Abstract:
A drive system for an imaging device of the type having a curved arm. The drive system includes a carrier that engages and supports the curved arm such that the curved arm can be moved along the carrier. The drive system includes a belt extending through the carrier and secured about the periphery of the curved arm. The drive system receives and drives the belt to move the curved arm relative to the carrier. The drive system includes a tensioning mechanism configured to move in such a direction relative to the carrier in order to increase the tension on the belt and to move in such a direction relative to the carrier in order to decrease the tension on the belt.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a system for tensioning a belt. More particularly, certain embodiments of the present invention relate to a pivot plate that engages a belt on a mobile C-arm to increase the tension of the belt. 
     Before and during a medical procedure, medical professionals may need to take several different images of a patient&#39;s body from a number of different orientations. Often it is difficult to effectively capture images from certain orientations where the imaging device is fixed and stationary. Therefore, imaging devices are mounted on large, mobile structures known as C-arm imaging machines. C-arm imaging machines typically include a mobile support structure, a carrier, and a curved, C-shaped positioning arm, (or C-arm). The carrier is mounted on the support structure and the C-arm is, in turn, slidably mounted to the carrier. An imaging source is located on one distal end of the C-arm and an imaging receiver is located on the other distal end of the C-arm. The C-arm imaging machine may be moved and rotated about a patient in a number of different orientations such that the patient is positioned between the imaging source and the imaging receiver. The C-arm imaging machine operator may then take an image of the patient. 
     The C-arm typically may be rotated about the patient in at least two ways. The support structure includes a rotation arm that is connected to the carrier. The C-arm has tracks along an outer periphery thereof that capture rollers on the carrier such that the C-arm is movably retained to the carrier along the rollers. A large belt extends from the carrier around the arms of the C-arm. The rotation arm may be rotated about a rotational axis such that the C-arm also rotates about the rotational axis. This is known as the rotational rotation of the C-arm. Additionally, the C-arm may be rotated along the plane of the C-arm about a transverse axis by moving the belt such that the C-arm moves, or rotates, along the carrier. This is known as orbital rotation of the C-arm. By being rotatable about at least two different axes, the C-arm may be positioned at many different orientations about a patient in order to take images from different desirable perspectives. Thus, the mobile C-arm imaging machine greatly increases the efficiency and ease of taking images of a patient before and during a medical procedure. 
     However, the conventional mobile C-arm imaging machine has a number of drawbacks. First, many C-arms may only be moved manually for either orbital or rotational rotation. That is to say, an operator must manually release a brake and then manipulate the C-arm to move the C-arm to a desired position. The operator then manually stops the movement of the C-arm when it reaches its desired position and activates the brake to lock the C-arm in place. This method of adjusting the position of the C-arm can be difficult and time-consuming, especially if the person performing the medical procedure must also manipulate the C-arm. Additionally, this method of adjusting the position of the C-arm may lead to imprecise positioning by the operator or any other number of problems caused by human error. 
     Some conventional C-arms have a drive train that is connected to the C-arm such that an operator can use the drive train to mechanically drive the C-arm to orbitally rotate about the carrier. The operator can thus control the movement of the C-arm by operating a joystick that is electrically connected to the drive train. However, often the C-arm imaging machines that incorporate such drive trains are large fixed-room devices that cannot be moved out of a room for use. Additionally, the drive train is in a fixed position such that is cannot be moved with the C-arm and thus may take up space and get in the way of operation of the C-arm. Additionally, there are other conventional C-arms that are mobile and incorporate a drive train, but these C-arms do not use a belt to drive the C-arm. 
     Another problem associated with conventional C-arm imaging machines is maintaining tension in the belt as it engages the C-arm, and, if applicable, the drive train. The belt needs to be tensioned about the C-arm and the carrier in order that an operator can effectively move the belt and thus cause the C-arm to rotate orbitally. If the belt is not adequately tensioned, the belt may be delayed in engaging the distal ends of the C-arm. Also, in C-arms that include drive trains, if the belt is not adequately tensioned, the drive train may not fully engage the belt or the belt may lay even loosely about the rotating pulleys of the drive train. 
     Thus, many conventional C-arms include a tensioning system, or spring, located at a first distal end of the C-arm that resistibly engages the belt and pushes the belt away from the C-arm in order to tension the belt about the C-arm. The C-arms do not necessarily include a spring at the opposite second distal end of the C-arm. Because the spring is located at only the first end of the C-arm, the tension in the belt decreases at points further away from the first end. If the C-arm includes a drive train, the drive train engages the belt between the two distal ends of the C-arm. Therefore, the tension of the belt is different on either side of where the belt is connected to the drive train. For example, the section of the belt extending from the drive train to the second distal end is not as tensioned as the section of the belt extending from the drive train to the first distal end. Because of the increased slack in the belt between the second distal end and the drive train, rotation of the C-arm may be delayed where the operator tries to rotate the second distal end toward the drive train. 
