Patent Publication Number: US-2022227321-A1

Title: Locking device for a safety bar, passenger accommodation and amusement ride having a locking device of this kind

Description:
The present invention relates to a locking device for a safety bar, comprising a fluid channel having a magneto-rheological fluid and a locking element with the features of claim  1 , a passenger accommodation with the features of claim  17  and an amusement ride with the features of claim  18 . 
     Safety bars with locking devices are known from prior art in various embodiments. Amusement rides of this kind are, for example, roller coasters in which passengers are subjected to strong accelerations. While traveling on an amusement ride, passengers are held in their passenger accommodation by a safety bar and the safety bar is locked via a locking system. According to standard DIN EN  13814 , depending on the acceleration that acts on the passenger, a corresponding locking system is prescribed. 
     To get in and out of the passenger accommodation, the safety bars are typically pivoted about an axis of rotation by means of actuators. During the ride, however, the safety bar is locked by means of a mechanical lock in such a way that said bar remains in the closed position even in the event of a failure of the actuator. 
     The disadvantage of prior art is that the known mechanical locks are subjected to heavy wear due to the constant use and load and are therefore costly to maintain. Mechanical locks are also associated with additional weight, which means that greater energy expenditure is required for acceleration due to higher vehicle weights. 
     Hydraulic locking devices or actuators with a conventional hydraulic valve have the disadvantage of causing valve leakage at high pressure differences, which reduces the locking or actuating force of the locking devices or actuators and increases the need for maintenance. 
     This is where the present invention begins. 
     It is therefore the object of the present invention to propose an improved locking device for a safety bar, which expediently improves the locking devices known from prior art and is both fail-safe and unsusceptible to leakage and wear. 
     According to the invention, these objects are achieved by a locking device for a safety bar with the features of claim  1 , a passenger accommodation having a locking device according to claim  17  and by an amusement ride with the features of claim  18 . 
     Further advantageous embodiments of the present invention are specified in the dependent claims. 
     The locking device for a safety bar with the features of claim  1  has a fluid channel having a magneto-rheological fluid, a movable locking element and a magnet device, the locking element forcing the fluid through the fluid channel when there is a movement. The locking element is therefore in a kinematic operative connection to the magneto-rheological fluid and is thus hydraulically coupled to the magneto-rheological fluid and can transfer a movement or pivot movement of the safety bar to the magneto-rheological fluid in the fluid channel. In addition, the fluid channel has at least one channel portion, wherein the magnet device is arranged at least on two opposing side walls of the channel portion in such a manner that the magnetic field lines of the magnetic field of the magnet device can pass through the channel portion. The magnetic field lines of the magnetic field of the magnet device preferably pass through the channel portion transversely to a flow direction, wherein naturally by the curvature of the field lines and in the form of a preferred development—as will be explained in detail later—the field lines can be aligned so as to be specifically inclined or curved with respect to the flow direction in the channel portion. The magneto-rheological fluid is polarized in the magnetic field of the magnet device, as a result of which the particles of the magneto-rheological fluid align or are polarized in the magnetic field of the magnet device along the field lines, i.e., transversely to the flow direction. As a result, the viscosity of the magneto-rheological fluid in the channel portion is preferably increased up to a pressure-resistant solidification and the fluid channel, and thus the safety bar is blocked or a movement of the safety bar is greatly damped. 
     Here and in the following, a fluid channel is understood to mean an open or closed system that forcibly conveys the fluid—with as little leakage as possible. The fluid channel can preferably form a closed circle, i.e., a fluid circuit, or form a system that has at least one first end and at least one second end, there being at least one connection between the at least one first end and the at least one second end, by means of which connection the fluid can flow from the at least one first end to the at least one second end. 
     According to a development of the invention, the magnet device has a first state and a second state, wherein the magnetic field lines pass through the channel portion in the first state and wherein the magnetic field lines are diverted or deflected by the channel portion or weakened in the channel portion in the second state. The second state thus corresponds to the state in which the magnetic field of the magnet device is weakened or minimized in the channel portion, as a result of which the viscosity of the magneto-rheological fluid remains substantially unchanged and the magneto-rheological fluid flows through, or can flow through, the channel portion through the magnet device in the flow direction approximately without interference. The safety bar is released in the second state and can be moved or pivoted. 
     According to a further advantageous embodiment of the present invention, the magnet device surrounds the channel portion at least in some portions. It is particularly preferred if the channel portion has a circular cross section, so that the magnet device is arranged rotationally symmetrically, in particular completely rotationally symmetrically, around the channel portion. It is preferred in particular if the magnet device can be divided in the circumference into at least two regions, it being possible for the first region to form a north pole and the second region to form a south pole. Accordingly, the magnetic flux flows along the field lines from the north pole to the south pole, thereby passing through the channel portion of the fluid channel. 
     According to a further advantageous embodiment of the present invention, the magnet device can be switched or actuated mechanically and/or electrically. Mechanically, the magnetic field of the magnet device can be weakened, for example by deflecting the magnetic flux by means of flux-conducting components, and/or can be weakened by mechanically introducing a magnetically hard object. A switchable electromagnet can also be provided, which either generates the magnetic field of the magnet device and/or weakens the magnetic field of the magnet device. 
