The invention relates to an apparatus and a method for forming pre-shaped insulating sheets.

In stator assemblies insulating sheets are used for lining the walls of slots of a stator. In case of stator assemblies where more than one conductor is inserted into one slot, insulation sheets can also be used for providing an insulation between neighbouring conductors. For this purpose it is e.g. known to provide a sheet of insulating material bent into a S-shape, as it is e.g. shown in U.S. Pat. No. 8,860,278 (FIG. 6). U.S. Pat. No. 9,130,430 (FIG. 10a) shows an arrangement where in one slot of a stator four conductors are inserted and two S-shaped sheets are used for insulation. S-shaped insulators are also known from U.S. Pat. No. 5,965,965 (FIG. 4).

Before the insulator sheets can be inserted into the slots they have to be pre-shaped, typically from an initially flat continuous sheet.

WO2011/114360 A1 discloses an apparatus and method for making pre-shaped insulating sheets intended to be inserted into stator or rotor slots. According to WO2011/114360 A1 pairs of opposite rollers having a shaping profile are used for shaping a continuous strip of insulating material. The continuous strip of insulating material is passed between the rollers and thereby is shaped.

Such known apparatus and methods have, however, several disadvantages. In particular, the shape provided by the opposite rollers is predefined due to the pre-given profile of the rollers and cannot be changed or adjusted. The accuracy of sheets bent with such an apparatus is therefore limited and may even vary in the course of time.

It is therefore an object of the present invention to overcome the drawbacks of the prior art and in particular to provide an apparatus and a method which increase the accuracy of the shaping operation, in particular also in the course of time. The apparatus and method preferably should allow a fine tuning or adjustment of the shape.

According to the invention these and other objects are solved with an apparatus and a method according to the independent claims.

The apparatus for forming pre-shaped insulating sheets comprises a first and a second bending station. A flat sheet of insulating material is supplied from a continuous strip of material. The sheet material is provided with embossings which form predefined bending lines. The sheet will be formed into the desired S-shape along these bending lines, as will be explained hereinafter.

The first bending station is used for bending a flat sheet of insulating material into a Z-shaped sheet along two bending lines. The two bending lines define a center section. The second bending station is used for further bending the Z-shaped sheet into an S-shape along two or along four additional bending lines. In context with the present invention, an S-shape may refer to an open S-shape with two additional bending lines or a partially closed S-shape or a fully closed S-shape with four additional bending lines.

The first bending station comprises at least one holding mechanism for holding the flat sheet. The first holding mechanism comprises at least one first holding surface for contacting the centre section of the flat sheet. Typically, the holding mechanism comprises two opposing holding members each having a first holding surface between which the centre section of the flat sheet can be held. Typically, the holding members are translatable in a direction perpendicular to the holding surface in order to clamp and hold the centre section.

The first bending station further comprises at least one pair of first bending operators. The bending operators are used for bending tail end sections of the sheet neighbouring the centre section. The first bending operators are at least movable transversely with respect to the first holding surface. By actuating the first bending operators, the initially flat sheet which is held by the holding mechanism can be bent along two bending lines. A Z-shaped sheet may be formed thereby.

The second bending station comprises at least a second holding mechanism for holding the Z-shaped sheet. The second holding mechanism comprises a second holding surface for a part of the tail end sections of the Z-shaped sheet. Typically, the second holding mechanism has two second holding members which are arranged opposite each other and which each have two holding surfaces. A part of each of the two tail end sections of the Z-shaped sheet is held between two neighbouring holding surfaces of the two second holding members. The second holding surfaces hence define a cavity for receiving the Z-shaped sheet there-between. The second holding members can be movable towards each other in order to clamp the sheet. Alternatively, they also may be in a fixed position with respect to each other so that a sheet may be linearly inserted into the cavity without being tightly clamped.

