PRIORITY CLAIM

[0001] This application claims priority from Great Britain patent application GB1619977.0, filed 25 November 2016, the contents and elements of which are herein incorporated by reference for all purposes.

TECHNICAL FIELD

[0002] The present invention relates to a pulley block. More specifically, the present invention relates to a pulley block including a pulley wheel mounted to a frame of the pulley block via a mounting means.

BACKGROUND

[0003] Electrical power is transmitted between locations along conductors (also known as power lines). In general, conductors are cables, which are hung from pylons (also known as towers). A series of pylons, with conductors strung between them across spans, permit electrical power to be carried over large distances.

[0004] When building a power distribution network, or when replacing conductors, conductors need to be strung between pylons. To do this, the conductors are pulled, by for example a helicopter or ground-based pulling mechanism, over pulley wheels (also known as sheaves). The conductors are pulled until they are at a predetermined tension between a pair of pylons (a span).

[0005] A pulley wheel is mounted within a frame, the frame being a part of a pulley block. The pulley block may also be known as a pulling block, stringing block, or running-out block. The skilled person will appreciate there may also be other names used for a pulley block. Multiple pulley wheels may be mounted within a single frame of a single pulley block, for example three pulley wheels. The pulley block is hung from a pylon. The pulley wheel(s) is/are mounted to the frame to be each rotatable relative to the frame. Conventional prior art pulley wheels and frames of pulley blocks are engineered to be otherwise rigidly mounted to one another. The conductors are pulled through the pulley block and over the pulley wheels, each pulley wheel rotating freely beneath a conductor, until the correct tension in the conductors is achieved, whereupon the conductors are fixed to the pylons. The pulley blocks, which include the pulley wheels, are then removed from the pylons for reuse.

[0006] When pulling conductors, the conductors are pulled over the pulley wheel, which rotates beneath the conductor as it is pulled. To facilitate this, each pulley wheel has a peripheral channel in which the conductor sits as the pulley wheel rotates. Pulley wheels are typically mounted in the frame of a pulley block. The frame is generally rigid, although may have an opening mechanism (for example, a gate) through which the conductor can be placed into the channel of a pulley wheel. The opening mechanism can then be closed, retaining the conductor within the frame. When pulling/tensioning conductors, the frame is rigid, and any opening mechanism is closed.

[0007] A conventional pulley block can include a number of parallel and adjacent pulley wheels. A corresponding number of parallel and adjacent conductors can then be pulled simultaneously through the pulley block.

[0008] Conventional conductors have a circular cross-sectional shape along their length. However, recent conductor developments have led to conductors that have a non-circular cross-section along their length. For example, some conductors have multiple cores, for example two cores, which repeatedly wrap around one another along the length of the conductor. For example, a pair of cores can form a conductor with a helical structure along its length. The helical structure may have one full wrap of one core over another every 6 metres, for example. The cores may be clipped together periodically to prevent unwrapping of the cores. A clip may be applied to the conductor for each wrap of the cores. In this example, the helical structure results in the non-circular cross sectional shape. For example, the cross sectional shape of the conductor may be generally oval. Furthermore, the position of the non-circular cross-sectional shape effectively turns as a function of length along the conductor because of the helical wrapping of the cores.

[0009] One reason that such a multi-core conductor configuration is useful because, when the conductors are in place on the pylons, relative movement of the cores means that ice may be prevented from forming on the conductors and/or any existing ice may be shed from the conductor. This relative movement of the cores can be driven by wind, for example. This self-deicing property is useful, for example, because it prevents or reduces the build-up of ice on the conductors, which may otherwise lead to an excess weight on the conductors. Such an excess weight can cause the conductors to become detached and fall from the pylons. Such multicore conductors are particularly useful in potentially cold environments where long spans are used, for example in parts of the USA.

[0010] There may of course be other reasons for conductors with a non-circular cross-section, other than a multicore configuration.

[0011] Pulling conductors with a non-circular cross-section can cause a pulley block to swing beneath the pylon as the conductor(s) is/are pulled over the pulley wheel(s) in the pulley block. This swinging motion of the pulley block can be transmitted to the pylon. Pylons typically have a low-safety factor - that is to say that pylons are susceptible to damage if forces are applied that are outside the relatively narrow operating limits. Movement transmitted to the pylon by a moving pulley block can damage the pylon, therefore. The movement of the pulley block can be particularly damaging if it corresponds to a resonant frequency of the pylon. [0012] Furthermore, the movement of the pulley block causes movement of the conductors that are running over the pulley wheels in the pulley block. Consequently, the movement of the conductors can be transmitted along the conductors, damaging either adjacent pylons or the equipment used to pull the conductors. Pulling equipment may include a helicopter, and so movement of the pulley block can be particularly dangerous.

[0013] Furthermore, fully installed conductors may be attached to the rigid part of the pylon via an insulating element, which will ultimately electrically isolate the conductor from the pylon. During the stringing process the pulley block may therefore be attached to the insulating element hanging from the pylon, rather than directly to the pylon itself. The insulating element may include relatively brittle parts (such as ceramics) which are susceptible to damage. It is therefore desirable to avoid movement of the insulating element.

[0014] To reduce the effects of the movement of the pulley block on the pylon/other equipment, when pulling non-circular cross section conductors, operators have been forced to pull the conductors more slowly. Such a reduction in pulling speed can greatly increase the cost of pulling because it takes more time to pull the conductors.

[0015] Accordingly, it is an object of the present invention to provide an improved pulley block and pulley wheel.

SUMMARY

[0016] The present inventors have discovered that the motion induced in the pulley block when pulling a non-circular cross-section conductor is such that the pulley block executes a circular/oval swinging path in a plane perpendicular to the cable by which the block is mounted to the pylon. In other words, the pulley block moves along a circular or oval path beneath the point from which the pulley block hangs from the pylon. [0017] According to a first aspect of the present invention, there is provided a pulley block, including: a frame; at least one moveable pulley wheel, each moveable pulley wheel being mounted to the frame by a respective mounting means for rotation about a respective rotation axis and in a respective plane of rotation, each respective plane of rotation being orthogonal to the corresponding rotation axis; wherein each respective mounting means is configured to permit movement of the respective plane of rotation relative to the frame.

[0018] Advantageously, for each respective mounting means, the movement of the corresponding plane of rotation includes a turning movement about a turn axis.

[0019] Conveniently, each respective turn axis is orthogonal to the corresponding rotational axis.

[0020] Preferably, for each respective mounting means, the movement of the corresponding plane of rotation includes a tilt movement about a tilt axis.

[0021] Advantageously, each respective tilt axis is orthogonal to the corresponding rotational axis.

[0022] Conveniently, each respective mounting means includes a rigid arm and a moveable connector, the rigid arm connecting the moveable wheel to the frame via the moveable connector to thereby permit thereby the movement of the respective plane of rotation relative to the frame.

[0023] Preferably, the moveable connector includes an articulating joint between the respective rigid arm and the frame.

[0024] Advantageously, the moveable connector further includes an axle joint between the articulating joint and the frame to thereby permit relative movement of the respective articulating joint and the frame.

[0025] Conveniently, the mounting means further includes at least one connecting rod connecting the rigid arm to the frame. [0026] Preferably, the length of each of the at least one connecting rod between the frame and the rigid arm is variable.

