Operation drag hook for urinary surgery

Abstract

The invention relates to the technical field of medical apparatus and instruments, and discloses a urinary surgery operation drag hook which comprises a base assembly which comprises a fixed base and a movable base, and the movable base can rotate relative to the fixed base. Relative rotation of the upper plate body and the lower plate body is controlled through the driving assembly, and circumferential rotation movement of the plate bodies is converted into pure radial translation movement of the expansion pieces through sliding limiting of the upper sliding blocks and the lower sliding blocks in the upper guide grooves and the lower guide grooves correspondingly. By means of the design, smooth, uniform and stepless radial expansion of a surgical incision is achieved, and tissue damage caused by a traditional one-way tearing mode is avoided. Meanwhile, the upper plate body and the lower plate body which serve as the device main body are always located outside the incision of the patient in the expansion process, and the risk that the whole device main body slides into the body cavity of the patient is eliminated through the limiting effect of the sleeving limiting plate.

Description

Technical Field

[0001] This invention relates to the field of medical device technology, specifically a surgical retractor for urology. Background Technology

[0002] In minimally invasive urological surgery, establishing the surgical access and exposing the surgical field are crucial steps in determining the success of the operation. Surgical retractors or dilators are widely used to open incisions, subcutaneous tissues, and organ capsules to provide the necessary operating corridor for the subsequent entry and exit of endoscopes and surgical instruments. However, existing surgical retractors still have many shortcomings in practical applications.

[0003] First, traditional retractors often employ rigid bidirectional or unidirectional traction, making it difficult to achieve uniform radial expansion that conforms to the incision contour. Prolonged rigid support leads to excessive local pressure at the incision edge, which can easily cause ischemic necrosis and postoperative complications. Furthermore, doctors cannot visually obtain the actual support force exerted by the retractor on the tissue, lacking quantifiable safety standards.

[0004] Secondly, the environment around the incision in urological surgery is complex, containing irrigation fluid and blood, and the patient's body surface has physiological curvature. Traditional mechanical supports or suture fixation methods relying on retractors are prone to loosening and displacement under the interference of frequent insertion and removal of surgical instruments and swinging, resulting in the loss of the established surgical channel.

[0005] Furthermore, some expansion devices have main support components that extend too far into the incision, posing a significant medical risk of the device components slipping out and falling into the patient's deep tissues during minimally invasive blind puncture procedures.

[0006] In addition, the existing adjustable hooks are time-consuming and labor-intensive to adjust manually, while a few electric hooks cannot achieve rapid pressure relief and withdrawal in the event of power failure or jamming, posing a safety hazard in emergency situations. Summary of the Invention

[0007] This invention provides a surgical retractor for urology, which solves the problems mentioned in the background art.

[0008] This invention provides the following technical solution: a surgical retractor for urology, comprising: A base assembly comprising a fixed base and a movable base, the movable base being rotatable relative to the fixed base; Multiple expansion plates are arranged around the axis of the base assembly. The upper end of each expansion plate is slidably connected to the movable base, and the lower end of each expansion plate is slidably connected to the fixed base, such that when the movable base rotates relative to the fixed base, the multiple expansion plates move radially. A support assembly, located at the radial inner end of each expansion piece, is used to support the surgical incision; A drive assembly, connected to the movable base, is used to drive the movable base to rotate; A fixation component, located outside the base assembly, is used to fix the surgical hook to the patient's body surface.

[0009] As a preferred embodiment of the present invention, the movable base is an upper plate, the fixed base is a lower plate, the upper plate is provided with an upper guide groove, the lower plate is provided with a lower guide groove, the upper end of each expansion piece is provided with an upper slider that slides in cooperation with the upper guide groove, and the lower end of each expansion piece is provided with a lower slider that slides in cooperation with the lower guide groove.

[0010] As a preferred embodiment of the present invention, the upper plate and the lower plate are connected by a sleeve limiting structure. The sleeve limiting structure includes a sleeve limiting plate disposed on the lower plate and a central annular groove disposed on the upper plate. The end of the sleeve limiting plate is slidably sleeved with the central annular groove.

