Not applicable.
1. Field of the Invention
The present invention relates to the manufacture of transformer cores, and in particular, to an automatic system for stacking laminations from a core former.
2. Brief Description of the Related Art
A transformer includes a core that is formed from multiple stacked or nested metal laminations. The size and shape of the laminations is determined by the type and size of core. However, even for a particular core, the size and shape of each lamination must vary in order for the laminations to stack or nest together tightly.
A core former is a machine that accepts information from an operator as to the parameters of the particular transformer core desired. The system receives a roll of sheet metal, determines the dimensions of each individual lamination and automatically forms and cuts a series of laminations that the operator manually stacks to produce the desired core.
The manual process for operating a core former requires that an operator be present and perform the following actions at each one of several stationary systems:
(1) Post setup, the operator must ensure that the system is active and find the appropriate core mold (typically an I-beam) matching the dimensions of the inner window of the core to ensure that the produced core maintain its form.
(2) The operator must place the core mold upon the operator's workstation, ensure that all proper dimensions are input into the system PC and sent to the core former. Assuming that all parameters are inputted, the system starts feeding steel to begin its forming process.
(3) As each lamination exits the core forming system, the operator must grab every descending lamination and place it around the core mold, occasionally adjusting the build to ensure that the laminations fit securely.
(4) Upon completion of the core, the operator must move the core to a scale to ensure that core meets weight tolerances. If so, the operator must then bind the core with mild steel strapping, label the core and move the core to a conveyor for loading. If not, the operator must execute a build-up operation for additional laminations and continuously re-weigh until the core reaches the required weight.
The limitations of the prior art are overcome by the present invention as described below.
The present invention is a stacking system that operates in conjunction with a transformer core former. The present invention comprises a computer controlled robot arm with a machine vision system to locate each of a series of laminations formed by a core former and a hand and fingers to sequentially grasp each of the laminations and to transfer each lamination to a forming table which receives and shapes each lamination into a stack to form the desired transformer core. As used herein, the term “hand” refers to the entire robot end-of-arm tooling structure and the term “finger” refers to an apparatus located on the hand that procures the laminations with the use of any form of grasping mechanism. “Core” refers to a transformer core produced by stacking a set amount (in weight) of laminations. “Lamination” refers to a strip of core steel of a predetermined length, width, and shape. The term “extended arm” refers to a mechanism to square the most recently stacked lamination.
The stacking system of the present invention is loaded with the parameters for a particular type and size of transformer core. In particular, the system requires information about the current core, such as the size of the core (or size of beginning lamination) and desired total weight. This information may be obtained automatically from the core former or another type of input may be used.
When producing a lamination, the core former stops at a preset point before making the final cut that separates the lamination from the sheet metal coil. Once the stacking system has obtained the lamination, the final cut is made and the stacking system moves the lamination toward the stack area. The stacking system places the lamination over the existing stack, closes the fingers to shape the lamination and releases the lamination. As the empty hand returns to retrieve the next lamination, the extended arm is activated to square the stack. If the preset number of laminations has been stacked and the core has reached the desired weight, then the process is complete. Otherwise the stacking process continues. Because the laminations grow in size as the core is built, the stacking system determines if the distance between the fingers needs to be adjusted to grasp each lamination.
After a preset number of laminations have been stacked, an integrated load cell weighs the core and compares it to a preset value. If the desired core weight is not reached, the stacking system signals the core former to produce extra laminations as needed.
The present invention requires that an operator be present and perform these actions at only one hub, which may operate multiple systems:
(1) Ensure that all proper dimensions are input into the system computer processing system, which may include a computer processing system (also referred to herein as a “CPU” or “PC”) associated with the core former and a separate computer processing system associated with the robot arm (referred to herein as a “robot controller”). Each of the CPU and the robot controller includes machine readable storage media on which sets of executable instructions reside. The CPU and robot controller may be connected with a communications link such as an Ethernet connection. Assuming that all parameters are input, the system starts feeding steel to begin its forming process.
(2) As each lamination (being built to the proper dimensions) exits the core former, the stacking system's end-of-arm tooling procures the descending laminations using a grasping mechanism and places each one around the preceding laminations, occasionally using an extended arm to adjust the build and ensure that the laminations fit securely.
