Rectangular empty roof area support of moving inverted frame working face

Abstract

The invention relates to the technical field of coal mining support, in particular to a rectangular roof-free area support for a moving inverted support working face, which comprises an external support capable of lifting for supporting, an internal support, a pushing mechanism and a bottom lifting mechanism. The inner support is arranged on the middle front side of the outer support and connected to the outer support through a pushing mechanism. When the inner support is not in the supporting state, the outer support can push the inner support forwards through the pushing mechanism, and when the inner support is in the supporting state, the inner support can pull the outer support forwards through the pushing mechanism, so that self-moving of the support is achieved. The bottom lifting mechanism is arranged at the bottom of the outer support and used for lifting the side, close to the inner support, of the outer support. By means of the rectangular empty roof area support, the problems that in the roadway supporting process, occupied space is large, stability is poor, and working face support withdrawing efficiency is low and safety is insufficient due to the fact that automatic forward moving cannot be achieved are solved.

Description

Technical Field

[0001] The invention relates to the technical field of coal mining support, in particular to a rectangular empty top area support for a moving and inverted working surface. Background Art

[0003] At present, the protection contradiction of the rectangular empty top area during the withdrawal of the coal mine fully-mechanized working face is still prominent, which is a difficult and painful problem in the withdrawal work. In the traditional fully-mechanized working face withdrawal construction, the support of the rectangular empty top area generally uses traditional methods such as single body and wood pile. Both single body and wood pile are passive support, and the resistance of the support work is small, which cannot meet the pressure requirements of the roof. As the support is withdrawn and removed, the roof also sinks, which brings great safety risks to the withdrawal work and threatens the safety of construction workers at all times.

[0004] The support withdrawal is the key link after the comprehensive mining is completed, and it is the most important factor in determining the mining speed and efficiency of the working face. With the improvement of coal mining technology, the multi-channel and multi-auxiliary tunnel support withdrawal technology currently used in the Shenhua Mining Area can realize multi-point parallel operation and achieve the purpose of relatively fast withdrawal. However, the support of the rectangular empty top area has always been a difficulty in withdrawing the support. Generally, when the hydraulic support of the comprehensive mining working face is withdrawn, wood support is used. The higher the support height and the greater the roof pressure, the more wood is consumed. With the collapse of the roof, the support material cannot be recycled, resulting in a large amount of wood waste. In addition, the low strength of the wood support and the large empty top area bring many unstable factors to safe production. Summary of the invention

[0005] 1. Technical issues to be resolved

[0006] The present invention provides a rectangular empty top area bracket for a moving and inverted frame working surface, aiming to solve the problems faced by the rectangular empty top area bracket, such as large space occupation, poor stability, low bracket retraction efficiency due to inability to achieve automatic forward movement, and insufficient safety.

[0007] (II) Technical solution

[0008] In order to achieve the above-mentioned purpose, the present invention proposes a rectangular empty top area support for a moving frame work surface, comprising an external support that can be raised and lowered for support, an internal support, a pushing mechanism and a bottom lifting mechanism;

[0009] The internal support is arranged at the middle front side of the external support and is connected to the external support through the pushing mechanism;

[0010] When the internal bracket is not in a supporting state, the external bracket can push the internal bracket forward through the pushing mechanism, and when the internal bracket is in a supporting state, the internal bracket can pull the external bracket forward through the pushing mechanism to achieve self-movement of the bracket;

[0011] The bottom lifting mechanism is arranged at the bottom of the external support and is used for lifting a side of the external support close to the internal support.

[0012] A further technical solution is that the external support includes a first base and a first top beam, and the internal support includes a second base and a second top beam;

[0013] The first base and the first top beam are connected via a first hydraulic column that can be raised and lowered, and the second base and the second top beam are connected via a second hydraulic column that can be raised and lowered;

[0014] The first base is provided with a groove opening toward the internal bracket for installing the pushing mechanism.

[0015] A further technical solution is that the pushing mechanism is a double pushing mechanism, including a first pushing mechanism and a second pushing mechanism horizontally arranged in parallel in the groove, and the first pushing mechanism and the second pushing mechanism can be pushed synchronously or individually.

