TWM596708U - Bike hub clutch structure - Google Patents

Abstract

This creation includes: the hub housing and the ratchet seat are rotatably sleeved on the mandrel through the first, second, third, and fourth bearings, the hub housing is provided with an accommodating space, and the interior has a retaining wall and Internal thread; the ratchet seat is provided with a convex ring that can extend into the accommodating space, and the convex ring is provided with a plurality of first cogs; a driven gear plate has a first inner diameter sleeved on the outer periphery of the convex ring of the ratchet seat, the driven gear plate The outer periphery is provided with an external thread to be screwed with the internal thread of the hub housing, the driven gear is provided with a joint surface, and the joint surface is distributed with a plurality of first ratchet teeth; a clutch gear plate has a second inner diameter, and the second inner diameter is distributed with a plurality of second The cogs mesh with the first cogs of the ratchet seat. The clutch gear has an annulus, and a plurality of second ratchets are distributed on the annulus to mesh with the first ratchets of the driven gear; a biasing member is sleeved on the ratchet seat The outer circumference of the convex ring is located between the clutch gear plate and the retaining wall of the accommodating space to push the clutch gear plate and the driven gear plate to engage, thereby achieving the purposes of fast transmission response and convenient assembly.

Description

Clutch structure of bicycle hub

This creative department relates to bicycles, especially the bicycle hub structure.

Please refer to the ratchet structure of the bicycle hub of M534113 in my country, which includes: a hub, a sleeve on one side of the hub and a ratchet group. The center axis of the flower hub is provided with a center, and a receiving groove is recessed on one side of the flower hub. The inner edge of the receiving groove is ring-shaped to form an internal thread section. The flower hub is located at the innermost side of the receiving groove and the other side of the flower hub The sleeve is provided with a bearing. The sleeve is provided with at least one bearing on both inner sides, and a stepped edge portion with a convex outer diameter is formed on the outer side of the sleeve. The stepped edge portion is integrally formed with a detent seat on one side away from the sleeve. A plurality of pawl grooves are provided on the diameter, and a ring between each of the pawl grooves is provided on the pawl seat, and a plurality of pawl grooves are provided on the outer diameter of the pawl groove, and a ring between each pawl groove is provided on the outer diameter of the pawl seat. The inner end of the pawl groove is provided with an accommodating portion, and a coupling member is provided on one side of the sleeve away from the hub for interlocking and coupling with the vehicle core.

The ratchet group is composed of a plurality of ratchets, a plurality of elastic members and a ratchet ring. Each ratchet is accommodated in each ratchet groove of the ratchet seat, and the ratchet has an arc-shaped set end , And a plurality of outward-facing claws are extended toward the other end, so that the pawl can rotate relative to the pawl groove, the first end of the elastic member is accommodated in the accommodating portion of the sleeve, and the second end of the elastic member is Against the back of the pawl, provide the power of pawl recovery. The ratchet ring is locked by the external thread section and the internal thread section looped on the inner edge of the receptacle of the hub, the ratchet ring is provided with a plurality of ratchet teeth on the inner periphery, and the hub sleeve is installed on one side of the hub And interpenetrating with the car center. Through the rotation of the sleeve, the claws of the ratchets are engaged with the ratchet teeth of the ratchet ring to drive the ratchet ring and the hub to rotate. Conversely, when the sleeve is reversed, each pawl is pressed by the ratchet ring to press the elastic member, and several claws of the pawl are separated from the ratchet teeth of the ratchet ring, which cannot drive the hub, so that the hub can Unidirectional rotation. It is characterized by the fact that the angles of the claw tips of the claws of the claws increase in sequence.

In this way, each pawl is pressed against its back by an elastic member, so that several claws of the pawl and the ratchet teeth in the ratchet ring are caught, so that the sleeve drives the hub. On the contrary, when each ratchet and the ratchet ring are relatively reversed, the ratchet teeth of the ratchet ring are meshed with a relatively number of ratchet teeth to form an engagement length with a certain stroke. The angle becomes larger in sequence. When the claw tips of these claws are engaged with the relative number of ratchet teeth in the ratchet ring of the ratchet ring, they can be completely closed to form an engagement gap from a small to a large gap, which makes the The claws can be detached from the ratchet teeth of the ratchet ring more quickly and smoothly, and the elastic member is pressed to make the hub and the ratchets idle, achieving unidirectional transmission between the sleeve and the hub.

