A mower head with ease of replacement of broken line

Abstract

The application relates to a mowing head facilitating replacement of broken mowing lines, comprising a mounting base, a mowing line fixing mechanism arranged on the upper side of the mounting base, the mowing line fixing mechanism comprising a plurality of mowing line supports arranged in a circumferential array on the upper side of the mounting base, a positioning groove arranged on one side of the mowing line support, and a bevel gear ring rotationally matched on the upper side of the mounting base; the mowing line fixing mechanism is arranged to rotate the transmission ring and the bevel gear ring by rotating the operation ring, the bevel gear ring is meshed with a plurality of bevel gears, the bevel gears drive the polygonal rotating shaft to rotate, the polygonal rotating shaft drives the positioning external thread cylinder to be screwed into the positioning groove in the mowing line support in a threaded mode with the threaded hole, the mowing line support is positioned, the spring pushes the positioning column into the positioning groove, the bevel gear ring is positioned, the plurality of mowing line supports are quickly positioned, the replacement efficiency of the mowing line supports and the mowing lines is improved, and the working strength of the staff replacing the mowing lines is reduced.

Description

Technical Field

[0001] This invention relates to the field of lawn mower head technology, and in particular to a lawn mower head that facilitates replacement of broken wires. Background Technology

[0002] A lawnmower, also known as a lawn trimmer, lawn mower, or lawn mower, is a mechanical tool used for trimming lawns and vegetation. It consists of a blade disc, engine, wheels, a walking mechanism, blades, a handle, and a control unit. Currently, backpack lawnmowers on the market have three types of blades: metal serrated blades, plastic blades (two-tooth and three-tooth), and blades with a trimming rope. These blades save time for lawnmower workers and reduce manpower. Lawnmowers operate in reciprocating or rotary modes. Their high mowing efficiency significantly saves time and contributes to environmental protection and beautification. They are simple, convenient, and efficient to operate, hence their widespread use. The machines are compact and suitable for small to medium-sized lawns. When using a lawnmower, the stubble height should be determined according to requirements. They are very convenient to use. Hanging lawnmowers come in two forms: one is hung on the side, and the other is carried on the back. Comparatively, the side-mounted type is lighter, more durable, and more efficient.

[0003] A search revealed a lawnmower blade head with publication number CN205196320U, primarily composed of a base, blades, a trimming rope bracket, a trimming rope, and a round cover. The base has a central hole and hexagonal elongated holes on its inner side for connecting rods. It has eight through holes and four symmetrically distributed cylindrical sections around its circumference, along with four slots. The blades are available in stainless steel and nylon versions, each with small holes and slots around its circumference. The round cover has eight through holes and a nut hole. The blades are mounted between the base and the round cover, positioned by the four cylindrical sections and slots on the base, and then secured with screws and nuts. The trimming rope is attached to the trimming rope bracket. When the lawnmower rotates the blade head, the blades and trimming rope work simultaneously. This lawnmower blade head can be equipped with either stainless steel or nylon blades, both sizes come with a trimming rope. The blade teeth are angled downwards but higher than the round cover, allowing for safe cutting of various weeds and clearing of all corners.

[0004] When the device in the disclosed patent is in use, after the grass trimming rope is installed on the grass trimming rope bracket, each grass trimming rope bracket needs to be fixed individually with screws, which not only results in low positioning efficiency but also increases the workload of the workers. Summary of the Invention

[0005] In response to the technical problem in existing patents that, after the grass trimming rope is installed on the grass trimming rope bracket, each grass trimming rope bracket needs to be individually fixed with screws, which not only results in low positioning efficiency but also increases the workload of workers, this invention provides a grass trimming head that is easy to replace if the rope breaks.

[0006] The technical solution adopted in this invention is: a grass cutter head that facilitates replacement of broken cords, comprising: a mounting base, a grass cutter rope fixing mechanism disposed on the upper side of the mounting base, the grass cutter rope fixing mechanism comprising a plurality of grass cutter rope supports arranged in a circular array on the upper side of the mounting base, a positioning groove disposed on one side of the grass cutter rope supports, a bevel gear ring rotatably engaged on the upper side of the mounting base, a positioning external thread cylinder threaded in the mounting base and corresponding to the positioning groove, a polygonal rotating shaft rotatably engaged in the mounting base and corresponding to the positioning groove, a bevel gear disposed at one end of the polygonal rotating shaft and meshing with the bevel gear ring, a transmission ring rotatably engaged on the mounting base and fixedly connected to the bevel gear ring, and a limiting mechanism disposed on the upper side of the transmission ring, wherein the positioning external thread cylinder is slidably sleeved on the polygonal rotating shaft.

