# US 8,540,051 B2 · Silencer for a two-stroke motor of a power tool

> Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt

- Number: US 8,540,051 B2
- Document ID: US8540051B2
- Status: Granted
- Kind: B2
- Application number: 13/401,379
- Filed: 2012-02-21
- Published: 2012-09-13
- Granted: 2013-09-24
- Earliest claimed: 2011-03-09
- Assignees: Makita Corporation
- Applicants: Christian Kellermann
- Inventors: Christian Kellermann
- Web page: https://patentgrep.com/patent/US8540051B2

## CPC

- F01N 3/2885: {with exhaust silencers in a single housing}
- F01N 1/02: by using resonance
- F01N 1/089: {using two or more expansion chambers in series (F01N1/083, F01N1/084, F01N1/086 take precedence)}
- F01N 1/163: {by means of valves}
- F01N 13/002: {Apparatus adapted for particular uses, e.g. for portable devices driven by machines or engines}
- F02B 27/04: in exhaust systems only, e.g. for sucking-off combustion gases
- F01N 2240/36: an exhaust flap
- F01N 2470/20: Dimensional characteristics of tubes, e.g. length, diameter
- F01N 2490/14: Dead or resonance chambers connected to gas flow tube by relatively short side-tubes
- F01N 2490/16: Chambers with particular shapes, e.g. spherical
- F01N 2490/18: Dimensional characteristics of gas chambers
- F01N 2590/06: for hand-held tools or portables devices
- F02B 2075/025: {two}
- Y02T 10/12: Improving ICE efficiencies
- F01N: GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR MACHINES OR ENGINES IN GENERAL; GAS-FLOW SILENCERS OR EXHAUST APPARATUS FOR INTERNAL-COMBUSTION ENGINES (arrangements in connection with gas exhaust of propulsion units in vehicles B60K13/00; combustion-air intake silencers specially adapted for, or arranged on, internal-combustion engines F02M35/00; protecting against, or damping, noise in general G10K11/16)
- F02B: INTERNAL-COMBUSTION PISTON ENGINES; COMBUSTION ENGINES IN GENERAL (gas-turbine plants F02C; hot-gas or combustion-product positive-displacement engine plants F02G)
- Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION

## Abstract

A silencer for a two-stroke motor of a power tool, including a silencer inlet to which adjoins a flow channel of channel length so that the flow channel can be connected to an outlet of a combustion chamber of the two-stroke motor, whereby the flow channel at the channel end opposite the silencer inlet opens out into a first chamber of depth, between the silencer inlet and the first chamber the flow channel is so flow-beneficially designed, that due to its mass inertia the exhaust gas flowing into the silencer inlet predominantly flows into the first chamber and after filling the first chamber flows back again thereby creating a counterpressure in the direction of the combustion chamber, so that in spite of small geometric dimensions it provides a periodically actin counterpressure on the outlet of the combustion chamber of the two-stroke motor.

## Claims

### Claim 1

A silencer for a two-stroke motor of a power tool, comprising:
a silencer inlet that adjoins a flow channel having a flow channel length to an outlet of a combustion chamber of the two-stroke motor;
a first chamber having a first chamber depth, an end of the flow channel opposite to the silencer inlet opening into the first chamber; and
a second chamber into which exhaust gas flows through a main outlet branched from the flow channel, the second chamber having an outlet from which the exhaust gas flows, wherein
due to the inertial mass of the exhaust gas,
the exhaust gas first flows into the silencer inlet, predominantly filling the first chamber, and after filling the first chamber,
the exhaust gas flows back towards the combustion chamber, creating a counterpressure in a direction of the combustion chamber;
wherein a total length including the flow channel length and the first chamber depth is less than a calculated length L determined in accordance with:
L
=
c
s
·
φ
12
·
n
⁢
⁢
in
⁢
⁢
meters
where
cs=Speed of sound of the hot exhaust gas (m/s)
φ=Crank angle in degrees from opening of the outlet of the combustion chamber to closing of the flow channel
n=Motor Speed in 1 rev/min.

### Claim 2 (depends on 1)

The silencer in accordance with claim 1, wherein the total length corresponds to a value of ⅛ to ⅓ of the calculated length L.

### Claim 3 (depends on 1)

The silencer in accordance with claim 1, wherein the total length is such that the ratio of the numerical value of the total length in centimeters to the numerical value of a capacity of the two-stroke motor in cubic centimeters is 0.15 to 0.35.

### Claim 4 (depends on 1)

The silencer in accordance with claim 1, wherein the flow channel extends along a flow channel direction and the first chamber is arranged at the end of the flow channel such that the centre of the first chamber is approximately in a position corresponding to an extension from a centre of the flow channel.

### Claim 5 (depends on 1)

The silencer in accordance with claim 1, wherein the flow channel has a round cross-section, and the first chamber is spherical.

### Claim 6 (depends on 1)

The silencer in accordance with claim 1, wherein the flow channel is at least in section divided into a first partial channel and a second partial channel, and at least one valve is provided in at least one partial channel.

### Claim 7 (depends on 1)

The silencer in accordance with claim 1, wherein a catalytic converter is arranged in the flow channel and/or in the first chamber.

### Claim 8 (depends on 1)

The silencer in accordance with claim 1, wherein a ratio of a volume of the first chamber to a total volume of the silencer is between 1/40 and ½.