Dust collection focus fixing device for handheld laser cleaning machine

Abstract

The invention discloses a dust collecting and focus fixing device for a handheld laser cleaning machine, and relates to the technical field of laser cleaning equipment, the dust collecting and focus fixing device comprises a laser device and a laser cleaning head, a dust collecting mechanism is fixedly arranged at a light outlet of the laser cleaning head, the dust collecting mechanism comprises a barrel, and a laser channel is arranged in the middle of the interior of the barrel; a dust collection cavity is formed between the position, close to the first end, of the barrel and the laser channel, a support is fixedly arranged at the first end of the barrel, and a focus fixing mechanism is fixedly arranged on the inner side of the support. According to the laser cleaning device, the barrel covers the surface of a workpiece to be cleaned, smoke dust and residues generated in the laser cleaning process all enter the dust collecting cavity, the dust collecting fan sucks all the smoke dust and residues in the dust collecting cavity, and the problem that in the existing laser cleaning process, smoke dust and residues are not collected thoroughly is solved; the focus fixing mechanism can rapidly position and stably keep the focus position of the laser beam coinciding with the surface of the workpiece to be cleaned, and the cleaning efficiency and the cleaning effect are improved.

Description

Technical Field

[0001] The invention relates to the technical field of laser cleaning equipment, and in particular to a dust collecting and focusing device for a handheld laser cleaning machine. Background Art

[0002] Laser cleaning is a new, green, efficient and non-destructive cleaning method. Its working principle is to use laser beams to irradiate the surface of materials. The interaction between lasers and materials produces a series of physical or chemical reactions, which can effectively remove pollutants and impurity layers on the surface of materials. Compared with traditional physical cleaning such as mechanical friction, high-pressure water jets, chemical corrosion and ultrasonic cleaning, laser cleaning causes less damage to the substrate, does not produce waste liquid pollutants, can be used in conjunction with automated equipment, has high cleaning efficiency, and has received widespread attention in many fields such as aerospace, shipbuilding, and automobiles. With the increase in application scenarios and fields of use, laser cleaning technology has gradually developed towards a portable mode. Handheld laser cleaning machines are favored by the market. Handheld laser cleaning machines input the laser emitted by the laser into the optical fiber and complete the cleaning process through the laser cleaning head. The operator only needs to hold the laser cleaning head to complete cleaning of any shape and any angle. However, compared with large cleaning equipment, it is difficult to guarantee dust collection and fixed focus for handheld laser cleaning machines, and there is still room for improvement. (1) In terms of dust collection, laser cleaning will generate a large amount of smoke and rust residue during the rust and paint removal process. If not handled, it will cause damage to the environment and the health of the operator. The common dust collection method for handheld laser cleaning machines is to use an external dust collection device to collect smoke and rust residues close to the workpiece being cleaned. Because it is in an open area and is affected by the environment, this method has a poor effect on smoke collection. It is also very easy to be irradiated by the laser beam close to the cleaning area, causing damage to the dust collection equipment. In addition, the cleaning and dust collection operations cannot be completed by one person, resulting in a waste of manpower and material resources. (2) In terms of focusing, due to the characteristics of the laser itself, the cleaning effect is most ideal only at the focus of the laser beam. It is difficult for the operator to ensure that the laser beam is always at the focus during use, which will lead to a decrease in the cleaning effect. The common solution is to add a red light indicator light inside the laser cleaning head to achieve the focusing process. The operator observes the size of the red light indicator light spot to determine whether it is at the laser focus. This method has high requirements for operators and is difficult to promote and use. Therefore, it is necessary to provide a technical solution with good dust collection effect and fast focusing for a handheld laser cleaning machine. Summary of the invention

[0003] The purpose of the present invention is to provide a dust collection and focusing device for a handheld laser cleaning machine in order to solve the above-mentioned problem.

