Sewing Machines

Sewing Machines have been undergoing a continual process of development since 1830, when Barthelemy Thimonier, a French tailor, arranged a mechanically-moved crochet needle which drew loops of thread through the cloth, each succeeding loop being passed through the previous one, thus making a chain stitch, The modern machine practically originated with Walter Hunt, an American, who devised a needle with an eye near the point, and used two threads to make a lock stitch. Elias Howe, also an American, reinvented this anangement in 1834 and, after suffering for some years the neglect which is the fate of most inventors, laid the foundations of the present extensive trade in sewing machines. In all of the many modifications of Howe's device now in use, the needle is fixed to a vertical bar having an up and down motion given to it by a cam, and at each descent it carries the thread, which is passed through an eye near its point, through the fabric to be sewnh, and on its ascent the friction between the cloth and the thread causes the latter to be left under the cloth in the form of a loop on one side of the needle, as shown at A in the figure. A boat-sbaped shuttle containing a smail spool of thread and having a horizontal reciprocating motion is now passed through this loop, so that one thread is twisted half a turn round the other, and the further ascent of the needle draws the threads tight, at the same time pulling the twist into the centre of the fabric. While the needle is at the upper part of its movement the cloth is advanced by the length of one stitch, and the whole cycle of operations is repeated. This process results in the lock stitch shown at B, and forms a very neat and secure seam. The feed mechanism for advancing the cloth between the stitches consists of a small metal block having on its upper surface a series of saw-like teeth, which works neatly under the needle in a slot in the plate on which cloth rests. The fabric is pressed upon this block by a spring foot, through a hole in which the needle passes. While the needle is descending through the cloth, the feed block is raised and holds it securely while the stitch is being formed; when the needle is clear of the cloth, the block moves forwards through a distance equal to the length of one stitch; it then sinks and moves backwards and upwards to its first position. The chain stitch machine is somewhat simpler, as the shuttie and lower thread are dispensed with. A loop is formed on the underside of the cloth as above described, but on the ascent of the needle this is held by a hook, and the next descent of the needle is made through this loop. The first loop is released from the hook, which engages with the second loop, and on the thread being drawn tight by the rising of the needle, a crochet stitch shown at c is formed. This uses more cotton, and is less neat and secure than the lock stitch, but the machine is simpler, and therefore cheaper, and may be worked more rapidly than the lock stitch machine. About four-fifths of the machines now in use are ot the latter kind. Many attachments are sometimes used to facilitate special operations, such as hemming. The adjustments of sewing machines require more care than is usually bestowed upon them; both upper and lower threads are held tight by frictional devices which can be regulated, and it is important that the tensions of the two threads shou1d be equal, and should be suited to the kind of cloth and thread used, in order that a perfect stitch may be made. It is also advisable to proportion the size of the needle to the size of the thread.