Overload protection device for an electric stapler and electric stapler

Abstract

The present invention provides an overload protection device for an electric stapler, which includes a support shaft and an input gear, an elastic holding member, a torque limiting member, and an output gear that are sequentially installed on the support shaft. The axial positions of the input gear and the output gear on the support shaft are fixed; the torque limiting member is constantly engaged with the end face of the input gear, and the torque limiting member is engaged with the end face of the output gear; when the torque of the torque limiting member is greater than a specified threshold value, the engagement state between the torque limiting member and the output gear is disengaged. An electric stapler includes a driving mechanism, a push rod mechanism, an installation bracket and the above overload protection device. The overload protection device of the electric stapler and the electric stapler of the present invention can protect the driving mechanism and the transmission mechanism during overload, and avoid breakage or damage of relatively weak links such as driving and transmission in the stapler.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and particularly to an overload protection device for an electric stapler and an electric stapler. Background Art

[0002] Electric staplers include traditional manual laparoscopic staplers and electric staplers. Compared with the effect after cutting and suturing tissues by traditional manual laparoscopic staplers, the anastomotic stoma after cutting and suturing by electric laparoscopic staplers is smoother and neater, enabling the patient's wound to recover faster and better after surgery.

[0003] Currently, existing electric staplers are driven by an electric drive mechanism. For example, the drive mechanism, power handle, and stapler with the publication number CN111920471B can adopt an electric drive mechanism and a corresponding transmission structure in the stapler structure to drive the end effector to perform a cutting action, ensuring sufficient striking force and appropriate firing speed during cutting and suturing. However, after the electric drive mechanism jams or is impacted, the output force will be much greater than the normal operating load. Since the strength of the parts of the stapler itself is limited, if the working torque transmitted exceeds the limit torque allowed by the transmission structure during mechanical transmission, mechanical accidents such as the fracture or damage of the transmission mechanism and the burnout of the electric drive mechanism will occur. Therefore, it is urgent to design a torque protection mechanism for an electric stapler to avoid the fracture or damage of relatively weak driving and transmission links of the stapler. Summary of the Invention

[0004] In view of the above-mentioned disadvantages of the prior art, the purpose of the present invention is to provide an overload protection device for an electric stapler, which is characterized by including:

[0005] A support shaft;

[0006] An input gear, installed on the support shaft and used to connect the drive mechanism;

[0007] An output gear, installed on the support shaft and used to connect the push rod mechanism of the electric stapler; the axial positions of the input gear and the output gear on the support shaft are fixed;

[0008] A torque limiting component, sleeved on the support shaft and located between the input gear and the output gear. The first end face of the torque limiting component is constantly meshed with the mating end face of the input gear through first end face teeth, and the second end face of the torque limiting component is correspondingly provided with meshing second end face teeth with the mating end face of the output gear;

[0009] An elastic holding component, arranged between the torque limiting component and the input gear, and keeping the torque limiting component meshed with the output gear through the second end face teeth under normal conditions;

[0010] Wherein, a torsional sliding surface is provided on the second end face teeth of the torque-limiting component and / or the output gear. When the torque of the torque-limiting component is greater than a specified threshold value, relative sliding occurs between the torque-limiting component and the output gear through the torsional sliding surface, and the torque-limiting component moves axially towards the input gear against the elastic force of the elastic retaining component, so that the torque-limiting component disengages from the second end face teeth of the output gear.

[0011] Preferably, the overload protection device further includes a retracting shaft. The retracting shaft has a circumferential movement space relative to the output gear. The retracting shaft has a first position and a second position for circumferential movement within the movement space. When the retracting shaft is at the first position, it rotates synchronously with the output gear in a first direction; when the retracting shaft rotates in a second direction and moves from the first position to the second position, a jacking portion provided on the retracting shaft presses against the torque-limiting component to move away from the output gear. When the retracting shaft rotates to the second position, the meshing end face of the torque-limiting component and the output gear disengages, and the retracting shaft rotates synchronously with the output gear in the second direction. The first direction is opposite to the second direction.

[0012] Preferably, the retracting shaft is rotatably sleeved on the support shaft, the output gear is sleeved on the retracting shaft, and the retracting shaft and the output gear are matched through engaging teeth and slots. The engaging teeth of the retracting shaft have the first position and the second position for circumferential movement within the corresponding slots of the output gear.

