Machine and method for wrapping products

Abstract

A machine ( 1 ) and method for wrapping products ( 2 ), whereby a product ( 2 ) is applied with a respective sheet ( 3 ) of wrapping material, is fed by a wrapping conveyor ( 4 ) along a first path (P 1 ) to fold the sheet ( 3 ) of wrapping material about the product ( 2 ) to form a tubular wrapping ( 7 ), and is then fed by the wrapping conveyor ( 4 ) along a second path (P 2 ) to stabilize, by sealing, the tubular wrapping ( 7 ); a sealing element ( 11 ) being fed, by a further conveyor ( 12 ) and in time with the product, along a third path (P 4 ) parallel to the second path (P 2 ), so as to be applied to the second path (P 2 ), so as to be applied to the tubular wrapping ( 7 ) and seal two superimposed portions ( 8 ) of the tubular wrapping ( 7 ).

1 ) A machine ( 1 ) for wrapping products ( 2 ) the machine ( 1 ) comprising a first conveyor ( 4 ) for continuously feeding a the product ( 2 ), applied with a respective sheet ( 3 ) of heat-sealable wrapping material, along a first path (P 1 ) to fold the sheet ( 3 ) of heat-sealable wrapping material about the product ( 2 ) to form a wrapping ( 7 ), and for feeding the product ( 2 ) along a second path (P 2 ) subsequent to the first path (P 1 ); and heat sealing means ( 10 ) which are applied to the wrapping ( 7 ) along the second path (P 2 ) to stabilize, by heat sealing, the wrapping ( 7 ); the machine ( 1 ) being characterized by comprising a second conveyor ( 12 ) independent from the first conveyor ( 4 ) and for feeding the heat sealing means ( 10 ) in time with the product ( 2 ) and along a third path (P 3 ) parallel to the second path (P 2 ).  
     
     
         2 ) A machine ( 1 ) as claimed in  claim 1 , wherein the first conveyor ( 4 ) comprises a number of peripheral seats ( 6 ), each for receiving a relative the product ( 2 ) together with a respective sheet ( 3 ) of wrapping material; each the seat ( 6 ) being associated with a respective the heat sealing means ( 10 ).  
     
     
         3 ) A machine ( 1 ) as claimed in  claim 1  or  2 , wherein the first, the second and the third path (P 1 , P 2 , P 3 ) are curved paths.  
     
     
         4 ) A machine ( 1 ) as claimed in one of claims  1 ,  2  and  3 , wherein the first conveyor ( 4 ) is a wrapping wheel ( 4 ), and the first, the second and the third path (P 1 , P 2 , P 3 ) are defined by coaxial arcs of a circle.  
     
     
         5 ) A machine ( 1 ) as claimed in one of  claims 1  to  4 , wherein the wrapping ( 7 ) is a tubular wrapping.  
     
     
         6 ) A machine ( 1 ) as claimed in one of  claims 1  to  5 , wherein the heat sealing means ( 10 ) comprise a plurality of heat sealing heads ( 11 ).  
     
     
         7 ) A machine ( 1 ) as claimed in one of  claims 1  to  6 , wherein the second conveyor ( 12 ) is a belt conveyor ( 12 ) and comprises an endless belt ( 13 ) supporting the heat sealing means ( 10 ); the second conveyor ( 12 ) comprising guide means ( 15 ) for feeding the belt ( 13 ) along the third path (P 3 ).  
     
     
         8 ) A machine ( 1 ) as claimed in  claim 7 , wherein the guide means ( 15 ) comprise a track ( 19 ) of the same shape as the third path (P 3 ); and connecting means ( 20 ) for connecting the belt ( 13 ) to the track ( 19 ).  
     
     
         9 ) A machine ( 1 ) as claimed in  claim 8 , wherein the track ( 19 ) extends along the whole path (P 4 ) of the belt ( 13 ).  
     
     
         10 ) A machine ( 1 ) as claimed in  claim 8  or  9 , wherein the track ( 19 ) is defined by two grooves ( 21 ) formed in two flat plates ( 22 ) located on opposite sides of the belt ( 13 ).  
     
     
         11 ) A machine ( 1 ) as claimed in  claim 10 , wherein the connecting means ( 20 ) comprise a number of carriages ( 23 ) running inside the groves ( 21 ) and integral with the belt ( 13 ).  
     
