Ground Marking Vehicle This invention relates to ground marking vehicles.

Ground marking is done in a number of ways. Playgrounds are marked with hopscotch and other designs by applying pre-cut pieces of plastic sheet and bonding them to a concrete or tarmacadam substrate using gas torches. Advertising and promotional logos and like ground markings for sporting arenas are made by directional brushing or painting through stencils.

WO2004/100044 discloses creating a visual representation on a plane surface using a free roaming marking device with exchangeable tools that can deposit paint, or bend or cut grass. WO02/18J 48 discloses Ink jet printing on to contoured rigid panels such as office partitions and automobile interior panels, with a multi-jet print head carriage where the print heads are maintained at a fixed distance above the contoured surface. The print head carriage traverses over the print surface on a frame that moves over the surface to print different areas of it. US2013/01221 86 discloses a surface coating arrangement in which a spray head is traversed over successive strips of a surface to coat it. US8696089 describes a large surface are printer comprising a frame on which a print head traverses that is attached to the surface using suction cups. These, and other, disclosures appear to have been, at best, academic disclosures of the way things might be done if there was a demand, scale-ups of conventional ink jet printers. No commercially available such equipment is used for large area printing, especially for printing on concrete or tarmacadam ground surfaces or grass, the principal methods in common use being gas torch bonding pre-cut plastic sheets and stencils, as noted above, with the addition of computer guided line painting for marking out sports pitches.

The transition from a desk-top Inkjet printer, which is static, with a paper feed under a laterally traversing print head that also carries the ink supply, to a mobile, large area printer that has to be transported to and deployed at the printing site, and that uses substantial quantities of ground marking material, is not straightforward. The present invention provides a solution to the transition problem.

The invention comprises a mobile ground marking printer comprising a frame and a print head traversable on the frame to deposit ground marking material on ground under the area of the frame, the frame being mounted on a transport and deployment carriage and depioyabie on the carriage between a stowed, transport position and an operative position, the latter being ground-parallel, the carriage having provision for a supply of ground marking material fixed relative to the carriage and material delivery means connecting the supply to the print head. z

The stowed, transport position may be raised about one side of the frame from the horizontal, and may be vertical or substantially so. A deployment mechanism, which may be a hydraulic strut, may be provided. The carriage may have ground wheels and be adapted for towing.

5

The frame may have ground engaging members that engage the ground in its deployed position. The ground engaging members may be on corners of the frame, and may comprise feet, or wheels or castors, allowing the frame to be fixedly positioned with respect to an area of ground for printing that area, and to allow the frame to be moved for 10 printing another area of ground.

Feet, which may be spiked for fixedly positioning the frame, may be lifted for movement of the frame, wheels or castors may be locked for fixedly positioning the frame.

15 The carriage may house control means for traversing the print head and for marking

material selection from a plurality of sources. The sources may be sources of different colours of marking material, which may comprise CYM, or, if good black is required, CYMK colours, and, since the substrate will not usually be white, a white will be required for any print that has white or paler shade than the primary colours. The image

20 may be printed in small adjacent discrete dots which, when viewed from a suitable

distance to appear to blend into colours depending on the relative quantities of the four colours laid down, and may be halftoned as with paper and fabric printing. However, where, as may often be the case, only one or a small number of solid colours are required, these may be sourced as such and laid down as solid colour areas.

z J

The carriage may also house frame positioning control means for moving the frame to an adjacent ground area for marking areas greater than the frame area, and for correctly positioning the frame with respect to an already marked area. Correct positioning may be ensured by a dead reckoning arrangement, in which, for example, wheels' or castors' 30 rotation is monitored by a rotary encoder, or a GPS arrangement, in either case final positioning of the frame, or traverse limits of the print head in the frame, being possibly under the control of a machine vision arrangement stitching adjacent images together in the fashion of a panoramic camera imaging arrangement.

35 The frame positioning control means may be autonomous, sensing when one print area has been completed and effecting movement to an adjacent area.

The provision for the supply of ground marking material may comprise support or holder means for one or more marking material containers, which may be adapted for

40 connection to the print head through flexible ducting. If the ground marking material is a plastic that is applied to the ground molten, the containers may be heated and the ducting insulated. The container may be pressurised to force material to the print head. Heating and/or pressurisation means external to the containers may be built into the carriage, or containers may have internal such means, which may be electrically operated, which may

45 be from a power source carried by or connectable to the carriage. Desirably, the containers will have a sufficient capacity to print an image within the area of the frame without needing to be changed.

Usually, the printed image will be viewed from a greater, often a substantially greater, distance than images from desk top paper printers, and the print resolution can be correspondingly coarse. A resolution of 500 pixels per metre may be adequate for many purposes, with a dot resolution of 1000 to 2000 dots per metre. Standard printing techniques such as dithering and error diffusion may be used. Resolution may, however, depend on the nature of the material being printed as well as on the nature of the substrate. It will be difficult, for example, to get fine resolution on a grass substrate, though usually designs printed on grass comprise blocks of solid colour such as are achieved by stencilling. And when laying down a plastics material, it will tend to splat to some extent depending on its viscosity and the speed at which it lands on the substrate, and this will dictate the smallest dot size.

