Apparatus for low-pressure casting

Abstract

An apparatus for low-pressure casting includes a furnace wall bounding a furnace chamber, a melting crucible unit located in the furnace chamber, a heating device for heating the melting crucible unit, and at least one pressurizing unit for applying overpressure to the melting crucible unit. The furnace chamber in a top view has a length which is greater than its width, so that the furnace chamber has an elongated shape in a longitudinal direction, wherein preferably several riser pipes extending vertically are distributed roughly evenly over around 60% to 95% of the length in the longitudinal direction of the melting crucible or crucibles.

Claims

1. Apparatus for low-pressure casting including a furnace wall bounding a furnace chamber, a melting crucible unit located in the furnace chamber, a heating device for heating the melting crucible unit, at least one pressurizing unit for applying overpressure to the melting crucible unit, wherein the furnace chamber in a top view has a length which is greater than its width, so that the furnace chamber has an elongated shape in a longitudinal direction, wherein riser pipes extending vertically are distributed roughly evenly over at least 60% of a length in the longitudinal direction of the melting crucible unit; and wherein the riser pipes form a riser pipe array that includes in the longitudinal direction between four and twelve riser pipes and, in a width direction running transversely to the longitudinal direction, two or more riser pipes.

2. The apparatus according to claim 1, wherein the riser pipes are distributed roughly evenly over 95% of the length in the longitudinal direction of the melting crucible unit.

3. The apparatus according to claim 1, wherein a minimum distance of two riser pipes each arranged endwise in a longitudinal direction is at least 105 centimeters.

4. The apparatus according to claim 1, wherein a minimum distance of two riser pipes each arranged endwise in a longitudinal direction is at least 110 centimeters.

5. The apparatus according to claim 1, wherein a minimum distance of two riser pipes each arranged endwise in a longitudinal direction is at least 135 centimeters.

6. The apparatus according to claim 1, wherein a minimum distance of two riser pipes each arranged endwise in a longitudinal direction is at least 180 centimeters.

7. The apparatus according to claim 1, wherein the melting crucible unit is a trough-like melting crucible with a roughly elongated shape in a top view.

8. The apparatus according to claim 1, wherein the melting crucible unit has at least two melting crucibles, roughly circular in a top view.

9. The apparatus according to claim 8, wherein the at least two melting crucibles are separated from one another spatially by a common partition wall.

10. The apparatus according to claim 8, wherein each melting crucible has a pressurizing unit.

11. The apparatus according to claim 1, wherein the heating device surrounds a jacket wall of the melting crucible unit and/or the heating device is arranged in the vertical direction in the area of a base bounding the melting crucible unit.

12. The apparatus according to claim 1, wherein the riser pipe array is rectangular and/or oval shaped.

13. The apparatus according to claim 1, wherein the riser pipe array comprises in the longitudinal direction between six and eight riser pipes and, in the width direction, three to four riser pipes.

14. The apparatus according to claim 1, wherein the furnace wall has a furnace outer wall, a furnace partition wall and a refractory coating.

15. The apparatus according to claim 14, wherein the furnace outer wall is made of steel and/or the furnace partition wall is made of a refractory material, a refractory lining, a refractory gunning material or refractory concrete.

16. The apparatus according to claim 15, wherein the refractory coating is an aluminum oxide coating or is made of a refractory lining, ceramic material, a refractory ramming mix, a refractory gunning material or refractory concrete.

17. The apparatus according to claim 1, wherein the heating device is located in the vicinity of a base or is integrated in the base.

18. The apparatus according to claim 1, wherein the heating device comprises several electrically operated heating rods.

19. The apparatus according to claim 18, wherein each of the heating rods is surrounded by an aluminium-titanate tube.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) In the accompanying drawings, reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale; emphasis has instead been placed upon illustrating the principles of the invention. Of the drawings:

(2) FIG. 1 is a side cutaway view of an apparatus according to a first embodiment of the invention for low-pressure casting, without a furnace cover;

(3) FIG. 2 is a top view of the apparatus according to the first embodiment, with a furnace cover;

(4) FIG. 3 is a top view of the apparatus according a second embodiment, without a furnace cover; and

(5) FIG. 4 is a top view of the apparatus according to the second embodiment in which the apparatus includes a melting crucible covered by a cover which has six riser pipes.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(6) The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which illustrative embodiments of the invention are shown. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art.

