IPC분류정보
국가/구분 |
United States(US) Patent
등록
|
국제특허분류(IPC7판) |
|
출원번호 |
US-0499217
(1983-05-31)
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발명자
/ 주소 |
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출원인 / 주소 |
|
대리인 / 주소 |
Renner, Otto, Boisselle & Lyon
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인용정보 |
피인용 횟수 :
26 인용 특허 :
2 |
초록
▼
Landing gear mechanism includes a built-in hydraulic actuator which may be actuated to provide a heavy load range, soft spring rate during take-off with a heavy take-off weight and a lower load range, softer spring rate after take-off and prior to landing with a lighter landing weight to yield more
Landing gear mechanism includes a built-in hydraulic actuator which may be actuated to provide a heavy load range, soft spring rate during take-off with a heavy take-off weight and a lower load range, softer spring rate after take-off and prior to landing with a lighter landing weight to yield more shock strut stroke for a given range of vertical load during landing. A special taxi valve allows for some fluid to bypass the main orifice more freely to and from the lower piston damping chamber to the shock strut air-oil chamber as soon as the landing energy stroke is complete to greatly reduce or eliminate high damping loads that might otherwise take place as the gear negotiates bumps. Such a valve may automatically be set to close for landing by the action of the gear extension during a subsquent take-off, thus reactivating the main orifice. For normal bounce, air in the primary chamber drives oil through an orifice in a rebound damper valve to the lower piston chamber in order to lift the supported weight of the aircraft as part of the return stroke. However, when riding over a hole, the air acts freely on the differential or net piston area of the gear which area is too small to lift the supported weight of the aircraft, but is large enough to accelerate the unsprung mass of the gear quickly into the hole. An anti-cavitation bypass valve assures oil refill in the lower portion of the piston chamber as the gear extends. Also, a pressure actuated valve may be provided in the metering pin which, upon sensing cavitation in the lower piston chamber during extension, will open a series of holes both above and below the main orifice, providing a flow path for oil around the main orifice, to eliminate the aforementioned cavitation. The metering pin is part of this flow path. A check valve may be provided at the top of the metering pin to keep the metering pin full of oil by allowing free flow of oil upward but not allowing downward flow, thus preventing the intake and down flow of shock strut air during the anti-cavitation re-fill of the lower piston chamber. An extension snubber valve may also be provided to develop piston rebound damping during the last portion of stroke of the landing gear before full extension thereof during take-off.
대표청구항
▼
1. A landing gear mechanism comprising a main cylinder, a main strut piston axially movable within said main cylinder, means for controlling the rate of instroke of said main strut piston within said main cylinder including restrictor means defining with the outboard end of said main strut piston a
1. A landing gear mechanism comprising a main cylinder, a main strut piston axially movable within said main cylinder, means for controlling the rate of instroke of said main strut piston within said main cylinder including restrictor means defining with the outboard end of said main strut piston a lower piston chamber therebetween, said restrictor means having a restricted flow passage therethrough for controlling the rate of flow of hydraulic fluid between said lower piston chamber and the opposite side of said restrictor means, overload relief valve means for relieving excess pressure from said lower piston chamber in the event that an overpressure condition should develop during instroke movements of said landing gear mechanism while taxiing, and means for blocking communication between said overload relief valve means and said lower piston chamber during landing, said means for blocking communication between said overload relief valve means and said lower piston chamber comprising a rotary valve vane movable between a first position covering said overload relief valve means during landing and a second position uncovering said overload relief valve means after landing has taken place. 2. A landing gear mechanism comprising a main cylinder, a main strut piston axially movable within said main cylinder, means for controlling the rate of instroke of said main strut piston within said main cylinder comprising restrictor means defining with the outboard end of said main strut piston a lower piston chamber therebetween, said restrictor means having a restricted flow passage therethrough for controlling the rate of flow of hydraulic fluid between said lower piston chamber and the opposite side of said restrictor means, and means for providing a bypass flow path for hydraulic fluid from said lower piston chamber to the opposite side of said restrictor means whenever said landing gear mechanism engages a bump during taxiing to reduce the damping loads that would otherwise