TW202108099A - Foot warmer - Google Patents

Abstract

Provided is a foot warmer that resists uneven distribution of an exothermic material within a pack and has a reduced maximum temperature on the warming surface, and in which localized high increases in temperature can be suppressed. A foot warmer is disposed between a user's foot and a shoe. The foot warmer comprises: a pack formed into a pouch shape via a front sheet and a rear sheet; and an exothermic material sealed within the pack. The pack has a joined part where the front sheet and the rear sheet are joined. The joined part includes an edge part formed along at least a portion of the outer periphery of the pack, and a projecting part that projects from the edge part toward the exothermic material.

Description

Heating element for foot

The present invention relates to a heating element for the foot.

Background technique

Patent Document 1 discloses the previous heating element. The heating element described in Patent Document 1 includes: a heating composition (heating material) which can generate heat by contact with air; and a storage bag (bag body) which contains the heating composition. The storage bag is formed into a bag shape by laminating two sheets and sealing the outer peripheral edge portion. Advanced technical literature Patent literature

[Patent Document 1] Japanese Patent Laid-Open No. 11-354

Summary of the invention The problem to be solved by the invention

In outdoor environments with cold winters such as agricultural operations, markets, and snowy mountains, since the feet are very cold, the heating element described in Patent Document 1 described above may be used between the soles of the feet and the insoles of shoes.

However, in the heating element described in Patent Document 1, since the heating element is tightly attached to the foot inside the shoe, the heating composition tends to move inside the bag when walking, and there is a fear of the heating composition in the bag. The case where the inside of the body is biased toward one end. Also, if the temperature distribution of the heating surface is observed, the temperature tends to be higher in the center when viewed from the front. Since the heating element for the foot is clamped between the foot and the inner surface of the shoe, a localized high temperature rise occurs on the heating surface. not good. In response to the localized high temperature rise on the heating surface of the heating element for the foot, various countermeasures have been taken in the past, but better countermeasures are expected.

The present invention has been completed in view of the above circumstances, and its object is to provide a heating element for underfoot, which is not easy to deflect the inside of the bag to one side, and can reduce the maximum temperature of the heating surface and suppress localized high temperature rise. Means to solve the problem

The heating element for the foot of one aspect of the present invention is arranged between the user's foot and the shoes, and includes: a bag body formed by a front side sheet portion and a back side sheet portion into a bag shape; and heat generation The material is enclosed in the aforementioned bag. The bag body has a joining part formed by joining the front-side sheet part and the back-side sheet part. The joint portion includes: an edge portion formed along at least a part of the outer circumference of the bag body; and a protrusion portion that protrudes from the edge portion toward the heating material side.

In addition, in the heating element for underfoot, the protrusion dimension of the protrusion is 15% or more and 35% or less of the inner dimension of the bag body corresponding to the protrusion in the direction in which the protrusion protrudes.

In addition, in the heating element for the foot, in the direction in which the protrusion protrudes, the dimension between the protrusion and the portion facing the protrusion is relative to the inner dimension of the bag body at the position corresponding to the protrusion , Is 30% or more and 70% or less.

In addition, the heating element for underfoot preferably includes a plurality of the protrusions, and the protrusion direction of the plurality of protrusions is preferably along a straight line.

In addition, it is preferable that the heating element for underfoot is provided on the outer edge of the bag body, and a recessed portion is formed at a position corresponding to the protruding portion. Invention effect

The heating element for underfoot in the above aspect of the present invention has the following advantages: the heating material is not easy to deviate from the inside of the bag to one side, and the maximum temperature of the heating surface can be lowered and localized high temperature rise can be suppressed.

The form used to implement the invention

(1) Implementation form (1.1) Summary As shown in FIG. 1, the heating element 1 for underfoot of the present embodiment can be arranged between the user's foot 5 (including the toes) and the shoes 6 to locally give the user's foot 5 a warming effect. The heating element 1 of the present embodiment includes a bag body 2 formed in a bag shape, and a heating material 4 enclosed in the bag body 2.

The bag body 2 is formed in a bag shape by the front side sheet part 21 and the back side sheet part 22, and has the junction part 3 in at least one part. The joining part 3 is a part which joins the front-side sheet part 21 and the back-side sheet part 22. As shown in FIG. 2, the joining part 3 of this embodiment includes an edge part 31 and a protruding part 32.

The edge portion 31 is formed along at least a part of the outer circumference of the bag body 2 (in this embodiment, the entire length of the outer circumference of the bag body 2). The protruding portion 32 protrudes from the edge portion 31 toward the heat generating material 4 side.

Compared with the heating element for underfoot that does not have the protrusion 32, the heating element 1 for underfoot of the present embodiment can keep the area of the high temperature region on the heating surface equal to or more and lower the maximum temperature. Therefore, the heating element 1 of the present embodiment can lower the maximum temperature of the heating surface and suppress a localized high temperature rise.

In the present invention, the "high-temperature region" refers to a temperature region of (the highest temperature-5°C) or more and below the highest temperature in the temperature region of the heating surface. In addition, in the present invention, the “heat-generating surface” refers to the portion of the bag 2 surrounded by the edge 31 of the surface of the bag 2. In the heating element 1 for the foot of the present embodiment, the front side sheet portion 21 and the back side sheet portion 22 each have a heating surface, and the front view and the bottom view of the heating element 1 for the foot are the directions in which the heating surface is viewed from the front.

In addition, in the heating element 1 for the foot of the present embodiment, since the movement of the heating material 4 is prevented by the protrusion 32 in the interior of the bag body 2, it is possible to suppress the heating material 4 from deviating to one side. Therefore, even if the underfoot heating element 1 is arranged between the user’s foot 5 and the shoes 6, while walking the foot 5 or the sole 51 stepping on the heating material 4, the underfoot heating element 1 of this embodiment generates heat. The material 4 is also not easy to deflect the inside of the bag body 2 to one side.

(1.2)Detailed Hereinafter, the heating element 1 for the foot of the present embodiment will be described in detail. As shown in FIG. 1, the heating element 1 for underfoot is disposed between the user's foot 5 and the shoes 6 for use. In this embodiment, it is arranged between the toe-side part of the user's sole 51 and the toe-side part of the insole 61 of the shoe 6. The shoes 6 include, for example, sports shoes, sneakers, shoes, leather shoes, boots, boots (including boots), slippers, etc., and are not particularly limited. In addition, the "user's foot 5" in the present invention refers to a foot or bare foot in a state of wearing shoes, socks, pantyhose, etc.

