US3468364A - Riser former - Google Patents

Description

Sept. 23, 1969 s. R. RUSK ET AL RISER FORMER 2 Sheets-Sheet 1 Filed Oct. 20, 1966 Sept. 23, 1969 G. R. RUSK ET AL 3,468,364

RISER FORMER Filed Oct. 20, 1956 2 Sheets-Sheet :5

mum u////// Y W Y 0 y 8 .3 v 6 Mm United States Patent 3,468,364 RISER FORMER Gerald R. R usk, Naumee, and Marshal W. Wical, Sydney,

Ohio, asslgnors to The Freeman Supply Company, To-

ledo, Ohio, a corporation of Ohio Filed Oct. 20, 1966, Ser. No. 588,149 Int. Cl. 1322c 7/00; B28b 7/28; B29b N06 US. Cl. 164-235 9 Claims ABSTRACT OF THE DISCLOSURE A riser form which can be placed on a pattern, and sand tamped thereabout, following which the riser form can be raised part way out of the tamped sand and additional sand tamped thereabout, and the process repeated as desired to produce an opening in packed sand that is longer than the riser form without sand falling into the cavity thus formed.

The present invention relates to forms for producing risers in sand castings and the like; and to a method of making hollow walled frusto-conical sections usable therein.

Sand molds for casting metals include passageways leading from the mold cavity to the exterior surface of the sand for an accessway for the molten metal to the mold cavity. Usually at least one other passageway leading to the exterior surface of the sand is also provided for permitting the escape of air from the mold cavity as the air is displaced by the molten metal. These passageways are also used to store excess molten metal under conditions which allow the molten metal to flow into the mold cavity during the time that the molten metal cools and shrinks. These passageways are usually called risers. In some instances the risers through which the molten metal is poured are called sprues, while the venting passageways are called risers, or vents; but in the present application, no distinction is made, and the word risers will be used to refer to both sprues and vents.

A considerable depth of sand is usually provided above the mold cavity to provide insulation for molten metal in the mold cavity, and to insulate molten metal stored in the riser cavities. It will be apparent that it is necessary to hold the metal in the risers molten while the metal in the main mold cavity is cooled in order that material from the risers can flow back into the mold cavity during the time that the material in the mold cavity is cooling and shrinkage is taking place. In some instances the depth of sand above the mold cavity may be two feet or more. A sizable percentage of the total time required to form sand molds, therefore, is taken up in the formation of risers. In some instances risers are formed by scooping out the sand by hand after the sand is compacted about the pattern. In other instances, solid wooden forms have been positioned adjacent the pattern, and the sand compacted about the wooden forms to form riser cavities. Wooden forms have never been completely satisfactory because the molding sand abraids the wood. The rate of abrasion of wood forms is quite high; particularly when the sand is blown into position around the forms, and wooden forms are usually erroded to a concave configuration. Riser forms must have a controlled very slight taper in order that they can be pulled longitudinally out of the sand without disrupting the sand. Wooden forms have had such a short useful life that they are unsatisice factory and costly to used. In addition, foundry equipment 1s handled roughly as it is moved about by the heavy foundry equlpment, with the result that a large percentage of wooden riser forms become dented, chipped or split before their useful life has otherwise been brought to an end. In addition, wood absorbs moisture from the sand to prevent the sand adjacent the wooden form from being held together. This unbonded sand sometimes falls into the mold cavity when the wooden form is withdrawn.

The risers for sand molds must be of appreciable cross section, and must extend to the outer top surface of the sand in order that the riser form can be withdrawn. It is a quite common occurrence for sand from the compacted body of sand to fall back into the mold cavity during the withdrawal of the riser form. In addition, loose sand and dirt quite often fall from adjacent equipment into the riser passageways. Sand and debris in the bottom of the mold cavity is not flushed out by molten metal, nor is its presence discovered before casting; so that the art is plagued with an appreciable percentage of casting rejects caused by foreign material in the mold cavities.

