US1720377A - Machine for arranging paving materials - Google Patents

Description

July 9, 1929. c. s. POPE MACHINE FOR ARRANGING PAVING MATERIALS Filed May 8, 1928 Patented July 9, 1929 CHARLES STOCKTON POPE, 0F SACRAMENTO, CALIFORNIA.

unc'nmn non ARBANG Application filed May 8,

This invention relates to a machine for arranging paving materials between the conventional forms such as are used in roadway construction.

The invention has for its object to pro vide a machine capable ofperforming the following operationsi to evenly spread asphaltic or concrete pavement mixtures; to thoroughly rakethe mixture so spread to an even and uniform texture and density; to so rake the mixture that the coarser particles are lifted to the upper part of the layer of asphaltic or other mixtures and the finer particles are deposited in the lower part of the layer; to cause a uniform distribution of coarser particles throu bout the mixture without undue accumu ation of the same sized material in any one location; to form small furrows in the mixture which will permit of better and easier compacting of the same and which will tend to provide that deformation, if any, shall take place in a direction longitudinally of or parallel with the direction of traflic on any pave- Inent rather than transverse to the same; to redistribute the material already spread and raked in a uniform and smooth manner over the entire road cross section of a uniform thickness and in the most economical manner.

The invention applies to a machine constructed especially for the mechanical spreading and arranging of hot or cold asphaltic or cement mixtures such as asphaltic or cement concrete, Topeka mixture or sheet asphalt, or other form of mixed pavement base or surface, including Portland cement concrete.

One form which my invention may assume is exemplified in the following description and illustrated in the accompanying drawing, in which Fig. 1 shows a side elevation of the machine; v

Fig. 2 shows a front elevation of the same;

Fig. 3 shows a vertical transverse sectional view, taken adjacent the raking elements; Y

ING PAVING MATERIALS.

1928. Serial no. 276,147.

by the motor 13 mounted upon the main frame.

At the front of the frame is a screed or strike-off blade 14 suspended by vertically adjustable devices such as screws 15 mounted in brackets 16 secured to a cross-frame 17. This cross-frame is mounted slidably on a rod 18 and reciprocates transversely of the roadway, being actuated by suitable connections such as cranks and links 19 driven by the motor. The reciprocating cross-frame is stabilized and guided by vertical rollers 20 mounted on the main frame and the screed in turn is supported and guided at'its ends in vertical guideways 21 fixed to the reciprocating cross-frame. The details of this construction, however, form no part of my present invention, and there are numerous other arrangements capable of being used to mount the screed for reciprocating movement transversely of the roller. The bottom edge of the screed is preferably given a curvature corresponding to the crown of the roadway, and its function is to level off and spread the paving mixture between the forms. In order that enough material may be deposited between the forms to permit of subsequent compacting, the

' blade is held spaced above the forms by ,shoes 22 secured to the blade and riding upon the forms.

Behind the front screed I provide one or more sets of raking elements, two sets being shown in the present instance, and designated by the numerals 23 and 24, one being' arranged immediately behind the other. Each set includes a transversely extending bar provided with teeth extending throughout the width of the space between the forms, the teeth being evenly spaced and the teeth of the second row being Staggered with relation to those in the front row. A convenient spacing for this purpose has been found to be four inches between adjacent teeth, which, in view of the staggered relationship of the teeth, provides an effective 26 fixed to one bar and having a link and crank arm connection 27 with-the other bar, said lever being provided with suitable quadrant and detent mechanism 28.

I also find it desirable and advantageous to impart to these rake teeth a fore-and-aft,

lineal, reciprocating motion. This can be provided for by mounting the bearings 25 slidablyon fore-and-aft extending shafts 29, secured t -the main frame and transmitting reciprocating motion to'the slidable bearings by means of rocker arms 30 pivotally mounted on the main frame and actuated by suitable cranks and connecting rods 31 driven by a motor. The teeth, however, should not be permitted any motion transversely of the roadway.

In cases where asphaltic paving materials are being laid, it is preferable to provide a screed or leveling blade 32 behind the rakes. I

This blade. may be similar in construction and operation to the front 'blade 14, and serves to level off the material to the desired height above the forms, smoothing the same and partially filling the furrows caused by the rake teeth.

On asphalt concrete work, the operation of the machine is as follows:

The machine performs its best work on mixture which has been previously spread by means of spreader boxes to approximately an even surface of the proper thickness to provide a slight wave of mixture in front of the first strike-01f blade.

The forward strike-off blade is set at the proper elevation for the first spreading of the material, usuall about one inch above the surface of the ished grade as determined'by the correct cross-section.

The function of the first strike-ofl' blade is to uniformly spread the material, but not to'compact it.

The rake teeth are set to the proper depth,

and during the operation of the machine they perform several purposes, as follows: (a1) They flufi' up the mixture to a uniform and regular density over all portions of the pavement surface, a condition not obtained by hand raking;

(6) They arrange the rock particles in symmetrical and regular order, eliminating the chance arrangement of the particles in relation to each other which occurs in hand raking;

(0) They form the surface into longitudinal furrows in which the particles are uniformly and symmetrically arranged with relation to each other;

(J) The larger particles of the mixture are brought to the surface by the rakes placing them in a position whence they may be rolled again into the surface, forming a mosaic, non-skid wearing surface;

(6) The formation of longitudinal fur rows places the mixture in such a condition that when a roller is subsequently passed over the furrowed mixture, the first compression tends to be lateral to the direction of rolling rather than in line with it.

