Automatic trip gate

An automatic trip gate for installation in a gate support structure at a bank of an impounded body of water. The automatic trip gate controls a release of an overflow of water through the gate support structure upon the occurrence of an overflow event. The automatic trip gate includes a plate supported by a hinge assembly that attaches to the support structure. A trough attached to the plate catches and retains overflow water. When the level of overflow water in the trough reaches a tipping level, the plate pivots from a substantially vertical orientation wherein the impounded body of water is maintained behind the plate, to a tipped position wherein the impounded body of water is released o through the gate support. A plunge pool is located below the automatic trip gate that absorbs the energy imparted by the plate when tripped.

BACKGROUND OF THE INVENTION

A device for diverting flow from a canal drop, small earthen dam or branch to an emergency spillway should a primary diversion fail unexpectedly was required at a small hydroelectric project being developed by the inventors. Several commercial products were available, such as the Obermeir Hydro, Inc. Pneumatically Operated Spillway Gate. This gate consists of a hinged plate held in place by an air bladder. In order to operate, this product includes a control valve, which could fail to operate. In the interest of providing a gate with no controls, a simple, economical alternative was required.

SUMMARY OF THE INVENTION

The present invention is directed to a device and method for directing or diverting a flow of water from a first water channel to an emergency spillway in the case of a spillover or other control event wherein water from a first water channel overflows. An automatic trip gate is installed in a gate support structure at a bank of an impounded body of water. The automatic trip gate controls a release of an overflow of water through the gate support structure upon the occurrence of an overflow event. The automatic trip gate includes a plate supported by a hinge assembly that attaches to the support structure. A trough attached to the plate catches and retains overflow water. When the level of overflow water in the trough reaches a tipping level, the plate pivots from a substantially vertical orientation wherein the impounded body of water is maintained behind the plate, to a tipped position wherein the impounded body of water is released through the gate support. In a preferred embodiment of the invention, a plunge pool is located below the automatic trip gate that absorbs the energy imparted by the plate when tripped.

In one embodiment, the automatic trip gate is installed or constructed in feed canal at a hydroelectric plant. The flow and head for the plant was developed at an intersection of two earthen irrigation canals. The plant took flow from a branch that dropped 38 feet from the upper canal to a lower canal. Flow normally passes through the plant turbines. When the plant is shutdown, flow is bypassed through an existing flume by opening two small radial gates via an automated control system. In the event that the bypass failed the canal would be over topped, and possibly wash out. In the described embodiment and installation, a separate spillway fitted with multiple automatic trip gates provided the solution to this concern.

The automatic trip gate and spillway of the present invention may be used at any impoundment, dam or canal where overtopping could cause failure of the structure due to erosion. In many cases, a lowered section in the dam acts as an emergency spillway and discharges into some form of channel. This, however, reduces head or storage behind the dam. With the automatic trip gate, the operating level can be higher, near the top of the gate, which will tip over and discharge into a channel when water level exceeds a set point.

DETAILED DESCRIPTION

FIG. 1a typical installation of automatic trip gate system50including in this installation three separate automatic trip gates20A,20B and20C. In the instance represented inFIG. 1, automatic trip gate system50is installed at a location on canal C, where a low head hydroelectric plant, (not shown), has been established. Intake structure IS provides a flow of water to the hydro-electric plant during generation. When the hydroelectric plant experiences an unexpected shut down, overflow of canal water is handled by automated bypass AB, which is controlled in conjunction with the control of operation of the hydroelectric plant such that while water is flowing through the intake structure IS to the turbine, (not shown), located in the hydroelectric plant, a controlled valve, (not shown), of the automated bypass AB is closed so that flow is diverted through the intake structure IS. When the hydro-electric plant is out of service or operation, the controlled valve of the automated bypass AB is opened so that flow is diverted to a stilling basin or canal, (not shown).

In the event that the hydro-electric plant experiences an unexpected shut down, i.e. no water flow is being diverted through the turbine, and the controlled valve of the automated bypass AB is inoperative and fails to open for any of a number of reasons, flow, in an overtopping situation, will be diverted by operation of the automatic trip gate system50to a stilling basin or canal through outlet pipe46.