[0027] Advantageously, the length of each of the at least one connecting rod between the frame and the rigid arm is constrained within a range of rod lengths.

[0028] Conveniently, the length of each of the at least one connecting rod between the frame and the rigid arm is constrained by inner and outer stop members attached to the respective connecting rod, the inner and outer stop members being located on opposing sides of a respective rod connector that connects the respective rod to the frame or to the rigid arm.

[0029] Preferably, the mounting means includes a restoring means that provides a restoring force on the respective moveable pulley wheel, to thereby act to urge the moveable pulley wheel towards an equilibrium position relative to the frame.

[0030] Advantageously, the restoring means includes at least one resilient member configured to provide the restoring force to act on at least one of the at least one connecting rods.

[0031] Conveniently, the restoring means includes at least one resilient member located between one of the rod connectors connecting the respective connecting rod to the frame or the rigid arm and the respective outer stop member.

[0032] Preferably, the at least one resilient member includes at least two resilient members, wherein a second of the resilient members is located between the respective rod connector and the inner stop member.

[0033] Advantageously, an equilibrium position of the pulley wheel relative to the frame is adjustable. [0034] Conveniently, an equilibrium position of the pulley wheel relative to the frame is adjustable by movement of at least one of the inner and outer stop members relative to the respective connecting rod.

[0035] Conveniently, the pulley block further includes a fixed pulley wheel, the fixed pulley wheel being mounted to the frame by a fixed mount, the fixed mount being configured to permit only rotation of the fixed pulley wheel.

[0036] Preferably, the pulley block comprises two or more moveable pulley wheels.

[0037] Advantageously, the movement of the plane of rotation of a first moveable pulley wheel of the two or more moveable pulley wheels is independent of the movement of the plane of rotation of a second moveable pulley wheel of the two or more moveable pulley wheels.

[0038] Conveniently, the fixed pulley wheel is located between the first moveable pulley wheel and the second moveable pulley wheel.

[0039] Preferably, the first moveable pulley wheel, the fixed pulley wheel, and the second moveable pulley wheel are located co-axially within the frame.

[0040] Advantageously, each said mounting means includes a spherical bearing.

[0041] Conveniently, each said mounting means includes: a restoring means that provides a restoring force on the respective moveable pulley wheel, to thereby act to keep the moveable pulley wheel in an equilibrium position.

[0042] Preferably, each restorative means includes first and second elastomeric rings, wherein the first and second elastomeric rings sandwich the spherical bearing, the first elastomeric ring being located on a first side of the spherical bearing and the second elastomeric ring being located on a second side of the spherical bearing. [0043] Advantageously, the first and second elastomeric rings are each bonded to an inner surface of a central hub of the corresponding moveable pulley wheel.

[0044] Conveniently, each said mounting means includes a pair of arms and an axle, the axle being located between the arms, the moveable pulley wheel being configured to rotate about the axle, and wherein each of the arms is mounted to the frame via at least one spring member, the at least one spring member permitting the movement of the respective plane of rotation relative to the frame.

[0045] According to another aspect of the present invention, there is provided a pulley wheel assembly for mounting to a pulley block, the pulley block having a frame, the pulley wheel assembly including a moveable pulley wheel and mounting means; the moveable pulley wheel being configured for mounting to the frame by via the mounting means for rotation about a respective rotation axis and in a respective plane of rotation, the plane of rotation being orthogonal to the corresponding rotation axis; wherein the mounting means is configured to permit movement of the plane of rotation relative to the frame.

[0046] According to another aspect of the present invention, there is provided a method of pulling a conductor, the method including the following steps: hanging a pulley block from a pylon, the pulley block being a pulley block as described above; placing a conductor into a peripheral channel of the moveable pulley wheel, the conductor having a non-circular cross-sectional shape, and; pulling the conductor through the pulley block. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] So that the invention may be more readily understood, and so that further features thereof may be appreciated, embodiments of the invention will now be described by way of example with reference to the accompanying drawings in which:

[0048] Figure 1 is a view of three examples of prior art pulley blocks;

[0049] Figure 2 is a side view of a pulley block according to a first embodiment;

[0050] Figure 3 is a front/back view of the pulley block of figure 2;

[0051] Figure 4 is a front/back view of a second pulley block according to the first embodiment;

[0052] Figure 5 is a side view of a pulley wheel assembly in accordance with the first embodiment;

[0053] Figure 6 is a cross-sectional view of the pulley wheel assembly of figure 5;

[0054] Figure 7 is an exploded view of the pulley wheel assembly of figure 5;

[0055] Figure 8 is a cross-sectional view of the hub region of the pulley wheel assembly of figure

5;

[0056] Figure 9 is a side view of a pulley wheel assembly in accordance with a second embodiment;

[0057] Figure 10 is a cross-sectional view of the pulley wheel assembly of figure 9;

[0058] Figure 11 is a cross-sectional view of an axle attachment region of the pulley wheel assembly of figure 10;

[0059] Figure 12 is a cross-sectional view of the pulley wheel assembly of figure 9;

[0060] Figure 13 is an exploded view of the mounting means of the pulley wheel assembly of figure 9;

[0061] Figure 14 is a front/back view of a pulley block according to the second embodiment; [0062] Figure 15 is a front/back view of a second pulley block according to the second embodiment;

[0063] Figure 16 is a front/back view of a prototype pulley block according to the second embodiment;

[0064] Figure 17 is a perspective view of a pulley block according to a third embodiment;

[0065] Figure 18 is an enlarged view of a portion of the pulley block of Figure 17;

[0066] Figure 19 is an enlarged view of a portion of the pulley block of Figure 17, and;

[0067] Figure 20 is an enlarged view of a portion of the pulley block of Figure 17.

DETAILED DESCRIPTION

[0068] More specifically, figure 1 shows first, second and third pulley blocks 1A, IB, and 1C according to the prior art. The first, second and third pulley blocks 1A, IB, 1C shown in figure 1 each includes a frame 2A, 2B, 2C, respectively. The first, second and third pulley blocks 1 A, IB, 1C shown in figure 1 also include a first, second and third pulley wheel 3A, 3B, 3C, respectively.

[0069] In the first pulley block 1 A, the first pulley wheel 3 A is rotatably mounted to the first frame 2A. In the first pulley block 1A, this rotatable mounting is achieved by a rigid axle that extends between two parallel arms of the first frame 1 A. The wheel is mounted to the axle via a bearing, which permits the first pulley wheel 3A to rotate about the axle. The first pulley wheel 3A can thereby rotate within the frame 2A about an axis of rotation, the axis of rotation being defined by the longitudinal axis of the axle.

[0070] Orthogonal to the axis of rotation is a plane of rotation for the first wheel. The first wheel rotates in the plane of rotation. That is to say that, when the first pulley wheel 3 A is rotating about the axis of rotation, a given point on the first pulley wheel 3 A remains within a single plane during rotation. That plane is the so-called plane of rotation. It will be appreciated that the plane of rotation is a mathematical concept, and is not a tangible element. It will further be noted that the plane of rotation is not to be thought of as rotating with the first pulley wheel 3A. The plane of rotation remains static relative to the first frame 2A, while the first pulley wheel 3 A rotates within the plane of rotation. As such, when the first pulley wheel 3 A is rotating about its axis of rotation, the plane of rotation does not move relative to the first frame 2A. Detailed description of the second and third pulley blocks IB and IC is omitted because the second and third pulley blocks IB, IC are generally similar to the first pulley block 1 A in the aforementioned respects. .

