Sealing assembly and alkaline water electrolyzer

Abstract

The present disclosure discloses a sealing assembly and an alkaline water electrolyzer, belonging to the technical field of alkaline water electrolysis. The sealing assembly comprises a sealing gasket and a diaphragm, the sealing gasket is provided with an accommodation area and a guide channel that is located outside the accommodation area and is in communication with the accommodation area, and the diaphragm is provided in the accommodation area. The guide channel comprises a guide boss, a guide hole and a flow passage, which communicate successively, the guide boss is provided on a surface of the sealing gasket, and the flow passage is provided on an opposite surface of the sealing gasket and in communication with the accommodation area. The sealing assembly provided in the present disclosure is applicable to a stacked structure of the alkaline water electrolyzer. For any two adjacent sealing assemblies of the alkaline water electrolyzer, a guide boss of one sealing assembly is embedded into and cooperated with a flow passages of the other sealing assembly, which is convenient for assembly and disassembly and ensures that no fluid leaks out from the alkaline water electrolyzer due to thermal expansion or cold shrinkage, thereby achieving a good sealing property.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to the field of alkaline water electrolysis, and specifically relates to a sealing assembly and an alkaline water electrolyzer.BACKGROUND

[0002] An alkaline water electrolyzer usually includes many components and structural designs, such as a diaphragm, a bipolar plate, a cathode, an anode, a cathode plate frame, an anode plate frame, a current-carrying part, and a sealing assembly. The alkaline water electrolyzer may consist of 5 to 300 identical electrolysis units stacked together. To simplify assembly, there are some nested structures in the electrolyzer, so that the various components of the eletrolyzer can be nested into each other or be stacked together, and then press-fitted by screws. After the press-fitting process, metal endplates are fixed and connected to an electrical system, an electrolyte is injected, and the electrolyzer gets access to a gas pipeline.

[0003] As an important component of the electrolyzer, the sealing assembly is critical to the overall lifetime and safety of the electrolyzer. A traditional sealing assembly is inconvenient for assembly and disassembly in an electrolyzer, and is difficult to ensure the sealing of the electrolyzer after installation, which may easily lead to leakage of the electrolyzer, and even damage to the electrolyzer, resulting in decreased service life of the electrolyzer.

[0004] Therefore, there is an urgent need to develop a sealing assembly that is convenient for assembly and disassembly and has a good sealing property, so as to meet the performance requirements of the alkaline water electrolyzer for the sealing assembly.SUMMARY OF THE DISCLOSURE

[0005] In view of the shortcomings in the prior art, an objective of the present disclosure is to provide a sealing assembly that is convenient for assembly and disassembly and has a good sealing property, and an alkaline water electrolyzer.

[0006] In order to achieve the above objective, the present disclosure adopts the following technical solution.

[0007] In a first aspect, the present disclosure provides a sealing assembly, which comprises a sealing gasket and a diaphragm, wherein the sealing gasket is provided with an accommodation area passing through the sealing gasket and a guide channel which is located outside the accommodation area and in communication with the accommodation area, the diaphragm is arranged in the accommodation area; the guide channel comprises a guide boss, a guide hole and a flow passage which communicate successively, the guide boss is provided on a surface of the sealing gasket, and the flow passage is provided on an opposite surface of the sealing gasket and is in communication with the accommodation area.

[0008] As a preferable embodiment of the present disclosure, the sealing assembly further comprises a rigid skeleton, an inner wall of the accommodation area is provided with a groove, the rigid skeleton is provided in the groove, and the diaphragm is sandwiched between an inner wall of the groove and the rigid skeleton.

[0009] Further, the rigid skeleton is made from an acid-resistant, alkali-resistant and corrosion-resistant plastic or an acid-resistant, alkali-resistant and corrosion-resistant metal. Embedding the rigid skeleton in the sealing gasket can effectively prevent unevenness of the diaphragm due to the overall contraction of the sealing gasket during the vulcanization process, and the rigid skeleton can also increase the stiffness and strength of the sealing gasket.

[0010] Further, the inner wall of the accommodation area is provided with a convex rim, and the rigid skeleton is accommodated in the groove and abuts against the convex rim.

[0011] In the present disclosure, the convex rim arranged within the accommodation area has a good limiting effect, which enables the rigid skeleton to be stably clamped in the groove, thereby making the structure of the sealing assembly more stable.

