Induction heating apparatus with hinged support and filtered air cooling

A radio frequency heating apparatus incorporating a radio frequency generater valve (5), a radio frequency impedance matching transformer (7) and a heating coil/element arrangement (14) which is arranged to be selectively displaceable with respect to a working zone, wherein the heating coil or heating element (14) is integrally associated with the radio frequency impedance matching transformer (7) and is so physically separated from the radio frequency generator valve (5) that on displacement of the heating coil/element arrangement the transformer is constrained to move therewith without mechanically displacing the generator valve (5).

BACKGROUND OF THE INVENTION 
The present invention is concerned with induction heating apparatus, and 
more particularly with apparatus used for commercial and industrial 
heating purposes. 
Induction heating is utilized for a wide range of activities such as, for 
example, the heating of materials such as metals, for the purposes of 
brazing, soldering, material hardening, material melting, plastics 
material curing, molding and gluing materials together and so on. 
In the case of known apparatus the induction heating equipment involves a 
radio frequency electrical generator for the generation of the high 
frequency electric power field which produces the requisite heating effect 
in the articles/material to be induction heated. 
Commonly, the radio frequency generator apparatus includes, for example, a 
radio frequency generator, a radio frequency impedance matching 
transformer, radio frequency concentrator unit and various associated 
capacitors. The concentrator unit is in turn is operationally coupled to 
the actual heating coil or heating element. 
In practice, it is essential to ensure that this unit is radio frequency 
radiation safe. 
The radio frequency power generator unit when in operation generates 
considerable quantities of heat so that it is essential to provide 
arrangements for cooling the various components involved in the high 
frequency generation arrangements. Generally, the cooling system involves 
a combination of air cooling and liquid cooling in relation to the actual 
induction heating coil/element, valve etc. The liquid cooling involves 
pumping coolant liquid though a fluid circuit including cooling sections, 
radiator arrangements for enabling the cooling of the coolant itself, and 
coolant pumping means. 
The air cooling arrangements are used to produce a flow of cooling air 
through the radiator and any components that are more easily cooled by air 
flows. 
Bearing in mind that induction heating equipment is likely to be utilized 
in a dirty environment it is conventionally necessary to pass any air used 
for the air cooling through suitable filtration arrangements. 
It is a frequent requirement that relative movement should take place 
between any article or material to be subjected to heat and the heating 
coil or heating element. 
With the known arrangements this relative movement involves inherent 
problems in that the construction of the power generation system is such 
that the when it is necessary to displace the heater coil the movements of 
the heater coil simultaneously moves the radio frequency valve thereby 
subjecting the latter to the possibility of unnecessary mechanical 
disturbances and thus damage. 
OBJECT OF THE INVENTION 
It is an object of the present invention to provide a radio frequency 
current generating installation which avoids some of the problems met with 
known apparatus. 
STATEMENTS OF INVENTION 
According to a first aspect of the invention there is provided a radio 
frequency heating apparatus incorporating a radio frequency generator 
valve, a radio frequency impedance matching transformer and a heating 
coil/element arrangement which is arranged to be selectively displaceable 
with respect to a working zone, wherein the heating coil or heating 
element is integrally associated with the radio frequency impedance 
matching transformer and is so physically separated from the radio 
frequency generator valve that on displacement of the heating coil/element 
arrangement the transformer is constrained to move therewith without 
mechanically displacing the generator valve. 
Preferably, the radio frequency heating apparatus includes a tiltable 
support for the transformer is supported by a tiltable support, and a tilt 
producing unit for controlling the tilt of the tiltable support, the 
arrangement being such the tilting of the support simultaneously displaces 
the heating coil/element. 
In accordance with a further aspect of the invention there is provided a 
radio frequency heating apparatus as including a control valve and means 
for ducting cooling air therethrough, the control valve having its 
operational setting arranged to be responsive to the flow of cooling air 
therethrough, the arrangement being such that provided the air flow is 
above a threshold value the valve is remains open to air flow; and 
whenever the airflow falls below said threshold level the apparatus being 
cooled by the cooling air is switched OFF or otherwise switched to a 
quiescent condition. 
Conveniently, the tilt producing unit includes a ramp and follower 
arrangement. 
Conveniently, the ramp and follower arrangement is arranged for control by 
a double acting piston.

