Abstract:
A medical headlamp assembly, having a headband subassembly, including an electrical network, including a battery and an electrical jack, and a headlamp mount. Also, an electrical headlamp subassembly, has a mounting element matingly and removably engaged to the headlamp mount, and an electrical plug, matingly and removably engaged to the jack and an electrical headlamp, electrically connected to the plug. Further, the headband subassembly produces an electrical input for the headlamp subassembly and the headband subassembly includes a key resistor, the resistance value of which sets a characteristic of the electrical input.

Description:
RELATED APPLICATIONS 
     This application is a continuation-in-part of application Ser. No. 14/162,244 filed on Jan. 23, 2014 which is itself a continuation-in-part of application Ser. No. 14/057,351, filed on Oct. 18, 2013, which are incorporated herein by reference as if fully set forth herein, and which, in turn, claims priority from provisional application Ser. No. 61/822,493, filed May 13, 2013, which is also incorporated by reference as if fully set forth herein. 
    
    
     BACKGROUND 
     Medical headlamp providers have attempted to make a single design that serves a variety of purposes, and in so doing have diminished the capability of such a design to perform any single specialized purpose. For example, many designs feature an adjustable iris, to permit a user to set the beam width of the light produced. Unfortunately, such an iris blocks a good deal of the light, thereby requiring a brighter light source, needing more power. 
     It is an undesirable expense, however, to purchase a separate head lamp assembly for each purpose that a physicians&#39; office or hospital department may require. It would be desirable to find a way to eliminate at least part of this expense. 
     SUMMARY 
     The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements. 
     In a first separate aspect, the present invention may take the form of a medical headlamp assembly, having a headband subassembly, including an electrical network, including a battery and an electrical jack, and a headlamp mount. Also, an electrical headlamp subassembly, has a mounting element matingly and removably engaged to the headlamp mount, and an electrical plug, matingly and removably engaged to the jack and an electrical headlamp, electrically connected to the plug. Further, the headband subassembly produces an electrical input for the headlamp subassembly and the headband subassembly includes a key resistor, the resistance value of which sets a characteristic of the electrical input. 
     In a second separate aspect, the present invention may take the form of a method of switching out a medical headlamp that utilizes a medical headlamp assembly having a headband assembly, including a mounting element, an electrical jack and a power supply assembly electrically connected to the electrical jack. Also, a first headlamp assembly is removably engaged to the mounting element and includes a conductor terminating in a plug that is plugged into the jack, and a first key resistor for setting an electrical input. Also, a second headlamp assembly is removeably engageable to the mounting element and includes a conductor terminating in a plug that is engageable to the jack and a second key resistor for setting the electrical input differently than for the first headlamp. In the method, the first headlamp assembly is removed from the mounting element, the first headlamp plug is unplugged from the jack, the second headlamp is engaged on the mounting element, and the second headlamp plug is plugged into the jack. 
     In addition to the exemplary aspects and embodiments described above, further aspects and embodiments will become apparent by reference to the drawings and by study of the following detailed descriptions. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Exemplary embodiments are illustrated in referenced drawings. It is intended that the embodiments and figures disclosed herein are to be considered illustrative rather than restrictive. 
         FIG. 1  shows an isometric view of a medical headlamp assembly, having an attached medical headlamp of a first type. 
         FIG. 2  shows an isometric view of a medical headlamp assembly, having a detached medical headlamp of the first type. 
         FIG. 3  shows an isometric view of a medical headlamp assembly, having an attached medical headlamp of a second type. 
         FIG. 4  shows an isometric view of a medical headlamp assembly, having a detached medical headlamp of the second type. 
         FIG. 5  shows an isometric view of a medical headlamp assembly, having an attached medical headlamp of a third type. 
         FIG. 6  shows an isometric view of a medical headlamp assembly, having a detached medical headlamp of the third type. 
         FIG. 7  shows an audio plug and the scheme of use of the poles of the audio plug that is used in a preferred embodiment of the present invention. 
         FIG. 8  shows a simplified schematic of the electrical network of the medical headlamp assembly of  FIGS. 1-6 . 