(7) As used herein, the term and/or includes any and all combinations of one or more of the associated listed items. Further, the singular forms and the articles a, an and the are intended to include the plural forms as well, unless expressly stated otherwise. It will be further understood that the terms: includes, comprises, including and/or comprising, when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Further, it will be understood that when an element, including component or subsystem, is referred to and/or shown as being connected or coupled to another element, it can be directly connected or coupled to the other element or intervening elements may be present.

(8) Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

(9) An apparatus 1 for low-pressure casting according to the invention is described by way of example below with the aid of a first embodiment (FIGS. 1 and 2).

(10) The apparatus 1 includes a furnace chamber 2. The furnace chamber 2 is bounded by a furnace wall 3.

(11) The furnace wall 3 has a furnace outer wall 4 which is made of steel. The furnace wall 3 also has a furnace partition wall 5 which is made of a refractory material, e.g. a refractory lining, ceramics, refractory ramming mix, refractory gunning material or refractory concrete.

(12) The furnace partition wall 5 is coated with a refractory coating 6, in particular an aluminum oxide coating, a refractory lining, ceramics, refractory ramming mix, refractory gunning material or refractory concrete. The aluminum oxide coating may be applied with a binder to the furnace partition wall or applied in the form of panels.

(13) The ceramic material is preferably a dense, not easily wetted refractory oxide ceramic material with low thermal expansion.

(14) In use, the refractory coating is in contact with the melt, thus forming a melting crucible unit 6. According to the first embodiment, this melting crucible unit 6 is trough-like in shape, and the furnace wall 3 thus forms a trough-like melting crucible 7.

(15) The melting crucible 7 has an elongated shape extending, in the horizontal plane, in a longitudinal direction 8.

(16) The length 9 of the trough-like melting crucible 7 in the longitudinal direction 8 comes to around 190 cm to 250 cm.

(17) Provided transversely to this longitudinal direction 8 in the horizontal plane is a width direction 10, over which the trough-like melting crucible extends over a width 11 of around 120 cm to 150 cm.

(18) Due to a corresponding extension in the vertical direction 16 or in height, the melting crucible 7 is able to hold a content of 4000 kg to 5000 kg of melt, in particular aluminum melt.

(19) Provided in the area of a base 12 of the melting crucible is a heating device 13.

(20) The heating device 13 comprises preferably several electrical heating rods 14, extending horizontally in the area of the base 12.

(21) The apparatus 1 also has a furnace top 15 covering the furnace chamber and in particular the melting crucible 7.

(22) According to this embodiment, eighteen riser pipe sleeves 17 are provided in the furnace top 15. Corresponding riser pipes 18 are arranged in the riser pipe sleeves 17. The eighteen riser pipes 18 form a rectangular riser pipe array 19 (broken line).

(23) A casting mold (not shown), for example in two parts, may be arranged on the riser pipe array 19.

(24) This casting mold may for example have a movable top part and an immovable or stationary bottom part. The casting mold bounds a mold cavity which may be filled by the melt rising through the riser pipes. A casting mold of this kind also has at least one plunger.

(25) With the furnace top 15 fitted on to the furnace wall 3, the furnace chamber 2 becomes an airtight container or space.

(26) The furnace chamber 2 also has at least one port for connection to a pressurizing unit (not shown) for the application of overpressure to the furnace chamber. The apparatus is preferably in the form of a furnace for low-pressure casting. The overpressure is generated by the feeding of dried air (dew point ca. 40 C.).

(27) Filling holes (not shown) which can be closed by flaps may be provided in the furnace top 15.

(28) These holes are so dimensioned that a circulation device (not shown), such as e.g. a rotor or an impeller, may be guided through them.

