HK1118181A1 - Hand drying apparatus - Google Patents

Abstract

Disclosed is a hand dryer, comprising a box main body(1), a high-pressure draft generator(2), front and back air nozzles(6a,6b). A concave hand insertion part(3) is arranged at the upper part of the box main body(1); the high-pressure draft generator(2) is disposed in the box main body(1); the front and back air nozzles(6a,6b) eject the high-pressure draft generated by the high-pressure draft generator(2) to the hand insertion part(3); a plurality of outlets(7) shaped like lineal slits form the front and the back nozzle parts and the interval between the slit-like outlets(7)or/and the length of the slit-like outlets(7) on the front side is/are different from that on the back side. In this way, a hand dryer which can prevent noise, with good drying performance and using effect and without adopting a complicated structure, can be obtained.

Description

Hand drying device

The present application is a divisional application of an application entitled "hand dryer" and having an application number of 200580001769.4, filed by mitsubishi motor corporation on 18.08/2005.

Technical Field

The present invention relates to a hand drying device for hygienically drying wet hands after washing by jetting a high-speed airflow.

Background

A hand drying device has been developed which performs a sanitary hand drying process of blowing off moisture and drying by jetting a high-speed air stream to wet hands after washing without wiping them with a towel, a handkerchief, or the like. Such a device uses the kinetic energy of the high-speed air flow to blow off moisture adhering to the hand, and therefore has a problem that the collision between the opposing jets causes turbulence and noise.

In patent document 1, therefore, one nozzle is formed as a slit discharge hole, and the opposing nozzle is formed as a structure in which circular hole discharge holes are arranged substantially in a line, and the occurrence of noise is suppressed by reducing turbulence generated by collision between opposing jets.

Patent document 1: japanese unexamined patent application publication No. 2001-104212

In patent document 1, although turbulence generated by collision between the jets can be reduced, since a circular jet having a drying efficiency lower than that of a slit jet is used on one side, there is a problem that the drying performance of the front and back surfaces of the integrated hand is poor, and the feeling of use is impaired.

The present invention has been made in view of the above problems, and an object of the present invention is to provide a hand dryer which can prevent noise without using a complicated structure, and which has high drying performance and good feeling of use.

Disclosure of Invention

In order to solve the above problems and achieve the object, the present invention is a hand drying device including: a main body case having a hand insertion portion formed in a concave shape at an upper portion thereof, a high-pressure air flow generating device, and front and rear side air nozzle portions facing each other; the high-pressure airflow generating device is arranged in the body box body which generates high-pressure airflow; the front-side and back-side air nozzle portions are formed by a plurality of slit-shaped discharge ports arranged in a line shape, and the length of the slit-shaped discharge ports and/or the arrangement interval of the slit-shaped discharge ports are made different between the front side and the back side.

The next invention is a hand drying device having: a main body case having a hand insertion portion formed in a concave shape at an upper portion thereof, a high-pressure air flow generating device, and front and rear side air nozzle portions facing each other; the high-pressure airflow generating device is arranged in the body box body which generates high-pressure airflow; the front-side and back-side air nozzle portions are formed by a plurality of slit-shaped discharge ports provided in a line shape, respectively, and the slit-shaped discharge ports on the front side are formed to be longer than the slit-shaped discharge ports on the back side so as to sandwich a region where the opposing high-pressure air streams do not collide and form regions where the high-pressure air streams having different lengths collide on both sides.

Another invention is a hand drying device including: a main body case having a hand insertion portion formed in a concave shape at an upper portion thereof, a high-pressure air flow generating device, and front and rear side air nozzle portions facing each other; the high-pressure airflow generating device is arranged in the body box body which generates high-pressure airflow; the front-side and back-side air nozzle portions are formed by a plurality of slit-shaped discharge ports arranged in a line shape, respectively, and the arrangement interval of the slit-shaped discharge ports on the front side is formed shorter than that of the slit-shaped discharge ports on the back side so as to sandwich a region where the opposing high-pressure air streams do not collide and form regions where the high-pressure air streams having different lengths collide on both sides.

According to the hand drying device of the present invention, since the front-side air nozzle portion and the back-side air nozzle portion are formed by the plurality of slit-shaped outlets which are respectively arranged in a linear shape, and the length of the slit-shaped outlets and/or the arrangement interval of the slit-shaped outlets are made different between the front side and the back side, it is possible to obtain a hand drying device which can prevent noise without using a complicated structure, and which is excellent in drying performance and feeling of use.

