GB2425741A

GB2425741A - Line marking apparatus

Info

Publication number: GB2425741A
Application number: GB0509261A
Authority: GB
Inventors: Mark Rodman
Original assignee: Linemark UK Ltd
Current assignee: Linemark UK Ltd
Priority date: 2005-05-06
Filing date: 2005-05-06
Publication date: 2006-11-08
Also published as: GB0509261D0

Abstract

A line marking apparatus comprising a body (fig 2) which is translatable over a surface onto which a line is to be marked. The body is provided with a mechanism for dispensing line marking fluid. The mechanism includes a nozzle 16 which is arranged such that line marking fluid dispensed through the nozzle 16 forms a conically shaped web. Additional features of a nozzle 16 include inlet 30, tube 32, vanes 31 and helical channel 33.

Description

LINE MARKING APPARATUS

The present invention relates to a line marking apparatus.

Conventional line marking apparatus have been used for many years to mark out playing areas, such as football pitches, rugby pitches and athletics tracks.

A known line marking machine comprises a frame having an axle on which surface engaging wheels are journaled and a tank filled with paint mounted on the frame. A pump is provided to circulate paint from the tank, through a hydraulic circuit and to a nozzle, where the paint is dispensed.

It is desirable for line marking machines to dispense a thick column of paint.

However, when paint emerges from a nozzle, it forms a web (a structure formed by interwoven liquid ligaments), air resistance and surface tension being operable to cause the web to separate into droplets. It is therefore presently desirable to generate a web presenting the smallest profile to air, decreasing the effective air resistance and reducing the likelihood of creating droplets. As a direct result, all known line marking apparatus use a flat fan nozzle. Flat fan nozzles produce a narrow elliptical spray pattern (i.e. a narrow column of paint) and as such, deposition of spray is heaviest at the centre of the spray pattern, directly under the nozzle.

It is an aim of an embodiment of the present invention to provide an improved line marking apparatus.

In accordance with the present invention there is provided a line marking apparatus comprising a body which is translatable over a surface onto which a line is to be marked, the body being provided with a mechanism for dispensing line marking fluid, the mechanism including a nozzle which is arranged such that line marking fluid dispensed through the nozzle forms a conically shaped web.

I

Nozzles that dispense line marking fluid in a conically shaped web are known as hollow cone nozzles. Such nozzles tend to provide the smallest droplets produced by hydraulic spray nozzles. The inventors of the present invention have recognised that by reducing the droplet size, for a constant volume of line marking fluid, the surface area marked can be increased i.e. if it is assumed that all droplets are spherical.

Reducing the droplet diameter by half and maintaining the total volume of line marking fluid, produces eight times as many droplets and twice as much total surface area. The inventors of the present invention have thereby overcome a technical prejudice by not trying to produce a column of paint. Rather the inventors have tried to produce a thin web of paint that emerges from the nozzle and so causes the dispensed web of paint to separate into droplets.

Further, it has also been found that by using a nozzle that produces droplets, not only does the amount of area that can be marked increase, but also the drying time of the paint is reduced Furthermore, irregular surfaces such as grass are better marked using a hollow cone nozzle than other hydraulic nozzles as, for example, both sides of grass blades are covered with line marking fluid, whereas due to the force exerted by the column of paint dispensed by a flat fan nozzle, only one side is generally covered by conventional line marking apparatus.

A specific embodiment of the present invention will now be described by way of example only, with reference to the accompanying drawings, in which:- Figure 1 is a schematic drawing of a cross-sectional view of a line marking apparatus in accordance with the present invention; Figure 2 is a perspective view of a line marking mechanism that forms part of the line marking apparatus shown in figure 1; Figure 3 is a cross-sectional view of a nozzle assembly that forms part of the line marking apparatus shown in figure 1; Figure 4 is a schematic representation of the structure of the hydraulic circuit contained within the line marking apparatus of figure 1; and Figure 5 shows a section of the hydraulic circuit of figure 4 that serves to control the flow of paint from a nozzle.