This condition causes the mixture to be compressed without pushing ahead of the roller, as is common with asphaltic mixture not arranged in longitudinal furrows. (f) The rake teeth are inclined forwardly and downwardly instead of being vertical, for the purpose of digging under and lifting the asphaltic concrete mixture.

(g) The teeth are made to vibrate for the purpose of relieving pressure, which purpose is also promoted by the inclination of the teeth.

(It) Propulsion of the machine is facilitated by the reciprocating, inclined teeth, due to the fact that on the rearward stroke the teeth will meet greater resistance than on the forward stroke.

The second strike-off blade is set approximately one-half inch above the plane of the theoretical surface and spreads the raked mixture'to a true and uniform surface.

At the same time, the second blade partially fills the furrows with the coarser particles of surface thrown up by the rake teeth.

While the machine may pass over the surface but once, it may be advisable in some cases to pass the machine over the surface a number of times, in order to secure a perfect surface.

ForPortland cement concrete pavement, the operation and purpose of the machine is as follows:

The cement concrete is struck off and leveled as before by means of the forward strike-off blade.

The rakes then operate to bring the coarser stone to the surface and to drop the mortar and finer particles to the subgrade.

A tamping-board, as in the Lakewood machine, or a kneading-screed, as in the 0rd machine, takes the place of the second strike-off blade and smooths the concrete to an even surface, in which the coarse stone is largely near the surface of the pavement.

' The advantage of this method over the results obtained by the usual methods of finishing concrete pavement is as follows:

In the operation of. the usual type of tamping and finishing machine, the concrete is tamped or kneaded with the idea of bringing the mortar to the surface and burying the stone in the mass of the concrete. This method quite often results in the construction of a slab in which the portion in contact with the'subgrade is more or less open and porous, while the upper portion of the slab consists largely of mortar. As a consequence, in the thicker pavements, the full strength of the slab may not be developed, because of the voids in the base, and the Wear of traffic will come on mortar instead of on the harder and coarser aggregate. Agglomeration ofcoarse aggregates in certain areas also occurs due to faulty distribution which leads to lack of uniform strength in different areas.

By the use of the rake, three objects are accomplished, as follows:

First, the mortar is dropped to the bottom of the slab, whence it must be lifted by the tamping action toward the top, thus tending to produce a slab free from voids where it comes in contact with the subgrade.

Second, the coarser particles are brought to the surface, whence they can be tamped back into the slab to form a hard and durable wearing surface.

Third, the aggregates are all so distributed by the raking process that the texture and arrangement of particles of materials under the various surface areas of the'slab are uniformly arranged with relation to each other.

The intent of the whole process is to produce a slab which will have uniform strength and texture at all points of the surface.

It is important that the rake teeth, in case of asphaltic concrete, have no motion transversely of thdroadway, as it would tend to create furrows in a direction which would create, rather than hinder, the ultimate formation of transverse corrugations -in the finished surface.

Having thus described it my invention, what I claim as new and desire to secure by Letters Patent is:

1. The combination with a machine adapted to travel over the side rails of a conventional pavement form and having means to spread the paving materialbetween the forms, of a transversely extending raking element provided with teeth to penetrate the paving material, said teeth being stationary in a direction transversely of the paving strip, whereby to form in the latter furrows extending uniformly longitudinally of said strip, and means for imparting motion to said teeth parallel with the direction of travel of the machine.

2. The combination with a machine adapted to travel over the side rails of a conventional pavement form and having means to spread the paving material between adapted to travel over the side rails of a conventional pavement form and having means to spread the paving material between the forms, of a transversely extending raking element provided with teeth to penetrate the paving material, said teeth being stationary in a direction transversely of the paving strip, whereby to form in the latter furrows extending uniformly longitudinally of said strip, said teeth being inclined forwardly and downwardly.

4. The combination with v a machine adapted to travel over the side rails of a conventional pavement form and having means to spread the paving material between the forms, of a transversely extending raking element provided with teeth to penetrate the paving material, said teeth being inclined forwardly and downwardly, whereby to tend to lift the larger particles contained in the paving material towards the upper crust of the layer.

5. In combination with a machine adapted to travel over the side rails of a conventional pavement form, a screed to spread the paving mixture between the forms, means for reciprocating the screed transversely of the forms, and a raking element arranged behind the screed and provided with teeth so arranged as to penetrate the paving material and form therein longitudinally extending furrows.

6. In combination with a machine adapted to travel over the side rails of a conventional pavement form, a screed to spread the paving mixture between the forms, means for reciprocating the screed transversely of the forms, a raking element arranged behind the screed and provided with teeth so arranged as to penetrate the paving material and form therein longitudinally extending furrows, and means behind the teeth for smoothing off the paving material.

7. The combination with a machine adapted to travel over-the side rails of a conventional pavement form and having means to spread the, paving material between the forms, of a pair of raking elements, one 5 in advance of the other, each provided with teeth to penetrate the paving material and form longitudinal furrows therein, said teeth being inclined forwardly and downwardly, the teeth in one row being staggered with relation to those in the other row, and 10 means for imparting a fore-and-aft lineal movement to said teeth.

CHARLES STOCKTON POPE.

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