FIELD OF THE INVENTION
The present invention relates to contact heating of steel slabs/ billet or steel
sheets/strips by means of direct contact of two plates heated by electrical
heating. Particularly, the present invention relates to a system and an
improved method of heating metal sheets by direct contact. Presently
disclosed system and method of heating is an improved version of invention
taught by the present applicant under Indian patent application No.
321/KOL/2013 of 14-03-2014. Earlier patent filed concerns with increase of
the test plate temperature up to a lower level where as the present
invention enables the system to reach a higher temperature of 350 Degree
Celsius and the energy transfer was continuous by complete contact. Earlier
system kept a distance between the energy transferring bodies. The present
invention is based on the use of the contact heating of steel sheets/strips
from the direct contact with the plates already heated by coil heating. To be
precise, the invention relates to a system of efficient method of faster heat
transfer.
BACKGROUND OF THE INVENTION
It has been the attempt of research community to enhance the heat transfer
process in an effective and faster manner. Generation of heat in an effective
way has been attempted since very early days (stone age) by means of
rubbing two pieces of stones when a very little idea was present about the
concept of heat. Later attempt and evolution of efficient method has been
noted in the other forms of heat generation and effective way of transfer has
been devised. The early invention of heat from rubbing two stones can be
described as nothing but the heat generation by direct contact. Since then,
progress of science and through further endeavour new process has been
observed through engineering and technological means.

Apart from cooling, the other important process in any industrial plant is the
heating the material or the stock. Optimization of energy consumption to be
used for heating and cooling purposes is an ongoing effort by the
researcher/scientists. One of the major heating application in steel industries
is a furnace where by slabs/billets are heated to a high temperature before
further forming operations or giving a particular shape to the stock in the
form of strip or wire.
In real plant life applications, reheating furnaces utilize fossil fuels to
generate considerable amount of heat energy that is used for heating
billets/slabs in the steel industry. Although a large amount of heat is supplied
through burners in an industrial furnace, a large fraction of the supplied heat
remains unutilized and not used in slab/billet heating as has been observed
from practical cases. Apart from the same fact, billets/slabs require a large
amount of energy from the furnace so that the initial temperature of the
billets/slabs is raised considerably from cold condition. Though the required
discharge slab/billet temperature is around 1200 Degree Celsius, the initial
rate of the increase of the slab/billet temperature is very slow. Hence, it may
be beneficial if the initial energy can be supplied to billets/slabs in the initial
phase so that the required slab/billet temperature can be reached quickly.
Hence, the faster heating and retention of the heat remains a challenge for
the design methodology/processes of heating billets/slabs. For faster heating,
induction heaters use coils. Similarly, heat exchangers using coils have
existed since a long time. Coils are indirect contact heat exchangers that
transfer heat between air and another medium (such as water, refrigerant,
steam or brine) for the purpose of heating, cooling, dehumidifying or doing a
combination thereof.

Most of heating process through induction heating have been performed
and related literature on alternative heating can be found in Ref [1-12].
US patent No. 3349222[6] describes a device for contact heating of a moving
sheet material having an image including lines of printing. This can be
potentially used mostly for photocopying purpose in Xerox machine.
US patent No. 4,078,392[7] describes a heat transfer system in which a
primary fluid is brought into intimate contact with a ferromagnetic fluid
(secondary fluid) which is immiscible with primary fluid and can be
separated therefrom by magnetic means.
However, none of the prior art teaches about heat transfer from other solid
bodies to solid body by contact and subsequent retention of heat.
INVENTION DISCLOSURE STATEMENT (IDS)
1. T. Marten, J. Niewel and T. Tröster, Investigation on alternative
heating concepts for the hot sheet metal forming process, HTM -
Journal of Heat Treatment and Materials 2011/06, Page 309-315,
Direct link: http://www.htm-journal.com/HT110119.
2. Kolleck, R.; Veit, R.; Hofmann, H.; Lenze, F.J.; "Alternative heating
concepts for hot sheet metal forming"; In: Proceedings of the 1st
International Conference on Hot Sheet Metal Forming of High-
Performance Steel, pp. 239-246; Kassel, Germany 2008; ISBN 978-3-
937057-18-7 .

