US2513142A - Method of casting annular articles - Google Patents

Description

June 27, 1950 F. G. CARRINGTON METHOD oF CASTING ANNULAR ARTICLES 5 Sheets-Sheet l Original Filed July 8, 1943 June 27, 1950 F. G. cARRlNGToN METHOD oF CASTING ANNULAR ARTICLES 3 Sheets-Sheet 2 Original Filed July 8, 1945 @MK (ipk/w70# June 27, 1950 F. G. cARRlNGToN METHOD oF CASTING ANNULAR ARTICLES Original Filed July 8, 1943 3 Sheets-Sheet 3 f/Tm//s (www/"0M 3 hr1/6; 5mg WMM mmf/ms Patented June 27, 1950 METHD OF CASTING ANNULAR ARTICLES Frank G.: Carrington, Lynchburg, Va.,` assigner' to Max- Kuniansky, Lynchburg, YVa..

` Original application July 8, 1943, Serial No. 493,908. Divided and this application June 20, 1946, Serial No. 677968 2 Claims. l

The present invention relates to a method of cooling a mold lused in the centrifugal casting of pipe and more especially to a method of cooling such ya mold in which the'rate of i'low of the cooling liquid is controlled in accordance with temperature changes occurring in the mold during casting operations to provide an increased now of liquid to the hottest portions ofthe mold. The presen-t application is a division of mycopending Patent No @2,412,601.

This invention isA particularly adaptable tocentrifugal pipe casting machines of theDeLavaud type which employ a non-rotating water-box in which is mountedv forrotation a metallic mold. These molds have certain inherent, deleterious features which both lower their efficiency and materially reduce their useful life. The molds are made-usually from steel in lengths of `18 feet and in diameters tocast 3 and larger pipe and considering these molds asbeams supported adjacent their ends, it Willbe 'seen that they will be subjected, especiallyin the smaller sizes, to bending stresses *andv in the' larger sizes to stresses which tend tollatten or distort them of round. Both of theseV 'effects are accentuated'and may become undesirably 'great when the molds are heated to the temperatures reachedA in casting.

In addition,itl*iey4 are subject to warpage Vand cracking irom'stresses setup in the'mold lWall when the mold is heated during the lcasting cycle. If the thicknessof the'mold wall is increased to overcome the bending and Aflattening tendency, an increase in expansion stresses vvillresult,y due to a lesseningo the heat transfer property of the meid', resulting in distortions and cracks-in the: mold wall. As any example, it has been found thatwhile a mold having a one-inchwall thickness'will cast approximately 4,00o1pipe, if the wall'is increased to 1'1/2 inches, the useful life of themold will be reduced to'approximately 1,000 pipa From the above, 'it `will; beseen ltlratvvhile .a thin -wall mold has distinctfadvantages, inorder to obtain its lmaximum efficiency, its beam strengthmustfbeincreased oristiflened lto countera'ct its warping tendencies. Various attempts have been made in the pastto accomplish this, none of which have beenentirely-satisfactory. Reinforcingsleeves'have been placed around 'the mold but their positions with respect to the mold have resultedin low coolingiemciency andtheir method of attachment to the mold has introduced new destructive stresses in the mold. l

Another deleterious feature-found inpipescast ing machines oiA the: above type-is wide-variations in mold temperature whichl occur during the castingv` operation. These variations occur both in the temperature 'of different sections of the mold and in the mean temperature ofthe mold at different times as pipe are cast; While the mass of the cooli'ngfmedium is maintainedat an optimum cooling temperature;noiprovision. is lmad'e either to vary this: temperature over different longitudinal' elements of dthe'mold orto vary its cooling eiect at different times in the casting-cycle, or to crmtrol the meant temperature of the cooling medium in contact with thel mold to -suit different casting conditions.

OneA of theobjects of theipresent invention is to overcome these disadvantages of the .prior art by providing a method of cooling a'centrifugal mold.

-Another object-oi the present'invention is to provide a method of the type described in which the cooling liquid is circulated simultaneously towards the ends of the mold.

`Still another object of the present invention is' toprovideamethod of the type described in which a. portion `of the cooling `*medium in contact with the mold surfaceis removed and replaced with other cooling'liquidduring passage of the liquidy towardsV the ends ofthe mold.

A further object of the presentinvention is to provide a method of the typedescribed in vwhich the rate of ilowI oi the diverging-streams is regulated to provide afla'rger flow'towards the hottest portion of the mold during. the casting operation.

