NOVEL MACHINE AND PROCESS OF COPPER ROTOR DIE CASTING USED IN AC ELECTRIC MOTOR

Abstract

The invention relates to pressure die casting process and its machine to produce highly efficient copper rotor for AC Induction Motors widely used in various industries. The invention is made in melting and casting process as well as die casting machine and its components. The invented method and machine components are improving efficiency and performance of AC Induction motor by maximum filling of copper with minimum porosity. The invention also reduce cost, complexity, space and time for production of copper rotor. It also reduce the waste of raw material. The invention further providing a compact and convenient method to cast wide range of copper rotor of various extensive length. In various aspects, this invention is simplifying rotor casting process and reducing the overall cost of copper rotor.

Claims

1. Apparatus to produce highly efficient copper rotors used in AC Induction Motors, comprising: Hydraulic injection cylinder and Injection Piston to inject molten copper into steel lamination stack; First primary palate holding gate cavity and gate die plate; Second Primary Plate holding Adjustable Core Length Segment, Middle Die Palate, Back Cavity, End Die Plate, Hydraulic Ejector Cylinder and Ejection Piston Rod; Running Primary Plate, combined with second primary plate; End Primary Plate containing Hydraulic locking cylinder, locking cylinder rod to lock the die set by pushing running primary plate.

2. Apparatus as defined in claim 1 wherein the gate cavity is made from medium carbon steel.

3. Apparatus as defined in claim 1 wherein the gate cavity is having wide gate ways to flow molten copper featuring porosity free copper rotor and damage free ejection of copper rotor.

4. Apparatus as defined in claim 1 wherein the height of gate ways of gate cavity is 90% of the height of end ring.

5. Apparatus as defined in claim 1 wherein gate cavity is having two gates to flow melted copper.

6. Apparatus as defined in claim 1 wherein gate cavity is having four gates to flow melted copper.

7. Apparatus as defined in claim 1 wherein gate cavity is having more than four gates to flow melted copper.

8. Apparatus as defined in claim 1 wherein the core length segment is made in multi-sections featuring easy adjustment of length of core length segment in accordance to the length of copper rotor to be casted.

9. Apparatus as defined in claim 1 wherein the core length segment is made from Ci casting material preventing thermal fatigue cracking in core length segment.

10. Apparatus as defined in claim 1 wherein the core length segment is made from 98% Ci casting material and 2% nickel.

11. Apparatus as defined in claim 1 wherein the die holding studs & nuts keep holding and supporting the die set.

12. Apparatus as defined in claim 1 having four primary plates design wherein the hydraulic locking system attached with End Primary Plate will apply and maintained locking pressure on running primary plate.

13. Apparatus as defined in claim 1 wherein running primary plate and second primary plate are combined using coupling stud.

14. Apparatus as defined in claim 1 having four plate compact design, wherein the opening stroke of machine is extendable, enabling to cast copper rotor of various length from 5 mm up to 1000 mm and more.

15. Apparatus as defined in claim 1 having four plate compact design, wherein the ejecting stroke of hydraulic ejector is extendable, enabling to cast copper rotor of various length from 5 mm up to 1000 mm and more.

16. Induction furnace for melting copper wherein the furnace top is covered with clay graphite cover, isolating the melting copper from atmosphere.

17. A method to produce highly efficient copper rotors used in AC Induction Motors, comprising the steps of: Melting copper raw material in furnace; Preparing Steel Lamination Stack in accordance to the size of copper rotor to be casted; Assembling Core length segment in accordance to the size of copper rotor to be casted; Assembling the Die Set comprising of Gate Cavity, Core Length Segment, Gate Die Plate, Middle Die Palate, End Die Plate, Die Holding Stud, Die locking nuts and Back Cavity; Attaching die set with second primary plate of machine using die holding stud and die locking nuts; Fixing gate cavity and gate die plate into first primary plate of machine; High pressure locking the second primary plate with the first primary plate using hydraulic pressure; Further locking the die set using die holding stud and die locking nuts to prevent die opening during copper injection process; Injecting melted copper into die set through novel gate cavity featuring the minimum porosity in copper rotor; Solidifying the melted copper inside die set; Horizontally ejecting the casted copper rotor using hydraulic ejector; Removing runner from copper rotor.

