Method for manufacturing artificial heart valve cusp

FIELD: medical engineering.

SUBSTANCE: method involves precipitating pyrocarbon layer on graphite substrate surface by carrying out carbonaceous gas from gas flow in flow reactor, separating pyrocarbon layer from the substrate and mechanically manufacturing cusp with paired supporting projections. Constant graphite substrate orientation is provided with relative to gas flow direction in the reactor during the whole pyrocarbon layer sedimentation process. The paired supporting projections are arranged in a way that their imaginary axis remains coinciding with carbonaceous gas flow direction when precipitating pyrocarbon layer. Graphite substrates are mainly shaped as plates placed into flow reactor along its lateral walls without spaces available between them. Six and more plates are placed into the reactor. The most convenient carbon compound for producing pyrocarbon by decomposition is methane. Propane and trichloroboron availability in gas flow is desirable. Additional inert carrier gas like nitrogen is available in the gas flow in addition to active ingredients. Pyrocarbon sedimentation and its final characteristics are controlled by varying nitrogen and active substances proportion in the gas flow.

EFFECT: high reliability of design.

3 cl, 2 dwg

 

The invention relates to medical equipment and can be used in the manufacture of artificial heart valves.

Artificial heart valves can contain one, two or more folds of pyrocarbon or other material with a pair of protrusions for attaching to the valve body. When the valve on the tabs have the greatest mechanical load.

A known method of manufacturing a sash artificial heart valve made of titanium alloy with a coating of pyrocarbon (patent RU №2012284, 1994). However, the shutter of the two-layer material does not have sufficient reliability for continuous operation. In addition, when placing the tabs fold in nests housing having problems with friction "metal on metal".

Also known is a method of obtaining pyrocarbon layer of a controlled thickness on the substrate surface of graphite by deposition by decomposition of carbon compounds from the gas stream in the flow reactor and subsequent separation of the layer of pyrocarbon from the substrate (US patent No. 6274191, 2001). Deposition of pyrocarbon on the substrate produced in the fluidized bed mode, when the substrate is suspended in a disordered position that provides the isotropy of the properties of obtained pyrocarbon.

However, it is found experimentally that the pyrocarbon material mo is ut to have some degree of anisotropy. When this strength characteristics, in particular the tensile strength in bending, the highest values reached in samples obtained from pyrolysis in the direction of the gas flow at a fixed position of these samples relative to the gas stream. Tensile strength Flexural strength in the direction along the gas flow at the specimens thus obtained is 20% greater than the tensile strength of samples obtained in the absence of a specific orientation of the substrate relative to the directed gas flow, and 30% greater than the tensile strength of the samples located in the direction across the gas stream.

The technical result of the invention is to improve reliability, design of an artificial heart valve in the most loaded areas. To do this, in the manufacture of the valves of the pyrocarbon material an imaginary axis connecting the pair of protrusions must be so, to coincide with the axis of the gas stream from which it was formed (deposited) pyrocarbon layer.

The invention consists in that for the manufacture of the valves used monolithic pyrocarbon material obtained by decomposition in vacuum, gaseous hydrocarbons or other carbon substances in the presence of a heated substrate, which will be produced by deposition, p and that the gas flow has a strong direction along the substrate and the rate of deposition of pyrocarbon correlates with the velocity of the gas stream.

A method of manufacturing a sash artificial heart valve includes deposition of pyrocarbon layer on the substrate surface of graphite by decomposition of gaseous compounds of carbon from the gas stream in the flow reactor, a separation layer of pyrocarbon from the substrate and mechanical manufacturing sash with a pair of support ledges. During all the time of deposition of pyrocarbon layer substrate of graphite provide a constant orientation relative to the direction of gas flow in the reactor, and the pair of supporting protrusions is formed so that the connecting imaginary axis coincides with the direction of flow of the gaseous carbon compounds in the deposition of pyrocarbon.

A substrate of graphite mostly have the form of plates and are placed in a flow reactor along its side wall with no gap at the joints between them. The number of simultaneously placed in the reactor plates substrates may be six or more.

The most appropriate combination of carbon, the decomposition of which is deposited pyrocarbon is methane. Additionally, in the gas stream preferably in the presence of propane and boron trichloride. Propane, starting to decompose at temperatures below the temperature of decomposition of methane produces soot particles, which act as nucleating or crystallization centers for the education of the layer of pyrocarbon. Trichloride boron promotes the formation of more dense pyrocarbon layer.

In addition to the active components in the gas stream can additionally contain inert carrier gas, which best fits the nitrogen. By adjusting the ratio in the gas flow between the active components and nitrogen, it is possible to control the rate of deposition of pyrocarbon and its final properties.

The invention is illustrated the accompanying drawings.

Figure 1 illustrates the location of the six reactor graphite plates 1, which are simultaneously applied pyrocarbon coating. Broad arrow shows the direction of the gas stream 2. Simultaneous deposition of pyrocarbon at seven, eight or more substrates (wafers), provided that they are placed in a flow reactor along its side wall with no gap at the joints between them.

Figure 2 shows the formation of pyrocarbon material 3 on the graphite substrate 1 through the decomposition of thread 2 hydrocarbon gases, as well as the orientation of the imaginary axis 4 connecting the pair of protrusions 5 on the frame 6 in their manufacture. One of the two shown in figure shutters designed for double valve, the other for tricuspid.

An example implementation of the method:

In a tubular flow reactor was installed above the th graphite plates dimensions 170× 47×5.0 mm as shown in figure 1. After heating plates up to 1400 - 1500°in the reactor was allowed to enter the gas stream, consisting of N2- 45%, SSC - 45%, BCl3. - 10%. The deposition of pyrocarbon layer on the surface of the graphite plates were 10-12 hours, to achieve a layer thickness of 3.5-4.5 mm during the whole time of deposition of the position of the graphite plates relative to the direction of gas flow is not changed. Then from the pyrocarbon deposited on graphite plates made shutters for artificial heart valve, keeping the orientation of the projections of the valves as shown in figure 2. This pyrocarbon separated from the graphite substrate. Measurement of tensile strength in bending of the samples showed that in the direction along the gas flow it is 27 ±to 0.6 kgf/mm2that is 28% higher than in the perpendicular direction (across the gas stream).

1. A method of manufacturing a sash artificial heart valve, comprising the deposition of pyrocarbon layer on the substrate surface of graphite by decomposition of gaseous compounds of carbon from the gas stream in the flow reactor, the separation of the substrate from the layer of pyrocarbon and mechanical manufacturing sash with a pair of supporting protrusions, characterized in that during the whole time of deposition of pyrocarbon layer substrate of graphite provide the constant orientation relative to the direction of gas flow in the reactor, and the pair of supporting protrusions is formed so that the connecting imaginary axis coincides with the direction of flow of the gaseous carbon compounds in the deposition of pyrocarbon.

2. The method according to claim 1, characterized in that a substrate of graphite are in the form of plates and are placed in a flow reactor along its side wall with no gap at the joints between them.

3. The method according to claim 1, characterized in that the gas stream as carbon compounds include methane, but also contains nitrogen with the addition of trichloride boron.



 

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FIELD: medical equipment.

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1 ex

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1 tbl, 3 ex

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7 cl, 10 dwg

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2 ex

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1 dwg

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