JPH01103694A - Method and apparatus for compacting coke oven charge material - Google Patents

Abstract

PURPOSE:To improve nonuniform carbonization in an oven in the coke production using a chamber oven-type coke oven, by hooking up or down a load plate during advance or retreat of a beam main frame so as to apply a pressure onto the upper face of charge coal by means of a pressure face plate part of the load plate. CONSTITUTION:A load plate 15 comprising a pressure face plate part 17 which abuts against the upper face of charge coal in a carbonization chamber and a leveling part 18 which is disposed so as to retreat in a slant, upward direction as viewed against the pressure face plate part 17 is connected at the rear upper edge thereof, using a hinge 16 structure, to at least the tip of a beam main frame disposed so as to come in contact with the upper face of charge coal fed to the carbonization chamber of a coke oven and to enable advancing or retreating along the whole length of the carbonization chamber. When the beam main frame is advanced, the load plate 15 is hooked up so as to position within the frame. When the beam main frame is retreated, the beam main frame is hooked down so as to position outside the main frame. In this manner, the upper face of charge coal is compacted at 10-100g/cm<2> by the pressure face plate part 17, by which the wt. of the load is applied.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for consolidating coke in the upper part of coke charged in a furnace and for improving non-uniform carbonization in the furnace when producing coke in a room furnace type coke oven. This is related to the device.

[Prior Art] Fig. 7 shows an example of a side view showing the mechanism of a chamber-type coke oven. Normally, coke production is carried out by dropping coking coal 4 from the top of the furnace through the charging ports 2 into a coking chamber 1, which has 4 to 5 charging ports 2 at the top, using a coking coal loading car 3. A leveler 7 is inserted through the upper opening 6 of the kiln mouth, and leveled by moving it forward and backward over the entire length of the coking chamber in contact with the upper surface of the coking coal.
After leveling the upper surface level so as to secure the generated gas path 8, it is manufactured by heating the carbonization chamber 1 through bricks from both sides of the combustion chamber (front and rear combustion chambers in FIG. 4). The coke produced is opened to the front S door 9,10 of the carbonization chamber 1, pushed out to the front door 9 side by the extruder 5, and loaded onto the fire extinguisher 12 via the guide car 11.

The coke produced by this method is
It is known that there are large quality deviations and carbonization temperature deviations in the three directions of the furnace width.

One of the causes of these deviations is that the raw materials charged into the furnace have extremely large bulk density deviations in the furnace length, furnace height, and furnace width directions. That is, as a result of coking coal being dropped and charged from the charging port 2 above the furnace, the bulk density deviation in the furnace height direction is lower in the upper part of the furnace than in the lower part of the furnace, and
The bulk density between the charging ports and at the kiln mouth tends to be lower than that directly below. In addition, in the furnace width direction, the bulk density tends to be higher in the furnace center due to friction between the furnace wall and the raw coal contact area. As an example of the bulk density deviation in the furnace, the inventors' investigation revealed that the average bulk density was 735 kg/n? Approximately ±50kg/
/ It has been confirmed that a large deviation occurs.

Such deviations in the bulk density of the charged raw materials in the furnace naturally result in deviations not only in the coke quality but also in the carbonization temperature. become. Therefore, the development of technology for uniformly adjusting the bulk density of charged coking coal has become an extremely important issue.

[Problem that the invention seeks to solve]

Against this background, in recent years, various attempts have been made to improve the bulk density deviation in the upper part of the charged coking coal by adding innovations to the leveler.

The structure of a conventional leveler is shown in Figures 1 (a) and 2 (a), in which the leveler main body 7 has partition plates 14 installed at regular intervals inside side plates 13 and 13 extending in the length direction of the furnace. Due to its ladder-like structure without a top plate or bottom plate, the top surface of the charging coking coal 4 is directly below the charging port 2 and the charging port, as shown in the schematic cross-sectional view of the main part of the coke oven in the longitudinal direction of the coke oven in Figure 5 (a). It only serves to level the charged pile of coking coal between the charging port and the charging port, but does not have the function of consolidating the upper surface of the charged coking coal 4. Furthermore, it was not sufficient to completely level the charging height between the charging port 2 and between the charging ports 2. Further, as shown in the schematic cross-sectional view of the main part of the coke oven in the width direction of the coke oven in FIG.

