Hydraulic support used for arched roadway and provided with arc-shaped side protection plates

Abstract

The utility model relates to the technical field of coal mining in a coal mine, in particular to a hydraulic support with an arc-shaped side guard plate for an arched roadway, which comprises the side guard plate, a support jack and a top beam, and the shape of the outer surface of the side guard plate is matched with that of a top plate of the arched roadway. When the side protection plate is pushed by the supporting jack to be in the opening position, the outer surface of the side protection plate and the outer surface of the top beam can be simultaneously attached to the top plate of the arched roadway in a large area, the roof protection area is greatly increased, and therefore the arched roadway can be better supported to improve the safety of the roadway.

Description

TECHNICAL FIELD

[0001] The utility model relates to the technical field of coal mining, especially relates to a hydraulic support with arc type side guard plate for arched roadway. BACKGROUND

[0002] At present, in order to realize the efficient mining of coal in the fully mechanized coal mining face of China, two roadways are arranged at both ends of the working face, which are respectively air inlet chute roadway and air return chute roadway. The air inlet chute roadway is mainly used to transport fresh air to the working face, to ensure the breathing needs of underground workers, and also to provide part of the operation space for the coal mining equipment. Its position is usually on one side of the working face and is arranged perpendicularly to the working face. The air return chute roadway is used to discharge the dirty air and harmful gas such as gas generated in the working face, to ensure a good ventilation environment in the working face. It is generally located on the other side of the working face and opposite to the air inlet chute. The shapes of the two roadways are generally excavated into rectangles and arches. Rectangular roadways are mostly used in China, but arch-shaped roadways also have a large number of applications in coal mine working faces according to their unique advantages. The advanced hydraulic support placed in the roadway is configured with side guard plates on both sides of the top beam of the hydraulic support in order to better support and manage the roof. The larger the roof protection area of the side guard plate is, the higher the safety of the roadway is. However, the traditional side guard plate is generally a flat side guard plate designed for rectangular roadways. When it is applied to the arch-shaped roadway, the roof protection area is greatly reduced due to the shape of the roadway, and it can only support the straight section of the arch-shaped roadway, and cannot support the section with the arc, so the safety is very low.

[0003] Therefore, there is an urgent need for a hydraulic support that can adapt to the shape of the arch-shaped roadway, which is used to specially support the arch-shaped roadway, to improve the safety of the arch-shaped roadway. CONTENT OF THE UTILITY MODEL

[0004] (I) Technical problem to be solved

[0005] In view of the above-mentioned shortcomings and deficiencies of the prior art, the utility model provides a hydraulic support with arc type side guard plate for arch-shaped roadway, which solves the technical problem of small roof protection area of the traditional hydraulic support with flat type side guard plate applied in the arch-shaped roadway, resulting in low safety.

[0006] (II) Technical scheme

[0007] In order to achieve the above-mentioned purpose, the main technical scheme adopted by the utility model includes:

[0008] The utility model provides a kind of for arched roadway with circular arc type side guard board's hydraulic support, including side guard board, supporting jack and roof beam, one end of side guard board is detachably connected in the side surface position of roof beam, and the shape of the outer surface of side guard board is circular arc type and is compatible with the shape of the roof of arched roadway.Supporting jack one end is detachably connected in side guard board, and the other end is detachably connected in roof beam.Supporting jack telescopes, can pull side guard board compared with roof beam and rotate to the position of being retracted or push side guard board compared with roof beam and rotate to open position.Side guard board is in open position, and the outer surface of side guard board and the outer surface of roof beam are simultaneously attached with the roof of arched roadway.

[0009] Optionally, the inner surface of the side guard board is provided with a plurality of transverse ribs and a plurality of longitudinal ribs which are perpendicular to each other.

[0010] Optionally, the plurality of longitudinal ribs at least includes two first vertical ribs arranged at the leftmost end and the rightmost end of the side guard board and two second vertical ribs evenly arranged between the two first vertical ribs. The two second vertical ribs each extend outward from the plate surface of the side guard board at one end close to the roof beam to form a lug with a first circular hole, and the first circular holes of the two second vertical ribs are coaxially arranged.

