axes of the ducts 24 and 25. The end 27 of the inlet passage 26 nearer the concentrate inlet 22 feeds into an elongate mixing chamber 28, the further end of which communicates with a working solution outlet 29. Both of the inlets 22 and 23 and the outlet 29 are internally threaded, to receive respective threaded connectors 30,31 and 32.

Connectors 30 and 31 associated with the inlets include non-return valves 33 and 34 at the further ends of which are flexible pipe compression connectors 35

and 36. Connector 32 associated with the outlet 29 is a simple flexible pipe compression connector for a pipe leading to the dosing pump 18.

A bore 37 is formed in the main body of the dilution unit to extend transversely to and intersect the inlet passage 26, between the concentrate and water ducts 24 and 25. The outer part of the bore 37 is screw-threaded to receive an adjusting screw 38 having a threaded head engaged with the threads of the counter-bore. The shank of the screw is plain, an annular groove being formed therein to receive an O-ring 39, to effect a seal between the shank and the bore 37. As shown, rotational adjustment of the screw allows the free end 40 of the shank to project to a greater or lesser extent across the inlet passage 26.

The mixing chamber 28 is of circular cross-section and received therewithin is a mixing element 41 fabricated from a pair of strips twisted into helical form but of opposite-hand threads. The liquid flow through the mixing chamber becomes highly turbulent as it passes over element 41, thereby ensuring efficient and complete mixing of the concentrate and water received in that chamber from the inlet passage 26.

In use, the dosing pump 18 is operated to reduce the pressure at the outlet 29. This draws concentrate from the container 19 and also water from the tank 21, the flow of water being restricted by the screw 38. This screw is adjusted until a required mixing ratio of concentrate to water is achieved, this ratio typically being 1: 8 for highly concentrated chemical washing agent suitable for use in vehicle washing plants. Such highly concentrated chemical washing agent has much greater viscosity than water, so that the volume of agent drawn through the duct 24 into the mixing chamber is significantly less than the

volume of water drawn through duct 25, even with the partial restriction of the inlet passage 26 by screw 38. The concentrate and water are thoroughly mixed within the mixing chamber to produce a diluted working solution which is pumped to the spray bar 11, for further dilution and application to a vehicle to be washed.

Claims

CLAIMS 1. A dilution unit for use in a washing plant dilution system where a concentrated cleaning chemical is diluted in a controlled manner prior to the mixing of the diluted chemical with water, which unit has an inlet passage leading to one end of an elongate mixing chamber, a first inlet for concentrated cleaning chemical which first inlet communicates through a first restricting duct with the inlet passage adjacent the mixing chamber, a second inlet for dilution water which second inlet communicates through a second restricting duct with the inlet passage further from the mixing chamber than the first inlet duct, the other end of the mixing chamber leading to the outlet, and a screw-threaded flow-restrictor arranged in the passage between the second and first inlet ducts whereby the mixing chemical dilution ratio may be controlled by adjusting the restrictor.
2. A dilution unit as claimed in claim 1, wherein the inlet passage is generally linear and each of the first and second inlet ducts extends substantially at right angles to the inlet passage.
3. A dilution unit as claimed in claim 1 or claim 2, wherein the screwthreaded restrictor is provided in a screw-threaded bore extending transversely across said inlet passage.
4. A dilution unit as claimed in claim 3, wherein the restrictor comprises a screw threaded into said bore, the screw being adjustable to have the inner end thereof obstruct to a greater or lesser extent the inlet passage thereby to effect adjustment of the mixing ratio.
5. A dilution unit as claimed in claim 4, wherein the screw has a plain shank provided with a seal member to prevent leakage along the bore.
6. A dilution unit as claimed in any of the preceding claims, wherein a mixing element is disposed in the mixing chamber to promote mixing of the chemical and water passing therethrough.
7. A dilution unit as claimed in claim 6, wherein the mixing element comprises a helically-formed rod extending along the mixing chamber and over which the chemical and water pass.
8. A dilution unit as claimed in claim 7, wherein the mixing element comprises a rod disposed in the mixing chamber which rod is double-helical form with the two helixes being of opposite hands.
9. A dilution unit as claimed in any of the preceding claims, wherein each of the first and second inlets and the outlet are screw-threaded to permit the connection thereto of a respective connector for a flexible pipe.
10. A dilution unit as claimed in any of the preceding claims, wherein each of the first and second inlets are fitted with a respective non-return valve.
11. A dilution unit as claimed in claim 1 and substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.
12. A dilution system for diluting a concentrated cleaning chemical prior to the mixing of the diluted chemical with water in a washing plant, in which system there is provided a dilution unit as claimed in any of claims 1 to 9, a first pipe connecting the unit first inlet to a reservoir for concentrated chemical, a second pipe connecting the unit second inlet to a dilution water reservoir, and an outlet pipe connecting the unit outlet to a pump arranged to draw liquid from the mixing unit and to supply that liquid to a washing unit of the washing plant.
13. A washing plant comprising a dilution system as claimed in claim 10 in combination with a washing unit in the form of a spray bar, the spray bar having

an inlet for diluted chemical to which the output from the pump is connected and further having an inlet for water, whereby additional dilution of the diluted chemical takes place within the spray bar prior to the issue of the cleaning chemical therefrom.
14. A washing plant as claimed in claim 11, wherein the spray bar has a plurality of spray nozzles out of which the diluted chemical and further water issue.
15. A washing plant as claimed in claim 13 or claim 14, wherein the spray bare is mounted for movement over the surface of an article to be washed by the diluted cleaning chemical.
16. A washing plant as claimed in claim 15 and arranged as a vehicle-wash plant, the spray bar being mounted on an arch of the plant for movement over a vehicle stationary beneath the arch.