Transformer core stacking device and method

Abstract

 The invention relates to a transformer core stacking device (100) for stacking metal sheet cut-outs (210) onto a stack (300), comprising at least one intermediate stacking conveyor (130) configured to transport the metal sheet cut-outs (210) and having a feeding direction (135), wherein the transformer core stacking device (100) comprises one or more stacking conveyors (110,120) configured to receive metal sheet cut-outs (210) from the intermediate stacking conveyor (130) along the feeding direction (135) and configured to stack the metal sheet cut-outs (210) onto the stack (300), wherein at least one of the one or more stacking conveyors (110,120) is rotatable with respect to the feeding direction (135).

Description

FIELD OF THE INVENTION

[0001] The invention relates to a transformer core stacking device for stacking metal sheet cut-outs onto a stack. The invention also relates to a method for stacking metal sheet cut-outs onto a stack to form a transformer core.

BACKGROUND OF THE INVENTION

[0002] A transformer is a device that transforms an AC input voltage into a higher or lower AC output voltage. A transformer is typically composed of electrical equipment designed to transfer energy by inductive coupling between winding circuits. There are different configurations possible, but a typical transformer has two or more coils that share a common metal core.

[0003] The efficiency of a transformer is highly dependent on the characteristics of the transformer core. Elements such as the geometry of the core, the amount of air gap in the circuit, the properties of the core material and the design or configuration of the transformer core play an important role in the efficiency of a transformer. In order to reduce power loss due to eddy currents, the transformer core is typically made out of thin lamination sheets.

[0004] Laminated transformer cores are comprised of thin metallic laminate plates. The plates are stacked on top of each other to form a plurality of layers. Such a stacked transformer core is typically rectangular in shape and can have a rectangular or cruciform cross-section. Transformer cores typically comprise of a top and a bottom yoke connected to each other through two or more legs, for example resulting in an E- or U-stacked transformer core.

[0005] Laminated or stacked transformer cores can be produced by cutting the desired forms of the yokes or legs out of a metal sheet and by positioning these sheets manually on top of each other to assemble the transformer core. This requires a lot of manual labor and the economic cost is very high. Where the cutting of the sheets can occur at a high velocity, the positioning of the sheets and the assembly of the transformer core are slow processes, rendering the complete process relatively inefficient. In addition, the manual manipulation of the metal sheet cut-outs (210) (requiring up to four people, depending on the size of the sheets) is a process step which is prone to errors.

SUMMARY OF THE INVENTION

[0006] The present invention provides in a transformer core stacking device and/or stacking method, which are used for stacking metal sheet cut-outs onto a stack, wherein one or more stacking conveyors transport and position the different metal sheet cut-outs to a predetermined stack position and wherein at least one of the one or more stacking conveyors makes a rotating movement with respect to the feeding direction of the metal sheet cut-outs.

[0007] According to a first aspect of the invention, there is provided a transformer core stacking device (100) for stacking metal sheet cut-outs (210) onto a stack (300), comprising at least one intermediate stacking conveyor (130) configured to transport the metal sheet cut-outs (210) and having a feeding direction (135), wherein the transformer core stacking device (100) comprises one or more stacking conveyors (110,120), preferably at least two stacking conveyors (110,120), configured to receive metal sheet cut-outs (210) from the intermediate stacking conveyor (130) along the feeding direction (135) and configured to stack the metal sheet cut-outs (210) onto the stack (300), wherein at least one of the one or more stacking conveyors (110,120) is rotatable with respect to the feeding direction (135).

[0008] In some embodiments, the one or more stacking conveyors (110,120), preferably at least two stacking conveyors (110,120), are laterally and/or longitudinally movable with respect to the feeding direction (135).

[0009] In some embodiments, the one or more stacking conveyors (110,120) comprise one or more servomotors (112,114,116,118,122,124,126,128) configured to drive the stacking conveyors (110,120) in a lateral, longitudinal, and/or rotational direction.

[0010] In some embodiments, the transformer core stacking device (100) comprises one or more, preferably at least two, guide rails (140) for at least one stacking conveyor (120), configured such that a rotation of the at least one stacking conveyor (120) is obtained by a lateral or longitudinal motion actuated by servomotors (112, 114, 116, 118, 122, 124, 126, 128).

[0011] In some embodiments, the one or more stacking conveyors (110,120) are adjustable in height. Preferably the intermediate stacking conveyor (130) is also adjustable in height.

[0012] According to a second aspect of the invention, there is provided a method for stacking metal sheet cut-outs (210) onto a stack (300) to form a transformer core, comprising the steps of:

a) feeding a first metal sheet cut-out to a first stacking conveyor (110) by an intermediate stacking conveyor (130);

b) positioning the first stacking conveyor (110) and releasing the first metal sheet cut-out onto the stack (300);

c) preferably, feeding a second metal sheet cut-out to a second stacking conveyor (120) by the intermediate stacking conveyor (130); and

d) preferably, positioning the second stacking conveyor (120) and releasing the second metal sheet cut-out onto the stack (300);
wherein one or more of steps b) and d) comprises the rotation, and optionally translation, of the first or second stacking conveyor (110,120) with respect to the feeding direction (135).
In some embodiments, the method further comprises the steps of:

e) feeding a third metal sheet cut-out to the first stacking conveyor (110) by the intermediate stacking conveyor (130);

f) positioning the first stacking conveyor (110) and releasing the third metal sheet cut-out onto the stack (300);

g) feeding a fourth metal sheet cut-out to the second stacking conveyor (120) by the intermediate stacking conveyor (130);

h) positioning the second stacking conveyor (120) and releasing the fourth metal sheet cut-out onto the stack (300);
wherein any of steps f) and h) optionally comprise the rotation and/or translation of the first or second stacking conveyor (110,120) with respect to the feeding direction (135) and wherein the method further comprises steps of:

i) feeding a fifth metal sheet cut-out to the intermediate stacking conveyor (130);

j) positioning the intermediate stacking conveyor (130) and releasing the fifth metal sheet cut-out onto the stack (300).

