Hydraulic and earth engineering – Fluid control – treatment – or containment – Flow control
Reexamination Certificate
1999-01-12
2001-03-06
Taylor, Dennis L. (Department: 3673)
Hydraulic and earth engineering
Fluid control, treatment, or containment
Flow control
C405S087000, C405S092000, C405S100000
Reexamination Certificate
active
06196764
ABSTRACT:
The present invention relates to an automatic flashboard for a hydraulic structure such as a weir, or a spillway on a dam or on a protective embankment, the flashboard being of the type comprising a watertight or substantially watertight wall installed on said structure so as to be capable of passing from an erect, first position for retaining a mass of water to a lowered, second position in which said wall allows water to pass practically without obstruction, and at least one elongate retaining element for holding said wall in its first position against the horizontal thrust exerted by the mass of water, said elongate retaining element being subjected in operation under thrust from the water to a longitudinal force, extending between said wall and a reaction point counterbalancing said longitudinal force, and being connected to the reaction point via a connection that can be eliminated automatically when the water reaches a certain level, such that said wall passes automatically to its second position.
Automatic flashboards of that type are well known. Usually, such automatic flashboards are installed, e.g. on the top of a weir disposed across a river, in order to raise the level of water in the river upstream from the weir. They can also be installed on a dam spillway in order to raise the level of the reservoir retained by the dam. They can also be installed on the top of the spillway of an embankment bordering a river and intended to protect adjacent regions against the river flooding, in which case the spillway is installed in the embankment at a location that is chosen so that in the event of a flood, water flows into a storage reservoir or onto selected ground without danger for other regions adjacent to the river. Automatic flashboards can be of the non-overflow type or of the overflow type, i.e. in the second case they can allow a certain quantity of water to pass over the top thereof so long as the water level upstream from the flashboard does not exceed a predetermined height. Nevertheless, in all cases, automatic flashboards must be capable of moving out of the way automatically if the water level upstream from the flashboard reaches a predetermined level during a flood in order to release the mass of water it is retaining and thus avoid flooding regions adjacent to the river or, as the case may be, damaging the embankment or the dam.
FIG. 1
of the accompanying drawings is a diagram in side elevation of a known automatic flashboard of the above-defined type, which can be considered representing the state of the art closest to the present invention. A model of that known automatic flashboard was exhibited at the International Congress on Large Dams which was held at Durban in the Republic of South Africa in November 1994. The known automatic flashboard shown in
FIG. 1
is essentially constituted by a vertical or sloping plate
1
whose base is hinged to the top
2
of a masonry weir or spillway
3
by means of a hinge
4
or other similar element. The plate
1
is held in its erect position as shown in solid lines in
FIG. 1
by means of a tension member
5
having one end connected to the plate
1
near the top thereof and having its other end connected to the masonry of the weir or spillway
3
by means of a fastening
6
which is shown in greater detail in
FIG. 2
of the accompanying drawings. As shown in
FIG. 2
, the fastening
6
comprises two parts
6
a
and
6
b
which are fixed respectively to the masonry of the weir or spillway
3
and to the tension member
5
, and a pin
6
c
which is engaged in aligned holes formed through parts
6
a
and
6
b
and which couples those two parts together.
In operation, the mass of water
7
retained by the plate
1
exerts thrust thereon. As a result, the tension member(s)
5
are under tension and consequently the pin
6
c
of the fastening
6
is subjected to a shear force. The magnitude of the shear force is proportional to the magnitude of the tension in the member
5
which is itself proportional to the magnitude of the thrust exerted by the mass of water
7
on the plate
1
. The magnitude of said thrust is itself an increasing function of the level of the mass of water
7
, i.e. the height of the water above the top
2
of the weir or spillway
3
. When the magnitude of the shear force reaches and exceeds the shear strength of said pin
6
c
due to the water level rising, the pin
6
c
breaks, and under the thrust of the water, the plate
1
automatically drops down onto the top
2
of the weir or spillway
3
by pivoting about the axis of the hinge
4
until it takes up the position shown in dashed lines in FIG.
1
.
Thus, by selecting the diameter and/or the material (generally steel) of the pin
6
c
so that it has appropriate shear strength, it is possible to ensure that the pin
6
c
of the fastening
6
breaks under predefined water loading, and thus when the water level upstream from the plate
1
reaches a predefined level. However, in practice, experience shows that the water level that causes the pin
6
c
to shear is not precise and can vary over a range of several tens of centimeters. Even assuming that the steel used has excellent properties, and also assuming consistent production quality, results of strength tests performed on steel samples cut from a single steel bar of diameter machined with great accuracy generally present a large amount of dispersion.
In spite of the apparent simplicity of the known automatic flashboard described above, it is highly probable that the plate
1
will be triggered prematurely, i.e. folded down to its low position before the water level reaches the predefined level, or that the plate
1
will be triggered too late, i.e. when the water level is higher than the predefined level; with these situations constituting a drawback from the reliability point of view in the first case and a drawback from the safety point of view in the second case. It is therefore highly desirable for the automatic flashboard to be capable of being triggered automatically with greater precision concerning water level.
Other designs of flashboard are described in U.S. Pat. No. 2,118,535 and in the publication “Engineering for dams” by W. P. Creager, Vol. III, pp. 870 to 878, published by Chapman and Hall, London, 1945. The flashboard described in U.S. Pat. No. 2,118,535 and the flashboard shown in
FIG. 1
on page 872 of the publication “Engineering for dams” are entirely similar in structure. Those two flashboards are essentially constituted by vertical plates or panels which are held against water thrust by vertical stakes whose bottom ends are embedded in the masonry of the weir or spillway and which have the downstream faces of the vertical plates or panels pressing against the full height thereof. In both cases, the flashboards are automatic. The stakes are made of steel bars or tubes of section selected so that the stakes fold or break for a given water loading applied to the vertical plates or panels. Concerning the precision of the water level that causes the stakes to fold or break, those known flashboards suffer from the same fault as the known automatic flashboard described above with reference to
FIG. 1
of the accompanying drawings (in this respect, reference may be made to the publication “Engineering for dams”, page 872, 3rd paragraph and page 874, 8th paragraph).
The flashboard shown in
FIG. 5
on page 877 of the above-specified publication “Engineering for dams” is essentially constituted by one or more panels whose bottom ends press against a seat formed on the masonry of the weir or spillway and whose top ends are attached by means of bolts to a gangway passing over the weir or spillway. Each panel is constituted by a metal frame slidably receiving bulkhead plates. The metal frame is connected to the gangway by slack chains. The bolt(s) must be actuated by an operator to detach the panel(s) and release the mass of water retained thereby, which means that that flashboard does not operate automatically. It would be easy to design means for causing said flashboard to opera
Amster Rothstein & Ebenstein
Hydroplus
Taylor Dennis L.
LandOfFree
Automatic wicket for a hydraulic structure does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Automatic wicket for a hydraulic structure, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Automatic wicket for a hydraulic structure will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2548353