Tower type bottom-driven pumping unit

Abstract

The invention relates to a tower-type bottom-driven pumping unit which is characterized by comprising a tower body supporting base, a tower body, a power module and a supporting rod, the power module is installed at the bottom of the tower body, the output end of the power module is connected with a bottom traction module of the tower body through a transmission component, and the supporting rod is connected with the tower body. The traction module is used for driving a traction wheel of the traction module to rotate forwards and backwards to provide power; the tower body is fixedly installed on a cement foundation above a well mouth and comprises a stand column, a bottom traction module, a stand column top guide wheel assembly, a counterweight assembly and a traction belt, a built-in counterweight design enables a counterweight block to operate in the closed stand column and to be directly balanced with a suspension center load, and a tower body supporting base is foldable and convenient to transport or move; the power module is arranged at the bottom, installation, overhaul and maintenance are convenient and fast, a tower structure is adopted, and a large-stroke heavy-load pumping unit is easy to manufacture.

Description

Technical Field

[0001] This invention relates to the field of oil extraction equipment technology, and in particular to a tower-type bottom-driven pumping unit. Background Technology

[0002] The pumping unit is the core surface equipment in oilfield mechanical oil production. Its function is to convert the rotational motion of the power unit into the vertical reciprocating motion of the sucker rod, thereby driving the downhole pump to lift crude oil to the surface. Currently, the walking beam pumping unit is widely used in oilfields. This type of pumping unit has a simple structure and is durable, but it also has obvious disadvantages: its motion characteristics are simple harmonic motion, with large changes in acceleration during the up and down strokes, resulting in severe load fluctuations, uneven motor operating current, and high energy consumption; its large counterweight and walking beam structure make the overall weight and footprint of the unit very large; due to structural limitations, its stroke length is limited, resulting in low efficiency in deep wells, ultra-deep wells, or heavy oil extraction where long strokes and low stroke rates are required.

[0003] To overcome the shortcomings of beam pumping units, various long-stroke pumping units have been developed in this field, such as chain-driven, belt-driven, and drum-driven units. While these pumping units achieve long strokes to some extent, their drive systems are typically located at the top. This top-drive design introduces new problems: First, the high placement of heavy power components such as motors and gearboxes results in a high center of gravity, poor stability, and extremely high requirements for the strength and rigidity of the frame structure, increasing manufacturing costs and infrastructure expenses. Second, maintenance and replacement of top-mounted power equipment require high-altitude operations, which are inconvenient and pose safety hazards. Third, many existing long-stroke pumping units have separate balancing and drive systems, resulting in a less compact structure, unoptimized balancing performance, and untapped energy-saving potential.

[0004] Therefore, there is an urgent need in the existing technology for a new type of long-stroke pumping unit that can solve the stability and maintainability problems caused by top drive, while having an efficient and reliable balancing system to achieve smoother operation, lower energy consumption and a more power-friendly working environment. Summary of the Invention

[0005] The purpose of this invention is to overcome the defects in the prior art and provide a tower-type bottom-driven oil pump.

[0006] To achieve the above objectives, the technical solution of the present invention is to design a tower-type bottom-driven pumping unit, comprising: a tower support base, a tower body, a power module, and a support rod, wherein the power module is installed at the bottom of the tower body, and its output end is connected to the bottom traction module of the tower body through a transmission component, for driving the traction wheel to rotate forward and backward to provide power; the tower body includes a column, a bottom traction module, a column top guide wheel assembly, a counterweight assembly, and a traction belt, wherein the column is a vertically erected hollow frame structure, and the counterweight assembly is provided inside, which can be vertically lifted and lowered; the bottom traction module is fixed at the bottom of the column and includes the traction wheel driven by the power module; the column top guide wheel assembly is installed at the top of the column and... The system includes a guide wheel for changing the direction of the traction belt; the traction belt includes a load traction belt and a counterweight traction belt, wherein one end of the load traction belt is fixedly wound around both ends of the traction wheel, and the other end extends upward, passes over the guide wheel, and then connects downward to the bare rod hanger for connecting the sucker rod; one end of the counterweight traction belt is fixedly wound around the middle part of the traction wheel, and the other end extends upward, passes over the guide wheel, and then connects downward to the top of the counterweight assembly; the tower support base is connected to the tower body through a hinge mechanism, used to support the tower body during operation and fold during transportation; the upper end of the support rod is hinged to the upper part of the tower body, and the lower end is hinged to the tower support base, used to assist in supporting the tower body to enhance stability.