[0012] As a preferred embodiment of the present disclosure, the diaphragm is made from polyphenylene sulfide (PPS).

[0013] As a preferred embodiment of the present disclosure, the guide boss is integrally formed on the surface of the sealing gasket, and the flow passage is formed by recessing the opposite surface of the sealing gasket.

[0014] As a preferred embodiment of the present disclosure, a convex shoulder is provided in the flow passage.

[0015] For any two adjacent sealing assemblies of an alkaline water electrolyzer, a guide boss of a sealing assembly is embedded into and coordinated with a flow passage of an adjacent sealing assembly and abuts against a convex shoulder in the flow passage of the adjacent sealing assembly, so that guide channels of the two sealing assemblies are interconnected with each other. Besides, a clearance is left between the guide boss of the sealing assembly and the flow passage of the adjacent sealing assembly, thereby avoiding blocking the communication between the guide hole and the flow passage in any one of the guide channels. The convex shoulder extends along an extension direction of the flow passage, and can prevent the flow passage from being deformed and clogged during the stacking and installation process of the alkaline water electrolyzer.

[0016] Further, there is a clearance between the convex shoulder and the accommodation area, and there is also a clearance between the convex shoulder and the guide hole. Such clearances can effectively prevent the convex shoulder from being easily damaged due to stress concentration during the assembly and compression process.

[0017] As a preferred embodiment of the present disclosure, at least three guide channels are provided in the sealing gasket, wherein at least one of the guide channels is used for flowing of a liquid and at least two of the guide channels are used for flowing of a gas.

[0018] The guide bosses of the plurality of guide channels may be provided on a same surface of the sealing gasket, or may be provided on different surfaces of the sealing gasket.

[0019] As a preferred embodiment of the present disclosure, the sealing gasket is made from a rubber material, and the rubber material is at least one selected from the group consisting of ethylene-propylene rubber, ethylene vinyl acetate (EVA) rubber, natural rubber, neoprene rubber, chlorinated polyethylene rubber, polyacrylate rubber, ethylene-acrylate rubber, nitrile rubber, and fluorine rubber. The sealing gasket made of such rubber material has long-lasting resilience, and can withstand high temperatures and high pressures and ensure long-term reliability of sealing, which is conducive to extending the overall service life of the alkaline water electrolyzer.

[0020] In a second aspect, the present disclosure provides an alkaline water electrolyzer comprising two endplates and a plurality of electrolysis units that are stacked between the two endplates, wherein each of the plurality of electrolysis units comprises an polar plate complex and a sealing assembly according to the first aspect, and the polar plate complex is stacked with the sealing assembly; the polar plate complex is provided with a locating hole corresponding to the guide boss of the sealing assembly, and each of the endplates is provided with a through hole corresponding to the guide boss of the sealing assembly.

[0021] As a preferred embodiment of the present disclosure, each of the plurality of electrolysis units further comprises a limit stop provided outside the sealing gasket.

[0022] Further, the limit stop is provided with a limit post, the polar plate complex is provided with a first limit hole adapted to the limit post, and each of the endplates is provided with a second limit hole adapted to the limit post.

[0023] Further, for any two adjacent electrolysis units, the limit stop of one electrolysis unit and the limit stop of the other electrolysis unit are staggered with each other in a stacking direction of the electrolysis units, which allows the whole electrolyzer to be stressed more uniformly during stacking and compression process, and avoids uneven deformation or displacement of the sealing gasket.

[0024] Further, the limit stop is made from a plastic or a metal, wherein the plastic is any one selected from the group consisting of polytetrafluoroethylene (PTFE), polysulphone (PSU), polyphenylene sulfide (PPS) and polyurethane (PU), and the metal is selected from stainless steel, nickel, and chromium. Such materials have high hardness, which can ensure that the limit stop has good limiting and supporting effects when the electrolyzer is assembled.

[0025] As a preferred embodiment of the present disclosure, the polar plate complex is provided with a limit ring adapted to the sealing assembly, and the locating hole is provided in the limit ring.

[0026] As a preferred embodiment of the present disclosure, each of the endplates is provided with a fastening screw hole adapted to a fastening screw, and the endplates are connected with each other by the fastening screws.

