A METHOD OF CLEANING THE INSIDE SURFACE OF DUCTS

Abstract: Solid carbon dioxide, preferably in the form of granules, is supplied under pressure (12, 13) to the inside surface (2) of ducting (1). Thus, grease on the surface (2) is hardened by the thermal shock and is dislodged by the abrasive action. The carbon dioxide sublimates without leaving any residue, and the dislodged grease may be more easily removed.

Description: A Method of Cleaning the Inside Surface of Ducts The present invention relates to a method of cleaning the inside surface of a kitchen extraction duct or other grease duct which often become coated with a layer of grease, which is very difficult to remove. Present duct cleaning systems involve blasting compressed air through the ducts and this has proven to be very effective in removing dry dirt such as dust. It does not, however, achieve good results when used to remove grease and similar deposits. This problem is presently overcome by manually scraping and scrubbing the ducts, where access is possible, but it is still difficult to ensure that the duct surfaces are cleaned thoroughly. Manual cleaning also requires considerable effort and is significantly restricted by the lack of accessibility to the ducts. A build-up of grease in extraction ducts is a serious fire risk and possible health risk, and should be avoided. An object of the present invention is to provide a method of cleaning the inside surface of a kitchen extraction duct or other grease duct which enables grease to be removed from the inside surface thereof without the need for cutting-in and installing the large numbers of access doors required for manual cleaning. The present invention provides a method of cleaning the inside surface of a kitchen extraction duct or other grease duct as claimed in Claim 1. An embodiment of the invention will now be described, with reference to the accompanying drawings, wherein: Fig. 1 is a sectional side view of a kitchen extraction duct illustrating a cleaning method according to the invention, Fig. 2 is a section taken along line A-A of Fig. 1 , and Fig. 3 is a part-secional diagrammatic view of an extraction unit for use with the extraction duct of Fig. 1. In Figs. 1 and 2 a kitchen extraction duct 1 has an inside surface 2 and a flexible outlet duct 3. The outlet duct 3 leads via an access door or panel 4 to an extraction unit 5 having a plenum 6, a filter 7, and an extraction fan 8, as shown in Fig. 3. Apparatus for cleaning the inside surface 2 of the extraction duct 1 comprises a cleaning trolley 9 having a nozzle 10, a guide rod 11 and a hose 12. The trolley 9 is propelled along the duct 1 by means of the guide rod 11 , which is controlled remotely from the surface being cleaned, eg from outside the extraction duct 1. The trolley 9 could be controlled by other remote means such as radio control, or it could be self-driven. For example, the trolley 9 could be equipped with a motor and be pre-programmed to travel slowly along the extraction duct 1 during cleaning, or to stop periodically to carry out cleaning. Solid carbon dioxide is fed under pressure to the nozzle 10 via the hose 12, which leads from a solid carbon dioxide supply (not shown). This supply is preferably in the form of solid carbon dioxide granules. Solid carbon dioxide is then applied under pressure to the inside surface 2 of the extraction duct 1 through the nozzle 10. The thermal shock and the abrasive action caused by the blasting of the solid carbon dioxide through the nozzle 10 against the inside surface 2 of the extraction duct 1 hardens any grease on the surface 2 and dislodges it therefrom. The hardened grease flakes/particles are then more easily extracted, eg by suction, along the extraction duct 1 towards the outlet duct 3 which leads to the extraction unit 5 where they are collected in the filter 7, which can be emptied or exchanged periodically. Alternatively, the grease flakes/particles could be removed mechanically, eg by sweeping. The solid carbon dioxide sublimes, therefore leaving no excess residue to be removed from the extraction duct 1. In order to optimise cleaning, a distance D, which is the distance between an expulsion end 13 of the nozzle 10 and the inside surface 2 of the extraction duct 1 , is preferably as short as possible (about 15 cm or less). Preferably, the nozzle 10 is rotatable so as to facilitate cleaning of all areas of the inside surface 2 of the extraction duct 1 and adjustably mounted on a support, eg on adjustable plates 14, so that the distance D may be maintained within the above recommended limit as the nozzle 10 is rotated. The nozzle 10 may be interchangeable to permit cleaning of ducts of different diameters and cross sections. Instead of a nozzle in the form of a right-angled arm as shown in Figs. 1 and 2, the nozzle 10 could be circular with peripheral openings through which the dry ice would be blasted under pressure. To ensure cleaning of all the surfaces 2, such a circular nozzle should also be rotatable. Different diameter circular nozzles could be supplied depending on the diameter/cross section of the extraction duct 1. The above-described cleaning method is particularly useful in cleaning kitchen extraction ducts in restaurants or fast-food outlets, or any other ducts in which other sticky deposits occur.

Claims: Claims: 1. A method of cleaning the inside surface of a kitchen extraction duct or other grease duct, wherein solid carbon dioxide is applied under pressure to the inside surface of the duct so that grease thereon is hardened and dislodged therefrom. 2. A method as claimed in Claim 1, wherein the solid carbon dioxide is in the form of granules. 3. A method as claimed in Claim 1 or 2, wherein the solid carbon dioxide is supplied via a nozzle on a trolley moving along the inside of the duct. 4. A method as claimed in Claim 3, wherein the movement of the trolley is controlled remotely. 5. A method as claimed in Claim 3 or 4, wherein the nozzle is arranged as close as possible to the inside surface being cleaned. 6. A method as claimed in Claim 5, wherein the nozzle is arranged at a distance of substantially 15 cm or less from the inside surface being cleaned. 7. A method as claimed in any one of Claims 3 to 6, wherein the nozzle is rotatably mounted on the trolley. 8. A method as claimed in any one of Claims 3 to 7, wherein the nozzle is interchangeable depending on the diameter or cross section of the duct. 9. A method as claimed in any one of Claims 3 to 8, wherein the nozzle is adjustably mounted on the trolley to alter the distance of the nozzle from the inside surface of the ducting. 5 10. A method as claimed in Claim 9, wherein the nozzle is mounted on an adjustable support on the trolley. 11. A method as claimed in any one of Claims 3 to 10, wherein trolley is self- driven. 12. A method of cleaning the inside surface of ducts substantially as herein described with reference to the accompanying drawing.

Inventors: HORRIDGE GRAHAM, HORRIDGE, GRAHAM
Applicants: HORRIDGE GRAHAM, SYSTEM HYGIENICS LIMITED, HORRIDGE, GRAHAM
Application year: 1999
Main classification: B24C1
IPC codes: B08B7, B08B9, B24C1, B24C3