[0011] As a preferred embodiment of the present invention, the support assembly includes a support swing rod, the upper end of which is rotatably connected to the expansion plate via a connecting shaft, and the lower end of which is used to contact the surgical incision.

[0012] As a preferred embodiment of the present invention, the support assembly further includes a pressure sensor disposed between the expansion plate and the support swing rod, for detecting the supporting force of the support swing rod on the surgical incision.

[0013] As a preferred embodiment of the present invention, the top end of the support swing rod is provided with a compression push block, and the pressure sensor is fixed on the expansion plate and disposed opposite to the compression push block.

[0014] As a preferred embodiment of the present invention, the fixing component includes a flexible connector and a skin-fitting ring, one end of the flexible connector is connected to the base component, and the other end is connected to the skin-fitting ring.

[0015] As a preferred embodiment of the present invention, a negative pressure suction cup is engaged within the skin-adhesive ring.

[0016] As a preferred embodiment of the present invention, the drive assembly includes a servo motor and a worm gear, and the output end of the servo motor is connected to the movable base through the worm gear.

[0017] As a preferred embodiment of the present invention, the drive assembly further includes a clutch mechanism, which includes a clutch gear and a gravity throttle. The clutch gear can selectively engage with the output end of the servo motor. When the gravity throttle is raised, the clutch gear engages to achieve manual drive. When the gravity throttle is lowered, the clutch gear disengages.

[0018] The present invention has the following beneficial effects: This urological surgical retractor uses a drive assembly to control the relative rotation of the upper and lower plates. By utilizing the sliding limits of the upper and lower sliders within upper and lower guide grooves, the circumferential rotation of the plates is converted into pure radial translational motion of several expansion pieces. This design achieves smooth, uniform, and stepless radial expansion of the surgical incision, avoiding tissue damage caused by traditional unidirectional tearing methods. Simultaneously, the upper and lower plates, as the main body of the device, remain outside the patient's incision throughout the expansion process. The limiting effect of the sleeved limiting plate eliminates the risk of the entire device slipping into the patient's body cavity.

[0019] The fixation component of this invention, through the design of the flexible connector and the skin-adhesive ring, can adapt to the uneven physiological curvature of the patient's abdomen or waist. As a preferred embodiment, the negative pressure suction cup snapped into the skin-adhesive ring can, with the assistance of an external negative pressure device, firmly anchor the device to the patient's skin surface through vacuum adsorption. This "flexible atmospheric pressure surface contact adsorption" replaces the traditional "mechanical rigid point clamping," not only avoiding secondary damage to normal skin but also greatly improving the device's ability to resist the interference torque generated by the insertion and oscillation of surgical instruments, ensuring the absolute stability of the surgical channel.

[0020] The support assembly of this invention incorporates a lever-driven force-measuring structure. When the expansion plate pushes the support lever and its selective arc-shaped cannula at the bottom to support the incision tissue, the minute deformation of the support lever is transmitted to the pressure sensor through the compression pusher at the top, thereby quantifying the support stress borne by the incision edge tissue in real time and with high precision. Based on this data, the surgeon can precisely control the expansion force, maintaining the pressure within a safe range and effectively avoiding tissue microcirculation obstruction and ischemic necrosis caused by excessive local pressure. Simultaneously, the selective arc-shaped cannula design allows the device to flexibly adapt to the needs of surgical channels with different aperture specifications.

[0021] The drive assembly of this invention integrates a clutch avoidance mechanism comprising a clutch gear and a gravity throttle. Under normal operation, the servo motor drives the upper plate to rotate via the meshing of the worm gear and the end gear teeth, achieving smooth and precise automated expansion. The worm gear mechanism also features a self-locking function, maintaining the expansion state even in the event of a power outage. In emergencies or when rapid adjustments are required, the gravity throttle can be operated to engage or disengage the clutch gear from the end transmission teeth, seamlessly switching between "electric high-precision fine-tuning" and "manual rapid adjustment or emergency pressure relief" modes. This significantly improves the device's fault tolerance and overall safety in complex surgical environments. Attached Figure Description

[0022] Figure 1 This is a three-dimensional structural diagram of the present invention; Figure 2 This is a schematic diagram of the expansion plate structure of the present invention; Figure 3 This is a schematic diagram of the upper channel structure of the present invention; Figure 4 This is a schematic diagram of the lower channel structure of the present invention; Figure 5 This is a schematic diagram of the fixed component structure of the present invention; Figure 6 This is a schematic diagram of the drive component structure of the present invention; Figure 7 This is a schematic diagram of the end tooth groove structure of the present invention; Figure 8 This is a schematic diagram of the structural support components of the present invention; Figure 9 This is a schematic diagram of the fixed component of the present invention from another perspective.

