An explosion-proof electric heater

Abstract

The present invention discloses an explosion-proof electric heater, which includes an electric heating mechanism. A dehumidification mechanism is arranged on the electric heating mechanism. The dehumidification mechanism includes an arc-shaped block, a mounting hole, a humidity sensor, two mounting blocks and an external threaded pipe. A heat insulation plate is fixed on the surface of the arc-shaped block. A controller is installed on the top of the heat insulation plate. A sealing ring is fixed inside the mounting hole. A gear ring is fixedly sleeved on the outer wall of the external threaded pipe. A pipe cover is installed on the top of the external threaded pipe. A cavity cylindrical block is fixed between the same sides of the two mounting blocks. Concave discs are fixed on both sides of the inner wall of the cavity cylindrical block. By setting the dehumidification mechanism, the present invention can reduce the dryness of the air inside the protective shell of the electric heater, effectively protect the stability of the connection between the heating rod in the electric heater and the external control switch wire, avoid the short circuit of the electric heater, resulting in damage and reducing the service life.

Description

Technical Field

[0001] The present invention relates to the technical field of electric heaters, and particularly to an explosion-proof electric heater. Background Technique

[0002] An electric heater is a process of converting electrical energy into heat energy, which is used for heating, keeping warm and heating flowing liquid and gaseous media, and is widely used in fields such as production, scientific research and experiments.

[0003] Although the existing electric heaters can heat gases during actual use, if the electric heaters are used in a space with high humidity for a long time, the air humidity inside the protective shell of the electric heaters will increase greatly, which is very likely to cause the connection position between the electric heating rod joint in the electric heater and the external control switch wire to be unstable, and even short-circuit, resulting in damage to the electric heater and reducing its service life.

[0004] Therefore, a new type of explosion-proof electric heater needs to be proposed to solve the problems mentioned above. Summary of the Invention

[0005] The purpose of the present invention is to provide an explosion-proof electric heater to solve the problem that when the electric heater is used inside a space with high humidity, the air humidity inside the protective shell of the electric heater increases, resulting in the connection position between the electric heating rod joint in the electric heater and the external control switch wire being unstable, and even short-circuit, resulting in damage to the electric heater and reducing its service life.

[0006] To achieve the above purpose, the present invention provides the following technical solution: An explosion-proof electric heater, including an electric heating mechanism, and a dehumidification mechanism is arranged on the electric heating mechanism;

[0007] The dehumidification mechanism includes an arc-shaped block, a mounting hole, a humidity sensor, two mounting blocks, and an external threaded pipe. A heat insulation plate is fixed on the surface of the arc-shaped block, and a controller is installed on the top of the heat insulation plate. A sealing ring is fixed inside the mounting hole. A gear ring is fixedly sleeved on the outer wall of the external threaded pipe. A pipe cap is installed on the top of the external threaded pipe. A cavity cylinder block is fixed between the same sides of the two mounting blocks. Concave discs are fixed on both sides of the inner wall of the cavity cylinder block. A plurality of arc-shaped strips are equidistantly distributed and fixed between the opposite sides of the two concave discs. A hollow column is fixed between the opposite sides of the two concave discs. A bolt rod threadedly penetrates through the outer wall of the cavity cylinder block. A plurality of ventilation holes are equidistantly distributed and opened on the opposite sides of the two concave discs. A round sealing column is arranged inside the hollow column. A U-shaped frame is fixed on the top of the sealing column. A connecting block is fixed on the outer wall of the cavity cylinder block. A micro air pump is installed on the top of the connecting block. Connecting pipes are fixedly penetrated through both sides of the cavity cylinder block. The output end of one of the connecting pipes is installed with an air inlet pipe. A plurality of discharge holes are equidistantly distributed and opened on the front surface and the rear surface of the inner wall of the hollow column.

[0008] Preferably, the controller is electrically connected to the humidity sensor, the controller is electrically connected to the micro air pump. The bottom end of the external threaded pipe threadedly penetrates through the outer wall of the cavity cylinder block. The top end of the bolt rod movably penetrates through the outer walls of a plurality of arc-shaped strips, which is convenient for controlling the start and stop of the micro air pump under the cooperation of the controller and the humidity sensor.

