Gripping Unit And A Method For Gripping A Paper

Abstract

A gripping unit for gripping a paper from a top surface of a stack includes a first and second wheel having rotation axes that are mainly parallel with respect to each other. The first wheel is arranged to exert a friction force on sections of a paper during removal of the paper. The gripping unit further comprises an actuator on which the first wheel is mounted for moving the first wheel in a moving direction towards the second wheel. In addition, the gripping unit comprises an airflow generator for providing an air flow following a flow path directed substantially along the moving direction of the first wheel towards a side surface of the stack and upon approaching said side surface directing away from the stack in a direction substantially transverse with respect to the top surface of the stack.

1 . A gripping unit for gripping a paper from a top surface of a stack, comprising a first and second wheel having rotation axes that are mainly parallel with respect to each other, the first wheel being arranged to exert a friction force on sections of a paper during removal of the paper, the gripping unit further comprising an actuator on which the first wheel is mounted for moving the first wheel in a moving direction towards the second wheel, wherein the gripping unit further comprises an additional actuator for moving the second wheel towards the paper on the top surface of the stack and wherein the gripping unit also comprises an airflow generator for providing an air flow following a flow path from adjacent a paper surface directed away from the stack in a direction substantially transversely with respect to the top surface of the stack. 
     
     
         2 . A gripping unit according to  claim 1 , wherein the flow path is directed substantially along the moving direction of the first wheel towards a side surface of the stack and upon approaching said side surface directing away from the stack in a direction substantially transversely with respect to the top surface of the stack. 
     
     
         3 . A gripping unit according to  claim 1 , further comprising a curved cylindrical surface substantially oriented parallel to the rotation axis of the first wheel for inducing the flow path from the moving direction of the first wheel towards away from the stack in the direction substantially transversely with respect to the top surface of the stack. 
     
     
         4 . A gripping unit according to  claim 3 , wherein the curved cylindrical surface is formed by a cylinder that is coupled to the first wheel. 
     
     
         5 . A gripping unit according to  claim 1 , wherein the airflow generator is arranged for generating a turbulent air flow. 
     
     
         6 . A gripping unit according to  claim 1 , wherein the first wheel is arranged to rotate with respect to its axis during and after and/or during the movement towards the second wheel such that a paper section gripped between the first and second wheel is removed from the stack. 
     
     
         7 . A gripping unit according to  claim 1 , further comprising a further actuator for moving the first wheel away from the stack surface after a paper section has been gripped between the first and second wheel. 
     
     
         8 . A gripping unit according to  claim 1 , wherein the rotation of the first wheel is driven by the actuator for moving the first wheel towards the second wheel. 
     
     
         9 . A gripping unit according to  claim 1 , wherein the first wheel is driven by a tooth wheel transmission. 
     
     
         10 . A gripping unit according to  claim 1 , wherein the first wheel is fixedly provided with a gear wheel cooperating with a gear rack that is fixed with respect to the axis of the second wheel. 
     
     
         11 . A gripping unit according to  claim 1 , wherein the first wheel is mounted on a first axle being provided with one or more additional wheels. 
     
     
         12 . A gripping unit according to  claim 1 , wherein the second wheel is mounted on a second axle being provided with one or more additional wheels. 
     
     
         13 . A gripping unit according to  claim 1 , further comprising a guiding element for removing from the stack an element having a surface above the paper to be gripped. 
     
     
         14 . A gripping unit according to  claim 1 , wherein the second friction wheel is allowed to rotate in one direction only. 
     
     
         15 . A method for gripping a paper from a top surface of a stack, comprising the steps of exerting a friction force on a section of the paper being gripped between a first and a second wheel, respectively, the wheels having rotation axes that are mainly parallel with respect to each other, moving the second wheel towards the paper on the top surface of the stack, moving the first wheel towards the second wheel, wherein the method further provides the step of providing an air flow following a flow path from adjacent a paper surface directed away from the stack in a direction substantially transversely with respect to the top surface of the stack.