CN118645900A - A shock-absorbing and heat-dissipating power cabinet for electric power engineering - Google Patents

Abstract

The present invention discloses a shock-absorbing and heat-dissipating power cabinet for power engineering, comprising: a cabinet body, an outer shell, an inner shell being movably installed inside the outer shell, and the left and right sides of the inner shell being limit-connected with the inner wall of the outer shell through limit assemblies; a shock-absorbing module, comprising a first shock-absorbing assembly arranged at the bottom center of the inner shell, and second shock-absorbing assemblies being arranged on both sides of the first shock-absorbing assembly; and a heat-dissipating module, which can play a role of limiting support for the bottom of the inner shell through the second shock-absorbing assembly, and at the same time, the second shock-absorbing spring can play a role of buffering and shock-absorbing for the inner shell, and further play a role of supporting and buffering for the middle part of the bottom end of the inner shell through the first shock-absorbing assembly, thereby reducing the force on the second shock-absorbing assembly, thereby solving the problem of fast aging of the spring and improving the shock-absorbing effect.

Description

A shock-absorbing and heat-dissipating power cabinet for electric power engineering

Technical Field

The invention relates to the technical field of electric power equipment, in particular to a vibration-absorbing and heat-dissipating electric power cabinet used in electric power engineering.

Background Art

The power cabinet is a commonly used power infrastructure, which contains a large number of power components. With the rapid development of power technology, outdoor transformer boxes, power cabinets and other cabinets used to install various electrical components have also been fully developed.

However, when the existing power cabinet is in use, the springs arranged at the bottom of the power cabinet completely bear the gravity of the electronic cabinet and internal components, and there is no other support to share the burden of the springs. The springs age quickly after long-term use, and it is difficult to ensure the shock absorption effect. At the same time, the power cabinet usually dissipates heat inside the cabinet through an exhaust fan arranged on the top, but the heat deposited at the bottom of the cabinet is difficult to discharge, and the heat dissipation effect is poor. In this regard, we propose a shock-absorbing and heat-dissipating power cabinet for power engineering.

Summary of the invention

The purpose of this section is to summarize some aspects of embodiments of the present invention and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the specification abstract and the invention title of this application to avoid blurring the purpose of this section, the specification abstract and the invention title, and such simplifications or omissions cannot be used to limit the scope of the present invention.

In view of the above problems and/or the problems existing in the prior art, the present invention is proposed.

Therefore, the technical problem to be solved by the present invention is that after the wire strippers are used, a large amount of debris will remain on site, which is not easy to clean.

In order to solve the above technical problems, the present invention provides the following technical solutions: a shock-absorbing and heat-dissipating power cabinet for electric power engineering, comprising a cabinet body, an outer shell, an inner shell movably installed inside the outer shell, and the left and right sides of the inner shell are limitedly connected to the inner wall of the outer shell through a limit assembly;

A shock absorbing module, comprising a first shock absorbing assembly arranged at the center of the bottom of the inner shell, second shock absorbing assemblies are arranged on both sides of the first shock absorbing assembly, and the bottom of the inner shell is elastically connected to the inner bottom wall of the outer shell through the first shock absorbing assembly and the second shock absorbing assembly; and

The heat dissipation module comprises a first heat dissipation component arranged at the top end of the inner shell, a transmission component is arranged at the rear end of the first heat dissipation component, and a second heat dissipation component is transmission-connected to the bottom end of the transmission component.

As a preferred solution of the shock-absorbing and heat-dissipating power cabinet for power engineering described in the present invention, a first exhaust hole is provided at the rear end of the outer shell, limiting grooves are provided on both sides of the outer shell, and a second exhaust hole is provided at the rear end of the inner shell.

As a preferred solution of the shock-absorbing and heat-dissipating power cabinet for power engineering described in the present invention, the limit assembly includes a limit rod arranged in the limit groove, the outer surface of the limit rod is sleeved with a telescopic spring, the top of the telescopic spring is connected to a limit block, and one end of the limit block is sleeved on the outer surface of the limit rod, and the other end is fixedly connected to the outer wall of the inner shell.