     
         12 ) A machine ( 1 ) as claimed in  claim 11 , wherein each the carriage ( 23 ) comprises a shaft ( 26 ) integral with the belt ( 13 ); and two end wheels ( 27 ) fitted idly to the shaft ( 26 ).  
     
     
         13 ) A machine ( 1 ) as claimed in  claim 12 , wherein the belt ( 13 ) has an outer face ( 14 ) to which the heat sealing means ( 10 ) are fixed; and an inner face ( 25 ) from which project appendixes ( 24 ) supporting the shafts ( 26 ).  
     
     
         14 ) A machine ( 1 ) as claimed in one of  claims 6  to  13 , wherein each the heat sealing head ( 11 ) comprises a heating resistor of relatively low thermal inertia and relatively high electric resistance.  
     
     
         15 ) A machine ( 1 ) as claimed in  claim 14 , wherein the heating resistors are connected in series to form a single endless turn ( 41 ); means ( 42 ) for generating a time-variable magnetic field being connected magnetically to the turn ( 41 ).  
     
     
         16 ) A machine ( 1 ) as claimed in  claim 14  or  15 , wherein each the heating resistor is short-circuitable to adjust the actual length of the third path (P 3 ).  
     
     
         17 ) A machine ( 1 ) as claimed in one of  claims 6  to  16 , wherein each the heat sealing head ( 11 ) is connected to the belt ( 13 ) by a respective frame ( 28 ) hinged to the belt ( 13 ) at two points.  
     
     
         18 ) A machine ( 1 ) as claimed in  claim 17 , wherein the frame ( 28 ) has a first end hinged directly to the belt ( 13 ), and a second end connected to the belt ( 13 ) via the interposition of a connecting rod ( 34 ).  
     
     
         19 ) A machine ( 1 ) as claimed in  claim 17  or  18 , wherein each the heat sealing head ( 11 ) is connected to the respective the frame ( 28 ) so as to move, with respect to the frame ( 28 ), from a work position to a rest position in opposition to elastic means ( 35 ).  
     
     
         20 ) A machine ( 1 ) as claimed in  claim 19 , wherein each the heat sealing head ( 11 ) is hinged to the respective the frame ( 28 ); return means ( 31 ) being provided to swing the heat sealing head ( 11 ) from a work position to a rest position in opposition to the elastic means ( 35 ).  
     
     
         21 ) A machine ( 1 ) as claimed in  claim 20 , wherein each the return means ( 31 ) comprises an armature ( 37 ) made of ferromagnetic material, connected to the relative the heat sealing head ( 11 ), and movable with the heat sealing head ( 11 ) along the third path (P 3 ); and electromagnets ( 40 ) distributed along the third path (P 3 ).  
     
     
         22 ) A machine ( 1 ) as claimed in  claim 17  or  18 , wherein each the heat sealing head ( 11 ) is connected to the respective the frame ( 28 ) so as to move, with respect to the frame ( 28 ), from a rest position to a work position in opposition to elastic means ( 35 ).  
     
     
         23 ) A machine ( 1 ) as claimed in  claim 22 , wherein each the heat sealing head ( 11 ) is hinged to the respective the frame ( 28 ); return means ( 31 ) being provided to swing the heat sealing head ( 11 ) from a rest position to a work position in opposition to the elastic means ( 35 ).  
     
     
         24 ) A method of wrapping a product ( 2 ); the method comprising applying the product ( 2 ) with a respective sheet ( 3 ) of wrapping material; feeding the product ( 2 ) and the sheet ( 3 ) of wrapping material along a first path (P 1 ) by means of a wrapping conveyor ( 4 ) to fold the sheet ( 3 ) of wrapping material about the product ( 2 ) to form a wrapping ( 7 ); and feeding the wrapping ( 7 ), by means of the wrapping conveyor ( 4 ), along a second path (P 2 ) to stabilize the wrapping ( 7 ); the method being characterized by feeding heat heat sealing means ( 10 ), in time with the product, along a third path (P 3 ) parallel to the second path (P 2 ) by means of a second conveyor ( 12 ) independent from the first conveyor ( 4 ), so as to apply the heat sealing means ( 10 ) to the wrapping ( 7 ) and stabilize, by heat sealing, the wrapping ( 7 ).  
     
     
         25 ) A method as claimed in  claim 24 , wherein the length of time the heat sealing means ( 10 ) are applied to the wrapping ( 7 ) is maintained constant, alongside variations in the traveling speed of the wrapping ( 7 ) along the second path (P 2 ), by varying the actual length of the third path (P 3 ).