JPS62129048A - Improved electric heating cutter blade and automatic temperature control method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to an improved electrically heated cutting blade and a method for automatically adjusting its temperature, and more specifically, to an improved method for automatically adjusting the heating temperature using the Curie temperature of a ferromagnetic material. Adjustable electric heating cutter 1
This invention relates to a folding blade and its automatic temperature adjustment method.

[Conventional technology]

Conventionally, methods for automatically controlling heat generation due to Joule heat of current using the Curie temperature of ferromagnetic materials have been proposed, for example, in Japanese Utility Model Publication No. 48-35676 and Japanese Patent Application Laid-open No. 49-760.
As seen in No. 58 or Japanese Patent Application Laid-Open No. 51-122983, it is used as an electrically heated cutting blade in fields such as surgical tools.

The basic principle utilized in the present invention is the above-mentioned Japanese Patent Application Laid-Open No. 51-1'
This is conventionally known as described in Japanese Patent No. 22983. That is, high frequency current in a ferromagnetic conductor tends to concentrate on the outer periphery of the conductor. The current density is maximum at the conductor surface and decreases as the distance from the surface to the interior increases. The distance from the surface to the interior at which this current density is 37% of the maximum current density at the surface is generally referred to as the "surface layer depth." This surface depth is a function of the magnetic permeability of the ferromagnetic conductor [where d is the surface depth, ρ is the resistance of the ferromagnetic material, f is the current frequency, and μ is the magnetic permeability of the ferromagnetic material. ] This relationship has been known for a long time; for example, Bozos,
[Described in Ferromagnetism J (1951).

Generally, a ferromagnetic material has a temperature of 100.20 at a temperature lower than its Curie point temperature (hereinafter simply referred to as "Curie point").
While having a magnetic permeability of zero or greater, at temperatures above the Curie point the magnetic permeability of ferromagnetic materials is approximately one. As can be seen from the above equation, the surface depth of the ferromagnetic material can be more than 10 times greater at temperatures above the Curie point than at temperatures below the Curie point.

On the other hand, the amount of electrical power supplied to the heating element and the resulting Joule heat generated within the heating element is a function of the current flowing through the heating element and the resistance of the heating element.

This function is expressed by the formula [where P is Joule heat, ■ is current, and R is the resistance value of the heating element. ] Represented by Since the magnitude of the current in the heating element is constant and does not change during use, as can be seen from this equation, the amount of Joule heat generated within the heating element is a function of the resistance value of the heating element.

Therefore, in heating bodies made of ferromagnetic materials, when the temperature rises above the Curie point, the surface layer thickness increases,
As a result, the cross-sectional area through which the current flows increases and the resistance value decreases. Thus, when the temperature is higher than the Curie point, less electric power is supplied to the heating element than when the temperature is lower than the Curie point, thereby reducing the generated Joule heat. This reduction in Joule heating continues until the temperature of the heating body falls below the Curie point and is reduced due to the increase in magnetic permeability in the ferromagnetic material when the surface depth in the heating body is below the Curie point.

Furthermore, the current flowing through the heating element can be set to a predetermined magnitude. Therefore, based on the above basic principle, the temperature of a heating body made of ferromagnetic material can be automatically adjusted within a predetermined temperature range around its Curie point.

A surgical scalpel constructed according to such a basic principle is disclosed in Japanese Patent Application Laid-Open No. 51-122983. That is, the temperature of the cutting blade is automatically adjusted within a range near the Curie point by changing the magnetic permeability of the ferromagnetic material thermally coupled to the cutting blade, with the Curie point as the boundary.

[Problems that the invention attempts to resolve]

However, in these conventional ferromagnetic materials, their self-temperature-regulating ability is still affected by the relatively high resistance of the ferromagnetic materials, whose current resistance above the Curie point (and thus the resulting Joule heating) This means that there is a drawback in automatically adjusting the temperature more sensitively within an extremely small range.

Therefore, it is an object of the present invention to more sensitively increase the efficiency of automatic temperature adjustment based on the above basic principle in response to changes in the cooling body that contacts various regions of the heated cutting blade in an unpredictable manner.

[Means for solving problems]

This object is achieved according to the invention by a composite laminate of a ferromagnetic structure consisting of a ferromagnetic material of high permeability and a layer of material with low effective permeability and high electrical and thermal conductivity. Ru.

