# US 8,783,786 B2 · Cutter assembly for tunnel boring machine with pressure compensation > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,783,786 B2 - Document ID: US8783786B2 - Status: Granted - Kind: B2 - Application number: 13/397,997 - Filed: 2012-02-16 - Published: 2012-08-23 - Granted: 2014-07-22 - Earliest claimed: 2011-02-17 - Assignees: The Robbins Company - Applicants: Aaron J. Shanahan; Stephen M. Smading; Timothy A. Lang; Zachary J. Box; Brian B. Khalighi; Brad D. Grothen; Carl E. Lenaburg; Jay M. McNeeley; Shinichi Konda - Inventors: Aaron J. Shanahan; Stephen M. Smading; Timothy A. Lang; Zachary J. Box; Brian B. Khalighi; Brad D. Grothen; Carl E. Lenaburg; Jay M. McNeeley; Shinichi Konda - Web page: https://patentgrep.com/patent/US8783786B2 ## CPC - E21D 9/104: {Cutting tool fixtures (devices with percussive tools E21D9/106)} - A61K 31/7076: containing purines, e.g. adenosine, adenylic acid - A61K 45/06: Mixtures of active ingredients without chemical characterisation, e.g. antiphlogistics and cardiaca - E21B 10/10: with roller axle supported at both ends - E21B 10/22: characterised by bearing, lubrication or sealing details - E21D: SHAFTS; TUNNELS; GALLERIES; LARGE UNDERGROUND CHAMBERS (soil-conditioning or soil-stabilising materials C09K17/00; drilling or cutting machines for mining or quarrying E21C; safety devices, transport, rescue, ventilation or drainage E21F) - A61K: PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES (devices or methods specially adapted for bringing pharmaceutical products into particular physical or administering forms A61J3/00; chemical aspects of, or use of materials for deodorisation of air, for disinfection or sterilisation, or for bandages, dressings, absorbent pads or surgical articles A61L; soap compositions C11D) - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS ## Abstract A pressure-compensated cutter assembly for a tunnel boring machine includes a shaft a cutter ring assembly rotatably mounted on the shaft, and first and second end retainers non-rotatably attached to the shaft. Rotary seal groups, immersed in lubricant, provide a moving seal between the rotating cutter ring assembly and the end retainers. A movable piston member is exposed to ambient pressures, and contacts the lubricant, such that increasing ambient pressure will increase the lubricant pressure, thereby keeping the pressure differential across the seal small. In one embodiment, the piston is a floating retainer portion. In another embodiment, the piston is an annular piston, and in another embodiment, the piston is a plurality of smaller pistons disposed in the first retainer. ## Claims ### Claim 1 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 fixed retainer with a pressure port therethrough and a movable piston portion with an outer surface subject to a local hydrostatic pressure, the movable piston portion comprising a floating retainer that slidably engages the fixed retainer such that a gap is defined between the fixed retainer and the floating retainer that is in fluid communication with the pressure port; 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; such that the first rotary seal group is immersed in a lubricant that is in fluid communication with the port and fills the gap between the fixed retainer and the floating retainer such that the movable piston portion is configured to increase the pressure of the lubricant in response to an increase in the local hydrostatic pressure; and further 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. ### Claim 2 (depends on 1) The cutter assembly of claim 1, wherein the floating retainer further comprises a through port to facilitate injecting lubricant into the gap and a plug that sealingly closes the through port. ### Claim 3 (depends on 1) The cutter assembly of claim 1, wherein the cutter ring assembly comprises a hub rotatably mounted to the shaft with tapered roller bearings and a cutter ring extending radially outwardly from the hub. ### Claim 4 (depends on 1) The cutter assembly of claim 1, where the first rotary seal group comprises a duo-cone seal. ### Claim 5 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. ### Claim 6 (depends on 5) The cutter assembly of claim 5, wherein the at least one pressure port comprises a plurality of pressure ports. ### Claim 7 (depends on 5) The cutter assembly of claim 5, further comprising a retaining element disposed in the annular channel and operable to retain the annular piston in the annular channel. ### Claim 8 (depends on 5) The cutter assembly of claim 5, wherein the first rotary seal group comprises a duo-cone seal. ### Claim 9 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. ### Claim 10 (depends on 9) The cutter assembly of claim 9, further comprising a plurality of extendable seals, wherein each extendable seal is attached near an outer edge of a corresponding one of the plurality of cylindrical recesses. ### Claim 11 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. ### Claim 12 (depends on 11) The pressure-compensated cutter assembly of claim 11, wherein the floating retainer further comprises at least one through port to facilitate injecting lubricant into the gap. ### Claim 13 (depends on 11) The pressure-compensated cutter assembly of claim 11, wherein the cutter ring assembly comprises a hub rotatably mounted to the shaft with tapered roller bearings and a cutter ring extending radially outwardly from the hub. ### Claim 14 (depends on 11) The pressure-compensated cutter assembly of claim 11, wherein the first rotary seal group comprises a duo-cone seal. ### Claim 15 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. ### Claim 16 (depends on 15) The pressure-compensated cutter assembly of claim 15, wherein the at least one pressure port comprises a plurality of pressure ports. ### Claim 17 (depends on 15) The pressure-compensated cutter assembly of claim 15, wherein the at least one pressure port and the portion of the annular channel disposed inwardly of the annular piston are filled with the lubricant. ### Claim 18 (depends on 15) The pressure-compensated cutter assembly of claim 15, further comprising a retaining element disposed in the annular channel and operable to retain the annular piston in the annular channel. ### Claim 19 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. ### Claim 20 (depends on 19) The pressure-compensated cutter assembly of claim 19, further comprising a plurality of extendable seals, wherein each extendable seal is attached near an outer edge of a corresponding one of the plurality of cylindrical recesses.