US2956318A

US2956318A - Forming pattern or form bar

Info

Publication number: US2956318A
Application number: US738061A
Authority: US
Inventors: Roy C Hathorn; Gordon L Turner
Original assignee: Individual
Current assignee: Individual
Priority date: 1958-05-27
Filing date: 1958-05-27
Publication date: 1960-10-18
Anticipated expiration: 1977-10-18

Description

Oct. 18, 1960 R. c. HATHORN EI'AL 2,956,318

FORMING PATTERN OR FORM BAR Filed May 27, 1958 POYCHATHORN GORDON L.TURNER INVENTORS United States Patent FORMING PATTERN OR FORM BAR Roy C. Hathorn, 1309 Kilby Terrace, and Gordon L. Turner, P.0. Box 133, both of Anniston, Ala.

Filed May 27, 1958, Ser. No. 738,061

9 Claims. (Cl. 22-22) This invention relates to mold forming apparatus and particularly to a pattern or form bar for forming hollow molds and compacting and shaping mold forming material within hollow flasks employed in casting hollow cylindrical products, such as cast iron soil pipe, or the like.

More specifically the present invention relates to a sand or other mold forming material compacting pattern or mandrel particularly adaptable for use in machines for centrifugally casting hollow cylindrical products and may be employed in various types of such machines now on the market, one such machine or apparatus being disclosed in Patent No. 2,449,900 issued September 28, 1948,

to L. L. Johnston.

In the forming of molds for use in casting cylindrical objects dilficulty has been heretofore encountered in maintaining concentricity between the flask and the mold cavity and in providing uniform hardness throughout the entire mold, so as to produce a cast product of uniform thickness and true concentricity throughout, and various forms of mold forming bars or patterns have been devised to provide such results, one such being disclosed in Patent No. 2,449,387 issued March 7, 1950. While the mold forming bars or patterns heretofore devised have in some measure improved on the formation of the sand molds, they have not satisfactorily overcome the difliculties.

While the mold forming bars or patterns of the type just referred, to provide very concentric molds, their use occasions much trouble with the diameter of the mold due to the fact that the mandrel or pattern is loaded on one side. Any variation in moisture or green compression strength of the sand used for making the mold is reflected in variation of load on the mandrel or pattern causing the mandrel to deflect more with dry sand and less with wet sand. This brings about a variation of mold diameter which limits the minimum mold diameter that can be made.

The mandrels or forming bars now in use whip or are subject to deflection when in use resulting in lack of uniform concentricity between flask and mold cavity and thick and thin walls of the mold causing uneven thicknesses and lack of uniform outer surface of the cast product. Various shapes of mold forming bars have been provided to compensate for such whipping or deflection of parts of the mandrel or forming bar, but since such deflection of the forming bar is not a constant at all operating conditions such devices cure the fault only partially and often not at all.

The present invention provides a pattern or forming bar which under all operating conditions will provide a mold of uniform thickness and hardness throughout and one which is so shaped that symmetrical loading on the bar is provided which results in uniform concentricity between the flask and the mold cavity, thereby producing a product of uniform thickness, and straight outer surface throughout, as well as one which irrespective of variation of moisture or green compression strength of the sand used, will provide correct, desired and uniform diameters of mold, even in small diameter pipe.

With these and other objects in view, as may appear from the accompanying specification, the invention consists of various features of construction and combination of parts, which will be first described in connection with the accompanying drawings, showing a forming pattern or form bar of a preferred form embodying the invention and the features forming the invention will be specifically pointed out in the claims.

In the drawings,

Figure 1 is a longitudinal section through a flask showing the pattern or forming bar therein, in side elevation.

Figure 2 is a cross section through the flask, mold and forming bar taken on the line 22 of Figure 1.

Figure 3 of the drawing is a cross-section,'similar to Figure 2 only showing a modified form of the forming bar or mandrel.

Figure 4 is a view similar to Figures 2 and 3 only showing a still further modified form of the forming bar or mandrel.

Referring more particularly to the drawings, there is shown a cylindrical flask 1 formed of any suitable material (preferably cast iron) and as is used in centrifugal casting machines as above referred to. The flask 1 has the usual one or two enlarged end portions 2 to permit formation of the hell or bell ends of a pipe cast therein.-

While in the drawings the flask 1 is shown as having both its ends enlarged, it is to be understood that'the present invention is not limited for use in such specific flasks, but

embodies the use of various forms of flasks, such as those of uniform diameter throughout, or with only one enlarged end.

Cooperating with the flask to form a mold therein such;

shown in Figure 2 of the drawings and it has a maximum diameter substantially equal to the interior diameter of the mold to be formed in the flask 1, with a minimum diameter a predetermined amount less than the maximum diameter.

The minimum diameter of the forming bar 4 is such that substantially crescent shaped spaces, indicated at 6 are provided within the interior of the mold at opposite sides of the forming bar 4. The forming bar 4 and any enlargements on its ends are elliptical throughout their entire length, and the forming bar 4 proper is of uniform diameters of varying radial degrees throughout its entire ength.

The flask and forming bar 4 are adapted for use with various type of centrifugal casting apparatus or machines on the market and in some instances the flask 1 will be rotated during formation of the mold and in others the forming bar 4 will be rotated, depending upon conditions and the particular type of apparatus with which the flask 1 and forming bar.4 are used. The effectiveness and efficiency of the forming bar is equal in either instance.

