FIELD OF THE INVENTION
This invention generally relates to an Electrical Mould Preheater for Foundry
applications. In particular, the present invention relates to an Improved Mould
Preheating System for Foundry Applications and a manufacturing process for the
improved system.
BACKGROUND OF THE INVENTION
Castings of all metal types are manufactured in foundries. Out of them some of
the sand castings, especially Steel Castings, SG Iron and some critical Grey Iron
Castings necessitate appropriate preheating of mould as well as core assemblies
prior to pouring of liquid metal. The preheating of the total mould cavity along
with the mould inner surface has to be up to 35- 75°C.
Due to the moisture pick up and entrapped gases in the mould there is every
possibility of shrinkages occurring in the sand casting. Hydrogen is normally
produced by the reaction of the metal with humidity or residual moisture in the
mold. Drying the mold can eliminate this source of hydrogen formation.
Especially, in case of critical shaped steel castings the shrinkage occurs in the
inaccessible areas leaving no scope for inspection and further repair welding etc.
the only way to eliminate such defects is to ensure preheating of the mould
cavity in the final assembled condition just prior to liquid metal pouring. The
temperature uniformity within the mould cavity while preheating shall be within
35- 75°C.

According to prior art, after the mould assembly is completed, the mould cavity is
heated by introducing producer gas torches into each of the risers to heat them
simultaneously in order to achieve an uniform temperature in the mould cavity.
Accordingly, the prior art entail the following major drawbacks:
1. The heating of the mould cavity cannot be attained up to the desired
temperature due to inadequate and non-uniform heating of the chamber,
which result in developing shrinkage defects, especially in case of steel
castings.
2. The tar produced due to use of the producer gas, fall inside the mould
cavity causing rejection of castings due to inclusions.
3. The increased shrinkage defects, especially in case of steel castings,
necessitate large repair welding and in turn increasing the manufacturing
cost of the casting.
In order to achieve the desired preheat temperature, various methodologies are
known in the art. But preheating of the mould by a hot air blower is one of the
effective methods.
However, all the prior art blowers have some user disadvantages.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose an improved industrial mould
preheating system for foundry applications, which eliminates the disadvantages
of prior art.
Another object of the present invention is to propose an improved industrial
mould preheating system for foundry applications, which is mobile and caters to
more than one mould at a time.
Yet another object of the present invention is to propose an improved industrial
mould preheating system for foundry applications, which provides uniform
distribution of heat to various parts of the mould cavity.
A further object of the invention is to propose a manufacturing process for
producing of an improved industrial mould preheating system for foundry
applications.
SUMMARY OF THE INVENTION
Accordingly, there is provided an improved Electrical Mould Preheater to preheat
mould assemblies prior to pouring of the castings, especially in case of steel
castings to achieve high quality products. A plurality of heating elements are
arranged radially inside a number of Ceramic heat resistant grooved refractory
pads which in turn are attached to a cylindrical chamber in the form of an arch.
An Impeller along with an electrical Motor assembly is attached to a flange on

the input side of the cylindrical chamber.
A first end of a conical shaped chute with input side diameter matching with that
of the chamber is fitted with a flange to the output side of the chamber. A
second end of the chute is fitted to a point connecting three outgoing Nozzles.
From the Nozzles, plurality of Flexi Metallic Hose Pipes are attached to carry the
hot air to the intricate cavities of the mould assembly. Moreover, the input side
of the chamber can also be attached with an Induced fan assembly by
dismantling the impeller assembly to enable induced air into the chamber for
achieving lower heating range. The preheater is further having accessories like
lifting stands for holding the flexi pipes on the moulds and a Ring Distributor with
multiple outlet vents to distribute air evenly to various sections of the mould
assembly. The main heating chamber along with the preheater and the chute is
mounted on a mobile platform. The blower assembly can be used for heating
moulds necessitating lower temperature range to higher range. Also the blower
assembly is used for heating more than one mould assemblies simultaneously.
In accordance with a second aspect of present invention, there is provided a
method of manufacturing preheating system that has dual provision of heating
the mould cavity with an Induced fan or with an impeller. The system has also
the provision of heating more than one mould at a time. This is a mobile
electrical preheating system allowing placement of the blower hoods into the
mould cavities without damaging the mould wall as well as the mould coating
during heating.