An object of the invention is the provision of a new and improved riser form which is inexpensive to manufacture, is rugged in its construction, is not abraided by the sand to any significant degree, and which has almost indefinite life.

Another object of the invention is the provision of a new and improved riser form which can be made of a standard length less than the total depth of sand in which it is capable of forming a riser.

A more specific object of the invention is the provision of a new and improved riser form of the immediately above described type having a collapsible handle which permits sand tamping machinery to pass over the riser form while compacting sand about the riser form.

Another object of the invention is the provision of a new and improved riser form having replaceable inner neck portions which can be quickly changed as the need arises.

A still further object of the invention is the provision of a new and improved riser form, which when withdrawn from the sand, leaves a heat destructible disk at the bottom of the riser cavity adjacent the pattern to prevent debris from entering the mold cavity.

A still further object of the invention is the provision of a new and improved riser form of the immediately above mentioned type wherein the heat destructible disk is contoured to provide a notch in the metal which solidifies in the riser, to permit the solidified metal to be knocked from the casting without damage to the casting.

The invention resides in certain constructions and combinations and arrangements of parts; and further objects and advantages of the invention will become apparent to those skilled in the art to which it relates from the following description of several preferred embodiments described with reference to the accompanying drawings forming a part of this specification, and in which:

FIG. 1 is an elevational view in section through a sand tamped flask having a pattern, and a riser form embodying the present invention, therein;

FIG. 2 is a longitudinal sectional view through a riser form embodying the invention;

FIG. 3 is an elevational view of a collapsible form that is used in the preferred method of manufacture of the riser form of the present invention;

FIG. 4 is an elevational view similar to FIG. 2, but

showing the collapsible form coated with hardenable material;

FIG. is an elevational view in section of apparatus that includes a mold having an internal cavity in which the collapsible form shown in FIG. 4 is positioned;

FIG. 6 is a longitudinal sectional view through an object molded by the apparatus shown in FIG. 5;

FIG. 7 is a longitudinal sectional view similar to FIG. 2 but showing another embodiment of the invention; and

FIG. 8 is a longitudinal sectional view similar to FIG. 7 but showing still another embodiment of the invention.

The riser forms of the invention are intended to be used in the manner shown in FIG. 1. A flask 10 is placed upon a pattern plate or board 12 having a pattern 14 thereon. The riser form 16 of the present invention is positioned with its lower end resting against the pattern 14, and sand 18 is tamped about the pattern 14 and riser form 16 until the level of the sand reaches the top of the riser form 16. The riser form 16 includes a collapsible handle H, and after the sand has been tamped to a level approximately coextensive with the top of the riser form, the handle H is extended to the position shown in FIG. 1, following which it is pulled outwardly to raise the riser form 16 outwardly of the tamped sand. The riser form 16 will usually be raised by a distance approximately equal to half of the height of the riser form, following which another layer of sand is positioned about the riser form and is tamped in place. This process is repeated until the tamped sand reaches a desired level usually coextensive with the top surface of the flask 10. During each tamping operation, the collapsible handle H is allowed to fall back upon the main body of the riser form, so that the tamping apparatus can pass over and around the riser form without danger of striking the handle and disrupting the tamped sand.

The riser form shown in FIG. 2 generally comprises a frustrum 20 of a right circular cone, the side walls 22 of which are thin and light but yet rugged. The outer surface of the side walls 22 must be smooth so that the riser form can be pulled outwardly, in the manner above described, without disrupting the packed sand. In addition, the sidewalls must have a closely controlled taper of approximately of an inch per foot of longitudinal length of the riser form, so that the riser form can be pulled outwardly without disrupting the sand, and so that a large annular area does not exist between the tamped sand and the partially withdrawn riser form through which latter applied sand can fall into the void formed by the partially withdrawn riser form. The bottom end of the riser form 20 will usually be provided with an annular end wall 24 having a centrally located opening 26 therethrough for access to the inside of the riser form for reasons which will later be apparent. In order that sand which falls upon the riser form will not pass through the riser form, the upper end of the riser form 20 is closed off by the upper end wall 28. Sand tamped about the frustrum, tapered as above described, develops a considerable grip on the riser form. The preferred handle arrangement H therefore, for pulling the riser form outwardly, is one about which the fingers can be wrapped.

