Abstract:
This invention provides an exchange jig for assisting work of exchanging a heavy object such as an X-ray tube. This exchange jig has a detachable unit, which enables attaching/detaching the exchange jig to/from the top plate of a bed. In exchange work, the exchange jig is attached to the top plate of the bed. The elevating function and top plate slide function of the bed realize a forklift function together with the support function of the arm unit of the exchange jig. If exchange work is not performed, the exchange jig can be detached from the top plate of the bed. The arm unit is attached to the detachable unit through a rotating unit. The rotating unit freely rotates about an almost vertical axis. This rotation facilitates work of transferring the heavy object between the arm unit and a gantry, and work of transferring the heavy object between the arm unit and a truck.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application i s based upon and claims the benefit of priority from the prior Japanese Patent Application No. 11-084335, filed Mar. 26, 1999, the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     The present invention relates to an exchange jig for a heavy object such as an X-ray tube incorporated in the gantry of a medical image sensing apparatus such as an X-ray computed tomography apparatus (X-ray CT) or magnetic resonance imaging apparatus (MRI), a bed device, and an X-ray computed tomography. 
     FIG. 1A is a sectional view showing the gantry of a conventional X-ray computed tomography apparatus. A gantry frame  41  supports a rotating ring  42 . The rotating ring  42  can rotate. An X-ray tube  44 , high-voltage generator  45 , X-ray detector  46 , and the like are mounted on the rotating ring  42 . 
     The X-ray tube  44  is as heavy as 25 kg for a light tube and 65 kg for a heavy tube. The high-voltage generator  45  and X-ray detector  46  are also heavy. Exchange work of dismounting an old X-ray tube from the rotating ring  42  and mounting a new one is very hard work. To assist this exchange work, the gantries of most conventional X-ray computed tomography apparatuses incorporate exchange jigs (crane mechanisms) for assisting work of exchanging an old X-ray tube or the like with a new one. 
     A column  50  of an exchange jig  48  is attached almost perpendicularly to, e.g., a holder  49  of the gantry frame  41 . The column  50  is coupled to an almost horizontal arm  51 . A reel  53  hangs from the distal end of the arm  51 . A hook  52   b  is connected to the end of a wire  55  of the reel  53 . 
     In exchange work, an old X-ray tube  44  is tied with a rope  54 , which is hooked on the hook  52   b . The X-ray tube  44  is dismounted from the rotating ring  42 , and pulled up by the reel  53 . As shown in FIG. 1B, the column  50  is axially rotated to remove the X-ray tube  44  outside the gantry. The X-ray tube  44  is put down on the floor by the reel  53 . The X-ray tube  44  is released from the rope  54 , and loaded on a truck. A new X-ray tube  44  is mounted in a reverse order to the dismounting order. 
     FIG. 2A shows another exchange jig  61 . A slide rail  61   a  is almost horizontally attached to a gantry frame  41 . A slide frame  61   b  can slide along the slide rail  61   a . A hook  63  hangs from the reel  65  of the distal end of the slide frame  61   b.    
     In exchanging an X-ray tube  44 , a rope  64  which ties an old X-ray tube  44  is hooked on the hook  63 . The slide frame  61   b  is slid and the reel  65  is lowered, to remove the X-ray tube  44  outside the gantry frame  41 . Then, the X-ray tube  44  is loaded on a transport truck. A new X-ray tube  44  is mounted in a reverse order to the dismounting order. 
     As described above, the gantries of most conventional X-ray computed tomography apparatuses incorporate exchange jigs. This is one of factors that enlarge the gantry. 
     Since the rotation radius of the arm  51  and the slide length of the exchange jig  61  are short, the X-ray tube cannot be directly loaded from the exchange jig on the truck. The X-ray tube must be temporarily put down on the floor, and then loaded from the floor on the truck. This decreases the workability, and may inhibit exchange work using the exchange jig in a small CT room. 
     BRIEF SUMMARY OF THE INVENTION 
     It is an object of the present invention to simplify exchange work of a heavy object such as an X-ray tube. 
