Shell sand core machine

Abstract

An automated core molding machine, including a method and apparatus for blowing and curing of cores wherein the special core box remains in a fixed vertical plane during the core forming and curing stages.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to automated core molding systems and, more particularly, to a method and apparatus for the blowing and curing of cores wherein the special core box (matrix) remains in a fixed vertical plane during core formation and curing.

2. Description of Related Art

Metal castings are typically produced by the introduction of molten metal into a mold in the form of the casting, also termed a “core,” typically utilizing sand as the core material. As an initial step in the process, the core must be formed and cured. This occurs in a core box (matrix). The forming of the core is termed “blowing,” and involves the introduction of resin coated sand into a core box (matrix) to produce a core in the desired casting shape. A problem with the prior art is the difficulty in retaining the proper shape of the uncured core during the movement of the core box (matrix) prior to curing. This results in cores of variable quality, and consequently results in castings of unacceptably variable quality.

The removal of the cured core from the core box (matrix) can be very difficult when the draft angle of the core box cavity is very small. Should a portion of the cured core break off of the larger removed core and is retained in the core box it will be very troublesome. The cured core is hard and could be difficult to remove. The use of any sharp tools or excessive force can mar or damage the core box (matrix) which will acerbate the condition and subsequently made cores might not be drawn (removed) easily.

Accordingly, special emphasis is needed in the machine design to allow for a very controlled drawing of the core. Provisions also are needed to assist in ejecting (removal) of the core from the core box (matrix).

Another problem with the prior art is that the sand fill station is not sufficiently isolated from the cure station. Curing of the cores involves the application of heat. The curing process ensures that the sand core retains the proper shape of the casting, and more particularly, retains the proper shape to the required dimensional tolerances. The resin coated core sand that is used in producing the shell cores is very special and expensive. In the typical prior art arrangement, sand is introduced into the core box (matrix) from a reservoir, or fill station proximal to the cure station. Consequently, heat from the cure station may initiate the curing process in the sand while it is stored in the fill station prior to blowing into the core box, whereby the sand in the fill station becomes partially or fully hardened before it is introduced into the core box and is unable to produce a core in the desired consistency and casting shape.

Another problem with a hollow core, the sand in the inside is not totally cured and the grains of sand have little or no strength and are not bonded together. This can result in quality problems during subsequent manufacturing operations.

Operation of the prior art is typically accomplished by the use of pressurized air to deliver sand to the core box (matrix), as well as for cylinder and valve operation. A problem with the prior art is that, if a single source of air is utilized to provide both “control air” and “blow air,” erratic machine movement can result from the decompression of the control air during the blowing process, which results in cores of variable quality.

SUMMARY OF THE INVENTION

These and other problems of the prior art are overcome in accordance with this invention by a core molding system that incorporates a separate sand fill station, a separate clamp, blow and cure station, and a separate cope eject and unload station. Specially designed equipment is used to remove unneeded core sand from the core cavity. In addition, external heat is applied to the hollowed out core to aid in curing the core. In accordance with one aspect of the invention, the core box (matrix) remains in a fixed vertical plane during the core formation and the clamping, blowing and curing stages. In accordance with another aspect of the invention, a special tooling mount on the clamp table, or pattern pins, move up and down in a vertical plane and eliminate the possibility of sand shift prior to curing of the sand with heat.

In one particular embodiment of the invention, the sand fill station, is adapted to keep the heat-curable sand away from the blow, and cure stations. A sand supply hopper gate discharges sand into a fabricated sand magazine which is attached to a transfer car. The transfer car moves the sand magazine horizontally in and out of the separate clamp, blow, cure station stages, as required.

Advantageously, after the sand filled core has been blown in a shell-type or solid mold, and prior to being totally cured, a specially-designed sand removal device or vacuum manifold is introduced into the core box to remove any excess resin-coated sand, and to reclaim from the inside of the core any resin-coated sand that is not required before the sand in the core or mold is cured. Advantageously, this improves the quality and precision of the molds.

After the core has been cured, utilizing a heating element or burner, the resulting core is stripped from the drag and remains in the cope section of the core box tooling. The cope section is shuttled out away from the vacuum manifold and heating manifold on transfer arms that are attached to another transfer car, and into an eject and unload station. The transfer arms also have the ability to move up and down as well as adjusting the levelness of the core box. A special pattern blow-off and spraying of pattern release agents is incorporated into the machine.