`With these `and other objects in view which will be apparent'to those skilled' in the art from the following vf description, `the ypresent invention embraces broadly `a method ofcooling a mold surface by applying a cooling liquid'to the Aouter surface Yof vthe mold -`and creating a flow)y of the applied cooling liquid towards the ends of the mold in two streams. )During the progress of lthe cooling liquid towards the ends ofthe mold, portions Vof fthe liquid are removed from the streams and.' replacedwith` other cooling liquid. Therate ofilovvv of thecooiingfliquid-is also controlled to increase the yflow towards the :end of the kmold in whichfthe-metalfis being deposited. Asthis point moves'towards theA other end' of lthe mold, an increased flow is directed towards-this-hotter portion.

In this manner,- extreme variations in temperature between `the jdiiierent sections-of the-mold is vprevented and the life'ofsthe mold is substantially increased.1 '11n' the drawings: f Figure =l; isfa longitudinalfsectionalview ofa along the line 5 5 of Figure 1 lookingin thev direction of the arrows.

Figure 6 is a longitudinal sectional View taken along the line 6-6 of Figure 5 looking in the direction of the arrows.

Figure 7 is a longitudinal sectional view taken along the line 1 1 of Figure 5 looking in the direction of the arrows.

Figure 8 is a longitudinal sectional view taken along the line 8 8 of Figure 9 looking in the direction of the arrows.

Figure 9 is a transverse sectional View taken along the line 9-9 of Figure 8 looking in the direction of the arrows.

Figure 10 is a View in side elevation of the impeller provided at the spigot end of the apparatus.

For purposes of illustration there is shown in the drawings an improved centrifugal pipe casting machine of the De Lavaud type by means of which the method embodying the present invention can be practiced. However, it will be appreciated that other types of structure can be devised for this purpose As best shown in Figure 1, this apparatus includes a non-rotating water box I which 'is substantially cylindrical in cross section and is provided with end walls 2 and 3. Rotatably mounted axially withinthe water box I is a cylindrical pipe mold '4 having a flared end 5, adapted to form the bell of the pipe, and a spigot end vIi.

It is to be noted that while a mold for casting bell end pipe has been shown, the improvements herein described are equally'adaptable to other types of cylindrical molds.

The bell end 5 is provided with a ring or flange 'I which has attached to the outer periphery thereof a rearwardly extending sleeve 'I'. The sleeve 'I' is formed with an external flange 8 adapted to be journaled in an internal annular groove 9 machined in the end plate 2 of the water box. It will be seen that this construction will permit rotation of the mold but will fix the bell end against axial displacement with respect to the water box. The sleeve I'also carries torque transmitting means, such asfgear teeth I0, to effect rotation ofthe mold from a source of'power (not shown) The spigot end "6 of the mold is also provided with a ange, represented by the numeral VI I, .to form the squared spigot enfdof the pipe. This flange II is provided with a peripheral collar I2 by means of which it is journaled in the end wall 3 4for both rotary and sliding movement. Suitable packing elements I3 are provided at each end of the water box to effect a substantial liquid seal between the mold and water box.' A stiffening sleeve which I have designated generallyy as I5 surrounds the mold 4 and extends the full length of the casting surface there-` of. At the bell end, the sleeve is flared as at I 6 to `follow the general 'contour "of the bell of the end of the sleeve.

mold and is attached to the mold by means of a spacer ring I'I with just sufficient clearance to allow for radial expansion of the mold at this point without exerting undue stresses. It is to be noted that the ange I6 at this point and the ange II at the spigot end of the mold will both tend to conduct the heat away from the mold in these zones'thereby resulting in a reduced heating and expansion at the ends.

The spigot end is spaced from the mold by rigid lugs I8 projecting radially inward from a ring I9 secured to the inner periphery of the These lugs permit a sliding engagement between the sleeve and the spigot end of the mold and also permit egress of water from between the mold and sleeve at this end,

` as will be later described.

Intermediate its ends, the sleeve is spaced from the mold by a series of circumferential rows of diametrically opposed and adjustably radial pins 20. The mold and stiifener assembly is rotatably supported on pairs of rollers 2| journaled in bearings 22 aixed to the inner surface of the water box I adjacent each end thereof.

