BACKGROUND OF THE INVENTION
[0001] 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.
[0002] 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 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.
[0003] 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.
[0004] Document
JP H05 124800 A discloses a system for protecting an operator on an aerial work platform from a crushing
hazard, the aerial work platform including a floor structure, a safety rail coupled
with the floor structure and defining a personnel work area, and a control panel area,
the system comprising a sensor positionable adjacent the control panel area, the sensor
including a first transmitter unit positioned on one side of the control panel and
a first receiver unit positioned on an opposite side of the control panel area, the
first transmitter unit emitting a light beam across the control panel area to the
first receiver unit, the system further comprising a control system communicating
with the sensor and cooperable with driving components of the aerial work platform,
the control system being programmed to control operation of the driving components
based on signals from the sensor, and wherein the sensor comprises a housing for each
of the first transmitter unit and the first receiver unit, the housings being attachable
to the safety rail.
JP H05 124800 A also discloses another sensor including a second transmitter unit; a second receiver
unit, wherein the second transmitter unit and the second receiver unit are positioned
on an operator side of the first transmitter unit and the first receiver unit, respectively;
and wherein the second transmitter unit emits a second light beam across the control
panel area to the second receiver unit.
BRIEF SUMMARY OF THE INVENTION
[0005] It would be desirable for a platform to incorporate protective structure to enhance
protection of the operator from continued involuntary operation of the machine upon
impacting 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.
[0006] In some embodiments, an opto-electric sensor based system provides enhanced protection
against sustained operation for aerial work platforms. The sensor is designed to be
clamped to the safety rail of the platform. The system incorporating an opto-electric
sensor is an improvement over existing systems that utilize physical contact with
a switch or the like for activation. In the previous systems, the operator must make
physical contact with a switch in order to activate an enhanced operator protection
system. The system according to the described embodiments resolves drawbacks of the
existing system with respect to obstruction of visibility and sensitivity of the shear
blocks to accidental shear that result in a service call.
[0007] Disclosed herein but not claimed is a personnel lift includes a vehicle chassis,
a lifting assembly secured to the vehicle chassis, and a work platform attached to
the lifting assembly. The work platform includes a floor structure, a safety rail
coupled with the floor structure and defining a personnel work area, and a control
panel area. A control box is disposed in the control panel area and includes an operator
input implement. Driving components cooperable with the lifting assembly provide for
lifting and lowering the work platform. A sensor is positioned adjacent the control
panel area and includes a transmitter unit mounted to the safety rail on one side
of the control box and a receiver unit mounted to the safety rail on an opposite side
of the control box. The transmitter unit emits a light beam across the control panel
area to the receiver unit. A control system communicating with the driving components,
the control box, and the sensor controls operation of the driving components based
on signals from the operator input implement and the sensor.
[0008] Relative to the floor structure, the sensor may be positioned above and in front
of the control panel area. The control system may be programmed to shut down the driving
components when the light beam from the transmitter unit may be not received by the
receiver unit. The control system may be programmed to modify operating parameters
of the driving components when the light beam from the transmitter unit is not received
by the receiver unit.
[0009] The sensor may include two receiver units that are positioned to receive the light
beam from the transmitter unit. In this context, the control system may be programmed
to prevent operation of the driving components when one or both of the receiver units
do not detect the light beam. Additionally, the control system may be programmed to
reverse a last operation by the driving components when one or both of the receiver
units do not detect the light beam for a predetermined period of time, which may be
at most one second.
[0010] The lift may include an override switch communicating with the control system to
permit operation of the driving components at creep speed despite that the receiver
unit does not detect the light beam.
[0011] The sensor may include a first housing in which the transmitter unit is disposed
and a second housing in which the receiver unit is disposed, where the first and second
housings include respective clamps for attaching the housings to the safety rail.
A window opening may be provided in each of the first and second housings and a window
may be disposed in each of the window openings, where the windows are positioned adjacent
the transmitter unit and the receiver unit, respectively. The windows may protrude
from a surface of the housings.
[0012] The lift may additionally include a warning system positioned adjacent the control
panel area on an operator side of the sensor. The warning system may include a warning
transmitter unit mounted on the one side of the control box, a warning receiver unit
mounted on the opposite side of the control box, and an indicator lamp. The warning
transmitter unit emits a second light beam across the control panel area to the warning
receiver unit. In this context, the control system may be programmed to change the
indicator lamp when the second light beam from the warning transmitter unit is not
received by the warning receiver unit.
