Background of the Invention

Field of the Invention

The invention relates to installation of overhead cables or wires in general and more specifically to a device and a method for aerial installation or stringing of overhead cables or wires, suitable for installation by helicopter, or other type of aircraft.

Background Art

Installation of overhead cables, wires, lines, etc., such as for example power lines, can be done using a helicopter, or other type of aircraft, that holds and pulls an end of a cable forward while stringing it through a series of pulley blocks, each arranged at the top of a tower. The cable may be a wire, a power cable or other current-carrying wire or cable, or it may be an installation wire used as a guide for later installation of the wire or current-carrying cable. The cable or wire is typically run out and guided via pulley blocks suspended or fastened at the top of a tower or pole, for later disengagement from the pulley block and permanent installation of the cable at the top of the towers.

As the cables to be installed have requirements for the minimum bending radius which is permitted in order to ensure that the cable is not damaged by overbending, it is important that the pulley blocks or pulley block assemblies are designed to ensure that the bending of the cable is restricted in order to meet the specified requirements for the cable.

Often, there is a need for one or more operators in the tower or on a platform at height, to assist in guiding and/or inserting the cable into the pulley block. Such towers can be up to 120 m tall, or even more, and there is a significant risk involved, as well as time spent climbing the towers and for safeguarding. When the cable is inserted, the helicopter, or other type of aircraft, moves on to the subsequent tower.

State of the art is reflected in pulley blocks arranged at the top of a tower, wherein the cable is laid over a sheave or roller to support the hanging cable between each tower or mast. In certain areas, for example in a valley or other locations with towers having significant height difference, the cable will experience upwards tension resulting from adjacent towers where the pulley block is located at a higher level. In such a scenario, the cable will be pulled upwards and out of the pulley block of the lower tower, and there is a need for a type of pulley block that can restrain the cable, holding it down in the pulley block.

Such pulley blocks can be referred to as hold-down pulleys or hold-down pulley blocks.

Since installation or stringing of aerial cables or wires in towers are often performed using a helicopter, or other type of aircraft, with the assistance of an operator in the top of the tower in order to properly position the cable in relation to the pulley block and to insert it, the operation involves a huge risk for the operators in the tower and the aircraft pilot. Even in situations where an operator in the tower is not necessary, helicopter pilots, or other type of aircraft pilots, may have to perform difficult and possibly dangerous manoeuvres in order to approach and lay the cable or wires correctly.

From prior art one should refer to JPS59117405 A which discloses an arrangement with three horizontal rollers and two vertical rollers wherein one roller is hinged allowing it to swing open. JPH10243512 A discloses four rollers perpendicular to each other, wherein one roller is hinged for inserting a wire.

LIS2017229848 A1 discloses an arrangement with two rollers and a spring-loaded gate in relation to a guide arm for use with helicopter.

US2020220338 A1 discloses an arrangement with multiple rollers and a spring-loaded gate in relation to a guide arm.

JP2006340484 A discloses an arrangement with eight rollers for holding an overhead wire.

One should further refer to KR102079472 which discloses a wire holder for working with live wires and an auxiliary crossarm having the holder attached thereto.

US 4129287 A discloses a conductor stringing block adapted to be threaded with a hauling line dropped by helicopter and having a suspension yoke connected at its ends to the opposite sides of the block frame.

US 4301994 A discloses a bundle conductor stringing block having a main frame constructed essentially of structural steel components and including a cantilever suspension yoke positioned to form a tow-line receiving passage through which a helicopter can dispense a conductor tow-line onto a central one of multiple sheaves. KR 20040039701 A discloses an electric wire guide roller for exchanging an electric line, provided to prevent the generation of a short circuit, a malfunction, and an electric shock by installing temporarily electric wires at an arm of an electric pole in a process for exchanging electric wires.

KR 101311453 B1 discloses a cabling pulley and a cable replacement method using the same, provided to improve construction quality by guiding a cable cover not to be peeled off form a cable during a cable replacement work.

