Fire escape – ladder – or scaffold – With indicator – signal or alarm
Reexamination Certificate
1999-06-03
2001-01-16
Chin-Shue, Alvin (Department: 3634)
Fire escape, ladder, or scaffold
With indicator, signal or alarm
C182S017000, C182S002700
Reexamination Certificate
active
06173810
ABSTRACT:
FIELD OF THE INVENTION
This invention is directed to a trailer personnel lift and, more specifically, to a trailer personnel lift incorporating manually set outriggers.
BACKGROUND OF THE INVENTION
Personnel lifts are used for a wide variety of applications. A typical personnel lift includes a work platform that can be raised or lowered to position a worker at a desired height. The work platform and the worker can be raised to a position where the worker can paint overhead surfaces, trim tree branches, or work on overhead fixtures, for example.
Recently, personnel lifts have become a popular rental item. Rental provides a relatively inexpensive way for an individual or company to use a personnel lift for a short period of time. The user does not have to store the personnel lift, and is not responsible for periodic maintenance of the personnel lift.
Personnel lifts can be bulky and large, and transporting a rented personnel lift to a work site may be difficult. Often, with larger personnel lifts, the rental of a truck or other transportation vehicle to move the rented personnel lift to a work site may exceed the cost of rental of the personnel lift.
To aid in mobility, and decrease the cost thereof, manufacturers have recently started providing personnel lifts on trailers. For ease of reference, the trailer-mounted personnel lifts will hereinafter be referred to as “trailer personnel lifts.” A trailer personnel lift may be towed behind a vehicle with a conventional trailer hitch. Once the trailer personnel lift is towed to the work site, the personnel lift is ready for stabilization, leveling, and use.
A trailer personnel lift typically employs four outriggers at the right front, left front, right rear, and left rear of the device for stabilizing the trailer personnel lift. On most prior art trailer personnel lifts, outriggers are manually lowered to stabilize the personnel lift. A simple tilt sensor, such as a pendulum-based electronic sensor, is used to determine whether the trailer is level and provide a lockout that prevents the operation of the personnel lift until the trailer is level. The pendulum-based electronic sensor consists of a disk that is suspended by a cable into a vertically oriented cylinder. If the disk contacts one side of the cylinder, the sensor indicates that the trailer is not “level”. The pendulum-based sensor, however, does not indicate the direction in which the trailer is leaning. Instead, leveling bubbles are provided between the outriggers that indicate the direction of trailer tilt. Using the leveling bubbles and the pendulum-based electronic sensor, workers adjust the outriggers on the trailer until the trailer is level.
There are several problems with the leveling system that utilizes a pendulum-based electric sensor and bubble levels. As discussed above, a pendulum-based sensor does not indicate the direction in which a trailer is leaning. Leveling a trailer may be difficult because the individual bubble levels can only indicate level along one axis. Operators often attempt to level a trailer by eye-balling two or more bubble levels. Unfortunately, bubble levels are not very accurate and are often confusing to an untrained operator. In addition, “level” on the bubble levels and “level” on the tilt sensor may not correspond.
Further, as noted above, a pendulum-based electronic sensor does not indicate how level a trailer is, only that the trailer is not level. During setup, an operator can adjust the outriggers such that while the pendulum-based electronic sensor indicates that the trailer is level, the pendulum is not centered in the cylinder. Rather, the pendulum is nearer one side of cylinder than the other sides. During operation of the personnel lifts, a slight shift of the trailer may cause a pendulum near one side of the hanging cylinder to come into contact with that side. Due to its lockout function, such contact will disable the lifting system of the personnel lift. Specifically, the “up” function for the work platform will be shut down. Some models also shut down all functions, which leaves an operator stranded on the aerial work platform until a worker is available at ground level to re-level the trailer by adjusting the outriggers, or manually lower the operator by using a set of override controls located at the base.
Thus, there exists a need for a new and improved leveling system for a trailer personnel lift. The leveling system should be capable of determining how level the personnel lift is, so that slight shifts of the trailer personnel lift during operation will not cause the personnel lift to shut down.
SUMMARY OF THE INVENTION
In accordance with the present invention, a level-sensing system that displays instructions for manipulating manually-set outriggers so as to level a personnel lift is provided. The personnel lift includes a base and a vertical lift assembly defining upper and lower ends, the lower end being attached to the base. An aerial work platform is attached to the upper end of the vertical lift assembly. The personnel lift includes a lift system for extending the vertical lift assembly and raising the aerial work platform. A plurality of manually-set outriggers are provided for stabilizing the base. The level-sensing system determines the magnitude and direction of tilt of the personnel lift and, based on that magnitude and direction information, determines which of the plurality of outriggers needs to be changed in elevation so as to level the personnel lift. A level-indicator display is linked to the level-sensing system. The level-indicator display includes a plurality of indicators corresponding to the plurality of outriggers, the indicators displaying a first signal if the corresponding outrigger needs an elevation change and a second signal if the outrigger does not need an elevation change.
In accordance with flier aspects of this invention, an elevation change is a lowering of the outriggers.
In accordance with other aspects of this invention, the personnel lift is mounted on a trailer.
In accordance with yet another aspect of this invention, the level-indicator display includes a representation of the personnel lift.
In accordance with still another aspect of this invention, the number of outriggers is preferably four.
In accordance with another aspect of this invention, the level-sensing system comprises a tilt sensor and a microprocessor. Preferably, the tilt sensor is a dual axis, signal-conditioned tilt sensor.
In accordance with still another aspect of this invention, the outriggers are capable of locking into at least three positions, a first position in which the outrigger extends substantially horizontal to the surface upon which the personnel lift is to be located, a second position in which the outrigger extends substantially vertically from the base, and a third position that is intermediate of the first and second positions, the third position being selected so that the outriggers may be stabilized in the third position on an upward slope.
In accordance with yet another aspect of this invention, the second signal must be displayed by all indicators for the lift system to function. The display of the second signal preferably requires the level-sensing system to determine if the level of the personnel lift is within a first range. If so, the lift system is enabled to operate until the level-sensing system determines that the personnel lift is outside of a second range, the second range being greater than the first range.
In accordance with other aspects of this invention, the present invention provides a method of leveling a personnel lift. The method includes providing a personnel lift having a base and a plurality of manually-set outriggers for stabilizing the base. The personnel lift also includes a level-sensing system for determining the mag de and direction of tilt of the personnel lift and, based on that magnitude and direction information, determining which of the plurality of outriggers needs an elevation change so as to level the personnel lift. A level-indicator display is linked
Busuttil John
Citron Steven D.
Davis Michael F.
Kraemer Matthew G.
Chin-Shue Alvin
Genie Industries Inc.
Perkins Coie LLP
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