A telescopic multifunctional teaching aid

Abstract

The invention discloses a telescopic multifunctional teaching aid, comprising a main support shaft, a main ruler, a middle ruler, an inner ruler and a secondary ruler, one end of the main ruler and the secondary ruler are rotatably arranged on the main support shaft respectively, and a dividing circle scale line is arranged on the top of the secondary ruler around the main support shaft; the middle ruler is telescopically arranged in the main ruler, and the inner ruler is telescopically arranged in the middle ruler; the rear surfaces of the main ruler, the middle ruler and the inner ruler are continuously provided with a chalk clip sliding groove, and a chalk clip is slidably arranged in the chalk clip sliding groove. The invention has a simple and compact structure, avoids teachers carrying multiple teaching tools, reduces the time for teachers to frequently change tools when drawing on the blackboard, and alleviates the difficulty of teachers carrying teaching tools to class. At the same time, the telescopic ruler facilitates carrying and also ensures the basic requirements of drawing size during teaching.

Description

Technical Field

[0001] The invention relates to the technical field of teaching tools, and in particular to a telescopic multifunctional teaching aid. Background Art

[0002] Most of the blackboard drawing tools used in the current teaching process are separate compasses, rulers, protractors, etc. These drawing tools have defects such as being too large in size and too many types. They are not convenient for teachers to carry with them, and they take up a lot of space and are not convenient to store. When teaching drawing, teachers need to frequently replace compasses, rulers, protractors, etc., which is inconvenient to operate and reduces the teaching speed.

[0003] There are also multifunctional teaching rulers in the prior art, but these teaching rulers are either too complicated and difficult to manufacture; or they have many functions but are large in size, which is inconvenient for teachers to carry into various classrooms; or they are very small in size and do not meet the needs of daily teaching and drawing. Therefore, it is urgent to develop a multifunctional teaching aid that is convenient for teachers to use in the classroom. Summary of the invention

[0004] The object of the present invention is to provide a telescopic multifunctional teaching aid, aiming to solve the problems in the prior art raised by the above background technology.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A telescopic multifunctional teaching aid, comprising a main support shaft, a main ruler, a middle ruler, an inner ruler and a secondary ruler, one end of the main ruler and the secondary ruler are respectively rotatably arranged on the main support shaft, the top of the secondary ruler is provided with a dividing circle scale line around the main support shaft, one side of the main ruler, the middle ruler and the inner ruler is provided with a continuous scale, the side provided with the scale is defined as the rear side, and the side where the main support shaft is located is the left side;

[0007] The middle ruler is telescopically arranged in the main ruler, and a mounting angle cover is provided at the front upper right corner of the open end of the main ruler; a chamfered surface β is provided on the front upper side of the middle ruler along the length direction, and an inclined surface α is continued obliquely upward at one end of the β surface close to the main support shaft; a β' surface matching the β surface is provided on the inner side of the mounting angle cover, and an inclined surface α' surface corresponding to the α surface is continued obliquely upward at one side of the β' surface close to the main support shaft; a connecting rod having a rear side and a bottom surface lower than the middle ruler is formed on the left end of the middle ruler body The connecting section and the middle scale body are provided with a transition slope at the connection point, and the right end surface of the rear side and the bottom side of the main scale matches the transition slope; when the middle scale slides in the main scale, the β surface fits with the β' surface; when the middle scale extends outward, the α surface and the α' surface cooperate to enable the middle scale to move downward and rearward to the right, until the bottom surface and the rear side surface of the middle scale are flush with the bottom surface and the rear side surface of the main scale respectively; the right end of the main scale is provided with a locking screw for locking the relative position of the middle scale and the main scale;

[0008] The inner ruler is telescopically arranged in the middle ruler, and the connection structure between the inner ruler and the middle ruler is the same as the connection structure between the middle ruler and the main ruler;

[0009] Chalk clip sliding grooves are continuously provided on the rear surfaces of the main ruler, the middle ruler and the inner ruler, and a chalk clip is slidably provided in the chalk clip sliding grooves.

[0010] Preferably, a positioning groove is provided at the rear lower corner near the right end of the main ruler, and a positioning protrusion matching the positioning groove is provided at the rear lower corner of the connecting section of the middle ruler; the left sides of the positioning groove and the positioning protrusion are both inclined surfaces; when the middle ruler is in an extended state, the positioning protrusion is embedded in the positioning groove.

