Abstract:
A high accuracy medical trailer leveling system capable of detecting at least three level orientations including level along a longitudinal direction, level along a lateral direction at the front of the trailer, and level along a lateral direction at the rear of the trailer. The system also includes sensors that detect a level orientation in the longitudinal direction at the front of the trailer and a level orientation in the longitudinal direction at the rear of the trailer. A touch pad has buttons for controlling the system and a display screen, the display screen being capable of displaying a level condition in a particular location of the trailer and direction. The display screen can display the level orientation of side to side, front; side to side, rear; and front to back, and can also display the angle of inclination. One set of lights on the control pad indicates which jacks to actuate to level the vehicle, and another set of lights indicates which jacks are being actuated.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Not applicable. 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable. 
     FIELD OF THE INVENTION 
     The invention relates to a method of leveling a mobile trailer that contains medical imaging or other clinical equipment. 
     BACKGROUND OF THE INVENTION 
     In the area of recreational vehicles such as travel trailers and motor homes, and other general transportable vehicles, there is a need for leveling when these vehicles are parked for use. Recreational vehicles and campers are usually parked in campsites where the parking area is not always level. Various systems are found in the prior art relating to leveling such vehicles. These systems comprise at least a lift mechanism and a level sensing device. Generally, the designs use mechanical, electromechanical, or hydraulic jacks and level sensors for leveling the vehicles. The devices are strategically mounted to the underbody or chassis of the vehicle to achieve the leveling quickly and efficiently. The number of jacks and level sensors used in each application are dependent on the size of the vehicle and the weight of the vehicle being supported, among other things. In one example, a recreational vehicle is equipped with four jacks in the form of hydraulic cylinders mounted to the vehicle frame. Two jacks are located adjacent to the rear of the vehicle and two jacks are located adjacent to the front of the vehicle. 
     In another example, a vehicle leveling system has three jacks, two of which are located at the rearward end of the vehicle and one of which is located at the forward end of the vehicle. The use of a single front jack reduces twisting of the vehicle frame, however, it makes the system less stable because two corners of the vehicle are left unsupported. 
     There is a need for transportable medical equipment in our society today. In areas where medical facilities are not readily accessible, or in areas that experienced disaster and the infrastructure is in a state of disrepair, a mobile medical facility is essential. Manufacturers are sensitive to this need and are providing equipment to meet this demand. Transportable medical equipment trailers are known in the prior art. The need for leveling of these equipment trailers is greater than for the recreational vehicles and campers because of the sophistication and the sensitivity of the medical equipment. Types of equipment used in a transportable medical trailer include, PET/CT scan machines, MRI machines, and CT machines The medical equipment transported in a mobile unit can include at least two machines mounted together such as PET/CT machine. These machines need to be aligned prior to operation. Any deviation from the recommended alignment of the machines in the trailer could result in parallax errors, and possibly, error in diagnosis. 
     These trailers are typically towed behind a semi-tractor and dropped off at a clinical location. The front jacks will be used to lift and support the front of the trailer when it is detached from the tow vehicle and the driver will initially level the trailer, and then leave. Through the course of the day, as environmental conditions change, the level of the trailer may change and need to be re-leveled. It is important that medical clinical personnel be able to perform this function as conditions change, or else use of the machines in the trailer may have to be suspended until the trailer can be re-leveled. 
     The current invention addresses the shortcomings of the prior art. 
     SUMMARY OF THE INVENTION 
     The invention provides a high accuracy medical trailer leveling system capable of detecting at least three level orientations including level along a longitudinal direction, level along a lateral direction at the front of the trailer and level along a lateral direction at the rear of the trailer. 
     The system may have sensors that detect a level orientation in the longitudinal direction at the front of the trailer and a level orientation in the longitudinal direction at the rear of the trailer, in addition to the functions of those sensors detecting lateral level at the front and rear. 
     A touch pad of the system preferably has buttons for controlling the system and a display screen, the display screen being capable of displaying a level condition in a particular location of the trailer and direction. The display screen can display the level orientation of side to side, front; side to side, rear; and front to back, and can also display the angle of inclination. 
     In another preferred aspect, one set of lights on the control pad indicates which jacks to actuate to level the vehicle, and another set of lights indicates which jacks are being actuated. 
     These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a trailer used in conjunction with the present invention; 
         FIG. 2  is a diagram of a controller and level sensors according to the present invention; 
         FIG. 3  is a plan view of the medical trailer leveling touch-pad of  FIG. 2 ; 
         FIG. 3A  is a detail view of the directional keypad portion of the touchpad of  FIG. 3 ; and 
         FIG. 4  is a plan view of the lift mechanism of  FIG. 1 . 