Furthermore, in one particular embodiment of the invention, the clamp, blow, and cure station is supplied with separate control air and blow air sources, including a reservoir of pressurized blow air, which avoids the compression of control air during the blow cycle and eliminates the resultant erratic machine movement during peak air demand. Also, the control air needs to be lubricated to allow for valves and cylinders to function more reliably; however, oil in the blow air would be a detriment to the core making process.

In accordance with another aspect of the invention, the core molding system is in a particular position and operation of the fill station and cure station, such that the reservoir of sand in the fill station is positioned with respect to the cure station to minimize premature curing of the sand prior to its introduction into the core box and the initiation of the curing process.

Another advantage of the core molding system in accordance with this invention is the use of a fixed core box for the forming and curing process. The single station utilized for both forming and curing the core eliminates movement of the core box after formation and before curing which frequently causes settling and shifting of the sand prior to curing in the prior art.

BRIEF DESCRIPTION OF DRAWINGS

The invention will now be described with reference to the drawings wherein:

FIG. 1 is a frontal view of a core molding machine 10, incorporating principles of the invention;

FIG. 2 is a front elevation view of the machine frame assembly 12 for the core molding machine of FIG. 1;

FIG. 3 is a right hand end elevation view of the core molding machine of FIG. 1;

FIG. 4 is a the left hand end elevation view of the machine frame assembly 12 for the core molding machine of FIG. 1;

FIG. 5A is the left hand end view of the core molding machine of FIG. 1;

FIG. 5B is a front elevation view of the core unloader table portion of the machine frame assembly 12;

FIG. 6A-D are multiple views of the unloader car assembly 43;

FIG. 7A is a right-hand elevation view of the vacuum manifold 27, upper burner manifold 31, attached to the machine frame assembly 12; and

FIG. 7B is a plan view of the vacuum manifold 27 and the upper burner manifold 31.

DETAILED DESCRIPTION

Depicted in FIG. 1 is a frontal view of the core molding machine 10 incorporating a heavy machine frame assembly 12 (FIG. 2) which supports a sand hopper 14, an air reservoir 16, and a blow head 17. A clamp table 22 and pattern pins 24 support a core box (matrix) 26 which consists of a cope 28 resting on a trunnion system 20 that is compressed against the drag 32 to form a core 34. The core box (matrix) 26 is brought adjacent to a sand chamber transfer car 36.

As shown in FIG. 1, the blow head/sand magazine 17 and sand chamber transfer car 36 are aligned with the sand hopper 14 in a position to receive the sand. Sand is introduced from the sand hopper 14 to the blow head/sand magazine 17 through the operation of the sand hopper cylinder 47 which opens and closes a valve in the sand hopper 14 which releases the sand by gravity when the sand hopper cylinder 47 is extended. The sand hopper 14 is closed by retraction of the sand hopper cylinder 47 after the sand has been introduced into the blow head/sand magazine 17.

The sand chamber transfer car 36 with the blow head/sand magazine 17 filled with sand is then moved laterally on Osborn v-wheels 38 that move across an upper horizontal track 40 through the action of the sand chamber transfer car cylinder 50 towards the core box (matrix) 26 until the blow head/sand magazine 17 is aligned with the center line of the core box (matrix) 26, the clamp table 22, and the blow chamber 18. The clamp table 22 is raised to elevate the core box (matrix) 26 to a position immediately below the blow head/sand magazine 17 by means of an extended clamp cylinder 46. After the clamp table 22 is raised to place the core box (matrix) 26 in a position immediately below the blow head/sand magazine 17, the blow valve 52 is opened and pressurized air from the blow air reservoir 16 delivers air to the blow chamber 18 to the blow head/sand magazine 17 into the core box (matrix) 26. After the correct volume of sand is delivered to the core box (matrix) 26, the blow valve 52 is closed and excess air is released from the blow exhaust chamber 54.

FIG. 2 schematically illustrates the machine frame assembly 12 supporting an upper horizontal track 40, a lower horizontal track 41, pattern pins 24, a stripper plate 45, and an unloader table 48.

