Note: Descriptions are shown in the official language in which they were submitted.
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SAFETY DEVICE
The present invention relates to a safety device,
and in particular to a device enabling personnel to perform
maintenance or inspection procedures on large items, such as
the wing or tail sections of an aircraft, the sides of
storage tanks, ships, submarines and other large structures.
Because of the large open spans required in hanger
buildings suitable for large aircraft, it is impractical to
install fixed safety lines in these structures since the sag
that would be induced in a line by the weight of a person
falling and being arrested by the line could cause that
person to strike a lower obstruction before their fall was
arrested or to slide in an uncontrolled manner onto a
protruding platform or lower part of an aircraft.
According to a first aspect of the present
invention there is provided a fall protection system of a
type that movably connects a person to a support structure
at a dangerous height above ground, comprising: at least
one portable anchor configured for attachment by suction to
a surface on the support structure, and including a means
for coupling and decoupling the at least one portable anchor
to a vacuum supply line; and a safety line configured for
interconnection between the person and the at least one
portable anchor.
It is thus possible to provide a safety device
which can be positioned on a structure in the vicinity where
a person is working thereby ensuring that the person is
attached to the safety device by a relatively short safety
line.
Preferably the anchor attaches to the surface by
means of suction. Alternatively, other
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forms of attachment may be used, such as magnetic attraction generated by an
electromagnet or a permanent magnet.
Preferably the anchor comprises a rigid element having a sealing element
extending from
a first side thereof. The rigid element may be formed as a plate. The sealing
element
may be formed as a seal extending around the periphery of the rigid element.
The plate may, for example, be circular or rectangular. A substantially square
plate having
chamfered corners has been found to be particularly useful in an embodiment of
the present
invention.
The plate is preferably made of a lightweight and strong material, such as
aluminium or
an aluminium alloy, as this enables a physically strong anchor to be formed
which is still
sufficiently light to be manually handled with ease. In .an embodiment of the
present
invention, the plate is substantially 450mm x 450mm with a thickness of
approximately
lOmm. The plate may be planar or it may be curved in order to accommodate the
curvature of a structure such as an aircraft fuselage. A planar plate may be
used as an
anchor on a curved fuselage provided that the radius of curvature is not too
small.
Similarly. a curved plate may be attachable to both a curved surface and a
plane surface
provided that the radius of curvature induced in the plate is not too small.
Advantageously, the seal is profiled to have a plurality of sealing lips. The
provision of
a plurality of lips provides enhanced integrity against gas leakage through
the seal. In
a preferred embodiment, the seal comprises a primary sealing lip and
secondary, tertiary,
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and quaternary lips which act as backup seals.
a Preferably, the seal is made of a rubber or rubber-like material. Nitrile
rubber is
especially preferred as it has excellent resistance to chemical attack from
items such as
fuel, skvdrol or mineral based oils used in aircraft systems.
The plate and seal cooperate to define a working volume of the anchor. This
working
volume becomes a sealed working chamber when the anchor is attached to the
surface.
Preferably, each anchor carries its own control valves. One or more valves may
be
attached to the rear surface of the plate. Advantageously, the valves are
positioned in a
protective enclosure so that the valves cannot be inadvertently operated, for
example, by
someone accidentally tripping over the anchor. The valve or valves are
operable to
selectively to connect the working chamber to a vacuum source, or to vent the
working
chamber to the atmosphere. Advantageously the valve or valves may enable the
working
chamber to be isolated.
Preferably, each anchor comprises at least one coupling to enable it to be
attached to or
uncoupled from a vacuum supply line. Advantageously the couplings are quick
release
couplings. Preferably, each anchor carries two or more couplings in gas flow
communication with one another such that a plurality of anchors may be
connected
together in series. Preferably, each coupling includes a self-sealing valve
such that air
is not admitted into the anchor in the event of accidental disconnection of a
coupling.
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Preferably. each anchor includes a vacuum reservoir. The reservoir can be
selectively
coupled to the working chamber of the anchor in order to reduce the gas
pressure within
the working chamber even when the vacuum supply to the anchor has been
interrupted or
removed.
Advantageously, the or each anchor carries a centrally mounted rotatable arm
on its rear
surface. The arm has an aperture formed therein for accepting a karabiner or
other clip
by which a connection can be made between the anchor and a safety line. The
arm is
rotatable thereby enabling a person to work safely within a predetermined
radius of the
anchor.