     Additionally, locating the tensioning system at either end or both ends of the C-arm takes up space such that the tensioning system may limit the mobility of the C-arm or get in the way of the operator or medical procedure taking place. 
     Therefore, a need exists for an improved tensioning and drive system for a belt used to move a C-arm. 
     BRIEF SUMMARY OF THE INVENTION 
     Certain embodiments of the present invention include a drive system for an imaging device of the type having a curved arm. The drive system includes a carrier that engages and supports the curved arm such that the curved arm can be moved along the carrier. The drive system includes a belt extending through the carrier and secured about the periphery of the curved arm. The drive system receives and drives the belt to move the curved arm relative to the carrier. The drive system includes a tensioning mechanism configured to move in such a direction relative to the carrier in order to increase the tension on the belt and to move in such a direction relative to the carrier in order to decrease the tension on the belt. 
     Certain embodiments of the present invention include a drive system. The drive system includes a mobile curved arm and a carrier that engages the curved arm. The carrier includes a spring mechanism connected thereto. The drive system includes a belt that extends through the carrier and is secured about the periphery of the curved arm. The drive system is configured to pivot about the carrier. The drive system receives and drives the belt such that the curved arm moves relative to the carrier. The drive system is configured to receive an engagement piece such that the engagement piece engages the spring mechanism. The spring mechanism resists the engagement piece such that the drive system is pivoted in such a direction relative to the carrier that the drive system is pulled away from the curved arm and the belt increases in tension about the curved arm. 
    
    
     
       BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
         FIG. 1  is an isometric side view of a mobile imaging machine formed according to an embodiment of the present invention. 
         FIG. 2  is a rear isometric side view of the mobile imaging machine of  FIG. 1 . 
         FIG. 3  is a side view of the imaging machine of  FIG. 1  with a drive train exposed and the C-arm removed. 
         FIG. 4  is a top cutaway view of a drive train formed according to an embodiment of the present invention. 
         FIG. 5  is an isometric view of a drive train and a cutaway isometric view of a C-arm carrier formed according to an embodiment of the present invention. 
         FIG. 6  is a rear isometric view of the drive train of  FIG. 2 . 
     
    
    
     The foregoing summary, as well as the following detailed description of certain embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there is shown in the drawings, certain embodiments. It should be understood, however, that the present invention is not limited to the arrangements and instrumentality shown in the attached drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  is an isometric side view of a mobile imaging machine  10  formed according to an embodiment of the present invention. The imaging machine  10  includes a mobile support structure  14 , a carrier  18  and a curved positioning arm  22  (which is illustrated as a C-arm). Although the curved arm  22  is illustrated as a C-arm, it will be appreciated the arm  22  may have different shapes. For example, the arm  22  may be spiral in shape. The mobile support structure  14  has wheels  16 , which allow the entire imaging machine  10  to be moved. The C-arm  22  is semi-circular in shape and carries an imaging receiver  26  at a first distal end  25  and an imaging source  30  at a second distal end  27 . By way of example and not limitation, the imaging source  30  may be an x-ray source. Alternatively, the C-arm  22  may have different shapes, for example, the C-arm  22  may be spiral in shape. A partially covered drive train  34  is mounted to the carrier  18 . 
       FIG. 3  is a partial side view of the imaging machine  10  of  FIG. 1  with the drive train  34  exposed and the C-arm  22  ( FIG. 1 ) removed. The mobile support structure  14  includes a rotational knuckle  20  that extends to the carrier  18 . The rotational knuckle  20  may be manually rotated about a longitudinal axis  24  such that the entire C-arm  22  is rotated about the longitudinal axis  24 . Alternatively, the rotational knuckle  20  may be driven by a motor, such as an electric motor (not shown). The motor in turn is electrically connected to a controlling device (not shown) such as a joystick to allow the operator to control the movement of the rotational knuckle  20  with the joystick. 
       FIG. 2  is a rear isometric view of the mobile imaging machine  10  of  FIG. 1 . The C-arm  22  is movably mounted to the carrier  18 . A belt  42  extends from the drive train  34  through the carrier  18 , about the outer periphery of the C-arm  22  and is connected to the C-arm  22  at each distal end  25  and  27 . Alternatively, the belt  42  may extend about the inner periphery of the C-arm  22 . Alternatively, the belt  42  may be connected to the C-arm  22  at any number of different points besides the distal ends  25  and  27 . 
