Abstract:
A drawworks having a main drum spool, a main drum shaft which passes through and is rotatably and concentrically supported by the main drum spool, an auxiliary drum spool, respective drum shafts passing through and rotatably and concentrically supported by the drum spools in a manner in which wireline pull from the spools is isolated therefrom, a clutch mechanism rotatably connected to the shafts and brake mechanisms respectively connected to the main drum spool and the auxiliary drum spool outside the working area of the drawworks.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Application Ser. No. 60/483,469, filed Jun. 30, 2003. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The invention relates generally to a drawworks apparatus having a drive mechanism and a brake mechanism that are positioned externally relative to the operating area of the drawworks frame and a shaft which is isolated from wireline pull generated during operation of the drum spool.  
         [0004]     2. Description of the Related Art  
         [0005]     The drawworks is a type of winch used in the oil well drilling and service industry as a portion of a drilling or servicing rig to raise and/or lower items such as tools and lengths of pipe from a well bore from which oil or other hydrocarbons are produced.  
         [0006]     The drawworks typically includes a large-diameter spool that typically supports a length of cable, one or more brakes, a drive system connecting the spool to a power source, and other auxiliary devices that may assist in the lowering and raising items into a well bore.  
         [0007]     However, major disadvantages plague conventional drawworks designs: for instance, a major portion of the cost of manufacturing a conventional drawworks is due to the complexity of its design.  
         [0008]     Also, a significant portion of the cost of operating a well servicing or drilling rig is maintenance. The maintenance cost is influenced greatly by the number of components requiring servicing and their accessibility.  
         [0009]     Moreover, drumshaft failures cause the loss of braking ability in conventional drawworks and are much more likely to occur in a conventional drawworks due to the fact that it carries the line pull and must also absorb shock loads transmitted through the wire line spool.  
         [0010]     Still another common problem with conventional drawworks is the pliability of the brake bands. The pliable nature of the brake bands is often caused by insufficient anchoring of the dead end of the brake band.  
         [0011]     Yet and still another problem in conventional drawworks designs occurs at the brake live end, particularly, as the brake blocks wear, the brake band wraps further around the brake flange to allow the brake live end linkage to break over center and unexpectedly release the brakes.  
         [0012]     It is still another problem with conventional drawworks designs of experiencing failure due to contamination of the clutches&#39; frictional surfaces with oil or other foreign debris and materials. This problem is also associated with the conventional internal mounting of the brakes and other components within the drawworks frame.  
         [0013]     An additional problem associated with conventional drawworks the use of various types of seals, usually in the form of some type of labyrinth, to prevent oil from traveling to the clutch. This is not a very reliable technique and results in many drawworks failures.  
         [0014]     Yet and still a further problem associated with conventional drawworks apparatus is the fact that the wire line clamp is virtually hidden by the brake flange, the drawworks frame and guards, or the wear plates placed on the inside surface of the drum end.  
       SUMMARY OF THE INVENTION  
       [0015]     It is one aspect of the invention to provide a drawworks apparatus that reduces the complexity in conventional drawworks design without sacrificing performance, versatility or durability. The reduction of design complexity is accomplished by eliminating parts, which is made possible by a novel arrangement of drawworks components.  
         [0016]     It is another aspect of the invention to provide a drawworks apparatus in which those components that have been traditionally shown of frequent servicing more accessible by locating them outside of the drawworks frame. For instance, the drawworks apparatus in accordance with the invention provides a novel location for connecting the wire line spool to the drawworks frame via a set of bearings, thereby making it possible to locate the brakes externally, i.e., outside the drawworks frame and the working or operating area of the drawworks wherein the raising and lowering of equipment occurs. Two resulting benefits of arranging the brakes outside the drawworks frame are cooler running brakes and easier maintenance of the brakes. The bearings provided to connect the wire line spool to the drawworks frame are selected on the basis of size and not according to load capacity. Consequently, the fatigue-life rating greatly exceeds the life expectancy of the rest of the rig. Another advantage of locating the bearings for connecting the wire line spool to the drawworks frame in such a manner is that it removes the wire line pull from the drumshaft of the main drum spool and the sand drum spool, thereby reducing its required size and strength as well as improving its reliability.  
