FIELD OF INVENTION
This invention relates to an automatic welding machine for welding of transformer cores and a process for automatic welding of transformer cores.
BACKGROUND/PRIOR ART OF THE INVENTION
The construction of large transformer cores is a time and labor intensive task due to the clamp fixturing, lamination alignment, temporary assembly, clamp welding and final assembly which is required in the assembly process when assembling larger transformers. The weight of the cores of these transformers ranges from 1000 pounds to more than 15000 pounds and therefore requires an extremely strong clamp. The core laminations are supported and held in position by clamps, one on each side of the core. It has been a practice to make the clamp from sections of structural steel channel or a combination of structural steel channels and structural steel angles. The sizes of structural channels and angles selected for making the clamps are generally those with dimensions closest to the width of the core laminations. Therefore, the clamps provide little if any protection to the edges of the core laminations. The core assembly process starts by fixturing each channel section of the first clamp in proper position with respect to the other channel or angle sections of the clamp. The fixturing must be strong enough to maintain the respective positions of each channel or angle section of the clamp during the laying up of the core laminations. The flanges of channel sections are placed down in the fixture such that the core laminations can be laid on the flat surface of the clamp. Angle sections can be positioned such that flanges are either up or down. When channel and angles are used together, tie straps, which provide a means for alignment and attachment, are welded to each end of the channels. This is done as a sub-assembly process before the core assembly is started. Alignment pins are placed in holes provided in the channels or angles for threaded fasteners used during final assembly of the core. The alignment pins
are smooth and slightly smaller in diameter than the threaded fasteners used for the final assembly. Each of the many lamination layers of the core consist of thin segments of magnetizable metal, each individually slidably placed on the alignment pins. Each lamination segment has mitered ends which must be positioned with respect to the adjacent mitered end of the other lamination segments of that layer and with respect to the position of the mitered ends of the previously laid lamination layer segments. After the final core laminations are placed on the stack, the channel and angle sections making up the second clamp are positioned on top of the core stack. A final alignment of the core laminations and clamps is completed and the core assembly is temporarily secured by strapping or banding placed around each leg of the core. Lifting eyes are attached to the clamps and the core assembly is lifted to the upright position. The alignment pins are removed and threaded fasteners installed and tightened. The core assembly is then moved to a welding station where the channel and/or angle sections forming each of the first and second clamps are welded together. After welding, the core assembly is moved to a final assembly area where the coil and various electrical connectors and brackets are installed.
Reference may be made to the following known arts:-
Publication No. CN101954525 describes an argon-arc welding process of an E-I-type transformer iron core comprising: separating an E wafer from I wafer by a pneumatic wafer separator according to specified lamination thickness; then, pressing the laminated E wafer in a solenoid by using a pneumatic jig, buckling the laminated I wafer on the E wafer and carrying out the argon-arc welding on the joint of the E wafer and the I wafer by adopting an argon-arc welding machine to form an E-I iron core; and finally, testing the electric performance of the E-I iron core.
Publication No. JP4284979 relates to reduction of the iron core weight and winding weight of a welding transformer to miniaturize it and to facilitate transfer of the welding machine on a metal plate by regulating application frequency of the welding transformer to a specified value and making secondary side winding of the welding transformer to single winding.
Publication No. CN101577466 describes an automatic argon arc welding laminating apparatus consisting of two lamination stations and one pressing automatic welding station.
Publication No. CN201084524 provides a novel welding transformer, comprising a frame, an iron core, a primary coil and a secondary coil, wherein, the iron core, the primary coil and the secondary coil are arranged in the frame; the secondary coils are welded with copper tubes; the primary coil is clung tightly with the secondary coil; the primary coil and the secondary coil are wound on the central column of the iron core of the welding transformer and are arranged circularly.
Publication No. CN201017751 describes an iron core of an inverter welding transformer with 1-4 kHZ operating frequency. The iron core of the inverter welding transformer comprises two O-shaped iron core bodies formed by winding silicon steel bands, each O-shaped iron core body is cut off in the middle, to form a pair of opposite C-shaped units, and the two pairs of opposite C-shaped units are arranged in parallel and are fixed as a whole through a shroud ring with a tightening device on the periphery. The said process is for welding m/c's transformer.
Publication No. JP2011082478 provides a welding transformer for an inverter type resistance welding machine, capable of responding to further downsizing and energy saving by solving a problem where a maximum current is lowered when increasing a control frequency, in a welding transformer for an inverter type resistance welding machine.
Edson machinery provides a welding and core stacking equipment capable of welding laminations from EI 54 to EI 174. Change over takes no more than 4 minutes. The machine uses a single adjustable tool to hold the transformer, eliminating the need for expensive tooling costs when welding various sizes.
