A duri-halam unmanned aerial vehicle

Abstract

The utility model relates to a kind of jackfruit picking unmanned aerial vehicle, including four-axis eight unmanned aerial vehicle main body propeller outside is equipped with protective net to protect propeller, unmanned aerial vehicle main body side is equipped with mechanical claw and shearing mechanism, mechanical claw is used to grasp jackfruit, shearing mechanism is used to cut jackfruit stem, the mechanical claw includes artificial joint connecting rod mechanism, screw stepper motor and mechanical arm, one end of mechanical arm is installed in the side of fuselage, the other end of mechanical arm installs screw stepper motor, screw stepper motor is connected with artificial joint connecting rod mechanism, screw stepper motor drives artificial joint connecting rod mechanism to retract along vertical direction, unmanned aerial vehicle main body below is equipped with fruit collecting basket for collecting picked jackfruit.The unmanned aerial vehicle is also equipped with flight control system and machine vision, can accurately position jackfruit and efficiently pick, reduce artificial cost and risk, improve picking efficiency and fruit quality, suitable for orchard automated picking operation.

Description

Technical Field

[0001] This utility model relates to the field of agricultural harvesting drone technology, and in particular to a special drone for durian harvesting. Background Technology

[0002] Traditional durian harvesting relies primarily on manual labor. Since durians typically grow on tall, leafy tropical trees, manual harvesting is not only inefficient but also carries numerous risks, such as falls from heights and scratches from branches. Furthermore, manual harvesting is costly. While existing harvesting equipment has improved, it still has significant limitations. As a highly valuable tropical fruit, durian harvesting has long been heavily reliant on manual labor. Durian trees are generally tall (reaching 15-25 meters), with dense and complex canopies, and the fruit often grows at the tips of branches high above the ground. Traditional manual harvesting methods rely on experienced harvesters climbing trees or using simple ladders for high-altitude work. This method has significant drawbacks:

[0003] 1. High risk: Climbing and operating at heights can easily lead to falls. Workers are also prone to being pricked by the hard, sharp thorns of durians or scratched by rough branches, making it difficult to guarantee work safety.

[0004] 2. Low efficiency: Manual climbing, positioning, and manual pruning are time-consuming and labor-intensive, and the number of fruits that a single worker can pick per day is limited, making it difficult to meet the centralized harvesting needs of large-scale orchards.

[0005] 3. High costs: Skilled picking workers are scarce, labor costs continue to rise, and additional expenses due to safety protection investments and potential work injury risks keep picking costs high.

[0006] 4. Risk of fruit damage: During manual harvesting, accidental fruit falling or improper handling may cause the durian shell to crack or the internal flesh to be damaged, seriously affecting its commercial value and shelf life.

[0007] To overcome the limitations of manual harvesting, research and application of automated harvesting equipment have gradually emerged. In recent years, drone-based intelligent harvesting technology has shown potential in some fruits (such as citrus and apples), with the advantage of quickly reaching high-altitude work sites and reducing the risks of manual climbing. However, existing publicly available harvesting drone technologies have revealed significant limitations and inadequacies when applied to durian harvesting:

[0008] 1. Center of gravity stability issues: For example, in a digitally based intelligent fruit-harvesting drone (CN115735561B), the design uses a suspended fruit collection basket. Durian fruits are large and heavy (typically 2-5 kg ​​per fruit) and irregularly shaped. When one or more durians are placed in the collection basket, the weight distribution is easily shifted, causing the drone's center of gravity to become unbalanced, generating a significant tilting moment, which seriously affects flight stability and safety, and may even lead to a crash.

[0009] 2. End effector (cutting mechanism) is unsuitable: The stem of a durian is exceptionally thick and tough (typically 5-10 mm in diameter), far exceeding that of ordinary fruits. The ordinary shearing mechanism equipped with the robotic arm in the digitally-based intelligent fruit-harvesting drone (CN115735561B) lacks sufficient cutting force and structural strength, making it unable to effectively and quickly cut such a thick and tough stem in one go. Forced operation may damage the robotic arm or only cause partial damage to the stem. Similarly, the fixed blade structure used in the smart orchard-based harvesting drone (CN221127995U) is not designed for thick and tough stems, lacking sufficient shearing force output and adaptability, making it completely incapable of cutting durian stems.