The control means for the print head and, when present, for frame positioning, may be instructed remotely, a print file being loaded into a controller, for example, from a computer or a suitably apped smartphone that can call on a library, which might be in the Cloud, of print files.

A mobile ground marking printer according to the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a side elevation; and

Figure 2 is a plan view.

The drawings illustrate a mobile ground marking printer 11 comprising a frame 12 and a print head 13 traversable on the frame 12 to deposit ground marking material on ground under the area of the frame 12, the frame 12 being mounted on a transport and deployment carriage 14 and deployabie on the carriage 14 between a stowed, transport position (chain line) and an operative position (solid line), the latter being ground- parallel, the carriage 14 having provision for a supply 16 of ground marking material fixed relative to the carriage 14 and material delivery means 17 connecting the supply 16 to the print head 13.

The print head 13 is traversable on a cross member 13 as indicated by the arrows so as to cover the area within the frame 12. The stowed, transport position is raised about one side of the frame 12 from the horizontal, and is substantially vertical. A deployment mechanism is provided in the form of a hydraulic strut 15 (not shown in Figure 2). The carnage 14 has ground wheels 18, one, front one of which, 18a, is steerable. The carriage 14 is adapted for towing by a towing connection 19. The frame 12 has ground engaging wheels 18b that engage the ground in its deployed position. The ground engaging wheels 18b are on corners of the frame 12, and, instead of wheels, could comprise feet, or castors, allowing the frame 12 to be fixedly positioned with respect to an area of ground for printing that area, and to allow the frame 12 to be moved for printing another of ground.

If the ground engaging members are feet, they may be spiked for fixedly positioning the frame in soft ground, and they be lifted for movement of the frame 12; wheels 18b or castors may be Socked for fixedly positioning the frame 12.

The carriage 14 houses control means 21 for traversing the print head 12 and for marking material selection from a plurality of supply sources 16 which comprise containers of different colours of marking material, which may comprise CYM, or, if good black is required, CYMK colours, and, since the substrate will not usually be white, a white may be required for any print that has white or paler shade than the primary colours. The image may be printed in small adjacent discrete dots which, when viewed from a suitable distance to appear to blend into colours depending on the relative quantities of the four colours laid down, and may be half-toned as with paper and fabric printing. However, where, as may often be the case, only one or a small number of solid colours are required, these may be sourced as such and laid down as solid colour areas.

The control means 21 also controls movement of the frame 12 to an adjacent ground area for marking areas greater than the frame area, and for correctly positioning the frame with respect to an already marked area. Correct positioning is ensured by a dead reckoning arrangement, in which, for example, wheels' or castors' rotation is monitored by a rotary encoder, or a GPS arrangement, in either case final positioning of the frame, or traverse limits of the print head in the frame, being possibly under the control of a machine vision arrangement stitching adjacent images together in the fashion of a panoramic camera imaging arrangement.

The frame positioning control means may be autonomous, sensing when one print area has been completed and effecting movement to an adjacent area.

The ground marking material is held in marking material containers 16a, which are adapted for connection to the print head 12 through flexible ducting 17. If the ground marking material is a plastic that is applied to the ground molten, the containers 21a can be heated and the ducting 17 insulated. The containers 16a can be pressurised to force material to the print head 12. Heating and/or pressurisation means external to the containers can be built into the carriage 14, or containers 21a can have internal such means, which can be electrically operated, which can be from a power source carried by or connectable to the carnage.

Desirably, the containers 21a will have a sufficient capacity to print an image within the area of the frame 12 without needing to be changed. However, for large images, that require more ink than can be conveniently carried, the printer 11 can move autonomously to a docking station to reload its material containers and also to recharge its batteries. Usually, the printed image will be viewed from a greater, often a substantially greater, distance than images from desk top paper printers, and the print resolution can be correspondingly coarse. A resolution of 500 pixels per metre may be adequate for many purposes, with a dot resolution of 1000 to 2000 dots per metre. Standard printing techniques such as dithering and error diffusion may be used. Resolution may, however, depend on the nature of the material being printed as well as on the nature of the substrate. It will be difficult, for example, to get fine resolution on a grass substrate, though usually designs printed on grass comprise blocks of solid colour such as are achieved by stencilling. And when laying down a plastics material, it will tend to splat to some extent depending on its viscosity and the speed at which it lands on the substrate, and this will dictate the smallest dot size.

The control means 21 for the print head 1 and frame 12 positioning, can be instructed remotely, a print file being loaded into a controller, for example, from a computer or a suitably apped smartphone that can call on a library, which might be in the Cloud, of print files.