     The present invention provides an exchange jig for assisting work of exchanging a heavy object such as an X-ray tube. This exchange jig has a detachable unit, which enables attaching/detaching the exchange jig to/from the top plate of a bed. In exchange work, the exchange jig is attached to the top plate of the bed. The elevating function and top plate slide function of the bed realize a forklift function together with the support function of the arm unit of the exchange jig. If exchange work is not performed, the exchange jig can be detached from the top plate of the bed. The arm unit is attached to the detachable unit through a rotating unit. The rotating unit freely rotates about an almost vertical axis. This rotation facilitates work of transferring the heavy object between the arm unit and a gantry, and work of transferring the heavy object between the arm unit and a truck. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. 
     FIGS. 1A and 1B are views showing a conventional exchange jig incorporated in the gantry of an X-ray computed tomography apparatus; 
     FIGS. 2A and 2B are views showing another conventional exchange jig incorporated in the gantry of an X-ray computed tomography apparatus; 
     FIG. 3A is a plan view showing an exchange jig attached to the top plate of a bed according to the first embodiment of the present invention; 
     FIG. 3B is a front view showing the exchange jig attached to the top plate of the bed according to the first embodiment; 
     FIG. 3C is a side view showing the exchange jig in the first embodiment; 
     FIGS. 4A to  4 D are views showing X-ray tube dismounting work procedures in the first embodiment; 
     FIG. 5A is a side view showing an exchange jig in the second embodiment of the present invention; 
     FIG. 5B is a sectional view showing the headrest mount of a top plate in the second embodiment; 
     FIG. 5C is a plan view showing the exchange jig attached to the headrest mount of the top plate in the second embodiment; 
     FIG. 6A is a side view showing an exchange jig in the third embodiment of the present invention; 
     FIG. 6B is a plan view showing the exchange jig in the third embodiment; and 
     FIG. 6C is a plan view showing the exchange jig attached to the headrest mount of a top plate in the third embodiment. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The gist of the present invention is to use a bed as a forklift by attaching an exchange jig to the top plate of the bed. That is, the bed functions as a forklift with the support function of the arm unit of the exchange jig in addition to the elevating function and top plate slide function of the bed. Preferred embodiments of the present invention will be described in detail below. 
     First Embodiment 
     FIGS. 3A to  3 C show the structure of an exchange jig according to the first embodiment of the present invention. An exchange jig  1  is detachable from a top plate  2  of a bed. The bed comprises a slide mechanism for slidably supporting the top plate  2  in a longitudinal direction, and an elevating mechanism for elevating the top plate  2 . 
     [Structure of Top Plate] 
     As shown in FIG. 3B, the top plate  2  has an almost semi-arcuated sectional shape. An upper surface  2   a  of the top plate  2  on which a patient lies is formed into an arcuated recessed shape. As shown in FIG. 3A, a headrest mount  5  for mounting a headrest for resting a patient&#39;s head is formed at one end of the mounting surface  2   a.    
     A lower surface  2   b  of the top plate  2  is formed into an arcuated projecting shape. The top plate  2  is supported slidably in the longitudinal direction of the top plate by a main roller  4   b  arranged immediately below the top plate  2  and sub-rollers  4   a  and  4   c  arranged at the left and right edges of the top plate  2 . The sub-rollers  4   a  and  4   c  are newly added to prevent distortion and rolling of the top plate  2  under a heavy load from the left and right upon mounting the exchange jig  1 . 
     [Structure of Exchange Jig] 
     The exchange jig  1  comprises a detachable unit  11  detachable from the top plate  2 , the slide rail  16  attached to the unit  11 , a rotating unit  21  attached to the detachable unit  11  rotatably about an almost vertical axis, and an arm unit  22  attached to the rotating unit  21  to support a heavy object such as an X-ray tube, a high-voltage generating unit and a X-ray detector. 
