Patent GB-212022-A (GB)
Abstract: 212,022. McDonald, L. R. Jan. 5,1923. Sheets and like elements, travelling.-Apparatus for displaying selectively one of a series of placards comprises a casing in the upper part of which are displayed the index and the required placard and in the lower part the placards are stored and positioned. The index is carried by three leaves 90, 91, 92 which can be swung simultaneously to display the middle one 91 together with either of the end ones 90, 92. The swing- ing means consists of a bar 101 having an offset arm 102 connected by a rod 103 to a crank 104 turned by a manually-operated knob 106. The placards 27 are hung from flat rods 25 the ends of which rest in notches 26 in racks 18 which form with cross-bars 19, 20 a rigid frame slidable horizontally with ball-bearings 22 on rails 17. The under sides of the racks 18 have V-shaped grooves to accommodate the balls 22, so that the travel of the balls relative to the racks is less than their travel on the rails 17. The mechanism for positioning the required placard above the lifting means comprises a handle 6 containing a spring push-button 7 which actuates a pivoted latch 9. The handle 6 slides between two guides 4, and is first of all moved till the latch 9 enters a notch in a spring-pressed member 30 pivoted on the cross-bar 19, the engaging action first swinging the member 30 and thereby pulling a one-way rod 32 which turns a locking rack 31 on the cross-bar 19 out of engagement with a fixed rack 35. On moving the handle 6 till an arrow points to a scale number determined from the index leaves 90, 91, 92 the frame 18, 19, 20 will be moved to bring the required placard under the lifting mechanism. Depressing the button 7 then forces the rack 31 into engagement with the rack 35 and locks the frame 18, 19, 20. The lifting mechanism comprises two slotted uprights 70 in which slide blocks 76 are connected by a crossbar 75. The blocks 76 each carry a U-shaped arm 80 and a pivoted arm 77 notched on the underside and having a cross-pin 78 which engages a pair of cams 79 on the upright 70, Fig. 8. To the outer end of one arm 77 is attached a cord 84 which passes over pulleys 72, 71 in one upright 70, round an adjustable pulley 57, and then round pulleys 38, 51, 39, 52, 40, adjustable pulley 58, and pulleys 73, 74 in the other upright 70, and is fixed to the outer end of the other arm 77 on the other block 76. The pulleys 38, 39, 40 are mounted on a cross-head 37 carrying a spring- held pivoted catch 55 and connected by pistonrods 43, 44 to pneumatic dash-pots 45, 46 pivoted at 47, 48 and communicating by a tube 49 having a control plug 50. The handle 6, with the button 7 still depressed after locking the frame 18, 19,20, is moved forward till the latch 9 engages the catch 55, when, on pulling back the handle 6. the placard is raised by the cord 84 lifting the blocks 76, this lifting action gripping the rod 25 between the grooved pivoted arm 77 and the arm 80. Towards the end of the travel of the handle 6 a spring-controlled pivoted finger 65 engages a recess 67 in the handle' to lock same. A rod 66 pivoted to the finger 65 has a bent. end engageable by the cross-head 37, and when the button 7 is released to free the catch 55, the placard falls by the weight of the parts, controlled by the dash-pots 45, 46. The cross-bar 37 in its backward movement pulls the end of the. rod 66 and frees the handle 6 from the finger 65.