Patent Application
20080230311
This invention pertains to a fall-arresting mechanism of a type useful with a generally vertical and/or curved structure, such as a ladder, tower, wall, or pole, which is equipped with a generally vertical rail.
A fall-arresting mechanism of the type noted above, in widespread use, is available commercially from North Safety Products Canada Ltd. of Toronto, Ontario, Canada, and is similar to the fall-arresting mechanisms disclosed in U.S. Pat. No. 2,616,609 and U.S. Pat. No. 4,111,280. The disclosures of U.S. Pat. No. 2,616,609 and U.S. Pat. No. 4,111,280 are incorporated by reference herein.
The fall-arresting mechanism disclosed in U.S. Pat. No. 2,616,609 and U.S. Pat. No. 4,111,280 comprises a sleeve and a locking pawl, which may be also called a detent. The sleeve is movable along a generally vertical and/or curved rail, with which a ladder is equipped. One end of the locking pawl is connected to a belt, which is worn by a user, via a flexible chain. At spaced intervals along the rail, the rail is provided with similar notches. If the end that is connected to the belt and/or full body harness is pulled downwardly, as a consequence of the user falling, the locking pawl is pivoted so that another end of the locking pawl moves toward the rail, into one of the notches.
This invention provides a fall-arresting mechanism for a generally vertical structure, such as a ladder, tower, wall, or pole, which is equipped with a generally vertical rail. The fall-arresting mechanism comprises an upper plate having an aperture, through which the generally vertical rail can extend, a lower plate having an aperture, through which the generally vertical rail can extend, and an elongate, linking member, which is connected to one of the upper and lower plates.
The upper and lower plates are linked so that the upper plate is pressed against the generally vertical rail, in a given direction, while the lower plate is pressed against the generally vertical rail, in an opposite direction, when the generally vertical rail extends through the apertures in the upper and lower plates and the elongate, linking member is pulled downwardly or downwardly and away from the carrier rail. The upper plate may be biased in the given direction and the lower plate may be biased in the opposite direction.
The upper and lower plates may be so linked via a linkage on each of two sides of the fall-arresting mechanism. The linkage on each of the sides may be a parallelogram linkage. The linkage may comprise means for biasing the upper plate in the given direction and the lower plate in the opposite direction.
The fall-arresting mechanism may comprise a friction-enhancing means, which is arranged to press against the generally vertical rail when the generally vertical rail extends through the apertures in the upper and lower plates. The friction-enhancing means may be biased against the generally vertical rail when the generally vertical rail extends through the apertures in the upper and lower plates. The friction-enhancing means may comprise a wheel, which is biased against the generally vertical rail and is rotatable around a generally horizontal axis when the generally horizontal rail extends through the apertures in the upper and lower plates. The wheel may be mounted operatively to the upper plate and/or the lower plate.
This invention also provides, for a ladder, tower, or pole, a combination comprising a rail, which is mountable to the ladder, tower, or pole so as to be generally vertical, and the fall-arresting mechanism described in the preceding four paragraphs.
As illustrated, a fall-arresting mechanism 10 embodying this invention is used with a generally vertical or curved ladder 20, which is equipped with a generally vertical or curved rail 30. The rail 30 is clamped to rungs 22 of the ladder 20, in a manner disclosed in U.S. Pat. No. 2,616,609 and U.S. Pat. No. 4,111,280. The rail 30 includes a series of spaced notches 32. These notches 32 can be used to interact with the fall-arresting mechanism 10 as discussed below. Alternatively, the rail 30 is useful with another generally vertical, similarly equipped structure, such as a tower, wall, pole, water tank and other similar structures.
Broadly, the fall-arresting mechanism 10 comprises an upper plate 40 having an aperture 42, which has an open mouth 44 and through which the rail 30 extends, a lower plate 50 having an aperture 52, which has an open mouth 54 and through which the rail extends, and an elongate, linking member 60, one end 62 of which is connected to the lower plate 50, at an upper surface 56 of the lower plate 50.The mouths 44, 54, of the apertures 42, 52, of the upper and lower plates 40, 50, enable the fall-arresting mechanism 10 to be removed from the rail 30, at dismount locations, which are not illustrated, in a manner disclosed in U.S. Pat. No. 4,111,280. The fall-arresting mechanism is also generally removable at the top and bottom of the rail.
