WO2022082841A1

WO2022082841A1 - Head-mounted eyeglasses-type eye-tracking instrument having easy adjustment

Info

Publication number: WO2022082841A1
Application number: PCT/CN2020/124839
Authority: WO
Inventors: 李华京; 杜鑫; 陈芳
Original assignee: 垒途智能教科技术研究院江苏有限公司; 贝利尔科技发展南京有限公司; 杭州禾士医疗科技有限公司
Priority date: 2020-10-20
Filing date: 2020-10-29
Publication date: 2022-04-28
Also published as: CN112244763A

Abstract

Provided is an eye-tracking instrument, comprising a lens frame (1), a mounting member (3), connecting members (5), a first fixing strap (7), a second fixing strap (8), a connecting strap (9), and a fixing frame (12); the upper parts of both ends of the lens frame (1) are fixedly connected to the connecting members (5); the connecting members (5) are provided in two sets in parallel to each other; one end of the connecting member (5) is connected vertically to the lens frame (1); each of the first fixing strap (7) and the second fixing strap (8) is fixedly connected to the end of the connecting member (5) away from the lens frame (1); the first fixing strap (7) is connected to the second fixing strap (8) by means of the connecting strap (9); the bottom end of the lens frame (1) is snap-fittingly provided with the mounting member (3); the mounting member (3) is fixedly connected to the lens frame (1) by means of a second screw (16) and a third screw (21); the lens frame (1) is provided with through-holes (25) used for mounting lenses (2); the through-holes (25) are provided in two sets in parallel to each other; the lens frame (1) is also provided with mounting holes (22) used for mounting a first camera (4). The head-mounted eye-tracking instrument having easy adjustment has a reasonable design, is simple to operate, and meets the usage requirements of the consumer.

Description

A head-mounted glasses-type eye tracker that is easy to adjust

technical field

The invention belongs to the technical field of head-mounted eye trackers, and the international classification numbers are G02C11/00 and A61B3/113, in particular to a head-mounted glasses-type eye tracker that is easy to adjust.

Background technique

Eye trackers are used by users to obtain eye movement information, complete gaze tracking or complete information interaction, etc., and are important instruments for basic research in psychology. Eye trackers are used to record the characteristics of human eye movements when processing visual information, and are widely used in the research of attention, visual perception, reading and other fields. The structure of modern eye trackers generally includes four systems, namely the optical system, the pupil center coordinate extraction system, the visual and pupil coordinate superposition system, and the image and data recording and analysis system. There are three basic types of eye movements: fixation, saccades and following movements. Eye movement can reflect the selection mode of visual information, which is of great significance for revealing the psychological mechanism of cognitive processing. From the research report, the data or parameters commonly used in psychological research using eye trackers mainly include: fixation point trajectory map, eye movement Time, average velocity time and distance in saccade direction, pupil size and blinking.

Existing eye trackers are mostly flashlight type (or desktop type), eye patch type or head-mounted type. The flashlight type (desktop type) has many and miscellaneous parts, and the eye patch type affects the line of sight. There are some head-mounted eye trackers in the prior art, but the stability of the existing head-mounted eye trackers is not good, and the head-mounted eye trackers are easy to slide during the use of consumers, and the existing head-mounted eye trackers are easy to slide. The lenses of the head-mounted eye tracker are all fixed installations. Once the lens is damaged, the entire head-mounted eye tracker needs to be replaced, which cannot meet the needs of consumers. For example, Chinese patent document CN209269661U discloses a head-mounted device for an eye tracker, which improves the wearing comfort of the eye tracker by adjusting the size of the inner ring to adapt to the shape and size of the heads of different people. For example, Chinese patent documents CN109106334A, CN109199321A, CN107212851A disclose a wireless eye tracker, including a frame carrier and an eye movement recorder, camera, gyroscope, etc. integrated on the frame carrier, which can automatically cut out invalid visual information. Next, keep more valid information. However, these eye trackers have poor stability and are not easy to fix when consumers use them. Therefore, there is an urgent need for a glasses-type structure that can stably wear eye trackers, so that consumers can wear them and use them even when they are walking. carry out testing.

SUMMARY OF THE INVENTION

In view of the above technical problems, the purpose of the present invention is to provide a head-mounted eye tracker that is easy to install, light and portable, can be worn firmly, and is easy to adjust.