On the other hand, as a method for improving the bulk density of charging coking coal especially in the upper part of the furnace, for example,
No. 5, Japanese Patent Publication No. 59-18437 and Japanese Patent Publication No. 62-1
No. 1794 discloses a leveler equipped with a pressure vibration mechanism, and attempts to consolidate the upper surface of coking coal using this leveler. However, there are concerns that the vibration may cause joint breakage and damage to the furnace wall bricks, and since it is mechanically complex to incorporate the vibration device into the leveler, it is not possible to continue using it for a long period of time from a maintenance management perspective. It is doubtful.

In addition, these have a structure in which the tip of the leveler is bent by a cylinder device or the entire leveler is tilted, so the tilting angle is fixed at a constant level, so the vibration consolidation effect is uniform on the uneven coking coal surface. There is a possibility that it will not happen.

In addition, there is also a leveler as disclosed in Japanese Patent Publication No. 59-18435 which pressurizes the surface of raw coal by tilting the entire leveler equipped with a pressure plate using a guide member provided near the kiln mouth as a fulcrum.
Tilting the entire leveler is not a large-scale facility, and the one with a fixed tilting angle as described above has no effect on consolidating the peaks of coking coal that has peaks and valleys. It seems that consolidation of the valley area is not effective.

Furthermore, as in Japanese Patent Application Laid-Open No. 61-272284, a partition plate is provided on the bottom surface of the leveler so that each box has an I11
There is also a method that uses an inclined bottom plate to achieve a consolidation effect, but this does not seem to have a large bulk density improvement effect as it only slightly consolidates the upper surface of the coking coal.

Recognizing the problems of the prior art, the present invention seeks to provide a method and apparatus for improving the bulk density of coking coal charged in the upper part of a coke oven, which is effective in a direct manner.

[Means to solve the problem]

The present invention is based on a beam body that is movable back and forth over the entire length of the coke oven in contact with the upper surface of the coking coal charged into the coke oven carbonization chamber, for example, as shown in FIG. 1 (B) and FIG. 2 (B). The present invention is characterized by a method and apparatus in which a load plate 15 is connected to at least the tip of the leveler by a hinge 16, and the upper surface of the charged raw material is compacted by the weight of the load plate when the leveler is retracted.

That is, the invention of claim 1 has a beam main body provided in contact with the upper surface of the coking coal charged into the coke oven carbonization chamber so as to be movable back and forth over the entire length of the coke oven.
As shown in the figure, a load plate 15 having a pressure plate part 17 that contacts the upper surface of the raw material charged in the carbonization chamber and a leveling part 18 that recedes diagonally upward from the pressure plate part 17 is connected to the beam body at its rear upper end by a hinge 16 structure, When the beam body moves forward, the load plate 15 is lifted into the beam body, and when the beam body retreats, the load plate 15 is suspended outside the beam body, and due to the weight of the load plate, its pressure plate portion 17 presses the upper surface of the coking coal from 10 to
The gist is a method of consolidation at 100 g/c+J.

Next, the invention of claim 2 provides a method and apparatus for improving the bulk density of coking coal charged in the upper part of the various coke ovens described above. As shown in Figure 6 (a) and (b), this is a further improvement on the point that it was not possible to level or consolidate only about 3/4 of the central part in the width direction of the oven. At least at the tip of the beam main body, as shown in FIG. 2(B), a load plate 15 is provided with a pressure plate part 17 that comes into contact with the upper surface of the raw material charged in the carbonization chamber and a leveling part 17 that recedes obliquely upward from the pressure plate part 17. is connected to the beam body at its rear upper end with a hinge 16 structure, and when the beam body moves forward, the load plate 15 is suspended inside the beam body, and when the beam body retreats, the load plate 15 is suspended outside the beam body, and the weight of the load plate is suspended. In the method of consolidating the upper surface of coking coal with the pressure plate part 1, as shown in Figs. 3 and 4', the pressure plate part 1 is
It consists of a plurality of pressure plates 17', IT'' that try to spread outward to the left and right with a weak force that can repel the beam body 7 inward, and at least when the beam body retreats, the plurality of suspended load plates The gist of this method is to expand the pressure plates 17', 1?'' outward to the left and right to consolidate the coking coal over the entire width of the furnace.

