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A dual fuel common rail fuel injector includes a first and second control valve assembly and a first and second check needle. The dual fuel injector is capable of selectively injecting two different fuels such as diesel and liquid natural gas. The first and second control valve assemblies operate us

A dual fuel common rail fuel injector includes a first and second control valve assembly and a first and second check needle. The dual fuel injector is capable of selectively injecting two different fuels such as diesel and liquid natural gas. The first and second control valve assemblies operate using a single fuel, such as diesel, as the control medium. The dual fuel common rail injector further includes a hydraulic lock assembly.

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1. A dual fuel injector comprising: an injector body defining a dual fuel inlet configured to receive high pressure diesel fuel and medium pressure gaseous fuel, a medium pressure gaseous supply passage, a high pressure diesel supply passage, at least one low pressure drain, a diesel check cavity, a

1. A dual fuel injector comprising: an injector body defining a dual fuel inlet configured to receive high pressure diesel fuel and medium pressure gaseous fuel, a medium pressure gaseous supply passage, a high pressure diesel supply passage, at least one low pressure drain, a diesel check cavity, a gaseous check cavity, at least one diesel nozzle outlet, and at least one gaseous fuel nozzle outlet;a gaseous control valve assembly disposed at least partially within the injector body and having a control valve member that selectively allows fluid communication between the high pressure diesel supply passage and the at least one low pressure drain;a diesel control valve assembly disposed at least partially within the injector body and having a control valve member that selectively allows fluid communication between the high pressure diesel supply passage and the at least one low pressure drain;a diesel check disposed in the diesel check cavity and movable between a first diesel check position wherein the diesel check blocks fluid communication between the high pressure diesel supply passage and the at least one diesel nozzle outlet, and a second diesel check position wherein the diesel check at least partially unblocks fluid communication between the high pressure diesel supply passage and the at least one diesel nozzle outlet, and wherein the movement between the first diesel check position and the second diesel check position is controlled by the diesel control valve assembly;a gaseous check disposed in the gaseous check cavity and movable between a first gaseous check position wherein the gaseous check blocks fluid communication between the medium pressure gaseous supply passage and the at least one gaseous nozzle outlet, and a second gaseous check position wherein the gaseous check at least partially unblocks fluid communication between the medium pressure gaseous supply passage and the at least one gaseous nozzle outlet;a hydraulic lock in fluid communication with both the high pressure diesel supply passage and gaseous check cavity. 2. The dual fuel injector of claim 1, wherein the dual fuel inlet is further configured to receive high pressure diesel fuel and medium pressure gaseous fuel delivered in a coaxial fashion. 3. The dual fuel injector of claim 1, wherein the diesel check and the gaseous check are positioned side by side within the dual fuel injector. 4. The dual fuel injector of claim 1, wherein the diesel check includes a separate upper portion and lower portion operably connected to one another, and is biased toward the first diesel check position by a biasing spring. 5. The dual fuel injector of claim 1, wherein the gaseous check includes a separate upper portion and lower portion operably connected to one another, and is biased toward the first gaseous check position by a biasing spring. 6. The dual fuel injector of claim 1, wherein the gaseous control valve assembly further comprises an electrical actuator. 7. The dual fuel injector of claim 1, wherein the diesel control valve assembly further comprises an electrical actuator. 8. The dual fuel injector of claim 1, wherein the high pressure diesel fuel is at a pressure approximately 5 MPa higher than the medium pressure gaseous fuel. 9. The dual fuel injector of claim 1, wherein the high pressure diesel fuel is distillate diesel fuel, and the medium pressure gaseous fuel is liquefied natural gas. 10. A dual fuel common rail fuel system comprising: a gaseous fuel source;a diesel fuel source;a medium pressure gaseous raila high pressure diesel railat least one gaseous pump configured to pressurize gaseous fuel from the gaseous fuel source to a medium pressure and deliver medium pressure gaseous fuel to the medium pressure gaseous rail;at least one diesel pump configured to pressurize diesel fuel from the diesel fuel source to a high pressure and deliver high pressure diesel fuel to the high pressure diesel rail;a quill configured to receive both medium pressure gaseous fuel from the medium pressure gaseous rail and high pressure diesel from the high pressure diesel rail;a dual fuel injector configured to receive both medium pressure gaseous fuel and high pressure diesel fuel from the quill, and further comprising: an injector body defining a dual fuel inlet configured to receive high pressure diesel fuel and medium pressure gaseous fuel, a medium pressure gaseous supply passage, a high pressure diesel supply passage, at least one low pressure drain, a diesel check cavity, a gaseous check cavity, at least one diesel nozzle outlet, and at least one gaseous fuel nozzle outlet;a gaseous control valve assembly disposed at least partially within the injector body and having a control valve member that selectively allows fluid communication between the high pressure diesel supply passage and the at least one low pressure drain;a diesel control valve assembly disposed at least partially within the injector body and having a control valve member that selectively allows fluid communication between the high pressure diesel supply passage and the at least one low pressure drain;a diesel check disposed in the diesel check cavity and movable between a first diesel check position wherein the diesel check blocks fluid communication between the high pressure diesel supply passage and the at least one diesel nozzle outlet, and a second diesel check position wherein the diesel check at least partially unblocks fluid communication between the high pressure diesel supply passage and the at least one diesel nozzle outlet, and wherein the movement between the first diesel check position and the second diesel check position is controlled by the diesel control valve assembly;a gaseous check disposed in the gaseous check cavity and movable between a first gaseous check position wherein the gaseous check blocks fluid communication between the medium pressure gaseous supply passage and the at least one gaseous nozzle outlet, and a second gaseous check position wherein the gaseous check at least partially unblocks fluid communication between the medium pressure gaseous supply passage and the at least one gaseous nozzle outlet;a hydraulic lock in fluid communication with both the high pressure diesel supply passage and gaseous check cavity. 11. The dual fuel common rail system of claim 10, wherein the dual fuel inlet of the dual fuel injector is further configured to receive high pressure diesel fuel and medium pressure gaseous fuel delivered from the quill in a coaxial fashion. 12. The dual fuel common rail system of claim 10, wherein the diesel check and the gaseous check are positioned side by side within the dual fuel injector. 13. The dual fuel common rail system of claim 10, wherein the diesel check includes a separate upper portion and lower portion operably connected to one another, and is biased toward the first diesel check position by a biasing spring. 14. The dual fuel common rail system of claim 10, wherein the gaseous check includes a separate upper portion and lower portion operably connected to one another, and is biased toward the first gaseous check position by a biasing spring. 15. The dual fuel common rail system of claim 10, wherein the gaseous control valve assembly further comprises an electrical actuator. 16. The dual fuel common rail system of claim 10, wherein the diesel control valve assembly further comprises an electrical actuator. 17. The dual fuel common rail system of claim 10, wherein the high pressure diesel fuel is at a pressure approximately 5 MPa higher than the medium pressure gaseous fuel. 18. The dual fuel common rail system of claim 10, wherein the high pressure diesel fuel is distillate diesel fuel and the medium pressure gaseous fuel is liquefied natural gas.