Background for the Invention Windows and glass type facades are exposed to pollution, dirt, soot particles and the like in the air.

In order to obtain optimal visibility and a decent appearance frequent washing and cleaning of the window is required. Standard cleaning method incorporates manual work, using soap and water and applying a cloth and/or a wiper.

Such type of work is both time consuming and expensive, complicated and represent in certain situation risks of and hazard to the persons performing the washing operations. Accessories such as ladders, lifts or chairs are in many instances used in order to gain access to the surfaces to be cleaned and/or washed. In case of large building facades the safety measures required may be excessive.

GB 2 081 558A describes an anti-mist film, especially for applying to a vehicle window, comprising a transparent substrate and a plurality of electrically conductive heating lines integrally performed on the substrate. The substrate may be coloured. The film is adhered to a window by a self-adhesive agent with its edges extending over bars adhered to he window, a conductive tie rod being

inserted at each edge to make connection with the heating line.

JP 11173028 describes use of a heat generation film composed of various kind of metallic thin film having transmissibility and electric conductivity with a transmissible, heat resistant and nonconductive protection film thereon. Electric current can be conducted to the heat generation film to heat the film. The purpose of the this solution is to partly reflect sunlight in summer and conduct electric current and heat in winter to prevent cooling and condensation of the indoor air.

US Patent Specification No. 4,768, 256 describes an ultrasonic wiper for conveying a fluid off of a windshield glass of a vehicle characterized by comprising ultrasonic oscillators which excite progressive waves in the glass in a predetermined directional movement.

US Patent Specification No. 4,180, 886 describes a windshield wiper system comprising a wiper blade having two wiper lips extending in spaced parallel relationship.

The wiper lips are interconnected at the ends thereof by further wiper lip portions to define a continuous seal cooperating with the surface of the windshield to be cleaned to define an essential closed cavity. The latter communicates with cleaning liquid supply means adapted to completely fill said cavity and establish a positive temperature therein. An ultrasonic transducer assembly is acoustically coupled to the surface of the windshield by the mass of water contained in the cavity. By moving the wiper blade together with the ultrasonic transducer assembly across the windshield the dirt clinging to the surface of the windshield becomes detached and suspended in the cleaning liquid.

Summary of the Invention An objective of the present invention is provide a system and a method wherein the entire washing operations may be m ore or less fully automatic, thereby eliminating the need for manual work.

Another objective is to provide a system and a method for cleaning windows allowing predetermined cleaning cycles, for example to be performed at periods with low energy consumption, such as during night hours.

A further objective of the invention is to provide a system and a method which more or less eliminates risks and hazards for the human beings.

A still further objective is to provide a cost effective solution for cleaning large more or less vertical window surfaces.

According to the present invention it will be possible to perform the cleaning process in periods with low peak energy consumption, such as during night hours.

Further, it should be appreciated that the required period requiring energy will also be reduced, as each cleaning cycle for a window will be limited to for example one or two minutes.

Further, the system according to the present invention allows manual initiation of the cleaning process.

A principle of the proposed system and method is that the surface to be cleaned firstly is sprayed with a liquid, preferably containing a detergent. At the same time the window is exposed to ultrasonic mechanical vibrations, for example with a frequency in the order 50- 300 kHz.

The ultrasonic vibrations are produced by ultrasonic transducers. The combination of ultrasonic vibrations and the spraying of cleaning liquid loosen the particles fixed to the window surface, the particles being carried away by the flowing liquid due to the gravitational force. Subse- quent to the cleaning cycle, the window is sprayed with a rinsing liquid and at the same time again subjected to ultrasonic vibration, whereby the remaining dirt, soap or detergent and possible oil film are removed, reducing the tendency of droplet formation and stains on the window surface. Drying of the window surface is preferably achieved by natural air drying.

The length of each period for ultrasonic vibration may be as short as 5-10 seconds.

The unit for distributing liquid and vibrating the surface to be cleaned is preferably attached to the external surface of the window, along the upper edge of the window.

