US Patent 9205189 Reservoir module comprising a piston rod

A product dispensing apparatus including a reservoir module, a dosing module and a dose setting member. The reservoir module includes a front casing section, a block, a first connector, a piston, and a piston rod moveable in a dispensing movement and against the dispensing movement, and including a return block engageable with the block, wherein engagement between the block and the return block prevents the piston rod from moving against the dispensing movement. The dosing module includes a rear casing section, including a second connector which is engageable with the first connector to form a detachable connection between the reservoir module and the dosing module, and a dosing and drive device. The dose setting member engages the piston rod such that it is moveable together with and in the same direction as the piston rod during the dispensing movement and is moveable relative to the piston rod against the dispensing movement.