3. V.Rudnev, D.Loveless, R.Cook, and M.Black, Handbook of Induction
Heating, Marcel Dekker, NY, 2003.
4. V.Rudnev, Metallurgical insights for induction heat treaters; Part 4.
Obtaining fully martensitic structures using water spray quenching.
Heat Treating Progress, March/April, 2008.
5. V.Rudnev, How do I select inductors for billet heating?, Heat Treating
Progress, May/June, 2008.
6. US patent: 3349222, Device for direct contact heating of moving
sheet material
1964.
7. US patent: 4,078,392, Direct contact heat transfer system using
magnetic fluids,, March 14, 1978.
8. Filed patent No. 321KOL 2013 dated 14-03-2014, A method for
heat transfer by direct contact.
9. T. Marten, J. Niewel and T. Tröster, Investigation on alternative
heating concepts for the hot sheet metal forming process, HTM -
Journal of Heat Treatment and Materials 2011/06, Page 309-315,
Direct link: http://www.htm-journal.com/HT110119.
10. Kolleck, R.; Veit, R.; Hofmann, H.; Lenze, F.J.; "Alternative heating
concepts for hot sheet metal forming"; In: Proceedings of the 1st
International Conference on Hot Sheet Metal Forming of High-
Performance Steel, pp. 239-246; Kassel, Germany 2008; ISBN 978-3-
937057-18-7 .

11. Merklein, M.; Lechler, J.; Stöhr, T.; Svec, T.; "Herstellung von
funktionsoptimierten Bauteilen im Presshärtprozess"; In: Stahl und
Eisen, Verlag Stahleisen GmbH, 06/2010, pp. 51-57 .
12. Veit et al., 2010] Veit, R.; Hofmann, H.; Kolleck, R.; Sikora, S.;
"Untersuchung der Phasenbildung bei der Erwärmung Al/Si-
beschichteter Formplatinen"; In: Tagungsband zum 5. Erlanger
Workshop Warmblechumformung, pp. 29-36; Erlangen, Germany
2008; ISBN 978-3-87525-311-5 .
OBJECTS OF THE INVENTION
It is therefore an object of the invention to provide a continuous heating
method of plates/slabs by direct contact. The main objective of this invention
is the improvement of heat transfer by a relatively faster rate of heat transfer
and reduction of heat loss during heat transfer by direct contact. It is also the
objective of this invention to investigate the retention mechanism of the heat
by the test plate through this process of heat transfer. The present system
has been conceived with a view to adopt in heating for plates once this
proves to be viable. This also fulfills the objective of preheating a plate by
pressing two already heated plates by direct contact.
Another object of the invention is to propose a system having high insulating
materials for maximum heat transfer to the subjected material/plate.

SUMMARY OF THE INVENTION
By adaptation of conduction method to transfer heat, this invention uses the
economic of heat transfer by direct contact from two hot plates to a third
cold plate at lower temperature. This invention devises the economic way and
improved way of transfer heat rather than the separate heating of plate. For
this purpose, the plate with a higher thermal conductivity e.g. Copper, has
been chosen so that it reaches higher temperature quickly. This is an
improved version than earlier devised method because copper plates are
raised directly to a higher temperature and that enables the other plates to
reach close to the hot copper temperature. Copper plate during heating
absorbs heat quickly and the same heat is transferred by direct contact
through conduction mechanism. Earlier invention involved a creation of hot
environment and transfer of heat as detailed in the filed patent application.
According to the invention, the system comprises of at least two hot plates
(copper in this case) with the facility of heating the plates, one fixed plate
(test/target plate), installation of thermocouples for temperature recording in
all the plates, and the insulated enclosure.
The steps involves in the method are:
• Two plates (or heating plates) and one fixed plate inside a box type
enclosure that has minimum possible amount of leakage of heat to
outside ambient. Heating plates have been equipped with heating
arrangement and the movement facilities while fixed plate has been
kept stationary.
• Use of copper as the material for heating plates for quicker heating
and steel as the material for the fixed plate.
• Heating arrangement mounted on the two copper plates.
• Fixing thermocouples on the two moving plates and the test plate.

