US2821755A - Molding apparatus having mandrel with eccentric portion - Google Patents

Description

Feb.4, 195 8 J. A.ILASATER 2,821,755

MOLDING APPARATUS HAVING MANDREL WITH ECCENTRIC PORTION "iFiled' Nov. 1, 1955 2 Shets-Sheet 1 FIG INVENTOR. JOHN A. LASATER Feb. 4, 1958 J. A.'L.=A-SATER 2,821,755.

MOLDING APPARATUS HAVING MANDREL WITH ECCENTRIC PORTION Filed Nov. l,- 1955 2'Sheets-Sheet 2 INVENTOR. JOHN A LASATER United States Patent@ MOLDING APPARATUS HAVING MANDREL WITH ECCENTRIC PORTION John A. Lasater, Chattanooga, Tenn., assignor to Herman Pneumatic Machine Company, Pittsburgh, Pa, a corporation of Pennsylvania Application November 1, 1955, Serial No. 544,219

3 Claims. (Cl. 22-22) This invention relates to molding apparatus having a mandrel with an eccentric portion. It is concerned primarily with the formation of an elongated generally cylindrical mold of small diameter of compacted mold forming material such as may be employed in the casting of elongated articles such, for example, as elongated hollow articles such as lengths of pipe.

United States Patent No. 2,449,900 discloses apparatus for forming molds for centrifugal casting and centrifugally casting products therein. The present invention is applicable to the apparatus of said patent. Another form of apparatus adapted for modification in accordance with the present invention is disclosed in copending United States application Serial No. 427,842, filed May 5, 1954.

The patent and application above referred to disclose apparatus including a rotary hollow flask in which mold forming material may be compacted to form a mold whereafter the flask with the mold of compacted mold forming material therein is employed for the centrifugal casting of elongated hollow objects. The present improvement in the art is concerned particularly with the forming of the elongated hollow mold. After the mold is formed in accordance with my invention the elongated hollow ob ject may be cast as disclosed in said patent and application. Indeed, while I contemplate forming a mold of compacted mold forming material while rotating the flask at centrifugal speed, the mold which I form has utility otherwise than in the centrifugal casting field; it may be employed in non-centrifugal casting.

The patent and application above referred to disclose the introduction into a flask of finely divided mold forming material such as sand, graphite, a mixture of sand and graphite or other similar mold forming material, the initial spreading of the mold forming material about the interior of the flask through rotation of the flask at cenl flask while the flask rotates and the compacting of the mold forming material in the flask by the action of the mandrel. The mandrel is mounted for rotation but is not driven in its rotative movement. It turns through contact with the mold forming material. The mandrel is of smaller diameter than the mold being formed so the mandrel in effect rolls generally along the inside of the flask during mold formation While the flask is rotated at centrifugal speed. The mandrel is mounted in cantilever fashion in a bearing mounted in a carriage and the carriage may be advanced to project the mandrel into and through the flask, a complementary bearing being provided at the opposite end of the flask so that when the mandrel has been projected through the flask it is mounted in bearings adjacent both ends of the flask and is free to rotate. The relative transverse movement between the mandrel and the flask may be effected bymoving either the mandrel or the flask or both. In the above mentioned patent the mandrel is moved while in the above mentioned application the flask is moved. The patent and application disclose machines in which a plurality or battery of flasks are employed side by side. The present iiinvintion is applicable to a machine having one or more as s.

The apparatus disclosed in the patent and application above mentioned is suitable for forming pipe such as soil pipe of three-inch and four-inch size. If that apparatus is attempted to be utilized for forming pipe of smaller size such, for example, as two-inch soil pipe, a Very slender mandrel has to be used, the mandrel being so slender that if it were pressed continuously against the mold forming material in the flask during compacting of the mold forming material the mandrel would bend inwardly so that the mold formed thereby would be of undesirably reduced diameter at the center. When it is desired to form a mold which is cylindrical and of uniform diameter the bending or deflection of a slender cylindrical mandrel will result in the formation of a mold which is somewhat necked in at the center. To overcome the above explained difliculty in the making of molds for casting small diameter pipe and other elongated hollow objects the so-called bellied mandrel of United States Patent No. 2,499,387 was developed. The theory of the bellied mandrel is to compensate for deflection of the mandrel so that when the mandrel 1s deflected it will form a straight mold. However, with the bellied mandrel there may be some difficulty in obtaining uniform accuracy in mold size and shape.

