US2235105A - Adjustable screed - Google Patents

Description

13, 1941- J. w. HELTZEL ADJUSTABLE SCREED Filed May 16, ,1939 Sheets-Sheet 1 KN. hw.

a u@ NN @M March 18, 1941.

J. w. HELTZEL 2,235,105 ADJUSTABLE SCREED Filed May 16, 1959 2 Smets-Sheet 2 Snnentor mgm@ (I ltornegS Patented Mar. 18, 1941 UNITED STATES PATENT OFFICE 2,235,105 ADJUSTABLE SCREED Application May `16, 1939, Serial No. 274,056

11 Claims.

The present invention relates to improvements in adjustable screed-s, and more particularly refers to the adjustment of the bottom of the screed whereby the bottom may be warped or curved to accommodate variations in the crown to be given to the road.

The present invention involves certain improvements over the invention shown; described and claimed in my prior Patent. No. 1,741,459, granted December 31, 1929.

It is an object of the-invention to provide a number of operating units connected to suooes sive local points along the length of the screed which may be actu-ated simultaneously by a cornmon operating member from a single point, and in which the various units may be adjusted. independently oi one another'whereby to `vary the degree of the raising or the lowering of thescreed bottom at each unit in conformity with the angle of curvature to be imparted to the road.

1t is an important object of the present invention to provide improved units having -a common effect and affording a two-fold adjustment; "the one adjustment being for roughly determining the effect of the throw of .the cam on the screed bottom and for also effecting the throw ofthe cam itself with respect to the degree of movement of the operating member; and secondly a nner or more minute adjustment `independently of the cam adjustment whereby the pitman length may be varied, the pitman being the cam actuating member and thus having a direct eect upon the angular or rotational throw of the cam.

A further object of the invention is to provide an improved push rod by which the screed is pushed forwardly, by,iand in advance of, the finishing machine, `to the endthat the screed may partake of a true rectilinear reciprocating movement cross-wise of the roadway 4,while it is being pushed forward by the finishing `machine and not be required to execute u an arc-like or swinging movement across the roadway `which has always been attended by a mutilating action of the screed on the concrete and lresulted in the formation of ridges in the road.

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

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

`Figure 1 is a top plan view of an improved (CI.v S34-45) `adjustable screed constructed in accordance with the present invention.

FigureZ is a front elevation of the same with 'parts Abroken away and parts shown in section.

`Figure is an enlarged fragmentary section taken on the line 3--3 in Figure 1.

Figure 4 is anenlarged fragmentary top plan vview with partsbroken away and parts shown in section.

. Figure 5 is a vertical cross-section taken on .the line 5-#5 in Figure 4.

Figure 6 is asimilar 1.6--6 inFigure 1.

Figure 'I is an `enlarged horizontal section taken through one of the operating units, and

Figure 8 is a fragmentary perspective view of -theimproved push rod employed with its connections to the screed and nishing machine shown partly broken away and partly in section.

vReferring more particularly to the drawings, which show'only a lsingle embodiment of the present invention, I0 designates a rear screed and I I a front screed, the device being illustrated as` applied to a dou-ble screed; although it will be apparent to those skilled in the art that such invention is equally applicable to a single screed.

Thexrear screed truss beam l2 may be ofthe channel shape shown. Thefront screed truss `bearnris shown at I3 and is preferably of the channel form as shown. A dash board I5 is oarriediat the front of the screed to buck the mass of concrete.

In .accordance with prevailing practice, the bottom of the screed is warped or curved by the use of the adjusting bolts l1. A set of these bolts is provided for each screed. Such bolts I1 are disposed substantially vertically through the flanges'of the beams I2 and I3. The bolts extend in a series longitudinally of the screed and are spaced apart. at relativelyshort intervals. The heads I8 of these bolts I1, -as shown in Figure 6, are disposed in sockets I9 in the socket pieces 20 which are bolted or otherwise secured to the base members of the screeds I0 and II. The adjustingbolts I1 play freely through openings in the horizontal flanges 2l and 22 of the beams l2 andv I3.

rIhe adjustment is secured by means of upper nuts 23 :and lower nuts' 24. The upper nuts 23 may 'be screwed down against the upper sides of the flanges 2l, while the lower nuts 24 may be screwed up on `the bolts I'I against the lower sides of saidflangesZI. This produces a locked condition of the bolt wherebysu'chbolt is restrained `against' vertical'movement. By rotating View taken onthe line the upper nut 23 so that it rises along the threaded portion of the bolt and moves upwardly away from the ange 2| the lower nut 24 may be accordingly turned upwardly against the lower side of said flange 2| to force the bolt vertically downward and thus push down upon the 1bottom members of the screeds l0 or or both, thus diminishing or eliminating the crown. By reversing the process, the nut 24 may be from flange 2| and down on the bolt such bolt Il is placed; to increase the .crown at this point.

practice, to secure. the local adjustment of the screed bottom along its entire length it is necessary to adjust by hand the various nuts 23 and 24. on all of the bolts the road. formed, the screed bottoms must be again adjusted through the bolts l1 and their nuts 23 and part of the operators of the machines.

