A fluid injector, for example for injecting liquid fuel into a combustion chamber, comprises a valve housing and an injector assembly which may be removably mounted on the valve housing. The injector assembly includes discharging means for discharging fluid from the injector assembly, ducting for conveying the fluid between the valve housing and the discharging means and a control valve movable to a first position in response to flow of the fluid in a first direction through the ducting to close the discharging means and return the fluid from the discharging means to the valve housing and movable to a second position in response to flow of the fluid in a second direction through the ducting to open the discharging means to allow at least some of the fluid conveyed to the discharging means to be discharged therefrom and to return any surplus fluid to the valve housing. Provided in the valve housing are inlet and outlet passages for conveying the fluid into and from the valve housing, and a change-over valve. The change-over valve comprises a valve member adjustable into a first position to condition the injector for flow of the fluid from the inlet passage through the ducting in said first direction and into a second position to condition the injector for flow of the fluid from the inlet passage through the ducting in said second direction. In the valve housing there is also provided a spill return valve for varying the proportion between the amount of the fluid that is allowed to discharge from the discharging means and the amount that is returned from the discharging means to the valve housing when the control valve is in its second position.

A fluid injector, for example for injecting liquid fuel into a combustion chamber, comprises a valve housing and an injector assembly removably mounted on the valve housing. The injector assembly includes discharging means for discharging fluid from the injector assembly, ducting for conveying the fluid between the valve housing and the discharging means and a control valve movable to a first position in response to flow of the fluid in a first direction through the ducting to close the discharging means and return the fluid from the discharging means to the valve housing and movable to a second position in response to flow of the fluid in a second direction through the ducting to open the discharging means to allow at least some of the fluid conveyed to the discharging means to be discharged therefrom and to return any surplus fluid to the valve housing. Provided in the valve housing are inlet and outlet passages for conveying the fluid into and from the valve housing, and a change-over valve. The change-over valve comprises a valve member adjustable into a first position to condition the injector for flow of the fluid from the inlet passage through the ducting in said first direction and into a second position to condition the injector for flow of the fluid from the inlet passage through the ducting in said second direction. A control means for the change-over valve is actuable to move the valve member into a third position in which the change-over valve prevents the flow of fluid from the inlet passage to the ducting. This control means comprises a mechanical interlock preventing removal of the injector assembly from the valve housing unless the valve member has been moved into its third position by the control means.

The invention relates to a nozzle for a paint spraying device having a radially inward valve needle that is connected in a coaxial arrangement with the nozzle. A radially outward paint supply pipe is connected to the valve at one end and a paint source at the other. The valve needle is hollow for paint supply purposes and has a forwardly inclined bore in its tip which opens axially in front of the valve into an annular chamber created between the valve needle and the supply pipe.

A tip shut-off fluid injector F has its injection device 1 inset to a fixed female interlocking terminal 2 when in the firing position with which a change-over valve 4 is connected by pipes P or is made integral. The terminal 2 includes valves 8 and 9 and, optionally, a by-pass valve 10. A gearbox 12 connects between the valves 8, 9 and 10 and a handwheel 11. Rotation of the handwheel 11 inserts or retracts the injection device 1 to or from the firing position and also, via the gearbox 12, rotates the valves 8, 9 and 10 between open and closed positions. Before the injection device 1 can be retracted, the handwheel 11 must be initially rotated to rotate the valves 8 and 9 to closed positions to isolate the fluid supply from the injection device 1 and, optionally, to open the by-pass valve 10 to allow fluid to circulate from the supply through the terminal 2 back to return. Conversely, it is not until the injection device 1 is inserted that the valves 8 and 9 can be rotated by the handwheel 11 to open positions to communicate the fluid supply with the injection device 1 and, optionally, close the by-pass valve 10. The change-over valve 4 may include a direct flow path interconnecting the fluid supply and return when the injection device 1 is retracted. Other kinds of fluid injectors incorporating the invention are envisaged.

An engine exhaust braking method and apparatus. The method includes injecting a predetermined amount of fuel per stroke into an engine cylinder during engine braking, wherein the predetermined amount of fuel cools the fuel injector nozzle, thereby allowing the engine braking to be performed without damage to the fuel injector nozzle due to excessive heat. The apparatus includes a fuel injector having a nozzle and capable of injecting a predetermined amount of fuel into an engine, and a processor connected to the fuel injector, with the processor monitoring engine operation and capable of causing the fuel injector to inject the predetermined amount of fuel into the engine, wherein a predetermined amount of fuel is injected into the engine to cool the fuel injector nozzle, thereby allowing the exhaust braking to be performed without damaging the fuel injector nozzle due to excessive heat.