CN111803020A

CN111803020A - Head fixing device for ophthalmologic examination

Info

Publication number: CN111803020A
Application number: CN202010816075.2A
Authority: CN
Inventors: 张振华; 张丽君; 于梦丹; 史琦
Original assignee: Qingdao Central Hospital
Current assignee: Qingdao Central Hospital
Priority date: 2020-08-14
Filing date: 2020-08-14
Publication date: 2020-10-23

Abstract

The invention discloses a head fixing device for ophthalmologic examination, and particularly relates to the field of ophthalmologic examination, which comprises a head fixing plate, an inspector and a chin fixing seat, wherein the inspector and the chin fixing seat are vertically distributed and are fixedly arranged on the head fixing plate; the rear side of the head fixing plate is provided with a lifting mechanism which drives the head fixing plate to move up and down; head fixed plate both sides are articulated to be connected with the head limiting plate, head fixed plate front side is opened and is equipped with uncovered, it is equipped with the connecting rod to slide in uncovered, connecting rod front end and chin fixing base fixed connection, the inside drive storehouse that is equipped with of head fixed plate, be equipped with actuating mechanism in the drive storehouse. The invention can adjust the height of the head fixing plate and the detector by utilizing the lifting mechanism, leads the checked person to be comfortable in the checking process, can simultaneously realize the chin support and the limit fixation of the head by utilizing the electric telescopic rod, has convenient operation and can adapt to the use of people of different ages.

Description

Head fixing device for ophthalmologic examination

Technical Field

The embodiment of the invention relates to the field of ophthalmologic examination, in particular to a head fixing device for ophthalmologic examination.

Background

General examination of the eye, including eye appendage and anterior segment examination. The eye attachment examination includes examination of eyelids, conjunctiva, lacrimal apparatus, eyeball position and eye sockets, and in long-term clinical practice, in order to prevent patient from moving around to obstruct treatment or detection during ophthalmic examination, the head is usually fixed by clamping and fixing at two sides, and the fixing effect is not obvious, so that the treatment or detection cannot achieve good effect. Therefore, adopting an effective fixing method becomes a development direction of modern medicine;

often, the head of part of patients such as the old, children and the like shakes left and right, and the normal examination is affected.

The invention with the patent publication number of CN107550453B discloses a novel head fixing device for ophthalmologic examination, which comprises a head fixing frame, a base and an examination device, wherein the examination device is arranged on the base, the head fixing frame is arranged in front of the examination device, the bottom of the head fixing frame is connected to the side surface of the base, the head fixing frame consists of a supporting column, a fixing frame, a nut, a lifting rod, a chin fixing seat, a left fixing frame, a right fixing frame, a perforation, a forehead pad and a clamping block, the supporting column is L-shaped, a cross rod of the supporting column is arranged at the bottom and connected to the side surface of the base, one end of a vertical rod of the supporting column is connected with the middle of the bottom of the fixing frame to form an integral structure, the novel head fixing device for ophthalmologic examination comprises a left fixing frame and a right fixing frame which are formed by a fixing plate, the arc design of arc piece pastes tight human ear structure, and fixed effectual prevents that the patient from controlling and rocking.

However, the patent has the following disadvantages when in use: when in use, the head needs to be fixed by the auxiliary operation of a doctor, and the use is very inconvenient.

Disclosure of Invention

Therefore, the embodiment of the invention provides a head fixing device for ophthalmologic examination, which can adjust the heights of a head fixing plate and a detector through a lifting mechanism, so that an examined person can stand or sit at a comfortable height in an examination process, and in addition, the driving of a head limiting plate can be realized while driving a chin fixing seat to support a chin by utilizing an electric telescopic rod, namely, the chin support and the head are simultaneously limited and fixed.

