Opening degree display device for rising stem gate valve

Abstract

This invention discloses an opening degree display device for a rising stem gate valve, comprising a transmission assembly, a detection assembly, and a protective assembly. The transmission assembly includes a lead screw, a valve stem, and a valve plate. One end of the lead screw is coaxial with and fixedly connected to the valve stem. A driving worm gear is disposed at the end of the lead screw away from the valve stem, meshing with a driven worm wheel. The driven worm wheel is connected to the detection assembly via a transmission component, which amplifies the rotation angle of the driving worm gear and transmits it to the detection assembly. The detection assembly includes a rotary encoder, a signal processor, and a display screen. The rotary encoder is electrically connected to the signal processor and is connected to the transmission component to convert the rotation angle of the driving worm gear into an electrical signal. The display screen is electrically connected to the signal processor. The protective assembly includes a sealing cover, which is fitted outside the transmission assembly and fixedly connected to the valve body. The opening degree display device for a rising stem gate valve provided by this invention has the advantages of high accuracy and minimal susceptibility to external influences.

Description

Technical Field

[0001] This invention relates to the field of gate valve opening technology, and more particularly to an opening display device for a rising stem gate valve. Background Technology

[0002] The technical water supply system of a hydropower station is responsible for providing water to important equipment such as generating units for cooling and lubrication. Gate valves, as key components controlling water flow, have their opening accuracy directly impacting the system's operational efficiency and safety. However, currently, most rising stem gate valve opening detection methods rely on visual inspection or simple scale displays, which cannot accurately determine the valve's opening. This crude detection method easily leads to improper opening or closing of the rising stem gate valve, affecting the precise regulation of water flow and failing to meet the high-precision monitoring requirements of hydropower stations for rising stem gate valve opening, thus impacting the normal functioning of hydropower station equipment. Summary of the Invention

[0003] This invention is based on the inventor's discoveries and understanding of the following facts and problems:

[0004] Currently, the accuracy of aperture detection is low and the division is coarse.

[0005] The present invention aims to at least partially solve one of the technical problems in the related art.

[0006] To address this, embodiments of the present invention provide an opening degree display device for a rising stem gate valve, comprising a transmission assembly, a detection assembly, and a protective assembly. The transmission assembly includes a lead screw, a valve stem, and a valve plate. The lead screw is coaxial with and fixedly connected to one end of the valve stem. A driving worm gear is disposed at the end of the lead screw away from the valve stem. The driving worm gear meshes with a driven worm wheel. The driven worm wheel is connected to the detection assembly via a transmission component. The transmission component amplifies the rotation angle of the driving worm gear and transmits it to the detection assembly. The detection assembly includes a rotary encoder, a signal processor, and a display screen. The rotary encoder is electrically connected to the signal processor to send a signal. The rotary encoder is connected to the transmission component to convert the rotation angle of the driving worm gear into an electrical signal. The signal processor receives the signal and converts it into a gate valve opening degree value. The display screen is electrically connected to the signal processor to display the gate valve opening degree value. The protective assembly includes a sealing cover, which is fitted outside the transmission assembly and fixedly connected to the valve body.

[0007] The embodiments of the present invention have the advantages and technical effects of high precision and minimal susceptibility to external influences.

[0008] In some embodiments, a handle is also included, which is sleeved on the lead screw and threadedly connected to the lead screw. The handle is spaced a certain distance from the driving worm and can drive the lead screw to rotate.

[0009] In some embodiments, a limiting boss is further included, which is disposed between the handle and the drive worm gear to prevent the handle from interfering with the drive worm gear.

[0010] In some embodiments, a zero-position calibration switch is also included, which is disposed on the valve body to zero the signal processor when the valve plate is in the fully closed position.

[0011] In some embodiments, the transmission component is a speed-increasing gear set, the input end of which is connected to the driven worm gear, and the output end of which is connected to the rotary encoder to amplify the number of encoder pulses per unit rotation angle of the lead screw.

[0012] In some embodiments, the speed-increasing gear set includes a multi-stage bevel gear set, wherein a primary bevel gear rotates synchronously with the driven worm gear, a secondary bevel gear meshes with the primary bevel gear, and other bevel gears mesh with the secondary bevel gear in sequence, wherein the primary bevel gear is larger than the secondary bevel gear and the other bevel gears.

[0013] In some embodiments, a displacement sensor is also included, which is arranged on the valve stem to detect changes in the distance between the end of the valve stem and the valve body.

