Patent Application
20090321984
The invention relates to foundry equipment and more particularly to a method for forming sand cores used in casting of metal parts.
Sand cores are commonly used within the foundry industry in the production of metal castings having complex interior and exterior geometry. These metal castings are formed by pouring molten metal around or into the sand core. After the casting process, the metal casting is extracted by destructively removing the sand core. Specifically, the metal casting is extracted by breaking the sand core or shaking the sand out of the casting. Hence, the casting of metal parts can require the use of one or more sand cores that correspond to the part geometry that is to be cast.
In general, the sand cores are formed in a core box. The core box typically includes two halves which cooperate to define a volume having the geometry of a desired sand core. Sand to be formed enters the core box through one or more blow tubes, which allow passage from a sand reservoir or magazine to the hollow interior of the core box. Before entering the magazine, the sand is coated with a liquid binder, often referred to as resin. The sand is conveyed from the magazine into the core box, via the blow tubes, by pressurizing the magazine with compressed air. Air is able to escape from the core box during the forming of the sand core through narrow vent passages in the core box.
In addition to filling the core box with sand, other steps are necessary before the desired sand core is completed. To refine the sand core shape before it is hardened, tamping may be used at the blow tube locations. Tamping involves flattening the residual sand at the blow tube locations to allow the sand core to best resemble the desired geometry. In past methods, tamping is accomplished by moving the magazine and blow tubes away from the core box, and subsequent positioning of a gassing head with tamping mechanisms over the core box. Tamping pins that correspond to the shape and location of the blow tubes are lowered into the blow tubes locations by a relative movement between the tamping mechanism, where the tamping pins are mounted, and the core box. Upon completion of the tamping, the catalyst gas is introduced to the sand core to cause a solidification thereof. The gas is introduced to the sand core via a gassing manifold encompassing the blow tube openings and the vents in the upper side of the core box. The gases exit the core box through vents in the lower side of the core box. After a suitable curing time, the core box is purged with air to remove any residual catalyst vapor. To complete the process, the core box halves are separated and the finished sand core is removed from the core box.
Recently, methods have been proposed that require complex blow tubes to facilitate the multiple functions of sand conveyance, tamping, sealing of the blow tube, and catalyst gas and purge air conveyance. U.S. Pat. No. 7,284,588 B2, hereby incorporated herein by reference in its entirety, discloses a complex blow tube that eliminates the need to interchange the sand magazine and gassing manifold during the machine cycle. This invention provides substantial advantages in terms of equipment cost and cycle time. However, the integration of separate conduits used for the conveyance of the sand and catalyst gas into the tamping pin and the necessity of maintaining adequate sealing is the source of disadvantages for this method. Examples of these disadvantages are the creation of a complex and tortuous flow path for the sand, a high risk of catalyst leakage causing blow tube plugging, laborious and costly cleaning of plugged blow tubes, and numerous rubber O-rings that are prone to fail with repeated use.
It would be desirable to have a sand core forming apparatus adapted to convey the sand, tamp the sand, and militate against an undesirable exposure of uncured sand residing within the blow tube to catalyst gases, while providing a non-tortuous flow path for the sand.
Presently provided by the invention, a sand core forming apparatus tailored to convey the sand, tamp a sand core, and militate against the undesirable exposure of uncured sand to catalyst gases, while providing a non-tortuous flow path for the sand, has surprisingly been discovered.
In one embodiment, the sand core forming apparatus comprises a core box having a cavity formed therein; a gassing manifold in fluid communication with said core box; a blow tube having a resilient tip in fluid communication with the cavity of said core box; a sand magazine having a sand reservoir formed therein; a connector tube providing fluid communication between the reservoir of said sand magazine and the cavity of said core box; and a tamping pin coupled to said sand magazine, wherein said tamping pin cooperates with the resilient tip to selectively control flow of sand from said sand magazine to the cavity of said core box.
In another embodiment, the sand core forming apparatus comprises a core box having a cavity formed therein; a gassing manifold in fluid communication with said core box; a blow tube having a resilient tip in fluid communication with the cavity of said core box; a sand magazine having a sand reservoir formed therein; a connector tube providing fluid communication between the reservoir of said sand magazine and the cavity of said core box; and a tamping pin coupled to said sand magazine by one or more supporting legs, wherein said tamping pin cooperates with the resilient tip to selectively control flow of sand from said sand magazine to the cavity of said core box.
The invention also provides methods for the forming of sand cores.
