You are an expert at summarizing long articles. Proceed to summarize the following text:

You are an expert at summarizing long articles. Proceed to summarize the following text: 
BACKGROUND OF INVENTION 
       [0001]      1 . Field of the Invention 
         [0002]    This invention relates to apparatus for placing tubulars in a well using a drilling rig. More particularly, apparatus is provided for remotely controlling alignment of joints of tubulars before joining. 
         [0003]      2 . Description of Related Art 
         [0004]    The placement of tubulars in wells is normally carried out by hoisting a single joint of tubular (normally 30-45 ft. in length) into a vertical position over an assembly of tubulars (string) already placed in the well, aligning the hoisted joint of tubular with the string of tubulars, which is hanging in the well and supported by slips, rotating the hoisted tubular to thread the tubular into the string, raising the extended string to release the slips and lowering the extended string into the well. The process is repeated to make up a tubular string of the required length. 
         [0005]    Tubulars having an outside diameter from about 2⅜ inches to about 36 inches are placed in wells. Tubulars placed in a well after the hole is drilled are called “casing,” and the diameter is normally more than 5 inches. Smaller tubulars, used as conduits for fluid flow in the well, are called “tubing.” Tubing is usually placed in a well using a “work over” rig, but it has the same type apparatus for running tubulars as a drilling rig, and is included in the designation “drilling rig” herein. A variety of automated equipment has been developed for placing both tubing and casing in wells. In most wells, where automated equipment is not available or is not economically justified, the placement of tubulars is still a “hands on” operation. The pipe tongs used to rotate tubulars during a placement operation are often hydraulically powered. Slips are usually handled manually, but may be hydraulic. The hoisting of each joint of tubular into a vertical position is performed with a small hoist in a mast over the well. The lowering of the entire string in the well is performed with the block-and-cable apparatus common to drilling rigs. The required lifting capacity of the mast is usually determined by the weight of the casing. 
         [0006]    When a joint of tubular is in the vertical position, it must be aligned so that threading into the string of tubulars will not damage threads in the tubular. Generally, the joint being added has the male connection and the process of bringing the joints into position for threading is called “stabbing” the upper joint. When casing is being placed in a well each joint is much heavier than tubing joints, so aligning and stabbing casing are more difficult operations. The alignment operation is normally performed by a man standing on a platform in the mast (“derrick man”), which may be 30-50 ft. above the rig floor. Safety considerations arise when a man is required to stand above the level of the rig floor, because of the danger of falling. At the same time, it is necessary to thread the joints together without damaging threads in the tubular, which, with casing, can cause fluid to leak from the well and require expensive remediation steps to prevent an environmental risk. 
         [0007]    U.S. Pat. App. No. 2012/0085550 discloses method and apparatus for stabbing tubular goods using an assembly attached to an elevator in a conventional drilling rig or a casing-running tool used in top drive drilling rigs. U.S. Pat. No. 7,770,654 discloses a pipe handling device for use with a top drive rig. 
         [0008]    What is needed is apparatus for aligning tubulars for joining, without the need for a person positioned above the rig floor, that is economical to build and operate and that easily adapts for use with the variety of drilling rigs widely used in industry. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    Apparatus is provided to be placed on the floor of a drilling rig, either conventional or top drive, which can be remotely operated to align tubulars, such as casing, for making threaded connections at the drill floor. Hydraulic or pneumatic cylinders or electrically-driven sources of force operate plates and fingers to control the location and orientation of a tubular as it hangs in an elevator and align the tubular with a connector on a mating second tubular, such that lowering and rotation of the first tubular with low torque makes a threaded connection. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING(S) 
         [0010]      FIG. 1  shows an isometric view of the tubular aligning assembly. 
           [0011]      FIG. 2  shows an isometric front view of the finger assembly of the tubular arm assembly. 
           [0012]      FIG. 3  shows an isometric rear view of the finger assembly of the tubular arm assembly. 
           [0013]      FIG. 4  shows an isometric detail view of one embodiment of a driving mechanism for fingers of the tubular arm assembly. 