I provide molding apparatus in which a slender mandrel may be employed for forming a mold for the casting of small diameter pipe, the mandrel being so slender that if it were pressed continuously against the mold forming material in the flask during compacting of the mold forming material the mandrel would bend inwardly so that the mold formed thereby would be of undesirably reduced diameter at the center. I form the mandrel with an eccentric portion which strikes the mold form-ing material with successive blows as the mandrel and flask rotate and the mandrel moves relatively to the flask away from the axis of the flask. Due to the fact that the mandrel is not pressed continuously against the mold forming material in the flask during compacting of the mold forming material the tendency to bend the slender mandrel is obviated. While at the moments when the mandrel is in contact with the mold forming material there may be a slight tendency to bend the mandrel that tendency is immediately overcome by the mandrel parting contact with the mold forming material. As the flask rotates the eccentric portion of the mandrel subjects the mold forming material in the flask to a succession of blows at circumferentially spaced apart portions of the flask. The mold forming material in the flask is intermittently engaged successively at circumferentially spaced apart zones extending lengthwise of the flask and thereby compacted against the flask. The intermittent engagement of the mold form-ing material in the flask by the mandrel is continued until a substantially circular uniformly compacted mold has been formed. Preferably during rotation of the flask with mold forming material therein at centrifugal speed the mold forming material is intermittently rolled in the flask successively at circumferentially spaced apart zones extending lengthwise of the flask whereby the mold forming material is compacted against the flask.

In referring to circumferentially spaced apart zones of the mold forming material with which the eccentric mandrel comes into engagement 1 do not necessarily mean that each such zone of engagement is separated from the zones at either side of it by a space; I simply mean that the zones progress circumferentially of the flask. Theymay overlap one another and indeed such overlapping is conducive to efliciency and efiective mold 3. formation. It is found that as the flask rotates the zones of engagement of the mandrel with the mold forming material creep along the flask circumferentially so that the result in the end'is a smooth-cylindrical mold rather than a fluted mold such as might be formed if the mandrel engaged the mold forming material at precisely the same places upon each revolution of the flask. The flask and mandrel are not geared together, the rotation of the mandrel being derived entirely from its contact with the mold forming material. There is, of course. some slippage and no special precaution need be taken to guard against tracking of the mandrel with the mold forrning material and consequent formation of a fluted mold.

Preferably the rotary hollow flaskhas an enlargement at an end thereof and the mandrel has an enlargement at an end thereof generally radially aligned with the enlargement in the flask, the enlargement in the mandrel being coaxial with the axis of rotation of the mandrel, the mandrel having an eccentric portion which strikes the mold forming material with successive blows as-the mandrel and flask rotate and the mandrel moves relatively to the flask away from the axis of the flask. For the formation of so-called double hub pipe the mandrel and flask have such enlargements at both ends.

In a preferred form of molding apparatus a rotary hollow flask is provided together with bearing means for supporting for rotation a mandrel extending within the flask and adapted to rotate therein as the flask rotates to compact mold forming material against the inside of the flask, means for relatively moving the flask and bearing means transversely of the axes thereof and a mandrel having a portion of circular cross section disposed in the bearing means so that the axis of said portion of. the mandrel is the axis about which the mandrel rotates in the bearing means, the mandrel having within the flask a portion which is eccentric to the axis of rotation of the mandrel, the eccentric portion of the mandrel striking the mold forming material in the flask with successive blows as the mandrel and flask rotate and the mandrel moves relatively to the flask away from the axis of the flask. Desirably bearing means are provided at both ends of the flask for rotatablysupporting the mandrel as above mentioned.

