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FIELD OF THE INVENTION 
     The present invention relates to drilling and servicing equipment for oil and gas wells generally, and in particular relates to a trolley hoisting system for use in rigs which transport and/or operate equipment for continuous coiled tubing drilling, for conventional joined pipe handling and drilling, and/or for wireline applications. 
     BACKGROUND OF THE INVENTION 
     Our U.S. Pat. No. 6,003,598 and corresponding Canadian Patent 2,235,555 for a “Mobile Multi-Function Rig” disclose a dual winch arrangement atop a pivotable derrick, or masts, for performing various functions relating to drilling and servicing either oil or gas wells. One of the winch systems, namely the derrick or mainblock winch, is used to raise and lower certain equipment along the mast, such as an injector and lubricator for continuous or coiled tubing (referred to herein as “CT”). A secondary, or fastline, winch is used to manipulate other equipment, such as a blow-out-preventer (“BOP”). For operations requiring use of a traveling block and elevators to lift and lower conventional joined pipe sections, the injector must first be brought to rest at the bottom of the mast and moved laterally out of the plane of the mast. The traveling block and the mainblock winch are then decoupled from the injector so that they are free to manipulate the joined pipe sections as in a conventional derrick. 
     We have not been able to locate or identify any conventional derricks, whether they use a single winch or a similar multiple (i.e. two or more) winch system, which would allow one winch arrangement to handle multiple tasks without having to decouple the winch from the injector and remove the injector from the mast, or where the injector superstructure is not thereafter interfering with movement of the mainblock winch lines and the joined pipe or other downhole equipment being handled. In particular, there are time and labour costs associated with handling of the injector upon switching tasks. Removal of the injector from the plane of the mast to enable access and use of a winch or hoisting system is labour and time consuming. The costs and difficulties are further augmented if the winch line moving the injector must also be disconnected or moved from the injector mechanism before using it for another desired task. Further, in a multiple winch system where the primary winch line is not disconnected from the injector, the secondary winch is typically slower and has less capacity than the primary line, leading to further inefficiencies. 
     What is desired therefore is a novel trolley hoisting system for use in rigs, particularly multi-task rigs, which transport and/or operate equipment for oil and gas operations, including continuous coiled tubing drilling and conventional joined pipe handling and drilling operations. The novel system should allow a single winch arrangement to perform various task without having to detach from or connect to the injector, as in some conventional rig arrangements, when switching between tasks. In particular, the winch system should be capable of moving the injector along the rig&#39;s derrick and, upon fixing the injector at a desired location along the derrick, the winch should be immediately available for performing other desired tasks, such as a joined pipe operation. 
     SUMMARY OF THE PRESENT INVENTION 
     According to the present invention, there is provided in one aspect a trolley hoisting system for use in a rig comprising a winch line extending from an upper end of a rig derrick having a traveling block at a lower end thereof, and an injector housing having at least one cavity for allowing the winch line passage therethrough and being adapted to engage the traveling block so that the winch line may be used to raise and lower the injector and injector housing along the derrick, and a lock arrangement for fixing the injector housing to the derrick at an upper end thereof to allow the traveling block to extend below the injector housing for performing other desired tasks on the rig. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
     Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein: 
     FIG. 1 is a side view of a mobile multi-function rig which employs a trolley and traveling block system according to a preferred embodiment of the present invention showing two selected locations of the injector when moved laterally out of the plane of the rig&#39;s derrick; 
     FIG. 2 is an end view of the derrick of the rig of FIG. 1 showing the traveling block supporting the trolley and injector in two selected locations; 
     FIG. 3 is a view similar to FIG. 2 but showing the injector fixed, or “parked”, at an upper end of the derrick and the traveling block projecting downwardly from the injector&#39;s trolley for performing other desired tasks, such as manipulating pipe sections; 
     FIG. 4 is an enlarged perspective view of the injector and trolley arrangement in isolation, providing a closer view of a chimney for receiving the traveling block; 
     FIG. 5 is a side view along line  5 — 5  of an upper portion of the trolley of FIG. 4; 
     FIG. 6 is a transparent view of FIG. 5 showing the traveling block supported by its cables exiting/entering a bottom end of the chimney; 
     FIG. 7 is a cross-sectional view along line  7 — 7  of an upper portion of the trolley of FIG. 4 to show a safety lock mechanism of the present invention; and, 
     FIG. 8 is a close-up view of the circled area in FIG. 7, indicated by reference numeral  8 , showing the locating arms of the safety lock mechanism. 