[0007] Furthermore, the mowing rope bracket has a T-shaped block structure, with a mounting groove on the bottom surface and a limiting post on the top surface of the inner wall of the mounting groove. The upper side of the mounting base has a T-shaped slot corresponding to the mowing rope bracket, and the mowing rope bracket is located in the T-shaped slot. A spring ball is embedded in the inner wall of the T-shaped slot. The side of the mowing rope bracket has a limiting groove corresponding to the spring ball. The upper side of the mounting base has an annular groove. The vertical cross-section of the transmission ring is L-shaped, and a first bearing is provided in the annular groove. The middle part of the transmission ring is fixed in the first bearing. The bevel gear ring is fixedly sleeved on the lower part of the transmission ring, and the bevel gear and the bevel gear ring are located in the annular groove.

[0008] Furthermore, the annular groove has a threaded hole on its side that communicates with the T-shaped slot, the positioning external threaded cylinder is threaded into the threaded hole, the vertical cross-section of the inner wall of the positioning external threaded cylinder is a polygonal structure, one end of the threaded hole has a first smooth curved surface, one end of the threaded hole is fixed with a second bearing, one end of the polygonal rotating shaft has a second smooth curved surface, and one end of the polygonal rotating shaft is fixed in the second bearing.

[0009] Furthermore, the limiting mechanism includes an operating ring that is elastically slidably fitted on the upper side of the transmission ring, a plurality of positioning posts arranged in a circumferential array at the bottom end of the operating ring, and a positioning groove provided on the upper side of the mounting base and corresponding to the positioning posts. The bottom surface of the transmission ring is provided with a groove, and the upper side of the transmission ring is provided with a guide hole. The guide hole communicates with the groove. The positioning posts are slidably fitted in the guide hole. A limiting plate is fixedly sleeved on the lower part of the positioning post. A spring is provided between the limiting plate and the inner wall of the groove. The limiting plate is slidably fitted in the groove.

[0010] Furthermore, the mounting base has multiple blades arranged in a circumferential array on its upper side, a protective cover is provided above the mounting base, a rotating shaft is provided on the upper side of the mounting base, a third bearing is installed through the upper side of the protective cover, the upper part of the rotating shaft is fixed in the third bearing, the protective cover has an inverted box-shaped structure, and an opening is provided on the side of the protective cover.

[0011] Furthermore, the protective cover is provided with a telescopic bracket on its upper side. The telescopic bracket includes a U-shaped frame fixed to the upper side of the protective cover away from the opening, two support columns slidably engaged with the bottom end of the U-shaped frame, a threaded support rod rotatably engaged with the upper side of the U-shaped frame and threadedly engaged with the support columns, a flywheel fixedly sleeved on the threaded support rod, and a chain engaged with the two flywheels. The bottom end of the support column is provided with a universal wheel, the bottom end of the U-shaped frame is provided with a guide groove corresponding to the support column, and a connecting groove provided between the two guide grooves. The support column is slidably engaged in the guide groove, the chain is located in the connecting groove, the upper side of the threaded support rod is provided with a handwheel, a third bearing is installed through the upper side of the U-shaped frame, the upper outer side of the threaded support rod is provided with a third smooth curved surface, and the upper part of the threaded support rod is fixed in the third bearing.

[0012] The beneficial effects of this invention are:

[0013] By setting up a mowing rope fixing mechanism, it is easy to put the mowing rope ring onto the limiting post in the mounting groove of the mowing rope bracket. Then, the mowing rope bracket is placed into the T-shaped slot, and the spring ball is locked into the limiting groove, elastically and initially positioning the mowing rope bracket. After replacing multiple mowing ropes on the mounting base in sequence, the rotating operating ring drives the transmission ring and bevel gear ring to rotate. The bevel gear ring meshes with multiple bevel gears, which drive the polygonal rotating shaft to rotate. The polygonal rotating shaft drives the positioning external threaded cylinder to engage with the threaded hole and screw it into the positioning groove on the mowing rope bracket, positioning the mowing rope bracket. At the same time, the spring pushes the positioning post into the positioning groove, positioning the bevel gear ring. This facilitates the quick positioning of multiple mowing rope brackets, improves the replacement efficiency of the mowing rope bracket and mowing rope, and reduces the workload of the workers when replacing mowing ropes.

