US3009400A - Concrete finishing machines - Google Patents

Description

NOV. 21, 1961 GERBER ET AL 3,009,400

CONCRETE FINISHING MACHINES Filed May 10, .1954 12 Sheets-Sheet 1 PLACEMENT LONGITUDINAL TRAVEL I G. I.

HYDRAULIC CYLINDER SCREED DRIVE LONGITUDAL TRAVEL F I G 2 LATERAL DISPLACEMENT LATERAL DI 'E SGUFF I I m \PITMAN PATTERN i D 6 m LONGITUDAL TRAVEL F |G' 3 5 I E E F HYDRAULIC CYLINDER DRIVEN E 34 SCREED PATTERN E 3 J J a H LONGITUDAL TRAVEL F IG. 4 D

K INVENTORS Robert E. Gerb er John L Morkls BY Robert E. Hel'rzel AT ORNEYS I Nov. 21, 1961 R. E. GERBER ET AL 3,009,400

CONCRETE FINISHING MACHINES Filed May 10, 1954 12 Sheets-Sheet 2 VENTOR-S' R0 t E. Gerber Joh .Morkis BY Rober eltzel ATTOR E YS i Nov. 21, 1961 R. E. GERBER ETAL CONCRETE FINISHING MACHINES 12 Sheets-Sheet 3 Filed May 10. 1954 INVENTORS Robert E. Gerber John L. Morkis Robert E Heltzel ATTOEVEXS Nov. 21, 1961 Filed May l0, 1954 R. E. GERBER r AL 3,009,400

CONCRETE FINISHING MACHINES l2 Sheets-Sheet 4 FIGLQ.

JNVENTORS Robert E Gerb er John L. Markus Robert E. Heltzel Nam ATTO NEYS 12 Sheets-Sheet 5 R. E. GERBER ET AL CONCRETE FINISHING MACHINES Nov. 21, 1961 Filed May 10, 1954 Nov. 21, 1961 R. E. GERBER ET AL 3,0 ,4 0

CONCRETE FINISHING MACHINES Filed May 10, 1954 12 Sheets-Sheet 6 n m 2 y o E Q 3 8 co M IN V EN TORS Robert E. Gerber BY Re #535 AT TORNE YS Nov. 21, 1961 R. E. GERBER ET AL 3,009,400

CONCRETE FINISHING MACHINES Filed May 10, 1954 12 Sheets-Sheet '7 nvwszvrozas Robert E. Gerbgr John L. Morkls Robert E Heltzel 1 ATTORNEYS Nov.21, 1961 R. E. GERBER ETAL ,0

CONCRETE FINISHING MACHINES Filed May 10, 1954 12 Sheets-Sheet 8 INVENTORS Robert E. Gerber John L. Markus Robert E. Heltzel MMQWWMQM ATTORNEYS Nov. 21, 1961 R. E. GERBER ETAL 3,009,400

CONCRETE FINISHING MACHINES l2 Sheets-Sheet 9 Filed May 10, 1954 on C ru ibU sl m e ms R a m mEL n E fi m .Dl w 0 O O R R T T A Nov. 21, 1961 R. E. GERBER ETAL CONCRETE FINISHING MACHINES Filed May 10, 1954 12 Sheets-Sheet 11 I58 I I6 REGIPROATING SCREED INVENTORS Robert E. Gerbger J L. Murkls E. Heltzel BY q ATTORNEYS FIG. 22?? FIG 22E Nov. 21, 1961 R. E. GERBER ET AL 3,009,400

CONCRETE FINISHING MACHINES Filed May 10, 1954 12 Sheets-Sheet 12 INVENTORS Robert E. Gerber [{IIHIIIIIIIIHH mm kw BY John L. Markis- Robert E. Heltzel ATTORNEYS 3,009,400 CONCRETE FINISHING MACHINES Robert E. Gerber, Indianapolis, Ind., and John L. Markis,

Bristolville, and Robert E. Heltzel, Warren, Ohio, assignors, by mesne assignments, to The Heltzel Steel Form & Iron Company, Warren, Ohio, a corporation of Ohio Filed May 10, 1954, Ser. No. 428,468 7 Claims. (CI. 94-45) The present invention relates to concrete finishing machines and has for an object to provide a machine for the finishing of roadway surfaces in a smooth even manner eliminating the heretofore objectionable honey combed slabs having peaked surfaces.

Another object of the present invention is to provide a finishing machine having multiple screeds, the speed of reciprocation of each being controllable independently of the other without necessitating bulky, expensive gear boxes and clutches heretofore thought necessary in this art.

A further object of the invention is to provide a free floating screed having instantaneously reversible reciprocating movement across a plastic mix and which is not subjected to an upward thrust vector and dwell period ever present in a pitman driven screed common to this art.

