CN220962239U - Liquid level protection mechanism - Google Patents

Abstract

The application provides a liquid level protection mechanism, which comprises a liquid storage container; the liquid supply channel is communicated with the liquid storage container through a liquid outlet; the floating switch is positioned in the liquid storage container and connected with the liquid outlet of the liquid supply channel, and when the liquid level in the liquid storage container reaches a first height, the liquid outlet is blocked by the floating switch; the secondary protection mechanism comprises a floating assembly which is positioned in the liquid storage container and slides along a set direction, and a protection switch which is connected to the liquid supply channel and used for controlling the opening and closing of the liquid supply channel; when the liquid level in the liquid storage container reaches a second height, the floating assembly triggers the protection switch to block the liquid supply channel. Through the secondary protection mechanism that sets up, in the circumstances thing that floating switch broke down and damages, realize the control of liquid level height in the stock solution container through secondary protection mechanism, avoid lasting to supply liquid in the stock solution container and lead to the problem that overflows, avoid the wasting of resources to guarantee the normal operation of relevant equipment.

Description

Liquid level protection mechanism

Technical Field

The application relates to the field of liquid level adjustment, in particular to a liquid level protection mechanism.

Background

In both domestic and industrial applications, there are situations where it is necessary to control the liquid in a certain container to a certain amount, in which case the level is regulated and controlled mostly by means of a float switch.

Illustratively, the water supply pipe is used for supplying water into the water tank, and the float switch is arranged in the water tank and is connected with an opening communicated with the water supply pipe into the water tank; when the water level in the water tank is in a lower state, the opening of the water supply pipe is in a communicating state, and the water supply pipe is stopped by driving the floating ball type switch to close the opening of the water supply pipe through buoyancy generated by the water level on the floating ball part of the floating ball type switch after the water level rises to a set position.

However, in actual use, the floating ball type switch fails due to the failure of mechanical parts or overlong use time, etc., and water is continuously supplied to the water tank under the condition, so that the water in the water tank overflows, the resource waste is caused, and the work cannot be normally performed.

Disclosure of utility model

The application provides a liquid level protection mechanism, which improves the stability of liquid level control and avoids the problem of liquid level regulation failure.

The application provides a liquid level protection mechanism, which comprises,

A liquid storage container for storing liquid;

The liquid supply channel is communicated with the liquid storage container through a liquid outlet;

the floating switch is positioned in the liquid storage container and connected with the liquid outlet of the liquid supply channel, and when the liquid level in the liquid storage container reaches a first height, the liquid outlet is blocked by the floating switch;

The secondary protection mechanism comprises a floating assembly which is positioned in the liquid storage container and slides along a set direction, and a protection switch which is connected to the liquid supply channel and used for controlling the opening and closing of the liquid supply channel;

When the liquid level in the liquid storage container reaches a second height, triggering the protection switch to block the liquid supply channel;

Wherein the second height is above the first height.

Through the secondary protection mechanism, when the floating switch fails and is damaged, the liquid level height in the liquid storage container is controlled through the secondary protection mechanism, so that the problem of overflow caused by continuous liquid supply into the liquid storage container is avoided, the resource waste is avoided, and the normal operation of related equipment is ensured; and the liquid level is regulated and controlled in an electric control mode and the like, so that energy sources are saved, and the risk of danger is reduced.

In a specific embodiment, the device further comprises a limiting piece fixedly connected with the liquid storage container, and the floating assembly is in sliding fit with the limiting piece.

The direction of the floating assembly is guided by the limiting piece, so that the position stability of the floating assembly is guaranteed, and the problem that the floating assembly cannot be matched with the protection switch normally and cannot trigger the protection switch due to sliding of the floating assembly is avoided.

In a specific embodiment, the limiting member is tubular, and the interior of the limiting member is in communication with the interior of the reservoir;

And part of the floating assembly is positioned in the limiting piece.

The limiting piece is of a tubular structure, and limiting of the moving position of the floating assembly can be conveniently achieved.

In a specific embodiment, the floating assembly comprises a floating ball and a trigger fixedly connected to the floating ball;

the protective switch is provided with a trigger rod;

When the liquid level reaches the second height, the floating ball drives the trigger rod to close the protection switch through the trigger piece, so that the liquid supply channel is blocked.

