Composite insulator for electric overhead lines

Abstract

The application belongs to the technical field of power equipment insulation, and is especially a composite insulator for power overhead line, which comprises a core rod, the core rod is rigidly arranged, and the two ends of the core rod are fixedly connected with a first fitting and a second fitting respectively, the first fitting is used for being connected with a tower, and the second fitting is used for hanging a conductor, a full-peripheral sealing patch is fixedly attached to the outer surface of the core rod along the length direction; and an umbrella skirt body, the umbrella skirt body is a one-piece molding structure of silicon rubber, and the inner side wall of the umbrella skirt body is adapted to the outer surface of the full-peripheral sealing patch. The application has the advantages of reliable sealing performance, high mechanical strength, good pollution flashover resistance, convenient installation and maintenance, and can effectively prevent water, dust and corrosive medium from invading, improve the stability and service life of the insulator in complex environment, and meet the high performance requirements of the power overhead line on the insulating components.

Description

Technical Field

[0001] This invention relates to the field of electrical equipment insulation technology, and in particular to a composite insulator for overhead power lines. Background Technology

[0002] Composite insulators, as the core insulation components of overhead power lines, directly determine the safety and reliability of line operation. With the development of power systems towards higher voltage, longer distances, and larger capacities, insulators need to serve in complex natural environments for extended periods, facing multiple challenges such as pollution accumulation, drastic temperature and humidity changes, wind and rain vibrations, and corrosive media erosion. Traditional porcelain insulators suffer from drawbacks such as heavy weight, brittleness, easy breakage, and poor resistance to flashover, making them prone to flashover accidents in heavily polluted areas. Early composite insulators often used an integrated structure where the core rod and skirts were directly bonded together. While this offered advantages such as light weight and good toughness, the bonding interface was susceptible to environmental factors, leading to debonding and aging. This allowed moisture and contaminants to penetrate the core rod, causing corrosion, insulation deterioration, and ultimately, a decrease in mechanical strength or even fracture failure.

[0003] Meanwhile, the sheds of traditional composite insulators are mostly integrally molded structures, requiring installation by inserting them from the end of the core rod. This places high demands on construction space, and maintenance and replacement require disassembling the line, making the operation cumbersome and costly. Some segmented sheds use a straight-line butt joint design, which has poor sealing performance. The joints are prone to moisture and dust intrusion, significantly reducing the insulator's resistance to flashover and its service life. In addition, existing locking structures mostly use metal clamps or ordinary rubber tapes. Metal clamps are prone to electro-corrosion, and ordinary rubber tapes have poor high and low temperature resistance and rapid elastic decay, making them prone to loosening after long-term use. This cannot effectively guarantee the sealing reliability of the shed butt joints, making it difficult to meet the needs of extreme temperature environments and heavily polluted and highly corrosive scenarios such as coastal areas and chemical industrial zones.

[0004] To address the aforementioned issues, the industry urgently needs to develop a composite insulator with reliable sealing performance, high mechanical strength, strong resistance to flashover, and convenient installation and maintenance. By optimizing the connection structure between the core rod and the skirts, improving the sealing method and locking mechanism, the insulator can effectively prevent the intrusion of moisture, dust, and corrosive media, thereby enhancing its stability and service life in complex environments and meeting the high-performance requirements of overhead power lines for insulation components. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and to propose a composite insulator for overhead power lines.

[0006] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a composite insulator for overhead power lines, comprising a core rod, wherein the core rod is rigidly set, and a first fitting and a second fitting are respectively fixedly connected to both ends of the core rod, wherein the first fitting is used to connect to the tower, the second fitting is used to attach the conductor, and a full-circumference sealing patch is fixedly pasted on the outer surface of the core rod along the length direction.

[0007] The umbrella skirt body is a one-piece molded structure of silicone rubber, and the inner side wall of the umbrella skirt body is adapted to the outer surface of the full-circumference sealing patch. The umbrella skirt body has a spiral-shaped disconnected seam along the axial direction with the axis of the mandrel as the center, and the spiral angle is 15-30°. The umbrella skirt body includes alternating large-diameter umbrella skirts and small-diameter umbrella skirts. Both sides of the spiral-shaped disconnected seam have sealing overlap surfaces with a 45° right angle.

