Abstract: An upright concrete mixing chamber having an inlet formed in the top thereof and an outlet formed in the bottom thereof is supported in a lowered position upon a horizontal working surface so as to provide operator access to the inlet when the operator is standing upon the working surface. A plurality of elongate members are pivotably connected at one end to a base member in engagement with the working surface, and at the other end are pivotably connected to the mixing chamber so as to define a parallelogram that is generally horizontal to the working surface when the mixing chamber is in the lowered position.