Patent GB-354389-A (GB)
Title: Improvements in and relating to reproducing mechanism for metal cutting or welding machines
IPC: B23K7/00
Filed: 1930-05-10
Abstract: 354,389. Uniting and dividing by fusion. KREBS, C., 70, Lansdowne Street, Boston, U.S.A. May 10, 1930, No. 14477. [Class 83 (iv).] A pantograph machine for guiding one or more cutting or welding torches in accordance with a pattern or templet comprises a carriage 11, Fig. 1, movable along rails 12 and carrying two vertical pivots 14, 14<1> supporting horizontally movable arms 15, 15<1> which are linked together by arms 19, 20. The arm 20 carries the tracing head 26 and one or more torches 21 arranged either on the arm or on an adjustable bracket 22. The arms 15, 15<1> are supported by vertical pins 32 provided with rollers or castors rolling over the surface of the carriage 11, the connection to the arms being preferably through springs. The weight of the torches and linkage is balanced about the arms 15, 15<1> by a balance weight 30 and the pantograph is balanced longitudinally by a weight 31. The arms 15, 15<1> are geared together to eliminate the effect of backlash in the pivots, either by means of gears 41 secured to the arms and meshing with racks 42 supported by rollers 45, 46 and bushes 47, or by cranks on the arms coupled together by rods, or by bevel gears on the arms connected bv a shaft and bevel pinions, or alternatively by helical gears on the arms and helical pinions on transverse parallel shafts. The pivots 14, 141 carry antifriction bearings for the arms 15, 151. The tracer head comprises an electric motor 80, Fig. 3, which together with its reduction gearing 81, 82, 86 is carried by a revoluble platform 100 on the arm 20. The gearing rotates a vertical shaft 87 which is arranged immediately over the point of contact of the tracer roller 90 with a pattern 140, the roller being driven from the shaft through a bevel gear 94 and spur gears 97. The roller is narrow as shown in Fig. 11 so as to follow a line-drawing easily and rollers 150 may be provided to act on opposite sides of a pattern strip 140 at a point slightly in advance of the roller 90 to guide the tracer along the strip. The rollers are carried by levers 151, Fig. 3, pivoted on the axis 91 of the tracer roller and provided with a handle 152 which co-operates with a perforated segment 154 to define the position of the rollers 150 or to raise them above the roller 90 to permit hand control by means of the handle 152. The bracket 102 which carries the rollers and gears is attached to a sleeve 101 rotatable within a sleeve 104 secured to the arm 20 and carries at the upper end the revoluble platform 100. The tracer roller is thus capable of rotation about a vertical axis and of sliding vertically relatively to the arm 20, the supply of current to the motor being maintained by two insulated slip-rings 110, 111 engaging a pair of contacts 113 pressed downwards by springs 130 and mounted on an arm 118 pivoted at 119 to a pillar 120. A spring 126 normally depresses the arm 118, a stop 125 limiting its downward movement, and a hand-lever 132, engaging the platform 100 at 134, provides for raising the tracer roller and motor to allow the tracer to be moved to any position on the pattern. A locking lever 137 may be engaged in a bifurcation 136 in the lever 132 to maintain the tracer in a raised position. The vertically slidable mounting of the tracer relieves the pantograph from distortion due to the weight of the motor, gearing, &c.