The invention concerns a tensioning system in applications where a cable, wire, rope, or hose is required to suspend and be tensioned at the same time, such as those to be used in port, industrial or other facilities, in gantry cranes, cranes, quarries and other applications.

Tensioning systems are already known. For example, in container loading- unloading systems in port facilities, the cables used to transfer motion from the engine room to the lifting-lowering and container transferring platform (spreader), are many (usually up to 50 cables) and are located within a single housing. They namely comprise a multicore cable. Many ports do not even use cable tensioning systems and the multicore cable is usually rolled in a metal basket, so that even with the slightest air blowing (at a much lower velocity than the maximum one allowable for work in height) the cable either comes out of the basket or is cut, therefore causing immediate interruption of loading-unloading operations. The drawback of these cable tensioning systems (of the multicore cable essentially), used in the market today, is that they are in their majority either complicated or heavy systems. A typical example is the case where the cable is rolled on a reel and the tensioning system features a brush carrier with rings and brushes - which in many cases still does not provide the required security to smoothly guide the cable in the event of adverse weather conditions (mainly wind) - because the brushes are displaced due to platform (spreader) vibrations. In addition, complex tensioning systems have the added problem of difficult maintenance and repair, which apart from being time-consuming, requires that loading- unloading operations are interrupted again, thus causing high costs and delays. The above systems are also very heavy, which adds even more to the already heavy platform (spreader). The above disadvantages are remedied by the cable tensioning system of the present invention, which apart from offering high stability, durability and safety of construction, without the cable being able to come out of the basket where it is rolled, solves at the same time a further technical problem, i.e. that depending on the speed of the cable, the tensioning system engine gets the required speed through a voltage converter (inverter), allowing the cable to be always tensioned under all weather conditions, following the platform (spreader). There are also other advantages such as regulating the pressure in the pair of the cable driving pulleys, the smooth entry of the cable in the cable storage basket and "spreading" of system legs and system operation in the "spread" position in case of repair-maintenance of the system.

The special feature in the tensioning system according to the present invention is that through the voltage converter (inverter) the engine speed of the system is adjusted according to the engine speed of lifting-lowering of the platform (spreader). In addition, the drive from the system's engine is transfered to the clutch and from there to the driving pulley. In addition, one of its two legs (where the loose pulley is mounted) carries a cylindrical rod with screwing, bearing a spring and a nut, through the rotation of which the loose pulley is somewhat moved, thus setting the clamping of the cable between the two pulleys (driving and loose pulley). To drive the cable, a pair of rollers and a pair of pulleys are used with axes parallel to one another, as well as a pair of rollers with axes in transverse plane to the foregoing ones, to prevent the cable from moving in horizontal direction. The material of the outer ring -featuring the groove all around- of the pulleys is either rubber or plastic, or synthetic, depending on the use of the tensioning system. To smoothly drive the cable into the basket, the inner diameter of the fixed base collar of the tensioning system is greater than the inner diameter of the basket. In addition, the base collar has two hinges, each of which has two parallel plates transverse to the collar level, each bearing two circular holes, through which pins with fuses are passed, around the axis of which the two legs of the tensioning system rotate while it features free round holes as well, through which pins with fuses are passed, after its legs have spread and in order to be fixed in the "spread" position. The voltage converter (inverter) is either mounted in the engine room or on the platform (spreader) and is regulated in such a way that, when the voltage of the lifting-lowering engine of the platform (spreader) exceeds a critical voltage (~30-40 Volt), the engine of the tensioning system is turned on, initially with 30-40% of the speed, and then when the platform (spreader) reaches its maximum speed, i.e. the lifting-lowering engine of the platform (spreader) reaches its maximum voltage, the tensioning system engine reaches the 100% of its speed too. Power supply to the system engine is interrupted for safety reasons either when current intensity is lower than required, or when current intensity is higher than required (overcharging) or when there is lack the current voltage through the voltage converter (inverter). The same happens when the engine of the lifting-lowering platform (spreader) runs backwards, i.e. when the spreader descends (lowering); then also the voltage converter (inverter) does not get activated and therefore neither does the system engine, but in this case just because the cable is moving, the clutch rotates only on the inner side, but without transmitting any drive to the drive pulley. The tensioning system of the present invention is suitable for application in a wider port loading-unloading system, wherein the tensioning system is connected to the upper side of the storage basket of the cable suspending from the engine room. Figure 1 shows a perspective view of the tensioning system of the present invention.

Figure 2 shows a perspective view of the tensioning system in operating position, in a clamping position of the threaded rod-spring, where the correct guiding of the cable through a system of pulleys-rollers pairs is shown, and an indicative cooperating with the cable storage basket.

Figure 3 shows a plan view of the collar of the tensioning system and its relative position in relation to the cable storage basket.

Figure 4 shows a side view of the tensioning system in its "spread" position, in case of e.g. repair, maintenance. Figure 5 shows two alternative ways of mounting the voltage converter (inverter) in collaboration with the tensioning system.

Figure 6 shows a loading-unloading system at a port facility, where the tensioning system of the present invention is used.