In one embodiment, the method for the forming of sand cores comprises the steps of providing a core box having a cavity formed therein; providing a gassing manifold in fluid communication with said core box; providing a blow tube in fluid communication with the cavity of said core box; providing a sand magazine having a sand reservoir formed therein; providing a connector tube affording fluid communication between the reservoir of said sand magazine and the cavity of said core box; and providing a tamping pin coupled to said sand magazine, wherein the tamping pin cooperates with the resilient tip to selectively control flow of sand from said sand magazine to the cavity of said core box; filling the cavity of said core box with sand; wherein sand is introduced to the cavity through said blow tube; tamping the sand core with said tamping pin, wherein the tamping is performed by a movement of said sand magazine; sealing the blow tube with said tamping pin, wherein the sealing is performed by a movement of said sand magazine; and introducing a catalyst to the sand core through at least one venting location in said core box.
The sand core forming apparatus provided by the present invention is specifically advantageous for providing a non-tortuous flow path for sand, militating against an undesirable exposure of uncured sand to catalyst gases, tamping the sand core, and conveying sand.
The above, as well as other advantages of the present invention, will become readily apparent to those skilled in the art from the following detailed description of embodiments of the invention when considered in the light of the accompanying drawings in which:
The following detailed description and appended drawings describe and illustrate an embodiment of the invention. The description and drawings serve to enable one skilled in the art to make and use the invention, and are not intended to limit the scope of the invention in any manner. In respect of the methods disclosed, the steps presented are exemplary in nature, and thus, the order of the steps is not necessary or critical.
The gassing manifold 14 is made from a durable material such as steel, and is made to correspond with the shape of the core box 12. The gassing manifold 14 includes side wall members 42 and an upper wall member 44 disposed intermediate a height of the wall members 42. The upper wall member 44 has an aperture 45, formed therein and substantially aligned with the aperture 32 formed in the core box 12. The aperture 45, defined at least partially by an inner wall 46, may be threaded as a means of attaching the blow tube 16 to the gassing manifold 14. A volume between the upper wall member 44 and core box 12, forms a manifold chamber 47. The upper wall member 44 may also include a counter bore 48, concentric with the aperture 45, as a means of locating and securing a position of the collapsible connector tube 22. The gassing manifold 14 is selectively secured to the core box 12 by any conventional means such as clamping, and can be disengaged from the core box 12 to allow the core box 12 to be removed from the sand core forming apparatus 10.
The blow tube 16 is made from a durable material such as steel, and is adapted to be coupled to the gassing manifold 14. The blow tube 16 is hollow, forming a portion of a conveyance cavity 50, through which the sand 38 is conveyed. A resilient tip 52 is disposed on an end of the blow tube 16, to allow the blow tube 16 to sealingly engage walls forming the aperture 32 when the sand core forming apparatus 10 is in a position of sand conveyance. The blow tube 16 has a length appropriate to allow the blow tube 16 to engage the aperture 32 when the gassing manifold 14 is secured to the core box 12.
The blow plate 18 is made from a durable material such as steel. An aperture 54 is formed in the blow plate 18 and is substantially aligned with the aperture 32 and the aperture 45. The blow plate 18 is disposed adjacent the gassing manifold 14 and has a first and a second position. The first position, illustrated in
The sand magazine 20 includes wall members 58 that abut the blow plate 18. The wall members 58 may be made from any conventional material, such as steel. A cavity 60 is formed between the wall members 58 and the blow plate 18. The cavity 60 provides a location for the sand 38 to be stored and pressurized before being conveyed to the core box 12.
The connector tube 22 is typically formed from a resilient material, such as plastic. The connector tube 22 is disposed between the upper wall member 44 and the blow plate 18, and is substantially aligned with the aperture 45. A portion of the conveyance cavity 50 is formed by the connector tube 22. Annulets are formed on each end of the connector tube 22. The annulets militate against a leakage of the sand 38 from the conveyance cavity 50. In the embodiment shown, the connector tube 22 is collapsible, thereby allowing a deformation of the connector tube 22. A tension device 62 is disposed on the connector tube 22, the tension device being a coil spring 62. Other tension devices, such as a leaf spring or resilient rubber could be employed as desired.
The tamping pin 24 is made from a durable material such as steel, and is coupled to the blow plate 18. The tamping pin 24 may be coupled by any conventional means, such as welding or fastening. In the embodiment shown, the tamping pin 24, has supporting legs 64, interconnecting the tamping pin 24 and the blow plate 18. The tamping pin 24 includes a central cylinder 66, which is attached to the supporting legs 64 by any conventional means, such as welding, fastening, or a press fit. The supporting legs 64 may be individually attached or may be attached simultaneously through the use of a central hub, which receives the central cylinder 66. The central cylinder 66 is received in the aperture 54, the connector tube 22, the aperture 45, and the blow tube 16. In the embodiment shown, the tamping pin 24 is a solid cylinder and has three supporting legs 64, substantially “L” shaped. As illustrated in
From the foregoing description, one ordinarily skilled in the art can easily ascertain the essential characteristics of this invention and, without departing from the spirit and scope thereof, make various changes and modifications to the invention to adapt it to various usages and conditions.
