Note: Descriptions are shown in the official language in which they were submitted.
FI~ LI~TING ~ICE
BACKGROIJND OF THE INVENTION
Th~ inv~ntion relates to the field of fish elevators
which use the principle of the Archimedes' screw to raise fish
from a body of water to a storage area.
The Archimedes' screw has been applied to the raising
of fish from a body of water for the purpose of transportation,
sorting an~ the like. For efficient operation of such a device
it is important that sufficient dewatering of the lifting screw
be provided to avoid carrying too much water up with the fish,
and also that the structure of the entry portion be such that
fish are not repelled. For example, Canadian patent no.
1,093,400 issued January 13, 1981 to Faivre discloses an
Archimedes' screw adapted for lifting fish. This device has two
screw sections rotating on a common shaft - a lifting screw which
is a solid helix, and a catching screw which is a lattice-work
helix. The fish are transferred from the catching screw to the
lifting screw by means of a deflector formed in the cylindrical
drum around the lifting screw. The lattice-work screw portion
serves to dewater the transported fish. Typically the lattice-
work must be m~tal and so the sheath around the entry portion is
also of metal, adding to the cost of construction.
A problem with existing designs results from the fact
that fish prefer to swim into a current and are frightened by an
area of low water pressure. Further, the lattice-work helix
design is expensive to mass-produce. Also, since it draws no
water at its point of entry, a longer auger is needed for a
particular length of lift.
SUMMARY OF ~HE INVENTION
The present invention provides a device for lifting
fish which attracts fish to the entrance of the device using a
`~:
~3~ l3
counterflow current. The device comprises a solid auger of
constant pitch and diameter ~or mosk o~ its length and which
flares out to a greater diameter at its lower entry end. The
auger is bonded to a solid fibreglass outer cylindrical sheath
which is turned with the auger as a single unit. The outer
cylinder is provided with dewate.ring slots in the vicinity of
the flared end to dewater the auger. Slots are cut in the outer
edge of the entry revolution of the auger to create a current
away from the entrance to the device. There is a smooth
transition from the flared portion of the auger into the main
length of the auger.
BRIEF DESCRIPTION OF THE DRAWINGS
In drawings which illustrate a preferred embodiment
of the invention:
Fig. 1 is a perspective view of the auger and sheath
of the invention;
~0
Fig. 2 is a side view of the invention shown in Figure
1 mounted in its supporting frame;
Fig. 3 is a cross-sectional view taken along lines
~5 III-III of Fig. 2;
Fig. 4 is a cross-sectional view taken along lines IV-
IV of Figure 3;
Fig. 5 is a detailed view of a portion of the section
shown in Figure 4;
Fig. 6 is a cross-sectional view taken along lines VI-
VI of Figure 2; and
Fig. 7 is a cross-sectional view taken along lines
VII-VII of Figure 2.
~ ~ _ RED EMBODIMENT
With rPference to the drawings, the ~ish lifting device
(hereinafter referred to as a fish elevator) is designated
generally as 1. It consists generally of a screw or auger 3
typically formed of glass fibre, and mounted within a cylindrical
sheath 5. The screw and sheath rotate about a cen~ral shaft 7.
The sheath is also typically made of glass fibre and is
translucent in the upper region 13 to allow monitoring of the
fish. The sheath and screw assembly is mounted in a supporting
frame 9.
The screw and sheath assembly consists of two sections,
an entry section 11 and a transport section 13. The screw and
sheath of the transport section 13 form a cylinder of constant
diameter. The entry section flares outwardly to a cylindrical
portion 15 of greater diameter than the transport section. The
screw 3, however, is continuous and of constant pitch as between
the entry and transport sections, and varies only in diameter.
Typical dimensions for the device would be a 36" diameter for the
transport section, a 60" diameter for the entry section, and a
24" pitch for the screw. However other siæes are appropriate for
different applications.
As shown in Figure 2, the sheath of the entry section
has a number, shown as two sets of three, of parallel slots 16
in the angled or flaring portion of the sheath. Typically there
will be six slots 12" long by 1/2" wide. These slots serve to
dewater the first revolution of the screw as set out in further
detail below. The lower section 13 is painted black using gel
coat or the like to make it friendlier to the fish.
Along the outer edge of the screw in the region 17 of
the first revolution, there are provided a series of slots or
vents 19 which are approximately 3/4" wide by 14" long. The
-- 3 --
13
purpose o~ these vents is to crea~e a downwardly ~nd outw~rdly
directed current in the vicinity o~ the entry section which will
attract rather than repel the fish. In operation, the sheath and
screw assembly is mounted so that a porkion o~ the entry section
extends beneath the water line 21 as shown in Figure 2. The
assembly is rotated about shaft 7 causing, as in the typical
Archimedes' screw, water to be drawn up the inner surface of the
screw. The angle formed between the water line and the shaEt 7
is optimally greater than 20 degrees.
Frame 9 consists of rigid longitudinal frame elements
41 and 43, cross-piece 45, square support elements 47 and 49,
and adjustable supporting legs 31 and 33 which have feet 35 and
36 and pivot points 37. Forward foot 35 is connected to support
leg 31 which in turn is fixed ~o frame element 41. Rear foot 36
is connected to leg 33 on which slides an adjustable element 40
connected also to the frame 9. In this way the angle of entry
of the screw can be adjusted.
In the prior art device, an external frame is used to
support a central bearing-mounted axle on which the sheath and
screw rotate. The supporting ~rame must extend in front of the
entry section and this causes obstructions to the entry of fish.
In the present invention, the sheath is supported externally and
this also supports the internal screw. There are no obstructions
in the area of fish entry, and the entire device can be made
lighter.
The structure of the supporting elements 47 and 49 is
shown in Figures 6 and 7 respectively. The top element 47 has
four rollers 51 mounted for rotation in corner pieces 53. The
rollers are positioned to bear snuggly against the sides of
sheath 5, thereby holding it firmly in position while allowing
rotation. A drive band 55 of rubber or the like extends around
sheath 5 and a drive pulley 57 is motor-driven to rotate the
sheath and screw. The lower support element 49 has two rollers
61 mounted for rotation in corner elements 63 in the two lower
corners of the frame. Rollers 61 bear ayainst the sides of
sheath 5. Two further rollers 65 are mounted ~or rotation about
axes of rotation perpendicular to shaft 7 in frames 66. A
circular collar 67 fixed to the sheath 5 bears against the
rollers 65 due to the force of gravity and holds the sheath in
vertical position while allowing it to rotate.
In operation the entry end of the screw is inserted
into the body of water as shown in Figure 2 and the sheath is
rotated by drive band 55. Water and fish are drawn up the screw.
A certain portion of the water drawn up by the screw (to levels
22 or 23 in Figure 1) drains through vents 19 and causes a
counter-current as indicated by the arrows in Figure 1,
attracting the fish. As ~he fish and water are drawn further up
the screw, the desired amount of dewatering is done by slots 16.
Some of the water from point of entry, however, travels the full
length of the device.
The present invention, due to the fact that the auger
provides lift of the water right from the end of the device, does
not require the degree of submerging of the prior art device,
where the fish entry end is latticework and does not lift water.
Thus the present invention can be used in shallower water, and
provides a higher lift with an auger of the same length.
As will be apparent to those skilled in the art,
various modifications and adaptations of the structure above
described may be made without departing from the spirit of the
invention, the scope of which is to be construed in accurdance
with the accompanying claims.
- 5 -