The heating element 1 for the feet of the present embodiment is a heating element for the feet that uses the reaction heat generated when an oxidation reaction occurs as a heat source, such as a disposable warm pack. The heating element 1 for the foot is housed in an airtight outer bag (not shown) that does not allow air to pass, for example, before use.

As shown in FIG. 2, the heating element 1 for a foot of this embodiment is formed in a substantially D shape in front view. The end of the heating element 1 for the foot is formed in an arc shape in the front direction, and the end in the rear direction is formed in a linear shape in the left-right direction. Hereinafter, the direction parallel to the front-rear direction is defined as the "length direction", and the direction parallel to the left-right direction perpendicular to the length direction is defined as the "width direction". Furthermore, the definition of these directions is not intended to limit the usage of the heating element 1 for the foot. The arrows in each direction in the drawing are shown for illustration only, and do not accompany the entity.

The heating element 1 for the foot of the present embodiment is formed in a substantially D-shape in front view, but the shape is not particularly limited as shown in "(3) Modification Example" described later.

The heating element 1 for the feet is usually used to warm the feet, and its heating temperature is 25°C or more and 50°C or less, preferably 30°C or more and 45°C or less in an environment of 20°C (temperature measurement method is It is designed in accordance with the method of measuring the temperature of the warm warm bag at the foot of the warm warm pack industry association).

(1.2.1) Heating material The heat-generating material 4 is a material that can generate heat, and in this embodiment is a powder material that can generate heat by contact with air. The heat generating material 4 is enclosed in the bag body 2.

The heat generating material 4 includes, for example, an oxidizable metal, activated carbon, carbon black, a water-retaining agent, a metal salt (for example, common salt), and water. The oxidizable metal is a metal that emits the heat of oxidation reaction. For example, one or two or more powders or fibers selected from iron, aluminum, zinc, manganese, magnesium, and calcium can be cited. Among them, it is determined by operability, safety, From the viewpoint of manufacturing cost, preservation and stability, iron powder is preferred. Regarding the iron powder, one kind or two or more kinds selected from reduced iron powder and atomized iron powder can be exemplified. As for the water-retaining agent, for example, wood powder, vermiculite, diatomaceous earth, polished iron, silica gel, alumina, water-absorbing resin, etc. can be cited. However, as for the heat generating material 4, the composition used in the previous disposable warm pack can be directly used, and there is no particular limitation.

Regarding the heat-generating material 4, materials other than materials that generate heat by contact with air may also be used. Regarding the heat generating material 4, for example, a material that can generate heat by being irradiated with microwaves by a microwave oven or the like (for example, ceramic powder such as ferrite magnets, red beans, etc.).

(1.2.2) Bag body The bag 2 has a storage space in which the heat generating material 4 is stored. The bag body 2 of this embodiment is formed in a flat shape as shown in FIG. 3(A), and is provided with the front side sheet part 21 and the back side sheet part 22. As shown in FIG. The bag body 2 joins the front side sheet part 21 and the back side sheet part 22 by the joining part 3, thereby forming a storage space inside.

The bag body 2 of this embodiment is formed into a substantially D-shape with a width and a length in a front view as shown in FIG. 2. However, for example, it may be formed in a substantially rectangular shape in a front view, a square shape in a front view, a triangular shape in a front view, and a five There are no restrictions on the shape of polygons above a polygon, a round shape in the front view, and an elliptical shape in the front view.

(1.2.2.1) Front side sheet part The front-side sheet portion 21 is a sheet-like portion forming one surface of the bag body 2. As shown in FIG. 3(A), the front-side sheet part 21 of this embodiment is comprised by one sheet. The front side sheet part 21 of this embodiment has flexibility. Thereby, the heating element 1 for the foot can be deformed along the sole of the user's foot.

From the viewpoints of strength and durability against heat generated by the heat generating material 4, it is preferable to use a resin film for the front side sheet portion 21 of the present embodiment. Regarding the resin used for the resin film, a thermoplastic resin is preferable. As for the thermoplastic resin, for example, polyethylene, polypropylene, polyester, polyamide, polyurethane, polystyrene, polyvinyl alcohol, polyvinyl chloride, polyvinylidene chloride, polycarbonate, Ethylene-vinyl acetate copolymer, etc. These resins can be used alone or in combination of two or more kinds.

In addition, from the viewpoint of making the skin feel of the feet 5 of the heating element 1 for the feet good, the front-side sheet portion 21 is preferably provided with a woven fabric or a non-woven fabric on the outer side of the resin film.

Regarding the fiber materials of woven or non-woven fabrics, for example, natural fibers such as cotton, linen, silk, and paper, semi-synthetic fibers such as rayon and acetate, nylon, vinylon, polyester, acrylic, polyethylene, etc. Synthetic fibers such as polypropylene, polyvinyl chloride, polybutylene terephthalate, and mixed fibers of these fibers, etc. Among them, from the viewpoint of making the skin feel good, the fiber material is preferably nylon, polyester, or polypropylene. These fiber materials can be used alone or in combination of two or more kinds. The weight per unit area of the woven fabric or non-woven fabric is not particularly limited as long as it can prevent the heat generating material 4 from leaking out of the bag body 2, and examples thereof include 20 g/m ² or more and 70 g/m ² or less.

However, the front-side sheet portion 21 does not need to be a laminate of a resin film and a woven fabric or a non-woven fabric, and may be composed of a separate resin film, or may be composed of a separate woven fabric or non-woven fabric.

The front side sheet part 21 of this embodiment has air permeability. In the front-side sheet portion 21 of the present embodiment, the front-side sheet portion 21 has a plurality of holes because the resin film is a porous resin film or a resin film formed with a plurality of holes (not shown). Therefore, the front-side sheet portion 21 can ventilate the inside and outside of the bag body 2 through a plurality of holes. A plurality of holes may be formed evenly on the entire surface of the front-side sheet portion 21, or may be formed densely in a part. Moreover, the diameter of each hole should just be a size which can suppress the leakage of the heat-generating material 4 through the hole, for example, 0.1 μm or more and 30 μm or less can be exemplified. In addition, the shape and number of holes are not particularly limited. The body temperature of the heating element 1 for the foot changes according to the air permeability of the bag 2, so the size, shape and number of holes can be considered appropriate considering the body temperature of the heating element 1 for the foot and the degree of suppression of the heating material 4 set up.

In addition, regarding the front-side sheet portion 21, when the non-woven fabric is used alone, a plurality of holes may not be formed.

