Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to suspended scaffolds or work
platforms, and in particular, to a suspended platform for use
with a mobile crane for bungee (bungie) jumping.
Suspended platforms or scaffolds are used for many purposes,
such as in construction, the mining industry, building
maintenance and window washing, etc. Most of these platforms are
suspended from wire ropes or cables that are wound onto a capstan
or windlass to retract or advance the cable, thus raising or
lowering the platform.
For safety reasons, it is often desirable and often required
by regulatory authorities, that some sort of safety line be
provided for people working on these platforms. One end of the
safety line usually has to be attached to a fixed object located
above the highest point to which the platform will be raised, and
the other end of the line usually passes beside the platform and
goes down to the ground. Some type of clamping mechanism is
mounted on the safety line and is attached to the person working
on the platform or to the platform itself so that if the main
lifting cable that suspends the platform breaks or loses tensio~,
the clamping mechanism clamped onto the safety line prevents the
person or platform from falling.
A difficulty with this type of safety line system in the past
is that the clamping mechanism must be disengaged and re-engaged
each time the platform is raised or lowered. While the clamping
mechanism is disengaged, of course, there is no safety backup
line available. Another difficulty is that the safety line often
gets tangled up or twisted with the main platform lifting cable,
especially if the safety line clamping mechanism is attached
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rectly to the person working on the platform. Another very
serious drawback with this type of safety line system is that the
person could get caught or trapped in the falling platform and
be attached to the safety line resulting in serious, if not fatal
injury to the person.
The suspended platform of the present invention is
particularly useful for the sport of bungee jumping. In this
application, one end of a bungee cord is attached to the platform
and the other end of the cord is attached to a person who jumps
off the raised platform. In this application, safety lines as
described above would be totally unsuitable, because the bungee
cord would become tangled in the safety line resulting in serious
injury to the person jumping.
The present invention provides for an automatic safety line
that prevents a platform from falling, leaves a clear space below
the platform, and avoids the safety line being tangled with the
platform or the main cable lifting the platform.
According to the invention, there is provided a suspended
work platform for attachment to an overhead lifting device, such
as a crane, the work platform comprising a floor, a suspension
member located above the floor for releasable connection to the
lifting device, and an attachment means connected between the
suspension member and the floor for supporting the floor in
horizontal position. A safety line is connected to the work
platform and is adapted to be connected to a stationary object
located at a point above the highest point to which the platform
will be raised. A locking member is slidably mounted on the
safety line and is attached to a connection on one of the
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platform and the stationary object, the locking member having
releasable gripping means for clamping onto the safety line. Take
up means is coupled to the safety line between the locking member
and said connection for shortening and lengthening the safety
S line as the platform is raised and lowered relative to the
stationary object. Also, an actuator is operably coupled to the
locking member and sensitive to a lifting force on the suspension
member for causing the gripping means to clamp onto the safety
line upon discontinuous of the lifting force on the suspension
member.
Preferred embodiments of the invention will now be described,
with reference to the accompanying drawings, in which:
Figure 1 is an elevational view of one embodiment of a
suspended work platform according to the present invention;
Figure 2 is an enlarged plan view taken along lines 2-2 of
Figure 1;
Figure 3 is an enlarged bottom view looking up taken along
lines 3-3 of Figure 1;
Figure 4 i6 an enlarged elevational view of a portion of the
suspended platform indicated by chain-dotted circle 4 in Figure
l;
Figure 5 is an elevational view taken in the direction of
arrow 5 in Figure 4 showing the platform suspension member;
Figure 6 is an elevational view similar to Figure 4, partly
broken away, illustrating the operation of the locking member;
and
Figure 7 is an elevational view similar to Figure 1 but
showing another embodiment of a suspended work platform according
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~o the present invention.
