Abstract:
A mobile X-ray apparatus for a circuit examination, which includes an X-ray tube with a collimator, a mobile base having a pair of driven wheels, a holder attached and movable to the base, the holder holds the X-ray tube. A motor driver is disposed in the base which drives the wheels. An operation handle bar is disposed in the base providing a signal for driving the motor driver. An input means, separated from the handle bar, provides a signal for driving the motor driver slightly. A controller controls the motor driver according to the signal from the handle bar or the input means.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention is related to a mobile X-ray apparatus for a circuit examination. 
     2. Description of the Related Art 
     A mobile X-ray apparatus for a circuit examination by a doctor in a conventional cordless condenser type is shown in FIG. 4 a- FIG. 4 c.  FIG. 4 a  is an elevational view, FIG. 4 b  is a side view, and FIG. 4 c  is a plane view thereof. This apparatus has an X-ray tube  18 , an arm  19  holding the X-ray tube  18 , a collimator  7 , a truck  21 , a column  20  which is rotatably mounted on the truck  21 , a up-down motion part which moves the arm  19  up and down along the column  20 . The truck  21  has a pair of pivotable front wheels  23  and a pair of unpivotable rear wheels  22  (a right wheel  2  and a left wheel  1 ). This apparatus also has a X-ray controller in the truck  21 . A lower disposed drive motors (a right motor  6  and a left motor  5 ) move the truck  21  forward or backward corresponding to manipulating an operation handle bar  14  forward and backward. The operation handle bar  14  is attached to the handle holding base  17  disposed in the truck  21 . 
     The arm  19  has a structure for supporting and rotating the X-ray tube  18 . The arm  19  also has a structure for horizontally extending and shortening itself. This apparatus is structured to keep its balance when the arm  19  moves up and down along the column  20 . Therefore, the X-ray irradiation aperture of the X-ray tube  18  can be target in all directions and positions, according to a target part of an examined body. 
     Weight of this mobile X-ray apparatus for a circuit examination could be more than 450 kg. In that case, it is very difficult to move the truck  21  without power assist. The truck  21  generally has the rear wheels  22 , which are not pivotable, and the front wheels  23  which are pivotable like casters. The rear wheels  22  are generally driven by drive motors (the right motor  6  and the left motor  5 ). 
     The truck  21  has an internal power supply with a car battery and an inverter, a high voltage transformer, a condenser, and a control circuit (not shown). The internal power supply provides 100-120V and 60 Hz power through the control circuit. An automatically programmed one-touch system is frequently used for photographing operation. 
     Rubber tires are used for the truck  21 , and the truck  21  is designed such that it can freely move into and out of a patient&#39;s room, an operation room or an elevator, for example. Further, the truck  21  includes a braking system, a cassette box, and accessory devices (also not shown). 
     It is important for a circuit examination by a doctor for the mobile X-ray apparatus to be small and light weight, and have good mobility so that the mobile X-ray apparatus can be moved to a bedroom, a technician room, an operation room, a children room, an X-ray room, an infant room, or the like in a hospital so as to take an X-ray photographing easily at these sites. 
     A block diagram for controlling the mobile X-ray apparatus is shown in FIG.  5 . The left wheel  1  and right wheel  2  shown in the upper part of the diagram are driven by the left motor  5  and the right motor  6 , respectively. The left motor  5  and the right motor  6  are independently controlled by the motor drive circuit  9 . The PWM control circuit  10  carries out a switching control of the motor drive circuit  9  by pulse width modulation. The duty ratio in the switching control is controlled through signals from the CPU  35 . When an operator manipulates the operation handle bar  14  of the truck  21  back and forth, signals from the left force sensor  15  and the right force sensor  16  attached to each end of the operation handle bar  14  are independently provided, as a left input Fl and a right input Fr to the CPU  35 , respectively. On the other hand, signals of the left wheel rotation speed Vl and the right wheel rotation speed Vr from the left encoder  3  and the right encoder  4  which are placed at each spindle of the left wheel  1  and the right wheel  2  are provided to the CPU  35 . The CPU  35  provides the PWM control circuit  10  with the duty width control signal in switching control corresponding to a back and forward input signal Ft(Fl, Fr) from the left force sensor  15  and right force sensor  16 , and also a velocity signal Vt(Vl, Vr) from the left encoder  3  and the right encoder  4 . The PWM control circuit  10  controls the motor drive circuit  9 , and the motor drive circuit  9  controls the rotation speed of the left motor  5  and the right motor  6 . The left force sensor  15  and right force sensor  16  include a flexible spring member, a Hall Effect Sensor, and a linear magnet, respectively. 