In order to achieve the above purpose, the present invention provides the following technical solutions: a head-mounted eye tracker that is easy to adjust, comprising a mirror frame, a mounting piece, a connecting piece, a first fixing belt, a second fixing belt, a connecting belt and a fixing frame, so The upper parts of the two ends of the mirror frame are fixedly connected with connecting pieces, the connecting pieces are provided with two groups in parallel with each other, one end of the connecting pieces is vertically connected with the mirror frame, and the end of the connecting pieces away from the mirror frame is fixedly connected with the first fixing belt, The second fixing belt, the first fixing belt and the second fixing belt are connected by a connecting belt, the bottom end of the mirror frame is clamped with a mounting piece, and the mounting piece is fixedly connected to the mirror frame by the second bolt and the third bolt ;

The mirror frame is provided with through holes for installing lenses, and two sets of the through holes are relatively parallel to each other. The mirror frame is also provided with installation holes for installing the first camera, and the installation holes are located in the two sets of the through holes. between the holes;

There are also mounting seats between the two sets of through holes, and two sets of mounting seats are arranged opposite to each other. A connecting block is fixedly installed on the mounting seat through a fourth bolt, and the end of the connecting block away from the mounting seat is fixedly connected. with mirror holder;

The side of the mirror frame close to the mirror holder is provided with a groove, the groove is communicated with the through hole, the groove is provided with two groups, the inner wall of the groove is provided with a limit groove, the groove and the limit groove The groove is provided with a fixing frame, and two sets of the fixing frame are arranged in parallel with each other.

Preferably, the mounting seat is provided with two opposite groups, at least one in each group, and the connecting block is longitudinally provided with a through hole, so that the fourth bolt can pass through the through hole and abut the fixing frame inside the mirror frame. An open long slot is arranged on the sides of the left and right mirror frames close to the mirror holder, so that the mounting seat can move longitudinally along the long slot.

Preferably, the lens holder is further fixedly connected by installing a plurality of the mounting seats in the longitudinal direction, and the connecting wires of the first camera, the second camera and the light projector are also accommodated in the open long slot, so as to be connected with the connecting piece. The power connection of the inlaid installation is connected to the fixing frame of the mirror frame through the mounting seat through a plurality of the fourth bolts, so that the fixing frame maintains the inward pressing force, and the mirror is further firmly fixed on the mirror frame. In the fixing frame, the connecting block is connected to the mirror holder through the other end of the bolt through the mounting piece.

Preferably, the connecting block and the mirror holder are provided with two groups opposite each other, the mirror holder is a rubber block, the mirror holder is located at the position of the bridge of the user's nose, the second bolt is provided with multiple groups, and the third bolt There are at least two groups.

Preferably, a second camera and an infrared light projector are respectively installed on the side of the mounting member close to the mirror holder, two sets of the second camera and the infrared light projector are respectively installed, and one end of the second bolt and the third bolt are installed through The piece is screwed to the frame.

Preferably, a lens is inlaid and installed on the fixing frame, a sealing strip is fixed and glued between the lens and the fixing frame, the sealing strip is provided with two groups, and the fixing frame is threadedly connected with a first bolt, so One end of the first bolt is threadedly connected to the mirror frame through the fixing frame.

Preferably, a power supply is embedded in the connector, and there are two groups of the power supply. The power supply is electrically connected to the first camera, the second camera and the infrared projector respectively, and the first camera is fixedly assembled in the installation hole. Inside.

Preferably, a limiting member is fixedly connected to one side of the fixing frame, a rubber pad is fixedly glued on a side of the limiting member away from the fixing frame, and both the limiting member and the rubber pad are located in the limiting groove.

Preferably, a first threaded hole and a second threaded hole are further opened on the side of the mirror frame close to the fixing frame, the first threaded hole and the second threaded hole are each provided with multiple groups, and the first threaded hole is connected to the second threaded hole. A bolt is matched, and the second threaded hole is matched with the second bolt.

Preferably, one side of the first fixing belt and the second fixing belt are fixedly connected with limit rods, the limit rods are provided with two groups, and limit holes are formed on the connecting belt, and the limit holes are equidistant. There are multiple groups, the limiting rod is located in the limiting hole, and the connecting band is a rubber band.