         [0017]     It is still another aspect of the invention to provide a drawworks apparatus that continues to provide braking function even in the event of drumshaft failure. This is a result of positioning the drumshafts relative their respective main drum spool and sand drum spool in a manner in which they are only required to carry chain pull, the weight of relatively light-weight components, and the torsional loads need to rotate the spools. This novel arrangement prevents the loss of braking capacity in the event of a drumshaft failure.  
         [0018]     Yet and still another aspect of the invention is to provide a drawworks apparatus that uses a novel design of dead-end components in a brake system that permits the use of many common components on various sizes of drawworks while utilizing the basic drawworks design. Among the common components are such major items as the drawworks frame, brake beam, bell cranks and an equalizer screw. This is either impossible or impractical for conventional drawworks designs. Thus, the cost of producing a particular piece of machinery can be reduced by using as many common components as possible and also by using components of other similar equipment.  
         [0019]     Still a further aspect of the invention is to provide a drawworks apparatus which eliminates the need for outside equipment such as cranes, gin pole trucks, and heating devices to conduct field repairs and maintenance. The use of such equipment is common for conventional drilling and well servicing rigs. For example, hubs are commonly shrink or press fitted the drive spool drum shafts on which they are mounted, and thus, heating devices such as torches are required to remove them. Because the drive system and the brake assembly of the drawworks apparatus in accordance with the invention are located outside of the working area of the drawworks frame, the drawworks components may be arranged and sized in such a manner that they can be disassembled and reassembled by hand without having to pull hubs from the drive spool drum shafts using outside equipment such as heating devices.  
         [0020]     It is still another aspect of the invention to provide a drawworks apparatus having an arrangement of working components that positions the crutches and the brakes outside both the drawworks frame, i.e., the working or operating area, and the chain drive cases. While some conventional drawworks designs locate the clutch outside the drawworks frame and the chain case, it is not physically separated from the chain case. The external mounting of the clutches and brakes in the drawworks apparatus of the invention reduces the likelihood of failure due to contamination of the clutches&#39; frictional surfaces with oil or other foreign debris and materials. Since the clutches and brakes are used to control the raising and lowering of very heavy loads on the rig, any failure of these devices could have disastrous consequences.  
         [0021]     Yet and still an additional aspect of the invention is to provide a drawworks apparatus that positions the brakes, flanges and the clutch relative to the drawworks frame that permits ease in inspection and servicing of the wire line clamp located at the drum end side of the wire line spool. Experienced professionals in the operation of oil well drilling and well drilling and servicing rigs find it absolutely essential to keep the wire line clamp properly tightened at all times, therefore, easy accessibility is very desirable. Therefore, unlike conventional drawworks designs, there are no such obstructions on the drawworks of the present invention.  
         [0022]     The novel configuration of the drum spool allows the drumshaft bearings to be located very close to the only applied radial loads, keeping the applied bending moments to a minimum for a given chain pull. This condition permits the user of a smaller, light-weight drumshaft that would be otherwise possible, and at the same time maintains a high factor of reliability.  
         [0023]     The novel placement of the brake flange facilitates the design of a very narrow, lightweight drawworks frame. The drawworks frame in accordance with the invention may be sized sufficiently narrow so that its side panels can be attached (via a welding operation) directly to the main structural members of the carrier or trailer upon which it is mounted. The relatively large weld length afforded in this design significantly reduces to a low level the weld stresses at the point of the drawworks attachment, thereby enhancing the reliability of the weld. Moreover, since the drawworks requires no gusseting for attachment to the carrier frame, both costs and complexity in design are reduced. Accordingly, the direct attachment of the drawworks side plate to the carrier frame increases the strength and rigidity of both members.  
         [0024]     The drawworks apparatus in accordance with the invention also utilizes a strong structural member called a brake beam in which to anchor the brake band. This member is sized for a minimum deflection that yields an extremely strong member. A contributing factor in the pliable brake band used in conventional drawworks designs is the eccentric force exerted on the dead end of the brake brand. Besides being too pliable, conventional brake bands are prone to lift upwardly relative to the flange surface. This problem is cured in the drawworks apparatus of the invention by anchoring the brake bands using a component(s) that exerts a tangential pull on the brake band.  
