GB2280597A

GB2280597A - Gully cleaning apparatus with depth compensation

Info

Publication number: GB2280597A
Application number: GB9316192A
Authority: GB
Inventors: Michael Aneurin Bealing
Original assignee: Rentokil Ltd
Current assignee: Rentokil Ltd
Priority date: 1993-08-04
Filing date: 1993-08-04
Publication date: 1995-02-08
Anticipated expiration: 2013-08-04
Also published as: GB2280597B; GB9316192D0

Abstract

Gully-cleaning apparatus comprises a housing 1 arranged to extend over a portion of a gully G to be cleaned and sprayer means 16 arranged to extend from the housing into the gully. The sprayer means 16 is arranged to emit one or more jets of cleaning liquid for impingement upon at least a portion of the surface that defines the gully G. The housing 1 is arranged to decrease or substantially to prevent the escape into ambient air above the gully G of cleaning liquid emitted by the sprayer means 16. The sprayer means rides on a wheel 23 and is movable relative to the housing to accommodate a change in depth of the gully as the housing is moved along it. <IMAGE>

Description

"ImProvements in and relating to cleaning gullies" The invention relates to cleaning gullies, and especially to apparatus for, and a method of, cleaning gullies including drainage channels, gutters and other open conduits for the flow of liquid. More especially, the invention relates to cleaning gullies in indoor locations such as, for example, the floors of factories, kitchens and other food preparation areas.

The invention provides gully-cleaning apparatus which comprises a housing arranged to extend over a portion of a gully, and sprayer means arranged, in use, to extend from the housing into the gully, the sprayer means being arranged to emit one or more jets of cleaning liquid for impingement upon at least a portion of the surface that defines the gully, the housing being arranged to decrease or substantially to prevent the escape into ambient air above the gully of cleaning liquid emitted by the sprayer means, the housing and the sprayer means being movable in a direction extending along the axis of the gully so that the housing can extend over successive portions of the gully, and the sprayer means being movable relative to the housing to accommodate a change in depth of the gully as the housing is moved along it.

The invention also provides a method oi cleaning a gully which comprises arranging a housing so that it extends over a portion of the gully with sprayer means extending from the housing into the gully, supplying cleaning liquid to the sprayer means so that it emits one or more jets of cleaning liquid, which cleaning liquid impinges upon at least a portion of the surface that defines the gully, the housing decreasing or substantially preventing the escape into ambient air above the gully of cleaning liquid emitted by the sprayer means, and moving the housing and the sprayer means in a direction extending along the axis of the gully so that the housing extends over successive portions of the gully, the sprayer means being movable relative to the housing to accommodate a change in depth of the gully as the housing is moved along the gully.

The apparatus and method of the invention can be used to clean gullies of many different shapes and configurations. Thus, for example, the apparatus and method of the invention can be used to clean a gully of rounded or substantially U-shaped cross-section, or a gully having a flat base separating two side walls. The invention can also be used in cleaning a gully which is substantially V-shaped, or even substantially L-shaped in cross-section. The expressions "the surface that defines the gully" and "the surface of the gully" are used throughout the specification to include references to the surface or surfaces of any of those configurations.

In the apparatus and method of the invention, the sprayer means is movable relative to the housing so as to accommodate changes in depth of a gully being cleaned.

The sprayer means can be arranged to move upwards relative to the housing if the depth of the gully decreases in the direction of movement of the housing along the gully and/or the sprayer means can be arranged to move downwards relative to the housing if the depth increases so that cleaning of the gully can be effected in spite of variations in depth.

Although the dimensions and configuration of individual gullies vary, gullies in indoor locations, with which the present invention is especially concerned, generally increase gradually in depth from an upstream point towards a sink or soakaway so as to allow waste liquid to flow away. With the apparatus and method of the invention, cleaning of such gullies is advantageously effected by arranging the housing over an upstream portion of the gully to be cleaned and moving it along the gully in a downstream direction, the sprayer means moving downwards into the gully as the housing is moved along it.

