US2349213A - Centrifugal molding of concrete products - Google Patents

Description

May '16, 394 R. J. VAN NIEKERK CENTRIFUGAL MOLDING OF CONCRETE PRODUCTS Filed Aug. 20, 1942 Jane 1. 250/ jisseZJTk Patented May 16, 1944 Russell .Iuan van Niekerk, Florida, Transvaal, Union of South Africa Application August 20, 1942, Serial No. 455,513

' In the Union'of South Africa October 7, 1941 4 Claims.

This invention relates to the centrifugal molding of concrete products, particularly concrete poles and pipes, and the lining of pipes with concrete, bitumen or like material.

Hitherto, in the centrifugal molding of concrete products and lining of pipes, the initial distribution of the concrete in the mold or the lining material in the pipe has been a process occupying considerable time or involving a considerable expense of labor. The customary method of 'distribution has been to introduce the concrete' or liningmaterial in successive charges and to ro-' tate the mold or pipe slowly, with or without vibration, until the charge has become distributed along the length of the mold or pipe. It has a1s0 been proposed to mount the mold or pipe for charging purposes in a stationary position on a beam or frame which can be tilted-so as to bring the mold or pipe to an inclined position with its charging end upwards, whereafter the concrete or lining material is delivered into the open end and descends down the mold or pipe by gravity. This method, however, involves the subsequent process of bringing the beam ,or frame to the horizontal, then removingrthe mold or pipe therefrom and placing it in a separat machine for spinning the mold or pipe, themachine being first rotated at a relatively slow speed so as to -com plate the "distribution" of the concrete or lining material. j One of the: objects of the present invention is to facilitate and expedite the distribution-of the concrete or lining material in the mold or' pipe. A further objectis to facilitate the spinning'of the mold or pipe in a manner best calculated to ensure the" consolidation of the concrete or lip.- ing material in a uniform,man ner throughout the product or lining to be formed.

A, still further object is to enable hollow poles, pipes or likeproducts to be spun with a-wallof substantially the same thickness throughout the length thereof, or with a wallvaryingin'thickness in a predetermined manner and degree. In particular, it is an'object of th invention'to enable'tapered hollow poles, pipesjand like tapered products to be spun with a-wall of uniform thickness throughout, 1. 'e., with-a tapered external surface and an internal surface tapered similarly-, thus'avoiding" wastage of material and effectin a-savmgjm w ei htof the product,jas Com -j pared with tapered hollow products manufactured hithertii, n which the bore or inte na surface is cylindrical 1 or parallel, or at any=rate not tapered inia greementiwiththe external ta e: 'of the wall; and the thickness bf th wauat the wider end of the product consequently in excess of what is required'for purposes of strength.

Another object of the invention is to provide a simple and inexpensive machine for distributing and spinning the concrete or lining material.

According to this invention, I provide a method of centrifugally molding concrete products or centrifugally linning pipes in which the mold or pipe, during the charging of theconcrete or lining material, is rotatably supported in an inclined position and is rotated in this position so as to distribute the concrete or lining material along and within the pipe by a combined gravity and rotational action.

In accordance with a further feature of the invention, the method is such that the mold or pipe, when the concrete or material has been properly distributed therein, is spun at any desired speed, while lying at any desired inclination, so as to consolidate the concrete or linin material by centrifugal force, While still keeping non-consolidated concrete or lining material under the combined control of the centrifugal force and-gravity.

According to another feature of the invention, a machine for centrifugally molding concrete products and lining pipes comprises means whereby the mold or pipe is rotatably supported and whereby it is, while so supported, variable in inclination, and means for rotating or spinning the mold or pipe at any given inclination at different speeds. V

The invention will now be described, by way of example, with reference to theannexed drawing, in which- Fig. 1 is a View in side elevation of a machine embodying the invention and showing a mold therein;

Fig. 2 is a plan view of the machine shown in Fig.1 without the mold;

Fig. 3 is a relatively enlarged view of part of themachine shown in Figs. 1 and 2.

Referring to the drawing:

The machine comprises a beam 1 (e. g. con

sisting of a pair of plate girders suitably braced) which is pivotally mounted on a trunnion bearing'or fulcrum 2, which in the'case illustrated is offset a distance'from the middle of'the beam towards the right-hand end. The fulcrum '2 is supported in a bearing block or blocks 3 which is or are mounted on a foundation or floor 4 in which a well 5 is formed in order to permit the beam to be tilted to any angle within a given range. The beam l is' provided towards the end thereof remote fromthe' fulcrum 2 with a transverse bar Ii, over the ends of which are adapted to be fitted rings 1 provided on the ends of chains 8 which are connected to an electric crane, hydraulic jack or other suitable means (not shown) for the purpose of raising and lowering the beam I to the particular inclination desired, e. g., the position shown in dotted lines in Fig. 1.

