WO2023154526A1

WO2023154526A1 - Casting furnace

Info

Publication number: WO2023154526A1
Application number: PCT/US2023/012943
Authority: WO
Inventors: Mike TOMASSI; Tomas MAZALEK; Robert POKLADNIK
Original assignee: Pyrotek, Inc.
Priority date: 2022-02-14
Filing date: 2023-02-13
Publication date: 2023-08-17

Abstract

A casting furnace for low pressure casting comprises a furnace chamber, an insert disposed within the furnace chamber, a valve in the insert, a riser to expose a much lower surface of a melt to compressed gas, and a channel for supplying and/or discharging gas into and out of the insert.

Description

CASTING FURNACE

[0001] The present application claims priority to US Provisional Application No.

63/309,959, filed February 14, 2002, the disclosure of which is herein incorporated by reference.

BACKGROUND

[0002] The present exemplary embodiment relates to a casting furnace for low pressure casting. Low-pressure casting is a frequently used process for the production of castings, from light metals such as aluminum or magnesium. During the casting process a furnace chamber is pressurized to lift a melt through a riser into a mold. The present disclosure is directed to a pressurized insert for immersion in a casting furnace.

[0003] The low pressure casting is a frequently used procedure for the production of cast parts, in particular from light alloys such as aluminum or magnesium. Usually for this procedure pressure tight furnace containers with or without crucibles are used. During the casting procedure the entire furnace body is pressurized, in order to let the melt ascend by a tubing into the mold.

[0004] EP 0,609,196 A1 , herein incorporated by reference, discloses a casting furnace with which the melt from a storage vessel is led over an air-lock into a withdrawal chamber. EP 1 ,894,648 A1 , herein incorporated by reference, discloses a casting furnace including a dipping cylinder and rams. The melt can be pressed by the ram actively into a riser.

[0005] The casting furnaces from the state of the art have the disadvantage that high flow rates of a compressed gas are necessary. Compressing and drying of the compressed gas is very energy complex. In addition, the quality of the melt worsens by oxidation processes at the surface of the melt. This has the consequence that the melt must be treated during the casting process and an increased cyclic cleaning need results from the deposit of oxides. [0006] DE 10206123595, herein incorporated by reference, addresses some of these problems by employing a casting furnace with a furnace tub. A housing is arranged within the furnace tub so that a part of the housing is within a melt contained in the enterprise of the casting furnace. The housing includes a first valve for controlling flow of a melt from the furnace tub into the chamber, a tube for supplying melt from the chamber into a mold, and a channel to drive off from gas. By employing a housing in the furnace tub only a small part of the entire melt is pressurized and moved and smaller quantities of dried compressed gas are required. A further favorable effect consists of the fact that in the housing a substantially smaller surface of the melt is exposed to the compressed gas. Accordingly, oxidation and accompanying impurities are decreased. This leads too reduced cleaning cycles and an improved charging rate.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The following is a brief description of the drawings, which are presented for the purposes of illustrating the exemplary embodiments disclosed herein and not for the purposes of limiting the same.

[0008] Fig. 1 A is a perspective view of an exemplary embodiment of the casting furnace according to the present disclosure;

[0009] Fig. 1 B is an end view thereof;

[0010] Fig. 1C is a cross-section view thereof;

[0011] Fig. 2 is a cross-section view of an exemplary embodiment of the casting furnace;

[0012] Fig. 3A is an exemplary embodiment of an insert of the casting furnace;

[0013] Fig. 3B is a cross-section view thereof;

[0014] Fig. 3C is a detail cross-section view of the lower most intersection of a sidewall and a bottom wall thereof;

[0015] Fig. 3D is a detail cross-section view of the intersection of the insert rim and a cup-shaped body;

[0016] Fig. 4A is an exemplary embodiment of an alternative insert;

[0017] Fig. 4B is a cross-section view thereof; [0018] Fig. 4C is a detail cross-section view thereof;

[0019] Fig. 5A is an exemplary valve assembly embodiment of the casting furnace;

[0020] Fig. 5B is a bottom view thereof;

[0021] Fig. 5C is a cross-section view thereof;

[0022] Fig. 6 is a cross-section of a riser tube according to the present disclosure;

[0023] Fig. 7 is a top view of an embodiment of an insert lid; and

[0024] Fig. 8 is a perspective view from a bottom end of the insert.

