Saturated liquid/vapor generating and dispensing

A method of making a number of foundry cores serially in which a foundry aggregate mixed with a curable binder is introduced into a core box cavity to form each green core and each green core is gassed by passing into it a predetermined dose of a vapor under pressure of a normally liquid curing agent for the binder and an inert carrier gas and then a purging gas is passed through the body to drive out the residual gas and complete the cure, the improvement comprising,

• providing a supply of said liquid agent and an overlying supply of vapor in a pressure vessel under a predetermined pressure,
• gassing a plurality of cores in series by dispensing vapor from the vapor space in a continuous series of intermittent bursts one to each core in succession, each burst producing a pressure drop within the vessel intervened by a short nondispensing period,
• during each nondispensing period, flushing through each core a purging gas,
• responsive immediately to the pressure drop caused by each burst introducing a carrier gas under pressure into a bottom zone of the vessel during each burst and following nondispensing period until equilibrium pressure is restored therein and the vapor lost in said burst is replaced by the introduction of additional gas,
• finely dividing said carrier gas as it is introduced to form in said liquid a mass of bubbles having an initial size not greater than about 25 microns in diameter whereby intimate contact is made between the gas and the liquid and a saturated vapor is formed and conveyed to the vapor space in an amount to replace the dose dispensed,
• maintaining a head of liquid above said bubbling zone of at least about 8 inches whereby the intercontact time between the gas bubbles and liquid is such as to ensure the presence in the vapor space of a true saturated vapor to the exclusion of liquid,
• maintaining a relationship between the depth of the vapor space, the head of liquid above the introduction zone, the relative volume of each burst to that of the vapor space, the frequency of the bursts, and the initial size of the bubbles so as to ensure the presence in the vapor space of a true saturated vapor substantially free of entrained liquid.

An apparatus for the gassing of cold box cores with the saturated vapor in a carrier gas of a curing substance which is normally liquid at ambient temperatures, comprising,

• a cold box having a core cavity for a core of finely divided aggregate and curable binder,
• a pressure vessel for containing a body of liquid covered by an atmosphere of saturated vapor of a normally liquid curing substance under pressure,
• a vapor-dispensing communication from an upper position in the vapor space in the vessel leading to the core cavity,
• means for controlling the vapor-dispensing communication whereby saturated vapor of a curing agent for said binder is dispensed from the vessel in bursts of predetermined size,
• near the bottom of the liquid space in the vessel a partition of a porous medium having in contact with the liquid an extensive surface having pores of mean diameter not greater than about 10 microns,
• a source of carrier gas under pressure and communication therefrom to the side of the partition remote from the liquid,
• a source of purging gas under pressure and a purging gas communication therefrom to the core cavity,
• means for controlling the purging gas communication whereby purging gas is supplied to the core cavity in predetermined amount,
• timing means for synchronizing the means for controlling the vapor communication with the means for controlling the purging gas communication, whereby, in a continuous cycle, an amount of vapor is dispensed effective to cure the core and immediately following an amount of purging gas is dispensed effectively to purge the core,
• means for regulating the pressure of the carrier gas supplied to a predetermined pressure whereby gas of substantially said pressure is passed through the partition to the liquid to form bubbles, responsive immediately to the pressure drop caused by the dispensing of each burst of vapor until equilibrium pressure is restored and the vapor lost in said burst is replaced by the introduction of additional gas.