In order to achieve the above object, the embodiments of the present invention provide the following technical solutions: a head fixing device for ophthalmologic examination comprises a head fixing plate, an inspector and a chin fixing seat, wherein the inspector and the chin fixing seat are vertically distributed and are fixedly arranged on the head fixing plate;

the rear side of the head fixing plate is provided with a lifting mechanism which drives the head fixing plate to move up and down;

the two sides of the head fixing plate are hinged with head limiting plates, an opening is formed in the front side of the head fixing plate, a connecting rod is arranged in the opening in a sliding mode, the front end of the connecting rod is fixedly connected with the chin fixing seat, a driving bin is arranged in the head fixing plate, a driving mechanism is arranged in the driving bin and drives the head limiting plates to do rotary motion, and the driving mechanism drives the chin fixing seat to do vertical linear motion through the connecting rod;

actuating mechanism includes electric telescopic handle, pinion rack, gear, connecting rod, bevel gear group and articulated shaft, the rod end and the connecting rod fixed connection of electric telescopic handle bottom, the horizontal pole difference fixed connection pinion rack is passed through at the connecting rod both ends, and the gear sets up to two and sets up respectively in two pinion rack rear sides top, gear and pinion rack meshing, electric telescopic handle's the equal fixed connecting rod of one end is kept away from to every gear, the articulated shaft sets up to two and sets up respectively in one side that the gear was kept away from to two connecting rods, connecting rod and articulated shaft vertical distribution just through bevel gear group transmission connection, all seted up the hinge hole on the head fixed plate that every articulated shaft front side corresponds, two head limiting plates run through hinge hole and articulated shaft fixed connection respectively.

Furthermore, elevating system includes lead screw, guide arm and lead screw slide, lead screw slide and lead screw threaded connection, the lead screw slide is fixed to be set up in head fixed plate rear side wall, the guide arm sets up in the lead screw both sides and respectively with the lead screw slide cup joint, lead screw one end is driven by servo motor.

Further, the drive bin includes a bin one and two bins two, and two bins two set up respectively in bin one both sides and are linked together with bin one, electric telescopic handle, connecting rod, gear and pinion rack all set up in bin one, uncovered and bin one are linked together, bin two sets up to the L type, articulated shaft, bevel gear group and connecting rod all set up in bin two, the hinge hole communicates with bin two.

Furthermore, the bevel gear set comprises a large bevel gear and a small bevel gear, the large bevel gear and the small bevel gear are vertically distributed, the large bevel gear is fixedly connected with the articulated shaft, the small bevel gear is fixedly connected with the connecting rod, and the diameter of the large bevel gear is larger than that of the small bevel gear.

Furthermore, the top end and the bottom end of the hinged shaft are respectively connected with the inner wall of the second cabin through bearings, and the outer walls of the two sides of the connecting rod are connected with the inner wall of the second cabin through bearings.

Furthermore, a plurality of balls are embedded on the surface of one side, close to the inner wall of the bin, of the toothed plate, and the balls are attached to the inner wall of the bin.

Furthermore, the elevating system front side that the head fixed plate bottom corresponds still is equipped with the disinfect box, a side that the disinfect box is close to elevating system sets up to the opening, fixed mounting has sterilamp on disinfect box and the corresponding inside wall of opening, the disinfect box top is equipped with the head fixed plate import.

Further, be equipped with removable cover in the head fixed plate import, the fixed pivot that is equipped with in removable cover bottom both sides, the pivot tip passes through the bearing and is connected with the disinfect box, the outside cover of pivot is equipped with the torsional spring, removable cover is close to and has seted up on elevating system's the lateral wall with lead screw and guide arm matched with logical groove.

Furthermore, a rubber pad is fixedly arranged on the inner side wall of the head limiting plate.

The embodiment of the invention has the following advantages:

1. the height of the head fixing plate and the height of the detector can be adjusted by utilizing the lifting mechanism, so that a person to be inspected can stand or sit at a comfortable height in the inspection process, in addition, the electric telescopic rod can drive the chin fixing seat to support the chin and simultaneously realize the driving of the head limiting plate, namely the chin support and the limiting and fixing of the head are realized simultaneously, the structure is simple, the operation is convenient, the device can be suitable for people of different ages to use, and the applicability is wide;

2. the head fixing plate can be protected and disinfected by the arrangement of the disinfection box, when the head fixing plate is not used at ordinary times, the head fixing plate can be driven to the inner side of the disinfection box by the lifting mechanism, the disinfection box provides a protection effect for the head fixing plate, and meanwhile, the ultraviolet germicidal lamp on the inner wall of the disinfection box can sterilize and disinfect the head fixing plate and other components on the head fixing plate, so that the head fixing plate is convenient to use safely next time.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below. It should be apparent that the drawings in the following description are merely exemplary, and that other embodiments can be derived from the drawings provided by those of ordinary skill in the art without inventive effort.