The housing serves to decrease or substantially to prevent the escape into ambient air of droplets or particles of the cleaning liquid, which, once airborne, might otherwise travel considerable distances and, on deposition, contaminate the surroundings. In particular, the housing serves to decrease the escape of aerosols of the cleaning liquid formed on its emission from the sprayer means and on contact of the cleaning liquid with the surface of the gully. The cleaning liquid can instead be retained within the gully and allowed to drain away through the gully's sink or soakaway. The escape of such aerosols of cleaning liquid into the surrounding atmosphere is especially undesirable because they may well carry with them waste material and harmful organisms, for example, bacteria from the gully being cleaned, and they can quickly cause contamination of the surroundings over a relatively widespread area.

The apparatus of the invention may include means for urging the sprayer means to move downwards relative to the housing so that, in use, the sprayer means is moved further into the gully as the depth of the gully increases. Thus, the apparatus may include, for example, a piston and cylinder arranged to operate pnuematically to urge the sprayer means to move downwards into the gully. Advantageously, however, the sprayer means is so arranged that, in use, it is supported on the surface of the gully, preferably on the bottom or lowermost portion of the surface of the gully, and is movable relative to the housing to an extent that allows it to remain supported on the surface of a gully of varying depth during movement of the apparatus along that gully.

Advantageously, the apparatus is so arranged that, when the sprayer means extends into the deepest portion of the gully being cleaned, cleaning liquid from the sprayer means is caused to impinge on, and effect cleaning of, the entire surface area of that portion of the gully. It is then possible for the entire surface area of the gully along its whole length to be cleaned in a single pass of the apparatus, although in practice a second or third pass may be required to effect cleaning of the gully to the desired standard. With such an arrangement, when the apparatus is located over a portion of gully that is shallower, some of the cleaning liquid emitted by the sprayer means may not impinge upon the surface of the gully at all, but the housing can substantially prevent, or at least decrease to an acceptable level, the escape of cleaning liquid to the surroundings.

The number and arrangement of the jets emitted by the sprayer means that will be required for effective cleaning of a gully of a particular configuration without contamination of the surroundings can readily be determined in practice. In determining a suitable arrangement, the following considerations should be taken into account. Assuming use of a cleaning liquid of suitable chemical composition and concentration, applied at a suitable temperature, some cleaning of the surface of the gully can be effected merely upon contact with the cleaning liquid from the sprayer means. It is, however, preferable that the jet or jets are so arranged as to cause physical removal of waste material, for example, dirt or grease, from the surface of the gully by the impact of the cleaning liquid onto that surface. The ability of the or each jet to do that and the area over which it will effect such physical removal of waste material will depend, at least in part, on the length of travel of the jet from the sprayer means to the surface of the gully and the pressure at which cleaning liquid is supplied to the sprayer means. If the supply pressure is increased, the length of the or each jet, and hence the area of the surface of the gully over which that jet can effect removal of waste material, can also be increased.

An increase in the supply pressure will, however, generally increase the volume of aerosols formed per unit time, and will therefore increase the risk of such aerosols escaping to the surroundings and contamination of the environment as described above.

The sprayer means may be so arranged that, in use, the axis of the or each jet extends along the normal to the surface of the gully at the position at which the jet contacts the surface of the gully, or the axis of the or each jet may be inclined to the normal. Advantageously, however, the sprayer means is so arranged that the axis of the or each jet of cleaning liquid from the sprayer means extends in a direction which has a component in the direction of movement of the apparatus along the gully.

Such an arrangement can considerably enhance removal of waste substances from the surface of the gully.

