US3460284A - Device for opening trawl nets - Google Patents

Device for opening trawl nets Download PDF

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Publication number
US3460284A
US3460284A US650959A US3460284DA US3460284A US 3460284 A US3460284 A US 3460284A US 650959 A US650959 A US 650959A US 3460284D A US3460284D A US 3460284DA US 3460284 A US3460284 A US 3460284A
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US
United States
Prior art keywords
fin
roller
rollers
trawl
buoyancy
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US650959A
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English (en)
Inventor
Kenneth Stather
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
COLONIAL TREASURER Inc
Original Assignee
COLONIAL TREASURER Inc
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Filing date
Publication date
Application filed by COLONIAL TREASURER Inc filed Critical COLONIAL TREASURER Inc
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Publication of US3460284A publication Critical patent/US3460284A/en
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    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01K—ANIMAL HUSBANDRY; AVICULTURE; APICULTURE; PISCICULTURE; FISHING; REARING OR BREEDING ANIMALS, NOT OTHERWISE PROVIDED FOR; NEW BREEDS OF ANIMALS
    • A01K73/00—Drawn nets
    • A01K73/02—Trawling nets
    • A01K73/04—Devices for spreading or positioning, e.g. control thereof
    • A01K73/045—Devices for spreading or positioning, e.g. control thereof for lateral sheering, e.g. trawl boards
    • A—HUMAN NECESSITIES
    • A01—AGRICULTURE; FORESTRY; ANIMAL HUSBANDRY; HUNTING; TRAPPING; FISHING
    • A01K—ANIMAL HUSBANDRY; AVICULTURE; APICULTURE; PISCICULTURE; FISHING; REARING OR BREEDING ANIMALS, NOT OTHERWISE PROVIDED FOR; NEW BREEDS OF ANIMALS
    • A01K73/00—Drawn nets
    • A01K73/02—Trawling nets
    • A01K73/04—Devices for spreading or positioning, e.g. control thereof

