A direct current permanent magnet brushless motor stator structure

Abstract

This invention relates to the field of motor stator technology and discloses a stator structure for a DC permanent magnet brushless motor, including a cooling ring and an airbag valve installed at one end of the cooling ring. In this invention, when the temperature in the brushless motor is high, the opening size of the airbag valve at one end of the motor rotor increases, allowing cooling oil to enter the cooling ring. After flowing over the surface of the salient pole winding, the cooling oil flows towards the opening and closing assembly. The oil impacts the turbine blades, pushing the turbine blades to drive the first fixed ring to rotate against the elastic force of the torsion spring. At this time, when the cooling oil passes through the inside of the turbine blades, it impacts the turbine blades through uniform gaps, ensuring that the turbine blades can evenly deliver the cooling oil forward into the cooling ring when rotating. This maintains a suitable flow speed for the cooling oil within the cooling ring, ensuring that the oil can fully remove the heat generated by the stator salient pole winding and improve heat dissipation efficiency.

Description

Technical Field

[0001] This invention relates to the field of motor stator technology, specifically to a stator structure for a DC permanent magnet brushless motor. Background Technology

[0002] DC permanent magnet brushless motors are widely used in power tools, transportation, home appliances and industrial control due to their advantages such as high efficiency, low noise and light weight. However, when the motor runs for a long time or under high load, a lot of heat will be generated inside. If it cannot be dissipated in time and effectively, the motor temperature will rise, which will affect the motor's performance, life and safety. At present, the main heat dissipation methods of DC permanent magnet brushless motors include natural cooling, built-in fan cooling and external system cooling. Among them, built-in fan cooling is achieved by the fan or rotor inside the motor driving the fan blades to rotate, blowing cooling air to the air gap between the rotor and stator or inside the motor for heat dissipation.

[0003] For example, Chinese Patent Publication No. CN118713335B discloses a stator structure for a DC permanent magnet brushless motor, relating to the field of motor stator technology. The stator structure includes a ring body with multiple salient poles arranged on its inner sidewall. Windings are wound around the salient poles. The stator structure further includes: a cooling ring, fixedly sleeved on the outer sidewall of the ring body, with a cooling flow channel penetrating both ends of the cooling ring; and a first side ring, located at one end of the cooling ring, with a current-collecting channel corresponding to the cooling flow channel. The current-collecting channel penetrates both ends of the first side ring, with one end close to the cooling flow channel and the other end close to the central axis of the first side ring.

[0004] The cited documents above demonstrate that efficient heat dissipation can be achieved through cooling rings and heat collection channels; additional heat dissipation can also be provided in high-temperature emergency situations.

[0005] However, in the aforementioned cited documents, after the cooling oil is introduced into the cooling channel, the size of the outlet opening cannot be automatically adjusted according to the flow rate of the cooling oil. When the oil flow rate is small, the fixed outlet opening will reduce the flow velocity of the oil in the cooling ring, making it impossible for the oil to fully carry away the heat generated by the stator, resulting in low heat dissipation efficiency. When the oil flow rate is large, the fixed outlet opening cannot match the flow rate change, which can easily cause oil accumulation, increase the overall weight of the motor, and affect the stability of motor operation. Summary of the Invention

[0006] The purpose of this invention is to provide a stator structure for a DC permanent magnet brushless motor that automatically adjusts the size of the oil outlet opening based on the flow rate of cooling oil under different heat generation conditions of the motor stator. This ensures that the cooling oil maintains a suitable flow rate within the cooling ring, guaranteeing that the oil can effectively remove the heat generated by the stator salient pole windings, thereby improving heat dissipation efficiency. At the same time, it avoids oil accumulation when the oil flow rate is too high, ensuring the stability of motor operation.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a stator structure for a DC permanent magnet brushless motor, comprising a cooling ring, and further comprising: An airbag valve is installed at one end of the cooling ring body opening. The airbag valve is used to control the cooling oil to enter the cooling ring body. The salient pole winding is installed on the circumference of the inner wall of the cooling ring. A flow guiding component is installed at the opening of the cooling ring body near the airbag valve. The flow guiding component includes a rotating ring sleeve and is used to uniformly guide the cooling oil inside the cooling ring body. An opening and closing assembly is installed at the opening of the cooling ring body away from the airbag valve. The opening and closing assembly includes a sealing hinge and is used to guide the cooling oil inside the cooling ring body. A synchronization adjustment component is installed outside the opening and closing component. The synchronization adjustment component includes a positioning ring. The opening and closing component is used to synchronize the flow guiding component and the opening and closing component.

