Chapter 4

_Fixed Rotating Hooks_.--Wilson's rotating hook for lock stitch machines, and Gribbs' hook for single thread machines, are both well known. In the year 1872, the Wheeler & Wilson company introduced a new hook, forming an improvement upon Wilson's original device (Fig. 3). Its chief peculiarity consists in the extension of the termination of the periphery, forming a long tail piece, quite overlapping the point, and serving as a guard, both to keep off the bobbin thread and to prevent collision between bobbin and needle.

This improved class of hooks are provided with a much deeper cavity than those first introduced, an arrangement permitting of the employment of a more commodious bobbin, which is generally covered by a cap, as in the revolving shuttle, but free to revolve. In some cases the cap carries a tension plate preventing its revolution with the hook. But beyond these improvements on Wilson's original device, the utility of the hook mainly depends upon two things quite apart from the hook itself. These are the dispensing with the old fashioned check brush and the use of a positive take-up.

Thus, in the original machine, the stitch was pulled up by the succeeding revolution of the hook. For while one revolution sufficed to cast it over the spool, a second turn was requisite to complete the stitch. In this way, to make a first stitch with such an apparatus required two turns of the rotating hook. The improvements mentioned enable the machine to complete a stitch with one turn of the hook--an important step in advance, when we consider that by the old method each length of slack thread must be tightened up solely through the fabric and the needle eye. But this particular arrangement bears so much upon the introduction of the positive take-up itself that further reference to it must be reserved until that device has been described.

_Simple Thread Hooks_.--The best known of these is Willcox & Gibbs. It has been so often described, that no further reference to it may be made. It continues to make the same excellent twisted stitch as it produced twenty-five years ago.

_Of Vibrating Shuttles_.--These are shuttles of the long description, moving in a segment of a circle. There are several varieties. The most novel machine of this kind is the vibrating shuttle machine just produced by the Singer Manufacturing Company. In this case the shuttle itself consists of a steel tube, into the open end of which the wound reel is dropped, and is free to revolve quite loosely. Variation of tension is thus obviated in a very simple manner. The chief point of interest in the machine is undoubtedly the means employed in transferring the motion from the main shaft to the underneath parts, an arrangement as ingenious and effective as any device ever introduced into stitching mechanism. It is the invention of Mr. Robert Whitehall, and consists of a vertical rocking shaft situated in the arm of the machine Motion is imparted to it by means of an elbow formed upon the main shaft acting upon two arms, called wipers, projecting from the rocking shaft, the angle formed by the arms exactly coinciding with that of the elbow in its revolution. This admirable motion will no doubt attract much attention from mechanists and engineers.

_The Lock Stitch from Two Reels_.--In the early days of the sewing machine, the makers of it often met with the question, "Why do you use a shuttle at all? Can you not invent a method of working from a reel direct?" The questioner generally means a reel placed upon a pin, just as the upper reel is placed. The reply to such a query is, of course, that to produce the lock stitch in that way is impossible--as indeed it is.

But many ingenious machinists have pondered long over the problem, and several clever contrivances have been invented with a view to its solution. It may scarcely be necessary to say that the best manufacturers of sewing machines have conducted experiments with the same object in view, and the result has always been a return to the shuttle, with its steel bobbins.

Why is this, and how is it that a very big shuttle cannot be used, large enough, indeed, to accommodate any bobbin within itself? The answer is very simple. It has been done over and over again.

Since the whole bulk of the under thread must pass through the loop of the upper one, it, is quite clear that the size of that loop must be proportioned to the bulk of the shuttle. Thus, a small shuttle would, perhaps, be covered by an inch of thread, while our supposed mammoth shuttle might require ten times that amount. Now, let us consider that to sew an inch of thread into lock stitches frequently involves its being drawn up and down through both needle and fabric twenty times. This means considerable chafing, and possible injury to the thread.

But if we were to sanction the use of capacious shuttles, ten inches of thread must undergo this chafing and seesaw treatment, and under the above conditions every part of the ten inches must pass up and down two hundred times--treatment that might reasonably be expected to leave little "life" in the thread. But in spite of this tremendous drawback, there are machines offered for sale made with such shuttles.

