Page:Popular Science Monthly Volume 89.djvu/366

 The Paving Blocks of Paris

���An Important Part of the Machine Is a Conveyor Which Supplies the Timbers

��LIKE many another modern city Paris is paved in part with wooden blocks. The municipal workshop has to supply twenty-five million blocks a year. A large amount of blocks must be kept in stock because the supply of wood is not constant.

It was consequently necessary to construct a machine that could turn out the desired amount of paving a year while subject to these interruptions of supply. This was done by a M. Josse who produced a wood cross-cutting machine with seventeen circular blades that can make two hundred and forty thousand wooden paving-blocks in a day of ten hours. It economizes both wood and lal)or. Twenty workmen can run it. The important part of the machine is a conveyor which is held in a frame which can be swung up or down. Two endless belts carry a series of fingers. Th^se are mounted on bars which run from belt to belt, and there are sixteen fingers to each cross-bar. The fingers catch each beam as it comes up to the table and feed it to the saws. The saws are not arranged in just a

��single row, but in several rows. One row cuts the center of the beam only; the other rows, the sides. The wood is brought by trucks to the foot of the machine where two workmen place the beams on the chain of the conveyor.

The cross-bars carrying the fingers are provided each with two little brooms to sweep off the chips and sawdust.

The saws, seventeen in number, are circular blades twenty-six inches in diameter. They are divided into three groups so as to avoid the vibrations which would result from using only one shaft of a diameter in proportion to that of the blades running at ihe high speed of two thousand revolutions a minute.

The first two sets of saws trim otT the exterior edge of the wood and cut four blocks each; then the following set of seven saws ruts the central section of the beam into blocks. After this the blocks, drawn along continually by the fingers, pass under rollers, eventually to be pushed out by the following series of blocks. TJie blocks slide down a chute upon tables from which workmen take tliein and throw them onto small cars.

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