CN217708903U - Sight glass device and reduction furnace - Google Patents

Abstract

The utility model discloses a sight glass device, sight glass device include barrel, first sight glass and stifled piece, and the barrel has relative first end and second end, and the first end of barrel is used for linking to each other with the window pipe detachably of reducing furnace, and first sight glass is installed in the barrel, and stifled piece links to each other with the barrel and is located one side that first sight glass deviates from the reducing furnace, and stifled piece is used for the second end opening of shutoff barrel. The utility model provides a sight glass device has the waste that can reduce the pressurized gas and the operating efficiency's of assurance reducing furnace advantage.

Description

Sight glass device and reduction furnace

Technical Field

The utility model relates to a reduction furnace window technical field specifically relates to a sight glass device and reduction furnace.

Background

In the process of producing the polycrystalline silicon by adopting the improved Siemens method, the growth condition of the polycrystalline silicon in the reduction furnace/CVD furnace needs to be observed and the temperature needs to be measured through a window arranged on the reduction furnace/CVD furnace.

The air tightness test of the sight glass in the related art generally needs to be performed by charging nitrogen after all sight glasses are installed on a reduction furnace. In the operation process of the reduction furnace, the furnace is filled with flammable and combustible media such as hydrogen, trichlorosilane and the like, and the reduction furnace operates at a high temperature (generally 1000-1050 ℃). Once a mirror has cracked, it is often necessary to shut down the furnace for safety reasons. The operation mode influences the operation efficiency of the reduction furnace, and meanwhile, the cost for replacing silicon cores and the like is greatly increased due to the fact that the silicon cores are discharged from the reduction furnace again.

Thus, the related art has problems in that the charged gas is wasted and the reduction furnace is affected by the cracks of the sight glass to reduce the operation efficiency.

SUMMERY OF THE UTILITY MODEL

The present invention aims at solving at least one of the technical problems in the related art to a certain extent. Therefore, the embodiment of the utility model provides a sight glass device, this sight glass device has the advantage that can reduce the waste of pressurized gas and guarantee the operating efficiency of reducing furnace.

The embodiment of the utility model also provides a reducing furnace.

The sight glass device comprises a cylinder body, a first sight glass and a blocking piece, wherein the cylinder body is provided with a first end and a second end which are opposite, and the first end of the cylinder body is detachably connected with a window pipe of a reduction furnace; the first sight glass is arranged in the barrel; the blocking piece is connected with the barrel and is positioned on one side, away from the reduction furnace, of the first sight glass, and the blocking piece is used for blocking the second end opening of the barrel.

According to the utility model discloses sight glass device because the barrel can be dismantled for the reduction furnace, from this, sight glass device and reduction furnace have formed split type structure, when carrying out the gas tightness inspection to first sight glass, can pull down sight glass device from the window pipe of reduction furnace, carry out the gas tightness inspection to sight glass device alone. Therefore, in the process of carrying out air tightness inspection on the sight glass device, the reduction furnace is prevented from being filled with the pressurized gas, the using amount of the pressurized gas is reduced, and therefore the waste of the pressurized gas is reduced.

When the first sight glass has cracks, the blocking piece can be arranged in the cylinder body, so that the effect of blocking the second end opening of the cylinder body is realized, and the gas in the reduction furnace is effectively prevented from overflowing. The emergency mode ensures that the reduction furnace does not need to be blown out, ensures the continuous operation of the reduction furnace and ensures the operation efficiency of the reduction furnace.

In some embodiments, the sight glass apparatus further comprises a first ring platform, a second ring platform and a first pressure ring, wherein the first ring platform is arranged in the barrel and coaxially connected with the barrel; the second annular table is arranged on the inner side of the first annular table and is coaxially connected with the first annular table, two end faces of the second annular table are located between the two end faces of the first annular table, and the first end face of the first sight glass abuts against the first end face of the second annular table; the first end face of the first pressing ring is abutted to the second end face of the first sight glass, a first limiting flange is arranged at the second end of the first pressing ring, and the first limiting flange is abutted to the first end face of the first ring platform and connected with the first ring platform.

In some embodiments, the first end surface of the first annular table is provided with a plurality of first threaded holes distributed at intervals in the circumferential direction of the barrel, the first limiting flange is provided with first mounting holes corresponding to the first threaded holes one to one, the sight glass device further comprises first bolts, the number of the first bolts is equal to that of the first mounting holes, the first bolts correspond to the first mounting holes one to one, and the first bolts penetrate through the corresponding first mounting holes and are connected with the corresponding first threaded holes.

