CN108568959B

CN108568959B - Molding process of wood-plastic floor

Info

Publication number: CN108568959B
Application number: CN201810390655.2A
Authority: CN
Inventors: 张亚
Original assignee: Zhangjiagang Kafu New Material Co ltd
Current assignee: Zhangjiagang Kafu New Material Co ltd
Priority date: 2018-04-27
Filing date: 2018-04-27
Publication date: 2020-07-14
Anticipated expiration: 2038-04-27
Also published as: CN108568959A

Abstract

The invention relates to a molding process of a wood-plastic floor, which comprises the following steps: 1) feeding the mixed materials into a plastic extruding machine, and extruding the materials from a discharge port of a die to form a wood-plastic floor blank; 2) horizontally feeding the blank into a fixed cavity of a water-cooling metal part, and taking away the heat of the blank by water flow in the water-cooling cavity to quickly realize the shaping and cooling of the extruded sheet; 3) further cooling the extruded sheet by water flow flowing in the soaking tank; 4) the cooled extruded sheet is sent out from the correction module and then drained, and the quick air drying of the blank is realized by air drying air flows on the two sides of the extruded sheet; 5) and conveying the air-dried extruded sheet to a cutting system under the action of a traction system, and then cutting. On the one hand, on the premise of realizing the shaping of the extruded sheet, the extruded sheet is quickly cooled by the water-cooling metal piece; on the other hand, under the draining of the draining groove, the cooled extruded sheet can quickly enter the next procedure in an air drying mode, and the continuous flow production is met.

Description

Molding process of wood-plastic floor

Technical Field

The invention relates to a forming process of a wood-plastic floor.

Background

In recent years, solid wood floors, solid wood composite floors and the like are widely used as ground decoration materials for interior decoration. The solid wood floor has the problems of shortage of high-quality wood and low wood utilization rate, and some strengthened floors and composite floors appear on the market to meet the requirements of consumers, but in use, glue adopted in compounding can emit a lot of harmful substances (such as formaldehyde), so that the health of people is seriously influenced, and therefore, a novel environment-friendly wood-plastic composite product is gradually formed.

However, in actual processing, the floor is formed into a rough shape after being discharged from a die of an extruder, and the floor is prevented from being deformed due to a high temperature, and thus, it is necessary to perform rapid cooling and setting, and also to secure the strength of the floor itself. The cooling mode includes two modes of water cooling and air cooling, but the water cooling is more adopted in view of the convenience of operation and processing cost.

At present, the adopted water cooling mode is a soaking mode, although water in a soaking tank is in a flowing state, the cooling effect is general, and the extruded sheet cannot be shaped; meanwhile, water on the surface of the extruded sheet cannot be removed after water cooling, and the continuity of production and processing is directly influenced.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a forming process capable of continuously realizing the production and processing of wood-plastic floors.

In order to solve the technical problems, the technical scheme adopted by the invention is as follows:

a molding process of a wood-plastic floor comprises the following steps:

1) feeding the mixed materials into a plastic extruding machine, and extruding the materials from a discharge port of a die to form a wood-plastic floor blank;

2) horizontally feeding the blank into a fixed cavity of a water-cooling metal piece with the fixed cavity and a water-cooling cavity, and taking away the heat of the blank by water flow in the water-cooling cavity to quickly realize the shaping and cooling of the extruded sheet;

3) conveying the extruded sheet sent out from the fixed cavity to a soaking tank, and further cooling the extruded sheet by water flow flowing in the soaking tank;

4) a correction module is arranged at an outlet of the soaking tank, the cooled extruded sheet is sent out from the correction module, surface water is drained in a draining tank, and crossed air flows are formed by air drying assemblies at two sides of the extruded sheet to quickly air-dry the upper surface and the lower surface of the extruded sheet;

5) and conveying the air-dried extruded sheet to a cutting system under the action of a traction system, and then cutting according to the required size.

