Note: Descriptions are shown in the official language in which they were submitted.
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SPECIFICATION
This invention relates to a vibratory screed
for use in finishing freshly placed concrete pavements.
A variety of screeding devices is disclosed in
the prior art. U.S. Patent No. 4,030,873 (Morrison)
discloses a screed device having multiple elongated frame
sections with vibratory action imparted by a motor-driven
rotating shaft The screed bars are L-shaped metallic
members.
U.S. Patent No. 3,435,740 (McGall) discloses a
screed device having multiple elongated frame sections
from which depend rectangular, reciprocating, metallic
screed bars, and further having hand winch advancing
means.
U.S. Patent No. 4,249,327 (Allen) discloses a
screed device with multiple elongated frame sections,
hand winch advancing means and pneumatic vibrators. The
front screed bar is an inverted T-shaped metallic member
and the rear screed bar is an L-shaped metallic member.
Other screed devices known to those skilled in
this art include features such as self-propelled hydraulic
winches, adjustable crown or sag means, eccentric weights
spaced along a rotating vibrator shaft, and fine grader
attachment devices.
Heretofore, screed devices of the type to which
the present invention relates have had screed bars with
but one useable wearing surface for downwardly engaging
the fresh concrete. When that surface is no longer use-
able due to the abrasive effects of the concrete, the worn
screed bar must be removed, discarded and replaced with a
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new one at significant expense.
The present invention solves this problem by
providing a screed device with detachable screed bars which
are invertible about their longitudinal axes to provide
two useable wearing surfaces. Furthermore, the screed
device of the invention combines other advantageous
features in a unique manner to provide a highly effective
device.
According to the invention, a vibratory concrete
screed device is provided with forward and rear elongated
screed bars depending from a plurality of inverted
U-shaped brackets secured to an elongated space truss.
The screed bars are rectangular and hollow in cross-
section. Bores are provided through the vertical surfaces
of the brackets and through the screed bars midway between
the upper and lower surfaces thereof so that the screed
bars are secured within and below the brackets by the
insertion of bolts through the aligned holes.
When the lower surface of the screed bar has
worn to the extent that it no longer produces an accept-
able concrete finish, the bolts are removed, the screed
bar is inverted, and the bolts are reinserted to furnish
a new screed bar wearing surface.
The screed device of the invention is provided
in multiple sections of various lengths so that pavements
of various widths may be finished and portability is
enhanced. Turnbuckle means are placed between sections
so that the screed device may be adjusted to produce a
crown or sag.
An internal combustion engine mounted on the
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screed device drives a longitudinal rotating shaft with
counterweights spaced therealong to impart vibratory
action. The engine also drives a hydraulic system which
in turn drives winches for self-propelling the screed
device along the line of work.
The screed device of the invention has hol~ow
rectangular screed bars with opposed vertical faces and
coextensive with said framework; bracket means for
securing the screed bars to the framework; lateral support
openings and lateral connection openings in the vertical
faces of the screed bars; upper and lower horizontal wear-
ing surfaces; lateral connection openings employed in
conjunction with interconnection elements between adjacent
interconnectable screed bar sections when a screed bar is
constructed of more than one section; lateral support
openings through the bracket means in positions coinciding
with the lateral support openings in the screed bars;
fastener means for insertion through the support openings
and the screed bars and in the bracket means to secure the
screed bars to the bracket means; and lateral connection
openings and lateral support openings lying midway between
the first and second wearing surfaces of the screed bars
so that the screed bars and screed bar sections may be
inverted and resecured to the bracket means to provide a
fresh wearing surface for contacting the concrete.
ON THE DRAWINGS
FIG. 1 is a perspective view showing a screed
device embodying the principles of the invention as used
in screeding and finishing a freshly poured concrete
pavement;
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FIG. 2 is an end view looking inwardly at the
left hand end of the screed device shown in FIG. l;
FIG. 3 is a fragmentary sectional view taken
substantially along the line III-III of FIG. 2;
FIG. 4 is a perspective view of one section
and a fragment of an adjacent section of the screed device
of FIG. 1 with one screed bar disassembled;
FIG. 5 iS a sectional view taken substantially
along the line V-V of FIG. 4; and
FIG. 6 is a fragmentary sectional view taken
of one end of the upper chord member showing the floating
nut of the turnbuckle means.
As shown in FIG. 1, the screed device S of this
invention may be oriented transversely atop a concrete
pavement to be screeded and finished, the ends of the
screed bars 11, 12, 13 and 14 resting upon the side forms
A and B. The screed device is suitable for use with a
variety of concrete pavements including floors, slabs,
bridge decks, streets, sidewalks, and approaches.
