Camera assembly mounting device and blackboard

Abstract

The utility model provides a kind of camera assembly mounting device, it is related to educational apparatus technical field, comprising: first assembly shell, second assembly shell and connecting device, accommodating groove is opened in first assembly shell, and the opposite two side walls of accommodating groove are provided with the positioning slide rail for the installation positioning of control circuit board;Second assembly shell and the top and bottom of first assembly shell are detachably connected by detachable connecting assembly, and the mounting end portion for detachably installing camera assembly is provided on second assembly shell;Connecting device includes assembly connecting piece arranged on the side of second assembly shell away from first assembly shell.

Description

Technical Field

[0001] This utility model relates to the field of educational equipment technology, and in particular to a camera component mounting device and a blackboard. Background Technology

[0002] The smart blackboard is an innovative intelligent teaching device that combines the traditional blackboard with modern multimedia technology. Utilizing advanced capacitive touch technology, it makes teaching more flexible and interactive. It can freely switch between chalk writing and multimedia applications, offering the dual functionality of a traditional blackboard and a modern touchscreen. On this device, teachers can not only use chalk for traditional writing and explanations, but also easily access multimedia resources such as videos, images, and animations through touch operation, injecting more interactivity and fun into the classroom.

[0003] Existing smart blackboards can display the written content on a display device by analyzing the trajectory of the writing action captured by a camera and then through a control component. However, existing smart blackboards do not have a dedicated component for mounting the camera and control component, making the mounting of the camera and control component quite troublesome. Utility Model Content

[0004] The purpose of this utility model is to address the defects and shortcomings of the existing technology by providing a camera component installation device, which solves at least one of the above-mentioned technical problems and has the advantage of quickly installing cameras and control components.

[0005] To achieve the above objectives, this utility model provides a camera component mounting device, comprising:

[0006] A camera assembly, the camera assembly including a first camera and a second camera;

[0007] An assembly assembly includes an assembly plate group, an upper mounting end disposed at the top of the assembly plate group, and a lower mounting end disposed at the bottom of the assembly plate group, wherein the first camera and the second camera are respectively mounted on the upper mounting end and the lower mounting end;

[0008] A control component, wherein the camera component is electrically connected to the control component, and the control component is provided with an illumination component for supplementing light to the camera component;

[0009] A communication component is used to transmit written content to a communication receiving component;

[0010] When the first camera is installed on the upper mounting end, its camera face is tilted downwards, and when the second camera is installed on the lower mounting end, its camera face is tilted upwards.

[0011] Optionally, the assembly plate assembly includes a first assembly plate and a second assembly plate. The upper mounting end is mounted on the top of the first assembly plate, and the lower mounting part is mounted on the bottom of the second assembly plate. The upper mounting end includes a first mounting part and a second mounting part disposed above the first mounting part. A first inclined plate is disposed on one side of the first mounting part, and a first engaging groove is disposed on the first inclined plate. A second inclined plate is disposed on the side of the second mounting part near the first mounting part, facing the first inclined plate. A second engaging groove is disposed on the second inclined plate that matches the first engaging groove.

[0012] The lower mounting end includes a third mounting part and a fourth mounting part disposed above the third mounting part. A third inclined plate is disposed on one side of the third mounting part, and a third engaging groove is disposed on the third inclined plate. A fourth inclined plate is disposed on the side of the fourth mounting part near the third mounting part, facing the third inclined plate, and a fourth engaging groove is disposed on the fourth inclined plate that matches the third engaging groove.

[0013] Optionally, the second inclined plate is provided with a first locking limiting plate that cooperates with the first locking groove and the second locking groove to lock the first camera;

[0014] The fourth inclined plate is provided with a second locking limiting plate that cooperates with the third locking groove and the fourth locking groove to lock the second camera.

[0015] Optionally, both the first camera and the second camera include a mounting plate and a camera body detachably connected to the mounting plate, wherein the mounting plate can be snapped into the first locking groove and the second locking groove.

