Method and apparatus for optically monitoring and controlling a moving fiber of material

A method of monitoring or controlling a fiber moving generally from a discharge opening to a substrate in a repeating pattern, comprising the steps of:

• a) determining a period of the pattern;
• b) determining a symmetry of the pattern;
• c) comparing the period and the symmetry of the pattern to a respective reference;
• d) in response to said comparison, performing at least one of the following steps:
• i) changing the rate at which the fiber is dispensed from the discharged opening,
• ii) varying the period of the pattern,
• iii) indicating the status of the pattern, and
• iv) repeating steps a) through d).

A method of dispensing a fiber of material comprising the steps of:

• dispensing the fiber of material from a discharge opening of a dispensing means;
• causing the dispensed fiber of material to propagate in a moving pattern through a space between the discharge opening and a substrate;
• transmitting a beam of light such that, under normal operating conditions, the fiber of material will pass through the beam of light at least twice as it propagates in the moving pattern;
• detecting said beam of light and generating in response to the absence or presence of said beam of light a signal;
• generating an edge signal in response to said signal when an edge of the fiber of material bears a relationship to the beam of light;
• generating a symmetry signal indicative of, or proportional to, either a time interval between a first said edge signal and a second edge signal or a time interval between the second said edge signal and a third edge signal;
• generating a period signal indicative of, of proportional to, the time interval between said first edge signal and said third edge signal;
• and
• determining the status of the motion of the pattern in response to said period and symmetry signals.

A method comprising the steps of:

• a) dispensing a bead of adhesive from a discharge opening of a dispensing means at a flow rate;
• b) causing the dispensed bead of adhesive to propagate in a rotating pattern through a space between the discharge opening and a substrate;
• c) transmitting a beam of light such that, under normal operating conditions, the bead of adhesive will pass through the beam of light at least twice as it moves in said pattern;
• d) detecting said beam of light and generating in response to the presence or absence of said beam of light a signal;
• e) comparing said signal to a reference;
• and in response to said comparison performing at least one of the following steps:
• i) varying the rate at which the bead of material is dispensed from the discharged opening;
• ii) varying the rate at which the bead of material rotates in said pattern, and
• iii) indicating the status of the pattern.