Advantageously, the housing is arranged to provide a boundary region around the sprayer means, the said boundary region being in communication with a source of reduced pressure. By decreasing the pressure of air within the boundary region below that of ambient air, the escape from the housing of aerosols of cleaning liquid can be significantly decreased because it is possible to arrange not only that the aerosols are drawn into the boundary region, but also that air from outside the housing and in the gully is drawn into the boundary region, the incoming air impeding the escape of the aerosols. To define the said boundary region, the housing may have an inner wall and an outer wall, the said boundary region being that region between the inner and outer walls.

The housing will generally be arranged to rest on a floor on one or both sides of the gully. To ensure that there is good contact between the housing and the floor, flexible contact means, for example, brushes or strips of rubber, is advantageously provided around the edges of the housing that, in use, are in contact with the floor.

The use of brushes or other similar means as the flexible contact means is advantageous because brushes allow air to be drawn into the housing, and into the boundary region, while having a filtering effect on aerosols seeking to escape, droplets or particles of cleaning liquid that encounter the brushes being taken out of suspension and being deposited on the brushes from where they can drain into the gully.

Advantageously, the sprayer means is provided with baffle means arranged so to extend into the gully upstream and downstream of the sprayer means and beneath the housing as to decrease or substantially to prevent the escape of cleaning liquid from the portion of the gully beneath the housing into ambient air above the gully. The baffle means is advantageously so arranged that, in use, it is supported on the surface of the gully, preferably the bottom or lowermost portion of the surface of the gully, and is movable relative to the housing to an extent that allows it to remain supported on the surface of a gully of varying depth during movement of the apparatus along that gully. When the sprayer means is also arranged to be supported on the surface of the gully, as is advantageous, then the baffle means is preferably fixed relative to the sprayer means.

The baffle means is advantageously provided with flexible contact means, for example, brushes, around its margins for contacting the surface of the gully and reducing further the escape of airborne droplets or particles of cleaning liquid to the surroundings while allowing cleaning liquid in the gully and air to flow through them. With such an arrangement of baffles in combination with a boundary region as referred to above, it is possible using the apparatus and method of the invention to decrease significantly disruption caused to a site during cleaning of its gullies. Thus, it is possible to effect cleaning without temporarily closing down the site or taking protective steps, for example, covering sensitive equipment. Such measures are often necessary with conventional methods of gully cleaning using hand-held high pressure lances.

The optimum dimensions of the baffle means in any particular case will of course depend on the dimensions of the gully being cleaned, and the profile of the baffle means is advantageously such that it matches that of the gully. The baffle means is preferably so arranged that it can be readily replaced by baffle means of a different profile when required. Preferably, guide means is provided in the housing to guide movement of the baffle means, and hence the sprayer means, into and out of the gully as the depth of the gully varies.

Advantageously, the arrangement is such that the sprayer means and the baffle means, if provided, can be withdrawn into the housing and retained therein in order to facilitate transport of the apparatus.

The sprayer means and the baffle means, if provided, may be secured to a projecting member arranged to extend outside the housing. The position of such a projecting member relative to the housing can give to an operator an indication of the depth of the sprayer means in the gully, and can also be used by the operator, should the sprayer means encounter any obstruction and become jammed in the gully, in order to free the sprayer means for continued operation.

Apparatus for, and a method of, cleaning a gully will now be described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a vertical section through the apparatus located over a portion of a gully, the section being taken along the axis of the gully; Fig. 2 is a vertical section through the apparatus taken along the line II-II of Fig. 1 and normal to the axis of the gully; Fig. 3 is a vertical section similar to that of Fig.

2 but with some parts indicated schematically and showing the apparatus in position over a portion of the gully of greater depth than the portion shown in Figs. 1 and 2; Fig. 4 is a vertical section similar to that of Fig.

2 but with some parts indicated schematically and showing the apparatus in a retracted state; and Fig. 5 is a plan view of the apparatus.

