NAME OF THE APPLICANT: MAKROCAST PVT. LTD

METHOD AND APPARATUS FOR MANFACTURING HOLLOW BODIES

FIELD OF INVENTION

The present invention relates to a method for manufacturing hollow bodies like cylinder liner for an engine block. More particularly, the present invention relates to production of hollow bodies by means of centrifugal casting technique using different grades of cast irons. Further, the present invention relates to an apparatus for manufacturing hollow bodies like cylinder liner. Advantageously, the present invention helps to improve aspects of quality and productivity of hollow bodies in an economical way.

BACKGROUND ART

It is well known art that centrifugal casting is a casting technique that is typically used to cast thin-walled cylinder liner. In this process, a control amount of molten metal is poured into the hollow shaped-permanent die, which rotates in its axis. The molten metal is centrifugally thrown towards the inside die wall, where it solidifies after cooling. Metal cooling rate depends upon the rotation of the shaft and external profile of the die. External profile of the die should have maximum contact surface to transfer heat so that inner casting will be cooled fast. As molten metal rotates with simultaneous cooling process, enhance the compactness and tensile strength of the hollow metal bodies. Thus, obviously it will withstand large amount of shock loads and so that, decrease in amount of wear and tear in engine applications.

In between centrifugal permanent die and metal, there is a need of application of some media such as insulation powders or liquid powders to avoid metal sticking to the die. It incurs additional cost as well as requires skilled technicians for the application of insulation powder.

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

Due to the higher temperature of operation, it will stick to the die and then the hot metal will be poured. After removing castings, then die has to be cleaned, and again this cycle starts. This cleaning process of die releases those media powders, which will create lot of dust and pollution to the environment. And also the inclusion rate of this insulation powder in the castings has an average rate of 6-7% because of the improper sticking of those powders with the permanent die.

Minimum wall thickness will vary based on the length and diameter irrespective of the final product requirement. Rapid cooling rate of the metal increases the length and thickness of the casted metal. In addition, casting micro objects will have major variation in its length around 10% from customer specification. This leads to the increment in casting weight than the final product requirement. Moreover, as there is no uniform cooling rate when the metal touches the centrifugal die, the external surface will be hard due to chilling. Thus, further post operations cost and slowdown in productivity will be incurred because of this excess stock.

According to the permanent die size and its temperature requirement, only one model production could be done using one die. For changing over to another model production, sleeves and its accessories are to be placed and pre heating has to be carried out again. The die pre-heating has to be carried out to ensure them in non-chilling effect with a shift efficiency of 8-10% based on model weight. They are suitable for production of plain components only. The scope of liner crack is also higher. In the machining process, parting off for the both the ends has to be done. In the inner diameter, rough and finish operation has to be done and in the outer diameter, machining has to be done for removing hard layer by keeping the stock for finish.

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

US8201611 discloses a method of for the production of centrifugal castings like water and soil pipes by means of permanent mould.

GB489084 discloses a process for manufacturing liner of hard metal in a light-metal cylinder. This is useful for lightweight engine blocks for internal combustion engines.

GB503109 relates to a process of manufacturing hollow aluminium alloy or other light metal piston casting process to avoid micro shrinkages.

GB762524 provides a method and means for the production of hollow bodies by means of permanent mould in the centrifugal casting process.

GB543810 disclosed a method and apparatus for casting metal bodies with cored holes by centrifugal action of the die.

GB1218106 relates to a method of production of hub less pipes with flanges by means of permanent core.

GB411133 relates to a method of production of hollow shaped castings in different shapes and length by means of rotation moulding.

Thus, there is a persistent need to develop a method for manufacturing hollow bodies by means of centrifugal casting with in an aspects of improving quality and productivity that would be capable to eliminate the above discussed limitations of the state of the art and justify technical advancement over prior knowledge in the field by way of providing a core means and preferably a sand core for centrifugal casting adapted to ensure on one hand cost-effective, safe, user

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

friendly application in their production, and on the other hand also enhancing quality of such cast eliminating the major conventional process and post operations in said improved process for manufacturing hollow bodies.