• A mechanism, operated by a Pneumatic control mechanism, allows
the axial movement of heating plates. By pneumatic control, heating
plates can be moved close to the fixed plate. Either a gap between
copper plates and the test plate can be maintained or no gap can be
maintained when direct contact allows the heat transfer by direct
contact and conduction. The fixed plate (test plate) was kept static
while a pneumatically operated piston facilitates the axial movement
of two heating plates.
• The system of enclosure has been properly insulated apart from the
cover at the top of the box type enclosure. This minimizes the heat
loss to the surroundings from the heated fixed steel plate (test plate)
and two moving copper plates.
• Heating the copper plates to a higher temperature than the
environmental temperature throughout its body and recording of the
temperature by means of thermocouples throughout the period of
heating. Once heated to a higher temperature, the two hot Copper
plates are brought close to the fixed plate and kept in direct contact
with the fixed plate.
• Other option lies with the heating the copper plate in different steps
of 150 Degree Celsius, followed by direct contact for 5 minutes with
the fixed steel plate. The same procedure of raising the copper
temperature to a higher level of 200, 250, 300 and 350 Degree
Celsius can also be enabled in steps. After reaching every level of
temperature steps viz., 200, 250, 300 and 350 Degree Celsius, steel
plate is kept in contact with heating copper plate for 5 minutes.

• Next step is recording of trend of temperature with time for fixed
plate.
• A data recorder records all thermocouple temperatures from the fixed
plate as well as from the moving plates when heat transfer occurs. It
records temperature throughout the time period and a time come
when all bodies (two moving plates that are brought close to the fixe
plate) and fixed plate come to an equilibrium temperature.
Improvement made in this system:
• Leakage of heat from the system has been arrested by further
insulation and this enables better temperature rise.
• System has been made reliable to withstand higher
temperature.
• Testing made at higher temperature.
• Previous filed patent showed the capability of the system to
increase the test plate temperature upto 100 to 184 degree C.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
FIG. 1: Schematic diagram of conceptual Rapid heating System with
Enclosure, Fixed (test)plate and moving (auxiliary) plates for heating.
FIG. 2: Locations of thermocouples on Fixed Test Plate (a metal sheet).
FIG. 3: Locations of thermocouples on Copper plates.

FIG. 4: System with Enclosure by parts and intervening medium fitted with
pneumatic cylinders for movement of moving copper plates.
FIG. 5: Contact heating system with the lid and insulation.
FIG. 6: View of fixed steel plate and copper plates fitted with heating coil in
the system after the lid is removed.
FIG. 7: Complete experimental set up along with the data recorder
FIG. 8: Comparison of rise of temperature profile with time for ( from system
of early phase) by maintaining a gap of 10 mm between steel plate and
copper plates and also with no gap( filed patent)
FIG. 9: Temperature profile when copper plates reached 350 oC by copper
plates and subsequently power was turned off (from system of early phase).
Copper plates brought into complete contact with steel plate at that time
onwards (filed patent).
FIG. 10: Temperature profile of test plate and copper with time for direct
contact when step wise temperature increase made for copper and brought
to steel plate and remain stayed for 5 minutes.
FIG. 11: Temperature profile of test plate and moving copper plate with time
when hot copper plates no gap between moving plates and the test plate.

DETAILED DESCRIPTION OF THE INVENTION
The present invention will be better understood from the following brief
description of the system in conjunction with reference to the accompanying
drawings, viz., Figure 1 to Figure 11 given at the end of this description. An
insulating box or enclosure (shown in Fig. 1) is formed to have the shape of
a box. The box type enclosure houses two copper plates (for heating plate to
give energy) and one test steel plate (Fixed plate). An enclosure containing
the moving plates and test plate has been shown in FIG. 1.
Mild steel (MS) has been selected in the system as the fixed plate (Test
body/plate) at present. Steel, though a material with low thermal conductivity
has been chosen for the reason of its wide applicability and manufacturing in
industries. For future design or test purposes, the fixed steel plate may be
replaced by copper material or any other material. That will be dependent for
confirmation tests or change of experiments to satisfy the test conditions.
Each copper plate and the fixed steel plate is 10 mm in thickness while
dimensions of length and breadth are 150 mm X 150 mm. For present system
purpose and test purpose, all verifications of the claims have been made with
the use of steel as the test plate.
Thermocouples have been inserted by drilling the plates to reach the middle
of thickness of steel and copper plates. FIG. 2 depicts the locations of six
thermocouples on steel test plate. Similarly FIG. 3 illustrates the locations of
thermocouples on the copper plate on left hand side and also on the copper
plate on right hand side. The copper plate located on the left side of the box
(when viewed from controller display locations) has six thermocouples and
similarly, six thermocouples are drilled on the copper right hand side heating

