BRITISH PATENT 1.971 - 1857
1.971 John Henry Johnson, of 47, Lincoln's Inn Fields, in the County of Middlesex and of 166, Buchanan Street, in the City of Glasgow, North Britain, Gentlemen, for an invention for improvements in sewing machines. A communication from J. E. A. Gibbs, of Virginia, U.S.A. According to one arrangement it is proposed to produce a single thread, chain, or tambour stitch, by means of a needle and revolving hook, each loop of the stitch being twisted half a revolution after it has been drawn through its predecessor, by which means a firmer and more secure chain stitch is obtained than has hitherto been accomplished by sewing machines of this class. The needle is jointed to the vibrating needle arm, which is actuated by a cam. The shaft which carries the needle cam is fitted or formed into a hook at its front end, such hook being of a peculiar construction. It is gradually increased in thickness from its point, which enters the needle loop towards its shank or shaft and is concavely shaped at the part where the needle loop is in contact with it, for the purpose of not drawing more thread than is requisite. After the loop has thus been drawn open, it will slip off the hook and lodge in an angular recess which the book forms with the shaft. This is effected while the hook revolves from a horizontal to a vertical downward position, such motion giving a twist to the loop through the aid or a spur or cast off on the back of the hook.This cast off is so arranged, in relation to the hook and angular recess, that the loop is spread for the nose of the hook to pass through it on taking a fresh loop from the needle. At this moment the hook has two loops engaged with it, the fresh loop at the joint or nose and the preceding loop, which now bears against the convex part or the hook.The further motion of the hook will allow the latter loop to slip off entirely from the flook, which loop is drawn tight by the opening or spreading of the new loop. Motion is imparted to the machine by drawing the cloth, which is to be sewn through it by hand.The cloth is pressed up the roughened periphery of a revolving wheel which carries a spur wheel gearing into a pinion on a second shaft. This second shaft carries a conical drum, which imparts motion by means of a strap or belt to a second conical drum, the shaft of which carries a spur wheel gearing into a pinion on the cam or hook shaft.The strap or belt is adjusted along the conical drums, so as to vary the relative speeds of the shaft which works the actual sewing mechanism and the feed shaft and consequently regulates the size of stitch, since, if the cloth is drawn through the machine faster or slower in relation to the movements of the needle and hook, it follows that a greater or less length of cloth will be drawn along between each stitch.The joint in the head of the needle is to enable the needle to play laterally and thus admit of the cloth being moved even when the needle is still in it. Modifications of the foregoing arrangements are included in the invention.
Letters Patent sealed. July 15, 1857