Fishing – trapping – and vermin destroying – Fishing – Nets
Reexamination Certificate
2001-02-21
2002-08-20
Poon, Peter M. (Department: 3643)
Fishing, trapping, and vermin destroying
Fishing
Nets
C043S007000, C066S195000, C066S16900R, C210S241000, C112S440000
Reexamination Certificate
active
06434879
ABSTRACT:
TECHNICAL FIELD
The present invention relates generally to the technical field of hydrodynamics and, more particularly, a lift generating shape used for a trawl system component.
BACKGROUND ART
Published Patent Cooperation Treaty (“PCT”) International Patent Application, International Publication Number WO 97/13407, International Publication Date Apr. 17, 1997, entitled “Trawl System Cell Design and Methods” (“the First PCT patent application”) describes a trawl system that uses corkscrew shaped mesh bars to improve the shape and performance of the trawl system. As set forth in the First PCT patent application,
FIG. 1
depicts a towing vessel
10
at a surface
11
of a body of water
12
that is towing a mid-water trawl
13
of a trawl system
9
. The trawl
13
is positioned between the surface
11
and an ocean bottom
14
. The trawl
13
can be connected to the towing vessel
10
in many ways, such as by a main towing line
18
connected through doors
19
, towing bridles
20
and mini-bridles
21
,
22
. A series of weights
23
is attached to mini-bridle
22
. Likewise, the shape and pattern of the trawl
13
can vary as is well known in the art. As shown, the trawl
13
has a forward section
24
that includes forward projecting wings
25
for better herding at mouth
26
. The forward section
24
, including wings
25
, is seen to define a mesh size that is larger than that used for a mid-section
27
, back-end
28
, or codend
29
of the trawl
13
.
FIG. 2
illustrates the wing
25
of the trawl
13
of
FIG. 1
in more detail and includes a series of mesh cells
30
of quadratic cross-section that are part of panel
31
and are offset from axis of symmetry
32
of the trawl
13
. The size of mesh cells
30
is determined by a distance between adjacent knots or equivalent couplers
34
. Different sections of the trawl
13
, and even different regions within a section, use different size mesh cells
30
, which generally form a repeating pattern within that section or region of a section.
As shown in
FIG. 3
, the mesh cells
30
each have a longitudinal axis of symmetry
30
a
, and are formed by mesh bars
35
a
,
35
b
,
35
c
and
35
d
each of which includes several product strands
36
,
37
. The product strands
36
,
37
may be twisted about a longitudinal axis of symmetry
38
in either one of two lay directions: right-hand or left-hand as viewed axially along longitudinal axis of symmetry
38
and in a receding direction established upstream of the trawl
13
thereby establishing the cork-screw shape disclosed in the First PCT patent application.
As disclosed in the First PCT patent application, the mesh bars
35
may be formed either by product strands
36
,
37
as depicted in
FIG. 3
, or by straps which are not illustrated in any of the FIGs. Published PCT International Patent Application, International Publication Number WO 98/46070, International Publication Date Oct. 23, 1998, entitled “Improved Cell Design for a Trawl System and Methods” (“the Second PCT patent application”) further discloses that the product strands
36
,
37
of the mesh bars
35
are preferably formed from a substantially incompressible material. Both the First and the Second PCT patent applications are hereby incorporated by reference.
As the towing vessel
10
draws the trawl system
9
through the body of water
12
along a straight-line course, water flows through the trawl
13
substantially parallel to an arrow
50
, illustrated in
FIGS. 1 and 2
, which is oriented parallel to the axis of symmetry
32
. However, it is to be noted that as illustrated in
FIG. 3
the direction in which water flows through individual mesh cells
30
of the trawl
13
is not, in general, parallel to the axis of symmetry
30
a
. It should also be noted that hydrodynamically the mesh bars
35
both of conventional trawl systems
9
and of trawl systems
9
assembled in accordance with the First and Second PCT patent applications are properly characterized as “bluff body” shapes. This is to be contrasted with another class of shapes, such as airplane wings, which hydrodynamicists characterized as being “streamline” shapes.
