GB1165617A - Dispensing Unit. - Google Patents

Abstract

1,165,617. Syringes. S.A.C. CONSULTANTS Ltd. April 23, 1968 [May 3, 1967], No.20596/67. Heading F1R. A dispenser, for dispensing paste from a cartridge having a nozzle at its forward end and containing a sliding plunger behind the paste, comprises a body to receive the cartridge and providing a gas-tight working space behind the plunger of the cartridge, an inlet for admitting successive pulses of gas under pressure to the working space, and means for maintaining the volume of the working space substantially constant notwithstanding advance movement of the plunger in the cartridge. Workpieces 52, Fig. 9, to be soldered are carried in succession by a conveyer 51 beneath the dispenser 50, which deposits through a nozzle 10 an accurately metered volume of solder paste on to each workpiece. The solder paste is contained in a removable cylindrical cartridge 2, Figs.2 and 3, of polyethylene which is closed with a tightly fitting plunger 4 of polyethylene. An adaptor 6 screwed into the cartridge carries the nozzle 10. To permit insertion of the cartridge, the body of the dispenser is divided into two parts 12, 15 locked together by a thumb screw 40. A hollow piston 16 is inserted into the body to rest under its own weight against the plunger 4. A timer T controls a solenoid valve 54 to supply pulses of compressed air of predetermined duration through a line 56 leading via a valve 20 into the hollow piston 16. Each pulse acts on the plunger 4 to extrude a corresponding amount of solder paste through the nozzle 10, upward movement of the hollow piston 16 being prevented by a ball ratchet 24, 26. At the end of the pulse, the valve 20 opens a vent E 2 to vent the hollow piston 16 to atmosphere, and the hollow piston then drops under its own weight to the new position of the plunger 4 so that the volume of the working space above the plunger remains substantially constant. Distension of the wall of the cartridge 2 during application of pressure and subsequent dribbling from the nozzle 10 while the wall is recovering from the distension are prevented by equalizing the pressures inside and outside the wall by means of a compensating hole 38. For operation in other than a vertical position, the hollow piston 16 may be spring-loaded.