Preferably, the water-cooling metal part comprises a water-cooling module, a water inlet pipe and a water outlet pipe, wherein a fixed cavity matched with the extruded sheet and a water-cooling cavity for cold water to flow are formed in the water-cooling module, the water inlet pipe and the water outlet pipe are communicated with the water-cooling cavity, the extending direction of the fixed cavity is intersected with the extending direction of the water-cooling cavity, and the extruded sheet formed from a discharge port of the extruder is horizontally conveyed into the soaking tank through the fixed cavity.

Preferably, the extension direction of the fixed cavity is perpendicular to the extension direction of the water cooling cavity. Therefore, the shorter the water flowing time of the water cooling cavity is, the faster the cold water is updated, and the quick cooling of the extruded sheet is facilitated.

According to a specific implementation and preferable aspect of the invention, a plurality of partition plates are arranged in the water cooling cavity along the length direction of the sizing cavity, wherein the plurality of partition plates divide the water cooling cavity into a plurality of relatively independent water flow channels. The water flow speed is further improved by arranging a plurality of water flow channels, and a quick heat exchange effect is achieved.

Preferably, a plurality of baffles are evenly distributed along the length direction of the shaping cavity, a plurality of relatively independent water flow channels are arranged in parallel, and the water inlet pipe, the water outlet pipe and the water flow channels are arranged in one-to-one correspondence and are respectively communicated with two end parts of each water flow channel.

According to another specific implementation and preferable aspect of the invention, the water cooling module comprises an upper module and a lower module which are rotatably closed from one side edge along the length direction of the sizing cavity, and the sizing cavity is formed by splicing the upper module and the lower module after the upper module and the lower module are closed.

Preferably, the water cooling cavity is respectively arranged on the upper module and the lower module and is positioned at the upper part and the lower part of the shaping cavity after the mold is closed.

Further, it is preferred that the flow direction of the water in the upper water-cooling chamber is opposite to the flow direction of the water in the lower water-cooling chamber. Further improve the heat transfer effect, realize the cooling fast, ensure the quality after the extruded sheet shaping.

According to another specific implementation and preferable aspect of the invention, the water-cooled metal part further comprises a guide plate arranged at the water inlet end of the water-cooled cavity, and an arc-shaped guide block arranged inside the water-cooled cavity and arranged at a corner forming the fixed cavity, wherein water flow can rapidly flow in the water-cooled cavity after passing through the guide plate and the arc-shaped guide block. The speed of water flow is improved to the maximum extent.

In addition, foretell water cooling system still includes a plurality of guide rollers of setting in soaking groove, and wherein guide roller can rotate the setting round self axis direction, and a plurality of guide rollers tops level and horizontal plane parallel arrangement.

Preferably, a correction module capable of being adjusted along the vertical direction is arranged at the outlet of the soaking tank, wherein a standard-style channel is arranged in the correction module, and the water-cooled extruded sheet passes through the channel.

According to another embodiment of the present invention, a carrier wheel for carrying the extruded sheet is disposed in the draining tank, wherein the carrier wheel is rotatable about a horizontal axis, and the air drying assembly comprises a blower, ventilation ducts, and ventilation nozzles, wherein the ventilation nozzles are disposed on opposite sides of the extruded sheet, and the direction of the ejected air flow is vertical.

Preferably, the aeration nozzles are located at the discharge end of the draining tank.

Preferably, the traction module comprises a first connecting part connected with the upper endless chain or the lower endless chain, and a second connecting part far away from the end part of the upper endless chain or the lower endless chain from the first connecting part, wherein a traction channel with the thickness equal to that of the extruded sheet is formed between the second connecting parts positioned at the lower part of the upper endless chain and the upper part of the lower endless chain.

According to a specific implementation and preferred aspect of the invention, the anti-slip portion is formed on the side of the second connecting portion forming the traction channel.

Preferably, the anti-slip parts extend in a prism shape along the width direction of the upper and lower endless chains, and a groove is formed between two adjacent anti-slip parts.