Alternatively, two anchors may be provided with a safety line that runs
between them.
A further safety line is then connected in sliding arrangement to the line
secured between
the two anchors. Such an arrangement enables a greater working area to be
covered than
is possible using a single anchor alone.
Preferably, one or more anchors are provided in combination with a
substantially rigid
track. Use of a rigid track reduces the shearing loads applied to the or each
anchor when
restraining a falling body. In a preferred embodiment, anchors are provided at
opposing
ends of track sections. Each track section is approximately 2.5 metres long
and is
provided with male and female ends, or another coupling arrangement, such that
adjacent
sections of track can be secured together. It is thus possible to form
continuous track
sections to any desired length. Advantageously, a carriage engages the track
and is
longitudinally moveable with respect thereto in order to give maintenance
personnel easy
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access to a large area of structure whilst still providing
excellent fall restraint.
Advantageously, a trolley is provided for storing
the anchors or the track sections having anchors attached
5 thereto. The trolley may also include a vacuum source
together with flexible piping. The vacuum source may be
driven from an electrical supply, a compressed air supply, a
hydraulic supply or an internal combustion engine.
Advantageously, the vacuum source also includes a safety
system which will give an audible and/or visible warning in
the event of failure of the vacuum system and/or the vacuum
pump power source.
According to a second aspect of the present
invention, there is provided a fall protection system of a
type that movably connects a person to a support structure
at a dangerous height above ground, comprising: a first
anchor and a second anchor, wherein each said anchor
cooperates with an exterior surface on the support structure
to define a respective chamber; at least one low pressure
source in fluid communication with each said chamber; a
track interconnected between the first anchor and the second
anchor; and a safety line adapted to be interconnected
between the track and the person.
According to a third aspect of the present
invention, there is provided a method of fall restraint
comprising placing at least one vacuum anchor against a
suitable surface, operating the anchor so as to secure it to
the surface without damaging the surface and attaching a
safety line to the anchor.
The present invention will be further described,
by way of example, with reference to the accompanying
drawings in which:
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Figure 1 is a plan view of an anchor constituting an embodiment of the present
invention;
Figure ? is a side view of the anchor shown in Figure 1;
Figure 3 is a cross-section through the seal of the anchor shown in Figure l;
Figure 4 is a schematic diagram of a safety system using two anchors tethered
together;
Figure ~ is a plan view of a frame section of a safety system constituting a
second
embodiment of the present invention;
Figure 6 is a cross-section through the carriage shown in Figure 5;
Figure 7 schematically illustrates a plurality of frame sections assembled
together;
Figure 8 schematically illustrates an end of the safety system illustrated in
Figure 7;
Figure 9 schematically illustrates the side view of a trolley for transporting
the safety
system shown in Figure 7;
Figure 10 illustrates the trolley of Figure 9 in plan view; and
Figure 1 I schematically illustrates a trolley for a plurality of anchors of
the type shown in
Figure I.
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The anchor ! shown in Figure 1 comprises a back-plate 2 which carries a
nitrite rubber
seal ~ around its periphery. The seal 4 has a dished profile and faces away
from the plate
~. The rear surface of the plate ? carries first and second quick-release
vacuum couplers
6 and 8 which incorporate in-built check valves (one-way valves) and which are
in pas
flow communication with each other. A vacuum reservoir (not shown) is in gas
flow
communication via a one-way valve with the couplers 6 and 8 such that the
reservoir
becomes evacuated when either of the couplers 6 and 8 is connected to a vacuum
supply
line. An outlet of the vacuum reservoir is connected via a manually operable
valve 10
to a working volume or chamber 12 defined by the plate 2 and the seal 4. A
pressure
gauge 14 is in communication with the working volume 12 and measures the
pressure
therein. The connectors 6 and 8, the vacuum reservoir, the valve 10 and the
pressure
gauge 14 are covered by a second plate 16 to protect them from accidental
damage. The
second plate 16 is firmly secured to the plate 2 and has an upstanding pin 18
thereon
which forms the pivot for a rotatable arm 20. The arm 20 has a recess 22
formed therein
which acts a point of attachment for a safety line.