           [0014]      FIG. 5  shows a plan view of fingers of the assembly in an open position. 
           [0015]      FIG. 6  shows a plan view of fingers of the assembly in a closed position. 
           [0016]      FIG. 7  shows an isometric detail view of a second embodiment of a driving mechanism for fingers of the tubular arm assembly. 
           [0017]      FIG. 8  shows a plan view of fingers of the assembly in an open position. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    Referring to  FIG. 1 , one embodiment of a tubular aligning assembly  10  is shown. Assembly  10  is adapted to be placed on the drilling floor of a top drive drilling rig or to be placed on the rotary table of a conventional rotary rig. Base plate  11 , which may be 2-inch thick steel, forms the base of the assembly. Attached plate  11   a  contains slot  11   b  and is preferably removable from base plate  11  by operation of fasteners  11   c.  The size of slot  11   b  is determined by the size of the tubulars being placed in a well. Attached plate  11   a  may have pad eyes  11   c  that are adapted to receive slots on the bottom of slips. Post base assembly  12   a  supports gear  12  having teeth that mesh with a motor attached to  12   a  such that post  13  may be rotated by operation of the motor. Post base assembly  12   a  may have supports  12   b.  Post  13  may be adjustable in height by a movable pin passing through holes in two concentric sections of the post and post support  13   a,  or, in another embodiment, height may be remotely controlled by a hydraulic or pneumatic cylinder inside post  13  (not shown). Extendable box assembly  15  supports finger assembly  20 . Fixed box member  14  may be attached to support member  14   a  and post  13 . Movable box member  15  may be extended and retracted within fixed box member  14  by operation of cylinder  16 , which is attached to member  14  and member  15 . Finger assembly  20  is attached to movable box member  15 . Fixed box member  14  may include slot  14   b,  which allows retraction of finger assembly  20  nearer post  13 . 
         [0019]    Alternatively, in another embodiment, fixed box member  14  may be attached to a fixed structure of a drilling rig, such as one or more vertical members of the mast of the rig. In this embodiment, base  11  and post  13  are not used, and operations of the apparatus may be performed with other elements as if base  11  and post  13  were supporting fixed box member  14 . 
         [0020]      FIG. 2  illustrates an isometric front view of finger assembly  20 . Finger base plate  21  supports upper pair of fingers  22 , having distal pasts  22   a  and  22   b,  and lower pair of fingers  23 , having distal parts  23   a  and  23   b . Pair of fingers  22  and  23  may include roller bearings or ball bearings (not shown) inside each finger to decrease resistance to rotation of a tubular confined by and being aligned by the fingers. Distal parts  22   a  and  22   b  of upper fingers  22  are preferably in different horizontal planes, such that the distal parts of the fingers overlap when the fingers close. The same feature may be used for distal parts  23   a  and  23   b  of lower fingers  23 . Distal parts of all fingers may not be necessary and may be omitted for some pipe sizes and applications. Rotary bearing  25  provides for rotation of finger base plate  21  around box member  15 . 
         [0021]    In another embodiment, only one pair of pairs of fingers  22  or  23  may be present in finger assembly  20 , but not both. It may not be necessary to have two pairs of fingers, as shown in  FIG. 2  and  FIG. 3 , in some applications. The thickness of the fingers in one pair of fingers may be increased to provide an adequate source of torque transverse to the axis of a tubular. The driving mechanism for only one pair of fingers is required in this embodiment. 
         [0022]      FIG. 3  illustrates an isometric rear view of finger assembly  20  having two pairs of fingers. Finger support plate  30  is attached to finger base plate  21  and the extended end of box member  15  by horizontal pin  34 , disposed so as to allow tilting of support plate  30  by rotation around the pin. Force for control of tilting is supplied by cylinder  31 . Rotation of finger base plate  21  with respect to finger support plate  30  is provided by rotary bearing  25  ( FIG. 2 ). Force for rotation is supplied by cylinder  32 . Alternatively, the force may be supplied by an electric motor. Cylinders  37  and  38  supply the forces to operate the finger assembly, as described below. 
