Abstract:
This invention relates to a portable winch assembly ( 10; 210 ) comprising a footplate ( 12; 212 ), a support frame ( 14; 214 ) which is locatable upon the footplate, a magazine ( 16; 216 ) which is locatable upon the support frame, and a drive mechanism ( 22; 222 ) which is connectable to the magazine to drive the magazine to rotate. The foot plate, support frame, magazine and drive mechanism comprise separable components which may be transported separately to a site of use and assembled into the winch at the site of use. The invention can provide a portable winch assembly capable of generating a tensile force of up to 10 tonnes, and is therefore suitable for pipe pulling and pipe bursting applications for example, and yet is made up of parts which can readily be carried to the site of use, which site of use may be inaccessible for vehicles.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates to a portable winch assembly. The portable winch assembly is likely to find its greatest utility in relation to the splitting or bursting of underground pipes, or the removal of underground pipes, and the following description relates primarily to such applications. The invention is not however limited to those applications. 
         [0002]    In this specification, directional and orientational terms such as “top”, “bottom”, “below” etc., refer to the components of the winch assembly in their normal orientation of use, as shown for example in  FIG. 1 . 
       BACKGROUND OF THE INVENTION 
       [0003]    Water and gas are supplied to domestic and commercial properties by way of large underground (mains) pipes which are laid by the utility suppliers. Smaller pipes connect the mains pipe to the individual building or dwelling. To enable the water or gas supply to be cut off from a particular building (in the event of a leak upon that property), the smaller pipes contain a valve or stopcock, the stopcock usually being located (underground) at the edge of the user&#39;s property, for example at the end of the driveway serving the property. Access to the stopcock is provided by way of an access hole. 
         [0004]    Waste water is removed from domestic and commercial properties by way of underground waste water pipes, the waste water pipes forming a network joining each property to a waste water treatment facility. Access holes are provided at intervals along the pipe, the larger access holes (for the larger pipes) being manholes which are large enough to accommodate a person. 
         [0005]    It is periodically necessary to replace an underground pipe, for example a pipe providing water to the property may become insufficient if the water consumption for the property grows beyond the capacity of the pipe. Also, a water or gas supply pipe, or a waste water pipe, may become damaged and start to leak, and so require replacement. In addition, it may be necessary to pass a cleaning tool along a pipe, for example to remove limescale encrustation within a waste water pipe. 
       DESCRIPTION OF THE PRIOR ART 
       [0006]    One method of replacing an existing pipe is to dig a trench along the line of the pipe and to remove the existing pipe and replace it with a new pipe by way of the trench. Clearly, digging a trench is an expensive and time-consuming activity, and can result in damage to the property and/or to a garden or roadway under which the existing pipe passes. 
         [0007]    To avoid the requirement to dig a trench, several trenchless methods of replacing an existing pipe have been developed. In all of these methods it is first necessary to locate the ends of the pipe to be replaced. For example, with a waste water pipe the length of pipe which is to be replaced is identified and an access hole is excavated adjacent to each end (or an existing access hole is used). The pipe is cut so as to open the ends of the length of pipe which is to be replaced. A cable is then passed along the pipe from a first end to the second end. When the cable reaches the second end of the pipe it is secured to a “pipe burster” or “pipe splitter”. The pipe burster is also secured to the end of the replacement pipe. 
         [0008]    The burster or splitter is a tool which has a tapered leading end and a central portion which is larger than the inside diameter of the existing pipe. The exact form of the splitter will depend upon the material of the existing pipe, but it can for example include a blade to cut open the existing pipe. 
         [0009]    A trench around three metres long is excavated adjacent to the first end of the pipe, and the pipe bursting equipment is located in the trench. The cable is connected to the pipe bursting equipment, and is thereby pulled through the pipe, in turn pulling the pipe burster. The existing pipe is thereby progressively burst as the pipe burster passes therealong, and at the same time is replaced by the replacement pipe. 
         [0010]    The requirement to excavate a trench for the pipe bursting equipment avoids much of the advantage of a trenchless method of replacing the pipe. In addition, for an approx. 10 cm diameter waste water pipe made of ceramic or plastics material, the pipe bursting equipment must typically be able to impart a tensile force of around 10 tonnes upon the cable. Such pipe bursting equipment is therefore heavy and cumbersome, and must be transported to the site of use on a vehicle, so that a roadway or the like is required. 