In use, the anchor is placed against a surface, such as an aircraft wing or
fuselage and a
vacuum supply line is connected to one of the couplers 6 and 8. This causes
the
reservoir to become evacuated. Once the anchor has been placed at the desired
position,
the valve 10 is then opened so as to connect the working chamber 12 formed by
the back
plate, the seal and the surface to the vacuum supply line via the vacuum
reservoir. The
seal 4 makes a gas tight seal with the surface 30 and consequently the
pressure within the
working chamber 12 becomes reduced causing the anchor to be held against the
surface
30 by virtue of the atmospheric pressure acting on the plate ?. Once the
anchor has
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become secured to the surface 30, a safety line can be attached to the arm 20.
The valve
can be left open so as to provide a continuous path to vacuum (via the various
one-way
valves r so that minor leaks do not cause the anchors to release from the
surface.
The anchor has dimensions of approximately 450mm x 450mm. However,, . the
distance
between the innermost sealing lips of the anchor seals is approximately 400mm.
When
the working volume is evacuated to a vacuum~level of substantially 150mBar.
The force
required to pull the anchor away from the surface 30 is approximately 1500daN,
i.e.
equivalent to 1500Kgf. The maximum shear load that the anchor can withstand
before moving is dictated by the coefficient of friction between the rubber
and the surface
30. However, typically the coefficient between rubber and a clean aluminium
surface (i.e.
the skin of an aircraft) is N = 0.55. Thus, the anchor is able to stand a
shearing force
in the region of 800daN.
The pressure gauge 14 is calibrated to show the level of vacuum but the face
is also
divided into a red portion and a green portion. The needle of the pressure
gauge does
not become aligned with the green portion until the vacuum level is down to
approximately
300mBar. The anchor should not be used until such a level of vacuum has been
achieved.
Figure 3 schematically shows the cross-section of the seal 4 in greater
detail. The seal
has a primary outer lip 32 which forms the main seal between the anchor I and
the surface
30. However, the seal 4 is also provided with secondary, tertiary and
quaternary lips 34,36
and 38 respectively, which provide backup seals in the event that the primary
seal 32 is
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breached. It will be appreciated that the anchor can be used if any one of the
four sealing
elements 32 to 38 is intact. Furthermore, the anchor is still useable if all
of the sealing
elements 32 to 38 are damaged provided that the breaches occur at different
circumferential
positions around the seal. Under such circumstances, the seal can still
function as a
labyrinth seal in order to maintain the vacuum within the working volume 12..
Figure 4 schematically illustrates a fall restraint system comprising two
vacuum anchors.
The vacuum anchors 40 and 42. are tethered together via a flexible safety line
44. A
further safety line 46 connected to a proprietary safety harness (not shown)
is connected
to the safety line 44 via a karabiner 48. Typically the safety line 46 is 1.8
metre lanyard
fitted with a built-in shock absorber comprising a folded portion of webbing
stitched to
itself with severable stitching. The lanyard is designed such that the
stitching fails when
the load on the lanyard is in the region of SOOKgf. This allows the web
portion to unravel
and the energy of the falling person is dissipated during the process of
breaking the
stitching. Thus, the load applied transversely to the line interconnecting the
vacuum
anchors 40 and 42 is limited to approximately SOOKgf. It will be appreciated
that the
transverse load is converted by the safety line 44 into a substantially
longitudinally acting
shear force. The magnitude of the force is dependent upon how much the line 44
can
be deviated from the straight line path between the anchors 40 and 42 before
the line 44
becomes taut. Resolving the loads into a triangle of forces indicates that the
safety line
should be sufficiently slack in order that it can assume an angle of at least
30° with respect
to the nominal line interconnecting the vacuum anchors.
The applicants realized that the load carrying capability of the safety system
could be
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further enhanced if the connection between adjacent anchors did not flex to
any substantial
extent when it was loaded.
Figure 5 schematically illustrates a further embodiment of the present
invention in which
a track 50 interconnects pairs of vacuum anchors 52 and 54. The anchors 52 and
54 are
similar to the anchor shown in Figure l, although the rotatable arm 20 has
been replaced
by fixed joints to the frame 50. Additionally, each anchor now only carries
one releasible
vacuum coupling, and a fixed vacuum line 56 now extends between the anchor 52
and 54.
