A thermal expansion and contraction observation device

Abstract

The utility model discloses a thermal expansion and cold shrink observation device belongs to physical experiment teaching aid technical field. The device includes base, support, scissors -shaped articulated fixed arm and movable arm, clamping groove, laser, elastic reset piece and heating device. After 4-7 m projection, total amplification multiple can reach 80-140 times, can convert 0.1-0.3 mm thermal expansion into 8-42 mm light spot displacement. The device integrates "clamping - heating - amplification" in one, and the regular or irregular solid can be "clamping sample - opening laser - heating / cooling - observation light spot" four steps to complete the experiment, phenomenon is intuitive, simple structure, low in cost, especially suitable for primary and secondary school physics teaching and popular science display.

Description

Technical Field

[0001] This utility model relates to the field of physics experimental teaching aids, specifically to a thermal expansion and contraction observation device based on a laser lever, which is mainly used for qualitative exploration of the thermal expansion and contraction phenomena of various solids (including irregular samples) in primary and secondary school physics teaching. Background Technology

[0002] Thermal expansion and contraction of solids is one of the core knowledge points in primary and secondary school physics teaching. Existing classroom demonstrations often use the "copper ball-iron ring" method: after heating the copper ball, try to pass it through an iron ring with an inner diameter slightly smaller than the ball's diameter to prove that the ball expands when heated. This method has the following shortcomings: (1) The operation process is cumbersome, requiring open flame heating and manual judgment of whether it can pass through, making it difficult for students to conduct experiments independently; (2) The sample shape is limited, only suitable for regular objects such as copper balls, and cannot be used to observe irregular solids such as stones and metal blocks with uneven surfaces, making it difficult to fully present the general law of thermal expansion and contraction of solids. CN206379082U (thermal expansion and contraction demonstration device, 2017.08.04) discloses a pointer-type magnification structure, but its magnification is only 5 times, which cannot handle the 0.1 mm level displacement resolution, and the sample shape is specially made and inconvenient to change. Therefore, it is necessary to provide a thermal expansion and contraction observation device with a simple structure, high magnification, and adaptive clamping of irregular solids to meet the needs of intuitiveness and universality in teaching demonstrations. Summary of the Invention

[0003] This invention addresses the shortcomings of existing solid thermal expansion and contraction demonstration devices, such as "complex operation, limited sample shape, and low magnification." It aims to provide a solid thermal expansion and contraction observation device that integrates "clamping-heating-magnification" functions, has high magnification, and allows for unrestricted sample shape, thereby improving the intuitiveness of teaching and the rate of students' independent experiments.

[0004] To achieve the above objectives, this utility model adopts the following technical solution: a thermal expansion and contraction observation device, the core components of which include a base, a bracket, a fixed arm, a movable arm, a laser, a slot, an elastic reset component, a clamp, and a heating device.

[0005] (1) Scissor-shaped structure: Two straight metal bars are hinged to the crossbeam of the support through a pivot pin, forming a scissor-shaped lever with a front section of 72 mm and a rear section of 108 mm. The fixed arm is stationary, while the movable arm can rotate to meet the driving requirements when the volume of the object changes.

[0006] (2) Laser-lever magnification: Two Class 1 or Class 2 lasers with ≤1 mW are inserted into the front slot. The output optical axis is made parallel and perpendicular to the projection surface (wall) by rotating the slot. The initial spot spacing d0 = 25-35 mm; the projection distance (D) is 4-7 m, and the total magnification k = (2 / 3) × (D / d0).

[0007] (3) Adaptive clamping: The rear ends of both arms are equipped with vertical plates of the same material to form a clamping opening with a natural opening of 35-40 mm; a stainless steel tension spring (wire diameter 0.3-0.4 mm) provides a clamping force of 0.5-2 N, which is compatible with irregular samples.

[0008] (4) Dual heat source heating: Place a 150 ml glass-shell alcohol lamp or a 5 W-20 W ceramic infrared heating element directly below the clamp. The outer surface temperature rise is ≤60 K, the heat transfer zone temperature is ≤250 ℃, and the heating area is ≥20 mm×20 mm. Attached Figure Description

[0009] Figure 1 This is a three-dimensional structural diagram of a thermal expansion and contraction observation device.

