Magnetic coupling gearless speed reducer

Abstract

The application discloses a kind of magnetic coupling gearless speed reducer and its torque equalization control method, speed reducer includes drive motor assembly, two-stage magnetic coupling transmission assembly, torque equalization adjusting assembly, sealed housing assembly;Rotor body lower end installs first permanent magnet and first magnetic coupling disc and transmission shaft, second permanent magnet and second magnetic coupling disc and complete two-stage magnetic coupling deceleration;Torque equalization adjusting assembly sets up the magnetic convergence plate of left, right area of different sheltering area, using electromagnet and the like drive actuator, cooperate reset spring changes the effective sheltering area of magnetic convergence plate to magnet;Control method is according to normal rotation, reverse rotation, standby, different operating conditions of stop, dynamically adjust the position of magnetic convergence plate, adjust the magnetic coupling torque of positive direction and reverse direction;The application cancels gear structure, no wear, lubrication-free, transmission precision is high;Active equalization positive, reverse output torque can effectively improve the heavy load capacity of magnetic coupling speed reducer, can expand multi-stage deceleration structure, applicable to industrial servo, precision conveying, new energy power deceleration scene.

Description

Technical Field

[0001] This invention relates to the field of speed reduction and transmission machinery technology, and in particular to a magnetically coupled gearless speed reducer. It also relates to a bidirectional torque equalization control method for the speed reducer, which is applicable to industrial servo equipment, precision conveying, and new energy power speed reduction scenarios. Background Technology

[0002] Traditional gear reducers rely on gear meshing for power transmission, inevitably suffering from mechanical wear, high operating noise, high processing and assembly costs, reduced positioning accuracy due to tooth backlash, and the need for lubrication, which is prone to oil leakage and contamination. Existing gearless magnetic transmission reducers mostly employ a fixed magnet coupling transmission structure, which cannot separately adjust the magnetic coupling force under forward and reverse rotation conditions. The difference between the forward and reverse output torque is significant, resulting in limited overall load-bearing capacity. They are generally only applicable to light-load, low-speed conditions and cannot replace traditional gear reducers in heavy-duty industrial applications. Currently, the industry lacks a magnetically coupled gearless reducer that can balance forward and reverse output torque, has high load-bearing capacity, and requires no lubrication, along with a corresponding torque balancing control method. Summary of the Invention

[0003] Purpose of the invention The purpose of this invention is to overcome the shortcomings of existing gear reducers, such as wear and oil leakage, poor positioning accuracy, large difference in forward and reverse torque, and insufficient heavy load capacity of existing gearless magnetic reducers. This invention provides a magnetically coupled gearless reducer and a control method that can balance the forward and reverse output torque.

[0004] I. Product Solution A magnetically coupled gearless reducer includes a drive motor assembly, a two-stage magnetically coupled transmission assembly, a torque equalization adjustment assembly, and a sealed housing assembly. The drive motor assembly includes a housing stator and a rotor assembly, with a first permanent magnet fixed at the lower end of the rotor body of the rotor assembly; The two-stage magnetic coupling transmission assembly includes a first magnetic coupling disk and a second magnetic coupling disk; a transmission shaft is assembled inside the first magnetic coupling disk, and a second magnet is fixed at the lower end of the transmission shaft; an output shaft for power output is assembled inside the second magnetic coupling disk; the first permanent magnet and the first magnetic coupling disk, and the second magnet and the second magnetic coupling disk, rely on magnetic coupling to form a two-stage reduction transmission structure. The sealing housing assembly includes a first toothed shell, a second toothed shell, and a toothed shell rear cover. The first toothed shell has a sliding groove, and the toothed shell rear cover has a sliding groove. The torque equalization adjustment component is an adjustable magnetic concentrator component, which includes a magnetic concentrator plate, a connecting arm that serves as a sliding guide, a fixed plate, an electromagnetic drive component, a guide rail, a return spring, and a protective baffle. The connecting arm is provided with a sliding column, which passes through the first sliding groove and the second sliding groove respectively. A positioning shaft, a bearing, and a sealing end cap are mounted on the sliding column. The magnetic plate is radially divided into a left region and a right region with unequal blocking areas; the electromagnetic drive drives the magnetic plate to move along the slide groove, changing the blocking area of ​​the magnetic plate on the first permanent magnet and the second magnet; the reset spring is used to drive the magnetic plate to reset after the electromagnetic drive is de-energized. The torque adjustment drive structure consists of an electromagnetic drive component and a shape memory alloy drive component.