[0004] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0005] A dust collection and focusing device for a handheld laser cleaning machine comprises a laser and a laser cleaning head, wherein the laser is connected to the laser cleaning head through an optical fiber, a dust collection mechanism is fixedly arranged at a light outlet of the laser cleaning head, the dust collection mechanism comprises a cylinder, a first end of the cylinder is a light outlet, a second end of the cylinder is fixedly connected to the laser cleaning head, a laser channel is arranged at a middle position inside the cylinder, the laser channel is approximately in the shape of a quadrangular pyramid near the first end of the cylinder, a dust collection cavity is formed between the cylinder near the first end and the laser channel, and a dust collection cavity is arranged on the outer side of the cylinder near the dust collection cavity A dust suction port is provided, and the dust suction port is connected to the dust collecting fan through a dust suction pipe; a bracket is fixedly provided on the first end position of the cylinder, and a focusing mechanism is fixedly provided on the inner side of the bracket; the cylinder is covered on the surface of the workpiece to be cleaned, and the laser beam emitted by the laser passes through the optical fiber, the laser cleaning head and the laser channel in sequence, and the focus of the laser beam is located outside the first end of the cylinder, and the smoke and residue generated during the cleaning process enter the dust collecting chamber, and the dust collecting fan absorbs the smoke and residue in the dust collecting chamber; the focusing mechanism can be adjusted according to the focal position of the laser beam so that the focus of the laser beam always coincides with the surface of the workpiece to be cleaned.

[0006] Preferably, there are two dust suction ports located on the upper and lower outer sides of the cylinder.

[0007] Preferably, the focusing mechanism includes a connecting column and a universal ball, the bracket is annular, and a plurality of mounting plates arranged in sequence are fixedly provided on the inner side of the bracket, one of the connecting columns is fixedly installed in the middle position of one of the mounting plates, a groove is provided at one end of the connecting column away from the bracket, and an adjustment column is fixedly provided at one end of the universal ball, the adjustment column cooperates with the groove and the two are connected by threads, and the length of the adjustment column in the groove is adjusted so that the outermost top of the ball of the universal ball is coplanar with the focus of the laser beam.

[0008] Preferably, the mounting plate is provided with a through hole, and there are a plurality of the through holes, which are distributed around the connecting column.

[0009] Preferably, a laser lens protection mechanism is provided in the cylinder, and the laser lens protection mechanism includes two air knives. The two air knives are symmetrically fixedly installed on the upper and lower outer sides of the laser channel in the dust collecting chamber. A first air inlet is provided on the outer side of the cylinder, and the first air inlet is connected to the air knife through a pipeline. The first air inlet is connected to the air compressor through a first air pipe. The intersection point of the gas blown out of the nozzles of the two air knives coincides with the focus of the laser beam to prevent smoke and residue in the dust collecting chamber from entering the laser channel.

[0010] Preferably, a protective gas channel is provided near the second end of the cylinder, and the protective gas channel is distributed around the laser channel. An air outlet is provided on the inner side of the cylinder near the protective gas channel, and the air outlet connects the protective gas channel and the laser channel. There are multiple air outlets, and the multiple air outlets are arranged in sequence in a ring-shaped distribution around the laser channel. The air outlets are inclined toward the first end of the cylinder, and the multiple air outlets simultaneously blow out gas inside the laser channel to form a conical air curtain for preventing smoke and residue from contaminating the laser lens. A second air inlet is provided on the outer side of the cylinder near the protective gas channel, and the second air inlet is connected to the air compressor through a second air pipe.

[0011] Preferably, the angle between the air outlet and the inner side of the cylinder is 30°.

[0012] Preferably, there are two second air inlets and they are located on the left and right outer sides of the cylinder; partitions are fixedly arranged in the protective gas channel, there are two partitions and they are both distributed along the length direction of the cylinder, and the two partitions divide the protective gas channel into two spaces.

[0013] Preferably, a brush is fixedly provided at one end of the bracket away from the barrel, the brush is distributed in a ring shape along the end of the bracket, the length of the bristles of the brush is greater than the focal position of the laser beam, and the bristles of the brush are made of flame-retardant material.