Shree Khodiyar Transformer provides moving core type welding machine that are based on advanced technologies and are compact in shape & design.
All the methods described in prior arts for assembling transformer core are time consuming and labor intensive. Therefore, there is a need to eliminate many of these steps to reduce time and labor cost.
In order to overcome above listed prior art, the present invention provides an improved transformer welding machine for automatically stacking laminated stacks and welding the transformer core which improves the working efficiency and saves the labor cost.
OBJECTS OF THE INVENTION
The primary object of the present invention is to provide an automatic welding machine for welding of transformer cores and a process for automatic welding of transformer cores from a plurality of stacked U and I type laminations.
Another object of the present invention is to provide an automatic welding machine for welding of transformer cores and a process for automatic welding of transformer cores which is cost effective.
Yet another object of the present invention is to provide an automatic welding machine for welding of transformer cores and a process for automatic welding of transformer cores that automatically stacks and aligns the laminated transformer core.
Still another object of the present invention is to provide an automatic welding machine for welding of transformer cores and a process for automatic welding of transformer cores which permits rapid changeover to different core sizes and styles.
Another object of the present invention is to provide an automatic welding machine for welding of transformer cores and a process for automatic welding of transformer cores having various improved operative functions.
Yet another object to provide an automatic welding machine for welding of transformer cores and a process for automatic welding of transformer cores in which adjustments to the core may be made without complete disassembly of the clamping frame.
Still another object of the present invention is to provide an automatic welding machine for welding of transformer cores and a process for automatic welding of transformer cores that simplifies the manufacturing process of the transformer and shortens the production time limit.
Another object of the present invention is to provide an automatic welding machine for welding of transformer cores and a process for automatic welding of transformer cores that reduces the production cost of the transformer.
Yet another object to provide an automatic welding machine for welding of transformer cores and a process for automatic welding of transformer cores which reduces rejection of cores i.e. utilization of core is more as is compared with manual process.
Another object to provide an automatic welding machine for welding of transformer cores and a process for automatic welding of transformer cores which eliminates the need to fix the clamp separately with screws, nuts, washers and bushes.
SUMMARY OF THE INVENTION
Accordingly the present invention provides a transformer welding apparatus for automatically stacking and welding different types of transformer cores. The welding apparatus comprises a plurality of hydraulic clamping cylinders to engage the lamination stack during the welding process. The clamping system is operative to apply a first higher compression pressure and a second lower welding pressure against the lamination stack. The welding apparatus is preferably equipped with atleast two welding torch driven by a servo-controlled mechanism for four point or two point axial weld along the lamination stack.
In a preferred embodiment of the present invention, the welding apparatus is used to weld at four points along the lamination stack, wherein the arrangement comprising of locating the selected fixture on the machine bed for different types of transformers and connecting hydraulic and pneumatic connection with easy locator coupler; placing the foot plate/clamp in the cavity of fixture; placing the U or E auto counted 8B welded lamination in the fixture followed by placing bobbin in the U or E lamination with particular out wire direction: and placing the auto counted 8B welded I lamination over the bobbin and E/U core. In a similar manner, the second set is positioned.
In another preferred embodiment of the present invention, the welding apparatus is designed to weld mounting foot clamp also in each cycle. "E" & "I" and "U" 85 "I" welding, both facilities incorporated in a single machine. Thus only pressing fixture needs to be changed as per the size and stack of cores. This is two stages welding. At first stage, "E" wafer & "I" wafer are pressed 8B welded separately as per pre-specified core size 85 stack according to particular model/rating. Then it is subjected to the second stage for EI wafer insert within the transformer's wounded coil, pressed and the argon welding is carried out at the E & I joint.
In another preferred embodiment of the present invention, the welding apparatus comprises of atleast two hydraulic clamping cylinders that move at a time with servo control pressure regulators.
In yet another preferred embodiment of the present invention, two
pneumatic slide pads are provided to align U/E and I core of transformer.
In still another embodiment of the present invention, the welding apparatus comprises two cylinders for pressing U/E and I laminate. One of the cylinders is a pneumatically operated cushioned cylinder and the other is a hydraulically operated cushioned cylinder to exert pressing force.
In another embodiment of the present invention, the welding apparatus has two torches to weld 4 points of welding. Each torch has 3 axes to control the movement of the torch with respect to the weld distance and weld angle for different types of transformers.
In yet another embodiment of the present invention, the welding apparatus is equipped with the light protection safety guard which is pneumatically operated and has an interlock with the machine.
In still another embodiment of the present invention, the welding apparatus comprises two welding sets and two welding guns for welding the transformer core.
In an alternative embodiment of the present invention, the welding apparatus is used to weld at two points along the lamination stack, where the arrangement comprises: one clamping cylinder of different NB size on each fixture; loader cum pusher cylinder to hold the transformer after welding and pushing the material to operator side.