According to the next invention, since the front-side and back-side air nozzle portions are formed by the plurality of slit-shaped outlets respectively provided in a linear shape, and the slit-shaped outlets on the front side are formed longer than the slit-shaped outlets on the back side so as to sandwich the region where the high-pressure air flows opposed to each other do not collide and to form the regions where the high-pressure air flows having different lengths collide on both sides, noise generation can be prevented without using a complicated structure, dryness and feeling in use can be improved, and the palm, the back and the hand can be dried uniformly.

According to another aspect of the invention, the front-side and back-side air nozzle portions are formed by a plurality of slit-shaped outlets arranged in a line, and the arrangement interval of the slit-shaped outlets on the front side is formed shorter than the arrangement interval of the slit-shaped outlets on the back side so as to sandwich a region where the opposing high-pressure air streams do not collide and to form regions where the high-pressure air streams having different lengths collide on both sides, so that the occurrence of noise can be prevented without using a complicated structure, the dryness and the feeling of use can be improved, and the palm, the back and the hand can be dried uniformly.

In addition, the present invention provides a hand dryer having a hand insertion part and a high-pressure air flow generating device, wherein the hand insertion part is provided with air nozzle parts in a mutually opposite manner, and the air nozzle parts comprise parts which are arranged in a straight line and form a plurality of elongated holes; the high-pressure air flow generating device is communicated with the air nozzle portion via an air blowing passage, and the air nozzle portion jets out the high-pressure air generated in the high-pressure air flow generating device as a high-speed air flow, and the center positions of the inner ends of the two adjacent elongated holes of one air nozzle portion of the air nozzle portion are shifted from the center positions of the elongated holes of the other air nozzle portion in the direction in which the plurality of elongated holes are linearly arranged.

The present invention also provides a hand dryer including a hand insertion unit provided with an air nozzle unit including a plurality of elongated holes arranged in a straight line, the air nozzle unit being disposed to face each other, and a high-pressure air flow generating unit; the high-pressure air flow generator is communicated with the air nozzle section via an air blowing passage, and the air nozzle section blows out the high-pressure air generated in the high-pressure air flow generator as a high-speed air flow, and the center position of the elongated hole of one air nozzle section of the air nozzle section is shifted from the center position of the elongated hole of the other air nozzle section in the direction in which the plurality of elongated holes are linearly arranged.

In addition, the present invention provides a hand drying device having a hand insertion part provided with an air nozzle part including a part constituting a plurality of elongated holes in a linear arrangement in a manner opposed to each other and a high-pressure air flow generating device; the high-pressure air flow generating device is communicated with the air nozzle part through an air supply passage, and the air nozzle part ejects high-pressure air generated in the high-pressure air flow generating device as high-speed air flow, wherein between two adjacent elongated holes of one air nozzle part in the air nozzle part and opposite elongated holes of the other air nozzle part are in a mutual overlapping position relation, and the length of overlapping between one elongated hole of the two adjacent elongated holes and the opposite elongated hole is different from the length of overlapping between the other elongated hole of the two adjacent elongated holes and the opposite elongated hole.

In addition, the present invention provides a hand drying device including: a body having a hand insertion opening at an upper portion thereof; a hand insertion portion having a front wall surface extending downward from the hand insertion opening and a rear wall surface extending downward from the hand insertion opening so as to face the front wall surface; a front-side air nozzle portion that is provided on the front wall surface and includes a portion that forms a plurality of elongated holes in a linear arrangement; a rear-surface-side air nozzle portion that is provided on the rear-surface wall surface and includes a portion that linearly arranges a plurality of elongated holes; a high-pressure air flow generator that communicates with the front-side air nozzle unit and the back-side air nozzle unit via an air blowing passage, wherein the front-side air nozzle unit discharges high-pressure air generated by the high-pressure air flow generator as a high-speed air flow, and slits are formed in the front-side air nozzle unit so as to be arranged obliquely downward from the center toward both sides; the rear-side air nozzle portion discharges the high-pressure air as a high-speed air flow, slits are formed in the rear-side air nozzle portion so as to be arranged obliquely downward from the center toward both sides, and the center positions of the end portions inside two adjacent elongated holes of the rear-side air nozzle portion are shifted from the center positions of the elongated holes of the front-side air nozzle portion in the direction in which the elongated holes are arranged linearly.