BRIEF DESCRIPTION

[0025] Various details of the present disclosure are hereinafter summarized to provide a basic understanding. This summary is not an extensive overview of the disclosure and is neither intended to identify certain elements of the disclosure, nor to delineate scope thereof. Rather, the primary purpose of this summary is to present some concepts of the disclosure in a simplified form prior to the more detailed description that is presented hereinafter.

[0026] According to a first embodiment, a casting furnace for low pressure casting is provided. The furnace includes a furnace chamber and an insert for receiving a melt. The insert is at least partially disposed within the furnace chamber such that a portion of the insert is in contact with the melt. The insert has a first valve for controlling a flow of the melt from the furnace into the insert, a riser for feeding melt from the insert into a mold, and a passage for supplying and/or discharging gas into and out of the chamber. The valve has an elongated body defining a melt passage and a post disposed in the melt passage. The post includes a top end wider than the melt passage and a bottom end wider than the passage.

[0027] According to another embodiment, a casting furnace for low pressure casting is provided. The furnace includes a furnace chamber and an insert for receiving a melt. The insert is at least partially disposed within the furnace chamber such that a portion of the insert is in contact with the melt. The insert includes a valve for controlling a flow of melt from the furnace into the chamber, a riser for feeding melt from the insert into a mold, and a channel for supplying and discharging gas into and out of the insert. The insert includes a rim extending from a cup-shaped body. The lower most intersection between the rim and cup-shaped body is a curved surface and a bottom wall of the cup-shaped body includes a curved surface at the intersection of a side-wall of the cup-shaped body and the bottom wall.

DETAILED DESCRIPTION

[0028] A more complete understanding of the components, processes and apparatuses disclosed herein can be obtained by reference to the accompanying drawings. These figures are merely schematic representations based on convenience and the ease of demonstrating the present disclosure, and are, therefore, not intended to indicate relative size and dimensions of the devices or components thereof and/or to define or limit the scope of the exemplary embodiments.

[0029] Although specific terms are used in the following description for the sake of clarity, these terms are intended to refer only to the particular structure of the embodiments selected for illustration in the drawings, and are not intended to define or limit the scope of the disclosure. In the drawings and the following description below, it is to be understood that like numeric designations refer to components of like function.

[0030] The singular forms "a," "an," and "the" include plural referents unless the context clearly dictates otherwise.

[0031] As used herein, the terms about, generally and substantially are intended to encompass structural or numerical modifications which do not significantly affect the purpose of the element or number modified by such term.

[0032] As used in the specification and in the claims, the term "comprising" may include the embodiments "consisting of' and "consisting essentially of." The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that require the presence of the named ingredients/steps and permit the presence of other ingredients/steps. However, such description should be construed as also describing compositions or processes as "consisting of' and "consisting essentially of the enumerated ingredients/steps, which allows the presence of only the named ingredients/steps, along with any impurities that might result therefrom, and excludes other ingredients/steps.

[0033] Referring now to Figs. 1A-1C and 2, casting furnace 10 is provided. Casting furnace 10 includes a furnace chamber 11 and an insert 12. A melt 13 is disposed within the furnace chamber 11 . The insert 12 includes a valve 14 disposed in an opening 18 of the insert 12 for controlling a flow of melt from the furnace chamber into the insert. A riser 15 feeds melt from the insert into a mold (not shown). Passage 16 is provided for supplying and/or discharging gas into and out of the insert. The insert can be formed of a heat-conducting material such as graphite or ceramic.

[0034] The insert 12 includes a pressure-tight lockable insulated lid 17. The upper end of the riser 15 extends through the lid 17. Probes 23 extend through the lid to determine the height and temperature of the melt.

[0035] In operation, the insert is immersed in the melt. The insert fills with melt through the valve. To cast, the insert is pressurized by introducing a gas. The gas presses on the melt and shoots the melt through the riser into a mold. As long as an overpressure in the insert exists, the valve locks and prevents melt from backflowing into the furnace. The outflow of melt ends when the insert melt level reaches a desired level. This can be determined by the probes and the influx of gas stopped. The inflow can also be stopped if a defined volume of melt has flowed into the mold through the riser. All of these actions can be managed by a controller in communication with the gas introduction device and the probes.