The line 56 carries a single vacuum gauge for the assembly and the vacuum
reservoirs
have been omitted (although they can be retained). However, the line 56 (which
has
check valves at each end) effectively acts as a vacuum reservoir. Each anchor
52 and 54
is fitted with a vacuum gauge, a check valve, and has a manually operated
valve 58 and
60 respectively, which can be operated to evacuate the working space of each
anchor or
to allow the working space to be vented to atmospheric pressure. The track 50
comprises
two parallel rails 62 and 64 which are held in spaced relationship and against
flexing by
a plurality of cross members. The opposing ends of the rails are profiled such
that one
end forms a male connector 66 and the other end forms a female connector 68
(as
illustrated in Figure 9). A carriage 70 is provided in sliding engagement with
the rails 62
and 64. The carriage is shown in greater detail in Figure 6. The carriage
comprises
opposed pairs of guide wheels 71 and 72 which are held in engagement with the
tracks 62
and 64 by a metal frame 74. A substantially D-shaped guide ring 76 extends
from one
side of the carriage to the other, and carries a sliding link 78 thereon. A
karabiner 80
of a safety lanyard can be attached to the link 78 in order to secure a work
person to the
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safety system.
Figure 8 illustrates an end section of the safety system. The end sections
additionally
carry buffer plates 82 which act to prevent the carriage 70 from sliding off
the end of the
rails.
Each track section is approximately 2.5 metres long. A plurality of track
sections 50 can
be joined end-to-end, as shown in Figure 7, to form an elongate section of
track. As
noted hereinabove, the tracks are provided with male and female end connectors
such that
the tracks firmly engage one another and a load borne by one track can be
substantially
supported by an adjacent track section. As an alternative to profiling the
ends of each
track so as to form male and female connectors, the ends may be identical and
back-to
back connectors may be provided for securing adjacent sections of track to one
another.
As shown in Figure 7, the end-most element of the completed assembly comprises
an end
anchor 90. Thus, the anchors occur in pairs and each pair is separated from a
neighbouring
pair by a track element. It should be noted that two end anchors 90 could be
joined
together to form a short complete track. The end anchor 90 is illustrated in
greater
detail in Figure 8. The construction of the anchor 90 is identical to the
construction of
anchors 52 and 54 in the track section. However, the anchor 90 is only
provided with
a short section of track approximately 45cm long and the track is provided
with the buffers
82. Once the work has been completed, the anchors can be released by venting
them to
atmosphere.
Figure 9 illustrates a trolley for carrying a plurality of frame sections. The
trolley
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includes a vacuum source 100 in the form of a vacuum pump and a vacuum
reservoir 102.
As shown, the pump 100 is electrically operated and is controlled by a switch
104. A
backup supply 106 in the form of a battery is also provided to operate an
alarm system in
the event that the mains power fails. The alarm system may include a klaxon or
other
audible indicator to warn of a powei supply failure or loss of vacuum. The
trolley can
support a plurality of frame sections, as Shown in the plan view of Figure 10,
together with
sufficient vacuum hose to connect the trolley to the first of the frame
sections.
Depending upon the operator's requirements, the trolley may also include an
internal
combustion engine, either coupled to a generator or directly coupled to a
vacuum pump,
or a compressed air vacuum generator.
A similar design of trolley may also be provided to carry the single vacuum
anchor units
of the type shown in Figure 1. Such a trolley is illustrated in Figure 11 and
includes
storage for a plurality of anchors, a source of vacuum comprising a pump 110
and reservoir
112 together with vacuum line i 14 for intG~~onnecting the anchors to the
trolley and the
anchors to one another.
In use, it is advantageous to check tha: each anchor is safely positioned over
a surface and
that air is not leaking past the seal or rt~rc~ugi~ a fracture or defect in
the surface. In order
to check the functionality of the ,y~tem. ea~:l; anchor is placed on the
surface and
connected to the vacuum supply. 'The waive on the anchor is then operated to
the
"HOLD" position so as to attach the anchor to the surface. The vacuum gauge
should
immediately register in the green segment of the dial. The vacuum hose is then
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disconnected and the vacuum level shown on the gauge should not fall. If the
vacuum
level does decrease (noticeably within approximately thirty seconds), the
anchor should not
be used. Inspection may reveal debris breaking the seal or rivet holes in the
surface.
It is thus possible to provide a safety system for restraining falls in which
vacuum operated
anchors can be attached to the surface of a structure such as an aircraft
wing, fuselage or
tailplane without damage to the surface. Additionally, the anchors can be
interconnected
by rigid rails to form an elongate track allowing ease of movement along the
structure
while enabling a short length of safety line to be used, thereby decreasing
the risk of injury
in a fall.
