Lockable hammer-drill chuck

A drill chuck comprising:

• a chuck body rotatable about a chuck axis and formed centered on the axis with
• an axially forwardly open tool receiving hole,
• an array of axially extending guides opening axially forward into the hole,
• an axially forwardly directed rear shoulder and
• a front shoulder having an axially forwardly directed front surface;
• respective externally toothed jaws axially displaceable in the guides;
• an internally threaded actuating ring meshing with the jaws and rotatable on the chuck body about the axis to axially displace the jaws in the respective guides;
• an elastically deformable support washer bearing axially forward on the actuating ring and having an inner periphery bearing axially backward on the rear chuck-body shoulder, the washer having a radial dimension and bearing on the rear chuck-body shoulder over a radial distance equal to at most one-half the washer dimension such that the support ring projects at least halfway from the chuck body;
• a tightening sleeve axially and rotationally coupled to the actuating ring and having an axially rearwardly directed front surface axially confronting the front chuck-body shoulder surface, the sleeve and ring being axially displaceable on rearward elastic deformation of the support washer from a forward position with the front shoulder surface out of contact with the front sleeve surface when the washer is generally undeformed and a rear position with the front sleeve surface bearing axially backward on the front shoulder surface when the washer is elastically rearwardly deformed;
• and
• means on at least one of the surfaces for increasing the coefficient of friction thereof relative to the other of the surfaces.