According to another embodiment of the present invention, the ends of the groove have a drop height and are inclined toward one end, the non-slip part is made of a flexible water absorbing material, and the traction system further includes a pressing roller disposed above the upper endless chain and below the lower endless chain to press water in the non-slip part to dry, wherein the pressed water is discharged from the groove to opposite sides of the upper endless chain and the lower endless chain.

Preferably, the press roll can force the non-slip portion to be deformed toward the groove and pressed by the transmission of the upper and lower endless chains. In this case, the grooves are provided to facilitate drainage of water and to facilitate pressing of the plurality of water-absorbing nonslip portions of the second connecting portion one by one.

Preferably, the traction modules on the upper and lower endless chains are arranged symmetrically with respect to the length direction of the traction channel. That is, the traction channels are formed in a relatively small pitch landing pattern.

Due to the implementation of the technical scheme, compared with the prior art, the invention has the following advantages:

on the one hand, on the premise of realizing the shaping of the extruded sheet, the extruded sheet is quickly cooled by the water-cooling metal piece; on the other hand, under the draining of the draining groove, the cooled extruded sheet can quickly enter the next procedure in an air drying mode, and the continuous flow production is met.

Drawings

FIG. 1 is a schematic front view of an automated manufacturing facility according to the present invention;

FIG. 2 is a schematic front view of the extruder and water cooling system of FIG. 1;

FIG. 3 is a schematic sectional view taken along line A-A in FIG. 2 (the direction of the arrows indicates the direction of water flow);

FIG. 4 is a schematic front view of the configuration of the traction system of FIG. 1;

wherein: 1. a plastic extruding machine; 10. an extruder body; 11. a feeding device; 12. a mold;

A. a water cooling system; 2. a soaking tank; 3. water-cooling the metal piece; 30. a water cooling module; 30a, forming a cavity; 30b, a water cooling cavity; 30c, a partition plate; 30d, a water flow channel; 301. an upper module; 302. a lower module; 31. a water inlet pipe; 32. a water outlet pipe; 33. a baffle; 34. an arc-shaped flow guide block; 4. a guide roller; 5. a correction module; 6. a draining tank; 60. a load wheel; 7. air-drying the assembly; 71. and (4) a ventilation nozzle.

B. A traction system; b1, a traction assembly; b10, upper endless chain; b11, lower endless chain; b12, a traction module; 121. a first connection portion; 122. a second connecting portion; q, a traction channel; a. an anti-slip portion; b. a trench; b4, pressing rolls; b5, width limiting component; b50, a limiting wheel; 500. a wheel groove;

C. a cutting system; c1, cutting a platform; c2, cutting tools; c3, a driving mechanism.

Detailed Description

The invention is described in further detail below with reference to the figures and specific examples.

In order to make the aforementioned objects, features and advantages of the present application more comprehensible, embodiments accompanying the present application are described in detail below with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. This application is capable of embodiments in many different forms than those described herein and that modifications may be made by one skilled in the art without departing from the spirit and scope of the application and it is therefore not intended to be limited to the specific embodiments disclosed below.

In the description of the present application, it is to be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the present application and for simplicity in description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the present application.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present application, "plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In this application, unless expressly stated or limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can include, for example, fixed connections, removable connections, or integral parts; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art as appropriate.

In this application, unless expressly stated or limited otherwise, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through intervening media. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

It will be understood that when an element is referred to as being "secured to" or "disposed on" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and the like as used herein are for illustrative purposes only and do not denote a unique embodiment.

The embodiment relates to a forming process of a wood-plastic floor, which comprises the following steps:

As shown in FIG. 1, in this embodiment, in order to complete the above process steps, a flow line type full-automatic production apparatus is adopted, which comprises an extruder 1, a water cooling system A, a traction system B, and a cutting system C.