One way of applying the invention is described with reference to drawings. Figures 1 and 2 show the tensioning system in operating position, consisting of the engine (1), which drives the clutch (2), whereby rotational drive is transmitted to the driving pulley (4). Depending on the speed of the platform (spreader) (12), the engine (1) gets through voltage converter (inverter) (6) the required speed, allowing the cable (11) to be always stretched under all weather conditions, following the platform (spreader) (12). The leg (8) has bearings (38) through which a pin is passed (39), around the axis of which an arm (10) rotates consisting of two parallel metal curved level plates, the end of which carries the loose pulley (5). The arm (10) has a second pair of parallel curved metal plates (9), of greater length, the ends of which support the axes of rollers (19) and (23). The two parallel plates of the arm (10) are also connected by a cylindrical component (40) in the centre of which there is a cylindrical hole (41) through which a cylindrical rod (20) with screwing in a spring (21) passes, bearing also a nut (22). Regulating the tightening of the cable (11) between pulleys (4) and (5) occurs by tightening the nut (22). By tightening the nut (22), the free pulley (5) is somewhat moved by pressing or releasing the cable (11) to achieve the appropriate pressure. The cylindrical rod (20) is screwed at its base to a T-shape part (42) of cylindrical section, the long side of which constitutes the rotation axis passing through holes (43) of plates (44), which are firmly attached to the leg (8).

To drive the cable (11), the system has a pair of rollers (19) and (23), a pair of pulleys (4) and (5) with axes parallel to the axes of the rollers (19) and (23) and a pair rollers (24) and (25), whose axes are at a level transverse to the level of the rollers (19) and (23) and the pulley (4) and (5), to thus prevent the cable (11) from moving in a transverse horizontal direction. The material of the outer ring (45) -featuring the groove of the pulley all around- of the pulleys (4) and (5) is either rubber or plastic, or synthetic, depending on the use of the tensioning system.

Figure 3 shows that to smoothly drive the cable (11) into the basket (16), the inner diameter of the fixed collar (28) of the tensioning system must be greater than the inner diameter (26) of the basket (16). It would be good to have rubber rollers (27) all around at the upper collar of the basket (16), or under the collar (3) for better rolling and for avoiding damage to the cable (11), when the system operates in an "spread" position. Figure 4 shows the cable tensioning system in the "spread" position in case the system needs servicing, e.g. in case of engine (1), clutch (2) etc. failure. In this case, the tensioning system is easily opened by means of two hinges (18) welded at the fixed base collar (3) and connecting the two individual legs (7) and (8) of the system to the base collar (3). The legs (7) and (8) are fixed in the "spread position" for the purpose of repair. Spreading is implemented under the following procedure: After the pair of rollers (24) and (25) are removed from the tensioning system, the roller (19) needs then to be removed to release the cable (11). Open [rotate around the hinge (18)] the leg (8) of the system along with all the components mounted on it (e.g. loose pulley (5), the arm (9), the arm (10), etc.). Then open the second leg (7) as well in a similar manner with all components mounted on it (e.g. the engine (1), clutch (2), the driving pulley (4) etc.). Each hinge (18) has two parallel plates (29), transverse to the base collar level (3), each of which has two circular holes (30) and (31). A pin (32) with fuses (33) passes through the holes (30) around the axis whose leg (7) rotates on one side and the leg (8) on the opposite side of the collar (3). After spreading legs (7) and (8), pins (35) with fuses pass through the holes (34) to stabilize them in the "spread" position. In this case, the cable (11) can function normally only with the basket (16), as long as weather conditions permit it.

Figure 5 shows two alternative methods of mounting the voltage converter (inverter) (6). The first method (a) is to have a panel (14) in the engine room (13) with converters (inverter) (6), which power the tensioning system engine (1) using wireways of the multicore cable. The engine (1) works only when the platform (spreader) (12) lifts (heaves up), either carrying a container (15) or not, when it also rolls the cable (11) into the basket (16), while when the platform (spreader) descends (lowering) (12), the engine (1) does not work and the cable (11) is smoothly unrolled. The second method (b) is to mount the voltage converter (inverter) (6) above the spreader (12). In both cases (a and b) depending on the speed of the lifting platform (spreader) (12) engine (17), the engine (1) of the cable tensioning system is also automatically regulated through the voltage converter (inverter) (6). More specifically, the spreader (12) lifting engine (17) (or more synchronized engines in parallel connection) operates with DC of 0 to about 520 Volt voltage. The higher the voltage, the faster the spreader (12) moves and the cable (11) is rolled into the basket (16). The voltage converter (inverter) (6) is regulated in such a way that, when the voltage of the engine (17) exceeds a critical voltage (~30-40 Volt), the engine (1) is turned on, initially with 30- 40% of the speed, and then when the platform (spreader) (12) reaches its maximum speed, i.e. the lifting-lowering engine (17) of the platform (spreader) (12) reaches its maximum voltage, the engine (1) reaches the 100% of its speed too. Power supply to the engine (1) is interrupted for safety reasons either when current intensity is lower than required, or when current intensity is higher than required (overcharging) or when there is lack the current voltage through the voltage converter (inverter). Also when the lifting-lowering engine (17) of the platform (spreader) (12) operates backwards, i.e. when the spreader descents (lowering), then the voltage converter (inverter) (6) is not activated and therefore neither is the engine (1). Since the cable (11) is of course moving in this case , only the clutch (2) rotates but without driving the pulley (4). Figure 6 shows a port facility loading-unloading system, which is an example of a broader system, where the tensioning system of the present invention is integrated, applied and used. The metal frame (36) of the facility, which may be a port gantry crane or other structure, the engine room (13) where the electrical panels are located, the engine of the lifting-lowering (17) platform (spreader) etc., the lifting-lowering (15) and container-transferring platform (spreader) (12), which is hung from the engine room by means of a rope's and pulley's system, the cable (11) which connects the engine room and the platform (spreader) (12), the cable (11) storage basket (16) and the tensioning system (37) of the present invention, which keeps the cable (11) stretched, are shown.

In the drawings displayed here, emphasis has been given to the implementation of the tensioning system for cables in a loading-unloading system at port facilities. We would like to stretch out, however, that it may be implemented in any other application such as industrial plants, gantry cranes, cranes, quarries and any other installation where stretching a suspending cable or wire or rope or hose is required.