[0007] A further preferred technical solution is that the load traction belt has two sections located on the outer side, and the counterweight traction belt is located in the middle; both are high-strength flexible strips. When the traction wheel rotates clockwise, the load traction belt is wound around to pull the polished rod upward, while the counterweight traction belt is released to lower the counterweight assembly to assist in lifting the load. If the traction wheel rotates counterclockwise, the load traction belt is released to lower the polished rod, while the counterweight traction belt is wound around to pull the counterweight assembly upward to store potential energy. The extension direction of the load traction belt and the counterweight traction belt is changed by the guide wheel to obtain continuous reciprocating motion. The stroke length of the pumping unit is determined according to the winding length of the traction belt to adapt to different well depth requirements.

[0008] In a further preferred embodiment, the tower support base is connected to the tower body via the hinge mechanism. During transport, it folds to one side of the tower body and flips over to secure it to the wellhead foundation during operation. The upper end of the support rod is hinged to the upper part of the tower body, and the lower end is hinged to the tower support base, forming a triangular support structure to enhance the stability of the column and its wind load resistance. If the tower support base flips over, it becomes integrally fixed with the tower body, supporting the tower body. The hinged connection of the support rod enhances the stability of the tower body.

[0009] A further preferred technical solution is that the transmission component includes a chain and sprocket mechanism or a synchronous belt and synchronous pulley mechanism: if a chain and sprocket mechanism is used, the output end of the power module is connected to the input shaft of the bottom traction module via a chain; if a synchronous belt and synchronous pulley mechanism is used, the rotational power of the motor is transmitted via a synchronous belt; the speed and torque of the traction wheel are determined according to the type of the transmission component to match the load requirements; the brake acts on the brake disc to obtain the stopping control of the transmission component.

[0010] A further preferred technical solution is that the counterweight assembly is disposed inside the column, and its shape is adapted to the inner side of the column, enabling low-friction vertical lifting and lowering motion; the weight configuration of the counterweight assembly is balanced with the suspension load, so that the motor operates in a near-balanced state during the working cycle; if the counterweight traction belt is released, the counterweight assembly descends under gravity, releasing potential energy to assist in lifting the load; the guiding function of the guide rail is determined according to the lifting path of the counterweight assembly to ensure sway-free movement; the total weight is adjusted by the number of stacked blocks of the counterweight assembly to optimize the balance effect.

[0011] In a further preferred embodiment, one end of the load traction belt is fixed to both ends of the traction wheel, and the other end is connected to the polished rod for transmitting traction force; if the traction wheel winds around the load traction belt, it pulls the polished rod upward to drive the sucker rod; the downward traction path of the load traction belt is determined by the rotation of the guide wheel.

[0012] A further preferred technical solution is that the power module includes a motor, a brake disc, and a brake, wherein the motor drives the input shaft of the bottom traction module through the transmission component to achieve the rotation of the traction wheel; the transmission component is a chain and sprocket mechanism or a synchronous belt and synchronous pulley mechanism, which transmits power from the motor to the bottom traction module; if the motor rotates forward, the transmission component drives the traction wheel to wind the load traction belt and release the counterweight traction belt; the winding or releasing state of the load traction belt and the counterweight traction belt is determined according to the rotation direction of the traction wheel to achieve coordinated movement of load lifting and counterweight lowering; the brake disc is controlled by the brake to stop the rotation of the traction wheel, resulting in a stable stopping state.

[0013] In a further preferred embodiment, the column has an internal guide rail or uses the inner side of the column as a guide rail. The counterweight assembly is composed of multiple counterweight blocks stacked together and equipped with a counterweight guide wheel or slider, which cooperates with the guide rail to ensure vertical and stable movement. The bottom traction module is fixed at the bottom of the column and includes the traction wheel, which is driven by the power module to achieve forward and reverse rotation. The top guide wheel assembly of the column has multiple guide wheels for changing the direction of the load traction belt and the counterweight traction belt respectively. If the counterweight assembly descends, the release of the counterweight traction belt assists the winding of the load traction belt to lift the load. The required driving force of the traction wheel is determined based on the balance between the weight of the counterweight assembly and the load to reduce energy consumption.

