CN118419829B - Two-stage lifting platform and application method thereof - Google Patents

Abstract

A two-stage lifting platform and a use method thereof relate to the technical field of lifting platforms, and the technical scheme is as follows: the lifting device comprises a lifting table, wherein a bearing box is connected to the lower portion of the lifting table, a first U-shaped frame is connected to the bearing box in a sliding mode, two first rollers are connected to two vertical sections of the first U-shaped frame, the two first rollers are connected through a first connecting rope, and a second U-shaped frame is connected to the first U-shaped frame in a sliding mode. The beneficial effects of this technical scheme are: through the setting of first U type frame, second U type frame and movable seat, when the elevating platform goes up and down to corresponding position, can control the lifter plate and upwards remove once more, carry staff or heavy object, do not need the drive arrangement of control elevating platform like this and work once more to the lift of lifter plate is the staff's operation that is located the elevating platform, can carry staff or heavy object to suitable position.

Description

Two-stage lifting platform and use method thereof

Technical Field

The present invention relates to the technical field of lifting platforms, and in particular to a two-stage lifting platform and a use method thereof.

Background Art

A lifting platform is a device for vertically transporting heavy objects. With the development of social science and technology, lifting platforms have been popularized in every corner of social life. The free lifting characteristics of lifting platforms have been widely used in municipal maintenance, cargo transportation at docks and logistics centers, building decoration and other fields.

Most lifting platforms are single-stage lifting devices, which generally include a load-bearing platform and a hydraulic drive device that drives the load-bearing platform to perform lifting movements. When in use, they generally lift workers or heavy objects to appropriate positions. However, current lifts are generally single-stage lifts, and the lifting height of a single-stage lifting mechanism is limited, which does not meet the requirements for different heights during work. When lifting heavy objects, the load-bearing platform is first moved to the corresponding position for operation, and then the corresponding drive device is controlled to move upward again. Due to the height difference, it is inconvenient for the staff to control the position of the load-bearing platform again, and the workers or heavy objects cannot be moved to appropriate positions as required. Current lifting platforms have a limited operating range. If they need to move left or right, the lifting platform needs to be reset and then the lift needs to be controlled to move to the corresponding position for lifting. This operation is cumbersome and inefficient.

Summary of the invention

The purpose of the present invention is to overcome the shortcomings that after the current lifting platform is lifted to a suitable position, it is inconvenient for the staff to control the height of the lifting platform due to the height, and the height of the lifting platform is limited and cannot meet the needs of different heights during work, and cannot be moved to the appropriate position as required, and a two-stage lifting platform and a method of using the same are proposed.

In order to achieve the above object, the present invention adopts the following technical solutions:

A two-stage lifting platform comprises a lifting platform, wherein the lower part of the lifting platform is connected with a carrying box, a first U-shaped frame is slidably connected in the carrying box, two vertical sections of the first U-shaped frame are connected with two first rollers, the two first rollers are connected by a first connecting rope, the first U-shaped frame is slidably connected with a second U-shaped frame, two vertical sections of the second U-shaped frame are connected with two second rollers, the two second rollers are connected by a second connecting rope, a moving seat is slidably connected to the second U-shaped frame, the upper end of the moving seat is connected with a lifting plate, a first opening is provided in the middle part of the lifting platform, and the lifting plate is arranged opposite to the first opening; fourth connecting blocks are connected to two side walls of the moving seat, second connecting blocks are fixed on two opposite side walls in the carrying box, the first connecting blocks are connected to the opposite sides of the two vertical sections of the second U-shaped frame, the ends of the first connecting rope are respectively connected to the second connecting block and the first connecting block, the opposite sides of the two vertical sections of the first U-shaped frame are connected to the third connecting block, the ends of the second connecting rope are respectively connected to the fourth connecting block and the third connecting block, and a driving component is provided on the first U-shaped frame.

The upper end of the moving seat is connected to a lifting plate, which pushes the lifting plate to move when the moving seat moves up and down. The lifting plate is convenient for staff to stand or place heavy objects on. When the lifting platform moves to a suitable position, the lifting plate is controlled to rise and fall again. The position of the lifting plate is confirmed by the staff on the lifting platform to facilitate the movement of the lifting plate. A driving component is provided on the first U-shaped frame, which controls the up and down movement of the first U-shaped frame. The setting of the first U-shaped frame, the second U-shaped frame and the moving seat controls the movement of the lifting plate, and the support is stable, which is convenient for the staff or objects to rise and fall again.