In some embodiments, the first end face of the first land is adjacent the first end of the barrel and the first end face of the second land is adjacent the first end of the barrel, the first land and the second land each having a second end face opposite the respective first end face and adjacent the second end of the barrel.

In some embodiments, the second end surface of the first annular table is provided with a plurality of second threaded holes distributed at intervals in the circumferential direction of the cylinder, the blocking piece comprises second mounting holes in one-to-one correspondence with the plurality of second threaded holes, the sight glass device further comprises second bolts, the number of the second bolts is equal to that of the second mounting holes, the second bolts correspond to the second mounting holes in one-to-one correspondence, and the second bolts penetrate through the corresponding second mounting holes and are connected with the corresponding second threaded holes.

In some embodiments, the blocking piece further comprises a second sight glass, a second press ring and a second limit flange, wherein the first end surface of the second sight glass abuts against the second end surface of the second annular platform; the first end face of the second pressure ring is abutted against the second end face of the second sight glass; the second limiting flange is arranged at the second end of the second pressure ring and is abutted against the second end face of the first annular table, and the plurality of second mounting holes are formed in the second limiting flange.

In some embodiments, the plug further comprises a blind plate and a third stop flange, the first end surface of the blind plate being stopped against the second end surface of the second land; the third limiting flange is arranged at the second end of the blind plate and is abutted against the second end face of the first annular table, and the second mounting holes are formed in the third limiting flange.

In some embodiments, the first end and the second end of the cylinder are both provided with a connecting flange, the connecting flange is provided with a plurality of third mounting holes distributed at intervals along the circumferential direction of the cylinder, and the cylinder is connected with the window tube through the connecting flange at the first end.

According to the utility model discloses reduction furnace includes as above-mentioned any embodiment sight glass device, still include the window pipe, the quantity of window pipe has a plurality ofly and interval arrangement on the length direction of reduction furnace, the quantity of sight glass device with the quantity of window pipe is equal and the one-to-one, the window pipe with corresponding sight glass device links to each other.

According to the utility model discloses reducing furnace, the operator of being convenient for observes the inside condition of reducing furnace from the window pipe of different positions for it is more comprehensive to survey, has improved the effect of surveing.

According to the utility model discloses other technical advantages of reduction furnace are the same with the technical advantage of the sight glass device of above-mentioned embodiment, and this is no longer described herein.

In some embodiments, a window flange is disposed on the window tube, and the first end of the barrel in the viewing mirror device is connected to the window flange.

Drawings

Fig. 1 is a schematic view of a sight glass apparatus according to an embodiment of the present invention.

Fig. 2 is a schematic view of a reduction furnace according to an embodiment of the present invention.

Reference numerals: 100. a sight glass device; 1. a cylinder body; 11. a first ring table; 12. a second ring table; 13. a first threaded hole; 14. a second threaded hole; 15. a connecting flange; 16. a third mounting hole; 2. a first sight glass; 21. a first seal member; 22. a second seal member; 3. blocking the piece; 31. a second mounting hole; 32. a second sight glass; 33. a second pressure ring; 34. a second position-defining flange; 35. a third seal member; 36. a fourth seal; 37. a blind plate; 38. a third position-defining flange; 4. a first pressure ring; 41. a first stop flange; 42. a first mounting hole; 5. a window tube; 51. a window flange.

Detailed Description

Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the drawings are exemplary and intended to be used for explaining the present invention, and should not be construed as limiting the present invention.

In the related art, the sight glass device does not have an independent air tightness inspection function, and can be inspected uniformly after being mounted on a CVD furnace, and once the sight glass cracks or the air tightness is unqualified in the inspection process and the sight glass needs to be replaced, the whole reduction furnace needs to be replaced after pressure relief, so that the efficiency is low, and the waste of pressurized gas is caused.

A sight glass apparatus 100 and a reduction furnace according to an embodiment of the present invention will be described below with reference to fig. 1 and 2.

As shown in fig. 1, the viewing mirror device 100 according to the embodiment of the present invention includes a barrel 1, a first viewing mirror 2 and a blocking member 3, the barrel 1 has a first end and a second end opposite to each other, and the first end of the barrel 1 is detachably connected to a window tube 5 of a reduction furnace. The first view mirror 2 is mounted in the barrel 1. The blocking piece 3 is connected with the cylinder body 1 and is positioned on one side, away from the reducing furnace, of the first sight glass 2, and the blocking piece 3 is used for blocking a second end opening of the cylinder body 1.

