PURPOSE: To decrease the size of a machine tool itself, by a method wherein a means, which prevents production of rolling moment on a cross rail guiding a main spindle head and a column and inclination of the cross rail, is located to the weight compensating device of the main spindle head of a portal type machine tool.
CONSTITUTION: In a weight compensating device, the weight of a main spindle head 18 is supported by a pair of balance beams 22 positioned facing each other with a balance therebetween, and thereby a bending force and rolling moment are prevented from being exerted on a cross rail 16. Further, both ends of the balance beam 22 are hung by means of a chain 26, and a load 28, balanced with the weight of the main spindle head 18 and its balance beam 22, is exerted on the chain 26 from the side opposite to a column 14. Thus, rolling moment produced by dint of the weight of the main spindle head 18 is prevented from being exerted on the column 14. Further, since the moving amounts of the chain 26 lifting the both ends of the balance beam 22 are coincided with each other, even if the main spindle head 18 is located in any position in a horizontal direction, a chain support part is always held in the smale level, and the cross rail 16 is inhibited against inclination.
ITO YOSHITOSHI
KOREDA NORIYUKI
IMAMURA YOSHITERU
WATABE TAKESHI
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