The front-side sheet portion 21 preferably has a certain moisture permeability. The moisture permeability of the front-side sheet portion 21 is preferably 300g/(m ² ･day) or more and 1000g/(m ² ･day) or less, preferably 400g/(m ² ･day) or more and 900g/(m ² ･) day) or less. However, the moisture permeability of the front-side sheet portion 21 is not particularly limited.

(1.2.2.2) Back side sheet part The back side sheet portion 22 is a sheet-like portion formed on the opposite side of the front side sheet portion 21 in the bag body 2. The back side sheet part 22 of this embodiment is comprised by one sheet. The back side sheet part 22 of this embodiment has flexibility similarly to the front side sheet part 21. As shown in FIG.

It is preferable to use a resin film for the back side sheet part 22 and the front side sheet part 21 similarly. However, the back side sheet portion 22 does not need to have the same structure and the same material as the front side sheet portion 21. Regarding the back side sheet portion 22, it is preferable to be the same as the front side sheet portion 21 and be composed of a laminate of a resin film and a woven or non-woven fabric, but it is not limited to this. It may be composed of a single resin film or a single resin film. Made of woven or non-woven fabric.

The back side sheet part 22 of this embodiment has air permeability. The back-side sheet portion 22 of this embodiment is the same as the front-side sheet portion 21. The back-side sheet portion 22 is a porous resin film or a resin film formed with a plurality of holes (not shown). It has a plurality of holes. However, the back side sheet part 22 does not necessarily have air permeability, and may be non-air permeability.

The thickness of each of the front side sheet part 21 and the back side sheet part 22 is not specifically limited, For example, 0.1 mm or more and 2.0 mm or less are suitable. Thereby, the heating element 1 for the foot can be made soft and easy to conform to the sole 5 of the foot, and on the other hand, a certain strength that can withstand the foot sole 5 can be ensured even if it is stepped on continuously.

The back side sheet portion 22 preferably has a certain moisture permeability as the front side sheet portion 21. The moisture permeability of the back side sheet portion 22 is preferably the same as that of the front side sheet portion 21, which is 300g/(m ² ･day) or more and 1000g/(m ² ･day) or less, preferably 400g/(m ² ･day) ) Above and below 900g/(m ² ･day). However, the moisture permeability of the back side sheet part 22 is not specifically limited.

The heating element 1 for the foot of this embodiment is equipped with the anti-slip part 7. The anti-slip part 7 suppresses the displacement of the underfoot heating element 1 between the sole 5 of the user's foot and the inner sole 61 of the shoe 6. The anti-slip part 7 of this embodiment is constituted by a plurality of small protrusions 71 formed on the back side sheet part 22. The plurality of small protrusions 71 are evenly formed on the entire surface (outer surface) of one surface (outer surface) of the back side sheet portion 22 in this embodiment, but may be formed in at least a part of the area in the present invention.

The small protrusion 71 is made of, for example, rubber or acrylic resin. However, the anti-slip part 7 can also be implemented by printing a foam ink having an anti-slip function on the back side sheet part 22. In addition, the anti-slip part 7 may be formed not only in the back side sheet part 22 but also in the front side sheet part 21, and may be formed in both the back side sheet part 22 and the front side sheet part 21.

In addition, in the heating element 1 for underfoot of the present invention, instead of the anti-slip part 7, an adhesive layer may be provided. The adhesive layer is provided in any one of the back side sheet part 22 or the front side sheet part 21. In this way, the heating element 1 for the foot can be pasted on the sole 5 of the user's foot for use, and can also be pasted on the inner sole 61 of the shoe 6 for use.

(1.2.2.3) Joint The joining part 3 is a part which joins the front-side sheet part 21 and the back-side sheet part 22. The joining part 3 of this embodiment is comprised by welding (heat sealing) a part of the front side sheet part 21 and a part of the back side sheet part 22. As shown in FIG. However, the joint 3 may not be welded, for example, it may be implemented by bonding, sewing, crimping, etc., or a combination thereof. As shown in FIG. 2, the joining portion 3 includes an edge portion 31 and a plurality of (here, two) protrusion portions 32.

The rim portion 31 is a portion formed along the outer circumference of the bag body 2 in the joining portion 3. The edge portion 31 of this embodiment is continuous across the entire length of the outer circumference of the bag body 2. The width dimension of the edge portion 31 is not particularly limited, and for example, it is preferably 1 mm or more and 10 mm or less, and preferably 3 mm or more and 7 mm or less. The edge part 31 of this embodiment is formed in substantially the same width dimension over the full length.

The edge portion 31 of this embodiment includes a pair of first straight portions 315 formed along the length direction, a second straight portion 316 formed along the width direction, and an arc-shaped portion 317 connecting the pair of first straight portions 315. The pair of first linear portions 315 are formed substantially linearly and parallel to each other in this embodiment.

The protruding portion 32 is a portion of the joining portion 3 that protrudes from the edge portion 31 toward the heat generating material 4 side. In the heating element 1 for the foot of the present embodiment, by the protrusions 32 protruding from each of the first straight portions 315, the maximum temperature of the heating surface can be lowered and localized high temperature rise can be suppressed. In addition, with the protrusion 32, the heat generating material 4 is difficult to move in the longitudinal direction in the inside of the bag body 2, and the heat generating material 4 is not easily deflected to one side in the longitudinal direction.

The protrusion 32 of this embodiment extends along the width direction of the bag body 2. The width dimension H1 of the protruding portion 32 is substantially the same as the width dimension of the edge portion 31 in this embodiment.

From the viewpoint of lowering the maximum temperature of the heating surface and suppressing localized high temperature rise, the protrusion size of the protrusion 32 (hereinafter referred to as the protrusion size L1) should be set as follows. That is, the protrusion dimension L1 of the protrusion 32 relative to the inner dimension D2 of the position corresponding to the protrusion 32 of the bag body 2 in the direction in which the protrusion 32 protrudes is preferably set to 5% or more, preferably 10% or more and 40% Or less, more preferably 15% or more and 35% or less.

Here, in the present invention, the "inner dimension D2 of the position corresponding to the protrusion 32 of the bag body 2 in the direction in which the protrusion 32 protrudes" refers to the position where the protrusion 32 is formed, assuming that there is no protrusion 32 The size of the time from the position of the edge 31 to the position of the opposite edge 31. Furthermore, the so-called "projection size L1 of the projecting portion 32" herein refers to the projecting size L1 of one projecting portion 32. Therefore, when the plurality of protrusions 32 are located on the straight line T1, "the protrusion size L1 of the protrusion 32" refers to the protrusion size of one of the protrusions 32.

