Abstract:
The present invention relates to problems how to keep cable arrangement functional, or at least make the damage as little as possible, after being exposed to different types of mechanical overloads. The problems are solved by methods and arrangements in which the securing means and the contact material of the securing means are arranged so that the cable can slide through the securing means when it is exposed to mechanical overloads.

Description:
FIELD OF INVENTION 
       [0001]    The present invention relates to a cable suspension device. In more detail a cable suspension device adapted to reduce the effects of mechanical overload on a cable suspension system. 
       BACKGROUND OF THE INVENTION 
       [0002]    One common way to route a cable, e.g. cables for electrical power, in a landscape is to hang them between poles. The cables, such as self-supporting overhead cables, cables reinforced with helically wound reinforcements, transmission lines, etc., are normally secured to the poles with the aid of suspension devices. 
         [0003]    One problem with this arrangement is that it is exposed to e.g. falling trees. This could heavily damage the arrangement and might, as a consequence of the damage, cause interruptions in the functions of the cable system. Repair of the system and interruptions, e.g. in electricity supply, can be very costly. 
         [0004]    One feature of the cable suspension arrangement is that it should be resistant to different circumstances that can affect the system, e.g. weather and falling air-planes. Heavy wind or snowfall can cause trees to fall down on the arrangement and cause mechanical overloads. The cable suspension arrangement should also be easy to mount or repair in a short period of time and be cost-effective. It is desirable to have a cable suspension arrangement that will eliminate the need of repair, and when repair is necessary, make the repair cost-effective with minimal use of tools and spare parts. 
         [0005]    One way to solve the problem with falling trees is so make broad roads where the cable is hanging, by cutting down all the trees around it. If possible at all, it is very costly and it does not solve the problem if an air-plane crash on the arrangement. 
         [0006]    The French patent application no 2798 783 describes a cable suspension device that will detach the cable when it is exposed to mechanical overload. This causes the cable to fall down on the ground. To repair, it will be necessary to have advanced tools for putting the cable up on the pole again. This could be costly. It could also be so that the function of the cable arrangement must be cut if the cable is situated on the ground, e.g. for security reasons. It is also very critical to have the right configuration of the cable suspension device so that the cable detach at the right moment. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention relates to problems how to keep cable arrangement functional, or at least make the damage as little as possible, after being exposed to different types of mechanical overloads. 
         [0008]    The problems are solved by methods and arrangements which let a secured cable have the possibility to slide through the cable securing means used for fixing the cable to e.g. a pole. 
         [0009]    In more detail the problems are solved by methods and arrangements in which the securing means and the contact material of the securing means are arranged so that the cable can slide through the securing means when it is exposed to mechanical overloads. 
         [0010]    According to the invention the problems are solved by arrangements and methods according to the claims. Further embodiments can be found in the independent claims. 
         [0011]    One major advantage of the invention is that the cable can take a lot of mechanical load before anything brakes and the cable fall down on the ground. The cable can be exposed to heavier mechanical force than with other solutions before it is out of function. 
         [0012]    Another advantage is that the pressure acting on the cable is reduced so that it will not permanently deform the cable. 
         [0013]    Another advantage is that the function of the cable suspension device is not very little dependant of the form and material of a secured cable. 
         [0014]    Another advantage is that even if the cable or the cable suspension devices need some repair or adjustment it is not critical to be fast, the system will still work without any risk of danger on the surroundings. 
         [0015]    Another advantage is that the maintenance of the system is simple and cost effective. 
         [0016]    The invention will now be described more in detail with the aid of preferred embodiments in connection with the enclosed drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0017]      FIGS. 1   a  and  1   b  illustrates a first embodiment of a cable suspension device. 
           [0018]      FIG. 2  illustrates a second embodiment of a cable suspension device comprising two cable securing means. 
           [0019]      FIG. 3   a  and  3   b  illustrates a cable securing means 
           [0020]      FIG. 4  illustrate details of a cable securing means 
           [0021]      FIG. 5  illustrate details of the contact material in the cable securing means 
       
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0022]      FIGS. 1   a  and  1   b  illustrates a first embodiment of a cable suspension device CSD comprising cable securing means CSM and a cable suspension device fastening means CSDF. The CSD could be mounted on e.g. a pole and a cable CE could be secured in the securing means CSM. 
         [0023]    The CSM comprises a first part CSMF and a second part CSMS suitable for securing a cable CE between them when brought together into a closed state. They can be hold together by e.g. bolts, hinges, springs or similar arrangements. In this case four bolts SSB keep CSMF and CSMS together. The CSMF and the CSDF is integrated in this embodiment. 
