Propeller-propelled floating detection ball for karst pipeline detection

Abstract

The invention discloses a propeller-propelled floating detection ball for karst pipeline detection, and relates to the technical field of karst pipeline detection, the propeller-propelled floating detection ball comprises an outer shell, an inner shell, a power assembly and a detection assembly, and the detection assembly comprises a core circuit board, an inertial positioning unit, a wireless data transmission unit and an information storage unit. According to the invention, the propeller pushes the detection ball to move, so that the detection ball has continuous and controllable propelling capability under the condition of a gentle karst pipeline or a low flow rate, and the risk of static or hovering is remarkably reduced, thereby ensuring continuous track acquisition and detection coverage; the inertial positioning unit, the wireless data transmission unit and the information storage unit are used for carrying out three-in-one measurement and fusion on data, so that real-time telemetering and remote control can be realized, and original data can be completely reserved when a link is interrupted so as to facilitate post recovery and analysis.

Description

Technical Field

[0001] This invention relates to the field of karst conduit detection technology, specifically to a propeller-driven floating detection ball for karst conduit detection. Background Technology

[0002] Karst pipelines are widely distributed in karst landform areas. Their channel structures are complex, their routes varied, and their cross-sectional and segmental dimensions differ significantly. They are often accompanied by geological structures such as collapses, siltation, and irregular shafts. Detailed exploration of karst tunnel sites and underground pipelines is crucial not only for project site selection, geological hazard assessment, and tunnel and utility tunnel construction, but also directly relates to the long-term safe operation of urban underground infrastructure. Compared to conventional open-cut or shallow surface exploration, the spatial morphology, obstacle distribution, and fluid environment parameters (such as local flow velocity, turbidity, temperature, and chemical indicators) inside the pipeline can only be obtained through in-depth exploration. Furthermore, these explorations typically must be conducted continuously in narrow, winding, low-velocity, or silt-blocked sections, placing stringent requirements on the size, accessibility, power, and durability of the instruments used.

[0003] Existing pipeline detection technologies each have their advantages and disadvantages, but all have significant shortcomings in engineering applications. Towed or wired camera systems offer real-time imaging and cable power / communication advantages, but cables are prone to jamming in complex bends or narrow sections, resulting in high deployment and retrieval costs. Passive floaters or unpowered buoys are easy to deploy and inexpensive, but they often get stuck or have blind spots in calm sections or static waters, leading to data loss. Small propulsion AUVs / ROVs can actively traverse complex sections and have attitude control, but their size, sealing, and endurance requirements increase manufacturing and on-site maintenance costs, and they still face jamming and reliability issues in narrow or silty karst channels. In addition, satellite positioning cannot be used in groundwater environments, acoustic positioning is affected by multipath and absorption, resulting in decreased accuracy, and long-term integration of inertial navigation causes drift, making trajectory recovery and high-precision positioning difficult. Wireless backhaul is also often unstable in complex underground structures due to channel attenuation and obstruction. Relying solely on real-time links or local storage cannot simultaneously meet the dual requirements of real-time alarms and data integrity.

[0004] Therefore, from an engineering perspective, there is an urgent need for an in-pipe detection device that is of moderate size, modular in structure, and possesses controllable propulsion capabilities. This device should be able to actively maintain its forward movement in low-velocity or gentle flow sections to avoid stagnation; improve trajectory recovery capabilities through short-term positioning strategies such as inertial measurement and data fusion in the absence of satellites; ensure reliable local storage and retransmission after link recovery when communication is limited; and provide engineering solutions for sealing, corrosion prevention, energy management, and on-site maintenance (such as battery replacement and module replacement). Based on these comprehensive requirements, developing a propeller-propelled floating detection sphere that satisfies both throughput and propulsion efficiency while also considering positioning accuracy, data reliability, and maintainability has become a key technological direction for achieving high-coverage and continuous detection of karst pipelines. Summary of the Invention

[0005] The purpose of this invention is to provide a propeller-driven floating detection ball for karst conduit detection, in order to overcome the above-mentioned shortcomings of the prior art.

[0006] To achieve the above objectives, the present invention provides the following technical solution:

[0007] A propeller-propelled floating detection sphere for karst conduit detection includes an outer shell, within which an inner shell is rotatably disposed. The outer shell is composed of two semi-shells screwed together, and the inner shell is also composed of two semi-circular shells screwed together. A sealing ring is provided between the two semi-shells and the two semi-circular shells. The sphere also includes:

[0008] A power assembly is disposed within the inner shell. The power assembly includes an electric motor, which is mounted within the semi-circular shell via a fixed base. A drive shaft is provided at the output end of the electric motor, passing through the semi-circular shell and the semi-shell. A propeller is provided at the end of the drive shaft away from the electric motor.

[0009] A detection component is disposed within the inner shell and on the side away from the power component. The detection component includes a core circuit board electrically connected to a power source. The core circuit board integrates an inertial positioning unit, a wireless data transmission unit, and an information storage unit. The inertial positioning unit includes a three-axis gyroscope, a three-axis accelerometer, and a three-axis magnetometer. The wireless data transmission unit includes a wireless communication module and an antenna. The inertial positioning unit is used to achieve autonomous navigation, the wireless data transmission unit is used to receive remote commands, and the information storage unit is used to store detection information.

[0010] As described above, the power assembly also includes a motor drive board, which is electrically connected to the electric motor and electrically connected to the power source.

[0011] As described above, the power assembly also includes a protective cover disposed on the outside of the half-shell, and the propeller disposed inside the protective cover.

[0012] The electric motor described above is a brushed DC motor and / or a brushless DC motor. The electric motor is equipped with a Hall sensor and / or a photoelectric encoder. The motor drive circuit board is provided with a corresponding drive interface. The motor drive circuit board is provided with overcurrent protection and power management interfaces.

[0013] As described above, the information storage unit is a pluggable memory card slot, which is electrically connected to and detachable from the core circuit board.

[0014] As described above, the electric motor is connected to the fixed base and the core circuit board is connected to the semi-circular shell in a movable manner. The core circuit board is electrically connected to the inertial positioning unit and the wireless data transmission unit by plugging in, and the core circuit board is also provided with an expansion slot.

[0015] The above also includes a balancing component, which is disposed on the outside of the semi-circular shell and is used to balance the position of the inner shell.

[0016] As described above, the balancing component includes a balancing block disposed on the outside of the semi-circular shell, and a hammer is disposed at the lower end of the balancing block. The hammer is disposed at the lower end of the balancing block via a ball joint, and the hammer is used to increase the weight of the balancing block.

[0017] In the above technical solution, the beneficial effects of the present invention are as follows:

[0018] 1. This invention uses a propeller to move the probe ball, enabling the probe ball to have continuous and controllable propulsion capability in gentle karst pipes or low flow conditions, significantly reducing the risk of being stationary or hovering, thereby ensuring continuous trajectory acquisition and detection coverage;

[0019] 2. This invention performs three-in-one measurement and fusion of data through an inertial positioning unit, a wireless data transmission unit, and an information storage unit, enabling real-time telemetry and remote control, while also preserving the original data completely in the event of a link interruption for subsequent recovery and analysis. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0021] Figure 1A three-dimensional structural diagram of a propeller-driven floating detection sphere for karst pipeline detection provided in an embodiment of the present invention;

[0022] Figure 2 A schematic diagram of the first planar structure of a propeller-driven floating detection sphere for karst pipeline detection provided in another embodiment of the present invention;

[0023] Figure 3 A schematic diagram of the second planar structure of a propeller-driven floating detection sphere for karst pipeline detection provided in another embodiment of the present invention;

[0024] Figure 4 Provided for another embodiment of the present invention Figure 2 Sectional view at point AA;

[0025] Figure 5 A three-dimensional structural schematic diagram of a detection component (excluding the power supply) provided in another embodiment of the present invention;

[0026] Figure 6 Provided for another embodiment of the present invention Figure 4 A magnified view of a portion of point M.

[0027] Explanation of reference numerals in the attached figures:

[0028] 1. Outer shell; 10. Half shell; 2. Inner shell; 20. Semi-circular shell; 3. Power assembly; 30. Electric motor; 31. Drive shaft; 32. Propeller; 33. Motor drive board; 34. Protective cover; 4. Detection assembly; 40. Core circuit board; 400. Expansion slot; 41. Power supply; 42. Inertial positioning unit; 43. Wireless data transmission unit; 44. Information storage unit; 5. Balancing assembly; 50. Balancing block; 51. Hammer. Detailed Implementation

[0029] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0030] In the description of this invention, it should be understood that the terms "upper", "lower", "vertical", "horizontal", "side", "inner", "outer", "one end", "the other end", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0031] like Figures 1-6As shown in the figure, an embodiment of the present invention provides a propeller-driven floating detection ball for karst pipeline detection, comprising an outer shell 1, an inner shell 2 rotatably disposed inside the outer shell 1, the outer shell 1 being composed of two half-shells 10 screwed together, and the inner shell 2 also being composed of two semi-circular shells 20 screwed together, with a sealing ring provided between the two half-shells 10 and the two semi-circular shells 20, and further comprising:

[0032] The power assembly 3 is located inside the inner shell 2. The power assembly 3 includes an electric motor 30, which is mounted inside the semi-circular shell 20 via a fixed base. The output end of the electric motor 30 is provided with a drive shaft 31, which passes through the semi-circular shell 20 and the semi-shell 10. The drive shaft 31 is dynamically sealed with the semi-circular shell 20 and the semi-shell 10. A propeller 32 is provided at the end of the drive shaft 31 away from the electric motor 30.

[0033] The detection component 4 is located inside the inner shell 2 and on the side away from the power component 3. The detection component 4 includes a core circuit board 40, which is electrically connected to the power supply 41. The core circuit board 40 integrates an inertial positioning unit 42, a wireless data transmission unit 43, and an information storage unit 44. The inertial positioning unit 42 includes a three-axis gyroscope, a three-axis accelerometer, and a three-axis magnetometer. The wireless data transmission unit 43 includes a wireless communication module and an antenna. The inertial positioning unit 42 is used to achieve autonomous navigation, the wireless data transmission unit 43 is used to receive remote commands, and the information storage unit 44 is used to store detection information.

[0034] In another embodiment of the present invention, the power assembly 3 further includes a motor drive board 33, which is electrically connected to the electric motor 30 and electrically connected to the power supply 41.

[0035] The specific implementation method is as follows: When the detection ball is assembled and put into the karst pipeline, the power supply 41 supplies power to the motor drive board 33 and the electric motor 30. This causes the output end of the electric motor 30 to drive the drive shaft 31 to rotate, which in turn causes the drive shaft 31 to drive the propeller 32 to rotate. In turn, the electric motor 30 provides power through the propeller 32, which drives the detection ball to move in the karst pipeline so that the detection ball can detect data such as the branches of the karst pipeline.

[0036] Furthermore, the inertial positioning unit 42 is an inertial measurement unit, consisting of a three-axis gyroscope, a three-axis accelerometer, and a three-axis magnetometer. The core circuit board 40 is equipped with a processing module capable of filtering and estimating the state of the inertial measurement unit output. The processing module preferably uses an extended Kalman filter or an equivalent fusion algorithm to estimate attitude and short-term relative displacement. The wireless data transmission unit 43 is preferably a long-range low-power wireless communication module and antenna (e.g., LoRa technology), supporting data packetization, verification, and retransmission. It can also configure transmission parameters according to the spectrum regulations of the deployment area to ensure reliable uploading of key status information (such as voltage, remaining power, attitude, etc.) under limited bandwidth and to receive remote commands for mission start / stop or parameter adjustment. The inertial positioning unit 42 operates completely autonomously, unaffected by external interference, avoiding signal loss and ensuring navigation continuity. It receives remote commands through the wireless data transmission unit 43 via the wireless communication module and antenna.

[0037] In another embodiment of the present invention, the power assembly 3 further includes a protective cover 34, which is disposed on the outside of the half-shell 10, and the propeller 32 is disposed inside the protective cover 34.

[0038] The specific implementation is as follows: the protective cover 34 can protect the propeller 32 during the movement of the probe ball, so as to prevent the probe ball from colliding with the propeller 32 in the karst pipe and causing damage to the propeller 32. In addition, the protective cover 34 can prevent impurities in the karst pipe (such as weeds, branches or scraping the pipe wall) from jamming the propeller 32.

[0039] In another embodiment of the present invention, the electric motor 30 is a brushed DC motor and / or a brushless DC motor, the electric motor 30 is equipped with a Hall sensor and / or a photoelectric encoder, and the motor drive circuit board is provided with a corresponding drive interface; the motor drive circuit board is provided with overcurrent protection and power management interface 41.

[0040] The specific implementation method is as follows: The motor drive circuit board is equipped with a pulse width modulation drive interface, a speed closed-loop control interface (supporting PID or equivalent control algorithms), current detection and overcurrent protection, short circuit and overheat protection, and a power supply 41 management interface. The electric motor 30 obtains speed / angular position signals by being equipped with a Hall sensor and / or photoelectric encoder to achieve closed-loop speed / torque control, etc. In this way, the motor drive board 33 can implement closed-loop speed or torque control based on the speed / angular position signals from the Hall sensor and / or photoelectric encoder, ensuring that the propeller 32 outputs stable thrust, and taking timely current limiting or stopping actions to protect the electric motor 30 and the power supply 41 in the event of sudden load (such as being entangled by aquatic plants or scraping the pipe wall).

[0041] In another embodiment of the present invention, the information storage unit is a pluggable memory card slot, which is electrically connected to and detachable from the core circuit board 40.

[0042] The specific implementation method is as follows: the information storage unit is a pluggable memory card slot, such as an SD card slot. During detection, a memory card is inserted into the pluggable memory card slot. The pluggable memory card slot can be accessed by removing and removing the memory card. When the wireless link is interrupted, the collected data is written to the local storage in real time and automatically retransmitted in time sequence after the link is restored. This ensures that complete original data (original quantities of inertial measurement unit, timestamps, drive status, sensor temperature, voltage, etc.) can be written locally in real time when the wireless link is limited or interrupted.

[0043] In another embodiment of the present invention, the electric motor 30 and the fixed base, the core circuit board 40 and the semi-circular shell 20 are all connected in a movable manner, the core circuit board 40 is electrically connected to the inertial positioning unit 42 and the wireless data transmission unit 43 by plugging, and the core circuit board 40 is also provided with an expansion position 400.

[0044] The specific implementation method is as follows: the movable connection facilitates the disassembly and replacement of the electric motor 30 or the core circuit board 40, and the electrical plug-in connection facilitates the disassembly and replacement of the inertial positioning unit 42 and the wireless data transmission unit 43. In this way, damaged electric motors 30 or core circuit boards 40 can be quickly replaced on site, shortening downtime. Furthermore, by electrically plugging different modules or sensors through the expansion slot 400, the core circuit board 40 can be functionally expanded by replacing different sensors or communication modules according to task requirements.

[0045] In another embodiment of the present invention, a balancing component 5 is also included. The balancing component 5 is disposed on the outside of the semi-circular shell 20 and is used to balance the position of the inner shell 2.

[0046] The specific implementation method is as follows: the balancing component 5 is located at the lower end of the outer side of the semi-circular shell 20, and the inner shell 2 is always in the optimal traveling position through the balancing component 5. In this way, after the probe ball is hit, the inner shell 2 returns to its original position after rotating rapidly inside the outer shell 1 through the balancing component 5.

[0047] In another embodiment of the present invention, the balancing component 5 includes a balancing block 50, which is disposed on the outside of the semi-circular shell 20. A hammer block 51 is disposed at the lower end of the balancing block 50. The hammer block 51 is disposed at the lower end of the balancing block 50 through a ball joint. The hammer block 51 is used to increase the weight of the balancing block 50.

[0048] The specific implementation is as follows: the balance block 50 is set on the outside of the semi-circular shell 20, and the semi-circular shell 20 can rotate inside the semi-shell 10 due to the gravity of the balance block 50. After the probe ball is hit, the inner shell 2 returns to its original position after rotating rapidly inside the outer shell 1 through the balance block 50. In addition, a hammer block 51 is set at the lower end of the balance block 50 through a ball joint, so that when the probe ball is hit, the hammer block 51 can maintain the position of the inner shell 2 through its own gravity and its swing, reducing or even avoiding the situation where the inner shell 2 rotates inside the outer shell 1.

[0049] Working principle: When the detection ball is assembled and placed into the karst pipe, the power supply 41 supplies power to the motor drive board 33 and the electric motor 30. This causes the output of the electric motor 30 to drive the drive shaft 31 to rotate, which in turn drives the propeller 32 to rotate. The electric motor 30 then provides power to the propeller 32, which in turn drives the detection ball to move within the karst pipe, allowing the detection ball to detect data such as karst pipe branches. The motor drive circuit board is equipped with a pulse width modulation drive interface, a speed closed-loop control interface (supporting PID or equivalent control algorithms), current detection and overcurrent protection, short circuit and overheat protection, and a power supply 41 management interface. The electric motor 30 is equipped with a Hall sensor and / or photoelectric encoder. The encoder acquires speed / angular position signals to achieve closed-loop speed / torque control, etc. Thus, the motor drive board 33 can implement closed-loop speed or torque control based on the speed / angular position signals from the Hall sensor and / or photoelectric encoder, ensuring that the propeller 32 outputs stable thrust, and taking timely current limiting or stopping actions to protect the electric motor 30 and power supply 41 in the event of sudden load (such as being entangled by aquatic plants or scraping the pipe wall). In addition, the protective cover 34 can protect the propeller 32 during the movement of the probe ball, preventing the probe ball from colliding with the karst pipe and causing damage to the propeller 32. The protective cover 34 can also prevent impurities in the karst pipe (such as weeds, branches, or scraping the pipe wall) from jamming the propeller 32.

[0050] The inertial positioning unit 42 is an inertial measurement unit, consisting of a three-axis gyroscope, a three-axis accelerometer, and a three-axis magnetometer. The core circuit board 40 is equipped with a processing module capable of filtering and estimating the state of the inertial measurement unit output. The processing module preferably employs an extended Kalman filter or an equivalent fusion algorithm to estimate attitude and short-term relative displacement. The wireless data transmission unit 43 is preferably a long-range, low-power wireless communication module and antenna (e.g., LoRa technology), supporting data packet segmentation, verification, and retransmission. It can also configure transmission parameters according to the spectrum regulations of the deployment area to ensure reliable uploading of critical status information (such as voltage, remaining battery power, attitude, etc.) under limited bandwidth and to receive remote commands for task start / stop or... Parameter adjustment; the inertial positioning unit 42 operates completely autonomously, unaffected by external interference, avoiding signal loss and ensuring navigation continuity. It receives remote commands via wireless data transmission unit 43 through wireless communication module and antenna; the information storage unit is a pluggable memory card slot, such as an SD card slot. During detection, a memory card is inserted into the pluggable memory card slot, which can be accessed by removing and removing the memory card. When the wireless link is interrupted, the collected data is written to the local storage in real time and automatically retransmitted according to the time sequence after the link is restored, ensuring that complete original data (original quantities of inertial measurement unit, timestamps, drive status, sensor temperature, voltage, etc.) can be written locally in real time when the wireless link is limited or interrupted.

[0051] The balancing component 5 is located at the lower outer end of the semi-circular shell 20. The inner shell 2 is kept in the optimal traveling position by the balancing component 5. In this way, after the probe ball is hit, the inner shell 2 will quickly rotate within the outer shell 1 and return to its original position by the balancing component 5. Specifically, the balancing block 50 is set on the outer side of the semi-circular shell 20. Due to the gravity of the balancing block 50, the semi-circular shell 20 can rotate within the semi-shell 10. After the probe ball is hit, the inner shell 2 will quickly rotate within the outer shell 1 and return to its original position by the balancing block 50. In addition, a hammer block 51 is set at the lower end of the balancing block 50 by a ball joint. When the probe ball is hit, the hammer block 51 can maintain the position of the inner shell 2 by its own gravity and its swing, reducing or even avoiding the rotation of the inner shell 2 within the outer shell 1.

[0052] In addition, the mobile connection method facilitates the disassembly and replacement of the electric motor 30 or the core circuit board 40, and the electrical plug-in method facilitates the disassembly and replacement of the inertial positioning unit 42 and the wireless data transmission unit 43. In this way, damaged electric motors 30 or core circuit boards 40 can be quickly replaced on site, reducing downtime. Furthermore, by electrically plugging different modules or sensors through the expansion slot 400, the core circuit board 40 can be functionally expanded by replacing different sensors or communication modules according to task requirements.

[0053] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A propeller-driven floating detection ball for karst pipe detection, comprising an outer shell (1), wherein an inner shell (2) is rotatably disposed within the outer shell (1), the outer shell (1) is composed of two half-shells (10) screwed together, the inner shell (2) is also composed of two semi-circular shells (20) screwed together, and a sealing ring is provided between the two half-shells (10) and the two semi-circular shells (20), characterized in that, Also include: Power assembly (3), the power assembly (3) is arranged in the inner shell (2), the power assembly (3) includes electric motor (30), the electric motor (30) is arranged in the half circle shell (20) by fixing seat, the output end of the electric motor (30) is provided with drive shaft (31), the drive shaft (31) passes through the half circle shell (20) with the half shell (10), and the drive shaft (31) is provided with propeller (32) away from the electric motor (30) one end; Detection assembly (4), the detection assembly (4) is arranged in the inner shell (2) and is arranged away from the power assembly (3) side, the detection assembly (4) includes core circuit board (40), the core circuit board (40) is electrically connected between power supply (41), the core circuit board (40) is integrated with inertial positioning unit (42), wireless data transmission unit (43) and information storage unit (44), the inertial positioning unit (42) includes three-axis gyroscope, three-axis accelerometer and three-axis magnetometer;The wireless data transmission unit (43) includes wireless communication module and antenna, the inertial positioning unit (42) is used to realize autonomous navigation, the wireless data transmission unit (43) is used to receive remote command, and the information storage unit (44) is used to store detection information.

2. The propeller propelled floating probe ball for karst conduit detection according to claim 1, characterized in that, The power assembly (3) further includes motor drive board (33), the motor drive board (33) is electrically connected between the electric motor (30), and the motor drive board (33) is electrically connected between the power supply (41).

3. The propeller propelled floating probe ball for karst conduit detection according to claim 1, characterized in that, The power assembly (3) further includes protective cover (34), the protective cover (34) is arranged outside the half shell (10), and the propeller (32) is arranged in the protective cover (34).

4. The propeller propelled floating probe ball for karst conduit detection according to claim 1, characterized in that, The electric motor (30) is a brush DC motor and / or brushless DC motor, the electric motor (30) is provided with a Hall sensor and / or photoelectric encoder, the motor drive circuit board is provided with a corresponding drive interface, and the motor drive circuit board is provided with an overcurrent protection and power supply (41) management interface.

5. The propeller propelled floating probe ball for karst conduit detection according to claim 1, characterized in that, The information storage unit is a pluggable memory card seat, the memory card seat is electrically connected with the core circuit board (40) and can be detached.

6. The propeller propelled floating probe ball for karst conduit detection according to claim 1, characterized in that, The electric motor (30) is connected in a movable manner between the fixing seat, the core circuit board (40) and the half circle shell (20), the core circuit board (40) is electrically connected in a plug-in manner between the inertial positioning unit (42) and the wireless data transmission unit (43), and the core circuit board (40) is further provided with an expansion site (400).

7. The propeller propelled floating probe ball for karst conduit detection according to claim 1, characterized in that, Also include balancing assembly (5), the balancing assembly (5) is arranged outside the half circle shell (20), and the balancing assembly (5) is balanced for balancing the position of the inner shell (2).

8. The propeller propelled floating probe ball for karst conduit detection according to claim 7, characterized in that, The balance assembly (5) comprises a balance block (50) arranged outside the semicircular shell (20), a hammer block (51) arranged at the lower end of the balance block (50), and a ball hinge arranged between the balance block (50) and the hammer block (51), wherein the hammer block (51) is used to increase the weight of the balance block (50).

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