1. Field of the Invention
The present invention relates to conduits for the delivery of gases, and in particular to conduits for the delivery of gases to patients in a medical environment.
2. Summary of the Prior Art
Many methods are known in the art for supplying humidified gases to a patient requiring breathing assistance. It is known in the art to provide a heater to minimise condensation on the internal surfaces of the conduit. In that regard it is known to provide a plain or coiled heater wire within the lumen of the conduit, such an embodiment being illustrated in for example U.S. Pat. No. 6,078,730. In this case the heater wire is disposed within the gases flow and maintain the temperature of the gases flow to reduce condensation. It is also known to provide a heater wire on the conduit, for example disposed helically on the outer wall of the conduit as in U.S. Pat. No. 5,454,061. This heats the conduit wall, to in turn heat the gases flowing through the lumen of the conduit.
While these heated wall conduits are reasonably effective there is still room for improvement. Furthermore, the forming method involves winding the conduit from a thin narrow tape applied to a mandrel with adjacent turns overlapping. This forming method is comparatively slow, making these conduits expensive to manufacture.
It is therefore an object of the present invention to provide a gases conduit which goes some way to overcoming the above mentioned disadvantages, or which will at least provide a useful choice.
In a first aspect the invention consists in a gases delivery conduit for the supply of humidified medical gases, said conduit comprising:
Preferably the cross sectional profile of said extruded plastic tube includes inwardly extending ribs on its inner surface, such that total collapse or total occlusion is not possible during bending.
Preferably the heating element is embedded within the inwardly extending internal ribs of the tube.
Said heating element may be an elongate flattened tape at least as long as the tube, and having a width and a thickness, with said width being greater than said thickness.
Said tape may include a said conductor disposed along each of a pair of side edges, with a web of said PTC material spanning between said conductors.
Alternatively said tape may include an elongate flattened ribbon of said PTC material with a first face and a second face, a said conductor is distributed over said first face, and another said conductor is distributed over said second face.
Preferably the heating element is spiralled or braided within the tube wall.
Preferably said conduit includes a connector at each end, at least one said connector having one or more electrical contacts contacting and connecting with one or more of the conductors of said heating elements, said connector having an external connection interface and an electrical connection between each said contact and said external connection interface.
Preferably said connector with said external connection interface has a gases port configured to make a connection with a mating gases port in a first direction, and said connection interface is configured to make connection with a mating connection interface also in said first direction.
Preferably said positive temperature coefficient material has a phase transformation temperature between 28° C. and 45° C.
In a further aspect the present invention consists in a method of manufacturing a conduit for the supply of humidified medical gases comprising:
Preferably said method includes spiralling the heating elements within the tube wall by twisting the extruded tube during forming.
Alternatively said method includes moving the points where the heating elements enter the melt of the extruded tube to spiral or braid the heating elements within the tube wall.
Preferably said method includes in a continuous process:
Preferably said method includes the further steps of:
Preferably said method includes between steps (a) and (b), the further step of:
In a yet further aspect the invention consists in a method of terminating an extruded plastic tube with an embedded heating element, the heating element including a pair of electrical conductors separated by a positive temperature coefficient (“PTC”) material wherein the localised resistance of said material is positively related to the localised temperature, the method comprising the steps of:
Preferably said method includes between steps (a) and (b), the further step of: bending back one of the exposed conductors of said heating element over the untrimmed section of said tube;
To those skilled in the art to which the invention relates, many changes in construction and widely differing embodiments and applications of the invention will suggest themselves without departing from the scope of the invention as defined in the appended claims. The disclosures and the descriptions herein are purely illustrative and are not intended to be in any sense limiting.
The present invention provides a conduit with heating elements embedded within the tubing walls.
Referring to
Although
A conduit in this embodiment enables the gases flowing through the centre 5 of the conduit to be heated, maintaining an appropriate moisture content and temperature. Furthermore, the ribs 2 provide the added advantage that if the conduit is pressed, crushed or bent the ribs prevent total occlusion of the conduit.
The heater element of the present invention is formed including a positive temperature coefficient (PTC) material.
The resistance of a PTC material increases markedly once it reaches a threshold temperature, resulting in reduced power consumption and subsequent cooling. The delivery tube may pass through more than one environment, or may have localised drafts present on certain parts of the tube.
