Abstract:
A lift apparatus for lifting a patient includes a sling bar ( 60 ) adapted to have a sling ( 110 ) secured thereto, a controller ( 138 ) and a status indicator ( 160 ) responsive to the controller for indicating the status of at least two parameters associated with the lift apparatus. The lift apparatus also including an interpretive indicator ( 164 ) for indicating which of the parameters the status indicator is referring to.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application is a continuation of application Ser. No. 13/666,198 entitled “Lift System with Status Indicators” filed on Nov. 1, 2012, the contents of which are incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The subject matter described herein relates to lifts of the type used in hospitals and other facilities to move patients from place to place, and particularly to a lift having status indicators for indicating the acceptability of lift related parameters. 
       BACKGROUND 
       [0003]    Lift systems are used in hospitals, other health care facilities, and sometimes in home care settings to move a patient from one location to another or to assist the patient in moving. One type of lift system includes a lift motor unit translatably mounted on a rail that extends along the ceiling of the room. The components of the lift motor unit include a motor operably connected to a strap or tether that extends vertically downwardly from the lift motor unit. The lift system also includes a sling bar attached to the end of the tether remote from the motor. The lift system also includes a sling. To use the lift system a caregiver secures a patient in the sling, attaches the sling to the sling bar, and uses a control device to operate the motor to lift the patient to a higher elevation or lower the patient to a lower elevation. In one typical example the caregiver operates the motor to raise the patient off a bed, pulls on the sling to cause the motor unit to translate along the rail until the patient is positioned over a desired destination location, and then operates the motor again to lower the patient to the destination. 
         [0004]    Despite the merits and advantages of existing lift systems, manufacturers continue to develop improvements such as those described herein. 
       SUMMARY 
       [0005]    A lift apparatus for lifting a patient comprises a sling bar adapted to have a sling secured thereto, a controller and a status indicator responsive to the controller for indicating the status of at least one parameter associated with the lift apparatus. The associated parameters comprise height, speed, sling securement state, sling compatibility, and fault state. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]    The foregoing and other features of the various embodiments of the lift system described herein will become more apparent from the following detailed description and the accompanying drawings in which: 
           [0007]      FIG. 1  is a perspective view of a room in a health care facility showing, among other things, a lift system for transferring patients from a source location to a destination location. 
           [0008]      FIG. 1A  is a schematic view of a lift motor unit showing a lift motor and a lift motor control unit. 
           [0009]      FIG. 2  is a view of a sling bar for the lift system of  FIG. 1 . 
           [0010]      FIG. 3  is a closer view of a coupling between the sling bar and a tether. 
           [0011]      FIG. 4  is a closer view of a hook on one end of the sling bar. 
           [0012]      FIG. 5  is a schematic diagram showing selected components of the sling bar and the lift motor control unit 
           [0013]      FIG. 5A  is a view of a sling hooked onto the sling bar. 
           [0014]      FIG. 6  is a block diagram showing the inputs and outputs of algorithms for producing indications related to the status of the lift system, in particular sling bar height, sling suitability and security, and lifting speed. 
           [0015]      FIGS. 7-8  are a decision matrix related to one of the algorithms of  FIG. 6  and a diagram defining parameters used in the decision matrix. 
           [0016]      FIG. 9  is a decision matrix related to another of the algorithms of  FIG. 6 . 
       
    
    