[0010] Figure 2 This is a schematic diagram of the operation of a thermal expansion and contraction observation device.

[0011] In the diagram: 1-base; 2-bracket; 3-fixed arm; 4-movable arm; 5-shaft pin; 6-elastic reset component; 7-slot; 8-laser; 9-clamp; 10-heating device; 11-projection surface (wall); 12-stone; 13-light spot. Detailed Implementation

[0012] like Figure 1 As shown, a thermal expansion and contraction observation device includes a base 1, a bracket 2, a fixed arm 3, a movable arm 4, a shaft pin 5, an elastic reset component 6, a slot 7, a laser 8, a clamp 9, a heating device 10, and a projection surface (wall) 11. The base 1 has M6 threaded adjustable feet for leveling. A fixed bracket 2 is mounted on the base 1. Fixed arms 3 and movable arms 4 are stainless steel straight bars, hinged to the bracket beam via pins 5, forming a scissor-like lever with a front section of 72 mm and a rear section of 108 mm. Vertical stainless steel plates at the outer edges of the two arms form clamping openings 9, with a natural opening of 35-40 mm. The front ends of both arms are hinged to slots 7, with a center distance d0 = 25-35 mm. Two Class 2 lasers 8, each ≤1 mW, are inserted into the slots, with their output axes parallel and perpendicular to the projection surface (wall) 11. An elastic reset element 6 is a stainless steel tension spring (0.3-0.4 mm wire diameter, 6 mm outer diameter), providing a clamping force of 0.5-2 N. A heating device 10 is installed on the base 1 directly below the clamping openings. This heating device is a 150 ml glass-shell alcohol lamp or a ceramic infrared heating element with a rated power of 5 W-20 W, an outer surface temperature rise ≤60 K, and a heat transfer zone temperature ≤250 K. ℃; the laser spot is projected onto a 4-7 m wall, with a total magnification of k=(2 / 3)×(D / d0)=80-140, causing a 0.1-0.3 mm clamp displacement to produce an 8-42 mm spot displacement on the wall.

[0013] Working principle: Two lasers and a scissor lever form a laser lever. The micro-displacement ΔL of the clamp is amplified by the arm ratio (72 / 108) and the projection distance D, forming a spot displacement ΔS of k=(2 / 3)·(D / d0) times on the projection surface (wall).

[0014] Alternative options and key parameter ranges: 1. Fixed arm 3 and movable arm 4 are 180 mm × 15 mm × 2 mm stainless steel perforated straight bars. Other sizes or materials such as aluminum alloy can be used depending on actual needs. 2. In addition to a 150 ml glass-shell alcohol lamp, heating device 10 can also use an electric heating element or ceramic infrared heater with a rated power of 5 W-20 W. The heating area should cover the clamped sample. 3. Elastic reset element 6 is a stainless steel tension spring. It is recommended to use a stainless steel tension spring with a wire diameter of 0.4 mm and an outer diameter of 6 mm to ensure adaptive clamping force for irregular samples. If the clamping force is too large, a wire diameter of 0.3 mm can be used instead. 4. Laser 8 should be a laser product that meets the requirements of Class 1 or Class 2 in GB 7247.1—2012 "Safety of Laser Products Part 1: Classification and Requirements of Equipment", i.e., a laser with a power ≤1 mW. 5. The recommended projection distance is 4 m-7 m. At this distance, the magnification of the light spot displacement is 80-140, which can cover the observation needs of small displacements of 0.05 mm-1 mm. If you want to obtain a larger magnification, you can increase the projection distance.

[0015] Example 1: Experimental procedure as follows Figure 2 A small stone 12 is clamped at clamp 9, allowing the elastic reset piece 6 to automatically clamp. The laser 8 on the fixed arm 3 and the movable arm 4 is turned on, projecting the light spot onto the projection surface (wall) 11. The slot 7 is adjusted so that the optical axis is parallel and perpendicular to the projection surface (wall) 11. At this time, the room temperature T0 is recorded, and the distance between the two light spots 13 is measured as A. The sample is heated to a stable temperature T1 (≤80 ℃) using a 150 ml glass-shell alcohol lamp 10, and then the alcohol lamp is removed. The distance is B. After natural cooling to room temperature T0, the distance is C. B > A and C < B, indicating that the sample expands first and then contracts. The above heating-cooling cycle is repeated 3 times for the same sample. The distance between the light spots changes monotonically with temperature and can recover after cooling. This phenomenon can eliminate the influence of bracket deformation and laser temperature drift.

