CN219677077U

CN219677077U - Strip-shaped non-excitation tapping switch

Info

Publication number: CN219677077U
Application number: CN202321220473.3U
Authority: CN
Inventors: 杨梦蛟; 章宏仁
Original assignee: Zhejiang Tenglong Electrical Apparatus Co ltd
Current assignee: Zhejiang Tenglong Electrical Apparatus Co ltd
Priority date: 2023-05-16
Filing date: 2023-05-16
Publication date: 2023-09-12
Anticipated expiration: 2033-05-16

Abstract

The utility model discloses a strip-shaped non-excitation tapping switch, which comprises: the lower part of the operating mechanism is fixedly provided with a gear; the insulating rod is transversely provided with a plurality of static contact groups, each static contact group comprises a plurality of static contacts, the left side and the right side of each static contact group are respectively provided with a shielding ring, and the shielding rings are fixedly arranged on the insulating rod; the rack is transversely provided with a plurality of moving contact groups, each moving contact group comprises two moving contacts, and the upper side and the lower side of each moving contact group are respectively provided with a shielding cover; the gear on the operating mechanism is meshed with the rack, and the operating mechanism is rotated to enable the gear to drive the rack to move transversely, so that the moving contact moves transversely between the fixed contacts in the corresponding fixed contact groups, and gear switching is achieved. According to the scheme, the shielding rings are respectively arranged on the left side and the right side of each fixed contact group, and the shielding covers are respectively arranged on the upper side and the lower side of each movable contact group, so that the connection positions of the fixed contacts and the movable contacts are shielded and protected.

Description

Strip-shaped non-excitation tapping switch

Technical Field

The utility model relates to the technical field of power transformers, in particular to a strip-shaped non-excitation tapping switch.

Background

The transformer tapping switch is a voltage regulating device for changing tapping connection position of transformer winding, and the common bar-type non-excitation tapping switch is used for realizing switching among taps in the transformer winding, and the connection of the taps is changed through the bar-type non-excitation tapping switch so as to change the number of turns of a high-voltage coil, thereby regulating the output voltage of the transformer.

The strip-type non-excitation tapping switch generally comprises an operating mechanism, an insulating rod, a driving rod, a fixed contact arranged on the insulating rod and a moving contact arranged on the driving rod, wherein the operating mechanism drives the driving rod to move relative to the insulating rod through a gear, so that the moving contact on the driving rod is matched with the fixed contact on the insulating rod. As disclosed in the patent application with publication number CN214123742U, the strip-shaped non-excited tap switch with high insulation strength is provided with shielding rings at two sides of the static contact group, so that electric field distribution between the static contact and the moving contact is balanced, partial discharge is reduced, and a good voltage equalizing effect is achieved. However, in the utility model, the distance between the shielding rings at the two sides of the single fixed contact group is longer, the shielding effect is general, the tips at the connecting positions of the fixed contact and the moving contact are more, and the insulation at the connecting positions of the fixed contact and the moving contact is easy to break down when the external voltage is too high, so that the fixed contact and the moving contact are damaged.

Disclosure of Invention

In order to solve the technical problems, the utility model aims to provide the strip-shaped non-excitation tapping switch with good insulation effect, and the shielding effect of a single static contact group is enhanced, the connection position of the static contact and the moving contact is protected, and the insulation performance of the tapping switch is greatly improved by arranging the shielding cover at the connection position of the static contact and the moving contact.

In order to achieve the above purpose, the present utility model adopts the following technical scheme:

a bar off-circuit tap-changer comprising:

the lower part of the operating mechanism is fixedly provided with a gear;

the insulating rod is transversely provided with a plurality of fixed contact groups, each fixed contact group comprises a plurality of fixed contacts, the left side and the right side of each fixed contact group are respectively provided with a shielding ring, and the shielding rings are fixedly arranged on the insulating rod;

the rack is transversely provided with a plurality of moving contact groups, each moving contact group comprises two moving contacts, and the upper side and the lower side of each moving contact group are respectively provided with a shielding cover;

the gear on the operating mechanism is meshed with the rack, and the operating mechanism is rotated to enable the gear to drive the rack to move transversely, so that the moving contact moves transversely between the fixed contacts in the corresponding fixed contact groups, and gear switching is achieved.

