INTEGRAL HYDRAULIC BLOCKING AND RELIEF VALVE

Abstract: An integral hydraulic blocking and relief valve (12) for use in an aircraft night power actuator (60) includes a unique stepped piston assembly (PA and PB) referenced to return or relieve system pressure (P) at the same, predetermined level, independent of any influence due to the system pressure (P), and control valve means (20) for controlling hydraulic system fluid to the hydraulic blocking and relief valve (12) for actuating the night power actuator (60).

Description: INTEGRAL HYDRAULIC BLOCKING AND RELIEF VALVE BACKGROUND OF THE INVENTION The present invention pertains to the hydraulic valve art and, more particularly, to an improved integral blocking and relief valve. Numerous hydraulic blocking valves have been developed in the prior art. A common application for such valves is -in the aircraft flight power control actuator art wherein, for example, blocking valves are used in spoiler actuator systems. During flight, it is crucial to the safe operation of the aircraft that the spoiler be in its retracted position when not commanded otherwise. Thus, to prevent spoiler surface motion as a result of reduced system pressure or external loading, it has been common practice to employ- a blocking valve which traps hydraulic fluid in the actuator thereby locking the spoiler in place. The pressure of this trapped hydraulic fluid can increase due to thermal effects or external loading. To prevent an excessively high pressure build up, the prior art has utilized a thermal relief valve which bleeds fluid to system return until the pressure is relieved. Attempts have been made in the prior art to combine both ' the blocking and relief valve functions in a single valve unit, thereby saving in weight, construction cost and space. A problem with one such design is that pressure relief is biased upwards by system pressure. That is, in this prior design the pressure relief occurs at nearly twice the pressure with system pressure on than it does when system pressure is off. A weight penalty is incurred in such actuator designs to accommodate the higher than desired working pressures. O PI In another previous integral blocking and relie valve design, the system is successful in providing constant relief setting regardless of system pressure However, this design utilizes a large number of parts thu rendering it expensive to manufacture and potentially les reliable in operation. SUMMARY OF THE INVENTION It is an object of this invention, therefore, t provide an improved integral blocking and relief valv which provides pressure relief at a fixed level independen of system pressure. It is a further object of the invention t provide the above described improved integral blocking an relief valve which requires a minimum number of parts suc that it is simple to manufacture and reliable in operation. Briefly, according to the invention, th inventive integral blocking and relief valve blocks th flow of a hydraulic fluid unless the pressure of th blocked fluid exceeds a predetermined value. The valve i comprised of a first input port adapted to be connected t the hydraulic fluid source to be blocked and relieved. first piston P A is slidably contstrained in a firs chamber, which first chamber is connected to the firs input port. The piston P A has an area A A at a first en exposed to the hydraulic pressure in the first -chamber. second" piston Pg has a first portion which is slidabl constrained in a pressure relief chamber. A second portio of piston P B is integral with the first end of the firs portion and is slidably constrained in, and has an expose area A SB to a relief bias chamber. A plunger portio extends from the second end of the first portion of pisto P B . A provided pressure bias port is adapted to b connected to a source of system hydraulic pressure. A bia chamber connects to the pressure bias port and joins the first chamber such that the second end of the first piston P A is in position to abut the free end of the second portion. A relief port is connected to the relief bias chamber and is adapted to be connected to the system return pressure. The second input port is connected to the pressure relief chamber and is adapted to be connected to a system controlled hydraulic flow line. A poppet valve is slidably constrained in a poppet chamber. The poppet chamber joins with the pressure relief chamber and the first input port such that hydraulic fluid at the first input port is controllably passed to the pressure relief chamber dependent on the position of the poppet. The poppet exposes an area Ap to the pressure relief chamber and is engagable by the plunger portion of the second piston to drive the poppet to a position thereby allowing flow from the input port to the pressure relief chamber. Preferably, the relationship between the second piston second portion exposed area, the first piston exposed area and the poppet exposed area is given by the relationship: A SB^ A A " A P- A design, according to this relationship provides pressure relief independent of the level of system pressure. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view of the preferred embodiment of the integral blocking and relief valve in an aircraft spoiler actuator application; FIG. 2 illustrates operation of the system shown in FIG. 1 in the spoiler extend mode; and FIG. 3 illustrates the system of FIG. 1 in the spoiler retract mode and also shows the blocking and relief characteristics of the valve. OMPI DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT OF THE INVENTION FIG. 1 is a cross-sectional view of an aircraf spoiler actuator system incorporating a preferre embodiment of the instant integral blocking and relie valve. The basic system components include a control valv 10, the integral blocking and relief valve 12 and th actuator 14. The control valve 10 is of conventional desig being comprised of a spool 20 having a series of three lan portions 22-24 provided thereon. The spool 20 and land 22-24 are slidabley constrained within a cylinder 26. series