[0010] 3. Design flaws in the harvesting system: The opening of the harvesting basket equipped with the smart orchard-based harvesting drone is relatively small. Durian fruits are large and covered with hard, sharp spikes, making it extremely difficult to accurately place them into a narrow-opening basket. During operation, the fruit is prone to hitting the edge of the basket and bouncing off, or the spikes may get stuck at the opening, preventing smooth entry. This significantly reduces the success rate and efficiency of harvesting and increases the risk of fruit damage from impact.

[0011] In summary, traditional manual durian harvesting methods suffer from inherent drawbacks such as low efficiency, high risk, and high cost. While existing intelligent harvesting drone technology is conceptually advanced, its specific design has not yet effectively solved the harvesting challenges of this unique crop. Therefore, there is an urgent need to develop a specialized drone harvesting device designed specifically for the physical characteristics and growing environment of durian. This device must possess high stability and load-bearing capacity to cope with center of gravity shifts, a powerful and reliable cutting mechanism to efficiently sever the thick, hard fruit stems, and a dedicated, non-destructive storage system suitable for large-volume, spiky fruits. Ultimately, this will achieve efficient, safe, and low-cost durian harvesting to meet the growing demands of the durian industry for large-scale and modern production. Utility Model Content

[0012] The present invention aims to provide a durian-picking drone to solve the problems of low efficiency and high risk of manual durian picking in the prior art, as well as the limitations of existing mechanical picking equipment.

[0013] This utility model is achieved through at least one of the following technical solutions.

[0014] A durian-picking drone includes a drone body, a mechanical claw, a shearing mechanism, and a fruit collection basket. The drone body includes a fuselage and multiple shafts mounted on the fuselage. Each shaft is equipped with a propeller. A protective net is provided on the outside of the propeller to protect it.

[0015] The machine is equipped with mechanical claws and a cutting mechanism on both sides of the body. The mechanical claws are used to grab the durian, and the cutting mechanism is used to cut off the durian stem.

[0016] A fruit collection basket is located at the bottom of the machine to hold the harvested durians.

[0017] Furthermore, the mechanical gripper includes a simulated joint linkage mechanism, a lead screw stepper motor, and a first mechanical arm. One end of the first mechanical arm is mounted on the side of the machine body, and the other end of the first mechanical arm is mounted with a lead screw stepper motor. The lead screw stepper motor is connected to the simulated joint linkage mechanism, and the lead screw stepper motor drives the simulated joint linkage mechanism to extend and retract in the vertical direction.

[0018] Furthermore, a shock-absorbing spring is provided at one end of the lead screw stepper motor, and the other end of the shock-absorbing spring is connected to the rotary joint of the simulated joint linkage mechanism.

[0019] Furthermore, the simulated joint linkage mechanism includes a rotary joint, a fixed base, and multiple multi-stage hinged links; the multiple multi-stage hinged links are respectively mounted on the fixed base and the rotary joint.

[0020] Furthermore, each multi-stage hinged connecting rod includes a crank, a first-stage hook pawl connecting rod, a second-stage hook pawl connecting rod, and a hook pawl; the upper end of the crank is hinged to the lower end of the fixed base; the lower end of the crank and the upper end of the first-stage hook pawl connecting rod are both hinged to the upper end of the rotary joint; the lower end of the first-stage hook pawl connecting rod is hinged to the upper end of the hook pawl; the upper end of the second-stage hook pawl connecting rod is hinged to the lower end of the rotary joint; and the lower end of the second-stage hook pawl connecting rod is hinged to the hook pawl.

[0021] Furthermore, the upper end face of the rotary joint is connected to the end face of the lead screw stepper motor via a connecting post to support the rotary joint.

[0022] The shock-absorbing spring has fixing blocks at both ends. The end of the lead screw of the lead screw stepper motor is connected to the fixing block at one end of the shock-absorbing spring, and the fixing block at the other end of the shock-absorbing spring is connected to the fixed base.

[0023] Furthermore, a deep groove ball bearing is built into the fixing block connected to the end of the lead screw of the lead screw stepper motor. The end of the lead screw of the lead screw stepper motor is connected to the bearing and the lead screw and the bearing are fixed together by a retaining ring.