However, the aforementioned sleeve drives the hub to rotate, but only the ratchet teeth of several pawls mesh with some ratchet teeth of the ratchet ring to drive the hub to rotate forward, and its driving power is quite limited, and the hub is driven to rotate The reaction speed is slow, especially when the ratchet teeth of the ratchet ring are engaged with a number of pawls, and each of the pawls and an elastic piece is pressed against the back of the pawl, which can make the pawls outside the pawl and the ratchet ring The relative number of ratchet teeth meshes, and there are many integral parts, which is quite time-consuming and complicated to assemble.

Here, this creation provides a bicycle hub clutch structure. The clutch gear of the ratchet seat can be engaged with the driven gear by the elastic force of a biasing member, which in turn causes the driven gear to rotate the hub casing. The bicycle moves forward, with a minimum of components to drive the hub to rotate, and the number of teeth meshed between the clutch gear and the driven gear is large, and the bite area is large, which can achieve fast transmission response and assembly. The purpose of convenience.

Another purpose of this creation is that the driven gear has a conical joint surface and the clutch gear has a conical torus. When the clutch gear is pushed against the driven gear by the elastic force of the biasing member, When the second ratchet tooth on the ring surface of the clutch gear disc is engaged with the first ratchet tooth on the joint surface of the driven gear disc, the conical ring surface of the clutch gear disc has a guiding function, which can quickly and accurately make the clutch tooth The second ratchet teeth of the disc mesh with the first ratchet teeth of the driven gear disc, so as to achieve the purpose of precise adhesion and fast transmission.

To achieve the above purpose, the present invention discloses a bicycle hub clutch structure, which includes: a mandrel, a hub housing, a ratchet seat, a driven gear disc, a clutch gear disc and a biasing member. A mandrel. The flower hub shell is rotatably sleeved on the mandrel, the flower hub shell is provided with an accommodating space, and an internal thread and a retaining wall are provided inside the accommodating space, and the inner diameter of the retaining wall is smaller than the The inner diameter of the accommodating space; the ratchet seat is rotatably sleeved on the mandrel, the ratchet seat is provided with a convex ring toward the hub housing, and a plurality of first cogs are radially provided on the outer circumference of the convex ring The driven gear plate has a first inner diameter sleeved on the outer periphery of the convex ring of the ratchet seat. The outer circumference of the driven gear plate is provided with an external thread. The external thread is screwed with the internal thread of the hub housing. The driven gear is provided with a joint surface facing the hub housing, the joint surface is annularly distributed with a plurality of first ratchet teeth; the clutch gear plate has a second inner diameter, and the second inner diameter is annularly distributed with a plurality of second inserts Teeth, the second cogs mesh with the first cogs of the ratchet seat, the clutch gear plate has a torus facing the ratchet seat, the torus has a plurality of second ratchets distributed in a ring shape, the second ratchets and the The first ratchet teeth of the driven gear wheel are engaged; the biasing member is disposed between the clutch gear wheel and the retaining wall of the hub housing to push the clutch gear wheel into engagement with the driven gear wheel.

Wherein, the engaging surface of the driven gear and the toroidal surface of the clutch gear are cones shape.

Wherein, the accommodating space group of the hub housing is equipped with a retaining ring, the retaining ring has a radial surface and a ring wall, the radial surface is in close contact with the retaining wall, the annular wall of the retaining ring and the accommodating space The peripheral wall cooperates, and the biasing member is wound with a spiral ring into several turns and is tapered. The end of the biasing member in contact with the diameter surface of the retaining ring is a large circular diameter, and the end of the biasing member in contact with the clutch gear disc is Small round path.

Wherein, the outer periphery of the ratchet seat is provided with a stop ring, the outer diameter of the stop ring is larger than the outer diameter of the convex ring, the outer periphery of the stop ring is provided with an annular dust cover, the dust cover seals the flower The opening of the accommodating space of the hub shell.

Wherein, one side of the driven gear disc facing the ratchet seat is provided with a tool engagement configuration for the tool to engage to force the driven gear disc on the hub housing.

Wherein, the hub housing is rotatably sleeved on the mandrel by a first bearing and a second bearing, and the ratchet seat is rotatably sleeved in the heart by a third bearing and a fourth bearing axis.