The visual information in front of the wearer is obtained through the first camera installed on the outside of the spectacle frame, and the eye movement information of the wearer is obtained through the second camera installed on the inner side of the spectacle frame. The camera can be installed at the center of the frame or at a left or right position. The infrared light projector is used to provide infrared light to the second camera when the ambient light is weak, so that the user's eye movement information can be clearly obtained. The infrared light projector is arranged near the second camera, and the second camera is provided with one for each of the left and right eyes. Correspondingly, one infrared light projector is provided on the left and right.

In addition, in order to record audio information, a microphone can also be set on the side of the frame. For storage convenience, a USB port can also be provided on the side of the frame. In order to exchange data with other terminals, communication modules can also be set up.

The technical effects and advantages of the present invention: the easy-to-adjust head-mounted eye tracker facilitates the installation and disassembly of the lens through the design of the fixed frame, and facilitates the installation of the lens holder through the design of the mounting seat, and through the second bolt , The design of the third bolt makes it easy to install the mounting piece on the mirror frame. The design of the stopper and rubber pad makes the connection between the fixed frame and the mirror frame more closely. The length of the two fixing straps can be adjusted, so that the head-mounted eye tracker can be adjusted according to the wearer's needs, and the head-mounted eye tracker can be effectively fixed on the wearer's head, which is convenient for adjustment. The head-mounted eye tracker has reasonable design and simple operation, which can meet the needs of consumers.

Description of drawings

1 is a schematic structural diagram of a glasses-type eye tracker related to a specific embodiment of the present invention;

Fig. 2 is the rear view of the glasses-type eye tracker related to the specific embodiment of the present invention;

Fig. 3 is the rear view of the fixing frame of the glasses-type eye tracker related to the specific embodiment of the present invention;

4 is a schematic structural diagram of a fixed frame limit groove of a spectacle-type eye tracker according to a specific embodiment of the present invention;

5 is a perspective view of a fixing frame of a glasses-type eye tracker according to an embodiment of the present invention.

In the picture: 1 frame, 2 lens, 3 mounting piece, 4 first camera, 5 connecting piece, 6 power supply, 7 first fixing belt, 8 second fixing belt, 9 connecting belt, 10 limit hole, 11 limit rod , 12 fixed frame, 13 sealing strip, 14 first bolt, 15 connecting block, 16 second bolt, 17 mirror holder, 18 mounting seat, 19 second camera, 20 infrared projector, 21 third bolt, 22 mounting hole, 23 Groove, 24 limit groove, 25 through hole, 26 first threaded hole, 27 second threaded hole, 28 fourth bolt, 29 limit piece, 30 rubber pad.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

The present invention provides a head-mounted eye tracker that is easy to adjust as shown in Figures 1-5, including a frame 1, a mounting member 3, a connecting member 5, a first fixing strap 7, a second fixing strap 8, and a connecting strap 9 and the fixing frame 12, the upper parts of the two ends of the mirror frame 1 are fixedly connected with connecting pieces 5, the connecting pieces 5 are provided with two groups in parallel with each other, and one end of the connecting pieces 5 is vertically connected with the mirror frame 1, and the connecting pieces 5 One end away from the mirror frame 1 is fixedly connected with a first fixing belt 7 and a second fixing belt 8 respectively. The first fixing belt 7 and the second fixing belt 8 are connected by a connecting belt 9, and the bottom end of the mirror frame 1 is clamped. There is a mounting member 3 , and the mounting member 3 is fixedly connected to the mirror frame 1 through the second bolt 16 and the third bolt 21 .

The mirror frame 1 is provided with a through hole 25 for installing the lens 2 , and two sets of through holes 25 are relatively parallel to each other. The mirror frame 1 is also provided with a mounting hole 22 for installing the first camera 4 . The hole 22 is located between the two sets of the through holes 25 .