     It has proven to be particularly advantageous if the magnet device has at least one permanent magnet and/or at least one electromagnet. The magnet device can preferably be formed from a plurality of permanent magnets, in particular neodymium magnets, which can be arranged simply and inexpensively on the at least two opposing side walls of the channel portion of the fluid channel. 
     According to a further advantageous embodiment of the present invention, the channel portion has at least one throttle, by means of which the channel portion of the fluid channel has a locally reduced cross section. It is particularly preferred if the cross section through the throttle is at most ½, more preferably ¼, even more preferably ⅛, also further preferably 1/16, and even more preferably not more than 1/32, of the cross-sectional area of the channel portion beyond the throttle. By locally reducing the cross section in the throttle through which the fluid flows, the polarized particles of the magneto-rheological fluid can “clog” the channel portion and block it against large pressures. 
     According to a further embodiment of the present invention, the at least one throttle can have a cascade, a link, a perforated sheet, a honeycomb structure, a sieve structure and/or a lattice structure. In particular, it is preferred if the throttle has a cascade by means of which the cross section through which the fluid flows is considerably reduced and additionally the effective length of the channel portion is extended in the flow direction due to deflections. The cascade can have any shape, for example a zigzag shape or a meandering shape. The cascade increases the blocking effect of the polarized particles of the magneto-rheological fluid and the fluid channel can be effectively blocked against large compressive forces. 
     Furthermore, the cascade or link can preferably be formed from a plurality of deflector profiles, which can protrude alternately from the at least two opposing side walls into the channel portion. The deflector plates can be made of a magnetizable or non-magnetizable material, the deflector plates being particularly preferably made of a magnetizable material, as a result of which the field lines are aligned particularly effectively between at least two opposing side walls. 
     A perforated sheet, a honeycomb structure, sieve structure or lattice structure divides the channel portion into a large number of individual channels, which can be blocked particularly well by the polarized particles of the magneto-rheological fluid. The perforated sheet, honeycomb structure, sieve structure and/or lattice structures can also be made of a magnetizable or non-magnetizable material, wherein it is particularly preferred in this case if the above-mentioned structures are made of a non-magnetizable material, preferably a light metal. 
     According to a further embodiment of the present invention, the channel portion can have a tapered portion in the form of a diffuser or a nozzle. Whereas a diffuser causes a delay of the flow in the channel portion, the nozzle accelerates the flow in the channel portion. In the present case, a channel portion designed as a diffuser corresponds to an expansion of the cross section through which the fluid flows and the nozzle corresponds to a taper of the cross section through which the fluid flows, transversely to the flow direction. The field lines of the magnet device can be aligned in the diffuser or in the nozzle as precisely as possible, perpendicular to the flow direction. When there is a delay in the diffuser, the static pressure increases, during which time the static pressure decreases in the nozzle due to acceleration. A one-way or non-return valve can be realized through the diffuser or through the nozzle, as a result of which the channel portion—in the presence of the magnetic field—is blocked in a first flow direction and allows flow in a second flow direction. The first flow direction corresponds to the flow direction that points in the direction of the tapering of the tapered portion. 
     Furthermore, it has proven to be advantageous if a tapered portion in the form of a diffuser and/or in the form of a nozzle is arranged upstream and/or downstream of the channel portion in the flow direction. The nozzle and/or the diffuser can particularly preferably reduce the cross section in the fluid channel upstream of the entry into the channel portion, as a result of which the cross section through which the fluid flows is small. The solidifications in the channel cross section that are generated by the magnetic field can also block the fluid channel against large pressure differences. 
     It has also proven to be advantageous if the locking element comprises a piston, wherein the piston is preferably designed to perform a linear movement. The piston can be coupled or connected to the safety bar by means of a piston rod. Furthermore, it is preferred if the fluid channel has a cylindrical pressure chamber in which the piston is arranged. The piston has a first pressure side and a second pressure side and divides the pressure chamber of the cylinder into two regions, namely a first region and a second region, wherein depending on the load on the piston, one of the regions forms a pressure side and the other region forms a suction side. The first region and the second region of the pressure chamber of the cylinder are preferably separated without leakage by means of a piston seal. The first region and the second region are connected to one another by means of the fluid channel, so that the magneto-rheological fluid enclosed in the pressure chamber can flow through the fluid channel from the first region, the pressure side, into the second region, the suction side, when the locking element moves. 
     Furthermore, a conventional hydraulic valve can be arranged in the fluid channel. The valve can additionally secure the fluid channel and mechanically block the connection between the two pressure sides of the piston. Furthermore, the channel portion can be arranged in the fluid channel with respect to the hydraulic valve in such a way that the pressure in the channel portion is lowered to such an extent that the pressurization of the hydraulic valve is lowered even at extremely high pressures and leaks are prevented. 