There is therefore a need for a device and a method to overcome the above- mentioned problems. In particular, there is a need for a device that provides for an easy, efficient and safe way to guide and install an overhead cable or wire into a pulley block installed in the top of a tower, and especially the forces involved in installing the cables.

Summary of the Invention

Problems to be Solved by the Invention

Therefore, a main objective of the present invention is to provide a cable or wire pulley block with improved safety during installation. It is an object to reduce or avoid the need for manual assistance at height, for example in the top of a tower or pole, during installation of the cable or wire in the pulley block and more specifically to avoid having operators manually inserting a cable or a wire into the pulley block. Furthermore, it is an object to avoid the need for operators in a tower or a platform at height during installation and/or to avoid having a helicopter, or other type of aircraft, in the air located directly above or in the vicinity of the operators in the tower. It is also an object of the invention to aid the pilot of the aircraft in aiming, positioning and inserting the cable or wire into the pulley block, thereby providing a safer and more reliable installation process and also more time efficient.

Furthermore, it is an object to provide a cable or wire pulley block suitable for installation of overhead cables or wires, in particular by use of helicopter, or other type of aircraft, that is capable of supporting cable loads in particular during installation. In addition, the rollers of the pulley block should be able to handle pulling of up to 6 km or more of cable through the pulley block by use of a pre-installed stringing wire.

Yet another object of the invention is to provide a cable or wire pulley block that prevents overbending of cables and/or wires. Overbending of cables or wires may result in internal damage or breakage of wires which is not visible from an outside of the cable and thus it is important to prevent this from happening.

Means for Solving the Problems

The objective is achieved according to the invention by a pulley block for installation of an overhead cable or wire as defined in the preamble of claim 1 , having the features of the characterising portion of claim 1 .

A number of non-exhaustive embodiments, variants or alternatives of the invention are defined by the dependent claims.

The present invention attains the above-described objectives by a pulley block with an enclosure to retain the cable or wire from sideways (transverse) and/or up/down movements and that allows and aids in the cable or wire being pulled through the pulley block for transport towards the subsequent structure along the route. The enclosure is made up of rollers arranged to create a channel for accommodating and retaining the cable or wire and for restricting movement of the cable or wire in its transverse plane. The channel comprises a closable entrance, to allow the cable or wire to be inserted transversely into the enclosure. A guiding means, such as an inclined guide arm, is arranged such that when the cable or wire is laid onto the arm, the cable or wire will, due to gravity and/or pulling forces, glide down towards the entrance, open the entrance, if not already open, and the entrance will automatically close as the cable or wire has passed the entrance.

Thus, in a first aspect of the invention, a pulley block for installation of an overhead cable or wire is provided. The pulley block comprises a plurality of rollers arranged in spaced relation to create a channel for accommodating and retaining the cable and restricting movement of the cable in its transverse plane, the channel having a closable entrance for inserting a cable or wire into the channel. The closable entrance is provided by at least one roller being a gate roller moveable between at least a closed position and an open position. The at least one gate roller is configured to be automatically movable from the open position to the closed position when the cable or wire is inserted into the channel. The pulley block further comprises means for guiding the cable or wire towards the entrance. The pulley block is suitable for installation above ground on a structure, such as being suspended or fastened in a tower or pole, or fastened to a building structure.

In an embodiment, the at least one gate roller is arranged vertically or inclined in its closed position, such that a cable or wire can be inserted from a side of the pulley block. In a preferred embodiment, the pulley block comprises means for moving the at least one gate roller from the closed position to the open position. Preferably, the at least one gate roller is initially in closed position before inserting a cable into the channel. The means for moving the at least one gate roller from the closed position to the open position comprises in one embodiment an opening device actuated by at least one of the group comprising a pressure from the cable, a remotely operated controller, and a sensor for registering the presence of a cable on the means for guiding. Furthermore, the means for moving the at least one gate roller from the closed position to the open position may comprise a hinge mechanism configured to allow the at least one gate roller to pivot open in response to pressure from the cable or wire. In an embodiment, a biasing mechanism is provided, biasing the at least one gate roller in the closed position. In a preferred embodiment, the hinge mechanism comprises at least one spring for biasing the at least one gate roller in the closed position.