     The operation handle bar  14  is attached to the truck  21  through stiff but flexible spring members. The two spring members at each end of the truck  21  are hard leaf springs which make it possible to move the operation handle bar  14  back and forth a small distance corresponding to a force put on the operation handle bar  14  by its forward and backward operation. A pair of linear magnets (not shown) are attached to both ends of the operation handle bar  14 . 
     A pair of Hall Effect (not shown) sensors are attached to the truck  21 , corresponding to the linear magnets. The Hall Effect sensors are connected to a power supply (not shown in the Figures). When the Hall Effect sensor is placed at the center of the magnet, its output signal is zero level. On the other hand, when the Hall Effect sensor deviates from the center of the magnet, its output signal changes linearly between the positive maximum value and the negative maximum value. Polarity of the sensor signal corresponds to the direction of the displacement of the operation handle bar  14 . Magnitude of the sensor signal is in proportion to this displacement. 
     The spring members make it possible to move easily the operation handle bar  14  by manipulating it back and forth and also to move it rapidly back to the neutral position just by release it. 
     As described above, the conventional mobile X-ray apparatus has a structure having both ends of the operation handle bar  14  being supported by laminated springs, and also that the operation handle bar  14  goes back at the neutral position, supporting its gravitative load by the laminated springs, when no operation force is added. Operation force is detected by detecting a position of magnets attached to the operation handle bar  14  by using the Hall Effect sensors. Operation force may also be detected by using strain gages stuck on the laminated springs supporting the operation handle bar  14 . The apparatus is structured to move at a speed depending on operation force detected. 
     To use the device, an operator may push the apparatus at the operation handle bar  14  and move the apparatus to a bed side with power assist. The operator releases the operation handle bar  14  to stop the device and moves to the X-ray tube  18 . Beside the X-ray tube  18 , the operator may move it vertically up and down along the column  20 , rotate it, and extend or shorten the arm  19  horizontally so as to aim the X-ray radiation aperture of the collimator  7  at the target part of the patient. 
     When a position of the X-ray tube  18  is adjusted, it may be impossible in some cases to aim it at the specified position without moving the whole apparatus again. When that happens with the conventional apparatus, the operator must go back near the apparatus body and manipulate the operation handle bar  14  again to adjust the position of the apparatus. This operation can take a long time to adjust the position of the X-ray tube  18  and also reduces examination efficiency. 
     Accordingly, the present invention has been made to solve the aforementioned problems. One object of the present invention is to provide a mobile X-ray apparatus for a circuit examination which makes it possible to adjust the position of the X-ray tube  18  rapidly when moving the apparatus to a position in order to photograph a patient. 
     SUMMARY OF THE INVENTION 
     To achieve the above objects, the present invention provide a mobile X-ray apparatus for a circuit examination, which includes an X-ray tube with a collimator, a mobile base having a pair of driven wheels, a holder attached and movable to the base, the holder holds the X-ray tube. A motor driver is disposed in the base which drives the wheels. An operation handle bar is disposed in the base providing a signal for driving the motor driver. An input means, separated from the handle bar, provides a signal for driving the motor driver slightly. A controller controls the motor driver according to the signal from the handle bar or the input means. 
     The input means may be placed at a part which can move independently from the mobile base. The part may be the collimator. The part may be the X-ray tube. The part may also be the holder. 
     The controller may stop the motion of the mobile base when receiving a signal from the handle bar during the receiving of a signal from the input means. 
     The controller may stop the motion of the mobile base when receiving a signal from the input means over a predetermined time. The predetermined time is, preferably, 10 seconds to 20 seconds. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a schematic block diagram of a mobile X-ray apparatus for a circuit examination in an embodiment of this invention; 
     FIG. 2 is a schematic block diagram of a CPU driving circuit of a mobile X-ray apparatus for a circuit examination in an embodiment of this invention; 
     FIG. 3 is a view of a compensation function in an embodiment of this invention; 
     FIG. 4 is a schematic view of a mobile X-ray apparatus for a circuit examination in an embodiment of this invention; and 
     FIG. 5 is a schematic block diagram of the conventional mobile X-ray apparatus. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     An embodiment of the present invention is described referring to FIG.  1 . FIG. 1 is a schematic block diagram of a mobile X-ray apparatus. This apparatus has a pair of driven wheels (the left wheel  1 , the right wheel  2 ), attached to a truck  21 , which are driven respectively. The truck  21  has an operation handle bar  14  at both ends of which a left force sensor  15  and a right force sensor  16  are attached respectively. The left force sensor  15  and the right force sensor  16  detect each operation force put on both ends of the operation handle bar  14  respectively. The left wheel  1  and the right wheel  2  are connected to the left motor  5  and the right motor  6  respectively. The left encoder  3  and the right encoder  4 , which are attached to each spindle of the left wheel  1  and the right wheel  2 , detect each rotation speed thereof. A micro motion switch  8  for moving the apparatus slightly is attached to the side of an X-ray tube  18  or a collimator  7  at the end of an arm  19  which are attached to a column  20 . A CPU  11  receives the input signal F(Fl, Fr) from the left force sensor  15  and the right force sensor  16 , the wheel rotation speed input signal V(Vl, Vr) from the left encoder  3  and the right encoder  4 , and a signal from the micro motion switch  8 , and provides a PWM control circuit  10  with a duty width control signal. The PWM control circuit  10  carries out pulse width control of a motor drive circuit  9 . The motor drive circuit  9  controls the left motor  5  and the right motor  6 . 
