CN109775608B

CN109775608B - Mounting trolley

Info

Publication number: CN109775608B
Application number: CN201910061354.XA
Authority: CN
Inventors: 龙钢; 赖黎颖; 曾冕; 马斌
Original assignee: Chengdu Jouav Automation Tech Co ltd
Current assignee: Chengdu Jouav Automation Tech Co ltd
Priority date: 2019-01-23
Filing date: 2019-01-23
Publication date: 2020-05-26
Anticipated expiration: 2039-01-23
Also published as: CN109775608A

Abstract

The invention discloses an installation trolley which comprises a moving frame and an adjustable support component arranged on the moving frame, wherein the adjustable support component comprises an upper frame part, a middle frame part and a lower frame part which are sleeved from inside to outside in sequence, a support frame is arranged at the top of the upper frame part, balance weight boxes are arranged on the outer walls of two sides of the lower frame part in a sliding mode, lower steel wire rollers are arranged at the tops of the side walls of the lower frame part on the same side with the balance weight boxes, lower steel wires are wound on the lower steel wire rollers, one ends of the lower steel wires are fixedly connected with the balance weight boxes, the other ends of the lower steel wires are fixedly connected with the middle frame part, upper steel wire rollers are arranged at the tops of the side walls of the middle frame part on the same side with the lower steel wire rollers, upper steel wires are wound on the upper steel wire rollers, one ends of the upper steel wires. The lifting mechanism is convenient to move, can be driven to be installed by applying force easily, and greatly reduces the installation difficulty of being separated from the ground.

Description

Mounting trolley

Technical Field

The invention relates to the field of auxiliary mounting tools, in particular to a mounting trolley.

Background

At present, a lot of auxiliary tools for installation are available on the market, but the tools for installing medium-sized articles are very few, and especially the tools need to be lifted off the ground for installation, such as cylindrical and heavy articles like motors, missiles, pipelines and the like. If the installation is very troublesome by purely depending on manual lifting, the installation is also inconvenient by matching with hoisting tools such as a crane and the like, so that an auxiliary tool integrating the movement and the installation is required to be designed, and the difficulty in the operation of installation operation on the ground is reduced.

Disclosure of Invention

The invention aims to provide an installation trolley which is convenient to move, can drive a lifting mechanism to be installed through easy force application, and greatly reduces the installation difficulty of being separated from the ground.

The purpose of the invention is realized by the following technical scheme: an installation trolley comprises a moving frame and an adjustable support component arranged on the moving frame, wherein the adjustable support component comprises an upper frame part, a middle frame part and a lower frame part which are sequentially sleeved from inside to outside, the upper frame part can be vertically and slidably arranged in an inner cavity of the middle frame part, the middle frame part can be vertically and slidably arranged in an inner cavity of the lower frame part, a support frame is arranged at the top of the upper frame part, a rack is arranged on the outer wall of one side of the upper frame part, a gear meshed with the rack is arranged on the inner side wall of the middle frame part, a locking mechanism used for locking the gear is arranged on the middle frame part, counterweight boxes are slidably arranged on the outer walls of two sides of the lower frame part, counterweight blocks are contained in the counterweight boxes, at least one lower steel wire roller is arranged at the top of the side wall of the lower frame part on the same side as the counterweight boxes, a lower steel wire winds around the lower steel wire roller, one, the other end of the upper steel wire roller is fixedly connected with the middle frame piece, the upper steel wire roller is arranged on the top of the side wall of the middle frame piece on the same side as the lower steel wire roller, the upper steel wire is wound on the upper steel wire roller, one end of the upper steel wire is fixedly connected with the lower frame piece, the other end of the upper steel wire is fixedly connected with the upper frame piece, and the outer side wall of the lower frame piece is provided with a recovery mechanism for pulling back the upper frame piece.

Further, the recovery mechanism comprises a mounting frame and a driving shaft which is rotatably arranged on the mounting frame, the mounting frame is fixed on the lower frame, a steel wire reel is arranged on the driving shaft, a threading hole is formed in the side wall of the lower frame installation recovery mechanism, a wire guide wheel is arranged on the bottom wall of the inner cavity of the lower frame, a recovery steel wire is arranged on the steel wire reel, one end of the recovery steel wire penetrates through the threading hole and is fixedly connected with the bottom surface of the upper frame, the middle part of the recovery steel wire is wound on the wire guide wheel, a ratchet wheel is processed on one side end face of the steel wire reel, an adjusting mechanism for controlling the rotation of the ratchet wheel is arranged on the mounting frame, the adjusting mechanism comprises a pawl, a shift shaft and a shift pin, the shift shaft is rotatably arranged on the mounting frame, the pawl is sleeved on the shift shaft, the pawl is mutually abutted against the ratchet wheel, and the shift pin is, and a locking bolt is arranged on the shifting pin.