As a preferred solution of the shock-absorbing and heat-dissipating power cabinet for power engineering described in the present invention, wherein: the first shock-absorbing component includes an elastic ring fixedly connected to the bottom center of the inner shell body, the bottom end of the elastic ring is provided with a supporting portion, and telescopic portions are provided on both sides of the elastic ring, the telescopic portions are movably connected to the inner bottom wall of the outer shell body, and the bottom of the supporting portion is fixedly connected to the inner bottom wall of the outer shell body through a first shock-absorbing spring.

As a preferred solution of the shock-absorbing and heat-dissipating power cabinet for power engineering described in the present invention, the second shock-absorbing assembly includes a fixed column fixedly connected to the bottom wall of the inner shell body, the upper end of the fixed column is movably connected to a telescopic column, the outer surfaces of the fixed column and the telescopic column are sleeved with a second shock-absorbing spring, and the top ends of the second shock-absorbing spring and the telescopic column are fixedly connected to the outer bottom wall of the inner shell body.

As a preferred solution of the shock-absorbing and heat-dissipating power cabinet for power engineering described in the present invention, the first heat dissipation component includes a servo motor fixedly installed at the center of the top end of the inner shell, the output end of the servo motor is connected to the drive shaft through a coupling, the bottom end of the drive shaft passes through the outer top wall of the inner shell, and extends to the interior thereof and is fixedly connected to a fan.

As a preferred solution of the shock-absorbing and heat-dissipating power cabinet for power engineering described in the present invention, the transmission assembly includes a driving wheel fixedly mounted on the outer surface of the driving shaft, the outer surface of the driving wheel is transmission-connected with a belt, the inner side of the rear end of the belt is transmission-connected with a driven wheel, and a rotating shaft is fixedly mounted at the center of the driven wheel.

As a preferred solution of the shock-absorbing and heat-dissipating power cabinet for power engineering of the present invention, the second heat-dissipating assembly comprises a rotating rod fixedly connected to the bottom end of the rotating shaft, the outer surface of the rotating rod is provided with a first external thread and a second external thread, the outer surface of the rotating rod is threadedly connected with a slide plate, and tooth plates are symmetrically installed on the left and right sides of the front end of the slide plate;

The second heat dissipation assembly further comprises a fixing rod arranged at the bottom end of the inner shell, the outer surface of the fixing rod is rotatably connected to a fan plate, and toothed rings adapted to the toothed plate are symmetrically arranged on the left and right sides of the rear end of the fan plate, and the rear end of the fan plate is meshed and connected to the toothed plate through the toothed ring;

The first external thread and the second external thread have opposite thread rotation directions, and upper and lower ends of the first external thread are connected to upper and lower ends of the second external thread.

Beneficial effects of the present invention:

1. The second shock-absorbing assembly can play a role of limiting support for the bottom of the inner shell. At the same time, the second shock-absorbing spring can play a role of buffering and shock-absorbing for the inner shell. The first shock-absorbing assembly can further play a role of supporting and buffering for the middle part of the bottom end of the inner shell, reducing the force on the second shock-absorbing assembly, thereby solving the problem of rapid aging of the spring and improving the shock-absorbing effect.

2. Through the first heat dissipation component arranged in the heat dissipation module, the gas in the upper part of the inner shell can be discharged to the outside of the device through the first heat dissipation hole and the second heat dissipation hole, and then through the transmission component arranged, the second heat dissipation component can be driven to operate while the first heat dissipation component is operating, so that the fan plate in the second heat dissipation component fans up and down, thereby the gas at the bottom end of the inner shell is discharged to the outside of the device through the first heat dissipation hole and the second heat dissipation hole, which solves the problem of poor heat dissipation effect of traditional power cabinets.

3. The setting of the limit assembly can play a role in limiting and fixing the two sides of the inner shell. At the same time, the limit block is sleeved on the limit rod and will not affect the up and down movement of the inner shell, ensuring that the shock absorbing module can be used normally.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative labor. Among them:

FIG. 1 is a perspective view of the overall structure of the present invention.

FIG. 2 is a side sectional view of the present invention.

FIG. 3 is a front cross-sectional view of the present invention.