OBJECTS OF INVENTION
Accordingly, it is the primary object of the present invention to provide a method for manufacturing hollow bodies like cylinder liner, which overcomes the above-noted disadvantages.

It is another object of the present invention to provide a method for production of hollow bodies by means of centrifugal casting technique using different grades of cast irons.

It is another object of the present invention, wherein the method is useful in the production of plain or profiled hollow bodies.

It is another object of the present invention, to provide an apparatus for manufacturing hollow bodies like cylinder liner.

It is another object of the present invention, wherein the method provides improvement in the quality and productivity of hollow bodies by introducing one or more cores between permanent centrifugal die and casting, the core being a sand core and is of a split type core.

It is another object of the present invention, wherein the insertion of the core eliminates direct contact of casting material with the die thereby eliminating the requirement of pre-heating of the die.

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

It is another object of the present invention, wherein the method provides slow and uniform metal cooling by use of sand core metal as compared to conventional casting methods.

It is another object of the present invention, wherein the slow and uniform metal cooling eliminates the need to provide extra length at lower and upper ends and thus casting weight will be less.

It is another object of the present invention, wherein to avoid core crack and core fusion, the core is coated with heat resistant coats such as graphite, zirconium and aluminium silicate.

It is another object of the present invention, wherein the method is an eco-friendly process with less dependency on skilled man power requirement.

It is another object of the present invention, wherein the method reduces the major variations in casting length, thickness and weight than the final product requirement.

It is further object of the present invention, wherein the method eliminates the scope of occurring crack during casting.

It is another aspect of the present invention, wherein to improve core strength anti veining compound is added in the sand, the said anti veining compound is iron oxide.

It is another object of the present invention, wherein the process eliminates the major post operation of machining such as parting off, outer diameter (OD) and inner diameter (ID) roughing.

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

It is another object of the present invention, wherein the ease of production of special designs in core is attained by means of same die sets in the casting.

It is another object of the present invention, wherein the method helps to produce wet or dry centrifugal liners with the combination of internal and external cores with minimum machining stocks and uniform microstructure throughout its length to meet its applications.

It is another aspect of the present invention, wherein core thickness and finished product dimension has a minimum ratio of 1: 1 and maximum ratio of 1:2.

SUMMARY OF INVENTION

Thus according to the basic aspect of the present invention, there is provide a method for manufacturing hollow bodies like cylinder liner by means of centrifugal casting technique, comprising:

inserting one or more cores within die sleeve of die assembly and locking the core;

cleaning the die assembly with air when it is rotating;

pouring centrifugally casting material through an orifice provided in front door of the die assembly and simultaneously cooling the casted material; and

removing the casted liner and cleaning the die assembly for each cycle, wherein the die sleeve is coaxially fitted to die holder of the die assembly and is configured to hold the cores,

wherein the core with a hole in its center is co-axially inserted within the die sleeve through its cylindrical outer portion forming external shape of the liner,

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

wherein the die sleeve is provided with excess recess to accommodate another core forming internal shape of the liner resulting in profiled cylinder liner and thereby reducing weight of casting, and
wherein the cores releasably holds the centrifugally casting material supplied to the inner surface thereof.
It is another aspect of the present invention, wherein the liner includes plain cylinder liner and profiled cylinder liner.

It is another aspect of the present invention, wherein the core is a sand core.

It is another aspect of the present invention, wherein to improve core strength anti veining compound is added in the sand, the said anti veining compound being iron oxide.

It is another aspect of the present invention, wherein the core is a split type core.

It is another aspect of the present invention, wherein the insertion of the core within the die sleeve eliminates direct contact of casting material with the die thereby eliminating the requirement of pre-heating of the die.

It is another aspect of the present invention, wherein to avoid core crack and core fusion, the core is coated with heat resistant coats such as graphite, zirconium and aluminium silicate.

