US3545432A - Body electrode assembly - Google Patents

Description

United States Patent 72| Inventor RleltardMJermln Dreshenlennsylvania |2l| Appl No 655,508 [22] Filed JI|24,1967 l45| Patented Dec.8,l970 l l Asatgnee Gnltonlndustrmlnc.

acorporationofbelaware I54] BODY ELECTRODE ASSEMBLY 7Clalms,5l)rawlngl"igs.

I52] U.S.Cl. RUIZ-06. 339/105 [5H lnt.CI. A6lb5/04 sm FieldofSearch.............. 174173. 9; 339/l05; 128/2 06(El. 21.404.4IO. 4! I 4l6. 4l7.4l8.(Digest4l I56] RefereneesCited UNITED STATES PATENTS 877.383 lll908 Swan. 339/[05 l.989.282 Ill935 Kimbleetal..... 128/416 .170.459 2/1965 Phippsetal. l28/2.06 1295.5 "1967 Kahn. i28/2.06 3.340.868 9/1967 Darling l28/2.06 3.420123 lll969 Day et l28/2.06

Primary Examiner-William E. Kamm Anomey- Wallenstein, Spangenberg, l-lattis & Strampel ABSTRACT: The electrode assembly of the invention most advantageously comprises an electrode housing made of molded insulating material and having a base portion with a skin-contacting surface interrupted by a conductive pastereceiving recess located completely within the margins of said skin-contacting surface The housing has a head portion with a cavity therein intersecting the recess in the base portion thereof A conductive electrode-fonning; disk closes the opening between the recess in the base portion of the housing and the cavity in the head portion thereof. An insulated signal lead extends through the head portion of the housing and said cavity therein 'and then bends tightly back into the housing around two corners where the ends of the signal lead terminate in the cavity in the head portion of the housing. The conductor of c the signal lead is soldered to the electrode-forming disk and the cavity is filled with an encapsulation material. To apply the electrode assembly. the paste-receiving recess in the housing is filled with a conductive paste and the electrode assembly is placed upon the patients skin and secured and sealed thereto by a patch of cushioning material which envelopes the housing. The patch has a pressure sensitive adhesive layer which holds the patch tightly around the electrode housing and prevents any drying of the paste from the electrode assembly.

3 8 2| (3 82 Rid-mm: MBERM I- YEA/TOR connect such equipment as electrocardiogram, electroencephalogram, electroocculogr'am and electromyogram equip ment to a skin surface. n

Until recently, medical electronic equipment for diagnostic or therapeutic purposes has been of the nonportable variety where the patient being tested or treated is confined to the hospital or doctors office because of the size and weight of the measuring or treating equipmentinvolved; Generally, the electrodes connected to the equipment are applied to the patient for a relativelyshort period of time while the patient is maintained relatively immobile. However, recently miniaturized electronic medical equipment has been developedwhich is so light in weight that it can be carried on the patient so that measuring or treatment procedures can be carried out for a long period of time at locations away from the hospital or doctors office and while the patient is performing his normal routine work or bodily exercises. For example, portable electrocardiogram equipment of this type is now available permitting dynamic electrocardiograms to be taken off the patient while his is engaged in his normal physical activities. However, the use of the portable electromedical equipment referred to imposes many severe requirements upon the body connecting electrodes. Thus, the electrodes must be small and light-in-weight and must also be held securely in place and make continuous very low resistance contact with a given location of the body'to which it is applied while the patient is performing a variety of movements. Also, the leads extending to the electrodes must be such that they can withstand appreciable pulling forces without breakage.

The body electrodes heretofore developed proved unsatisfactory and less than ideal because they failed to satisfy one'or more of the aforementioned objectives. Perhaps one of the most significant deficiencies inthe electrodes heretofore developed was their inability to withstand repeated large pulling forces on the leads extending to the electrodes without breakage. As will appear, the preferred form of the present invention satisfies all of the aforementioned objectives.