Preferably, the driving assembly includes a motor arranged below the carrying box, the lower parts of the two vertical sections of the first U-shaped frame are commonly connected to a connecting plate, the bottom of the carrying box is connected to a first screw rod, the output shaft of the motor is connected to the first screw rod, the first screw rod is threadedly connected to the connecting plate, the moving seat is hollow, and the upper end of the first screw rod extends into the moving seat.

The output shaft of the motor is connected to the first screw rod, the first screw rod is threadedly connected to the connecting plate, the motor controls the first screw rod to rotate, and the first screw rod controls the first U-shaped frame to move up and down, thereby controlling the movement of the moving seat.

Preferably, a second opening is provided on the lifting platform, the second opening is communicated with the first opening, a placement cavity is provided inside the lifting platform, and two side walls of the second opening are communicated with the placement cavity.

The second opening is provided to facilitate the passage of the second screw rod, thereby facilitating the meshing of the gear on the second screw rod with the corresponding rack.

Preferably, two extension plates are slidably connected in the placement cavity, placement grooves are provided on the two extension plates, mounting plates are provided in the two placement grooves, second screw rods are installed on the two mounting plates, ends of the two second screw rods respectively pass through the side walls of the two second openings and extend into the second openings, two limit plates are installed at the bottom of the placement cavity, a light rod is commonly connected between the two limit plates, and both ends of the light rod are slidably connected to the two extension plates respectively.

The setting of the extension plate increases the area on the left and right sides of the lifting platform. When movement within a small range is required, the staff can operate on the extension plate without controlling the overall movement of the equipment, thereby improving efficiency.

Preferably, the ends of the two second screw rods are connected to gears, the side wall of the movable seat is connected to a fixed plate, a mounting seat is installed on the fixed plate, the mounting seat is arranged along the length direction of the movable seat, and connecting grooves are arranged on two opposite sides of the mounting seat, racks are installed in the two connecting grooves, and the two racks are arranged opposite to the two gears.

Preferably, the rack is slidably connected in the connecting groove, and a pull rod is provided through both side walls of the connecting groove. A spring is sleeved on the pull rod, and both ends of the spring are respectively installed on the pull rod and the side wall of the connecting groove. A mounting hole is provided on one side of the rack, and the mounting hole is correspondingly arranged with the pull rod.

When the staff observes that the extension plates are not needed, or the terrain and other factors prevent the two extension plates from being fully extended, the staff pulls the two pull rods, and the ends of the pull rods extend from the mounting holes. At this time, the rack is slid downward to misalign the mounting holes on the rack with the pull rods. When the mounting base moves upward afterwards, the corresponding rack will not engage with the gear.

Preferably, support rods are slidably connected to both side walls of the carrying box, the lower ends of the support rods are rotatably connected to the lower part of the extension plate, and the support rods are telescopic rods.

The support rod supports one side of the lower end of the extension plate, and a certain number of support rods are provided according to the width of the extension plate.

Preferably, two first grooves are provided on the two vertical sections of the first U-shaped frame, and the first roller is located in the corresponding first grooves; two second grooves are provided on the two vertical sections of the second U-shaped frame, and the second roller is located in the corresponding second grooves.

A method for using a two-stage lifting platform, using the two-stage lifting platform as described above, includes the following steps:

S1: First, lift the lifting platform to a suitable height, and control the rotation of the first screw rod through the motor. The first screw rod first drives the first U-shaped frame to move upward through the connecting plate. When the first U-shaped frame moves, it drives the corresponding two first connecting ropes to move upward together. Due to the setting of the second connecting block, the first connecting rope rotates on the first roller, and the first connecting rope moves upward. The first connecting rope drives the second U-shaped frame to move upward through the first connecting block;

S2: The second connecting rope on the second U-shaped frame drives the moving seat to move upward through the setting of the third connecting block, and the moving seat pushes the lifting plate out of the lifting platform;

S3: When the moving seat moves upward, the moving seat drives the mounting seat to move through the fixed plate, and the two racks on the mounting seat control the rotation of the gear;

S4: The gear controls the second screw to rotate, and the second screw moves the extension plate out of the placement cavity.

