Patent Publication Number: US-2004050286-A1

Title: Work cart for temporary cableway and a method for use of such work cart

Description:
[0001] This invention relates to a vehicle to be mounted on a cable line comprising at least two cables, and a system comprising this, and a method for application of such a vehicle on a track line.  
       BACKGROUND OF THE INVENTION  
       [0002] For maintenance work onshore and offshore it has been a common practice to use scaffolding, thereby providing a working platform for the operators. For maintenance work on large structures, such as bridges and oil platforms, this becomes excessively expensive and work intensive solutions. At the same time, the safety requirements for such type of scaffolding are extremely rigid, making such solution even more expensive.  
       [0003] In particular, for maintenance of the underside of offshore platforms the installation and use of scaffolding are time consuming and expensive, both due to the construction and due to weather and working conditions in general. In addition to the working conditions on the scaffolding, installation and dismantling operations are connected with danger.  
       PRIOR ART  
       [0004] It is known to apply hanging scaffolding, suspended from wires and which may be moved vertically along walls, used for installation, painting and maintenance works. The known scaffolding may, however, neither be used under overhanging projections, nor along the underside of bridges and the underside of platform decks.  
       [0005] Vehicle with a trolley running on a track cable such as for example a guy line or of mountain lift type having gondolas on a rail cable with a separate pull wire, is also known. It is further known to provide the rail cables for the gondolas with intermediate supports, consisting of cable supports mounted on poles in order to reduce the free lengths, thereby reducing sagging of the track cables.  
       OBJECT OF THE INVENTION  
       [0006] The object of the present invention is to provide a more simple solution which is independent of scaffolding, and providing a system which permits work to be performed on the underside of or between large structures. Thus, the invention relates to a vehicle to be installed on a track line, and a cable vehicle system for movement of such vehicle, as further defined in the enclosed claims. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0007] The present invention will be described below, referring to the enclosed drawings which illustrate the invention by means of preferred embodiments.  
     [0008]FIG. 1 is an illustration in perspective of a vehicle according to the invention, suspended from temporary track cables which are installed on the underside of e.g. a deck on an oil platform.  
     [0009]FIG. 2 is a side view of the vehicle suspended from an inclined track cable.  
     [0010]FIG. 3 is an end view in perspective of the vehicle, seen along the its platform deck and seen along the track cables.  
     [0011]FIG. 4 a, b  and  c  show various side views of a vehicle according to alternative embodiments of the invention.  
     [0012]FIG. 5 illustrates a separately installed safety equipment comprising safety wires and corresponding safety harness, as safety against dropping, functioning independent of the present invention.  
     [0013]FIG. 6 illustrates a cradle compensating for support of the vehicle on inclined track cables.  
     [0014]FIG. 7 illustrates a wheel support or a trolley running with its wheels on the track cables.  
     [0015]FIG. 8 a, b  and  c  shows a wheel suport passing over a wire support which is fixed by an intermediate anchorage. The arrow shows the direction of motion.  
     [0016]FIG. 9 a  and  b  show alternative embodiments of the wheel support.  
     [0017]FIG. 10 shows a view and a partly section of an intermediate anchorage, seen in direction of the wire.  
     [0018]FIG. 10 b  is a perspective view of a track cable system suspended from the underside of horizontal surface under a structure or a construction, with associated safety lines and access route. The overhanging structure or construction is for the sake of clarity not shown.  
     [0019]FIG. 11 is a perspective view of an operator operating a driving means according to a preferred embodiment of the invention.  
     [0020]FIG. 12 is a perspective view of a vehicle and its wire pulling system according to a preferred embodiment of the invention. For the sake of clarity, both the overhanging structure and the track cables are not shown.  
     [0021]FIG. 13 is a top view of the vehicle according to a preferred embodiment of the invention.  
     [0022]FIG. 14 is a top view of a vehicle equipped with an alternative driving means according to the invention.  
