US2449710A - Concrete spreading apparatus - Google Patents

Description

Sept. 21, 1948. A. E. MILLER ET AL r 2,449,710

CONCRETE SPREADING APPARATUS Filed March 15, 1945 5 Sheets-Sheet l Sept. 21, 1948.

Filed March 15, 1945 A. E. MILLER ET AL CONCRETE SPREADING APPARATUS -5 Sheets-Sheet 4 GGOIyK and fiudolphELz'ndaw,

Sept. 21, 1948. A. E. MILLER ET AL 2,449,710

CONCRETE SPREADING APPARATUS Filed March 15, 1945 5 Sheets-Sheet 5 Patented Sept. 21, 1948 CONCRETE SPREADING APPARATUS Arthur E. Miller and George K. Viall, Milwaukee,

and Rudolph F. Lindow, Wauwatosa, Wis., assignors to Chain Belt Company, Milwaukee, Wis, a corporation of Wisconsin 1 Application March 15, 1945, Serial No. 582,862

(Cl. 94-44) f The invention relates to apparatus for spreading plastic concrete mixtures and the like, and

has for its principal object the provision or an improved machine intended primarily for use in the construction of concrete roads and pavements to secure substantially uniform distribution of concrete deposited unevenly or in piles upon a prepared bed or sub-grade.

In the building of concrete roads by present day methods, it is the common practice to prepare a bed or sub-grade of the desired width extending along. the right-of-way, and to stake or otherwise secure metal rails or forms along each side of the sub-grade which serve to laterally confine concrete deposited upon the latter and thus define the lateral limits of the resulting slab. The concrete is usually furnished. by a paving mixer which advances along the bed between the forms and deposits successive batches of mixed concrete upon the bed by means of a paver bucket during discharge, the concrete, being merely deposited upon the sub-grade in paced piles which are then hand-spread by the workmen.

The machine of the present invention is in- 20 Claims.

tended to economically effect proper spreading of concrete deposited upon a road bed in either of the above manners, or in any other manner which does not secure the desired distribution of the mixture, whereby aconcrete layer of the desired thickness may be secured, extending completely across the bed from form to form, and having a substantially uniform top surface adapted for further finishing by hand or machine inany appropriate manner.

A preferred form of the apparatus, and a slight modification of one feature thereof, are illustrated in'the accompanying drawings forming a part of this specification, in which like reference characters designate like parts throughout the views, and in which:

Figure 1 is a top plan view of the machine, partly broken away and in section;

Fig. 2 is a front elevational view of the machine shown in Fig. 1, also partly broken away and in section i Fig. 3 is a side elevational view, asseen from the left of Fig. 2;

Fig. 4 is a partial vertical sectional view, on a somewhat larger scale, on approximately. the planeindicated bythe line 4-4 of Fig. 2, looking in the direction of the arrows;

r Fig. 5 is a partial vertical sectional view at right angles to Fig. 4, and taken approximately on'the planes indicated by the line 5-5 of Fig. (i;

. Fig. 6 is a partial sectional-plan view, on approximately the plane indicated by the line 6 -6 of Fig. 4, looking down;

Fig. 7 is a partial plan view, partly broken'away and in section, showing a modified form of spreading mechanism;

Fig. 8 is a sectional view on approximately the plane indicated by the line 8-43 of Fig. 7, looking in the direction of the arrows; Fig. 9 is a horizontal sectional view, on an enlarged scale, on approximately the plane indicated by the line 9-9 of Fig. 8, looking down; and FiglO is an enlarged elevational view, partly broken away and in section of the modified spreader mechanism as seen .from the left of Fig. 8.

As will be readily understood from the drawings, the machine is designed to travel upon the forms l5, and to this end its frame I6 is provided with Wheels ll, l8, Land 20. for engagement with such forms. The. wheels Hand I9 at one side of the frame are preferably relatively narrow and flanged at each end, whereby they may guide the machine along the forms, while the wheels l8 and 29 at the other side of the frame are preferablyu wider and may be uniianged, whereby to accommodate the slight inequalities in the lateral spacing of the forms commonly encountered in this class of work.