     Furthermore, it has proven to be advantageous if the fluid channel is a circular channel, wherein the circular channel is arranged between a circular, preferably circular-cylindrical inner shaft, which forms the first side wall, and a circular, preferably hollow-cylindrical outer shaft, which forms the opposite second side wall. The inner shaft, the outer shaft and the circular channel can be arranged coaxially with a longitudinal axis. Furthermore, the magnet device can be arranged in such a way that the field lines extend substantially radially and pass through the circular channel. The inner shaft preferably forms the locking element and can be rotated about the longitudinal axis relative to the outer shaft. When the locking element, or the safety bar, moves, the movement is transferred to the magneto-rheological fluid in the circular channel, or through the fluid channel, and the magneto-rheological fluid is forced into a flowing movement. 
     It has proven to be advantageous if at least one rolling element is arranged in the fluid channel. The rolling element is in operative contact with both the inner shaft and the outer shaft and is forced into a rolling movement when the inner shaft is rotated relative to the outer shaft. It is particularly preferred if the fluid channel is designed as a circular channel with a constant width, as a result of which a kind of roller bearing is formed. The field lines of the magnetic field of the magnet device polarize the particles of the magneto-rheological fluid and preferably align them radially in the circular channel Due to a wedge effect, the polarized particles block a rolling movement of the rolling elements and a block a rotation of the locking element. When the magnetic flux or the field lines are deflected or weakened in the circular channel, the rolling elements or the actuator formed as an inner shaft are released and the inner shaft can be rotated with respect to the outer shaft. 
     According to a further embodiment of the present invention, the inner shaft is mounted eccentrically within the outer shaft, as a result of which the circular channel does not have a constant channel cross section around the circumference. The inner shaft forms the locking element and is arranged within the outer shaft in the manner of an eccentric disk pump and forms a constriction at a circumferential position, which constriction is moved about the longitudinal axis of the inner shaft together with a rotation of the inner shaft in order to displace the magneto-rheological fluid. The polarized particles of the magneto-rheological fluid form chain-like structures along the field lines of the magnetic field of the magnet device, which structures, by means of the wedge effect of the constriction, block the relative position between the inner shaft and the outer shaft and thus block the safety bar. 
     According to a further advantageous embodiment of the present invention, the fluid channel has a conveying means which allows the magneto-rheological fluid to be pressurized in the fluid channel or allows said fluid to flow through the fluid channel. The conveying means is preferably a pump which is designed to adjust and maintain the pressure in the fluid channel and, optionally, to adjust a flow in the fluid channel in order to advance the movable locking element. 
     It has also proven to be advantageous if the fluid channel has at least one pressure compensation device, by means of which the pressure in the fluid channel is maintained and pressure fluctuations, for example due to volume changes or temperature fluctuations, can be compensated for. It is particularly advantageous if the pressure compensation device has a compensation reservoir connected to the fluid channel, in which reservoir the magneto-rheological fluid is stored proportionally, and a pressure medium. The pressure medium can preferably be a compressible gas, in particular nitrogen or a nitrogen mixture. This ensures that a substantially constant pressure is always maintained in the fluid channel under different ambient conditions. 
     The pressure compensation device can further preferably be an energy store. When the safety bar is closed, the energy store is charged due to the different volumes in the first region and in the second region of the pressure chamber—on account of the piston rod in the second region. Accordingly, when the safety bar is closed, the pressure in the magneto-rheological fluid increases and this stored energy can be used in the second state of the magnet device for opening the safety bar. 
     The magneto-rheological fluid preferably comprises polarizable particles, in particular carbonyl iron powder, and a suspension, in particular a mineral oil, a synthetic oil, ethylene glycol or water, wherein the foregoing list of ingredients of the magneto-rheological fluid is not exhaustive. Rather, any polarizable particles and any suspensions can be used. The above-mentioned combinations are merely an exemplary and preferred combination. 