occur if all such hydraulic fluid were required to pass through said restricted flow passage, said means for providing a bypass flow path comprising a bypass passage around said restricted flow passage, and means for opening said bypass passage as soon as pressure equilibrium is established within said landing gear mechanism on opposite sides of said restricted flow passage after landing to permit sudden compression of said landing gear mechanism for faster instroke as necessitated by said landing gear mechanism going over bumps and the like, said means for opening said bypass passage comprising a rotary valve vane movable between a first position closing said bypass passage and a second position opening said bypass passage, and means for moving said rotary valve vane from said first position to said second position after said landing gear mechanism has been partially compressed after landing. 3. The landing gear mechanism of claim 2 further comprising a pressure actuated valve means for blocking fluid flow through said bypass passage when said landing gear mechanism is fully extended and for permitting fluid flow through said bypass passage after landing has taken place. 4. The landing gear mechanism of claim 3 further comprising spring means for urging said pressure actuated valve means out of the path of said bypass passage, said pressure actuated valve means having a valve port which when open to the hydraulic fluid in said lower piston chamber during landing causes said pressure actuated valve means to move into the path of said bypass passage in opposition to said spring means, said rotary valve vane when moved between said first and second positions also respectively opening and closing said valve port to the hydraulic fluid in said lower piston chamber. 5. The landing gear mechanism of claim 4 further comprising a radial slot extending radially outwardly from said valve port beyond said rotary valve vane when in said second position closing said valve port to permit restricted flow of hydraulic fluid from said valve port to said lower piston chamber after such pressure equilibrium has been established to permit movement of said pressure actuated valve means out of the path of said bypass passage. 6. The landing gear mechanism of claim 4 further comprising restrictor means in said valve port for causing delayed movement of said pressure actuated valve means into the path of said bypass passage after said valve port has been opened by movement of said rotary valve vane to said first position. 7. The landing gear mechanism of claim 2 further comprising a rebound flapper valve at the end of said bypass passage opposite said lower piston chamber, said rebound flapper valve being movable away from said bypass passage to permit unrestricted flow through said bypass passage during instroke movements of said landing gear mechanism while taxiing, and being movable towards said bypass passage to restrict the flow through said bypass passage during outstroke movements of said landing gear mechanism while taxiing to dampen the outstroke of said landing gear mechanism when weighted for normal bounce during taxiing. 8. The landing gear mechanism of claim 7 wherein said rebound flapper valve when moved towards said bypass passage still provides a restricted flow passage to said bypass passage. 9. The landing gear mechanism of claim 2 further comprising overload relief valve means for relieving excess pressure from said lower piston chamber in the event that an overpressure condition should develop during instroke movements of said landing gear mechanism while taxiing. 10. The landing gear mechanism of claim 2 wherein said main strut piston includes a net annular surface area which is acted upon by the air pressure in said main cylinder tending to outstroke said main strut piston, said surface area being large enough to accelerate the upsprung mass of said landing gear mechanism into a hole but too small to lift the supported weight of the aircraft, and anticavitation means for preventing cavitation in said lower piston chamber during sudden outstroking of said landing gear mechanism into a hole. 11. The landing gear mechanism of claim 2 wherein said restrictor means comprises a restrictor orifice assembly supported by said main cylinder within said main strut piston against axial movement relative to said main cylinder, said restrictor orifice assembly defining with the outboard end of said main strut piston said lower piston chamber therebetween, said restrictor orifice assembly having an opening therethrough, a metering pin assembly attached to said main strut piston for movement therewith, said metering pin assembly including a metering pin extending through said opening defining an orifice therebetween for controlling the rate of flow of hydraulic fluid between said lower piston chamber and the opposite side of said restrictor orifice assembly, said means for moving said rotary valve vane comprising a ramp on said metering pin, and roller means operatively connected to said rotary valve vane, said roller means being engageable with said ramp when said landing gear mechanism is fully extended to move said rotary valve vane to said first position closing said bypass passage and being disengageable from said ramp after landing has taken place to move said rotary valve vane to said second position opening said bypass passage. 