[0011] Preferably, the outer contour of the positioning protrusion is flush with the outer contour of the middle ruler.

[0012] Preferably, the outer contour of the mounting angle cover is flush with the outer contour of the main scale, and the rear and lower sides of the mounting angle cover are respectively provided with plug-in plates, and the main scale is correspondingly provided with plug-in slots, so that the plug-in plate of the mounting angle cover can be inserted into the plug-in slot from the right end of the main scale.

[0013] Preferably, a boss is provided at the right end of the upper surface of the main ruler, the boss is provided with a threaded hole running through it from top to bottom, and the locking screw is threadably matched with the threaded hole; a through hole for the locking screw to pass through is provided on the plug-in plate on the rear side of the mounting angle cover.

[0014] Preferably, the upper surface of the middle ruler is provided with locking countersunk holes corresponding to the extended state and the retracted state respectively.

[0015] Preferably, a lifting shaft mounting hole is axially provided in the main support shaft and passes through from top to bottom, and a lifting shaft is arranged in the lifting shaft mounting hole; an internal thread is provided at the relatively upper portion of the lifting shaft mounting hole, and an external thread is provided at the relatively upper portion of the lifting shaft, and the lifting shaft and the lifting shaft mounting hole have a threaded fit at the relatively upper portion and a clearance fit at the relatively lower portion; a magnet frame is provided at the bottom of the lifting shaft, and a first magnet is arranged in the magnet frame.

[0016] Preferably, the free end of the secondary ruler is penetrated by a secondary support shaft which can move up and down, the bottom end of the secondary support shaft is provided with a second magnet, and the top end of the secondary support shaft is provided with a limiting nut; the upper surface of the main ruler is provided with a countersunk hole corresponding to the second magnet, and a third magnet is provided in the countersunk hole.

[0017] Preferably, a strip groove is provided in the middle of the secondary ruler along the length direction; the main ruler is provided with an alignment line, and when the secondary ruler coincides with the main ruler, the 0° scale line of the secondary ruler coincides with the alignment line; and a V-shaped groove is provided at the right end of the inner ruler.

[0018] Preferably, the chalk clip comprises a chalk clip body, a clamping screw and a slider, wherein the slider is fixed on the chalk clip body and matches the sliding groove of the chalk clip; the chalk clip body is a two-ear open clamp structure, wherein the two ears of the chalk clip body are respectively provided with holes, and the clamping screw passes through the holes on the two ears of the chalk frame body for tightening.

[0019] Compared with the prior art, the present invention has the following beneficial effects: the present invention has a simple and compact structure, avoids teachers carrying multiple teaching tools, reduces the time for teachers to frequently change tools when drawing on the blackboard, and alleviates the difficulty of teachers carrying teaching tools to class; at the same time, the ruler is convenient to carry through the extension and retraction of the ruler, and also ensures the basic requirements of drawing size during teaching, and the ruler can ensure that its scale ends are flush after extension and retraction; by setting a support shaft lifting mechanism, the friction between the ruler and the blackboard when drawing a circle is avoided, and the problem of drawing a circle is easily solved; accurate angles can be drawn through the auxiliary ruler; the slidable chalk clip not only changes the posture when drawing a circle on the blackboard in the past, but also saves more effort, and the chalk can be moved left and right on the ruler, and circles of different diameters can be drawn, thereby effectively replacing the previous drawing tools. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the overall structure of the present invention.

[0021] Figure 2 It is an exploded schematic diagram of the present invention.

[0022] Figure 3 It is a detailed schematic diagram of the ends of the main scale and the middle scale in the present invention (forward).

[0023] Figure 4 It is a detailed schematic diagram of the ends of the main scale and the middle scale in the present invention (backward).

[0024] Figure 5 The present invention is to install the corner cover and Figure 2 Schematic diagram of the matching details at B in the middle.

[0025] Figure 6 The present invention Figure 2 Schematic diagram of the matching details at A and B in the middle.

[0026] Figure 7 It is a partial cross-sectional schematic diagram of the main support shaft in the present invention.

[0027] Figure 8 It is a schematic diagram of the development of teaching aids of the present invention.

[0028] Fig. 9 It is a structural schematic diagram of the present invention when drawing an angle.

