Patent GB-190911156-A (GB)
Title: Printing Mechanism for Typewriters.
Inventor: FAIRWEATHER WALLACE
IPC: B41J7/02
Filed: 1909-05-11
Granted: 1909-10-21
Abstract: 11,156. Fairweather, W., [Emerson Typewriter Co.]. May 11. Type-lever actions; letter-spacing mechanism.- The key-levers, key-lever springs and stops, cranked type-levers, universal bar, and other parts of the mechanism are arranged so that the keys all require the same stroke or blow to produce equal impressions on the paper. The keys are arranged in three or more banks, three being shown, and in groups of three, the key-levers 17, 18, 19 of each group being successively of greater length and extendiog into the three banks. The key-levers are mounted on a pivot-red 20, and are individually spaced by means of guide-slots 23 in a wall 14 of the framework. The rear ends of the key-levers are provided with arms 25, 28 ; the arms 28 have bosses 29, 30, 31 and the distances of these bosses from the pivot 20, and the lengths of the arms 25 are approximately proportional to the lengths of the key-levers. The arms 28 are guided in slots in a wall 33. The bosses 29, 30, 31 are adapted to act respectively upon prongs 37, 38, 39 of a universal bar 34, constructed as shown in Fig. 6, which is pivoted at 35. By this arrangement, inequalities of movement of the universal bar are avoided. A vertically movable type-lever frame comprises rails 40 connected by rails 43, 44 and a cross-head 48. The rails 40 are provided with journal recesses for the type-levers ; and a frameplate 47, secured thereto, retains the type-levers. The type-levers are in two sets ; and each lever comprises a cranked shaft, an intermediate part 55, and a type-head 56, bearing three types adapted to swing in an horizontal plane. The lengths of the shafts and parts 55 vary, and the normal disposition of the type-levers, Fig. 1, is such that the inner lighter levers swing through a greater angle to the printing-point than the outer heavier levers, the intermediate levers being disposed at uniformly varying angles. The levers are of flat formation, and nest together closely ; the flattening of the intermediate parts 55 reinforces the typelevers against bending &c. when printing takes place. The arms 25 of the key-levers are connected with the type-levers by links 59, which are adjustable in length by means of turn-buckles 62, and are loosely hooked around the cranks 54 and to holes in the arms 25. After the initial adjustments, the turn-buckles may be soldered or otherwise rigidly secured in position. The rear ends of the links are guided between horizontal rods 70. The cranks 54 are normally disposed in various planes, as shown in Fig. 4. The initial pull on the outer type-lever is perpendicular to the crank 54 ; at the end of the stroke the crank is almost in its dead-centre position, and the pull on the crank is practically eliminated. In the case of the innermost type-lever, the crank moves from a position of small efficiency to one in which it is at a substantial angle to the link, and none of the momentum acquired at the beginning of the stroke is lost. This arrangement tends to equalize the differences due to the varying weights and dispositions of the type-levers. Further equalization is secured by means of a spring plate 63, the prongs of which are of three different lengths, and bear against the arms 25. The strength of the prongs v@aries inversely as the lengths of the key-levers. In addition, the prongs of the groups increase in length, and thus diminish in strength, from the centre to the sides of the machine, owing to the fact that the groups of arms 25 of the key-levers increase in length from the sides to the centre of the machine, the arm 25 of the long centre keylever engaging its link 59 at the greatest distance from the pivot 20. The innermost type-levers may be weighted to correspond more closely with the outer levers. A notched stop-bar 66 enables the key-levers to be depressed through angles which are inversely proportional to their lengths, and a rubber-covered bar 69 limits their return movement. Coiled springs on the shafts hold the type-levers in normal position against rests comprising members 73, 75, 76 secured to the typelever frame. Leather buffers are provided on the bars 73 and the tension of the springs may be graduated. These springs prevent the links 59 from impeding the vertical movements of the typelever frame, but they may be dispensed with, in which case the spring prongs on the bar 63 may serve the same purpose ; otherwise, the sphere of action of the spring prongs is limited by the bar 69. Shields 79 overlie the type-levers. Alining for impression.-A yoke on the crosshead 48, Fig. 1, carries a type-lever guide 50 of V-formation, a hole in which is adapted to receive pins 72, Fig. 2, on the type-levers and lock the levers firmly at the printing-point. Case-shift mechanism; shift-key actions.-The type-lever frame is lifted into position to print capitals from the lowermost type by means of a key-lever 80, 81 having a cam 82 engaging a pin 83 on a lever 84 which is slotted at 86 for engagement with a pin 87 on the type-lever frame. A lever similar to 84 is provided at the other end of the shaft 85 A key-lever 89, 90 normally prevents the pin 83 from moving under the influence of the weight of the type-lever frame, but when depressed, allows the frame to drop in order that punctuation marks may be printed from the uppermost type. Springs 88 tend to lift the frame, and springs 92 secured to fingers on the shift-levers serve to return the levers; the return of the lever 89, 90 lifts the type-lever frame to normal position.