THE STITCH REGULATOR.

The principle of the various appliances for regulating the length of stitch is the same, the feeder being detained towards the completion of its return motion by a projection attached to some part of the framework of the machine. Either this projection is moveable, or, as shown in Fig. 2, Plate I., a set screw (k) in the feeder itself regulates the length of the stitch. When the feed motion is effected by a wheel with serrated periphery, the connecting-rod is so constructed as to be lengthened or shortened as required. The best regulators, and which are most in use, are constructed with scale attached, and consist of an eccentric disc against which the feeder strikes on its return motion. The scale is marked on the periphery of this disc, and as the disc is turned to increase or diminish the length of the stitch, indicates the number of stitches contained in an inch. This arrangement is shown Fig 16, Plate IV., Fig. Plate VII.

11, Plate V., Fig. 6,

Fig. 4, Plate II., and Fig. 8, Plate VI., show arrangements without a scale, in which the eccentric disc is regulated by a lever handle.

D. THE TENSION APPARATUS.

The necessary tension is given to the thread either by applying friction direct to the thread itself, or to the spool on which it is wound, or to a roller over which the thread is made to pass in its passage from the spool to the eye of the needle.

TENSION BY FRICTION OF THE THREAD.

An apparatus constructed on this principle is shown Plate IV., Figs. 1 and 5. To a knee, t, affixed to the bracket of the machine a horizontal metal cylinder, s, is attached, 1 to 2 in. in length, and to 1 in. in diameter. To this fixed cylinder a thin metal disc, a, is screwed, which is capable of being easily turned, and whose diameter is to in. greater than that of the cylinder. The thread passes through an eye in the projecting part of the disc, round the cylinder, through a second eye in the knee to the reel, w. These eyes are constructed either of glass or porcelain, to prevent the thread cutting grooves in the metal disc or knee. The number of turns of the thread round the cylinder can be regulated by the disc, d, which is kept fixed by the spring, u.

In Fig. 5, Plate V., the thread is conducted between two discs, v and n, either of metal or glass, the upper of which is pressed against the lower by a spiral spring, y, regulated by the screw z. The disadvantage of this arrangement is, that variations in the thickness of the thread affect the tension, on which account linen thread cannot be well employed, being spun much more unevenly than silk or cotton.

TENSION BY FRICTION ON THE SPOOL.

In this arrangement a kind of drag is applied to the flange of the spool, which is constructed of boxwood, with a tolerably large diameter and proportionately small flanges, one of which is about 4 in. thick, to allow of the pressure of a spring regulated by a screw.

The

spring is frequently covered, at the point of contact with the spool, with a small piece of felt or cloth to soften the friction. The same rule applies to the dimensions of the spool as was given in the description of the shuttle spool.

A better arrangement is shown, Fig. 26, Plate I. The spool, b, revolves on the axis, a, which is screwed to the machine. A spiral spring, d, encircling this axis, presses against the spool. The pressure of the spring, and therefore the tension of the thread, is regulated by the set screw, e. Discs of cloth or felt, g and h, above and below the spool serve to soften the motion, and a metal ring, f, is introduced for the spring to press against. The same arrangement is shown in Fig. 6, except that the spiral spring is replaced by a flat one, c, the pressure of which is regulated by the screw, d.

To avoid applying the friction to the wood of the spool, the latter is sometimes affixed to a conical metal axis, to the conical points of which pressure is applied

A bent spring, a, Fig. 5, attached to the framework of the machine, carries the axis of the spool, and the pressure is increased or diminished by the screw, c, attached to the bolt, b. A modification of this arrangement is shown in Fig. 7, Plate II. The spool is fitted on a hollow cylindrical axis, e, revolving round another fixed axis. The ends of the hollow axis are bored out conically, so that the one end fits on the cone, b, attached to the fixed axis, while in the other the cone turned on the piece, g, is inserted. The piece, g, is also hollow, and is prevented from turning on the cylinder by a small screw fitting in the groove, c, of the axis. A ring

of gutta-percha, h, replacing a spiral spring, presses against g, the pressure being regulated by a screw. Similar arrangements are shown, Figs. 16 & 1, Plate VI.

TENSION BY A ROLLER.

The thread is in this case carried over a special, socalled tension roller, and is frequently first stretched before reaching the roller by means of an arrangement shown in Fig. 4, Plate II., consisting of a hollow cylinder with a slot, d, in it, and containing two plugs between which the thread passes. The lower one, a, is pressed against the upper one, b, by a spiral spring, c. The tension-roller has a deep slot round its circumference diminishing in depth, so that the thread, however fine it may be, catches on it, causing the roller to rotate. A drag is applied to the roller by means of a flat or spiral spring.

In Plate VII., Figs. 3 and 20, a tension apparatus of this description is represented. The spool, b, revolves round a spindle, and the thread after passing the preliminary stretcher, c, is passed once round the tensionroller, d, and conveyed to the eye of the needle. The roller revolves round a cylinder, k, fitted on the squarefixed axis, g, but capable of sliding in the direction of the axis. Washers of felt or cloth on either side of the roller serve to soften the motion. Pressure is applied to the moveable axis, k, by a spiral spring, e, regulated by the screw f.

THE THREAD GUIDE.

The tension apparatus being affixed to the bracketarm of the machine, the thread is conveyed over the

head of the bracket through an eye provided for this purpose to the eye of the needle. Assuming, now, the machine in work and the needle at its highest point, with the thread tightly stretched, the needle commences its descent without altering the tension or position of the thread till it reaches the material; it then carries the thread with it, unwinding the thread equal to double the distance from the surface of the material to the lowest point reached by the eye of the needle. The needle having reached its deepest point, the action of the tension apparatus ceases, and the formation of the loop below the material commences, and on its completion is caught by the lower mechanism and more or less extended or lengthened, more or less firmly held and at last released. In many cases indeed the loop is held till the needle in making the succeeding stitch has reached its lowest position, and again formed a loop which has been caught by the lower mechanism. It is evident, therefore, that more thread is unwound for the formation of each stitch than is necessary for the stitch itself. The consequence of this would be that the loop would remain as formed; as, though fresh thread would be requisite for the formation of this succeeding stitch, the friction of the cloth is mostly found to be greater than that of the tension apparatus. Only in thin open materials is the formation of the succeeding stitch sufficient to take up the slack of the previous one.

We have seen that at certain periods both the needle, as also the lower mechanism, consume thread, and that both at certain periods release a portion of the thread in use. It might occur that the needle required thread just at the moment of the release of the same length of