Abstract:
An access system for controlling access of a user to one of several unique operative modes of an electronic device used to communicate with an implantable medical device. The access system includes a portable keycard, which is held by a user. The keycard has embedded magnets arranged in a unique predetermined pattern. The electronic device has a housing that provides a slot and a channel for receiving the keycard by the user. A sensing circuit and a processing circuit are both provided. The sensing circuit includes Hall-effect transducers positioned next to the channel so that upon inserted of the keycard, certain ones of these Hall-effect transducers will reside adjacent a magnet, depending on the particular unique pattern. A magnet positioned adjacent a Hall-effect transducer will cause the transducer to send an output signal to the processor indicating the presence of a magnet at the location of the Hall-effect transducer. The Hall-effect transducers collectively generate an electronic pattern representing the particular identity of the keycard. The processor compares this electronic pattern with one of several stored in electronic memory and provides selective access to the device in response to successfully identifying a match. A doctor, a technician, a salesperson and a factory assembly worker are examples of users of this system and each will be granted predetermined access rights to operate the device. Additional Hall-effect transducers may be provided to help detect the intrusion of magnetic fields produced from magnets not located with the keycard. The process will deny any access to the device should any such remove magnetic fields be detected.

Description:
BACKGROUND OF THE INVENTION  
       [0001]    1) Field of the Invention 
         [0002]    The present invention generally relates to controlled access systems for controlling the access to select users of equipment, and more particularly, to magnetic-based key access systems for controlling the access to select users of medical equipment. 
         [0003]    2) Discussion of Related Art 
         [0004]    Magnetically encoded cards have been used successfully for years to help control access to machines, doors, and locks. So called magnetic locks were originally mechanical locking devices. This type of lock includes magnetically controllable tumblers. A magnetic key used with this lock has embedded therein permanent magnets arranged in a prescribed pattern. If the pattern of the magnets within the key match the combination of the lock, the fields of each magnet exactly align with the tumblers of the lock. The field strength and field orientation of each aligned magnet within the “correct” key causes the tumblers to displace to a mechanically-open position. The tumblers of the lock are spring-biased and the magnets displace each tumbler against the action of each spring. The spring bias returns each tumbler to the locked position when the key is removed. Furthermore, if the device being controlled is electric, then an appropriate electric switch operating the device becomes moveable only when the tumblers move to an open position. 
         [0005]    One benefit of this type of magnetic key locking system is that a typical key-slot or keyhole is not required to actuate the lock. The lock may be designed so that the magnetic key need only be positioned against a surface that lies adjacent to the tumblers of the lock. This is a great benefit for use in corrosive areas or areas where environmental conditions do not favor the delicate tumbler mechanisms of a lock. Also, if the tumblers are not physically accessible, they cannot be picked in a traditional manner, making this type of lock system more secure than conventional locks. 
         [0006]    Unfortunately, mechanical locks have their limitations. Disadvantages include the expense of manufacture and the fact that many applications for this type of lock are electrically controlled, such as computer equipment, electrical medical devices, lighting, etc. The latter disadvantage led to the development of a magnetically-operated lock that uses electronic magnetic-field detecting devices which effectively replace the mechanical tumblers used in earlier lock versions, described above. Such magnetic-field detecting devices include reed switches and more reliable, more accurate and durable Hall effect sensors in an IC package. 
         [0007]    A Hall effect sensor is a well known electronic device that can be used to detect the presence of a magnetic field. The Hall effect refers to the potential difference (Hall voltage) on the lateral sides of an electrical conductor crossed by an electric current when a magnetic field is applied perpendicularly. By measuring the lateral voltage potential, the strength and field orientation of the adjacent magnet can be determined. Such Hall effect sensors can be used to measure very small and slow fluctuations in a magnetic field, down to a hundredth of a gauss. 
         [0008]    With the introduction of electronic magnetic-field sensing devices, key-card controlled access systems could be more reliable, less expensive and provide a greater number of key-combinations than with the above-described magnetically-controlled mechanical tumbler security system. The electronic magnetic-field sensors can also more directly and more reliably control the electronic security device whose access is being controlled. 
