Helicopter fuel tank strap elastic force setting device

Abstract

The present application belongs to the field of helicopters, and is a kind of elastic force guaranteeing clamping force, specifically a kind of elastic force guaranteeing device for a helicopter fuel tank binding belt. It is composed of the following components: an adjusting knob, a screw, an upper support, a sliding block, a spring, a force measuring scale, a lower support and a fixing bolt. The current tension of the binding belt can be read very intuitively without any equipment or indirect measurement; the tension can be adjusted very quickly without special equipment, tooling and tools; the binding belt can be continuously guaranteed to have qualified tension within a certain range; for some components that may slightly deform during work (such as fuel tanks, cooling water tanks and other liquid-containing structures that are prone to deformation), effective tension can be provided for a long time, so that the tension is not too large or fails due to structural deformation; the structure is simple, the cost is low, and the failure rate is low; all parts are made of lightweight, corrosion-resistant materials, and can realize all-weather effective tensioning with Kevlar binding belts.

Description

Technical Field

[0001] This invention belongs to the field of helicopters and is a device that uses elasticity to ensure clamping force, has the ability to intuitively judge whether the clamping force is qualified and can quickly adjust the clamping force. Specifically, it is a helicopter fuel tank strap elastic force holding device. Background Technology

[0002] Light helicopters typically use rigid-shell fuel tanks (made of metal or composite materials), secured to the fuselage structure with loop straps for easy disassembly and maintenance. Taking the AC311A as an example, its main fuel tank is made of fiberglass, has a volume of 830L, and is manufactured using a composite unibody molding process. The fuel tank is secured to the bottom two crossbeams of the helicopter's central bulkhead by two straps. The straps are made of Kevlar braided straps (a material characterized by high strength, fatigue resistance, and no elasticity). Each strap wraps around the fuel tank, with the connection point located on the left side of the fuselage. It is secured and tensioned using a combination of positive and negative threaded fasteners, implemented as follows: each end of the strap is secured with a threaded fixing block, and the middle is connected using a hexagonal stud with both positive and negative threads. During installation, a wrench is used to rotate the double-ended stud clockwise or counterclockwise, adjusting the thread tension to control the fuel tank's clamping force. The tightening torque of the bolts is converted into the tension of the straps for clamping force control.

[0003] The technical challenges faced are:

[0004] 1. The bolt tightening force is not directly proportional to the strap tension. The tightening force is greatly affected by factors such as thread manufacturing errors, the presence or absence of lubricating oil between the threads, and even the coefficient of thermal expansion caused by temperature. This can lead to insufficient or excessive clamping force, which can damage the fuel tank. In some aircraft, the threads are even tightened to their limit, and the fuel tank is significantly deformed, but the required tightening torque is still not met. As a result, the tightening torque parameter cannot accurately reflect the actual tension of the strap, which has a significant impact on flight safety.

[0005] 2. The fuel tank will deform when it is full of fuel or when the temperature rises. After deformation, the diameter of the fuel tank changes, but the straps cannot expand and contract accordingly. This causes the strap tension to change after each flight (switching between empty and full fuel), requiring frequent adjustments. Moreover, the loosening during flight causes the fuel tank to shake, which can easily lead to accidents.

[0006] 3. Adjusting the tightness of the straps requires a special torque wrench to set the force. Torque wrenches are expensive and large in size, making field adjustments inconvenient. In addition, torque wrenches need to be calibrated regularly, which is costly. Summary of the Invention

[0007] A tooling system using a threaded screw structure and spring force has been invented that can directly display whether the current strap tension is qualified without the need for torque control by a torque wrench; and effectively ensures that the strap tension is continuously adjusted as the oil tank deforms within a certain range, avoiding the strap from becoming too loose or too tight.

[0008] Technical solution

[0009] A helicopter fuel tank strap elastic force-holding device, which consists of the following components: adjustment knob 1, lead screw 2, upper support 3, slider 4, spring 5, force measuring scale 6, lower support 7 and fixing bolt 8.