The rear wheels I!) and. 2B are mounted upon an axle 2 l' which is driven by a chain and sprocket drive 22 from a transverse shaft .23 journaled on the frame I6, which shaft in turn is driven by a chain and sprocket drive 24 and a conventional reduction gear and clutch mechanism 25 from an internal combustion engine or other suitable motor mounted within a housing 26 on the rear portion of the frame. The drive from the chain ,and sprocket mechanism 22 to the wheel axle 2| is preferably through a conventional reversinggear transmission 21 whereby the machine may be traversed upon the forms in either direction at will, as will be readily understood. The clutch element 28 of the said transmission is controlled by a shifting lever 29, and has a neutral position (shown in Fig. 1) in which the wheel drive is brokenand the machine may remain stationary on the forms "while other of its instrumentalities to be later described continue to function.

The forward portion of the frame l6 includes a pair of spaced transversely extending beams or frame members 38 and 3! which serve as tracks for the supporting wheels 32 and 33 ofa carriage 34, which is thus mounted on the said frame 16 for reciprocating movements from side to side thereof, The wheels 32 are loosely mounted on an axle or shaft 35 journaled in bearing brackets 35 and 31 carried by the frame of thecarriage 34, while the wheels 33 are rigidly mounted on an axle 38 journaled in similar brackets 39 and 40; and the carriage is movedback and forth on the 'track members 3.0 and 31 by power transmitted fromthe shaft 23 to the axle 38 and wheels 33 by mechanism best shown in Figs, 4, 5 and 6.

As will be clear from these figures, the carriage 34 is mounted to travel above and longitudinally of the shaft 23, which may be splined, or of square cross section as shown. The carriage frame is provided with a depending stirrup 4|, the arms of which embrace a sprocket 42 Which is, slidably mounted on the shaft .23. Through a chain 43 the said sprocket-drives a sprocket wheel 4 carried bya stub shaft 45 journaled in a bearing bracket 46 carried by the carriage frame 34. The said stub shaft also carries a bevel pinion d! which Lmeshes with a pairof bevel gears 11B and 49 which are loosely mounted on the shaftor axle 35. As will be readily understood fromthe drawings, the said gears 48 and 49 are disposed one to either side 'of the pinion 4i so that they will be driven in opposite directions thereby; and While loose upon the shaft 35, they may be alternatively coupled thereto by clutches 5i! and 5i which are controlled by a shifting lever 52 and appropriate linkage '53.

'Power thus transmitted to .theshaft35 is in turn transmitted to the aXleSB and Wheels 33 by means of a chain and sprocket drive 54 extending between the shafts3-5 and 38, andthus the carriage ,34 may be moved upon the tracks 30 and 31 in .one' direction or the other, depending upon which of the clutches 50 and 56 is engaged. Since the shaft 3.5 is employed t drive otherinstrumentali- 'ties of the machine, a clutch 55is preferably pro- ;vided for controllin the transmission of ,power from the chain and sprocket mechanism 54 to the axle 38 so that the carriage movements may be interrupted if .desired, Without stopping the shaft 35 and .the other mechanism driven there- :"by. This clutch 55 may becontrolled by a hand lever 56 and suitable linkage 57.

Distribution of concrete deposited on the road "gbed between the forms .is accomplished by spreading mechanism carried by the carriage .34,

as a result of reciprocating traverse of the said carriage on the frame members 38 and 3 I, coupled with either continuous or intermittent advance- 'ment of the entire machine along the saidforms. As best shown in Figs. 4, 5 and 6, the spreading mechanism comprises a blade or paddle 6U rigidly carried by the lower end of a vertical shaft 6| which is splined within a'sleeve '62 journaled in "bearings 53 mounted by the framework of carriage 3d. The upper end of the sleeve 62 has a worm Wheel 64 keyed thereto, with which meshes a Worm 65 loosely carried by a horizontal shaft 66 which is journaled in bearings 61 mounted on the top of the carriage. The said worm 65 has a clutch 68 associated with it by means of which the worm may be coupled to the shaft 66 at will, the said clutch being operable by a hand lever 69 and shifting fork Ill. The shaft 66 is driven from the shaft Z.35 .by.a spur gear train H 12, I13, 14.