FIG. 4 is an enlarged schematic diagram of the structure at point A in FIG. 3 of the present invention.

FIG. 5 is a perspective view of a second heat dissipation assembly according to the present invention.

FIG. 6 is a top cross-sectional view of the present invention.

FIG. 7 is an enlarged schematic diagram of the structure of the transmission assembly of the present invention.

DETAILED DESCRIPTION

In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the accompanying drawings.

In the following description, many specific details are set forth to facilitate a full understanding of the present invention, but the present invention may also be implemented in other ways different from those described herein, and those skilled in the art may make similar generalizations without violating the connotation of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

Secondly, the term "one embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The term "in one embodiment" that appears in different places in this specification does not necessarily refer to the same embodiment, nor does it refer to a separate or selective embodiment that is mutually exclusive with other embodiments.

Example

1 to 7 , this embodiment provides a shock-absorbing and heat-dissipating power cabinet for power engineering, including a cabinet 100 , a shock-absorbing module 200 and a heat-dissipating module 300 , wherein the shock-absorbing module 200 can provide buffering protection for electrical components in the cabinet 100 , and the heat-dissipating module 300 improves the heat-dissipating performance inside the cabinet 100 .

Specifically, the cabinet 100 includes an outer shell 101, and an inner shell 102 is movably installed inside the outer shell 101. The left and right sides of the inner shell 102 are limitedly connected to the inner wall of the outer shell 101 through a limit assembly 103. The inner shell 102 is connected to the inside of the outer shell 101 through a shock absorbing module 200 and a limit assembly 103. A cavity is opened inside the inner shell 102 to provide space for the installation of electrical components.

The shock absorbing module 200 includes a first shock absorbing assembly 201 arranged at the bottom center of the inner shell 102, and second shock absorbing assemblies 202 are arranged on both sides of the first shock absorbing assembly 201. The bottom of the inner shell 102 is elastically connected to the inner bottom wall of the outer shell 101 through the first shock absorbing assembly 201 and the second shock absorbing assembly 202. By setting up two groups of shock absorbing assemblies, it is possible to avoid the problem of excessive force on the spring in a single shock absorbing assembly, which leads to a high aging speed. At the same time, setting up two groups of shock absorbing assemblies further improves the shock absorbing effect of the device, so that the electrical components can be best protected.

The heat dissipation module 300 includes a first heat dissipation component 301 arranged at the top of the inner shell 102, and a transmission component 302 is arranged at the rear end of the first heat dissipation component 301. The bottom end of the transmission component 302 is transmission-connected to the second heat dissipation component 303. Through the first heat dissipation component 301, the gas in the upper part of the inner shell 102 can be discharged to the outside of the device through the first heat dissipation hole 101a and the second heat dissipation hole 102a. Then, through the transmission component 302, while the first heat dissipation component 301 is running, the second heat dissipation component 303 can be driven to operate, so that the fan plate 303g in the second heat dissipation component 303 is fanned up and down, so that the gas at the bottom end of the inner shell 102 is discharged to the outside of the device through the first heat dissipation hole 101a and the second heat dissipation hole 102a, thereby solving the problem of poor heat dissipation effect of traditional power cabinets.

Furthermore, the first shock absorbing assembly 201 includes an elastic ring 201a fixedly connected to the bottom center of the inner shell body 102, a supporting portion 201b is provided at the bottom end of the elastic ring 201a, telescopic portions 201c are provided on both sides of the elastic ring 201a, the telescopic portions 201c are movably connected to the inner bottom wall of the outer shell body 101, and the bottom of the supporting portion 201b is fixedly connected to the inner bottom wall of the outer shell body 101 through a first shock absorbing spring 201d.

The elastic ring 201a has a certain telescopic performance. When the inner shell 102 applies downward pressure, the elastic ring 201a can be compressed downward, and the telescopic parts 201c on both sides of the elastic ring 201a can move toward the inner side of the telescopic groove of the inner bottom wall of the outer shell 101 (as shown in Figure 4). The support part 201b will also move downward with the compression of the elastic ring 201a and squeeze the first shock-absorbing spring 201d. When the downward pressure of the inner shell 102 disappears, the inner shell 102 can rebound to its initial position under the action of the rebound force of the first shock-absorbing spring 201d and the elastic ring 201a.