A source of power such as an internal combustion
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engine 15 is mounted at one end of the screed device S and
drives a rotating shaft 16 which extends for the length
of the screed device S by means of a pulley and belt
arrangement 17. Eccentric weights 18 spaced along the
rotating shaft 16 impart vibratory action to the screed
device thus aiding in consolidation of the fresh concrete.
At eàch end of the screed device S there is
mounted a hydraulic pump 19 coupled to the end of the
rotating shaft 16. Also mounted at each end there is a
10 winch 21 and a hydraulic motor 22. The winch cables 23
descend from the winches 21, pass through pulleys 24 and
extend longitudinally generally parallel to the line of
work to remote points D and E where they are anchored.
In operation, the internal combustion engine 15
and pulley arrangement 17 cause the shaft 16 to drive the
hydraulic pumps 19, which in turn drive the hydraulic
motors 22, causing the winches 21 to take up the cables
23. In this manner, the screed device S is self-propelled
forward across the fresh concrete C.
Hydraulic fluid is stored in tanks 25. Valving
means may be provided at each hydraulic motor 22 so that
the forward travel speed may be adjusted independently
of the engine speed and vibrational frequency.
The screed device S is formed of interconnected
25 longitudinal sections 27, 28 and 29. It is convenient
to provide the sections in various lengths to accommodate
pavements of differing widths. Each section comprises a
space truss 31, 32 and 33, brackets 34, and hollow
rectangular screed bars 35, 36 and 37 depending from the
30 brackets 34. The screed bars 35, 36 and 37 may be detached
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from the brackets 34, inverted, and reattached to the
brackets 34 to provide a new wearing surface as will be
discussed more fully below.
Referring now to FIG. 2 and FIG. 3, the
arrangement of the self-propelling features of the screed
device S of the invention may be seen in more detail.
As shown on FIG. 2, at the end of the screed device there
is attached an end frame comprising two vertical members
38 and 39, two horizontal members 41 and 42, a web plate
43, and two brackets 45 at the lower corners. The
brackets 45 straddle the forward and rear screed bars 37
and 46 and are attached thereto by bolts 47 inserted
through co-aligned holes formed through the brackets 45
and screed bars 37 and 46.
As best seen in FIG. 3, an internal combustion
engine 15 is mounted atop a platform 44 near the end of
the screed section 27. One end of the platform is
supported by a post 48 which has a bracket at its lower
end for bolting to the forward screed bar 46. The other
end of the platform 44 is secured to the upper cord of
the screed section 27 by U-bolts 50.
At the end ofthe output shaft 51 of the internal
combustion engine 15, there is a centrifugal clutch 52.
Below the centrifugal clutch 52 there is affixed to the
rotating shaft 16 a pulley 53. A belt 54 drivingly con-
nects the centrifugal clutch 52 and the pulley 53.
Attached to the end frame lower member 42 by
means of a bracket 52, there is a hydraulic pump 19.
The input shaft 56 of the pump is drivingly connected
to the rotating shaft 16 by connector means such as a
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universal joint or a coupling 57.
As best seen on FIG. 2, there is attached to
the upper end of the'vertical end frame member 39 a
hydraulic motor 22 and a winch 21. Hydraulic fluid stored
in the tank 26 and carried to the motor 22 from the pump
19 by means of a hydraulic hose causes the motor 22 to
drive the winch 19 which takes up cable 23 through the
pulley. If the hook 60 is attached to a remote fixed
point, it can be seen that the screed device will be
propelled forward across the fresh concrete.
At the other end of the screed device S there
is a similar arrangement of an end frame with a pump 19,
motor 22, winch 21, and tank 25. The other end of the
rotating shaft 16 is coupled to the pump 19, thus similarly
driving the motor 22, winch 21 and propelling the screed
device S. Valving means such as a flow regulator may be
provided at each end of the screed device S so that the
travel speed may be adjusted or arrested independently
of the engine speed. The centrifugal clutch 52 allows
the travel and vibration to be stopped without shutting
off the engine 15. Furthermore, the vibrational frequency
may be adjusted within limits without affecting travel
speed.
Edge guides 80 may be attached at each end of
the screed bars 37 and 46. The edge guides 80 are
substantially rectangular plates having their upper ends
attached to the vertical members 38 and 39 by U-bolts 81.
m e lower ends of the edge guides 80 extend below the
bottom surfaces of the screed bars 37 and 46 thereby
limiting lateral movement of the screed device. m e edge
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guides are of particulax effectiv~ness in preventing
downward sliding of the screed device when in use on super-
elevated pavements.