12. A landing gear mechanism comprising a main cylinder, a main strut piston axially movable within said main cylinder, means for controlling the rate of instroke of said main strut piston within said main cylinder, and means for dampening the outstroke of said landing gear mechanism as said landing gear mechanism reaches its fully extended position during take-off to reduce shock loads in said landing gear mechanism, said means for dampening comprising a retaining ring between said main strut piston and main cylinder, means mounting said retaining ring on the outer surface of said main strut piston for movement therewith, said retaining ring having a plurality of longitudinal grooves in the radial outer surface thereof, and snubber plates axially movable within said grooves between a first position in which hydraulic fluid is permitted to readily flow through said grooves during the majority of the outstroke of said landing gear mechanism during take-off and a second position restricting such flow through said grooves as the landing gear mechanism approaches its fully extended position. 13. The landing gear mechanism of claim 12 wherein said snubber plates have longitudinal slots therein of a length greater than the length of said grooves in said retaining ring, said snubber plates when in said first position permitting flow of hydraulic fluid into said grooves through opposite ends of said slots which extend beyond the ends of said grooves, and said snubber plates when in said second position substantially restricting the flow of hydraulic fluid into said grooves through the lower ends of said slots. 14. The landing gear mechanism of claim 13 wherein said slots in said snubber plates have extensions at the lower ends thereof through which restricted flow is permitted when said snubber plates are in said second position. 15. The landing gear mechanism of claim 14, further comprising spring means for biasing said snubber plates towards said first position for movement of said snubber plates with said retaining ring during the majority of the outstroke of said landing gear mechanism during take-off, and stop means for restraining said snubber plates against further movement with said retaining ring when said landing gear mechanism approaches its fully extended position. 16. The landing gear mechanism of claim 15 wherein said stop means comprises a bearing adjacent the outboard end of said main cylinder. 17. The landing gear mechanism of claim 13 further comprising a restricted orifice in said retaining ring through which hydraulic fluid may pass from one side of said retaining ring to the other after said grooves in said retaining ring are substantially closed by said snubber plates as said landing gear mechanism approaches its fully extended position during take-off. 18. A landing gear mechanism comprising a main cylinder, a main strut piston axially movable within said main cylinder, means for controlling the rate of instroke of said main strut piston within said main cylinder, means for setting the air spring load range of said landing gear mechanism to provide a load setting for said landing gear mechanism while in the static condition prior to take-off, and means for altering the air spring load range of said landing gear mechanism after take-off to provide a lighter load setting for said landing gear mechanism for landing, said means for altering the air spring load rnage of said landing gear mechanism after take-off comprises a hydraulic actuator within said landing gear mechanism, said hydraulic actuator comprising a hydraulic piston axially movable within said main cylinder, said hydraulic piston having one side exposed to an air chamber within said main cylinder between said hydraulic piston and the outboard end of said main strut piston, and having the other side exposed to a hydraulic chamber between said hydraulic piston and the head end of said main cylinder, means for introducing hydraulic fluid into said hydraulic chamber to move said hydraulic piston away from said head end of said main cylinder for reducing the length of said air chamber while said landing gear mechanism is in the static position prior to take-off, and means for removing hydraulic fluid from said hydraulic chamber after take-off to permit movement of said hydraulic piston toward the head end of said main cylinder by the air pressure in said air chamber acting on said hydraulic piston to increase the length of said air chamber to establish a lighter load setting for said landing gear mechanism after take-off. 19. The landing gear mechanism of claim 18 further comprising a secondary piston in said main cylinder between said hydraulic piston and the outboard end of said main strut piston, said secondary piston cooperating with said hydraulic piston to define said air chamber therebetween, and means for supplying air pressure to said air chamber. 