A still further object is to provide a finishing machine having screeds which may be instantly raised and lowered to working position and which may be rigged in within the horizontal limits of the machine frame to give a minimum clearance for over-the-highway transportation from one job to another without the necessity of removing the screeds prior to transportation and upon arriving at the new job losing time getting started due to the time required to reattach the screeds to the machine.

A still further object is to provide a machine having front and rear screeds, the reciprocating speed of each of which may be controlled independently of the other whereby the front screed may be driven at a relatively high speed to attack a batch of plastic mix directly from the mixer and spread the same while simultaneously vibrating the mix to remove air voids therefrom performing a prefinishing operation heretofore done by a separate and distinct machine while the rear screed may be reciprocated at a slower speed to give the desired final finish to the plastic surface.

With the foregoing and other objects in view, the invention will be more fully described hereinafter, and will be more particularly pointed out in the claims appended hereto.

In the drawings, wherein like symbols refer to like or corresponding parts throughout the several views.

FIGURE 1 is a graph of the sine wave generated by a pitman drive.

FIGURE 2 is a graph of the wave form generated by an instantaneously reversible hydraulic reciprocating drive.

FIGURE 3 is a graphic pattern of the path of a screed reciprocated by a pitman drive.

FIGURE 4 is a graphic pattern of the path of a screed reciprocated by an instaneaneously reversible hydraulic drive.

FIGURE 5 is a perspective view of one form of a complete machine constructed in accordance with the present invention.

FIGURE 6 is a top plan view of the central portion of the base frame of the form of finishing machine shown in FIGURE 5.

FIGURE 7 is a front elevational view, having parts broken away and parts shown in section, taken on the line '77 of FIGURE 6.

States Patent I 3,009,400 Patented Nov. 21, 1961 FIGURE 8 is a fragmentary perspective view of a form of a screed elevating and lowering mechanism employed with the present invention.

FIGURE 9 is a fragmentary top plan view of a screed constructed in accordance with the present invention having parts broken away showing the reciprocating drive for the screed.

FIGURE '10 is a front elevational view of the construction of FIGURE 9.

FIGURE 11 is a top plan view of the screed reciprocating mechanism of FIGURES 9 and 1-0, taken on an enlarged scale.

FIGURE 12 is a front elevational view of the mechanism of FIGURE 11.

FIGURES 13 through 15 inclusive are vertical sections taken through the screed at the raising mechanism showing the screed being elevated from its free floating condition of FIGURE 13.

FIGURE 16 is a perspective view having portions shown in solid and chain lines of a screed reciprocating and elevating device.

FIGURE 17 is a fragmentary perspective view of a portion of the machine central frame showing a form of Vernier adjustment for the screed lift arms.

FIGURE 18 is a fragmentary side elevational view of a finishing machine showing the screed in its free floating condition upon a road form.

FIGURE 19 is a view similar to FIGURE 18 with a screed raised to an intermediate position.

FIGURE 20 is a side elevational view of a finishing machine having both screeds raised for over-the-highway transportation.

FIGURE 21 is a schematic of the hydraulic circuitry of a finishing machine constructed in accordance with the present invention.

FIGURE 22 is a schematic of the reciprocating mechanism employed in the screeds of a machine constructed in accordance with the present invention.

FIGURE 22-A is a cross-section taken through a form of pilot valve employed showing the valve in one position.

FIGURE 22-B is a similar view in a subsequent position of the valve.

FIGURE 22-0 is a longitudinal sectional view of a form of directional control valve employed showing the valve in one position.

FIGURE 22 -D is a similar view showing the'valve in a subsequent position.

FIGURE 22-E is a cross-section taken on the line 22-E-22E of FIGURE 22-C.

FIGURE 22-F is a cross-section taken on the line 22 F-22F of FIGURE 22-0.

FIGURE 23 is a plan view taken on an enlarged scale of a form of wheeled end frame employed.

FIGURE 24 is an end view thereof with parts broken away and parts shown in section.

FIGURE 25 is an end view of a form of wheel scraper employed.

FIGURE 26 is an edge view of the same; and

FIGURE 27 is a vertical sectional view taken through a form of screed thrust head showing the supports for the pilot valve and directional control valve.