The plastic extruding machine 1 comprises an extruding machine body 10, a feeding device 11 and a mould 12 which is arranged at an extruding opening and forms the wood-plastic floor;

referring to fig. 2 and 3, the water cooling system a includes a soaking tank 2 connected to the discharge port of the mold 12, wherein the water in the soaking tank 2 is in a flowing state, a water-cooled metal part 3 disposed between the inlet of the soaking tank 2 and the discharge port of the plastic extruding machine 1, a draining tank 6 connected to the outlet of the soaking tank 2, and an air drying assembly 7 disposed on the draining tank 6 for drying the surface of the extruded sheet.

Specifically, the water-cooling metal part 3 comprises a water-cooling module 30, a water inlet pipe 31 and a water outlet pipe 32, wherein a shaping cavity 30a matched with the extruded sheet and a water-cooling cavity 30b for cold water to flow are formed in the water-cooling module, and the water inlet pipe 31 and the water outlet pipe 32 are communicated with the water-cooling cavity 30 b.

In this example, the extension direction of the shaping chamber 30a is perpendicular to the extension direction of the water cooling chamber 30 b. Therefore, the shorter the water flowing time of the water cooling cavity is, the faster the cold water is updated, and the quick cooling of the extruded sheet is facilitated.

The water-cooling module 30 comprises an upper module 301 and a lower module 302 which are rotated and closed from one side edge along the length direction of the fixed cavity 30a, and the fixed cavity 30a is formed by splicing the upper module 301 and the lower module 302 after being matched.

The water cooling cavities 30b are respectively arranged on the upper module 301 and the lower module 302 and are positioned at the upper part and the lower part of the die assembly rear shaping cavity 30 a.

In this embodiment, the water flow speed and the heat exchange effect are further improved, and a plurality of partition plates 30c are respectively arranged in the water cooling cavity 30b, wherein the extending direction of the partition plates 30c is consistent with the width direction of the shaping cavity 30 a.

Therefore, the water cooling cavity 30b is divided into a plurality of relatively independent water flow channels 30d by the plurality of partition plates 30c, and meanwhile, the water inlet pipe 31 and the water outlet pipe 32 are arranged in one-to-one correspondence with the water flow channels 30d and are respectively communicated with two end parts of each water flow channel 30 d. That is, the plurality of water flow passages 30d are spliced to form the water cooling chamber 30b described above.

Specifically, the plurality of partition plates 30c are uniformly distributed along the length direction of the fixed cavity 30a, and the plurality of relatively independent water flow passages 30d are arranged in parallel with each other.

Meanwhile, the flow direction of the water in the upper water-cooled chamber 30b is opposite to the flow direction of the water in the lower water-cooled chamber 30 b. Further improve the heat transfer effect, realize the cooling fast, ensure the quality after the extruded sheet shaping.

In this example, the extruded sheet formed from the discharge port of the extruder 1 is horizontally transferred into the dipping tank 2 through the fixed cavity 30 a.

The water-cooling metal piece 3 further comprises a guide plate 33 arranged at the water inlet end of the water-cooling cavity 30b, an arc-shaped guide block 34 arranged inside the water-cooling cavity 30b and arranged at the corner of the fixed cavity 30a, and water flows in the water-cooling cavity 30b quickly after passing through the guide plate 33 and the arc-shaped guide block 34. The speed of water flow is improved to the maximum extent.

In addition, the water cooling system further comprises a plurality of guide rollers 4 arranged in the soaking of the soaking groove 2, wherein the guide rollers 4 can rotate around the axis direction of the guide rollers, and the tops of the guide rollers 4 are flush and parallel to the horizontal plane.

Meanwhile, a correcting module 5 capable of being adjusted along the vertical direction is arranged at an outlet of the soaking tank 2, a channel of a standard style is arranged in the correcting module 5, and the water-cooled extruded sheet penetrates through the channel.

In this example, the drain tank 6 is provided to drain the surface of the extrusion plate.

Specifically, a bearing wheel 60 for bearing the extruded sheet is provided in the draining tank 6, wherein the bearing wheel 60 is arranged to rotate around the horizontal axis.

