Classifications

• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
  • G01M5/0041—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress
  • G01M5/005—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings by determining deflection or stress by means of external apparatus, e.g. test benches or portable test systems
• • G—PHYSICS
  • G01—MEASURING; TESTING
  • G01M—TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR
  • G01M5/00—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings
  • G01M5/0016—Investigating the elasticity of structures, e.g. deflection of bridges or air-craft wings of aircraft wings or blades

Definitions

• This invention relates to fluid control circuits for controlling the pressure applied to an article.
• the article may be a workpiece or a structure undergoing testing.
• the invention has been particularly designed for and will be described with reference to testing aircraft wings to which stress is applied to simulate flight conditions although other uses are possible.
• hydraulic jacks have been used. Such jacks have been arranged in either of two ways: (1) an open loop system in which all jacks are controlled through a single valve, or (2) a closed loop system in which each jack is controlled independently through its own control valve.
• the closed loop system is preferred because it permits more accurate simulation of stress conditions, but it has suffered some instability.
• one or more of the jacks may apply abnormal loading thereby creating an undesirable stress condition which may damage the wing(s) under test.
• a fluid control circuit for controlling the pressure applied to an article by a plurality of fluid operable thrusting means drivable from a source of pressurized driving fluid, the circuit including a fluid supply line for carrying driving fluid to and from each thrusting means and locking means operable in response to detection of an abnormal condition to interrupt fluid supply to or from each thrusting means by closing each fluid supply line to fluid flow and thereby locking the thrusting means in their respective conditions when the abnormal condition is detected.
• the locking means comprises a cutoff valve in each fluid supply line, each cutoff valve being operable to close the respective fluid supply line to fluid flow when the abnormal condition is detected.
• Each cutoff valve may be a pilot operable check valve operable to hold the respective fluid supply line open to fluid flow as long as a supply of pressurized pilot fluid is connected thereto.
• each check valve is connected to the supply of pressurized pilot fluid by a respective pilot supply line, the pilot supply line including a pilot control valve for selectively disconnecting the supply of pilot fluid from the associated check valve.
• the pilot control valve is operable, when it disconnects the supply of pilot fluid from the associated check valve, to open the pilot supply line between the pilot control valve and the check valve to a sump to thereby relieve the pressure of pilot fluid at the check valve and cause the check valve to close the associated fluid supply line.
• Each fluid supply line may be connected to a sump through a respective fluid dump line, each fluid dump line having a selectively operable dump valve therein which is operable to normally hold the dump line closed to fluid flow and to open the dump lines when pressure on the article is being relieved.
• One or more of the fluid dump lines may be provided with a bleed control valve operable to control the rate of fluid flow through the dump line when the dump valve is open.
• the thrusting means may be drivable in one direction and be adapted to return to their inoperative positions due to reaction of the article which is being worked upon. In this arrangement the fluid supply line would be a single line to each thrusting means.
• each thrusting means is positively drivable in both directions so that it can apply both compressive and tensile loads to the article.
• each thrusting means is connected to a respective input fluid supply line and an output fluid supply line, the locking means being operable to close both input and output fluid supply lines to fluid flow when the abnormal condition is detected.
• the fluid control circuit illustrated is operable to control the pressure applied to an article by a plurality of fluid operable thrusting means 10 drivable from a source of pressurized driving fluid (not shown).
• One thrusting means 10 is shown as an hydraulic jack 12 of generally known construction.
• the jack 12 is positively drivable in both directions for applying both compressive and tensile loads to the article.
• the circuit includes a fluid supply line 14 for carrying driving fluid to and from each thrusting means 10.