[0013] Preferably, the jacking portion of the retracting shaft includes third end face teeth that mesh with the inner ring of the second end face teeth of the torque-limiting component. The second end face teeth of the output gear are located on the outer ring of the third end face teeth. The torsional sliding surface is provided on the second end face teeth and / or the third end face teeth of the torque-limiting component; when the retracting shaft is at the first position, the third end face teeth are aligned with the second end face teeth of the output gear; when the retracting shaft is at the second position, the third end face teeth are misaligned with the second end face teeth of the output gear. When the retracting shaft rotates synchronously with the output gear in the first direction, the third end face teeth are aligned with the second end face teeth of the output gear and mesh with the second end face teeth of the torque-limiting component; when the retracting shaft rotates in the second direction, the retracting shaft moves from the first position to the second position relative to the output gear, and relative sliding occurs between the second end face teeth of the torque-limiting component and the third end face teeth through the torsional sliding surface. The third end face teeth axially push the torque-limiting component towards the input gear and compress the elastic retaining component, so that the meshing end face of the torque-limiting component and the output gear disengages.

[0014] Preferably, a limiting portion is provided on the retracting shaft, and the output gear cooperates with the limiting portion to axially limit the retracting shaft.

[0015] Preferably, the second end face teeth and the third end face teeth include tooth tops, tooth grooves, and the torsional sliding surfaces extending from the tooth tops to the bottoms of adjacent tooth grooves, and the torsional sliding surfaces are tooth surfaces inclined relative to the axial cross-section of the torque limiting member and / or the output gear.

[0016] Preferably, a tool withdrawal knob for manually rotating the tool withdrawal shaft is arranged on the tool withdrawal shaft.

[0017] Preferably, the tooth tops of the second end face teeth of the torque limiting member and the output gear are both smooth planes.

[0018] Preferably, the tooth profile of the first end face teeth is rectangular end face teeth with a rectangular cross-section, and the axial position of the first end face teeth of the torque limiting member relative to the first end face teeth of the input gear is adjustable.

[0019] Preferably, both the input gear and the output gear are connected with thrust bearings and the axial positions are fixed through the thrust bearings.

[0020] There is also provided an electric stapler, including a driving mechanism and a push rod mechanism. The key lies in that it includes a mounting bracket and the overload protection device described in any one of the above examples. The overload protection device is mounted through the mounting bracket. The input gear of the overload protection device is connected to the driving mechanism, and the output gear of the overload protection device is connected to the push rod mechanism.

[0021] As described above, the overload protection device and the electric stapler of an electric stapler according to the present invention have at least the following beneficial effects: the resistance generated by the engagement between the torque limiting member and the output gear through the torsional sliding surfaces of the second end face teeth to maintain a stable meshing state between the two; but when the torque transmitted by the driving mechanism is greater than the normal use load, the first end face teeth of the input gear drive the torque limiting member to rotate overload, and the excessive torque will break the resistance generated by the engagement between the torsional sliding surfaces, the meshing state is damaged, and relative sliding is generated between the torque limiting member and the output gear through the torsional sliding surfaces. The torque limiting member moves axially towards the input gear against the elastic force of the elastic retaining member, so that the second end face teeth of the torque limiting member and the output gear are disengaged, and the transmission of torque to the output gear is stopped, thereby achieving the purpose of protecting the driving mechanism and the transmission mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a schematic internal structure diagram of an electric stapler shown in an exemplary embodiment of the present application;

[0023] Figure 2 is Figure 1 exploded view of

[0024] Figure 3It is a schematic structural diagram of an overload protection device of an electric stapler in its normal state shown in an exemplary embodiment of the present application;

[0025] Figure 4 is Figure 3 a schematic diagram of the state of the overload protection device of the electric stapler in the present application when it is overloaded;

[0026] Figure 5 It is a schematic diagram of the mating state of the torque-limiting component for the retraction of the retraction shaft, the retraction shaft, and the output gear;

[0027] Figure 6 It is a schematic diagram of the mating state of the torque-limiting component for the retraction of the retraction shaft and the retraction shaft;

