US2002661A - Machine for paving highways - Google Patents

Description

MACHINE FOR PAVING HI GHWAYS Filed May 14, 1928 6 Sheets-Sheet l May 28, 1935. A. w. FRENCH MACHINE FOR PAVING HIGHWAYS 6 Sh eets-Sh eet 2 Filed May 14', 1928 V MT H H O I 0 F a .90. l u l L G hnP-fll I. I. i Y) I II I will i 6 Sheets-Sheet 3 frlr a .1:- .imi m i Q @a May 28, 1935. A. w. FRENCH MACHINE FOR PAVING HIGHWAYS Filed May 14, 1928 May 28, 1935. A. w. FRENCH 2,002,661

MACHINE FOR PAVING HIGHWAYS l iled May 14, 1928 e Sheets-Sheet 4 m Q w ,W X n May 28 1935. A. w. FRENCH MACHINE FOR PAVING HIGHWAYS Filed'May 14, 1928 6 Sheets-Sheet 5 Ill/II VIII/A y 28, 1935' A. w. FRENCH MACHINE FOR PAVING HIGHWAYS e Sheets-Sheet 6 Filed Ma 14, 1928 few Patented May 28, 1935 UNITED STATES PATENT OFFICE 2,002,661 MACHINE FOR PAVING HIGHWAYS Application 'May 14, 1928, Serial No. 277,613

8 Claims. (01. 94-45) This invention relates to the road paving art and has several objects, the first. of which is to provide a novel method of treatingthe paving materials, such as cement and bituminous concretes, respectively, and second course of finishing coat material following deposit thereof upon the subgrade to first render the same of substantially uniform density throughout and rid the same of air pockets while also loosening up the mass to primarily reduce rather than increase density prior to the subsequent compaction of the mass and effecting such compaction at least in part directly after the aforesaid primary step is completed and before the material can settle to any appreciable extent by gravity. l

A further function of the primary step of the method above mentioned is to effect a more uni; form distribution of the coarse aggregate of the concrete mass throughout the finer portion thereof and particularly to prevent such coarser aggregate from becoming disposed in greater proportion in the lower than in the upper portion of the mass. V

The second object of the invention is to provide a method of the above general type which can be successfully carried out by a. conventional compacting and surfacing machine without necessitating increase in the motive power of the latter and whereby such portion of the power as is required for carrying out the said method is utilized to propel the machine over the subgrade. .7

Further objects of the invention include the provision of mechanism for accomplishing the two first-mentioned objects in the form of a single or multiplicity of attachments for the con-' ventional machines as heretofore used in order that the owners of such machines may adapt the same at small cost to uses not originally contemplated by the manufacturer or manufacturers,

Other objects relate more particularly to certain details of construction of the mechanism or mechanisms for carrying out the aforesaid method and will be made clear in the following specification.

In the accompanying drawings illustrating the mechanisms involved in the invention and constituting meansfor carrying out the method.

Fig. 1 is a plan view of a machine constructed in accordance with the invention.

Fig. 2 is aside elevation of the same.

Fig. 3 is a vertical transverse section of the same on the line 33 of Fig. 1.

. Fig. 4- is-a fragmentary vertical longitudinal section on the line 4-4 of Fig. 1.

Fig. 5 is a vertical transverse section on the line 5-5 of Fig.2.

Fig. 6 is a fragmentary front elevation of the front strike-off and'compacting element or screed of the machine.

Figs. '7 and Bare sectional views on the lines 'll and 8 8, respectively, of Fig. 6.

, Fig. 9 is a fragmentary front elevation of a frame member of the carriage seen from the line 99 of Fig. 4. I

Fig. 10 is a sectional view on the line llll0 of Fig. 9.

Figs. 11, 12 and 13 are vertical transverse sec tional views of a conventional two-course bituminous or asphaltic pavement except as to surface grooves shown.

Fig. 14 is a fragmentary detail vertical section showing a modified surface scoring or grooving mechanism;

. Fig. 15 is a fragmentary rear view of the machineshowing the mechanism for effecting reciprocation of the screeds and strike-off members.

A brief review of the modern method of constructing pavements will serve to make clear the distinctions between present practice and that contemplated by this invention as expressed in terms of method.

