Abstract:
A finger oximeter has a fixed first finger grip member and a second finger grip member that is movable relative to the first fixed finger grip member. The finger grip members are mounted to a casing, with the first finger grip member being fixedly coupled to a top portion of the casing and the second finger grip member being movable vertically within the casing. A force is continuously applied against the movable finger grip member to bias it towards the fixed finger gripping member. This biasing force has sufficient yield so that when a finger is inserted between the two finger grip members, the movable finger grip member would yield to the incoming finger. At the same time the biasing force is of a sufficient magnitude to push the movable finger grip member towards the fixed finger grip member to effect a firm grip of the finger. The biasing force is evenly distributed to the movable finger grip portion to effect a floating finger grip suspension system for the finger oximeter.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to finger oximeters and more particularly to a finger oximeter having a suspension system that enables the finger gripping portions of the oximeter to firmly and evenly grasp a patient&#39;s finger.  
         BACKGROUND OF THE INVENTION  
         [0002]    There are a number of known finger oximeters. Generally, these finger oximeters are pulse oximetry units that utilize a sensor, and a coacting photodetector that detects the light emitted by the sensor, for determining the blood oxygen saturation of the arterial blood passing through the finger of a subject. To illuminate the finger of the subject, and to detect the light passing through the subject&#39;s finger, a prior art finger oximeter usually would have a finger gripping mechanism that has two finger gripping portions. The prior art teaches that these finger gripping portions hingedly coact with each other, usually by pivots. The following U.S. patents specifically disclose finger gripping portions that open to accept a finger via some hinge mechanism that enables the finger gripping portions of the finger oximeter to pivot about one end point of the finger oximeter: U.S. Pat. Nos. 4,658,464; 5,490,523; 5,792,052; 5,313,940; 5,676,139; 5,810,724; 5,957,840; and 6,041,247.  
           [0003]    There are other methods of enclosing two finger gripping portions about a finger. One such method is the taping of a finger to a photodetector by means of a tape that has a light emitter, as disclosed in U.S. Pat. No. 5,209,230. Another method clamps two finger gripping portions together by means of coacting teeth at the respective sidewalls of the finger gripping portions. This is disclosed in U.S. Pat. No. 5,339,810. The use of a single piece U-shaped flexible holder that expands with the insertion of a finger is disclosed in U.S. Pat. No. 5,311,865.  
           [0004]    For those finger oximeters that use two piece finger gripping portions which are tightened by coacting grasping teeth at their respective sidewalls, there is the disadvantage that it is difficult to remove the finger from the finger gripping portions since the finger gripping portions are locked at a given dimension. And for those finger oximeters that utilize a hinged pivoting mechanism, the force that the finger gripping portions applies to a finger tends to be uneven along the finger, and gets weaker the further the finger is away from the hinged location.  
         SUMMARY OF THE PRESENT INVENTION  
         [0005]    The present invention finger oximeter has a floating suspension system that results from one of the finger gripping portions being movable vertically relative to the other finger gripping portion, which is fixed. A biasing force is applied against the movable finger gripping portion so that the movable finger gripping portion is constantly biased towards the fixed finger gripping portion. The two coacting finger gripping portions are configured such that their opposing surfaces are contoured to form an opening for accepting a finger inserted therebetween. The biasing force applied against the movable finger gripping portion is such that the movable finger portion is yieldable when a finger is inserted between the fixed and movable finger portions, and yet at the same time has a sufficient large biasing force to push the movable finger portion towards the fixed finger gripping portion with an even distribution of force along the length of the finger, to thereby cause the two finger gripping portions to firmly grasp the finger placed therebetween.  
           [0006]    The force applied against the movable finger gripping portion to bias it towards the fixed finger gripping portion is supplied by a plurality of coiled springs interposed between the movable finger gripping portion and a casing along which sidewalls the movable finger gripping portion guidingly moves. The springs may be secured to ledges extending from the lower portion of the respective sidewalls of the casing so that the biasing force is applied against the movable finger gripping portion in such a way that the movable finger gripping portion is movable vertically with respect to the fixed finger gripping portion.  
           [0007]    The fixed finger gripping portion may be mounted to the upper part of the casing, and is configured such that its upper surface is adaptable to receive a printed circuit board that has mounted thereto or etched thereon a number of electronic components or circuits that effect the operation of the finger oximeter. A display, LED or otherwise, is also mounted to the PC circuit board for displaying values that represent the physical parameters of the patient measured via the patient&#39;s finger.  
           [0008]    The finger gripping portions are further configured to have respective apertures through which light from a light emitter may be directed from one of the finger gripping portions to a corresponding aperture of the other finger gripping portion, which is equipped with a receptive photodetector.  
