GB2567228A

GB2567228A - Spray head with flushing arrangement

Info

Publication number: GB2567228A
Application number: GB1716440.1A
Authority: GB
Inventors: Peter Mcguffie Iain
Original assignee: FLEET LINE MARKERS Ltd
Current assignee: FLEET LINE MARKERS Ltd
Priority date: 2017-10-06
Filing date: 2017-10-06
Publication date: 2019-04-10
Anticipated expiration: 2037-10-06
Also published as: GB2567228B; GB201716440D0

Abstract

A spray head 1 is described which comprises a body 2, which may be manufactured as a single block, and preferably from a transparent material, comprises a paint inlet 3, a water inlet 4, paint conduit 23, water conduit 24, paint exit region 19, nozzle exit region 18, and nozzle tip 7 with orifice 7'. Control valve 10 may be included to prevent the return of fluid from the paint exit region 19 towards the paint inlet conduit 23. Whenever the paint supply to the paint inlet 3 is stopped, a small amount of water is automatically introduced into water inlet 4 so as to dilute the paint in the nozzle exit conduit 18. In this way, concentrated paint is not left static in the nozzle orifice 7'; it is always diluted as soon as the paint flow stops.

Description

Spray head with flushing arrangement

Field of the invention

The invention relates to the field of spray nozzles such as may be used, for example, for spraying aqueous suspensions such as emulsion paint. In particular, but not exclusively, the invention relates to spray nozzles for spraying marking material to mark lines on ground surfaces such as grass sports fields.

Background of the invention

The following text uses the example of line marking to explain the advantages and the functioning of the invention. It should be understood, however, that the invention may find application in other fields in which spray nozzles are used.

Modern line marking systems, such as the MAQA® satellite-guided marker, enable an operator to mark sports field very quickly, as the marking head is automatically guided with great accuracy by the guidance system. The operator is thus free to push or drive the line marking apparatus fast. Whereas the marking of a full sports field might have taken half a day in the past, the same marking can easily be accomplished in less than an hour.

Marking at higher speeds means that the line marking material is deposited more thinly on the ground (eg grass). It also means that the operator can do more marking in a given time, preferably without frequent stops for re-filling the paint tank of the line marking apparatus, and without the need to carry around cumbersome quantities of paint. In order to meet these conflicting demands, new highlyconcentrated paints have been developed which provide much higher pigment coverage, and can therefore be used at the new higher speeds without the need for a large tank or frequent refilling.

However, an emulsion with a high concentration of dispersed pigment solids (eg 30% or more) tends to dry and clog much more quickly than paints with lower concentrations. They also tend to be used with finer spray nozzles, in order to achieve the required marking quality and control. The combination of fine nozzles and concentrated paint increases the risk of the nozzle becoming fully or partially clogged.

Even a partial clogging can dramatically affect the quality of the marked line. These problems are particularly acute when marking in conditions such as hot sunshine or wind, which tend to increase the rate of drying of the paint. To avoid clogging, an operator will typically replace the fine nozzle with a larger one; this may relieve the immediate problem of clogging, but will greatly increase the amount of line marking material used, and thereby the cost of the line marking activity.

Prior art

It has been proposed in W02015052116A1 to use a manual system for flushing the nozzle. A small quantity of water is introduced under pressure (provided manually by a syringe) into the pipework at or near the nozzle to flush the paint out. When the operator finishes marking, he or she may use the flushing system to manually inject water into the pipework at or near the nozzle so as to clear the paint from the nozzle. The flushing solution proposed in W02015052116A1 is relatively complex, and relies on the intervention of the operator. Furthermore, it results in a small but nevertheless significant volume of water in the nozzle which must be sprayed out at the beginning of the next marking. This water may cause an unsightly washing out of the first two or three centimetres of the next line when it is marked.

Brief description of the invention

The present invention aims to overcome at least some of the above disadvantages of the prior art. To this end, a spray head according to the invention is described in the attached claim 1, a flushing method according to the invention is described in claim 6, a line marking apparatus according to the invention is described in claim 9, and a line-marking method according to the invention is described in claim

14. Further variants of the invention are described in the dependent claims. By introducing a small amount of water into a nozzle exit conduit which has a very small volume, the concentration of the paint can be quickly reduced to a level at which it will not clog, but without diluting it so much that wash-out occurs when spraying recommences.

The invention will be described in detail with reference to the attached drawings, in which:

Figure 1 shows in simplified schematic cross-section a first example of a nozzle assembly according to the invention.

Figure 2 shows in simplified schematic cross-section a second example of a nozzle assembly according to the invention.

