HK1078518B - Method and apparatus for assisting removal of sand moldings from castings - Google Patents

Description

Method and apparatus for facilitating removal of sand molds from castings

Technical Field

The present invention relates generally to the manufacture of metal castings, and more particularly to the manufacture of castings in sand mold fillers (packs) and to facilitate the removal of sand mold fillers and cores from castings.

Background

A common casting process for forming metal castings generally uses a mold or die, such as a permanent metal or sand mold, having external features of the desired casting (e.g., cylinder head) formed on its internal surface. A sand core comprising sand and a suitable binder material, which defines the internal features of the casting, is typically disposed within the mold to further define the features of the casting. Sand cores are commonly used to create contours and internal features of metal castings, and it is also necessary to remove and recover the sand material of the cores from the castings after the casting process is completed.

Depending on the application, the binder for the sand core and/or sand mold may comprise a phenolic resin binder, a phenolic urethane "cold box" binder, or other suitable organic binder material. The mold or die is then filled with a molten metal alloy that can be cooled to a certain suitable degree in order to solidify the alloy. After the alloy solidifies into a casting, the casting is sent to a treatment furnace for further processing, including heat treatment, sand reclamation from the sand core, and aging. Heat treatment and aging are treatments to condition metal alloys so that they will be provided with different physical characteristics suitable for different uses. The heat treatment may comprise a treatment and/or a heat treatment.

The sand molds and/or cores are typically removed from the castings prior to completion of the heat treatment. The sand molds and/or cores are typically separated from their castings by one or a combination of means. For example, sand may be chiseled from the casting, or the casting may be physically shaken or vibrated to break up the sand mold and internal sand cores within the casting and remove the sand. Further, when the sand molds and castings are passed through a heat treatment and/or heat desliming furnace, the organic or thermally degradable binders for the sand molds and cores are typically destroyed or burned by exposure to the high temperatures used to heat treat the castings to the appropriate metal properties so that the sand of the molds and cores can be removed from the castings and recovered, leaving the heat treated castings. Furnace systems and methods for heat treating castings are known from U.S. patent nos. 5957188, 5829509, and 5439045, which are incorporated herein in their entirety by reference. Once the sand is removed from the casting, heat treatment and aging of the casting are typically completed in subsequent steps.

The techniques described in the above patents, for example, have driven technological advances due to competition, for example, by increasing the cost of raw materials, energy, labor, waste disposal, and environmental management. These factors continue to require improvements in the areas of heat treatment and sand recovery from the metal castings.

Disclosure of Invention

The present invention includes a method and system for facilitating the removal of sand molds and cores from castings formed within sand molds. According to one embodiment of the invention, the sand mold may be removed from the casting by scoring the mold at predetermined locations or points about the mold and applying a force sufficient to cause the mold to fracture and break into pieces. For example, the mold may be fractured by thermal expansion of the casting heated therein by application of radiant energy or inductive energy to the mold, or by application of other forces and/or energy to the mold or casting. In addition, high pressure fluid, pulses or vibration waves may also be directed at the outer wall of the mold to help break the mold. Once the molds break and break into pieces, they are typically removed from the castings. After the mold is removed, the casting may be heat treated while the sand mold block is heated to a temperature sufficient to burn its binder material, thereby fracturing the mold and core and recovering the sand.

The present invention relates generally to the use of precision sand molds, green sand molds, semi-permanent sand molds, and the like, which are typically designed to be broken down and removed from their castings, such as during heat treatment. Other types of molds having portions that mate together, for example, along a joint line, may also be used with the present invention. For example, the invention may be used in core-locking type moulds, where the mould forms parts held together by a central locking core piece that will be broken and/or fractured by applying a pulse wave or force to it, resulting in the release and falling off of the parts of the sand mould from the casting.

In another embodiment, a method of removing a mold from a casting may include disposing one or more explosives or organic or thermally degradable materials at one or more selected locations within an exterior wall of the mold. The explosive charges are detonated at specific times in the process in order to fracture and break the mold into pieces. The broken pieces are then removed from the casting.

Alternatively, the score may be added to a mold containing explosive charges or organic or thermally degradable or reactive materials. The score lines are combined with explosive charges and/or organic or thermally degradable materials at predetermined locations to facilitate the breaking up and removal of the mold sections from the castings by the activation of the explosive charges. After the mold is removed, the casting may begin or continue to be heat treated.

Another embodiment includes a method of removing a mold from a casting formed in the mold by energizing the mold with high energy pulsations. After being subjected to high energy pulsating excitation, the mold typically fractures and the fractured portions can then be removed from the casting. The high energy pulsations typically comprise vibration waves, pressure waves, sound waves, electromagnetic waves, or combinations thereof, generated by mechanical devices such as cannons or pressurized gas supply systems, electromechanical devices, microwaves and/or electromagnetic waves, or other pulse wave generators. Thus, scoring may also be applied to the mold to assist in breaking and removal of the mold from the casting.