         [0024]    The CSM comprise a contact surface CS. A cable is secured by being in contact with the contact surface CS comprising the contact material SCM. 
         [0025]    The cable suspension fastening means CSDF is in this particular embodiment a hole at the top for hanging the CSD in a hook on e.g. a pole. The CSD can swing around the hook. 
         [0026]    Other types of fastening means are of course possible. It could e.g. be fixed mounted to a pole or integrated in the pole. 
         [0027]    It is however an advantage if the cable suspension device, or at least the CSM, have the possibility to swing. This will reduce the bending force on the cable when e.g. a tree falls down. The contact surfaces CS, between the CSM and a secured cable CE, is able to automatically position itself better along the line followed by the cable in the proximity of a pole. As a result, less bending stresses will-be applied to the cable, and the contact surface CS can be utilised optimally. This results in a low mean value of the mechanical stresses and strains on the cable, since the whole of said surface is constantly used. 
         [0028]    The cable securing means CSM could also be shaped so that the contact surface CS substantially follows the line of a secured cable CE. This could be a straight line or a line curvature in the proximity of a pole. 
         [0029]    The CSM is configured so that a cable secured in the CSM can slide through it if it is exposed to mechanical overload, e.g. if a tree falls on the cable between two poles. This has the effect that the system can take heavier load before anything breaks. Furthermore, if a mounted cable slides through the CSM, the angel between the cable CE and the pole will decrease and the force on the system will be less. 
         [0030]    A secured cable will slide on the contact material SCM when exposed to a mechanical overload. The SCM must therefore allow the cable to slide on it. The coefficient of friction between a secured cable and the contact surface CS, SCM could be between 0.1-0.6, preferable between 0.2-0.4. 
         [0031]    It is an advantage if the SCM is elastic so the contact surface CS could adapt to the shape of the cable. This will keep the pressure on the cable CE on a substantial constant level. Another advantage is that the pressure acting on the cable is reduced so that it will not permanently deform the cable. Furthermore, the CS could change its form when the cable is sliding on it. This is an extra advantage if the cable is not circular or symmetric. 
         [0032]    The SCM should preferably be softer than the material used for the secured cable, e.g. Thermoplastic Elastomers (TPE), thermoplastic rubber, rubber, Styrene Butadiene Styrene (SBS), Styrene Ethylene Butylene Styrene (SEBS), Ethylene Vinyl Acetate (EVA), Ethylene Butyl Acetate (EBA), Sylomer, sylodyn, Nitrile Butadiene Rubber (NBR), Styrene Butadiene Rubber SBR or silicone. The elasticity module of the SCM material should preferably be between 40-500 MPA. A secured cable should preferably have an elasticity module between 170-1200 MPA in the polymeric material. 
         [0033]      FIG. 5  illustrates a surface contact material SCM. It is and advantage if the SCM is foamed or foamed like, e.g. by having build-in cavities BIC. By using BIC it will be possible to make the material itself harder. A harder material makes it easier to attach the SCM to the CSM, CSMF and the CSMS in a resistant way. Softer material will easily deform when a secured cable is exposed to force. BIC also have the advantage that their size and form can be adapted to different parts of the SCM. There could e.g. be no BIC where the material is attached to the CSM and thereby make the fastening points stronger. The BIC is also easier and cheaper to produce than foamed material. A foamed or foamed like material also make the material adaptable to different types of cable. The sliding force between the material and a sliding cable is very little dependant on the dimension and form of the cable. 
         [0034]    If the cable has been exposed to mechanical overload and it has changed its position in the securing means CSM it is an easy operation to put it back in the right position again. The CSM can be opened up and the cable could be put in the right position. After putting the cable CE in its position, the cable CE can be secured by closing the CSM. The cable need never to be released from the suspension device. 
       Embodiment 2 
       [0035]      FIG. 2  illustrates a cable suspension device CSD comprising two cable securing means CSM 1 , CSM 2 . The CSD could be mounted on e.g. a pole and a cable could be secured in the two securing means CSM 1  and CSM 2 . In this particular embodiment there are two cable securing means, CSM 1  and CSM 2 , but it could be possible to have only one or more than two. In  FIG. 2  the first parts CSMF 1 , CSMF 2  of the CSM 1  and CSM 2  is illustrated. The second parts of CSM 1  and CSM 2 , CSMS 1  and CSMS 2 , which can be seen in the detailed illustration of  FIG. 3 , is not illustrated in  FIG. 2 . 