[0027] Compared with the prior art, the alkaline water electrolyzer provided in the present disclosure has relatively fewer components, and the sealing assemblies, the polar plate complexes, the limit stops and the endplates are all separated, which facilitates assembly and disassembly, and thus reduces the installation cost.

[0028] Compared with the prior art, the present disclosure has the following beneficial effects.

[0029] The sealing assembly provided in the present disclosure is applicable to the stacked structure of the alkaline water electrolyzer. For any two adjacent sealing assemblies of the alkaline water electrolyzer, a guide boss of a sealing assembly is embedded into and coordinated with a flow passage of an adjacent sealing assembly, which is convenient for assembly and disassembly and ensures that no fluid leaks out from the alkaline water electrolyzer due to thermal expansion or cold shrinkage, so that the sealing assembly has a good sealing property.BRIEF DESCRIPTION OF DRAWINGS

[0030] FIG. 1 is a perspective view of a sealing assembly according to the present disclosure; FIG. 2 is a front view of the sealing assembly according to the present disclosure; FIG. 3 is a sectional view of the sealing assembly according to the present disclosure, taken along the A-A line in FIG. 2; FIG. 4 is an enlarged view of Part A in FIG. 3; FIG. 5 is a perspective view of a sealing gasket according to the present disclosure; FIG. 6 is a perspective view of an electrolysis unit according to the present disclosure; FIG. 7 is an explosive view of the electrolysis unit according to the present disclosure; and FIG. 8 is a perspective view of an alkaline water electrolyzer according to the present disclosure.

[0031] In the figures: 1-sealing gasket, 11-accommodation area, 12-guide channel, 121-guide boss, 122-guide hole, 123-flow passage, 124-convex shoulder, 13-groove, 14-convex rim, 2-diaphragm, 3-rigid skeleton, 4-polar plate complex, 41-locating hole, 42-first limit hole, 5-limit stop, 51-limit post, 6-endplate, 61-second limit hole, 62-fastening screw hole, and 63-through hole.DETAILED DESCRIPTION

[0032] In order to better illustrate the objective, technical solutions and advantages of the present disclosure, the present disclosure will be further described hereinafter in conjunction with examples and comparative examples, which are intended to understand the present disclosure in detail, rather than to limit the present disclosure. All other embodiments obtained by those skilled in the art, without creative labor, shall fall within the scope of protection of the present disclosure.

[0033] With reference to FIGs.1-5, in a first aspect, a sealing assembly is provided in the present disclosure, comprising a sealing gasket 1 and a diaphragm 2. The sealing gasket 1 is provided with an accommodation area 11 passing through the sealing gasket 1, and a guide channel 12 which is located outside the accommodation area 11 and interconnected with the accommodation area 11. The diaphragm 12 is arranged in the accommodation area 11. The guide channel 12 comprises a guide boss 121, a guide hole 122 and a flow passage 123 which communicate. The guide boss 121 is provided on a surface of the sealing gasket 1, and the flow passage 123 is provided on an opposite surface of the sealing gasket 1 and is in communication with the accommodation area 11.

[0034] The sealing assembly provided in the present disclosure is applicable to a stacked structure of an alkaline water electrolyzer. For any two adjacent sealing assemblies of the alkaline water electrolyzer, a guide boss 121 of a sealing assembly is nested into a flow passage 123 of an adjacent sealing assembly, which is convenient for assembly and disassembly and ensures that no fluid leaks out from the alkaline water electrolyzer due to thermal expansion or cold shrinkage, so that the sealing assembly has a good sealing property.

[0035] In an embodiment, the sealing assembly further comprises a rigid skeleton 3, an inner wall of the accommodation area 11 is provided with a groove 13 in which the rigid skeleton 3 is provided, and the diaphragm 12 is sandwiched between an inner wall of the groove 13 and the rigid skeleton 3.

[0036] Specifically, the rigid skeleton 3 is made from an acid-resistant, alkali-resistant and corrosion-resistant plastic or an acid-resistant, alkali-resistant and corrosion-resistant metal. Embedding the rigid skeleton 3 in the sealing gasket 1 can effectively prevent unevenness of the diaphragm 2 due to the overall contraction of the sealing gasket 1 during the vulcanization process, and the rigid skeleton 3 can also increase the stiffness and strength of the sealing gasket 1.