Further, the inventions of claims 3 and 4 relate to a consolidating device for coke oven charging material suitable for carrying out the invention of claim 2, and the former has a carbonization chamber as shown in FIG. 2(b). A load plate 15 comprising a pressure plate part 17 that contacts the upper surface of the charged raw material and a leveling part 18 that recedes obliquely upward from the pressure plate part 17.
is connected to the beam body 7 at its rear upper end by a hinge 16 structure, and when the beam body moves forward, the load plate is lifted up, and when the beam body retreats, it is suspended outside the beam body, and the weight of the load plate causes the pressure plate part to In an apparatus for compacting the upper surface of coking coal, as shown in FIGS. 3 and 4, a plurality of pressure surface plates 17' and I that can expand the pressure surface plate portion outward to the left and right are provided.
A linear protrusion or linear notch 23 forming an appropriate angle 24 with respect to the advancing direction axis is provided on the surface of the pressure plate in contact with the upper surface of the coking coal, so that when the beam body retreats, the plurality of pressure plate lT The gist is a consolidating device for coke oven charging material configured such that the pressure plates 1', IT'' automatically spread over the entire width of the oven.
', 1? In addition, a guide 2 having an inclined guide surface that contacts the beam body when the load plate is lifted into the beam body.
The gist of the present invention is a consolidating device for coke oven charging material, which is configured such that a plurality of open pressure plates 17', 17'' automatically narrow inward when a load plate is attached to the load plate.

[For production]

In the method of the present invention according to claim 1, as described above and as can be understood from FIGS. This load plate 15 is connected to the main body of the leveler 7 by a hinge 16, and when the leveler moves forward, it is hoisted into the leveler main body using, for example, a wire 20, and when the leveler retreats, the wire 20 is loosened and the load plate 15 is set around the hinge 16 as a fulcrum. A pressure plate part 17 applies a load to the upper surface of the coking coal suspended outside the leveler. This state is as understood from the schematic longitudinal cross-sectional view of the main part of the coke oven in FIG. 5(B) and FIG. 6(B). The raw coal directly below the charging port 2, where the charging level is high, is scraped down to the kiln mouth or between the charging ports with a low bag charging level, and the material is not scraped down to improve the leveling effect, but due to its hinge structure, the raw material at the pressure surface plate part 17 is scraped down. Since the amount of load on the top surface of the coal can also be maintained constant, the compaction effect is maintained constant in the furnace length direction.

Moreover, the present invention of claims 2 and 3 provides, in addition to the above-mentioned effects,
For example, when the leveler is retracted, a plurality of pressure plates 17' of the load plate 15 apply a load to the upper surface of the raw coal.

17" extends outward to the left and right, and as can be seen from Figure 6 (c), it has the effect of consolidating the charged coking coal evenly over the entire furnace width, and the charging material in the furnace length, furnace height, and furnace width direction The bulk density deviation can be corrected.

Furthermore, the device provided with the guide 21 according to claim 4 is provided with a load plate 1
5 is lifted, the expanded pressure plates 17', 17'' automatically narrow inward and are accommodated in the leveler. Therefore, when inserting and removing the leveler, the upper opening 6 of the kiln mouth is not damaged, and the left and right The leveler can be moved forward without fear of damaging the furnace walls 25, 25.

〔Example〕

Next, an embodiment of the invention according to claim 1 will be described, taking as an example a case where a normal leveler main body is used as a beam main body.

In FIG. 1(b) and FIG. 2(b), 7 is a leveler main body, and the leveler used in the method of the present invention has a load plate 15 at least at its tip.

The load plate 15 includes one pressure plate part 17 parallel to the upper surface of the raw coal in the coking chamber, and a leveling part 18 that recedes diagonally upward from the pressure plate part 17.
The load plate 15 has a structure in which it is connected to the leveler 7 main body by a hinge 16 at the rear upper part thereof, and the load plate 15 can freely swing around this hinge 16.

In order to keep the load plate 15 suspended within the leveler body when the leveler 7 moves forward over the entire length of the carbonization chamber 1, the illustrated example employs a method using wires and pulleys. That is, the wire 20 tied to the tip 21 of the load plate 15 is guided rearward through a pulley 22 provided on a portion of the leveler directly above the wire 20, and is wound around a winch (not shown). That is, when moving the leveler 7 forward, the wire 20 is pulled with a winch, the tip 21 of the load plate 15 is lifted around the hinge 16, and the load plate is stored in the leveler body 7 (shown by solid lines in Fig. 2 (b)). .