[0071] The first frame 2A includes an opening portion, which permits access to the first pulley wheel 1A. This opening portion can be unlocked from the remainder of the frame, and opened downwards, the opening movement being permitted by a hinge that connects the opening portion to the remainder of the first frame 2A. When the conductor is being pulled over the pulley wheel, that is to say when the first pulley wheel is rotating, the opening portion is conventionally in a closed position. As such, in use the opening portion and the remainder of the first frame 2A are rigidly connected to one another. In use therefore, there is no relative movement between any part of the first frame 2A and the plane of rotation of the first wheel 3 A. The movement of the opening portion of the first frame 2A relative to the first wheel 3A when the opening portion is opened should not be thought of as relative motion between the first frame 2A and the first pulley wheel 3A.

[0072] Figure 2 shows a pulley block 1 according to a first embodiment. The pulley block 1 includes a frame 2 and a moveable pulley wheel 3. The moveable pulley wheel 3 is mounted to the frame 2 via an axle 4. The moveable pulley wheel 3 is mounted to the axle 4 via a mounting means. The mounting means is not visible in figure 2. The mounting means permits the moveable pulley to rotate in a conventional manner about a rotation axis 10; such rotation about the rotation axis 10 is signified by the rotation direction 5. It will be understood that the moveable pulley wheel 1 can rotate in the rotation direction 5 in either sense (i.e. forwards or backwards).

[0073] In figure 2, the moveable pulley wheel 3 is shown in an equilibrium positon (described later), in which the rotation axis 10 is coincident with the central longitudinal axis of the axle 4, and is running into, and out of, the page. Orthogonal to the rotation axis 10 is the plane of rotation 11. In the equilibrium position, the plane of rotation 11 of the moveable pulley wheel 3 as shown in figure 2 is in, or parallel to, the plane of the page. In the first embodiment, when the moveable pulley wheel is in the equilibrium position, the rotation axis 10 is coincident with the longitudinal axis of the axle 4.

[0074] The mounting means (described below) permits the plane of rotation 1 1 of the moveable pulley wheel 3 (and accordingly the pulley wheel 3 itself) to turn 6 about a turn axis 7, relative to the frame 2. The turn axis 7 is perpendicular to the rotation axis 10 when the pulley wheel is in the equilibrium position. It will be noted that in the first embodiment the tilt axis 9 and turn axis 7 each pass through the geometric centre of the moveable pulley wheel.

[0075] The mounting means (described below) also permits the plane of rotation 11 of the moveable pulley wheel 3 (and accordingly the pulley wheel 3 itself) to tilt 8 about a tilt axis 9. The tilt axis 9 is perpendicular to the rotation axis 10 in the equilibrium position. The tilt axis 9 is also perpendicular to the turn axis 7 in the equilibrium position.

[0076] Figure 3 shows a front/back view (looking along the path of a conductor) of the pulley block 1 shown in figure 2. Again, the moveable pulley wheel 3 is shown mounted to the frame 2 via mounting means (not visible in figure 3). The mounting means is connected to the axle 4, about which the moveable pulley wheel rotates 5 (see arrow) about the rotation axis 10. The plane of rotation 11 (which in figure 3 is perpendicularly into, and out of, the page in a vertical orientation) is permitted by the mounting means to turn 6 about the turn axis 7, and to tilt 8 about the tilt axis 9 (in figure 3, the tilt axis is into, and out of, the page). In figure 3, the moveable pulley wheel 3 is shown in an equilibrium position. In the equilibrium position, the plane of rotation 11 of the moveable pulley wheel is orthogonal to the longitudinal axis of the axle 4, and thus the plane of rotation is substantially parallel to the sides 12 of the frame 2, in the particular arrangement illustrated.

[0077] Figure 4 shows another embodiment of a pulley block 15. The pulley block 15 includes a frame 16, first and second moveable pulley wheels 17A, 17B, and a fixed pulley wheel 18. The first and second moveable pulley wheels 17A, 17B and the fixed pulley wheel 18 are each connected to the axle 19 via respective independent mounting means (not visible in figure 4). The first and second moveable pulley wheels 17A, 17B are each mounted for movement relative to the frame in the same manner as the previously described single moveable pulley wheel embodiment. The first and second pulley wheels 17A and 17B are shown having been moved from their respective equilibrium positions. The fixed pulley wheel 18 is permitted only to rotate about its rotation axis. As such, the plane of rotation of the fixed pulley wheel is not permitted to move in a tilt and/or turn sense relative to the frame.

[0078] In figure 4, the first moveable pulley wheel 17A has a respective plane of rotation 20A. The plane of rotation 20A of the first pulley wheel (which is going into and out of the page in figure 4) is shown moved relative to the frame 16 of the pulley block 15. In this example, the plane of rotation 20A of the first moveable pulley wheel 17A has been tilted about its respective tilt axis 21A (which is running into and out of the page).

[0079] Also in figure 4, the second moveable pulley wheel 17B has a respective plane of rotation 20B. The plane of rotation 20B of the second moveable pulley wheel (which is running into and out of the page) is shown moved relative to the frame 16 of the pulley block 15. In this example, the plane of rotation 20B of the second moveable pulley wheel 17B has been tilted about its respective tilt axis 2 IB (which is running into and out of the page).

[0080] It will be noted that the movement of the plane of rotation 20A of the first moveable pulley wheel 17A is independent of the movement of the plane of rotation 20B of the second moveable pulley wheel 17B, and vice-versa. In other words, the relative movements of the planes of rotation of the moveable pulley wheels (in the rotation, turn, and/or tilt senses) are independent from one another both in direction and in magnitude (as illustrated with respect to tilt in figure 4).

[0081] Also shown in figure 4 are the respective turn axes 22A, 22B of the first and second moveable pulley wheels 17A, 17B. Whilst no movement of the respective planes of rotation in a turn-sense is shown in figure 4, it will be appreciated that the respective planes of rotation can also each turn, independently of the illustrated tilt. The potential tilt and turn components of movement of the plane of rotation 20 A of the first moveable pulley wheel 17A are independent. Similarly, the potential tilt and turn components of movement of the plane of rotation 20B of the second moveable pulley wheel 17B are independent.

[0082] Figure 5 shows a pulley wheel assembly 30 according to the first embodiment without a pulley block or frame in place. The pulley wheel assembly 30 includes the moveable pulley wheel 3, and the above-mentioned mounting means 31 which will now be described in more detail. The moveable pulley wheel 3 includes six spokes 32. The spokes 32 connect a pair of spaced apart peripheral rims 33 (only one rim is visible in figure 5) of the pulley wheel 3 to a central hub 34. Located within the central hub 34 is the mounting means 31. The mounting means 31 includes a spherical bearing (not visible in figure 5), and a pair of polymeric, elastomeric resilient members 35 (only one of which is visible in figure 6). The mounting means 31 defines a central aperture 36. When the pulley wheel 3 is mounted to the frame of a pulley block, the central aperture 36 receives the axle (for example, axle 4 shown in figures 2 and, 3, and axle 19 shown in figure 4) about which the moveable pulley wheel 3 will rotate.

