GB2091428A - Measuring temperature electrically while welding plastics - Google Patents

Measuring temperature electrically while welding plastics Download PDF

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Publication number
GB2091428A
GB2091428A GB8201495A GB8201495A GB2091428A GB 2091428 A GB2091428 A GB 2091428A GB 8201495 A GB8201495 A GB 8201495A GB 8201495 A GB8201495 A GB 8201495A GB 2091428 A GB2091428 A GB 2091428A
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changes
coil
voltage
parameter
temperature
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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/36—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction
    • B29C65/3604—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the type of elements heated by induction which remain in the joint
    • B29C65/362—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the type of elements heated by induction which remain in the joint comprising at least a single wire, e.g. in the form of a winding
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/36—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction
    • B29C65/3604—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the type of elements heated by induction which remain in the joint
    • B29C65/3644—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the type of elements heated by induction which remain in the joint being a ribbon, band or strip
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/50—General aspects of joining tubular articles; General aspects of joining long products, i.e. bars or profiled elements; General aspects of joining single elements to tubular articles, hollow articles or bars; General aspects of joining several hollow-preforms to form hollow or tubular articles
    • B29C66/51—Joining tubular articles, profiled elements or bars; Joining single elements to tubular articles, hollow articles or bars; Joining several hollow-preforms to form hollow or tubular articles
    • B29C66/52—Joining tubular articles, bars or profiled elements
    • B29C66/522—Joining tubular articles
    • B29C66/5221—Joining tubular articles for forming coaxial connections, i.e. the tubular articles to be joined forming a zero angle relative to each other
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/90—Measuring or controlling the joining process
    • B29C66/91—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux
    • B29C66/912—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by measuring the temperature, the heat or the thermal flux
    • B29C66/9121—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by measuring the temperature, the heat or the thermal flux by measuring the temperature
    • B29C66/91221—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by measuring the temperature, the heat or the thermal flux by measuring the temperature of the parts to be joined
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/90—Measuring or controlling the joining process
    • B29C66/91—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux
    • B29C66/912—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by measuring the temperature, the heat or the thermal flux
    • B29C66/9131—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by measuring the temperature, the heat or the thermal flux by measuring the heat or the thermal flux, i.e. the heat flux
    • B29C66/91311—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by measuring the temperature, the heat or the thermal flux by measuring the heat or the thermal flux, i.e. the heat flux by measuring the heat generated by Joule heating or induction heating
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/90—Measuring or controlling the joining process
    • B29C66/91—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux
    • B29C66/914—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux
    • B29C66/9141—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the temperature
    • B29C66/91411—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the temperature of the parts to be joined, e.g. the joining process taking the temperature of the parts to be joined into account
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/90—Measuring or controlling the joining process
    • B29C66/91—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux
    • B29C66/914—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux
    • B29C66/9161—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the heat or the thermal flux, i.e. the heat flux
    • B29C66/91651—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the heat or the thermal flux, i.e. the heat flux by controlling or regulating the heat generated by Joule heating or induction heating
    • B29C66/91653—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the heat or the thermal flux, i.e. the heat flux by controlling or regulating the heat generated by Joule heating or induction heating by controlling or regulating the voltage, i.e. the electric potential difference or electric tension
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/90—Measuring or controlling the joining process
    • B29C66/91—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux
    • B29C66/914—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux
    • B29C66/9161—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the heat or the thermal flux, i.e. the heat flux
    • B29C66/91651—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the heat or the thermal flux, i.e. the heat flux by controlling or regulating the heat generated by Joule heating or induction heating
    • B29C66/91655—Measuring or controlling the joining process by measuring or controlling the temperature, the heat or the thermal flux by controlling or regulating the temperature, the heat or the thermal flux by controlling or regulating the heat or the thermal flux, i.e. the heat flux by controlling or regulating the heat generated by Joule heating or induction heating by controlling or regulating the current intensity
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C66/00—General aspects of processes or apparatus for joining preformed parts
    • B29C66/90—Measuring or controlling the joining process
    • B29C66/96—Measuring or controlling the joining process characterised by the method for implementing the controlling of the joining process
    • B29C66/961—Measuring or controlling the joining process characterised by the method for implementing the controlling of the joining process involving a feedback loop mechanism, e.g. comparison with a desired value
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/36—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using magnetic elements, e.g. magnets, coils
    • G01K7/38—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements using magnetic elements, e.g. magnets, coils the variations of temperature influencing the magnetic permeability
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/3472—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the composition of the heated elements which remain in the joint
    • B29C65/3476—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" characterised by the composition of the heated elements which remain in the joint being metallic
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C65/00—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor
    • B29C65/02—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure
    • B29C65/34—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement"
    • B29C65/36—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction
    • B29C65/3672—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the composition of the elements heated by induction which remain in the joint
    • B29C65/3676—Joining or sealing of preformed parts, e.g. welding of plastics materials; Apparatus therefor by heating, with or without pressure using heated elements which remain in the joint, e.g. "verlorenes Schweisselement" heated by induction characterised by the composition of the elements heated by induction which remain in the joint being metallic