Next, when the leveler 7 is moved back over the entire length of the carbonization chamber l, the winch is turned to loosen the wire 20 and the load plate 15 is suspended outside the leveler 7 by its own weight around the hinge 16 (see Fig. 2). ) (shown with dashed line).

When the leveler 7 is moved backward in this state, as shown in Figure 5 (b), the loading plate acts to level out the coking coal directly below the charging port 2, where the charging level is high, to the kiln opening or between the charging ports where the charging level is low. The load plate 15 swings freely, and its pressure plate part 17 applies a load to the upper surface of the charged raw coal 4 to consolidate it, instead of the leveling part 18.

What is important here is that the load plate 15 is connected to the leveler 7 with a hinge 16 so that it can swing freely.
The method of lifting and suspending is not necessarily the method using the pulley 22 and wire 20 described above, but may be performed using other suitable alternative means.

Figures 3 and 4 (A) and (B) are 2 and 3 of the present invention.
They are a back side plan view, a side view, and a front view of the pressure plate portion of the load plate according to each claim of claim 4. The load plate used in these methods and devices is similar to that in the invention of claim 1, and the load plate 15 has a pressure plate portion 17 parallel to the upper surface of the coking coal in the coking chamber.
It has a leveling part 18 that recedes diagonally upward from the leveling part 18, and is connected to the leveler main body by a hinge at the rear upper part, and is structured to be able to swing freely around this hinge. It is composed of multiple pressure plates that can be expanded.

That is, in the example shown in FIG. 4, the rear end is connected to the leveling part 18 with a hinge 16' structure, and it is composed of two overlapping pressure plate plates 17' and 17'' that can be expanded outwardly to the left and right in a fan shape. The structure in which the rear end is hinged and spread outward to the left and right like a fan is one example, and is not limited to this.
For example, any structure that can freely expand outward to the left and right over the entire width of the furnace may be used, such as a structure in which a plurality of pressure plates are joined by a sash-like hinge and can be expanded left and right like an accordion.

A plurality of pressure plates 17' are connected as described above.

17'', as shown in Fig. 3, is provided with a linear protrusion or linear notch 23 on the back side that forms an appropriate angle with respect to the axis of movement, so that when the leveler main body retreats, it will not be able to touch the coking coal in the coking chamber. The pressure plate, which is crimped by its own weight, converts the drag force received from the charged material into a component force in the width direction of the furnace through the linear protrusions or linear cuts, and automatically spreads outward over the entire width of the furnace on the left and right sides, spreading the raw material over the entire width of the furnace. The charcoal is consolidated. In this case, the force that tries to spread outward to the left and right is weak enough to be repelled inward, so it hardly affects the both side furnace walls 25, 25.

The angle 24 between the linear protrusions or linear notches 23 with the traveling direction axis varies depending on the weight of the load vi15, the height, depth, length, and number of the linear protrusions or notches 23. Determined by the conditions for the pressure plate to spread smoothly. For example, if the load of the load plate 15 is 50g/c+J, the height of the linear protrusion is 5mm, and the length of the layer is 150m, the angle is 30° to 6
0° is suitable; if it is narrower than 30°, the pressure plate will not spread smoothly, and if it exceeds 60°, the pressure applied to the furnace wall 25 by the open pressure plate will become large, which is undesirable. is just one example, and instead of using the drag force received from the upper surface of the coking coal, other suitable means such as spreading with a spring may be used.

21 in Fig. 4 (A) 1 port) is the pressure plate IT', 1? When the load plate 15 is lifted into the leveler by the wire 20 in order to advance the leveler 7 shown in FIG. It comes into contact with the leveler side plate 13 in Figure 1 (b),
The pressure plate IT', 17'' in the open state automatically acts to narrow inward.

Figure 8 shows the load 1 that the load plate 15 applies to the top surface of the charged coking coal 4.
This is a chart examining the relationship between g/c+1, depth distance (m) from the top surface of coking coal, and bulk density kg/r/.
g/J, an improvement in bulk density was observed within a depth distance of about 1 m, and it was also found that applying a load exceeding 100 g/J had a small effect and was meaningless.