Furthermore, the locking mechanism is a shaft locking device, the gear is mounted on the inner side wall of the upper frame through a gear shaft, one end of the gear shaft penetrates out of the upper frame, and the shaft locking device is mounted on the outer side wall of the upper frame and used for locking a penetrating part of the gear shaft.

Further, moving vehicle frame includes frame plate and sets up the universal gyro wheel in frame plate bottom, lower frame spare fixed mounting is on frame plate, and lower frame spare both sides bottom all is provided with the supporting shoe that is used for spacing counter weight box, install the free bearing on the frame plate, it has the handle to articulate on the free bearing.

Further, frame plate both ends all are provided with at least one supporting mechanism, and supporting mechanism includes adjusting hand wheel, lifter, sleeve and supporting legs, the through-hole fit in adjusting hand wheel center has the cover of straining, and the cover of straining rotationally sets up in the sleeve through the bearing, the lifter rotationally the suit is in the sleeve, the supporting legs is fixed in the lifter bottom, and the processing of lifter top has rectangular screw rod, rectangular screw rod and the screw-thread fit of straining.

Further, the support frame includes supporting panel and supporting baseplate, and supporting baseplate fixes on last frame spare, and it has the removal pilot hole to open at the supporting baseplate middle part, be provided with spherical slewing mechanism between supporting panel and the supporting baseplate, spherical slewing mechanism includes the anticreep bolt and through spherical complex motion spherical seat and fixed spherical seat, the spherical seat of motion is fixed in the supporting panel bottom surface, fixed spherical seat is installed on supporting baseplate, and just fixed spherical seat bottom is opened there is the swing hole, anticreep bolt one end pass the swing hole and with the spherical seat screw-thread fit of motion.

Further, the bottom cambered surface of fixed spherical seat is arranged in the removal pilot hole, there is a round slip journal ring outside the upper surface of fixed spherical seat along integrated into one piece, be provided with a plurality of balls that are used for supporting the slip journal ring on the supporting baseplate, and still be fixed with the limit clamp plate who is used for restricting fixed spherical seat moving range on the supporting baseplate.

Furthermore, the bottom surface of the supporting panel is provided with a plurality of positioning apexes, and the upper surface of the supporting bottom plate is provided with a plurality of positioning sleeves matched with the positioning apexes.

Furthermore, an upper limiting block is fixed on the lower surface of the supporting bottom plate, and a lower limiting block is fixed on the lower portion of the upper frame piece.

Further, be provided with the slide rail on the lateral wall of last frame spare, be provided with on the chamber wall of well frame spare with last slide rail sliding fit's top shoe, be provided with down the slider on the lateral wall of well frame spare, be provided with on the inner chamber wall of lower frame spare with lower slider sliding fit's lower slide rail.

The invention has the beneficial effects that:

1. by arranging the adjustable supporting component, the adjustable supporting component comprises an upper frame part, a middle frame part and a lower frame part which are sequentially sleeved in a sliding manner, the balancing weight and the adjustable supporting component are in a dynamic balance state by utilizing the fixed pulley, the upper frame part can be lifted after the force is easily applied to the upper frame part, so that articles on the upper frame part can be easily lifted, the installation operation of separating from the ground can be carried out without adopting the cooperation of manpower or other lifting tools, and the installation difficulty is greatly reduced;

2. the spherical rotating mechanism is arranged between the supporting panel and the supporting bottom plate, so that the supporting panel can perform spherical rotation to a certain degree relative to the supporting bottom plate, the working surface of installation operation is increased, and the difficulty of installation operation is reduced;

3. the limiting pressure plate is arranged on the supporting bottom plate, so that the fixed spherical seat can perform plane movement within the limiting range of the limiting pressure plate, and the difficulty of installation operation is reduced to a certain extent;

4. through set up a plurality of supporting mechanism on the frame board, when the frame board removed when target in place, control supporting mechanism and ground contact to make universal gyro wheel break away from ground, increase the stability of whole removal frame, prevent that the movable carriage from sliding when the installation.

