US3901307A

US3901307A - Vent hole-making mechanism for a foundry mold

Info

Publication number: US3901307A
Application number: US425218A
Authority: US
Inventors: John R Nieman
Original assignee: Caterpillar Tractor Co
Current assignee: Caterpillar Inc
Priority date: 1973-12-17
Filing date: 1973-12-17
Publication date: 1975-08-26
Anticipated expiration: 1992-08-26

Abstract

Means are provided for automatically making vent holes in foundry casting molds. The vent hole-making means includes a hollow body slideably engaging the head end of a pin member therein. The pin member is also provided with a smaller diameter pin end, which extends beyond the body through a bore in the upper wall thereof. Biasing means are provided within the hollow body for urging the pin member head end against the upper wall and for storing energy absorbed during the mold making process. In use, the base of the body is attached to a mold pattern, and molding sand is tamped around the pattern and vent hole-making means, concurrently causing the pin member to retract within the body against the urging of the biasing means. Removal of the tamping means releases the energy stored in the biasing means, projecting the pin member upward through the molding sand surface, thereby creating a vent hole.

Description

Nieman [4 1 Aug. 26, 1975 l l VENT HOLE-MAKING MECHANISM FOR A FOUNDRY MOLD [75] inventor: John R. Nieman, Pekin, ill.

['73] Assignee: Caterpillar Tractor Company,

Peoria, 111.

[22] Filed: Dec. 17, 1973 [2l] Appl. No: 425,218

[52] US. Cl. 164/410; 164/244 [5 l] Int. Cl. B22C 23/00 [58] Field of Search 164/242, 243, 244, 410,

[5 6] References Cited U NITED STATES PATENTS Primary liraminer-Francis S. Husar Assistant E.\'aminer-J0hn S. Brown Attorney, Agent, or FirmPhillips, Moore, Weissenberger Lempio & Strabala l 5 7 1 ABSTRACT Means are provided for automatically making vent holes in foundry casting molds. The vent hole-making means includes a hollow body slideably engaging the head end of a pin member therein. The pin member is also provided with a smaller diameter pin end, which extends beyond the body through a bore in the upper wall thereof. Biasing means are provided within the hollow body for urging the pin member head end against the upper wall and for storing energy absorbed during the mold making process. In use, the base of the body is attached to a mold pattern, and molding sand is tamped around the pattern and vent holemaking means, concurrently causing the pin member to retract within the body against the urging of the biasing means. Removal of the tamping means releases the energy stored in the biasing means, projecting the pin member upward through the molding sand surface, thereby creating a vent hole.

6 Claims, 5 Drawing Figures VENT HOLE-MAKING MECHANISM FOR A FOUNDRY MOLD BACKGROUND OF THE INVENTION This invention relates to foundry mold-casting, and more particularly to the provision of means for automatically making vent holesin a casting mold to permit the expulsion of gases therefrom which have been accumulated during the casting process.

At present, vent holes are typically provided for foundry molds in a manual operation, as by hand punching these holes prior to.the introduction of molten metal into the pattern. The placementrand number of these holes is therefore subject to human error, and it has frequently been found that such manual operations have resulted in inaccurately placed vent holes, or the provision of an insufficient numberof these holes for a given casting. Such errors usually result in gas hole inclusions which may weaken or irreparably damage the casting, necessitating the repair or rejection of the casting. Since many such inclusions are not discovered until final machining operations are being performed, repairing or scrapping the casting is relatively costly. Also, many inclusions are not discovered in the foundry or manufacturing facility, and often result in field failures of the casting due to weaknesses of the metal caused by these inclusions.

SUMMARY AND OBJECTS OF THE INVENTION The invention provides automatic vent hole-making means including a hollow body slideably engaging a pin member therein. The pin member includes a head end slideably engaged within the hollow portion of the body, and a pin end of lesser diameter than the head end which extends beyond the body through a bore in the upper end wall thereof. The head end of the pin member is normally urged against the upper wall of the body by biasing means disposed within the body between the base thereof and the head end of the pin member. In use, the vent hole-making means is secured by the base of the body to a pattern, and molding sand is tamped around the pattern in conventional manner, causing the pin member to retract into the body against the urging of the biasing means. Withdrawal of the tamping elements and their exerted forces results in the release of energy stored in the biasing means, e.g. a spring, forcing the pin member through the surface of the molding sand to the atmosphere. The pattern and vent hole-making means are then removed, leaving a clean, accurately placed vent hole in the mold.

It is therefore an object of this invention to provide automatic vent hole-making means for making vent holes in foundry casting molds.

It is another object of this invention to provide vent hole-making means which reduce gas hole inclusions in castings by accurate placement of vent holes of the required number.

It is a further object of this invention to provide vent hole-making means which reduce manufacturing costs by reducing the number of casting repairs and scrap castings by reducing gas hole inclusions.

It is an additional object of this invention to provide automatic vent hole-making means which reduces field failure of castings by reducing the incidence of gas hole inclusions.

Other objects and advantages of the invention will be apparent to those skilled in the art from the following description and appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS FIG, 1 is an enlarged cross-sectional elevation view of the automatic vent hole-making means of this invention showing details thereof; and

FIGS. 2-5 represent sequential stages of a conventional casting mold-making process employing the automatic vent holemaking means of this'invention.