Therefore, the present invention provides a laminated electrically heated cutting blade that automatically adjusts the temperature of a heated part within a predetermined range, including a layer of a ferromagnetic material having a Curie transition point of magnetic permeability near the upper limit temperature of the predetermined range; a layer of conductive material in electrical contact with the layer of magnetic material and having higher electrical conductivity and higher thermal conductivity than the ferromagnetic material, and a high frequency current source coupled to the two layers; When the temperature is lower than the Curie point, the surface depth of the current is smaller than the thickness of the ferromagnetic material layer, and when the stack is at a temperature higher than the Curie point, the surface depth of the current is smaller than the thickness of the ferromagnetic material layer. To provide a laminated electrically heated cutting blade which is characterized by being larger than the width.

In this laminated electrically heated cutting blade, in order to automatically adjust temperature changes more sensitively, it is preferable that the conductive material layer is made of copper or silver, which has a higher thermal conductivity than the ferromagnetic material layer.

This laminated electrically heated cutting blade can be used in particular as a surgical scalpel with sharpened edges.

A layer of electrically insulating material disposed on the outer surface of the layer of ferromagnetic material and a layer of electrically conductive material disposed on the insulating material along at least a portion of the length of the layer of ferromagnetic material. Further, if this layer of conductive material is connected to the layer of ferromagnetic material only near one end thereof to form a conductive path from the layer of conductive material to the layer of ferromagnetic material, the effectiveness of automatic temperature regulation is enhanced. The above is more suitable.

Thus, according to another aspect of the invention, when automatically adjusting the heating temperature within a narrow range depending on the amount of high-frequency current, one conductive path having a Curie transition point of magnetic permeability near the upper limit temperature of the range is provided. A part of the high frequency current is applied to the
adjacent to and in electrical contact with one conductive path and said one conductive path;
Another part of the high lvl wave current is passed through other conductive paths having lower effective magnetic permeability and higher electrical conductivity and thermal conductivity than the one conductive path, and the relative proportion of the high frequency current flowing through each conductive path is A method of automatic temperature regulation of the heating temperature of a cutting blade is also provided that varies as a function of the temperature of the conductive path.

Additionally, careful selection of the other materials in the composite laminate can further enhance the self-adjusting action by increasing the shunting of heat between the various regions of the cutting blade. Careful selection of other materials in the composite can also increase the sharpness and durability of the cutting blade.

[Effect]

In the laminated heated cutting blade of the present invention, the surface layer depth is smaller than the thickness of the ferromagnetic material layer at temperatures lower than the Curie point, while the surface layer depth is smaller than the thickness of the ferromagnetic material layer at temperatures higher than the Curie point. also becomes larger. Therefore, when raised above the Curie point, the surface depth through which the current flows will include not only a layer of ferromagnetic material but also a conductive layer, which has a much lower resistance than the layer of ferromagnetic material. As a result, at temperatures above the Curie point, the current resistance in the laminated heating cutting blade is much lower than in conventional cutting blades of this type, and proportionally less Joule heat is generated. Thus, the present invention provides much improved self-temperature control capabilities than conventional cutting blades.

As described above, according to the present invention, due to the cooperation between the highly electrically conductive and highly thermally conductive layer and the ferromagnetic material layer, at temperatures above the Curie point where the surface layer depth becomes thicker than the ferromagnetic material layer, The proportion of high frequency current flowing through the highly conductive layer (eg copper layer) is increased and the Joule heat generated by the combined laminated heating cutting blade is significantly reduced. This effect is obtained independently of the part to be heated.

〔Example〕

Hereinafter, with reference to the attached FIGS. 1 and 2, the present invention will be described in detail with respect to an embodiment as a cutting blade.

In Figures 1 and 2, the blade support 9 is made of a suitable plastic material and is attached to the handle 11 of the surgical instrument. A structure 13 forming the cutting blade 15 of the instrument is attached to the blade support 9 and has a starting end 1 close to the handle 11.
7 to the end 19 remote from the handle part 1. This laminated structure 13 is made of a central material having a hardness to ensure a sharp cutting edge 15 and preferably of low magnetic permeability, such as non-magnetic steel or hardened carbon steel, as shown in cross-section in FIG. A layer 21 is provided.

The adjacent N23 located on either side of the central layer 21 are made of a material with low magnetic permeability and high thermal and electrical conductivity, such as copper or silver, to reduce temperature variations along the cutting blade 15. Provides excellent heat conduction from high temperature to low temperature areas along the length of the cutting blade. Additionally, these layers 23 form highly conductive paths that reduce Joule heating generated by high frequency currents, as will be discussed below. ff1 combined like this
21 and 23 form the effective low permeability and high electrical and thermal conductivity portion of the composite laminate.