The air-drying assembly 7 comprises a fan, ventilation ducts and ventilation nozzles 71, wherein the ventilation nozzles 71 are positioned on two opposite sides of the extruded sheet, and the direction of the sprayed air flow is vertical. The air drying rate of the surface of the extrusion molding plate is realized to the maximum extent by an airflow flowing mode.

The ventilation nozzles 71 are located at the discharge end of the draining tank 6.

Therefore, after the water cooling system A is adopted, the following advantages are achieved:

1. on the premise of shaping the extruded sheet, the heat of the extruded sheet is quickly taken away through the arrangement of the water flow channels above and below the shaping cavity, so that the quick cooling is realized;

2. the flow directions of the water flows in the upper water flow channel and the lower water flow channel are opposite, so that the cooling efficiency and the cooling quality are further improved;

3. the arrangement of the guide plate and the arc-shaped guide block ensures that the water flow is rapid and stable;

4. the extruded sheet is quickly cooled by a water-cooling metal part and is cooled in soaking, so that the cooling interval can be effectively shortened, the equipment is simplified, and the cost is reduced;

5. under the draining of the draining groove, the cooled extruded sheet can quickly enter the next procedure in an air drying mode, and the continuous flow production is met.

Meanwhile, as shown in fig. 4, a drawing system B, which includes a drawing assembly B1 for holding the water-cooled extruded sheet moving horizontally.

The traction assembly B1 comprises an upper annular chain B10 and a lower annular chain B11 which are movably adjusted up and down, a plurality of traction modules B12 which are respectively distributed around the upper annular chain B10 and the lower annular chain B11 at intervals in the circumferential direction, and a driving unit which respectively drives the upper annular chain B10 and the lower annular chain B11 to synchronously rotate.

The traction module B12 includes a first link portion 121 connected to the upper endless chain B10 or the lower endless chain B11, a second link portion 122 located apart from an end of the upper endless chain B10 or the lower endless chain B11 from the first link portion 121, wherein a traction passage Q having a thickness equal to that of the extruded sheet is formed between the second link portions 122 located at a lower portion of the upper endless chain B10 and an upper portion of the lower endless chain B11.

Specifically, the traction modules B12 on the upper endless chain B10 and the lower endless chain B11 are symmetrically arranged with respect to the length direction of the traction passage Q. That is, the traction channels are formed in a relatively small pitch landing pattern.

Meanwhile, in order to further ensure that no slip occurs during the conveyance, in this example, the anti-slip portion a is formed on the side of the second connecting portion 122 where the drawing path Q is formed.

The anti-slip parts a extend along the width direction of the upper annular chain B10 and the lower annular chain B11 to form a convex prism shape, and a groove B is formed between every two adjacent anti-slip parts a.

The two ends of the groove B are provided with fall heads and are obliquely arranged towards one end, the antiskid part a is made of flexible water-absorbing materials, the traction system further comprises a pressing roller B4 which is arranged at the upper part of the upper annular chain B10 and the lower part of the lower annular chain B11 and presses the water of the antiskid part a dry, wherein the pressed water is discharged from the groove B to the opposite sides of the upper annular chain B10 and the lower annular chain B11.

The pressing roller B4 can force the non-slip portion a to be deformed toward the groove B and pressed by the driving of the upper and lower endless chains B10 and B11. In this example, the grooves b are provided to facilitate drainage of water and to facilitate pressing of the plurality of water-absorbing nonslip portions of the second connecting portion one by one.

Meanwhile, the upper annular chain B10 and the lower annular chain B11 can be tensioned and adjusted, and the horizontal state of the conveying surface forming the traction channel Q is ensured.

In addition, width limiting assemblies B5 are arranged on two sides of the inlet end and the outlet end of the drawing channel Q, wherein each width limiting assembly B5 comprises limiting wheels B50 which rotate around the axis in the vertical direction and are positioned on two sides of the drawing channel Q in the width direction, and wheel grooves 500 with the same thickness as the extruded sheet are formed on the outer peripheral surfaces of the limiting wheels B50. Therefore, through the arrangement of the width limiting assembly B5, the shaking in the width and thickness directions of the extruded sheet is limited during the moving process of the extruded sheet, and the stable translation of the extruded sheet is ensured.