The structures, ratios, sizes, and the like shown in the present specification are only used for matching with the contents disclosed in the specification, so as to be understood and read by those skilled in the art, and are not used to limit the conditions that the present invention can be implemented, so that the present invention has no technical significance, and any structural modifications, changes in the ratio relationship, or adjustments of the sizes, without affecting the effects and the achievable by the present invention, should still fall within the range that the technical contents disclosed in the present invention can cover.

FIG. 1 is an overall front view provided by the present invention;

FIG. 2 is a rear view of a head fixation plate provided by the present invention;

FIG. 3 is a schematic view of the internal structure of the head fixing plate according to the present invention;

fig. 4 is a schematic view of a toothed plate and gear mating structure provided by the present invention;

FIG. 5 is a schematic view of the structure of part A of FIG. 3 according to the present invention;

FIG. 6 is a rear view of a sterilization case provided by the present invention;

FIG. 7 is a front view of a sterilization case provided by the present invention;

in the figure: 1 head fixed plate, 2 actuating mechanism, 21 electric telescopic rod, 22 toothed plate, 23 gears, 24 connecting rods, 25 bevel gear sets, 26 articulated shafts, 3 chin fixing seats, 4 lifting mechanisms, 41 lead screws, 42 guide rods, 43 lead screw sliding seats, 44 servo motors, 5 head limiting plates, 6 openings, 7 connecting rods, 8 actuating bins, 81 bin I, 82 bin II, 9 inspectors, 10 articulated holes, 11 balls, 12 sterilizing boxes, 13 ultraviolet sterilizing lamps, 14 head fixed plate inlets, 15 movable cover plates, 16 rotating shafts, 17 torsion springs, 18 rubber pads and 19 through grooves.

Detailed Description

The present invention is described in terms of particular embodiments, other advantages and features of the invention will become apparent to those skilled in the art from the following disclosure, and it is to be understood that the described embodiments are merely exemplary of the invention and that it is not intended to limit the invention to the particular embodiments disclosed. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to the attached drawings 1-4 of the specification, the head fixing device for ophthalmologic examination of the embodiment comprises a head fixing plate 1, an examination device 9 and a chin fixing seat 3, wherein the examination device 9 and the chin fixing seat 3 are distributed vertically and are fixedly arranged on the head fixing plate 1;

the rear side of the head fixing plate 1 is provided with a lifting mechanism 4, and the lifting mechanism 4 drives the head fixing plate 1 to move up and down;

the two sides of the head fixing plate 1 are hinged with head limiting plates 5, an opening 6 is formed in the front side of the head fixing plate 1, a connecting rod 7 is arranged in the opening 6 in a sliding mode, the front end of the connecting rod 7 is fixedly connected with the chin fixing seat 3, a driving bin 8 is arranged in the head fixing plate 1, a driving mechanism 2 is arranged in the driving bin 8, the driving mechanism 2 drives the head limiting plates 5 to do rotary motion, and the driving mechanism 2 drives the chin fixing seat 3 to do vertical linear motion through the connecting rod 7;

actuating mechanism 2 includes electric telescopic handle 21, pinion rack 22, gear 23, connecting rod 24, bevel gear group 25 and articulated shaft 26, the rod end and the 7 fixed connection of connecting rod of electric telescopic handle 21 bottom, 7 both ends of connecting rod are through horizontal pole difference fixed connection pinion rack 22, and gear 23 sets up to two and sets up respectively in two pinion rack 22 rear side tops, gear 23 and pinion rack 22 meshing, the equal fixed connecting rod 24 of one end that electric telescopic handle 21 was kept away from to every gear 23, articulated shaft 26 sets up to two and sets up respectively in one side that gear 23 was kept away from to two connecting rods 24, connecting rod 24 and articulated shaft 26 vertical distribution just connect through bevel gear group 25 transmission, have all seted up hinge hole 10 on the head fixed plate 1 that every articulated shaft 26 front side corresponds, and two head limiting plates 5 run through hinge hole 10 and articulated shaft 26 fixed connection respectively.