[0013] According to a first aspect of the present invention there is provided a system for
protecting an operator on an aerial work platform from a crushing hazard, the aerial
work platform including a floor structure, a safety rail coupled with the floor structure
and defining a personnel work area, and a control panel area, the system comprising
a sensor positionable adjacent the control panel area, the sensor including a first
transmitter unit positioned on one side of the control panel area and a first receiver
unit positioned on an opposite side of the control panel area, the first transmitter
unit emitting a light beam across the control panel area to the first receiver unit,
the system further comprising a control system communicating with the sensor and cooperable
with driving components of the aerial work platform, the control system being programmed
to control operation of the driving components based on signals from the sensor, the
sensor comprising a housing for each of the first transmitter unit and the first receiver
unit, the housings being attachable to the safety rail, and wherein the sensor further
comprises a warning system including: a second transmitter unit disposed in one of
the housings; a second receiver unit disposed in the other of the housings, wherein
the second transmitter unit and the second receiver unit are positioned on an operator
side of the first transmitter unit and the first receiver unit, respectively; and
an indicator lamp, wherein the second transmitter unit emits a second light beam across
the control panel area to the second receiver unit, and wherein the control system
is programmed to change the indicator lamp when the second light beam from the second
transmitter unit is not received by the second receiver unit.
[0014] Also disclosed but not claimed is a personnel lift including a vehicle chassis, a
lifting assembly secured to the vehicle chassis, and a work platform attached to the
lifting assembly. A control box is disposed in the control panel area and includes
an operator input implement. Driving components cooperable with the lifting assembly
lift and lower the work platform. An opto-electric sensor positioned adjacent the
control panel area is configured to detect an object entering the control panel area.
A control system communicating with the driving components, the control box, and the
sensor controls operation of the driving components based on signals from the operator
input implement and the sensor.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] These and other aspects and advantages will be described in detail with reference
to the accompanying drawings, in which:
FIG. 1 illustrates an exemplary lift vehicle;
FIGS. 2-3 show a work platform including a protection envelope of a first embodiment;
FIG. 4 shows a control panel area and a protective envelope including a platform switch;
FIG. 5 is a cross-sectional view of the platform switch;
FIGS. 6-7 show an alternative design of the protection envelope including the platform
switch;
FIG. 8 shows the platform switch connected with shear elements;
FIG. 9 is a perspective view showing an alternative platform design including the
switch bar and platform switch;
FIG. 10 is a detailed view of the switch bar and platform switch secured to the platform
of FIG. 9;
FIG. 11 is a close-up view of the switch bar secured to a sensor support bar of the
platform shown in FIG. 9;
FIGS. 12 and 13 are perspective views of a work platform incorporating an opto-electric
sensor system;
FIG. 14 is a section view of a sensor housing;
FIG. 15 is a perspective view of the opto-electric sensor system incorporating an
extra transmitter/receiver pair; and
FIG. 16 shows an alternative embodiment with the sensors integrated with the platform
control box.
DETAILED DESCRIPTION OF THE INVENTION
[0016] 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.
[0017] 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.
[0018] 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 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.
[0019] 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 platform
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.
[0020] 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 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.
[0021] 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.
[0022] 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.
[0023] 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, the control system 12
may reverse the last operation when the platform switch 30, 302 is tripped.
[0024] 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.
[0025] 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 function
include main lift, tower lift, main telescope (e.g., telescope out only), and swing.
[0026] 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.
[0027] Disengaging the footswitch also terminates the reversal function at any time.
[0028] 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.
[0029] 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.
[0030] 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 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 arrangement 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.
[0031] 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.
[0032] 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.
[0033] FIGS. 12-14 show another alternative embodiment, which utilizes an opto-electric
sensor for detecting an object such as an operator entering the control panel area
124. Like previous embodiments, the personnel lift includes a vehicle chassis, a lifting
assembly secured to the vehicle chassis, and a work platform attached to the lifting
assembly. The work platform includes a floor structure, a safety rail 122 coupled
with the floor structure and defining a personnel work area, and a control panel area.
See, for example, FIGS. 1-3 and 9. A control panel or control box 14 is disposed in
the control panel area 124 and includes one or more operator input elements 125. Like
previously described embodiments, driving components are cooperable with the lifting
assembly for lifting and lowering the work platform.
[0034] With reference to FIGS. 12 and 13, a sensor 402 is positioned adjacent the control
panel area 124. Relative to the floor structure 20 (see FIGS. 2, 3 and 9), the sensor
402 is positioned above and in front of the control panel area. The sensor 402 includes
a transmitter unit 404 mounted to a side bar 130 of the safety rail 122 on one side
of the control box 14 and a receiver unit 406 mounted to a side bar 130 of the safety
rail 122 on an opposite side of the control box 14. The transmitter unit 404 emits
a light beam across the control panel area 124 to the receiver unit 406. The control
system 12 (shown schematically in FIG. 1) communicates with the driving components,
the control box 14 and the sensor 402. The control system 12 controls operation of
the driving components based on signals from the operator input element(s) 125 and
the sensor 402.