According to the utility model discloses sight glass device 100 because barrel 1 can be dismantled for the reduction furnace, from this, sight glass device 100 and reduction furnace have formed split type structure, when carrying out the gas tightness inspection to first sight glass, can pull down sight glass device 100 from the window pipe 5 of reduction furnace, carry out the gas tightness inspection to sight glass device 100 alone. After the inspection is qualified, the sight glass device 100 is installed on a reduction furnace. Therefore, in the process of performing the airtightness test on the sight glass device 100 in the embodiment, the reduction furnace is prevented from being filled with the pressurized gas, and the amount of the pressurized gas is reduced, so that the waste of the pressurized gas is reduced.

In addition, the airtightness testing method of the sight glass apparatus 100 in the present embodiment eliminates a process of attaching and detaching the sight glass apparatus 100 to and from a reduction furnace in a large batch, compared to a method of testing the airtightness of the sight glass apparatus 100 using a reduction furnace in the related art, thereby improving the work efficiency.

When the first sight glass 2 has cracks, the blocking piece 3 can be arranged in the cylinder body 1, so that the effect of blocking the second end opening of the cylinder body 1 is realized, and the gas in the reducing furnace is effectively prevented from overflowing. The emergency mode ensures that the reduction furnace does not need blowing out, ensures the continuous operation of the reduction furnace and further ensures the operation efficiency of the reduction furnace.

As can be understood, the first sight glass 2 is used for observing the growth of the silicon rod inside the reduction furnace.

The air tightness test and the pressure test of the sight glass apparatus 100 are performed on a specially-made tool.

For ease of understanding, arrow a in fig. 1 indicates the side of the mirror apparatus 100 facing the reduction furnace, and arrow B indicates the side of the mirror apparatus 100 facing away from the reduction furnace.

In some embodiments, as shown in fig. 1, the sight glass apparatus 100 further comprises a first ring platform 11, a second ring platform 12 and a first press ring 4, wherein the first ring platform 11 is disposed in the barrel 1 and coaxially connected to the barrel 1. The second annular platform 12 is arranged on the inner side of the first annular platform 11 and is coaxially connected with the first annular platform 11, two end faces of the second annular platform 12 are located between two end faces of the first annular platform 11, and the first end face of the first sight glass 2 is abutted to the first end face of the second annular platform 12. The first end face of the first pressing ring 4 is abutted against the second end face of the first sight glass 2, the second end of the first pressing ring 4 is provided with a first limiting flange 41, and the first limiting flange 41 is abutted against the first end face of the first ring platform 11 and is connected with the first ring platform 11.

Therefore, the effect that the first sight glass 2 is detachably mounted on the barrel body 1 is achieved, and replacement of the first sight glass 2 is facilitated.

Specifically, the mirror device 100 further includes a first sealing member 21 and a second sealing member 22, the first sealing member 21 is interposed between a first end surface of the first mirror 2 and a first end surface of the second annular stage 12, and the second sealing member 22 is interposed between a second end surface of the first mirror 2 and a first end surface of the first compression ring 4.

The first sealing member 21 and the second sealing member 22 are used for sealing the installation position of the first lens to prevent the overflow of the gas in the reduction furnace.

The first sealing element 21 is a gasket, and the material may be a high temperature resistant material such as graphite.

The second sealing element 22 is a gasket, and the material may be a high temperature resistant material such as graphite.

In some embodiments, as shown in fig. 1, the first end surface of the first annular platform 11 is provided with a plurality of first threaded holes 13 distributed at intervals in the circumferential direction of the barrel 1, the first limiting flange 41 is provided with first mounting holes 42 corresponding to the plurality of first threaded holes 13 one by one, and the sight glass apparatus 100 further includes first bolts, the number of the first bolts is equal to that of the first mounting holes 42, and the first bolts pass through the corresponding first mounting holes 42 and are connected to the corresponding first threaded holes 13.

From this, realized dismantling of first position-limiting flange 41 and first ring platform 11 and linked to each other, realized dismantling of first clamping ring 4 and first ring platform 11 promptly and linked to each other, be convenient for first clamping ring 4 dismantles from first ring platform 11 to be convenient for change first sight glass 2.

