Acoustics – Sound-modifying means – Muffler – fluid conducting type
Patent
1997-08-11
1999-03-02
Dang, Khanh
Acoustics
Sound-modifying means
Muffler, fluid conducting type
181231, F01N 302
Patent
active
058774610
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The subject invention refers to a muffler for portable working tools, particularly chain saws at which the muffler is directly mounted to the exhaust gas outlet of the cylinder.
BACKGROUND OF THE INVENTION
The muffler for portable working tools is usually directly mounted to the cylinder's exhaust gas outlet as compactly as possible. For these tools there is a very strong demand for a low total weight and small size. This leads to a demand for a small and light muffler, which at the same time gives a satisfactory silencing function. It is also important that the user does not get injured if he comes into contact with the tool's muffler or its exhaust gases. Furthermore, it is obviously important that the exhaust gases do not set fire to adjacent objects, for example grass or twigs in the case of a chain saw. This has lead to the existence of special legal requirements concerning the muffler's surface contact temperature and the exhaust gas temperature in the vicinity. The working tool is usually supplied with a cooling fan and various safety covers around the cylinder and partly around the muffler. It is desirable to achieve a good mix of the exhaust gases in the cooling-air to reduce the temperature. However, in reality this is hard to achieve due to lack of space and with regard to weight.
PURPOSE OF THE INVENTION
The purpose of the subject invention is to substantially reduce the above outlined problems.
SUMMARY OF THE INVENTION
The above purpose is achieved in a muffler in accordance with the invention having the characteristics appearing from the appended claims.
The muffler in accordance with the invention is thus essentially characterized in that the muffler's exhaust gas outlet is located on an upper side of the muffler, i.e. a side which is turned in the same direction as the upper side of the cylinder, i.e. turned away from the engine's crankcase. Furthermore, the muffler's exhaust gas outlet is supplied with a deflecting device, for instance a bent tube, which deflects the exhaust gas flow, so that it leaves the muffler in a plane which is relatively parallel to the upper side of the muffler. By locating the exhaust gas outlet on the upper side of the muffler it is made possible to take advantage of the large amount of cooling air, which usually blows over the upper sides of the cylinder and muffler. Hereby an effective mix of exhaust gases and cooling-air can take place, assuming that a deflecting device directs the exhaust gases relatively parallel to the upper side of the muffler. Problems with space and temperature have most likely lead to that this solution has not previously been used, as far as the applicant is aware of. According to a further development of the preferred embodiment of the invention the exhaust gas outlet is shaped and directed so that a substantial part of the exhaust gases flow sideways across the muffler's upper side. This contributes to a good mix of exhaust gases and cooling-air and to a lower temperature around the tool. Further characteristics and advantages of the invention will be apparent from the ensuing description of preferred embodiments and with the support of the drawing figures.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will be described in closer detail in the following by way of various embodiments thereof with reference to the accompanying drawing figures.
FIG. 1 shows a chain saw schematically seen from above. The saw's guide bar and chain as well as various safety covers have been removed, to more clearly show the muffler and its cooling.
FIG. 2 shows the muffler in FIG. 1 from above, although in a larger scale and in more detail.
FIG. 3 shows the muffler in FIG. 2 from the front.
FIG. 4 shows a cross section of the muffler in the previous figures seen from the side along line A--A in FIG. 3.
FIG. 5 shows a further preferred embodiment of a muffler according to the invention.
DESCRIPTION OF EMBODIMENTS
In FIG. 1, numeral reference 1 designates a muffler, which is directly mounted to the cylinder's 16 exhaust gas
REFERENCES:
patent: 3650354 (1972-03-01), Gordon
patent: 3798769 (1974-03-01), Bailey
patent: 4142607 (1979-03-01), Landwehr et al.
patent: 4231221 (1980-11-01), Mathner et al.
patent: 4286675 (1981-09-01), Tuggle
patent: 4370855 (1983-02-01), Tuggle
patent: 4846301 (1989-07-01), Granath et al.
patent: 5177962 (1993-01-01), Hall et al.
patent: 5315075 (1994-05-01), Junginger et al.
Karlsson Egon
Ludvigsson Kent
Stark Stefan
Aktiebolaget Electrolux
Dang Khanh
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