[0036] Stopping the inflow of gas can cause the valve to open and the insert to refill with melt. If desired, to quickly refill the insert chamber, a vacuum can be applied through passage 16. When the vacuum is applied, the valve opens and allows for the flow of melt from the furnace chamber. A desired level can be determined by the probes and the vacuum halted. Again, these steps of the process can be managed by the controller.

[0037] With reference to Figs. 3A-3D, the insert 12 includes a rim 31 extending from a sidewall 32 of cup-shaped body 33. The lower most intersection between the rim 31 and the sidewall 32 is a curved surface 35. In addition, a bottom wall 37 of the cupshaped body 12 includes a curved surface 39 at the intersection of the sidewall 32 and the bottom wall 37. [0038] As used herein, the curved surface in certain embodiments can encompass a change between the adjacent surfaces (e.g. sidewall and bottom wall or sidewall and rim) of between 70 and 110 degrees occurring over a distance of at least 5% of a diameter of the bottom wall.

[0039] As illustrated in Figs. 4A-4C, an internal surface 51 of the bottom wall 37 can include a partition wall 53 engaging the bottom wall 37 and extending at each end 55 and 57 from the side wall 32 and surrounding the valve receiving opening 18.

[0040] As illustrated in Figs. 5A-5C, the valve 14 can be comprised an elongated body 71 defining a passage 73 and a post 75 disposed in the passage. The post 75 includes a top end 77 wider than the passage 73 and a bottom end 79 wider than the passage 73. The top end can include a distal edge 81 wider than the elongated body 71. The top end 77 can include a canted surface 83 shaped to mate with an inclined surface 85 in the elongated body 71 defining an outlet to the passage.

[0041] Top end 77 can further include a circumferential ring 87 exposed to the passage 73 to facilitate displacement of the post 75 at the designated time to enable flow of melt therethrough.

[0042] The bottom end 79 can comprise a removeable pin 89 passing through a hole 91 in the post. Pin 89 can be wider than a diameter of passage 73 to limit travel of post 73 when the melt is flowing through the valve 14.

[0043] The elongated body 71 can include a groove 93 configured to receive cement.

[0044] The elongated body 71 can include a conical outer surface with the opening 17 in the bottom wall 37 having a complimentary conical shape.

[0045] In some embodiments, the valve 14 is comprised of a ceramic material.

[0046] In some embodiments, the post is at least 10% longer than the elongated body.

In some embodiments, the top end has a greater molten metal contacting surface area than the bottom end.

[0047] With reference to Fig. 6, the riser 15 can be a cylindrical body including an integral ridge 101 disposed between a first and second end. The ridge can have rounded corners 103 and 105 at an interface with the cylindrical body.

[0048] With reference to Figs. 7 and 8, the casting furnace can include a trough 111 joined to the riser 15. The trough 111 can include an at least substantially cylindrical depending first end 113, an at least substantially cylindrical depending second end 115, and an open top intermediate section 117 extending between the depending first and second ends.

[0049] The casting furnace lid 17 can include a metallic frame including rings 121 and 123 which encompass the rim 31 of insert 12. At least one gasket 127 can be located between the metallic frame 121 and the insert. The rings can be coupled by at least one fastener 131.

[0050] The first ring can include at least one lifting element 133. The lid 17 is removable, for example via a lift mechanism 125, to allow access to the chamber and to the riser. This facilitates cleaning.

[0051] In one embodiment, the insert includes probes 141 , in particular temperature probes, for detecting status of the melt in the chamber. By means of the probes, for example, the temperature of the melt, the viscosity of the melt, the composition of the gas above the bath in the chamber, or the fill level in the chamber can be detected. The probes make it possible to run the casting process in a controlled manner using the controller.

[0052] For example, based on the programming of the controller and the information provided by the probes, the introduction of a casting gas through delivery line 143 and/or drawing of a vacuum via line 145 is performed.

[0053] In one embodiment, the valve is arranged in a bottom of the insert and the bottom of the insert is in the filled state of the cast furnace below a bath level of the melt in the furnace. The valve is thus always below the bath level of the melt in the furnace. This ensures that when a vacuum is applied to the housing, melt will always flow from the furnace pan into the insert.

[0054] In one embodiment, the insert is made of a thermally conductive material, in particular ceramic. There may be a heat transfer between the melt in the furnace and the insert. The insert can be co-heated by the heating elements of the furnace. This reduces the energy consumption.