[0010] The top of the lead screw 2 has a crown gear. The two lead screws 2 are respectively inserted into the corresponding bushing holes of the upper support 3. The adjusting knob 1 is inserted into the two coaxial holes of the upper support 3, ensuring that the spur gear of the adjusting knob 1 and the crown gears of the two lead screws 2 are meshed respectively. The inner holes of the two sliders 4 are threaded and screwed into the screws of the two lead screws 2 respectively. The two springs 5 ​​are respectively fixed on the two sliders 4. The other end of the springs 5 ​​is fixed to the lower support 7 by the fixing bolts 8. The force measuring scale 6 is fixed on the lower support 7, and the slider 4 is equipped with a pointer that points to the scale area of ​​the force measuring scale 6.

[0011] The upper support 3 is provided with a long groove, and the slider 4 is provided with a protrusion. The slider 4 is inserted into the long groove to realize the movement of the slider 4 along the screw axis of the lead screw 2 and prevent rotation.

[0012] The upper support 3 and the lower support 7 are provided with mounting positions for straps 9.

[0013] The upper support 3 and the lower support 7 are made of 7075 aluminum alloy.

[0014] A butterfly-shaped handle is provided on one side of adjustment knob 1.

[0015] The spur gear of adjustment knob 1 and the crown gear of lead screw 2 are made of aluminum bronze.

[0016] The upper support 3 is used to install the two coaxial holes of the adjusting knob 1, which are equipped with ball bearings; the upper support 3 is used to install the two bushing holes of the lead screw 2, which are equipped with thrust bearings.

[0017] A flexible steel cable is installed in the middle of spring 5 as a protective rope, and the length of the protective rope is less than the maximum elongation of the spring.

[0018] The maximum and minimum values ​​of the force scale 6 were calibrated and verified using an electronic spring scale.

[0019] Technical effect

[0020] The advantages of this device:

[0021] 1) The tension of the current strap can be read very intuitively, without any equipment or indirect measurement;

[0022] 2) The tension can be adjusted very quickly without the need for special equipment, fixtures, or tools;

[0023] 3) Within a certain range, the straps can continuously maintain qualified tension. For some components that may undergo slight deformation during operation (such as fuel tanks, coolant tanks and other liquid-containing, easily deformable structures), the straps can provide effective tension for a long time, so as not to cause excessive tension or failure due to structural deformation.

[0024] 4) Simple structure, low cost, and low failure rate; all parts are made of lightweight and corrosion-resistant materials, and can achieve effective tension in all weather conditions when used with Kevlar straps.

[0025] The device's gain effect and expanded application effects:

[0026] 1) Replacing the original positive and negative thread locking device can greatly reduce the workload of helicopter ground maintenance personnel. When maintaining the tension of the fuel tank straps, no tools are needed, and the adjustment can be checked and adjusted visually.

[0027] 2) After replacing the original positive and negative thread locking device, there is no need to worry about the oil tank deformation causing the tension to exceed the design requirements during the switching process of the oil tank from no load to full load. It can maintain a stable tension state for a long time without being too loose or too tight.

[0028] 3) This device can be extended to any location where tension needs to be maintained and the device itself is subject to thermal expansion and contraction. For example, when transporting large quantities of elastomers (such as low-density sponges) in automobiles, where tight binding and maintaining a certain degree of elasticity are required, this device can be used for effective fixation. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the fixing of a certain type of engine oil tank;

[0030] Figure 2 Exploded views of the components of the device;

[0031] Figure 3 This is a detailed drawing of the gear and thread assembly of the device. Detailed Implementation

[0032] The present invention will be further described below with reference to embodiments. The following description represents only a portion of the embodiments of the present invention, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0033] The working principle of this device is as follows:

[0034] Rotating the adjustment knob 1 causes the two cylindrical gears on the knob to rotate simultaneously. These gears then drive the crown gears on the two lead screws 2, ensuring that the two lead screws rotate simultaneously in the same direction. The rotation of the lead screws causes the two sliders 4 to move up and down simultaneously, ensuring that the displacement is the same. The guide rails on both sides of the upper support 3 prevent the sliders 4 from rotating. The two springs 5 ​​extend and retract with the up and down movement of the sliders 4.