During the casting cycle, the mold is subjected to warpage and the maximum warpage for a mold of a given length, wall thickness and diameter and under given conditions of heating has been learned from experience. For example, in

a six-inch mold having a one-inch wallA and a length of eighteen feet, the amount of this warping has been found to be about one-quarter inch.' This factor being known, it is a simple matter from well-known formulae, to calculate the number, distribution and amount of loads necessary to counteract this warping throughout the length of the mold. In calculating these loads, the tendency of the vcylindrical mold to corrugate during expansion at the points at which they are applied must also be considered. Here again well-known formulae may be applied to determine the maximum load which will not exceed the strength of' the wall section of the cylinder. From these calculations. considering a mold of 6 diameter and 18 length having a Wall thickness of 1", it is determined that if six loads, each capable of exerting a known force, are radially spaced at equal distances about the circumference of the mold and eachcircumferential row of loads arranged at three foot intervals along the length of the mold, the force necessary to counteract the M1" warpage normally to be expected will be several times less than that which will produce corrugating distortion of the cylinder.

Cooling of a De Lavaud mold is effected by means of water circulated through the water box and'maintained at an optimum mean temperature, the :degree of cooling of the mold being controlled by the temperature of the mass of the water in the water'box. This system of cooling, however, has proved inecient due partly to the progressive method of pouring the metal, changes in rotational speed of the mold to suit varying casting conditions, differential heating over the length of the mold and to other reasons. I propose, therefore, to incorporate with my stiifening sleeve means to control the circulation of water about'the mold whereby the cooling rate may be variedl to suit the varying heating conditions.`

To accomplish this, I perforate the stiffening sleeve I5 over its length with inlet and discharge ports designated 4U and 4I respectively. These' ports are radially spaced around the sleeve and are arranged 'longitudinally of the mold so that circumferential groups of inlet ports will alter#` nate withcircumferential groups 'of .discharge ports. It is'to be noted that the capacityfofthe Vinlet 'ports is made'greater than that of thev dischargefportsand that the axial arrangement of the ports issuch that there. is an inow :of'water near the center of the sleeve and a. longitudinal flow toward each end'` from` that point. It will .be also notedfromFigure l: that each circumferential row of ports is indexed with respect to the adjoining rowand also with Vrespect torthe loading elements to minimizeweakening the sleeve.

Referring to Figures 2 and 3, I have shown the inlet ports 4I) and the discharge ports 4I are drilled atan angle to thesurface of the sleeve, the inlet ports being inclined outwardly in the direction of rotation while the discharge ports 4I are inclined in a direction opposite the direction of rotation. These ports form, in eiect, a pump to induce a ow of the water into tlievspace between the sleeve and the mold and move it longitudinally in this space when the mold is vrotating. To assist this pumping action, radial baies 42 are secured tothe inner wall of the water box I as shown at 43 inthe areas adjacent the inlet portsto inhibit spinning of the water r which would normally be caused in theseareas by therotation lof the mold. Additionally, under certain conditions of operation it may be desirable to induce a more vigorous circulation of the water. This can be accomplished by hooding the discharge ports as indicated at 44 in Figure 4 to create areas of reduced pressure adjacent the discharge ports.

As shown in Figures 5 and 6, the bell end I6 of the stiffening sleeve I5 is provided with a series of radial discharge ports 45. Since the water between the mold and sleeve is discharged through these ports on a greater diameter, a flow will be induced toward the bell end of the mold. Means are provided to control this longitudinal flow which include a ring 46 slidably positioned around the bell end I6 of the stiffener adjacent a circumferential row of the discharge ports 45 in a manner to be capable of restricting these ports. Movement of the ring is effected by means of headed screws 41 positioned in counterbored apertures 48 located in the flanged end 49 of the stilfener I5. Since the inner face of the mold flange 1 lies adjacent this flange 49, access holes 5I) are provided therein coaxially with the screws 41. These holes 50 are drilled a smaller diameter than the heads of the screws 4'! to prevent longitudinal displacement of the screws when the ring 46 is adjusted to regulate the ports 45.

In order to induce a flow from the center toward the spigot end of the mold, I provide the spigot end of the stiffener I5 with a series of discharge slots 5I located between the spacing lugs I8 of the ring I9. Adjacent these slots 5I is a flanged ring 52 adjustably mounted exteriorly of the stiffener by means of set screws 53. A series of angularly disposed vanes 54 are integrally attached to the flanged ring, as best shown in Figures 9 and 10, to accelerate water circulation. This structure form, with the spigot ring I2, a pump whose inlet is the series of slots 5I and whose outlet is the space 55 formed between the peripheral edge of the flange 52 and the free end of spigot ring I2. The space 55 is variable in size depending upon the heat of the mold and. as shown in Figure 8 by dotted lines, as the mold expands during the casting operation, the bell end being fixed, the spigot end will tend to move longitudinally outward. This increase in size ofthe discharge gap 55 resultsinan increase in the discharge rate of the pump and a consequent increase in water circulation over the:mold.

zInoperation, the mold 4 is put in rotation and moltenmetal isrdeposited therein progressively from the bellk to the spigot end, adhering to the inner surface ofthe mold by centrifugal action Where it is cooledland solidified by `transfer of itsA heat through the wall of the mold to the cooling liquid invthe water box. After the pipe has solidied, the moldis stopped, the pipe withdrawn 'from-themold andthe mold then put in `operati'onfor'the next casting.