[0009] Preferably, the sealing column is movably sleeved inside the external threaded pipe. The output end of the air inlet pipe is connected to the input end of the micro air pump. The wire end of the micro air pump is movably sleeved inside the sealing ring, which is convenient for blocking all the discharge holes on the hollow column under the action of the sealing column.

[0010] Preferably, the electric heating mechanism includes a barrel body. Two symmetrically arranged support frames are fixed on the outer wall of the barrel body. A first concave shell is fixed inside the barrel body, which is convenient for installing the electric heater at the required position under the action of the support frames, effectively improving the stability of the electric heater during operation.

[0011] Preferably, an explosion-proof frame is fixed inside the first concave shell. A second concave shell is fixed on the inner wall of the explosion-proof frame. A heat preservation shell is fixed on the inner wall of the second concave shell. Two symmetrically arranged round pipes are fixedly penetrated through the outer wall of the barrel body, which is convenient for improving the explosion-proof effect of the electric heater under the cooperation of the explosion-proof frame, the first concave shell and the second concave shell.

[0012] Preferably, the bottoms of the two round tubes movably penetrate through the outer wall of the first concave shell, the interior of the explosion-proof frame, the outer wall of the second concave shell, and the outer wall of the heat preservation shell from top to bottom in sequence. A protective shell is installed on one side of the barrel body. The arc-shaped block is installed on the outer wall of the protective shell. The mounting hole is formed in the outer wall of the protective shell. The humidity sensor is installed on the outer wall of the protective shell, which is convenient for improving the heat preservation effect of the electric heater under the action of the heat preservation shell. At the same time, under the action of the protective shell, the components inside it can be protected.

[0013] Preferably, the detection end of the humidity sensor extends into the interior of the protective shell. The bottom end of the external thread tube movably penetrates through the outer wall of the protective shell. A cover plate is installed on one side of the protective shell. Both of the mounting blocks are installed on the other side of the cover plate by bolts. Two heating rods fixedly penetrate through the other side of the protective shell. A plurality of stabilizing disks are equidistantly distributed and fixed on the outer surfaces of the two heating rods, which is convenient for heating the gas entering the interior of the heat preservation shell under the action of the heating rods.

[0014] Preferably, a plurality of circular ring blocks are equidistantly distributed and fixed on the inner wall of the heat preservation shell. Each stabilizing disk is respectively located inside each circular ring block. A plurality of arc-shaped holes are equidistantly distributed on one side of each circular ring block. A plurality of cylindrical holes are equidistantly distributed on one side of each stabilizing disk. A porous sealing plug is installed at the outlet of the wiring hole of the protective shell, which is convenient for providing a certain supporting force for the heating rods under the cooperation of the stabilizing disks and the circular ring blocks.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0016] 1. By setting the dehumidification mechanism, the present invention can reduce the dryness of the air inside the protective shell of the electric heater, effectively protecting the stability of the connection between the heating rod and the external control switch wire in the electric heater, avoiding short circuits in the electric heater, causing damage, and reducing the service life. Under the action of the humidity sensor, the air humidity inside the protective shell can be monitored at all times. Under the cooperation of the controller and the humidity sensor, the start and stop of the micro air pump can be controlled. Under the action of the heat insulation board, the controller can be thermally insulated and protected. Under the cooperation of the pipe cap and the U-shaped frame, the sealing column can be tightly fixed between the inside of the external thread tube and the inside of the hollow column. Under the action of the gear ring, the external thread tube can be removed from the cavity cylindrical block. Under the action of the bolt rod, it is convenient for the replacement of the desiccant particles in the later stage and prevents the desiccant particles from flowing out of the space composed of the cavity cylindrical block, the concave disc, and the arc-shaped strip.