[0013] In some embodiments, steps a)-d) or a)-j), optionally with additional steps, are iterated, thereby forming the transformer core layer-by-layer.

[0014] In some embodiments, at least one combination of steps b) and i); d) and i); f) and i); or h) and i) is performed simultaneously or overlaps in time, optionally also wherein at least one combination of steps b) and j); d) and j); f) and j); or h) and j); is performed simultaneously or overlaps in time.

[0015] In some embodiments, a first positioning step that is simultaneously performed or overlapping with a feeding step, optionally also with a second positioning step, comprises rotation of the first or second stacking conveyor (110,120) with respect to the feeding direction (135).

[0016] In some embodiments, the metal sheet cut-outs (210) are stacked on one or more stacking cars, wherein said stacking cars remain immobilized during the stacking steps a)-d) or a)-j).

[0017] In some embodiments, the metal sheet cut-outs (210) comprise a bottom yoke (212) and a top yoke (211), and wherein the feeding and positioning steps of the bottom yoke (212) and the top yoke (211) occur simultaneously or overlap in time.

[0018] In some embodiments, the bottom yoke (212) and the top yoke (211) are stacked on separate stacking cars, preferably wherein the bottom yoke (212) is stacked on an E-core stack (310) on a first stacking car, and wherein the top yoke (211) is stacked on a top yoke pile (320) on a second stacking car.

[0019] In some embodiments, the metal sheet cut-outs are re-positioned using an in-line control and correction system.

[0020] Preferably, the method according to second aspect of the invention is performed with the transformer core stacking device (100) according to the first aspect of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 depicts an illustration of the typical shape of an E-stacked (A) and a U-stacked (B) transformer core.

FIG. 2 illustrates a preferred cutting sequence of the metal sheet into metal sheet cut-outs (210).

FIG. 3 shows (A) a preferred position of the two transformer core stacks with respect to each other and (B) the position of the intermediate stacking conveyor with respect to the two other stacking conveyors.

FIG. 4 illustrates a preferred stacking sequence according to the methods of the present invention.

FIG. 5 illustrates an embodiment of the transformer core stacking device.

FIG. 6 illustrates several working steps of the transformer core stacking device.

FIG. 7 illustrates several servomotors on the transformer core stacking device.

FIG. 8 illustrates alternative cutting sequences and alternative transformer core shapes.

DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention aims to provide a transformer core stacking device which solves one or more of the aforementioned disadvantages. Preferred embodiments of the present invention aim to provide a transformer core stacking device which solves one or more of the aforementioned disadvantages. The present invention also aims to provide a method which solves one or more of the aforementioned disadvantages. Preferred embodiments of the present invention aim to provide a method which solves one or more of the aforementioned disadvantages.

[0023] To solve one or more of the above-described problems, at least one embodiment of the present invention adopts the following constructions as illustrated in the embodiments described below, which are illustrated by the drawings. However, parenthesized or emboldened reference numerals affixed to respective elements merely exemplify the elements by way of example, with which it is not intended to limit the respective elements.

[0024] Before the present system and method of the invention are described, it is to be understood that this invention is not limited to particular systems and methods or combinations described, since such systems and methods and combinations may, of course, vary. It is also to be understood that the terminology used herein is not intended to be limiting, since the scope of the present invention will be limited only by the appended claims.

[0025] As used herein, the singular forms "a", "an", and "the" include both singular and plural referents unless the context clearly dictates otherwise.

[0026] The terms "comprising", "comprises" and "comprised of" as used herein are synonymous with "including", "includes" or "containing", "contains", and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps. It will be appreciated that the terms "comprising", "comprises" and "comprised of" as used herein comprise the terms "consisting of", "consists" and "consists of".

[0027] The recitation of numerical ranges by endpoints includes all numbers and fractions subsumed within the respective ranges, as well as the recited endpoints.

[0028] Whereas the terms "one or more" or "at least one", such as one or more or at least one member(s) of a group of members, is clear per se, by means of further exemplification, the term encompasses inter alia a reference to any one of said members, or to any two or more of said members, such as, e.g., any ≥3, ≥4, ≥5, ≥6 or ≥7 etc. of said members, and up to all said members.

[0029] Unless otherwise defined, all terms used in disclosing the invention, including technical and scientific terms, have the meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. By means of further guidance, term definitions are included to better appreciate the teaching of the present invention.

[0030] In the following passages, different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

[0031] Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to a person skilled in the art from this disclosure, in one or more embodiments. Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the appended claims, any of the claimed embodiments can be used in any combination.

[0032] In the following detailed description of the invention, reference is made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration only of specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilised and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense.

[0033] The present invention provides in a transformer core stacking device and/or stacking method, which is used for stacking metal sheet cut-outs onto one or more stacks, wherein one or more stacking conveyors transport and position the different metal sheet cut-outs to a predetermined stack position and wherein at least one of the one or more stacking conveyors makes a rotating movement with respect to the feeding direction of the metal sheet cut-outs.

[0034] The assembly of the metal sheet cut-outs for a transformer core typically occurs manually by taking the metal sheet cut-outs from for instance a cutting machine and assembling the transformer core on a stacking table. In more automated processes metal sheet cut-outs are automatically positioned on a stacking table. However, as each different type of metal sheet cut-out (e.g. a leg or a yoke) needs to be positioned in a different location, the position of the stacking table is altered by translating or rotating the table, thereby bringing the new position in line with the feed of the metal sheet cut-outs. The repositioning of the stacking table has the disadvantages that the assembly time depends largely on the time required for repositioning the stacking table and this has to occur every time a new type of metal sheet cut-out is made. The repositioning of the stacking table also becomes more difficult during the course of the transformer core manufacturing process because the weight of the assembly on the stacking table increases constantly from a few kg at the beginning of the process to often more than 1000 kg at the end. This change in weight also renders the table translation process more prone to errors, in particular because the calibration of the movement of the stacking table, which has to occur with a high accuracy, is difficult due to the weight variation.