[0028] Figure 7 It is a schematic diagram of the mating state of the retraction shaft and the output gear when the retraction shaft retracts;

[0029] Figure 8 It is a schematic diagram of the state of the teeth and slots of the retraction shaft and the output gear at the first position when the retraction shaft is in its normal state;

[0030] Figure 9 It is a schematic diagram of the state of the teeth and slots of the retraction shaft and the output gear at the second position when the retraction shaft retracts;

[0031] Figure 10 It is a schematic diagram of the upward plane of the third end face teeth of the retraction shaft and the second end face teeth of the output gear at the first position when the retraction shaft is in its normal state;

[0032] Figure 11 It is a schematic diagram of the upward plane of the third end face teeth of the retraction shaft and the second end face teeth of the output gear at the second position when the retraction shaft retracts;

[0033] Figure 12 It is a schematic structural diagram of the retraction shaft and the retraction knob.

[0034] Wherein 1 - driving mechanism; 2 - push rod mechanism; 3 - mounting bracket; 4 - overload protection device; 401 - support shaft; 402 - input gear; 403 - output gear; 404 - torque-limiting component; 405 - elastic holding component; 4a - first end face teeth; 4b - second end face teeth; 4c - third end face teeth; 5 - torsional sliding surface; 6 - retraction shaft; 601 - limiting portion; 7 - retraction knob; 8 - tooth top; 9 - tooth groove; 10 - thrust bearing. Detailed implementation manners

[0035] The following describes the embodiments of the present invention through specific examples. Those skilled in the art can easily understand the other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments. Various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be understood that the preferred embodiments are only for illustrating the present invention, rather than for limiting the protection scope of the present invention.

[0036] In the following description, a large number of details are explored to provide a more thorough explanation of the embodiments of the present invention. However, it is obvious to those skilled in the art that the embodiments of the present invention can be implemented without these specific details. In other embodiments, well-known structures and devices are shown in the form of schematic diagrams rather than in detail to avoid making the embodiments of the present invention difficult to understand.

[0037] Figure 1 FIG. is a schematic internal structure diagram of an electric stapler shown in an exemplary embodiment of the present invention. The illustrated electric stapler can be used in laparoscopic surgery, for example, introduced into the surgical area through a trocar, and can also be used in open surgery. In some embodiments, the electric stapler is configured to be reusable with multiple disposable staple cartridges. In other embodiments, the handle and a part of the elongated cannula of the electric stapler can be reused, while the jaw assembly and the remaining part of the elongated cannula form a disposable staple magazine. At this time, the staple cartridge and the staple magazine are integrated. In still other embodiments, although the staple magazine is detachably connected to the rest of the electric stapler, the staple cartridge can still be detached from the staple magazine so that after one firing, a new staple cartridge can be replaced and loaded for reuse. In the illustration, the electric stapler uses a disposable staple magazine and integrates the staple cartridge with the staple magazine. It should be understood that the electric stapler herein is applicable to any of the above configurations and is not limited to these configurations.

[0038] Figure 2 For Figure 1 the exploded schematic diagram of, please refer to the attached Figure 1 and Figure 2 shown, an electric stapler includes a drive mechanism 1, a push rod mechanism 2, a mounting bracket 3, and an overload protection device 4. The overload protection device 4 is installed through the mounting bracket 3. The drive mechanism 1 drives the overload protection device 4 to transmit torque to the push rod mechanism 2. The push rod mechanism 2 pushes the cutting knife to perform actions such as tissue cutting and jaw closing. For the specific configuration and drive mode of the stapler jaw position, reference can be made to the published Chinese patent application CN113729823A, the authorized Chinese patents CN112914644B, CN111920471B, etc. The disclosure content of the above patent documents is incorporated herein by reference.

[0039] Figure 3 The following is a schematic structural view of an overload protection device 4 of an electric stapler shown in an exemplary embodiment of the present invention. Please refer to the appended Figure 3 illustrations and in combination with Figure 1 and 2 for description. An overload protection device 4 of an electric stapler includes a support shaft 401, an input gear 402, an output gear 403, a torque limiting member 404, and an elastic holding member 405. The input gear 402 is rotatably mounted on the support shaft 401 with the support shaft 401 as the central axis, and is used to connect the drive mechanism 1 of the electric stapler. The output gear 403 is rotatably mounted on the support shaft 401 with the support shaft 401 as the central axis, and is used to connect the push rod mechanism 2 of the electric stapler. The axial positions of the input gear 402 and the output gear 403 on the support shaft 401 are fixed.

