RU2356794C2 - Landing gear (versions) - Google Patents

Abstract

FIELD: aircraft engineering.

SUBSTANCE: invention relates to aircraft engineering, particularly, to aircraft landing gear. The proposed landing gear incorporates mobile supports, hydraulic cylinders connected by a pipeline with a gate or gates. Hydraulic cylinders are filled partially, while the gate or gates are located to separate the hydraulic cylinders at contact with the ground by all landing gear legs or at increase of pressure in hydraulic cylinders.

EFFECT: landing gear for landing on irregular surface.

6 cl, 4 dwg

Description

The invention relates to aviation and is intended for airplanes and especially for airplanes with vertical take-off and helicopters.

Known helicopter chassis, consisting of 3-4 wheels or two longitudinal skis. Their disadvantage is increased requirements for the horizontal and even landing site (see, for example, US Pat. 2030328).

Option 1. The essence of the simplest version of the invention is that the chassis has two or more hydraulic cylinders connected by a pipeline to the valve (s).

The simplest option for a three-wheeled chassis consists of only two hydraulic cylinders and one valve in the pipeline between them and compensates for the unevenness of the landing site only in roll (which is more important than in pitch).

When the ground surface is touched by one stable landing gear, it begins to rise with this force, and fluid flows from it into the second hydraulic cylinder, which begins to lower (if it was originally in the middle position). As soon as a second touch occurs, pressure will begin to increase in the pipeline. If the pressure rises, the valve should be closed or it will close automatically, and the movement of the hydraulic cylinder rods will be blocked. The chassis is ready to handle the full load. The helicopter lands vertically on an uneven surface (figure 2).

The valve can be manual, remote, automatic with an electro- or electro-pneumatic or electro-hydraulic actuator from the readings of an electric contact pressure gauge or pressure switch in the specified pipeline, or from the sum of the readings of the rocking sensors of the earth by all racks with hydraulic cylinders, or automatic direct action (i.e. hydraulic driven by the same pressure).

If the number of racks is 3 or more, a special multi-way valve is required or the number of single-line valves is required, one less than the number of racks (for reliability - equal to the number of racks). For reliability, the single-line valves should be located as close to the hydraulic cylinders as possible.

Hydraulic cylinders with a sufficient diameter can themselves perform the function of landing gears or perform only the function of fixing and damping on the chassis of any kinematic scheme. In the latter case, part of the pipeline must be flexible (hose).

The invention is applicable to a ski chassis. In this case, the ski racks must be movable in the form of a parallelogram with one rocker mount, and the chassis is calculated as a 4-post.

The diameters of the hydraulic cylinders must be proportional to the square root of the load on the rack. If the weight of the piston with the rod and the supporting part of the chassis in kilograms exceeds the piston area in sq. see, that is, it will exceed atmospheric pressure on the piston, both chassis can lower to the lower position with the formation of a vacuum cavity in the hydraulic system. In order to prevent liquid rupture (it is accompanied by a sharp jump in force), a small cavity with nitrogen can be specially left in the upper part of each hydraulic cylinder.

Option 2. To avoid this phenomenon, the rod cavity of the hydraulic cylinder can be sealed and is an oil-pneumatic (hereinafter "pneumatic") cavity of high pressure (compensating for the weight of the moving parts of the chassis). In this case, two sub-options are possible:

a) the cavity is individual for each hydraulic cylinder. When this pneumatic capacity may be a hollow rod of the hydraulic cylinder (lower part of figure 3),

b) the pneumatic cavities of all hydraulic cylinders are connected by a pipeline (to distinguish it from a hydraulic fluid pipeline, we will call it a "non-pipeline"). It is advisable that this system be filled with nitrogen. In this case, the pneumatic cavities can be in the rods of the hydraulic cylinder, or there may be a separate common pneumatic cavity, or both. This solution is preferable, as it equalizes the compensating force in all racks. With different weights of the moving parts of the uprights, the piston rod surface area should be proportional to this weight, that is, having the cylinder diameter specified in the conditions of Option 1, the diameter of the rod is selected.

Option 3. If the chassis is required to absorb shock absorption on the ground (which is more typical for aircraft landing gears), then the hydraulic line of each hydraulic cylinder should have a pneumohydrocavity (not to be confused with the mentioned pneumatic cavity), perceiving the flow of hydraulic fluid under pressure. It is most rational to place it in the same hydraulic cylinder, separating it from the main part of the hydraulic cylinder with an auxiliary piston with a limited stroke (abutting against a partition with an opening). See the top of FIG. 3

In this case, after closing the valve (s), the hydraulic cylinder rod may continue to compress. But if before that it was practically effortless (only the friction forces in the seals - from which, by the way, it follows that they should be minimized), then after closing the valve, the compression will occur with great effort, determined by the nitrogen pressure in the pneumohydrocavity.

A small hole, and possibly a non-return valve (s) in the baffle, will contribute to damping shock and damping the rebound of the chassis.

For helicopters, option 3 is not required.

Option 4. The chassis according to option 2 with a slight improvement can immediately perform 5 additional functions:

a, b) Determination of take-off weight and centering of an airplane or helicopter. For this, the hydraulic line of each hydraulic cylinder must have a pressure gauge or differential pressure gauge (if there is a pneumatic cavity). Comparing the readings of all differential pressure gauges they judge the alignment - it is equal to the calculated one with equal pressures. By the sum of their testimonies, take-off weight is judged, if the readings of the differential pressure gauges are equal, one of them is multiplied by the total difference in the areas of all the pistons and all the rods, to which is added the product of the sum of the readings of the differential pressure gauge and manometer in the air cavities (air cavities) and the total area of all rods. Since this coefficient at a constant pressure in the pneumatic cavity is a common constant coefficient, one of the pressure gauges can have two scales, one of which will be calibrated immediately in units of weight, for example, in tons. Having correctly placed the load and checked the pressure in the pneumatic cavity, one glance at this scale is enough to find out the exact take-off weight.

c) Cleaning the chassis, or at least installing it in the flight position. To do this, it is enough to install a reversible compressor (or a conventional compressor with two three-way cranes) between the common section of the pneumatic line and the pneumatic cavity and equip the chassis hydraulic system with a tank with a valve and level sensors. To facilitate the release of the chassis, the tank should have a blow, in this case, the pressure of the blow should be taken into account by a differential pressure gauge. By opening a multi-line valve or individual valves of the hydraulic cylinders and tank, we communicate their cavities with the tank. Then applying pressure to the rod cavity of the hydraulic cylinders by the compressor, we will force the rods to retract into the hydraulic cylinders. In this case, the chassis will occupy the upper position. Having pumped out part of the nitrogen, we will release the chassis.

If the tank is not pressurized, small springs may be present in the hydraulic cylinders to facilitate the release of the chassis.

d) Moreover, you can release the chassis to the end or partially. To do this, with a certain decrease in the level in the tank, it is turned off by the valve (gas pumping is also turned off), and the further exit of the chassis stops. At the same time, the ability to adapt the chassis to the terrain remains. That is, the chassis acquires the ability to regulate clearance - with a flat landing site, you can sit down, almost touching the ground with the fuselage, which will facilitate landing, disembarkation and loading and unloading. And when landing on a mountainside, you can turn on the maximum clearance.

e) In an emergency landing on autorotation, you can configure the chassis to maximize shock absorption. To do this, it is enough to equip all hydraulic cylinders with safety valves.

Before an emergency landing, pressure is released from the rod cavities (by compressor or emergency valve) and the chassis is maximally discharged. Then the multi-line valve or individual valves of the hydraulic cylinders are closed, disconnecting them from each other. For reliability - and the tank valve. When it hits the ground, the pressure in the hydraulic cylinders immediately rises to the maximum, limited by the safety valve. The valve ejects fluid (into or out of the tank), and the stem enters the cylinder, providing maximum rated resistance.

Such a system is also useful for compensating for a pilot’s error during a “hard landing.”

In the presence of a pneumohydrocavity (aircraft version of the chassis), the shock is first suppressed due to the compression of nitrogen in it. Moreover, the efficiency of shock absorption can be somewhat increased by disconnecting the pneumohydrocavity (if this is provided for by the design).

So, option 4 should additionally have: pressure gauges and differential pressure gauges, pressure gauges in the pneumatic cavity, a reversible compressor in the pneumatic line, a tank with a valve and level sensors, safety valves in the hydraulic cylinders and, optionally, disconnectors of the hydraulic hydraulic cavities, if any (for example, spools in the walls of the hydraulic cylinders) . Considering that pressure gauges and safety valves are parts of minimum weight and cost, and a hydraulic fluid tank is still desirable (to compensate for leaks), an additional detail compared to options 2 and 3 is only a small-capacity reversible compressor. Due to its low power, its weight and cost will also be minimal and will “pay off” with the 5 additional features mentioned.

Figure 1 shows the simplest chassis system, where 1 - hydraulic cylinders, 2 - rods, 3 - pipeline, 4 - valve.

Figure 2 shows a helicopter standing on a hillside, where 5 is a helicopter, 2 are rods or landing gear.

Figure 3 shows in cross section a hydraulic cylinder with a pneumatic cavity 6 and a hydropneumatic cavity 7, where 8 is a piston of a hydraulic cylinder, 9 is an auxiliary piston of a hydropneumatic cavity, 10 is a partition, 11 is a pipeline.

Figure 4 shows the chassis according to option 4, where 12 is a tank, 13 is a tank valve, 14 is a reversible compressor, 15 is a common pneumatic cavity, 16 is an emergency release valve for the chassis. The solid line is the pipeline, the dotted line is the pneumatic pipe.

The chassis of Fig. 1 works like this: when one rod 2 touches the ground (directly or through a rack), the fluid flows through pipeline 3 into another hydraulic cylinder 1, pushing it out. When the second rod touches the ground (Fig. 2), the pressure in the system rises and the valve closes (in Fig. 1, the simplest option is manually). The rods are fixed.

The hydraulic cylinder in FIG. 3 works as follows: the stem is prevented from falling out by pressure in the pneumatic cavity 6 and the hollow stem 2. When touching the ground, it works similarly to FIG. 1. After closing the valve, a possible push from touching the ground is absorbed by the air cavity 7, while the liquid passes through the holes in the baffle 10 and raises the piston 9.

The chassis in figure 4 works as follows: when the rods touch the ground 2, the liquid begins to be squeezed out into the tank 12. Upon reaching a certain level in the tank, determined by the desired clearance, the valve 13 closes. The adaptation of the chassis to the terrain begins. When all the rods touch the ground, the pressure in the hydraulic line will increase, and valves 4 will close (manually or automatically). The rods will be fixed or, if there was a hydropneumatic cavity in the hydraulic cylinders, the chassis begins to absorb shock during landing.

To clean the chassis, the compressor 14 supplies pressure in the pneumatic cavity of the hydraulic cylinders 1, valves 4 and 13 open.

To release the chassis, nitrogen is pumped out of the pneumatic cavities to the total pneumatic capacity 15, valves 4 and 13 remain open, and the rods under the influence of their weight (and the weight of the supports) and under the influence of excessive nitrogen pressure in the tank 12 or springs are lowered.

For emergency landing valve 16 opens, the rods are lowered, valves 4 and 13 are emergency closed. The chassis is as ready to perceive the impact as possible. Upon impact, excess pressure in each individual hydraulic cylinder is released by a safety valve (not shown).

Claims (6)

1. The chassis, including movable supports, hydraulic cylinders connected by a pipeline to a valve or valves, characterized in that the hydraulic cylinders are partially filled, and the valve or valves are located with the possibility of separation of the hydraulic cylinders when the landing gear touches the ground or when the pressure in the hydraulic cylinders increases. 2. The chassis according to claim 1, characterized in that it has an automatic direct-acting valve, which is a valve with a hydraulic actuator from pressure in the hydraulic system or in the hydraulic cylinder. 3. The chassis according to claim 1, characterized in that the rod cavities of the hydraulic cylinders are pneumatic cavities of high pressure connected to the hollow rods of the hydraulic cylinders and / or with a common pneumatic cavity. 4. The chassis according to claim 1, characterized in that in the hydraulic line of each hydraulic cylinder or directly in the hydraulic cylinder there is a hydro-pneumatic cavity, in the latter case separated from the main cavity of the cylinder by a piston with limited mobility and a baffle with an opening. 5. The chassis according to claim 1, characterized in that the hydraulic system has a tank with a valve, and the pneumatic line has a common air capacity and a reversing compressor or compressor and two three-way valves. 6. The chassis according to claim 1, characterized in that the hydraulic cylinders contain springs.

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