JPH06313540A - Peep window device for furnace - Google Patents

Abstract

PURPOSE:To provide a furnace peeping window device provided in a furnace wall, which is capable of opening and/or closing selectively, small in size, simple in constitution and easy in maintenance. CONSTITUTION:A cylindrical casing 5, in which a sliding rod body 9 having a penetrating hole 33 is inserted into a through hole 11 slidably in air-tight condition an opening section 19 communicating with the through hole 11 and opened and/or closed by the driving of the sliding rod body 9 is formed. A guide to which shielding plates are secured on both sides of the same is mounted to a cylindrical casing 5. This casing 5 is attached in such a way that the opening in the furnace wall 1 is opposed to the opening section 19. While a window glass 17 for sealing the outside of a casing 5 is attached detachably to the outside of the casing 5 gastightly. Gas for purging is guided through a space 27, formed between the casing 5 and the guide 7 and blocked from the inside of the furnace, and the gas is guided to the inside of the window glass 17 through a gap between the casing 5 and the shielding plate as well as a separating plate 47. An optical passage connecting the inside and the outside of a furnace through the window glass 17 is formed selectively by driving the sliding rod body 9.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an in-furnace peep window device suitable for monitoring the conditions inside a high-heat furnace such as a blast furnace, a heating furnace, and a heat treatment furnace.

[0002]

2. Description of the Related Art Conventionally, in order to monitor the inside of a high-heat furnace, a window having a predetermined diameter is formed on a furnace wall, a window glass is attached, an objective lens is provided facing the window, and light collected by the objective lens is provided. Is led to a television camera through an eyepiece lens. In this case, the window glass is purged with clean gas to clean and cool the surface. Furthermore, since the airtightness is required between the objective lens and the inside of the furnace, the window glass is cleaned when the high temperature furnace is stopped.

In the above-mentioned conventional in-furnace peep window device, since a shield which can be selectively shielded is not provided between the inside of the furnace and the window glass provided in the furnace wall, it is extremely inconvenient for maintenance management. There was a problem. In order to solve such a problem, a window glass is interposed between a window formed in a furnace wall and an objective lens, a pedestal provided with the window glass is configured to be rotatable, and the pedestal is rotationally driven. There is also a configuration in which the objective lens and the inside of the furnace are selectively shielded based on the position of the pedestal.

[0004]

However, as described above, when the in-furnace peep window device is constructed so as to rotate the window glass provided on the pedestal to selectively shield the objective lens and the inside of the furnace from each other. Maintenance is easier than in the case of the conventional example without the above-mentioned shield, but it is still not sufficient, and the drive mechanism of the pedestal provided with the window glass becomes complicated, and a large space is required for pedestal rotation. As a result, the size of the device becomes large, and the structure for airtightness becomes complicated.

The present invention provides a peep window device in a furnace which is capable of selectively opening and closing a peep hole provided in a furnace wall with a simple drive mechanism, which is more compact, has a simple structure, and is easy to maintain. With the goal.

[0006]

An in-furnace peep window device of the present invention comprises a cylindrical casing concentrically attached to an opening provided in a furnace wall, and heat resistant glass, pressure resistant glass, or heat resistant / pressure resistant glass. A window glass that is detachably attached to the outside of the furnace of the casing concentrically with the opening provided in the furnace wall and seals the outside of the furnace of the casing; an insertion hole provided in an axial center; An opening that is formed concentrically with the opening provided in the wall and that communicates with the insertion hole and that connects the window glass side and the furnace wall side is formed, and between the furnace wall side and the window glass side of the casing. In a cylindrical guide that penetrates through the casing, there is a predetermined distance between the outer peripheral surface and the inner peripheral surface of the casing, and the window glass is provided on each side of the guide. Semicircular shields provided in parallel A plate and a through hole, which is slidably and airtightly inserted into the insertion hole of the guide, and when the through hole faces the opening of the guide, communicates with the window glass side and the furnace inside the furnace. , A sliding rod that seals the opening of the guide at the outer circumference when not facing each other, a first space formed between the window glass and the guide, and between the guide and the casing. A second space, which is formed on the furnace wall side and communicates with the first space through a gap between the shielding plate and the inner peripheral surface of the casing, and which is cut off from the inside of the furnace, and the second space. And a gas passage for introducing a gas for purging the window glass surface.

