A borehole drilling tool for coal seams and a method of borehole drilling

Abstract

The application discloses a coal seam hole forming drilling tool and a hole forming method thereof. The hole forming drilling tool comprises a main drill bit, a drill bit matrix, a driving member, a reamer and a magnetic attraction assembly. The drill bit matrix has opposite top and tail ends, and an accommodating cavity is defined in the drill bit matrix. The main drill bit is arranged at the top end, the tail end is connected with the driving member, the drill bit matrix is driven to rotate by the driving member, and a first gas-water passage is arranged between the tail end and the accommodating cavity. The first end of the reamer is pivotally connected in the accommodating cavity, a second gas-water passage is arranged along the extension direction of the reamer, and the second gas-water passage is communicated with the first gas-water passage. The magnetic attraction assembly is connected between the accommodating cavity and the second end of the reamer, and is configured to drive the reamer to perform a first movement in the accommodating cavity when the rotating speed of the main drill bit is less than a threshold rotating speed, and drive the second end of the reamer to perform a second movement to rotate to the outside of the accommodating cavity when the rotating speed of the main drill bit is greater than or equal to the threshold rotating speed.

Description

A coal seam cavity drilling tool and its cavity creation method Technical Field

[0001] This invention relates to the field of coal seam cavity-making equipment, and more particularly to a coal seam cavity-making drill and its cavity-making method. Background Technology

[0002] As shallow coal resources are gradually depleted, deep coal resources are an important reserve of coal resources for my country in the future. At present, the average mining depth of coal mines in my country is increasing at a rate of 8 to 12 meters per year, and the average mining depth in the central and eastern regions is even extending deeper at a rate of 10 to 25 meters per year.

[0003] The geological structure of deep coal seams is more complex, with a significant increase in gas content and gas pressure. The low permeability of the coal seam greatly increases the gas extraction time and significantly reduces extraction efficiency.

[0004] To effectively solve the problem of gas extraction from low-permeability coal seams, a series of enhanced permeability technologies have been developed, such as deep-hole pre-fracturing blasting, hydraulic fracturing, and slotting techniques. These measures share the common feature of using high-energy external forces to disturb the coal seam, creating fissures and increasing the inner surface area of ​​the extraction holes, thereby increasing the permeability of the coal seam. However, high-energy disturbance of the coal seam can easily induce outbursts, placing high demands on the mine ventilation system and the safety protection measures taken during construction. Therefore, this invention proposes a gas extraction method using mechanical drilling. This method can increase the inner surface area of ​​the extraction holes, thereby increasing the permeability of the coal seam, but it also brings problems such as low hole enlargement efficiency, large workload, and excessively long working cycle. Summary of the Invention

[0005] This solution addresses the problems and needs raised above by proposing a coal seam cavity-creating drill and its cavity-creating method. Due to the adoption of the following technical features, it can achieve the above-mentioned technical objectives and bring about several other technical effects.

[0006] This invention proposes a coal seam cavity drilling tool, comprising:

[0007] Main drill bit;

[0008] The drill bit body has a top end and a tail end, and defines a receiving cavity with one end open inside. The top end is equipped with a main drill bit, and the tail end is connected to a drive unit. The drill bit body is driven to rotate by the drive unit, and a first air-water channel is provided between the tail end and the receiving cavity.

[0009] A reaming drill bit, the first end of which is pivotally connected to the receiving cavity, and a second air-water channel is provided along the extension direction of the reaming drill bit, and the second air-water channel is connected to the first air-water channel;

[0010] A magnetic suction assembly is connected between the receiving cavity and the second end of the reaming drill bit, configured such that when the rotational speed of the main drill bit is less than a threshold rotational speed, the reaming drill bit performs a first movement within the receiving cavity; and when the rotational speed of the main drill bit is greater than or equal to the threshold rotational speed, the second end of the reaming drill bit performs a second movement rotating to the outside of the receiving cavity.