(3) Upon completion of the core, a scale built into the workstation ensures that each core meets weight tolerances. If so, an off-loading mechanism moves the completed core to a conveyor for unloading. If not, the stacking system executes a build-up by having the core former produce additional laminations. The system continuously re-weigh on its own until the core reaches the required weight.
These and other features, objects and advantages of the present invention will become better understood from a consideration of the following detailed description and accompanying drawing where:
With reference to
The present invention is a automated lamination stacking system that operates in conjunction with a transformer core former. With reference to
As shown in
The core former 30 forms a series of laminations 33 that together form the desired transformer core. The laminations are formed from a roll of metal 31. Each lamination 33 is formed with a number of creases corresponding to the corners of each lamination as it is stacked around the previous laminations to form the transformer core. Although not so limited, the operation of the system will be described with respect to one embodiment in which the creases define five segments of the lamination 33—the back 36 of the lamination 33, the two sides 37 of the lamination 33, a long segment 38 of the front of the lamination 33 and a short segment 39 of the front of the lamination 33. The long segment 38 and the short segment 39 when nested together meet to form the front 40 of the lamination 33. The lengths of each of the five segments 36, 37, 38, 39 are continuously adjusted by the core former 30 so that each lamination 33 is formed with the correct dimensions to nest securely around each previous lamination. After shaping the lamination 33 to produce the creases at the appropriate locations, the final action of the core former 30 is to cut each lamination 33 free from the metal roll 31. The core former 30 carries out these actions automatically after being provided with the desired core sizes by the operator 41.
The core former 30 is operated by a set of executable software instructions residing on computer readable media associated with the core former 30. Such software will necessarily be modified to interface with the executable software instructions that operate the stacking system of the present invention. The software instructions for the stacking system of the present invention comprise a set of executable instructions residing on computer readable storage media associated with the computer processing system CPU 50 and interfaced with and controlling the automatic operation of the core former 30. The CPU 50 also receives information from load cells 87 and camera 64 as described herein. CPU 50 interfaces with a separate computer processing system referred to herein as a robot controller 140. Robot controller controls the operation of robot arm 10, hand 70, fingers 71, 72, shapers or wipers 91, and conveyors 96. Robot controller 140 received information from vacuum sensors 90. Robot controller 140 and CPU 50 are interfaced by means of a communications link 141 such as an Ethernet connection.
As the core former 30 produces each lamination 33, it stops before making the final cut. The lamination 33 hangs vertically from the core former 30 with the creases 62 in the lamination 30 oriented substantially horizontally. For a particular example of a core former 30, some structural modification may be required to allow the lamination 33 to hang vertically.
As shown in
From a head-on perspective, the reference line 61 appears straight, but due to creases 62 formed in the lamination 33 by the core former 30, from an angle to the side of the centerline of the core former 30, the vertical laser reference line 61 has a series of peaks 63 corresponding to the creases 62 in the lamination 33. A camera 64 located off the centerline of the core former 30 is able to visualize the peaks 63 in the laser reference line 61. This information is transmitted and interpreted by a machine vision system which calculates where the creases 62 are located in space with respect to a coordinate system based on the face plane of the core former 30. The machine vision system includes a set of executable instructions residing on the computer readable storage medium within the computer processing system (CPU) 50. The executable instructions residing on the robot controller 140 translate the coordinate system into robot coordinates based on the 6-axis robot arm 10 through training the finger positions and then calibrating the machine vision camera 64 with the robot arm 10. The system thus is able to direct the robot arm 10 to a position where it can grasp the laminations 33 securely as described following. At higher speeds of operation, it is possible that the lamination 33 may tend to move for a period of time following its production from the core former 30. In this situation, the machine vision system may have difficulty in capturing the position of the lamination 33. In one embodiment, an electromagnet (not shown) may be placed on the core former 30 alongside the exit area of the lamination 33. The electromagnet may be activated just before the core former 30 guillotine releases the lamination 33 thus stabilizing the position of the lamination 33 and allowing the laser 60 and camera 64 to capture the image faster and more accurately.
