JPH0351179B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an improved electrically heated cutting blade and a method for automatically adjusting the heating temperature thereof, and more specifically, to an improved method for adjusting the heating temperature using the Curie temperature of a ferromagnetic material. The present invention relates to an automatically adjustable electrically heated cutting blade and a method for automatically adjusting its heating temperature.

[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, Japanese Patent Application Laid-Open No. 49-76058, or Japanese Patent Application Laid-open No. 122983-1983. As seen in , 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
It is conventionally known as described in Japanese Patent No.-122983. 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 depth at which this current density is 37% of the maximum current density at the surface (distance from the surface to the inside) is generally called the "surface depth".
It is called. This surface depth is a function of the magnetic permeability of the ferromagnetic conductor and is given by: [In the formula, d is the surface depth, ρ is the resistance value 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, and is described, for example, in Bozos's ``Feromagnetism'' (1951).

In general, ferromagnetic materials have a magnetic permeability of 100, 200, or more at temperatures below their Curie point temperature (hereinafter simply referred to as the "Curie point"); The magnetic permeability is approximately 1. As can be seen from the above equation, the surface depth of a 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 passing through the heating element and the resistance of the heating element. This function is expressed by the formula P=I ² R [where P is Joule's heat, I is electric current, and R is the resistance value of the heating element. ] is 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 a heating body made of a ferromagnetic material, when the temperature rises above the Curie point, the surface layer thickness increases, and 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 heat continues until the temperature of the heating element 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 element 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,
A heating element made of ferromagnetic material can automatically adjust its temperature within a predetermined temperature range around its Curie point.

A surgical scalpel constructed according to the original principle is disclosed in Japanese Patent Application Laid-Open No. 122983/1983. That is, the temperature of the cutting blade is automatically adjusted within a certain 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.

[Problem that the invention seeks to solve]

However, in these conventional ferromagnetic materials, their self-temperature regulating ability is limited by the relatively high resistance of the ferromagnetic materials, where the current resistance (and therefore the amount of Joule heat generated) above the Curie point remains This means that there is a drawback in automatically adjusting the temperature more sensitively within a very small range.

Therefore, it is an object of the present invention to sharply 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, according to the invention, is achieved by forming a ferromagnetic structure by a composite laminate consisting of a ferromagnetic material with high permeability and a layer of material with low effective permeability and high electrical and thermal conductivity. achieved.

Therefore, the present invention provides a laminated electrically heated cutting blade that automatically adjusts the temperature of a heated part within a predetermined range, which comprises: 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 ferromagnetic material and having higher electrical conductivity and higher thermal conductivity than the ferromagnetic material; and a high frequency current source coupled to the stack of the two layers. In the laminate, the surface depth of the current flowing through the ferromagnetic material layer is smaller than the thickness of the ferromagnetic material layer at a temperature below the Curie point, and the surface depth of the current flowing through the ferromagnetic material layer at a temperature above the Curie point. A laminated electrically heated cutting blade is provided, characterized in that it is composed of a layer of ferromagnetic material and an electrically conductive material having a thickness such that the depth is greater than the thickness of the ferromagnetic material layer.

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 has one edge sharpened so that it can be used, in particular, as a surgical scalpel.

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.

The present invention also provides an AC electrical resistance heating member electrically connected to a high frequency current source, wherein the heating member has an electrical resistance that decreases as the temperature rises over at least a predetermined temperature range, and further has high thermal conductivity and high conductivity. an electrically conductive non-magnetic support member made of a magnetic material, the support member having a thin layer of magnetic material over at least a portion of its surface, the magnetic material having an electrically conductive non-magnetic support member having an electrically conductive non-magnetic support member having an electrically conductive non-magnetic support member having an electrically conductive non-magnetic support member having a thin layer of magnetic material over at least a portion of its surface; It has a maximum relative magnetic permeability and a minimum relative magnetic permeability of approximately 1 at temperatures above the Curie point, and when the heating member is electrically connected to the high frequency current source, an alternating current flows at a high frequency to generating Joule heat in the heating element, the alternating current is limited to the thin layer of the magnetic material in accordance with the effect of the maximum magnetic permeability at temperatures below the Curie temperature of the layer of magnetic material, while the alternating current is Provided is an alternating current electrical resistance heating member, characterized in that it is configured to diffuse into the non-magnetic support member when the temperature rises and approaches the Curie point and the magnetic permeability decreases.