    
    
     
       In the following, two exemplary embodiments of a locking device according to the invention and developments thereof are described in detail with reference to the accompanying drawings. In the drawings: 
         FIG. 1  shows a passenger accommodation of an amusement ride having a safety bar, wherein the safety bar can be locked by a locking device according to the invention; 
         FIG. 2  shows an enlarged representation of the locking device for a safety bar according to  FIG. 1 , comprising a fluid channel having a magneto-rheological fluid, a movable locking element designed as a piston and comprising a magnet device, wherein the magnet device is arranged at least around a channel portion of the fluid channel and the field lines of the magnet device passing through the channel portion in such a way that the magneto-rheological fluid in the channel portion can be polarized in order to block the channel portion transversely to the flow direction; 
         FIG. 3  shows a development of the first exemplary embodiment according to  FIG. 1 or 2 , wherein a pressure compensation device is provided, by means of which the pressure in the fluid channel can be kept constant; 
         FIG. 4  shows a second development of the first exemplary embodiment according to  FIG. 1 or 2 ; 
         FIG. 5  shows a third development of the first exemplary embodiment according to  FIG. 1 or 2 ; 
         FIG. 6  shows a fourth development of the first exemplary embodiment according to  FIG. 1 or 2 ; 
         FIG. 7  shows a fifth development of the first exemplary embodiment according to  FIG. 1 or 2 ; 
         FIG. 8  shows a sixth development of the first exemplary embodiment according to  FIG. 1 or 2 ; 
         FIG. 9  shows a passenger accommodation of the amusement ride, comprising a safety bar and a locking device according to a second exemplary embodiment, wherein the fluid channel is arranged as a circular channel between an inner shaft and an outer shaft; 
         FIG. 10  shows a detailed representation of the locking device according to  FIG. 9 , wherein the inner shaft is arranged eccentrically with respect to the outer shaft; 
         FIG. 11 a    shows a first development of the second exemplary embodiment according to  FIG. 9 or 10 ; 
         FIG. 11 b    shows a detailed representation according to  FIG. 11   a;    
         FIG. 12 a    shows a second development of the second exemplary embodiment according to  FIG. 9 or 10 ; 
         FIG. 12 b    shows a detailed representation according to  FIG. 12   a;    
         FIG. 13 a    shows an enlarged and greatly simplified schematic representation of an embodiment of the channel portion with the magnet device; 
         FIG. 13 b    shows a schematic sectional representation of the channel portion along the intersection line X-X according to  FIG. 13   a;    
         FIG. 14  shows an enlarged and greatly simplified schematic representation of a second embodiment of the channel portion with the magnet device; 
         FIG. 15  shows an enlarged and greatly simplified schematic representation of a third embodiment of the channel portion with the magnet device, the channel portion having a tapered portion and being designed in the manner of a non-return valve; 
         FIG. 16  shows an enlarged and greatly simplified schematic representation of a fourth embodiment of the channel portion with the magnet device; and 
         FIG. 17  shows an enlarged and greatly simplified schematic representation of the channel portion according to  FIG. 13 a   , wherein an additional hydraulic valve is provided. 
     
    
    
     Identical or functionally identical components are identified below with the same reference symbols. Identical features of the individual exemplary embodiments and their developments can be combined with one another and are not limited to the respective exemplary embodiments. 
       FIG. 1  shows a passenger accommodation  3  of an only partially shown amusement ride  2 , comprising a seat receptacle  4 , a seat cushion  5 , a back cushion  6  and a safety bar  8 , which is arranged on the seat receptacle  4  so as to pivot or rotate about an axis of rotation. The safety bar  8  can be moved from an open position (not shown) to a closed position in order to keep a passenger (not shown) safely in the passenger accommodation  3  while traveling on the amusement ride  2 . The safety bar  8  can be moved from the open position to the closed position and vice versa manually or by corresponding actuators and can also have a locking system as a primary safeguard, whereby the safety bar  8  is held in the closed position while traveling. In the event that the actuators or the primary safeguard of the safety bar  8  fails, a locking device  1  is provided as a secondary safeguard, by means of which the safety bar  8  is held in the closed position. Alternatively, the locking device  1  can form the primary safeguard of the safety bar  8 . 
       FIG. 2  shows an enlarged representation of the locking device  1  according to the invention for a safety bar  8  according to  FIG. 1 , comprising a fluid channel  10  having a channel portion  20 , a magnet device  30  and a movable locking element  40 , wherein the locking element  40  is coupled to the safety bar  8  at one end and transfers a movement of the safety bar  8  to a magneto-rheological fluid  11  located in the fluid channel  10 . 
     The fluid channel  10  is filled with the magneto-rheological fluid  11 , the magneto-rheological fluid  11  comprising at least two components, specifically a suspension and polarizable particles. The suspension can preferably be a mineral oil, a synthetic oil, ethylene glycol or water, it being possible to use any suspension that does not chemically react with the polarizable particles and the materials used for the locking device  1 . The polarizable particles may contain carbonyl iron powder or the like. The magneto-rheological fluid may additionally contain stabilizers. 
     In the exemplary embodiment shown, the fluid channel  10  is a self-contained fluid circuit and comprises a cylinder  15  in which the locking element  40 , which is designed as a piston  42 , is arranged. The cylinder  15  surrounds a pressure chamber  14  and the piston  42  divides the pressure chamber  14  of the cylinder  15  into a first region  16  and a second region  17 . Depending on the load on the pressure chamber  14 , one of the regions  16 ,  17  forms the pressure side and the other region  16 ,  17  forms the suction side. The first region  16  and the second region  17  communicate with each other by means of a line  12  of the fluid channel  10  and the magneto-rheological fluid  11  can flow through the line  12  from the pressure side to the suction side—as is shown in  FIGS. 13 a    to  17 —in a first flow direction A and can flow back again in a second flow direction B. 
     The locking element  40  is held in the cylinder  15  so as to be linearly movable and is coupled to the magneto-rheological fluid  11  enclosed in the fluid channel  10 . A movement of the safety bar  8  is transferred by the locking element  40  or by the piston  42  to the magneto-rheological fluid  11 , as a result of which said fluid is displaced from the pressure side of the piston  42  through the fluid channel  10  or through the line  12  in one of the flow directions A, B to the piston  42 . 
     The piston  42  may have a seal  44  which seals a pass gap  43  between the piston  42  and a wall of the cylinder  15 . By means of a piston rod  45 , the piston  42  is connected to the safety bar  8 , see  FIG. 1 , of the passenger accommodation  3 , the piston rod  45  being arranged preferably coaxially in the cylinder  15  and being led out of the cylinder  15  at a free end through an opening in the cylinder  15 . The opening in the cylinder  15  can also be sealed by means of a seal in order to prevent leakage. 
