HK1189643B - Cutter assembly for tunnel boring machine with pressure compensation - Google Patents

Description

Cutter assembly for tunnel boring machine with pressure compensation

Cross reference to related patent applications

This application claims priority to U.S. provisional application No.61/444,081, filed on 17/2/2011, which is hereby incorporated by reference in its entirety.

Background

Tunnel boring machines ("TBMs") are excavating equipment commonly used to tunnel through soil and rock formations. Conventional TBMs produce smooth circular tunnel walls, typically with minimal parallel perturbations. A breakthrough development that made TBM efficient and reliable was the invention of a rotating head with a rotatable cutter assembly proposed by james. Initially, the TBM of Robbins used strong spikes fixedly mounted to the rotating head, but the spikes frequently broke. He found that this problem could be significantly reduced by replacing these grinding spikes with a longer continuously rotating disc cutter assembly.

Accordingly, modern TBMs typically employ a rotating head having a disc cutter assembly rotatably mounted to the head. The head is urged against the target surface with extreme force such that at least some of the cutter assemblies engage the surface. As the head rotates, the cutters separate, comminute and/or loosen material that is carried away by the TBM. The TBM continues to tunnel as the loosened material is removed.

A wide variety of earth conditions are encountered during the excavation of certain tunnels. Sandstone, marl, limestone, clay and chalk are all possible. Sometimes, several types of soil may be encountered simultaneously. The disc cutter assembly must typically operate under extreme conditions and must operate reliably under high loads. For example, the cutter disc or blade may exert more than 75,000 pounds of force normal to the rock surface.

The ground water level along the tunnelling track may also vary significantly. In certain applications, TBMs encounter highly saturated and flowable materials. Hydrostatic pressure on the cutter assembly may be significant when loose and/or saturated soil conditions are encountered. If dust or other foreign matter enters the cutter bearing assembly, the cutter assembly may jam, requiring the user to repair or replace the cutter assembly before continued use. The cutter assembly is provided with a durable and robust seal to avoid the intrusion of dust into the bearing assembly. However, if the hydrostatic load on both sides of the seal becomes very high, the seal may be broken.

There remains a need for an improved sealing mechanism to prevent the intrusion of dust and other foreign matter into the cutter assembly of a tunnel boring machine operating under high hydrostatic pressure conditions.

Disclosure of Invention

This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features of the claimed subject matter, nor is it intended to be used as an aid in determining the scope of the claimed subject matter.

The present invention discloses a cutter assembly for a tunnel boring machine which is suitable for use in, for example, highly saturated soils and at high ambient pressures. The cutter assembly includes a shaft, a cutter ring assembly rotatably mounted on the shaft, and oppositely disposed first and second end retainers non-rotatably attached to the shaft. A seal pack (e.g., a mechanical face seal or a double cone seal) provides a seal between the rotating and non-rotating components, and the available volume in the cutter assembly is filled with a lubricant, such as oil. By engaging the movable piston portion into the at least one end retainer, the amount of pressure on both sides of the seal pack is reduced when the cutter assembly is operating at depth. The movable piston portion has an outer surface exposed to a local ambient pressure and is configured to increase a pressure of the lubricant in response to an increase in the ambient pressure. The cutter ring assembly may be formed as a unitary structure, or may be formed with a hub that is removably attached to one or more cutter rings.

In one embodiment, at least one of the end retainers includes a fixed retainer having a pressure port in fluid communication with the lubricant and a floating retainer slidably engaging the fixed retainer to define a gap filled with the lubricant. The floating retainer may include an outer wall configured to receive the fixed retainer and an inner wall configured to slidably engage the annular groove in the fixed retainer.

In one embodiment, at least one of the end retainers includes an outwardly facing annular groove having a pressure port extending through the end retainer and an annular piston slidably disposed in the groove. The lubricant fills the volume between the groove and the piston. The annular piston is exposed to a local ambient pressure such that increasing the ambient pressure will increase the lubricant pressure. The groove may include a plurality of pressure ports.

In one embodiment, at least one of the end retainers has a plurality of cylindrical recesses and corresponding ports extending from the recesses through the end retainer. A piston is slidably disposed in each recess, and a volume between each piston and the port is filled with a lubricant. In one embodiment, an extendable seal is provided on each recess.

In one embodiment, a pressure compensated cutter assembly for a tunnel boring machine includes a shaft, a cutter ring rotatably mounted on the shaft, first and second end retainers non-rotatably attached to the shaft, a seal pack immersed in lubricant and disposed between the cutter ring and the first and second end retainers, and a piston device incorporated into at least one of the end retainers and configured to transfer at least a portion of an external ambient pressure into the lubricant.