The in-furnace viewing window device of the present invention comprises a cylindrical casing which is mounted concentrically with the opening provided in the furnace wall,
A window glass made of heat-resistant glass, pressure-resistant glass, or heat-resistant / pressure-resistant glass, and detachably attached to the outside of the furnace of the casing concentrically with the opening provided in the furnace wall to seal the outside of the furnace of the casing. An insertion hole provided in the shaft center, an opening formed concentrically with the opening provided in the furnace wall and communicating with the insertion hole, and communicating the window glass side and the furnace wall side, and Between the furnace wall side of the casing and the window glass side, a cylindrical guide that penetrates through the casing, and has a predetermined distance between the outer peripheral surface and the inner peripheral surface of the casing, and Each of the guides has a semi-circular shield plate provided substantially parallel to the window glass on each side of the guide, and a through hole. The guide plate is slidably and airtightly inserted into the insertion hole of the guide to penetrate the guide plate. When the hole faces the opening of the guide A sliding rod body that communicates with the window glass side and the furnace inside the furnace, and seals the opening of the guide at the outer periphery when they do not face each other, and a first space formed between the window glass and the guide. Is formed on the furnace wall side between the guide and the casing, communicates with the first space through a gap between the shield plate and the inner peripheral surface of the casing, and is isolated from the inside of the furnace. The second space has a through hole that allows the window glass side and the opening provided in the furnace wall to communicate with each other through the through hole of the sliding rod and the opening of the guide. In a plate-like separation plate provided near the window glass and substantially parallel to the shielding plate, and a gas passage for guiding gas for purging the window glass surface to the second space. And

The in-furnace peep window device of the present invention is characterized in that the space volume between the guide and the window glass is enlarged by cutting out the portion of the guide facing the window glass.

[0009]

According to the in-furnace peep window device of the present invention, when the sliding rod is driven to make the through hole of the sliding rod and the opening of the guide face each other, the through hole of the sliding rod is formed. An optical path connecting the inside and outside of the furnace is formed through the opening of the guide and the through hole of the separation plate, and the inside of the furnace can be seen through the window glass, and the situation inside the furnace can be observed. When the sliding rod is driven from the above position, the opening is closed by the sliding rod and the optical path is blocked. In this case, the sliding rod shuts off the inside of the furnace from the first space, and the high-temperature gas, dust, and water vapor inside the furnace are not discharged outside the furnace, which facilitates maintenance such as window glass replacement. Becomes further,
Since the sliding bar slides in the guide, the structure is simple and the space required is small.

When the purging gas is supplied with the optical path formed, the purging gas is supplied from the second space to the first space, and the gas is supplied to the inner peripheral surface of the casing and the shielding plate. The gas flows into the first space through the gap with the outer peripheral surface of the window glass, and the furnace inner surface of the window glass is purged and cooled, so that the window glass is heated by the high temperature gas, dust and water vapor from the furnace. The inner surface of the furnace will not get dirty.

Further, the gas for purging is supplied to the first space between the inner peripheral surface of the casing and the outer peripheral surface of the shielding plate, so that the gas flow flowing into the first space is a window. It becomes a parallel flow with respect to the surface of the glass, and negative pressure parts do not occur because vortices do not occur, and high-temperature gas and dust as well as gas containing water vapor and fine particles (hereinafter,
It does not inhale steam, etc., and does not damage the surface of the window glass.

Further, when the separating plate is provided, the gas for purging that has flowed into the first space is separated by the separating plate into a first gas flow on the shield plate side and a second gas flow on the window glass side. To be done. Since the separation plate is provided near the window glass, the flow velocity of the second gas flow is faster than that of the first gas flow, and the second gas flow slides through the through hole of the separation plate. There is no generation of a negative pressure portion on the surface side of the window glass that flows out into the through hole of the rod body, and water vapor or the like that has entered the first space does not accumulate on the side surface of the window glass.

When the portion of the guide facing the window glass is cut out, the volume of the first space is enlarged, and as a result, the air flow flowing into the space between the guide and the window glass becomes more parallel. Thus, the surface of the window glass can be protected more than the above.

[0014]

EXAMPLES The present invention will be described below with reference to examples. FIG. 1 is a sectional view showing the configuration of the main part of one embodiment of the present invention,
2 is a cross-sectional view taken along the line AA in FIG. 1, and FIG. 3 is a front view of an embodiment of the present invention.

