U.S. patent application number 14/361154 was filed with the patent office on 2014-10-02 for apparatus, module, device and method for shearing objects.
The applicant listed for this patent is DPIR LTD. Invention is credited to Peter Hall, David Mudie.
Application Number | 20140290949 14/361154 |
Document ID | / |
Family ID | 45508892 |
Filed Date | 2014-10-02 |
United States Patent
Application |
20140290949 |
Kind Code |
A1 |
Hall; Peter ; et
al. |
October 2, 2014 |
Apparatus, Module, Device and Method for Shearing Objects
Abstract
An apparatus, a module, a device and a method for shearing
objects are disclosed. The apparatus is configured for insertion
into a borehole. The apparatus comprises: a primary axis; a movable
shearing means; and a deflecting means. The deflecting means and
the movable shearing means are mutually configured such that, when
the movable shearing means is driven by a driving force in a
direction parallel to the primary axis, the movable shearing means
slides along the deflecting means and at least a portion of the
movable shearing means is deflected in a direction towards to the
primary axis.
Inventors: |
Hall; Peter; (Nicosia,
CY) ; Mudie; David; (Nicosia, CY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DPIR LTD |
Nicosia |
|
CY |
|
|
Family ID: |
45508892 |
Appl. No.: |
14/361154 |
Filed: |
November 15, 2012 |
PCT Filed: |
November 15, 2012 |
PCT NO: |
PCT/IB2012/056443 |
371 Date: |
May 28, 2014 |
Current U.S.
Class: |
166/298 ;
166/55 |
Current CPC
Class: |
E21B 29/08 20130101;
E21B 33/063 20130101 |
Class at
Publication: |
166/298 ;
166/55 |
International
Class: |
E21B 29/08 20060101
E21B029/08 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 29, 2011 |
GB |
1120530.9 |
Claims
1. An apparatus for shearing, wherein the apparatus is configured
for insertion into a borehole, the apparatus comprising: a primary
axis; a movable shearing means; and a deflecting means; wherein the
deflecting means and the movable shearing means are mutually
configured such that, when the movable shearing means is driven by
a driving force in a direction parallel to the primary axis, the
movable shearing means slides along the deflecting means and at
least a portion of the movable shearing means is deflected in a
direction towards to the primary axis.
2. An apparatus as claimed in claim 1, wherein the deflecting means
and the movable shearing member comprise respective abutment
surfaces, wherein the abutment surfaces are mutually configured
such that, in use, the at least a portion of the driven movable
shearing member glances off the deflecting member towards the
primary axis.
3. An apparatus as claimed in claim 1, wherein the shape of the
deflecting means and the shape of the movable shearing member are
mutually configured such that, when the movable shearing member is
driven by the driving force in the direction parallel to the
primary axis, the at least a portion of the movable shearing member
glances from the deflecting means in a direction towards the
primary axis.
4. An apparatus as claimed in claim 1, wherein the direction
towards the primary axis comprises at least one of: a direction
towards a centre of the apparatus and a direction substantially
perpendicular to the primary axis.
5. An apparatus as claimed in claim 1, wherein the apparatus is
configured to have an aperture therethrough defining the primary
axis and wherein the apparatus is configured to shear an object
located within the aperture.
6. An apparatus as claimed in claim 1, wherein the apparatus has
only two movable shearing members.
7. An apparatus as claimed in claim 1, further comprising means for
providing the driving force to the movable shearing member.
8. An apparatus as claimed in claim 7, wherein the means for
providing the driving force to the movable shearing member
comprises either: an aperture therethrough parallel to the primary
axis, or a plurality of means each configured to provide a driving
force to plurality of movable shearing members.
9. An apparatus as claimed in claim 1, wherein the driving force is
provided via a hydraulic mechanism.
10. An apparatus as claimed in claim 1, wherein the apparatus is
configured for movement within a borehole and/or within a pipe.
11. An apparatus as claimed in claim 1, wherein the apparatus is
configured for operation within a borehole and/or within a
pipe.
12. A module comprising the apparatus as claimed in claim 1.
13. A device comprising the apparatus of claim 1.
14. A shear ram tool, a pressure control equipment (PCE), a surface
test tree (STT), a sub-sea test tree (SST), a string run into an
well or a landing string comprising an apparatus as claimed in
claim 1.