     
    
    
     Like reference symbols in the various drawings indicate like elements. 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIG. 1 , a representation of a medical equipment trailer  10  useful for the present invention is shown. Also shown in  FIG. 1  is a lift mechanism  26  located at the front right side of medical equipment trailer  10 . Lift mechanism  26  is one of a plurality of lift mechanisms that are employed in this system. The present invention employs at least four lift mechanisms, including mechanisms  24 ,  26 ,  28 , and  30 , ( FIG. 2 ). The operation of the lift mechanisms will be discussed in more detail with reference to  FIGS. 2 and 4 . Included in the medical equipment trailer  10  is a chassis structure  20  (not shown) that will also be discussed in more detail with reference to  FIG. 2 . Chassis structure  20  represents the structural frame of medical equipment trailer  10 , on which the equipment inside the trailer is supported and to which the walls, wheels and lift mechanisms are mounted. 
     Referring to  FIG. 2 , a depiction of trailer chassis structure  20  is shown. Chassis structure  20  contains lift mechanisms  24 ,  26 ,  28 , and  30  that are used in part to level medical equipment trailer  10 . Lift mechanisms  24  and  26  are located at the front end of medical equipment trailer  10  and serve as landing gear. Landing gear should be understood to be the front lift mechanisms that are extended prior to detaching trailer  10  from the truck. Lift mechanism  26  is located at the right hand side and lift mechanism  24  on the left hand side. Lift mechanisms  28  and  30  are located at the rear end of medical equipment trailer  10  with lift mechanism  28  located on the left hand side and lift mechanism  30  on the right hand side. Activation of lift mechanisms  24 ,  26 ,  28 , and  30  are initiated from touchpad  40 . The lift mechanisms can be activated individually or in pairs. More details on the operation of touchpad  40  are given with reference to  FIGS. 3-3A . 
     Still referring to  FIG. 2 , the present invention uses two bidirectional level sensors  34  and  36 , located at the front and rear of medical equipment trailer  10 . The level sensors used in this invention are known in the art and can include bubble level sensors, accelerometers, or any other type that detects a level mismatch. Each sensor senses longitudinal (front-rear) level and also senses lateral (side to side) level, so each sensor is oriented in the trailer to have one of its axes lined up with the longitudinal axis of the trailer and the other axis of the sensor lined up with a lateral axis of the trailer. Preferably, the sensors are on or close to the lateral center of the trailer. Alternatively, if unidirectional sensors were used, four sensors could be used, one longitudinally oriented and one laterally oriented at each end of the trailer. 
     With bi-direction sensors, level sensor  36  is located at the front end of medical equipment trailer  10  and is used in conjunction with lift mechanisms  24  and  26  to make level adjustments to the front end of medical equipment trailer  10  for proper functioning of the equipment housed in medical equipment trailer  10 . Conversely, level sensor  34  is located at the rear end of medical equipment trailer  10  and is used in conjunction with lift mechanisms  28  and  30  to attain the recommended leveling. Both level sensor  34  and level sensor  36  are used to ensure that medical equipment trailer  10  is level relative to a horizontal plane as determined by gravity. Level sensors  34  and  36  are configured for accuracy levels of 0.1° front to rear, 0.05° side to side (left to right) in the front, and 0.05° side to side (left to right) in the rear of medical equipment trailer  10 . These accuracy limits are relative to the horizontal plane. Also shown in  FIG. 2  is a controller  38  remotely attached to level sensors  34  and  36 . Controller  38  is used in conjunction with lift mechanisms  24 ,  26 ,  28 , and  30  to process level information from sensor  34  and sensor  36  to screen  52 , as well as receive input commands from keypad  40  and provide outputs thereto. Controller  38  may be positioned inside a compartment that is accessible from outside of the trailer, and another controller  38  (not shown) could be provided inside the trailer. 
