1. Field of the Invention
The present invention relates to safety devices, and more particularly, to a fall prevention construction for providing fall prevention to persons climbing vertical antenna structures.
2. Description of the Prior Art
Workers employed to perform construction and maintenance on elevated structures are typically in need of some form of fall prevention system. Such fall prevention systems are preferably permanently installed on the structure in order to ensure the availability of a safety mechanism to the worker at all times, including when climbing the structure. In the case of some structures, it has not been possible or convenient to provide fall prevention systems for the entire height of the structure due to the nature of the operations performed by the structure. For example, vertical television broadcasting towers having top mounted antennas have historically not included permanent fall prevention systems in that fall prevention systems have typically included a metal cable extending vertically along a side of the structure, which are known to distort the radio waves transmitted by the antenna. Therefore, in some instances it has been necessary to exclude a safety cable type fall prevention system along at least a portion of the television broadcasting tower which includes the vertical transmission area of the antenna. Not only does this pose an increased safety risk to workers, but the worker is also usually required to work on the tower in the dark, during early morning hours when the antenna is not transmitting, in order to avoid exposing the worker to harmful radiation energy. Accordingly, workers on such transmission towers are subjected to increased risks in the absence of an adequate and durable fall prevention mechanism.
In an attempt to address this need, U.S. Pat. No. 5,964,316 has proposed a fall prevention system in which a rope is provided in place of a steel or aluminum cable. A specific rope is provided comprising a polyurethane resin impregnated aramid fiber core, such as a Kevlar® rope, covered by a protective jacket of polyurethane. Grip clips are engaged with end portions of the rope to form loops at the end portions for engagement with mounting hardware of the system. While the '316 patent provides an alternative to the prior metal cable systems, there remains a potential source of cable degradation in the event the exterior of the rope is damaged by the grip clips. For example, if a breach occurs in the surface of the jacket for the rope, such as at the attachment point of the grip clips, water may seep inside the jacket and form a media to be excited by radio waves, resulting in heating of the safety rope, including the surrounding jacket, during activation of the antenna.
Accordingly, there remains a need for a durable safety system capable of being used in an adverse environment formed by radio frequency energy transmissions on tower structures.
The present invention provides a fall prevention construction for permanent attachment to a vertical tower, where the fall prevention construction includes a rope for receiving a security device attached to a worker, the security device being freely slidable along the rope except if the worker should begin to fall, in which case the security device grips the rope to prevent the worker from falling. The present fall prevention construction is particularly designed for use with a tower supporting a radio-frequency wave antenna such that radio waves from the antenna will impinge on the rope portion of the fall prevention construction.
In one aspect of the invention, a fall prevention construction for permanent attachment to a vertical tower including a radio-frequency wave antenna is provided. The fall prevention construction comprises a safety rope having first and second ends, and upper and lower anchor members for attachment to the first and second ends, respectively. The safety rope comprises a dry finish polyester core material, and an outer jacket is formed over the safety rope for preventing moisture from contacting the safety rope.
In another aspect of the invention, a fall prevention construction for permanent attachment to a vertical tower including a radio-frequency wave antenna is provided including a safety rope having first and second ends, and upper and lower anchor members for attachment to the first and second ends, respectively. An outer jacket is formed over the safety rope for preventing moisture from contacting the safety rope. At least the first end of the safety rope is formed in a loop for connecting engagement with a cooperating member of the upper anchor member, the loop being located adjacent a terminal portion of the first end and a laterally adjacent section of the safety rope. In addition, a water barrier surrounds the terminal portion of the first end and the laterally adjacent section of the safety rope.
In a further aspect of the invention, a fall prevention construction attached to a vertical tower including a radio-frequency wave antenna is provided including a safety rope having first and second ends, and upper and lower anchor members for attachment to the first and second ends, respectively. The safety rope comprises a dry finish polyester core material and an outer jacket is formed over the safety rope and extends substantially the length of the safety rope for preventing moisture from contacting the safety rope. At least the first end of the safety rope is formed in a loop for connecting engagement with a cooperating member of the upper anchor member, where the loop is located adjacent a terminal portion of the first end and a laterally adjacent section of the safety rope. Sleeve members surround the terminal portion of the first end and the laterally adjacent section of the safety rope, where the sleeve members are swaged into contact with the terminal portion and the laterally adjacent section. In addition, a water barrier surrounds the terminal portion of the first end, the laterally adjacent section of the safety rope and the sleeve members. The water barrier comprises a potting material substantially filling spaces between the terminal portion, the laterally adjacent section and the sleeve members.