In a further embodiment, the means for guiding the cable comprises an inclined guide arm terminating at the entrance of the channel. By inclined, it is also meant that the guide arm may be curved sloping downwards, the purpose being to provide a sliding surface guiding the cable towards the entrance.

In an yet an embodiment, the pulley block comprises a locking mechanism for preventing the rollers in connection with the closable entrance to spread apart when exposed to loads from the cable, i.e. restraining deformation of the closable entrance axially, thus preventing misalignment of the at least one gate roller when in closed position. Said locking mechanism may be configured for retaining a swinging end of the gate roller axially when in closed position.

In an embodiment, the pulley block comprises a locking mechanism and/or an adjusting device.

In an embodiment, the pulley block comprises two sets of vertical rollers and two sets of horizontal rollers, wherein one set of vertical rollers are arranged on each side of the pulley block, and wherein one set of horizontal rollers are arranged at the upper and one set at the lower end of the pulley block, and wherein the rollers of one of the sets of vertical rollers are gate rollers, providing the closable entrance.

In an embodiment, the pulley block comprises means for indicating that the cable or wire is actually inserted into the channel of the pulley block, such that it is easier to confirm from a distance that the cable is installed into the channel of the pulley block.

In a second aspect of the invention, a method is provided for installing an overhead cable or wire in a series of structures, the method comprising: a) installing a pulley block according to any of the preceding paragraphs at a distance above ground on each structure in the series, b) pulling an end of the cable or wire towards and beyond a first installed pulley block, c) arranging the cable or wire on the means for guiding the cable of said first pulley block, d) continuing to pull the cable or wire so that the cable or wire moves into the channel through the closable entrance, causing the at least one gate roller of the closable entrance to automatically close, e) continuing to pull the cable or wire towards the subsequent structure of the series, and repeating steps c and d for each subsequent pulley block .

The structures referred to above includes, but is not limited to, towers, poles or building structures and parts thereof extending a distance above ground.

Pulling of the cable or wire is preferably done by an aircraft, such as a helicopter.

Effects of the Invention

The present invention comprises a technological advantage over known systems in that at least one gate roller comprises means for automatic closing when the cable is inserted through an entrance to an enclosure of the pulley block and means for guiding the cable towards the entrance. The effect of this is that a cable can be installed in the pulley block without assistance from an operator in the tower. The helicopter pilot, or other type of aircraft pilot, can insert the cable/wire on his/her own from the aircraft, and there is no need for an operator in the tower. Since the enclosure can be made up of rotatable rollers, the cable/wire may be pulled through the pulley block and towards the subsequent tower without any significant resistance or friction. The pulley block is thus capable of handling loads in multiple directions, such as upwards, downwards, and transverse pulling forces from the cable.

The present invention provides several further advantageous effects such as reduced risk, higher efficiency, and reliability.

It also makes it possible to install cables/wires in areas where the cable/wire will be pulled upwards or sideways from the pulley block without assistance from an operator in the tower. Brief Description of the Drawings

The above and further features of the invention are set forth with particularity in the appended claims and together with advantages thereof will become clearer from consideration of the following detailed description of an [exemplary] embodiment of the invention given with reference to the accompanying drawings.

