Liquid droplet forming apparatus

The Figure shows an ink jet head 10 comprising a housing 12 having a cylindrical passage 20 containing a cylindrical tube 19 formed of piezo-electric material. A nozzle plate 49 is attached to the housing to register with a portion 46 of the housing wall of reduced thickness. Apertures 47 through the wall portion 46 register with nozzles 48 in the plate 49. The tube 19 is subject to an electric field established between an electrode formed internally of the tube and pressurized conductive ink in the passage 20. Longitudinal vibrations in the tube 19 are absorbed by resilient mountings 22, 23. When tube 19 is electrically excited pressure waves are set up in the ink in passage 20 and the ink jets issuing from nozzles 48 are caused to break-up into similar streams of ink drops. … In a modification the wall portion 46 is removed and the aperture so formed oovered by a flexible sheet diaphragm held against the housing by a manifold plate interposed between the none plate and the housing. The manifold plate has an open-sided recess registering with the housing wall aperture and communicating with the nozzles through an array of outlets through the bottom of the recess. In this modification the passage 20 is filled with liquid and ink is supplied under pressure to the manifold plate recess. Pressure waves established in the passage 20 are transmitted through the diaphragm in the ink in the manifold plate recess.