The second bending station further comprises at least one pair of second bending operators. The second bending operators are used for bending the tail end sections of the Z-shaped sheet into an S-shape at least along second bending lines. The S-shape can be an open S-shape (bent along four lines in total, where the tail end sections run approximately parallel to the centre section of the sheet), a partially closed S-shape (bent along six lines in total, where the tail end sections first run approximately parallel to the centre section and then are inclined towards the centre section) or a fully closed S-shape (again bent along six lines in total, where the tail end sections are bent back towards the centre section such as to run approximately perpendicularly with respect to the centre section). The second bending operators are movable transversely with respect to the second holding surface.

The first and the second bending station of course may include more than one holding mechanism and more than one pair of bending operators each, e.g. for reducing manufacturing cycle time.

By providing holding mechanisms for holding the sheet and movable bending operators, the accuracy of the bending can be increased. In particular, it is also possible to fine tune or adjust the degree of bending by adjusting movements and/or forces applied to the holding members and/or operators.

According to a preferred embodiment of the invention, the second bending station comprises at least one pair of third bending operators. The third bending operators are used for bending the tail end section of the open S-shaped sheet into the partially closed S-shape along third bending lines. The third bending operators are movable in a direction parallel to the second holding surface.

By providing independent bending operators for bending the sheet along first, second and third preformed bending lines, each bending step can be separately controlled and adjusted. Alternatively it is also possible to provide bending operators having additional degrees of freedom, so that more than one bending operations can be carried out by one bending operator. In such a case the function of two or even three bending operators might be provided by the same physical operator.

While preferably the first, second and third pair of bending operators comprise operators which are arranged opposite each other, other arrangements might be conceivable.

According to a further preferred embodiment, the apparatus comprises a third bending station for bringing the tail end sections of the sheet in the partially closed S-shape into the fully closed S-shape. Since the sheets are not yet bent to the fully closed S-shape when they are removed from the second bending station, the second holding members can be easily removed from the sheet in the partially closed S-shape.

The third bending station preferably may comprise a cone channel. The cone channel is provided with an entry opening which has a cross-section adapted to receive the sheet in the partially closed S-shape. The channel has a cross-section which changes its shape from the entry opening towards an exit opening, the cross-section of which corresponds to the fully closed S-shape of the sheet. By guiding the sheet through the cone channel the tail end section will be brought into the fully closed S-shape.

The first and second bending operator typically are mounted translatably, the first operator in a direction perpendicular to the first holding surface and the second bending operator in a direction perpendicular to the second holding surface. Of course, other movements such as rotational movements also might be conceivable.

The third bending operators are preferably pivotably mounted around an axis parallel to the second holding surface. While it is preferred that the second and third bending operators may be mounted on a common carrier, other arrangements with separate carriers for the second and third bending operators might be conceivable.

According to a further preferred embodiment of the invention, the apparatus further comprises an insertion station. The insertion station is used for inserting the preformed sheets which are in the fully closed S-shape into slots of a stator. Preferably, the insertion station has a receiving unit for receiving the sheets which are in the fully closed S-shape. Such an insertion station allows an online process for directly forming and inserting the sheets into the stator.

Preferably the first and the second bending stations each have a loading and an unloading position. In the loading position, the sheet can be loaded into the respective station. Typically, the sheet will be inserted between the holding surfaces by a translational movement when the bending stations are in their respective loading position. In the unloading position the bent sheet can be removed from the respective station, typically by a translational movement of the sheets. While it is preferred that the bending stations can be movable between their respective loading and unloading positions it is also conceivable to keep the bending stations in the same position for loading and unloading and to use movable loading and unloading mechanisms for loading and unloading the sheets.

The first and the second bending stations are preferably aligned or alignable with respect to each other such that the Z-shaped sheet can be transferred from the first bending station in its unloading position to the second bending station in its loading position, in particular by a translational movement.

Preferably, the first bending station has a first pusher for transferring the sheet in its Z-shape from the first bending station into the second bending station.

If, according to a preferred embodiment as described hereinabove, the apparatus has an insertion station, the insertion station may also have a loading and an unloading position. In this case, the second bending station and the insertion station are preferably aligned or alignable such that the partly or fully S-shaped sheet is transferable from the second bending station in its unloading position to the insertion station in its loading position. In this case, the second bending station preferably has a second pusher for transferring the sheet from the second bending station to the insertion station.

