Friction retard feeder with improved sheet separation

Abstract

A substrate feeding apparatus and a printing machine is provided herein for feeding substrates from a substrate stack having a nudger roll being selectively movable between a first position and a second position. In the first position, the nudger roll is in contiguous contact with a first substrate of the substrate stack for advancing the first substrate from the substrate stack. The first substrate having a lead edge and a trail edge, with the lead edge leading in a direction of advancement. In the second position, the nudger roll is not in contiguous contact with the substrate stack or the first substrate. A feed roll for further advancing the first substrate in the direction of advancement. A retard member forming a nip with the feed roll. The retard member is used for separating the first substrate from an adjacent second substrate. A guide baffle extending between the substrate stack and the nip, with the guide baffle configured to contact, and to guide, the first substrate as it advances in the direction of advancement from the nudger roll to the nip. The guide baffle provides an angular change in direction to the first substrate as the first substrate advances from the substrate stack to the nip. The guide baffle is configured such that as the lead edge of the first substrate enters the nip, the first substrate has portions thereof spaced from the guide baffle, with the spaced portions sagging towards the guide baffle to provide the first substrate with a concave profile. The nudger roll moves from the first position to the second position after the lead edge of the first substrate enters the nip.

1 . A substrate feeding apparatus for feeding substrates from a substrate stack comprising:
 a nudger roll selectively movable between a first position and a second position, wherein in said first position, said nudger roll is in contiguous contact with a first substrate of said substrate stack for advancing said first substrate from the substrate stack, said first substrate having a lead edge and a trail edge, said lead edge leading in a direction of advancement, and wherein, in said second position, said nudger roll is not in contiguous contact with said substrate stack or said first substrate;   a feed roll for further advancing said first substrate in the direction of advancement;   a retard member forming a nip with said feed roll, said retard member for separating said first substrate from an adjacent second substrate; and   a guide baffle extending between said substrate stack and said nip, said guide baffle configured to contact, and guide, said first substrate as it advances in the direction of advancement from said nudger roll to said nip, said guide baffle providing an angular change in direction to said first substrate as said first substrate advances from said substrate stack to said nip, wherein, said guide baffle being configured such that as said lead edge of said first substrate enters said nip, said first substrate has portions thereof spaced from said guide baffle, said spaced portions sagging towards said guide baffle to provide said first substrate with a concave profile;   wherein said nudger roll moves from said first position to said second position after the lead edge of said first substrate enters said nip.   
     
     
         2 . The apparatus of  claim 1 , wherein said retard member is an active retard roll. 
     
     
         3 . The apparatus of  claim 2 , wherein said active retard roll separates said first substrate from an adjacent second substrate by advancing said adjacent second substrate in a direction opposite of the direction of advancement while the feed roll advances said first substrate in the direction of advancement. 
     
     
         4 . The apparatus of  claim 1 , wherein said retard member is a semi-active retard roll. 
     
     
         5 . The apparatus of  claim 1 , wherein said retard member is a pad. 
     
     
         6 . The apparatus of  claim 1 , wherein a first angle is formed between said guide baffle and said substrate stack, said first angle is about 10 degrees to about 70 degrees. 
     
     
         7 . The apparatus of  claim 1 , wherein a first angle is formed between said guide baffle and said substrate stack, said first angle is about 30 degrees to about 40 degrees. 
     
     
         8 . The apparatus of  claim 1 , wherein said guide baffle is fixed between said substrate stack and said nip. 
     
     
         9 . The apparatus of  claim 1 , wherein the orientation of said feed roll and said retard member is rotated to align the roll center lines approximately perpendicular to said guide baffle, wherein said feed roll rotates about a first axis and wherein said guide baffle is oriented to be generally perpendicular to a reference axis which intersects said nip and said first axis. 
     
     
         10 . The apparatus of  claim 1 , wherein a second angle is formed between a reference plane coinciding with an initial position of said substrate stack and a current position of said substrate stack, said second angle being less than said first angle. 
     
     
         11 . The apparatus of  claim 1 , further comprising an elevator plate extending adjacent to said substrate stack with a pivot point and a lift mechanism, wherein said elevator plate has a lead ledge and a trail edge, said pivot point being located adjacent to said trail edge of said elevator plate and said lift mechanism configured to pivotally adjust said lead edge of said elevator plate to allow said lead edge of said first substrate to contact and align with said guide baffle as said first substrate advances from said substrate stack to said nip. 
     
     
         12 . A printing machine comprising:
 a substrate feeder including:
 a nudger roll selectively movable between a first position and a second position, wherein in said first position, said nudger roll is in contiguous contact with a first substrate of a substrate stack for advancing the first substrate from the substrate stack, said first substrate having a lead edge and a trail edge, said lead edge leading in a direction of advancement, and wherein, in said second position; said nudger roll overlaps said substrate stack but is not in contiguous contact with said substrate stack or said first substrate; 
 a feed roll for further advancing said first substrate in the direction of advancement; 
 a retard member forming a nip with said feed roll, said retard member for separating said first substrate from an adjacent second substrate; and 
 a guide baffle extending between said substrate stack and said nip, said guide baffle configured to contact, and guide, said first substrate as it advances in the direction of advancement from said nudger roll to said nip, said guide baffle providing an angular change in direction to said first substrate as said first substrate advances from said substrate stack to said nip, wherein, said guide baffle being configured such that as said lead edge of said first substrate enters said nip, said first substrate has portions thereof spaced from said guide baffle, said spaced portions sagging towards said guide baffle to provide said first substrate with a concave profile; 
   wherein said nudger roll moves from said first position to said second position after the lead edge of the first substrate enters the nip.   
     
     
         13 . The printing machine of  claim 12 , wherein said retard member is an active retard roll, said active retard roll separates said first substrate from an adjacent second substrate by advancing said adjacent second substrate in a direction opposite of the direction of advancement while the feed roll advances said first substrate in the direction of advancement. 
     
     
         14 . The printing machine of  claim 12 , wherein said retard member is a semi-active retard roll. 
     
     
         15 . The printing machine of  claim 12 , wherein said retard member is a pad. 
     
     
         16 . The printing machine of  claim 12 , wherein a first angle is formed between said guide baffle and said substrate stack, said first angle is about 10 degrees to about 70 degrees. 
     
     
         17 . The printing machine of  claim 12 , wherein a first angle is formed between said guide baffle and said substrate stack, said first angle is about 30 degrees to about 40 degrees. 
     
     
         18 . The printing machine of  claim 12 , further comprising an elevator plate extending adjacent to said substrate stack with a pivot point and a lift mechanism, wherein said elevator plate has a lead ledge and a trail edge, said pivot point being located adjacent to said trail edge of said elevator plate and said lift mechanism configured to pivotally adjust said lead edge of said elevator plate to allow said lead edge of said first substrate to contact and align with said guide baffle as said first substrate advances from said substrate stack to said nip. 
     
     
         19 . The printing machine of  claim 12 , wherein the orientation of said feed roll and said retard member is rotated to align the roll center lines approximately perpendicular to said guide baffle, wherein said feed roll rotates about a first axis and wherein said guide baffle is oriented to be generally perpendicular to a reference axis which intersects said nip and said first axis. 
     
     
         20 . The printing machine of  claim 12 , wherein a second angle is formed between a reference plane coinciding with an initial position of said substrate stack and a current position of said substrate stack, said second angle being less than said first angle.