US3127643A

US3127643A - Process and apparatus for producing centrifugally cast metal tubes

Info

Publication number: US3127643A
Application number: US113846A
Authority: US
Inventors: Welz Werner
Original assignee: BuderusSche Eisenwerke AG
Current assignee: Buderus AG
Priority date: 1960-05-31
Filing date: 1961-05-31
Publication date: 1964-04-07
Anticipated expiration: 1981-04-07

Description

April 7, 1964 w. W'ELZ 3,127,643 PROCESS AND APPARATUS FOR PRODUCING CENTRIFUGALLY CAST METAL TUBES Filed May 31, 1961 J 7 ,la

7 [all 6 I. l I I I I5 INVENTOR WERNER WELZ BY mstem, m oss 6 msi'erfi United States Patent 3,127,643 PROCESS AND APPARATUS FQR PRODUCING CENTRIFUGALLY CAST METAL TUBES Werner Weiz, Staifel (Lahn), Germany, assignor to Buderussche Eisenwerke, Wetziar, Germany, a

corporation of Germany Filed May 31, 1%1, Ser. No. 113,846 Claims priority, application Germany May 31, 1960 2 Claims. (Cl. 2265) My present invention relates to a device and a process for producing centrifugally cast metal tubes and, more particularly, for simultaneously producing two centrifugally cast iron tubes each terminating in a bell at one end.

It is an object of the present invention to provide a device and a process for the production of faultless centrifugally cast metal tubes suitable for sewage lines, water and gas distribution systems, and the like.

It is another object of the present invention to provide a device in which such tubes can be serially manufactured in a highly economical manner designed to simplify the problem of maintenance between productive cycles and to minimize the cleaning and trimming operations required.

It is a further object of the present invention to provide a device and a process insuring a clean separation between a pair of tubular members cast in a single centrifugal operation.

In accordance with the invention I provide a tubular casting mold open at both ends and rotatable about a horizontal axis, these ends being preferably flared to form bell terminations on the metal bodies to be molded therein, in combination with stationary inlet means for introducing liquid metal into the mold at one end. At an intermediate location the mold is formed with an annular obstruction, e.g. as an integral ridge or as an insertable ring, of a height which is a small fraction of the inner mold radius but at least equal to the wall thickness of the finished castings so that they become separated from each other during the centrifuging process; this separation should occur, at the latest, during shrinkage of the metal in the final or cooling stage of the process. The introduction of the molten metal may take place through one of the two terminal mold cores which are inserted into the flared ends to define the bell recesses at the female ends of the castings; advantageously, for this purpose, a feed pipe is inserted through such mold core at the inlet end of the mold so as to extend from the metal injector to a point just beyond this mold core. The quantity of molten metal introduced into the centrifugal chamber, i.e. into the interior of the rotating mold, should be suiiicient to insure that the annular obstruction will initially be overflown freely by the metal whereby the latter is distributed to substantially uniform depth in the two chamber sections formed on opposite sides of this obstruction.

According to a more specific feature of the present invention, the inner cylindrical portions of the mold on both sides of the separator ring can be of slightly different diameters, preferably with the section having the smaller diameter located at the side of the mold at which the molten metal is introduced, the difference in the height of opposite sides of the ring improving its separating effect. Even a small difference of diameters, e.g. within the tolerances admissible for tubes of the same nominal dimensions, has a marked effect on easing the otherwise strict requirements as to the exact amount of introduced metal.

The above, and other objects, advantages and features of my present invention will be better understood from the following description, given with reference to an accompanying drawing in which:

3,127,643 Patented Apr. 7, 1964 FIG. 1 is a longitudinal sectional view of a device according to the present invention; and

FIGS. 2, 3 and 4 are fragmentary sectional views of different types of separator rings as utilized in the above device.

FIG. 1 shows a hollow, elongated metal mold 1 having a cylindrical horizontally disposed through-going bore 15 and diverging at both ends into bell-shaped sockets 16. A separator ring 6, rigid with mold 1, protrudes inwardly from the periphery of the bore 15 at an intermediate location between sockets 16, thereby dividing bore 15 into two sections for the molding of two tubular castings 7, 8. Two tubular cores 4, 4', each with a flange 18 fitting into a respective groove at one of the mold faces, extend for a short distance into the bore 15 to define with its flared extremities a form for a tube bell 3.

An inlet tube 5 of slightly frustoconical configuration so as to diverge radially from right to left as shown in FIG. 1, traverses the actual channel of right-hand core 4 and with its enlarged end extends a short distance beyond that core into bore 15. The tube 5 is provided at its projecting extremity with a threaded portion 10 rigid with a grip bar 11 which may be welded to the tube. A bent bifurcate holder 9, firmly fastened to a sleeve 19 surrounding the tube portion 10 in threaded engagement therewith, is welded to a collar 21 having bayonet teeth 22 entering mating slots 20 along the outer periphery on the right-hand side of the mold 1. A stationary injector 2, schematically represented by dot-dash lines, is used for introducing molten iron into tube 5 and thence into mold 1. Rotation of grip 11 threads tube 5 into sleeve 19, thereby pressing a shoulder 12 on the tube against flange 18 of core 4 to lock the latter in position. The other core 4', which may be removably held in place by similar means not shown, provides an overflow outlet for any excess metal capable of clearing the mouth of this core.