[0014] By setting a T-shaped slot and a T-shaped structure for the mowing rope bracket, it is easy for the mowing rope bracket to be inserted into the T-shaped slot, avoiding horizontal sliding of the mowing rope bracket, and thus reducing the probability of the mowing rope bracket being thrown out by high-speed rotation.

[0015] By setting up a telescopic bracket, it is easy to rotate any handwheel, which, in conjunction with the flywheel and chain, drives the two support columns to slide. The distance between the protective cover and the ground allows the mower head to be moved using the casters, facilitating fixed-height mowing and reducing the burden on workers carrying the mower. Attached Figure Description

[0016] Figure 1 This is a three-dimensional structural schematic diagram of the present invention;

[0017] Figure 2 This is the bottom view in this invention;

[0018] Figure 3 This is a schematic diagram of the mounting base structure in this invention;

[0019] Figure 4 This is a cross-sectional structural diagram of the present invention;

[0020] Figure 5 This is a schematic diagram of the grass-cutting rope support structure in this invention;

[0021] Figure 6 This is a cross-sectional view of the telescopic support structure in this invention.

[0022] The diagram is marked as follows:

[0023] 1. Mounting base; 101. T-shaped slot; 102. Spring ball bearing; 103. Annular groove; 104. Threaded hole; 105. Blade; 106. Protective cover; 107. Shaft; 108. Opening; 109. Telescopic bracket; 1091. U-shaped frame; 1092. Support column; 1093. Threaded support rod; 1094. Flywheel; 1095. Chain; 1096. Caster wheel; 1097. Guide channel; 1098. Connecting channel; 1099. Handwheel; 2. Grass cutting rope Fixed mechanism; 201, mowing rope bracket; 2011, mounting groove; 2012, limiting post; 202, positioning groove; 203, bevel gear ring; 204, positioning external thread cylinder; 205, polygonal rotating shaft; 206, bevel gear; 207, transmission ring; 208, limiting mechanism; 2081, operating ring; 2082, positioning post; 2083, positioning groove; 2084, groove; 2085, guide hole; 2086, limiting plate; 2087, spring; 209, limiting groove. Detailed Implementation

[0024] In the description of this invention, it should be noted that the terms "front", "up", "down", "left", "right", "vertical", "horizontal", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0025] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0026] The following is in conjunction with the appendix Figure 1-6 The present invention will be further described below.

[0027] To address the problems existing in the background art, this application proposes the following technical solution:

[0028] A lawnmower head that facilitates replacement of broken cords includes: a mounting base 1, a lawnmower cord fixing mechanism 2 disposed on the upper side of the mounting base 1, the lawnmower cord fixing mechanism 2 including a plurality of lawnmower cord supports 201 arranged in a circumferential array on the upper side of the mounting base 1, a positioning groove 202 disposed on one side of the lawnmower cord support 201, a bevel gear ring 203 rotatably engaged on the upper side of the mounting base 1, a positioning external thread cylinder 204 threadedly engaged in the mounting base 1 and corresponding to the positioning groove 202, a polygonal rotating shaft 205 rotatably engaged in the mounting base 1 and corresponding to the positioning groove 202, a bevel gear 206 disposed at one end of the polygonal rotating shaft 205 and meshing with the bevel gear ring 203, a transmission ring 207 rotatably engaged on the mounting base 1 and fixedly connected to the bevel gear ring 203, and a limiting mechanism 208 disposed on the upper side of the transmission ring 207, the positioning external thread cylinder 204 being slidably sleeved on the polygonal rotating shaft 205.

