System for measuring the repeat length of a moving web
AssigneeAM International, Inc.
InventorsRobert M. Montgomery, Robert A. Dessert, Dinesh G. Punater
Life of this patent
Estimating the term…
Abstract
A method and apparatus for measuring the repeat length (L) of a moving web includes forming a plurality of detectable marks along the length of the web at a repeated length interval. First and second detectors positioned along the web path are separated by a known distance (S). The repeat length of the web is obtained by detecting a mark moving past the first detector and then detecting a mark moving past the second detector, determining the time (t) separating the detections, and measuring the speed of the moving web (V), wherein the repeat length is calculated using the formula L=S+Vt.
Claims12
A method of measuring a repeat length L of a web moving along a web path, comprising the steps of:
- forming a plurality of detectable marks along the length of the web, said marks being formed at a nominal repetitive length interval along the web;
- a nominal value for said repeat length being selected such that said nominal repeat length is an integer multiple of said length interval;
- positioning along the web path first and second detectors separated by a known distance S, each detector sensitive to movement there past of one of said detectable marks;
- measuring the speed of the moving web V;
- detecting
- with said first detector the movement of a mark there past;
- detecting with said second detector the next movement of a mark there past;
- measuring the time interval t separating said detections;
- and
- calculating the repeat length according to the relation L=S +Vt.
Apparatus for measuring a repeat length L of a moving web, comprising:
- a frame;
- path defining means connected to said frame for defining a web path;
- means for advancing the web along said web path;
- mark forming means for forming a plurality of detectable marks along the length of the web, said marks being formed at a nominal repetitive length interval along the web, whereby a nominal value for said repeat length is selected such that said nominal repeat length is an integer multiple of said length interval;
- first and second detectors mounted to said frame and located along said web path, said detectors separated by a known distance S, each detector sensitive to movement there past of one of said detectable marks;
- means for measuring the speed of the moving web V;
- control means connected to said first and second detectors and said web speed measuring means, said control means operating in response to detection by said first detector of the movement of a mark there past, and detection by said second detector of the next movement of a mark there past, to:
- measure the time interval t separating said detections;
- and
- calculate the repeat length according to the relation L=S+Vt.
Dependencies are inferred from the claim text.