         [0023]    Referring to  FIG. 4 , one embodiment of a driving mechanism  40  for upper and lower pairs of fingers is illustrated. The same driving mechanism is used for upper and lower pairs of fingers. The position of piston  41  of cylinder  37 , extending through a hole in finger base  18  controls the position of fingers  22 . H-member  43  is rigidly attached to piston  41 . The proximate ends of links  45  are pivotally and moveably attached to H-member  43  by bushings  44 . The distal ends of links  45  are pivotally and moveably attached to fingers  22  by bushings  46 . Fingers  22  are pivotally and rigidly attached to horizontal U-member  42  by bushings  47 . Therefore, bushings  44  and  46  move linearly (hence, are “movably attached”) in response to linear movement of piston  41 , while bushings  47  remain fixed (hence, pivotally and rigidly attached). Driving mechanism  40  converts linear movement of the piston into angular movement of the fingers. In another embodiment, opening and closing of fingers may be achieved by a rack and pinion mechanism, described below. It should be understood that, although hydraulic or pneumatic cylinders are illustrated and described herein to provide driving forces, in other embodiments, driving forces provided by any or all of the cylinders can be provided by electric motors and associated gears. 
         [0024]      FIG. 5  illustrates fingers  22  in an open position, to be used for placing the fingers around a tubular and beginning to grasp the tubular.  FIG. 6  illustrates fingers  22  in a closed position. Contour  22   c  may be adapted for different diameters or ranges of diameters of tubulars. 
         [0025]    Referring to  FIG. 7 , another embodiment of a driving mechanism for a pair of fingers is shown. Driving mechanism  70  operates as a rack and pinion. Finger base plate  78  supports horizontal U-member  72 . Fingers  79  are pivotally and rigidly attached to member  72  by bushings  77 . Movement of piston  71  (or other source of force) causes member  74 , having teeth  73 , to move linearly. Teeth  75  in fingers  79  translate linear movement into angular movement of fingers  79 . 
         [0026]    All embodiments of a tubular aligning assembly disclosed herein may be used for placing any tubulars in a well with a rig; only casing will be discussed here. Assembly  10  may be placed on the floor of a drilling or completion rig. In another embodiment, post base assembly may be rigidly attached to one or more rigid members of the rig, such as a vertical member of the mast or the drill floor or substructure. Finger assembly  20  may then be operated to align the tubular being added to the tubulars in the well. A joint of casing, normally with male threads, is suspended in the mast by elevators. Slips support a string of casing that has been placed in a well, with a female connector above the slips. Normally, the position of elevators in a horizontal plane does not allow a joint to align with the connector such that the joint can be rotated at low torque, which is necessary to insure that threads on the joint and connector are properly mated. Preferably, some threads are engaged by manual force before tongs are applied to torque the connection to the recommended level. This minimizes the risk of cross-threading the connection, which is especially important in placing casing in a well. Operation of the cylinders or other apparatus to supply a driving force in the apparatus from a control panel allows alignment of a joint such that it can be joined to a connector by pipe threads at low torque even if the elevator is not vertically above the joint. The control panel may be on or off the drill floor. Observation of tubular alignment may be by visual observation and communication to an operator of the control panel, by a video camera and viewing screen for the panel operator or other sensors and communication channels for detecting the location of a joint with respect to a connector and communicating data to the panel operator. 
         [0027]    Although the present invention has been described with respect to specific details, it is not intended that such details should be regarded as limitations on the scope of the invention, except to the extent that they are included in the accompanying claims.

Summary:
Apparatus is provided for aligning tubulars when a drilling rig is used to lower a string of tubulars into a well. A joint of tubular can be moved to a vertical position above a connector to which it is to be joined and placed at the angle where threads on the joint and connector can be joined at low torque without damage to the threads. The apparatus can be used on a variety of drilling rigs and provides a safer environment for workers on the rig.