     [0023]FIG. 15 a, b, c  and  d  illustrate different alternative embodiments of the invention of working platforms assembled with different width, orientation and having varying heights.  
     [0024]FIG. 16 a, b  and  c  illustrate a method for sidewise transfer of the vehicle according to the invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     [0025] Vehicle and Track Line  
     [0026]FIG. 1 illustrates a cable vehicle  1  suspended from a track line system comprising at least two cables  2  via a support comprising two wheel supports. FIG. 2 is a side view of a vehicle according to a preferred embodiment of the invention where each of the wheel supports  3  are fixed directly or indirectly on poles or columns  14  which preferably are arranged at the corners of the working platform  16  on the vehicle. The poles  14  are equipped with struts  15  in order to provide a secure and stable connection between the working platform  16  and the poles  14 . The struts  15  may be fixed directly to the poles  14  or on horizontal brazings fixed to the poles  14  by means of scaffolding couplings, extending between the platform and the wheel support. According to a preferred embodiment the vehicle  1  may be ajusted to a situation where the two parallel extending cables  2  are inclined. This is achieved according to a preferred embodiment by allowing each of the wheel supports  2  to be pivotally arranged on a horizontal axis  9  of a centre bolt in a cradle  21  close to the middle  21  of an upper girder  20  which is mounted in the direction of the wires  2  on the poles  14 , on both sides of the platform. A means  8  for adjusting the height or the platform  16  is shown by means of a chain hoist  8  arranged between each of the upper girders  20  or an ear on the lower edge of the cradle  21  and the platform  16 . By adjusting the means  8  for adjusting the height differently below the track cables  2  the operator may in addition compensate for difference in height between the two cables  2 , so that the vehicle may be kept in a horizontal position. Different embodiments of the means  8  for adjusting the height will be described below, referring to FIGS. 4 a, b  and  c.    
     [0027] The Platform  
     [0028] The platform  16  may be of a type as disclosed on FIG. 3, for instance comprising a plate braced by means of a truss work in order to give the operator  4 , for instance a maintenance operator, a stable and secure work station. According to a preferred embodiment of the invention the platform  16  comprises a plate, e.g. with the dimensions 1500 mm×800 mm, and welded in a between the bottom and the top of a rectangular frame with corresponding outer dimensions and a height of 350 mm, so that the rectangular frame constitute a skirting around the entire platform. According to the embodiment shown the platform is hinged at the lower edge of the poles  14 , making it pivotalble around a horizontal shaft and thus make it applicable on both sides. According to one embodiment of the invention the platform may comprise of a module system where parts are exchangeable in order to modify the platform for required operation, such as to extend the platform or to mount on specially designed equipment. This feature will be described in further details below.  
     [0029] Means for Adjusting the Height of the Working Platform  
     [0030]FIG. 4 a  illustrates an alternatively preferred embodiment of the invention where the means  8  for adjusting the height of the working platform comprises a ratchet jack  8 , which elevates the platform  20  along ratchets on the pole  14 . In such way the platform front and back side may be adjusted height wise with respect to each other. On FIG. 4 b  the means for adjusting the height comprises a tackle system  8  and wires or ropes, where the lower tackle is fixed to the platform  16  while the ratchet jack arranged on the platform the upper tackle is fixed to the middle of the upper girder or the lower side of the cradle  21 . On FIG. 4 c  the means  8  for adjusting the height comprises a ratchet jack arranged on the platform  16 , where the ratchet jack runs on a ratchet, suspended from the upper girder  20  or from the cradle  21 .  
     [0031] Safety Wire  
     [0032] Reference is made to FIG. 5. In order to secure the operator who are to transported by or to use the vehicle  1 , the system also comprises a known, independently functioning safety system  5  comprising a safety harness and a separate safety line. The safety line may be arranged in parallel between the two track cables  2  and shall only be used to secure the operator  4  in case the operator should fall out of the vehicle or in case the vehicle should fail. One of the advantages related to the invention is that the since operator  4  is secured by a separately approved safety system  5 , the vehicle  1  and the track cables  2  may be given smaller dimensions than otherwise required, thereby achieving reduced weight and providing a substantially easier, simpler and faster installation procedure for the track cables  2  and the vehicle.  