[0023] In the diagram: 1. Radial expansion component; 2. Fixing component; 3. Support component; 4. Drive component; 101. Upper plate; 102. Upper channel; 103. Upper guide groove; 104. Lower plate; 105. Lower channel; 106. Lower guide groove; 107. Expansion plate; 108. Upper slider; 109. Lower slider; 110. Inner transition groove; 111. Middle annular groove; 112. End toothed groove; 113. Sleeve limiting plate; 201. Flexible connector; 202. Skin-contact ring; 203. Negative pressure suction cup; 301. Supporting swing arm; 302. Connecting shaft; 303. Pressure sensor; 304. Extrusion push block; 305. Selective arc-shaped sleeve; 401. Motor bracket; 402. Servo motor; 403. Transmission spindle; 404. Worm gear; 405. Support bearing; 406. End transmission gear; 407. Clutch gear; 408. Gravity throttle; 409. Clearance groove. Detailed Implementation

[0024] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] Please see Figure 1 - Figure 9In minimally invasive urological surgeries, such as percutaneous nephrolithotomy (PCNL), a surgical channel needs to be created on the patient's body surface to allow the endoscope and surgical instruments to enter and exit. The retractor device of this invention is designed for such scenarios, and its primary function is to safely and stably expand and maintain this surgical channel.

[0026] Figure 1 The overall structure of a surgical retractor for urology provided in an embodiment of the present invention is shown. For example... Figure 1 As shown, an embodiment of the present invention provides a surgical retractor for urology, which includes a radial expansion component 1. A fixing component 2 is fixedly mounted on the outer wall of the radial expansion component 1. A support component 3 is provided at the moving end of the radial expansion component 1's axis. A drive component 4 for driving the radial expansion component 1 is also provided on the outer wall of the radial expansion component 1. By controlling the movement of the radial expansion component 1 through the drive component 4, power can be transmitted to the support component 3, enabling it to provide uniform radial support to the surgical incision. At the same time, the fixing component 2 can firmly fix the entire device to the patient's body surface, ensuring the stability of the surgical channel during instrument operation. The upper plate 101 and lower plate 104, as the main body of the device, are always located outside the incision, fundamentally avoiding the risk of the entire device slipping into the patient's body.

[0027] In this embodiment, the radial expansion assembly 1 is selected to include an upper plate 101, a lower plate 104, and a plurality of expansion pieces 107. Specifically, the radial expansion assembly 1 includes an upper plate 101 and a lower plate 104. The outer wall of the upper plate 101 is provided with an upper guide groove 103, and an upper channel 102 is provided at the center of the upper plate 101. The top outer wall of the lower plate 104 is provided with a lower guide groove 106, and a lower channel 105 is provided at the center of the lower plate 104. The radial expansion assembly 1 also includes a plurality of expansion pieces 107 arranged around the perimeter. An upper slider 108 is fixedly mounted on the top of the expansion piece 107 on the side away from the upper channel 102, and the upper slider 108 is slidably sleeved with the inner wall of the upper guide groove 103. A lower slider 109 is fixedly mounted on the bottom of the expansion piece 107 on the side away from the upper channel 102, and the lower slider 109 is slidably sleeved with the inner wall of the lower guide groove 106. When the upper plate 101 rotates relative to the lower plate 104, the expansion piece 107 is restricted to purely radial translational motion by the sliding of the upper slider 108 in the upper guide groove 103 and the sliding of the lower slider 109 in the lower guide groove 106. This achieves stepless and uniform radial expansion of the channel formed by the upper channel 102 and the lower channel 105. The number of expansion pieces 107 can be set as needed, for example, four, six, or eight, evenly distributed around the perimeter to achieve balanced expansion.