[0037] Specifically, the inner wall of the accommodation area 11 is integrally formed with a convex rim 14, and the rigid skeleton 3 is accommodated in the groove 13 and abuts against the convex rim 14.

[0038] In the present disclosure, the convex rim 14 arranged in the accommodation area 11 has a good limiting effect, which enables the rigid skeleton 3 to be stably clamped in the groove 13, thereby making the structure of the sealing assembly more stable.

[0039] In an embodiment, the diaphragm 2 is made from polyphenylene sulfide (PPS).

[0040] In an embodiment, the guide boss 121 is integrally formed on the surface of the sealing gasket 1, and the flow passage 123 is formed as a recess on the opposite surface of the sealing gasket 1.

[0041] In an embodiment, a convex shoulder 124 is provided in the flow passage 123.

[0042] For any two adjacent sealing assemblies of the alkaline water electrolyzer, a guide boss 121 of a sealing assembly is embedded into and cooperated with a flow passage 123 of an adjacent sealing assembly and abuts against a convex shoulder 124 in the flow passage 123 of the adjacent sealing assembly, so that guide channels 12 of the two sealing assemblies are in communication with each other. Besides, a clearance is left between the guide boss121 of the sealing assembly and the flow passage 123 of the adjacent sealing assembly, thereby avoiding blocking the communication between the guide hole 122 and the flow passage 123 in any one of the guide channels 12. The convex shoulder 124 extends along a length direction of the flow passage 123, and can prevent the flow passage 123 from being deformed and clogged during the stacking and installation process of the alkaline water electrolyzer.

[0043] In particular, there is a clearance between the convex shoulder 123 and the accommodation area 11, and there is also a clearance between the convex shoulder 123 and the guide hole 122. Such clearances can effectively prevent the convex shoulder 124 from being easily damaged due to stress concentration during the assembly and compression process.

[0044] In an embodiment, at least three guide channels 12 are provided in the sealing gasket 1, wherein at least one of the guide channels is used for flowing of a liquid and at least two of the guide channels are used for flowing of a gas.

[0045] The guide bosses 121 of the plurality of guide channels 12 may be provided on a same surface of the sealing gasket 1, or may be provided on different surfaces of the sealing gasket 1.

[0046] In an embodiment, the sealing gasket is made from a rubber material, and the rubber material may be at least one selected from the group consisting of ethylene-propylene rubber, ethylene vinyl acetate (EVA) rubber, natural rubber, neoprene rubber, chlorinated polyethylene rubber, polyacrylate rubber, ethylene-acrylate rubber, nitrile rubber, and fluorine rubber. The sealing gasket 1 made of such rubber material has long-lasting resilience, and can withstand high temperatures and high pressures and ensure long-term reliability of sealing, which is conducive to extending the overall service life of the alkaline water electrolyzer.

[0047] It should be understood that in the present disclosure, the sealing gasket 1 and the diaphragm 2 may also be integrally formed.

[0048] It should be understood that in the present disclosure, there is no particular limitation on shapes and sizes of various components in the sealing assembly. Those skilled in the art may design the shapes and sizes of the various components in the sealing assembly according to actual situations. For example, a thickness of the sealing gasket 1 may be in a range of from 8 mm to 9 mm, a depth of the flow passage 123 may be in a range of from 3 mm to 4 mm, and a width of the flow passage 123 is larger than a diameter of the guide hole 122; and a thickness of the convex shoulder 124 may be in a range of from 2 mm to 3 mm.

[0049] With reference to FIGs.1-8, in a second aspect, an alkaline water electrolyzer is provided in the present disclosure, comprising two endplates 6 and a plurality of electrolysis units that are stacked between the two endplates 6. Each of the plurality of electrolysis units comprises a polar plate complex 4 and a sealing assembly according to the first aspect, and the polar plate complex 4 is stacked with the sealing assembly. The polar plate complex 4 is provided with a locating hole 41 which passes through the polar plate complex 4 and is adapted to the guide boss 121 of the sealing assembly. The endplates 6 each are provided with a through hole 63 which passes through the respective endplate 6, and is adapted to the guide boss123 of the sealing assembly.

