Fire escape – ladder – or scaffold – With storage device for supple escape – Reel
Reexamination Certificate
2001-07-05
2004-11-02
Thompson, II, Hugh B. (Department: 3634)
Fire escape, ladder, or scaffold
With storage device for supple escape
Reel
C182S233000
Reexamination Certificate
active
06810997
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a controlled descent device intended for use in industrial or recreational settings. More particularly, in industrial settings, the present invention is used for emergency rescue or evacuation of personnel from a height by lowering them to safety at a controlled rate. In recreational settings, such as artificial rock climbing walls, it serves as a hands free belay device which lowers a climber to the ground at a controlled rate.
BACKGROUND OF THE INVENTION
Controlled descent devices of various types have been in use in general industry as a component in rescue and evacuation systems on buildings, bridges, towers, derricks, ladders, roofs and tanks and in a variety of settings including manufacturing, construction, oilfield, refinery and maintenance. An example of one such device is currently manufactured by Rose Manufacturing under the product name Dynescape® descender.
As shown in
FIGS. 1-3
, the Dynescape® descender is a controlled descent device
100
that consists principally of a steel housing
101
with an installation bracket
120
, an internal spring-loaded drum
103
on which a wire line
102
is wound, and a snaphook
105
on the line for attachment to a full body harness (not shown) worn by the user. Attached to the housing
101
is a centrifugal brake mechanism
107
which acts upon the drum
103
to limit the rate of descent. The wire line
102
passes around a pulley
123
and through a nozzle
104
before exiting the housing
101
.
During forced line extraction, line
102
which is wrapped around the drum
103
produces a moment, causing the drum
103
to rotate on its axle
108
. During line retraction, a constant force spring
106
biased in the direction of retraction acts on the drum
103
causing it to rotate in the direction that feeds line onto the drum
103
. A bull gear
109
rigidly fixed to the drum
103
rotates with the drum
103
. The bull gear
109
is meshed with a pinion gear
110
. The axis of rotation of the pinion gear
110
is aligned with the centrifugal brake mechanism
107
. The pinion gear
110
is linked to a pinion shaft
111
and is coupled in such a manner that when rotation is in the direction produced during line extraction, the two rotate together. During line retraction, the pinion shaft
111
and pinion gear
110
remain uncoupled, such that the pinion gear
110
spins freely on the pinion shaft
111
, and the pinion shaft
111
remains stationary. Through this interaction of the pinion gear
110
and pinion shaft
111
, the centrifugal brake mechanism is only engaged to rotate during line extraction.
The pinion shaft
111
is supported by two roller bearings
112
, and is rigidly linked to a brake hub
113
. Three dowel pin spokes
114
protrude axially from the hub, and engage with three brake shoes
115
. The brake shoes
115
are formed of arc shaped steel masses with a brake liner material
121
bonded to their outer surfaces. The end of each spoke
114
is situated within a bore
122
centered in the brake shoes
115
. The bore
122
is oversized with respect to the spoke diameter, providing a loose fit that permits both axial and rotational degrees of freedom of the brake shoe
115
within the confines of the brake housing
116
. The three brake shoes
115
are contained in a brake housing
116
with a cylindrical interior
117
. During braking, this cylindrical surface
117
mates with the curved brake shoe liner material
121
. During line extraction, the pinion gear
110
, pinion shaft
111
, hub
113
, spokes
114
and brake shoes
115
all rotate in unison within the housing. As the brake shoes
115
rotate with sufficient angular velocity, they are forced outward, along the axis of the spokes
114
, towards the brake housing
116
, due to centripetal acceleration. The centripetal acceleration acting on the brake shoe
115
forces the brake shoe
115
against the housing cylindrical surface
117
, producing friction that resists line extraction. The friction force is increased by the camming action of the brake shoes
115
. Because the bore
122
in the brake shoe is oversized with respect to the spoke
114
, the shoe
115
will tilt when in sliding contact with the brake housing
116
. This tilting cams the leading end of the shoe braking surface towards the housing
116
, increasing the braking friction force.
As mentioned previously, the mechanism linking the pinion shaft
111
to the pinion gear
110
permits relative rotation between these two components in one direction only. The pinion shaft
111
has a rectangular slot (see
FIG. 3
) cut perpendicular to its axis. This slot contains a double ended sliding key
118
. The key interacts with an internal cam profile
119
cut into the shoulder of the pinion gear. The cam profile
119
is a one-way ratchet shape with three high points, three low points, and three steps. This shape produces forced engagement of the sliding key
118
against the ratchet step when rotation of the pinion is in the direction of line extraction. The high point of the profile pushes one end of the sliding key
118
, such that the opposite end is forced into the low point and against the ratchet step on the opposite side of the cam profile. During line retraction, a relief angle on the key
118
and cam profile
119
allow the key
118
to flutter back and forth in the slot without engaging against the step of the cam profile
119
. The pinion gear
110
is thereby free to rotate about the pinion shaft
111
during line retraction, keeping the brake mechanism uncoupled from the drum
103
. During line extraction, the pinion gear
110
remains rotationally fixed to the pinion shaft
111
, keeping the brake mechanism engaged to rotate as the drum
103
rotates.
As the Dynescape® descender is intended for emergency use it typically is not subject to prolonged use. During prolonged use, components of the Dynescape® descender may need to be replaced due to increased wear. The sliding key
118
may become worn by the cam profile during prolonged use. The sliding key
118
may also become bent or deformed when subject to impact loading. Impact loading can occur in recreational applications when a climber attempts to jump for a hold that is out of reach, and free-falls on the line. Such prolonged use or abuse will eventually lead to compromised performance of the braking mechanism, which may engage during both line retraction and extraction.
A need exists, therefore, for a more robust design that will withstand repeated use and impact loading and whose components are not susceptible to wear during prolonged use.
Another feature of the Dynescape® device is that the line
102
is a wire rope. Over prolonged use this wire rope line
102
is prone to bird-caging (unraveling or kinking). Bird-caging is felt to be a result of the line material and the manner in which the line is layered onto the drum. Because the line is not stacked in consecutive layers and can cross itself, it can bind with itself and rub against itself as it is reeled on and off the drum during line retraction and extraction. Additionally, because the wire line
102
is a stiff member it is not capable of absorbing considerable energy in the event that a user free-falls on a slack line.
Another need exists, therefore, to develop a line that is not prone to bird-caging and which is capable of serving as a shock absorber during a user fall. An additional need exists for a field-replaceable line which allows a worn or deteriorated line to be replaced by a new line without having to return the device to the factory.
SUMMARY OF THE INVENTION
The present invention comprises a controlled descent device for use in industrial or recreational settings for lowering a user to the ground at a controlled rate.
Like the Dynescape® descender device, the controlled descent device of the present invention includes a steel housing containing a line wound on a spring loaded drum. The line feeds out of the housing through a nozzle. A snap hook or carabiner on the free end of the line is
Ecker Timothy W.
Schreiber Philip H.
Mine Safety Applicances Company
Thompson II Hugh B.
Uber James G.
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