A taper-shaped opening 3 is provided at a predetermined position on the furnace wall 1 of the high-temperature furnace so as to look into the furnace. The furnace peep window device of this embodiment has an opening on the furnace wall 1. A flange portion of a cylindrical casing 5 which is concentric with 3 is attached by appropriate means. A cylindrical guide 7 is airtightly attached to the casing 5 so as to penetrate the casing 5. Guide 7
Is provided with an insertion hole 11 for inserting the sliding rod 9 airtightly and slidably, and the sliding rod 9 is inserted airtightly and slidably into the insertion hole 11. .

A flange portion 13 is formed on the inner periphery of the casing 5 at a position outside the furnace facing the guide 7 and concentrically with the casing 5. An annular fixing member 15 is detachably fixed to the flange portion 13. -1 and 15-2 are detachably and airtightly attached to the window glass 17 concentrically with the casing 5, and the collar portion 13, the fixing members 15-1 and 15-2, and the window glass are attached. The outside of the furnace of the casing 5 is sealed by 17. Here, the window glass 17 is a pressure resistant glass that withstands the pressure of the purging gas described later, a heat resistant glass that withstands the temperature corresponding to the temperature in the furnace, or a pressure resistant glass that withstands the pressure of the purging gas and withstands the temperature corresponding to the temperature in the furnace. -Glass that is heat resistant glass and that transmits light of a predetermined wavelength is selected.

As shown in FIG. 1 and FIG. 4 which is partially omitted, a part of the guide 7 on the side of the window glass is cut out. 1
7, the sliding rod 9 is notched at a part of the portion facing the window glass 17, and the notched surface 91 of the sliding rod 9 faces the window glass 17. . Here, a space 31, which is a first space, is formed between the notch surface 71 of the guide 7, the notch surface 91 of the sliding rod body 9, the flange 13, the fixing member 15-1 and the window glass 17. The notch surface 71 of the guide 7, which is formed and surrounds the space 31, the sliding rod body 9
Notch surface 91, surface of collar 13 and fixing member 15
The surface of -1 is formed smoothly.

The guide 7 is provided with an opening portion 19 having a width in the direction perpendicular to the axis of the sliding rod body 9 smaller than the diameter of the sliding rod body 9 and communicating with the insertion hole 11. is there. Both sides of the guide 7 face the window glass 17 in a direction substantially orthogonal to the axis of the insertion hole 11 and substantially orthogonal to the axis of the space portion 21 described later, and are substantially parallel to the window glass 17 as shown in FIGS. As shown in FIG. 4, a semicircular shield plate 23 that forms a predetermined gap between the outer peripheral surface and the inner peripheral surface of the casing 5.
And 25 are stuck.

Further, there is a through hole 49 for communicating the window glass 17 side with the opening 3 provided in the furnace wall 1 through the through hole 33 of the sliding rod 9 and the opening portion 19 of the guide 7. In the space 31, close to the window glass 17 side and the shield plate 23
A disk-shaped separating plate 47 is fixed to the fixing members 15-1 and 15-2 substantially in parallel with 25 and 25. The separation plate 47
May be fixed to the guide 7. By providing the separation plate, the space 31 is separated into the spaces 31A and 31B at the portion facing the window glass 17.

Further, in the guide 7, a space portion 21 which spreads like a cone from the opening portion 19 to both end surfaces of the inside of the furnace and the outside of the furnace.
Is formed between the guide 7 and the casing 5 so as to sandwich the space 21 between the guide 7 and the casing 5 so as to be insulated from the inside of the furnace, and between the inner peripheral surface of the casing 5 and the outer peripheral surfaces of the shielding plates 23 and 25. It is configured to form second spaces, spaces 27 and 29, which communicate with the space 31 through the formed gap.

On the other hand, the sliding rod 9 has a through hole 33 for penetrating the inside and outside of the sliding rod 9 to form an optical path from the outside of the furnace to the inside of the furnace, and the end of the through hole 33. Conical portions 35 and 37 extending from the portion are formed.

A purging gas such as nitrogen having a predetermined pressure higher than the pressure in the furnace is supplied to the space 27 from a purging gas source (not shown) through a through hole 39 provided in the casing 5, and the furnace is passed through the space 31. Discharge inside.

