Internal-combustion engines – Accessories – Covers – trays – vibrators – corrosion inhibitors – air filters
Reexamination Certificate
1998-11-12
2001-05-08
Wolfe, Willis R. (Department: 3747)
Internal-combustion engines
Accessories
Covers, trays, vibrators, corrosion inhibitors, air filters
C123S041560
Reexamination Certificate
active
06227162
ABSTRACT:
TECHNICAL FIELD
The subject invention refers to a system for cleaning of intake air for a fan-cooled combustion engine intended for a working tool, such as a chain saw, cutting machine, grasstrimmer or lawn-mower, whose engine is equipped with a fan wheel enclosed in a fan cover for cooling of the engine.
BACKGROUND OF THE INVENTION
Many types of working tools, such as chain saws, cutting machines, grasstrimmers or lawn-mowers operate in dirty environments. These tools themselves are supplying the surrounding air with a lot of particles from wood, concrete, grass etc., as well as exhaust gases. Traditionally airfilters are used for cleaning the intake air to the engine. However, these airfilters will soon be stopped up by larger or smaller particles and must therefore be exchanged and cleaned often. Different types of deflection cleaners have been designed in order to clean the intake air before it reaches the airfilter. In several cases the deflection takes place at the inlet of a duct or similar, which debouches in the cooling air outlet. Examples of such solutions are shown in DE 44 20 530, DE 42 03 885, U.S. Pat. No. 5,317,997, SE 93 02 187. The cooling air outlet has a substantially varying cross section in its longitudinal direction. Firstly it expands heavily at the very outlet as from the fan wheel after it will be compressed against the cooling fins of the cylinder. Among other things this leads to a high extent of turbulence in the cooling air outlet. In order to achieve a satisfactory cleaning effect it is therefore important that the flow at the deflection point has high speed and low turbulence to prevent the particles from being deflected. By testing of deflection cleaners with deflection ducts running into the cooling air outlet, it has turned out that the placing of the deflection point in the cooling air outlet is very decisive, in particular since the turbulence picture in the cooling air outlet also is affected by the engine speed. Furthermore these solutions often lead to a complicated drawing of the deflection duct as well as a complicated design at the deflection point. DE 29 03 832 shows a new cleaning air system, which utilizes air cleaning by deflection in two different steps. As described above the first deflection takes place at the inlet of an intake air duct, which runs into the cooling air outlet, resulting in the disadvantages earlier described. The intake air duct then leads in underneath the air filter house. A lot of holes are drilled in the connecting wall between the intake air duct and the air filter house. Those holes are so arranged that most of them are placed downstreams other holes. This means that the upstream hole creates an extra turbulence in the duct and this turbulence contributes to reduce the cleaning effect in the downstream hole. Furthermore are several holes placed entirely at the end of the duct which also creates turbulence and reduces the cleaning effect. Moreover the intake air duct has not an even section but varies. The whole duct is, on the one hand poorly widening in its whole length, and on the other hand there is a strong throttling just upstreams that area with holes. The filter house is simply being partly immersed into the intake air duct. This creates a strong turbulence upstreams the deflection holes and this turbulence contributes to reducing the cleaning effect in every hole. Furthermore the inlet mouth of the intake air duct is placed in one part of the cooling air outlet which has a rapidly varying cross section where accordingly the turbulence is great. For cleaning purposes a strong deflection takes place into the intake air duct. This means that the incoming air to the intake air duct has high turbulence and low speed. Naturally, this is very negative with regard to the cleaning result in the second step. Moreover, as mentioned above, there is also a lot of turbulence creating disturbances at the area of the deflection openings. These openings are increasing the turbulence even more. This means that the deflection is taking place in two steps while the cleaning result in the last step will become very poor at the same time as there is a risk that the cleaning result in the first step will be poor at many engine speedranges.
PURPOSE OF THE INVENTION
The purpose of the subject invention is to substantially reduce the above outlined problems.
SUMMARY OF THE INVENTION
The above mentioned purpose is achieved in a system for cleaning of intake air, in accordance with the invention, having the characteristics appearing from the appended claims.
The system for cleaning of intake air according to the invention is thus essentially characterized in that a flow duct is connected to the fan cover, at least at one side of its both ends, and a deflection duct is arranged in the wall of the flow duct, so that the ducts form a T-like crossing, and the deflection duct leads to the inlet duct of the engine, usually via an inlet volume and a filter. Consequently, in comparison with earlier known solutions a flow duct has been added and the deflection is taking place from the flow duct into the deflection duct. From a cleaning point of view the main purpose of the flow duct is to create a advantageous flow, i.e. a flow with high speed and low turbulence at different engine speeds. From this point of view it can be given a design which is much more advantageous than that of the cooling air outlet. Furthermore the both ducts can be given a very simple design which also reduces the risk of stopping-up. These and other characteristic features and advantages of the invention will become more apparent from the following detailed description of various embodiments with the support of the annexed drawing.
REFERENCES:
patent: 4233043 (1980-11-01), Catterson
patent: 4537160 (1985-08-01), Shirai
patent: 5363815 (1994-11-01), Pretzsch et al.
patent: 5367988 (1994-11-01), Collins
patent: 3708289 (1991-02-01), None
Adolfsson Mikael
Dahlberg Goran
Aktiebolaget Electrolux
Harris Katrina B.
Pearne & Gordon LLP
Wolfe Willis R.
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