Other details, objects and advantages of the invention will become apparent as the following description of cer-- tain present preferred embodiments thereof proceeds.

In the accompanying drawings I have shown certain present preferred embodiments of the invention in which:

Figure l is a side view, partly in cross section and with parts broken away, of a mandrel having an eccentric portion, a member forming an enlargement applicable to the mandrel for forming the portion of the mold for casting of a pipe hub or bell being shown in chain lines;

Figure 2 is a transverse cross-sectional view to enlarged scale taken on the line 1III of Figure 1;

Figure 3 is a fragmentary detail view showing the support for the forward end of the mandrel in operative mandrel-supporting position; and

Figure 4 is a view similar to Figure 3 showing the support for the forward end of a mandrel provided with a member cooperating with the mandrel for forming in the mold at the end thereof shown in the figure a portion for casting one of the hubs of double hub pipe, the support for the forward end of the mandrel and said member being in operative position.

Referring now more particularly to the drawings, the centrifugal casting apparatus is of the type disclosed in the above mentioned patent and application and-comprises a rotatable flask with, of course, means for rotating theflask and a freely rotatable mandrel mounted in cantilever fashion for movement into the flask with a bearing for the forward end of the shaft when it is disposed within the flask andmeans for relatively adjusting at' will the distancebetween the axis of the flask and the axis of the mandrel.

I show in Figure 3 a flask 16 for the casting of single hub soil pipe and in Figure 4 a flask 16a for the casting of double hub soil pipe, it being understood that in each case a hub is cast in the pipe at the right hand end of the flask which is not shown in the drawings. Elongated articles other than lengths of pipe may be centrifugally cast and materials other than iron may be employed. For example, other metals or non-metallic materials of suitable structural characteristics may be utilized.

To avoid complexity of the drawings I havenot shown in detail the structure for rotatably mounting the flasks. Such structure is now a matter of knowledge to those skilled in the art. The flasks, may, for example, be mounted for rotation as shown in United States Patent No. 2,449,900.

Means are provided for rotating the flasks 16 at centrifugal speed so as to form therein centrifugally cast hollow elongated articles. Such means are'so well known that they are not shown. A mandrel 25 is shown in Figure 3 for casting single'hub pipe and a mandrel 20 is shown in Figure 4 for casting double hub pipe. The

mandrels are mounted to'be rotated by frictional engagement with the finely divided mold formingmaterial used for forming molds in the flasks as will presently be described. The mandrels partake of only two motions, the rotative motion just mentioned and axial movement into and out of the flasks. The mandrels 20 and 25 are respectively coaxial with the flasks 16a and 16 when the mandrels are moved into and out of'the flasks. When the mandrels are in coaxial relationship with the flasks and finely divided mold forming material has beenintroduced into the flasks and the flasks are rotated themandrels are introduced into the flasks.

Referring now more in detail to the structure and operation of the mandrels 20 and 25, as stated above the mandrel 25 is shown in Figures 1 and 2. At its righthand end it is provided with a cylindrical bearing portion 25a adapted to be mounted in suitable bearings in a mandrel support so that the mandrel is freely rotatable about its axis. To the left of the bearing portion 25a viewing Figure l the mandrel 25 has an enlargement 25b and projecting to the left therefrom a cylindrical portion 250. A member 25d, shown in chain lines,.for forming in the mold a portion for casting of a pipe hub or bell is applied to the mandrel and fastened in place by bolts 25c. All of the parts of the mandrel thus far described, to Wit, parts 25a, 25b, 25c and 25d, .are of circular cross section and coaxial.

Coaxial with the mandrel portions 25a, 25b, 25c and 25d is an annular outward projection 66 for the purpose of forming in the mold a depression for casting of the spigot at the end of a length of single hub pipe opposite the end at which the hub or bell of the pipe is disposed. To the left of the projection 66 and coaxial therewith are a reduced portion 67 and a bearing portion 61 adapted to enter a hearing as will presently be described to rotatably support the end of the mandrel remote from the end having the bearing portion 25a. All of the portions 25a, 25b, 25c, 25d, 66, 67 and 61 are of circular cross section and coaxial.