         [0025]     The drawworks apparatus in accordance with the invention utilizes a novel feature of a dead end equalizer by incorporating a threaded trunnion block for removing the bending moment form the trunnion pin located in the bell crank. Conventional drawworks designs threads the equalizer screw through a threaded hole in the trunnion pin which absorbs the axial load placed on the equalizer screw when the brakes are applied. The drawworks apparatus of the invention utilizes a trunnion pin with a drilled rather than threaded hole through which the equilizer screw passes. This is advantageous since the trunnion pin is placed in a shear-loaded condition, essentially eliminating any bending loads. In the conventional design, the trunnion pin is strong in shear but relatively weak in bending due to both the moment arm of the applied load and the loss of material caused by the hole through which the equalizer screw passes.  
         [0026]     Unlike conventional designs, the drawworks apparatus in accordance with the invention includes a linkage system that does not permit the brake shaft to rotate over center. Such a feature is very important to crew safety since the correction of the condition on a conventional rig requires a crew member to place himself virtually inside the drawworks, where the slightest error can have fatal results. The load may drop out of control when the brakes pass over center if the operator fails to catch the load with the slips.  
         [0027]     These and other objects, features and advantages of the invention will become more apparent from the following description when taken in conjunction with the detailed drawings that show, for purposes of illustration only, the preferred embodiments of the invention.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]     The advantages of the invention will become more apparent to those skilled in the art in conjunction with the detailed description of the preferred embodiments of the invention, in which:  
         [0029]      FIG. 1  is a top plan of the drawworks apparatus in accordance with the invention;  
         [0030]      FIG. 2  is a top cross-sectional view of the main drum section of the drawworks apparatus;  
         [0031]      FIG. 3  is a top cross-sectional view of the sand drum section of the drawworks apparatus;  
         [0032]      FIGS. 4A and 4B  are side and front cross-sectional views of the brake system of the drawworks apparatus;  
         [0033]      FIGS. 5A-5C  are top cross-sectional views of the brake linkage assemblies of the drawworks apparatus. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0034]     Referring now to drawing  FIGS. 1-5 , which show in detail a winch or power transmission apparatus, commonly called a drawworks, including drawworks frame  34 , main drum spool  17  and auxiliary or sand drum spool  18  in substantially parallel relation to main drum spool  17 . Also provided is a suitable drive device and a brake assembly  31 ,  32  for main drum spool  17  and sand drum spool  18 . By way of suitable bearings  14 , main drum spool  17  and sand drum spool  18  are directly attached to the drawworks frame  34 . Particularly, main drum spool  17  is supported for rotation on drawworks frame  34  via bearings  14  while sand drum spool  18  is supported for rotation on drawworks frame  34  via bearings  14 .  
         [0035]     Central shaft  15  of main drum spool and central shaft shaft  16  of sand drum spool  18  are concentric with their respective drum spool  17 ,  18  and extend longitudinally outward through respective shaft bores of the spools  17 ,  18 . Shafts  15 ,  16  are rotatably mounted preferably via anti-friction bearings  13  at each end of its respective drum spool  17 ,  18 . Thus, main drum spool  17  and sand drum spool  18  are supported by frame  34 , and main drum shaft  15  is supported by main drum spool  17  and sand drum shaft  16  is supported by sand drum spool  18 . Accordingly, by arranging main drum spool  17  and sand drum spool  18  to support their respective drum shafts  15 ,  16 , any applied radial loads are transmitted back to drawworks frame  34 . In a manner that will be explained hereafter, the structural configuration and relationship between shafts  15 ,  16 , drum spools  17 ,  18  and frame  34  is advantageous since the braking ability of the drawworks is unaffected by any failure to drum shafts  15 ,  16  during hoisting operation.  
         [0036]     As shown in  FIG. 2 , a suitable drive device  1 ,  2  is provided for driving main drum spool  17  and sand drum spool  18 . A driving source (not shown) is connected to transmission chain  100  which is in turn connected via sprocket  5  mounted to sand drum shaft  16 . Drumshaft  15  for main drum spool  17  supports clutch  29  on one end and sprocket  4  on the other end. Thus, the torque necessary to rotate main drum spool  17  is input through sprocket  4 . The torque is transmitted through key  35  loaded in shear to drumshaft  15 , and from there the torque is transmitted through another key  6  to the hub of friction clutch  29 . Upon any application of air pressure, the torque is transmitted through clutch drive ring  31  to spider  29  mounted on the drum spool extension. Spider  21  is also the component to which one of the brake flanges  20  is mounted. The torque applied to sprocket  4  which is mounted on the end of the main drum drumshaft  15  is transmitted to sprocket  4  by way of chain drive system  1 ,  2 , whereby driver sprocket  5  of which is located on the end of sand drum drumshaft  16 . During the time that the main drum spool  17  is in operation, sand drum drumshaft  16  functions as a jackshaft, i.e., it functions as an intermediate shaft between the prime mover and the driven shaft (in this case, main drum drumshaft  15 ). It should be understood by those of ordinary skill that any conventional driving device known in the art may be used to drive both main drum spool  17  and sand drum spool  18 .  
