Cutter assembly for tunnel boring machine with pressure compensation

A cutter assembly for a tunnel boring machine comprising:

• a shaft;
• a cutter ring assembly rotatably mounted on the shaft;
• a first end retainer attached to one end of the shaft and a second end retainer attached on an opposite end of the shaft, the first end retainer having a movable piston portion with an outer surface subject to a local hydrostatic pressure;
• a first rotary seal group having a first portion engaging the cutter ring assembly and a second portion engaging the first end retainer;
• and
• a second rotary seal group having a first portion engaging the cutter ring assembly and a second portion engaging the second end retainer;
• wherein the first rotary seal group is immersed in a lubricant;
• wherein the movable piston portion is configured to increase the pressure of the lubricant in response to an increase in the local hydrostatic pressure;
• and
• wherein the first end retainer comprises an outer surface defining an annular channel with at least one pressure port that extends from the annular channel through the first end retainer to provide fluid communication with an inner side of the first rotary seal group, and an annular piston slidably disposed in the annular channel and exposed to the hydrostatic pressure, and further comprising means for retaining the annular piston in the annular channel, wherein the annular channel volume between the annular piston and the pressure port is filled with the lubricant.

A cutter assembly for a tunnel boring machine comprising:

• a shaft;
• a cutter ring assembly rotatably mounted on the shaft;
• a first end retainer attached to one end of the shaft and a second end retainer attached on an opposite end of the shaft, the first end retainer having a movable piston portion with an outer surface subject to a local hydrostatic pressure;
• a first rotary seal group having a first portion engaging the cutter ring assembly and a second portion engaging the first end retainer;
• and
• a second rotary seal group having a first portion engaging the cutter ring assembly and a second portion engaging the second end retainer;
• wherein the first rotary seal group is immersed in a lubricant;
• wherein the movable piston portion is configured to increase the pressure of the lubricant in response to an increase in the local hydrostatic pressure;
• and
• wherein the first end retainer comprises a plurality of cylindrical recesses defined in an outer surface of the first end retainer, and a plurality of pressure ports extending from a corresponding one of the plurality of cylindrical recesses to the first rotary seal group, and a plurality of pistons slidably disposed in a corresponding one of the plurality of cylindrical recesses, wherein the pistons are exposed to the hydrostatic pressure.

A pressure-compensated cutter assembly for a tunnel boring machine comprising:

• a shaft;
• a cutter ring assembly rotatably mounted on the shaft;
• a first end retainer non-rotatably attached to one end of the shaft and a second end retainer non-rotatably attached to an opposite end of the shaft;
• a first rotary seal group having a first portion engaging the cutter ring assembly and a second portion engaging the first end retainer;
• and
• a second rotary seal group having a first portion engaging the cutter ring assembly and a second portion engaging the second end retainer;
• wherein the first and second rotary seal groups are enclosed within a closed volume defined by the shaft, the cutter ring assembly, and the first and second end retainers, and further wherein the closed volume is otherwise filled with a lubricant;
• and
• wherein the first end retainer includes a movable portion having an outer surface that is exposed to an ambient pressure and an inner surface exposed to the lubricant such that the movable portion will increase the pressure of the lubricant in response to an increase in the ambient pressure;
• wherein the first end retainer comprises a fixed retainer having at least one pressure port that is in fluid communication with the lubricant, and the movable portion comprises a floating retainer that slidably engages the fixed retainer such that a gap is defined between the fixed retainer and the floating retainer, wherein the gap is filled with the lubricant;
• and
• wherein the fixed retainer further comprises an annular channel and an outer perimeter, and further wherein the floating retainer comprises an annular wall that slidably engages the annular channel and an outer wall that slidably engages the outer perimeter of the fixed retainer.

A pressure-compensated cutter assembly for a tunnel boring machine comprising:

• a shaft;
• a cutter ring assembly rotatably mounted on the shaft;
• a first end retainer non-rotatably attached to one end of the shaft and a second end retainer non-rotatably attached to an opposite end of the shaft;
• a first rotary seal group having a first portion engaging the cutter ring assembly and a second portion engaging the first end retainer;
• and
• a second rotary seal group having a first portion engaging the cutter ring assembly and a second portion engaging the second end retainer;
• wherein the first and second rotary seal groups are enclosed within a closed volume defined by the shaft, the cutter ring assembly, and the first and second end retainers, and further wherein the closed volume is otherwise filled with a lubricant;
• wherein the first end retainer includes a movable portion having an outer surface that is exposed to an ambient pressure and an inner surface exposed to the lubricant such that the movable portion will increase the pressure of the lubricant in response to an increase in the ambient pressure;
• wherein the first end retainer comprises a fixed retainer having at least one pressure port that is in fluid communication with the lubricant, and the movable portion comprises a floating retainer that slidably engages the fixed retainer such that a gap is defined between the fixed retainer and the floating retainer, wherein the gap is filed with the lubricant;
• and
• wherein the first end retainer comprises an outer surface defining an annular channel with at least one pressure port that extends from the annular channel through the first end retainer and is in fluid communication with the first rotary seal group, and an annular piston slidably disposed in the annular channel and exposed to the ambient pressure, and further comprising means for retaining the annular piston in the annular channel.

A pressure-compensated cutter assembly for a tunnel boring machine comprising:

• a shaft;
• a cutter ring assembly rotatably mounted on the shaft;
• a first end retainer non-rotatably attached to one end of the shaft and a second end retainer non-rotatably attached to an opposite end of the shaft;
• a first rotary seal group having a first portion engaging the cutter ring assembly and a second portion engaging the first end retainer;
• and
• a second rotary seal group having a first portion engaging the cutter ring assembly and a second portion engaging the second end retainer;
• wherein the first and second rotary seal groups are enclosed within a closed volume defined by the shaft, the cutter ring assembly, and the first and second end retainers, and further wherein the closed volume is otherwise filled with a lubricant;
• and
• wherein the first end retainer includes a movable portion having an outer surface that is exposed to an ambient pressure and an inner surface exposed to the lubricant such that the movable portion will increase the pressure of the lubricant in response to an increase in the ambient pressure;
• wherein the first end retainer comprises a plurality of cylindrical recesses defined in an outer surface of the first end retainer, and a plurality of pressure ports extending from a corresponding one of the plurality of cylindrical recesses to the first rotary seal group, and a plurality of pistons slidably disposed in a corresponding one of the plurality of cylindrical recesses, wherein the plurality of pistons are exposed to the ambient pressure.