     [Structure of Detachable Unit] 
     The detachable unit  11  has a frame  11   a  mounted on the top plate  2 , and a slide rail  16  supported by the frame  11   a  slidably in the widthwise direction of the top plate. The frame  11   a  has an almost equal length to the width of the top plate  2 , and has a U sectional shape, as shown in FIG.  3 C. The slide rail  16  is fitted in the frame  11   a.    
     Holding members  12  for holding the top plate  2  together with the frame  11   a  are attached to the two ends of the frame  11   a  with wing nuts  13  and threaded blocks  14 . Each threaded block  14  is curved to conform to the shape of the upper surface  2   a  of the top plate  2 . The frame  11   a  is set at an arbitrary position on the top plate  2 , and the wing nuts  13  are screwed into the threaded blocks  14  to tightly sandwich the top plate  2  between the holding members  12  and the threaded blocks  14 . Accordingly, the frame  11   a  can be fixed to an arbitrary position on the top plate  2 . The threaded block  14  prevents damage to the upper surface  2   a  of the top plate  2  and suppresses distortion of the top plate  2 . 
     [Structure of Slide Rail] 
     The slide rail  16  is longer than the frame  11   a . The slide rail  16  has two slits  16   c . Wing nuts  18  are screwed into nuts  11   c  through the slits  16   c  of the slide rail  16  and holes  11   b  formed in the frame  11   a . Loosing the wing nut  18  allows the slide rail  16  to slide within the range of the slit  16   c . Securely tightening the wing nut  18  fixes the slide rail  16  to the frame  11   a.    
     [Structure of Rotating Unit] 
     The rotating unit  21  is attached to the distal end of the slide rail  16  through a spacer  23  rotatably about an almost vertical axis. The distal end of a wing nut  24  is screwed into the threaded hole of the rotating unit  21  through the hole of the distal end of the slide rail  16  and the hole of the spacer  23 . Loosing the wing nut  24  allows the rotating unit  21  to freely rotate on the slide rail  16 . Securely tightening the wing nut  24  fixes the rotating unit  21  to the slide rail  16 . The rotating unit  21  has an almost L shape, and the arm unit  22  is attached to the lower portion of the vertical surface of the L-shaped rotating unit  21 . The L-shaped rotating unit  21  can hold arms  22   a  at lower positions than the upper surface  2   a  of the top plate  2  together with the spacer  23 . This makes it possible to put down a heavy object such as an X-ray tube on a lower position than the lowest position of the top plate  2 . The heavy object can be easily transferred between the arm unit  22  and a truck. 
     [Structure of Arm Unit] 
     The arm unit  22  has a pair of arms  22   a . The arms  22   a  have a columnar shape and are coated with an elastic material such as rubber so as not to damage an object to be mounted. The pair of arms  22   a  are attached perpendicularly to the rotating unit  21  to be parallel to each other at a predetermined interval, like tips of a fork. The arm  22   a  can take various lengths and thicknesses. The arm  22   a  is detachable from the rotating unit  21  by a bolt  22   b  so as to be exchanged with an arm having a length and thickness corresponding to the shape and weight of an object to be mounted. 
     Operation of First Embodiment 
     Exchange operation of a predetermined unit of the bed device having this structure according to the first embodiment will be described. An X-ray computed tomography apparatus will be exemplified. As is well known, the X-ray computed tomography apparatus is constituted by a bed on which an object to be examined lies, a gantry for collecting projection data about the object, and a computer for reconstructing tomographic image data based on the collected projection data. The gantry has a rotating ring which rotates about an almost horizontal axis. The rotating ring holds an X-ray tube, a high-voltage generator for applying a high voltage to the X-ray tube, an X-ray detector for detecting X-rays having passed through the object, and other components. The X-ray tube, high-voltage generator, and X-ray detector are heavier than other components. Hence, exchange work of the X-ray tube, high-voltage generator, and X-ray detector requires assistance of the exchange jig. In particular, the exchange jig is indispensable for exchange work of the heaviest X-ray tube. In this case, exchange work of the X-ray tube will be exemplified. 