         [0037]     The drawworks of the invention is provided with a brake assembly  31 ,  32  for controlling the rotation of each drum spool  17 ,  18  during the operation of the drawworks apparatus, i.e., when cable is being payed out to lower items. The respective brake assemblies  31 ,  32  for main drum spool  17  and sand drum spool  18  includes brake shaft  45  for main drum spool  17  and brake shaft  46  for sand drum spool  18 , each brake shaft  45 ,  46  being rotatably mounted within a shaft bore to drawworks frame  34 . Main drum spool  17  is provided with a pair of brakes located at each end of frame  34  while sand drum spool  18  is provided with a single brake located opposite drive system.  
         [0038]     Brake flanges  20  are mounted to each drum spool  17 ,  18  on an extended portion of each respective drum spool  17 ,  18 . The mounting of the brake flanges  20  is accomplished through the use of spider  21  with a keyed hub  22 . The main drum spool  17  has two brake flanges  20  mounted on it, and are positioned externally relative to the drawworks frame  34 . Sand drum spool  18  has a single brake flange  20  that is also mounted externally relative to the drawworks frame  34 . Anti-friction bearings  13  are mounted within the bore of each drum spool  17 ,  18  to support a respective drumshaft  15 ,  16  in a manner which does not restrict rotation of the shafts  15 ,  16 . This produces what is commonly known as a “live shaft.” Accordingly, the braking ability of the drawworks apparatus is unaffected by any failure to shafts  15 ,  16  because the brake assemblies  31 ,  32  are structurally connected directly to drum spools  17 ,  18  instead of to shafts  15 ,  16  (i.e., shafts  15 ,  16  are structurally isolated from the brake assembly). While the sand drum spool  18  has one brake flange  20  mounted on it in accordance with this aspect of the invention, it could have two brake flanges  20  attached to it.  
         [0039]     As shown in  FIG. 3 , the sand drum drumshaft  16  at one end is rotatably connected to sprocket  5  having two sets of sprocket teeth attached to it by way of a keyed hub  7 . The opposite end of sand drum drumshaft  16  is rotatably connected to clutch  30  mounted via key  36 . The torque necessary to rotate the sand drum spool  18  is input through sprocket  5  mounted on sand drum drumshaft  16 , and is transmitted through key  36  which is loaded in shear to sand drum drumshaft  16 . From there the torque is transmitted through key  7  loaded in shear to the hub of clutch  30 , and upon application of air pressure, the torque is transmitted through clutch drive ring  32  to spider  21  mounted on an extension to sand drum spool  18 . Spider  21  is also the component to which brake flange  20  for sand drum spool  18  is mounted.  
         [0040]     The torque applied to sprocket  5  which is mounted to one end of sand drum drumshaft  16  is transmitted thereto by way of chain drive system  1 ,  2  and  3 . Chain drive system  1 ,  2 , and  3  is also available for use in transmitting power to an assist brake, which may be in the form of a band, water or electric brake used to absorb the tremendous energy generated when the drawworks apparatus is engaged in an operation of lowering a length of pipe or casing into a well bore.  
         [0041]     As illustrated in  FIGS. 4A and 4B , the drawworks in accordance with the invention utilizes band brake  19  having at least one brake blocks for reducing the speed of rotation of both main drum spool  17  and sand drum spool  18  so as to control the rate at which the length of cable from drum spools  17 ,  18  are payed out. As also shown in  FIGS. 5A-5C , band brake  19  is mounted at a “live end” thereof via a first linkage system which includes ears  49 , pin  50 , retaining ring  51 , link  52 , to brake shaft  46  and at the “dead end” via a pivotably adjustable linkage system which includes bell crank  42  and equilizer  64 .  
