Lymphedema treatment system

Information

  • Patent Grant
  • 6179796
  • Patent Number
    6,179,796
  • Date Filed
    Friday, April 11, 1997
    27 years ago
  • Date Issued
    Tuesday, January 30, 2001
    23 years ago
Abstract
Apparatus for providing mechanical stimulation of the lymphatic system within the trunk of the body for the treatment of lymphedema. A wrap contains a plurality of bladders which are applied to the trunk of the body. The bladders are pressurized and depressurized on an individual basis to stimulate the lymphatic system to provide for drainage of pooled fluids by massaging the pooled fluids within the trunk section of the body toward selected lymph node groups.
Description




BACKGROUND OF THE INVENTION




1. Field of the Invention




This invention relates to an apparatus for the treatment of lymphedema. More particularly it relates to a wrap having a series of bladders applied to the trunk of the body, wherein the bladders are compressed and decompressed on an individual basis to stimulate the lymphatic system.




2. Description of the Prior Art




The lymphatic system consists of lymph vessels, lymph nodes and lymphoid tissues and is a secondary system within the circulatory system that removes waste. Unlike the closed-loop blood circulatory system, the lymphatic system works according to a one-way principal. That is, the lymphatic system is a drainage system to drain away lymph which continually escapes from the blood in small amounts. The lymph is first collected at the lymph capillaries, which in turn drain into larger vessels. The lymph is pumped in and out of these vessels by movements of adjacent muscles and by contractions of the walls of the larger vessels, and moves through the lymphatic system in one direction. Foreign matter and bacteria are filtered at various lymph node groups after which the fluid empties into the venous portion of the blood system, mainly through the thoracic duct. A healthy person will drain one to two liters of lymph fluid through this duct every 24 hours. Without proper drainage into the duct, lymphedema results.




Lymphedema is an accumulation of a watery fluid in the body causing a swelling or edema of the affected area. The swelling causes pain, discomfort, disfigurement and interference with wound healing and, if left untreated, can cause fibrosis. Fibrosis is a hardening of the tissue in the affected area which may further complicate the drainage process and can cause life-threatening conditions, such as infections. Lymphedema may result from surgery when the lymph nodes are removed in order to prevent the further spread of cancerous conditions, such as with a mastectomy or prostectomy, and may also be caused by filariasis. Lymphedema may be primary or congenital.




In recent years, several common therapies for lymphedema have been proposed. Special bandages, such as a limb compression sleeve or stocking, have been utilized to help prevent accumulation of fluid in a limb by holding the tissue tightly. This treatment is incomplete, however, because it treats the limb only and does nothing to actually move the fluid. This treatment is also uncomfortable (and may be painful) and is not easily adaptable to the trunk of the body. In application to the limb, this treatment may interfere with mobility.




Pneumatic compression devices have also been used to assist limb lymph drainage by increasing the tissue pressure, thus, forcing fluid along the lymphatic system. This treatment approach, however, is incomplete because it treats the limb only. This treatment approach may cause fibrosis or accumulation of fluids in non-affected areas. The high pressure required to force the fluid along the system is uncomfortable or painful, while lower pressure devices result in an increase in therapeutic time.




Another approach is manual lymph drainage (MLD), a gentle manual treatment technique which improves lymphatic system functioning through a highly specific massage, which provides mild mechanical stimuli to the lymphatic system. MLD has the advantage of being able to treat the entire lymphatic system, including the arms, legs and trunk of the body. The MLD treatment technique applies just enough pressure to massage pooled fluids from larger areas toward specific lymph nodes within the body by mechanically stimulating the lymphatic system to cause contraction of the lymph collectors sufficient to help move the pooled fluids by promoting reabsorption of the pooled fluids within the surrounding tissues. Too much applied pressure will cause the lymph collectors to go into spasm. This technique is effective but also expensive, however, as a person trained in the MLD technique is required to perform the massage therapy.




U.S. Pat. No. 5,453,081, issued to Hansen, suggests an apparatus for generating air pressure pulses which are delivered to a vest or mattress accommodating a person. A diaphragm located within a housing is connected to a wave generator and amplifier operable to vibrate the diaphragm. The vibrating diaphragm produces air pressure pulses, which are delivered to the air accommodating receiver, and which subject the person to repetitive force pulses. The housing has an enclosed chamber accommodating the diaphragm, which divides the chamber into two separate portions, wherein air under pressure may be supplied with a pump to the chamber to pressurize the apparatus, as well as the receiver. A coil connected to the diaphragm is operable to vibrate the diaphragm to pulsate air in the chamber.




