Abstract: A supply unit 1 is provided for maintaining a desired level of a viscous liquid in a supply tank 2. The liquid is supplied through an inlet passageway 5 down to a horizontal portion 8 and then to a vertical portion 9 communicating with one side of a valve piston 11. When the tank 2 is full of a liquid, this liquid will be drawn up through a passageway 14 in a body 6 by a gear pump 15 which pumps the liquid through a supply line 18 to act on the other face of the piston 11. When the level of liquid within the supply tank 2 falls so that it cannot be drawn up through the passageway 14, the pressure on the upper face of the piston 11 will be relieved and the inlet pressure of the liquid in the inlet passageway 5 will then cause the piston valve 11 to open to allow the liquid to pass through an outlet passageway 13 leading into the supply tank 2.

Abstract: A supply tank 11 from which adhesive will be dispensed by an applicator wheel 12 to the flap of a carton incorporates a valve assembly 16 connected through an inlet 20 to a pressurized supply of molten adhesive. The adhesive will enter pockets 19 in a rotating feed member 14 carried by a shaft 13 and mounted in a housing 15. If the level of adhesive in the supply tank 11 falls below the top of an outlet 21 from the housing 15 then any charge of adhesive within a pocket 19 passing the opening 21 will be dispensed into the supply tank 11 by gravitation. There is no direct connection between the pressurized supply to the inlet 20 and the outlet 21.