Drawings

The foregoing aspects and many of the attendant advantages of this invention will become more readily appreciated as the same become better understood by reference to the following detailed description, when taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a cross-sectional front view of a prior art cutter assembly;

FIG. 2 is a front cross-sectional view of a first embodiment of a pressure compensated cutter assembly according to the present disclosure;

FIG. 3 is a cross-sectional side view of a pressure compensating retainer assembly for the cutter assembly shown in FIG. 2;

FIG. 4 is a front cross-sectional view of a second embodiment of a pressure compensated cutter assembly according to the present disclosure;

FIG. 5 is a side view of the cutter assembly shown in FIG. 4;

FIG. 6 is a close-up detail cross-sectional view of a pressure port for the cutter assembly shown in FIG. 4;

FIG. 7 is a perspective view of a third embodiment of a pressure compensated cutter assembly according to the present invention;

FIG. 8 is a cross-sectional front view of the cutter assembly shown in FIG. 7; and

FIG. 9 is a detailed cross-sectional view of a piston and pressure port for the cutter assembly shown in FIG. 7.

Detailed Description

Figure 1 is a cross-sectional view of a prior art cutter assembly 80 for a tunnel boring machine. An exemplary tunnel boring machine is disclosed in U.S. patent No.7,832,960, which is hereby incorporated by reference in its entirety.

Cutter assembly 80 includes a shaft 81 configured to be fixedly attached to the TBM rotating head. The annular cutter ring 82 is attached to the hub 83 with a retainer ring 84 to form a ring assembly 85. The ring assembly 85 is rotatably mounted to the shaft 81 using a pair of bearing assemblies comprising an inner bearing race 87, an outer bearing race 88 and a plurality of tapered roller bearings 89. A pair of end retainers 90, 91 are provided on either side of the hub 83. During operation, the ring assembly 85 is able to rotate about the shaft 81, and the end retainers 90, 91 are fixed to the shaft 81.

A rotary seal pack 92 is provided at the interface between each end retainer 90, 91 and the ring assembly 85. The rotary seal pack for the cutter assembly is typically a mechanical face seal, also known as a double cone seal. A particular double cone seal assembly is disclosed in U.S. patent No.3,985,366, which is hereby incorporated by reference in its entirety. The mechanical face seal is used to protect equipment that operates under the most adverse conditions and comprises a pair of annular metal seal rings 93 and a pair of resilient toroidal members 94 (e.g., O-rings). The outer metal seal ring 93 is engaged and secured with the associated end retainer 90 or 91 by a toroidal member 94, and the associated inner metal seal ring 93 engages the ring assembly 85 by a toroidal member 94. Two associated metal seal rings 93 abut to form a moving seal interface. Typically, the available internal volume between the end retainers 90, 91 is filled with a lubricant, such as oil or grease.

The rotating seal pack 92 provides a seal against the ingress of dust that could damage or destroy the bearing assembly. Mechanical face seals are specifically designed to provide reliable seal protection in very harsh environments. However, if the cutter assembly 80 is used in an environment with high hydrostatic pressure loads (e.g., very deep in saturated media), the external pressure may overcome the rotary seal pack 92, which may cause the cutter assembly to fail.

Fig. 2 is a cross-sectional view of a pressure compensated cutter assembly 100 according to the present invention. The pressure compensated cutter assembly 100 is similar in many respects to the prior art cutter assembly 80 described above. A ring assembly 105 is shown which includes an annular cutter ring 102 mounted on a hub 103 and secured with a retainer ring 104. Other configurations of the ring assembly are contemplated. For example, in an alternative embodiment, the cutter ring and hub may be formed as a single integral component, rather than as the presently preferred assembly. The ring assembly 105 is rotatably mounted on the shaft 101 using left and right bearing assemblies, each bearing assembly comprising an inner race 107, an outer race 108 and a plurality of tapered roller bearings 109 captured in a bearing cage 106. A pair of rotary seal sets 112, including mechanical face seals, provide protection for the bearing assembly.

A conventional end retainer 110 is attached to the shaft 101 on one side (on the left side of fig. 2) and a pressure compensating retainer assembly 115 is attached to the shaft 101 on the opposite side (on the right side of fig. 2). In this embodiment, pressure compensating end retainer 115 includes a fixed retainer 116 and a floating retainer 117 that functions as a piston to increase the pressure of the lubricant within cutter assembly 100, as described below.