Wherein, a hollow set of tubes is provided between the third bearing and the fourth bearing, and the sleeve is sleeved on the mandrel.

Wherein, the number of teeth of the first ratchet and/or the second ratchet is 72 teeth, 90 teeth or 120 teeth.

Wherein, the first cog and the second cog are arranged parallel to the mandrel.

Wherein, a first cover is screwed on the first end of the mandrel, and a second cover is screwed on the second end of the mandrel.

Therefore, this creation has at least the following advantages:

1. This creation is a group in which the ratchet seat drives the hub shell to rotate, so that the wheels go forward With fewer components and simple structure, it is easy to assemble and greatly reduce the cost. In addition to the fact that the ratchet seat drives the hub hub to rotate, the component ring, biasing member, clutch gear and driven gear are all arranged in the hub The housing space of the housing is sealed by the dust cover of the ratchet seat, which can prevent the dust from entering from outside, and ensure that the clutch gear and the driven gear in the housing space are accurately meshed and transmitted, so that the pedal can drive the bicycle to Going forward is more reliable, and greatly reduces the failure rate.

2. The direction of the driven sprocket facing the hub shell is a conical joint surface, which can increase the number of teeth of the first ratchet arranged on the surface. The clutch sprocket has a conical shape facing the ratchet seat. The torus can increase the number of teeth of the second ratchet teeth arranged on the surface, so that the more teeth the clutch gear and the driven gear mesh with each other, the more powerful and stable the power is, and the smooth transmission of the stepping bicycle And solid.

3. Because the joint surface of the driven gear plate is conical and the annular surface of the clutch gear plate is conical in this creation, when the clutch gear plate is pushed against the driven gear plate by the elastic force of the biasing member, the clutch gear plate ring is made When the second ratchet on the surface meshes with the first ratchet on the joint surface of the driven gear, due to the guiding effect of the conical ring surface, the second ratchet of the clutch gear can be quickly and accurately The first ratchet teeth of the movable sprocket are meshed, and the closeness is accurate, which achieves fast transmission, so that the ratchet seat quickly drives the hub hub rotation to make the bicycle move forward quickly.

10: Mandrel

101: the first end

102: second end

103: the first bearing

104: second bearing

105: first cover

106: second cover

107: third bearing

108: fourth bearing

109: casing

110: locating ring

20: Flower hub shell

21: accommodating space

22: Retaining wall

23: retaining ring

231: radial surface

232: ring wall

24: internal thread

30: Ratchet seat

31: Convex ring

32: The first cog

33: stop ring

34: dust cover

40: driven chainring

41: The first inner diameter

42: external thread

43: Joint surface

44: first ratchet

45: outside diameter surface

46: Tool engagement configuration

50: clutch chainring

51: second inner diameter

52: second cog

53: Torus

54: second ratchet

60: biasing member

FIG. 1 is a combined perspective view of an embodiment of creation.

FIG. 2 is an exploded perspective view of the creative embodiment.

FIG. 3 is an exploded perspective view of another direction of the creative embodiment.

FIG. 4A is a combined cross-sectional view of the authoring embodiment.

FIG. 4B is a partially enlarged view of FIG. 4A.

FIG. 4C is an operation diagram of FIG. 4B.

The detailed content and technical description of this creation are now further explained with examples, but it should be understood that these examples are for illustrative purposes only and should not be construed as limitations on the implementation of the creation.

Please refer to FIG. 1 to FIG. 3 and FIG. 4A to FIG. 4C, this creation discloses a bicycle hub clutch structure, including a mandrel 10, a hub housing 20, a ratchet seat 30, a driven gear 40, a Clutch gear 50 and a biasing member 60.

The mandrel 10 has a first end 101 and a second end 102 in different directions. The mandrel 10 passes through the center of the hub housing 20. The hub housing 20 borrows a first bearing 103 and a second bearing 104 Rotatably sleeved on the mandrel 10, the first bearing 103 is adjacent to the first end 101 of the mandrel 10, the second bearing 104 is located in the middle of the mandrel 10, the first end 101 of the mandrel 10 is screwed with a first The cover 105 and the second end 102 of the mandrel 10 are screwed to a second cover 106.