As for the above-described cutting system C, it includes a cutting table C1, a cutting tool C2 capable of moving in synchronization with the extruded sheet, and a driving mechanism C3 for driving the cutting tool C2 to perform cutting in the synchronized movement of the extruded sheet.

Specifically, the cutting is directly purchased by the applicant, belongs to a conventional means, and the structure of the cutting is not described in detail.

The present invention has been described in detail in order to enable those skilled in the art to understand the invention and to practice it, and it is not intended to limit the scope of the invention, and all equivalent changes and modifications made according to the spirit of the present invention should be covered by the present invention.

Claims

1. A molding process of a wood-plastic floor comprises the following steps:

2) horizontally feeding the blank into a fixed cavity of a water-cooling metal part with the fixed cavity and a water-cooling cavity, taking away the heat of the blank by water flow in the water-cooling cavity, and quickly realizing the shaped cooling of an extruded sheet, wherein the water-cooling metal part comprises a water-cooling module, a water inlet pipe and a water outlet pipe, the water-cooling module is internally provided with the fixed cavity matched with the extruded sheet and the water-cooling cavity for cold water to flow, the water-cooling module is communicated with the water-cooling cavity, the extending direction of the fixed cavity is intersected with the extending direction of the water-cooling cavity, the extruded sheet formed from a discharge port of a plastic extruding machine is horizontally conveyed into a soaking groove through the fixed cavity, the water-cooling cavity is internally provided with a plurality of clapboards along the length direction of the fixed cavity, the clapboards separate the water-cooling cavity into a plurality of relatively independent water flow channels, and the water inlet pipe, and are respectively communicated with two end parts of each water flow channel,

the water-cooling module comprises an upper module and a lower module which are rotationally closed from one side edge along the length direction of the shaping cavity, the shaping cavity is formed by splicing the upper module and the lower module after the upper module and the lower module are assembled,

the water cooling cavities are respectively arranged on the upper module and the lower module and are positioned at the upper part and the lower part of the fixed cavity after the modules are assembled, wherein the flow direction of water flow in the water cooling cavity at the upper part is opposite to that of water flow in the water cooling cavity at the lower part;

2. The molding process of the wood-plastic floor according to claim 1, wherein: the partition plates are uniformly distributed along the length direction of the shaping cavity, and the water flow channels which are relatively independent are arranged in parallel.

3. The molding process of the wood-plastic floor according to claim 1, wherein: the water-cooling metalwork still including setting up the water-cooling chamber the water inlet end be equipped with the guide plate, set up inside the water-cooling chamber and just forming the corner of deciding the die cavity is equipped with arc water conservancy diversion piece, rivers pass through the guide plate with behind the arc water conservancy diversion piece, can be quick the water-cooling intracavity flows.

4. The molding process of the wood-plastic floor according to claim 1, wherein: traction system is including the traction assembly who is used for the extruded sheet horizontal migration behind the centre gripping water-cooling, traction assembly includes upper annular chain and lower annular chain that relative activity adjusted from top to bottom, respectively round a plurality of traction module of upper annular chain and lower annular chain circumference interval distribution and drive respectively go up the annular chain with annular chain synchronous revolution's drive unit down, wherein traction module include with go up the first connecting portion that annular chain or lower annular chain are connected, certainly first connecting portion are kept away from go up the second connecting portion of annular chain or lower annular chain tip, wherein be located go up annular chain lower part with annular chain upper portion down form the traction passageway that equals with extruded sheet thickness between the second connecting portion.

5. The molding process of the wood-plastic floor according to claim 4, wherein: the traction system further comprises compression rollers which are arranged on the upper part of the upper annular chain and the lower part of the lower annular chain and press the water of the anti-slip parts to be dry, wherein the pressed water is discharged from the grooves to the opposite sides of the upper annular chain and the lower annular chain.