Patent GB-190505302-A (GB)
Title: Drafting Machines.
Inventor: LITTLE CHARLES HENRY
Filed: 1905-03-14
Granted: 1905-10-05
Abstract: 5302. Little, C. H. March 14. Draft i n g machines.-Relates to a drawing - board, fitted with a parallel-ruler d e - vice, means for moving the paper on the board, a drawing-instrument carried on the ruler, and an adjustable reference table. A drawing - board 50 is carried by side pieces 53, 54, secured to its under face, and to it are attached side bars 51,' 52, which in turn carry the bottom rail 55 and the top rail 56. The ruler bar 57 is carried by two cord sections 58, 59, which comprise one endless cord. The cord 58 starts from the top left-hand end of the ruler, and passes over the sheave 60, a tension device, a sheave immediately behind the sheave 64 at the upper right-hand corner of the board, and thence downward and over the sheave 62, whence it leads to the right-hand lower edge of the ruler. The cord 59 leads upwardly from where the cord 58 finishes, over the sheave 64 and the tension device, and thence over a sheave behind the sheave 60 and downward over the sheave 66, and finishes at the left-hand end of the ruler 57. This endless cord is made up of a plurality of strands of a material having a high modulus of elasticity, such as brass, steel, &c. The tension device for keeping the cord taut is situated below the board'and comprises two pairs of sheaves 70, 71, carried on two levers fulcrumed on the bracket 67. The levers may be oscillated by links 76, 77, each enclosed by a spring acting between the bracket 75 and set-nuts 80. Each nut may be rotated to the same extent by means of an endless sprocket chain 78, which is kept taut by a spacing-bar 79. The rods 76, 77 are each clamped in any position by means of a pair of spring plates embracing the rod and drawn together by a thumb-screw. In a modification of the tension device, the four sheaves are mounted on a single bar, placed between the two sets of sheaves. The tension of the cord sections is controlled by one link instead of two, but, in this case, the cord sections pass over the sheaves in a different way. The sheaves 62, 66 at the bottom corners of the board may be arranged as shown in Fig. 33, the U-shaped frames 177 being slidab!e on pins 180. This mechanism provides means for trueing up the ruler 57 and also for regulating the tension in the cord sections; in fact, it may ba relied on, if desired, instead of the tension devices described above. The sheaves are constructed as shown in Fig. 22, a ball race being provided between the two blocks 88, 89 and the two riveted plates 86, 85. The parts are secured together by two rings 90, 91 and an internal rivet 92. The bowed portions of the blocks 88, 89 provide a suitable seat for the sheave, in that they are of greater width than the rim of the sheave. A protractor 106 with arrangements 107, 108 for receiving the ends of rulers is pivoted by a single ball bearing 110, between members secured to a traveller 94 slidable on the ruler 57. The edge of the protractor is notched for the engagement of a point 114 on a spring arm 115, the notcher being arranged to correspond with the more commonly used angles. A locking-screw 116 is provided. The traveller is provided with ball bearings contained in ball races formed by grooves in superimposed plates. The balls project through the inner edges of the grooves and engago in grooves formed on the edges of the ruler 57. The two lower bearings are controlled by springs 104. Longitudinal movement of the ruler 57 is prevented by one or, if desired, two rollers 117, carried on the underside of the ruler and engaging with either the edge of the drawing-board or that of the side bars 51, 52. The cord sections are attached to the ruler by means of binding-screws 120, arranged on plates 118 beneath the ruler. A sheet of drawing- material is adjustably secured to the surface of the board by means of two bars 121, 122, one above and the other below the board. The material is held on the bar 121 by means of clamps 130, 131, the latter being spring-controlled so as to stretch the material, and to the bar 122 by straps 142, 143 passing over a roller 126. The straps are adjustable and also arranged divergently so as to keep the drawing-material tight. The bars 121, 122 are moved by cords arranged in a similar manner to those of the ruler movement, a tension device 125 being also provided as before. Preferably, instead of the bar 121, a thin sheet-metal bar 135, Fig. 14, is used, the drawing-material being fastened to it by binding-disks 136, some of which are adjustable longitudinally. A clip consisting of two jaws spring together and adapted to be opened by a cam action may be used to hold the material on the bar 135. The roller 126 is journaled in a yokeshaped spring frame 147, Fig. 14, its trunnions being guided in slots in the bars 63. Anadjusting- lever 149, pivoted in the side bar 51 and adjustable by a ratchet arrangement on the bar 52, seves to give the necessary tension and adjustment to the drawing-sheet. A simpler arrangement is shown in Fig. 1, in which the roller 126 is controlled by springs encasing the rods 201. 'A different method of attachment of the drawing-sheet is obtained by attaching the lower edge of the sheet by binding- screws to a bar carried on the forward end of an apron passing over the roller 126 and secured to the bar 122. In the same way, two drawing sheets, i.e. a sheet of paper and a sheet of tracing-linen, may be mounted together, if desired, by a mere duplication of the attaching mechanism. A method is shown in the Specification by which two drawing-sheets are secured by clamping to two aprons carried over the roller 126, from two spring- controlled rollers situated on the bar 122. A reference table is mounted on the board so that it may be drawn forward or pushed back out of the way of the draughtsman. The device is shown in Fig. 24, and comprises a table 157 pivoted at its lower edge to U -shaped side-pieces 155 carrying rollers engaging in grooves in the side bars 51, 52. A cross-bar 159 supported by two standards 160 secured to the U-pieces 155 forms a support for the table, but the latter when pushed back is supported by the roller 162 on the bracket 161 in the dotted-line position, thereby bringing the drawing carried by it more plainly into view. A counterweight in the form of a bar 163 is suspended by a pair of cords 165, and it may be supplemented or supplanted by an apron 187 secured to the table 157, passing over a cross-bar 189, and attached at its other end to a spring roller 188. This apron keeps the table square with the board and also serves as a covering for the drawing-sheet. An instrument tray 182 and stop 158 are provided on the table, as well as an adjustable frame 167 for carrying a series of lamps.