Personal disposable emergency breathing system with radial flow

Information

  • Patent Grant
  • 6761162
  • Patent Number
    6,761,162
  • Date Filed
    Monday, December 23, 2002
    22 years ago
  • Date Issued
    Tuesday, July 13, 2004
    20 years ago
Abstract
The breathing system includes an annular filtration unit having apertures opening radially through inner and outer walls thereof, a central passageway and filtration material between the walls. The filtration unit is disposed in a canister containing a hood, a mouthpiece, a closure and an annular filter in the annular space between the filtration unit and the wall of the canister. Upon removal of the closure, the hood and mouthpieces are deployed and the hood is drawn about an individual's head through an opening in the hood. With the mouthpiece in the individual's mouth, ambient air from a toxic gas or smoke-filled environment is drawn into the canister through the annular filter, and passes radially inwardly through the filtration unit into the central passageway, where the filtered air reverses direction for flow axially into the mouthpiece such that the individual may breathe filtered air. Exhaled air passes into the hood and out through the hood opening.
Description




BACKGROUND OF THE INVENTION




The present invention relates to a compact, self-contained, low-cost, integrated, disposable and personal emergency breathing system for breathing filtered air in toxic gas or smoke-filled environments.




Personal breathing systems for use in emergency situations, for example, in toxic gas or smoke-filled environments, have been designed and constructed in the past. For example, in each of my prior U.S. Pat. Nos. 5,186,165 and 5,315,987, the disclosures of which are incorporated by reference, there is provided a canister containing a filtration unit, a hood, and a mouthpiece, the canister also including a closure for containing the hood, mouthpiece and filtration unit within the canister in an unused but ready-for-use condition. Upon removal of the closure and deployment of the mouthpiece and hood from the canister, the individual may don the hood by pulling the hood over the individual's head and locate the deployed mouthpiece in his/her mouth. The canister remains attached to the mouthpiece and hood and is supported by the individual by the mouthpiece. By breathing filtered air, the individual may escape from the toxic gas or smoke-filled environment.




In one form, a tab is removable from the bottom of the canister to expose apertures to ambient air whereby ambient air is supplied to the filtration unit and filtered air is provided to the individual for breathing through the mouthpiece. In another form, the removal of the closure not only permits deployment of the hood and mouthpiece but also exposes an inlet into the canister so that ambient but toxic gas or smoke-filled air is passed axially through the filtration unit so that the individual can breathe filtered air. Canisters of this type have been eminently successful and have enabled individuals to escape environments filled with smoke or toxic gases.




BRIEF DESCRIPTION OF THE INVENTION




In accordance with a preferred embodiment of the present invention, there is provided a similar type of personal compact breathing system, including a canister containing a filtration unit, a hood and a mouthpiece wherein the filtration unit is specifically configured to have an increased mass of filtration material and a reduced pressure drop. As in the prior systems, the hood and mouthpiece are deployable from the canister upon removal of the closure. In accordance with an aspect of the present invention, however, the filtration unit is provided in an annular configuration. The annular filtration unit defines with the interior walls of the canister an annular passage about the filtration unit. The inner and outer walls of the filtration unit have apertures for passing ambient air received within the annular passage about the filtration unit in a direction generally radially inwardly of and through the filtration unit. The filtration unit also includes a central passageway for directing the filtered breathable air axially away from the filtration unit and into the mouthpiece.




Additionally, the annular passage about the filtration unit includes an annular filter in communication with an air inlet into the canister. Particularly, and in a preferred embodiment, the air inlet is exposed to receive ambient air upon removal of the closure. The filter in the annular passage is closed at one end and open at its opposite end to receive the ambient air from the air inlet whereby air passes through the filter for passage radially inwardly through the filtration unit and into the central passageway. The filtration unit also includes interior linings along the inner and outer walls to confine the particulate material of the filter and any fines of, for example, activated charcoal, within the annular unit.




The end of the filtration unit adjacent the lower end of the canister includes a cap and annular resilient material along an inside surface of the cap facing and in registration with the particulate material in the filtration unit. The resilient material maintains the particulate material in a compacted or compressed condition within the filtration unit, avoiding settling. Also, an annular rib or rim is carried by the end cap as well as by an annular ring of the opposite end of the filtration unit to preclude channeling or air bypass about the filtration material.