(29) For cleaning the furnace it is then provided that the circulation device is dipped into the melt and gas is supplied. The gas used is preferably nitrogen or argon. The gas bubbles convey the dirt to the surface, where it can be removed as skimmings.

(30) This process may also be effected by lifting the furnace top 15. The greater the open surface of the holes which may be closed by flaps, or the surface of the melting crucible in a top view, the easier is the cleaning process.

(31) The holes may also be provided for filling the melting crucible.

(32) For cleaning the furnace or the melt contained therein, the furnace may be provided with several sinks, via which purge gas may be fed into the furnace.

(33) One or more filling channels may also be provided. Such filling channels allow filling of the furnace without the need to traverse the furnace out of an associated machine. Filling is effected preferably via a filter device, so as to limit the ingress of dirt.

(34) The apparatus 1 according to the invention for low-pressure casting will be explained below with the aid of a second embodiment (FIGS. 3 and 4). Unless otherwise described, this apparatus has the same technical features as an apparatus according to the first embodiment. Identical components are provided with the same reference numbers.

(35) The apparatus 1 includes the furnace chamber 2. The furnace chamber 2 is bounded by the furnace wall 3.

(36) The furnace wall 3 has the furnace outer wall 4, which is made of steel. The furnace wall 3 also has the furnace partition wall 5, which is made of ceramic material.

(37) The furnace chamber 2 is roughly oval in shape, viewed from above or in a horizontal cross-section.

(38) The melting crucible unit 6 is located in the furnace chamber 2.

(39) The melting crucible unit 6 comprises at least two melting crucibles 7, which are located in the furnace chamber 2. The melting crucibles 7 are substantially made of graphite with a silicon content.

(40) The melting crucibles 7 are cylindrical with a circular cross-section with a diameter of around 1.3 m.

(41) The heating device 13 is located in the area between the furnace partition wall 5 and the two melting crucibles 7.

(42) The heating device 13 surrounds jacket walls of the two melting crucibles in a horizontal top view from above at an angle of around 270.

(43) The apparatus 1 also has one or two furnace tops 15 covering the furnace chamber and in particular the melting crucibles 6.

(44) Provided according to this embodiment, on the furnace top or tops 15 are riser pipe sleeves 17 spaced equally apart from one another. The furnace top 15 is of similar design in the area of both melting crucibles 6, so that according to this embodiment, twelve riser pipe sleeves 17 are provided.

(45) The riser pipes 18 are mounted in the riser pipe sleeves 17. In each case six riser pipes 18 of a melting crucible 6 are arranged at right-angles and spaced equally apart.

(46) The twelve riser pipes 18 from the riser pipe array 19 (broken line).

(47) The riser pipe array 19 is therefore similarly rectangular in the present embodiment. A casting mold (not shown), for example in two parts, may be mounted on this riser pipe array 19.

(48) The casting mold may for example have a movable top part and an immovable or stationary bottom part. The casting mold bounds a mold cavity which may be filled by the melt rising through the riser pipes. A casting mold of this kind also has at least one plunger.

(49) Depending on the casting mold, the riser pipe array may have almost any desired number of riser pipes. In each melting crucible, one, two, three, four, five, six, seven, eight, nine, ten, eleven, twelve or more riser pipes may be fitted. Preferably, however, the riser pipes are always spaced equally apart from one another and generally form, in accordance with the oval furnace chamber or on account of the two melting crucibles 6, a riser pipe array 16 extending in a plane perpendicular to the crucible longitudinal direction.

(50) The riser pipes may also be in the form of multiple riser pipes.

LIST OF REFERENCE NUMBERS

(51) 1 apparatus 2 furnace chamber 3 furnace wall 4 furnace outer wall 5 furnace partition wall 6 melting crucible unit 7 melting crucible 8 longitudinal direction 9 length 10 width direction 11 width 12 base 13 heating device 14 heating rods 15 furnace top 16 vertical direction 17 riser pipe sleeve 18 riser pipe 19 riser pipe array

(52) While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.