         FIG. 9  shows a simplified schematic diagram of an alternative preferred electrical network of the of the medical headlamp assembly of  FIGS. 1-6 . 
         FIG. 10  shows a simplified schematic diagram of an additional alternative preferred electrical network of the of the medical headlamp assembly of  FIGS. 1-6 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIGS. 1-6 , in a first preferred embodiment a medical headlamp assembly  10  includes a headband  12 , supporting a mounting column  14 . A low intensity headlamp assembly  16  includes a low intensity headlamp  18 , a linkage  20 , a slider  22 . Also included is an electrical conductor  26  terminating in a four pole audio plug  28 , which plugs into a four pole audio jack  30 . 
     As shown in  FIG. 2 , when a user decides that he would like to remove assembly  16  from mounting column  14 , he pulls assembly  16  upwardly to disengage slider  22  from column  14  and unplugs plug  28  from jack  30 . He may do this simply to replace a worn out assembly  16 , or (referring to  FIG. 3 ) to install an assembly having different characteristics, such as medium intensity assembly  16 ′, having medium intensity light  18 ′ and plug  28 ′ which is plugged into jack  30 . Referring to  FIGS. 5 and 6 , in like manner assembly  16 ′ can be switched out and assembly  16 ″, having high intensity light  18 ″ and plug  28 ″, can be installed onto slider  22  on column  14 , and with plug  28 ″ plugged into jack  30 . 
     Referring to  FIG. 7 , although plugs  28 ,  28 ′ and  28 ″ appear identical, each one has a different active pin (longitudinally arranged electrical contact) that is electrically connected to the light emitting diode (not shown) of lamp  18 ,  18 ′ or  18 ″, respectively, and serving as the return, with the current being delivered into lamp  18 ,  18 ′ and  18 ″ in all cases through the ground. Pin  1  of plug  28  serves as the LED return for lamp  18 , pin  2  serves as the LED return for lamp  18 ′, and pin  3  serves as the LED return for lamp  18 ″. Pin  1 , pin  2 , and pin  3  of plug  28  connects to pin  2 , pin  3  and pin  4  of jack  30 , respectively. Pin  1  of jack  30  connects to the ground of plug  28 . 
     Referring to  FIG. 8 , a DC-to-DC converter  50  acts as a power supply to whichever one of lamps  18 ,  18 ′ or  18 ″ is connected to jack  30 . A feedback loop is formed by the output of converter  50  powering the LED line, where all of the current in which flows to the LED return line, and at least a portion of which passes through a current sense resistor R 1 , which in turn drives the feedback pin FB of converter  50 . (The modification of the voltage at feedback pin FB through a voltage increase circuit  54  is described below.) The output of converter  50  increases if the voltage of feedback pin FB is below 0.5 volts and decreases if the voltage of feedback pin FB is above 0.5 volts, thereby setting that voltage at pin FB at 0.5 volts. Accordingly, when the voltage increase circuit  54  is not active, the voltage across resistor R 1  is set at 0.5 volts, and accordingly, I R1 =R 1 /0.5 VDC. For the 800 mAmp lamp, for which the return current exits at Pin  2  of the jack  30 , a few equations apply: 
     
       
         
           
             
               
                 
                   
                     I 
                     
                       R 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       1 
                     
                   
                   = 
                   
                     
                       800 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       mAmps 
                     
                     - 
                     
                       
                         I 
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           2 
                         
                       
                       . 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   1 
                 
               
             
             
               
                 
                   
                     I 
                     
                       R 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       1 
                     
                   
                   = 
                   
                     
                       
                         800 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         mAmps 
                         * 
                         
                           ( 
                           
                             
                               R 
                               2 
                             
                             + 
                             
                               R 
                               3 
                             
                             + 
                             
                               R 
                               4 
                             
                           
                           ) 
                         
                       
                       