plate. Hence there are twelve (12) thermocouples for copper plates and six
(6) thermocouples for test plates.
Leads of thermocouples from two copper plates and one fixed steel plate are
taken out and connected to the data recorder or the data acquisition system.
The data recorder monitors the temperature of copper and steel plate from
the temperature readings of thermocouples. These temperatures are
recorded after every 10 seconds from reading of 18 numbers of
thermocouples as displayed by the reading of 18 channels. A data recorder
from Yokagowa make with 20 channels has been used for this purpose.
To obtain a faster heat transfer, test with copper material has been preferred
for heating material than any other material. Accordingly, two copper plates
equipped with heating coils have been used so that they can be heated to a
desired set temperature. Heating coils have been placed on one side of the
copper plates along with the ceramic insulating material to eliminate the
possibility of the short circuiting of the plate. Similar to copper plates, only
one side of the fixed steel plates has been fitted with thermocouples. There is
no heating coil placed on steel plate. Copper plates and the steel plate along
with the heating system have been designed in such a way that the whole
system can withstand a maximum temperature of 500 to 600 Degree Celsius.
A pneumatically operated piston-cylinder system has been fitted to a rod so
that the rod can be made to move in axial direction. Accordingly, the copper
plates have been mounted on two rods on two opposite sides of the box type
enclosure. Two pneumatic cylinders for movement of copper plates and the
intervening medium between outer case and inner case of the enclosure, are
shown in the FIG. 4. The intervening medium is designed so as to minimize
heat loss to the outside ambient does not become hot while copper plates are
heated inside the enclosure.

The view of total system of heating looks like FIG. 5, when covered with lid
and insulation. When the top lid of the enclosure is removed, two copper
plates (capable of moving) fitted with heating coils, thermocouples, and the
fixed steel plate (fitted with thermocouples) can be seen from the top, as
illustrated in FIG. 6.
Copper plates are mounted on two axially aligned rods, which are pushed by
the piston of the pneumatic cylinder and the movement of rods in turn enable
the movement of two copper plates. Moving copper plates have been
designed to move towards each other i.e., close to the fixed steel plate from
each side and also in the reverse manner, they can be moved away further
from the fixed steel plate. Hence, the copper plates can be made to come
to a either a very close distance by maintaining a gap, say 10 mm or 20
mm, or they can be clasped to touch on the surface of the fixed test
plate.
A data recorder, used as the data acquisition system, has been connected to
the leads of thermocouples from the copper plates and the fixed plate, as
shown in FIG. 7, for recording of the temperature of the plates. The
temperature values are displayed on data recorder and the values get
updated after every 10 seconds. Recording frequency of thermocouple data
can be set at 10 seconds or at higher interval of one minute. For the present
cases of tests, it has been set to 10 seconds. The box enclosure shown in
FIG. 7 is thermally insulated from the outside ambient conditions. As a
matter of fact, there is a hollow portion between the inner chamber and the
outer chamber so as to minimize the heat loss. The whole box enclosure and
the data recorder have been placed on different tiers or platforms of a trolley.
A switch board to operate the heater, “ON” or “OFF”, is also mounted on one
side of the trolley.

Arrangement has been made so that two copper plates can be brought close
to the fixed steel plate, used for test purpose, very quickly once two copper
plates reach a temperature upto 500 - 600 Degree Celsius by heating. Hot
copper plates have been designed to be kept in contact with the fixed steel
plate that is originally at the ambient temperature inside the chamber and
can be maintained to stay at that position for a long duration of one hour (to
observe the pattern of heat transfer from hot to cold object and the
corresponding temperature of the plates).
The controller temperature has been set to a preset temperature of 350
Degree C at the beginning of the test. Once the heater is turned “ON” by
means of the switch from the switch board, the temperature of two copper
plates are noticed to be increasing with the time and accordingly the
temperature reaches up to the set temperature. Two copper plates are
heated so that their temperatures can be raised upto the desired set
temperature. Heat can be transferred to the fixed plate by direct contact
when the moving plates are brought in direct contact with the fixed plate.
The temperature of the steel plate is bound to increase with time when it is
brought in contact with the copper plates, and correspondingly, temperature
of copper plates fall with time. In the later phase of present tests, the heating
circuit was maintained to be “ON” even after copper plates touch the steel
plate and remain in that position. The controller has been set such that the
temperature of copper plates can maintain a tolerance of 5 Degree Celsius
either above or below the set temperature of 350 Degree Celsius.
Earlier filed version of the patent has encompassed three different types of
tests to prove the suitability of the system. First one was the switching off of
the heating power to the two copper plates already heated to a set
temperature and then two copper plates are made to touch to the test steel