[0008] Preferably, the cooling ring body has an annular groove at one end near the opening and closing component, a retaining ring is fixedly installed in the inner wall of the annular groove, and a first side ring is fixedly installed at the opening of the cooling ring body near the opening and closing component.

[0009] Preferably, a second side ring is fixedly installed at the opening of the cooling ring body away from the coupling assembly, the airbag valve is installed on the outside of the second side ring, the rotating ring sleeve is fixedly installed on the inside of the second side ring, and a turbine fan blade is rotatably installed on the inner wall of the rotating ring sleeve.

[0010] Preferably, a first fixing ring is fixedly installed at the shaft center of the turbine blade, and the turbine blade is rotatably mounted on the internal shaft of the cooling ring body through the first fixing ring. A torsion spring is fixedly installed between the first fixing ring and the internal shaft of the cooling ring body.

[0011] Preferably, a second fixing ring is installed at the center of the sealing hinge, and the sealing hinge is rotatably mounted on the internal shaft of the cooling ring body through the second fixing ring. Connecting shafts are fixedly installed on the arc surfaces at both ends of the sealing hinge, and the connecting shafts on the arc surfaces at both ends of the sealing hinge are rotatably mounted between the second fixing ring and the inner wall of the first side ring.

[0012] Preferably, sealing grooves are provided on both sides of the sealing hinge, and adjacent sealing hinges are sealed together through the sealing grooves. A swing block is fixedly installed at the end of the connecting shaft away from the second fixing ring of the sealing hinge.

[0013] Preferably, the positioning ring is movably sleeved outside the first side ring, and both the first side ring and the positioning ring are located in the inner wall of the annular groove with a clearance fit.

[0014] Preferably, a connecting seat is fixedly installed at equal intervals on the outer circumference of the first side ring, and a guide wheel is rotatably installed in the inner wall of the connecting seat, and the positioning ring slides between two adjacent guide wheels.

[0015] Preferably, a linkage rod is fixedly installed at equal intervals on the circumference between the positioning ring and the outer ring surface of the turbine blade, and a connecting protrusion is fixedly installed at equal intervals on the outer circumference of the positioning ring.

[0016] Preferably, a stop plate is fixedly installed at the outer end of the connecting protrusion, and a path roller is rotatably installed on the outside of the connecting protrusion, and the path roller is slidably installed in the inner wall of the corresponding swing block.

[0017] Compared with the prior art, the beneficial effects of the present invention are: In this invention, when the temperature in the brushless motor is high, the opening size of the air bladder valve at one end of the motor rotor increases, allowing cooling oil to enter the cooling ring. After flowing over the surface of the salient pole winding, the cooling oil flows towards the opening and closing assembly. The oil impacts the turbine blades, pushing them to drive the first fixed ring to rotate against the force of the torsion spring. At this time, when the cooling oil passes through the inside of the turbine blades, it impacts the inside of the turbine blades with uniform gaps, ensuring that the rotating turbine blades can evenly deliver the cooling oil forward into the cooling ring. This maintains a suitable flow speed for the cooling oil within the cooling ring, ensuring that the oil can fully remove the heat generated by the stator salient pole winding and improve heat dissipation efficiency.

[0018] In this invention, while the turbine blades rotate, the positioning ring sleeve slides along the outside of the first side ring via the linkage rod. When the positioning ring sleeve slides, it drives the connecting cam to move synchronously. The connecting cam pushes the swing block to rotate around the connecting shaft via the path roller, which in turn drives the sealing hinge to rotate synchronously. This causes the opening size of the sealing hinge to increase with the increase of the turbine blade rotation amplitude, so that the oil outlet opening increases synchronously with the oil flow rate. When the oil flow rate decreases, the torsion spring drives the first fixed ring and the turbine blade to rotate in the opposite direction to reset. The linkage rod pulls the positioning ring sleeve to reset, which in turn drives the sealing hinge to rotate in the opposite direction to reduce the oil outlet opening. This ensures that the cooling oil maintains a suitable flow rate within the cooling ring body, ensuring that the oil can fully remove the heat generated by the salient pole winding, improving heat dissipation efficiency, and preventing oil accumulation when the oil flow rate is too high, thus ensuring the stability of motor operation. Attached Figure Description