It is another aspect of the present invention, wherein the insertion of sand core provides slow and uniform cooling rate thereby eliminating front and back parting off of the cylinder liner.

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

It is another aspect of the present invention, wherein due to slow and uniform cooling rate, casting thickness is as per final requirement.

It is another aspect of the present invention, wherein the simultaneous cooling eliminates crack in the casted liner.

It is another aspect of the present invention, wherein micro and hardness is achieved by cooling the outer surface of the cylinder liner and avoiding rapid cooling.

It is another aspect of the present invention, wherein inner diameter and outer diameter roughing operation is eliminated and thereby outer diameter finishing operation is directly performed on the cylinder liner.

It is another aspect of the present invention, wherein core thickness and finished product dimension has a minimum ratio of 1: 1 and maximum ratio of 1:2.

It is another aspect of the present invention, wherein core draft is 0.3 degree and core draft alignment in relation to the die assembly is 0.3 degree.

It is another aspect of the present invention, wherein core ejection is by means of stripper.

A further aspect of the present invention is directed to provide an apparatus for manufacturing hollow bodies like plain cylinder liner comprising:

at least two die assemblies each comprising of:

at least two bearings rotatably mounted in bearing blocks;
shaft;

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

die holder; die sleeve; and core,

wherein the bearings are pre-fitted with the shaft before assembling into the bearing blocks,

wherein the assembled shaft is fitted over base frame,

wherein front end of the shaft is fitted with the die holder and rear end of the shaft is fitted with shaft pulley,

wherein the die sleeve is coaxially fitted to the die holder and is configured to hold the core,

wherein the core with a hole in its center is co-axially inserted within the die sleeve through its cylindrical outer portion,

wherein the core releasably holds a centrifugally casting material supplied to the inner surface thereof, and wherein the die assemblies are fitted adjacently and driven to a motor through a belt.

A still further aspect of the present invention is directed to provide an apparatus for manufacturing hollow bodies like profiled cylinder liner comprising: at least two die assemblies each comprising of:

at least two bearings rotatably mounted in bearing blocks;
shaft;

die holder;
die sleeve; and

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

one or more cores,

wherein the bearings are pre-fitted with the shaft before assembling into the bearing blocks,

wherein the assembled shaft is fitted over base frame,

wherein front end of the shaft is fitted with the die holder and rear end of the shaft is fitted with shaft pulley,

wherein the die sleeve is coaxially fitted to the die holder and is configured to hold one or more cores,

wherein one of the cores with a hole in its center is co-axially inserted within the die sleeve through its cylindrical outer portion to form external shape of the liner, wherein the another core is co-axially inserted within the die sleeve through excess recess provided in the die sleeve to form internal shape of the liner, wherein the cores releasably holds a centrifugally casting material supplied to the inner surface thereof, and wherein the die assemblies are fitted adjacently and driven to a motor through a belt.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGRURES

Figure 1: illustrates the die assembly for manufacturing of hollow plain bodies/liners by means of centrifugal casting technique according to the present invention.

Figure 2: illustrates the die assembly for manufacturing of hollow profiled bodies/liners by means of centrifugal casting technique according to the present invention.

Figure 3: illustrates core shooting arrangement according to the present invention.

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING FIGURES

The present invention relates to a method for production of hollow bodies by means of centrifugal casting technique using different grades of cast irons. The method is useful in the production of plain or profiled hollow bodies and provides improvement in the quality and productivity of hollow bodies in an economical way. The method provides slow and uniform metal cooling rate by use of sand core metal as compared to conventional casting methods and helps to reduce major variations in casting length, thickness and weight than final product requirement. The present invention also relates to an apparatus for manufacturing hollow bodies like cylinder liner.