[0016] A further technical solution is that the first pushing mechanism includes a first pushing jack and a first pushing rod, and the second pushing mechanism includes a second pushing jack and a second pushing rod;

[0017] The first pushing jack and the second pushing jack are both connected to the first base, and the first pushing rod and the second pushing rod are both connected to the second base.

[0018] A further technical solution is that the bottom lifting mechanism includes a bottom lifting jack and a bottom lifting rod;

[0019] Two groups of the bottom lifting jacks are symmetrically arranged on both sides of the groove and are respectively fixedly installed on the first base;

[0020] Corresponding to the push-out rod of each group of the bottom lifting jacks, a through hole is provided on the first base, and the push-out rod can pass through the through hole and extend outward to abut against the bottom lifting rod;

[0021] One end of the bottom lifting rod is movably arranged in a notch at the bottom of the first base, and the other end is connected to the second base.

[0022] A further technical solution is that the bottom lifting mechanism further includes a carrying rod, a connecting shaft and a connecting rod;

[0023] The carrying rod is arranged on the second base and is fixedly connected via a connecting piece, and both ends of the carrying rod are rotatably connected to the connecting shaft;

[0024] One end of the connecting rod is hinged to the lower end of the connecting shaft, and the other end is hinged to the connecting ear at the end of the bottom lifting rod.

[0025] A further technical solution is that the internal bracket further includes a clamping sleeve and a fixing ring;

[0026] The second base is an I-beam structure, and the clamping sleeve is arranged at the upper horizontal beam of the second base, and the fixing ring is installed inside the clamping sleeve for fixing the second hydraulic column of the internal bracket.

[0027] A further technical solution is that the external support also includes a shielding beam, which is connected to the first base through a connecting rod group and is hinged to the first top beam.

[0028] A further technical solution is that a hemispherical column socket is provided at a connection between the first base and the first hydraulic column, and at a connection between the second base and the second hydraulic column.

[0029] A further technical solution is to further include a hydraulic system for driving the first hydraulic column, the second hydraulic column, the first push jack and the second push jack.

[0030] (III) Beneficial effects

[0031] The beneficial effects of the present invention are as follows: the internal support and the external support are connected by an internal and external combination through a push mechanism, which not only saves the layout space, but also enables the two supports to move forward by pulling from the front and pushing from the back, so as to achieve the purpose of self-movement. When the internal support is not in a supporting state, the external support can push the internal support forward through the push mechanism; and when the internal support is in a supporting state, it can pull the external support forward through the push mechanism. This method can replace the heavy physical labor of manual lifting, pulling, and carrying, which can effectively improve the safety factor of the withdrawing workers, ensure the operating safety of the workers, reduce the labor intensity, and greatly improve the working efficiency, and finally realize the autonomous and safe operation of the working surface. The bottom lifting mechanism is arranged at the bottom of the external support, which can lift one side of the external support as needed, thereby reducing the resistance of the external support to move forward and adapting to different terrains and working environments. This makes the support more flexible when dealing with complex geological conditions, and can better support and protect the working surface. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 This is a schematic diagram of the overall use layout of the rectangular empty top area support of the moving and inverting working surface;

[0033] Figure 2 It is a schematic diagram of the overall structure of the rectangular empty top area support of the moving and inverted working surface;

[0034] Figure 3 for Figure 2 Schematic diagram of top view;

[0035] Figure 4 is a schematic diagram of the structure of the external bracket;

[0036] Figure 5 is a schematic diagram of the structure of the internal bracket;

[0037] Figure 6 It is a schematic diagram of the structure of the clamping sleeve;

[0038] Figure 7 It is a structural schematic diagram of the bottom lifting rod;

[0039] Figure 8 This is a schematic diagram of the structure of the carrying pole.