[0024] Furthermore, the shearing mechanism includes a shearing blade, a crank-connecting rod mechanism, a high-frequency drive motor, and a second robotic arm. One end of the second robotic arm is mounted on the side of the machine body opposite to the first robotic arm, and the other end of the second robotic arm is mounted on the fixed seat of the crank-connecting rod mechanism.

[0025] The crank-connecting rod mechanism includes a fixed base, a crank disc, and a connecting rod. The crank disc is connected to a high-frequency drive motor, which drives the crank disc to rotate. The crank disc and the connecting rod are hinged, and the connecting rod drives the slider to reciprocate. One end of the slider is hinged to the connecting rod, and the other end of the slider is hinged to the connection point of the two blades of the shearing blade. The roots of the two blade handles of the shearing blade are connected to pins, which are limited by a limiting guide groove. The limiting guide groove is fixed to the fixed base by a short connecting post. The slider pushes the two blades of the shearing blade to reciprocate under the limitation of the limiting guide groove through the connection point of the blades, thus performing the shearing action. The cutting edge of the shearing blade is serrated.

[0026] Furthermore, the fruit collection basket is an open metal basket, and the open metal basket is equipped with an elastic buffer layer silicone pad.

[0027] Compared with existing technologies, the beneficial effects of this utility model are as follows:

[0028] 1. This utility model uses a mechanical claw and a shearing mechanism to fix and cut the durian, minimizing damage to the durian, protecting the fruit, and ensuring fruit quality.

[0029] 2. The quadcopter and eight-propeller design and protective net of this utility model enhance the stability and safety of the drone, making it suitable for complex orchard environments.

[0030] 3. The fruit collection basket of this utility model is fixed under the machine body, and the center of gravity is stable. Attached Figure Description

[0031] Figure 1 This is a front view of the overall structure of the durian-picking drone in the example embodiment;

[0032] Figure 2 This is a top view of the overall structure of the durian-picking drone in the example embodiment;

[0033] Figure 3 This is a schematic diagram of the mechanical claw structure in an embodiment;

[0034] Figure 4 This is a schematic diagram of a multi-stage hinged linkage structure for an embodiment.

[0035] Figure 5 This is a top view of the shearing mechanism in the embodiment;

[0036] Figure 6 Side view of the shearing mechanism in the embodiment;

[0037] Figure 7This is a schematic diagram of the propeller and protective cover in an embodiment;

[0038] In the diagram, the markings are as follows: 100 - UAV body, 110 - Flight control system, 120 - Propeller, 121 - Protective net, 130 - Fuselage, 140 - Machine vision, 150 - Arm, 200 - Mechanical gripper, 210 - Articulated linkage mechanism, 211 - Multi-stage articulated link, 2111 - Crank, 2112 - First-stage hook link, 2113 - Second-stage hook link, 2114 - Hook, 212 - Fixed base, 213 - Rotary joint, 214 - Connection. Column, 220-Shock-absorbing spring, 230-Screw stepper motor, 240-First robotic arm, 300-Shearing mechanism, 310-Shearing blade, 311-Blade connection, 320-Crank connecting rod mechanism, 321-Crank disc, 322-Connecting rod, 330-High-frequency drive motor, 340-Second robotic arm, 350-Fixed seat, 360-Limiting guide groove, 361-Short connecting column, 370-Pin, 380-Slider, 400-Fruit collection basket. Detailed Implementation

[0039] The present invention will now be described in detail with reference to the accompanying drawings.

[0040] The present invention and its embodiments are described below. This description is not restrictive, and the actual embodiments are not limited thereto. In short, if those skilled in the art are inspired by this description and design similar structures and embodiments without departing from the inventive spirit of the present invention, such designs should fall within the protection scope of the present invention.

[0041] Example 1

[0042] like Figures 1-7 As shown, this embodiment provides a drone specifically for durian harvesting, including: drone body 100, mechanical claw 200, shearing mechanism 300, and fruit collection basket 400.

[0043] The main body 100 of the drone includes a flight control system 110, a propeller 120, a fuselage 130, and a machine vision system 140.

[0044] like Figures 1-2 As shown, the main body of the drone 100 adopts a quadcopter-eight-propeller structure, that is, it has four shafts 150 and eight propellers 120. This structure is commonly used in civilian drones (such as the DJI T40 agricultural drone), and will not be described in detail here. Figure 7 As shown, a protective net 121 is installed on the outside of the two parallel propellers 120.

