US1986448A - Muffler - Google Patents

Description

Jan. 1, 1935. T. s. SAI-FORD 1,986,448

Filed July 2, 1950 Patented Jan. 1, 1935 UNITED STATES PATENT OFFICE 1 Claim.

This invention relates to a muffler for engines of the intermittent fluid expansion type and particularly for internal combustion engines.

An object of the invention is to produce a 5 greater silencing of the exhaust, and at the same time to lessen the back pressure and preferably actually to create suction on the exhaust. To this end I have found that by cutting off from the exhaust stream small parts of the gases thereof, subjecting them to an impact to destroy the identity of puffs therein, and recombining said parts in a different arrangement to form a new stream the exhaust can be effectively silenced and preferably with an actual decrease in the pressure in the exhaust manifold.

In the accompanying drawing I have shown in:

Figure l a plan view of a preferred embodiment of my invention,

Figure 2 a cross section taken on line 2-2 of Figure l.

Referring particularly to Figures l and 2, I have shown a muffler lo which receives exhaust gases from a manifold 11 and discharges them thru the exhaust pipe 12. The muffler l0 is in the preferred embodiment a centrifugal blower having within its casing a rotor with blades or vanes i3 which closely t the interior of the casing except where it leads to the outlet 14. In Figure 2 I have shown only one vane within the scope of the inlet opening. It will be understood, how ever, that there may be more. The number of the vanes is not material except to determine the proper speed relative to the motor at which the blower should be driven. I prefer to use four to six vanes and to connect the rotor to the motor so that one vane thereof will move from one edge of the inlet opening to the other each time a cylinder I have found that this speed is particularly advantageous since it allows each space between vanes to receive from the exhaust the same cycle of pressures, that is the saine part of the wave produced by the opening of an exhaust valve.

The shaft l5 of the blow-er rotor is shown hollow and mounted behind the fan so that it will be cooled by the current of air passing therethru. The shaft bearings are advantageously separated from the body of the casing so as not to receive the full heat transmitted by the casing from the hot exhaust gases.

In the embodiment illustrated I have shown the blower driven from the fan belt. It will be understood however that it may be driven in any other suitable way as by gearing or silent chain from the crank shaft, timing shaft or generator shaft, etc. The drive should however be such as will drive the blower at the proper speed relative to that of the motor.

I have found the speed as described above, i. e. such that each vane moves across the inlet opening in the period between exhaust impulses, to be a particularly advantageous one. Operating in this manner the space between each two vanes receives an amount of gas equivalent to the exhaust from one cylinder and discharges it in a direction transverse to its original direction and parallel to the wave front from the original stream. Thus the original stream which was composed of surges of gas at high pressure grading off to lower pressures to be followed by another surge, is converted into a stream which is substantially uniform along its length, and which if it varies at all to any important degree varies only about its axis. It may thus be discharged to the atmosphere without causing the propagation of sound waves corresponding to the opening of the exhaust valves. t the same time the blower, by its centrifugal and impelling action, has decreased the pressure in the exhaust manifold, and thereby made for a more complete exhausting of the burnt gases from the cylinders and a correspending increase in the efficiency of the motor.

From what has already been said it will be obvious that the inlet to the blower should be away from the outlet 14, and should have an angular separation therefrom in the direction of rotation of the rotor at least as great as the angular separation of the vanes on the rotor. In other words, it should be impossible at any position of the rotor for gases to pass directly from the inlet to the outlet. It is of course possible to position the inlet closer and still to obtain some of the advantage of my invention, but it is not desirable, and insofar as that is done, the function of the blower is impaired.

Altho I have found it most advantageous to drive the blower so that each vane travels completely across the inlet opening in the period be tween opening of successive exhaust valves, nevertheless the muffler of my invention may be operated quite satisfactorily at a slower speed such that more than the period between opening of valves is required for the vane to completely cross the inlet.

Altho I have shown and described above several, specific embodiments of my invention, it is to be understood that these are given by way of example only, and that my invention may be embodied in many other forms all of which are to be included within the scope of this application.

What I claim is:

A muiiier comprising a blower having a rotor with a plurality of approximately radial vanes, and an approximately circular casing tting closely over said rotor so as substantially to oonfine gases between the blades thereof, and having a tangential outlet and an inlet near its center but to one side thereof and angularly spaced from the outlet so that it is always separated from the outlet by at least one of the vanes of the rotor, and means for rotating the impeller at a speed such that the blades thereof cross the inlet at intervals substantially timed to those of the puis so that the charges cut 01T by successive impellers Will have substantially the same average pressures.

TRUMAN S. SAFFORD.

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