U.S. patent application number 09/911161 was filed with the patent office on 2001-12-27 for connection system for connecting equipment to underwater cables.
Invention is credited to Olivier, Andre W..
Application Number | 20010054373 09/911161 |
Document ID | / |
Family ID | 23352480 |
Filed Date | 2001-12-27 |
United States Patent
Application |
20010054373 |
Kind Code |
A1 |
Olivier, Andre W. |
December 27, 2001 |
Connection system for connecting equipment to underwater cables
Abstract
A connection system for connecting external devices to specified
locations on a marine seismic streamer. Inner collars are clamped
to the cable at specified locations along its length. Each inner
collar forms a circular race encircling the cable. A cuff attached
to an external device is in the form of a C-shaped cylindrical ring
with a circular inner surface. A gap in the ring interrupts the
inner surface. A throat is formed in the ring by the gap, which
extends the full length of the cuff across the ends of the C. The
spacing between the ends of the C across the throat defines the
width of the gap. The width of the gap is slightly larger than the
diameter of the cable so that the cuff can be slipped over the
cable through the throat. The width of the gap is smaller than the
diameter of the circular race so that, when the cuff is slid into
position on the race, the cuff cannot be removed radially from the
race. The inner surface of the cuff rides on the race to allow the
cable to rotate inside the cuff. The race can include a
circumferential groove for retaining a retractable pin extending
from the external device to snap the device in place and a raised
circumferential shoulder to further restrain the cuff and attached
device from sliding along the cable.
Inventors: |
Olivier, Andre W.; (River
Ridge, LA) |
Correspondence
Address: |
JAMES T. CRONVICH
THE LAITRAM CORPORATION
220 LAITRAM LANE
HARAHAN
LA
70123
US
|
Family ID: |
23352480 |
Appl. No.: |
09/911161 |
Filed: |
July 23, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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09911161 |
Jul 23, 2001 |
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09344884 |
Jun 25, 1999 |
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6263823 |
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Current U.S.
Class: |
114/245 ;
441/133 |
Current CPC
Class: |
B63B 21/663 20130101;
G01V 1/3817 20130101; F16L 1/16 20130101; G01V 1/201 20130101 |
Class at
Publication: |
114/245 ;
441/133 |
International
Class: |
B63G 008/14; B63B
022/00 |
Claims
I claim:
1. A connection system for connecting an external device to a
location on an underwater cable, the connection system comprising:
a first collar affixable around an underwater cable at a specified
location; a second collar affixable around the underwater cable at
a spaced apart location; a first C-shaped cuff rotatably attachable
around the first collar, the first C-shaped cuff including
attachment means for attaching to an external device; a second
C-shaped cuff rotatably attachable around the second collar, the
second C-shaped cuff including attachment means for attaching to
the external device.
2. A connection system as in claim 1 wherein the first collar
further comprises a race for rotatably receiving the first C-shaped
cuff.
3. A connection system as in claim 2 wherein the first collar
further comprises a circumferential groove and the first C-shaped
cuff further forms an aperture therethrough to admit a pin
extendable into the circumferential groove.
4. A cuff for connecting an external device to a seismic cable
having a cylindrical collar, the cuff comprising: a C-shaped
cylinder rotatably attachable around a cylindrical collar affixed
to a seismic streamer; a throat formed in the C-shaped cylinder by
a longitudinal gap extending the full length of the C-shaped
cylinder between the ends of the C, wherein the gap is sized to
admit the seismic cable radially into the C-shaped cylinder and to
prevent radial removal of the C-shaped cylinder from the
cylindrical collar.
5. A cuff as in claim 4 wherein the cuff further defines an
aperture therethrough to admit a pin through the C-shaped
cylinder.
6. A connection system for connecting an external device to an
underwater cable, the connection system comprising: a collar
attachable around an underwater cable, the collar including a
shoulder defining an end of a circumferential bearing race; and a
C-shaped cuff having an inner cylindrical surface for riding in the
bearing race of the collar.
7. A connection system as in claim 6 wherein the collar further
includes a circumferential groove in the bearing race and wherein
the C-shaped cuff includes an aperture therethrough to admit a pin
into the circumferential groove.
Description
TECHNICAL FIELD
[0001] This invention relates to marine seismic prospecting and,
more particularly, to a connection system for attaching equipment
to and detaching equipment from marine seismic cables.