The upper and lower plates 40, 50, are linked by two parallelogram linkages 70, each of which comprises two parallel links 72 on one of two sides of the fall-arresting mechanism 10, so that the upper plate 40 is pressed against the rail 30, in a given direction, i.e., away from the ladder 10, and the lower plate 50 is pressed against the rail 30, in an opposite direction, i.e., toward the ladder 10, when the rail extends generally vertically, through the apertures in the upper and lower plates 40, 50, and the elongate, linking member 60 is pulled downwardly or downwardly and away. The fall-arresting mechanism 10 may also include linkages 70 on two sides of the fall-arresting mechanism 10.
The upper plate 40 has two similarly curved surfaces 48, one at each side of the mouth 44 of the aperture 42, which are shaped so as to be pressed snugly against the rail 30 when the upper plate 40 is pressed against the rail 30, in the given direction, i.e., away from the ladder 10. The lower plate 50 has a curved surface 58, which is opposite the mouth 54 of the aperture 52 and which is shaped so as to be pressed snugly against the rail 30 when the lower plate 50 is pressed against the rail 30, in the opposite direction, i.e., away from the ladder 10. One of the parallelogram linkages 70 is provided with a coiled spring 74, which is tensioned so as to bias the upper plate 40 against the rail 30, in the given direction, i.e., away from the ladder 10, and the lower plate 50 against the rail 30, in the opposite direction, i.e., toward the ladder 10. It should be understood that two of the parallelogram linkages 70 may be provided with a coiled spring 74. Furthermore, it should be understood that there may be two or more coiled springs 74.
Additionally, one of the upper and lower plates 40,50 has a locking tooth 68 which is arranged to interlock with one of the series of spaced notches 32 of the carrier rail 30. As seen in
When the upper plate 40 thus is pressed against the rail 30, in the given direction, i.e., away from the ladder 10, and the lower plate 50 thus is pressed against the rail 30, in the opposite direction, i.e., toward the ladder 20, as a consequence of the user falling so as to pull the elongate, linking member 60 downwardly, or downwardly and toward or away from the ladder 20, frictional engagement of the curved surfaces 48 of the upper plate 40 with the rail 30 and frictional engagement of the curved surface 58 of the lower plate 50 with the rail 30 arrest the generally downward movement of the fall-arresting mechanism 10 along the rail 30 and, consequently, arrest the user's fall. Furthermore, the locking tooth 68 interlocks with one of the notches 32 of the rail 30 as the fall-arresting mechanism is pulled downwardly or downwardly and away from the rail 30. It should be understood by those skilled in the art that the linking member 60 may be flexible so as to absorb some of the force of the user falling.
The fall-arresting mechanism 10 further comprises a friction-enhancing wheel 80, which is mounted operatively to the upper plate 40 and may be biased against the rail 30, via coiled springs (not shown), and is rotatable around a generally horizontal axis when the rail extends through the apertures 42, 52, in the upper and lower plates 40, 50. The fall-arresting mechanism 10 further comprises two guiding wheels 90, which are mounted operatively to the lower plate 50. The friction-enhancing wheel 80 and the guiding wheels 90 are positioned so that the fall-arresting mechanism 10 is pulled upwardly along the rail 30, as the user climbs the ladder 20, while the friction-enhancing wheel 80 keeps the fall-arresting mechanism 10 from sliding downwardly along the rail 30. Furthermore, it should be understood that the fall-arresting mechanism 10 may include additional wheels 81.
As illustrated, the elongate, linking member 60 comprises a fabric strap 130, such as a nylon or polyester strap, which is connected at the end 62, to the lower plate 50. Alternatively, the elongate, linking member 60 comprises a cable or a chain. As best illustrated in
The linking member 60 may also include a severable member, such as a shear pin 140. The shear pin 140 can be used to provide a severable connection between the connecting members 132, 134. In this form, the connecting member 132, 134 and shear pin 140 receive most of the forces from ascending and descending by the user. However, in an instance where the user falls, the shear pin 140 will sever, thereby separating the connection members 132, 134 and permitting the strap 130 to slow and absorb the force of the fall. Therefore, wear on the strap 130 is minimized as it does not absorb any force unless the user is falling. Additionally, the linking member 60 may also include a sheath 142 which can be used to house the strap 130. The sheath 142 can be used to prevent the strap from being abraded and/or caught on various protrusions, thereby further maintaining the integrity of the strap 130.
As illustrated, the rail 30 is tubular with an outer wall that is generally circular in cross-section, as disclosed in U.S. Pat. No. 2,616,609 and U.S. Pat. No. 4,111,280. Alternatively, the rail 30 may have a different cross-sectional shape, such as the cross-sectional shape of a box beam or of an I-beam, whereupon the apertures 42, 52, of the upper and lower plates 40, 50, must be shaped conformably.