The method and system for removing the molds and/or cores from the castings can be used as part of an overall casting process in which the castings are cast and after the castings have cooled sufficiently to solidify at least a portion of the outer surfaces of the castings, the molds are removed prior to or in conjunction with an initial step of a solid solution heat treatment of the castings, and then the removed portions of the molds and cores are collected and subjected to a reclamation process while the castings are heat treated. Alternatively, the molds and cores can be fractured and removed from the castings, the castings can then be transferred to a quench tank where the water soluble cores of the castings can be fractured and removed, and/or the castings can then be aged as desired. Typically, the pulse wave or force used to dislodge and/or break up the mold sections and to initiate the breakdown of the sand cores in the castings will be applied in a chamber or along a transfer path from the casting station to a heat treatment, quenching or aging line.

Applicator means (e.g., pressure nozzles, acoustic or electromechanical vibration wave generators, or similar pulse generating means) are located at spaced apart locations or stations and are oriented to align with appropriate points around the mold, e.g., against or with scores or joints in the mold. The mold is typically conveyed to a known marking location for directing a pulse wave (e.g., high pressure fluid stream, vibration wave, microwave, or other mechanically, electromechanically, or electrically applied force) at a suitable point or location, such as along a score formed in the mold, or at a joint between mold portions, to cause the mold to separate and break apart into several pieces for more efficient and rapid removal of the mold. When the mold is broken by application of the pulse wave, the portions or pieces of the mold are free to fall off the casting for collection and recovery. Thus, various transport or transfer methods or systems may be used with the present invention, including rotary conveyors such as turntables, linear conveyors (including horizontally and vertically oriented conveyor systems), screw conveyors, indexing saddles, or similar mechanisms.

In another embodiment, the castings can be moved between indexed positions for applying pulse waves or forces at appropriate locations by a robotic transfer mechanism that can also be used to assist in breaking up and removing the sand mold sections, such as by physically engaging and removing the mold sections. Alternatively, the casting and mold may be held in a substantially fixed position and a pulse wave generator or other force applicator may be moved about to the appropriate orientation.

Various objects, features and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following specification in conjunction with the accompanying drawings.

Drawings

In the drawings, there is shown in the drawings,

FIGS. 1A-1B are cross-sectional views of a sand mold illustrating the formation of a score in place and the formation of a crack along the score by the mold;

FIGS. 2A-2B are cross-sectional views of a sand mold and casting illustrating the use of score lines and explosives disposed within the sand mold and the cracking and movement of the mold by the initiation of the explosives;

FIG. 3 shows a cross-sectional view of a mold through an energy pulse chamber in or near a treatment furnace, showing mold fillers and castings being treated by high energy pulses;

4A-4B illustrate movement of the mould tools through an oxygen-enriched chamber for providing a flow of oxygen to promote combustion of the organic or thermally degradable adhesive of the mould tools;

FIGS. 5A-5C illustrate the application of a pulse wave to a mold to break the mold;

6A-6B illustrate an embodiment of a chamber or cell for applying a pulse wave to a mold;

FIG. 7 is a schematic illustration of the use of the present invention as part of the overall casting process; and

Detailed Description

The present invention generally comprises a method for promoting the breakdown and removal of molds and sand cores from castings formed therein to accelerate the exposure of the castings to heat treatment temperatures and to promote the breakdown and reclamation of sand from the sand molds and cores. The mold may be removed from around its castings prior to introduction of the sand molds and castings into a heat treatment furnace or unit, or in a heat treatment furnace or unit that itself is used for heat treatment and sand reclamation within the unit. Moreover, the system and method of the present invention for promoting mold breakdown and removal from castings can be part of an overall or continuous metal casting and/or heat treatment. The present invention may also be used as a separate or stand-alone process for removing molds from "hot" (freshly cast and fully solidified) and/or "cold" castings, depending on the application. In use, the method of the present invention will generally be carried out while the molten metal of the casting is at least partially solidified along the outer surface of the casting to avoid deformation of the casting.

Examples of heat treatment furnace systems for heat treating castings and at least partially fracturing and removing sand molds and sand cores and recovering sand are described in U.S. patent nos. 5294994, 5565046, 5738162 and 5957188 and U.S. patent application nos. 09/313111 (7/27/2000) and 10/066383 (1/31/2002), the contents of which are incorporated herein by reference. By promoting the breakdown and removal of the molds from their castings, the castings are more quickly exposed to the ambient heating environment of the heat treatment furnace or chamber. Thus, less energy and time is required to raise the temperature of the casting when the mold is removed from the casting in order to obtain proper handling and to impart the proper metal properties to the casting.