As shown in FIG. 3, one end of the sliding rod 9 is connected to a piston of an actuator 45 fixed by a pedestal member 43 attached to the casing 5,
The reciprocating motion of the piston drives the sliding rod 9 up and down in FIG. By driving the sliding rod 9 by the piston, an optical path communicating selectively with the inside and outside of the furnace is formed. When the sliding rod 9 is driven to a position where the through hole 33 is substantially concentric with the opening 3 of the furnace wall 1, an optical path is formed by the through hole 33, and the situation in the furnace is It can be observed from outside the furnace through 17 and the through hole 33.

Purging gas is supplied through the through hole 39 in the state where the optical path is formed. The supplied purging gas flows into the space 31 through between the outer peripheral surfaces of the shielding plates 23 and 25 and the inner peripheral surface of the casing 5, and purges the surface of the window glass 17 on the space 31 side. This purging prevents dust and water vapor from the furnace from being blown onto the surface of the window glass 17 on the side of the space 31 and from adhering to the surface of the window glass 17, and cools the window glass 17. The purging gas may be supplied from the through hole 41 instead of the through hole 39 by sealing the through hole 39, or may be supplied from both the through holes 39 and 41.

In this case, the purging gas is the casing 5
Of the guide rod 7 and the sliding rod body 9 of the guide 7 which flows uniformly between the inner peripheral surface of the guide plate 7 and the outer peripheral surfaces of the shield plates 23 and 25 to be guided to the space 31 and which forms the space 31. Since the notch surface 91, the surface of the collar 13 and the surface of the locking member 15-1 are formed smoothly, the purging air flowing along the surface of the window glass and purged is not disturbed, and the window glass is not disturbed. 1
7 does not generate a vortex part in parallel with the surface of 7 and therefore a low pressure part formed after the vortex part does not occur, so that high temperature gas, dust, water vapor, etc. from the furnace are sucked in. Nothing.

As a result, dust can be effectively prevented from adhering to the surface of the window glass 17 on the side of the space 31, and high temperature gas from the inside of the furnace can be attached to the surface of the window glass 17 on the side of the space 31.
It is also prevented that water vapor and dust are blown and the surface of the window glass on the side of the space 31 is damaged.

Further, FIG. 5 is shown in a simplified and schematic manner.
The operation of the separating plate 47 will be described with reference to FIGS. The purge gas flows into the space 31 as shown in FIG. 5, and if the separation plate 47 is not provided, the opening 1
9 and the through hole 33 to flow into the furnace. While it is prevented that water vapor and dust by the purge gas flow F ₀ to the inflow to the window glass surface 17 sprays blown, occurs negative pressure M ₁ on a portion of the surface side of the glass 17, negative pressure M ₁ There is a case where water vapor stays in. This convection may hinder the observation inside the furnace.

However, since the separating plate 47 is provided, the purging gas flow F ₀ flowing into the space 31 as shown in FIG.
A gas flow F ₁ of the and partial flow of the second purge gas flow F ₂ flowing space 31B side. However, since the separating plate 47 is provided closer to the window glass side, the flow rate of the _second purging gas flow F ₂ is faster than that of the first gas flow F ₁ and flows toward the space 31B side. Purge the surface of 17,
The purged second gas flow F ₂ flows into the through hole 33.

As a result, the negative pressure portion M ₁ shown in FIG. 5 is reduced to a negative pressure portion M ₂ as shown in FIG. 6, and the amount of the invading water vapor is retained on the surface side of the window glass 17. Becomes so small that it does not substantially obstruct the observation inside the reactor. Further, the negative pressure portion M _{3 at} the confluence of the first gas flow F ₁ and the second purge gas flow is filled with the pressure of the second purge gas flow flowing into the through hole 33,
The negative pressure portion M ₃ disappears, and there is no portion for retaining the vapor that has entered this portion.

When the sliding rod 9 is driven from the above position for a predetermined length by the piston, the through hole 33 is located outside the optical path, and the opening 19 is sealed by the sliding rod 9. In this state, the inside and outside of the furnace are blocked by the sliding rod 9, and the optical path is also blocked. In this state, the through hole 39
Supply of purging gas to the chamber is stopped. Therefore, in this state, since the inside and outside of the furnace are shut off, the window glass 17 can be easily replaced, and the window glass 17 can be easily maintained.

