Patent Publication Number: US-10779742-B2

Title: Medical electrode and limb clamp for an ECG device

Description:
CROSS-REFERENCE TO PRIOR APPLICATIONS 
     This application is a divisional application of co-pending U.S. Ser. No. 14/895,250 filed on Dec. 2, 2015, now U.S. Pat. No. 10,182,731, which in turn is the U.S. National Phase application under 35 U.S.C. § 371 of International Application No. PCT/IB2014/061829. filed on May 30, 2014, which claims the benefit of Chinese Patent Application No. PCT/CN2013/076906, filed on Jun. 7, 2013. These applications are hereby incorporated by reference herein. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to an improved medical electrode, in particular to a medical electrode and a limb clamp for an ECG (electrocardiogram) device comprising such a medical electrode. 
     BACKGROUND OF THE INVENTION 
     An ECG device is widely used to obtain medical (i.e. biopotential) signals containing information indicative of electrical activity associated with the heart and pulmonary system. The signals obtained are one of the important bases for some disease diagnosis. The ECG device generally comprises a plurality (for example six) of torso electrodes which are applied to a torso portion of a patient and two pairs of limb electrodes which are mounted on a respective limp clamp and applied to the left and right limbs of the patient, respectively. These electrodes connect with an ECG module via the respective cables. In use, cable failure often occurs because of excessive bending cycles caused by various factors such as inappropriate placement of the electrodes, movement of the patient&#39;s body and/or their use model. Especially the cables connecting with the limb electrodes are easier subject to cable failure due to their unique use model. 
       FIG. 1  shows a conventional limb clamp  1  for an ECG device. The limb clamp  1  generally comprises a first clamp portion  3 , a second clamp portion  5 , a spring element  7  interconnecting the first clamp portion  3  and the second clamp portion  5 , and a medical electrode  9  mounted at the first clamp portion  3 . The medical electrode  9  generally comprises a conductive support cylinder  11  that is fixed relative to the first clamp portion  3 . When a cable  13  is inserted into and fixed to the support cylinder  11  of the medical electrode  9  that is fixed relative to the first clamp portion  3 , the movement of the medical electrode  9  directly results in bending of the respective cable  1 , thereby possibly causing cable failure. Further, it is possible for the left and right limb clamps to be applied reversely to the right and left limbs, which causes worse bending of the respective cables as shown in  FIG. 1  and thus results in cable failure. Cable failure contributes to wrong or inaccurate signals, which in turn result in wrong or inaccurate diagnosis. Replacing a failed cable not only increases total cost of ownership for the ECG device but also is a waste of time and causes the ECG device to be out of service for a period of time. All in all, this issue has a big impact on the ECG industry all the time. 
     Past efforts focused primarily on increasing the durability of the cable itself, for example, thickening the lead wire of the cable, which further increases the cost of the ECG device and makes the patient feel uncomfortable. 
     Thus, there is a need to make improvements on the conventional medical electrode. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is desirable to provide a medical electrode which may prevent the cable connecting with the medical electrode from flexing, thereby avoiding cable failure. 
     It is also desirable to provide a limb clamp for an ECG device which may prevent the cable connecting with an electrode of the limb clamp from flexing, thereby avoiding cable failure. 
     According to one aspect of the present invention, the present invention provides a medical electrode comprising: 
     a conductive metal base comprising a plate element and a boss formed on the plate element; and 
     a conductive support cylinder separate from the conductive metal base; 
     wherein the conductive support cylinder is rotatably mounted to the conductive metal base while remaining in electrical communication with the conductive metal base. 
     Preferably, a recess is formed in one of the boss and a lower end of the conductive support cylinder, the other one of the boss and the lower end of the conductive support cylinder being rotatably mounted into the recess. 
     Preferably, a recess is formed in the boss and a lower end of the conductive support cylinder is rotatably mounted into the recess. 
     Preferably, a conductive bearing is disposed within the recess and the lower end of the conductive support cylinder is mounted into the conductive bearing. 
     Preferably, a plurality of conductive and elastic strips extending along the longitudinal axis of the conductive support cylinder and projecting radially outward are disposed on the circumferential surface of the lower end of the conductive support cylinder and the lower end of the conductive support cylinder is inserted snugly into the recess. 
     Preferably, the plurality of conductive and elastic strips are distributed evenly on the circumferential surface of the lower end of the conductive support cylinder. 
     Preferably, a spherical head is formed at the lower end of the conductive support cylinder, a corresponding spherical recess is formed in the boss, and the spherical head is received snugly in the spherical recess to form the universal joint knuckle. 
     Preferably, the conductive metal base comprises a first half portion and a second half portion. 