20. The landing gear mechanism of claim 19 wherein there is another air chamber within said main cylinder between said secondary piston and the outboard end of said main strut piston, and means for supplying air pressure and hydraulic fluid to said another chamber. 21. The landing gear mechanism of claim 20 wherein said means for controlling the rate of instroke of said main strut piston within said main cylinder comprises a restrictor orifice assembly at the outboard end of said another chamber, said restrictor orifice assembly defining with the outboard end of said main strut piston a lower piston chamber therebetween, said restrictor orifice assembly having an opening therethrough, and a metering pin assembly attached to said main strut piston for movement therewith, said metering pin assembly including a metering pin extending through said opening in said restrictor orifice assembly defining an orifice therebetween for controlling the rate of flow of hydraulic fluid to and from said lower piston chamber. 22. The landing gear mechanism of claim 21 further comprising means for providing for increased flow of hydraulic fluid from said lower piston chamber to said another chamber whenever said landing gear mechanism engages a bump during taxiing to reduce the damping loads that would otherwise occur if all of such hydraulic fluid were required to pass through said orifice. 23. The landing gear mechanism of claim 22 wherein said means providing for increased flow of hydraulic fluid from said lower piston chamber comprises a bypass passage around said orifice, and means for opening said bypass passage as soon as pressure equilibrium is established within said landing gear mechanism on opposite sides of said restrictor orifice assembly after landing to permit sudden compression of said landing gear mechanism for faster instroke as necessitated by said landing gear mechanism going over bumps. 24. The landing gear mechanism of claim 23 wherein said means for opening said bypass passage comprises a rotary valve vane movable between a first position closing said bypass passage and a second position opening said bypass passage, and means for moving said rotary valve vane from said first position to said second position after said landing gear mechanism has been partially compressed after landing. 25. The landing gear mechanism of claim 24 wherein said means for moving said rotary valve vane comprises a ramp on said metering pin, and roller means operatively connected to said rotary valve vane, said roller means being engageable with said ramp when said landing gear mechanism is fully extended to move said rotary valve vane to said first position closing said bypass passage and being disengageable from said ramp after landing has taken place to move said rotary valve vane to said second position opening said bypass passage. 26. The landing gear mechanism of claim 25 further comprising a pressure actuated valve means for blocking fluid flow through said bypass passage when said landing gear mechanism is fully extended and for permitting fluid flow through said bypass passage after landing has taken place. 27. The landing gear mechanism of claim 26 further comprising spring means for urging said pressure actuated valve means out of the path of said bypass passage, said pressure actuated valve means having a valve port which when open to the hydraulic fluid in said lower piston chamber during landing causes said pressure actuated valve means to move into the path of said bypass passage in opposition to said spring means, said rotary valve vane when moved between said first and second positions also respectively opening and closing said valve port to the hydraulic fluid in said lower piston chamber. 28. The landing gear mechanism of claim 27 further comprising a radial slot extending radially outwardly from said valve port beyond said rotary valve vane when in said second position closing said valve port to permit restricted flow of hydraulic fluid from said valve port to said lower piston chamber after such pressure equilibrium has been established to permit movement of said pressure actuated valve means out of the path of said bypass passage. 29. The landing gear mechanism of claim 28 wherein said bypass passage and pressure actuated valve means are contained within said restrictor orifice assembly. 30. The landing gear mechanism of claim 27 further comprising restrictor means in said valve port for causing delayed movement of said pressure actuated valve means into the path of said bypass passage after said valve port has been opened by movement of said rotary valve vane to said first position. 31. The landing gear mechanism of claim 23 further comprising a rebound flapper valve at the end of said bypass passage opposite said lower piston chamber, said rebound flapper valve being movable away from said bypass passage to permit unrestricted flow through said bypass passage during instroke movements of said landing gear mechanism while taxiing, and being movable towards said bypass passage to restrict the flow through said bypass passage during outstroke movements of said landing gear mechanism while taxiing to dampen the outstroke of said landing gear mechanism when weighted for normal bounce during taxiing. 