Pneumatically Operated Stop Shaft Seal

Abstract

The stop seal prevents leakage of the process fluid when the shaft is not rotating. The seal comprises a flexible band surrounding the shaft, the flexible band comprising a thick, substantially rectangular central region from which thin lateral regions extend. By applying pressurized control fluid to the backside of the band, the central region extends through the gap between the cover plates and forms a seal with the shaft or intermediate structure. By depressurizing the control fluid, the central region is pulled away from the shaft entirely by the resilience of the band or with the assistance of a spring. In various embodiments, the seal is formed radially inward or axially. The lateral regions may be substantially flat or curved. The stop seal may be integral with the rotary shaft seal and may be upstream or downstream of it. The control fluid may be a process fluid.

Description

Related Applications

[0001] This application claims priority to U.S. Non-provisional Application No. 17 / 742,851, filed May 12, 2022, which is incorporated by reference in its entirety for all purposes. [Technical field]

[0002] The present invention relates to stop seals, and more particularly to pressure-actuated stop seals applicable for sealing against high pressure differentials. [Background technology]

[0003] Many rotating shaft sealing approaches are known for limiting leakage of process fluids through a housing penetrated by a rotating shaft. One example is the rotating face mechanical seal, which provides a contactless seal with minimal process fluid leakage, even with highly pressurized gas process fluids. In some cases, grooves or other features are provided on at least one face of the rotating face mechanical seal that function to repel process fluid from the seal when the shaft is rotating.

[0004] In many cases, for example when sealing gases that are toxic or otherwise hazardous to personnel and to the environment, it is desirable to form a hermetic seal with the shaft even when the shaft is not rotating. Many rotating shaft seals are inefficient for forming a seal under these "rest" conditions. Instead, a separate rest seal may be provided that is pulled away from the shaft when the shaft is rotating and pressed against the shaft to form a seal when the shaft is not rotating. Process fluid is thereby prevented from reaching the environment under rest conditions by preventing the process fluid from reaching the rotating shaft seal or by preventing the process fluid from reaching the outside environment if it leaks past the rotating shaft seal. Often a controller is implemented both to control the start and stop of shaft rotation and to control the opening and closing of the rest shaft seal.

[0005] Referring to FIG. 1A, one approach is to provide a solid rigid sealing annulus 100 that surrounds the shaft 102 and can be pressed into axial contact with a radial structure 104 that is sealed to the shaft 102 via a support structure 106. In the example of FIG. 1A, the sealing annulus 100 is pneumatically driven towards the radial structure 104 when the shaft 102 is not rotating, and is pulled away from the shaft 102 by a spring 108 when the shaft is rotating. In a similar example, the sealing annulus 100 is driven by a bidirectional pneumatic piston or by a mechanical mechanism such as a solenoid. Typically, a stop shaft seal is activated and deactivated by a controller (not shown), which may be, but is not necessarily, the same controller that controls the starting and stopping of the shaft rotation.

[0006] While this approach is durable and capable of sealing high pressure process fluids (such as high pressure gases), it is inherently complex and expensive to manufacture.

[0007] 1B and 1C, another approach is to surround the shaft 102 with a hollow elastomeric tube 110 that is constrained by a housing 112 and in fluid communication with an inflation source (not shown) (e.g., a pressurized nitrogen gas source) via an inflation flow inlet 116. The cross section of the tube 110 is shaped so that it does not normally extend beyond the housing 112 to the shaft 102. However, when the interior 114 of the tube 110 is pressurized by an inflation source, the tube 110 expands radially inwardly beyond the housing 112 to form a seal with both the housing 112 and the shaft 102. FIG. 1B shows the stop shaft seal when open, and FIG. 1C shows the seal when closed.

[0008] 1B and 1C is simple and relatively easy to manufacture, however, it can be difficult to provide complex cross-sectional shapes for the tube 110 because the tube 110 is typically extruded rather than cast.

[0009] 1D and 1E, in a similar approach, a molded elastomeric band 118 is fastened onto a support foam 120 and placed within the housing 112. The support foam 120 is pierced by an inflation inlet 116, which faces the backside of the band 118. Referring to FIG. 1D, when no pressure is applied through the inflation inlet 116, the elastomeric band 118 remains flush against the support foam 120 and does not extend beyond the housing 112. However, referring to FIG. 1E, when pressure is applied through the inflation inlet 116, a pocket of fluid forms between the band 118 and the support foam 120, such that the band 118 is stretched radially inward from the housing 112 and pressed against the shaft 102 to form a seal.