In a further embodiment of the present invention, a monolith filter is provided for converting carbon monoxide to carbon dioxide by a catalyzation process. The monolith filter overlies the upper annular end of the filtration unit and defines an annular plenum therewith. The tube defining the central passage terminates below the monolith filter and above the end of the annular filtration unit to define an annular plenum. As a consequence, filtered air from the first filter passes through the disk-like monolith filter from the plenum and from the central tube. The monolith filter is a ceramic substrate dipped in precious metals, such as palladium or platinum.




In a preferred embodiment according to the present invention, there is provided a personal emergency breathing system comprising a canister having an opening and a closure removably carried by the canister for closing the opening, a generally annular air filtration unit within the canister containing air filtering material and defining with the canister an annular passage about the filtration unit for receiving ambient air from an air inlet to the canister, the filtration unit having an axially extending central passageway and inner and outer walls with apertures enabling transmission of ambient air in a generally radial direction from the annular passageway through the walls and filtering material and into the central passageway, a mouthpiece carried by the canister in communication with the central passageway for receiving filtered air from the central passageway and deployable from the canister, a hood carried by the canister enveloping the mouthpiece and deployable from the canister, the hood having an opening for receiving an individual's head and neck whereby the hood, when deployed from the canister, may envelop an individual's head, the mouthpiece and the hood being disposed in a collapsed condition in the canister adjacent the canister opening and between the filtration unit and the closure whereby, upon removal of the closure from the opening, the hood and the mouthpiece are deployable from the canister through the canister opening to a location external to the canister, with the mouthpiece in communication with and receiving filtered air from the filtration unit.




In a further preferred embodiment according to the present invention, there is provided a personal emergency breathing system comprising a canister having an opening and a closure removably carried by the canister for closing the opening, a generally annular air filtration unit within the canister containing air filtering material and defining with the canister an annular passage about the filtration unit for receiving ambient air from an air inlet to the canister, the filtration unit having an axially extending central passageway and inner and outer walls with apertures enabling transmission of ambient air in a generally radial direction from the annular passageway through the walls and filtering material and into the central passageway, a plenum in the canister for receiving the filtered air from the central passageway, a secondary filter for receiving the filtered air from the plenum and further filtering the air, a mouthpiece carried by the canister in communication with the secondary passageway for receiving the further filtered air and deployable from the canister, a hood carried by the canister enveloping the mouthpiece and deployable from the canister, the hood having an opening for receiving an individual's head and neck whereby the hood, when deployed from the canister, may envelop an individual's head, the mouthpiece and the hood being disposed in a collapsed condition in the canister adjacent the canister opening and between the filtration unit and the closure whereby, upon removal of the closure from the opening, the hood and the mouthpiece are deployable from the canister through the canister opening to a location external to the canister, with the mouthpiece in communication with and receiving the further filtered air.











BRIEF DESCRIPTION OF THE DRAWINGS





FIG. 1

is a side elevational view of a personal disposable emergency breathing system according to a preferred embodiment of the present invention and illustrates a canister containing various elements of the system prior to use;





FIG. 2

is a schematic side elevational view of the breathing system hereof in use by an individual;





FIG. 3

is a fragmentary enlarged cross-sectional view of the breathing system hereof through the canister when the mouthpiece and hood are deployed;





FIG. 4

is a perspective view of various component parts forming the present system;





FIG. 5

is an enlarged cross-sectional view of the canister with parts broken out and in cross-section for ease of illustration; and





FIG. 6

is a view similar to

FIG. 3

illustrating an annular filtration unit in combination with a monolithic filter within the canister.











DETAILED DESCRIPTION OF THE INVENTION




Referring now to the drawings, particularly to

FIG. 1

, there is illustrated a personal disposable emergency breathing system, generally designated


10


, constructed in accordance with the present invention. The breathing system


10


, as illustrated in

FIG. 1

, is in a stored condition prior to use. The system


10


includes a canister


12


having a canister body


14


, an intermediate ring


16


and a closure


18


. As in my prior patents noted above, the canister is preferably formed of a flame-retardant plastic material such as PC and is preferably closed at its lower end.




The breathing system


10


is illustrated in use in FIG.


2


. Particularly, the canister body


14


contains a hood


20


and a mouthpiece


22


which, upon removal of closure


18


, are deployed from the canister, as illustrated. The mouthpiece


22


also includes nose clips


24


. The hood


20


includes an opening bounded by a closing means, e.g., a drawstring, drawtape, elastic or rubber seal


26


by which the individual can don the hood over his head with the drawstring


26


forming a loose collar about the individual's neck, permitting air exhaled into the hood to egress from the hood. The hood


20


is preferably transparent and is preferably constructed of Kapton® and preferably includes a titanium coating, for example, as described and illustrated in U.S. Pat. No. 5,113,527, incorporated herein by reference.