[0011] The inner side surface position of the roof beam is provided with an embedded lug, and the position and number of the embedded lug are compatible with the position and number of the lug. The lugs of the two second vertical ribs are hinged to the embedded lug of the roof beam by a pin shaft.

[0012] Optionally, a reinforcing lug is fixedly connected to each of the two side walls of the second vertical rib at the end close to the roof beam. The shape and size of one end of the reinforcing lug are the same as those of the lug, and a second circular hole coaxial with and the same size as the first circular hole is provided on the reinforcing lug. The other end of the reinforcing lug extends into the plate surface of the side guard board and is fixedly connected to the inner surface of the side guard board. The side guard board and the roof beam are hinged by inserting the pin shaft into the first circular hole, the second circular hole and the mounting hole on the embedded lug.

[0013] Optionally, two lug seats are symmetrically arranged along the extension direction of the transverse rib in the 1 / 3 region of the side guard board close to the roof beam in the longitudinal direction. The lower bottom surface of the lug seat is fixedly connected to the inner surface of the side guard board, and the rear end surface of the lug seat is fixedly connected to the transverse rib adjacent thereto. The number of supporting jacks is compatible with the number of lug seats, and the side guard board is hinged to the supporting jacks by the lug seats using a pin shaft.

[0014] Optionally, the two lug seats are respectively arranged in the 1 / 5 region of the leftmost end and the rightmost end of the side guard board in the transverse direction.

[0015] Optionally, the roof beam is provided with a connecting seat at a position close to its axis, and the position and number of the connecting seat are compatible with the position and number of the supporting jacks. The roof beam is hinged to the supporting jacks by the connecting seat using a pin shaft.

[0016] Optionally, the side guard plate is divided into a plurality of detachable connection segments extending along the direction close to the roof beam to the distal end, and each segment is hingedly connected to allow each segment to be individually adjusted according to the shape of the arch-shaped tunnel roof, and locking bolts are provided at the connection of each segment for locking and fixing after adjustment.

[0017] Optionally, the side guard plate is divided into three segments, and the supporting jack is connected to the middle segment of the side guard plate.

[0018] (Three) beneficial effects

[0019] The beneficial effects of the utility model are:

[0020] The hydraulic support with the arc-shaped side guard plate for the arch-shaped tunnel of the utility model, because the shape of the outer surface of the side guard plate in the hydraulic support is set to be compatible with the shape of the arch-shaped tunnel roof, when the side guard plate is pushed by the supporting jack and is in the open position, the outer surface can be simultaneously attached to the outer surface of the roof beam and the arch-shaped tunnel roof in a large area, greatly increasing the roof protection area, so that better support can be formed for the arch-shaped tunnel to improve the safety of the tunnel. BRIEF DESCRIPTION OF DRAWINGS

[0021] Figure 1 Application diagram of the traditional hydraulic support with the flat side guard plate in the rectangular tunnel;

[0022] Figure 2 Application diagram of the traditional hydraulic support with the flat side guard plate in the arch-shaped tunnel;

[0023] Figure 3 Application diagram of the hydraulic support with the arc-shaped side guard plate for the arch-shaped tunnel of the utility model in the arch-shaped tunnel;

[0024] Figure 4 is a top view of the top beam and the side guard plate in Figure 3 ;

[0025] Figure 5 is a bottom view of the top beam and the side guard plate in Figure 4 ;

[0026] Figure 6 is a structure diagram of the side guard plate in Figure 3 .

[0027]

Explanation of reference signs

[0028] 1: side guard plate; 11: transverse rib plate; 12: longitudinal rib plate; 121: first vertical rib; 122: second vertical rib; 123: first circular hole; 124: lug; 13: reinforcing lug plate; 131: second circular hole; 14: lug seat;

[0029] 2: support jack;

[0030] 3: roof beam; 31: embedded ear plate; 32: connecting seat;

[0031] 4: stowed position;

[0032] 5: open position;

[0033] 6: flat side guard;

[0034] 7: rectangular roadway;

[0035] 8: arched roadway;

[0036] A: effective distance of flat side guard in arched roadway support;

[0037] B: effective distance of arc side guard in arched roadway support. DETAILED DESCRIPTION

[0038] In order to better explain the utility model, so as to facilitate understanding, below, through specific implementation, the utility model is described in detail. Wherein, the "upper", "lower", "left", "right" and other orientation terms mentioned in this paper are with the orientation of the figure as the reference. Figure 1

[0039] The utility model embodiment proposes a kind of hydraulic support with arc side guard for arched roadway, by the shape of the outer surface of the side guard in hydraulic support is set to the shape compatible with the shape of arched roadway roof, when the side guard is in open position by support jack push, its outer surface can be simultaneously and arched roadway roof large-area adhesion with roof beam outer surface, greatly increase the roof area, to form better support to arched roadway, so as to improve the safety of roadway.