[0017] 2. The present invention is provided with an electric heating mechanism, which can heat the gas entering the interior of the heat preservation shell. Meanwhile, with the cooperation of the explosion-proof frame, the first concave shell and the second concave shell, the explosion-proof effect of the electric heater can be improved. With the cooperation of the circular ring block and the stabilizing disk, a supporting force can be provided for the heating rod. With the cooperation of the circular ring block, the stabilizing disk, the cylindrical hole and the arc-shaped hole, the flow rate of the gas flowing inside the heat preservation shell can be reduced. Under the action of the porous sealing plug, the entry of external gas into the interior of the protection shell can be reduced. Under the action of the cover plate, it is convenient to repair the components inside the protection shell. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a perspective view of an explosion-proof electric heater of the present invention;

[0019] Figure 2 is another perspective view of an explosion-proof electric heater of the present invention;

[0020] Figure 3 is a partially sectional perspective view of an explosion-proof electric heater of the present invention;

[0021] Figure 4 is a partial perspective view of the dehumidifying mechanism of an explosion-proof electric heater of the present invention;

[0022] Figure 5 is another partial perspective view of the dehumidifying mechanism of an explosion-proof electric heater of the present invention;

[0023] Figure 6 is a partially sectional perspective view of the dehumidifying mechanism of an explosion-proof electric heater of the present invention;

[0024] Figure 7 is another partially sectional perspective view of the dehumidifying mechanism of an explosion-proof electric heater of the present invention;

[0025] Figure 8 is another partially sectional perspective view of an explosion-proof electric heater of the present invention.

[0026] In the figure: 1. Electric heating mechanism; 101. Barrel body; 102. Support frame; 103. First concave shell; 104. Explosion-proof frame; 105. Heat preservation shell; 106. Circular tube; 107. Protection shell; 108. Cover plate; 109. Heating rod; 110. Stabilizing disk; 111. Circular ring block; 112. Arc-shaped hole; 113. Cylindrical hole; 114. Porous sealing plug; 115. Second concave shell;

[0027] 2. Dehumidification mechanism; 201. Arc-shaped block; 202. Heat insulation plate; 203. Controller; 204. Mounting hole; 205. Sealing ring; 206. Humidity sensor; 207. Discharge hole; 208. External threaded pipe; 209. Gear ring; 210. Pipe cover; 211. Mounting block; 212. Cavity cylindrical block; 213. Concave disc; 214. Arc-shaped strip; 215. Hollow column; 216. Bolt rod; 217. Ventilation hole; 218. Sealing column; 219. U-shaped frame; 220. Connecting block; 221. Micro air pump; 222. Connecting pipe; 223. Intake pipe. Detailed implementation manner

[0028] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0029] Please refer to Figure 1 - Figure 8 As shown in the figure, the present invention provides a technical solution: an explosion-proof electric heater, including an electric heating mechanism 1, and a dehumidification mechanism 2 is arranged on the electric heating mechanism 1;

[0030] The dehumidification mechanism 2 includes an arc-shaped block 201, a mounting hole 204, a humidity sensor 206, two mounting blocks 211 and an external threaded pipe 208. The surface of the arc-shaped block 201 is fixed with a heat insulation plate 202, the top of the heat insulation plate 202 is provided with a controller 203, the inside of the mounting hole 204 is fixed with a sealing ring 205, the outer wall of the external threaded pipe 208 is fixedly sleeved with a gear ring 209, the top of the external threaded pipe 208 is provided with a pipe cover 210, a cavity cylindrical block 212 is fixed between the same sides of the two mounting blocks 211, concave discs 213 are fixed on both sides of the inner wall of the cavity cylindrical block 212, a plurality of arc-shaped strips 214 are equidistantly distributed and fixed between the opposite sides of the two concave discs 213, a hollow column 215 is fixed between the opposite sides of the two concave discs 213, a bolt rod 216 is threadedly penetrated through the outer wall of the cavity cylindrical block 212, a plurality of ventilation holes 217 are equidistantly distributed and opened on the opposite sides of the two concave discs 213, a circular sealing column 218 is arranged inside the hollow column 215, a U-shaped frame 219 is fixed on the top of the sealing column 218, a connecting block 220 is fixed on the outer wall of the cavity cylindrical block 212, a micro air pump 221 is installed on the top of the connecting block 220, connecting pipes 222 are fixedly penetrated through both sides of the cavity cylindrical block 212, the output end of one of the connecting pipes 222 is provided with an intake pipe 223, and a plurality of discharge holes 207 are equidistantly distributed and opened on the front surface and the rear surface of the inner wall of the hollow column 215.