Referring now to

FIG. 3

, the canister body


14


is generally cylindrical and preferably closed at its lower end. An interior ring


32


having external interrupted threads secures the intermediate ring


16


and the body


14


one to the other. The interior ring


32


has a plurality of circumferentially spaced openings


34


for admitting ambient air into the canister, as explained below.




A filtration unit


36


in the form of an annulus is disposed within the body


14


. The filtration unit


36


is elongated in an axial direction and has inner and outer walls


38


and


39


, respectively, spaced radially from one another. The inner and outer walls


38


and


39


, respectively, of the filtration unit


36


have a plurality of apertures


40


and


42


, respectively, through which air is passed in a generally radial direction. The apertures are preferably rectilinear-shaped slots to maximize air passage and to minimize pressure drop. The interior surfaces of the inner and outer walls


38


and


39


, respectively, are provided with linings


46


and


48


, respectively, formed of a flexible porous material. Within the lining and filling the annulus between the inner and outer walls of the filtration unit is particulate filtering material


50


. The material


50


may, for example, comprise activated charcoal particles. An annular ring


52


. is threaded between the inner and outer walls at the upper end of the filtration unit


36


to maintain the particulate material in the filtration unit annulus. The lower end of the filtration unit includes a cap


54


which is screwthreaded onto the lower end of the filtration unit. In a preferred embodiment, the cap


54


along its inner surface may include an upwardly projecting annular rib


56


. An annular rib


57


also projects downwardly into the filtration material from the annular ring


52


at the upper end of the filtration unit. Ribs


56


and


57


preclude channeling or bypass of the air as the air flows radially inwardly to the central passage.




As illustrated in

FIG. 3

, the inner wall


38


of the annular filtration unit


36


comprises a central passageway


57


which receives filtered air flowing radially inwardly through the outer and inner walls


39


and


38


, respectively, the liners


46


and


48


and the particulate material


50


of the filtration unit for flow axially into the mouthpiece


22


.




From a review of

FIG. 3

, it will be appreciated that the outer walls


39


of the filtration unit


36


are radially spaced from the interior surfaces of the canister defining an annular passageway


58


in communication with the ambient air inlets


34


. An annular flexible filter


60


is received within the annular space between the canister wall and the outer wall of the filtration unit. The annular filter


60


may comprise a HEPA filter having 99.97 efficiency down to 0.3 microns or an N95 filter having 95% efficiency down to 0.5 microns or any type of similar filter suitable to a particular application. The filter


60


is formed of a flexible material open at an annular upper end and closed at its lower end, forming an annular envelope for receiving the ambient air from inlet apertures


34


. The upper margins of the annular filter


60


may be secured between the interior ring


32


and the outer wall of the canister and between the interior of the securing ring and the filtration unit. Thus, ambient air flowing into the annular passageway


58


between the filtration unit outer wall and the canister wall first passes through the envelope formed by the annular filter


60


.




Referring to

FIGS. 3 and 4

, the mouthpiece


22


forms part of a plenum


70


connected at a large diameter end to the interior ring


32


and in communication with the central passage


57


for receiving the filtered air. The mouthpiece


22


includes bite wings


72


for gripping the mouthpiece between the individual's teeth and inhalation and exhalation check valves


74


and


76


, respectively, adjacent the smaller diameter end of the plenum


70


.




To use the system hereof, it will be appreciated that the filtration unit, mouthpiece and hood are stored within the canister, with the closure secured to the canister whereby the canister is effectively sealed and ready for use. The hood and mouthpiece are collapsed in this stored condition within the canister and between the filtration unit and the closure. Upon recognition that an individual requires an emergency breathing system, for example, should the individual be in a smoke-filled or toxic gas environment, the individual removes the closure


18


, enabling the hood


20


and the mouthpiece


22


to be deployed from the canister. The individual then places the hood


20


over his/her head and tightens the closing means, e.g., drawstring


26


, about the neck to form an imperfect but comfortable seal. The individual grasps the mouthpiece in his/her mouth by biting down on the bite wings and applies the nose clips to his/her nose. It will be appreciated that by removing the closure


18


, the inlet openings


34


are exposed to the ambient air, including the smoke and toxic gases.