[0019] Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2 This is a schematic diagram of the internal structure of the cooling ring in this invention; Figure 3 This is a schematic diagram of the opening and closing component structure in this invention; Figure 4 This is a schematic diagram of the flow guiding component structure in this invention; Figure 5 This is a schematic diagram of the salient pole winding structure in this invention; Figure 6 for Figure 4 A magnified view of the structure at point A in the middle; Figure 7 for Figure 5 A magnified schematic diagram of the structure at point B in the middle.

[0020] In the diagram: 100, Cooling ring; 200, Airbag valve; 300, Salient pole winding; 400, Flow guiding assembly; 500, Opening and closing assembly; 600, Synchronous adjustment assembly; 11, Annular groove; 12, Retaining ring; 13, First side ring; 14, Second side ring; 41, Rotating ring sleeve; 42, Turbine fan blade; 43, Torsion spring; 44, First fixed ring; 51, Sealing hinge; 52, Connecting shaft; 53, Swing block; 511, Second fixed ring; 512, Sealing connecting groove; 61, Positioning ring sleeve; 62, Connecting seat; 63, Guide wheel; 64, Linkage rod; 65, Connecting protrusion; 651, Stop plate; 652, Path roller. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. The described embodiments are only some embodiments of the present invention, and not all embodiments.

[0022] Example 1: This embodiment provides a stator structure for a DC permanent magnet brushless motor, such as... Figures 1-7 As shown, it includes a cooling ring 100, and also includes: The airbag valve 200 is installed at one end of the cooling ring 100 opening. The airbag valve 200 is used to control the cooling oil to enter the cooling ring 100. The salient pole winding 300 is installed on the inner circumference of the cooling ring 100; The flow guiding component 400 is installed at the opening of the cooling ring 100 near the airbag valve 200. The flow guiding component 400 includes a rotating ring sleeve 41. The flow guiding component 400 is used to uniformly guide the cooling oil inside the cooling ring 100. The opening and closing assembly 500 is installed at the opening of the cooling ring 100 away from the airbag valve 200. The opening and closing assembly 500 includes a sealing hinge 51 and is used to guide the flow of cooling oil inside the cooling ring 100.

[0023] Among them, the cooling ring 100 has an annular groove 11 at one end near the opening and closing component 500, and a retaining ring 12 is fixedly installed in the inner wall of the annular groove 11. A first side ring 13 is fixedly installed at the opening of the cooling ring 100 near the opening and closing component 500. The stator of the brushless motor senses the internal temperature of the motor through the air bladder valve 200 at one end of the cooling ring 100. When the internal temperature of the motor is high, the opening of the air bladder valve 200 gradually increases, so that the cooling oil enters the stator and forms a rapid flow state.

[0024] In this design, a second side ring 14 is fixedly installed at one end of the cooling ring 100 away from the opening of the coupling assembly 500. An airbag valve 200 is installed on the outside of the second side ring 14. A rotating ring sleeve 41 is fixedly installed inside the second side ring 14. A turbine blade 42 is rotatably mounted on the inner wall of the rotating ring sleeve 41. A first fixing ring 44 is fixedly installed at the shaft center of the turbine blade 42. The turbine blade 42 is rotatably mounted on the internal shaft of the cooling ring 100 via the first fixing ring 44. A torsion spring 43 is fixedly installed between the first fixing ring 44 and the internal shaft of the cooling ring 100. When the temperature in the brushless motor is high, the motor rotor... The opening size of the airbag valve 200 at the end is increased, allowing the cooling oil to enter the cooling ring 100. After flowing over the surface of the salient pole winding 300, the cooling oil flows towards the opening and closing assembly 500. The oil impacts the turbine blade 42, pushing the turbine blade 42 to drive the first fixed ring 44 to rotate against the elastic force of the torsion spring 43. At this time, when the cooling oil passes through the inside of the turbine blade 42, it impacts the inside of the turbine blade 42 with uniform gaps, so that the cooling oil always maintains a suitable flow speed in the cooling ring 100, ensuring that the oil can fully remove the heat generated by the stator salient pole winding 300 and improve the heat dissipation efficiency.

[0025] The sealing hinge 51 has a second fixing ring 511 installed at its axis. The sealing hinge 51 is rotatably mounted on the internal shaft of the cooling ring body 100 via the second fixing ring 511. Connecting shafts 52 are fixedly installed on the arc surfaces at both ends of the sealing hinge 51. These connecting shafts 52 are rotatably mounted between the second fixing ring 511 and the inner wall of the first side ring 13. Sealing grooves 512 are provided at the edges of both sides of the sealing hinge 51. Adjacent sealing hinges 51 are sealed together via the sealing grooves 512. A swing block 53 is fixedly installed at the end of the connecting shaft 52 away from the second fixed ring 511. When the turbine fan blade 42 rotates, the positioning ring sleeve 61 is driven to slide along the outside of the first side ring 13 through the linkage rod 64. When the positioning ring sleeve 61 slides, it drives the connecting protrusion 65 to move synchronously. The connecting protrusion 65 pushes the swing block 53 to rotate around the connecting shaft 52 through the path roller 652, thereby driving the sealing hinge 51 to rotate synchronously. This makes the opening size of the sealing hinge 51 increase with the increase of the rotation amplitude of the turbine fan blade 42, so that the oil outlet opening increases synchronously with the oil flow rate.

[0026] In this embodiment, when the temperature in the brushless motor is high, the opening size of the air bladder valve 200 at one end of the motor rotor increases, allowing cooling oil to enter the cooling ring 100. After flowing over the surface of the salient pole winding 300, the cooling oil flows towards the opening and closing assembly 500. The oil impacts the turbine blade 42, pushing the turbine blade 42 to drive the first fixed ring 44 to rotate against the elastic force of the torsion spring 43. At this time, when the cooling oil passes through the inside of the turbine blade 42, it impacts the inside of the turbine blade 42 with uniform gaps, so that when the turbine blade 42 rotates, it can evenly deliver the cooling oil forward into the cooling ring 100, so that the cooling oil always maintains a suitable flow speed in the cooling ring 100, ensuring that the oil can fully remove the heat generated by the stator salient pole winding 300 and improve the heat dissipation efficiency.

[0027] Example 2: Based on Example 1, this example provides a stator structure for a DC permanent magnet brushless motor, such as... Figures 3-7 As shown, it includes: Synchronous adjustment component 600 is installed outside opening and closing component 500. Synchronous adjustment component 600 includes positioning ring sleeve 61. Opening and closing component 500 is used to synchronize and link flow guiding component 400 and opening and closing component 500.

[0028] The positioning ring sleeve 61 is movably fitted outside the first side ring 13. Both the first side ring 13 and the positioning ring sleeve 61 are located in the inner wall of the annular groove 11 with a clearance fit. Connecting seats 62 are fixedly installed at equal intervals on the outer circumference of the first side ring 13. Guide wheels 63 are rotatably installed in the inner wall of the connecting seats 62. The positioning ring sleeve 61 slides between two adjacent guide wheels 63. Linkage rods 64 are fixedly installed at equal intervals on the circumference between the positioning ring sleeve 61 and the outer ring surface of the turbine blade 42. Connecting protrusions 65 are fixedly installed at equal intervals on the outer circumference of the positioning ring sleeve 61. A stop plate 651 is fixedly installed at the outer end of the connecting protrusion 65. A path roller 652 is externally mounted and slidably installed in the inner wall of the corresponding swing block 53. When the oil flow rate decreases, the torsion spring 43 drives the first fixed ring 44 and the turbine fan blade 42 to rotate in the opposite direction and reset. The linkage rod 64 pulls the positioning ring sleeve 61 to reset, which in turn drives the sealing hinge 51 to rotate in the opposite direction and reduce the oil outlet opening. This ensures that the cooling oil maintains a suitable flow rate in the cooling ring 100, ensuring that the oil can fully carry away the heat generated by the salient pole winding 300, improving the heat dissipation efficiency. At the same time, it avoids oil accumulation when the oil flow rate is too large, ensuring the stability of motor operation.

[0029] In this embodiment, while the turbine blade 42 rotates, the positioning ring sleeve 61 slides along the outside of the first side ring 13 via the linkage rod 64. When the positioning ring sleeve 61 slides, it drives the connecting protrusion rod 65 to move synchronously. The connecting protrusion rod 65 pushes the swing block 53 to rotate around the connecting shaft 52 via the path roller 652, thereby driving the sealing hinge 51 to rotate synchronously. This makes the opening size of the sealing hinge 51 increase with the increase of the rotation amplitude of the turbine blade 42, so that the oil outlet opening increases synchronously with the oil flow rate. When the oil flow rate decreases, the torsion spring 43 drives the first fixed ring 44 and the turbine blade 42 to rotate in the opposite direction to reset. The linkage rod 64 pulls the positioning ring sleeve 61 to reset, thereby driving the sealing hinge 51 to rotate in the opposite direction to reduce the oil outlet opening. This ensures that the cooling oil maintains a suitable flow speed within the cooling ring 100, ensuring that the oil can fully carry away the heat generated by the salient pole winding 300, improving heat dissipation efficiency, and preventing oil accumulation when the oil flow rate is too high, thus ensuring the stability of motor operation.

[0030] Working principle: When this type of DC permanent magnet brushless motor stator structure is in use, when the stator salient pole winding 300 generates heat and the overall temperature of the motor rises, the air bladder inside the air bladder valve 200 expands due to heat, automatically opening a larger opening to allow more cooling oil to enter the cooling ring 100. The cooling oil flows along the axial direction of the cooling ring 100, passing over the surface of all salient pole windings 300, carrying away the heat generated by the salient pole windings 300 during operation, and then flows towards the oil outlet. Before entering the salient pole winding 300, the oil impacts the turbine blade 42 of the flow guide assembly 400. The greater the oil flow rate, the greater the impact force on the turbine blade 42, the greater the rotation amplitude of the turbine blade 42, and the greater the angle of rotation to overcome the spring force of the torsion spring 43. After the turbine blade 42 rotates, the gap between its blades increases, which not only allows more oil to pass through evenly, but also guides the oil evenly to various areas within the cooling ring 100 through its own rotation, thus avoiding the oil from concentrating in some areas and causing uneven local heat dissipation. While the turbine blade 42 rotates, it pulls the positioning ring sleeve 61 to slide along the outside of the first side ring 13 through multiple linkage rods 64. The guide wheel 63 supports and limits the positioning ring sleeve 61 to ensure that the positioning ring sleeve 61 slides smoothly without jamming. After the positioning ring sleeve 61 slides and drives the connecting protrusion 65 to move synchronously, the path roller 652 slides along the inner wall of the swing block 53, pushing the swing block 53 to rotate around the connecting shaft 52, and then synchronously drives all the sealing hinges 51 to rotate and open synchronously. The greater the oil flow, the greater the rotation amplitude of the turbine blade 42, and the larger the oil outlet opening of the sealing hinges 51, so that the oil outlet speed increases synchronously with the oil inlet speed, avoiding the accumulation of oil in the cooling ring 100, increasing the overall weight of the motor and affecting the operational stability. When the stator heat generation decreases and the temperature drops, the air bladder valve 200 contracts, reducing the opening and decreasing the flow rate of the incoming oil. The torsion spring 43 drives the turbine fan blade 42 to reset and rotate. The turbine fan blade 42 pulls the positioning ring sleeve 61 to reset via the linkage rod 64, which in turn drives the sealing hinge 51 to rotate synchronously, reducing the oil outlet opening. This allows the cooling oil to maintain a suitable flow rate, ensuring that the remaining heat is fully carried away. It also prevents the oil flow rate from being too low and the flow rate from being too high, which would prevent sufficient heat absorption and ensure heat dissipation efficiency.

[0031] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes and modifications can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A stator structure for a DC permanent magnet brushless motor, comprising a cooling ring (100), characterized in that, Also includes: An airbag valve (200) is installed at one end of the cooling ring (100) opening. The airbag valve (200) is used to control the cooling oil to enter the cooling ring (100). A salient pole winding (300) is installed on the inner circumference of the cooling ring (100); A flow guiding assembly (400) is installed at the opening of the cooling ring (100) near the airbag valve (200). The flow guiding assembly (400) includes a rotating ring sleeve (41). The flow guiding assembly (400) is used to uniformly guide the cooling oil inside the cooling ring (100). An opening and closing assembly (500) is installed at the opening of the cooling ring (100) away from the airbag valve (200). The opening and closing assembly (500) includes a sealing hinge (51). The opening and closing assembly (500) is used to guide the cooling oil inside the cooling ring (100) to flow. A synchronous adjustment component (600) is installed outside the opening and closing component (500). The synchronous adjustment component (600) includes a positioning ring (61). The opening and closing component (500) is used to synchronously link the flow guiding component (400) and the opening and closing component (500).

2. The stator structure of a DC permanent magnet brushless motor according to claim 1, characterized in that: The cooling ring (100) has an annular groove (11) at one end near the opening and closing component (500), and a retaining ring (12) is fixedly installed in the inner wall of the annular groove (11). A first side ring (13) is fixedly installed at the opening of the cooling ring (100) near the opening and closing component (500).

3. The stator structure of a DC permanent magnet brushless motor according to claim 2, characterized in that: The cooling ring (100) is fixedly installed with a second side ring (14) at one end of the opening of the coupling assembly (500). The airbag valve (200) is installed on the outside of the second side ring (14). The rotating ring sleeve (41) is fixedly installed on the inside of the second side ring (14). A turbine fan blade (42) is rotatably installed on the inner wall of the rotating ring sleeve (41).

4. The stator structure of a DC permanent magnet brushless motor according to claim 3, characterized in that: A first fixing ring (44) is fixedly installed at the shaft center of the turbine fan blade (42). The turbine fan blade (42) is rotatably mounted on the internal shaft of the cooling ring body (100) through the first fixing ring (44). A torsion spring (43) is fixedly installed between the first fixing ring (44) and the internal shaft of the cooling ring body (100).

5. The stator structure of a DC permanent magnet brushless motor according to claim 4, characterized in that: A second fixing ring (511) is installed at the center of the sealing hinge (51). The sealing hinge (51) is rotatably mounted on the inner shaft of the cooling ring body (100) through the second fixing ring (511). Connecting shafts (52) are fixedly installed on the arc surfaces at both ends of the sealing hinge (51). The connecting shafts (52) on the arc surfaces at both ends of the sealing hinge (51) are rotatably mounted between the second fixing ring (511) and the inner wall of the first side ring (13).

6. The stator structure of a DC permanent magnet brushless motor according to claim 5, characterized in that: Sealing joint grooves (512) are provided on both sides of the sealing hinge (51). Adjacent sealing hinges (51) are sealed and fitted through the sealing joint grooves (512). A swing block (53) is fixedly installed at the end of the connecting shaft (52) of the sealing hinge (51) away from the second fixing ring (511).

7. The stator structure of a DC permanent magnet brushless motor according to claim 6, characterized in that: The positioning ring sleeve (61) is movably sleeved outside the first side ring (13), and the first side ring (13) and the positioning ring sleeve (61) are both located in the inner wall of the annular groove (11) with a clearance fit.

8. The stator structure of a DC permanent magnet brushless motor according to claim 7, characterized in that: A connecting seat (62) is fixedly installed at equal intervals on the outer circumference of the first side ring (13). A guide wheel (63) is rotatably installed in the inner wall of the connecting seat (62). The positioning ring sleeve (61) slides between two adjacent guide wheels (63).

9. The stator structure of a DC permanent magnet brushless motor according to claim 8, characterized in that: A linkage rod (64) is fixedly installed at equal intervals on the circumference between the positioning ring sleeve (61) and the outer ring surface of the turbine fan blade (42), and a connecting protrusion rod (65) is fixedly installed at equal intervals on the outer circumference of the positioning ring sleeve (61).

10. The stator structure of a DC permanent magnet brushless motor according to claim 9, characterized in that: A stop plate (651) is fixedly installed at the outer end of the connecting protrusion (65), and a path roller (652) is rotatably installed on the outside of the connecting protrusion (65). The path roller (652) is slidably installed in the inner wall of the corresponding swing block (53).

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