           [0009]    To power the finger oximeter of the instant invention, a battery pack or module is mounted to the underside of the movable finger gripping portion so as to move in unison with the movable finger gripping portion. To operate, a user needs to manually activate a switch mounted to the casing. To conserve energy, the device is automatically turned off after a predetermined time period, if it no longer is in use.  
           [0010]    It is therefore an objective of the present invention to provide a finger oximeter that has a floating suspension system.  
           [0011]    The finger oximeter of the instant invention has the further objective of evenly distributing the gripping force applied by its finger gripping portions to the being gripped finger. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The above-mentioned objectives and advantages of the instant invention will become apparent and the invention itself will be best understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:  
         [0013]    [0013]FIG. 1 is a perspective drawing that shows various components of the finger oximeter of the instant invention being in various superposed positions;  
         [0014]    [0014]FIG. 2 is a perspective view illustrating the various components shown in FIG. 1 as well as the coil springs, the casing and the cover of the device being in alignment with each other;  
         [0015]    [0015]FIG. 3A is a top view of an assembled device of the instant invention;  
         [0016]    [0016]FIG. 3B is a front view of the finger oximeter of the instant invention that shows the opening through which a finger may be inserted between the two finger gripping portions of the device;  
         [0017]    [0017]FIG. 3C is a back view of the finger oximeter of the instant invention;  
         [0018]    [0018]FIG. 3D is a side view of the FIG. 3A device; and  
         [0019]    [0019]FIG. 4 is an electrical schematic of the finger oximeter of the instant invention.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0020]    With reference to FIG. 1, the finger oximeter of the present invention is shown to include a lower finger grip portion  2  and an upper finger grip portion  4 . Fitted to lower finger grip portion  2  and upper finger grip portion  4  are lower finger pad  6  and upper finger pad  8 , respectively. The lower and upper finger grip portions, as well as their finger pads, are configured to conform to the shape of a human digit, such as for example a finger. This is best illustrated by the lower surface of finger pad  6  and the upper surface of finger pad  8 , which are opposed to each other. Thus, once the respective finger pads  6 ,  8  are attached to their corresponding finger grip portions  2 ,  4 , an opening  10 , best shown in FIGS. 2 and 3B, is provided when finger grip portions  2  and  4  are positioned adjacent to each other.  
         [0021]    As best shown in FIG. 1, lower grip finger portion  2  is an elongate member that has two sides  2   s  extending from a base  2   b . A space or void  2   v  is provided at approximately the center of base  2   b  onto which a photodetector  18  (D 1  in FIG. 4) may be positioned. The front end of base  2   b  is curved for forming one portion of opening  10 . The back end of elongate member  2  has a backstop  2   bs  that is configured to receive, in a sliding engagement fashion, a battery module  10 . Although not shown, battery module  10  is configured to enable the insertion of two batteries thereinto for providing power to the electronic components shown in FIG. 4 to thereby energy the finger oximeter, whose operation will be discussed later. A spring-like conductor  12  inserted to battery module  10  connects in series the batteries, thereby increasing the available voltage.  
         [0022]    Each of sidewalls  2   s  of elongate member  2  further has extending therefrom at least two ears, or catches  2   c   1  ( 2   c   1 ′) and  2   c   2  ( 2   c   2 ′). The purpose of catches  2   c  will be discussed with reference to FIG. 2.  
         [0023]    Lower finger pad  6 , which may be made of a rubbery material that is not compliant, is attached to base  2   b  of finger grip portion  2 . In addition to finger pad  6 , a conductive strip  14  is inserted to the back end of finger grip portion to provide an electrical path for the power supplied by battery module  10 . Connected to conductive end  14  is a flexible strip  16  which has attached thereto photodetector  18 . With photodetector  18  resting in space  2   v  of elongate member  2  and with finger pad  6  placed thereover, photodetector  18  is exposed, and is therefore adaptable to receive light directed thereto, per aperture  6   a  of finger pad  6 . As can be seen, finger pad  6  is configured, per its arcuate interior surface, to conform partially to the shape of a human finger.  
         [0024]    Upper finger grip portion  4 , which is also configured in the form of an elongate member, has attached to its underside finger pad  8 , which is curved in an opposing manner to finger pad  6  and contoured to partially conform to the shape of a finger. Finger pad  8 , also made of a non-compliant rubber material, may be attached to the lower surface of elongate member  4  by glue or other adhesive means, which is similar to the way by which finger pad  6  is attached to elongate member  2 . Once attached, aperture  8   a  of finger pad  8  is aligned with aperture  4   a  of elongate member  4 .  