[0040] Combined with the appended Figure 3 illustrations: The torque limiting member 404 is disposed between the input gear 402 and the output gear 403. The first end face of the torque limiting member 404 is meshed with the mating end face of the input gear 402 through the first end face teeth 4a. In the normal state, the torque limiting member 404 and the input gear 402 always remain in the meshed state. The second end face of the torque limiting member 404 is correspondingly provided with mating second end face teeth 4b with the mating end face of the output gear 403. The elastic holding member 405 is disposed between the torque limiting member 404 and the input gear 402. A torsional sliding surface 5 is provided on the second end face teeth 4b of the torque limiting member 404 and / or the output gear 403. In the actual implementation process, the elastic holding member 405 can adopt elastic elements such as a spiral spring and elastic rubber, and after being pre-compressed, it is installed between the torque limiting member 404 and the input gear 402, and is biased towards the direction of keeping the torque limiting member 404 and the output gear 403 in mesh. It can be imagined that in other embodiments, it is also feasible to pre-tension the elastic holding member 405 and keep it biased against the torque limiting member 404. The tooth profile of the first end face teeth 4a can be selected as rectangular end face teeth with a rectangular cross-section, and the axial position of the first end face teeth 4a of the torque limiting member 404 relative to the first end face teeth 4a of the input gear 402 is adjustable.

[0041] As Figure 3 illustrated: In the normal state, under the elastic force of the elastic holding member 405, the torque limiting member 404 and the output gear 403 are kept in mesh through the second end face teeth 4b.

[0042] As Figure 4As shown, during overload, for example, when the thickness of the anastomosed tissue is too large, the torque transmitted by the torque-limiting component 404 is greater than the specified threshold value, that is, when exceeding the normal operating load, relative sliding occurs between the torque-limiting component 404 and the output gear 403 through the torsional sliding surface 5. The torque-limiting component 404 moves axially towards the input gear 402 under the push of the torsional sliding surface 5 of the second end face teeth 4b of the output gear 403 and compresses the elastic holding component 405, causing the torque-limiting component 404 to disengage from the second end face teeth 4b of the output gear 403, resulting in gear slippage and the failure of the electric drive, thereby preventing the torque exceeding the normal operating load from being transmitted to the output gear 403.

[0043] In the actual implementation process, the input gear 402 can be directly mounted on the output shaft of the drive mechanism 1 or independently mounted on the support shaft 401. The entire electric drive mechanism 1 then transmits the electric power to the input gear 402 through a single-stage or multi-stage gear transmission method. Regardless of which method, it can be adaptively selected according to the specific installation space and structure of the electric stapler.

[0044] In order to avoid the huge surgical risks that the stapler jaws cannot be opened and the cutting blade cannot be retracted in some cases where the electric drive mechanism 1 fails, in some embodiments, in combination with the attached Figure 5 and 6 As shown, the overload protection device 4 further includes a retraction shaft 6 for manual blade retraction. The retraction shaft 6 is rotatably sleeved on the support shaft 401. As Figure 12 shown, a retraction knob 7 for manually rotating the retraction shaft 6 is arranged on the retraction shaft 6. The retraction knob 7 can be used as an additional accessory and installed on the retraction shaft 6 when manual blade retraction is required. The output gear 403 is sleeved on the retraction shaft 6. The retraction shaft 6 has a circumferential movement space relative to the output gear 403. The retraction shaft 6 can move back and forth between a first position and a second position along the circumferential direction within the movement space. When the retraction shaft 6 is in the first position, it rotates synchronously with the output gear 403 in a first direction; when the retraction shaft 6 rotates in a second direction and moves from the first position to the second position, the ejection portion provided on the retraction shaft 6 presses against the torque-limiting component 404 to move away from the output gear 403. When the retraction shaft 6 rotates to the second position, the meshing end face of the torque-limiting component 404 disengages from the output gear 403, and the retraction shaft 6 rotates synchronously with the output gear 403 in the second direction. The first direction is opposite to the second direction.