[0031] According to Figure 2 - Figure 7 As shown, the controller 203 is electrically connected to the humidity sensor 206, the controller 203 is electrically connected to the micro air pump 221, the bottom end of the external thread tube 208 threadedly penetrates through the outer wall of the cavity cylinder block 212, and the top end of the bolt rod 216 movably penetrates through the outer walls of a plurality of arc-shaped strips 214, facilitating the start and stop of the micro air pump 221 under the cooperation of the controller 203 and the humidity sensor 206.

[0032] According to Figure 2 - Figure 4 and Figure 6 As shown, the sealing column 218 is movably sleeved inside the external thread tube 208, the output end of the air inlet pipe 223 is connected to the input end of the micro air pump 221, and the wire end of the micro air pump 221 is movably sleeved inside the sealing ring 205, facilitating the blocking of all the discharge holes 207 on the hollow column 215 under the action of the sealing column 218.

[0033] According to Figure 1 、 Figure 2 and Figure 8 As shown, the electric heating mechanism 1 includes a barrel body 101, two symmetrically arranged support frames 102 are fixed on the outer wall of the barrel body 101, and a first concave shell 103 is fixed inside the barrel body 101, facilitating the installation of the electric heater at the required position under the action of the support frames 102, effectively improving the stability of the electric heater during operation.

[0034] According to Figure 2 and Figure 8 As shown, an explosion-proof frame 104 is fixed inside the first concave shell 103, a second concave shell 115 is fixed on the inner wall of the explosion-proof frame 104, a heat preservation shell 105 is fixed on the inner wall of the second concave shell 115, and two symmetrically arranged round tubes 106 are fixedly penetrated through the outer wall of the barrel body 101, facilitating the improvement of the explosion-proof effect of the electric heater under the cooperation of the explosion-proof frame 104, the first concave shell 103 and the second concave shell 115.

[0035] According to Figure 2 、 Figure 3 and Figure 8 As shown, the bottom ends of the two round tubes 106 sequentially and movably penetrate through the outer wall of the first concave shell 103, the inside of the explosion-proof frame 104, the outer wall of the second concave shell 115 and the outer wall of the heat preservation shell 105 from top to bottom. A protective shell 107 is installed on one side of the barrel body 101, an arc-shaped block 201 is installed on the outer wall of the protective shell 107, a mounting hole 204 is opened on the outer wall of the protective shell 107, and a humidity sensor 206 is installed on the outer wall of the protective shell 107, facilitating the improvement of the heat preservation effect of the electric heater under the action of the heat preservation shell 105, and at the same time, protecting the internal components under the action of the protective shell 107.

[0036] According to Figure 2 - Figure 4 and Figure 8 As shown, the detection end of the humidity sensor 206 extends to the inside of the protective case 107. The bottom end of the external thread tube 208 movably penetrates the outer wall of the protective case 107. A cover plate 108 is installed on one side of the protective case 107. Both mounting blocks 211 are installed on the other side of the cover plate 108 through bolts. Two heating rods 109 are fixedly penetrated through the other side of the protective case 107. A plurality of stabilizing disks 110 are fixedly distributed at equal intervals on the outer surfaces of the two heating rods 109, facilitating heating operation of the gas entering the inside of the heat preservation case 105 under the action of the heating rods 109.

[0037] According to Figure 2 , Figure 3 and Figure 8 As shown, a plurality of circular ring blocks 111 are fixedly distributed at equal intervals on the inner wall of the heat preservation case 105. Each stabilizing disk 110 is respectively located inside each circular ring block 111. A plurality of arc-shaped holes 112 are evenly distributed on one side of each circular ring block 111. A plurality of cylindrical holes 113 are evenly distributed on one side of each stabilizing disk 110. A porous sealing plug 114 is installed at the outlet of the wiring hole of the protective case 107, facilitating providing a certain supporting force for the heating rods 109 under the cooperation of the stabilizing disks 110 and the circular ring blocks 111.