FIGS. 1 and 2show automatic trip gate system50is installed in a trip gate support structure, in this case spillway40which is constructed at a bank B of an impoundment of water W, in this case canal C. Each of the three separate automatic trip gates20A,20B and20C are installed between support structures of the spillway40. Automatic trip gate20A is installed between spillway sidewall41A and first pier42A. Similarly, automatic trip gate20B is installed between first and second piers42A and42B. Automatic trip gate20C is installed between spillway sidewall41B and second pier42B.

As shown inFIG. 2, each of the automatic trip gates20A,20B and20C include a trough21A,21B and21C respectively. Spillway40is also constructed such that below each of the three separate automatic trip gates20A,20B and20C, a plunge pool is located. Thus plunge pool45A is formed below automatic trip gate20A, plunge pool45B is formed below automatic trip gate20B and plunge pool45C is formed below automatic trip gate20C. Each plunge pool45A,45B and45C is formed behind a retaining wall43A,43B and43C respectively.

Referring toFIGS. 3,4,5and6automatic trip gate20A is shown supported by gate support structure47and installed against spillway sidewall41A. Plunge pool45A is shown formed below automatic trip gate20A and behind retaining wall43A. Automatic trip gate20A is shown including trough21A attached to plate35by gate top plate22. The top of the trough21A is covered by trash screen27which prevents trash and other debris from filling trough21A. Automatic trip gate20A is pivotably supported by hinged support arm assembly30. Hinged support arm assembly30is typical of the plurality of hinged support arm assemblies that pivotably support trough21A.

Referring toFIGS. 4,5and6, hinged support arm assembly30includes foot31that extends between and is connected at one end to plate35and at a second end to hinge end support34by hinge pin32. Hinge end support33attaches to gate support structure47using hardware36. Hinge pin32is supported in hinge end support34by bushing33. In a preferred embodiment, bushing33is a nylon, molybdenum impregnated self-lubricating which provides low friction for the overturning action. Also in a preferred embodiment, foot31is welded to plate35.

FIGS. 4,5and6show automatic trip gate20A as it goes from standby position wherein water W retained behind automatic trip gate20A is maintained at a desired operating level L1as shown inFIG. 4, to tipped position as seen inFIG. 6, wherein automatic trip gate20A is shown in a tripped position and water W is maintained at a post-trip level L3.

FIG. 5shows water W behind automatic trip gate20A has reached an overflow level L2, wherein water W has crested plate35, and begins to flow over trip gate top plate22filling trough21A. InFIG. 5, trough21A is shown retaining overflow water OF which, when it reaches a tripping level TL, causes trough21A and the attached trip gate top plate22and plate35to pivot at the axis of rotation A of hinge pin32along trip path P releasing water W through spillway40.

Referring toFIGS. 4 and 5it will be noted that a plunge water level PL is controlled in plunge pool45A. At a desired operating level L1some splash will invariably come over the top of plate35, flowing over trip gate top plate22filling trough21A. Drain hole23in trough21A drains water from trough21A that has entered by casual wave action or precipitation so that the level of overflow water OF does not reach tripping level TL when an overflow event has not occurred. The speed at which overflow water OF drains from trough21A, and therefore also the speed at which the level of overflow water OF rises and reaches tripping level TL, can be regulated by the size and number of drain holes23incorporated in trough21A. Troughs21A,21B and21C may be constructed in such a manner that they reach a trip level substantially at the same time or in a sequence.

As the level of water W in canal C rises, more water W begins to come over plate35and trip gate top plate22filling trough21A. When the water level in trough21A reaches tripping level TL, plate35and the attached trip gate top plate22and trough21A tip rotating at the axis of rotation A of hinge pin32along path P. Plunge water level PL in plunge pool45A is high enough that the water contained in plunge pool45A acts to absorb the energy imparted by the plate35and the attached trip gate top plate22and trough21A. Plunge water level PL may be filled initially by diverting water from canal C, i.e. through a hose or other conduit, not shown. Alternately plunge water level PL is filled following a tripping of plate35. Plunge water level PL is maintained by precipitation or minor leakage around the seals. Excess plunge water level PL flows over the top of wall43A. Plunge pool45A may be drained by opening drain valve44.