U.S. Pat. No. 5,437,610, issued to Cariapa et al., suggests a portable hydraulic extremity pump apparatus for the treatment of edema. This apparatus consists of a flexible compression unit that wraps around an individual's extremity. The unit includes a plurality of prefilled bladders, each containing a separate compression bladder which are connected to a hydraulic pump through valves. The valves, pump, and pressure sensors, which connect to the prefilled bladders, all connect to a programmable control processor to operate the valves and to pump and monitor the bladder pressures. The occurrence of edema is detected by monitoring an increase in pressure in the prefilled bladders. Once edema is detected, the control processor activates the pump and opens valves connected to the compression bladder in a sequential manner to create a sequential pressurization and wave of compression moving proximally on the extremity.




U.S. Pat. No. 5,052,377, issued to Frajdenrajch, suggests an apparatus for massaging parts of the body by sequential cyclic pressure having a massaging boot comprising a plurality of juxtaposed inflatable cells. An inflating conduit is connected to each cell through a series of distributors for receiving a control fluid. Each distributor has a movable membrane arranged to permit passage of the inflating fluid in a downstream direction when the local inflating pressure reaches a value which is a function of the pressure of the control fluid. The cells are inflated in series, one after another, and then deflated in a cyclic manner.




U.S. Pat. No. 5,014,681, issued to Neeman et al., suggests a method and apparatus for treating a body part by applying intermittent compression through an inflatable sleeve applied to and enclosing the body part. The inflatable sleeve is divided into successively overlapping inflatable cells. Pressurized fluids are applied cyclically to successive groups of cells to successively inflate each group, while at the same time deflating a preceding group. As successive groups of cells are inflated (while the remaining cells are deflated), a compression wave is introduced in the sleeve which subjects successive portions of the body part to compression.




U.S. Pat. No. 4,573,453, issued to Tissot, suggests a pneumatic massage apparatus which includes an inflatable sleeve having an inner and outer sheath with lateral partition walls extending between the inner and outer sheaths. The inner and outer sheaths are formed of air-impermeable, non-elastic material and the lateral partition walls are formed of a flexible air-impermeable, non-elastic material. The partition walls and inner and outer sheaths define separate inflatable chambers, adjacent chambers being separated by a partition wall. When a first chamber has been inflated, its feed conduit is closed and the following chambers are inflated in turn to the same feed pressure. The result causes a deformation of the walls of the first chamber, and a slight increase in the internal pressure in this first chamber. Step by step, with the same feed pressure, the appearance of a pressure gradient is created.




U.S. Pat. No. 2,361,242, issued to Rosett, suggests a pneumatic suit or garment adapted to be applied to limbs of a patient, wherein the pneumatic suit has a series of laterally disposed pockets, each of which is provided with a fluid-type flexible bag. The bags are inflated one after another in groups, so as to cause the exertion of waves of pressure from the extremities of the limbs and from the lower portion of the torso of the patient towards the region of the heart. After each bag is inflated, it is immediately subjected to a source of sub-atmospheric pressure to accelerate the removal of air therefrom and to accentuate the effect. Rosett suggests the pneumatic suit or garment being applied to areas including the arms and legs and lower trunk.




SUMMARY OF THE INVENTION




The present invention provides an apparatus for mechanical stimulation of the lymphatic system for the treatment of lymphedema. A lymphedema treatment system in accordance with the present invention includes a wrap having a plurality of elongate and flexible bladders applied to the trunk of the body. The bladders are compressed and decompressed on an individual basis to stimulate the lymphatic system to provide for drainage of pooled fluids by massaging the pooled fluids within the trunk section of the body towards lymph nodes in the arms, neck or groin of the body. Compression and decompression of the bladders may be provided by a pump.




In a preferred embodiment of the present invention, the apparatus for the treatment of lymphedema may comprise a plurality of elongate and flexible bladders, wherein the plurality of bladders has an orientation adapted to engage the trunk of the body and move pooled fluids within the lymphatic system towards a particular region of the body or away from a particular region of the body. The particular regions of the body may be specific lymph node groups which include the axillary node group, the pelvic node group or the groin node group as well as the thoracic duct. The orientation of the plurality of bladders relative to the particular region may be arcuate so that the plurality of bladders being coextensive and sequentially arranged in a fixed relation may engage the trunk of the body to radially move the pooled fluids within the lymphatic system to the particular region of the body.