In another embodiment of the present invention, the welding machine is used to weld the transformer core of different sizes.
STATEMENT OF INVENTION
According to this invention, there is provided a process for automatic welding of transformer cores comprising steps of:- locating selected fixture on the device bed for different types of transformers; connecting hydraulic and pneumatic cylinder; positioning E counted lamination with bobbin in the fixture; placing the auto counted and welded I lamination wafer over the bobbin and E/U counted and welded core wafer.
Further, according to this invention, there is provided an automatic welding machine for welding of transformer cores comprising of clamping system, E/U and I aligner, E/U and I pressing system and welding torch connected to each other as shown in fig. 1 and working in a combination such as herein described.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Further objects and advantages of this invention will be more apparent from the ensuing description when read in conjunction with the accompanying drawings and wherein:
FIG. 1 shows block diagram according to the present invention;
FIG. 2 illustrates the flow diagram of sequence of operation of the welding machine;
DETAIL DESCRIPTION OF THE INVENTION WITH REFERENCE TO THE ACCOMPANYING DRAWINGS:
The present invention provides a solution to the extensive clamp fixing,
laminates alignment, temporary assembly and core welding that are required in
assembling the transformer cores.
Reference may be made to figure 1A, B which shows two stages automatic argon arc welding device and figure 2A, B, C which shows the process for EI and UI electrical grade lamination cores for core assembly of transformer. Referring to fig. 1A, wherein four point welding machine comprises Side pad for E&I alignment to align the E&I stacks. A torch slide assembly is provided which moves left/ right/up/down or back and forth with the help of servo slide motor. One torch assembly comprises two torches for four point welding. Guide, pressing side cylinder, and fixed position cylinder, are provided around the Component over a base. Pillar support, are provided to support the pressing assembly. Guide rods guide the pressing cylinder assembly for correct positioning repeatedly. Referring to fig. 1B, wherein the machine comprises servo motor which moves the slide assembly and hence the torch assembly is moved. Clamp insert helps in locating the four components which are -mounted on the base plate. A clamping cylinder is provided to help lock and hold the four components in place for welding operation.This process is performed at two sets of special purpose machines. This device is flexible to weld the different size of transformers according to different sizes & stacks of the cores of "EI" or "UI" laminations. Only pressing fixture is required to be changed according to the size of the cores for different type of transformers.
In first stage, Auto gauging E/U and I as per specification in particular models and placing them in the pressing fixture. Under pressure clamping of E&I or U&I core in transformers automatic 2 points welding operation performed on
the middle of the surface of both E/U and I core. Four transformers' stacked can be pressed and welded simultaneously in one operation. This operation is carried out to reduce iron loss as well as humming sound/noise in the transformers. In second stage, under pressure clamping of "E" & "I" or "U" & "I" cores wafer assembly is carried out in the transformers followed by automatic 4 points welding operations on each transformer. Two transformers are placed in the fixture in each operation. Two welding torch from home position are moved forward to weld the "E"& "I" or "U" 8B "I" butt joint on both upper side of transformers in linear Z-axis. Then in reverse movement, the bottom side of transformers is welded with special designed mounting foot clamps. So, opposite surface of Z-axis has two welding run on each transformer.
Thus, each transformer has the four independent welded run and two with foot clamp welded run.
The device comprises clamping cylinder that moves at a time with servo control pressure regulators for different types of transformers, wherein the pressure is controlled by a digital control system. A number of core laminates are sandwiched between the two clamp cylinders. These core laminates are supported and held in position by the two clamp cylinders. This provides some protection for the core laminations but at the same time makes an unstable core assembly since the ratio of the width of the core assembly to the height of the core assembly is small. Therefore, the core assembly is susceptible to being tipped over. To prevent this, the welding machine is provided with pneumatically operated slide pads to align the U/E and I core of transformer. These pads are changeable for different types of transformers to be welded, wherein the pads keep the laminates in an aligned position and also resist the movement of the laminates.
After a final alignment of the core laminates and clamping, the core assembly is temporarily secured by U/E 8B I pressing system. The system has two cylinders, one of them is pneumatically operated cushioned cylinder and the other is hydraulically operated to exert pressing force. While placing the U 8B I core the pneumatically operated cylinder holds the component with a holding plate. Further, there is provision of a three flange bobbin to locate and retain I and U/E core lamination members during mechanical assembly operations. When both transformers are loaded, the pressing cylinder moves the transformer to the welding station for welding with the help of cushioned cylinder.