     In addition, the fluid channel  10  comprises a pressure compensation device  19  which can keep the pressure in the fluid channel  10  approximately constant. 
     The pressure compensation device  19  can have a reservoir in which a pressure medium and the magneto-rheological fluid  11  are stored. The pressure medium pressure pressurizes the magneto-rheological fluid  11  and can, for this purpose, be a compressible medium, in particular a gas, even more preferably nitrogen or a nitrogen mixture. Different volumes from pressure side to suction side in the cylinder  15  as well as different volumes due to fluctuations in the ambient conditions, in particular the temperature, can be compensated for by the pressure compensation device  19 . The pressure compensation device  19  can also be used as an energy store which stores energy in the form of pressure in the manner of a spring accumulator and releases it again when required. 
     In the present case, when the safety bar  8  is closed, the magneto-rheological fluid  11  can be displaced from the second region  17  into the first region  16  of the pressure chamber  14 . Due to the piston rod  45  of the piston  42 , which rod is located in the first region  16 , the volume enclosed in the fluid channel  11  is reduced and the pressure is increased. The magneto-rheological fluid  11  is forced into the pressure compensation device  19  and the pressure medium, for example the compressible gas, is preloaded. This preload can be used for opening the safety bar  8 , whereby the passenger, after traveling on the amusement ride  2 , has to apply less force in order to swing open the safety bar  8 . 
     In the exemplary embodiment shown in  FIG. 2 , the channel portion  20  is arranged in the line  12  between the first region  16  and the second region  17  of the pressure chamber  14  and can be designed as shown by way of example in  FIGS. 13 a    to  17 . It is essential here that the magnet device  30  is arranged on at least two opposing side walls  21 ,  22  of the channel portion  20  in such a way that the field lines  31  of the magnetic field of the magnet device  30  can pass through the channel portion  20 . For improved understanding, the field lines  31  are shown in an idealized way in  FIG. 13 b    in the form of arrow lines. 
     The magnet device has a first state and a second state. In the first state of the magnet device  30 , the magnetic field lines  31  of the magnetic field of the magnet device  30  pass through the channel portion  20  and polarize the particles of the magneto-rheological fluid  11  in order to align them approximately transversely to the flow directions A, B in the channel portion  20 . 
     Due to the reluctance force, also called Maxwell&#39;s force, the polarized particles of the magneto-rheological fluid  11  form chain-like solidifications which extend along the magnetic field lines  31 . The solidifications result in increased viscosity, culminating in the formation of rigid or pressure-resistant solidifications, as a result of which the channel portion  20  is blocked in the first state and the movable locking element  40  or the piston  42  is fixed in its position. The blocking of the channel portion  20  can be pressure-resistant and block against pressures of more than 10 bar, 25 bar, 50 bar, 100 bar, 200 bar or more. 
     In the second state of the magnet device  30 , the magnetic flux of the magnetic field is either deflected in such a way that it does not passes through the channel portion  20  or only passes through it in a weakened form. This can be done, for example, by deflecting around the channel portion  20  by means of a magnetically soft conductor. Alternatively, the magnetic field of the magnet device  30  can be weakened by a second magnet unit  32 —see  FIG. 13 b   . This can occur by virtue of the magnetic fields of the magnet device  30  and the second magnet unit  32  canceling each other out or weakening each other at least in the region of the channel portion  20 . In this second state, the magneto-rheological fluid  11  can flow unhindered through the channel portion  20  and the safety bar  8  can be opened. In this state, a passenger can take a seat on the passenger accommodation  3  or get off after traveling on the amusement ride  2 . 
     The magnet device  30  can preferably have at least one permanent magnet  35 , with neodymium magnets being particularly preferably used. Furthermore, it is preferred for the magnet device  30  to completely surround the channel portion  20 . In the case of a circularly symmetrical cross section of the channel portion  20 , the magnet device  30  can be designed as a ring magnet with a diametric magnetization. By means of the permanently magnetic magnet device  30 , the locking device  1  can be designed analogously to a “normally closed” valve, which ensures that the channel portion  20  is blocked in an unactuated first state and the safety bar  8  cannot be released. 
     The second magnet unit  32  can be provided for actuating the magnet device  30 . The second magnet unit  32  can be arranged adjacent to the magnet device  30  and have at least one permanent magnet  35  and/or electromagnet  36 . 
     According to an embodiment that is not shown, at least one permanent magnet of the second magnet unit  32  can weaken or cancel the magnetic field of the magnet device  30  depending on the position of said magnet. To actuate or switch the magnet device  30  from the first state to the second state, the polarity of the permanent magnet relative to the magnet device  30  can be changed or vice versa. 
     According to  FIG. 13 b   , the at least one electromagnet  36  of the second magnet unit  32  can generate a magnetic field when energized, which field cancels or weakens the magnetic field of the magnet device  30  in the channel portion  20 . The magnetic field in the channel portion  20  can be canceled or weakened to such an extent that the magneto-rheological fluid  11  can flow freely through the channel portion  20 . 