[0014] The beneficial effects of the present invention are as follows: (1) The barrel of the present invention covers the surface of the workpiece to be cleaned, and all the smoke and residues generated during the laser cleaning process enter the dust collecting chamber. The dust collecting fan completely removes the smoke and residues in the dust collecting chamber, thereby solving the problem of incomplete collection of smoke and residues in the existing laser cleaning process, and the laser beam cannot affect the dust collecting mechanism, thereby ensuring that the dust collecting mechanism is not easily damaged; (2) The dust collecting mechanism is fixedly installed on the laser cleaning head, and the cleaning and dust collecting operations are carried out simultaneously, and only one operator is required, saving manpower and material costs; (3) The focusing mechanism can quickly locate and stably maintain the focal position of the laser beam to coincide with the surface of the workpiece to be cleaned, thereby improving the cleaning efficiency and cleaning effect, and the requirements for the operator are relatively low, and it is easy to use; (4) The laser lens protection mechanism forms two protective walls to prevent smoke and residues from contaminating the laser lens, thereby extending the service life of the laser lens; (5) The dust collecting mechanism, the focusing mechanism and the laser lens protection mechanism adopt an integrated structural design, which occupies a small space and can be operated by one person, thereby reducing the cost of use. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a first stereoscopic diagram of the overall structure of the present invention;

[0016] Figure 2 It is a second stereoscopic diagram of the overall structure of the present invention;

[0017] Figure 3 It is a first stereoscopic view of the cylinder of the present invention;

[0018] Figure 4 It is a second stereoscopic view of the cylinder of the present invention;

[0019] Figure 5 It is a first cross-sectional view of the cylinder of the present invention;

[0020] Figure 6 It is a first stereoscopic diagram of the focusing mechanism of the present invention;

[0021] Figure 7 is a second stereoscopic diagram of the focus fixing mechanism of the present invention;

[0022] Figure 8 It is a second cross-sectional view of the cylinder of the present invention;

[0023] Fig. 9 A three-dimensional diagram of the air knife of the present invention;

[0024] Fig.10 It is a third cross-sectional view of the cylinder of the present invention;

[0025] Fig.11 It is a schematic diagram of the working principle of the present invention.

[0026] Description of reference numerals:

[0027] 1. Dust collecting mechanism; 11. Cylinder; 111. First end; 112. Second end; 113. Laser channel; 114. Dust collecting chamber; 115. Dust suction port; 116. Second air inlet; 117. First air inlet; 118. Protective gas channel; 119. Air outlet; 12. Dust collecting fan;

[0028] 2. Focusing mechanism; 21. Connecting column; 211. Groove; 22. Universal ball; 221. Ball bearing; 23. Adjusting column;

[0029] 3. Laser lens protection mechanism; 31. Air knife; 311. Nozzle; 32. Air compressor;

[0030] 4. Laser cleaning head;

[0031] 51. Dust suction pipe; 52. Second air pipe;

[0032] 6. Flange;

[0033] 7. bracket; 71. mounting plate; 711. through hole;

[0034] 8. Partition;

[0035] 9. Brush. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the accompanying drawings:

[0037] like Figure 1 , Figure 2 , Figure 3 and Figure 5 As shown, the present invention provides a dust collection and focusing device for a handheld laser cleaning machine, comprising a laser and a laser cleaning head 4, wherein the laser is connected to the laser cleaning head 4 through an optical fiber. A dust collecting mechanism 1 is fixedly arranged at the light outlet of the laser cleaning head 4. The dust collecting mechanism 1 comprises a cylinder 11, wherein the first end 111 of the cylinder 11 is the light outlet, and the second end 112 of the cylinder 11 is fixedly connected to the laser cleaning head 4, wherein the second end 112 is provided with a flange 6, which facilitates the fixed installation of the cylinder 11 and the laser cleaning head 4. A laser channel 113 is arranged at the middle position inside the cylinder 11, and the laser channel 113 is approximately in the shape of a quadrangular pyramid, i.e., a duckbill shape, near the first end 111 of the cylinder 11. A dust collecting chamber 114 is formed between the position of the cylinder 11 near the first end 111 and the laser channel 113, and the laser channel 113 and the dust collecting chamber 114 are two independent spaces. A dust suction port 115 is provided on the outer side of the cylinder 11 near the dust collecting chamber 114, and a flange 6 is provided at the position of the dust suction port 115. The dust suction port 115 is connected to the dust collecting fan through a dust suction pipe 51. In this embodiment, there are two dust suction ports 115 located on the upper and lower outer sides of the cylinder 11, and the dust suction pipe 51 cooperates with the flange 6 of the dust suction port 115 through the flange 6 to achieve a fixed connection between the two. A bracket 7 is fixedly provided at the first end 111 of the cylinder 11, and the bracket 7 and the cylinder 11 can be fixedly connected by screws. A focusing mechanism 2 is fixedly provided on the inner side of the bracket 7. When in use, the cylinder 11 is covered on the surface of the workpiece to be cleaned, and the laser beam emitted by the laser passes through the optical fiber, the laser cleaning head 4 and the laser channel 113 in sequence. The focus of the laser beam is located outside the first end 111 of the cylinder 11, and the smoke and residue generated during the cleaning process enter the dust collecting chamber 114, and the dust collecting fan removes the smoke and residue in the dust collecting chamber 114. The focusing mechanism 2 can be adjusted according to the focal position of the laser beam so that the focal point of the laser beam always coincides with the surface of the workpiece to be cleaned.

