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: 
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     Not Applicable.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not Applicable.  
       BACKGROUND  
       [0003]     The present invention relates generally to equipment for handing pipe in an oilfield environment. More particularly, the present invention relates to elevators used to engage and lift vertically oriented tubular members.  
         [0004]     Many different types of tubular members are handled during drilling, completion, and workover of wells. Among the tubular members used in well construction and servicing are drill pipe, drill collars, casing and tubing. Many different specialized types of equipment are used in handling tubular members during various phases of the drilling, completion, and workover processes.  
         [0005]     Elevators are often used when handling tubular members when the tubular members are in or being moved to a vertical, or close to vertical, orientation. Most elevators are configured to interface with a shoulder, or upset, on the outer surface of the tubular member. The engagement of the elevator with this shoulder allows the elevator to support the weight of the tubular member and prevents the tubular member from falling through the elevator.  
         [0006]     Many elevators are equipped with swinging doors that open to allow the tubular member to be received in the elevator and are then secured in a closed position to retain the member. These doors are often characterized by hinges that support the swinging doors and lock assemblies that keep the doors closed. These doors and lock assemblies are often manually operated and have thus been a focus of efforts to improve the safety and operation of these devices.  
         [0007]     There remains a need to develop methods and apparatus for pipe elevators that overcome some of the foregoing difficulties while providing more advantageous overall results.  
       SUMMARY OF THE PREFERRED EMBODIMENTS  
       [0008]     The embodiments of the present invention are directed toward an elevator comprising a body having a longitudinal axis therethrough. The body is operable to at least partially surround and support a tubular member aligned with the longitudinal axis. The body also has a longitudinal opening that is sized so as to allow the tubular member to pass therethrough. A door is rotatable about the longitudinal axis of the body and has a closed position wherein the tubular member is retained within the body and an opened position wherein the tubular member can pass through the longitudinal opening.  
         [0009]     Thus, the present invention comprises a combination of features and advantages that enable it to overcome various problems of prior devices. The various characteristics described above, as well as other features, will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments of the invention, and by referring to the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]     For a more detailed description of the preferred embodiment of the present invention, reference will now be made to the accompanying drawings, wherein:  
         [0011]      FIG. 1  shows a top view of an elevator constructed in accordance with embodiments of the invention;  
         [0012]      FIG. 2  shows a partial sectional view of the elevator of  FIG. 1 ;  
         [0013]      FIG. 3  shows a partial sectional view of an open elevator constructed in accordance with embodiments of the invention;  
         [0014]      FIG. 4  shows a cross-section view of the locking pin of the elevator of  FIG. 3 ;  
         [0015]      FIG. 5  shows a partial sectional view of a closed elevator constructed in accordance with embodiments of the invention;  
         [0016]      FIG. 6  shows a cross-section view of the locking pin of the elevator of  FIG. 5 ;  
         [0017]      FIG. 7  shows a tubular member being received by an elevator constructed in accordance with embodiments of the invention;  
         [0018]      FIG. 8  shows a tubular member fully engaged by an elevator constructed in accordance with embodiments of the invention;  
         [0019]      FIG. 9  shows a cross-sectional view of the engaged elevator of  FIG. 8 .  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0020]     Referring now to  FIGS. 1 and 2 , elevator assembly  1   0  comprises body  12 , bottom ring  14 , door  16 , top ring  18 , and locking pin  20 .  FIG. 2  is a sectional view of elevator assembly  10  taken along section line A-A of  FIG. 1 . Body  12  comprises lower shoulder  22 , upper shoulder  24 , bail pins  26 , handle  28 , and locking slot  30 . Bottom ring  14  and top ring are rotatably fixed relative to body  12  by pins  32  and  33 , respectively. Locking pin  20  is coupled to door  16  and is guided by locking slot  30 . Snap ring  32  engages body  12  and holds top ring  18 , door  16 , and bottom ring  14  within the body.  
         [0021]     Body  12  has a substantially cylindrical shape having an opening  34  on one side. Bail pins  26  are arranged on opposite sides of body  12  for attaching to bails, or other lifting members. In certain embodiments, bail pins  26  may be replaced by lugs, lifting ears, or other means for connecting elevator  10  to a lifting appliance. Locking slot  30  extends through body  12  and includes counterbore  36  sized so as to interface with locking pin  20 .  
