method and device for control of a wechselstromasynchronmotors by indirect measurement of luftspaltspannung.

摘要

A device is proposed for applying material such as solder paste and glue in discrete points, particularly for applying solder paste on electronic circuit boards. The device comprises a pump house (202-205; 301, 307), a tube or a channel (206) by means of which material is fed to the pump house, a nozzle (111, 205) for feeding material from the pump house (202-205; 301, 307). Suitable upper and lower valve devices are arranged to block, at predetermined times, the feeding of material to and from the pump house (202-205; 301, 307). The lower valve device may possibly be replaced by a restriction device. As is conventional the pump house (202-205; 301, 307) comprises an outer pump cylinder (203; 307) and an inner piston (204; 301). The displacement of the piston (201; 301) is obtained by the fact that the piston is connected to a magnetostrictive rod (202; 308). This rod (202; 308) cooperates with a coil (208) arranged around the rod (202; 308). When an electric current is fed to this coil (208) the length of the rod will increase. A very rapid application of the material is achieved.