Specifically, the first mounting hole 42 may be a through hole or a threaded hole matched with the first bolt, and the embodiment is not limited thereto.

In some embodiments, as shown in fig. 1, a first end face of the first land 11 is adjacent to the first end of the barrel 1, a first end face of the second land 12 is adjacent to the first end of the barrel 1, and each of the first land 11 and the second land 12 has a second end face opposite the respective first end face and adjacent to the second end of the barrel 1.

The second end surfaces of the first 11 and second 12 ring lands thus provide a further mounting location for facilitating the mounting of the closure 3.

It will be appreciated that the closure 3 is mounted on the second end faces of the first land 11 and the second land 12.

In some embodiments, as shown in fig. 1, the second end surface of the first annular platform 11 is provided with a plurality of second threaded holes 14 distributed at intervals in the circumferential direction of the barrel 1, the plug 3 further includes second mounting holes 31 corresponding to the plurality of second threaded holes 14 one to one, and the sight glass apparatus 100 further includes second bolts, the number of the second bolts is equal to that of the second mounting holes 31, and the second bolts pass through the corresponding second mounting holes 31 and are connected to the corresponding second threaded holes 14.

From this, the effect of detachably installing on first loop platform 11 has been realized to closure member 3, is convenient for change first lens.

Specifically, the plurality of second threaded holes 14 are distributed at equal intervals in the circumferential direction of the cylinder 1.

Specifically, the second mounting hole 31 may be a through hole or a threaded hole matched with the second bolt, and the embodiment is not limited thereto.

In some embodiments, as shown in fig. 1, the blocking element 3 further comprises a second viewing mirror 32, a second press ring 33 and a second position-limiting flange 34, wherein a first end face of the second viewing mirror 32 abuts against a second end face of the second annular platform 12. The first end surface of the second press ring 33 is stopped against the second end surface of the second sight glass 32. The second limiting flange 34 is disposed at the second end of the second pressing ring 33 and is stopped against the second end surface of the first annular stage 11, and the plurality of second mounting holes 31 are disposed on the second limiting flange 34.

When the first sight glass 2 has local cracks or slight leakage, the second sight glass 32 and the second press ring 33 can be arranged on the second end faces of the second annular platform 12 and the first annular platform 11. Therefore, the leakage stoppage of the barrel body 1 is realized, and the gas in the reduction furnace is prevented from overflowing through the barrel body 1, so that the furnace blowing out of the reduction furnace is avoided, and the continuous operation of the reduction furnace is ensured. Therefore, the operation efficiency of the reduction furnace is ensured.

In addition, the second sight glass 32 also has a perspective function, so that an operator can continuously observe the running condition in the reduction furnace while stopping leakage.

Specifically, the blocking element 3 further includes a third sealing element 35 and a fourth sealing element 36, the third sealing element 35 is interposed between the first end surface of the second view mirror 32 and the second end surface of the second annular stage 12, and the fourth sealing element 36 is interposed between the second end surface of the second view mirror 32 and the first end surface of the second press ring 33.

The third seal 35 and the fourth seal 36 are used to seal the installation position of the second lens, further avoiding the overflow of the gas in the reduction furnace.

The third sealing element 35 is a gasket, and may be made of a high temperature resistant material such as graphite.

The fourth sealing element 36 is a gasket, and may be made of a high temperature resistant material such as graphite.

In some embodiments, as shown in fig. 1, the plug 3 further comprises a blind plate 37 and a third stop flange 38, wherein a first end surface of the blind plate 37 abuts against a second end surface of the second annular land 12. The third position-limiting flange 38 is disposed at the second end of the blind plate 37 and abuts against the second end surface of the first annular platform 11, and the plurality of second mounting holes 31 are disposed on the third position-limiting flange 38.

When the first sight glass 2 has local cracks or leaks, blind plates 37 can be arranged on the second end surfaces of the second annular platform 12 and the first annular platform 11. The blind plate 37 realizes leakage stoppage of the cylinder body 1, and prevents gas in the reduction furnace from overflowing through the cylinder body 1, thereby avoiding blowing out of the reduction furnace and ensuring continuous operation of the reduction furnace. Therefore, the operation efficiency of the reduction furnace is ensured. In addition, the blind plate 37 completely seals the cylinder 1, so that safety risks are prevented and controlled.

In particular, the plug 3 also comprises a fifth seal, which is interposed between the first end face of the blind plate 37 and the second end face of the second annular land 12. The fifth sealing member is used for sealing the installation position of the blind plate 37, and further avoiding the overflow of the gas in the reduction furnace.