Referring to Figs. 1 and 2 of the accompanying drawings, a housing, indicated generally by the reference numeral 1, has an outer wall 2 and an inner wall 3, which walls both extend around front la, sides 1b and Ic, and top id of the housing, and a single rear wall le secured to the outer and inner walls, it being secured to a flange 2e of the outer wall by screws (not shown) for easy removal. The walls 2, 3 and 1e together define an inner compartment 4, open at its base 4a, and a boundary region 5 between the inner and outer walls and extending across, and directly inside, the front la of the housing 1, the sides ib and ic, respectively, and the top 1d of the housing. At the lowermost edges 2a and 3a, respectively, the outer and inner walls 2 and 3 are each provided with a double row of brushes 6 with flexible bristles which contact floor F on each side of a gully G to be cleaned. A pair of wheels 7 (only one of which is shown - see Fig. 1) are mounted on the inner wall 3 and a pair of wheels 8 (of larger diameter that the wheels 7) are mounted on the outer wall 2 of the housing 1 to allow the housing to be moved along the gully G in a direction indicated by an arrow D by an operator pushing a handle 9 secured to the housing 1.

The boundary region 5 is in communication with an electrically-powered suction pump 10 mounted on the outside of the housing 1 via a flexible connecting hose 11 and a paper filter 12.

Through corresponding apertures in the walls 2 and 3 of the housing 1 extends a projecting guide rod 13 of circular cross-section and formed with a neck 13a. The guide rod 13 is freely movable vertically relative to the housing 1, a collar 14 around the aperture in the outer wall 2 allowing such movement of the guide rod. To the lower end of the guide rod 13 is secured a supporting structure 15 of a sprayer assembly, indicated generally by the reference numeral 16. The sprayer assembly 16 comprises a hollow brass sprayer rod 17 extending downwardly from the supporting structure 15. The sprayer rod 17 is supplied with cleaning liquid by a flexible hose 18 and a connecting member 19, which also serves to mount the sprayer rod on the supporting structure 15.

The flexible hose 18 is connected via a pressure gauge P and filter (not shown) mounted on the rear of the housing 1 to a separate supply tank (not shown) arranged to supply cleaning liquid at the required pressure and temperature to the sprayer assembly 16.

The sprayer rod 17 is of hexagonal cross-section.

To its two forwardly-inclined faces 17a and 17b, on either side of its front face 17c, are arranged two sets of four spray nozzles 20a to 20d and 21a to 21d, respectively. A further downwardly pointing nozzle 22 is arranged on the front face 17c of the rod 17. The nozzle 22 and the two lowermost nozzles 20a, 20b and 21a, 21b of each set of nozzles are each arranged to emit a jet of cleaning liquid that subtends an angle of 1200 at its nozzle. The two uppermost nozzles 20c, 20d and 21c, 21d of each set of nozzles are each arranged to emit a jet of cleaning liquid that subtends an angle of 700 at its nozzle. Each of the nozzles 20a to 20d, 21a to 21d and 22 is so arranged that the axis of the jet emitted by it extends in a direction having a component in the direction of movement D of the apparatus along the gully G. A wheel 23 mounted on the bottom of the sprayer rod 17 rests on the bottom of the gully G to assist in the movement of the sprayer assembly 16 along the gully.

A pair of baffles 24 is detachably secured to the supporting structure 15 so that the baffles extend down into the gully G in front of, and behind, the sprayer rod 17. The profile of each of the baffles 24 matches that of the gully G, and a double row of brushes 25 with flexible bristles arranged around the edges of the baffles 24 provide good contact with the surface of the gully G. A strut 26 extending between the baffles 24 gives the sprayer assembly 16 rigidity. Guide wheels 27 rotatably mounted on the inner wall 3 and the rear wall 1e of the housing 1 are arranged to run in channels 28 secured to the outer surfaces of the baffles 24 to guide vertical movement of the baffles, and hence the entire sprayer assembly 16, relative to the housing 1. If the depth of the gully G increases from the depth shown in Figs. 1 and 2 to, for example, the depth shown in Fig. 3, then, as the apparatus is moved to the portion of the gully shown in Fig. 3, the sprayer assembly 16 including the baffles 24 drops downwardly relative to the housing 1 and takes up the position shown in Fig. 3.