[0028] In this embodiment, a central annular groove 111 is formed in the middle of the outer wall of the upper plate 101, and a plurality of fixedly assembled sleeve limiting plates 113 are arranged in a ring on the outer wall of the lower plate 104. The ends of the sleeve limiting plates 113 are slidably sleeved with the interior of the central annular groove 111. This structure realizes axial limiting and axial rotational cooperation between the upper plate 101 and the lower plate 104, ensuring that the two remain coaxial and move smoothly when rotating relative to each other. An end toothed groove 112 is formed on the outer end of the upper plate 101 near the lower plate 104 for meshing and transmission with the drive assembly 4. Except Figure 1 Besides the structure shown, the groove shapes of the upper guide groove 103 and the lower guide groove 106 can also be designed as other trajectories that can convert rotational motion into linear motion, such as Archimedean spiral grooves or logarithmic spiral grooves. Archimedean spiral grooves can achieve a strictly linear ratio between the expansion distance and the rotation angle, facilitating precise control; while logarithmic spiral grooves are gentler in the initial expansion stage, which is beneficial for protecting fragile tissues. Different groove designs provide choices for different expansion characteristics.

[0029] In this embodiment, the fixing component 2 is selected as a structure including a flexible connector 201 and a skin-adhesive ring 202. The fixing component 2 includes a flexible connector 201 that is fixedly assembled to the outer wall of the sleeve limiting plate 113, and a skin-adhesive ring 202 is fixedly assembled to the end of the flexible connector 201. The flexible connector 201 can be made of flexible materials such as medical silicone tubing, corrugated tubing, or braided flexible tubing, so that it can be bent to adapt to the physiological curvature of the patient's abdomen or waist. The skin-adhesive ring 202 is usually a ring-shaped soft pad, which can be attached to the patient's skin with medical tape to achieve initial fixation of the device. This flexible connection method avoids discomfort or pressure sores on the patient's body surface caused by rigid support.

[0030] In a preferred embodiment, a negative pressure suction cup 203 is internally engaged with the skin-adhesive ring 202. The negative pressure suction cup 203 can be connected via tubing to an external negative pressure device (not shown in the figure), such as a wall-mounted negative pressure suction device commonly found in operating rooms. When the negative pressure device is activated, negative pressure is generated within the suction cup 203, using atmospheric pressure to tightly adhere the entire skin-adhesive ring 202 area to the patient's skin. This surface-contact suction fixation method provides significantly greater pull-out and overturning resistance than traditional point fixation or suture fixation, especially resisting the "piston effect" and swaying caused by frequent entry and exit of surgical instruments. Compared to using only adhesive tape, negative pressure suction fixation is more secure and reliable, and removal is painless and does not cause secondary damage to the skin.

[0031] In this embodiment, the support assembly 3 is selected as having a structure including a support swing rod 301, a connecting shaft 302, a pressure sensor 303, a pressing push block 304, and a selective arc-shaped sleeve 305. An inner transition groove 110 is provided at the end of the expansion plate 107 near the axis of the upper plate 101. The support assembly 3 includes a support swing rod 301, with a connecting shaft 302 fixedly mounted at its upper end. The support swing rod 301 is rotatably connected to the inner transition groove 110 via the connecting shaft 302, allowing the support swing rod 301 to swing at a small angle relative to the expansion plate 107. A pressing push block 304 is connected to the outer wall of the top of the support swing rod 301, and a pressure sensor 303 is fixedly mounted on the outer side of the pressing push block 304. The pressure sensor 303 is fixedly mounted to the outer wall of the top of the expansion plate 107. A selective arc-shaped sleeve 305 is sleeved at the bottom of the support swing rod 301. When the expansion plate 107 moves radially outward, pushing the support lever 301 and the selective arc-shaped sleeve 305 to contact and support the incision tissue, the support lever 301 acts as a lever. The reaction force from the tissue at its bottom end causes a slight deformation or displacement at its top, which in turn applies pressure to the pressure sensor 303 through the compression pusher 304. The pressure sensor 303 (such as a thin-film pressure sensor or a micro-strain gauge) converts the pressure signal into an electrical signal and transmits it to external monitoring equipment, thereby displaying the supporting stress borne by the incision edge tissue in real time and quantitatively. Doctors can precisely control the expansion force based on this data to avoid exceeding the tissue's safe threshold (usually capillary perfusion pressure), effectively preventing ischemic necrosis of the tissue.