• Locking means 16 is operable in response to detection of an abnormal condition to interrupt fluid supply to or from each thrusting means 10 by closing each fluid supply line 14 to fluid flow and thereby locking the thrusting means 10 in their respective conditions when the abnormal condition is detected.
• the jack 12 which can be positively driven in both directions, the jack 12 is connected to an input fluid supply line 18 connected to one side of the jack piston and output fluid supply line 20 connected to the other side and the locking means 16 is operable to close both input and output fluid supply lines 18 , 20 to fluidflow when the abnormal condition is detected.
• Control means 22 is provided for selectively switching supply of driving fluid to the thrusting means 10.
• the control means 22 may comprise a control valve for simultaneously operating all the thrusting means 10.
• the control means 22 preferably comprises a selectively operable control valve 23 for each thrusting means 10 and located in the respective fluid supply line 14.
• Each control valve 23 comprises a control servo valve having a valve member 24 with a supply position allowing supply of driving fluid to the respective thrusting means 10, a central cutoff position (as shown) in which the fluid supply line 14 is closed to fluid flow, and a drain position allowing draining of driving fluid from the thrusting means 10, the control servo valve being solenoid driven so as to allow selective changing of the position of the valve member 24 .
• the valve member 24 is adapted to be positively driven by the solenoid(s) in either direction from its central cutoff position so that the valve 23 has a relatively rapid response to electrical control signals.
• the rapid response characteristic may be used to provide an oscillating load to the article. For example in the case of aircraft wings, an oscillating load at a frequency of up to 2 hertz may be applied to the wings to simulate flight conditions.
• the locking means 16 comprises a cutoff valve 25, 26 in each of the fluid supply lines 18,20 responsive to a predetermined fault condition to close the respective fluid supply line 18, 20 to fluid flow and hold the thrusting means in its condition at the instant of detection of the fault condition.
• Each cutoff valve is a selectively operable check valve.
• Each cutoff check valve is a 'pilot operable check valve 27,28 operable to hold the associated fluid supply line 13,20 open to fluid flow as long as a supply of pressurized pilot fluid is connected to the check valve 27,28.
• a pilot supply line 29 to each cutoff check valve 27,28 associated with the thrusting means 10.
• the pilot supply line 29 is divided at a T-connection 30 to supply the two check valves 27, 28.
• the pilot supply line 29 is provided with a pilot control valve 31 for selectively disconnecting the supply of pilot fluid from the cutoff check valves 27,28.
• the pilot control valve 31 is solenoid operated. As shown, the pilot control valve 31 is located in the common pilot supply line 29 and is arranged to maintain that line 29 open to the source of pressurized pilot fluid as long as the solenoid is energized and to close that line on interruption of power to the solenoid thus providing a fail safe mode of operation. Thus an electrical fault that interrupts power supply to the solenoid will result in closing the pilot supply line 29.
• pilot control valve 31 When the pilot control valve 31 closes it is arranged toopen the pilot supply lines to the cutoff valves 27,28 to a sump 32 to relieve the pressure of pilot fluid at the cutoff valves 27,28 so that the cutoff valves 27,28 close the fluid supply lines 18,20 to and from the jack 12 and thereby hold the jack 12 in its condition at the time the pilot control valve 31 is operated.
• the fluid control circuit may be coupled to sensing means (not shown) operative to detect the load applied to the article by each thrusting means 10.
• the sensing means may include a plurality of transducers in the form of load cells.
• the outputs of the load cells may be fed to an electrical monitoring circuit for monitoring the load at each point of the aircraft wing where the thrusting means 10 is operating, the monitoring circuit being operative to detect any loading above a predetermined level to activate the locking means 16, which in the preferred embodiment includes the solenoid operated pilot control valves 31.
• Each fluid supply line 18,20 is connected to a sump 35,36 through a respective fluid dump line 37,38 each fluid dump line 37,38 having a selectively operable dump valve 39,40 therein which is operable to normally hold the dump line 37,38 closed to fluid flow and to open the dump lines 37,38 when pressure on the article is being relieved.