[0083] Figure 6 shows a diametric cross-sectional view of the pulley wheel assembly 30 (see figure 5) along line A- A as shown in figure 5. On either side of the moveable pulley wheel, the two peripheral rims 33 are visible. Each of the two rims 33 extend circumferentially around the periphery of the moveable pulley wheel 3, the two rims 33 each being parallel to one another. Between the rims 33 is a circumferential channel 38, which also extends around the circumferential periphery of the moveable pulley wheel 3. The channel 38 has a generally concave channel surface 39. The inner part of the channel 38 is formed by a polymeric covering 40. The polymeric covering 40 prevents damage to a conductor located in the channel 38 during use.

[0084] When in use, a portion of a conductor sits in the channel 38. It will be appreciated that the conductor does not extend around the full circumference of the pulley wheel 3 at any one time, but instead sits in a top portion of the channel 38. The moveable pulley wheel 3 rotates beneath the conductor as the conductor is pulled.

[0085] In the central region of the moveable pulley wheel 3, the hub 34 can be seen. The hub 34 is the central part of the moveable pulley wheel 3, which receives the mounting means 31. The hub 34 has an inner circumferential surface 41, which is directed inwardly towards the centre of the pulley wheel 3. In the embodiment shown in figure 6, the inner surface 41 has a raised central ring 42, which forms a raised circumferential inner surface portion. At the two edges of the raised central ring 42, a respective outwardly-directed shoulder 43 is formed.

[0086] Generally, in the centre of the mounting means 31 there is located is a spherical bearing 44. The spherical bearing 44 is held within a two-part bearing housing 45 A, 45B. The two parts of the housing 45A and 45B are interconnected by screws 46. An outwardly directed surface the bearing housing 45 A, 45B abuts against the raised central ring 42 of the inner surface 41 of the hub 34.

[0087] The spherical bearing 44 is sandwiched between two spring support bushes 47A, 47B. The two support bushes 47A, 47B and the spherical bearing 44 therebetween cooperate to define a channel 48 which extends from one side of the wheel to the other and which is centred on the rotational axis 10 of the wheel (in the equilibrium position). The channel 48 receives an axle when the pulley wheel assembly 30 is mounted to a frame of a pulley block. The spring support bushes 47A, 47B and the spherical bearing 44 allow the pulley wheel 3 to rotate about the axle. Each of the spring support bushes 47A, 47B, extend beyond the hub 34 of the pulley wheel 3.

[0088] Positioned radially outwardly of each of the spring support bushes 47A, 47B is a respective polymeric spring block 49A, 49B. Each of the two polymeric spring blocks 49A, 49B is a generally annular polymeric element, which surrounds and engages an outwardly directed outer surface of a respective spring support bush 47 A, 47B. Elastomeric, polymeric resilient members are particularly advantageous because they typically have a wide effective operating temperature range (for example, -50 degrees centigrade to +40 degrees centigrade). Of course, non-circular cross-section conductors are more likely to be used in cold locations, as described above. Thus, elastomeric resilient members are particularly advantageous.

[0089] In the embodiment shown in figure 6, a radially outwardly directed surface of each of the polymeric spring blocks 49A, 49B is bonded to the inner surface 41 of the hub 34. Such bonding may be achieved by gluing the outwardly directed surface of each of the polymeric spring blocks 49A, 49B to the inner surface 41 of the hub 34, for example. Such bonding is a not a requirement of the present invention. [0090] In the embodiment shown in figure 6, a radially inwardly directed surface of each of the polymeric spring blocks 49A, 49B is bonded to the outer surface of the respective spring bush that is surrounded by said spring block 49A, 49B. Such bonding may be achieved by gluing the inwardly directed surface of each of the polymeric spring blocks 49A, 49B to the outer surface of the respective spring support bush 47A, 47B, for example. Such bonding is a not a requirement of the present invention.

[0091] Figure 7 shows an exploded view of the elements of the mounting means 31 and moveable pulley wheel 3 of the pulley wheel assembly 30 (as shown in figure 2).

[0092] The spherical bearing 34 is shown located between the first and second parts 45A, 45B of the bearing housing. The screws 46 that interconnect the first and second parts 45A, 45B of the bearing housing are also shown. The second part of the housing 45B includes an aperture 50, which is the opening of a small radially-extending passage that leads into the bearing housing 45A, 45B to permit the application of lubricant to the spherical bearing 34. The passage allows lubricant to be introduced into the bearing housing 45A, 45B. The aperture 50 may be closed by a screw that is screwed into the passage to seal the passage.

[0093] Figure 7 also shows the two spring support bushings 47A, 47B, which are described in more detail above. Also shown are the two polymeric spring blocks 49A, 49B.

[0094] Figure 8 shows a cross section through the hub region of the pulley wheel shown in figure 2. Figure 8 shows the hub 34 with the mounting means located therein. The mounting means includes the spherical bearing 44 and the first and second parts 45 A, 45B of the bearing housing. The hub 34 is shown tilted over at a drilling angle 51 to the vertical. The drilling angle 51 may be 30 degrees, for example. The aperture 50 in the bearing housing is shown. The aperture 50 is the opening of the passage into the second part 45B of the bearing housing. As can been the passage extends from outside the hub 34 to the spherical bearing 44. The passage 52 can therefore be used to introduce lubricant to the spherical bearing 44. The passage 52 may be drilled through the hub 34 and through the bearing housing 45B (for example) after the mounting means is located in the hub 34.

[0095] The spherical bearing 44 allows the moveable pulley wheel 3 to rotate about the rotation axis. In an equilibrium position, the rotation axis is coincident with the longitudinal axis of the axle to which the mounting means is mounted. Orthogonal to the rotation axis is a plane of rotation in which the moveable pulley wheel 3 rotates. That is to say that, any given point on the moveable pulley wheel 3, during a single rotation of the moveable pulley wheel about the rotation axis remains in a single, flat plane, which is the plane of rotation.

[0096] The mounting means, including the spherical bearing, permits a movement of the plane of rotation to introduce an angle between the rotation axis and a longitudinal axis of the axle to which the spherical bearing is mounted. Thus, the spherical bearing permits movement of the moveable pulley wheel such that the rotation axis may move out of alignment with the longitudinal axis of the axle, so as to make an acute angle thereto. Because the plane of rotation of the moveable pulley wheel is always orthogonal to the rotation axis, the spherical bearing effectively permits the plane of rotation of the pulley wheel to move relative to the frame of a pulley block to which the moveable pulley wheel and mounting means are mounted. By permitting the plane of rotation of the moveable pulley wheel to move relative to the frame, the peripheral channel 38 of the pulley wheel 3 can move relative to the frame. Of course, in use, the conductor runs in the channel 38.

