1. TECHNICAL FIELD OF THE INVENTION

The present invention relates generally to air- conditioning apparatus and more particularly to outdoor unit of an air-conditioning apparatus, the outdoor unit being provided with an improved base pan having feature for draining off water accumulation from the inside of the out door unit main housing. 2. BACKGROUND OF THE INVENTION

Air-conditioning apparatuses are known in the art. Air-conditioner generally functioned to transport heat from inside to the outside using refrigerant as the heat transferring means. The refrigerant traditionally includes Freon or, currently the more environmental-friendly CFC-free refrigerant. The process involves three major components i.e., a compressor, an outdoor heat exchanger (also known as a condenser in cooling mode) , an indoor heat exchanger (also known as an evaporator in cooling mode) and an expansionary device such as capillary tube. The compressor and the outdoor heat exchanger are usually equipped in the outdoor unit.

The initial structure and behavior of a fundamental refrigerant cycle is hereby described. The refrigerant arrives at the compressor as a cool, low-pressure gas. Then the compressor compresses the refrigerant, so that their enthalpy and pressure increase. The refrigerant leaves the compressor as a hot, high pressure gas and flows into the condenser. The condenser has metal fins that assist the refrigerant in transferring heat to the surrounding outdoor air. As this transfer takes place, releasing additional thermal energy into the surrounding air and causing the refrigerant to transform into a liquid or almost liquid.

This high-pressure liquid then flows into the evaporator through an expansion device. This expansion device allows the liquid's pressure to drop while keeping its enthalpy. As it evaporates, it absorbs heat from the air around the evaporator and changes its phase from liquid into gas. The evaporator also has metal fins to assist it in exchanging thermal energy with the surrounding air. By the time the refrigerant leaves the evaporator, it becomes a cool, low pressure gas. It then returns to the compressor to begin its circulation all over again. In general, the refrigerant releases heat into the outside air and absorbs heat from the inside air. The process is further assisted by the presence of a fan arranged corresponding with a heat exchanger in the outdoor unit and in the indoor unit . In most air-conditioning apparatus, an outdoor unit that houses the compressor, accumulator, heat exchanger assembly, expansion device and the related electrical/electronic control components is provided. Typically, the housing of the outdoor unit is compartmentalized by partition plates to separate them into chambers, i.e., chamber for the heat exchanger and blower fan (also known as heat exchanger chamber) and chamber for the compressor, electrical /electronic components, control box and the accumulator (also known as machine chamber) . Typical in the known outdoor unit assembly, the partition plates are made of steel. Further, in the typical outdoor unit, the heat exchanger is typically consists of multiplicity of fins along with headers and plates to help in transferring heat to the surrounding outdoor air.

As the outdoor unit is located outdoor, it is exposed to weather elements including rain, pollutant and sun among others. The most critical from these weather elements would be rain as rain may cause corrosion to the metallic material of the outdoor unit including the casing, the heat exchanger assembly and the other structures. In an all aluminium heat exchanger assembly which is the preferred choice for the current outdoor unit application, aluminium may be exposed to galvanic corrosion due to contact of dissimilar material of the heat exchanger assembly, mounting structure and other metallic component having less reactive character compared to aluminium. In this respect, water may also act as electrolyte that provides electrical path between the aluminium heat exchanger and the other metallic components of the outdoor unit that otherwise be not presence in a dry outdoor unit housing.

The present invention proposes a solution to effectively drain off water accumulation in the outdoor unit of an air conditioner apparatus, such water accumulation may be due to rain, condensation and other sources. In particular, it is proposed that the base pan of the outdoor unit is provided with multiplicity of apertures or small openings strategically arranged throughout the surface or the plane of the base pan for the water to flow through. Further, the bottom plate of the base pan is also arranged to be mounted in a slightly slanted configuration, advantageously to further assisting in water drainage. Such water draining feature advantageously prevents or eliminates water accumulation that could creates electrolyte solution due to retained water in the outdoor unit particularly to reduce or prevent galvanic corrosion of the all aluminum heat exchanger assembly. Preferably, the base pan is made of steel or other suitable material and provided having raised and lowered section forming path of water to flow through .

3. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a main housing of an outdoor unit that is provided having a base pan formed with multiplicity of apertures or small openings for dispersing water accumulation in the outdoor unit main housing. This and other objects of the present invention are accomplished by providing,

An outdoor unit (1) of an air-conditioning apparatus, said outdoor unit includes a main housing (2) that encloses at least an outdoor unit fan (3), a compressor (4) and a heat exchanger (5), characterized in that said main housing (2) is provided having a base pan (6) secured at the lower portion of said main housing (2), said base pan (6) is formed with multiplicity of apertures (7) .

It is preferable that base pan is having a generally slanted mounting profile for further assisting in the dispersion of water out of the main casing.

Yet it is also preferable that the base pan is provided having raised and lowered sections that form path for the accumulated water to flow through.

4. BRIEF DESCRIPTION OF THE DRAWINGS

The embodiments of the invention will now be described, by way of example only, with reference to the accompanying figures in which:

Figure 1 shows perspective view of unfinished assembly of outdoor unit of an air-conditioning apparatus configured according to the preferred embodiment of the present invention. Figure 2 shows perspective view of the outdoor unit of Figure 1 shown in unassembled state.