It will be readily understoodfrom the .foregoing that the spreading blade 60 may be continuously or intermittently rotated (depending upon the period of engagement of the clutch 68) by power derived from shaft 35 and transmitted to the blade through the gears H, 72, 13 and 14, shaft 66, clutch t8, worm 65, worm wheel 64, sleeve 52 and vertical shaft 6!. For some purposes continuous rotation of the blade may be desirable, in which event the clutch 68 will be maintained in continuous engagement. In other cases it may be desirable to set and maintain the blade at an appropriate angle, such for example as that shown in the drawings, whereby a forward as well as a lateral component may be impartedto the concrete mass as the carriage travelsl across the road bed. In this event the clutch .68 Will be engaged only long enough to bring the blade to the desired angular position, and then disengaged. The worm and worm Wheel 64 arepre'ferably of such pitch that the wheel cannot drive .the worm and they Will thereforeserve to lock the end of each traverse may be accomplished by manual operation of the clutch lever 52, but in 'order to relieve the operator of this duty, means are preferably provided for effecting automatic reversal of the travel. One form of such means is here shown, comprising a lever 15 pivotally mounted on the carriage as at 1'6 and having a pair of fork arms H and I8 straddling the clutch shiftinglever 52. Stops l9 and 8.0 are mounted upon the main frame It of the machine, [in the path of travel of the lever '15, said stops being so "positioned as to be alternately engaged by the said lever as the carriage approaches the respective sides of the said .main frame. The lever will 'thus be arcuately moved about its pivot 16 .and through the engagement of one or the otherof its lforkfarms T! or 18 with the clutch shifting lever *52, "the appropriate clutch '50 or .5! controlled thereby will be disengaged and the other one engaged, as will be readily understood.

The automatic reversing lever i5 is preferably provided with a snap-action and detent spring 8! one end of which is secured to the lever as at "82, while its other end is anchor-ed on the carriage .as at '83. As willbe clear from Fig. 1, this spring tends to retain thelever in the position shown until the lever engages the stop Bil, whereupon the spring yields to permit counterclockwise movement of the lever. When "this movement brings thespring anchor 82 to the left-of a plane passing through the axes of the lever pivot Is and the spring anchor 83, the springs force then tends to move the lever counterclock and the shifting of the clutch. lever 52 is thus completed witha snap- .action. The spring of course then tends to hold the lever in its new posit'ion.

Obviously too, for some purposes the bladetfl may be set and held in a desired angular position as above described, and spreading accomplished through longitudinal travel of the machine along the forms, with the clutch disengaged and the carriage 34 stationary on its trackways 30 and 3|. v

The main frame it is provided with depending side plates 85 which extend downwardly just inside of the respective forms I5 to a plane somewhat below the tops of the said forms, which plates serve to prevent the blade from pushing the concrete over and beyond the forms. The

said main frame is also provided with a sti ike oil plate extending transversely between the side plates 85 to the rear of the blade 60. As best seen in FigsA and 5, this strike-off plate may be conveniently positioned below and supported from the transverse frame member 30 and it is preferablyvertically adjustable relative to the frame I 6, as by bolt and slot connections 81, 88. The ends of the strike-on plate are preferably provided with curved portions or members 89 which substantially conform to the path of travel of the ends of the blade 60 as it is rotated at theend of eachwcarriagetraverse, which portions or members prevent the concrete from banking up in the corners at the jun-ctures of the strike-off plate with the side plates 05. 1

Most concrete roads are now constructed with metallic reinforcing mesh incorporated in the slabs and the usual mode of laying such roads is to deposit upon the road bed a layer or course of concrete of less thickness than that of the finished slab, laythe mesh upon such course, and then deposit additional concrete over the mesh to bring the slab up to the desired thickness. The present machine is designed for use in carrying out such mode of construction, and to this end the blade 60 as well as the strike-off plate 86 are vertically adjustable. As was mentioned above, the spindle '6! of the blade is s-plined in the sleeve 02 so that it may slide therein, and the upper end of said spindleis bored and threaded as at, 08 (see 'Fig. i) for the reception of a screw BI carred by a hand wheel 92 disposed above the worm wheel fi l, prefer-ably with a suitable thrust bearing 93 interposed between the two. Thus, by manipulatingthe hand wheel 92 in the proper direction the spindle SI and blade 60 may be raised and lowered as desired.

The parts are illustrated imposition for spreading an initial course of concrete of approximately one half the depth of the forms ,I 5. Afterthis has beendone, the machine is returned to its startin point, and while the reinforcing mesh is being laid upon such course and additional concrete-is beingcleposited upon the mesh, the strike-01f plate 86 is raised and the hand wheel 92 manipulated to raise the blade 60 until its lower edge 60 is in approximately the plane of the top'of thetform-s I5, whereupon a second. run of the machine along the forms will spread and strike-off the concrete of the second course. I

To prevent the carriage 34 from being displaced from, the track members 30 and BI, the bearing brackets 36 which journal the forward ends of the axles 35 and 38 may be extended downwardly as indicated at '94 and provided with rollers engageable with the under face of the track member 3|, see FigsZand 4.