[0035] According to a first aspect of the invention, there is provided a transformer core stacking device (100) for stacking metal sheet cut-outs (210) onto a stack (300), comprising at least one intermediate stacking conveyor (130) configured to transport the metal sheet cut-outs (210) and having a feeding direction (135), wherein the transformer core stacking device (100) comprises one or more stacking conveyors (110,120), preferably at least two stacking conveyors (110,120), more preferably exactly two stacking conveyors (110,120), configured to receive metal sheet cut-outs (210) from the intermediate stacking conveyor (130) along the feeding direction (135) and configured to stack the metal sheet cut-outs (210) onto the stack (300), wherein at least one of the one or more stacking conveyors (110,120) is rotatable with respect to the feeding direction (135).

[0036] As referred to herein, the term "transformer core stacking device" refers to a piece of equipment as described herein, which is adapted to transport metal sheet cut-outs (210) or plates along a certain distance and position said metal sheet cut-outs (210) or plates on a predetermined, specific and accurate position, thereby assembling a laminated transformer core.

[0037] As referred to herein, the term "transformer core" refers to one of the main parts of a transformer. The transformer core as referred to herein is a stacked or laminated transformer core, meaning that the core is comprised of thin metallic laminate plates, also referred to as "metal sheet cut-outs" (210), typically cut from a metal sheet. The laminate plates are stacked on top of each other to form a plurality of layers. A stacked transformer core typically comprises different types of laminate plates or metal sheet cut-outs (210). Figure 1 shows the typical shape of an E-stacked (Figure 1A) or a U-stacked (Figure 1 B) transformer core. E-stacked transformer cores typically comprise a top yoke (211), a bottom yoke (212), two outer legs (213, 214) and a center leg (215). A U-stacked transformer core typically comprises a top yoke (211), a bottom yoke (212) and two outer legs (213, 214). Depending on the shape of the transformer core, other configurations (comprising for instance a larger number of legs and yokes) can be considered as well. Upon manufacturing these stacked transformer cores, one of the yokes (typically the top yoke (211)) is assembled separately, while the other metal sheet cut-outs (210) are assembled in an E or U configuration. This allows the electrical coils of the transformer to be positioned around the legs of the core, after which the top yoke (211) can be positioned and the entire transformer core can be assembled accordingly.

[0038] Preferably, the metal for the metal sheet cut-outs (210) is magnetic steel, preferably grain oriented magnetic steel. The metal sheet, from which the metal sheet cut-outs (210) were cut, preferably has a thickness of from 0.15 to 0.35 mm, for example of from 0.18 to 0.30 mm, for example of from 0.20 to 0.27 mm. For example, the metal sheet can have a thickness of about 0.18mm, about 0.20mm, about 0.23mm, about 0.27mm, or about 0.30mm. The metal sheet preferably has a width of from 40 to 1200 mm, for example of from 60 to 1000 mm, for example of from 80 to 800 mm, for example of from 100 to 600 mm, for example of from 120 to 400 mm, for example of about 300 mm.

[0039] As referred to herein, the term "stack" refers to a plurality of metal sheet cut-outs (210) being positioned on top of each other, thereby forming a pile of metal sheet cut-outs (210). By stacking the metal sheet cut-outs (210) as referred to herein accurately, a transformer core can be assembled for use in a transformer. As referred to herein, a stack refers to a bundle of metal sheet cut-outs (210). Upon assembling E- and U-type transformer cores, typically two separate stacks are assembled, a first stack which comprises the metal sheet cut-outs (210) forming the E or U shape and a second stack which forms the top of the transformer core and which is only attached to the top of the E or U shape once the electrical coils are positioned around the legs.

[0040] As referred to herein, the term "conveyor" refers to a technical piece of equipment that that moves metal sheet cut-outs (210) from one location to another. Typical conveyors used in the devices and methods as referred to herein are conveyor belts, roller systems, magnetic conveyors, etc. Preferably magnetic conveyors are used in the devices and methods according to the present invention. Magnetic conveyors lift the metal sheet cut-outs (210) using magnets, for example permanent magnets or electromagnets. For releasing the metal sheet, the magnets may be lifted away from the metal sheet, thereby dropping the metal sheet cut-outs (210) onto the stack. Alternatively, the magnets may be switched off or the metal sheet cut-out may be tapped and removed from the conveyor. Alternatively, the metal sheet cut-outs (210) are transported by the conveyor using another attachment system, such as for instance a vacuum system. The complete supporting frame of the conveyor belts is preferably adjustable in height to limit the drop height for the metal sheet cut-outs (210).

[0041] As referred to herein, the term "feeding direction" refers to the direction into which the metal sheet cut-outs (210) are transported into the stacking device (100).

[0042] The transformer core stacking device (100) according to the invention receives metal sheet cut-outs (210) from a feeding direction (135). Preferably, the metal sheet cut-outs are fed to the transformer core stacking device (100) through a conveyor system (110,120,130). Once the metal sheet cut-outs (210) enter the transformer core stacking device (100) an intermediate stacking conveyor (130) transports the metal sheet cut-outs through the stacking device as disclosed herein and delivers the metal sheet cut-outs (210) to at least one of the one or more stacking conveyors (110,120), which stack the metal sheet cut-outs (210) onto their correct position. Optionally, some types of metal sheet cut-outs (210), such as the top yoke (211), are stacked by the intermediate stacking conveyor (130).