The invention will be further described below in connection with exemplary embodiments which are schematically shown in the drawings, wherein:

Fig. 1A shows schematically a front view of a pulley block according to an embodiment of the invention with the at least one gate roller in closed position,

Fig. 1B shows schematically a side view of a pulley block according to an embodiment of the invention with the at least one gate roller in closed position,

Fig. 2 shows schematically a front view of a pulley block according to an embodiment of the invention with the at least one gate roller in open position,

Fig. 3 shows schematically a hinge mechanism and a lock bolt for a pulley block according to an embodiment of the invention,

Fig. 4 shows schematically a front view of a pulley block according to an embodiment of the invention comprising a lock bolt with a locking mechanism and an adjusting bolt,

Fig. 5 shows schematically a sideview of a pulley block according to an embodiment of the invention comprising ten rollers, of which three vertical rollers are configured as gate rollers and shown in closed position,

Fig. 6 shows schematically a sideview of a pulley block according to Fig. 5, wherein the gate rollers are shown in open position,

Fig. 7 shows schematically a sideview of a pulley block according to an embodiment of the invention comprising fourteen rollers, of which three vertical rollers are configured as gate rollers and shown in closed position, and

Fig. 8 shows schematically a sideview of a pulley block according to Fig. 7, wherein the gate rollers are shown in open position.

Description of the Reference Signs

The following reference numbers and signs refer to the drawings:

Detailed Description of the Invention

Various aspects of the disclosure are described more fully hereinafter with reference to the accompanying drawings. This disclosure may, however, be embodied in many different forms and should not be construed as limited to any specific structure or function presented throughout this disclosure. Rather, these aspects are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the disclosure to those skilled in the art. Based on the teachings herein one skilled in the art should appreciate that the scope of the disclosure is intended to cover any aspect of the disclosure disclosed herein, whether implemented independently of or combined with any other aspect of the disclosure. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method which is practiced using other structure, functionality, or structure and functionality in addition to or other than the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim. When using the terms up, upwards, down, or downwards throughout this description, it refers to the pulley block as it is intended to be installed, for example suspended in a cross-beam in the top of a tower. The term transverse, in relation to the pulley block, thus refers to a plane normal to a longitudinal axis going through the channel of the pulley block.

The invention is described in relation to overhead cables or wires. When using the term “cable” or the term “wire”, this is intended to also include transmission lines, conductors, wires, or other types of cables, with or without current, for installation in the air between towers, masts, poles or other structures. The invention may be used to install a cable or wire by use of a helicopter, or other type of aircraft, or to first install a stringing wire along a predetermined path using helicopter, or other type of aircraft, in order to later use this stringing wire for pulling a cable through each pulley block of the path.

The invention will be further described in connection with exemplary embodiments which are schematically shown in the drawings, wherein Fig. 1a and 1b shows a front view and a side view, respectively, of a pulley block 10 according to an embodiment of the invention with the at least one gate roller 30 in closed position, and wherein Fig. 2 shows a front view of a pulley block 10 according to an embodiment of the invention with the at least one gate roller 30 in open position. Although the following embodiments are described for installation of a cable 60, it is to be understood that this includes also the possibility of installation of a wire or other type of cable as defined above. The pulley block 10 is suitable for being suspended or fastened above ground to a structure and may for this purpose be provided with a fastening arrangement 12. The pulley block 10 may for example comprise means for attaching to a cross-bar of a tower. In the embodiment of Fig. 1a and 1 b (best seen in Fig. 1b), the pulley block 10 comprises an upper set of horizontal rollers comprising two upper rollers 20, and a lower set of horizontal rollers comprising two lower rollers 20. The pulley block 10 further comprises a first set of vertical rollers 20 comprising two vertical rollers 20 arranged on the left-side (as seen on Fig. 1a) of the pulley block and a second set of vertical rollers comprising two vertical gate rollers 30 arranged on the opposite, right-side (as seen on Fig. 1a) of the pulley block 10. Only the fore most rollers 20 and gate roller 30 are visible in Fig. 1a. The rollers 20 and gate rollers 30 are arranged to create a square-shaped enclosure providing a channel 50 for retaining the cable 60 (only shown in Fig. 1a). Fig. 1b shows a side view of the channel 50, wherein a cable 60 when installed, will enter the channel 50 at an entry side 52, and exit at an exit side 53 of the channel 50, or vice versa. When installing the cable 60 using an aircraft, the cable 60 will be installed transversely into the channel 50 by use of entrance 51. The rollers 20 and gate rollers 30 are rotatably arranged for example around a shaft arranged in a frame 11 , using ball bearings or similar, in order to allow the cable 60 to easily glide through the pulley block 10 in the longitudinal direction of the cable 60. Furthermore, the rollers 20 and gate rollers 30 must be able to withstand the weight of the cable 60 once installed, and the loads acting from the cable 60 during installation. Typically, loads acting upwardly or downwardly are highest.