Compared with the prior art, the utility model has the advantages that the shielding rings are respectively arranged on the left side and the right side of each fixed contact group, and the shielding covers are respectively arranged on the upper side and the lower side of each movable contact group and are positioned between the two shielding rings of the corresponding fixed contact groups, so that the connection positions of the fixed contacts and the movable contacts are shielded and protected, and the insulation performance of the tapping switch is greatly improved.

Preferably, the shielding case is circular, and the shielding case is arranged in a circular shape to avoid tip discharge.

Preferably, each moving contact group further comprises two moving contact brackets, the two moving contact brackets are respectively arranged on the upper side and the lower side of the rack, the two moving contacts are respectively fixed on the corresponding moving contact brackets, the two moving contacts are respectively in corresponding contact with the upper side and the lower side of the fixed contact in the corresponding fixed contact group, clamping grooves are further formed in the moving contact brackets, the clamping grooves in the two moving contact brackets in each moving contact group are oppositely arranged, the moving contact groups are clamped with the upper side and the lower side of the insulating rod through the two clamping grooves, the shielding cover is located on one side, far away from the rack, of the moving contact brackets, two connecting pieces are arranged on the lower portion of the shielding cover, the two connecting pieces are respectively located on the left side and the right side of the moving contact brackets, a first mounting hole is formed in each connecting piece, a second mounting hole corresponding to the first mounting hole is formed in the moving contact brackets, and the first mounting holes on the two connecting pieces are not coaxial, and fasteners are arranged in the first mounting holes and the corresponding second mounting holes so that the shielding cover is fixed on the moving contact brackets. Like this the insulating rod plays the guide effect, can be along insulating rod parallel movement when making rack, moving contact group remove, through coaxial fastener with shield cover and moving contact support fixed connection not, easy to assemble.

Preferably, the shielding ring and the shielding cover are made of metal, and the outer surfaces of the shielding ring and the shielding cover are coated with epoxy resin. The epoxy resin has good electrical insulation property, good arc resistance and surface leakage resistance, and the insulation property of the shielding ring and the shielding cover is further improved by coating the epoxy resin on the outer surfaces of the shielding ring and the shielding cover, so that the service life is long.

Preferably, the operating mechanism comprises a handle, an operating rod, a flange plate and a positioning plate, the gear is fixed at the lower part of the operating rod, the handle is arranged on the operating rod, the flange plate is sleeved on the operating rod, the positioning plate is arranged on the flange plate, a plurality of positioning grooves are distributed in a circumferential dispersing mode, the lower positioning nails of the handle are embedded into one of the positioning grooves, and when the positioning nails are pulled up and the handle is rotated, the lower positioning nails of the handle can be switched between different positioning grooves, so that the gear is driven to rotate.

Preferably, the operating rod comprises a first rod piece, a universal joint and a second rod piece which are sequentially arranged from top to bottom, the upper end of the first rod piece is fixedly connected with the handle, and the lower end of the first rod piece is rotationally connected with the universal joint; the upper end of the second rod piece is rotationally connected with the universal coupling, and the gear is fixedly sleeved on the lower part of the second rod piece. Through setting up universal joint to can easily pull up the handle, connect first member and second member through universal joint, even first member and second member are not at same axis, can realize the continuous gyration of first member and the second member that connects under the condition that there is the axis contained angle, and reliably transmit torque and motion.

Preferably, the universal joint is a telescopic universal joint.

Preferably, the shielding rings are mounted on the insulating rod through shielding ring supports, and two shielding rings in each static contact group are respectively connected with adjacent static contacts, so that the shielding rings and the adjacent static contacts form equipotential.

Preferably, the lower part of the operating mechanism is provided with at least one fixing piece, the fixing piece is fixedly connected with the insulating rod, the fixing piece is provided with a through hole, and the lower end of the operating mechanism is arranged in the through hole of the fixing piece in a penetrating way; the control mechanism is positioned at the end part of the insulating rod, and one side, close to the insulating rod, of the control mechanism is provided with a shielding ring; or, the insulating rod comprises a first plate and a second plate, the operating mechanism is positioned between the first plate and the second plate of the insulating rod, and the left side and the right side of the operating mechanism are respectively provided with a shielding ring.

