Woodworking – Process – Timber harvesting or processing
Reexamination Certificate
1999-09-08
2001-01-16
Bray, W. Donald (Department: 3725)
Woodworking
Process
Timber harvesting or processing
C144S003100, C144S162100, C144S268000, C144S208300, C144S242100, C144S367000, C144S369000, C144S364000, C181S252000
Reexamination Certificate
active
06173748
ABSTRACT:
This invention relates to a method of reducing the noise caused by a barking drum and a chipper in a barking plant, on the log conveying line between the drum and the chipper.
In barking plants, big barking drums, chippers and other devices related to the process are used. They all cause a lot of noise. The background noise in a barking plant, when the drum and the chipper are not operating, is 80-85 dB (A). When the process is running, the noise may be 95-100 dB (A). In the proximity of the drum and of the chipper the noise may be 100-115 dB (A). In some new Scandinavian barking plants the objective is to lower the noise level so that it does not exceed 85 dB (A) in any part of the plant. Thus, more and more interest has been shown in developing means of reducing the noise caused by each machine of a barking plant, especially the noise caused by the drum and the chipper.
A barking drum causes noise as the logs to be barked hit against one another and against the shell of the drum. The low-frequency noise peaks occur at frequencies lower than 1000 Hz. The noise caused by a barking drum can be reduced by housing the drum in a concrete structure or in a structure composed of another soundproofing material. Furthermore, the drum can be placed in a separate room with respect to the other machines of the barking plant. In Scandinavia, the feeding of logs into a drum is performed by means of a thawing conveyor. The closed conveyor soundproofs the inlet of the drum effectively, but soundproofing the opening of the discharging end of the drum is more problematic. The conveyors between the drum and the chipper comprise a metal detector for detecting pieces of metal carried with the logs. The metal detector may stop the process even 10 times an hour. The removal of logs containing metal and of other pieces of metal from the stopped conveyors is performed manually, which is why the conveyors have to be easily accessible.
When removing the metal-containing logs, the workers are often subjected to a noise level of about 90-100 dB (A).
Not only drums can be isolated from their surroundings; the same can be done to a chipper.
In this case, isolating the feed opening of the chipper is as difficult as isolating the discharge end of a drum. The feed opening cannot be closed to a sufficient degree, in order not to prevent the inconsistent log flow from freely entering the feeding chute.
The characteristics of this invention are set forth in claim
1
. The characteristics of the barking drum, chipper and conveying line according to the invention are set forth in claims
4
,
5
and
6
. The invention makes it possible to reduce the noise coming from the discharge opening of a drum and from the feeding chute of a chipper in such a way that it does not become substantially more difficult to work at the conveyors between the drum and the chipper. According to the invention, the openings through which the logs flow are closed by means of a water curtain.
The invention and the details thereof will now be described in more detail with reference to the accompanying drawings wherein
FIG. 1
shows a typical section between a barking drum and a chipper in a barking plant,
FIG. 2
shows the noise-reducing method according to the invention applied to conveyors working between a barking drum and a chipper, and
FIG. 3
shows a method of forming a water curtain.
REFERENCES:
patent: 4582106 (1986-04-01), Huhta et al.
patent: 667223 (1963-07-01), None
Bray W. Donald
Burns Doane , Swecker, Mathis LLP
Valmet Woodhandling Oy
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