After setting the side rails or side forms and preparing the subgrade between said forms, the paving material consisting of either Portland cementor bituminous cement concrete containing a large percentage of coarse aggregate, is deposited on the subgrade and is usually primarily spread or distributed by hand labor to reduce the heaps to a lower level which is somewhat higher than the ultimate level of said mass. In two-' course pavements this concrete is reduced to a level below the tops of. the side forms and the manual spreading is followed by I striking off, usually by means of a machine adapted to that purpose. Two-course pavements are seldom composed of Portland cement concrete and'a top dressing of finer material except in instances where the top course is to consist of an asphaltic material. In such cases the foundation course of Portland cement concrete is suitably compacted after or at the time of striking off.

In the manual spreading of the paving material the operators step into the plastic mass and, in the case of bituminous substance, and where the Portland cement concrete is of the type known as dry mix containing very little water, the foot prints of the operators cause local portions of the aggregate to be compacted. In bituminous concrete these spots of compaction are undesirable in that they cause lack of uniformity in the hardness of the pavement which, in time, become appreciable at the surface.

It is also well known that in the heaps of paving material deposited on the sub-grade and superficially manually distributed there are air pockets which, if not broken to release contained air, leave weak spots in the finished pavement which break down under trafiic. Hence it is Very desirable that following the deposit and superficial manual distribution of the paving material in both single and multiple course paving, the still plastic mass should be agitated to, so to speak, fiufi it up to break up the foot-compacted portions and break up the air pockets.

It hasbeen heretofore proposed to accomplish the superficial spreading, the fiuffing up, etc. by means of machines equipped with laterally reciprocable rakes which, in effect, perform the same general function as the manually manipulated rakes'now used for the same purpose but practice has clearly demonstrated that this type of raking cannot extend to any appreciable'clepth because of the resistance of the mass being manipulated so that only a superficial agitation can be effected and this causes a settling and partial compaction of the portion below the zone or level of action of the tines of the rakes used and serves to more completely trap rather than release air in pockets in the mass.

v The method of the present invention distinguishes from the now commonly practiced meth- 0d of treating or manipulating the plastic mass after deposit upon the subgrade in that it consists in subjecting that mass to agitation from the lowermost to and through the surface thereof by means of rakes or the substantial equivalent of rakes which penetrate to any desired depth and move upwardly through said mass to lift and cut through the same to thereby not only vent the air pockets but effect a more uniform distribution of the coarse aggregate thereof through and with respect to the finer aggregate and serves also to break up the foot-compacted portions of the mass.

This flufling up, breaking up and venting of the mass precedes the striking-01f and compaction of the same and serves to promote uniform density of the whole mass when compacted.

In the case of bituminous concrete and finishing or top course, the striking-01f and primary compaction is efiected at a sufiiciently higher level than the ultimate surface of the compacted mass to allow for secondary compaction by means of heavy rollers.

Consistently with the above mentioned main objects of the invention which include that of adding the mechanism for carrying out the above described method to existing conventional types of pavement finishing machines in the form of an attachment or attachments thereto, I have herein illustrated said mechanism as added to the machine described and claimed in United States Letters Patent to William Ord, No. 1,522,138, dated January 6, 1925, the said drawings corresponding with the latest embodiment of the patented structure differing from those of the said patent only in minor details.

The machine comprises a carriage consisting of side members I and cross-beams, which include the front beam 2 consisting of a conventional channel-bar. This carriage is supported upon the trucks 3 and 4 at each side of the machine.. The engine 5 on the carriage is suitably geared to the wheels of the truck 3 for propelling the carriage over the side forms 6 bordering the subgrade which receives the pavement.

In front of the trucks 3 and between the latter and the trucks 4 there are mounted reciprocable strike-off, compacting and surfacing members 1 and 8, respectively, consisting of channelbars rigidly associated with I-beams 9 and II], respectively, in such manner as to permit said channel-bars to be flexed to a curvature corresponding with the predetermined crown of the pavement surface. The channel-bars l and 8 are termed screeds and normally rest at their ends (which are equipped with renewable wearing shoes ll) upon the side forms 6 which serve as guides for said screeds. The latter are suitably geared to the engine 5 for reciprocation relatively to the carriage and transversely of the side forms. Suitable manually operable lever mechanism I2 is associated with the carriage and said screeds for lifting either or both the latter out of operative relation to the paving material.

