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carries a perforated plunger F working in an oil cylinder E, the upper part D of the plunger terminates in a lead weight covered with brass. The quadrant and arm G. G.' carry a pair of catches and a weight 7, which latter supplies the necessary strain required to break the yarn. When a test has to be made the arm G' is brought down, and a square catch L' takes into the detent L until the thread is placed in position as already mentioned. L' is now lowered, and catch K lifted. This allows the frame to descend and put strain on the yarn, the weight 7 is slowly raised until the thread breaks when the load is shown on the quadrant. Whilst the frame descends, and the thread is still unbroken, the graduated scale M descends at the same speed, but as soon as the thread breaks the scale is released and stops; and the elongation is shown on the scale by the pointer N, which is connected with B, and consequently comes down at the same rate.
The machines are provided with two scales on the quadrant, one having a range of sixteen ounces, and the other a range of four pounds; for the finer yarns, the front portion of the weight is removed, when the break is read on the upper or sixteen. ounce scale. The speed of the plunger is set to one inch in five seconds by regulating the aperture through which the oil flows.
In practice a double thread test is found most convenient, and a large number of tests can be made in a short time by a girl or a youth. The length of yarn tested is 18 inches for single and 36 inches for double thread tests.
There are a good many of these machines at work, they are reliable and easy to manipulate. All the double thread tests shown on the diagrams have been made by one of these machines.
Automatic Single Thread Tester, Cook & Co., Manchester, (Moscrop's Patent.) This machine recently introduced belongs to the automatic type, and is very ingenious and useful. A general view of the machine is shown at Figure 20.
The action of the machine may be gathered from the follow
ing description. The cops or bobbins are placed on skewers mounted upon a frame having a traversing motion, each thread is passed through the tensioning hooks and eyes, and between a clip. When the machine is started the frame moves forward, and a plate lying underneath the threads rises and lays each thread into the jaws of another series of clips which immediately close. When the frame or carriage has receded about 12", the clips in the carriage close on the threads, and as the carriage continues its outward movement for about another 4", strain is put on the threads, the strain distends a series of springs mounted at the rear end of the second set of clips, this distension draws a series of pointers along until the several threads are broken, then the pointers are pressed down into the diagram slip, at the positions to which the pointers have been pulled, and thus a record of the breaking load is made. The broken ends are cleared away from the clips, the pointers pushed back to zero and the whole cycle of movements is repeated about eighty times when the machine is stopped automatically. The record of the breaking strength of the several threads is shown on a punctured slip, and the variations are readily observed.
Different strengths of springs are used for various qualities. and counts of yarn.
The only apparently weak part of the machine is the spring, and to eliminate error the greatest possible care is exercised in the selection of the springs.
Records of Tests. In order to demonstrate the value of double thread testing as a means of determining the quality of the yarn, and with a view to making a comparison with lea testing, a series of graphic diagrams have been prepared, and these are shown at Figures 21 to 24.
Now, seeing that at the present time most people who deal in yarn speak of its strength in pounds per lea, and as these customs are inclined to continue, and if they die at all they die hard, it was thought that it would be interesting to make a comparison between the breaking strength of leas, and the breaking strength of double threads, and if possible to establish a ratio between the two.
In the graphic diagrams shown on Figures 21 to 24 it will be observed that the double threads tests disclose a much greater variation in the strength of the yarn than is shown in the lea tests taken from the same bobbins, the variation in the double thread tests extending from 25 per cent. to 59 per cent., whilst the variation in the lea tests extends from 7.6 per cent. to 31.7 per cent.
A great many tests have been made to determine the actual differences existing in yarns, and from these a few typical examples only are given, but sufficient to demonstrate the superiority of double thread testing over lea testing.
This is a matter of as much importance to spinners as manufacturers, particularly spinners who have a reputation to make or to maintain.
The table, Figure 25, shows the percentage of variation in strength between maximum and minimum in the same yarn from lea and double thread tests, and also in the last column the relation that a double thread bears to a lea break. From this column it will be seen that the ratio between the mean lea break and the mean double thread break is as 100 is to 1.76 approximately, and this figure is substantially the same for both American and English spun yarn.
It is hoped that these investigations which have proved so interesting to the author may prove equally interesting to others and be carried still further.
Thanks are due to the firms who have kindly lent drawings and blocks for Figures 1, 6, 10, 12, 15, 16, 19 and 20 and to those who have supplied a number of samples of yarn for testing. and these are gratefully tendered by the author, who also desires to thank those of his colleagues and students in the Municipal School of Technology, Manchester, who have rendered willing help in various ways.
- theo d.t break
14.045 (actual mean dit, bread) -10.63.445 und
This calculation shews that the actual mean dit break
This means that the actual mean dit break is
26.9% greater than the calculated d.t. break taken from the mean lea break