[0016] Optionally, a threaded seat is provided on one side of the mounting plate, and an external thread adapted to the threaded seat is provided on the outer wall of the camera body, so that the camera body and the threaded seat can be threadedly connected by the external thread and the threaded seat.

[0017] Optionally, the first snap-fit ​​limiting plate is provided with a first wire through hole, and the second snap-fit ​​limiting plate is provided with a second wire through hole.

[0018] Optionally, the control component includes a control circuit board, and a detachable connector is provided on one side of the assembly board assembly. The assembly board assembly is detachably connected to the control circuit board through the detachable connector.

[0019] Optionally, the control circuit board is provided with a housing on its outer side. The detachable connector includes a threaded post for insertion on the assembly plate, a first through hole on the control circuit board, and a second through hole on the housing. The threaded post for insertion passes through the first through hole, and a bolt passes through the second through hole. The control circuit board and the assembly plate can be connected by the bolt threadedly engaging with the threaded post for insertion.

[0020] Optionally, the control circuit board is provided with a wiring cover, and multiple wires for connecting to external electrical appliances extend from the wiring cover. The lighting assembly includes LED beads evenly distributed along the length of the control circuit board.

[0021] A blackboard is improved, including a camera assembly mounting device, the mounting assembly being disposed on the left and / or right side of the blackboard body, with the first camera and the second camera tilted toward the center of the blackboard body.

[0022] Compared with the prior art, the advantages of this application are:

[0023] This invention achieves precise positioning by mounting the control circuit board within the receiving groove of the first assembly housing via a positioning slide rail. The camera assembly is detachably mounted on the second assembly housing via its mounting end. The first and second assembly housings are connected by a detachable connecting component to form a single integrated structure. An assembly connector is used to connect the blackboard to the second housing. The positioning slide rail and detachable connecting component enable rapid positioning and installation of the control circuit board and camera, while the assembly connector ensures stable alignment between the entire device and the blackboard body, thus solving the cumbersome assembly problem of the camera and control component in existing technologies. Attached Figure Description

[0024] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0025] Figure 1 This is an isometric schematic diagram of an embodiment of the present invention;

[0026] Figure 2 This is a side view of an embodiment of the present invention;

[0027] Figure 3 As described in the embodiments of the present invention Figure 2 Enlarged schematic diagram of part a;

[0028] Figure 4This is an exploded view diagram of an embodiment of the present invention;

[0029] Figure 5 As described in the embodiments of the present invention Figure 4 Enlarged diagram of part b;

[0030] Figure 6 As described in the embodiments of the present invention Figure 4 Enlarged schematic diagram of part c;

[0031] Figure 7 This is an isometric view of the shell being removed in an embodiment of the present invention;

[0032] Figure 8 As described in the embodiments of the present invention Figure 7 Enlarged schematic diagram of part d;

[0033] Figure 9 This is an isometric schematic diagram of the blackboard mounting component in an embodiment of the present invention;

[0034] Figure 10 This is an isometric view of the second assembly housing in an embodiment of the present invention;

[0035] Figure 11 This is a top view of the second assembly housing in an embodiment of the present invention.

[0036] Explanation of reference numerals in the attached figures:

[0037] 100. Camera assembly; 101. First mounting housing; 102. Receiving groove; 103. Positioning slide rail; 104. Second mounting housing; 106. Mounting end; 109. L-shaped snap-fit ​​plate; 110. Snap-fit ​​groove; 111. Control circuit board; 112. Lighting assembly; 113. Clearance gap; 114. First mounting plate; 115. Second mounting plate; 116. Connecting plate; 117. First guide slide rail; 118. 119. Second guide groove; 120. First mounting part; 121. Second mounting part; 122. First inclined plate; 123. First engaging groove; 124. Second inclined plate; 125. Second engaging groove; 126. Insertion internal thread post; 127. First connecting through hole; 129. Second connecting through hole; 130. Engagement limiting plate; 131. Connecting locking plate; 132. Third connecting through hole; 134. Oval hole; 135. Blackboard body;

[0038] 201. First mounting vertical plate; 202. Mounting horizontal plate; 203. Mounting eaves; 204. Second mounting vertical plate; 205. Fourth connecting through hole; 206. Fifth connecting through hole; 207. Mounting bracket; 208. Sixth connecting through hole; 209. Seventh connecting through hole; 210. Eighth connecting through hole. Detailed Implementation

[0039] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0040] It should be noted that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "top," "bottom," "inner," "outer," "back," "side," and "circumferential" used in this utility model to indicate the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model. In addition, the terms "first" and "second" are only used to distinguish multiple parts or structures with the same or similar structures, and do not indicate any special limitation on the arrangement order or connection relationship.