[0029] Furthermore, the mowing rope bracket 201 has a T-shaped block structure. The bottom surface of the mowing rope bracket 201 has an installation groove 2011, and the top surface of the inner wall of the installation groove 2011 has a limiting post 2012. The upper side of the mounting base 1 has a T-shaped slot 101 corresponding to the mowing rope bracket 201. The mowing rope bracket 201 is located in the T-shaped slot 101. The inner wall of the T-shaped slot 101 is embedded with a spring ball 102. The side of the mowing rope bracket 201 has a limiting groove 209 corresponding to the spring ball 102. The upper side of the mounting base 1 has an annular groove 103. The vertical section of the transmission ring 207 is an L-shaped structure. The annular groove 103 has a first bearing. The middle part of the transmission ring 207 is fixed in the first bearing. The bevel gear ring 203 is fixedly sleeved on the lower part of the transmission ring 207. The bevel gear 206 and the bevel gear ring 203 are located in the annular groove 103.

[0030] Furthermore, the annular groove 103 has a threaded hole 104 on its side that communicates with the T-shaped slot 101. The positioning external threaded cylinder 204 is threaded into the threaded hole 104. The vertical cross-section of the inner wall of the positioning external threaded cylinder 204 is a polygonal structure. One end of the threaded hole 104 has a first smooth curved surface. A second bearing is fixed to one end of the threaded hole 104. One end of the polygonal rotating shaft 205 has a second smooth curved surface. One end of the polygonal rotating shaft 205 is fixed in the second bearing.

[0031] Furthermore, the limiting mechanism 208 includes an operating ring 2081 that is elastically slidably fitted on the upper side of the transmission ring 207, a plurality of positioning posts 2082 arranged in a circumferential array at the bottom end of the operating ring 2081, and a positioning groove 2083 located on the upper side of the mounting base 1 and corresponding to the positioning posts 2082. The bottom surface of the transmission ring 207 is provided with a groove 2084, and the upper side of the transmission ring 207 is provided with a guide hole 2085, which communicates with the groove 2084. The positioning posts 2082 are slidably fitted in the guide hole 2085, and a limiting plate 2086 is fixedly sleeved on the lower part of the positioning post 2082. A spring 2087 is provided between the limiting plate 2086 and the inner wall of the groove 2084, and the limiting plate 2086 is slidably fitted in the groove 2084.

[0032] Furthermore, the mounting base 1 has multiple blades 105 arranged in a circular array on its upper side, a protective cover 106 is provided above the mounting base 1, a rotating shaft 107 is provided on the upper side of the mounting base 1, a third bearing is installed through the upper side of the protective cover 106, the upper part of the rotating shaft 107 is fixed in the third bearing, the protective cover 106 has an inverted box-shaped structure, and an opening 108 is provided on the side of the protective cover 106.

[0033] Furthermore, a telescopic bracket 109 is provided on the upper side of the protective cover 106. The telescopic bracket 109 includes a U-shaped frame 1091 fixed to the upper side of the end of the protective cover 106 away from the opening 108, two support columns 1092 slidably engaged with the bottom end of the U-shaped frame 1091, a threaded support rod 1093 rotatably engaged with the upper side of the U-shaped frame 1091 and threadedly engaged with the support columns 1092, a flywheel 1094 fixedly sleeved on the threaded support rod 1093, and a chain 1095 drivingly engaged between the two flywheels 1094. The bottom end of the support column 1092 is provided with a universal joint. The bottom of the U-shaped frame 1091 is provided with a guide channel 1097 corresponding to the support column 1092 and a connecting channel 1098 between the two guide channels 1097. The support column 1092 is slidably fitted in the guide channel 1097. The chain 1095 is located in the connecting channel 1098. A handwheel 1099 is provided on the upper side of the threaded support rod 1093. A third bearing is installed through the upper side of the U-shaped frame 1091. A third smooth curved surface is provided on the upper outer side of the threaded support rod 1093. The upper part of the threaded support rod 1093 is fixed in the third bearing.