Reference is now invited to the accompanying Figure 1 that illustrates the die assembly for manufacturing of hollow plain bodies/liners by means of centrifugal casting technique, the apparatus comprising of at least two die assemblies each comprising of at least two bearings rotatably mounted in bearing blocks (1, 2); shaft (3); die holder (9); die sleeve (10); and core (11). The bearings are pre-fitted with the shaft (3) before assembling into the bearing blocks. The bearing blocks are sealed by means of bearing covers (5, 6, 7, 8) to protect from the foreign particles. The assembled shaft is fitted over base frame (18). The front end of the shaft (3) with flange (4) is fitted with the die holder (9) and rear end of the shaft is fitted with shaft pulley (17). The die sleeve (10) is coaxially fitted to the die holder (9) and is configured to hold the core (11). The design of the die sleeve (10) is based upon the size and shape of the casting (21) required. External size of die sleeve (10) is common for all models and internal shape is based upon the casting required. The core (11) with a hole in its center is co-axially inserted within the die

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

sleeve (10) through its cylindrical outer portion. The core is made up of any type of sand, which will be inserted in to the permanent centrifugal die. The shape and size of the casting is determined by the core.

After inserting core, it will be locked with face plate/front door (12), which is designed with a hole in its centre, thereby locking core movement. The core (11) releasably holds a centrifugally casting material supplied to the inner surface thereof. The die assemblies are fitted adjacently by a belt (13) and driven to a motor (14) through the motor pulley (15) and belt (16). The motor (14) is supported by a motor supporting channel (19). Reference is now invited to the accompanying Figure 2, which illustrates the die assembly used for the manufacture of profiled bodies like cylinder liners, wherein additional core (23) is provided to obtain the internal shape of the hollow bodies like liner. While the core (11) is disposed to form the external shape, the additional core (23) is co-axially inserted within the die sleeve (10) through excess recess provided in the die sleeve to form internal shape of the liner, thereby reducing weight of casting. The core (11) is split type, which has to be assembled outside and inserted into the die sleeve (10). According to the shape of the casting it is necessary to use more than one additional core to obtain the different shapes of the casting.

A method for manufacturing hollow bodies like cylinder liner by means of centrifugal casting technique, comprising the steps of inserting one or more cores (11, 23) within die sleeve (10) of the die assembly and locking the core; switching on the die assembly, cleaning the die assembly with air when it is rotating; pouring centrifugally casting material/hot metal by spout (20) through an orifice provided in front door (12) of the die assembly and simultaneously cooling the casted material; switching off the die and removing the casted liner and cleaning the die assembly for each cycle. Simultaneous cooling of the casted material eliminates crack in the

NAME OF THE APPLICANT: MAKROCAST PVT. LTD
casted liner. The flow (22) of molten metal is shown in the Figures 1 and 2. The core (11) is co-axially inserted within the die sleeve (10) through its cylindrical outer portion forming external shape of the plain cylinder liner and the additional core (23) accommodates the die sleeve, which is provided with excess recess forming internal shape of the liner, resulting in profiled cylinder liners. The insertion of the core within the die sleeve eliminates direct contact of casting material with the die thereby eliminating the requirement of pre-heating of the die. Also, the insertion of sand core provides slow and uniform cooling rate thereby eliminating front and back parting off of the cylinder liner. Due to slow and uniform cooling rate, casting thickness is as per final requirement. Micro and hardness is achieved by cooling the outer surface of the cylinder liner and avoiding rapid cooling. Further, the method of the present invention eliminates the inner diameter (ID) and outer diameter (OD) roughing operation and thereby outer diameter finishing operation is directly performed on the cylinder liner.