The gear sets associating the engine with the traction wheels of the front truck 3 and associating the same with the screeds, respectively, includes suitable manually controlled clutches for causing the machine to travel forward and reversely or remaining idle and for causing the screeds to reciprocate or remain idle.

The front screed, which I will refer to as screed 1, includes, in the aforesaid Ord patent and in its commercial embodiment, a vertically disposed front plate or apron which permits the accumulation of a relatively high level mass of the paving material which is struck off from the mass, and is advanced by the machine, and, by what may be aptly termed the equivalent of hydrostatic head, exerts pressure on the underlying material for compaction thereof as is fully described in said Letters Patent.

In the instant case, this apron It includes a section l5 which is made of such total width as the distance between the side forms 6 less the length of reciprocatory stroke of the front screed 1 plus an allowance for clearance. It is also vertically adjustable relatively to said screed l, the latter being, for this purpose, equipped with brackets IS in which the screw-shafts I? threaded into the hand-wheels [8 are rotatably mounted. The lower ends of said shafts I? are non-rotatably engaged with the brackets at the upper edge of the apron section I5. The latter will be hereinafter referred to as the low-level strikeoff member which, in combination with the screed l constitutes an important feature of the present invention in that, so far as I am informed, the screed guided by the side forms for striking-off paving material to the level determined by said side forms, in combination with an adjustable member for striking-off at a lower level, is entirely novel in this art and affords the advantage of constituting a simple and inexpensive expedient for adapting a machine designed and'intended for striking-oi only at the level determined by the side forms, as for single course paving, for also striking-01f at lower levels for multiple course paving.

The main portion ofthe present invention, however, consists of a carriage 20 which includes the side bars so designated and suitable cross bars and which is supported upon the wheels 2! which also travel on the side forms. This carriage is attachable to and detachable from the carriage l and carries the mechanism whereby the aforesaid method of theinvention is carried out.

This mechanism consists of a, skeleton trussframe 22 comprising parallel front and rear bars 23 and 24 connected by cross bars 25 and reinforced by means of two trusses 26 and 21 which extend at acute angles to eachother, are joined along their upper edges and of which thebars 23 and 24 constitute the lower edge members, the whole resulting structure being substantially triangular in cross-section. This truss-frame is equipped with triangularend plates 28 which carry hub members 29 journalled in bearings 30 mounted on the side bars of the carriage 2|].

Rigid with said plates 28 are hand levers 3| which, in turn, are associated with substantially semi-circular perforated members 32 mounted on theside bars of the carriage 20, there being latch mechanism associated with said levers and engaging in the perforations of the members 32 to retain said levers in any desired position relativelyto the latter.

The cross bars 25 connecting the bars 23 and 24 of the truss-frame at the ends of the latter are bent or formed so that their middle portions are appreciably offset from and below said bars 23 and 24. Said bars 25 carry bearings 34 in which the shaft 35 which, preferably, is hollow, is journalled. Secured to said shaft 35 are the tines or teeth 36 of which there are preferably four sets spaced approximately'ninety degrees from each other circumferentially. Each set of said tines or teeth is disposed somewhat helically of the shaft 35 so that the several teeth of said set .will successively engage in the material to be penetrated and agitated thereby and the several sets so arranged with relation to each other, by reason of the helical disposition aforesaid, that substantially the same number of teeth or the same proportion of the aggregate number ofteeth will, at all times, be partially embedded in the said material. In the ends of the hollow shaft 35 are stud-shafts 3'! which'engage in the bearings 34 and mounted upon one of said stud-shafts 31 is a sprocket wheel 38. l

J ournalled in one of the hub members 29 and in a bearing 39 disposed inwardly thereof and carried by the truss-frame, is a shaft 40 which is equipped with a sprocket wheel 4| which is geared to the sprocket wheel 38 by means of the chain 42. At the outer end of the shaft 49 is another sprocket pinion 43 whichis geared bymeans of the chain 44 with a sprocket wheel 45 on a shaft 46 journalled in bearings 41 mounted upon the side members of the frame 20. The shaft 46 carries a spur-gear 48 which meshes with the spur-pinion 49 on the shaft 50 which is journalled in bearings 5| on the side members of the frame I.

The shaft 53 carries a sprocket wheel 52 which is suitably geared to the engine, said gearing being controlled by a clutch 53.