15. A method comprising: inserting into a borehole an apparatus for
shearing, the apparatus comprising: a primary axis; a movable
shearing means; and deflecting means; driving the movable shearing
means by a driving force in a direction parallel to the primary
axis; sliding the driven movable shearing means along the
deflecting means; and deflecting at least a portion of the driven
movable shearing means from the deflecting means in a direction
towards the primary axis.
Description
FIELD OF THE INVENTION
[0001] Embodiments of the present invention relate to an apparatus,
module and device for shearing. In particular, though without
prejudice to the foregoing, certain embodiments relate to an
apparatus, module, device and method suitable for use down
boreholes or wellbores of oil, gas or geothermal wells, wherein the
apparatus configured to be inserted therein to remotely shear
objects passing through the apparatus such as tubing and/or
wirelines.
BACKGROUND TO THE INVENTION
[0002] Surface Pressure Control Equipment (PCE) and surface Blow
Out Preventers (BOP) can include multiple surface shear rams to cut
coil tubing or wireline passing therethrough. Such shearing devices
use shear rams which are driven by horizontally aligned hydraulic
pistons. Such shearing devices are physically too large to operate
down hole below a rotary table and are designed for surface use
only.
[0003] Subsea safety tools, such as a Sub Sea Test Tree (SSTT) are
either unable to cut/shear larger size coil tubing passing
therethrough (for example coil tubing whose external diameter is
greater than 2 inches/50.8 mm) or are prone to sustaining damage to
their sealing faces when attempting to cut coil tubing of such a
diameter. If the subsea safety tool is unable to sever the coil
tubing, there is no ability to pull the coil tubing out of the
landing string before master valves, e.g. in the PCE or BOP are
closed. If damaged is sustained due to forces applied to the SSTT
during a shearing process, this might compromises the sealing
integrity of the SSTT which is one of its primary functions.
[0004] The listing or discussion of a prior-published document or
any background in this specification should not necessarily be
taken as an acknowledgement that the document or background is part
of the state of the art or is common general knowledge. One or more
aspects/embodiments of the present disclosure may or may not
address one or more of the background issues.
BRIEF DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION
[0005] The invention is as set out in the independent claims.
[0006] According to one example, there is provided an apparatus for
shearing, wherein the apparatus is configured for insertion into a
borehole, the apparatus comprising: a primary axis; a movable
shearing means; and a deflecting means; and wherein the deflecting
means and the movable shearing means are mutually configured such
that, when the movable shearing means is driven by a driving force
in a direction parallel to the primary axis, the movable shearing
means slides along the deflecting means and at least a portion of
the movable shearing means is deflected in a direction towards to
the primary axis.
[0007] According to another example, there is provided a method
comprising: inserting into a borehole an apparatus for shearing,
the apparatus comprising: a primary axis; a movable shearing means;
and deflecting means; driving the movable shearing means by a
driving force in a direction parallel to the primary axis; sliding
the driven movable shearing means along the deflecting means; and
deflecting at least a portion of the driven movable shearing means
from the deflecting means in a direction towards the primary
axis.
[0008] According to one aspect of the disclosure, there is provided
an apparatus comprising:
[0009] a first member comprising an aperture therethrough defining
a primary axis through the first member; and
[0010] at least one movable shearing member;
[0011] wherein the first member is configured such that, when the
at least one movable shearing member is driven by a driving force
in a direction parallel to the primary axis, the at least one
movable shearing member is guided by the first member in a
direction towards the aperture.
[0012] In various but not necessarily all embodiments of the
invention the shearing members are driven by a linear actuator
which is aligned parallel to the primary axis, i.e. in use in a
typical well bore, aligned vertically and parallel to the well
bore. The vertical motion of the shearing members is at least
partly transferred to motion in a perpendicular direction, e.g.
horizontal motion towards a centre of the apparatus, by a
deflection means/guiding member which re-directs at least part of
the vertical motion to sideways motion such that the shearing
members shear objects, such as coil tubing or wireline, located
within the centre of the apparatus.
[0013] Embodiments of the invention enable the use of a driving
means aligned with the primary axis of the apparatus, i.e. the
linear stroke of the driving means is aligned with the primary
axis. Advantageously this enables the apparatus to have reduced
dimensions in a plane perpendicular to the primary axis, i.e. the
horizontal plane, such that embodiments can have a substantially
cylindrical form factor with an inside diameter of up to 9'' (22.86
cm) that enables the apparatus to fit below Pressure Control
Equipment (PCE), down hole below the rotary table, below a Subsea
Test Tree (SSTT) and within a Blowout Preventer (BOP) stack. For
example, an apparatus according to embodiments of the invention may
comprise a module of a subsea landing string. An apparatus
positioned at the lower end/bottom of such a landing string would
enable cutting of objects passing within the landing string such as
coil tubing and the disconnecting of the landing string allowing
removal of the upper sections of the landing string and riser.