Preferably, 2 fixing pieces are arranged at the lower part of the operating mechanism, the two fixing pieces are respectively located at the upper side and the lower side of the gear, the two fixing pieces are arranged relative to the gear in a mirror image mode, protruding columns are arranged on the fixing pieces, the rack is located between the protruding columns of the two fixing pieces, the upper side and the lower side of the rack are respectively attached to the two protruding columns, a guide wheel is further arranged between the two protruding columns, the rack is located between the guide wheel and the gear, and the side wall of the rack is attached to the guide wheel. This can prevent the rack from rocking when moving laterally.

The utility model has the following beneficial effects due to the adoption of the technical scheme: according to the utility model, the shielding rings are respectively arranged on the left side and the right side of each fixed contact group, and the shielding covers are respectively arranged on the upper side and the lower side of each movable contact group, and are positioned between the two shielding rings of the corresponding fixed contact groups, so that the connection positions of the fixed contacts and the movable contacts are shielded and protected, and the insulation performance of the tapping switch is greatly improved.

Drawings

FIG. 1 is a schematic diagram of the structure of the present utility model;

FIG. 2 is a schematic view of the structure of FIG. 1 at another angle;

FIG. 3 is a schematic view of the mounting structure of the moving contact holder, moving contact and shield;

FIG. 4 is a schematic structural view of a fastener;

fig. 5 is a schematic illustration of the cooperation of the steering mechanism, the mount and the guide wheel.

Reference numerals:

1. an operating mechanism; 11. a gear; 12. a handle; 131. a first rod member; 132. a universal coupling; 133. a second rod member; 14. a flange plate; 15. a positioning plate; 151. a positioning groove; 2. an insulating rod; 21. a stationary contact; 22. a shielding ring; 23. a shield ring holder; 3. a rack; 31. a moving contact; 32. a shield; 321. a connecting sheet; 33. a moving contact support; 331. a clamping groove; 4. a fixing member; 41. a through hole; 42. a protruding column; 5. a guide wheel; 6. and a fixing plate.

Detailed Description

Embodiments of the present utility model are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present utility model and should not be construed as limiting the utility model.

In the description of the present utility model, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "clockwise", "counterclockwise", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings are merely for convenience in describing the present utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present utility model.

Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present utility model, unless otherwise specified, the meaning of "a plurality" is two or more, unless otherwise clearly defined.

In the present utility model, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present utility model can be understood by those of ordinary skill in the art according to the specific circumstances.

In the present utility model, unless expressly stated or limited otherwise, a first feature "above" or "below" a second feature may include both the first and second features being in direct contact, as well as the first and second features not being in direct contact but being in contact with each other through additional features therebetween. Moreover, a first feature being "above," "over" and "on" a second feature includes the first feature being directly above and obliquely above the second feature, or simply indicating that the first feature is higher in level than the second feature. The first feature being "under", "below" and "beneath" the second feature includes the first feature being directly under and obliquely below the second feature, or simply means that the first feature is less level than the second feature.

A bar-type off-circuit tap-changer as shown in fig. 1 to 5, comprising:

the lower part of the operating mechanism 1 is fixedly provided with a gear 11;

the insulating rod 2 is horizontally arranged, a plurality of static contact groups are transversely arranged on the insulating rod 2, each static contact group comprises a plurality of static contacts 21, a shielding ring 22 is respectively arranged on the left side and the right side of each static contact group, and the shielding rings 22 are fixedly arranged on the insulating rod 2;

the rack 3 is horizontally arranged, a plurality of moving contact groups are horizontally arranged on the rack 3, each moving contact group comprises two moving contacts 31, and a shielding cover 32 is respectively arranged on the upper side and the lower side of each moving contact group;

the gear 11 on the operating mechanism 1 is meshed with the rack 3, and the operating mechanism 1 is rotated to enable the gear 11 to drive the rack 3 to move transversely, so that the moving contact 31 moves transversely between the fixed contacts 21 in the corresponding fixed contact groups, and gear switching is achieved.