         [0011]    It is also known, especially for the replacement of smaller pipes, to pull the cable by way of a winch mechanism located above the ground. Specifically, a winch mechanism is located on a trailer and the trailer is manoeuvred over the access hole at the first end of the pipe. The use of a trailer-mounted winch reduces the excavation required. However, such a winch can again only be used in applications where the pipe to be replaced can be accessed by a roadway or the like along which the trailer can be moved. 
         [0012]    In my copending international patent application WO2008/071997 there is described another trenchless method of replacing an existing pipe. In that method, a portable winch is used, the winch having a pulley which can be located in the access hole adjacent to the first end of the pipe, the remainder of the winch mechanism being located above-ground and thereby avoiding or reducing additional excavation. 
         [0013]    The present invention is directed to the detailed construction of a winch which is suitable for use in the method of WO2008/071997, and which can also be used in other pipe replacement methods as well as other applications requiring a portable winch. 
       SUMMARY OF THE INVENTION 
       [0014]    It is an object of the present invention to provide a portable winch assembly which can readily be carried to the site of use, so that a trailer (and therefore an access roadway or the like) is not required. 
         [0015]    It is another object of the invention to provide a portable winch assembly which is capable of providing a tensile force of up to 10 tonnes. 
         [0016]    Typically, a winch which is capable of providing such a large force would be much too heavy to be portable, and would require a trailer or some other vehicle as described above. However, the inventor has realised that a suitable winch can be provided as an assembly of smaller and lighter parts, each of which can be carried to the site of use where the winch can be assembled. 
         [0017]    It is expected that the separate parts of the winch assembly will be transported (disassembled) in the user&#39;s vehicle, and if a roadway to the site of use is available the operator may not have to carry the separate parts of the winch assembly more than a few metres. However, if the site of use is more remote or less accessible, the winch assembly has been designed so that the operator can carry the separate parts to the site of use if that is required, and assembly the winch at the site of use. Alternatively, the parts of the winch assembly can be designed to fit (disassembled) onto a purpose-built trolley for transporting to and from the site of use. 
         [0018]    According to the invention, there is provided a portable winch assembly comprising a foot plate, a support frame which is locatable upon the footplate, a magazine which is locatable upon the support frame, and a drive mechanism which is connectable to the magazine to drive the magazine to rotate. 
         [0019]    Preferably, the footplate has at least one pulley. In a desired method of use for replacing a length of underground pipe the footplate is located within an access hole so that the pulley is adjacent to the (first) end of the pipe, and the cable or the like which is connected to the pipe burster passes from the pipe to the magazine by way of the pulley. The support frame projects from the hole so that the magazine and drive mechanism are located above ground. This has the advantage that the moving mechanical parts are not in the hole where they can become damaged, and also are more easily accessible. This has another advantage in that a full magazine is at a height where it can more easily be removed from the winch assembly. 
         [0020]    Preferably also the footplate has a recess to receive a part of the support frame. Ideally, the support frame is mounted upon the footplate by locating the part of the support frame in the recess, the cooperating recess and part of the support frame being configured so that when the winch assembly is not in use the mounting can be maintained by gravity without any fixing means. The avoidance of fixing means reduces the complexity of the winch components, and expedites assembly and disassembly of the winch. 
         [0021]    In some embodiments, the bottom of the recess in the footplate is located below the axle of the pulley, and ideally below the bottom of the pulley. This helps to ensure that tension in a cable which engages the pulley acts to push the support frame into the recess, rather than acting to tip the support frame out of the recess. 
         [0022]    Desirably, the magazine is connected to a drive mechanism which is in turn mounted upon the support frame. In some embodiments the drive mechanism includes a pair of drive rollers. 
         [0023]    In alternative embodiments, the drive mechanism includes a gear wheel which can be driven to rotate by two motors. Ideally the motors are substantially diametrically opposed relative to the gear wheel. Desirably, the gear wheel is connected to the magazine by way of a spider mechanism, the spider mechanism preferably permitting relative radial movement between the gear wheel and the magazine. The permitted radial movement can accommodate stresses and wear which occur during use of the winch assembly. 
