Locking drill chuck with protection against overtightening

Claim 1

A drill chuck comprising: a chuck body centered on and rotatable about an axis and formed with a plurality of guides spaced about and extending at an acute angle to the axis; respective jaws displaceable along the guides between axial front positions relatively close together and axial back positions spaced relatively far apart; an adjustment ring carried on the body and operatively connected to the jaws for movement from the outer to the inner positions on rotation of the adjustment ring about the axis in a tightening direction on the chuck body, the adjustment ring being formed with an array of inwardly directed ratchet teeth; an antiloosening detent engageable generally radially outwardly with the teeth of the adjustment ring; a spring braced between the antiloosening detent and the body and urging the antiloosening detent outward into engagement with the teeth, the antiloosening detent being angled relative to the adjustment ring such that when engaging between the teeth of the adjustment ring, the antiloosening detent substantially blocks rotation of the adjustment ring on the body opposite to the tightening direction while ratcheting and permitting rotation of the adjustment ring on the body in the tightening direction; an antitightening detent engageable generally radially outwardly with the teeth of the adjustment ring; a spring braced between the antitightening detent and the body and urging the antitightening detent outward into engagement with the teeth, the antitightening detent being angled relative to the adjustment ring such that when engaging between the teeth of the adjustment ring, the antitightening detent generally blocks rotation of the adjustment ring on the body in the tightening direction while ratcheting and permitting rotation of the adjustment ring on the body opposite to the tightening direction; a lockout element engageable with both of the detents and displaceable between a holdback position holding the detents out of engagement with the adjustment ring and a freeing position permitting the detents to engage with and block rotation of the adjustment ring; a guide surrounding the antitightening detent and defining at least one stop therefor, the antitightening detent being displaceable angularly in the guide; and a side spring urging the antitightening detent angularly opposite to the tightening direction in the guide away from the stop, whereby when the antitightening detent is engaged with the teeth it can move in the tightening direction with the adjustment ring only until it engages the stop.