Thus, according to another aspect of the invention, in a method for automatically adjusting the temperature rise of a multilayer structure within a narrow range of upper and lower limits in response to the supply of high-frequency current, the multilayer structure comprises a pair of material layers. said one layer being configured to undergo a varying cooling load in each region of the multilayer structure and identifying a first conductive path having a Curie transition point of magnetic permeability at a temperature near the upper limit of a narrow temperature range; a layer specified as a second conductive path having a lower effective value of magnetic permeability and higher electrical conductivity and thermal conductivity than the one layer; passing another portion of said high frequency current through said other layer forming a laminate with a layer; as a function of the cooling load and temperature of the multilayer material to maintain said multilayer structure within a narrow range of temperatures; heating regions of the multilayer structure that receive a greater cooling load more than regions that receive a lower cooling load by varying the relative proportions of high-frequency current flowing through each layer; There is also provided a method for automatically adjusting the temperature rise of a multilayer structure, characterized in that:

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 the temperature rises above the Kyrie point,
The surface depth through which the current flows includes not only the ferromagnetic material layer but also the conductive layer, and this layer has a lower resistance value than the ferromagnetic material layer. As a result, at temperatures higher than the Curie point, the current resistance value of the laminated heating cutting blade becomes gradually lower than that of conventional cutting blades of this type, and the generated Joule heat decreases proportionally. Thus, according to the present invention, the automatic temperature adjustment ability is gradually improved over 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, resulting in a significant reduction in the Joule heat generated by the laminated electrically heated cutting blade. 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.

1 and 2, the blade support 9 is made of a suitable plastic material and 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 extends from a starting end 17 near the handle 11 to an end 19 distal to the handle 11. 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.

Adjacent layers 23 arranged on either side of the central layer 21 are made of a material with low magnetic permeability and high thermal resistance, such as copper or silver.
The cutting blade 1 is made of a material having electrical conductivity.
Provides excellent heat transfer from hot to cold areas along the length of the cutting blade to reduce temperature variations 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. Layer 21 combined in this way
and 23 form an 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 limit of the desired operating temperature range is disposed adjacent layers 21,23. Low electrical conductivity and high magnetic saturation values are also desirable properties for the material of layer 25.

There is a starting end 17 between the ferromagnetic layer 25 and the conductor 29.
An electrically insulating layer 27 is disposed over substantially the entire length of the ferromagnetic layer 25 from the end 19 to the end 19, and this electrical conductor 29 is connected to the ferromagnetic layer 25. In this way, the high frequency signal applied to the laminated structure 13 from the signal source 23 is transmitted along the conductor 29 to the terminal end 19 and then via the return layers 21, 23 and 25 to the signal source 23.
2. 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 in FIG.
9 may be arranged symmetrically on one side, connected to the ferromagnetic composite structure at the end 19 and commonly connected to one conductor 29 of the signal source near the starting end 17. Should.

The high-frequency magnetic permeability of the ferromagnetic layer 25 in the operating temperature range is, for example, 200 to 200, so that it becomes gradually larger than the effective magnetic permeability of the composite laminates 21 and 23.
It can be easily selected to be around 1000. On the other hand, the effective conductivity of the composite laminates 21, 23 can be easily selected to be much larger (for example, on the order of 10 to 20 times) than in the ferromagnetic layer 25. The depth of the surface layer through which high-frequency current flows is
It 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. The dimensions of the ferromagnetic layer 25 and its magnetic permeability can be selected such that when energized with a current of sufficiently high frequency, surface effects substantially concentrate the current in the ferromagnetic layer 25. As the temperature increases toward the Curie point, the magnetic permeability of the material of the ferromagnetic layer 25 decreases toward 1, increasing the depth through which the high-frequency current flows. This makes the proportion of high frequency current flowing through the ferromagnetic layer 25 smaller, while the composite laminates 21, 2
This results in a larger proportion of the high frequency current flowing through 3. from the ferromagnetic layer 25 to the composite laminate 21, which occurs as the temperature increases towards the Curie point.
The redistribution of current into the ferromagnetic layer 2 and the opposite redistribution that occurs as the temperature decreases from the Curie point
This is further aided by the electrical conductivity of the composite laminates 21, 23 which is significantly greater than 5.

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 value of the ferromagnetic layer 25 is substantially higher than the effective electrical resistance of the composite laminates 21 and 23. Therefore, each layer 2 occurs as a function of temperature change.
The distribution change of high frequency current between 1, 23 and 25 is
A corresponding change in the Joule heat generated by the high frequency current results in increased heating at lower temperatures and decreased heating at higher temperatures.

