US3747668A

US3747668A - Centrifugal casting apparatus

Info

Publication number: US3747668A
Application number: US00185793A
Authority: US
Inventors: J Schroll; W Sroke
Original assignee: SCHIFFBAU ING BUERO VEB
Current assignee: SCHIFFBAU ING BUERO VEB; VEB INGENIEURBURO SCHIFFBAU DL
Priority date: 1970-10-16
Filing date: 1971-10-01
Publication date: 1973-07-24
Anticipated expiration: 1990-07-24

Abstract

A centrifugal casting apparatus is provided with means for supporting an article in a predetermined position with respect to a mold pattern in the casting apparatus whereby the article will be imbedded in the centrifugally cast body; counterweights are provided within the casting apparatus for compensating for the buoyancy of an article being imbedded where such article has a specific gravity that is less than the casting material.

Description

United States Patent [191 Schroll et al.

[4 1 Jul 24, 1973 CENTRIFUGAL CASTING APPARATUS [75] Inventors: Josef Schroll; Werner Sroke, both of Rostock, Germany [73] Assignee: VEB Ingenieurburo Schiifbau,

Rostock-Osthafer, Germany 22] Filed: o1.1,1971

[21] App1.No.: 185,793

[30] Foreign Application Priority Date Oct. 16, 1970 Germany WP 31 b2/l50 720 Jan. 29, 1971 Germany P 21 04 148.5

[52] US. Cl. 164/287 [51] Int. CL B2211 13/00 [58] Field of Search 164/286, 287, 288,

[56] References Cited UNITED STATES PATENTS 2,052,043 8/1936 Weaver 164/300 X 1,552,246 9/1925 Thompson 164/332 X 1,963,400 6/1934 Campbell 164/298 X Primary Examiner-J. Spencer Overholser Assistant Examiner-John S. Brown Attorney-Cushman, Darby & Cu shman [57] ABSTRACT A centrifugal casting apparatus is provided with means for supporting an article in a predetermined position with respect to a mold pattern in the casting apparatus whereby the article will be imbedded in the centrifugally cast body; counterweights are provided within the casting apparatus for compensating for the buoyancy of an article being imbedded where such article has a specific gravity that is less than the casting material.

2=Claims, 1 Drawing Figure CENTRIFUGAL CASTING APPARATUS The present invention relates to an improved centrifugal casting apparatus, and more specifically to an apparatus having means for positioning an article in a predetermined position with respect to the mold pattern whereby the article will become imbedded in the object being cast. The present invention further provides means for compensatingfor the differences in specific gravities between the article being imbedded and the material from which the cast article is to be made.

BACKGROUND OF THE INVENTION The superior structural quality of metal articles that are formed by centrifugal casting has long been known since articles made by a centrifugal casting process may be formed with very precise engineering tolerances and yet can be produced in large quantities at costs that are generally less than those of articles which are formed by static casting methods.

However, when it is desired to form a cast article having a precisely located openings, ducts or borings, diffrculties have been encountered in constructing suitable mold patterns for casting such articles particularly where it was desired to imbed objects having a specific gravity or density differing from that which the cast article is made. In particular, when it was desired to imbedhollowbodies such as tubes into the wall of an article being cast, centrifugal castng methods could not be employed since it was difficult to precisely maintain the positionof the hollow bodies with respect to the molten casting material, when the casting apparatus was rotated at high speeds resulting in the creation of large centrifugal forces which'tended to separate the hollow bodies from the casting material.

SUMMARY OF THE INVENTION The improved centrifugal casitng apparatus of the present invention consists in the provision of support members which securely locate and maintain an article which is destined to be imbedded in the cast article in a predetermined position with respect to the mold pattern which is formed in the centrifuge housing. By way of example, where the article being cast is a cylinder bushing and the article being imbedded in the wall of the cylinder bushing is a cooling tube, during the rotation of the centrifuge, the tube, which is a hollow body, will experience a radial force on account its lighter specific gravity or density with respect to the molten iron which is used to formthe cylinder bushing. As the centrifuge operates, the molten metal will experience a centrifugal force forcing it into intimate contact with the sand pattern whereas the hollow tube will become buoyant as the depth of the molten metal increases and surrounds the tube. To counteract such buoyancy and to maintain the tube in the desired position, the present invention provides support means including one or more counter-weights which are securely attached to the tube during the casting process. The mass of the counter-weights is determined by the difference in specific gravities or densities of the two articles.

' Use of the apparatus of the present invention will facilitate the casting of pieces wherein articles may be very precisely imbedded within such pieces without adversely affecting the quality of the casting.

BRIEF DESCRIPTION OF THE DRAWING In the single FIGURE, there is illustrated a cross sectional view taken along a portion of the longitudinal axis of a generally cylindrical, centrifugal casting apparatus of the present invention.