     A development of the locking device  1  is shown in  FIG. 3 . In contrast to the embodiment shown in  FIG. 2 , the pressure compensation device  19  is not arranged on the line  12  between the first region  16  and the second region  17  of the pressure chamber  14  of the cylinder  15 , but is integrated into the pressure chamber  14  of the cylinder  15 . 
     The pressure compensation device  19  comprises a compensation piston which is also arranged movably in the cylinder  15 , preferably in the first region  16 , and divides the pressure chamber  14  of the cylinder  15  into a further, third region. The compensation piston can have a seal, which seals a pass gap between the compensation piston and the cylinder  15 . A reservoir is thus formed at a free end in the third region of the cylinder  15 , in which the pressure medium can be enclosed. 
     The development according to  FIG. 4  differs from the above-mentioned embodiments in that no pressure compensation device  19  is provided and in that the piston  42  has a piston rod  45  on the first pressure side  46  and on the second pressure side  47 , which can be led out of the cylinder  15  through the first region  16  and through the second region  17  through the respective free ends of the cylinder  15 , in each case through an opening. 
       FIG. 5  shows a development of the locking device  1  with a particularly compact structure, wherein the fluid channel  10  is integrated into the cylinder  15  or the locking element  40 . 
     The channel portion  20  is integrated into the piston  42  or into the pass gap between the piston  42  and the cylinder  15 . Furthermore, the magnet device  30  is arranged on the outer lateral surface of the piston  42  facing the cylinder  15  in such a way that the field lines of the magnetic field of the magnet device  30  pass through the pass gap  43  and the particles of the magneto-rheological fluid  11  are polarized transversely to the channel portion  20  formed by the pass gap  43 . In the first state of the magnet device  30 , the viscosity of the magneto-rheological fluid  11  in the pass gap is increased in such a way that it is solidified in the pass gap and blocks it. The locking element  40 , which is designed as a piston  42 , is thus fixed and the safety bar  8  of the passenger accommodation  3  is locked. 
     Analogously to the exemplary embodiment according to  FIG. 5 , the fluid channel  10  is also integrated into the cylinder  15  in  FIG. 6 . The pass gap  43  between the piston  42  and the cylinder  15  can be sealed by means of a seal. The channel portion  20  is arranged within the piston  42  and connects the first region  16  and the second region  17  of the cylinder  15 . To this end, at least one, preferably a plurality of lines  12  are arranged in the piston  42  between the outer lateral surface of the piston  42  facing the cylinder  15  and the piston rod  45 , the channel portion  20  in each line  12  being arranged or formed in the manner of a passage opening within the piston  42 . 
     The magnet device  30  is arranged on at least two opposing side walls  21 ,  22  of the channel portion  20  and is designed in such a way that the field lines  31  of the magnetic flux of the magnet device  30  pass through the channel portion  20 , preferably transversely to the flow direction. 
     Another development of the present locking device  1  can be seen in  FIG. 7 . The locking device  1  comprises a cylinder  15  having a piston  42  arranged in the cylinder  15 , which piston, in contrast to the above-mentioned exemplary embodiments, does not have a piston rod  45 , but rather teeth  48  which are formed between the first pressure side  46  and the second pressure side  47  on the outer lateral surface of the piston  42 . 
     The pass gap  43  of the piston  42  is sealed both in the region of the first pressure side  46  and of the second pressure side  47 , preferably by means of a seal, and the cylinder  15 , or the cylinder housing, has a gap through which a gear  49  protrudes through the cylinder housing into the cylinder  15  and meshes with the teeth  48 . The gear  49  is mounted in a rotationally movable manner and the operative connection between the gear  49  and the teeth  48  transfers a rotational movement of the gear  49  into a linear movement of the piston  42 . 
     The piston  42  divides the cylinder  15  into the two regions  16 ,  17 , which are assigned to the first pressure side  46  and the second pressure side  47 , the two regions  16 ,  17  being connected by means of the line  12 , and the channel portion  20  together with the magnet device  30  being arranged in the line  12 . 
     The gear  49  can be coupled to the axis of rotation of the safety bar  8 , as a result of which a rotational movement of the safety bar  8  is transferred to the piston  42 . When the field lines  31  of the magnetic flux of the magnet device  30  pass through the channel portion  20 , the channel portion  20  is blocked and the magneto-rheological fluid  11  cannot flow from the first region  16  of the cylinder  15  into the second region  17  and vice versa, thereby locking the position of the piston  42  or the position of the safety bar  8  and holding the safety bar  8  in its position. 
       FIG. 8  shows a combination of the exemplary embodiments according to  FIG. 6  and  FIG. 7 , wherein the line  12  with the channel portion  20  is incorporated into the piston  42  according to  FIG. 6  in such a way that the line  12  connects the first pressure side  46  to the second pressure side  47  of the piston  42 . The fluid channel  10  is therefore completely integrated into the cylinder  15 , as a result of which the locking device  1  is designed to be particularly compact and robust. 
