GB625903A - Improvements in apparatus for sealing containers of powdered milk and other light powdered materials - Google Patents

Abstract

625,903. Sealing containers of milk &c. powder. TRUFOOD OF AUSTRALIA, Ltd. May 8, 1946, No. 13961. Convention date, May 8, 1945. [Class 49] [Also in Group XVII] Containers of powdered milk are sealed in chambers mounted on a rotary table, each chamber holding a container being subjected to a first, partial, evacuation during the early stages of which the air is withdrawn through an orifice or orifices of relatively small area at such a rate as to avoid distrubance of the container contents, and a second evacuation to a pressure approaching absolute vacuum; the container is then sealed in the chamber, after which the chamber is vented to atmosphere and the container removed. After the second evacuation, the chamber may be supplied with inert gas at low pressure. As shown, cans 71, which have been previously filled with powdered milk and on the upper ends of which lids 72 have been placed, Fig. 13, are transferred by means of a reciprocating arm from a conveyor on to platforms 73 located beneath and rotating with chambers 45 mounted on a rotary table 42, Fig. 1. As rotation proceeds each platform 73 is raised by can track 77 to introduce the can into the chamber 45 above and to seal the lower end of the chamber. Down and up movement of a roller 94 on a can track 95 moves a yoke 90 and with it an arm 89<SP>1</SP>, Fig. 13, to lower a magnet 83 against spring pressure into contact with the lid 72 and to lift the lid from the can. Chamber 45 is connected by pipe 46 to a port in a valve seat plate communicating successively with ports 57, Fig. 5, in a stationary valve plate 49 connected to a suction pump. Ports 57 are connected by a groove 52 tapered towards the end with which each port in the valve seat plate is first in register, and ports 57 are provided with needle valves adjusted so that the effective size of the ports increases progressively, sc that air is withdrawn at low velocity during the early stages of the exhaustion and more rapidly later in order to avoid disturbance of the powdered contents of the can. A vacuum equivalent to 27 inches of mercury is applied to channel 52; the chamber 45 is then connected through a further channel 53 similar to channel 52 with a second vacuum pump to reduce the pressure to within quarterinch of mercury of absolute vacuum. The chamber is now connected through a port 69, Fig. 5, with a pressure gauge and then through port 68 with a supply of inert gas at low pressure, preferably nitrogen at a pressure equivalent to 20 inches of mercury. The lid 72 is now lowered on to the can, a gasket or sealing composition in a peripheral recess 82 of the lid engaging a lip surrounding the opening in the can, and the chamber is vented to atmosphere through a further port 70 in the valve plate, after which platform 73 is lowered and the can unloaded on to a conveyer. More than two channels may, if desired, be provided in valve plate 49 connected to an equivalent number of vacuum pumps.