[0029] In the figure: 1. main ruler; 2. middle ruler; 3. inner ruler; 4. installation angle cover; 5. positioning groove; 6. positioning protrusion; 7. plug-in plate; 8. plug-in groove; 9. boss; 10. locking screw; 11. locking countersunk hole; 12. chalk clip sliding groove; 13. chalk clip; 14. chalk clip body; 15. clamping screw; 16. slider; 17. lifting shaft; 18. magnet frame; 19. first magnet; 20. secondary ruler; 21. main support shaft; 22. secondary support shaft; 23. second magnet; 24. limit nut; 25. countersunk hole; 26. strip groove; 27. alignment line; 28. V-groove. DETAILED DESCRIPTION

[0030] In the description of the present invention, it should be noted that the directions or positional relationships indicated by terms such as “upper”, “lower”, “front”, “backward”, “left” and “right” are based on the directions or positional relationships shown in the accompanying drawings and are only for the convenience of describing the present invention and simplifying the description. They do not indicate or imply that the device or element referred to must have a specific direction, be constructed and operated in a specific direction. Therefore, they cannot be understood as limitations on the present invention.

[0031] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] Reference Figure 1-9 A telescopic multifunctional teaching aid comprises a main support shaft 21, a main ruler 1, a middle ruler 2, an inner ruler 3 and a secondary ruler 20, wherein one end of the main ruler 1 and the secondary ruler 20 are rotatably arranged on the main support shaft 21, the main ruler 1 is at the bottom, and the secondary ruler 20 is at the top. A circle of graduated circle scale lines is arranged around the main support shaft 21 on the top of the secondary ruler 20, and continuous scales are arranged on one side of the upper surface of the main ruler 1, the middle ruler 2, and the inner ruler 3. Figure 2 The direction shown in is used as a reference, and the side with scale is defined as the rear side, and the side where the main support shaft 21 is located is the left side.

[0033] In the above structure, a cavity with an opening at the right end is provided in the main ruler 1 and the middle ruler 2, the middle ruler 2 is telescopically arranged in the main ruler 1, and the inner ruler 3 is telescopically arranged in the middle ruler 2. The overall length of the ruler is extended by the extension of the middle ruler 2 and the inner ruler 3, and the overall size of the teaching aid can be reduced after contraction, which is convenient for carrying and storage. The telescopic mechanism and principle of the inner ruler 3 in the middle ruler 2 in the present invention are consistent with the telescopic mechanism and principle of the middle ruler 2 in the main ruler 1. This embodiment only takes the telescopic mechanism and principle of the middle ruler 2 in the main ruler 1 as an example for explanation.

[0034] In this embodiment, there is a notch at the front upper right corner of the open end of the main ruler 1, and a mounting angle cover 4 is detachably installed at the notch; a chamfered surface β is provided on the front upper side of the middle ruler 2 along the length direction, and the end of the β surface close to the main support shaft 21 is continued obliquely upward with an inclined surface α, and the end away from the main support seat 21 is a limiting surface for limiting the position during contraction; a β' surface matching the β surface is provided on the inner side of the mounting angle cover 4, and a side of the β' surface close to the main support shaft 21 is continued obliquely upward with an inclined surface α' surface corresponding to the α surface; the left end of the body of the middle ruler 2 is formed with a rear side and a bottom surface lower than The connecting section d of the middle ruler 2, the rear side surface and the bottom surface of the connecting section d are connected with the body of the middle ruler 2 with transition slopes δ and ε respectively, the rear right end surface δ' surface and the bottom right end surface ε' surface of the main ruler 1 are also inclined, and match the transition slopes δ and ε respectively; a positioning groove 5 is provided at the rear lower corner near the right end of the main ruler 1, and a positioning protrusion 6 matching the positioning groove 5 is provided at the rear lower corner of the connecting section of the middle ruler 2, the left sides of the positioning protrusion 6 and the positioning groove 5 are both inclined, which are γ and γ' surfaces respectively, and the outer contour of the positioning protrusion 6 is flush with the outer contour of the middle ruler 2.