On the other hand, from the viewpoint of ensuring the heating effect of the heating element 1 for the foot, in the direction in which the protrusion 32 protrudes, the dimension D1 between the protrusion 32 and the portion facing the protrusion 32 becomes the following condition In this way, the protrusion size L1 of the protrusion 32 is set. That is, the size D1 is set to preferably 20% or more and 95% or less, more preferably 25% or more and 85% or less, and still more preferably 30% or more and 70% or less with respect to the inner size D2.

Here, the base point of "inner dimension D2" and "projection dimension L1" is the center point in the width direction of the projection 32 on the inner periphery of the edge 31 (actually the extension of the inner periphery of the storage space). The "extended line forming the inner periphery of the storage space" does not actually appear because the protrusion 32 and the edge 31 are integrated. It is an imaginary line that smoothly connects the inner periphery of the edge 31 on both sides of the protrusion 32 .

In addition, the "projection size L1" is the maximum value of a line parallel to the inner periphery of the edge 31 on which the projection 32 is formed, and having an intersection with the projection 32, and the distance between the inner periphery. In addition, the so-called "direction in which the protrusion 32 protrudes" is a direction orthogonal to the inner peripheral edge when the inner peripheral edge of the edge 31 where the protrusion 32 is formed is linear, and the edge where the protrusion 32 is formed When the inner peripheral edge of the portion 31 is curved, it is a direction perpendicular to the tangent to the inner peripheral edge of the center point of the width direction of the protrusion 32 on the inner peripheral edge of the edge portion 31. In this embodiment, since the inner peripheral edge of the edge 31 on which the protrusion 32 is formed is linear, the "direction in which the protrusion 32 protrudes" is parallel to the width direction of the heating element 1 for the foot.

In addition, in this embodiment, the pair of protrusions 32 are located on the straight line T1. The dimension D1 is the dimension obtained by subtracting the total protrusion dimension L1 of the protrusion 32 (that is, L1+L1) from the inner dimension D2. At this time, D1=D2-(L1+L1).

In contrast, for example, as shown in FIG. 7 (modification 2) or FIG. 8 (modification 3-1), when there is only one protrusion 32 on the straight line T1, the dimension D1 is the protrusion of the protrusion 32 minus the inner dimension D2 The size of size L1. At this time, D1=D2-L1. Furthermore, when a plurality of line segments are drawn between the protrusion 32 and the portion opposite to the protrusion 32 in the direction in which the protrusion 32 protrudes, the so-called "dimension D1" here is the shortest line segment among the plurality of line segments size of.

However, the protrusion dimension L1 and the width dimension H1 of the protrusion 32 are not particularly limited. In addition, the protruding direction of the protruding portion 32 may not be along the width direction of the bag body 2, and may be inclined with respect to the width direction, for example.

The protruding portion 32 of this embodiment is formed at the boundary portion between a first straight portion 315 and the arc-shaped portion 317. However, the protruding portion 32 may also be provided in any one of the first straight portion 315, the arc-shaped portion 317, or the second straight portion 316.

The pair of protrusions 32 are located on the straight line T1 in this embodiment. That is, the protrusion directions of the plurality of protrusions 32 are along the straight line T1. In the heating element 1 for the foot of the present embodiment, since the heating material 4 does not exist in the portion where the protrusion 32 is located, the position of the protrusion 32 is easily bent along the straight line T1.

As shown in FIG. 2, a plurality of (here, two) recesses 33 recessed from the outer edge of the bag body 2 are formed in the joint 3. The recess 33 in this embodiment is a notch formed at a position corresponding to the protrusion 32. The recess 33 may be formed when the sheet is formed, or may be cut after the bag body 2 is formed. The periphery of the recess 33 is formed in an arc shape in this embodiment, but it may be formed in an acute angle or an obtuse angle, and it is not particularly limited. In the heating element 1 for the foot of the present embodiment, by forming the recess 33 at the position corresponding to the protrusion 32, the bonding strength of the joint 3 can be maintained and it is easy to bend at the position corresponding to the protrusion 32.

(2) Effect As described above, the protruding portion 32 of the heating element 1 for the foot of the present embodiment protrudes from the edge portion 31 formed along at least a part of the outer periphery of the bag 2 toward the heating material 4 side. According to this, the maximum temperature of the heating surface in the heating element 1 can be lowered, and the localized high temperature rise can be suppressed. Here, by forming the protruding portion 32 at the center of the longitudinal direction of the bag body 2, since the maximum temperature drops and the high-temperature area increases, the temperature distribution can be uniformized and the foot can be warmed in a wide range. On the other hand, by forming the protruding portion 32 at a position deviated from one end side in the longitudinal direction of the bag body 2, the maximum temperature is lowered and the high-temperature region moves from the center portion of the bag body 3 in the longitudinal direction, for example, The toes (finger) are warm.

In addition, the heat generating material 4 enclosed in the bag body 2 is prevented from moving by the protrusion 32. Therefore, even if the heating element 1 for the foot of the present embodiment is stepped on with the foot 5, the heating material 4 is not likely to deviate from the inside of the bag 2 to one side. In addition, the heating element 1 for underfoot of this embodiment is easy to bend along the part of the protrusion 32, and it is easy to be adhered along the foot 5.

In addition, in the heating element 1 for the foot of the present embodiment, the protrusion dimension L1 of the protrusion 32 is 15% or more of the inner dimension D2 of the bag body corresponding to the position 2 of the protrusion 32 in the direction in which the protrusion 32 protrudes. And below 35%. Therefore, the maximum temperature of the heating surface of the heating element 1 can be lowered more effectively, the localized high temperature rise can be suppressed, and the heating material 4 can be prevented from deviating to one side in the inside of the bag 2.

In addition, in the heating element 1 for the foot of the present embodiment, in the direction in which the protrusion 32 protrudes, the dimension D1 between the protrusion 32 and the portion facing the protrusion 32 is relative to the sum of the bag body 2 The inner dimension D2 of the corresponding position of the protrusion 32 is 30% or more and 70% or less. Therefore, according to this aspect, a certain warming effect in the heating element 1 for the foot can be ensured.

In addition, the heating element 1 for the foot of the present embodiment includes a plurality of protrusions 32, and the protrusion direction of the plurality of protrusions 32 is along the straight line T1. Therefore, the heating element 1 for the foot is easily bent along the straight line T1, and the heating element 1 for the foot is further easily deformed along the foot 5.