DESCRIPTION OF RELATED ART
[0002] A marine seismic streamer is a cable, typically several
thousand meters long, that contains arrays of hydrophones and
associated electronic equipment along its length. One purpose of
the streamer is to position the hydrophone array at a known depth
and orientation relative to a towing vessel in a survey area.
Externally mounted equipment, such as depth controllers, called
"birds," emergency recovery pods, and acoustic pods, performs the
functions of positioning and controlling the cable. Individual
units of these kinds of external equipment are attached to the
streamer at various positions along its length. All of these
external units should be both attached to and removed from the
cable as quickly and reliably as possible. Operational expenses of
seismic vessels require rapid attachment and detachment of these
external units. Because these external units typically cost
thousands of dollars, they demand the highest degree of reliability
from any attachment scheme. Cable attachment failures caused by
connector failures or by cable accidents result in a significant
financial loss both in time and in expensive equipment.
[0003] Today's typical cable attachment solutions consist of a
collar arrangement that relies on a hinge and latch mechanism for
operation. Examples of these mechanisms are described in U.S. Pat.
No. 5,507,243, "Connector For Underwater Cables," Apr. 16, 1996,to
Oneil J. Williams et al. and in U.S. Pat. No. 5,709,497, "Latching
Device," Jan. 20, 1998, to David W. Zoch et al. External units
attached to the collars are clamped around races on the cable as
the cable is payed out from the back deck of a survey vessel. The
races allow the cable to rotate inside the collars while the
external units do not rotate as they are towed along. Conventional
connector schemes usually require one operator to position and hold
the awkward external unit in place while a second operator secures
the manual latching collars to the cable, often while trying to
maintain balance on a rolling survey vessel. Requiring two
operators significantly increases the cost of operation.
[0004] These conventional mechanisms also incorporate springs or
pins having dissimilar metals in contact with the collar.
Dissimilar metals in contact in seawater corrode because of
galvanic reactions. While conventional hinge-and-latch collars
offer quick attachment and removal when new, exposure to salt water
degrades their performance and can eventually lead to their
complete failure. A failed collar can result in the loss of an
external electronic unit or a jammed connector on the seismic
cable, which costs time in removing external devices as the cable
is reeled in.
[0005] A thick cross section (typically of aluminum) is required to
safely imbed a conventional latching mechanism within the collar.
Such a large cross section creates hydrodynamic noise and lateral
accelerations on the seismic cable as it is towed through the
water. These undesirable characteristics corrupt the sensitive
measurement of seismic acoustic signals by the hydrophones.
[0006] Clearly there is a need for an apparatus and a method for
avoiding these serious shortcomings that significantly add to the
cost of a seismic survey at sea.
SUMMARY OF THE INVENTION
[0007] This need is satisfied and other shortcomings are overcome
by an innovative cable connection system having features of the
invention. The connection system includes a cuff attached to a
piece of equipment to be connected to the streamer cable at a known
location. The C-shaped cylindrical cuff has a circular inner
surface interrupted by a gap. A throat is formed by the gap in the
cuff extending the length of the cuff. The spacing between the ends
of the C across the throat defines the width of the gap. The width
of the gap is slightly larger than the diameter of the streamer
cable so that the cuff can slip onto the cable. An inner collar
having a race is affixed to the cable at a known location. The
diameter of the race is greater than the width of the gap formed by
the cuff's throat. The inner surface of the cuff can be slid into
position on the race of the inner collar. Because the diameter of
the race exceeds the width of the gap of the throat, the cuff and
the attached equipment cannot disconnect radially from the inner
collar. Structural elements on the collar further prevent
longitudinal displacement of the cuff along the inner collar. In
this way, equipment is connected to the cable at a known
location.
[0008] In a preferred version of the system, the inner collar has a
circumferential groove that admits a retractable pin extending from
the external unit through an aperture in the cuff. The groove
constrains the pin and prevents longitudinal movement of the
external unit along the cable and off the inner collar. A single
operator can remove the unit with the cuff from the inner collar by
manually retracting the pin and sliding the cuff longitudinally off
the inner collar and then radially off the cable. In an alternative
version, the inner collar has a raised circumferential shoulder
just aft of the race to act as a precise longitudinal stop for the
cuff. Forward motion of the cable through the water will hold the
cuff against the shoulder. Preferably, the cuff itself is of
unitary construction with no moving parts.