The fixed retainer 116 is fixed to the shaft 101, and the floating retainer 117 slidably engages the fixed retainer 116. In the current embodiment, the fixed retainer 116 has a threaded central bore 118 that engages with a corresponding thread on the shaft 101.

Referring now also to fig. 3, a cross-sectional view of a separate pressure compensating retainer assembly 115 is shown. The stationary retainer 116 has a peripheral inner recess 119 configured to engage a non-rotating portion of the rotary seal pack 112. One or more apertures 120 are provided through the recessed portion 119. For example, in the current embodiment, there are four evenly spaced apertures 120 (two can be seen in FIG. 3). An external annular groove 121 is also provided at a radial location between the recessed portion 119 and the central aperture 118.

Floating retainer 117 is a generally annular ring having a U-shaped cross-section with an outer wall 122 sized and positioned to slidably engage the outer periphery of fixed retainer 116 and an inner wall 123 sized and positioned to slidably engage annular groove 121. A first O-ring 124 provides a seal between the outer wall 122 of the floating retainer 117 and the fixed retainer 116. A pair of O-rings 125, 126 provide a seal between the inner wall 123 and the annular groove 121 of the fixed retainer 116. One or more threaded apertures 127 through the floating retainer 117 provide a means for injecting lubricant into the gap 129 between the fixed retainer 116 and the floating retainer 117. The threaded aperture 127 is closed with a corresponding threaded plug 128.

Based on the above-described volume available in the cutter assembly 100 also being filled with lubricant, the operation of the pressure compensated cutter assembly 100 can now be understood. When hydrostatic pressure on the cutter assembly 100 increases, such as when a ripping operation encounters highly saturated mud at an extreme depth, the high hydrostatic pressure will cause the floating retainer 117 to move inwardly toward the fixed retainer 116, thereby pressurizing the oil (or other lubricant) in the gap 129 and, thus, the volume behind the seal pack 112. Thus, by the action of the floating retainer 117, a small pressure differential is automatically maintained across the seal pack 112 and the risk of foreign material intrusion into the bearing assembly is greatly reduced.

Fig. 4-6 illustrate another embodiment of a pressure compensated cutter assembly 200 according to the present invention. Fig. 4 is a cross-sectional view of cutter assembly 200, fig. 5 is a side view of cutter assembly 200, and fig. 6 is a close-up detail cut-away view showing the pressure port.

This exemplary embodiment shows a dual disc cutter assembly 200 having a toothed spacer 211 and two cutter rings 202 mounted to a hub 203 and secured with a retainer ring 204. A bearing assembly 207, similar to the bearing assembly described above, rotatably couples ring assembly 205 with central shaft 201. Oppositely disposed pressure compensating end retainers 215 are fixed to shaft 201, for example end retainer 215 may be attached to shaft 201 with bolts 206. A pair of rotary seal assemblies 212 similar to those described above provide a seal between the rotating and stationary components.

In this embodiment, each end retainer 215 defines an outwardly open annular groove 230. A plurality of ports 216 extend through the end retainer 215 from the annular groove 230 to the interior of the cutter assembly 200. An annular piston 231 is slidably disposed in the groove 230 and sealingly engages the wall of the annular groove 230 by an O-ring 224. An annular piston 231 may be retained in the groove 230 using a C-clip 232 or the like.

As described above, the interior of the cutter assembly 200 is filled with a lubricant, such as oil. In this embodiment, the port 216 and the inward portion of the annular groove 230 are also filled with oil.

It should now be appreciated that if the cutter assembly encounters high hydrostatic pressure, the external pressure P will tend to push the annular piston 231 inwardly to pressurize the oil and through the port 216, thereby pressurizing the area behind the rotating seal pack 212 so that the pressure on both sides of the seal pack 212 is substantially equalized. Thus, by the action of annular piston 231, a small pressure differential is maintained across seal pack 212, and the risk of foreign matter intrusion into the bearing assembly is greatly reduced.

Fig. 7-9 illustrate another embodiment of a pressure compensated cutter assembly 300 according to the present invention. Fig. 7 is a perspective view of cutter assembly 300, fig. 8 is a cross-sectional view of cutter assembly 300, and fig. 9 is a close-up detail cut-away view showing a pressure port.

The cutter assembly 300 is also a dual disc cutter having a toothed spacer 311 mounted to a hub 303 with a retainer ring 304 and two cutter rings 302, similar to the cutter assembly 200 described above. A pair of tapered roller bearing assemblies 307 rotatably couple ring assembly 305 with central shaft 301. An oppositely disposed pressure compensating end retainer 315 is also attached to the shaft 301. A pair of mechanical face seal rotary seal sets 312 provide a seal between the rotary ring assembly 305 and the stationary components.