plate. In other two cases, copper plates are heated to a preset temperature
and then turned off, but kept at a distance of 10 mm and 20 mm away from
the stationary steel test plate respectively. Hence, a distance or a gap was
maintained between the copper plates and the steel plate in last two cases of
the earlier filed patent. Temperature rise was noted in the previous set up of
patent application.
It was found in the previously filed patent that if the copper plates are not
brought in direct contact with the steel plates and kept at a gap of 10 mm
from the copper plates, then a maximum temperature of 82 Degree Celsius
is achieved by the test plate. This has been illustrated in FIG. 8.
Thermocouples fitted to the test steel plate record the temperature readings
and they are transferred to the data recorder. FIG.8 shows the pattern or
behavior of steel plate temperature when two copper plates are brought in
contact with and held against the steel plate by touching. Although the
copper plates were heated upto a temperature of about 350 Degree Celsius,
the direct contact with copper plates enabled the steel plate to reach a
maximum achieve a temperature of 184 Degree Celsius in a short duration
of 1200 sec. On the other hand, the same figure shown that a gap of 10
mm maintained for the steel plate away from the hot copper plate has
enabled the steel plate to reach a temperature of 82 Degree Celsius in
about 2500 sec or 40 minutes.
Details of temperature pattern of one of copper plates and the fixed steel
plate in earlier filed patent has been displayed in FIG. 9, a temperature of
184 Degree Celsius was reached by the steel plate in a time of 1200 sec or 20
minutes. The same diagram of the filed patent showed the equilibrium state

reached with temperature values from the thermocouples copper plate and
steel plate were very close.
In the present work, two different types of tests have been carried out. The
first type encompasses the test where the copper plates have been increased
in phase wise manner. At first the temperature was raised to 150 Degree
Celsius and then copper plates were brought to touch the steel plate (while
heating was made off for copper plates) and kept in direct contact with the
steel plate for about 5 minutes. After gaining the heat by the steel plate
during these 5 minutes, two copper plates have been moved away from the
steel plate. Then, again heaters were made “ON” to enable the copper plates
reach 200 in the next phase. Once 200 Degree Celsius is reached by copper
plates, they are brought in touch with the steel plate and maintained in that
position for another 5 minutes. Thus, the stepwise heating of two copper
plates has been done to reach the temperature of 150, 250, 300 and 350
Degree Celsius respectively. For every step wise temperature jump, energy
supplies to the copper plates were turned off and direct contact with the steel
plate was made for the next 5 minutes. The overall energy transfer to the
fixed steel plate and temperature rise for all plates have been depicted in
FIG. 10.
As can be observed from FIG. 10, a maximum temperature of 339 Degree
Celsius has been reached by the steel plate as recorded by the thermocouple
TC3 located on the steel plate. This achievement has been made in 2584 sec
or 43 minutes. There is always a difference of temperature between the
donor material and the receiver material. An equilibrium state with a
difference of temperature exists between steel plate temperature and copper
temperature. The same figure shows the temperature pattern recorded by
the thermocouples of the left hand side copper plate and the right hand side

copper plate. It may also be a matter of interest to note that there are some
thermocouples which shows either a large temperature drop or a steep
increase of temperature when the controller makes the heating off or on. The
steep increase of temperature can be attributed to the inertia to exceed the
set temperature by the respective thermocouple for energy balance in that
region of the plate.
As can be observed from all plots for temperature profile of the steel and
copper plates plate recorded over time by the data recorder, TC1, TC2,…TC6
are the thermocouples located on the steel plate. TC7, TC8 …TC12 are the
six thermocouples located on the left hand side copper plate. On the other
hand, TC13, TC14, …TC18 are other six thermocouples mounted on the right
hand side copper plate.
The other test of the present work deals with the direct raise of temperature
of copper plate upto 350 Degree Celsius and its effect has been shown in
FIG. 11. When Copper plates reach a temperature of 350 Degree Celsius,
they are moved to touch the centrally located steel plate directly. Once
copper plates touch the steel plate, they are kept in that position. This is
continued until the steel temperature reach a temperature very close to that
of copper plates. As can be found from the same FIG. 11, the temperature
increase curve for the steel plate is more or less smooth than more zigzags in
the other tests. Copper plates have transferred the heat energy through
direct contact to the steel plate for the whole duration of contact. It took
about 2200 seconds (about 36 minutes) for the steel plate to reach 338
Degree Celsius. Hence, similar to previous pattern, the steel plate
temperature profile is asymptotic in nature during its last phase when it has
never reached exactly 350 degree C.