The floater goes up and down along with the liquid level change to realize protection switch's switching through trigger piece and trigger lever cooperation, comparatively convenient realization is comparatively stable to the control of liquid level height in the stock solution container to the intercommunication of feed liquid passageway or the control of closing, the difficult problem that takes place the inefficacy.

In a specific implementation manner, the trigger piece comprises a connecting rod fixedly connected to the floating ball and an abutting block arranged at the end part of the connecting rod;

The abutting block abuts against the trigger rod.

In a specific implementation manner, the abutting block is provided with a limiting groove, and the trigger rod is positioned in the limiting groove;

the extending direction of the limiting groove is the same as the moving direction of the trigger rod relative to the abutting block.

Through the spacing groove that sets up, when butt piece and trigger lever butt pull the trigger lever, the trigger lever is located the spacing inslot, guarantees the stability of butt piece and trigger lever relative position, avoids appearing butt piece relative trigger lever skew, causes unable stable trigger protection switch's problem, promotes the stable realization to liquid level height control function in the reservoir.

In a specific embodiment, there are two abutment blocks, two of which are symmetrical about the link, one of which is intended to abut against the trigger lever.

The two butt blocks are symmetrically arranged, so that the overall structural stability of the trigger piece can be improved, the skew problem is not easy to occur, and the stability of the floating ball and the lifting process of the trigger piece is improved.

In a specific implementation manner, the device further comprises a sliding block which is connected to the connecting rod in a sliding way, wherein a locking piece for locking the sliding block is arranged on the sliding block;

the abutting block is fixedly connected with the sliding block.

The position of the relative floater of adjustment butt piece that can be comparatively convenient through the slider that sets up, when in actual use, protection switch's position determination, adjustment butt piece are the position of relative floater, can make the liquid level trigger protection switch shutoff feed liquid passageway when not high, and during the concrete use, can adjust the position of butt piece according to actual need for shutoff feed liquid passageway when the liquid level reaches required height.

In a specific implementation mode, a guide block is fixedly connected to the connecting rod, and the guide block is attached to the inner side wall of the limiting piece.

The sliding direction of the trigger piece can be conveniently limited, the condition that the trigger piece shakes relative to the limiting piece is avoided, the stability of the abutting block and the triggering rod in cooperation is improved, and the problem that the protective switch cannot be smoothly triggered due to the fact that the abutting block deflects relative to the triggering rod is avoided.

In a specific embodiment, the inner ring of the cross section of the limiting piece is a non-circular polygon;

The cross section shape of the guide block is matched with the shape of the inner ring of the cross section of the limiting piece.

Limiting the guide block to rotate relative to the limiting piece, namely limiting the position of the abutting block, avoiding the situation that the abutting block rotates relative to the limiting piece, keeping the position of the abutting block relative to the triggering rod stable, and ensuring that the abutting block stably triggers the protection switch to be closed along with the rise of the liquid level.

In a specific implementation manner, the upper end of the guide block is provided with a limiting part, and the cross section size of the limiting part is larger than that of the limiting part.

In the above technical scheme, through the spacing portion that sets up, the position of restriction floating subassembly relative locating part avoids under the circumstances that the liquid level in the stock solution container is too low, and the floating subassembly descends the condition that the height is too much, promotes the speed of secondary protection mechanism response under the circumstances that the liquid level risees.

Drawings

FIG. 1 is a schematic diagram of the overall structure of a liquid level protection mechanism according to an embodiment of the present application;

FIG. 2 is a schematic view of a floating assembly according to an embodiment of the present application;

FIG. 3 is a schematic diagram of a trigger according to an embodiment of the present application;

Fig. 4 is a schematic structural diagram of an abutment block according to an embodiment of the present application.

Reference numerals illustrate: 1. a liquid storage container; 2. a liquid supply channel; 21. a liquid outlet; 3. a floating switch; 4. a floating assembly; 41. a floating ball; 42. a trigger; 421. a connecting rod; 422. an abutment block; 4221. a limit groove; 423. a guide block; 424. a limit part; 425. a slide block; 426. a locking member; 5. a protective switch; 51. a switch body; 52. a trigger lever; 6. and a limiting piece.

Detailed Description

The application is further described in detail below by means of the figures and examples. The features and advantages of the present application will become more apparent from the description.