32. The landing gear mechanism of claim 31 wherein said rebound flapper valve when moved towards said bypass passage still provides a restricted flow passage to said bypass passage. 33. The landing gear mechanism of claim 18 wherein said main strut piston has a net annular surface area which is acted upon by the air pressure within said main cylinder tending to outstroke said landing gear mechanism, said surface area being large enough to accelerate the unsprung mass of said main strut piston into a hole but being too small to lift the supported weight of the aircraft supported thereby. 34. The landing gear mechanism of claim 21 further comprising check valve means for supplementing the flow of hydraulic fluid to said lower piston chamber during the outstroke of said landing gear mechanism during taxiing. 35. The landing gear mechanism of claim 34 wherein said check valve means is contained within said restrictor orifice assembly. 36. The landing gear mechanism of claim 21 further comprising overload relief valve means for relieving excess pressure from said lower piston chamber in the event that an overpressure condition should develop during instroke movements of said landing gear mechanism while taxiing. 37. The landing gear mechanism of claim 36 further comprising means for blocking communication between said overload relief valve means and said lower piston chamber during landing. 38. The landing gear mechanism of claim 37 wherein said means for blocking communication between said overload relief valve means and said lower piston chamber comprises said rotary valve vane which covers said overload relief valve means when in said first position. 39. The landing gear mechanism of claim 21 wherein said main strut piston includes a net annular surface area which is acted upon by the air pressure in said main cylinder tending to outstroke said main strut piston, said surface area being large enough to accelerate the unsprung mass of said landing gear mechanism into a hole but too small to lift the supported weight of the aircraft, and anticavitation means for preventing cavitation in said lower piston chamber during sudden outstroking of said landing gear mechanism into a hole. 40. The landing gear mechanism of claim 39 wherein said anticavitation means comprises a bypass sleeve valve axially movable within said metering pin, said bypass sleeve valve and metering pin each having a plurality of axially spaced holes therein which may be brought into and out of alignment with each other upon moving said bypass sleeve valve in opposite directions, said holes when in alignment with each other allowing for flow of hydraulic fluid through said bypass sleeve valve around said orifice to supplement the flow of hydraulic fluid through said orifice to said lower piston chamber, means for moving said bypass sleeve valve to a first position in which said holes are out of alignment with each other whenever the hydraulic fluid pressure in said lower piston chamber is below a predetermined level and for moving said bypass sleeve valve to a second position in which said holes are in alignment with each other whenever the hydraulic fluid pressure in said lower piston chamber drops below such predetermined level. 41. The landing gear mechanism of claim 40 wherein said means for moving said bypass sleeve valve comprises a spring urging said bypass sleeve valve to said second position, and a differential surface area on said bypass sleeve valve acted upon by the hydraulic fluid pressure in said lower piston chamber to move said bypass sleeve valve to said first position only when the hydraulic fluid pressure in said lower piston chamber is above such predetermined level. 42. The landing gear mechanism of claim 40 further comprising check valve means for allowing for flow of hydraulic fluid through the center of said metering pin during the instroke of said landing gear mechanism and for blocking such flow through said metering pin when said landing gear mechanism suddenly starts to outstroke into a hole to keep hydraulic fluid inside said metering pin and prevent trapped vapors from entering said metering pin during such sudden outstroke of said landing gear mechanism. 43. The landing gear mechanism of claim 18 further comprising rebound damper means for dampening the outstroke of said landing gear mechanism as said landing gear mechanism reaches its fully extended position during take-off to reduce shock loads in said landing gear mechanism. 44. The landing gear mechanism of claim 18 wherein said means for controlling the rate of instroke of said main strut piston within said main cylinder comprises restrictor means defining with the outboard end of said main strut piston a lower piston chamber therebetween, said restrictor means having a restricted flow passage therethrough for controlling the rate of flow of hydraulic fluid between said lower piston chamber and the opposite side of said restrictor means. 45. The landing gear mechanism of claim 44 further comprising means for providing a bypass flow path for hydraulic fluid from said lower piston chamber to the opposite side of said restrictor means whenever said landing gear mechanism engages a bump during taxiing to reduce the damping loads that would otherwise occur if all such hydraulic fluid were required to pass through said restricted flow passage. 