The hub member 29 at the other end of the truss-frame is equipped with end plates 54 and 55 held in place by means of the bolt 56, one of said plates constituting a stop-collar engaging one of the bearings 30 to prevent longitudinal or endwise movement of the truss-frame relatively to the carriage 29.

The latch mechanism for engaging in the perforations of the members 32 is best illustrated in Fig. 5 and comprises straps 51 on the levers 3| for confining the members '32, reciprocable latch bolts 58. at the ends of rods 59 and 60, and a lever 6| pivotally supported between its ends on the pivot element 62 and also pivotally associated with the rods 59 and 60 above and below said pivot element 62 to thereby cause said rods to move simultaneously in opposite directions responsively to movement of said lever.

It will be noted that the rake teeth or tines 36 are substantially L-shaped and have chisel shaped free ends for easy penetration of the mass of material. Initial penetration is effected by the shorter end-arms of said teeth or tines (which travel substantially in circles) before the radial portions or shanks of the teeth ortines enter the mass. The direction of rotation of the shaft 35 and said teeth 36 is the same as that of the wheels 2| in forward travel of the machine but at higher speed of rotation than said wheels. Consequently the action of the teeth in the mass is such that agitation thereof is effected mainly by the short end arms of said teeth because the travel of the radial shanks of the latter through the mass equals the speed of rotation of said shanks minus the speed of forward travel of the carriage of the machine.

It will be observed that because of the direction of rotation of the rake teeth with respect to forward travel of the carriage, the tendency of the rakes will be to draw the carriage forward at a higher speed than that at which it is normally propelled through the gearing from the engine to the wheels of the truck 3. Hence, when the rakes are active, the last-mentioned gearing acts to retard travel of the carriage just as throwing the engine of an automotive vehicle into low and shutting ofi the spark will act to retard coasting of the vehicle. Thus the operation of the rakes effects propulsion of the carriage and causes the power otherwise consumed in propelling the carriage via the traction wheels to be applied via the rakes.

By means of the levers 3| the rakes are raised and lowered for throwing them out of operative relation to the paving material and to regulate the depth to which they penetrate the latter. Thus the rakes can be adjusted to treat the material of each course of material as it is deposited upon the next preceding course.

In the paving of roads with concrete it is the present practice to manually insert spades between the side forms and the paving material in order to crowd coarse aggregate away from said forms and cause a film of the finer aggregate or mortar to become disposed between the inner faces of the side forms and the coarse aggregate so that when the side forms are removed the side faces of the pavement will not present voids and a general rough aspect.

In the instant machine, I provide means for obviating this spading which are exemplified by dished disks 63, similar to harrow-disks, which are non-rotatably mounted upon the ends of the stud shafts 31 in such position that the circumferential edges of said disks are in contact with the inner faces of the side forms and their convex faces opposed to each other. These disks 63 are of the same diameter as that of the cylindrical plane of travel of the points of the rake teeth 36 so that said disks will penetrate as deeply as said rake teeth. Other means may, obviously, be substituted for said disks, the latter being however, very well and possibly better adapted to perform this function than other devices. The disks 63 are slidable on said stud shafts 31 and are held by light springs 63 in contact with the inner faces of the side forms.

The several wheels of the carriages and 20 are flanged along both edges. One of the main purposes of these flanges is to retain on the forms 6 strips of metal of such thickness as may be desired for enabling-the screeds l and 8 tot strike-off and smooth the finishing course of ma terial at a sufficiently higher level than the ultimate pavement surface to allow for subsequent compaction by heavy rollers as in bituminous or asphaltic pavements, the rollers reducing the top surface to the proper level.

It has been proposed to render asphaltic pavements, which are very slippery when wet, less liable to cause skidding of vehicles by providing longitudinal grooves in the top' surfacesof said pavements. 1

In the instant machine this may be easily accomplished by means of the series of teeth 6 carried by a vertically adjustable bar 65 suitably mounted on the member 2 of the frame and which may be raised and lowered by means of hand screws 56.

As illustrated in Figs. 12 and 13, the teeth 64 are lowered to score the still soft or plastic finishing course to a depth greater than the thickness of the strips on the side forms 5 which determine the higher strike-off level so that in the subsequent compaction of this course the grooves El will be reduced in depth to the extent desired.