The hub housing 20 is a hollow body penetrating at both ends. A housing space 21 is provided in the direction facing the ratchet seat 30. The circular diameter inside the housing space 21 is smaller than the circular diameter of the housing space 21 to form a block The wall 22 and the inner assembly of the accommodating space 21 are equipped with a retaining ring 23. The retaining ring 23 has a radial surface 231 and a ring wall 232. The radial surface 231 of the retaining ring 23 is attached to the retaining wall 22. The peripheral wall of the accommodating space 21 cooperates, and the external opening of the accommodating space 21 is provided with an internal thread 24.

The ratchet seat 30 is a hollow body. A convex ring 31 is provided in the direction of the hub housing 20. The convex ring 31 extends into the accommodating space 21 of the hub housing 20. The outer periphery of the convex ring 31 is annular There are a plurality of first cogs 32, the first cogs 32 are arranged parallel to the mandrel 10, and the outer periphery of the ratchet seat 30 is sleeved There is a stop ring 33, the outer diameter of the stop ring 33 is larger than the outer diameter of the convex ring 31, the outer periphery of the stop ring 33 is sleeved with a ring-shaped dust cover 34, the dust cover 34 seals the housing of the hub housing 20 Opening of space 21. The ratchet seat 30 is rotatably sleeved on the mandrel 10 by a third bearing 107 and a fourth bearing 108, so that the ratchet seat 30 can rotate around the mandrel 10, and a hollow is provided between the third bearing 107 and the fourth bearing 108 A set of tubes 109, the sleeve 109 is sleeved on the mandrel 10, a positioning ring 110 is provided between the second bearing 103 and the third bearing 107, and the positioning ring 110 is sleeved on the mandrel 10.

The driven sprocket 40 is a circular ring body having a first inner diameter 41 which is sleeved on the outer periphery of the convex ring 31 of the ratchet seat 30. The outer circumference of the driven sprocket 40 is provided with an external thread 42. The external thread 42 is screwed with the internal thread 24 of the hub housing 10, and the driven gear 40 has a conical engagement surface 43 facing the hub housing 10, and the engagement surface 43 is annularly distributed with a plurality of first ratchet teeth 44, An outer diameter surface 45 of the driven sprocket 40 facing the ratchet seat 30 is connected to a stop ring 33 of the ratchet seat 30. A tool engagement configuration 46 is provided on one side of the driven sprocket 40 facing the ratchet seat 30 for When the tool is engaged to force the driven gear 40 on the hub housing 20, the tool engagement configuration 46 of the present embodiment is provided with a plurality of grooves on a side diameter surface ring of the ratchet seat 30.

The clutch gear 50 is a circular ring body having a second inner diameter 51. The second inner diameter 51 is annularly distributed with a plurality of second cogs 52. The second cogs 52 are arranged parallel to the mandrel 10, and the second cogs 52 meshes with the first cog 32 of the ratchet seat 30, and the clutch gear plate 50 has a conical ring surface 53 facing the ratchet seat 30, and the ring surface 53 is circularly distributed with a plurality of second ratchet teeth 54, the second ratchet teeth 54 meshes with the first ratchet 44 of the driven gear 40, and the number of teeth of the first ratchet 44 and/or the second ratchet 54 may be 72 teeth, 90 teeth, or 120 teeth.

The biasing member 60 is wound by a spiral coil into several turns to be axially expandable and contractable. According to the axial view of the mandrel 10, the biasing member 60 has a taper and is sleeved on the outer periphery of the convex ring 31 of the ratchet seat 30. The piece 60 is located between the clutch gear 50 and the retaining wall 22 of the hub housing 20. In this embodiment, the biasing member 60 is bounded between the clutch gear 50 and the radial surface 231 of the retaining ring 23 The end of the pressing member 60 contacting the diameter surface 231 of the retaining ring 23 has a large circular diameter, and the end of the biasing member 60 contacting the clutch gear 50 is a small circular diameter. The biasing member 60 pushes the clutch gear 50 and the driven gear 40 engages so that the second ratchet 54 of the clutch gear 50 meshes with the first ratchet 44 of the driven gear 40.