The word "exemplary" is used herein to mean "serving as an example, embodiment, or illustration. Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are illustrated in the accompanying drawings, the drawings are not necessarily drawn to scale unless specifically indicated.

In addition, the technical features described below in the different embodiments of the present application may be combined with each other as long as they do not collide with each other.

In order to facilitate understanding of the liquid level protection mechanism provided by the embodiment of the application, the structure of the liquid level protection mechanism is introduced first, and the liquid level protection mechanism comprises a water tank, a water inlet pipe and a floating ball switch, wherein the water inlet pipe is connected with a water source, and the water outlet is communicated with the inside of the water tank; the floating ball switch is positioned in the water tank and connected with the water outlet of the water inlet pipe and used for controlling the communication and closing of the water inlet pipe; when the water level in the water tank is at a lower level, the floating ball type switch is in an on state, the water inlet pipe supplies water to the water tank, and when the water level rises to a set height, the floating ball type switch is driven to close the water inlet pipe, and water supply to the water tank is stopped, so that the water level in the water tank is kept at the set height.

However, as the service time is prolonged or mechanical parts are failed, the floating ball switch fails, the water inlet pipe continuously supplies water to the water tank, water in the water tank overflows, resources are wasted, and the work cannot be normally performed.

The embodiment of the application provides a liquid level protection mechanism, which improves the stability of a liquid level regulation function and avoids the problem of liquid level regulation failure. The following detailed description is made with reference to the specific drawings and examples.

Referring to fig. 1, fig. 1 shows a schematic structural diagram of a liquid level protection mechanism according to an embodiment of the present application. The liquid level protection structure provided by the embodiment of the application comprises a liquid storage container 1, a liquid supply channel 2, a floating switch 3 and a secondary protection mechanism, wherein the liquid storage container 1 is used for storing liquid, for example, a water tank used for storing water, and of course, the liquid level protection structure can also be used for storing other liquid, such as cooling liquid, gasoline and the like; the liquid outlet 21 of the liquid supply channel 2 is communicated with the inside of the liquid storage container 1, the other end of the liquid supply channel 2 is connected with corresponding liquid storage equipment or a source, and corresponding types of liquid are introduced into the liquid storage container 1 related to the liquid supply channel 2; the floating switch 3 is positioned in the liquid storage container 1 and is connected with the liquid outlet 21 of the liquid supply channel 2, and when the liquid level in the liquid storage container 1 reaches the first height, the floating switch 3 is triggered to block the liquid outlet 21, and the liquid supply into the liquid storage container 1 is stopped.

The secondary protection structure comprises a floating assembly 4 and a protection switch 5, wherein the floating assembly 4 is communicated with the inside of the liquid storage container 1 and slides along the set direction along with the lifting of the liquid level in the liquid storage container 1; the protection switch 5 is connected to the liquid supply channel 2 and used for controlling the opening and closing of the liquid supply channel 2; when the liquid level in the liquid storage container 1 rises to the second height, the floating assembly 4 triggers the protection switch 5, so that the protection switch 5 seals the liquid supply channel 2. Wherein the second height is above the first height; the setting direction only needs to have a component in the vertical direction to realize the position adjustment of the floating assembly 4 through the liquid level height, and the setting direction is taken as the vertical direction for illustration in the embodiment of the application.

Under the condition that the floating switch 3 works normally, when the liquid level in the liquid storage container 1 reaches a first height, the liquid level in the liquid storage container 1 is maintained at the first height in a state that the floating switch 3 closes the liquid supply channel 2; subsequently, the liquid level in the liquid storage container 1 is lower than the first height due to use, the floating switch 3 is opened, and liquid is supplied to the liquid storage container 1 to the first height.

If the floating switch 3 is damaged, the liquid supply channel 2 still cannot be closed when the liquid level in the liquid storage container 1 reaches the first height, the liquid is continuously supplied to the liquid storage container 1, the liquid level in the liquid storage container 1 is continuously increased, and the problem of liquid overflow occurs.

Through the secondary protection mechanism provided by the embodiment of the application, in the process that the liquid level continuously rises and exceeds the first height to the second height, the floating assembly 4 is driven to rise, the final liquid level rises to the second height, the floating assembly 4 triggers the protection switch 5, the liquid supply channel 2 is closed, the liquid supply into the liquid storage container 1 is stopped, the problem of liquid overflow in the liquid storage container 1 is avoided, and the normal operation of equipment is ensured.