Further, the lifting mechanism 4 comprises a screw rod 41, a guide rod 42 and a screw rod slide seat 43, the screw rod slide seat 43 is in threaded connection with the screw rod 41, the screw rod slide seat 43 is fixedly arranged on the rear side wall of the head fixing plate 1, the guide rod 42 is arranged on two sides of the screw rod 41 and is respectively in sliding sleeve connection with the screw rod slide seat 43, and one end of the screw rod 41 is driven by a servo motor 44.

Further, drive bin 8 includes a bin 81 and two bins 82, and two bins 82 set up respectively in bin 81 both sides and are linked together with bin 81, electric telescopic handle 21, connecting rod 7, gear 23 and pinion rack 22 all set up in bin 81, uncovered 6 is linked together with bin 81, bin 82 sets up to the L type, articulated shaft 26, bevel gear group 25 and connecting rod 24 all set up in bin two 82, hinge hole 10 is linked together with bin two 82.

Further, the top end and the bottom end of the hinge shaft 26 are respectively connected with the inner wall of the second chamber 82 through bearings, and the outer walls of the two sides of the connecting rod 24 are connected with the inner wall of the second chamber 82 through bearings.

Further, a rubber pad 18 is fixedly arranged on the inner side wall of the head limiting plate 5.

The implementation scenario is specifically as follows: when the device is used, the height of a person to be inspected can be adjusted according to the height of the person to be inspected when the person to be inspected sits down or stands up, the servo motor 44 is started to drive the screw rod 41 to rotate, and the screw rod sliding seat 43 is in threaded fit with the screw rod 41, so that the device can be driven by the servo motor 44 to do linear reciprocating motion, namely, the head fixing plate 1 can be driven to move up and down, after the person to be inspected stands or sits up to find a comfortable position, the head fixing plate 1 moves to the head position of the person to be inspected, the inspector 9 corresponds to the eye of the person to be inspected, the head limiting plate 5 is in an open state, and the chin fixing seat 3 is far away from the; then, starting the electric telescopic rod 21, driving the chin fixing seat 3 to move upwards to be close to the chin of the person to be inspected through the connecting rod 7 by the electric telescopic rod 21, and stopping moving upwards when the chin is attached to the chin fixing seat 3; in the upward moving process, the connecting rod 7 moves upward and simultaneously drives the toothed plate 22 to move upward through the cross rods on the two sides, the toothed plate 22 is meshed with the gear 23 on the rear side to rotate clockwise, the gear 23 rotates to drive the bevel gear set 25 to rotate through the connecting rod 24, the bevel gear set 25 drives the hinge shaft 26 to rotate clockwise, the clockwise rotation of the head limiting plate 5 can be realized, and the head of the inspected person is wrapped to realize the limiting of the head; when detecting children, because child's head is little, consequently highly great at the detector is arrived to eyes, the rotatory angle of articulated shaft 26 will be bigger this moment, head limiting plate 5 will give the restriction with less head promptly, and on the contrary, the adult only needs the flexible adjustment that can realize eyes, chin and the fixed of head fast of electric telescopic handle 21 short distance, and because the setting of rubber pad 18, can adapt to the deviation of head size in the same age bracket.

The inspector 9 is OCT, is a high-end fundus disease diagnosis device with the highest image definition at present, is a brand new imaging diagnosis technology after ophthalmologic radiation diagnosis, ultrasonic diagnosis and angiography diagnosis, can detect the position of eyes by using the inspector 9, and can drive the lifting mechanism 4 to accurately adjust the height of the head fixing plate 1 by matching with the use of an external host;

whole device at first utilizes elevating system 4 can adjust head fixed plate 1 and detector height, lets the in-process of being examined personnel can stand or sit at comfortable height, utilizes electric telescopic handle 21 can realize the drive of head limiting plate 5 when driving chin fixing base 3 support chin in addition, realizes the spacing of chin support and head promptly simultaneously and fixes, simple structure, and convenient operation can adapt to the people of different age groups and use, and the suitability is wider.

Referring to the attached fig. 3 of the specification, the bevel gear set 25 includes a large bevel gear and a small bevel gear, the large bevel gear and the small bevel gear are vertically distributed, the large bevel gear is fixedly connected with a hinge shaft 26, the small bevel gear is fixedly connected with a connecting rod 24, and the diameter of the large bevel gear is larger than that of the small bevel gear.