Intermediate the portions 250 and 25d to the right, and the portion 66 to the left, viewing Figure l, the mandrel has a portion 251 which is non-coaxial or eccentric with respect to the portions above mentioned. The portion 25 is shown as of circular cross section but may be of other cross section since normally only the part thereof farthest from the axis of rotation of the mandrel is operative in forming a mold, that being the part shown at the top in Figures 1 and 2. The same structure is shown in Figure 3 but in that figure the mandrel has been rotated from the position shown in Figures 1 and 2. Thus when the mandrel turns it turns about the common axis of the parts 25a, 25b, 25c, 25d, 66, 67 and '61 and the part 25) partakes of eccentric rotation, i. e., turns about an axis offset from its own axis as is characteristic of eccentric movement.

I have shown the mandrel parts 66, 67 and61 as though they were formed integrally with the remaining parts of the mandrel although if desired they may be formed separately and applied to the remainder of the mandrel as shown in the above mentioned copending application. Since the feature to which attention is being primarily directed in the present application is the eccentricity of the portion 25 of the mandrel and since the detailed structure of the bearing portion of the mandrel may be varied so longas provision is made for supporting of the mandrel to rotate about the common axis of the parts 25a, 25b, 25c, 25d, 66, 67 and 61 I have not attempted to show or describe in detail the bearing portion of the mandrel.

The mandrel 20 is identical with the mandrel 25 except that instead of having a spigot forming projection 66 the mandrel 2d has a cylindrical portion 86 to which a member 84 to be referred to further below may be applied for forming in the mold a portion for the casting of a hub when double hub pipe is to be made. The member 84 may be applied from the left-hand end of the mandrel 2% viewing Figure 4. The mandrel 20 has a bearing portion 61a which may be identical with the bearing portion 61 of the mandrel 25. The portions of the mandrel 29 corresponding with the portions 25a, 25b, 25c and 25d of the mandrel 25" and the portions 86, 84 and 61a of the mandrel 20 are all coaxial. The mandrel 20 has an eccentric portion 25g which may be identical with the eccentric portion 2d of mandrel 25.

As above indicated the apparatus is adaptable for forming either single hub or double hub pipe, Figure 3 showing apparatus for forming a mold for the casting of single hub pipe and Figure 4 showing apparatus for forming a mold for the casting of double hub pipe. When single hub pipe is to be cast the hub is formed at the right-hand end of each flask viewing Figures 3 and 4, the spigot being formed at the lefthand end, which is the end shown in Figure 3. Each of Figures 3 and 4 shows mechanism cooperating with one flask; it is to be understood that the mandrel support shown in those figures as well as the core holder shown in Figure 4 when double hub pipe is to be formed are duplicated for each flask.

i provide a carrier 77 having means for supporting the forward end of the mandrel 20 or 25 positioned in alignment with the mandrel. The body of the carrier 77 is of generally hollow shape as shown in Figures 3 and 4. The wall of the carrier which is disposed toward the right viewing Figures 3 and 4 has a circular opening 78 therein, such opening being substantially coaxial with the flask 16 or 16a. Applied to the carrier 77 at the opening 78 is a bearing bracket 79. The bearing bracket 79 is falstened to the carrier 77 by any suitable fastening means, not shown, and which may, for example, be as disclosed in copending application Serial No. 285,213, filed April 30, 1952. Disposed within the bearing bracket 79 is a bearing unit 86 of any suitable type, such, for example, as a Dodge bearing unit. The bearing unit 80 may be maintained within the bearing bracket 79 by being pressed therein. The bearing unit 80 has a generally cylindrical opening therethrough as known to those skilled in the art for receiving a rotatable machine part.

i provide for rotatably mounting in the bearing unit 80 a part whose form is determined by whether the pipe being cast is single hub pipe or double hub pipe. For casting single hub pipe that part is in the form of a flanged sleeve 81 shown in Figure 3 serving as a pilot or mandrel support. The flange of the pilot is designated 82 and serves as a guard to prevent mold forming material from getting into the bearing unit. The bore of the pilot is dimensioned to snugly and guidingly receive the mandrel portion 61 as shown in- Figure 3. The pilot supports the end of the mandrel while the mandrel is performing its mold forming function.

