Waterproof keyboard keycap structure

Abstract

The utility model discloses a waterproof keyboard keycap structure, and relates to the technical field of keyboard keycap structure design, the waterproof keyboard keycap structure comprises a keycap main body, a waterproof protection unit and a clamping pressing unit, the keycap main body adopts a conical structure, the four corners of the keycap main body are respectively provided with a circular chamfer, the upper side surface of the keycap main body is provided with a limiting groove, and the waterproof protection unit is connected with the clamping pressing unit. A waterproof protection unit is arranged in the limiting groove, the clamping pressing unit comprises a supporting cylinder, a hollow pipeline, an auxiliary sliding column, a movable sliding block and a compression spring, the supporting cylinder is fixedly connected to the surface of the top end in the key cap body, and a limiting circular groove is formed in the surface of the lower side of the supporting cylinder. According to the waterproof keyboard keycap structure provided by the utility model, the structure of the connecting and pressing part at the lower part of the keycap is redesigned, so that water is prevented from entering the keyboard from the connecting and pressing part in a long-time use process, and the keycap is relatively convenient to use.

Description

Technical Field

[0001] The utility model relates to the technical field of keyboard key cap structure design, in particular to a waterproof keyboard key cap structure. Background Art

[0002] The keyboard is a device for inputting instructions and data to operate computer equipment. It also refers to a set of function keys that are arranged by the system to operate a machine or equipment. The keyboard is the most commonly used and most important input device. English letters, numbers, punctuation marks, etc. can be input into the computer through the keyboard, so as to issue commands to the computer and input data, etc. The keyboard cap is an important part of the keyboard. The user inputs the corresponding instructions to the computer by tapping the keyboard cap. When tapping the keyboard cap, the keyboard cap reciprocates up and down. In order to improve the performance of the key cap, a waterproof keyboard key cap structure is needed.

[0003] The existing waterproof keyboard keycap structure has an unsatisfactory waterproof effect at the connection point between the keycap and the keyboard. During long-term use, such as when a drink is spilled, water will enter the keyboard from the connection point between the keycap and the keyboard, thereby damaging the electronic components inside the keyboard. Utility Model Content

[0004] The technical problem to be solved by the utility model is to overcome the existing defects and provide a waterproof keyboard keycap structure. The structure of the connection and pressing part at the bottom of the keycap is redesigned to prevent water from entering the keyboard from here during long-term use, which can effectively solve the problems in the background technology.

[0005] In order to achieve the above purpose, the utility model provides the following technical solutions:

[0006] A waterproof keyboard keycap structure, comprising a keycap body, a waterproof protection unit and a clamping and pressing unit;

[0007] Keycap body: the waterproof protection unit is located in the limiting groove at the top of the keycap body;

[0008] The snap-on pressing unit comprises a connecting ring, a hollow pipe, an auxiliary sliding column and an external connecting ring; the external connecting ring is connected to the keyboard, the hollow pipe is located on the external connecting ring, the supporting cylindrical sleeve at the lower end of the keycap body is arranged on the periphery of the hollow pipe, and is elastically slidably connected to the hollow pipe through a movable slider; the connecting ring is located on the periphery of the hollow pipe, and is movably connected to the external connecting ring through a waterproof telescopic sleeve.

[0009] Furthermore, the top surface of the key cap body is fixedly connected to a supporting cylinder, a limiting circular groove is provided on the lower surface of the supporting cylinder, four movable sliders in an annular array are fixedly connected in the limiting circular groove on the supporting cylinder, a hollow pipe is provided at the lower side of the supporting cylinder, the upper end of the hollow pipe is provided in the limiting circular groove, four sliding grooves in an annular array are provided on the outer surface of the hollow pipe, the four sliding grooves respectively correspond to the movable sliders, an auxiliary sliding column is fixedly connected in each sliding groove, the four movable sliders are slidably connected in the corresponding sliding grooves, the sliding holes on the four movable sliders are slidably connected on the corresponding auxiliary sliding columns, and a compression spring is fixedly sleeved on the position of each auxiliary sliding column at the lower side of the movable slider.