Drawings

FIG. 1 is a schematic structural view of the present invention;

FIG. 2 is a schematic front view of the present invention;

FIG. 3 is a schematic structural view of the stand of the present invention;

FIG. 4 is a schematic top view of the support base of the present invention;

FIG. 5 is a schematic structural view of an upper frame member according to the present invention;

FIG. 6 is a top view of the middle frame member of the present invention;

FIG. 7 is a front view of the lower frame member of the present invention;

FIG. 8 is a top view of FIG. 7;

FIG. 9 is a schematic view of the recovery mechanism of the present invention;

fig. 10 is a schematic structural view of the support mechanism of the present invention.

The labels in the figure are: 1-moving the frame; 2-upper frame piece; 3-a middle frame piece; 4-upper frame piece; 5-a support frame; 6-a support mechanism; 7-a recovery mechanism; 8-a weight box; 9-a balancing weight; 11-a frame plate; 12-universal rollers; 13-handle; 21-a rack; 22-a lower limit block; 23-upper sliding rail; 31-a gear; 32-gear shaft; 33-shaft locking device; 34-an upper slide block; 35-a lower slider; 36-feeding a steel wire roller; 37-a wire holder; 41-lower steel wire roller; 42-threading holes; 43-a wire guide wheel; 44-lower slide rail; 45-support block; 51-a support panel; 52-support floor; 53-kinematic spherical seat; 54-fixed spherical seat; 55-a swinging hole; 56-anti-drop bolt; 57-moving assembly holes; 58-a ball bearing; 59-limiting pressure plates; 510-a positioning sleeve; 511-positioning the tip; 512-sliding fulcrum ring; 513 — an upper limit block; 61-a sleeve; 62-a lifting rod; 63-a long screw; 64-adjusting the handwheel; 65-tensioning the sleeve; 66-supporting feet; 71-a mounting frame; 72-a drive shaft; 73-wire reel; 74-ratchet wheel; 75-a pawl; 76-shift shaft; 77-shift pin; 78-locking bolt.

Detailed Description

As shown in fig. 1 to 10, the mounting cart provided in this embodiment includes a moving frame 1 and an adjustable supporting member mounted on the moving frame 1, in this embodiment, the moving frame 1 includes a frame plate 11 and four universal rollers 12 disposed at the bottom of the frame plate 11, a hinged support is mounted on an upper surface of one side of the frame plate 11, and a handle 13 is hinged to the hinged support, so as to facilitate manual pulling. In order to increase the stability of moving frame 11, frame plate 11 both ends all are provided with two supporting mechanism 6, and the position of supporting mechanism 6 matches with universal gyro wheel 12's position, and supporting mechanism 6 includes adjusting hand wheel 64, lifter 62, sleeve 61 and supporting legs 66, the through-hole fit at adjusting hand wheel 64 center has taut cover 65, and taut cover 65 rotatably assembles in sleeve 61 through two sets of bearings, and the middle part shaping of taut cover 65 has the arch, and this arch is spacing between two sets of bearings, can prevent that taut cover 65 from breaking away from sleeve 61. Lifting rod 62 rotationally the suit is in the sleeve 61 of taut cover 65 below, supporting legs 66 is fixed in lifting rod 62 bottom, and the processing of lifting rod 62 top has rectangular screw rod 63, and rectangular screw rod 63 and taut cover 65 screw-thread fit make supporting legs 66 relative sleeve 61 oscilaltion through rotating adjusting hand wheel 64 to make universal gyro wheel 12 break away from ground, increase the support stability of moving vehicle frame 1.