     [0033] The Cradle  
     [0034] The cradle  21  and the upper girder  20  are illustrated in more detail on FIG. 6. According to the preferred embodiment the cradle  21  is arranged on horizontal shafts extending perpendicular with respect to the upper girder, enabling the wheel support  3  to be rotated around the horizontal shaft  9 . Hence, the wheel support  3  may follow the varying inclinations of the track cables  2 . A jacking hoist  8  is also shown where possible changes of level of the platform  16  is made possible since the poles  14  may move vertically on vertical guiding sleeves  22  arranged at each end of the upper girder.  
     [0035] The Wheel Support  
     [0036]FIG. 7 illustrates a wheel support  3  shown in a position carried by a track cables  2 . The wheel support according to the embodiment illustrated runs on the track cables by means of wheels  12  arranged between an inner and an outer elongate wheel support plate  3 A,  3 B, near each end of said twin wheel support side plates  3 A,  3   b.  The wheel support is designed to run in a vertical upright position on the track cables  2 . The wheel support is according to the preferred embodiment of the present invention as shown on FIG. 6, rotatably arranged on the vehicle, permitting the vehicle to rotate around the shaft  9  on the cradle  21 , arranged on the upper girder  20 . In this manner the vehicle may be installed and run on and be removed from inclined track cables  2 . This may be of practical importance when used in connection with work under inclined structures. The wheel support  3  may rotate freely in the cradle  21  or be fixed in any suitable inclination during use, making it possible to move the vehicle on track cables having varying inclination, e.g. when the vehicle is to be used under arched bridge spans or when the distance between the wires fixing or suspension points becomes so large that the wire obtains a curved shape, and where it may be a larger inclination at the point of suspension.  
     [0037] System for Driving the Vehicle  
     [0038] In order to move the vehicle  1  along the track cables  2 , a number of solutions are feasible. As shown on FIGS. 3, 11,  12 , and  13  the means  6  for moving the vehicle comprises two crank winches which are connected with separate pull wires or lines  7 , fixes at separate points of connection, in order to pull the vehicle  1  forward. FIG. 14 shows the vehicle connected to a separate pull wire  7  and the driving means  6  may be a winch on the vehicle, for example an air driven winch. According to an alternative embodiment of the invention, the driving means may be a remotely operated means, pulling the vehicle by means of a pull wire  7  from the point of suspension. A corresponding driving means may of course be arranged behind the vehicle in order to make it possible to drive the vehicle both ways. Alternatively, the wheel support  3  may be equipped with motors for moving the vehicle along the. cables. In such case the vehicle must be provided with a power supply (not shown).  
     [0039] According to the preferred embodiment of the driving means, there are, due to stability requirements of the vehicle, arranged two crank winches  6 , each connected to a separate pull wire or pull rope/line  7 , running in parallel with the track cables  2  of the construction which comprises an end fixture for the guidance wire  2  and running twice around the drum of the crank winch and running back along the track cables  2  and are fixed to the end of the wheel support  3  as further shown on FIG. 7. On the opposite end of the wheel support  3 , the other end of the pull wire  7  extends to the corresponding winch drum at the opposite fixture for the track cable  2  and back via a yoke  24  on the platform  16  and under the platform  16 , back to the crank winch  6 . The crank winch  6  is according to the preferred embodiments of the invention movably arranged by means of a horizontally arranged pivoted support structure  6 ′, pivotally arranged on the shaft of the cradle  9  and, shown on FIG. 13, turned to the end of the vehicle  1  which is in the direction of motion. The crank winches  6  may be of a type applied on sailing boats. The winches is operated by means of crank handles and according to the preferred embodiment shown may preferably have opposite drive gears, one right handed and one left-handed, thus enabling the operator to crank in a natural manner for the operator. According to a preferred embodiment the pivoted support structure  6 ′ is lockable, whereby the operator may adjust it to obtain a suitable height of operation.  