Metal casting processes are generally known to those skilled in the art and ordinary casting processes will be described only briefly for reference. It will be appreciated by those skilled in the art that the present invention may be used in any type of casting process, including metal casting processes for forming castings of aluminum, iron, steel, and/or other types of metals and metal alloys. Thus, the present invention is not limited to use with only a particular casting process or a particular type of metal or metal alloy.

As shown in fig. 1A-1B, a molten metal or metal alloy is poured into a mold or die 10 at a casting or casting station to form a casting 11, such as a cylinder head or engine block or the like. Typically, cores 12 formed of sand and an organic binder (e.g., phenolic resin) are packed or disposed within the molds 10 to create hollow cavities and/or cast parts or core prints in the castings formed within each mold. The molds typically comprise "precision sand mold" type molds and/or "green sand molds" that are typically formed from a sand material (e.g., silica sand or zircon sand) mixed with a binder (e.g., phenolic resin or other binders known in the art), similar to the sand casting core 12. The molds may also include no-bake cold and hot box type sand molds and semi-permanent sand molds, which typically have exterior mold walls formed of sand and binder, metal such as steel, or a combination of both materials. Also, a locking core type of mold may be used, wherein the mold is formed as interlocking parts or sections that are locked together by a sand core. It should be noted that the term "mould" described later is generally used to refer to all the above types of moulds.

Methods of dislodging the mold from the casting include "scoring" the sand mold and thereby forming fault lines, notches or weakened areas in the sand mold. When the binder material is burned, the mold typically fractures and breaks along score lines provided in the mold to facilitate dislodging and removal of the mold from the casting contained therein. The scores are typically arranged at predetermined locations along or around the sides and/or top and bottom of each mold, with these locations typically being selected to optimize the destruction of the molds. The placement of the score line at the predetermined location depends on the shape of the mold and the casting formed within the mold.

The term "score" can include any type of cut, line, score, indentation, groove, or other such indicia formed in the top, bottom, and/or side walls of the mold by any mechanism, including cutters, milling devices, and other similar automatic and/or manually operated cutting or grooving devices, etc. The scoring is typically performed on the exterior of the mold, but is not limited to the exterior surface of the mold, and it should be understood that the interior surface of the mold may be scored or grooved in addition to scoring the exterior surface. The individual molds may be scored by any conventional means, such as by placing or forming molded or scored lines on the exterior and/or interior surfaces of the molds during formation of the molds, or at some later time (until the molds with the castings therein are introduced into a heat treatment furnace).

Force may also be applied to the mold to cause the mold to crack and break into pieces which can then be easily removed or released from the casting. The force may be applied to the inner wall of the mold, to the outer wall of the mold, or a combination of both. The forces exerted on the inner walls of the mold are generally generated by thermal expansion of the casting in the mold, and heating the casting by radiant energy, inductive energy, or a combination thereof will further enhance or accelerate the expansion of the casting. The energy source used to heat the casting may include electromagnetic energy, lasers, radio waves, microwaves, and combinations thereof.

The energy source for heating the mold and/or casting may also include lasers, radio waves, microwaves, or other forms of electromagnetic energy and/or combinations thereof. Typically, these and other energy sources are radiated toward the exterior or directed at specific areas of the mold or casting for heating the mold and casting to cause thermal expansion, resulting in cracking or breaking of the mold and/or sand core. Alternatively, the induction energy generally involves enclosing the casting and mold in an electromagnetic energy field that induces a current in the casting, thereby heating the metal and lowering the temperature of the mold. Typically, the mold is insulated and not electrically conductive, and induction energy may have limited effect to heat directly within the mold, but does not affect the heat generated within the casting. Of course, there may be other ways to heat and expand the casting to break the mold. Additionally, scores may be added to the mold or to the mold itself to assist in removing the mold from the casting.

The energy pulse may also be applied in a specially designed process chamber, such as a furnace. Design features may include the ability to withstand the pulsations and resulting effects for feeding the mold/casting into and out of the chamber for precise control of the pulsations. The energy pulsations generally enhance heat transfer to the mold core and the casting to some extent. The pulsing also enhances mass transport of the decomposed binder gas out of the mold and core, oxygen-bearing process gas to the mold and core, and loose sand out of the casting. The pulsing may be at a lower or higher frequency, with lower frequency pulsing typically being used to generate forces that fracture the mold or core and higher frequencies being used to enhance delivery, mass delivery, and cracking on smaller scores. The higher frequency pulsations cause vibration effects in the casting to a certain extent, thereby enhancing the mechanical effects of the above-mentioned treatment.

Further, the molds and/or cores may be broken by applying any or all of these energy sources to the molds and/or cores so as to enhance the decomposition of the organic or thermochemical binder of the sand molds and/or cores, which binder decomposes when heated, thereby facilitating the cracking of the molds. Additionally, the mold may be broken by applying a high pressure fluid, such as air, combustion products, oxygen-enriched gas, or other fluid material, to the outer wall of the mold.