In a preferred embodiment, each particular one of the plurality of bladders may be sequentially pressurized and depressurized in a sequence to provide mechanical stimulation of the lymphatic system similar to Manual Lymph Drainage (MLD) massage. In the preferred embodiment, a pumping system is in fluid communication with each particular one of the plurality of bladders and is programmable to sequentially pressurize and depressurize each particular one of the plurality of bladders. The pumping system may be comprised of a pneumatic pump and a plurality of pneumatic hoses to couple the pneumatic pump to each particular one of the plurality of bladders. Each particular one of the one of the plurality of bladders may be pressurized to engage the trunk of the body at a therapeutic pressure. The lymphatic system is mechanically stimulated when each particular one of the plurality of bladders being both pressurized to the therapeutic pressure and depressurized causes contraction of lymph collectors sufficient to move pooled fluids by promoting reabsorption of the pooled fluids within the surrounding tissues without causing the lymph collectors to go into spasm. In the preferred embodiment there may be a predetermined waiting period between a first particular one of the plurality of bladders being fully pressurized and fully depressurized. In addition, depressurization of the first particular one of the plurality of bladders may begin before pressurization of a second particular one of the plurality of bladders begins.




The preferred embodiment may further comprise a wrap sized to wrap around a portion of the trunk of the body to receive and hold each one of the plurality of bladders within a corresponding one of a plurality of compartments. The plurality of bladders are held in an orientation to engage the trunk of the body and move pooled fluids within the lymphatic system either towards or away from specific lymph node groups which include the axillary node group, the pelvic node group or the groin node group. The orientation may be arcuate relative to the particular lymph node group. The wrap may maintain the plurality of bladders in a coextensive relationship such that each particular one of the plurality of bladders is adjacent to one or two other ones of the plurality of bladders. The wrap may be constructed of a stretchable material to accommodate expansion and contraction of the bladders as the bladders are sequentially pressurized and depressurized. The wrap may also limit the maximum diameter under pressurization of each one of the plurality of bladders within the plurality of compartments.











BRIEF DESCRIPTION OF THE DRAWINGS




Other objects of the present invention and many of the attendant advantages of the present invention will be readily appreciated as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, in which like reference numerals designate like parts throughout the figures thereof and wherein:





FIG. 1

is a perspective view of the preferred embodiment of a “Lymphedema Treatment System” in accordance with the present invention;





FIG. 2

is a perspective view of the human body showing specific lymph node groups and the thoracic duct;





FIG. 3

is a detailed cross-section view of the embodiment of

FIG. 1

showing various levels of bladder pressurization;





FIG. 4

is a detailed cross-section view of the embodiment of

FIG. 1

showing the means to provide bladder pressurization;





FIG. 5

is a perspective view showing an alternate embodiment in accordance with the present invention; and





FIG. 6

is a perspective view showing a further alternate embodiment in accordance with the present invention.











DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS




Referring now to the drawings, wherein like reference numerals refer to like elements throughout the several views,

FIG. 1

is a perspective view of a preferred embodiment of a lymphedema treatment system in accordance with the present invention. The lymphedema treatment system is shown generally at


10


and consists of a wrap


12


and a pneumatic pump


14


. Wrap


12


is shown applied to lower trunk


16


of human body


18


. Wrap


12


is positioned on lower trunk


16


by placement on human body


18


when in an open position, then pulling first end


20


over second end


22


until wrap


12


is firmly and completely engaging lower trunk


16


. Wrap


12


is then secured by attaching first end


20


to second end


22


through fasteners well known in the art, such as Velcro (not shown). Wrap


12


is comprised of compartments


24


,


26


,


28


,


30


,


32


,


34


,


36


,


38


,


40


and


42


. Each one of compartments


24


,


26


,


28


,


30


,


32


,


34


,


36


,


38


,


40


and


42


is sized to receive and hold a particular one of a plurality of elongate and flexible bladders


44


,


46


,


48


,


50


,


52


,


54


,


56


,


58


,


60


and


62


, respectively. In the preferred embodiment, compartments


36


,


38


,


40


and


42


and bladders


56


,


58


,


60


and


62


are not required, but are shown here to illustrate that many configurations of wrap


12


are within the scope of the present invention. Each of bladders


44


,


46


,


48


,


50


,


52


,


54


,


56


,


58


,


60


and


62


are in fluid communication with pneumatic pump


14


via pneumatic hoses


45


where pneumatic pump


14


is both portable and programmable and may be programmed to individually and sequentially pressurize and depressurize each particular one of the plurality of bladders in a desired sequence (see also, FIG.