[0010] The keycap body is used to assemble the device, the circular chamfer is used to make the four corners of the keycap smoother, making the device more convenient to use, the supporting cylinder is used to fix the moving slider, the hollow pipe is used to fix the auxiliary sliding column, the auxiliary sliding column is used to make the moving slider move more stably, the compression spring is used to reset the moving slider after being pressed, thereby pressing and using it, and the pressing control mechanism passes through the round hole on the hollow pipe to facilitate the supporting cylinder to be pressed and used, thereby using it.

[0011] Furthermore, an external connecting ring is fixedly sleeved on the hollow pipe at a position below the slide groove, a connecting ring is fixedly sleeved on the supporting cylinder, a waterproof telescopic sleeve is fixedly connected between the connecting ring and the external connecting ring, and a hollow pipe is arranged inside the waterproof telescopic sleeve.

[0012] The connecting ring cooperates with the external connecting ring to fix the waterproof telescopic sleeve. The waterproof telescopic sleeve is convenient for dustproofing and prevents dust and water from entering the pressing device, thereby achieving waterproof use. The waterproof telescopic sleeve adopts a dustproof elastic telescopic sleeve.

[0013] Furthermore, the snap-on pressing unit also includes external connecting pins, and four external connecting pins in a circular array are arranged on the external connecting ring at the edge of the waterproof telescopic sleeve, and the external connecting ring is connected to the keyboard via the external connecting pins.

[0014] The external connecting pins are used to fix the keycaps on the keys for fixed use.

[0015] Furthermore, the waterproof protection unit includes a limit block, a symbol fixing plate, a fill light strip and a snap-in magnetic sheet. Four limit blocks in a rectangular array are fixedly connected in the limit groove on the key cap body. A symbol fixing plate is arranged on the key cap body between the four limit blocks. A fill light strip is arranged on the conforming edge of the symbol fixing plate. A snap-in magnetic sheet is fixedly connected to the four corners of the symbol fixing plate respectively. Permanent magnet blocks are respectively arranged on the bottom end surface of the limit groove on the key cap body at positions corresponding to the four snap-in magnetic sheets. The four snap-in magnetic sheets are fixedly snap-in to the corresponding permanent magnet blocks respectively. The symbol fixing plate is fixedly snap-in to the key cap body through the snap-in magnetic sheet. The input end of the fill light strip is electrically connected to the output end of the external power supply through an external control switch group.

[0016] The limit block is used for limiting the position, the symbol fixing plate is used for fixing the characters for observation, the snap-on magnetic sheet is used for fixing the symbol fixing plate on the key cap body, thereby facilitating use, the fill light strip is used for illuminating the characters, making it convenient for the operator to observe, and thus for use, the fill light strip adopts an LED light strip.

[0017] Furthermore, the waterproof protection unit also includes a light-transmitting plate and a stable connecting block. The left and right end faces of the upper limit groove on the keycap body are respectively provided with snap-in sliding holes, and the two snap-in sliding holes respectively penetrate the front and rear sides of the keycap body. A light-transmitting plate is arranged at a position on the upper side of the symbol fixing plate in the limit groove. The left and right end faces of the light-transmitting plate are respectively fixedly connected with a snap-in sliding strip, and the two snap-in sliding strips are respectively slidably snap-in with the corresponding snap-in sliding holes. A stable connecting block is respectively arranged at the four corners on the front and rear sides of the light-transmitting plate, and the light-transmitting plate is fixedly connected to the keycap body through the stable connecting block.

[0018] The light-transmitting plate is made of light-transmitting plastic material, which makes it easy to observe the characters on the symbol fixing plate and facilitates use. The stable connecting block is used to fix the light-transmitting plate on the keycap body for use.

[0019] Furthermore, the waterproof protection unit also includes an arc-shaped groove, and the upper surface of the light-transmitting plate is provided with an arc-shaped groove.

[0020] The arc-shaped groove is used to facilitate the operator to press, and the arc-shaped groove is used to make the upper side of the device smoother and improve the comfort of pressing.