         [0009]    Such key-access systems using electronic magnetic-field sensing devices generally provide consistent, accurate and reliable use and are generally durable in many different types of harsh environments, except one-magnetic environments. 
         [0010]    On a regular basis, hospitals and clinics use a variety of electronic devices, many of which emit strong electromagnetic energy. Such strong-emitting devices include MRI units, monitors and defibrillators. Unless property shielded, these and almost every electronic device used everyday within the medical environment emits a certain amount of electromagnetic energy. The emitted electromagnetic energy creates weak and strong magnetic fields which can affect the operation of other electronic devices operating nearby. One type of device that could easily be affected by these fields is magnetically-controlled access systems which are relying on magnetic-field sensing components. Even relatively weak magnetic fields could interfere with the operation of the Hall-effect sensors and thereby prevent the access control device from accurately reading a key card. This magnetic interference could either provide improper access to an unauthorized user or prevent access to legitimate users. 
         [0011]    It is a first object of the present invention to provide an access control system that overcomes the deficiencies of the prior art. 
         [0012]    It is a second object of the present invention to provide an access control system that allows an authorized individual access to select and predetermined mode of operation to an electrical device. 
         [0013]    It is another object of the present invention to provide an access control system that includes provisions to control and mitigate the effects of any outside interference caused by nearby electromagnetic fields. 
       SUMMARY OF THE INVENTION  
       [0014]    An access system for controlling access of a user to one of several unique operative modes of an electronic device used to communicate with an implantable medical device. The access system includes a portable keycard which is held by a user. The keycard has embedded magnets arranged in a unique predetermined pattern. The electronic device has a housing that provides a slot and a channel for receiving the keycard by the user. A sensing circuit and a processing circuit are both provided. The sensing circuit includes Hall-effect transducers positioned next to the channel so that upon inserted of the keycard, certain ones of these Hall-effect transducers will reside adjacent a magnet, depending on the particular unique pattern. A magnet positioned adjacent to a Hall-effect transducer will cause the transducer to send an output signal to the processor indicating the presence of a magnet at the location of the Hall-effect transducer. The Hall-effect transducers collectively generate an electronic pattern representing the particular identity of the keycard. The processor compares this electronic pattern with one of several stored in electronic memory and provides selective access to the device in response to successfully identifying a match. A doctor, a technician, a salesperson and a factory assembly worker are examples of users of this system and each will be granted predetermined access rights to operate the device. Additional Hall-effect transducers may be provided to help detect the intrusion of magnetic fields produced from magnets not located with the keycard. The process will deny any access to the device should any such remove magnetic fields be detected. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0015]    The invention can be more fully understood from the following detailed description taken in conjunction with the accompanying drawings, in which: 
           [0016]      FIG. 1  is a perspective assembly view of a key card according to a first embodiment of the invention including a top section, a bottom section, and several magnets used to form a key combination; 
           [0017]      FIG. 2  is a perspective view of a key holder attached to a printed circuit board and showing a key card located in a fully inserted position, according to the first embodiment of the invention; 
           [0018]      FIG. 3  is a perspective view of the key receiver and key card of  FIG. 2  located in a fully removed position, showing details of a mechanical locking tab and the Hall effect sensors, according to the first embodiment of the invention; 
           [0019]      FIG. 4  is a perspective view of the basic components of an exemplary medical device that incorporates the access control system of  FIG. 3  and further includes an antenna, a display, an input interface, a memory circuit, a processor circuit and a sensor interface circuit, and showing the layout of several Hall-effect sensors, according to the first embodiment of the invention; 
           [0020]      FIG. 5  is a perspective view of the basic components of the device of  FIG. 4 , furthering including the key-holder of  FIG. 2  and showing a key card in the fully inserted position, according to the first embodiment of the invention; 
           [0021]      FIG. 6  is a top plan view of the key receiver of  FIG. 2  showing in phantom lines the relative position of the magnets located within the key card and Hall-effect sensors located on the printed circuit board and showing the key card in a fully removed position, according to the first embodiment of the invention; 
           [0022]      FIG. 7  is a top plan view of the key receiver of  FIG. 2  showing in phantom lines the relative position of the magnets located within the key card and the Hall-effect sensors located on the printed circuit board and showing the key card in a “wake-up” inserted position, according to the first embodiment of the invention; 