Further, the present invention provides a hand drying device including: a body having a hand insertion opening at an upper portion thereof; a hand insertion portion having a front wall surface extending downward from the hand insertion opening and a rear wall surface extending downward from the hand insertion opening so as to face the front wall surface; a front-side air nozzle portion that is provided on the front wall surface and includes a portion that forms a plurality of elongated holes in a linear arrangement; a rear-surface-side air nozzle portion that is provided on the rear-surface wall surface and includes a portion that linearly arranges a plurality of elongated holes; a high-pressure air flow generator that communicates with the front-side air nozzle unit and the back-side air nozzle unit via an air blowing passage, wherein the front-side air nozzle unit discharges high-pressure air generated by the high-pressure air flow generator as a high-speed air flow, and a plurality of elongated holes are formed in the front-side air nozzle unit so as to be arranged obliquely downward from the center toward both sides; the rear-side air nozzle unit discharges the high-pressure air as a high-speed air flow, and has a plurality of elongated holes arranged obliquely downward from the center toward both sides of the rear-side air nozzle unit, and two adjacent elongated holes of the rear-side air nozzle unit are in a positional relationship in which the two elongated holes overlap each other with the opposing elongated hole of the front-side air nozzle unit, and the length of overlap between one of the two adjacent elongated holes and the opposing elongated hole is different from the length of overlap between the other of the two adjacent elongated holes and the opposing elongated hole.

Drawings

Fig. 1 is a perspective view showing a hand dryer according to an embodiment.

Fig. 2 is a front view showing the overall structure of the air flow nozzle unit of the hand dryer according to the embodiment.

Fig. 3 is a sectional view showing the structure of a slit-shaped discharge port of the hand dryer according to the embodiment.

Fig. 4 is a conceptual diagram illustrating a conventional colliding jet operation.

Fig. 5 is a conceptual diagram illustrating the collision jet operation of the hand dryer according to the embodiment.

Fig. 6 is a conceptual diagram illustrating the arrangement of the film-like jet flow according to the embodiment.

Fig. 7 is a conceptual diagram illustrating the collision jet operation.

Fig. 8 is a waveform diagram showing pressure and noise in the related art.

Fig. 9 is a conceptual diagram illustrating the arrangement of the film-like jet flow in the hand dryer according to the embodiment.

Fig. 10 is a waveform diagram showing pressure and noise of the hand dryer according to the embodiment.

Detailed Description

Hereinafter, embodiments of the hand dryer of the present invention will be described in detail with reference to the accompanying drawings. The present invention is not limited to this embodiment.

An embodiment of the present invention will be described with reference to fig. 1 to 10. Fig. 1 is a diagram showing an external configuration of a hand dryer according to the present embodiment. As shown in fig. 1, the hand dryer includes a main body case 1, and the main body case 1 constitutes a housing having a hand insertion portion 3 at an upper portion thereof. A hand insertion portion 3 is formed on the upper side of the main body casing 1 as a recessed space formed by a hand insertion opening 4 and a drying space 5 continuous with the hand insertion opening. The hand insertion portion 3 is formed in a deep-bottomed inclined open groove shape having both side surfaces open and allowing insertion and extraction of a hand, and both hands can be inserted and extracted in an inclined up-down direction in a state of being aligned in a plane.

The high-pressure airflow generator 2 is assembled in the main body casing 1, and the high-pressure airflow generated by the high-pressure airflow generator 2 is guided to the air nozzle sections 6a and 6b provided on the front wall surface and the rear wall surface of the hand insertion portion 3 by air blowing paths (not shown) divided into two on the front side and the rear side of the hand insertion portion 3. In this hand dryer, high-speed air is jetted into the hand insertion portion 3 through the air nozzle portions 6a and 6b provided to face each other, the water attached to the hand inserted into the hand insertion portion 3 is blown off to the drying processing space 5, the blown-off water is collected by the water receiving portion with an inclination at the bottom of the concave space, and the collected water is stored in the drain tank 20 through the drain port and the drain pipe, not shown, at the inclined lower end. The drain tank 20 is detachably attached to the main body casing 1, and is provided with a detachable lid.

