# US 9,435,449 B2 · Pilot valve controlled positive and negative pressure relief valves > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 9,435,449 B2 - Document ID: US9435449B2 - Status: Granted - Kind: B2 - Application number: 13/440,494 - Filed: 2012-04-05 - Published: 2013-10-10 - Granted: 2016-09-06 - Earliest claimed: 2012-04-05 - Assignees: The Boeing Company - Applicants: Mark Alan Shelly - Inventors: Mark Alan Shelly - Web page: https://patentgrep.com/patent/US9435449B2 ## CPC - F16K 17/10: with auxiliary valve for fluid operation of the main valve - B60K 15/03519: {Valve arrangements in the vent line} - F16K 17/196: spring-loaded - B60K 2015/03296: {Pressure regulating valves} - Y10T 137/0379: By fluid pressure - Y10T 137/7764: Choked or throttled pressure type - Y10T 137/7771: Bi-directional flow valves - F16K: VALVES; TAPS; COCKS; ACTUATING-FLOATS; DEVICES FOR VENTING OR AERATING {(devices for emptying and evacuating the excess liquid in valves or conduits F16L55/07)} - B60K: ARRANGEMENT OR MOUNTING OF PROPULSION UNITS OR OF TRANSMISSIONS IN VEHICLES; ARRANGEMENT OR MOUNTING OF PLURAL DIVERSE PRIME-MOVERS IN VEHICLES; AUXILIARY DRIVES FOR VEHICLES; INSTRUMENTATION OR DASHBOARDS FOR VEHICLES; ARRANGEMENTS IN CONNECTION WITH COOLING, AIR INTAKE, GAS EXHAUST OR FUEL SUPPLY OF PROPULSION UNITS IN VEHICLES - Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION ## Abstract Concepts and technologies disclosed herein for relief valves (“relief valves”). A relief valve can include a flow path, a primary valve poppet that is urged or biased into a closed position by a tensioned spring, and a pilot valve in communication with a valve compartment of the relief valve. When an exterior space pressure overcomes the tensioned spring, the primary valve poppet can be overcome and pressure between an interior space and the exterior space can equalize, at least partially. When the pressure within the interior space increases beyond a defined threshold, which can be defined by a spring of the pilot valve, the pilot valve can open, the valve compartment can vent, and the tensioned spring again can be overcome and can open to allow at least partial equalization of pressures within the interior space and the exterior space. ## Claims ### Claim 1 A fuel tank, comprising: a relief valve that includes a valve body, the valve body being positioned within an interior space of the fuel tank and including a valve compartment being configured to provide a fluid pathway between the interior space of the fuel tank and an exterior space, the valve compartment comprising: a primary valve poppet located within the valve compartment; a poppet shaft connected to the primary valve poppet, at least a portion of the poppet shaft passing through a poppet shaft bore annulus, the poppet shaft bore annulus being configured to allow fluid flow between the interior space and the valve compartment; and a pilot valve located in an opening into the valve compartment and within the interior space of the fuel tank such that one end of the pilot valve abuts the valve compartment and an opposing end of the pilot valve abuts the interior space of the fuel tank, a further opening into an ambient pressure sense line between the pilot valve and the exterior space, wherein the relief valve is configured to at least partially relieve a positive and a negative pressure differential between the interior space and the exterior space. ### Claim 2 (depends on 1) The fuel tank of claim 1, wherein the valve compartment and the exterior space via the ambient pressure sense line has a first flow rate that exceeds a second flow rate between the interior space and the valve compartment. ### Claim 3 (depends on 1) The fuel tank of claim 1, wherein the pilot valve further comprises: a pilot valve body; a pilot valve poppet located within the pilot valve body and comprising the exposed end that is directly exposed to the interior space; and a pilot valve spring located between at least a portion of the pilot valve poppet and at least a portion of the pilot valve body, the pilot valve spring being configured to urge the pilot valve poppet into a sealed position at which the opening is obstructed by a pilot valve seal attached to the pilot valve poppet. ### Claim 4 (depends on 1) The fuel tank of claim 1, further comprising a primary valve poppet spring located within the valve compartment, the primary valve poppet spring being configured to bias the primary valve poppet into a sealed position at which the fluid pathway is obstructed. ### Claim 5 (depends on 1) The fuel tank of claim 1, wherein the pilot valve is configured to open at a crack pressure, and wherein opening of the pilot valve allows fluid to flow between the valve compartment and the exterior space via the ambient pressure sense line. ### Claim 6 (depends on 2) The fuel tank of claim 2, further comprising: a valve seal between the primary valve poppet and at least a portion of a tank boundary of the fuel tank; and a poppet seal between the primary valve poppet and at least a further portion of the tank boundary of the fuel tank, wherein the primary valve poppet comprises a portion exposed to the interior space via a flow path formed in the valve compartment. ### Claim 7 (depends on 1) The fuel tank of claim 1, wherein the relief valve is configured to open when a pressure within the interior space exceeds a defined positive pressure threshold, and wherein the relief valve is further configured to open when a pressure within the interior space drops below a defined negative pressure threshold. ### Claim 8 (depends on 1) The fuel tank of claim 1, wherein the relief valve is configured to increase force on the primary valve poppet when the pressure in the interior space increases until the pilot valve opens.