[0014] In a further preferred embodiment, the number of support rods is two, one end of each support rod is hinged to the column, and the other end is hinged to the tower support base. The column and the tower support base are respectively provided with hinge seats, and the end of the support rod is connected to the hinge seat by bolts and nuts.

[0015] The advantages and beneficial effects of the present invention are as follows: 1. The whole machine is designed as an integrated unit, mainly composed of a tower body and a tower body support base. The tower body support base is foldable, which facilitates transportation or relocation.

[0016] 2. Easy to achieve long stroke: The stroke is achieved by winding the traction belt. The stroke is only limited by the length of the traction belt and the height of the frame, making it easy to achieve ultra-long strokes, meeting the extraction process requirements of deep wells and heavy oil wells, and improving pump efficiency.

[0017] 3. Convenient and safe maintenance: All drive, transmission and traction core components are located on or near the ground, allowing for daily inspection, maintenance and repair without the need for working at heights, which greatly improves operational safety and maintenance efficiency.

[0018] 4. High efficiency and energy saving: The built-in counterweight design allows the counterweight to operate within a closed column, directly balancing the load at the suspension point. This design significantly reduces the net power required by the motor during the up and down strokes, resulting in a substantial reduction in peak torque and current, significant energy savings, and allows for the selection of smaller, lower-cost motors and braking systems.

[0019] 5. High stability and low foundation requirements: Heavy components such as the power module are all located at the bottom of the equipment, which greatly lowers the center of gravity of the whole machine, making the equipment run more smoothly and with strong wind resistance, while reducing the load-bearing requirements of the well site foundation. Attached Figure Description

[0020] Figure 1 The axial side of the present invention Figure 1 ; Figure 2 The axial side of the present invention Figure 2 ; Figure 3 This is an isometric view of the power module of the present invention; Figure 4 This is one of the axonometric views of the tower body of the present invention; Figure 5 This is the second axonometric view of the tower body of the present invention; In the diagram: 100, tower support base; 200, transmission components; 300, power module; 310, motor; 320, brake disc; 330, brake; 400, support rod; 500, tower body; 510, column; 520, top guide wheel assembly of column; 521, guide wheel; 530, traction belt; 531, counterweight traction belt; 532, load traction belt; 540, counterweight assembly; 550, bottom traction module; 551, traction wheel; 552, input shaft; 560, counterweight guide wheel. Detailed Implementation

[0021] The specific embodiments of the present invention will be further described below with reference to the accompanying drawings and examples. The following examples are only used to more clearly illustrate the technical solutions of the present invention and should not be construed as limiting the scope of protection of the present invention.

[0022] like Figure 1-5 As shown in the figure, this embodiment of a tower-type bottom-driven pumping unit includes a tower support base 100, a tower body 500, a power module 300 and a support rod 400. The power module 300 is installed at the bottom of the unit, and its output end is connected to the bottom traction module 550 of the tower body 500 through a transmission component 200, which is used to drive the traction wheel 551 to rotate forward and backward to provide power.

[0023] In practice, the bottom configuration of the power module 300 facilitates daily maintenance and repair.

[0024] The power module 300 includes a motor 310, a brake disc 320, and a brake 330. The motor 310 drives the input shaft 552 of the bottom traction module 550 via a transmission component 200 to rotate the traction wheel 551. The selection of the motor 310 needs to be calculated and determined based on parameters such as suspension point load, stroke, and stroke rate. In practical applications, the selection of the motor 310 power usually needs to consider a safety factor to cope with load fluctuations and starting shocks. The speed regulation method of the motor 310 can adopt frequency conversion speed regulation, which adjusts the stroke rate of the pumping unit by changing the operating frequency of the motor 310, achieving energy-saving operation.

[0025] The brake 330, in conjunction with the brake disc 320, provides reliable shutdown protection for the pumping unit. The brake disc 320 is mounted on the drive shaft of the motor 310. When the system detects an abnormality or receives a shutdown command, the brake 330 can quickly act on the brake disc 320, stopping the traction wheel 551 from rotating. The braking torque of the brake 330 needs to be sufficient to safely stop the fully loaded pumping unit within a specified time, while avoiding impact damage caused by excessive braking.

