Note: Descriptions are shown in the official language in which they were submitted.
TITLE OF THE INVENTION
WORK PLATFORM WITH PROTECTION AGAINST SUSTAINED
INVOLUNTARY OPERATION
STATEMENT REGARDING FEDERALLY
SPONSORED RESEARCH OR DEVELOPMENT
[00021 (NOT APPLICABLE)
BACKGROUND OF THE INVENTION
[00031 The invention relates to work platforms and, more
particularly, to
a work platform including provisions to enhance protection for an operator
from sustained involuntary operation resulting in an impact with an
obstruction
or structure.
[00041 Lift vehicles including aerial work platforms, telehandlers
such as
rough terrain fork trucks with work platform attachments, and truck mounted
aerial lifts are known and typically include an extendible boom, which may be
positioned at different angles relative to the ground, and a work platform at
an
end of the extendible boom, On or adjacent the platform, there is typically
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provided a control console including various control elements that may be
manipulated by the operator to control such functions as boom angle, boom
extension, rotation of the boom and/or platform on a vertical axis, and where
the lift vehicle is of the self-propelled type, there are also provided
engine,
steering and braking controls.
[0005] A safety hazard can occur in a lift vehicle including a work
platform when an operator is positioned between the platform and a structure
that may be located overhead or behind the operator, among other places. The
platform may be maneuvered into a position where the operator is crushed
between that structure and the platform, resulting in serious injury or death.
BRIEF SUMMARY OF THE INVENTION
[0006] It would be desirable for a platform to incorporate protective
structure to enhance protection of the operator from continued involuntary
operation of the machine in proximity to an obstruction or structure. The
protecting structure can also serve as a physical barrier to enhance
protection
for the operator and/or cooperate with the drive/boom functions control system
to cease or reverse movement of the platform. If cooperable with the operating
components of the machine, it is also desirable to prevent inadvertent
tripping
of the protective structure.
[0007] In an exemplary embodiment, a work platform includes a floor
structure having a width dimension and a depth dimension and a safety rail
coupled with the floor structure and defining a personnel work area. A control
panel area is cooperable with the safety rail and includes a sensor support
bar
having a top cross bar extending along the width dimension and side bars
extending substantially perpendicularly from the top cross bar. The side bars
define a width of the control panel area. Each of the side bars includes an
upper section extending from the top cross bar inward in the depth dimension
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to a bent section, and a lower section extending from the bent section outward
in the depth dimension to the safety rail.
[0008] In one embodiment, a platform switch that is configured to trip
upon an application of a predetermined force is attached to the sensor support
bar. A switch bar is secured to the control panel area, and the platform
switch
is attached to the switch bar.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] These and other aspects and advantages will be described in
detail with reference to the accompanying drawings, in which:
[0010] FIG. 1 illustrates an exemplary lift vehicle;
[0011] FIGS. 2-3 show a work platform including a protection envelope
of a first embodiment;
[0012] FIG. 4 shows a control panel area and a protective envelope
including a platform switch;
[0013] FIG. 5 is a cross-sectional view of the platform switch;
[0014] FIGS. 6-7 show an alternative design of the protection envelope
including the platform switch;
[0015] FIG. 8 shows the platform switch connected with shear elements;
[0016] FIG. 9 is a perspective view showing an alternative platform
design including the switch bar and platform switch;
[0017] FIG. 10 is a detailed view of the switch bar and platform switch
secured to the platform of FIG. 9; and
[0018] FIG. 11 is a close-up view of the switch bar secured to a sensor
support bar of the platform shown in FIG. 9.
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DETAILED DESCRIPTION OF THE INVENTION
[0019] FIG. 1 illustrates an exemplary typical aerial lift vehicle
including a vehicle chassis 2 supported on vehicle wheels 4. A turntable and
counterweight 6 are secured for rotation on the chassis 2, and an extendible
boom assembly is pivotably attached at one end to the turntable 6. An aerial
work platform 10 is attached at an opposite end of the extendible boom 8. The
illustrated lift vehicle is of the self-propelled type and thus also includes
a
driving/control system (illustrated schematically in FIG. 1 at 12) and a
control
console 14 on the platform 10 with various control elements that may be
manipulated by the operator to control such functions as boom angle, boom
extension, rotation of the boom and/or platform on a vertical axis, and
engine,
steering and braking controls, etc.
[0020] FIGS. 2 and 3 show an exemplary work platform 10 including a
protection envelope according to a first embodiment of the invention. The
platform 10 includes a floor structure 20, a safety rail 22 coupled with the
floor
structure 20 and defining a personnel work area, and a control panel area 24
in
which the control panel 14 is mounted. The protection envelope surrounds the
control panel area 24 and serves to enhance protection for the operator from
an
obstruction or structure that may constitute a crushing hazard.