The object of the present invention is to elimicated across the roadway.

In the use of this new device the nuts 23 and 24 may be backed away from the iianges 27|, the

Inaccordance with the invention a bar 25 is slidably mounted on each screed. TheA bar 25 slides in supportsV 26. The supports 26 isustain bar 25 and require it to move horizontally in a substantially rectilinear path back and forth longitudinally ofthe screed.

One sliding bar 25 is provided for each screed, the bar lying atthe forward portion ofthe beam |2 or 3 and on the side of the beam oppositeto that on which project the flanges 2| and 22 as seen in Figures 5 and 6. The brackets'or supports 26 are secured to the webs of the beams I2 and I3..

The bar carries pins 21 at suitable intervals between the supports 26. These pins are provided whenever it is desirable to have one of the local adjusting devices or units. Such, local addistances 1n order to secure nice and minute adjustments. Such periorations are in a row extending lengthwise of the arm 3U or being in a with a tangent to the cam 28. are adapted to receive The pins are also received through -eyes on rods 5|, the pins having heads to retain thevrods 5| in pivotal connection with the arms 30 v and collar is possible.

Revertng to Figure 3, the cam 28 with a circular series of perforations is provided extendis to pivotally unite to the active part of the cam 28 the upper end of a link 58. The lower end of this link is articulated with, or pivoted in, an

carried upon the forward end of a bolt 1l. `Cover plates 12 may be carried by the segment on both upper and lower faces thereof for `closing the socket 69 and for confining the universal head 1l] therein.

The bolt 1| extends slidablythrough'an opening in the vertical web 13 of an angle iron or other part `which is affixed to the finishing machine designated generally at 14. This web 13 forms thrust surfaces `or a fixed abutment on which the curvilinear surfaces 56 and 61 of the segment 65 may roll or rotate. Thebolt 1| has a coil spring 15 extending aboutthesame and held to its free end by one or more adjusting'nuts 15 whereby to vary the tensionof the spring. The other end of the coilspring abuts against 4a ring 11, which ring engages the inner wall of the abutment 13. The spring tends toretain the bolt 1| in a backwardly `withdrawn position. At such times as the pushrod may draw thebolt 1l forwardly, the spring 15 will be compressed and react on the universal head and on the push rod to draw the same back; and the function of the spring 15 is to normally maintain the curvilinear surfaces 56 and 61 in contact against the front wall of the abutment 13. It will be noted from Figure 8 that the slot B8 is` considerably `wider than the diameter of the shank of the bolt 1l to permit the rocking of the `segment 65 on the abutment while the bolt 1l remains unaltered by this movement. The surf- aces 56 and 61 will preferably not be circular, that is not precisely concentric with the center of pin 53. It will be understood that the lscreed is reciprocated transversely of the roadway as thefinishing machine pushes forward upon the screed through the push bars 62. Therefore the center 63 shifts with respect to the curvilinear surfaces 66 and 61 and it will be necessary for these surfaces to be elliptical. g

The slide bar 2'5 carries athreaded collar 34 at or near one end. This collar is internally threaded to engage with the threads upon a screw adjusting shaft 35. This adjusting shaft is carried by one end of the screed and is affixed against axial travel but permitted to rotate. `Appropriate means for causing the rotation of the shaft is provided. Where there is a double screed two shafts 35 are provided. On one of these shafts an operating handle or crank 31 is mounted and a chain drive 38 is provided from this shaft to the companion shaft 35.

In the use of the device, the finishing machine thrusts forward upon the push bars 62, and in turn the push bars compel the screed to advance in front of the finishing machine. The screed is reciprocated laterally of the roadway as it advances so that the push bars 62 must not only push forward but they must at the same time partake of a laterally oscillating motion which is permitted upon the circular` heads 10 and upon the elliptical curvilinear surfaces 66 and 61.