       FIG. 9  shows a passenger accommodation  3  having a locking device  1  according to a second exemplary embodiment. The passenger accommodation  3  has the seat receptacle  4  with the seat cushion  5  and the back cushion  6  and the safety bar  8  which is arranged in front of the seat cushion  5  and designed to keep a passenger safely in the passenger accommodation  3  while traveling on the amusement ride  2 . The safety bar  8  is arranged on a holder  7  such that it can rotate or pivot in the axis of rotation. 
     A detailed view of the locking device  1  according to  FIG. 9  is shown in  FIG. 10 , in which the fluid channel  10  is designed as a circular channel  50 . The circular channel  50  forms the channel portion  20  between an inner shaft  51  and an outer shaft  52 , the respective opposing side walls  21  of the channel portion  20  being formed by the inner shaft  51  and the outer shaft  52 . The outer shaft  52  can be formed by a hollow shaft or cylindrical recess in the holder  7 . 
     The inner shaft  51  forms the locking element  40  and is arranged eccentrically with respect to the outer shaft  52 , as a result of which the circular channel  50  has a variable width around the circumference about the longitudinal axis L. Due to the eccentric mounting of the inner shaft  51 , the channel portion  20  of the fluid channel  10  has a constriction  55 , which is also displaced when the inner shaft  51  rotates. 
     The circular channel  50  is filled with the magneto-rheological fluid  11  and the magnet device  30  is arranged around the fluid channel  10  in such a way that the field lines  31  of the magnetic field of the magnet device  30  pass through the channel portion  20  or the circular channel  50 . In the presence of the magnetic field lines, the particles in the magneto-rheological fluid  11  form chain-like solidifications along the magnetic field lines, which solidifications preferably extend substantially radially. The solidifications block in a wedge-like manner the inner shaft  51  from rotating in the magnetic field of the magnet device in the region of the constriction  55 , as a result of which a rotation between the inner shaft  51  and the outer shaft  52  is prevented. The inner shaft  51  can be coupled directly or indirectly to the safety bar  8 . 
     A development of the exemplary embodiment of the locking device  1  according to  FIGS. 9 and 10  is shown in  FIGS. 11 a  and 11 b   . The inner shaft  51  and the outer shaft  52  are arranged coaxially with one another in the longitudinal axis L. The circular channel  50  has a constant width around the circumference about the longitudinal axis L of the inner shaft  51  or the outer shaft  52 . 
     A large number of rolling elements  54  are arranged in the circular channel  50  and, in the manner of a roller bearing, are in operative contact with the inner shaft  51  as well as in operative contact with the outer shaft  52  and perform a rolling movement when the inner shaft  51  is rotated relative to the outer shaft  52 . 
     The circular channel  50  is filled with the magneto-rheological fluid  11  and the magnet device  30  is arranged around the fluid channel  10  in such a way that the field lines  31  of the magnetic field of the magnet device  30  pass through the channel portion  20  or the circular channel  50 . In the presence of the magnetic field lines, the particles in the magneto-rheological fluid  11  form solidifications along the magnetic field lines. As shown in  FIG. 11 b   , the solidifications block the rolling elements  54 , thereby blocking a rotation of the inner shaft  51 . The inner shaft  51  can be coupled directly or indirectly to the safety bar  8 . 
       FIG. 12 a    shows a third development of the second exemplary embodiment of the locking device  1 , the inner shaft  51  and the outer shaft  52  being aligned and mounted coaxially with respect to each other analogously to the exemplary embodiment shown in  FIGS. 11 a  and 11 b   , and the fluid channel  10  is formed as a circular channel  50  between the inner shaft  51  and the outer shaft  52 . A large number of throttles  23  are arranged on an outer lateral surface  53  of the inner shaft  51  and protrude from the outer lateral surface  53  of the inner shaft  51  in the direction of the outer shaft  52 . Each throttle  23  is designed as a link  26 , each link  26  being formed from a first flank  26   a  and a second flank  26   b . The first flank  26   a  extends approximately tangentially from the outer lateral surface  53  and the second flank  26   b  extends approximately radially. The first flank  26   a  and the second flank  26   b  meet at a point which forms a constriction  55  and thus constitutes the narrowest cross section of the fluid channel  10 . 
     The particles of the magneto-rheological fluid  11  polarized along the magnetic field lines  31  of the magnetic field of the magnet device  30  are forced by the second flank into the narrowest cross section like a wedge when the inner shaft  51  rotates in a first direction according to  FIG. 10 b    and block a further rotation in the first direction A. In contrast, even in the presence of the magnetic field in the fluid channel  10 , a rotation in the second direction B according to  FIG. 12 b    is not completely blocked, but merely damped. As soon as the magnetic field of the magnet device  30  is deflected, weakened or destroyed, the inner shaft  51  can be rotated unhindered both in a first direction A′ and in a second direction B′. The locking device  1  therefore forms a freewheel in the first state. The freewheel can be used, for example, to block a pivoting of the safety bar  8  in the first direction A′; the first direction A′ would cause the safety bar  8  to be opened and the second direction B would cause the safety bar  8  to be closed. Therefore, while traveling on an amusement ride  2 , the passenger cannot open the safety bar  8 , but can readjust the safety bar  8  so that it holds them even more securely in the passenger accommodation  3 . 