         [0024]    Desirably, the magazine is mounted upon the support frame by resting a part of the magazine upon a part of the drive mechanism, the drive mechanism in turn being rested upon the support frame. The mounting of the magazine upon the drive mechanism and support frame is desirably maintained by gravity without any fixing means. In embodiments in which the drive mechanism has drive rollers, desirably the drive rollers are mounted upon the support frame by resting a part of the drive rollers upon guide rollers of the support frame, and the magazine is mounted upon the drive rollers by resting a part of the magazine against a part of the drive rollers. The arrangement of magazine, support frame and drive rollers (when present) is such that, when the winch assembly is not in use, the mounting of the magazine upon the support frame can be maintained by gravity without any fixing means. The avoidance of fixing means for the magazine (and also for the drive rollers if present) reduces the complexity of the winch components, and expedites assembly and disassembly of the winch. 
         [0025]    When the winch assembly is in use, it is arranged that tension in a cable between the footplate and the magazine helps to secure the support frame in position upon the footplate, and helps to secure the magazine in position relative to the support frame, in addition to the force of gravity. 
         [0026]    Preferably, in the assembled winch the axis of rotation of the magazine is perpendicular to the axis of rotation of the pulley of the footplate. This helps to ensure that unbalanced forces acting upon the magazine during the winching operation can be better resisted by the support frame and footplate, and are less likely to cause the support frame to pivot about the axis of the pulley. 
     
    
     
       BRIEF DESCRIPTION OF THE PREFERRED EMBODIMENTS 
         [0027]    The invention will now be described in more detail, by way of example, with reference to the accompanying drawings, in which: 
           [0028]      FIG. 1  is a perspective view of a portable winch assembly according to a first embodiment of the present invention; 
           [0029]      FIG. 2  is a perspective view of the footplate of the first embodiment from above; 
           [0030]      FIG. 3  is a perspective view of the footplate of  FIG. 2  from below; 
           [0031]      FIG. 4  is a perspective view of the support frame of the first embodiment; 
           [0032]      FIG. 5  is a perspective view of the drive mechanism of the first embodiment; 
           [0033]      FIG. 6  is a perspective view of the magazine of the first embodiment; 
           [0034]      FIG. 7  is a side view of the magazine of  FIG. 6 ; 
           [0035]      FIG. 8  is a perspective view of the clamp mechanism of the first embodiment; 
           [0036]      FIG. 9  is a side view of the clamp mechanism of  FIG. 8 , with some of the internal components shown in dotted outline; 
           [0037]      FIG. 10  is a perspective view from the front of a portable winch assembly according to a second embodiment of the present invention; 
           [0038]      FIG. 11  is a perspective view from the rear of the portable winch assembly of  FIG. 10 ; 
           [0039]      FIG. 12  is a perspective view of the footplate and bottom of the support frame of the second embodiment; 
           [0040]      FIG. 13  is a front view of the footplate and bottom of the support frame of the second embodiment; 
           [0041]      FIG. 14  is a perspective view of the drive mechanism, fitted magazine and magazine cover of the second embodiment; 
           [0042]      FIG. 15  is a view as  FIG. 14  with the magazine cover removed; 
           [0043]      FIG. 16  is a view of the drive mechanism of the second embodiment; and 
           [0044]      FIG. 17  is a perspective exploded view of the magazine, gear wheel and spider of the second embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0045]    The winch assembly  10  shown in  FIG. 1  comprises a footplate  12 , a support frame  14 , a magazine  16 , and a drive mechanism  22  ( FIG. 5 ). The drive mechanism  22  includes a pair of hydraulic drive motors  20 . 
         [0046]    In the first embodiment of the invention the drive mechanism  22  is mounted upon the support frame  14  by resting the drive rollers  24 ,  26  upon the guide rollers  30 . The magazine  16  is in turn mounted upon drive rollers  24 ,  26 . 
         [0047]    The drive motors  20  cause the drive rollers  24 ,  26  to rotate (in the same direction). Each of the drive rollers  24 ,  26  carries a respective drive gear  32  which engage a gear wheel  34 . The gear wheel  34  has three lugs (not seen), each of which locates into a respective opening  36  ( FIG. 6 ) in the end wall  40  of the magazine  16 . 
         [0048]    The footplate  12  of the first embodiment is shown in more detail in  FIGS. 2 and 3 . The footplate  12  comprises a substantially flat bottom plate  42  and a substantially flat back plate  44 , the back plate  44  being substantially perpendicular to the bottom plate  42 . A pair of side plates  46  are rigidly connected (suitably by screws as shown in  FIG. 3 ) to the bottom plate  42  and the back plate  44 , and each of the side plates  46  mounts an end of an axle  50  of a pulley  52 . The back plate  44  (and in this embodiment also the bottom plate  42 ) has an aperture  48  through which the cable may be passed in use. 