Compared with the prior art, the beneficial effects of the present invention are: through the arrangement of the first U-shaped frame, the second U-shaped frame and the moving seat, when the lifting platform is lifted to the corresponding position, the lifting plate can be controlled to move upward again to transport the staff or heavy objects, so there is no need to control the driving device of the lifting platform to work again, and the lifting and lowering of the lifting plate is operated by the employees on the lifting platform, which can transport the staff or heavy objects to the appropriate position.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solution of the present invention, the drawings required for use in the description will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a schematic structural diagram of a specific embodiment of the present invention.

FIG. 2 is a schematic diagram of the structure inside the carrying box in a specific implementation manner of the present invention.

FIG. 3 is a schematic structural diagram of the connection between the first U-shaped frame and the second U-shaped frame in a specific embodiment of the present invention.

FIG. 4 is a schematic diagram of the structure inside the lifting platform in a specific implementation manner of the present invention.

FIG. 5 is a schematic structural diagram of a vertical section of a first U-shaped frame in a specific implementation manner of the present invention.

FIG. 6 is a schematic structural diagram of a lifting platform in a specific embodiment of the present invention.

FIG. 7 is a schematic diagram of the structure of a rack in a specific embodiment of the present invention.

In the figure: 1 lifting platform, 2 carrying box, 3 extension plate, 4 support rod, 5 first connecting rope, 6 second connecting rope, 7 first U-shaped frame, 8 first connecting block, 9 second U-shaped frame, 10 connecting plate, 11 second connecting block, 12 third connecting block, 13 first roller, 14 second roller, 15 first screw rod, 16 motor, 17 second screw rod, 18 first slider, 19 second slider, 20 moving seat, 21 third slider, 22 first groove, 23 second groove, 24 fourth connecting block, 25 spring, 26 pull rod, 27 connecting groove, 28 fixing plate, 29 mounting seat, 30 rack, 31 first opening, 32 gear, 33 light rod, 34 limit plate, 35 mounting hole, 36 second opening, 37 placement groove.

DETAILED DESCRIPTION

In order to make the purpose, features and advantages of the present invention more obvious and easy to understand, the technical scheme of the present invention will be clearly and completely described below in conjunction with the drawings in this specific embodiment. Obviously, the embodiments described below are only part of the embodiments of the present invention, not all of them. Based on the embodiments in this patent, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this patent.

Referring to Figures 1-7, a two-stage lifting platform includes a lifting platform 1, a carrying box 2 is connected to the lower part of the lifting platform 1, a first U-shaped frame 7 is slidably connected in the carrying box 2, two vertical sections of the first U-shaped frame 7 are connected to two first rollers 13, the two first rollers 13 are connected by a first connecting rope 5, the horizontal section of the first U-shaped frame 7 is connected to the side wall in the carrying box 2 by a first slider 18, so as to facilitate the up and down movement of the first U-shaped frame 7, a second U-shaped frame 9 is slidably connected to the first U-shaped frame 7, the horizontal section of the second U-shaped frame 9 is connected to the horizontal section of the first U-shaped frame 7 by a second slider 19, two vertical sections of the second U-shaped frame 9 are connected to two second rollers 14, and the two second rollers 14 are connected by a second connecting rope 6, a moving seat 20 is slidably connected to the second U-shaped frame 9, and the moving seat 20 is connected to the second U-shaped frame 9 by a third slider 21, which is convenient for the moving seat 20 to move up and down, and a lifting plate is connected to the upper end of the moving seat 20. When the moving seat 20 moves up and down, it will push the lifting plate to move, and the lifting plate is convenient for workers to stand or place heavy objects. When the lifting platform 1 moves to a suitable position, the lifting plate is controlled to rise and fall again. The position of the lifting plate is confirmed by the staff on the lifting platform 1, which is convenient for the movement of the lifting plate. A first opening 31 is provided in the middle of the lifting platform 1, and the lifting plate is arranged opposite to the first opening 31. When the lifting plate is not in use, the lifting plate blocks the first opening 31;