[0035] The strap 9 encircles the fuel tank, with its two ends passing over the upper support 3 and the lower support 7 respectively. Rotating the adjustment knob 1 changes the distance between the upper and lower supports (3, 7) to adjust the tension of the strap 9, and the elasticity of the spring 5 ensures that the strap is taut. The arrow on the slider 4, together with the force measuring scale 6, can read the current strap tension in real time and make it easy to adjust the tension.

[0036] The device's operating specifications are as follows:

[0037] 1) Calibrate the spring 5: After assembling the elastic constant force device, place the slider 4 in the neutral position of the lead screw 2 to ensure sufficient space for adjustment both above and below;

[0038] 2) Referring to the strap tension standard in the helicopter manual, use an electronic spring scale to tighten the device. After reading the maximum and minimum allowable values ​​of the electronic spring scale, mark the maximum and minimum tension of the strap on the force measuring scale 6.

[0039] 3) Wrap the strap 9 around the fuel tank, with both ends passing over the upper support 3 and the lower support 7 respectively. Then manually tighten the strap 8 to ensure that the arrow of the slider 4 falls within the qualified marking range of the force measuring scale 6, and then fix the strap.

[0040] 4) During routine maintenance, if the arrow of slider 4 is found to be close to or exceeds the qualified limit position of force measuring scale 6, simply rotate the adjustment knob to adjust the distance between the upper and lower supports to easily change the tension of the strap.

[0041] 5) Field verification of this elastic force device is also very simple, requiring only a precise spring scale. If large-scale verification and calibration of this elastic force device is required, counterweights conforming to the maximum and minimum tension force masses can be manufactured according to regulations. Using these counterweights, the device can be calibrated quickly and in large quantities, which is very beneficial for batch production.

[0042] The helicopter fuel tank strap elastic force device consists of the following components: adjustment knob 1, lead screw 2, upper support 3, slider 4, spring 5, force measuring scale 6, lower support 7, and fixing bolt 8.

[0043] The top of the lead screw 2 has a crown gear. The two lead screws 2 are respectively inserted into the corresponding bushing holes of the upper support 3. The adjusting knob 1 is inserted into the two coaxial holes of the upper support 3, ensuring that the spur gear of the adjusting knob 1 and the crown gears of the two lead screws 2 are meshed respectively. The inner holes of the two sliders 4 are threaded and screwed into the screws of the two lead screws 2 respectively. The two springs 5 ​​are respectively fixed on the two sliders 4. The other end of the springs 5 ​​is fixed to the lower support 7 by the fixing bolts 8. The force measuring scale 6 is fixed on the lower support 7, and the slider 4 is equipped with a pointer that points to the scale area of ​​the force measuring scale 6.

[0044] The upper support 3 is provided with a long groove, and the slider 4 is provided with a protrusion. The slider 4 is inserted into the long groove to realize the movement of the slider 4 along the screw axis of the lead screw 2, to prevent rotation, to avoid the spring being subjected to torsional force, and to ensure that the pointer can accurately point to the force measuring scale 6.

[0045] The upper support 3 and the lower support 7 are provided with strap 9 mounting positions, which can make the strap 9 fit better on the upper support 3 and the lower support 7, and avoid the sharp edges causing the strap 9 to be scratched or torn.

[0046] The upper support 3 and the lower support 7 are made of 7075 aluminum alloy, which reduces weight while ensuring strength and corrosion resistance.

[0047] A butterfly handle is provided on one side of adjustment knob 1 for easy and quick adjustment of tension.

[0048] The spur gear of adjustment knob 1 and the crown gear of lead screw 2 are made of aluminum bronze, which improves self-lubrication and rust prevention while ensuring gear strength, and avoids jamming or corrosion during field use.

[0049] The upper support 3 has two coaxial holes for installing the adjustment knob 1, which can be fitted with ball bearings to reduce sliding friction and ensure smooth rotation; the upper support 3 has two bushing holes for installing the lead screw 2, which can be fitted with thrust bearings to reduce sliding friction while ensuring the transmission of axial tension and preventing jamming.

[0050] A flexible steel cable can be installed in the middle of spring 5 as a protective rope. The length of the protective rope is less than the maximum elongation of the spring to avoid the failure of the strap due to spring breakage in extreme situations.