It has been found that handles about which ones fingers can be wrapped when permanently located above the top surface of the riser form, is struck occasionally by the sand tamping machinery. The preferred handle arrangement, therefore, normally rests on the top surface of the riser form, and is extensible to an outer position where the fingers can surround the grip portion 30. This is accomplished in the embodiment shown in FIG. 2 by an axially extending rod 32 projecting from the grip 30, and which extends through a centrally located opening 34 in the upper end wall 28. The bottom of the rod 32 is provided with an abutment 36 which is larger than the opening 34 and which bears against the bottom of the upper end wall 28 when the handle H is pulled upwardly. The

grip 30 has a length and a width which is greater than the opening 34, so as to close off the opening 34 when the handle engages the upper end wall 28. This arrangement, therefore, prevents sand that is being tamped about the riser form from falling through the riser form into the partially completed riser cavity. The grip 30 is preferably rectangularly shaped, so that it can be rotated or otherwise moved to sweep loose sand away from the center portion of the upper end Wall 28. In addition, the opposite side walls of the handle are preferabl recessed as at 38 to facilitate grasp of the handle while it is hearing against the upper end wall 28.

In order that an invention will have large scale commercial acceptance, it must be capable of being produced inexpensively. As previously indicated, the taper of the outer surface of the side walls 22 must be accurately controlled. In the preferred method of manufacture, the controlled taper is inexpensively produced by the process shown in FIGS. 3 through 6 of the drawings. In the process shown, a generally cylindrical rubber bag 40 capable of inflation is coated with a hardenable resinous material, and the coated bag is inserted in a mold 42 having a cavity 44, the inside surfaces 46 of the side walls of which are provided with the desired taper. The bag 40 includes a boss 48 having a conventional tire valve 50 therein to which an air hose can be attached for inflating the bag. In the preferred manner of use, several layers of plastic impregnated fibrous reinforcing 54, preferably a glass fabric, are embedded in the plastic. Plastic impregnated fabric 52 is also applied to both ends of the bag 40. The edges of the fabric 52 are folded over the generally cylindrical surfaces of the bag 40, and one or more layers of fibrous reinforcing are wrapped around the generally cylindrical surfaces 56 of the bag. A hardenable resinous material 58, preferably a cross linking polyester is then applied to the fibrous reinforcing 54 in a manner which will impregnate the fibrous reinforcing. This is preferably accomplished using a brush, not shown, which simultaneously applies a mixture of the cross linking resin and a curing agent onto the reinforcing material.

The bag 40 having the reinforcing and resin thereon is then slipped into the central cavity 44 of the mold 42, with the small diameter end 60 of the mold positioned against a fixed abutment plate 62 and the boss 48 of the bag projecting through a hole 64, of the plate 62. A movable abutment plate 66 is thereafter positioned against the opposite end 68 of the mold 42. A lead screw 70 supported by a threaded abutment 72 is turned down upon the movable abutment plate 66 to sandwich the mold 42 between the end abutment plates 62 and 66. Thereafter the bag 40 is inflated to expand the layer of fibrous reinforcing and resin outwardly against the side surfaces 46 of the mold cavity 44. During this movement, the layers of glass fabric move relative to each other, and they are held in this position until the resin has had time to set. The air bag 40 is then collapsed, the lead screw is loosened, and the mold removed. In most instances it will be desirable to use a parting agent such as a silicone, a talc, or a soap on the surfaces of the mold cavity and air bag, to facilitate the removal of the molded article from the mold cavity. The opening 26 is cut in the end 24, the air bag 40 is removed through the opening 26, and the resulting structure finish cured. The molded article will have the general shape shown in FIG. 6. Thereafter, the opening 34, seen in FIG. 2, is drilled through the end wall 28, the rod 32 is slid through the opening 34, and the abutment 36 is fixed to the inner end of the rod 32. The opening 26 facilitates the attachment of the abutment 36 to the rod 32.