[0014] In some embodiments, the system further includes an elastic compensation element for eliminating gear backlash. The elastic compensation element includes a compression spring and a sleeve. At least one bevel gear in the multi-stage gear set is a sliding gear. The compression spring and the sleeve are sleeved on the rotating shaft of the sliding gear. One end of the compression spring abuts against the sliding gear, and the other end of the compression spring is located inside the sleeve. The other end of the sleeve is provided with an external thread and is threaded to the housing of the speed-increasing gear set.

[0015] In some embodiments, the sealing cover is sealed and fixedly connected to the valve body of the gate valve, and an access door is pivotally connected to the side wall of the sealing cover.

[0016] In some embodiments, a double-lip seal and a lubrication channel are provided at the opening where the sealing cover contacts the lead screw, and the lubrication channel guides lubricating oil to flow to the surface of the lead screw.

[0017] This application offers the following advantages: The transmission assembly converts the linear motion of the valve stem into rotational motion, which is then amplified by the transmission components. This, combined with the detection assembly, completes the conversion, calculation, and visualization of the valve opening electrical signal, solving the problems of low accuracy and susceptibility to environmental interference inherent in traditional detection methods. The handle and lead screw are threaded together, driving the lead screw to rotate. Manual operation is flexible, and the spaced arrangement of the handle and the driving worm gear avoids interference risks. A limiting boss prevents mechanical collisions or transmission interference between the handle and the driving worm gear during rotation. The zero-position calibration switch establishes a precise reference zero point for gate valve opening detection, eliminating zero-point deviation. The speed-increasing gear set increases the number of encoder pulses collected per unit angle of the lead screw, capturing minute changes in the gate valve opening and improving detection accuracy. The multi-stage bevel gear structure achieves progressive amplification of the rotation angle, ensuring smooth transmission and adapting to limited installation space. The displacement sensor detects changes in the distance between the valve stem and the valve body, directly acquiring the actual linear displacement data of the valve stem for verification, avoiding opening deviations inherent in single detection methods. The elastic compensation component applies a continuous preload to the sliding bevel gear via a compression spring, pushing the bevel gear teeth to fit tightly together, eliminating gear meshing backlash, and avoiding transmission lag and angle detection errors. The sealing cover is sealed and fixedly connected to the valve body, achieving overall protection and ensuring the service life of the equipment. A double-lip seal ring forms a double seal at the interface between the sealing cover and the lead screw, preventing the intrusion of external dust and water stains; the lubrication channel guides lubricating oil to the lead screw surface, reducing friction and wear in the lead screw transmission. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the opening degree display device of the rising stem gate valve according to an embodiment of the present invention.

[0019] Reference numerals in the attached diagram: 1. Lead screw; 2. Valve stem; 3. Valve plate; 4. Driving worm gear; 5. Driven worm wheel; 6. Transmission component; 7. Rotary encoder; 8. Display screen; 9. Handle. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] An embodiment of the present invention provides an opening degree display device for a rising stem gate valve, comprising a transmission assembly, a detection assembly, and a protective assembly. The transmission assembly includes a lead screw 1, a valve stem 2, and a valve plate 3. The lead screw 1 is coaxial with and fixedly connected to one end of the valve stem 2. A driving worm gear 4 is provided at the end of the lead screw 1 away from the valve stem 2. The driving worm gear 4 meshes with a driven worm wheel 5. The driven worm wheel 5 is connected to the detection assembly through a transmission component 6. The transmission component 6 amplifies the rotation angle of the driving worm gear 4 and transmits it to the detection assembly. The detection assembly includes a rotary encoder 7, a signal processor, and a display screen 8. The rotary encoder 7 is electrically connected to the signal processor to send signals. The rotary encoder 7 is connected to the transmission component 6 to convert the rotation angle of the driving worm gear 4 into an electrical signal. The signal processor receives the signal and converts it into a gate valve opening degree value. The display screen 8 is electrically connected to the signal processor to display the gate valve opening degree value. The protective assembly includes a sealing cover, which is fitted outside the transmission assembly and fixedly connected to the valve body.

[0022] The gate valve opening is accurately detected, displayed intuitively, and operated stably through the coordinated operation of the transmission, detection, and protection components. The coaxial fixed structure of the lead screw 1 and valve stem 2 ensures the synchronous transmission of the linear motion of the valve stem 2 and the rotational motion of the lead screw 1. The driving worm gear 4 at the end of the lead screw 1 meshes with the driven worm wheel 5, realizing the conversion of motion modes. The transmission component 6 amplifies the rotation angle of the driving worm gear 4 and transmits it to the detection component, allowing the detection component to capture minute changes in the gate valve opening and improve the precision of the opening detection. The rotary encoder 7 in the detection component is connected to the transmission component 6, converting the amplified mechanical rotation angle into an electrical signal. The signal processor receives the electrical signal and calculates the gate valve opening value. The display screen 8 presents the opening value intuitively, allowing operators to accurately obtain the gate valve opening information. The sealing cover is fitted outside the transmission component and fixedly connected to the valve body, isolating it from external adverse factors such as dust, water stains, and corrosive media, preventing contamination, corrosion, or collision of the internal transmission and detection components, ensuring transmission accuracy and detection performance, and extending the overall service life of the device.