[0010] While these approaches may be effective under some circumstances, they tend to fail when attempting to form a seal against high pressure fluids (such as gases pressurized to 70 or 90 bar). Referring to FIG. 1F, when the seal is closed and very high pressure is applied by the process fluid upstream of the seal, with no corresponding pressure downstream of the seal, the elastomeric seal 118 may deform and even be forced 122 into the gap between the shaft 102 and the housing 112, such that the band 118 does not fully come off the shaft 102 when pressure is no longer applied via the expansion inlet 116. In such cases, it may be necessary to use a rigid mechanical approach such as that shown in FIG. 1A.

[0011] Therefore, there is a need for a stop shaft seal that is simple in design, relatively inexpensive to manufacture, and capable of producing a seal that reliably withstands high pressures of process fluids. Summary of the Invention

[0012] The present invention is a fluid pressure actuated stop shaft seal that is simple in design, relatively inexpensive to manufacture, and capable of producing a seal that reliably withstands high pressure process fluids (such as process gases pressurized to 70 bar or more).

[0013] The disclosed seal comprises a flexible band mounted within an annular housing and surrounding a rotatable shaft. The flexible band comprises a thick, substantially rectangular central region flanked by thinner side regions. The thinner side regions of the flexible band provide radial or axial flexibility to the thicker central region such that it can be stretched through and subsequently retracted from an annular opening in the housing. The thickness of the central region allows it to resist being deformed or extruded when pressed against the shaft and subjected to a high fluid pressure differential. Pressurized control fluid is applied to the back side of the central region via a control fluid inlet to close the stop seal.

[0014] The pressurized control fluid applied to the backside of the flexible band is controlled by a controller, which in embodiments also controls the rotation of the shaft. While the shaft is rotating, no pressure is applied to the backside of the central region of the flexible band, so that the central region remains partially or completely within the annular housing and does not contact the shaft. When the shaft is not rotating (i.e., at rest), fluid pressure is applied by the controller through the control fluid inlet to the backside of the central region of the flexible band. As a result, the central region of the flexible band is forced through the annular opening in the housing and toward the shaft or toward an intermediate structure that is sealed against the shaft and forms a rest seal therewith. In radial embodiments, the change in diameter of the central region is only a small percentage of the overall diameter of the flexible band, so that the central region can easily accommodate the circumferential compression required as it is forced radially inward toward the shaft.

[0015] In some embodiments, the source of the control fluid is independent of the process and can be, for example, a source of pressurized nitrogen gas, pressurized air, or pressurized liquid. In other embodiments, the control fluid is a process fluid. In some of these embodiments, a pressure boost device is utilized to increase the pressure of the process fluid applied to the back side of the flexible band.

[0016] In various embodiments, the flexible band is made of a material (such as an elastomer) that is sufficiently elastic to ensure that it returns to its original shape when it is no longer deformed by the applied fluid pressure, so that the elasticity of the elastomer allows the central region to be fully pulled away from the shaft when the applied fluid pressure is removed. In other embodiments, the flexible band is made of a flexible and durable, but less elastic material (such as PTFE), so that the flexible band may not be able to fully pull the central region away from the shaft when the control fluid pressure is stopped. Some of these embodiments include a pair of annular toothed springs, each having a solid annular region fixed in place within the housing and a toothed annular region that underlies at least a portion of the side regions of the flexible band. The toothed springs provide an additional restoring force that ensures that the central region is fully pulled away from the shaft.

[0017] The embodiment further includes a pair of rigid annular rings on either side of the thickened central region that completely eliminates the possibility of the thickened region being extruded into the gap between the housing and the shaft when the stop seal is engaged. The annular rings may be attached to the central region of the flexible band or may be fixed to the housing and extend into the gap between the shaft and the housing.

[0018] The stop seal of the present invention can be implemented with at least one rotating shaft seal (rotating face mechanical seal). The stop seal can be implemented upstream or downstream of the rotating shaft seal. Alternatively, if multiple rotating shaft seals are provided, the stop seal may be implemented between the rotating shaft seals. In some embodiments, multiple disclosed stop seals are provided, for example, one is provided upstream of the rotating shaft seal and one is provided downstream of the rotating shaft seal.

[0019] While the disclosed stationary seals are sometimes described herein as acting radially inward, it will be apparent to one skilled in the art that in other embodiments the stationary seals are axial. For example, in an embodiment, a central region of the flexible band is forced axially against a radially extending surface that is fixed and sealed to a rotating shaft by an intermediate support structure.

[0020] The invention is a stop seal configured to form a seal with a rotatable shaft to prevent leakage of process fluid past the stop seal when the rotatable shaft is not rotating, the stop seal comprising a flexible band surrounding the shaft, the flexible band having a relatively thick central region from which extend longitudinally relatively thinner lateral regions, the central region being substantially rectangular in cross section, a housing configured to receive the flexible band, a pair of cover plates underlying the lateral regions of the flexible band, the cover plates configured to prevent the lateral regions from extending beyond the cover plates, a gap being provided between the cover plates through which the central region of the flexible band can extend, a control fluid inlet configured to provide fluid communication between a source of pressurized control fluid and a back surface of the flexible band, and a controller.