Referring more particularly to the drawings, FIGURE 1 shows the sine wave form 30 generated by a pitman driven screed having a longitudinal vector of forward travel of the screed over the plastic road surface imposed upon the transverse or lateral reciprocating motion of a pitman drive. This sine wave has a crest portion 31 defined on each side of the peak of both left and right hand reciprocations. At the crest 31 it will be noted that the longitudinal vector 32 is greater than the lateral displacement vector 33 by many units which means that the mass below a pitman driven screed passing through the crest portion 31 of the sine wave is not receiving a vibratory or settling action proportional to the slope on each side of the half wave. The result is in effect that the screed scuffs, drags or scrapes over the top surface of the mix. This is best illustrated in FIGURE 3 in which the line AB is a slope of the wave during which the mix beneath the screed is worked transversely proportional to the longitudinal travel of the screed over the mix. The line BC in FIGURE 3 represents the resultant work of the screed upon the mix while the pitman is in its dwell period or the crest 31 of the wave 30. The line C-D is of course the slope of the reverse vectors imparted to the screed. The lines DE are similar to AB but of opposite directivity while the line EF is similar to BC but is defined by the pitman reaching the dwell diametrically opposite to the dwell causing line BC, and the line FG is a slope line opposite in directivity but equal to D-E. In effect the screed imparts a pass of truncated triangles upon the surface and body of the mix. Such a practice has been found to result in a slab having air voids therein beneath the area defined by lines BC and E-F. This is called honey combing and results in a structurally imperfect slab.

The present invention eliminates this objectionable honey combing by imparting an instantaneous reversal vector to the screed as shown graphically in its sawtoothed wave form 34 in FIGURE 2. In this wave form the slope is constant and directivity is instantly reversed. This highly desirable wave form 34 in FIGURE 2 is attained by eliminating the pitman drive and replacing same with an instantaneously reversible hydraulic drive not subject to dwell periods during forward movement of the screed over the mix. As seen in FIGURE 4 the line H--I is a slope of the saw-toothed wa-ve during which the mix beneath the screed is worked transversely proportional to the longitudinal travel of the screed over the mix. Upon the screed arriving at point I it is instantly reversed and the wave slope IJ is impressed upon the screed. Upon arriving at point I the wave form slope is maintained past the center line of the slab being finished until the maximum opposite transverse travel is completed at K, at which time the screed is instantly reversed and an equal and reversely directed slope K-L is imparted to the screeding action. It will be noted that the screed makes successive passes over the mix defining isosceles triangles. A slab formed and finished in accordance with the practice described above in connection with FIGURES 2 and 4 has been found to be of uniform cross section and absent of the heretofore objectionable voids of air resulting from a pitman driven finishing screed. In short honey combing has been eliminated.

Another problem solved by the hydraulic reciprocating mechanism for driving the screed of the present invention is the elimination of a roughened or peaked surface slab ever present in a slab finished by a pitman driven screed. The pitman drive exerts a working force upon the screed from several angles of attack, one of which is in a vertical direction having the effect of either physically lifting the screed from the surface being finished or releasing the downward weight movement exerted upon the screed thereby permitting the screed to ride up over the plastic mix. The result of either of the above actions of the pitman driven screed is a finished slab having a roughened or peaked surface. The present invention imparts a working reciprocating thrust to the screed in one plane only, that being in a plane parallel to the surface being worked by the screed.

Referring more particularly to FIGURE 5, in which one form of a completely hydraulically operated machine is illustrated, 35 designates an operators seat or chair installed on a platform or deck 36 mounted on the main central frame 37 adjacent the housing 38 for the engine, transmission and hydraulic pump and accessories where the operator will have convenient access to the control panel 39.

On this panel will be found the forward and reverse gear shift lever 40, the propulsion speed regulating variable-orifice hydraulic valve control 41, the forward screed lift lever 42 adjacent its speed regulating variable-orifice hydraulic valve control 43, the rear screed lift lever 44 together with its speed regulating variable-orifice hydraulic valve control 45, steering tiller 46, relief valve 47, shut-off valve 48 for the hydraulic system, control lever 49 for the hydraulic lift 50, control lever 51 for the over-the-road retractible supporting transportation wheels 52, and electrical instrumental panel 53.

The housing 38 may consist in part of a reticulated or mesh cage 54 to permit access of cooling air to the engine and other working parts and to protect the persons of the operator and workmen from accidential contact with the mechanism.

Side wheel frames 55 may be connected to the central main frame 37 directly for short width road lanes or indirectly through intermediate extension frames 56 which are added at opposite sides of the main frame in suitable numbers to increase the overall width of the machine for operation upon slabs of increased width. The wheels 57 travel on the side forms 58 and are driven from transverse propeller shafts 59 extending from the engine housing to the side frames 55. The hydraulic lines to the jack 50 are shown at 60.