Advantageously, allowing the removal of the objects within the
landing string protects the integrity of safety valves located
above the apparatus which do not have to, themselves, close around
and sever the objects within the landing string.
[0014] According to another aspect of the disclosure there is
provided an apparatus comprising:
[0015] guiding means comprising a passage therethrough defining a
primary axis through the apparatus; and
[0016] at least one movable shearing means;
[0017] wherein the guiding means is configured such that, when the
at least one movable shearing means is driven by a driving force in
a direction parallel to the primary axis, the at least one movable
shearing means is guided by the guiding means in a direction
towards the passage.
[0018] The apparatus may be implemented in a module, such as a
component of a landing string.
[0019] The apparatus may be configured for use in a borehole or
wellbore. The apparatus may be implemented in a device, such as a
shear ram tool, a pressure control equipment (PCE), a surface test
tree (STT), a subsea test tree (SSTT), a blow out preventer (BOP),
a string run into an oil/gas/geothermal well or a sub-sea landing
string component.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] For a better understanding of various examples of
embodiments of the present invention reference will now be made by
way of example only to the accompanying drawings in which:
DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION
[0021] The Figures illustrate an apparatus 100 comprising: [0022] a
deflecting means/first member 101 comprising an aperture 102
therethrough defining a primary axis 103 through the first member;
and [0023] at least one movable shearing member 104, 105; [0024]
wherein the first member is configured such that, when the at least
one movable shearing member is driven by a driving force 106 in a
direction parallel to the primary axis, the at least one movable
shearing member slides along the first member and at least a part
of the movable shearing member is deflected by/glanced from the
first member in a direction 107 towards the aperture.
[0025] FIG. 1A schematically illustrates a side on view of an
embodiment of the invention in a first state;
[0026] FIG. 1B schematically illustrates a side on view of the
embodiment of FIG. 1A in a second state;
[0027] FIG. 2A schematically illustrates a cross sectional view of
the embodiment of FIG. 1A along the line A-A;
[0028] FIG. 2B schematically illustrates a cross sectional view of
the embodiment of FIG. 1B along the line B-B;
[0029] FIGS. 3A to 3C schematically illustrate side on views of
further embodiments of the invention;
[0030] FIG. 4A schematically illustrates a side on view of a
further embodiment of the invention;
[0031] FIG. 4B schematically illustrates a cross sectional view of
the embodiment of FIG. 4A along the line A-A;
[0032] FIG. 5A schematically illustrates a side on view of a
further embodiment of the invention;
[0033] FIG. 5B schematically illustrates a cross sectional view of
the embodiment of FIG. 5A along the line A-A; and
[0034] FIG. 6 schematically illustrates a side on view of a further
embodiment of the invention.
[0035] The first member 101 may correspond to a deflecting means or
guiding means which comprises a passage 102 therethrough that
defines a primary axis through the apparatus 100. The at least one
movable shearing member 104 105 may correspond to at least one
movable shearing means. The deflecting means 101 may be configured
such that, when the at least one movable shearing means is driven
by a driving force in a direction parallel to the primary axis, the
at least one movable shearing means slides along and is deflected
by the deflecting means in a direction towards the passage.
[0036] The first member 101 is annular and has an outer diameter
108 and an inner diameter 109. The inner diameter defines the
central aperture of the first member. The apparatus is configured
such that, in a first state, a passage is provided through the
apparatus parallel to the primary axis through which objects, such
as coil tubing 111, wireline and/or fluids may pass. An inner
surface 110 of the first member, located between the outer and
inner diameters, is shaped so as to be able to receive a first
movable shearing member 104. The inner surface is shaped such that
when the first movable shearing member is driven in a direction
parallel to the primary axis towards the inner surface, the first
moveable shearing member glances from the inner surface towards the
centre of the aperture in the direction 107 substantially
perpendicular to the primary axis.
[0037] Likewise, on an opposite side the apparatus, a further inner
surface of the first member is shaped so as to receive a second
movable shearing member 105 and to deflect/glance the movable
shearing member along the inner surface in a direction towards the
centre of the aperture when driven in a direction parallel to the
primary axis.
