Tuesday, December 22, 2009

The Mechanical Loom

Programmable textile machinery provided inspiration for the player piano and the early computer

A master weaver in 18th-century Lyon, France, Jean-Charles Jacquard was able to fabricate no more than six inches of silk brocade a week. Even that production rate was feasible only with the aid of an apprentice to sit atop his wooden draw loom, raising individual warp threads by hand while the maître slid through brightly colored threads of weft. The unrelenting tedium of weaving a pattern line by line may explain why his son, Joseph-Marie, avoided it even before the French Revolution briefly put brocade out of fashion. Only after squandering his family inheritance did Joseph-Marie reconsider—and even then, instead of becoming a master weaver, he invented a machine to save himself the labor.

Jacquard’s key idea was to store brocade patterns on perforated cards that could be fed through the loom, with one card per line of weaving. The loom would read the arrangement of holes punched on a card with a lattice of spring activated pins connected to hooks that would each individually lift a warp thread wherever a pin entered a hole. In this way, the loom could be programmed, and patterns could be modifi ed or switched by rearranging or replacing the card deck. Patented in 1804, an expertly operated Jacquard loom could produce two feet of brocade a day, a feat impressive enough, given France’s dependence on textile exports, to merit the device a visit from Napoleon. Yet not even the notoriously ambitious emperor could have appreciated the significance that Jacquard’s invention would have to future generations.

As it turned out, holes punched in paper provided a ready-made solution for developing any kind of programmable machine. Inside the pneumatic mechanism of a pianola, one punched roll would play a Bach toccata, while another would play a Gershwin rag. Vastly greater was the versatility inside a computer, as 19th-century British scientist Charles Babbage imagined with his unbuilt Analytical Engine and as American engineer Howard Aiken realized in the 1930s when he constructed the Harvard Mark I at IBM. Following Babbage’s lead, Aiken made stacks of Jacquard punch cards operate in tandem, with one stack setting the operation applied to read data from another.

In modern computers the cards are gone (as are Aiken’s electromechanical switches), but computers still embody essentially the same architecture. And although industrial looms are no longer manned by masters of the craft such as Jacquard’s father, Joseph-Marie’s innovation brings even weaving to ever higher levels of efficiency through the computer consoles that control the patterning of modern textiles.—Jonathon Keats

Source of Information : Scientific American September 2009

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