The machine embodying the parti-coloured ribbons and tabulator devices are generally known as "invoicing" machines, and by simple arrangements, every phase—not only of correspondence, but also of office and statistical work—can be accomplished, with an enormous saving of time. Items can be made on sheets, which may be taken from the machine with absolute certainty that when re-inserted, the subsequent entries will fall into their proper places.
Card Indexing.—For greater convenience in card indexing, special platens are obtainable, or the ordinary platens can be temporarily fitted with a metal clip. Both can be fitted to or removed from the machine in a few seconds, and the cards can be adjusted in an instant. The increasing use of the card file system for a wide variety of purposes lends special importance to the value of the type-writer for this class of work.
Interchangeable Carriages.—For years the thousand and one wide forms, statements, and blanks common in every business office, have been filled by the pen, the reason being that there was no machine practicable for both wide and ordinary work. The manufacturers of most of the modern type-writers now have models embodying interchangeable carriages, which enable any one possessing a machine with this improvement to have at the same time a set of carriages from the largest to the smallest, all of which can be used upon one machine. In one or two makes this is additional to interchangeable platens.
Fig. 231. Interchangeable carriage
Duplicators.—The value of a mechanical contrivance for the rapid and effective multiplication of copies of documents is fully recognized at the present time.
Duplicating machines have been on the market for several years. They will produce from one typescript original up to 3,000 copies, of any size, from a post card to a sheet of brief, every copy having the exact appearance of an original. While there are various makes and styles of duplicators, the main principle is the same throughout. The original is prepared by the now well-known stencil process; that is, writing the matter required with a type-writer on a sheet of waxed paper. The pressure of the type expels the wax out of the paper and leaves openings through which the ink can penetrate. In the Roneo rotary duplicator, a metal frame supports a cylinder of thin, perforated steel. On the outer surface of the cylinder is stretched a linen ink-pad, and over this is placed the stencil. The pad is inked by a rubber roller resting in an ink receptacle suspended between the two sides of the framework. By means of a simple lever this roller can be brought into contact with the cylinder, and ink is thus supplied as required. The cylinder is rotated by a handle. Paper fed into the machine is gripped by a rubber impression roller, which presses it against the stencil as the cylinder revolves, and the sheet perfectly printed, is then automatically discharged on the other side. The rotary can be fitted with three devices, namely a feeder, a simple contrivance, which automatically feeds the sheet into the machine, reducing hand labour to a minimum; an interlever, which automatically drops an interleaving sheet as each copy is printed—thus permitting of the use of highly glazed or very hard paper; a cyclometer for registering the number of copies. The rotary system is far superior to the hand duplicators in the matter of speed; such a machine will print ten copies while the hand device prints one. There is no lost motion, a copy being printed and discharged at every revolution.
Press Copying.—At the present time, there are four methods of letter copying in vogue, namely: (1) The letter-book method, damping sheets and screw press. (2) Roller process, water bath and drying drum. (3) Carbon paper. (4) The chemical letter copier.
The roller copies employ a water bath, and give but little if any improvement in the regulation of the degree of moisture. The copies are wound on a drying drum to prevent off-setting, and subsequently have to be cut apart for filing purposes.