Fire escape – ladder – or scaffold – Means maintaining platform level on angularly movable support – Swingable support
Reexamination Certificate
1998-11-02
2001-07-31
Chin-Shue, Alvin (Department: 3634)
Fire escape, ladder, or scaffold
Means maintaining platform level on angularly movable support
Swingable support
C182S069600
Reexamination Certificate
active
06267200
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a lift method and apparatus for moving an arm structure such as a boom of a crane.
2. Description of the Background Art
Various devices for moving an arm structure such as a lifting arm currently exist. These devices typically employ connecting plates joining relatively movable first and second arm structures. Known arrangements of this type require an excessive amount of force from a moving device that is attached to one of the arm structures and the connecting plate. Furthermore, the conventional art provides a limited range of movement of the second arm structure relative to the first arm.
For example, the conventional art of
FIG. 9
shows a first arm structure
10
and a second arm structure
12
fastened together by connecting plate
14
. Arm
12
pivots about pin
18
, mounted in plate
14
. A hydraulic piston and cylinder arrangement
16
is connected to the second arm structure
12
and to connecting plate
14
. As shown with the dashed lines in
FIG. 9
, when the second arm structure
12
approaches a fully extended position, the movement of the second arm structure
12
with respect to the first arm structure
10
is limited by the orientation of the hydraulic piston and cylinder arrangement
16
relative to arm structure
12
.
In the fully extended position, the hydraulic piston and cylinder arrangement
16
contacts the pin connection
18
that fastens the second arm structure
12
to the connecting plate
14
. This limits the range of motion of arm
12
.
As illustrated in
FIG. 9
, the conventional arm structure arrangement is highly inefficient when the second arm structure
12
approaches a fully extended position. This inefficiency can be explained with reference to the angle &thgr; between longitudinal axis B
1
of moving device
16
and longitudinal axis A
1
of arm structure
12
. This angle &thgr;°
0
affects the respective forces generated by the second arm structure
12
(denoted as F
12
) and the hydraulic piston and cylinder arrangement
16
(denoted as F
16
).
As the arm
12
approaches a fully extended position, a longitudinal axis B
1
of the piston and cylinder
16
is nearly parallel to a longitudinal axis A
1
of arm
12
, where angle &thgr; substantially approaches 0°. The extending force F
16
generated by the hydraulic piston and cylinder arrangement
16
is nearly perpendicular to force F
12
, which is the component of force tending to rotate arm
12
counter-clockwise due to the weight of arm
12
plus any loads carried by arm
12
. Force F
16
, which has component forces F
16a
and F
l6b
, therefore, cannot efficiently counteract force F
12
.
Accordingly, a need in the art exists for a lift method and apparatus for moving an arm structure that substantially increases a range of motion of a second arm structure relative to a first arm structure and which also provides a moving device with a mechanical advantage whereby work required to move the second arm structure relative to the first arm structure is substantially reduced while lifting capacity of the moving device is substantial increased.
SUMMARY OF THE INVENTION
Accordingly, it is a primary object of the present invention to provide a lift method and apparatus for moving an arm structure which substantially increases a range of motion of a second arm structure relative to a first arm structure while providing a mechanical advantage for the moving device whereby work required to move the second arm structure relative to the first arm structure is substantially reduced while lifting capacity of the moving device is substantially increased.
It is a further object of the present invention to provide a lift method and apparatus for moving an arm structure which substantially lowers the overall height and center of gravity of a first arm structure, a second arm structure, and a connecting plate system when the first arm structure and second arm structure are in a stowed position.
A further object of the present invention is to provide a lift method and apparatus for moving an arm structure which includes means for displacing a moving device relative to a said first arm whereby the moving device is provided with a mechanical advantage with respect to forces which oppose the moving device that are created by the arm structure.
A further object of the present invention is to provide a lift method and apparatus for moving an arm structure which substantially increases a range of motion of the second arm structure relative to the first arm structure when at least the second arm structure substantially approaches an extended position.
An additional object of the present invention is to provide a lift method and apparatus for moving an arm structure wherein the apparatus and method can be employed in a crane environment such that a first arm structure is a riser while the second arm structure is a boom connected to the riser by a riser connecting plate. A specific object is to provide a moving device in the form of a hydraulic piston and cylinder arrangement which is provided with a substantially increased lifting capacity due to a displacing device which movably connects the hydraulic piston and cylinder arrangement to the connecting plate.
Another object of the present invention is to provide a lift method and apparatus for moving an arm structure that substantially maximizes the lift of the moving device as the moving device moves through its operating range.
A further object of the present invention is to provide a lift method and apparatus for moving an arm structure that allows for increased lifting capacity, weight savings, manufacturing cost savings, and a reduction in work performed by the moving device or a reduction in hydraulic pressure. Another object of the present invention is to make more compact the mechanical elements which connect the moving device to the arm structure, while substantially achieving a shorter load radius for a given boom length or second arm structure length.
These and other objects of the present invention are fulfilled by providing a lift apparatus for moving an arm structure comprising: a first arm structure; a second arm structure having first longitudinal axis, said second arm structure being rotatable relative to the first arm structure; a moving device for applying a force along a second longitudinal axis; and at least one means for displacing the moving device relative to the first arm and the second arm during at least a portion of the range of motion of the second arm for increasing a range of motion of the second arm structure relative to the first arm structure and for providing said moving device with an increased mechanical advantage for moving the second arm structure relative to the first arm structure.
In addition, these and other objects of the present invention are also accomplished by providing a method of operating an apparatus comprising a first arm structure, a second arm structure pivotally attached to the first arm structure, and a moving device for creating relative pivotal movement between the first and second arm structures, the method comprising: activating the moving device to move the first and second arms relative to each other; and during at least a portion of the range of relative movement of the first and second arms, displacing the moving device with respect to at least one of the first arm or the second arm so as to improve the mechanical advantage of the moving device in generating the relative movement.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
REFERENCES:
patent: 4440235 (1984-04-01), Colistro
patent: 4602462 (1
Birch & Stewart Kolasch & Birch, LLP
Chin-Shue Alvin
Grove U.S. LLC
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