18. A method as defined in claim 17 wherein copper raw material is melted in furnace isolated with clay graphite cover to gain minimum excessive oxygen from the atmosphere not more than 300 ppm additional oxygen, increasing the electrical conductivity of copper rotor.

19. A method as defined in claim 17 wherein molten copper is injected into rotor stack without friction in flow, featuring the minimum porosity in copper rotor.

20. A method as defined in claim 17 wherein the length of core length segment can be increased or decreased in accordance to the size of copper rotor to be casted, simply by adding or removing additional section in core length segment.

21. A method as defined in claim 17 wherein the copper rotor is casted without affixing with inner surface of core length segment.

22. A method as defined in claim 17 having four primary plates design wherein the locking pressure is applied and maintained by hydraulic locking system attached with End Primary Plate, locking the die set components until the molten copper is fully solidified.

23. A method as defined in claim 17 wherein the casted copper rotor is ejected horizontally from die set.

24. A method as defined in claim 17 wherein the copper runner is having not more than 300 ppm additional oxygen, which can be used as raw material for the next cycle of copper rotor casting.

Description

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

[0047] FIG. 1 is an elevational view of invented copper rotor casting machine assembled in accordance with the invention.

[0048] FIG. 2 is a fragmentary section of casting machine and illustrating assembly of die set component.

[0049] FIG. 3 is another fragmentary section of casting machine and illustrating the assembly of invented core length segment.

[0050] FIG. 4 is an elevational view of invented copper rotor casting machine during copper injecting process.

[0051] FIG. 5 is fragmentary section of casting machine and illustrating the invented gate cavity, copper rotor and runner.

[0052] FIG. 6 is illustrating the core length segment of prior art.

[0053] FIG. 7 is an elevational view of invented copper rotor casting machine during ejecting the caster copper rotor.

[0054] FIG. 8 is fragmentary section of casting machine and illustrating the attachment of die set assembly with primary plate.

[0055] FIG. 9 is fragmentary section of casting machine and illustrating the gate cavity having four gates.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0056] The invented copper rotor die casting machine is consist of various component. Mainly, consist of four primary plates namely First Primary Plate1, Second Primary Plate2, Running Primary Plate3, End Primary Plate4. All the other components are attached with said four primary plates. First Primary Plate1 and, End Primary Plate4 are permanently fixed into machine table 23. However the said plates can be moved if required eventually to cast extra-long copper rotor of extensive size.

[0057] A description will be given of an embodiment in accordance with the present invention with reference to the accompanying drawings. The present invention can be performed in following steps.

Step-1 Melting Copper

[0058] Copper is melted in high frequency induction furnace wherein the furnace top is fully covered with clay graphite cover (not shown). The clay graphite cover will isolate the copper from atmosphere during melting process. Unlike the prior art, the invented melting process will prevent the copper from gaining additional oxygen from the atmosphere during melting process. The finished copper rotor produced by the invented method will merely gain as low as up to 300 ppm additional oxygen.

Step-2 Preparing Steel Lamination Stack

[0059] The solid core of the Copper Rotor 8 is built with stack7 of electrical steel laminations. In the second step, steel lamination stack 7 are grouped and set in accordance to the size of copper Rotor 8 to be casted. Then the said steel lamination stack 7 is fitted into Core Length Segment9. In further step, melted copper is to be injected and solidified into the said steel lamination stack 7. Copper Rotor 8 is combination of steel lamination stack & solidified copper casted into steel lamination stack 7. In other words, the said steel lamination stack 7 is converted into die casted Copper Rotor 8 at the end of casting process.