Duringtlie casting operation water enters the spacebetweentthe mold and the sleeve through theinletfports 40 and its' flow is induced longitudinally toward'bcth ends. This water is heated upon coming in contact with the mold but, be-

cause of .the proportion and disposition of the inlet Vand outlet ports intermediate the center andfendsand becausey of the discharge arrangement `provided 'at each end of the sleeve, the heated water is rapidly replaced by cool water from outside the sleeve. As the pouring progresses andthe mold becomes increasingly hotter it'will expand longitudinallyand widen the discharge gap '55, increase the rate of now toward the'spi'gotendof the mold, and thereby displace the mean point of intake toward the bell end. With pouring terminating at the spigot end, this end of the mold becomes hottest at the finish of the casting cycle and the above cooling conditions are found to be highly advantageous in that they automatically provide for more Vigorous cooling for the hottest portions of the mold. Another distinct advantage which results from this automatic increase in circulation with increase in mold temperature is that it effectively prevents overheating and damage to the mold.

Automatic control of cooling is likewise provided to vary the rate of circulation with varying pouring rates. For efficient operation of the mold the cooling rate should be in proportion to the rate at which the molten metal is being admitted into the mold, and, as the pouring rate is governed by the mold speed, the rate of coolant circulation, because of the pumping properties of the sleeve, will also automatically be controlled by the rotational speed of the mold. In other words, when the speed of the mold has been increased to provide for a faster pouring rate, the water circulation will also increase resulting in a consequent increase in heat transfer as the hot water in the space between the mold and sleeve is replaced more rapidly by cool.

Beside the automatic control of the ilow of water between the mold and sleeve, as described above its circulation, particularly in regard to the means point of intake, may be further controlled by manipulation of the closure element 46 to increase or decrease the amount of water discharged at the bell end of the sleeve. This control is effected by the operator between casting operations to provide the optimum cooling for given casting conditions.

After the casting cycle is completed and the mold stopped, the circulation is continued through both the inlet and discharge ports and ends by the heated water in contact with the mold rising upwardly.

While for purposes of illustration only one apparatus for performing the method embodying the invention has been shown it will be appreciated that other apparatus may be devised for 7 this purpose without departing fromthe Yspirit of the invention. -V

I claim: I 1. A method of cooling moldsemployed in the centrifugal casting of pipe comprising.:applying a cooling liquid tothe outer surface'of the mold, creating a regulated ow of applied cooling liquid from the center portion of the mold towards both ends of the mold, removingy portions of the cooling liquid from the flow as the liquid travels towards the ends of the mold, replacing Athe removed liquid with other cooling liquid, progressively depositing molten metal from the bell end of the mold towards the spigot end, and increasing the ilow of the applied cooling liquid towards the spigot over the ilowtowards the bell lend as the point of depositing the molten metal goes towards said spigot end. l

2. A method of cooling molds employed in the centrifugal casting of `pipe comprising applying a cooling liquid to the outer surface of the mold between the mold and a perforated stiffening sleeve,

rotating the mold to create a regulated ow of the applied cooling liquid between the sleeve and .the mold simultaneously towards both ends of the mold, removing portions of the cooling ,liquid from the flow through outlet apertures inthe sleeve as the liquid travels towards the ends of 'the.mold, replacing the removed liquid with other cooling liquid through inlet apertures in the sleeve, progressively depositingmolten metal in the mold from the bell end towards thespigot end, and increasing the flow of the applied cooling liquid towardsthe spigot end of the mold over thelow towards the bell end as the point of depositing the molten metal moves towards the spigot end by enlarging the clearance between the sleeve and the mold at the spigot end.

FRANK G. CARRINGTON.

REFERENCES CITED The following references' are of record in the le of this patent:

` UNITED STATES PATENTS Number 2,412,601 Carrington Dec. 17, 1946

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