Flow over the tripped automatic trip gate20A determines the length and height of automatic trip gate20A using the formula Q=KLH 3/2, using a K factor of 3.33 for a flat, broad-crested weir. The length of automatic trip gate20A can be selected first and the height can be calculated using the above formula. The converse is true, the height of automatic trip gate20A can be selected and the length is then a function of the formula. Referring toFIG. 5, a desired water level L1is held approximately 7.62 centimeters, (three inches), below the top of plate35. This level can be selected based on the top of the canal or dam embankment. For example, the top of the embankment48can be approximately 22.86 centimeters, (nine inches), above the desired operating level L1to provide a safety factor for waves or other brief disturbances.

Plate35is made of a thick steel plate. Trough21A and trip gate top plate22are made of a thin steel plate. The weight of plate35and the length of foot31extending between plate35and hinge pin32provide the moment to resist the opposite hydraulic force from water W. As seen inFIG. 4, trough21A is located at least partially behind or downstream from an axis of rotation A of hinge pin32so that as trough21A fills, it adds overturning moment.

FIG. 7shows details of lower gate seal26which is of the solid bulb and tail seal type, as manufactured by Seals Unlimited of Beaverton, Oreg. Lower gate seal26is held in place by steel support angle28and pinch bar29. A compressive force is maintained between steel support bar28and pinch bar29by a plurality of screws27.

FIG. 8is an overhead plan view showing an installation of a single automatic trip gate120installed between side structure141and142of spillway140. Automatic trip gate120is shown including trough121attached to plate135by gate top plate122. The top of trough121is covered by trash screen127which prevents trash and other debris from filling trough121. Trough121includes a plurality of drain holes123which regulate a water level maintained in trough121. Plunge pool145is shown formed below automatic trip gate120and behind retaining wall143. Automatic trip gate120is shown including lower gate seal126and lateral gate seal125respectively. Lateral gate seal125is typical of the lateral gate seals installed at either side of plate135. Plate135is manufactured having a clearance at either side with respect to side structure. For instance in one embodiment, a width of plate135is approximately 1.27 centimeters, (½ inch), less than a distance between side structure giving approximately 0.64 centimeters, (¼ inch), clearance on each side to prevent interference with side structure141and142.

FIG. 9shows details of lateral gate seal125comprises solid bulb and tail seal123, as manufactured by Seals Unlimited of Beaverton, Oreg. Lateral gate seal125is typical of the seal fitted to both sides of plate135. Lateral gate seal125is held in position by steel support angle126and pinch bar29. A compressive force is maintained between steel support bar124and pinch bar123by a plurality of screws126.

FIG. 10shows automatic trip gate220including trough221attached to plate235by gate top plate222. Automatic trip gate220is fabricated with integrated trip gate support structure, namely side plates241and242. Side plates241and242not only provide integrated support for hinged support arm assembly230and the pivotally attached plate235and trough221, but the side plates241and242also provide a smooth, flat surface that promotes the life of seals, (not shown inFIG. 10. Side plates241and242also reduce if not eliminate the incidence of jamming during tipping. The top of trough221is covered by trash screen227. Automatic trip gate220is pivotably supported by hinged support arm assembly230. Hinged support arm assembly230is typical of the plurality of hinged support arm assemblies that pivotably support trough221.

The foregoing description of the illustrated embodiments has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form or to exemplary embodiment(s) and implementation(s) disclosed. Numerous modifications and variations will be apparent to practitioners skilled in this art. Process steps described might be interchangeable with other steps in order to achieve the same result. At least one preferred embodiment was chosen and described in order to best explain the principles of the invention and a best mode of practical application, thereby to enable others skilled in the art to understand the invention for various embodiments and with various modifications as are suited to the particular use or implementation contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents. Reference to an element in the singular is not intended to mean “one and only one” unless explicitly so stated, but rather means “one or more.” Moreover, no element, component, or method step in the present disclosure is intended to be dedicated to the public regardless of whether the element, component, or method step is explicitly recited in the following claims. No claim element herein is to be construed under the provisions of 35 U.S.C. Sec. 112, sixth paragraph unless the element is expressly recited using the phrase “means for . . . .”