[0041] Please refer to Figures 1 to 11 This utility model provides a camera component installation device, including: a first assembly housing 101, a second assembly housing 104 and a connecting device. The first assembly housing 101 has a receiving groove 102, and the two opposite side walls of the receiving groove 102 are provided with positioning slide rails 103 for mounting and positioning the control circuit board 111.

[0042] The second assembly housing 104 is detachably connected to the top and bottom of the first assembly housing 101 via a detachable connection assembly. The second assembly housing 104 is provided with a mounting end 106 for detachably mounting the camera assembly 100. The connection device includes an assembly connector disposed on the side of the second assembly housing 104 away from the first assembly housing 101.

[0043] The receiving groove 102 refers to a recessed structure inside the assembly housing for placing the control circuit board 111. Specifically, it can be achieved by machining or injection molding a rectangular groove into the inner wall of the housing, providing a fixed mounting space for the control circuit board 111. The positioning slide rail 103 refers to a linear guide structure on both sides of the receiving groove 102. Specifically, it can be a grooved track component made of metal or plastic, integrally molded and installed inside the groove. Its function is to achieve precise positioning and rapid assembly of the control circuit board 111 through sliding contact. The detachable connection component refers to a mechanical structure that temporarily fixes the two assembly housings. Its function is to allow for rapid separation and reassembly of the housings through standardized interfaces, facilitating maintenance or replacement of internal components. The mounting end 106 refers to the area at the end of the assembly housing for supporting the camera assembly 100. Specifically, it can be a mounting platform with a slot or magnetic structure, adapting to the camera's fixing requirements and ensuring the stability and compatibility of the device connection. Assembly connectors refer to functional components set on the outside of the housing for docking with other equipment. Their function is to achieve rigid fixation of the entire installation device to the blackboard body 134 or other external components through mechanical connection.

[0044] This application constructs a camera assembly 100 mounting platform through a combination design of modular assembly housing and standardized connection structure. It utilizes positioning slide rail 103 and detachable connection components to achieve rapid positioning and installation of control circuit board 111 and camera. At the same time, it ensures stable docking of the entire device with blackboard body 134 through assembly connectors, thereby solving the technical problem of cumbersome assembly of camera and control components in the prior art.

[0045] During operation, the control circuit board 111 is mounted in the receiving groove 102 of the first assembly housing 101 via the positioning slide rail 103, achieving precise positioning. The camera assembly 100 is detachably mounted on the second assembly housing 104 via the mounting end 106. The first assembly housing 101 and the second assembly housing 104 are connected by a detachable connecting assembly to form a single integrated structure. The assembly connector is used to connect the blackboard to the second housing.

[0046] In this embodiment, an L-shaped snap-fit ​​plate 109 is provided on the side of the first assembly plate 114 near the second assembly plate 115. The L-shaped snap-fit ​​plate 109 and one side of the first assembly plate form a snap-fit ​​groove 110. The L-shaped snap-fit ​​plate 109 extends vertically from the edge of the first assembly plate 114 to form a transverse support portion. The end of the transverse support portion is bent to form a longitudinal limiting portion. A snap-fit ​​space with a limiting function is formed between the longitudinal limiting portion and the side wall of the first assembly groove. The snap-fit ​​groove 110 allows the blackboard body 134 to be inserted, thereby positioning the blackboard body 134.