     One difference between this apparatus and the conventional apparatus is that this apparatus has the micro motion switch  8 , for moving the apparatus slightly, at very low speed compared to a speed by manipulating the operator handle bar  14 . The micro motion switch  8  is attached to the side of the X-ray tube  18  or the collimator  7  at the end of the arm  19  attached to the column  20 . 
     The micro motion switch  8  may be set on parts other than the operation handle bar  14 , such as the X-ray tube  18  or the collimator  7 , which travels off the apparatus body. Therefore, an operator can move the apparatus slightly through manipulating the micro motion switch  8  without manipulating the operation handle bar  14 , and adjustment of the X-ray tube  18  can be carried out rapidly since the operator does not have to go back to the operation handle bar  14  to move the apparatus. 
     In an embodiment shown in FIG. 1, the micro motion switch  8  is set at the side of the collimator  7 , and the apparatus moves slightly backward and forward by inclining the micro motion switch  8  forward or backward. One of the left wheel  1  and the right wheel  2  rotates by inclining the micro motion switch  8  left or right, and the apparatus may moves slightly along a circular line in the left or right direction. 
     The apparatus may be configured to stop automatically when the micro motion switch  8  is kept inclined in a direction for a given period of time. In this configuration, the apparatus can not be moved a long distance by using the micro motion switch  8 , but repeating the operation of inclination of the micro motion switch  8  at intervals makes it possible to move the apparatus a long distance. 
     When the operation handle bar  14  is operated mistakenly during operation of the micro motion switch  8 , the apparatus may be configured to stop automatically. The micro motion switch  8  may be a handle type for operation by inclining. The micro motion switch  8  may be also a separate button type (including a touch film type button). 
     The CPU  11  controls the PWM control circuit  10  to move the apparatus at a constant speed by operation of the micro motion switch  8 . However, the CPU  11  may control the PWM control circuit  10  to move the apparatus at a variable speed in proportion to the amount of inclination of the micro motion switch  8  (or in the case of a button, the number of times it is pressed, or how hard it is pressed, etc.). The CPU  11  may also control the PWM control circuit  10  to move the apparatus at a speed according to a force put on the micro motion switch  8 . 
     The operation handle bar  14  may be attached to the truck  21  through spring members which are relatively stiff (hard) but flexible. Two spring members connected respectively to both sides of the truck  21  may be, for example, hard laminate springs. These spring members make it possible to displace the operation handle bar  14  slightly according to an operation force put on the operation handle bar  14 , generated by pushing or pulling it. 
     A pair of linear magnets which move with the operation handle bar  14  are attached to both ends thereof. On the other hand, a pair of Hall Effect sensors (parts of the left force sensor  15  and the right force sensor  16 ) may be attached to the truck  21  corresponding to the linear magnets. 
     When each Hall Effect sensor is placed at each center of the linear magnets, its output signal is zero level. When each Hall Effect sensor deviates from each center of the linear magnets, its output signal changes linearly between a positive maximum value and a negative maximum value. 
     The explanation has been made for operation of the CPU  11 . FIG. 2 shows a circuit of the CPU  11  which receives signals from the micro motion switch  8  and the operation handle bar  14 . The CPU  11  receives signals, as the left input Fl and the right input Fr, generated from the left force sensor  15  and the right force sensor  16 , according to manipulation of the operation handle bar  14 . The drive instruction circuit  36  determines the absolute value Fla and Flb of the left input Fl and the right input Fr from these signals. The direction determination circuit  30  determines each code of the left input Fl and the right input Fr from these signals, and then determines each rotation direction of the left wheel  1  and the right wheel  2  to provide the PWM control circuit  10  with their direction information. 
     The left encoder  3  and the right encoder  4 , which are attached to spindles of the left wheel  1  and right wheel  2  and detect rotation speeds thereof respectively, provide the CPU  11  with the wheel rotation speed input signal V(Vl, Vr). 