Other features and advantages of the invention will be apparent from the following description, the accompanying drawings and the appended claims.
Referring to
The safety rope 16 of the present invention is intended for use in combination with a security device to be engaged on the safety rope 16 for securely attaching a worker to the safety rope 16. An example of such a security device is described in U.S. Pat. No. 5,855,251, which patent is incorporated herein by reference.
Referring to
The polyester dry rope 26 for the safety rope 16 of the present invention provides the characteristic of a water resistant core material to ensure that the interior of the safety rope 16 is free of moisture. The avoidance of moisture in the safety rope 16 is important in that water or moisture within the safety rope 16 could interact with the high energy radio waves emitted by the antenna 12, resulting in undesirable heating and possible deterioration of the safety rope 16. The polyester material of the dry rope 26 is further selected for its resistance to degradation in the presence of high energy radio waves as well as its lack of interference to the transmitted waves, while providing a strong, low-stretch support core for the safety rope 16.
The jacket 32 generally comprises a copolymer plastic material. Specifically, in one embodiment, the jacket 32 comprises a polyethylene copolymer for protecting the exterior of the dry rope 26 from the elements. The polyethylene copolymer of the jacket 32 is additionally substantially unaffected by the high energy radio waves produced by the antenna 12, and is resistant the ultraviolet rays of sunlight. Accordingly, the polyethylene jacket 32 provides an effective protective jacket for the dry rope 26 to ensure operational longevity of the safety rope 16.
Referring to
The first end 18 of the safety rope 16 comprises a loop portion 38 formed through the eye portion of the eye bolt 36 and extending around a steel thimble 40 which engages with the eye bolt 36. A terminal portion 42 of the safety rope 16 extends down from one side of the loop 38 and lies parallel to a laterally adjacent section 44 of the safety rope 16 extending down from the other side of the loop 38.
The terminal portion 42 and laterally adjacent section 44 are retained in a predetermined position relative to each other, to permanently maintain the loop 38, by means of substantially identical copper sleeve members 46 which are swaged into frictional engagement with the terminal portion 42 and laterally adjacent section 44 of the safety rope 16. In the preferred embodiment, three sleeve members 46 are provided in spaced relation to each other located at three attachment regions 43, 45, 47 (see
Referring to
As illustrated in
It should be noted that the sleeve members 16 are formed of copper because copper is a relatively malleable material which will not form fractures or cracks when sufficient force is applied to create the frictional engagement with the safety rope 16. The outwardly flared passages at the ends 48, 50 of the sleeve members avoids damage to the plastic material of the jacket 32 and well as to the material of the safety rope 16 during the swaging operation. In addition, the outwardly flared passages at the ends 48, 50 of the sleeve members 46 provide additional clearance space within the sleeve members 46 for accommodating movement of the polyethylene material of the jacket 32 as swaging pressure is applied through the sleeve members 46. It has been found that by providing the flared end passages, in combination with use of a relatively highly malleable material, e.g., copper, bulging of the material of the jacket 32 adjacent the ends of the sleeve members 46 can be avoided or minimized when performing the swaging operation. Avoidance of distortions of the jacket 32 is of particular importance in the application of the present invention in that maintenance of the integrity of the jacket is necessary to ensure long term protection of the dry rope 26 against moisture. It should be noted that protection against ingress of moisture into the safety rope 16 is particularly important in the area of the upper anchor member 22 where any moisture entering the jacket 32 could travel down between the jacket 32 and the dry rope 26 and pass into the area between the upper and lower anchor members 22, 24 where radio waves are emitted from the antenna 12.
In order to additionally ensure long term protection of the safety rope 16 against damage that may occur if moisture should pass through the jacket 32, a water barrier 56 is constructed around the terminal portion 42, the adjacent section 44 and the sleeve members 46, and extends down below the lower end of the terminal portion 42, as illustrated in
It should be understood that the lower, second end 20 of the safety rope 16 may be provided with a similar attachment configuration to that described for the upper end 18 of the safety rope 16.
Accordingly, it can be seen that in addition to providing a dry core safety rope 16, the present invention further ensures that the connection area of the safety rope 16, which experiences stresses to provide attachment to the tower structure 14, is provided with an additional protecting barrier against the elements.
While the form of apparatus herein described constitutes a preferred embodiment of this invention, it is to be understood that the invention is not limited to this precise form of apparatus, and that changes may be made therein without departing from the scope of the invention which is defined in the appended claims.