     DETAILED DESCRIPTION 
       [0017]      FIGS. 1 and 1A  show one example of a lift system of the type used in hospitals, other health care facilities and home care settings for transferring patients from a source location, for example a bed  20 , to a destination location such as a wheelchair  22 . The lift system includes a pair of stanchions  24  affixed to opposite walls  26  of a room. The stanchions extend vertically from floor  28  to a stationary rail  30  that extends laterally across the room between the stanchions and along the ceiling  34  of the room. A lift motor unit  36  engages the rail and is translatable along the rail in left and right lateral directions as indicated by the arrows labelled L and R (the left and right directions are based on the perspective of a supine occupant of bed  20 ). As seen best in  FIG. 1A  the lift motor unit includes a lift motor  38  and a lift motor control unit  40  (also referred to as a lift motor control box). A strap or tether  42  extends vertically downwardly from the lift motor unit. Operation of the lift motor in response to a user command causes the tether to retract into the lift motor unit or deploy from (i.e. extend out of) the lift motor unit. 
         [0018]    Referring additionally to  FIGS. 2-4 , an attachment fixture  44  is secured to the lower end of the tether. A female connector  46  is pivotably secured to fixture  44  so that the connector is pivotable about female connector axis  50 . 
         [0019]    The lift system also includes a sling bar  60  which includes a beam  62  and a hook  64  at each end of the beam. Each hook has a base  70 , a lower elbow  72 , an upper elbow  74  and a terminus  76 . The terminus  76  of each hook  64  is spaced from beam  62  to define a gap or space  90 . A retainer  92  is pivotably secured to the terminus of each hook so that each retainer is pivotable or rotatable about a retainer axis  94 , only one of which is shown in  FIG. 2 . Gravity causes the retainer to bridge across gap  90  from the terminus of the hook to the base of the hook where contact between retainer  92  and base  70  prevents further rotation of the retainer in direction D C . The hook is therefore in a naturally closed state in which it has a perimeter defined by base  70 , elbows  72 ,  74 , terminus  76  and retainer  92 . Each retainer can be easily rotated in direction D O  to open the hook and allow an object to pass into the hook through space  90 . However contact between retainer  92  and hook base  70  prevents the retainer from rotating in further in direction D C  than is shown in the illustration in response to, for example, a force exerted on the retainer from within the hook perimeter. As a result the retainer prevents objects from passing out of the hook through space  90  unless the retainer has been first intentionally rotated in direction D O . 
         [0020]    The sling bar also includes a male connector  100  pivotably attached to beam  62  so that the beam can rotate about male pivot axis  102 . Male connector  100  and female connector  46  are pivotably connected to each other for rotation about joint axis  104 , which is perpendicular to female axis  50 . 
         [0021]    Referring additionally to  FIG. 5 , control unit  40  includes a position sensor  136  such as a potentiometer that provides a resistance-position relationship to enable detection of how much of tether  42  has been deployed from lift motor unit  36 . Control unit  40  also includes an RFID reader  134 , a controller  138  such as a microprocessor, and a height governing system  142 . The height governing system  142  is configured to regulate the distance between sling bar  60  and the floor  28 . The lift motor control unit also includes one or more connectivity modules  144  to facilitate communication with other devices and other networks such as a hospital communication network. 
         [0022]    Sling bar  60  also includes an ambient light sensor such as photoresistor  150 , and hook force sensors  152  for detecting the application of force to the lower elbows  72  of the sling bar hooks. An example of a suitable hook force sensor is a contact switch that includes an array of force sensing resistors. Such a hook force sensor is better suited to sensing the presence or absence of a force being exerted on the hooks rather than providing an accurate indication of the magnitude of the force. Sling bar  60  also includes a distance sensor  130  such as an ultrasonic transceiver. Sling bar  60  also includes a communication terminal  154 . The sling bar communication terminal encapsulates information from the various sensors and provides the data to controller  138  by way of, for example, a serial data structure such as SPI. The controller processes this data and repackages it before transmission to connectivity modules  144  which can be Wifi, bluetooth, wired LAN or others. The communication terminal is a communication channel which operates under supervision of controller  138  which issues instructions to the terminal to start or stop communication. Suitable interface technologies for the communication terminal include Serial Peripheral Interfaces (SPI&#39;s), Universal Serial Bus (USB) interfaces, Parallel Peripheral Interfaces, TCP/IP interfaces, or other communication interfaces. 