[0060] The said steel lamination stack is having slot finger to enable copper filling. Eventually, while using the stack having less broadness of slots finger, the stack can be de-shaped and bend into wide gates of gate cavity due to high locking pressure. To solve this eventual problem, the cavity having four gates is used as illustrated in FIG. 9. Wherein the width of Flow Ways 6 are divided into four gates. This prevents the stack to bend during injecting process. The number of gates in cavity can be increased as per requirement.

Step-3 Assembling Core Length Segment

[0061] In this step, the length of Core Length Segment9 is set in accordance to the size of Copper Rotor 8 to be casted. Core Length Segment9 is fixed between Middle Die Palate11 and End Die Plate 12 using Die Holding Stud 13 & Die locking nuts 14. The Back Cavity 15 is fixed into End Die Plate 12 as illustrated in FIG. 2.

[0062] The invented Core Length Segment 9 is having multi sectional design featuring adjustable core length. As illustrated in FIG. 3, the length of Core Length Segment9 can be increased or decreased by adding or removing Length Segment 16 of core length segment. Length adjustment step became easy due to the invented Die Holding Stud 13 & Die locking nuts 14. Die Holding Stud 13 is fully threaded and hence can be easily adjusted to hold various length of core length segment 9.

Step-4 Assembling the Die Set

[0063] Die Set is assembled in this step. As illustrated in FIG. 2 Die Set is assembly of several components namely Gate Cavity 5, Gate Die Plate 10, Steel Lamination Stacks 7, Core Length Segment 9, Middle Die Palate 11, Back Cavity 15, End Die Plate 12, Die Holding Stud 13 and Die locking nuts 14.

[0064] As illustrated in FIG. 1, Gate Cavity 5, Gate Die Plate 10, is attached with first primary plate 1. The combination of, Steel Lamination Stacks 7, Core Length Segment9, Middle Die Palate 11, End Die Plate 12 is attached with Second primary plate2 using four sets of Die Holding Stud 13, Die locking nuts 14 as illustrated in FIG. 8.

[0065] Copper Rotor 8 is casted inside Die Set as illustrated in FIG. 7.

Step-5 Attachment with Primary Plate As illustrated in FIG. 1, the combination of Core Length Segment9, Middle Die Palate11 and End Die Plate12 are attached with Second primary plate2 using Die Holding Stud 13 & Die locking nuts 14.

[0066] At the same time, the Gate Cavity5 and Gate Die Plate10 are fixed into first primary plate 1.

Step-6 High Pressure Locking

[0067] As illustrated in FIG. 4, the Hydraulic locking cylinder 21 & locking cylinder rod 22 will be activated. The Hydraulic locking cylinder21 is attached with End Primary Plate4. Moreover, locking cylinder rod 22 is joining the Hydraulic locking cylinder21 with Running Primary Plate3, as illustrated in FIG. 4.

[0068] Hydraulic locking cylinder 21 will push the Running Primary Plate3 with high pressure. As illustrated in FIG. 4, Running Primary Plate3 and Second Primary Plate2 are combined using coupling stud 18.

[0069] As a result, the hydraulic pressure will be applied on the combination of Running Primary Plate3 and Second Primary Plate2. The said combination will move towards first primary plate1. Finally the said hydraulic pressure will lock Middle Die Palate11 & Gate Die Plate10 with high pressure as illustrated in FIG. 4.

Step-7 Safety Lock

[0070] After high pressure locking, middle die palate11 is further tightly locked with second primary plate2 using die holding stud13 and die locking nuts 14. It keeps tightly holding the core length segment to prevent die opening during copper injection process as well as rotor ejection process. Molten copper is injected into core die using Hydraulic Injection Cylinder 25. During this step, hydraulic pressure can open the die set consist of the combination of Core Length Segment9, Middle Die Palate11 and End Die Plate12. At this step die holding stud13 and die locking nuts 14 will keep holding the die. It further supports the die from bottom.

