1. Field of the Invention
The invention relates to hoods as used on powered vehicles such as lawn tractors.
2. Description of the Related Art
Many conventional lawn vehicles provide painted metal hoods. The powder painting method is an economical way to paint these metal hoods. This method involves electrically charging the hood while charging paint powder with an opposite electrical charge. The opposite electrical charge holds the powder against the hood, and the hood and powder are heated to melt the powder and provide a smooth finished surface. However, irregular shaped surfaces such as slotted openings or louvers formed in the hood for drawing in air to the engine's cooling system during operation can not generally be painted well using the powder paint method. It is known to produce these louver pieces separately for later attachment to an otherwise powder painted hood. These louvers have been seperately manufactured by injecting colored plastic into a mold to form the louvers and require attachment to the hood by means such as bolts and attachment bosses which raise the cost of manufacture.
Hoods have been manufactured using the injection molding process in an effort to reduce costs. These hoods are molded in color to eliminate the separate painting step. However, several factors inherent in the injection molding process tend to detract from the appearance of conventional plastic hoods. The plastic injected within a die can only be forced a certain distance within the die. The length that the plastic can be forced within the die is dependent on several factors, including the cross sectional area of the piece to be formed, the pressure at which the plastic is injected into the mold, and the material characteristics of the plastic. If the size of the hood is larger than the distance that the plastic can be forced within the die, then the plastic must be introduced into the die at several locations called gates. Therefore, many conventional hoods are gated at a plurality of locations so that the distance the plastic must flow does not exceed the material's flow limit. As the plastic is forced outwardly from the gates the flowing plastic, or flow fronts, emanating from the various gates will meet. A knit line or blemish can occur where these flow fronts meet, causing an undesirable defect in the surface appearance.
In an effort to reduce costs and eliminate the defects in the appearance of plastic hoods molded in color, conventional hoods have been manufactured by the injection molding process and then painted in a subsequent step. The paint is sprayed in a conventional manner since the plastic hood can not withstand the heat involved in the powder painting method. Wet painting a plastic hood therefore requires a painting step that is not involved in injection molding plastic in color. Also, wet painting can leave an"orange peel" surface shine that is not perfectly reflective or shiny, whereas a plastic hood molded in color reflects light more accurately and sharply. Therefore, the wet painting process does not produce a finished surface as aesthetically pleasing as the plastic hood molded in color.
Conventional injection molded hoods are generally less rigid than metal hoods. The flimsiness associated with plastic hoods can be perceived by the operator as undesirable or an indication of low quality.
It is known to provide openings or air ducts in the hoods for allowing air to pass through the hood to the cooling system. Many of these hoods provide conduits for channeling this air to the cooling system. Such conduits generally require attachment within the hood, which adds cost to the manufacture of the hood. Also, these conduits can channel air past or near portions of the engine that are hot. The air in the conduit heats up as it passes these hot areas, which results in the air being heated after entering the hood and before reaching the cooling system, thereby reducing the effectiveness of the cooling system.
It is known to provide hoods with air ducts located at or near the top of the hood. Air at or near the top of the hood during operation is cleaner than air located near the bottom of the hood, since the vehicle wheels and the mower blade each propel dirt and dust into the atmosphere near the bottom of the hood. Therefore, placing the air inlets as remotely as possible from the lower portion of the vehicle is desirable. Further, the larger the opening of the air inlet the slower the velocity of the air passing therethrough. A slower air velocity facilitates drawing in clean air, since only the smallest, lightest particles of debris are drawn in when the suction force is low. The air utilized by the cooling system is thereby cleaner.
Therefore, it would be desirable to provide a more rigid plastic hood made by injection molding plastic in color, and that eliminates or reduces the visual effect of knit lines associated with multi-gating injection. It would be desirable to provide such a mower with large inlets through which air for the cooling system may pass, said openings being located near the top of the hood and away from the ground. It would be desirable for such a hood to eliminate the need for separately attaching a conduit extending between the opening and the cooling system, and to provide for a low velocity of air so that large particles are not drawn in to the cooling system.