[0023] In some embodiments, a handle is also included. The handle is sleeved on the lead screw 1 and threadedly connected to the lead screw 1. The handle is spaced a certain distance from the driving worm gear 4 and can drive the lead screw 1 to rotate.

[0024] Specifically, the handle and the driving worm gear 4 are spaced apart and can drive the lead screw 1 to rotate, providing convenient manual drive without relying on external electric drive equipment. This allows for flexible operation and rapid response in emergency situations or when there is no power supply. The spacing between the handle and the driving worm gear 4 avoids mechanical collisions when the handle is rotated, preventing damage to the transmission components due to interference.

[0025] The handle has a non-slip textured split structure, with one end being the operating part and the other end being the transmission part. A wear-resistant bushing is added at the threaded connection between the handle and the lead screw 1 to improve service life.

[0026] In some embodiments, a limiting boss is also included, which is arranged between the handle and the driving worm 4 to prevent the handle from interfering with the driving worm 4.

[0027] Specifically, the limiting boss forms a physical barrier between the handle and the driving worm gear 4, preventing mechanical collisions and transmission interference between the handle and the driving worm gear 4 due to factors such as operational deviation and equipment vibration during rotation, thus protecting the transmission structure of the driving worm gear 4 from damage by external forces. The fixed-distance arrangement of the limiting boss also limits the handle, preventing it from sliding towards the driving worm gear 4 due to excessive turning.

[0028] The limiting boss is a metal base with wear-resistant rubber on its outer circumference. The metal base ensures the structural support strength, and the wear-resistant rubber avoids wear caused by hard contact with the handle and buffers slight vibrations. An anti-slip damping pad is arranged on the side of the limiting boss facing the handle. When the handle is in contact with the limiting boss, it forms a damping positioning to prevent the handle from rotating randomly when not in operation.

[0029] In some embodiments, a zero-position calibration switch is also included, which is arranged on the valve body to zero the signal processor when the valve plate 3 is in the fully closed position.

[0030] Specifically, zero-position calibration resets the signal processor to zero when valve plate 3 is fully closed, establishing a reference zero point for detection. This effectively eliminates zero-point deviations caused by factors such as mechanical transmission backlash, wear, and signal drift during operation, ensuring that the opening value calculated by the signal processor always uses the fully closed valve plate 3 as a precise starting point, thus improving accuracy. The automated zeroing of the zero-position calibration switch reduces errors caused by manual intervention, making calibration more convenient and accurate. Optionally, a wear-resistant buffer pad can be installed at the trigger end of the zero-position calibration switch to prevent damage to both the valve plate 3 and the switch from a hard collision when fully closed, extending the switch's service life.

[0031] In some embodiments, the transmission component 6 is a speed-increasing gear set, the input end of which is connected to the driven worm gear 5, and the output end of which is connected to the rotary encoder 7 to amplify the number of encoder pulses per unit rotation angle of the lead screw 1.

[0032] Specifically, the speed-increasing gear set connects to the driven worm gear 5 at its input end and to the rotary encoder 7 at its output end. This amplifies the rotational angle transmitted by the driven worm gear 5, increasing the number of pulses collected by the rotary encoder 7 per unit rotation angle of the lead screw 1. The encoder can capture the rotational angle change corresponding to the minute linear displacement of the gate valve stem 2, converting the previously difficult-to-detect minute opening changes into identifiable pulse signals, thus improving the accuracy of gate valve opening detection. The rigid transmission structure of the speed-increasing gear set ensures the stability of the rotational angle transmission, avoiding signal lag and deviation, accurately reflecting the actual rotational angle of the driving worm gear 4, and improving the accuracy and reliability of the detection system.

[0033] Optionally, an observation window and a lubricating oil filling port can be provided on the housing of the speed-increasing gear set to facilitate operators' observation of the gear meshing status and allow for regular lubrication to maintain the gear set and extend its transmission life.

[0034] In some embodiments, the speed-increasing gear set includes a multi-stage bevel gear set, wherein the primary bevel gear rotates synchronously with the driven worm gear 5, the secondary bevel gear meshes with the primary bevel gear, and the other bevel gears mesh with the secondary bevel gears in sequence, and the primary bevel gear is larger than the secondary bevel gears and the other bevel gears.