     Returning to  FIG. 1 , an operator may activate the drive train  34  by pressing a button or switch connected to the drive train  34  such that the drive train  34  engages the belt  42  ( FIG. 2 ) in order to orbitally rotate the C-arm  22  along the carrier  18  in the direction of either arrow A or B. Alternatively, the drive train  34  may be electrically connected to an electronic controlling device (not shown) such as a joystick in order that the operator can control the movement of the C-arm  22  with the joystick. 
     In operation, an operator may roll the mobile imaging machine  10  proximate a patient that is to be imaged. The operator may rotate the C-arm  22  about the longitudinal axis  24  of the rotational knuckle  20  ( FIG. 3 ) to position the C-arm  22  about the patient. The operator may also activate the drive train  34  in order to orbitally rotate the C-arm  22  along the carrier  18  and about the patient in the direction of either arrow A or B. The operator orbitally rotates the C-arm  22  along the belt  42  ( FIG. 2 ) in order to position the C-arm  22  about the patient such that the patient is situated between the imaging source  30  and imaging receiver 26 . The operator may take an image (or series of images) of the patient and then move the C-arm  22  away from the patient. 
     Returning to  FIG. 3 , the drive train  34  is mounted on a flat, substrate-shaped plate  38 . Alternatively, the plate  38  may have any number of different shapes or thicknesses. The plate  38  is connected to a foot  50  extending from a backside  37  of the carrier  18  by a pin  46  such that the plate  38  can rotate about the pin  46  in the directions of arrows C and D. The belt  42  extends from the drive train  34  through the plate  38  to the carrier  18 . The belt  42  extends through a hole (not shown) located midway along the carrier  18  from the backside  37  of the carrier  18  to an inner side  39  of the carrier  18  to engage the C-arm  22  ( FIG. 1 ). The carrier  18  has an upper portion  58  on one side of the hole and a lower portion  62  on the other side of the hole. The upper and lower portions  58  and  62  each have an idler wheel  52  proximate the hole. The belt  42  extends about the idler wheels  52 , and the idler wheels  52  direct the belt  42  along the carrier  18 . The idler wheels  52  do not engage the C-arm  22 . The upper and lower portions  58  and  62  also each have sets of rollers  54  located on the inner side  39  of the carrier  18 . The belt  42  extends through the hole such that a first portion of the belt  42  extends along the upper portion  58  and a second portion of the belt  42  extends along the lower portion  62 . 
     Returning to  FIG. 2 , the C-arm  22  has tracks  28  extending along the outer periphery thereof that capture the rollers  54  ( FIG. 3 ) in order to retain the C-arm  22  to the carrier  18 . In operation, when the C-arm  22  is connected to the belt  42  and the rollers  54 , the drive train  34  activates the belt  42  such that the belt  42  can pull the C-arm  22  along the rollers  54  in the direction of either arrow A or B. 
       FIG. 6  is a rear isometric view of the drive train  34  of  FIG. 2 . The drive train  34  includes a motor  82  connected to a drive shaft  86  ( FIG. 4 ) through a gear box  70 . The gear box  70  is mounted to the plate  38 . The drive shaft  86  is connected to a drive pulley  90 . The drive pulley  90  drives the belt  42  to effect orbital rotation of the C-arm  22  ( FIG. 1 ) as explained below. A clutch release handle  94  can be rotated to disengage the drive pulley  90  from a drive shaft  86  to allow manual manipulation of the C-arm  22 . 
       FIG. 4  is a top cutaway view of the drive train  34  formed according to an embodiment of the present invention. A drive shaft  86  extends from the gear box  70  to the clutch release handle  94 . The motor  82  is configured to drive the drive shaft  86 . The drive shaft  86  engages gears within the gear box  70 . The drive shaft  86  is not back-drivable, which is to say that the drive shaft  86  cannot be turned to engage the gears within the gear box  70  or the motor  82 . The cylindrical drive pulley  90  is mounted to the drive shaft  86 . The belt  42  ( FIG. 2 ) is wrapped around the drive pulley  90  and extends through the plate  38  to the carrier  18  ( FIG. 2 ). The drive pulley  90  and the belt  42  both have teeth (not shown) that engage each other in order that the belt  42  engages and moves along with the drive pulley  90  when the drive pulley  90  rotates instead of remaining stationary as the drive pulley  90  rotates. 