[0009] Thus, the novel connection system includes a cuff having no
moving parts and no dissimilar metals in contact to provide a
connector that is significantly more reliable, even after long
exposure to seawater. The connection system does not require two
operators as do conventional systems. One operator suffices because
the connection system requires no activation of a latch for a
secure attachment.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] These and other features, aspects, and advantages of the
invention are better understood by referring to the following
description, appended claims, and accompanying drawings in
which:
[0011] FIG. 1 is a perspective view of one version of a connector
for use in a system for connecting devices to an underwater cable
embodying features of the invention;
[0012] FIG. 2 is a perspective view of two connectors as in FIG. 1
shown attached to an external unit, in this example, a
cable-leveling bird;
[0013] FIG. 3 is an exploded perspective view of an inner collar
showing its attachment to a section of an underwater cable; and
[0014] FIGS. 4A-4D are front (FIG. 4A) and side elevation (FIGS.
4B-4D) views of a section of an underwater cable showing a system
according to the invention and an associated procedure for
attaching an external unit to the cable at a known location.
DETAILED DESCRIPTION
[0015] One example of a system embodying features of the invention
for connecting external units to an underwater cable is shown in
FIGS. 1-4. A key component of the system, which achieves a
reliable, mechanism-free, connection to the seismic cable, is a
C-shaped cylindrical ring, or cuff 10, serving as an outer collar.
The cuff has an opening, or throat 12, formed by a gap in the cuff
along the length of the cuff between the ends of the C. The width
of the gap between the ends of the C across the throat is slightly
larger than the diameter 14 of an underwater seismic cable 16. The
cuff is preferably of unitary construction, i.e., no dissimilar
metals or moving parts, fabricated from a material that will
survive long term exposure to seawater and can withstand extensive
mechanical loads. Because the cuff freely rotates about the cable
similar to the outer race of a journal bearing, friction,
especially along its inner surface 26, must be minimized. Materials
such as aluminum, titanium, and engineering grade plastics are
preferred for the cuff. Each external unit 18, such as a
cable-leveling bird as depicted in FIGS. 2 and 4, an acoustic
transmitter, receiver, or transceiver, a cable recovery device, or
a float tube, to be connected to the cable typically has two attach
points requiring two cuffs. (Of course, external units with a
single cuff are also possible.) The cuffs are attached to the
external units, for example, by attachment means using conventional
external device hardware 20 as shown in the cutaway portion of FIG.
4D and described, for example, in U.S. Pat. No. 5,214,612, "Swing
Plate Latch Mechanism," May 25, 1993, to Andr W. Olivier et al.,
the disclosure of which is hereby incorporated by reference. In the
version shown, two keyways 22 machined 180.degree. apart around the
circumference of the cuff accept a dovetail pin 24 extending from
the external unit through an outer surface 27 of the cuff. The
keyway has a circular opening 28 at one end to accept the head of
the dovetail pin and a narrower slotted portion 30 extending from
the circular opening to the other end of the keyway. The dovetail
pin acts as a self-centering guide and swivel. Two keyways are
provided to enable the mounting of two external units, such as a
bird and a float tube, per connection location on a seismic cable.
The throat is preferably positioned about midway between the two
keyways so that the throat assumes an orientation on the cable not
facing upward. The important point is that the throat should not be
positioned on the cuff diametrically opposite an attached external
unit. In other words, the throat should be spaced circumferentially
around the cuff less than 180.degree. from the attached external
unit.