[0032] The selective arc-shaped cannula 305 is designed to better conform to the contour of a circular incision, providing surface support and reducing pressure. The selective arc-shaped cannula 305 is detachable from the support lever 301 for easy replacement. The selective arc-shaped cannula 305 is available in different outer diameter specifications, such as 18Fr, 20Fr, 22Fr, and 24Fr, to meet different surgical channel requirements. By replacing different sizes of selective arc-shaped cannulas 305, this device can flexibly adapt to surgical incisions of various sizes, improving its versatility. (Except for...) Figure 1 In addition to the detachable sleeve structure shown, the support component 3 can also be designed as a support head with a specific curvature directly formed at the bottom of the support lever 301, forming an integrated structure. The integrated structure is more stable, but lacks the flexibility to replace different sizes. Detachable and integrated structures each have their advantages, and the choice can be made based on specific clinical usage habits and cost considerations.

[0033] In this embodiment, the drive assembly 4 includes a motor bracket 401 fixedly mounted to the outer wall of the lower plate 104, and a servo motor 402 fixedly mounted on the top of the motor bracket 401. The servo motor 402 is a drive element known in the art, typically including a motor body and a controller, capable of receiving commands for precise forward / reverse rotation and angle control. A transmission spindle 403 is fixedly mounted at the output end of the servo motor 402, and the transmission spindle 403 is rotatably supported by a support bearing 405. A worm gear 404 is machined in the middle of the transmission spindle 403, and the worm gear 404 meshes with the end tooth groove 112 of the upper plate 101. When the servo motor 402 starts and drives the transmission spindle 403 and the worm gear 404 to rotate, the worm gear 404 drives the end tooth groove 112, thereby causing the upper plate 101 to rotate relative to the fixed lower plate 104. The worm gear mechanism has the advantages of smooth transmission, low noise, and self-locking. That is, when the servo motor 402 stops working, the worm 404 can effectively prevent the upper plate 101 from rotating in the opposite direction under the reaction force of the cut tissue, thus maintaining the stability of the expansion state.

[0034] An end drive gear 406 is fixedly mounted on the end of the drive shaft 403 away from the servo motor 402. A clutch gear 407 meshes with the end of the end drive gear 406. A gravity throttle 408 is fixedly mounted on the axis of the clutch gear 407, and the gravity throttle 408 is aligned with the axis of the radial expansion assembly 1. A clearance groove 409 is provided on the top of the motor bracket 401 corresponding to the clutch gear 407. When the gravity throttle 408 is not in use, it and the clutch gear 407 naturally droop under their own weight, causing the clutch gear 407 to fall into the clearance groove 409 and disengage from the end drive gear 406. At this time, the drive assembly 4 is in electric mode, precisely driven by the servo motor 402 through the worm gear 404. When rapid manual adjustment or emergency pressure relief is required, the operator can lift the gravity throttle 408 upwards to re-engage the clutch gear 407 with the end drive gear 406. At this point, manually rotating the gravity handle 408 will drive the worm gear 404 to rotate via the clutch gear 407, end transmission gear 406, and transmission main shaft 403, thus manually controlling the expansion. This achieves a safety redundancy between electric precision control and manual rapid intervention, allowing for quick switching to manual operation in case of power failure or motor malfunction, ensuring surgical safety.

[0035] The pressure sensor 303 and the controller of the servo motor 402 can be electrically connected to form a simple closed-loop control system. When the monitored support pressure exceeds the preset safety limit, the controller can automatically stop the expansion action of the servo motor 402 or issue an audible and visual alarm to alert the doctor, thereby achieving intelligent overload protection.