         [0049]    Each of the side plates  46  is shaped to provide a recess  54 , which recess is shaped to accommodate one of the two bottom ends  56  ( FIG. 4 ) of the support frame  14 . The recesses  54  are flanked by additional plates  60 ,  62 , which facilitate location of the bottom ends  56  in the recesses  54 , and also protect the pulley  52 . The additional plates  60 ,  62  are apertured so as to reduce weight, although in other embodiments an aligned pair of apertures could be used to locate a locking pin passing through a corresponding aperture in the bottom ends  56 . In this embodiment, however, there are no fixing means for the support frame  14  and footplate  12 , and the support frame is mounted upon the footplate merely by locating the bottom ends  56  in the respective recess  54 . 
         [0050]    The footplate  12  is designed to be relatively compact, so that it may be located in a relatively small access hole (not shown) adjacent to the (first) end of a pipe (also not shown), with the bottom plate  42  resting upon the ground at the bottom of the access hole. The footplate  12  may be small enough to be located within an existing access hole such as that provided for the stopcock, although a (minimum) amount of excavation may be required to allow the footplate  12  to be positioned so that the bottom of the pulley  52  is substantially aligned with the centre of the pipe which is to be replaced. 
         [0051]    A pin  64  is mounted between the side plates  46 , above the pulley  52 , and helps to stabilise the side plates, but it has the additional function as a carrying handle for the footplate  12 . 
         [0052]    The support frame is better shown in  FIG. 4 . The bottom ends  56  are both connected to a column  66  comprising a fabricated network of beams. At the top of the column the support frame has four sets of guide rollers  30 , a pair of support trays  70 , and a backing plate  72  mounting a pair of pins  74 . 
         [0053]    The drive mechanism is better shown in  FIG. 5 . The drive mechanism  22  comprises two drive motors  20  and two (substantially identical) drive rollers  24 ,  26 , each of which carries a gear  32 . In the portable winch assembly as shown in  FIG. 1  the end walls  40  of the magazine  16  lie upon the surface of each of the drive rollers  24 ,  26 . To locate the magazine  16  a part  76  of the surface of each of the drive rollers  24 ,  26  is defined by respective tapering flanges  68 , the spacing between the flanges  68  closely matching the thickness of the end plate  40 . As will be seen from  FIG. 1 , the part  76  of each of the drive rollers  24 ,  26  also engages respective guide rollers  30  on the support frame  14 , so that the flanges  68  serve to locate the drive mechanism  22  relative to the support frame  14 , and also serve to locate the magazine  16  relative to the drive mechanism  22 . 
         [0054]    The spacing between the part  76  and the drive gear  32  on each of the drive rollers  24 ,  26  is determined so that when one of the end plates  40  of the magazine  16  engages the part  76  the gear wheel  34  carried by the other end plate  40  will engage the drive gear  32 , as is shown in  FIG. 1 . 
         [0055]    It will be seen from  FIG. 1  that the periphery of the teeth of the gear wheel  34  project slightly beyond the periphery of the end plate  40 . An annular groove  80  is formed in the drive rollers  24 ,  26  adjacent to the gear  32 , so as to prevent the teeth engaging the surface of the drive roller. 
         [0056]    The drive rollers  24 ,  26  are each rotatably mounted in a respective support plate  82 ,  84 , the support plates carrying the respective drive motors  20 . The drive motors  20  in this embodiment are hydraulic drive motors and are driven by a hydraulic power pack (not shown), in known fashion. Actuation of the hydraulic drive motors causes the drive rollers  24 ,  26  to rotate (in the same direction). Any suitable drive means may be used, and the two motors  20  could be replaced by a single motor (or a set of three or more cooperating motors), if desired. However, two hydraulic drive motors  20 , with suitable gearing provided by the gears  32  and the gear wheel  34 , are desired. 
         [0057]      FIG. 5  represents the drive mechanism  22  as a single component, and some embodiments could be made in that way (with for example a single support plate replacing the separate support plates  82 ,  84 ). In the present embodiment the support plate  82  is separable from the support plate  84 , so that the drive mechanism can be separated into two substantially equal parts, for ease of transportation and to enhance portability. 
