DE2923062A1 - Vacuum filling of cavities, esp. boxes used for mfg. sand cores - where vacuum is also used to remove noxious gases evolved during core mfr. - Google Patents

Abstract

The vacuum is used to ensure complete filling of a cavity or box, and/or for the direct removal by suction of noxious gases or fumes created when filling the box. The pref. appts. employed to create the vacuum does not permit the noxious gases to come into contact with sliding machine parts which could create a spark and thus ignite the gases. A vacuum of min. 500 mm water column is pref. used; and the mould or core box is pref. provided with evacuated cavities forming min. 10% of the total vol. of the box cavity, and facilitating the removal of noxious gases.

Description

Direct coupling only when the system is closed

has approached and establishes the connection to the evacuation line.

Claim 7 Method according to Claims 1 - 6, characterized in that that the device generating the negative pressure is as close as possible to the mold or Evacuation cavity is arranged.

Claim 8 Method according to Claims 1 - 6, characterized in that that the suction point is connected to a suction system with pipes. At the Extraction of harmful gases, for example, can generate these upstream or downstream of the negative pressure System must be rendered harmless (e.g. by rinsing in washers).

Claim 9 Method according to Claims 1 - 8, characterized in that that on or behind the molds a false air metering when reaching a Once the negative pressure has been set, there is a constant minimum volume flow is retained during suction.

There are therefore suction systems installed, which essentially the All circulating air around the core mold production to capture and try to suck off. As a result, however, residues of the gases remain in the, e.g. when fumigating with amines Core shape and in the core and only evaporate later. Only very long rinsing with Air can help here, which in mechanized production leads to reduced performance leads.

The concentrated suction from the immediate vicinity is also already there tried and tested as well as suction from encapsulated core molds.

The process according to the invention has set itself the task of a) improved To create manufacturing conditions (e.g. mold filling) and b) to eliminate the problems to simplify or even make possible of harmful gases.

Procedure 1. To avoid greater resistance when sucking through To overcome porous bodies is one more, depending on the permeability of the body or less high vacuum required. A wide variety of Units are used, such as fans (also multi-stage), rotary piston pumps, Screw pumps, water ring pumps, etc., - but also simple ones, e.g. based on the Venturi principle working compressed air nozzles. The latter generally have the advantages of a) without moving To work parts, b) to be able to generate high negative pressures and amounts of suction air, c) Only compressed air is required as a drive and thus when extracting explosive gas-air concentrations (e.g. amine / air) not being able to generate ignition; d) through adjustable compressed air supply different and in use appropriate vacuum or suction air quantities to be able to generate.

In the case of a Venturi annular gap nozzle, this can still be done via the additional Controllability of the annular gap can be achieved.

2. It has proven itself, depending on the intended use, the core mold bottom part (Lower part of the core box, slide), e.g. to be evacuated when gassing with amines or possibly the side panels.

When making large core moldings by hand, suction lances, consisting of a tube with a porous end part (or perforated), to extract gases.

With the possible variety of core shapes, the cheapest way to be found in the form.

In order to improve the filling of the mold, e.g. when shooting in with binding agents In order to achieve the core shape of mixed sand, it makes sense, as tests have shown, that the vacuum is high (depending on the shape and size of the core, 2,000 - 6,000 mm water column under normal pressure). In the case of more complex core forms, lower values were not successful in that Insertion of the nozzles into the molded parts for the purpose of air removal can be reduced could.

3. When using a compressed air injector, for example, the extracted Gases can be fed directly into an exhaust duct without having to deal with machine parts (friction surfaces = Ignition) to come into contact.

4. To get a relatively constant optimal suction power, it is It makes sense to have the device generating negative pressure in the immediate vicinity, if possible in to be assigned to the machine in machine production because of longer cable routes Suction losses arise. This applies primarily to injectors (e.g. Venturi nozzles), because due to their characteristic curve with increased negative pressure, the air flow rate is considerable decreases. In this case, it is still useful to work in the area of the tool, e.g. on a evacuated cavity in the slide or core mold lower part, with a vacuum regulator to work through false air metering.

