In machine tools with motor-driven work spindles, enormous impact forces act on the work spindles for a brief period of time with tool collisions at high feed speeds. In order to ensure protection for impact-sensitive components during collisions, special safety concepts for making possible a deflection of work spindles are used.
From DE 10 2007 032 498 A1, a safety device for a motor spindle is known, arranged in a housing, with an outside ring and an inside ring arranged axially, so it can be displaced and tipped, within the outside ring, to hold the motor spindle. The inside ring is pretensioned, relative to the outside ring, in the axial direction, by several compression springs, distributed over the circumference. By means of the axially acting compression springs, the inside ring is pressed, with a prespecified pretension force, into an operating or starting position within the outside ring. For an additional holder of the inside ring in the operating position, radial barrier elements, which are impinged by springs, so as to mesh into corresponding indentations of the outside ring, are provided on the outside of the inside ring. Only when a threshold force is exceeded are the barrier elements pressed against the force of the springs, wherein the inside ring can disengage and move against the force of the axial compression springs. With this known device, the holding force, however, is produced exclusively by springs, which can have a disadvantageous effect on the rigidity of the entire arrangement.