Harmonic composite grind

Claim 1

Apparatus for automatically grindIng pneumatic tires to correct both for radial composite road force variations and a harmonic of said force variations comprising in combination: means mounting a tire for rotation about a first fixed axis; grinding means for removing small amounts of rubber from the tread shoulder of a tire; a load wheel mounted on an axis parallel to said first axis; means to rotate said tire in contact with said load wheel so as to positively rotate said load wheel; means for sensing force variations caused by the force reactions between said tire and said load wheel and for converting said force variations to first analog electrical signals; peak detector means connected to receive said signals; storage means connected to receive and store said signals; means providing a pair of further signals, the magnitude of which are pre-determined and proportional to the acceptable amount of composite radial force variation and the maximum amount beyond which a tire may not be ground; comparator means connected to receive and compare said first analog signals with said further pair of signals; means for driving said grinding means if said analog lies between said pair of signals and to continue to grind said tire until said analog reaches a predetermined value; means for generating second analog signals which are a harmonic of said first analog signals; means for comparing said second analog with predetermined reference signals; means for driving said grinding means if said second analog lies between predetermined limits; and means for terminating the grinding of the tire when said second analog signal falls to a predetermined value.