A clip 29 pivotally mounted on the top 1d of the housing 1 is formed with an aperture 29a containing a collar 30 which can engage the neck 13a of the guide rod 13 (see Fig. 5) and hold the sprayer assembly 16 in a retracted, upper, position within the housing 1 (see Fig.

4). To release the sprayer assembly 16, the clip 29 can be rotated in the direction R by an operator (who can lift the guide rod 13 slightly if necessary) until the guide rod 13 occupies aperture 29b in the clip, through which it is freely movable in a vertical direction relative to the housing 1, and the sprayer assembly 16 can move down to rest with its wheel 23 on the bottom of the gully G (see Fig. 2). The guide rod 13 provides further guidance to the vertical movement of the sprayer assembly 16 including the baffles 24 relative to the housing 1.

In operation, initially the clip 29 maintains the sprayer assembly 16 in its retracted state as shown in Fig. 4 for transport to the site of the gully G to be cleaned. When the apparatus is placed over a portion of the gully G, generally the shallowest most upstream portion of the gully, then the clip 29 is rotated to release the sprayer assembly 16 which can drop into the gully G and rest with its wheel 23 on the floor of the gully as shown in Figs. 1 and 2. That inital drop can be controlled by an operator, if desired, by means of the guide rod 13.

Once the sprayer assembly 16 is in position, the suction pump 10 is switched on to reduce the pressure of the air in the boundary region 5 to a pressure below that of the ambient air. Cleaning liquid of an appropriate composition and concentration, is brought to its operating temperature in the supply tank, and is then supplied at a suitable pressure (indicated by the pressure gauge P), for example, 1000psi, to the sprayer rod 17 via the hose 18. From the sprayer rod 17, jets of the cleaning liquid are emitted by the nozzles 20a to 20d, 21a to 21d and 22.

As shown in Figs. 1 and 2, when the apparatus is over the shallower portions of the gully G, only jets from the lowermost nozzles 20a, 21a and 22 encounter the walls and bottom of the gully G. Cleaning liquid from those jets, however, impinges on, and effects cleaning of, the surface of those portions of the gully G around their entire profiles. As the cleaning liquid is emitted from the nozzles 20a, 21a and 22, and on impact of the jets from those nozzles on the surface of the gully G, droplets of the cleaning liquid become airborne and aerosols of the cleaning liquid are formed. Those aerosols are prevented from escaping to the air surrounding the housing 1 by the boundary region 5, which being at reduced pressure, draws in the aerosols, the filter 12 preventing cleaning liquid from reaching the suction pump 10. Air is also drawn into the boundary region 5 from outside the housing 1 through the brushes 6 and the gully G, and that incoming air further impedes the escape of aerosols of cleaning liquid to the surroundings. The brushes 6 have a filtering effect on aerosols reaching them, droplets or particles of cleaning liquid, on contacting the bristles of the brushes, being taken out of suspension and draining into the gully G.

The baffles 24 help to prevent the escape of aerosols of the cleaning liquid from the gully G and retain the cleaning liquid in the gully, the brushes 25 allowing the cleaning liquid to flow away along the gully but reducing the escape of airborne droplets or particles. In the position shown in Figs. 1 and 2, jets from the nozzles 20b to 20d and 21b to 21d are emitted at a level above the top of the gully G, but the housing 1 is arranged to prevent escape of cleaning liquid from those jets to the surroundings.

The apparatus is then moved along the gully G by the operator in the direction of the arrow D. As the apparatus is moved along, the jets of cleaning liquid that encounter the surface of the gully G have a chiselling action on waste material, for example, dirt and/or grease, on the surface of the gully, and cause the physical removal of those substances from the surface.