[0047] In this embodiment, the camera assembly 100 is electrically connected to the control circuit board 111. The control assembly is provided with an illumination component 112 for supplementing light to the camera assembly 100. A clearance 113 is provided between the L-shaped snap-fit ​​plate 109 and the second mounting plate 115 to avoid obstructing the illumination component 112. Furthermore, the width of the clearance 113 is determined according to the size of the illumination component 112 and the light projection angle, and the longitudinal extension direction of the clearance is consistent with the installation direction of the illumination component 112.

[0048] Specifically, during assembly, the clearance 113 between the L-shaped snap-fit ​​plate 109 and the second mounting plate 115 forms a continuous light-transmitting channel, through which the light from the illumination component 112 is directly projected onto the shooting area of ​​the camera component 100. When the control circuit board 111 is fixed by the snap-fit ​​slot 110, the installation position of the illumination component 112 is directly below the clearance 113, and its light source central axis coincides with the central axis of the clearance 113. When the camera component 100 performs a shooting action, the control circuit board 111 sends a drive signal to the illumination component 112, and the light passes through the clearance 113 to cover the field of view of the camera component 100, avoiding the loss of light spots due to structural obstruction.

[0049] In this embodiment, the first assembly housing 101 includes a first assembly plate 114 and a second assembly plate 115 disposed opposite to each other. The first assembly plate 114 and the second assembly plate 115 are connected by a connecting plate 116. A first guide groove 117 is provided on one side of the first assembly plate 114, and a second guide groove 118 is provided on the side of the second assembly plate 115 near the first assembly plate 114. The first guide groove 117 and the second guide groove 118 cooperate to form the positioning slide rail 103. Furthermore, the symmetrical distribution of the first guide groove 117 and the second guide groove 118 forms a track constraint structure, and the vertical connection relationship of the connecting plate 116 defines the relative position of the first assembly plate 114 and the second assembly plate 115. The depth of the first guide groove 117 is equal to the depth of the second guide groove 118, and the sum of their widths forms a clearance fit with the thickness of the control circuit board 111. The thickness of the connecting plate 116 and the spacing between the first assembly plate 114 and the second assembly plate 115 form a cavity structure for accommodating the control circuit board 111. In this embodiment, when the first assembly housing 101 and the second assembly housing 104 are connected, the second assembly housing 104 will block the positioning slide rail 103 to prevent the control circuit board 111 from detaching from the positioning slide rail 103.

[0050] Specifically, the first assembly plate 114 and the second assembly plate 115 form a U-shaped frame structure through the connecting plate 116. The first guide groove 117 and the second guide groove 118 extend along the length of the assembly plates, forming a continuous guide channel. The two side edges of the control circuit board 111 are embedded in the tracks formed by the first guide groove 117 and the second guide groove 118, and longitudinal positioning is achieved by the limiting effect of the inner wall of the groove. The connecting plate 116 serves as a lateral support structure to prevent deformation of the first assembly plate 114 and the second assembly plate 115 during assembly. The symmetrical distribution of the first guide groove 117 and the second guide groove 118 ensures that the control circuit board 111 is subjected to uniform force during insertion, avoiding tilting or jamming caused by a single-sided slide rail. The clearance fit of the grooves allows the control circuit board 111 to undergo slight displacement under thermal expansion or vibration conditions, while maintaining the stability of the overall structure.

[0051] In this embodiment, the second assembly housing 104 has two parts, respectively disposed at the top and bottom of the first assembly housing 101. The mounting end 106 includes a first mounting portion 119 and a second mounting portion 120. A first inclined plate 121 is provided on one side of the first mounting portion 119, and a first engaging groove 122 is provided on the first inclined plate 121. A second inclined plate 123 is provided on the side of the second mounting portion 120 near the first mounting portion 119, directly opposite the first inclined plate 121. A second engaging groove 124 adapted to the first engaging groove 122 is provided on the second inclined plate 123. Furthermore, the second assembly housing 104 is divided into two groups, a top group and a bottom group, forming a symmetrical support structure. The first mounting portion 119 and the second mounting portion 120 form an angle through the first inclined plate 121 and the second inclined plate 123, and the mating surfaces of the first engaging groove 122 and the second engaging groove 124 have complementary geometric shapes. Specifically, the camera assembly 100 is clamped between the first engaging slot 122 and the second engaging slot 124, and the inclined surface of the tilting plate guides the assembly to slide in along a predetermined path. When the engaging limiting plate 129 is inserted into the first engaging slot 122, the second tilting plate 123 undergoes elastic deformation to form a positioning structure. The second mounting housing 104 at the top and bottom simultaneously applies a vertical clamping force, so that the center of gravity of the camera assembly 100 is located on the vertical line connecting the two sets of engaging slots.