[0038] like Figure 6 and Figure 7As shown, in this embodiment, the focus mechanism 2 includes a connecting column 21 and a universal ball 22, the bracket 7 is annular, and a plurality of mounting plates 71 arranged in sequence are fixedly arranged on the inner side of the bracket 7. The mounting plates 71 and the bracket 7 can be manufactured in an integral molding manner, or the mounting plates 71 can be fixedly mounted on the bracket 7 by screws. The number of mounting plates 71 is determined according to actual needs. For example, in this embodiment, the number of mounting plates 71 is 6. One connecting column 21 is fixedly mounted in the middle position of a mounting plate 71, and an external thread can be set on the side of the connecting column 21 close to one end, and a mounting groove with an internal thread can be set on the mounting plate 71, so that the connecting column 21 and the mounting plate 71 are connected by threads. A groove 211 is set at the end of the connecting column 21 away from the bracket 7, and an adjustment column 23 is fixedly set at one end of the universal ball 22. The adjustment column 23 cooperates with the groove 211 and the two are connected by threads. When focusing, the adjusting column 23 is driven to rotate by rotating the universal head forward and backward, and the length of the adjusting column 23 in the groove 211 is changed so that the outermost top of the ball 221 of the universal ball 22 is coplanar with the focus of the laser beam, that is, the focus of the laser beam is always on the plane to be cleaned during the laser cleaning process. The mounting plate 71 is provided with a through hole 711, and there are a plurality of through holes 711, and the plurality of through holes 711 are distributed around the connecting column 21. The through holes 711 can reduce the blocking effect of the mounting plate 71 on smoke and residue in the dust collecting chamber 114.

[0039] like Figure 1 , Figure 5 , Fig. 9 , Fig.10 and Fig.11 As shown, in this embodiment, a laser lens protection mechanism 3 is provided in the cylinder 11, and the laser lens protection mechanism 3 includes an air knife 31. There are two air knives 31, and the two air knives 31 are symmetrically fixed on the upper and lower outer sides of the laser channel 113 in the dust collecting chamber 114 by screws. A first air inlet 117 is provided on the outer side of the cylinder 11, and the first air inlet 117 is connected to the air knife 31 through a pipeline, and the first air inlet 117 is connected to the air compressor 32 through a first air pipe. The intersection point of the blown gas of the nozzles 311 of the two air knives 31 coincides with the focus of the laser beam to prevent the smoke and residue in the dust collecting chamber 114 from entering the laser channel 113. At the same time, the two air knives 31 can also play a role in cleaning the residue on the surface of the workpiece. During the laser cleaning process, affected by the temperature, some residues are heated and cooled and adhere to the cleaning surface of the workpiece. At this time, the gas blown out by the two air knives 31 can blow it up during its cooling process, helping the dust collecting mechanism 1 to smoothly absorb it, so that the cleaning effect is better.

[0040] like Figure 1 , Figure 4 , Figure 5 , Figure 8 and Fig.11As shown, in this embodiment, a protective gas channel 118 is provided near the second end 112 of the cylinder 11, and the protective gas channel 118 is distributed around the laser channel 113. An air outlet 119 is provided on the inner side of the cylinder 11 near the protective gas channel 118, and the air outlet 119 connects the protective gas channel 118 and the laser channel 113. There are multiple air outlets 119, and the multiple air outlets 119 are arranged in sequence around the laser channel 113 in a circular distribution. The air outlet 119 is inclined toward the first end 111 of the cylinder 11. Specifically, the angle between the air outlet 119 and the inner side of the cylinder 11 is 30°. Multiple air outlets 119 simultaneously blow out gas to form a conical air curtain inside the laser channel 113 to prevent smoke and residue from contaminating the laser lens. A second air inlet 116 is provided on the outer side of the cylinder 11 near the protective gas channel 118, and the second air inlet 116 is connected to the air compressor 32 through the second air pipe 52. There are two second air inlets 116 located on the left and right outer sides of the cylinder 11. A partition 8 is fixedly arranged in the protective gas channel 118. There are two partitions 8 and both are distributed along the length direction of the cylinder 11. The two partitions 8 divide the protective gas channel 118 into two spaces. Both the first air pipe and the second air pipe 52 can use PU pipes.