a In Figs. 7-10 there is illustrated a modified form of distributing or spreading blade which may be employed in lieu of the flat blade 50 shown in Figs. 1-6. This modified blade structure comprises a body member I00 to each end of which a wing I DI is pivotally connected by a hinge pin I02 for swinging movements about a vertical axis. Each wingis provided with a pair of oppositely disposed arms I03, each of which carries an adjustable stop screw I04 the head of which is adapted to engage pads I05 carried by flanges 'Idli extending from the topof the body member I00. The swinging movements of the wings are thus limited 'to approximately 90, as will be clear from Fig. 9, the parts occupying the full line positions of said figure when the blade is moving in a clockwise dire-ction, I and assuming the broken line positions when the blade is moved in a counterclockwise direction. l

The wings I0'I may be of the full depth of the body member I00, or as here shown they maybe shorter than the said body member, with their lower" portions provided with feather-able flap members I01 which are hinged'to the wing elements by pins I08 for swinging movements about horizontal axes. Means are provided whereby each of the flaps I0! is held in verticalalinement with its wing member I0! during that portion of the rotatational travel of the blade structure in which such wing is biting into a pile of concrete, and then as the wing leaves the pile its-flap is feathered upwardly, thereby tending to prevent adherence of the concrete to the fiap.

The feathering means comprise an arm I09 extending from each flap, to which the lower end of a drag link III] is connected as by a ball and socket joint I I I. The upper end of said link is connected by a ball and socket joint I I! to a lever II3 which is pivotally mounted at I I 4 in ears H5 carried on arm H6 rigid withthe blade member I00. The levers H3 carry rollers Ill which are disposed in thegroove H8 of a cam llfl whi-ch is journaled on the lower end of the lower bearing 63of the carriage 34. The cam H9 has a gear I 20 secured to it, and a rack I2I mounted in suitable guides IZZ'meshes withthe gear, The said cam remains stationary during the major portion of each traverse of the carriage so that if the blade structure be rotatedby the shaft Blthe flaps I01 will be alternately feathered upwardly and returned to vertical alinement with the wings I! as the rollers Ill of their levers Il3'successively traverse thehigh and low portions of the cam groove H8. These portions areeach substantially in length and since the rollers III are located in the groove H8 at substantially diametrically opposite points, the one flap wil1be raised when the other is lowered andVice versa.

As the carriage 34 approaches each end ofjits travel on the rails 30 andtl, an end of the rack IZI will engage a stop" I23 on the frame I6 wherebytravel of the rack will be arrested while carriage travel-continues for a short distance. This relative movement between the carriage and rack will cause the gear Iilll to rollfupon the rack, thereby rotating the cam M9 was journal through an angle of 180?, thus reversing the positionsof the high and low portions of the cam groove. Thus the proper timing of the raising and lowering of the flaps I0'I will be preserved when thecarriage motion is reversed.

In some cases the wings I0! may be omitted and the flaps I0Imounted directly on the body member I80, which then of course would be somewhat longer than shown in Figs. 7-10. i

Whatis claimed is:

1. In apparatus for spreading concrete do posited upon a roadbed, a mainframe traversable longitudinally along the road bed; 'acarriage mounted on said frame for movements trans versely of the bed; meansfor reciprocating said marriage upon the frame; a spreading blade mounted-bythe'carria'ge for movement about a vertical axis; means operable to rotate the blade about :saidqaxis during said transverse movements :of the carria-ge; and means for controlling said :rotati-ng means wherebyatthe volitionof-the operator the blade may be either rotated -01" maintained-in anydetermined angular relation to the carriage during the transverse movements of the latter.

2. In apparatus for spreading concrete deposited "uponv a road bed, a mainframe 'traversable longitudinally along the road bed; a, carriage mounted on said frame for movements transyersely of the bed; means for reciprocating said carriage upon the frame; a spreading blade mounted by the carriage for movements about a vertical-axis; means operable from said carriage vreciprocatingmeansto rotate the blade about said axis during 'said transverse movements -of the carriage; means for controlling said blade rotating means whereby during said carriage movements:the blade maybe either rotated or maintained in any determined angular relation to the carriage, as desired; and means for controlling a portion of said carriage reciprocating -means whereby movements of the :carriage may be interrupterd at will without affecting rotational movement of the blade.

