Patent Application
20110048852
This invention is related to the devices used to lower, rappel, or otherwise permit descent of a person or object down a rope or line in a controlled manner.
Individuals engaged in many different types of activities above the ground use ropes or safety lines to secure and protect themselves from a fall. Such activities may include utility workers working atop poles or other equipment; firefighters or other rescue personnel working atop or alongside a building; and construction workers working on tall buildings. The use of safety lines is not limited to work applications. The safety of various recreational activities is dramatically increased by the use of ropes or safety lines. These activities include, for example, rock climbing and spelunking. In addition, hunters who hunt from elevated platforms also can benefit from the use of safety ropes.
A rope alone, however, does not provide a complete solution. The rope should be secured to the person in a manner that allows the person to adjust his position on the rope (such as by when climbing or descending) but still protects the person from a fall. A variety of devices to provide fall protection have been developed, which typically operate as follows. A rope threads through the device, and the device is securely attached to a harness worn by a person with a carabineer. The rope slides through the device so long as the rope is relatively slack. Tension upon the rope usually causes a movable cam in the device to rotate into a position that binds the rope and thereby halts the passage of the rope through the device. If the tension is caused by a person falling, the device jams the rope and arrests the fall.
Some devices also include a lever attached to the cam that can be used to open the cam and release the rope. With the cam in open position on such devices, however, there is no appreciable friction on the rope, such that the rate of descent is quite rapid. If the operator were to panic and hold the lever such that the cam in the open position while descending, the rapid rate of descent could result in injury.
Another shortcoming of existing devices is that they cannot be operated remotely. If a person were to become unconscious and fall, or become unconscious as a result of the fall, or otherwise be injured such that he could not operate the device, his fall may be arrested. However, it may be impossible to lower him in a controlled manner without requiring a rescuer to go to the same perilous situation as the incapacitated person.
Thus, there exists a need for a safety device that provides automatic fall arrest, but allows for a safe, maximum rate of descent as an anti-panic feature. It would be further advantageous if such a device could be operated by remotely.
Embodiments of the present invention satisfy these needs. One embodiment of the present invention comprises a descender for controlling the descent of a person along a rope comprising an entry pin, a fixed guide member comprising an internal lateral face and an oblong end, with the internal lateral face including a first jamming surface; a cam pivotable about a pivot axis from an open position to a closed position, the cam having a peripheral face comprising a second jamming surface and an arcuate shoulder with a trailing edge; and an exit pin. The entry pin and the oblong end define a rope entry. The exit pin and the trailing edge of the cam's shoulder define a rope exit. The internal lateral face and the peripheral face of the cam define a rope travel path between the rope entry and the rope exit. This embodiment also includes a cam stop positioned to stop the pivoting of the cam in its open position; and a torque arm coupled to the pivot axis of the cam for pivoting the cam from its closed position to its open position. In the absence of force applied to the torque arm, tension on a rope passing through the rope travel path causes the cam to pivot into its closed position, in which the rope is jammed between the jamming surface of the fixed guide member and the jamming surface of the cam. This halts rope travel through the device. As force is applied to the torque arm to pivot the cam to its open position, the jamming surfaces separate to permit rope travel and the trailing edge of the cam's shoulder pivots away from the exit pin, which increases the friction between the rope and the exit pin and the cam's shoulder to thereby limit the rate of rope travel through the device.
The present invention will be explained, by way of example only, with reference to certain embodiments and the attached Figures, in which:
Referring to
The peripheral face of the cam 30 comprises an arcuate shoulder 32 and a jamming surface 35. The shoulder 32 is preferably eccentrically shaped and has a trailing edge 33. The cam 30 pivots about a pivot axis 38 from a closed position, shown in
The fixed guide member 40 is somewhat elongate in shape and terminates in an oblong end 45. The guide member 40 includes an internal lateral face 42 that is generally concave in shape, but preferably includes a raised or convex portion 43 against which the rope may be pressed or jammed by the jamming surface 35 of the cam 30. Likewise, in a preferred embodiment, the oblong end 45 of the guide member 40 may be provided with ridges 46 to increase the friction on a rope bearing against its surface.