• Each fluid dump line 37,38 extends from a point between the cutoff valve
• Each dump valve 39,40 is a pilot operated check dump valve 43,44 coupled to a respective or, as illustrated, a common dump pilot supply line 45.
• the pressure in the common dump supply line 45, and hence at all the dump valves 43,44 may be controlled by a central dump control valve (not shown) to selectively open and close the dump valves 43,44.
• the central dump control valve may be operated simultaneously with the pilot control valve
• control valves 24 may be operated to return to their cutoff conditions.
• Each fluid dump line 37,38 includes a bleed control valve
• bleed valves 41,42 are temperature and pressure compensating so that the rate of discharge of fluid through the bleed valves 41,42 may be controlled.
• different pressures may be exerted on the various jacks by the wings during pressure relief and it is desirable to be able to individually control or set the rate of discharge of each jack so that a wing is not damaged.
• fluid temperature can vary particularly when an oscillating load is applied and this can affect the viscosity of the fluid and hence its discharge rate.
• Each fluid supply line 18,20 includes an auxiliary check valve 47,48 operable, when the associated dump line 37,38 is open, to close the fluid supply line 18,20 against leakage flow other than through the bleed control valve 41,42. In some cases it may occur that leakage flow through the control valve 23 negates the setting of the bleed control valves 41,42.
• the auxiliary check valves 47,48 prevent such leakage flow and ensure that pressure relieving flow is controlled as desired by the bleed control valves 41, 42.
• the auxiliary check valves 47, 48 as shown can be operated from the common dump supply line 45 so that the auxiliary check valves 47, 48 close when the dump valves 43, 44 open.
• the hydraulic jack 12 is connected to a source of pressurized liquid through the associated control valve 23.
• the control valve 23 is open in response to an electrical signal from a central control location to commence the loading operation of the respective jacks and this may occur simultaneously for all jacks.
• Each jack 12 has associated therewith a sensing means (not shown) which is connected to the electrical monitoring circuit (not shown) so that the loaded condition of the jack 12 or stress on the wing can be monitored and controlled through the control valve 23.
• the pilot control valves 31 will operate to interrupt pilot fluid supply to the cutoff valves 25,26 in the fluid supply lines 18,19 of the jacks 12.
• the jacks 12 therefore will be held in the active or load applying condition. For example if one jack "sticks" while all the other jacks are relieving pressure on the aircraft wing the detection of the abnormal stress at the sticking jack will initiate locking of all the jacks in the condition at the instant the fault is detected. The faulty jack may then be inspected and serv- iced so that it will operate correctly.
• the pilot control valve associated with the faulty jack may be independently operated to ensure that that jack is then operating correctly. While the jacks are being held in their load applying condition any excess pressure in the circuit on the side of the cutoff valves 25,26 remote from the jacks 12 can be purged through the dump lines 37,38 through operation of the pilot operated dump valves 37,40.
• the pilot supply to the cutoff valves 25,26 is reconnected by energizing the solenoid of the pilot control valve 31.
• the cutoff valves 25,26 in the supply lines 18,20 are still maintained open and the fluid dump valves 39,40 are opened so that pressure relieving flow to and from the respective sumps 35,36 can take place.
• the pilot control valve 31 will still be operative in response to detection of a fault condition to close the fluid supply lines 18,20 to pressure relieving flow so that the circuit can operate to protect the aircraft wing at all stages throughout the the testing operation.

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• Engineering & Computer Science (AREA)
• Aviation & Aerospace Engineering (AREA)
• Physics & Mathematics (AREA)
• General Physics & Mathematics (AREA)
• Fluid-Pressure Circuits (AREA)

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Publications (2)

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ID=3768957

Family Applications (1)

Country Status (3)

Citations (3)

Family Cites Families (4)

• 1982
  • 1982-02-03 WO PCT/AU1982/000007 patent/WO1982002749A1/en not_active Application Discontinuation
  • 1982-02-03 EP EP19820900331 patent/EP0070842A4/de not_active Ceased
  • 1982-02-11 IT IT19609/82A patent/IT1149621B/it active

Patent Citations (3)

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