     Preferably, a flange is formed on an outer surface of the conductive support cylinder, a conductive spring is disposed between the flange and the boss, a nut having an inner flange is screwed to the boss to mount the conductive support cylinder to the conductive metal base. 
     Preferably, the medical electrode further comprises an electrolyte gel applied to the lower surface of the plate element. 
     Preferably, the conductive support cylinder comprises a through hole transverse to its longitudinal axis for receiving a cable. 
     Preferably, the conductive support cylinder further comprises a threaded hole formed along its longitudinal axis and communicating with the through hole. 
     According to the other aspect of the present invention, the invention provides a limb clamp for an ECG device comprising: 
     a first clamp portion; 
     a second clamp portion; 
     a spring element interconnecting the first clamp portion and the second clamp portion; and 
     an above-mentioned medical electrode mounted at the first clamp portion. 
     Preferably, an outer thread is formed on the outer surface of the boss, the boss passes through a through hole formed in the first clamp portion and a nut is screwed onto the outer thread so that the medical electrode is mounted onto the first clamp portion. 
     Preferably, the nut for mounting the medical electrode onto the first clamp portion and the nut for mounting the conductive support cylinder to the conductive metal base are the same nut. 
     These and other objects, features and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a conventional limb clamp for the ECG device showing a bend of a cable connecting with an electrode of the limb clamp. 
         FIG. 2  is an exploded perspective view of a limb clamp for the ECG device with a medical electrode according to a first embodiment of the present invention. 
         FIG. 3A  is a top view of the limb clamp of  FIG. 2  in an assembled state. 
         FIG. 3B  is a cross sectional view taken along a line A-A of  FIG. 3A . 
         FIG. 3C  is an enlarged view of an encircled portion A of  FIG. 3B . 
         FIG. 4A  is a cross sectional view similar to  FIG. 3B , showing a limb clamp for the ECG device with a medical electrode according to a second embodiment of the present invention. 
         FIG. 4B  is an enlarged view of an encircled portion A of  FIG. 4A . 
         FIG. 4C  is a perspective view of a support cylinder shown in  FIG. 4B . 
         FIG. 5A  is a cross sectional view similar to  FIG. 3B , showing a limb clamp for the ECG device with a medical electrode according to a third embodiment of the present invention. 
         FIG. 5B  is an enlarged view of an encircled portion A of  FIG. 5A . 
         FIG. 5C  is an exploded perspective view of a medical electrode shown in  FIG. 5B . 
         FIG. 6A  is a cross sectional view similar to  FIG. 3B , showing a limb clamp for the ECG device with a medical electrode according to a fourth embodiment of the present invention. 
         FIG. 6B  is an enlarged view of an encircled portion A of  FIG. 6A . 
         FIG. 6C  is an exploded perspective view of a medical electrode shown in  FIG. 6B . 
         FIG. 7  is a schematic view showing that the medical electrodes and the limb clamps according to the present invention connect with an ECG module via the respective cables and are applied to the patient to record ECG signals. 
         FIG. 8  is a perspective view of a limb clamp for the ECG device according to the present invention showing that there is no bending of the cable connecting with the electrode of the limb clamp. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The preferred embodiments of the present invention will be described in detail with reference to the drawings. 
       FIG. 2  is an exploded perspective view of a limb clamp for the ECG device with a medical electrode according to a first embodiment of the present invention.  FIG. 3A  is a top view of the limb clamp of  FIG. 2  in an assembled state.  FIG. 3B  is a cross sectional view taken along a line A-A of  FIG. 3A .  FIG. 3C  is an enlarged view of an encircled portion A of  FIG. 3B . The limb clamp for the ECG device with a medical electrode according to a first embodiment of the present invention is generally designated by reference numeral  100 . As shown in  FIGS. 2, 3A, 3B and 3C , the limb clamp  100  for the ECG generally comprises a first clamp portion  101 , a second clamp portion  103 , a spring element  105  interconnecting the first clamp portion  101  and the second clamp portion  105 , and a medical electrode  107  mounted at the first clamp portion  101 . The structure and the connection of the first clamp portion  101 , the second clamp portion  103  and the spring element  105  are known in the art. 