[0008] The locking and fixing unit consists of multiple flexible insulating locking strips, which are pre-positioned and wrapped between the corresponding large-diameter and small-diameter umbrella skirts. Each flexible insulating locking strip has a stepped groove on the inner side of one end and the outer side of the other end. Each stepped groove has multiple ratchet teeth arranged in a barbed manner. The flexible insulating locking strip is fixed by engaging with the multiple ratchet teeth after wrapping around the umbrella skirt body.

[0009] The mandrel is fixedly connected to the first and second fittings using a hydraulic pressing process.

[0010] Preferably, the width of the spiral disconnected seam is 1-2 mm, and the inner wall of the umbrella skirt body is coated with a silane coupling agent coating that is tightly adhered to the outer surface of the full-circumference sealing patch.

[0011] Preferably, the diameter of the large-diameter umbrella skirt is 150-200mm, the diameter of the small-diameter umbrella skirt is 100-130mm, and the height difference between the two is controlled at 20-30mm.

[0012] Preferably, the mandrel is made of alkali-free glass fiber reinforced epoxy resin pultruded rod, and the diameter of the mandrel is 20-30mm.

[0013] Preferably, the flexible insulating locking band is made of reinforced fluorosilicone rubber and its surface is treated with a nano-ceramic coating.

[0014] Preferably, each of the two stepped grooves has a slot, and each of the two stepped grooves has a locking block that is compatible with the corresponding slot. The two locking blocks are respectively locked into the corresponding slots.

[0015] Preferably, an anti-slip pad is fixedly installed on the inner side of the flexible insulating locking band, and the anti-slip pad is made of fluorosilicone rubber elastic pad with a thickness of 2.5mm.

[0016] Preferably, the full-circumference sealing patch is made of fluorosilicone rubber, and the width of the full-circumference sealing patch is adapted to the circumference of the mandrel and is tightly fixed to the outer surface of the mandrel in a non-overlapping wrapping manner.

[0017] Preferably, the overlapping surfaces of both ends of the full-circumference sealing patch are arranged in a right-angled shape.

[0018] Preferably, the seams of the full-circumference sealing patch do not intersect with the spiral discontinuous seams.

[0019] The beneficial effects of this invention are:

[0020] This invention achieves a reliable seal between the umbrella skirt and the core rod by setting a rigid core rod and covering its outer surface with a full-circumference sealing patch, combined with an integrally molded silicone rubber umbrella skirt body and a spiral disconnected joint design. At the same time, a flexible insulating locking tape made of reinforced fluorosilicone rubber, through a structure such as stepped grooves, ratchet teeth and anti-slip pads, can tightly wrap the umbrella skirt body and press and seal the overlapping surface, effectively preventing moisture and dust intrusion, improving the resistance to flashover. The overall structure has excellent mechanical and insulating properties, can adapt to different polluted environments and extreme temperature conditions, and is easy to install and maintain, which can significantly extend the operational reliability and service life of overhead power lines. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1 This is a three-dimensional structural diagram of a composite insulator for overhead power lines proposed in this invention;

[0023] Figure 2 for Figure 1 Front view structural diagram;

[0024] Figure 3 for Figure 1 A schematic diagram of the cross-sectional structure;

[0025] Figure 4 for Figure 3 A schematic diagram of the three-dimensional structure from another perspective;

[0026] Figure 5 for Figure 3 A schematic diagram of the three-dimensional structure of part A in the middle;

[0027] Figure 6This is a partial three-dimensional structural diagram of the flexible insulating locking strip portion in this invention;

[0028] Figure 7 for Figure 6 A schematic diagram of the three-dimensional structure from another perspective;

[0029] Figure 8 This is a partial three-dimensional structural diagram of the flexible insulating locking strip in the locked state in this invention;

[0030] Figure 9 This is a three-dimensional structural diagram of the mandrel, the first fitting, and the second fitting as proposed in this invention;

[0031] Figure 10 This is a partial three-dimensional structural diagram of the full-circumference sealing patch proposed in this invention.

