Idler roller and corresponding pallet wrapping machine

Abstract

An idle roller for pallet wrapping machine includes a hollow cylindrical body configured to rotate around an axis and a load cell provided with at least one rigid element and at least one deformable element, a fixed support coaxial to the cylindrical body and integral with the structure of a carriage configured to support at least one roll of plastic film, connecting means between the cylindrical body and the load cell, the load cell being interposed between the cylindrical body and the support and being configured to detect the pressure difference exerted by the plastic film on the cylindrical body and on the support.

1 . An idle roller for pallet wrapping machine comprising a hollow cylindrical body configured to rotate around an axis and a load cell provided with at least one rigid element and at least one deformable element, the roller being characterized by comprising a fixed support that entirely traverses the cylindrical body, the fixed support being coaxial to the cylindrical body and being integral with the structure of a carriage configured to support at least one roll of plastic film, and connecting means between the cylindrical body and the load cell, the load cell being interposed between the cylindrical body and the support and being configured to detect a pressure difference exerted by the plastic film on the cylindrical body and on the support. 
     
     
         2 . The roller according to  claim 1 , wherein the deformable element of the load cell comprises at least one sensor configured to detect a deformation of the load cell itself. 
     
     
         3 . The roller according to  claim 1 , wherein the support comprises a recess wherein the load cell is housed, the load cell being constrained to the support through the rigid element. 
     
     
         4 . The roller according to  claim 1 , wherein the connecting means comprise at least one bearing and at least one elongated coupling element having a surface configured to be fixed to the deformable element of the load cell, the coupling element occupying the space between the load cell and the cylindrical body, so as to ensure backlash for the deformable element of the load cell. 
     
     
         5 . The roller according to  claim 4 , wherein the coupling element has an at least partially semicircular cross-section. 
     
     
         6 . The roller according to  claim 1 , wherein the load cell has a cylindrical shape and comprises a through-hole along its axis, in which the support is inserted. 
     
     
         7 . The roller according to  claim 2 , wherein the sensor is a strain gauge, a capacitive sensor, a piezoelectric sensor or an ultrasonic sensor. 
     
     
         8 . The roller according to  claim 1 , wherein it comprises regulating means connected to the load cell and configured to orient in space the load cell itself. 
     
     
         9 . The roller according to  claim 1 , wherein it comprises an additional hollow cylindrical body, configured to maintain a fixed position, interposed between, and connected to, the cylindrical body and the load cell. 
     
     
         10 . The roller according to  claim 1 , wherein an external surface of the main cylindrical body is made of anti-slip material. 
     
     
         11 . A pallet wrapping machine comprising a carriage supporting a main roller configured to hold a roll of plastic film, at least one pre-stretching unit, provided with at least one pair of pre-stretching rollers and at least one actuator configured to drive the pair pre-stretching rollers at different speeds, the machine being characterized by comprising an idle roller according to  claim 1 , installed immediately downstream of the pre-stretching unit. 
     
     
         12 . A machine according to  claim 11 , wherein the idle roller comprises at least one processing unit configured to process the signal received from the load cell so as to determine a change in the rotational speed of the pre-stretching rollers based on the detected pressure difference, and to send a signal containing indications regarding the required correction to the actuator, which consequently adjusts the speed of the pre-stretching rollers.