US1887341A - Method of and machinery for forming pavements - Google Patents

Description

NOV. 8, 1932. w M VENABLE 1,887,341

METHOD OF AND MACHINERY FOR FORMING PAVEMENTS Filed Feb. 7. 1928 2 Sheets-Sheet 1 wnwess INVENTQR W4 01124421) in Wm 0 mar/1.0

Nov. s, 1932. w. M, VENABLE 1,887,341

METHOD OF AND MACHINERY FOR FORMING PAVEMENTS Filed Feb. 7, 1928 2 Sheets-Sheet 2 WITNESS INVENTOR Patented Nov. 8, 1932 UNITED STATES PATENT OFFICE WILLIAM ILVENABLE, OI PITTSBURGH, PENNSYLVANIA, ASSIGNOB TO BMW-KNOX COMPANY, OF BLAWNOX, PENNSYLVANIA, A CORPORATION OF NEW JERSEY METHOD OF AND MACHINERY FOR FORMING rAVE'MEN'IS Application filed February 7, 1928. Serial No. 252,528.

My invention relates to improvements in methods of and machinery for forming pavements, and finds practical application in the forming of concrete highways. In that par ticular' application I shall describe it. The object is the production of a well compacted and durable pavement whose surface is relatively free of unevenness and irregularity, and free particularly of fortuitous areas of depression.

\The accompanying drawings illustrate somewhat diagrammatically a road-building machine in which and in the operation of which my invention is embodied and achieved. Fig. I is a View of the'apparatus in side elevation, resting in position for operation, upon the road rails of a road under construction. Fig. II is a View of the machine in plan-from above. Fig. III is a view in vertical and transverse section, on a broken plane indicated by the line III-III, Fig. II. IV is a fragmentary view in vertical and transverse section, on the plane indicated at IVIV, Fig. I.

My invention is applicable to the finishing of roadways, so as to obtain a proper spreading and smoothing of the concrete surface, with economy and without inconvenience. The primary concern is to produce from matcrial which from the necessities of the case is non-uniform in composition and character a finished structure which is to the highest attainable degree uniform. In the practice of building concrete roads as it is now wide-- ly carried on, the concrete as it leaves the mixer is a mechanical mixture of stone, or other coarse aggregate, sand or other finer aggregate, cement, and water. This mixture is produced in batches; that is to say, a meas-. ured quantity of stone, a measured quantity of sand, a measured quantity ofcement, and

a measured quantity of water are stirred together in the mixer. If it were possible always to have raw material of exactly the same quality and of the same degree of fineness, and always by practical means of measurement to introduce exactly the same quantity of each component into each batch, the concrete produced would be uniform in consistency, batch after batch; and, of course, uniform concrete uniformly spread might be expected to afford a uniform road. In practice, however, it is im ossible to obtain the raw material with per ect uniformity of size of particles, of degree of fineness, and of qualit and character; and especially it is impossible, under practical conditions, to have uniformity in the quantity of water present in successive batches. Always there is moisture present in the sand and stone employed, and the moisture so present is variable in quantity. This variability of water content disturbs the proportioning of the batch, and, particularly in the matter of water component, has the effect of causing successive batches to be irregular beyond control in thematters of wetness and consequent fluidity, The water content of the completed batch as it is dumped from the mixer to the road surface may vary in a degree as great as 40% of the actually desired quantity.

In any case, the road-spreading operation requires a mixed concrete of great fluidit a concrete whose water content is larger t an necessary to effect setting. In the road-building operation so much of the surplus water as may be, should be removed, and this without removing with the water any appreciable part of the cement. The water content of the batches being variable beyond practical control, the removal of surplus water to leave a uniform body of concrete is diflicult, because the quantity of the surplus is variable.

In road building it is necessary to employ machinery to spread the concrete; the slow and laborious hand spreading is inadequate, to meet the demands of speed and quantity. Ooncretespreading machinery hitherto employed acts upon the concrete as though it were uniform in composition and consistency, and as thou h its water content always were the same. I Iachine-spread roads, when finished, are liable to manifest undesired irregularities of surface, and particularly de- 1 pressions of surface, in which water will lie. The road on that account is inferior and is liable to more rapid deterioration.

Let it be assumed that two successive batches of mixed concrete are spread upon the sub-grade of a road, and that one batch has more water in it than the other. Such a condition may easily exist in what is considered a well conducted job. Let it be assumed that the ratio of cement, sand, and

stone used is 1:2:4, by volume. To mix 'theseeqlualities of the solid components to the foot of concrete.