The implementation scenario is specifically as follows: according to the invention, when the electric telescopic rod 21 drives the chin fixing seat 3 to move upwards, the toothed plate 22 drives the gear 23 to rotate, at the moment, the gear 23 drives the small bevel gear to rotate at a speed of 1:1 through the connecting rod 7, and the small bevel gear drives the large bevel gear to rotate to realize speed reduction, so that the articulated shaft 26 can drive the head limiting plate 5 to rotate and adjust within a small range, and the head is clamped.

Referring to the attached drawings of the specification and fig. 4-5, a plurality of balls 11 are embedded in the surface of one side of the toothed plate 22 close to the inner wall of the first chamber 81, and the balls 11 are attached to the inner wall of the first chamber 81.

The implementation scenario is specifically as follows: when the electric telescopic rod 21 drives the toothed plates 22 to move up and down, the two toothed plates 22 are limited by the two inner side walls of the first chamber 81, so that the toothed plates 22 are ensured to stably drive the gear 23 to rotate, and when the toothed plates 22 move up and down, in order to avoid large static friction between the toothed plates 22 and the inner walls of the first chamber 81, the design of the balls 11 is adopted, the static friction between the toothed plates 22 and the inner walls of the first chamber 81 is changed into rolling friction by the balls 11, so that the friction force is reduced, and the toothed plates 22 can move up and down smoothly.

Referring to the attached drawings 6-7 of the specification, a disinfection box 12 is further arranged on the front side of the lifting mechanism 4 corresponding to the bottom of the head fixing plate 1, an opening is formed in one side face, close to the lifting mechanism 4, of the disinfection box 12, an ultraviolet germicidal lamp 13 is fixedly installed on the inner side wall, corresponding to the opening, of the disinfection box 12, and an inlet 14 of the head fixing plate is formed in the top of the disinfection box 12.

Further, be equipped with removable cover 15 in the head fixed plate import 14, the fixed pivot 16 that is equipped with in removable cover 15 bottom both sides, the pivot 16 tip is connected with disinfect box 12 through the bearing, the outside cover of pivot 16 is equipped with torsional spring 17, removable cover 15 is close to and has seted up logical groove 19 with lead screw 41 and guide arm 42 matched with on the lateral wall of elevating system 4.

The implementation scenario is specifically as follows: according to the invention, the head fixing plate 1 can be protected and disinfected by the arrangement of the disinfection box 12, when the head fixing plate 1 is not used at ordinary times, the head fixing plate 1 can be driven to the inner side of the disinfection box 12 by the lifting mechanism 4, the disinfection box 12 provides a protection effect for the head fixing plate 1, and meanwhile, the ultraviolet germicidal lamp 13 on the inner wall of the disinfection box can sterilize and disinfect the head fixing plate 1 and other components on the head fixing plate 1, so that the safe use at the next time is facilitated;

in addition, the movable cover plate 15 is arranged in a mode of being capable of rotating and hinging up and down, so that the movable cover plate 15 can be smoothly moved into and out of the disinfection box 12 when the lifting mechanism 4 drives the head fixing plate 1 to move up and down, and the movable cover plate 15 can be automatically closed due to the arrangement of the torsion spring 17, so that the use is very convenient.

Although the invention has been described in detail above with reference to a general description and specific examples, it will be apparent to one skilled in the art that modifications or improvements may be made thereto based on the invention. Accordingly, such modifications and improvements are intended to be within the scope of the invention as claimed.

Claims

1. The utility model provides a head fixing device is used in ophthalmology inspection, includes head fixed plate (1), finder (9) and chin fixing base (3), finder (9) are fixed and distribute from top to bottom with chin fixing base (3) and all fix and set up on head fixed plate (1), its characterized in that:

the rear side of the head fixing plate (1) is provided with a lifting mechanism (4), and the lifting mechanism (4) drives the head fixing plate (1) to move up and down;

the two sides of the head fixing plate (1) are hinged with head limiting plates (5), an opening (6) is formed in the front side of the head fixing plate (1), a connecting rod (7) is arranged in the opening (6) in a sliding mode, the front end of the connecting rod (7) is fixedly connected with the chin fixing seat (3), a driving bin (8) is arranged inside the head fixing plate (1), a driving mechanism (2) is arranged in the driving bin (8), the driving mechanism (2) drives the head limiting plates (5) to do rotary motion, and the driving mechanism (2) drives the chin fixing seat (3) to do vertical linear motion through the connecting rod (7);