[0097] When the moveable pulley wheel 3 is mounted to an axle, the spherical bearing 34 permits the moveable pulley wheel 3 to move relative to the axle (in a sense other than normal rotation about the rotation axis). For example, an angular offset between the rotation axis and the axle is possible. When such an angular change occurs, the spring blocks 49A, 49B, which have resilient properties, are compressed or stretched by the movement of the axle. For example, in figure 6, if an axle that is initially in a horizontal orientation is displaced in an anti -clockwise manner, then the top portion of the first spring block 49A, will be compressed between the outwardly directed surface of the first spring bush 47A and inner surface 41 of the hub 34. Conversely, the bottom portion of the first spring block 49A, will be stretched between the outwardly directed surface of the first spring bush 47A and inner surface 41 of the hub 34. As such the top and bottom sides (as seen in figure 6) of the first spring block 49A act in concert to apply a restoring force to the first spring bushing 47A to act to correct the anti-clockwise displacement of the rotation axis. In other words, the first spring block acts as a resilient means that acts to resist the compression and stretching by applying a restoring force between the axle and the moveable pulley wheel. The restoring force therefore acts to return the plane of rotation to its equilibrium position.

[0098] It will be appreciated that a similar, but reversed, situation occurs in the second spring block 49B. Specifically, a top portion of the second spring block 49B, will be stretched between the outwardly directed surface of the second spring bush 47B and inner surface 41 of the hub 34. Conversely, a bottom portion of the second spring block 49B, will be compressed between the outwardly directed surface of the second spring bush 47B and inner surface 41 of the hub 34. As such the top and bottom (as seen in figure 6) of the second spring block 49B also act in concert to apply a restoring force to the second spring bushing 47B to act to correct the anti -clockwise displacement of the axis of rotation 10. In other words, the second spring block acts a resilient means that acts to resist the compression and stretching by applying a restoring force between the axle and the moveable pulley wheel. The restoring force therefore acts to return the plane of rotation to its equilibrium position. [0099] The spring blocks 49 A, 49B act as shock absorbers between movement of the pulley wheel 3 (described by tilt and/or turn of the plane of rotation) and the frame to which the pulley wheel is attached. Thus, when the rotation axis (and consequently the plane of rotation) is moved by the action of a non-circular cross section conductor in the peripheral channel 38, two actions occur to prevent and/or reduce the transmission of that movement to the axle and consequently to the frame. First, the spherical bearing permits the movement of the pulley wheel relative to the frame in a tilt and/or turn sense (i.e. other than rotation). Second, the spring blocks 49A, 49B absorb some of the force due to the movement of the conductor by virtue of their compression and/or stretching.

[0100] Furthermore, the spring blocks 49A, 49B limit the maximum angular range of movement of the pulley wheel relative to the axle 40 in a tilt or a turn sense. In other words, the maximum angular displacement of the axis of rotation/plane of rotation from the equilibrium position may be defined by the maximum compression of a spring block.

[0101] It will be appreciated that the spring blocks 49A, 49B are only one suitable means of applying a restoring force to restore the plane of rotation to an equilibrium position after a displacement.

[0102] Figure 9 shows a pulley wheel assembly 60 for use with a pulley block according to a second embodiment. The pulley wheel assembly 60, includes a moveable pulley wheel 61, which includes six spokes 62. The spokes 62 connect two spaced-apart peripheral rims 63 of the moveable pulley wheel 61 to a central hub 64 (only one of the peripheral rims 63 is visible in figure 9) Located within the central hub 64 is a bearing (not visible in figure 9). The moveable pulley wheel 61 is configured to be attached to the frame of a pulley block using the mounting means 65. The mounting means 65 includes a pair of arms 66 (only one of the arms can be seen in figure 9). Each arm 66, has an axle end 67 and a mount end 68. The mount end 68 of each arm 66 is attached via screws 69 (for example) to a pivot block 70. At the axle end 67 of each arm 66, an axle 71 is connected. The axle 71 spans between the axle ends 67 of the arms 66. The moveable pulley wheel 61 is rotatably mounted to the axle 71.

[0103] During rotation of the moveable pulley wheel 61 about the axle 71, a given point on one of the peripheral rims 63 moves within a plane of rotation of the pulley wheel 61. Indeed, any single point on the pulley wheel moves within a plane of rotation. Because the pulley wheel is a rigid body, all potentially definable planes of rotation are parallel to one another. As will be apparent, some of the potentially definable planes are coincident.

[0104] The pivot block 70 is connected via four leaf springs 72 to base pivot block 73 (only two of the leaf springs 72 are visible in figure 9). The leaf springs 72 permit the pivot block 70 to move relative to the base pivot block 73. The leaf springs form a resilient connection between the pivot block 70 and the base pivot block 73. In turn, the connection between the pivot block 70 and the arms 66 means that the arms 66 can move relative to the base pivot block 73. When fitted to a pulley block, the base pivot block 73 is configured to be rigidly attached to the frame of the pulley block. Thus, the arms 66 are moveable relative to the frame of the pulley block. The moveable pulley wheel 61 is rotatably attached to the axle 71 between the arms 66. The movement of the arms 66 allows for movement of the axle 71, which in turn, allows for movement of the pulley wheel 61, relative to the frame. Such movement of the pulley wheel is described in terms of a turn and/or tilt of a plane of rotation of the moveable pulley wheel. It will be appreciated that while the second embodiment includes four leaf springs, that the resilient connection between the arms and the frame may comprise any suitable spring means that permits the relative movement of the arms and frame. Such means may include a different number of leaf springs or different types of spring, for example. Such means may also include other suitable resilient means. [0105] Figure 10 shows a diametric cross sectional view of pulley wheel assembly 60 along cross- section position A-A (as shown in figure 9).

[0106] The two arms 66 are shown on opposite sides of the pulley wheel 61. The axle 71 extends between the axle ends 67 of the two arms 66. The pulley wheel 61 is rotatably mounted on the axle 71.

[0107] As also described above, the mount end of each arm 66 is attached via screws 69 to a pivot block 70. Alternatives to screws 69 are also possible; for example, the arms may be integrally formed with the pivot block, or the arms may be welded to the pivot block. The pivot block 70 is resiliently connected via four leaf springs 72 to base pivot block 73 (only two of the leaf springs are visible in figure 10).

[0108] An axle attachment region is identified by dotted line C in figure 10.

[0109] Figure 11 shows an enlarged view in the axle attachment region (see region C in figure 10). The axle end 67 of one of the arms 66 can be seen. On the internal face of the arm 66, a recess 74 is formed. Into the recess 74, an end of the axle 71 is inserted. The end of the axle 71 is secured to the arm 66 by an axle securing screw 75. A shim 76 is placed around the axle end to separate the arm 66 from the hub 64. Clearly, figure 11 only shows the interconnection between one of the arms and one end of the axle. It will be appreciated however that the opposite end of the axle and the other arm are attached in a similar manner as that shown generally in figure 10.

[0110] It will be noted that the moveable pulley wheel 61 of the assembly 60 of the second embodiment could be a standard pulley wheel, as are known in the art. Of course, such a standard pulley wheel may take into consideration the size and profile shape of the groove, which may in turn be defined by engineering standards according to the conductor type, cross-sectional shape and dimensions to be pulled. [0111] Figure 12 shows a cross sectional view of pulley wheel assembly 60 along cross-section position B-B (as shown in figure 9).