         [0023]    Referring additionally to  FIG. 5A  the lift system also includes a sling  110 . The sling includes a seat portion  112  and straps  114  extending from the seat portion. Numerous models and styles of slings are commercially available, and not all slings are necessarily compatible with all sling bars and/or with all patients. The sling therefore includes an RFID tag  120  which, when interrogated by an RFID reader, reveals at least the model designation of the sling. The RFID tag may be programmable in which case the tag can be loaded with information concerning the identity of the patient assigned to the sling and/or any special requirements or restrictions related to the use of the sling with the patient. 
         [0024]    Height governing system  142  governs the distance between the sling bar and the floor by monitoring the electric potential provided from position sensor  136  and the data from distance sensor  130 . The position sensor (such as a potentiometer) provides distance information between the sling bar  60  and motor unit  36  by reading the number of revolutions of motor  38 , which correlates to the distance between the sling bar and the motor unit. The distance sensor  130  provides distance information between the sling bar and the floor. It is expected that the information collected from the position sensor and the distance sensor would correlate with each other. In other words, referring to  FIG. 8 , the distance H F  between the sling bar and the floor as determined from distance sensor  130 , plus distance H C  between the sling bar and the ceiling determined from position sensor  136  should equal the known height H of the ceiling relative to the floor. If not there is a possible fault in the system, for example in the system electronics or the calibration of position sensor  136 , which the system can report. 
         [0025]    The height governing system  142  receives raw data from the position and distance sensors and puts it in a prescribed format ready for transmission to controller  138 . The controller receives information from the height governing system and from one or more other modules such as RFID reader  134 , connectivity module  144 , hook force sensor  152 , tether force sensor  156  and ambient light sensor  150  and determines the timing of control signals to other peripherals (such as providing status indicators described below). The height governing system also includes current sensing circuitry to measure the electrical current delivered to motor  38  and voltage sensing circuitry to measure the motor voltage. The controller uses the data to calculate and provide the appropriate current drive for the motor. 
         [0026]    The lift system also includes a tether force sensor  156  such as a load cell ( FIGS. 2-3 ) that senses tension on the tether or force exerted through attachment fixture  44  and female and male connectors  46 ,  100 . Although  FIGS. 2-3  depict the sensor as being integrated into tether  42 , it can also be integrated into attachment fixture  44 , female connector  46 , male connector  100  or some combination thereof. Suitable force sensors other than load cells may also be used. The tether force sensor is provided to give an accurate measurement of force exerted on the tether, specifically to give an indication of the amount of patient weight supported by the sling bar. 
         [0027]    The tether force sensor  156  is used to determine patient weight. The hook force sensors  152  are used to sense the presence or absence of a load applied to hooks  64  and therefore to determine if a sling is properly attached, i.e. if sling straps  114  are securely captured on both hooks  64 . 