Figure 3 shows in cross-section a first implementation of a nozzle assembly according to the invention.

Figure 4 shows a perspective view of the nozzle assembly of figure 3.

Figure 5 shows an exploded view of the nozzle assembly of figures 3 and 4.

The figures are provided merely as an aid to understanding the principles underlying the invention, and should not be taken as limiting the scope of protection sought. Where the same reference numbers are used in different figures, these are intended to indicate similar or equivalent features. It should not be assumed, however, that the use of different reference numbers is intended to indicate any particular degree of difference between the features to which they refer.

Detailed description of the invention

Figure 1 shows a nozzle assembly 1, also referred to as a spray head, comprising a body 2, which may advantageously be manufactured (eg cast, moulded or machined) in a single block, and comprises a paint inlet 3, a water inlet 4, paint conduit 23, water conduit 24, paint exit region 19, nozzle exit region 18, and spray nozzle 7. Nozzle tip 7 may be a cone or fan spray nozzle, for example, and has a nozzle orifice 7'. As described above, if the spray head 1 is used for spraying highquality paint with a high concentration of pigment solids, the nozzle orifice may be have a small cross-sectional area (eg less than 0.5mm²). Control valve 10, which may advantageously be included to prevent the return of fluid from the paint exit region 19 towards the paint inlet conduit 23, may comprise a solenoid valve, a non-return (oneway) valve or other suitable device. Alternatively, the non-return function may be provided by a device external to the spray head 1 (eg a one-way valve upstream of the paint inlet 3). For the purposes of illustration in this text, the spray head 1 will be illustrated as having a control valve 10 which is a so-called drip-control valve (DCV), which opens to allow the passage of paint when the pressure in the paint inlet conduit is greater than a predetermined pressure Pi. As will be described below, the control valve 10 may be arranged such that the opening pressure Pi can be adjusted.

During normal spraying operation, paint is supplied under pressure via inlet 3 and inlet conduit 23. The water inlet is shut off, so that no water flows into the water inlet 4 and water inlet conduit 24. If the paint pressure is greater than the opening pressure Pi of control valve 10, the paint flows through the nozzle assembly body 2 from the paint inlet conduit 23 to the paint exit conduit 19, through the nozzle exit conduit 18 and out through the nozzle orifice 7' of nozzle 7. If the paint pressure is reduced, or the paint flow to the spray head 1 is cut off, the paint stops flowing into the paint exit conduit 19, and spraying stops. If the spray head 1 is left in this state for more than a few minutes, especially when using highly-concentrated paint, the paint in the nozzle orifice 7' and the nozzle exit conduit 18 will begin to dry and harden. The finer the nozzle, the faster it will become clogged by the drying paint. For this reason, when the paint flow is stopped, water (or other flushing fluid) is supplied under pressure via the water inlet conduit 24 into the nozzle exit conduit 18. The water dilutes the paint in the exit conduit 18 while the paint in the paint exit conduit 19 upstream of the junction with the water inlet conduit 24 remains largely undisturbed. The volume of the nozzle exit conduit 18 (ie the part downstream of the water inlet junction and upstream of the nozzle orifice 7') is preferably less than 4cm³, or more preferably less than 2cm³, or more preferably less than 1cm³. Just a small amount of water (or other flushing liquid), supplied under pressure into the nozzle exit conduit 18, can quickly dilute the pigment concentration of the paint remaining in the nozzle exit conduit 18. In practice, a few millilitres of water is enough to dilute the concentration to less than 50% of its former value.

A control system (not illustrated) is provided which automatically adjusts the relative timing of the water supplied into the water inlet 4, and the total amount of water supplied, so as to achieve the desired amount of dilution of the paint in the nozzle exit conduit 18. In this way, the spray head 1 can be operated such that a small amount of water is pumped or otherwise supplied into the water inlet 4 under pressure every time the paint flow into the spray head stops. Note that the aim may not be to flush all the paint out of the nozzle exit conduit 18. Indeed, this may be disadvantageous because when spraying recommences, the first sprayed fluid would be mainly water. So, instead of reducing the concentration to near zero, the control system may be configured to reduce the concentration to a level (eg 50%) at which clogging is prevented, yet there is sufficient pigment to provide instant pigment coverage when spraying recommences (no wash-out effect).

The control system may be fully automatic and/or it may have an interface by means of which an operator can instruct the spray-head to be flushed.