         [0058]    To assemble the drive mechanism  22  to the support frame  14 , the drive motors  20  are placed upon the support trays  70 , with the holes  86  in the support plates  82 ,  84  are aligned with the pins  74 . The drive mechanism  22  is moved relative to the support frame  14  so as to insert the pins  74  into the holes  86 , the pins  74  being secured in their relative positions by the backing plate  72 , and thereby securing the support plates  82 ,  84  (and the drive mechanism  22 ) together. 
         [0059]    It is arranged that when the support plates  82 , 84  engage the backing plate  72 , the parts  76  of the rollers  24 ,  26  engage the guide rollers  30  of the support frame (see  FIG. 1 ). 
         [0060]    The first embodiment of magazine  16  is shown in more detail in  FIGS. 6 and 7 . The magazine  16  comprises a central cylindrical shaft  78  and two end plates  40 . Each of the end plates  40  has three openings  36  therethrough. The first function of the openings  36  is to accept the three lugs (not shown) of the gear wheel  34  as previously described, the lugs being a sliding fit into the openings so that when the assembly is under tension the gear wheel  34  and the magazine are effectively secured together. The second function of the openings  36  is as a carrying handle for the magazine. The magazine itself is ideally substantially symmetrical as shown, and only becomes “handed” once the gear wheel  34  has been fitted to one or the other end plate  40 . 
         [0061]    In the assembled winch, the end plate  40  to which the gear wheel  34  is attached engages the rollers  24  and  26  adjacent to the respective groove  80 , and the other end plate  40  engages the parts  76  of the rollers  24  and  26 . The gear wheel  34  engages the gears  32 . As the rollers  24 ,  26  are driven to rotate, the magazine  16  is also driven to rotate, mainly by the gears  32 , gear wheel  34  and the lugs of the gear wheel engaging the openings  36  in one of the end plates  40 , but also by the friction between the drive rollers  24 ,  26  and the end plates  40 . 
         [0062]    It is a feature of this embodiment that the drive gears  32  alone do not need to provide all of the force required to provide a tensile load of 10 tonnes into a cable wound about the magazine. The magazine  16  is also driven to rotate by the drive rollers  24  and  26  engaging the end plates  40 . The effective radius of the drive gears  32  is the same as the radius of the drive rollers  24 ,  26 , and the effective radius of the gear wheel  34  is the same as the radius of the end plates  40 , so that the frictional drive of the drive rollers  24 ,  26  and end plates  40  matches the geared drive. In use, as the tension in a cable wound about the magazine increases, the frictional engagement between the end plates  40  and the drive rollers  24 ,  26  increases, so that more of the rotational force of the drive motors  20  is transmitted by way of the frictional drive. This has the advantage that only a small proportion of the maximum rotational force of the motors  20  is required to be transmitted by the drive gears  32 , so that the drive gears can be of reduced size and therefore reduced weight. 
         [0063]    The central cylindrical shaft  78  of the magazine  16  is hollow, and has an opening  90  to receive an end of a cable (not shown). Located within the shaft  78  is a clamping mechanism  92 , which is shown in more detail in  FIGS. 8 and 9 . 
         [0064]    The clamping mechanism  92  comprises two face plates  94  and  96  which are substantially mirror-images of each other. Between the face plates  94 , 96  are located two clamp wheels  100 . The axle of each of the clamp wheels passes through a substantially linear opening  102  in the face plate, and locates in a first channel part  104 . The first channel part  104  is connected to a second channel part  106  which is guided to slide along a rail  108 , there being a rail  108  fixed to each of the face plates  94 ,  96 . 
         [0065]    The clamp wheels  100  have the form of gear wheels with the gears having rounded ends, so as to give the clamp wheels an undulating periphery. Alongside the clamp wheels are a pair of rails  110  with a similarly undulating surface. 
         [0066]    The face plates  94 ,  96  have aligned tapering parts  112 , between which can be mounted a bush  114  (the bush  114  is not shown in  FIG. 8 , but the two bushes  114 , each lying between a pair of aligned tapering parts  112 , are shown in  FIG. 9 ). The bushes  114  are similarly tapered, with the effect that as the face plates  94  and  96  are moved together (by way of the fixing bolts  116 ) the bushes  114  are forced outwardly. 