One or more screeds are supplied, two such screeds 61 and 62 being shown. The front screed 61 is carried forwardly of the machine by two or more pairs of outriggers or davits. The lift outrigger arms 63 are pivoted at 64 on the main frame 37 while the stabilizing outrigger arms 65 are pivoted at 66 upon the side wheel frames 55 or intermediate extension frames 56. In a similar way the rear screed 62 is carried rearwardly of the machine by pivoted lift outrigger arms 67 and stabilizing outrigger arms 68. The lift arms 63 and 67 are connected to hydraulic or other mechanism for lifting the screeds 61 and 62 from the side forms 58 and slab and swinging the same inboard of the machine frames at front and rear portions to diminish the width of the machine when it is being towed endwise by a tractor hitched to the hitch tongue 69 after the machine has been raised by swinging down the retractible transportation wheels 52 and elevating the jacks 50 to raise the hitch tongue 69 to a level with the drawbar of the tractor.

The screeds 61 and 62 are reciprocated transversely of the roadway by hydraulic or other mechanism, such mechanism being conveniently contained within the screeds and supplied with motive fluid through the hydraulic or other lines 70.

The several frame units 37, 55 and 56 have overlapping parts perforated, as indicated at 71, to receive bolts 72 by which the units are secured in assembled relation.

Referring more particularly to FIGURES 23-26 a form of end frame 55 is shown to include transverse insert beams 73 carrying the bolts 72 for securing the end frames to adjacent overlapped perforated parts of the intermediate frames 56 or main frame 37. The transverse insert beams 73 are joined by pairs of spaced end rails 74 and 75 between which are accommodated endless chains 76 and 77 trained over drive sprockets 78 and 79 and also meshing with driven sprockets 80 and 81 fast on the shafts 82 and 83 of the propulsion wheels 57 which travel on the side forms 58. The drive sprockets are fast on a stub shaft 84 journaled in the rails 74 and 75 and having a coupling 85 for attachment to the engine driven propeller shaft 59.

The propulsion wheels 57 are flanged to straddle the top rail of the conventional road form 58. In order to prevent the plastic road material from solidifying between the flanges and on the treads of the wheel scrapers 86 may be employed in the form of fiat strips of spring metal bent or bowed to embrace the wheels and having free ends 87, 88 yieldably engaging the treads of the wheels at opposite sides thereof so as to scrape the road material from the wheels irrespective of the forward or reverse rotation of such wheels. The scrapers 86 may be carried by bolts 89 attached to the end frames and extending through eyes 90 of the scrapers.

Referring more particularly to FIGURES 6, 7 and 8, the central or main frame 37 is provided with separate mechanism for raising and lowering the front and rear screeds 61 and 62. Such mechanism comprises two hydraulic motors 91, 92 installed upon the main frame 37 in any suitable locations and cable connections between the motors and the front and rear pairs of lift arms 63, 67. As both hydraulic motors and their connections may be the same, one only has been illustrated in FIGURE 8 where the motor or ram drives a crosshead 93 carried by the plunger rod 94 to which are attached the inner ends of cables 95, 96 having their outer ends secured to lugs 97 upstanding from the outrigger arms 63 near the pivoted ends 64. Adjacent the lugs 97 grooved segmental blocks-98 are carried by the arms 63 over which the cables 95, 96 are trained after passing over systems of sheaves 99, 1011 for directing outer end portions of the cables in alinement with the arms 93 and their lugs 97 and segmental blocks 98. By pulling on the cables, as where the cross-head 93 is moved out, the outrigger arms 63 will be raised in an angular movement about the pivots 64 which may be journaled in U-shaped clip bearings 1111 or other forms of bearings appropriately mounted on the main frame 37 for which see FIGURES 6 and 7.

Referring more particularly to FIGURES 13-20, the outer free ends of the outrigger arms 63, 67 are bent into elbows or goose-necks 102 downwardly directed and having sockets 163 (FIGURES 13-15) to slidingly and telescopically receive the spindles 104 of screed carriers, each of which besides the spindles 164 may include a pair of thrust wheels 1135, 106 rotating freely around the spindle 104 and separated by a non-rotating spacer plate 107, together with a rotary base plate 108 having a roller 1119 for rolling around the bottom wall of the screed when the carrier is lowered to the position of FIGURES 13-14. The base plate may be carried around with the lower wheel 166.

As best seen in FIGURES 13-15 the carrier is of less height than the interior space of the screed 61 to permit the carrier to move from the position of FIGURE 13 to that of FIGURE 15 relatively to the screed without exerting any lifting action on the screed. In other words the carriers are fitted to the screed with lost-motion. A second lost-motion is afforded by the set screws 110 on the lift arms 65 in their cooperation with the grooves 111 of the spindles 164. The upper ends of shoulders 112 of the grooves 111 cooperate with the set screws 110 to arrest the separating movement of the spindles 104 from the sockets 103. When the lift arms 63 are raised the set screws 110 travel in the sockets 103 a prescribed distance before the set screws 111) encounter the shoulders 112 which provide the second lost-motion referred to.