Referring to the drawings, a suspended work platform
according to the present invention is generally indicated in
Figure 1 by reference numeral 10. Platform 10 is suspended from
a cable 12 having the usual hook 14 and weight ball 16 as
commonly employed in mobile cranes. A wire rope pennant 18 having
loops on each end is coupled between hook 14 and D-shackle or
clevis 20. Pin 22 of clevis 20 passes through a hole 24 (see
Figure 5) in a suspension member 26, as will be described further
below. Neither cable 12, pennant 18 nor clevis 20 is considered
to be part of the present invention, so will not be described in
further detail. It will be appreciated that hook 14 could be
attached directly to suspension member 26 by passing hook 14
through holé 24. Also, any other type of lifting device could be
attached to suspension member 26 to raise and lower platform 10,
as desired.
A safety line 30 in the form of a wire rope or cable is
connected to platform 10 and has an upper end connected to a
stationary object (not shown) located at a point above the
highest point to which platform 10 is desired to be raised. For
example, this stationary object could be the boom of a mobile
crane, or if platform 10 is suspended over a side of a building,
the stationary object could be the roof of the building.
Referring in particular to Figures 1 to 3, platform 10
includes a hexagonal base 32 having a floor 34 formed of an
expanded metal surface supported by a tubular frame 36. A
peripheral skirt 38 extends downwardly and outwardly from floor
34, skirt 38 having one open side 40. Three equi-spaced feet 42
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are provided along the bottom peripheral edge of skirt 38, so
that when platform lO is placed on uneven ground, platform lO
will not rock or tip. It will be appreciated that feet 42 can be
placed at any location around the periphery of skirt 38.
5A rigid, central tube 44 is attached at its bottom end to
floor 34 and extends upwardly to an upper end portion 46 in which
suspension member 26 is telescopically mounted, as will be
described further below. Tube 44 forms attachment means for
supporting the floor in a horizontal position when platform 10
10is suspended by cable 12.
Floor 34 is formed with a pair of openings 48 located
adjacent to tube 44, and a tubular retaining member 50 is spaced
above floor openings 48. Retaining member 50 is intended for the
attachment of elongate, flexible members, such as bungee cords,
15suspended therefrom passing through openings 48. However, other
ropes or cables, electrical wires, etc. could be directed through
openings 48 into platform 10 as desired.
A tubular cage 52 is attached to floor 34 and extends
upwardly and inwardly to upper end portion 46 to form an
20enclosure for platform 10. Cage 52 includes a peripheral,
upright, integral railing 54 formed around the periphery of floor
34. In Figure 7, cage 52 includes only the railing 54. A pair of
hingeably mounted gates 56 is located in railing 54 adjacent to
the open side 40 of skirt 38. Gates 56 are held in the closed
25position by a releasable latch 58. Optional lockers 60 and seats
62 are provided for the storage of tools and equipment, the seats
being hinged to swing up for access to the lockers. A toeboard
64 is provided around the lower periphery of railing 54. An
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upper, tubular retaining member 66 is attached to central tube
44. Retaining member 66 is for the attachment of personal safety
harnesses for the people working on platform 10.
Referring next to Figures 4 to 6, it will be seen that safety
line 30 passes through a locking member 70 and through a lower
tube 72 to be directed through an opening in the wall of tube 44
to pass downwardly through the inside of tube 44. At the lower
end of tube 44, floor 34 has an opening communicating with the
interior of central tube 44 to allow safety line 32 to pass
through floor 34 as described further below. Locking member 70
is mounted so that safety line 30 is spaced radially from tube
44 to clear lifting cable 12 as seen best in Figures l and 7.
Locking member 70 includes internal releasable gripping means
(not shown) for clamping onto safety line 30. A lever 74, when
in the position shown in Figure 6, releases the gripping means,
so that the locking member is slidably mounted on safety line 30,
or in other words, safety line 30 is free to pass through locking
member 70. When lever 74 is in the position shown in Figure 4,
the locking means firmly clamps onto safety line 30 to prevent
locking member 70 and thus platform 10 from moving relative to
safety line 30. The specific construction of locking member 70
is not considered to be part of the present invention and is
described further in United States patent No. 3,021,918. Any
suitable locking member 70 could be employed in the present
invention.