[0055] In one embodiment, immersion heating elements are arranged in the region of a furnace bottom. The arrangement of the immersion heaters on a bottom of the furnace creates an uneven heat distribution within the melt. This creates a vertical circulation within the melt. The circulation prevents heavier components of the melt settling on the bottom of the furnace trough. The heavier components of the melt are held in suspension and co-processed. The quality of the melt can thus be kept constant high over a longer period.

[0056] Advantageously, the actual casting process requires substantially smaller amounts of melt than are usually kept in a furnace. By using a further housing in the casting furnace only one quantity of melt required for one shot has to be moved. Accordingly, much smaller amounts of preheated, dried compressed gas are necessary and the casting process can run faster. In addition, a much lower surface of the melt is exposed to the compressed gas. As a result, oxidation is reduced.

[0057] Advantageously, the insert can be integrated into existing cast furnaces. Pouring furnaces are therefore retrofittable with the device and can be made more economical.

[0058] The exemplary embodiment has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiment be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.

[0059] To aid the Patent Office and any readers of this application and any resulting patent in interpreting the claims appended hereto, applicants do not intend any of the appended claims or claim elements to invoke 35 U.S.C. 112(f) unless the words “means for” or “step for” are explicitly used in the particular claim.

Claims

CLAIMS:

1. A casting furnace for low pressure casting comprising a furnace chamber and an insert for receiving a melt, said insert at least partially disposed within the furnace chamber such that a portion of the insert is in contact with the melt, the insert including a valve for controlling a flow of melt from the furnace into the insert, a riser for feeding melt from the insert into a mold, and a channel for supplying and/or discharging gas into and out of the insert, wherein the valve is comprised an elongated body defining a passage and a post disposed in said passage, said post including a top end wider than said passage and a bottom end wider than said passage.

2. The casting furnace of claim 1 , wherein the top end includes a distal end wider than the elongated body.

3. The casting furnace according to one of the preceding claims, wherein the top end includes a curved surface shaped to mate with a curved surface defining an entrance to the passage.

4. The casting furnace according to one of the preceding claims, wherein the bottom end comprises a removeable pin passing through a hole in the post.

5. The casting furnace according to one of the preceding claims, wherein the elongated body includes a groove configured to receive cement.

6. The casting furnace according to one of the preceding claims, wherein the valve is comprised of a ceramic material.

7. The casting furnace according to one of the preceding claims, wherein the post is at least 10% longer than the elongated body.

8. The casting furnace according to one of the proceeding claims, wherein the top end has a greater molten metal contacting surface area than the bottom end.

9. The casting furnace according to one of the preceding claims, wherein the elongated body includes a conical outer surface.

10. The casting furnace according to one of the preceding claims, wherein the riser is a cylindrical body including an integral ridge disposed between a first and second end, the ridge having rounded corners at an interface with the cylindrical body.

11. The casting furnace according to any of the proceeding claims including a trough joined to the riser, said trough including a cylindrical depending first end, a cylindrical depending second end, and a open top intermediate section extending between the depending first and second ends.

12. A casting furnace for low pressure casting comprising a furnace chamber and an insert for receiving a melt, said insert is at least partially disposed within the furnace chamber such that a portion of the insert is in contact with the melt, the insert including a valve for controlling a flow of melt from the furnace into the insert, a riser for feeding melt from the chamber into a mold, and a channel for supplying and/or discharging gas into and out of the insert, wherein the insert includes a rim extending from a cup-shaped body, and wherein the lower most intersection between the rim and cup-shaped body is a curved surface, and wherein a bottom wall of the cup-shaped body includes a curved surface at an intersection of a side-wall of the cup-shaped body and the bottom wall.

13. The casting furnace of claim 12 including a metallic frame enclosing a refractory disc forming a lid.

14. The casting furnace of claim 13 including at least one gasket between the rim and the furnace chamber.

15. The casting furnace of claim 12, wherein an internal surface of the bottom wall includes a partition wall extending at each end from the side wall and surrounding the valve.

16. The casting furnace of claim 13, wherein the frame includes a first ring above the rim and a second ring below the rim, said rings being coupled by at least one fastener.

17. The casting furnace of claim 16, wherein the first ring includes at least one lifting element.