         [0025]    Elongate member  4  has two sides  4   s  extending upwards from its base  4   b  to form a semi-closed enclosure at its upper surface for accepting a printed circuit board or module  18 . Although not shown clearly, mounted to module  18  are a number of electronic components, the circuitries of which are shown in detail in FIG. 4. Extending from each side  4   s  of elongate member is an extension  4   e  that has two fingers  4   f  pointing downwards. The purpose of extensions  4   e  will be discussed with respect to FIG. 2. Also mounted to module  18  is a display  20  that includes a number of digits for displaying information that corresponds to the physical parameters of a patient, such as for example the blood oxygen saturation of arterial blood, as measured from the patient&#39;s finger being inserted between finger grip portions  2  and  4 . To effect the measurement of the physical attribute of the patient, a light source, such as for example a light emitting diode, is mounted to the underside of module  18  to be in alignment with aperture  4   a  of elongate member  4 . The power provided to module  18  comes from the flexible conductive strip  16 .  
         [0026]    With reference to FIG. 2, the various components illustrated in FIG. 1 of the finger oximeter of the instant invention are shown as having been assembled, with upper finger grip portion  4  being adjacent to lower finger grip portion  2 . As was mentioned previously, when in such close contact, opening  10  is formed at the front of the two finger gripping members. It is through this opening that a finger is placed between the finger grip portions  2  and  4 .  
         [0027]    As further shown in FIG. 2, the in contact finger grip portions  2 ,  4  are superposed over a casing  22 , which has the form of a U-shaped skirt. Casing  22  has a back wall  22   b  and two sidewalls  22   s . Extending from the lower portion of sidewalls  22   s  are respective ledges  22   l . In the inside of the respective sidewalls  22   s  are receptacles  22   r , which are configured to receive fingers  4   f  of extension  4   e  of upper finger grip portion  4 . Upon insertion of fingers  4   f  to receptacles  22   r , finger grip portion  4  is fixedly coupled to the top or upper part of casing  22 . An adhesive may be used to further ensure that upper finger grip portion  4  is fixedly coupled to casing  22 .  
         [0028]    At the two distal ends of sides  22   s  there are formed respective gripping edges or fingers  22   g . Formed at the respective ledges  22   l  are a number of fingers or extensions  22   e  that provide the respective anchors each for securely receiving a corresponding spring  24 . As shown, there are four springs  24 , each securedly anchored by one of the extensions  22   e  at one corner of casing  22 . Springs  24  may each be conventional compression coil springs.  
         [0029]    As further shown in FIG. 2, once anchored to extensions  2   e , when lower finger grip portion  2  is inserted to casing  22 , each of catches  2   c  in the form of ears extending from sidewalls  2   s  of elongate member  2  catches and presses down on a corresponding spring  24 . Springs  24  are chosen to have a given elasticity so that, in combination, those springs provide a biasing force against elongate member  2  in an upwards direction, with reference to upper finger grip portion  4 , which is fixedly attached to the upper part of casing  22 . Thus, once elongate member  4  is fixedly coupled to casing  22 , elongate member  2  nonetheless remains movable relative to elongate member  4 , and is guidedly movable along the respective sidewalls  22   s  of casing  22 .  
         [0030]    Given the fact that elongate member  2  is supported by independent springs  24  at different locations along its sidewalls  2   s , when a finger is inserted to opening  10 , although giving way to the finger, the biasing force exerted by springs  24  would act against elongate member  2  vertically so as to firmly bias elongate member  2  against the inserted finger, to thereby firmly grip the inserted finger against fixed elongate member  4 . Further, by providing springs  24  at the four corners of elongate member  2 , a four point suspension system is effected to evenly distribute across elongate member  2  the biasing force. Accordingly, a finger gripped by elongate members  2  and  4  is gripped evenly along its length. Furthermore, by hiding the springs at the respective corners of casing  22  and elongate member  2  so that no support base is required for elongate member  2 , the respective sizes of the case  22  and elongate member  2  could be reduced, thereby leading to a reduction in the size of the entire device. So, too, by hiding the springs between the respective sidewalls of casing  22  and elongate member  2 , the springs are sealed from dirt and isolated from potential mechanical abuse.  
         [0031]    Although only four springs are shown in the being discussed embodiment, it should be appreciated that a three spring configuration, with one spring at each sidewall and one spring at the back wall of casing  22  may also be used. Conversely, a greater number of springs, with more than two springs along each sidewall of casing  22 , may also be used in other embodiments of the instant invention.  
         [0032]    To complete the assembled device of the instant invention, a filtered cover  26  that allows the digits to be seen from display  20 , is placed over elongate member  4  so as to be fixedly coupled either to elongate member  4  or to the upper edges of casing  22 .  
         [0033]    With reference to FIGS.  3 A- 3 D, different views of the assembled finger oximeter of the instant invention is shown. FIG. 3A shows a plan view of the assembled device  28 , with the digits displaying the blood oxygen saturation, and also the heart rate that may be obtained by measuring the physical attributes of a patient by means of her finger.  