     The operation handle process circuit  12  of the CPU  11  determines the absolute value Vla and Vlb from signals of the left rotation speed Vl and the right rotation speed Vr. The operation handle process circuit  12  also determines the absolute value Tla, and Tra of each element of the torque signal T(Tl, Tr) which the motor drive circuit  9  should output by the following formula. 
     
       
           Tla=α ( Vla )· Fla   
       
     
     
       
           Tra=α ( Vra )· Fra   
       
     
     The above α is a compensation function, as shown in FIG.  3 . In FIG. 3, Va is the absolute value of velocity and Ta is the absolute value of torque. The compensation function a compensates the output torque determined by the left input Fl and the right input Fr according to each rotation speed of the left wheel  1  and the right wheel  2  because of the nature that the more the speed increases, the less the torque decreases. 
     The PWM control circuit  10  drives the left motor  5  and the right motor  6  through the motor drive circuit  9  using each output of the direction determination circuit  30  and operation handle process circuit  12  so that the left motor  5  and the right motor  6  drive the left wheel  1  and the right wheel  2  at the determined torque T(Tl, Tr). 
     The operator moves the apparatus to a place for photographing through manipulation of the operation handle bar  14 . Then the operator leaves the operation handle bar  14  and moves to the collimator  7 . The operator then aims the irradiation aperture of the collimator  7  of the X-ray tube  18  at the target part of a patient to be examined. 
     Precise adjustment of the collimator  7  can be carried out, moving the apparatus slightly by manipulation of the micro motion switch  8  attached to the side of the collimator  7  (or the X-ray tube or an appropriate position for simultaneous positioning of the collimator  7  and the apparatus). Manipulation of the micro motion switch  8  provides the drive instruction circuit  36  and the direction determination circuit  31  of the CPU  11  with a signal by which the direction determination circuit  31  determines whether to move forward, move backward, turn left, or turn right. When the apparatus stands, both rotation speeds of the left wheel  1  and the right wheel  2  are zero. The micro movement process circuit  13  of the CPU  11  outputs to the PWM control circuit  10  the duty width control signal which makes the torque output of the motor drive circuit  9  to be Ta which is β (β is a constant). The direction determination circuit  31  of the CPU  11  determines which direction the micro motion switch  8  is manipulated. When the direction determination circuit  31  recognizes that a direction of the manipulation of the micro motion switch  8  is forward or back, it outputs to the PWM control circuit  10  a signal which indicates to drive both wheels forward or back. When the direction determination circuit  31  recognizes that direction of the manipulation of the micro motion switch  8  is left or right, it outputs to the PWM control circuit  10  a signal which indicates to drive the left wheel  1  or the right wheel  2 , respectively. 
     The PWM control circuit  10  controls the motor drive circuit  9  to drive both or one of the left motor  5  and the right motor  6  at the determined torque (Ta=β) and in the determined direction based on signals from the CPU  11 . 
     When the micro motion switch  8  is kept inclined in a direction for a given time, for example 10 seconds to 20 seconds, the drive instruction circuit  36  stops output of its signal and movement of apparatus for safety until manipulation of the micro motion switch  8  stops once. In this configuration, using the micro motion switch  8  will not allow the apparatus to move a long distance at a time, but repeating the operation of inclination of the micro motion switch  8  at intervals makes it possible to move the apparatus for a long distance. 
     When the operation handle bar  14  is manipulated mistakenly during operation of the micro motion switch  8 , the drive instruction circuit  36  of the CPU  11  may be configured to recognize both signals from the operation handle bar  14  and the micro motion switch  8  and then stop output of its signal. Therefore, the apparatus may be safely stopped automatically. 
     In the mobile X-ray apparatus of the present invention, when the apparatus is moved near the bed and so on, and the operator moves to the collimator  7  to aim the collimator  7  of the X-ray tube  18  at the target part of the patient, since the micro motion switch  8  for moving the apparatus slightly is placed near the collimator  7  of the X-ray tube  18 , the operator does not have to go back to neighborhood of the operation handle bar  14  to adjust the direction of the collimator  7 . Therefore, adjustment of the collimator  7  of the X-ray tube  18  can be carried out rapidly and examination efficiency improves. 
     In the mobile X-ray apparatus of the present invention, manipulation of the micro motion switch  8  can be manipulated safely because when the operation handle bar  14  is manipulated by others mistakenly during operation of the micro motion switch  8 , the apparatus may be stopped automatically. 
     The micro motion switch  8  can also be manipulated safely because when the micro motion switch  8  is kept inclined in a direction for a given time, the drive instruction circuit  36  may stop the output of its signal and movement of apparatus can be stopped until manipulation of the micro motion switch  8  stops once.