Further, the mold, core or casting may be directly subjected to forces in the form of pulses or waves of vibration, pressurized fluid, sonic or other mechanical, electromechanical or electromagnetic pulses, or combinations thereof, to help break and fracture the mold into pieces. In one embodiment, the mold and/or core is excited by a high energy pulse for directly applying a force, which high energy pulse may also penetrate the walls of the mold, causing the mold to heat up to further assist in the binder burning of the mold and breaking the mold. The pulsating energy may be a constantly repeating or intermittent force or pulse and may be a vibrational wave, a pressure wave, a sonic wave, or any combination thereof generated by mechanical, electromechanical, electrical, and/or other known means such as a compression gun or pressurized gas. Hereinafter, the application of such energy pulses or forces will be collectively referred to as "pulse waves," and it is to be understood that this term will cover the application of such energy pulses and other known mechanical, electrical and electromechanical forces. Alternatively, a low explosive charge or an organic or thermally degradable material may be disposed in the mold and detonated or initiated by heating the mold to assist in breaking up and dislodging the mold from around its casting.

More specifically, the present invention contemplates several alternative embodiments and/or methods for performing the function of dislodging or fracturing sand molds prior to or during heat treatment of the castings. It should also be appreciated that any of the methods described may be used in combination with each other or alone. These methods are shown in fig. 1A to 6B.

In a first embodiment of the invention shown in fig. 1A and 1B, a sand mold 10 having a casting 11 therein is shown having at least one (and typically a plurality of) score lines 13 or relief lines formed in the exterior side walls 14A of the mold 10. Score/relief line 13 is typically cut or otherwise formed as a groove or recess in the outer sidewall of the mold and serves as a break line for the outer wall of the mold fill. Score/relief lines 13A may also be cut or formed in the inner wall 14B of the mold 10 (as shown in fig. 1A) and/or in the top and bottom walls 16 and 17 of the mold 10.

As also shown in fig. 1B, these score/release lines weaken the mold walls to predetermine the location and position of cracks or splits in the mold 10, such that when a force F is applied to the walls of the mold, cracks and splits in the walls of the mold along these score/release lines are caused, as indicated at 18 in fig. 1B. Generally, the force F comprises the pressure exerted by the casting itself against the inner walls 14 of the mold 10 due to thermal expansion of the metal of the casting as the casting is heated or elevated in temperature for heat treatment of the casting. As the metal of the casting expands in response to the heat in the heat treatment furnace, it presses and pushes outwardly against the walls of the mold, causing the mold to crack and break apart at the weakened points created by the score/relief lines. Portions of the mold will be easily removed from the mold and its casting prior to or during the initial stages of heat treatment of the casting, rather than simply cracking and slowly degrading the mold because its binder material is burned for a period of time in the heat treatment furnace.

Fig. 2A-2B illustrate an alternative embodiment of the invention for fracturing and removing the mold 20 from the casting 21 formed therein. In this alternative method, low impact explosive 22 is installed at one or more points in the sidewall 23 of the mold charge 20. The explosive charge is typically located at a strategic location within the mold filler structure, typically near a strategic junction 24 within the wall, such as between the side wall 23 and the top and bottom walls 26 and 27, to facilitate removal of the mold from the casting while still maintaining the integrity of the casting. In addition, as shown in fig. 2B, after the low intensity explosive is exploded, a gap or channel 28 is formed in the mold filling 20 and extends deeper through the side walls and upper and lower portions of the mold. The mold is thus substantially weakened at or along these channels or gaps, and as a result, the mold will readily break up into portions or pieces along these channels 28 in response to thermal expansion of the casting, and/or along these channels 28 as the binder material of the mold burns to facilitate removal of the mold from its casting.

Fig. 3 illustrates yet another embodiment of the present invention for breaking apart the mold 30 and facilitating removal of the mold 30 from the casting. In this embodiment of the invention, the vibratory forces that cause the mold/core to crack are applied to the mold by high energy pulses or waves 32 directed at the mold 30 as the mold 30 passes through a treatment chamber 33, with the treatment chamber 33 typically being located at the front or input end of the heat treatment furnace so that the mold and the casting generally pass through the treatment chamber before the casting is heat treated. The high energy pulses are typically of variable frequency or wavelength and are directed generally from one or more pulsing or wave generators 37 mounted in the chamber to the side walls 34 and/or upper or top wall 36 of the mold. The high energy pulsations or waves generated are typically in the form of vibrational, pressure or acoustic waves propagating through the air of the process chamber. Alternatively, the electromagnetic energy may be pulses emitted at the walls of the mold to promote the formation of cracks, heat sinks, binder degradation, or other treatment effects for dislodging the mold and sand core from the casting. Such electromagnetic radiation may be in the form of laser light, radio waves, microwaves, or in other forms that create the above-described treatment effects.