[0038] A driving force 106 in a direction parallel to the primary
axis is provided to each of the shearing members. This driving
force is provided by driving means (not shown in FIGS. 1A and 1B
but is described below and shown in FIG. 4A and 5A).
[0039] FIG. 1A shows the apparatus in a first operational state in
which the shearing members are located outside of the aperture and
outside of the passage through the apparatus, such that the
apparatus 100 is hollow with the passage therethrough enabling
objects and fluids to pass through the apparatus.
[0040] FIG. 1B shows the apparatus in a second operational state in
which the shearing members have been provided with a force in a
(vertical) direction parallel to the primary axis which causes the
shearing members to move in the vertical direction. When the
shearing members come into contact with the inner surface of the
first member, the shape of the inner surface causes the shearing
members to glance therefrom and to rotate and move inwards in a
direction towards the centre of the aperture and passage. The
opposingly located shearing members are thereby moved towards one
another until their shearing edges abut one another (alternatively,
the shearing members may be configured such that they overlap one
another) so that an object located within the aperture/passage is
sheared by the shearing members.
[0041] In use, an object, such as coil tubing 111 or wireline may
be located within the aperture. According to various but not
necessarily all embodiments, a tube 111 within the passage having
an outer diameter greater than 2'', 50.8 mm and a wall thickness of
greater than 0.157'' 3.99 mm could be cut. For example a tube with
an outer diameter of 31/2'', 88.9 mm and a wall thickness of 0.2''
5.08 mm could be cut with embodiments of the present invention.
Embodiments of the invention could be configured to shear tubing
having a wall thickness of less than: 3 mm, 4 mm, 5 mm, 6 mm or 7
mm.
[0042] Once sheared, the object may be extracted. For example,
where the apparatus is used down hole in an oil or gas well and
coil tubing is passed through the apparatus. Following a shearing
process, the coil tubing above the shearing point can be extracted
and removed. Advantageously, where the apparatus is used in a
landing string located below an SSTT within a BOP, i.e. such that
the apparatus is located below safety valves of the SSTT and BOP,
the apparatus enables the coil tubing to be severed and pulled
upwards through the safety valves before their closure which
preserves the integrity of the safety valves.
[0043] In the embodiments show in FIG. 1A, the apparatus consists
of only two movable shearing members. The first movable shearing
member is located at one side of the aperture and passage through
the apparatus and a second movable shearing member located
substantially at an opposite side of the aperture and passage. The
apparatus is configured such that at least a part of the two
movable shearing members are moved towards each other.
[0044] Advantageously, by providing the first and second shearing
members in such diametrically opposing positions with respect to
one another, opposing forces in a (horizontal) direction
perpendicular to the primary axis on either side of the first
member generated during the shearing process cancel one another
out. For example, the resultant force in a left direction on the
first member due to the force in a right direction on the first
movable shearing member is cancelled out by the opposing resultant
force in a right direction on the first member due to the force in
a left direction on the second movable shearing member. Such an
arrangement means that no extraneous horizontal forces, i.e. forces
perpendicular to the primary axis are present or transmitted to
other parts of the apparatus, such as an external pressure bearing
housing (not shown).
[0045] Certain embodiments of the invention include a housing and
means for coupling the apparatus to other devices, such as modules
in a landing string. The above mentioned configuration avoids
horizontal forces being transmitted to the housing during a
shearing operation, which might otherwise compromise the coupling
and sealing integrity between the apparatus and a device to which
is it attached. Accordingly, certain embodiments of the invention
seek to maintain a reliable and secure coupling between devices and
the apparatus's housing.
[0046] FIG. 2A schematically illustrates a cross sectional view of
the apparatus 100 of FIG. 1A, i.e. in the first operational state
prior to a shearing process, along the line A-A. The first member
101 is annular having an outer diameter 108 and an inner diameter
109 defining an aperture 102 and passage through the apparatus
centered on the primary axis 103. In use, an object, such as coil
tubing 111 or wireline may be located within the aperture.
[0047] FIG. 2B schematically illustrates a cross sectional view of
the apparatus 100 of FIG. 1A, i.e. again in the first operational
state prior to a shearing process, along the line B-B. Here, the
outer diameter 108 of the annular first member 101 and a point
along the inner surface 110 are shown. Also, a cross sectional cut
through of each wedge shaped shearing members shown. The shearing
members are configured, i.e. shaped, dimensioned and made of a
suitably hard material so as to prove a shearing edge for shearing
objects within the aperture/passage of the apparatus.
