Energy-efficient automatic sluice gate for sustaining a fluid level

An energy-efficient automatic sluice gate for sustaining a fluid level, separating an upstream pool from a downstream pool in an irrigation system and enabling the level of water in one of the pools to be kept constant at a settable value. A sluice gate separates an upstream pool (1) from a downstream pool (2) and enables the level of one of the pools to be kept constant at a settable value, said gate comprising a baffle (3) movable about a horizontal rotational shaft (4) whereby the rotation of the baffle about its shaft determines the flow of water downstream, said baffle constituting a segment of a cylinder having the said rotational shaft as its axis, and further comprising a box member (7A) and a second box member (7B), both moving with the baffle and dipping respectively in the upstream pool and in the downstream pool, means (9, 13, 15) for at least partially filling the box members, means (20) for keeping constant the level in the first or the second box member according to whether the level in the upstream pool or in the downstream pool is to be kept constant and means (50) of setting said constant level value.

The present invention concerns a sluice gate separating an upstream pool 
supplied with water and a water-supplying downstream pool, said gate 
enabling the water level in one of the pools to be automatically 
maintained at an adjustable set point. 
BACKGROUND OF THE INVENTION 
Alsthom's French Pat. No. 2,071,299 describes valves satisfying the same 
requirement, comprising a moving baffle which tilts about a horizontal 
shaft and is actuated by an adjustable-ballast float. 
Such valves have the following disadvantages: they make it necessary to 
select the operating mode (regulation either of the upstream level or the 
downstream level) on a permanent basis; and require that the level to be 
kept constant also be set permanently, said level setting being impossible 
or very difficult to modify. 
Preferred embodiments of the present invention provide an automatic level 
sustaining valve or sluice gate enabling the changeover from regulation of 
the upstream level to regulation of the downstream level to be easily 
accomplished and also enabling the set point to be adjusted, both either 
manually or by remote control by means of a low-level signal transmitted, 
for example, via a telephone line. 
SUMMARY OF THE INVENTION 
The present invention provides a sluice gate for automatically sustaining a 
level, using a small amount of energy, wherein said gate controls the flow 
of water from an upstream pool to a downstream pool and comprises: 
a closing baffle carried by a framework movable about a horizontal rotating 
shaft located downstream from the baffle such that rotation of said 
framework about said shaft controls the section of water flowing from 
upstream to downstream, said baffle constituting one segment of a 
revolving cylinder with the said rotating shaft as its axis; 
and a box member, which carried by the above framework, dips into the pool, 
the level of which must be maintained so that the angular position of the 
framework is determined by the water level therein, said box member having 
an opening at the bottom for the passage of water and an opening at the 
top for the passage of air to enable the amount of water in the box member 
to be varied; 
said gate further comprising an upstream box member and a downstream box 
member, both carried by the framework, located opposite one another across 
from said shaft such as to be held partially immersed respectively in the 
upstream and downstream pools, the pools being separated by the 
abovementioned baffle and both box members having openings in their tops 
and bottoms as described; 
and pressure regulating means communicating with said openings via 
switching valves such that they may be caused to operate alternately in an 
upstream regulation mode and a downstream regulation mode, said regulating 
means controlling the water level in a "regulating" box member, which 
would be the upstream box member in the upstream regulation mode and the 
downstream box member in the downstream regulation mode, so as to 
automatically maintain the water level in a "regulated" pool or basin, 
being the one in which the box member dips, said switching valves allowing 
water and air to flow through the openings in the other box member to 
balance the water levels obtaining in said non-regulating box member and 
in the unregulated pool. 
Depending on the circumstances, one or more of the following features may 
be preferably adopted: 
Each of said box members is given an approximately uniform horizontal cross 
section over its entire useful height and the center of gravity of the 
assembly attached to the framework is located approximately at the height 
of said rotational shaft such that the rotational torque applied to the 
framework is determined exclusively by the difference between water levels 
in the regulating box member and the regulated pool. 
Control means are provided, comprising a limited-flow compressed gas supply 
fitted with tubing whose open end is immersed in the upstream pool at a 
height controlled by said regulating means, a switching valve to connect 
said supply with the upper opening in the regulating box member and a 
switching means to connect the lower opening of the downstream box member 
with the upstream or downstream pool, according to the box member's 
regulating or non-regulating status, such that the lower opening of the 
upstream box member issues into the upstream pool even when it is 
non-regulating. 
Said regulating means are provided with an outlet spout of adjustable 
height, some means of filling said outlet spout with a limited flow and 
means for connecting the lower opening of the regulating box member with 
said filling means, the upper opening of said box member being vented to 
the atmosphere. 