In Fig. 14, I have illustrated a modified form of grooving mechanism which consists of a series of rollers 68 which may be shaped as desired to form ll-shaped or similarly shaped grooves in the uncompacted but leveled pavement surface, the number of said rollers corresponding with the number of. teeth 6% for which they may be substituted or in conjunction with which they may be used as will be obvious without special illustration. That is to say the teeth 6 may be associated with on of the cross-members of the frame I and the rollers 68 with another member either in front or behind that with which the teeth 6&- are associated. The rollers 633 may be arranged in several groups and each group carried by a shaft 69 of proper length which is journalled atits ends in bearings at the ends of arms 18' pivotally associated with a cross-beam of the frame I, as for example, the beam 2. Adjustment of the depth to which the rollers 58 groove the pavement surface is suitably regulated by means of hand-screws ll operatively associated with the beam and the arms l'il.

In the case of the rake teeth 36, the free end portions or short arms must be looked upon as the teeth or tines per se and the shanks-as the equivalent of the ordinary rake handle. It will be noted that the said teeth penetrate the mass of material in a general direction parallel with the general plane of the surface thereof and that, following such penetration or undercutting, the general direction of movement of said teeth is upwar .ly through the mass. The speed of rotation of the shaft 35 relatively to the speed of travel of the machine over the side forms is such that the rake tee h 3t and the shanks thereof would produce continuous rifts or furrows in the mass corresponding in number with the total number of teeth or sets thereof provided on said shaft 35 from end to end of the latter. These rifts or furrows are quite closely spaced from each other and are quite essential to proper venting of the mass. By reason of the fact that the mass is either plastic or in loose state, the rifts or furrows close instantly and leave only shallow surface depressions to indicate Where the rakes have passed through the same.

In the case of Portland cement concrete, it not infrequentlyhappe'ns that the material is dumped upon the subgrade far in advance of the finishing machine and becomes partially set. In such cases the rake teeth not only perform the aforesaid functions but also effect what is termed a retempering or reconditioning of the mass just preceding compaction and finishing operations.

In practice it is. found that in manipulating the plastic concrete as hereinabove described, the coarser elements are brought to the surface while the mortar constituent sinks to the lower levels. In the brief interval elapsing between the operation of raking and that of compacting and finishing, the coarse elements settle back into the mortar to the extent that sufiicient of the latter is brought to the surface to cover said coarse elements and completely fill the superficial voids between the latter so that a perfectly smooth sur face is obtained while at the same time, the coarse elements are so arranged that fiat surfaces thereof are presented immediately below the thin coating of cement mortar which is soon worn away by traffic to expose said coarse elements to wear, which is most desirable because of the fact that such coarse elements are far more wear-resistant than set cement mortar or, in the case of bituminous concrete, the thin layer of normally fluffy bituminous substance constituting the substantial equivalent of the cement mortar of Portland cement concrete.

It has also been found that paving material manipulated as above described, is far denser and harder than is true of paving material compacted and smoothed without first being stirred up as hereinabove described so that the actual volume of paving material per lineal foot of roadway required to be supplied is appreciably greater than is otherwise required which clearly indicates that more of the air or gas. content of the material is freed by the aforesaid manipulation and that by reason of also bringing the coarse elements to the surface, the degree of compaction of the mass is appreciably increased.

In order to disassociate the carriage 29 from the carriage l, pins or bolts 72 which pass through openings in extension flanges 13 of the side members of the frame 2% and through the side members of the frame 5 are withdrawn. The extension flanges 13 are so arranged that when the pins or bolts 712 are withdrawn, the frames I and 2H may be moved toward each other a sufficient distance to permit the sprocket chain 74 to be removed from the sprockets 52 and 75, whereupon the two carriages are free from each other.

The reciprocation of the screeds 3 and 9 and the strike-off member (i5) attached to the screed 3 is effected by means of the shaft (8!?) (Fig. 1) which isgeared to the engine and is equipped at its ends with cranks (ill) which are connecting by means of connecting rods or pitmen (32) with the rocking segments (83). The latter are mounted on stud-shafts which are paralleled in bearings (84) on the machine frame and are connected by means of connecting rods (85) with the screeds 8 and 9 as particularly illustrated in Fig. 5.