As depicted in FIG. 3, the clamp table 22 and the core box (matrix) 26 are lowered by the operation of the clamp cylinder 46 to the cure position. The blow head/sand magazine 17 is moved away from the core box (matrix) 26 during curing. The blow head/sand chamber transfer car 36 (FIG. 1) returns by means of retraction of the blow head/sand chamber transfer car cylinder 50 to a position in alignment with the center line of the sand hopper 14. As shown in FIGS. 7A and 7B, a vacuum manifold 27 is provided to a set depth inside the blow openings to remove excess resin coated sand from the top of the cope 28. The vacuum manifold 27 extends by the operation of a vacuum cylinder 29 to the core box (matrix) 26 and removes excess resin coated sand from the core box (matrix) 26. The sand is returned to the sand hopper 14 for the next core 34 forming cycle. The vacuum manifold 27 remains extended through the operation of the vacuum cylinder 29.

The upper burner manifold 31 extends by operation of the burner cylinder 33 to the core box (matrix) 26 and heats the core box (matrix) 26 to cure the core 34. Proper cure temperature is maintained by the use of thermocouples. Heat may be provided through the use of gas-powered or electric-powered heating elements, or, as is contemplated here, a combination of the two. After curing is completed, the upper burner manifold 31 and vacuum manifold 27 are retracted by operation of the burner cylinder 33 and vacuum cylinder 29 together.

The clamp table 22 is lowered by means of the clamp cylinder 46, placing the cope 28 and core box (matrix) assembly 26 on the unloader transfer arms 44 (FIG. 6B). Vibrators mounted on the core box are activated and the clamp cylinder 46 lowers the drag 32 away from the cope 28 and core box (matrix) assembly 26. The unloader transfer arms 44 move the cope 28 and core box (matrix) 26 assembly laterally by means of the core unloader cylinder 56 (FIG. 5B) to a position above the core unloader table 48. The core unloader table 48 is raised by means of the core unloader cylinder 56 to a position beneath the core box (matrix) 26. The core 34 is removed from the core box (matrix) 26 by pressing the core against stripper plate 45 (FIG. 5A) and controlled lift of core unloader cylinder 56 and placing the core on the core unloader table 48. The core unloader table 48 is lowered by means of the core unloader cylinder 56 with the core 34 ejected from the core box (matrix) 26. The unloader transfer arms 44 move the empty cope 28 laterally to the clamp table 22 by means of the core unloader cylinder 56.

The core box (matrix) 26 is reassembled utilizing the cope 28 and drag 32 sections by elevating the clamp table 22 to bring the cope 28 adjacent the drag 32.

The core molding machine 10 also incorporates an air supply unit providing air under pressure, a hydraulic unit providing hydraulic fluid under pressure, an electrical supply box, and an electronic controller that are standard components in the art. The electronic controller may be a programmed logic array designed to provide electrical signals to operate various air and/or hydraulic valves and/or relays. The electric box provides electrical power when required.

While particular embodiments of the invention have been shown, it will be understood that the invention is not limited thereto since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings. Reasonable variation and modification are possible within the scope of the foregoing disclosure of the invention without departing from the spirit of the invention.

Claims

1. A process for casting and curing said cores, in which a core box remains in a fixed vertical plane during core formation, said casting and curing further comprising:

filling a movable blow head with sand;

moving the blow head away from a sand hopper towards the core box;

positioning the blow head in line with a blow valve;

filling the core box with sand from the blow head, wherein the filling includes applying air pressure to the core box through a blow valve and retracting the blow head; and

removing excess sand from a core cavity of the core box by introducing a vacuum manifold and returning unused vacuumed sand to the sand hopper for use in the next cycle.

2. (canceled)

3. A process as defined in claim 1, and including the application of heat to the sand core by introducing an upper burner manifold.

4. A process as defined in claim 3, and including elevation of the cope and core of the core box away from the drag of the core box.

5. A process as defined in claim 4, and transferring the cope and core to a core unloader table, by lowering the cope and core onto the unloader transfer arms and laterally translating the cope and core to the core unloader table.

6. A process as defined in claim 5, and including removal of the core from the cope onto the core unloader table.