the driving mechanism (2) comprises an electric telescopic rod (21), toothed plates (22), gears (23), connecting rods (24), bevel gear sets (25) and hinge shafts (26), the rod end of the bottom of the electric telescopic rod (21) is fixedly connected with the connecting rods (7), the two ends of the connecting rods (7) are respectively and fixedly connected with the toothed plates (22) through transverse rods, the gears (23) are arranged in two and are respectively arranged above the rear sides of the two toothed plates (22), the gears (23) are meshed with the toothed plates (22), one end of each gear (23), which is far away from the electric telescopic rod (21), is respectively fixed with one connecting rod (24), the hinge shafts (26) are arranged in two and are respectively arranged on one side, which is far away from the gears (23), of the two connecting rods (24), the connecting rods (24) and the hinge shafts (26) are vertically distributed and are in transmission connection through the bevel gear sets (25), and hinge shaft holes (10) are respectively formed in the head, the two head limiting plates (5) respectively penetrate through the hinge holes (10) and are fixedly connected with the hinge shafts (26).

2. The head fixing device for ophthalmologic examination as set forth in claim 1, wherein: elevating system (4) include lead screw (41), guide arm (42) and lead screw slide (43), lead screw slide (43) and lead screw (41) threaded connection, lead screw slide (43) are fixed to be set up in head fixed plate (1) rear side wall, guide arm (42) set up in lead screw (41) both sides and slide respectively with lead screw slide (43) and cup joint, lead screw (41) one end is driven by servo motor (44).

3. The head fixing device for ophthalmologic examination as set forth in claim 1, wherein: drive storehouse (8) include one bin (81) and two bins two (82), and two bins two (82) set up respectively in bin (81) both sides and are linked together with bin (81), electric telescopic handle (21), connecting rod (7), gear (23) and pinion rack (22) all set up in bin (81), uncovered (6) are linked together with bin (81), bin two (82) set up to the L type, articulated shaft (26), bevel gear group (25) and connecting rod (24) all set up in bin two (82), articulated hole (10) are linked together with bin two (82).

4. The head fixing device for ophthalmologic examination as set forth in claim 1, wherein: bevel gear group (25) are including big bevel gear and bevel pinion, big bevel gear and bevel pinion vertical distribution, big bevel gear and articulated shaft (26) fixed connection, bevel pinion and connecting rod (24) fixed connection, big bevel gear diameter is greater than bevel pinion diameter.

5. The head fixing device for ophthalmologic examination as set forth in claim 3, wherein: the top end and the bottom end of the hinged shaft (26) are respectively connected with the inner wall of the second chamber (82) through bearings, and the outer walls of the two sides of the connecting rod (24) are connected with the inner wall of the second chamber (82) through bearings.

6. The head fixing device for ophthalmologic examination as set forth in claim 1, wherein: the utility model provides a plurality of balls (11) are inlayed to a side surface that pinion rack (22) are close to bin (81) inner wall, ball (11) and bin (81) inner wall laminate mutually.

7. The head fixing device for ophthalmologic examination as set forth in claim 1, wherein: elevating system (4) front side that head fixed plate (1) bottom corresponds still is equipped with disinfect box (12), a side that disinfect box (12) are close to elevating system (4) sets up to the opening, fixed mounting has sterilamp (13) on disinfect box (12) and the corresponding inside wall of opening, disinfect box (12) top is equipped with head fixed plate import (14).

8. The head fixing device for ophthalmologic examination as set forth in claim 7, wherein: be equipped with removable cover (15) in head fixed plate import (14), removable cover (15) bottom both sides are fixed and are equipped with pivot (16), pivot (16) tip is passed through the bearing and is connected with disinfect box (12), pivot (16) outside cover is equipped with torsional spring (17), seted up on removable cover (15) the lateral wall that is close to elevating system (4) and led screw (41) and guide arm (42) matched with logical groove (19).

9. The head fixing device for ophthalmologic examination as set forth in claim 1, wherein: and a rubber pad (18) is fixedly arranged on the inner side wall of the head limiting plate (5).