The high-pressure airflow generating device 2 is composed of a dc brushless motor (which may be a normal rectifier motor or an induction motor), a drive circuit for driving the motor, and a turbo fan rotated by the dc brushless motor, and in this embodiment, is attached to the lower side of the hand insertion portion 3 of the main body casing 1, and is automatically operated by a control circuit (not shown). The air inlet side of the high-pressure airflow generating device 2 faces the air inlet channel arranged in the main body box 1, and air outside the device can be sucked from the air inlet at the end of the air inlet channel.

A hand detection sensor 9 is provided on a wall surface forming the drying processing space 5, and whether or not a hand is inserted into the drying processing space 5 through the hand insertion portion 3 is detected based on a detection signal of the hand detection sensor 9. The detection signal of the hand detection sensor 9 is inputted to the control circuit equipped with a microcomputer, and when the control circuit determines that a hand is inserted, the high-pressure airflow generation device 2 is energized to eject a high-speed airflow through the air nozzle portions 6a and 6 b.

In this hand drying device, when both hands are inserted into the hand insertion portion 3 through the hand insertion port 4 in a state in which both hands are naturally aligned, the hands are detected by the hand detection sensor 9, the high-pressure airflow generation device 2 is operated by the processing of the control circuit, and the high-speed airflows 8a and 8b are ejected from the air nozzle portions 6a and 6b into the hand insertion portion 3, and hit the front and back surfaces of the inserted hands to blow moisture adhering to the hands to the bottom side of the hand insertion portion 3. Further, by inserting and extracting the hand into and from the hand insertion portion 3, it is possible to completely remove water droplets adhering to the entire hand and dry the hand. After the hand drying process is completed, when the hand is completely pulled out from the hand insertion portion 3, the hand detection sensor 9 detects this and the high-pressure airflow generation device 2 is stopped. The water droplets blown off from the hands adhere to the inner wall surface of the hand insertion portion 3, gradually flow down toward the bottom, and are stored in the drain tank 20 through the drain pipe from the drain port.

The air nozzle portions 6a and 6b, which are main components of the present embodiment, will be described in detail below with reference to fig. 2 and 3. Fig. 2 is a conceptual front view showing the air nozzle 6a on the front side and the air nozzle 6b on the back side which are oppositely provided, for example, as viewed from the front side. In the air nozzle portions 6a and 6b of the present embodiment, the plurality of slit-shaped ejection ports 7a and 7b are formed in a linear shape on both the front surface side and the back surface side, and in this case, a linear shape curved at the central portion is adopted. The slit-shaped outlets 7a and 7b are formed to be slightly inclined downward so that the high-speed air flows 8a and 8b are slightly discharged downward.

Here, as shown in fig. 2, in the air nozzle 6a on the front surface side and the air nozzle 6b on the back surface side, the length La of the slit-shaped discharge port 7a on the front surface side is different from the length Lb of the slit-shaped discharge port 7b on the back surface side, and the arrangement interval Ca of the slit-shaped discharge port 7a on the front surface side is different from the arrangement interval Cb of the slit-shaped discharge port 7b on the back surface side. In this case, the length of the slit-shaped ejection orifices is La > Lb, and the arrangement interval of the slit-shaped ejection orifices is Ca < Cb. In the air nozzle 6a on the front side, the length La and the arrangement interval Ca of each slit-shaped ejection port 7a are the same, and in the air nozzle 6b on the back side, the length Lb and the arrangement interval Cb of each slit-shaped ejection port 7b are the same.

Fig. 3 is a cross-sectional view showing one slit-shaped discharge port 7a or 7 b. A plurality of concave portions 10 (and convex portions 11) extending in the flow direction of the airflow are formed inside the wall surface where the slit-shaped discharge port 7 is formed, and the airflow is finely turbulent by these concave portions. In this case, as shown in fig. 3, a plurality of concave portions 10 and convex portions 11 are formed inside the upper and lower wall surfaces forming the slit-shaped discharge port 7.