[0021] The stop seal is configured to stretch a central region of the flexible band through the gap when the controller applies pressurized control fluid to the control fluid inlet, the central region of the flexible band contacting and forming a seal with the shaft or with an intermediate structure sealed to the shaft, and the stop seal is further configured to pull the central region of the flexible band away from the shaft or intermediate structure when the controller stops applying pressurized control fluid to the flexible band.

[0022] In an embodiment, the stop seal is configured to abut a central region of the flexible band radially inwardly against the shaft or against the intermediate structure.

[0023] In any of the above embodiments, the stop seal may be configured to abut a central region of the flexible band axially against the intermediate structure.

[0024] Any of the above embodiments may further comprise a pair of rigid annular support rings configured to support sides of the central region of the flexible band when the central region is stretched through the gap between the cover plates.

[0025] In any of the above embodiments, the stop seal may be configured to abut a central region of the flexible band radially inward against the shaft or intermediate structure, and the annular support ring may include a ring gap that allows the annular support ring to radially compress when the central region is stretched radially inward toward the shaft or intermediate structure. In some of these embodiments, the annular support ring is fixed to the central region of the flexible band. And, in any of these embodiments, the annular support ring may extend from the housing.

[0026] In any of the above embodiments, the flexible band has sufficient elasticity to cause the central region to pull away from the shaft or intermediate structure when the controller stops applying pressurized control fluid to the flexible band.

[0027] Any of the above embodiments may further include a spring configured to assist in pulling the central region of the flexible band away from the shaft or intermediate structure when the controller stops applying pressurized control fluid to the flexible band.

[0028] In some of these embodiments, the stop seal is configured to abut a central region of the flexible band radially inward against the shaft or intermediate structure.

[0029] In some of these embodiments, the spring comprises a pair of spaced apart annular bands having solid annular portions with teeth extending axially toward each other under the lateral regions of the flexible bands, with axial gaps between the teeth through which a central region of the flexible bands can be stretched into contact with the shaft or intermediate structure, and the teeth are deflected radially inward when the central region of the flexible bands is forced toward the shaft. In some of these embodiments, the stop seal further comprises a pair of rigid annular support rings extending radially inward from the spring, the rigid annular support rings configured to support the sides of the central region of the flexible bands when the central region is urged radially inward against the shaft or intermediate structure.

[0030] In others of these embodiments, the stop seal comprises a pair of rigid annular support rings that support opposite sides of a central region of the flexible band when the central region is stretched through the gap between the cover plates, the support rings having a circumferential gap that allows radially inward compression of the support rings, and the springs are compression springs applied in the gaps in the support rings.

[0031] In another embodiment with a spring configured to assist in pulling the central region of the flexible band away from the shaft or intermediate structure when the controller stops applying pressurized control fluid to the flexible band, the stop seal is configured to abut the central region of the flexible band axially against the intermediate structure, the spring comprises a pair of radially concentric annular disks having solid annular portions with teeth extending radially inwardly and radially outwardly toward each other under the lateral regions of the flexible band, with radial gaps between the radially inwardly and radially outwardly directed teeth through which the central region of the flexible band can be stretched into contact with the intermediate structure, and the teeth are bent axially when the central region of the flexible band is pushed toward the shaft.

[0032] In any of the above embodiments, the side regions of the flexible band may include portions having curved longitudinal cross-sections, thereby allowing stretching of the side regions as the central region is stretched through the gap.

[0033] In any of the above embodiments, the stop seal may be integrated with a rotary shaft seal that is configured to form a seal with the shaft when the shaft is rotating. In some of these embodiments, the stop seal is configured to form a seal with the shaft or intermediate structure upstream of the rotary shaft seal, while in other of these embodiments, the stop seal is configured to form a seal with the shaft or intermediate structure downstream of the rotary shaft seal.

[0034] In any of the above embodiments, the control fluid may be a gas or the control fluid may be a process fluid.

[0035] In any of the above embodiments, the controller may be configured to start and stop rotation of the shaft and control the application of pressurized control fluid to the flexible band.

[0036] The features and advantages described herein are not exhaustive, and many additional features and advantages will become apparent to those skilled in the art, especially upon consideration of the drawings, specification, and claims. Furthermore, it should be noted that the terminology used herein has been selected primarily for ease of reading and instructional purposes, and not to limit the scope of the inventive subject matter. [Brief description of the drawings]

[0037] [Figure 1A] 1 is a cross-sectional view of a prior art stop seal pressing a rigid sealing element against an intermediate structure.

[0038] [Figure 1B] 1 is a cross-sectional view showing an open configuration of a prior art stop seal that forms a seal by expanding a hollow tube against a shaft or intermediate structure.