     (Mounting of Exchange Jig) 
     The frame  11   a  is located at a desired position on the top plate  2 , and the wing nut  13  is tightened to fix the frame  11   a  to the top plate  2 . The slide rail  16  is slid to project from the frame  11   a  by a desired length. The wing nuts  18  are tightened to fix the slide rail  16  to the frame  11   a . The arms  22   a  are rotated and fixed to the rotating unit  21  in a desired direction. 
     (Exchange Work) 
     The gantry cover of the X-ray computed tomography apparatus is removed. As shown in FIG. 4A, an X-ray tube  31  in a gantry  30  is moved, e.g., from a position immediately above the top plate  2  to a position rotated through 90°. The top plate  2  is properly elevated by the operation of an elevating mechanism  32  of the bed. The arms  22   a  of the exchange jig  1  are then located at positions slightly lower than the bottom of the X-ray tube  31 . As shown in FIG. 4B, the top plate  2  is properly slid in a forward direction F by the operation of a slide mechanism  33  of the bed. Accordingly, the arms  22   a  of the exchange jig  1  are located immediately below the X-ray tube  31 . The top plate  2  is slightly moved up by the operation of the elevating mechanism  32 . The X-ray tube  31  is brought into contact with the arms  22   a  of the exchange jig  1 . In this state, the X-ray tube  31  is detached from the rotating ring and completely mounted on the arms  22   a  of the exchange jig  1 . 
     The top plate  2  is slightly slid in a backward direction R by the operation of the slide mechanism  33 . As shown in FIG. 4C, the X-ray tube  31  is removed outside the gantry  30 . Since the arms  22   a  are located on the side of the top plate  2 , the top plate  2  may be distorted by the weight of the X-ray tube  31  upon supporting the X-ray tube  31  by the arms  22   a . However, the two sides of the top plate  2  are supported by the sub-rollers  4   a  and  4   c , so the top plate  2  does not distort. 
     After the X-ray tube  31  is removed outside the gantry  30 , the top plate  2  is moved down in a downward direction D by the operation of the elevating mechanism  32 . As shown in FIG. 4D, the X-ray tube  31  is put down on a truck  34 . Since the arms  22   a  are located at lower positions than the lowest position of the top plate  2  by the rotating unit  21  and spacer  23 , as described above, a heavy object such as the X-ray tube can be directly loaded on the truck  34 . 
     In attaching a new X-ray tube, it is loaded by the truck  34 , and the above-described procedures are executed in a reverse order from FIG.  4 D→FIG.  4 C→FIG.  4 B→FIG.  4 A. More specifically, the support arm unit  22  is moved down to flush with the transport truck  34 , the new X-ray tube is placed on the arms  22   a , and the arms  22   a  are moved up to a predetermined level. In this state, the arms  22   a  are slid toward the gantry  30 . Accordingly, the new X-ray tube can be easily attached to the rotating ring in the gantry  30 . 
     Effect of First Embodiment 
     As is apparent from the above description, since the bed can function as a forklift by attaching the exchange jig to the bed, exchange work can be done in a small exchange space accurately, safely, and easily. Since no exchange jig need be incorporated in the gantry, the gantry can be downsized. Since the sub-rollers attached to the bed prevent distortion of the top plate, damage to the bed can be prevented, and the safety of exchange work can be improved. 
     Second Embodiment 
     In the first embodiment, the exchange jig is attached to the top plate  2  through the frame  11   a . In the second embodiment, the exchange jig is attached to a headrest mount which exists on the top plates of most beds. Note that the first and second embodiments are different only in this point, only the different feature will be described, and a repetitive description thereof will be omitted. 
     Structure of Second Embodiment 
     FIGS. 5A to  5 C show the structure of an exchange jig according to the second embodiment. In an exchange jig  1  of the second embodiment, a fitting portion  36  to be fitted in a headrest mount  5  of a top plate  2  is attached to one end of a slide rail  35  having an almost U sectional shape. The headrest mount  5  of the top plate  2  has an almost trapezoidal cross section. The fitting portion  36  is formed into an almost trapezoidal shape so as to be fitted in the headrest mount  5 . This effectively prevents the fitting portion  36  from slipping off upward and laterally from the headrest mount  5 . Stoppers  5   a  of the headrest mount  5  effectively prevent the fitting portion  36  from slipping off forward from the headrest mount  5 . 