           [0023]      FIG. 8  is a top plan view of the key receiver of  FIG. 2  showing in phantom lines the relative position of the magnets located within the key card and the Hall-effect sensors located on the printed circuit board and showing the key card in a first partially inserted position, according to the first embodiment of the invention; 
           [0024]      FIG. 9  is a top plan view of the key receiver of  FIG. 2  showing in phantom lines the relative position of the magnets located within the key card and the Hall-effect sensors located on the printed circuit board and showing the key card in a second partially inserted position, according to the first embodiment of the invention; 
           [0025]      FIG. 10  is a top plan view of the key receiver of  FIG. 2  showing in phantom lines the relative position of the magnets located within the key card and the Hall-effect sensors located on the printed circuit board and showing the key card in a fully inserted and locked position, according to the first embodiment of the invention; 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0026]    By way of introduction, the present invention is a keycard-controlled-access system that receives one of several keycards at a time and includes a keycard holder, sensors for reading an inserted keycard and a processing circuit for determining access in response to the outputs of the sensors. This invention is meant to be included into the design of any of a variety of electronic devices used in a medical environment to which access is to be controlled. However, the present invention is most suited for such electronic medical devices that are mobile (such as handheld devices) because these devices are more likely to experience stray magnetic fields from other electronic sources as the device is moved throughout the hospital or clinic. 
         [0027]    Although the present invention can easily be adapted to many different types of electronic medical equipment, it is preferably incorporated into a portable control unit that is used to communicate with and control the operation of an implanted infusion pump, pace maker or any other implanted device that requires RF communication and control from a remote device. This control unit includes an RF antenna, controlling and processing circuitry, a keypad for entering data and a display for reading data, and also a key slot into which the above introduced keycard is inserted by authorized personnel. As can be appreciated by those skilled in the art, the keycard holder, reading and processing circuitry, and the above listed components are enclosed or mounted to a housing that is not described or shown in any great detail in the immediate application since such details are considered beyond the scope of this invention. Only the above-described main components are shown to help explain the structure and operation of the invention. 
         [0028]    Keycard 
         [0029]    Referring to  FIG. 1  an assembly view of a key card  10  is shown according to a first embodiment of the invention, including a top section  12  and a bottom section  14 . The two sections  12 ,  14  are preferably made from a strong durable plastic, manufactured by an injection molding process. Top section  12  and bottom section  14  are sized and shaped to mate with each other at a common plane  16  and will eventually (after assembly) be bonded to each other at this plane using either an appropriate adhesive or preferably hermetically bonded using an ultrasonic welding process. To aid in manufacturing, top section  12  and bottom section  14  are preferably identical. 
         [0030]    According to this first embodiment of the invention, both top section  12  and bottom section  14  include several bores  18   a - 18   f.  Bores  18   a - 18   f  of top section  12  are positioned to align with the corresponding bores  18   a - 18   f  of bottom section  14  when the two sections are mated to each other. The combined bores  18   a - 18   f  are each sized and shaped to snugly receive a magnet  20 . Bores  18   a - 18   f  are preferably cylindrically shaped so that the combined bores can receive a cylindrically shaped permanent magnet. The magnets are preferably press-fit into their respective bore  18   a - 18   f  or bonded therein using an appropriate adhesive in such a manner that prevents magnets  20  from moving or rotating from within their bore. 
         [0031]    In the example shown in the figures, the keycard  10  includes six bores  18   a - 18   f  that are arranged in the shape of a “T” with two “corner” bores  18   a  and  18   b  being located at the two corners of a front edge  22  of the generally rectangular keycard  10  and four axial bores  18   c,    18   d,    18   e  and  18   f  being positioned perpendicular to front edge  22  and extending down the middle of the keycard, as shown in  FIG. 1 . This particular arrangement is just one example used to explain the present invention. It should be understood that many other different bore arrangements (and therefore magnet arrangements) can be used to increase the possible key permutations. Also, the number of bores can be increased or decreased as necessary, depending on the particular application and the required number of unique key combinations. As describe below, magnets  20  located within corner bores  18   a,    18   b  are used to provide initial announcement to the controlling circuitry that a keycard  10  is being inserted into the device and also to indicate when the keycard reaches the fully inserted position. Bores  18   c,    18   e  and  18   f  are combination bores and are reserved for encoding the keycard  10  with a unique code. Magnets  20  are selectively arranged in these combination bores during assembly following a prescribed order. The “combination” or unique identity of the keycard is determined by which ones of the three combination bores  18   c,    18   e  and  18   f  are supplied with a magnet. 