As shown in FIG. 2 , mounting seats 18 are further provided between the two groups of the through holes 25 . The mounting seats 18 are oppositely provided with two groups, at least one in each group, and the mounting seats 18 are fixed by the fourth bolts 28 . A connecting block 15 is installed, and a mirror holder 17 is fixedly connected to the end of the connecting block 15 away from the mounting seat 18; the connecting block 15 is longitudinally provided with a through hole (not shown), so that the fourth bolt 28 passes through the through hole. The hole can abut the fixing frame 12 on the inner side of the mirror frame 1, and an open long groove is provided along the left and right mirror frames 1 near the mirror holder side, so that the mounting seat 18 can move longitudinally along the long groove. Correspondingly, the mounting member 3 is the same The position is also synchronously provided with narrow grooves, so that the mirror holder 17 can be further fixedly connected by installing a plurality of mounting seats 18 in the longitudinal direction, so that it can be adapted to wearers with different face shapes and nose shapes. The opening slot also accommodates the connecting wires of the first camera 4 , the second camera 19 and the light projector 20 to connect with the power source 6 embedded in the connector 5 . A plurality of the fourth bolts 28 abut against the fixing frame 12 of the mirror frame 1 through the mounting seat 18, so that the fixing frame maintains the inward pressing force, and the lens 2 is further firmly fixed in the fixing frame 12. On the one hand, a rubber gasket is arranged at the free end of the fourth bolt 28 , and the mounting seat 18 is arranged in a rectangular parallelepiped shape to avoid undesired rotation with the screwing of the fourth bolt 28 . The connecting block 15 passes through the mounting piece 3 and is connected to the mirror holder 17 through the other end of the bolt 28, so that the mounting piece 3 can be further firmly installed on the mirror frame 1, and the mirror holder 17 can be firmly fixed. On the nose side of frame 1.

The inner ring surface of the mirror frame 1 is also provided with a groove 23, the groove 23 communicates with the through hole 25, the groove 23 is provided with two groups, the inner wall of the groove 23 is provided with a limit groove 24, and the concave The groove 23 communicates with the limiting groove 24 . The groove 23 is provided with a fixing frame 12 . The fixing frame 12 is provided with two groups in parallel. The design of the fixing frame 12 facilitates the installation and removal of the lens 2 .

The connecting block 15 , the mounting seat 18 , and the mirror holder 17 are each provided with two groups opposite each other. The number of the connecting block 15 corresponds to the mounting seat 18 . The mirror holder 17 is a rubber block or a silicone block. The mirror holder 17 Located at the bridge of the user's nose, the second bolts 16 are provided with multiple groups, and the third bolts 21 are provided with at least two groups. The design of the mounting seat 18 facilitates the mounting of the mirror holder.

Specifically, a second camera 19 and an infrared light projector 20 are respectively installed on the side of the mounting member 3 close to the mirror holder 17 . The second camera 19 and the infrared light projector 20 are each provided with two groups. One end of the three bolts 21 is threadedly connected to the mirror frame 1 through the mounting member 3 , and the mounting member 3 is easily installed on the mirror frame 1 through the design of the second bolt 16 and the third bolt 21 .

FIG. 3 is a rear view of the fixing frame of the eye-tracker of the glasses type; FIG. 4 is a schematic structural diagram of the limiting groove of the fixing frame, and some structures other than the fixing frame are omitted in FIGS. 3 and 4 for the convenience of understanding.

As shown in FIG. 3 , a lens 2 is mounted on the fixing frame 12 on the inner side of the frame 1 , and a sealing strip 13 is fixedly glued between the lens 2 and the fixing frame 12 , and the sealing strip 13 is provided with two groups A first bolt 14 is threadedly connected to the fixing frame 12 , and one end of the first bolt 14 is threadedly connected to the mirror frame 1 through the fixing frame 12 .

A power supply 6 (see FIG. 1 ) is embedded in the connector 5, and the power supply 6 is provided with two groups. The power supply 6 is electrically connected to the first camera 4, the second camera 19 and the infrared projector 20 respectively, so The first camera 4 is fixedly assembled in the mounting hole 22 . The visual information in front of the wearer is obtained through the first camera 4 installed on the outside of the spectacle frame, and the eye movement information of the wearer is obtained through the second camera 19 installed on the inner side of the spectacle frame. The

cameras

4 and 19 may be installed at the center of the frame or at a left or right position. The infrared light projector 20 is used to provide infrared light to the second camera 19 when the ambient light is weak, so that the user's eye movement information can be clearly obtained. The infrared light projector 20 is arranged near the second camera 19 , and the second camera 19 is provided with one for each of the left and right eyes. Correspondingly, one infrared light projector 20 is provided on the left and right.

