Web tracking apparatus

Passive web tracking apparatus including a frame and web support means mounted on said frame for imparting lateral stability and for maintaining uniform tension in a flexible closed loop web moving in a closed loop path, said support means comprising:

• a first cylindrical roller disposed at a first location adjacent to the path and mounted for rotation substantially in non-slipping engagement with the web, said first roller supporting the web and determining the lateral angular position of the web at the first location;
• and
• a web support disposed at a second location spaced along said path from the first location for constraining at the second location the lateral spatial position of the web without significantly constraining the lateral angular position of the web, said web support having (a) a second cylindrical roller mounted (i) for rotating movement in supporting engagement with the web, (ii) for castering movement to align itself with the web without imposing substantial resistance to lateral angular movement of the web, and (iii) for gimballing movement to angularly decouple the web exiting from said web support to maintain uniformity of tension in the exiting web;
• and (b) edge guide means for engaging the edges of the moving web at the second location to establish the spatial lateral position of the web at the second location.

A passive web tracking apparatus including a frame and web support means mounted on said frame for imparting lateral stability to a flexible closed loop web moving in a closed loop path, said support means comprising:

• a first web support including a rotatable member disposed at a first location adjacent to the path and mounted for rotating in supporting engagement with the web, said first support constraining lateral angular movement of the web at the first location;
• a second web support disposed at a second location adjacent to said path for constraining at the second location the lateral spatial position of the web without constraining substantially the lateral angular position of the web, said second web support having (a) a second rotatable member mounted for rotating in supporting engagement with the web and for castering to align itself with the web without imposing substantial lateral forces on the web, and (b) edge guide means for engaging the edges of the moving web at the second location to establish a fixed spatial lateral position of the web at the second location;
• and
• a third web support disposed at a third location adjacent to said path downstream from the first location and upstream from the second location and including non-constraining means for engaging and supporting the web at the third position with uniformity of tension in the moving web.

A passive web tracking apparatus including a frame and web support means mounted on said frame for imparting lateral stability to a flexible closed loop web moving in a closed loop path, said web support means comprising:

• a first web support disposed at a first position adjacent to and within the periphery of the path for driving the moving web in the path and for angularly constraining the lateral position of the moving web;
• a second web support disposed at a second position adjacent to and within the periphery of the path upstream from the first position, for constraining at the second position the lateral spatial position but not the angular position of the moving web, thus imparting to the moving web freedom to change angular direction in response to changing downstream conditions, said second web support including (i) a web-engaging surface which rotates in supporting engagement with the web and which presents substantially no resistance to lateral movement of the moving web at the second position, and (ii) edge guide means mounted adjacent to said surface in a predetermined spatial relation to said frame and having spaced opposed web engaging portions a maximum fixed distance apart which corresponds substantially to the width of the moving web for engaging the edges of the moving web at the second position;
• and
• a third web support positioned adjacent to and within the periphery of the path downstream from the first position and upstream from the second position for engaging the web without laterally constraining the moving web, and for imparting to the moving web freedom to change direction, said third web support including a web engaging cylinder mounted to rotate gimbal and caster about mutually perpendicular axes.

Passive tracking apparatus in an office copier for establishing a path of movement of an endless photoconductive web relative to a plurality of processing stations located to act on the web, said apparatus comprising:

• a frame;
• and
• a plurality of web engaging members consisting exclusively of a first web support, a second web support, and other web engaging members, said web engaging members maintaining substantially uniform tension in said web, and determining the spatial lateral position and the angular lateral position of said web relative to said frame throughout said path of movement;
• said first web support being disposed at a first location and rotatably engaging said web to determine the lateral angular position of said web;
• said second web support being disposed at a second location spaced along said path of movement from the first location and rotatably engaging said web to determine the lateral spatial position of said web without constraining the lateral angular position of said web;
• and
• said other web engaging members engaging said web without constraining the lateral angular or spatial position of said web.

Passive tracking apparatus in an office copier for establishing a path of movement of an endless photoconductive web relative to a plurality of processing stations, said apparatus comprising:

• a frame;
• first, second and third web engaging members for maintaining substantially uniform tension in said web, and determining the lateral spatial position and the lateral angular position of said web relative to said frame, throughout said path of movement;
• said first web support being disposed at a first location and rotatably engaging said web to determine the angular lateral position of said web;
• said second web support being disposed at a second location spaced from the first location along the path of movement and rotatably engaging said web to determine the lateral spatial position of said web without constraining the angular lateral position of said web;
• and
• said third web engaging member engaging said web to tension said web without constraining the lateral angular or spatial position of said web.