46. The landing gear mechanism of claim 45 wherein said means for providing a bypass fluid path comprises a bypass passage around said restricted flow passage, and means for opening said bypass passage as soon as pressure equilibrium is established within said landing gear mechanism on opposite sides of said restricted flow passage after landing to permit sudden compression of said landing gear mechanism for faster instroke as necessitated by said landing gear mechanism going over bumps. 47. A landing gear mechanism comprising a main cylinder, a main strut piston axially movable within said main cylinder, means for controlling the rate of instroke of said main strut piston within said main cylinder, means for setting the air spring load range of said landing gear mechanism to provide a load setting for said landing gear mechanism while in the static condition prior to take-off, means for altering the air spring load range of said landing gear mechanism after take-off to provide a lighter load setting for said landing gear mechanism for landing, and rebound damper means for dampening the outstroke of said landing gear mechanism as said landing gear mechanism reaches its fully extended position during take-off to reduce shock loads in said landing gear mechanism, said rebound damper means comprising a retaining ring between said main strut piston and main cylinder, means mounting said retaining ring on the outer surface of said main strut piston for movement therewith, said retaining ring having a plurality of longitudinal grooves in the radial outer surface thereof, and snubber plates axially movable within said grooves between a first position in which hydraulic fluid is permitted to readily flow through said grooves during the majority of the outstroke of said landing gear mechanism during take-off and a second position restricting such flow through said grooves as the landing gear mechanism approaches its fully extended position. 48. The landing gear mechanism of claim 47 wherein said snubber plates have longitudinal slots therein of a length greater than the length of said grooves in said retaining ring, said snubber plates when in said first position permitting flow of hydraulic fluid into said grooves through opposite ends of said slots which extend beyond the ends of said grooves, and said snubber plates when in said second position substantially restricting the flow of hydraulic fluid into said grooves through the lower ends of said slots. 49. The landing gear mechanism of claim 48 wherein said slots in said snubber plates have extensions at the lower ends thereof through which restricted flow is permitted when said snubber plates are in said second position. 50. The landing gear mechanism of claim 49 further comprising spring means for biasing said snubber plates towards said first position for movement of said snubber plates with said retaining ring during the majority of the outstroke of said landing gear mechanism during take-off, and stop means for restraining said snubber plates against further movement with said retaining ring when said landing gear mechanism approaches its fully extended position. 51. The landing gear mechanism of claim 50 wherein said stop means comprises a bearing adjacent the outboard end of said main cylinder. 52. The landing gear mechanism of claim 48 further comprising a restricted orifice in said retaining ring through which hydraulic fluid may pass from one side of said retaining ring to the other after said grooves in said retaining ring are substantially closed by said snubber plates as said landing gear mechanism approaches its fully extended position during take-off. 53. A landing gear mechanism comprising a main cylinder, a main strut piston axially movable within said main cylinder, and means for controlling the rate of instroke of said main strut piston within said main cylinder comprising a restrictor orifice assembly supported by said main cylinder within said main strut piston against axial movement relative to said main cylinder, said restrictor orifice assembly defining with the outboard end of said main strut piston a lower piston chamber therebetween, said restrictor orifice assembly having an opening therethrough, a metering pin assembly attached to said main strut piston for movement therewith, said metering pin assembly including a metering pin extending through said opening defining an orifice therebetween for controlling the rate of flow of hydraulic fluid between said lower piston chamber and the opposite side of said restrictor orifice assembly, and means for providing a bypass flow path for hydraulic fluid from said lower piston chamber to the opposite side of said restrictor orifice assembly whenever said landing gear mechanism engages a bump during taxiing to reduce the damping loads that would otherwise occur if all such hydraulic fluid were required to pass through said orifice, said means for providing a bypass flow path comprising a bypass passage around said orifice, and means for opening said bypass passage as soon as pressure equilibrium is established within said landing gear mechanism on opposite sides of said orifice after landing to permit sudden compression of said landing gear mechanism for faster instroke as necessitated by said landing gear mechanism going over bumps, said means for opening said bypass passage comprising a rotary valve vane movable between a first position closing said bypass passage and a second position opening said bypass passage, and means for moving said rotary valve vane from said first position to said second position after said landing gear mechanism has been partially compressed after landing. 