[0021] Compared with the prior art, the beneficial effects of the utility model are:

[0022] 1. This scheme is a waterproof keyboard keycap structure, which has the following advantages: a snap-on pressing unit is provided, a supporting cylinder is used to fix a moving slider, a hollow pipe is used to fix an auxiliary sliding column, the auxiliary sliding column is used to make the moving slider move more stably, a compression spring is used to reset the moving slider after being pressed, a connecting ring and an external connecting ring cooperate to fix the waterproof telescopic sleeve, the waterproof telescopic sleeve is convenient for waterproofing, and prevents dust and water from entering the pressing device, thereby achieving waterproof use, and an external connecting pin is used to fix the keycap on the key for use.

[0023] 2. This scheme is a waterproof keyboard keycap structure with the following advantages: a waterproof protection unit is provided, which is limited by a limit block, a symbol fixing plate is used to fix characters for observation, a snap-on magnetic sheet is used to fix the symbol fixing plate on the keycap body, thereby facilitating use, a fill light is used to illuminate the characters, a translucent plate is made of translucent plastic material, which is convenient for observing the characters on the symbol fixing plate and facilitating use, a stable connecting block is used to fix the translucent plate on the keycap body, an arc-shaped groove is used to facilitate the operator to press, and the arc-shaped groove is used to make the upper side of the device smoother.

[0024] 3. This scheme is a waterproof keyboard keycap structure, which has the following advantages: when used for a long time, the symbols on the keycaps are not easy to disappear, which does not affect the use, can isolate water, and the keys are more convenient to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The utility model is a three-dimensional structural schematic diagram of a waterproof keyboard keycap structure.

[0026] Figure 2 The utility model is a schematic diagram of a top partial cross-sectional structure of a waterproof keyboard keycap structure.

[0027] Figure 3 The utility model is a schematic diagram of a side partial cross-sectional structure of a waterproof keyboard keycap structure.

[0028] Numbers in the figure:

[0029] 1 keycap body, 2 circular chamfer, 3 waterproof protection unit, 31 limit block, 32 symbol fixing plate, 33 fill light strip, 34 snap-on magnetic sheet, 35 light-transmitting plate, 36 stable connection block, 4 snap-on pressing unit, 41 support cylinder, 42 connecting ring, 43 hollow pipe, 44 auxiliary sliding column, 45 moving slider, 46 compression spring, 47 external connecting ring, 48 waterproof telescopic sleeve, 49 external connecting pin. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.

[0031] See also Figure 1-3 , this embodiment provides a technical solution: a waterproof keyboard keycap structure, including a keycap body 1, a waterproof protection unit 3 and a clamping pressing unit 4;

[0032] The key cap body 1 has a conical structure, and the four corners of the key cap body 1 are respectively provided with round chamfers 2. A limit groove is provided on the upper surface of the key cap body 1, and a waterproof protection unit 3 is provided in the limit groove;

[0033] The snap-on pressing unit 4 includes a connecting ring 42, a hollow pipe 43, an auxiliary sliding column 44, and an external connecting ring 47; the external connecting ring 47 is connected to the keyboard, the hollow pipe 43 is located on the external connecting ring 47, and the supporting cylinder 41 at the lower end of the keycap body 1 is sleeved on the outer periphery of the hollow pipe 43, and is elastically slidably connected to the hollow pipe 43 through a movable slider 45; the connecting ring 42 is located on the outer periphery of the hollow pipe 43, and the connecting ring 42 is movably connected to the external connecting ring 47 through a waterproof telescopic sleeve 48, and the waterproof telescopic sleeve 48, the connecting ring 42 and the supporting cylinder 41 can form a wrapping seal for the hollow pipe 43, thereby achieving waterproof and dustproof effects.

[0034] A supporting cylinder 41 is fixedly connected to the top surface of the keycap body 1, and a limited circular groove is provided on the lower surface of the supporting cylinder 41. Four circular array movable sliders 45 are fixedly connected in the limited circular groove on the supporting cylinder 41. A hollow pipe 43 is provided at the lower side of the supporting cylinder 41. The upper end of the hollow pipe 43 is provided in the limited circular groove. Four circular array slide grooves are provided on the outer surface of the hollow pipe 43. The four slide grooves correspond to the movable slider 45 respectively. An auxiliary slide column 44 is fixedly connected in each slide groove. The four movable sliders 45 are slidably connected in the corresponding slide grooves. The sliding holes on the four movable sliders 45 are slidably connected on the corresponding auxiliary slide columns 44. A compression spring 46 is fixedly sleeved on the position of each auxiliary slide column 44 located at the lower side of the movable slider 45; the top of the compression spring 46 abuts against the movable slider 45, and the bottom abuts against the bottom surface of the slide groove.