         [0032]    As introduced above, the present invention is intended to be incorporated into a particular type of medical device, a control unit that is used to communicate and control an implantable medical device. This particular application only requires a limited number of different key combinations. In this first embodiment, different key combinations are determined by the number of magnets inserted into the three “combination” bores  18   c,    18   e,  and  18   f,  and which of the four bores  18   c - f  are used. 
         [0033]    As shown in  FIG. 1 , top section  12  and bottom section  14  each include integrally-formed alignment pins  24  and mating bores  26  which are both used to help register the two sections  12 ,  14  together when bonded. Also, each section  12 ,  14  includes a notch  28  located along each side edge  30  of each section  12 ,  14 , which align to form a common notch  28  on each side of the assembled keycard  10 . These notches are used to help hold the keycard  10  into a fully inserted position with respect to reading circuitry, described in greater detail below. 
         [0034]    According to this exemplary application, the control unit used to communicate with and control the operation of an implanted device requires just four keycards  10 , each with a unique combination. One keycard  10  is intended for use by a physician, a second one is intended to be used by a technician, a third by a salesman, and finally, a fourth one is meant to be used by an assembly worker in the factory that manufactures the device. If no key is inserted into the control unit, the control unit will operate in a “patient” mode. In each case, a level of access to the different features and data is provided, according to the particular access required by that user to perform their particular task while using the control unit. 
         [0035]    The magnet combinations which determines the unique code or identity of the particular keycard is established before top section  12  and bottom section  14  are bonded to each other. Once keycard  10  is bonded, the combination cannot be changed. Since only four key combinations are required for this particular exemplary application, the specific magnet arrangement for each key combination can be designed to mitigate misreads by the sensors during use so that a keycard meant for the doctor will never be misread by the sensors and circuitry as a salesman keycard, etc. 
         [0036]    Keycard Holder 
         [0037]    Referring now to  FIG. 2 , a keycard holder  40  is shown with a keycard  10  in a fully inserted position. Referring now to  FIGS. 2 and 3 , as described below, keycard holder  40  is a simple open-frame structure that includes an accessible slot  42  at a front end  44  that is sized and shaped to receive keycard  10  and has two side walls  46  and an end wall  48 . Together, this structure defines an appropriately sized and shaped channel  50  into which keycard  10  may freely slide after being inserted into slot  42 . The purpose of keycard holder  40  is to receive and firmly hold an inserted keycard  10  so that adjacent circuitry and sensors can “read” the magnet key combination and actuate the control unit (or other electronic device) accordingly. 
         [0038]    Keycard holder  40  is preferably made from plastic using an appropriate injection molding process and includes projections (not shown here) so that it can be firmly secured to a printed circuit board  52 . Keycard holder  40  includes integrally formed spring-biased locking arms  54  on each side  46 . Each arm  54  includes a locking tab  56  which is sized and shaped to align and engage with notch  28  of keycard  10  when keycard  10  reaches its fully inserted position. As is understood by those skilled in the art, spring arms  54  provide a spring-bias based on the resiliency of the material used to make the keycard holder  40  and certain dimensional factors, which forces each respective locking tab  56  inwardly into contact with the respective side edges  30  keycard  10  as keycard slides within channel  50  to its fully inserted position. The engagement between locking tabs  56  and notches  28  is strong enough to effectively hold keycard  10  in place during use, but this engagement is meant to be easily overcome by the user when so desired, by merely pulling out the keycard  10 . As shown in  FIGS. 2 and 3 , keycard holder  40  further includes appropriate overhang tabs  58  to help guide and hold keycard  10 . 