[0026] The brake 330 can be either an electromagnetic brake or a hydraulic brake. Electromagnetic brakes offer fast response and high control precision, making them suitable for frequent start-stop operations; hydraulic brakes provide high braking torque and good heat dissipation, making them suitable for heavy-duty, long-term operation. The material selection for the brake disc 320 needs to consider wear resistance and heat dissipation performance; it is typically made of cast iron or steel, and the surface can be heat-treated to improve hardness and wear resistance.

[0027] The transmission component 200 can be selected from either a chain and sprocket mechanism or a synchronous belt and synchronous pulley mechanism according to different working conditions. The chain and sprocket mechanism has the characteristics of stable transmission ratio and strong load-bearing capacity, and is suitable for heavy-duty working conditions; the synchronous belt and synchronous pulley mechanism has the advantages of smooth operation and low noise, and is suitable for working environments with high noise requirements.

[0028] The tower body 500 is installed on a cement foundation at the wellhead and includes a column 510, a bottom traction module 550, a column top guide wheel assembly 520, a counterweight assembly 540, and a traction belt 530, which constitute the main structure of the pumping unit.

[0029] The column 510 is a vertically erected hollow frame structure, and its interior is equipped with a vertically lifting counterweight assembly 540. The column 510 needs to meet the requirements of strength, rigidity and stability, and at the same time provide guidance and support for the movement of the counterweight assembly 540.

[0030] The cross-sectional shape of the column 510 can be square, circular, or polygonal. A square cross-section has the advantages of simple manufacturing and convenient connection; a circular cross-section has the characteristics of good torsional resistance and low wind resistance; a polygonal cross-section achieves a balance between strength and manufacturing cost. The height of the column 510 is determined according to the required maximum effective stroke.

[0031] The column 510 has an internal guide rail or uses its inner surface as a guide rail. The counterweight assembly 540 is composed of multiple stacked counterweight blocks and is equipped with a counterweight guide wheel 560 or a slider, which cooperates with the guide rail to ensure vertical and stable movement. The guide rail directly affects the stability of the movement of the counterweight assembly 540 and the service life of the system. The guide rail can be made of a special guide rail profile, or the inner surface of the column 510 can be used as the guide rail surface.

[0032] The guiding device for the counterweight assembly 540 can employ either a counterweight guide wheel 560 or a slider. In the counterweight guide wheel configuration, the counterweight guide wheel 560 is typically made of polyurethane or nylon, offering wear resistance and shock absorption. The arrangement of the counterweight guide wheels 560 must ensure the stability of the counterweight assembly 540 in all directions; usually, one counterweight guide wheel 560 is placed at each of the four corners of the counterweight assembly. In the slider configuration, the slider material can be a self-lubricating bearing material or engineering plastic, offering advantages such as a low coefficient of friction and maintenance-free operation.

[0033] The bottom traction module 550 is installed at the bottom of the column 510 and includes a traction wheel 551 and an input shaft 552. It achieves forward and reverse rotation through the drive of the power module 300. The traction wheel 551 is the core component of the entire system, and its strength, wear resistance, and winding performance need to be comprehensively considered. The diameter of the traction wheel 551 affects the bending stress and winding layer number of the traction belt 530. If the diameter is too small, the bending stress of the traction belt 530 will be too large, affecting its service life; if the diameter is too large, it will increase the size and cost of the equipment.

[0034] The bottom traction module 550 needs to bear all the loads transmitted by the traction wheel 551, including the load weight, the counterweight weight, and the dynamic load.

[0035] The traction belt 530 includes a load traction belt 532 and a counterweight traction belt 531. One end of the load traction belt 532 is fixedly wound around both ends of the traction wheel 551, and the other end extends upward, passes over the top guide wheel assembly 520 of the column, and then connects downward to the bare rod hanger used to connect the sucker rod.

[0036] One end of the counterweight traction belt 531 is fixedly wound around the middle of the traction wheel 551, and the other end extends upward, passes over the top guide wheel assembly 520 of the column, and then connects downward to the top of the counterweight assembly 540. The load borne by the counterweight traction belt 531 is relatively stable, mainly the weight of the counterweight assembly 540.