[0011] In this technical solution, before the reaming begins, the reaming drill bit is driven by the drive unit to drill forward at a rated speed n0; at this time, the centrifugal force F0 experienced by the reaming drill bit is less than the magnetic attraction force F experienced by the reaming drill bit. s The reaming drill bit closes; secondly, as the reaming drill bit drills into the reaming section, the drill bit speed gradually increases, increasing to the threshold speed n. max When the rotational speed remains constant, the centrifugal force F0 acting on the reaming bit is greater than the magnetic attraction force F0 acting on the reaming bit. s The reaming drill bit opens and the opening angle gradually increases until it is fully open; after the reaming is completed, the rotation speed of the reaming drill bit gradually decreases to the rated speed n0, the centrifugal force F0 on the reaming drill bit gradually decreases, the reaming drill bit gradually closes, and when it approaches the magnetic attraction component, the reaming drill bit is attracted and closed by the magnetic force; the above steps are repeated until the reaming operation is completely completed.

[0012] In addition, the coal seam cavity drilling tool and cavity drilling method according to the present invention may also have the following technical features:

[0013] In one example of the present invention, the magnetic attraction component includes:

[0014] A magnet block, fixedly connected within the receiving cavity, is configured to generate a magnetic force that attracts the second end of the reaming drill bit; wherein, when the rotational speed of the main drill bit is less than a threshold rotational speed, the magnet block attracts the second end of the reaming drill bit; when the rotational speed of the main drill bit is greater than or equal to the threshold rotational speed, the magnet block separates from the second end of the reaming drill bit.

[0015] In one example of the invention, the magnet block is either a permanent magnet or an electromagnet.

[0016] In one example of the invention, the magnetic force of the magnet block is adjustable, so that the threshold rotational speed of the main drill bit is adjustable.

[0017] In one example of the present invention, the magnetic attraction component further includes:

[0018] At least one elastic mechanism is disposed between the magnet block and the receiving cavity, configured such that the magnet block has an elastic force that moves toward the reaming drill bit.

[0019] In one example of the present invention, the elastic mechanism includes:

[0020] The base is fixed inside the receiving cavity and has a guide hole.

[0021] A guide rod, one end of which is inserted into the guide hole, and the other end of which is fixedly connected to the magnet block;

[0022] An elastic element, one end of which is connected to the guide hole and the other end of which is connected to the guide rod, is configured to cause the guide rod to generate an elastic force that moves toward the reaming drill bit.

[0023] In one example of the present invention, the elastic mechanism comprises a plurality of such mechanisms, and the plurality of elastic mechanisms are arranged at equal angular intervals along the circumferential direction of the magnet block.

[0024] In one example of the invention, the receiving cavity has a groove, the elastic mechanism is connected in the groove, and the magnet block extends at least partially out of the groove.

[0025] In one example of the present invention, the elastic element includes one of a tension spring, a compression spring, and a spring sheet.

[0026] Another object of the present invention is to provide a method for creating a cavity using a coal seam cavity drilling tool as described above, comprising the following steps:

[0027] S10: Before reaming begins, the reaming drill bit advances forward at its rated speed n0 under the drive of the drive unit; at this time, the centrifugal force F0 acting on the reaming drill bit is less than the magnetic attraction force F acting on the reaming drill bit. s The reaming drill bit closes;

[0028] S20: When the reaming drill bit reaches the reaming section, the drill bit speed gradually increases until it reaches the threshold speed n. max When the rotational speed remains constant, the centrifugal force F0 acting on the reaming bit is greater than the magnetic attraction force F0 acting on the reaming bit. s The reaming drill bit opens and the opening angle gradually increases until it is fully open;

[0029] S30: After the hole is enlarged, the speed of the enlarged drill bit gradually decreases to the rated speed n0, the centrifugal force F0 on the enlarged drill bit gradually decreases, the enlarged drill bit gradually closes, and when it approaches the magnetic attraction component, the enlarged drill bit is attracted and closed by the magnetic force.

[0030] S40: Repeat steps S10 to S30 until the hole enlargement operation is completed.

[0031] The preferred embodiments of the invention will be described in more detail below with reference to the accompanying drawings, so as to facilitate an understanding of the features and advantages of the invention. Attached Figure Description

[0032] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings of the embodiments of the present invention will be briefly described below. The drawings are merely illustrative of some embodiments of the present invention and are not intended to limit the scope of the present invention to all embodiments.

[0033] Figure 1 is a schematic diagram of the structure of the reaming drill bit when it is closed according to an embodiment of the present invention;

[0034] Figure 2 is a schematic diagram of the structure of the reaming drill bit when it is opened according to an embodiment of the present invention;

[0035] Figure 3 is a schematic diagram of the structure of the reaming drill bit when it is fully opened according to an embodiment of the present invention;

[0036] Figure 4 is a schematic cross-sectional view of the magnetic attraction device according to an embodiment of the present invention;

[0037] Figure 5 is a top view of the magnetic attraction device according to an embodiment of the present invention.

[0038] List of reference numerals in the attached diagram:

[0039] Hole-making drill bit 100;

[0040] Main drill bit 110;

[0041] Drill bit body 120;

[0042] Top 121;

[0043] Tail end 122;

[0044] Receiving cavity 123;

[0045] First gas-water channel 124;

[0046] Groove 125;

[0047] 130mm reaming drill bit;

[0048] Second gas-water channel 131;

[0049] Connecting pin 132;

[0050] First end 133;

[0051] Second end 134;

[0052] Magnetic assembly 140;

[0053] Magnetic block 141;

[0054] Flexible mechanism 142;

[0055] Base 1421;

[0056] Guide hole 14211;

[0057] Guide rod 1422;

[0058] Elastic component 1423;

[0059] Flexible pad 150. Detailed Implementation

[0060] To make the objectives, technical solutions, and advantages of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. The same reference numerals in the drawings represent the same components. It should be noted that the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the described embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0061] Unless otherwise defined, the technical or scientific terms used herein shall have the ordinary meaning understood by one of ordinary skill in the art to which this invention pertains. The terms “first,” “second,” and similar terms used in this patent application specification and claims do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, “an” or “a” and similar terms do not necessarily indicate a quantity limitation. Terms such as “comprising” or “including” mean that the element or object preceding the word encompasses the element or object listed following the word and its equivalents, without excluding other elements or objects. Terms such as “connected” or “linked” are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as “upper,” “lower,” “left,” and “right” are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described object changes.

[0062] A coal seam cavity drilling tool 100 according to a first aspect of the present invention, as shown in Figures 1 to 3, comprises:

[0063] Main drill bit 110;

[0064] The drill bit body 120 has a top end 121 and a tail end 122, and defines a receiving cavity 123 with one side open inside. The top end 121 is equipped with a main drill bit 110, and the tail end 122 is connected to a drive member. The drill bit body 120 is driven to rotate by the drive member. A first air-water channel 124 is provided between the tail end 122 and the receiving cavity 123. For example, the drive member is a drill rod, and the drill rod and the drill bit body 120 are fastened together by a threaded connection.

[0065] The reaming drill bit 130 has a first end 133 pivotally connected to the receiving cavity 123, and a second air-water channel 131 is provided along the extension direction of the reaming drill bit 130, and the second air-water channel 131 is connected to the first air-water channel 124.

[0066] The magnetic suction assembly 140 is connected between the receiving cavity 123 and the second end 134 of the reaming drill bit 130, and is configured such that when the rotational speed of the main drill bit 110 is less than a threshold rotational speed, the reaming drill bit 130 performs a first movement within the receiving cavity 123; and when the rotational speed of the main drill bit 110 is greater than or equal to the threshold rotational speed, the second end 134 of the reaming drill bit 130 performs a second movement to rotate to the outside of the receiving cavity 123.

[0067] The working principle of the coal seam cavity drilling tool 100 is as follows:

[0068] Before the reaming begins, the reaming drill bit 130 (and the main drill bit 110) advances forward at a rated speed n0 under the drive of the drive unit; at this time, the centrifugal force F0 experienced by the reaming drill bit 130 is less than the magnetic attraction force F experienced by the reaming drill bit 130. s The reaming drill bit 130 closes; then, as the reaming drill bit 130 drills into the reaming section, the rotational speed of the reaming drill bit 130 gradually increases, increasing to the threshold rotational speed n. max When the rotational speed remains constant, the centrifugal force F0 acting on the reaming drill bit 130 is greater than the magnetic attraction force F acting on the reaming drill bit 130. s The reaming drill bit 130 opens and the opening angle gradually increases until it is fully open; after the reaming is completed, the rotation speed of the reaming drill bit 130 gradually decreases to the rated rotation speed n0, the centrifugal force F0 on the reaming drill bit 130 gradually decreases, the reaming drill bit 130 gradually closes, and when it approaches the magnetic attraction component 140, the reaming drill bit 130 is attracted and closed by the magnetic force; the above steps are repeated until the reaming operation is completely completed.

[0069] The magnetic attraction force of the magnetic component 140 enables the reaming drill bit 130 to close, ensuring normal drilling of the drill rod; by controlling the rotation speed of the reaming drill bit 130, the centrifugal force of the reaming drill bit 130 is changed, enabling the reaming drill bit 130 to open or close; the present invention has a simple structure and is easy to operate, and can realize the reaming operation without changing the length of the reaming cutter, which can reduce the gas extraction time and improve the gas extraction efficiency.

[0070] In one example of the present invention, as shown in Figures 4 and 5, the magnetic attraction component 140 includes:

[0071] A magnet 141 is fixedly connected within the receiving cavity 123 and configured to generate a magnetic force to attract the second end 134 of the reaming drill bit 130. When the rotational speed of the main drill bit 110 is less than a threshold rotational speed, the magnet 141 attracts the second end 134 of the reaming drill bit 130; when the rotational speed of the main drill bit 110 is greater than or equal to the threshold rotational speed, the magnet 141 separates from the second end 134 of the reaming drill bit 130.

[0072] In other words, firstly, before the reaming begins, the magnetic attraction of the magnet block closes the reaming drill bit 130, ensuring normal drilling of the drill rod; secondly, as the reaming drill bit 130 drills into the reaming section, its rotational speed gradually increases until it reaches the threshold rotational speed n. max At that time, the centrifugal force F0 acting on the reaming drill bit 130 is greater than the magnetic attraction force F acting on the reaming drill bit 130. s The reaming drill bit 130 opens and the opening angle gradually increases until it is fully open; after the reaming is completed, the rotation speed of the reaming drill bit 130 gradually decreases to the rated speed n0, the centrifugal force F0 on the reaming drill bit 130 gradually decreases, the reaming drill bit 130 gradually closes, and when it approaches the magnet block 141, the reaming drill bit 130 is attracted and closed by the magnetic force; the magnet block 141 can realize the opening and closing of the reaming drill bit 130 under the driving speed of the drive component, which is convenient to control.

[0073] In one example of the present invention, the rotation range of the reaming drill bit 130 is 0 to 90°;

[0074] In other words, as the rotational speed of the reaming drill bit gradually increases from 130 rpm to the threshold rotational speed n... max At that time, the centrifugal force F0 acting on the reaming drill bit 130 is greater than the magnetic attraction force F acting on the reaming drill bit 130. s The reaming drill bit 130 makes a second movement and the open end of the receiving cavity 123 opens and the opening angle gradually increases until it is fully open (90°).

[0075] In one example of the invention, the first end 133 of the reaming drill bit 130 is pivotally connected to the receiving cavity 123 via a connecting pin 132;

[0076] This allows the reaming drill bit 130 to rotate around the first end 133, and it can also be connected to the first air-water channel 124 and the second air-water channel 131 through a flexible pipe. In order to ensure that the first air-water channel 124 and the second air-water channel 131 remain connected during the rotation of the reaming drill bit 130, the length of the flexible pipe is made with a margin to ensure that the reaming drill bit 130 can adapt to the changing connection distance between the first air-water channel 124 and the second air-water channel 131 during the rotation.

[0077] In one example of the present invention, the magnet block 141 is either a permanent magnet or an electromagnet; that is, both the permanent magnet and the electromagnet can attract the reaming drill bit 130. Specifically, the reaming drill bit 130 can be attracted when its rotational speed is below the threshold speed under the magnetic force of the permanent magnet or the electromagnet, and can be in an open state when the rotational speed of the reaming drill bit 130 is above the threshold speed.

[0078] In one example of the present invention, the magnetic force of the magnet block 141 is adjustable, so that the threshold rotational speed of the main drill bit 110 is adjustable;

[0079] In other words, when the magnet block 141 is a permanent magnet, the magnetic force of the permanent magnet can be controlled by adjusting the magnet strength and area. The magnet area can be processed by wire cutting. Therefore, in actual production, the magnetic force can be adjusted by replacing the permanent magnet. Preferably, the permanent magnet is a neodymium iron boron magnet with strong magnetic force. The size of the magnet block 141 is determined by the magnitude of the magnetic attraction force Fs on the top of the reaming drill bit 130, which satisfies the formula and is combined with the magnetic strength.

[0080] When the magnet 141 is an electromagnet, the magnitude of the magnetic force is controlled by controlling the magnitude of the current; by controlling the magnitude of the magnetic force of the magnet 141, the threshold rotation speed of the reaming drill bit 130 is changed, that is, by changing the magnitude of the threshold rotation speed, the centrifugal force of the reaming drill bit 130 is changed, thereby realizing the adsorption closure and opening of the reaming drill bit 130 under different threshold rotation speed conditions.

[0081] In one example of the present invention, the magnetic attraction component 140 further includes:

[0082] At least one elastic mechanism 142 is disposed between the magnet block 141 and the receiving cavity 123, and is configured such that the magnet block 141 has an elastic force that moves toward the reaming drill bit 130;

[0083] By setting the elastic mechanism 142, the magnet block 141 can be attached to the second end 134 of the reaming drill bit 130, so that the magnet block 141 can reliably and stably attract the reaming drill bit 130, avoiding the formation of a gap between the reaming drill bit 130 and the magnet block 141, which would affect the magnetic force of the magnet block 141.

[0084] In one example of the present invention, the elastic mechanism 142 includes:

[0085] The base 1421 is fixed inside the receiving cavity 123 and has a guide hole 14211.

[0086] The guide rod 1422 has one end inserted into the guide hole 14211 and the other end fixedly connected to the magnet block 141;

[0087] The elastic element 1423 has one end connected to the guide hole 14211 and the other end connected to the guide rod 1422, and is configured to cause the guide rod 1422 to generate an elastic force that moves toward the reaming drill bit 130.

[0088] In other words, during the non-reaming stage, i.e., when the rotational speed of the reaming drill bit 130 is lower than the threshold speed, the guide rod 1422 is driven by the elastic element 1423 to move along the extension direction of the guide hole 14211 toward the reaming drill bit 130. This causes the magnet block 141 connected to the guide rod 1422 to abut against the reaming drill bit 130. Under the magnetic force of the magnet block 141, the reaming drill bit 130 is in a closed state, i.e., the first movement. During the reaming stage, as the rotational speed of the reaming drill bit 130 reaches the threshold speed, the centrifugal force of the reaming drill bit 130 is greater than the magnetic attraction force of the magnet block 141. This causes the reaming drill bit 130 to separate from the elastic mechanism 142 and open for the second movement. The elastic mechanism 142 can realize a flexible connection between the magnet block 141 and the reaming drill bit 130, which helps to reduce the vibration of the reaming drill bit 130 during rotation and also helps to improve the reliability of the connection between the magnet block 141 and the reaming drill bit 130.

[0089] In one example of the present invention, the elastic mechanism 142 includes a plurality of such mechanisms, and the plurality of elastic mechanisms 142 are arranged at equal angular intervals along the circumferential direction of the magnet block 141.

[0090] For example, the elastic mechanism 142 includes three parts, and the three elastic mechanisms 142 are arranged at equal angular intervals along the circumferential direction of the magnet block 141. This can improve the uniform elastic force that the magnet block 141 can withstand, thereby further improving the reliability and stability of the flexible connection.

[0091] In one example of the present invention, a groove 125 is provided in the receiving cavity 123, and the elastic mechanism 142 is connected in the groove 125, wherein the magnet block 141 extends at least partially out of the groove 125;

[0092] On one hand, the groove 125 facilitates the connection and installation of the elastic mechanism 142 within the receiving cavity 123; on the other hand, the groove 125 also provides support for the elastic mechanism 142, thereby improving its stability.

[0093] In one example of the present invention, a flexible pad 150 is provided inside the groove 125, and the elastic mechanism 142 is connected to the flexible pad 150;

[0094] For example, a rubber pad is adhered to the inner wall of the groove 125, and the elastic mechanism 142 is fixedly connected to the rubber pad by fasteners. This can achieve a flexible connection between the elastic mechanism 142 and the groove 125, further reducing the vibration of the reaming drill bit 130 and improving the reliability of the connection between the magnet block 141 and the reaming drill bit 130.

[0095] In one example of the present invention, the elastic element 1423 includes one of a tension spring, a compression spring, and a sheet spring;

[0096] For example, when the elastic element 1423 is a tension spring, the tension spring is sleeved on the guide rod 1422, and one end of it abuts against the upper end of the base 1421, and the other end of it abuts against the magnet block 141, so that the magnet block 141 has an elastic force that moves toward the reaming drill bit 130.

[0097] For example, when the elastic element 1423 is a compression spring, the compression spring is located inside the guide hole 14211, with one end abutting against the guide rod 1422 and the other end abutting against the bottom of the guide hole 14211, so that the magnet block 141 has an elastic force that moves toward the reaming drill bit 130.

[0098] For example, when the elastic element 1423 is a spring sheet, the spring sheet is located inside the guide hole 14211, with one end abutting against the guide rod 1422 and the other end abutting against the bottom of the guide hole 14211, so that the magnet block 141 has an elastic force that moves toward the reaming drill bit 130.

[0099] A method for creating a cavity using the coal seam cavity-creating drill bit 100 as described above, according to a second aspect of the present invention, includes the following steps:

[0100] S10: Before the reaming begins, the reaming drill bit 130 advances forward at its rated speed n0 under the drive of the drive component; at this time, the centrifugal force F0 acting on the reaming drill bit 130 is less than the magnetic attraction force F acting on the reaming drill bit 130. s The reaming drill bit 130 is closed; for example, the driving component is a drill rod, and the drill rod and the drill bit body 120 are fastened together by a threaded connection.

[0101] S20: When the reaming drill bit 130 drills into the reaming section, the rotational speed of the reaming drill bit 130 gradually increases, increasing to the threshold rotational speed n. max When the rotational speed remains constant, the centrifugal force F0 acting on the reaming drill bit 130 is greater than the magnetic attraction force F acting on the reaming drill bit 130. s The reaming drill bit 130 opens and the opening angle gradually increases until it is fully open;

[0102] S30: After the hole is enlarged, the rotation speed of the enlarged drill bit 130 gradually decreases to the rated rotation speed n0, the centrifugal force F0 on the enlarged drill bit 130 gradually decreases, the enlarged drill bit 130 gradually closes, and when it approaches the magnetic attraction component 140, the enlarged drill bit 130 is attracted and closed by the magnetic force.

[0103] S40: Repeat steps S10 to S30 until the hole enlargement operation is completed.

[0104] It should be noted that when the rotational speed of the reaming drill bit 130 is n0, the angular velocity ω0 at the tip of the reaming drill bit 130 satisfies the formula:

[0105] ω0=2πn0

[0106] The centrifugal force F0 acting on the tip of the reaming drill bit 130 satisfies the formula

[0107]

[0108] Where: l is the top length of the reamer bit 130, in meters;

[0109] The reaming drill bit has a rotational speed of 130 n. max At that time, the centrifugal force F on the top of the reaming drill bit 130 0max Satisfy the formula

[0110]

[0111] Where: L is the length of the reaming drill bit, in meters;

[0112] The magnitude of the magnetic attraction Fs at the tip of the 130 reaming drill bit satisfies the formula:

[0113] G+F 水 <F s <F 0max +F c

[0114] Where: G is the weight of the reamer, N; F is the pressure generated by the water flow, N; F c The resistance exerted by the coal wall when the reamer opens, in N.

[0115] The magnetic attraction force of the magnetic component 140 enables the reaming drill bit 130 to close, ensuring normal drilling of the drill rod; by controlling the rotation speed of the reaming drill bit 130, the centrifugal force of the reaming drill bit 130 is changed, enabling the reaming drill bit 130 to open or close; the present invention has a simple structure and is easy to operate, and can realize the reaming operation without changing the length of the reaming cutter, which can reduce the gas extraction time and improve the gas extraction efficiency.

[0116] Specific Implementation

[0117] A high-pressure water pump is connected to the reaming tool via a threaded connector and provides a pressurized water flow with a pressure P of 0.25 MPa to the reaming tool. During normal drilling, the rated rotational speed n0 of the reaming bit 130 is 80 rpm, and the top length l of the reaming bit 130 is 2 cm. At this time, the centrifugal force F0 on the top of the reaming bit 130 is approximately 19324 N. The pressurized water flow passes through the first air-water channel 124 and the second air-water channel 131, generating a water pressure Fwater of 100 N at the top of the second air-water channel 131. The diameter of the second air-water channel 131 is 4 cm, and the area of ​​the pressurized water flow is 4 cm². 2 To ensure a tight attraction between the magnet block and the reaming drill bit 130, the magnetic attraction force F s The value should be greater than 19424N. After the reaming drill bit advances 20m, the reaming operation begins. At this time, the rotational speed n of the reaming drill bit 130 is increased, and the centrifugal force acting on the top of the reaming drill bit 130 begins to exceed the magnetic attraction force Fs, causing the reaming drill bit 130 to gradually open. Simultaneously, pressurized water flows out through the top of the second air-water channel 131. After the reaming operation is completed, the rotational speed n of the reaming drill bit 130 is reduced and kept stable, allowing the reaming drill bit to continue drilling forward and prepare for the next stage of reaming operation.

[0118] Determining the magnitude of the magnetic attraction and selecting the size of magnet block 141:

[0119] The magnitude of the magnetic attraction Fs at the tip of the 130 reaming drill bit satisfies the formula:

[0120] G+F 水 <F s <F 0max +F c

[0121] Where: G is the weight of the reamer, N; F is the pressure generated by the water flow, N; F c The resistance exerted by the coal wall when the reamer opens, in N.

[0122] The foregoing has described in detail, with reference to preferred embodiments, exemplary implementations of the coal seam cavity-creating drill and cavity-creating method proposed in this invention. However, those skilled in the art will understand that various modifications and alterations can be made to the above specific embodiments without departing from the concept of this invention, and various combinations can be made to the various technical features and structures proposed in this invention without exceeding the protection scope of this invention, which is determined by the appended claims.

Claims

1. A coal seam cavity drilling tool, characterized in that, include: A main drill bit (110); a drill bit body (120), the drill bit body (120) having opposing top end (121) and tail end (122), and defining a receiving cavity (123) with one side open, wherein the main drill bit (110) is mounted on the top end (121), the tail end (122) is connected to a drive member, the drill bit body (120) is driven by the drive member to rotate, and a first air-water channel (124) is provided between the tail end (122) and the receiving cavity (123); a reaming drill bit (130), the first end (133) of which... A second air-water channel (131) is pivotally connected within the receiving cavity (123) and extends along the extension direction of the reaming drill bit (130), and the second air-water channel (131) communicates with the first air-water channel (124); a magnetic suction assembly (140) is connected between the receiving cavity (123) and the second end (134) of the reaming drill bit (130), configured such that when the rotational speed of the main drill bit (110) is less than a threshold rotational speed, the reaming drill bit (130) performs a first movement within the receiving cavity (123); when the rotational speed of the main drill bit (110) is less than a threshold rotational speed, the reaming drill bit (130) performs a first movement within the receiving cavity (123); when the rotational speed of the main drill bit (110) is less than a threshold rotational speed, the reaming drill bit (130) performs a second movement. When the rotational speed of the head (110) is greater than or equal to the threshold rotational speed, the second end (134) of the reaming drill bit (130) performs a second movement to rotate to the outside of the receiving cavity (123); the magnetic attraction assembly (140) includes: a magnet block (141), which is fixedly connected in the receiving cavity (123) and configured to generate a magnetic force to attract the second end (134) of the reaming drill bit (130); wherein, when the rotational speed of the main drill bit (110) is less than the threshold rotational speed, the magnet block (141) attracts the second end (134) of the reaming drill bit (130). When the rotational speed of the main drill bit (110) is greater than or equal to the threshold rotational speed, the magnet block (141) separates from the second end (134) of the reaming drill bit (130); the magnetic force of the magnet block (141) is adjustable, so that the threshold rotational speed of the main drill bit (110) is adjustable; at least one elastic mechanism (142) is disposed between the magnet block (141) and the receiving cavity (123), configured to give the magnet block (141) an elastic force that moves toward the reaming drill bit (130).

2. The coal seam cavity drilling tool according to claim 1, characterized in that, The magnet block (141) is either a permanent magnet or an electromagnet.

3. The coal seam cavity drilling tool according to claim 1, characterized in that, The elastic mechanism (142) includes: a base (1421) fixed in the receiving cavity (123) and having a guide hole (14211); a guide rod (1422), one end of which is inserted into the guide hole (14211) and the other end of which is fixedly connected to the magnet block (141); and an elastic element (1423), one end of which is connected to the guide hole (14211) and the other end of which is connected to the guide rod (1422), configured to cause the guide rod (1422) to generate an elastic force that moves toward the reaming drill bit (130).

4. The coal seam cavity drilling tool according to claim 1, characterized in that, The elastic mechanism (142) includes a plurality of them, and the plurality of elastic mechanisms (142) are arranged at equal angular intervals along the circumferential direction of the magnet block (141).

5. The coal seam cavity drilling tool according to claim 1, characterized in that, The cavity (123) has a groove (125) and the elastic mechanism (142) is connected in the groove (125), wherein the magnet (141) extends at least partially out of the groove (125).

6. The coal seam cavity drilling tool according to claim 3, characterized in that, The elastic element (1423) includes one of a tension spring, a compression spring, and a spring sheet.

7. A method for creating a cavity using a coal seam cavity-creating drill bit as described in any one of claims 1 to 6, characterized in that, The steps include: S10: Before reaming begins, the reaming drill bit (130) is driven by the drive unit at a rated speed. n0 Drill forward; at this time, the centrifugal force on the reaming bit (130) is... F0 The magnetic attraction force is less than that experienced by the reaming drill bit (130). Fs S20: When the reaming drill bit (130) enters the reaming section, the rotational speed of the reaming drill bit (130) gradually increases until it reaches the threshold rotational speed. nmax When the rotational speed remains constant, the centrifugal force on the reaming drill bit (130) is... F0 The magnetic attraction force is greater than that experienced by the reaming drill bit (130). Fs S30: After reaming is completed, the reaming drill bit (130) opens and the opening angle gradually increases until it is fully open; S30: After reaming is completed, the rotational speed of the reaming drill bit (130) gradually decreases to the rated speed. n0 The centrifugal force on the reaming drill bit (130) F0 As the diameter gradually decreases, the reaming drill bit (130) gradually closes, and when it approaches the magnetic suction assembly (140), the reaming drill bit (130) is attracted and closed by the magnetic force; S40: Repeat steps S10 to S30 continuously until the reaming operation is completed.

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