In the above-described embodiment, the guide 7 and the sliding rod 9 are partially cut out to increase the volume of the space 31, but the guide 7 and the sliding rod 9 are partially cut off. Even if the notch is omitted, it is inferior when the notch is provided, but the same effect as when the notch is provided can be obtained.

Further, in the above-described embodiment, the sliding rod body 9 is provided with the conical portions 35 and 37, and the guide 7 is provided with the conical shaped space portion 21. However, the conical portions 35 and 37 are omitted, and the space portion 2 that expands in a conical shape only with the opening portion 19 in the guide 7 is illustrated.
There is no problem even if 1 is omitted. However, the cones 35, 37
When the space portion 21 spreading in the shape of a cone is formed, an optical path is formed through the cone portions 35, 37 and the space portion 21 when the inside and outside of the furnace are communicated with each other, and the cone portions 35, 37 and the space portion 21 are formed. Since the angle of the cone is larger than that in the case where the cone is formed on the sphere, the formed optical path spreads at a wide angle from the through hole 33 to the inside and outside of the furnace, which facilitates observation inside the furnace. Further, it is possible to obtain an effect that the diameter of the through hole 33 of the sliding rod body 9 can be small.

An example of the use of the in-furnace viewing window device of the embodiment configured as described above will be described by taking the case of photographing the inside of the blast furnace as an example.

As shown in FIG. 7, in order to look into the furnace opening of the blast furnace 50, the in-furnace viewing window devices of the present embodiment are provided at two locations in close proximity to each other, and one in-furnace viewing window device is provided. An infrared light source device 55 for illumination is provided on the end surface 53 of the flange portion of the casing 5 of A.
Wide-angle lens 5 that is installed to transmit light in the infrared wavelength range
The infrared light source device 55 for illumination is irradiated via 7 to illuminate the inside of the furnace.

An image pickup device 54 is installed on the end face 52 of the flange portion of the casing 5 of the other in-furnace window device B, and infrared rays reflected from the inside of the incinerator by the above-mentioned illumination are detected in the in-furnace window device B.
The image pickup device 54 receives light through the wide-angle lens 56 that transmits light having a wavelength in the infrared region and is configured to pick up an image, and the television signal output from the image pickup device 54 is displayed by the receiver.

When the inside of the blast furnace 50 is imaged with the above-mentioned structure, the actuators 45 of the peep window devices A and B in both furnaces
Is driven to form an optical path through the through holes 33 of the peep window devices A and B in the furnace. The blast furnace 5 is irradiated with the infrared light emitted from the infrared light source device 55 for illumination through the formed optical path.
The predetermined range C to D within 0 is illuminated. This illumination also illuminates the dark areas within the predetermined range C to D, and the predetermined range C
The images within D are captured by the image capturing device 54.

In this case, since the window glass 17 of the peep window devices A and B in the furnace is purged by the purging gas and cooled and dust is removed, high temperature in the furnace, water vapor from the furnace and It is possible to obtain a good image without being affected by dust. In addition to photographing the situation inside the furnace, it can also be used for measuring the temperature inside the furnace through the furnace viewing window device of the present invention.

[0038]

As described above, according to the in-furnace peep window device of the present invention, when the sliding rod is driven so that the through hole and the opening face each other, the sliding rod is kept inside and outside the furnace. An optical path is formed through the through hole and the opening, and when the sliding rod is slid for a predetermined length from this state, the opening is closed by the sliding rod. It has an effect that it can be selectively formed and closed by driving, and the selection of optical path formation is easy. Furthermore, since the sliding rod slides in the guide, the structure is simple and
It has the effect of requiring less space.

Further, according to the present invention, when the optical path is cut off, the opening is closed by the sliding rod, and the inside of the furnace and the outside of the furnace are airtightly closed by the sliding rod. The high temperature gas in the furnace is not discharged to the outside of the furnace, which has an effect of facilitating maintenance such as replacement of the window glass.