[0034] Working principle: When the mowing rope needs to be replaced, pulling up the operating ring 2081 causes the positioning post 2082 to slide out of the positioning groove 2083. The positioning post 2082 causes the limiting plate 2086 to slide and compress the spring 2087. By rotating the operating ring 2081, the transmission ring 207 and the bevel gear ring 203 rotate. The bevel gear ring 203 meshes with multiple bevel gears 206. The bevel gears 206 drive the polygonal rotating shaft 205 to rotate. The polygonal rotating shaft 205 drives the positioning external threaded cylinder 204 to engage with the threaded hole 104 and be screwed out into the positioning groove 202 on the mowing rope bracket 201, facilitating the quick release of multiple mowing rope brackets 201. 1. Positioning: Place the mowing rope loop onto the limiting post 2012 in the mounting groove 2011 of the mowing rope bracket 201. Then, place the mowing rope bracket 201 into the T-shaped slot 101. The spring ball 102 engages with the limiting groove 209, providing initial elastic positioning of the mowing rope bracket 201. After replacing multiple mowing ropes on the mounting base 1, the rotating operating ring 2081 drives the transmission ring 207 and the bevel gear ring 203 to rotate. The bevel gear ring 203 meshes with multiple bevel gears 206, which drive the polygonal rotating shaft 205 to rotate. The polygonal rotating shaft 205 drives the positioning external threaded cylinder 204 to engage with the threaded hole 10. 4. The threaded joint is screwed into the positioning groove 202 on the mowing rope bracket 201 to position the mowing rope bracket 201. At the same time, the spring 2087 pushes the positioning post 2082 into the positioning groove 2083 to position the bevel ring 203. This prevents the bevel ring 203 from rotating relative to the mounting base 1 when the mounting base 1 is turned on or off, which would affect the positioning of the mowing rope bracket 201. This facilitates the quick positioning of multiple mowing rope brackets 201, improves the efficiency of replacing the mowing rope brackets 201 and the mowing rope, and reduces the workload of workers replacing the mowing rope. The T-shaped slot 101 and the T-shaped structure of the mowing rope bracket 201 facilitate the locking of the mowing rope bracket 201. The grass cutting rope bracket 201 is inserted into the T-shaped slot 101 to prevent it from sliding horizontally, thereby reducing the probability of the grass cutting rope bracket 201 being thrown out by high-speed rotation. By rotating any handwheel 1099, the flywheel 1094 and chain 1095 are engaged to drive the two support columns 1092 to slide. The distance between the protective cover 106 and the ground makes it easy to support the movement of the grass cutting head through the caster wheel 1096, which is convenient for fixed-height grass cutting and reduces the burden on the staff carrying the grass cutter. The blade 105 is fixed to the mounting base 1 with screws, which makes it easy for the blade 105 and the grass cutting rope to work at the same time, which can clear various weeds and clean corners.

[0035] All standard parts used in this invention can be purchased from the market, and irregular parts can be customized according to the description and drawings. The specific connection methods of each part adopt conventional methods such as bolts, rivets, and welding that are mature in the prior art. The machinery, parts and equipment adopt conventional models in the prior art, and the circuit connection adopts conventional connection methods in the prior art, which will not be described in detail here. The contents not described in detail in this specification belong to the prior art known to those skilled in the art.

[0036] Although embodiments of the invention have been shown and described, the scope of the invention will be defined by the appended claims and their equivalents by those skilled in the art.

Claims

1. A lawnmower head that facilitates replacement of broken wires, characterized in that, include: Mounting base (1), and a mowing rope fixing mechanism (2) disposed on the upper side of the mounting base (1). The mowing rope fixing mechanism (2) includes a plurality of mowing rope supports (201) arranged in a circumferential array on the upper side of the mounting base (1), a positioning groove (202) disposed on one side of the mowing rope support (201), a bevel tooth ring (203) rotatably fitted on the upper side of the mounting base (1), a positioning external threaded cylinder (204) threadedly fitted in the mounting base (1) and corresponding to the positioning groove (202), and a rotatably fitted on the upper side of the mounting base (1). The mounting base (1) contains a polygonal rotating shaft (205) corresponding to the positioning groove (202), a bevel gear (206) located at one end of the polygonal rotating shaft (205) and meshing with the bevel gear ring (203), a transmission ring (207) rotatably fitted on the mounting base (1) and fixedly connected to the bevel gear ring (203), and a limiting mechanism (208) located on the upper side of the transmission ring (207). The positioning external threaded cylinder (204) is slidably sleeved on the polygonal rotating shaft (205). The limiting mechanism (208) includes an operating ring (2081) that is elastically slidably fitted on the upper side of the transmission ring (207), a plurality of positioning posts (2082) arranged in a circular array at the bottom end of the operating ring (2081), and a positioning groove (2083) provided on the upper side of the mounting base (1) and corresponding to the positioning posts (2082). The bottom surface of the transmission ring (207) is provided with a groove (2084), and the upper side of the transmission ring (207) is provided with a guide hole (2085). The guide hole (2085) communicates with the groove (2084). The positioning post (2082) is slidably fitted in the guide hole (2085). A limiting plate (2086) is fixedly sleeved on the lower part of the positioning post (2082). A spring (2087) is provided between the limiting plate (2086) and the inner wall of the groove (2084). The limiting plate (2086) is slidably fitted in the groove (2084).

