Patent ID: 7036977

Claim:
A precision regulating device for a timepiece having an oscillating system with a hairspring, said precision regulating device comprising: a balance cock; an index regulator pivotally mounted on said balance cock such that said index regulator is pivotable in a pivoting direction about a regulator axis, said index regulator having a hairspring key arranged at a radial distance from said regulator axis for changing an active length of the hairspring of the oscillating system of the timepiece in response to pivoting of said index regulator about said regulator axis, said index regulator further comprising a regulator pointer extending radially from said regulator axis; a regulating screw threadably connected to one of said balance cock and a component connected to said balance cock; and a counterpressure spring comprising a resilient arm and having first and second ends regions, said first end region of said counterpressure spring connected to said balance cock and said second end region comprising a free end region prestressed against said regulator pointer for urging said regulator pointer in the pivoting direction into abutment against said regulating screw such that said regulating screw provides a force on said regulator pointer opposing the urgency of said counterpressure spring, said resilient arm of said counterpressure spring having a holding-down region positionable on an axial side of said regulator pointer relative to said regulator axis.