Piston-cylinder-assembly for a coffee brewing apparatus and a method of its operation

A piston-cylinder-assembly for use in a coffee brewing apparatus, comprising:

• spaced first and second frame members;
• a cylindric cavity formed in the second frame member, said cylindric cavity serving as a brewing chamber into which coffee powder to be scalded is filled, and having a first open end facing the first frame member and a second open end remote from said first frame member;
• a piston member mounted on said first frame member coaxially with said cylindric cavity and displaceable axially toward and away from said cylindric cavity, said piston member comprising internal brewing water channels merging to the outside in the region of its front surface adjacent to said first open end of said cylindric cavity, and connected to a brewing water supply pipe;
• first drive means mounted on said first frame member and operatively coupled to said piston member for displacing said piston member between a rest position in which the front surface of said piston member is spaced from said first open end of said cylindric cavity to permit access to said first open end, and an operative position in which the piston member closes said first open end of said cylindric cavity;
• closing means mounted on said second frame member and displaceable between an operative position in which said closing means closes said second open end of said cylindric cavity, and a rest position in which said closing member does not hinder access to said second open end of said cylindric cavity, said closing means being fixed with respect to the central axis of said cylindric cavity;
• second drive means operatively coupled to said closing means for displacing said closing means between said operative and rest positions;
• said first drive means comprising a stepping motor, gear means driven by said stepping motor, and control means comprising counting means for determining the number of steps performed by said stepping motor when it displaces said piston member from said rest position to said operative position and for generating a signal to stop operation of said stepping motor when a preselected number of steps is reached.

A piston-cylinder-assembly for use in a coffee brewing apparatus, comprising:

• spaced first and second frame members;
• a cylindric cavity formed in the second frame member, said cylindric cavity serving as a brewing chamber into which coffee powder to be scalded is filled, and having a first open end facing the first frame member and a second open end remote from said first frame member;
• a piston member mounted on said first frame member coaxially with said cylindric cavity and displaceable axially toward and away from said cylindric cavity, said piston member comprising internal brewing water channels merging to the outside in the region of its front surface adjacent to said first open end of said cylindric cavity, and connected to a brewing water supply pipe;
• first drive means mounted on said first frame member and operatively coupled to said piston member for displacing said piston member between a rest position in which the front surface of said piston member is spaced from said first open end of said cylindric cavity to permit access to said first open end, and an operative position in which the piston member closes said first open end of said cylindric cavity;
• closing means mounted on said second frame member and displaceable between an operative position in which said closing means closes said second open end of said cylindric cavity, and a rest position in which said closing member does not hinder access to said second open end of said cylindric cavity, said closing means being fixed with respect to the central axis of said cylindric cavity;
• second drive means operatively coupled to said closing means for displacing said closing means between said operative and rest positions;
• said first drive means comprising a stepping motor, gear means driven by said stepping motor, and control means comprising a pressure sensor for sensing the pressure exerted by the front face of said piston member on the coffee powder in said cylindric cavity and for generating a stop signal to stop the operation of said stepping motor when a preselected pressure is reached.

An assembly for use in a coffee brewing apparatus, comprising:

• means defining a brewing chamber into which coffee powder to be scalded is filled, said brewing chamber having first and second open ends;
• a piston member displaceable axially toward and away from said brewing chamber;
• first drive means coupled to said piston member for displacing said piston member between a rest position in which said piston member is spaced from said first open end of said brewing chamber and an operative position in which the piston member closes said first open end of said brewing chamber and reduces the internal volume of said brewing chamber containing the coffee powder to exert a preselected pressure on the coffee powder;
• control means for sensing the pressure exerted by said piston member on the coffee powder in said brewing chamber and for generating a stop signal to stop the operation of said first drive means when the preselected pressure is reached;
• means for directing hot water into said brewing chamber;
• and
• outlet means communicating with said brewing chamber and through which prepared coffee beverage is dispensed.

A method of preparing coffee comprising the steps of:

• directing a selected amount of coffee powder into a brewing chamber in which the coffee powder is to be scalded;
• displacing a piston member axially toward the brewing chamber by actuating first drive means coupled to the piston member for axially displacing the piston member between a rest position in which the piston member is spaced from a first open end of the brewing chamber, to an operating position in which the piston member closes the first open end of the brewing chamber and reduces the internal volume of the brewing chamber containing the coffee powder to exert a preselected pressure on the coffee powder;
• sensing the pressure exerted by the piston member on the coffee powder in said brewing chamber and generating a stop signal when the preselected pressure is reached to stop the operation of the first drive means;
• directing a preselected amount of hot water into the brewing chamber;
• and
• dispensing the prepared coffee beverage through outlet means communicating with the brewing chamber.