54. The landing gear mechanism of claim 53, wherein said means for moving said rotary valve vane comprises a ramp on said metering pin, and roller means operatively connected to said rotary valve vane, said roller means being engageable with said ramp when said landing gear mechanism is fully extended to move said rotary valve vane to said first position closing said bypass passage and being disengageable from said ramp after landing has taken place to move said rotary valve vane to said second position opening said bypass passage. 55. The landing gear mechanism of claim 54 further comprising a pressure actuated valve means for blocking fluid flow through said bypass passage when said landing gear mechanism is fully extended and for permitting fluid flow through said bypass passage after landing has taken place. 56. The landing gear mechanism of claim 55 further comprising spring means for urging said pressure actuated valve means out of the path of said bypass passage, said pressure actuated valve means having a valve port which when open to the hydraulic fluid in said lower piston chamber during landing causes said pressure actuated valve means to move into the path of said bypass passage in opposition to said spring means, said rotary valve vane when moved between said first and second positions also respectively opening and closing said valve port to the hydraulic fluid in said lower piston chamber. 57. The landing gear mechanism of claim 56 further comprising a radial slot extending radially outwardly from said valve port beyond said rotary valve vane when in said second position closing said valve port to permit restricted flow of hydraulic fluid from said valve port to said lower piston chamber after such pressure equilibrium has been established to permit movement of said pressure actuated valve means out of the path of said bypass passage. 58. The landing gear mechanism of claim 57 wherein said bypass passage and pressure actuated valve means are contained within said restrictor orifice assembly. 59. The landing gear mechanism of claim 56 further comprising restrictor means in said valve port for causing delayed movement of said pressure actuated valve means into the path of said bypass passage after said valve port has been opened by movement of said rotary valve vane to said first position. 60. The landing gear mechanism of claim 53 further comprising a rebound flapper valve at the end of said bypass passage opposite said lower piston chamber, said rebound flapper valve being movable away from said bypass passage to permit unrestricted flow through said bypass passage during instroke movements of said landing gear mechanism while taxiing, and being movable towards said bypass passage to restrict the flow through said bypass passage during outstroke movements of said landing gear mechanism while taxiing to dampen the outstroke of said landing gear mechanism when weighted for normal bounce during taxiing. 61. The landing gear mechanism of claim 53 further comprising overload relief valve means for relieving excess pressure from said lower piston chamber in the event that an overpressure condition should develop during instroke movements of said landing gear mechanism while taxiing. 62. The landing gear mechanism of claim 53 wherein said main strut piston includes an annular surface area which is acted upon by the air pressure in said main cylinder tending to outstroke said main strut piston, said surface area being large enough to accelerate the unsprung mass of said landing gear mechanism into a hole but too small to lift the supported weight of the aircraft, and anticavitation means for preventing cavitation in said lower piston chamber during sudden outstroking of said landing gear mechanism into a hole. 63. A landing gear mechanism comprising a main cylinder, a main strut piston axially movable within said main cylinder, and means for controlling the rate of instroke of said main strut piston within said main cylinder comprising a restrictor orifice assembly supported by said main cylinder within said main strut piston against axial movement relative to said main cylinder, said restrictor orifice assembly defining with the outboard end of said main strut piston a lower piston chamber therebetween, said restrictor orifice assembly having an opening therethrough, a metering pin assembly attached to said main strut piston for movement therewith, said metering pin assembly including a metering pin extending through said opening defining an orifice therebetween for controlling the rate of flow of hydraulic fluid between said lower piston chamber and the opposite side of said