With this structure, please refer to FIG. 4A and FIG. 4B again. When the bicycle is stepped forward, the ratchet seat 30 will be driven to generate forward rotation, due to the second cog 52 of the clutch gear 50 and the first engagement of the ratchet seat 30 The meshing of the teeth 32 will drive the clutch gear 50 to rotate forward, and the biasing member 60 constantly pushes the clutch gear 50 against the driven gear 40, so that the second ratchet 54 of the clutch gear 50 and the driven tooth The first ratchet teeth 44 of the disk 40 mesh, which in turn drives the driven gear disk 40 to rotate and the external thread 42 on the outer periphery of the driven gear disk 40 is screwed together with the internal thread 23 of the hub hub housing 10, so the hub hub shell can be driven The body 20 rotates forward, causing the wheels to walk forward.

When the bicycle is reversed, the ratchet seat 30 will be driven to produce reverse rotation. The second cog 52 of the clutch gear 50 meshes with the first cog 32 of the ratchet seat 30, which will drive the clutch gear 50 to rotate in reverse. When the second ratchet 54 of the clutch gear 50 rotates in the reverse direction, it will be pushed away by the first ratchet 44 of the driven gear 40 to move toward the biasing member 60 and cause the biasing member 60 to be compressed as shown in FIG. 4C Since the driven gear 40 is not driven by the clutch gear 50, the hub housing 20 is in an idle state and cannot drive the wheels forward.

On the transmission, the clutch gear 50 on the ratchet seat 30 can be engaged with the driven gear 40 by the elastic force of the biasing member 60, and then the driven gear 40 drives the hub housing 10 to rotate, so that the bicycle moves forward Compared with the above-mentioned conventional technology, the smallest component drives the hub hub 10 to rotate, and the number of teeth meshed between the clutch gear 50 and the driven gear 40 is large. It should be quick and easy to assemble.

It is worth mentioning that in this creation, the driven gear 40 has a conical joint surface 43, and the clutch gear 50 has a conical ring surface 53. When the clutch gear 50 is biased by the elastic force of the biasing member 60, To the driven gear 40, when the second ratchet 54 on the ring surface 53 of the clutch gear 50 is engaged with the first ratchet 44 on the engaging surface 43 of the driven gear 40, the conical shape of the clutch gear 50 is conical The annulus 53 has a guiding function, which can quickly and accurately mesh the second ratchet teeth 54 of the clutch gear 50 with the first ratchet teeth 44 of the driven gear 40 to achieve the purpose of precise and fast transmission.

This creation has at least the following advantages:

1. In this creation, the ratchet seat 30 drives the hub housing 20 to rotate to make the wheel move forward with fewer components, which makes the structure simple and convenient to assemble, which greatly reduces the cost. In addition to the ratchet seat 30 driving the hub housing 20 to rotate The component retaining ring 23, the biasing member 60, the clutch gear 50, and the driven gear 40 are all arranged in the accommodating space 21 of the hub housing 20, and are sealed by the dust cover 33 of the ratchet seat 30. Preventing outside dust from entering can ensure that the clutch gear 50 and the driven gear 40 in the accommodating space 21 are accurately meshed and transmitted, so that the pedals can drive the bicycle forward and the failure rate is reduced.

2. The direction of the driven sprocket 40 facing the hub housing 10 in this creation is a conical joint surface 43, which can increase the number of teeth of the first ratchet 44 arranged on its surface, and the clutch sprocket 50 faces the ratchet seat The 30 direction has a conical ring surface 53 which can expand the number of teeth of the second ratchet teeth 54 arranged on the surface, thereby increasing the number of teeth of the clutch gear 50 and the driven gear 40 to mesh with each other, making the bicycle step forward The driving speed is fast and stable.

3. Since the joint surface 43 of the driven gear 40 is conical in this creation, the annular surface 53 of the clutch gear 50 is conical. When the clutch gear 50 is pushed against the driven gear by the elastic force of the biasing member 60 40. When the second ratchet 54 on the ring surface 53 of the clutch gear 50 engages with the first ratchet 44 on the joint surface 43 of the driven gear 40, the conical ring surface 53 has a guiding effect. Quickly and accurately make the second ratchet 54 of the clutch gear 50 mesh with the first ratchet 44 of the driven gear 40, which can achieve good closeness and fast transmission, so that the ratchet seat 30 can quickly drive the hub housing 20 to rotate To drive the bicycle forward.

This creation has been disclosed in the above with preferred embodiments. However, those skilled in the art should understand that this embodiment is only for depicting this creation, and should not be interpreted as limiting the scope of this creation. It should be noted that all changes and replacements equivalent to this embodiment should be included in the scope of this creation. Therefore, the scope of protection of this creation shall be as defined in the scope of patent application below.

