Electric heating – Heating devices – With power supply and voltage or current regulation or...
Patent
1985-05-08
1988-05-17
Paschall, M. H.
Electric heating
Heating devices
With power supply and voltage or current regulation or...
219494, 219549, 219535, 219487, 1563047, 1562739, 1562751, H05B 102
Patent
active
047452633
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to improvements in carpet seaming apparatus and relates particularly to improved apparatus for use with a carpet seaming tape or the like to produce a seam between adjacent edge portions of a carpet or other material.
In my Australian Pat. No. 529,440 and Patent Application No. 10491/83, I have described apparatus which includes means for passing a current through a strip of metal foil which is associated with or incorporated in a carpet joining tape, the apparatus having means to control the current flow through the metal foil so that heat generated thereby will act to soften an adhesive on the carpet joining tape, the apparatus further including means to hold the current flow at a selected predetermined value to maintain the adhesive in a softened condition and means selectively operated to increase the current to fully melt the adhesive.
The particular form of apparatus previously described utilized a power transformer the output of which was controlled by a Triac which, in turn, was controlled by a trigger module which sensed both the output voltage and current. A rheostat was used to vary the output voltage and current as desired.
While this apparatus functions well in most circumstances, it has been found that the weight of the apparatus is relatively high thus making it difficult to move from place to place. Further, the components of the apparatus must be completely redesigned for use on the various overseas main power systems.
SUMMARY OF THE INVENTION
It is desirable to provide improved apparatus for use in forming edge-to-edge seams in carpets or other sheet material which avoids at least some of the above disadvantages.
It is also desirable to provide an improved carpet seaming apparatus which is economical to manufacture and is relatively safe to use.
According to one aspect of the invention there is provided apparatus for use in joining abutting edges of carpet or other material using a heating element in conjunction with a joining tape having heat softenable adhesive thereon, said apparatus comprising an oscillator means having an output frequency in the range of 100 to 50,000 hertz, power output means driven by the oscillator to produce an output voltage having a frequency which is a function of the oscillator means frequency, pulse width modulator means to vary the pulse width of the output voltage to thereby vary the output current which is to be applied to the heating element, sensing means to sense the output current, control means to adjust the pulse width modulator means in accordance with sensed output current to thereby maintain a predetermined selected output current, and switch means operable to select the desired output current.
In a preferred embodiment, the power output means comprises a power amplifier which is driven by the oscillator means. The pulse width modulator means controls the width of the output pulses of the oscillator means which thereby controls the Rms value of the output current.
A differential amplifier receives a reference voltage from a reference voltage source and a signal voltage derived from the output current sensing means, which may comprise a current transformer and Rms-to-DC convertor. Any differences between the reference and signal voltages results in the differential amplifier providing an output signal to the pulse width modulator means which either increases or decreases the output current pulse width to reduce the voltage differences.
The switch means is operable to change the selected reference voltage to thereby change the selected desired output current.
According to another aspect of this invention there is provided apparatus for use in joining abutting edges of carpet or other material using a heating element in conjunction with a joining tape having heat softenable adhesive thereon, said apparatus comprising an oscillator having an output frequency of between 100 and 50,000 hertz, a pulse width modulator to adjust the pulse width of the oscillator output, a drive amplifier driven by the
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patent: 4377739 (1983-03-01), Eckert, Jr. et al.
patent: 4416713 (1983-11-01), Brooks
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