[0035] The keycap body 1 is used for assembling the device, the circular chamfer 2 is used to make the four corners of the keycap smoother, making the device more convenient to use, the supporting cylinder 41 is used to fix the moving slider 45, the hollow pipe 43 is used to fix the auxiliary sliding column 44, the auxiliary sliding column 44 is used to make the moving slider 45 move more stably, the compression spring 46 is used to reset the moving slider 45 after being pressed, thereby pressing and using it, and the pressing control mechanism passes through the circular hole on the hollow pipe 43 to facilitate the supporting cylinder 41 to be pressed and used, thereby using it.

[0036] The snap-on pressing unit 4 also includes a connecting ring 42, an external connecting ring 47 and a waterproof telescopic sleeve 48. An external connecting ring 47 is fixedly sleeved on the hollow pipe 43 at the lower side of the slide groove, a connecting ring 42 is fixedly sleeved on the supporting cylinder 41, a waterproof telescopic sleeve 48 is fixedly connected between the connecting ring 42 and the external connecting ring 47, and a hollow pipe 43 is arranged inside the waterproof telescopic sleeve 48.

[0037] The connecting ring 42 and the external connecting ring 47 cooperate to fix the waterproof telescopic sleeve 48. The waterproof telescopic sleeve 48 is convenient for dustproofing and prevents dust and water from entering the pressing device, thereby achieving waterproof use. The waterproof telescopic sleeve 48 adopts a dustproof elastic telescopic sleeve.

[0038] The snap-on pressing unit 4 further includes external connecting pins 49 . Four external connecting pins 49 in a circular array are arranged on the external connecting ring 47 at the edge of the waterproof telescopic sleeve 48 . The external connecting ring 47 is connected to the keyboard via the external connecting pins 49 .

[0039] The external connection pin 49 is used to fix the key cap on the key for fixed use.

[0040] The waterproof protection unit 3 includes a limit block 31, a symbol fixing plate 32, a fill light strip 33 and a snap-on magnetic sheet 34. Four limit blocks 31 in a rectangular array are fixedly connected in the limit groove on the key cap body 1. A symbol fixing plate 32 is arranged between the four limit blocks 31 on the key cap body 1. A fill light strip 33 is arranged at the conforming edge of the symbol fixing plate 32. A snap-on magnetic sheet 34 is fixedly connected to the four corners of the symbol fixing plate 32 respectively. Permanent magnet blocks are respectively arranged on the bottom end surface of the limit groove on the key cap body 1 at positions corresponding to the four snap-on magnetic sheets 34. The four snap-on magnetic sheets 34 are fixedly snap-on with the corresponding permanent magnet blocks respectively. The symbol fixing plate 32 is fixedly snap-on with the key cap body 1 through the snap-on magnetic sheet 34. The input end of the fill light strip 33 is electrically connected to the output end of the external power supply through an external control switch group.

[0041] The limit block 31 is used for limiting, the symbol fixing plate 32 is used for fixing characters for observation, the snap-on magnetic sheet 34 is used for fixing the symbol fixing plate 32 on the key cap body 1, thereby facilitating use, the fill light strip 33 is used for illuminating the characters, and facilitates observation by the operator, thereby using, and the fill light strip 33 adopts an LED light strip.

[0042] The waterproof protection unit 3 also includes a light-transmitting plate 35 and a stable connecting block 36. The left and right end faces of the upper limit groove on the keycap body 1 are respectively provided with snap-in sliding holes, and the two snap-in sliding holes respectively penetrate the front and rear sides of the keycap body 1. A light-transmitting plate 35 is arranged at a position on the upper side of the symbol fixing plate 32 in the limit groove. The left and right end faces of the light-transmitting plate 35 are respectively fixedly connected with a snap-in sliding bar, and the two snap-in sliding bars are respectively slidably snap-in with the corresponding snap-in sliding holes. A stable connecting block 36 is respectively arranged at the four corners on the front and rear sides of the light-transmitting plate 35, and the light-transmitting plate 35 is fixedly connected to the keycap body 1 through the stable connecting block 36.