For reasons that I have now pointed out, it is quite clear that a large shuttle or bobbin is by no means an unmixed advantage. Indeed, the very best makers of sewing machines have always striven to keep down the bulk of the shuttle, and in those splendid machines shown here to-night the use of the small shuttles is conspicuous. It may be contended that small bobbins frequently require refilling, which is quite true, but the saving of the thread effected thereby, not to mention that of the machine itself, amply compensates for the use of small shuttles. Apart from this, however, it is no longer necessary to wind bobbins at all. Dewhurst & Sons, of Skipton, and Clark & Co., of Paisley, have produced ready wound "cops" or bobbins of thread for placing direct into shuttles. Thus no winding of bobbins is necessary, and indeed the bobbins themselves are dispensed with. I believe that the slightly increased cost of the thread thus wound is the only present bar to the extensive introduction of ready wound "cops."

_Of Thread Controllers_.--One of the earliest difficulties encountered by the maker of a sewing machine was that of effectually controlling the loose thread after it had been cast off the shuttle. In some machines this slack thread amounts to six, in others to one or two inches. Howe got over the difficulty by passing his thread, on its way to the needle, over the upper extremity of the needle bar--the ascent of the bar, then, sufficed to pull up the slack. Singer improved upon this by furnishing his machine with a spring take-up lever, partially controlled by the needle bar.

Wilson, in the Wheeler-Wilson machine, had neither of those arrangements, but depended upon the succeeding revolution of the hook to draw up the slack of the preceding stitch. These devices were all far from perfect in their operation, chiefly because they commenced to act too soon. In each case the pulling up commenced with the rise of the needle, and the tightening operation subjected the thread to all the friction of rubbing its way through both needle eye and fabric. Now, an ideal take-up should not commence to act until the needle has ascended above the fabric, and one of the most important steps toward perfection in sewing machines was undoubtedly attained when such a device was actually invented. In effecting this, the means employed consists of a differential or variable cam, rotating with the main shaft. This controls the movements of a lever called the take-up, pivoted to the machine (Fig. 4). Not only has it been possible by these means to control the tightening of the stitch, but the paying out of the thread for enveloping the shuttle also, and both the paying out and pulling up are actually effected after the needle has ascended above the cloth. The introduction of the positive take-up, the first forms of which appeared in 1872, not only simplifies the movements of the shuttle or hook, but for the first time renders the making of the lock stitch possible, while the needle has a direct up and down motion. Thus, we find that in most of the swiftest sewing machines, the needle bar is actuated by a simple crank pin or eccentric, there being no loop dip or pause in its motion.

The diagram shows a positive take-up in three positions--at the commencement of the needle's descent, during the detention of the loop by the beak, and during the casting off of the loop. The dotted lines indicate the path of the cam to produce these positions. The intermittent movements of the take-up have thus led to the abandonment of variable motions in both needle and shuttle, and particularly so in oscillating shuttle machines.

_Wheeler & Wilson's Variable Motion_.--But while the simple and direct movement is now preferred for shuttles, both oscillating and rotary, the revolving hooks of Wheeler & Wilson are provided with a differential motion, and the way it is effected appears sufficiently interesting to call for a short description. When the rotating hook has seized the loop of thread, it makes half a revolution with great rapidity; its speed then slackens, and becomes very slow for the remaining half a revolution. In the first machines introduced, this was effected by means of a revolving disk, having slots in which worked pins attached to the main shaft and hook shaft respectively.

In the later and more improved machines, the variable device is much simplified (Fig. 5). The main shaft, leading to the rotating hook, is separated into two portions, the axis of one portion being placed above that of the other. A crank pin is attached to each, and these pins are connected together by a simple link. An examination of the device itself shows that, while the motion of the main shaft portion is uniform, that of the hook shaft is alternately accelerated and retarded.

The picture on the screen gives a general view of the No. 10 D machine, in which these motions are embodied, and showing the position of the positive take-up affected by those motions, a position which is preferred for very high speeds in this machine, especially for threads possessing little elasticity.

_Motions of the Feeder_.--The speed attained by the fastest sewing machines is due more to the reduction and simplification of the movements than to any other improvement. Heavy concessions and reactions have been replaced by direct motions, and cams have been excluded as much as possible. Mr. A.B. Wilson's famous invention of the four motion feeder depended upon both gravity and a reacting spring for two motions. Singer improved upon it by making three of the motions positive, a spring being used for the drop. But a really positive four motion feeder was long sought by inventors.