The line marking apparatus shown schematically in figure 1 comprises four ground engaging wheels 1 a, lb (only two of which are shown) mounted on two axles 2a, 2b, the axles 2a, 2b in turn being mounted on a chassis 3. The chassis 3 supports a paint tank 4 and a water tank 5. A frame 6 extends upwards from the chassis 3 and forms a handle 7 at its upper end, the handle 7 allowing the line marking apparatus to be pushed across a surface by an operator. A switch 8 is provided on the handle 7 to allow an operator to remotely control a motor 9 which powers the rotation of the wheels 1 and so drives the apparatus. A socket 10 for recharging a battery 11 that powers the motor 9 is provided and disposed for easy access by the operator.

Although the embodiment of the invention shown in Figure 1 is provided with wheels, it will be appreciated that some or all of the wheels may be replaced by other suitable means, for example runners or tracks.

The chassis 3 also supports a pump 12 and a filter 13, which are interconnected with the paint tank 4 and the water tank 5 by a series of pipes and valves. An array of valves 14 is provided towards the rear end of the line marking apparatus, near the handle for ease of access by the operator. The function of the array of valves 14 will be described in more detail later with reference to figures 4 and 5.

Extending from the front of the chassis 3 is a line marking mechanism 15. The line marking mechanism 15 is coimected to the paint tank 4 so that line marking fluid can be dispensed from a nozzle 16 which forms part of the line marking mechanism.

Referring to figure 2, the line marking mechanism 15 comprises a nozzle assembly 17, which includes the nozzle 16; two circular guards I 8a, 1 8b; and a bar 19.

The guards 1 8a, 1 8b are slidably mounted on the bar 19 by arms 20a, 20b and can be positioned a predetermined distance away from the nozzle 16. The guards 1 8a, 1 8b can also be positioned so that they engage with the ground, such that when the line marking apparatus is moved by an operator, the guards 1 8a, I 8b rotate on the arms 20a, 20b and so roll along the ground.

By positioning the guards 1 8a, 1 8b so that line marking fluid from the nozzle 16 impinges on them, the edges of the line being marked are set relative to the nozzle 16.

Thus, by altering the positions of the guards 18a, 18b relative to the nozzle 16 the width of the line being marked can be fixed.

The arms 20a, 20b are slidably mounted on the bar 19 by annular collars 21a, 2lb.

The collars 21 a, 21 b are formed integrally wit the arms 20a, 20b, and fit tightly around the bar 19. The arms 20a, 20b are thereby able to rotate and slide along the bar 19. The arms 20a, 20b are each provided with a grub screw 22a, 22b. By tightening the grub screw 22a, 22b, the collars 21a, 21b, and therefore the arms 20a, 20b and the guards 1 8a, I 8b, are fixed in position. It is currently preferred to maintain the guards 1 8a, 1 8b equidistant from the nozzle 16.

The line marking mechanism 15 is attached to the chassis 3 via an axle 23. The axle 23 is fixed to the end of the bar 19. The axle 23 fits inside a tube 23' (shown in Figure 1) on the chassis 3 and so allows the line marking mechanism 15 to rotate relative to the tube 23'. The line marking mechanism 15 can be positioned in an up or a down orientation by tipping the line marking mechanism 15 upwards and towards or downwards and away from the chassis 3. In the down orientation, the guards I 8a, 18b engage with the ground and so limit the disposition of the line marking fluid. In the up orientation, the line marking mechanism 15 rests on the chassis 3.

The nozzle assembly 17 is shown in cross-section in figure 3 and comprises a nozzle body 24, an insert 25, an annular rubber washer 26, a nozzle 16 and an annular cap 27.

The nozzle body 24 is formed by a first and second hollow cylinder 24a, 24b, the first cylinder 24a having a larger diameter than the second cylinder 24b with an annular flange 28 connecting the two cylinders 24a, 24b together. As shown in figure 3, the first cylinder 24a has a screw thread 28' provided on its exterior.

The insert 25 comprises a tubular portion 25a that fits tightly within the second cylinder 24b and a lip 25b that projects radially outward, preventing the insert 25 from being fully enclosed by the second cylinder 24b. The insert 25 is inserted into the nozzle body 24 so that the tubular portion 25a is within the second cylinder 24b and the lip 25b abuts the annular flange 28 of the nozzle body 24.