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It is manifest that, if the excess quantity of water in the wet batch is not worked out before the final spreading operation either the concrete in the portion of the road produced from the wet batch will be relatively porous,

- or some surplus water will escape or be worked out subsequent to the spreading operation. In the latter event, although the grade and Y I the surface may have been correct, as left by the finishing machine, unequal settlement continues and the surface is found irregular half an hour later. In point of fact, such settlement actually occurs in very many cases in concrete roads as ordinarily built. The settlement is not uniform, but occurs in spots, so that the finished and hardened road presents an uneven surface, with numerous hol lows, below the normal surface. The depth of these hollows due to this cause may be as great as one quarter, or even one half an inch.

- Although irregularities of surface are commonly produced by faulty finishing due to other causes, as well as to lack of uniformity in water content, I have perceived such irregularities of surface as cannot be eli' inated by great care in the manipulation of ices now in use to be chiefly and primarily uhto the variation in the water content of adjacent portions of the layer of concrete when freshliy spread; and I have further perceived that a jacent portions of a road may differ in the matter of hardness and of friability, because of the differences in water content in the layer of concrete when spread. My invention lies in method and in machine which, instead of treating the concrete as though it were uniform in content and consistency from batch to batch as received from the mixer, spreads the concrete in a manner which renders it more instead of less uniform, and, removes from the concrete as it is spread a greater or less quantity of water, according as the particular 7,

batch is relatively wet or relatively dry; and so I produce a road of better uniformity, more satisfactory and more durable.

Referring to the drawings, a carriage 1 of suitable construction is mounted upon wheels 2, to travel along the rails 3, such as are customarily provided, both to carry the road-fin-' ishing machine, and to afford temporary walls or forms, between which the concrete is s read, and, until it has hardened, confined. he carriage may be understood to be equi ped with a' prime mover. This ordinari y will be a asoline engine, thou h manifestly it mightie a prime mover 0 another sort, an electric motor, for exam le. In the drawings I show diagrammatica y a sprocket wheel 4, which may be understood to be driven by the prime mover, and I have diagrammatically indicated operative connections with this sprocket wheel, for driving a shaft 5, mounted transversely in carriage 1. From the prime mover, and conveniently from the shaft 5, the carriage may be driven along the rails 3, through suitable driving connections; such, for instance, as those shown in Figs. I and II. Shaft 5 is equipped with a bevelled gear wheel 6, and a gear wheel 7 is integrated with one of the wheels 2 of the carriage. A connecting rod 8 equipped at one end with a bevel gear 9 and at the other with a worm 10, simultaneously engages gear wheels 6 and 7 and transmits rotation to the carriage wheel. The drive may be alternatelyforward, in the direction indicated by an arrow, Fig. I, or rearward.

The carriage is equipped with a plurality of rows of pressure shoes, in this instance two rows, which extend row by row transversely, and are spaced apart row from row in the direction of machine'travel. The shoes are singly reciprocable in vertical direction. The shoes of the forward row are indicated by the numeral 11, those of the second row by 12. As best seen in Figs. II and III, these shoes are conveniently rectangular in plan; their ne er surfaces are plane surfaces, or approxim tely plane surfaces, extending horizontally, or approximately horizontally, and conforming in these respects to the surface to which the concrete is to be shaped. Their forward lower edges are rounded. The shoes are situated side by side in close succession. The shoes are conveniently formed as steel castings. Those of the forward row are preferably wider in their front to rear extent than those to the rear. The shoes of the front row additionally are equipped with vertically standing plates 13 which constitute extensions of their front faces and which serve as limiting and pushingwalls for the.

soft concrete. The shoes are vertically reciprocable between suitable guides, and these guides may be beams such as 14, constituting part of the carriage structure.

Means are provided for reciprocating the shoes 11 and 12, causing succeeding shoes in the row to rise and descend successively, and for effecting reciprocation throughout a range so limited and defined as -to spread and press the concrete to the desired form and position. It is a matter of simple engineering to provide for such reciprocation of the pressure shoes, and the means which I show will be understood to be exemplary of suitable means to that end.