[0021] As shown in FIGS. 2 and 3, the protection envelope may include
protection bars 26 on either side of the control panel area 24 extending above
the safety rail 22. The safety rail 22 includes side sections (the longer
sections
in Figs. 2 and 3) and end sections (the shorter sections in Figs. 2 and 3).
The
control panel area 24 may be positioned within one of the side sections. In
one
construction, the protection bars 26 are disposed intermediately within the
one
of the side sections adjacent the control panel area 24. In an alternative
construction, the protection bars 26 may be disposed in alignment with the end
sections of the safety rail 22 (as shown in dashed line in FIG. 3).
Preferably,
the protection bars 26 extend above the safety rail 22 by an amount sufficient
to
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accommodate an anteroposterior diameter of an adult human (i.e., a distance
between a person's front and back). In this manner, if an obstacle is
encountered that could result in crushing the operator between the structure
and
the control panel 14, the operator will be protected from injury by the
protection bars 26 with sufficient space between the control panel 14 and a
top
of the protection bars 26 to accommodate the operator's torso. FIG. 3 shows
the user in a "safe" position where an encountered structure is prevented from
crushing the operator by the protection bars 26.
[0022] An alternative protection envelope is shown in FIG. 4. In this
embodiment, the protection envelope includes a switch bar 28 secured in the
control panel area 24. A platfoim switch 30 is attached to the switch bar 28
and includes sensors for detecting the application of a force, such as by an
operator being pressed into the platform switch by an obstruction or
structure.
The platform switch 30 is configured to trip upon an application of a
predetermined force. The force causing the platform switch 30 to be tripped
may be applied to the platform switch 30 itself or to the switch bar 28 or to
both. It has been discovered that inadvertent tripping can be avoided if the
predetermined force is about 40-50 lbs over a 6" sensor (i.e., about 6.5-8.5
lbs/in). As shown, the switch bar 28 and the platform switch 30 are positioned
between the personnel work area and the safety rail 22. Relative to the floor
structure, the switch bar 28 and the platform switch 30 are positioned above
and in front of the control panel area 24. Based on an ergonomic study, it was
discovered that the switch bar 28 and platform switch 30 should be positioned
about 50" above the platform floor.
[0023] Although any suitable construction of the platform switch 30
could be used, a cross section of an exemplary switch 30 is shown in FIG. 5.
The switch 30 includes a switch housing 32 with internal ribs 34 connected
between the switch housing and a pressure switch 36. Sensitivity can be
adjusted by selecting a different rating pressure switch 36 and/or by
adjusting
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the number, shape and stiffness of the ribs 34. The switch bar 28 and platform
switch 30 also serve as a handle bar that an operator can grab in an
emergency.
[0024] An alternative platform switch assembly 301 is shown in Figs. 6
and 7. The switch assembly 301 includes a platform switch 302 with injection
molded end caps 303 and die cast mounting brackets 304. The platform switch
302 operates in a similar manner to the switch 30 shown in FIGS. 4 and 5. An
exemplary suitable switch for the platform switch is available from Tapeswitch
Corporation of Farmingdale, NY.
[0025] With reference to FIG. 8, the platform switch 30, 302 and switch
bar 28 may be secured to the control panel area 24 via a shear element 38. The
shear element 38 includes a reduced diameter section as shown that is sized to
fail upon an application of a predetermined force. With this construction, in
the event that the machine momentum or the like carries the platform beyond a
stop position after the platform switch is tripped, the shear elements 38 will
fail/break to give the operator additional room to avoid entrapment. The
predetermined force at which the shear element 38 would fail is higher than
the
force required to trip the platform switch 30, 301. In one construction, nylon
may be used as the material for the shear element 38, since nylon has low
relative elongation to plastic. Of course, other materials may be suitable.
[0026] In use, the driving components of the vehicle that are cooperable
with the lifting assembly for lifting and lowering the work platform are
controlled by an operator input implement on the control panel 14 and by the
driving/control system 12 communicating with the driving components and the
control panel 14. The control system 12 also receives a signal from the
platform switch 30, 302 and controls operation of the driving components
based on signals from the operator input implement and the platform switch 30,
302. At a minimum, the control system 12 is programmed to shut down
driving components when the platform switch 30. 302 is tripped. Alternatively,
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the control system 12 may reverse the last operation when the platform switch
30, 302 is tripped.
[0027] If function cutout is selected, when the platform switch is
tripped,
the active function will be stopped immediately, and all non-active functions
shall not be activated. If a reversal function is selected, when the platform
sensor is tripped during operation, the operation required RPM target is
maintained, and the active function only when the trip occurred is reversed
until the reversal function is stopped. A ground horn and a platform horn can
be activated when the reversal function is active. After the reversal function
is
completed, engine RPM is set to low, and all functions are disabled until the
functions are re-engaged with the foot switch and operator controls. The
system may include a platform switch override button that is used to override
the function cut out initiated by the platform switch. If the override button
is
pressed and held, it enables the hydraulic functions if the foot switch and
controls are re-engaged sequentially. In this event, function speed is set in
creep mode speed automatically. The controller is programmed to avoid the
cut out feature being disabled before the platform switch is tripped
regardless
of whether the override button is pressed or released. This assures that the
cut
out feature will still be available if the override button is stuck or
manipulated
into an always-closed position.