The cam stop 70 is positioned to limit the range of motion of the cam 30 as it pivots from the closed position to the open position. In a preferred embodiment, the cam 30 includes a stopping surface 39, which pivots into and against a lateral face of the cam stop 70, as shown in
The descender 10 also includes a torque arm 90 coupled to the pivot axis 38 of the cam 30. The cam 30 may be moved from its open position to its closed position by applying force to the torque arm 90. The torque arm 90 may include an attachment point 92, to which a rope, line, or lanyard may be secured to allow a person remote from the descender 10 to apply force to the torque arm 90 and thus open the cam.
A rope passes through the descender 10, as follows. The rope threads between the entry pin 50 and the oblong end 45 of the fixed guide member 40, defining a rope entry. The rope then passes along the internal lateral face 42 of the fixed guide member 40 and then between the jamming surfaces 35 and 43 of the cam and fixed guide member, respectively. The rope continues along the peripheral face of the cam 30 to its shoulder 32. The rope threads between the shoulder's trailing edge 33 and the exit pin 60, defining a rope exit.
The upper end of the rope, as shown
A sufficient opposing force applied to the torque arm 90 causes the cam 30 to pivot to its open position. As shown in
The descender 10 includes another mechanism for controlling rope travel through the device and thereby rate of descent. The path of the rope at the rope entry, relative to the placement of the entry pin 50 and oblong end 45 of the fixed guide, affect the frictional force applied to the rope as it passes through the device. As a person moves the rope entering the rope entry away from the descender 10, the rope bears against the entry pin 50, increasing the friction on the rope and slowing the rate of descent. In addition, the device may be provided with a plurality of orifices 62 sized and adapted to hold the entry pin 50, as shown in
When the descender 10 is put in use, the foregoing structures and functions offer a number of benefits. One intended use for the descender is as a safety device for a person sitting on an elevated platform, to protect him from an accidental fall or to allow a controlled descent. This will be illustrated with the example of a hunter on a deer stand, although the principles and operation of the descender 10 apply to any person similarly situated, such as utility personnel, construction crews working on roofs or high buildings, and the like.
The hunter wears a harness, and the descender 10 is attached to the harness by a carabineer or similar device at attachment point 49. A rope, fixed at its upper end on or near the platform, passes through the descender 10 and hangs to the ground below. If the hunter falls from the platform, the tension on the rope applied by his body weight, in conjunction with the spring, causes the cam 30 to lock into the closed position and jam the rope between the jamming surface 35 of the cam and jamming surface 43 of the fixed guide member, thus rapidly arresting his fall.
His fall having been safely arrested, the hunter may then apply force to the torque arm 90 to open the cam to descend the rope to the ground. As the rope is released from the jamming surface 43 of the fixed guide member, the rope begins to pass through the descender. The cam 30 may be opened only slightly, allowing very slow rope travel, or it may be opened more widely, permitting faster rope travel. As the cam 30 is opened, the rope bears against oblong end 45 of the fixed guide member 40, the peripheral face of the cam 30 including the jamming surface 35 and shoulder 32, and finally against the exit pin 60. The friction generated by rope contact with these surface limits the rate of rope travel. Further, if the hunter were to panic and hold the torque arm such that the cam 30 is fully open and bearing against the cam stop 70, the frictional force on the rope generated by shape and placement of the internal components, as described above, limits the maximum rate of descent of the hunter to a safe rate. If the panicked hunter were to completely release the torque arm, the cam 30 automatically pivots to its closed position, jamming the rope and stopping the descent.
As noted above, a line or lanyard may be attached to the torque arm 90 at attachment point 92. The line should be of sufficient length to reach the ground below the platform or other place on which the person attached to the descender is located. Such a line provides an added measure of safety to the descender 10 as it permits remote operation of the device. Again, using the example of the hunter, if the hunter were to lose consciousness, become injured, or otherwise become incapacitated and fall off the deer stand, the descender 10 would arrest his fall as described above. Then, if the incapacitated hunter were unable to apply force to the torque arm 90 to descend, a person on the ground could pull the line attached to the torque arm 90 and control the descent.
A second embodiment 200 is shown in
In use, a person or object (the “load”) is secured to the rope on that portion of the rope extending beyond the exit pin 60, i.e., the right-hand part of the rope as shown in
Although the present invention has been described and shown with reference to certain preferred embodiments thereof, other embodiments are possible. The foregoing description is therefore considered in all respects to be illustrative and not restrictive. Therefore, the present invention should be defined with reference to the claims and their equivalents, and the spirit and scope of the claims should not be limited to the description of the preferred embodiments contained herein.