of cavities 32-34 are associated with each lan 22-24. In the present system, a source of high pressur hydraulic fluid is coupled to the cavity 33 whereas th return, or reservoir system pressure is coupled to cavit 32. Associated with each cavity is an exit port 36-38 wit additional exit ports 40-42 being provided from the cavit 26. Thus, the control valve 10 responds to the position o the spool 20 within the cylinder 26 to meter hydrauli fluid into, and out of various of its ports. As with the control valve 10, the actuator 14 i of conventional design. Thus, a piston 50 is slidabl constrained within a cylinder 52. Packing material 54 such as an "0" ring, seals the piston 50 against th cylinder walls thereby forming an extend chamber 56 and retract chamber 58. A rod 60 extending from the piston 5 connects through suitable linkage to an aircraft spoile (not shown) . As shown, hydraulic fluid is coupled to th actuator extend chamber 56 directly from the output port 4 of the control valve 10 whereas fluid from the retrac chamber 58 passes through the integral blocking and relie valve 12 before reaching the control valve. Thus, the ■ OMPI blocking and relief provided by valve 12 operates on fluid in the actuator retract chamber 58. The preferred construction of the integral blocking and relief valve 12 includes an input port 70 which couples fluid to a first chamber 72. A first piston P & is slidably constrained in the first chamber 72. At its first end 74 the piston P & has an area & exposed to hydraulic fluid coupled through the input port 70. Suitable packing 76 seals the piston P & in its chamber 74. A second piston Pg has a first portion 80 which is slidably constrained in a pressure relief chamber 83. Suitable packing 84 seals the first portion 80 within the chamber 83. Integral with th_. first portion 80 of the second piston Pg is a second portion 82. Second portion 82 is slidably constrained in, and exposes a total area Agβ t0 - relief bias chamber 86. Suitable packing 88 seals the second portion 82 within the chamber 86. A plunger 90 extends from the second end of the first portion 80. A second input port 92 connects to the pressure relief chamber 82 and, as shown, is coupled to an output port 40 of control valve 10. A pressure bias port 100, which connects to the etered system high pressure output port 37 of control valve 10, accesses a pressure bias chamber 102. The pressure bias chamber 102 joins the first chamber 72 with the relief bias chamber 86 such that the second end 75 of the first piston P A can abut the free end of the second portion 82. A relief port 120, which connects to system return pressure via port 36 of control valve 10, connects to the relief bias chamber 86. A poppet valve 130 is slidably constrained in a poppet chamber 132. The poppet chamber 132 joins with the pressure relief chamber 83 and the first input port 70 su that hydraulic fluid at the first input port 70 controllably passed to the pressure relief chamb dependent upon the position of the poppet 130. The poppet 130 has a face portion 134 whi exposes an effective area Ap to the pressure reli chamber. Further, the poppet face portion 134 is engagab by the plunger portion 90 of the second piston P-g such th the poppet may be driven to a position allowing the fl from the input port 70 to the pressure relief chamber 83. A passageway 136 provided in the poppet 1 allows equalization of hydraulic pressure throughout t poppet chamber 132. A spring pair 140 biases the second piston Pg o of engagement with the poppet 130. A second spring pa 142 biases the poppet 130 such that it tends to block flu flow from the first input port 70 to the pressure reli chamber 83. SYSTEM OPERATION Identical reference numerals are used througho FIGS. 2 and 3 to correspond to identical parts shown FIG. 1. FIG. 2 illustrates operation of the system sho in FIG. 1 in the cylinder extend mode. Here, via suitable control (not shown) from the flight deck, t control valve spool 20 slides to the right within cylind 26. Thus, the system pressure P forces hydraulic flu into the cavity 33, out output port 42 and into the exte chamber 56 of the actuator 14. Thus, the piston 50 is driven to the rig whereby rod 60 deflects the spoiler (not shown) to i extend position. Fluid in the retract chamber 58 is routed to the first input port 70 where it is coupled both to the exposed area A & of the first piston P^ and to the poppet chamber 132. Also, system high pressure is routed through the pressure bias port 100 to the pressure bias chamber 102. In this mode, the net forces on the second piston Pβ are sufficient to overcome the forces due to the spring pair 140 such that second piston Pβ is deflected to the left. In so doing, the plunger 90 engages the poppet 130 such that it is driven to the left in opposition to its spring pair 142. Now, fluid from the retract chamber 58 is permitted to flow from the first input port 70 to the pressure relief chamber 83. The fluid then flows out port 92 and into port 40 of control valve 10 and, finally, out of cavity 32 to the system return reservoir. FIG. 3 illustrates operation of the system in the cylinder retract mode. Here, a suitable signal from the flight deck moves the spool 20 to the left within cylinder 26 of control valve 10. This allows fluid in the extend chamber 56 to pass into control valve port 42, chamber 34 and through port 36 to chamber 32 and, thus, to system return pressure. The piston 50 moves to a "bottomed" position within its cylinder thereby activating the spoiler (not shown) to its retract position. Fluid pressure in the retract chamber 58 rises to system pressure. Now, system, pressure as metered through cavity 33, output port 40 and second input port 92, along with the force exerted by the spring pair 140 drives the second piston Pβ to the right against system pressure in the pressure bias chamber 102. This results in the poppet 130 closing (shown in dashed lines) thereby acting as a blocking valve to prevent movement of the piston 50 (and, thus, the spoiler) due to loads on the spoiler. By