Compared with the prior art, the utility model has the advantages that the shielding rings 22 are respectively arranged on the left side and the right side of each fixed contact group, the shielding covers 32 are respectively arranged on the upper side and the lower side of each movable contact group, and the shielding covers 32 are positioned between the two shielding rings 22 of the corresponding fixed contact group, so that the connection positions of the fixed contacts 21 and the movable contacts 31 are shielded and protected, and the insulation performance of the tapping switch is greatly improved.

The shield 32 is circular, and a tip discharge is never avoided. In the present utility model, the shield ring 22 and the shield can 32 are made of metal, and the outer surfaces of the shield ring 22 and the shield can 32 are coated with epoxy resin. The epoxy resin has good electrical insulation property, good arc resistance and surface leakage resistance, and the insulation property of the shielding ring and the shielding cover is further improved by coating the epoxy resin on the outer surfaces of the shielding ring and the shielding cover, so that the service life is long.

As shown in fig. 1 and 3, each moving contact group further includes two moving contact brackets 33, the two moving contact brackets 33 are respectively mounted on the upper and lower sides of the rack 3, the two moving contacts 31 are respectively fixed on the corresponding moving contact brackets 33, the two moving contacts 31 are respectively in corresponding contact with the upper and lower sides of the fixed contact 21 in the corresponding fixed contact group, the moving contact brackets 33 are further provided with clamping grooves 331, the clamping grooves 331 on the two moving contact brackets 33 in each moving contact group are oppositely arranged, the moving contact groups are clamped with the upper and lower sides of the insulating rod 2 through the two clamping grooves 331, at this time, the insulating rod 2 plays a guiding role, and the moving contact groups can move along the length direction of the insulating rod 2. The shielding cover 32 is located one side of the moving contact support 33 far away from the rack 3, two connecting pieces 321 are arranged at the lower portion of the shielding cover 32, the two connecting pieces 321 are located on the left side and the right side of the moving contact support 33 respectively, a first mounting hole is formed in each connecting piece 321, a second mounting hole corresponding to the first mounting hole is formed in the moving contact support 33, the first mounting holes in the two connecting pieces 321 are different in axis, and the shielding cover 32 is fixed on the moving contact support 33 through arranging fasteners in the first mounting holes and the corresponding second mounting holes, so that the shielding cover and the moving contact support are fixedly connected through the fasteners of different axes, and the installation is convenient. The fastening piece is a locating pin, a screw and the like.

As shown in fig. 5, the operating mechanism 1 includes a handle 12, an operating lever, a flange 14 and a positioning disk 15, the gear 11 is fixed at the lower part of the operating lever, the handle 12 is mounted on the operating lever, the flange 14 is sleeved on the operating lever, the positioning disk 15 is configured on the flange 14, a plurality of positioning grooves 151 are distributed on the positioning disk 15 in a circumferential direction in a dispersed manner, the lower positioning nail of the handle 12 is embedded in one of the positioning grooves 151, and when the positioning nail is pulled up and the handle 12 is rotated, the lower positioning nail of the handle 12 can be switched between different positioning grooves 151, so as to drive the gear 11 to rotate.

The operating lever comprises a first rod piece 131, a universal joint 132 and a second rod piece 133 which are sequentially arranged from top to bottom, the upper end of the first rod piece 131 is fixedly connected with the handle 12, and the lower end of the first rod piece 131 is rotatably connected with the universal joint 132; the upper end of the second rod member 133 is rotatably connected with the universal joint 132, and the gear 11 is fixedly sleeved on the lower portion of the second rod member 133. In the present utility model, the universal joint 132 is a telescopic universal joint.

During operation, the positioning nail is lifted, the lower positioning nail of the handle 12 is separated from the corresponding positioning groove 151, the rotary handle 12 is switched to the next positioning groove 151, the gear 11 rotates along with the handle 12 and drives the rack 3 to move transversely, so that the moving contact 31 moves transversely between the fixed contacts 21 of the corresponding fixed contact group to realize gear switching, and the gear can be fixed after the lower positioning nail of the handle 12 is inserted into the corresponding positioning groove 151.