Referring more particularly to FIGURES 17-20 the lift arms 63, 67 and idler stabilizing arms 65, 68 may encounter stops 113 in their lower positions, which stops may be in the form of set screws for adjustment of the stops 113 to determine the degree of tilt of the screed with reference to the material being screeded. The various arms 63, 67, 65, 68 may carry legs 114 positioned to enter sockets 115 (FIGURE 17) of the front and rear beams of the frame when the arms and screeds are lowered to brace the stabilize the arms and connected parts especially in counteracting the reciprocating thrust of the screeds 61, 62.

Referring more particularly to FIGURES 9-12 and 16, the screeds are reciprocated by direct right-line or rectilinear thrust motors, preferably of the hydraulic type, comprising cylinders 116 having reciprocating plungers and their plunger rods 117. The cylinders 116 and rods 117 constitute a motor couple adapted to move in and out in a straight line path as distinguished from the compound movement of an eccentric or crank driven pitman, one component of which is an angular swinging motion which cuts across a parallel to the ideal rectilinear path of movement of the working faces of the screed. The motor is connected to the screed and to a fixed abutment which takes the reaction of motor thrust. It is preferred that the plunger rod 117 be the fixed member of the motor couple and that the cylinder 116 shall reciprocate back and forth on the rod 117 incident to driving the screed. Pursuant to this plan the rod 117 is coupled to the spacer plate 107, for example by suitable mating flanges 118, 119 on the spacer plate 107 and plunger rod 117 respectively, the flanges being removably attached as by bolts 120.

The spacer plates 107, carriers and arms 63, 67 constitute abutments which have their support from the machine frame members. While these abutments are movable up and down angularly about the pivots 64, such abutments are fixed or stationary with reference to the transverse reciprocating motion of the screeds and hence the abutments are well calculated to absorb the reactions to the rectilinear movements of the motors 116, 117.

To permit the screeds to float upon the side forms and move up and down to a limited extent it is preferable that the cylinders be connected to the screeds by pivot pins 121 arranged on an axis which is substantially horizontal in the lowered positions of the screeds.

The motors and carriers are contained wholly within hollow screeds with the axis of the cylinders 116 and plunger rods 117 disposed substantially parallel with the bottom pan of the screedand also with the front strikeoif wall of the screed. The said axis may be made to coincide with the longitudinal axis of the screed.

The cylinder 116 drives the screed through any suitable connection, preferably through a thrust head consisting in part of side plates 122 having perforated flanges 123 secured by bolts 124 or other appropriate fastenings to desired screed parts. The plates 122 are connected by webs or the like and by a bar 125 carrying lugs 126 in which the pivots 121 are fitted. Similar lugs 127 on the ends of the cylinders 116 overlap the lugs 126. The pivot pins 121 pass through the pairs of overlapping lugs.

To the ends of the cylinders 116 are connected fluid supply and return lines 128, 129. The flow of Working fluid into and out of the cylinders 116 is controlled by a valve mechanism supported on the thrust head 122 and moving with the cylinder and screed. The valve mechanism may consist of a rotary pilot valve 130 and a directional control valve 131. These valves are not per se parts of the present invention, being manufactured by Vickers Incorporated, Detroit, Michigan and illustrated and described in Bulletin 44-7 and Bulletin 49-7 of that corporation.

In addition to FIGURES 9-12 and 16, FIGURES 22-A, 22-B and 22-C illustrate a form of application of such rotary pilot valves and directional control valves to the actuation of reciprocating screeds in a road building machine in which instantaneous reversal of the reciprocating strokes of the screeds is achieved by a right-line or rectilinear moving motor, preferably of the hydraulic type, where the superior weight of the cylinders 116 of the motors and of the pilot and control valves 130 and 131 is utilized in a unitary arrangement to be carried by the screeds which are better able than the carriers and outrigger arms to sustain such weight and whereby the weight of such unitary arrangement is taken advantage of to add to the stability of the screeds and the effectiveness of screed operation, particularly in that the hydraulic motor unit is installed in the screed in such relationship that its rectilinear developed thrust is substantially parallel to the working surface of the screed.

As shown in FIGURES 22-A and 22-B the pilot valve comprises principally a casing 132 containing a rotary spool 133 having two passages 134 and 135 adapted to I rock back and forth between the position of FIGURE 22-A in which the pressure connection 136 is open through passage 134 to conduit 137 to one end of the directional control valve 131 While the other end of the control valve is being evacuated through conduit 138, passage 135 and return conduit 139 to the tank 140, and the position of FIGURE 22B where the pump pressure through the connection 136, passage 134 and conduit 138 is supplied to the other end of the control valve, the first mentioned end being evacuated through conduit 137, spool passage 135 and return conduit 139 to the tank 140.