The two side walls of the movable seat 20 are connected with the fourth connecting block 24, the two opposite side walls in the carrying box 2 are fixed with the second connecting block 11, the two vertical sections of the second U-shaped frame 9 are connected with the first connecting block 8 on the opposite sides, and the ends of the first connecting rope 5 are respectively connected to the second connecting block 11 and the first connecting block 8. When the first U-shaped frame 7 moves upward, due to the setting of the second connecting block 11, the first connecting rope 5 moves with the first U-shaped frame 7, and the first connecting rope 5 rotates to control the first connecting block 8 to move upward. The first connecting block 8 controls the second U-shaped frame 9 to move upward. Due to the setting of the third connecting block 12, the first connecting rope 5 is connected to the second connecting block 11 and the first connecting block 8. The second connecting rope 6 rotates, and the second connecting rope 6 drives the moving seat 20 to move upward through the fourth connecting block 24. The moving seat 20 controls the movement of the lifting plate to move the lifting plate to a suitable position. The opposite sides of the two vertical sections of the first U-shaped frame 7 are connected to the third connecting block 12. The ends of the second connecting rope 6 are respectively connected to the fourth connecting block 24 and the third connecting block 12. A driving assembly is provided on the first U-shaped frame 7. The driving assembly controls the first U-shaped frame 7 to move up and down. The setting of the first U-shaped frame 7, the second U-shaped frame 9 and the moving seat 20 controls the movement of the lifting plate, and the support is stable, which is convenient for the staff or objects to lift again.

1-2, the driving assembly includes a motor 16 arranged below the carrying box 2, the lower parts of the two vertical sections of the first U-shaped frame 7 are commonly connected to a connecting plate 10, the bottom of the carrying box 2 is connected to a first screw rod 15, the output shaft of the motor 16 is connected to the first screw rod 15, the first screw rod 15 is threadedly connected to the connecting plate 10, the motor 16 controls the rotation of the first screw rod 15, the first screw rod 15 controls the up and down movement of the first U-shaped frame 7, thereby controlling the movement of the moving seat 20, the moving seat 20 is hollow, the upper end of the first screw rod 15 extends into the moving seat 20, the motor 16 and the first screw rod 15 can also use gears, racks or cylinders to control the up and down movement of the first U-shaped frame 7.

2, 4 and 6, a second opening 36 is provided on the lifting platform 1, and the second opening 36 is connected to the first opening 31. A placement cavity is provided in the lifting platform 1, and the two side walls of the second opening 36 are connected to the placement cavity. The second opening 36 is provided to facilitate the passage of the second screw rod 17, thereby facilitating the meshing of the gear 32 on the second screw rod 17 with the corresponding rack 30. Two extension plates 3 are slidably connected in the placement cavity, and support rods 4 are slidably connected on both side walls of the carrying box 2. The lower end of the support rod 4 is rotatably connected to the lower part of the extension plate 3. The support rod 4 is a telescopic rod. The support rod 4 supports one side of the lower end of the extension plate 3. According to the width of the extension plate 3, a certain number of support rods are provided. Rod 4, a placement groove 37 is provided on the two extension plates 3, a mounting plate is provided in the two placement grooves 37, a second screw rod 17 is installed on the two mounting plates, the ends of the two second screw rods 17 respectively pass through the side walls of the two second openings 36 and extend into the second openings 36, the second screw rod 17 rotates through the mounting plate to push the extension plate 3 to slide, two limit plates 34 are installed at the bottom of the placement cavity, a light rod 33 is commonly connected between the two limit plates 34, the two ends of the light rod 33 are respectively slidably connected to the two extension plates 3, the light rod 33 facilitates the extension plate 3 to slide along a straight line, two placement grooves 37 can be provided on one extension plate 3, and the mounting plate corresponding to the light rod 33 is slidably connected to the light rod 33.

