In the food packaging industry packages are manufactured and filled with food in large machines transforming packaging material into packages which are filled with food content, either during the formation of the package or after the package has been created. In these packaging machines, packages and equipment for handling the packages or the packaging material need to be conveyed.
WO 2015/101492 discloses a solution for the problem of molding plastic objects onto cardboard-based packaging material intended to form packages while the packaging material is conveyed. Multiple molding stations are pulled by a linear synchronous motor along an annular track such that the molding stations are aligned over a moving sheet of packaging material. For a period of time a moving molding station is aligned to an area of the packaging material so as to mould an object on said area. This solution has the advantage that work can be made on the packaging material without stopping the feeding of the packaging material in a packaging machine. In addition, precise alignment of each molding station with the corresponding area of the packaging material can be achieved.
In WO 2015/101492 the molding stations are operated by cams in a mechanical manner. In other situations, however, the operation that is to be performed on the packages needs electrical power. Such electrical power transfer to moving objects has traditionally been accomplished with brush connectors. Brush connectors are however a mechanical solution that is subject to wear and leads to maintenance needs.
WO 2006/048441 shows a solution where the brush connectors have been replaced by an induction energy transfer system to provide sealing jaws moving along a chain in a packaging machine with power to perform an induction heating operation.
WO 93/02888 discloses a further enhanced system for linear drive of vehicles using a synchronous linear motor where electric power is transferred to each moving vehicle using induction. This solution uses the same electromagnetic mechanism that is used by the synchronous linear motor for movement of the vehicles to also transfer electrical power. In a synchronous linear motor, a field of travelling waves is generated in individual sections of a long stator opposite to an exciter part located on a vehicle. The field of travelling waves cooperates with the field generated in the exciter winding by direct current supply, so as to move the vehicle forward. The alternative current supplied to the stator section in order to generate the field of travelling waves induces practically no voltage in the exciter winding. In order to ensure an inductive energy transfer, a higher-frequency alternative current is superimposed on the alternative current available to generate the field of travelling waves. The higher-frequency alternative current induces a high-frequency voltage in the exciter winding that can be considered as the secondary winding of a transformer comprising the stator winding and the exciter winding. This solution for wireless transfer of electrical power to a moving vehicle is, however, complicated and expensive due to the need of a non-standard power-supply or the use of multiple power supplies for achieving the alternative current for moving the vehicles with a high frequency alternative current superimposed for transferring electrical power.
Based on the above, there is a need for a simpler solution for transferring electrical power to vehicles in a linear synchronous motor.