The second shock absorbing assembly 202 includes a fixed column 202a fixedly connected to the inner bottom wall of the outer shell 101, and the upper end of the fixed column 202a is movably connected to the telescopic column 202b, and the outer surfaces of the fixed column 202a and the telescopic column 202b are sleeved with a second shock absorbing spring 202c, and the top ends of the second shock absorbing spring 202c and the telescopic column 202b are fixedly connected to the outer bottom wall of the inner shell 102.

Among them, a telescopic groove is opened inside the fixed column 202a, and the bottom end of the telescopic column 202b can be telescoped inside the fixed column 202a. When the inner shell 102 applies downward pressure, the telescopic column 202b and the second shock-absorbing spring 202c can move downward. After the downward pressure on the inner shell 102 disappears, the inner shell 102 can rebound to its initial position under the action of the rebound force of the second shock-absorbing spring 202c.

Furthermore, the first heat dissipation assembly 301 includes a servo motor 301a fixedly mounted at the top center of the inner shell 102, the output end of the servo motor 301a is connected to a drive shaft 301b via a coupling, the bottom end of the drive shaft 301b passes through the outer top wall of the inner shell 102, and extends to the interior thereof where a fan 301c is fixedly connected.

The servo motor 301a is a prior art and its specific structure is not described in detail. When the servo motor 301a is started, the servo motor 301a can drive the driving shaft 301b to rotate, and the driving shaft 301b can drive the fan 301c at the bottom to rotate. The fan 301c can form a fast-flowing airflow for the gas inside the inner shell 102, and discharge it through the second heat dissipation holes 102a opened at the rear end of the inner shell 102, and then through the first heat dissipation holes 101a opened on both sides of the outer shell 101, the hot gas can be discharged to the outside of the cabinet 100, thereby achieving the purpose of heat dissipation.

The transmission assembly 302 includes a driving wheel 302a fixedly mounted on the outer surface of the driving shaft 301b, the outer surface of the driving wheel 302a is transmission-connected with a belt 302b, the inner side of the rear end of the belt 302b is transmission-connected with a driven wheel 302c, and a rotating shaft 302d is fixedly mounted at the center of the driven wheel 302c.

When the driving shaft 301b rotates, it can drive the driving wheel 302a to rotate at the same time, the driving wheel 302a can drive the belt 302b to rotate, the belt 302b can drive the driven wheel 302c to rotate, and the driven wheel 302c can drive the rotating shaft 302d to rotate.

Furthermore, the second heat dissipation component 303 includes a rotating rod 303a fixedly connected to the bottom end of the rotating shaft 302d, the outer surface of the rotating rod 303a is provided with a first external thread 303b and a second external thread 303c, the outer surface of the rotating rod 303a is threadedly connected to a slide plate 303d, and tooth plates 303e are symmetrically installed on the left and right sides of the front end of the slide plate 303d. The second heat dissipation component 303 also includes a fixed rod 303f arranged at the bottom end of the inner shell 102, the outer surface of the fixed rod 303f is rotatably connected to a fan plate 303g, and the left and right sides of the rear end of the fan plate 303g are symmetrically provided with tooth rings 303h adapted to the tooth plate 303e, the rear end of the fan plate 303g is meshed with the tooth plate 303e through the tooth ring 303h, the first external thread 303b and the second external thread 303c have opposite thread rotation directions, and the upper and lower ends of the first external thread 303b are connected to the upper and lower ends of the second external thread 303c.

When the rotating shaft 302d rotates, it can drive the rotating rod 303a at the bottom to rotate. The slide plate 303d threadedly connected to the rotating rod 303a can first move downward along the first external thread 303b, and when it moves to the connection between the first external thread 303b and the second external thread 303c at the bottom, it can move upward along the second external thread 303c, and repeat this cycle. Under the continuous rotation of the rotating rod 303a, the slide plate 303d can realize up and down reciprocating motion, and the slide plate 303d can drive the two tooth plates 303f to reciprocate up and down, and the fan plate 303g meshing with the tooth plate 303f through the gear ring 303h can fan up and down, so that under the continuous fanning of the fan plate 303g, the gas at the bottom of the inner shell 102 can be discharged through the second heat dissipation hole 102a, and then through the first heat dissipation holes 101a opened on both sides of the outer shell 101, the hot gas can be discharged to the outside of the cabinet 100, thereby further improving the heat dissipation effect inside the cabinet 100.

