Feed control apparatus for a machine tool carriage

A feed control apparatus for a carriage which is drivingly connected to a servomotor through a feed screw for slide movement on a guide base of a machine tool, comprising:

• a numerical controller responsive to numerical control information for outputting feed pulses sselectively at a first frequency for rapid feed, a second frequency for slow-down feed and a third frequency for machining feed;
• servomotor control means connected to said numerical controller and said servomotor for controlling rotation of said servomotor in response to said feed pulses output from said numerical controller;
• detection means for detecting whether or not said carriage has reached a velocity checking point defined within a slow-down feed range of said carriage, so as to emit a velocity checking signal when the reaching of said carriage to said velocity checking point is detected;
• abnormality confirmation circuit means capable of confirming whether or not the actual feed rate of said carriage has been reduced below a reference feed rate, which is lower by a predetermined value than a rapid feed rate, and responsive to said velocity checking signal for outputting an abnormality signal when it is confirmed that the actual feed rate of said carriage still exceeds said reference feed rate;
• and
• emergency stop circuit means connected to said servomotor control means and said abnormality confirmation circuit means and responsive to said abnormality signal for causing said servomotor control means to immediately discontinue rotation of said servomotor.