     [0040] Alternative Platform Configurations  
     [0041]FIG. 15 a  shows a top view of an alternative embodiment of the invention where four platform plates  16  are joined together, forming an entity having double width and length. FIG. 15 b  shows a vehicle having rails or side barriers. FIG. 15 c  illustrates a vehicle having three platform plates  16  in transverse direction, in order to enable coverage of a wider area between the track cables  2 . FIG. 15 d  illustrates a view of a platform  1 , comprising three platform plates  16  in transverse direction and where the middle platform plate  16  is at a lower level than the adjacent platform plates  16 , forming a span extending between and along a structure arranged between and extending along the track cables  2 , for instant a pipe line. The purpose is to ease the operators access to the underside or the lower sides of said structure, in order to perform maintenance work and painting of the pipe line.  
     [0042] The Intermediate Anchorage for the Track Cables  
     [0043]FIG. 10 shows an intermediate anchorage  10 , fixed to the subsurface of an overhanging structure, and which may be used for maintaining the track cables at predetermined level along long spans. FIG. 10 b  shows such a situation where the overhanging structure from a point of illustration is omitted, but with a number of intermediate anchorages  10 , maintaining the track cables at approximately constant height, whereby the vehicle  1  may be kept in required position with respect to the overhanging structure. The Figure shows in addition a longitudinally extending cable for the safety system, also shown on FIG. 1. The ends of the cables may preferably be fixed at areas equipped with separate access nets with a separate safety cable  5 ′, scaffolding or a safe haven where the operators may enter or leave the platform in a safe manner, and to connect or disconnect the personal safety means onto or from the safety wires  5 .  
     [0044]FIG. 10 shows an embodiment of an intermediate anchorage  10 . The intermediate anchorage comprises a cable support  11 , fixed to the cable in any known manner. The main part of the intermediate anchorage is given a ark shaped form, enabling the track guides to be kept in a position straight below the point of anchorage  13  and with the track cable on the upper side of the cable support  11 , so that the wheels  12  on the wheel support  3  may roll unaffected over the cable support. A horizontal shaft  18  is fitted in a reinforced horizontal casing at the lower end of the main part of the intermediate anchorage. The shaft  18  runs through the casing and the bow shaped main part  19 , and supports a ball bearing  17  and further the cable support  11 , so that the entire wheel support  3  with its side plates  3 A and  3 B may pass over the cable support  11  and the cable  2 . The ball bearing may be substituted by a roller bearing or slide bearing. The ball bearing is designed to support the wheel support  3  and relieve the cable  2  when the wheel support  3  passes over the intermediate anchorage  10 . According to the preferred embodiment, the wheel support comprises two substantially horizontal side plates  3 A and  3 B, where one side plate  3 B is equipped with a straight or substantially straight lower edge  23 , intended to run over the ball bearing  17 . According to this embodiment shown on FIG. 10, the side plate  3 B is intended to run over the ball bearing  17 . I such way the ball bearing  17  relieves the cable  2  and the wheels  12  when passing. Thus, unnecessary bending of the cable  2  over the cable support  11  is avoided. It is also possible to arrange an additional ball bearing  17 ′ on the shaft  18 , on opposite side of the ball bearing  17  with respect to cable support  11 , enabling the side plate  3 A to run over the ball bearing  17 ′.  
     [0045] Passage Over an Intermediate Guidance  
     [0046]FIGS. 8 a,    8   b  and  8   c  illustrates this interaction between the intermediate anchorage  10  and the wheel support  3  in more detail, at a stage where the wheel support  3  is about to pass over an intermediate anchorage  10 . As shown, the outer side plate  3 B has a central lower edge  23  having a concave shape, enabling the ball bearing  17  to bear against the lower surface of the lower edge  23 , evenly distributing the weight on the cable via the wheels  12 , and the ball bearing  17  via the intermediate edge  23 . The wheels  12  are pulley wheels equipped with a groove intended to receive the cable  2  and to retain the wheel  12  in position on the cable  2 . The cable support  11  supports the underside of the cable and is formed in such a way that it does not obstruct the motion of the wheel past the intermediate anchorage.  