The spout-filling means comprise tubing issuing into the upstream pool, the 
spout itself pouring into the downstream pool. 
The spout-filling means further comprise an auxiliary pool or basin 
supplied with clean water. 
The lower opening of the non-regulating box member communicates with the 
unregulated pool via a circuit equivalent in terms of pressure losses to a 
cross-sectional area from 2 to 0.02% of that of the free surface of the 
water in the box member, the upper opening of said box member allowing the 
air to flow virtually unhindered between the inside of said box member and 
the air, such as to provide a partial, temporary servo control of the 
level in the unregulated pool, in particular during changeovers between 
upstream and downstream regulation.

MORE DETAILED DESCRIPTION 
Referring to FIG. 1, reference 1 depicts the level in an upstream pool and 
reference 2 the level in a downstream pool constituting two successive 
reaches of an irrigation ditch. 
The automatic sluice gate shown is designed to maintain the level upstream 
or downstream at a constant value. It comprises a baffle 3, movable about 
a rotating shaft 4. The baffle is connected to the shaft by means of a 
framework 5 and it controls the size of the water passage over a concrete 
ground sill 27. 
An upstream box member 7A, moving with the baffle, is partly immersed in 
the upstream pool and a downstream box member 7B, moving with the 
framework, is partly immersed in the downstream pool. 
The lower end wall 8A of box member 7A has a "lower" opening 9 enabling 
partial filling of the box member. The opening is protected by a screen 
10, preventing the ingress of refuse into the box member. 
Partial filling of the downstream box member 7B is obtained by means of a 
switching valve 15 which connects said member either with the upstream 
pool, via tubing 13, or with the downstream pool. 
Both box members are connected to a limited-flow compressed air source 20 
via tubings 22, 23A and 23B as well as via switching valves 28A and 28B 
which establish a connection between tubing 22 and either the upstream or 
the downstream box member, leaving the unconnected box member vented to 
the atmosphere. Valves 28A, 28B and 15 are actuated at the same time. Gas 
escape in bubbles via tubing 24, which communicates with tubing 22 and the 
end 25 of which is immersed in the upstream pool to a depth d below the 
level 1 of said pool. 
In order to regulate the level upstream (the case shown in the figure), box 
member 7A, which becomes the regulating box member, is made to communicate 
with the gas supply; the other box member 7B remains passive and serves as 
a damper, being vented to the atmosphere and connected to the downstream 
pool via switching valve 15. In order to regulate the level downstream, 
box member 7B serves as the regulating member and is made to communicate 
with the gas supply as well as, via component 15, with the upstream pool. 
Box member 7A is vented to the atmosphere and becomes the damping member. 
The system is so assembled that the pressure in the tubing and inside the 
box member serving as regulator is constant and equal to d expressed in 
terms of meters of water. The water level inside the regulating box member 
is thus always at the height of the bottom end 25 of tubing 24, regardless 
of the level obtaining in the upstream pool. 
The upstream and downstream walls of the box members, as well as the 
baffle, are sections of surfaces revolving about the rotating shaft such 
that hydrostatic pressures against the walls cannot induce a rotational 
torque. Only the lower end walls 8A and 8B of the box members can apply a 
pressure on the movable framework, said pressure being proportional to the 
difference in water levels inside and outside the relevant box member. 
The sluice gate framework is so designed as to have the center of gravity 
12 of the moving assembly be located upstream from the rotational axis 4, 
near the horizontal plane intersecting the rotational axis, when the gate 
assembly is in an intermediate position. 
The mechanical torque stemming from the weight of said moving assembly is 
balanced either by the hydrostatic pressure on box member 7A when said 
upstream box member serves as the regulator, or by the greater weight of 
water in box member 7B in the case when said downstream box member serves 
as regulator, said pressures and forces being proportional to the 
difference between the level upstream and the level in box member 7A in 
the case of upstream regulation, and proportional to the difference 
between the level downstream and the level in box member 7B in the case of 
downstream regulation. It should be appreciated that the level in the 
nonregulating box member is the same as that in the pool in which it is 
partly immersed, thanks to the simultaneous operation of valves 28A, 28B 
and 15. A difference in these levels occurs only during quick transitions, 
because of the limitation on the rate at which water can flow into or out 
of the box members under a given pressure. The inventors have found that 
this flowrate limitation improves the stability of upstream pool-sluice 
gate-downstream pool system operation where said pools are canal reaches, 
thus improving regulation precision. Consequently, in cases where the 
water flows through a simple opening in a sheet metal part, the cross 
sectional area of said opening should be given suitable dimensions in 
relation to the free surface area of the water in the box member. Said 
cross sectional area will depend on the nature of the upstream and 
downstream reaches of the irrigation ditch, but it will generally fall 
within the previously-mentioned limits. In cases where water is made to 
circulate through a pipe system, the cross sectional area of an opening 
which would be equivalent to said pipe system in terms of pressure losses 
should be considered. 