The gate rollers 30 are hinged for pivoting inwardly from an initial, preferably closed, position when a force acts on the gate rollers 30 from the outside and are provided with a closing mechanism to ensure that the gate rollers 30 automatically close from the open position. This can be a biasing mechanism, such as a spring, biasing the gate rollers 30 in the closed position. Thus, one end 31 of each gate roller 30 is fixed in position in the pulley block 10 and allowed to rotate, providing a pivoting point, while the other end 32 of the gate roller 30 is free to swing inwardly into the channel 50. A stopper or abutment may be arranged to prevent the gate roller 30 swinging outwardly from closed position, thus ensuring that the cable 60 does not exit the channel 50 unintentionally. The hinge 70 is spring-loaded, such that the gate rollers 30 will automatically snap back to the initial, closed position. In an embodiment, the gate rollers can be held in open position by a retaining device configured to release the gate rollers 30 as the cable 60 is inserted, for moving to the closed position. Such retaining device may for example be a hook or a clip attached to the free, swinging end 32 of one or more of the gate rollers or lock bolt 81 (see below), that is pushed off by the cable when inserted into the channel 50.

The length of the gate rollers 30, the size of the channel 50 created by the rollers 20 and gate rollers 30 and the size of the cable 60, must be configured such that the cable 60 is allowed to pass the gate rollers 30 when in open position, such that the gate rollers 30 can return back to closed position.

A guide arm 40 is arranged in relation to and slanted towards entrance 51 , i.e. the gate rollers 30, such that the cable 60, when laid onto the guide arm 40, will slide downwards due to gravity and/or due to pulling forces from for example a helicopter, or other type of aircraft. The guide arm can also be curved, sloping downwardly towards the entrance. In an embodiment, the guide arm 40 terminates closer to the free, swinging end 32 than the fixed end 31 of the gate rollers 30. The gate rollers 30 opens due to the pressure from the cable 60 and allows the cable 60 to be inserted into the channel 50 of the pulley block 10, upon which the gate rollers 30 returns to closed position. The guide arm 40 may be a single rod, or preferably an arched or II- shaped rod, as shown in Fig. 1b and Fig. 5-8. In other embodiments, the guide arm 40 may be a slanted or curved plate, or multiple parallel rods etc.

Fig. 3 shows schematically a hinge mechanism 70 for the gate rollers 30 of a pulley block 10 according to an embodiment of the invention. The hinge mechanism 70 is provided with a spring 71 that pulls the hinge 70 back to its initial position when rotated away from initial position. In an embodiment, as shown in Fig.3, a lock bolt 81 having a T-shaped bottom end is rotating with the gate rollers 30. Fig. 4 shows schematically a front view of a pulley block 10 comprising such lock bolt 81 and a locking device 82. In the embodiment of fig. 4, the pulley block 10 is also provided with an adjusting device, such as an adjusting bolt 90. This is an optional feature, explained more in detail below.

The lock bolt 81 and the locking device 82 are parts of a locking mechanism 80, with the purpose of providing additional support and rigidity to the pulley block 10 which is beneficial due to one side of the pulley block 10 being provided with gate rollers 30. The T-shaped bottom of lock bolt 81 fits with a corresponding U-shaped recess in a part 82 of the frame 11 of the pulley block 10, for retaining the T-shaped bottom part. When exposed to high upwards or downwards loads, the vertical distance between the upper and lower rollers 20 may, without a locking mechanism 80, increase, especially on the side provided with gate rollers 30, and the locking mechanism 80 is intended to prevent such deformation of the pulley block 10. The locking device 82 can also be used to prevent further rotation of the gate rollers 30 outwards from the channel 50.