3. In apparatus for spreading "concrete deposited rupona road bed, a main frame traversable longitudinally of the road bed; a carriage mounted on said frame for movements transversely-'of the bed; reversible means for reciprocating ssaid-oarriagenpon the frame; a spreading blade mounted by the carriage for rotation about aivertical-axis; means-operable from said carriage reciprocating means to rotate said blade relative torthe carriage during said transverse movements of thenlatter; and means for automatically reversing said carriage reciprocating means as the carriage approaches-each side of the mainframe, to reversethe direction ofcarriage-travel and the direction-of rotation of said blade.

4. In apparatus for spreading concrete deposited upon a road bed, a main frame traversab'le longitudinally along the road bed; a carriage mounted --on said frame for movements transversely :ofthe bed; reversible means for reciprocating'saidca-rr-iage upon the frame; a spreading blade'mounted by the carriage for rotation-about a vertical axis; means operable from saidcarriage reciprocating means to rotate the blade relative to-the carriage during said transverse movements of the latter; mean for automatically reversing said carriage reciprocating means as thecarriage approaches each side of the main frame, to reverse the direction of carriage travel and the di rection of rotation of the blade; and means for controlling :said blade rotating means whereby at the volition of the operator the blade may be either .rotated or maintained in any-determined angular relation-to the carriage-duringsaid movements of the latter.

5. In apparatus :for spreading concrete deposited upon a road bed, a main frame traversable longitudinally along'the road bed; a carriage mounted on said frame for movements tnansversely of the-bed; reversible means for reciproeating said carriage upon the frame; a'spreading blademounted by the carriage for rotation'about a :vertical axis; means operable from said carriage reciprocating means to rotate the blade about said axis during said reciprocating movements of the carriage; means for automatically reversingsaicl carriage reciprocating means as the carriage approaches each side of the "main frame, to reverse the direction of carriagetravel and the directionof rotation of the blade; means for controlling said blade rotating means whereby during said carriage movements the blade may be either rotated or maintained in any determined langular relation to the carriage, as desired; and means for controlling a portion of said lcarriage reciprocating means whereby movements of the carriage may be interrupted at will without affecting rotation of the blade.

6. In apparatus for spreading concrete deposited upon 'a'road bed, a main frame traversa'ble longitudinally of the road bed; a-carriage mounted on said frame for movements transversely thereof; reversible rmeans forso moving said carriage; a spreading blade mounted bythe carriage for movements about a vertical axis; means for so moving said blade; and means for causing rotational movement of the blade or maintenance thereof in any determined angular relation-to the carriage during movements of the latter, at the volition of the operator, comprising means for connecting and disconnecting theblade'rotating means and the carriage moving means.

7. In apparatus for spreading concrete deposited upon a, road bed: a mainframe traversable longitudinally along the road bed, said frame having a trackway extending tarnsversely of the roadway? a carriage having wheels mounted upon said trackway; reversible means for driving said wheells whereby to reciprocate the carriage upon the trackway; "a spreading blade mounted by the carriage for rotation about a vertical axis;

means for rotating said blade; and means operable at will for controlling said rotating means.

8. In apparatus for spreading concrete :deposited upon a road bed: a main frame traversable longitudinally along the road bed, said frame having a transverse trackway; a wheeled carriage mounted on said trackway for movements from side to "side of the road bed; reversible means for driving the carriage wheels to-so move the carriage; a spreading blade mounted bythe carriage for rotation about a vertical axis; and means operable at will for rotating said blade from said carriage driving means.

9. In apparatus for spreading concrete deposited upon a road bed, a 'main frame traversable longitudinally of the road bed, said frame having a transverse trackway; a carriage having two sets of supporting wheels mounting it for movement on said trackwlay, said carriage also having a shaft loosely mounting one set of said wheels"; reversible means for driving said shaft; controllable means for driving the other set of wheels from said shaft at will; a spreadingblade mounted by said'icarriage for movement about 'a vertical axis; means operable by said reversible shaft for moving said blade during motion of the carriage; and means for controlling said blade moving means whereby the blade may be maintained in any determined relation to the carriage if desired.

10. In apparatus for spreading concrete deposited upon a road bed: a main frame traversable longitudinally along the road-bed; a carriage mounted on said main frame for movements transversely of the road bed; a power driven shaft extending transversely of the main frame; means for traversing the carriage on the frame, comprising drive mechanism mounted by the carriage and having a slidable driving connection with .said shaft; a rotatable spreading blade mounted by the carriage; and connections scontro llable at will for driving said blade from said drive mechanism.