[0035] Specifically, the speed-increasing gear set is set as a multi-stage bevel gear set, with a large-sized primary bevel gear rotating synchronously with the driven worm gear 5. The primary bevel gear meshes with and drives the smaller secondary bevel gears and other bevel gears to achieve progressive speed increase. This structure relies on the meshing characteristics of the large bevel gear driving the small bevel gear to achieve efficient progressive amplification of the rotation angle. Compared with ordinary cylindrical gear sets, the bevel gear structure can flexibly adjust the transmission direction. The sequential meshing of the multi-stage small bevel gears significantly amplifies the angle, increasing the number of pulses collected by the rotary encoder 7 per unit rotation angle of the lead screw 1.

[0036] In some embodiments, a displacement sensor is also included, which is arranged on the valve stem 2 to detect changes in the distance between the end of the valve stem 2 and the valve body.

[0037] Specifically, the displacement sensor detects the change in distance between the end of the valve stem 2 and the valve body, reflecting the actual linear displacement of the valve stem 2. This displacement is then compared with the opening value of the rotary encoder 7, avoiding the opening detection deviation of a single detection method. The displacement sensor acts directly on the valve stem 2, and the detection data intuitively reflects the actual opening state of the gate valve. This helps correct the accumulated errors of the transmission components, ensuring that the opening value displayed on the screen 8 matches the actual opening of the gate valve.

[0038] Optionally, a temperature detection module can be installed next to the displacement sensor to simultaneously detect the ambient temperature around the valve stem 2. When the temperature exceeds the normal operating range of the equipment, an early warning signal can be sent to prevent high or low temperatures from affecting the normal operation of the transmission and detection components.

[0039] In some embodiments, the system further includes an elastic compensation element for eliminating gear backlash. The elastic compensation element includes a compression spring and a sleeve. At least one bevel gear in the multi-stage gear set is a sliding gear. The compression spring and the sleeve are sleeved on the shaft of the sliding gear. One end of the compression spring abuts against the sliding gear, and the other end of the compression spring is located inside the sleeve. The other end of the sleeve is provided with an external thread and is threaded to the housing of the speed-increasing gear set.

[0040] Specifically, the preload of the compression spring can be adjusted by screwing on the sleeve. The spring's elastic force pushes the sliding bevel gear axially along the shaft, ensuring a tight fit between the meshing tooth surfaces of the bevel gears. This eliminates gear backlash at the meshing points of the multi-stage bevel gear set, preventing transmission lag and angular deviations caused by backlash, ensuring accurate transmission of the speed-increasing gear set's rotational angle, and reducing errors in opening detection. The threaded connection between the sleeve and the housing facilitates preload adjustment, allowing for real-time adjustment based on gear wear to maintain backlash elimination. The sliding gear provides the foundation for the axial clamping of the spring, making the elastic compensation action smoother.

[0041] The compression spring is made of stainless steel precision spring, which improves the spring's fatigue resistance. A scale marking is provided at the end of the sleeve, allowing operators to accurately adjust the preload without repeated adjustments. A buffer pad is added at the contact end between the compression spring and the sleeve to prevent deformation of the spring end due to hard impact during compression.

[0042] In some embodiments, the sealing cover is fixedly connected to the valve body of the gate valve, and an access door is pivotally connected to the side wall of the sealing cover.

[0043] Specifically, the sealing cover forms a protective space outside the device, isolating it from dust, water stains, corrosive media, and external impacts. This prevents wear, short circuits, or decreased transmission accuracy in the transmission and detection components due to environmental interference, extending their service life and allowing the device to adapt to complex and harsh industrial conditions. The pivotable access door allows for inspection, debugging, maintenance, and component replacement without disassembling the entire sealing cover, reducing maintenance difficulty and costs. Oil- and corrosion-resistant rubber gaskets are used in the sealing fit of the cover, and an antistatic and anti-corrosion coating is applied to the outside of the cover to enhance the sealing effect. A magnetic maintenance lighting strip is installed inside the access door; the light illuminates when the door is opened, providing illumination for internal maintenance without requiring additional lighting equipment.

[0044] In some embodiments, a double-lip seal and a lubrication channel are provided at the opening where the sealing cover contacts the lead screw 1, and the lubrication channel guides the lubricating oil to flow to the surface of the lead screw 1.