The rubber washer 26 is placed on top of the lip 25b within the nozzle body 24. The rubber washer 26 is sized and dimensioned so that it fits tightly within the first cylinder 24a of the nozzle body 24. The washer 26 may also serve as a strainer, but in such a case would typically not be annular in shape but in the shape of a disc with a centrally disposed filter material.

The nozzle 16 has an external shape, which is similar to the insert 25, i. e. having a tubular portion 16a and a radially projecting lip 16b. The nozzle 16 is placed so that its lip 16b abuts the rubber washer 26 and extends axially out of the nozzle body 24.

The centrally disposed hole in the annular cap 27 has a diameter which is greater that the diameter of the tubular portion 16a of the nozzle and which is less than the diameter of the lip I 6b of the nozzle. As a result, the tubular portion 1 6a of the nozzle can be threaded through the hole in the annular cap 27. On the interior of the cap 27, there is a screw thread 29 that corresponds to the screw thread 28' on the exterior of the nozzle body 24. By screwing the cap 27 onto the nozzle body 24, the nozzle 16, rubber washer 26 and insert 25 are squeezed together causing the rubber washer 26 to radially expand and thereby form a seal with the interior of the nozzle body 24.

The nozzle 16 comprises an inlet 30, vanes 31 and a tube 32 which is tapered to form a conical frustrum shape. A helical channel 33 is engraved in an inner surface of the tube 32 (more than one helical channel may be provided). The tube 32 is provided with an outlet 33' in the form of a circular nozzle orifice.

The line marking fluid passes through the inlet 30 and on reaching the vanes 31 is subject to the Venturi effect (i.e. the vanes 31 reduce the area through which the line marking fluid can flow and in so doing cause the line marking fluid to flow more quickly). The vanes 31 also direct the line marking fluid so that it enters the whirl chamber 32 along the start of the helical channel 33. The line marking fluid is therefore naturally inclined to follow the helical channel 33. As a direct result, a centrifugal force is exerted on the line marking fluid, driving the line marking fluid against the wall, leaving a core of air in the centre.

The line marking fluid exits the nozzle 16 momentarily in the form of conically shaped web of line marking fluid due to the centrifugal force generated by the whirl chamber 32. If the nozzle 16 is pointed directly downwards, the web will stretch to a point where it ruptures, creating a spray with line marking fluid concentrated in a conical shape. The line marking fluid is concentrated in a conical shape because the resultant force on all parts of the line marking fluid acts in a direction which is a fixed angle from the vertical, due to the weight and centrifugal force on all parts of the line marking fluid being substantially equal. In contrast, if, for example, the nozzle is pointed horizontally, the line marking fluid will still exit the nozzle 16 in the form of conically shaped web, but due to the effect of gravity the line marking fluid will be unlikely to be concentrated in a conical shape when the spray hits the surface to be marked. A conically shaped web should be understood to include, but not be limited to, frustro-conically shaped webs, webs of a shape which have a base that is not circular, but, for example, elliptical and webs where the line marking is only concentrated in a conical shape.

Suitable nozzle assemblies are HCX3, 4, 6, 8 and 10 sold by Hypro EU Ltd of Station Road, Longstanton, Cambridge, England.

The preferred range of the rate of deposition is 0.2 to 0.66 liters of line marking fluid dispensed per minute. The most preferred rate of deposition is 0.33 liters per minute as it provides a suitable amount of paint to mark a good quality line at a moderate walking speed.

To help produce a hollow cone spray, the paint is pressurized by the pump 14 to between 5-l45psi (0.035-1.0 MPa), preferably 30-lOOpsi (0.21-0.69 MPa) and most preferably S0psi (0.34 MPa).

Figure 4 is a schematic representation of the structure of the hydraulic circuit within the present embodiment.

Figure 5 shows a section of the hydraulic circuit of Figure 4, which serves to control the flow of line marking fluid from the line marking mechanism 15 of the line marking apparatus. This section of the hydraulic circuit comprises the paint tank 4, the pump 12, a filter 13 and the line marking mechanism 15.