     The medical electrode  107  according to the first embodiment of the present invention generally comprises a conductive metal base  109  and a conductive support cylinder  111 . The conductive metal base  109  comprises a plate element  109   a  and a boss  109   b  formed on the plate element  109   a . In use, the lower surface of the plate element  109   a  contacts the body of a patient. Of course, an electrolyte gel may be applied to the lower surface of the plate element  109   a . Although the boss  109   b  is shown to be formed integrally with the plate element  109   a , the boss  109   b  may be formed separately from and attached to the plate element  109   a  in a known way, for example, by means of gluing, welding, or a thread connection. A recess  109   c  is formed in the boss  109   b . Although the conductive support cylinder  111  is shown to be substantially cylindrical in shape, it may be in any suitable shape. The conductive support cylinder  111  may comprise a through hole  111   a  transverse to its longitudinal axis for receiving a cable. Preferably, the conductive support cylinder  111  further comprises a threaded hole  111   b  formed along its longitudinal axis and communicating with the through hole  111   a . When a cable is inserted into the through hole  111   a , a thumb screw  113  may be screwed into the threaded hole  111   b  to keep the cable in place in a reliable manner. Of course, it is also feasible that the conductive support cylinder  111  does not have the through hole  111   a  and the threaded hole  111   b . In this case, the cable is attached to the conductive support cylinder  111  directly or by means of a sheath. 
     A bearing  115  made from a conductive material is disposed within the recess  109   c  formed in the boss  109   b . The lower end of the conductive support cylinder  111  is mounted into the bearing  115  so that the conductive support cylinder  111  may rotate relative to the conductive metal base  109 . Although the lower end of the conductive support cylinder  111  is shown to be thinner than the other portion of the conductive support cylinder  111 , the lower end of the conductive support cylinder  111  may be as thick as or thicker than the other portion of the conductive support cylinder  111 . In the shown embodiment, the bearing  115  is disposed within the recess  109   c  formed in the boss  109   b . It should be understood that the bearing  115  alternatively may be disposed within a recess formed in the lower end of the conductive support cylinder  111 . In this case, the upper end of the boss  109   b  is mounted into the bearing  115 . The conductive bearing  115  allows the conductive support cylinder  111  to be rotatable relative to the boss  109   b  while keeping the conductive support cylinder  111  in electrical communication with the boss  109   b.    
     An outer thread  109   d  is formed on an outer surface of the boss  109   b . The boss  109   b  may pass through a through hole  101   a  formed in the first clamp portion  101  and then a nut  117  may be screwed onto the outer thread  109   d  of the boss  109   b  so that the medical electrode  107  is mounted onto the first clamp portion  101 . 
       FIGS. 4A-4C  illustrates a limb clamp for the ECG device with a medical electrode according to a second embodiment of the present invention.  FIG. 4A  is a cross sectional view similar to  FIG. 3B .  FIG. 4B  is an enlarged view of an encircled portion A of  FIG. 4A .  FIG. 4C  is a perspective view of a support cylinder shown in  FIG. 4B . The limb clamp for the ECG device with a medical electrode according to a second embodiment of the present invention is generally designated by reference numeral  200 . Parts of the limb clamp for the ECG device with the medical electrode according to the second embodiment corresponding to parts of the limb clamp for the ECG device with the medical electrode according to the first embodiment are indicated by the same reference numerals, plus “100”. The description for the same parts is omitted for simplicity. 
     The limb clamp  200  for the ECG device with a medical electrode according to the second embodiment is substantially similar to the limb clamp  100  for the ECG device with the medical electrode according to the first embodiment, but does not include the bearing  115 . In this embodiment, a plurality of conductive and elastic strips  211   c  extending along the longitudinal axis of the conductive support cylinder  211  and projecting radially outward are disposed on the circumferential surface of the lower end of the conductive support cylinder  211 . The lower end of the conductive support cylinder  211  is inserted snugly into the recess  209   c  formed in the boss  209   b . The elasticity of the elastic strips  211   c  allows the conductive support cylinder  211  to be rotatable relative to the boss  209   b , while keeping the conductive support cylinder  211  in electrical communication with the boss  209   b . Preferably, the plurality of conductive and elastic strips  211   c  is distributed evenly on the circumferential surface of the lower end of the conductive support cylinder  211 . Further, the plurality of conductive and elastic strips  211   c  may be formed integrally with or separately from the conductive support cylinder  211 . For example, a sleeve comprising the plurality of conductive and elastic strips  211   c  may be attached to the lower end of the conductive support cylinder  211 . 
       FIGS. 5A-5C  illustrate a limb clamp for the ECG device with a medical electrode according to a third embodiment of the present invention.  FIG. 5A  is a cross sectional view similar to  FIG. 3B .  FIG. 5B  is an enlarged view of an encircled portion A of  FIG. 5A .  FIG. 5C  is an exploded perspective view of a medical electrode shown in  FIG. 5B . The limb clamp for the ECG device with a medical electrode according to a third embodiment of the present invention is generally designated by reference numeral  300 . Parts of the limb clamp for the ECG device with the medical electrode according to the third embodiment corresponding to parts of the limb clamp for the ECG device with the medical electrode according to the first embodiment are indicated by the same reference numerals, plus “200”. The description for the same parts is omitted for simplicity. 
