Device and method for hardening foundry cores

Abstract

A device for hardening foundry cores of a sand-containing molding material, wherein the core, for its hardening, is subjected in a core molding tool to a catalyst vapor/carrier gas mixture and subsequently to a pressurized air stream is provided. Each of the vapor/carrier gas and air stream are at a predetermined pressure and a predetermined temperature, wherein a heating and mixing stage, is connected to a container containing an organic catalyst in liquid form and to a pressurized air source. The liquid organic catalyst and the pressurized air are heated together in the heating and mixing stage. The device has a separate flushing line, wherein a first cutoff valve is arranged in the line to the heating and mixing stage, which is closed at the beginning of the flushing, and a second cutoff valve is arranged in the flushing line, which is open at the beginning of the flushing.

Claims

1. Device for hardening foundry cores of a sand-containing molding material, wherein the device is adapted in order to subject the core, for its hardening, in a core molding tool, to a catalyst vapor/carrier gas mixture and subsequently to a pressurized air stream, each at a predetermined pressure and a predetermined temperature, wherein the device comprises: a heating and mixing stage (12), which is upstream of the core molding tool and which is in fluidic connection with a container (7) containing an organic catalyst in liquid form by means a first line (L), wherein the liquid organic catalyst is fed to the heating and mixing stage (12) dosed via dosing means (8-11), wherein the heating and mixing stage (12) furthermore is in fluidic connection with a pressurized air source (1) via at least one first pressure regulator (6a) by means of a second separate line (L2), so that the pressurized air used as carrier gas is fed in a dosed form to the heating and mixing stage (12), wherein the liquid organic catalyst fed to the heating and mixing stage (12) and the pressurized air fed to the heating and mixing stage (12) are heated in the heating and mixing stage (12), so that the organic catalyst assumes its gaseous state, and together with the pressurized air, a catalyst vapor/carrier gas mixture is produced, wherein the heating and mixing stage (12) is moreover connected via a third line (L3), which is closed by a valve (5), to the core molding tool, so that the catalyst vapor/carrier gas mixture is passed through the sand-containing molding material in the core molding tool, wherein, for a time-controlled flushing after the passage of the catalyst vapor/carrier gas mixture through the sand-containing molding material, the core molding tool, by a fourth line (L4) which is closed with a valve (4), is in fluidic connection with the pressurized air source (1) via a heating source (3) which is adapted in order to heat the pressurized air streaming from the pressurized air source (1) through the heat source (3) to a predetermined temperature, characterized in that the device has no preheater that heats the pressurized air (1) before it is fed to the heating and mixing stage (12) or to the heat source (3), so that the organic catalyst and the pressurized air are heated together in the heating and mixing stage (12), and a first cutoff valve (2a) is arranged in the second line (L2), which is closed at the beginning of the flushing, and a second cutoff valve (2b) is arranged in the fourth line (L4), which is open at the beginning of the flushing.

2. Device according to claim 1, characterized in that the device has two pressurized air sources (1), of which the first is connected to the heating and mixing stage (12) and the second is connected to the heat source (3).

3. Device according to claim 1, characterized in that a temperature control for the heat source (3) is connected.

4. Device according to claim 1, characterized in that, before the feeding of the catalyst in liquid form into the heater and mixing device (12), the feed of the liquid catalyst container (7) is rerouted temporarily by means of one of the dosing means (8-11) via a switching valve to a return line to the liquid catalyst container (7), for the pressure equalization in the feed system.

5. Device according to claim 1, characterized in that the third line (L3) and the portion of the fourth line (L4) which adjoins the heat source (3) is heated.

6. A method for hardening foundry cores of sand-containing molding materials, wherein the core, for its hardening, is subjected in a core molding tool to a catalyst vapor/carrier gas mixture and subsequently to a pressurized air stream, each at a predetermined pressure and a predetermined temperature, comprising the steps of: feeding in a dosed form to a heating and mixing stage, an organic catalyst in liquid form and converting it there into its gaseous state; passing pressurized air within a predetermined time period and under a proportional pressure increase, through the heating and mixing stage charged with the catalyst gas after gas-tight coupling of a gassing plate, for a time-controlled gassing; passing the pressurized air, as a catalyst vapor/carrier gas mixture, through the sand-containing molding material in the core molding tool; and then passing the pressurized air, for a time-controlled flushing, within a predetermined time period, by a separate feed line through a gassed sand-containing molding material in the core molding tool, characterized in that, the pressurized air which is passed through the heating and mixing stage for a time-controlled gassing, is heated only once when it is in the heating and mixing stage, together with the organic catalyst, and the pressurized air used for the time-controlled flushing is conducted and heated by means of a heating source in a separate line.

7. Method according to claim 6, characterized in that, before feeding the catalyst in liquid form to the heating and mixing stage (12), a pressure equalization is performed in the feed.

8. Method according to claim 6, characterized in that the catalyst vapor/carrier gas mixture is accompanied by heat on its way to the core molding tool.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S)

(1) Below, the invention is explained in further detail in reference to the appended drawing which merely represents an embodiment example.

(2) FIG. 1 shows: a diagrammatic representation of a device according to the invention for hardening foundry cores.

DETAILED DESCRIPTION OF THE INVENTION

(3) In reference to FIG. 1, a device for hardening foundry cores of a sand-containing molding material is represented and described, which can be connected to a core molding tool, not shown in further detail, of a core shooting machine, not shown in further detail. The device first comprises a gassing plate or hood 20, which can be coupled in a gas-tight manner to the core molding tool, with an upstream heating and mixing stage 12 for converting the liquid organic catalyst, which is preferably an amine, to its gaseous state, and for generating a catalyst vapor/carrier gas mixture used for gassing of the core, as will also be explained in further detail below.