[0045] Specifically, the double-lip seal ring fits tightly against the outer circumference of the lead screw 1 through its double-layered lips, forming a barrier at the opening of the sealing cover. This prevents external dust, water stains, and corrosive media from intruding through the gap between the lead screw 1 and the sealing cover, thus preventing the leakage of lubricating oil from the device. The lubrication channel guides the lubricating oil to flow continuously to the surface of the lead screw 1, achieving lubrication, reducing friction and wear, and the oil film formed on the surface of the lead screw 1 enhances the sealing effect of the seal ring, extends the service life of the lead screw 1, and maintains the transmission accuracy of the transmission components. The double-lip seal ring is made of oil-resistant and wear-resistant fluororubber.

[0046] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of describing this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0047] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0048] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection, an electrical connection, or a connection that allows communication between them; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0049] In this invention, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "over," and "on top" of the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0050] In this invention, the terms "one embodiment," "some embodiments," "example," "specific example," or "some examples," etc., refer to a specific feature, structure, material, or characteristic described in connection with that embodiment or example, which is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples. Moreover, without contradiction, those skilled in the art can combine and integrate the different embodiments or examples described in this specification, as well as the features of different embodiments or examples.

[0051] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention.

Claims

1. An open display device for a gate valve of the rising stem type, characterized in that, include: The system comprises a transmission assembly, a detection assembly, and a protection assembly. The transmission assembly includes a lead screw, a valve stem, and a valve plate. One end of the lead screw is coaxial with and fixedly connected to the valve stem. A driving worm gear is provided at the end of the lead screw away from the valve stem. The driving worm gear meshes with a driven worm wheel. The driven worm wheel is connected to the detection assembly through a transmission component. The transmission component amplifies the rotation angle of the driving worm gear and transmits it to the detection assembly. The detection component includes a rotary encoder, a signal processor, and a display screen. The rotary encoder is electrically connected to the signal processor to send signals. The rotary encoder is connected to the transmission component to convert the rotation angle of the drive worm gear into an electrical signal. The signal processor receives the signal and converts it into a gate valve opening value. The display screen is electrically connected to the signal processor to display the gate valve opening value. The protective component includes a sealing cover, which is fitted over the transmission component and is fixedly connected to the valve body.

2. The stem valve opening display device according to claim 1, characterized by It also includes a handle, which is sleeved on the lead screw and threadedly connected to the lead screw. The handle is spaced a certain distance from the driving worm and can drive the lead screw to rotate.

3. The stem valve opening display device according to claim 2, wherein It also includes a limiting boss, which is arranged between the handle and the driving worm gear to prevent the handle from interfering with the driving worm gear.

4. The opening degree display device for the rising stem gate valve according to claim 1, characterized in that, It also includes a zero-position calibration switch, which is arranged on the valve body to zero the signal processor when the valve plate is in the fully closed position.

5. The opening degree display device for the rising stem gate valve according to claim 1, characterized in that, The transmission component is a speed-increasing gear set. The input end of the speed-increasing gear set is connected to the driven worm gear, and the output end of the speed-increasing gear set is connected to the rotary encoder to amplify the number of encoder pulses per unit rotation angle of the lead screw.

6. The opening degree display device for the rising stem gate valve according to claim 5, characterized in that, The speed-increasing gear set includes a multi-stage bevel gear set, wherein the first-stage bevel gear rotates synchronously with the driven worm gear, the second-stage bevel gear meshes with the first-stage bevel gear, and the other bevel gears mesh with the second-stage bevel gear in sequence, and the first-stage bevel gear is larger than the second-stage bevel gear and the other bevel gears.

7. The opening degree display device for the rising stem gate valve according to claim 1, characterized in that, It also includes a displacement sensor, which is arranged on the valve stem to detect changes in the distance between the end of the valve stem and the valve body.

8. The opening degree display device for the rising stem gate valve according to claim 6, characterized in that, It also includes an elastic compensation component for eliminating gear backlash. The elastic compensation component includes a compression spring and a sleeve. At least one bevel gear in the multi-stage gear set is a sliding gear. The compression spring and the sleeve are sleeved on the rotating shaft of the sliding gear. One end of the compression spring abuts against the sliding gear, and the other end of the compression spring is located inside the sleeve. The other end of the sleeve is provided with an external thread and is threaded to the outer shell of the speed-increasing gear set.

9. The opening degree display device for the rising stem gate valve according to claim 1, characterized in that, The sealing cover is fixedly and sealed to the valve body of the gate valve, and an inspection door is pivotally connected to the side wall of the sealing cover.

10. The opening degree display device for the rising stem gate valve according to claim 1, characterized in that, A double-lip seal and a lubrication channel are provided at the opening where the sealing cover contacts the lead screw, and the lubrication channel guides the lubricating oil to flow to the surface of the lead screw.

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