[0052] In this embodiment, the detachable connection assembly includes a threaded post 125 disposed on the second assembly housing 104, a first connecting through hole 126 disposed on the control circuit board 111, and a second connecting through hole 127 disposed on the first assembly housing 101. The threaded post 125 passes through the first connecting through hole 126, and a bolt passes through the second connecting through hole 127. The control circuit board 111, the first assembly housing 101, and the assembly plate assembly can be connected by the bolt and the threaded post 125. Furthermore, the threaded post 125 and the second assembly housing 104 are fixed by integral molding or welding. The inner diameter of the first connecting through hole 126 is clearance-fitted with the outer diameter of the threaded post 125. The second connecting through hole 127 is disposed on the side wall of the first assembly housing 101, and its axis coincides with the axis of the threaded post 125. Specifically, during the assembly process, the threaded post 125 is inserted through the first connection through hole 126 of the control circuit board 111, and then the bolt is inserted from the second connection through hole 127 of the first assembly housing 101, and engages with the internal thread of the threaded post 125.

[0053] In this embodiment, the second inclined plate 123 is provided with a locking limiting plate 129 that cooperates with the first locking groove 122 and the second locking groove 124 to lock the camera assembly 100. Specifically, when the camera assembly 100 is inserted into the mounting end 106 in the inclined direction, the locking limiting plate 129 generates a restraining force by contacting the side wall of the first locking groove 122, while its bottom surface contacts the bottom of the second locking groove 124 to form a limit.

[0054] In this embodiment, the assembly connector includes a connecting locking plate 130 disposed on one side of the second assembly housing 104. The connecting locking plate 130 has a third connecting through hole 131 penetrating its opposite sides and an oblong hole 132 penetrating its opposite sides. The connecting locking plate 130 is directly fixed to the outer surface of the second assembly housing 104. The third connecting through hole 131 is a circular through hole, and the oblong hole 132 is an elongated through hole extending along its length. The third connecting through hole 131 is used to pass a bolt through to connect with the blackboard. A threaded hole adapted to the third connecting through hole 131 can be drilled on the blackboard. The oblong hole 132 allows the bolt to slide within the elongated hole to adjust the connection position. The connecting locking plate 130 and the second assembly housing 104 are connected by welding or integral molding to ensure structural stability.

[0055] Specifically, the combined design of the third connecting through hole 131 and the oblong hole 132 allows the connecting locking plate 130 to simultaneously meet the dual requirements of fixed connection and position adjustment. When the bolt passes through the third connecting through hole 131 and engages with the external component through the thread, a fixing point is formed; the other bolt can slide inside the oblong hole 132 after passing through it. By adjusting the position of the bolt in the oblong hole 132, the second assembly housing 104 can be finely adjusted laterally or longitudinally relative to the external component.

[0056] In this embodiment, the first and second mounting shells are disposed on the left and / or right sides of the blackboard body 134, and the first and second cameras are tilted toward the center of the blackboard body 134. In this embodiment, the tilt angle of the first and second cameras can be 30°-60°, preferably 45°.