In order to confirm the effects of the present invention, an experiment was conducted using a model furnace.

The coke model oven has a carbonization chamber with a height of 7.125 m.
Only the length of the actual operating furnace is 460 m in width and 16.5 m in length.
It was installed at the end of the furnace group of the actual operating furnace, so that raw materials could be charged into the model furnace using the actual coal loading car.

Figure 9 schematically shows the side surface of the model furnace. In order to measure the bulk density of the charged coking coal, the sampling holes were set at 1.5, 3, and 4.5 degrees from the bottom of the furnace in the furnace height direction. .5.6.6.
Six locations at 5 m, two locations directly below the two charging ports in the furnace length direction, and two locations between the charging port and the kiln mouth.
A total of 36 holes were installed in two locations between the charging ports.

The experiment was carried out using blended coal used in normal operations (raw material particle size of 3 m or less 83
% by weight, water content 9.2% by weight) was charged into a model furnace using an ordinary loading car, and then the method of the present invention was carried out using the leveler used in the present invention, and the effect was evaluated based on the charging bulk density. Evaluation was made by measuring and measuring the height of charged coking coal. The pressure plate used in the experiment had a load of 50 g/cd as an example of claim 1.
As an example of a case where there is one pressure plate having the shape shown in FIG. One set at 45° was used. For comparison, an experiment using a leveler used in the conventional method shown in FIG. 1(a) was also conducted.

As shown in Figure 10, the results of the above experiment show that the bulk density distribution at the 6w1 position from the bottom of the furnace is (
・Compared with the method of the present invention, the load was 50g
- When the top surface of the charged coal is consolidated (marked with * and ×), the difference in bulk density between the area directly below the charging port in the furnace length direction and the kiln opening or charging port is greatly improved, and the amount of 25 to 55 kg is improved. /rrr bulk density improvement effect was observed.

In addition, in the method using two pressure plates, the entire area is consolidated, so the bulk density improvement effect was found to be greater than in the case of one pressure plate.

In addition, as shown in Figure 11, the charging height measurements conducted at the same time showed that in the case of the conventional method (marked with a *), the difference in charging height between the charging port and the kiln opening, or between the charging port, was 40 ~ 60c1
1, but by implementing the method of the present invention, the load was 50g/
- When the top surface of the charged coal was leveled (marked with * and x), the difference was improved to within 10 cm, and it was confirmed that the leveling effect was also high.

Next, as for the effect of the load amount by the load plate 15 in the method of the present invention, the results of a test using a single pressure plate were shown in Fig. 12, and the effect of the load was similar to the above basic experiment results (Fig. 8). is about 1m from the top of the coking coal in the furnace height direction, and if the load is 10g/- or more, the top 1m
It is possible to suppress a decrease in bulk density of about
A range of 0 to 100 g/aJ was judged to be appropriate as the load amount.

〔Effect of the invention〕

As can be understood from the above, according to the method and apparatus of the present invention, the bulk density of the charged coking coal is uniform over the furnace length and furnace height direction of a chamber furnace type coke oven, and even over the entire width of the furnace in an example where the pressure plate is widened. This has the remarkable effect of making the charging height uniform.

[Brief explanation of the drawing]