4


). Pneumatic hoses


45


comprise a plurality of hoses wherein each hose couples one of the bladders to pneumatic pump


14


. The desired sequence provides individual sequential pressurization and depressurization of each one of bladders


44


,


46


,


48


,


50


,


52


,


54


,


56


,


58


,


60


and


62


to provide mechanical stimulation of the lymphatic system similar to manual lymph drainage massage. Pneumatic pump


14


pressurizes each one of bladders


44


,


46


,


48


,


50


,


52


,


54


,


56


,


58


,


60


and


62


to a maximum inflation pressure of 5 PSI where at the maximum inflation pressure each bladder is elastic and has a diameter from 0.5″ to 2″. In the preferred embodiment, wrap


12


is constructed of a stretchable material to accommodate expansion and contraction of each one of bladders


44


,


46


,


48


,


50


,


52


,


54


,


56


,


58


,


60


and


62


and limits the maximum diameter of each bladder.




In the preferred embodiment, bladders


44


,


46


,


48


,


50


,


52


, and


54


are held within compartments


24


,


26


,


28


,


30


,


32


, and


34


of wrap


12


so that the bladders have a generally arcuate shape and are sequentially pressurized and depressurized to engage lower trunk


16


of human body


18


to radially move pooled fluids. The pooled fluids are moved within the lymphatic system of human body


18


either in the direction shown by arrows


64


,


66


and


68


, or in a direction opposite to the direction shown by arrows


64


,


66


and


68


. The bladders are oriented to be arcuate relative to three lymph node groups such that radial lines extending from each bladder converge (or diverge) towards each one of the lymph node groups (see also, FIG.


2


). Bladders


44


,


46


,


48


,


50


,


52


, and


54


, each being sequentially pressurized and depressurized, engage lower trunk


16


of human body


18


at a therapeutic pressure to provide mechanical stimulation of the lymphatic system. This mechanical stimulation provides for drainage of pooled fluids within the lymphatic system by applying the therapeutic pressure to lower trunk


16


of human body


18


sequentially to move the pooled fluids either towards or away from the selected lymph node groups within the arms, neck or groin of the body by promoting reabsorption in the surrounding tissues. If the applied pressure is to high, the lymph collectors may go into spasm (see also, FIG.


2


). In the preferred embodiment, the therapeutic pressure measured between the bladders and the body is between 20 mmHg and 45 mmHg.




In the preferred embodiment, there is a predetermined waiting period of one to three seconds between pressurization and depressurization of each bladder. Thus, each of bladders


44


,


46


,


48


,


50


,


52


, and


54


are pressurized for one to three seconds to provide the mechanical stimulation to the lymphatic system. Each bladder is depressurized before pressurization of the next bladder begins. In

FIG. 1

, for example, bladder


44


would be depressurized before bladder


46


is pressurized. Each of bladders


44


,


46


,


48


,


50


,


52


, and


54


are pressurized to apply the therapeutic pressure over a time period which is a predetermined minimum pressurization time period, and are depressurized over a time period which is a predetermined minimum depressurization time period. It is understood that the embodiment shown in

FIG. 1

is just one of many possible configurations of a lymphedema treatment system in accordance with the present invention.





FIG. 2

is a perspective view of the human body showing the location of specific lymph node groups. The lymph node groups shown in

FIG. 2

do not comprise all the lymph node groups within human body


18


, but are representative and described for illustrative purposes.

FIG. 2

shows axillary node group


80


, pelvic node group


82


including a portion of the thoracic duct, and groin node group


84


and diverging arrows


64


,


66


and


68


. An application of wrap


12


as shown in

FIG. 1

provides for drainage of pooled fluids by massaging the pooled fluids in the direction shown by arrow


64


towards axillary node group


80


, in the direction shown by arrow


66


towards pelvic node group


82


, and in the direction shown by arrow


68


towards groin node group


84


. In the human body, the lymph capillaries reabsorb tissue fluid and drain through precollectors to the lymph angions. The lymph angions contract in sequence to help move the fluid along the lymphatic system. The application of the wrap, as shown in

FIG. 1

, stimulates this natural drainage through sequentially pressurizing and depressurizing each particular one of bladders


44


,


46


,


48


,


50


,


52


, and


54


to stimulate the initial lymph capillaries and provide for contraction of the lymph angions. Pooled fluids may be moved to axillary node group


80


, pelvic node group


82


, or groin node group


84


, where foreign matter and bacteria are filtered out and the fluid is emptied into the vein portion of the human body blood system.