[0037] The load traction belts 532 consist of two belts located on the outer sides, with a counterweight traction belt in the middle; both are made of high-strength, flexible material. This arrangement ensures uniform load distribution and stable system operation. The use of two load traction belts 532 enhances system safety; even if one fails, the other can still bear part of the load, preventing safety accidents caused by sudden unload.

[0038] The load-bearing capacity of the load-bearing traction belt 532 needs to be determined based on the load it will bear and the required safety factor. The lengths of the two traction belts must be strictly consistent to ensure even load distribution. During installation, the two traction belts need to be pre-tensioned to ensure that their initial tensions are equal.

[0039] The load traction belt 532 and the counterweight traction belt 531 are made of high-strength flexible belt material. The selection of the high-strength flexible belt material needs to take into account factors such as strength, flexibility, wear resistance and corrosion resistance.

[0040] The column top guide wheel assembly 520 is provided with multiple guide wheels 521 for changing the direction of the load traction belt 532 and the counterweight traction belt 531 respectively. The guide wheel assembly needs to ensure the smoothness and reliability when the traction belt direction is changed. The number and arrangement of the guide wheels 521 are determined according to the number and direction of the traction belts; typically, the load traction belt and the counterweight traction belt each correspond to one or more guide wheels.

[0041] The selection of bearings for the guide wheel 521 needs to consider the load size and the operating environment. For applications with large loads, roller bearings can be selected; for applications with small loads but high speeds, ball bearings can be selected. The bearing sealing type needs to be determined based on the operating environment; guide wheel bearings used outdoors need to have good dustproof and waterproof performance.

[0042] The guide wheel 521 can be made of cast iron, cast steel, or engineering plastics. Cast iron guide wheels are low in cost and have good wear resistance, but are relatively heavy; cast steel guide wheels have high strength and good toughness, and are suitable for heavy-duty applications; engineering plastic guide wheels are lightweight and corrosion-resistant, but have relatively low load-bearing capacity.

[0043] The bare rod is a key component connecting the load traction belt 532 and the sucker rod, and the reliability of the connection and the uniformity of force transmission must be ensured. The rod is typically made of forged steel with a corrosion-resistant surface treatment. The connection between the rod and the load traction belt 532 can be achieved using a snap ring connection or direct splicing, and the connection strength must meet the requirements of the maximum load.

[0044] The lifting and lowering process of the counterweight assembly 540 needs to be stable to avoid impact and vibration. The gap between the counterweight assembly 540 and the guide rail should be appropriate; too large a gap will cause swaying, while too small a gap will increase frictional resistance.

[0045] When the traction wheel 551 rotates forward, the load traction belt 532 is wound around it to pull the smooth rod upward, while the counterweight traction belt 531 is released to lower the counterweight assembly 540 to assist in lifting the load. This coordinated action requires precise mechanical design and a well-coordinated control system. When the traction wheel 551 rotates forward, the load traction belt 532 is wound around the surface of the traction wheel 551; the neatness of this winding directly affects the service life of the traction belt 530 and the smoothness of the system operation.

[0046] If the traction wheel 551 reverses direction, the load traction belt 532 is released, causing the bare rod to descend. Simultaneously, the counterweight traction belt 531 is wound to pull the counterweight assembly 540 upward to store potential energy. During the downstroke, the energy flow direction of the system changes, and the upward movement of the counterweight assembly 540 stores gravitational potential energy, providing auxiliary power for the next upstroke.

[0047] The tower support base 100 is located on one side of the tower body 500 and is connected to the tower body 500 via a hinge mechanism. It supports the tower body during operation and folds during transport. The tower support base 100 needs to meet requirements for support strength, ease of transport, and ease of installation. The design of the hinge mechanism is crucial to achieving the folding function; it must withstand all loads transmitted by the tower body, including static and dynamic loads.

[0048] The tower support base 100 is connected to the tower body 500 via a hinge mechanism. During transport, it folds to one side of the tower body 500, and during operation, it flips over and secures itself to the wellhead foundation. The design of the folding mechanism must consider both ease of operation and safety. The folding process can be hydraulically driven, electrically driven, or manually operated.

[0049] When folded, the tower support base needs to be reliably secured to prevent shaking and collisions during transportation. The securing device can employ methods such as pin locking, snap-locking, or bolt connection.