[0028] The reversal function is implemented for various operating
parameters of the machine. For vehicle drive, if drive orientation shows that
the boom is between the two rear wheels, reversal is allowed only when the
drive backward is active and the platform switch is tripped. If a drive
forward
request is received when the platform switch is tripped, it is treated as a
bump
or obstacle in the road and will not trigger the reversal function. If the
drive
orientation shows that the boom is not in line with the rear wheels, then both
drive forward and drive backward may trigger the reversal function.
Additional operating parameters that are implemented with the reversal
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function include main lift, tower lift, main telescope (e.g., telescope out
only),
and swing.
[0029] Reversal function terminates based on the platform switch signal,
footswitch signal and time parameters that are set for different functions,
respectively. If the platform switch changes from trip status to non-trip
status
before the maximum reversal time is elapsed, then the reversal function will
be
stopped; otherwise, the reversal function is active until the maximum reversal
time is elapsed.
[0030] Disengaging the footswitch also terminates the reversal function
at any time.
[0031] If an operator is trapped on the platform, ground control can be
accessed from the ground via a switch. In the ground control mode, if the
platform switch is engaged, boom operation is allowed to operate in creep
speed. If the platform switch changes status from engaged to disengaged, then
operation is maintained in creep speed unless the ground enable and function
control switch is re-engaged.
[0032] FIGS. 9-11 show an alternative work platform 110 including a
floor structure 120, a safety rail 122 coupled with the floor structure 120,
and a
control panel area 124 to which the control panel (not shown) is mounted. The
switch bar 28 and platform switch 30 are secured in the control panel area
124.
The control panel area 124 includes a sensor support bar 126 having a top
crossbar 128 extending along a width dimension (W in FIG. 9) and sidebars
130 extending substantially perpendicularly from the top crossbar 128. The
sidebars 130 define a width of the control panel area 124.
[0033] The sensor support bar 126 is preferably bent from a single piece
of material, although multiple pieces can be attached to one another in the
arrangement shown. Each of the sidebars 130 may include an upper section
extending from the top crossbar inward in a depth dimension (D in FIG. 9) to a
bent section. A lower section preferably extends from the bent section outward
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in the depth dimension to the safety rail 122. With continued reference to
FIG.
9, the upper section of the sidebars 130 may be angled downwardly from the
top crossbar 128 to the bent section. The lower section may extend at an angle
from the bent section to the safety rail 122. As shown, the lower section may
extend in a substantially straight line from the bent section to the safety
rail. In
the an-angement shown, the safety rail 122 extends above the floor structure
120 to a rail height, where the lower sections of the sidebars 130 connect to
the
safety rail 122 at a position about halfway between the floor structure 120
and
the rail height. AS also shown in FIG. 9, the top crossbar 128 is preferably
positioned above the rail height.
[0034] The switch bar 28 and the platform switch 30 may be connected
to the sensor support bar 126 at the bent sections of the sidebars 130 as
shown.
The platform switch is positioned inward in the depth dimension D of the floor
structure such that an operator in the control panel area is closer to the
platform
switch 30 than to the safety rail 122. Preferably, the switch bar and platform
switch are under-mounted on the sensor support bar 126 relative to an operator
standing on the floor structure 120. That is, as shown in FIGS. 10 and 11, the
switch bar 28 is preferably coupled to an outside surface of the sensor
support
bar 126 on an opposite side of the sensor support bar 126 relative to a
position
of an operator standing on the platform. The under-mounted configuration
results in a simpler assembly (e.g., without brackets 304) and improved
ergonomics.
[0035] FIG. 11 is a close¨up view of the switch bar 30 secured to the
sensor support bar 126. In a preferred construction, a block 132 is fixed
(e.g.,
by welding) to the sensor support bar 126, and a block holder 134 is fixed
(e.g.,
by welding) to the block 132. The block holder 134 receives a shear block 136
of the switch bar 30 and is secured by a fastener 138 such as a bolt or the
like.
A similar bolt (not shown) secures the switch bar 30 to the shear block 136.
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[0036] The protection envelope provided by the described embodiments
serves to enhance protection for operators from an obstruction and continued
involuntary operation. The protection envelope can include physical/structural
protection in the form of protection bars or the like and/or a platform switch
that is tripped upon the application of a predetermined force (such as by an
operator being driven toward or into the control panel by an obstruction or
structure).
[0037] While the invention has been described in connection with what
is presently considered to be the most practical and preferred embodiments, it
is to be understood that the invention is not to be limited to the disclosed
embodiments, but on the contrary, is intended to cover various modifications
and equivalent arrangements included within the spirit and scope of the
appended claims.