[0040] [Description of Reference Numerals]

[0041] 1: External support; 11: First base; 12: First top beam; 13: First hydraulic column; 14: Protective beam; 2: Internal support; 21: Second base; 22: Second top beam; 23: Second hydraulic column; 24: Clamping sleeve; 25: Fixed ring; 3: Pushing mechanism; 31: First pushing mechanism; 32: Second pushing mechanism; 4: Bottom lifting mechanism; 41: Bottom lifting jack; 42: Bottom lifting rod; 43: Lifting rod; 44: Connecting shaft; 45: Connecting rod; 5: Connecting rod group; 6: Column socket; 7: Support to be removed from the working surface; 8: Protective support. DETAILED DESCRIPTION

[0042] In order to better explain the present invention and facilitate understanding, the present invention is described in detail below through specific implementation modes in conjunction with the accompanying drawings.

[0043] This embodiment provides a rectangular empty top area bracket for the moving and inverted working surface, such as Figure 1-Figure 3 As shown, it includes an internal support 2 that can be lifted and lowered for support, an external support 1, a pushing mechanism 3 and a bottom lifting mechanism 4. The internal support 2 is arranged at the middle front side of the external support 1, and is connected to the external support 1 through the pushing mechanism 3. When the internal support 2 is not in a supporting state, the external support 1 can push the internal support 2 forward through the pushing mechanism 3. When the internal support 2 is in a supporting state, the internal support 2 can pull the external support 1 forward through the pushing mechanism 3 to achieve self-movement of the support. The bottom lifting mechanism 4 is arranged at the bottom of the external support 1, and is used to lift the side of the external support 1 close to the internal support 2.

[0044] It should be noted here that when the underground mining face reaches the end of the coal mining, the mining is completed and the working face support needs to be withdrawn and transported to the next working face.

[0045] Among them, since the internal support 2 and the external support 1 are mainly used to bear the pressure from the working surface of the empty top area, the internal support 2 and the external support 1 are preferably made of steel structural steel to improve the bearing capacity. The internal support 2 is arranged on the middle front side of the external support 1. The middle front side here specifically means that the internal support 2 is nested inside the external support 1 and can move forward under the push of the pushing mechanism 3. It should be noted here that during the movement of the internal support 2, it is necessary to always ensure that there is an overlapping part with the external support 1, so that the external support 1 can ensure the stability of the support of the external support 1 by clamping the internal support 2 on the top to resist the lateral force from the collapsed roof of the goaf.

[0046] In the above scheme, the internal support 2 and the external support 1 are connected by the push mechanism 3, which not only saves the layout space, but also enables the two supports to move forward by pulling forward and pushing backward, so as to achieve the purpose of self-movement. When the internal support 2 is not in the supporting state, the external support 1 can push the internal support 2 forward through the push mechanism 3; and when the internal support 2 is in the supporting state, it can pull the external support 1 forward through the push mechanism 3, replacing the heavy physical labor of manual lifting, pulling and carrying, which can effectively improve the safety factor of the withdrawing workers, ensure the operating safety of the workers, reduce the labor intensity, and greatly improve the working efficiency, and finally realize the autonomous and safe operation of the working surface. The bottom lifting mechanism 4 is arranged at the bottom of the external support 1, which can lift one side of the external support 1 as needed, thereby reducing the resistance of the external support 1 to move forward, adapting to different terrains and working environments, making the support more flexible in dealing with complex geological conditions, and better adapting to the bottom plate of the working surface.

[0047] Specific, combined Figure 4 and Figure 5 In this embodiment, the external support 1 includes a first base 11 and a first top beam 12, and the internal support 2 includes a second base 21 and a second top beam 22. The first base 11 and the first top beam 12 are connected by a first hydraulic column 13 that can be raised and lowered, and the second base 21 and the second top beam 22 are connected by a second hydraulic column 23 that can be raised and lowered. The first base 11 is provided with a groove that opens toward the internal support 2 and is used to install the push mechanism 3.

[0048] Specifically, the first top beam 12 includes a left top beam and a right top beam, and the left top beam and the right top beam are connected by a dumbbell box and a pin shaft. The wedge box is fixed on the top of the left top beam and the right top beam by a threaded pin to hold the top plate of the working surface tightly. The wedge-shaped top plate structure of the wedge box can enable the external support 1 to better withstand the horizontal force from the collapsed top plate of the goaf area.