(4) According to the invention, for a time-controlled gassing, the organic catalyst in liquid form runs from a storage tank or a liquid catalyst container 7 dosed by means of dosing means such as, for example, dosing valves 8 and 11, a dosing unit 9, a flowmeter 10 or the like, through a line L1 to the heating and mixing stage 12, where it is converted to its gaseous state. The heating and mixing stage 12 is additionally in fluidic connection with a pressurized air source 1 by a separate line L2, which can be closed with a cutoff valve 2a, and a proportional or a 2-stage pressure regulator 6a, in order to pass the pressurized air fed from the pressurized air source 1 via the cutoff valve 2a, for the time-controlled gassing, within a predetermined time period, through the heating and mixing stage 12 charged with the catalyst gas, wherein the pressurized air fed and the catalyst gas are heated together in the heating and mixing stage 12, resulting in a catalyst vapor/carrier gas mixture.

(5) Furthermore, the heating and mixing stage 12 is connected by a line L3, which can be closed by a valve 5 and is preferably heatable, to the core molding tool or the gassing plate 20, in order to pass the catalyst vapor/carrier gas mixture through the sand-containing molding material in the core molding tool.

(6) Furthermore, for a time-controlled flushing with the pressurized air, the pressurized air source 1 is in fluidic connection, via a separate line L4 which can be closed by a cutoff valve 2b, and optionally via a proportional or a 2-stage pressure regulator 6b and a heat source 3, as well as via a cutoff valve 4, with the core molding tool or the gassing plate 20.

(7) Not shown in the FIGURE is that, before the feeding of the catalyst in liquid form into the heating and mixing stage 12, the feed of the liquid catalyst container 7 can be temporarily rerouted through a switching valve to a return line to the storage tank 7 for the pressure equalization in the feed system.

(8) Furthermore, the gassing plate 20 is provided with a ventilation valve 21.

(9) For example, a temperature control can be connected to the heat source 3 for a regulated heating of the pressurized air. Similarly, a temperature control can also be connected to the heating and mixing stage 12. In accordance with current technology, the switching means, the valves, the dosing means and the controls can be controlled by program using a control circuit that is not shown.

(10) Thus, for the gassing process, it is now possible to feed the organic catalyst in liquid form dosed together with the pressurized air from a pressurized air source through respective separate lines to a heating and mixing stage, and to heat it there together with the pressurized air to a temperature which is sufficient for gassing the catalyst, so that the result is a catalyst vapor/carrier gas mixture, which is passed through the sand-containing molding material in the core molding tool through an additional line. During this gassing process, the cutoff valve of the line which feeds the pressurized air via the heat source to the gassing plate is closed, and the cutoff valve which feeds the pressurized air to the heating and mixing stage is open. For example, the required temperature of the amine as catalyst for gassing is between 80 C. and 110 C., wherein this depends on the type of the amine. Thus, it should be understood that the heating in the heating and mixing stage occurs in accordance with the gassing temperature of the catalyst used.

(11) Furthermore, the pressurized air required for the flushing process, i.e., for a time-controlled flushing, can be passed within a predetermined time period through the gassed sand-containing molding material in the core molding tool, after it has been fed through a separate line to a heat source and heated there to a temperature that is higher than the temperature required for the gassing of the catalyst. The temperature for flushing is preferably between 150 C. and 180 C., more preferably 170 C. During this flushing process, the cutoff valve of the (fourth) line which feeds the pressurized air via the heat source to the gassing plate is open, and the cutoff valve which conducts the pressurized air through the second line to the heating and mixing stage is closed.

(12) As gas source, a single gas source 1 can be used. In this case, both the second line L2 and also the fourth line L4 are connected to the gas source used as pressurized air source. However, it is also possible to use two separate pressurized air sources 1 (not shown in the drawing). In this case, the fourth line L4 is connected to the first pressurized air source for the flushing, and the heating and mixing stage is connected via the second line L2 to the second pressurized air source.

(13) An advantage of two separate pressurized air sources and/or two separate gas lines L2 and L4 each with a respective cutoff valve 2a or 2b is that the use of two cutoff valves, in contrast to a switching valve, is more cost effective and, due to the simpler control of the valve, a greater safety is achieved with respect to the switching process. In addition, it is ensured that no catalyst gas remains in the flushing line or heat source, which would delay the flushing process due to the resulting contamination. Furthermore, by means of the much higher temperature of the supplied flushing air (pressurized air heated by the heat source), the amount of catalyst needed can be strongly reduced, since catalyst condensed on the surface of the core becomes gaseous again much more rapidly and is thus driven rapidly into the core. By reducing the quantity of catalyst, the environmental pollution can be reduced, the costs of disposal of the catalyst gas are reduced, and the expense for cleaning the device is reduced.

(14) Moreover, due to the separate feeding of the heated pressurized air to the gassing plate, it is possible to dispense with a safety temperature regulator, which has been needed in the previous installations in order to ensure that the temperature in the heating and mixing stage does not exceed a certain predetermined limit value, so that the safety of the installation is guaranteed.

(15) Furthermore, no preheater is needed, since the gassing of the catalyst requires less heating power than the heating of the pressurized air for the flushing process. In this manner, energy can be saved, since the pressurized air to be heated for the flushing process is not cooled by line losses and since it does not need to be heated again subsequently possibly by means of a reheater.

(16) As a result of these measures according to the invention, a compact reliable device which reduces environmental pollution by reducing the required amount of catalyst gas is achieved, and which overcomes the disadvantages of the prior devices and can work at the same speed (cycle time) as the known devices.