[0040] In order to better understand the above technical solutions, the exemplary embodiments of the utility model will be described in more detail below with reference to the drawings. Although the exemplary embodiments of the utility model are shown in the drawings, it should be understood that the utility model can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable clearer and more thorough understanding of the utility model, and to enable the scope of the utility model to be completely conveyed to those skilled in the art.

[0041] Example 1:

[0042] ​The arched roadway 8 has unique structural advantages. Firstly, it has good supporting effect. The arched structure has good bearing capacity and stability, can better resist ground pressure and surrounding rock deformation, effectively solves the problem of roof separation prone to occur in rectangular or trapezoidal cross section roadway, and is beneficial to the management of two roadways of fully mechanized working face. Secondly, it has high space utilization. Compared with other shaped roadways, the arched roadway has higher space utilization under the same span, which can meet the passing demand of fully mechanized equipment and personnel. Thirdly, it has uniform stress distribution. The mechanical properties of the arched structure make the stress of the rock around the roadway more uniform, reducing the stress concentration phenomenon, which helps to maintain the stability of the roadway. Therefore, the arched roadway 8 is also frequently applied in the fully mechanized working face of the coal mine, and the traditional straight guard wall cannot meet the supporting needs of the arched roadway 8.

[0043] Referring to Figure 1 and Figure 2 , Figure 1 , the application of the traditional hydraulic support with flat side guard plates 6 in the rectangular roadway 7 is shown. Since the roof of the rectangular roadway 7 is a straight surface, it is only necessary to adjust the length of the flat side guard plates 6 on both sides of the top beam 3 in actual application to form a good supporting effect on the rectangular roadway 7. Figure 2 , the application of the traditional hydraulic support with flat side guard plates 6 in the arched roadway 8 is shown. Since the two sides of the roof of the arched roadway 8 are in the shape of a large circular arc, the length of the flat side guard plates 6 can only be set to be relatively short to enter the arched roadway 8 to form support, which will result in a shorter effective distance A of the side guard plate in the arched roadway support, i.e. a smaller supporting area, which can only support a small section of the flat roadway in the roof of the arched roadway 8, and cannot form support for the large area of the circular arc section of the roadway.

[0044] As shown in Figures 3 to 6 , the embodiment proposes a hydraulic support with circular arc side guard plates for arched roadway, which comprises side guard plates 1, supporting jacks 2 and a top beam 3 (wherein the side of the side guard plates 1 and the top beam 3 in contact with the roof of the roadway is the outer surface, and the opposite side is the inner surface, the parallel direction of the side guard plates 1 and the top beam 3 is the transverse direction, and the direction perpendicular to the top beam 3 is the longitudinal direction).

[0045] One end of the side guard plate 1 is detachably rotatably connected to the side of the roof beam 3, the support jack 2 is located inside the side guard plate 1 and the roof beam 3, one end of which is detachably connected to the side guard plate 1, and the other end is detachably connected to the roof beam 3. The shape of the outer surface of the side guard plate 1 is a circular arc type and is matched with the shape of the roof of the arched tunnel 8, that is, the outer surface of the side guard plate 1 has a straight edge segment with the same length as the straight edge of the arched tunnel except the area of the roof beam 3 and a circular arc segment with the same size as the circular arc of the arched tunnel. By the extension and retraction of the support jack 2, the side guard plate 1 can be pulled to rotate downward compared with the roof beam 3 to the stowed position 4 or pushed to rotate upward compared with the roof beam 3 to the open position 5, when the side guard plate 1 is in the open position 5, the outer surface of the side guard plate 1 and the outer surface of the roof beam 3 are in contact with the roof of the arched tunnel 8 at the same time.