The system for cleaning windows according to the invention comprises ultrasonic transducers, a drive unit for the transducers, a time switch controlling the operation of the cleaning system, i. e. supply of cleaning and/or rinsing liquid and supply of energy to the driver for the ultrasonic transducers, a pump driven by a motor for pumping cleaning and/or rinsing liquid from reservoirs on to the window surface and an associated pipe system and electrical conductors.

Various embodiments and configuration of the system and the method of the invention will be apparent to those of ordinary skilled in the art from the following detailed description of the invention, referring to the drawings.

Brief Description of the Drawings Figure 1 shows in principle a vertical front view of an embodiment of the invention, installed in connection with a window in a building ; Figure 2 shows a vertical section of the embodiment shown in Figure 1, seen along the line 2-2, Figure 3 shows in principle one embodiment of the moistening and ultrasonic unit to be arranged on the external side of the vertical surface; and Figure 4 shows a schematic electrical diagram illustrating a preferred embodiment of the invention, also indicating the system for moistening the window surface.

Detailed Description of Preferred Embodiments Figure 1 shows a front view of a typical conventional window 10 while Figure 2 shows a vertical section of the window 10, seen along the line 2-2 in Figure 1. The window 10 shown in Figures 1 and 2 comprises a windowpane 11 and

casement 12 in a wall structure 13. A window cleaning unit 14 according to the present invention is arranged along the upper edge of the window 10.

According to the embodiment shown in Figures 1 and 2, the window cleaning unit 14 is placed on the exterior side of the window 10. The window cleaning unit 14 applies fluids to the surface to be cleaned. Such fluid could be water containing a detergent and/or water containing a cleaning agent. The fluids are according to the embodiment shown in Figure 1 and 2 supplied from reservoirs 15 arranged inside the building. The reservoir 15 may for example comprise several containers, a container for each liquid, communicating with the window cleaning unit 14 by means of one or more fluid supply lines 16. Alternatively, the reservoir may only contain water, while the detergent and/or cleaning fluid or other additives may be supplied by separate dispensers linked to the liquid supply line 16. In such latter case, the supply lines and/or the dispensers may be provided with valves (not shown). Such valves may either be remotely and/or automatically operated by the system or manually operated. The supply line may preferably extend through the wall structure 13 or through the casement 12.

Figure 3 shows an exploded view of the window cleaning unit 14. The unit comprises a tubular casing 17, terminated at each with a plug 18. The casing 17 is intended to be attached to the surface to be cleaned, for example by means of glue. The glue may be of any suitable type, preferably of a solid type with a melting point in the order of approximately 100 °, securing proper adhesion to the surface to be cleaned. Further, the casing 17 comprises one or more transponders 19. The transponders 19 are connected to a driver unit (not shown) by means of electrical conductors (not shown), the driver unit being preferably arranged inside the building and connected to a main energy source, for example a 110-220 V AC source.

At its lower end the casing 17 is provided with a plurality of nozzles or openings 20, communicating with

the reservoir (s) 15 through fluid supply lines (not shown on Figure 3). The nozzles or openings 20 may preferably be arranged along the entire length of the casing 17.

The opening 20 may have a size which is sufficient to produce fluid jets washing the surface 10 to be cleaned at a defined pressure. The openings 20 may for example have a diameter of 1 mm and may for example be places 10-20 mm apart, ensuring that the entire surface 10 being wetted.

Several casings 17 may be interconnected by means of fixing joints of any known type, enabling communication of fluid from one casing 17 to the another casing 17. For the sake of clarity, the fluid supply line (s) and the cables for supply of energy to the transducer (s) 19 are not shown.

The casing (s) 17 may be made of a stable material, such as for example aluminium, plastic materials, carbon fibres or other similar stable materials being able to withstand weather, wind and temperature exposure or mechanical strain.

