Price's machine differs in the following respects :—(1) The stripping is done between the beaters and the lower feod•roller, which is a east-iron, smooth, hollow cylinder ; being 3 in. in diameter, and constantly revolving, it presents a greater change of surface to the beaters, and thus lasts much longer, but when worn down, the machine has to be stopped, and taken to pieces, while the old cylinder is withdrawn, and a new one substituted. The old one can be re-ground. (2) The pro portion of undressed leaf is reduced to a minimum, by the beating on the lower roller; but the smoothness of the latter sometimes permits the thin end of the leaf to be pulled through by the beaters.
692. 693.
There is no appreciable difference in the practical value of the three machines as far as the quality of the fibre produced is concerned. The number of green leaves passed through in a given time depends on the diameter and velocity of the feed-rollers, on the size and shape of the leaven taken in, on the liability to stoppage by fibre getting round the shafts, and on the ease with which the machine may be cleaned when choked. The first condition is about the same in all : 30-35 leaves a minute is quite as much as the out-taker can manage, without entangling or losing a large part of them, and it is in this direction that improvement may be directed. Feeding at the rate of 2f ft. a second, will pass through 33 average sized leaves a minute, or 5 cwt. an hour. Gibbons' and Fraser's machines have an advantage over Price's, in admitting leaves with large butts, cut square at the end.
An improved arrangement is that known as White's, which consists of several different machines. The first machine is for breaking and stripping the leaves : a general view of it is given in Fig. 694 ; plan, in Fig. 695 ; and longitudinal section, in Fig. 696. The leaves are introduced through an iron feeding-mouth, 3 in. broad, and in. deep, which leads close to a pair of horizontal fluted fecd-rollers C, about 6 in. long. These work into each other, so that the leaf is thoroughly crushed before it reaches the hori zontal stripping-drums E, about 6 in. long, and placed immediately behind the feed-rollers. After being turned, these drums are provided with grooves on the surface, about in. deep, and at an angle of 35° to the length of the drums. These revolve outwards from the feed-rollers, at the rate of about 2200 a minute, or about 8 times the speed of the feed-rollers ; they have a slow reciprocating action, and strip both sides of the leaf at once. The necessary gearing is fixed on the shafts of the drums, and springs are provided, so as to accom modate thick and thin leaves. When the ribs are worn down, the grooves may be re-cut.
After leaving this machine, the leaves are passed through one consisting of a pair of plain feed rollers, and a pair of circular revolving brushes, the latter being arranged as shown in Fig. 697.
These brush off all the fleshy matter which the stripping-drume have brought to the surface, and pass out the fibre in a clean state.
The fibre is then passed into the'` finishing "-machine, entering first between a pair of plain feed rollers, and then between a pair of smooth rollers having a rapid reciprocating action, which divides the fibre into very fine filaments, and makes it particularly soft. The two latter machines can keep four of the first in constant work. The fibre is then soaked in water for some time, and finally dried and baled. The rate of feed is 200 ft. of green leaf a minute, and the fibre produced is much superior to that from the other machines. The different machines may be combined in one, as shown in Fig. 698: a, feed rollers ; b, strippers ; e, revolving brushes ; d, delivery rollers; e, finishing- and drying-rollers ; f, wringing rollers; for the travelling delivery-band h.
The many other machines for operating upon the leaf in its natural state may be classified as follows :—(a) By percussion on elastic surface : Booth's (New Zealand patents, No. 67), Nodding's (N. Z. pat., No. 71), Pownall's (N. Z. pat., No. 62). (b) By percussion on non-elastic surface : Purchas and Ninnis' (N. Z. pat., No. 1), Scherff's (N. Z. pat., No. 43), Howland's. (c) By combing on elastic) metallic surface : Trent's (N. Z. pat. No. 60), Cox'e (N. Z. pat., No. 38). (d) By scraping on elastic metallic surface: Pownall's (N. Z. pat., Sep. 1370).
Thorough washing of the fibre immediately after leaving the stripper much improves the quality. Long soaking is not suitable ; therefore, in order effectually to remove the adherent matter, mechanical force must be added, to shorten the duration of the washing. When water can be applied abundantly and with some force, the fibre is beet washed in a strong jet with slight percussion, and in no case may the permission be carried to such a point as to break up the fibre. Handling and bruising the liberated fibre except under water, should be avoided till all vegetable tissue has been removed. When the washing is complete, rolling may be used, to save time in drying, and to con solidate and define the fibrous bundles. Ordinarily the stripping-machine leaves much adherent tissue, which can only be removed by washing, a process that tends to entangle the bundles, and deprive them of the clean defined form so essential for rope-making. Washing is performed in two ways, known respectively as " cold-water " dressing, and" warm-water" dressing. In the former, bundles of about 20 leaves are suspended in cold water, and allowed to soak for 2 hours; in the latter, the fibre is washed, and then left to steep for 6-24 hours in tanks of warm water, kept at an even temperature of, say 32° (90° F.) by means of steam or fire-heat.