In accordance with one of the features of the invention, the lead extending to each electrode is connected to the electrode housing in a manner where the strain placed on the lead is relievedfrom the point of connection of the lead to the electrode in a very simple and inexpensive manner. i

In the most preferred form of the invention, the electrode includes a relatively thin molded housing body preferably having a relatively wide base portion and a relatively narrow upper or head portion. The small overall thicknessof the housing makes it comfortable for application to the skin and adaptable to all skin surface irregularities. The head portion of the housing preferably has a cavity provided with a voltagereceiving electrode surface to which is fed the skin voltage in a measuring application or the applied current or voltage in a treating application. The signal lead, which comprises an inner conductor and'an outer insulating sleeve, passes through a passageway extending completely through the head portion of the housing and intersecting the aforementioned cavity. The signal lead passes through this housing passageway and cavity and bends snugly around a corner of the housing at the periphery thereof, then bends snugly around another corner and then reenters the housing and passes through a second passageway which also intersects the aforesaid cavity. The end of the signal lead conductor is located in the housing cavity where it is stripped of insulation and connected by soldering or otherwise to the aforementioned voltage-receiving electrode surface within the cavity of the housing. Means are provided in the cavity for immovably anchoring the spaced portions of the signal lead which pass into the cavity. This means most advantageously is an encapsulation material, such as an epoxy resin, which fills the cavity and immovably anchors the signal lead and seals the bared end portion of the signal lead conductor. With this construction, longitudinal pulling forces applied to the signal lead is substantially eliminated at the FIG. 3 taken along section line 4-4; and

point of connection of the bare end of the signal lead conductor to the electrode surface: in the housing cavity.

In accordance with another feature of the invention, the base portion of the electrode housing has a flat skin-contacting surface which is interrupted by a conductive paste-receiving recess or well located within all of the margins of the skin contacting surface of the housing which aids in sealing or closing the recess on all sides so that a conductive paste placed in the recess will normally be trapped' between the skin and the defining walls of the recess. To ensure theretension of the paste, an auxiliary seal is formed around the periphery of the recess so that none of the paste can escape by evaporation or otherwise from the electrode. This auxiliary seal is most advantageously provided by a cushioning, anchoring and sealing pad which may comprise a body of resilient compressible material having a pressure sensitive adhesive on one side thereof, the pad having an area much greater than the elec trode housing so the pad while enveloping the electrode housing can be pressed against the portion of the skin surrounding the electrode housing toanchor and seal the same to the skin.

The paste-receiving recess and said housing cavity are most advantageously separated by a silver disc or pellet whose outer surface constitutes the electrode surface to which the signal lead conductor is preferably soldered. The design and arrangement of the silver disc, conductive paste-receiving recess and adhesive-coated cushioning pad allows for large variations in pressure against the electrode without causing distortion of the electrical signal being sensed. This is important when clothing is present over the electrode and/or the subject presses on or lies on top of the electrode.

The above and other advantages and features of the invention will become apparent upon making reference to the specification to follow, the claims and the drawings wherein:

' FIG. 1 is a top perspective viewof an electrode assembly incorporating features of the presentinvention;

FIG. 2 is a bottom perspective view of the electrode assembly shown in FIG. 1;

FIG. 3 is an enlarged, partly broken away top view of the electrode assembly of FIGS. 1 and 2;

FIG. 4 is a sectional view through the electrode assembly of FIG. 5 is a broken away perspective view of the electrode assembly applied to the skin surface ofa patient with conductive paste in the electrode-housing recess.