When double hub pipe is to be cast the pilot 81 is replaced by a combination pilot and hub 83 as shown in Figure 4. The combination pilot and hub 83 may be formed in one piece as shown or in two pieces bolted or otherwise fastened together. The hub portion is the member 84 and projects axially from the pilot portion as shown in Figure 4. The hub 84 is adapted to be engaged by the portion 36 of the mandrel when the mandrel is introduced into the flask, the hub lying within the flask to form an enlargement at the end of a mold of compacted mold forming material in the flask to form one of the hubs or bells on the pipe being cast. The nose of the hub 84 is tapered as shown at 85 and has a bore 86a of such size as to snugly receive the portion 86 of the mandrel 20. The rearward portion of the hub 84 is hollowed out and has passages 87 to permit mold forming material pushed into the hub by the end of the mandrel to be discharged centrifugally upon rotation of the mandrel and hub.

The axial distance from the end of the mandrel to the tapered shoulder between the portions 61a and 86 is greater than the axial distance between the extremity of the hub 84 and the mouth of the pilot. This is to insure that the mandrel will be in guided relationship to the pilot when the portion 86 of the mandrel 20 enters the bore 86a of the hub 84 whereby to avoid damage to the hub.

I shall now describe a present preferred method of casting single hub pipe by use of my apparatus. At the end of a cycle the flask is in generally upright position and is open top and bottom since the pipe cast during that cycle has been discharged downwardly therefrom. The mold and core or cores have likewise been so discharged. The first step is to close the lower end of the flask. When the lower end of the flask has been closed finely divided mold forming material is introduced downwardly into the flask. The flask may be used to measure the quantity of finely divided mold forming material introduced as disclosed in Patent No. 2,598,554. As soon as the finely divided mold forming material has been introduced into the flask rotation of the flask is commenced and at the same time the flask is turned to a position in which its axis is substantially horizontal. The rotation of the flask centrifuges the mold forming material so that an opening is formed in the mold forming material extending generally axially of the flask. About the time the flask reaches horizontal position the end of the flask which was originally the lower end (the right hand end viewing Figures 3 and 4) is opened. The mandrel 25 is moved from right to left viewing Figures 1 and 3 to introduce the mandrel into the flask through the opening in the finely divided mold forming material formed by the initial centrifuging of the mold forming material above described and to dispose the mandrel portion 61 in the pilot 81.

When the mandrel is supported in coaxial relationship with the flask (i. e., with the portion of the mandrel except the eccentric portion 25 thereof in coaxial relationship with the flask) with the leading end of the mandrel disposed in the pilot 81 as shown in Figure 3, and while rotation of the flask continues, the flask is moved transversely of its axis as disclosed in said copending application Serial No. 427,842 whereby the mandrel consolidates and smooths the mold forming material in the flask. The portion 25d of the mandrel forms in the mold the portion for casting of the pipe hub or bell and the portion 66 forms the portion of the mold for casting of the spigot. The portions 25d and 66 are concentric with the axis of rotation of the mandrel and engagement thereof with the mold forming material causes turning of the mandrel as the flask rotates and the mandrel is pressed against the mold forming material. As the eccentric portion 25] of the mandrel turns about the mandrel axis it strikes the mold forming material with repeated blows and thereby consolidates and smooths the mold forming material without substantial bending or deflection of the mandrel despite the fact that the mandrel is so slender that if it were pressed continuously against the mold forming material in the flask during compacting of the mold forming material the mandrel would bend inwardly so that the mold formed thereby would be of undesirably reduced diameter at the center. It is found that the mandrel does not strike the mold forming material at the same points at each revolution of the flask so that a uniform cylindrical compacted mold rather than a fluted mold is formed.