[0048] FIGS. 3A to 3C schematically illustrate side on views of
further embodiments with differing shaped inner surfaces 110 of the
first member and differing shaped shearing members 104, 105. The
shearing members 104 105 drawn in solid lines represent the sharing
members in the first operational state/pre-shearing configuration
and the shearing members 104' 105' drawn in dashed lines represent
the sharing members in the second operational state/post-shearing
configuration.
[0049] In FIG. 3A, instead of having a gradually curving inner
surface, the cross sectional shape of each side of the annular
first member is substantially "L" shaped. The shearing members are
shaped so that their outer surface/abutment surface 301 which
contacts the inner surface/abutment surface 110 is curved so as to
cause the shearing members to rotate and move in an inward
direction towards the aperture when driven towards the first
member.
[0050] In FIG. 3B, the inner abutment surface 110 is shaped as in
FIG. 1A. However, instead of wedged shaped shearing members, the
outer abutment surface 301 of the shearing members which are
incident on and contact the inner abutment surface is curved.
[0051] In FIG. 3C, instead of having a gradually curving inner
abutment surface, the inner abutment surface's cross sectional
shape on each side is triangular, i.e. the such that the radius of
the aperture gradually reduces in a linear manner.
[0052] It is to be appreciated that any shape of first member's
inner abutment surface and shearing members' outer abutment surface
(i.e. the surface of the shearing member which in incident to and
contacts with the first member's inner surface) may be utilized
which causes the shearing members, when driven by a force parallel
to the primary axis, to move in a direction inwards towards the
aperture/passage of the apparatus. The shapes and/or angles of the
first member and the shearing members may be adjusted to change the
operational stroke, i.e. the extent of movement of the shearing
members inwards towards the aperture/passage. Thus, in various
embodiments of the invention, the respective abutment surfaces are
mutually configured and shaped to as to cause at least a part of
the shearing members to be deflected and glanced from the
deflecting means towards the central passage way 102.
[0053] The shearing members may comprise rams shears and may be
hardened steel shears.
[0054] FIG. 4A schematically illustrates a side on view of an
apparatus 400 of a further embodiment of the invention wherein the
apparatus 400 includes a means 401 for providing a force in a
direction parallel to the primary axis. Furthermore, a housing 406
is provided to surround the various members and the driving
means.
[0055] The driving means 401, may correspond to a linear actuator
for providing linear motion in a direction parallel to the primary
axis. This linear motion is transferred to sideways motion via the
interaction of the sharing members with the first members as
discussed above.
[0056] In one embodiment, the driving means comprises a hydraulic
mechanism. The driving means could be a remotely operable piston
405 that is actuated via hydraulic pressure provided to the piston
via a control line 402 which provides the pressurized hydraulic
fluid. The piston is biased such that the apparatus remains in its
first (open) state (as shown in FIG. 1A) negating the necessity for
a holding spring. Other forms of linear actuators would also be
usable with embodiments of the present invention.
[0057] The linear actuator is aligned such that the linear movement
is provides, i.e. its stroke, is in a direction parallel to the
primary axis, for example, in use in a well bore, the driving means
is vertically aligned as opposed to being horizontally aligned.
[0058] FIG. 4B schematically illustrates a cross sectional view of
the apparatus of FIG. 4A along the line A-A. This shows that a
single linear actuator 405 provides both the driving force for the
first movable shearing member 104 as well as the driving force for
the second movable shearing member 105. Moreover, the linear
actuator itself comprises an aperture 403 therethrough parallel to
the primary axis so as to maintain a passageway through the
apparatus enabling objects to freely pass through the apparatus
prior to a shearing process.
[0059] Coupling means or a linking mechanism 403 is provided to
link the shearing members to the driving means to enable the
shearing members to be rotatably coupled to the driving means.
Advantageously, such a rotatable coupling allows the linear force
parallel to the primary axis from the driving means to be
transmitted to the shearing members causing movement of the same,
whilst still allowing the shearing members to move towards the
aperture by rotating towards the aperture due to the guiding action
of the guiding means 101. Furthermore, a rotatable coupling could
allow reciprocal movement, i.e. to revert back to the first state
of FIG. 1A from the second state of FIG. 1B, by vertical motion of
the driving means in an opposite direction to its initial driving
stroke direction.