The shaft 5 is conveniently mounted in an intermediate position in the length of the carriage, and at a substantial interval above tically above the forward row. The shaft 15 is driven from shaft 5 and simultaneously with shaft 5, and means to that end, in the form of a sprocket chain drive 16,. are dia grammatically indicated in Fig. I. f

The shaft 5 carries a series of eccentrics 17 and the shaft 15 carries a series of eccentrics 18, and each eccentric is engaged by a block 19 (2(1) and to the blocks 19 and 20 the shoes 11 and 12 are severally pivotally secured. The eccentrics through such connections effect the limited reciprocation of the shoes, and manifestly the positioning of the succeeding eccentrics upon the shafts determines the intervals at which .the individual shoes succeed one another in their rise and descent.

Shaft 15 extends at a somewhat greater interval than does shaft 5 above the level of i the rails 3, the eccentrics 18 borne by shaft 15 are larger than those borne by shaft 5, and-the driving connections are indicated to be such in character that shaft 15 rotates at slower speed than shaft 5. Accordingly the range of reciprocation of shoes 11 is greater than that of shoes 12, a feature which though not essential is desirable. The positions of the two shafts 5 and 15 are minutely adjustable in vertical direction, by means of the slot and bolt connections indicated at 21, between the standards in which they are journaled and the frame of the machine.

The construction and adjustment are such that each shoe 11 comes to the limit of its downward thrust with its nether surface slightly higher than the ideal surface to which the concrete is being shaped. This particular position, being by the means described adjustable, will be determined in each particular case according to circumstances,

and primarily according to the thickness of the layer to which the concrete is to be spread. The shaft 5 is so minutely positioned in its vertical adjustment that the shoes 12 come to their limit of downward thrust in a surface more closely approaching, but still slightly higher than the ideal surface.

The shoes 11 are preferably of greater extent in front and rear direction than are the shoes 12. They are heavier, and, as has been explained,'their range of reciprocation is greater.

To the rear of the shoes 12 the machine frame carries a beam 22 extending transversely across the width of the space between the wheels, whose nether surface is of considerable extent in forward 'and'rear d1-- rection and whose nether surface conforms face, which comes. into contact with the concrete. The plates with which it is shod may be renewable and replaceable.

At the front of the machine ard members 24 are fixed. These afford 1n effect upward continuations of the vertical inner faces of the rails 3. At their forward tips they are turned and extend obliquely across the treads of the rails 3. These guard members hold the concrete and prevent it from spreading laterally, and they keep the rails clear for the advancing machine.

In operation the rails are set, the machine placed on the rails, and, the sub-grade having been properly prepared, concrete is dumped from the mixing machine in front of the finishing machine, and the finishing machine is advanced upon the roughly spread-out, mushy mass. As the machine advances, the shoes 11 and 12 work up'and down, and in each row the succeeding shoes work successively: One descends, then the next, and the next; and presently they rise again and descend again in the same succession. The first row of shoes acts on the mass of concrete both by pushing and treading, and shapes it to a layer of approximately the desired thickness. The second row of shoes, actin in like manner, reduces it more nearly to t e exact, desired thickness, and, finally, the beam 22 brings the layer to the ultimate desired thickness and gives to it its surface character.

The shoes 11, approximately flat over their nether surfaces and rounded at their forward edges, both press the concrete downward and push forward the surplus. There will be some flowing of the concrete rearward beneath the shoes 11 and some consequent rising of the mass to rearward of the down-pressed shoe. The shoe is however of sufficient length in the direction of travel, to prevent any considerable movement of that sort. The fact will be particularly noted that the concrete is more thoroughly worked beneath the plurality of 'vertically moving shoes than it would be, were the several shoes merged in a single and continuousbar, and more thoroughly than would be the case were such a single bar reciprocated horizontally in transverse direction. And in these respects the method is distinguished from that now commonly performed.

As the machine advances, the body of concrete immediately to the rear of the line of shoes 11 is at approximately the proper grade; the minute adjustment of the shoes 11 has, however, been such that the bod is somewhat above that proper grade. he value of the excess will in a given case be proportioned to the thickness of the layer which is being spread.

Between the rows of shoes 11 and 12 there is a stretch of concrete, reduced approximate- 1y to grade, but which has not yet received its final shaping and finishing. The body of concrete in this stretch is in a state of constant, though slight, movement, imparted to it by the shoes reciprocating immediately to the front and immediately to the rear. The effect is to compact the mass, causing water to work upward and flow away. The com- 39 ponent solid particles of the mass are not widely displaced. The operation is unlike that known as puddling. There is no kneading of the mass. The particles rock and tip one upon another, they move apart and together again through very slight intervals, but there is no appreciable sliding. In consequence, the particles assume positions of closer fit, and the water alone percolates upward to the surface. If the concrete has 39 a relatively large water content, the wa- I ter will escape more freely, and that without carrying away any substantial amount of cement. And because of the rise and escape of water in this region, the body of concrete upon which the shoes 12 work is stiffer and firmer than that upon which the shoes 11 work. Furthermore, the compacting efiect is greatest at the bottom of the layer. From that part the water is, by the minute movement described, in largest measure expelled.