[0045] Specifically, in some embodiments, in combination with the attached Figure 8 and 9As shown, the retracting shaft 6 and the output gear 403 are engaged through a tooth and a groove. The moving space of the tooth in the corresponding groove is used as the moving space for the retracting shaft 6 to rotate axially relative to the output gear 403. The tooth of the retracting shaft 6 has a first position and a second position for circumferential rotation in the corresponding groove of the output gear 403. The tooth moves back and forth between the first position and the second position in the corresponding groove in the circumferential direction. More specifically, in combination with the attached Figure 7 As shown, the ejecting portion of the retracting shaft 6 includes a third end face tooth 4c that meshes with the inner ring of the second end face tooth 4b of the torque limiting member 404. The second end face tooth 4b of the output gear 403 is located on the outer ring of the third end face tooth 4c. The second end face tooth 4b and / or the third end face tooth 4c of the torque limiting member 404 are provided with the torsional sliding surface 5.

[0046] In combination with the attached Figure 8 and 10 As shown, when the retracting shaft 6 is in the first position, the third end face tooth 4c is aligned with the second end face tooth 4b of the output gear 403. At this time, the third end face tooth 4c and the second end face tooth 4b of the output gear 403 are simultaneously engaged with the second end face tooth 4b of the torque limiting member 404 and can maintain transmission when rotating in the first direction.

[0047] In combination with the attached Figure 9 and 11 As shown: when the retracting shaft 6 is in the second position, the third end face tooth 4c is misaligned with the second end face tooth 4b of the output gear 403. At this time, the tooth groove regions of the third end face tooth 4c and the second end face tooth 4b of the output gear 403 are opposite to each other. Similarly, the tooth groove regions of the second end face tooth 4b of the output gear 403 and the third end face tooth 4c are opposite to each other. Therefore, the second end face tooth 4b of the torque limiting member 404 cannot be engaged with the third end face tooth 4c and the second end face tooth 4b of the output gear 403, so that the second end face tooth 4b of the torque limiting member 404 is disengaged from the output gear 403. When the retracting shaft 6 and the output gear 403 rotate synchronously in the second direction, the torque will not be transmitted to the input gear 402.

[0048] In some embodiments, in combination with the attached Figure 6 As shown: a limiting portion 601 is provided on the retracting shaft 6. The output gear 403 cooperates with the limiting portion 601 to axially limit the retracting shaft 6. The axial position of the retracting shaft 6 is fixed by the output gear 403 with a fixed axial position.

[0049] In some embodiments, in combination with the attached Figure 7As shown: The second end face teeth 4b and the third end face teeth 4c further include tooth tops 8 and tooth grooves 9. The surface extending from the tooth top 8 to the bottom of the adjacent tooth groove 9 is the torsional sliding surface 5, and the torsional sliding surface 5 is a tooth surface inclined relative to the axial section of the torque limiting member 404 and / or the output gear 403. In the actual implementation process, the meshing state is maintained by the resistance generated by engaging with the torsional sliding surface 5. When the maximum resistance generated by the torsional sliding surface 5 is exceeded, relative sliding occurs, and the resistance can be controlled and adjusted by the friction coefficient of the torsional sliding surface 5, the pressure of the elastic holding member 405 on the torque limiting member 404, and the selection of the inclination angle of the torsional sliding surface 5. The tooth tops 8 of the second end face teeth 4b of the torque limiting member 404 and the output gear 403 are both smooth planes, and when the torque limiting member 404 and the output gear 403 slide relative to each other, they contact in a surface-to-surface manner, and the rotation is more stable.

[0050] In order to ensure the stable rotation of the input gear 402 and the output gear 403 within a limited space and also axially limit the two, in some embodiments, in combination with the attached Figure 1 and 2 As shown: Both the input gear 402 and the output gear 403 are connected with thrust bearings 10 and their axial positions are fixed by the thrust bearings 10.

[0051] The above embodiments only exemplarily illustrate the principles and effects of the present invention, rather than limiting the present invention. Any person familiar with this technology can modify or change the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or changes completed by those with ordinary knowledge in the technical field without departing from the spirit and technical idea disclosed by the present invention should still be covered by the claims of the present invention.