Adjustable supporting member includes last frame 2, center frame 3 and the lower frame 4 that from inside to outside overlaps in proper order and establish, lower frame 4 fixed mounting is on frame board 11, but go up frame 2 and install in center frame 3's inner chamber vertically with sliding, center frame 3 can install in lower frame 4's inner chamber vertically with sliding, specifically, be provided with on the lateral wall of going up frame 2 and slide rail 23, be provided with on the chamber wall of center frame 3 with last slide rail 23 sliding fit's last slider 34, be provided with down slider 35 on the lateral wall of center frame 3, be provided with on the chamber wall of lower frame 4 and slide rail 44 down with down slider 35 sliding fit, realize the mode of going up frame 2, center frame 3 and lower frame 4 suit from inside to outside through the cooperation of slider with the slide rail. The top of the upper frame piece 2 is provided with a support frame 5, and the support frame 5 can be used for supporting and placing columnar parts or articles so as to carry out installation operation separated from the ground. The outer wall of one side of the upper frame member 2 is provided with a rack 21, the inner side wall of the middle frame member 3 is provided with a gear 31 meshed with the rack 21, and the middle frame member 3 is provided with a locking mechanism used for locking the gear 31, in the embodiment, the locking mechanism is preferably a shaft locking device 33, the gear 31 is installed on the inner side wall of the upper frame member 2 through a gear shaft 32, one end of the gear shaft 32 penetrates out of the upper frame member 2, and the shaft locking device 33 is installed on the outer side wall of the upper frame member 2 and used for locking a penetrating part of the gear shaft 32.

Similarly, the outer walls of the two sides of the lower frame 4 are provided with counterweight boxes 8 by means of matching of a slide rail and a slide block, a counterweight 9 is contained in the counterweight box 8, the top parts of the side walls of the lower frame 4 on the same side with the two counterweight boxes 8 are provided with two lower steel wire rollers 41, the lower steel wire rollers 41 are wound with lower steel wires (not shown), one end of each lower steel wire is fixedly connected with the bottom of the counterweight box 8 through a steel wire fixer 37, the other end of each lower steel wire is fixedly connected with the bottom of the middle frame 3 through a steel wire fixer 37, the top parts of the two side walls of the middle frame 3 on the same side with the lower steel wire rollers 41 are provided with upper steel wires (not shown), one end of each upper steel wire is fixedly connected with the bottom of the inner wall of the lower frame 4, the other end of each upper frame 2 is fixedly connected with the bottom of the upper frame, in order to prevent operation errors, the bottom parts of the two sides of the lower frame 4 are, an upper limiting block 513 is fixed on the lower surface of the supporting frame 5, and a lower limiting block 22 is fixed on the lower part of the upper frame member 2. Through increasing balancing weight 9 in counter weight box 8, make the balancing weight of both sides and whole adjustable supporting component reach a state that approaches dynamic balance with waiting to install article, only need artificial application of force gently, alright lifting upper frame spare 2, then hold gear shaft 32 tightly, make upper frame spare 2 and 3 unable relative movement of center frame spare to article or part on the final lifting support frame 5 are installed the operation.

After the article or the part is installed, the balance weight is out of balance with the upper frame 2, the descending difficulty of the upper frame 2 is increased, in order to reduce the descending difficulty of the upper frame 2, a recovery mechanism 7 for pulling back the upper frame 2 is installed on the outer side wall of the lower frame 4, the recovery mechanism 7 comprises a U-shaped mounting frame 71 and a driving shaft 72 rotatably arranged on the mounting frame 71, the mounting frame 71 is fixed on the outer wall of the lower part of the lower frame 4, a steel wire reel 73 is installed on the driving shaft 72, a threading hole 42 is formed in the outer wall of the lower frame 4 on the same side with the mounting frame 71, a guide wire wheel 43 is installed on the bottom wall of the inner cavity of the lower frame 4, a recovery steel wire (not shown) is hung on the steel wire reel 73, one end of the recovery steel wire is fixed on the steel wire reel 73, the other end of the recovery steel wire penetrates through the threading hole 42 and is wound on the guide wire wheel 43, and, the spinning reel 73 pulls the recovery wire to lower the upper frame 2 and the middle frame 3 in sequence. In order to prevent wire reel 73 from slipping, ratchet 74 is processed on one side end face of wire reel 73, be provided with control ratchet 74 pivoted adjustment mechanism on mounting bracket 71, adjustment mechanism includes pawl 75, dial grade axle 76 and dial grade round pin 77, dial grade axle 76 rotationally sets up on mounting bracket 71 and is parallel to each other with drive shaft 72, pawl 75 fixed cover dress is on dial grade axle 76, and pawl 75 and ratchet 74 butt each other and make ratchet 74 can only unidirectional rotation, dial grade round pin 77 and dial grade axle 76 one end fixed connection, dial and be provided with locking bolt 78 on the round pin 77, dial grade round pin 77 through dialling, make dial grade axle 76 rotate. Thereby rotating the pawl 75 and eventually disengaging the pawl 75 from the ratchet 74, allowing the ratchet 74 to rotate in both directions.