Locking member 70 is operated by an actuator coupled thereto
and is sensitive to a lifting force being applied to suspension
member 26. This actuator includes a linkage 76 attached to a
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transverse bar 78 in turn attached to suspension member 26. When
suspension member 26 moves up and down inside upper end portion
46, linkage 76 moves lever 74 as shown in Figures 4 and 6.
Suspension member 26 has a central opening 80 and upper end
portion 46 has a corresponding slot 82. A key 84 passes through
slot 82 and opening 80 to prevent suspension member 26 from
rotating relative to tube 44. Upper end portion 46 includes a cap
86 to limit the upward movement of key 84 in slot 82. A spring
88 compressed between the underside of cap 86 and a stop 90
attached to the lower end of suspension member 26 biases
suspension member 26 down into tube 44 in a non-extended
position. When a lifting force is not being applied to suspension
member 26 as indicated by relaxed pennant 18' in Figure 4, bar
78 is in its lowermost position causing the gripping means inside
locking member 70 to clamp the safety line 30. When lifting force
is again applied to suspension member 26 as indicated in Figure
6, bar 78 is in its uppermost position causing lever 74 to rotate
to the position shown in Figure 6 again allowing platform 10 to
move freely up or down relative to safety line 30.
Referring again to Figures 1 and 3, the lower end of safety
line 30 is attached to plaform 10 and is stored beneath floor 34
and above the lower peripheral edge of skirt 38 by a take-up
means including a capstan or reel 90 driven by a spring motor 92.
Safety line 30 exists from the lower end of central tube 44,
passes through floor 34, and is turned around a pulley or sheave
94 to be wound onto or wound off reel 90 as platform 10 risea or
descends. In this way, safety line 30 is shortened or lengthened
as the platform is raised or lowered relative to the stationary
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object to which the upper end of safety line 30 is attached. It
will be appreciated that reel 90 is large enough to store all of
the safety line 30 necessary to move platform 10 from the ground
to the highest point to which it is desired to be lifted.
Having described preferred embodiments of the invention, it
will be appreciated that various modifications may be made to the
structures described. For example, in place of the cage 52 having
its upper and inwardly directed radial tubular members supporting
upper end portion 46, radially extended cables or wire ropes
could be used as the attachment means. In fact, central tube 44
could be eliminated. Safety line 30 could then pass straight down
through the floor to be wound onto reel 90. Means other than the
spring biased telescopic suspension member could be used to
actuate locking member 70. Any device activated by tension in
lifting cable 12 could be used to activate or release locking
member 70. Lever 74 could be linked directly to hook 14 or
pennant 18.
Platform 10 can be made any size or shape desired. It will
be appreciated that safety line 30 must be sized to handle the
load of platform 10 with a suitable safety factor. For a platform
with a width or diameter of about 2 meters and a height of about
5 meters, a wire rope safety line with a 14,000 kilogram breaking
strength normally would be adequate.
If desired, the reel and spring motor could be mounted at the
upper end of the safety line such as on the boom of a crane, to
take up the slack in the safety line as the platform is raised.
In this case, the locking member or device would be attached or
connected to the boom of the crane as well. The safety line would
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,,
come off the reel and pass through the locking member and then
go down to be attached to the platform. The locking member mu6t
be attached to a fixed connection on one of the platform or the
stationary object, such as the boom of the crane. The reel and
spring motor take-up means is thus mounted on the ~afety line
between the locking member and the fixed connection. In this way,
when the main lifting cable fails, the locking member prevents
the safety line from being unwound from the reel and prevents the
platform from falling. When the reel and the locking member are
attached to a stationary object above the platform, some other
mechanism sen6itive to the lifting force on the main cable must
be provided to actuate the locking member when the main lifting
cable fails. A horizontal cable with a spring loaded block or
pulley coupled between the main lifting cable and the locking
member actuator lever would suffice for this purpose.
From the above, it will be appreciated that the suspended
work platform of the present invention is a very efficient device
with an automatic safety line that is uncluttered and leaves the
space below the platform free and clear.
While the present invention has been described and
illustrated with respect to preferred and alternative
; embodiments, it will be appreciated that numerous variations ofthese embodiments may be made without departing from the scope
of the invention, which is defined in the appended claims.