Moreover, the secondary protection mechanism also adopts a mechanical structure to control the liquid level, if an electric control mode is adopted, larger energy waste exists because the liquid level needs to be in a working state in real time for a long time, and the secondary protection structure can control the liquid level in the liquid storage container 1, avoid the problem of energy waste, and is safer than the electric control mode, so that the risk of danger is reduced.

In addition, the secondary protection mechanism further comprises a limiting piece 6 fixedly connected in the liquid storage container 1, and the floating assembly 4 is in sliding fit with the limiting piece 6; the sliding direction of the floating assembly 4 is guided by the limiting piece 6, the floating assembly 4 is limited to slide along the set direction in the page lifting process in the liquid storage container 1, the triggering of the protection switch 5 is stably realized, and the stability of the sliding process of the floating assembly 4 is ensured.

Specifically, the limiting piece 6 is a limiting pipe and is in a tubular shape, the inside of the limiting pipe is communicated with the inside of the liquid storage container 1, and the height of the liquid level in the limiting pipe synchronously changes with the height of the liquid level in the liquid storage container 1 in the process of injecting liquid into the liquid storage container 1.

The limiting tube is fixedly connected in the liquid storage container 1, and through holes are formed in the peripheral surface of the limiting tube, which is positioned at the middle bottom of the liquid storage container 1, so that the limiting tube is communicated with the inside of the liquid storage container 1. In another embodiment, the limiting tube is fixedly connected to the outer wall of the liquid storage container 1 and is communicated with the inside of the liquid storage container 1. In the embodiment of the application, the limiting pipe is fixedly connected to the outer wall of the liquid storage container 1, and the limiting pipe extends along the vertical direction in combination with the limitation of the set direction.

The protection switch 5 is located on one side of the liquid supply channel 2, where the liquid outlet 21 faces the liquid supply source, and comprises a switch body 51 fixedly connected to the liquid supply channel and a trigger rod 52 installed on the switch body 51, and the protection switch 5 is opened and closed by operating the trigger rod 52.

Referring to fig. 1 and 2, part of the floating assembly 4 is located in the limiting pipe, the floating assembly 4 comprises a floating ball 41 and a trigger piece 42 fixedly connected to the floating ball 41, the floating ball 41 is located in the limiting pipe and is kept in contact with the inside of the limiting pipe, and the floating ball 41 is lifted in the limiting pipe along with the lifting of the liquid level; the trigger piece 42 is fixedly connected to the floating ball 41, is positioned above the floating ball 41 and extends out of the upper end opening of the limiting pipe, and is arranged corresponding to the trigger rod 52. When the page reaches the second height, the floating ball 41 rises along with the page height, the trigger piece 42 drives the trigger rod 52 to close the protection switch 5, the liquid supply channel 2 is plugged, and the liquid supply in the liquid storage container 1 is stopped.

Through spacing pipe and floater 41 that sets up and spacing pipe inner wall paste mutually, can be comparatively convenient, stable prescribe a limit to the direction of movement of floater 41, guarantee that floater 41 height is along with the liquid level height variation and steadily go up and down, just also can comparatively conveniently guarantee the correspondence between trigger 42 and the trigger lever 52, avoid leading to the problem that the cooperation between trigger 42 and the trigger lever 52 appears error because of floater 41 position rocks.

In other embodiments, the limiting member 6 may also be configured as a limiting rod, which, of course, is only required to be directly and fixedly connected to the inside of the liquid storage container 1 in this case; the floating ball 41 is provided with a through hole for the limiting rod to pass through, the limiting rod is arranged in the through hole in a penetrating way, the floating ball 41 is in sliding fit with the limiting rod, and the floating ball 41 can be limited to stably slide along the set direction along with the change of the liquid level.

Referring to fig. 2 and 3, the trigger 42 includes a link 421 fixedly coupled to the float 41 and an abutment block 422 provided at an end of the link 421, the abutment block 422 abutting against the trigger lever 52; of course, when the abutment block 422 and the trigger lever 52 are in abutment with each other and the liquid level in the liquid storage container 1 is raised to a certain height, and when the liquid level is low, the abutment block 422 is positioned below the trigger lever 52, and as the liquid level is raised, the abutment block 422 is raised until it abuts against the trigger lever 52 and pulls the trigger lever 52, thereby closing the protection switch 5.