Preferably, a first exhaust hole 101a is provided at the rear end of the outer shell 101, limiting grooves 101b are provided on both sides of the outer shell 101, and a second exhaust hole 102a is provided at the rear end of the inner shell 102. The limiting assembly 103 includes a limiting rod 103a arranged in the limiting groove 101b, and the outer surface of the limiting rod 103a is sleeved with a telescopic spring 103b, the top of the telescopic spring 103b is connected to a limiting block 103c, and one end of the limiting block 103c is sleeved on the outer surface of the limiting rod 103a, and the other end is fixedly connected to the outer wall of the inner shell 102.

The setting of the limit assembly 103 can limit and fix the two sides of the inner shell 102. At the same time, the limit block 103c in the limit assembly 103 is sleeved on the limit rod 103a, and will not affect the up and down movement of the inner shell 102, thereby ensuring that the shock absorbing module can be used normally. The setting of the telescopic spring 103b can move the limit block 103c downward and rebound it to its initial position after losing its force.

Importantly, it should be noted that the construction and arrangement of the present application shown in a number of different exemplary embodiments are only exemplary. Although only a few embodiments are described in detail in this disclosure, it should be readily understood by those who refer to this disclosure that many modifications are possible (e.g., the size, scale, structure, shape and proportion of various elements, and parameter values (e.g., temperature, pressure, etc.), mounting arrangements, use of materials, color, changes in orientation, etc.) without substantially departing from the novel teachings and advantages of the subject matter described in the application. For example, an element shown as integrally formed may be composed of multiple parts or elements, the position of the element may be inverted or otherwise changed, and the nature or number or position of the discrete element may be changed or changed. Therefore, all such modifications are intended to be included within the scope of the present invention. The order or sequence of any process or method steps may be changed or reordered according to an alternative embodiment. In the claims, any "device plus function" clause is intended to cover the structure described herein that performs the function, and is not only structurally equivalent but also equivalent structure. Other substitutions, modifications, changes and omissions may be made in the design, operating conditions and arrangement of the exemplary embodiments without departing from the scope of the present invention. Therefore, the invention is not limited to a specific embodiment, but extends to numerous modifications still falling within the scope of the appended claims.

Additionally, in order to provide a concise description of exemplary embodiments, all features of an actual embodiment may not be described (ie, those features that are not relevant to the best mode presently contemplated for carrying out the invention or those that are not relevant to implementing the invention).

It will be appreciated that in the development of any actual implementation, as in any engineering or design project, numerous implementation-specific decisions may be made. Such a development effort may be complex and time-consuming, but will be a routine task of design, fabrication, and production for those of ordinary skill having the benefit of this disclosure without undue experimentation.

It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims (8)