Claims

1. An overload protection device for an electric stapler, characterized in that, Comprising: Support shaft; Input gear, mounted on the support shaft for connecting to a drive mechanism; Output gear, mounted on the support shaft for connecting to the push rod mechanism of an electric stapler; the axial positions of the input gear and the output gear on the support shaft are fixed; Torque-limiting component, sleeved on the support shaft and located between the input gear and the output gear. The first end face of the torque-limiting component meshes with the mating end face of the input gear through first end face teeth, and the second end face of the torque-limiting component is correspondingly provided with mating second end face teeth with the mating end face of the output gear; Elastic retaining component, arranged between the torque-limiting component and the input gear, and keeping the torque-limiting component and the output gear in meshing through the second end face teeth under normal state; Wherein, a torsional sliding surface is provided on the second end face teeth of the torque-limiting component and / or the output gear. When the torque of the torque-limiting component is greater than a specified threshold value, relative sliding occurs between the torque-limiting component and the output gear through the torsional sliding surface, and the torque-limiting component moves axially towards the input gear against the elastic force of the elastic retaining component, so that the second end face teeth of the torque-limiting component and the output gear are disengaged; The overload protection device further includes a retracting shaft. The retracting shaft has a circumferential movement space relative to the output gear. The retracting shaft has a first position and a second position for circumferential movement within the movement space. When the retracting shaft is in the first position, it rotates synchronously with the output gear in a first direction; when the retracting shaft rotates in a second direction and moves from the first position to the second position, a jacking portion provided on the retracting shaft jacks up the torque-limiting component to be away from the output gear. When the retracting shaft rotates to the second position, the meshing end face of the torque-limiting component and the output gear is disengaged, and the retracting shaft rotates synchronously with the output gear in the second direction. The first direction and the second direction are opposite; The retracting shaft is rotatably sleeved on the support shaft, the output gear is sleeved on the retracting shaft, and the retracting shaft and the output gear are in cooperation through a tooth and a groove. The tooth of the retracting shaft has the first position and the second position for circumferential movement within the corresponding groove of the output gear in cooperation; 2. The overload protection device of the electric stapler according to claim 1, characterized in that: The jacking portion of the retracting shaft includes third end face teeth meshing with the inner ring of the second end face teeth of the torque-limiting component. The second end face teeth of the output gear are located on the outer ring of the third end face teeth. The torsional sliding surface is provided on the second end face teeth of the torque-limiting component and / or the third end face teeth; when the retracting shaft is in the first position, the third end face teeth are aligned with the second end face teeth of the output gear; when the retracting shaft is in the second position, the third end face teeth are misaligned with the second end face teeth of the output gear; 3. The overload protection device of the electric stapler according to claim 1 or 2, characterized in that: A limiting portion is provided on the retracting shaft, and the output gear cooperates with the limiting portion to axially limit the retracting shaft; 4. The overload protection device of the electric stapler according to claim 2, characterized in that: The second end face teeth and the third end face teeth include a tooth top, a tooth groove, and the torsional sliding surface extending from the tooth top to the bottom of the adjacent tooth groove. The torsional sliding surface is a tooth surface inclined relative to the axial section of the torque-limiting component and / or the output gear; 5. The overload protection device of the electric stapler according to claim 3, characterized in that: A retracting knob for manually rotating the retracting shaft is arranged on the retracting shaft.

6. The overload protection device of the electric stapler according to claim 4, wherein: The tooth tops of the second end face teeth of the torque limiting component and the output gear are both smooth planes.

7. The overload protection device of the electric stapler according to claim 1, characterized in that: The tooth profile of the first end face teeth is rectangular end face teeth with a rectangular cross-section, and the axial position of the first end face teeth of the torque limiting component relative to the first end face teeth of the input gear is adjustable.

8. The overload protection device of the electric stapler according to claim 1, characterized in that: Both the input gear and the output gear are connected with thrust bearings and their axial positions are fixed through the thrust bearings.

9. An electric stapler, comprising a driving mechanism and a push rod mechanism, characterized in that: It includes a mounting bracket and the overload protection device according to any one of claims 1-7. The overload protection device is mounted through the mounting bracket. The input gear of the overload protection device is connected to the driving mechanism, and the output gear of the overload protection device is connected to the push rod mechanism.

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