2-4, the ends of the two second screw rods 17 are connected to gears 32, the side wall of the movable seat 20 is connected to a fixed plate 28, and a mounting seat 29 is installed on the fixed plate 28. The mounting seat 29 is arranged along the length direction of the movable seat 20, and the two opposite sides of the mounting seat 29 are provided with connecting grooves 27, and racks 30 are installed in the two connecting grooves 27. The up and down movement of the racks 30 will control the rotation of the gears 32, thereby controlling the rotation of the second screw rods 17 to move the extension plate 3 out of the placement cavity. The two racks 30 are arranged opposite to the two gears 32, and the racks 30 are slidably connected in the connecting grooves 27. The racks 30 slide along the length direction of the connecting grooves 27, and the two side walls of the connecting grooves 27 are penetrated by pull rods 26 A spring 25 is sleeved on the pull rod 26, and both ends of the spring 25 are respectively installed on the pull rod 26 and the side walls of the connecting groove. A mounting hole 35 is set on one side of the rack 30, and the mounting hole 35 is set corresponding to the pull rod 26. When the staff observes that the extension plate 3 is not needed, or the terrain and other reasons make it impossible to fully extend the two extension plates 3, the staff pulls the two pull rods 26, and the ends of the pull rods 26 extend from the mounting holes 35. At this time, the rack 30 is slid downward to make the mounting hole 35 on the rack 30 misaligned with the pull rod 26. After that, when the mounting seat 29 moves upward, the corresponding rack 30 will not mesh with the gear 32. According to needs, the pull rod 26 can be replaced with a bolt, and the rack 30 and the mounting seat 29 are detachable.

4 , two first grooves 22 are provided on the two vertical sections of the first U-shaped frame 7, and the first roller 13 is located in the corresponding first groove 22; two second grooves 23 are provided on the two vertical sections of the second U-shaped frame 9, and the second roller 14 is located in the corresponding second groove 23; the first groove 22 and the second groove 23 facilitate the placement of the corresponding rollers.

A method for using a two-stage lifting platform, using the two-stage lifting platform as described above, includes the following steps:

S1: First, lift the lifting platform 1 to a suitable height, and control the first screw rod 15 to rotate through the motor 16. The first screw rod 15 first drives the first U-shaped frame 7 to move upward through the connecting plate 10. When the first U-shaped frame 7 moves, it drives the corresponding two first connecting ropes 5 to move upward together. Due to the setting of the second connecting block 11, the first connecting rope 5 rotates on the first roller 13, and the first connecting rope 5 moves upward. The first connecting rope 5 drives the second U-shaped frame 9 to move upward through the first connecting block 8;

S2: The second connecting rope 6 on the second U-shaped frame 9 drives the moving seat 20 to move upward through the third connecting block 12, and the moving seat 20 pushes the lifting plate out of the lifting platform 1;

S3: When the moving seat 20 moves upward, the moving seat 20 drives the mounting seat 29 to move through the fixing plate 28, and the two racks 30 on the mounting seat 29 control the gear 32 to rotate;

S4: The gear 32 controls the second screw rod 17 to rotate, and the second screw rod 17 moves the extension plate 3 out of the placement cavity.

The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims (4)

1. The utility model provides a two-stage lift platform which characterized in that: the lifting device comprises a lifting table (1), wherein the lower part of the lifting table (1) is connected with a bearing box (2), a first U-shaped frame (7) is connected in the bearing box (2) in a sliding manner, two first rollers (13) are connected to two vertical sections of the first U-shaped frame (7), the two first rollers (13) are connected through a first connecting rope (5), a second U-shaped frame (9) is connected to the first U-shaped frame (7) in a sliding manner, two second rollers (14) are connected to two vertical sections of the second U-shaped frame (9), two second rollers (14) are connected through a second connecting rope (6), a movable seat (20) is connected to the second U-shaped frame (9) in a sliding manner, a lifting plate is connected to the upper end of the movable seat (20), a first opening (31) is formed in the middle of the lifting table (1), and the lifting plate is arranged opposite to the first opening (31); the two side walls of the movable seat (20) are connected with a fourth connecting block (24), two opposite side walls in the bearing box (2) are respectively fixed with a second connecting block (11), one surface of the two vertical sections of the second U-shaped frame (9) opposite to each other is respectively connected with a first connecting block (8), the end parts of the first connecting ropes (5) are respectively connected to the second connecting block (11) and the first connecting block (8), one surface of the two vertical sections of the first U-shaped frame (7) opposite to each other is respectively connected with a third connecting block (12), and the end parts of the second connecting ropes (6) are respectively connected to the fourth connecting block (24) and the third connecting block (12), and the first U-shaped frame (7) is provided with a driving assembly;