[0050] The upper end of the support rod 400 is hinged to the upper part of the tower body 500, and the lower end is hinged to the tower support base 100, which is used to assist in supporting the tower body to enhance stability. The triangular support structure formed by the support rod 400 can effectively improve the stability and wind resistance of the tower body 500.

[0051] The loads borne by the support rod 400 mainly include the lateral force from the tower body 500, wind load, and seismic load. The lateral force comes from the unbalanced force and equipment vibration during the oil pumping process; the wind load is calculated based on local wind speed and wind pressure standards; and the seismic load is determined according to the seismic fortification intensity. The cross-section of the support rod 400 can be made of round tube, square tube, or angle steel, etc.

[0052] The hinge point of the support rod 400 needs to meet the requirements of flexible rotation and reliable connection. The hinge point is typically connected by a pin. To prevent accidental dislodgement of the pin, a locking device such as a cotter pin or a spring retaining ring is required. Lubrication of the hinge point is important for reducing friction and extending service life; grease lubrication can be used, or a grease nipple can be installed to periodically replenish the lubricant.

[0053] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A tower-type bottom-driven oil pumping unit, characterized in that, include: The tower body includes a support base, a tower body, a power module, and a support rod. The power module is installed at the bottom of the tower body, and its output end is connected to the bottom traction module of the tower body through a transmission component to drive the traction wheel of the traction module to rotate forward and backward to provide power. The tower body is fixedly installed on a cement foundation above the wellhead and includes a column, a bottom traction module, a column top guide wheel assembly, a counterweight assembly, and a traction belt. The column is a vertically erected hollow frame structure with the counterweight assembly inside, which can be vertically raised and lowered. The bottom traction module is fixed at the bottom of the column and includes the traction wheel driven by the power module. The column top guide wheel assembly is installed at the top of the column and has guide wheels for changing the direction of the traction belt. The traction belt includes a load traction belt and a counterweight traction belt. One end of the load traction belt is fixedly wound around both ends of the traction wheel, and the other end extends upward around the top guide wheel assembly of the column and then downward to connect with the bare rod hanger for connecting the sucker rod. One end of the counterweight traction belt is fixedly wound around the middle part of the traction wheel, and the other end extends upward around the top guide wheel assembly of the column and then downward to connect with the top of the counterweight assembly. The tower support base is connected to the tower body via a hinge mechanism, which is used to support the tower body during operation and fold during transportation. The upper end of the support rod is hinged to the upper part of the tower body, and the lower end is hinged to the tower support base.

2. The tower-type bottom-driven pumping unit according to claim 1, characterized in that, The bottom traction module is fixed at the bottom of the column and includes the traction wheel, which can rotate in both directions by the drive of the power module.

3. The tower-type bottom-driven pumping unit according to claim 1, characterized in that, The column top guide wheel assembly is provided with multiple guide wheels, which are used to change the direction of the load traction belt and the counterweight traction belt respectively.

4. The tower-type bottom-driven pumping unit according to claim 1, characterized in that, The load traction belt consists of two belts located on the outer side, while the counterweight traction belt is located in the middle; both belts are made of high-strength, flexible material.

5. The tower-type bottom-driven pumping unit according to claim 1, characterized in that, The tower support base is connected to the tower body through the hinge mechanism. It is folded to one side of the tower body during transportation and flipped and fixed to the wellhead foundation during operation.

6. The tower-type bottom-driven pumping unit according to claim 1, characterized in that, The power module includes a motor, a brake disc, and a brake, wherein the motor drives the input shaft of the bottom traction module through the transmission component to rotate the traction wheel.

7. The tower-type bottom-driven pumping unit according to claim 1, characterized in that, The column is equipped with a guide rail inside or the inner side of the column is used as a guide rail. The counterweight assembly is composed of multiple counterweight blocks stacked together and is equipped with guide wheels or sliders, which cooperate with the guide rail to ensure vertical and stable movement.

8. The tower-type bottom-driven pumping unit according to claim 1, characterized in that, The upper end of the support rod is hinged to the upper part of the tower body, and the lower end is hinged to the tower body support base, forming a triangular support structure to enhance the stability of the column and its wind load resistance.

9. The tower-type bottom-driven pumping unit according to claim 2, characterized in that, The transmission components include a chain and sprocket mechanism or a synchronous belt and synchronous pulley mechanism.

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