[0038] The effects achieved by the entire mechanism are as follows: When gas heating operation is required, the heating rod 109 is directly connected to an external control switch by a wire under the cooperation of the porous sealing plug 114 and the wiring holes of the protective shell 107. At the same time, the two round tubes 106 are respectively connected to two gas delivery tubes and an output tube. Then, the tube cap 210 is removed, and the sealing column 218 is directly pulled out from the inside of the external thread tube 208 by using the U-shaped frame 219. When the sealing column 218 is completely removed, desiccant particles are continuously injected into the external thread tube 208. At this time, the desiccant particles entering from the external thread tube 208 will directly enter the inside of the hollow column 215. Then, through the cooperation of multiple discharge holes 207, the desiccant particles can be guided into each space composed of the cavity cylindrical block 212, the concave disc 213, and the arc-shaped strip 214. When each space is filled with desiccant particles, the sealing column 218 is directly placed back between the inside of the external thread tube 208 and the inside of the hollow column 215 by using the U-shaped frame 219. When the sealing column 218 completes the reset operation, the sealing column 218 will block all the discharge holes 207. Then, the tube cap 210 is reinstalled. When everything is ready, gas is continuously injected into the heat preservation shell 105 of the electric heater through the round tube 106. At the same time, the two heating rods 109 are started. At this time, the started heating rods 109 will heat the gas entering the heat preservation shell 105. At this time, under the cooperation of the stabilizing plate 110, the ring block 111, the cylindrical hole 113, and the arc-shaped hole 112, the flow of the gas entering the heat preservation shell 105 to the position of the other round tube 106 can be reduced. At this time, the gas entering the heat preservation shell 105 will be fully heated. When the heated gas moves to the input end of the other round tube 106, under the suction force at the input end of the external output tube, the heated gas entering the other round tube 106 will be directly sucked away, that is, the heating of the gas is completed. When the inside of the heater is continuously heated, under the cooperation of the explosion-proof frame 104, the first concave shell 103, the heat preservation shell 105, and the second concave shell 115, the explosion-proof effect of the heater can be improved. When the electric heater is not in use and the external air humidity is relatively high, and moisture enters the protective shell 107 from the gap between the outer wall of the wire connecting the through hole of the porous sealing plug 114 and the heating rod 109, the air humidity inside the protective shell 107 will increase. At this time, when the heating of the heating rod 109 is stopped, the controller 203 can be directly started, and the minimum humidity value and the maximum humidity value are set. At the same time, the started controller 203 will energize the humidity sensor 206 and start it. At this time, the started humidity sensor 206 will directly detect the air humidity inside the protective shell 107 and transmit the detected data to the inside of the controller 203 in the form of an electrical signal. At this time, the controller 203 will compare the received air humidity data with the minimum humidity value and the maximum humidity value previously set by the controller 203.When the air humidity value received by the controller 203 is less than the minimum humidity value previously set by the controller 203, the controller 203 will control the micro air pump 221 to start at this time. At this time, a relatively large suction force will be generated at the input end of the started micro air pump 221. At this time, with the cooperation of the cavity cylinder block 212, the intake pipe 223 and the corresponding connecting pipe 222, the input end of another connecting pipe 222 will directly obtain the suction force. At this time, the gas inside the protective case 107 will be directly sucked into the input end of the connecting pipe 222 that obtains the suction force. After that, the sucked gas will be respectively guided to each corresponding space through the corresponding ventilation holes 217. When the gas is respectively guided to the corresponding space, under the action of the desiccant particles in the corresponding space, the moisture mixed in the gas can be absorbed. Then, the dried gas will directly pass through another ventilation hole 217 in the corresponding space. After that, the exported dried gas will directly enter the connecting pipe 222 connected to the intake pipe 223. Then, the gas entering the connecting pipe 222 will be directly guided to the inside of the intake pipe 223. Finally, the dried gas will directly enter the micro air pump 221 and be ejected from its output end, and be guided to the inside of the protective case 107, that is, the dehumidification operation is completed, that is, the stability of the connection between the heating rod 109 and the external control switch wire is effectively protected, and no short - circuit situation occurs.