FIG. 3

is a detailed cross-sectional view of a preferred embodiment in accordance with the present invention showing the construction of wrap


12


and various levels of bladder pressurization.

FIG. 3

shows a portion of wrap


12


comprising bladders


44


,


46


and


48


. Bladders


44


,


46


and


48


may each be constructed of an elastic material to provide stretchability when going from a depressurized state to a fully pressurized state. Bladder


44


is shown in a fully pressurized state, bladder


46


is shown in a partially pressurized state, and bladder


48


is shown in a depressurized state.




Compartments


24


,


26


and


28


are constructed of a combination of materials. A first layer


90


overlays each of bladders


44


,


46


and


48


and is the side of wrap


12


that is in a contact relationship with lower trunk


16


of human body


18


. First layer


90


is preferable constructed of a stretchable material and stretches when any of bladders


44


,


46


or


48


are fully pressurized to provide the therapeutic pressure to lower trunk


16


. The therapeutic pressure is between 20 mmHg and 45 mmHg. Second layer


92


overlays each of bladders


44


,


46


and


48


on the side of wrap


12


opposite first layer


90


. Second layer


92


is preferably constructed of a durable cotton material. Third layer


94


overlies second layer


92


and provides an outer cover for wrap


12


. Third layer


94


is preferably constructed of a cotton material.





FIG. 4

is a detailed cross-section view showing the means to provide bladder pressurization. Pneumatic pump


14


is coupled to and is in fluid communication with each of bladders


44


,


46


and


48


via couplings


96


,


98


and


100


, respectively. Couplings


96


,


98


and


100


couple to pneumatic hoses


45


allowing pneumatic air pressurization to be applied individually and sequentially to bladders


44


,


46


, and


48


to pressurize and depressurize each bladder. In

FIG. 4

, pneumatic hoses


45


comprise at least three hoses wherein each hose couples one of couplings


96


,


98


or


100


to pneumatic pump


14


.





FIG. 5

is a perspective view showing another embodiment of the present invention. Wrap


110


is shown being applied to an upper trunk


112


of human body


18


. Wrap


110


has compartments


114


,


116


,


118


,


120


,


122


and


124


containing bladders


126


,


128


,


130


,


132


,


134


and


136


, respectively. Pneumatic pump


14


is not shown. Bladders


126


,


128


,


130


,


132


,


134


and


136


may be sequentially pressurized and depressurized to provide movement of pooled fluids within the lymphatic system towards axillary node group


80


in the direction shown by arrows


138


,


140


, and


142


.




Bladders


126


,


128


,


130


,


132


,


134


and


136


when pressurized and depressurized provide a gentle massaging action which provides a mechanical stimulation similar to manual lymph drainage massage to the lymphatic system so that proper drainage may occur. The stimulus is provided by sequential inflation of each bladder to a pressure of approximately 5 pounds per square inch. The bladders may be constructed of up to 1.5 inch diameter elastic tubes which provide the therapeutic pressure. The therapeutic pressure is measured between bladders


126


,


128


,


130


,


132


,


134


and


136


and upper trunk


112


and is between 20 mmHg and 45 mmHg in order to promote reabsorption from the surrounding tissues. Too much pressure against upper trunk


112


will cause the lymph collectors to go into spasm and reduce effectiveness. The plurality of bladders may be individually and sequentially pressurized and depressurized in the direction shown by radial arrows


138


,


140


, and


142


(converging toward axillary node group


80


) to promote drainage of fluids in a direction towards axillary group


80


. In terms of the present invention, the bladders


126


,


128


,


130


,


132


,


134


and


136


are “oriented” (configured and sequentially pressurized and depressurized) to direct drainage in a direction towards axillary group


80


. The bladder configuration is generally arcuate, while the “radial” arrows


138


,


140


and


142


point in a direction generally perpendicular to a tangent of the arcuate bladder.





FIG. 6

is a perspective view showing a further embodiment in accordance with the present invention.