[0046] Specifically, a plurality of transverse rib plates 11 and longitudinal rib plates 12 perpendicular to each other are arranged on the inner surface of the roof beam 1, the longitudinal rib plates 12 at least include two first vertical ribs 121 arranged at the leftmost and rightmost ends of the side guard plate 1 and two second vertical ribs 122 evenly arranged between the two first vertical ribs 121, in the embodiment, as shown in the drawings, preferably two transverse rib plates 11 and four longitudinal rib plates 12 are arranged, wherein the longitudinal rib plates 12 include two first vertical ribs 121 located at the leftmost and rightmost ends of the side guard plate 1 and two second vertical ribs 122 arranged between the two first vertical ribs 121, the four vertical ribs and two transverse rib plates 11 are as evenly distributed as possible on the inner surface of the side guard plate 1, so as to achieve better support and strengthening effect. Figure 6

[0047] ​The two second vertical ribs 122 each extend outwardly from the plate surface of the side guard plate 1 at one end close to the roof beam 3 to form a lug 124 with a first circular hole 123, and the two first circular holes 123 of the two second vertical ribs 122 are coaxially arranged. Meanwhile, two reinforcing lugs 13 are respectively welded and fixed on the two side walls of the one end of the second vertical rib 122 close to the roof beam 3. The reinforcing lug 13 at one end is the same in shape and size as the lug 124, and a second circular hole 131 coaxial with and the same size as the first circular hole 123 is arranged on the reinforcing lug 13. When the reinforcing lug 13 is welded, the side wall thereof is in close contact with the side wall of the lug 124, and the first circular hole 123 and the second circular hole 131 should be completely aligned. The other end of the reinforcing lug 13 extends into the plate surface of the side guard plate 1 and is welded and fixed with the inner surface of the side guard plate 1. The reinforcing lug 13 can strengthen and disperse stress at the position where the side guard plate 1 and the roof beam 3 are connected, so as to avoid stress concentration on the lug 124 and fatigue problems. An embedded lug 31 is arranged on the inner side surface of the roof beam 3. The position and number of the embedded lug 31 are adapted to the position and number of the lug 124, that is, the number of the embedded lug 31 is equal to that of the lug 124, and the positions of the embedded lug 31 and the lug 124 are corresponding. When the side guard plate 1 and the roof beam 3 are connected, the side guard plate 1 and the roof beam 3 are hingedly fixed by penetrating a pin shaft into the first circular hole 123, the second circular hole 131 and the mounting hole of the embedded lug 31.

[0048] Meanwhile, two lug seats 14 are symmetrically arranged in the 1 / 3 region of the side guard plate 1 close to the roof beam 3 along the extension direction of the horizontal rib plate 11. The lower bottom surface of the lug seat 14 is welded and fixed with the inner surface of the side guard plate 1, and the rear end surface of the lug seat 14 is welded and fixed with the horizontal rib plate 11 close thereto. The two lug seats 14 are respectively arranged in the 1 / 5 region of the leftmost end and the rightmost end of the side guard plate 1 in the horizontal direction.

[0049] The roof beam 3 is provided with a connecting seat 32 close to the central axis thereof, and the position and number of the connecting seat 32 are adapted to the position and number of the support jack 2, that is, the number of the connecting seat 32 is equal to that of the support jack 2, and the positions of the connecting seat 32 and the support jack 2 are corresponding. One end of the support jack 2 is hingedly connected with the connecting seat 32 on the roof beam 3, and the other end is hingedly connected with the lug seat 14 on the inner surface of the side guard plate 1.

[0050] Of course, it is not limited to this. The skilled in the art can reasonably arrange the number and position of the horizontal rib plate 11 and the vertical rib plate 12 according to the actual size of the side guard plate 1, but the position of the lug 124 in the vertical rib plate 12 should be adapted to the position and number of the embedded lug 31 on the roof beam 3, and at least one horizontal rib plate 11 in the 1 / 3 region close to the roof beam 3 can be connected with the lug seat 14. The number of the lug seat 14 should be the same as that of the support jack 2, and should be adapted to the position and number of the connecting seat 32 on the roof beam 3.