Referring to figure 5, line marking fluid from the paint tank 4 can be pumped through the filter 13 and then through the pump 12. The filter 13 extracts particles within the line marking fluid above a certain size. This prevents coagulated line marking fluid from reaching the pump 12 and thereby reducing the efficiency of the pump 12.

On exiting the pump 12, the line marking fluid may flow in one of two directions. The first direction is toward the line marking mechanism 15 and the second direction is back toward the paint tank 4 via a recirculation path 34.

A nozzle valve 35 is provided between the nozzle 16 and the pump 12, the nozzle valve 35 having a closed orientation and an open orientation. Once the nozzle valve is opened, line marking fluid can flow freely from the paint tank 4 to the line marking mechanism 15, where it is dispensed.

A recirculatjon valve 36 is provided in the recirculation path 30 between the pump 14 and the tank 4. The recirculatjon valve 36 controls the flow of line marking fluid from the pump 12 back to the paint tank 4 and thereby controls the amount of line marking fluid dispensed by the line marking mechanism 15. For instance, when the nozzle valve 35 is open and the recirculation valve 34 is fully closed, all the line marking fluid pumped from the paint tank 4 will be dispensed. When the nozzle valve 35 is open and the recirculation valve 36 is open, some of the paint pumped from the paint tank 4 will not be dispensed, as it will be recirculated back to the paint tank 4. In this way, the recirculation valve 34 controls the amount of line marking fluid dispensed by the line marking mechanism 15. Furthermore, when the nozzle valve 35 is closed, the recirculation valve 34 should be at least a little open, otherwise the motor which drives the pump 12 is liable to stall.

Figure 4 shows the entirety of the hydraulic circuit, and so shows all the components of the section of the hydraulic circuit shown in figure 5 and as well as a water tank 5, a drain valve 37 and a three-way valve 38. The three-way valve 38 is positioned between the paint tank 4, the water tank 5 and the pump 12.

Line marking fluid, water or a mixture thereof is moved around the circuit by the pump 12. Whether fluid from the paint tank 4 or water tank 5 is pumped around the circuit is dependent on the orientation of the three-way valve 38. When the three-way valve 38 is in the position shown in figure 4, line marking fluid from the paint tank 4 is supplied to the pump 12.

After using the line marking apparatus, line marking fluid is emptied from the paint tank 4 via the drain valve 37. Water may also be poured into the paint tank 4 and allowed to drain via the drain valve 37 to remove any remaining line marking fluid.

The drain valve 37 is subsequently closed.

The nozzle valve 35 and the recirculation valves 34 are placed in their open positions and the three-way valve 38 is arranged to allow water from the water tank 5 to the pump 12.

The pump 12 is then started, causing water to travel around the circuit, through the pump 12 and either out through the nozzle 16 or into the paint tank 4 via the recirculatjon valve 34.

Once the paint tank 4, the recirculation path 34 and the pipe between the paint tank 4 and the three-way valve 38 are full with water, the nozzle 16 will dispense all the water pumped from the water tank 5. By maintaining the paint tank 4 full of water, any remaining line marking fluid is prevented from drying.

Once the water tank 5 is empty, the pump 12 is switched off and the line marking apparatus put into storage.

The nozzle valve 35, the recirculation valve 36, the drain valve 37 and the three-way valve 38 form part of the array of valves 14 disposed near the frame 6 on the chassis 3 of the line marking apparatus as shown on figure 1.

A line marking apparatus in accordance with the present invention may be used in conjunction with any conventional line marking fluid but is particularly suitable for relatively low viscosity paints such as those disclosed in UK Patent No. 2247690. UK Patent No. 2247690 discloses paint compositions that are particularly suitable for use with the present invention including: paint mixed with water and a non-aqueous dispersion of thickening agent; titanium dioxide based paint; paint that contains one or more additives selected from a filler, an anti foaming agent, a dispersant, a biocide and a binder; and a mixture of the following ingredients in the quantities stated: TitaniumDioxide 50 kgm; China Clay 12.5 kgm; Anti-Foaming Agent 0.4 kgm; Dispersant 0.4 kgm; Biocide 4.0 kgm; Binder 25 kgm; Water 700 kgm, where these ingredients are thoroughly mixed prior to the addition of 4.8 kgm of the non-aqueous dispersion of thickening agent, and the non-aqueous dispersion comprises :Acrylamide Copolymer 60 (%w/w); Odourless Kerosene 40(%w/w).

