GB2496703A

GB2496703A - Fish door spring retarder

Info

Publication number: GB2496703A
Application number: GB1203141.5A
Authority: GB
Inventors: Kevin Malcolm Scott
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-11-20
Filing date: 2012-02-23
Publication date: 2013-05-22
Also published as: GB201119995D0; GB201203141D0

Abstract

The invention relates to a fish retarder and comprises a door (no item number) a winch (shown generally as item 9), a wire 10 connected to the winch and the door, and a housing containing a spring which is mounted to the wire between the winch and the door. The spring enables the door to close slowly as the head of water increases and overcomes the spring s tension to force the door to close. As the water recedes, the head of water becomes less allowing the spring to open the door.

Description

Fish Retarder.

DESCRIPTION.

This device enables the doors that allow water to pass to and fro from a main tidal river into streams and ditches along waterways to close and open slowly when the head of water in the river is at the correct pressure thus enabling the fish to swim up the streams and ditches and spawn and to return to the main river safely.

A problem was identified that the fish were unable to swim freely into streams and ditches due to the doors on the river being held in a closed position by the head of water in the river pushing against them. When the river level dropped the water that had built up in the streams and ditches would force open the doors to let the water out but would not allow the fish to swim up as the tidal river was at a too lower level. A European directive was issued to find a solution to this problem.

The device is based on a springs, supports, steel wire and winch system. The doors are winched open to a set distance (200mm) and the steel wire cable is locked off at the back of the spring mechanism. The spring then takes the load as the steel wire cable is unwound from the winch. As the river rises the pressure from the head of water pushes against the door and pulls on the steel wire cable which then compresses the spring. The more the pressure the more the spring compresses until the door is ftilly closed. As the tide in the main river recedes and the water pressure drops the spring extends and the door begins to open until the spring has returned to it original shape and the door is open to the correct gap.

Figure (1) The steel wire cable is attached to an eye bolt at the bottom of the door using u bolt clamps.

Figure (2) The steel wire cable is passed over a guide wheel which is held by support steelwork which gives the correct angle for the wire cable safety loadings. The dimensions of the support steelwork are determined by the distance between the top of the banking and the top of the door. These have to be calculated.

Figure (3) The steel wire cable is passed through the centre of the spring and spring housing as well as the locking plate and attached to the winch.

Figure (4) The winch is wound up so that the door opens to an approximately a 200mm gap. The steel wire cable locking plate is locked off using u bolt clamps (see figure 5). The winch is released so that the spring takes the load.

Figure (6) When the water level in the tidal river begins to rise the head of water applies a force against the door forcing it to close.

Figure (7) The steel wire cable is pulled as the door closes at a controlled rate and compresses the spring that has had its strength calculated by the head of water and time needed for the door to shut (approx 3Ornins).

As the water in the tidal river begins to recede the head of water and therefore the force being applied to the door becomes less and the door begins to open. This happens by the spring expanding back to its original shape pulling against the locking plate and therefore pulling the steel wire cable with it. As the spring is returning to its original shape the door will be going back in the open position and the water and fish will be able to return back into the river.