EP0095829A1

EP0095829A1 - Method and apparatus for de-finning metal castings

Info

Publication number: EP0095829A1
Application number: EP83301698A
Authority: EP
Inventors: John Turner Politz
Original assignee: ERVIN INDUSTRIES Inc; Ervin Ind Inc
Current assignee: ERVIN INDUSTRIES Inc; Ervin Ind Inc
Priority date: 1982-05-27
Filing date: 1983-03-25
Publication date: 1983-12-07
Also published as: ES8406925A1; AU1262383A; JPS58211858A; ES520998A0

Abstract

A method of and apparatus for removing fins and other excess metal from metal castings in which the centrifugal force of a rotating member (16) propels impact pellets toward the casting. The mass of the moving pellets striking the fins must be sufficient to knock the fins off the casting and as a result the pellets must be of a large size. A plurality of radially extending blades (20) are mounted on the rotating member (16) and have inner ends (22) which terminate at positions spaced radially from the axis of rotation (18) of the rotating member. A supply conduit (24) extends into the space between the axis or rotation and the inner ends of the blades, and terminates at a distance from the path of the blade which is slightly greater than the largest diameter of the impact pellets. Impact pellets are fed into the conduit, whereupon air is introduced into the conduit at a force sufficient to pre-accelerate the pellets through the conduit and onto the inner ends of the blades.

Description

BACKGROUND OF THE INVENTION

In the casting of metal objects, the objects tend to emerge from the molds with undesirable excess material attached. For example, sand from the mold may cling to the object after removal. Rough edges may form around openings and projections. Perhaps the biggest problem, especially in the casting of large objects with thick walls, is the appearance of "fins" or excess metal in the form of projections. Fins are most likely to form at the mold parting lines and at areas where cores are set in the mold. These fins may have substantial thickness and may cover a substantial area.
Some of the excess material can be removed by exposing the molded part to a centrifugal blasting machine in which an impeller throws shot against the part. These machines are generally satisfactory in removing many types of materials from the cast object and in cleaning the object. However, these machines have not been effective in removing fins. The force produced by conventional size shot at practicable impeller speeds is insufficient to remove the fins.
The force with which a particular piece of shot strikes a fin is a function of the mass of the shot and the impeller speed. Impeller speeds cannot be increased significantly without risk of pitting the surface of the casting. In fact, it would be desirable to reduce the impeller speed. Increasing the size of the shot has heretofore been impracticable as well. The largest shot size recognized by The Society of Automotive Engineers, is SAE-S1320 (ninety percent must be retained on a screen having .1320 inch diameter openings and 100 percent must pass through a .187 inch diameter opening). Typically, the largest shot used in centrifugal blast machines is about one-sixteenth inch; this shot is too small to remove fins. Even the largest SAE standard size (S-1320) produces too small a force. Furthermore, conventional blasting machines have not been readily adaptable to large size shot which can bind conventional impeller mechanisms because of insufficient clearance between the feed mechanism and the impeller blades.
It is an object of the present invention, therefore, to provide a method and apparatus for removing fins and other excess material from metal castings. In particular, it is an object of this invention to provide a method and apparatus for propelling particles of a sufficient size to accomplish the de-finning process.

SUMMARY OF THE INVENTION

According to this invention, a rotating member is provided with a plurality of radially extending blades. The rotating member is aligned so that its axis of rotation is perpendicular to the line between the member and the casting to be de-finned. A plurality of impact particles are fed onto the inner ends of the blades, so that the centrifugal force of the rotating member causes the impact particles to move outwardly on the blades and to be subsequently propelled toward the casting. This process of removing fins and other excess material by centrifugal propulsion of particulate matter is unique in the field.
The invention also provides a machine that is capable of centrifugally propelling particles of sufficient size to accomplish the de-finning process. The machine consists of a rotatably supported member on which a plurality of radially extending blades are mounted. The blades have inner ends which terminate at positions spaced a uniform and predetermined distance from the axis of rotation of the rotating member. A particle supply conduit is also provided which extends into the space between the axis of rotation and the inner ends of the blades and terminates in a closely spaced relation with the blades. A plurality of impact pellets are contained on the machine in a feed spout which communicates with the supply conduit. A forced air source also communicates with the supply conduit and operates to force the impact pellets through the conduit and onto the inner ends of the blades. Rotation of the rotating member causes the impact pellets to fly off the blades in a discernable pattern and impact against a casting. The distance between the terminal end of the supply conduit path and the inner ends of the blades is greater than the largest diameter of the impact pellets, so that the flow of pellets onto the blades does not interfere with blade movement. The machine is thus adaptable to impact pellets of sizes which exceed the maximum standard SAE size.
The amount of force, and thus the size of impact pellets, required to de-fin a particular object depends to some extent on the size and shape of the object, the wall thickness, the type of metal and various other factors involved in the casting process. For example, it has been found that in the de-finning of engine blocks for automobiles, an impact pellet size of one-fourth inch is optimal.
The machine of this invention is capable of performing other functions additional to and other than de-finning. The machine can also be used in removing sand and other excess materials or for smoothing rough edges. It can be used for cleaning and for polishing. It may also be desirable to provide a rotating wheel which rotates at variable speeds and to adapt the feed means to various sizes of impact pellets so that the machine can most efficiently perform the various functions.
In the drawings:

Fig. 1 is a perspective view of the de-finning apparatus of this invention with portions thereof broken away for the purpose of clarity;
Fig. 2 is a perspective view of a cast engine block prior to the de-finning process, showing fins, rough edges, sand and other excess materials attached thereto;
Fig. 3 is a fragmentary bottom view of the cast engine block prior to de-finning;
Fig. 4 is a perspective view similar to Fig. 2 but showing the cast engine block subsequent to the de-finning process;
Fig. 5 is. a somewhat diagrammatic side sectional view of a cast engine block and three machines constructed according to this invention for de-finning the block according to this invention;
Fig. 6 is a view showing a sample of the largest SAE standard size shot (SAE 1320); and
Fig. 7 illustrates the impact pellets of the present invention, showing impact pellets of the preferred size for de-finning cast engine blocks (.25 inch).

The de-finning apparatus 10 includes a main frame 12 in which an opening 14 is provided. The frame 12 is fixed relative to the object to be de-finned, and is aligned so that the opening 14 faces the object. A rotating member 16 is mounted on the frame 12 for rotation about an axis 18. A plurality of radially extending blades 20 are replaceably mounted on the rotating member 16. The blades 20 have inner ends 22 that terminate at positions spaced a uniform and predetermined distance from the axis 18.
The machine 10 further includes a supply conduit 24 which extends into the space between the axis 18 and the inner ends 22 of the blades 20. An opening 26 is provided in the terminal end 28 of the conduit 24. The distance between the blade inner ends 22 and the conduit terminal end 28 is greater than the largest diameter of the particles to be propelled by the machine 10.
A plurality of impact pellets 30 (Fig. 7) are carried on the machine 10 in a supply hopper (not shown) which supplies a feed spout 32. As can be seen from a comparison of Figs. 6 and 7, the impact pellets 30 are of a size substantially greater than the largest of the SAE standard sizes of shot 31 shown in Fig. 6. The pellets shown in Fig. 7 are approximately one-fourth inch in diameter, which has been found to be the preferred size for de-finning cast engine blocks. Different sizes of pellets 30 will be required for different types of cast objects, and it is to be understood that the invention is not limited to pellets 30 of the size shown in Fig. 7 nor to pellets 30 of any particular size. Each of the pellets shown in Fig. 7 has a diameter which is 1.33 times as large and a mass which is 2.37 times as large as the largest SAE standard size shot. In comparison with one-sixteenth inch shot, which is the largest size typically used in conventional machines, the pellets 30 are 4 times as large and 64 times as heavy.
With reference again to Fig. 1, it is seen that the feed spout 32 communicates with the supply conduit 24 so that impact pellets 30 are fed under the force of gravity into the conduit 24. An inner passage 34 is provided on the machine 10 and also communicates with the supply conduit 24. A turbine or other forced air source (not shown) is connected to the passage 34 and directs a flow of forced air through the conduit 24 toward the blades 20. The flow of air within the passage 34 and conduit 24 is maintained at a sufficient pressure to force the impact pellets 30 through the conduit 24 and onto the inner ends 22 of the blades 20. The initial velocity of the air flow must be sufficient to deliver the impact pellets 30 onto the blades 20; the velocity required varies with the weight of the pellets 30 and the length of the gap between the conduit end 28 and the blade inner ends 22.
The invention is particularly well adapted for operations involving cast objects such as engine blocks, as seen in Figs. 2-5. However, the invention is capable of being used with other types of objects such as crank shafts, manifolds, and engine heads and is not limited to use with engine blocks. After removal from a mold, a typical cast object 36 contains various imperfections such as sand, indicated at 38, clinging to the surface of the casting, rough edges, indicated at 40, and fins, indicated at 42. These various defects are removed as follows. As seen in Fig. 5, the cast object 36 is supported within the cabinet 44. The casting 36 can be rotatably or otherwise movably mounted in the cabinet 44 so that all its surfaces are exposed to the spray of impact pellets 30 or it can be manipulated so that only certain surfaces are subjected to the pellets 30. One or more of the machines 10 are mounted on the cabinet 44 with the openings 14 thereof facing the interior of cabinet and in particular facing the object 36. The number of machines 10 chosen will depend on various factors including the shape of the spray pattern desired. Impact pellets 30 and forced air are then fed into the conduit 24 of each machine 10. The pellets 30 are delivered to the inner ends 22 of the blades 20. As the member 16 rotates, centrifugal force causes the pellets 30 to move outwardly on the blades 20. When a pellet 30 reaches the tip of the blade 20, it is propelled from the blade toward the cast object 36. The accumulative effect of centrifugal propulsion of a plurality of pellets 30 is a spray pattern which covers the surface of the cast object 36.
The invention thus provides a new method and apparatus for removing fins and other excess materials from metal castings. The method of this invention involves centrifugal propulsion of particles which impinge upon the cast object with a force sufficient to remove fins. The machine 10 is adapted to propel impact pellets 30 which are of a size substantially greater than the particulate shot used in conventional blasting machines. The invention thus removes the need to manually chip away fins and other excess materials, thereby saving substantial time and expense.
Following de-finning of the object 36 by the apparatus 10, shot can be loaded into the feed spout 32, and the same apparatus 10 can be used, if desired, to shot blast the object 36. It should also be understood that the apparatus 10 can be equipped with two supply hoppers communicating with the spout 32, one containing shot and the other impact pellets 30 for subjecting a casting to the simultaneous action of the pellets and shot or first the action of the pellets and then the shot. Alternatively, other apparatus can be used for blast cleaning and objects 36 can be successively subjected to impact pellets 30 from the apparatus 10 for de-finning purposes.