     [0047] Alternative Wheel Supports  
     [0048] Throughout the disclosure a vehicle having two wheel supports  3 , each comprising two wheels  12  for movement along the cables  2 . It is, however, possible to use a wheel support  3  arranged on each of the four corners of the vehicle, the relative height of each wheel support may be adjusted individually to compensate for misalignments in the wheel support  3  and the angle of the cable  2 . In such case one wheel may be sufficiently in each wheel support to give stability.  
     [0049] The wheel support  3  shown on FIG. 9 a  and  9   b  may also be equipped with several wheels, preferably equipped with springs between the wheels  12  and the wheel support  3 , e.g. to provide a more equal motion and provide a more secure grip on the cable, in particular when passing over an intermediate anchorage  10 . An embodiment having two wheel supports  3 , each with one wheel, may also be used. For such solution, however, it may be more difficult to exploit the ball bearing  17  and consequently, an uneven passage over the intermediate anchorage  10 . In such later case, a stabilising solution for the vehicle may be considered necessary.  
     [0050] Installation of Track Cables Below an Overhanging Structure.  
     [0051] Installation of the safety system  5  and the track cables  2  is performed by certified climbers following procedures for climbing as described in Aaks method description for access technique. The safety system  5  is installed separately from the track cables  2 , but preferably running in parallel direction between the track cables, thus avoiding any conflict with the track cables when the vehicle is moved along the track cables. According to a preferred embodiment of the invention the track cables  2  are arranged parallel in same vertical height. The distance may according to a preferred embodiment be approximately  3  meter. The ends of the cables may be fixed to girder clamps in shackles or straps of a suitable type and tensioned by means of a suitable cable tensioning means, such as for example a jacking pulley. The intermediate anchorage is fixed by means of suitable shackles or straps at suitable places under the overhanging structure, for example by means of girder clamps on the girder.  
     [0052] The method is performed by fixing at least two track cables  2  and a safety wire  5  to a first end fixture on the structure, for example a bridge or a platform deck; attaching a hoisting rope to the free ends of the track cables  2  and the safety wire  5 ; climbing along the underside of the structure and pulling the hoisting rope with the attached track cables and safety wires to the second point of end fixture on the structure, the track cables running parallel under the structure; tensioning the track cables and the safety wire by means of wire tensioning means; and finally mounting the vehicle  1  on to the track cables by setting at least two of the vehicle wheel supports  3  with pulley wheels  12  on respective track cables. When the vehicle is mounted on the tensioned track cables, the vehicle may be moved along the track cables, using the vehicle as a working platform for fixing the intermediate anchorages and fixing the track cables on to the intermediate anchorages in order to relieve the end fixtures and to reduce sagging of the track cables.  
     [0053] The intermediate anchorages  10  reduces the sagging of the track cables  2  and reduces the load exposure on the end fixtures of the track cables. The vehicle  1  is mounted on the track cables  2  by setting the vehicle between the track cables  2  and lower for example the two wheel supports  3  with the wheels  12  down on to the track cables  2 . The pulling wires or pulling rope  7  for driving the vehicle may be mounted according to the description above. Further, the pulling wires may be connected to the driving means  6  as described above. According to a preferred embodiment, at least one additional track cable  2  is arranged parallel with the existing track cables in such a way that at least two parallel tracks along which the vehicle can be moved, is established. The track cables, the vehicle, the pulling cables and the safety system may be installed temporarily and be removed subsequent to completion of the work.  