According to further embodiment of the present invention, the welding machine has two torches to weld at 4 points of transformer core. Each torch has 3 axes to control the movement. These axes perform the function of linear movement traveling for welding; distance changing across axes for different types of transformers and maintaining the weld distance while changing the angle of torch from bracket side to U/E 8B I core weld points. Changing angle is very important because when the transformer is welded from foot mount plate side, at a predetermined angle of torch form the vertical top axis and form the vertical top axis when welded from U/E8BI weld point. Further, the U/E 8BI weld points axes are the same for all the transformers but the base axes are changed. Therefore, the torch is lifted upward to change the angle against X axes.
Pneumatically operated light protection safety guard is provided which is interlocked with the machine.
The welding machine can weld atleast two transformers at a time. The quantity will be less or more depending on the length of the weld 8B core size.
According to an alternative embodiment of the present invention, the machine can be adjusted to weld at two points on the laminate core. In this embodiment, the welding machine locates U/E 8B I wafers on to the fixture with
spacer to separate the one by one. In this arrangement the clamping system comprises one clamping cylinder of different NB depending on the size of wafer sizes. These are provided as per the transformer requirement on each fixture.
The clamping force is automatically configured for different types of transformer cores. The torch slide is moved on hard pillars and dry line bearing with servo motor and ball screw nut. The slide moves at a higher speed where weld is not required and gets slower when the weld is required. The torch angle is manually adjusted for change in the transformer size. Two adjustments are required for height adjustment of the transformer and one for the width of the transformer. The main slide is run by servo motor as per parameters. The speed of the torch slide can be adjusted according to the requirement.
In this alternate arrangement of the present invention, the two point welding machine comprises two welding sets with welding guns and it welds the transformers as per the shift.
This process removes all clamping arrangement or accessories like screw, nuts, washers and plastic bushes from transformers. The major advantage of this process is to reduce inventory, labor head count & cost, cores bending rejection and eliminate core locking process. Also it increases the production speed & space utilization.
Further advantage of the present invention is that, it permits the automatic stacking of a laminated stack having a plurality of distinguishable outer perimeter configurations. The need to manually handle and stack laminates to form a stack having a plurality of outer perimeter configurations and/or a lamina layer comprising a plurality of discrete segments is thereby eliminated. The pressing and stack securing equipment used in the traditional manual assembly method are also eliminated by the present invention.
Thus, the present invention reduces rejection of cores i.e. utilization of core is more as compared to manual process, reduces man power as well as RM like screws, nuts, washers, nylon bushes etc.
It is to be noted that the present invention is susceptible to modifications, adaptations and changes by those skilled in the art. Such variant embodiments employing the concepts and features of this invention are intended to be within the scope of the present invention, which is further set forth under the following claims:-

WE CLAIM
1. A process for automatic welding of transformer cores comprising steps
of:-
- locating selected fixture on the device bed for different types of transformers;
- connecting hydraulic and pneumatic cylinder;
- positioning E counted lamination with bobbin in the fixture;
- placing the auto counted and welded I lamination wafer over the bobbin and E/U counted and welded core wafer.

2. A process as claimed in claim 1, comprising of placing foot plate in the cavity of fixture prior to said positioning of E counted lamination, wherein said bobbin is placed in the E lamination with particular out wire direction.
3. An automatic welding machine for welding of transformer cores comprising of clamping system, E/U and I aligner, E/U and I pressing system and welding torch connected to each other as shown in fig. 1 and working in a combination such as herein described.
4. An automatic welding machine as claimed in claim 3, wherein the welding is carried out at four points or two point on the transformer laminate.
5. An automatic welding machine and a process as claimed in any of the preceding claims, wherein the clamping system comprises two clamping cylinder for four point operation and single cylinder for two point operation, wherein the cylinders move at a time with servo control pressure regulators for different types of transformers.
6. An automatic welding machine and a process as claimed in any of the preceding claims, wherein the E/U & I aligner comprises atleast two pneumatically operated slide pads to align E and I core of the transformer.
7. An automatic welding machine and a process as claimed in any of the preceding claims, wherein the E/U & I pressing system comprises a pneumatically operated cylinder and a hydraulically operated cushioned cylinder to exert pressing force and to move the transformer to the welding place, wherein the pneumatic cylinder holds the component with holding plate while placing the E/U 8B I core.
8. An automatic welding machine and a process as claimed in any of the preceding claims, wherein the welding torch comprises three axes for controlling linear movement of traveling for welding; distance changing across axes for different types of transformers and maintaining the weld distance while changing the angle of the torch from bracket side to E/U & I core weld points; for changing angle of the torch.
9. An automatic welding machine and a process as claimed in any of the
preceding claims, wherein said device comprises two welding sets and
two welding guns for welding.
10. An automatic welding machine and a process as claimed in any of the preceding claims, wherein the device comprises pneumatically operated light protection safety guard that is interlocked with the machine.