This can be done, for example, by attaching a poppet valve with a tension spring happen. This valve is regulated by the tension of the spring. For example, should the If the maximum negative pressure is 2,000 mm WS, the valve is checked by means of a negative pressure meter set and opens when it reaches 2,000 mm water column, so that false air flows in can and no higher pressure is reached. The outside air can thus e.g. after the Shooting process, when the filled core form creates a great resistance, thereby occur and ensures a volume flow of exactly a certain size. this is important for the extraction of explosive gases, as this ensures that the ignition limits (concentrations) are not reached.

5. Are there several systems or extraction points, e.g. if there are several Core molding systems, so you can work with large suction systems that have suction lines are connected to the individual suction points. Large suction pumps (rotary piston blowers, Screw compressors, multi-stage fans, etc.) are used. To the volume flow To ensure that there is also a vacuum regulation at the end of the pipeline, for example with false air metering - as described above - to be provided.

6. Almost all mechanized core manufacturing processes on machines have e.g. a so-called slide as a core carrier. This forms partly also the lower part of the core box. By evacuating a cavity in this slide plate can be sucked off gas.

The Venturi nozzle to be used, for example, can be very easily turned on a stationary machine part (e.g. cylinder, whose Piston rod the movement of the slide) and the connection e.g. via a Make a plug-in nozzle that only connects when the slide is in its end position to the suction system. Absolute tightness of all connection transitions is here not necessary, as more air can always be sucked in than e.g. through one Gassing process is introduced to gas. Tests have shown that at a low vacuum (about up to 300 mm water column - negative pressure depending on the shape of the core) no significant Improvement of the process advantages outlined is achieved.

From about 500 mm water column negative pressure can be more sufficient with smaller, simpler cores Success can be achieved while large volume cores have significantly higher negative pressure values demand.

Claims (1)

The following claims can be derived from this: Claim 1 Applying a vacuum directly in or on a cavity Core mold) for the purpose of achieving better mold filling and / or direct suction of harmful gases during the formation or after the supply. Claim 2 Method according to Claim 1, characterized in that a device is used to generate the vacuum which does not allow the extracted gases to come into contact with machine parts that are moving, for example rubbing or generating sparks Claim 3 Method according to Claim 1 and / or 2, characterized in that the vacuum applied is at least 500 mm water column under normal pressure. Claim 4 Method according to Claims 1 - 3, characterized in that that cavities in the molded parts are evacuated and targeted connection to the cavity is established will. Claim 5 method according to claim 4, characterized in that the voids amount to at least 10% of the total main volume, e.g. of the core. Claim 6 Method according to Claims 1-5, characterized in that in the case of mechanical systems z, B, i a plug-in nozzle or the like. Applying a vacuum to cavities for the purpose of filling them with porous materials as well as on porous bodies for the purpose of removing gases odor in the foundry industry For example, sand cores are required to form casting cavities in the mold. It is known to produce these cores in a wide variety of core shapes manually or on machines to produce. Series cores are generally inserted into the core molds by means of compressed air "shot (blown or similar, depending on the method). This core shooting should take place in fractions of a second take place. The core molds must be 100% filled. In any case, it is difficult to run out of breath in the shortness of time to remove the core molds. In many cases, air cushions are formed by suitable Measures (air discharge to the outside via channels, slot nozzles in the walls of the Core forms) must be eliminated. After the core molds are filled, the filled must be loose Crowds are heard. A wide variety of cold temperatures are used for hardening and are called procedures. E.g. the sands are coated with binding agents that either through catalysts (e.g. cold box process, gas generally with amine hardening) or in the heat (e.g. hot box and croning process) or by adding Reagents (e.g. water glass / C02 process, furan resin acid hardening, phenolic resin acid hardening) or harden other reactions. In almost all processes, some harmful gases are either used Hardening used (e.g. cold box water glass C02 process) or during hardening free (hot box croning, resin-acid process). These pollutants should be handled by the operating or processing personnel as well as do not harm the environment.