When then the shoes 12 have acted upon the layer, and the bar 22 has followed, the layer,

although in its upper part it contains somewhat more water than in its lower part, will still not contain any such large quantity of surplus water as to cause any considerable amount of subsequent settling of the spread and compacted layer.

The shoes 12 as here shown are of less extent in the direction of carriage travel than the shoes 11. The beam 22 is of such extent in the direction of carriage travel that, as it holds down the now relatively stifi concrete, there is no flow of concrete to rearward beneath it and no consequent rise of concrete behind it.

The shoes 11 are of such dimensions,-and preferably the shoes 12 also are of such dimensions and so related in their period of reciprocation to the speed of advance of the machine, that the areas pressed upon successively by each shoe are overlapping areas.

Necessarily it is true of the machine when operating in the manner described, that concrete gradually accumulates, not only in front J of the row of shoes 11, but also in front of apart parallel transverse strips to successive the row of shoes 12. When such accumulations have increased to a considerable amount, the parts 11, 12, and 22 are raised bodily and brought to position again to rearward of the accumulation which had gathered immediately in front of the beam 22. Thisresetting of the work-engaging parts is, in the machine here illustrated, effected by lifting the whole carriage body and placing it again on the rails at a point to rearward. The machine is then caused to advance again, operating as before. In practice, in laying a road nine or ten inches thick, the machine will advance thirty feet or more, before the accumulations make resetting desirable. The machine then is reset five or six feet to rearward. Thus the accumulations are not wasted but are carried forward and incorporated in the road as it is progressively shaped and finished.

I call attention to the fact that in the operation of my machine there is no transverse racking strain exerted upon the rails 3. They stand firm at all times. This results in a better compacted body of concrete, more accurate cooperation of shaping instrumentalities, and a better job. Incidentally, deterioration of equipment is less rapid.-

I claim. as my invention:

1. The method herein described of spreadin g forward supplies of concrete heaped upon the sub-grade of a road and bringing the Worked-upon body to desired contour, which consists in subjecting the mass step by step, and over successive longitudinally overlapping relatively narrow transversely fractional areas to vertical pressure and at the same time restraining it to rearward of such areas from upward flow.

2. The method herein described of spreading to desired contour concrete heaped upon the sub-grade of a road and removing from the spread-out concrete :1 content of superfluous water which consists in subjecting localized areas of the layer along two spaced compressive strains.

3. In apparatus for spreading to layer form concrete heaped upon the sub-grade of a road, a transverse row of vertically reciprocable pressure plates, means for causing the said row of plates to advance upon and to engage immediately the heaped concrete, and means for reciprocating the pressure plates through a definite and predetermined range, the means for causing the plates to advance and the means for reciprocating the plates'being correlated, whereby each plate in its advance exerts pressure over overlapping areas.

4. In apparatus for spreading to layer form concrete heaped upon the sub-grade of a'road,

. a transverse row of vertically reciprocable pressure plates, means for reciprocating said plates in alternation through a definite and predetermined range, and means for causing the said row of plates to advance upon and to engage immediately the heaped concrete, the means for reciprocating the plates and the means for causing the row of plates to advance being correlated, whereby each plate in its advance exerts pressure over overlapping areas.

5. In a road-finishing machine, a carriage mounted on wheels and adapted to travel on a pair of road rails, two rows of pressure plates mounted in the carriage and extending transversely of the direction of carriage travel and vertically reciprocable in their mounting, means for reciprocating successively through a definite and predetermined range the plates within each row, and a broad transversely extending float beam arranged to rearward of the second row of pressure plates.

6. In apparatus for the shaping of a road surface to desired contour, a car mounted to move forward upon spaced-apart rails, a row of vertically reciprocable .pressure shoes mounted on said car, means for reciprocating said shoes in sequence between predetermined upper and lower limits, and a float beam broad relatively to said shoes arranged to rearward of said row of shoes for the purpose of preventing the rise of the concrete to rearward of the shoes, the nether side f said beam presenting to the concrete a smooth surface of desired profile.

In testimony whereof I have hereunto setmy hand.

WILLIAM M. VENABLE.

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