[0016] Example 2: Clamping an aluminum strip with dimensions of 50 mm × 10 mm × 2 mm, replacing the 150 ml alcohol lamp with a 20 W ceramic infrared heating element, repeating the steps of Example 1, the measured spot displacement and temperature change showed a linear relationship, confirming that the device is also applicable to metal samples, and also confirming that both heat sources are applicable.

[0017] Beneficial effects

[0018] This invention offers significant advantages: First, the scissor-shaped clamps, combined with elastic reset, allow for the rapid clamping of regular or irregular solids such as metals, stones, glass, and ceramics, overcoming the sample limitations of traditional "copper ball-iron ring" devices. Second, the laser-lever composite amplification structure enables a total magnification of 80-140 times, and 0.1-0.3 mm thermal expansion can be converted into 8-42 mm spot displacement, allowing for direct observation without auxiliary tools. Third, the experiment requires only four steps: "clamping the sample - turning on the laser - heating / cooling - observing the spot," which can be operated by a single person, reducing the difficulty of independent experiments. Fourth, the dual heat source design balances the low cost of alcohol lamps with the constant temperature stability of ceramic infrared heating elements. Furthermore, the device is simple in structure, low in cost, and easy to maintain, making it suitable for primary and secondary school teaching and science popularization demonstrations. Its overall performance is superior to traditional pointer-type devices or "copper ball-iron ring" devices.

[0019] The above embodiments are only used to illustrate the technical solution of this utility model, and are not intended to limit it; those skilled in the art should understand that any modifications, equivalent substitutions, improvements, etc. in form or detail to the technical solution should be included within the protection scope of the claims of this utility model.

Claims

1. A device for observing thermal expansion and contraction, characterized in that, include: The base and the bracket fixed on it; A scissor-shaped lever mechanism hinged to a support beam, the lever mechanism including a fixed arm and a movable arm hinged by a pivot pin, the hinge point dividing the arm into a front section of 72 mm and a rear section of 108 mm, the rear section forming a clamping opening for holding the sample. The slots, which are hinged to the front ends of the two arms respectively, are used to fix the laser. The center distance (d0) between the two slots is 25-35 mm. The tension spring connecting the front of the two arms acts as an elastic reset element, providing a clamping force of 0.5-2 N. A heating device located below the clamp, wherein the heating device is an alcohol lamp or a ceramic infrared heating element, and the center of the heating area is aligned with the center of the clamp; The parallel beam emitted by the laser is projected onto the remote projection surface, and the thermal expansion and contraction displacement of the sample is magnified by the lever ratio and projection distance (D). The total magnification is k = (72 / 108) × (D / d0) = (2 / 3) × (D / d0).

2. The apparatus according to claim 1, characterized in that, The projection distance D = 5 m, the center distance of the card slot d0 = 30 mm, and the total magnification k ≈ 111.

3. The apparatus according to claim 1, characterized in that, The tension spring keeps the clamp open by 35-40mm in its natural state, which can accommodate samples with a thickness of ≤30mm.

4. The apparatus according to claim 1, characterized in that, The fixed arm and movable arm are made of 304 stainless steel or 6061 aluminum alloy, and their average coefficient of linear expansion in the range of 0-250℃ does not exceed 23.6×10⁻ 6 / ℃.

5. The apparatus according to claim 1, characterized in that, The surface temperature of the ceramic infrared heating element is ≤250 ℃, and the heating rate is ≤2 ℃ / s under natural convection environment at 25 ℃.

6. The apparatus according to claim 1, characterized in that, The base is equipped with M6 threaded adjustable feet, which can be adjusted to a height of ±5 mm for leveling.

7. The apparatus according to claim 1, characterized in that, The laser is a Class 1 or Class 2 laser with a power of ≤1 mW, an initial spot spacing equal to d0, and a perpendicularity deviation between the output axis and the projection plane of ≤±2°.

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