[0057] In this embodiment, a blackboard mounting component is also included. The blackboard mounting component includes a first mounting vertical plate 201. The top and bottom of the first mounting vertical plate 201 are integrally formed with a mounting horizontal plate 202. The mounting horizontal plate 202 extends towards the middle of the blackboard body 134 from the side near the blackboard body 134 to form a mounting eave 203 for connecting with the blackboard body 134. The side of the first mounting vertical plate 201 near the blackboard body 134 is bent to form a second mounting vertical plate 204 for connecting with the blackboard body 134. The mounting eave 203 is provided with a fourth connecting through hole 205 penetrating its opposite sides. The second mounting vertical plate 204 is provided with a fifth connecting through hole 206 penetrating its opposite sides. The mounting horizontal plate 202 is provided with a sixth connecting through hole 208. A mounting bracket 207 is provided on one side of the mounting horizontal plate 202. The mounting bracket 207 is provided with a seventh connecting through hole 209 corresponding to the sixth connecting through hole 208 and an eighth connecting through hole 210 for connecting the mounting bracket 207 to external objects.

[0058] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the substance of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A camera component mounting device, characterized in that, include: The first assembly housing (101) has a receiving groove (102) inside, and positioning slide rails (103) for mounting and positioning the control circuit board (111) are provided on the opposite side walls of the receiving groove (102). The second assembly housing (104) is detachably connected to the top and bottom of the first assembly housing (101) via a detachable connection assembly. The second assembly housing (104) is provided with an installation end (106) for detachably installing the camera assembly (100). A connecting device, the connecting device including an assembly connector disposed on the side of the second assembly housing (104) away from the first assembly housing (101).

2. The camera component mounting device as described in claim 1, characterized in that, The first assembly housing (101) includes a first assembly plate (114) and a second assembly plate (115) disposed opposite to each other. The first assembly plate (114) and the second assembly plate (115) are connected by a connecting plate (116). A first guide groove (117) is provided on one side of the first assembly plate (114), and a second guide groove (118) is provided on the side of the second assembly plate (115) close to the first assembly plate (114). The first guide groove (117) and the second guide groove (118) cooperate to form the positioning slide rail (103). An L-shaped snap-fit ​​plate (109) is provided on the side of the first assembly plate (114) near the second assembly plate (115), and the L-shaped snap-fit ​​plate (109) and one side of the first assembly plate form a snap-fit ​​groove (110).

3. The camera component mounting device as described in claim 2, characterized in that, The camera assembly (100) is electrically connected to the control circuit board (111). The control circuit board (111) is provided with an illumination assembly (112) for supplementing light to the camera assembly (100). A clearance gap (113) is left between the L-shaped snap-fit ​​plate (109) and the second mounting plate (115) to avoid obstructing the illumination assembly (112).

4. The camera component mounting device as described in claim 2, characterized in that, The second assembly housing (104) has two parts, which are respectively disposed at the top and bottom of the first assembly housing (101). The mounting end (106) includes a first mounting part (119) and a second mounting part (120). A first inclined plate (121) is provided on one side of the first mounting part (119), and a first engaging groove (122) is provided on the first inclined plate (121). A second inclined plate (123) is provided on the side of the second mounting part (120) close to the first mounting part (119), which is directly opposite to the first inclined plate (121). A second engaging groove (124) that is adapted to the first engaging groove (122) is provided on the second inclined plate (123).

5. The camera component mounting device as described in claim 4, characterized in that, The detachable connection assembly includes a threaded post (125) on the second assembly housing (104), a first connection through hole (126) on the control circuit board (111), and a second connection through hole (127) on the first assembly housing (101). The threaded post (125) passes through the first connection through hole (126), and a bolt passes through the second connection through hole (127). The control circuit board (111), the first assembly housing (101), and the assembly plate assembly can be connected by the bolt and the threaded post (125).

6. The camera component mounting device as described in claim 5, characterized in that, The second inclined plate (123) is provided with a snap-fit ​​limiting plate (129) that cooperates with the first snap-fit ​​groove (122) and the second snap-fit ​​groove (124) to snap-fit ​​the camera assembly (100).

7. The camera component mounting device as described in claim 4, characterized in that, The assembly connector includes a connecting locking plate (130) disposed on one side of the second assembly housing (104). The connecting locking plate (130) is provided with a third connecting through hole (131) penetrating its opposite sides and an oval hole (132) penetrating its opposite sides.

8. A blackboard, comprising the camera component mounting device as described in claim 1, characterized in that, The first assembly shell and the second assembly shell are disposed on the left and / or right side of the blackboard body (134).

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