1. A shock-absorbing and heat-dissipating power cabinet for electric power engineering, characterized in that: it includes: A cabinet (100) comprises an outer shell (101), an inner shell (102) being movably mounted inside the outer shell (101), and left and right sides of the inner shell (102) being position-limitingly connected to the inner wall of the outer shell (101) via a position-limiting assembly (103); A shock absorbing module (200), comprising a first shock absorbing component (201) arranged at the center of the bottom of the inner shell (102), second shock absorbing components (202) being arranged on both sides of the first shock absorbing component (201), the bottom of the inner shell (102) being elastically connected to the inner bottom wall of the outer shell (101) via the first shock absorbing component (201) and the second shock absorbing component (202); and The heat dissipation module (300) comprises a first heat dissipation component (301) arranged at the top end of the inner shell (102), a transmission component (302) being arranged at the rear end of the first heat dissipation component (301), and a second heat dissipation component (303) being transmission-connected to the bottom end of the transmission component (302). 2. The shock-absorbing and heat-dissipating power cabinet for power engineering as claimed in claim 1 is characterized in that: a first heat dissipation hole (101a) is provided at the rear end of the outer shell (101), limiting grooves (101b) are provided on both sides of the outer shell (101), and a second heat dissipation hole (102a) is provided at the rear end of the inner shell (102). 3. The shock-absorbing and heat-dissipating power cabinet for power engineering as claimed in claim 1 is characterized in that: the limit assembly (103) includes a limit rod (103a) arranged in the limit groove (101b), the outer surface of the limit rod (103a) is sleeved with a telescopic spring (103b), the top of the telescopic spring (103b) is connected to a limit block (103c), and one end of the limit block (103c) is sleeved on the outer surface of the limit rod (103a), and the other end is fixedly connected to the outer wall of the inner shell (102). 4. A shock-absorbing and heat-dissipating power cabinet for power engineering as claimed in any one of claim 3, characterized in that: the first shock-absorbing component (201) comprises an elastic ring (201a) fixedly connected to the center of the bottom of the inner shell (102), a supporting portion (201b) is provided at the bottom end of the elastic ring (201a), telescopic portions (201c) are provided on both sides of the elastic ring (201a), the telescopic portions (201c) are movably connected to the inner bottom wall of the outer shell (101), and the bottom of the supporting portion (201b) is fixedly connected to the inner bottom wall of the outer shell (101) through a first shock-absorbing spring (201d). 5. The shock-absorbing and heat-dissipating power cabinet for power engineering as claimed in any one of claims 1 to 4, characterized in that: the second shock-absorbing component (202) includes a fixed column (202a) fixedly connected to the inner bottom wall of the outer shell (101), the upper end of the fixed column (202a) is movably connected to a telescopic column (202b), the outer surfaces of the fixed column (202a) and the telescopic column (202b) are sleeved with a second shock-absorbing spring (202c), and the top ends of the second shock-absorbing spring (202c) and the telescopic column (202b) are fixedly connected to the outer bottom wall of the inner shell (102). 6. The shock-absorbing and heat-dissipating power cabinet for power engineering as claimed in claim 5, characterized in that: the first heat dissipation component (301) includes a servo motor (301a) fixedly mounted at the center of the top end of the inner shell (102), the output end of the servo motor (301a) is connected to a drive shaft (301b) through a coupling, and the bottom end of the drive shaft (301b) passes through the outer top wall of the inner shell (102) and extends to the inside thereof to be fixedly connected to a fan (301c). 7. The shock-absorbing and heat-dissipating power cabinet for power engineering as claimed in claim 6, characterized in that: the transmission component (302) includes a driving wheel (302a) fixedly mounted on the outer surface of the driving shaft (301b), the outer surface of the driving wheel (302a) is transmission-connected with a belt (302b), the inner side of the rear end of the belt (302b) is transmission-connected with a driven wheel (302c), and a rotating shaft (302d) is fixedly mounted at the center of the driven wheel (302c). 8. The shock-absorbing and heat-dissipating power cabinet for electric power engineering according to claim 7, characterized in that: the second heat-dissipating assembly (303) comprises a rotating rod (303a) fixedly connected to the bottom end of the rotating shaft (302d), the outer surface of the rotating rod (303a) is provided with a first external thread (303b) and a second external thread (303c), the outer surface of the rotating rod (303a) is threadedly connected with a slide plate (303d), and tooth plates (303e) are symmetrically installed on the left and right sides of the front end of the slide plate (303d); The second heat dissipation component (303) further comprises a fixing rod (303f) arranged at the bottom end inside the inner shell (102); the outer surface of the fixing rod (303f) is rotatably connected to a fan plate (303g); tooth rings (303h) adapted to the tooth plate (303e) are symmetrically arranged on the left and right sides of the rear end of the fan plate (303g); the rear end of the fan plate (303g) is meshedly connected to the tooth plate (303e) via the tooth ring (303h); The first external thread (303b) and the second external thread (303c) have opposite thread rotation directions, and the upper and lower ends of the first external thread (303b) are connected to the upper and lower ends of the second external thread (303c).