The driving assembly comprises a motor (16) arranged below the bearing box (2), the lower parts of two vertical sections of the first U-shaped frame (7) are connected with a connecting plate (10) together, the bottom in the bearing box (2) is connected with a first screw rod (15), an output shaft of the motor (16) is connected with the first screw rod (15), the first screw rod (15) is in threaded connection with the connecting plate (10), the movable seat (20) is in hollow arrangement, and the upper end of the first screw rod (15) extends into the movable seat (20);

The lifting table (1) is provided with a second opening (36), the second opening (36) is communicated with the first opening (31), a placing cavity is arranged in the lifting table (1), and two side walls of the second opening (36) are communicated with the placing cavity; the placing cavity is slidably connected with two extension plates (3), the two extension plates (3) are provided with placing grooves (37), mounting plates are arranged in the two placing grooves (37), second screw rods (17) are arranged on the two mounting plates, and the end parts of the two second screw rods (17) respectively penetrate through the side walls of the two second openings (36) and extend into the second openings (36);

two limiting plates (34) are arranged at the bottom of the placing cavity, a polish rod (33) is connected between the two limiting plates (34) together, and two ends of the polish rod (33) are respectively connected with the two extending plates (3) in a sliding manner; the ends of the two second screw rods (17) are connected with gears (32), the side wall of the movable seat (20) is connected with a fixed plate (28), the fixed plate (28) is provided with a mounting seat (29), the mounting seat (29) is arranged along the length direction of the movable seat (20), two opposite side surfaces of the mounting seat (29) are respectively provided with a connecting groove (27), racks (30) are respectively arranged in the two connecting grooves (27), and the two racks (30) are arranged opposite to the two gears (32);

The rack (30) is slidably connected in the connecting groove (27), two side walls of the connecting groove (27) are respectively provided with a pull rod (26) in a penetrating mode, springs (25) are sleeved on the pull rods (26), two ends of each spring (25) are respectively arranged on the side walls of the pull rods (26) and the connecting groove, one side face of the rack (30) is provided with a mounting hole (35), and the mounting holes (35) are correspondingly arranged with the pull rods (26).

2. The two-stage lift platform of claim 1 wherein: the two side walls of the bearing box (2) are both connected with support rods (4) in a sliding manner, the lower ends of the support rods (4) are connected to the lower parts of the extension plates (3) in a rotating manner, and the support rods (4) are telescopic rods.

3. The two-stage lift platform of claim 1 wherein: two first grooves (22) are formed in two vertical sections of the first U-shaped frame (7), the first rollers (13) are located in the corresponding first grooves (22), two second grooves (23) are formed in two vertical sections of the second U-shaped frame (9), and the second rollers (14) are located in the corresponding second grooves (23).

4. A method of using a two-stage lift platform according to any one of claims 1 to 3, comprising the following steps:

S1: firstly, lifting a lifting table (1) to a proper height, controlling a first screw rod (15) to rotate through a motor (16), driving a first U-shaped frame (7) to move upwards through a connecting plate (10) by the first screw rod (15), and driving two corresponding first connecting ropes (5) to move upwards together when the first U-shaped frame (7) moves, wherein due to the arrangement of a second connecting block (11), the first connecting ropes (5) rotate on a first roller (13), the first connecting ropes (5) move upwards, and the first connecting ropes (5) drive a second U-shaped frame (9) to move upwards through a first connecting block (8);

s2: the second connecting rope (6) on the second U-shaped frame (9) drives the movable seat (20) to move upwards through the arrangement of the third connecting block (12), and the movable seat (20) pushes the lifting plate out of the lifting table (1);

s3: when the movable seat (20) moves upwards, the movable seat (20) drives the mounting seat (29) to move through the fixed plate (28), and two racks (30) on the mounting seat (29) control the gear (32) to rotate;

S4: the gear (32) controls the rotation of the second screw (17), and the second screw (17) enables the extension plate (3) to be removed from the placement cavity.