[0035] In the above structure, the outer contour of the mounting angle cover 4 is flush with the outer contour of the main scale 1, and the rear and lower sides of the mounting angle cover 4 are respectively provided with plug-in plates 7, and the main scale 1 is correspondingly provided with a plug-in slot 8, so that the plug-in plate 7 of the mounting angle cover 4 can be inserted into the plug-in slot 8 from the right end of the main scale 1, and a boss 9 is provided at the right end of the upper surface of the main scale 1, and the boss 9 is provided with a threaded hole penetrating up and down, and a locking screw 10 is matched in the threaded hole; a through hole for the locking screw 10 to pass through is provided on the plug-in plate 8 on the rear side of the mounting angle cover 4, and the inner diameter of the through hole is larger than the outer diameter of the locking screw 10. After the locking screw 10 passes through the threaded hole and the through hole on the plug-in plate on the rear side of the mounting angle cover 4, the position of the middle scale 2 can be fixed; preferably, the upper surface of the middle scale 2 is provided with locking countersunk holes 11 corresponding to the extended state and the retracted state, respectively. When the middle scale 2 is fully extended or fully retracted, the position of the middle scale 2 is fixed by tightening the locking screw 10 to make it rest against the corresponding locking countersunk hole 11.

[0036] When the middle ruler 2 is in the contracted state, the middle ruler 2 is located at the leftmost end of the main ruler 1, and the upper, lower, front and back four surfaces of the middle ruler 2 are in contact with the inner cavity wall of the main ruler 1, and the β surface is in contact with the β' surface; in the process of the middle ruler 2 extending outward, before the α surface contacts the α' surface, the β surface and the β' surface remain in contact; when the α surface and the α' surface just contact, the γ surface and the γ' surface are located on the same plane, but have not begun to contact, similarly, the δ surface and the ε surface are respectively in the same plane with the δ' surface and the ε' surface, but have not begun to contact; continue to pull the middle ruler 2 outward to close the The cooperation between the α surface and the α' surface makes the middle ruler 2 move to the "lower rear right" direction until the bottom surface and the rear side surface of the middle ruler 2 are flush with the bottom surface and the rear side surface of the main ruler 1 respectively. At this time, the positioning protrusion 6 is completely embedded in the positioning groove 5, and the γ surface and the γ' surface are in contact with each other, and the δ surface and the ε surface are in contact with the δ' surface and the ε' surface respectively. The rear side surface and the bottom surface of the connecting section d of the middle ruler 2 are in contact with the rear inner wall and the bottom inner wall of the main ruler 1 respectively; then tighten the locking screw 10 to make it rest against the locking countersunk hole 11 on the middle ruler 2 in the corresponding extended state, and the expansion of the middle ruler 2 is completed.

[0037] When the ruler needs to be retracted, loosen the locking screw 10 and push the middle ruler 2 to the left. By utilizing the relative sliding of the γ surface and the γ' surface, and the relative sliding of the δ surface and the ε surface with the δ' surface and the ε' surface respectively, the middle ruler 2 is pushed to the "upper front left" side. At the same time, the α surface contacts the α' surface and slides relative to each other until the β surface and the β' surface are in contact and fit. At this time, the middle ruler 2 no longer produces longitudinal displacement and can only move to the left. Continue to push the middle ruler 2 to the leftmost end, and then tighten the locking screw 10 so that it rests on the locking countersunk hole 11 on the middle ruler 2 corresponding to the retracted state, and the middle ruler completes the retraction.

[0038] The telescopic structure and principle between the middle ruler 2 and the inner ruler 3 are the same, and will not be repeated in this embodiment.

[0039] In this embodiment, the rear surfaces of the main ruler 1, the middle ruler 2, and the inner ruler 3 are respectively provided with a chalk clip sliding groove 12, and when the ruler is unfolded, the chalk clip sliding grooves 12 on the main ruler 1, the middle ruler 2, and the inner ruler 3 can be connected into a straight line. A chalk clip 13 is arranged in the chalk clip sliding groove 12, and the chalk clip 13 includes a chalk clip body 14, a clamping screw 15, and a slider 16. The slider 16 is fixed on the chalk clip body 14, and the slider is H-shaped and matches the chalk clip sliding groove 12; the chalk clip body 14 is a two-ear open clamp structure, and holes are respectively opened on the two ears of the chalk clip body 14, one of which is a threaded hole and the other is a light hole. The inner diameter of the threaded hole is smaller than the inner diameter of the light hole. The front end of the clamping screw 15 is provided with an external thread matching the threaded hole. The clamping screw 15 passes through the light hole and is connected to the threaded hole, so that the chalk can be clamped in the chalk clip body 14, and the chalk clip 13 as a whole can slide along the chalk clip sliding groove 12.