In order to reduce the difficulty of installing the parts or objects to be installed, the support frame 5 can perform plane movement and spherical rotation with a certain angle, specifically, the support frame 5 comprises a support panel 51 and a support base plate 52, the support base plate 52 is fixed on the top of the upper frame 2, a movement assembly hole 57 is formed in the middle of the support base plate 52, a spherical rotation mechanism is arranged between the support panel 51 and the support base plate 52, the spherical rotation mechanism comprises an anti-drop bolt 56, a movement spherical seat 53 and a fixed spherical seat 54 which are matched through spherical surfaces, the movement spherical seat 53 and the fixed spherical seat 54 are preferably hemispherical, the movement spherical seat 53 is fixed on the lower surface of the support panel 51, the convex arc surface of the bottom of the fixed spherical seat 54 is positioned in the movement assembly hole 57 of the support base plate 52, a swing hole 55 is formed in the bottom of the fixed spherical seat 54, one end of the anti-drop bolt 56 passes through the swing hole 55 and is in threaded, the structure of the swing hole 55 and the anti-slip bolt 56 enables the moving spherical seat 53 to perform spherical rotation at a certain angle relative to the fixed spherical seat 54, so that the inclination angle of the object placed on the supporting panel 51 can be changed, thereby reducing the difficulty of installation. In order to ensure that the fixed spherical seat 54 can move stably in the movable assembling hole 57, a circle of sliding support ring 512 is integrally formed outside the upper surface of the fixed spherical seat 54, a plurality of balls 58 for supporting the sliding support ring 512 are arranged on the support base plate 52, L-shaped limit pressing plates 59 for limiting the moving range of the fixed spherical seat 54 are further fixed on two sides of the upper surface of the support base plate 52, the fixed spherical seat 54 drives the movable spherical seat 53 to move in the movable assembling hole 57 in a plane, the transverse plate parts of the limit pressing plates 59 and the balls 58 provide support for the sliding support ring 512 and limit the vertical displacement of the sliding support ring 512, and the vertical plates of the limit pressing plates 59 limit the horizontal displacement of the sliding support ring 512, so that the size can be designed as required, thereby controlling the plane moving range of the spherical rotating mechanism to adapt to the requirement of article installation.

In order to prevent the spherical rotating mechanism from moving during transportation of the articles, the bottom surface of the supporting panel 51 is provided with a plurality of positioning apexes 511, the upper surface of the supporting base plate 52 is provided with a plurality of positioning sleeves 510 matched with the positioning apexes 511, and the supporting panel 51 is slightly lifted, so that the positioning apexes 511 are matched with the positioning sleeves 510 in an inserted manner, and the relative movement of the supporting panel 51 and the supporting base plate 52 is limited.

The above description is only a preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any modification and replacement based on the technical solution and inventive concept provided by the present invention should be covered within the scope of the present invention.

Claims

1. The utility model provides an installation dolly, includes moving vehicle frame and installs the adjustable support component on moving vehicle frame which characterized in that: the adjustable supporting component comprises an upper frame part, a middle frame part and a lower frame part which are sequentially sleeved from inside to outside, the upper frame part can be vertically and slidably arranged in an inner cavity of the middle frame part, the middle frame part can be vertically and slidably arranged in an inner cavity of the lower frame part, a supporting frame is arranged at the top of the upper frame part, a rack is arranged on the outer wall of one side of the upper frame part, a gear meshed with the rack is arranged on the inner side wall of the middle frame part, a locking mechanism used for locking the gear is arranged on the middle frame part, a counterweight box is slidably arranged on the outer walls of two sides of the lower frame part, a counterweight block is arranged in the counterweight box, at least one lower steel wire roller is arranged at the top of the side wall of the lower frame part, which is at the same side as the counterweight box, a lower steel wire winds around the lower steel wire roller, one end of the lower steel wire is fixedly connected with the counterweight box, the other end of the lower steel wire is fixedly, an upper steel wire is wound on the upper steel wire roller, one end of the upper steel wire is fixedly connected with the lower frame piece, the other end of the upper steel wire is fixedly connected with the upper frame piece, and a recovery mechanism for pulling back the upper frame piece is installed on the outer side wall of the lower frame piece;