Hitherto the reaction of the feeder--that is, its descent and recession--was generally attained by means of a spring. The drop and ascent are now effected by means of a separate eccentric in Singer's machine. Uncertainty of action in the feed, once a cause of much inconvenience, may now be said to be overcome. A peculiarity of the four motion feeder in Wheeler & Wilson's machine is an arrangement enabling the operator to feed in either direction at will.

Not less worthy of note are improvements that have been made in wheel feeders. The wheel feed was originally much used for cloth sewing machines, especially in Singer's system. But in recent years the drop or four motion feeder has entirely superseded it for such purposes. The wheel feed still holds its own, however, for sewing leather, especially in the "closing" of boot uppers, in this country. Singer's original wheel feeder was actuated by a friction shoe riding upon the flange of the wheel. The friction grip, however, had certain faults, owing to the tendency of the shoe to slip when the surfaces became covered with oil.

A later form of Howe's machine used a pair of angular clutches, embracing the flange of the wheel. In both Singer's and Wheeler & Wilson's latest styles of machines this arrangement is simplified and improved by the use of a single angle clutch, which is found to work even when the surfaces are freely oiled (Fig. 6).

Any motion of the free extremity of the lever upon which the biting clutch is formed binds the latter upon the flange of the wheel, which then advances so long as the lever continues to move in that direction. When the stitch is completed, the clutch is allowed to recede, and is pulled back by a reacting spring. The bite of the clutch is given by the two opposite corners.

The feed wheel itself is free to revolve in a forward direction, but is prevented from rocking backward in Singer's machine by an ingenious little device, recently introduced. It consists of a small steel roller, situated within the angle formed by an inclined plane and the flange of the wheel, and constantly pulled into the angle by a spiral spring. Any backward tendency of the wheel binds the roller more firmly in the angle and stops the wheel. Former feed wheels were checked by a brake spring or block, which retarded the motion of the whole machine when heavily adjusted.

_Feeders for Button Hole Sewing Machines_ are almost invariably of the wheel type, but in this case the cloth is usually carried by a clamping device, and moved in a pear-shaped path by means of a cam cut in the feed wheel, as shown in the samples of this wonderful kind of mechanism exhibited here to-night.

_The Compensating System of Construction_.--Compensation for wear is a part of the mechanist's art that appears just as essential to him as compensation for variation of temperature is to a maker of chronometers. In the construction of sewing machines to be run in factories by power at their utmost speed, such a system is of the greatest importance. An effective _system_ of compensation has been eagerly sought by the best machine makers ever since the introduction of fast speed sewing.

Compensation has been attempted here and there in the machines for many years, but no sewing apparatus could be said to be so compensated until the cone compensator came into use, a device which has been taken advantage of by various makers. Save in the shuttle race itself there is not a part of the oscillating shuttle machine subject to serious wear that cannot be instantly adjusted to full motion by the turning of a screw, while wear in the shuttle race can be compensated for in the usual way. This effective system depends upon the union of two mathematical forms, long used in mechanism--the _cone_ and the _screw_. In screw cones we possess a perfect compensator, and it is surprising that parts of mechanism so hung appear subject to very little wear. Another advantage, too, is gained by the introduction of screw cone bearings; the friction is always greatly reduced by their use. In every case the fine adjustment of the cones is securely maintained by locknuts (Fig. 7).

But the screw cone system is not the only compensator used in sewing machinery; where it cannot be easily introduced, other devices have been employed.

The well known tapering needle bars of former years have been superseded by cylindrical needle bars. The Wheeler & Wilson Company appear to be the first who utilized the engineer's shifting box as an antifriction device for round needle bars. They packed their bars round with felt rings, and compressed the whole by a screw cap.

In the Singer machines the same excellent device has been adopted, hemp packing and screw bushes being used (Fig. 8); _f_ and _g_ show the direct action on the needle bar. This method of forming needle bar bearings, partially of metal and partially of felt or hemp, has afforded the most surprising results.

When the bars are of hard or finely polished steel, no perceptible wear can be detected in them, even after they have been in daily use in factories for twelve months, whereas bars not so bushed might show considerable wear in that space of time. The packing, to be effective, should be sufficiently close to prevent as much as possible friction of the steel with the cast iron needle bar ways. Lubrication of the steel is insured by keeping the hemp packing moistened with oil.

Cylindrical needle bars, when combined with an effective system of brushing, have proved themselves superior to every other form of slide for lock stitch machines. But their introduction is by no means a thing of yesterday. They were used freely in sewing machines as far back as 1860, but were never very successful until united with the lubricating brush. Some makers go a step further, and elaborate the system by the introduction of steel brushes, easily renewable.