     Detailed representations of different embodiments of the channel portion  20  can be seen in  FIGS. 13 a    to  17 . For a better understanding, some of the detailed representations are provided with circuit signals E, which reflect a function of the channel portion  20 . 
     A detail of the line  12  of the fluid channel  10  with the channel portion  20  and the magnet device  30  is shown in  FIGS. 13 a  and 13 b   . The magnet device  30  is arranged on at least two opposing side walls  21 ,  22  around the channel portion  20 , as a result of which the magnetic field lines  31  of the magnetic field of the magnet device  30  pass through the channel portion  20 . 
     As shown in  FIG. 13 b   , the magnet device  30  can comprise a magnetically soft iron circuit  37  with an air gap  38 , wherein the channel portion  20  is arranged in the air gap  38 . The magnet device  30  can also have at least one permanent magnet  35  which introduces a magnetic flux into the iron circuit  37 , the field lines  31  of which pass through the channel portion  20  in the air gap  38 . Furthermore, a coil which can be supplied with electrical energy and which forms the second magnet unit  32  can be arranged on the iron circuit  37 . 
     Upstream and downstream of the channel portion  20 , a tapered portion  25  is arranged which forms a cross-sectional reduction or expansion, as a result of which, in comparison with the remaining line  12 , the channel portion  20  has a reduced flow cross section which is preferably less than ½, more preferably less than ¼, even more preferably less than ⅛ or even less than 1/16. 
     The embodiment of the channel portion  20  according to  FIG. 12  has a throttle  23  which is formed by a cascade. By means of the cascade, the magneto-rheological fluid  11  is guided through a tapered cross section. By means of the multiple deflection, the effective length of the channel portion  20  is extended, thereby further increasing the blocking effect in the channel portion  20  when the magnet device  30  is in the first state. 
     A further embodiment of the channel portion  20  can be seen in  FIG. 15 , in which the channel portion  20  has a cross-sectional taper through a tapered portion  25  along the first flow direction A. The tapered portion  25  tapers the flow channel in the first flow direction A and widens the flow channel in the second flow direction B. This embodiment of the channel portion  20  forms a kind of one-way valve. The channel portion  20  blocks in the first flow direction A, during which time the second flow direction B is released in a damped manner. This effect is due to the fact that the polarized particles or the solidifications formed by the particles clog or block in the magnetic field in the second flow direction A due to the wedge action of the nozzle of the channel portion  20 . 
     The magnet device  30  can be a conically diametrically magnetized permanent magnet, the magnetic field lines passing through the channel portion  20  in a slightly curved manner, thereby enhancing the characteristics of the freewheel. 
     A development of the channel portion  20  according to  FIG. 15  is shown in  FIG. 16 , wherein the tapered portion  25  and/or the magnet device  30  is movable in the first flow direction A or the second flow direction B. By means of the variable relative position between the tapered portion  25  and the magnet device  30 , the properties of the channel portion  20  or the properties of the one-way valve thus formed can be adjusted. 
     A movable tapered portion (not shown) can also be arranged in the magneto-rheological fluid  11  in the inner (flown-through) area of the tapered portion  25 , and, depending on the flow direction of the magneto-rheological fluid  11 , either mechanically tapers the tapered portion  25  or is pushed out of the tapered portion  25 , thus reducing the blocking effect. By means of the movable tapered portion within the channel portion  20 , the characteristics of the one-way or non-return valve can be improved. 
     In addition, the channel portion  20  can have a conventional hydraulic valve  70 . By combining the channel portion  20  with a conventional hydraulic valve  70 , valve leakage can be accomplished by reducing the pressure acting on the hydraulic valve  70  through the channel portion  20 . The channel portion  20  thus forms a leakage safeguard for the hydraulic valve  70 . 
     LIST OF REFERENCE NUMERALS 
     
         
           1  Locking device 
           2  Amusement ride 
           3  Passenger accommodation 
           4  Seat receptacle 
           5  Seat cushion 
           6  Back cushion 
           7  Holder 
           8  Safety bar 
           10  Fluid channel 
           11  Fluid 
           12  Line 
           14  Pressure chamber 
           15  Cylinder 
           16  First region 
           17  Second region 
           18  Conveying means 
           19  Pressure compensation device 
           20  Channel portion 
           21  Side wall 
           22  Side wall 
           23  Throttle 
           25  Tapered portion 
           26  Link 
           30  Magnet device 
           31  Field lines 
           32  Second magnet unit 
           35  Permanent magnet 
           36  Electromagnet 
           37  Iron circuit 
           38  Air gap 
           40  Locking element 
           42  Piston 
           43  Pass gap 
           44  Seal 
           45  Piston rod 
           46  First pressure side 
           47  Second pressure side 
           48  Teeth 
           49  Gear 
           50  Circular channel 
           51  Inner shaft 
           52  Outer shaft 
           53  Lateral surface 
           54  Rolling element 
           55  Constriction 
           70  Hydraulic valve 
         A First flow direction 
         B Second flow direction 
         D Axis of rotation 
         L Longitudinal axis