A rock shaft 141 is aflixed to the rotary spool 133 and projects up above the casing 132 where it has affixed thereto two arms 142 and 143 at different levels and angularly displaced in position to strike limit stops 144 and 145 at or near the ends of the reciprocating strokes of the cylinder 116 and its entrained screed 61, 62. The stops 144, 145 are carried by set collars 146 and 147 at different levels corresponding respectively to those of the arms 142 and 143 with which they cooperate. The set screws 143 and 149 slide adjustably in longitudinal grooves 150 and 151 in a rod 152 but are prevented from rotation to maintain the stops at all times at the designated levels. The rod 152 is non-rotatable and nonsliding being affixed to the plate 107 by the coupling flange 119 or otherwise. Such rod 152 is supported in arms 153, 154 of a sliding bracket 155 afiixed to and moving with the thrust head or screed.

Referring more particularly to FIGURES 22-C, 22-D, 22-E and 22-F, the directional control valve 131 comprises generally a casing 156 containing a reciprocating plunger 157 driven back and forth by hydraulic pressure supplied alternatively through conduits 137 and 138 incident to throw-over movements of the pilot valve 130. The plunger is open in both positions to hydraulic pressure from the pump supply line 158 and is traversed by passages 159 and 160 for alternately registering with the fluid lines 128 and 129 to the opposite ends of the cylinder 116. When supplying pressure to one end of the cylinder 116 the other end is being evacuated to the tank 140 through the return conduit 161 which registers with the passage 159, 16th which is at the time out of alinement with either conduit 128 or 129.

The supply passages 159, 160 may be arcuate, as seen in FIGURE 22F, and they are displaced axially so that in the position of FIGURE 22C the passage 159 registers with the supply 158, while the passage 160 is cut off from the supply. In the position of FIGURE 22-B where the plunger 157 has moved to the other end of the casing 156, the passage 160 is now in communication with the supply 158 and the passage 159 has shifted to a neutral position. The outlet ends of the passages 159 and 160 are arranged to alternately register with the conduits 128 and 129.

The valve plunger 157 also has exhaust passages 162 and 163 which may be of the form shown in FIGURE 22-E with diametric portions also adapted to register alternately with the conduits 128 and 129 and with the tank return 161. As shown in FIGURES 22-C and 22-D adjacent ends of all four passages 159, 160, 162 and 163 are in axial alinement and in alinement with the conduits 128, 129 so that in the position of FIGURE 22C the conduit 128 is receiving working fluid from inlet passage 159 while conduit 129 is evactuating the other end of cylinder 116 through the exhaust passage 163 which at the same time registers conduit 129 with the tank return 161. When the valve plunger 157 has shifted to the position of FIGURE 22D the supply is through 160 to conduit 129 and the exhaust from conduit 128 to and through 162 to tank return 161.

The rotary pilot valves 130 operate repeatedly with great rapidity and provide means for adjustment of speed of reversal of main directional control valves 131.

In FIGURE 22 stationary stop 145 is at level of lever arm 143 and cylinder 116 is being driven to the left.

When the lever arm 143 strikes the stop the rock shaft 141 and its spool 133 will be thrown over to the opposed position which will raise the companion lever arm 142 into a position in the path of the stop 144 so that when the screed and cylinder 116 arrive at the end of the following stroke the shaft 141 and its spool 133 will be rocked back to the position of FIGURE 22. In this way the positions of FIGURES 22A and 22B alternate and cause the control valv plungers 157 to alternate between the positions of FIGURES 22-C and 22-D. In this way the cylinders 116 and the connected screeds are reciprocated back and forth without dwell periods and in straight line paths at all times.

Referring more particularly to FIGURE 27, 164 designates a web or shelf extending across between the side plates 122 for supporting the pilot valve 130 for movement back and forth with the screed, and 165 represents a bottom plate also connected between the side plates of the thrust head for supporting the directional control valve 131 so that it too partakes of the reciprocating movement of the screed.

In FIGURE 20 both front and rear screeds 61, 62 are shown in raised position with a flexible or other connection 166 dctachably maintaining the same so raised during movement of the machine from one job to another.

FIGURE 21 shows one system of hydraulic circuits that may be employed with appropriate legends to designate the several units. The hydraulic supply tank, pump and the engine which drives the same are installed on the central frame in the casing containing the control panel.

The machine constructed in accordance with the present invention and as described above may be employed to finish a concrete roadway surface in the following manner, particular attention being invited to FIGURES 5 and 21.