DETAILED DESCRIPTION OF THE DRAWING 
Referring now to the drawing the schematically illustrated radio frequency 
heating apparatus can very conveniently be regarded as incorporating three 
principle sections 1, 2, and 3 located one above the other within a main 
housing 4 which is thus common to all of the sections. The main housing 4 
is such as to afford high frequency radiation shielding. 
The uppermost section 1 incorporates a radio frequency current generating 
valve 5 mounted from a support platform 6 provided in the housing 4. A 
radio frequency impedance matching transformer 7 is mounted to a rockable 
support table 8 which is pivotally connected to the platform 6 so as to be 
displaceable up and down. The table 8 is pivoted to the support platform 6 
by a pivot element 9 and is raised or lowered by a slidable wedge/ramp 10 
cooperating with a follower 11 carried by the table 8. The wedge/ramp 10 
is displaceable by a double acting ram 12 which is actuatable by control 
means (not shown). An adjustable stop arrangement 13 is provided to set 
the extent of maximum lift of the table 8. 
It will be appreciated that other arrangements can be provided for raising 
and lowering the table 8. 
Output from the impedance matching transformer 7 is delivered to a radio 
frequency heating coil or heating element 14 which is connected to the 
transformer directly to receive the output therefrom and which moves with 
the up and down movement of the table. 
The support arrangement 15 for the coil/element 14 is such that the actual 
coil/element is positioned as close as possible to the transformer, and 
also such that only the actual coil/element projects outwards from the 
interior of the housing. 
In other words all of the components of the apparatus are located within 
the housing 4 and are thus effectively within a radiation shield. 
The heating coil/element 14 is of a tubular form and is cooled by a flow of 
cooling liquid through a liquid cooling system including an air cooled 
radiator 16 which is installed at the lowermost section 3 of the 
apparatus. The liquid cooling system will be discussed hereinafter. 
The facilities for air flow cooling include an air circulating fan 18 which 
draws in air into the interior of the housing section 4 by way of an air 
cleaner filter 17 and the radiator 16. 
The air from the downstream side of the fan is enabled to pass into the 
second section 3 by way of an air flow control valve arrangement 19. This 
is shown as a flap valve 20 whose setting is controlled by the 
pressure/flow of the cooling air passing from the lowermost section 3 into 
the central section 2. With this arrangement provided the air being drawn 
into the section 3 is at a rate which exceeds a threshold level the flow 
of air will keep the flap valve 20 open, and as soon as the flow level 
falls below such threshold value the flap valve will progressively lower 
towards a closed position. 
To prevent continuation of operation of the high frequency power generation 
in the absence of cooling air the flap valve is arranged when it has 
closed to a predetermined level of air flow, to operate a microswitch 21, 
this micro switch being included in the control system (not shown) for the 
apparatus. Operation of the microswitch either causes complete switching 
OFF of the apparatus or the switching of the apparatus to a quiescent 
condition. 
The lowering of the flap valve is indicative that the flow of air has 
reduced and, in practice, this is a result of the clogging of the filter 
by detrius removed from the air, and that by the time the flap valve 20 
has operated the microswitch the filter needs to be changed or cleaned. 
With the air cooling arrangements shown, after the air has passed into the 
middle section 2, it is utilised to cool the radio frequency valve 5 by 
providing air outlet from the section 2 into the uppermost section 1 by 
way of the valve 5. A further flow path from the section 2 to the section 
1 is by way of the transformer 7. These air flows have been schematically 
indicated by arrows 24 and 25. It will be appreciated that the support 6 
will be suitably apertured to provide for the air flows. 
Furthermore, the air, whilst in the middle section 2, will cool any 
apparatus components installed in the middle section. 
The liquid cooling system includes a liquid reservoir and pump unit 26 
which is located in the lowermost section 3. 
As will be noted from the Figure cooled liquid from the radiator 16 is fed 
via a conduit 27 to the pump 26 and travels therefrom via a conduit 28 to 
a cooling coil 29 associated with the transformer 7. After cooling the 
transformer 7 the cooling liquid passes back to the radiator 16 by way of 
a conduit 30 that passes through a guide duct 31 to the radiator 16. 
The cooling air finally passes out from the upper section 1 by way of 
outlets 32.