[0032] In the diagram: 1. Core rod; 11. First fitting; 12. Second fitting; 2. Skirt body; 201. Silane coupling agent coating; 21. Large-diameter skirt; 22. Small-diameter skirt; 3. Full-circumference sealing patch; 4. Flexible insulating locking band; 41. Stepped groove; 42. Locking block; 43. Locking groove; 44. Ratchet; 45. Anti-slip pad layer. Detailed Implementation

[0033] The technical solution of the present invention will now be clearly and completely described with reference to specific embodiments. Obviously, the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0034] Reference Figure 1-10 A composite insulator for overhead power lines, comprising the above-mentioned technical objective of the present invention, is achieved through the following technical solution: A composite insulator for overhead power lines, comprising

[0035] Core rod 1 is a rigid component made of alkali-free glass fiber reinforced epoxy resin pultruded rod. This material combines the high strength reinforcement of alkali-free glass fiber with the excellent insulation properties of epoxy resin, giving core rod 1 a tensile strength of not less than 1200 MPa and a tensile strength greater than 10¹. 4 With an insulation resistance of Ω·m, it also has good anti-aging properties and corrosion resistance, and can withstand conductor tension, wind load and environmental erosion for a long time. The diameter of the core rod 1 is set to 20-30mm. This size range has been optimized by mechanical simulation. While meeting the load-bearing requirements of 110kV-500kV high-voltage lines, it can effectively match the assembly accuracy of the subsequent full-circumference sealing patch 3 and umbrella skirt body 2.

[0036] The two ends of the core rod 1 are respectively fixedly connected to a first fitting 11 and a second fitting 12. The first fitting 11 is used to connect to the pole and tower, and the second fitting 12 is used to hang the conductor. The first fitting 11 and the second fitting 12 at both ends of the core rod 1 are made of hot-dip galvanized high-strength alloy steel. The first fitting 11 is designed as a ball-and-socket type connection structure to adapt to the hanging point device on the side of the pole and tower. The second fitting 12 adopts a wedge-shaped wire clamp structure for reliable hanging of the conductor.

[0037] A full-circumference sealing patch 3 is fixedly pasted on the outer surface of the mandrel 1 along the length direction. The full-circumference sealing patch 3 is made of fluorosilicone rubber, which combines the weather resistance and corrosion resistance of fluororubber with the elastic sealing performance of silicone rubber. It can maintain stable elastic deformation ability in a temperature range of -40℃ to 120℃. The width of the full-circumference sealing patch 3 is adapted to the circumference of the mandrel 1 and is tightly fixed to the outer surface of the mandrel 1 in a non-overlapping wrapping manner.

[0038] In order to form an interlocking structure when the full-circumference sealing patch 3 wraps around the core rod 1, the contact area at both ends can be significantly increased. With the use of the silane coupling agent coating 201, the sealing performance at the overlap can be further improved, effectively preventing external moisture, dust and corrosive media from penetrating the surface of the core rod 1 from the joint, thereby ensuring the insulation performance and mechanical strength of the core rod 1 and extending the service life of the composite insulator. The overlapping surfaces at both ends of the full-circumference sealing patch 3 are set in a right-angled shape. This structure makes the overlapping form an interlocking stepped contact. Compared with the planar overlap, the contact area is increased by more than 30%. With the silane coupling agent coating 201 on the inner wall of the umbrella skirt body 2, a double bonding and sealing effect can be formed.

[0039] The umbrella skirt body 2 is a one-piece molded structure made of silicone rubber. The inner wall of the umbrella skirt body 2 is adapted to the outer surface of the full-circumference sealing patch 3. The umbrella skirt body 2 has a spiral-shaped break joint along the axial direction, centered on the axis of the core rod 1, with a spiral angle of 15-30°. The umbrella skirt body 2 includes alternating large-diameter umbrella skirts 21 and small-diameter umbrella skirts 22. Both sides of the spiral-shaped break joint have sealing overlap surfaces at a 45° right angle. The width of the spiral-shaped break joint is 1-2 mm. The inner wall of the umbrella skirt body 2 is coated with... The silane coupling agent coating 201, which is tightly adhered to the outer surface of the full-circumference sealing patch 3, can significantly improve the interfacial bonding strength between the skirt body 2 and the full-circumference sealing patch 3, effectively preventing the intrusion of external impurities such as moisture and dust, and ensuring the long-term insulation performance of the composite insulator. At the same time, in order to effectively increase the creepage distance and improve the insulator's resistance to flashover in polluted environments, the diameter of the large-diameter skirt 21 is 150-200mm, the diameter of the small-diameter skirt 22 is 100-130mm, and the height difference between the two is controlled at 20-30mm.