After the mold forming material has been thus acted upon by the mandrel and the mold has been completely formed within the flask the flask is moved back to its original position coaxial with the mandrel whereupon the mandrel'is withdrawn toward the right viewing Figure 3 to its inoperative position/as shown in that figure.

The cycle of operations is the same when double hub pipe is being formed except that when the mandrel is introduced into the flask to consolidate and smooth the mold forming material therein to form the mold the hub but may be otherwise variously embodied within the scope of the following claims.

I claim:

1. Molding apparatus comprising a rotary'hollow flask, means for rotating the flask, a freely rotatable undriven slender flexible mandrel adapted to be disposed within the flask and to rotate therein as the flask rotates tocompact mold forming material against the inside of the flask and means for relatively adjusting at will the distance beween the axis of the flask and the axis o'f'the mandrel, the mandrel having an eccentric portion which strikes "the mold forming material with successive blows as the mandrel and flask rotate and the mandrel moves relatively to the flask away from the axis of the flask, such striking of the eccentric portion of the mandrel against the mold forming material compacting the mold forming material against the inside of the flask and rotating the mandrel, the mandrel intermediate blows against the mold forming material being substantially relieved of bending stress, whereby a mold of small diameter may be formed using a slender flexible mandrel with the mold being substantially free of distortion which would result from bending of the mandrel.

2. Molding apparatus comprising a rotary hollow flask having an enlargement at an end thereof, means for rotating the flask, a freely rotatably undriven slender flexible mandrel adapted to be disposed within the flask and to rotatetherein as the flask rotates to compact mold formr. it)

ing material against the inside of the flask, the mandrel having an enlargement at an end thereof generally radially aligned with the enlargement in the flask, the enlargement in the mandrel'being' coaxial with the axis of rotation of the mandrel, and means for relatively adjusting at will the di'stance'between the axis of the flask and the axis of the-mandrel, the mandrel having an eccentric portion which 'strikes the mold forming material with successive blows as-the mandrel and flask rotate and the mandrel moves relatively to the flask away from the axis of the-flask, such striking of the eccentric portion of the mandrel against the mold forming material compacting the mold forming material against the inside of the flask and rotating the mandrel, themandrel intermediate blows against the moldforming material being substantially relieved of bending stress, whereby a mold of small diameter may be formed using a'slender flexible mandrel with the mold being substantially free of distortion which would result frombending of the mandrel.

3. Molding apparatus comprising a rotary hollow flask having enlargements at the ends thereof, means for rotating the flask,-a freely rotatably undriven slender flexible mandrel adapted'to be disposed within the flask and to'rotate therein as the flask rotates to compact mold forming material against the inside of the flask, the mandrel having enlargements at the ends thereof respectively generally radially aligned with the enlargements in the flask, the enlargements in the mandrel being coaxial with the axis of rotation of themandrel, and means for relatively adjusting at will the distance between the axis of the flask and the axis ofthe mandrel, the mandrel having an eccentric portion intermediate the enlargements which strikes the mold forming-material with successive blows as the mandrel and flask rotate and the mandrel moves relatively to the flask away from the axis of the flask, such striking of the eccentric portion of the mandrel against the mold forming material compacting the mold forming material against the inside of the flask and rotating the mandrel, the mandrel intermediate-blows against the mold forming material being substantially relieved of bending stress, whereby a mold of small diameter may be formed using a slender flexible mandrel with the mold being substantially free of distortion which would result from bending'of the mandrel.

References Cited in the file of this patent UNITED STATES PATENTS 804,329 Martin Nov. 14, 1905 853,633 Gurry May 14, 1907 2,076,790 Myers Apr. 13, 1937 2,138,623 Campbell Nov. 29, 1938 2,340,262 Crawford Jan. 25, 1944 2,499,387 Johnston Mar. 7, 1950 2,631,342- Romine Mar. 17, 1953 2,729,865 Kaveny Jan. 10, 1956

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