A fifth seal is first placed on the second end face of the second land 12 prior to installation of the blind plate 37. Then, the first end surface of the blind plate 37 is stopped against the fifth sealing member, thereby achieving the fixation of the fifth sealing member and ensuring the effect that the fifth sealing member is clamped between the first end surface of the blind plate 37 and the second end surface of the second annular table 12.

The fifth sealing element is a gasket and can be made of high-temperature-resistant materials such as graphite.

In some embodiments, as shown in fig. 1, the first end and the second end of the cylinder 1 are provided with a connecting flange 15, the connecting flange 15 is provided with a plurality of third mounting holes 16 distributed at intervals along the circumference of the cylinder 1, and the cylinder 1 is connected with the window tube 5 through the connecting flange 15 at the first end.

Therefore, the reliability of connection between the cylinder body 1 and the window tube 5 is ensured.

As shown in fig. 2, the reduction furnace according to the embodiment of the present invention includes the sight glass device 100 as in any one of the above embodiments, and further includes the sight glass tube 5, the sight glass tube 5 has a plurality of numbers and is arranged at intervals in the length direction of the reduction furnace, the number of the sight glass device 100 and the number of the sight glass tube 5 are equal and are in one-to-one correspondence, and the sight glass tube 5 is connected to the corresponding sight glass device 100.

Therefore, operators can observe the internal conditions of the reduction furnace from the window pipes 5 at different positions conveniently, so that the observation is more comprehensive, and the observation effect is improved.

Other technical advantages of the reduction furnace according to the embodiment of the present invention are the same as the technical advantages of the sight glass apparatus 100 according to the above-mentioned embodiment, and are not described herein again.

In some embodiments, as shown in fig. 1 and 2, the window tube 5 is provided with a window flange 51, and the first end of the barrel 1 in the sight glass apparatus 100 is connected to the window flange 51.

Therefore, the effect of detachable connection of the cylinder body 1 and the window flange 51 is ensured, and the effect of detachable connection of the sight glass device 100 and the window tube 5 is ensured.

Specifically, the attachment flange 15 at the first end of the barrel 1 is attached to the window flange 51.

It is understood that the reduction furnace may further include third bolts, the number of the third bolts is equal to and corresponds to the number of the third mounting holes 16, and the third mounting holes 16 are connected to the window flange 51 through the corresponding third bolts.

Specifically, the reduction furnace further comprises a sealing gasket, and the sealing gasket is clamped between the connecting flange 15 of the first end of the barrel 1 and the window flange 51 in the sight glass device 100. The gasket is used to ensure the sealing of the connection between the sight glass assembly 100 and the sight glass tube 5, and to prevent the escape of gas from the reduction furnace.

According to the utility model discloses sight glass device 100 and reduction furnace, after the reduction furnace operation one stove, can dismantle sight glass device 100 from the reduction furnace and wash the stoving, will use sight glass device 100 again when installing sight glass device 100 on the reduction furnace again.

Additionally, the utility model discloses sight glass device 100 has following technological effect:

(1) The tightness detection can be independently carried out, the pressurized gas is reduced, the cost is saved, and the working efficiency is improved.

(2) And emergency measures such as additionally installing a blind plate 37 or a second sight glass 32 and the like can be adopted, so that the operation stability of the reduction furnace is ensured, and the safety of the reduction furnace and/or the sight glass device 100 is improved.

(3) The cleaning device can be detached from the reduction furnace and then cleaned independently, and cleaning cleanliness is improved. First sight glass 2 can be installed in barrel 1 and wash along with sight glass device 100 together, has avoided the frequent dismouting of first sight glass 2, has reduced the damage of first sight glass 2, from this, has prolonged the life of first sight glass 2, has reduced the replacement cost of first sight glass 2, in addition, has still improved sight glass device 100's cleaning efficiency.

In the description of the present invention, it is to be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only for convenience of description of the present invention and to simplify the description, but do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore should not be construed as limiting the present invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of the feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," and "fixed" are to be construed broadly and may, for example, be fixedly connected, detachably connected, or integrally formed; may be mechanically coupled, may be electrically coupled or may be in communication with each other; they may be directly connected or indirectly connected through intervening media, or they may be interconnected within two elements or in a relationship where two elements interact with each other unless otherwise specifically limited. The specific meaning of the above terms in the present invention can be understood according to specific situations by those of ordinary skill in the art.

