Mixing machine

Claim 1

A machine for mixing chemical solutions contained in a plurality of glassware containers, said machine comprising: a rack structure adapted to hold the containers in upright positions in spaced apart relation to one another; a frame adapted to rest on a support surface; a tumbler mounted on said frame for rotation about a substantially horizontal rotational axis, said tumbler being adapted to closely receive said rack structure; power means for driving said tumbler about said rotational axis to tumble said containers, thereby mixing the chemical solutions contained therein; means for maintaining the containers substantially stationary relative to said tumbler during rotational movement thereof, whereby to prevent shifting of the containers in the tumbler; an electric circuit activating said power means when completed and deactivating said power means when interrupted; a timing switch in said circuit which is closed to effect completion of said circuit for a preselected time period and which opens following elapse of said time period; a normally closed switch arranged in said circuit in parallel with said timing switch to normally maintain said circuit in a completed condition regardless of the state of the timing switch; and means for opening said normally closed switch each time said tumbler is oriented to orient said containers in upright positions, whereby said timing and normally closed switches are both open to interrupt said circuit only after said preselected time period has elapsed and said tumbler has reached an orientation to orient the containers in upright positions.