The strong action of the jet stream on the surface of the hand is advantageous for blowing off moisture adhering to the hand. It is known that the force of the jet can be assessed by the amount of movement of the air-fluid, i.e. the product of air density, flow rate. However, the force of the colliding jet immediately after the collision with the hand directly acts on the moisture attached to the hand. As shown in fig. 4, in the case of a nozzle in which a plurality of circular holes 50 are formed in a row, the colliding jet ejected from each circular hole 50 forms a wall surface flow 15 that spreads radially, and therefore, further collides with the adjacent wall surface flow 15 to form a large stagnation region 16. In the stagnant area 16, since the force that is held by the hand acts on the moisture adhering to the hand, the moisture remains in the form of stripes in the moving direction of the hand during the insertion and extraction operation of the hand.

On the other hand, in the slit-shaped ejection opening 7, the length of the ejection opening 7 is generally appropriately divided in order to prevent deformation of the nozzle due to internal pressure and suppress turbulence inside the nozzle. The partitioning method has the same effect as the case where a plurality of individual nozzles are formed and the case where a rib is provided as a partition wall in one nozzle. As shown in fig. 5, when the impinging jet of the slit-shaped discharge port 7 after the division is used, a wall flow 15 is formed in a direction perpendicular to the length of the discharge port. This is because the flow of the air flow in the longitudinal direction of the discharge port is restricted, and the wall surface flow 15 is formed only at the longitudinal end portion which is not restricted, and therefore, in the case of the slit-shaped discharge port 7, the stagnation region 16 generated between the adjacent discharge ports is very small compared with the case of the circular hole 50, and therefore the amount of moisture remaining on the hand is small compared with the circular hole 50 in the slit-shaped discharge port 7, and the drying efficiency is high.

However, when the slit-shaped spout 7 is opposed to each other, as shown in fig. 6, when the film-like jet flows 8a and 8b ejected from the slit-shaped spout 7 collide with each other in the hand insertion portion 3, turbulence and a large noise accompanied by the turbulence are generated in the collision portion. As shown in fig. 7, when the jets 8a and 8b collide with each other at a slight angle, particularly above the collision portion, when one of the airflows is largely bent and split, a movement amount corresponding to the bent angle changes, and thus a jet force pushing back the opposite split flow is generated. Once pushed back, it shunts in the opposite direction past the equilibrium state. The series of self-excited vibrations form pressure changes and apply the changes to the flow dividing portion below the collision portion, and propagate to the entire film-like jet shown in fig. 6, thereby generating large-scale turbulence and pressure changes having a jet length. Since the pressure change generates a loud noise, the user feels uncomfortable. When the change is large, the pressure change propagates in the jet flow direction inside the jet, and may reach the high-pressure airflow generation device 2 through the air nozzle portion 6 on the upstream side. In this case, the pressure discharged from the high-pressure airflow generation device 2 also changes, and therefore, the change further forms a feedback loop in the entire discharge system in conjunction with the jet collision portion from the air nozzle portion 6, and a fluctuation accompanying a large-scale pressure change is generated, and may cause damage to the high-pressure airflow generation device 2.

In particular, as shown in fig. 6, when the lengths La of the opposing slit-shaped ejection orifices 7a and 7b are Lb, the lengths of the adjacent ejection orifices are the same, and the installation interval Ca of the slit-shaped ejection orifices 7a and 7b is Cb, as shown in fig. 8, the pressure waveform increases, and uncomfortable noise having a high peak is generated.

In order to suppress the pressure change, in the present embodiment, as described above, the length La of the slit-shaped discharge ports 7a on the front surface side is made different from the length Lb of the slit-shaped discharge ports 7b on the back surface side, and the arrangement interval Ca of the slit-shaped discharge ports 7a on the front surface side is made different from the arrangement interval Cb of the slit-shaped discharge ports 7b on the back surface side. According to such a configuration, as shown in fig. 9, regions 13 and 14 having different lengths and colliding with the jet flow are formed on both sides in the jet flow so as to sandwich a region 12 where the opposing jet flow does not collide, and the pressure changing portions 13 and 14 having different phases are alternately sandwiched by the regions 12 where the pressure change does not occur, so that as shown in fig. 10, smooth noise is generated and the generation of noise can be suppressed.

