Fire escape – ladder – or scaffold – Ladder – Flexible
Reexamination Certificate
2000-01-15
2001-08-07
Stodola, Daniel P. (Department: 3634)
Fire escape, ladder, or scaffold
Ladder
Flexible
Reexamination Certificate
active
06269908
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention disclosed and claimed herein is generally related to ladders. In particular, the present invention is related to portable ladders for use with inflatable rafts and other small watercraft.
Portable ladders used in connection with small watercraft must be capable of being lowered over the side of the watercraft to a depth beneath the surface of the water that is sufficient to permit their use by a person in the water who wishes to climb into the watercraft. However, if the ladder extends beneath the surface of the water to any significant depth, the ladder is subject to displacement whenever the watercraft is moving through the water, posing problems for the ladder, the watercraft, or both.
Rigid ladders must be either secured to the side of the watercraft or pulled aboard when the watercraft is underway, if damage to the ladder or the watercraft is to be avoided. Either alternative poses disadvantages. If the ladder is secured to the side of the watercraft it is subject to damage by impact with docks or objects in the water. If it is stowed aboard the watercraft, it is not automatically available to a person in the water without assistance, and can be awkward or even impractical to deploy quickly in an emergency.
Simple rope ladders are flexible and thus are not normally damaged as a consequence of motion through the water, nor do they tend to damage the watercraft. However, they tend to twist and become fouled if left overboard while the watercraft is underway and are thus not always immediately available to a person in the water.
White water river rafts pose additional and unique problems. They are subject to violent motion in all directions while in the water, as well as occasional collisions with rocks and other objects. Nevertheless, it is desirable to be able to quickly deploy a ladder overboard when necessary to retrieve a person who has fallen overboard. In white water situations rigid ladders are impractical and even dangerous, and ordinary rope ladders suffer from twisting and fouling, as already noted, and pose the additional danger of entanglement with a person in the water.
Accordingly, it is the object and purpose of the present invention to provide an extendible, self-retracting ladder.
It is a particular object and purpose of the present invention to provide a flexible yet retractable ladder for use with small watercraft such as rafts.
It is yet another object of the present invention to provide a retractable ladder which can be made readily available and immediately extended and deployed overboard when desired, yet which does not interfere with the operation of the watercraft.
It is yet another object of the present invention to provide a retractable ladder which is flexible and can withstand violent water motion, yet which is resistant to twisting or fouling.
Finally, it is an object of the present invention to provide a flexible ladder which can be stowed above the waterline on a watercraft, and yet which can be deployed and used in an emergency by a person in the water without requiring assistance from other persons aboard the watercraft.
These and other objects and purposes are attained in the present invention as described below and defined in the appended claims.
SUMMARY OF THE INVENTION
The present invention provides an extendible, self-retracting ladder having at least one retractable rung assembly. The retractable rung assembly includes a tubular rung and a pair of retractable rope stiles which extend into the rung at each end. The rung assembly further includes internal tensioning mechanisms mounted within the tubular rung and which are connected respectively to the pair of rope stiles. The tensioning mechanisms function to maintain sufficient tensile force on the rope stiles to withdraw the stiles into the rung and raise the rung when the ladder is not in use. When weight is applied to the rung, the stiles are drawn out of the rung and the rung is thereby extended downwardly to deploy the rung in a useful position. Where multiple rung assemblies are connected in sequence, all of the rung assemblies self-retract in the absence of weight to form a compact assembly with the rungs abutting one another. When weight is applied, all of the stiles deploy to selected lengths to space the rungs as appropriate for use as a ladder.
The tensioning mechanism in each rung assembly preferably includes a pair of axle assemblies journalled within and transversely to the tubular rung at each end of the rung, with the axle assemblies each including a pulley around which the respective rope stile passes inwardly into the tubular rung. Tension is preferably applied to the rope stiles by a pair of shock cords located in each rung, which are connected to the rope stiles and which are anchored at their opposite ends to the axle assemblies.
In accordance with another aspect of the invention, the axle assemblies may include multiple shock cord pulleys, around which the shock cords extend, in order to extend the lengths of the shock cords and thereby obtain a tensile force applied to the rope stiles which is relatively constant and which is relatively independent of the position of the rung.
These and other aspects of the present invention will be apparent from the more detailed description of the invention set forth below, when taken with the accompanying drawings and the appended claims.
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Yeamans Bwnjamin J.
Yeamans David R.
Stodola Daniel P.
Thompson Hugh B.
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