[0036] It should be noted that a gravity sensor switch is installed inside the clearance groove 409. When the gravity of the gravity throttle 408 and the clutch gear 407 is applied to the gravity sensor switch, its servo motor 402 is energized. When the gravity of the gravity throttle 408 and the clutch gear 407 is not applied to the gravity sensor switch, its servo motor 402 is de-energized.

[0037] It should be noted that the connection between the flexible connector 201 and the sleeve limiting plate 113, the snap-fit ​​between the skin-adhesive ring 202 and the negative pressure suction cup 203, and the sleeve-fit between the selective arc sleeve 305 and the support swing rod 301 can all be achieved using methods well-known to those skilled in the art, such as snap-fit, threaded, interference fit, or quick-release interface, and are not limited to a single method here. The signal output method of the pressure sensor 303 can be wired or wireless transmission. The power supply of the drive component 4 can be a battery or a special power supply for the operating room. These are all conventional choices and adaptive modifications that those skilled in the art can make according to actual needs.

[0038] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0039] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A surgical retractor for urology, characterized in that, include: A base assembly comprising a fixed base and a movable base, the movable base being rotatable relative to the fixed base; Multiple expansion plates (107) are arranged around the axis of the base assembly. The upper end of each expansion plate (107) is slidably connected to the movable base, and the lower end of each expansion plate (107) is slidably connected to the fixed base, such that when the movable base rotates relative to the fixed base, the multiple expansion plates (107) move radially. A support assembly (3) is located at the radial inner end of each expansion piece (107) to support the surgical incision; Drive component (4), which is connected to the movable base, is used to drive the movable base to rotate; Fixation component (2), which is located outside the base component, is used to fix the surgical hook to the patient's body surface.

2. The surgical retractor for urology according to claim 1, characterized in that, The movable base is an upper plate (101), and the fixed base is a lower plate (104). The upper plate (101) is provided with an upper guide groove (103), and the lower plate (104) is provided with a lower guide groove (106). The upper end of each expansion piece (107) is provided with an upper slider (108) that slides in cooperation with the upper guide groove (103), and the lower end of each expansion piece (107) is provided with a lower slider (109) that slides in cooperation with the lower guide groove (106).

3. A surgical retractor for urology according to claim 2, characterized in that, The upper plate (101) and the lower plate (104) are connected by a sleeve limiting structure. The sleeve limiting structure includes a sleeve limiting plate (113) provided on the lower plate (104) and a central annular groove (111) provided on the upper plate (101). The end of the sleeve limiting plate (113) is slidably sleeved with the central annular groove (111).

4. A surgical retractor for urology according to claim 1, characterized in that, The support assembly (3) includes a support swing rod (301), the upper end of which is rotatably connected to the expansion piece (107) via a connecting shaft (302), and the lower end of which is used to contact the surgical incision.

5. A surgical retractor for urology according to claim 4, characterized in that, The support assembly (3) also includes a pressure sensor (303), which is located between the expansion plate (107) and the support swing rod (301) and is used to detect the support force of the support swing rod (301) on the surgical incision.

6. A surgical retractor for urology according to claim 5, characterized in that, The top end of the support swing rod (301) is provided with a compression push block (304), and the pressure sensor (303) is fixed on the expansion plate (107) and is arranged opposite to the compression push block (304).

7. A surgical retractor for urology according to claim 1, characterized in that, The fixing component (2) includes a flexible connector (201) and a skin-adhesive ring (202). One end of the flexible connector (201) is connected to the base component, and the other end is connected to the skin-adhesive ring (202).

8. A surgical retractor for urology according to claim 7, characterized in that, A negative pressure suction cup (203) is attached inside the skin-adhesive ring (202).

9. A surgical retractor for urology according to claim 1, characterized in that, The drive assembly (4) includes a servo motor (402) and a worm gear (404), and the output end of the servo motor (402) is connected to the movable base through the worm gear (404).

10. A surgical retractor for urology according to claim 9, characterized in that, The drive assembly (4) further includes a clutch mechanism, which includes a clutch gear (407) and a gravity throttle (408). The clutch gear (407) can selectively engage with the output end of the servo motor (402). When the gravity throttle (408) is raised, the clutch gear (407) engages to achieve manual drive. When the gravity throttle (408) is lowered, the clutch gear (407) disengages.

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