[0043] Preferably, the one or more (preferably at least two, more preferably exactly two) stacking conveyors (110,120) are configured to receive and assemble the metal sheet cut-outs (210) onto a first stack (310), whereas the intermediate stacking conveyor (130) is configured to assemble the metal sheet cut-outs (210) onto a second stack (320), wherein preferably said first stack is the E-core or U-core stack comprising the metal sheet cut-outs (210) for the bottom yoke (212) and the legs (213,214,215) of the transformer core, and wherein said second stack is the top yoke stack comprising the metal sheet cut-outs (210) for the top yoke (211). In a preferred embodiment the first of the two stacking conveyors (110) is configured to position the laminate sheets for the center leg (215) and one outer leg (214), whereas the second of the two stacking conveyors (120) is configured to position laminate sheets for the other outer leg (213) and the bottom yoke (212). For the positioning of the laminate sheets for the bottom yoke (212) a rotational movement is required.

[0044] By providing a transformer core stacking device (100) for stacking metal sheet cut-outs (210) onto one or more stacks, comprising one or more stacking conveyors (110,120) configured to receive metal sheet cut-outs (210) along the feeding direction (135), wherein at least one of the one or more stacking conveyors (110,120) is rotatable with respect to the feeding direction (135), a system is provided that allows the stacking location for assembling the transformer core to be at a fixed position, not requiring the reposition of the stacking location depending on the type of metal sheet cut-out (210) that is fed. The rotating conveyor allows the direct assembly of the transformer core in line with the feed of the metal sheet cut-outs (210), as such reducing the lag time in the process. It has been observed that this particular device allows the assembly of the transformer core at a velocity which equals the velocity of the cutting system, thereby tremendously decreasing the assembly time while at the same time providing a high degree of accuracy.

[0045] In some embodiments, the one or more stacking conveyors (110,120), preferably at least two stacking conveyors (110,120), are laterally and/or longitudinally movable with respect to the feeding direction (135). While some of the metal sheet cut-outs (210) (typically the laminate sheets for the bottom yoke (212)) need a rotating movement for their positioning, other types of metal sheet cut-outs (typically the laminate sheets for the legs (213,214,215) and the top yoke (211)) will require transport in a lateral and/or longitudinal direction.

[0046] In some embodiments, the one or more stacking conveyors (110,120), preferably at least two stacking conveyors (110,120), comprise one or more servomotors (112,114,116,118,122,124,126,128) configured to drive the stacking conveyors (110,120) in a lateral, longitudinal, and/or rotational direction.

[0047] As used herein, the terms "longitudinal direction" and "X direction" are used to refer to the feeding direction (135). As used herein, the terms "lateral direction" and "Y direction" are used to refer to the direction perpendicular to feeding direction (135), but still in the same plane as the plane of the metal sheet cut-outs (210). In some preferred embodiments, at least one of the one or more stacking conveyors comprises one or more servomotors for the longitudinal direction (112,114,122,124) and one or more servomotors for the lateral direction (116,118,126,128). In some preferred embodiments, at least two stacking conveyors (110,120) each comprise one or more servomotors in the longitudinal direction (112,114,122,124) and one or more servomotors in the lateral direction (116,118,126,128). In some embodiments, at least one of the one or more stacking conveyors (110,120) comprises two servomotors (112,114,122,124) for the longitudinal direction and two servomotors for the lateral direction (116,118,126,128). In some preferred embodiments, at least two stacking conveyors (110,120) comprise two servomotors (112,114,122,124) for the longitudinal direction and two servomotors for the lateral direction (116, 118, 126, 128). One of the advantages of such combinations is that lateral, longitudinal, and rotational movement is made possible. Preferably, the servomotors (112,114,116,118,122,124,126,128) are moved over a gear rack. Furthermore, the stacking conveyors (110,120) and intermediate conveyor (130) may also comprise one or more conveyor drive motors (111,121,131), which are preferably also servomotors.

[0048] With the servo-drive of the conveyors, it can also be possible to stack a number of laminations with an off-set, for example with an off-set in longitudinal direction, with the same precision of stacking. This off-set may be repetitive until the maximum height of the stacks is attained.

[0049] In some embodiments, the transformer core stacking device (100) comprises one or more guide rails (140) for at least one stacking conveyor (120), configured such that a rotation of the at least one stacking conveyor (120) is obtained by a lateral and/or longitudinal motion actuated by servomotors (112,114,116,118,122,124,126,128).

[0050] In some embodiments, the one or more stacking conveyors (110,120), preferably at least two stacking conveyors (110,120), are adjustable in height. Preferably, in some embodiments also the intermediate stacking conveyor (130) is adjustable in height. One of the advantages of such a system is that the drop height can be limited, thereby providing greater accuracy.

[0051] The invention also encompasses a cutting and stacking line comprising a cutting line and a transformer core stacking device (100) according to the first aspect of the invention. For example, the cutting line may be a 40mm - 400mm cutting line, a 60mm - 600mm cutting line, a 80mm - 800mm cutting line, a 100mm - 1000mm cutting line, or a 120mm - 1200mm cutting line (referring to the minimal and maximal width of the sheets that can be cut).

[0052] The cutting line can be used to cut a metal sheet (200) into metal sheet cut-outs (210). Preferably, 5 metal sheet cut-outs (210) per layer are cut from the metal sheet: a top yoke (211) and a bottom yoke (212); a first outer (213), a second outer (214), and a center leg (215). A preferred cutting sequence is shown in Figure 2. The top and bottom yoke (211,212) are preferably trapezoidal with a v-shaped notch, the first and second outer legs (213,214) are preferably trapezoidal, and the center leg (215) is preferably shaped as an elongated hexagon. The invention also comprises situations with more than 5 metal sheet cut-outs (210) per layer, such as for example 7, 9, 11, 13, 15, or more metal sheet cut-outs (210). In some embodiments when more than 3 legs are present, the yoke(s) can be comprised of 2 or more sheets, for example 4, 6, 8 or more. Figure 8A shows an alternative cutting sequence for a U-shaped transformer core stack and a separate top-leg stack. Figure 8B shows an alternative cutting sequence for a 5-leg core with split middle legs.