[0039] [Figure 1C] FIG. 1C is a cross-sectional view of the prior art seal of FIG. 1B in a closed configuration.

[0040] [Figure 1D] FIG. 2 is a cross-sectional view showing an open configuration of a prior art stop seal comprising a thin molded elastomeric band fastened onto a supporting foam.

[0041] [Figure 1E] FIG. 1E is a cross-sectional view of the prior art seal of FIG. 1D in a closed configuration.

[0042] [Figure 1F] FIG. 1C is a cross-sectional view of the prior art seal of FIG. 1E with the elastomeric band extruded into the gap between the shaft and the seal housing by a pressure differential.

[0043] [Figure 2A] FIG. 2 is an axial cross-sectional view of an open configuration of one embodiment of the present invention in which the seal is opened entirely by the elasticity of the flexible band pulling the central region of the flexible band radially away from the shaft.

[0044] [Figure 2B] FIG. 2B is an axial cross-sectional view of the embodiment of FIG. 2A in a closed configuration.

[0045] [Figure 3A] FIG. 2 is an axial cross-sectional view of an open configuration of one embodiment of the present invention in which radial pulling of the central region away from the shaft is assisted by a spring with flexible fingers.

[0046] [Figure 3B] FIG. 3B is an axial cross-sectional view of the embodiment of FIG. 3A in a closed configuration.

[0047] [Figure 3C] FIG. 3B is a perspective view of one of the springs of FIG. 3A.

[0048] [Figure 4] FIG. 13 is an axial cross-sectional view of an open configuration of one embodiment of the present invention in which radial pulling away of the central region from the shaft is assisted by an elastomeric compression tube.

[0049] [Figure 5A] FIG. 3B is an axial cross-sectional view of an embodiment similar to FIG. 3A, but further comprising a pair of rigid support rings attached to a central region of the flexible band and configured to laterally support the central region of the flexible band.

[0050] [Figure 5B] 5B is a radial cross-sectional view of one of the support rings of FIG. 5A in a closed configuration.

[0051] [Figure 5C] FIG. 5C is a radial cross-sectional view of the support ring of FIG. 5B in a closed configuration.

[0052] [Figure 5D] FIG. 5C is a radial cross-section similar to FIG. 5B, but further including a central region of the flexible band.

[0053] [Figure 5E] FIG. 5B is an axial cross-sectional view similar to FIG. 5A, but showing an embodiment in which the support ring is integral with the spring.

[0054] [Figure 5F] FIG. 2B is an axial cross-sectional view similar to FIG. 2A, but showing an embodiment in which a compression spring is used to assist in opening the stop seal by applying a circumferentially extending force to the gap support ring.

[0055] [Figure 5G] A radial cross-section of one of the support rings in the embodiment of FIG. 5F showing a compression spring that assists in opening the stop seal by applying a circumferentially extending force to the gap in the support ring.

[0056] [Figure 5H] FIG. 5B is an axial cross-sectional view similar to FIG. 5A, but showing an embodiment in which the rigid support ring is fixed to the cover plate.

[0057] [Figure 6] FIG. 2B is an axial cross-sectional view of an integrated dual seal incorporating the embodiment of FIG. 2A upstream of an end face mechanical rotary shaft seal.

[0058] [Figure 7A] FIG. 2 is an axial cross-sectional view of one embodiment of the present invention in which the seal is closed by pressing axially against a central region intermediate structure of the flexible band.

[0059] [Figure 7B] FIG. 7B is a radial cross-sectional view of a spring included in the embodiment of FIG. 7A. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0060] The present invention is a fluid pressure actuated stop shaft seal that is simple in design, relatively inexpensive to manufacture, and capable of producing a seal that reliably withstands high pressure process fluids (such as process gases pressurized to 70 bar or more).

[0061] Referring to the cross-sectional view of FIG. 2A, the disclosed stop seal comprises a flexible band 200 mounted within an annular housing 112 and covered by a pair of annular cover plates 206. The flexible band 200, the housing 112, and the cover plates 206 all surround the rotatable shaft 102. The flexible band 200 comprises a thick, substantially rectangular central region 202 with thinner lateral regions 204 disposed on either side. In the embodiment of FIG. 2A, the thinner lateral regions 204 of the flexible band 200 provide radial flexibility to the thick central region 202 such that the thick central region 202 can extend radially inward through and then retract from the axial gap 208 between the cover plates 206. The thickness of the central region 202 allows it to withstand a high axial pressure differential when pressed against the shaft 102, so that the central region 202 is not deformed or extruded when the stop seal is closed.

[0062] Pressurized control fluid (such as pressurized nitrogen gas, pressurized liquid, or pressurized process fluid) is applied to the back side of central region 202 via control fluid inlet 116 to close the stop seal. The pressurized control fluid can be controlled by a controller (not shown), which in embodiments also controls the rotation of shaft 102. As shown in FIG. 2A, while shaft 102 is rotating, no pressure is applied to the back side of central region of flexible band 200, so that the central region remains partially or completely within annular housing 112 and cover plate 206 and does not contact shaft 102.