[0041] like Figure 5 , Figure 6 and Fig.10 As shown, in this embodiment, a brush 9 is fixedly provided at one end of the bracket 7 away from the cylinder 11, and the brush 9 is distributed in a ring shape along the end of the bracket 7, and the brush 9 can be fixedly connected with the bracket 7 by clamping. The length of the bristles of the brush 9 is greater than the focal position of the laser beam. Specifically, the length of the bristles of the brush 9 can be selected to be greater than the focal length of the laser beam by 1 mm, so that the bristles are always in contact with the surface of the workpiece to be cleaned. The bristles of the brush 9 are made of flame-retardant material. The function of the brush 9 is that, first of all, the brush 9 can help the integrated cavity 114 of the cylinder 11 to form a closed space, and the smoke and residue generated during the laser cleaning process are sealed in the dust collecting cavity 114, and then, it can also play a role of pretreatment before laser cleaning, and preliminarily brush the surface of the workpiece to be cleaned.

[0042] like Figures 1 to 11As shown, when working, (1) the laser is started, and the laser emits a laser beam through the laser lens of the laser cleaning head 4, and then the laser beam is emitted along the laser channel 113 in the cylinder 11 toward the first end 111, and the focus of the laser beam is coplanar with the outermost top of the ball 221 of the universal ball 22. (2) Then, the laser cleaning head 4 is held, and the ball 221 of the universal ball 22 is brought into contact with the surface of the workpiece to be cleaned, and then the laser cleaning head 4 is pushed so that the ball 221 of the universal ball 22 rolls on the surface of the workpiece to be cleaned. At this time, the laser beam can clean the surface of the workpiece to be cleaned. At the same time, since the cylinder 11 covers the cleaning surface of the workpiece to be cleaned, the smoke and residue generated during the laser beam cleaning process enter the dust collecting chamber 114 of the cylinder 11, and then the dust collecting fan is started to absorb the smoke and residue in the dust collecting chamber 114. (3) At the same time, the air compressor 32 is started to deliver gas to the air knife 31 and the protective gas channel 118 of the cylinder 11 respectively. The gas in the two air knives 31 is blown out through the nozzle 311. The intersection point of the gas blown out by the nozzle 311 of the two air knives 31 coincides with the focus of the laser beam, which is used to prevent the smoke and residue in the dust collecting chamber 114 from entering the laser channel 113. This is the first protective wall; the gas in the protective gas channel 118 is blown out through multiple air outlets 119 at the same time. The blown gas forms a conical air curtain inside the laser channel 113 to prevent smoke and residue from contaminating the laser lens. This is the second protective wall, which prevents smoke and residue from contaminating the laser lens and prolongs the service life of the laser lens. In addition, the two air knives 31 can also play a role in cleaning the residue on the surface of the workpiece.

[0043] The above are only preferred embodiments of the present invention, and the scope of the present invention is not limited thereby. It should be understood by those skilled in the art that various changes, modifications, substitutions and deformations may be made to these embodiments without departing from the principles and purposes of the present invention, and all of them should be included in the protection scope of the present invention. The protection scope of the present invention is defined by the claims and their equivalents.

