BACKGROUND ART Prior patent specifications and applications to the present applicant describe agricultural equipment effective to deliver sprays to plants and particularly to spot spray weeds with herbicides. This style of equipment operates best with scanning sensors, including cameras, and the like, outputting ideally digital electrical signals representing a scan over a field of view, that are typically mounted atop or associated with a hood enclosing the sprays, mounted preferably together with lighting which is arranged so as to maintain more constant illumination of the surface being scanned for weeds. A problem with equipment of this type is that the sprays which are operated in conjunction with the sensors create an aerosol, mist or vapour which is subject to drift. Liquid droplets and condensation may deposit on or wet the surfaces of a sensor and, when used, any lights which might be used therewith, and that moisture, and any dust which might be present, can create a film over the face of the sensors and/or lights, which film results in a degradation in performance of the equipment. A cleaning regime is then necessary,

implemented at regular intervals, so as to maintain effective performance.

It is desirable to reduce the need for this, or eliminate it.

OBJECT OF THE INVENTION It is an object of the invention to provide a protective means or assembly whereby what drift might exist to otherwise contaminate critical surfaces in apparatus of the above defined kind, is reduced or overcome. Other objects and advantages will hereinafter become apparent.

NATURE OF THE INVENTION The invention achieves its object in the provision of a protective means or assembly for application to a sensor, or the like, in apparatus of the above defined kind, wherein an effect is created in the zone of a sensor, and/or a light operative therewith, which effect has the result of resisting intrusion of any liquid, and other particles, or vapour, drifting in air in the vicinity of the sensor or light, from contact with the sensor and lights.

The invention is herein referred to as a protective means or assembly, being something which effects as a result of its operation a reduced degree of deposition of spray and dust in the vicinity of at least the sensor, and, preferably also any lighting which is associated therewith, used in an otherwise adverse environment, which is equivalent to an automatic clearing means, with the result that manual cleaning is rendered unnecessary, or is needed less often. A typical spray apparatus to which the invention is applied is seen in PCT/CA95/00595. It is

typically mounted over the hood which contains the spot sprays and weed sensors.

The protective means or assembly preferably includes a main housing in which ideally exists an air distribution pocket or channel into which air can be directed under pressure sufficient to create an adequate flow (typically at from around one half up to around two psi), for delivery to or distribution at an end cap into side pockets or channels and subsequent flow then via openings to zones beneath a sensor, ideally a camera and/or a light. An effect achieved by the foregoing is a longer flow path through the protective means or assembly to better convey any heat generated by lighting therefrom. A first end cap applied to an end of the main housing, is preferably fitted with a spigot at which may be fitted an air hose which feeds air to the distribution pocket or channel, the first end cap preferably mating with the main housing in a manner to effect a seal, or with a seal therebetween, to seal to the distribution pocket or channel at this end (to contain the flow of air in the distribution pocket or channel). A second end cap is mated in similar sealed manner to the main housing at an end opposite to that at which is attached the first end cap, the second end cap providing a flow path between the distribution pocket or channel and the side pockets or channels. When the main housing is used to mount lights, the flow of air therethrough provides a means by which heat which might otherwise build up therein can be conducted away. The pockets through which air is flowed might be fitted with fins or other surface area increasing features which are effective to

speed the flow of heat from the housing. A material is best chosen which is suited to this process, such as aluminium, which is both a good conductor of heat and which can be shaped appropriately (as illustrated) by common processes such as extrusion.

The protective means or assembly typically has one or more sensors such as cameras mounted in respective enclosures, separate from and mounted to the main housing, preferably including lighting, each sensor or camera enclosure being mounted off a side or top of the main housing, with air which is flowed in a side pocket or channel being directed from the side pocket or channel in the main housing to the front of at least the sensor. The protective means or assembly is preferably a separate unit which is mounted, in use, to the top of a hood whereat are openings through which to pass light and through which the sensor, typically a camera might operate.

BRIEF DESCRIPTION OF THE DRAWINGS.