Figure 1 (a) is a perspective view of a conventional leveler, Figure 1 (b)
Figure 2 (a) is an example of a load plate used in the present invention, and is a perspective view showing how it is attached to the leveler body.
FIG. 2(b) is a side view of the tip of FIG. 1(b), FIG. 3 is a back side plan view of the flat plate of another example of the load plate used in the present invention, and FIG. Figure 4 (a) is a side view of the same as above;
FIG. 4(b) is a front view of the same as above, FIG. 5(a) is a schematic cross-sectional view of the main part of a coke oven in the oven length direction showing an embodiment of leveling by the conventional method, and FIG. FIG. 6(a) is a schematic cross-sectional view of the main part of a coke oven in the oven width direction showing an embodiment of leveling in the conventional method. A schematic cross-sectional view in the oven width direction of a main part of a coke oven showing an embodiment of the present invention according to claim 1,
FIG. 6(c) is a schematic cross-sectional view of main parts of a coke oven in the oven width direction showing an embodiment of the present invention according to claim 2, FIG. 7 is a side view showing an outline of a chamber oven type coke oven, and FIG. A diagram showing the relationship between the amount of load on the top surface of charged coking coal, the distance from the top surface of coking coal, and the bulk density. Figure 9 is a cross-sectional view of the experimental model coke oven. Figure 10 is the bottom of the model coke oven at various positions in the longitudinal direction. Figure 11 is a comparison diagram of the nature of the bulk density of coking coal charged at a position of 6 m and the conventional method, and Figure 11 is a comparison diagram of the nature of the bulk density of coking coal charged at each position in the longitudinal direction of a model coke oven and the leveling effect of the conventional method. , and FIG. 12 shows the amount of load on the upper surface of the charging coking coal and the bulk density at each height from the bottom of the furnace directly below the charging port. In the figure, 1: carbonization chamber, 2: charging port, 3: coal loading car, 4: coking coal, 5: extruder, 6: upper opening of kiln mouth, 7: leveler, 8
: Generated gas path, 9: Front door, lO: Front door, 11 Ni guide vehicle, 12: Fire engine, 13 Nilevera side plate, 14 Nilevera
Partition plate, 15: Load plate, 16, 16': Hinge, 1
7: Pressure plate part, IT', 1? ”: pressure plate, 18 leveling part, 19: trolley, 20: wire, 21 guide,
22: Pulley, 23: Linear projection or linear notch, 25
: Furnace wall. Figure 7 Figure 8 Bulk density (k@β) Is the arrogant 4Q aphrodisiac? Kitabe (Materialism ε

Claims (1)

[Scope of Claims] 1. At least the tip of a beam main body that is provided in contact with the upper surface of the coking coal charged into the coke oven carbonization chamber and capable of advancing and retreating over the entire length of the coking chamber is brought into contact with the upper surface of the raw material charged in the coke oven. A load plate, which has a pressure plate part and a leveling part that recedes diagonally upward from the pressure plate part, is connected to the beam body at its rear upper end using a hinge structure, and when the beam body moves forward, the load plate is lifted into the beam body, and the beam body Consolidation of raw material charged in a coke oven characterized by suspending a load plate outside the beam body when the load plate retreats, and consolidating the upper surface of coking coal at the pressure plate part at a pressure of 10 to 100 g/cm^2 due to the weight of the load plate. Method. 2. At least at the tip of the beam body, which is provided in contact with the upper surface of the coking coal charged into the coke oven coking chamber and can move forward and backward over the entire length of the coking chamber, has a pressure plate portion that contacts the upper surface of the raw material charged in the coking chamber, and a pressure plate portion diagonally extending from the A load plate having a leveling part that retreats upward is connected to the beam body at its rear upper end by a hinge structure, and when the beam body moves forward, the load plate is lifted into the beam body, and when the beam body moves back, the load plate is suspended. In this method, the upper surface of coking coal is suspended from the beam body and used to compact the upper surface of the coking coal using the weight of the load plate. A coke comprising a pressure plate, and characterized in that at least when the beam body retreats, the plurality of pressure plates of the suspended load plate are expanded outward to the left and right to consolidate the coking coal surface over the entire width of the furnace. Consolidation method for furnace charging raw materials. 3. A load plate with a pressure plate part in contact with the upper surface of the raw material charged in the carbonization chamber and a leveling part that recedes diagonally upward from the pressure plate part is connected to the beam body at its rear upper end with a hinge structure, so that the beam body can handle the load when moving forward. In a device that lifts a plate and suspends it outside the beam body when the beam body retreats, and compacts the upper surface of the coking coal with the pressure plate part due to the weight of the load plate, a plurality of pressure plates that can expand the pressure plate part outward to the left and right are used. A linear protrusion or linear notch forming an appropriate angle with respect to the advancing direction axis is provided on the surface of the pressure plate in contact with the upper surface of the coking coal, so that when the beam body retreats, the plurality of pressure plates automatically move into the furnace. A device for consolidating raw material charged in a coke oven, characterized in that it is configured to spread over the entire widthwise direction. 4. In the consolidation apparatus according to claim 3, a guide having an inclined guide surface that comes into contact with the beam body when the load plate is lifted into the beam body is further attached to the plurality of pressure plate plates, and the load plate is lifted. 1. A device for consolidating raw materials charged in a coke oven, characterized in that a plurality of pressure plates in an open state are configured to automatically narrow inward during the process.