[0045] The flight control system 110 is used to control the movements of the mechanical gripper 200, the shearing mechanism 300, and the flight attitude of the UAV. Both the flight control system 110 and the machine vision 140 are based on existing mature technologies (such as PX4 / YOLOv8 / SLAM, etc.). This solution has been successfully applied in the field of agricultural automation (such as the DJI T40 UAV), and its technical feasibility is clear. The integration of the flight control system and the machine vision ensures the shearing accuracy and reliability.

[0046] The machine body 130 is equipped with a mechanical claw 200 and a shearing mechanism 300 on both sides, respectively. The mechanical claw 200 is used to grasp and fix the durian, and the shearing mechanism 300 is used to cut the durian stem. The shearing mechanism 300 works in cooperation with the mechanical claw 200. After the mechanical claw 200 grasps the durian stem, it is within the shearing range of the shearing mechanism 300, ensuring that the shearing mechanism 300 can accurately cut the stem.

[0047] The mechanical gripper 200 includes a simulated joint linkage mechanism 210, a shock-absorbing spring 220, a lead screw stepper motor 230, and a first mechanical arm 240. The first mechanical arm 240 is mounted on the side of the body 130, and the lead screw stepper motor 230 is mounted at the end of the first mechanical arm 240. The simulated joint linkage mechanism 210 includes multiple multi-stage hinged links 211, a fixed base 212, and a rotary joint 213. Each multi-stage hinged link 211 includes a crank 2111, a first-stage hook link 2112, a second-stage hook link 2113, and a hook 2114. The upper end of the crank 2111 is hinged to the lower end of the fixed base 212; the lower end of the crank 2111 and the upper end of the first-stage hook link 2112 are both hinged to the upper end of the rotary joint 213; the lower end of the first-stage hook link 2112 is hinged to the upper end of the hook 2114. The upper end of the secondary hook link 2113 is hinged to the lower end of the rotary joint 213; the lower end of the secondary hook link 2113 is hinged to the lower end of the hook 2114. These components combine to form a multi-stage hinged link 211, as shown below. Figure 4 As shown.

[0048] The upper end face of the rotary joint 213 is connected to the end face of the lead screw stepper motor 230 via a connecting post 214 to support the rotary joint 213.

[0049] Both ends of the shock-absorbing spring 220 are equipped with fixing blocks. The end of the lead screw of the lead screw stepper motor 230 is connected to the fixing block at one end of the shock-absorbing spring 220. A deep groove ball bearing is built into the fixing block at the end of the shock-absorbing spring. The end of the lead screw is connected to the bearing and fixed to the bearing with a retaining ring. The fixing block at the other end of the shock-absorbing spring 220 is welded to the upper end of the fixed base 212. When the lead screw stepper motor 230 moves vertically, due to the action of the deep groove ball bearing, the shock-absorbing spring 220 only moves vertically. The vertical movement of the shock-absorbing spring 220 will cause the fixed base 212 to move vertically as well. The vertical movement of the fixed base 212 will drive the lower crank 2111 to rotate, causing the first-stage hook connecting rod 2112, the rotary joint 213, and the second-stage hook connecting rod 2113 to swing, thereby causing the hook 2114 to perform a grasping action.

[0050] like Figure 5 , Figure 6 As shown, the shearing mechanism 300 includes a shearing blade 310, a crank-connecting rod mechanism 320, a high-frequency drive motor 330, and a second robotic arm 340. One end of the second robotic arm 340 is mounted on the other side of the machine body 130 (opposite to the first robotic arm 240), and the other end of the second robotic arm 340 is mounted on the fixed seat 350 of the crank-connecting rod mechanism 320. The crank-connecting rod mechanism 320 consists of a crank disc 321 and a connecting rod 322. The center of the crank disc 321 of the crank-connecting rod mechanism 320 is connected to the high-frequency drive motor 330. The high-frequency drive motor 330 drives the crank disc 321 to rotate. The crank disc 321 and the connecting rod 322... 22. The connecting rod 322 drives the slider 380 to reciprocate. One end of the slider 380 is hinged to the connecting rod 322, and the other end is hinged to the connection point 311 of the two blades of the shearing blade 310. The root of the two blade handles of the shearing blade 310 is connected to the corresponding pins 370. The pins 370 are located in the through grooves on the limiting guide groove 360 ​​and are limited by the limiting guide groove 360. The limiting guide groove 360 ​​is fixed to the fixed base 350 by the short connecting post 361. The slider 380 pushes the two blades of the shearing blade 310 to reciprocate under the restriction of the limiting guide groove 360 ​​through the blade connection point 311 to perform the shearing action. The shearing blade edge is serrated.