[0039] Among them, the controller 203, the humidity sensor 206 and the micro air pump 221 are all prior arts, and their components and working principles are all public technologies, and no more explanations will be made here. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An explosion-proof electric heater, characterized in that: It includes an electric heating mechanism, and a dehumidification mechanism is arranged on the electric heating mechanism; The dehumidification mechanism includes an arc-shaped block, a mounting hole, a humidity sensor, two mounting blocks and an external thread tube. A heat insulation plate is fixed on the surface of the arc-shaped block, and a controller is installed on the top of the heat insulation plate. A sealing ring is fixed inside the mounting hole. A gear ring is fixedly sleeved on the outer wall of the external thread tube. A pipe cover is installed on the top of the external thread tube. A cavity cylinder block is fixed between the same sides of the two mounting blocks. Concave disks are fixed on both sides of the inner wall of the cavity cylinder block. A plurality of arc-shaped strips are equidistantly distributed and fixed between the opposite sides of the two concave disks. A hollow column is fixed between the opposite sides of the two concave disks. A bolt rod threadedly penetrates through the outer wall of the cavity cylinder block. A plurality of ventilation holes are equidistantly distributed and opened on the opposite sides of the two concave disks. A round sealing column is arranged inside the hollow column. A U-shaped frame is fixed on the top of the sealing column. A connecting block is fixed on the outer wall of the cavity cylinder block. A micro air pump is installed on the top of the connecting block. Connecting pipes are fixedly penetrated through both sides of the cavity cylinder block. The output end of one of the connecting pipes is installed with an air inlet pipe. A plurality of discharge holes are equidistantly distributed and opened on the front surface and the rear surface of the inner wall of the hollow column.

2. The explosion-proof electric heater according to claim 1, wherein: The controller is electrically connected to the humidity sensor, and the controller is electrically connected to the micro air pump. The bottom end of the external thread tube threadedly penetrates through the outer wall of the cavity cylinder block, and the top end of the bolt rod movably penetrates through the outer walls of a plurality of arc-shaped strips.

3. The explosion-proof electric heater according to claim 1, wherein: The sealing column is movably sleeved inside the external thread tube. The output end of the air inlet pipe is connected to the input end of the micro air pump. The wire end of the micro air pump is movably sleeved inside the sealing ring.

4. The explosion-proof electric heater according to claim 1, characterized in that: The electric heating mechanism includes a barrel body. Two symmetrically arranged support frames are fixed on the outer wall of the barrel body, and a first concave shell is fixed inside the barrel body.

5. The explosion-proof electric heater according to claim 4, characterized in that: An explosion-proof frame is fixed inside the first concave shell. A second concave shell is fixed on the inner wall of the explosion-proof frame. A heat preservation shell is fixed on the inner wall of the second concave shell. Two symmetrically arranged round pipes are fixedly penetrated through the outer wall of the barrel body.

6. The explosion-proof electric heater according to claim 5, wherein: The bottom ends of the two round pipes sequentially and movably penetrate through the outer wall of the first concave shell, the inside of the explosion-proof frame, the outer wall of the second concave shell and the outer wall of the heat preservation shell from top to bottom. A protective shell is installed on one side of the barrel body. The arc-shaped block is installed on the outer wall of the protective shell. The mounting hole is opened on the outer wall of the protective shell. The humidity sensor is installed on the outer wall of the protective shell.

7. The explosion-proof electric heater according to claim 6, characterized in that: The detection end of the humidity sensor extends into the protective shell. The bottom end of the external thread tube movably penetrates through the outer wall of the protective shell. A cover plate is installed on one side of the protective shell. Both of the mounting blocks are installed on the other side of the cover plate by bolts. Two heating rods are fixedly penetrated through the other side of the protective shell. A plurality of stabilizing disks are equidistantly distributed and fixed between the outer surfaces of the two heating rods.

8. The explosion-proof electric heater according to claim 7, wherein: A plurality of circular ring blocks are fixedly distributed at equal intervals on the inner wall of the heat preservation shell. Each of the stabilizing discs is respectively located inside each circular ring block. A plurality of arc-shaped holes are evenly distributed and opened on one side of each circular ring block. A plurality of cylindrical holes are evenly distributed and opened on one side of each stabilizing disc. A porous sealing plug is installed at the outlet of the wiring hole of the protective shell.

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