Page:Cassier's Magazine Volume XV.djvu/323

Rh requires consideration when choosing a machine.

A Decoudin ironer has been made, having the surface of the hollow cylinder perforated with many thousand holes, for the purpose of letting the steam generated pass off through them at once. It is a praiseworthy endeavour to overcome a real difficulty in a simple manner, but has not made any headway, probably because the moisture does not pass through the padding, and the extra heating power of the steam in the cylinder is lost. One of the faults of most of the machines hitherto described is that the padding on the rollers or cylinders rapidly becomes compressed by use after being put on fresh, and then the reduced diameter does not fit correctly into the bed hollowed out for the larger size when new.

Of ironing machines which handle the goods by the use of endless broad bands, the simplest is illustrated in Fig. 15. It consists of an endless band of heavy felt, guided by passing over rollers, which, being made to revolve, cause it to progress, and are so arranged as to make it press against the polished convex surface of a hollow metal bed heated by steam pressure inside. The details of this machine have been well worked out. The bed can be rotated on trunnions, so that the polished surface can be carried away from the damp bands when not in use, and also for cleaning. The band is held against the heated surface at two places with considerable pressure by means of two loose rollers, A A, which, not being driven independently, have no action either to stretch or loosen the linen passing under them. The lower roller can be depressed or raised so as to give the right degree of tension to the band; and to overcome the difficulty of the band contracting and narrowing in width under certain conditions, this lower roller is made with one-half having a shallow right-hand thread upon its surface and the other half a left-hand thread of such coarse pitch that the effect is to stretch the band wider.

The machine is not made to revolve quickly, because if it were, the band would probably not get dry during the time that it is not being held against the hot bed. It is run at about 12 feet per minute, and at this speed the goods

are found to be properly dried by once passing through. The band is said to last for 12 months, but is expensive to renew. The use of this machine is said to consume little steam; but there does not appear to be any reason why this should really be the case.

The machine illustrated in Fig. 16 consists of four steam chests, or a smaller number, connected together by an end chest, and of an endless band of cotton duck, which is so guided by rollers as to pass over all the steam-chest surfaces and to be pressed heavily against the recesses of the end chest by means of padded rollers. A lower roller, B, is used for regulating the