Patent Publication Number: US-7913742-B2

Title: Integral blow tube and tamping pin

Description:
FIELD OF THE INVENTION 
     The invention relates to foundry equipment and more particularly to a method for forming sand cores used in casting of metal parts. 
     BACKGROUND OF THE INVENTION 
     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. 
     SUMMARY OF THE INVENTION 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is a schematic side cross sectional view of a sand core forming apparatus according to the present invention, the apparatus being shown in a position of sand conveyance; and 
         FIG. 2  is a schematic side cross sectional view of the sand core forming apparatus of  FIG. 1 , shown in a position of catalyst introduction. 
     
    
    
     DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS OF THE INVENTION 
     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. 
       FIG. 1  illustrates a sand core forming apparatus  10  according to an embodiment of the invention. The sand core forming apparatus  10  includes a core box  12 , a gassing manifold  14 , a blow tube  16 , a blow plate  18 , a sand magazine  20 , a connector tube  22 , and a tamping pin  24 . The core box  12  is made from a durable material such as steel, that can be machined accurately. The core box  12  consists of a cover  26  and a box  28 , where the box  28  is the bottom of the core box  12 . A horizontally parted core box  12  is shown. However, the apparatus  10  could be used with a vertically parted core box as well. The assembled cover  26  and box  28  rest on a supporting surface  30 , which provides for movement of the core box  12  during removal of the finished core. The core box  12  has an aperture  32  formed in the cover  26  in communication with a cavity  34  formed between the cover  26  and the box  28 . A shape of the cavity  34  corresponds to a shape of the sand core that is desired. The aperture  32  formed in the cover  26  allows the blow tube  16  to sealingly engage the core box  12  in a manner so the blow tube  16  is substantially aligned with an inner surface of the core box  12  forming the cavity  34 . Passages  36  are provided in the cover  26  to allow air to escape the core box  12  as it is filled with the sand  38  and to allow a catalyst gas to be introduced to the core box  12  as well. Vents  40  are also located on the cover  26  and the box  28 , which allow air to escape the core box  12  as it is filled with the sand  38 . 
     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  FIG. 1 , is a position of sand conveyance. In the first position, the blow plate  18  does not contact the gassing manifold  14 . In the second position, the blow plate  18  abuts the gassing manifold  14 . The blow plate  18  also includes a counter bore  56 , concentric with the aperture  54 , the counter bore  56  facilitates a locating and a securing of the collapsible connector tube  22 . 
     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  FIG. 1 , when the blow plate  18  is in a first position of sand conveyance, the central cylinder  66  has a length that allows sand  38  to flow freely through the conveyance cavity  50 , around the central cylinder  66 , and into the cavity  34  in the core box  12 . As illustrated in  FIG. 2 , when the blow plate  18  is in a second position of catalyst introduction, the central cylinder  66  performs a tamping and sealing function. The central cylinder  66  has a tamping surface  68  which performs a tamping function when the blow plate  18  is moved from the first position to the second position. The central cylinder  66  also militates against an introduction of catalyst gasses to the blow tube  16  when the blow plate  18  is in the second position. 
       FIG. 2  illustrates the sand core forming apparatus  10  in the second position of catalyst introduction, where the core box  12  has been filled with the sand  38 . The second position is achieved by the blow plate  18  moving into contact with the gassing manifold  14 . The core box  12 , having the aperture  32  sealed by the central cylinder  66  of the tamping pin  24 , can be exposed to a catalyst. The movement of the blow plate  18  to the second position also causes the connector tube  22  to be elastically deformed. The catalyst is released in the manifold chamber  47  and enters the cavity  34  through the apertures  36 , which exposes the uncured sand core  70  thereto. Pressurization of the sand magazine  20 , at either the same pressure of the gassing manifold or slightly greater at this time by air may be used to militate against an introduction of catalyst gases into the blow tube  16  from the core box  12 . After an appropriate curing time, the manifold chamber  47  is purged with air to remove any remaining catalyst, ending the core hardening process. The box  28  is then lowered from the cover  26 . The cured sand core can then be removed. The box  28  is then raised to the cover  26 . The sand core forming apparatus  10  is then returned to a position of sand conveyance by a movement of the blow plate  18 . The core making cycle can then be repeated. 
     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.