Method for gas-aided dispensing of liquid materials

DETAILED DESCRIPTION The invention provides an improved apparatus and method for dispensing liquid material to form a deposit having a desired conformation on the surface of a workpiece.
The liquid material is discharged under pressure from the nozzle of a dispensing gun which can be manipulated by a robot to lay the deposit along a programmed pattern.
One or more gas jets are directed toward the liquid material after the material is discharged from the nozzle to impart a desired conformation to the deposit of liquid material.
According to a first aspect of the invention, the flow rate of the gas jets is modulated by an electropneumatic transducer in accordance with at least one parameter such as the flow rate of liquid material discharged from the nozzle to maintain substantial uniformity of the conformation of the deposit despite perturbations in liquid flow rate.
Where the liquid flow rate is itself controlled in accordance with changes in the relative speed between the workpiece and the dispensing gun to provide a deposit containing a controlled amount of liquid material per unit length along the pattern, a further aspect of the invention contemplates modulating the flow of the gas jets in accordance with a toolspeed signal correlated to the same relative speed.
Yet a further aspect of the invention provides an apparatus and method for selectively varying the conformation of the deposit of liquid material over different portions of the pattern formed on a given workpiece and/or different workpieces by modulating the flow rate of the gas jets in accordance with an auxiliary signal which may conveniently comprise a programmed signal generated by the robot controller.
This auxiliary signal may itself be combined with a liquid flow rate signal to maintain substantial uniformity of each conformation selected by the auxiliary signal despite perturbations in the liquid flow rate.
Where the liquid flow rate is itself modulated in accordance with a toolspeed signal, the toolspeed signal may also be utilized according to the invention to derive a control signal for modulating the flow of the gas jets