The laminations 33 are grasped by a tool at the end of the robot arm 10. As shown in
As shown in
As shown in
In one embodiment each of the fingers 71, 72 comprise a pair of vacuum cups 76 spaced apart horizontally on a gripper 77. The vacuum cups 76 should be suitable for use on oily metal surfaces. BFF-P Suction Cups (PIAB, Hingham, Mass.) have been found to be suitable for use in the practice of the present invention. The gripper 77 is mounted to the hand 70 by means of a bearing (not shown) that allows the gripper 77 to rotate to a limited degree. This rotation allows the gripper 77 to accommodate itself to some movement of the lamination 33 during the grasping process. A pair of vacuum cups 76 on each finger 71, 72 is desirable for stability in grasping the lamination 33. Each of the vacuum cups 76 is also provided with a vacuum sensor 90 so that the system is able to determine that the vacuum cups 76 have securely grasped the lamination 33.
In operation, the core former 30 produces a lamination 33 and then pauses before cutting the lamination 33 free from the roll of metal 31. Based on location information derived from the machine vision system—the laser line projector 60, the camera 64 and the set of executable instructions residing on the computer readable storage medium within the CPU 50—the lower finger 71 first contacts and grasps the lower point 74 on the lamination 33. The lower point 74 is grasped first since the lower end of the lamination 33 is free to move and thus is more susceptible to an alteration in the position of the point at which the lower finger 71 is directed to grasp the lamination 33. If the upper point 73 were grasped first, it is likely that the point toward which the lower finger 71 is directed would be moved by the act of grasping the upper point 73. The upper portion of the lamination 33 is more stable since it has not at this point in time been cut from the roll of metal 31 to which it remains attached. After the lower finger 71 has securely grasped the lamination 33 at the lower point 74, the upper finger 72 is rotated and translated so as to contact and grasp the lamination 33 at the upper point 73 while the lower finger 71 maintains its grip on the lamination 33 at the lower point 74.
The fingers 71, 72 are mounted on brackets 78 for rotation about pivots 79 toward each other. The rotation is produced by effectors such as pneumatic cylinders 80. Rotation of the fingers 71, 72 toward each other allow for the lamination 33 to be shaped about the stack of previously stacked laminations as described below.
Once both the upper finger 72 and the lower finger 71 have securely grasped the lamination 33 at the upper and lower points 73, 74, respectively, the final cut is made by the core former 30 freeing the lamination 33 from the roll of metal 31. The robot arm 10 then moves the lamination 33 from a position in which it is hanging vertically from the core former 30 to a position horizontally disposed above the forming table 11.
With reference to
The forming table 11 (also referred to herein as a “build table”) may be mounted on a base 85 having a plurality of legs 86. A load cell 87 is disposed beneath the lower end of each leg 86. Information from the load cells is transmitted to the CPU 50 to allow the calculation of the weight of a stack of laminations 33.
With the distances between the forming posts 81 set and the forming posts extended above the common plane 82 of the forming table 11, the robot arm 10, by appropriate rotation and translation, places the lamination 33 about the forming posts 81. The fingers 71, 72 are mounted for rotation toward each other to form the lamination 33 loosely around the forming posts 81 in a position that approximates the desired position of the lamination 33 on the stack of previously stacked laminations that constitute the partially formed core 35 as shown in
As shown in
The shapers 91 are desirably provided with a degree of resilient compliance to ensure firm contact between the inner faces 92 of the shapers 91 and the sides 37 of the lamination 33. However, to avoid excessive compliance the shapers 91 also have a roller 93 as shown in
Once the lamination 33 has been snugly formed around the partially formed core 35, the core 35 is weighed. As noted above, the forming table 11 is mounted on a base 85 that is disposed on a series of load cells 87 that perform the weighing function. If the partially formed core 35 is found to weigh less than the desired weight, a signal is sent by the CPU 50 to the core former 30 to form the next lamination 33. The process is then repeated until a sufficient number of laminations 33 have been added to the core 35 to reach the desired weight. At this point, the forming posts 81 are retracted to a position below the common plane 82 of the forming table 11. The completed transformer core 35 rests on a pair of conveyors, such as chain conveyors 96, that are positioned slightly above the common plane 82 of the forming table 11 as shown in
As outlined in the flow chart of
The present invention has been described with reference to certain preferred and alternative embodiments that are intended to be exemplary only and not limiting to the full scope of the present invention as set forth in the appended claims.
This application claims the benefit of U.S. Provisional Patent Application No. 61/210,608 filed Mar. 20, 2009, the disclosure of which is incorporated herein by reference in its entirety.
Number | Date | Country | |
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61210608 | Mar 2009 | US |