Ski attachments 82 may be provided near the
ends of the forward screed bar 37. Each ski attachment 82
is a plate having its forward and rearward edges bent
upward. When secured under the forward screed bars 37,
the ski attachment 82 rides atop the side form B, thus
slightly elevating the front screed bar above the final
grade level and allowing the rear screed bar to carry a
roll of concrete. In this manner, an improved finish
may be achieved with greater compaction.
As shown in FIG. 4, the structural details of
the screed sections may be seen. A screed section 28
comprises an elongated space truss 32 generally triangular
in cross-section having web members 58, cross-bracing
members 59, lower transverse members 61 and an upper chord
member 49.
The rotating shaft 16 passes longitudinally
through the space truss 32 supported above the transverse
members 59 by bearings such as pillow blocks 62. At
each end of the rotating shaft, there is a coupling for
connection to the rotating shaft of an adjacent screed
section or to the input shaft 56 of the pump 19 as better
shown in FIG. 3.
At least one eccentric weight 18 is secured
along the rotating shaft 16 by U-bolts 63. The weight
imparts vibratory action to the screed section with the
vibrational frequency controllable by adjusting the
engine speed. The number and spacing of the weights 18
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along the rotating shaft 16 may be determined by the
operator in the field according to the concrete work-
ability.
At the ends of the lower transverse member 61
and the lower ends of the web members 58, there are
attached screed bar brackets 34. These brackets 34
are inverted U-shaped with two diagonally opposite
corners being clipped at an angle. A hole is formed in
each vertical face of the brackets 34.
The screed bars 64, 65, 66 and 67 are hollow,
rectangular metallic members, preferably of aluminum for
light weight and durability. Opposing pairs of holes
are foxmed at intervals along the vertical faces of the
screed bar as at 68 and 69. The holes are midway between
the upper and lower surfaces of the screed bar. A channel
member 71 is inserted in the ends of the screed bars 64,
65, 66 and 67. Holes 72 are formed in the sides of the
channel members 71 so that when the holes 72 are brought
into alignment with the holes 68 of ad]acent screed bars
and bolts are inserted therethrough, the ends of the bars
will be held in abutting relation.
FIG. 5 shows the cooperation of the screed bars
and screed bar brackets of the invention. The screed
bar 66 is nested securely within the screed bar bracket 34.
The bolt 72 inserted through the co-aligned holes of the
screed bar 66 and screed bar bracket 34 secure the screed
bar 66 to the screed section 28.
In operation, the lower surface of the screed
bar slides ovex the surface of the fresh concrete C
preferably pushing a small roll R of concrete in front
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of the leading surface of the screed bar. Eventually,
the lower surface of the screed bar will wear out due
to the abrasion of the concrete and will no longer
produce an acceptable finish. Rather than discard the
screed bar, the present invention doubles screed bar life
by providing two useable finishing surfaces. The bolts 72
are removed from the screed bar 64, 65, 66 and 67, the
screed bars are inverted, replaced in the brackets 34,
and the bolts 72 are reinserted and tightened.
Furthermore, the rectangular screed bars possess
greater stiffness than L-shaped or T-shaped bars, and
therefore produce a more level concrete surface. Also,
there is no tendency for the leading edge of the screed
bar to pick up and accumulate concrete as with T or
L-shaped bars.
The ends of the upper cord members 49 are
fitted with turnbuckle means 74. Rotating the turnbuckles
74 causes the adjacent upper cord member ends to be either
pulled together or pushed apart, thus creating a sag or
crown concrete surface respectively.
To accommodate the angle produced between screed
sections 28 and 29 by rotating the turnbuckles 74, a
floating nut arrangement is provided at the ends of the
upper chord members 49. As shown in FIG. 6, the nut 85
having internal threads 86 has an outer diameter somewhat
smaller than the inside diameter of the upper chord
member 49. Horizontal dowels 88 protruding within the
upper chord member 49 enter holes 87 provided in the
nut 85. The holes 87 are of a diameter large enough to
allow the nut 85 to rotate about a horizontal axis
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defined by the dowels 88. In this manner, binding of
the turnbuckle 74 is prevented when the screed device
is used on pavements having a crown or sag.
The winches 21 may be provided with clutch
means so as to allow the cables 23 to be played out
rapidly. Furthermore, with valving means at the hydraulic
motors 22, the flow of hydraulic fluid may be regulated
so that the vibrational frequency of the screed device
is not affected.
As is now apparent, a new and useful vibratory
concrete screed is provided having invertible screed
bars with two wearing surfaces. Although modifications
might be suggested by those skilled in the art, it will
be understood that I wish to embody within the scope
of the patent described herein all such modifications as
reasonably and properly come within the scope of my
contribution to the art.
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