Every effort is now made to reduce, as much as possible, not only the extent of movement of the parts in high speed machines, but the weight of the parts themselves. Indeed, so far has this been carried that, in some of the Wheeler & Wilson machines now shown, the needle bars consist really of steel tubes. Small moving parts are made as light as possible, but rigidity is secured by the free use of strengthening ribs. Many of the parts are of cast iron, rendered malleable by annealing, and finally casehardened. Such parts are found to be quite as durable as if made of forged steel, and are, of course, less costly. As to the automatic tools now used in the construction of the machines, it may be said that scarcely a file, hammer, or chisel touches the frame or parts while they are being assembled to work together. The interchangeable system of construction is, of course, the only one possible for the accurate production of the millions of sewing machines now manufactured annually.

_High Arm Construction_.--Sewing machines, as now constructed, exhibit a rather short and very high arm, a form of framework that has been found to contribute in no small degree to the light running capabilities of fast speed machines. While it reduces the length of the various parts concerned in the transference of the motive power, it adds to their rigidity and diminishes their weight, maintaining at the same time the capacity of the machine to accommodate the largest garments beneath the arm.

But the specific improvements in plain sewing machines, to which I have had the honor of drawing your attention, do not exhaust the list, and, time permitting, it might be considerably augmented. Nor must it be inferred that advancement has taken place exclusively in those systems of sewing machinery now before us.

_Accessories to Sewing Machines_.--The number of special attachments that have been successfully adapted to plain sewing machines has multiplied so rapidly of late, that only one or two of the more notable can be spoken of on this occasion. Perhaps the most generally useful of these is the trimmer, an arrangement consisting of a vibrating knife, which trims off the superfluous edge of a seam as the machine stitches it. These are in extensive use in the factories at Leicester, Nottingham, and elsewhere, while Northampton and Norwich use the same device for paring the seams in boot upper manufacture. The chisel-like knife is usually actuated by a cam rotating with the main shaft, and one or two of the usual forms of this attachment are to be seen here this evening on both lock and loop stitch machines.

When machines are moved by the foot, there are many objections to running the whole machine while winding the shuttle reels. We have, therefore, several useful devices for releasing the balance wheel of the machine from the main shaft, while winding. These are to be found both on Wheeler & Wilson's manufacturing machine and upon Singer's highly finished "Family" machine, which also carries a most ingenious automatic reel winder, capable of doing all the work itself, and ceasing to act as soon as the bobbin is filled.

The setting of the needle in a sewing machine was once quite a task. Ofttimes it had to be adjusted by chance, in other instances by certain guiding marks upon the needle bar. It is gratifying to know that all this has been done away with, and that the needle has only to be inserted into the bar, and fastened by turning a small screw. These are styled self-setting needles, and are usually so arranged that they cannot be adjusted wrongly as to the position of the eye.

In the Willcox & Gibbs machine, and in Singer's single thread machine, shown here, we have an intermittent tension arrangement, which clamps the thread at the right moment, and differs from ordinary tension devices, inasmuch as it may be said to be automatic. The feeder, too, on these machines is of excellent design, while the arrangements that have been introduced into the Willcox & Gibbs straw hat sewing machine are surprisingly effective in spinning up a hat from a loose roll of braid. Speaking of straw hat machines, mention should be made of Wiseman's hand stitch apparatus, as improved by Messrs. Willcox & Gibbs, and shown here this evening. This machine employs two needles, and makes a stitch resembling hand work at intervals, producing a short stitch at the center of the hat, and automatically widening the space between the stitches as the distance from the center increases. The machine itself is of wonderful ingenuity, and must be examined to be understood.

The stitch making itself is, I believe, quite new, and is also of much interest. A pair of needles, the width of a stitch apart, rise from beneath through the material. One of these is an ordinary machine needle, threaded; the other is a barbed needle. After rising above the surface, the loop of the threaded needle is seized by a "threader," and thrown into the barb of the barbed needle. The needles then descend, and the feed occurs, being the length between stitches. Upon the ascent of the needles again against the material, the loop is both given off the barb and is entered by the threaded needle, completing the stitch.

_Of Button Hole Machines_.--The mechanism of button hole machines is so intricate, that I can only attempt on this occasion to partially elucidate the construction of one of them, recently introduced, namely, Singer's, which automatically cuts, guides, and stitches the work.