[0112] The pivot block 70 is shown connected to the arms 66 via screws 69 (only the ends of the arms that are attached to the pivot block are shown). The pivot block 70 is attached to spring anchor block 77, which is in turn secured to spring anchor plate 78. The upper ends of a pair of the leaf springs 72 are trapped between the spring anchor block 77 and the spring anchor plate 78, the spring anchor block 77 and the spring anchor plate 78 being held fast to one another by screws. The base pivot block 73 is also attached to a spring anchor block 77, the spring anchor block being secured to a spring anchor plate 78. The lower ends of a pair of the leaf springs 72 are trapped between the spring anchor block 77 and the spring anchor plate 78, the spring anchor block 77 and the spring anchor block 78 being held fast to one another by screws. The function of each spring anchor block-spring anchor plate combination is to anchor an end of the leaf spring to the pivot block or base pivot block.

[0113] It will be appreciated that there are many different ways to anchor the ends of the leaf spring to the pivot block/base pivot block, other than the spring anchor block-spring anchor plate combination.

[0114] Figure 13 shows a partially exploded view of the elements of the mounting means 65 of the pulley wheel assembly 60 (as shown in figure 9, for example).

[0115] As described above, at an axle end of the arms 66, the recess 74 for receipt of the axle 71 can be seen. The shim 76, which will be placed over the axle 71, is also shown for one of the ends of the axle 71.

[0116] One of the arms 66 (on the right hand side of figure 13) is shown connected to the pivot block 70 via screws 69. The other arm 66 (on the left hand side of figure 13), is shown in an unconnected, exploded view relative to the pivot block 70. The spring anchor block 77 is shown unattached to the base pivot block 73. On the left hand of figure 13, the leaf springs 72 are shown anchored between the spring anchor block 77 and the spring anchor plate 78. On the right hand side of figure 13, the leaf springs 72, the spring anchor block 77, the spring anchor plate 78 and the base pivot block 73 are shown in an exploded view.

[0117] Figure 14 shows a schematic view of a pulley block according to the second embodiment. The view of figure 14 is one looking generally along the path of a conductor (not shown). The pulley wheel 61 is shown mounted to the frame 80 via the mounting means 65. The pulley wheel 61 is connected to the axle 71, around which the pulley wheel rotates 81 (see arrow) about the rotation axis 82. The plane of rotation 83 (which in figure 14 is perpendicularly into, and out of, the page in a vertical orientation) is permitted by the mounting means to turn 83 about the turn axis 84, and to tilt 85 about the tilt axis 86 (in figure 14, the tilt axis is into, and out of, the page). It will be noted that the tilt axis 86 does not pass through the centre of the wheel, as it does in the first embodiment. Instead, the tilt axis 86 passes through a point beneath the pulley wheel, generally between the pivot block and the base pivot block.

[0118] Figure 15 shows a schematic view of another pulley block according to the second embodiment. The view of figure 15 is one looking along the path of a conductor (not shown). The pulley block includes a frame 90, and first, second, and third pulley wheels 61A, 61B, 61C. The first, second and third pulley wheels 61A, 61B, 61C are each connected to the frame 90 via respective independent mounting means 65A, 65B, 65C. The three separate mounting means 65A, 65B, 65C allow for independent movement of the planes of rotation of the pulley wheels 61A, 6 IB, 61C. Specifically, the frame 90 has a base 91, to which each of the mounting means 65 A, 65B, 65C is attached. The relative movements of the pulley wheels (in the rotation, turn or tilt senses) are independent from one another both in direction and in magnitude.

[0119] The pulley block shown in figure 15 includes three pulley wheel assemblies, each of which is mounted via a respective mounting means to the frame to permit the movement of the plane of rotation of the pulley wheel relative to the frame. It will be appreciated, however, that an alternative configuration of the pulley block may be provided in which only one of the pulley wheels is configured for movement of its plane of rotation relative to the frame. For example, the pulley block may include a first number of moveable pulley wheel assemblies according to the present invention, and a second number of fixed pulley wheel assemblies. The first number may be equal to one or greater. The second number may be equal to zero or greater. For each fixed pulley wheel, whilst the pulley wheel is permitted to rotate about its rotation axis, the plane of rotation of the fixed pulley wheel is not permitted to move in a tilt and/or turn sense relative to the frame.

[0120] Figure 16 shows a prototype pulley block in accordance with the second embodiment. The pulley block has a frame 90. Mounted to the base 91 of the frame 90 via independent mounting means are three pulley wheels 61A, 61B, 61C.

[0121] It will be noted that the pulley block shown in figure 16 is a prototype used for testing. Clearly, there is a gap at the top right of the frame as seen in figure 16. This gap forms an access point, and is present so that conductors can be easily placed onto the pulley wheels, and removed from the pulley wheels during testing. A production pulley block may not have such a gap in the frame. Alternatively, the frame may include a frame gate that can be used to close such an access point. Any of the pulley blocks described herein may include an openable frame gate to permit access to the pulley wheels (moveable and/or fixed). [0122] In the case of pulley wheel assemblies according to the first embodiment, more than one moveable pulley wheels assembly may be mounted to a single axle. This is because in the first embodiment, the axle does not move relative to the frame. For this reason, a particular advantage of the first embodiment is that pulley wheels according to the first embodiment may be fitted to conventional pulley blocks.

[0123] Figure 17 shows a view of a portion of a pulley block according to a third embodiment. The pulley block 92 includes a frame 93 and a moveable pulley wheel 94. Only a portion of the frame 93 is shown, however, it will be appreciated that the frame 93 extends substantially around the pulley wheel or wheels within the frame.

[0124] The moveable pulley wheel 94 is connected to the frame 93 via a respective mounting means. The mounting means includes a rigid arm 95. The rigid arm 95 is moveably connected to the frame 93 via a moveable connector 96. The wheel axle means that the moveable pulley wheel 94 is rotatably connected to the rigid arm 95 and thus rotatably connected to the frame 93. The mounting means thus permits the respective moveable pulley wheel 94 to rotate in a conventional manner about a rotation axis passing through the wheel axle. It will be understood that the moveable pulley wheel 94 can rotate in the rotation direction in either sense (i.e. forwards or backwards).

[0125] The rigid arm has a pair of opposed flanges 95A, 95B. An arm axle extends between the two flanges 95 A, 95B. The arm axle passes through a bearing located generally between the two flanges 95A, 95B. The bearing is connected to a lug of a short extension arm 96C (see below). The two flanges of the arm 95 are spaced apart by a distance greater than the width of the lug of the short extension arm 96C, thus permitting the lug to move in the gap between the flanges 95 A, 95B in more dimensions than rotation about the arm axle. In other words, there is space between the flanges 95A, 95B to accommodate the lug and bearing therein, and thus to allow the relative movement of the flanges 95A, 95B and the lug (see below).

[0126] In Figure 17, the bearing is obscured from view by the flanges 95 A, 95B of the rigid arm 95.

