Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B22—CASTING; POWDER METALLURGY
  • B22C—FOUNDRY MOULDING
  • B22C9/00—Moulds or cores; Moulding processes
  • B22C9/12—Treating moulds or cores, e.g. drying, hardening
  • B22C9/123—Gas-hardening

Definitions

• the present invention relates to a method for hardening foundry cores from a mass containing sand, in which the core is exposed to a gas stream enriched with a catalyst and subsequently to a compressed air stream to harden it in the core molding tool.
• Such cold-curing processes are known, such as the so-called coldbox process, in which two components of a synthetic resin system are added to the core sand, which then harden with the sand as soon as an amine, for example an alkylamine or a methyl formate, as Catalyst is added.
• One component here could be, for example, a polyester resin, a polyether resin or any synthetic resin with a liquid consistency with reactive hydroxyl groups; the second The component is definitely an organic isocyanate.
• the two components are thoroughly mixed with the molding sand and then molded. So far, various efforts have been made to catalyze the reaction here and to make the handling and use of the amines in particular reliable.
• the known methods have a common disadvantage in that the curing process takes a considerable amount of time.
• the shaping of the core sand mixture in the mold on a core shooting machine often takes only fractions of a second, whereas the subsequent gassing to harden the core has to take place over several seconds, which means that the gassing na ⁇ naturally makes it an enormous cost bearer.
• a further method has subsequently become known, according to which metering pumps between the catalyst source and the mixing point of carrier gas and catalyst are to be switched on in order to be able to meter the catalyst better, which, however, can only lead to an unsatisfactory result here .
• the catalyst Lysator is supplied in liquid form to a nozzle upstream of the heating stage, the outlet jet of which disintegrates under the influence of an atomizing gas additionally flowing through the nozzle.
• This gas-assisted atomization of the catalytic converter achieves an optimal metering of the catalytic converter and an equally optimal mixture of liquid and gas, generally compressed air, without the hitherto customary use of metering containers, metering pumps and the like.
• the metering and the mixing ratio is carried out only via pressure regulator and spray characteristics of the atomizing nozzle.
• the present invention relates to a device for performing the method with an arrangement for producing a catalyst vapor / carrier gas mixture and with a compressed air source.
• This device is characterized by an atomizing nozzle connected upstream of the heating stage, which is in flow connection with a gas source, in particular compressed air source, and also with a catalyst source via pressure-controlled feed lines.
• Such a device can, as is readily recognizable, with the smallest, commercially available means, is extremely precise to control and practically maintenance-free.
• the present invention relates to the use of the method according to the invention on a core shooting machine.
• the device shown which can be connected to a core molding tool 1 of a core shooting machine (not shown in any more detail), for curing foundry cores, preferably using the cold box method, initially comprises, in a known manner, an arrangement 2 for producing a catalyst vapor / carrier gas mixture sches with connecting lines 3 and 4, which via control valves 5 and 6 to a catalyst source, not shown, respectively.
• Compressed air source can be connected, and with a heating stage 7 upstream of the core molding tool 1 in the form of a heat exchanger or the like. in the feed line 8 to the core mold.
• the catalyst is now in liquid form Directly fed to the atomizing nozzle 10 upstream of the heating stage 7 via an intermediate line 9 via a pressure regulator stage 11 downstream of the control valve 5 in the connecting line 3.
• the compressed air is fed directly to this atomizing nozzle 10 via a pressure regulator stage 12 in the connecting line 4 which is connected downstream of the control valve 6.
• the atomizing nozzle 10 can also be bridged by means of bypass 13 and bypass valve 14 in order to be able to press a larger amount of purging air through the core in the same time unit through this line with a larger flow cross section.
• the atomizing nozzle 10 can be of different, conventional construction.
• the liquid is applied to a film surface through a relatively large opening and flows, driven by the shear stress of the superimposed compressed air flow, in the form of a thin film Atomizing opening at which the film disintegrates.
• the liquid is transported separately from the atomizing gas to the nozzle opening and flows in the form of a thin jet through the nozzle opening into one or more gas jets, where the liquid jet decays.
• the atomizing nozzle 10 is preferably supplied with the liquid catalyst and also the carrier gas, here air, under pressure.
• control valves 5 and 6 the pressure control stages 11 and 12 and the bypass valve 14 in a programmable and fully automatic manner via a computer and control stage 15.
• any desired liquid concentration of the catalyst-gas mixture can be achieved, changes in the ambient temperature being able to be compensated for without further action, so that an option which has not been possible until now ⁇ lubrication of the curing process can be achieved with comparatively minimal effort.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Molds, Cores, And Manufacturing Methods Thereof (AREA)

Applications Claiming Priority (2)

Publications (1)

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Country Status (3)

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Family Cites Families (5)

• 1989
  • 1989-07-14 CH CH264889A patent/CH679913A5/de not_active IP Right Cessation
• 1990
  • 1990-07-11 EP EP19900909613 patent/EP0434795A1/de not_active Withdrawn
  • 1990-07-11 WO PCT/CH1990/000168 patent/WO1991001189A1/de not_active Application Discontinuation

Non-Patent Citations (1)

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