     Medical equipment trailer  10  will generally weigh in excess of 50,000 lbs., with the bulk of the weight concentrated toward the rear end. The front of medical equipment trailer  10  is reserved for such things as a waiting area, prep area, and computer equipment. Because of the weight of medical equipment, trailer  10  and the installed machines and its distribution, it is inherently difficult to achieve the system level within tolerance limits which permit proper functioning of the installed machines. Advantageously using two bidirectional level sensors  34  and  36 , and strategically placing level sensor  36  at the front end and level sensor  34  at the rear end of medical equipment trailer  10 , helps to substantially reduce twist, and compensate for it during leveling. Twist is regarded as the deformation of chassis  20  as a result of overly extending any one corner relative to the diagonally opposite corner. Level sensor  36  is used in conjunction with both lift mechanism  24  and lift mechanism  26  to achieve and maintain the recommended level position for the front end of medical equipment trailer  10 . Likewise, level sensor  34  is used in conjunction with both lift mechanism  28  and lift mechanism  30  to achieve the recommended level states for the rear end of medical equipment trailer  10 . Twist is minimized by maintaining a zero level between level sensor  36  and level sensor  34 . Zero level should be understood to mean that the two sensors are equal elevation above the ground and the sides of each sensor are equal elevation above the ground. 
     Referring to  FIG. 3  a touchpad  40  for use in the leveling operation of medical equipment trailer  10  is shown. Touchpad  40  is enclosed in an accessory panel that is mounted on the side of medical equipment trailer  10 . The accessory panel (not shown) is accessible from outside of medical equipment trailer  10 . Touchpad  40  is activated by pressing power button  42 . Amber LED  44 , when illuminated, indicates that power is on and touchpad  40  is ready for operation. Screen  52  displays the leveling states of the trailer. Select button  46  is used for scrolling through the displayed information on touchpad screen  52 . Green LED  48 , when illuminated, indicates that medical equipment trailer  10  is level. Red LED  50 , when illuminated, indicates that medical equipment trailer  10  is not level. If Red LED  50  is illuminated, error messages will be shown on screen  52 , including, low voltage, end of stroke, pump time out, etc. Select button  46  is additionally used to cycle through three defined states of leveling. The three states of level are side to side front, side to side rear, and front to rear. 
     Still referring to  FIG. 3 , auto button  56  is used to initiate the automatic level cycle for medical equipment trailer  10 . Amber LED  66 , when illuminated, indicates that auto button  56  is activated. In certain examples, automatic leveling is the first option used once medical equipment trailer  10  is parked in its working location. Lift mechanisms  24  and  26  are extended by activating manual button  54  in conjunction with extend button  58 . It is recommended that lift mechanisms  24  and  26  be extended prior to removing from the truck. Lift mechanisms  24  and  26  serve as landing gear. With lift mechanisms  24  and  26  extended, the automatic leveling cycle can be initiated by pressing auto button  56 . The leveling states information is transmitted from level sensor  36  in conjunction with lift mechanisms  24  and  26  through controller  38  and displayed on touchpad screen  52 . Level state is annunciated by the illumination of green LED  80  and message “Platform Level”. Green LED  80  remains illuminated as long as the trailer  10  is level. 
     Referring again to  FIG. 3 , manual button  54  is used to initiate the manual leveling of medical equipment trailer  10 . Manual leveling is required when auto leveling does not attain the required accuracy level for proper functioning of medical equipment trailer  10 . For example, if the front jacks need to be extended extraordinarily to detach the tow vehicle, it may be necessary to manually lower the front of the trailer before attempting automatic leveling of the trailer. Activation of manual button  54  is confirmed by the illumination of amber LED  62 . In manual mode, extend button  58  and retract button  60  can be pressed to extend or retract, respectively, individual pairs of lift mechanisms  24  and  26 , or  28  and  30 . Extend button  58  facilitates the manual extension of lift mechanisms  24 ,  26 ,  28 , and  30  in pairs. For example, front button  72  extends jacks  24  and  26 , left button  78  extends jacks  24  and  28 , right button  74  extends jacks  26  and  30  and rear button  76  extends jacks  28  and  30 . The jacks may also be extended individually, if for example the front and right buttons pressed simultaneously and held down result in only jack  26  extending. Activation of extend button  58  is confirmed by the illumination of amber LED  68 . Retract button  60  is used to retract lift mechanism  24 ,  26 ,  28 , and  30  in manual mode, indicated by LED  62  and LED  64 . When manual button  54  and retract button  60  are actuated as indicated by the two LEDs  62  and  64 , the directional keypad  70  works similarly to the way it works in manual extension mode, described above, to retract the jacks in pairs or individually. 
     Referring to  FIG. 3A , keypad  70  contains directional buttons front  72 , right  74 , rear  76 , and left  78 , which are momentary contact switches. Keypad  70  also shows status LEDs  80 ,  82 ,  84 ,  86 , and  88  used in conjunction with the directional buttons in both auto and manual leveling of medical equipment trailer  10 . Keypad  70 , used in conjunction with touchpad screen  52 , is used to attain the desired accuracy level for medical equipment trailer  10 . Directional buttons and LEDs on keypad  70  can be used to ‘fine tune’ the level states. In one example, screen  52  displays that the side to side rear is not level. Pressing left button  78  along with rear button  76  simultaneously engages lift mechanism  28  resulting in side to side rear achieving the desired accuracy level. 