[0063] 2B, when the shaft 102 is not rotating (i.e., at rest), pressurized control fluid is applied by the controller through the control fluid inlet 116 to the backside of the central region 202 of the flexible band 200. As a result, in the illustrated embodiment, a gap 210 filled with pressurized control fluid is formed behind the central region 202 of the flexible band 200, causing the central region of the flexible band 200 to be forced radially inward through the axial gap 208 between the annular cover plates and against the shaft 102, forming a stop seal with the shaft 102. In other embodiments, the thickened central region 202 is forced axially against an intermediate structure sealed to the shaft 102, as will be described in more detail below with reference to FIG.

[0064] In the radial embodiment of Figures 2A and 2B, the change in diameter of the central region 202 when deployed is only a small percentage of the overall diameter of the flexible band 200 so that the central region 202 can easily accommodate the circumferential compression required as the central region 202 is forced radially inward toward the shaft 102.

[0065] 2A and 2B, the flexible band 200 is formed from an elastomer or other material that has sufficient elasticity to reliably return to its original shape when no longer deformed by the applied fluid pressure. In the embodiment of Figures 3A-3C, the flexible band 200 is formed from a material (such as PTFE) that is flexible and durable, but has less elasticity and that, alone, may not be able to reliably pull the central region 202 away from the shaft 102 when the controlled fluid pressure is discontinued.

[0066] 3A and 3B thus includes a pair of opposed annular toothed springs 300 that provide additional radial restoring force to the side regions 204 of the flexible band 200 to ensure that the central region 202 is fully pulled away from the shaft 102 when the control fluid pressure behind the flexible band 200 is stopped. In the illustrated embodiment, the side portions 204 of the flexible band 200 are configured to be substantially axial when no control fluid pressure is applied such that they may rest on the axial teeth 306 of the springs 300. The flexible band is secured within the housing 116 by two O-rings 302.

[0067] The curved shape of the side regions 204 of the flexible band 200 in the embodiment of Figure 3A provides the additional length needed when the stop seal is closed, as shown in Figure 3B. Figure 3C is a side perspective view of one of the springs 300 of Figures 3A and 3B. It can be seen that the spring 300 comprises a solid annular portion 304 and a ring of axial teeth 306 that can be bent radially inward when the central region 202 of the flexible band 200 is forced towards the shaft 102.

[0068] 4 shows an embodiment similar to FIG. 3A, except that the "spring" 400 is an elastomeric tube that surrounds the shaft 102 below the side portions 204 of the flexible bands 200 within the housing 112. When the central region 202 is deployed, the hollow tube 400 collapses, and when the control fluid pressure is released, the resiliency of the hollow tube 400 helps return the central region 202 to its previous position within the housing 112.

[0069] 5A, the embodiments further include a pair of rigid annular support rings 500 pressed against either side of the thickened central region 202 to further support the central region 202 and completely eliminate the possibility that the thickened central region 202 may be squeezed 122 between the annular cover plate 206 and the shaft 102 when the stop seal is engaged. Of course, the space between the two cover plates 206 is made large enough in these embodiments to accommodate the thickness of the support rings 500 and the thickness of the central region 202 of the flexible band 200.

[0070] 5B-5D, in the illustrated embodiment, annular support ring 500 does not extend a full 360 degrees around shaft 102 due to a gap 506. Gap 506 allows support ring 500 to compress radially inwardly with central region 202 of flexible band 200. In FIG. 5B, a cross-sectional view of support ring 500 is shown in an uncompressed state, while in FIG. 5B, support ring 500 is shown in a compressed state. FIG. 5D illustrates the relationship between support ring 500 and central region 202 of flexible band 200 of FIG. 5B.

[0071] Referring to FIG. 5E, in a similar embodiment, the support ring 500 is integrated with a spring 300 that helps reopen the stop seal when the control fluid is depressurized.

[0072] In the embodiment of Figures 5F and 5G, a compression spring 508 is used rather than a toothed spring 300 to help open the stop seal when the control fluid is depressurized. Figure 5F is a cross-sectional view similar to Figure 2A, and Figure 5G is a close-up of the gap area of ​​the support ring 500 showing the location and operation of the spring 508. Instead of applying a "lifting" force to the side regions 204 of the flexible band 200, the compression spring 508 in Figure 5G applies a circumferentially extending force to the support ring 500, thereby helping to pull the central region of the flexible band 200 back off the shaft 102.

[0073] Referring to FIG. 5H, in another embodiment, a support ring 502 is secured to the cover plate 206 and extends into the gap 504 between the shaft 102 and the cover plate 206 .