[0040] To prevent the seams of the full-circumference sealing patch 3 from forming a connecting channel with the spiral disconnected seam, further reducing the risk of external impurities intruding and ensuring the integrity of the sealing structure, the seams of the full-circumference sealing patch 3 and the spiral disconnected seam do not intersect. Through the non-intersecting staggered design, the sealing paths of the full-circumference sealing patch 3 and the umbrella skirt body 2 are independent of each other. Even if a minor defect occurs in one of the seals, the other can still play an effective blocking role, thereby greatly improving the overall sealing reliability of the composite insulator.

[0041] The locking and fixing unit consists of multiple flexible insulating locking strips 4. These strips are made of reinforced fluorosilicone rubber with a nano-ceramic coating, enabling them to withstand extreme temperatures ranging from -40℃ to 120℃. They possess a tensile strength of no less than 8MPa and an elongation at break greater than 200%, exhibiting excellent arc resistance and anti-aging properties. They effectively prevent moisture, dust, and corrosive media from penetrating the core rod 1 surface. Furthermore, through their elastic contraction characteristics, they tightly wrap around the outside of the skirt body 2, firmly pressing the sealing overlap at the spiral disconnected joint, further enhancing the sealing reliability between the skirt body 2 and the core rod 1. Even during long-term outdoor operation affected by temperature changes, wind vibrations, and other factors, they maintain a good sealing effect, preventing the core rod 1 from experiencing insulation performance degradation due to moisture or contamination. In addition, the installation and replacement of these flexible insulating locking strips 4 are simple and quick, requiring no special tools, significantly reducing on-site maintenance workload and costs, and providing strong support for the long-term stable operation of the composite insulator.

[0042] Multiple flexible insulating locking straps 4 are pre-positioned and wrapped between the corresponding large-diameter umbrella skirt 21 and small-diameter umbrella skirt 22. Stepped grooves 41 are provided on the inner side of one end of the flexible insulating locking strap 4 and the outer side of the other end of the flexible insulating locking strap 4. Multiple ratchet teeth 44 are provided in the two stepped grooves 41. After the flexible insulating locking strap 4 wraps around the umbrella skirt body 2, it is locked by the multiple ratchet teeth 44. In order to connect the ends of the flexible insulating locking strap 4 after it wraps around and presses against the umbrella skirt body 2, and at the same time, with the interlocking action of the multiple ratchet teeth 44, the locking straps are effectively prevented from loosening due to vibration or temperature deformation during long-term use. Thus, the flexible insulating locking strap 4 can be effectively fixed to the umbrella skirt body. Each of the two stepped grooves 41 is provided with a slot 43. Each of the two stepped grooves 41 is fixedly installed with a locking block 42 that matches the corresponding slot 43. The two locking blocks 42 are respectively locked into the corresponding slot 43.

[0043] The mandrel 1 is fixedly connected to the first fitting 11 and the second fitting 12 using a hydraulic crimping process. In practice, the first fitting 11 and the second fitting 12 are first fitted onto the preset positions at both ends of the mandrel 1. A set pressure of 80-120MPa is applied by a special hydraulic device, causing the inner walls of the first fitting 11 and the second fitting 12 to undergo plastic deformation, forming a tight fit with the anti-slip texture on the outer surface of the mandrel 1. This results in a connection structure with high mechanical strength and stable electrical contact. To further improve the sealing performance, a layer of epoxy adhesive with a thickness of 0.5mm is uniformly coated on the connection area between the mandrel 1 and the fitting before crimping. During the crimping process, this adhesive fills the tiny gaps between the inner wall of the fitting and the outer surface of the mandrel 1. After curing, it forms a dense sealing layer, effectively preventing the intrusion of rainwater, moisture and corrosive media, and avoiding electrochemical corrosion or insulation deterioration at the connection interface.

