loom

loom, frame or machine used for weaving; there is evidence that the loom has been in use since 4400 b.c.

Modern looms are of two types, those with a shuttle (the part that carries the weft through the shed) and those without; the latter draw the weft from a stationary supply. There are basically three kinds of shuttleless looms. The dummy shuttle, the most widely used, contains no weft but moves through the shed depositing a trail of yarn. A second type, the newest of looms, makes use of jets of air or water to force the weft through the shed. A third kind, called the rapier type and widely used in carpet weaving, uses steel rods to move the weft into the shed.

The fundamental parts of all looms are the warp beam, a cylinder on which the warp threads are wound; heddles (rods or cords), each with an eye through which is drawn a warp thread; the harness, a rectangular frame set with a series of heddles operated to form a shed between the warp threads for the insertion of the weft threads; the reed, a comblike frame that pushes the filling yarn firmly against the finished cloth after each pick, or row; the breastbeam, over which the cloth is wound creating a tension with the warp beam; the cloth beam, on which the cloth is rolled as it is constructed; and the shuttle, if it is not a shuttleless loom.

Vertical looms, such as the Navajo and some tapestry looms, developed from the practice of hanging the warp beam from a tree and holding the yarns taut with stones, pegs, or a weighted pole. The horizontal form, at first two poles holding the warp extended on the ground, was widely used for the Western European handloom and for the foot loom, the forerunner of the modern power loom. In the foot loom the harnesses were operated by treadles, leaving the hands free to pass and catch the shuttle. John Kay invented (1733) the automatic fly shuttle, and in 1760 his son Robert devised a drop box by which trays automatically brought bobbins of colored threads in line as desired. These aids to weaving encouraged inventions to speed up spinning, which in turn made faster weaving essential.

Edmund Cartwright patented (1785) the first practical power loom, the basis of the modern loom with its multiplicity of automatic devices. By 1804, Joseph Marie Jacquard had perfected an attachment applicable to the power loom whereby any design might be woven on it. In the modern Jacquard, one repeat of the design is laid out on squared paper, then punched on cards that are laced into a continuous chain rotated on an overhead device. The cards are brought in contact with needles, each controlling a wire that lifts a heddle when the needle passes through a hold in the card. In the Lefier robot, a design made on copper with insulating paint is transmitted by electricity to needles that lift the heddles.

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