Step-8 Injecting Melted Copper

[0071] Finally, melted copper is injected using Hydraulic Injection Cylinder 25, and Injection Piston 26 with Hydraulic pressure.

[0072] As illustrated in FIG. 5, Gate cavity contains Flow Ways6 for flowing melted copper. The novel Flow Ways 6 are designed wide and deep to enable the flow of melted copper with minimum friction. Hence, the melted copper will pass through the gate cavity 5 with minimum friction. The invented gate cavity 5 will guide the melted copper to fill in Rotor 8 stack with full force and velocity.

[0073] Novel gate cavity 5 is featuring obstacle-free flow of melted copper. Hence, entire force & velocity is applied to filling process. The melted copper will entirely fill into steel lamination stack 7 enabling the minimum porosity in finished product i.e. copper Rotor 8. Unlike the prior art, the invented gate cavity is featuring highly efficient copper rotor with minimum waste of energy, raw material and time.

[0074] Due to minimum friction, there are rare chances of welding melted copper with gate cavity 5. This will feature damage-free copper Rotor 8 as well as long life of gate cavity 5. Subsequently, the present invention will cost effective in term of minimum damage in gate cavity 5 and copper Rotor 8. Moreover, with compare to the prior art the copper Rotor 8 is not stuck or weld with gate cavity 5. Which enable easy ejection of end product i.e. copper Rotor 8 from the die set. Which makes the present invention cost effective and consuming less time with compare to the prior art.

Step-9 Solidifying the Melted Copper

[0075] Core length segment 9 will keep holding the steel lamination stack 7 until the melted copper is filled and fully solidified and converted to copper Rotor 8.

[0076] The invented Core Length Segment 9 can be used to cast rotor of multiple length. For example, the core length segment used to cast rotor of 100 mm length, the same core length segment can be used to cast rotor of 125 mm simply by attaching an additional Length Segment 28 of 25 mm with core length segment9. This feature saves time, energy and manpower required for casting rotor, especially to cast rotor of various length sequentially. It also saves overall cost of machine as it can be used to cast rotor of various length. It further simplifies the overall casting process by enabling easy ejection of casted rotor. Moreover, the invented core length segment9 is divided in multiple sections, it can be loaded & unloaded easily with compare to prior art.

[0077] As illustrated in FIG. 6, core length segment in the prior art is halved into two equal fraction. As this segment is divided in only two fractions, each fraction is very heavy in weight. It requires much energy, manpower and time to load core length segment into casting machine. The same way it will require much resources to change core length segment for casting rotor of different size. The upper fraction is movable by hydraulic cylinder from where the casted rotor can be ejected at the end of casting process in the prior art. Moreover, in prior art, the said fraction shaped design of core length segment 17 is very expensive to make as it made as a single & long piece of metal. Further, a separate pair of core length segment 17 is required for all different size of copper rotor to be casted. For example, the core length segment 17 which is used to cast rotor 8 of 100 millimetre length will NOT usable to cast rotor of 150 millimetre length. A separate pair of longer core length Segment 17 will be required, which makes the prior art much expensive with compare to the present invention.

Step-10 Unlocking and Opening the Die Set

[0078] As illustrated in FIG. 7, once the molten copper is fully solidified and copper rotor 8 is casted, the Hydraulic Locking Cylinder21 and Locking Cylinder Rod22 attached with End Primary Plate 4 will be activated. It will pull the combination of Running Plate 3 and Second Primary Plate 2. The extendable space between End Primary Plate4 and Running Primary Plate 3 should be grated than two times the width of copper rotor 8.

[0079] As the combination of Copper Rotor 8, Core Length Segment9, Middle Die Palate 11, End Die Plate 12 are attached with Second primary plate2 the die set will be unlocked and opened. This will create space between Middle Die Plate 11 and Gate Die Plate 10. This will enable hydraulic ejector set 19 & 20 to push and eject the copper rotor 8 from die set. This space is defined as ejecting stroke space.