The mold is rotated around its longitudinal axis, during the centrifugal casting by mechanism shown sche matically as a motor 25 having a pinion 26 in mesh with gear teeth 17 on mold 1; the mold body is rotatably supported by suitable bearing means such as roller 27.

The separator ring 6 illustrated in greater detail in FIG. 2 is of trapezoidal cross-section and integral with mold 1; the portions of bore 15 on both sides of the ring 6 have equal diameters and, if desired, the same length. While this arrangement enables the simultaneous casting of tubes of identical cross-section, it may lead to the formation of a burr 13 which must be subsequently removed. This inconvenience is largely avoided by increasing the depth of one flank of the separator ring as shown in FIGS. 3 and 4.

In FIG. 3 the ring 6, separating two tubes 7' and 8' of slightly different diameters, has flanks of unequal heights, designated h and h A similar arrangement is shown in FIG. 4 wherein a detachable separator ring 6" of trapezoidal cross-section overlies the step 14 between the axially separated parts of mold 1 and is provided with a depression 23 on its outer face for a fastening bolt 24 radially threaded into the wall of mold 1. The height I1 of the distal face of ring 6' or 6" as seen from the inlet (5) may be so small as to afiord a smooth passage of the molten metal over this ring, the separation between casting 7', 8 being nevertheless insured by the larger height h of the proximal face. Ring 6' can, of course, be readily removed for repair or replacement, e.g. for purposes of adapting the mold for the casting of tubes of different thickness. It will be apparent that such detachability may also be provided for symmetrical rings such as the one shown in FIGS. 1 and 2.

The centrifugal casting device according to the invention operates in the following manner: Molten metal is introduced into mold 1 by the injector 27 With mold 1 set into rotation by motor 25, the metal spreads along the walls of bore 15. The amount of injected metal is such that the molten metal passes over the separator ring 6,

.6 or 6" and spreads equally along both sides of the mold 1, thereby filling the cavities for the bells 3. As

themetal cools, the tubular layer formed by it along the mold wall shrinks so that the ring 6 separates the resulting casting into the two portions 7 or 7 and 8 or 8', each with a bell termination 3. These tubes can be pulled out of the mold 1 after the cores 4, 4 have been .removed, whereupon the mold 1 can be used for further casting;

The invention as described admits many modifications .readily apparent to persons skilled in the art, as for instance the application of injectors from both sides of the mold simultaneously, and/ or the optional provision of means for cooling the mold (e.g. by Water). modifications are, therefore, intended to be included with- Such in the scope of the invention as defined by the appended claims.

I claim:

1. An apparatus for centrifugally casting pairs of metal tubes, comprising a tubular mold rotatable about a substantially horizontal axis and having a bore extending along said axis, said bore having two open ends; stationary inlet means at one of said open ends for introducing'a molten metal into said bore, said bore being prohaving the smaller diameter being disposed between said l inlet means and said ridge with the section having the larger diameter being disposed beyond said ridge remote from said inlet means, said ridge having flanks of different height rising respectively from said sections with the flank having the smallest height facing said inlet means; and drive means for rotating said mold about said axis.

2. An apparatus for centrifugally casting pairs of metal tubes, comprising a tubular mold rotatable about a substantially horizontal axis and having a bore extending along said axis, said bore having two open ends; stationary inlet means at one of said open ends for introducing a molten metal into said bore, said bore being provided intermediate said openings with two adjacent generally cylindrical sections of diiferent diameter forming an annular step at their junction; a ring centered on said axis and seated against said step, said ring forming an'annular ridge intermediate said sections projecting inwardly beyond the walls of said sections a fraction ofthe radius of said bore, the section having the smaller diameter being disposed between said inlet means and said ridge with the section having the larger diameter being disposed beyond said ridge remote from said inlet means, said ring having flanks of diflerent height rising respectively from said sections with the flank having the smallest height facing said inlet means; locking means for removably fixing said ring axially along said bore; and drive means for rotating said mold about said axis.

References Cited in the file of this patent UNITED STATES PATENTS 1,551,590 Stresau Sept. 1, 1925 1,678,633 Burchartz July 31, 1928 1,795,637 Carrington Mar. 10. 1931

Claims

1. AN APPARATUS FOR CENTRIFUGALLY CASTING PAIRS OF METAL TUBES, COMPRISING A TUBULAR MOLD ROTATABLE ABOUT A SUBSTANTIALLY HORIZONTAL AXIS AND HAVING A BORE EXTENDING ALONG SAID AXIS, SAID BORE HAVING TWO OPEN ENDS; STATIONARY INLET MEANS AT ONE OF SAID OPEN ENDS FOR INTRODUCING A MOLTEN METAL INTO SAID BORE, SAID BORE BEING PROVIDED INTERMEDIATE SAID OPENINGS WITH TWO ADJACENT GENERALLY CYLINDRICAL SECTIONS OF DIFFERENT DIAMETER AND AN AXIALLY FIXED ANNULAR RIDGE INTERMEDIATE SAID SECTIONS, SAID RIDGE PROJECTING INWARDLY BEYOND THE WALLS OF SAID SEC-