     The limb clamp  300  for the ECG device with a medical electrode according to the third embodiment is substantially similar to the limb clamp  100  for the ECG device with the medical electrode according to the first embodiment, but does not include the bearing  115 . In this embodiment, a universal joint knuckle is formed between the lower end of the conductive support cylinder  311  and the boss  309   b . Specifically, a spherical head  311   c  is formed at the lower end of the conductive support cylinder  311  and a corresponding spherical recess  309   c  is formed in the boss  309   b . The spherical head  311   c  is received snugly in the spherical recess  309   c  to form the universal joint knuckle. The universal joint knuckle allows the conductive support cylinder  311  to be rotatable relative to the boss  309   b , while keeping the conductive support cylinder  311  in electrical communication with the boss  309   b . To allow easy assembly of the medical electrode  307 , the conductive metal base  309  may comprise a first half portion  309   d  and a second half portion  309   e.    
       FIGS. 6A-6C  illustrate a limb clamp for the ECG device with a medical electrode according to a fourth embodiment of the present invention.  FIG. 6A  is a cross sectional view similar to  FIG. 3B .  FIG. 6B  is an enlarged view of an encircled portion A of  FIG. 6A .  FIG. 6C  is an exploded perspective view of a medical electrode shown in  FIG. 6B . The limb clamp for the ECG device with a medical electrode according to a fourth embodiment of the present invention is generally designated by reference numeral  400 . Parts of the limb clamp for the ECG device with the medical electrode according to the fourth embodiment corresponding to parts of the limb clamp for the ECG device with the medical electrode according to the first embodiment are indicated by the same reference numerals, plus “300”. The description for the same parts is omitted for simplicity. 
     The limb clamp  400  for the ECG device with a medical electrode according to the fourth embodiment is substantially similar to the limb clamp  100  for the ECG device with the medical electrode according to the first embodiment, but does not include the bearing  115 . In this embodiment, a flange  411   c  is formed on the outer surface of the conductive support cylinder  411 . When the lower end of the conductive support cylinder  411  is inserted loosely into the recess  409   c  formed in the boss  409   b , a conductive spring  419  is disposed between the flange  411   c  and the boss  409   b . Further, the nut  417  having an inner flange  417   a  may be used to mount the conductive support cylinder  411  to the conductive metal base  409  and fix the metal electrode  407  to the first clamp portion  401 . The conductive spring  419  allows the conductive support cylinder  411  to be rotatable relative to the boss  409   b , while keeping the conductive support cylinder  411  in electrical communication with the boss  409   b.    
       FIG. 7  is a schematic view showing that the medical electrodes  107  and the limb clamps  100  according to the present invention connect with an ECG module  121  via the respective cables  123  and are applied to the patient to record ECG signals. The other pair of limb clamps  100  are not shown for simplicity. When the medical electrodes according to the present invention are applied to the patient&#39;s torso as torso electrodes, they are attached to the patient&#39;s torso by an adhesive plaster or a suction cup. The ECG module  121  connects with a computer  125  to show and analyze the recorded ECG signals.  FIG. 8  is a perspective view of a limb clamp for the ECG device according to the present invention showing no bending of the cable connecting with the electrode of the limb clamp. A cable post  127  connecting with the cable  123  is inserted into the through hole  111   a  of the conductive support cylinder  111  of the medical electrode  107 . Because the conductive support cylinder  111  of the medical electrode  107  may rotate relative to the conductive metal base  109  of the medical electrode  107 , the cable  123  also rotates with the conductive support cylinder  111  as shown by a double-arrow line. Thus, no bending of the cable  123  connecting with the medical electrode  107  occurs irrespective of how the medical electrodes and the limb clamps move, thereby avoiding any cable failure. 
     In  FIGS. 7 and 8 , as an example, the medical electrodes and the limb clamps are the medical electrodes  107  and the limb clamps  100  according to the first embodiment of the present invention. Obviously, the medical electrodes and the limb clamps may be the medical electrodes and the limb clamps according to any one of the other embodiments of the present invention. 
     While the medical electrode according to the present invention is explained as a part of the ECG device in the embodiments, it should be understood that the medical electrode may be used with other medical instruments and may comprise additional components for other functions. Although the invention has been described in detail for the purpose of illustration based on what are currently considered to be the most practical and preferred embodiments, it is to be understood that such detail is solely for that purpose and that the invention is not limited to the disclosed embodiments, but on the contrary, is intended to cover modifications and equivalent arrangements that are within the spirit and scope of the appended claims.