2. The lawnmower head for easy replacement of broken wires according to claim 1, characterized in that, The mowing rope bracket (201) is a T-shaped block structure. The bottom surface of the mowing rope bracket (201) is provided with an installation groove (2011). The top surface of the inner wall of the installation groove (2011) is provided with a limiting post (2012). The upper side of the mounting base (1) is provided with a T-shaped slot (101) corresponding to the mowing rope bracket (201). The mowing rope bracket (201) is located in the T-shaped slot (101).

3. A lawnmower head for easy replacement of broken wires according to claim 2, characterized in that, The inner wall of the T-shaped slot (101) is embedded with a spring ball (102), and the side of the grass cutting rope bracket (201) is provided with a limiting groove (209) corresponding to the spring ball (102).

4. A lawnmower head for easy replacement of broken wires according to claim 3, characterized in that, The mounting base (1) has an annular groove (103) on its upper side. The transmission ring (207) has an L-shaped vertical section. A first bearing is provided in the annular groove (103). The middle part of the transmission ring (207) is fixed in the first bearing. The bevel gear ring (203) is fixedly sleeved on the lower part of the transmission ring (207). The bevel gear (206) and the bevel gear ring (203) are located in the annular groove (103).

5. A lawnmower head for easy replacement of broken wires according to claim 4, characterized in that, The annular groove (103) has a threaded hole (104) on its side that communicates with the T-shaped slot (101). The positioning external threaded cylinder (204) is threaded into the threaded hole (104). The vertical cross section of the inner wall of the positioning external threaded cylinder (204) is a polygonal structure. One end of the threaded hole (104) has a first smooth curved surface. One end of the threaded hole (104) is fixed with a second bearing. One end of the polygonal rotating shaft (205) has a second smooth curved surface. One end of the polygonal rotating shaft (205) is fixed in the second bearing.

6. A lawnmower head for easy replacement of broken wires according to claim 1, characterized in that, The mounting base (1) has multiple blades (105) arranged in a circumferential array on its upper side. A protective cover (106) is provided above the mounting base (1). A rotating shaft (107) is provided on the upper side of the mounting base (1). A third bearing is installed through the upper side of the protective cover (106). The upper part of the rotating shaft (107) is fixed in the third bearing. The protective cover (106) has an inverted box-shaped structure. An opening (108) is provided on the side of the protective cover (106).

7. A lawnmower head for easy replacement of broken wires according to claim 6, characterized in that, The protective cover (106) is provided with a telescopic bracket (109) on the upper side. The telescopic bracket (109) includes a U-shaped frame (1091) fixed on the upper side of the protective cover (106) away from the opening (108), two support columns (1092) slidably engaged with the bottom end of the U-shaped frame (1091), a threaded support rod (1093) rotatably engaged with the upper side of the U-shaped frame (1091) and threadedly engaged with the support column (1092), a flywheel (1094) fixedly sleeved on the threaded support rod (1093), and a chain (1095) driven between the two flywheels (1094). The bottom end of the support column (1092) is provided with a universal wheel (1096).

8. A lawnmower head for easy replacement of broken wires according to claim 7, characterized in that, The bottom end of the U-shaped frame (1091) is provided with a guide channel (1097) corresponding to the support column (1092) and a connecting channel (1098) between the two guide channels (1097). The support column (1092) is slidably fitted in the guide channel (1097). The chain (1095) is located in the connecting channel (1098). A handwheel (1099) is provided on the upper side of the threaded support rod (1093). A third bearing is installed through the upper side of the U-shaped frame (1091). A third smooth curved surface is provided on the outer side of the upper part of the threaded support rod (1093). The upper part of the threaded support rod (1093) is fixed in the third bearing.

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