Information
-
Patent Grant
-
6269908
-
Patent Number
6,269,908
-
Date Filed
Saturday, January 15, 200024 years ago
-
Date Issued
Tuesday, August 7, 200122 years ago
-
Inventors
-
-
Examiners
- Stodola; Daniel P.
- Thompson; Hugh B.
-
CPC
-
US Classifications
Field of Search
US
- 182 196
- 182 197
- 182 198
- 182 199
- 182 70
- 242 342
- 242 3791
- 242 38891
- 242 904
-
International Classifications
-
Abstract
An extendible, self-retracting ladder particularly suitable for use with inflatable white water rafts and other watercraft. The ladder includes one or more rung assemblies which include tubular rungs supported by rope stiles. The rope stiles extend into the ends of the tubular rungs and are engaged with a tensioning mechanism that utilizes a pair of shock cords to apply continuous tension to the rope stiles. In the absence of weight on the ladder, the shock cord tensioning mechanisms retract the rope stiles into the tubular rungs and thereby raise the rungs into a compact retracted assembly. When a person's weight is applied to the rungs, the rope stiles are drawn out of the rungs and the rungs are extended downwardly into a conventional ladder configuration. The ladder can be stowed above the waterline when not in use, yet can be deployed and used by a person in the water without requiring any assistance from other persons aboard the watercraft.
Description
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.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings are incorporated into and form a part of this specification. In the drawings:
FIG. 1
is an isometric view of a preferred embodiment of an extendible, self-retracting ladder constructed in accordance with the present invention and shown in its retracted position;
FIG. 2
shows two ladders of the kind shown in
FIG. 1
, as deployed on a river raft in both the retracted and extended positions;
FIG. 3
is an isometric view of the ladder of
FIG. 1
, with the two rung assemblies extended, and including a phantom outline of the rung assemblies in their retracted positions;
FIG. 4
is an expanded isometric schematic view of the stile retraction mechanisms that are located in each tubular rung;
FIG. 5
is an end view in partial cross section of one of the stile retraction mechanisms contained in each tubular rung; and
FIG. 6
is a top view of an expanded schematic illustration of the stile retraction mechanisms of FIGS.
4
and
5
.
DETAILED DESCRIPTION OF THE INVENTION
Referring to
FIGS. 1 through 3
, a preferred embodiment of the present invention is presented in the form of an extendible, self-retracting ladder
10
which includes a rigid top cross member
12
, beneath which is suspended two extendible rung assemblies
14
and
16
.
The rung assemblies
14
and
16
are substantially identical, including tubular rungs
18
and
20
, respectively; and pairs of left and right retractable rope stiles
22
and
24
, and
26
and
28
, respectively, which are maintained in a state of tension by elastomeric tensioning mechanisms contained in the rungs
18
and
20
, described further below. Briefly, when the ladder
10
is not in use the rope stiles
22
through
28
are withdrawn into the tubular rungs
18
and
20
, such that the rungs
18
and
20
are drawn up close to one another in a compact retracted arrangement, as shown best in FIG.
1
. When a person pulls down on the rungs
18
and
20
in order to use the ladder
10
, the weight of the person causes the rope stiles
22
through
28
to be drawn out of the rungs until the rungs are spaced as appropriate for ordinary use as a ladder.
FIG. 3
illustrates the rung assemblies
14
and
16
in their extended positions, with their retracted positions shown in phantom outline.
FIG. 2
shows a pair of ladders, illustrated for purposes of explanation with one in the retracted position and one in the extended position.
As noted above, the rung assemblies
14
and
16
are functionally identical, and thus for simplicity will be further described by reference to rung assembly
14
.
Referring particularly to
FIGS. 3 through 6
, rung assembly
14
includes the tubular rung
18
, which is preferably a seamless tube of a rigid polymer such as polyvinyl chloride. Removable end caps
30
and
32
are emplaced over the ends of the rung
18
. Journalled transversely within the end caps
30
and
32
are axle assemblies
34
and
36
, illustrated schematically in
FIGS. 4 and 6
. A schematic end view of axle assembly
36
is shown in FIG.
5
.
Axle assembly
36
includes an axle
38
, which is mounted transversely within the endcap
32
and secured to the walls of the endcap
32
by rivets or other suitable fasteners. Journalled on the axle
38
are a rope pulley
40
and three smaller shock cord pulleys,
42
,
44
and
46
. The pulleys
40
through
46
are journalled for free rotation on the axle
38
. Shock cord pulley
42
is located on one side of the rope pulley
40
, and pulleys
44
and
46
are located on the opposite side of the rope pulley
40
.
Axle assembly
34
similarly includes an axle
48
, on which is journalled a rope pulley
50
, and three smaller shock cord pulleys
52
,
54
and
56
. Shock cord pulley
52
is located on one side of the rope pulley
50
, and the other two shock cord pulleys
54
and
56
are located on the opposite side of the rope pulley
50
.
