Road structure – process – or apparatus – Apparatus – Screed or drag
Reexamination Certificate
2000-05-15
2003-07-22
Will, Thomas B. (Department: 3671)
Road structure, process, or apparatus
Apparatus
Screed or drag
Reexamination Certificate
active
06595719
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is concerned with a road-paving vehicle such as asphalt finisher, repaver or remixer which paves the road with a composite material. More specifically, the invention relates to a screed device in a road-paving vehicle such as asphalt finisher equipped with an extensible screed capable of extending the paving width to about three times as large as the width of a main screed.
2. Prior Art
Referring to
FIG. 8
, an asphalt finisher
1
is equipped with a hopper
2
for receiving composite material from a dump truck, and a conveyer-bar-feeder
3
for conveying the composite material in the hopper
2
to the rear side (toward the front in the drawing). The composite material conveyed to the rear side by the conveyer-bar-feeder
3
falls on the road and is conveyed in the direction of width of pavement by a screw spreader
4
installed at the rear part of the main body of the asphalt finisher
1
. At the back of the screw spreader
4
, the composite material is paved by a screed device
6
coupled by screed arms
5
to the main body of the asphalt finisher
1
.
According to the conventional screed device
6
capable of changing the width of pavement, a main screed
7
is provided, at the back or in front thereof, with extensible screeds
8
,
8
having a width of about one-half the width of the main screed
7
on the right and left sides, respectively, and these extensible screeds
8
,
8
are moved in the directions of width of pavement but opposite to each other by the feeding or extending devices such as hydraulic cylinders or threaded rods that are not shown in order to extend the width of pavement.
During the execution of works, the screed arms
5
move up and down causing the paving angle to change due to the holding amount of the composite material or due to various factors, and the height of the rear end of the lower surface of the main screed
7
becomes no longer in agreement with the height of the rear end of the lower surface of the extensible screeds
8
. Accordingly, stripes are formed on the paved surface
9
(
FIG. 9
) due to a step between the main screed
7
and the extensible screeds
8
. To prevent this, the extensible screeds
8
are moved up or down relative to the main screed
7
, or the step is adjusted between the main screed
7
and the extensible screeds
8
depending upon a change in the paving angle, so that the rear end of the lower surface of the main screed
7
and the rear end of the lower surface of the extensible screeds
8
acquire the same height from the paved road surface
10
.
The operation for paving the composite material can be finished within a shortened period of time if the total width of the screed device
6
is increased to extend a range of pavement. In order for the asphalt finisher to be transported by using a truck, however, the minimum width of the screed device
6
(nearly the same as the main screed width L (FIG.
8
)) is limited to be not wider than the width of the rear body of the truck. With the constitution shown in
FIG. 8
, therefore, the range L max of pavement is smaller than two times the width L of the main screed at the greatest. In order to execute the pavement maintaining a range which is in excess of two times width L of the main screed, therefore, it becomes necessary to attach extension screeds
12
,
12
(
FIG. 11
) to the outer ends of the extensible screeds
8
,
8
by using bolts or by utilizing hinges, or it becomes necessary as shown in
FIG. 10
to provide extensible screeds
11
,
11
that can be extended and contracted by the feeding or extending devices such as hydraulic cylinders that are not shown at the back on in front of the extensible screeds
8
,
8
provided at the back or in front of the main screed
7
like a screed apparatus disclosed in Japanese Unexamined Patent Publication (Kokai) No. 102521/1995.
Referring to
FIG. 12
, furthermore, extensible screeds
13
and
14
having a width nearly equal to the width of the main screed
7
are provided in front and at the back of the main screed
7
, and are extended in the directions opposite to each other by the feeder devices such as hydraulic cylinders that are not shown in order to extend the range of pavement to be more than two times the width L of the main screed (FIG.
12
).
When the extensible screed
11
is provided at the back or in front of the extensible screed
8
. of
FIG. 10
as shown in
FIG. 13
, steps must be adjusted so that the rear end of the lower surface of the extensible screed
8
and the rear end of the lower surface of the extensible screed
11
acquire the same height from the paved road surface
10
and, hence, the adjustment must be effected at a total of four places on the right side and the left side. The operation for adjusting the steps requires a considerable time, laborious work and a high degree of skill.
Next, when the extension screeds
12
,
12
are attached by bolts to the outer ends of the extensible screeds
8
,
8
as shown in
FIG. 11
, the extension screeds
12
become heavy, and considerable work and time are required for the attachment and detachment before executing the work and before the transportation. Further, a skill is required for adjusting the lower surfaces of the extension screeds
8
to be in match with the lower surfaces of the extension screeds
12
.
It was described above that the paving angle of the screed device changes depending upon the holding amount of the composite material. However, the paving angle of the screed device is further affected by the holding amount of the composite material in front of the main screed
7
. A change in the paving angle of the screed device results in a change in the thickness of pavement. To execute the pavement maintaining a predetermined thickness, therefore, the paving angle must be maintained as constant as possible during the execution of works. In the case of the screed device shown in
FIG. 12
, however, the holding amount of the composite material in front of the main screed
7
changes depending upon the amount of extension of the extensible screed
13
in front of the main screed
7
. Therefore, the paving angle of the screed device is not maintained constant, making it difficult to execute the pavement maintaining the predetermined thickness.
In order to solve the above-mentioned problems, there has been proposed a screed device as taught in Japanese Patent Application No. 155974/1998 (referred to as prior application) (see
FIG. 14
) filed by the present applicant, according to which extensible screeds
15
,
16
having a width nearly the same as the width of the main screed
7
are arranged in a pair back and forth at the back of the main screed
7
, holes that are not shown are perforated in instruction arms
17
,
18
protruding from both sides at the rear upper portions of the main screed
7
, guide shafts
19
and
20
are slidably supported thereby, both ends of the guide shafts
19
and
20
are secured to both ends of the extensible screeds
15
and
16
, feeding or extending devices such as hydraulic cylinders that are not shown are provided at the upper portions of the main screed
7
in the directions opposite to each other, and the extensible screeds
15
and
16
are moved by the feeding or extending devices from the rear positions of the main screed in the directions of pavement but opposite to each other, in order to extend the range of pavement to be about three times as large as the width L of the main screed.
In order to broaden the range of pavement even by a small amount, however, the width of the instruction arms
17
and
18
must be narrowed, whereby the width for supporting the guide shafts
19
,
20
becomes narrow making it difficult to maintain rigidity of the screed device. In executing the works, therefore, both ends of the extensible screeds
15
,
16
jump up from the paved surface due to the reaction, and the thickness of pavement does not become constant in the direction of width of pavement.
Referring to
FIG. 15
, the composite
Ogura Akishi
Ohseki Masayuki
Tameike Kouji
Addie Raymond W.
Fattibene Arthur T.
Fattibene Paul A.
Fattibene & Fattibene
Sumitomo (Shi) Construction Machinery Co., Ltd.
LandOfFree
Screed device in a road-paving vehicle such as asphalt finisher does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Screed device in a road-paving vehicle such as asphalt finisher, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Screed device in a road-paving vehicle such as asphalt finisher will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3015348