The cores (11, 23) are manufactured in any one of the known methods with necessary prints for keeping the core in position inside the die sleeve (10). Customized core shooter is used to manufacture the cores to meet the final production requirement, to reduce its manufacturing cost and to meet rapid production rate. Minimum core thickness is provided to achieve cost without compromising final product requirement. The core thickness and finished product dimension has a minimum ratio of 1:1 and maximum ratio of 1:2. And also to overcome core filling issues at shooting area, special shooting arrangements are made to ensure the sand pressure and to meet fast production. The shooting arrangement as illustrated in Figure 3 comprises of a shooting point (24), shooting point nozzle (25), core box (26), core sand (27) and man drill (28). Since core cross section is very less and it is prone for cracks during core ejection, core box (26) design

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

made into split type and core ejection is by means of stripper. Core draft is 0.3 degree and core draft alignment in relation to the die assembly is 0.3 degree. For improving core strength, anti veining compound such as iron oxide is added in the sand. Further, the core is coated with heat resistant coats like graphite, zirconium based coat to avoid core crack and coated with aluminium silicate to ensure no core fusion occurs, which will affect casting quality.

The following ensures the advantages and benefits of the method according to the present invention:

• Die pre-heating is not required as metal is not having direct contact with permanent die. First casting production itself complies as per product requirement. By the new method, 8-10% of production is saved from forming excess wastages.

• The realizing media between permanent die and casting is sand core, which does not create any dust and or pollution and even the used sand could be recycled. Thus, ensures eco-friendly process.

Also, for the insertion of core, skilled technicians are not required.

• Sticking issues are eradicated, since the core is coated with aluminium silicate. Further, there will be 1-2% sand inclusions rejections. 5% of castings saving could be saved on account of inclusion.

• Sand core costs well-economical and the cost of core could be decreased by manufacturing special design.

• Simultaneous cooling of casting in its length ensures only a micro amount of variation of 5% from customer specified final product.

• Since the method according to the present invention employs sand core asbestos which acts as a refractory material eliminates the chilling effect on the outer diameter and also

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

the front and back ends of the casting. Therefore, constant rate cooling renders an opportunity of minimum amount of stock for machining operation on outer diameter and also on the both ends of the casting. Thus, excess stock of outer diameter, front and back parting is eliminated; saves usage of machine time and nearly 43% of casting weight could be reduced.

• Because of the special design of the core and its manufacturing process, it could be used by same die set up for all models and also, no pre-heating required. The method is able to produce different models at a time, based on its post operations requirement. Thus, provides comfort zone for planning and process to execute the different number of models production at any time, so as to avoid the loss in production. As pre-heating process is also eliminated between models to model production, tooling cost is reduced and the maintenance is reduced up to 80%.

• Nearly, 30-40% weight could be saved by manufacture of profiled liner or wet liner as per the present invention. Any type of profiled models of hollow bodies could be done by the improved centrifugal process technique.

• During post operation like machining process, parting off on the both sides is completely eliminated. Inner diameter is finished in single stage and directly taken for the outer diameter finishing operation, without any requirement of roughing process.

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

WE CLAIM:

1. A method for manufacturing hollow bodies like cylinder liner by means of centrifugal casting technique, comprising:

inserting one or more cores (11, 23) within die sleeve (10) of die assembly and locking the core;

cleaning the die assembly with air when it is rotating;

pouring centrifugally casting material through an orifice provided in front door (12) of the die assembly and simultaneously cooling the casted material; and

removing the casted liner and cleaning the die assembly for each cycle,

wherein the die sleeve (10) is coaxially fitted to die holder (9) of the die assembly and is configured to hold the cores (11, 23),

wherein the core (11) with a hole in its center is co-axially inserted within the die sleeve (10) through its cylindrical outer portion forming external shape of the liner,

wherein the die sleeve is provided with excess recess to accommodate the core (23) forming internal shape of the liner resulting in profiled cylinder liner and thereby reducing weight of casting, and

wherein the cores (11, 23) releasably holds the centrifugally casting material supplied to the inner surface thereof.

2. The method as claimed in claim 1, wherein the liner is a plain cylinder liner.

3. The method as claimed in claim 1, wherein the liner is a profiled cylinder liner.

4. The method as claimed in claim 1, wherein the core (11,23) is a sand core.

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

5. The method as claimed in claim 4, wherein to improve core strength anti veining compound is added in the sand, the said anti veining compound being iron oxide.