    
    
     LIST OF REFERENCE NUMBERS IN DRAWINGS 
       10  mobile rig 
       12  carrier 
       14  front end of  12   
       16  rear end of  12   
       18  cab 
       20  cartridge assembly 
       22  ground surface 
       24  wellhead 
       26  stabilizers 
       30  derrick 
       32  masts ( 2 ) 
       34  passage through masts 
       36  crown of  30   
       38  hydraulic legs 
       39  hollow tubular member 
       40  safety lock mechanism 
       42  locating arms 
       43  hydraulic cylinder for  42   
       44  locking pin mechanism 
       46  solenoid 
       48  pin 
       50  injector 
       52  trolley 
       54  tracks for  50   
       56  guide/chimney 
       58  hollow chamber of  56   
       60  bottom opening of  58   
       62  slots ( 4 ) above  58   
       64  top end of  56   
       66  openings on sides of  52   
       70  winch assembly 
       72  winch/drive motor 
       73  control panel 
       74  steel cables 
       76  sheaves 
       78  traveling block 
       80  loop beneath  78   
       82  joined pipe 
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     FIG. 1 shows a mobile rig  10  for transporting drilling and servicing equipment to an oil or gas well site. The equipment, such as a cartridge assembly  20  capable of holding various sizes of continuous or coiled tubing (“CT”) reels, is located aboard a self-propelled carrier  12  having a tandem axle front end  14  and a triple axle rear end  16 . A cab  18  houses an engine for driving the front and/or rear axles, and incorporates conventional controls for steering the carrier over a ground surface  22  and for locating the carrier&#39;s rear end over a well. The term “well” is understood herein to mean either an oil or gas well to be drilled, or an existing well or wellhead  24  which is to be tested or serviced. The carrier  12  incorporates a number of hydraulically operated stabilizers  26  for lifting the carrier off the ground and enhancing lateral stability during well operations. The front and rear axle designs may vary depending on the anticipated weight of equipment to be carried and the type of terrain to be encountered. The carrier&#39;s design is generally symmetrical about its longitudinal axis. 
     The rig  10  incorporates a number of drilling and servicing features aboard the mobile carrier  12 , including a derrick or mast  30  pivotally mounted to the rear of the carrier. The derrick is capable of supporting a blow out preventer (“BOP”) and an injector  50  for moving CT into and out of the well. The derrick also incorporates a novel single winch arrangement, generally designated by  70 . An important advantage of the rig of the present invention over the prior art is that the single winch arrangement  70 , in conjunction with novel features of the trolley  52 , is designed to perform multiple tasks, such as raising and lowering the injector and lubricator, as well as running joined pipe segments, handling various lengths of down hole tools, and hoisting other equipment as may be needed, including wireline equipment. 
     Referring now to the derrick  30  in some greater detail, it has two longitudinally spaced mast members  32  (as best seen in FIGS.  2  &amp;  3 ), each formed by a triangular (in cross-section) truss arrangement having a longitudinal central passage  34  along its length. The masts  32  are joined at the top end by a generally hollow structural tie member, or crown  36 , housing a pair of conventional pulley wheels (also referred to as “drums” or “sheaves”) of the winch assembly  70 . In the embodiment shown the sheaves are grooved to accept ⅞ inch (about 22 mm) wire rope or like cables. The derrick shown is about 60 feet (about 18 m) in length from ground to crown so as to accommodate multiple sections of conventional joined pipe  82 . A telescoping hydraulic cylinder or leg  38  is attached to each mast, and is operated from a control panel at the rear of the carrier, to tilt the derrick  30  between a transportation mode and an operating mode, as set out in more detail in applicant&#39;s U.S. Pat. No. 6,003,598. 
     A drive unit, namely in this case a hydraulic winch  72 , of the winch assembly  70  is located underneath the carrier&#39;s deck and is operated via an upstanding control panel  73 . The control panel  73  is folded out onto the side of the carrier when bringing the derrick to rest on the carrier&#39;s deck for transport. The winch  72  incorporates two sets of steel cables  74 , each set extending up a respective mast through its open passage  34  and over a respective sheave in the crown  36 . The cables  74  then extend downwardly away from the crown and about respective rotatable pulleys or sheaves  76  which operatively engage and support a “traveling” block  78 . The sheaves and block are sometimes referred to as a “block and tackle” arrangement. A loop element  80  is bolted to the bottom of the block  78  for attaching and carrying drilling/servicing equipment or other loads. The winch  72  therefore controls the movement of the traveling block  78  along the elevated derrick  30  for performing desired functions. 
     Referring now more particularly to the injector  50 , a cradle or trolley  52  supports the injector and rides on the masts&#39; rails  32  to guide the injector to any number of desired locations along the derrick, with two selected locations being illustrated in FIGS. 1 &amp; 2. The trolley has a set of tracks  54  for moving the injector laterally (i.e. perpendicularly to the plane of the derrick) out of the derrick. In the embodiment shown, the tracks  54  provide up to 54 inches of lateral movement, and the trolley is capable of traveling along the derrick whether the injector is located within the derrick or is slid laterally out of the plane of the derrick. 