I claim as my invention:

1. A machine of the kind specified including a carriage equipped with drive wheels for travel on the side forms of a road bed, a rake rotatable on a horizontal axis disposed at the front of the carriage and having its rake teeth disposed substantially helically about the axis and arranged to cause a substantially uniform number of said teeth at all times engaged in plastic paving material disposed in advance of said carriage, said teeth rotatable in a direction to cause the same to exert propelling force on the carriage, and an engine on the latter geared tosaid rake and said drive wheels for propelling the latter at less than the speed of propulsion exerted by said rake to thereby retard travel of the carriage under the influence of said rake.

2. In a paving machine equipped with drive wheels for travel on the side forms of a road bed, a rotary rake, an engine on the carriage operatively associated with said rake for actuating the latter in a direction to cause said rake to coact with manipulable paving material onthe road bed to exert propelling force on said carriage in its normal direction of travel, gearing between said engine and said drive wheels for retarding the speed of travel of said carriage against the action of said rake, and means associated with said rake for rotation coincidentally therewith and disposed contiguous to the inner faces of the side rails for temporarily crowding paving material inwardly from said forms.

3. A paving machine comprising a carriage adapted for travel over a road-bed, a rotary rake spanning the road-bed mounted at the forward end of said carriage and adapted to penetrate and manipulate concrete deposited on the roadbed, a reciprocable strike-off member on the carriage behind said rake, an engine on the carriage for actuating said rake and said member and effect travel of said carriage, said rakes arranged to rotate in the same direction and at higher speed than the wheels of said carriage during forward travel of the latter.

4. In a machine of the kind specified, a wheeled carriage adapted to travel on the side rails of a road-bed, a horizontal shaft mounted upon the forward end of the carriage frame and spanning the road-bed, opposed disks having convex inner opposed faces mounted upon opposite end portions of said shaft and arranged to have their peripheral edges in contact with the inner faces of the side forms from the tops to points below the normal level of concrete deposited upon the road-bed, rake teeth on said shaft between the said disks arranged to penetratethe said concrete to substantially the same depth as said disks, and an engine on the carriage geared to the wheels thereof and to said shaft for rotating the latter in the same direction as and at greater speed than said carriage wheels.

5. In a machine of the kind specified, a wheeled carriage adapted to travel on the side rails of a road-bed, a horizontal shaft mounted upon the forward end of the carriage frame and spanning the road-bed, opposed disks having convex inner opposed faces mounted upon opposite end portions of said shaft and arranged to have their peripheral edges in contact with the inner faces of the side forms from the tops to points below the normal level of concrete deposited upon the road-bed, rake teeth on said shaft between the said disks arranged to penetrate the said concrete tosubstantially the same depth as said disks, a reciprocable strike-01f member rearwardly of said shaft, and an engine on the carriage for actuating said member and geared to the carriage wheels and said shaft to rotate the same in a common direction at respectively different speeds.

6. In a machine of the kind specified, a wheeled carriage adapted to travel on the side forms of a road-bed containing manipulable concrete, means at the forward end of'the carriage for agitating the concrete over the entire width of the roadbed, said means including devices for crowding concrete inwardly from the inner faces of the side rails, a reciprocable strike-off member behind said means, and an engine on said carriage for actuating said means, devices and member and propelling the carriage.

7. A machine of the kind specified including a wheeled carriage adapted to travel on-the side forms of a road-bed containing manipulable concrete, means on the forward end of the carriage rotatable about a horizontal axis and spanning the road-bed for penetrating and agitating said concrete, a reciprocable strike-off member disposed behind said means, and devices associated with said means and member for scraping concrete from the inner faces of the side rails and moving the same into the path of said means and said member, an engine on the carriage for actuating said means, member and devices and propelling said carriage.

8. A machine of the kind specified including a wheeled carriage adapted to travel on the side forms of a road-bed containing manipulable concrete, means on the forward end of the carriage rotatable about a horizontal axis and spanning the road-bed for penetrating and agitating said concrete, a reciprocable strike-01f member disposed behind said means, and devices associated with said means and member for scraping concrete from the inner faces of the side rails and moving the same into the path of said means and said member, an engine on the carriage for actuating said means, member and devices and geared to the carriage wheels for rotating the latter in the same direction as said means and at less speed.

ALFRED W. FRENQH.

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