         [0022]      FIGS. 3 and 5  show a cross-section of elevator assembly  10 , taken along section line B-B of  FIG. 2 .  FIG. 3  shows elevator assembly  10  is shown in an open position wherein door opening  38  is aligned with body opening  34 . In the open position, bushing  40  of locking pin  20  is retracted and rests against body  12 . Referring now to  FIG. 4 , locking pin  20  comprises bushing  40 , rod  42 , bushing spring  44 , lock button  46 , and button spring  48 . Bushing  40  comprises shoulder  50  and counterbore  52 . Rod  42  comprises T-shaped front end  54  that engages door  16  and flanged back end  56  that slidably engages lock button  46 , such as with a dove-tail slot. Bushing spring  44  is disposed between shoulder  50  and back end  56  so as to bias bushing  40  toward front end  54  of rod  42 . In order to move bushing  40  toward back end  56 , lock button  46  must be centered so as to move past counterbore  52 . Lock button  46  is biased to an offset position by button spring  48 .  
         [0023]     Door  16  is rotated to a closed position, as shown in  FIG. 5 , by moving locking pin  20  through slot  30  until locking pin  20  engages counterbore  36 . The engaged locking pin is shown in  FIG. 6 . In the closed position, door  16  completely closes body opening  34  and locking pin  20  is disposed at the end of slot  30 . Bushing  40  is urged into counterbore  36  by bushing spring  44 . As bushing  40  moves into counterbore  36 , lock button  46  enters bushing counterbore  52  and is urged to one side by button spring  48 .  
         [0024]     From the locked position the only way to unlock and rotate door  16  is to follow the steps described below. First, lock button  46  us centered within bushing  40 . This allows bushing  40  to be pulled out of counterbore  36 . Once bushing  40  is out of counterbore  36 , door  16  can be rotated by moving locking pin  20  through slot  30  to the open position shown in  FIG. 4 .  
         [0025]      FIGS. 7-9  illustrate the engagement of a tubular member  100  with elevator assembly  10 . As shown in  FIG. 7 , elevator assembly  10  is in the open position wherein door opening  38  is aligned with body opening  34 . Tubular member  100  is inserted into openings  34 ,  38  such that elevator  10  is disposed close to tool joint  104 . Elevator  10  may be attached to tubular member  100  when the tubular member is vertical, horizontal, or at any angle in between. Once tubular member  100  is received in elevator  10 , locking pin  20  is moved through slot  30  such that door  16  rotates to capture the tubular member.  
         [0026]     Once in the closed position, as shown in  FIGS. 8 and 9 , angled surface of top ring  18  engages the tapered shoulder of tool joint  102 . Door  16  holds tubular member  100  in close engagement with top ring  18  and bottom ring  14 . Thus, tubular member  100  is securely fastened within elevator  10  and ready to be lifted up. Once the handling of tubular member  100  is completed, door  16  is rotated back to the open position of  FIG. 7  and elevator  10  can be removed from the tubular member.  
         [0027]     As can be seen in  FIG. 8 , the relationship between top ring  18 , door  16 , and bottom ring  14  and tubular member  100  is critical to the performance of elevator  10 . As the diameter and type of tubular member changes, one or more of bottom ring  14 , door  16 , and top ring  18  may have to be changed so as to properly engage pipes with different diameters or tool joint shoulders. Many of the other components of elevator  10 , such as body  12  and locking pin  20  may be used for a wide range of pipe sizes without replacement. Thus, elevator  10  may be designed to allow for simple assembly and disassembly.  
         [0028]     Referring back to  FIGS. 2 and 3 , elevator  10  can be disassembled by first removing snap ring  32 , allowing top ring  18  to be removed from body. Door  16  can then be lifted up through body  12 . As door  16  is lifted locking pin  20  will slide out of the T-shaped slot in the door, thus allowing the locking pin to be removed from slot  30 . After door  16  is removed, bottom ring  14  can then be removed from body  12 .  
         [0029]     In the above described embodiments, locking pin  20  is used to manually open and close elevator  10 . In other embodiments, the door could have gear teeth cut on its outside surface and the locking pin could be replace by pinion and hydraulic motor which would rotate the door. The hydraulically actuated elevator may find particular usefulness in allowing for remote control of the elevator and for larger elevator sizes where manual operation would be difficult.  
         [0030]     While preferred embodiments of this invention have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teaching of this invention. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the system and apparatus are possible and are within the scope of the invention. For example, elevators capable of handling a wide array of sizes and tubular members can be constructed in accordance with the embodiments discussed herein. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.

Summary:
An elevator comprising a body having a longitudinal axis therethrough. The body is operable to at least partially surround and support a tubular member aligned with the longitudinal axis. The body also has a longitudinal opening that is sized so as to allow the tubular member to pass therethrough. A door is rotatable about the longitudinal axis of the body and has a closed position wherein the tubular member is retained within the body and an opened position wherein the tubular member can pass through the longitudinal opening.