         [0034]    [0034]FIG. 3B is a front view of the device showing opening  10  through which the finger of a patient is inserted. As further shown, upper finger grip portion  4  is protected by cover  26  so that only a portion thereof, and a portion of finger pad  8 , are shown. However, movable finger grip portion  2  is shown to be mounted within casing  22 , with battery module  10  removably coupled to the underside thereof. Movable finger grip member  2 , which, in response to the bias force suppled by springs  24 , is movable bidirectionally as indicated by directional arrow  30 .  
         [0035]    [0035]FIG. 3C shows the back side of the finger oximeter of the instant invention. As shown, casing  22 , or rather the back walls  22   b  thereof, has mounted thereto a switch  32 , which enables a user to manually activate the device, i.e., by energizing the electronic components mounted to circuit board  18 . The back side of battery module  10  is also shown in FIG. 3C.  
         [0036]    [0036]FIG. 3D is a side view of device  28  of the instant invention which shows cover  26  attached to casing  22 . Battery pack  10  is shown to form the bottom base of the device.  
         [0037]    [0037]FIG. 4 is a schematic of the electronic circuitry representative of the electronic components mounted to circuit board  18  of the device. For ease of discussion, the various major functions of the circuitry of the instant invention device are separately grouped together by dotted lines. In particular, as shown in dotted box  34 , a photodiode D 1  ( 18  in FIG. 1) is mounted onto a flexible circuit support strip that is fitted to space  2   v  of lower grip member  2 . Switch SW 1 , also mounted to and in electrical connection to the flexible circuit strip  34 , when turned on by the user, causes light from the LED in circuit  40  to be directed to the finger placed between the finger grip portions  2  and  4 . Once the finger is removed from the finger grip portions, microprocessor U 1  is programmed to turn off device  28  after a predetermined time period, for example 8 seconds, so as to conserve energy.  
         [0038]    The photodetector and switch SW 1  are connected to the main circuit by means of a conventional coupling. In particular, circuit  34  mounted on the flexible strip is connected to functional circuit  36 , which is an analog detector pre-conditioning circuit. As shown, the input electrical current signal measured from the finger of the patient is sent to an op amp U 2 A, where the analog current signal is converted to an analog voltage signal. The analog voltage signal is amplified by op amp U 2 C to output an amplified analog voltage signal VSIG. The dynamic range of the signal is controlled by IC circuit U 4 , which in essence is an integrated digital potentiometer.  
         [0039]    The amplified analog voltage signal VSIG is input to microprocessor U 1  at input A 2 . This analog voltage signal is converted by microprocessor U 1  to a corresponding digital signal and output to circuit  38 , which is a LED driver circuit comprising driver IC circuits U 8  and U 9 . The driver circuit  38  provides the signal to the various digits DIG 1 -DIG 6  for displaying the information collected from the patient on display  20 .  
         [0040]    Another major functional component of the circuitry of FIG. 4 includes circuit  40 , which is a variable LED driver circuit that drives the two LEDs that emit the light directed to the finger of the patient through apertures  4   a  and  8   a  of the upper finger grip portion and the upper finger pad  8 , respectively. The light, after diffusing through the finger of the patient, is sensed by photodetector D 1  ( 18 ), which in turn outputs the resulting current signal to analog detector pre-conditioning circuit  36 .  
         [0041]    Sub-circuit  44  of the FIG. 4 circuitry is a switching power supply circuit that regulates the power to be supplied to the various components of the FIG. 4 circuitry.  
         [0042]    Circuit  46  is a battery measurement voltage divider circuit that identifies when the voltage from battery pack  10  is low.  
         [0043]    Circuit  48  is a timing circuit for the components of the finger oximeter of the instant invention. A clock pulse is generated from circuit  48  for microprocessor U 1  by component U 6 A. Components U 6 B and U 6 C in combination ensure that there is enough voltage from battery pack  10  if the voltage output is less than 3 volts, so that the appropriate clocking signals are provided for the various components of the circuitry of FIG. 4.  
         [0044]    The present invention is subject to many variations, modifications and changes in detail. For example, instead of springs  34  being anchored to extensions  22   e  of ledges  22   l  of casing  22 , the biasing mechanism for lower grip portion  2  could be an elastic one piece spring mechanism such as a leaf spring that biases elongate member  2  against the sidewalls  22   s , and/or back wall  22   b  of casing  22 . To anchor such leaf spring to the casing, the ledges at the base of the casing may have to be expanded. So, too, could an elastic material such as rubber that has sufficient biasing characteristics be used to keep a force biasing movable elongate member  2  towards fixed elongate member  4 . Thus, it is intended that all matter described throughout this specification and shown in the accompanying drawings be interpreted as illustrative only and not in a limiting sense. Accordingly, it is intended that the invention be limited only by the spirit and scope of the hereto appended claims.