Machine for sealing vacuum packs and a control method therefor

Abstract

A machine for sealing vacuum packs, include a pump for aspirating air from inside a pack; an electric motor, the electric motor is powered by an electricity grid supply; at least a welding element that is placed in contact with the pack, for welding and sealing the pack; a supply circuit configured to connect the welding element to the electricity grid supply; a control unit that controls the supply circuit to supply energy to the welding element; and a measuring device for measuring a value of a parameter indicating the electrical energy supplied to the welding element. The measuring device is connected to the control unit, which is configured to determine the value of electrical energy supplied to the welding element from the start of the welding, and interrupts supply of the electrical energy to the welding element on reaching a predetermined value of the electrical energy.

1 ). A machine ( 1 ) for sealing vacuum packs ( 100 ), comprising:
 a pump ( 3 ) for aspirating air from inside a pack ( 100 );   at least one electric motor ( 4 ) for actuating the pump ( 3 ), the at least one electric motor ( 4 ) is configured to be powered by an electricity grid supply;   at least a welding element ( 5 ) configured to be placed in contact with the pack ( 100 ), for welding and sealing the pack ( 100 );   a supply circuit ( 6 ) configured to connect the welding element ( 5 ) to the electricity grid supply; and   a control unit ( 7 ) configured to control the supply circuit ( 6 ) in order to supply electrical energy to the welding element ( 5 ); wherein the machine comprises a measuring instrument ( 8 ) for measuring a value of a parameter indicating the electrical energy that the supply circuit ( 6 ) supplies to the welding element ( 5 ), the measuring instrument ( 8 ) is connected to the control unit ( 7 ), the control unit ( 7 ) is configured such as to determine the value of the electrical energy supplied to the welding element ( 5 ) from a start of a welding operation according to the measured parameter, and in order to interrupt supply of the electrical energy to the welding element ( 5 ) on reaching a predetermined value of the electrical energy.   
     
     
         2 ). The machine of  claim 1 , wherein the measuring instrument comprises a voltmeter. 
     
     
         3 ). The machine of  claim 1 , wherein the supply circuit ( 6 ) comprises a transformer ( 11 ) configured to be supplied by the electricity grid supply, and configured to transform the electricity grid supply tension into a low-voltage tension in order to supply the welding element ( 5 ). 
     
     
         4 ). The machine of  claim 3 , wherein the at least one electric motor ( 4 ) of the pump ( 3 ) comprises at least two coils, of which a first coil functions as a stator coil of the at least one electric motor ( 4 ), and a second coil, electrically insulated from the first coil, functions as a primary coil of the transformer of the supply circuit ( 6 ). 
     
     
         5 ). The machine of  claim 1 , comprising a first switch ( 12 ) arranged in series with the at least one electric motor ( 4 ), which is controlled by the control unit ( 7 ) in order to activate or deactivate the at least one electric motor ( 4 ). 
     
     
         6 ). The machine of  claim 5 , comprising a second switch ( 13 ) arranged in series with the welding element ( 5 ), which is controlled by the control unit ( 7 ) in order to activate or deactivate the supply to the welding element ( 5 ). 
     
     
         7 ). The machine of  claim 1 , comprising a sensor ( 9 ) configured to measure a degree of depression generated by the pump ( 3 ) internally of the pack ( 100 ). 
     
     
         8 ). A control method of the machine of  claim 1 , the method comprising the steps of:
 activating the pump ( 3 ) for aspirating air from inside a pack ( 100 );   supplying electrical energy to the welding element ( 5 ) via the supply circuit ( 6 );   interrupting the functioning of the pump;   establishing a desired value of the electrical energy to be supplied to the welding element ( 5 ) during a welding operation;   measuring a value of an electrical parameter indicating the electrical energy supplied to the welding element ( 5 );   calculating a value of the electrical energy effectively supplied to the welding element ( 5 ) from a start of the welding operation, as a function of the measured value of the electrical parameter; and   interrupting the electrical supply to the welding element ( 5 ), when the value of the electrical energy effectively supplied to the welding element ( 5 ) reaches the desired value.   
     
     
         9 ). The control method of  claim 8 , further comprising:
 measuring a depression generated by the pump ( 3 ) internally of the pack ( 100 ); and   supplying electrical energy to the welding element ( 5 ) once the depression generated by the pump ( 3 ) reaches a predetermined value.