         [0036]    To make it easier to put a cable in place the CSM 1  and CSM 2  can be turned around the bolt B 1 , B 2 . This is illustrated in  FIG. 2  where the CSM 1 , CSMF 1  is hanging upside down compared to CSM 2 , CSMF 2 . When a cable is put into the CSD the two cable securing means have the position of CSM 1  in  FIG. 1 , hanging upside down. After the cable is in place, CSM 1 , and CSM 2  are turned around and a second part CSMS 1 , CSMS 2 , as can been seen in  FIGS. 3   a  and  3   b , of the cable securing means is attached, and the cable is secured by the securing screw bolt SSB 1 , SSB 2 . There are of course several possibilities to make it easier to put a cable into the CSD. This is only one example. 
         [0037]    The cable suspension device has fastening means CSDF, in this case a hole at the top for hanging the CSD in a hook on e.g. a pole. The CSD can swing around the hook. Other types of fastening means are of course possible. It could e.g. be fixed mounted to a pole or integrated in the pole. 
         [0038]    In this particular embodiment with two cable securing means, CSM 1  and CSM 2  are each one pivotably mounted on the CSD around a bolt B 1 , B 2 . 
         [0039]      FIG. 2  also illustrates, a rotable cable support RCS that forms a part of a cable carriage function in the suspension device. This has the function of making it easy to put the cable into the CSD. It has the form of a roller or wheel centred on a bolt RSB, having enlarged end regions that enable the cable to be centred in the suspension device when pulling the cable into and out of said device, in addition to a cable supportive function. It is possible to move the rotable support RCS away from the cable after having drawn the cable into or out of said cable suspension device CSD, so that the cable is able to rest on the cable securing means CSM 1 , CSM 2 . The rotable support RCS is moved away from the cable by loosing the bolt RSB and let the bolt slide through the slot ST 2 . 
         [0040]      FIGS. 3   a ,  3   b  illustrates a cable securing means CSM 1 , CSM 2  in detail. This is one example and other possibilities are of course possible. In  FIG. 3   a  a secured cable CE is illustrated. In order to enable the cable to be secured in the suspension device and to easily put it in and out of the CSM 1  and CSM 2 , the CSM 1  and CSM 2  consist of a first part CSMF 1 , CSMf 2  and a second part CSMS 1 , CSMF 2 . These are pivotally connected and can be secured to each other by a securing screw bolt SSB 1 , SSB 2 . The second part CSMS 1 , CSMS 2  can be attached to the first part CSMF 1 , CSMF 2  in different positions. In this embodiment by having different slots ST 1  for attaching a pivot PT, see also  FIG. 4 . This is to make it possible to adapt the CSM 1  and CSM 2  to different kinds of cables, especially if they have different dimensions. All kind of securing means are of course possible, several bolts, with or without hangings, one or several parts in different material etc. as long as there is a contact surface CS that can hold a cable in position. A cable is secured by being in contact with the contact surface CS comprising the contact material SCM. 
         [0041]      FIG. 4  illustrates the first part of the cable securing means CSMF 1 , CSMF 2  without the contact surface CS and the contact material SCM. The CSMF 1  is pivotaly mounted on the CSD around a bolt B 1 , B 2 . B 1  and B 2  passes through the CSM 1 , CSM 2  by a hole ST 3 ,  FIG. 3   b  and  4 . 
         [0042]    Apart from that the CSM 1  and CSM 2  are pivotably mounted, they are also movable mounted. The hole ST 3 ,  FIG. 3   b  and  4 , is made like a slot, and the bolt B 1 , B 2  is mounted so that the CSM 1  and CSM 2  can move by sliding in the slot ST 3 . 
         [0043]    As a result of the pivotal suspension of the CSM 1  and CSM 2 , the two contact surfaces CS, between the CSM 1 , CSM 2  and a secured cable CE, are able to position themselves automatically along the line followed by the cable in said device. This could be a straight line or a line curvature in the proximity of a pole, e.g. if a tree fall onto the cable and cause the cable to bend. As a result, no additional bending stresses will be applied to the cable, and the contact surface CS can be utilised optimally. This results in a low mean value of the mechanical stresses and strains on the cable, since the whole of said surface is constantly used. If the CSD is mounted on a hook and thereby can swing around it, like in this particular embodiment, it could be possible to have only one of the CSM 1 , CSM 2  pivotably mounted on the CSD, and still have the effect of that the two cable securing means CSM 1 , CSM 2 , and thereby the contact surfaces CS, positioning themselves in line with a secured cable CE. 
         [0044]    A cable secured in the CSM 1  and CSM 2  can slide if it is exposed to mechanical overload. This has the effect of that the system can take heavier load before anything breaks. If a mounted cable slides through CSM 1  and CSM 2 , e.g. if a tree falls on the cable between two poles, the angel between the cable CE and the pole will also decrease and the force on the system will be less. If the CSM 1  and CSM 2  are pivotaly mounted, like in this embodiment, the system can take even heavier load before anything breaks down. 