         [0028]    The sling bar hooks also include one or more sources of light such as light emitting diodes (LED&#39;s)  160 . LED&#39;s  160  are status indication LED&#39;s that indicate the status of the lift system as described below in more detail. LED&#39;s  160  are mounted behind a lens  162  which wraps around the hook from base  70  to terminus  76 . The lens protects the LED&#39;s from damage and may perform certain optical functions such as directing the light emitted from the LED&#39;s in one or more preferred directions. By way of examples, the light source may comprise a single LED which can emit light of at least three colors (e.g. red, amber, green), or may comprise multiple LED&#39;s each of which can emit light of at least three colors, or may comprise multiple LED&#39;s each of which emits light of only a single color but which collectively emit light of at least three colors. The sling bar also includes a second light source exemplified as a set of LED&#39;s  164  such as the three LED&#39;s  164 A,  164 B,  164 C labelled “HEIGHT”, “SLING ATTACHMENT” and “SPEED”. The second set of LED&#39;s is an interpretive indicator so that a user understands how to interpret indications provided by LED&#39;s  160 . The output of photoresistors  150  can be input to controller  138 . The controller can then regulate the intensity of the light from the LED or LED&#39;s, as a function of light intensity in the room. 
         [0029]    To use the system a caregiver secures a patient in the sling and attaches the sling to sling bar hooks  64  by passing sling straps  114  through sling bar openings  90 . The caregiver may then use a control device, such as a touch screen or a hand-held remote control device, not shown, to operate the motor and lift the patient to a higher elevation or lower the patient to a lower elevation. In one typical example the caregiver operates the motor to raise the patient off the bed, then pulls on the sling to cause motor unit  36  to translate along rail  30  until the patient is positioned approximately above a wheelchair pre-positioned under the rail. The caregiver then operates the motor to lower the patient onto the wheelchair. 
         [0030]    The components of the disclosed lift system cooperate to provide a number of status indications, specifically a sling height indication, a sling attachment indication and a lifting speed indication as described in the following paragraphs. 
       Sling Height Indication: 
       [0031]    Referring principally to  FIGS. 4, 5, and 6-8 , ultrasonic transceiver  130  emits ultrasonic signals toward the floor of the room and measures the return signal reflected off the floor. Controller  138  processes the information from the ultrasonic transceiver to determine the height H F  of the sling relative to the floor. Controller  138  executes an algorithm  170  to compare height H F  to one or more height thresholds and, depending on the outcome of the determination, issues a height indication command  172  to command red, amber, or green illumination of LED&#39;s  160 .  FIGS. 7-8  show elements of an algorithm for making the determination. If the sling is at its lowest possible height plus or minus a tolerance (e.g. h1≦H F ≦h2) the controller issues a height indication command  172  to command green illumination of LED&#39;s  160  to signify that the height is satisfactory. If the sling is at an intermediate height (e.g. h2&lt;H F ≦h3) the controller commands amber illumination to signify that the height is undesirable. If the sling is at height higher than the upper end of the intermediate range (e.g. H F &gt;h3) the controller commands red illumination to signify that the height is unsatisfactory. If the controller commands amber or red illumination of LED&#39;s  160  the controller also commands illumination of LED  164 A ( FIG. 4 ) to signify that the amber or red indication relates to sling height. 
         [0032]    In one possible enhancement of the sling height indication, a height reading that would otherwise cause a satisfactory (green) indication will instead cause an undesirable (yellow) or unsatisfactory (red) indication if the height reading persists for more than a prescribed period of time. Three possible alternatives are summarized in tables 1-3 below. Table 1 shows an alternative that specifies an undesirable or unsatisfactory indication, at the choice of the system designer, if the sling bar is at a height that would otherwise be satisfactory but is at that height for a time t longer than t A . 
         [0000]                                    TABLE 1                       Height   time   indication                           h1 ≦ H F  ≦ h2   t &gt; t A     undesirable (amber) or                   unsatisfactory (red) at the                   discretion of the system designer                        
Table 2 specifies an undesirable indication (amber) if the sling bar is at a height that would otherwise be satisfactory but is at that height for a time t at least as long as time t A  but less than time t B . Table 2 also specifies an unsatisfactory indication (red) if the sling bar is at a height that would otherwise be satisfactory but is at that height for a time t which is at least as long as time t B .
 