[0060] FIG. 5A schematically illustrates a side on view of an
apparatus 500 of a further embodiment. FIG. 5B schematically
illustrates a cross sectional view of the apparatus 500 along the
line A-A. The apparatus 500 of FIGS. 5A and 5B is similar to the
apparatus 400 of FIGS. 4A and 4B, except that instead of a single
hollow linear actuator, two linear actuators 501 502 are provided
each with their own control line 503 504 via which the actuators
can be individually controlled. The two linear actuators are
provided on opposing sides of the aperture and passage 506 through
the apparatus to enable objects to pass therethrough.
[0061] The shearing members are located, on their respective side,
between the outer and inner diameters of the first member. One
linear actuator 501 provides the driving force to the first
shearing member 104 and the another linear actuator 502 provides
the driving force to the second shearing member 105.
[0062] FIG. 5B schematically illustrates a cross sectional view of
the embodiment of FIG. 5A along the line A-A, and clearly shows the
two distinct driving means 501 502 located on opposing sides of the
aperture and passage 506 through the apparatus.
[0063] FIG. 6 schematically illustrates a side on view of a further
embodiment of the invention. This embodiment comprises the
apparatus 400 of FIG. 4A and 4B with its inner housing 406.
However, the apparatus 600 further comprises an outer housing 601.
This outer housing is separate from and distinct to the first
member 101.
[0064] The outer housing is provided with coupling means/joining
mechanism 602 and 603 via which the apparatus 600 can be attached
to other devices, such as modules of a landing string, a wear
bushing or casing hanger below a rig's BOP stack and SSTT.
[0065] As previously discussed, the configuration of the first
member and the shearing members ensures that any forces
perpendicular to the primary axis that might arise during the
shearing process are cancelled out due to the symmetry and opposing
locations of the shearing members. Advantageously, this ensures
that no horizontal forces due to the shearing process are
transmitted to the outer housing 601 which might otherwise affect
the tensile stress of the housing and the integrity of the coupling
means 602 and the seal provided thereby to an assembly of connected
devices.
[0066] The apparatus of may be generally of a cylindrical shape,
having a diameter configured so as to enable passage through a
circular passage or aperture, such as a borehole, wellbore, tube or
pipe.
[0067] In certain embodiments designed for oil, gas and geothermal
drilling, it is to be appreciated that the selection of materials
for various components, such as external components, would be
governed by: American Petroleum Institute (API), American Society
of Mechanical Engineers (ASME) and National Association of
Corrosion Engineers (NACE) standards. However, the certain internal
components could be substituted for other materials having
properties required for their intended function, e.g. appropriate
hardness for the shearing members.
[0068] The apparatus, in particular the operation of the driving
means, may be remotely operable, e.g. at the surface. The apparatus
may be incorporated in a standalone device or module. As used here
`module` refers to a unit or apparatus that excludes certain
parts/components that would be added by an end manufacturer or a
user. The apparatus may comprise a module in a landing string that
is located between a Retainer valve and a lubricator valve.
[0069] The apparatus may be incorporated or integrated in a shear
ram tool, a pressure control equipment (PCE), a surface test tree
(STT), a sub-sea test tree (SST), a blow out preventer (BOP), a
string run into an oil/gas well or a sub-sea landing string.
[0070] In the above description, the wording `connect` and `couple`
and their derivatives mean operationally connected/coupled. It
should be appreciated that any number or combination of intervening
components can exist (including no intervening components).
[0071] Although functions have been described with reference to
certain features, those functions may be performable by other
features whether described or not. The components of the figs are
functional and the functions described may or may not be performed
by a single physical entity as shown.
[0072] Although features have been described with reference to
certain embodiments, those features may also be present in other
embodiments whether described or not. Features described in the
preceding description may be used in combinations other than the
combinations explicitly described.
[0073] Although various embodiments of the present invention have
been described in the preceding paragraphs with reference to
various examples, it should be appreciated that modifications to
the examples given can be made without departing from the scope of
the invention as claimed.
[0074] Whilst endeavouring in the foregoing specification to draw
attention to those features of the invention believed to be of
particular importance it should be understood that the Applicant
claims protection in respect of any patentable feature or
combination of features hereinbefore referred to and/or shown in
the drawings whether or not particular emphasis has been placed
thereon.
* * * * *