[0051] The shearing mechanism employs a high-frequency shearing method, enabling rapid and efficient cutting of durian stems. The crank-connecting rod mechanism 320 is a mature existing mechanical structure, widely used in engineering fields to convert rotary motion into linear reciprocating motion, driven by a motor.

[0052] Grasping phase: The mechanical claw 200 extends vertically to both sides of the durian via the lead screw stepper motor 230, the joint-like linkage mechanism 210 covers the surface of the durian like a human hand, and the shock-absorbing spring 220 buffers the impact force of grasping.

[0053] Cutting stage: After the mechanical claw 200 fixes the durian, the fruit stem is automatically positioned between the serrated blades 310 of the cutting mechanism 300; the high-frequency drive motor 330 (frequency 15Hz) drives the crank connecting rod mechanism 320 to realize the reciprocating cutting action, cutting off the thick and hard fruit stem (5-10mm in diameter) in one go.

[0054] The fruit collection basket 400 is an open metal basket, directly fixed to the underside of the drone body 130, used to hold the harvested durians. The robotic gripper 200 places the cut durians into the fruit collection basket 400. The capacity of the fruit collection basket 400 is designed according to the drone's payload capacity. As one embodiment, the capacity of the fruit collection basket 400 is 30L.

[0055] The open metal basket is equipped with an elastic buffer layer of silicone pads to prevent durians from stacking and colliding after falling in; when fully loaded, the flight control system automatically plans the return path.

[0056] Example 2

[0057] Based on Example 1, this example further optimizes the mechanical gripper 200 and the shearing mechanism 300.

[0058] The mechanical claw 200's articulated linkage mechanism 210 is made of high-strength aluminum alloy to reduce weight and increase structural strength. The hook 2114 is covered with a rubber layer to increase friction with the durian's surface and prevent it from slipping during grasping. The shock-absorbing spring 220 is made of high-elasticity stainless steel to improve shock absorption and extend service life.

[0059] The shearing blade 310 of the shearing mechanism 300 is made of high-hardness alloy steel to improve the sharpness and durability of the blade. The high-frequency drive motor 330 is a brushless motor to improve the efficiency and reliability of the motor. The crank-connecting rod mechanism 320 uses precision machining technology to improve the motion accuracy and stability of the mechanism.

[0060] Example 3

[0061] Based on Examples 1 and 2, this example further optimizes the drone body 100 and the fruit collection basket 400.

[0062] The fuselage 130 of the drone body 100 is made of carbon fiber composite material to reduce weight and increase structural strength. The propeller 120 is made of high-strength plastic material to improve the propeller's durability and impact resistance. The protective net 121 is made of stainless steel to improve the net's strength and corrosion resistance.

[0063] The open metal basket of the Fruit Collection Crate 400 is made of high-strength aluminum alloy to reduce weight and increase structural strength. The elastic cushioning layer with silicone pads is made of highly elastic silicone to improve cushioning effect and service life. The capacity of the Fruit Collection Crate 400 is designed according to the payload capacity of the drone, with selectable volumes of 30L, 50L, and 100L.

[0064] The preferred embodiments of this utility model disclosed above are merely illustrative of the present utility model. These preferred embodiments do not exhaustively describe all details, nor do they limit the utility model to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of this utility model, enabling those skilled in the art to better understand and utilize it.

Claims

1. A durian-picking drone, comprising a drone body (100), a mechanical claw (200), a shearing mechanism (300), and a fruit collection basket (400), characterized in that: The main body (100) of the drone includes a fuselage (130) and multiple shafts (150) mounted on the fuselage (130). Each shaft (150) is equipped with a propeller (120). A protective net (121) is provided on the outside of the propeller (120) to protect the propeller (120). Mechanical claws (200) and shearing mechanisms (300) are respectively provided on both sides of the body (130). The mechanical claws (200) are used to grab the durian, and the shearing mechanisms (300) are used to cut the durian stem. A fruit collection basket (400) is provided below the body (130) for holding the harvested durians.