[0050] In an embodiment, the polar plate complex 4 comprises a bipolar plate, and two sides of the bipolar plate are each provided with a nickel mesh. The nickel mesh is provided with a membrane electrode on a surface, and the locating hole 41 is disposed outside the nickel mesh and the membrane electrode.

[0051] In particular, two side surfaces of the bipolar plate each are provided with a limit ring adapted to the sealing gasket 1. The limit ring is formed by recessing a surface of the bipolar plate to an opposite surface of the bipolar plate. The locating hole 41 is provided in the limit ring. During assembly, the sealing gasket 1 can be fitted within the limit ring.

[0052] In an embodiment, each of the plurality of electrolysis units further comprises a limit stop 5 provided outside the sealing gasket 1.

[0053] Specifically, the limit stop 5 and the bipolar plate are integrally formed or welded.

[0054] Specifically, the limit stop 5 is provided with a limit post 51 which passes through two opposite surfaces of the limit stop 5 and protrudes from the limit stop 5 at two ends. The limit stop 5 and the limit post 51 are integrally formed.

[0055] The polar plate complex 4 is provided with a first limit hole 42 which passes through the polar plate complex 4 and is adapted to the limit post 51.

[0056] The endplates 6 are each provided with a second limit hole 61 which passes through the respective endplate 6 and is adapted to the limit post 51.

[0057] Specifically, for any two adjacent electrolysis units, the limit stop 5 of one electrolysis unit and the limit stop 5 of the other electrolysis unit are staggered with each other in a stacking direction of the electrolysis units, which allows the whole electrolyzer to be stressed more uniformly during the stacking and compression process, and avoids uneven deformation or displacement of the sealing gasket 1.

[0058] Specifically, a thickness ratio of the limit stop 5 to the sealing gasket 1 is in a range of (0.6-0.9):1, and a ratio of a compression modulus of the limit stop 5 to a compression modulus of the sealing gasket 1 is not less than 10.

[0059] Specifically, the limit stop 5 may be in contact with an outer wall of the sealing gasket 1. Alternatively, the limit stop 5 may not be in contact with the outer wall of the sealing gasket 1. For example, a clearance in a range of from 3 mm to 10 mm is retained between the limit stop 5 and the sealing gasket 1. The clearance allows the rubber sealing gasket to deform laterally during the stacking and compression process of the electrolyzer, ensuring that a stress concentration point does not occur prematurely.

[0060] Specifically, at least two limit stops 5 are provided in each electrolysis unit and evenly distributed outside the sealing gasket 1.

[0061] Specifically, the limit stop 5 is made from a plastic or a metal, wherein the plastic is any one selected from the group consisting of PTFE, PSU, PPS and PU, and the metal may be a hard alloy, such as, a titanium alloy or a stainless steel. Such materials have high hardness, which can ensure that the limit stop 5 has good limiting and supporting effects when the electrolyzer is assembled.

[0062] In an embodiment, each of the endplates 6 is provided with a fastening screw hole 62 adapted to a fastening screw, and the endplates 6 are connected with each other by the fastening screws.

[0063] It should be understood that in the present disclosure, there is no particular limitation on shapes and sizes of the polar plate complex 4, the limit stop 5, the limit post 51 and the endplates 6, and those skilled in the art may design these components according to actual situations. For example, a thickness of the polar plate complex 4 may be in a range of from 2 mm to 3 mm, and the thickness of the polar plate complex 4 is preferably less than a height of a guide boss 121. Compared with the prior art, the use of the polar plate complex 4 with such a thickness in the present disclosure can relatively reduce the overall weight of the electrolyzer.

[0064] It should be understood that in the present disclosure, there is no particular limitation on quantities of the limit post 51, the first limit hole 42, the second limit hole 61 and the fastening screw hole 62, and those skilled in the art may design them according to actual situations. For example, none of the quantities of the first limit hole 42, the second limit hole 61 and the fastening screw hole 62 is less than three, and the first limit holes 42, the second limit holes 61 and the fastening screw holes 62 are all evenly distributed.

[0065] Compared with the prior art, the alkaline water electrolyzer provided in the present disclosure has relatively fewer components, and the sealing assemblies, the polar plate complexes 4 and the endplates 6 are all separated, which facilitates assembly and disassembly and thus reduces the installation cost. Besides, more electrolysis units can be accommodated in the alkaline water electrolyzer provided in the present disclosure when a same space is occupied, thereby achieving higher electrolysis efficiency.