In the present embodiment, as described above, the length La of the slit-shaped discharge port 7a on the front surface side is made longer than the length Lb of the slit-shaped discharge port 7b on the back surface side. Generally, the palm side is less likely to dry than the back side because the skin keratin has a large amount of moisture. Therefore, if the force of the jet is increased on the palm side, the palm and the back of the hand can be dried uniformly. Since the air nozzle portion 6a on the front side is opposed to the palm side, if the air nozzle portion 6a on the front side is formed with a slit jetting port longer than the air nozzle portion 6b on the back side, the palm and the back of the hand can be dried more uniformly. However, when the length La of the slit-shaped discharge port 7a on the front surface side is made longer than the length Lb of the slit-shaped discharge port 7b on the back surface side, as shown in fig. 9, it is preferable to form the slit-shaped discharge port 7a on the front surface side longer than the slit-shaped discharge port 7b on the back surface side so as to sandwich the region 12 where the opposing high-pressure airflows do not collide and to form the regions 13 and 14 where the high-pressure airflows having different lengths collide on both sides, thereby obtaining an effect of suppressing the generation of noise.

In the present embodiment, as described above, the installation interval Ca of the slit-shaped discharge ports 7a on the front surface side is set shorter than the installation interval Cb of the slit-shaped discharge ports 7b on the rear surface side. When the front side is formed with the ejection port arrangement interval shorter than the back side, the jet stream hits the palm side over a wider range, and thus the palm back can be dried more uniformly. In addition, the distance between the ejection holes is preferably set to 1 to 3mm on the front side and 4 to 6mm on the back side from the viewpoint of both drying performance and noise. However, when the installation interval Ca of the slit-shaped discharge ports 7a on the front surface side is shorter than the installation interval Cb of the slit-shaped discharge ports 7b on the back surface side, as shown in fig. 9, it is preferable that the installation interval Ca of the slit-shaped discharge ports 7a on the front surface side is shorter than the installation interval Cb of the slit-shaped discharge ports 7b on the back surface side so as to sandwich the region 12 where the opposing high-pressure airflows do not collide and the regions 13 and 14 where the high-pressure airflows having different lengths collide on both sides, thereby obtaining an effect of suppressing the generation of noise.

In the present embodiment, as shown in fig. 3, a plurality of irregularities are formed inside the slit spout 7, so that minute turbulence is actively generated inside the collision region so as not to fluctuate on the scale of the collision width in the collision region. The shape of the recess for generating turbulence is not particularly limited, and only the recess may be used.

In the above-described embodiment, the length La of the slit-shaped discharge ports 7a on the front surface side is made different from the length Lb of the slit-shaped discharge ports 7b on the back surface side, and the arrangement interval Ca of the slit-shaped discharge ports 7a on the front surface side is made different from the arrangement interval Cb of the slit-shaped discharge ports 7b on the back surface side, but only the length La of the slit-shaped discharge ports 7a on the front surface side may be made different from the length Lb of the slit-shaped discharge ports 7b on the back surface side, or only the arrangement interval Ca of the slit-shaped discharge ports 7a on the front surface side may be made different from the arrangement interval Cb of the slit-shaped discharge ports 7b on the back surface.

As described above, the hand drying device of the present invention is a hand drying device for hygienically drying wet hands after washing by jetting a high-speed airflow.

Claims (5)

1. A hand drying device comprises a hand insertion part and a high-pressure airflow generating device, wherein the hand insertion part is provided with an air nozzle part in a mutually opposite mode, and the air nozzle part comprises a part which forms a plurality of slender holes in a linear arrangement mode; the high-pressure airflow generating device is communicated with the air nozzle part through an air supply passage,

the air nozzle unit ejects the high-pressure air generated in the high-pressure air flow generating device as a high-speed air flow, and the center position of the elongated hole of one air nozzle unit of the air nozzle unit is shifted from the center position of the elongated hole of the other air nozzle unit in a direction in which the elongated holes are linearly arranged.

2. The hand drying apparatus of claim 1, wherein the elongated hole of one air nozzle portion is longer than the opposing elongated hole of the other air nozzle portion.

3. The hand drying apparatus of claim 1, wherein a distance between adjacent two elongated holes of the front side air nozzle portion is 1mm or more and 3mm or less.

4. The hand drying device of claim 1, wherein a distance between adjacent two elongated holes of the back side air nozzle portion is 4mm or more and 6mm or less.

5. The hand drying apparatus of claim 1, wherein the distance between the adjacent two elongated holes of the front side air nozzle portion is 1mm or more and 3mm or less; the distance between two adjacent elongated holes of the back-face side air nozzle portion is 4mm or more and 6mm or less.