[0049] The external support 1 and the internal support 2 are connected to their respective bases and top beams through the first hydraulic column 13 and the second hydraulic column 23 that can be raised and lowered, respectively, so that the support can adjust its height according to different work requirements. Especially under complex geological conditions, the lifting function of the hydraulic column can ensure that the support is always close to the top plate to prevent safety accidents caused by the sinking or falling of the top plate. The opening on the first base 11 is set toward the groove of the internal support 2, which is used to install the push mechanism 3. It saves installation space and improves space utilization. The push mechanism 3 enables the external support 1 and the internal support 2 to push or pull each other, realizes the self-movement of the support, and further improves safety and work efficiency.

[0050] Reference Figure 3 As shown, in this embodiment, the push mechanism 3 is a double push mechanism 3, including a first push mechanism 31 and a second push mechanism 32 horizontally arranged in parallel in the groove, and the first push mechanism 31 and the second push mechanism 32 can be pushed synchronously or individually. Specifically, the first push mechanism 31 includes a first push jack and a first push rod, and the second push mechanism 32 includes a second push jack and a second push rod. The first push jack and the second push jack are both connected to the first base 11, and the first push rod and the second push rod are both connected to the second base 21.

[0051] The base is a semi-rigid integral structure with two push jacks and two push rods arranged in parallel in the middle of the base; the bottom lifting jacks 41 are arranged symmetrically on both sides of the base. The two bottom lifting jacks 41 simultaneously feed and return liquid to ensure the synchronization of bottom lifting; the two push jacks can feed and return liquid simultaneously to ensure the pushing effect, or they can feed and return liquid separately to fine-tune the bracket.

[0052] Reference Figure 2 , Figure 3 , Figure 7 and Figure 8 In this embodiment, the bottom lifting mechanism 4 includes a bottom lifting jack 41 and a bottom lifting rod 42; two groups of bottom lifting jacks 41 are symmetrically arranged on both sides of the groove, and are respectively fixedly installed on the first base 11. Corresponding to the push rod of each group of bottom lifting jacks 41, a through hole is arranged on the first base 11, and the push rod can pass through the through hole and extend outward to abut against the bottom lifting rod 42. One end of the bottom lifting rod 42 is movably arranged in the notch at the bottom of the first base 11, and the other end is connected to the second base 21.

[0053] The bottom lifting mechanism 4 can flexibly lift one side of the external support 1 through the cooperation of the bottom lifting jack 41 and the bottom lifting rod 42, and can effectively reduce the resistance of the ground to the forward movement of the external support 1. The support can better adapt to the needs of different terrains and working surfaces, especially when encountering soft bottom plates or uneven ground, the bottom lifting mechanism 4 can ensure the stability and support effect of the support. Two groups of bottom lifting jacks 41 are symmetrically arranged on both sides of the groove and fixedly installed on the first base 11. The hydraulic cylinders of the bottom lifting jacks 41 are synchronously filled with liquid or returned with liquid, which can ensure the uniform distribution of the bottom lifting force and enhance the stability of the support during the lifting process. At the same time, one end of the bottom lifting rod 42 is movably arranged in the notch at the bottom of the first base 11, and the other end is connected to the second base 21, which further enhances the overall stability of the support and prevents the support from tilting during the lifting process. The bottom lifting mechanism 4 makes the movement of the support more convenient. By controlling the extension and contraction of the bottom lifting jack 41, the lifting and lowering of the front end of the first base 11 of the support can be easily achieved, so that the support can move forward smoothly.

[0054] Specifically, in this embodiment, the bottom lifting mechanism 4 further includes a carrying rod 43, a connecting shaft 44 and a connecting rod 45. The carrying rod 43 is disposed on the second base 21 and fixedly connected by a connecting member, and both ends of the carrying rod 43 are rotatably connected to the connecting shaft 44. One end of the connecting rod 45 is hinged to the lower end of the connecting shaft 44, and the other end is hinged to the connecting ear at the end of the bottom lifting rod 42.