As the apparatus is moved along the gully G, the sprayer assembly 16, resting on the bottom of the gully, drops further down with respect to the housing 1 as shown in Fig. 3, the nozzles 20b, 21b (the position of which is indicated schematically in Fig. 3) sinking below the level of the top of the gully so that cleaning liquid emitted by them impinges on the uppermost portions of the surface of the gully. As the depth of the gully G increases, so the nozzles 20c and 21c and then the nozzles 20d and 21d enter the gully, so that finally cleaning liquid from all the nozzles impinges on the surface of the gully, and the entire surface of the gully is cleaned of dirt and/or grease. Although it is possible to clean the gully G in a single pass of the appartus along it, in practice a second or third pass may be necessary or desirable to clean the gully to the required standard.

The apparatus can be dismantled for cleaning purposes. The sprayer assembly 16 can be completely withdrawn from the housing 1 and the outer wall 2 separated from the rear wall le of the housing.

As an example of suitable dimensions for the apparatus, the length of the sprayer rod 17 may be 56cm, the distance between the nozzles of each set of nozzles 20a to 20d and 21a to 21d may be 10cm, and the vertical distance between the nozzles 20a, 21a and the nozzle 22 may be 4cm. The height of the inner compartment 4 may be 60cm and the overall height of the housing 1 may be 63cm.

Such an arrangement is suitable for cleaning a gully of approximately 20cm in width with cleaning liquid supplied to the sprayer rod 17 at a pressure of between 950 and 1100psi, preferably, approximately 1000psi, the length of the jets from the nozzles to the surface of the gully being approximately 10cm. The suction pump 19 may have a 1 kilowatt motor.

Claims

What we claim is:

1. Gully-cleaning apparatus which comprises a housing arranged to extend over a portion of a gully, and sprayer means arranged, in use, to extend from the housing into the gully, the sprayer means being arranged to emit one or more jets of cleaning liquid for impingement upon at least a portion of the surface that defines the gully, the housing being arranged to decrease or substantially to prevent the escape into ambient air above the gully of cleaning liquid emitted by the sprayer means, the housing and the sprayer means being movable in a direction extending along the axis of the gully so that the housing can extend over successive portions of the gully, and the sprayer means being movable relative to the housing to accommodate a change in depth of the gully as the housing is moved along it.

2. Gully-cleaning apparatus as claimed in claim 1, wherein the arrangement is such that, as the housing is moved along a gully of a depth which increases in the direction of movement, the sprayer means can move downwards relative to the housing into the gully.

3. Gully-cleaning apparatus as claimed in claim 1 or claim 2, wherein the sprayer means is so arranged that, in use, it is supported on the surface of the gully, preferably on the bottom or lowermost portion of the surface of the gully, and is movable relative to the housing to an extent that allows it to remain supported on the surface of a gully of varying depth during movement of the apparatus along that gully.

4. Gully-cleaning apparatus as claimed in any one of claims 1 to 3, which is so arranged that, in use, when the sprayer means extends into the deepest portion of the gully being cleaned, cleaning liquid from the sprayer means is arranged to impinge on the entire surface area of that portion of the gully.

5. Gully-cleaning apparatus as claimed in any one of claims 1 to 4, wherein the sprayer means is so arranged that the axis of the or each jet of liquid from the sprayer means extends in a direction which has a component in the direction of movement of the apparatus along the gully.

6. Gully-cleaning apparatus as claimed in any one of claims 1 to 5, wherein the housing is arranged to provide a boundary region around the sprayer means, the said boundary region being in communication with a source of reduced pressure.

7. Gully-cleaning apparatus as claimed in claim 6, wherein the housing has an inner wall and an outer wall, the said boundary region being that region between the inner and outer walls.

8. Gully-cleaning apparatus as claimed in any one of claims 1 to 7, wherein the housing is arranged to rest on a floor on one or both sides of the gully, and flexible contact means is provided around the edges of the housing that, in use, are in contact with the floor.