The paint disclosed above has a viscosity of the order of 1500 centipoise. The viscosity of this paint, or indeed the viscosity of any other conventional paint, may be reduced to below 1500 centipoise by the addition of synthetic colloidal clay. The synthetic colloidal clay is a very high efficiency thixotropic synthetic smectite additive which hydrates at relatively high paint solid levels and remains pourable for extended periods. The addition of synthetic colloidal clay to paint has be found to allow significantly reduced amounts of content and thickness to be used thereby significantly reducing viscosity without detriment to the solids content of the paint, in other words, without detriment to the qualities of the paint when applied to a surface (as for instance in line-marking). For instance, the addition of about 0. 003kg of synthetic colloidal clay per litre of paint can enable reduction in the thickener acrylamide copolymer by about 90% so that the non- aqueous dispersion comprises only about 6% w/w acrylamide copolymer, the remainder for instance being kerosene and the synthetic colloidal clay.

It has been found that the addition of synthetic colloidal clay to paint used in conjunction with a line marking apparatus with a hollow cone type nozzle reduces the amount of paint required to mark a predetermined area. This occurs as a web of paint dispensed by such a nozzle is more likely to separate into droplets when the paint contains synthetic colloidal clay.

Preferred paints for use with the present invention have a relatively high solids content (for instance greater than about 30% solids by weight - and preferably between 40% and 50%) and can include 0.001 kg to 0.006kg, preferably 0.003kg, of synthetic colloidal clay per litre of paint as an additive.

Addition of about 0.003kg of synthetic colloidal clay per litre of paint as disclosed in UK Patent No. 2247690 has been shown to reduce the viscosity of the paint by about 48O-ô00centipoise as measured on a Brookfield RV viscometer spindle 2 speed 20 on a factor of 20.

Hollow cone nozzles without vanes, which are less likely to clog are also known and can be used in accordance with the present invention.

In an alternative embodiment of the present invention, a nozzle 9 comprises a fixed plate positioned downstream of the nozzle orifice 13. The fixed plate is arranged so that it deflects paint being dispensed, so forming a conically shaped web of line marking fluid. This embodiment however suffers from the disadvantage that the line marking fluid which impinges on the fixed plate will not be properly dispensed, and so will be wasted.

Claims

1. A line marking apparatus comprising a body which is translatable over a surface onto which a line is to be marked, the body being provided with a mechanism for dispensing line marking fluid, the mechanism including a nozzle which is arranged such that line marking fluid dispensed through the nozzle forms a conically shaped web.

2. A line marking apparatus as claimed in claim 1, wherein the nozzle comprises a tube, an inner surface of the tube being provided with one or more helical channels.

3. A line marking apparatus as claimed in claim 2, wherein the nozzle further comprises vanes that direct the flow of line marking fluid into the tube.

4. A line marking apparatus as claimed in claim 3, wherein the vanes direct the flow of line marking fluid towards an end of the one or more helical channels.

5. A line marking apparatus as claimed in any one of claims 2, 3 or 4, wherein the vanes are arranged to cause a venturi effect on the line marking fluid.

6. A line marking apparatus as claimed in any one of claims 2, 3, 4 or 5, wherein the tube narrows downstream of the flow of the line marking fluid.

7. A line marking apparatus as claimed in claim 6, wherein the tube is tapered.

8. A line marking apparatus as claimed in claim I, wherein the nozzle comprises a nozzle orifice from which line marking fluid is dispensed, and a plate positioned relative to the nozzle orifice so that at least some of the line marking fluid dispensed from the nozzle orifice impinges on the plate and is thereby deflected so that a conically shaped web is generated.

9. A line marking apparatus as claimed in any one of the preceding claims, further comprising line marking fluid that includes synthetic colloidal clay.

10. A method of line marking using the line marking apparatus according to any of claims 1 to 8, wherein the method comprises using line marking fluid that includes synthetic colloidal clay.

11. A line marking apparatus substantially as hereinbefore described