It ought to be explained that the term cheese is applied to the kind of bobbin of yarn which is formed upon this particular machine, one or two being placed as shown on the frame work.
Doubling Machine.—The machine just described does not put any twist into the thread, although twisting is a process which is absolutely indispensable for the proper combination of the several single threads so as to produce a strong doubled thread.
The twisting operation is therefore performed on the machine illustrated in [Fig. 37], and termed the "Ring doubling machine."
In the creel of this machine are placed the cheeses formed on the winding machine, and the threads are conducted downward and usually under a glass rod in trough containing water, as the addition of water helps to solidify the single threads better into one doubled thread. From the water trough the threads are conducted between a pair of revolving brass rollers which draw the threads from the cheeses and pass them forward to the front of the machine. Here each doubled thread extends downwards and passes through a "traveller" upon the bobbin.
This machine is a modification of the ring spinning frame previously described and therefore does not call for detailed treatment at our hands.
The two machines are practically identical in principle, the chief difference being that in the doubler there are no drawing rollers, as the cotton is not attenuated in any degree at this stage.
Other differences consist in having larger "travellers" and "rings" and "spindles," and in a different kind of bobbin being formed.
Fig. 37.—Ring doubling machine.