In addition, in the heating element 1 for the foot of the present embodiment, a recessed portion is formed at a position corresponding to the protruding portion 32 in the outer edge of the bag body 2. Therefore, the heating element 1 for the underfoot is easier to bend along the straight line T1, and the heating element 1 for the underfoot is further easily deformed along the foot 5.

(3) Variations The above-mentioned embodiment is only one of various embodiments of the present invention. As long as the embodiment can achieve the purpose of the invention, various changes can be made according to the design and the like. Hereinafter, a modified example of the embodiment will be described. The modified examples described below can be appropriately combined and applied.

(3.1) Examples of changes in the outer shape of the bag (variation example 1) (3.1.1) Variation 1-1 The heating element 1 for the foot of the above-mentioned embodiment is formed in a substantially D-shape in a front view, but as shown in FIG. 4, it may be formed in a shape along the inner sole 61 of the shoe 6.

The heating element 1 for the foot of the modified example 1-1 has two pairs of protrusions 32. A pair of protrusions 32 are located on a straight line T1. A pair of protrusions 32 of the two sets are separated from each other in the longitudinal direction of the heating element 1 for the foot.

The protrusion dimension L1 of the protrusion 32 is preferably set to 5% or more, more preferably 10% or more and 40% or less, and still more preferably 15% or more and 35% or less relative to the inner dimension D2. In addition, the protrusion size of the protrusion 32 is set such that the dimension D1 relative to the inner dimension D2 is preferably 20% or more and 95% or less, preferably 25% or more and 85% or less, more preferably 30% or more and 70% or less. L1.

Here, the base point of "inner dimension D2" and "projection dimension L1" is the center point in the width direction of the projection 32 on the inner periphery of the edge 31 (actually forming the extension of the inner periphery of the storage space). The "extended line forming the inner periphery of the storage space" does not actually appear because the protrusion 32 and the edge 31 are integrated. It is an imaginary line that smoothly connects the inner periphery of the edge 31 on both sides of the protrusion 32 .

The heating element 1 for the foot of the modified example 1-1 can also exhibit the same effect as the above-mentioned embodiment.

(3.1.2) Variations 1-2 The heating element 1 for the foot of the above-mentioned embodiment is formed in a substantially D-shape in a front view, but as shown in FIG. 5, it may be formed in a rectangular shape in a front view. In the heating element 1 for the foot of Modification 1-2, the edge portion 31 includes a pair of long side portions 311 formed along the length direction, and a pair of short side portions 312 and four corner portions 313 formed along the width direction. The pair of long side portions 311 are formed substantially linearly and parallel to each other. The pair of short side portions 312 are curved so as to protrude outward in the longitudinal direction, but may be formed in a linear shape. Each corner portion 313 connects an end of a long side portion 311 and an end of a short side portion 312. The corner portion 313 is formed in a rounded shape, but for example, it may be formed in a C-chamfered shape, an obtuse-angled shape, an acute-angled shape, or the like.

Each protrusion 32 protrudes from each long side portion 311 toward the heat generating material 4 side, and is located on a straight line T1. The protrusion dimension L1 of the protrusion 32 is preferably set to 5% or more, more preferably 10% or more and 40% or less, and still more preferably 15% or more and 35% or less relative to the inner dimension D2. In addition, the protrusion size of the protrusion 32 is set such that the dimension D1 relative to the inner dimension D2 is preferably 20% or more and 95% or less, preferably 25% or more and 85% or less, more preferably 30% or more and 70% or less. L1.

The heating element 1 for the foot of the modified example 1-2 can also exert the same effect as the above-mentioned embodiment.

(3.1.3) Variations 1-3 The heating element 1 for the foot of the above-mentioned embodiment is formed in a substantially D-shape in a front view, but as shown in FIG. 6, it may be formed in an oblong shape in a front view. Here, the “oblong” in the present invention refers to a circle extending in one direction, and includes, for example, an oval, an ellipse, an oval shape, and a rectangle with rounded corners.

In the heating element 1 for the foot of the modification 1-3, the edge part 31 is formed in a curve shape. The protruding portion 32 protrudes from the edge portion 31 toward the heat generating material 4 side. The protrusion dimension L1 of the protrusion 32 is preferably set to 5% or more, more preferably 10% or more and 40% or less, and still more preferably 15% or more and 35% or less relative to the inner dimension D2. In addition, the protrusion size of the protrusion 32 is set such that the dimension D1 relative to the inner dimension D2 is preferably 20% or more and 95% or less, preferably 25% or more and 85% or less, more preferably 30% or more and 70% or less. L1.

Here, the base point of "inner dimension D2" and "projection dimension L1" is the center point in the width direction of the projection 32 on the inner periphery of the edge 31 (actually forming the extension of the inner periphery of the storage space). The "extended line forming the inner periphery of the storage space" does not actually appear because the protrusion 32 and the edge 31 are integrated. It is an imaginary line that smoothly connects the inner periphery of the edge 31 on both sides of the protrusion 32 .

The heating element 1 for the foot of the modification 1-3 can also exhibit the same effect as the above-mentioned embodiment.

(3.2) Variations on the number of protrusions (variation 2) The heating element 1 for the foot of the above-mentioned embodiment has two protrusions 32, but as shown in FIG. 7, it may have only one protrusion 32. As shown in FIG. In the heating element 1 for the underfoot of Modification 2, the protruding portion 32 protrudes from only one of the long side portions 311 of the pair of long side portions 311.

The protrusion dimension L1 of the protrusion 32 is preferably set to 5% or more, more preferably 10% or more and 40% or less, and still more preferably 15% or more and 35% or less relative to the inner dimension D2. In addition, the protrusion size of the protrusion 32 is set such that the dimension D1 relative to the inner dimension D2 is preferably 20% or more and 95% or less, preferably 25% or more and 85% or less, more preferably 30% or more and 70% or less. L1.

The heating element 1 for the foot of the modified example 2 can also exhibit the same effect as the above-mentioned embodiment.

(3.3) Modification of the arrangement of the protrusion (modification 3) (3.3.1) Variation 3-1 The heating element 1 for the foot of the above-mentioned embodiment has two protrusions 32 formed on a straight line T1. However, as shown in FIG. 8, when viewed in the protrusion direction of the protrusions 32, the two protrusions 32 are staggered from each other. In the heating element 1 for the underfoot of Modification 3-1, a pair of protrusions 32 are formed to be shifted from each other in the longitudinal direction of the heating element 1 for the underfoot.