Claims

1. A dust collection and focusing device for a handheld laser cleaning machine, comprising a laser and a laser cleaning head, wherein the laser and the laser cleaning head are connected via an optical fiber, and characterized in that: A dust collecting mechanism is fixedly arranged at the light outlet position of the laser cleaning head, the dust collecting mechanism comprises a cylinder, the first end of the cylinder is the light outlet, the second end of the cylinder is fixedly connected to the laser cleaning head, a laser channel is arranged at the middle position inside the cylinder, the laser channel is approximately in the shape of a quadrangular pyramid near the first end of the cylinder, a dust collecting chamber is formed between the cylinder near the first end and the laser channel, a dust suction port is arranged on the outer side of the cylinder near the dust collecting chamber, and the dust suction port is connected to the dust collecting fan through a dust suction pipe; a bracket is fixedly arranged at the first end position of the cylinder, and a focusing mechanism is fixedly arranged on the inner side of the bracket; the cylinder is covered on the surface of the workpiece to be cleaned, the laser beam emitted by the laser passes through the optical fiber, the laser cleaning head and the laser channel in sequence, the focus of the laser beam is located outside the first end of the cylinder, the smoke and residue generated during the cleaning process enter the dust collecting chamber, and the dust collecting fan absorbs the smoke and residue in the dust collecting chamber; the focusing mechanism can be adjusted according to the focal position of the laser beam so that the focus of the laser beam always coincides with the surface of the workpiece to be cleaned.

2. The dust collection and focusing device for a handheld laser cleaning machine according to claim 1, characterized in that: The dust suction ports are two and are located on the upper and lower outer sides of the cylinder.

3. The dust collection and focusing device for a handheld laser cleaning machine according to claim 1, characterized in that: The focusing mechanism includes a connecting column and a universal ball. The bracket is annular, and a plurality of mounting plates arranged in sequence are fixedly arranged on the inner side of the bracket. One of the connecting columns is fixedly installed in the middle position of one of the mounting plates. A groove is provided at one end of the connecting column away from the bracket, and an adjustment column is fixedly provided at one end of the universal ball. The adjustment column cooperates with the groove and the two are connected by threads. The length of the adjustment column in the groove is adjusted so that the outermost top of the ball of the universal ball is coplanar with the focus of the laser beam.

4. The dust collection and focusing device for a handheld laser cleaning machine according to claim 3, characterized in that: The mounting plate is provided with a through hole, and there are a plurality of through holes, which are distributed around the connecting column.

5. The dust collection and focusing device for a handheld laser cleaning machine according to claim 1, characterized in that: A laser lens protection mechanism is provided in the cylinder body, and the laser lens protection mechanism includes two air knives. The two air knives are symmetrically fixedly installed on the upper and lower outer sides of the laser channel in the dust collecting chamber. A first air inlet is provided on the outer side of the cylinder body, and the first air inlet is connected to the air knife through a pipeline. The first air inlet is connected to the air compressor through a first air pipe. The intersection point of the gas blown out of the nozzles of the two air knives coincides with the focus of the laser beam to prevent the smoke and residue in the dust collecting chamber from entering the laser channel.

6. The dust collection and focusing device for a handheld laser cleaning machine according to claim 5, characterized in that: A protective gas channel is arranged near the second end of the cylinder, and the protective gas channel is distributed around the laser channel. An air outlet is arranged on the inner side surface of the cylinder near the protective gas channel, and the air outlet connects the protective gas channel and the laser channel. There are multiple air outlets, and the multiple air outlets are arranged in sequence in a ring-shaped distribution around the laser channel. The air outlets are inclined toward the first end of the cylinder, and the multiple air outlets simultaneously blow out gas inside the laser channel to form a conical air curtain for preventing smoke and residue from contaminating the laser lens. A second air inlet is arranged on the outer side surface of the cylinder near the protective gas channel, and the second air inlet is connected to the air compressor through a second air pipe.

7. The dust collecting and focusing device for a handheld laser cleaning machine according to claim 6, characterized in that: The included angle between the air outlet and the inner side of the cylinder is 30°.

8. The dust collecting and focusing device for a handheld laser cleaning machine according to claim 6, characterized in that: There are two second air inlets located on the left and right outer sides of the cylinder; partitions are fixedly arranged in the protective gas channel, there are two partitions and both are distributed along the length direction of the cylinder, and the two partitions divide the protective gas channel into two spaces.

9. The dust collection and focusing device for a handheld laser cleaning machine according to claim 1, characterized in that: A brush is fixedly arranged at one end of the bracket away from the barrel, and the brush is distributed in a ring shape along the end of the bracket. The length of the brush bristles is greater than the focal position of the laser beam, and the brush bristles are made of flame-retardant material.

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