In order to ensure the abutting between the abutting block 422 and the trigger rod 52 and the stability in the process of pulling the trigger rod 52, referring to fig. 3 and 4, a limiting groove 4221 is formed on the abutting block 422, and the trigger rod 52 is positioned in the limiting groove 4221; the extending direction of the limiting groove 4221 is the same as the moving direction of the trigger lever 52 relative to the abutment block 422. In the process of moving the trigger rod 52 upwards by the limiting block, the trigger rod 52 rotates relative to the switch body 51 and slides relative to the limiting block, the two are limited to be opposite in position firstly by the limiting groove 4221, the problem that the trigger rod 52 is separated from the abutting block 422 is avoided, and the closing stability of the trigger protection switch 5 is improved.

In the embodiment of the present application, referring to fig. 2, the trigger piece 42 further includes a guide block 423 fixedly connected to the connecting rod 421, where the guide block 423 is attached to the inner wall of the limiting tube, so that the stability of lifting the floating ball 41 and the connecting rod 421 can be further improved, and the problem of shaking of the connecting rod 421 during the lifting process can be avoided. In addition, the inner ring provided with the cross section of the limiting pipe is a non-circular polygon, the cross section of the guide block 423 is matched with the shape of the inner ring of the cross section of the limiting pipe, so that the floating assembly 4 can be limited to rotate relative to the limiting pipe, and the stable alignment of the abutting block 422 and the trigger rod 52 is ensured.

In addition, in the embodiment where the limiting member 6 is a limiting rod, the cross section of the limiting rod may be a non-circular polygon, and the cross section of the through hole on the floating ball 41 is adapted to the cross section of the limiting rod, so that the floating assembly 4 can be limited to rotate relative to the limiting rod, and stable alignment of the abutting block 422 and the triggering rod 52 is ensured.

Referring to fig. 2, the upper end of the guide block 423 is provided with a limiting portion 424, where the cross-sectional dimension of the limiting portion 424 is greater than the cross-sectional dimension of the limiting tube, and the cross-sectional dimension of the limiting tube refers to the inner ring dimension of the cross-section of the limiting tube, and of course, in order to avoid that the guide block 423 falls into the limiting tube completely, the pseudo-face dimension of the limiting portion 424 may be set to be greater than the outer ring dimension of the cross-section of the limiting tube when actually set.

Through the spacing portion 424 that sets up, after liquid level in liquid storage container 1 reduces, the condition that floater 41 decline height is too much can not appear, even directly drop to the bottom in the spacing pipe, avoids appearing the liquid level in-process, and floater 41 is difficult to rise along with the liquid level rising smoothly.

Further, referring to fig. 2 and 3, two abutment blocks 422 are provided, and the two abutment blocks 422 are symmetrically provided with respect to the connecting rod 421; one of the abutting blocks 422 is used for abutting against the trigger rod 52, and the other abutting block 422 is used as a counterweight balance structure; the abutment block 422 as a counterweight balance structure is provided with a stopper 4221 as needed. In actual design, the weight of the abutting block 422 abutting against the trigger lever 52 is smaller than that of the other abutting block 422, and the balance of the entire trigger 42 can be improved to some extent in a state where the abutting block 422 and the trigger lever 52 have an interaction force.

Referring to fig. 3, the trigger member 42 further includes a slider 425 and a locking member 426, the slider 425 is slidably connected to the connecting rod 421, and the abutment block 422 is fixedly connected to the slider 425; the locking piece 426 is used for locking the sliding block 425, and illustratively, the locking piece 426 is a jacking bolt, the jacking bolt is in threaded connection with the sliding block 425, the end portion of the jacking bolt is abutted with the connecting rod 421, and the locking of the sliding block 425 relative to the connecting rod 421 can be achieved by tightly tightening the jacking bolt and the connecting rod 421.