Typical dimensions may be chosen such that sufficient volumes of fluid may pass through the casing 17 and that ultrasonic transducer (s) may be housed inside the casing 17. According to one embodiment of the invention, the casing 17 may have a height of 20 mm and a width of 5 mm while the wall thickness of the casing 17 may be in the order of 1 mm.

Figure 4 shows in principle the system for washing and cleaning more or less vertical surfaces 10 according to the invention. The system is electrically driven and comprises a supply conductor 21 through which electricity is supplied from the net, a timer 22, such as a clock, starting and stopping the cleaning interval. The supplied electricity drives both a pump 23 and the driver 24, driving the ultrasonic transducer 19 inside the casing 17 of the cleaning unit 14. The energy from the driver 24 and the cleaning or washing liquids are supplied through a line 16. The washing liquid is drawn from a washing liquid container 25, while the cleaning liquid is drawn from a

cleaning liquid container 26. A valve 27 is included in the line 16, making it possible to switch between the two containers.

The system according to the invention functions as follows: Firstly, required liquid is filled into the two containers 25,26. Supply of liquid may either be manually operated or automatically operated, water being for example drawn from the public water supply, while deter- gents may be supplied from dispensers (not shown). The timer initiates both the driver 24 producing energy for the ultrasonic transducer (s) 19 and powering the pump 23 for delivery of liquid either from the washing liquid container 25 or the cleaning liquid container 26 for delivery of liquid to the window cleaning unit 14. Liquid is flushed over the window surface, while the window pane 11 is subjected to ultrasonic vibration. The liquid supplied to the window cleaning unit is sprayed on to the window surface through a number of nozzles 20, arranged on the lower part of the window cleaning unit 14.

Due to the ultrasonic vibrations and/or the flushing liquid, particles and dirt are loosened from the window surface and transported away, either by the flushing liquid or merely because of the gravitational force.

The length of the vibration cycle is governed by the extent of required washing and cleaning requirement. Such period may for example be as short as 2-5 seconds, or longer.

Washing liquid may be applied in a first cycle, whereupon the valve 27 is activated and cleaning water is applied in a second cycle, rinsing the surface 10. During both cycles, the window is preferably also subjected to ultrasonic vibrations.

The system is installed on a large building, the washing and cleaning process may start at the top floor and then the floor below and so on until the entire floors or facade is washed and cleaned.

It should be appreciated that the present invention

is not limited to cleaning of windows. The proposed solution may be used for cleaning any vertical or inclined surface made of a material which may be subjected to and suitable to be exposed to ultrasonic and/or harmonic vibrations. The invention is particularly useful in connection with surfaces where the cleaning or washing liquid preferably may flow as a consequence of the gravitational force. Typical surfaces may be housing facades, (either of glass, plastic materials or thin metal plates), motor vehicle windows, lamp lenses on vehicles, speed boat windows or the like.

The system according to the present invention may also be employed in conjunction with machines for cleaning solid articles of glass or the like, cleaning of cloths, carpets, clothes, curtains or the like or applied to washing machines or disc washing machines.

Combination of ultrasonic vibrations and water flushing over surfaces may also in principle be used for cleaning of thin-walled hulls on boats. In such case a plurality of transponders may be arranged on the interior surface of the hull, with liquid flushing means on the exterior surface of the hull. The hull may be subjected to vibration during cleaning periods, or more or less permanently during motion. Such vibration may clean the hull and/or prevent growing of marine organisms below the water line, thereby reducing fuel consumption.

The cleaning water used may for example be water mixed with a detergent, such as for example common dish washing soap, while the rinsing liquid may be water mixed with a common rinsing compound. In areas or during periods where frost may occur the liquid may also be mixed with an antifreeze solution. Other ingredients may also be added to the cleaning and/or rinsing water without deviating from the inventive concept.

It should be appreciated that the detergent used is of a type which has a dirt, filth or removing properties, while the rinsing compound preferably are of a type which removes possible oil film left on the surface as a result of the cleaning process.

Although a timer is shown, it should be appreciated that the system also may be manually activated.