Upon inspiration, the ambient toxic gas and/or smoke-filled air flows through the annular filter


60


for a first filtering and then flows radially inwardly from the annular space between the canister wall and the outer wall


39


of the air filtration unit, through the apertures


42


, outer filter liner


48


and particulate filtering material


50


. The air continues to flow radially through the interior filter liner


46


and the apertures


40


along the interior wall


38


of the filtration unit


36


until the filtered air flows into the central passageway


57


. The filtered air then changes direction and flows axially along passageway


57


into the plenum


70


, through the one-way inhalation check valve


74


such that the individual may breathe filtered air. Upon exhalation through the individual's mouth, the inlet check valve


74


closes, preventing exhaled air from returning to the filtration unit


36


, while the exhalation check valves


72


open, enabling the exhaled air to flow from the mouthpiece into the interior of the hood


20


about the individual's head. Since the exhaled air will create an over-pressure condition within the hood


20


, the exhaled air leaks past the imperfect/comfortable seal formed by the opening in the hood about the individual's neck.




Note that a pair of filters generally in annular shape, i.e., the annular filter


60


and the annular filtration unit


36


are utilized. Note also that an increase in the mass of filtering particulate mass combined with a significant increase in effective surface area is achieved, with a resulting decrease in pressure drop by employing a radial flow system as compared with straight axial flow filtering elements as in the two prior patents noted above. This is highly beneficial, as it facilitates breathing by the individual, while simultaneously affording necessary filtered air.




Referring now to

FIG. 6

, like reference numerals are applied to like parts as in the prior embodiment. Here, however, separate axial flow filter


80


may be provided above the air filtration unit


36


in communication with the central passageway


58


. The filter comprises a monolithic filter


80


for converting carbon monoxide to carbon dioxide by a catalyzation process. The axial flow filter


80


comprises a monolith filter in the form of a disk disposed above the filtration unit


36


. Preferably, the cap


82


at the upper end of the filtration unit


36


is funnel-shaped to define with the lower end of the disk-shaped monolith filter


80


a plenum


84


. The upper end of the central tube defining the axial passage through the filtration unit


36


terminates short of the lower face of the monolith filter disk


80


and in a further filter screening element


86


. In the preferred embodiment, the filter element


80


is maintained within the filtration unit by a friction fit, including an O-ring


88


between the outer margin of the filter


80


and the interior wall of the filtration unit. As a consequence of this construction, the filtered air from the initial filtration unit


36


flows into plenum


84


where it passes axially through the monolithic filter, converting carbon monoxide to carbon dioxide by a catalyzation process. This design provides a unit which will protect against NBC gases and fire gases including CO. There may also be a further stage in the axial flow passageway


58


, for example, a lithium peroxide filter for converting carbon dioxide to oxygen.




While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.