The protrusion dimension L1 of the protrusion 32 is preferably set to 5% or more, more preferably 10% or more and 40% or less, and still more preferably 15% or more and 35% or less relative to the inner dimension D2. In addition, the protrusion size of the protrusion 32 is set such that the dimension D1 relative to the inner dimension D2 is preferably 20% or more and 95% or less, preferably 25% or more and 85% or less, more preferably 30% or more and 70% or less. L1.

The heating element 1 for the foot of the modified example 3-1 can also exhibit the same effect as the above-mentioned embodiment.

(3.3.2) Variation 3-2 The heating element 1 for the foot of the above-mentioned embodiment is formed on a pair of long side portions 311 with protruding portions 32 respectively. Although not shown in particular, it may be diagonally formed at the four corner portions 313 (refer to FIG. 5). A pair of corners 313 of the slab is formed with protrusions 32.

In the heating element 1 for the foot of the modified example 3-2, the protruding portion 32 protrudes from the edge portion 31 along the diagonal line that is a straight line. A pair of protrusions 32 are located on a diagonal line.

The heating element 1 for the foot of the modified example 3-2 can also exert the same effect as the above-mentioned embodiment.

Furthermore, the protruding portion 32 can also protrude from the short side portion 312 of the edge portion 31.

(3.4) Variations on the structure of the bag body (variation 4) In the heating element 1 for the foot of the above embodiment, the bag body 2 is formed by stacking two sheets of the same shape and then joining the outer peripheries to form a bag shape. However, as shown in FIG. 9, one sheet may be folded After that, the three sides are joined to form a bag shape. In the heating element 1 for the foot of the modification 4, the edge portion 31 is formed along three of the four sides of the bag body 2.

In the heating element 1 for the foot of the modified example 4, one surface of the bag body 2 is the front side sheet portion 21, and the opposite side is the back side sheet portion 22. The front side sheet portion 21 and the back side sheet portion 22 are formed integrally. The part denoted by the symbol 34 in FIG. 9 is the folded part. From the viewpoint of ensuring strength, the folded portion 34 may also be welded.

The protrusion dimension L1 of the protrusion 32 is preferably set to 5% or more, more preferably 10% or more and 40% or less, and still more preferably 15% or more and 35% or less relative to the inner dimension D2. In addition, the protrusion size of the protrusion 32 is set such that the dimension D1 relative to the inner dimension D2 is preferably 20% or more and 95% or less, preferably 25% or more and 85% or less, more preferably 30% or more and 70% or less. L1.

The heating element 1 for the foot of the modification 4 can also exhibit the same effect as the heating element 1 for the foot of the above-mentioned embodiment.

In addition, although illustration is omitted, it is also possible to use a sheet in which the back side sheet portion 22 and the front side sheet portion 21 are connected in a cylindrical shape, and the two sides thereof are joined to form the bag-shaped bag body 2. In addition, from the viewpoint of ensuring strength, the remaining two sides can also be welded.

(3.5) About the modification of the shape of the protrusion (modification 5) In the heating element 1 for the foot of the above-mentioned embodiment, the protruding portion 32 is elongated in the protruding direction, but the shape of the protruding portion 32 may be the shape of the following modification examples 5-1 to 5-6.

(3.5.1) Variation 5-1 In the heating element 1 for the foot of the modified example 5-1, the protrusion 32 is formed in a semicircular shape as shown in FIG. 10(A), and the inner corner formed by the edge 31 and the protrusion 32 is not smoothly connected Curved, with corners. The center of the arc forming the edge on the side of the heating material 4 in the protrusion 32 is located on the edge portion 31 or closer to the side of the heating material 4 than the edge portion 31.

(3.5.2) Variation 5-2 In the heating element 1 for underfoot of Modification 5-2, the protrusion 32 is formed in a substantially rectangular shape as shown in FIG. 10(B), and the outer corner portion 321 on the front end side in the protrusion direction of the protrusion 32 is substantially a right angle.

(3.5.3) Variation 5-3 In the heating element 1 for the foot of the modified example 5-3, the protruding portion 32 includes a convex portion 322 and a triangular portion 323 as shown in FIG. 10(C). The convex portion 322 is the base of the protrusion 32. The triangular portion 323 protrudes from the front end surface of the convex portion 322 in the protruding direction. The triangular portion becomes sharper in a way that its width becomes narrower as it goes to the front end.

(3.5.4) Variations 5-4 In the heating element 1 for the foot of the modified example 5-4, the protrusion 32 is formed in a substantially triangular shape as shown in FIG. 10(D). The protruding portion 32 becomes sharper in such a manner that the width becomes narrower as it goes in the protruding direction.

(3.5.5) Variations 5-5 In the heating element 1 for the foot of the modified example 5-5, as shown in FIG. 10(E), the protruding part 32 is formed in such a way that the width becomes larger as it goes in the protruding direction. The edge of the protrusion 32 in the width direction is curved.

(3.6) Other changes In the following, other modified examples are listed.

The heating element 1 for the foot of the above embodiment is arranged between the sole 51 of the user and the inner sole 61 of the shoe 6, but in the present invention, it may also be arranged between the instep of the foot 5 and the shoe 6, or the side surface of the foot 5 Between 6 shoes.

The heating element 1 for the foot of the above-mentioned embodiment has two protrusions 32, but it may have three or more protrusions 32. As shown in FIG.

In the heating element 1 for the foot of the above-mentioned embodiment, the protruding portion 32 is formed at the central portion of the bag body 2 in the longitudinal direction, but the protruding portion 32 may be formed at a position on the one end side in the longitudinal direction.

In the heating element 1 of the above-mentioned embodiment and each modified example, the recess 33 is provided at a position corresponding to the protrusion 32, but the recess 33 may not be provided.

In the present invention, like "substantially parallel" or "substantially orthogonal", the situation accompanied by the expression of "substantially" is used. For example, the so-called "substantially parallel" refers to the state of being "parallel" in nature, not strictly "parallel", and it also means an error of several percent. The performance of other accompanying "approximate" is also the same.

In addition, in the present invention, expressions such as "front end" and "front end" are used to distinguish between "...end" and "...end". For example, the so-called "front end" refers to a part having a certain range including the "front end". The performance of other accompanying "...ends" is also the same.

(4) Example Hereinafter, with regard to Examples, a test was conducted to confirm the effect due to the provision of the protrusion 32 in the present invention. However, the present invention is not limited to the following examples.