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • General Physics & Mathematics (AREA)
  • Lining Or Joining Of Plastics Or The Like (AREA)

Abstract

In the welding together of plastics pipes (10, 14), a band (16) of electrically conductive material locates between the pipes at the joint and the latter is surrounded by a coil (18). A voltage is applied across a tuned circuit including the coil (18) and current is induced in the band (16) to heat the joint to the fusion temperature. The magnetic permeability of the band (16) alters and the effect on the tuned circuit results in changes in the phase angle of the coil voltage relative to the applied voltage. Comparison of the phase angles can give an indication of the temperature of the band (16) and further comparison with a reference can produce a signal for controlling the applied voltage and thus the temperature of the band (16).

Description

SPECIFICATION Sensing Temperature Variations in a Material This invention relates to a method of and apparatus for sensing temperature variations in a material. The invention is particularly but not exclusively used in the joining of plastics pipes whilst inductively heating the joint with a conductive/magnetic material located at the region to be heated.
It is currently the practice in the welding together of plastics pipes to heat the joint parts separately and then fuse the parts together.
Difficulties are however encountered in checking the correct location of the joint parts together.
According to one aspect of the present invention there is provided a method of sensing temperature variations in a material, said method comprising utilising means at a location remote from the material to both induce an electric current in the material and sense changes in a parameter of the material which occur in accordance with the changes in temperature in the material, and processing said changes in the parameter so as to determine the temperature of the material.
Preferably the inducing and sensing means to heat the material and comparing said changes in the parameter with a reference so as to produce a differential signal after comparison for controlling the current being induced and thus the temperature of the material.
Preferably also the changes in the parameter effect changes which can be sensed in voltage developed across the coil. Alternatively the changes in the parameter effect changes which can be sensed in the phase of voltage developed across the coil relative to the phase of input voltage to the tuned circuit.
The parameter in which the changes are sensed may be the magnetic permeability or resistivity of the material.
According to another aspect of the present invention there is provided apparatus for sensing temperature variations in a material, said apparatus comprising means at a location remote from the material arranged to both induce an electric current in the material and sense changes in a parameter of the material which occur in accordance with changes in temperature in the material, and means for processing said changes in the parameter so as to determine the temperature of the material.
Preferably the sensing means comprises a coil in a tuned circuit, the quality factor and resonant frequency of which change in accordance with changes in the magnetic permeability and/or resistivity of the material.
An embodiment of the present invention will now be described by way of example only with reference to the accompanying drawings in which:~ Fig. 1 is a diagrammatic view of an arrangement for welding a pair of plastics pipes together, the control of which welding is effected by a method and apparatus according to the invention; Fig. 2 is a circuit diagram of the apparatus for sensing temperature variations in a material used in the welding of Fig. 1 including a voltage phase comparison circuit; Fig. 3 shows a comparison circuit; Fig. 4 shows a modified comparison circuit; and Fig. 5 is a circuit diagram of a modified apparatus.
In various industrial processes it is desirable to sense the temperature of a material in a region where it is not possible to mount a temperature sensor with electrical connections connected thereto. For example, it may be desired to sense the temperature inside a sealed vessel to which access cannot be obtained with conventional sensors, or the temperature of an internal, inductively heated component in a surrounding material where a conventional sensor with connecting wires would degrade the integrity of the joint or assembly.
One particular example is the welding together of plastics pipes which may be butt welded or, as shown in Fig. 1 be connected by a spigot and socket arrangement.
Referring to the drawings, a pipe 10 formed of a thermoplastic material has a socket portion 12 arranged to receive an end portion of a further pipe 14 which is to be welded into the socket portion 12 and which is also formed of a thermoplastic material. A band 16 of an electrically conductive material is located around the end of the pipe 14 between the latter and the spigot portion 12 of the pipe 10 and a coil for inducing an electric current in the band 16 as hereinafter described is located around the socket portion 12 co-axially with the band 1 6.