At intervals alongthe beam I, pairs of supporting rollers 9, ID are mounted on bearing brackets II. The drive of an electric motor I2 mounted on the beam I is transmitted by means of belt or other gearing I3 to one of the pair of supporting rollers, vig. the pair of rollers 9, III above the fulcrum 2.

In Fig. 1, a tapered mold I4 made-in two halves is shown mounted in the machine. This/par ticular mold is one adapted for: the 1 centrifugal molding of a tapered reinforced concrete pole. It is fitted with a reinforcement positioning device comprising a clamp or holder I5 at one end of the mold, and a positioning plate or element IS, a second clam-por holder I'l, and a screwtensioning meansI8 at the other'endof the mold,-all as specified in my. co-pending applicationNo. 455,514.

On the mold I4, spinning rings I9 are provided at the same intervals apart as the pairs of supporting rollers 9, I0. These rings are fixed rigily and coaxially upon the mold I4 and rest, and are adapted'to roll, upon the rollers 9, I0. Thus, on the electric motor I2 being set in operation, the rollers 9, lfl'driven by the belt or other gearing I3 cause rotation of the mold I4 about its axis, the speed of this rotation being varied by variation of the speed of the motor.

As indicated in Fig.3, a displaceable jockeyroller carried by a bent-arm lever 2I is associated with each pair of supporting rollers 9, III. This jocket-roller 20 is adapted to be brought into rolling contact with the top of the corresponding spinning ring I9 and to be held in such contact with a greater or smaller degree of pressure by an adjustment nut or handle 22 which is turnable on the screw-threadedend 23 of a retaining lever 24. In this manner, the mold I4 is retained on the rollers 9, I0 during spinning, and-chattering or undue vibration of the mold isavolded.

In order to prevent lengthwise movement of the mold I4, the end spinning rings I9 are formed with double flanges 25, 26 and the intermediate spinning rings I9 are formed with single flanges 21, the side surfaces ofthe flanges 25, 26 and 21 being adapted to take up end-thrust by contact with the corresponding side surfaces of 'the respective supporting rollers 9, III.

The end of the beam I remote from the fulcrum 2 may be termed the charging end ofthe machine, and is fitted with a charging hopper 28, the mouth or forward part 28 of which is tapered and adapted to project a short distance into the adjacent end of the mold I4. The mold I4 (or the pipe, as the case may be) is placed in the machine so that its larger end is the end into which the concrete (or lining material) is charged. This end is the end which is elevated when the beam I is tilted. For the purpose of charging the concrete into the mold from the hopper 28, the reinforcement clamp or holder I5 is made of annular shape so as to provide the necessary opening through which the concrete may enter the mold.

The method of molding (or lining) with the machine described is as follows: 1

The beam 1 is set in a horizontal position in order to receive the mold I4, this latter, in the particular case described, having previously had the reinforcing wires (parts of which are indicated diagrammatically by dotted lines 29 in Fig. 1) positioned therein by the positioning devices I5 to I8 already referred to.

The mold I4 is placed so that the spinning rings I9 rest upon the supporting rollers 9, I0 and is retained in this position by bringing over on top of the spinning rings I9 the jockey-rollers 20, and securing them in place by the handles 22 andscrew-threaded levers 24.

The hopper 28 is charged with the quantity of concrete required, and the electric crane or other hoisting means (not shown) connected by the chains "8 and rings 1 to the transverse bar 6 is operated so as to-tilt the beam I and mold I4 thereon toafai-rly substantial inclination, such as the position shown in Fig. 1 in dotted lines. In this position, the electric motor I2 is switched onso as to set themold I4 rotating slowly,andthe concrete in .the hopper. 28- is charged into the large end of the mold. By virtueof therotation, and inclinationof the mold, the concrete is distributed around its interior.

