Page:EB1911 - Volume 27.djvu/521

Rh for two or more characters. For example, in the former class there is one key for the capital A and another for the small a, the keys being arranged in two banks corresponding to the upper and lower cases of a printer's type-case; in the latter, one key is capable of striking both the small and the capital letter, and it does one or other according as a subsidiary key is or is not brought into simultaneous use with it. In type-bar machines designed on this plan, each bar carries two or more letters (cf. fig. 1). This form of keyboard is also applied to type-wheel machines. Though there are numberless differences in detail, all type three times as wide as would be possible in had a hanger to itself (fig. 2); in addition can be taken up by the screws seen on the ¢ right of the bearings, and as=a further precaution each type-bar is locked at the, conical pins, which centre it exactly in the V required place. In the Yost and the Empire the type-bars pass through guides. The centre guide of the former is shown

printing point by falling between a pair of at. G-in fig. 3, the type being just about to strike the paper. Pressure on one of the keys works the lever and pushes up the connecting-rod C, when the type leaves

FIG.  - Central Guide an Type-bar of Yost Machine. the same space if each the wear of the pivots writers, apart from the index machines, bear a general resemblance to each other in their mechanical arrangements. The really essential operations may be reduced to two; the machine must print a letter when a key is struck, and it must have a device by which the paper may be moved a short distance to the left with each stroke in order that the letters may be printed separately, not one on the ink-pad P and passes through the guide, which is slightly bevelled so as to guide it exactly to the printing point. In the Smith Premier the shafts upon which the type/W-

top of the other. Of the many f subsidiary appliances that are fitted -a bell to warn the operator that he is approaching the end of a line, a lock to prevent the machine

-»   iffrom working after the end of the line has been passed, attachments for facilitating insertion of fresh paper, corrections, and tabulation, &c.-some are certainly of advantage, but others are more useful to the manufacturer in drawing up his advertisements than to the expert operator, whose first care often is to disconnect them from the machine. Similarly with the “ visible writing, ” which is some recommendation of extraordinary importance; doubtless the novice who is learning the keyboard finds a natural satisfaction in being able to see at a glance that 1 he has struck the key he was aiming at, but to the practised operator it is not a matter of greatmomentwhetherthewriting = is always in view or whether it is only to be seen by moving the carriage, for he should as little need to test the accuracy of his performance by constant inspection as the piano-player needs to look at the notes to discover

F IG. x.-Type-bar of Oliver Machine. times, put forward as a whether he has struck the right ones. The one important desideratum, without which no type::|

FIG. 4.-Type-bar Bearings, Smith Premier. bars' swing are mounted tangentially on the ring (fig. 4), so that long supporting bearings are obtained, while the shortness of the tlype-bars themselves renders it possible to make them. very stiff. he rocking-shaft mechanism (Hg. 5), by which the power is transmitted from the keys to the type-bars, admits of each key havin the same leverage ang tends to uniformity of 2 touch. This last quality is also aimed at by interposing an intermediate parallel bar between the A key levers and the typebar, as in the New Century Caligraph. In the Dens-, I ~more the friction ~of .the '“ movements is minimized by the employment of ball Fig. 2.-Type-bars of Bar-Lock Writer can produce work of satisfactory appearance, is accuracy of alignment. For the attainment of this the use of type-bars has given wide scope to the ingenuity of inventors, who have been confronted with the problem of making a system of levers at once strong, rigid and light, and of supporting them on bearings which are steady and adjustable for wear in conditions Where space is much restricted.

Machine. In the Oliver machine the ty e-bar is of the form shown in fig. I, to secure stiffness and a double bearing. In the Bar-Lock, the type bars are arranged three in one hanger, so that each has a bearing pivots, Electrical typewriters, in which the, de pression of a key does not work a type-bar directly, but merely closes a circuit bearings for the type-bar that energizes an electromagnet, have been suggested as a means of obtaining uniformity of touch combined with ease and rapidity, but have not as yet displaced the

FIG. 5.-Rocking-shaft Mechanism of Smith Premier. I, Key with stem. 2, Rocking shaft. 3, Connecting-rod. 4, Type-bar. A and B, Conical bearings, 1% in. apart; ordinary machines to any extent. One special form of typewriter, the Elliott-Fisher, is designed to write in a book such as a ledger. One leaf is clamped between. the platen and an open frame which holds the paper smoothly. The, operative parts slide on this frame, and move up and down the page so as to space the -lines properl, the keyboard, with the typebars, ribbon, &c., travelling step by step across the page. An adding device may be combined with this machine.