         [0000]                                    TABLE 2                       Height   time   indication                           h1 ≦ H F  ≦ h2   t A  ≦ t &lt; t B     undesirable (amber)           h1 ≦ H F  ≦ h2   t ≧ t B     unsatisfactory (red)                        
Table 3 specifies an unsatisfactory indication (red) if the sling bar is at a height that would otherwise be undesirable (amber) but is at that height for a time t which is greater than t A .
 
         [0000]                                    TABLE 3                       Height   time   indication                           h2 &lt; H F  ≦ h3   t &gt; t A     unsatisfactory (red)                        
In another enhancement a satisfactory indication results from a sling bar height that would otherwise produce an amber or red indication if the load exerted on the sling bar as indicated by, for example, tether force sensor  156 , is small enough to indicate that the sling bar is not supporting the weight of a patient.
 
       Sling Attachment Indication: 
       [0033]    Referring principally to  FIGS. 4, 5, 6, and 9 , RFID reader  134  interrogates the RFID tag  120  associated with a sling  110  brought into the vicinity of the lift system (i.e. so that the RFID tag attached to the sling is in range of the RFID reader). In addition hook force sensors  152  detect the application of force to the hooks. Controller  138  executes an algorithm  180  to processes the information from the RFID reader and hook force sensors to determine if the proper sling is attached properly or to facilitate such determination. For example if the sling is correct (as indicated by patient identifying data loaded onto the RFID tag of a patient-specific sling) and is properly attached to the sling bar (as indicated by at least a minimum force being exerted on each of the two hook force sensors  152 ) controller  138  issues a sling indication command  182  to command green illumination of LED&#39;s  160  to signify the correctness of the sling and its proper securement to the sling bar.  FIG. 9  shows elements of an algorithm for making the determination. If the sling is correct but is improperly attached (e.g. less than a minimum force being exerted on at least one hook force sensor), controller  138  commands red illumination of the LED&#39;s to signify improper attachment of the correct sling. If the sling is incorrect but is properly attached, controller  138  commands amber illumination of the LED&#39;s to signify incorrectness of a properly attached sling. If the sling is incorrect and is improperly attached controller  138  commands either red illumination of the LED&#39;s or a combination of red and amber illumination. If the controller commands amber or red illumination of LED&#39;s  160  the controller also commands illumination of LED  164 B to signify that the amber or red indication relates to sling height. Other relationships between LED illumination color and the sling and sling attachment suitability may be used instead of those in the table. 
       Lift Speed Indication 
       [0034]    Referring to  FIGS. 4, 5 and 10 , controller  138  executes an algorithm  190  to determine the suitability of the lifting speed. The system governs lifting speed by commanding an appropriate amount of current to drive lift motor  38 . Heavier loads (i.e. higher patient weight) require more current to maintain a given speed; lighter loads (i.e. lower patient weight) require less current to maintain a given speed. An example table of required voltage and nominal current as a function of patient weight is shown in table 4 below for the case of raising the sling bar, and therefore the patient, to a higher elevation. An example table of required voltage and current as a function of patient weight is shown in table 5 below for the case of lowering the sling bar, and therefore the patient, to a lower elevation. The tables also show the resulting speed and the approximate time required to cause the tether to extend or retract approximately 50 cm. The tables as presented are independent of strap length however tables for other strap lengths can be developed if it is determined that the current should also be a function of strap length. 
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 4 
               
             
             
               
                   
               
               
                 Raising the Sling Bar 
               
             
          
           
               
                 Weight while 
                 Time 
                   
                   
                   
               
               
                 lifting up 
                 taken 
                 Voltage 
                 Current 
                 Speed 
               
               
                 (kg) 
                 (sec.) 
                 (V) 
                 (A) 
                 (cm/s) 
               
               
                   
               
             
          
           
               
                 350 
                 11.31 
                 24 
                 18 
                 4.4 
               
               
                 300 
                 10.46 
                 25 
                 17 
                 4.8 
               
               
                 250 
                 9.81 
                 25 
                 15 
                 5.1 
               
               
                 200 
                 9.28 
                 26 
                 13 
                 5.4 
               
               
                 150 
                 8.78 
                 26 
                 12 
                 5.7 
               
               
                 100 
                 8.34 
                 27 
                 9 
                 6 
               
               
                 50 
                 7.88 
                 27 
                 6.5 
                 6.4 
               
               
                 0 
                 7.3 
                 27 
                 3.5 
                 6.8 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
               
             
               
               
               
               
               
             
           
               
                 TABLE 5 
               
             
             
               
                   
               
               
                 Lowering the Sling Bar 
               
             
          
           
               
                 Weight while 
                 Time 
                   
                   
                   
               
               
                 lifting down 
                 taken 
                 Voltage 
                 Current 
                 Speed 
               
               
                 (kg) 
                 (s) 
                 (V) 
                 (A) 
                 (cm/s) 
               
               
                   
               
             
          
           
               
                 350 
                 12.53 
                 27 
                 0 
                 4 
               
               
                 300 
                 12.97 
                 27 
                 0 
                 3.9 
               
               
                 250 
                 13.03 
                 27 
                 0.5 
                 3.8 
               
               
                 200 
                 13.21 
                 27 
                 1 
                 3.8 
               
               
                 150 
                 13.47 
                 27 
                 1.25 
                 3.7 
               
               
                 100 
                 13.75 
                 27 
                 1.3 
                 3.6 
               
               
                 50 
                 13.88 
                 27 
                 1.5 
                 3.6 
               
               
                 0 
                 13.5 
                 27 
                 1.4 
                 3.7 
               
               
                   
               
             
          
         
       
     
