32 FOREST PRODUCTS 



are conveyed in the bolt form to the barking or rossing machine which 

 removes the wood. The modern barker consists of a heavy, circular, 

 steel disk from 52 to 72 in. in diameter, inclosed in a heavy, iron frame. 

 The steel disk has three knives inserted in it radially in such a manner 

 that the knives cut away the bark as the blocks are held against the 

 rapidly revolving surface. A log rolling attachment is provided to hold 

 the logs in place after the operator has inserted them. The toothed 

 chain revolving around two sprockets, turns the log and the sharp knives 

 automatically remove the bark from the wood. 



When the logging of pulp wood is done in the spring or early summer, 

 the bark can best be removed by the use of a bark spud or even an axe. 

 When fall or winter logging is practised the logs are sent directly to the 

 mill in the unbarked condition. There is very little loss of good wood by 

 peeling in the woods, but there is a loss, estimated at 15 to 25 per cent of 

 the solid wood, when the bark is removed by the barking machine. If 

 the bolts were perfectly symmetrical there would be very little loss, but, 

 owing to the unsymmetrical character of the bolts, together with seams, 

 crotches, taper, knots, etc., considerable wood must be removed in order 

 to cut off all the bark. The rapid revolving and rossing take off large 

 quantities of wood along with the bark. Bolts of small diameter lose 

 a greater percentage of wood than large bolts. 



A rotary or drum barker has been devised which minimizes this loss. 

 The drum barker consists of a heavy, circular, iron cylinder made of 

 angles or channels fitted with projections to scrape the bark from the 

 logs. As the drum revolves the bark is removed partly by attrition 

 and direct contact with the projecting surfaces. It is estimated that 

 from 10 to 20 per cent of solid wood is removed, but modern devices and 

 improvements are correcting this difficulty. The wood enters the 

 rotary or drum barker at one end and is discharged at the other, while 

 pieces of bark which have been removed fall through the open spaces 

 in the drum. 



In many pulp mills where both chemical and ground wood pulp are 

 made the better classes of bolts, that is, those which are relatively free 

 from dirt and contain few knots, are used for chemical pulp, while those 

 of inferior quality are sent to the ground wood mill. 



Very often the barking process is carried on more rapidly than the 

 grinding operation which follows it, so that the surplus blocks are carried 

 out into the yard on a cable conveyor or a similar device and stored until 

 needed. In winter, many of the bolts contain ice and dirt, accumulated 

 in the woods. These are sent into a hot box or tub of water where 