In the present application, unless expressly stated or limited otherwise, the first feature may be directly on or directly under the second feature or indirectly via intermediate members. Also, a first feature "on," "above," and "over" a second feature may be directly on or obliquely above the second feature, or simply mean that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the present disclosure, the terms "one embodiment," "some embodiments," "an example," "a specific example," or "some examples" or the like mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present disclosure. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Moreover, various embodiments or examples and features of various embodiments or examples described in this specification can be combined and combined by one skilled in the art without being mutually inconsistent.

Although the above embodiments have been shown and described, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations to the above embodiments by those of ordinary skill in the art are intended to be within the scope of the present invention.

Claims (10)

1. A sight glass apparatus, comprising:

the device comprises a barrel body, a first end and a second end, wherein the first end and the second end are opposite, and the first end of the barrel body is detachably connected with a window pipe of a reduction furnace;

a first sight glass mounted within the barrel; and

the blocking piece is connected with the barrel and located on one side, away from the reduction furnace, of the first sight glass, and the blocking piece is used for blocking the second end opening of the barrel.

2. The sight glass apparatus of claim 1, further comprising:

the first annular table is arranged in the cylinder and is coaxially connected with the cylinder;

the second ring platform is arranged on the inner side of the first ring platform and is coaxially connected with the first ring platform, two end faces of the second ring platform are positioned between two end faces of the first ring platform, and the first end face of the first sight glass abuts against the first end face of the second ring platform; and

the first end face of the first pressing ring is abutted to the second end face of the first sight glass, a first limiting flange is arranged at the second end of the first pressing ring, and the first limiting flange is abutted to the first end face of the first ring platform and connected with the first ring platform.

3. The sight glass apparatus of claim 2, wherein the first end surface of the first annular platform is provided with a plurality of first threaded holes spaced apart from each other in the circumferential direction of the barrel, the first limiting flange is provided with first mounting holes corresponding to the first threaded holes, the sight glass apparatus further comprises first bolts, the first bolts and the first mounting holes are equal in number and correspond to each other, and the first bolts pass through the corresponding first mounting holes and are connected with the corresponding first threaded holes.

4. The sight glass apparatus of claim 3, wherein the first end surface of the first land is adjacent the first end of the barrel and the first end surface of the second land is adjacent the first end of the barrel, the first land and the second land each having a second end surface opposite the respective first end surface and adjacent the second end of the barrel.

5. The sight glass apparatus of claim 4, wherein the second end surface of the first annular platform is provided with a plurality of second threaded holes distributed at intervals in the circumferential direction of the cylinder, the plug comprises second mounting holes corresponding to the second threaded holes in a one-to-one manner, the sight glass apparatus further comprises second bolts, the number of the second bolts is equal to that of the second mounting holes in a one-to-one manner, and the second bolts penetrate through the corresponding second mounting holes and are connected with the corresponding second threaded holes.

6. The sight glass apparatus of claim 5, wherein the blocking piece further comprises:

the first end surface of the second sight glass is abutted against the second end surface of the second annular platform;

the first end face of the second pressing ring is abutted against the second end face of the second sight glass; and

and the second limiting flange is arranged at the second end of the second pressure ring and is abutted against the second end surface of the first annular table, and the plurality of second mounting holes are arranged on the second limiting flange.

7. The sight glass apparatus of claim 5, wherein the blocking piece further comprises:

the first end face of the blind plate is abutted against the second end face of the second annular platform; and

the third limiting flange is arranged at the second end of the blind plate and is abutted against the second end face of the first annular table, and the plurality of second mounting holes are formed in the third limiting flange.

8. The viewing mirror apparatus according to claim 1, wherein the barrel is provided at both the first end and the second end with a connection flange provided with a plurality of third mounting holes spaced circumferentially around the barrel, the barrel being connected to the viewing window tube via the connection flange at the first end.

9. A reduction furnace, comprising the sight glass apparatus according to any one of claims 1 to 8, and further comprising a plurality of the sight glass tubes spaced apart in a longitudinal direction of the reduction furnace, wherein the number of the sight glass apparatuses is equal to the number of the sight glass tubes and corresponds to one another, and the sight glass tubes are connected to the sight glass apparatuses.

10. A reduction furnace according to claim 9, wherein a window flange is provided on the window tube, and the first end of the cylinder in the viewing mirror unit is connected to the window flange.

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