For conventional trawl systems and trawls not assembled in accordance with the disclosure set forth in the First PCT patent application, drag forces caused by movement of the trawl system through the water entrained environment tends to draw the mesh cells
30
of the trawl
13
closer to the axis of symmetry
32
thereby closing the trawl
13
. Appropriately orienting the cork-screw shape of the mesh bars
35
in accordance with the description set forth in the First PCT patent application as depicted in
FIG. 3
yields a trawl system
9
in which movement of mesh bars
35
through the water entrained environment generates a force on each mesh bar
35
which has a component that is directed at a right angle from the drag force component, and away from the axis of symmetry
32
. The effect of the force components generated by such movement of the individual mesh bars
35
that are oriented at a right angle from the drag force component is to make the trawl system
9
, particularly the trawl
13
, “self-spreading” thereby expanding the trawl
13
away from the axis of symmetry
32
.
As set forth above, the size of mesh cells
30
is determined by the length of the mesh bars
35
between adjacent knots or equivalent couplers
34
. As indicated in
FIGS. 1 and 2
, the size of the mesh cells
30
, and correspondingly the length of mesh bars
35
, varies along the length of the trawl
13
. For example, the mesh bars
35
in the forward section
24
have a length of at least 10 ft (304.8 cm). Alternatively, the mesh bars
35
in the mid-section
27
of the trawl
13
have length between 10 ft. (304.8 cm) and 0.75 ft (22.86 cm). The mesh bars
35
of the back-end
28
have a length less than 0.75 ft (22.86 cm). While manual assembly of mesh cells
30
of the forward section
24
is commercially practical, as the mesh bars
35
become ever shorter toward the codend
29
manual assembly becomes progressively more costly, and therefore less and less commercially viable. Consequently, to reduce the cost of trawls
13
the general practice is to incorporate netting woven by machines into the “back-end” of trawls
13
such as in the codend
29
, in the back-end
28
, and even perhaps in some instances in the mid-section
27
.
FIG. 4
illustrates a pattern used in knitting prior art, machine-made netting
51
of a type used for the “back-end” of conventional trawls. The knitting process for machine-made netting
51
may be understood as progressing row-by-row, from top to bottom in the illustration of FIG.
4
. Knitting of machine-made netting
51
proceeds basically at approximately a right angle to the ultimate direction of water flow past the trawl
13
, indicated by the arrow
50
, after the machine-made netting
51
has been incorporated into a trawl
13
, and the trawl system
9
is being towed through a water entrained environment.
In knitting conventional machine-made netting
51
a number of individual spools, perhaps as many as 100, concurrently feed product strands in parallel while the net knitting machine knots or braids pairs of them together at the couplers
34
alternating back-and-forth horizontally to establish a zig-zag path for the product strands
36
. Thus a vertical column of L-shaped arrows
52
a
in
FIG. 4
indicate the zig-zag path along which a single product strand, the longitudinal axis of symmetry
38
of which turns at each coupler
34
, crosses the machine-made netting
51
from top to bottom of FIG.
4
. Similarly a vertical column of L-shaped arrows
52
b
in
FIG. 4
, immediately to the right of the L-shaped arrows
52
a
, indicate the zig-zag path along which an immediately adjacent product strand crosses the machine-made netting
51
from top to bottom. In the illustration of
FIG. 4
, three additional vertical columns of L-shaped arrows
52
c
,
52
d
and
52
e
, to the right of the columns of L-shaped arrows
52
a
and
52
b
in
FIG. 4
, indicate paths a
Perevoshchikov Valentin G.
Safwat Sherif
Griles Bethany
OTTER Ultra-Low-Drag, Ltd.
Poon Peter M.
Schreiber D. E.
LandOfFree
Bi-directional, manufacturable, lift-generating mesh bar does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Bi-directional, manufacturable, lift-generating mesh bar, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Bi-directional, manufacturable, lift-generating mesh bar will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2898407