Further, the gas for purging the surface of the window glass inside the furnace is guided to the surface of the window glass inside the furnace through the space between the outer peripheral surface of the shielding plate and the inner peripheral surface of the casing. The gas flowing on the surface side inside the furnace becomes a parallel flow, and neither dust from inside the furnace nor water vapor adheres to the surface inside the furnace of the window glass, and the high temperature gas, steam and dust from inside the furnace It is also possible to prevent the glass from being blown onto the surface of the inner side of the furnace, and it is possible to prevent damage to the window glass.

Further, since the separation plate is provided near the window glass surface side of the first space to divide the gas flow for purging into two fluid flows, the window glass surface is not contaminated and the window glass surface portion is removed. Water vapor will not stay in the furnace, and the inside of the furnace can be effectively observed through the window glass.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a configuration of a main part of an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA in FIG.

FIG. 3 is a front view of an embodiment of the present invention.

FIG. 4 is a perspective view of a guide and a shielding plate in which a part of an embodiment of the present invention is omitted.

FIG. 5 is a schematic diagram for explaining the operation of one embodiment of the present invention.

FIG. 6 is a schematic diagram for explaining the operation of one embodiment of the present invention.

FIG. 7 is a schematic diagram showing an application example of an embodiment of the present invention.

[Explanation of symbols]

 1 Furnace Wall 5 Casing 7 Guide 9 Sliding Rod 11 Insertion Hole 17 Window Glass 19 Openings 23 and 25 Shielding Plates 27, 29 and 31 Spaces 33 and 49 Through Hole 47 Separation Plate

Claims (3)

[Claims] 1. A cylindrical casing mounted concentrically with an opening provided on a furnace wall, and made of heat-resistant glass, pressure-resistant glass, or heat-resistant / pressure-resistant glass, and concentrically with the opening provided on the furnace wall. A window glass which is detachably attached to the outside of the furnace of the casing to seal the outside of the furnace of the casing, an insertion hole provided in an axial center, and the insertion hole formed concentrically with the opening provided in the furnace wall. A cylindrical guide that is attached to penetrate through the casing between the furnace wall side and the window glass side of the casing, and an opening that communicates with the window glass side and the furnace wall side is formed. And a semi-circular shield plate having a predetermined distance between the outer peripheral surface and the inner peripheral surface of the casing and provided on both sides of the guide, respectively, substantially parallel to the window glass. Has a hole for inserting the guide When the through hole faces the opening of the guide, the window glass side and the furnace inside the furnace are communicated with each other. A sliding rod that stops, a first space formed between the window glass and the guide, a furnace wall side between the guide and the casing, and the shielding plate and the casing. A second space that communicates with the first space through a gap between the inner peripheral surface of the furnace and the inside of the furnace, and a gas passage that guides gas for purging the window glass surface into the second space. An in-furnace peep window device characterized by being equipped with. 2. A cylindrical casing mounted concentrically with the opening provided in the furnace wall, and made of heat resistant glass, pressure resistant glass, or heat resistant / pressure resistant glass, and concentrically with the opening provided in the furnace wall. A window glass which is detachably attached to the outside of the furnace of the casing to seal the outside of the furnace of the casing, an insertion hole provided in an axial center, and the insertion hole formed concentrically with the opening provided in the furnace wall. A cylindrical guide that is attached to penetrate through the casing between the furnace wall side and the window glass side of the casing, and an opening that communicates with the window glass side and the furnace wall side is formed. And a semi-circular shield plate having a predetermined distance between the outer peripheral surface and the inner peripheral surface of the casing and provided on both sides of the guide, respectively, substantially parallel to the window glass. Has a hole for inserting the guide When the through hole faces the opening of the guide, the window glass side and the furnace inside the furnace are communicated with each other. A sliding rod that stops, a first space formed between the window glass and the guide, a furnace wall side between the guide and the casing, and the shielding plate and the casing. The window glass through a second space that communicates with the first space through a gap between the inner peripheral surface of the chamber and the inside of the furnace, and a through hole of the sliding rod and an opening of the guide. A plate-shaped separation plate that has a through hole that connects the side and an opening provided in the furnace wall, and that is provided near the window glass in the first space and substantially parallel to the shielding plate; A gas passage that introduces a gas for purging the window glass surface into the second space. A peep window device in a furnace characterized by having a passage. 3. The in-furnace peep window device according to claim 1 or 2, wherein a portion of the guide facing the window glass is cut out to increase a space volume between the guide and the window glass. Peep window device in the furnace.