In operation the flask is positioned to receive sand;

or other mold forming material and the forming bar 4 is inserted axially into the mold and held therein by outside means (not shown). Such holding means depends upon the type of casting apparatus with which the forming bar is used. After the forming bar 4 is axially located in the flask, either the flask 1, of the forming bar 4 is rotated, again depending upon the type of casting apparatus with it is used. During such rotation sand is blowin into the flask from one end. The rotary motion causes successive formation of the crescent shaped spaces 6 about the in- Patented Oct. 18, 1960 the'bar; 4 rotates within the flask 1, the crescent: shaped spaces (St atany givenpoint' relative to the flask 1 open and close, and itsclosing action forces the sand outward.

or radially resulting in compacting the sand and toelimh natevoid's or soft spots in the-sand mold, as well aspro-.

vidinga mold of uniform thicknessthroughout its length. The rate of pulsation or opening and closing of the spaces 6 is controlled by the speed of rotation of eitherthe flask 1- orforming bar 4 and therefore the moldhardness may be very closely controlled. rectly proportional to reduction in cross sectional area of the mold creates a strong tendency to center the forming bar 4' in theflask 1. In other words, if the forming bar or pattern 4i's oft center or eccentric with the'flask 1 and the sand mold becomes harder on the thin side (formed because of'the eccentric position of the forming bar 4') the forming bar 4 will be forced back to center of the flask 1. d

This concentn'city of the mold will be maintained within very close limits which is necessary for good results in centrifugal casting.

Whe-n large patterns or forming bars 4 are used for making large diameter cylindrical products the above procedure is varied slightly.

In such instances the flask 1 and forming bar 4 are stationary while sand in a measured quantity is injected into the flask. After the sand is injected into the flask the rotation is started and due to the elliptical cross secion formation of the forming bar 4 the sand will be compacted to the desired mold hardness, with uniformity oft-he mold throughout and freedom from soft spots or .voidswith a few rotations, in some instances one or two complete turns of the forming bar 4 or flask 1.

Thus it will be seen that by providing a forming bar of elliptical cross section with its maximum diameter substantially equal to the desired interior diameter of the rnold to be formed and its minimum diameter such as to provide the substantially crescent shaped sand receiving spaces great flexibility of use is provided, permitting its use to cover the entire range of soil pipe from 2" diameter through 15" diameter, the size of the forming bar! and its various diameters being dependent of course npon'the size of pipe to be cast.

While in the foregoing the mold forming bar or mandrel has been described as elliptical in cross section and forming crescent shaped sand receiving recesses or pockets in advance of the sweeping maximum diametrical portions of the bar, it is'to be understood that mold forming bars of cross section other than elliptical (but not round) may be employed so long as such cross-sectional configuration is symmetrical about its axis and provides sand receiving recesses, confined between two major diameter portions of the bar and in advance of a successive sweeping major diametrical portion.

In Figure 3 of the drawings the mold forming bar 20 is shown as triangular in cross section with its apices rounded as shown at 21. With the mold forming bar or mandrel triangular in cross section three sand receiving recesses, 22 are formed in the mold 23, each space confinedbetween two major diameter portions of the bar, as are the crescent shaped recesses or spaces 6 confined between two major diameter portions of the el1ipti- Mold hardness being di-.

cal bar 4, so that upon rotation of either the mold forming bar 20 orthe flask 25 the action will be the-same as that hereinabove described in connection with the structure shown in Figures 1 and 2 of the drawings.

Figure 4 of the drawings shows a mold forming bar or mandrel 30 which is square in cross section with its mold surface engaging corners rounded, This form while providing four points of major diameter and four sand receiving spaces or pockets operates. in the same: manner as the forms of the invention shown in Figures 1, 2 and 3 of the drawings;

The present invention is not limited in use to-the making of molds for'centrifug-al casting, but may be employed in making cores for foundry use or for compacting any practical material in cavities.

What is claimed is:

1. Mold forming apparatus comprising a flask adapted 7 to contain a hollow body of mold form-ing material, and

a mold forming bar extending axially within said flask,

said mold forming bar beingnon-circular incross section and shaped to be symmetrical of its axis to form a-true geometrical figure in cross section and free'of surfaces projecting beyond its true geometrical sides and topro vide in each cross-sectional plane thereof at least two portions of major radius andat least two portions ofminor radius to form sand receiving recesses between said major and minor radius portions in the flask each of said major radius portions connected to aminor radius: portion by a convexly curved surface, whereby in use sand will be swept from the spaces into uniform compact thickness within the flask.

2. Mold forming apparatus as claimed in claim 1,

wherein saidmold forming bar has at least one enlarge ment on its ends of the same cross-sectional configura tion as the bar.

3; Mold? forming apparatus as claimed in claim 1,

wherein said mold forming bar is elliptical in cross sec. tion and of uniform maximum and minimum diameters.

throughout its length.

4. A mold forming bar as claimed in claim 1, where-.

wherein said mold forming bar is elliptical in cross sec tion.

7. Mold forming apparatus as claimed in claim 1, wherein said mold forming bar is substantially square in cross section.

8. Mold forming apparatus as claimed in claim 1, wherein said mold forming bar is substantially triangular.- in cross section.

9. A mold forming bar as claimed in claim 3, having at least one enlargement on its ends, said enlargement" being elliptical in cross section.

References Cited in the file of this patent UNITED STATES PATENTS 402,029 McNeal et' a1. Apr. 23, 1889 1,302,816 Lemoine May 6, 1919' 2,499,387 Johnston Mar. 7, 1950 FOREIGN PATENTS 193,075 Germany Dec. 13, 190-7.