     In operation, the motor  82  is activated remotely by a joystick as described above such that the motor  82  causes the drive shaft  86  to rotate. As the drive shaft  86  rotates, the drive pulley  90  is rotated with it. The rotating drive pulley  90  causes the belt  42  ( FIG. 3 ) to move in the direction of the rotation of the drive pulley  90 . Thus, as the belt  42  moves across the drive pulley  90  through the drive train  34 , one of the distal ends  25  or  27  of the C-arm  22  ( FIG. 1 ) is pulled toward the carrier  18  ( FIG. 1 ) such that the C-arm  22  rotates. The drive train  34  is configured such that the drive shaft  86  may be rotated either clockwise or counter-clockwise to effect the movement of either distal end  25  or  27  of the C-arm  22  toward the carrier  18 . Additionally, an operator can rotate the clutch release handle  94  in order to disengage the drive pulley  90  from the drive shaft  86  and thus manipulate the C-arm  22  manually instead of by the drive train  34 . 
       FIG. 5  is an isometric view of the drive train  34  and a cutaway isometric view of the carrier  18  formed according to an embodiment of the present invention. As shown, the belt  42  is wrapped around the drive pulley  90  ( FIG. 6 ) and extends through a hole  94  in the plate  38  to the carrier  18 . The drive train  34  includes an additional pulley  98  in the hole  94  that engages a first portion  102  of the belt  42  extending from a first side of the drive pulley  90  through the hole  94 . The pulley engages the first portion  102  of the belt  42  such that the first portion  102  is redirected in order to be generally aligned with a second portion  106  of the belt  42  extending from a second side of the drive pulley  90  through the hole  94 . Thus, the pulley  98  tightens the belt  42  around the drive pulley  90  and aligns the first and second portions  102  and  106  of the belt  42  as the belt  42  is fed through the hole in the carrier  18  to the rollers  54  ( FIG. 3 ). 
     As shown, the idler wheels  52  are mounted along the inner side  32  of the carrier  18  on a frame  77 . Each idler wheel  52  has rims  74  positioned at opposite ends of a cylinder  78 . The rims  74  have a first diameter and the cylinder  78  has a second diameter, with the first diameter being greater than the second diameter. Thus, the belt  42  extending through the carrier  18  is positioned between the rims  74  and along the cylinder  78  of each idler wheel  52  to guide the belt  42  to the rollers  54  ( FIG. 3 ). As described above in regard to  FIG. 4 , the drive train  34  operates to move the belt  42 , and thus the C-arm  22  in the direction of arrow A or B, depending on the preference of the operator. 
     The drive train  34  is held in position about the backside  37  of the carrier  18  by the pin  46  and by the belt  42  which is wrapped around the drive pulley  90  ( FIG. 4 ). As can be seen in  FIG. 5 , the carrier  18  includes an L-shaped spring block  110  that is screwed therein. A spring plunger  114  is fastened into the spring block  110  and extends through a gap  118  in the carrier  18  to a position proximate the plate  38 . The spring plunger  114  includes a cylindrical shaft  122  and a spring  126  disposed about the shaft  122 . One end of the shaft  122  is slidably mounted in the spring block  110  such that the shaft  122  may be slid into and out of the spring block  110 . A cap  120  is connected to the other end of the spring plunger  114 . The spring  126  is positioned on the shaft  122  between the spring block  110  and the cap  120  such that the spring  126  pushes against the cap  120 . The plate  38  carries a screw  134  that is threaded through a hole in the plate  38  and is aligned to engage the cap  120 . 
     Returning to  FIG. 3 , the screw  134  is shown extending through the plate  38 . A first portion  138  of the screw  134  extends from a first side of the plate  38  and a second portion  142  of the screw  134  extends from a second side of the plate  38 . In operation, an operator may engage the first portion  138  of the screw  134  by hand or with a tool to screw the screw  134  further into the plate  38  such that the second portion  142  of the screw  134  extends further out the opposite side of the plate  38 . As the second portion  142  of the screw  134  extends further out of the plate  38 , the second portion  142  engages the cap  120 . 