Regarding Examples 1 to 3, the heating elements with protrusions were produced in the joints. For the comparative example, the heating elements without protrusions were produced in the joints. The temperature of the heating surface during heating was photographed with an infrared thermal imager, and the temperature distribution was compared. .

Regarding the heating elements of Examples 1 to 3 and Comparative Examples, as shown in Figure 11 (A) to Figure 11 (D), the heating surface is formed into a substantially rectangular shape, and the length dimension of the heating surface E1 (longest part) = 181mm , The heating element with the width of the heating surface W=116mm. In the heating elements of Examples 1 to 3 and the comparative example, the materials of the heating material and the bag body are the same as the above-mentioned embodiment, and all the same are used. In addition, the amount of the heat-generating material in each of Examples 1 to 3 and the comparative example was set to 70 g, and all were set to the same weight.

Regarding the heating element of Example 1, as shown in FIG. 11(A), a pair of protrusions are formed at one end of the heating surface, that is, E2=90.5mm (ie the center in the longitudinal direction), and each protrusion is The protrusion size is set to L2=20mm.

Regarding the heating element of Example 2, as shown in FIG. 11(B), a pair of protrusions are formed at one end of the heating surface, that is, E2=90.5mm (ie the center in the longitudinal direction), and each protrusion is The protrusion size is set to L3=35.5mm.

Regarding the heating element of Example 3, as shown in Figure 11(C), a pair of protrusions are formed at one end from the heating surface, that is, E3=134.75mm, and the protrusion size of each protrusion is set to L3=35.5 mm.

Fig. 12 shows the results of photographing with an infrared thermal imaging camera in parallel with Examples 1 and 2 and the comparative example (Result 1). In addition, the area of each temperature range was calculated from the results of shooting with an infrared thermal imager, and the relationship between each temperature range and the area ratio of the temperature range relative to the whole area is shown in Table 1-1. In addition, the area ratio of the high temperature region (the temperature region above the maximum temperature -5°C and below the maximum temperature) is shown in Table 1-2, which is extracted from Table 1-1.

In addition, the shooting position is different from the result 1. FIG. 13 shows the result of shooting with an infrared thermal imaging camera in parallel with Examples 2 and 3 and the comparative example (result 2). In addition, the area of each temperature range was calculated from the result of shooting with an infrared thermal imager, and the relationship between each temperature range and the area ratio of the temperature range to the whole area is shown in Table 2-1. In addition, the area ratio of the high-temperature region is extracted from Table 2-1 and shown in Table 2-2.

The graph of Table 1-1 is shown in FIG. 14, and the graph of Table 2-1 is shown in FIG. 15. In the graph, the vertical axis is the area ratio (%) and the horizontal axis is the temperature (°C).

In Result 1, the maximum temperature of each of Examples 1 and 2 and Comparative Example was extracted from Table 1-1, and the difference between the maximum temperature of Comparative Example and Examples 1 and 2 was calculated. Furthermore, the average temperature of the heating surface of each of Examples 1 and 2 and the Comparative Example was calculated, and the difference between the average temperature of the Comparative Example and Examples 1 and 2 was calculated. The results are shown in Table 3. [Table 1-1] Temperature [℃] Example 1 [%] Example 2 [%] Comparative example [%] Above 50, less than 51 0.00 0.00 0.00 49 or more, less than 50 0.00 0.00 0.02 More than 48, less than 49 0.00 0.00 12.54 47 or more, less than 48 13.11 0.00 15.77 Above 46, less than 47 20.54 8.67 13.90 45 or more, less than 46 14.84 26.78 12.17 More than 44, less than 45 9.97 15.31 8.62 Above 43, less than 44 7.33 11.10 6.69 42 or more, less than 43 7.01 7.64 5.07 41 or more, less than 42 5.35 5.85 3.98 40 or more, less than 41 4.26 4.91 4.00 More than 39, less than 40 3.80 3.98 2.75 38 or more, less than 39 2.32 3.48 2.75 37 or more, less than 38 2.19 3.05 2.09 36 or more, less than 37 2.21 2.30 2.52 35 or more, less than 36 1.36 1.80 1.71 34 or more, less than 35 1.28 1.94 1.73 More than 33, less than 34 2.30 1.93 1.59 More than 32, less than 33 1.53 0.68 1.39 31 or more, less than 32 0.55 0.39 0.52 30 or more, less than 31 0.02 0.20 0.21 More than 29, less than 30 0.00 0.00 0.00 [Table 1-2] Example 1 Example 2 Comparative example High temperature area [℃] 42.9-47.9 41.8-46.8 44-49 Area ratio of high temperature area [%] 66.6 70.7 63.0 [table 2-1] Temperature [℃] Example 2 [%] Example 3 [%] Comparative example [%] More than 52, less than 53 0.00 0.00 0.01 More than 51, less than 52 0.34 0.01 4.78 Above 50, less than 51 6.68 1.25 20.76 49 or more, less than 50 24.81 18.34 17.15 More than 48, less than 49 18.66 18.80 14.12 47 or more, less than 48 14.15 15.40 11.78 Above 46, less than 47 11.60 11.96 10.33 45 or more, less than 46 7.55 9.61 8.21 More than 44, less than 45 5.74 7.49 5.06 Above 43, less than 44 3.24 5.67 2.76 42 or more, less than 43 1.92 3.85 2.30 41 or more, less than 42 1.41 2.73 1.07 40 or more, less than 41 1.17 1.66 0.70 More than 39, less than 40 0.98 1.07 0.43 38 or more, less than 39 0.70 0.64 0.24 37 or more, less than 38 0.47 0.55 0.14 36 or more, less than 37 0.32 0.34 0.10 35 or more, less than 36 0.22 0.28 0.06 34 or more, less than 35 0.04 0.20 0.01 More than 33, less than 34 0.00 0.10 0.00 More than 32, less than 33 0.00 0.04 0.00 31 or more, less than 32 0.00 0.00 0.00 [Table 2-2] Example 2 Example 3 Comparative example High temperature area [℃] 46.4-51.4 46-51 47-52 Area ratio of high temperature area [%] 72.0 65.8 68.6 [table 3] Maximum temperature [℃] Difference with the maximum temperature of the comparative example [℃] Average temperature [℃] The difference between the average temperature of the comparative example [℃] Comparative example 49 44 Example 1 47.9 -1.1 44.1 0.1 Example 2 46.8 -2.2 43.4 -0.6

In result 1, it can be seen from FIG. 12 that the white part showing a higher temperature in the center of the heating surface in the comparative example is thicker and clearly present, but the white part of the heating element of Examples 1 and 2 is thinner than that of the comparative example. Furthermore, as can be seen from Table 1-1, Table 1-2, and Fig. 14, compared with the comparative example, the area ratio of the high-temperature region of the heating elements of Examples 1 and 2 increased and the maximum temperature decreased by 1°C to 2°C.