     [0054] Sidewise, Lateral Transfer of the Vehicle  
     [0055] For sidewise transfer of the vehicle from hanging on two parallel track cables A and B to be suspended from track cable B and a corresponding parallel track cable C, arranged in approximately same distance as between A and B, the vehicle may by simple means be disconnected from the track cables A and B and connected to the track cables B and C. Due to operational consideration or from a safety point of view, it may, however, be inconvenient to disconnect the entire vehicle from both track cables. FIGS. 16 a, b  and  c  illustrates a method for transferring the vehicle in lateral direction of the track cables in a case where the system according to the invention comprises three cables  2 , marked A, B and C, where the vehicle comprises hinges or the like between the poles  14  and the platform  16  on the vehicle  1 , whereby the poles may be rotated around an axis parallel with the cables. Possible braces  15  may in addition be loosened.  
     [0056] In the first position shown on FIG. 16 a,  the vehicle is hanging on the cables A and B. The bracing struts  15  are released from the platform  16  or from the poles  14 . The wheel support  3  is unhooked from the first track cable A and the vehicle is rotated in such way that the platform is hanging straight down below the second track cable B, as illustrated in FIG. 16 b.  The released wheel support may then be lifted and rotated upwards as shown on FIG. 16 c.  It is thereafter hooked on to the cable C, enabling said wheel support to run along said third cable C, arranged on the opposite side of the the cable B with respect to the cable A. The distance between cables B and C is in general the same as the distance between cables A and B. The reinforcing struts  15  are fixed to the platform  16  or the poles  14 , dependent upon where they were released from prior to the transfer. In this way a simple method of transferring the vehicle in lateral direction is provided, for example in case the underside of a larger area are to be painted or maintained. Since the preferred embodiment has wheel supports where the wheels do not run vertically over the poles, but slightly out of line, the distance between the wheel suspensions will be shorter when the wheel supports are in its inner position as shown on FIG. 16 c.  Hence, the cable marked C must be arranged slightly closer to the cable marked B, than the corresponding distance between the cables marked A and B.  
     [0057] Alternative Track Lines  
     [0058] In the disclosure above, the vehicle  1  travels along track cables  2 . It should be appreciated, however, that other types of track lines may be used without deviating from the invention. Such alternative may be rails, ropes, pipes, rods or the like.  
                                                       1   Vehicle            2   Track cable, support wires (or rail, rope, tube etc.)            3   Wheel support, trolley            3A   Inner wheel support plate on the trolley 3            3B   Outer wheel support plate on the trolley 3, having a               horizontal lower edge 23 extending below the wheel 12,               intended to roll on the ball bearing internally of the               wire support 11.            4   Operator, the user of the vehicle            5   Safety wire/harness for the operator 4            6   Driving means for the vehicle 1            6′   Support structure for the driving means S            7   Pull wire for the driving means 6            8   Height adjusting means for the platform 16 (pulley               system, jacking pulley, ratchet jack, etc.)            9   Shaft for the wheel support/trolley 3           10   Intermediate anchorage           11   Wire support for the track cable/wire 2           12   Wheel on the wheel support to run on the track cable 2           13   A suspension means for the intermediate anchorage 10 on               the underside of the construction           14   Pole/column between the platform 10 and the upper.               girder 20, also carrying the wheel support 3 mounted on               a shaft 9           15   Braces for the poles/columns 14           16   Platform on the vehicle 1, intended to be kept in a               horizontal position to provide support for operator to               work and required equipment.           17   Ball bearing (inner ball bearing) (roller bearing,               slide bearing) mounted on the shaft 18 in order to               support the outer wheel support plate 3B. (Possible               outer ball bearing 17′supporting an inner wheel               support plate 3A.)           18   Horizontal shaft on which the ball bearing 17 is               mounted           19   Main support of the intermediate anchorage 10 with the               wire support 11 at its upper end and the horizontal               shaft 18, arranged below the track cable/wire 2.           20   Upper girder intended to support the wheel support 3 on               a cradle 21 with shaft 9 and to support the               poles/columns 14.           21   Cradle on the upper girder 20 with shaft 9 for the               wheel support 3.           22   Guide bushings           23   Horizontal lower edge 23 on the outer wheel support               plate 3B.