The coil 18 is located in parallel with a capacitor 20 in a tuned circuit, the latter being connected across a voltage generating apparatus 22. The latter is arranged to have a high output impedance by having an added output ballast impedance 23. Then the circuit is energised the coil 1 8 creates a magnetic field having an operating frequency in the range from 50 Hz to high radio frequencies, the choice of frequency being influenced by the power level required, the generator circuit adopted, and the various statutory legislations and regulations relating to radio frequency interference and equipment safety regulations.
An induced current is therefore caused to flow in the band 16, the latter being of such material that the magnetic permeability thereof alters with variation in temperature within the temperature range to be measured. The band 16 is preferably a nickel steel alloy with a Curie point slightly higher than the temperature of fusion of the plastics pipes. The change in permeability results in the magnetic coupling co-efficient, the magnitude of the circulating current and hence the power drawn from the inducing coil, and the self inductance of the energising coil changing.These changes result in changes in the quality factor and resonant frequency of the tuned circuit, with the quality factor WL Q= R where R is the combined effective resistance of the coil winding and reflected load due to power dissipation in the band 1 6 and L is the effective inductance when in operating position relative to the band 16. At resonance, the voltage Vc, across the coil is in quadrature with the voltage Vg developed by the generator 22, and changes in the quality factor and resonant frequency of the tuned circuit effect changes in phase angle of the coil voltage relative to the generator voltage.
Changes in phase angle are pre-calibrated against changes in temperature in the band 16, such that when the voltages Vg and VcL are compared in a phase comparator circuit 24 there is an indication of the temperature of the band 1 6.
An output from the circuit 24 can be compared with a reference in a comparative amplifier 26 to produce a signal for passing to an amplitude control input of the generator 22 and correspondingly controlling the induced current and the temperature of the band 16. It will be appreciated that in an application such as the welding together of two plastics pipes, the fusion temperature and the time during which heating takes place at the fusion temperature can be critical to production of an acceptable joint quality. The system has numerous advantages over the current welding practice.
This phase demodulation technique also allows the circuit to sense that the band 1 6 is in position and of the correct material since absence of the band 16 will alter the resonant frequency and quality factor of the tuned circuit.
The band 16 can be perforated, or several small bands inserted close together to give a labyrinth seal. The use of a material having a low Curie temperature and being non-corrosive is obviously beneficial and there are a range of such alloy materials commercially available. As an alternative, the band may be formed of a plastics material loaded with a material giving electrically conductive and magnetic properties. Further the band may be an integral part of a pipe.
In a modification as shown in Fig. 4 the change in permeability of the material results in a change in the voltage developed across the coil 18. The coil voltage Vc, can then be related to the generator voltage Vg in a divider circuit 28.
Changes in voltage ratio are pre-calibrated against changes in temperature in the band 16 such that, in operation, the changes give an indication of the temperature of the band 16. The output from the divider circuit 28 is compared with a reference in a comparative amplifier 30 and a differential signal provided which can be passed to the amplitude control input of the generator 22 for control of the input voltage, the induced current, and therefore the heating of the band 16.
In a further modification the coil 18 can be provided in series with capacitor 20 in a tuned circuit and driven by a voltage generator.
In a modified apparatus shown in Fig. 5, the drive voltage Vg is generated by a system including a self oscillating power amplifier 32 controlled by a comparator feedback loop which includes a phase shifting circuit 34, and which senses amplitude and/or phase relationship ratios, and/or frequency of oscillation of Vg and Vac,.
This configuration allows for a range of induction coils for different work piece assemblies to be utilised with one generator without the need for the circuit operating frequency adjustment as the system is self tuning.
The feedback signal to the phase shifting circuit can be direct from Vg as shown or from additiorial turns on the inducing coil 18.
The invention can also be utilised to sense the temperature of a material whose resistivity varies with variation of temperature within the temperature range to be measured. Further, as an alternative to the voltage generator with the output ballast impedance, a constant current/constant power generator may be utilised in order to provide the high output impedance.
The drive voltage can be square wave or sine wave, as the quality factor of the tuned circuit reduces the magnitude of the harmonics and any spurious high frequency components in the generator output. A degree of "self regulation" of the temperature of the band 16 is achieved since a reduction in coil voltage as the magnetic permeability reduces also reduces the voltage induced in the band 16.