         [0039]    Control Unit 
         [0040]    Referring now to  FIGS. 4 and 5 , the main components of a control unit  60  are shown as an exemplary application of the access system of the present invention. Control unit  60  includes circuit board  52  (introduced above and in  FIGS. 2 and 3 ) including several Hall-effect sensors—a “start” sensor  62   b,  a stop sensor  62   a,  three “combination” sensors  62   c,    62   d  and  62   f  and at least one reference sensor  64 , but preferably three reference sensors,  64 ,  62   b  and  62   e.  Sensors  62   a - f  and reference sensor  64  are each electrically connected to a sensor interface IC chip  66  which includes an analog to digital converter and other known electronic logic components and is used to read and process the voltage readings of each of the seven Hall-effect sensors  62   a - f,    64  and send either a “high” or a “low” signal to the processor  68 . The sensor interface IC chip  66  is connected to a processor chip  68 . Also connected to processor  68  is a keypad input  70 , a display  72 , a memory chip  74  and an RF antenna interface chip  76 , which includes known circuitry to help receive, transmit and process RF signals, as instructed by processor chip  68 . An antenna  78  is electrically connected to antenna interface chip  76  so that RF signals may be transmitted to and received from the implanted device located within a nearby patient. 
         [0041]    The above-described components of control unit  60  are introduced here only to help explain the operation of the present invention. Not all of these components are described in great detail because such details are beyond the scope of this invention. Also, keycard holder  40  and the keycard  10  are not shown in  FIG. 4  so that the details of Hall-effect sensors  62   a - f,    64  may be revealed.  FIG. 5  shows the same components as shown in  FIG. 4  with the addition of keycard holder  40  and a keycard  10  inserted therein. 
         [0042]    As described above, it is not uncommon in medical environments, such as hospitals for electronic devices to experience stray magnetic fields. This is a concern with the present device since the above-described control unit relies on carefully positioned magnet fields to unlock and provide operational access to the device by select personnel. To help eliminate or at least mitigate the adverse effects of any incoming stray magnetic fields entering control unit  60 , reference sensors  64 ,  62   b  and  62   e  are provided within the array of sensors  62   a - f  on circuit board  52 . Reference sensor  64  is used to read the magnetic field present in the immediate vicinity of sensors  64 ,  62   b  and  62   e.  These three reference sensors are logically wired so that during use, if any of the three reference sensors  64 ,  62   b  and  62   e  detects a magnetic field above a certain predetermined threshold value, the sensor that detects the field will send a logic low (effectively change its output signal) to processor  68  which will prevent the card from being read. 
         [0043]    In operation, as described below, when a keycard  10  is being “read” by combination sensors  62   c,    62   d  and  62   f,  their respective output voltages will be converted into digital high and low signals and sent to processor  68 . Processor will then “read” the logic outputs of reference sensors  64 ,  62   b  and  62   e.  If any or more of these reference sensors are found to be at a logic low, then processor will postpone reading the combination sensors  62   c,    62   d  and  62   f  because in this example, a magnetic field outside the device is influencing onboard components. In this manner, detection of stray magnetic fields generated by magnets other than the magnets located on keycard  10  will prevent the reading of an inserted keycard  10 . Since such stray magnetic fields could cause processor  68  to misread the “combination” of keycard  10 , when any stray magnetic fields are detected, it is preferred that processor  68  does not provide any access to the medical device. Reference sensors  64 ,  62   b,  and  62   e  are preferably only operational when keycard  10  is being “read” by control unit  60 . 
         [0044]    As introduced above, combination sensors  62   c,    62   d  and  62   f,  start sensor  62   b  and stop sensor  62   a  are provided on circuit board  52  in a predetermined pattern and are positioned to be immediately adjacent to keycard  10  when the keycard is inserted into slot  42  and along channel  50  of keycard holder  40 . Sensors  62   a - f  should be positioned as close to keycard  10  as possible to help ensure accurate reading of an inserted keycard. As described in greater detail below, as the keycard is further inserted into the slot  42 , eventually either of the two corner magnets will move immediately adjacent to stop sensor  62   a.  When this sensor moves to a “low” state, it means that the sensor  62   a  detected the magnetic field of the magnet indicating that the keycard is now fully inserted into slot  42  and that processor  68  should interrogate the reference sensors  64 ,  62   b  and  62   e  to determine their respective state. If the state of those reference sensors remains at a high state, processor  68  can then proceed to summon the state of combination sensors  62   c,    62   d  and  62   f.    
