GB847358A - Improvements in or relating to drawing office appliances - Google Patents

Abstract

847,358. Drafting machines. HALL HARDING Ltd. Aug. 21, 1957 [Aug. 14, 1956], No. 26436/57. Divided out of 847,357. Class 97(3) In a drafting machine having a drafting head movable parallel to a drawing board the drafting head carries a pivotally mounted scale arm unit bearing a pair of spaced limit stops engageable by a retractable member to allow the unit to be swung between two angular positions determined by the abutment of each limit stop with the retractable member. As shown in Fig. 1 the drafting head is movable along a tube 34 itself movable transversely across the drawing board 12, and carries two scale arms 96, 98 mounted on a plate 86, Fig. 2, pivoted at 82 to a plate 80 on a carriage 60 movable along the tube 34 as in Specification 847,357. The plate 86 has a clamping nut 110, Fig. 1, moving in a slot 106 in the plate 50. To allow the tubes to be located in two positions spaced at angles 45 to 90 degrees and 30 to 60 degrees the plate 86, Fig. 2, has attached thereto a sector plate 116 having two insets 118, 120, Fig. 3, engaged respectively by a retractable pin 122, 124, the inset 118 defining two angular positions of 40 and 90 degrees and the inset 120 two angular positions of 30 and 60 degrees. The pins 122, 124 are carried by an arm 132 centrally pivoted at 134 and rocked by a pivoted lever 142. With the lever in central position both pins are free of the plate 116. On rotating the lever the arm 132 is tilted to lower one or other pin into engagement with a recess in the plate 116 to bring the stops into operation. A modification of essentially similar construction is also described.