tension apparatus, w, Fig. 3, and from thence to the looper.

The same tension apparatus is applied to the upper thread, which, however, is then conveyed through a slit in the rod k, round which is a thin spiral spring of brass pressing the thread gently in an upward direction. This arrangement is shown in full size, Fig. 12. A T-shaped steel plate, h, Fig. 11, together with another similar-formed piece, but with only one arm, are attached by a screw to the needle lever. Their projecting arms are covered with cloth at their point of contact, and between them the thread coming from the spiral spring is held tight when the needle has completed in. of its ascent, as otherwise the thread would be held taut by the spiral spring, thus preventing the formation of the loop. This apparatus, rising however with the needle lever, draws the thread with it, only however to the extent of half the quantity set free by the ascent of the needle, and it is on this account that the ascent of the needle for the formation of the loop must be made double as long as would otherwise be necessary.

D. MACHINES FOR QUILTING-STITCH, WITH MOVEABLE

SHUTTLES.

The first machine of this description was constructed in 1834, in America, by Walter Hunt; but although the principle was the same as that now employed, yet defects in the mechanical arrangements prevented its application till 1846, in which year Elias Howe introduced a similarly-constructed machine with great success. This machine was still further improved upon by Singer, of New York, who first introduced the method

of imparting motion to the shuttle by a crank and connecting rod.

1. SINGER'S SYSTEM.

Singer's machine is shown in Plate IV., Figs. 1, 2, 3, and 4. It has two driving shafts parallel with the axis of the machine, one of which is above, the other below the sewing plate. Cog-wheels are generally affixed to these shafts, driven by a larger wheel, which is generally cast in one piece with the sheave of the machine. This arrangement is shown in Fig. 18, Plate III. The following arrangement is shown in Figs. 1, 2, 3, 4, Plate IV. To the hinder-ends of the two driving shafts are attached two sheaves of 3 in. diameter, each provided with a stud, at a distance of 1 in. from its centre. A perfectly similar sheave works on a pin attached to the lower part of the machine, parallel and at the same level as the lower driving shaft, and at a distance of 4 in. from it. The studs of these three discs are connected together by a cast-iron triangle, communicating the rotary motion of the lower to the upper sheave. To prevent the occurrence of a dead point, the third disc is introduced; for a dead point occurring in the position of the two main shafts, as is shown in Fig. 3, Plate IV, the lower shaft still presses against the stud of the third disc, and this pressure is transmitted to the upper sheave, and an equable motion is thus produced. In the front of the upper shaft is a disc having a roller attached, working in a kidney-shaped groove in the needle carrier. The shuttle is propelled by a crank on the lower shaft by means of a connecting rod. The driver is, as shown in Fig. 1, constructed of two pieces screwed

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together, the lower of which has a long continuation the lower end of which is exactly on a level with the lower shaft, so that the connecting-rod, acting on this end, moves in a horizontal direction. The driver has, on both sides, projections, between which the shuttle lies; the one on the left side, a, Fig. 18, acting on the heel of the shuttle remains in. from the guide plate, which facilitates the tightening of the loop of the upper thread when the shuttle has passed through it, as the thread of the loop must pass between the projection, a, and the heel of the shuttle. The front projection, b, fits into a corresponding cavity, p, in the upper surface of the shuttle point, and effects the return motion of the shuttle. The latter has about in. play between the two projections of the driver, so that when the projection, a, is in contact with the shuttle, there is sufficient space between the projection, b, and the shuttle point to allow the thread of the loop to pass freely, as shown in Fig. 22, A. This shape of the driver has the advantage over others which will be described later, that the pressure of the projection on the point does not cause an increase of friction between the shuttle and the guides. The driver is sometimes constructed of brass, sometimes of cast-iron.

1 2

The shuttle has a length of 24 in. Its point being at the commencement of the motion, in. distant from the needle, Fig. 22, E, and its heel having at the conclusion of the stroke exactly escaped the needle, Fig. 22, C, 24 in. result as the length of the motion of the shuttle, giving 1 in. for the length of the driving crank. The needle after penetrating the material enters a groove in the shuttle guide, intended to protect the needle, and varrying

from to in. in width, and of at least the same depth. The needle must fit into the groove so that the shuttle passes close to it without touching. If the needle is too far back the shuttle is apt to miss the loop, and if it projects either it or the shuttle point is liable to injury. If we imagine the shuttle in the middle of the loop of the upper thread the thread would be caught between the shuttle and the guide, the latter is therefore slightly hollowed out, k, Fig. 18.

To determine the form of the kidney-shaped groove in the needle carrier we must revert to the motion of the needle and shuttle which are dependent one on the other. The piece containing the groove is shown in Fig. 20. The centre of the roller driving the needle carrier describes the line k c d e. In Fig. 19 the inner circle shows the path described by the roller. The outer one, that described by the crank, imparting motion to the shuttle. The direction of the motion is shown by the two arrows, and the numbers 1, 2, 3, 4 and 5, the cotemporary positions of the roller and crank, to which again the relative positions of the needle and shuttle in Fig. 22, A, B, C, D, and E, correspond. The line k c d e consists of three parts, of two straight lines, k c and d e, and of a curved line, c d. It is evident that the points k and e must be at the same distance from the perpendicular axis of the needle carrier as the roller is from the axis of the upper main shaft. Imagining the roller to commence its motion at k, it will, on arriving at 5, have depressed the needle carrier, h, 5. On passing 5 it again raises the needle and has, on arriving at 1, raised it sufficiently for the formation of the loop, so that the needle can remain stationary. As

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the ascent necessary for the formation of the loop is in., the difference between 5 h and 1 c must also be in. The length of 5 h is ascertained from the position of 5 in the circle described by the roller, and this is determined by the curve, 5 k, being half a right angle. The length of 5 h being found it follows that 1 c = 5 h, -in., and from this the position of 1 is determined. The corresponding point in the crank circle is derived from the condition that the shuttle must have accomplished the first in. of its motion when the needle has formed the loop. The needle commences slowly to ascend when the shuttle has completed its motion, at the moment the shuttle has reached the point shown in B, Fig. 22. This gives the position of 2 on the crank, and of the corresponding point on the roller circle, from which follows the end, d, of the curve described round the centre, b (a b= 1 c.), with the diameter of the roller circle. The line dc forms the rectilinear continuation of this curve, so that the central line of the kidney-shaped groove is now complete. The shuttle having completed its advance the needle rises, Fig. 22, C, and having reached its highest point, 4, the shuttle has already commenced its return motion, Fig. 22, D, which being completed, the needle has again reached its deepest point, Fig. 22, E. It now only remains to determine the diameter of the circle described by the roller. The ascent of the needle is composed of the distance necessary for the formation of the loop, and the diameter of the before-mentioned circle, or the diameter is equal to the difference of the ascent of the needle, and the portion necessary for the formation of the loop. We must, therefore, first determine the distance of the ascent.