Temperature-Controlled Impulse Sealing
Some years ago I borrowed an innovative high-power audio amplifier from the founder of Holdsworth Electronic Developments Ltd. The occasion was a party to which all my neighbours were invited; this ensured freedom from complaints about the loud music. The amplifier had a feature, unusual at that time, which allowed comparison of the output audio with the input signal and applied correction to minimize distortion. This was achieved by interrupting the output (at a frequency above the audible range) enabling use of the loudspeakers as a microphone to sample the sound in the room. The quality was great, but I don't think that it ever went into production.
For years I looked for impulse sealers using a similar technique to constantly measure the wire temperature, thereby enabling control of the electrical input and thus the temperature. Now I have found one.
This is an extract from the manufacturer's website description of its impulse sealers:
TOSS Technology is Variable Resistance Controlled (VRC) Heat Sealing that is more accurate and repeatable than other methods of heat sealing plastic materials.
The heatseal band temperature is controlled with instant feedback because the controller constantly monitors the change in resistance of the heatseal band and compensates based upon Ohm's Law.
The electrical resistance of the heatseal band is directly proportional to the band temperature. With VRC the actual band temperature is immune from external thermal influences and the controller responds instantly (every 16 milliseconds) based solely on the precise feedback signal from the heat seal band.
At last the sealing wire temperature can be measured. We can now look forward to discarding the old unreliable measuring methods, such as tucking a sensor under the wire, or any other method that actually disturbs pressure and temperature distribution.
It would be interesting to hear from users of this VRC system.
Rolande Hall, FIMMM Pkg Prof