[0040] In this embodiment, the main support shaft 21 is divided into an external thread section, an optical axis section, and a base from top to bottom. The end of the main ruler 1 is sleeved on the optical axis section and can rotate freely around it; the end of the secondary ruler 20 is threadedly matched with the external thread section; and a cavity is provided at the bottom of the base. The interior of the main support shaft 21 is axially provided with a lifting shaft mounting hole that passes through from top to bottom, and a lifting shaft 17 is provided in the lifting shaft mounting hole; the relative upper part of the lifting shaft mounting hole is provided with an internal thread, and the relative upper part of the lifting shaft 17 is provided with an external thread. The lifting shaft 17 and the relative upper part of the lifting shaft mounting hole are threadedly matched, and the relative lower part is clearance matched; the bottom of the lifting shaft 17 is provided with a magnet frame 18, and the magnet frame 18 is provided with a first magnet 19; the top of the lifting shaft 17 passes through the top of the secondary ruler 20 and is formed with a knob.

[0041] In the above structure, the lifting shaft 17 can be moved up and down by turning the knob through the internal thread of the lifting shaft mounting hole and the external thread of the lifting shaft 17. When the lifting shaft 17 rises to the limit position, the magnet frame 18 and the first magnet 19 are accommodated in the cavity at the bottom of the base of the main support shaft 21, and the bottom surface of the first magnet 19 is flush with the bottom surface of the main ruler 1. When it is necessary to draw a circle, the user holds the main support shaft 21, rotates the lifting shaft 17 to make it descend, and then drives the magnet frame 18 to move downward, and then attracts the blackboard with the first magnet 19 as the center of the circle. At this time, there will be a gap between the bottom surface of the main ruler 1 and the blackboard to avoid friction with the blackboard. After the circle is drawn, the lifting shaft 17 is rotated in the opposite direction to reset it.

[0042] In this embodiment, the auxiliary ruler 20 is used to draw angles. Its free end is penetrated by an auxiliary support shaft 22 that can move up and down. The bottom end of the auxiliary support shaft 22 is provided with a second magnet 23, and the top end is provided with a limit nut 24; the upper surface of the main ruler 1 is provided with a countersunk hole 25 corresponding to the second magnet 23, and preferably, a third magnet is provided in the countersunk hole 25. In addition, a strip groove 26 is provided in the middle of the auxiliary ruler 20 along the length direction, and the strip groove 26 corresponds to the 0° scale line; the main ruler 1 is provided with an alignment line 27, and when the auxiliary ruler 20 coincides with the main ruler 1, the 0° scale line of the auxiliary ruler 20 coincides with the alignment line 27; the right end of the inner ruler 3 is provided with a V-shaped groove 28.

[0043] When drawing an angle, the user first draws a straight line on the blackboard with the main ruler 1, and the main ruler 1 rotates around the main support shaft 21. The user aligns the straight line on the blackboard through the strip groove 26 on the top of the secondary ruler 20, and then stretches the secondary support shaft 22 downward to make the second magnet 23 contact the blackboard. When the main ruler 1 and the secondary ruler 20 form the required angle, use chalk to draw a point at the top of the V-shaped groove 28 on the right end of the inner ruler 3, then pull the secondary support shaft 22 upward, rotate the secondary ruler 20 back to zero position, so that the second magnet 23 at the bottom of the secondary support shaft 22 is embedded in the countersunk hole 25 on the top surface of the main ruler 1, and produces an adsorption effect with the third magnet to prevent it from falling out, and finally use the main ruler 1 to connect the drawn point with one end point of the straight line to form the required angle.