The invention will now be described with reference to a preferred embodiment, as is illustrated in the accompanying drawings in which : FIG. 1 is an end view of a protective means or assembly in accordance with a preferred embodiment of the invention ; FIGS. 2 and 3 are respective back and front views of an end cap for the protective means or assembly of FIG. 1 ; FIGS. 4 and 5 are front and back views of another end cap for use with the protective means or assembly of FIG. 1 ; and

FIG. 6 is a perspective view of a protective means or assembly in accordance with an embodiment of the invention.

PREFERRED EMBODIMENTS In FIG. 1 is seen a main housing 10 in which exists a distribution pocket or channel 11 into which air can be injected or directed. A flow of air is what is significant, and the pressure needed to deliver air at a satisfactory velocity, or sufficient volume, need not be large. Flow is controlled at an end cap (see below) for distribution thereby into side pockets 12,13. The air may flow then via openings 14, 15 and 17 to the zones 16,18 beneath light 19 and a sensor which may be CCD type imagining device, the optics of the camera 20 being seen in the figure. The flow of air into these zones and away therefrom acts to protect against drift of aerosois, vapours and the like, and dust, into the vicinity of the light and camera (thus preventing deposition of contaminate). The main housing is ideally made as an assembly of aluminium extrusions as seen in the transverse section of FIG. 1. This realises a weight reduction whilst at the same time bringing the invention's general object into being in a form, with an additional attribute which is effective to both conduct and radiate heat which is generated inside by the lights (as will be explained in greater detail below).

In FIGS. 2 and 3 is seen a first end cap 21 with a spigot 22 at which may be fitted an air hose (not shown), which feeds compressed air to the distribution pocket 11. The first end cap mates with the main housing with a seal thereto, to seal distribution pocket 11 at this end. The

first end cap (and the second, described hereinbetow) is most conveniently formed in plastic, and the like, by a moulding process as will be clear to those in that art.

In FIGS. 4 and 5 is seen a second end cap 24 which mates to the main housing at the end opposite to that at which is attached the first end cap 21 of FIGS. 2 and 3. The wall 25 between the distribution pocket 11 and side pocket 13 is open to allow flow of air therebetween (and the same is so between pockets 11,12). By this means, what air is fed to distribution pocket 11 is distributed to side pockets 12,13.

It will be clear to those skilled in the art that air inlet spigot 22 in FIG 2 might be located differently. Another ideal position is somewhere midway along the pocket or channel 11, seen in FIG 1, creating a flow to each end. In this circumstance the end caps will each be in the form of FIGS 4 and 5, each distributing air into the side pockets 12, 13 of FIG 1. One might be holed to take the power lead 36, seen in FIG 6, to connect with the lights. The power lead 36 enters via opening 37 in FIGS 2 and 3.

The end caps 21, 24 may be screwed to the extrusions forming the protective means or assembly 10 by means known to those in the art. The hole 38 in FIGS 2 and 3 will allow passage of a self tapping screw which can engage in flute 39. It will be clear to those skilled in the art that the main housing can be assemble from a number of extrusions as a means of establishing all the features seen. Extrusions 40,41, and 42 create a suitable assembly with a second length of extrusion 41

forming the second side. Heat generated in the pocket or channel 43 by lights 19 will heat the main housing. Fins 44 in pocket or channel 11 enhance the loss of heat to air flowed there through.

In FIG. 6 is seen a protective means or assembly 10 extended between end caps 21,24. An air hose 34 is attached or clamped at 26 to the spigot of the first end cap 21. A sensor or camera housing 27 is mounted off the side of the main housing. Power to the sensor and lights and data communications from the sensor might be via cable 28, with coupling to the sensor, ideally a camera at 29, and with output 30 to relays to operate spray devices (not shown). In use, the clearing means effectively mounts lights (not shown) and sensor or camera (not shown) to the top 30 of a hood whereat are openings such as 32 through which to pass light and 33 through which the camera might operate. Studs such as 31 may be used to bolt the two together.

The flow of air past the lights in the main housing, with moderate flow rates, with a reasonable surface area in contact therewith, will pick up considerable heat from within the main housing with a useful cooling function therein. Warm air flowed to the zone of the camera and lights has an additional positive effect in warming the faces of the lights and camera to reduce the degree of condensation which might otherwise occur and this way add to the positive effect of the system.