When this preliminary distribution is complete, the beam I'is loweredfromthe dottedposition (Fig. 1) to the level or'to an inclination suitable for high-speed. spinning, i. .e. for consolidating the pole or-other product "by centrifuging. In the case of a-cylindrical or parallelsided product, this level will be the horizontal position as shown in full lines in Fig, 1.

reinforced-concrete pole particularly described above), the inclination-will be at an angle approximating tothe horizontal, but considerably less than theang-le of the beam shown in dotted lines in Fig; 1. More specifically, the inclination is necessarily such that the effect, during centrifuging, of the taper of the mold (viz. to'cause creeping of the centrifuged concrete from the smaller to thelarger endof the mold) will be counteracted by thegravitational-effect onthe concrete produced by the inclination of the-mold. These two opposing .efiec-ts being balanced-the concrete during centrifuging will be subjected purely to a centrifugal or radical consolidation, and the original-uniformity of distribution of the concrete in the mold will not be distunbed,-and a productwith a uniformly thick wall, with'its internal and external surfaces tapered: alike, will be obtainable.

Thus during centrifuging, the whole or the concrete, includingiconcrete-not yet consolidated; is under the combined control of centrifugal force and gravity, .in such a mannerv as to-makeepossible whatever distribution and-consolidation of concrete is desired.

When .moldingor consolidation of the product is complete, rotation of themold I.4--is stopped by switchingofithemotor I2. Thereaftent mold and beam lare lowered to "the horizontal position, the handles. 22' are.unscrewed,-.the levers 2| carrying the jockey-rollers '20 'swungmback, and I the mold removed 7 from the machine, for eventual withdrawal therefrom-of the 'molded product.

As wilirbeappreciatedthe inclination ofthe mold, and itsspeed-of rotation, may both be varied at will in thecourse.cf-thedistributingIand/or centrifuging operations, without the necessity of stopping,--or in any- :wa-y interfering-with, the work. Th mold (or therpipeiinthe case-orig pipe'being. centrifugally lined) 1s alwaysunder In the, case of a tapered product (suchas the tapered complete control, so that any tendency towards lengthwise creeping of the concrete (or linin material), or incorrect rate or degree of consolidation at one end or another of the mold (or pipe) can immediately be rectified.

While the method of operation has been particularly described with reference to the molding of a tapered reinforced-concrete pole, it will be obvious from the indications already given that the machine may also be used for molding parallel or cylindrical poles and tapered or parallel hollow bodies or pipes, and for the centrifugal lining of hollow bodies or pipes.

Various modifications may be made in the machine described, without departing from the scope of the invention. For example, instead of retaining the spun body on the supporting rollers 9, II] by means of jockey-rollers 20, I may employ for this purpose endless belts or equivalent means.

In the appended claims, the term centrifuging is intended to include centrifugally molding concrete products and centrifugally lining pipes, the term hollow body is intended to include a mold to be charged with concrete and a pipe to be charged with lining material, and the term material is intended to include the concrete or lining material.

I claim:

1. A method of molding a hollow tapering concrete product, consisting in inclining and slowly rotating an appropriate mold with its larger end uppermost while charging the same with material, and then subjecting the mold and material to a rapid rotation while maintaining the inclination of the mold at a degree to cause an incident gravital influence on the material sufiicient to overcome the tendency of the material to creep toward the larger end of the mold under the centrifugal operation.

2. A method of molding a tapering concrete product to produce an article having substantially even wall thickness throughout, consisting in slowly rotating a tapered mold while steeply inclined downwardly from its larger end, feeding the material into the larger end and distributing such material throughout the mold through such rotation and initial inclination, then materially increasing the rotation while varying the inclination to a degree to develop a gravital influence on the material to overcome the tendency of the material to creep under the centrifugal influence, whereby to insure a wall of substantially uniform thickness throughout.

3. A method of molding hollow concrete products of tapered form with substantially uniform wall thickness throughout, consisting in mounting an appropriate mold for pivotal and rotative movement, inclining the mold with the larger end uppermost and slowly rotating to insure gravital feed and rotative spread of the material, feeding the material onto the mold, and then rotating the mold to develop centrifugal action for increasing the rapidity of setting of the material while at the same time arranging the inclination of the mold at a degree to influence the material by gravity to overcome the tendency of the material to creep toward the larger end of the mold incident to the cetrifugal influence.

4. A method of molding hollow tapered concrete products with substantially uniform wall thickness, consisting in inclining the mold for gravital feed of the material lengthwith the same, placing the material in the mold, and rotating the mold at a relatively slow speed for distributing the material, and then rotating the mold at a relatively high speed for centrifugal placement and to increase the rapidity of setting of the material while maintaining the mold at a predetermined inclination to develop a gravital influence to counteract creeping influence of the material under centrifugal action.

RUSSELL JUAN VAN NIEKERK.

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