The axle assemblies
34
and
36
function, together with a pair of elastic shock cords
60
and
62
, as a pair of tensioning mechanisms within the rung
18
, which independently apply tension to the left and right rope stiles
22
and
24
. In particular, one end of shock cord
60
is connected, inside the rung
18
, to the end of left rope stile
22
. In this regard, the left rope stile
22
passes downwardly through a bore
30
a
in the end cap
30
(FIG.
3
), then downwardly around the rope pulley
50
, where it terminates at a crimp-type connector
64
, by which it is attached to one end of shock cord
60
(FIGS.
4
through
6
). From that end the shock cord
60
passes around shock cord pulley
44
of axle assembly
36
, thence back and around shock cord pulley
52
of axle assembly
48
, thence back and around shock cord pulley
46
of axle assembly
36
, and thence back to axle
48
, where it is looped around axle
48
and anchored by means of a crimp-type connector
66
. It will be seen that the function of shock cord
60
is to maintain constant tension on the left rope stile
22
, such that it is normally withdrawn into the rung
18
to the maximum extent possible.
The crimp-type connector
64
that connects the lower end of rope stile
22
to the shock cord
60
also serves as a stop, preventing the lower end of the rope stile
22
from passing upward through the bore
30
a
of the end cap
30
. Thus the connector
64
effectively limits length of rope stile
22
that passes through the bore
30
a
during extension, and thus limits the extension of rung
18
from its rest position to a length that is determined by the length of rope stile
22
normally contained in the rung
18
. Ordinarily the length of the rope stile
22
contained inside the rung
18
will be selected such that, when it is fully extended to the limit set by the stop
64
, the rung
18
is displaced downwardly by a distance constituting a convenient step height for a person using the ladder.
The connector
64
, by functioning as a stop, also ensures that the weight of a person on the rung
18
is borne by the rope stile
22
and the connector
64
, and not by the shock cord
60
. This approach permits the use of relatively small shock cords that are only as strong as necessary to retract the rope stiles and raise the rung assemblies
14
and
16
to the retracted position, since the shock cords need not bear the weight of a person on the ladder. With this arrangement, the rope stile
22
can be selected and sized as appropriate to bear the weight of a person using the ladder; and the shock cord
60
can be selected and sized as necessary to only provide sufficient tensile force to retract the ladder and maintain the rung
18
positioned snugly in its upper retracted position when not in use, while readily giving way to the weight of a person when the ladder is put to use.
Similarly, the right rope stile
24
passes downwardly through a bore
32
a
in end cap
30
, around the rope pulley
40
, and is similarly connected at its end, inside the rung
18
, to the second shock cord
62
by means of a crimp-type connector
68
. The shock cord
62
passes successively around shock cord pulleys
54
,
42
, and
56
, and terminates at axle
38
, where it is tied off by a crimp-type connector
70
. The connector
68
serves as a stop to prevent the end of rope stile
24
from passing through the bore
32
a,
and ensures that all weight on the rung
18
is borne by the rope stile
24
and the connector
68
.
The end cap
30
includes a lower bore
30
b.
The upper end of rope stile
26
passes through the bore
30
b
and terminates at a crimp-type connector
72
(FIG.
5
), which functions as a stop to prevent the end of the rope stile
26
from passing through the bore
30
b,
and by which the upper end of the rope stile
26
is thus fastened to and depends from end cap
30
. Identical bores and connectors (not shown) are use to connect the upper ends of the other rope stiles to the adjacent rung assemblies.
It is further noted that, once the stiles and shock cords are installed, the removable end caps
30
and
32
are maintained in position by the tension of the shock cords, yet can be removed if necessary to service or inspect the shock cords and axle assemblies. The end caps
30
and
32
may be additionally secured in place with screws or other fasteners (not shown).
The rigid top cross member
12
has several functions. It functions to space the upper ends of rope stiles
22
and
24
by a distance approximately equal to the length of the rungs
18
and
20
, thereby providing adequate clearance between the rope stiles
22
and
24
for a person using the ladder. It also functions as a stop, against which the rung
18
abuts in its fully retracted position. It also functions as a handle and as a top step to a person using the ladder. The cross member
12
may be fastened to a boat, raft or other structure by any suitable means; for example by simple extensions of the upper rope stiles
22
and
24
passing through the cross member
12
. Where the rope stiles
22
and
24
pass through the cross member
12
, knots or crimp-type connectors are preferably utilized to secure the cross member at the desired location on the stiles
22
and
24
, and to prevent the cross member from sliding down the stiles
22
and
24
when the rung
18
is extended.
It will be recognized that in the retracted position the ladder is raised out of the water where it is unlikely to become tangled or damaged in rough conditions. At the same time, the ladder is always both readily visible and readily available to a person in the water, and simply grabbing the ladder will result in its deployment to the extended position. No assistance from anyone in the watercraft is necessary for a person in the water to deploy and use the ladder. The simplicity of deployment and use, even in emergency conditions by a person altogether unfamiliar with its construction or internal operation, renders the ladder particularly suitable for use in rough water or emergency conditions.
