The invention relates to a system providing simultaneous rotation of the blanking die and the blank punch in a tool for blanking out electrical sheet laminations having non- circular and non-continuous geometry along the outer diameter and is used in tools for producing laminated stator and rotor packages with indexing.

The process for blanking out laminations of electrical metal strip is a process wherein a desired end product, identified as a lamina, is punched out from electrical sheet .

Laminated packages are manufactured by assembling individual laminations together. The process of blanking laminations out of an electrical steel strip is described, for example, in US6536318. The assembling of laminations may vary depending on the particular technology employed.

Individual laminations may be assembled by using conventional welding methods, usually by using the laser- TIG process. It is a drawback of welding that the weld affects the electromagnetic properties of the package as a whole, while with high-alloyed sheet metal welding becomes challenging due to the presence of alloy elements.

Laminations may also be assembled by using sheet metal coated with a special enamel which reacts at an elevated temperature and pressure, thereby binding the laminations into a compact package. It is a deficiency of said technique that laminations have to be pressed to a predetermined pressure and heated for a certain time.

The most commonly used method for assembling laminations is by making use of interlocking clamps. Said system is disclosed in e.g. US6223417, US60118207 and 4. It is a disadvantage of non-indexed packages that the required tolerances are more difficult to achieve due to the nonuniform strip thickness.

The process for manufacturing interlocking packages with indexation is set forth in e.g. US4619028, US4272579 and US5918359. In said patents, indexing is achieved b rotating the blanking die. By rotating the blanking die, producing packages of more complex external shapes becomes feasible, there is however a possibility that the blank punch which is fixed relative to the blanking die may assume an incorrect position. As a result of such incorrect position of the blank punch relative to the blanking die, chipping of the blanking die, or the blank punch, or both, may occur.

The technical problem which has not been adequately solved by prior patents dealing with indexed interlocking packages is that in the process of lamination blanking, when rotation required for indexing is carried out, the blank punch may strike against the bl-anking die, damaging the blank punch and the blanking die. In prior art solutions, only the blanking die is rotated in the tool, but there is no system for providing an adequate positioning of the blank punch relative to the blanking die at all times.

It is an object and purpose of the present invention to ensure that the blank punch and the blanking die are positioned appropriately and correctly at all times, so as to prevent the blank punch from potentially striking against the blanking die due to the incorrect position of the blank punch relative to the blanking die, and consequently from causing damage to the blank punch and to the blanking die.

In accordance with the present invention, said object is fulfilled with a system providing simultaneous rotation of the blanking die and of the blank punch in the tool. The blank punch and the blanking die rotate simultaneously by means of an electric motor, preventing the blank punch from being incorrectly positioned relative to the blanking die.

The invention shall hereinafter be described according to an embodiment thereof and the enclosed drawings, representing :

Figure 1: exemplary lamina having a non-circular and non- continuous geometry along the outer diameter;

Figure 2: schematic of the system in longitudinal sectional view;

Figure 3: the arrangement of the shaft and the gears, with respective cross-sections. The invention, described hereinafter in further detail, is an improvement over prior art methods of rotary die blanking. The advantage of the inventive system becomes more apparent in products not having a circular outer contour, which is to say, in laminations exhibiting a non- circular and non-continuous geometry along their outer diameter, as shown in Figure 1. In prior art, only the blanking die was capable of being rotated in order to achieve indexation.

The system of the invention consists of a lower portion 16 which moves the blanking die with the die insert 11 and is located in the lower region of the tool, which is to say inside the blanking die plate, and of an upper portion 17 which moves the blank punch guide with the blank punch 13 and is located in the upper region of the tool, which is to say, in the guide and mounting plate. Both portions are interconnected by means of a vertically positioned rigid shaft 6. For rotating the system there is provided an electric motor 1, connected to the vertically positioned rigid shaft 6 by means of standard gears, so that the angular pivot controlled by the electric motor 1 is transmitted to the rigid shaft 6. The rigid shaft 6 has a specific shape, being made such that it doesn't have a circular cross-section but presents four fixed bolts along its outer periphery, which are staggered by 90° and enable the angular pivot to be transmitted to both portions simultaneously. Due to the shaft 6 not being long and the rotations, or angular pivots, of the system taking place in the absence of load, the resulting torsion in the shaft is small, which ensures that while the angular pivot is being performed there is no staggering of the lower part of the shaft relative to the upper part thereof, which would result in the lower portion 16 with the die insert 11 staggering relative to the upper portion 17 with the blank punch 13. On the lower part of the rigid shaft 6 a drive gear 8 is fixed which rotates the blanking die. On the upper part of the rigid shaft 6 a drive gear 7 is fixed which rotates the blank punch guide with the blank punch. Both gears are identical. Likewise, the gears along the periphery of the blank punch guide and along the periphery of the blanking die are identical, thereby ensuring that the speeds and the angular pivots of the blank punch 13 and of the die insert 11 are identical. Thus the blank punch 13 is prevented from striking against the die insert 11 and consequently damaging the tool.