         [0067]    The diameter of the face plates  94  and  96  is slightly smaller than the inside diameter of the shaft  78 . Accordingly, the clamp mechanism  92  can be assembled, with the face plates  94  and  96  loosely held together by way of the fixing bolts  116 , and slid into the shaft  78 . When the clamp mechanism  92  has been correctly positioned, with the hole  90  substantially aligned with the point  118  and substantially aligned with the mid-line of the clamp mechanism  92 , the fixing bolts  116  can be tightened so as to secure the parts of the clamp mechanism together, and also to drive the bushes  114  into engagement with the inside surface of the shaft, securing the clamp mechanism  92  in place. 
         [0068]    The clamp wheels  100  are biased by relatively weak springs (not shown) towards the point  118 , i.e. until they engage one another. When the end of a cable (not shown) is passed through the hole  90  it engages the clamp wheels  100 . The cable will be sufficiently stiff to allow it to be pushed into the central shaft, overcoming the biasing springs of the clamp wheels  100  and moving the axles of the clamp wheels along the openings  102  until the cable can pass between the clamp wheels. As soon as a short length of the cable has passed between the clamp wheels  100  it will be retained thereby, i.e. attempts to pull the cable out of the hole  90  will be resisted by the clamp wheels  100  being forced together by the converging rails  110 . 
         [0069]    Once the end of the cable is clamped to the magazine  16 , the magazine can be rotated so as to wind the cable onto the magazine. 
         [0070]    It will be understood that positioning the clamp mechanism  92  within the central shaft  78  of the magazine  16  protects the clamp mechanism from damage and from the ingress of dirt. The clamp mechanism  92  can be removed by loosening the bolts  116  and sliding it out of the central shaft  78 . 
         [0071]    The tension which can be provided to the cable will depend upon the components of the portable winch assembly  10 . By a suitable choice of materials, drive motors and gearing, a portable winch assembly capable of delivering a tensile force of 10 tonnes can be provided, and yet the winch assembly can be assembled and disassembled very quickly, and all of the components can be carried by hand. 
         [0072]    The heaviest component is likely to be the support frame  14 . The support frame is nevertheless designed to be carried by one person, but if desired a pair of wheels can be added to the ends of the shaft  120  ( FIG. 4 ), the wheels permitting the user to roll the support frame  14  rather than carry it. 
         [0073]    It will be understood that the support frame  14  is relatively unstable when first assembled, and one or more bracing pieces can be provided if desired, the bracing pieces being fitted between an upper part of the support frame and the ground adjacent to the access hole (see for example the bracing pieces  208  of the second embodiment shown in  FIGS. 10 and 11 ). The bracing pieces are ideally separable from the support frame, so that they do not increase the weight of the support frame. 
         [0074]    In use, however, the support frame  14  is very stable. This stability is provided in part by arranging the bottom of the recess  54  as low as possible, and in some embodiments below the axle  50 . Thus, it will be understood that attempts to tip the support frame  14  relative to the footplate  12 , namely in the directions towards the top left-hand corner of the sheet or the bottom right-hand corner of the sheet as drawn in  FIG. 1 , will increase the distance between the pulley  52  and the magazine  16 , so that tension in a cable wound about the magazine and pulley will resist any tendency of the support frame to tip over, and will instead act to maintain the support frame  14  in an upright position. 
         [0075]    Furthermore, the hook-like shaping of the bottom ends  56 , and the corresponding shaping of the recesses  54 , mean that the support frame  14  will not tip (towards the top left-hand corner of the sheet or the bottom right-hand corner of the sheet as drawn in  FIG. 1 ) relative to the footplate unless the support frame  14  is first lifted (at least partly) away from the footplate—and tension in the cable opposes such lifting. Thus, the stable location of the footplate  12  in the access hole, perhaps with the back plate  44  lying against a wall of the access hole adjacent to the end of the pipe to be removed, will result in a stable portable winch assembly  10 . 
         [0076]    It will be noted that the rotational axis of the magazine  16  is perpendicular to the axle  50  of the pulley  52 . Since the tensile force in the cable will act to one side of the magazine  16 , that force causes one of the bottom ends  56  to be pressed into its recess  54  with greater force than the other bottom end  56 . The bottom ends  56  are arranged to be sufficiently far apart to ensure that the tensile force is never sufficiently unbalanced to induce sideways tipping of the support frame  14 . This method of mounting the support frame  14  to the footplate  12  makes the winch assembly more stable, particularly when not under load. 
         [0077]    A second embodiment of portable winch assembly  210  is shown in  FIGS. 10-17 . The winch assembly  210  shown in  FIGS. 10 and 11  comprises a footplate  212 , a support frame  214 , a magazine  216  (see  FIG. 15 ), and a drive mechanism  222 . 
         [0078]    In this second embodiment the magazine  216  is covered in use by a removable magazine cover  202 . Also in this second embodiment the support frame  214  is made up of separable, stackable, sections  214   a ,  214   b  and  214   c . The section  214   c  may merely rest upon section  214   b , and the section  214   b  may merely rest upon the section  214   a , but in this preferred embodiment releasable catches (not shown) are provided to temporarily secure the sections together. The advantage of providing separable sections for the support frame is that the maximum weight of any particular component of the portable winch assembly is reduced, since as above explained the support frame of the first embodiment is likely to be the heaviest single component. In alternative embodiments the support frame may be separable into two, four or more components, as desired. 
         [0079]    The footplate  212  of the second embodiment is shown in more detail in  FIGS. 12 and 13 . The footplate  212  comprises a substantially flat bottom plate  242  and a substantially flat back plate  244 , the back plate  244  being substantially perpendicular to the bottom plate  242 . A pair of side plates  246  are rigidly connected to the bottom plate  242  and the back plate  244 , and each of the side plates  246  mounts an end of an axle  250  of a pulley  252 . The back plate  244  has an aperture  248  through which the cable may be passed in use. 
         [0080]    Unlike the first embodiment which uses a single pulley  52 , the present embodiment has one pulley  252  mounted upon the footplate  212 , and two further pulleys  201  mounted upon the support frame  214 , or more specifically upon the bottom support frame section  214   a . The pulleys  201 ,  252  are arranged so that in use they provide an arc around which the cable (not shown) may pass, the three pulleys  201 ,  252  together providing a large radius of curvature for the cable, equivalent to a large pulley, but with far less weight. 
         [0081]    Each of the side plates  246  is shaped to provide a recess  254 , which recess is shaped to accommodate one of the two bottom ends  256  of the support frame  214 . The recesses  254  are flanked by additional plates  260  which facilitate location of the bottom ends  256  in the recesses  254 . As in the first embodiment, there are no fixing means between the support frame  214  and footplate  212 , and the support frame is mounted upon the footplate merely by locating the bottom ends  256  in the respective recess  254 . However, suitable fixing means could be provided if desired. 
         [0082]    The top of the support frame  214 , or more specifically the top of the support frame section  214   c , is adapted to locate the drive mechanism  222  as shown in  FIG. 16 . In this embodiment the drive mechanism  222  incorporates guide rollers  230 , and so no guide rollers are needed upon the support frame  214 . Instead, the top of the support frame can be substantially flat, for example similar to the top of the support frame section  214   a  shown in  FIG. 12 , albeit with means to locate the drive mechanism  222  thereupon. Releasable fixing means can be provided to secure the drive mechanism  222  to the support frame  214  during use if desired. 
         [0083]    As shown in  FIG. 16 , the drive mechanism  222  comprises two drive motors  220 , each of which drives a respective gear  232 . The gears  232  each engage the gear wheel  234 . 
         [0084]    As in the first embodiment the gear wheel  234  is not permanently connected to the gears  232 . The gear wheel  234  is retained by a spring-biased locking pin  209  which urges the gear wheel  234  towards the cartridge  216 . When it is desired to remove the gear wheel  234  the locking pin is retracted by way of its handle  211 , allowing the gear wheel  234  to be slid towards the right as drawn in  FIG. 16 , until the teeth of the gear wheel  234  become free of the teeth of the gear wheels  231 . The gear wheel  234  can thereafter be lifted away from the remainder of the drive mechanism  222 . 
         [0085]    The possibility to remove the gear wheel  234  permits a reduction in the weight of the drive mechanism. In this second embodiment the drive mechanism may be the heaviest single component and it is desired that no component weigh more than 25 kg. In some embodiments the drive mechanism including the gear wheel  234  will weight more than 25 kg, and so may not be easy to carry for one person. Removing the gear wheel  234  can reduce the weight below 25 kg. 
         [0086]    In an alternative embodiment the gears  232  and the gear wheel  234  can be permanently and accurately secured together. 
         [0087]    Also, unlike the first embodiment the gears  232  are precisely (or at least almost precisely) diametrically opposed relative to the gear wheel  234 , the diametric opposition reducing any unbalanced forces which might otherwise tend to lift the gear wheel  234  and/or move the gear wheel laterally. 