Claims
  • 1. A personal emergency breathing system comprising:a canister having an opening and a closure removably carried by said canister for closing said opening; a generally annular air filtration unit within said canister containing air filtering material and defining with said canister an annular passage about said filtration unit for receiving ambient air from an air inlet to said canister, said filtration unit having an axially extending central passageway and inner and outer walls with apertures enabling transmission of ambient air in a generally radial direction from the annular passageway through the walls and filtering material and into the central passageway; an annular filter in said annular passage in communication with said air inlet for receiving and filtering ambient air for flow into said annular passage; a mouthpiece carried by said canister in communication with said central passageway for receiving filtered air from said central passageway and deployable from said canister; a hood carried by said canister enveloping said mouthpiece and deployable from said canister, said hood having an opening for receiving an individual's head and neck whereby the hood, when deployed from said canister, may envelop an individual's head, said mouthpiece and said hood being disposed in a collapsed condition in said canister adjacent said canister opening and between said filtration unit and said closure whereby, upon removal of said closure from said opening, said hood and said mouthpiece are deployable from said canister through said canister opening to a location external to said canister, with said mouthpiece in communication with and receiving filtered air from the filtration unit.
  • 2. A system according to claim 1 wherein said air inlet lies in communication with said canister opening for receiving ambient air upon removal of the closure.
  • 3. A system according to claim 2 wherein said annular filter in said annular passage includes inner and outer wall portions formed of filtration material, said inner and outer wall portions defining an opening at one end of said filter for communication with said air inlet and said annular filter being closed at an opposite end thereof, enabling flow of ambient air from said air inlet into said filter between said wall portions for flow into said annular passage.
  • 4. A system according to claim 1 wherein said air filtration unit includes a closure cap at one end thereof, said cap having resilient material along an inside face thereof for maintaining said filtering material within said filtration unit in a compressed condition.
  • 5. A system according to claim 1 wherein said air filtration unit includes porous liners comprising a filtering medium on inside surfaces of said inner and outer walls and confining the filtering material within said annular filtration unit.
  • 6. A system according to claim 1 wherein said filtering material includes activated charcoal said annular filtration unit having closures at opposite ends with at least one closure having a rib protecting in an axial direction into the filtering material to preclude or minimize bypass of the filtering material by the air flowing into the central passageway.
  • 7. A system according to claim 1 wherein said filtering material includes a catalyst for catalyzation of CO to CO2.
  • 8. A system according to claim 1 including a plenum between said mouthpiece and said filtration unit, first and second check valves disposed in said plenum, said first check valve enabling flow of filtered air from said filtration unit into said mouthpiece and preventing backflow of exhaled air into said filtration unit, said second check valve enabling air exhaled into said mouthpiece to flow into said hood and preventing backflow of air from said hood through said second check valve into said plenum.
  • 9. A personal emergency breathing system comprising:a canister having an opening and a closure removably carried by said canister for closing said opening; a generally annular air filtration unit within said canister containing air filtering material and defining with said canister an annular passage about said filtration unit for receiving ambient air from an air inlet to said canister, said filtration unit having an axially extending central passageway and inner and outer walls with apertures enabling transmission of ambient air in a generally radial direction from the annular passageway through the walls and filtering material and into the central passageway; a mouthpiece carried by said canister in communication with said central passageway for receiving filtered air from said central passageway and deployable from said canister; a hood carried by said canister enveloping said mouthpiece and deployable from said canister, said hood having an opening for receiving an individual's head and neck whereby the hood, when deployed from said canister, may envelop an individual's head, said mouthpiece and said hood being disposed in a collapsed condition in said canister adjacent said canister opening and between said filtration unit and said closure whereby, upon removal of said closure from said opening, said hood and said mouthpiece are deployable from said canister through said canister opening to a location external to said canister, with said mouthpiece in communication with and receiving filtered air from the filtration unit; an annular filter in said annular passage in communication with said air inlet for receiving and filtering ambient air for flow into said annular passage: said air inlet lying in communication with said canister opening for receiving ambient air upon removal of the closure; said annular filter including inner and outer wall portions formed of filtration material, said inner and outer wall portions being open at one end of said filter for communication with said air inlet and closed at an opposite end of the filter, enabling flow of ambient air from said air inlet into said filter between said wall portions for flow into said annular passage; and a mounting ring adjacent said opening having at least one aperture for receiving ambient air from said canister opening and passing the ambient air into said annular filter through said open one end thereof, said filter being secured in said canister by said ring.