                         
                           R 
                           1 
                         
                         * 
                         
                           ( 
                           
                             
                               R 
                               2 
                             
                             + 
                             
                               R 
                               3 
                             
                             + 
                             
                               R 
                               4 
                             
                             + 
                             1 
                           
                           ) 
                         
                       
                     
                     . 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   2 
                 
               
             
           
         
       
     
     For the 1.1 Amp lamp (from jack  30  pin  3 ) these equations become: 
     
       
         
           
             
               
                 
                   
                     I 
                     
                       
                         R 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                       
                       , 
                       
                         R 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         1 
                       
                     
                   
                   = 
                   
                     
                       1.1 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       mAmps 
                     
                     - 
                     
                       
                         I 
                         
                           
                             R 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             3 
                           
                           , 
                           
                             R 
                             ⁢ 
                             
                                 
                             
                             ⁢ 
                             4 
                           
                         
                       
                       . 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     1 
                     1.1 
                   
                 
               
             
             
               
                 
                   
                     I 
                     
                       
                         R 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                       
                       , 
                       
                         R 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         1 
                       
                     
                   
                   = 
                   
                     
                       
                         1.1 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         mAmps 
                         * 
                         
                           ( 
                           
                             
                               R 
                               3 
                             
                             + 
                             
                               R 
                               4 
                             
                           
                           ) 
                         
                       
                       
                         
                           ( 
                           
                             
                               R 
                               1 
                             
                             + 
                             
                               R 
                               2 
                             
                           
                           ) 
                         
                         * 
                         
                           ( 
                           
                             
                               R 
                               3 
                             
                             + 
                             
                               R 
                               4 
                             
                             + 
                             1 
                           
                           ) 
                         
                       
                     
                     . 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     2 
                     1.1 
                   
                 
               
             
           
         
       
     
     For the 1.4 Amp lamp (from jack  30  pin  4 ) these equations become: 
     
       
         
           
             
               
                 
                   
                     I 
                     
                       
                         R 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         3 
                       
                       , 
                       
                         R 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                       
                       , 
                       
                         R 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         1 
                       
                     
                   
                   = 
                   
                     
                       1.4 
                       ⁢ 
                       
                           
                       
                       ⁢ 
                       mAmps 
                     
                     - 
                     
                       
                         I 
                         
                           R 
                           ⁢ 
                           
                               
                           
                           ⁢ 
                           4 
                         
                       
                       . 
                     
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     1 
                     1.4 
                   
                 
               
             
             
               
                 
                   
                     I 
                     
                       
                         R 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         3 
                       
                       , 
                       
                         R 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         2 
                       
                       , 
                       
                         R 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         1 
                       
                     
                   
                   = 
                   
                     
                       
                         1.4 
                         ⁢ 
                         
                             
                         
                         ⁢ 
                         mAmps 
                         * 
                         
                           ( 
                           
                             R 
                             4 
                           
                           ) 
                         
                       
                       
                         
                           ( 
                           
                             
                               R 
                               1 
                             
                             + 
                             
                               R 
                               2 
                             
                             + 
                             
                               R 
                               3 
                             
                           
                           ) 
                         
                         * 
                         
                           ( 
                           
                             
                               R 
                               4 
                             
                             + 
                             1 
                           
                           ) 
                         
                       
                     
                     . 
                   
                 
               
               
                 
                   Equation 
                   ⁢ 
                   
                       
                   
                   ⁢ 
                   
                     2 
                     1.4 
                   
                 
               
             
           
         
       