         [0088]    In the second embodiment of portable winch assembly  210  the drive from the drive motors  220  is communicated to the magazine  216  wholly by the gears  232 , i.e. there is no friction drive in this embodiment (although friction drive is not precluded for modified embodiments). The drive mechanism  222  incorporates guide rollers  230  which in use are engaged by the respective end walls  240  of the magazine  216  as shown in  FIG. 15 . 
         [0089]    The drive motors  220  in the second embodiment are also hydraulic drive motors and are driven by a hydraulic power pack (not shown), in known fashion. Actuation of the hydraulic drive motors  220  causes the gear wheels  232  to rotate (in the same direction), so driving the gear wheel  234  to rotate. Any suitable drive means may be used, and the two motors  220  could be replaced by a single motor (or a set of three or more cooperating motors), if desired. However, two hydraulic drive motors  220 , with suitable gearing provided by the diametrically opposed gears  232  and the gear wheel  234 , are preferred. 
         [0090]    Located between the gear wheel  234  and the magazine  216  is a spider mechanism  203  as better seen in  FIG. 17 . The spider mechanism  203  has two elongated holes  204  which can accommodate the respective bosses  205  of the gear wheel  234 . When configured for use as shown in  FIG. 16 , the spider mechanism  203  is secured to the gear wheel  234  by way of two washers and circlips  206 , which are also shown in their fitted condition in the exploded view of  FIG. 17 . The spider mechanism  203  has additional bosses  207  which can locate in the elongated holes  236  in the end wall  240  of the magazine  216 . 
         [0091]    In this embodiment the holes  204 ,  236  are elongated by 10 mm. It will be understood that the elongated holes  204  and  236  are oriented orthogonally, and so provide up to 10 mm of movement in two perpendicular directions between the gear wheel  234  and the magazine  216 . This has advantages in accommodating wear and stresses which occur during use of the portable winch assembly, it being expected that the periphery of the end walls  240  will wear during use. Providing this relative movement between the gear wheel  234  and the magazine  216  avoids the need for any relative movement of the gear wheel  234  relative to the gears  232  (and so permits very tight tolerances to be maintained between the meshing teeth), and yet permits considerable tolerance in the relative positioning of the magazine, making use of the portable winch assembly considerably easier. 
         [0092]    To mount the magazine  216  upon the drive mechanism  222  the user retracts the locking pin  209  slightly and moves the gear wheel  234  towards the right as shown in  FIG. 16 , but with its gear teeth still partially meshing with the teeth of the gears  232 . The end walls  240  of the magazine  216  are laid upon the guide rollers  230  with the elongated holed  236  substantially aligned with the bosses  207  of the spider  203 . The handle  211  of the locking pin  209  is released, allowing the fitted spring to urge the gear wheel  234  towards the magazine  216 , the magazine being rotated slightly if necessary until the bosses  207  enter the elongated holes  236 . 
         [0093]    The magazine  216  can be constructed similarly to the magazine  16 , with a similar clamping mechanism for the cable. However, in many applications it will be possible to avoid a clamping mechanism, and merely pass the end of the cable through the central cylindrical shaft  278  and then bend the cable end to lie along the shaft  278 . By rotating the magazine two or more times and winding the cable over its free end the end of the cable can be effectively clamped to the magazine. 
         [0094]    Prior to use of the portable winch assembly, the user fits the magazine cover  202 , which protects the user from the rotating magazine  216 . It will be apparent from  FIG. 14  in particular that the user also fits a gear cover  213  which protects the user from the rotating gears  232  and gear wheel  234 . The gear cover  213  is separate from the magazine cover  202  in this preferred embodiment, so that the gear cover  213  does not need to be removed when the magazine is to be replaced. In addition, if the user wishes to carry the drive mechanism  222  without removing the gear wheel  234 , the gear cover  213  can be left in place during transportation, as well as during removal and replacement of a magazine. 
         [0095]    Following use of the portable winch assembly, when the cable has been wound onto the magazine, the (full) magazine can merely be lifted off the support frame. The winch can be used again with a different magazine. If the winch assembly is used to pull a pipe from the ground (as is disclosed in the method of my copending patent application WO2008/071997) then the removed pipe will be wound onto the magazine together with the cable, and will require refurbishment or disposal; a specialised facility can be provided for that.