[0005] Furthermore, a transmission unit consisting of a gear housing, a magnetic coupling disk, a drive shaft, bearings, a permanent magnet, and an adjustable magnetic assembly is added. The transmission unit is installed between the first gear housing and the second gear housing, thereby forming a magnetically coupled multi-stage deceleration structure.

[0006] Furthermore, an oil seal chamber is provided inside the second tooth housing, and an oil seal is installed in the oil seal chamber; sealing gaskets are installed on the mating surfaces of the first and second tooth housings; wiring holes are provided on the first tooth housing and the rear cover of the tooth housing; the wiring holes are used to supply power to the electromagnetic drive component.

[0007] Furthermore, the connecting arm includes a sliding column, a positioning shaft, bearings, and a sealing end cap; the sliding column passes through the first sliding groove of the first tooth housing and the second sliding groove of the tooth housing rear cover, the positioning shaft is mounted on the upper end of the sliding column, and bearings are press-fitted at both ends of the positioning shaft; the bearings roll on the front side of the first tooth housing and the front side of the tooth housing rear cover, and the connecting arm is rigidly connected to the magnetic plate and the fixing plate; the protective baffle is fixedly installed on the reverse side and the reverse side of the tooth housing rear cover, the guide rail is fitted with a return spring, and the two ends of the guide rail are respectively connected to the fixing plate and the protective baffle.

[0008] Furthermore, a flat key is used to achieve circumferential positioning between the first magnetic coupling disk and the drive shaft, and between the second magnetic coupling disk and the output shaft; the drive shaft and the output shaft are respectively provided with keyways and snap ring slots to achieve axial positioning of the components; an assembly step is provided inside the first gear housing, and the bearing abuts against the assembly step to complete axial positioning.

[0009] Furthermore, the first magnetic coupling disk and the second magnetic coupling disk are groove-shaped. The first magnetic coupling disk and the rotor body, and the second magnetic coupling disk and the transmission shaft are in a relationship where the lower end face of the rotor body and the lower end face of the transmission shaft do not contact the bottom of the groove. The first magnetic coupling disk and the second magnetic coupling disk are made of soft magnetic material.

[0010] Furthermore, a permanent magnet is fitted into the magnetic concentrator plate, with the outer periphery of the permanent magnet being nearly tangent to the magnetic coupling disk, and a certain gap being maintained between the outer periphery of the permanent magnet and the inner ring of the magnetic concentrator plate, and between the outer ring of the magnetic concentrator plate and the magnetic coupling disk.

[0011] Furthermore, the centers of the permanent magnet and the magnetic concentrator plate, and the magnetic concentrator plate and the magnetic coupling disk are designed to be on the same meridian, and the magnetic concentrator plate is divided into a left region and a right region according to this meridian.

[0012] II. Control Methods and Schemes A torque equalization control method for a magnetically coupled gearless reducer includes the following steps: S1. When the equipment is powered on and in standby mode, the reset spring pushes the magnetic plate to maintain the initial position. The area on the left side of the magnetic plate that blocks the first and second permanent magnets is larger than the area on the right side. S2. The controller receives the forward rotation command, the electromagnetic drive remains de-energized, the magnetic plate remains in the initial position, the magnetic coupling force on the left side of the first permanent magnet and the left side of the second permanent magnet is less than that on the right side, and the reducer outputs positive torque. S3. When the controller receives the reverse operation command, it controls the electromagnetic drive to be energized and move, pulling the magnetic plate to move along the slide. The right side of the magnetic plate blocks the first and second permanent magnets more than the left side, and the reverse magnetic coupling torque is increased, so that the reverse output torque and the forward output torque tend to be balanced. S4. After the shutdown command is issued, the electromagnetic drive is de-energized, and the reset spring pulls the magnetic plate to automatically reset to the initial standby position.

[0013] Furthermore, when an electromagnet is selected as the electromagnetic drive component, the electromagnet is continuously energized after receiving a reversal command; when a shape memory alloy drive component is selected as the torque adjustment drive structure, the shape memory alloy is continuously energized and heated after receiving a reversal command; after the machine stops, the heating stops, the shape memory alloy cools and deforms, and together with the reset spring, it drives the magnetic plate to complete the reset.