It will be recognized that the embodiment described above, including two substantially identical retractable rung assemblies
14
and
16
, is but one of several possible variations on the present invention. In its simplest embodiment, the ladder may include only a single retractable rung assembly, with or without the rigid top cross member. In other embodiments three or more rung assemblies may be strung together in the same manner as described above.
Accordingly, the foregoing description of a preferred embodiment of the invention is presented for purposes of illustration and explanation, and is not intended to be exhaustive or to limit the invention to the precise form disclosed. Various modifications, substitutions, and alterations may be possible in view of the foregoing description. Accordingly, it is intended that the scope of the invention be defined by the following claims.
Claims
- 1. An extendible, self-retracting ladder comprising at least one retractable rung assembly, said retractable rung assembly including:a tubular rung having first and second ends; first and second retractable rope stiles each having upper and lower ends, said lower ends extending into said rung at said first and second ends of said rung, respectively, and: first and second tensioning mechanisms mounted within said tubular rung and connected respectively to said first and second rope stiles, said tensioning mechanisms functioning to maintain sufficient tensile force on said rope stiles to retract said stiles into said tubular rung and thereby raise said rung when the ladder is not in use, while also functioning to allow the stiles to be drawn out of said rung and said rung to be extended downwardly in response to the weight of a person applied to said rung.
- 2. The extendible, self-retracting ladder defined in claim 1, wherein said tensioning mechanisms include:first and second axle assemblies journalled within and transversely to said tubular rung at said first and second ends respectively, said axle assemblies each including at least one pulley around which the respective rope stile passes inwardly into said tubular rung, and: first and second shock cords connected respectively to said lower ends of said rope stiles and anchored to said axle assemblies so as to maintain tension on said stiles.
- 3. The extendible, self-retracting ladder defined in claim 2 wherein each of said axle assemblies includes a plurality of shock cord pulleys, and wherein said first and second shock cords make multiple passes around said pulleys so as to extend the length of said shock cords and thereby exert relatively constant tension on said stiles independent of the extent of extension of said stiles.
- 4. The extendible, self-retracting ladder defined in claim 3 wherein said rung assembly includes first and second removable end caps emplaced on said first and second ends of said tubular rung, respectively, and wherein said first and second axle assemblies include axles which are affixed internally to and extend transversely with respect to said first and second end caps, respectively.
- 5. The extendible, self-retracting ladder defined in claim 4 wherein said first and second rope stiles pass through bores in said first and second end caps, respectively, and wherein said stiles are connected to said shock cords by connectors which are sized to not pass through said bores and which thereby function as stops, such that all weight placed on said rung is borne by said stiles and said connectors, and not by said shock cords.
- 6. The extendible, self-retracting ladder defined in claim 4 further including a rigid top cross member having first and second ends, said first and second rope stiles being affixed at their upper ends to said first and second ends of said cross member, and means for fastening said rigid cross member to a watercraft or other object.
- 7. The extendible, self-retracting ladder defined in claim 6 further comprising a plurality of said rung assemblies connected in sequence and depending from one another, and wherein the uppermost one of said rung assemblies is affixed to said rigid cross member, and where rung assemblies depending from said uppermost rung assembly are connect to one another by means of said upper ends of said stiles being affixed to the end caps of the next adjacent rung assembly.
- 8. The extendible, self-retracting ladder defined in claim 1 comprising a plurality of said rung assemblies connected in sequence.
- 9. The extendible, self-retracting ladder defined in claim 8 wherein said tensioning mechanisms include:first and second axle assemblies journalled within and transversely to said tubular rung at said first and second ends respectively, said axle assemblies each including at least one pulley around which the respective rope stile passes inwardly into said tubular rung, and: first and second shock cords connected respectively to said lower ends of said rope stiles and anchored to said axle assemblies so as to maintain- tension on said stiles.
- 10. The extendible, self-retracting ladder defined in claim 9 wherein each of said axle assemblies includes a plurality of shock cord pulleys, and wherein said first and second shock cords make multiple passes around said pulleys so as to extend the length of said shock cords and thereby exert relatively constant tension on said stiles independent of the extent of extension of said stiles.
- 11. The extendible, self-retracting ladder defined in claim 10 wherein said rung assembly includes first and second removable end caps emplaced on said first and second ends of said tubular rung, respectively, and wherein said first and second axle assemblies include axles which are affixed internally to and extend transversely with respect to said first and second end caps, respectively.
- 12. The extendible, self-retracting ladder defined in claim 11 wherein said first and second rope stiles pass through bores in said first and second end caps, respectively, and wherein said stiles are connected to said shock cords by connectors which are sized to not pass through said bores and which thereby function as stops, such that all weight placed on said rung is borne by said stiles and said connectors, and not by said shock cords.
- 13. The extendible, self-retracting ladder defined in claim 12 wherein there is an uppermost rung assembly among said plurality of connected rung assemblies, said upper ends of said rope stiles of said uppermost rung assembly being connected to opposite ends of a rigid cross member having means for affixing said cross member to a watercraft or other object.
US Referenced Citations (11)