[0053] The cutting line may comprise cutters such as one or more tip cutters or shears, one or more v-notch cutters, and/or one or more hole punching units. Preferably, the cutting line comprises two v-notch cutters on opposing sides. In some preferred embodiments, the tip cutters or shears cut at an angle of 45° or 135° with respect to the feeding direction (135). In some preferred embodiments, the v-notch cutters cut a 90° v-notch at an angle of 45° or 135° with respect to the feeding direction (135). The hole punching unit may be used to punch holes in the metal sheet cut-outs (210), which can then be placed over pins to ensure better placement. In some embodiments, the metal sheet cut-outs (210) comprise holes, which have the advantage of better placement and or allow the metal sheet cut-outs (210) to be released from a higher height. In some embodiments, the metal sheet cut-outs (210) do not comprise holes, thereby providing improved flow of flux for the transformer core.

[0054] The invention also encompasses an off-line stacking device, i.e. without a cutting line, for example comprising a de-stacking line, where separate stacks of the metal sheet cut-outs (210) are de-stacked, and are subsequently handled by the transformer core stacking device (100) to be re-stacked in a transformer core.

[0055] In some embodiments, the transformer core stacking device (100) also comprises a measuring system, which may be configured to measure the height of the stack at regular intervals. This may be connected to a CNC control system, to adjust the number of sheets (or layers) per core.

[0056] In some embodiments, the transformer core stacking device (100) also comprises supporting guides, suitable for supporting wider metal sheet cut-outs (210). These supporting guides may be adjustable in width, for example with a servomotor.

[0057] According to a second aspect of the invention, there is provided a method for stacking metal sheet cut-outs (210) onto a stack (300) (or one or more stacks (310,320) to form a transformer core, comprising the steps of:

a) feeding a first metal sheet cut-out to a first stacking conveyor (110) by an intermediate stacking conveyor (130);

b) positioning the first stacking conveyor (110) and releasing the first metal sheet cut-out onto the stack (300);

wherein step b) comprises the rotation, and optionally translation, of the first stacking conveyor (110) with respect to the feeding direction (135).

[0058] In the preferred embodiments according to the second aspect of the invention, there is provided a method for stacking metal sheet cut-outs (210) onto a stack (300) (or one or more stacks (310,320) to form a transformer core, comprising the steps of:

a) feeding a first metal sheet cut-out to a first stacking conveyor (110) by an intermediate stacking conveyor (130);

b) positioning the first stacking conveyor (110) and releasing the first metal sheet cut-out onto the stack (300);

c) feeding a second metal sheet cut-out to a second stacking conveyor (120) by the intermediate stacking conveyor (130); and

d) positioning the second stacking conveyor (120) and releasing the second metal sheet cut-out onto the stack (300);

wherein one or more of steps b) and d) comprises the rotation, and optionally translation, of the first or second stacking conveyor (110,120) with respect to the feeding direction (135).

[0059] One of the advantages of the present method is that the metal sheet cut-outs (210) remain attached to conveyors (110,120,130) until they are released. This avoids manual handling and relative displacement, which causes errors. Furthermore, this method may allow for cheaper assembly. In addition, this method may allow the assembly of relatively large transformer cores from relatively large metal sheet cut-outs (210).

[0060] The method according to the second aspect may also comprise preceding cutting steps, preferably using a cutting line as described above. A preferred cutting sequence is: center leg (215) - first outer leg (213) - second outer leg (214) - bottom yoke (212) - top yoke (211) as shown in Figure 2. One of the advantages of such sequence is reduced scrap metal.

[0061] The particular cutting sequence as shown in Figure 2: center leg (215) - first outer leg (213) - second outer leg (214) - bottom yoke (212) - top yoke (211), is also particularly useful in the method as described herein. When the metal sheet cut-outs (210) for the legs (213,214,215) are positioned and stacked in line with the feeding direction, and also the metal sheet cut-outs (210) for the top yoke (211) are positioned and stacked in line with the feeding direction (on a separate stack) only a single rotational movement needs to be performed for the metal sheet cut-out of the bottom yoke (212). The rotational displacement of the first (110), or the second (120) stacking conveyor is regarded as the slowest step in the stacking process, because the rotational movement results in the inactivation of the other stacking conveyor. Because the bottom yoke (212) is made first in the cutting sequence, immediately followed by the top yoke (211), one of the two staking conveyors (110,120) performs the rotational movement and the lag time is used by the intermediate stacking conveyor for positioning and stacking the top yoke (211) onto a separate stack (320).

[0062] The method according to the second aspect preferably provides in a method for stacking metal sheet cut-outs (210) onto a stack (300) to form a transformer core, comprising the steps of:

a) feeding a first metal sheet cut-out to a first stacking conveyor (110) by an intermediate stacking conveyor (130);

b) positioning the first stacking conveyor (110) and releasing the first metal sheet cut-out onto the stack (300);

c) preferably, feeding a second metal sheet cut-out to a second stacking conveyor (120) by the intermediate stacking conveyor (130); and

d) preferably, positioning the second stacking conveyor (120) and releasing the second metal sheet cut-out onto the stack (300);

wherein one or more of steps b) and d) comprises the rotation, and optionally translation, of the first or second stacking conveyor (110,120) with respect to the feeding direction (135) and wherein during the rotating displacement is steps b) and/or d) an additional metal sheet cut-out is positioned by the intermediate stacking conveyor (130) and released onto the stack (300).

[0063] The method according to the second aspect may also comprise preceding de-stacking steps, for example by a de-stacking line as described above.

[0064] The metal sheet cut-outs (210) can have the same width, or can have a different width. In some embodiments, some layers of metal sheet cut-outs (210) have a different width than others.