The unique features of the preheating system of the invention:
1. Multiple outlets with flexi pipe arrangement to position and lower the
pipes into the cavities of the mould assembly without physically damaging
the mould.
2. Portable and Mobile
3. Dual provision:
a. Induced Fan Heating where the preheating temperature is in the lower
range, i.e. 35-50°C. [For preheating of such sand castings, the cores of
castings require heating up to a maximum of 50°C, wherein the input
side impeller is replaced by the Induced Fan mechanism].
b. In case of bigger sand mould assembly, especially for Steel and SG Iron
Castings, it is advisable to have a separate provision to fix the Impeller
assembly to achieve a higher temperature range up to a maximum of
75°C.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1: Mobile Electrical Mould Preheating system of the invention
Figure 2: Main Heating Chamber (Inner view) of the system of Figure 1

Figure 3: Fabrication stage of the Main Chamber of the Preheater
Figure 4: Mould Preheater with Impeller assembly
Figure 5: Positioning of Flexi Pipes into the Mould cavities
Figure 6: Preheater with Induced Fan mechanism
Figure 7: Multiple Hood Outlets
DETAIL DESCRIPTION OF THE INVENTION
Embodiment of present invention
In order to achieve the foregoing and other objects, and in accordance with the
present invention, embodied and broadly described herein is a method of
manufacturing the electrical preheating equipment.
The heating chamber is made of a cylindrical shaped pipe of desired dia meter. A
plurality of refractory grooved segments along with the heating elements are
fixed to it with a bolting mechanism. Both the ends of the pipe are welded with
flanges to fix the accessories for example, an induced fan or an impeller system
on the rear side, and projected hoods with flexi metallic hose on the front side.
There are other accessories like supporting stands, Ring distributors for hood
support as well as effective heat distribution into the mould cavity.

According to the invention, and as shown in figure -1, the mould preheating
system is constructed with dual provision of induced fan heating or blower
heating which necessitates the following major parts:
1 Main Heating Chamber [Part-3 of Figure -1] comprises seven
basic devices:
A. MS Shell of Cylindrical shape:
This is the main body for the heating chamber which acts as a central
node supporting both the external and internal parts of the blower:
i. External Components:
a. The Multiple Outlet Hood on the front side
b. The Duo blower mechanism on the rear side
ii. Internal Components:
a. Asbestos sheet lined to the inner side of the shell along with
refractory material.
b. The ceramic grooved refractory pads fitted diametrically
opposite to the inner side of the shell
c. The heating element positioned inside the grooved portion of
the ceramic grooved refractory pads.
B. Ceramic Grooved Refractory Pads:
The ceramic grooved pads are designed in the rectangular brick shaped

segments having grooves on one side and plain circumference on the
other side touching the shell.
i. Each segment of ceramic grooved rectangular cube bricks is having
a plurality of grooves for fixing elements.
ii. Refractory Grooved bricks
iii. Bricks are clamped to each other.
C. Heating Elements:
i. Nichrome60 resistance heating wires coiled in the ceramic grooves
with an overall diameter of 10mm and 1200mm length.
ii. Total No of Heating Elements corresponds to the number of bricks.
iii. Electrical circuit designed for 415Volts, R (red) phase: 6 elements,
Y (yellow) phase 6 elements and B (blue) phase : 6 elements to
maintain alternate sequence for balancing current and also to have
uniform heating within the chamber.
iv. A plurality of heater coil/ elements are connected in star
connection.
v. Internal wiring / interconnections are made with Teflon insulated
wires/ Teflon sheets, stainless steel fasteners with spring washers.
vi. The Power rating: 42 Kw
vii. Three phase AC with 58 Amperes

2. Blower Fan Mechanism;
This is a dismountable unit which can be fitted to the rear side of the main
heating chamber. This is used when the requirement of preheating
temperature is at lower range e.g. for heating general cores, moulds etc
prior to assembly to remove moisture
Manufacturing process for blower fan mechanism:
a) A cylindrical pipe is cut to length and a flange is welded on the front
side to fit to the flange of main heating chamber.
b) On the rear side of the pipe, the bower fan is assembled.
3. Blower with Impeller Mechanism
This is also a dismountable unit which can be fitted to the rear side of the
main heating chamber. This is used when the requirement of preheating
temperature is at a higher range, i.e. 55-75°C e.g. for heating bigger core
assemblies in case of steel castings.
Manufacturing process for blower with impeller mechanism:
a) A structural support is made out of metal for positioning the Impeller
along with the motor.
b) The outlet of the impeller is welded to a chequered plate on the front

side so that the plate having a flange equal in size as that of the main
chamber, so that it can be fitted easily with bolts on the rear side of
the main chamber.
4. Multiple Outlet Hood
The purpose of it to distribute the generated hot air into three outlets for
heating different zones of the same mould assembly or two or three
different mould assemblies put together.
Manufacturing process for multiple hood:
a) A pipe is cut to the length is provided and material from the pipe is
removed by gas cutting so that the uncut portions can be bent down
to the desired angle so that they substantially form a conical shape
and then full welding is done.
b) Then a flange of desired size is cut and welded to the front side to
which three pipes of same sizes are welded as if projected in to three
different directions.
c) The front end of each of these pipes in turn have another flange to fix
the metallic flexi pipe.
5. Heating system:
Depending on the type of heating range required the Induced fan or