In this embodiment, the end retainers 315 include a plurality of cylindrical recesses 330 on the outer side of each retainer 315, the cylindrical recesses being connected to the interior of the cutter assembly 300 through associated ports 316. A floating disc piston 331 is disposed in each recess 330 and sealingly engages the cylindrical recess 330 by means of an O-ring 324. A seal 333 that is circularly pleated or otherwise extendable protects the cylindrical recess 330 from dust and other foreign matter. The seal 333 may be retained in the recess 330 using a C-clip 332 or the like.

As with the previous embodiments, cutter assembly 300 is filled with lubricant and cylindrical recess 330 is similarly filled with lubricant for at least the portion disposed inwardly from associated piston 331. As shown in FIG. 9, when cutter assembly 300 is subjected to external hydrostatic pressure P, piston 331 will be urged inwardly, thereby pressurizing the lubricant in the associated recess 330, and thus the interior of cutter assembly 300. Thus, the pressure in the interior of the cutter assembly 300 is substantially balanced with the external hydrostatic pressure P.

Although the end retainer 315 is shown with three cylindrical recesses 330 in the current embodiment, it is readily understood that more or fewer pressure compensation mechanisms may be employed.

Additionally, it should be understood that an externally expandable seal corresponding to the extendable seal 333 may be incorporated into the second embodiment 200 disclosed above, with simple modifications as will be apparent to those skilled in the art.

While the preferred embodiments of the invention have been illustrated and described, it will be appreciated that various changes can be made therein without departing from the spirit and scope of the invention.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows.

Claims (8)

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 to 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 localized hydrostatic pressure, the movable piston portion including a floating retainer slidably engaging the fixed retainer such that a gap is defined between the fixed retainer and the floating retainer, the gap being in fluid communication with the pressure port;

a first rotary seal pack having a first portion engaged with the cutter ring assembly and a second portion engaged with the first end retainer; and

a second rotary seal pack having a first portion engaged with the cutter ring assembly and a second portion engaged with the second end retainer;

wherein the first rotary seal set is immersed in a lubricant that is in fluid communication with the pressure port and fills a gap between the stationary retainer and the floating retainer such that the movable piston portion is configured to increase a pressure of the lubricant in response to an increase in the localized hydrostatic pressure; and is

Wherein the fixed retainer further comprises an annular groove and an outer periphery, and wherein the floating retainer comprises an annular wall slidably engaged with the annular groove and an outer wall slidably engaged with the outer periphery of the fixed retainer.

2. The cutter assembly for a tunnel boring machine according to claim 1, wherein the floating retainer further includes a through port for facilitating injection of lubricant into the gap and a plug for sealingly closing the through port.

3. The cutter assembly for a tunnel boring machine according to claim 1, wherein the cutter ring assembly includes a hub rotatably mounted to the shaft by a tapered roller bearing and a cutter ring extending radially outwardly from the hub.

4. The cutter assembly for a tunnel boring machine according to claim 1, wherein the first rotary seal pack includes a double cone seal.

5. 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 pack having a first portion engaged with the cutter ring assembly and a second portion engaged with the first end retainer; and

a second rotary seal pack having a first portion engaged with the cutter ring assembly and a second portion engaged with 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 wherein the closed volume is additionally filled with a lubricant;

wherein the first end retainer includes a movable portion having an outer surface exposed to 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 ambient pressure;

wherein the first end retainer comprises a fixed retainer having at least one pressure port in fluid communication with a lubricant, and the movable portion comprises a floating retainer slidably engaging 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 is

Wherein the fixed retainer further comprises an annular groove and an outer periphery, and wherein the floating retainer comprises an annular wall slidably engaged with the annular groove and an outer wall slidably engaged with the outer periphery of the fixed retainer.

6. The pressure compensated cutter assembly for a tunnel boring machine according to claim 5 wherein the floating retainer further includes at least one through port to facilitate injection of lubricant into the gap.

7. A pressure compensating cutter assembly for a tunnel boring machine according to claim 5 wherein the cutter ring assembly comprises a hub rotatably mounted to the shaft by means of tapered roller bearings and a cutter ring extending radially outwardly from the hub.

8. The pressure compensated cutter assembly for a tunnel boring machine according to claim 5 wherein the first rotary seal set includes a double cone seal.