Abstract:
The extensible segment in an anchor rode comprises a rubber core enclosed in a base rope along the central axis of the base rope. A braided cover further encloses an intermediate portion of the rubber core inside the base rope. The braided cover is made of braided cover strands embedded in the rubber core, and un-braided cover strands extending over the two ends of the rubber core. The un-braided cover strands are weaved into the base rope to retain the rubber core longitudinally inside the base rope.

Description:
FIELD OF THE INVENTION 
     This invention pertains to mooring ropes and cables and more particularly it pertains to an anchor rode having an extensible segment built therein and a method for manufacturing this extensible segment. 
     BACKGROUND OF THE INVENTION 
     Stretchable cordage are used as mooring cables and anchor rodes for partly absorbing the stresses caused by wave actions on small boats, on buoys or on similar floating structures, for preventing damage to these crafts and floating structures and for preventing the loosening of their anchors. Stretchable cordage are also used as tow ropes for dampening the shocks of pulling an object from rest. Some of the stretchable cordage of the prior art are described in the following documents: 
     U.S. Pat. No. 4,258,608 issued on Mar. 31, 1981 to John L. Brown; 
     U.S. Pat. No. 4,426,908 issued on Jan. 24, 1984 to Martin Ullmann; 
     U.S. Pat. No. 4,534,262 issued on Aug. 13, 1985 to Richard C. Swenson; 
     U.S. Pat. No. 4,597,351 issued on Jul. 1, 1986 to Edward C. Brainard, II; 
     U.S. Pat. No. 5,483,911 issued on Jan. 16, 1996 to Ronald N. Kubli, and 
     CA 1,087,930 issued on Oct. 21, 1980 to Bertil Brandt. 
     Generally, the stretchable ropes of the prior art are made of a rubber rod or tube enclosed in the central portion of a rope. A tension on the rope causes the braided outside layer of the rope to compress the rubber core radially, which causes the rope to elongate, thus providing the rope with elastic properties. The length and diameter of the rubber core is proportional to these elastic properties. 
     An anchor rode is often partially wound on a capstan or around sheaves, and has shackles or knots at both ends thereof. Therefore, an anchor rode needs to be non-elastic along the segments thereof which are used for tying and along the segments susceptible to slippage and sharp bending. Hence, it is often desirable to make only a short segment of the anchor rode extensible as opposed to its full length. 
     In the past, this characteristic has raised difficulties in preventing the longitudinal movements of rubber core inside the base rope during repeated elongations and retractions of the rope. The methods of the prior art to retain the rubber core inside the base rope consists of using high strength tape and ring clips to squeeze the base rope at each end of the rubber core. It is believed that theses tapes and clips are subject to deterioration from fatigue stress and exposure to the harsh environment in which these ropes are used. Consequently, the ropes must be inspected often and repaired in order to maintain their integrity. 
     Moreover, the rubber cores in the stretchable ropes of the prior art are generally not subject to elongation with the outside layer of the base rope. The relative movement of the outside braided layer over the rubber core during repeated elongations and retractions causes friction and wear of the outside braided layer and of the rubber core. It will be appreciated that all relative movements between the outside braided layer and the rubber core have an adverse effect on the useful life of the rope. 
     Although the elastic cordage of the prior art deserve undeniable merits, it is believed that a need still exists for an extensible segment in an anchor rode, in which the rubber core does not move inside the braided outside layer of the base rope and consequently reduces the friction wear inside the base rope in order to prolong the useful life of the anchor rode. 
     SUMMARY OF THE INVENTION 
     In the present invention, there is provided an extensible segment in an anchor rode in which the rubber core is held longitudinally along the central axis of the base rope, to reduce friction related wear of the base rope and of the rubber core. 
     Broadly, the extensible segment in an anchor rode comprises a rubber core enclosed in a braided base rope along the central axis of the base rope. A braided cover further encloses an intermediate portion of the rubber core inside the base rope. The braided cover is made of braided cover strands embedded in the rubber core, and un-braided cover strands extending over the two ends of the rubber core. The un-braided cover strands are weaved into the base rope to retain the rubber core longitudinally inside the base rope. 
     The extensible segment according to the present invention is advantageous to disperse peak load in an anchor rode. Its construction prevents the rubber core to move along the base rope during repeated elongation and retractions of the rope, and enhances the resiliency of the extensible segment by applying tension as well as compression stresses to the rubber core. Friction generated by relative movement between the rubber core and the base rope is practically eliminated due the encapsulated braided cover being in contact with the braids of base rope. 
     Still another feature of the present invention is that it is susceptible of a low cost of manufacture with regard to both materials and labour, and which accordingly is then susceptible of low prices of sale to the consumer, thereby making such extensible segment economically available to the public. 
     Other advantages and novel features of the present invention will become apparent from the following detailed description. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     One embodiment of this invention is illustrated in the accompanying drawings, in which like numerals denote like parts throughout the several views, and in which: 
     FIG. 1 is a perspective view of a rubber rod used to manufacture the extensible segment according to the preferred embodiment of the present invention; 
     FIG. 2 is a perspective view of the rubber rod enclosed in a braided cover; 
     FIG. 3 is a perspective view of the encapsulated rubber rod inserted into a base rope; 
     FIG. 4 is a perspective view of the encapsulated rubber rod inserted into the base rope, wherein the braided cover has been undone over a nominal distance at both ends of the rubber rod; 
     FIG. 5 is a partial view of the base rope with the encapsulated rubber rod inserted completely into the base rope, and the un-braided strands extending outside the base rope; 
     FIG. 6 is a partial view of the base rope with the encapsulated rubber rod inserted completely into the base rope, and the un-braided strands weaved into and with the braids of the base rope. 