design, the exposed area A A of the first piston P A is greater than the exposed area on the face 134 O PI of the poppet 130. Thus, if pressure in the retrac chamber 58 exceeds a predetermined level due to therma effects or external loading, then thi-^ pressure acting o the differential area A A - Ap creates a force urging th first piston P A to the left contacting piston P an driving the second piston P B to the left opening the poppe 130 and thereby relieving the trapped pressure into chambe 83 and, via port 92 and control valve 10, to the hydrauli system. A particular feature of the invention is that th stepped area Ags of the second portion 82 of the secon piston Pβ referenced to return is related to the expose area A A of the first piston P and to the exposed area A of the poppet 130 by the relationship: A SB~1 A A - Ap. This relationship assures that pressure in th retract chamber 58 will be relieved independent of th value of system pressure. Ideally, ignoring friction, this may b understood as follows. For the condition of zero syste pressure, the system will provide relief (i.e. poppet 13 will begin to open) in accordance with the followin relationship: P R = F S /(A A - Ap) where PR = relief pressure and Fs = spring force. For the condition of an existing system pressur Pg, and ignoring the force resulting from the stepped are Agβ of the second piston P β , pressure relief would b provided in accordance with the following relationship; p R = [F S /(A A - Ap)] + P S . Comparing the above relationships, it is apparen that relief pressure is directly related to syste pressure. - * &UR T Assuming a given system pressure Pg and assuming that return pressure is equal to zero, the following relationship, taking into account the ' contribution from the stepped area Ag β may be shown: (P R - P S ) (A A - Ap) + P S A S B = FS- Assuming A SB?^ A A ~ A P' the expression for the relief pressure reduces to: PR = F S /(A A - Ap). Comparing this last equation with the above equation for the condition wherein system pressure is zero, it can be seen that due to the contribution of the stepped area AQ-Q the present unique valve design relieves system pressure at the same, predetermined level, independent of any influence due to system pressure. In summary, an improved integral blocking and relief valve has been shown which provides pressure relief at a value independent of system pressure levels. In addition, the valve utilizes relatively few parts and, as such, is simple to construct and relatively reliable in use. While a preferred embodiment of the invention has been described in detail, it should be apparent that many modifications and variations thereto are possible, all of which are within the true spirit and scope of the invention. For example, while fluid blocking in the retract position of the spoiler has been described, it is apparent that such blocking could be provided in the extend position.

Claims: I Claim : 1. An integral blocking and relief valve fo blocking the flow of a hydraulic fluid unless th pressure of said fluid exceeds a predetermined value comprising: a first input port adapted to be connected to th hydraulic fluid source to be blocked and relieved; a first piston P A slidably. constrained in a firs chamber, said first chamber being connected to sai first input port and said piston P having an area A at a first end, said area A being exposed to hydrauli pressure in said first chamber; a second piston P β having a first portion bein slidably constrained in a pressure relief chamber and second portion integral with the first end of sai first portion and being slidably constrained in, an exposing an area Ag to a relief bias chamber, sai second piston Pβ further comprising a plunger portio extending from the second end of said first portion; a second input port connected to said pressur relief chamber and adapted to be connected to a syste controlled hydraulic flow line; a pressure bias port adapted to be connected to source of system hydraulic pressure; a bias chamber connected to said pressure bia port and joining said first chamber with said relie bias chamber such that the second end of said firs piston P can abut the free end of said second portion; a relief port connected to said relief bias chamber an adapted to be connected to the system return pressure and a poppet valve being slidably constrained in a poppet chamber, said poppet chamber joining with said pressure relief chamber and said first input port such that hydraulic fluid at said first input port is controllably passed to said pressure relief chamber dependent on the position of said poppet, said poppet exposing an area Ap to said pressure relief chamber and being engageable by said plunger portion of the second piston to drive the poppet to a position to allow flow from said input port to said pressure relief chamber. 2. The integral blocking and relief valve of claim 1 wherein the first piston exposed area A is greater than the poppet exposed area Ap such that for equal fluid pressures on the surface areas A A and Ap the first piston P A drives the second piston Pβ which engages the poppet and permits fluid flow between the first input port and the pressure relief chamber. 3. The integral blocking and relief valve of claim 2 wherein the first' piston exposed area A , the poppet exposed area Ap and the second piston second portion- exposed area Ag B are defined by: SB S A A -Ap whereby the poppet is driven to allow flow from the first input port to the relief chamber at a predetermined pressure of fluid in said first input port independent of the level of system pressure. 4. The integral blocking and relief valve of any of claims 1 to 3 further comprising: first spring bias means for biasing said second piston such that the plunger is out of engagement with the poppet; and second spring bias means for biasing said poppet to block flow from said input port to said pressure relief chamber. OMPI

Inventors: TURNER B
Applicants: BOEING CO
Application year: 1981
Main classification: F15B11
IPC codes: F15B13