In the present invention the PTC heater is provided as an elongate structure embedded in the wall of the delivery tube. The construction of the PTC heater according to one embodiment is illustrated in to
The tape may be provided in the tube wall as lengths of tape blindly terminated at one end and terminated with a power connector at the other end. The blind termination is without connection between the conductors. Preferably it is simply that the ribbon is cut off where the conduit is cut off.
Where multiple lengths of tape are provided in the tube wall the power connector connects the first terminal with one wire of each ribbon and a second terminal with the other wire of each ribbon.
With the pair of conductors provided along opposite edges of the ribbon the PTC material offers an amorphous array of parallel current paths along the entire length of the ribbon. Where the conduit temperature is lower the heater structure will have a lower resistance and more current will flow producing a greater heater effect. Where the conduit temperature is higher the PTC material will have a higher resistance, choking off current flow and reducing heating in that region of the conduit.
Referring now to
The laminate may be formed in wide sheets, rolled up and cut into narrow rolls of tape.
Alternatively the laminated tape may be formed directly in its narrow state. In the preferred form the conductive layers 104, 105 are thin and narrow sections or sheets of copper, copper alloy or other appropriate electricity conducting material.
With reference to
An additional embodiment of the present invention is illustrated in
A method of extruding a tube according to the present invention is described with reference to
Referring to
Rather than embedding wires into the molten outer surface of the conduit, the conduit may be extruded sequentially as a series of layers with the wires provided on the outer surface of a layer before the next outward layer is extruded over them. In this way elements may be provided over an extruded inner tube layer using a rotating braider through which the extruded tube layer is passed longitudinally. An outer tube layer is subsequently extruded over the inner tube and elements. An example of a resulting product is shown in
In the case of braiding heating elements will pass over and contact one another within the tube wall. Therefor it is necessary to guard against short-circuiting between heating elements. For example this method is more appropriate for the heating element of
Instead a conduit may be formed with separate spool carrying heads forming the spirals of each direction without any provision for the weaving effect produced by a braiding head. These heads may be provided with a cross head extruder between them providing an intervening layer of electrically insulating plastic material. A conduit in this way is illustrated in
The tube according to the present invention may be terminated as appropriate to allow electrical connection of the element conductors as necessary according to the form of heating element used.
One preferred method of termination is illustrated by the sequence of
A connector 85 is configured to fit over the trimmed and prepared end of conduit 80. The connector 85 has an open passage therethrough The open passage includes a gases port connection opening 86 at one end and a stepped cavity 87 at the other end. The stepped cavity 87 has inwardly facing cylindrical surfaces 88 and 89. Cylindrical surface 88 is of larger diameter than cylindrical surface 89. Surface 88 is sized to provide a slight interference fit over the outer most conductors 81 (turned back over the outside of conduit 80). The inner cylindrical surface 89 is sized to provide a slight interference fit over the exposed conductors 83 adjacent inner portion 84 of conduit 80. A first contact is provided embedded in the cylindrical surface 88 and a second contact is provided embedded in the cylindrical 89. The first contact is preferably in the form of an annular conductive ring 90 (for example of copper or other material having good surface conductivity). The second contact is preferably also an annular ring 91 of similar conductive material. The body of the connector is made from any suitable electrically insulating plastic material.
Electrical conductors are provided through the body of the connector 85 to allow an electrical connection to be made from the outside of the connector 85 to the first contact 90 and second contact 91. A conductor 92 is electrically connected to the first contact ring 90 and extends through the body of connector 85 to a connection pin 94. A conductor 93 is electrically connected with the second contact ring 91 and extends through the body of connector 85 and is electrically connected with a second pin 95. The conductors 92 and 93 may alternatively extend to be free of the body of connector 85 and be terminated for example with a plug or socket. However preferably the pins 94 and 95 are provided in an integral socket 96 on the connector 85. The socket 96 opens in the same direction as port 86. This allows for use of this particular connector in conjunction with appropriately configured gases supply equipment having a mutually configured plug portion adjacent its gases outlet port, so that electrical and pneumatic connections can be made simultaneously and in one action.
Referring to
A view of the completed terminated conduit end is provided in
It is preferred for the present invention that the PTC material is composed to provide a threshold temperature at or just above the preferred gases temperature (eg above the dew-point of the humidified gases) the PTC material will maintain itself at that threshold temperature (with some hysteresis fluctuation) and condensation on the conduit surface will be at least substantially eliminated. This provides more effective condensation control than maintaining an elevated temperature for the humidified gases where condensation may still form on the cold wall surfaces.