  • 10. A personal emergency breathing system comprising:a canister having an opening and a closure removably carried by said canister for closing said opening; a generally annular air filtration unit within said canister containing air filtering material and defining with said canister an annular passage about said filtration unit for receiving ambient air from an air inlet to said canister, said filtration unit having an axially extending central passageway and inner and outer walls with apertures enabling transmission of ambient air in a generally radial direction from the annular passageway through the walls and filtering material and into the central passageway; a mouthpiece carried by said canister in communication with said central passageway for receiving filtered air from said central passageway and deployable from said canister; a hood carried by said canister enveloping said mouthpiece and deployable from said canister, said hood having an opening for receiving an individual's head and neck whereby the hood, when deployed from said canister, may envelop an individual's head, said mouthpiece and said hood being disposed in a collapsed condition in said canister adjacent said canister opening and between said filtration unit and said closure whereby, upon removal of said closure from said opening, said hood and said mouthpiece are deployable from said canister through said canister opening to a location external to said canister, with said mouthpiece in communication with and receiving filtered air from the filtration unit; and a second annular filtration unit within said canister, said second unit being disposed between said filtration unit and said mouthpiece for receiving filtered air from the central passageway.
  • 11. A personal emergency breathing system comprising:a canister having an opening and a closure removably carried by said canister for closing said opening; a generally annular air filtration unit within said canister containing air filtering material and defining with said canister an annular passage about said filtration unit for receiving ambient air from an air inlet to said canister, said filtration unit having an axially extending central passageway and inner and outer walls with apertures enabling transmission of ambient air in a generally radial direction from the annular passageway through the walls and filtering material and into the central passageway; a plenum in said canister for receiving the filtered air from said central passageway; a secondary filter for receiving the filtered air from said plenum and further filtering the air; a mouthpiece carried by said canister in communication with said secondary passageway for receiving the further filtered air and deployable from said canister; a hood carried by said canister enveloping said mouthpiece and deployable from said canister, said hood having an opening for receiving an individual's head and neck whereby the hood, when deployed from said canister, may envelop an individual's head, said mouthpiece and said hood being disposed in a collapsed condition in said canister adjacent said canister opening and between said filtration unit and said closure whereby, upon removal of said closure from said opening, said hood and said mouthpiece are deployable from said canister through said canister opening to a location external to said canister, with said mouthpiece in communication with and receiving the further filtered air.
  • 12. A system according to claim 11 including an annular filter in said annular passage in communication with said air inlet for receiving and filtering ambient air for flow into said annular passage.
  • 13. A system according to claim 12 wherein said air inlet lies in communication with said canister opening for receiving ambient air upon removal of the closure.
  • 14. A system according to claim 13 wherein said annular filter includes inner and outer wall portions formed of filtration material, said inner and outer wall portions being open at one end of said filter for communication with said air inlet and closed at an opposite end of the filter, enabling flow of ambient air from said air inlet into said filter between said wall portions for flow into said annular passage.
  • 15. A system according to claim 14 including a mounting ring adjacent said opening having at least one aperture for receiving ambient air from said canister opening and passing the ambient air into said annular filter through said open one end thereof, said filter being secured in said canister by said ring.
  • 16. A system according to claim 11 wherein said air filtration unit includes a closure cap at one end thereof, said cap having resilient material along an inside face thereof for maintaining said filtered material within said filtration unit in a compressed condition.
  • 17. A system according to claim 11 wherein said air filtration unit includes porous liners comprising a fines filtering medium on inside surfaces of said inner and outer walls and confining the filtering material within said annular filtration unit.
  • 18. A system according to claim 11 wherein said secondary filter includes a catalyst for catalyzation of CO to CO2.
  • 19. A system according to claim 11 including a second plenum between said mouthpiece and said secondary filter, first and second check valves disposed in said plenum, said first check valve enabling flow of the further filtered air into said mouthpiece and preventing backflow of exhaled air into said secondary filter, said second check valve enabling air exhaled into said mouthpiece for flow into said hood and preventing backflow of air from said hood through said second check valve into said second plenum.
US Referenced Citations (44)
Number Name Date Kind
492980 Coquy Mar 1893 A
703948 Muntz Jul 1902 A
807666 Drager Dec 1905 A
1298404 Romanoff Mar 1919 A
1474205 Mase Nov 1923 A
1501286 Logan Jul 1924 A
1585113 Robert May 1926 A
1889015 Davis Nov 1932 A
1929343 Belloni Oct 1933 A
1931989 Jenness Oct 1933 A
2048059 Giraudet DeBoudemanage Jul 1936 A
2174528 Prentiss Oct 1939 A
3140590 Gleuckler Jul 1964 A
3277890 Warncke Oct 1966 A
3338238 Warneck Aug 1967 A
3525334 Braman Aug 1970 A
3565068 Bickford Feb 1971 A
3731678 Pyzel May 1973 A
3736927 Misaqi Jun 1973 A
3976063 Henneman et al. Aug 1976 A
4154235 Warncke May 1979 A
4277443 Van der Smissen et al. Jul 1981 A
4350507 Greenough et al. Sep 1982 A
4467795 Eckstein Aug 1984 A
4552140 Cowley et al. Nov 1985 A
4572178 Takase et al. Feb 1986 A
4614186 John Sep 1986 A
4764346 Lewis et al. Aug 1988 A
5003974 Mou Apr 1991 A
5036844 Pouchot et al. Aug 1991 A
5038768 McGoff et al. Aug 1991 A
5113527 Robertson-McKenzie May 1992 A
5186165 Swann Feb 1993 A
5222479 Brauer et al. Jun 1993 A
5315987 Swann May 1994 A
5394867 Swann Mar 1995 A
5524616 Smith et al. Jun 1996 A
5526804 Ottestad Jun 1996 A
5640952 Swann et al. Jun 1997 A
5848592 Sibley Dec 1998 A
5964218 Smith et al. Oct 1999 A
5964221 McKenna Oct 1999 A
5996580 Swann Dec 1999 A
6041778 Swann et al. Mar 2000 A