gear 5 with a torque opening mechanism 6 of known type here shown only schematically but illustrated and described fully in the prior art particularly the above mentioned patents an adapter sleeve 7 connects the chuck mechanism to drive means already fully known and particularly further described in the above mentioned patent and transmits the rotary motion of such drive means in a known manner to the chuck mechanism through the torque opening mechanism 6 in the parts of more concern to the present invention there is provided a spring 9 seated on the hub 11 of the drive gear 5 which latter is supported by means already known to the art and the other end of said spring bears against a collar 12 said collar is connected by means of an intermediate sleeve 13 to the upper extension 14 of the sleeve 4 the lower end of the sleeve 4 has an outwardly flaring flange 16 fig1 and 2 having cut in from its periphery notches 17 the chuck jaws each have a body portion 18 with an inwardly facing cam 19 for purposes appearing hereinafter an outwardly facing cam 21 and an inwardly facing groove 22 each of said grooves 22 has a pin 23 extending thereinto from the outward surface of the chuck jaw on the outer surface of the chuck jaw and spaced shortly above said groove is a fulcrum ridge 24 having a rounded outward surface and being of relatively limited circumferential extent the bottle engaging surface of the chuck.