Referring now to the drawings, the electrode assembly there illustrated and identified by reference numeral! includes an outer housing 2 of generally circular cross section form which a signal lead 3 extends. The signal lead comprises a relatively small conductor 3a and a surrounding insulating sleeve 3b which may be Teflon tubing which has been shrunk snugly around the conductor. The housing 2 may be a molded body made of any suitable material, such as a transparent synthetic plastic material. The exemplary housing has a relatively wide base portion 2a with a flat annular skin-engaging surface 6. The surface 6 is interrupted by a centered paste-receiving recess 8 which tapers inwardly of the housing and intersects and axially centered cavity 10 formed in a reduced head portion 2b of the housing. The illustrated cavity 10 is of cylindrical shape and of somewhat larger diameter than the inner narrow end of the recess 9, thereby providing an annular shoulder or ledge 12 on which is mounted an electrode-forming disc or pellet 13 which most advantageously is. made of a highly conductive silver-chloride composition. The electrode-forming disc 13 may be adhesively secured to the ledge 12 by a suitable cement or may be held in the cavity by encapsulation material 15 filling the cavity 10 which may be an epoxy resin. The disc 13 occupies only a small portion of the cavity 10 to provide space for the passage of the signal lead 3.

The head portion 2b of the electrode housing is provided with a first passageway I4preferably extending diametrically through the entire housing in a plane adjacent to the electrode-forming disc 13 and intersecting the cavity 10 which breaks the passageway 14 into two diametrically separated sections. The signal lead 3 passes through the passageway 14 where it bends tightly around a corner 16 at the end of the passageway 14 and .then extends circumferentially a small distance around the outside of the housing where it bends tightly around a corner 18 at theend of a second passageway 20 which extends in about the same plane as the passageway 14 through the housing wall to intersect the cavity 10 adjacent the electrode-forming disc 13. The end of the conductor 3a of the signal lead 3 within the cavity 10 is bared and soldered or otherwise electrically and physically attached at 17 to the electrode-forming disc 13. The spaced portions of the signal lead 3 within the cavity l are immovably anchored with respect to the housing 2 by means of encapsulating material 15 which is poured iii liquid form in the cavity and allowed to harden.

As best shown in FIG. 5, when the electrode assembly is applied to a patients skin, the recess 8 between the patients skin and the electrode-.formingdisc 13 which seals off one end of the recess 8 is filled with a'conductive paste 21 which forms a low resistance path between the surface of the patients skin 23 and the electrode-forming disc 13. The electrode assembly is fixedly attached to the patients skin by suitable means, most preferably a flexible and resilient cushioning patch 25 which is preferably of much larger diameter and thickness than the electrode assembly housing and may be made of a closed cell foam material like polyurethane or the like. The inner surface of the patch 25 is coated with a layer 27 of pressure-sensitive adhesive material, which readily sticks to the skin surface 23. When the patch 25 envelopes the electrode assembly and is pressed securely around the housing 2 thereof, the assembly is securely held in place and a continuous seal is formed around the housing which prevents the evaporated or fluid paste from escapingfrom 'the electrode assembly.

It should be appreciated that the various features of the present invention provide a very simple and inexpensive body electrode assembly which provides a very convenient sealed recess fora conductive paste so that a low resistance, long lasting connection is maintained between the patients skin and the electrode-forming disc 13. Moreover, any pulling force applied to the signal lead 3 is relieved from the solder connection at 17 because of the snug reverse bending of the signal lead around the comers 16 and 18 and the manner in which the signal lead is anchored to the housing 2 by the encapsulation material 15. As previously indicated, the invention allows for large variationsin pressure against the electrode without causing distortion of the electrical signal being sensed. This is important when clothing is present over the electrode and/or the subject presses on or lies on top of the electrode. Also, the electrode assembly is of a permanent reusable construction and is easily cleaned and refilled with paste.

It should be understood that numerous modifications may be made in the most preferred form of the invention described above without deviating from the broader aspects thereof.