Specifically, one side of the fixing frame 12 is fixedly connected to the limiting member 29 , and the side of the limiting member 29 away from the fixing frame 12 is fixedly glued with a rubber pad 30 , and the limiting member 29 and the rubber pad 30 are both located at In the limiting groove 24 , the fixing frame 12 and the mirror frame 1 are connected more tightly through the design of the limiting member 29 and the rubber pad 30 .

Specifically, a first threaded hole 26 and a second threaded hole 27 are formed on the side of the mirror frame 1 close to the fixed frame 12 , and multiple sets of the first threaded hole 26 and the second threaded hole 27 are provided. The first threaded hole 26 is matched with the first bolt 14 , and the second threaded hole 27 is matched with the second bolt 16 .

Specifically, one side of the first fixing belt 7 and the second fixing belt 8 is fixedly connected to a limit rod 11, and the limit rod 11 is provided with two groups, and the connecting belt 9 is provided with a limit hole 10, so The limit holes 10 are equidistantly provided with multiple groups, the limit rods 11 are located in the limit holes 10, and the connecting belt 9 is a rubber belt. The lengths of the two fixing straps 8 are adjusted, so that the head-mounted eye tracker can be adjusted according to the wearer's use requirements, and the head-mounted eye tracker can be effectively fixed on the wearer's head.

Specifically, when using the head-mounted eye tracker that is easy to adjust, the head-mounted eye tracker is firstly worn on the wearer's eye, and the first fixing belt 7 and the second fixing belt 8 are located on the wearer's head. Then, according to the head circumference of the wearer's head, connect the connecting belt 9 with the first fixing belt 7 and the second fixing belt 8, and the limit rods 11 on the first fixing belt 7 and the second fixing belt 8 are inserted into the It is located in the limiting hole 10 on the connecting strap 9, so that the head-mounted eye tracker is fixed on the wearer's head;

When the lens 2 on the head-mounted eye tracker needs to be replaced, first unscrew the first bolt 14 and the fourth bolt 28 on the fixing frame 12, then take out the fixing frame 12, and then remove the fixing frame 12. A new fixing frame 12 is installed in the groove 23, the fixing frame 12 is inserted into the limiting groove 24 on the mirror frame 1 through the limiting member 29, and then one end of the first bolt 14 is threaded through the fixing frame 12 to the mirror frame 1, The fourth bolt 28 is screwed on to install the lens holder 17. The easy-to-adjust head-mounted eye tracker has reasonable design and simple operation, and can meet the needs of consumers.

To sum up, the present invention has been described in detail with reference to the specific embodiments in conjunction with the specific embodiments. However, those skilled in the art understand that the technical solutions described in the foregoing embodiments may be modified, or some of the technical features may be modified. Equivalent replacements are made, as long as they do not depart from the spirit and purpose of the present invention, any modifications, equivalent replacements, improvements, etc. made fall within the protection scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

An eye tracker, comprising a mirror frame (1), a mounting piece (3), a connecting piece (5), a first fixing band (7), a second fixing band (8), a connecting band (9) and a fixing frame (12) ), it is characterized in that: the upper parts of the two ends of the mirror frame (1) are fixedly connected with connecting pieces (5), the connecting pieces (5) are provided with two groups in parallel with each other, and one end of the connecting pieces (5) is connected to the mirror frame ( 1) Vertical connection, one end of the connecting piece (5) away from the mirror frame (1) is fixedly connected with a first fixing belt (7) and a second fixing belt (8), the first fixing belt (7) and the The two fixing straps (8) are connected by a connecting strap (9), the bottom end of the mirror frame (1) is clamped with a mounting piece (3), and the mounting piece (3) is connected by a second bolt (16), a third The bolt (21) is fixedly connected with the mirror frame (1);

The mirror frame (1) is provided with a through hole (25) for installing the lens (2), the through holes (25) are provided with two groups in parallel with each other, and the mirror frame (1) is also provided with a first an installation hole (22) of the camera head (4), the installation hole (22) being located between the two groups of the through holes (25);