Claims

1. A machine (10) for removing fins (42) and other excess metal from metal castings (36) comprising a rotatably supported member (16) having a plurality of radially extending blades (20) mounted thereon, said blades having inner ends (22) which terminate at positions spaced a uniform and predetermined distance from the axis (18) of rotation of said member (16), a plurality of impact pellets (30) contained on said machine each of which has a nominal diameter greater than the largest diameter SAE grade shot for peening and blasting and further including a supply conduit (24) which extends into the space between said axis of rotation and the inner ends of said blades and terminates in a closely spaced relation with said blades, said supply conduit being operable to direct said impact pellets onto the inner ends of said blades, said predetermined distance between the terminal end of said supply conduit and the path defined by the inner ends of said blades being greater than the largest diameter of said pellets.

2. The machine according to claim 1 further including means (34) for introducing into said supply conduit air under sufficient pressure to force said impact pellets through said conduit and onto the inner ends of said blades.

3. A method for removing fins (42) and other excess metal from metal castings (36) comprising the steps of:

(a) aligning with the casting a rotatably supported member (16) on which a plurality of radially extending blades (20) are m6unted;

(b) rotating said member (16) at a high rate of speed; and

(c) feeding onto said blades a plurality of impact pellets (30) each of which has a nominal diameter greater than the largest diameter SAE grade shot for peening and blasting so that the centrifugal force of rotation of said member causes said impact pellets to be propelled against said casting and into engagement with said fins so as to knock the fins off the casting.

4. The method according to claim 3 wherein said blades have inner ends (26) which are spaced radially from the axis of rotation of said member and said impact pellets (30) are fed onto the inner ends of said blades.

5. The method according to claim 3 wherein said impact pellets are fed onto said blades by forced air directed toward said blades.

6. The method according to claim 5 wherein said impact pellets and said forced air are directed toward said blades through a supply conduit (24) which terminates at a distance from said blades slightly greater than the largest diameter of said impact pellets.

7. A method for de-finning a casting having fins projecting therefrom which consists of propelling against said casting a plurality of impact pellets so that some of said pellets strike said fins, said impact pellets being formed of metal and having sufficient mass to remove said fins from said casting upon impact.