         [0042]     Band brake  19  may take the form of a self-energizing actuated by a force applied by the driller or operator to a torque lever or handle (not shown) to tighten brake band  19  and thereby engage the brake blocks mounted to brake band  19  with the surface of the spool  17 ,  18 . Such actuation force may be transmitted using a pivotably adjustable linkage assembly to the “dead end” of brake bands  19 . The drawworks apparatus utilizes a tubular member or brake beam  140 ,  141  that longitudinally extends through drawworks frame  34  and is cantilevered at ends thereof. The brake bream  140 ,  141  includes a pair of brake beam anchors  40  at each thereof which are welded into drawworks frame  34  to anchor the “dead end” of brake band  19  via a cantilever arrangement. Brake beam  140 ,  141  is advantageous in that it maintains its strength regardless of the direction of the applied dead end brake force.  
         [0043]     For the main drum spool  17 , each anchor  40  of brake beam  140  extends past the side plates of drawworks frame  34 , and a bell crank  42  is pivotably mounted at each respective end thereof. Preferably, brake beam anchors  40  are not welded until the size of the brake becomes known as it may become necessary to rotate it about its axis to accommodate a specific flange size. Anchors  40  at each end of brake beam  140  have lugs with holes bored therein, and are rotatable to accommodate various sizes of brakes. Thus, the line of force from the dead end of brake band  19  passes through its centerline regardless of the size of brake band  19  without the need for repositioning brake beam  140 .  
         [0044]     Bell crank  42  which includes a hole bored at its pivot point is placed at the end of each anchor  40  and by way of pivot pin  41  attached thereto. A plurality of holes may be bored at the three locations in the bell crank  42 : one at pivot point  41 , one at the center of brake flange  20 , and one at the center of brake beam anchors  40 . Brake bands  19  are pivotably connected through an adjustable linkage to bell crank  42  with a pin hole through the bored holes at the center of the brake flange  20 . Substantially spherical bushings (not shown) are used at both ends of linkage to ensure a free, non-binding operation, while equalizer screw  64  connects the bell cranks  42  to the “dead end” of band brakes  19 .  
         [0045]     The following procedure should be used to install the equalizer screw  64 : Firstly, equalizer screw  64  should be inserted longitudinally through brake beam  140  through the hole in each anchor  40 . Equalizer screw  64  has left hand threads at one end and right hand threads at the other end; therefore, simply turning the screw  64  will either tighten or loosen the brake linkage. Secondly, before bell cranks  42  are attached to brake beam  140 , place threaded trunnion block  55  between the lugs of the bell crank  42 , making sure to align it with the trunnion pin holes of the bell crank  42 . Thirdly, insert trunnion pin  80  through the bored holes in bell crank  42  and threaded trunnion block  55 . Finally, take the three-pieced assembled piece, i.e., bell crank  42 , trunnion block  55  and trunnion pin  80 , and insert equalizer screw  64  through the hole in trunnion pin  80 , then rotate equalizer screw  64  for insertion into trunnion block  55 . Continue doing this until pivot pin  41  is installed to join bell crank  42  to each brake beam anchor  40 .  
         [0046]     The equalizer assembly  64  is provided for main drum spool  17  to ensure that an equal braking force is placed on each brake band  19 . The “live end” of brake band  19  is coupled to a rotating brake shaft  46  through a link pin  50  on one end to lugs welded to the brake shaft  46  on the other end. This linkage is similar to a convention design except that link  52  has lugs on its sides that connect bracket ears  49  to brake shaft  46  in such a manner that brake shaft  46  cannot rotate past center. Brake bands  19  are centered over brake flange  20  by a system of rollers  66 ,  67  and  68  and pull-off springs  72 . The brake centering system holds brake bands  19  off of flange  20  during operation of the drawworks and positions brake bands  19  to properly function when actuated by an operator.  
         [0047]     Support brackets  76 ,  77 ,  78  and  79  are formed around the brake band  19  and flange  20  with an adjustable roller  66 ,  67  and  68  strategically placed around it. Pull-off springs  72  are provided at the live end of the brake band  19  and at the drum center line. When actuated, springs  72  pull brake band  19  back against rollers  66 ,  67  and  68  which are adjustable to hold brake band  19  approximately ⅛ inch off of flange  20 .  
         [0048]     Sand drum brake assembly  32  is constructed similarly to main drum brake assembly  31  except that brake assembly  32  does not require an equalizer assembly since it preferably uses only one brake  19 .  
         [0049]     It is apparent that innumerable variations of the preferred embodiments described hereinbefore may be utilized. However, these as well as other variations are believed to fall within the spirit and scope of the invention as covered by the claims attached herein.