Fire escape – ladder – or scaffold – Suspended platform
Reexamination Certificate
2001-10-03
2003-11-18
Lev, Bruce A. (Department: 3634)
Fire escape, ladder, or scaffold
Suspended platform
C182S130000, C182S142000, C182S147000
Reexamination Certificate
active
06648102
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to cable-supported platforms used in dry dock ship repair and for other purposes.
BACKGROUND OF THE INVENTION
Although as explained below the present invention is not limited to such an application, one important application of the invention is in dry dock ship repair. In this regard, repairs in dry dock on the bow or stern of a ship and, in some instances, on the sides of a ship, present particular difficulties and both the bow and stern are inefficient to access using conventional “stick-built” scaffolding methods. For example, the time taken, and personnel needed, to assemble a single, fixed tower of sufficient height (80 feet) relative to the bow of a ship are quite substantial (on the order of 64 person-hours total).
Other important considerations in providing a workable, efficient support platform system for such an application include the need to provide attachment of the support platform system to a dry dock for ship repair with minimal modifications of the dry dock. Further, set-up and calibration of the system should be simple. In addition, it would be advantageous to be able to access exterior ship hull surfaces without the use of overhead support structures or scaffolding.
A traditional “Stewart Platform” cable configuration with overhead support points has a number of important advantages but does not allow access to some work sites such as a ship bow or stern. Exploring this point in more detail, the basic, six cable Stewart Platform is shown in schematic form in
FIG. 1
wherein six cables, denoted C
1
to C
6
, are connected between attachment or suspension points A
1
, A
2
and A
3
forming an upper or base triangle. A workpiece or moving platform P is supported by cables C
1
to C
6
. A platform edge, identified as PE, is supported by an associated suspension point A
1
. An important advantage of this configuration of cables C
1
to C
6
is that the configuration can control suspended loads, tools, equipment and the like in all six degrees of freedom with sway or rotations. Further, a spine (not shown) can be integrated between the platform P and the support structure to provide tension in all six cables C
1
-C
6
outside of the typical gravity-forced platform work volume. In other words, rather than hanging directly from the upper support points A
1
-A
3
down into a position dictated by gravity, the platform can be pushed to the side using such a spine. The prior art systems include control arrangement which provides control of each of cables C
1
-C
6
using a winch and is powered by a power amplifier. A computer is used to determine the amount of motion that the winch is to undergo to provide the desired cable control, based on sensor inputs. Joystick commands or other computer algorithm commands supplied to the winches can be used to provide complex platform movements which can be controlled throughout the work volume. Pre-programmed platform trajectories allow the operator to pre-plan movements with updated movement path information based on interaction with the environment. For example, the platform can be caused to maneuver around an obstacle placed in the pre-programmed movement path of the platform. Thus, Stewart Platform cable configurations possess a number of features but are limited insofar as providing access to some work sites.
Patents of interest here include the following, the subject matter of which is hereby incorporated by reference: U.S. Pat. No. 2,164,128 (Medenwald); U.S. Pat. No. 4,666,362 (Landsberger, et al.); U.S. Pat. No. 4,883,184 (Albus); and U.S. Pat. No. 5,585,707 (Thompson et al.). Briefly considering the three patents, the Medenwald patent discloses a basic Stewart Platform including a parallel-link manipulator configuration of six cables attached to a crane, with a single winch of the crane used as the lift device for all six cables. The cables stabilize attached loads in six degrees of freedom.
The Landsberger et al. patent discloses a Stewart Platform, parallel-link manipulator of six cables attached in a “tripod” configuration, including a telescoping support spine for the moving platform. Hydraulic power and hydraulic motors are used. The lengths of the cables are independently controlled through the use of power-spools.
The Albus patent discloses a cable and lifting platform of the Stewart Platform type which is used for stabilized load lifting. Load imbalance relative to the center of mass of the platform is sensed and the load is repositioned to control the imbalance. The cables stabilize the attached load in six degrees of freedom.
The Thompson et al. patent discloses a cable-driven Stewart Platform system, which is suspended from above, and also tensioned from below. Platform movement in six degrees of freedom is provided and the central system includes on-board winches, position sensing, optical sensing of tension, and a controller for these functions.
SUMMARY OF THE INVENTION
In accordance with the invention, a platform system is provided which affords a number of important advantages over prior art systems including the Stewart Platform system, and the variations thereon, discussed hereinbefore. As will become more apparent from the discussion below, the present invention enables attachment to a dry dock for use in ship repair with minimum modifications of the dry dock. Further, the system of the invention is simple to set up and to calibrate. In addition, the system of the invention permits accessing of the exterior surfaces of a ship's hull without the need for overhead support structures or scaffolding. Further, the system of the invention enables suspending of a moving platform for carrying workers, tools and equipment, and/or materials to a repair or conversion site, by providing intuitive control through the use of a hand-winch or joystick manual or computer control, throughout a large work volume.
According to the invention, there is provided a cabled platform suspension system comprising:
a platform including means defining first and second support points at spaced locations along a front work-access edge of the platform and a third, stabilizing/rotator support point;
a support structure for the platform defining first, second, third and fourth suspension points arranged in a substantially rectangular pattern and from which the platform is suspended; and
at least six cables connected between the platform and the support structure, the six cables comprising:
first and second cables respectively connected between the first and fourth suspension points and the first and second support points on the platform;
third and fourth cables respectively connected between the second and third suspension points and the first and second support points on the platform; and
fifth and sixth cables connected between the second and third suspension points and the third support point on the platform.
In one preferred embodiment, the platform includes first and second laterally and oppositely extending support members and the first and second support points are located at respective distal ends of the support members. Advantageously, the platform further includes a rearwardly extending support member having a distal end and the third support point is located at the distal end of said rearwardly extending support member. Preferably, the platform comprises a platform member and the rearwardly extending support member comprises a centrally disposed support strut affixed to a rear edge of the platform member and first and second tie elements extending between the distal end of the support strut and the rear edge of the platform member on opposite sides of the support strut.
In accordance with a preferred implementation, the suspension points are respectively located on the towers of a dry dock facility.
In a further preferred embodiment, the platform comprises a V-shaped platform member having a central portion and first and second angled leg portions and including a support strut extending rearwardly of the central portion and having a distal end, the first and second sup
Albus James
Bostelman Roger
Larson & Taylor PLC
The United States of America as represented by the Secretary of
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