PTC material behaviour is exhibited in a range of polymer compositions with electrically conductive fillers. The behaviour can be characterised by a general statement that “providing certain other conditions are fulfilled, the composition becomes electrically conductive when particles of electrically conductive filler form a continuous chain, penetrating the material from the point of entry of electric current to the place where it leaves the polymer material”. Polymer compositions containing electrically conductive filler can exhibit PTC properties due to the formation of a chain of filler particles that are close enough for current to flow at a certain temperature, generating heat which increases the temperature of the material until it reaches a phase transformation temperature. At the phase transformation temperature the crystalline polymer matrix changes to an amorphous structure. This change is accompanied by a small thermal expansion, forcing filler particles to move apart, breaking the conductive paths. Accordingly resistance rises sharply at this phase transformation temperature. As the material cools the small thermal conduction allows new conductive paths to form and current flow to resume. The rise and fall in temperature and the thermal contraction and expansion provides an inherent hysteresis in the cycle.
In producing a PTC material a number of factors have a bearing on the performance of the material. Particular factors include the quantity, type and particle size of the carbon black (or other conductive filler) used in the composite, the polymer that the carbon black binds with during mixing of the base materials and the process conditions such as temperature, pressure and time of mixing. It is important that the conductive filler particles are distributed evenly through the composite so that the composite exhibits uniform PTC behaviour.
For the present invention a PTC material having a phase transformation temperature not exceeding 40° C. is desired. One composition meeting these criteria has been developed and has the following composition:
This material was uniformly mixed and extruded to form a PTC ribbon with embedded conductors using a segmented screw extruder. The composite performance showed an acceptable level of self regulation without the temperature exceeding 40° C.
Varying the amount of carbon black up or down within this composition has the effect of varying the phase transition temperature. Where delivery of humidified gases to a patient a phase transition temperature in the range 30° C. to 45° C. may be appropriate, with the particular transition temperature required depending on the particular humidified gases treatment to be delivered. For example humidified gases delivery is being promoted for the treatment of chronic obstructive pulmonary disease (COPD). Whereas treatment humidified gases are delivered to the patient, usually via a nasal cannular, at between 35 and 45° C. Therefore for treatment of COPD a PTC material having a phase transition temperature in the range 35° C. to 45° C. is preferred. Similarly humidified gases are being promoted for use in patient insufflation for surgical procedures. In this application humidified gases are delivered at a temperature between 35° C. and 40° C. and accordingly a PTC material having a phase transition temperature in this range is preferred. This is also the preferred range for the temperature of humidified gases for respiration of an intubated patient, and therefore the preferred phase transition temperature for the PTC material used in manufacturing a conduit for that purpose. However where a patient is receiving humidified respiratory gases via a face mask it has been found that a somewhat lower delivery temperature is preferable, in the range 30° C. to 35° C. Accordingly for the manufacture of conduits for delivery of respiratory gases to a patient via a face mask a PTC material phase transition temperature of 30° C. to 35° C. is preferred.
It will be appreciated the present invention provides a gases conduit for delivering humidified gases to a patient which may be formed by extrusion, it includes heating in some form to prevent or minimise the formation of condensation. The conduit may include profile features which prevent occlusion by crushing or bending. The conduit includes PTC heating elements of various forms.
Number | Date | Country | Kind |
---|---|---|---|
503495 | Mar 2000 | NZ | national |
PCT/NZ01/00226 | Oct 2001 | NZ | national |
516387 | Dec 2001 | NZ | national |
521017 | Aug 2002 | NZ | national |
This is a continuation-in-part patent application of U.S. patent application Ser. No. 09/956,723 filed on Sep. 20, 2001 (pending) which is a continuation-in-part application of U.S. patent application Ser. No. 09/808,567 (pending) filed on Mar. 14, 2001.