[0051] The maximum and minimum values ​​of the force measuring scale 6 are calibrated and verified using an electronic spring scale. When the pointer of slider 4 falls between the maximum and minimum values ​​of the force measuring scale 6, it indicates that the tension of the strap is qualified.

[0052] The material, tension, and length parameters of spring 5 have been tested to ensure that the diameter change caused by the expansion and contraction of the oil tank during normal use is within the adjustment range of the spring force, and the pointer of slider 4 falls between the maximum and minimum values ​​of the force measuring scale 6, without the need for frequent adjustments.

[0053] When the pointer of slider 4 falls outside the maximum value of the force measuring scale 6, it indicates that the tension of the strap is too high. At this time, the butterfly handle of the adjusting knob 1 needs to be rotated counterclockwise, which will drive the lead screw 2 to rotate. The distance between slider 4 and upper support 3 will increase, the strap will stretch, and the tension will return to the allowable range.

[0054] When the pointer of slider 4 falls outside the minimum value of the force measuring scale 6, it indicates that the tension of the strap is too low. At this time, the butterfly handle of the adjusting knob 1 needs to be rotated clockwise to rotate the lead screw 2. The distance between slider 4 and upper support 3 will decrease, the strap will shorten, and the tension will be restored to the allowable range.

[0055] It will be understood by those skilled in the art that, unless otherwise defined, all terms used herein (including technical and scientific terms) have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. It should also be understood that terms such as those defined in general dictionaries should be understood to have the meaning consistent with their meaning in the context of the prior art, and should not be interpreted in an idealized or overly formal sense unless defined as herein. The specific embodiments described above further illustrate the purpose, technical solutions, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A helicopter fuel tank strap elastic force-holding device, characterized in that, The device consists of the following components: adjustment knob (1), lead screw (2), upper support (3), slider (4), spring (5), force measuring scale (6), lower support (7), and fixing bolt (8); The top of the lead screw (2) is equipped with a crown gear. The two lead screws (2) are respectively inserted into the corresponding bushing holes of the upper support (3). The adjustment knob (1) is inserted into the two coaxial holes of the upper support (3) and ensures that the spur gear of the adjustment knob (1) and the crown gears of the two lead screws (2) mesh respectively. The inner holes of the two sliders (4) are threaded and screwed into the screws of the two lead screws (2) respectively. The two springs (5) are respectively fixed on the two sliders (4). The other end of the spring (5) is fixed on the lower support (7) by the fixing bolt (8). The force measuring scale (6) is fixed on the lower support (7). The slider (4) is equipped with a pointer that points to the scale area of ​​the force measuring scale (6). The upper support (3) is equipped with a long groove. The slider (4) is equipped with a protrusion that is inserted into the long groove to realize the movement of the slider (4) along the screw axis of the lead screw (2) to prevent rotation. A flexible steel cable is set in the middle of the spring (5) as a protective rope. The length of the protective rope is less than the maximum elongation of the spring.

2. The helicopter fuel tank strap elastic force-holding device according to claim 1, characterized in that, The upper support (3) and the lower support (7) are provided with strap (9) mounting positions.

3. The helicopter fuel tank strap elastic force-holding device according to claim 1, characterized in that, The upper support (3) and the lower support (7) are made of 7075 aluminum alloy.

4. The helicopter fuel tank strap elastic force-holding device according to claim 1, characterized in that, A butterfly handle is set on one side of the adjustment knob (1).

5. The helicopter fuel tank strap elastic force-holding device according to claim 1, characterized in that, The spur gear of the adjustment knob (1) and the crown gear of the lead screw (2) are made of aluminum bronze.

6. The helicopter fuel tank strap elastic force-holding device according to claim 1, characterized in that, The upper support (3) is used to install ball bearings in two coaxial holes for the adjustment knob (1); the upper support (3) is used to install thrust bearings in two bushing holes for the lead screw (2).

7. The helicopter fuel tank strap elastic force-holding device according to claim 1, characterized in that, The maximum and minimum values ​​of the force measuring scale (6) are checked and verified by using an electronic spring scale.

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