[0051] In practical application, when the arch-shaped tunnel 8 needs to be supported, the supporting jack 2 can be elongated to push the side guard plate 1 to rotate upward compared with the roof beam 3 to the open position 5, at this time, the outer surface of the side guard plate 1 and the outer surface of the roof beam 3 are simultaneously attached to the roof of the arch-shaped tunnel 8, which can provide the largest supporting area; when the arch-shaped tunnel 8 does not need to be supported, the supporting jack 2 can be shortened to pull the side guard plate 1 to rotate downward compared with the roof beam 3 to the stowed position 4, which can reduce the occupation of space and facilitate transportation and movement operations.

[0052] As shown in Figure 2 and Figure 3 When the hydraulic support with the circular-arc type side guard plate shown in the embodiment is applied to the arch-shaped tunnel 8, the effective distance B of the circular-arc type side guard plate in the arch-shaped tunnel support is increased by nearly 2-2.5 times compared with the effective distance A of the flat type side guard plate in the arch-shaped tunnel support when the traditional hydraulic support with the flat type side guard plate is applied to the arch-shaped tunnel 8, which greatly increases the effective supporting area and thus increases the safety of the tunnel.

[0053] Embodiment 2:

[0054] The embodiment provides a hydraulic support with a circular-arc type side guard plate for an arch-shaped tunnel, which is different from the embodiment 1 in that the side guard plate 1 is a split structure, and other parts are the same as those of the embodiment 1, which will not be described here.

[0055] The side guard plate 1 in the embodiment is divided into a plurality of detachable connection segments along a direction close to the roof beam 3 and extending to a distal end, and the segments are connected through pin shaft hinged connection, so that each segment can be individually adjusted according to the shape of the roof of the arch-shaped tunnel 8, and a locking bolt is arranged at each segment connection position for locking and fixing after adjustment. Preferably, the side guard plate 1 is divided into three segments, and the supporting jack 2 is connected to the middle segment of the side guard plate 1. The segmented side guard plate 1 can better meet the needs of various arch-shaped tunnels 8, so that the outer surface of the side guard plate 1 can better attach to the roof of the arch-shaped tunnel 8 to provide a larger effective supporting area.

[0056] In the description of the utility model, it is understood that the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Therefore, the features limited by "first", "second" can explicitly or implicitly include one or more features. In the description of the utility model, the meaning of "multiple" is two or more than two, unless otherwise specifically limited.

[0057] In the utility model, unless another definite provision and limitation, the terms "mount", "link", "connect", "fix" and so on should do broad sense understanding, for example, can be fixed connection, also can be detachable connection, or be integrated;Can be mechanical connection, also can be electrical connection;Can be direct connection, also can pass through intermediate medium indirectly connect;Can be two element internal communication or two element mutual action relation.For ordinary skilled person in the art, can understand the specific meaning of above-mentioned terms in the utility model according to specific circumstances.

[0058] In the utility model, unless another definite provision and limitation, the first feature is "on" or "under" the second feature, which can be direct contact between the first and second features, or indirect contact between the first and second features through an intermediate medium. Moreover, the first feature "above", "over" and "on" the second feature, which can be directly above or obliquely above the first feature, or simply means that the first feature is higher than the second feature in horizontal height. The first feature "below", "under" and "under" the second feature, which can be directly below or obliquely below the first feature, or simply means that the first feature is lower than the second feature in horizontal height.

[0059] In the description of the present specification, the description of the terms "one embodiment", "some embodiments", "embodiment", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present utility model. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, the skilled in the art can combine and combine the different embodiments or examples described in the present specification and the features of the different embodiments or examples without contradiction.

[0060] Although the embodiments of the present utility model have been shown and described above, it can be understood that the above-mentioned embodiments are exemplary and cannot be understood as limiting the present utility model. The ordinary skilled in the art can make changes, modifications, replacements and variations to the above-mentioned embodiments within the scope of the present utility model.

