This invention provides a brewing head unit of a coffee machine for inserting and locking the filter and the filter holder into the brewing head of a coffee machine. The filter and the filter holder can be inserted into the coffee machine visually. This invention further provides a simpler and easier method for inserting filter holder into a pressurized coffee machine. This invention also provides a cabinet filter holder which can be inserted or placed into the brewing head assembly/unit of a coffee machine by sliding the filter holder into the brewing head unit from front or side; by swinging the filter holder into the brewing head assembly/unit on a pivot; or by inserting the filter holder from the top. This invention further provides a brewing head assembly/unit wherein the locking mechanism is motor-driven. In one aspect of this invention, the method for opening and closing the brewing head assembly/unit of the coffee machine can be operated by remote control. This invention further provides a cabinet filter design wherein the boiler or heating system is separated from the brewing head assembly/unit.