[0065] In some embodiments, the method further comprises the steps of:

e) feeding a third metal sheet cut-out to the first stacking conveyor (110) by the intermediate stacking conveyor (130);

f) positioning the first stacking conveyor (110) and releasing the third metal sheet cut-out onto the stack (300);

wherein one or more of steps b), d) and f) comprises the rotation, and optionally translation, of the first or second stacking conveyor (110,120) with respect to the feeding direction (135) and wherein during the rotating displacement is steps b), d) and/or f) an additional metal sheet cut-out is positioned by the intermediate stacking conveyor (130) and released onto the stack (300). A method where four metal sheet cut-outs (210) are iteratively positioned onto the stack is typically used for the production of U-shaped transformer cores.

[0066] In some embodiments, the method according to the second aspect further comprises the steps of:

e) feeding a third metal sheet cut-out to the first stacking conveyor (110) by the intermediate stacking conveyor (130);

f) positioning the first stacking conveyor (110) and releasing the third metal sheet cut-out onto the stack (300);

g) feeding a fourth metal sheet cut-out to the second stacking conveyor (120) by the intermediate stacking conveyor (130);

h) positioning the second stacking conveyor (120) and releasing the fourth metal sheet cut-out onto the stack (300);

wherein any of steps f) and h) optionally comprise the rotation and/or translation of the first or second stacking conveyor (110,120) with respect to the feeding direction (135) and wherein during the rotating displacement is steps b), d), f) and/or h) an additional metal sheet cut-out is positioned by the intermediate stacking conveyor (130) and released onto the stack (300). A method where five metal sheet cut-outs (210) are iteratively positioned onto the stack is typically used for the production of E-shaped transformer cores. Depending on the type of transformer core that needs to be manufactured, additional steps can be included, these additional steps being steps where an additional metal sheet cut-out to the first or second stacking conveyor (110,120) by the intermediate stacking conveyor (130); followed by the subsequent positioning the first or second stacking conveyor (110,120) and releasing the additional metal sheet cut-out onto the stack (300).

[0067] The method according to this aspect preferably provides in a method for stacking metal sheet cut-outs (210) onto a stack (300) to form a transformer core, comprising the steps of:

a) feeding a first metal sheet cut-out to a first stacking conveyor (110) by an intermediate stacking conveyor (130);

b) positioning the first stacking conveyor (110) and releasing the first metal sheet cut-out onto the stack (300);

c) feeding a second metal sheet cut-out to a second stacking conveyor (120) by the intermediate stacking conveyor (130); and

d) positioning the second stacking conveyor (120) and releasing the second metal sheet cut-out onto the stack (300);

e) feeding a third metal sheet cut-out to the first stacking conveyor (110) by the intermediate stacking conveyor (130);

f) positioning the first stacking conveyor (110) and releasing the third metal sheet cut-out onto the stack (300);

g) feeding a fourth metal sheet cut-out to the second stacking conveyor (120) by the intermediate stacking conveyor (130);

h) positioning the second stacking conveyor (120) and releasing the fourth metal sheet cut-out onto the stack (300);

i) feeding a fifth metal sheet cut-out to the intermediate stacking conveyor (130);

j) positioning the intermediate stacking conveyor (130) and releasing the fifth metal sheet cut-out onto the stack (300);

wherein any of steps b), d), f) and h) optionally comprise the rotation and/or translation of the first or second stacking conveyor (110,120) with respect to the feeding direction (135) and wherein during the rotating displacement is steps b), d), f) and/or h) an additional metal sheet cut-out is positioned by the intermediate stacking conveyor (130) and released onto the stack (300) according to steps i) and j).

[0068] In some embodiments, the metal sheet cut-outs (210) are held to the stacking conveyor by magnets, such as permanent magnets or electromagnets. The action of releasing the metal sheet cut-outs (210) may be performed by lifting off the magnets, by switching off the magnets, or by tapping the metal sheet cut-out (210).

[0069] In some embodiments, steps a)-d), a)-f), a)-h) or a)-j), optionally with additional steps, are iterated, thereby forming the transformer core layer-by-layer. One of the advantages of the present method is that the transformer core can be stacked layer-by-layer, thereby providing improved fitting and accuracy, and a smaller air gap between the different sections.

[0070] In some embodiments, at least one combination of steps b) and i); d) and i); f) and i); or h) and i); is performed simultaneously or overlaps in time, optionally also wherein at least one combination of steps b) and j); d) and j); f) and j); or h) and j); is performed simultaneously or overlaps in time.

[0071] Preferably, the steps that occur simultaneously relate to metal sheet cut-outs which have been fed to the stacking device one after the other (in succession).

[0072] In some embodiments, a first positioning step that is simultaneously performed or overlapping with a feeding step, optionally also with a second positioning step, comprises rotation of the first or second stacking conveyor (110,120) with respect to the feeding direction (135).

[0073] In some embodiments, the metal sheet cut-outs (210) are stacked on one or more stacking cars, and wherein said stacking cars remain immobilized during the stacking steps a)-d), a)-f), a)-h) or a)-j). The stacking cars may also be stacking tables. One of the advantages of this method is that the stacking cars can remain immobilized, thereby dispensing of the need to rotate the stacking cars, which can be particularly cumbersome for heavy transformer cores.

[0074] In some embodiments, the metal sheet cut-outs (210) comprise a bottom yoke (212) and a top yoke (211), and wherein the feeding and positioning steps of the bottom yoke (212) and the top yoke (211) occur simultaneously or overlap in time.

[0075] In some embodiments, the bottom yoke (212) and the top yoke (211) are stacked on separate stacking cars, preferably wherein the bottom yoke (212) is stacked on an E-core stack (310) on a first stacking car, and wherein the top yoke (211) is stacked on a top yoke pile (320) on a second stacking car.