Figure 2 shows a variant of the spray head 1 which includes a filter 8, for example a gauze or mesh filter arranged to prevent flakes or aggregated paint particle from reaching the orifice 7', where they could block the orifice or impair the spray pattern. The nozzle exit conduit 18 is shaped to accommodate the filter 8. Because of the displacement volume of the filter 8, the total volume of fluid in the exit conduit 18 may be reduced still further due to the presence of the filter 8. The junction of the water inlet conduit 24 with the nozzle exit conduit 18 is arranged adjacent to the top of the filter, so that the flushing/diluting operation ensures that all the liquid in contact with the filter 8 (as with the nozzle orifice 7') is diluted, so that the paint does not clog the filter 8 or the orifice 7'.

Figures 3 to 5 show an example implementation of a spray head 1 according to the invention. The control valve 10 is implemented as a drip control valve (DCV), with a pressure adjustment cap 11, a spring 12, DCV housing 13, plunger 14, diaphragm 15 and sealing rim 16 against which the diaphragm is pressed when it closes. Figure 3 shows the DCV in its open state. Nozzle tip 7 and filter 8 are held in place by a cap 9 and mutually sealed by washer seal 17. Paint and water inlets 3 and 4 are threaded for receiving connectors 5 and 6 respectively. Support mounting 20 is provided so that the spray head can be fixed to other equipment (such as a line-marking apparatus). The mounting 20 may be threadedly connected, as shown in figure 3. The nozzle cap 9 may be a bayonet-fit to the body 2.

The body 2 (shown shaded) is preferably made of a transparent material such as clear plastic. This allows easy inspection of the spray head 1 for blockages or paint deposits inside the body 2. The DCV cap 13 and/or the nozzle cap 9 may also be made of (the same or similar) transparent material.

The paint may be supplied to the spray head 1 at a pressure of between 40psi and 80 psi, for example. The water may be supplied at a pressure of between 30psi and 60 psi, for example.

Claims

1. Spray head (1) comprising:

a body (2), a nozzle (7, 7'), a paint inlet (3) and a paint inlet conduit (23), a flushing fluid inlet (4), a nozzle exit conduit (18) for conveying paint to the nozzle (7, 7'), a paint exit conduit (23) for conveying paint from the paint inlet conduit (23) to the nozzle exit conduit (18) a flushing fluid inlet conduit (24) for conveying flushing fluid from the flushing fluid inlet (4) to the nozzle exit conduit (18), characterised in that the flushing fluid inlet conduit (24) joins the nozzle exit conduit (18) at a conduit junction, wherein the volume of the nozzle exit conduit (18) downstream of the conduit junction and upstream of the nozzle (7, 7') is less than 4cm3, or preferably less than 2cm3, or preferably less than 1cm3.

2. A spray head (1) according to claim 1, in which the body is formed as a single piece of contiguous material.

3. A spray head (1) according to claim 1 or 2, wherein the material is substantially transparent.

4. A spray head (1) according to one of the preceding claims, comprising a control valve (10) for preventing a flow of paint from the paint exit conduit (19) to the paint inlet conduit (23)

5. A spray head (1) according to one of the preceding claims, comprising a filter (8) arranged in the nozzle exit conduit (18) for preventing particles in the paint from reaching the nozzle orifice (7').

6. Method of flushing a spray head (1) according to one of claims 1 to 5, comprising:

- stopping a flow of paint having a first concentration to the paint inlet (3) of the spray head (1),

- supplying a volume of water to the water inlet (4) under pressure, characterised in that the volume of water is selected to dilute the paint in the nozzle exit conduit (18) to a second concentration, wherein the second concentration is less than the first concentration.

7. Method according to claim 6, wherein the second concentration is less than half of the first concentration.

8. Method according to claim 6 or 7, wherein the second concentration is greater than 10%, or preferably greater than 25% of the first concentration.

9. Line marking apparatus comprising a spray head (1) according to one of claims 1 to 5.

10. Apparatus according to claim 9, comprising a control system configured to automatically introduce a predetermined amount of flushing fluid into the flushing fluid inlet (3) under pressure so as to displace fluid in the nozzle exit conduit (18) out through the nozzle orifice (7').

11. Apparatus according to claim 10, wherein the predetermined amount is determined as the amount required to reduce the first concentration of the paint in the nozzle exit conduit to a second, lower concentration.

12. Apparatus according to claim 11, wherein the second concentration is less than half of the first concentration.

13. Apparatus according to claim 11 or 12, wherein the second concentration is greater than 10%, or preferably greater than 25% of the first concentration.

14. Method of marking a line, comprising using a line marking apparatus according to one of claims 9 to 13.