[0127] In the third embodiment, the bearing is an articulating joint 96A connected to an upper part of the frame 93. The articulating joint 96A may be a so-called "rod end bearing", "rose joint", or "heim joint" through which the arm axle passes. Alternatively, the articulating joint may be a ball and socket joint. The rigid arm 95 effectively hangs beneath the articulating joint 96 A. The articulating joint 96 A permits the rigid arm 95 to move relative to the frame 93. The corresponding movement of the moveable pulley wheel 94 and its plane of rotation (other than the rotation about the axle) is described again in terms of a turn and/or a tilt of a plane of rotation of the moveable pulley wheel 94. A component of movement of the moveable pulley wheel may be permitted in forward and backward (i.e. along the direction of the cable) direction of the moveable pulley wheel 94. This corresponds to an angular offset of the rigid arm 95 about the articulating joint along the direction of cable pull, permitting a shift of a peripheral edge of the moveable pulley wheel 94 along the direction of the passage of the cable.

[0128] The articulating joint 96A may be the only moveable connection between the rigid arm and the frame. However, further moveable connections may be provided between the articulating joint 96A and the frame 93. For example, in the third embodiment, the articulating joint 96A is mounted to the frame 93 by the axle joint 96B via the short extension arm 96C. The pivotal connection provided by the axle joint 96B may allow for an increased range of motion of the moveable pulley wheel 94 in at least one sense. In the embodiment shown in Figure 17, that is in a tilt sense. [0129] In the third embodiment, the moveable connector 96 includes an articulating joint 96A and an axle joint 96B. Thus the bearing is the articulating joint 96A through which the arm axle passes. The respective mounting means of the third embodiment thus includes the wheel axle, the rigid arm 95, the articulating joint 96A and the axle joint 96B.

[0130] Figure 18 shows a view of the portion of the mounting means of the embodiment of Figure 17. The labelling of components if identical to that of Figure 17.

[0131] Returning to Figure 17, the rigid arm 95 generally hangs beneath the articulating joint 96A. The rigid arm 95 extends downwardly, generally adjacent to a side member 97 of the frame, the side member 97 being generally vertical in use. The moveable pulley wheel 94 includes a respective restoring means 97, which may be considered part of the mounting means.

[0132] Figure 19 shows the restoring means in more detail than Figure 17. In figure 19, the restoring means 97 includes a lateral bar 98 connected to the rigid arm 95. In the embodiment, the lateral bar 98 is connected to an outer portion of the axle of the wheel. The lateral bar 98 may also be configured to have some degree of rotation about the axle of the wheel.

[0133] Extending between the lateral bar 98 and the side frame member 97 are two rigid connecting members - in the illustrated embodiment these are connecting rods 99. The two connecting rods 99 in the embodiment pass on opposing sides of the frame side member 97. Proximate a first end, each connecting rod 99 is connected to the frame side member 97 via a rod connector 100. Proximate a second end, each connecting rod 99 is connected the lateral bar via another rod connector 100. Each rod connector 100 may be an axial bearing joint or an articulating joint.

[0134] Figure 19 shows a view of the portion of the mounting means of the embodiment of Figure 17. The labelling of components if identical to that of Figure 17. [0135] The rod connectors 100 and connecting rods 100 permit a range of movement between the lateral arm 98 and the frame 97.

[0136] In particular, each connecting rod 99 may be slideably received through at least one of the rod connectors 100 to which is it attached. Thus, the length of the connecting rod 99 between the respective rod connectors 100 may be changeable. For example, if the moveable pulley wheel 94 moves toward the adjacent frame side member 97, the length of the connecting rod 99 between the respective rod connectors 100 becomes shorter. If the moveable pulley wheel 94 moves away from the adjacent frames side member 97, the length of the connecting rod 99 between the respective rod connectors 100 becomes longer. Thus, the mounting means permits a change in distance between the moveable pulley wheel 94 and the frame.

[0137] In the embodiment of Figure 17, the connecting rod 99 is slideably received through one of the respective rod connectors 100 and fixedly connected to the other respective rod connector 100. For example, the connecting rod 99 may be slideably connected to the rod connector 100 located on the frame and fixedly connected to the rod connector 100 connected to the lateral bar 98.

[0138] Each rod connector 100 connected to the lateral bar may be rotatably mounted to the lateral bar 98 for movement about a first rod axis 100A. Each rod connector 100 connected to the frame side member 97 may be rotatably mounted to the frame side member 97 for movement about a second rod axis 100B. For a given connecting rod 99, the first and second rod axes 101A, 101B may be orthogonal to one another - as shown in Figure 20.

[0139] In the third embodiment, the change in distance between the moveable pulley wheel 94 and the frame side member 97 is permitted by the mounting means. In the third embodiment, the length of the connecting rod 99 between a rod connector pair 100 can vary as the respective connecting rod 99 undergoes slideable extension or retraction through at least one of the respective rod connectors 100. In other words, the length of the connecting rod 99 between the frame and the rigid arm 95 (and thus the moveable pulley wheel) is variable by sliding.

[0140] The extent of the slideable movement between a particular connecting rod 99 and a particular rod connector 99 may be constrained by a constraining means. The constraining means define a maximum length and minimum amount of permitted relative movement between the moveable pulley wheel and the frame.

[0141] In the third embodiment, the constraining means includes an inner stop member 101 A and an outer stop member 10 IB, each connected to the connecting rod 99 for each rod connector 99 connected to the frame side member 97. The inner stop member 101 A is located on the connecting rod 99 on a side of the respective rod connector 100 that is closer to the moveable pulley wheel 94. The outer stop member 10 IB is located on the connecting rod 99 on a side of the respective rod connector 100 that is further from the moveable pulley wheel 94 than the inner stop member 101A. In other words, a particular rod connector 100 is located between a respective inner stop member 101 A and outer stop member 101B. The inner and outer stop members 101 A, 101B allow for a range of relative movement of the rod connector 100 between the inner and outer stop members 101 A, 101B. In other words, there may be some "play" in the connecting rod 99, which can move slideably through the rod connector 100 to an extent defined by the inner and outer stop members 101 A, 101B. The inner and outer stop members 101 A, 101B thus constrain the slideable movement of the connecting rod 99 through the respective rod connector 99.

[0142] In the third embodiment, the restoring means includes a pair of resilient means 102 located between an inner stop member 101 A, 101B and the adjacent rod connector 100,. [0143] The resilient means 102 are shown more clearly in Figure 20, which is a view from below. Each resilient means 102 includes a restoring member 102 A (a spring, in the third embodiment) and a bump member 102B (a polymeric annulus or washer in the third embodiment). It will be noted that either the restoring member 102 A or the bump member 102B may be omitted from the resilient means 102. The resilient means serves to apply a restoring force to the connecting rod 99, and thus to the moveable pulley wheel 94, as the moveable pulley wheel is displaced from an equilibrium position relative to the frame side member 97, the restoring force acting to urge the moveable pulley wheel back towards its equilibrium position.

[0144] In the third embodiment, each bump member 102B is a polymeric annulus or washer (or "doughnut") through which the respective connecting rod 99 passes.

[0145] It will be appreciated that each resilient means 102 is configured to apply a restoring force to moveable pulley wheel 94, via the respective connecting rod 99 that serves to provide a force to act to return the moveable pulley wheel 94 to an equilibrium position relative to the frame. In the third embodiment, the resilient means may act to apply the restoring force to the respective connecting rod in an angular sense. In addition, or in the alternative, each resilient means may be configured to apply a restoring force to the connecting rod 99 that acts to move the connecting rod 99 in a slideable sense.

