Patent GB-1186031-A (GB)
Title: Improvements relating to Machines having a Support for Guiding a Movable Member along a Path with Precision
Inventor: SARTORIO FRANCO
IPC: B23Q11/00
Filed: 1967-04-07
Abstract: 1,186,031. Balancing. D.E.A. DIGITAL ELECTRONIC AUTOMATION S.p.A. 7 April, 1967 [8 April, 1966], No. 16130/67. Heading B3B. [Also in Divisions G1 and G3] A machine tool with measuring apparatus having a rail 100 for guiding a carriage 101 along a path with precision comprises elastic supporting means acting on the carriage 101 in opposition to its weight in order to compensate for at least a substantial part of that weight and the supporting means comprise another carriage 103 guided and supported by a rail 102 acting on the carriage 101 by means of an elastic interconnection which may comprise (a) a spring 115, Fig. 1, hooked on to the carriage 101 and secured to the carriage 103 by a turnbuckle 117 for adjusting its tension, or (b) a lever (118), Fig. 2 (not shown), pivoted on the carriage 103 and connected at one end to the carriage 101 by a cable (119) and connected at the other end to the carriage 103 by a spring (120) through a turnbuckle (121). If the precision required admits a camber of the rail 100 up to 0À01 mm. the rail 100 may be dimensioned to admit a camber up to 0À01 mm. under a load of only 100 kgs. say, if that is the maximum stress likely to be imposed upon it while being machined say by grinding, the supporting means compensating the remainder of the load, say 2000 kgs. of the carriage 101. The coefficient of elasticity of the spring 115, (120), may be chosen so that the required compensation is obtained with the rail 102 constructed with dimensions allowing considerable deformation under load, account being taken only of safety requirements and breakage coefficients. As applied to apparatus, Fig. 3, for determining the dimensions of very large parts in three dimensions the part 2 is placed on a table 1 and a detector head 12 is moved by applying independent displacements to a bridge 7 on rails 5, a carriage 10 on rails 8 of the bridge 7 and a telescopic support 11 on the carriage 10 by any suitable transmission means, each driven by its own electric motor. The three motors and the detector head 12 are electrically connected with a control device 13 which comprises a programmer for the bridge and carriage movements and apparatus for recording the emitted signals which correspond to the position of the head 12, carriage 11 and bridge 7 with respect to a selected system of co-ordinates. The bridge 7 is suspended by means of four resilient suspensions 15 from a bridge 14 supported on rollers 16 movable over a guide track comprising two rails 17 parallel to and overlying the rails 5. The rails 17 are secured to girders 18 fast on columns 3 and by choosing an appropriate coefficient of elasticity for the springs in the suspensions 15 the rails 5 can be relieved of a high proportion of the weight of the carriage 7 and suffer only a slight deformation say up to 0À01 mm. whilst the girders are of relatively light construction and may bend up to a few millimetres under the load transmitted thereto. Thus the rails 5 need only be strong enough to withstand the stresses applied to them when they are being machined to the shape required to define the guide path which may be rectilinear, circular or sinusoidal.