restrictor orifice assembly, means for providing a bypass flow path for hydraulic fluid from said lower piston chamber to the opposite side of said restrictor orifice assembly whenever said landing gear mechanism engages a bump during taxiing to reduce the damping loads that would otherwise occur if all such hydraulic fluid were required to pass through said orifice, said means for providing a bypass flow path comprising a bypass passage around said orifice, and means for opening said bypass passage as soon as pressure equilibrium is established within said landing gear mechanism on opposite sides of said orifice after landing to permit sudden compression of said landing gear mechanism for faster instroke as necessitated by said landing gear mechanism going over bumps, and a rebound flapper valve at the end of said bypass passage opposite said lower piston chamber, said rebound flapper valve being movable away from said bypass passage to permit unrestricted flow through said bypass passage during instroke movements of said landing gear mechanism while taxiing, and being movable towards said bypass passage to restrict the flow through said bypass passage during outstroke movements of said landing gear mechanism while taxiing to dampen the outstroke of said landing gear mechanism when weighted for normal bounce during taxiing, said rebound flapper valve when moved towards said bypass passage still providing a restricted flow passage to said bypass passage. 64. A landing gear mechanism comprising a main cylinder, a main strut piston axially movable within said main cylinder, and means for controlling the rate of instroke of said main strut piston within said main cylinder comprising a restrictor orifice assembly supported by said main cylinder within said main strut piston against axial movement relative to said main cylinder, said restrictor orifice assembly defining with the outboard end of said main strut piston a lower piston chamber therebetween, said restrictor orifice assembly having an opening therethrough, a metering pin assembly attached to said main strut piston for movement therewith, said metering pin assembly including a metering pin extending through said opening defining an orifice therebetween for controlling the rate of flow of hydraulic fluid between said lower piston chamber and the opposite side of said restrictor orifice assembly, and means for providing a bypass flow path for hydraulic fluid from said lower piston chamber to the opposite side of said restrictor orifice assembly whenever said landing gear mechanism engages a bump during taxiing to reduce the damping loads that would otherwise occur if all such hydraulic fluid were required to pass through said orifice, said main strut piston including an annular surface area which is acted upon by the air pressure in said main cylinder tending to outstroke said main strut piston, said surface area being large enough to accelerate the unsprung mass of said landing gear mechanism into a hole but too small to lift the supported weight of the aircraft, and anticavitation means for preventing cavitation in said lower piston chamber during sudden outstroking of said landing gear mechanism into a hole, said anticavitation means comprising a bypass sleeve valve axially movable within said metering pin, said bypass sleeve valve and metering pin each having a plurality of axially spaced holes therein which may be brought into and out of alignment with each other upon moving said bypass sleeve valve in opposite directions, said holes when in alignment with each other allowing for flow of hydraulic fluid through said bypass sleeve valve around said orifice to supplement the flow of hydraulic fluid through said orifice to said lower piston chamber, means for moving said bypass sleeve valve to a first position in which said holes are out of alignment with each other whenever the hydraulic fluid pressure in said lower piston chamber is below a predetermined level and for moving said bypass sleeve valve to a second position in which said holes are in alignment with each other whenever the hydraulic fluid pressure in said lower piston chamber drops below such predetermined level. 65. The landing gear mechanism of claim 64 wherein said means for moving said bypass sleeve valve comprises a spring urging said bypass sleeve valve to said second position, and a differential surface area on said bypass sleeve valve acted upon by the hydraulic fluid pressure in said lower piston chamber to move said bypass sleeve valve to said first position only when the hydraulic fluid pressure in said lower piston chamber is above such predetermined level. 66. The landing gear mechanism of claim 64 further comprising check valve means for allowing for flow of hydraulic fluid through the center of said metering pin during the instroke of said landing gear mechanism and for blocking such flow through said metering pin when said landing gear mechanism suddenly starts to outstroke into a hole to keep hydraulic fluid inside said metering pin and prevent trapped vapors from entering said metering pin during such sudden outstroke of said landing gear mechanism.
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