Impeller blower is fixed to the rear side of the heating chamber.
a) While the induced fan is connected, the heating element rating is
brought down by using potentiometer.
b) However, while heating with the impeller, the heating elements are
utilized at full capacity.
c) In order to enable proper insertion of the flexi pipes without
damaging the mould walls, at least three adjustable stands are
provided for support and also a ring type distributor is also made
out of MS pipe ring so as to have uniform distribution through
multiple risers arranged in circular pattern.
6. Flexible Metallic Wire Breaded Hose Pipes:
The flexible metallic wire breaded hose pipes of at least three numbers
are attached to the three outlets of the multiple outlet hood.
7. Ring Distributor and supporting stands :
The ring distributors are made in accordance with the casting size, the
number of inputs and the casting type along with the supporting devices
for the hose pipe to kept in position.

Example: The one manufactured in the present invention has the
following details:
1. Heating Chamber:
A. Heating Coil Circuit Design: Three phase with SIX elements in each phase
i. Heating element: Ni-Chrome Wire
ii. Total heating elements: 18 Nos
iii. Heating Element dia: 1mm
iv. Volts: 415, 3 Phase, 58 Amperage circuit
v. Heating coil dia: 10mm and Overall length: 1200 mm
vi. Star connection
vii. Internal wiring/ interconnections are made with Teflon insulated
wires /Teflon sheets, stainless steel fasteners with spring
washers, plain washers with well connectivity.
B. Refractory grooved brick size: 300mm x 220mm x 70m
i. Having Four groves in each brick
ii. Total No. of Bricks used: 18
C. Heating Chamber
i. Made of MS Pipe of Dia: 780mm
ii. Chute for fixing multiple hood:
Front dia:390mm & Rear dia:780 mm
iii. Flange Size: 916mm

2. Induced Fan Mechanism
A. Fan : Motor capacity: 500Watts
B. No of Blades: Four
C. Fan diameter: 600mm
3. Blower with Impeller mechanism
4. Provision of ring distributor for enabling multiple torch points depending
on the number of heating inlets for the mould cavity.

WE CLAIM
1. An improved mould pre-heating system for foundry applications,
comprising:
- a heating chamber having internal refractory lining;
- a plurality of grooved ceramic pads disposed along the internal walls of
the chamber;
- a plurality of heating elements each releasably fitted on each of said
grooved ceramic pads;
- a multiple outlet hood flanged on a front side of the chamber with a
multiple nozzle attache to a metallic hose; and
- a dual acting connecting means to allow heating of the mould cavity by
one of induced fan assembly and blower with impeller mechanism.

2. The system as claimed in claim 1, wherein the ceramic grooved refractory
pads have grooves on one side and plain circumference on the opposite
side, and wherein the pads are joined through clamping.
3. The system as claimed in claim 1, wherein the heating elements are formed
of resistance heating wires coiled in the ceramic grooves, and wherein the
electrical circuit is designed for 415V and equal number of three phase
elements (RYB).

4. The system as claimed in claim 1, wherein the plurality of heating elements
are connected in star connection.
5. The system as claimed in claim 1, wherein the blower fan mechanism is
made of a cylindrical pipe having a welded flange on front side to be fitted
with the flange of the heating chamber, and wherein a blower fan is
assembled on the opposite end of the cylindrical pipe.
6. The system as claimed in claim 1, wherein the blower with impeller
mechanism comprises an impeller with motor accommodated on a
structural support, and a metal plate including a flange welded on the
impeller outlet, the size of the flange matching with that of the heating
chamber.
7. The system as claimed in claim 1, wherein the multiple outlet hood is made
by forming a pipe gas-cut to remove materials, the uncut portions of the
pipe is bent to desired angle to form a conical shape before being fully
welded, wherein a first flange with three equal sized pipes projecting to
three different directions welded on the front portion of the pipe, and
wherein a second flange is provided on the front side of the projected pipes
to insert metallic flexi pipes.

ABSTRACT

The invention relates to an improved mould pre-heating system for foundry applications, comprising a heating chamber having internal refractory lining; a plurality of grooved ceramic pads disposed along the internal walls of the chamber; a plurality of heating elements each releasably fitted on each of said
grooved ceramic pads; a multiple outlet hood flanged on a front side of the chamber with a multiple nozzle attache to a metallic hose; and a dual acting connecting means to allow heating of the mould cavity by one of induced fan
assembly and blower with impeller mechanism.