DETAILED DESCRIPTION OF THE INVENTION Referring now to the drawing, there is illustrated a portion of a substantially cylindrical centrifugal casting apparatus generally designated as 10 which is adapted to cast hollow cylindrical bodies such as cylinder bushings, for example. The apparatus 1l0 consists of a cylindrical centrifuge housing 12 which is adpated to be rotated about its longitudinal axis 14. It will be understood, of course, that the housing 12 is formed to be rotationally balanced with respect to the axis 14 whereby the axis will pass through the center of mass of the housing 12. Within the housing 12, there is disposed a generally cylindrical container 16 which is mounted within housing 12 prior to the deposition of a pattern molding material as at 18 within container 16. Conventionally one end of both the housing 12 and container 16 are closed, the pattern, molding and casting materi als being-introduced at the other open end. The patern molding material 18 preferably consists of packed fine grain sand, but it will be understood that other mold material may be employed. In forming a pattern in material 18 a pattern 19 (not shown) which conforms in outer dimensions and shape tothe object to be centrifugally cast (but may be hollow) is introduced into cylinder 16 and the molding material 18 is tightly packed around pattern 19 whence the pattern is removed.

Subsequent to the forming of a pattern in material 18 within the housing 12, the housing 12 is then rotated by sutiable conventional means (not shown) such as rollers, gears or pulleys connected to a motor about its longitudinal axis l4, during which rotation, molten casting material 24 such as iron is gradually deposited in the interior of the mold pattern 18 as through opening 20 whereby the molten material will be spread evenly to a desired depth over the interior surface 22 of the mold pattern by virtue of the centrifugal force exerted thereon by virtue of the rotation of the apparatus.

When it is desired to embed an article such as a cooling tube 26 within the casting material 24, the present invention provides support members such as at 28, 29 and 30 which at one end securely support tube 26, the other end of each support member being securely attached to base members such as base member 32 for member 28, and base member 34- for

members

29 and 30, respectively. The material of construction of the supportmembers depends upon the casting material since the supports will remain within the cast article and thus should be compatible therewith. For example, if the casting material is gray iron, support members 28 through 30 may be conveniently fabricated from a steel containing about 0.15 percent carbon. The

base members

32 and 34 may, in turn, be positioned on locating

pads

36 and 38 which due to their shape allow the flat bottomed support members to be easily mounted on the curving interior surface of mold container 16.

Themanner in which the support members 28' through 30, the

basemembers

32 and 34 and the locating

pads

36 and 38 are assembled together will now be discussed. V

Pattern 19 discussed above includes dowel holes into which dowels are placed which are removable through the hollow center of pattern 19. These dowels press

base members

32 and 34 against

pads

36 and 38, respectively, while material 18 is being packed about pattern 19. The dowels and pattern are then removed and the pin-like lower portions of support members 28 through 30 are inserted through the holes formed in material by the dowels. The pin portions may be threaded and received within threaded apertures within

base members

36 and 38.

In the illustrated embodiment, the top portions of

support members

28, 29 and 30 are ring shaped at one end so that the cooling tube 26 may be inserted therethrough-and held as to lateral movement while yet allowing longitudinal expansion and contraction of tube 26 during casting and cooling. It will be understood, however, that for articles of differing shapes, the various support members may be appropriately designed to retain such articles in place.

Since the volume of casting material 24 displaced by the cooling tube 26 has a greater specific gravity and density than the cooling tube 26, during the centrifuging process, a bouyant force radially directed towards the axis of rotation 14 would normally arise. To counter-balance this bouyant force, the

base members

32 and 34 are constructed from a material and are so arranged so as to act, in effect as counter-weights so that the rotation equilibrium of the centrifuge housing, and casting material 24 will be maintained. Of course, the base members also exceed material 18 in specific gravity and thus do not tend to float upon this material. F urther, sincethe base members are recovered following casting and do not form a portion of the cast body they do not need to be made of a material compatible with casting material 24.

The foregoing has been a description of an illustrative embodiment of the principles of the present invention and it will be understood that various changes and modifications may be made therein without departing from the spirit and scope of the present invention as defined in the appended claims.

What is claimed is:

1. In a centrifugal casting apparatus of the type having a housing mounted for rotation about an axis passing through the center of mass of the housing, means removably positioned within said housing for containing a mold forming material, said mold forming material being spaced from said axis of rotation so that an opening is provided along at least a portion of said axis for receiving casting material within said housing, the improvement comprising support means supported by said containing means for maintaining an article having a specific gravity less than the specific gravity of the casting material in a predetermined position with respect to said axis of rotation during the rotation of said housing, said support means including at least one counterweight embedded in said mold forming material for counterbalancing the bouyancy of a said article.

2. The apparatus as claimed in claim 1 wherein said support means further includes at least one support member attached at one end to said counterweight and extending generally radially inwardly through the mold forming material toward said axis of rotation, the other end of said support member having means for securely engaging said article to hold said article in said predetermined position with respect to said axis.