         [0045]    Referring now to  FIGS. 6-10 , keycard  10  is shown being inserted into slot  42  from a fully removed position, shown in  FIG. 6 , to a fully inserted position, shown in  FIG. 10 . 
         [0046]    According to the invention, a magnet  20  is always located in the two corner bore positions  18   a  and  18   b,  the front corners of the keycard  10 . These two corner magnets  20  will be immediately detected, as keycard  10  is first inserted into slot  42  by start sensor  62   b  and sensor  64 , which are positioned adjacent to slot  42  and which are aligned with one of the two corner magnets. In the example shown in  FIGS. 1 ,  4 , and  7 , start sensor  62   b  aligns with the magnet located in corner bore  18   b.  Since a magnet  20  must be located within each corner bore  18   a,    18   b,  then the system can still “read” the keycard regardless if the keycard is inserted upright or inverted. This early detection by start sensor  62   b  is used to “wake up” the onboard circuitry, which preferably was in sleep mode to conserve battery power. So-called “sleep modes” are used often in a variety of electronic components and are well known in the art. 
         [0047]    As the keycard  10  continues to be pushed into channel  50  of key holder  40 , it is preferred that the combination of the particular keycard  10  is not “read” by the three combination sensors  62   c,    62   d  and  62   f  until stop sensor  62   a  reads the magnetic field of magnet  20  located in bore  18   b  (or  18   a,  if the card is inverted). The change in voltage of stop sensor  62   a  indicates to processor  68  that keycard  10  is fully inserted into channel  50  and combination bores  18   c,    18   e  and  18   f  of keycard  10  are now aligned with their corresponding combination sensors  62   c,    62   d  and  62   f,  respectively. 
         [0048]    At this point, following appropriate software commands, processor  68  “reads” combination sensors  62   c,    62   d  and  62   f  and uses logic high/low state readings of each combination sensor to determine which bores  18   c    18   e  and  18   f  contain magnets  20 . This information defines the particular combination of the inserted keycard  10 . Appropriate software then instructs processor  68  to compare the key combination of the inserted keycard  10  with the four combinations stored in memory chip  74 . Depending on the match, the software will allow the user access to only those modes of operation, functions, and displayed and stored data that are permitted to the particular combination of the inserted keycard  10 . In other words, the arrangement of magnets  20  located on the keycard  10 , within combination bores  18   c,    18   e  and  18   f  effectively tells the processor and the device  60  if the user is a physician, a salesman, a technician or a factory assembly worker and as long as the keycard  10  remains in its fully inserted position within the channel  50  (as continuously verified by stop sensor  62   a ). Processor  68  will operate the device following the prescribed access and control assigned to that particular identified user. 
         [0049]    Continuing with the example introduced earlier in this application, Applicants contemplate providing the assembly worker with the highest level of rights to operate the device. This is required so that during assembly all the required software calibration parameters and manufacturing initialization parameters may be utilized to ensure the device operates as intended. The technician and the salesman will be granted an intermediate level of access to certain software parameters. The physician will only be allowed access to the most restrictive level of rights to the software parameters, including access to select programmable parameters directly related to the patient and to the drug prescription. In this example, the physician will be denied any access to any calibration parameters or software used to adjust these calibration parameters since such actions are beyond the physician&#39;s level of need to operate the device. If access to such information and control were given to the physician, it is likely that the device would soon fail to operate or would operate inaccurately, placing the patient&#39;s health at risk. The levels of access to the particular users, such as the ones listed in the example above are provided as required by the particular user to enable that user to successfully perform the required task without risking the patient&#39;s health. 
         [0050]    The onboard software preferably instructs processor  68  to continually interrogate and read combination sensors  62   c,    62   d  and  62   f  and stop sensor  62   a  until stop sensor  62   a  detects that keycard  10  is being removed, at which point, processor causes the device to shut down or enter into a predetermined operating mode, eventually returning to sleep mode, after a prescribed time period has passed.