Number | Name | Date | Kind |
---|---|---|---|
485127 | Lynch | Oct 1892 | A |
3582968 | Buiting | Jun 1971 | A |
3584193 | Badertscher | Jun 1971 | A |
3695267 | Hirtz et al. | Oct 1972 | A |
3766914 | Jacobs | Oct 1973 | A |
3914349 | Stipanuk | Oct 1975 | A |
4013122 | Long | Mar 1977 | A |
4013742 | Lang | Mar 1977 | A |
4038980 | Fodor | Aug 1977 | A |
4060576 | Grant | Nov 1977 | A |
4110419 | Miller | Aug 1978 | A |
4172105 | Miller et al. | Oct 1979 | A |
4500480 | Cambio, Jr. | Feb 1985 | A |
4574188 | Midgley et al. | Mar 1986 | A |
4640804 | Mizoguchi | Feb 1987 | A |
4676237 | Wood et al. | Jun 1987 | A |
4684786 | Mann et al. | Aug 1987 | A |
4710887 | Ho | Dec 1987 | A |
4722334 | Blackmer et al. | Feb 1988 | A |
4753758 | Miller | Jun 1988 | A |
4780247 | Yasuda | Oct 1988 | A |
4829998 | Jackson | May 1989 | A |
4911157 | Miller | Mar 1990 | A |
4911357 | Kitamura | Mar 1990 | A |
4941469 | Adahan | Jul 1990 | A |
5031612 | Clementi | Jul 1991 | A |
5062145 | Zwaan et al. | Oct 1991 | A |
5092326 | Winn et al. | Mar 1992 | A |
5101820 | Christopher | Apr 1992 | A |
5148801 | Douwens et al. | Sep 1992 | A |
5224923 | Moffett et al. | Jul 1993 | A |
5336156 | Miller et al. | Aug 1994 | A |
5346128 | Wacker | Sep 1994 | A |
5367604 | Murray | Nov 1994 | A |
5388443 | Manaka | Feb 1995 | A |
5392770 | Clawson et al. | Feb 1995 | A |
5404729 | Matsuoka et al. | Apr 1995 | A |
5454061 | Carlson | Sep 1995 | A |
5482031 | Lambert | Jan 1996 | A |
5529060 | Salmon et al. | Jun 1996 | A |
5558084 | Daniell et al. | Sep 1996 | A |
5564415 | Dobson et al. | Oct 1996 | A |
5588423 | Smith | Dec 1996 | A |
5640951 | Huddart et al. | Jun 1997 | A |
5673687 | Dobson et al. | Oct 1997 | A |
5759149 | Goldberg et al. | Jun 1998 | A |
5769071 | Turnbull | Jun 1998 | A |
5988164 | Paluch | Nov 1999 | A |
6024694 | Goldberg et al. | Feb 2000 | A |
6050260 | Daniell et al. | Apr 2000 | A |
6078730 | Huddart et al. | Jun 2000 | A |
6095505 | Miller | Aug 2000 | A |
6125847 | Lin | Oct 2000 | A |
6158431 | Poole | Dec 2000 | A |
6311958 | Stanek | Nov 2001 | B1 |
6349722 | Gradon et al. | Feb 2002 | B1 |
6367472 | Koch | Apr 2002 | B1 |
6394084 | Nitta | May 2002 | B1 |
6397846 | Skog et al. | Jun 2002 | B1 |
6463925 | Nuckols et al. | Oct 2002 | B1 |
6474335 | Lammers | Nov 2002 | B1 |
6543412 | Amou et al. | Apr 2003 | B1 |
6564011 | Janoff et al. | May 2003 | B1 |
6694974 | George-Gradon et al. | Feb 2004 | B1 |
20020124847 | Smith et al. | Sep 2002 | A1 |
Number | Date | Country |
---|---|---|
3311811 | Oct 1983 | DE |
3311811 | Oct 1984 | DE |
3629353 | Jan 1988 | DE |
4034611 | May 1992 | DE |
94092311 | Nov 1994 | DE |
0258928 | Sep 1988 | EP |
481459 | Apr 1992 | EP |
556561 | Aug 1993 | EP |
0672430 | Sep 1995 | EP |
0885623 | Dec 1998 | EP |
1138341 | Oct 2001 | EP |
0556561 | Aug 2003 | EP |
1167551 | Oct 1969 | GB |
2277689 | Nov 1994 | GB |
0 5317428 | Dec 1993 | JP |
08061731 | Aug 1996 | JP |
0 9234247 | Sep 1997 | JP |
09234247 | Sep 1997 | JP |
379270 | Apr 1973 | SU |
WO 9826826 | Jun 1998 | WO |
WO0110489 | Feb 2001 | WO |
WO 0232486 | Apr 2002 | WO |
WO 0232486 | Apr 2003 | WO |
Number | Date | Country | |
---|---|---|---|
20030059213 A1 | Mar 2003 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 09956723 | Sep 2001 | US |
Child | 10270805 | US | |
Parent | 09808567 | Mar 2001 | US |
Child | 09956723 | US |