10: Mandrel

101: the first end

102: second end

103: the first bearing

104: second bearing

105: first cover

106: second cover

107: third bearing

108: fourth bearing

109: casing

110: locating ring

20: Flower hub shell

23: retaining ring

231: radial surface

232: ring wall

30: Ratchet seat

31: Convex ring

32: The first cog

33: stop ring

34: dust cover

40: driven chainring

41: The first inner diameter

42: external thread

43: Joint surface

44: first ratchet

45: outside diameter surface

46: Tool engagement configuration

50: clutch chainring

51: second inner diameter

52: second cog

53: Torus

54: second ratchet

60: biasing member

Claims (10)

A clutch structure of bicycle hub includes: A mandrel A flower hub shell is rotatably sleeved on the mandrel, the flower hub shell is provided with an accommodating space, and an internal thread and a retaining wall are provided inside the accommodating space, and the inner diameter of the retaining wall is less than The inner diameter of the accommodating space; A ratchet seat is rotatably sleeved on the mandrel, the ratchet seat is provided with a convex ring toward the hub housing, and a plurality of first cogs are radially provided on the outer circumference of the convex ring; A driven sprocket has a first inner diameter sleeved on the outer periphery of the convex ring of the ratchet seat. The outer circumference of the driven sprocket is provided with an external thread. The external thread is screwed with the internal thread of the hub housing. The driven gear is provided with a joint surface facing the direction of the hub housing, and the joint surface is annularly distributed with a plurality of first ratchet teeth; A clutch cog wheel has a second inner diameter, and a plurality of second cogs are annularly distributed in the second inner diameter, the second cog teeth mesh with the first cog teeth of the ratchet seat, and the clutch gear disc faces the ratchet seat The direction has an annulus, and the annulus is annularly distributed with a plurality of second ratchet teeth, and the second ratchet teeth mesh with the first ratchet teeth of the driven gear disc; A biasing member is disposed between the clutch gear plate and the retaining wall of the hub housing to push the clutch gear plate to engage with the driven gear plate. The clutch structure of the bicycle hub as described in item 1 of the patent application range, wherein the engaging surface of the driven gear and the ring surface of the clutch gear plate are conical. The bicycle hub clutch structure as described in item 1 of the patent application scope, wherein the housing space group of the hub housing is equipped with a retaining ring, the retaining ring has a radial surface and a ring wall, the radial surface is attached The retaining wall, the ring wall of the retaining ring cooperates with the peripheral wall of the accommodating space, the biasing member is spirally wound into several turns and is tapered, and the end of the biasing member in contact with the radial surface of the retaining ring is Large circular diameter, the end of the biasing member in contact with the clutch gear disc has a small circular diameter. The bicycle hub clutch structure as described in item 1 of the patent application scope, wherein the outer periphery of the ratchet seat is provided with a stop ring, the outer diameter of the stop ring is greater than the outer diameter of the convex ring, and the outer periphery of the stop ring A ring-shaped dust cover is provided, and the dust cover seals the opening of the accommodating space of the hub casing. The bicycle hub clutch structure as described in item 1 of the patent application scope, wherein the driven gear disc is provided with a tool engagement configuration on one side of the ratchet seat for tool engagement to force the driven gear disc On the hub shell. The bicycle hub clutch structure as described in item 1 of the patent application scope, wherein the hub hub housing is rotatably sleeved on the mandrel by a first bearing and a second bearing, and the ratchet seat is borrowed by a first Three bearings and a fourth bearing are rotatably sleeved on the mandrel. The bicycle hub clutch structure as described in item 6 of the patent application scope, wherein a hollow set of tubes is provided between the third bearing and the fourth bearing, and the sleeve is sleeved on the mandrel. The bicycle hub clutch structure as described in item 1 of the patent application scope, wherein the number of teeth of the first ratchet and/or the second ratchet is 72 teeth, 90 teeth or 120 teeth. The clutch structure of the bicycle hub as described in item 1 of the patent application scope, wherein the first cog and the second cog are arranged parallel to the mandrel. The bicycle hub clutch structure as described in item 1 of the patent application scope, wherein a first cover is screwed on the first end of the mandrel, and a second cover is screwed on the second end of the mandrel.

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