In result 2, it can be seen from FIG. 13 that the white part showing a higher temperature in the center of the heating surface in the comparative example is thicker and clearly present, but the white part of the heating element of Examples 2 and 3 is thinner than that of the comparative example. Furthermore, as can be seen from Table 2-1, Table 2-2, and Fig. 15, compared with the comparative example, the area ratio of the high-temperature region of the heating elements of Examples 2 and 3 is approximately the same or more, and the maximum temperature is lowered by about 1°C.

Therefore, in the heating elements of Examples 1 to 3, compared with the comparative example, it is possible to lower the maximum temperature while keeping the area ratio of the high temperature region of the heating surface equal or more. In short, the heating elements of Examples 1 to 3 can suppress the local high temperature rise of the heating surface.

Especially from Table 1-2 and Table 2-2, it can be seen that in the heating elements of Examples 1 and 2, the area of the high-temperature region is increased by about 3.4~6.7% compared with the comparative example, and the maximum temperature is 1℃~2℃ lower than that of the comparative example. . Therefore, it can be seen that if the protrusion is arranged at a position corresponding to the center of the heating surface, the maximum temperature of the heating surface can be lowered compared with the comparative example, and the area of the high temperature region can be increased. That is, by arranging the protrusion at a position corresponding to the center of the heating surface, the uniformity of the temperature distribution of the heating surface can be improved.

In addition, as can be seen from Table 3, the heating elements of Examples 1 and 2 have a maximum temperature difference of approximately 1 to 2°C compared with the comparative example, and the difference relative to this average temperature is 0.1 to 0.6°C. That is, compared with the comparative example, the heating elements of Examples 1 and 2 have a lower average temperature lower than that of the maximum temperature. That is, by arranging the protrusion at a position corresponding to the center of the heating surface, the maximum temperature of the heating surface can be lowered and the average temperature can be suppressed from decreasing.

In addition, it can be seen from FIG. 13 that, in the heating element of Example 3, compared with the comparative example, the high-temperature region moves in the longitudinal direction to a position leaning to the side opposite to the protrusion. That is, it can be seen that by forming the protruding portion at a position deviated from one end of the bag in the longitudinal direction, the high temperature region can be moved from the center in the longitudinal direction of the bag.

1: Heating element for foot 2: bag body 21: Front side sheet part 22: Back side sheet part 3: Joint 31: Margin 311: Long Side 312: Short side 313: corner 315: The first straight part 316: The second straight part 317: arc-shaped part 32: protrusion 321: Outer corner 322: Convex 323: Triangle 33: recess 34: Folding part 4: heating material 45: 5: feet 51: Sole of Feet 6: shoes 61: Insole 7: Anti-slip part 71: small protrusion D1: size D2: Inside size E1: Length dimension E2: Length dimension E3: Length dimension H1: Width size L1: Protruding size L2: Protruding size L3: Protruding size T1: Straight line W: width size

Fig. 1 is a cross-sectional view showing a usage state of a heating element for underfoot in one embodiment of the present invention. Fig. 2 is a front view of the heating element for underfoot. Fig. 3(A) is a cross-sectional view taken along the line A-A in Fig. 2. Fig. 3(B) is a bottom view of the heating element for underfoot. Fig. 4 is a front view of the heating element of Modification 1-1. Fig. 5 is a front view of the heating element of modification 1-2. Fig. 6 is a front view of the heating element of the modification 1-3. Fig. 7 is a front view of the heating element of Modification 2. Fig. 8 is a front view of the heating element of Modification 3-1. Fig. 9 is a front view of the heating element of Modification 4. Fig. 10(A) is an enlarged view of the protrusion of the heating element of Modification 5-1. Fig. 10(B) is an enlarged view of the protrusion of the heating element of Modification 5-2. Fig. 10(C) is an enlarged view of the protrusion of the heating element of Modification 5-3. Fig. 10(D) is an enlarged view of the protrusion of the heating element of Modification 5-4. Fig. 10(E) is an enlarged view of the protrusion of the heating element of Modification 5-5. Fig. 11(A) is a front view of the heating element of the first embodiment. Fig. 11(B) is a front view of the heating element of the second embodiment. Fig. 11(C) is a front view of the heating element of the third embodiment. Fig. 11(D) is a front view of the heating element of the comparative example. Figure 12 is a graph showing the temperature distribution of result 1. Figure 13 is a graph showing the temperature distribution of Result 2. Figure 14 is a graph showing the temperature distribution of result 1. Figure 15 is a graph showing the temperature distribution of result 2.

1: Heating element for foot

2: bag body

21: Front side sheet part

3: Joint

31: Margin

315: The first straight part

316: The second straight part

317: arc-shaped part

32: protrusion

33: recess

4: heating material

D1: size

D2: Inside size

H1: Width size

L1: Protruding size

T1: Straight line

Claims (5)

A heating element for underfoot, which is arranged between the user's foot and the shoe, and has: A bag body, which is formed into a bag shape by a front side sheet portion and a back side sheet portion; and Heating material, which is enclosed in the aforementioned bag; The bag body has a joining part formed by joining the front side sheet part and the back side sheet part; The aforementioned joint includes: A rim, which is formed along at least a part of the outer periphery of the aforementioned bag; and The protrusion part protrudes from the edge part toward the heat generating material side. Such as the heating element for the foot of claim 1, wherein the protrusion size of the protrusion is: the inner dimension of the bag body corresponding to the protrusion in the direction in which the protrusion protrudes is 15% or more and 35% the following. The heating element for the foot of claim 1 or 2, wherein in the direction in which the protruding portion protrudes, the dimension between the protruding portion and the portion facing the protruding portion is relative to the bag body and the protruding portion The inner dimension of the corresponding position is 30% or more and 70% or less. For example, the heating element for feet in any one of claims 1 to 4, which includes a plurality of the aforementioned protrusions The protrusion directions of the plurality of protrusions are along a straight line. The heating element for underfoot according to any one of claims 1 to 4, wherein a recess is formed at a position corresponding to the protrusion on the outer edge of the bag.

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