[0074] With reference to Fig. 6, the stop seal of the present invention may be implemented with at least one rotating shaft seal. In the embodiment of Fig. 6, the stop seal is implemented upstream of an end face mechanical seal with a rotating seal face 600 sealed against the shaft by an intermediate support structure 602, and a stationary seal face 604 sealed against a housing 610 and urged against the rotating seal face 600 by a spring 606. In the illustrated embodiment, the central region 202 of the flexible band 200 is configured to seal against the intermediate support structure 602 when the shaft 102 is not rotating, rather than sealing directly against the shaft 102. It can be seen that the illustrated embodiment integrates the stop seal and the end face mechanical seal into a single unit.

[0075] In some embodiments, the source of the control fluid is independent of the process and can be, for example, a source of pressurized nitrogen gas or pressurized air or a source of pressurized liquid. In the embodiment of Figure 6, the control fluid is a process fluid. In the illustrated embodiment, process fluid is drawn from the pressurized side 608 of the seal and passed through a pressure boost device 610 which increases the pressure of the process fluid before being applied to the back side of the flexible band 200. A valve 612 which controls the flow of process fluid to the pressure boost device 610 is actuated by a controller 614 which in some embodiments also controls the stopping and starting of rotation of the shaft 102.

[0076] In similar embodiments, the stop seal is implemented downstream of the rotary shaft seal, or may be implemented between the rotary shaft seals if multiple rotary shaft seals are provided. In some embodiments, multiple disclosed stop seals are provided, for example, one upstream of the rotary shaft seal and one downstream of the rotary shaft seal.

[0077] While the disclosed static seals are sometimes described herein as acting radially inward, it will be apparent to one skilled in the art that in other embodiments the static seals are axial rather than radial. For example, referring to FIG. 7A, in an embodiment, the central region 202 of the flexible band 200 is axially pressed against a radially extending surface 700 that is sealed against the rotating shaft 102 by an intermediate support structure 602. In the illustrated embodiment, the lateral regions 204 of the flexible band 200 are radially rather than axially extending, and referring to FIG. 7B, the springs 300a, 300b are concentric rather than opposed, with the teeth of the outer spring 300a oriented radially inward and the teeth of the inner spring 300b oriented radially outward, providing a gap 800 between the springs through which the central region 202 of the flexible band 200 can be deployed.

[0078] The foregoing description of the embodiments of the present invention has been presented for purposes of illustration and description. Every page of this submission and all of its contents, however characterized, identified or numbered, regardless of its form or location within the application, is considered to be a substantial part of this application for all purposes. This application is not intended to be exhaustive or to limit the invention to the precise form disclosed. Many modifications and variations are possible in light of this disclosure.