Therefore, the composite laminates 21, 23, 25 of the present invention
The first advantage is that it provides automatic temperature regulation that is superior to that obtained with conventional cutting blades that utilize structures made of all ferromagnetic materials.

The second advantage of the composite laminate of the present invention over conventional cutting blades that utilize only ferromagnetic alloys is that the effective thermal conductivity of the composite laminates 21 and 23 is lower than that of the ferromagnetic layer 2.
It is possible to select higher values than in 5.

In this way, the composite laminates 21 and 23 are
Heat transfer from the area of the cutting blade that is not cooled by contact with tissue to the area that is being cooled can be significantly increased, thereby improving self-temperature regulation. For example, low permeability laminates such as copper, non-magnetic steel and copper have thermal conductivities approximately 30 times higher 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 a high frequency current flowing through it, another advantage of the composite laminate is that it provides a sharper and more durable cutting edge than the central layer. The hardness can be selected as required. For example, if the center layer 21 is made of #302 stainless steel, this means that the entire cutting blade is made of typical iron-nickel steel, as in conventional cutting blades where the cutting blade itself conducts electrical current and directly generates heat. Compared to Rockwell C hardness of about 10 made of ferromagnetic alloy,
It will have a Rockwell C hardness of 30.

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 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 with 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. Conductor 36 is 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. All high frequency currents flow through the laminated conductor 36 to heat the cutting member by thermal conduction. Improvements in automatic regulation of Joule heat in conductive composite laminates
This 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 self-adjusting temperature 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.
FIG. 3 is a sectional view of another embodiment of the invention. DESCRIPTION OF SYMBOLS 11... Handle part, 13... Laminated structure, 15... Cutting blade, 17... Starting end, 19... End, 21, 23... Composite laminate, 25... Ferromagnetic layer, 27... Electrical insulation layer,
29... Conductor, 30... Center line, 36... Electric conductor, 3
7... Lamination, 38... Layer, 39... Lamination, 40... Cutting member.

Claims (1)

[Claims] 1. A laminated electrically heated cutting blade that automatically adjusts the temperature of a heated part within a predetermined range, comprising: 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 ferromagnetic material and having higher electrical conductivity and higher thermal conductivity than the ferromagnetic material; and a high frequency current source coupled to the stack of the two layers. In the laminate, the surface depth of the current flowing through the ferromagnetic material layer is smaller than the thickness of the ferromagnetic material layer at a temperature below the Curie point, and the surface depth of the current flowing through the ferromagnetic material layer at a temperature above the Curie point. A laminated electrically heated cutting blade characterized in that it is composed of a layer of ferromagnetic material and an electrically conductive material having a thickness such that the depth is greater than the thickness of the ferromagnetic material layer. 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. Laminated electric heating cutting blade. 3. The laminated electrically heated cutting blade of claim 1, wherein the layer of conductive material is selected from the group consisting of copper and silver. 4. In an AC electrical resistance heating member electrically connected to a high frequency current source, the heating member 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 permeability greater than 1 at a temperature below its Curie temperature; and has a minimum relative magnetic permeability of approximately 1 at a temperature higher than the Curie point, and when the heating member is electrically connected to the high frequency current source, an alternating current at a high frequency flows through the heating member to generating heat, the alternating current being confined to the thin layer of the magnetic material in accordance with the effect of the maximum magnetic permeability at a temperature below the Curie point of the layer of magnetic material, while the alternating current is flowing as the temperature increases. An alternating current electrical resistance heating member characterized in that it is configured to diffuse into the non-magnetic support member when the magnetic permeability decreases as the magnetic permeability approaches the Curie point. 5. A method for automatically adjusting the temperature rise of a multilayer structure within a narrow range of upper and lower limits according to the supply of high-frequency current, wherein the multilayer structure is composed of a pair of material layers, and the temperature rise in each region of the multilayer structure is passing a portion of a high frequency current through said one layer identifying a first conductive path that is configured to receive a cooling load of at least one layer and has a Curie transition point of magnetic permeability at a temperature near the upper limit of a narrow temperature range; A layer specified as a second conductive path having a lower effective value of magnetic permeability and higher electrical conductivity and thermal conductivity than the one layer, the other layer forming a lamination with the one layer. passing another portion of said high frequency current; and the relative proportion of high frequency current flowing through each layer as a function of temperature and cooling load of the multilayer material to maintain said multilayer structure within a narrow range of temperatures. heating a region of the multilayer structure receiving a larger cooling load more than a region receiving a smaller cooling load by changing the temperature of the multilayer structure. How to automatically adjust.