     
     In addition, for no lamp  18 ,  18 ′, or  18 ″ may the voltage drop through the lamp or the resistive network composed of R 1 , R 2 , R 3  and R 4  exceed a maximum that in one embodiment is about 3.4 volts. In addition, the power consumption of this resistive network must be minimized for all the lamps, leading to low values for all of the resistors, on the order of a little more than an ohm. 
     The voltage output of the brightness adjust rheostat  40  is fed into a pin of a microprocessor  56 , resulting in a periodic waveform having a duty factor that is related to the rheostat output voltage, appearing on an output pin of the microprocessor  56 . When the rheostat  40  is moved to a “dim” setting, this causes microprocessor  56  to produce a waveform that causes voltage increase circuitry  54  to amplify the voltage at its input, thereby reducing the current (and voltage) out of the DC-to-DC converter  50 , and reducing the current through resistor R 5 . In an alternative preferred embodiment voltage increase circuitry is set to always amplify its input signal, thereby permitting a lower value for the voltage drop across R 1 , when the lamp  18 ,  18 ′ or  18 ″ is not being dimmed. This permits a lower value of resistance for R 1 , and lower power loss through R 1  and through the entire resistance network R 1 , R 2 , R 3  and R 4 . For dimming positions of rheostat  40 , this amplification is increased. 
     When the brightness adjust knob  40  is set at its maximum, causing a voltage increase circuit  54  (described below) to pass the voltage from a current sense resistor R 1 , unchanged, then the voltage through the current sense resistor R 1  is forced to 0.5 volts by the feedback loop implemented by the converter  50  feedback pin FB (driven directly or indirectly by the current sense resistor R 1 , and the converter  50  output powering the lamp  18 ,  18 ′ or  18 ″, with the LED return line powering resistor R 1 ). 
     Referring to  FIG. 9 , in an alternative embodiment two of the pins of jack  30  are dedicated to connecting a key resistor R K , which together with R 1  forms a voltage divider that determines the voltage V CS , which drives amplifier  54 , that drives the feedback input of the DC-to-DC Converter  50 , which powers lamp  18 ,  18 ′, or  18 ″, having resistance value R L , depending on which is being utilized. When, as noted above in reference to  FIG. 8 , microprocessor  56  is causing amplifier  54  to simply pass through V CS  with unit gain to the feedback pin FB of convertor  50 , then, for a specified I L :
 
 I   L   *R   L   *R   1 /( R   K   +R   1 )=0.5 Volts; or
 
 I   L   *R   L /0.5=( R   K   +R   1 )/R 1 ; or
 
2* I   L   *R   L   =R   K   /R   1 +1;
 
 R   K =(2* I   L   *R   L −1)* R   1  
 
     Accordingly, if the designer were to set R 1  to 5*10 5  Ω to draw little current and save energy, R K  would be set to 5*10 5 *(1.6R L −1), to set the correct voltage at the lamp  18  input to drive 800 mAmps through lamp  18 . For  18 ′, requiring 1.1 Amps, R K  would be set at 5*10 5 *(2.2R L −1), (where R L  would reflect the load of lamp  18 ′, and would be somewhat different than the R L  for  18 ). Finally, for lamp  18 ″, R K  equals 5*10 5 *(2.8R L −1). 
     Now referring to  FIG. 10 , which sets the current through R L , if R L  is known precisely, then  FIG. 9  and  FIG. 10  will deliver the exact same current to R L . But if R L  differs slightly from an expected value, then the V L   2 /R L  power achieved by fixing the voltage to a specified level that will be achieved by the  FIG. 9  electrical network, will differ somewhat from the I L   2 *R L  power achieved by fixing current to a specified level, that will be achieved by the  FIG. 10  electrical network. In general, for the  FIG. 10  network:
 
 R   K   =R   1 /(2* I   L −1);
         where I L  is the specified value of current through the lamp.       

     For lamp  18 , drawing 800 mAmps, R K =(5/3)*R 1 ; for lamp  18 ′, drawing 1.1 Amps, R K =(5/6)*R 1 ; and for lamp  18 ″, drawing 1.4 Amps, R K =(5/9)*R 1 . 
     In the embodiment of  FIG. 9  it is power efficient to set R 1  and R K  to high values resistance, whereas in the embodiment of  FIG. 10 , it is efficient to set them to low values of resistance. 
     While a number of exemplary aspects and embodiments have been discussed above, those possessed of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope.