Hydraulic system and passenger restraint system

Abstract

The invention relates to a hydraulic system for an occupant restraint device, said hydraulic system comprising a hydraulic pump and a hydraulic unit with a hydraulic accumulator, a valve device and a hydraulic cylinder unit with a piston. A valve arrangement is connected to the hydraulic pump, the hydraulic accumulator and the hydraulic cylinder unit. The piston is movable between an open position and a first closed position. The hydraulic pump is configured to pressurize the hydraulic cylinder unit such that the piston moves from the first closed position to the open position. The hydraulic accumulator is configured to pressurize the hydraulic cylinder unit such that the piston moves from the open position to the first closed position. The valve device can be switched into at least a first switching position, in which the hydraulic cylinder unit is pressurized by the hydraulic pump at a first pressure stage, and a second switching position, in which the hydraulic cylinder unit is pressurized by the hydraulic pump at a second pressure stage, the second pressure stage being lower than the first pressure stage.

Description

Technical Field

[0001] The present invention relates to a hydraulic system for a passenger restraint device and a passenger restraint system including at least one passenger restraint device having such a hydraulic system. Background Art

[0002] Such passenger restraint devices are particularly used for rides such as roller coasters, simulators, or other amusement facilities. In certain cases, relatively large forces and accelerations act on the passengers in the ride. Therefore, for safety reasons, passenger restraint devices are provided to keep the passengers in their proper positions on the passenger seats they occupy. The passenger restraint devices typically have a hydraulically operated restraint bar for retracting and extending the passenger restraint device. If the restraint bar is retracted, the passenger restraint device is closed, thereby fixing the passenger to the passenger seat. However, if the restraint bar is extended, the passenger restraint device is open, so that the passenger can enter and exit the passenger seat.

[0003] The hydraulic system is used to open and close the passenger restraint system. For this purpose, such a hydraulic system typically includes a hydraulic pump, a hydraulic accumulator, and a hydraulic cylinder unit with a piston. The piston is movably arranged within the hydraulic cylinder unit to adjust the passenger restraint device. To open the passenger restraint device, the piston is pressurized by the hydraulic pump. On the other hand, to close it, the piston is pressurized by the hydraulic accumulator.

[0004] From the prior art, for example, from WO2019 / 229183A1, it is known that the corresponding hydraulic system typically has a fixed (e.g., lockable) closing position of the restraint bar. However, due to the different body sizes or body circumferences of the passengers, the fixed closing position may result in insufficient or excessive restraint of the passengers. This leads to a lack of safety and discomfort for the passengers. Summary of the Invention

[0005] The passenger restraint device in the sense of the present disclosure is a restraint device for passengers in 4D cinemas, simulators, VR amusement facilities, and rides such as roller coasters or carousels. Therefore, an object of the present invention is to provide an improved hydraulic system to improve the automation degree of the passenger restraint device, the safety, and the comfort of the passengers.

[0006] The solution to the problem is achieved by a hydraulic system according to claim 1 and a passenger restraint system according to claim 14. Preferred embodiments are described in the dependent claims.

[0007] The hydraulic system for a passenger restraint device according to the present invention includes a hydraulic pump and a hydraulic section. The hydraulic section includes a hydraulic accumulator, a valve device, and a hydraulic cylinder unit with a piston. The valve device is connected to the hydraulic pump, the hydraulic accumulator, and the hydraulic cylinder unit. The piston can move between an open position and a first closed position. The hydraulic pump is configured to pressurize the hydraulic cylinder unit such that the piston moves from the first closed position to the open position. The hydraulic accumulator is configured to pressurize the hydraulic cylinder unit such that the piston moves from the open position to the first closed position. The valve device can be switched to at least a first switching position and a second switching position. The hydraulic cylinder unit is pressurized by the hydraulic pump at a first pressure level in the first switching position. The hydraulic cylinder unit is pressurized by the hydraulic pump at a second pressure level in the second switching position, where the second pressure level is lower than the first pressure level.

[0008] In other words, the hydraulic pump opens the restraint bar of the passenger restraint device, and the hydraulic accumulator closes the restraint bar to the first closed position. The open position of the piston corresponds to the open position of the passenger restraint device so that passengers can get on and off the vehicle. The first closed position of the piston corresponds to the position where a passenger with the maximum conceivable body dimension is safely restrained by the passenger restraint device. By switching between the switching positions, the valve device can switch between two pressure levels such that the pressure borne by the hydraulic cylinder unit when the restraint bar is open is higher than the pressure borne when the restraint bar is closed.

[0009] When the hydraulic cylinder unit is pressurized at the second pressure level, this allows the passenger to manually adjust the restraint bar in a preferred manner. On the other hand, if the hydraulic cylinder unit is pressurized at the first pressure level, the passenger cannot adjust the restraint bar. The manual adjustability of the restraint bar in the second switching position allows the passenger to adjust the position of the restraint bar according to their body size and / or body girth, so that the passenger is firmly and safely restrained by the passenger restraint device. This further improves the safety of the passenger.

[0010] Furthermore, the hydraulic accumulator preferably operates at a pressure lower than the pressure of the hydraulic pump required to close the restraint bar. Since the hydraulic cylinder unit is under a higher pressure from the hydraulic pump when the restraint bar is open, when the piston moves to the open position, the hydraulic fluid is fed back to the hydraulic accumulator. This replenishes the hydraulic accumulator so that the full pressure of the accumulator can be used to close the restraint bar.

[0011] The hydraulic pump is preferably configured as a fixed displacement pump, i.e., the delivery rate of the pump is constant and non-adjustable. Compared with an adjustable variable displacement pump whose delivery rate can be changed, the manufacturing cost of the hydraulic system can be reduced. A safety relief valve can be provided between the hydraulic pump and the hydraulic cylinder unit to prevent overpressure or destructive pressure peaks in the hydraulic system.

[0012] Preferably, the valve device includes a first pressure relief valve and a first direction control valve, wherein the first direction control valve blocks the flow path leading to the first pressure relief valve in a first switching position of the valve device, and wherein the first direction control valve opens the flow path leading to the first pressure relief valve in a second switching position of the valve device, wherein the first pressure relief valve is configured to set a second pressure level. The second pressure level is preferably set by the first pressure relief valve to be lower than the first pressure level. The first direction control valve preferably enables the flow path leading to the first pressure relief valve to be blocked when the restraint lever is open, such that the hydraulic cylinder unit is subject to the first pressure level of the hydraulic pump. This prevents the hydraulic fluid from flowing out through the first pressure relief valve. When the piston is in the open position, the restraint lever can preferably be used as a handle for passengers to get on and off the vehicle because the relatively high pressure in the first pressure level holds the restraint lever in place.

[0013] Furthermore, the valve device preferably includes a second direction control valve and a second pressure relief valve, wherein the valve device is switchable to a third switching position. The hydraulic cylinder unit is pressurized by the hydraulic pump at a third pressure level in the third switching position, wherein the second direction control valve blocks the flow path leading to the first pressure relief valve and releases it to the second pressure relief valve in the third switching position of the valve device, whereby the second pressure relief valve is configured to set the third pressure level. This enables a preferred switching between the second pressure level and the third pressure level when the restraint lever is closed. In the third pressure level, the hydraulic system moves the piston from the open position to the first closed position by means of a hydraulic accumulator. When the first closed position is reached, the valve device switches to the second switching position, thereby applying the second pressure level so that the restraint lever of the passenger restraint device can now be manually adjusted. This further improves the degree of automation in a preferred manner and enables the position of the restraint lever to be improved in order to safely restrain the passenger.

[0014] Preferably, the hydraulic accumulator is configured to pressurize the hydraulic cylinder unit at a fourth pressure level, wherein the fourth pressure level is lower than the first pressure level. In other words, the operating pressure of the hydraulic accumulator is lower than the operating pressure of the hydraulic pump. Therefore, when the piston moves from the closed position to the open position, the hydraulic accumulator is preferably filled with the fluid discharged from the hydraulic cylinder unit.

[0015] Furthermore, the fourth pressure level of the hydraulic accumulator is lower than the second pressure level. The pressure difference between the fourth pressure level and the second pressure level is so small that the passenger can overcome this pressure difference. The passenger pulls the restraint lever towards himself and applies an additional pressure to the hydraulic cylinder unit to bring it to the already applied fourth pressure level and resist the second pressure level. The additional pressure and the fourth pressure level together exceed the second pressure level set on the first pressure relief valve, so that it can be manually closed.

[0016] Preferably, the fourth pressure level is higher than the third pressure level. The pressure difference between the fourth pressure level and the third pressure level is so small that the closing movement of the restraint lever can be adjusted by the third pressure level.

[0017] Preferably, the hydraulic cylinder unit is configured as a differential cylinder. The hydraulic cylinder unit includes a hydraulic cylinder housing having an interior, wherein a piston is movably disposed within the interior of the hydraulic cylinder housing. The piston divides the interior of the hydraulic cylinder housing into a first working chamber and a second working chamber, wherein the first working chamber is connected to a hydraulic accumulator and the second working chamber is connected to a hydraulic pump. Generally, a differential cylinder has a piston rod on one side of the piston surface. Thus, the entire piston surface acts on one side of the piston, while only the ring surface acts on the rod side surface. Therefore, the differential cylinder has two effective surfaces of different sizes. In this case, the rod side surface faces the second working chamber, and the entire piston surface faces the first working chamber. Due to the larger effective area, the pressure in the hydraulic accumulator can be lower, which preferably results in a more compact design. By configuring the hydraulic cylinder unit as a differential cylinder, the hydraulic cylinder unit can be made more compact.

[0018] Preferably, the valve device has a third direction control valve between the hydraulic cylinder unit and the hydraulic accumulator, wherein the third direction control valve can be switched between a passage position and a blocking position, wherein the third direction control valve blocks the flow path from the hydraulic cylinder unit to the hydraulic accumulator in the blocking position, but opens the flow path from the hydraulic accumulator to the hydraulic cylinder unit. Preferably, when the restraint rod is open, the third direction control valve switches to the passage position, and when the restraint rod is closed, the third direction control valve switches to the blocking position. When the restraint rod is in its final closed position, the passenger is fixed and the fluid is locked in the hydraulic system. This means that the restraint rod cannot be opened during the ride.

[0019] Preferably, the piston can be manually moved from a first closed position to a second closed position, wherein the first closed position is located between the open position and the second closed position. The second closed position of the piston is variable and corresponds to the position of the passenger restraint device at which the passenger is firmly fixed according to their body girth. Preferably, the restraint rod automatically moves from the open position to the first closed position so that the passenger can manually pull the restraint rod towards themselves until the restraint rod firmly fixes the passenger.

[0020] Preferably, when the piston moves from the open position to the first closed position, the valve device switches to a third switching position. Thus, the pressure of the hydraulic accumulator is greater than a third pressure level set by a second pressure relief valve, and the hydraulic system preferably automatically moves the piston from the open position to the first closed position.

[0021] Preferably, when the piston moves from the first closed position to the second closed position, the valve device switches to a second switching position. Thus, the pressure of the hydraulic accumulator is lower than a second pressure level set by a first pressure relief valve, such that the piston can only be moved to the second closed position by an additional manually applied pressure.

[0022] The first closing position of the piston is preferably adjustable. This enables the first closing position of the restraint bar to preferably adapt to the physical characteristics of a particular country or, for example, a children's ride. The ride may also differ in terms of load, stress, or acceleration values, and thus it may be necessary to more firmly secure the passengers.

[0023] Furthermore, the hydraulic unit has a detection unit and a control unit connected to the detection unit, such that the first closing position of the piston can be set in the control unit and / or the movement of the piston from the open position to the first closing position can be closed by the hydraulic accumulator. This enables the first closing position of the piston to be adjusted in a preferred manner. The detection unit can, for example, include a piston position sensor and / or a time closing device. The piston position sensor detects the position of the piston in the hydraulic cylinder unit, such that, for example, when the first closing position is reached, the valve device switches from the third switching position to the second switching position. The time closing device detects the time required for the piston to move to the first closing position and switches the valve device from the third switching position to the second switching position after this time has elapsed.

[0024] Preferably, the hydraulic unit is a first hydraulic unit, and the hydraulic system has at least one second hydraulic unit identical to the first hydraulic unit. Preferably, the first hydraulic unit is connected to the second hydraulic unit such that the piston of the first hydraulic unit can move independently of the piston of the second hydraulic unit, wherein at least one second hydraulic unit is connected to a hydraulic pump. In this way, multiple passenger restraint devices can be conveniently operated with only one hydraulic pump. Ideally, all passenger restraint devices in the ride are operated with only one hydraulic pump. This can reduce manufacturing and installation costs. To prevent interference between the individual hydraulic units, each hydraulic unit includes a check valve. For example, this allows the restraint bars to close independently of each other.

[0025] Preferably, the hydraulic system has a reservoir such that the hydraulic fluid flowing back from the hydraulic cylinder unit or flowing out through the pressure relief valve flows back to the reservoir. Preferably, the hydraulic system has a return channel connected to the reservoir for this purpose.

[0026] Preferably, the first direction control valve, the second direction control valve, and / or the third direction control valve are electrically controlled. Preferably, this allows for control by an electronic control unit.

[0027] It is also preferred if the third direction control valve can be operated both electrically and manually. In a ride with multiple carriages, such as a roller coaster, the carriages are typically only supplied with power in the station, for example, via a current collector. When leaving the station, the carriages are de-energized, such that the third direction control valve cannot be operated electrically. If a carriage stops on the open track or stops due to a power failure, the restraint bar can be opened by manually actuating the third direction control valve so that the passengers can leave the carriage and the ride.

[0028] Preferably, the hydraulic system includes a check valve located between the hydraulic cylinder unit and the hydraulic pump, which blocks the flow path from the hydraulic cylinder unit to the hydraulic pump. In combination with the first direction control valve whose flow is blocked, when the piston is in the open position, the hydraulic fluid is locked in the hydraulic cylinder unit. This means that the restraint bar of the passenger restraint device can be used as an entry and / or exit assistance device for passengers to grasp.

[0029] The passenger restraint system according to the present disclosure includes at least one passenger restraint device and the hydraulic system as described above. The passenger restraint system may include several passenger restraint devices, which can be actuated by the hydraulic system, so that each passenger restraint device is assigned a hydraulic section. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The present invention will be described in more detail below with reference to the embodiments shown in the drawings. In the figures:

[0031] Figure 1 is a hydraulic circuit diagram of the hydraulic system according to the present invention; and

[0032] Figure 2 is a passenger restraint system having a passenger restraint device and a hydraulic system. DETAILED DESCRIPTION

[0033] Now an embodiment of the present invention will be described with reference to the drawings, in which the same reference numerals represent corresponding or identical elements in the figures.

[0034] Figure 1 A hydraulic circuit diagram of a hydraulic system 1 of a passenger restraint device according to the present invention is shown. Figure 2 A passenger restraint system 2 having a passenger restraint device 3 is shown, which has a restraint bar 4 for fixing a passenger to a passenger seat 5 occupied by the passenger.

[0035] The hydraulic system 1 includes a hydraulic pump 6, which is configured as a fixed displacement pump with a constant delivery rate. The hydraulic pump 6 can also be configured as an adjustable variable displacement pump with a variable delivery rate. The hydraulic system 1 has at least one hydraulic section 5, and in this exemplary embodiment, there are three hydraulic sections 5, but the number is not limited thereto. Each hydraulic section 5 includes a valve device 8, a hydraulic accumulator 9, and a hydraulic cylinder unit 10 with a piston 11.

[0036] Still as Figure 1 shown, the hydraulic system 1 includes a reservoir 22 and a return channel 23 connected to the reservoir 22. The hydraulic fluid returning from the second working chamber 16 of the hydraulic cylinder unit 10 flows back to the reservoir 22 via the return channel 23, which will be described in more detail below.

[0037] The three hydraulic sections 5 of the hydraulic system 1 are connected to the hydraulic pump 6 via the supply channel 25 and to the reservoir 22 via the return channel 23.

[0038] The hydraulic cylinder unit 10 includes a hydraulic cylinder housing 12 having an interior 13 in which a piston 11 is movable. The piston 11 has a piston rod 14 which is connected to the restraint rod 4 of the passenger restraint device 3 in order to open and close the passenger restraint device 3. The hydraulic cylinder unit 10 is configured as a differential cylinder in the present example. The piston 11 divides the interior 13 into a first working chamber 15 and a second working chamber 16. The first working chamber 15 is connected to the hydraulic accumulator 9 and the second working chamber 16 is connected to the hydraulic pump 6.

[0039] The hydraulic pump 6 is configured to pressurize the second working chamber 16 of the hydraulic cylinder unit 10 in order to move the piston 11 from a first closed position to an open position. For this purpose, the second working chamber 16 is connected to the hydraulic pump 6 via a pressure line 28 branched off from the supply channel 25. As shown, a check valve 26 and an adjustable throttle valve 27 can be provided in the pressure line 28 in order to regulate the inflow on the one hand and to prevent backflow into the hydraulic pump 6 on the other hand. This prevents interaction between the hydraulic cylinder units 10 of the respective hydraulic sections 5. Due to the different line lengths between the hydraulic pump 6 and the respective hydraulic cylinder units 10, pressure losses can occur along the supply channel 25. In order to apply the same pressure to all hydraulic cylinder units 10, the respective hydraulic sections 5 achieve hydraulic balance with each other via the adjustable throttle valves 27.

[0040] On the other hand, the hydraulic accumulator 9 is configured to pressurize the first working chamber 15 of the hydraulic cylinder unit 10 in order to move the piston 11 from the open position to the first closed position. The open position of the piston 11 corresponds to the position of the extended restraint rod 4 and the passenger restraint device 3 is open so that the passenger can enter and leave the passenger seat 5. The first closed position of the piston 11 corresponds to the position of the retracted restraint rod 4 such that the passenger restraint device 3 closes to the maximum conceivable body girth of the passenger. In the open position, the piston 11 is fixed due to the relatively high pressure and the passenger can then also use the piston 11 as an armrest.

[0041] In addition, the piston 11 can be manually moved to a second closed position. The first closed position is located between the open position and the second closed position. The second closed position of the piston 11 is variable and corresponds to the position of the passenger restraint device 3 in which the passenger is firmly restrained according to his body girth. In order to move the piston 11 to the second closed position, the passenger pulls the restraint rod 4 from the first closed position towards himself until the passenger is firmly restrained.

[0042] The valve device 8 can be switched to a first switching position, a second switching position, and a third switching position. To this end, the valve device 8 includes a first pressure relief valve 17, a first direction control valve 18, a second direction control valve 19, and a second pressure relief valve 20. The first direction control valve 18 and the second direction control valve 19 are provided in a branch line 29 that branches between the second working chamber 16 of the hydraulic cylinder unit 10 and the hydraulic pump 6 and is connected to the return passage 23. The first direction control valve 18 is connected to the pressure line 28 and the second direction control valve 19. The second direction control valve 19 is provided downstream of the first direction control valve 18 and connects the first direction control valve 18 to the return passage 23 via the first pressure relief valve 17 or via the second pressure relief valve 20 provided in parallel therewith.

[0043] In the first switching position of the valve device 8, the first direction control valve 18 blocks the flow path from the pressure line 28 to the first pressure relief valve 17, and the hydraulic cylinder unit 10 is pressurized by the hydraulic pump 6 at a first pressure level. This causes the piston 11 to move to the open position and the restraint lever 4 to open.

[0044] In the second switching position of the valve device 8, the first direction control valve 18 opens the flow path through the branch line 29, and the second direction control valve 19 connects the first direction control valve 18 to the first pressure relief valve 17 so that the hydraulic pump 6 pressurizes the hydraulic cylinder unit 10 at a second pressure level. The first pressure relief valve 17 is configured to set the second pressure level. The pressure levels are selected such that the first pressure level of the hydraulic pump 6 is higher than the second pressure level of the first pressure relief valve 17. For example, the first pressure level may be 100 bar and the second pressure level may be 60 bar.

[0045] In the third switching position of the valve device 8, the second direction control valve 19 connects the first direction control valve 18 to the second pressure relief valve 20. In this switching position, the hydraulic cylinder unit 10 is pressurized by the hydraulic pump 6 at a third pressure level. The second pressure relief valve 20 is configured to set the third pressure level, which is lower than the second pressure level. The third pressure level may be, for example, 20 bar. Thus, when the passenger restraint device 3 is closed, the valve device can be switched between two different pressure levels.

[0046] The valve device 8 further includes a third direction control valve 21 provided between the first working chamber 15 of the hydraulic cylinder unit 10 and the hydraulic accumulator 9. The third direction control valve 21 can be switched between a passage position and a blocking position. In the passage position, the flow path between the first working chamber 15 and the hydraulic accumulator 9 is open in both directions. On the other hand, in the blocking position, the flow path from the first working chamber 15 to the hydraulic accumulator 9 is blocked, but the flow path from the hydraulic accumulator 9 to the first working chamber 15 is enabled.

[0047] The hydraulic accumulator 9 is configured to pressurize the hydraulic cylinder unit 10 at a fourth pressure level. The fourth pressure level is lower than the second pressure level but higher than the third pressure level. For example, the fourth pressure level can be 40 bar. When the hydraulic pump 6 pressurizes the hydraulic cylinder unit 10 at the first pressure level such that the piston 11 moves towards the open position, the third-way control valve 21 switches to the passage position, allowing the hydraulic fluid to flow back to the hydraulic accumulator 9. This charges the hydraulic accumulator 9 in order to move the piston 11 from the open position back to the first closed position.

[0048] However, if the piston 11 is in the open position, the valve device 8 switches to the first switching position, causing the first-way control valve 18 to block the branch line 29. Thus, the hydraulic cylinder unit 10 is pressurized at the first pressure level. Since the fourth pressure level of the hydraulic accumulator 9 is much lower than the first pressure level of the hydraulic pump 6, a passenger can support or grasp the restraint bar 4 of the passenger restraint device 3 and use it as an assist device for getting in and out. The selection of the first pressure level and the fourth pressure level is such that the sum of the fourth pressure level and the additional pressure exerted by the passenger on the restraint bar 4 when getting in and out and thus on the piston 11 is less than the first pressure level. Therefore, the passenger cannot overcome the first pressure level to move the restraint bar 4.

[0049] To move the piston 11 from the open position to the first closed position, the valve device 8 switches to the third switching position, thereby applying the third pressure level in the second working chamber 16 of the hydraulic cylinder unit 10. This allows the restraint bar 4 to perform a closing movement that can be controlled or specifically set. When the piston 11 reaches the first closed position, the valve device 8 switches to the second switching position, thereby applying the second pressure level in the second working chamber 16.

[0050] Since the second pressure level is only slightly higher than the fourth pressure level of the hydraulic accumulator 9, a passenger can apply sufficient pressure to the piston 11 by pulling the restraint bar 4 such that the sum of the fourth pressure level and the pressure applied by the passenger is greater than the second pressure level set by the first pressure relief valve 17. This means that the piston 11 can be manually moved to the second closed position.

[0051] The first, second, and third-way control valves 18, 19, 21 can all be electrically controlled. For example, they can be controlled by an integrated control unit. The third-way control valve 21 can also be manually actuated to manually open the restraint bar 4 in the event of a power failure. The first, second, and third-way control valves 18, 19, 21 all have a return spring that biases the respective direction control valve to the rest position when the respective direction control valve is not electrically actuated and thus de-energized. The first-way control valve 18 is pre-loaded such that the branch line 29 is blocked. The third-way control valve 21 is pre-loaded to the above-mentioned blocking position such that the restraint bar 4 can be further closed but opening of the restraint bar 4 is prevented.

[0052] The hydraulic system 1 also has a third pressure relief valve 24, which connects the supply passage 25 to the reservoir 22. The third pressure relief valve 24 is configured to set a first pressure level and prevent pressure peaks to prevent damage to the hydraulic system 1. The first pressure level can be, for example, 100 bar.

[0053] Although the terms "first", "second", "third", and "fourth" are used herein to distinguish different components, these components are not intended to be limited by these terms. These terms are only used to distinguish the components from each other and do not specify a particular order. Thus, for example, the first component described above could be referred to as the second component, and vice versa.

[0054] List of references 1 Hydraulic system 2 Passenger restraint system 3 Passenger restraint device 4 Restraint bar 5 Passenger seat 6 Hydraulic pump 5 Hydraulic section 8 Valve device 9 Hydraulic accumulator 10 Hydraulic cylinder unit 11 Piston 12 Hydraulic cylinder housing 13 Inside 14 Piston rod 15 First working chamber 16 Second working chamber 17 First pressure relief valve 18 First direction control valve 19 Second direction control valve 20 Second pressure relief valve 21 Third direction control valve 22 Reservoir 23 Return passage 24 Fourth pressure relief valve 25 Supply passage 26 Check valve 27 Throttle valve 28 Pressure line 29 Branch line

Claims

1. A hydraulic system (1) for a passenger restraint device (3), wherein, The hydraulic system (1) comprises: a hydraulic pump (6) and a hydraulic section (5) with a hydraulic accumulator (9), a valve device (8), and a hydraulic cylinder unit (10) with a piston (11), wherein the valve device (8) is connected to the hydraulic pump (6), the hydraulic accumulator (9), and the hydraulic cylinder unit (10), wherein the piston (11) is movable between an open position and a first closed position, wherein the hydraulic pump (6) is configured to pressurize the hydraulic cylinder unit (10) such that the piston (11) moves from the first closed position to the open position, wherein the hydraulic accumulator (9) is configured to pressurize the hydraulic cylinder unit (10) such that the piston (11) moves from the open position to the first closed position, wherein the valve device (8) is switchable to at least a first switching position and a second switching position, wherein, in the first switching position, the hydraulic cylinder unit (10) is pressurized by the hydraulic pump (6) at a first pressure level, and wherein, in the second switching position, the hydraulic cylinder unit (10) is pressurized by the hydraulic pump (6) at a second pressure level, wherein the second pressure level is lower than the first pressure level.

2. The hydraulic system (1) according to claim 1, characterized in that, The valve device (8) comprises a first pressure relief valve (17) and a first direction control valve (18), the first direction control valve (18) blocking the flow path to the first pressure relief valve (17) in the first switching position of the valve device (8), and wherein the first direction control valve (18) opens the flow path to the first pressure relief valve (17) in the second switching position of the valve device (8), wherein the first pressure relief valve (17) is configured to set the second pressure level.

3. The hydraulic system (1) according to claim 2, characterized in that, The valve device (8) comprises a second direction control valve (19) and a second pressure relief valve (20), wherein the valve device (8) is switchable to a third switching position, in which the hydraulic cylinder unit (10) is pressurized by the hydraulic pump (6) at a third pressure level, wherein the second direction control valve (19) in the third switching position blocks the flow path to the first pressure relief valve (17) and releases it to the second pressure relief valve (20), the second pressure relief valve (20) being configured to set the third pressure level.

4. The hydraulic system (1) according to one of the preceding claims, characterized in that, The hydraulic accumulator (9) is configured to pressurize the hydraulic cylinder unit (10) at a fourth pressure level, the fourth pressure level being lower than the first pressure level.

5. The hydraulic system (1) according to claim 4, characterized in that, The fourth pressure level of the hydraulic accumulator (9) is lower than the second pressure level, and wherein the third pressure level is preferably lower than the fourth pressure level.

6. The hydraulic system (1) according to one of the preceding claims, characterized in that, The hydraulic cylinder unit (10) is configured as a differential cylinder. The hydraulic cylinder unit (10) includes the hydraulic cylinder housing (12) having an interior (13). The piston (11) is movably disposed in the interior (13) of the hydraulic cylinder housing (12), and the piston (11) divides the interior (13) of the hydraulic cylinder housing (12) into a first working chamber (15) and a second working chamber (16). Wherein, the first working chamber (15) is connected to the hydraulic accumulator (9), and the second working chamber (16) is connected to the hydraulic pump (6).

7. The hydraulic system (1) according to one of the preceding claims, characterized in that, The valve device (8) includes a third direction control valve (21) located between the hydraulic cylinder unit (10) and the hydraulic accumulator (9). Wherein, the third direction control valve (21) can be switched between a passing position and a blocking position. Wherein, the third direction control valve (21) blocks the flow path from the hydraulic cylinder unit (10) to the hydraulic accumulator (9) in the blocking position, but releases the flow path from the hydraulic accumulator (9) to the hydraulic cylinder unit (10).

8. The hydraulic system (1) according to one of the preceding claims, characterized in that, The piston (11) can be manually moved from the first closed position to the second closed position, and the first closed position is located between the open position and the second closed position.

9. The hydraulic system (1) according to one of the preceding claims, characterized in that, When the piston (11) moves from the open position to the first closed position, the valve device (8) switches to the third switching position.

10. The hydraulic system (1) according to claim 8 or 9, characterized in that, When the piston (11) moves from the first closed position to the second closed position, the valve device (8) switches to the second switching position.

11. The hydraulic system (1) according to one of the preceding claims, characterized in that, The first closed position of the piston (11) is adjustable.

12. The hydraulic system (1) according to claim 11, characterized in that, The hydraulic part (5) has a detection unit and a control unit connected to the detection unit, such that the first closed position of the piston (11) can be set in the control unit and / or the movement of the piston (11) can be switched from the open position to the first closed position through the hydraulic accumulator (9).

13. The hydraulic system (1) according to one of the preceding claims, characterized in that, The hydraulic part (5) is the first hydraulic part (5), and the hydraulic system (1) includes at least one second hydraulic part (5) identical to the first hydraulic part (5). The first hydraulic part (5) is connected to the second hydraulic part (5) such that the piston (11) of the first hydraulic part (5) can move independently of the piston (11) of the second hydraulic part (5), and the at least one second hydraulic part (5) is connected to the hydraulic pump (6).

14. A passenger restraint system (2), comprising at least one passenger restraint device (3) and the hydraulic system (1) according to any one of the preceding claims.

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