[0076] A stacked transformer core typically comprises different types of laminate plates or metal sheet cut-outs. Figure 1 shows the typical shape of an E-stacked (Figure 1A) and a U-stacked (Figure 1 B) transformer core. E-stacked transformer cores typically comprise a top yoke (211), a bottom yoke (212), two outer legs (213, 214) and a center leg (215). A U-stacked transformer core typically comprises a top yoke (211), a bottom yoke (212) and two outer legs (213, 214). Depending on the shape of the transformer core other configurations comprising for instance a larger number of legs and yokes can be considered as well. Upon manufacturing these stacked transformer cores, one of the yokes (typically the top yoke) is assembled separately, while the other metal sheet cut-outs are assembled in an E or U configuration. This allows the electrical coils of the transformer to be positioned around the legs of the core, after which the top yoke can be positioned and the entire transformer core assembled accordingly. Figure 3A shows a preferred position of the two stacks with respect to each other. These stacks may be positioned on the same or a different stacking car. The E-core stack (310) is positioned behind the top yoke pile or stack (320). Figure 3B shows a preferred position of the intermediate stacking conveyor (130) with respect to the stacking conveyors (110,120). The stacking conveyors (110,120) preferable position and stack metal sheet cut-outs (210) onto the E-core stack (310), whereas the intermediate stacking conveyor (130) positions and stacks metal sheet cut-outs (210) on the top yoke stack (320).

[0077] In some embodiments, the metal sheet cut-outs are re-positioned using an in-line control and correction system.

[0078] The position of the metal sheet cut-outs (210) is checked at regular intervals, preferably during or after feeding, and before every new laminate sheet layer is deposited. In-line control and correction systems are used for this purpose.

[0079] Preferably, the method according to second aspect of the invention is performed with the transformer core stacking device (100) according to the first aspect of the invention.

[0080] In a preferred embodiment, the present invention relates to a method for stacking metal sheet cut-outs (210) onto a stack (300) to form a transformer core, wherein said metal sheet cut-outs (210) comprise of a center leg (215), first outer leg (214), second outer leg (213), bottom yoke (212) and top yoke (211), comprising the steps of:

a) feeding a center leg (215) to a first stacking conveyor (110) by an intermediate stacking conveyor (130);

b) positioning the first stacking conveyor (110) and releasing the center leg (215) onto the E-stack (310);

c) feeding a first outer leg (214) to a second stacking conveyor (120) by the intermediate stacking conveyor (130); and

d) positioning the second stacking conveyor (120) and releasing the first outer leg (214) onto the E-stack (310);

e) feeding a second outer leg (213) to the first stacking conveyor (110) by the intermediate stacking conveyor (130);

f) positioning the first stacking conveyor (110) and releasing the second outer leg (213) onto the E-stack (310);

g) feeding a bottom yoke (212) to the second stacking conveyor (120) by the intermediate stacking conveyor (130);

h) positioning the second stacking conveyor (120) and releasing the bottom yoke (212) onto the E-stack (310);

i) feeding a top yoke (211) to the intermediate stacking conveyor (130);

j) positioning the intermediate stacking conveyor (130) and releasing the top yoke (211) onto the top yoke stack (320);

wherein step h) comprises the rotation of the second stacking conveyor (120) with respect to the feeding direction (135) and wherein step i); j); or i) and j); are performed simultaneously or overlaps in time with step h).

[0081] The method and devices according to the present invention and as disclosed herein provide in stacking systems and stacking methods for transformer cores which are more cost efficient, minimize the amount of waste materials, allow assembly times to occur simultaneous and at the same velocity as the material processing and cutting processes, and/or provide in high quality and accurate transformer cores.

[0082] The invention also encompasses a computer program, or a computer program product directly loadable into the internal memory of a computer, or a computer program product stored on a computer readable medium, or a combination of such computer programs or computer program products, for performing the method according to the second aspect of the invention.

EXAMPLES

[0083] The present example provides a particular embodiment according to the invention.

[0084] Figure 4 represents a particular sequence of events and movements according to a particular embodiment of the invention for the production, assembly and stacking of an E-type laminated transformer core. The transformer core stacking device (100) comprises one intermediate stacking conveyor (130), a first stacking conveyor (110), and a second stacking conveyor (120). In the initial position (Figure 4A) the intermediate stacking conveyor (130) and the first stacking conveyor (110) are positioned along the feeding direction (135). The second stacking conveyor (120) is positioned alongside the first stacking conveyor (110). First, a metal sheet for the center leg (215) is fed to the stacking device (Figure 4A). The intermediate stacking conveyor (130) transports and delivers the center leg to the first stacking conveyor (110). The first stacking conveyor (110) positions the center leg on the E-stack (310). The positioning of the metal sheet cut-outs (210) onto their correct position can be established by having the conveyer deposit the metal sheet onto the correct position or by providing holes into the metal sheet cut-outs (210) and positioning the sheet over a pin and dropping them into the correct position. Once the center leg (215) is deposited, the first stacking conveyor (110) moves sideways (Figure 4B) to allow the second stacking conveyor (120) to move in line with the feeding direction (135) and receive one of the metal sheet cut-outs (210) for the outer leg (214). As soon as this metal sheet is carried completely (i.e. over its total length) by the second stacking conveyor (120) it starts moving (Figure 4C) to the stacking position on the outer leg of the E-stack. The moving preferably starts when the tail of a sheet passes a sensor so the system knows the full sheet is carried by a particular conveyor, so it can start moving (laterally, longitudinally, rotationally). While the metal sheet for the outer leg (214) is transported and deposited in the correct position, the first stacking conveyor (110) moves in line with the feeding direction (135) to receive one of the metal sheet cut-outs (210) for the outer leg (213). As soon as this metal sheet is carried completely (i.e. over its total length) by the first stacking conveyor (110) it starts moving (Figure 4D) to the stacking position on the outer leg of the E-stack. While the metal sheet for the outer leg (213) is transported and deposited in the correct position, the second stacking conveyor (120) moves in line with the feeding direction (135) to receive one of the metal sheet cut-outs (210) for the bottom yoke (212). As soon as this metal sheet is carried completely (i.e. over its total length), the second stacking conveyor (120) starts turning (Figure 4E) to the bottom yoke (212) position. The center of the second stacking conveyor (120) is preferably positioned above the fixed point where the center line of the center leg (215) and the center line of the bottom yoke (212) intersect. In order to make room for the rotating second stacking conveyor (120), the first stacking conveyor (110) is moved in a longitudinal direction.