High energy pulses directed at the molds excite the molds and cause them to vibrate without requiring physical contact with the mold filling. The excitation and vibration of the die will cause the die to crack and break apart as the pulse passes through the die. The pulses may be continuous pulses or discrete pulses. The discrete pulses may be controlled at regular intervals. The pulses, controlled in either a continuous or discrete form, will be carefully controlled in terms of frequency, application interval and intensity to achieve a treatment effect without damaging the casting. In addition, the mold may also be scored or pre-stressed/weakened at selected points (as shown at 38 in FIG. 3) as described above to facilitate or encourage the mold to break apart when vibrated or otherwise impacted by a high energy pulse.

Thus, as the castings enter the heating chamber of the heat treatment furnace or are otherwise processed, the molds break and are removed from their castings. Furthermore, as described in U.S. patent application Nos. 09/627109 (7/27/2000) and 10/066383 (1/31/2002), the entire contents of which are incorporated herein by reference, the energy pulse also typically causes the casting within the mold to heat, which further causes thermal expansion of the casting to apply a force to the inner sidewalls of the mold to further facilitate and encourage mold breakdown.

Fig. 4A-4B illustrate an alternative embodiment of the invention for heating and causing the mold 40 and possibly the sand core 41 to be broken and removed from the casting 42 contained within the mold. In this embodiment, the molds 40 and their castings 42 pass through a low velocity oxygen chamber 44 before or during their entry into a heat treatment furnace or chamber 43. The oxygen chamber is typically an elongated autoclave or similar pressurized heating chamber capable of operating at above ambient pressure. The oxygen chamber 44 provides an oxygen rich environment and includes a high pressure upstream side 46 and a low pressure downstream side 47 positioned opposite one another to assist in drawing a flow of oxygen therebetween.

As the mold passes through the low velocity oxygen chamber of the heating chamber 44, heated oxygen is directed toward the mold and forced through the mold as indicated by arrows 48 (fig. 4A) and 49 (fig. 4B). Oxygen is drawn or flowed under pressure from the high pressure side of the oxygen chamber to the low pressure side, thereby pushing or forcing oxygen into and possibly through the mold and/or core. Thus, a percentage of the oxygen combusts with the binder material of the sand mold/core to enhance combustion of the binder material in the heating chamber. This enhanced combustion of the binder materials of the molds and cores further provides energy from the enhanced combustion of the binder materials and oxygen, which helps to promote and/or accelerate the breakdown and removal of the molds from their castings. The mold breakage can be further assisted by scoring or forming relief lines in the mold (as described in more detail above) to pre-stress/weaken the mold. Thus, when the binder material burns, the mold walls will crack or split, causing the mold to break into multiple parts or pieces and fall out of their castings.

In addition, the enhanced combustion of the binder material can be used as an additional, usually conductive, heat source to increase the temperature of the castings in the molds and facilitate combustion of the binder material of the sand cores for easy removal and reclamation. As a result, the castings are more rapidly raised to their heat treatment temperature, which helps to reduce the residence time of the castings in the heat treatment furnace required to rapidly and completely heat treat the castings, as described in co-pending U.S. patent application Nos. 09/627109 (7/27/2000) and 10/066383 (1/31/2002), the contents of which are incorporated herein by reference.

Fig. 5A-5B illustrate yet another embodiment of the invention for promoting the breakdown and removal of sand molds 50 from castings 51 formed or contained within the molds, and (possibly) the breakdown and removal of sand cores located within the castings 51. In this embodiment, a series of pulse wave generators or force applicators 52 (e.g., air cannons, fluid nozzles, sonic wave generators or other mechanical and/or electromechanical mechanisms) are positioned at specific locations or positions (as part of the heat treatment furnace, such as in the initial prechamber of the furnace, or in a mold breakdown or treatment chamber 54, which is typically located in front of or upstream of the heat treatment furnace) generally along the path (arrows 53 in FIG. 6A) through which the molds/cores loaded with the castings travel into the heat treatment furnace, in order to assist in dislodging the sand cores from the castings. The force or pulse wave will be applied after the outer surface of the casting contained within the mold has solidified to a degree sufficient to prevent or avoid deformation or damage to the outer surface of the casting due to the application of the force or pulse wave.

The number of pulse generators or force applicators 52 (hereinafter "applicators") may be varied as desired depending on the design of the core print or the casting being formed in the mold, so that different types of castings having different core prints may be selectively used with different configurations or numbers of applicators within the chamber. As shown in fig. 5A, each applicator 52 is generally mounted in the interior 56 (fig. 6A) of the processing chamber 54, oriented in a known or aligned position relative to the side walls 57 (fig. 5A-5B), top wall 58 and/or bottom wall 59 of the mold 50, corresponding to the known indexed position of the cores and castings. For example, the applicators 52 may be mounted at spaced locations along the length of the chamber 54 (FIG. 6A) or along the path of travel of the molds and castings, such that the molds will enter different applicators directed at the same or different core openings, joints or scores formed in the molds at different points along their path of travel. As the mold moves along the cavity 54, the applicator applies a force against the joint or score of the mold to physically crack and/or fracture the mold.