As shown` in Figure 3, by shifting the operating bar 25 toward the right all of the cams 28 will be rotated so as to push down upon the links 58 and thus cause the screed bottoms to be depressed or flattened out, as when rounding a curve. By drawing the push bar 25 in the opposite direction or to the left, as seen in Figure 3, all of the arms 30 of the cams will be rocked causing the links 58 to be lifted and the screed bottom flexed upwardly.

As seen in Figure 3 the bottom of the screed at the left operating unit is raised only slightly as compared with the degree of raising of the screed bottom at the operating unit on the right. This is desirable as the screed bottom must progress in elevation from both sides of the road toward the centervwhere the crown is highest. This differential in operation isroughly secured by changing the throw of the cams 28. This is done by changing the radius of movement, as by selectively fitting pin 5l! in a perforation 30a. The closer to thevcenter 29 the effective connection of the pitman is made, the greater will be the rotational or angular `movement of the cam in a predetermined rectilinear movement of the operating bar 25. The farther away pin 50 is from cam center 29, the smaller will be the angular movement of the cam 2`8'on the same rectilinear movement of 15 the bar 25. Therefore in the units at the end of the device the `pin connections 50 will be farther from the cam centers 29. Progressively toward the center of the screed the pin connections 5i] may be set closer tothe cam centers 29. 4Also this effective throw of the cams on the screed bottom may be controlled to a considerable extent by the selective placing of pin `51 in one of the series of apertures 28a on the eccentric rim of the cam 23.

Also after the rough adjustment is made by the placement of the pins 5B and 51 in selected holes 3l]a and 25..a respectively, then the ner adjustment may be secured by changing the length of the vpitman as previously described or it may be necessary or desirable to change pitman length conformably tothe adjustment of pin 5U in a selected aperture a.

By rotating the crank or han-dle 31 in one or the other direction all of the cams may be simultaneously operated, or groups of cams may be simultaneously operated; or if preferred each cam may be individually operated and then held in the adjusted position by any suitable means as by a pin or by a ratchet arrangement.

It is obvious that various changes and modifications may be made in the details of construction and design of the above specifically described embodiment of this invention without departing from the spirit thereof, such changes and modifications being restricted only by the scope of the following claims.

What is claimed is:

l. ln a screed having a flexible bottom, means for flexing said bottom comprising a cam secured for angular movement to said screed and having a marginal operative portion eccentric to the axis of rotation of the cam and having along said margin a plurality of perforations spaced at variable distances from the center of rotation of the cam, a connection between the fiexible screed bottom and said marginal portion of the cam with means to selectively connect said connection to any one of said perforations, and means whereby the cam may be rotated in both directions selectively.

2. In a screed having a flexible bottom, means for flexing said bottom comprising a cam angularly carried by said screed, a connection between the operative part of said cam and said screed bottom, a substantially tangential arm projecting from said cam and having a number of perforations therein spaced at different points from the cam center of movement, a pitman, a pin for con necting one end of said pitman selectively in any one of said perforations, and means pivotally connected to the other end portion of the pitman for operating the same.

3. In a screed having a fiexible bottom, means for flexing said bottom comprising a cam carried by said screed, a connection between the operative part of said cam and the screed bottom,

a substantially tangential arm series of spaced threaded pitman having an eye, a

on said cam having a perforations therein, a threaded and headed ing two adjustable parts for varying the length of said pitman.

5. In a screed having a exible bottom, means for fiexing said bottom comprising a cam movably carried by the screed, a connection between the operative part of the cam and said screed bottom, a perforated arm on said cam, a pitman composed of threadedly telescoping parts, means for pivotally connecting one said part with said arm, and an operating member pivotally connected to the other said part of said pitman.

6. In combination with a transversely reciprocating screed and a finishing machine, an abutmachine, a

retired position,

and having curvilinear surfaces riding against said abutment, said push bar also having a socket for rotating on the head of said bolt.

7. In a screed having a flexible bottom, a reciprocating bar, a cam rotatable on the screed and having an eccentric edge, a connection to the flexible bottom, coupling means for detachably and selectively coupling said connection to variable points on said eccentric edge at diierent distances from the center of rotation of the cam adapted to cause predetermined angular movement of the cam to result in differential amplitude of movement in the connection and flexible screed bottom, and means to rotate the cam back and forth on reciprocating movement of the bar.

8. In a screed having a flexible bottom, a cam rotatably mounted on the screed, a connection on the cam to the bottom, a reciprocating bar,

of the bar,

bar back and forth to simultaneously operate said 4 Cams.

JOSEPH WILLIAM HELTZEL.

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