The electric motor 1 takes care of the simultaneous angular pivot of the blank punch and the blanking die. The angular pivot is transmitted from the electric motor 1 via the gears 2 and 3, as well as 9, which are used as standard elements in other tools, to the vertically positioned rigid shaft 6. Said shaft represents the connection between the part of the system, located in the lower portion of the tool 16, and the upper part of the system, located in the upper portion of the tool 17, given that the lower half of the shaft 6 is located in the lower portion of the tool 16, while the upper part of the shaft 6 is located in the upper portion of the tool 17. With its lower part, the shaft 6 is placed on a washer 4 which takes care of the positioning of the shaft 6 during blanking. On the lower part of the shaft 6 there is mounted a bush 5 which has its inner surface shaped so as to correspond with the shaft 6 and its outer surface turned on a lathe so that it exhibits a circular cross-section, except at the locations where the gears 9 and 8 are mounted thereon. At the said locations, the outer surface of the bush 5 is provided with cogs which engage with the cogs of the gears 9 and 8 and wherewith the positioning of the gears 9 and 8 is ensured. The gear 9 is driven, enabling the angular pivot of the shaft 6 to be performed. Above the gear 9 and under . the gear 8 there is a spacer 15 for ensuring the correct positioning of the drive gear 8 which, by way of the gear 10 along the outer periphery of the blanking die, drives the blanking die wherein the die insert 11 is placed.

Given that the rigid shaft has a specific shape and only the upper part of the tool travels up and down, a bearing 14 is fashioned in the upper part of the shaft 6, fitting the said shaft 6 with convenient precision. On the upper part of the shaft 6, a drive gear 7 is mounted over said bearing 14, identical to the drive gear 8. This means that both the gears 7 and 8 have the same number of cogs and the same module. The drive gear 7 transmits the rotational motion from the shaft 6 onto the gear 12 along the outer periphery of the rotating punch guide, which guides the blank punch 13. The gear 7 is mounted onto the shaft 6 over the bearing 14 because the upper portion of the tool 17 moves up and down during blanking, whereas the lower portion of the tool 16 is stationary at all times. The gear 12 along the outer periphery of the rotating blank punch guide has the same module and the same number of cogs as the gear 10 along the outer periphery of the blanking die, ensuring that the speed and the angular pivot of the blank punch 13 and of the die insert 11 are the same. Due to the shaft 6 not being long and the system being rotated in the absence of load, the resulting torsion in the shaft 6 is small, which ensures that there is no staggering of the lower part of the shaft 6 relative to the upper part of the shaft 6, which would result in the lower portion of the system with the die insert 11 staggering relative to the upper portion of the system with the blank punch 13.

Once the tool is assembled, the system of the invention ensures that the position of the blank punch 13 relative to the die insert 11 will be the same at all times, regardless of the position of the electric motor 1. If an error occurs, an incorrectly blanked lamina or a bad package may be identified, but it can not happen that the tool incurs damage as a result of the blank punch 13 striking against the die insert 11.

The system for lamination blanking by rotating the blanking die and the blank punch in the tools for manufacturing laminated stator and rotor packages with indexing is therefore characterized in that it consists of a lower portion 16 of the tool for moving the blanking die with the die insert 11, an upper portion 17 of the tool for moving the blank punch guide with the blank punch 13, a vertically positioned rigid shaft 6 interconnecting both said portions, and an electric motor 1 for simultaneously pivoting the blank punch 13 and the die insert 11, wherein the angular pivot is transmitted from the electric motor 1 by virtue of the gears 2, 3 and 9 to the vertically positioned rigid shaft 6 and then simultaneously via the drive gear 8 to the gear 10 along the outer periphery of the blanking die, wherein the die insert 11 is located, and via the drive gear 7 to the gear 12 along the outer periphery of the rotating punch guide which guides the blank punch 13. The drive gears 7 and 8 are identical, and the gears 10 along the outer periphery of the blanking die and 12 along the outer periphery of the blank punch guide are likewise identical. The rigid shaft 6 presents four fixed bolts along its outer periphery, which are staggered by 90° and enable the angular pivot to be transmitted to both portions simultaneously; with its lower part, the shaft 6 is placed on a washer 4 which takes care of the positioning of the shaft 6 during blanking; on the lower part of the shaft 6 there is mounted a bush 5 which has its inner surface shaped so as to correspond with the shaft 6, its outer surface being turned on a lathe and provided with cogs at the locations where the gears 9 and 8 are mounted thereon, said cogs engaging with the cogs of the gears 9 and 8, a bearing 14 being fashioned in the upper part of the shaft 6, and a drive gear 7 being mounted over said bearing 14.