         [0035]    Electrical current sensing electronics in the height governing system senses the actual current and determines if the actual current is within a tolerance band (for example plus or minus 10%) of the nominal value. If the speed is within the specified tolerance the speed is satisfactory, and controller  138  issues a sling indication command  192  to command green illumination of the LED&#39;s. If the speed is outside the specified tolerance, controller  139  commands red illumination of the LED&#39;s to signify the unsatisfactory speed. Alternatively three tolerance bands could be defined—a satisfactory tolerance band within, say, plus or minus 10% of nominal (green), an undesirable band between plus or minus 10% and plus or minus 12% of nominal (amber), and an unsatisfactory band for speeds outside the plus or minus 12% band (red). If the controller commands amber or red illumination of LED&#39;s  160  the controller also commands illumination of LED  164 C to signify that the amber or red indication relates to sling speed. 
         [0036]    The controller also includes data validation algorithms to check for certain faults in the sensors or system electronics. For example load cells  156  may be faulty, or the conversion of the analog signal from the load cells to a digital signal suitable for the controller may be erroneous. In another example a timer in controller  138  may not be functioning properly. In another example a sensed value of a parameter, such as motor current and/or voltage, may differ from commanded values of the parameter. The existence of such faults causes the controller to command appropriate illumination of LED&#39;s  160  and  164 . Table 6 below shows the commanded LED illumination as a function of whether or not patient weight, motor voltage and motor current comply with validation tests and whether or not the timer is determined to be functioning properly. The letter “X” in a table entry signifies that the parameter in the column heading is not taken into account in determining the LED illumination color. Faults or combinations of faults not shown in the table 6 will cause the controller to command red illumination. 
         [0000]                                                                      TABLE 6                           Timer                       Weight   Functioning   Voltage   Current   LED           Valid?   Properly?   Valid?   Valid?   Illumination                                    1   YES   YES   YES   YES   Green       2   NO   YES   YES   YES   Amber       3   YES   NO   YES   YES   Amber       4   YES   YES   NO   YES   Amber       5   YES   YES   YES   NO   Amber       6   NO   NO   X   X   Red       7   X   NO   NO   X   Red       8   X   X   NO   NO   Red       9   X   X   X   NO   Red                    
Faults or combinations of faults not shown in the table 7 will cause the controller to command red illumination.
 
         [0037]    An alternate data validation table is shown below in table 7 for a lift system that does not include a tether force sensor. 
         [0000]    
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
                 TABLE 7 
               
               
                   
                   
               
               
                   
                 Is distance 
                   
                   
                   
                   
               
               
                   
                 (H C ) from motor 
                 Timer 
               
               
                   
                 to sling bar 
                 Functioning 
                 Voltage 
                 Current 
                 LED 
               
               
                   
                 valid? 
                 Properly? 
                 Valid? 
                 Valid? 
                 Illumination 
               
               
                   
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 YES 
                 YES 
                 YES 
                 YES 
                 Green 
               
               
                 2 
                 NO 
                 YES 
                 YES 
                 YES 
                 Amber 
               
               
                 3 
                 YES 
                 NO 
                 YES 
                 YES 
                 Amber 
               
               
                 4 
                 YES 
                 YES 
                 NO 
                 YES 
                 Amber 
               
               
                 5 
                 YES 
                 YES 
                 YES 
                 NO 
                 Amber 
               
               
                 6 
                 NO 
                 NO 
                 YES 
                 X 
                 Red 
               
               
                 7 
                 X 
                 NO 
                 NO 
                 X 
                 Red 
               
               
                 8 
                 X 
                 X 
                 NO 
                 NO 
                 Red 
               
               
                 9 
                 X 
                 X 
                 X 
                 NO 
                 Red 
               
               
                   
               
             
          
         
       
     
         [0038]    If desired, LED&#39;s  160  can be arranged to shine on the floor of the room. As a result, a caregiver whose view of the LED&#39;s is blocked still has an opportunity to be informed of the status of sling height, lifting speed and sling suitability and attachment and also any fault indications. 
         [0039]    The output from indication commands  172 ,  182 ,  192  or other output from algorithms  170 ,  180 ,  190  can be provided to a facility information network by way of connectivity module or modules  144 . The information can be used for a number of purposes such as to update care records or to apprise a remote caregiver of an undesirable or unsatisfactory condition. Similarly, information can be conveyed from the information network to components of the system, such as RFID reader  134  to customize the RFID reader to be compatible with information on RFID tag  120 .