The applicators may also be automatically controlled by a control system for the heat treatment station or furnace which can be remotely operated to move the nozzles to different suitable positions around the side walls 57 and top and bottom walls 58 and 59 of the mold as shown by arrows 61 and 61 'and 62' in fig. 5B. Alternatively, as shown in FIG. 5C, the molds 50 may be physically manipulated or conveyed through the processing chamber by a conveyor 65 (FIG. 5C), such as a robotic arm 66 or overhead hoist or conveyor or other similar conveyance mechanism, wherein the castings are physically engaged with the conveyance mechanism, which may also be used to rotate the molds having the castings therein, as indicated by arrows 67 and 67 'and 68'. Thus, the molds can be reoriented relative to one or more applicators 52 to rotate or otherwise realign the known index positions so that the scores formed in the molds or joints formed between portions or blocks of the molds are aligned with the applicators 52 for the directional application of force or pulse waves to facilitate breaking apart and removal of the molds from their castings. Moreover, the robotic arm or other transfer mechanism can also be used to apply mechanical force directly to the mold, including picking or pulling the mold sections away from the casting. Such mechanical application of force to the mold can also be combined with the application of other forces or heating of the sand molds to more rapidly crack and remove the sand molds from their castings.

Fig. 6A and 6B illustrate an embodiment of the mold breakdown or processing chamber 54 of the present invention for rapidly breaking sand molds into significantly larger pieces or sections and removing them to facilitate more rapid removal of the molds from their castings. In this embodiment, applicator 52 is represented as a cannon 70 or fluid applicator that directs a stream or pulse of high pressure fluid medium through a series of directional nozzles or applicators 71. Each nozzle 71 is typically supplied with a high pressure heated fluid medium such as air, hot oil, water or other known fluid material from a storage unit such as a pressurized storage tank 72, pump or compressor connected to the nozzle or applicator 71. As shown in fig. 6B, nozzles 71 direct pressurized fluid streams toward the side, top and/or bottom walls of each mold/core, as indicated by arrows 73.

These pressurized fluid streams are converted to high fluid velocities at the outlet opening of the nozzle, which increases the energy of the fluid stream applied to the die/core in order to apply a force sufficient to at least partially crack and/or otherwise crack the die and/or core. Moreover, such high fluid velocities typically cause or promote higher heat transfer to the casting, mold, and core, which is more conducive to breaking the mold and sand core. The pressurized fluid streams controlled by the nozzles can be applied in a continuous or intermittent stream or pulse wave manner that impacts or contacts the mold walls to fracture or crack the mold walls and to promote more rapid decomposition and/or combustion of the binder material of the mold (and possibly the sand core) to assist in at least partial cracking or breaking of the mold. These fluid streams are applied at high pressure, in the range of about 5psi to about 200psi for a pulse of compressed air; for fuel-fired gas and air mixing pulses, in the range of about 0.5psi to about 5000 psi; for mechanically generated gas pulses, in the range of about 0.1psi to about 100 psi; but greater or lesser pressures may be used as desired for a particular casting application. For intermittent pulses, the pulses will typically be applied at a rate of about 1-2 pulses per second to 1 pulse per minute. In addition, the pressurized fluid stream may be directed at scores or joints formed in the mold in order to fracture the mold.

For example, when using a processing chamber as shown in fig. 6A and 6B, a series of molds will typically be indexed through chamber 54 at intervals of about 1 to 2 minutes, through about 5 locations or stations on the line, with the molds being processed at each location for about 1 to 2 minutes, although greater or lesser residence times may be used. These in-line stations or locations may typically include loading, top removal, side removal, end removal (and possibly bottom removal), and unloading stations, with the top, side, and end (and possibly bottom) removal stations typically being located inside a process chamber sealed within a jet door at each end. Fewer or more stations or locations with different applicators may also be provided as desired.

As shown in fig. 6A, the chamber will typically include up to 6 pulse generators, although a fewer or greater number of pulse generators may be used. The pulse generator will provide a high pressure air stream or air directed at the appropriate mold joint and/or score (when present) formed in the mold. Typically, each pulse generator will provide about 30 to 40 cubic feet of air/gas at about 70 to 100psig per charge or pulse of compressed air, which pulses will typically be provided at about 1 minute firing intervals (although larger or smaller firing intervals may also be used) to provide about 200 to 250cfm of air (up to about 300cfm or more of gas-air mixture) to the mold joints and/or scores.

Typically, a screw type or scroll compressor may be used to substantially continuously supply air directly to the pressurized reservoir of the pulse generator. For example, a 50 to 100 horsepower (hp) compressor may be used to supply a sufficient amount of compressed air to treat approximately 50-100 molds per hour. For gas-air energized pulses/flows, the power required is typically in the range of about 2-75 horsepower. Furthermore, the nozzle of the pulse generator may be externally adjusted by making the generator mount perform at least two-dimensional movements, while the nozzle or applicator of the pulse generator is usually pre-set to accommodate a suitable or specific mold filling. Furthermore, although the pulse generator is shown mounted at the top of the process chamber in fig. 6A, it is also contemplated that other types of pulse generators may be used in addition to the compressed air generator or applicator, and that the pulse generator can be positioned along the sides and/or near the bottom or ends of the process chamber.

The mold will typically be indexed by position on the line, for example at a nominal indexing speed of about 30 to 40 feet per minute, although different indexing speeds are contemplated depending on the size and configuration of the sand molds. The commanded motion and pulse firing of the pulser will typically be controlled according to a safety interlock by a computer control system, such as a PLC control or a relay logic type control system. When the mold breaks, the pieces or portions of the mold will typically fall into a collection chute located below the chamber that directs the collected pieces toward a feed conveyor for removal of the pieces. The recovered mould fragments can then be ground for recovery or passed through a magnetic separation device to first remove condensed metal (hill) or the like therefrom and then the sand mould can be passed through for recovery for later re-use. In addition, excess gas or flue gas may be collected and exhausted from the process chamber and sand conveyor.

As shown in fig. 6A and 6B, the present invention may utilize a variety of different types of transport mechanisms to bring the sand mold with the castings therein into a known, suitable or desired indexing position for applying a pulse wave or other directed force to the sand mold, such as along score lines or joint lines between mold sections. Such a transfer mechanism includes an indicating conveyor or chain conveyor 80, as shown in fig. 6A, and may include: a locator pin or other similar device for fixing the position of the mold on the conveyor; indicating saddles are described, for example, in U.S. patent application nos. 09/627109 (filed on 7/27/2000) and 10/066383 (filed on 1/31/2002); an elevator or a gantry conveyor; a robotic transfer arm or similar mechanism; and a screw conveyor 90, wherein the molds are encased in flights or portions 91 of the conveyor, as shown in fig. 6B. The chamber may be oriented horizontally or vertically, as desired.

Also, in all embodiments of the invention, the applicator and transfer mechanism are typically positioned or mounted within the chamber in such a manner that they do not interfere with the pieces being removed from the castings, so that the pieces exiting the castings fall under the force of gravity without interference. Alternatively, a conveyor or other mechanical system or mechanism (e.g., a robotic arm) can physically remove and transport the mold blocks or sections from the castings and accumulate them at a collection point, such as a bin or transport conveyor.

The method of the present invention is generally used to fracture and facilitate removal of sand molds from metal castings and is used as part of, or as a step in, an overall continuous casting process in which metal castings are formed from molten metal and heat treated, quenched and/or aged, or otherwise treated, as shown in fig. 7. As shown in fig. 7, a casting 100 is to be formed at a casting or casting station 102 from molten metal M cast into a mold 101. Typically, the mold 101 will form multiple sections along joint line 103, and may also include scores or notches (indicated at 104) formed in the exterior wall portions of the mold.

After casting, the mold with the casting contained therein will typically be transferred or conveyed to a mold breakdown or processing chamber (indicated at 106). In the mold fracturing or processing chamber 106, a force or pulse wave (as described with reference to fig. 5A-6B), a high or low energy pulse (fig. 3), and/or an oxygen-rich gas stream (fig. 4A-4B) is typically applied to the mold to enhance and promote rapid fracturing or breaking apart of the sand molds into fragments or portions 108 and to dislodge the sand mold fragments or portions 108 from the castings. Generally, the sand mold sections 108 broken up and removed in the mold break up or processing chamber 106 can fall down through a collection chute onto a transport conveyor 109 or into a collection bin for transporting or carrying away the recovered pieces and/or removing the condensed metal.

As shown in fig. 7, the castings, along with the molds that have been substantially removed therefrom, are then typically introduced directly into a heat treatment unit (indicated at 110) for heat treatment, and the heat treatment unit is capable of accomplishing any additional mold and sand core cracking and/or sand recovery in addition to the solid solution heat treatment, such as described in U.S. patent nos. 5294994, 5565046, 5738162, 5957188 and 6217317 and in co-pending U.S. patent application No.10/066383 (filed 2002, 7-31), the contents of which are incorporated herein in their entirety. After heat treatment, the castings generally enter a quench station 111 for quenching and can then be passed or conveyed to an aging station (indicated at 112) for aging or further processing of the castings as desired.

Alternatively, as shown by the dashed lines 113 in FIG. 7, after the molds are broken and removed from their castings, the castings can be conveyed directly to the quenching station 111 without heat treatment. The disintegration and removal of the core may be accomplished in a quench station, i.e., by immersing the water-soluble core of the casting in water or other fluid, or spraying the water or other fluid to further fracture and remove the water-soluble core from the casting. As yet another alternative, as indicated by the dashed line 114, the casting may be placed from the mold break chamber 106 directly into the aging station 112 for aging, or other processing of the casting as desired.