T he machine is first placed with its wheels 57 in alinement with the top rail of road form 58 between which a plastic mass of concrete to be finished is laid. The engine or prime mover 166 is started, driving the main hydraulic pump 16'] and building up the operating pressure to the hydraulic supply manifold 168, all valves being in the off or closed position.

The operator then places the operating handle 40 in the forward position and thereupon rotates the propulsion control valve 41, opening the hydraulic line from the high pressure or pump side to the transmission 169. In this way drive is imparted through the drive shafts 59 t0 the wheels 57. The wheels 57 are thereby driven forwardly, thus moving the machine up the cribbing on to the road forms 58.

When all four wheels 57 are firmly upon the road forms 58 the front and rear screeds may be lowered from the position of FIGURE 20 to that of FIGURES 5 and 18. This is accomplished by moving the levers 42 and 44 to the screed lowered position thereby permiting working fluid trapped in the cylinders 91 and 92 to bleed off and due to the weights of the screeds 61, 62 outboard of their pivotal connections 64 with respect to the frame of the machine, such screeds will be lowered into working positions. The rate of descent may be controlled by the positions of the levers 42, 44 for controlling the valve orifice openings in this hydraulic circuit.

The machine is now ready to be driven down the road forms 58 for placing the screeds in contact with the freshly dumped batches of plastic mix. Each type of concrete has its own special physical characteristics and due to its consistency a particular mix may require more troweling action to obtain the desired degree of finish than other mixes. Each particular mix is studied from which is decided the particular throw of the screed transversely of the mix. As an example, the screed may be given a transverse movement of six inches. This six inch seating is then put into the machine as by opening the screed cover and adjusting the position of the collars 146, 147

carrying the limit stops 145, 144 along the thrust limit bar 152 to the position necessary to give the six inch thrust.

The forward screed 61 initially attacks the plastic mix which is uneven and lumpy and therefore the reciprocating speed of the front screed 61 may have to be faster than the reciprocating speed of the rear screed 62. This can be done on the machine by varying the orifice opening of the screed controlled valves 43 and 45. The greater the opening, the greater is the volume of oil delivered to the supply lines 70 and hence the shorter the [time interval for the travel of the pilot valve arms 142, 143 between the limit stops 144, 145 which determines a period of half-cycle of a reciprocation. This rate of reciprocation is related to the forward speed of the machine or longitudinal travel of the screeds over the The operator observes the finish behind the front screed 61 and can determine the proper forward speed for a given rate of reciprocation of the screed. To coordinate the two speeds he need only adjust the rotary positioning of the control valve 4 1 and either or both of the screed control valves 43, 44.

The application of hydraulics to this construction eliminates predetermined gear range limitations of gear drives and permits minute or Vernier adjustments finer than the finest heretofore attainable.

To provide the desired finished surface the rear screed 62 may be reciprocated at a slower rate than the front screed 61. This can be done with the highest degree of accuracy. Should it become necessary to refinish a section of concrete plastic mix, the screed lift levers 42, 44 are shifted to the raise position and, while the screeds 61, 62 are being raised, which is practically instantaneously, the operator shifts the handle 40 to the reverse position and the machine backs down instantly over the road form. Upon traversing the area to be refinished the handle 40 is shifted to the forward position and the screed control levers 42, 44 are shifted to the lower position and the screeds are lowered as the machine commences forward movement over the road forms 58. The screed control valves 42, 44, FIGURE 21, are so constructed that when their levers are in the screed raise position the flow of working fluid to the rotary valve elements 43, 45 is cut off, blocking fuel flow to the reciprocating cylinders 116.

When the job is completed and the machine is to be moved to another location, the screeds 61, 62 are raised and rigged in to the position shown in FIGURE 20; which reduces the overall transverse dimensions of the machine for towing along a highway. The travel wheels 52 are thereupon lowered by operation of the control lever 51 which together with the lowering of the hydraulic pedestal 50 by operation of the control valve 49 causes the side form wheels 57 to be raised clear of the road forms. The towing tongue is then connected to the drawbar 69.

Although I have disclosed herein the best form of the invention known to me at this time, I reserve the right to all such modifications and changes as may come within the scope of the following claims.