The shielding rings 22 are arranged on the insulating rod 2 through shielding ring supports 23, and two shielding rings 22 in each static contact group are respectively connected with the adjacent static contacts 21 to form equipotential.

The lower part of the operating mechanism 1 is provided with at least one fixing piece 4, the fixing piece 4 is fixedly connected with the insulating rod 2, the fixing piece 4 is provided with a through hole 41, the lower end of the operating mechanism 1 is arranged in the through hole 41 of the fixing piece 4 in a penetrating mode, in the utility model, the lower part of the operating mechanism 1 is provided with 2 fixing pieces 4, the two fixing pieces 4 are respectively positioned at the upper side and the lower side of the gear 11, the two fixing pieces 4 are arranged in a mirror image mode relative to the gear 11, the fixing pieces 4 are provided with protruding columns 42, the rack 3 is positioned between the protruding columns 42 of the two fixing pieces 4, the upper side and the lower side of the rack 3 are respectively attached to the two protruding columns 42, so that the rack 3 is prevented from shaking in the moving process, a guide wheel 5 is further arranged between the guide wheel 5 and the gear 11, the side wall of the rack 3 is attached to the guide wheel 5, and the rack 3 is meshed with the gear 11 all the time in the moving process.

In one embodiment, the insulating rod 2 is a continuous rod, the operating mechanism 1 is located at the end of the insulating rod 2, and a shielding ring 22 is arranged on the side of the operating mechanism 1 close to the insulating rod 2.

In another embodiment, the insulating rod 2 comprises a first plate and a second plate, the operating mechanism 1 is located between the first plate and the second plate of the insulating rod 2, and the left side and the right side of the operating mechanism 1 are respectively provided with a shielding ring 22.

The strip-shaped non-excitation tapping switch further comprises a fixed plate 6, a first mounting opening and a second mounting opening are formed in the fixed plate 6, the first mounting opening and the second mounting opening are arranged in parallel, the insulating rod 2 is fixedly arranged in the first mounting opening of the fixed plate 6 in a penetrating mode, and the rack 3 is arranged in the second mounting opening of the fixed plate 6 in a penetrating mode.

All features described in the description, the appended claims and the drawings, either alone or in any combination, are important features of the present utility model.

Although embodiments of the present utility model have been shown and described above, it will be understood that the above embodiments are illustrative and not to be construed as limiting the utility model, and that variations, modifications, alternatives, variations, deletions of parts, additions of features, or re-combination of features may be made to the above embodiments by those skilled in the art without departing from the spirit and principles of the utility model, all such simple modifications, equivalents, and adaptations of the embodiments as may be made by the principles of the utility model and without departing from the scope of the utility model.

Claims

1. A bar-type off-circuit tap-changer comprising:

the lower part of the operating mechanism (1) is fixedly provided with a gear (11);

the insulating rod (2), a plurality of static contact groups are transversely arranged on the insulating rod (2), each static contact group comprises a plurality of static contacts (21), a shielding ring (22) is respectively arranged on the left side and the right side of each static contact group, and the shielding rings (22) are fixedly arranged on the insulating rod (2);

the rack (3) is transversely provided with a plurality of moving contact groups, each moving contact group comprises two moving contacts (31), and the upper side and the lower side of each moving contact group are respectively provided with a shielding cover (32);

the gear (11) on the operating mechanism (1) is meshed with the rack (3), and the operating mechanism (1) is rotated to enable the gear (11) to drive the rack (3) to move transversely, so that the moving contact (31) moves transversely between the fixed contacts (21) in the corresponding fixed contact group, and gear switching is achieved.