[0014] 1. Magnetic coupling gearless transmission completely eliminates gear meshing, resulting in no mechanical wear, low operating noise, no need for lubrication, avoidance of leakage and pollution, and a significant reduction in operation and maintenance costs; 2. Zero tooth backlash, high transmission repeatability and positioning accuracy, precise reduction ratio calculation, and suitable for precision servo equipment; 3. A sliding magnetic plate torque adjustment mechanism is adopted, along with a matching control method, to dynamically adjust the magnetic coupling torque in the forward and reverse directions, significantly reducing the difference in output torque between the forward and reverse rotation of the reducer and improving the heavy load-bearing capacity of the equipment; 4. The torque adjustment has two execution schemes: electromagnet electric control and shape memory alloy thermal control, which are suitable for different installation and electric control scenarios, and the product has strong versatility; 5. Simplified component structure and assembly process reduce processing and mass production costs; 6. This invention protects both the product hardware structure and the torque balance control method, thus expanding the scope of patent protection. Attached Figure Description

[0015] Figure 1: Schematic cross-sectional view of the overall structure of the present invention; Figure 2: Three-dimensional structural diagram of the rotor assembly; Figure 3: Three-dimensional structural diagram of the first toothed shell; Figure 4: Three-dimensional structural diagram of the second toothed shell; Figure 5: Structural diagrams of the front and back sides of the toothed shell rear cover; Figure 6: Schematic diagram of the assembly of the first magnetic coupling disk and the drive shaft; Figure 7: Schematic diagram of the assembly of the second magnetic coupling disk and the output shaft; Figure 8: Exploded view of the adjustable magnetic flux assembly; Figure 9: Schematic diagram of the torque adjustment principle of the magnetic plate; Reference numerals: 10 - Stator housing, 20 - Rotor assembly, 21 - Rotor body, 22 - Permanent magnet, 23 - Bearing, 24 - Snap ring, 30 - First gear housing, 301 - First groove, 302 - Wiring hole, 32 - Bearing, 40 - Second gear housing, 41 - Gasket, 42 - Oil seal, 50 - Gear housing rear cover, 501, 502 - Wiring holes, 503 - Second groove, 504, 505 - Bearing chamber, 506 - Threaded mounting hole, 52 - Gasket, 60 - First magnetic coupling disk, 601 - Shaft hole, 602 - Groove, 61 - Drive shaft, 611 - Keyway, 62 - Second permanent magnet, 70 - Second magnetic coupling disk, 701 - Shaft hole, 702 - Groove, 71 - Bearing, 72 - Output shaft, 721 - Keyway, 722 - 80 - Adjustable magnetic assembly, 81 - Magnetic plate, 811 - Left side area, 812 - Right side area, 82 - Connecting arm, 821 - Slide column, 822 - Positioning shaft, 823 - Bearing, 824 - Sealed end cap, 83 - Electromagnetic drive component, 84 - Fixing plate, 85 - Protective baffle, 86 - Guide rail, 87 - Return spring. Detailed Implementation

[0016] The present invention will now be described in further detail with reference to the accompanying drawings and embodiments.

[0017] Example 1: Electromagnet-driven magnetic plate scheme A magnetically coupled gearless reducer includes a drive motor assembly, a two-stage magnetically coupled transmission assembly, a torque equalization adjustment assembly, and a sealed housing assembly. The drive motor assembly includes a housing stator 10 and a rotor assembly 20, with a first permanent magnet 22 fixed at the lower end of the rotor body 21. The two-stage magnetic coupling transmission assembly includes a first magnetic coupling disk 60 and a second magnetic coupling disk 70; a transmission shaft 61 is assembled inside the first magnetic coupling disk 60, and a second permanent magnet 62 is fixed at the lower end of the transmission shaft 61; an output shaft 72 for power output is assembled inside the second magnetic coupling disk 70; the first permanent magnet 22 is magnetically coupled to the first magnetic coupling disk 60, and the second permanent magnet 62 is magnetically coupled to the second magnetic coupling disk 70, forming a two-stage reduction transmission structure. The sealing housing assembly includes a first toothed housing 30, a second toothed housing 40, and a toothed housing rear cover 50. The first toothed housing 30 has a sliding groove 301, and the toothed housing rear cover 50 has a sliding groove 503. The torque equalization adjustment component is an adjustable magnetic concentrator component 80, which includes a magnetic concentrator plate 81, a connecting arm 82 that serves as a sliding guide, an electromagnetic drive component 83, a fixing plate 84, a protective baffle 85, a guide rail 86, and a return spring 87. The connecting arm 82 is rigidly connected to the magnetic concentrator plate 81 and the fixing plate 84. The connecting arm 82 is provided with a sliding column 821, which passes through the first sliding groove 301 and the second sliding groove 503 respectively. The sliding column 821 is equipped with a positioning shaft 822, a bearing 823, and a sealing end cap 824. The bearing 823 rolls on the front side of the first toothed housing 30 and the front side of the toothed housing rear cover 50 respectively. The protective baffle 85 is fixedly installed on the back side of the first toothed housing 30 and the back side of the toothed housing rear cover 50. The guide rail 86 is fitted with the return spring 87, and the two ends of the guide rail 86 are respectively connected to the fixing plate 84 and the protective baffle 85. The magnetic plate 81 is radially divided into a left region 811 and a right region 812 with unequal shielding areas; after the electromagnetic drive 83 is powered on, it drives the magnetic plate 81 to move along the slide groove, changing the shielding area of ​​the magnetic plate 81 on the first permanent magnet 22 and the second magnet 62; the reset spring 87 is used to drive the magnetic plate 81 to reset after the electromagnetic drive 83 is powered off.

[0018] The first magnetic coupling disk 60 and the drive shaft 61, and the second magnetic coupling disk 70 and the output shaft 72 are circumferentially positioned by a flat key. The drive shaft 61 has a keyway 611 and a snap ring groove, and the output shaft 72 has a keyway 721 and a snap ring groove 722 to achieve axial positioning. The first gear housing 30 is provided with an assembly step for positioning the bearing 32, and the second gear housing 40 is provided with an assembly step for positioning the bearing 71. The second gear housing 40 has an internal oil seal chamber for installing an oil seal 42. A sealing gasket 52 is added to the mating surface of the first gear housing 30, and a sealing gasket 41 is added to the mating surface of the second gear housing 40. The first gear housing 30 has a reserved wiring hole 302, and the gear housing rear cover 50 has reserved wiring holes 501 and 502.

[0019] The torque equalization control process in this embodiment is as follows: S1. When the equipment is powered on and in standby mode, the reset spring 87 pushes the magnetic plate 81 to maintain the initial position. The area of ​​the left side region 811 of the magnetic plate 81 that blocks the first permanent magnet 22 and the second magnet 62 is larger than the right side region 812. S2. The controller receives the forward rotation command, the electromagnetic drive 83 remains de-energized, the magnetic plate 81 maintains the initial position, the magnetic coupling force on the left side of the first permanent magnet 22 and the second magnet 62 is less than that on the right side, and the reducer outputs positive torque. S3. When the controller receives the reverse operation command, the electromagnetic drive 83 is energized, which pulls the magnetic plate 81 to move along the slide. The area of ​​the right side region 812 of the magnetic plate that blocks the first permanent magnet 22 and the second magnet 62 is larger than that of the left side region 811, and the reverse magnetic coupling torque is improved, so that the reverse output torque and the forward output torque tend to be balanced. S4. After the shutdown command is issued, the electromagnetic drive component 83 is de-energized, and the reset spring 87 pulls the magnetic plate 81 to automatically reset to the initial standby position.

[0020] In this embodiment, a transmission unit can be added between the first gear housing 30 and the second gear housing 40 to achieve multi-stage deceleration. Each newly added transmission unit is equipped with an independent adjustable magnetic component.

[0021] Example 2: Shape memory alloy driven magnetic plate solution The main mechanical structure of this embodiment is basically the same as that of embodiment 1, except that the electromagnetic drive is replaced by an electrically heated shape memory alloy drive; one end of the shape memory alloy is connected to the magnetic plate 81 and the other end is fixed to the protective baffle 85, and the heating power supply line is led out through the wiring hole of the housing.

[0022] The torque equalization control process in this embodiment is as follows: S1. When the equipment is powered on and in standby mode, the reset spring 87 pushes the magnetic plate 81 to maintain the initial position. The area of ​​the left side region 811 of the magnetic plate 81 that blocks the first permanent magnet 22 and the second magnet 62 is larger than the right side region 812. S2. The controller receives the forward rotation command, the shape memory alloy remains unpowered and unheated, the magnetic plate 81 maintains the initial position, and the reducer outputs positive torque; S3. When the controller receives the reverse operation command, the controller continuously heats the shape memory alloy. The alloy shrinks due to heat and pulls the magnetic plate 81 to slide. The area of ​​the right side region 812 of the magnetic plate 81 that blocks the first permanent magnet 22 and the second magnet 62 is larger than that of the left side region 811. The reverse magnetic coupling torque increases and the positive and negative torques tend to be balanced. S4. After the shutdown command is issued, heating stops and the shape memory alloy cools down naturally to restore its original shape. Together with the reset spring 87, it drives the magnetic plate 81 to reset.

[0023] Working principle The rotor body 21 drives the first permanent magnet 22 to rotate, relying on the magnetic field attraction to drive the first magnetic coupling disk 60 and the transmission shaft 61 to complete the first stage of speed reduction; the transmission shaft 61 drives the second magnet 62 to rotate synchronously, and the magnetic force drives the second magnetic coupling disk 40 and the output shaft 72 to complete the second stage of speed reduction, with the power output by the output shaft 72. The magnetic plate 81 slides to change the effective shielding area of ​​the first permanent magnet 22 and the second magnet 62, adjusting the magnitude of the magnetic coupling force in the two rotation directions, thereby balancing the output torque in both directions and solving the problem of excessive difference in bidirectional torque in traditional fixed magnetic coupling mechanisms.

[0024] Formula for calculating multi-stage reduction ratio: i=(S1 / s1)×(S2 / s2)×…×(Sn / sn) Where: S1 is the circumference of the tangent plane of the first magnetic coupling disk 60; s1 is the outer diameter circumference of the first permanent magnet 22; S2 is the circumference of the tangent plane of the second magnetic coupling disk 70; s2 is the outer diameter circumference of the second permanent magnet 62; Sn is the circumference of the tangent plane of the nth magnetic coupling disk; sn is the outer diameter circumference of the nth permanent magnet; n is the total number of stages of the transmission unit.

Claims

1. A magnetically coupled gearless reducer, characterized in that, Includes drive motor assembly, two-stage magnetic coupling transmission assembly, torque equalization adjustment assembly, and sealed housing assembly; The drive motor assembly includes a housing stator (10) and a rotor assembly (20), with a first permanent magnet (22) fixed at the lower end of the rotor body (21) of the rotor assembly (20); The two-stage magnetic coupling transmission assembly includes a first magnetic coupling disk (60) and a second magnetic coupling disk (70); a transmission shaft (61) is assembled inside the first magnetic coupling disk (60), and a second permanent magnet (62) is fixed at the lower end of the transmission shaft (61); an output shaft (72) for power output is assembled inside the second magnetic coupling disk (70); the first permanent magnet (22) is magnetically coupled with the first magnetic coupling disk (60), and the second permanent magnet (62) is magnetically coupled with the second magnetic coupling disk (70), thus forming a two-stage reduction transmission; The sealing housing assembly includes a first toothed housing (30), a second toothed housing (40), and a toothed housing rear cover (50). The first toothed housing (30) has a first groove (301), and the toothed housing rear cover (50) has a second groove (503). The torque equalization adjustment component is an adjustable magnetic assembly (80). After the sliding column (821) passes through the first sliding groove (301) and the second sliding groove (503) respectively, a positioning shaft (822), a bearing (823) and a sealing end cap (824) are installed. The adjustable magnetic assembly (80) includes a magnetic plate (81), a sliding guide connecting arm (82), an electromagnetic drive (83) and a return spring (87). The magnetic plate (81) is radially divided into two regions: a left region (811) and a right region (812) with unequal shielding areas. The electromagnetic drive (83) drives the magnetic plate (81) to move along the sliding groove, changing the shielding area of ​​the magnetic plate (81) on the first permanent magnet (22) and the second permanent magnet (62). The return spring (87) is used to drive the magnetic plate (81) to reset when the power is turned off. The torque adjustment drive structure can be implemented using an electromagnetic drive (83) or a shape memory alloy drive, and the two can be used interchangeably.

2. The magnetically coupled gearless reducer according to claim 1, characterized in that: A combination of a gear housing, a magnetic coupling disk, a drive shaft, a bearing, a permanent magnet, and an adjustable magnetic assembly (80) is added and installed between the first gear housing (30) and the second gear housing (40) to form a magnetically coupled multi-stage deceleration.

3. The magnetically coupled gearless reducer according to claim 1, characterized in that: The second toothed housing (40) has an oil seal chamber inside, and the oil seal chamber is equipped with an oil seal (42); the mating surfaces of the housing are all equipped with sealing gaskets, and wiring holes are opened in the housing for power supply of the electromagnetic drive component.

4. The magnetically coupled gearless reducer according to claim 1, characterized in that: The connecting arm (82) includes a sliding column (821), a positioning shaft (822), a bearing (823), and a sealing end cap (824). After the sliding column (821) passes through the housing groove, its bearing (823) rolls freely on the front of the first toothed housing (30) and the front of the toothed housing rear cover (50). The connecting arm (82) is rigidly fixed to the magnetic plate (81) and the fixing plate (84). The torque equalization adjustment assembly also includes a fixing plate (84), a protective baffle (85), and a guide rail (86). The two ends of the return spring (87) are connected to the fixing plate (84) and the protective baffle (85) respectively.

5. A magnetically coupled gearless reducer according to claim 1, characterized in that: The first magnetic coupling disk (30) and the drive shaft (61), and the second magnetic coupling disk (40) and the output shaft (72) are circumferentially positioned by a flat key; the drive shaft (61) and the output shaft (72) are both provided with keyways and snap ring slots to achieve axial positioning of each component; an assembly step is provided inside the housing, and the bearing abuts against the step to complete axial positioning.

6. A magnetically coupled gearless reducer according to claim 1, characterized in that: The first magnetic coupling disk (60) and the second magnetic coupling disk (70) are groove-shaped. The first magnetic coupling disk (60) and the rotor body (21) and the second magnetic coupling disk (70) and the transmission shaft (61) are in a relationship based on the fact that the lower end face of the rotor body (21) and the lower end face of the transmission shaft (61) do not contact the bottom of the groove. The first magnetic coupling disk (60) and the second magnetic coupling disk (70) are made of soft magnetic material.

7. A magnetically coupled gearless reducer according to claim 1, characterized in that: The magnetic plate (81) is fitted with a permanent magnet. The outer periphery of the permanent magnet is nearly tangent to the magnetic coupling disk, and the outer periphery of the permanent magnet and the inner ring of the magnetic plate (81), as well as the outer ring of the magnetic plate (81) and the magnetic coupling disk, are all kept at a gap.

8. A torque equalization control method applied to the magnetically coupled gearless reducer according to any one of claims 1 to 7, characterized in that, Includes the following steps: S1. When the device is powered on and in standby mode, the reset spring (87) pushes the magnetic plate (81) to maintain the initial position. The area of ​​the left side region (811) of the magnetic plate (81) that blocks the first permanent magnet (22) and the second permanent magnet (62) is larger than the area on the right side (812). S2. When the controller receives the forward rotation command, the electromagnetic drive (83) is de-energized, the magnetic plate (81) maintains the initial position, the magnetic coupling force on the left side of the first permanent magnet (22) and the left side of the second permanent magnet (62) is less than that on the right side, and the positive torque is output. S3. The controller receives the reverse operation command and controls the electromagnetic drive (83) to be energized and pull the magnetic plate (81) to move along the slide. The area (812) on the right side of the magnetic plate (81) blocks the area of ​​the first permanent magnet (22) and the second permanent magnet (62) which is larger than the area on the left side (811), thereby increasing the reverse magnetic coupling torque and outputting a reverse power that is close to the forward torque. S4. After the shutdown command is issued, the electromagnetic drive (83) is de-energized, and the reset spring (87) pulls the magnetic plate (81) to automatically return to the initial standby position.

9. The torque equalization control method according to claim 8, characterized in that: When the electromagnetic drive unit (83) is an electromagnet, the electromagnet corresponding to the reverse command is continuously energized; When the electromagnetic drive (83) is replaced with a shape memory alloy, the reverse command corresponds to the continuous heating of the alloy. After the machine stops, the heating stops, and the alloy cools and deforms, causing the magnetic plate (81) to reset.

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