[0044] In this embodiment, in order to further enhance the friction between the flexible insulating locking band 4 and the umbrella skirt body 2, prevent the locking band from sliding relative to each other due to wind vibration or temperature changes during long-term operation, and ensure the continuous compression and sealing effect on the spiral disconnected joint, an anti-slip pad 45 is fixedly installed on the inner side of the flexible insulating locking band 4. The anti-slip pad 45 is made of 2.5mm thick fluorosilicone rubber elastic pad, which also has good elastic deformation ability and can adapt to the slight unevenness on the surface of the umbrella skirt body 2, making the contact between the flexible insulating locking band 4 and the umbrella skirt body 2 tighter, avoiding the occurrence of local gaps that could lead to the intrusion of moisture or dirt, and ensuring the long-term stability and reliability of the overall structure of the insulator.

[0045] Among them, the outer surface of the umbrella skirt body 2 is also uniformly distributed with nano-sized alumina particles with a particle diameter of 50-100nm. Through the encapsulation and curing of the silicone rubber matrix, the hardness and wear resistance of the umbrella skirt surface can be significantly improved, reducing the risk of umbrella skirt damage caused by friction and collision during installation or operation. At the same time, the presence of nanoparticles can also enhance the hydrophobicity of the umbrella skirt surface to water, reduce the adhesion of rainwater on the umbrella skirt surface, and improve the insulation performance of the insulator in humid environments.

[0046] Working principle: In use, firstly, the first fitting 11 and the second fitting 12 at both ends of the core rod 1 are connected and fixed to the tower and the conductor respectively to ensure that the insulator is in a stable working position. Then, according to the actual installation requirements, the umbrella skirt body 2 of the cut length is selected, and the silane coupling agent coating 201 on the inner wall of the umbrella skirt body 2 is aligned and bonded to the outer surface of the full circumference sealing patch 3 on the outer surface of the core rod 1. The high adhesion performance of the silane coupling agent is used to form a preliminary tight connection between the umbrella skirt body 2 and the full circumference sealing patch 3.

[0047] Next, the umbrella skirt body 2 is wrapped around the core rod 1 along the spiral discontinuous seam, and the 45° right-angled sealing overlap surfaces on both sides are precisely aligned. At this time, the silane coupling agent coating 201 on the inner wall of the umbrella skirt body 2 further plays its role, improving the interfacial bonding strength between it and the full-circumference sealing patch 3, effectively preventing the intrusion of external impurities. After that, multiple flexible insulating locking straps 4 are installed and respectively placed between the corresponding large-diameter umbrella skirt 21 and small-diameter umbrella skirt 22. Utilizing the elastic shrinkage characteristics of the reinforced fluorosilicone rubber material, it is tightly wrapped around the outside of the umbrella skirt body 2. At the same time, the stepped groove 41 on the inner side of one end of the flexible insulating locking strap 4 is aligned with the stepped groove 41 on the outer side of the other end, so that the locking block 42 is embedded in the locking groove 43. With the mutual interlocking of multiple barbed ratchet teeth 44, the head and tail of the flexible insulating locking strap 4 are firmly connected, preventing loosening due to vibration or temperature deformation during long-term use.

[0048] During this process, the 2.5mm thick fluorosilicone rubber anti-slip pad 45 on the inner side of the flexible insulating locking band 4 is in close contact with the surface of the umbrella skirt body 2, which enhances the friction to avoid relative slippage, and adapts to the slight unevenness of the umbrella skirt surface through its own elastic deformation, ensuring continuous compression of the spiral disconnected joint sealing overlap surface.

[0049] The overlapping surfaces of the right-angled ends of the full-circumference sealing patch 3 form an interlocking structure when wrapping the core rod 1. Combined with the silane coupling agent coating, the sealing performance is improved. Furthermore, the joints and the spiral disconnected joints adopt a non-intersecting staggered design, making the sealing paths of the two independent. Even if a minor defect occurs in one seal, the other can still effectively block the external medium. Finally, through the rigid support of the core rod 1, the creepage distance design of the umbrella skirt body 2 (large diameter umbrella skirt 150-200mm, small diameter umbrella skirt 100-130mm, height difference 20-30mm), and the multiple sealing and fixing effects of the locking and fixing unit, the composite insulator is guaranteed to have high strength (tensile strength ≥8MPa), high resistance to flashover and anti-aging performance in extreme temperature environments from -40℃ to 120℃, achieving long-term stable operation.