FIG. 5

shows wrap


110


applied to upper trunk


112


of human body


18


. Wrap


110


may undergo sequential pressurization and depressurization of bladders


126


,


128


,


130


,


132


,


134


and


136


to move pooled fluids away from axillary node group


80


towards other node groups, such as pelvic node group


82


and groin node group


84


.




The figures illustrate that alternative constructions in accordance with the present invention may move pooled fluids within human body


18


from several regions to a particular node group, or from a particular region to several node groups. Pooled fluids may be moved within the lymphatic system in a direction generally away from axillary node group


80


in the direction shown by arrows


150


,


152


,


154


, and


156


through the configuration of, and through sequential pressurization and depressurization of, bladders


126


,


128


,


130


,


132


,


134


and


136


.




Each bladder of the illustrated embodiments has a generally arcuate configuration. The configuration and sequential pressurization/depressurization provides an orientation towards one or more node group(s). That is, radial lines extending from each bladder along its length extend generally toward one or more node groups. Configuration and direction provide an “orientation”. Orientation is established by the direction of sequential pressurization/depressurization of the bladders and the configuration of the bladders on the body. The length of each bladder is optimally determined to move pooled fluids toward a node group. While it is expected that each bladder will be arcuate to some degree, the bladders need not be arcuate along their entire length nor need each bladder be arcuate so long as the bladders are “oriented” toward a node group, as described.




Having thus described the preferred embodiments of the present invention, those of skill in the art will readily appreciate that yet other embodiments may be made and used within the scope of the claims hereto attached.



Claims
  • 1. A lymphedema treatment apparatus adapted for placement on a trunk of a human body for mechanical stimulation of the lymphatic system, said apparatus comprising a wrap sized and configured to fit around a portion of the trunk of a human body, said wrap having a plurality of compartments wherein each particular one of said plurality of compartments receives and holds a bladder, each of the bladders and compartments having arcuate sides and being contiguously and sequentially arranged and aligned with said arcuate sides in adjoining side-by-side relation progressing radially outward from a predetermined point on the wrap that corresponds to a location of a preselected lymph node group on the trunk of the human body, pump means in fluid communication with each of said bladders for selectively pressurizing the bladders to a therapeutic pressure and to be depressurized so as to cause contraction of lymph collectors sufficient to move pooled fluids by promoting reabsorption of said pooled fluids within surrounding tissue.
  • 2. An apparatus according to claim 1 wherein said pumping means being in fluid communication with each particular one of the plurality of bladders to sequentially pressurize and depressurize each particular one of the plurality of bladders.
  • 3. An apparatus according to claim 1 wherein said means inflates each particular one of said plurality of bladders to engage the trunk of a human body at a said therapeutic pressure measured between said plurality of bladders and the trunk being between about 20 mmHg and 45 mmHg.
  • 4. An apparatus according to claim 1 wherein said pump means provides a predetermined waiting period between pressurization of a first particular one of said plurality of bladders and depressurization of said first particular one of said plurality of bladders.
  • 5. An apparatus according to claim 1 wherein said pump means inflate each particular one of said plurality of bladders is over a time period which is a predetermined minimum pressurization time period.
  • 6. An apparatus according to claim 5 wherein said pump means controls each particular one of said plurality of bladders is to be depressurized over a time period which is a predetermined minimum depressurization time period.
  • 7. An apparatus according to claim 6 wherein each particular one of said plurality of bladders has a diameter from 0.5″ to 2.0″ and is pressurized to a maximum inflation pressure of about 255 mmHg.
  • 8. An apparatus according to claim 6 wherein each particular one of said plurality of bladders is an elastic tube.
US Referenced Citations (16)
Number Name Date Kind
1147560 Shurtleff Jul 1915
1608239 Rosett Nov 1926
2345073 Rosett Mar 1944
2361242 Rosett Oct 1944
3880149 Kawaguchi Apr 1975
4057046 Kawaguchi Nov 1977
4552132 Ruscigno Nov 1985
4573453 Tissot Mar 1986
4753226 Zheng et al. Jun 1988
4762121 Shienfeld Aug 1988
5014681 Neeman et al. May 1991
5031604 Dye Jul 1991
5052377 Frajdenrajch Oct 1991
5437610 Cariapa et al. Aug 1995
5453081 Hansen Sep 1995
5496262 Johnson, Jr. et al. Mar 1996
Foreign Referenced Citations (1)
Number Date Country
1452523 Jan 1989 SU