DETAILED DESCRIPTION With particular reference to FIG. 1 of the drawings, the automatic vent hole-making means of this invention is generally indicated at 10, and includes an elongated, fr'ustoconical hollow body 11 slideably engaging a cylindrical headend 12 of a cylindrical 'pin member 13. The pin member 13 further includes a pin end 14 of substantially smaller diameterthan the head end 12, which extends beyond the body 11 through a bore 16 in the upper end wall 17 of the bodyQThe bore 16 is of suitable diameter to slideably engage the pin end 14 and at the same time form an annular stop 18 for the head end 12 with the upper wall 17. The bore 16 is provided with sealing means such as a circular wiper seal 19 of rubber or other suitable resilient material for preventing the entry of foreign material, such as molding sand, past the pin end 14 into the bore and the hollow portion 20 of the body 11.

Biasing means such as acompression spring 21 are disposed within the body 11 between a plug member 22 in the base end 23 thereof and the head end 12 of the pin member 13 for urging the pin member against the stop 18. The plug member 22 is threadably securable to the base 23, and is provided with a projecting screw stud portion 24 which is threadably securable to a mold pattern 27 at predetermined points (FIGS. 2-4) to support the body 11 thereon.

The operation of the vent hole-making means 10 is generally illustrated in FIGS. 25 which represent sequential stages of a conventional casting mold-making process. The process employs a foundry mold generally indicated at 25 which includes a mold flask 26, a pattern member 27 and molding sand 28 which is compacted by a plurality of tamper foot members 29 associated with a standard mold-making machine (not shown).

In FIG. 2 the pattern member 27 is shown provided with a plurality of vent hole-making means, one of which is shown at 10. The desired number of vent holemaking means are secured to the pattern member 27 in the desired positions by the screw stud portions 24 of the plug members 22 which are threadably secured in corresponding holes in the pattern members. The pattern member 27 and vent hole-making means 10 are illustrated in place in the flask 26 covered by the sand 28 which has been introduced in a conventional manner.

In FIG. 3, the mold 25 is shown after the sand 28 has been compacted by the action of the tamper foot members 29. The downward motion of the foot members while compacting the sand 28 has also forced the pin member 13 downward against the spring 21, thereby compressing the spring. The pin member 13 and spring 21 will remain in this retracted position as long as the foot members 29 exert downward pressure on the sand 28, usually until the sand is suitably compressed around the pattern member 27 and is flush with the top of the flask 26, as illustrated.

In FIG. 4, the tamper foot members 29 have been withdrawn upwardly by the molding machine, and the energy stored in the spring 21 has been released to force the pin member 13 upwardly sufficiently to break through the compacted surface of the sand 28 into the atmosphere.

In FIG. 5, the pattern member 27 and the vent holemaking means have been withdrawn from the mold, and a completed casting mold is shown. A clean, accurately-placed gas vent hole, having a frustoconical por tion 30 and a cylindrical portion 31, is now a part of the final mold, providing full assurance that all gases trapped in the mold 25 during the metal pouring operation will be expelled to the atmosphere, thereby providing a sound casting without gas pocket inclusions. The frustoconical shape of the body-forming portion 30 facilitates withdrawal of the body 11 from the mold.

Although the invention has been described by reference to a specific embodiment, it will be apparent to those skilled in the art that numerous equivalent modifications and variations are possible without departing from the spirit and scope of the invention. For example, a number of alternative biasing or energy-storing means are contemplated as substitutes for the spring 21, such as a suitable rubber member, or a compressible liquid or gas. Further, the vent hole-making means may be secured to the pattern member 29 by means other than the screw stud portion 24 of the preferred embodiment. No limitations of the inventive concept with respect to these or other elements of the invention is intended, except as specifically pointed out in the appended claims.

I claim:

1. Vent hole-making means for automatically making vent holes in foundry casting molds, said vent holemaking means including a body, defining a hollow and an upper end wall portion therein and a base portion;

a pin member having a head end and a pin end of lesser diameter than the head end, said head end being slidably engageable within the hollow portion of said body and said pin end extending beyond said body portion through a bore in said upper end wall of said body portion, said body being otherwise closed; said body further including wiper seal means mounted on said upper end wall and positioned about said pin end in sliding engagement therewith for preventing entry of foreign material into said hollow portion of said body and spring biasing means comprising a spring disposed within said hollow portion intermediate said base portion and said head for urging said head end of said pin member against said upper wall and for storing energy absorbed during the mold-making process.

2. The invention of claim I, wherein said body is provided with a plug member in the base thereof, said plug member including a means for engagement with a mold pattern for support thereof.

3. The invention of claim 2 wherein said means for engagement with a mold pattern comprises a threaded projection extending from said plug and adapted for mating with an accomodating bore in said mold pattern.

4. The invention of claim 1 wherein said wiper seal means comprises a wiper seal of resilient material.

5. The invention of claim 4, wherein said resilient material is rubber.

6. The invention of claim I, wherein said body is frustoconical in shape in order to facilitate removal from the mold.

Claims

1. Vent hole-making means for automatically making vent holes in foundry casting molds, said vent hole-making means including a body, defining a hollow and an upper end wall portion therein and a base portion; a pin member having a head end and a pin end of lesser diameter than the head end, said head end being slidably engageable within the hollow portion of said body and said pin end extending beyond said body portion through a bore in said upper end wall of said body portion, said body being otherwise closed; said body further including wiper seal means mounted on said upper end wall and positioned about said pin end in sliding engagement therewith for preventing entry of foreign material into said hollow portion of said body and spring biasing means comprising a spring disposed within said hollow portion intermediate said base portion and said head for urging said head end of said pin member against said upper wall and for storing energy absorbed during the mold-making process.

2. The invention of claim 1, wherein said body is provided with a plug member in the base thereof, said plug member including a means for engagement with a mold pattern for support thereof.

5. The invention of claim 4, wherein said resilient material is rubber.

6. The invention of claim 1, wherein said body is frustoconical in shape in order to facilitate removal from the mold.