[0055] The two ends of the carrying rod 43 are rotatably connected to the connecting shaft 44. This rotatable connection mode allows the carrying rod 43 to adjust the angle according to actual needs to cooperate with the fine adjustment of the self-moving direction of the double push mechanism 3. One end of the connecting rod 45 is hinged to the lower end of the connecting shaft 44, and the other end is hinged to the connecting ear at the end of the bottom lifting rod 42, which allows the connecting rod 45 to swing freely within a certain range to cooperate with the lifting and lowering of the front end of the first base 11 of the external bracket 1 under the action of the bottom lifting jack 41. Here, the lifting height range is 0mm-105mm.

[0056] Reference Figure 5 and Figure 6 In this embodiment, the internal support 2 further includes a clamping sleeve 24 and a fixing ring 25. The second base 21 is an I-beam structure, and a clamping sleeve 24 is provided at the upper horizontal beam of the second base 21, and a fixing ring 25 is installed inside the clamping sleeve 24 for fixing the second hydraulic column 23 of the internal support 2. The I-beam structure of the second base 21 provides excellent bending strength and bearing capacity, and can effectively support the weight and pressure from the second hydraulic column 23, thereby enhancing the stability of the entire structure. At the same time, the provision of the clamping sleeve 24 and the fixing ring 25 further ensures the stable installation of the second hydraulic column 23, avoiding safety hazards caused by shaking or displacement of the column.

[0057] In this embodiment, the external support 1 further includes a shielding beam 14, which is connected to the first base 11 through a connecting rod group 5 and is hinged to the first top beam 12. The four-link design enables the support shielding beam 14 to achieve a larger and reasonable back angle and improve the overall stability of the support.

[0058] In this embodiment, the connection between the first base 11 and the hydraulic column and the connection between the second base 21 and the hydraulic column are provided with a hemispherical column socket 6. The column is installed at the column socket 6, and the bottom of the column socket 6 is a box-shaped structure, and the bottom plate is a split structure. The external bracket 1 has a total of four hydraulic columns, divided into two rows, front and back, and arranged symmetrically on both sides of the first base 11. The two hydraulic columns in the front row are raised and lowered at the same time, and the two hydraulic columns in the back row are raised and lowered at the same time.

[0059] In this embodiment, a hydraulic system is also included to drive the first hydraulic column 13 and the second hydraulic column 23 to extend and retract.

[0060] The specific working process of the rectangular empty top area support of the moving and reversing working face provided in this embodiment is as follows: after the mining of the working face is completed, the support in this embodiment is placed in the rectangular empty top area formed by the intersection of the working face support and the shielding support 8, and ensure that it is perpendicular to the support 7 to be removed from the working face.

[0061] After that, the support to be removed is removed along the direction of the working surface. During this process, a rectangular empty top area will be formed. At this time, the external support 1 is in a supporting and fixed state, and the second hydraulic column 23 of the internal support 2 is retracted, and is pushed forward a step distance along the direction of the working surface under the action of the push jack until it reaches the newly formed rectangular empty top area. Then the second hydraulic column 23 extends out and supports the newly formed rectangular empty top area. After that, the first hydraulic column 13 of the external support 1 is retracted, and is pulled a step distance by the internal support 2 along the direction of the working surface under the action of the push jack until it is close to the internal support 2. This cycle is repeated until all the supports to be removed 7 in the working surface are completely withdrawn. Finally, the empty top area supports of this embodiment are withdrawn to achieve the moving and overturning of the supports.

[0062] It should be noted that all directional indications in this embodiment (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0063] In addition, in the present embodiment, the descriptions involving "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" or "second" may explicitly or implicitly include at least one of the features. In the description of the present embodiment, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0064] In this embodiment, unless otherwise clearly specified and limited, the terms "connection", "fixation", etc. should be understood in a broad sense. For example, "fixation" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this embodiment can be understood according to specific circumstances.

[0065] It should be understood that the above description of the specific embodiments of the present invention is only for illustrating the technical route and features of the present invention, and its purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly, but the present invention is not limited to the above specific implementation methods. Any changes or modifications made within the scope of the claims of the present invention should be included in the protection scope of the present invention.

Claims

1. A rectangular empty top area bracket for the work surface of a moving frame, characterized in that: It comprises an external support (1) that can be raised and lowered for support, an internal support (2), a pushing mechanism (3) and a bottom lifting mechanism (4); The internal support (2) is arranged on the middle front side of the external support (1), and is connected to the external support (1) via the pushing mechanism (3); When the internal support (2) is not in a supporting state, the external support (1) can push the internal support (2) forward through the pushing mechanism (3); when the internal support (2) is in a supporting state, the internal support (2) can pull the external support (1) forward through the pushing mechanism (3) to achieve self-movement of the support; The bottom lifting mechanism (4) is arranged at the bottom of the external support (1) and is used to lift a side of the external support (1) close to the internal support (2).

2. The rectangular empty top area bracket for the moving and reversing working surface as claimed in claim 1, characterized in that: The external support (1) comprises a first base (11) and a first top beam (12), and the internal support (2) comprises a second base (21) and a second top beam (22); The first base (11) and the first top beam (12) are connected via a liftable first hydraulic column (13), and the second base (21) and the second top beam (22) are connected via a liftable second hydraulic column (23); The first base (11) is provided with a groove with its opening facing the internal bracket (2) for mounting the pushing mechanism (3).

3. The rectangular empty top area bracket for the moving and reversing working surface as claimed in claim 2, characterized in that: The pushing mechanism (3) is a double pushing mechanism, comprising a first pushing mechanism (31) and a second pushing mechanism (32) which are arranged horizontally and in parallel in the groove, and the first pushing mechanism (31) and the second pushing mechanism (32) can be pushed synchronously or independently.

4. The rectangular empty top area support for the moving and reversing working surface as claimed in claim 3 is characterized in that: The first pushing mechanism (31) comprises a first pushing jack and a first pushing rod, and the second pushing mechanism (32) comprises a second pushing jack and a second pushing rod; The first push jack and the second push jack are both connected to the first base (11), and the first push rod and the second push rod are both connected to the second base (21).

5. The rectangular empty top area support for the moving and reversing working surface as described in any one of claims 1 to 4, characterized in that: The bottom lifting mechanism (4) comprises a bottom lifting jack (41) and a bottom lifting rod (42); Two groups of bottom lifting jacks (41) are symmetrically arranged on both sides of the groove and are respectively fixedly mounted on the first base (11); Corresponding to the ejection rod of each group of the bottom lifting jacks (41), a through hole is provided on the first base (11), and the ejection rod can pass through the through hole and extend outward to abut against the bottom lifting rod (42); One end of the bottom lifting rod (42) is movably arranged in a notch at the bottom of the first base (11), and the other end is connected to the second base (21).

6. The rectangular empty top area support for the moving and reversing working surface as claimed in claim 5, characterized in that: The bottom lifting mechanism (4) further comprises a carrying rod (43), a connecting shaft (44) and a connecting rod (45); The carrying rod (43) is arranged on the second base (21) and is fixedly connected via a connecting piece, and both ends of the carrying rod (43) are rotatably connected to the connecting shaft (44); One end of the connecting rod (45) is hinged to the lower end of the connecting shaft (44), and the other end is hinged to the connecting ear at the end of the bottom lifting rod (42).

7. The rectangular empty top area support for the moving and reversing working surface as claimed in claim 6, characterized in that: The internal support (2) further comprises a clamping sleeve (24) and a fixing ring (25); The second base (21) is an I-beam structure, and the clamping sleeve (24) is arranged at the upper horizontal beam of the second base (21), and the fixing ring (25) is installed inside the clamping sleeve (24) for fixing the second hydraulic column (23) of the internal bracket (2).

8. The rectangular empty top area support for the moving and reversing working surface as claimed in claim 6, characterized in that: The external support (1) further comprises a shielding beam (14), wherein the shielding beam (14) is connected to the first base (11) via a connecting rod group (5) and is hinged to the first top beam (12).

9. The rectangular empty top area support for the moving and reversing working surface as claimed in claim 6, characterized in that: A hemispherical column socket (6) is provided at the connection between the first base (11) and the first hydraulic column (13), and at the connection between the second base (21) and the second hydraulic column (23).

10. The rectangular empty top area support for the moving and reversing working surface as claimed in claim 8, characterized in that: It also includes a hydraulic system for driving the first hydraulic column (13), the second hydraulic column (23), the first push jack and the second push jack.

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