A thin layer 25 of a ferromagnetic material, such as an iron-nickel alloy, having high magnetic permeability and a Curie point near the upper end of the desired operating temperature range is disposed adjacent R21.23. Low electrical conductivity and high magnetic saturation values are also desirable properties for the material of layer 25.

An electrical insulating layer 27 is disposed between the ferromagnetic layer 25 and the conductor 29 over substantially the entire length of the ferromagnetic layer 25 from the starting end 17 to the end 19.
Connect to 5. In this way, the high frequency signal applied to the laminated structure 13 from the signal source 32 is guided along the conductor 29 to the end 19 and then via the return layers 21, 23 and 25 to the signal source 32. The frequency or amplitude of the high frequency current provided by signal source 32 can be varied to adjust the operating temperature of cutting blade 15.

The laminated structure of FIG. 1 is constructed symmetrically with a conductor 29 on one side with respect to the center line 30, connected to the ferromagnetic composite structure at the end 19, and connected to one of the signal sources near the beginning 17. It should be noted that a common connection to the conductor 29 may also be made.

The high frequency permeability of the ferromagnetic layer 25 in the operating temperature range can be easily selected to be much higher than the effective permeability of the composite laminates 21 and 23, for example on the order of 200 to 1000. On the other hand, composite laminate 2
An effective conductivity of 1.23 can easily be selected to be nominally larger (eg, on the order of 10 to 20 times) than in the ferromagnetic layer 25. The depth of the surface layer through which the high-frequency current flows is inversely proportional to the electrical conductivity and magnetic permeability of the material through which the current flows and the frequency of the applied high-frequency current. Ferromagnetic layer 2
The dimensions of ferromagnetic layer 25 and its magnetic permeability are such that when energized with a current of sufficiently high frequency, the surface effect causes the current to substantially flow through the ferromagnetic layer 25.
You can choose to focus on

As the temperature increases toward the Curie point, the magnetic permeability of the material of the ferromagnetic layer 25 decreases toward unity, increasing the depth through which the high frequency current flows.

This results in a smaller proportion of the high frequency current flowing through the ferromagnetic layer 25, and a larger proportion of the high frequency current flowing through the composite laminates 21 and 23. The redistribution of current from the ferromagnetic layer 25 to the composite stack 21.23 as the temperature increases towards the Curie point, and the opposite redistribution as the temperature decreases from the Curie point, This is further aided by the electrical conductivity of the composite laminate 21, 23 which is significantly greater than the ferromagnetic layer 25.

The Joule heat generated in each stack is a function of the electrical resistance of that layer and the strength of the high frequency current flowing through that layer.

The electrical resistance of the ferromagnetic layer 25 is substantially higher than the effective electrical resistance of the composite laminate 21.23. Therefore, a change in the distribution of high frequency current between each layer 21, 23 and 25 as a function of a change in temperature results in a corresponding change in the Joule heat generated by the high frequency current, increasing heating at lower temperatures and heating at higher temperatures. causes a decrease in

Thus, a first advantage of the composite laminates 21, 23, 25 of the present invention is that they provide superior automatic temperature regulation over that obtained with conventional cutting blades that utilize structures made entirely of ferromagnetic materials. That's true.

A second advantage of the composite laminate of the present invention over conventional cutting blades that utilize only ferromagnetic alloys is that the composite laminate 21.2
3 can be selected to be much higher than in the ferromagnetic layer 25.

In this way, the composite laminate 21.23 can significantly increase the heat transfer from the area of the cutting blade that is not cooled by contact with tissue to the area that is being cooled, thereby providing an automatic temperature 2M effect. improve. For example, low permeability laminates such as copper, non-magnetic steel and copper have approximately 30 times higher thermal conductivity than typical iron-nickel ferromagnetic alloys, resulting in improved temperature regulation due to this "thermal shunting" effect. is significantly larger than conventional similar structures made entirely of ferromagnetic materials.

In the embodiment shown in Figures 1 and 2, where the cutting member itself is electrically heated by high frequency current flowing through it, another advantage of the composite laminate is that the central layer provides a sharper and more durable cutting edge. The hardness can be selected to provide the desired hardness. For example, if the center layer 21 were to be made of #302 stainless steel, this would mean that the entire cutting blade would be made of typical iron-nickel steel, as in conventional cutting blades where the cutting blade itself conducts electrical current and generates Joule heat directly. It would have a Rockwell C hardness of 30, compared to a Rockwell C hardness of 10 constructed from a ferromagnetic alloy.