         [0045]    The CSM 1  an CSM 2  are, in this particular embodiment, also movably mounted. The CSM 1  and CSM 2  should be pushed towards or away from each other when a cable is secured. If a secured cable CE is exposed to a force, one of the cable securing means CSM 1 , CSM 2  will move in the slot ST 3  before it reaches its endpoint and the cable will start to slide on the surface CS. This means that the cable will start to slide in one of the cable securing means before it start to slides in the other. This has the effect that the start force is less than if the CSM 1 , CSM 2  have been fixed and thereby reduces the maximum force on the system when the cable is exposed to mechanical overload. 
         [0046]    Another solution to achieve the same effect is that e.g. CSM 1  is fixed to the CSD, and CSM 2  can slide in the slot ST 2  in two directions. This has the effect that the cable will slide in the cable securing means CSM 1  before it slides through the other cable securing means. It could be possible do configure the both cable securing means different to make the friction forces different and thereby reduce the start force even more. 
         [0047]      FIG. 5  illustrates the contact surface material SCM. The contact surface CS is made of a contact material SCM, integrated into the cable securing means CSM 1 , CSM 2 . The SCM of  FIG. 5  will fit into the first part of the cable securing means CSMF 1 , CSMF 2  of  FIG. 4 . A correspondent SCM will be fit into the second part CSMS of the cable securing means CSM 1  CSM 2 . 
         [0048]    A secured cable will slide on the SCM when exposed to a mechanical overload and thereby decreasing the damage on the system. The SCM must therefore allow the cable to slide on it. The coefficient of friction between a secured cable CE and the contact surface CS, SCM could be between 0.1-0.6, preferable between 0.2-0.4. 
         [0049]    It is an advantage if the SCM is elastic so the surface CS could adapt to the shape of the cable. This will keep the pressure on the cable CE on a substantial constant level. Another advantage is that the pressure acting on the cable is reduced so that it will not permanently deform the cable. Furthermore, the CS could change its form when the cable is sliding on it. This is an extra advantage if the cable is not circular or symmetric. 
         [0050]    The SCM should preferably be softer than the material used for the secured cable, e.g. TPE, thermoplastic rubber, rubber, SBS, SEBS, EVA, EBA, Sylomer, sylodyn, NBR, SBR or silicone. The elasticity module of the SCM material should preferably be between 40-500 MPA. A secured cable should preferably have an elasticity module between 170-1200 MPA in the polymeric material. 
         [0051]    The SCM should be foamed or foamed like, e.g. by having build-in cavities BIC. By using BIC it will be possible to make the material itself harder. A harder material makes it easier to attach the SCM to the CSM 1 , CSM 2 , CSMF 1 , CSMF 2 , CSMS 1 , CSMF 2  in a resistant way. Softer material will easily deform when a secured cable is exposed to force. BIC also have the advantage that there size and form can be adapted to different parts of the SCM. There could e.g. be no BIC where the material is attached to the CSM and thereby make the fastening points stronger. The BIC is also easier and cheaper to produce than foamed material. A foamed or foamed like material also make the material adaptable to different types of cable. The sliding force between the material and a sliding cable is very little dependant on the dimension and form of the cable. 
         [0052]    The form of the material SCM will change after being exposed to pressure. To keep the securing force on the first CSMF 1 , CSMF 2  and the second CSMS 1 , CSMS 2  parts of the CSM 1 , CSM 2  on a substantial stable level, a helical spring SG is mounted around the securing screw bolt SSB 1 , SSB 2 . When the SCM change its form, the spring will expand and pressure the first SCMF and the second part SCMS towards each other. Other solutions with different kind of springs are of course possible, e.g. using torsion springs. The spring SG could be configurated so that the pressure on a secured cable is on the appropriate level. Then it will be no need for controlling the momentum of which the bolt SSB is secured. 
         [0053]    If the cable has been exposed to mechanical overload and it has changed its position in the securing means CSM 1 , CSM 2  it is an easy operation to put it back in the right position again. The CSM 1 , CSM 2  can be opened up and the cable could be put in the right position. If necessary the rotable cable support RCS could be used by temporary putting in its upper position so that the device can be used as a cable carriage. After putting the cable CE in its position, the cable CE can be secured by closing the CSM 1 , CSM 2 . The cable need never to be released from the suspension device. 
         [0054]    The invention is of course not limited to the above described and in the drawings shown embodiments but can be modified within the scope of the enclosed claims.