An exhaust brake and method of operating an exhaust brake are disclosed. The exhaust brake may have a housing having a central opening and a boss with a central bore, wherein the central bore intersects the central opening. A butterfly gate may be pivotally mounted in the central opening. The butterfly gate may have a bypass opening provided in an outer edge of the butterfly gate, and an upstream side. A dual-diameter piston may be slide-ably disposed in the central bore. The piston may have a lower end received in the bypass opening and an upper end distal from the bypass opening. One or more passages may extend between the central opening and the central bore at the upstream side of the butterfly gate, and a spring may bias the piston lower end into the bypass opening. The piston lower end may selectively unblock the bypass opening responsive to the application of static exhaust gas pressure to the piston upper end. The shape of the bypass opening and the piston lower end may be selected so that piston lower end fits closely within the bypass opening and thereby removes soot build up in the opening as a result of operation of the exhaust brake.
1. A method of controlling exhaust pressure in an engine with an exhaust brake having a butterfly gate with a bypass opening provided in an outer edge of the butterfly gate and a slide-able piston having a lower end adapted to selectively block said bypass opening and having an upper end adapted to receive static exhaust gas pressure, said method comprising the steps of:
closing the butterfly gate;
blocking the bypass opening in the butterfly gate with the lower end of the piston as a result of closing the butterfly gate;
generating static exhaust gas pressure in the exhaust brake responsive to closing the butterfly gate and blocking the bypass opening;
applying the static exhaust gas pressure to the upper end of the piston; and
unblocking the bypass opening in the butterfly gate by sliding the lower end of the piston out of at least a portion of the bypass opening responsive to the application of the static exhaust gas pressure to the upper end of the piston.
2. The method of claim 1 , further comprising the step of biasing the upper end of the piston towards the static exhaust gas pressure.
3. The method of claim 2 , further comprising the step of restraining the upper end of the piston from rotating relative to the exhaust brake.
4. An exhaust brake comprising:
a housing having a central opening and a boss with a central bore, wherein the central bore intersects the central opening;
a butterfly gate pivotally mounted in the central opening, said butterfly gate having a bypass opening provided in an outer edge of the butterfly gate, and having an upstream side;
a piston slide-ably disposed in the central bore, the piston having a lower end received in the bypass opening and an upper end disposed in the central bore distal from the bypass opening;
one or more passages extending between the central opening and the central bore at the upstream side of the butterfly gate; and
a spring biasing the piston lower end into the bypass opening.
5. The exhaust brake of claim 4 , further comprising:
a slot provided in the piston upper end; and
a pin extending through the boss and into the slot.
6. The exhaust brake of claim 5 , further comprising:
an annular ring provided on an end face of the piston upper end.
7. The exhaust brake of claim 6 , further comprising:
an adjustable stop disposed in the central bore, wherein the spring is disposed between the adjustable stop and the piston upper end.
8. The exhaust brake of claim 7 , wherein the piston upper end has a diameter greater than the piston lower end.
9. The exhaust brake of claim 4 , wherein the piston lower end has a right-cylinder shape and the bypass opening has a mating square notch shape.
10. The exhaust brake of claim 4 , wherein the piston lower end has a spherical shape and the bypass opening has a mating spherical shape.
11. The exhaust brake of claim 4 , wherein the piston lower end has a frusto-conical shape and the bypass opening has a mating frusto-conical shape.
12. The exhaust brake of claim 4 , wherein the piston lower end has a wedge shape and the bypass opening has a mating wedge shape.
13. The exhaust brake of claim 4 , further comprising:
an annular ring provided on an end face of the piston upper end.
14. The exhaust brake of claim 4 , further comprising:
an adjustable stop disposed in the central bore, wherein the spring is disposed between the adjustable stop and the piston upper end.
15. The exhaust brake of claim 4 , wherein the piston upper end has a diameter greater than the piston lower end.
16. An exhaust brake comprising:
a housing having a central opening and a boss with a central bore, wherein the central bore intersects the central opening;
a means for selectively blocking the central opening, said means for selectively blocking the central opening having a bypass opening provided therein, and having an upstream side;
a means for selectively blocking the bypass opening, said means for selectively blocking the bypass opening having an upper end disposed in the central bore distal from the bypass opening;
one or more passages extending between the central opening and the central bore at the upstream side of the means for selectively blocking the central opening; and
a means for biasing the means for selectively blocking the bypass opening into the bypass opening.
17. The exhaust brake of claim 16 , wherein the means for selectively blocking the bypass opening has a right-cylinder shape and the bypass opening has a mating square notch shape.
18. The exhaust brake of claim 16 , wherein the means for selectively blocking the bypass opening has a spherical shape and the bypass opening has a mating spherical shape.
19. The exhaust brake of claim 16 , wherein the means for selectively blocking the bypass opening has a frusto-conical shape and the bypass opening has a mating frusto-conical shape.
20. The exhaust brake of claim 16 , wherein the means for selectively blocking the bypass opening has a wedge shape and the bypass opening has a mating wedge shape.