Claims (17)

Claims
1. A method of sensing temperature variations in a material, said method comprising utilising means at a location remote from the material to both induce an electric current in the material and sense changes in a parameter of the material which occur in accordance with the changes in temperature in the material, and processing said changes in the parameter so as to determine the temperature of the material.
2. A method according to claim 1, comprising utilising the inducing and sensing means to heat the material, and comparing said changes in the parameter with a reference so as to produce a differential signal after comparison for controlling the current being induced and thus the temperature of the material
3. A method according to claim 1 or 2, comprising applying a generating voltage across a coil which induces the electric current in the material, and comparing changes in phase angle of the coil voltage, resulting from changes in the parameter, with the generating voltage.
4. A method according to claim 1 or 2, comprising applying a generating voltage across a coil which induces the electric current in the material, and comparing changes in the ratio of the coil voltage to the generating voltage resulting from changes in the parameter.
5. A method according to any of claims 1 to 4, comprising sensing changes in the magnetic permeability of the material.
6. A method according to any of claims 1 to 4, comprising sensing changes in the resistivity of the material.
7. A method of connecting plastic pipes together, comprising locating an end portion of a first pipe within an end portion of a second pipe and providing an annular part formed of a material having electrically conductive and magnetic properties, and sensing temperature variations in the material of the annular part in accordance with the method of any of the preceding claims.
8. A method according to claim 7 when dependent on claim 3 or 4, wherein the coil is located around said end portion of said second pipe co-axially with the annular part.
9. Apparatus for sensing temperature variations in a material, said apparatus comprising means at a location remote from the material arranged to both induce an electric current in the material and sense changes in a parameter of the material which occur in accordance with changes in temperature in the material, and means for processing said changes in the parameter so as to determine the temperature of the material.
10. Apparatus according to claim 9, wherein the means for inducing the electric current and sensing changes in the parameter comprises a coil in a tuned circuit, the quality factor and resonant frequency of which change in accordance with changes in the magnetic permeability and/or resistivity of the material.
1 Apparatus according to claim 10, wherein the coil is arranged in parallel with a capacitor in the tuned circuit.
12. Apparatus according to claim 10, wherein the coil is arranged in series with a capacitor in the tuned circuit.
13. Apparatus according to any of claims 10 to 12, comprising a voltage generator, means for applying the generated voltage across the coil, and means for comparing changes in phase angle of the coil voltage resulting from changes in the magnetic permeability and/or resistivity of the material relative to the generator voltage.
14. Apparatus according to any of claims 10 to 12, comprising a voltage generator, means for applying the generated voltage across the coil, and means for comparing changes in the ratio of the coil voltage to the generating voltage resulting from changes in the magnetic permeability and/or resistivity of the material.
1 5. An arrangement for connecting plastics pipes together, said arrangement comprising apparatus for sensing temperature variations in the material according to any of claims 10 to 14, wherein the coil is adapted to locate co-axially around the intended joint between a pair of pipes.
1 6. A method of sensing temperature variations in a material substantially as hereinbefore described with reference to the accompanying drawings.
17. Apparatus for sensing temperature variations in a material substantially as hereinbefore described with reference to the accompanying drawings.
GB8201495A 1981-01-21 1982-01-19 Measuring temperature electrically while welding plastics Expired GB2091428B (en)

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GB2091428A true GB2091428A (en) 1982-07-28
GB2091428B GB2091428B (en) 1984-11-14

