Woodworking – Bark rosser – Hydraulically driven cutter or hydraulic jet
Patent
1995-09-01
1997-02-25
Bray, W. Donald
Woodworking
Bark rosser
Hydraulically driven cutter or hydraulic jet
144340, B27L 300, B27L 114
Patent
active
056051840
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The invention relates to an apparatus for debarking logs individually with the aid of high-pressure water jets, the apparatus comprising a number of spray nozzles intended to spray water in focused jets onto the log at the same time as the log moves past the spray nozzles.
PRIOR ART
Before cutting up the raw materials of wood in saw mills and the pulp industry, it is necessary to remove the bark from the logs. Two methods are mainly used for this purpose, these methods having their origins around the periods when these respective industries came into being.
Saw mills mainly use so-called Cambio debarking in which the bark is peeled off with the aid of knives which rotate around the log in an annular holder. This method leaves some of the bark remaining on the tree-trunk and is in addition energy-intensive and noisy. The equipment also requires careful servicing.
The pulp industry uses debarking drums with diameters of 3-6 m and lengths of up to 35 m. The drum lies at a slight incline, mounted on pulley brackets and is set in rotation by drive machinery. The logs are fed in at the upper end, and, as a result of the rotation and inclination of the drum, the logs are conveyed through the drum and eventually issue at the other end. The debarking is achieved by means of the logs scraping and striking against the walls of the drum and against other logs in the drum. A virtually one hundred percent debarking result is sought so as to ensure that residual bark does not impair the quality of the paper. This means that the dwell time in the debarking drum is determined by the logs which are most difficult to debark. This in turn means that most of the logs have too long a dwell time in the drum, which leads unnecessarily to a high energy expenditure. In the debarking drums the logs are sprayed continuously with water, which is required as "lubrication". Water is also used as a means for conveying the bark which has been peeled off. These large amounts of water have to be dealt with and cleaned at a later stage. This debarking method thus uses up large amounts of energy and water, and at the same time the debarking equipment is expensive and takes up a great deal of space.
Debarking with high-pressure water has also been proposed. As early as 1912 a Swedish patent 35392 was published relating to a method for debarking wood, in which "the wood is made to execute a spiralling movement past a pressure-medium jet, where appropriate provided with solid particles".
An American patent U.S. Pat. No. 2,463,084 from 1949 relates to debarking with high-velocity jets, in which the unit which comprises the spray nozzles moves around the log, so that the debarking is executed in a spiral as the log moves through the rotating instrument.
Another American patent U.S. Pat. No. 2,473,461 stresses the importance of the jets being directed radially with respect to the axis of the log at all times, regardless of the size and shape of the log, and of the spray nozzles being located at a predetermined optimal distance from the surface of the log. However, the apparatus which is described in the patent specification cannot satisfy the stated conditions in practice and it is additionally complicated and, in quite general terms, functionally unreliable.
The principle of using high-pressure water for debarking logs has therefore not as yet been applied in practice.
BRIEF DISCLOSURE OF THE INVENTION
The present invention has the object of providing an improved apparatus of the type which is mentioned in the introduction above. A particular object of the invention is to offer an apparatus for debarking logs individually with high pressure water which is sprayed against the log, requiring considerably less water, energy, space and maintenance compared with the abovementioned debarking apparatuses which are generally used in the forest industry at present.
The present invention also aims to offer a debarking apparatus in which the spray nozzle is held essentially within an optimal range of distance from the surface of the lo
REFERENCES:
patent: 3942565 (1976-03-01), Ratelle et al.
patent: 4047549 (1977-09-01), Ratelle et al.
patent: 4609021 (1986-09-01), Bengtsson
patent: 4640327 (1987-02-01), Krilov
Borjesson Lennart
Eriksson Roland
Nordin Ulf
Bednarek Michael D.
Bray W. Donald
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