Claims

1. A composite insulator for overhead power lines, characterized in that, Includes a core rod (1), which is rigidly set, and the two ends of the core rod (1) are respectively fixedly connected to a first fitting (11) and a second fitting (12). The first fitting (11) is used to connect with the tower, and the second fitting (12) is used to hang the conductor. A full-circumference sealing patch (3) is fixedly pasted on the outer surface of the core rod (1) along the length direction. The umbrella skirt body (2) is a one-piece molded structure of silicone rubber, and the inner sidewall of the umbrella skirt body (2) is adapted to the outer surface of the full-circumference sealing patch (3). The umbrella skirt body (2) has a spiral-shaped disconnected seam centered on the axis of the core rod (1) along the axial direction, and the spiral angle is 15-30°. The umbrella skirt body (2) includes alternating large-diameter umbrella skirts (21) and small-diameter umbrella skirts (22). Both sides of the spiral-shaped disconnected seam are provided with sealing overlap surfaces in the shape of 45° right angles. The locking and fixing unit consists of multiple flexible insulating locking straps (4). The multiple flexible insulating locking straps (4) are pre-positioned and wrapped between the corresponding large-diameter umbrella skirt (21) and small-diameter umbrella skirt (22). A stepped groove (41) is provided on the inner side of one end of the flexible insulating locking strap (4) and the outer side of the other end of the flexible insulating locking strap (4). Multiple ratchet teeth (44) arranged in a barb-like manner are provided in both stepped grooves (41). The flexible insulating locking strap (4) is locked and fixed by multiple ratchet teeth (44) after wrapping around the umbrella skirt body (2). The mandrel (1) is fixedly connected to the first fitting (11) and the second fitting (12) by hydraulic pressing.

2. The composite insulator for overhead power lines according to claim 1, characterized in that: The width of the spiral disconnected seam is 1-2 mm, and the inner wall of the umbrella skirt body (2) is coated with a silane coupling agent coating (201) that is in close contact with the outer surface of the full-circumference sealing patch (3).

3. The composite insulator for overhead power lines according to claim 1, characterized in that: The diameter of the large-diameter umbrella skirt (21) is 150-200mm, the diameter of the small-diameter umbrella skirt (22) is 100-130mm, and the height difference between the two is controlled at 20-30mm.

4. A composite insulator for overhead power lines according to claim 1, characterized in that: The mandrel (1) is made of alkali-free glass fiber reinforced epoxy resin pulverized rod, and the diameter of the mandrel (1) is 20-30mm.

5. A composite insulator for overhead power lines according to claim 1, characterized in that: The flexible insulating locking band (4) is made of reinforced fluorosilicone rubber and its surface is treated with a nano-ceramic coating.

6. A composite insulator for overhead power lines according to claim 1, characterized in that: Each of the two stepped grooves (41) has a slot (43) and a locking block (42) that matches the corresponding slot (43) is fixedly installed in each of the two stepped grooves (41). The two locking blocks (42) are respectively locked into the corresponding slots (43).

7. A composite insulator for overhead power lines according to claim 1, characterized in that: The inner side of the flexible insulating locking band (4) is fixedly installed with an anti-slip pad (45), and the anti-slip pad (45) is made of fluorosilicone rubber elastic pad with a thickness of 2.5mm.

8. A composite insulator for overhead power lines according to claim 1, characterized in that: The full-circumference sealing patch (3) is made of fluorosilicone rubber. The width of the full-circumference sealing patch (3) is adapted to the circumference of the mandrel (1) and is tightly fixed to the outer surface of the mandrel (1) in a non-overlapping wrapping manner.

9. A composite insulator for overhead power lines according to claim 1, characterized in that: The overlapping surfaces of both ends of the full-circumference sealing patch (3) are set in a right-angled shape.

10. A composite insulator for overhead power lines according to claim 1, characterized in that: The seam of the full-circumference sealing patch (3) does not intersect with the spiral disconnected seam.

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