In addition, according to another embodiment of the present invention, as shown in the cross section of FIG. It should also be noted that advantages are obtained. In this embodiment, the electrical conductor 36 consists of two laminated layers 39 and 37, one of which has a low conductivity, such as an iron-nickel alloy, and a high permeability having a high magnetic saturation and a Curie point at a given temperature. The other is made of a ferromagnetic material with low magnetic permeability and high electrical and thermal conductivity, such as copper or silver.

The electrical conductor 36 is electrically insulated from the cutting member 40 by a layer 38 (the cutting member 40 has a cutting blade 15 or the cutting member is fabricated from a non-conductive material such as ceramic or glass) and is thermally coupled thereto. There is. All high frequency currents flow through the laminated conductor 36 to heat the cutting member by thermal conduction. Improved self-regulation of Joule heating in conductive composite laminates is achieved by the mechanism described above.

〔Effect of the invention〕

The self-adjusting heated cutting blade described above is useful for surgical operations that simultaneously perform hemostasis. The temperature that should be automatically adjusted is
This is achieved by selecting a ferromagnetic material, such as an iron-nickel alloy, having a Curie point near that temperature as the ferromagnetic material layer in the composite stack.

[Brief explanation of drawings]

FIG. 1 is a plan view of a cutting blade according to an embodiment of the present invention, FIG. 2 is a sectional view taken along line 2-2 of the cutting blade in FIG. 1, and FIG. 3 is a sectional view of another embodiment of the present invention. . 11... Handle portion 13... Laminated structure 15.
...Cutting blade 17...Starting end 19...End
21.23...Composite laminate 25...Ferromagnetic layer 27...Electrical insulating layer 29...Conductor
30... Center line 36... Conductor 37...
Lamination 38... layer 39... layer 40
...cutting material

Claims (5)

[Claims] (1) In a laminated electric cutting blade that automatically adjusts the temperature of the heated part within a predetermined range, a layer of a ferromagnetic material having a Curie transition point of magnetic permeability near the upper limit temperature of the predetermined range; a layer of a conductive material in electrical contact and having a higher electrical conductivity and a higher thermal conductivity than the ferromagnetic material, and a high frequency current source coupled to the two layers, the stack being above the Curie point. When the temperature is low, the surface depth of the current is smaller than the thickness of the ferromagnetic material layer, and when the stack is at a temperature higher than the Curie point, the surface depth of the current is larger than the thickness of the ferromagnetic material layer. A laminated electrically heated cutting blade characterized by: (2) a layer of electrically insulating material disposed on an outer surface of the layer of ferromagnetic material; and a layer of electrically conductive material disposed on the insulating material along at least a portion of the length of the layer of ferromagnetic material. and the layer of conductive material is connected to the layer of ferromagnetic material only near one end thereof to form a conductive path from the layer of conductive material to the layer of ferromagnetic material. The laminated electrically heated cutting blade described in Section 1. (3) A laminated electrically heated cutting blade according to claim 1, wherein the layer of conductive material is selected from the group consisting of copper and silver. (4) In an AC electric resistance heating cutting blade electrically connected to a high frequency power source, the heating cutting blade has an electrical resistance that decreases as the temperature rises over at least a predetermined temperature range, and is further made of a material with high thermal conductivity and high electrical conductivity. an electrically conductive non-magnetic support member having a thin layer of magnetic material over at least a portion of its surface, the magnetic material having a maximum relative magnetic permeability greater than 1 at a temperature below its Curie point. and has a minimum relative magnetic permeability of approximately 1 at a temperature higher than the Curie point, and when the heated cutting blade is electrically connected to the high frequency power source, an alternating current at a high frequency flows through the heated cutting blade to generate joules. The alternating current is limited to the thin magnetic layer due to the maximum permeability acting below the Curie point of the layer of magnetic material, while the alternating current is limited to the Curie point as the temperature increases. An alternating current electric resistance heating cutting blade characterized in that it is configured to diffuse into the non-magnetic support member when approaching the magnetic permeability and decreasing the magnetic permeability. (5) When automatically adjusting the heating temperature within a narrow range according to the amount of high-frequency current, a part of the high-frequency current is passed through one conductive path having a Curie transition point of magnetic permeability near the upper limit temperature of the range, and another portion of the high frequency current in another conductive path adjacent to and in electrical contact with the one conductive path and having a lower effective magnetic permeability and higher electrical conductivity and thermal conductivity than the one conductive path. A method for automatically adjusting the heating temperature of a cutting blade, characterized in that the relative proportion of high-frequency current flowing through each conductive path is changed as a function of the temperature of the conductive path.