Water heater tank arrangement, control device and shaft extension therefor and methods of making the same

In the combination of a water heater tank having a heating means therefor, and a control device carried by said tank and having operating means to sense the temperature of said tank and to operate said heating means in relation to said sensed temperature and a selected temperature of said control device, said control device having a housing means and having a temperature selector means rotatably carried by said housing means to set said selected temperature, said selector means comprising a knob provided with a transverse slot means therein, the improvement comprising a shaft extension having a longitudinal axis and opposed ends one of which has a substantially flat end surface that is substantially transverse to said axis and has drive means thereon that is snap-fitted into said slot means so that said knob is adapted to be rotated upon the turning of the other of said ends of said shaft extension, said slot means of said knob and said drive means of said shaft extension providing a swivel connection therebetween so that said shaft extension can wobble relative to said knob while still providing a driving relation therewith, said drive means of said shaft extension comprising an elongated substantially rectangular part disposed transverse to and in alignment with said axis, said elongated part having a centrally located projection thereon that is spaced from said flat end surface and is substantially parallel to said flat end surface, said slot means of said knob having a first section that receives said elongated part of said shaft extension therein in a splined manner and has a second part that defines an internal shoulder means of said knob and receives said projection of said shaft extension therein with a portion of said projection being disposed behind said internal shoulder means.