[0085] While the metal sheet for the bottom yoke (212) is transported and deposited in the correct position, the metal sheet for the top yoke (211) is transported by the intermediate stacking conveyor (130) and deposited (Figure 4F) onto the top yoke stack (320), after which all stacking conveyors (110,120,130) return to their original position (Figure 4G) and the process is repeated.

[0086] Figures 6A to 6G show the same steps, wherein Figure 6A corresponds to the situation described for Figure 4A, and Figure 6B corresponds to the situation described for Figure 4B. Figures 6C and 6D correspond to the situation described for Figure 4C, while Figures 6E and 6F corresponds to the situation described for Figure 4D. Figure 6G corresponds to the situation described for Figure 4E. Figure 6H shows the separate assembly of the top yoke (211) stack.

Claims

1. A transformer core stacking device (100) for stacking metal sheet cut-outs (210) onto a stack (300), comprising at least one intermediate stacking conveyor (130) configured to transport the metal sheet cut-outs (210) and having a feeding direction (135),
characterized in that
the transformer core stacking device (100) comprises one or more stacking conveyors (110,120), preferably at least two stacking conveyors (110,120), configured to receive metal sheet cut-outs (210) from the intermediate stacking conveyor (130) along the feeding direction (135) and configured to stack the metal sheet cut-outs (210) onto the stack (300), wherein at least one of the one or more stacking conveyors (110,120) is rotatable with respect to the feeding direction (135).

2. The transformer core stacking device (100) according to claim 1, wherein the one or more stacking conveyors (110,120), preferably at least two stacking conveyors (110,120), are laterally and/or longitudinally movable with respect to the feeding direction (135).

3. The transformer core stacking device (100) according to claim 1 or 2, wherein the one or more stacking conveyors (110,120) comprise one or more servomotors (112,114,116,118,122,124,126,128) configured to drive the stacking conveyors (110,120) in a lateral, longitudinal, and/or rotational direction.

4. The transformer core stacking device (100) according to claim 3, further comprising one or more guide rails (140) for at least one stacking conveyor (120), configured such that a rotation of the at least one stacking conveyor (120) is obtained by a lateral or longitudinal motion of a servomotor (112, 114, 116, 118, 122, 124, 126, 128).

5. The transformer core stacking device (100) according to any of claims 1 to 4, wherein the one or more stacking conveyors (110,120) are adjustable in height.

6. A method for stacking metal sheet cut-outs (210) onto a stack (300) to form a transformer core, comprising the steps of:

a) feeding a first metal sheet cut-out to a first stacking conveyor (110) by an intermediate stacking conveyor (130);

b) positioning the first stacking conveyor (110) and releasing the first metal sheet cut-out onto the stack (300);

c) feeding a second metal sheet cut-out to a second stacking conveyor (120) by the intermediate stacking conveyor (130); and

d) positioning the second stacking conveyor (120) and releasing the second metal sheet cut-out onto the stack (300);

wherein one or more of steps b) and d) comprises the rotation, and optionally translation, of the first or second stacking conveyor (110,120) with respect to the feeding direction (135).

7. The method according to claim 6, further comprising the steps of:

e) feeding a third metal sheet cut-out to the first stacking conveyor (110) by the intermediate stacking conveyor (130);

f) positioning the first stacking conveyor (110) and releasing the third metal sheet cut-out onto the stack (300);

g) feeding a fourth metal sheet cut-out to the second stacking conveyor (120) by the intermediate stacking conveyor (130);

h) positioning the second stacking conveyor (120) and releasing the fourth metal sheet cut-out onto the stack (300);
wherein any of steps f) and h) optionally comprise the rotation and/or translation of the first or second stacking conveyor (110,120) with respect to the feeding direction (135) and wherein the method further comprises steps

i) feeding a fifth metal sheet cut-out to the intermediate stacking conveyor (130);

j) positioning the intermediate stacking conveyor (130) and releasing the fifth metal sheet cut-out onto the stack (300).

8. The method according claim 6 or 7, wherein steps a)-d) or a)-j), optionally with additional steps, are iterated, thereby forming the transformer core layer-by-layer.

9. The method according to any of claims 6 to 8, wherein at least one combination of steps b) and i); d) and i); f) and i); or h) and i) is performed simultaneously or overlaps in time, optionally also wherein at least one combination of steps b) and j); d) and j); f) and j); or h) and j); is performed simultaneously or overlaps in time.

10. The method according to claim 9, wherein a first positioning step that is simultaneously performed or overlapping with a feeding step, optionally also with a second positioning step, comprises rotation of the first or second stacking conveyor (110,120) with respect to the feeding direction (135).

11. The method according to any of claims 6 to 10, wherein the metal sheet cut-outs (210) are stacked on one or more stacking cars, and wherein said stacking cars remain immobilized during the stacking steps a)-d) or a)-j).

12. The method according to any of claims 6 to 11, wherein the metal sheet cut-outs (210) comprise a bottom yoke (212) and a top yoke (211), and wherein the feeding and positioning steps of the bottom yoke (212) and the top yoke (211) occur simultaneously or overlap in time.

13. The method according to claim 12, wherein the bottom yoke (212) and the top yoke (211) are stacked on separate stacking cars, preferably wherein the bottom yoke (212) is stacked on an E-core stack (310) on a first stacking car, and wherein the top yoke (211) is stacked on a top yoke stack (320) on a second stacking car (162).

14. The method according to any of claims 6 to 13, wherein the metal sheet cut-outs are re-positioned using an in-line control and correction system.

15. The method according to any of claims 6 to 14, performed with the transformer core stacking device (100) according to any of claims 1 to 5.

Drawing