Additionally or alternatively the insertion station may have a third pusher for transferring the sheet from the insertion station into a slot of a stator.

If the apparatus is provided with a third bending station with a cone channel, the cone channel is preferably alignable or aligned with the second bending station in its unloading position and with the insertion station in its loading position. Thereby, the sheet in the partially closed S-shape is transferable from the second bending station to the insertion station through the cone channel, preferably by means of the above-mentioned second pusher. Thereby, the sheet is transferred and simultaneously brought from the partially closed S-shape to the fully closed S-shape.

According to still a further preferred embodiment, the receiving unit may have a plurality of openings for receiving a plurality of formed sheets. The receiving unit can be movably arranged so that in a sequence, the plurality of openings can be filled with sequentially supplied sheets having a preformed S-shape. Thereby, two or three or even more preformed S-shaped sheets may be collected in the receiving unit and may subsequently be jointly inserted into one slot of a stator. While such a receiver is particularly advantageous in context with an apparatus described hereinabove it will be understood by a skilled person that receivers having such a plurality of openings might also be used in context with other apparatus for forming pre-shaped sheets having an S-shape.

According to still another preferred embodiment, the first bending station may be arranged on a first carousel and the second bending station may be arranged on a second carousel. In this case the first and second bending stations preferably comprise at least two first holding mechanisms, at least two pairs of first bending operators, at least two second holding mechanisms and a least two pairs of second bending operators, respectively. Preferably the insertion station may be arranged on a third carousel may comprise at least two receiving units.

The first, second and third carousel are rotatable between the respective loading and unloading positions. With such an arrangement the cycle time may be reduced and the transfer between the various stations may be facilitated.

The apparatus further may comprise a feed station for feeding insulating material from a continuous strip. The feed station comprises a cutter for cutting flat sheets of the continuously supplied sheet material. It further comprises an embossing unit for applying longitudinal embossings forming predefined bending lines. The feed station furthermore comprises a supply unit. The supply unit may either supplying the cut sheets to the first bending station or supply the continuous strip to the first bending station, where the sheets will be cut prior to the bending.

According to another aspect of the invention a method for forming pre-shaped insulating sheets is provided. Preferably the method is carried out with an apparatus as described hereinabove.

In a first step, a cut sheet of flat insulating material is provided in a first bending station. In the first bending station, a centre section of this flat sheet is contacted by a first holding surface of a first holding mechanism. Thereby, the sheet is held by the holding mechanism.

In a subsequent step, in the first bending station, tail end sections of the sheet which are neighbouring the centre section are bent along first bending lines by moving first bending operators transversely with respect to the first holding surface. Thereby, a Z-shaped sheet is formed.

In a further step, the Z-shaped sheet is transferred to a second bending station. In the second bending station the tail end sections of the Z-shaped sheet are contacted with a second holding surface of at least one second holding mechanism. Thereby, the Z-shaped sheet is held in the second bending station.

In the second bending station the Z-shaped sheet is then bent along second bending lines into an open S-shape or along second and third bending lines into a partially closed or fully closed S-shape. This bending is achieved by moving second bending operators transversely with respect to the second holding surface.

Preferably, the tail end sections of the open S-shaped sheet are bent from the open S-shape into a partially closed S-shape in a separate step by moving third bending operators in a direction parallel to the second holding surface.

According to a further preferred embodiment, in a further step, the tail end sections of the sheet in the partially closed S-shape are brought in a fully closed S-shape by means of a third bending station. Preferably the tail end sections are brought in the fully closed S-shape by translating the sheet in the partially closed S-shape through a cone channel with an entry opening having a cross-section adapted to receive the sheet in the partially closed S-shape and an exit opening which has a cross-section corresponding to the fully closed S-shape of the sheet. Thereby, the sheet can be easily brought into the final shape by a simple translational movement through the cone channel.

Preferably, in a final step, the sheets in the fully closed S-shape are inserted into slots of a stator by means of an insertion station. Such insertion preferably can be achieved by transferring the sheet in the fully closed S-shape to a receiving unit for receiving the sheets and by transferring the sheets from the receiving unit to the slot of the stator.