In order to adjust or correct any misalignment that may occur, an adjusting bolt 90 may be provided, preferably on a side of the pulley block 10 opposite the gate rollers 30. The adjusting bolt 90 may be a rod extending from top to bottom which may be tightened or loosened by tightening or loosening nuts 91 at the end points of the rod 90, thereby adjusting the gap of the enclosure 50. Alternatively, threads may be provided in the pulley block body or frame, for engagement with complementary threads on the bolt 90.

Fig. 5 and Fig. 6 shows a side view of a pulley block 10 according to an embodiment of the invention with three gate rollers 30 in closed position and open position, respectively. Similarly, the opposite side of the pulley block 10, relative to the gate rollers 30, comprises three vertical rollers 20 (not seen in Fig.5 and Fig. 6). The pulley block 10 further comprises two upper horizontal rollers 20 and two lower horizontal rollers 20. As can be seen from Fig. 5 and Fig. 6, the rollers 20, 30 thus create a channel 50 that extends a certain depth, i.e. in the same direction as the installed longitudinal axis of the cable 60. This allows for restricting bending of the cable 60, in order to comply with requirements for minimum bending radius to not risk damage to the cable 60 caused by overbending. The vertical rollers 20 and gate rollers 30 are shifted sideways compared to the horizontal rollers 20, and together they form an enclosure or envelope restricting the movement of the cable 60 over a certain length of the cable 60, other than movements along the longitudinal axis of the cable 60.

Fig. 7 and Fig. 8 show schematically a sideview of a pulley block 10 according to an embodiment of the invention comprising fourteen rollers 20, 30, of which three vertical rollers are configured as gate rollers 30 and shown in closed position and open position, respectively. An upper set of horizontal rollers 20 comprises four rollers 20 arranged following a curved path at an upper part of the pulley block and a lower set of horizontal rollers 20 comprises four horizontal rollers 20 arranged following a curved path at a lower part of the pulley block 10. The curved alignment of the upper and lower sets of horizontal rollers 20 provides a guide for bending of the cable 60 inside the pulley block 10, and ensures that overbending is avoided. The alignment of the horizontal rollers can be adjusted to obtain a steeper or a less steep curved path or even a straight path, depending on the properties of the cable 60 to be installed through the pulley block. The diameter of each roller 20, 30 can be adjusted. In the embodiment of Fig. 5, Fig. 6, Fig. 7 and Fig. 8, two lock bolts 81 are provided in order to obtain a more rigid pulley block 10. The number and placement of the lock bolts 81 may be adapted for obtaining the desired rigidity of the structure.

In another embodiment, the upper and/or lower sets of horizontal rollers 20 comprises three horizontal rollers each, preferably arranged in a curved path as in Fig. 7 and Fig. 8.

Principles forming the basis of the invention

The invention is based on automatic closing of an entrance to a pulley block 10 in order to eliminate the need for manual assistance to install the cable or wire 60. A guide arm 40 for the helicopter, or other type of aircraft, ensures that when the cable or wire 60 is laid onto the guide arm 40, the cable or wire 60 will move towards the entrance 51 and thus be guided into a channel 50 made up of rollers 20, 30 of the pulley block 10. The pulley block 10, once the entrance 51 is closed, retains the cable or wire 60 inside the channel 50, while allowing forwards or backwards movement of the cable or wire 60 in its longitudinal direction, thus supporting transverse, upwards, or downwards cable loads. This makes it possible to use the pulley block 10 also in areas where there is height difference or sideways leap between adjacent towers. Carrying Out the Invention