2. A bar off-circuit tap changer according to claim 1, wherein the shielding (32) is circular.

3. The strip-shaped non-excited tap changer according to claim 1, wherein each moving contact group further comprises two moving contact brackets (33), the two moving contact brackets (33) are respectively arranged on the upper side and the lower side of the rack (3), the two moving contacts (31) are respectively fixed on the corresponding moving contact brackets (33), the two moving contacts (31) are respectively in corresponding contact with the upper side and the lower side of the fixed contact (21) in the corresponding fixed contact group, clamping grooves (331) are further formed in the moving contact brackets (33), clamping grooves (331) in the two moving contact brackets (33) in each moving contact group are oppositely arranged, the moving contact groups are clamped with the upper side and the lower side of the insulating rod (2) through the two clamping grooves (331), the shielding cover (32) is positioned on one side of the moving contact brackets (33) far away from the rack (3), two connecting pieces (321) are respectively arranged on the left side and the right side of the moving contact brackets (33), a first connecting piece (321) is arranged on each connecting piece (321), a first connecting piece (321) is correspondingly provided with a first mounting hole and a second mounting hole (32) is formed in each connecting piece, and a second mounting hole (33) is correspondingly arranged on the first mounting hole and the second mounting hole (33).

4. The bar-type off-circuit tap changer according to claim 1, wherein the shielding ring (22) and the shielding case (32) are made of metal, and outer surfaces of the shielding ring (22) and the shielding case (32) are coated with epoxy resin.

5. The bar-type off-circuit tap changer according to claim 1, wherein the operating mechanism (1) comprises a handle (12), an operating lever, a flange plate (14) and a positioning plate (15), the gear (11) is fixed at the lower part of the operating lever, the handle (12) is arranged on the operating lever, the flange plate (14) is sleeved on the operating lever, the positioning plate (15) is arranged on the flange plate (14), a plurality of positioning grooves (151) are distributed in a circumferentially dispersed manner on the positioning plate (15), the lower positioning nail of the handle (12) is embedded in one of the positioning grooves (151), and when the positioning nail is pulled up and the handle (12) is rotated, the lower positioning nail of the handle (12) can be switched between different positioning grooves (151), so that the gear (11) is driven to rotate.

6. The bar-type off-circuit tap changer according to claim 5, wherein the operating lever comprises a first lever (131), a universal joint (132) and a second lever (133) which are sequentially arranged from top to bottom, the upper end of the first lever (131) is fixedly connected with the handle (12), and the lower end of the first lever (131) is rotatably connected with the universal joint (132); the upper end of the second rod piece (133) is rotationally connected with the universal coupling (132), and the gear (11) is fixedly sleeved at the lower part of the second rod piece (133).

7. The bar off-circuit tap changer of claim 6 wherein the universal joint (132) is a telescopic universal joint.

8. A bar-type off-circuit tap-changer according to claim 1, characterised in that the shielding rings (22) are mounted on the insulating rod (2) by means of shielding ring holders (23), the two shielding rings (22) in each static contact group being connected with their adjacent static contacts (21) respectively, forming an equipotential.

9. The bar-type off-circuit tap changer according to claim 1, wherein the lower part of the operating mechanism (1) is provided with at least one fixing piece (4), the fixing piece (4) is fixedly connected with the insulating rod (2), the fixing piece (4) is provided with a through hole (41), and the lower end of the operating mechanism (1) is arranged in the through hole (41) of the fixing piece (4) in a penetrating way;

the control mechanism (1) is positioned at the end part of the insulating rod (2), and one side of the control mechanism (1) close to the insulating rod (2) is provided with a shielding ring (22); or, the insulating rod (2) comprises a first plate and a second plate, the operating mechanism (1) is positioned between the first plate and the second plate of the insulating rod (2), and the left side and the right side of the operating mechanism (1) are respectively provided with a shielding ring (22).

10. The strip-shaped non-excitation tap changer according to claim 9, wherein 2 fixing pieces (4) are arranged at the lower part of the operating mechanism (1), the two fixing pieces (4) are respectively located at the upper side and the lower side of the gear (11), the two fixing pieces (4) are arranged in a mirror image mode relative to the gear (11), protruding columns (42) are arranged on the fixing pieces (4), the rack (3) is located between the protruding columns (42) of the two fixing pieces (4), the upper side and the lower side of the rack (3) are respectively attached to the two protruding columns (42), guide wheels (5) are further arranged between the two protruding columns (42), the rack (3) is located between the guide wheels (5) and the gear (11), and the side wall of the rack (3) is attached to the guide wheels (5).