[0079] Although the present application is presented in a limited number of forms, the scope of the present invention is not limited to these forms, and various modifications and variations are possible. The disclosure presented in this specification does not explicitly disclose all possible combinations of features that are within the scope of the present invention. The features disclosed in this specification for various embodiments are generally interchangeable and can be combined in any combination that is not self-contradictory without departing from the scope of the present invention. In particular, the limitations presented in the following claims can be combined with their corresponding dependent claims in any number and in any order without departing from the scope of the present disclosure, as long as the dependent claims are not logically inconsistent with each other. [Application Example 1] A stop seal configured to form a seal with a rotatable shaft to prevent leakage of a process fluid past the stop seal when the rotatable shaft is not rotating, comprising: a flexible band surrounding said shaft, said flexible band having a relatively thick central region from which extend longitudinally relatively thinner lateral regions, said central region being substantially rectangular in longitudinal cross section; a housing configured to receive the flexible band; a pair of cover plates underlying the lateral regions of the flexible band, the cover plates being configured to prevent the lateral regions from extending beyond the cover plates, and a gap being provided between the cover plates through which the central region of the flexible band can be stretched; a control fluid inlet configured to provide fluid communication between a source of pressurized control fluid and a back surface of the flexible band; A controller; Equipped with the stop seal is configured to urge the underside of the flexible band towards the gap when the controller applies the pressurized control fluid to the control fluid inlet, such that the central region of the flexible band extends through the gap and the central region of the flexible band contacts and forms a seal with the shaft or with an intermediate structure sealed against the shaft; The stop seal is configured to pull the central region of the flexible band away from the shaft or intermediate structure when the controller stops applying the pressurized control fluid to the control fluid inlet. [Application Example 2] A stop seal as described in Application Example 1, wherein the flexible band has sufficient elasticity to cause the central region to pull away from the shaft or intermediate structure when the controller stops applying the pressurized control fluid to the flexible band. [Application Example 3] A stop seal as described in any one of the above application examples, wherein the side regions of the flexible band have portions having curved longitudinal cross-sections, thereby enabling stretching of the side regions when the central region is stretched through the gap. [Application Example 4] A stop seal described in any one of the above application examples, wherein the stop seal is integrated with a rotating shaft seal configured to form a seal with the shaft when the shaft is rotating. [Application Example 5] A stop seal as described in Application Example 4, wherein the stop seal is configured to form a seal with the shaft or an intermediate structure upstream of the rotating shaft seal. [Application Example 6] A stop seal as described in Application Example 4, wherein the stop seal is configured to form a seal with the shaft or an intermediate structure downstream of the rotating shaft seal. [Application Example 7] The stop seal according to any one of the application examples described above, wherein the control fluid is a gas. [Application Example 8] The stop seal according to any one of the application examples described above, wherein the control fluid is the process fluid. [Application Example 9] A stop seal described in any one of the application examples above, wherein the controller is configured to start and stop rotation of the shaft and control the application of the pressurized control fluid to the flexible band. [Application Example 10] A stop seal described in any one of the above application examples, further comprising a pair of rigid annular support rings configured to support sides of the central region of the flexible band when the central region is extended through the gap between the cover plates. [Application Example 11] A stop seal according to Application Example 10, wherein the annular support ring is fixed to the central region of the flexible band. [Application Example 12] A stop seal according to Application Example 10, wherein the annular support ring extends from the housing. [Application Example 13] A stop seal described in any one of the above application examples, further comprising a spring configured to assist in the pulling away of the central region of the flexible band from the shaft or intermediate structure when the controller stops applying the pressurized control fluid to the flexible band. [Application Example 14] A stop seal described in any one of the above application examples, wherein the stop seal is configured to abut the central region of the flexible band radially inward against the shaft or against the intermediate structure. [Application Example 15] A stop seal described in any one of the above application examples, wherein the stop seal is configured to abut the central region of the flexible band axially against the intermediate structure. [Application Example 16] The stop seal according to Application Example 10 or Application Example 11, the stop seal is configured to abut the central region of the flexible band radially inward against the shaft or the intermediate structure; A stop seal, wherein the annular support ring includes a ring gap that allows the annular support ring to radially compress when the central region is stretched radially inward toward the shaft or the intermediate structure. [Application Example 17] A stop seal as described in Application Example 16, further comprising a compression spring applied to the gap in the support ring, the compression spring configured to assist in the pulling away of the central region of the flexible band from the shaft or intermediate structure when the controller stops applying the pressurized control fluid to the flexible band. [Application Example 18] The stop seal according to Application Example 13, the stop seal is configured to abut the central region of the flexible band radially inward against the shaft or the intermediate structure; A stop seal, the spring comprising a pair of spaced apart annular bands having solid annular portions with teeth extending axially towards each other under the lateral regions of the flexible bands, the teeth being provided with axial gaps between the teeth through which the central region of the flexible bands can be stretched into contact with the shaft or the intermediate structure, the teeth being bent radially inward when the central region of the flexible bands is forced towards the shaft. [Application Example 19] The stop seal according to any one of Application Examples 1 to 9, the stop seal is configured to abut the central region of the flexible band radially inward against the shaft or the intermediate structure; the stop seal comprises a spring configured to assist the separation of the central region of the flexible band from the shaft or intermediate structure when the controller stops applying the pressurized control fluid to the flexible band; The stop seal further comprises a pair of rigid annular support rings configured to support sides of the central region of the flexible band when the central region is extended through the gap between the cover plates, the rigid annular support rings extending radially inward from the spring. [Application Example 20] The stop seal according to any one of Application Examples 1 to 9, the stop seal is configured to abut the central region of the flexible band axially against the intermediate structure; the stop seal further comprising a spring configured to assist in the pulling away of the central region of the flexible band from the shaft or intermediate structure when the controller stops applying the pressurized control fluid to the flexible band; A stop seal, the spring comprising a pair of radially concentric annular disks having solid annular portions with teeth extending radially inwardly and radially outwardly towards each other under the lateral regions of the flexible band, with radial gaps between the radially inwardly and radially outwardly directed teeth through which the central region of the flexible band can be stretched into contact with the intermediate structure, the teeth being bent axially when the central region of the flexible band is forced towards the shaft.