     An important aspect of the present invention is the manner in which the traveling block  78  engages and moves the trolley along the derrick, and in which the cables  74  extend through the trolley. Referring now to FIGS. 4 to  6 , a central portion of the trolley  52  has an upwardly extending trolley guide or sleeve  56  (also referred to as a “chimney stack”), with a hollow interior chamber  58  configured to receive the traveling block  78  trough a bottom opening  60 . Each winch cable  74  extends through a respective one of four spaced slots  62  in the top end  64  of the chimney  56 . Hence, when the traveling block is located inside the chimney in an abutting relationship with the chimney&#39;s top end  64  for supporting the weight of the injector  50  and trolley  52 , the winch assembly is capable of controlling the location and travel of the injector and trolley along the derrick. 
     An additional feature of the present invention is a hydraulically and remotely operated “safety lock” mechanism  40  below the crown of the derrick for securely locking the trolley to the top of the derrick as shown in FIG.  3 . Referring as well to FIGS. 7 and 8, the masts incorporate a crown saver switching mechanism which is tripped by an upwardly moving trolley as it nears the crown  36  to slow the winch assembly and prevent collision of the trolley with the crown. Once tripped, the switching mechanism activates a pair of actuators, namely hydraulic cylinders  43 , one on each mast, to pivot outwardly (i.e. counterclockwise) respective locating arms  42  from the masts for positioning underneath the trolley  52 . The trolley is then lowered a short distance onto the locating arms  42 , allowing the arms to take up the weight of the seated trolley. Such seating results in alignment of an opening  66  on each side of the trolley with a respective hollow tube  39  mounted on the masts. A locking pin mechanism  44  is mounted on the trolley adjacent each opening  66 . A solenoid  46 , or like hydraulic cylinder, is activated to extend a pin  48  through the opening  66  and into the tube  39  to lock the trolley to the top of the derrick at the location shown. Sensors are provided for detecting/confirming that the pins are either safely engaged (or disengaged, as the case may be) with the mast. The injector is then moved to a “parked” position out of the plane of the derrick (as illustrated in FIG.  1 ), and the traveling block  78  may now be lowered out of engagement with the chimney  56  and below the trolley for performing other tasks, such as running conventional joined pipe  80  if desired, as illustrated in FIG.  3 . The safety lock mechanism  40  is preferably operable from the same console  73  as the trolley, and incorporates indicators which communicate with the sensors to confirm that the arms  42  and pins  48  are in their desired orientations, either safely engaged or disengaged with the trolley/masts, as the case may be. In addition, the arms  42  have indicators thereon for additional visual confirmation from ground level that the arms  42  are in their desired orientation. 
     An example of a typical multi-task operation for the rig  10  may now be described. With the derrick  30  in a raised and operative position, the traveling block  78  is pulled via cables  74  into the trolley&#39;s chimney  56  and is tensioned so as to carry the weight of the trolley  52  and associated equipment, including the injector  50 . With the safety lock mechanism  40  unlocked, the winch  72  is then used to move the trolley to a desired location on the derrick to perform a first set of tasks, such as CT operations. When it is desired to switch tasks which do not require use of the injector, such as a joined pipe operation, the winch mechanism pulls the traveling block, together with the trolley and injector, to the top of the derrick and the safety lock mechanism  40  is activated to lock the trolley in place with the locating arms  42  and the locking pin mechanism  44 . The injector is moved out of the way along the tracks  54  into the parked position, allowing the winch to drop the traveling block  78  out of the chimney  56  and through the trolley to perform the joined pipe operation independently of the trolley. When the trolley and injector must be used again, the reverse steps are taken. The block  78  is brought back up into the chimney  56 , weight is taken up by the cables  74 , and the safety lock mechanism  40  is released (i.e. the solenoids  46  disengage the pins  48  and the locating arms  42  are moved out of the way by cylinders  43 ) to make the trolley operational. 
     It will now be appreciated that, among other advantages, the present invention eliminates the need for a secondary fastline winch at the derrick&#39;s crown for performing other tasks, such as manipulating the BOP. The novel trolley and traveling block system allows a single winch arrangement to perform various task without having to detach from or connect to the injector, as in some conventional rig arrangements, when switching between tasks. In particular, the present system is capable of moving the injector along the rig&#39;s masts and, upon fixing the injector at a desired location along the masts, the traveling block is immediately available for performing other desired tasks, such as a joined pipe operation. 
     The above description is intended in an illustrative rather than a restrictive sense, and variations to the specific configurations described may be apparent to skilled persons in adapting the present invention to other specific applications. Such variations are intended to form part of the present invention insofar as they are within the spirit and scope of the claims below. For instance, it is understood that the trolley and traveling block system of the present invention is not restricted to use aboard a self-propelled carrier, but may be used in conjunction with other arrangements of equipment, such as on a derrick aboard a trailer which is pulled by a tractor truck.

Summary:
A trolley hoisting system for use in a rig has a derrick mounted to the rig, a winch line extending from an upper end of the derrick, and a traveling block located at one end of the winch line. An injector trolley has at least one cavity for allowing the winch line passage therethrough and is adapted to engage the traveling block so that the winch line may be used to raise and lower the injector trolley along the derrick. A lock arrangement for fixing the injector trolley to the derrick at an upper end thereof allows the traveling block to extend below the injector trolley for performing other desired tasks on the rig.