[0066] When an alkaline water electrolyzer is assembled, a plurality of polar plate complexes 4 may be stacked first, and then limit stops 5 are installed. Specifically, guide bosses 121 of a sealing gasket 1 each are inserted into the respective locating holes 41 of a polar plate complex 4 and then protrude out to achieve a sealing fit between the guide bosses 121 and the polar plate complex 4, so that an electrolysis unit is assembled; the assembled electrolysis unit is placed on an endplate 6, limit posts 5 of the assembled electrolysis unit are respectively inserted into second limit holes of the endplate 6, and the guide bosses 121 of the assembled electrolysis unit each are inserted into the respective through holes 63 of the endplate 6; a plurality of electrolysis units are assembled and then stacked to form a stack, and the guide bosses 121 of an electrolysis unit each are inserted into the respective flow passages 123 of an adjacent electrolysis unit; another endplate 6 is placed on the stack consisting of the plurality of electrolysis units, and the guide bosses 121 of the uppermost electrolysis unit each are inserted into the respective through holes 63 of the another endplate 6; and the two endplates 6 are fastened together by using fastening screws, so that the plurality of electrolysis units are tightly stacked, thereby completing the assembly of the alkaline water electrolyzer.

[0067] Finally, it should be noted that the above embodiments are only intended to illustrate the technical solutions of the present disclosure, rather than to limit the scope of protection of the present disclosure. Although the present disclosure has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that modifications or equivalent replacements can be made to the technical solutions of the present disclosure, without departing from the essence and scope of the technical solution of the present disclosure.

Claims

1. A sealing assembly, characterized in that the sealing assembly comprises a sealing gasket and a diaphragm, wherein the sealing gasket is provided with an accommodation area passing through the sealing gasket and a guide channel which is located outside the accommodation area and in communication with the accommodation area, and the diaphragm is arranged in the accommodation area; the guide channel comprises a guide boss, a guide hole and a flow passage which communicate successively, the guide boss is provided on a surface of the sealing gasket, and the flow passage is provided on an opposite surface of the sealing gasket and is in communication with the accommodation area.

2. The sealing assembly according to claim 1, characterized in that the sealing assembly further comprises a rigid skeleton, an inner wall of the accommodation area is provided with a groove, the rigid skeleton is provided in the groove, and the diaphragm is sandwiched between an inner wall of the groove and the rigid skeleton.

3. The sealing assembly according to claim 2, characterized in that the inner wall of the accommodation area is integrally formed with a convex rim, and the rigid skeleton is accommodated in the groove and abuts against the convex rim.

4. The sealing assembly according to claim 1, characterized in that a convex shoulder is provided in the flow passage.

5. The sealing assembly according to claim 4, characterized in that there is a clearance between the convex shoulder and the accommodation area, and there is a clearance between the convex shoulder and the guide hole.

6. The sealing assembly according to claim 1, characterized in that at least three guide channels are provided in the sealing gasket, wherein at least one of the guide channels is used for flowing of a liquid and at least two of the guide channels are used for flowing of a gas.

7. The sealing assembly according to claim 1, characterized in that the sealing gasket is made from a rubber material, and the rubber material is at least one selected from the group consisting of ethylene-propylene rubber, ethylene vinyl acetate rubber, natural rubber, neoprene rubber, chlorinated polyethylene rubber, polyacrylate rubber, ethylene-acrylate rubber, nitrile rubber, and fluorine rubber.

8. An alkaline water electrolyzer, characterized in that the alkaline water electrolyzer comprises two endplates and a plurality of electrolysis units that are stacked between the endplates, each of the plurality of electrolysis units comprises a polar plate complex and a sealing assembly according to any one of claims 1-7, and the polar plate complex is stacked with the sealing assembly; the polar plate complex is provided with a locating hole corresponding to the guide boss of the sealing assembly, and each of the endplates is provided with a through hole corresponding to the guide boss of the sealing assembly.

9. The alkaline water electrolyzer according to claim 8, characterized in that each of the plurality of electrolysis units further comprises a limit stop provided outside the sealing gasket.

10. The alkaline water electrolyzer according to claim 9, characterized in that the polar plate complex is provided with a limit ring adapted to the sealing assembly, and the locating hole is provided in the limit ring.

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