Bmd Badische Maschinenfabrik Durlach Gmbh

Thomas Parr

Norbert Damm

Ernst Schmitt

To improve the accuracy of making a casting pattern from a casting model or mold (2, 2') in a molding material (M) retained in a foundry form, a single pressure pulse (P) is applied to the molding material which, however, has two phases of pressure gradient, namely a first or initial phase (1) of low pressure gradient extending up to about 1 to 3 bar during between about 10-100 m/sec, for example about 50 m/sec, to initiate fluidization of the molding material. The then fluidized and still fluidized molding material is compacted by raising the pressure from the initial low pressure pulse abruptly at a second and much higher pressure gradient to the customary compaction pressure of between 3 to 6 bar. The two-phase pressure pulse can be applied, selectively, only in a region above the model or throughout the entire mold. The pressure pulse can be generated by applying the pulse but controlling a gas admission valve (11) for an initial slow valve-opening movement, for example by throttling hydraulic counterpressure (35, 36), and then permitting rapid opening movement of the valve (11) by inhibiting the throttling; or (FIG. 4) by applying the full pressure pulse from the valve and interposing a throttle (41) in the path of the air flow from a compressed air chamber (5) to the mold box (3, 4), for example by a relatively shiftable apertured plate operable above a similarly apertured counter plate for selective alignment and misalignment of the respective apertures.

Method and apparatus for compacting foundry molding material in a

To permit close matching of compaction pressure being applied to foundry mold making material, such as foundry sand, to the shape of a mold pattern (2) in a pattern box (3, 4), individual fluid pressure is applied to a plurality of press plungers (7) located on a pressure plate which is moved towards the sand in the mold box at a high rate of speed, the press plungers being biassed by fluid pressure to have a maximum difference (.DELTA.H) in stroke of penetration depth of at least 30% of the height (H) of the mold box; individual valves (14) can apply compressed air to individual cylinders under control, for example, of a microprocessor; the valves can be located in a matrix arrangement (FIG. 3). The method and apparatus can be used in combination with explosion or pressure impulse compaction and fluidizing of the foundry sand.

Method and apparatus for compacting foundry mold making material about a

In a process for mixing wet molding materials, particularly wet molding sands used for foundry purposes, the dry components of the molding materials are premixed in a container and, following the premixing of the moist components of the molding materials, are added and then homogenized with the dry components by further mixing. To reduce the mixing time, improve the mixing result and prevent contamination of mixer parts above free surface level of the dry components, the moist components are added under an overpressure to the premixed dry components below the surface level of the premixed dry components.

Process for mixing foundry molding materials

An apparatus for mixing solids with one another and with liquids, particularly for producing moulding sand mixtures, comprises a circular, fixed trough and at least two groups of mixing tools engaging with different spacings from the trough axis and trough bottom, which revolve about the trough axis and set with opposite angles with respect to the tangent of the circular path thereof. In order to obtain both a horizontal and vertical movement of the material being mixed in the case of maximum throughput, the mixing tools are formed in paddle-like manner from part cylindrical circumferential segments with roughly horizontal axis of curvature, the mixing paddles of the outer group point inwards with their concave side, while those of the inner group point outwards. There are also separate, revolving wall strippers for the inner and outer trough walls.

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Karlsruhe, Germany

Thomas Parr