What we claim is:

1. In a finishing machine for plastic roadways, a plurality of screeds adapted to be placed in working engagement with the mix to be finished, hydraulic screed raising and lowering means carried by said machine and being connected to said screeds for raising said screeds from a working position and lowering said screeds to a working position in contact with the mix to be finished, instantaneously reversible hydraulic reciprocating means, one element of which is connected to said screed raising and lowering means and another element of which is connected to impart a reciprocating thrust in a single plane to each of the screeds, speed control means on said machine in circuit with said hydraulic reciprocating means for controlling the speed of reciprocation of said screeds independently of one another and of the speed of longitudinal travel of the screeds over the mix, and elevating control means for said screed raising and lowering means in circuit with said speed control means whereby upon raising said screeds from said mix the hydraulic flow to said instantaneously reversible hydraulic reciprocating means is cut off stopping reciprocating movement of said screeds until said elevating means lowers said screeds into working contact with said mix.

2. In a road building machine, a screed member adapted to reciprocate while supported on side forms, at least one abutment member movably carried by the machine operatively associated with the screed for supporting the screed with a lost-motion connection to permit the weight of the screed to devolve on the side forms and to permit a limited up and down motion of the screed relatively to the abutment member, a reciprocating motor connected to the members with one connection at least a pivoted one in a direction to permit the up and down motion of the screed member without entraining the abutment member, said motor being of the straight-line reciprocating movement type with its axis of thrust arranged substantially parallel to the working surface of the screed member, and means for instantaneously reversing the direction of movement of the motor at the respective ends of its rectilinear thrust strokes.

3. In a road building machine, a screed adapted to rest and have reciprocating movement on the side forms and also to have a limited up and down motion, a rigid screed carrier entering said screed and having a lost-motion connection With the screed slackened when the screed is lowered on the side forms to permit the up and down motion without interference from the carrier, movable elevating means on the carrier having a lost-motion connection to the carrier for lifting the carrier and screed initially successively and thereafter together to elevate the screed above the road forms, and a motor to reciprocate the screed having parts relatively movable in a straight line of thrust coupled respectively to the carrier and screed, one of the couplings being a pivotal one to permit the carrier or screed or both to move up and down relatively to one another incident to the lifting movement of the carrier by the elevating means or said up and down motion of the screed.

4. In a road building machine, a hollow screed, a rigid carrier therein, thrust wheels on the carrier rotating within the front wall of the screed, said carrier being of inferior height compared to that of the screed whereby the carrier may move downwithin and relatively to the screed after the descent of the latter has been arrested by the side forms to leave the screed free floating on the side forms, and a motor for reciprocating the screed having relatively movable parts operating in a straight line of thrust, said parts being coupled between the carrier and screed, one coupling at least being a pivotal one to permit of. the initial raising movement of the carrier without entraining the screed until the carrier encounters the upper portion of the screed.

5. In a road building machine, a fixed abutment on the the machine, a reciprocating screed, a plunger rod fixed to the abutment, a cylinder slidable on the plunger rod and afiixed to the screed, pilot and directional control valves hydraulically connected to one another and to the cylinder for instantaneously reversing the direction of reciprocating movement of the screed at each end of its strokes, trip means for the pilot valve movable back and forth with the screed, and limit stops fixed with the abutment in position to be engaged by the trip means substantially at the ends of said strokes.

6. In a road building machine, a laterally immovable abutment on the machine, a transversely reciprocating screed, a plunger rod afiixed to the abutment, a hydraulic cylinder slidable on the rod, a thrust head carried by the screed to which the cylinder is drivingly connected, pilot and directional control valves carried to move with the head and hydraulically in circuit with one another and with the cylinder, trip means for the pilot valve movable therewith and limit stops fixed with the abutment in posi tion to be engaged by the trip means at substantially the ends of the reciprocating strokes of the screed.

7. In a road building machine, a laterally fixed abutment on the machine, a reciprocating hollow screed, a thrust head afiixed in the screed, a hydraulic cylinder pivoted to the thrust head, a plunger rod for the cylinder affixed to the abutment, the line of developed thrust of the rod and cylinder being substantially parallel to the working surface of the screed, a rotary hydraulic pilot valve carried by the thrust head, a reciprocating directional valve also carried by the thrust head, a reciprocating directional valve also carried to move with the thrust head for changing the direction of movement of the screed when shifted under the control of the pilot valve, a hydraulic circuit including both valves and the cylinder, rocking trip fingers for the pilot valve, and adjustable limit stops fixed to the abutment in the path of movement of the fingers.

References Cited in the file of this patent UNITED STATES PATENTS Ord Jan. 6, 1925 Noble Jan. 12, 1932 Day July 30, 1935 Lundbye Dec. 17, 1940 Maloon 2. Feb. 8, 1944 Millikin et al Sept. 12, 1944 Heltzel July 31, 1945 Pierce Aug. 14, 1945 Jackson Nov. 9, 1948 Hohnke et a1 Feb. 26, 1952 FOREIGN PATENTS Great Britain Sept. 8, 1891 Great Britain Sept. 4, 1930 Great Britain Sept. 24, 1935

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