     Returning to  FIG. 5 , the second portion  142  of the screw  134  pushes the cap  120  in the direction of arrow E. As the cap  120  is pushed in the direction of arrow E, the cap  120  pushes the shaft  122  further into the spring block  110 . The spring  126  is compressed between the cap  120  and the spring block  110  and resistibly engages the cap  120  in order to limit the distance the cap  120  and the shaft  122  travel in the direction of arrow E. As the second portion  142  of the screw  134  engages resistance from the spring plunger  114 , the plate  38  is resistibly pushed in the direction of arrow F about the pin  46  away from the carrier  18 . The plate  38  thus pushes the entire drive train  34  away from the carrier  18  in the direction of arrow F. As the drive pulley  90  ( FIG. 6 ) is pulled further away from the carrier  18 , the belt  42  is tightened or tensioned about the C-arm  22  ( FIG. 1 ), the idler wheels  52 , and the drive pulley  90 . By tensioning the belt  42  in this manner, the belt  42  is less likely to become slack or disengaged from the drive pulley  90 . Therefore, the C-arm  22  will be more effectively rotated about the carrier  18  in the directions of arrows A and B. 
     The operator may alter the tension in the belt  42  about the C-arm  22  ( FIG. 1 ) to a desired tension level by adjusting the screw  134  as necessary. For example, the further an operator screws the screw  134  into the plate  38 , the greater the tension in the belt  42 . Alternatively, should the operator wish to reduce the tension in the belt  42  about the C-arm  22  for maintenance or inspection purposes, the operator may screw the screw  134  out of the plate  38  away from the cap  120  such that the plate  38  then is allowed to move closer to the carrier  18 . 
     The tension system disclosed herein may include alternative embodiments. For example, the tension system is not limited to use with medical imaging C-arms  22 . Alternatively, the tension system may be used to control the tension in any other belt-driven machines where the belt  42  engages a curved arm. Alternatively, the drive train  34  may be configured to pivot and engage the spring plunger  114  without the use of the plate  38 . Alternatively, any number of different engagement pieces besides a screw  134  may be used to engage the spring plunger  114 . For example, the plate  38  may carry a bolt or pin that can be locked into the plate  38  at different depths such that the bolt or pin engages the spring plunger  114 . Alternatively, the drive train  34  and tensioning system may be located at other points along the carrier  18  besides at a midway point. Alternatively, the tension system may include a spring  126  that engages the carrier  18  and the engagement piece without the use of a plunger that extends into the spring block  110 . Alternatively, the tension system may not include a spring  126  at all, but may include a resistant, flexible member that engages the screw  134  or engagement piece. Alternatively, the spring plunger  114  may not include the cap  120 , but rather the screw  134  may be configured to engage the spring  126  directly. 
     The tensioning system of the embodiments provides several advantages over the prior art. First, by engaging the screw  134  with the spring loaded plunger  114 , the plate  38  is not rigidly held in place between the pull of the belt  42  and the push of the spring plunger  114 . Therefore, the plate  38  may still be moved far enough away from the carrier  18  to adequately increase the tension in the belt  42  while at the same time being able to move slightly back to the carrier  18  against the spring  126  to accommodate any tightening of the belt  42  as the belt  42  moves. 
     Additionally, as the belt  42  wears and becomes looser about the C-arm  22  and the idler wheels  52  due to use, the screw  134  does not necessarily have to be tightened further to increase the tension in the belt  42 . The spring plunger  114  will be under less compression from the screw  134  and plate  38  because the belt  42  is placing less pressure on the plate  38 , and thus the spring  126  can expand and push the plate  38  further from the carrier  18 . Thus, the interaction of the screw  134  and spring  126  continuously operate together to push the plate  38  further away from the carrier  18  in order to tighten the belt  42  as the belt  42  slackens after repeated use. 
     Also, by placing the tensioning system midway along the carrier  18  and thus midway along the C-arm  22 , the tensioning system is able to tension the belt  42  on both sides of the drive pulley  90  regardless of the direction the C-arm  22  is being rotated. Thus, the belt  42  is generally equally well tensioned at both distal ends  25  and  27  of the C-arm  22 . Furthermore, the tensioning system of the different embodiments is easy to use because the operator simply rotates the screw  134  to loosen or tighten the belt  42  about the C-arm  22 . Additionally, the tensioning system of the different embodiments takes up very little space. Instead of being positioned on either or both distal ends  25  and  27  of the C-arm  22 , the system is entirely localized behind the carrier  18  and thus out of the way of the patient, operator, or any other objects in the room. The tensioning system also saves space by positioning the drive train  34  on the carrier  18  instead of connecting a separate stationary drive train  34  to the carrier  18 . Thus, the drive train  34  is out of the way of the operator and moves with the carrier  18  so as not to limit or constrain the movement of the carrier  18 . Also, the tensioning system combines a drive train  34  with a mobile C-arm imaging machine  10 , which greatly increases the versatility and operator control of the C-arm imaging machine  10 . 
     While the invention has been described with reference to certain embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from its scope. Therefore, it is intended that the invention not be limited to the particular embodiment disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.