SELF-CONFIGURING INDUCTION SEALING DEVICE FOR USE TO PRODUCE POURABLE FOOD PRODUCT PACKAGES

摘要

An induction sealing device (10) for use to produce packages (7) of pourable food products from a tube (2) of heat-seal sheet packaging material (3). The sealing device (10) has a signal source (12) supplying an alternating power signal (S(?)); an inductor (13) receiving the alternating power signal (S(?)), and operable to induce electric current in the packaging material (3) to heat seal the packaging material (3); and an impedance matching circuit (11') connected between the signal source (12) and the inductor (13). The impedance matching circuit (H') has a pair of input terminals (11.1, 11.2) receiving the alternating power signal; a first (23) and second (24) line connected to the input terminals (11.1, 11.2); a variable-capacitance stage (21) having a number of capacitive modules (21.1-21.4) parallel-connected between the first and second line (23, 24), and each made up of a capacitive element (C1-C4) and a controlled switch (SW1-SW4) connected in series, each controlled switch (SW1-SW4) being selectively operable to connect the respective capacitive element (C1-C4) between the first and second line (23, 24); and a control stage (22) configured to control the operating statuses of the controlled switches (SW1-SW4). Each controlled switch (SW1-SW4) has a pair of input terminals (SWa, SWb) receiving a respective control signal from the control stage (22), wherein one (SWb) of the input terminals (SWa, SWb) of each controlled switch (SW1-SW4) is connected to the second line (24); and a single two-way controlled switching element (IGBT) having a control terminal connected to the other input terminal (SWb) of the controlled switch (SW1-SW4), a first current-conducting terminal connected to the first line (23) via the respective capacitive element (C1-C4), and a second current-conducting terminal connected to the second line (24).