[0044] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with the technology to understand the content of the present invention and implement it accordingly, and they cannot be used to limit the protection scope of the present invention. Any equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A telescopic multifunctional teaching aid, characterized in that: It includes a main support shaft, a main ruler, a middle ruler, an inner ruler and a secondary ruler. One end of the main ruler and the secondary ruler are rotatably arranged on the main support shaft. The top of the secondary ruler is provided with a dividing circle scale line around the main support shaft. One side of the main ruler, the middle ruler and the inner ruler is provided with continuous scales. The side provided with scales is defined as the rear side, and the side where the main support shaft is located is the left side. The middle ruler is telescopically arranged in the main ruler, and a mounting angle cover is provided at the front upper right corner of the open end of the main ruler; a chamfered surface β is provided on the front upper side of the middle ruler along the length direction, and an inclined surface α is continued obliquely upward at one end of the β surface close to the main support shaft; a β' surface matching the β surface is provided on the inner side of the mounting angle cover, and an inclined surface α' surface corresponding to the α surface is continued obliquely upward at one side of the β' surface close to the main support shaft; a connecting rod having a rear side and a bottom surface lower than the middle ruler is formed on the left end of the middle ruler body The connecting section and the middle scale body are provided with a transition slope at the connection point, and the right end surface of the rear side and the bottom side of the main scale matches the transition slope; when the middle scale slides in the main scale, the β surface fits with the β' surface; when the middle scale extends outward, the α surface and the α' surface cooperate to enable the middle scale to move downward and rearward to the right, until the bottom surface and the rear side surface of the middle scale are flush with the bottom surface and the rear side surface of the main scale respectively; the right end of the main scale is provided with a locking screw for locking the relative position of the middle scale and the main scale; The inner ruler is telescopically arranged in the middle ruler, and the connection structure between the inner ruler and the middle ruler is the same as the connection structure between the middle ruler and the main ruler; Chalk clip sliding grooves are continuously formed on the rear surfaces of the main ruler, the middle ruler and the inner ruler, and a chalk clip is slidably arranged in the chalk clip sliding grooves; A positioning groove is provided at the rear lower corner of the main ruler near the right end, and a positioning protrusion matching the positioning groove is provided at the rear lower corner of the connecting section of the middle ruler; the left sides of the positioning groove and the positioning protrusion are both inclined surfaces; when the middle ruler is in an extended state, the positioning protrusion is embedded in the positioning groove; The outer contour of the mounting angle cover is flush with the outer contour of the main ruler, and plug-in plates are respectively provided on the rear side and the lower side of the mounting angle cover, and the main ruler is correspondingly provided with a plug-in slot, so that the plug-in plate of the mounting angle cover can be inserted into the plug-in slot from the right end of the main ruler; A boss is provided at the right end of the upper surface of the main ruler, and a threaded hole is provided on the boss that passes through the boss from top to bottom, and the locking screw is threadably matched with the threaded hole; a through hole is provided on the plug-in plate on the rear side of the mounting angle cover for the locking screw to pass through.

2. A telescopic multifunctional teaching aid according to claim 1, characterized in that: The outer contour of the positioning protrusion is flush with the outer contour of the middle ruler.

3. A telescopic multifunctional teaching aid according to claim 1, characterized in that: The upper surface of the middle ruler is provided with locking countersunk holes corresponding to the extended state and the retracted state respectively.

4. A telescopic multifunctional teaching aid according to claim 1, characterized in that: A lifting shaft mounting hole is axially provided in the main support shaft and passes through from top to bottom, and a lifting shaft is provided in the lifting shaft mounting hole; an internal thread is provided at the relatively upper portion of the lifting shaft mounting hole, and an external thread is provided at the relatively upper portion of the lifting shaft, and the lifting shaft and the lifting shaft mounting hole are threadedly matched at the relatively upper portion and clearance matched at the relatively lower portion; a magnet frame is provided at the bottom of the lifting shaft, and a first magnet is provided in the magnet frame.

5. A telescopic multifunctional teaching aid according to claim 1, characterized in that: The free end of the secondary ruler is penetrated by a secondary support shaft that can move up and down, the bottom end of the secondary support shaft is provided with a second magnet, and the top end of the secondary support shaft is provided with a limiting nut; the upper surface of the main ruler is provided with a countersunk hole corresponding to the second magnet, and a third magnet is provided in the countersunk hole.

6. A telescopic multifunctional teaching aid according to claim 5, characterized in that: A strip groove is provided in the middle of the secondary ruler along the length direction; an alignment line is provided on the main ruler, and when the secondary ruler coincides with the main ruler, the 0° scale line of the secondary ruler coincides with the alignment line; a V-shaped groove is provided at the right end of the inner ruler.

7. A telescopic multifunctional teaching aid according to claim 1, characterized in that: The chalk clip comprises a chalk clip body, a clamping screw and a slider, wherein the slider is fixed on the chalk clip body and matches with the sliding groove of the chalk clip; the chalk clip body is a two-ear open clamp structure, wherein the two ears of the chalk clip body are respectively provided with holes, and the clamping screw passes through the holes on the two ears of the chalk frame body for fastening.

Images