The present invention relates to a safety device, and in paπicular 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 safety device

comprising an anchor which can be secured to a surface without damaging the surface, the anchor incoφorating attachment means for attachment to a safety line

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 b> a relatively short safety line

PreterabK the anchor attaches to the surface bv means oi suction Alterπameh other

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

10mm. 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 α preferred embodiment, the seal comprises a primary sealing lip and secondary, tertiary,

and quaternary lips which act as backup seals

Preferably, the seal is made of a rubber or rubber-like mateπal Nitrile rubber is especially preferred as it has excellent resistance to chemical attack from items such as

fuel, skydrol 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 compπses 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 α coupling

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 fuπher 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

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 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 arrest system

compπsing a plurality of track elements connectable together to form an elongate track and

a carnage moveable along the track, the carriage having a connector for connection to a

safety line, in which each track section has at least one vacuum anchor so that the track

can be secured to the surface of a structure without substantially damaging the surface.

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 fuπher described, by way of example, with reference to the

accompanying drawings in which-

Figure 1 is a plan view of an anchor constituting an embodiment of the present invention:

Figure 2 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 1 ,

Figure 4 is a schematic diagram of a safety system using two anchors tethered together;

Figure 5 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 transpoπing the safety

system shown in Figure 7;

Figure 10 illustrates the trolley of Figure 9 in plan view; and

Figure 1 1 schematically illustrates a trolley for α plurality of anchors of the type shown in

Figure 1

The anchor 1 shown in Figure 1 comprises a back-plate 2 which carries a nitrile rubber

seal 4 around its periphery. The seal 4 has a dished profile and faces away from the plate

2. The rear surface of the plate 2 carries first and second quick-release vacuum couplers

6 and 8 which incorporate in-built check valves (one-way valves) and which are in gas

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 agamst the surface

30 by virtue of the atmospheric pressure acting on the plate 2. Once the anchor has

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 α continuous path to vacuum (via the various one-way

\ alves ι 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 1500Kg force. 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 μ = 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 poπion. 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 α primary outer lip 32 which forms the main seal between the anchor 1 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

breached. It will be appreciated that the anchor can be used if any one of the tour sealing

elements 32 to 38 is intact. Fuπhermore, 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 withm 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 compπsing 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 500Kg. 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 500Kg. 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

G 97/01052

10 further enhanced if the connection between adjacent anchors did not flex to any substantial

extent when it was loaded.

Figure 5 schematically illustrates a fuπher 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 1 , 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

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 carnage 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 _j oined 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 secuπng adjacent sections of track to one another.

As shown in Figure 7, the end-most element of the completed assembly compπses 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

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 1 1 and includes

storage for a plurality of anchors, a source of vacuum compπsing a pump 1 10 and reservoir

1 12 together with vacuum line i 14 for interconnecting the anchors to the trolley and the

anchors to one another.

In use. it is advantageous to check that each anchor is safely positioned over a surface and

that air is not leaking past the seal or rhrougn a fracture or defect in the surface. In order

to check the functionality of the system, ea'-h anchor is placed on the surface and

connected to the vacuum supply The vaive 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

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.