     LED  80  lights when the system indicates level in all three orientations—front side to side, rear side to side and front to back. LEDs  82 ,  84 ,  86  and  88  light up when the jack they correspond to is being actuated. Their position on the keypad also indicates which corner of the trailer they are positioned at. Thus, LED  82  is between the front  72  and right  74  buttons and actuates the jack  26  which is at the front right corner of the trailer. Pressing buttons  72  and  74  lights up only LED  82  and actuates only jack  28 . This is the same for each of the jacks  24 ,  26 ,  28  and  30 , and the corresponding LEDs  88 ,  82 ,  86  and  84 . 
     LEDs  90 ,  92 ,  94  and  96  light up in the shape of arrows to indicate to the user which button to press to bring the trailer into level state in the manual mode. Thus, if the rear is lower than the front, LED  94  will light and user will press rear button  76  until LED  94  goes out. 
     Referring to  FIG. 4 , lift mechanism  24  of  FIGS. 1-2  is shown.  FIG. 4  is discussed here as a single lift mechanism  24 ; however, the discussion applies equally to lift mechanisms  26 ,  28 , and  30  as the devices and components are the same. Lift mechanism  24  can be any type of electromechanical jack, hydraulic jack, pneumatic jack or screw type jack. 
     In one embodiment, lift mechanism  24  is a hydraulic jack comprising a support base or foot  102 , an extending member or ram  104 , a housing  106 , a mounting support member  108 , an extend tube  110 , and a retract tube  112 . Support base  102  is used in the extend position of hydraulic jack  24  and is generally wider than the extending member  104  to reduce pressure applied to the ground. In the retracted position, support base  102  is lifted off the ground and positioned at a safe height for transportation. The ground clearance for each jack is 8 inches in the preferred embodiment. 
     In the extended position, jack  24 , in conjunction with jacks  26 ,  28 , and  30  are used to support the weight of medical equipment trailer  10  and elevate it far enough to achieve all three level states discussed above: front lateral level, rear lateral level and longitudinal level. Also shown in  FIG. 4  is housing  106  which contains a grease port  114 . Attached to housing  106  is supporting bracket  108  containing a plurality of mounting holes for fixedly attaching jack  24  to the frame of medical equipment  10 . Extend tube  112  is used to communicate pressurized hydraulic fluid to and from the bore side of cylinder housing  106  to facilitate jack extension. Retract tube  110  is used to communicate pressurized hydraulic fluid to and from the rod side of cylinder housing  106  to facilitate jack retraction. A heavy duty motor with a 50% duty cycle may be used to drive a pump to move hydraulic fluid between a reservoir and the jacks  24 ,  26 ,  28  and  30 . 
     The pump in this example has a flow rate of 0.25-0.40 gal/min at an operating pressure of 100 psi (no load) and a flow rate of 0.17-0.30 gal/min at an operating pressure of 2000 psi (typical load). These are small flow rates in comparison to other vehicle leveling systems because the accuracy of leveling required in this system is relatively high. As it takes time from the time that a level sensor detects a level or out of level orientation until an electrical valve controlled by the controller can be turned on or off, using a lower flow rate reduces the error introduced by the amount of time it takes. Accordingly, it is desirable to use a relatively low flow rate in practicing the present invention. The lift mechanism is not limited to the description given here. Other suitable embodiments will be apparent to anyone having ordinary skill in the art given the benefit of this disclosure. 
     A drawback to using a low flow rate pump for actuating hydraulic lift mechanisms  24 ,  26 ,  28  and  30  in the present invention is the amount of time it takes to move the jacks between the fully retracted and the touch-down positions, when there is no significant load on the jacks. One solution to this problem is using a two stage pump, that has a higher flow rate at low pressures, e.g., below 500 psi, and a lower flow rate at higher pressures, e.g., above 500 psi. The pump can incorporate a check valve so that it automatically shifts to the low flow, rate, high pressure mode when the load pressure exceeds the preset value, e.g. 500 psi. 
     Any suitable hydraulic circuit may be used for controlling the actuators  24 ,  26 ,  28  and  30 . Such circuits usually include one or two solenoid valves per jack, a pump, a reservoir and other valves, orifices or devices to assure operation of the system. Such systems are well known in the art, as are controllers for controlling such systems, and the programming of such controllers. 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein, but include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims.