Electric spindle for horizontal numerical control lathe

Abstract

This utility model belongs to the field of metal cutting technology, and in particular to an electric spindle for a horizontal CNC lathe, including a spindle box, spindle, hollow tie rod, three-jaw chuck, packing, front flange, rear flange, front bearing assembly, motor assembly, rear bearing assembly, encoder assembly, brake assembly, hydraulic cylinder assembly, and drainage assembly. The spindle box is equipped with heat dissipation grooves and water inlet / outlet holes, allowing coolant to enter the stator water jacket to cool the motor assembly. The front bearing housing is also equipped with water inlet / outlet holes, allowing coolant to enter the bearing water jacket to reduce the operating temperature of the front angular contact ball bearing and improve heat dissipation efficiency. The rear bearing housing is equipped with a single-tube clamp with one end fixed for fixing the encoder signal line. Identical grooves are formed on the rear bearing housing and rear flange, through which the motor assembly signal line passes. A hydraulic support is mounted on the spindle box and has two sets of cable management holes for encoder and motor wiring, respectively, improving wiring safety.

Description

Technical Field

[0001] This utility model relates to the field of metal cutting technology, specifically to an electric spindle for a horizontal CNC lathe. Background Technology

[0002] Horizontal CNC lathes, as an important type of machine tool, occupy a significant position in the machining of shaft and disc parts due to their advantageous machining space layout. Mechanical spindles and electric spindles, as core functional components of lathes, directly affect the machining efficiency and accuracy. Traditional mechanical spindles use belt or encoder gear drives, resulting in long transmission chains, high power losses, and speed fluctuations caused by belt expansion or encoder gear wear, affecting the accuracy and quality of machined parts. Electric spindles are classified into intermediate motor electric spindles and rear-mounted motor electric spindles based on the motor's mounting position relative to the bearings. The rear-mounted motor electric spindle layout leads to an increased axial length of the spindle, insufficient dynamic rigidity, and poor tool stability during heavy cutting.

[0003] Patent document CN218425636U discloses a lathe electric spindle and CNC lathe with an internal locking cylinder structure. The spindle includes a housing, a shaft rotatably mounted within the housing, a rear bearing located at the rear end of the shaft, an encoder wheel, and a locking structure. The encoder wheel and locking structure are arranged sequentially from front to back on the rear side of the rear bearing. The locking structure includes a first brake disc, a second brake disc, a brake disc connecting seat, a cylinder, a piston, and a return spring. The brake disc connecting seat is sleeved on the shaft, and its front outer side is fixedly connected to the second brake disc. The first brake disc is fixedly connected to the front side of the rear cover. Braking is achieved by the friction between the front side of the first brake disc and the rear side of the second brake disc. While the aforementioned disclosed lathe electric spindle and CNC lathe with an internal locking cylinder structure solves the problems of external locking cylinders occupying space, low locking force, and uneven application of locking force, it does not consider the high heat generation of the electric spindle, leading to low machining accuracy, and the lack of proper planning of encoder and motor wiring, which affects equipment safety. Utility Model Content

[0004] The purpose of this utility model is to provide an electric spindle for a horizontal CNC lathe to solve the technical problems mentioned in the background art, such as the high heat generation of the electric spindle and the reasonable layout of the encoder and motor wiring.

[0005] To achieve the above objectives, this utility model provides the following technical solution: an electric spindle for a horizontal CNC lathe, comprising a spindle box, a spindle, a hollow tie rod, a three-jaw chuck, packing, a front flange, a rear flange, a front bearing assembly, a motor assembly, a rear bearing assembly, an encoder assembly, a brake assembly, a hydraulic cylinder assembly, and a drainage assembly.

[0006] Furthermore, the spindle box body is provided with multiple heat dissipation slots, and is provided with water inlet and outlet holes for heat dissipation of motor components, positioning holes for fixing brake components, and hydraulic bracket mounting holes for wiring. The front end and rear end of the spindle box are respectively provided with a front bearing assembly and a rear bearing assembly. The front and rear bearing assemblies are provided with a centering structure to ensure the stability of the spindle unit structure.

[0007] Furthermore, the motor assembly adopts an embedded direct drive design, placed between the front and rear bearing assemblies, and is equipped with a stator water jacket and a rotor sleeve. The stator water jacket is provided with multiple rotating grooves, and the outer diameter of the stator water jacket at both ends where O-rings are installed is larger than the inner diameter, which facilitates the flow of coolant inside the stator water jacket. The rotor sleeve is connected to the main shaft through a pair of ordinary flat keys for transmitting torque.

[0008] Furthermore, the rear flange is provided with a groove for mounting the reading head, and a one-end fixed single tube clamp is installed on the rear flange. The one-end fixed single tube clamp is used for encoder wiring, and the spacer is used to adjust the mounting position of the encoder assembly.

[0009] Furthermore, the hydraulic support is used to support the cylinder assembly and is provided with two sets of cable outlet holes, which are used for wiring of the encoder assembly and the motor assembly, respectively.

[0010] Furthermore, the spacer is used to adjust the encoder mounting position, and there is a set of adjusting shims used to adjust the mounting position of the spindle box relative to the lathe bed.

[0011] Furthermore, the spindle is connected to the packing, the packing is equipped with a centering shaft, the centering shaft is connected to a three-jaw chuck, and a labyrinth seal structure is formed between the spindle, the front flange, and the packing to prevent internal oil from being thrown out and external impurities from entering. The front flange is provided with two water outlet holes for the discharge of processing coolant.

[0012] Compared with the prior art, the beneficial effects of this utility model are:

[0013] 1. This utility model improves heat dissipation efficiency through the design of the cooling system. The spindle housing is equipped with heat dissipation grooves and water inlet / outlet holes. These holes are connected to nylon tubing via quick-connect couplings, with two sets of quick-connect couplings and nylon tubing used for coolant inlet and outlet. The coolant enters the stator water jacket to cool the motor assembly. The front bearing housing is also equipped with water inlet / outlet holes, connected to nylon tubing via quick-connect couplings, with two sets of quick-connect couplings and nylon tubing used for coolant inlet and outlet. The coolant enters the bearing water jacket to reduce the operating temperature of the front angular contact ball bearing.

[0014] 2. This utility model improves equipment safety by arranging the signal lines of the encoder assembly and motor assembly. The rear bearing housing is equipped with three single-tube clamps with one end fixed for fixing the position of the encoder signal lines. The rear bearing housing and the rear flange are provided with the same grooves, through which the motor assembly signal lines pass. The hydraulic support is mounted on the spindle box and is provided with two sets of cable trays for the encoder and motor cables, respectively. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the overall internal structure of this utility model;

[0016] Figure 2 This is a schematic diagram of the overall external structure of this utility model;

[0017] Figure 3 This is a schematic diagram of the structure of the motor assembly and encoder assembly of this utility model.

[0018] Figure 4 This is a schematic diagram of the spindle front end connection structure of this utility model.

[0019] In the diagram: 1. Front bearing assembly; 2. Motor assembly; 3. Encoder assembly; 4. Brake assembly; 5. Drainage assembly; 6. Hydraulic cylinder assembly; 7. Rear bearing assembly; 8. Spindle box; 801. Water inlet 1; 802. Water outlet 1; 811. Second quick-connect coupling; 812. Second nylon tube; 9. Spindle; 10. Hollow tie rod; 11. Front flange; 111. Water outlet 3; 12. Packing; 121. Centering shaft; 13. Three-jaw clamp. 14. Disc; 15. First O-ring seal; 16. Front angular contact ball bearing; 17. Bearing water jacket; 18. Front bearing housing; 19. First quick-connect coupling; 10. First nylon tube; 11. Second water inlet hole; 12. Second water outlet hole; 13. Second O-ring seal; 14. Oil retainer ring; 25. First precision lock nut; 26. Third O-ring seal; 27. Rotor sleeve; 28. Rotor; 29. ​​Stator; 20. Power cord; 21. 25. Temperature sensor cable; 26. Stator water jacket; 27. Second precision lock nut; 28. Spacer; 29. ​​Encoder gear; 20. Reading head; 21. Signal cable; 30. Mounting plate; 31. Brake; 311. Compression fitting tapered thread straight pipe connector; 312. First precision cold-drawn seamless steel pipe; 32. Brake disc; 33. First hose clamp; 34. Water receiving box; 35. First braided pressure-resistant hose; 36. Second hose clamp; 37. Second braided hose. 38. Braided pressure-resistant hose; 39. Connector body; 30. Hollow hydraulic rotary cylinder; 31. Compression fitting tapered thread bend pipe connector; 392. Second precision cold-drawn seamless steel pipe; 40. Hydraulic support; 401. First hub hole; 402. Second hub hole; 41. Cylinder connector; 42. Third precision lock nut; 43. Rear flange; 431. One-end fixed clamp; 44. Rear angular contact ball bearing; 45. Rear bearing housing; 46. Adjusting shim. Detailed Implementation

[0020] The technical solutions of the present utility model will be clearly and completely described below with reference to the accompanying drawings of the embodiments. Obviously, the described embodiments are only some embodiments of the present utility model, and not all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the protection scope of the present utility model.

[0021] Please see Figure 1 , Figure 2 and Figure 4A horizontal CNC lathe electric spindle includes a front bearing assembly 1. The front bearing assembly 1 includes a first O-ring seal 14, a front angular contact ball bearing 15, a bearing water jacket 16, a front bearing housing 17, a second O-ring seal 18, and an oil retainer ring 19. The front angular contact ball bearing 15 is mounted on the spindle 9, and the three front angular contact ball bearings 15 are paired in a DBD (dual-phase) manner. The bearing water jacket 16 is mounted on the front angular contact ball bearing 15, and the front bearing housing 17 is mounted on the bearing water jacket 16. The front bearing housing 17 is provided with a second water inlet hole 173 and a second water outlet hole 174. A first quick-connect coupling 171 and a first nylon tube are connected by threads, and there are two sets of them. Each set is connected to the second water inlet hole 173 and the second water outlet hole 174 respectively. Coolant enters the bearing water jacket 16 through the second water inlet hole 173, thereby cooling the front angular contact ball bearing 15, and then exits through the second water outlet hole 174. Two second O-rings 18 are installed between the bearing housing 17 and the bearing to prevent coolant leakage. An oil baffle ring 19 is located at the rear end of the front angular contact ball bearing 15 to prevent lubricating oil leakage. A first O-ring 14 is located between the front flange 11 and the front bearing housing 17 to prevent coolant leakage. A first precision lock nut 20 is connected to the spindle 9 by threads and is installed on one end face of the oil baffle ring 19 to preload the front bearing assembly 1 axially. The assembly also includes a hydraulic support 40, which has a first cable management hole 401. The motor assembly 2 also includes a power cable 241 and a temperature sensor cable 242, which pass through the first cable management hole 401 on the hydraulic support 40. The hydraulic support 40 has a second cable management hole 402, and the signal cable 291 of the encoder assembly 3 passes through the second cable management hole 402 on the hydraulic support 40.

[0022] Please see Figures 1 to 3A horizontal CNC lathe spindle includes a motor assembly 2, which comprises a third O-ring seal 21, a rotor sleeve 22, a rotor 23, a stator 24, and a stator water jacket 25. A rear flange 43 and a rear bearing seat 45 are connected by screws and have identical slots for three power lines 241 and one temperature sensor line 242. The power lines 241 transmit power to drive the rotor 23 to rotate. The rotor 23 is mounted on the spindle 9, causing the spindle 9 to rotate synchronously. The temperature sensor line 242 monitors the temperature of the motor assembly 2. The stator 24 is mounted on the rotor 23, and the stator water jacket 25 is mounted on the stator 24. The spindle box 8 is... A second quick-change connector 811 is provided, which is connected to a second nylon tube 812 by threads. There are two sets of the second quick-change connector 811 and the second nylon tube 812. Each set is connected to the water inlet hole 801 and the water outlet hole 802 on the spindle box 8, respectively. Coolant enters the stator water jacket 25 to cool the motor assembly 2. Two third O-ring seals 21 are installed between the spindle box 8 and the stator water jacket 25 to prevent coolant leakage. The rotor sleeve 22 is connected to the spindle 9 by a pair of ordinary flat keys for transmitting torque. The second precision locking nut 26 is provided on the spindle 9 for axial positioning of the motor assembly 2.

[0023] Please see Figures 1 to 3 An electric spindle for a horizontal CNC lathe includes an encoder assembly 3. The encoder assembly 3 includes a spacer 27, an encoder gear 28, and a reading head 29. The encoder gear 28 is fixed on the spindle 9 and rotates synchronously with the spindle. A groove is provided on the rear flange 43. The reading head 29 is fixed to the rear flange 43 by screws and spring washers. The reading head 29 measures the rotational position and speed of the spindle 9 by contacting the encoder gear 28. The spacer 27 is used to adjust the installation position of the encoder assembly 3. Three one-end fixed clamps 431 are fixed to the rear flange 43 by screws. The signal line 291 of the reading head 29 passes through the three one-end fixed clamps 431 in sequence. A second cable management hole 402 is provided on the hydraulic support 40 for the signal line 291 to run, avoiding wire mess.

[0024] Please see Figure 1 and Figure 2A horizontal CNC lathe electric spindle includes a brake assembly 4. A mounting plate 30 is fixed to the upper end face of the spindle box 8 by screws. A brake 31 is fixed to the mounting plate 30 by screws and spring washers. A ferrule-type tapered thread straight pipe connector 311 is provided on the brake 31. The ferrule-type tapered thread straight pipe connector 311 is threadedly connected to a first precision cold-drawn seamless steel pipe 312. A brake disc 32 is fixed to a cylinder connector 41 by screws. The cylinder connector 41 is connected to the spindle 9 by a pair of ordinary flat keys. When braking is applied, a hydraulic oil pump delivers hydraulic oil through the first precision cold-drawn seamless steel pipe 312, pushing the brake 31 to contact the brake disc 32. The friction force is used to brake the cylinder connector 41, thereby controlling the spindle 9 to stop rotating.

[0025] Please see Figure 1 and Figure 2 A horizontal CNC lathe electric spindle includes a drainage assembly 5, which includes a first hose clamp 33, a water collection box 34, and a first braided pressure-resistant hose 35. The water collection box 36 is connected to a hollow hydraulic rotary cylinder 39 by screws and is also connected to the first braided pressure-resistant hose 37 through the first hose clamp 35. The coolant for machining the workpiece flows from the inner hole of the three-jaw chuck 13 through the inner hole of the hollow tie rod 10 and the inner hole of the hollow hydraulic rotary cylinder 39 to the water collection box 36, thereby collecting the coolant for machining the workpiece.

[0026] Please see Figure 1 and Figure 2 A horizontal CNC lathe electric spindle includes a hydraulic cylinder assembly 6. The hydraulic cylinder assembly 6 includes a second hose clamp 36, a second braided pressure-resistant hose 37, a connector body 38, a hollow hydraulic rotary cylinder 39, a hydraulic support 40, and a cylinder connector 41. The hollow hydraulic rotary cylinder 39 is connected to the cylinder connector 41 by screws, and a ferrule-type tapered thread bend pipe connector 391 is provided on the outer wall of the hollow hydraulic rotary cylinder 39. The ferrule-type tapered thread bend pipe connector 391 is threadedly connected to a second precision cold-drawn seamless steel pipe 392. The inner wall of the rotary cylinder 39 is connected to the hollow tie rod 10 by threads. The hollow tie rod 10 is connected to the inner wall of the three-jaw chuck 13 by threads. The hydraulic oil pump delivers hydraulic oil through the second precision cold-drawn seamless steel pipe 392 to drive the hollow hydraulic rotary cylinder 39 to work, causing the hollow tie rod 10 to rotate, which in turn causes the three-jaw chuck 13 to loosen and tighten the workpiece. The connector body 38 is connected to the hollow hydraulic rotary cylinder 39. The connector body 38 is connected to the second braided pressure-resistant hose 37 through the second hose clamp 36 to collect oil from the cylinder assembly 6.

[0027] Please see Figure 1An electric spindle for a horizontal CNC lathe includes a rear bearing assembly 7, which includes a rear angular contact ball bearing 44 and a rear bearing housing 45. The rear angular contact ball bearing 44 is mounted on the spindle 9, and the two rear angular contact ball bearings 44 are paired in a DF configuration to support the rear end of the spindle unit. The rear bearing housing 45 is mounted on the rear angular contact ball bearing 44 to protect the rear angular contact ball bearing 44.

[0028] Please see Figure 1 and Figure 4 An electric spindle for a horizontal CNC lathe includes a spindle box 8, a spindle 9, a front flange 11, packing 12, a three-jaw chuck 13, a front bearing housing 17, and adjusting shims 46. The packing 12 is mounted on the spindle 9, and one end face is connected to the spindle 9 by screws. A centering shaft 121 is mounted on the packing 12 and connected to the three-jaw chuck 13. The front flange 11 is connected to the front bearing housing 17 by screws, and the front flange 11 is provided with two water outlet holes 111 for discharging machining coolant. The front bearing housing 17 is connected to the spindle box 8 by screws, and a set of adjusting shims 46 is fixed to the spindle box 8 by screws for adjusting the installation position of the spindle box 8 relative to the lathe bed. A labyrinth seal structure is formed between the spindle 9, the front flange 11, and the packing 12 to prevent internal oil from splashing out and external impurities from entering. The connection structure of the front end components of the spindle 9 improves the reliability and stability of the front end connection of the spindle unit.

[0029] Working principle: The workpiece to be processed is loaded into the three-jaw chuck 13. The motor assembly 2 transmits power through the power line 241 to drive the spindle 9 to rotate, which in turn drives the three-jaw chuck 13 to clamp the workpiece and rotate. Data is transmitted in real time through the temperature sensor line 242 to monitor the internal temperature of the motor assembly 2. When the internal temperature of the motor assembly 2 is too high, the control system controls the coolant to enter the stator water jacket 25 through the water inlet 801 on the spindle housing 8 to cool the motor assembly 2, and then flows out through the water outlet 802. When the spindle 9 rotates too fast, it will cause the front angular contact ball bearing 15 to overheat. The control system controls the coolant to enter the bearing water jacket 16 through the water inlet 173 on the front bearing housing 17 to cool the front angular contact ball bearing 15, and then flows out through the water outlet 174. During the continuous rotation of the spindle 9, the encoder assembly 3 contacts the encoder gear 28 through the reading head 29 to measure the rotational position and speed of the spindle 9, and transmits the data through the signal line. 291 converts data into electrical signal output, facilitating further precise control and monitoring of the electric spindle by the control system. When braking is applied, the hydraulic oil pump delivers hydraulic oil through the first precision cold-drawn seamless steel pipe 312, pushing the brake 31 in the brake assembly 4 to contact the brake disc 32. The friction force is used to brake the cylinder connector 41, thereby controlling the spindle 9 to stop rotating and preventing the spindle 9 from continuing to rotate due to inertia, thus shortening the auxiliary time and improving production efficiency. During the continuous processing of the workpiece, the cutting fluid will flow from the inner hole of the three-jaw chuck 13 through the inner hole of the hollow tie rod 10 and the inner hole of the hollow hydraulic rotary cylinder 39 to the water collection box 36 of the drainage assembly 5 to collect the cutting fluid. During the workpiece processing preparation stage or processing completion stage, the hydraulic oil pump delivers hydraulic oil through the second precision cold-drawn seamless steel pipe 392 to drive the hollow hydraulic rotary cylinder 39 of the cylinder assembly 6 to work, driving the hollow tie rod 10 to rotate, thereby driving the three-jaw chuck 13 to loosen and tighten the workpiece.

[0030] It will be apparent to those skilled in the art that this invention is not limited to the details of the exemplary embodiments described above, and that it can be implemented in other specific forms without departing from the spirit or essential characteristics of this invention. Therefore, the embodiments should be considered illustrative and non-limiting in all respects, and the scope of this invention is defined by the appended claims rather than the foregoing description. Thus, it is intended that all variations falling within the meaning and scope of equivalents of the claims be included within this invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A horizontal CNC lathe motorized spindle, comprising a spindle box (8), a hollow pull rod (10), a cylinder assembly (6), a front flange plate (11), a drainage assembly (5), a rear flange plate (43), a first precision locking nut (20), a cylinder connecting piece (41), characterized in that: The inner and outer walls of the spindle box (8) are respectively provided with a motor assembly (2) and a brake assembly (4). The front and rear ends of the spindle box (8) are respectively provided with a front bearing assembly (1) and a rear bearing assembly (7). The inner wall of the spindle (9) is provided with a hollow tie rod (10). The outer wall of the spindle (9) is provided with a front bearing assembly (1), a motor assembly (2), an encoder assembly (3), a brake assembly (4), a rear bearing assembly (7), a packing (12), and a three-jaw chuck (13). The front and rear ends of the hollow tie rod (10) are respectively connected to the three-jaw chuck (13) and the cylinder assembly (6) by threads. The front bearing assembly (1) is connected to the front flange (11), the drainage assembly (5) is connected to the cylinder assembly (6), and the rear bearing assembly (7) is connected to the rear flange (43) by screws.

2. The electric spindle for a horizontal CNC lathe according to claim 1, characterized in that: The front bearing assembly (1) includes a first O-ring seal (14), a front angular contact ball bearing (15), a bearing water jacket (16), a front bearing housing (17), a second O-ring seal (18), and an oil retainer ring (19). There are three front angular contact ball bearings (15) mounted on the main shaft (9), and the three front angular contact ball bearings (15) are paired in a DBD configuration. The bearing water jacket (16) is mounted on the front angular contact ball bearings (15), and the front bearing housing (17) is mounted on the bearing water jacket (16). Two second O-ring seals (18) are installed between the bearing water jacket (16) and the bearing housing (17). The oil baffle (19) is located at the rear end of the front angular contact ball bearing (15) to prevent lubricating oil leakage. The first O-ring seal (14) is located between the front flange (11) and the front bearing housing (17) to prevent coolant leakage. The first precision lock nut (20) is connected to the main shaft (9) by threads and is installed on one end face of the oil baffle (19) to preload the front bearing assembly (1) axially.

3. The electric spindle for a horizontal CNC lathe according to claim 2, characterized in that: The front bearing housing (17) is provided with a second water inlet hole (173) and a second water outlet hole (174). The second water inlet hole (173) and the second water outlet hole (174) are both equipped with a first quick-change connector (171), and the first quick-change connector (171) is connected to a first nylon tube (172).

4. The electric spindle for a horizontal CNC lathe according to claim 1, characterized in that: The motor assembly (2) is located between the front bearing assembly (1) and the rear bearing assembly (7), and includes a third O-ring seal (21), a rotor sleeve (22), a rotor (23), a stator (24), and a stator water jacket (25). The rotor (23) is mounted on the main shaft (9), the stator (24) is mounted on the rotor (23), and the stator water jacket (25) is mounted on the stator (24). There are two third O-ring seals (21) and they are located between the main shaft housing (8) and the stator water jacket (25) to prevent coolant leakage. The main shaft housing (8) is provided with a water inlet hole (801) and a water outlet hole (802). The rotor sleeve (22) is connected to the main shaft (9) by a pair of ordinary flat keys for transmitting torque. The main shaft (9) is provided with a second precision locking nut (26) for axial positioning of the motor assembly (2).

5. The electric spindle for a horizontal CNC lathe according to claim 1, characterized in that: The encoder assembly (3) includes a spacer (27), an encoder gear (28), and a reading head (29). The spacer (27) and the encoder gear (28) are sequentially mounted on the main shaft (9). The rear flange (43) is provided with a groove for mounting the reading head (29). The rear flange (43) is provided with three one-end fixed clips (431) for fixing the signal lines (291) of the encoder assembly (3).

6. The electric spindle for a horizontal CNC lathe according to claim 3, characterized in that: It also includes a hydraulic support (40), which is provided with a first hub hole (401). The motor assembly (2) also includes a power line (241) and a temperature sensor line (242). The power line (241) and the temperature sensor line (242) pass through the first hub hole (401) on the hydraulic support (40). The hydraulic support (40) is provided with a second hub hole (402). The signal line (291) of the encoder assembly (3) passes through the second hub hole (402) on the hydraulic support (40).

7. The electric spindle for a horizontal CNC lathe according to claim 1, characterized in that: The brake assembly (4) includes a mounting plate (30), a brake (31), and a brake disc (32). The mounting plate (30) is fixed on the spindle box (8), the brake (31) is fixed on the mounting plate (30), the brake disc (32) is mounted on the cylinder connector (41), and one end face of the brake disc (32) is connected to the cylinder connector (41) by a spring washer and a screw. A third precision locking nut (42) is provided at the rear end of the spindle (9), and the encoder assembly (3) is axially positioned by the third precision locking nut (42) and the brake assembly (4).

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