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WO (1) WO1982002593A1 (en)

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EP0950608A1 (en) * 1998-04-15 1999-10-20 Tetra Laval Holdings & Finance SA Method of monitoring transverse sealing in a packaging unit for continuously forming sealed packages containing pourable food products
EP2164417A2 (en) * 2007-06-27 2010-03-24 Tessaron Medical, Inc. Systems and methods for inductive heat treatment of body tissue
WO2013106877A1 (en) * 2012-01-17 2013-07-25 Ke-Kelit Kunststoffwerk Gesellschaft M.B.H. Circuit for the inductive heating of a metal
US8653424B2 (en) 2003-09-01 2014-02-18 Pf-Schweisstechnologie Gmbh Compensation for induction heating in coil welding equipment

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MC1581A1 (en) * 1983-12-02 1985-02-04 Toutelectric METHOD FOR CONTROLLING THE WELDING TIME
US5125690A (en) * 1989-12-15 1992-06-30 Metcal, Inc. Pipe joining system and method
US5352871A (en) * 1991-02-20 1994-10-04 Metcal Inc System and method for joining plastic materials
EP0536447A1 (en) * 1991-10-11 1993-04-14 Koninklijke Emballage Industrie Van Leer B.V. Exposure meter for use with induction heat sealing of containers
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JP3398172B2 (en) * 1993-04-09 2003-04-21 電気興業株式会社 Heating temperature control method and high frequency induction heating temperature control device in high frequency induction heating
US5486684A (en) * 1995-01-03 1996-01-23 The Boeing Company Multipass induction heating for thermoplastic welding
US6486664B1 (en) 1998-07-01 2002-11-26 Lepel Corp. Magnetic field exposure sensor and analysis system
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SE536243C2 (en) * 2011-12-15 2013-07-16 Tsc Innovation Ab Method and apparatus for controlling cooling of a weld joint
CN102999061A (en) * 2012-08-20 2013-03-27 昆山万维通建筑系统科技有限公司 Temperature control circuit for coffee maker
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EP0921709A2 (en) * 1997-12-05 1999-06-09 Mitsubishi Heavy Industries, Ltd. Alloying system and heating control device for high grade galvanized steel sheet
EP0921709A3 (en) * 1997-12-05 1999-10-20 Mitsubishi Heavy Industries, Ltd. Alloying system and heating control device for high grade galvanized steel sheet
US6114675A (en) * 1997-12-05 2000-09-05 Mitsubishi Heavy Industries, Ltd. Alloying system and heating control device for high grade galvanized steel sheet
EP0950608A1 (en) * 1998-04-15 1999-10-20 Tetra Laval Holdings & Finance SA Method of monitoring transverse sealing in a packaging unit for continuously forming sealed packages containing pourable food products
WO1999052776A1 (en) * 1998-04-15 1999-10-21 Tetra Laval Holdings & Finance S.A. Method of monitoring transverse sealing in a packaging unit for continuously forming sealed packages containing pourable food products
US6732496B1 (en) 1998-04-15 2004-05-11 Tetra Laval Holdings & Finance Sa Method of monitoring transverse sealing in a packaging unit for continuously forming sealed packages containing pourable food products
US8653424B2 (en) 2003-09-01 2014-02-18 Pf-Schweisstechnologie Gmbh Compensation for induction heating in coil welding equipment
EP2164417A2 (en) * 2007-06-27 2010-03-24 Tessaron Medical, Inc. Systems and methods for inductive heat treatment of body tissue
EP2164417A4 (en) * 2007-06-27 2012-01-11 Tessaron Medical Inc Systems and methods for inductive heat treatment of body tissue
WO2013106877A1 (en) * 2012-01-17 2013-07-25 Ke-Kelit Kunststoffwerk Gesellschaft M.B.H. Circuit for the inductive heating of a metal
US10165628B2 (en) 2012-01-17 2018-12-25 Ke Kelit Kunststoffwerk Gesellschaft M.B.H. Circuit for the inductive heating of a metal

Also Published As

Publication number Publication date
EP0082842A1 (en) 1983-07-06
WO1982002593A1 (en) 1982-08-05
GB2091428B (en) 1984-11-14
AU8002682A (en) 1982-08-16

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