9. Gully-cleaning apparatus as claimed in claim 8, wherein the flexible contact means comprises brushes.

10. Gully-cleaning apparatus as claimed in any one of claims 1 to 9, wherein the sprayer means is provided with baffle means arranged to so extend into the gully upstream and downstream of the sprayer means and beneath the housing as to decrease or substantially to prevent the escape of cleaning liquid from the portion of the gully beneath the housing into ambient air above the gully.

11. Gully-cleaning apparatus as claimed in claim 10, wherein the baffle means is so arranged that, in use, it is supported on the surface of the gully, preferably on the bottom or lowermost portion of the surface of the gully, and is movable relative to the housing to an extent that allows it to remain supported on the surface of a gully of varying depth during movement of the apparatus along that gully.

12. Gully-cleaning apparatus as claimed in claim 11, wherein the baffle means is fixed relative to the sprayer means.

13. Gully-cleaning apparatus as claimed in any one of claims 10 to 12, wherein the baffle means is provided with flexible contact means around its margins for contacting the surface of the gully.

14. Gully-cleaning apparatus as claimed in claim 13, wherein the flexible contact means comprises brushes.

15. Gully-cleaning apparatus as claimed in any one of claims 10 to 14, wherein the profile of the baffle means matches that of the gully to be cleaned.

16. Gully-cleaning apparatus as claimed in any one of claims 10 to 15, wherein the baffle means is so arranged that it can be readily replaced.

17. Gully-cleaning apparatus as claimed in any one of claims 10 to 16, wherein guide means is provided in the housing to guide movement of the baffle means into and out of the gully as the depth of the gully varies.

18. Gully-cleaning apparatus as claimed in any one of claims 1 to 17, wherein the sprayer means and the baffle means, if provided, can be withdrawn into the housing and retained therein.

19. Gully-cleaning apparatus as claimed in any one of claims 1 to 18, wherein the sprayer means is secured to a projecting member arranged to extend outside the housing.

20. Gully-cleaning apparatus substantially as hereinbefore described with reference to, and as shown in, the accompanying drawings.

21. A method of cleaning a gully which comprises arranging a housing so that it extends over a portion of the gully with sprayer means extending from the housing into the gully, supplying cleaning liquid to the sprayer means so that it emits one or more jets of cleaning liquid, which cleaning liquid impinges upon at least a portion of the surface that defines the gully, the housing decreasing or substantially preventing the escape into ambient air above the gully of cleaning liquid emitted by the sprayer means, and moving the housing and the sprayer means in a direction extending along the axis of the gully so that the housing extends over successive portions of the gully, the sprayer means being movable relative to the housing to accommodate a change in depth of the gully as the housing is moved along the gully.

22. A method as claimed in claim 21, wherein the gully increases in depth in a downstream direction, and the housing is placed over an upstream portion of the gully and moved along the gully in a downstream direction, the sprayer means moving downwards relative to the housing into the gully.

23. A method as claimed in claim 21 or claim 22, wherein the sprayer means is supported on the surface of the gully, preferably the bottom or lowermost portion of the surface of the gully, and moves relative to the housing so as to remain supported on the surface of the gully in spite of variations in depth of the gully in the direction of movement of the apparatus along the gully.

24. A method as claimed in any one of claims 21 to 23, wherein the sprayer means extends into the deepest portion of the gully being cleaned and cleaning liquid from the sprayer means impinges upon the entire surface area of that portion of the gully.

25. A method as claimed in any one of claims 21 to 24, wherein the axis of the or each jet of cleaning liquid from the sprayer means extends in a direction which has a component in the direction of movement of the apparatus along the gully.

26. A method as claimed in any one of claims 21 to 25, wherein the housing is arranged to provide a boundary region around the sprayer means, and the pressure of air within the boundary region is reduced below that of the ambient air.

27. A method of cleaning a gully as claimed in any one of claims 21 to 26 using apparatus as claimed in any one of claims 1 to 20.

28. A method of cleaning a gully substantially as hereinbefore described with reference to the accompanying drawings.