Figure 3 shows detailed perspective view of the base pan of the present invention. 5. DETAILED DESCRIPTION OF THE DRAWINGS

As mentioned earlier and with reference to Figure 1 and Figure 2, the typical split-type air- conditioning apparatus generally includes an indoor unit (not shown) and an outdoor unit (1) . Installed within the outdoor unit's main casing (2) are fan (3), compressor (4), condenser or heat exchanger assembly (5) and a control box (not shown) . In all air-conditioning apparatuses, the operation is controlled through the control box (not shown) .

Various electronic components are arranged on the control board (also not shown) of the control box to ensure that the air-conditioner operates as intended. An end-plate (11) together with partition plate (10) are used to isolate the compressor and the control box chamber together with the related electronic components from the heat exchanger assembly (5) chamber to within the respective internal compartment or chamber of the outdoor unit. The heat exchanger assembly (5) is preferably made of an all aluminum material due to the advantages of the generally lower weight as well as lower cost. However, an all aluminum heat exchanger assembly suffers from galvanic corrosion if the all aluminum assembly is in contact with other less reactive material it may comes in contact. For example, the casing of the outdoor unit is typically made of steel and sometime provided with rust preventive coat and steel being less reactive than aluminum causes the aluminum to be exposed to galvanic corrosion process. In this respect, the heat exchanger assembly (5) is normally provided having tube header disposed on the upper (12) and lower (13) positions on the heat exchanger assembly as inlet and outlet means for the refrigerant to flow in and out of the heat exchanger. Specifically, these inlet & outlet tubes (12, 13) are used for connection to port (14) of the compressor (4, Figure 1) and 2,3 way valve (8). The headers are connected through the respective inlet and outlet ports upon exiting from openings (15, 16, Figure 2) of the end plate (11) . Preferably, the upper opening (15) is formed as a C-shaped opening whereas the lower opening (16) is formed as circular opening.

In this respect, an isolator device in the form of plastic, resin or other insulative clip holder (not clearly shown in the figure) is preferably used to secure the all aluminum heat exchanger assembly, particularly the tube headers (12, 13) of the heat exchanger through the steel end plate (11) . Such clip holder is preferably secured on each openings (19, 20) of the end plate (14) for use by the respective upper (12) or lower tube header (13). Apart from providing secure mounting of tube headers, the clip holder also acts as isolation device to prevent galvanic corrosion of the tube headers as well as preventing rain water from entering the machine chamber through the openings (15, 16) as the clip holder also acts as seal on the openings. Such specific configuration of clip holder is a subject of a separate patent application by the same applicant of the present invention.

Figure 2 shows another perspective view of the outdoor unit of Figure 1 but in unassembled state. In this figure, the outdoor unit includes the outdoor unit's base pan (6), fan (3), compressor (4, Figure 1), heat exchanger assembly (5), partition plate (10, Figure 1) and the end plate (11) . As also shown in the figure, the inlet and outlet tubes (12,

13) of the heat exchanger (5) that are formed having short bent profile.

Now with reference to both figures, the base pan (6) is mounted and secured at the bottom portion of the main housing (2) where the base pan (6) is formed having multiplicity of apertures (7) arranged throughout the surface of the base pan (6) . Preferably, the apertures (7) are arranged spaced apart of each other forming an apertures grid. Apart from having such apertures, the base pan (6) is also formed having raised section and lowered section among the surface of the base pan, where raised and lowered sections forming channel (8) or path for water flow on the base pan surface. Such raised and lowered sections also formed a generally slanted base pan profile for water path that advantageously further assisting in the flowing of water on the base pan. Optionally, the base pan (6) could also be secured slanted on the main housing (2) thus forming a generally slanted mounting profile of the bottom plate portion of the base pan for assisting the water flowing on the base pan.

Figure 3 shows further detailed perspective view of the base pan of the present invention. In this figure, there are shown multiplicity of apertures

(7) disposed on the surface of the base pan (6). Also shown in the figure, the channel (8) adapted to allow water flow on the base pan (6) . Such channel is formed by the raised and lower sections disposed on the base pan surface. The apertures (7) could be formed on the major portion of the base pan surface or throughout the surface of the base pan (6) forming an apertures grid.

It is envisaged that such base pan construction would help in eliminating water, usually from rain water, to be dispersed out through the apertures or through the water path thus ensuring a dry main housing of the outdoor unit. Such dry condition is preferred as it could eliminate accumulation water that could otherwise be an electrolyte solution causing corrosion to the outdoor unit assembly. Apart from providing an isolation barrier between the all aluminum heat exchanger assembly especially between the tube header and the end plate of the outdoor unit casing or cabinet thus preventing possible galvanic corrosion to the heat exchanger assembly (5), the present invention advantageously prevents rain water from being accumulated in the chamber. Such multiplicity of apertures (7) advantageously provides such advantages feature. Further, the apertures (7) should preferable be formed on the lowered section of the base pan surface particularly to ensure that the apertures would still be opened even if fallen leaves or dirt or even water accumulation due to rain or water condensation from the operating air-conditioning apparatus accumulates on the base pan surface. While the preferred embodiments of the present invention have been described, it should be understood that various changes, adaptations and modifications may be made thereto. It should be understood, therefore, that the invention is not limited to details of the illustrated invention shown in the figures and that variations in such minor details will be apparent to one skilled in the art .