I claim:

1. An electrode assembly for picking up or delivering small electrical signals from or to a skin surface, said electrode assembly comprising: a housing having a skin-contacting surface on the inner side thereof, a cavity containing an externally exposed conductiveelectrode-forming means to which a voltage is to be applied, a first passageway extending generally parallel to said skin-contacting'surface, a second passageway extending generally parallel to said skin-contacting surface and intersecting said cavity, and an outwardly facing surface extending between the ends of said passageways remote from said cavity and formingcorners at'the intersection of said outwardly facing surfaceand said passageways; a signal lead for connecting said electrode-forming, means in said housing to an external device, said signal lead having an inner end section passing through said first passageway in said housing, then along said outwardly facing surface of the housing and through said second passageway thereof. to terminate in said cavity, the signal lead tightly vending around said corners, the end of said signal lead being electrically connected to said electrodeforming means in said cavity; and means for immovably anchoring said inner end section of said signal lead to said housing so the signal lead to said housing so the signal lead remains tightly bent around said housing corners.

2. The electrode assembly of claim 1 wherein said first passageway also intersects said cavity so portions of said signal lead ahead of and beyond said housing corners pass into said cavity, and said anchoring means isa body of encapsulation material in the cavity which embeds said portions of the signal lead located in the cavity.

3. The electrode assembly of claim 1 wherein said housing has a hollow base portion including a recess and a hollow head portion containing said cavity communicating with said recess and opening onto the outer side of the housing, said conductive electrode-forming means in said cavity being a conductive disc mounted in said cavity so as to seal-off the opening between said recess and cavity, said signal lead is electrically connected and physically attached to the outer side of said disc and extends to the outside of said housing, and a body of encapsulation material in such housing cavity which seals and encapsulates the outer side of said disc and the portions of the signal lead passing into said cavity.

4. An electrode assembly for picking up or feeding electrical signals from or to a skin surface, said electrode assembly comprising: an outer housing havinga skin-contacting surface on the inner side thereof adapted to be placed on the skin surface, a voltage-receiving electrode in said housing, a signal lead extending to said housing and electrically connected to said electrode, said housing surface being interrupted by a conductive paste-receiving recess located within all the margins of said surface and defined by inner walls of the housing which seal said recess on all sides but the side facing the skincontacting side of the housing, so a conductive paste placed in the recess is held betweenthe skin'and the housing, said voltage-receiving, electrode being at least part of one of the defining walls of said recess, a body of cushioning material for isolating the housing from external forces on the side of said housing opposite the side containing said recess, said body of cushioning material being a separate piece of material which extends over an area much larger than that encompassed by said electrode housing to envelope all exposed sides of the housing, and said piece of cushioning material having a pressure sensitive adhesive layer on the inner side thereof for contact with the users skin along a continuous ring around said electrode housing.

5. An electrode assembly for picking up or feeding electrical signals from or to a skin surface, said electrode assembly comprising: and outer housing having a skin-contacting surface on the inner side thereof adapted to be placed on the skin.

surface; a signal lead extending to said housing and including an inner conductor surrounded by an insulating sleeve which terminates short of the end of the conductor to expose the end of the conductor; said housing surface being interrupted by a conductive paste-receiving recess located within all the margins of said surface and defined by inner walls of the housing which seal said recess on all sides but the side facing the skincontacting side of the housing, so a conductive paste placed in the recess is held between the skin and the housing; said housing being provided with a cavity; a voltage-receiving electrode which forms a wall between said cavity and recess; a first passageway which passes completely through the housing from one side to the other and intersects said cavity and a second passageway extending from the outside of the housing to said cavity; said signal lead passing through said first passageway andsaid cavity and after leaving said first passageway passing along the outside of said housing and then bending back into the housing where it enters said cavity through said second passageway; and said exposed end of said signal lead conductor overlying said electrode and attached thereto within said cavity.

6. The electrode assembly of claim 7 wherein the portion of the signal lead which extends into said first passageway and 3 ,5 45 ,432 l p 5 g 6' passes through said cavity is anchored in saidcavity by a body 7. The electrode assembly of claim SWherein there is proof encapsulation material embedding both the latter portion of vided means for anchoring the 1 portion of said signal lead the signal lead and the exposed end of the conductor thereof. passing through said first passageway and! entering said cavity.

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