The embodiment of riser form shown in FIG. 7, is generally similar to that shown in FIG. 2, and differs principally therefrom in that a neck portion 82 is aflixed to the small diameter end of the riser form. Those portions of the embodiment shown in FIG. 7 which correspond to similar portions of the embodiment shown in FIG. 2 are designated by a like reference numeral characterized further in that a prime mark is affixed thereto. While the neck portion 82 may be an integral part of the riser form 20, it is preferably made to be detachable from the frustoconical section. While any suitable quick disconnect means can be used to secure the neck portion 82 to the frustoconical portion, the neck portion 82 is conveniently molded from plastic to include an upper end projection 84 of a shape for insertion through the opening 26. The upper end of the projection 84 is provided with a radially deformable bulge 86 adapted to bear against the upper or inner surface of the end wall 24'. The neck portion 82 is installed upon the frusto-conical section by pressing the projection 84 through the opening 26 during which time the bulge 86 is deformed. Once the bulge 86 emerges from the opening 26, the bulge 86 expands outwardly over the top surface of the end wall 24' to lock the neck portion 82 in position.

The neck portion 82 has a reduced diameter end 88 spaced from the frusto-conical section, and toward which the side walls of the neck portion 82 slope in an uninterrupted manner, so that it is easily removed endwise of the sand packed in the vicinity of the pattern. The end surface 88 is adapted to bear against the pattern, and the side surfaces 90 preferably slope from the frusto-conical section to the end surface 88 with a reversed curvature to form a cup-shaped cavity adjacent the mold cavity and which cavities are separated by a narrow neck. A bevel 92 is preferably provided at the juncture of the side surface 90 and end surface 88 to provide a notch in the metal cast in the mold which it produces. This notch provided in the cast metal produces a weakened area which facilitates the removal of the riser metal from the molded object. The neck portion 82 may be made of any suitable material such as plastic, and may be secured to the riser section 20 in any suitable manner as by a bolt. The neck portion 82 can also be made of a plastic foam or other heat destructible material and be left in the mold. The portion 82 may have a simple press fit to the section 20, and the grip of the mold sand used to provide separation when the section 20 is withdrawn from the mold.

The embodiment shown in FIG. 8 is generally similar to that shown in FIG. 7 and dilfers principally therefrom in that it includes a separable notch forming disk 94 on the lower end of the neck portion. Those portions of the embodiment shown in FIG. 8 which correspond to similar portions of the embodiment shown in FIG. 7 are designated by a like reference numeral characterized further in that a double prime mark is afiixed thereto.

In some instances, the riser metal will not break cleanly outside of the molded object when the notch is located at the surface of the molded object. It has not been possible heretofore to mold a notch producing projection in the sand at a location spaced apart from the pattern, and where it was necessary to provide a notch at this location, it has been necessary for the pattern maker to carve out the juncture of the riser cavity and mold cavity so that the narrowest section of the riser cavity is spaced from the mold cavity. In the embodiment shown in FIG. 8, however, the notch forming disk 94 is outwardly fiaredso that the narrowest cross section of the riser cavity whlch it forms is spaced from the mold cavity. It is not possible to withdraw the notch producing disk 94 from the sand without disrupting the sand. In the embodiment shown in FIG. 8, the notch forming disk is made separable from the neck portion 82' so that the notch forming disk 94 stays in position in the sand when the remainder of the riser form is withdrawn. The notch forming disk 94 is made of a heat destructible material, preferably foamed polystyrene, so that it quickly disintegrates when left in place and when contacted by the molten metal. The disk 94 may be made easily detachable from the neck portion 82' in any suitable manner, and as shown in the drawing, the notch forming disk 94 is provided with an integral boss 96 that has a slight interference with the side walls of a cylindrical recess 98 in the lower end surface 88' of the neck portion 82'. The notch forming disks, therefore, can be simply and inexpensively produced so that they can be expendible, and it will be seen that a decided advantage exists in leaving these heat destructible disks in place to prevent sand and debris from entering the mold cavity prior to the time that the pour takes place.