     FIG. 7 is a partial view of an anchor rode having an extensible segment according to the preferred embodiment built therein. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will be described in details herein a specific embodiment, with the understanding that the present disclosure is to be considered as an example of the principles of the invention and is not intended to limit the invention to the embodiment illustrated and described. 
     Referring to FIGS. 1-7, the extensible segment  20  in an anchor rode according to the preferred embodiment comprises broadly, a rubber rod  22  encapsulated in a braided cover  24 . The braided cover  24  is embedded into the surface of the rubber rod  22 . The encapsulated rubber rod  26  forms the core of the extensible segment of a base rope  28 . The strands  30  of the braided cover  24 , at both ends of the encapsulated rubber rod  26 , are weaved into and with the braids  32  of the base rope  28  for retaining the rubber rod  22  firmly into and along the base rope  28 . 
     The preferred extensible segment  20  in an anchor rode comprises a rubber rod  22  having a diameter of about twenty-five (25) mm., and a length of about five (5) meters. 
     The preferred braided cover  24  embedded into the surface of the rubber rod  22  is made of high module polyethylene fibers which are applied at maximum pitch angle. The preferred braiding is referred to in the industry as twenty-four (24) carrier by two (2) ply, meaning there are forty-eight (48) strings of fibers that are paired; one half are left-handed, the other half are right-handed. 
     The preferred base rope  28  in which the rubber rod  22  is inserted is a twenty-five (25) mm., twelve (12) strand rope made of high module polyethylene. 
     A preferred method for manufacturing the extensible segment  20  is described as follows: 
     A. Obtaining an extruded rubber rod  22  as represented in FIG.  1 . The preferred rubber rod is crude natural rubber, non-vulcanized, and having a durometer value of seventy (70). 
     B. Applying a tack coat on the rubber rod  22  and allow the coat to dry. 
     C. Passing the rubber rod through a braiding machine, and forming the braided cover  24  at maximum pitch angle over the rubber rod  22 . 
     D. After the braided cover  24  is formed over the rubber rod  22 , as illustrated in FIG. 2, the encapsulated rubber rod  26 , is placed in an oven and vulcanized to give the rubber its resilience and to cause the fibers of the braided cover  24  to sink into and become embedded into the surface of the rubber rod  22 . The encapsulated rubber rod  26  has an outside diameter of about thirty (30) mm. 
     E. A coat of urethane marine finish paint is then applied to the encapsulated rubber rod and is allowed to dry completely. 
     F. The encapsulated rubber rod  26  is then inserted into the base rope  28  as illustrated in FIG.  3 . This is achieved by squeezing the base rope like an accordion to make room for the encapsulated rubber rod  26  to fit inside the base rope, and inserting the encapsulated rubber rod through the braids  32  of the base rope  28  without cutting any of the braids  32  of the base rope  28 . 
     G. Before completely inserting the encapsulated rubber rod  26  into the based rope  28 , a section ‘A’ of about half a meter of braiding at each end of the encapsulated rubber rod is undone to liberate six (6) strands  30  containing eight (8) strings of fibers per strand, as illustrated in FIG.  4 . 
     H. The entire length of the encapsulated rubber rod  26  is then pulled inside the base rope  28 , until the un-braided strands  30  are entirely within the base rope  28 . 
     I. The base rope  28  is pulled tight over the encapsulated rubber rod  26  to remove and wrinkle in the base rope  28  and to smoothen the base rope  28  over the encapsulated rubber rod  26 . 
     J. The un-braided strands  30  are then extracted from the base rope  28 , as illustrated in FIG. 5, using a pointed tool. The strands  30  of the braided cover are extracted at equal intervals around the circumference of the base rope  28 . The strands  30  of the braided cover are extracted through the base rope at the same place ‘A’ they leave the rubber rod  22 . 
     K. Once the strands  30  of the braided cover  24  have been extracted, these are pulled firmly and evenly. 
     L. The six (6) un-braided strands  30  are then weaved into the base rope  28  as illustrated in FIG. 6, by a process referred to as “over and under”. This process is carried out until all the un-braided strands  30  are tucked into the base rope  28 . 
     M. The other end of the extensible segment  20  is done in a same manner by repeating the steps J, K and L. 
     The extensible segment  20  according to the preferred embodiment is made relatively quickly, without cutting any braid in the base rope or otherwise affecting the tensile strength of the base rope  28 . The rubber rod  22  is held firmly inside the base rope  28  by the un-braided strands  30  such that there is no movement of the rubber core  22  inside the base rope  28 . 
     Furthermore, the weaving of the strands  30  of the braided cover  24  into the braids  32  of the base rope  28  transmits some of the longitudinal stresses in the base rope  28  to the rubber rod  22  causing the rubber rod  22  to stretch with the rope. Hence the rubber rod  22  is subject to both tensile stresses and compression stresses. The stiffness of the extensible segment  20  is thereby increased. 
     It will be appreciated that rubber rods and base ropes with other dimensions will provide extensible segments with different properties. Therefore, a rubber rod and a base rope must be selected according to the intended purpose of the rope. The extensible segment  20  described herein with a rubber rod length ‘B’ of about five (5) meter, as illustrated in FIG. 7, has been found convenient for use as anchor rodes for retaining small fishing boats, small sailing crafts, buoys and floating docks. 
     While one embodiment of this invention has been illustrated in the accompanying drawings and described hereinabove, it will be evident to those skilled in the art that changes and modifications may be made therein without departing from the essence of this invention, as set forth in the appended claims.