[0146] The equilibrium position of the moveable pulley wheel 94 may be configurable. In the third embodiment, the position of the inner and outer stop members 101A, 101B along the respective connecting rod 99 may be adjustable. That is, the stop members 101A, 101B may be configured to be independently locatable along the connecting rod 99. It will be apparent that by allowing such independent location of the stop members 101A, 101B, the equilibrium position of the connecting rod 99, and thus the moveable pulley wheel 94 is controllable by a user. For example, a user can, by changing the location of the stop members 101A, 101B, change the equilibrium position of the moveable pulley wheel 94. For example, the moveable pulley wheel 94 may be retained with an equilibrium position in which the plane of rotation of the wheel is not parallel to the adjacent frame side member 97. In other words, the equilibrium position may retain the moveable pulley wheel having a non-zero turn and/or tilt component when in the equilibrium position. For example, the equilibrium positon may have the plane of rotation of the moveable wheel that is not perpendicular to the ground when the frame is hanging freely from the top of the frame. In other words, the moveable wheel may be configured to have a predetermined tilt and/or turn.

[0147] A pulley block according to the third embodiment may include a plurality of the moveable pulley wheels of the third embodiment. For example, a pulley block may include two of the moveable pulley wheels according to the third embodiment. The first of the moveable pulley wheels may be on a first side of the pulley block, and substantially as shown in Figure 17. The second of the moveable pulley wheels may be on a second side of the pulley block, and substantially a mirror image of the moveable pulley wheel shown in Figure 17. Between the two moveable pulley wheels may be located at least one fixed pulley wheel.

[0148] For each of the embodiments, the advantageous movement of the plane of rotation for each moveable pulley wheel is permitted by the corresponding mounting means. The mounting means of the first embodiment is contained generally within the hub of the moveable pulley wheel, thus allowing the moveable pulley wheel to be connected to an axle of a conventional pulley block.

[0149] It will be appreciated also that in pulley blocks containing multiple pulley wheels according the first, second and third embodiments that it may be necessary to implement spacing between the pulley wheels (when in their equilibrium positions) so that there is sufficient space for the pulley wheels to move in to when the plane of rotation is tilted and/or turned. Such a spacing between moveable pulley wheels may prevent collisions between the pulley wheels when in use. Furthermore, in a pulley block including a moveable pulley wheel adjacent to a fixed pulley wheel it may still be necessary to implement a spacing therebetween. The spacing between a moveable pulley wheel and fixed pulley wheel may be smaller than the spacing between a moveable pulley wheel and an adjacent moveable pulley wheel.

[0150] The movement of the plane of rotation of each of the moveable pulley wheels is independent of the movement of the planes of rotation other pulley wheels in a pulley block including multiple moveable pulley wheels. This is advantageous when pulling multiple non- circular cross section conductors across multiple parallel moveable pulley wheels. As the conductors are being pulled, the movement of the cross-section of the conductors within the peripheral channel of the pulley wheel will not be in phase between the non-circular cross-section conductors. As such, independent movement of the planes of rotation of the moveable pulley wheels allows each moveable pulley wheel and corresponding mounting means to absorb at least some of the force imparted by the respective conductor to that moveable pulley wheel. This prevents that force from being transmitted to the pulley block, and consequently the structure/object to which the pulley block is ultimately attached (for example, a pylon, pulling equipment or helicopter).

[0151] It is quite common in the art of pulling conductors to attach multiple conductors to a pulling device (e.g. a helicopter) for simultaneous pulling. Such attachment may be via a single pulling cable. That is a number of cables are attached to the end of a single pulling cable. By way of example, the single pulling cable may be connected to a running board. In turn, the running board is attached to multiple (for example, two or three) conductors (each of which may have a non- circular cross-section). Initially, the pulling cable runs in one of the pulley wheels. As the pulling cable is pulled, eventually the running board passes through the pulley block. After the running board has passed through the pulley block, the pulling cable is beyond the pulley block, no longer located on a pulley wheel. Instead, the conductors, which are attached to the running board, are each located in respective pulley wheels. The single pulling cable may have a circular cross section, and thus there is no particular need for the pulling cable to run on a moveable pulley wheel according to the present invention. In this pulling cable set up, it can be particular advantageous to have a central fixed pulley wheel that is configured only to move in a normal rotational sense, while a pulley wheel according to the first or second embodiment is located on the each side of the fixed pulley wheel. Thus, the pulling cable runs on the fixed pulley wheel but the two conductors (with non-circular cross-sectional shapes) run on the outer pulley wheels according to the present invention.

[0152] The movement of the plane of rotation can be thought of as being about a number of axes. In the first embodiment, the tilt-movement and the turn-movement of the plane of rotation will each be about an axis that passes through the centre of the spherical bearing. The rotation axis in the first embodiment also passes through this point. In the second embodiment, the axes about which the tilt-movement of the plane of rotation takes place will be offset from the rotational axis. The turn axis in the second embodiment may intersect the rotation axis. The turn and tilt axes may generally intersect at a point located between the pivot block and the base pivot block. In the third embodiment, the turn axis is through the centre of the articulating joint. The tilt movement is about two axes in the third embodiment; through the articulating joint and about the axle joint.

[0153] In general, the ability of the peripheral channel of the pulley wheel, upon which the conductor is located during pulling, to move relative to the frame is where an advantage of present the invention lies. The potential for movement of the peripheral channel of the pulley wheel means that forces applied to the pulley wheel by the non-circular cross section conductor (which sits in the channel during puling), which would otherwise be transmitted to the pulley block, are not transmitted to the pulley block (or only transmitted at a reduced magnitude). Thus, the pulley block according to the present invention is less susceptible to movements caused by use of a non-circular cross-section conductor. It will also apparent to the skilled person that the present invention may also be useful when pulling conductors of a circular cross-section insofar as movement of the conductor may not be transmitted to the pulley block. Such movement may be due to wind, for example. Any reduction of movement of the pulley block is advantageous. In other words, there is no disadvantage to using the present invention with circular cross-section conductors. Indeed, insofar as the present invention acts as a movement isolator between the conductor and the pulling block, the present invention may also be advantageous when used with circular cross-section conductors. As such, pulley blocks and pulley wheels according to the present invention are versatile.

[0154] By way of example, conventional pulling of circular cross-section conductors using conventional pulley blocks may be performed at approximately 4 kilometres per hour (that is the speed of the conductor through the pulling block). With non-circular cross-section conductors and conventional pulling blocks, this pulling speed has to be reduced by a factor of four, for example, to approximately 1 kilometre per hour. This speed reduction is necessary to avoid damage to equipment and/or a safety risk due to movement of the pulley block caused by the conductor. Using a pulley block/pulley wheel according to the present invention allows non-circular cross- section conductors to be pulled more quickly than 1 kilometre per hour, thus reducing costs of a pulling operation. For example, the present invention may allow non-circular cross section conductors to be pulled at the same speed as circular cross-section conductors can be pulled, for example, 4 kilometres per hour.

[0155] When used in this specification and claims, the terms "comprises" and "comprising" and variations thereof mean that the specified features, steps or integers are included. The terms are not to be interpreted to exclude the presence of other features, steps or integers.

[0156] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0157] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.