In actual use, the distance between the abutting block 422 and the floating ball 41 is adjusted by loosening the jacking bolt and sliding the sliding block 425, and after the adjustment is in place, the sliding block 425 and the abutting block 422 can be directly locked by tightening the jacking bolt. When the position of the protection switch 5 is determined, the position of the abutment block 422 relative to the floating ball 41 is adjusted, so that the height of the floating ball 41, i.e., the height of the liquid level in the liquid storage container 1, can be adjusted when the protection switch 5 is triggered to be closed.

That is, when the liquid level in the liquid storage container 1 reaches different heights, the position of the abutting block 422 is adjusted, the triggering protection switch 5 is closed to block the liquid supply channel 2, and when in actual use, the triggering liquid level height of the secondary protection mechanism for blocking the liquid supply channel 2 can be adjusted conveniently according to actual needs, so that the applicability of the secondary protection mechanism is improved.

In the description of the present application, it should be noted that the directions or positional relationships indicated by the terms "upper", "lower", "inner", "outer", "front", "rear", "left", "right", etc. are directions or positional relationships based on the operation state of the present application are merely for convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements to be referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application.

In the description of the present application, it should be noted that the terms "mounted," "connected," and "connected" are to be construed broadly, unless otherwise specifically defined and limited; in addition, a plurality of the present application is referred to as two or more. The specific meaning of the above terms in the present application will be understood in specific cases by those of ordinary skill in the art.

The application has been described above in connection with preferred embodiments, which are, however, exemplary only and for illustrative purposes. On this basis, the application can be subjected to various substitutions and improvements, and all fall within the protection scope of the application.

Claims (11)

1. A liquid level protection mechanism is characterized by comprising,

A liquid storage container for storing liquid;

The liquid supply channel is communicated with the liquid storage container through a liquid outlet;

the floating switch is positioned in the liquid storage container and connected with the liquid outlet of the liquid supply channel, and when the liquid level in the liquid storage container reaches a first height, the liquid outlet is blocked by the floating switch;

The secondary protection mechanism comprises a floating assembly which is positioned in the liquid storage container and slides along a set direction, and a protection switch which is connected to the liquid supply channel and used for controlling the opening and closing of the liquid supply channel;

When the liquid level in the liquid storage container reaches a second height, triggering the protection switch to block the liquid supply channel;

Wherein the second height is above the first height.

2. The fluid level guard mechanism of claim 1, further comprising a stop fixedly coupled to the reservoir, the float assembly being in sliding engagement with the stop.

3. The liquid level protection mechanism according to claim 2, wherein the limiting member is tubular, and the inside of the limiting member is communicated with the inside of the liquid storage container;

And part of the floating assembly is positioned in the limiting piece.

4. The fluid level guard mechanism of claim 3, wherein the float assembly comprises a float ball and a trigger fixedly coupled to the float ball;

the protective switch is provided with a trigger rod;

When the liquid level reaches the second height, the floating ball drives the trigger rod to close the protection switch through the trigger piece, so that the liquid supply channel is blocked.

5. The liquid level protection mechanism according to claim 4, wherein the trigger member comprises a connecting rod fixedly connected to the floating ball and an abutting block arranged at the end part of the connecting rod;

The abutting block abuts against the trigger rod.

6. The liquid level protection mechanism according to claim 5, wherein the abutting block is provided with a limit groove, and the trigger rod is positioned in the limit groove;

the extending direction of the limiting groove is the same as the moving direction of the trigger rod relative to the abutting block.

7. The fluid level guard mechanism of claim 5, wherein there are two of said abutment blocks, two of said abutment blocks being symmetrical about said link, one of said abutment blocks being for abutment with said trigger lever.

8. The liquid level protection mechanism according to claim 5, further comprising a slider slidingly connected to the connecting rod, wherein a locking member for locking the slider is provided on the slider;

the abutting block is fixedly connected with the sliding block.

9. The liquid level protection mechanism according to claim 5, wherein a guide block is fixedly connected to the connecting rod, and the guide block is attached to the inner side wall of the limiting piece.

10. The liquid level protection mechanism according to claim 9, wherein the inner ring of the cross section of the limiting piece is in a non-circular polygonal shape;

The cross section shape of the guide block is matched with the shape of the inner ring of the cross section of the limiting piece.

11. The liquid level protection mechanism according to claim 9, wherein the upper end of the guide block is provided with a limiting portion, and the cross-sectional dimension of the limiting portion is larger than that of the limiting member.