11. In apparatus for spreading concrete deposited upon a road bed: a main frame traverslable longitudinally along the road bed; a carriage mounted on said main frame for movements transversely of the road bed; a power driven shaft extending transversely of the main frame; means for reciprocating said carriage on the frame, comprising reversible drive mechanism mounted by the carriage and having a slidable driving connection with said shaft; co-opcrating means mounted by the carriage and main frame respectively, for automatically reversing said drive mechanism as the carriage approaches the side of the road bed; a rotatable spreading blade mounted by the carriage; means including a worm and worm wheel for rotating said blade; and a clutch controlling transmission of power from the reversible drive mechanism to said worm.

12. In spreading mechanism for concrete having a rotatable shaft, a spreading blade comprising a body member mounted upon said shaft to extend transversely therefrom; and a wing element pivotally connected to an outer extremity of said body member for swinging movements relative to the latter about an axis substantially parallel to the axis of rotation of the shaft.

13. In spreading (mechanism. for concrete having a rotatable vertical shaft, a spreading blade comprising a body member mounted upon said shaft to extend laterallly therefrom in different directions; a wing element pivotally connected to each outer extremity of said body member for swinging movements about an axis substantially parallel to the axis of rotation of the shaft; and means for limiting said swinging movements of the Wings.

14. In spreading mechanism for concrete having a rotatable vertical shaft, a spreading blade comprising a body member mounted upon said shaft to extend laterally therefrom: a wing element pivotally carried by an outer extremital portion of said body member for swinging movements relative to the latter about a substantially vertical axis; a flap member pivotally carried by the lower portion of said wing member for swinging movements about a substantially horizontal axis; and means for controlling said movements of the flap member.

15. In spreading mechanism for concrete having a rotatable shaft, a spreading blade comprising a body member mounted upon said shaft to extend transversely therefrom, said body member being provided with a flap member mounted for swinging movements about an axis at substantially right angles to the axis of rotation of the shaft.

16. In spreading mechanism for concrete having a vertical rotatable shaft, a spreading blade comprising a body member mounted upon said shaft to extend laterally therefrom, said body member being provided with a flap member pivotally mounted for swinging movements about a substantially horizontal axis; and means for controlling such swinging movements of the flap member.

17. In spreading mechanism for concrete having a vertical rotatable shaft. a spreading blade comprising a body member mounted upon said shaft to extend laterally therefrom, said body member being provided with a depending flap member pivotally mounted for swinging move-' ments about a substantially horizontal axis; and means for moving said flap member alternately to and from a substantially vertical position.

18. In spreading mechanism for concrete having a vertical rotatable shaft, a spreading blade comprising a body member mounted upon said shaft to extend laterally therefrom, said body member being provided with a depending flap member pivotally mounted for swinging movements about a substantially horizontal axis; and means for swinging said flap member to and from a substantially vertical position in timed relation to the rotation of the blade structure.

19. In spreading mechanism for concrete having a vertical rotatable shaft, a spreading blade comprising a body member mounted upon said shaft to extend laterally therefrom, said body member being provided with a depending flap member pivotally mounted for swinging movements about a substantially horizontal axis; means including a cam for swinging said flap member to and from a substantially vertical position in timed relation to the rotation of the blade structure; and means for shifting said cam to vary the timing of the movements of the flap member.

20. In apparatus for spreading concrete deposited upon a road bed, having a carriage mounted for movements back and forth across the road bed: a spreading blade carried by the carriage, comprising a body member mounted for rotation about a substantially vertical axis and provided with a depending flap member pivotally mounted for swinging movements about a substantially horizontal axis; means for driving said carriage and rotating said blade; means for automatically reversing said drive means as the carriage approaches each side of the road bed, whereby to reverse the direction of carriage travel and the direction of rotation of the blade; means including a cam for swinging said flap member to and from a substantially vertical position in timed relation to the rotation of the blade; and means for automatically shifting said cam as the carriage motion and blade rotation are reversed to change the timing of the swinging movements of the flap member.

ARTHUR E. MILLER. GEORGE K. VIALL. RUDOLPH F. LINDOW.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,467,243 Fitzgerald Sept. 4, 1923 1,533,464 Robb Apr. 14, 1925 1,565,657 Lichtenberg Dec. 15, 1925 1,579,443 Greene Apr. 6, 1926 1,832,951 Thorson Nov. 24, 1931 1,946,972 Heltzel Feb. 13, 1934 2,361,377 Bushnell Oct. 31, 1944 2,373,828 Harrington Apr. 17, 1945

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