[0035] In some embodiments, the receiver unit 406 is actually two receiver units that are
both positioned to receive the light beam emitted from the transmitter unit 404 (see
FIG. 14). In use, if the light beam from the transmitter unit 404 is detected by the
receiver unit 406 (or both receiver units in the embodiment where two receiver units
406 are provided), the machine is allowed to operate normally. If the receiver unit
406 (or either or both receiver units 406 in the embodiment utilizing two receiver
units) does not detect the transmitter beam (such as if the operator leans over the
platform control box 14), the control system is programmed to stop machine functions,
and further operation from the platform is prevented. Additionally, the control system
may be programmed to reverse a last operation by the driving components when one or
both of the receiver units 406 do not detect the light beam for a predetermined period
of time, which at most may be one second or less.
[0036] Like previously described embodiments, the system may include an override switch
on the platform control box 14 to allow function use at reduced (creep) speed. Normal
operation of the machine is prevented until the receiver unit 406 (or both receiver
units 406) detect the transmitter beam.
[0037] With continued reference to FIGS. 12 and 13, the sensor 402 may include a housing
408 in which the transmitter unit 404 is disposed and a housing 410 in which the one
or more receiver units 406 are disposed (see also FIG. 14). The housings include respective
clamps 412 for securing the housings to the side bars 130 of the safety rail 122.
In some embodiments, the housings include a window opening 414 and a window 416 disposed
in each of the window openings 414. The windows 416 are positioned adjacent the transmitter
unit 404 and the receiver unit(s) 406, respectively. In some embodiments, the windows
416 protrude outward of the housing surface to facilitate cleaning (e.g., scraping
paint, removing dirt, concrete spray, etc.).
[0038] FIG. 15 shows a modified sensor system incorporating an extra transmitter/receiver
pair 418 as part of a warning or teaching system. That is, the extra transmitter/receiver
pair 418 communicates the status of the system to the operator and teaches the operator
of the location in which the sensor is active. The additional transmitter/receiver
pair 418 is positioned adjacent the control panel area 124 on an operator side of
the sensor 402. Specifically, the transmitter/receiver pair 418 includes a warning
transmitter unit mounted on one side of the control box 14, a warning receiver unit
mounted on the opposite side of the control box 14, and an indicator lamp 420. The
warning transmitter unit emits a second light beam across the control panel area 124
to the warning receiver unit, and the control system is programmed to change the indicator
lamp 420 when the second light beam from the warning transmitter unit is not received
by the warning receiver unit. When the warning beam is interrupted, the indicator
lamp 420 (or set of lamps) is changed, either turned off or changed from one color
to another such as green to red. The indicator light or lights provide the operator
with information that the system is ready and functioning and help the operator to
develop proper habits, e.g., teaching the operator to remain in the proper position
relative to the control box to facilitate smooth and uninterrupted operation of the
machine.
[0039] In some embodiments, when power is applied to the machine control system, the control
system may perform a diagnostic check of the receiver and transmitter system. The
control system applies power in a predetermined orderly way to the receiver unit(s)
and transmitter unit(s). The output values of the receiver units are evaluated by
the control system for each powered state in order to detect faults with the components
and/or wiring. For a system with two receivers and one transmitter, for example, the
possible states are:
R1 |
R2 |
T1 |
OFF |
OFF |
OFF |
OFF |
ON |
OFF |
ON |
ON |
OFF |
ON |
OFF |
OFF |
ON |
OFF |
ON |
OFF |
OFF |
ON |
OFF |
ON |
ON |
ON |
ON |
ON |
[0040] In some embodiments, the sensor may be integrated with the platform control box 14
as shown in FIG. 16. As shown, the sensor 4021 is positioned above and in front of
the control panel area and is integrated with the control box 14. The sensor 4021
includes a transmitter unit 4041 on one side of the control box 14 and a receiver
unit 4061 on an opposite side of the control box 14. The transmitter unit 4041 emits
a light beam 4022 across the control panel area to the receiver unit 4061. The remaining
operation is the same as that in the previously described embodiments.
[0041] The sensors are preferably industrial photoelectric "light barrier" type sensors,
where light and/or reference to a "light beam" is understood to cover a wide range
of wavelengths - visible, infrared, laser, etc. The system may utilize receiver units
with two complementary outputs. The complementary outputs are monitored in order to
detect possible faults in components and wiring. The system may include a dedicated
control module for operation and control of the transmitter, receiver and status lights
(if any) including a machine platform control module interface. The dedicated control
module may also perform diagnostics on the transmitter unit and the receiver unit(s).
The sensor may include two discrete receiver units to provide redundancy. The sensor
may include two discrete transmitter units and two discrete receiver units. Still
further, the sensor may include a single transmitter unit and two discrete receiver
units.
[0042] It is to be understood that the invention is not to be limited to the disclosed embodiments,
and may cover various modifications, within the scope of the appended claims.