[0080] To eject the copper rotor, the hydraulic locking set 21 and 22 will pull the Running Primary Plate 3 till the ejecting stroke space becomes greater than the length of copper rotor 8. For example, to cast copper rotor of 1000 mm, said the ejecting stroke space should be greater than 1000 mm.

[0081] As illustrated in FIG. 7, End Primary Plate4 and First Primary Plate1 are permanently fixed on Machine Table 23, however the said plates can be moved if required eventually. To cast extra-long copper rotor of extensive size, the extendable space between End Primary Plate4 and Running Primary Plate 3 can be further extended by increasing the distance between End Primary Plate4 and First Primary Plate1 should be increased.

Step-11 Horizontal Ejection of the Casted Copper Rotor

[0082] As illustrated in FIG. 7, the Ejection Piston Rod19 and Hydraulic Ejector Cylinder20 are attached with Second Primary Plate2. Once melted copper is fully casted and solidified in steel lamination stack 7, Hydraulic Ejector Cylinder20 and Ejection Piston Rod19 will be activated and eject the casted copper Rotor 8 from core length segment 9.

[0083] The novel Core Length Segment9 is made from CI Casting material and 2% nickel. Thermal fatigue cracking or heat checking is not affecting the inner surface of invented core length segment 9. Further, CI Casting material is softer with compare to steel. Moreover with compare to conventional steel material, invented core length segment's shape is not affected by heat during casting cycles. Hence, the casted rotor 8 is not affixed with inner surface of invented core length segment 9 as CI Casting material property. Thus, in invented core length segment, the casted rotor can be ejected horizontally without jamming.

[0084] As illustrated in FIG. 6, core length segment 17 of prior art is made from hot work steel H-13. Wherein, during casting process, significant thermal shock is created by the thermal cycling from molten copper being injected into the die. Continuous thermal cycling leads to thermal fatigue cracking or heat checking. The said heat checking cracks will grow gradually resulting into damaging inner surface of core length segment. Cracks grow to the extent that the molten copper will penetrate in the said cracks. Hence, horizontal ejection is not possible as casted rotor is affixed with inner surface of core length segment.

Extending Ejection Stroke of Hydraulic Ejector Set 19 & 20 as Per Requirement.

[0085] The hydraulic ejector set 19 & 20 with capacity of 1000 mm can be used to eject rotor of 5 mm up to 1000 mm. To cast & eject copper rotor longer than 1000 mm, the previous ejector set 19 & 20 can be replaced with extended hydraulic ejector set. The four plate design of casting machine enables to use various length of hydraulic ejector set 19 & 20 simply by increasing distance between Running Primary Plate 3 and Second Primary Plate2. The said distance can be increased by using extended coupling stud 18 as per the requirement.

Step-12 Removing Runner from Copper Rotor

[0086] At the end of casting process the molten copper is solidified in steel lamination stack 7 as well as in flow ways 6, as illustrated in FIG. 5. While the rotor is ejected from casting machine, the solidified copper is integrate with copper rotor 8 as well as flow ways6. The copper casted in gate cavity is called as Runner 27 which is excessive copper attached to the rotor and will be removed from the rotor 8.

Step-13 Reusing Runner as Raw Material

[0087] Melted copper in the present invention is gaining merely up to 300 ppm additional oxygen from atmosphere due to invented melting process as illustrated in Step-1. Copper in the Runner 27 is still having good electrical conductivity. Hence, the Runner 27 can be reused as raw copper material in next cycle of melting and casting of copper rotor without compromising electrical conductivity of finished rotor.

[0088] In prior arts, the melting copper is gaining excessive oxygen form the atmosphere hence Runner 27 will contain excessive oxygen. In prior arts Runner 27 cannot be reused as raw material in next cycle of casting as it will gain excessive oxygen during re-melting. In prior art if the runner is reused as raw copper, the ratio of oxygen will be doubled in re-melted copper. Hence, in the prior arts, the Runner 27 is scrapped every time.