Definitions

  • a trawl net opening device comprises a buoyant fin positioned upright in use, and two rollers hanging below the fin n chains or other flexible members to roll on the sea bed, the device as a whole having negative buoyancy.
  • the invention relates to a device for use in opening trawl nets and provides an alternative to or improvements in, the commonly used otter boards or doors.
  • the invention provides a net opening device comprising a buoyant fin positioned upright in use, and two (or more) rollers below the fin for rolling on the sea bed at least when bottom trawling, the device as a whole having negative buoyancy.
  • rollers hang below the fin on chains, cables or like tension members offering little or no resistance to compressive force whereby the rollers may ride over bumps on the sea bed without transmitting substantial upward forces to the fin.
  • one of the rollers is near the front of the fin and that the second hanging roller is behind the first.
  • the front roller may be heavier than the second roller, e.g. twice as heavy.
  • the arrangement may be that, in normal operation, the second roller is at a level above that of the first roller and is held off the bed.
  • the two rollers are held apart by a rigid spacer bar.
  • the buoyancy of the fin may be provided, wholly or partly, by a buoyancy member or fioat attached thereto or built as an integral part thereof and the resultant negative buoyancy may be due solely to the weight of the rollers and their attachment means or additional weight may be provided, preferably on the attachment means.
  • the device may be provided with stabilizing vanes in horizontal and/or vertical planes and preferably at the rear of the buoyancy member.
  • the buoyancy member may be of cylindrical form with its axis extending fore and aft in a generally horizontal plane and it may carry links for towing chains or cables.
  • the said axis lies in the plane of the fin and at the centre of the depth of the fin.
  • FIGURE 1 is an elevation of the device
  • FIGURE 2 is an end View of the device
  • FIGURE 3 is a plan view of the device
  • FIGURE 4 is a plan view of the device showing the various connections thereto,
  • FIGURE 5 shows the use of the device for bottom trawling
  • FIGURE 6 shows the use of the device for mid-water trawling
  • FIGURE 7 is a plan showing the device in use.
  • the device comprises a combined fin 10 and buoyancy cylinder 11, the cylinder having conical ends 12, 13.
  • the fin and cylinder are constructed of two metal sheets secured together and to bulkheads as later described.
  • the cylinder has four iron stabilizing vanes 15 at spacings. The outer ends of these fins are supported and protected by a ring 16.
  • rollers 20 Hanging from the fin there are two chains 18, 19 carrying heavy rollers 20, 21 held apart by a rigid spacer bar 22.
  • the front roller 20 hangs below the roller 21 and has about twice the weight thereof.
  • the rollers are carried in brackets 31 freely pivoted to the bar 22 preferably for universal pivotal movement by means of universal joints 32 at both ends of spacer bar 22. In normal use for bottom trawling only the roller 20 contacts the sea bed.
  • the fin is stiffened by an iron or steel rim 24 and straps 25, the latter carrying cable-attachment brackets and links 26 as well as the attachment links 27 for the chains 18, 19.
  • the links and brackets 26 are duplicated at each side of the fin so that the device is suitable for port or starboard use.
  • the two front links 26 at either side are for attachment of a chain towing pennant and the rear links or brackets are for attachment of the net gear.
  • the link 26a is for lifting purposes.
  • the buoyancy cylinder is filled with expanded polyurethane rigid foam divided by stitfening bulkheads 28, and tow longitudinal stiifeners 29, 30.
  • the devices are used in pairs as seen in FIGURES 5 to 7 and it is to be noted that when bottom trawling the rollers 20 run on the bottom and that when mid-water trawling the devices are raised from the bottom.
  • the depth of trawl can be determined and ascertained by the length of warp paid out and the angle of the warp to. the hori-.
  • the front roller 20 tends to hold the front of the fin down, against upward pull from the towing cable and, when bottom trawling, the front roller 20 runs on the sea bed.
  • the rear roller 21 normally rides clear of the bottom because of the disparity in length between chains 18 and 19.
  • the device rides horizontally in the water. Because fin 10 is bouyant, the tendency will be for it to hold the chains 18 and 19 taut with the rollers upright.
  • the area of the fin (including the projected area of the bouyancy chamber )is 15 sq. ft.
  • the fin and buoyancy cylinder together have a positive buoyancy (in sea water) of 43 lbs. and the rollers together with their suspension means have a negative buoyancy of 169 lbs.
  • the net negative buoyancy is 126 lbs. but the device stays upright in the water and the static load on the sea bed is only 126 lbs.
  • the invention resists capsizing, it rides relatively easily over varying sea-bed contours, and it is less likely than known otter boards to damage underwater cables or to sink into soft muddy sea beds.
  • a trawl net opening device having as a whole a negative buoyancy comprising a buoyant fin adapted to be maintained in an upright position as said fin is caused to travel through water, a first roller and a second roller suspended beneath said fin for rolling on a sea bed, a first flexible tension element having an end attached to said first roller and another end attached to the front,
  • a second flexible tension element having an end attached to said second roller and another end attached to the rear portion of said fin, said first tension element being of a greater length than said second tension element, and a rigid spacer member interconnecting said first and second rollers and operable to hold said rollers separated at a fixed distance.
  • a trawl net opening device as claimed in claim 1 in which universal joints are provided for connecting said rollers to said spacer member.
  • a trawl net opening device as claimed in claim 1 having at least one laterally extending stabilizer vane mounted on the rear portion of said fin.
  • a trawl net opening device as claimed in claim 1 in which the structure of said device is symmetrical in relation to a vertical fore and aft central plane and in which towing attachments are provided on both sides of said fin.
  • a trawl net opening device as claimed in claim 1 in which the fin is constructed of two metal sheets secured together face to face at the upper and lower parts of said tin and spaced apart intermediate in the height of said fin and having in addition end caps for covering the spaced apart portions of said fin thereby providing a buoyancy chamber intermediate in the height of said fin.
  • a trawl net opening device as claimed in claim 5 in which said buoyancy chamber is filled with a buoyant material.
  • a trawl net opening device as claimed in claim 1 in which said fin is constructed to have four stabilizing vanes extending outwardly from the rear end thereof and spaced one from the other at an angle of substantially 90.

