GB772047A - Improvements in, or relating to, drafting machines - Google Patents

Abstract

772,047. Draughting machines. MAVITTA DRAFTING MACHINES, Ltd. July 21, 1954 [July 24, 1953], No. 20559/53. Class 97(3) A head for a draughting machine has a domed knob rotatable relatively to an index plate carried upon an arm of the machine, the index plate has a ring of equally spaced recesses, a manually-operated trigger mounted within the knob is spring-driven into any of the recesses, and a spring-loaded plunger is installed in the knob to engage the trigger when it is disengaged from the index plate. As shown, an index plate 4 is secured to a housing 5 carried by an arm of a draughting machine. A bolt 3 journalled in the housing is fixed at its upper end to a degree plate 2 which carries a domed knob 1. A pair of arms 7 with straight edges 8 at right-angles is mounted on the lower end of bolt 3. An L-shaped trigger 21 is mounted on a spindle 17 mounted in lugs 15 on both sides of a slot 16 in the degree plate 2, and has a nose 23 urged by action of a spring 22 through slot 16 into one of a series of notches 9 formed in the index plate 4 in a ring with an angular separation of 15 degrees. A finger piece 25 secured to the trigged and projecting through the wall of knob 1 enables the nose 23 to be lifted out of engagement with the index plate. A plunger 27 slidably mounted in the knob 1 and urged outward by a spring 28, may be pushed in until its enlarged end 29 engages the trigger 21, when it is raised to hold it out of engagement with the index plate. A bracket (not shown) secured to the index plate carries a vernier 30 which, in conjunction with the scale on the degree plate 2, enables the straight edges to be set accurately to a desired angle. Specification 763,333 is referred to.