Claims

1. a stop seal configured to form a seal with a rotatable shaft to prevent leakage of process fluid past the stop seal when the rotatable shaft is not rotating, a flexible band surrounding the rotatable shaft, the flexible band having a central region with relatively thin lateral regions extending longitudinally therethrough, the central region being substantially rectangular in longitudinal cross section and symmetrical about a centerline extending transversely perpendicular to the longitudinal direction; a housing configured to receive the flexible band; a pair of cover plates having lower portions below the lateral regions of the flexible band, the cover plates being configured to prevent the lateral regions from extending beyond the cover plates, the lateral regions being everywhere thinner in the short direction than the lower portions of the cover plates, and a gap being provided between the cover plates through which the central region of the flexible band can be stretched; a control fluid inlet configured to provide fluid communication between a source of pressurized control fluid and a back surface of the flexible band; A controller; a sealing surface that is parallel to the cover plate and extends across the cover plate gap at a uniform offset from the cover plate and the cover plate gap, the sealing surface being a surface of the rotatable shaft or a surface of an intermediate structure sealed against the rotatable shaft; Equipped with The stop seal is configured to press the underside of the flexible band toward the gap when the controller applies the pressurized control fluid to the control fluid inlet, such that the central region of the flexible band extends through the gap and the central region of the flexible band contacts the sealing surface to form a seal by applying a substantially uniform pressing force to the sealing surface across substantially the entire width of the central region. The stop seal is configured to pull the central region of the flexible band away from the shaft or intermediate structure when the controller stops applying the pressurized control fluid to the control fluid inlet.

2. 2. The stop seal of claim 1, wherein the flexible band has sufficient elasticity to cause the central region to pull away from the sealing surface when the controller stops applying the pressurized control fluid to the flexible band.

3. 2. The stop seal of claim 1, wherein the side regions of the flexible band include portions having curved longitudinal cross-sections, thereby allowing stretching of the side regions when the central region is stretched through the gap.

4. 2. The stop seal of claim 1, wherein the stop seal is integrated with a rotary shaft seal configured to form a seal with the rotatable shaft when the rotatable shaft is rotating.

5. The stop seal of claim 4 , wherein the stop seal is configured to form a seal with the sealing surface upstream of the rotating shaft seal.

6. The stop seal of claim 4 , wherein the stop seal is configured to form a seal with the sealing surface downstream of the rotating shaft seal.

7. The stop seal of claim 1 , wherein the control fluid is a gas.

8. The stop seal of claim 1 , wherein the control fluid is the process fluid.

9. The stop seal of claim 1 , wherein the controller is configured to start and stop rotation of the rotatable shaft and control the application of the pressurized control fluid to the flexible band.

10. 2. The stop seal of claim 1, further comprising a pair of rigid annular support rings configured to support sides of the central region of the flexible band when the central region is stretched through the gap between the cover plates.

11. The stop seal of claim 10, wherein the annular support ring is secured to the central region of the flexible band.

12. The stop seal of claim 10, wherein the annular support ring extends from the housing.

13. 2. The stop seal of claim 1, further comprising a spring configured to assist in the pulling away of the central region of the flexible band from the sealing surface when the controller stops applying the pressurized control fluid to the flexible band.

14. The stop seal of claim 1 , wherein the stop seal is configured to abut the central region of the flexible band radially inwardly against the sealing surface.

15. The stop seal of claim 1 , wherein the stop seal is configured to abut the central region of the flexible band axially against the sealing surface.

16. 11. The stop seal of claim 10, the stop seal is configured to abut the central region of the flexible band radially inward against the sealing surface; A stop seal, wherein the annular support ring includes a ring gap that allows the annular support ring to radially compress when the central region is stretched radially inward toward the sealing surface.

17. 17. The stop seal of claim 16, further comprising a compression spring applied to the gap in the support ring, the compression spring configured to assist in the pulling away of the central region of the flexible band from the sealing surface when the controller stops applying the pressurized control fluid to the flexible band.

18. 14. The stop seal of claim 13, the stop seal is configured to abut the central region of the flexible band radially inward against the sealing surface; A stop seal comprising a pair of spaced apart annular bands having solid annular portions with teeth extending axially towards each other beneath the lateral regions of the flexible bands, the teeth being provided with axial gaps between the teeth through which the central region of the flexible bands can be stretched into contact with the sealing surface, the teeth being bent radially inward when the central region of the flexible bands is forced towards the rotatable shaft.

19. 2. The stop seal of claim 1, the stop seal is configured to abut the central region of the flexible band radially inward against the sealing surface; the stop seal comprises a spring configured to assist the separation of the central region of the flexible band from the sealing surface when the controller stops applying the pressurized control fluid to the flexible band; The stop seal further comprises a pair of rigid annular support rings configured to support sides of the central region of the flexible band when the central region is extended through the gap between the cover plates, the rigid annular support rings extending radially inward from the spring.

20. 2. The stop seal of claim 1, the stop seal is configured to abut the central region of the flexible band axially against the sealing surface; the stop seal further comprising a spring configured to assist in the pulling away of the central region of the flexible band from the sealing surface when the controller stops applying the pressurized control fluid to the flexible band; A stop seal comprising a pair of radially concentric annular disks having solid annular portions with teeth extending radially inwardly and radially outwardly towards each other under the lateral regions of the flexible band, with radial gaps between the radially inwardly and radially outwardly directed teeth through which the central region of the flexible band can be stretched into contact with the sealing surface, the teeth being bent axially when the central region of the flexible band is forced towards the rotatable shaft.

Images