Again, the temperature gain or the temperature upto which a steel plate can
be raised by direct contact is completely dependent on the final temperature
of the copper plate up to which the copper plate has been raised by heating.
On the other hand, it is the transfer property or mainly thermal conductivity
of the test plate (steel in this case) to transfer the heat during direct contact
by the fixed plate. This is an improved version over the system in the
previously filed patent and the steel plate in the present system has reached
a temperature of 338 Degree Celsius compared to the earlier achievement of
184 Degree Celsius.

WE CLAIM :
1. A system for heating metal sheets by direct contact with heating
means, the system comprising:-
- an insulated enclosure resembling a box with a top cover, the
enclosure provided with metallic and asbestos materials essentially
consisting of :-
- two copper plates for faster heating mounted on two rods enabled
to move in axial direction;
- a metal sheet disposed to hang vertically, wherein the copper
plates and steel plate are drilled and fitted with thermocouples;
- a plurality of heating coils embedded to each of said copper plates
for heating the metal sheets;
- characterized in that a pneumatic mechanism is connected to said
rods carrying the copper plates to move in axial direction so that
the copper plates in turn move back and forth in the axial
direction, in that the movement of the copper plates in axial
direction brings the two copper plates either close to the metal
sheets interposed in the enclosure for direct heating, and in that
the copper plates can be moved away from the metal sheets when
required by the operator.

2. The system as claimed in claim 1, wherein the heating coils are
embedded to one side (facing away from the metal sheets) of each of
the copper plates for heating the copper plates.
3. The system as claimed in claim 2, wherein a controller is provided to
control the operating sequence of the heating coils.

4. The system as claimed in claim 1, wherein all leads from
thermocouples from the said two copper plates and the metal sheet
are connected to a data acquisition device (data recorder) that reads
the temperature data from the thermocouples, wherein the
temperature variation over a period of time at different locations can
be recorded and stored in the data recorder for later use.
5. The system as claimed in claim 1, wherein the combination of material
of the moving plates and the metal sheet can be varied by change
from copper plate to any other alloyed plate and subjected to different
temperature by means of differently set temperature to allow different
amount of heating via the heating means, and wherein the different
set temperature can be attained from the control panel so that a pre-
fixed temperature is attained by the copper plates.
6. The system as claimed in claim 2, wherein the controller is so designed
that temperature variation will be +/- 5 Degree Celsius from the set
temperature, wherein the controller turns off the heating
arrangements once the set temperature of the thermocouples of
copper plates are reached, and wherein if, a temperature value is
lowered or increased by 5 Degree Celsius than the preset value the
controller is automatically re-started.
7. The system as claimed in one of the preceding claims, wherein the
copper plates can be moved towards the metal sheet and made to
touch the surfaces of the sheet by operating the pneumatic

mechanism, and wherein a provision exists to either to keep the
moving copper plates to rest on the surface of the fixed metal sheet
or to keep copper plates at a distance a distance with a small gap
(without direct touch or contact) or away from the metal sheet.
8. The system as claimed in one of the preceding claims, wherein the
copper plates is made to reach a pre-set temperature via a step wise
temperature rise of 150, 200, 250 and 3000C before bringing it to a
final temperature of 3500C and wherein the copper plates upon
attaining said intermediate temperatures, they are brought in contact
with the sheet metal and kept in contact for about 5 minutes.
9. The system as claimed in one of claims 1-8, wherein the moving
copper plates are raised directly to a temperature of 350 Degree
Celsius. and made to touch the fixed metal sheet and the heating
means is continued to operate till the fixed metal sheet attains a
temperature very close to the temperature of copper plates.
10. A system for heating metal sheet by contacting two hot bodies to the
metal sheet either by step wise increase of the temperature of the
transferring body and retention of heat as substantially described and
illustrated herein with reference to the accompanying drawings.

11. A system for heating metal sheet by direct raise of the temperature of
two heat transferring bodies with higher thermal conductivity and
subsequent transfer of the heat to said metal sheet by direct contact
and holding them together so that the metal sheet reaches
substantially the corresponding temperature, as substantially described
and illustrated herein with reference to the accompanying drawings.