     A wing nut  38  is screwed into the threaded hole of the fitting portion  36  through a slit  37  formed in the slide rail  35 . Loosening the wing nut  38  allows the slide rail  35  to slide on the fitting portion  36  and top plate  2  in a widthwise direction Y of the top plate  2 . Securely tightening the wing nut  38  fixes the slide rail  35  to the fitting portion  36  and top plate  2 . 
     Operation of Second Embodiment 
     The fitting portion  36  of the exchange jig  1  is fitted in the headrest mount  5  of the top plate  2 . The slide rail  35  is appropriately slid within the range of the slit  37 . The wing nut  38  is tightened at a position where the slide rail  35  projects from the top plate  2  by a proper length, thereby fixing the slide rail  35  to the top plate  2 . Arms  22   a  are appropriately rotated, and a wing nut  24  is tightened and fixed in a proper direction. 
     The subsequent exchange procedures are the same as in the first embodiment. 
     Effect of Second Embodiment 
     As is apparent from the above description, the bed device of the second embodiment can use the headrest mount  5  of the top plate  2  to attach the exchange jig  1 . Therefore, the exchange jig  1  can be attached to the top plate  2  without using the frame  11   a  described in the first embodiment. The second embodiment can simplify the structure and decrease the number of components to reduce the cost. In addition, the second embodiment can attain the same effects as those of the first embodiment. 
     Structure of Third Embodiment 
     FIGS. 6A to  6 C show the structure of an exchange jig according to the third embodiment. In an exchange jig  1  of the third embodiment, a short frame  40  is attached to a fitting portion  36   a  fitted in a headrest mount  5  of a top plate  2 . A rotating unit  21  and arm unit  22  are attached to the distal end of the short frame  40 . In the second embodiment, the slide frame is arranged to cross the top plate  2 . In the third embodiment, the short frame  40  is arranged parallel to the longitudinal direction of the top plate  2 . That is, the short frame  40  is arranged not on the side of the top plate  2  but in front of it. 
     A wing nut  38  is screwed in the threaded hole of the fitting portion  36   a  through a slit  41  formed in the frame  40 . Loosening the wing nut  38  allows the frame  40  to slightly slide on the fitting portion  36  and top plate  2  by the length of the slit  41  in a widthwise direction Y of the top plate  2 . Securely tightening the wing nut  38  fixes the frame  40  to the fitting portion  36  and top plate  2 . 
     Operation of Third Embodiment 
     The fitting portion  36   a  of the exchange jig  1  is fitted in the headrest mount  5  of the top plate  2 . The frame  40  is appropriately slid to the right and left within the range of the gantry frame  41 . The wing nut  38  is tightened to fix the frame  40  to the top plate  2 . Arms  22   a  are appropriately rotated, and a wing nut  24  is tightened and fixed in a proper direction. 
     The subsequent exchange procedures are the same as in the first embodiment. 
     Effect of Third Embodiment 
     As is apparent from the above description, the bed device of the third embodiment can use the headrest mount  5  of the top plate  2  to attach the exchange jig  1 . The exchange jig  1  can be attached to the top plate  2  without using the frame  11   a  described in the first embodiment. The third embodiment can simplify the structure and decrease the number of components to reduce the cost. Since the frame  40  is short, the exchange jig can be downsized. Further, since the arms  22   a  can be arranged on the central axis of the top plate  2 , the load on the top plate  2  can be reduced. 
     Modification 
     The above-mentioned embodiments are merely examples of the present invention, and do not limit the present invention. For example, in the above-mentioned embodiments, the bed device according to the present invention is applied to the bed of an X-ray computed tomography apparatus, but may be applied to the bed of another modality such as an MRI apparatus or X-ray diagnostic apparatus. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.