[0043] The light-transmitting plate 35 is made of light-transmitting plastic material, which is convenient for observing the characters on the symbol fixing plate 32 and for use. The stable connecting block 36 is used to fix the light-transmitting plate 35 on the keycap body 1 for use.

[0044] The waterproof protection unit 3 further includes an arc-shaped groove. The upper surface of the light-transmitting plate 35 is provided with an arc-shaped groove.

[0045] The arc-shaped groove is used to facilitate the operator to press, and the arc-shaped groove is used to make the upper side of the device smoother and improve the comfort of pressing.

[0046] The working principle of a waterproof keyboard keycap structure provided by the utility model is as follows:

[0047] The umbrella-shaped keycap body 1 can achieve the first layer of waterproof and dustproof, preventing water or dust from entering the interior of the keyboard.

[0048] The supporting cylinder 41 is sleeved on the upper periphery of the hollow pipe 43 to prevent water or dust from entering the hollow pipe 43 and then entering the interior of the keyboard.

[0049] The supporting cylinder 41 , the connecting ring 42 and the waterproof telescopic sleeve 48 form a fully sealed protection for the top, middle and bottom of the hollow pipe 43 , preventing water or dust from entering the hollow pipe 43 and then entering the keyboard.

[0050] When typing, the finger presses the keycap body 1, and the support cylinder 41 moves downward with the keycap body 1, and the support cylinder 41 moves downward relative to the hollow pipe 43. The movable slider 45 slides downward along the auxiliary slide column 44, so that the compression spring 46 is compressed to achieve force storage. The connecting ring 42 moves downward with the support cylinder 41, and the waterproof telescopic sleeve 48 is compressed to achieve dynamic sealing protection for the hollow pipe 43.

[0051] The supporting cylinder 41 is used to fix the moving slider 45, the hollow pipe 43 is used to fix the auxiliary sliding column 44, the auxiliary sliding column 44 is used to make the moving slider 45 move more stably, and the compression spring 46 is used to reset the moving slider 45 after being pressed.

[0052] The connecting ring 42 cooperates with the external connecting ring 47 to fix the waterproof telescopic sleeve 48. The waterproof telescopic sleeve 48 is convenient for dustproofing and prevents dust and water from entering the pressing device, thereby achieving waterproof use.

[0053] The external connecting pin 49 is used to fix the keycap on the key, and then the limit block 31 is used to limit the position, and the symbol fixing plate 32 is used to fix the characters for observation and use.

[0054] The snap-on magnetic sheet 34 is used to fix the symbol fixing plate 32 on the key cap body 1, which is convenient for use. The fill light strip 33 is used to illuminate the characters. The light-transmitting plate 35 is made of light-transmitting plastic material, which is convenient for observing the characters on the symbol fixing plate 32 and convenient for use.

[0055] The stable connection block 36 is used to fix the light-transmitting plate 35 on the keycap body 1, and the arc-shaped groove is used to facilitate the operator to press, and the arc-shaped groove is used to make the upper side of the device smoother for use.

[0056] It is worth noting that the core chip of the external control switch group disclosed in the above embodiment is a single chip microcomputer, which can be an 89C51 single chip microcomputer, which is an existing mature product. The fill light strip 33 uses an LED light strip, and the external control switch group controls the fill light strip 33 using a common method in the prior art.

[0057] The above description is only an embodiment of the present invention, and does not limit the patent scope of the present invention. Any equivalent structure or equivalent process transformation made by using the contents of the specification and drawings of the present invention, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present invention.

Claims

1. A waterproof keyboard keycap structure, characterized in that: It comprises a key cap body (1), a waterproof protection unit (3) and a clamping pressing unit (4); Key cap body (1): the waterproof protection unit (3) is located in a limiting groove at the top of the key cap body (1); The clamping pressing unit (4) comprises a connecting ring (42), a hollow pipe (43), an auxiliary sliding column (44), and an external connecting ring (47); the external connecting ring (47) is connected to the keyboard, the hollow pipe (43) is located on the external connecting ring (47), the supporting cylinder (41) at the lower end of the keycap body (1) is sleeved on the outer periphery of the hollow pipe (43), and is elastically slidably connected to the hollow pipe (43) through a movable slider (45); the connecting ring (42) is located on the outer periphery of the hollow pipe (43), and the connecting ring (42) is movably connected to the external connecting ring (47) through a waterproof telescopic sleeve (48).