The constancy of the position of the level in the box member selected to be 
the regulating member imparts a constant level to the corresponding pool. 
With reference to the example of upstream level regulation, if the water 
level in the upstream pool tends to rise, the water level 11A in box 
member 7A remaining stable, the hydrostatic pressure against the box 
member will increase and the sluice gate will fully open the passageway 
between the baffle and ground still 27 because, due to the location of the 
gate's center of gravity, the mechanical torque applied to the gate by its 
own weight and by the water pressure is nearly constant at all angular 
positions. 
The gate rotates in the reverse direction in the case of a lowering of the 
level in the upstream pool. Quick, accurate regulation is thus obtained. 
Regulation of the level in either pool can be obtained simply by raising or 
lowering tubing 24. Raising the tubing increases the value of the level 
set point and lowering the tubing decreases the value of the level set 
point. Tubing 24 can be raised or lowered by hand, or at a distance using 
a remote controlled motor. 
For example, as shown in FIG. 1, tubing 24 may be suspended from a fixed 
hook 51 by means of a chain 50 and its height adjusted by hooking 
different links of the chain (manual control). Alternatively, as per FIG. 
2, tubing 24 may be suspended from a cable 42 wound around a winch 40 
driven by a remotely controlled motor 41 powered from a self-contained 
energy source such as a solar battery (remote control). 
Pressurized gas may be supplied by a compressed air cylinder which must be 
replaced from time to time, or by a compressor driven by a self-contained 
power supply, such as a solar battery, or by the difference in water 
pressure between the upstream and downstream pools. 
Similarly, switching valves 15, 28A and 28B may be remotely controlled, 
thus affording a choice of the pool whose level is to be kept constant. 
Said valves, serving to control very small air flows, are small and are 
susceptible to being actuated by low-powered control means of generally 
less than 10 W. 
FIG. 2 depicts an alternative construction of the device shown in FIG. 1, 
having a simpler tubing and valve system. 
Features common to both figures have been given the same reference numbers. 
Valves 28A and 28B have been replaced by a single valve 80, which is 
actuated simultaneously with switching valve 15. 
Changeover from constant level control of the upstream pool (the case of 
FIG. 2) to constant level control of the downstream pool is obtained by 
simultaneously rotating valves 80 and 15 one quarter turn. 
FIG. 3 depicts an alternative construction of an automatic sluice gate for 
keeping constant the water level in the upstream or the downstream pool. 
Features common to FIGS. 1 and 3 bear the same reference numbers in both 
figures. 
Box members 7A and 7B are provided with upper openings 29A and 29B, but 
their bottoms 8A and 8B are closed. 
In this arrangement, levels 11A, 11B in the box members are kept constant 
thanks to an outlet spout 30, which is supplied with water from the 
upstream pool via tubing 31, empties into the downstream pool and links up 
with bottom end apertures 32A and 32B in the box members via tubes 33A and 
33B. Water therefore circulates between the upstream pool and the 
downstream pool via tubing 31 and pour spout 30. 
A pressure drop diaphragm 35 is installed in tubing 31 such that level 11A 
remains approximately equal to the level 36 of pour spout 30. 
Switching valves 34A and 34B connect either the upstream box member or the 
downstream box member with tubing 31 and spout 30, leaving the unconnected 
member directly connected with the pool in which it is partly immersed. 
With the level inside one of the box members constant, level 1 in the 
corresponding pool will also be constant. 
Regulation of the pool level is obtained by raising or lowering pour spout 
30, as described concerning tubing 24 of FIG. 1, for example. 
As in the preceding cases, valves 34A and 34B may be remotely controlled to 
select the pool to be regulated. 
FIG. 4 depicts a sluice gate according to the invention for keeping 
constant the water level in a pool, which differs from the gate of FIG. 3 
in that the box members are no longer fed from the upstream pool, but 
rather from an external pool or basin 52, via a tubing 53. The remainder 
of the device is the same as per FIGS. 1, 2 and 3. The set point remote 
control system is schematically represented by a winch and its motor. 
This alternative embodiment has the advantage of enabling the system to be 
partly supplied with water from a source other than the upstream pool, 
said other source possibly being cleaner and thus avoiding or lessening 
the chances of solid matter clogging the pipes or valves.