the recovery mechanism comprises a mounting frame and a driving shaft which is rotatably arranged on the mounting frame, the mounting frame is fixed on a lower frame piece, a steel wire reel is arranged on the driving shaft, a threading hole is formed in the side wall of the recovery mechanism for mounting the lower frame piece, a guide wire wheel is arranged on the bottom wall of the inner cavity of the lower frame piece, a recovery steel wire is arranged on the steel wire reel, one end of the recovery steel wire passes through the threading hole and is fixedly connected with the bottom surface of the upper frame piece, the middle part of the recovery steel wire is wound on the guide wire wheel, a ratchet wheel is processed on one side end surface of the steel wire reel, an adjusting mechanism for controlling the rotation of the ratchet wheel is arranged on the mounting frame, the adjusting mechanism comprises a pawl, a shift shaft and a shift pin, the shift shaft is rotatably arranged on the mounting frame, the pawl is sleeved on the shift shaft, the pawl is mutually abutted against the, and a locking bolt is arranged on the shifting pin.

2. The mounting trolley according to claim 1, wherein: the locking mechanism is a shaft locking device, the gear is installed on the inner side wall of the upper frame piece through the gear shaft, one end of the gear shaft penetrates out of the upper frame piece, and the shaft locking device is installed on the outer side wall of the upper frame piece and used for locking a penetrating part of the gear shaft.

3. The mounting trolley according to claim 1, wherein: the movable frame comprises a frame plate and universal idler wheels arranged at the bottom of the frame plate, the lower frame piece is fixedly installed on the frame plate, supporting blocks used for limiting counterweight boxes are arranged at the bottoms of two sides of the lower frame piece, hinged supports are installed on the frame plate, and handles are hinged to the hinged supports.

4. The mounting trolley according to claim 3, wherein: the frame plate both ends all are provided with at least one supporting mechanism, and supporting mechanism includes adjusting hand wheel, lifter, sleeve and supporting legs, the through-hole fit in adjusting hand wheel center has the tensioning cover, and the tensioning cover rotationally sets up in the sleeve through the bearing, the lifter rotationally the suit in the sleeve, the supporting legs is fixed in the lifter bottom, and the processing of lifter top has rectangular screw rod, rectangular screw rod and tensioning cover screw-thread fit.

5. The mounting trolley according to any one of claims 1 to 4, wherein: the support frame includes supporting panel and supporting baseplate, and supporting baseplate fixes on last frame spare, and it has the removal pilot hole to open at the supporting baseplate middle part, be provided with spherical slewing mechanism between supporting panel and the supporting baseplate, spherical slewing mechanism includes the anticreep bolt and through spherical seat of sphere complex motion and fixed spherical seat, the spherical seat of motion is fixed in the supporting panel bottom surface, fixed spherical seat is installed on supporting baseplate, and just fixed spherical seat bottom is opened there is the swing hole, anticreep bolt one end pass the swing hole and with the spherical seat screw-thread fit of motion.

6. The mounting trolley according to claim 5, wherein: the bottom cambered surface of fixed spherical seat is arranged in removing the pilot hole, there is the round slip journal ring outside the upper surface of fixed spherical seat along integrated into one piece, be provided with a plurality of balls that are used for supporting the slip journal ring on the supporting baseplate, and still be fixed with the spacing clamp plate that is used for restricting fixed spherical seat moving range on the supporting baseplate.

7. The mounting trolley according to claim 6, wherein: the bottom surface of the supporting panel is provided with a plurality of positioning apexes, and the upper surface of the supporting bottom plate is provided with a plurality of positioning sleeves matched with the positioning apexes.

8. The mounting trolley according to claim 7, wherein: an upper limiting block is fixed on the lower surface of the supporting bottom plate, and a lower limiting block is fixed on the lower portion of the upper frame piece.

9. The mounting trolley according to claim 8, wherein: the outer wall of the upper frame piece is provided with an upper sliding rail, the inner cavity wall of the middle frame piece is provided with an upper sliding block in sliding fit with the upper sliding rail, the outer wall of the middle frame piece is provided with a lower sliding block, and the inner cavity wall of the lower frame piece is provided with a lower sliding rail in sliding fit with the lower sliding block.