2. A waterproof keyboard keycap structure according to claim 1, characterized in that: The top surface of the key cap body (1) is fixedly connected to a supporting cylinder (41), and a limiting circular groove is provided on the lower surface of the supporting cylinder (41). The limiting circular groove on the supporting cylinder (41) is fixedly connected to four circular array movable sliders (45). A hollow pipe (43) is provided at the lower side of the supporting cylinder (41), and the upper end of the hollow pipe (43) is provided in the limiting circular groove. The outer surface of the hollow pipe (43) is provided with four circular array sliding grooves, and the four sliding grooves correspond to the movable sliders (45) respectively. An auxiliary sliding column (44) is fixedly connected in each sliding groove. The four movable sliders (45) are slidably connected in the corresponding sliding grooves. The sliding holes on the four movable sliders (45) are slidably connected on the corresponding auxiliary sliding columns (44), and a compression spring (46) is fixedly sleeved at the position of each auxiliary sliding column (44) located at the lower side of the movable slider (45).

3. A waterproof keyboard keycap structure according to claim 2, characterized in that: An external connecting ring (47) is fixedly sleeved on the hollow pipe (43) at a position located below the slide groove, and a connecting ring (42) is fixedly sleeved on the supporting cylinder (41). A waterproof telescopic sleeve (48) is fixedly connected between the connecting ring (42) and the external connecting ring (47), and the hollow pipe (43) is arranged inside the waterproof telescopic sleeve (48).

4. A waterproof keyboard keycap structure according to claim 3, characterized in that: The snap-on pressing unit (4) further comprises an external connection pin (49), and four external connection pins (49) in a circular array are arranged on the external connection ring (47) at the edge of the waterproof telescopic sleeve (48), and the external connection ring (47) is connected to the keyboard via the external connection pins (49).

5. A waterproof keyboard keycap structure according to any one of claims 1 to 4, characterized in that: The waterproof protection unit (3) comprises a limit block (31), a symbol fixing plate (32), a fill light strip (33) and a clamping magnetic sheet (34); four limit blocks (31) in a rectangular array are fixedly connected in the limit groove on the key cap body (1); a symbol fixing plate (32) is arranged at a position between the four limit blocks (31) on the key cap body (1); a fill light strip (33) is arranged at the edge of the symbol fixing plate (32); The four upper corners of the key cap (32) are respectively fixedly connected with a snap-on magnetic sheet (34); the bottom end surface of the limit groove on the key cap body (1) is located at the positions corresponding to the four snap-on magnetic sheets (34) and is provided with permanent magnetic blocks; the four snap-on magnetic sheets (34) are respectively fixedly connected with the corresponding permanent magnetic blocks; the symbol fixing plate (32) is fixedly connected with the key cap body (1) through the snap-on magnetic sheet (34); the input end of the fill light strip (33) is electrically connected with the output end of the external power supply through an external control switch group.

6. A waterproof keyboard keycap structure according to claim 5, characterized in that: The waterproof protection unit (3) further comprises a light-transmitting plate (35) and a stable connecting block (36). The left and right end faces of the upper limit groove of the key cap body (1) are respectively provided with snap-in sliding holes, and the two snap-in sliding holes respectively penetrate the front and rear sides of the key cap body (1). A light-transmitting plate (35) is arranged at a position located above the symbol fixing plate (32) in the limit groove. The left and right end faces of the light-transmitting plate (35) are respectively fixedly connected with a snap-in sliding bar, and the two snap-in sliding bars are respectively slidably snap-in with the corresponding snap-in sliding holes. A stable connecting block (36) is respectively arranged at the four corners of the front and rear sides of the light-transmitting plate (35), and the light-transmitting plate (35) is fixedly connected to the key cap body (1) via the stable connecting block (36).

7. A waterproof keyboard keycap structure according to claim 6, characterized in that: The waterproof protection unit (3) further comprises an arc-shaped groove, and the upper surface of the light-transmitting plate (35) is provided with an arc-shaped groove.

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