While several embodiments of the invention have been described as being formed from a polyester resin reinforced by a glass fabric, the invention is not limited thereto, and any suitable fibrous reinforcing and resin such as an epoxy resin can be used, although in some instances, the fibrous reinforcing may not be necessary.

While the invention has been described in considerable detail, we do not wish to be limited to the particular embodiments shown and described, and it is our intention to cover hereby, all novel adaptations, modifications, and arrangements thereof which come within the practice of those skilled in the art to which the invention relates.

We claim:

1. A riser form for sand molds, and the like, comprising: a thin walled frustrum of a right circular cone having large diameter and small diameter end surfaces, said frustrum having walls the surface of which is of a smooth molded plastic having a straight uninterrupted taper between said end surfaces of no more than approximately of an inch per foot, an end closure wall across said large diameter end and having at least one opening therethrough, a grip outwardly of said end closure wall, said grip being of a size and shape to completely overlie said opening, a projection on said grip extending through said opening, and abutment means on said projection to limit outward withdrawal of said grip.

2. The riser form of claim 1 wherein said surfaces of said projection have a sliding fit with respect to said opening, and said abutment means has sufiicient clearance to allow hand passage between said grip and said end wall.

3. The riser form of claim 1 wherein said walls are of a fiber reinforced polyester plastic.

4. A riser form for sand molds, and the like, comprising: a thin walled frustrum of a right circular cone having large diameter and smaller diameter ends, said frustrum having walls the surface of which is of a smooth molded plastic having a straight uninterrupted taper between said ends of approximately 7, of an inch per foot, an end closure section fixed across said large diameter end, a grip on said end closure section, and a short riser neck portion connected to said small diameter end, said neck portion being contoured to provide an end surface of predetermined cross section and having sharply diverging side surfaces terminating adjacent the periphery of said small diameter end, and whereby said form forms a sand cavity having a narrow cross section between a mold cavity and riser basin to cause molten metal to solidify first in the narrow cross section and thereafter restrict how of molten metal from the cavity to the riser basin.

5. The riser form of claim 4 wherein said neck portion is detachably mounted to said frustrum.

6. The riser form of claim 4 wherein said small diameter end of said frustrum includes an annular end wall with a centrally located opening therethrough, and said neck portion has an end projection with a radially deformable bulge positioned to extend over the opposite end surface of said end wall and retain said neck portion against said small diameter end of said frustrum.

7. The riser form of claim 6 having an outwardly flared notch forming disk removably retained on the end of said neck portion.

8. The riser form of claim 7 wherein said notch forming disk is made of a heat destructible foamed material.

'9. The riser form of claim 8 wherein said neck portion has a longitudinally extending opening and whereby the neck portion separates from said disk when sand is 7 8 packed around said riser former and the riser form is 3,177,537 4/ 1965 Horton 164244 X withdrawn from the packed sand. 3,340,923 9/1967 Benfield 164-244 References Cited I. SPENCER OVERHOLSER, Primary Examiner UNITED STATES PATENTS 5 JOHN 5. BROWN, Assistant Examiner 411,962 10/1889 Heaphy 164-244 695,146 3/1902 Davis 164-244 3,036,349 5/1962 Edgeflon 164-244 X 249-175

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