A mounting seat (18) is further provided between the two groups of the through holes (25), the mounting seat (18) is provided with two groups oppositely, and the mounting seat (18) is fixedly installed by a fourth bolt (28). There is a connecting block (15), and a mirror holder (17) is fixedly connected to one end of the connecting block (15) away from the mounting seat (18);

The side of the mirror frame (1) close to the mirror holder (17) is provided with a groove (23), the groove (23) is communicated with the through hole (25), and the groove (23) is provided with two groups, The inner wall of the groove (23) is provided with a limiting groove (24), the groove (23) is communicated with the limiting groove (24), and a fixing frame (12) is arranged in the groove (23), and the The fixed frame (12) is provided with two groups in parallel with each other.
The eye tracker according to claim 1, characterized in that: the mounting base (18) is oppositely provided with two groups, at least one in each group, and the connecting block (15) is longitudinally provided with a through hole, so that the fourth The bolts (28) pass through the through holes and can contact the fixing frame (12) inside the mirror frame (1), and an open long groove is provided along the side of the left and right mirror frames (1) near the mirror holder (17), so as to facilitate the installation The seat (18) moves longitudinally along the slot.
The eye tracker according to claim 2, characterized in that: the lens holder (17) is further fixedly connected by installing a plurality of the mounting seats (18) longitudinally, and the open long groove also accommodates the first lens holder (17). A connecting wire of the camera (4), the second camera (19) and the light projector (20) is connected to the power supply (6) inlaid in the connecting piece (5) through a plurality of the fourth bolts (28) ) abutting the fixing frame (12) of the mirror frame (1) through the mounting seat (18), so that the fixing frame maintains the inward pressing force, and further firmly fixes the lens (2) on the In the fixing frame (12), the connecting block (15) penetrates through the mounting piece (3) and is connected to the mirror holder (17) through the other end of the bolt (28).
The eye tracker according to claim 1, wherein the connecting block (15) and the mirror holder (17) are provided with two groups opposite each other, the mirror holder (17) is a rubber block, and the mirror holder (17) is a rubber block. (17) Located at the position of the bridge of the user's nose, the second bolts (16) are provided with multiple groups, and the third bolts (21) are provided with at least two groups.
The eye tracker according to claim 1, characterized in that: a second camera (19) and an infrared projector (20) are respectively installed on a side of the mounting member (3) close to the lens holder (17), and the second camera (19) The camera head (19) and the infrared light projector (20) are provided with two groups, and one end of the second bolt (16) and the third bolt (21) is threadedly connected to the mirror frame (1) through the mounting member (3).
The eye tracker according to claim 1, characterized in that: a lens (2) is inlaid and installed on the fixing frame (12), and a seal is fixed and glued between the lens (2) and the fixing frame (12). strip (13), the sealing strip (13) is provided with two groups, the fixing frame (12) is threadedly connected with a first bolt (14), and one end of the first bolt (14) passes through the fixing frame (12) ) is screwed to the frame (1).
The eye tracker according to claim 1, characterized in that: a power source (6) is embedded in the connector (5), and the power source (6) is provided with two groups, and the power source (6) is respectively connected with the power source (6). The first camera (4), the second camera (19) and the infrared projector (20) are electrically connected, and the first camera (4) is fixedly assembled in the installation hole (22).
The eye tracker according to claim 1, characterized in that: one side of the fixing frame (12) is fixedly connected with a limiting member (29), and the limiting member (29) is away from the side of the fixing frame (12). A rubber pad (30) is attached to the fixing glue, and the limiting member (29) and the rubber pad (30) are both located in the limiting groove (24).
The eye tracker according to claim 1, wherein a first threaded hole (26) and a second threaded hole (27) are further opened on the side of the mirror frame (1) close to the fixing frame (12), so The first threaded hole (26) and the second threaded hole (27) are provided with multiple groups, the first threaded hole (26) is matched with the first bolt (14), and the second threaded hole (27) ) and the second bolt (16).
The eye tracker according to claim 1, characterized in that: one side of the first fixing band (7) and the second fixing band (8) are fixedly connected to a limit rod (11), and the limit rod ( 11) There are two groups, the connecting belt (9) is provided with limit holes (10), the limit holes (10) are equidistantly provided with multiple groups, and the limit rods (11) are located in the limit holes In (10), the connecting belt (9) is a rubber belt.