2. The durian-picking drone according to claim 1, characterized in that: The mechanical claw (200) includes a joint-like linkage mechanism (210), a lead screw stepper motor (230), and a first mechanical arm (240). One end of the first mechanical arm (240) is mounted on the side of the body (130), and the other end of the first mechanical arm (240) is mounted with a lead screw stepper motor (230). The lead screw stepper motor (230) is connected to the joint-like linkage mechanism (210), and the lead screw stepper motor (230) drives the joint-like linkage mechanism (210) to extend and retract in the vertical direction.

3. The durian-picking drone according to claim 2, characterized in that: One end of the lead screw stepper motor (230) is equipped with a shock-absorbing spring (220), and the other end of the shock-absorbing spring (220) is connected to the fixed base (212) of the simulated joint linkage mechanism (210).

4. The durian-picking drone according to claim 3, characterized in that: The simulated joint linkage mechanism (210) includes a rotary joint (213), a fixed base (212), and multiple multi-stage hinged links (211); the multiple multi-stage hinged links (211) are respectively installed on the fixed base (212) and the rotary joint (213).

5. The durian-picking drone according to claim 4, characterized in that: Each multi-stage hinged connecting link (211) includes a crank (2111), a first-stage hook link (2112), a second-stage hook link (2113), and a hook (2114); the upper end of the crank (2111) is hinged to the lower end of the fixed base (212); the lower end of the crank (2111) and the upper end of the first-stage hook link (2112) are both hinged to the upper end of the rotary joint (213); the lower end of the first-stage hook link (2112) is hinged to the upper end of the hook (2114); the upper end of the second-stage hook link (2113) is hinged to the lower end of the rotary joint (213); and the lower end of the second-stage hook link (2113) is hinged to the hook (2114).

6. The durian-picking drone according to claim 4, characterized in that: The upper end face of the rotary joint (213) is connected to the end face of the lead screw stepper motor (230) through the connecting column (214) to support the rotary joint (213).

7. The durian-picking drone according to claim 4, characterized in that: The shock-absorbing spring (220) has fixed blocks at both ends. The end of the lead screw of the lead screw stepper motor (230) is connected to the fixed block at one end of the shock-absorbing spring (220), and the fixed block at the other end of the shock-absorbing spring (220) is connected to the fixed base (212).

8. The durian-picking drone according to claim 7, characterized in that: A deep groove ball bearing is built into the fixing block connected to the end of the lead screw of the lead screw stepper motor (230). The end of the lead screw of the lead screw stepper motor (230) is connected to the bearing and the lead screw and the bearing are fixed together by a retaining ring.

9. The durian-picking drone according to claim 1, characterized in that: The shearing mechanism (300) includes a shearing blade (310), a crank-connecting rod mechanism (320), a high-frequency drive motor (330), and a second robotic arm (340). One end of the second robotic arm (340) is mounted on the side of the body (130) opposite to the first robotic arm (240), and the other end of the second robotic arm (340) is mounted on the fixed seat (350) of the crank-connecting rod mechanism (320). The crank-connecting rod mechanism (320) includes a fixed base (350), a crank disc (321), and a connecting rod (322). The crank disc (321) is connected to a high-frequency drive motor (330), which drives the crank disc (321) to rotate. The crank disc (321) and the connecting rod (322) are hinged, and the connecting rod (322) drives the slider (380) to reciprocate. One end of the slider (380) is hinged to the connecting rod (322), and the other end of the slider (380) is hinged to the shear blade. 310) The two blades are hinged at the joint (311). The root of the two blade handles of the shearing blade (310) is connected to the pin (370). The pin (370) is limited by the limiting guide groove (360). The limiting guide groove (360) is fixed on the fixed base (350) by the short connecting post (361). The slider (380) pushes the two blades of the shearing blade (310) to reciprocate under the limitation of the limiting guide groove (360) through the joint (311) of the blades to perform the shearing action. The shearing blade edge is serrated.

10. The durian-picking drone according to claim 1, characterized in that: The fruit collection basket (400) is an open metal basket with an elastic buffer layer silicone pad inside.

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