Further, as shown in FIG. 7, after the molds have fractured and removed from their castings, the castings can be conveyed as indicated by dashed line 116 to a condensed metal removal/cutting station 117 prior to heat treatment, quenching and/or aging of the castings. In the condensed metal removal/cutting station 117, any condensed metal or other release-forming material will typically be removed from the castings for cleaning and reuse. The casting may be further subjected to a sawing or cutting operation in which risers or other unwanted portions formed in the casting are cut from the casting and/or a degating operation. The removal of the risers or other unwanted metals or portions of the castings will help facilitate quenching and reduce the amount of metal of the castings that must be treated or quenched, thereby reducing the furnace and/or reducing the quenching time. After removing the condensed metal and/or cutting off the risers or other unwanted portions of the castings, the castings are typically returned to the processing line, such as by introduction into the heat treatment unit 110, as indicated by the dashed line 118, although it will also be appreciated by those skilled in the art that the castings can thereafter be directed to the quenching station 111 or to the aging station 112 for further processing as desired.

Those skilled in the art will appreciate that the present invention, while promoting the breakdown and removal of molds from their castings, also promotes the breakdown and removal of sand cores from the castings. For example, when the castings are heated by high energy pulsations, as shown in FIG. 3, or when the binder combustion of the molds of the castings is promoted by the application of an oxygen-rich gas stream, the sand cores are likewise heated so that their binder material is combusted to cause the sand cores to more rapidly break up for easy removal when the molds or mold blocks are removed from the castings.

Moreover, the applied pulse wave or force may be directed at a core opening formed in the mold so as to be directed at the sand core itself, thereby promoting the breakdown of the sand core for easy removal from the casting. Thus, the present invention can be used with molds of the general locking core type, wherein the core forms a key lock that locks portions or pieces of the mold together around the casting. With the basic principles of the invention, a pulse of energy or application of a pulse wave or force can be directed at the lock core to facilitate fracturing and/or chipping of the lock core, so that by breaking the lock core, the mold portions are more easily pushed or removed from the casting in larger portions or pieces to facilitate rapid removal of the mold from the casting.

It will be appreciated by persons skilled in the art that while the invention has been described above with reference to preferred embodiments, various changes, modifications and additions can be made to the invention as described hereinbefore without departing from the spirit and scope of the invention.

Claims (16)

1. A method of removing a mold from a casting formed therein, comprising:

applying a force sufficient to fracture and break the mold into pieces;

manipulating or transporting the mold with at least one of a robotic arm, overhead hoist, conveyor, or transport mechanism;

the mold blocks are removed from the casting.

2. The method of claim 1, further comprising the step of scoring the mold, wherein: the mold is scored by forming a score in the outer wall of the mold.

3. The method of claim 2, wherein: the score lines are disposed at predetermined locations for breaking and dislodging the mold sections from the casting.

4. The method of claim 1, wherein: the force sufficient to fracture the mold includes thermal expansion of the casting against the mold.

5. The method of claim 4, wherein: to produce thermal expansion, the casting is heated by an energy source selected from the group consisting of: radiant energy, inductive energy, and combinations thereof.

6. The method of claim 5, wherein: the energy source is selected from the group consisting of: electromagnetic energy, laser light, radio waves, microwaves, and combinations thereof.

7. The method of claim 1, wherein: the mould is formed from sand and a degradable binder which burns when the mould is heated under high pressure in an oxygen-rich gas to facilitate the breaking of the mould.

8. The method of claim 1, wherein: the mold blocks are removed from the casting prior to heat treating the casting.

9. The method of claim 1, wherein: the force sufficient to rupture the mold includes directing a high pressure fluid at an outer wall of the mold.

10. A method of removing a mold from a casting formed therein, comprising:

exciting the mold;

manipulating or transporting the mold with at least one of a robotic arm, overhead hoist, conveyor, or transport mechanism;

breaking the mold;

the mold is removed from the casting.

11. The method of claim 10, wherein: the step of exciting the die includes high energy pulsations applied as a vibration wave.

12. The method of claim 10, wherein: the vibration wave is generated by at least one of the group: mechanical devices, cannons, pressurized gas and electromechanical devices, and combinations thereof.

13. The method of claim 10, further comprising: the mold is scored by forming a score in the outer wall of the mold.

14. The method of claim 10, wherein: the mold portions are removed from the casting prior to heat treating the casting.

15. The method of claim 10, further comprising: applying energy to the mold from an energy source selected from the group consisting of: radiant energy, inductive energy, and combinations thereof.

16. The method of claim 10, further comprising: the step of energizing the casting with high energy pulses includes directing high pressure fluid at the outer wall of the mold with a force sufficient to fracture the mold.