6. The method as claimed in claim 4, wherein the core (11) is a split type core.

7. The method as claimed in claim 1, wherein the insertion of the core within the die sleeve eliminates direct contact of casting material with the die thereby eliminating the requirement of pre-heating of the die.

8. The method as claimed in anyone of claims 1 to 7, wherein to avoid core crack and core fusion, the core (11, 23) is coated with heat resistant coats such as graphite, zirconium and aluminium silicate.

9. The method as claimed in claim 1, wherein the insertion of sand core provides slow and uniform cooling rate thereby eliminating front and back parting off of the cylinder liner.

10. The method as claimed in claim 9, wherein due to slow and uniform cooling rate, casting thickness is as per final requirement.

11. The method as claimed in claim 1, wherein the simultaneous cooling eliminates crack in the casted liner.

12. The method as claimed in anyone of claims 1 to 11, wherein micro and hardness is achieved by cooling the outer surface of the cylinder liner and avoiding rapid cooling.

13. The method as claimed in anyone of claims 1 to 12, wherein inner diameter and outer diameter roughing operation is eliminated and thereby outer diameter finishing operation is directly performed on the cylinder liner.

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

14. The method as claimed in anyone of claims 1 to 13, wherein core thickness and finished product dimension has a minimum ratio of 1:1 and maximum ratio of 1:2.

15. The method as claimed in anyone of claims 1 to 14, wherein core draft is 0.3 degree and core draft alignment in relation to the die assembly is 0.3 degree.

16. The method as claimed in anyone of claims 1 to 15, wherein core ejection is by means of stripper.

17. An apparatus for manufacturing hollow bodies like plain cylinder liner as claimed in anyone of claims 1 to 16 comprising:

at least two die assemblies each comprising of:
at least two bearings rotatably mounted in bearing blocks (1,2);
shaft (3);
die holder (9);
die sleeve (10); and
core (11),

wherein the bearings are pre-fitted with the shaft (3) before assembling into the bearing blocks,

wherein the assembled shaft is fitted over base frame (18),

wherein front end of the shaft (3) is fitted with the die holder (9) and rear end of the shaft is fitted with shaft pulley (17),

wherein the die sleeve (10) is coaxially fitted to the die holder (9) and is configured to hold the core (11),

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

wherein the core (11) with a hole in its center is co-axially inserted within the die sleeve (10) through its cylindrical outer portion,

wherein the core (11) releasably holds a centrifugally casting material supplied to the inner surface thereof, and wherein the die assemblies are fitted adjacently and driven to a motor (14) through a belt (16).

18. An apparatus for manufacturing hollow bodies like profiled cylinder liner as claimed in anyone of claims 1 to 16 comprising:

at least two die assemblies each comprising of:
at least two bearings rotatably mounted in bearing blocks (1,2);
shaft (3);
die holder (9);
die sleeve (10); and
one or more cores (11,23),

wherein the bearings are pre-fitted with the shaft (3) before assembling into the bearing blocks,

wherein the assembled shaft is fitted over base frame (18),

wherein front end of the shaft (3) is fitted with the die holder (9) and rear end of the shaft is fitted with shaft pulley (17),

wherein the die sleeve (10) is coaxially fitted to the die holder (9) and is configured to hold one or more core (11, 23),

NAME OF THE APPLICANT: MAKROCAST PVT. LTD

wherein one of the cores (11) with a hole in its center is co-axially inserted within the die sleeve (10) through its cylindrical outer portion to form external shape of the liner,

wherein the another core (23) is co-axially inserted within the die sleeve (10) through excess recess provided in the die sleeve to form internal shape of the liner,

wherein the cores (11, 23) releasably holds a centrifugally casting material supplied to the inner surface thereof, and wherein the die assemblies are fitted adjacently and driven to a motor (14) through a belt (16).