When the helicopter, or other type of aircraft, arrives with the cable or wire 60 hanging underneath and approaches the tower, or other structure, with the pulley block 10 wherein the cable 60 is to be inserted, the aircraft pilot aims towards the guide arm 40 and lays the cable 60 upon the guide arm 40. As the guide arm 40 is inclined towards the gate rollers 30, the cable 60 will slide downwards towards the gate rollers 30 as the helicopter, or other type of aircraft pulls on the cable 60. The cable 60 will eventually hit and push on the gate rollers 30 resulting in the gate roller 30 opening, and allowing the cable 60 to pass the gate rollers 30, whereupon the gate rollers 30 will snap back to its original, closed position due to the spring-loaded hinge 70. The cable 60 is now restricted from sideways or up/down movements, due to the rollers 20, 30 creating an enclosure 50 for accommodating the cable 60. At the same time, the rollers 20, 30 ensure that the cable 60 can glide unrestricted forwards and through the pulley block 10 when pulled towards the next tower by the helicopter, or other type of aircraft. Often, a stringing wire, typically made of steel, is first installed using helicopter, or other type of aircraft, in order to later be able to pull a current-carrying cable, typically with a steel wire core surrounded by an aluminium layer, through each pulley block 10 by use of the stringing wire. After the cable 60 has been inserted along the entire route, the cable 60 may later be permanently installed at each tower.

If deformation or misalignment of the pulley block 10 is discovered, for example after use, by finding a locking mechanism 80 not working properly or stuck, the adjusting bolt 90 may be adjusted to correct this misalignment.

A typical size diameter of the stringing wire is about 10mm, while a typical diameter of the cable is about 43mm.

Preferably, the size of the channel 50 is such that the cable or wire covers maximum % of the width and % of the height of the channel 50.

Alternative Embodiments

A number of variations on the above can be envisaged. For instance, the number and/or arrangement of rollers can be adjusted according to the type and size of cable. The cross-sectional shape of the channel 50 may form a square or rectangular shape, a triangle, or another polygonal shape, depending on the shape, number and arrangements of rollers 20, and gate rollers 30 in each plane. For example, the channel 50 may have a triangular shape having at least one horizontal bottom roller 20, at least one inclined gate roller 30, and at least another inclined roller 20 making up the triangular shaped enclosure of the channel 50. Also, the shape of the rollers 20, 30 can be a straight cylinder, concave shape, or other suitable shape. Using concave shapes, the enclosure 50 may obtain a circular or at least rounded shape. The rollers 20, 30 can be installed on ball-bearings or other bearings providing low-friction and/or improved rolling capability. The rollers 20, 30 can be made of plastic, steel, aluminium, wood, etc, and may be provided with a coating material or outer surface layer material to avoid damage to the cable 60 and/or to the roller 20, 30 and/or to provide the desired frictional capabilities.

The upper and lower horizontal rollers 20 should be rotatable about their respective longitudinal axis in order to ease pulling of the cable 60 through the enclosure 50 of the pulley block 10, however preferably also the vertical rollers 20 and/or the gate rollers 30, are rotatable.

Instead of having a separate lock bolt 81 for locking into a locking device 82, a locking mechanism 80 may be incorporated for example at the free, swinging end 32 of the gate roller 30, for example having a T-shaped end part for locking into a locking device 82.

The vertical gate rollers 30 may pivot about a point at an upper or a lower side of the pulley block 10. For example, the vertical gate rollers 30 may be pivotably fixed to the frame of the pulley block 10 at the bottom end of the roller 30, allowing the upper end of the roller 30 to swing inwards into the channel; opposite of what is illustrated in Figures 2, 6, and 8.

In order to verify to the pilot of the helicopter or other aircraft that the cable 60 is installed inside the enclosure 50 of the pulley block 10, an indicator, such as a flag or mark, may be used, triggered for example by the weight of or pressure from the cable 60 on one of the rollers 20.

The arrangement and number of horizontal rollers 20 and vertical rollers 20 or gate rollers 30, may adapted to certain requirements for a cable, such as minimum bending radius.

Industrial Applicability

The invention according to the application finds use in installation of overhead cables such as transmission lines or other types of wires or cables to be suspended at a height above the ground between towers or masts or other structures, such as building structures.