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  • Life Sciences & Earth Sciences (AREA)
  • Environmental Sciences (AREA)
  • Animal Husbandry (AREA)
  • Biodiversity & Conservation Biology (AREA)
  • Laying Of Electric Cables Or Lines Outside (AREA)
US650959A 1966-07-12 1967-07-03 Device for opening trawl nets Expired - Lifetime US3460284A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB31301/66A GB1096155A (en) 1966-07-12 1966-07-12 Device for opening trawl nets

Publications (1)

Publication Number Publication Date
US3460284A true US3460284A (en) 1969-08-12

Family

ID=10321101

Family Applications (1)

Application Number Title Priority Date Filing Date
US650959A Expired - Lifetime US3460284A (en) 1966-07-12 1967-07-03 Device for opening trawl nets

Country Status (12)

Country Link
US (1) US3460284A (de)
BE (1) BE701216A (de)
DE (1) DE1607116A1 (de)
DK (1) DK122052B (de)
FI (1) FI43508C (de)
FR (1) FR1537098A (de)
GB (1) GB1096155A (de)
IS (1) IS745B6 (de)
MY (1) MY6900047A (de)
NL (1) NL6709615A (de)
NO (1) NO120557B (de)
SE (1) SE331387B (de)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
ES2546742B2 (es) * 2014-03-28 2016-02-25 Universidade Da Coruña Método para determinar la resistencia a la apertura de las mallas de una red
CN109392853B (zh) * 2018-11-19 2024-08-13 中国科学院南京地理与湖泊研究所 自动化鱼类电捕科学调查装置

Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1047325A (de) *
GB190626589A (en) * 1906-11-23 1907-10-31 William Henry Thickett Improvements in or relating to "Otter" Boards for Spreading the Mouths of Trawl Nets.
FR400772A (fr) * 1909-03-13 1909-08-07 Jean Haentjens Engins pour la peche en mer
FR562325A (fr) * 1923-02-17 1923-11-08 Panneau de chalut
US1601893A (en) * 1924-04-23 1926-10-05 Vigneron Dahl & Cie Trawling gear
US2661562A (en) * 1947-09-18 1953-12-08 Fresh Frozen Foods Ltd Trawling otter
FR1050338A (fr) * 1951-09-12 1954-01-06 Procédé et dispositif de chalutage réglable à différentes profondeurs
US2671288A (en) * 1949-12-12 1954-03-09 Larsson Karl-Hugo Trawl net
US3190025A (en) * 1963-07-05 1965-06-22 Burney Charles Dennistoun Trawling otters

Patent Citations (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB1047325A (de) *
GB190626589A (en) * 1906-11-23 1907-10-31 William Henry Thickett Improvements in or relating to "Otter" Boards for Spreading the Mouths of Trawl Nets.
FR400772A (fr) * 1909-03-13 1909-08-07 Jean Haentjens Engins pour la peche en mer
FR562325A (fr) * 1923-02-17 1923-11-08 Panneau de chalut
US1601893A (en) * 1924-04-23 1926-10-05 Vigneron Dahl & Cie Trawling gear
US2661562A (en) * 1947-09-18 1953-12-08 Fresh Frozen Foods Ltd Trawling otter
US2671288A (en) * 1949-12-12 1954-03-09 Larsson Karl-Hugo Trawl net
FR1050338A (fr) * 1951-09-12 1954-01-06 Procédé et dispositif de chalutage réglable à différentes profondeurs
US3190025A (en) * 1963-07-05 1965-06-22 Burney Charles Dennistoun Trawling otters

Also Published As

Publication number Publication date
MY6900047A (en) 1969-12-31
IS1662A7 (is) 1968-01-13
BE701216A (de) 1967-12-18
NL6709615A (de) 1968-01-15
FI43508C (fi) 1971-04-13
FR1537098A (fr) 1968-08-23
IS745B6 (is) 1970-11-18
FI43508B (de) 1970-12-31
DK122052B (da) 1972-01-17
NO120557B (de) 1970-11-02
SE331387B (de) 1970-12-21
DE1607116A1 (de) 1970-07-09
GB1096155A (en) 1967-12-20

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