[0016] As shown in FIG. 3, an inner collar 32 is semi-permanently
clamped around the cable 14 and establishes a longitudinal mounting
position along the cable's length and forms the inner bearing race
34 for the cuff. The inner collar consists of two symmetrical
halves 36, which are screwed together around the cable with screws
or bolts 38 typically on top or in front of a cable spacer 40
located within the cable. Screw holes 42 on one side of the collar
halves admit the screw heads, which thread into threaded holes 44
on the other side of the collar halves. Structural elements, such
as a pair of raised circumferential ribs 46, are included along the
interior surface 48, which can be sized differently to match
different seismic cables. The elements prevent longitudinal
movement of the collar along the cable and, therefore, of an
attached external unit. As shown in FIG. 3, the ribs are spaced to
just span the fixed cable spacer, which holds the clamped inner
race in place. A beveled surface 50 at the fore end of the inner
collar facilitates self-centering of the cuff. A shoulder 52 at the
aft end prevents longitudinal translation of the external unit once
installed. A circumferencial groove 54 accepts a conventional
retractable pin 56 extending from the external unit. The
spring-biased, self-activating pin allows the external unit with
attached cuff to snap in place in the race and further prevents
forward translation of the external unit along the cable. The inner
collar 32 is preferably fabricated from a plastic that can
withstand harsh mechanical and seawater exposure. For low friction
and wear, an engineering grade plastic, such as acetal, nylon, and
polyethylene, is preferred.
[0017] As shown in FIG. 4A, the outer diameter 58 of the inner race
32 is slightly larger than the diameter 16 of the seismic cable.
The inside diameter 60 of the cuff is slightly larger in diameter
than the inner race. The width of the gap at the throat 12 of the
cuff is slightly larger than the cable diameter, but less than the
diameter of the inner race. These diametrical differences create an
interlocking condition and a highly reliable fault tolerant
connection.
[0018] A method for attaching an external unit to a streamer cable
is shown in FIGS. 4A-4D. First, an external device 18, retained to
the cuff 10 by the dovetail pin 24, is installed by positioning
each external cuff in front of and to the side of the inner races
(FIGS. 4A and 4B). Then a radial motion perpendicular to the cable,
as indicated by arrow 62, is required to slip the cuff and its
throat over the cable to suspend the external unit from the cable.
In this configuration, the cable temporarily supports the unit,
unlike existing methods where an operator supports the device. A
secondary longitudinal motion, indicated by arrow 64, along the
length of the cable (FIG. 4C) locates the unit onto the inner
collar 32 with the inner surface 26 of the cuff 10 riding in the
inner race 34 so that the cable can rotate inside the cuff. The
bearing shoulder 52 supports thrust loads and positive location.
The spring-loaded pin 56 located in the external device
automatically extends into the groove 54 in the inner race 34 and
prevents forward motion of the external unit. The device is ready
for deployment as shown in FIG. 4D. To detach the external unit
from the cable, the retractable pin is first lowered out of the
groove by downward pressure on a stub 66 extending out
perpendicularly from the pin through a vertical slot 68 in the
external device. The remainder of the detachment process is just
the reverse order of the attachment procedure.
[0019] Clearly, the invention, as illustrated by the preferred
example version described in detail, provides, among other
advantages: a marine cable connection having no moving parts, which
is more reliable than prior art connections; a marine cable
connection that performs the same whether brand new or aged as a
result of long term exposure to seawater; a marine cable connection
that requires fewer operators to safely operate; a marine cable
connection with a lower hydrodynamic noise profile because of the
lack of a salient attachment mechanism; a marine cable connection
that can readily be adapted to both existing seismic cables as well
as new technology cables; a marine cable connection that is lighter
and simpler than existing connectors; a marine cable connection
that consists of an inner race and an outer collar engaged by means
of geometrical features rather than a mechanism; and a marine cable
connection that is significantly quicker to operate than prior art
connectors.
[0020] Although the invention has been described in detail with
reference to a preferred version, other versions are possible. For
example, external devices requiring only a single attachment point
using a single cuff and inner race are possible with the invention.
In a two-cuff attachment, the rear inner race could have, but need
not have, a circumferential groove and a cooperating retractable
pin or a shoulder acting as a longitudinal stop. The gap forming
the throat could be of constant width, as shown in the drawings, or
could alternatively be narrower at one end than at the other. The
cuff could have only a single keyway if attachment of two external
units at a common location is not required. Instead of attaching to
an external unit by means of a dovetail pin retained in a keyway,
other attachment means are possible. For example, the cuff could be
semi-permanently fastened to the external unit by screws or other
fasteners or permanently attached by adhesives or formed as an
integral part of the external unit. The method of attachment can be
manually performed as described or performed by an automated device
handling system. The invention also has application on untowed
sea-bottom-deployed cables to which similar external units are
attached. Therefore, the spirit and scope of the claims are not
limited to the description of the preferred version.
* * * * *