Claims

1. A hydraulic support with arc-shaped side guard for arched roadway, characterized in that, it comprises a side guard (1), a supporting jack (2) and a roof beam (3); one end of the side guard (1) is detachably connected to the side of the roof beam (3), and the outer surface of the side guard (1) is in the shape of an arc and is adapted to the shape of the roof of the arched roadway (8); one end of the supporting jack (2) is detachably connected to the side guard (1), and the other end is detachably connected to the roof beam (3); the supporting jack (2) is telescopic, capable of pulling the side guard (1) to rotate downward compared to the roof beam (3) to a stowed position (4) or pushing the side guard (1) to rotate upward compared to the roof beam (3) to an open position (5); when the side guard (1) is in the open position (5), the outer surface of the side guard (1) and the outer surface of the roof beam (3) are in contact with the roof of the arched roadway (8) at the same time.

2. The hydraulic support with arc-shaped side guard for arched roadway according to claim 1, characterized in that, the inner surface of the side guard (1) is provided with a plurality of transverse ribs (11) and a plurality of longitudinal ribs (12) intersecting each other perpendicularly.

3. The hydraulic support with arc-shaped side guard for arched roadway according to claim 2, characterized in that, the plurality of longitudinal ribs (12) at least include two first vertical ribs (121) arranged at the leftmost and rightmost positions of the side guard (1) and two second vertical ribs (122) evenly arranged between the two first vertical ribs (121); both of the two second vertical ribs (122) extend outward from the plate surface of the side guard (1) at one end close to the roof beam (3) to form lugs (124) with first circular holes (123), and the first circular holes (123) of the two second vertical ribs (122) are coaxially arranged; the inner side of the roof beam (3) is provided with an embedded lug plate (31), and the position and number of the embedded lug plate (31) are adapted to the position and number of the lugs (124); the lugs (124) of the two second vertical ribs (122) and the embedded lug plate (31) of the roof beam (3) are hinged by a pin shaft.

4. The hydraulic support with arc-shaped side guard for arched roadway according to claim 3, characterized in that, a reinforcing lug plate (13) is fixedly connected to each of the two side walls of the second vertical rib (122) close to the roof beam (3); the shape and size of one end of the reinforcing lug plate (13) are the same as those of the lug (124), and a second circular hole (131) coaxial with and the same size as the first circular hole (123) is arranged on the reinforcing lug plate (13), and the other end of the reinforcing lug plate (13) extends into the plate surface of the side guard (1) and is fixedly connected to the inner surface of the side guard (1); the side guard (1) and the roof beam (3) are hinged by the pin shaft inserted into the first circular hole (123), the second circular hole (131) and the mounting hole of the embedded lug plate (31).

5. The hydraulic support with arc-shaped side shield for arched roadway according to claim 2, characterized in that: two ear seats (14) are symmetrically arranged along the extension direction of the transverse rib (11) in the 1 / 3 area of the side shield (1) close to the top beam (3) in the longitudinal direction; the lower bottom surface of the ear seat (14) is fixedly connected with the inner surface of the side shield (1), and the rear end surface of the ear seat (14) is fixedly connected with the transverse rib (11) close thereto; the number of the support jacks (2) is matched with the number of the ear seats (14); the side shield (1) is hingedly connected with the support jacks (2) through the ear seats (14).

6. The hydraulic support with arc-shaped side shield for arched roadway according to claim 5, characterized in that: the two ear seats (14) are respectively arranged in the 1 / 5 area of the leftmost end and the rightmost end of the side shield (1) in the transverse direction.

7. The hydraulic support with arc-shaped side shield for arched roadway according to claim 2, characterized in that: the top beam (3) is provided with a connecting seat (32) close to the axis thereof, and the position and number of the connecting seat (32) are matched with the position and number of the support jacks (2); the top beam (3) is hingedly connected with the support jacks (2) through the connecting seat (32).

8. The hydraulic support with arc-shaped side shield for arched roadway according to any one of claims 1-7, characterized in that: the side shield (1) is divided into multiple detachable segments along the direction extending away from the top beam (3), and the segments are hingedly connected, so that each segment can be individually adjusted according to the shape of the roof of the arched roadway (8), and locking bolts are arranged at the connection positions of the segments for locking and fixing after adjustment.

9. The hydraulic support with arc-shaped side shield for arched roadway according to claim 8, characterized in that: the side shield (1) is divided into three segments, and the support jacks (2) are connected to the middle segment of the side shield (1). ​ ​ ​ ​ ​

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